Olefin polymers, method of making, and use thereof

Field of the Invention

The present invention relates to polyolefin compositions, methods for producing polyolefin compositions, articles of manufacture using polyolefin compositions, and processes for producing articles of manufacture using polyolefin compositions. More particularly, the present invention relates to ethylene / 1-hexene copolymer compositions and methods for producing said compositions.

Background of the invention

Currently, several resins are used to produce numerous types and styles of pipes. For example, polyethylene resins have been used to produce a high rigidity pipe used in water, gas and other fluid transport applications. Polyethylene pipe classified as PE-100, MRS 10, or the typical ASTM D3350 345566C cell classification is especially suitable for use in conditions that require higher pressure ratings. Higher pressure ratings are partly due to the greater rigidity of the pipe. To obtain a classification of PE-100, the PE-100 pipe must meet certain standards that specify stiffness, resistance to chemical attack, and fragility, which is expressed as the rapid propagation of a crack in low temperature environments or applications. Moreover, said pipe must meet a deformation standard that is determined under high temperature pressure.

While certain polyethylene resins classified as PE-100 are commercially available, these polyethylene resins are of the "bimodal" type. Bimodal polyethylene resins are obtained in reactor systems that involve two or more reaction zones or by the combination of two or more different polymers. Unfortunately, despite the excellent hardness of these resins, bimodal resins are deficient when the pipe is formed by extrusion under certain conditions. Normally, bimodal resins perform adequately in the production of the standard pipe of small diameter, that is, pipes that have diameters between 1-12 inches. However, when a large diameter pipe and / or thick wall is formed, the bimodal resins begin to "comb" or "sink" as the newly formed pipe leaves the extrusion die. Obviously, the still semi-molten polymer does not have sufficient melt strength for a short time before the pipe cools and hardens to resist deformation due to gravitational force. This phenomenon causes a lack of uniformity in the pipe that causes the lower portion of the pipe to be thicker and heavier than the upper portion. A pipe manufacturer can compensate for this to some extent by adjusting the die to form a pipe that is "deviated from the circularity" as it exits the die, so that it subsequently flexes backwards in a better balance. However, such adjustments are complicated, and the degree to which the pipe manufacturer can compensate for the "rope" is limited. As a result, currently available PE-100 rated resins are generally only used to produce a small diameter pipe. Therefore, a PE-100 sized resin is needed that can be used to produce a small and large diameter PE-100 pipe.

During the production of high density olefin polymers or resins, such as high density polyethylene, conventional chromium support catalyst systems can be employed. However, as originally marketed, the use of these conventional chromium support catalyst systems is limited. Normally, conventional chrome support catalyst systems are used in solution polymerization processes. A cheaper way to produce many qualities of commercial olefin polymers employs a suspension process. In the suspension process, the polymerization reaction employs one or more monomers in the presence of a diluent and the catalyst system. Fortunately, the polymerization reaction occurs in the suspension process at a temperature that is low enough to allow the resulting polymer to be largely insoluble in the diluent. However, as explained below, catalytic systems with conventional chromium support are not suitable for use in a suspension process to produce a PE classified resin.

100 Therefore, a catalyst system with chromium support is needed which can be used in a suspension process to produce a PE-100 sized resin.

At present, mono-1-olefins, such as ethylene, are polymerized with catalyst systems that employ transition metals such as titanium, vanadium, chromium or other metals, either without support or on a support, such as alumina, silica. , aluminophosphate, titanium, zircon, magnesium and other refractory metals. Such catalyst systems are used to form ethylene homopolymers. Additionally, comonomers such as propylene, 1-butene, 1-hexene or other higher mono-1-olefins can be copolymerized with ethylene to provide resins adapted to specific uses.

Polymers that have a wide distribution of molecular weights and better physical properties, such as resistance to environmental stress fissure (ESCR), resistance to slow crack growth (PENT) and impact resistance, can be formed by the use of systems Chromium catalysts containing aluminophosphate supports, to include alumina (Al2O3). For example, polymers having a molecular weight distribution (Mw / Mn) of up to 30 can be obtained with catalyst systems with aluminophosphate support. Aluminophosphate supports are characterized by the amount of phosphate in the support, or more precisely, by the molar ratio of phosphorus to aluminum (P / Al) of the composition. The P / Al molar ratio may vary from 0, for example, alumina, to 1 for stoichiometric aluminum phosphate (AlPO2). At a P / Al molar ratio of 1, a crystalline solid of a very small surface area and minimum pore volume is obtained. As a result, the activity of catalyst systems employing an aluminophosphate support having a P / Al ratio of 1 is minimal. Additionally, catalyst systems that use chromium support alumina have very low activity. Consequently, in practice, the commercially preferred P / Al molar ratio of phosphorus to aluminum in chromium / aluminophosphate catalyst systems is 0.7 to 0.9. See The Structure of Coprecipitated Aluminophosphatoe Catalyst Supports; TTP Cheung, KW Willcox, MP McDaniel, and MM Johnson; Journal of Catalysis, Vol.102, p.10-20 (1986).

US 5,037,911 discloses a surface alumina silicate composition which can also be fluoride and / or phosphate. The resulting compositions are useful as supports for the chromium catalysts of olefin polymerization.

US 4,596,862 discloses an ethylene polymer suitable for the production of hard films that are produced under suspension conditions using an aluminophosphate fluoride support and a reaction temperature in the range of 93 ° C to 107 ° C in the presence of hydrogen and a small amount of trialkylboro cocatalyst, wherein said aluminophosphate has a phosphorus to aluminum ratio within a narrow range of 0.15 to 0.4.

Below a P / Al molar ratio of 0.3, the activity is considered too low for practice. Even, catalyst systems employing aluminophosphate supports having such molar ratios less than P / Al produce polymers that conveniently have the broadest molecular weight distribution, and consequently, the highest ESCR values ​​and impact resistance. Another disadvantage of conventional chromium / aluminophosphate catalyst systems is that they incorporate certain comonomers, such as 1-hexene, very sparingly. In conventional processes, 1-hexene can destroy the activity of chromium / aluminophosphate catalyst systems. Consequently, while conventional chromium / aluminophosphate catalyst systems are excellent for producing very high density blow molding resins, such catalyst systems have not gained acceptance for commercial production of lower density copolymers that are used to produce films and pipes.

Despite the existing catalyst systems, methods and resins, better catalyst systems, methods, and resins are needed to produce PE-100 pipes. The invention also relates mainly to the provision of catalyst systems, methods and resins that meet these needs.

The present invention also relates to polyolefin compositions, methods for producing polyolefin compositions, and processes for using polyolefin compositions to produce pipes. More specifically, the present invention relates to the production of PE-100 classification polyethylene pipe and the resin used to obtain the pipe.

The present invention relates to the polymerization and copolymerization of ethylene with 1-hexene.

The present invention also relates to the production with less cost of such ethylene copolymers of exceptional hardness, which can be processed in a large diameter pipe without the distortion caused by the commonly observed phenomenon of "camber" or "sinking" during the extrusion.

The present invention describes a new type of PE-100 polyethylene resin that does not exhibit this sinking behavior, and which can be used, for the first time, to produce a very large diameter pipe without problem. The present invention also describes the only catalyst system used to produce this polymer in a single reaction zone, which means that the resin can be manufactured more efficiently than common "bimodal" type resins.

Synthesis of the invention

The present invention relates to homo-polymers and copolymers of mono-1-olefins, a method of obtaining such polymers, and the uses of such polymers. The polymers of the present invention are formed by contacting ethylene and 1-hexene in a reaction zone under polymerization conditions in the presence of a hydrocarbon diluent, a catalyst system, and a cocatalyst. The catalyst system of the present invention comprises a source of chromium on an aluminophosphate support having a phosphorus to aluminum molar ratio of 0.05 to 0.15. On the other hand, the catalyst system is treated with less than 7 weight percent fluoride based on the weight of the support and calcined. Cocatalysts are selected from trialkylboro compounds, triarylboro compounds, alkylaluminum compounds, and combinations thereof.

In another aspect of the present invention, ethylene copolymers are used to produce a PE pipe.

100 These copolymers are formed by contacting ethylene and 1-hexene in a reaction zone under polymerization conditions in the presence of a hydrocarbon diluent, a catalyst system, and a cocatalyst. Such ethylene copolymers of the invention have a molecular weight distribution (Mw / Mn) greater than about 50 and a substantially constant branching distribution profile of molecular weights greater than about 1x104. On the other hand, these ethylene copolymers can be used to produce the PE100 pipe that has both small diameters and diameters in excess of 106.68 cm without substantially presenting combas or other gravitational deformations. The ethylene copolymers of the present invention have a high charge melt index (HLMI) within a range of 0.5 to 10 g / 10 minutes, a density within a range of 0.945 to 0.955 g / cc, a distribution molecular weight (Mw / Mn) greater than 50, a slow growth resistance value of the PENT fissure of more than 1000 hours, and a branching profile greater than 1 branching / 1000 carbons at a molecular weight of 1 million.

Brief description of the drawings

The following is a brief description of the Figures.

FIGURE 1 is a graph illustrating the distribution of substantially constant short chain branches through the molecular weight distribution of the PE-100 polyethylene copolymer obtained in accordance with the present invention in Example 1.

FIGURE 2 is a graph that further illustrates the distribution of substantially constant short chain branches through the molecular weight distribution of the PE-100 polyethylene copolymer obtained in accordance with the present invention in Example 19, even though the profile Molecular weight is considerably different from that shown for example 1.

FIGURE 3 is a graph showing the typical rheology curves at 190 ° C of the polyethylene copolymers as demonstrated in Examples 1 and 19.

FIGURE 4 is a graph of polymer density (g / cc) versus the percentage by weight of 1-hexene in the reactor.

FIGURE 5 is a graph of the relative activity of the catalyst system (g / g / h) versus the weight percentage of 1-hexene in the reactor.

FIGURE 6 is a graph of distributions of the short chain branches (SCB / 1000 total carbons) of a polymer given in Example VII versus molecular weight (Log M).

Detailed description of the invention

The polymers of the present invention are formed by contacting ethylene and 1-hexene in a reaction zone under polymerization conditions in the presence of a hydrocarbon diluent, a catalyst system, and a cocatalyst. The catalyst system of the present invention comprises a source of chromium on an aluminophosphate support having a phosphorus to aluminum molar ratio of 0.05 to 0.15. In addition, the catalyst system is treated with less than about 7 weight percent fluoride based on the weight of the support and calcined. The cocatalyst is selected from trialkylboro compounds, triarylboro compounds, alkylaluminum compounds and combinations thereof.

In another aspect of the present invention, ethylene copolymers are used to produce PE-100 pipes. These copolymers are formed by contacting ethylene with 1-hexene in a reaction zone under polymerization conditions in the presence of a hydrocarbon diluent, a catalyst system and a cocatalyst. Such ethylene copolymers of the invention have a molecular weight distribution (Mw / Mn) greater than 50 and a constant branching distribution profile for molecular weights greater than 1x104. On the other hand, these copolymers of ethylene can be used to produce PE-100 pipes that have small diameters and diameters in excess of 106.68 cm without substantially presenting combas or other gravitational deformations. The ethylene copolymers of the present invention have a high charge melt index (HLMI) in a range of 0.5 to 10 g / 10 minutes, a density in a range of 0.945 to 0.955 g / cc, a weight distribution molecular (Mw / Mn) greater than 50, a slow growth resistance value of the PENT fissure greater than 1000 hours, and a branching profile of more than 1 branching / 1000 carbons at 1 million molecular weight.

In accordance with yet another embodiment of the present invention, there is provided herein a composition comprising a copolymer of ethylene and 1-hexene, wherein said copolymer has a high charge melt index (HLMI) in a range of 0 , 5 to 10 g / 10 minutes, a density in a range of 0.947 to 0.953 g / cc, a molecular weight distribution (PM / Mn) of more than 80, a slow growth resistance value of the PENT fissure of more 1000 hours and a branching profile of more than about 1 branching / 1000 carbons at a molecular weight of 1 million. On the other hand, in another aspect of the present invention, the ethylene copolymers of the invention have a high charge melt index (HLMI) in a range of 0.5 to 10 g / 10 minutes, a density in a range of 0.945 to 0.955 g / cc, a molecular weight distribution (PM / Mn) greater than about 40, a slow growth resistance value of the PENT fissure of more than 1000 hours, and a branching profile of more than 1 branching / 1000 carbons at 1 million molecular weight

The polymers of the present invention can be formed or extruded into articles of manufacture, including pipes, by any method known in the art. Typically, the pipe is formed by extrusion of the polymers of the present invention into a molten state through a die to form the pipe, and the pipe is subsequently cooled to adjust the shape of the pipe. Additionally, pipe extrusion is described in US Patent No. 5,028,376.

Catalyst systems

As used in this description, the term "support" refers to a carrier for one or more catalytic components. In accordance with the present invention, the support may comprise materials and compositions that are inert with respect to polymerization reactions. On the other hand, the support may comprise materials or compositions that contribute to the catalytic activity and the selectivity of the polymerization reactions. In addition, other materials or components that do not adversely affect the catalyst system and / or the polymerization reaction of the present invention, or are present to produce some unrelated polymer results or properties, may also be present in the support.

Generally, the aluminophosphate support of the present invention can be prepared by any method known to those skilled in the art, such as, for example, use of a cogel. Examples of the preparations that can be used in the present invention are described in US Patent Nos. 4,364,842; 4,444,965; 4,364,855; 4,504,638; 4,364,854; 4,444,964; 4,444,962; 4,444,966; and 4,397,765. When the aluminophosphate support is prepared by cogelification, a hydrogel can be produced by contacting an aluminum compound and a phosphorus compound in the form of an aqueous solution. To contribute to the solution of the aluminum and phosphorus compounds, the mixture can be heated to a temperature sufficient to dissolve the compounds, for example, at least about 40 ° C (104 ° F). The base is added to bring the solution to an almost neutral pH, which results in the precipitation of aluminophosphate. By varying the amounts of aluminum and phosphorus added, the desired P / Al molar ratio can be obtained. Likewise, alcoholic or other organic solutions can be used, such as, for example, hydrolyzing aluminum alkoxides by the addition of aqueous phosphate solutions.

On the other hand, the aluminophosphate support employed in the present invention can be formed by contacting the alumina with an inorganic or organic phosphate compound in an aqueous or organic solution. Accordingly, phosphate, such as phosphoric acid can be impregnated in a high porosity preformed alumina. Optionally from this moment, the impregnated alumina is dried. Aluminophosphate supports prepared according to this method are called "phosphated aluminas."

When a phosphated alumina is used as a support, the alumina can optionally be calcined before phosphate treatment. Sometimes alumina takes the form of AlOOH, such as bohemite or other hydrates. The calcination of the alumina converts the hydrated alumina support partially or totally into aluminum oxide, such as gamma-alumina, Al2O3. The alumina can be calcined in an atmosphere of an inert gas, such as air or nitrogen, or under vacuum. The calcination can be carried out at temperatures between 100 ° C to 800 ° C. In one aspect of the present invention, the alumina is calcined before phosphate treatment at temperatures between 500 ° C to 700 ° C.

Aluminophosphate supports having a P / Al molar ratio below 0.7 are used in the present invention. On the other hand, the aluminophosphate supports employed in the present invention may have a P / Al molar ratio below 0.3, and generally, the P / Al molar ratio is in a range of 0.03 to 0.28. In another aspect of the present invention, the P / Al molar ratio of the aluminophosphate support is in a range of 0.05 to 0.28. Still, in another aspect of the present invention, the P / Al molar ratio of the aluminophosphate support is in a range of 0.04 to 0.20. Still, in another aspect of the present invention, a catalyst system activity, resin properties, and favorable pipe properties can be obtained with a P / Al molar ratio of the aluminophosphate support in a range of 0.05 to 0 ,fifteen.

Although not necessary, aluminophosphate can also be calcined before use or inclusion in the catalyst system of the present invention. The aluminophosphate can be calcined at a temperature in a range of 200 ° C (392 ° F) to 900 ° C, although temperatures up to 1000 ° C (1832 ° F) can be used. In another aspect of the present invention, aluminophosphate can be calcined at a temperature in a range of 400 ° C to 800 ° C (1472 ° F). Even in another aspect of the present invention, aluminophosphate can be calcined at a temperature in a range of 550 ° C to 700 ° C (1292 ° F) for 3 to 4 hours.

The chromium component of the catalyst system may be combined with the support component in any manner known in the art, such as by cogelification as described above, or by post-impregnation in which a chromium compound such as chromium trioxide (VI) , chromium (III) acetate, chromium nitrate

(III) and mixtures thereof can be dissolved in aqueous or alcoholic or other organic solvents. Other chromium compounds known in the art can also be used. The chromium solution is then impregnated in or on the aluminophosphate support and evaporated to dryness. The chromium component of the catalyst system comprises 0.1 to 5 percent by weight of chromium based on the weight of the support. In another aspect of the present invention, the chromium component comprises 0.8 to 3 weight percent based on the weight of the support. In yet another aspect of the present invention, the chromium component comprises 0.8 to 1.5 percent by weight of chromium based on the weight of the support. Still, in another aspect of the present invention, the chromium component comprises 1 to 2.5 percent by weight chromium based on the weight of the support.

Additionally, a fluorinating agent is used in the catalyst system of the present invention. Any organic or inorganic fluorinating agent that can form a surface fluoride with a support can be used in the invention. Suitable fluoridating agents include, but are not limited to, hydrofluoric acid (HF), ammonium fluoride (NH4F); ammonium bifluoride (NH4HF2), ammonium fluoroborate (NH4BF4), ammonium silicofluoride ((NH4) 2SiF6), ammonium fluorophosphate (NH4PF6), ammonium hexafluorotitanate ((NH4) 2TiF6), hexafluorocir 2 (NH4) ), and combinations of these. Due to the ease and availability of use, ammonium bifluoride can be used as the fluorinating agent. The amount of fluoride deposited in or on the support is generally in a range of 0.3 to 7 percent by weight based on the weight of the support. In another aspect of the present invention, the amount of fluoride present in the catalyst system of the present invention is 0.7 to 4 percent by weight based on the weight of the support. Still, in another aspect of the present invention, the amount of fluoride present in the catalyst system of the present invention is 1.3 to 3.5 percent by weight based on the weight of the support.

Generally, the fluorinating agent can be added to the support by forming a suspension of the support in a solution of the fluorinating agent and a suitable solvent, such as alcohol or water. Examples of solvents that can be employed in the present invention include, but are not limited to, alcohols containing molecules of about one to about three carbon atoms due to their volatility and low surface tension. A suitable amount of the solution can be used to provide the desired concentration of the fluoride ion on or in the support after drying. Drying can be carried out by any method known in the art. For example, drying can be completed by suction filtration followed by evaporation, by vacuum drying, by spray drying and rapid evaporation drying. Optionally, the support can be treated with the fluorinating agent during calcination. Any fluoridating agent capable of contacting the support during calcination can be used. In addition to the fluoridating agents, described above, organic fluoridating agents with high volatility can be used. Examples of organic fluoridating agents with high volatility include, but are not limited to, freons, perfluorohexane, perfluorobenzene, fluoromethane, trifluoroethanol, and mixtures thereof. On the other hand, such high volatility fluoridating agents can be employed in any combination with the fluorinating agents described above. It is also possible to use hydrogen fluoride gas or fluorine itself. A convenient method of contacting the support is to vaporize the fluorinating agent in a gas stream that can be used to fluidize the support during calcination.

The catalyst system, either before, during or after the fluorination treatment, is activated by calcination by any method (s) known in the art to produce a calcined catalyst system. In accordance with the present invention, the catalyst system can be calcined in an oxygen-containing environment in a manner conventionally used in the art. For example, the catalyst system can be calcined in any dry oxidizing gas, such as oxygen, nitrous oxide, air, mixtures of oxygen and other inert gas or gases. Due to the economy, air or dry air can be used as an oxygen-containing environment. The calcination temperature used is generally a range of 400 ° C (752 ° F) at 800 ° C. In another aspect of the present invention, the calcination temperature is in a range of 500 ° C (932 ° F) to 700 ° C (1292 ° F). Still, in another aspect of the present invention, the calcination temperature is in a range of 550 ° C (1022 ° F) to 650 ° C (1202 ° F).

The period of time to perform the calcination of the fluorinated catalyst system is generally in a range of 1 minute to 100 hours. In another aspect of the present invention, the calcination of the fluorinated catalyst system is performed from 1 hour to 30 hours. Still, in another aspect of the present invention, the calcination of the fluorinated catalyst system is performed from 3 hours to 10 hours. Under these calcination conditions, at least a substantial portion of any chromium of a lower valence is converted to a hexavalent form.

After calcination, the catalyst system can optionally be cooled and subjected to at least a partial reduction of the hexavalent chromium that may be present in a lower valence state. In one aspect of the present invention, a substantial portion of the chromium is in the divalent state (Cr (II)) after the reduction process.

Any compound capable of reducing chromium (VI) to a lower valence state can be used as a reducing agent. For example, carbon monoxide can be used as a reducing agent due to its easy availability, ease of use and absence of hydrogen, which can produce moisture as a byproduct. The reducing agents can be used at temperatures in a range of 150 ° C (752 ° F) to 600 ° C (1112 ° F). In another aspect of the present invention, the temperature is in a range of 200 ° C (392 ° F) to 500 ° C (932 ° F). Still, in another aspect of the present invention, the temperature is in a range of 300 ° C (572 ° F) to 400 ° C (752 ° F). The partial pressure of the reducing gas in the reduction process may vary from subatmospheric pressures to relatively high pressures, but the simplest reduction process is to use a dilute solution of a pure reducing agent at approximately atmospheric pressure. Usually, a 10% by volume solution of carbon monoxide can be used in an inert environment, such as, for example, nitrogen and / or argon.

The reduction time may vary from a few minutes to several hours or more. The degree of reduction can be followed by visual inspection of the color of the catalyst system. The color of the catalyst system activated by the initial gas is generally orange, indicating the presence of hexavalent chromium. The color of the reduced catalyst system is normally blue, indicating that the total, or substantially the total, of the initial hexavalent chromium has been reduced to lower oxidation states, generally to the divalent state.

After reduction, the catalyst system can be cooled to about room temperature, for example, 25 ° C (77 ° F), in an inert atmosphere, such as argon or nitrogen, to dislodge the reducing agent. After the wash treatment, the catalyst system is kept out of contact with the reducing agent or an oxidizing agent.

In order to obtain the desired resultant effects on the resin or polymer product, it is beneficial for the catalyst system to have a relatively high pore volume. For example, after calcination, the catalyst system must have a pore volume of at least 0.5 cc / g, measured by nitrogen sorption. In another aspect of the present invention, the pore volume of the catalyst system is at least 1.0 cc / g. Still, in another aspect of the present invention, the pore volume of the catalyst system is at least 1.2 cc / g. Additionally, the catalyst system after calcination must have a high surface area, measured by the BET method, usually in a range of 150 m2 / g to 1000 m2 / g. In another aspect of the present invention, the surface area of ​​the catalyst system is in a range of 200 m2 / g to 500 m2 / g. Still, in another aspect of the present invention, the surface area of ​​the catalyst system is in a range of 250 m2 / g to 450m2 / g.

Catalysts

As indicated above, a cocatalyst is used with the chromium-supported catalyst system of the present invention. Examples of catalysts useful in the present invention include, but are not limited to, one or more trialkylboro compounds, one or more triarylboro compounds, one or more alkyl aluminum compounds, and combinations thereof.

Trialquilboro compounds are effective agents to improve the properties of the polymer and increase the catalytic activity during polymerization. Examples of suitable trialkylboro compounds include those containing 1 to 12 carbon atoms per alkyl group. Another aspect of the present invention employs trialkylboro compounds containing from 2 to 5 carbon atoms per alkyl group. The trialkylboro compounds that can be employed in the present invention include, but are not limited to, trimethylborane, triethylborane (TEB), tri-n-butylborane, tributylborane, tripropylborane, and combinations thereof.

Triarylboro compounds can also be used as a cocatalyst in the present invention. Examples of suitable triarylboro compounds include, but are not limited to, triphenylborane and tribenzylborane.

Examples of suitable alkylaluminum compounds include, but are not limited to, those with the general formula (I):

AlR'nX3-n (I)

In formula (I), X is a hydride, alkoxide, siloxane, or halide; R 'is a hydrocarbyl radical having approximately 1 to 12 carbon atoms per radical group; and n is an integer from 1 to 3. Such aluminum compounds include, but are not limited to, trimethylaluminum, triethylaluminum (TEA), diethylaluminium chloride (DEAC), diethylaluminum epoxide (DEALE), tributyl aluminum, and combinations thereof. In one aspect of the present invention, the trialkylaluminum compounds employed are trimethylaluminum, triethylaluminum, tributylaluminum and combinations thereof. Aluminoxanes are alkylaluminum compounds that can also be used as cocatalysts in the present invention. Examples of aluminoxanes include, but are not limited to, methylaluminoxane, propylaluminoxane, n-butylaluminoxane, and isobutylaluminoxane.

Also, as indicated above, alkylsiloxyaluminum compounds are identified as alkylaluminum compounds that can be used as a cocatalyst of the present invention. In addition to the alkylsiloxyaluminum compounds included within the scope of the above formula (I), other suitable alkyloxyaluminium compounds include, but are not limited to, those of the general formula (II):

R3SiOAlR2 (II)

In formula (II), the R groups may be the same or different and are in the range of about 1 to 12 carbon atoms per alkyl group. Alkylsiloxyaluminium compounds include, but are not limited to, triethylsiloxyaluminium diethyl, trimethylsiloxyaluminium diethyl, tripropylsiloxyaluminium dimethyl, and combinations thereof. Preferred trialkylsiloxyaluminum compounds herein include, but are not limited to, diethyl triethylsiloxyaluminium.

The total amount of boron and / or aluminum cocatalyst compound (s) used is generally in a range between 0.1 to 100 parts by weight per 1000 parts by weight of the calcined catalyst system incorporated into the polymerization reactor. In a continuous particle-shaped process using a single loop reactor, for example, it is convenient to introduce the cocatalyst as a separate stream into the reactor, either continuously or in pulses, as a solution diluted in an inert hydrocarbon, for example 0.1 percent by weight in isobutane. The cocatalyst concentration can also be expressed in parts per million (ppm) based on the diluent used in the polymerization reactor. The concentration of the cocatalyst compound (s) is usually in a range between 0.1 ppm to 20 ppm, over the amount of the loaded or heavy diluent. In one aspect, the concentration of the cocatalyst compound (s) is in a range between 0.5 ppm to 15 ppm. In another aspect, the concentration of the cocatalyst compound is in a range between 0.5 ppm to 10 ppm. Still, in another aspect, the concentration of the cocatalyst compound is in a range between 0.5 ppm to 7 ppm. Even in another aspect, the concentration of the cocatalyst compound is in a range between 2 ppm to 12 ppm.

Reactants

The catalyst systems of the present invention can be used to polymerize ethylene and 1-hexene.

Generally, 1-hexene can be added to the polymerization reactor, or reactor zone, in an amount in a range of 1 to 20 percent by weight based on the weight of the monomer. In another aspect of the invention, it can generally be added in a range of 7 to 18 weight percent based on the weight of the monomer. Still, in another aspect of the invention, it is generally present in the reaction zone in a range of 10 to 16 percent by weight based on the weight of the monomer. The amount of 1-hexene can be adjusted to produce a copolymer that has the most desired physical properties.

When ethylene polymers are desired, 1-hexene can be added to the polymerization reactor, or reactor zone, in an amount in a range of 0.1 to 20 percent by weight of the hydrocarbon diluent in order to produce a polymer It has the most desired physical properties. Alternatively, it can be added in a range of 0.3 to 10 percent by weight based on the weight of the diluent. Still, it may be present in the reaction zone in a range of 0.7 to 5.0 weight percent based on the weight of the diluent. By varying the ratio of ethylene to 1-hexene in the reactor, the density of the polymer can be controlled. In addition, the molecular weight of the polymer can be controlled by various means known in the art, such as, for example, adjusting the temperature, introducing or varying the amount of hydrogen present, or varying the compounds of the catalyst system.

Polymerization

The polymerization can be carried out in a manner known to those skilled in the art, such as under conditions of gas phase polymerization, solution, multi-reactor, or suspension to effect polymerization. A stirred reactor can be used for a discontinuous process or the reaction can be carried out continuously in a loop reactor, such as a single loop reactor, or in a continuous stirred reactor. An easily usable polymerization technique in the present invention is what is called polymerization conditions in the form of particles or suspension, using a loop reactor. Under such conditions, the temperature is maintained below the temperature at which a polymer swells or enters solution. Suspension polymerization processes can be much easier to operate and maintain than other polymerization processes, in which a polymer product produced by a suspension process can be recovered much more easily. Such polymerization techniques are well known in the art and are disclosed, for example, in Norwood, US Patent No. 3,248,179. For example, two polymerization techniques that can be employed in the present invention for the suspension process are those that employ a loop reactor of the type described in Norwood and those that use a plurality of agitated reactors either in series, parallel, or combinations of these in which the reaction conditions may be different in different reactors.

The suspension process is generally carried out in an inert diluent (medium), such as, for example, a paraffin, cycloparaffin and / or aromatic hydrocarbon. An inert diluent that can be used in the present invention is an alkane having less than 12 carbon atoms per molecule, for optimal reactor operation and polymer product. Examples of diluents include, but are not limited to, propane, n-butane, isobutane, n-pentane, 2-methylbutane (isopentane) and mixtures thereof. Isobutane is an economically efficient diluent due to the low cost and ease of use. Examples of the use of isobutane as a diluent in suspension polymerization processes can be found in US Patent Nos. 4,421,341; 4,501,885; 4,613,484; 4,737,280; and 5,597,892. These techniques provide efficient polymerization of ethylene, for example, ethylene and a different mono-1-olefin, such as an alpha-1-olefin, or propylene.

The temperature of the polymerization reactor, or reaction zone, is usually in a range of 80 ° C to 110 ° C (212 ° F), although higher or lower temperatures can be used. In another aspect of the present invention, the temperature is in a range of 90 ° C (194 ° F) to 107 ° C (225 ° F). Still, in another aspect of the present invention, the temperature is in a range of 95 ° C (203 ° F) to 105 ° C (221 ° F).

The pressures of the suspended process can vary from 0.76-7.6 MPa (100 psia to 1000 psia). In another aspect of the present invention, pressures may vary in a range of 1380 kPa to 7830 kPa. Still, in another aspect of the present invention, the reaction zone is maintained at a pressure in a range of 2070 kPa to 4140 kPa to reach the optimum operating parameters of the reactor and the resulting polymer product.

The catalyst system is kept in suspension and contacted with the monomer and comonomer (s) at a pressure sufficient to maintain the medium and at least a portion of the monomer and comonomer (s) in the liquid phase. The medium and the temperature are accordingly selected so that the polymer or copolymer is produced as solid particles and recovered in this way. The concentrations of the catalyst system in the reactor may be such that the content of the catalyst system ranges from 0.0005 to 1 percent by weight based on the weight of the reactor content. During the production of ethylene polymers, the concentrations of the catalyst system in the reactor can be such that the content of the catalyst system ranges from 0.0005 to 0.05 percent by weight based on the weight of the reactor contents.

Polymer description

Polymers produced in accordance with the present invention are much easier to process than polymers produced in conventional polymerization processes. Additionally, polymers produced in accordance with the present invention may have extremely wide molecular weight distributions and may have excellent characteristics for high rigidity pipe applications.

The high charge melt index (HLMI) of the polymers produced in accordance with the present invention is usually in a range of 2 g / 10 minutes to 20 g / 10 minutes. Additionally, polymers produced in accordance with the present invention may have an HLMI in a range of 3 g / 10 minutes to 15 g / 10 minutes. In addition, the HLMI of the polymer product is in a range of 5 g / 10 minutes to 10 g / 10 minutes. With respect to the ethylene polymers obtained in accordance with the present invention, the HLMI is usually in a range of 0.1 g / 10 minutes to 20 g / 10 minutes. Even ethylene polymers can have an HLMI in a range of 1 g / 10 minutes to 10 g / 10 minutes. Even also, the HLMI of the polymeric ethylene product is in a range of 1.5 g / 10 minutes to 7 g / 10 minutes.

The polymers of the present invention have a wide molecular weight distribution that is evidenced by polydispersion, or weighted average molecular weight divided by the number average molecular weight (Mw / Mn). In general, the ratio of Mw / Mn for the polymers produced in accordance with the present invention is at least 50. In another aspect of the present invention, the ratio of Mw / Mn for the polymers of the invention is greater than 80. Still, in another aspect of the present invention, the ratio of Mw / Mn for the polymers of the invention is greater than 100. Still, in another aspect of the present invention, the ratio of Mw / Mn for the polymers of the invention is greater than 140 with an upper limit of 500. The polymers of the present invention also have a very narrow density range, usually in a range of 0.945 g / cc to 0.955 g / cc. Additionally, the polymers of the present invention can be produced with a density in a range of 0.947 g / cc to 0.953 g / cc. In addition, the polymers of the present invention can be produced with a density in a range of 0.948 g / cc to 0.952 g / cc.

Specifically, for ethylene copolymers produced in accordance with the present invention, usually the Mw / Mn ratio is at least 40. Ethylene copolymers produced in accordance with the present invention may have an Mw / Mn ratio greater than 50. In addition, ethylene copolymers produced in accordance with the present invention may have an Mw / Mn ratio greater than 60.

The polymers produced in accordance with the present invention also have high values ​​of resistance to slow growth of the PENT fissure. In general, the polymer has a PENT value of more than 750 hours. However, polymers produced in accordance with the present invention may have PENT values ​​greater than 1000 hours, greater than 1500 hours, greater than approximately 1800 hours and greater than 2000 hours.

The polymers produced in accordance with the present invention have a unique branching distribution. Until now, polymers produced from the process using conventional chromium catalysts have a branching content, or amount of incorporated comonomer, that decreases with the increasing molecular weight of the polymer. In contrast, the polymers of the present invention have a branching content that does not decrease with increasing molecular weight. In addition, the polymers of the present invention have a short chain branching content that is substantially compatible with the molecular weight of the polymer of a molecular weight of 104 and greater, at least up to 107. In general, these polymers of the invention are characterized for having a high concentration of branching in the molecular weight range of more than one million. The polymeric product in general has more than 0.5 short chain branching per thousand carbons (SCB / 1000C) at a molecular weight of one million (PM). On the other hand, the polymer can have more than 1 SCB / 1000C with a molecular weight of one million (PM). Still further, the polymeric product may have more than 1.5 SCB / 1000C with a molecular weight of one million (PM).

The polymer of the invention can also be characterized by having a high concentration of branching in the molecular weight range of more than ten million. The polymeric product in general has more than 0.5 short chain branching per thousand carbons (SCB / 1000C) with a molecular weight of ten million (PM). In addition, the polymer can have more than 1 SCB / 1000C with a molecular weight of ten million (PM). Still further, the polymeric product may have more than 1.5 SCB / 1000C with a molecular weight of ten million (PM).

The polymers of the present invention additionally are characterized by having a relatively high molecular weight. In general, these polymers of the invention have a weighted average molecular weight (Mw) in a range of 300,000 g / mol to 1 million g / mol. In addition, the polymers of the present invention may have an Mw in a range of 350,000 g / mol to 750,000 g / mol. Still further, the polymers of the present invention can have an Mw in a range of 400,000 g / mol to 600,000 g / mol. Still also, the polymers of the present invention can have an Mw in a range of 450,000 g / mol to 550,000 g / mol.

Despite the high molecular weight, the polymers of the present invention are unique in that they have a relatively low melt viscosity at relatively low shear rates, compared to polymers derived from conventional chromium-based catalysts. Without wishing to be excessively limited by theory, these unique combinations of high molecular weight and low melt viscosity are considered to be because the polymer has little or no long chain branching compared to conventional chromium-derived polymers. A measure of this characteristic is the zero shear melt viscosity, which is extrapolated from a rheology curve at 190 ° C. Sometimes called eta (0), the zero shear viscosity can be obtained by adjusting the Carreau-Yasuda equation to the experimental viscosity derived at 190 ° C as a function of the shear rate. See R. Byron Bird, Robert C. Armstrong, and Ole Hassager, Dynamics of Polimeric Liquids, Volume 1, Fluid Mechanics, (John Wiley & Sons, New York, 1987). Sometimes, during extrusion of various types of pipes, it is desired that the low shear viscosity is not too large. Otherwise, certain melting and other molding problems may result. In this aspect the polymers of the present invention have an eta (0) of less than 5X107 pa-sec. In another aspect of the present invention, the polymers have an eta (0) of less than 2.5X107 pa-sec. Still, in another aspect of the present invention, the polymers have an eta (0) of less than 1.5X107 paseg. Still, in another aspect of the present invention, the polymers have an eta (0) of less than 1X107 pa-sec.

Alternatively, in other applications, high melt viscosities with low shear rates are desired. This is particularly true in large diameter pipe applications where the pipe can "sink" or deform due to the gravity effect during the period of slow cooling. For these applications, the higher the shear viscosity, the greater the resistance of the molten polymer to the so-called "sinking" deformation. For applications that require sinking resistance, the polymers of the present invention generally have an eta (0) greater than 1X106 pa-sec. In another aspect of the invention, the polymers of the present invention have an eta (0) greater than 5X106 pa-sec. Still, in another aspect of the invention, the polymers of the present invention have an eta (0) greater than 1X107 pa-sec. Still, in another aspect of the invention, the polymers of the present invention have an eta (0) greater than 2X107 pa-sec.

Despite the high molecular weight, and the sometimes high shear melt viscosity, the polymers of the present invention are also characterized by having a relatively low melt viscosity at high shear rates. Because the extrusion in the pipe is carried out at relatively high shear rates, a low viscosity of high shear melt is convenient because molten polymer flows more easily during molding operations. In general, the polymers of the present invention have a melt viscosity of less than 6X103 pa-sec at 100 / sec shear rate, called eta (100). In another aspect of the present invention, the polymers of the present invention have an eta (100) of less than 3X103 pa-sec. Still, in another aspect of the present invention, the polymers of the present invention have an eta (100) of less than 2X103 pa-sec.

Another distinctive feature of these exclusive polymers of the invention is the narrow distribution of relaxation time. The amplitude of the relaxation time distribution, sometimes called the CY-a parameter, can also be derived from the Carreau-Yasuda equation mentioned above, when applied to the melt viscosity data obtained at 190 ° C as a function of Shear speed CY-a is usually greater than in polymers of similar molecular weight derived from conventional chromium catalysts. In general, the CY-a value of these polymers of the invention is greater than 0.2. In another aspect of the present invention, the polymers have a CY-a greater than 0.25. Still, in another aspect of the present invention, the polymers have a CY-a greater than 0.3.

A further distinctive feature of these polymers of the invention is that they are extruded into pipes that meet the strict standards of typical PE-100, MRS 10, or ASTM D3350 345566C cell classifications. This includes the circumferential tension test and rapid crack propagation, or S4 test, (see ISO / TC 138 / SC 4 Parts 1 & 2 dated 01-01-08).

EXAMPLES

The following examples are presented to further illustrate the invention and are not construed as excessive limitation of the scope of the invention. These examples illustrate the various aspects of the present invention; which include a description of the preparation of the catalyst system, the use of the catalyst system in a polymerization process to produce the desired resin, the physical properties of this resin, and its use to obtain a large diameter pipe classified as PE-100.

Preparation of chromium / aluminophosphate catalyst

The aluminophosphate catalyst system was prepared from a commercial alumina manufactured by WR Grace under the name "Alumina A". This material is substantially all alumina after calcination at approximately 600 ° C, which has a pore volume of approximately 1.5 cc / g and a surface area of ​​approximately 300 m2 / g. In the preparation of a typical catalyst batch, approximately 136.2 kg (300 pounds) of alumina A was calcined by passing it through a rotating calciner assembly at approximately 750 ° C in a countercurrent nitrogen flow. In a mixing tank equipped with a mechanical stirrer, approximately 408.6 kg of anhydrous methanol were added, followed by approximately 4.08 kg of ammonium bifluoride and 20.88 kg of 85% phosphoric acid. This mixture was stirred until it became a homogeneous solution. After calcining, the alumina was placed in a mechanical mixer to which the above methanolic solution was also added. The resulting suspension was stirred for approximately two hours, after which 17.7 kg of Cr (NO3) 39H2O was added. This mixture was stirred for approximately another two hours, after which heat was applied to evaporate the methanol solvent. The gentle agitation continued until most of it had been removed. The resulting powder was then transferred to a vacuum oven where it was heated at about 60 ° C for about 12 hours to remove almost all residual methanol. From this moment, the catalyst was passed through a 30 mesh screen to remove some large agglomerates.

Measurement of resin properties

The analysis of the resulting polymers was performed according to the following procedures. The density of the polymer was determined in grams per cubic centimeter (g / cc) on a compression molded sample, cooled to approximately 15 ° C per hour, and conditioned at room temperature, approximately 25 ° C, for approximately 40 hours. conforming to ASTM D1505-68 and ASTM D1928, condition C.

The high load melt index (HLMI) was determined in grams of polymer per 10 minutes (g / 10 min) in accordance with ASTM D1238, Condition 190 / 21.6, at 190 ° C with a weight of 21,600 grams.

The melt index (MI) was determined in grams of the polymer for ten minutes according to ASTM D1238, condition 190 / 2.16, at 190 ° C with a weight of 2,160 grams.

The slow growth resistance values ​​of the PENT fissure were obtained at 80 ° C (176 ° F) according to ASTM F1473 (2001).

Molecular weights and molecular weight distribution were obtained using a PL 220 SEG high temperature chromatography unit (Polymer Laboratories) with trichlorobenzene (TCB) as solvent, with a flow rate of 1 ml / minute at a temperature of approximately 145 ° C . BHT (2,6-di-tert-butyl-4-methylphenol) at a concentration of 0.5 g / l was used as a stabilizer in the TCB. An injection volume of 200 μL with a nominal polymer concentration of 1.5 mg / ml was used. Dissolution of the sample in stabilized TCB was carried out by heating at approximately 150 ° C for approximately 5 hours with occasional gentle agitation. Subsequently, the sample was maintained at approximately 130 ° C for approximately 18 hours (overnight) after which it was reheated to approximately 150 ° C for approximately 2 hours before injection. The columns used were three PLgel Mixed A LS columns (7.8x300 mm) and were calibrated with a wide linear polyethylene standard (Phillips Marlex® BHB 5003) for which the molecular weight was determined.

Molecular weight distributions and branching profiles were obtained through size exclusion chromatography using an FTIR detector. The chromatographic conditions are as described above, and the injection volume of the sample was 500 μl. Samples were introduced to the FTIR detector by means of a heated transfer line and the flow cell (KBr windows, 1 mm optical path, and ca. 70 μl cell volume). The temperatures of the transfer line and the flow rate were maintained at 143 ± 1 ° C and 140 ± 1 ° C, respectively. The Perkin Elmer FTIR spectrometer (PE 2000) equipped with a narrow band cadmium tellurium detector (MCT) was used in these studies.

All spectra were obtained using the Perkin Elmer Timebase computer program. The threshold spectra of the TCB solvent were obtained before each run. All IR spectra were measured with a resolution of 8 cm-1 (16 scans). Chromatograms were generated using the average quadratic value of the absorbance with respect to the spectral region of 3000-2700 cm -1 (ie, FTIR serves as a concentration detector). Molecular weight calculations were obtained as previously described using a wide molecular weight polyethylene (PE) standard. See Jordens K, Wilkes GL, Janzen J, Rohlfing DC, Welch MB. Polymer 2000; 41: 7175. The individual time band spectra of the chromatogram are subsequently analyzed for comonomer branching levels using chemometric techniques. All calibration spectra were taken at sample concentrations that greatly exceeded what was needed for a good noise signal (i.e.> 0.08 mg / ml in the detector).

Branching determination was obtained as follows. Calibration and verification studies were performed with solvent gradient fractions that have a narrow molecular weight distribution (Mw / Mn ~ 1.1 to 1.3). These fractions were composed of polyethylene homopolymers or copolymers of 1butene or 1-hexene ethylene and low molecular weight alkanes. The total methyl content of these samples ranged from 1.4 to 82.7 methyl per 1000 total carbons. The methyl content of the samples was calculated Mn or measured using C-13 NMR spectroscopy. C-13 NMR spectra were obtained in samples of 15% by weight of TCB using a 500 MHz Varian Unity spectrometer run at 125 ° C as previously described. See Randall JC, Hsieh ET, RMN and Macromolecules; Sequence, Dynamic, and Domain Structure, ACS Symposium Series 247, JC Randall, Ed., American Chemical Society, Washington DC, 1984. The methyl content per 1000 carbons per NMR was obtained by multiplying (X 1000) the ratio between the total methyl signals and the total intensity signal.

A partial minimum square (PLS) calibration curve was generated using a Pirouette chemometric computing program (Infometrix) to correlate changes in FTIR absorption spectra with NMR values ​​calculated or measured for methyl / 1000 total carbons for the 25 samples . The FTIR absorption spectra used in the calibration model were obtained as co-added spectra collected through the entire sample. Only a portion of the spectral region (2996 and 2836 cm -1) was used in the calibration stage to minimize the effects of residual solvent absorption. The preprocessing of the spectrum data included the normalization of the area, taking the first derivative of the spectra and the mean that centers the data. A three component calibration model was calculated and optimized using the cross validation process (RSQ = 0.999, SEV = 0.5). Atypical value detection for individual measurements was generated from the probability values ​​obtained by the Pirouette chemometric computing program. Samples that have probabilities> 0.99 were considered outliers.

Short chain branching levels were calculated by subtracting contributions from the end of the methyl chain. The number of methyl chain (NE) ends was calculated using the equation

NE = (14000) (2-VCE) / M

In this equation, VCE is the number of vinyl terminated chain ends and M is the calculated molecular weight for a particular piece of MWD. Normally, the termination of chromium catalyzed resins causes the formation of a vinyl moiety. See Witt, DR. Reactivity, Mechanism and Structure in Polymer Chemistry. Jenkins AD, Ledwith A. Eds. Ch 13. John Wiley and Sons. New York 1974 Conversely, the ends of the methyl chain are formed at the stage of termination of the chain of resins catalyzed with Zeigler-Natta. See Lenz, RW. Organic Chemistry of Synthetic High Polymers. Ch 15. John Wiley and Sons. New York 1967. Consequently, in the equation prior to VCE, 1 is assigned for chromium catalyzed resins and 0 for Zeigler-Natta catalyzed resins. Also, the assumption is made that the types of end groups (ie, methyl or vinyl) are fixed throughout the molecular weight distribution. The negative values ​​for methyl / 1000 total carbons that can be obtained as a result of the correction with respect to the ends of the methyl chain at low branching levels are given zero values. Other details of the procedure can be found in Polymer 2002: 43: 159, by DesLauriers PJ, Rohlfing DC, and Hsieh ET.

Rheology measurements were obtained as follows: Samples for viscosity measurements were compression molded at 182 ° C for a total of three minutes. The samples were allowed to melt at a relatively low pressure for one minute and then subjected to a high molding pressure for an additional two minutes. Molded samples were then quenched in a cold press (room temperature). Discs of 2 mm x 25.4 mm in diameter were extracted from the molded pieces for rheological characterization. The sponge samples were stabilized with 0.1% BHT by weight dispersed in acetone and then dried under vacuum before molding.

Low voltage oscillatory shear measurements were performed on a Rheometrics Inc. RMS-800 or ARES rheometer using a parallel plate geometry with respect to an angular frequency range of 0.03 - 100 rad / s. The rheometer test chamber was covered with nitrogen to minimize polymer degradation. The rheometer was preheated to the initial temperature of the study. After loading the sample and after thermal equilibrium, the specimens were crushed between the plates to a thickness of 1.6 mm and the excess was trimmed. A total of approximately 8 minutes elapsed between the time the sample was inserted between the plates and the time the frequency scan began.

The voltages in general were maintained at a single value throughout the frequency sweep, but larger values ​​were used for the low viscosity samples to maintain a measurable torque. The lower voltage values ​​were used for high viscosity samples to avoid overloading the torque transducer and staying within the linear viscoelastic limits of the sample. The instrument automatically reduces the voltage at high frequencies if it is necessary to prevent overload of the torque transducer.

These data were adjusted to the Carreau-Yasuda equation to determine the zero shear viscosity (η0), relaxation time (τ), and a measure of the amplitude of the relaxation time distribution (CY-a). See R. Byron Bird, Robert C. Armstrong, and Ole Hassager, Dynamics of Polymeric Liquids, Volume 1, Fluid Mechanics, (John Wiley & Sons, New York, 1987.

Pipe Extrusion

The extrusion of the pipe in the simplest terms is done by melting and transporting the polyethylene pellets to a particular shape (generally an annular shape), and solidifying this shape during a cooling process. There are numerous stages to extrude the pipe that include the following:

Raw material (pigmented pipe is assumed)

The raw material can be a pre-pigmented polyethylene resin or it can be a mixture of natural and concentrated color polyethylene (referred to as "salt and pepper mixtures"). In North America, the most common raw material for pipe extrusion is "Pepper Salt Mixes". In Europe and other areas of the world, the most common raw material for pipe extrusion is pre-pigmented polyethylene resin.

Rigid control is performed on the raw material to obtain the appropriate finished product (pipe) and final consumer specifications.

Extruder

The most common extruder system for the production of a pipe is a single screw extruder.

The purpose of the extruder is to melt, transport and homogenize the polyethylene pellets.

Extrusion temperatures typically vary from 178 ° C to 232 ° C according to the screw design of the extruder and the flow properties of polyethylene.

Matrix

The purpose of the matrices is to distribute the molten material of the homogeneous polyethylene polymer around a solid mandrel, which molds it into an annular shape.

Adjustments can be made at the exit of the die to try to compensate for polymer flexion during the rest of the process.

Pipe Size Adjustment

In order for the pipe to meet the appropriate dimensional parameters, adjusting the pipe size is the next stage of the process.

There are two methods for size adjustment - vacuum or pressure. Both employ different techniques and different equipment

Refrigeration

The next stages of the process are to cool the pipe and "freeze" in the desired dimensions.

The cooling is achieved by using several water tanks in which the external pipe is submerged

or water is sprayed on the outside of the pipe.

The pipe cools from the outer surface to the inner surface. The inner wall and the inner surfaces of the pipe can remain very hot for a long period of time, since polyethylene is a bad conductor of heat.

Engraving, winding or cutting

The final stages of the pipe extrusion process are engraved, and winding or custom cutting.

Catalyst Activation

The catalyst described above was activated by calcination in dry air at 600 ° C. In a typical activation batch, 227 kg (500 lb) of the catalyst was added to the commercial activator consisting of an inner porous plate 1.06 m (42 inches) in diameter from the Inconel cylinder approximately 6 m high. The catalyst rested on the porous plate, through which dry air was passed at the speed of 6.1 cm / sec (0.2 m / sec) in order to fluidize the bed. The temperature gradually rose to approximately 600 ° C over a period of 8-10 hours. Once at 600 ° C, the activator was allowed to remain at this temperature, while fluidizing, for approximately another 10 hours. The activated catalyst was then cooled to 300 ° C, at this temperature the activated catalyst was extracted from the activator. During the last 2-3 hours of the cooling period, the fluidizing air was replaced with dry nitrogen. After removal of the activator, the catalyst was stored under nitrogen in an airtight container until it was used in the polymerization reactor.

Polymerization

The activated catalyst described above was used to catalyze the copolymerization of ethylene and 1-hexene to obtain the new polymers of the present invention. The reactor system used was a three-legged loop reactor 0.6 m (24 inches) in diameter that contained approximately 102 m3 (27,000 gallons) of the polymer suspension. The diluent used was prepurified isobutane and the reactor contents were controlled so that they were normally 38% by weight of solid polymer and 62% by weight of liquid reactants and diluents. The catalyst, ethylene, 1-hexene, isobutane, triethylboro solution and hydrogen were added continuously to the reactor. The reactor temperature was set at 101 ° C. The polymer and liquid were continuously extracted by instant evaporation, in which a small increase in these was vented in a large collection tank. The liquid components then vaporized instantly, so that the polymer powder became dry. The production speed was 1360 kg (30000 lb) of polymer produced per hour. Ethylene was supplied on demand to maintain this rate and a concentration of ethylene dissolved in the diluent of 3 to 4 percent by weight of the reactor liquid content. Hydrogen was continuously supplied to maintain a high charge melt index (HLMI) of the polymer of 2.0 to 3.5, which resulted in a concentration in the reactor of 1.0 to 1.5 mol percent of the content liquids The 1-hexene comonomer was supplied on demand in order to maintain a polymer density of 0.950, which resulted in a concentration of 0.4 to 1.0 percent by weight of the liquid contents of the reactor. Triethylboro was continuously added to the reactor to maintain a concentration of 10 parts per million by weight of the liquid content of the reactor. The productivity of the catalyst was 590 kg (1300 lbs) of polymer per kg (pound) of the catalyst.

After the polymer left the reactor, it was purged with nitrogen at 50 ° C to 70 ° C for approximately two hours to extract the last traces of the hydrocarbon reaction mixture. It was subsequently pelleted in a Warner-Pfleider ZSK commercial continuous extruder with a small appropriate amount of antioxidants. The final high load fusion index was 2.3 and the density was found to be 0.950.

A study of the polymer of the invention of Example 1 and four commercially available PE100 bimodal polyethylene resins was conducted to compare various properties of the respective resins. The results are reported below in Table 1.

Another study was conducted to compare various properties of the pipe formed from the polymer of the invention of Example 1 and a non-PE-100 resin having commercially acceptable sinking characteristics. The results are reported in Table 2 below. The comparisons of Table 2 for pipe extrusion show the versatility of the resin of the invention. Pipes with a maximum diameter of 1.06 m (42 inches) with a wall thickness of 6.3 cm (2.5 inches) and a minimum diameter of 5 cm (2 inches) with a wall thickness 0.45 cm (0.18 inches) have been produced successfully. The resin of the invention is compared to typical PE3408 resins that perform well in these pipe sizes. PE3408 resins were an ethylene / 1-hexene copolymer from Chevron Phillips Chemical Company HD 943 that were obtained with a conventional chromium catalyst. Initially, PE3408 resins were extruded to give a pipe and from this moment on, the resin of the invention was extruded through the same matrix initially with the same matrix setting. As indicated in note (3) of Table 2, the pipe matrix with a diameter of 1.06 m (42 ") had not been adjusted to be out of circularity to accommodate the sinking of PE3408 resins. After extrusion of the resin of the invention of Example 1 through the matrix, the matrix was substantially adjusted to a truly circular shape, indicating that the resin of the invention had no or practically no sinking. Other PE-100 type resins, which are bimodal polyethylene resins, cannot be extruded successfully to give a 1.06 m (42 "IPS IPS 11 pipe) or suffer a serious disadvantage for the pipe extrusion speed due to excessive heat generation and subsequent rope sagging or sinking. While the resin of the invention of Example 1 produced a pipe that can be classified as PE-100 pipe, which was described above, conventional PE-100 resins are not used to produce a 1.06 m PE-100 pipe ( 42 "in diameter due to its excessive sinking characteristics.

For D2513 "Standard specification for pipe, pipe and thermoplastic gas pressure fittings", the eccentricity of the maximum wall thickness is 12% and the maximum ovality is 5%. The data in Table 2 show that the resin of the invention is included in these ranges for 1.06 m (42 ") and 5 cm (2") pipes.

Examples 2-11 and Reference Examples 1-8

Catalyst preparation

Several runs were performed on a pilot plant scale that employs the catalyst system of the present invention. The procedure used in Example 1 to prepare the catalyst was also used in these examples, except that the amount of phosphoric acid added to the preparation was adjusted to vary the P / Al molar ratio of the resulting catalyst. Other stages were identical. Catalyst activation was similarly performed in a bed fluidized in air at approximately 600 ° C in all cases. 0.68 kg (1.5 lb) of the catalyst was loaded into a 15.2 cm (6 inch) diameter cylinder with distributor plate for fluidization. Dry air was used to fluidize the catalyst since the temperature rose to 600 ° C. This process required eight hours, and the catalyst was allowed to continue fluidizing in dry air at 600 ° C for another six hours. The catalyst was washed with dry nitrogen during cooling and then kept under nitrogen until ready for use.

Polymerization

Ethylene polymers in Examples 2-11 and reference examples 1-8 were prepared in a continuous particle formation process (also known as a suspension process) by contacting the catalyst with the ethylene and 1-hexene comonomer. It was used as an ethylene monomer that had dried over activated alumina. Isobutane was used as diluent that had been degassed by fractionation and dried on alumina.

The reactor was a 15.2 cm diameter pipe loop filled with liquid that had a volume of 87 liters (23 gallons). Liquid isobutane was used as a diluent, and occasionally some hydrogen was added to regulate the molecular weight of the polymer product. The reactor pressure was 4 Mpa (approximately 580 psi). The reactor temperature varied in a range of 90 ° C to 105 ° C as indicated in each experiment. The reactor was operated to have a rest time of 1.25 hours. The catalyst was added through a 0.35 cc circulating ball retention feeder. Under steady state conditions, the isobutane feed rate was approximately 46 liters per hour, the ethylene feed rate was approximately 13.6 kg / hour (30 lbs / hour), and the feed rate of 1 hexene varied. to control the density of the polymer product. The concentration of ethylene in the diluent was 8-12 mol percent, indicated in each experiment. The polymer was removed from the reactor at the rate of 10.6 kg per hour (23 lb / hr) and recovered in an instant evaporation chamber. A Vulcan dryer was used to dry the polymer under nitrogen at 60 ° C to 80 ° C.

Catalysts were used, which include triethylaluminum (TEA), triethylboro (TEB), and a mixture of 3 parts by weight TEB and 1 part by weight of TEA. The total concentration of the cocatalyst varied from 2 ppm to 14 ppm, as indicated in each example, expressed with reference to the isobutane diluent. To prevent static accumulation in the reactor, usually a small amount (<5 ppm of the diluent) of a commercial antistatic agent, marketed as Stadis 450, was also added.

Resin test

Molecular weights, branching profiles, and rheology of the polymer were determined as described above. The pipe was obtained approximately 4.54 cm in diameter in a 4.5 cm extruder at 210 ° C.

Discussion of the results

Tables 3 and 4 show the results of the resin test and the pipe of 12 different experimental resins obtained in the pilot plant with the catalyst of the invention. As indicated in Tables 3 and 4, the type and quantity of the cocatalyst, reactor temperature and other reaction variables, and the molar ratio of the P / Al catalyst were varied. The circumferential stress test is shown for three different temperatures, together with the corresponding ISO requirements necessary for PE-100 certification. As indicated in Tables 3 and 4, many case values ​​were obtained with considerable excess of the PE-l00 rating values. Tests with extremely high PENT values ​​were also obtained and are reported in Tables 3 and 4.

Table 5 shows another series of experimental resins that were obtained with the same catalyst system. In these runs the catalyst had a P / Al molar ratio of 0.08 and was activated at 600 ° C. The reactor temperature was 100 ° C (213 ° F), the cocatalyst was TEB, and ethylene was added to keep 10 mol% in the reactor. 1hexene was added to the reactor at 0.36 to 0.45 kg / hr (0.8-1 lb / hr) and ethylene at 10.2 kg / hr (22.5 lb / hr). While these resins were not extruded to give pipes, physical properties were obtained, and Table 5 is presented to demonstrate the high CY-a parameters that can originate from the catalyst system of the present invention. As described above, CY-a varies inversely with the rheological amplitude, or the amplitude of the relaxation time distribution. The low CY-a indicates a greater amplitude. Conventional chromium catalysts generally produce resins that have CY-a between 0.1 and 0.2, and occasionally CY-a values ​​as high as 0.22 are obtained. However, as indicated in Tables 3 and 5, and especially in Table 5, the catalyst system of the present invention produces extraordinarily high CY-a values ​​for a chromium catalyst. In general CY-a decreases as the molecular weight increases and as the chromatographic amplitude (Mw / Mn) increases. This makes the CY-a values ​​of Tables 3, 4, and 5 more prominent, because the resins of the present invention encompass the chromatographic amplitude (Mw / Mn) previously impossible to obtain and were obtained with extremely high molecular weight. However, it is considered that the resins of the present invention give high CY-a values ​​that are higher than those of resins produced with conventional chromium-based catalysts. These seemingly contradictory data, that is, extreme chromatographic amplitude combined with extreme rheological narrowness, is again interpreted as evidence that these resins lack long chain branching to an unprecedented extent.

With reference to Figures 1 and 2, the number average molecular weights (Mw / Mn) at various molecular weights of the polymer were determined for the polymers of the invention of Examples 1 and 19. In addition, short chain branches were determined by 1000 carbons (SCB / l000C) for these polymers at various molecular weights of the polymer. As shown in Figures 1 and 2, the Mw / Mn and SCB / l000C, indicated as SCB / 1000TC, were plotted for the polymers of the invention of Examples 1 and 11 respectively, with respect to the molecular weight of the polymer. Both figures indicate that the polymers of the present invention have a flat or substantially flat short chain branching profile through a broad molecular weight profile. This indicates that the short chain branching of the polymers of the present invention remains substantially constant over a wide range of molecular weights.

With reference to Figure 3, melt viscosities and shear rates were determined and examined for the polymers of the invention of Examples 1 and 11. As shown in the figure, melt viscosity was plotted with respect to the shear rate to produce the respective curves. As indicated in Figure 3, each polymer of the invention has a high shear rate at a low melt viscosity and, in contrast, a low shear rate at a high melt viscosity. As a polymer for extrusion, it is convenient for the polymer to have a high shear rate with a low melt viscosity due to the polymer's ability to pass through the matrix. However, to contribute to the prevention or reduction of subsidence after the polymer passes through the extruder, it is desirable that the polymer has a high shear rate with a low melt viscosity. Figure 3 illustrates that the polymers of the present invention have both desirable properties for PE-100 pipe production.

TABLE 1 Commercial pipe properties for PE-100 resins TABLE 2 Commercial pipe extrusion processing data

<dl><dt>Property </dt><dd>Marlex® H516B Resin of the invention of Example 1 Dow GDA-2490 Atofina Finathene® XS10B BP Solvay Eltex® TUB121 </dd></dl>

<dl><dt>MI, g / 10 min. </dt><dd> 0,08 0,0 0,07 0,07 0,07 </dd></dl>

<dl><dt>HLMI, g / 1 min. </dt><dd> 7,1 2,1 7,0 10,1 8,8 </dd></dl>

<dl><dt>Density, g / cc </dt><dd> 0,962 0,950 0,949 0,960 0,959 </dd></dl>

<dl><dt>Density, g / cc (natural calculadal) </dt><dd> 0,952 0,951 0,950 </dd></dl>

<dl><dt>Carbon black content,% by weight </dt><dd> 2,4 0 0 2,4 2,2 </dd></dl>

<dl><dt>Rheology data</dt><dd /></dl>

<dl><dt> Eta 0 / sec </dt><dd>2.07E + 05 1.82E + 07 2.08E + 05 3.31E + 05 2.34E + 05 </dd></dl>

<dl><dt>Eta at 0.1 / sec </dt><dd>7.23E + 04 3.57E + 05 8.10E + 04 8.18E + 04 8.42E + 04 </dd></dl>

<dl><dt>Eta at 100 / sec </dt><dd>2.46E + 03 2.56E + 03 1.76E + 03 2.11E + 03 2.24E + 03 </dd></dl>

<dl><dt>Tau Eta </dt><dd> 1,2 432 5,4 2,8 2,0 </dd></dl>

<dl><dt>Tension properties Production voltage, MPa </dt><dd /></dl>

<dl><dt>Tension at break, MPa Elongation at break,% </dt><dd> 26,5 25,9 26,2 26,8 25,7 </dd></dl>

<dl><dt>36,0 </dt><dd> 29,7 35,2 32,4 35,9 </dd></dl>

<dl><dt>720 </dt><dd> 670 700 700 740 </dd></dl>

<dl><dt>Flexural modulus, 2% Secant MPa (psi) </dt><dd> 936 (135700) 846 (122700) 884 (128200) 912 (132200) 886 (128500) </dd></dl>

<dl><dt>Typical SEG data for natural resin</dt><dd /></dl>

<dl><dt> Mn (g / mol) </dt><dd> 16.000 7.500 </dd></dl>

<dl><dt> Mw (g / mol) </dt><dd> 280.000 490.000 </dd></dl>

<dl><dt>Mz (g / mol) </dt><dd> 1.600.000 3.500.000 </dd></dl>

<dl><dt> Mw / Mn </dt><dd> 18 65 </dd></dl>

<dl><dt>PENT hours </dt><dd> &gt;1100 &gt;1000 3360 &gt;2180 &gt;2300 </dd></dl>

<dl><dt>Extrusion properties </dt><dd>Resin of the invention of Example 1 PE3408 pressure-qualified resin in commercial gas phase </dd></dl>

<dl><dt>Production speed, kg / hr (lb / hr) </dt><dd> 782 (1725) 771 (1700) </dd></dl>

<dl><dt>Pipe Size </dt><dd>42 &amp; quot; IPS DR 17 42 &amp; quot; IPS DR 17</dd></dl>

<dl><dt>% ovality (1) </dt><dd> 2,5 2,2 </dd></dl>

<dl><dt>Eccentricity of wall thickness,% (2) </dt><dd> 9,9 5,6 </dd></dl>

<dl><dt>Pipe Extruder Size </dt><dd>6 &amp; quot; 6 &amp; quot; </dd></dl>

<dl><dt>Extruder L / D </dt><dd> 30:1 30:1 </dd></dl>

<dl><dt>Observations</dt><dd> (3) </dd></dl>

<dl><dt>Extrusion properties </dt><dd>Resin of the invention of Example 1 Commercial qualified pressure PF PE3408 resin </dd></dl>

<dl><dt>Production speed, kg / hr (lb / hr) </dt><dd> 354 (780) 363 (800) </dd></dl>

<dl><dt>Pipe Size </dt><dd>2 &amp; quot; IPS DR 11 2 &amp; quot; IPS DR 11</dd></dl>

<dl><dt>% ovality (1) </dt><dd> 0,54 0,51 </dd></dl>

<dl><dt>Eccentricity of wall thickness,% (2) </dt><dd> 3,5 2,2 </dd></dl>

<dl><dt>Pipe Extruder Size </dt><dd>4.5 &amp; quot; 4.5 &amp; quot; </dd></dl>

<dl><dt>Extruder L / D </dt><dd> 30:1 30:1 </dd></dl>

<dl><dt>(1) </dt><dd>The% ovality defined in ASTM D2513 is [(maximum OD - minimum OD) / (minimum OD + maximum OD)] x 200 </dd></dl>

<dl><dt>(2) </dt><dd>The eccentricity of the wall thickness (E) defined in ASTM D2513 is [(AB) / A] x 100 where A is maximum wall thickness and B minimum wall thickness </dd></dl>

<dl><dt>(3) </dt><dd>The sinking between the face of the die and the sleeve size adjustment was markedly smaller and required adjustment of the die to a substantially circular shape, indicating that it had or had virtually no sinking. </dd></dl>

TABLE 3 TABLE 4 TABLE 5

<dl><dt>Example </dt><dd>Ref. 1 Ref. 2 two 3 4 5 </dd></dl>

<dl><dt>P / To Molar Ratio </dt><dd> 0,09 0,12 0,12 0,12 0,12 0,08 </dd></dl>

<dl><dt>Reaction Temp (ºC) </dt><dd> 100 101,6 101,6 101,6 101,6 88 </dd></dl>

<dl><dt>Conc. Of ethylene (mol%) </dt><dd> 8,91 6,61 6,61 11,21 7,32 9,98 </dd></dl>

<dl><dt>Conc. Of H2 (mol%) </dt><dd> 1,87 0,79 0,79 1,23 0,25 2,29 </dd></dl>

<dl><dt>Conc. Of 1-Hexene (mol%) </dt><dd> 0,62 0,30 0,30 0,54 0,41 1,25 </dd></dl>

<dl><dt>Type of cocatalyst </dt><dd>TEB TEB: TEA 3: 1 TEB: TEA 3: 1 TEB: TEA 3: 1 TEB: TEA 3: 1 TEB: TEA 3: 1 </dd></dl>

<dl><dt>Cocaine Conc (ppm) </dt><dd> 10,2 2,6 2,6 3,9 11,7 3,0 </dd></dl>

<dl><dt>Hexene, kg / hr </dt><dd> 0,36 0,41 0,41 0,76 0,56 0,86 </dd></dl>

<dl><dt>Ethylene kg / hr </dt><dd> 11,5 9,8 9,8 10,3 9,9 11,6 </dd></dl>

<dl><dt>HLMI (g / 10min) </dt><dd> 5,1 4,7 4,7 5,7 5,8 2,23 </dd></dl>

<dl><dt>Density (g / cc) </dt><dd> 0,9501 0,9496 0,9492 0,9489 0,9489 0,9488 </dd></dl>

<dl><dt>Productivity Catalyst * kg / kg </dt><dd> 1851,85 1541 1541 2370 1388 2899 </dd></dl>

<dl><dt>SEG Mw / 1000 Mz / 1000 Mw / Mn </dt><dd> 7,5 368 3053 49,4 7,5 410 3133 54,3 8,2 442 3420 53,7 5,3 394 3431 73,9 5,2 441 4932 85,1 6 405 3127 67,8 </dd></dl>

<dl><dt>Rheology Eta (0) </dt><dd>6.75E + 06 8.70E + 06 1.07E + 07 1.02E + 07 1.90E + 07 1.32E + 07 </dd></dl>

<dl><dt>CY-a_eta</dt><dd> 0,2661 0,2855 0,2802 0,2903 0,2618 0,2943 </dd></dl>

<dl><dt>PENT, hours (2.4 MPa) </dt><dd> 3375 &gt;1411 &gt;1411 &gt;1680 &gt;1657 &gt;4822 </dd></dl>

<dl><dt>Pipe Extrusion </dt><dd /></dl>

<dl><dt>Kg / hr / rpm output </dt><dd> 0,8 0,77 0,78 0,76 0,81 </dd></dl>

<dl><dt>Head pressure, MPa </dt><dd> 20,5 20,5 15,5 15,3 17,8 </dd></dl>

<dl><dt>Matrix pressure, MPa </dt><dd> 9,0 8,3 5,9 5,2 7,7 </dd></dl>

<dl><dt>Temp. melting, ºC</dt><dd> 220 221 208 207 207 </dd></dl>

<dl><dt>Pressure test (ISO requirements) </dt><dd>He passed He passed He passed He passed Failure He passed </dd></dl>

<dl><dt>20C, 12.6 MPa, </dt><dd /></dl>

<dl><dt>hours </dt><dd /></dl>

<dl><dt>261,277, </dt><dd> 642,535, 585,608, 472,654,60 183,146,18 263,424, </dd></dl>

<dl><dt>(&gt; 100 hours) </dt><dd> 307 417 441 0 3 260 </dd></dl>

<dl><dt>80C, 53 MPa, </dt><dd> 720,864, 618,968, 916, 367, 26,20,38 &gt;1121, </dd></dl>

<dl><dt>hours </dt><dd /></dl>

<dl><dt>1109 </dt><dd> 955 &gt;1048, &gt;1066, 972, </dd></dl>

<dl><dt>(&gt; 165 hours) </dt><dd> &gt;1049 408 692 </dd></dl>

<dl><dt>80C 5.0 MPa, </dt><dd> 1429, 1740, &gt;1026, &gt;1007, &gt;1026, 210,189,24 &gt;1049, </dd></dl>

<dl><dt>hours </dt><dd> 2002 &gt;1026, &gt;1026, &gt;1026, 5 &gt;1049, </dd></dl>

<dl><dt>(&gt; 1000 hours) </dt><dd> &gt;1026 &gt;1026 &gt;1026 &gt;1049 </dd></dl>

<dl><dt>Example </dt><dd>6 Ref. 3 Ref. 4 Ref. 5 Ref. 6 7 </dd></dl>

<dl><dt>P / AL Molar Ratio </dt><dd> 0,08 0,08 0,08 0,12 0,12 0,12 </dd></dl>

<dl><dt>Reaction Temp (ºC) </dt><dd> 101 101 101 101,6 101,6 101,7 </dd></dl>

<dl><dt>Ethylene Conc (mol%) </dt><dd> 10,14 9,95 10,00 6,20 6,20 10,28 </dd></dl>

<dl><dt>Conc. Of H2 (mol%) </dt><dd> 1,62 1,49 1,36 2,61 2,61 1,07 </dd></dl>

<dl><dt>Conc. Of 1-Hexene (mol%) </dt><dd> 0,29 1,26 1,06 0,11 0,11 0,27 </dd></dl>

<dl><dt>Type of cocatalyst </dt><dd>TEB: TEA3: 1 TEB: TEA3: 1 TEB: TEA3: 1 TORCH TORCH TORCH </dd></dl>

<dl><dt>Cocaine Conc. (Ppm) </dt><dd> 3,1 12,0 12,3 1,04 1,04 5,02 </dd></dl>

<dl><dt>Hexene, kg / hr </dt><dd> 0,31 0,27 0,23 0,18 0,18 0,09 </dd></dl>

<dl><dt>Ethylene kg / hr </dt><dd> 11,6 11,4 11,4 10,6 10,6 9,8 </dd></dl>

<dl><dt>HLMI (g / 10 min) </dt><dd> 1,23 3,5 3,0 2,0 2,1 5,3 </dd></dl>

<dl><dt>Density (g / cc) </dt><dd> 0,9495 0,9493 0,9497 0,9487 0,9486 0,9498 </dd></dl>

<dl><dt>Catalyst Productivity * kg / kg </dt><dd> 2564 1818 1754 1053 1053 1531 </dd></dl>

<dl><dt>SEG Mn / 1000 Mw / 1000 Mz / 1000 Mw / Mn </dt><dd> 7 487 3235 70,8 6 452 3810 78,3 5,1 450 3394 88,6 8,2 410 3108 49,9 8,04 426 3192 52,9 4,2 427 3826 101,1 </dd></dl>

<dl><dt>Rheology Eta (0) </dt><dd>1.04E + 07 5.52E + 06 7.04E + 06 8.84E + 06 8.29E + 06 1.33E + 07</dd></dl>

<dl><dt> Cy-a_eta </dt><dd> 0,3610 0,3361 0,3319 0,2693 0,2723 0,249 </dd></dl>

<dl><dt>PENT, hours (2.4 MPa) </dt><dd> &gt;4822 &gt;1747 &gt;1774 &gt;1411 &gt;1367 &gt;1963 </dd></dl>

<dl><dt>Pipe Extrusion </dt><dd /></dl>

<dl><dt>Kg / hr / rpm output </dt><dd> 0,70 0,81 0,82 0,79 0,77 0,98 </dd></dl>

<dl><dt>Head pressure, MPa </dt><dd> 3550 2500 2710 2980 2950 2270 </dd></dl>

<dl><dt>Matrix pressure, MPa </dt><dd> 1480 1100 940 1450 950 </dd></dl>

<dl><dt>Melting temp, ºC </dt><dd> 210 209 209 209 209 207 </dd></dl>

<dl><dt>Pressure test (ISO requirements) </dt><dd>He passed Failure He passed He passed He passed Failure </dd></dl>

<dl><dt>20C, 12.4 MPa hours (&gt; 100 hours) </dt><dd> &gt;1031, &gt;1031, 627 167,240,13 4 356,473, 372 213, 297, 315 272, 272, 264 144,81, 102 </dd></dl>

<dl><dt>80C, 5.3 MPa hours (&gt; 165 hours) </dt><dd> &gt;1121, &gt;1119, &lt;1121 51,38,66 &gt;1145, &gt;1145, &gt;1141 &gt;716, &gt;716, &gt;716 &gt;716, &gt;716, &gt;716 105, 132, 87 </dd></dl>

<dl><dt>80C, 5.0 MPa hours (&gt; 1000 hours) </dt><dd> &gt;1031, &gt;1031, &gt;1031 &gt;498, &gt;498, &gt;498 &gt;1145, &gt;1145, &gt;1145 &gt;716, &gt;716, &gt;716 &gt;716, &gt;716, &gt;716 &gt;433, &gt;433, &gt;433 </dd></dl>

<dl><dt>Example </dt><dd>8 9 Ref 7 Ref 8 10 eleven </dd></dl>

<dl><dt>Conc. H2 (mol%) </dt><dd> 1,008 0,503 0,969 1,472 0,957 1,3 </dd></dl>

<dl><dt>Conc. 1-Hexene (mol%) </dt><dd> 0,339 0,389 0,376 0,377 0,476 2,33 </dd></dl>

<dl><dt>TEB concentration (ppm) </dt><dd>3.19 3.17 10.55 10.66 5.28 (3: 1 ASD / TEB) </dd></dl>

<dl><dt>Catalyst Productivity (kg / kg) </dt><dd> 2500 1923 2326 2703 1613 </dd></dl>

<dl><dt>HLMI (g / 10 min) </dt><dd> 1,53 0,93 1,76 2,75 1,09 9,4 </dd></dl>

<dl><dt>Density (g / cc) </dt><dd> 0,9492 0,9476 0,9488 0,9486 0,9484 0,9533 </dd></dl>

<dl><dt>SEG Data Mn / 1000 Mw / 1000 Mz / 1000 Mw / Mn </dt><dd> 6,86 483,5 2823,5 70,6 6,68 513,9 2861 77,2 6,34 490,1 2873,1 77,5 5,94 459,5 2808,5 77,7 6,36 498,7 2806,1 80,3. 4,84 324,0 2824,8 67,0 </dd></dl>

<dl><dt>Rheology data - Dynamics </dt><dd /></dl>

<dl><dt> Eta (0) </dt><dd>1.00E + 0 7 1.35E + 07 , 07E + 06 6.94E + 06 1.20E + 07 2.16E + 07</dd></dl>

<dl><dt> Cy-a_eta </dt><dd> 0,3486 0,3738 0,3811 0,3613 0,3723 0,2690 </dd></dl>

In the following examples, the data is included in the examples about the preparation of the catalyst system, the polymerization conditions, as well as the resulting polymers. All chemical handling, which includes reactions, preparations and storage, was performed in an inert, dry atmosphere (usually nitrogen), unless otherwise indicated.

Polymerization processes

Polymerization runs for the following examples were performed using both a laboratory scale reactor and a loop reactor. The laboratory scale polymerizations were performed in a 2.2 liter stirring autoclave reactor equipped with a steel jacket for precise temperature control. Unless otherwise indicated, a small amount (usually 0.01 to 0.10 grams) of catalyst containing solid chromium under nitrogen was first charged to the dry reactor. Then, 1.2 liters of liquid isobutene was charged and the reactor was heated to the specified temperature, usually at 95 ° C (203 ° F). When a cocatalyst was used, such as triethylboro (TEB) or triethylaluminum (TEA), a small amount (usually 1-2 ml) of a solution containing 1 percent by weight of the cocatalyst diluted in heptane was added halfway through the addition of isobutane. Finally, ethylene was added to the reactor to bring the total reactor pressure to 3.9 MPa (550 psig), which was maintained during the polymerization run. Stirring continued for a specified time, usually 1 hour, with the activity of the catalyst system indicated by the recording of the amount of ethylene flowing in the reactor necessary to maintain the set pressure. After the specified time, the ethylene flow was discontinued and the reactor was allowed to depressurize and subsequently opened to recover a granular polymer powder. In all cases, the reactor was clean without indication of any scale of wall, cladding or other forms of contamination. The polymer powder was extracted and weighed. The activity was specified as grams of polymer produced per gram of charged catalyst per hour.

The polymerization runs were also carried out under conditions of continuous particle formation process in a loop reactor (also known as a suspension process) by contacting a solid catalyst system containing chromium with ethylene and sometimes with 1-hexene as indicated. The ethylene used was polymerization grade ethylene (obtained from Union Carbide Corporation) which was purified through an alumina column and activated at 250 ° C (482 ° F) under nitrogen. The 1-hexene was polymerization grade 1-hexene (obtained from Chevron Chemicals Company) which was purified by nitrogen purging and storage on activated 13X molecular sieve at 250 ° C (482 ° F) under nitrogen. The loop reactor was a loop reactor, 15.2 cm in diameter, filled with liquid, which had a volume of 87 liters (23 gallons). Liquid isobutane was used as a diluent, and occasionally some hydrogen was added to regulate the molecular weight of the polymer product. The isobutane was polymerization grade isobutane (obtained from Phillips Petroleum Company, Borger, Texas) which was further purified by distillation and subsequently passed through an alumina column and activated at 250 ° C (482 ° F) under nitrogen.

The reactor conditions included a pressure of about 4 MPa (580 psi), and a temperature that ranged from about 65 ° C (149 ° F) to about 110 ° C (230 ° F) as indicated in the following examples. Also, the reactor was operated to have a rest time of 1.25 hours. The catalyst systems were added through a 0.35 cc circulating ball retention feeder. The concentrations of the catalyst system in the reactor were in a range of 0.001 to 1 percent by weight based on the weight of the total reactor contents. The polymer was removed from the reactor at the rate of 11.3 kg (25 lbs) per hour and recovered in an instant evaporation chamber. A Vulcan dryer was used to dry the polymers under nitrogen at 60-80 ° C (140-176 ° F).

Catalysts such as triethylaluminum (TEA) and triethylboro (TEB) (obtained from Akzo Corporation) were also used. These catalysts were obtained as molar solutions in heptane but then diluted to 1 percent by weight. The catalysts were added as indicated in a concentration in a range of 1 to 30 parts per million of the diluent in the polymerization reactor (s). To prevent static accumulation in the reactor, a small amount (less than 5 ppm, by weight, of diluent) of a commercial antistatic agent sold as "Stadis 450" is usually added.

Example 12

This example illustrates the preparation of various catalyst systems used in the following Examples.

Chromium / Aluminophosphate catalyst systems

The aluminophosphate catalyst systems were prepared from a concentrated syrup containing aluminum nitrate nonahydrate, monobasic ammonium phosphate and chromium nitrate. A small amount of water was added, usually about the same amount as aluminum nitrate, and heated to 40 ° C (104 ° F) to dissolve the mixture. Aluminum nitrate and monobasic aluminum phosphate were added in an amount necessary to produce the desired phosphorus to aluminum (P / Al) molar ratio. For example, to obtain a molar ratio of phosphorus to aluminum (P / Al) of 0.2 in the final catalyst system, 0.2 moles of monobasic ammonium phosphate was added for each mole of nonahydrated aluminum nitrate. Chromium nitrate was added in an amount necessary to produce 1 percent by weight of chromium in the final product. To this syrup was subsequently added, with rapid and vigorous stirring, concentrated ammonium hydroxide to form a gel with a pH of 5-7. This ge was broken and suspended in water to which more ammonium hydroxide was added to adjust the pH to 8-9. At this pH, the suspension was heated at 60 ° C (140 ° F) -80 ° C (176 ° F) for 1 hour, where it aged. The suspension was subsequently filtered, washed in about five times its volume in water, and filtered again. This process was repeated three times. A final wash of the filtrate was carried out with n-propanol, filtered again and dried at 110 ° C (230 ° F) under a vacuum of medium atmosphere for 12 hours. The dry catalyst system was subsequently passed through a 35 mesh screen containing a 0.50 mm hole.

Some catalyst systems were also treated with fluoride by dissolving the desired amount of ammonium bifluoride in methanol. This solution was adjusted so that the resulting impregnated catalyst systems could reach the point of incipient humidity and subsequently the solution was impregnated on or in the catalyst systems. The resulting wet powder was subsequently dried again under a medium atmosphere vacuum at 110 ° C (230 ° F) for 12 hours.

Other catalyst systems

Other polymerization catalyst systems were used in the following examples and loaded with approximately 1 percent by weight of chromium, unless otherwise indicated. 963 Magnapore®, 965 Silopore®, and 969 MS are three polymerization catalyst systems that were used and commercially available from Davison Chemical Company, a division of WR Grace &amp; amp; Co. 963 Magnapore®, a high-porosity silica-titanium catalyst system was prepared, in accordance with US Pat. No. 3,887,494. 963 Magnapore® contained 2.5 percent by weight of titanium, had a surface area of ​​550 m2 / g, and a pore volume of 2.2 to 2.5 cc / g. 965 Silopore®, a lower porosity silica-titanium catalyst system, was prepared in accordance with US Patent No.

4,981.83. 965 Silopore® contained 2.5 weight percent titanium, had a surface area of ​​380 m2 / g, and a pore volume of 0.9 cc / g. 969MS, a catalyst system with silica support had a surface area of ​​300 m2 / g and a pore volume of 1.6 cc / g.

Activation of catalyst systems

In the scale reactor, described above, the catalyst systems were activated by placing approximately 10 grams of the catalyst system in a 4.45 cm (1.75 inch) quartz tube equipped with a sintered quartz disk in the part lower. While the catalyst systems were supported on the disk, dry air was injected through the disk at a linear speed of 45 to 50 cm3 (1.6-1.8 cubic feet) per hour. An electric oven was subsequently ignited around the quartz tube and the temperature increased at a rate of 400 ° C (752 ° F) per hour at the desired temperature, such as, for example, 600 ° C (1112 ° F). The catalyst system was subsequently collected and stored under dry nitrogen, where it was protected from the atmosphere until the test.

For the 0.09 m3 (23 gallon) loop reactor, larger quantities of catalyst systems were activated similarly. The catalyst systems were activated by the load of 0.68 kg (1.5 pounds) of the catalyst system in a 15.2 cm diameter stainless steel electric oven that was heated by itself by means of electric coils around the oven. Dry air was allowed to rise through a plate with central metal grid at the rate of 3.6 to 6 cm per second (0.12-0.2 linear feet / sec) to flow from the catalyst system. The catalyst system was subsequently heated to the desired temperature for a period of 5 hours. It was maintained at this specified temperature for another 6 hours, and cooled to room temperature and stored under dry nitrogen until the test. 65 to 85 percent by weight of the charged catalyst system was recovered, the weight lost is water and very fine material.

In some cases, the catalyst systems were treated with carbon monoxide before being discharged from the reactor and kept under nitrogen. This was done in order to reduce at least some of the hexavalent chromium to a divalent state, which can increase the efficiency of the incorporation of 1-hexene, as described in Polymer Engineering and Science (SPE), Vol. 28, No. 22 , pp. 1469-1472 (1988). This was achieved by the fluidization of the carbon monoxide catalyst systems at approximately 350 ° C (700 ° F) for approximately 2 hours after the calcination step. Carbon monoxide can be used pure or diluted with up to 90 percent nitrogen. Laboratory scale activations usually use pure carbon monoxide for convenience while the 0.09 m3 (23 gallon) loop reactor used 10 percent carbon monoxide. After the treatment of carbon monoxide, the catalyst systems were washed with nitrogen for 1 hour, cooled in nitrogen, and subsequently preserved. The color of the reduced catalyst systems was usually blue or green, indicating that all, or substantially all, of the hexavalent chromium has been reduced to a lower oxidation state, in general the divalent state.

The analysis of the resulting polymers was performed according to the following procedures.

The density of the polymer in grams per cubic centimeter (g / cc) in a compression molded sample was determined, cooled to approximately 15 ° C (59 ° F) per hour, and conditioned at room temperature for approximately 40 hours of conforming to ASTM D1505-68 and ASTM D1928, condition C.

The high load melt index (HLMI) in grams of polymer was determined for 10 minutes (g / 10 min) in accordance with ASTM D1238, Condition 190 / 2.16, at 190 ° C (374 ° F) with a weight of 21,600 grams.

The melt index (MI) in grams of polymer was determined for ten minutes according to ASTM D1238, condition 190/2, at 190 ° C (374 ° F) with a weight of 2,160 grams.

Typical molecular weights and molecular weight distributions were obtained using size exclusion chromatography in Waters 150 CV (SEG) with trichlorobenzene (TCB) as solvent, with a flow rate of 1 ml / minute at a temperature of 140 ° C ( 284 ° F). BHT (2,6-di-tert-butyl-4-methylphenol) was used at a concentration of 1.0 g / l as a stabilizer in the TCB. An injection volume of 220 l with a polymer concentration of 1.4 mg / L (at room temperature) was used. Dissolution of the stabilized TCB sample was performed by heating at 160-170 ° C (320-338 ° F) for 4 hours with gentle, occasional stirring. The column was a two-column Waters HMW-6E system (7.8x300mm) and was calibrated with a wide linear polyethylene standard (Phillips Marlex® BHB 5003) for which the molecular weight was determined. As a measure of the volatile oligomeric components or smoke, the amount of material found in the molecular weight range of 100 to 1000 was listed.

A "Quantachrome Autosorb-6 nitrogen pore size distribution instrument" was used to determine the surface area and pore volume of the supports. This instrument was obtained from the Quantachrome Corporation, Syosset, New York.

The resistance of the environmental stress fissure (ESCR, hours) was determined in accordance with ASTM D1693, Condition A.

PENT environmental stress crack resistance values ​​were obtained at 80 ° C (176 ° F) according to ASTM F1473 (1997).

The determination of the SEG-FTIR branching as a function of molecular weight distribution was obtained as follows. For molecular weight determinations, a Polymer Laboratories, 210 GPC model equipped with two columns of Styragel HT 6E (Waters) was used. The resin samples were dissolved in trichlorobenzene (TCB) containing 0.034 weight percent butylated dihydroxytoluene (BHT) by heating the mixture for 1 hour at 155 ° C (311 ° F) in a Blue M air convection oven . Resin samples of approximately 1.8 mg / ml were chromatographed at 1 ml / min using TCB as the mobile phase, with a sample injection volume of 500 μl. The samples were introduced into a Perkin Elmer Model 2000 FTIR spectrophotometer equipped with a narrow band mercury cadmium tellurium (MCT) detector via a heated transfer line and flow cell (KBr windows, 1 mm optical path, and approximately 70 μL cell volume). The temperatures of the transfer line and the flow cell were maintained at 143 +/- 1 ° C (290 +/- 1 ° F) and 140 +/- 1 ° C (284 +/- 1 ° F), respectively . Threshold spectra were obtained with the cell filled with polymer-free solvent. All IR spectra were measured with resolutions of 8 cm-1 (16 scans).

Chromatograms were generated using the average square root (rms) of the absorbance with respect to the spectral region of 3000-2700 cm -1 and molecular weight calculations were performed using a PE standard of the broad PE molecular weight. The spectra of the individual time fractions of the chromatogram were subsequently analyzed to determine the comonomer branching levels using the chemometric techniques described below.

Narrow molecular weight distribution samples (Mw / Mn) of about 1.1 to about 1.3, solvent gradient fractions of ethylene / 1-butene, ethylene / 1-hexene, ethylene / 1- copolymers were used octene and polyethylene homopolymers in calibration, and in verification studies. Alkanes of low molecular weight were also used. The total methyl content of these samples was 1.4 to 83.3 methyl groups per 1000 total carbon molecules. The methyl content of the samples was calculated from Mn (number average molecular weight) or measured using C-13 NMR spectroscopy. NMR spectra of C-13 were obtained in samples at 15 percent by weight on TCB using a 500 MHZ Varian Unity spectrometer at 125 ° C (257 ° F) as described in JC Randall and ET Hseish; NMR and Macromolecules; Sequence, Dynamic, end Domain Structure ACS Symposium Series 247, JC Randall, Ed., American Chemical Society, Washington DC, 1984. The methyl content per 1000 carbon molecules per NMR was obtained by multiplying the ratio between branching signals and total signal intensity by 1000.

A calibration curve was generated using the Pirovette Chemometric computer program to correlate changes in the FTIR absorption spectra with values ​​calculated or measured in NMR for the number of methyl groups per 1000 carbon molecules for the samples. The calibration results are

obtained for the spectral region of 3000 cm-1 and 2700 cm-1 to avoid solvent interference in quantitative results for the prediction of the measured sample spectrum. Preprocessing of the spectral data included smoothing of the 9 data points, baseline correction and normalization. The additional preprocessing of the spectral data involved taking the first derivative of the spectra and the mean that centers all the data. A four-component calibration model was calculated and optimized using the cross-validation process (RSQ = 0.999, SEV = 0.7). The calibration model was verified using 13 additional samples. The predicted values ​​versus the actual values ​​for the validation data showed an excellent correlation (RSQ = 0.987) and exhibited an average square root of the prediction error equal to +/- 0.4 methyl groups per 1000 total carbon molecules.

Short chain branching levels were calculated by subtracting the terminal contributions of the methyl chain. The number of ends of the methyl chain were calculated using the equation Mece = C (2-Vce) / M, where Mece is the number of ends of the methyl chain per 1000 total carbon molecules, C is a constant equal to 14000, Vce is the number of vinyl terminated chain ends (1 for chromium catalyzed resins), and M is the calculated molecular weight for a particular fraction of the molecular weight distribution.

This example illustrates the traditional difficulties experienced in the art using chromium / aluminophosphate catalyst systems. Table 6 compares the activity response of chromium / aluminophosphate catalyst systems when the phosphorus to aluminum (P / Al) molar ratio varies and the activation temperature. Chromium / aluminophosphate catalyst systems were obtained from a laboratory reactor operating at 95 ° C (203 ° F) with 4 ppm of triethylboro (TEB) and 3.9 MPa (550 psig) of ethylene.

TABLE 6

<dl><dt>Activity response of several chromium / aluminophosphate catalyst systems (g pol / g cat / hr) at various P / Al molar ratios and activation temperatures </dt><dd /></dl>

<dl><dt>Catalyst system activity at different activation temperatures </dt><dd /></dl>

<dl><dt>molar ratio P / AL </dt><dd>300ºC 500ºC 700 ° C </dd></dl>

<dl><dt>0,0</dt><dd> 0 555 1340 </dd></dl>

<dl><dt>0,2 </dt><dd> 1085 1685 2295 </dd></dl>

<dl><dt>0,4 </dt><dd> 2000 4790 5400 </dd></dl>

<dl><dt>0,6 </dt><dd> 1970 6395 6300 </dd></dl>

<dl><dt>0,8 </dt><dd> 2910 4444 4235 </dd></dl>

<dl><dt>0,95</dt><dd> 2500 3565 3770 </dd></dl>

<dl><dt>1,0</dt><dd> 0 0 700 </dd></dl>

As shown in Table 6, the greatest activities of the catalyst systems were obtained with high P / Al molar ratios and high activation temperatures. Runs with catalyst systems with low P / Al molar ratios and low activation temperatures generally produced poor or unacceptable activity. However, at these low molar ratios of P / Al and low activation temperatures is where the widest molecular weight distribution (MWD) is found and consequently the most convenient polymer properties.

Example 13

This example compares the environmental stress crack resistance (ESCR) values ​​of the polymers obtained from the loop reactor using chromium / aluminophosphate catalyst systems of varying P / Al molar ratios. The polymers (homopolymers) of this example were obtained from a 0.09 m3 (23 gallon) loop reactor operating between approximately 93 ° C (200 ° F) to approximately 99 ° C (210 ° F) with 0.5 at 1 ppm of triethylboro. The catalyst systems were activated at 600 ° C (1112 ° F) and the polymers obtained had a melt index (MI) of 0.15 to 0.35 g / 10 minutes. As shown in Table 7, the highest ESCR values ​​were obtained with low P / Al molar ratios.

TABLE 7

<dl><dt>Values ​​of resistance to environmental stress fissure (ESCR) of polymers with varied molar ratios of P / Al </dt><dd /></dl>

<dl><dt>P / Al </dt><dd> 0 0,2 0,3 0,37 0,4 0,5 0,55 0,6 0,8 0,9 </dd></dl>

<dl><dt>ESCR, (hours) </dt><dd> &gt;100 &gt;100 525 300 240 150 95 100 24 0 </dd></dl>

Example 14

This example illustrates another problem associated with chromium / aluminophosphate catalyst systems and the

5 response to 1-hexene or other comonomers. Usually, commercial chromium (chromium / silica) catalyst systems incorporate 1-hexene well to easily produce ethylene / 1-hexene copolymers. The addition of 1hexene in an amount equal to about 4 percent of the liquid diluent is usually sufficient to cover the entire copolymer range, from the densities of 0.970 g / cc to densities as low as 0.920 g / cc for some catalyst systems. As 1-hexene is incorporated, the potential melt index of the system

10 The catalyst remains essentially unchanged due to the counterbalance effect of an increase in the melt index when 1-hexene is added and a decrease in the melt index when the reactor temperature is reduced to prevent swelling.

However, chromium / aluminophosphate catalyst systems respond in a completely different way. Even when 1-hexene can be added in large quantities, 1-hexene can be incorporated into the polymer

fifteen Only in a very small amount. As a result, 1-hexene can have a toxic effect on chromium / aluminophosphate catalyst systems that can decrease the activity of the catalyst system and cause the melt index to rise excessively, often out of control.

These effects are demonstrated in the following Table 8, and in Figures 4 and 5. These data were obtained in the loop reactor of 87.1 liters (23 gallons) under the conditions described above.

twenty TABLE 8

<dl><dt>Effect of 1-hexene on chromium / aluminophosphate catalyst systems compared to chromium / silica catalyst systems </dt><dd /></dl>

<dl><dt>Catalyst system </dt><dd>% 1hexene diluent Polymer density, g / cc % relative activity of the catalyst system </dd></dl>

<dl><dt>Chrome / Aluminum Phosphate </dt><dd /></dl>

<dl><dt>P / Al = 0.8 </dt><dd> 0,00 0,9369 100 </dd></dl>

<dl><dt>P / Al = 0.8 </dt><dd> 0,90 0,9595 59 </dd></dl>

<dl><dt>P / Al = 0.8 </dt><dd> 1,30 0,9595 55 </dd></dl>

<dl><dt>P / Al = 0.8 </dt><dd> 1,40 0,9578 52 </dd></dl>

<dl><dt>P / Al = 0.8 </dt><dd> 0,00 0,9672 100 </dd></dl>

<dl><dt>P / Al = 0.8 </dt><dd> 1,30 0,9621 52 </dd></dl>

<dl><dt>P / Al = 0.9 </dt><dd> 0,00 0,9650 100 </dd></dl>

<dl><dt>P / Al = 0.9 </dt><dd> 2,00 0,9640 41 </dd></dl>

<dl><dt>P / Al = 0.9 </dt><dd> 3,90 0,9605 36 </dd></dl>

<dl><dt>P / Al = 0.3 </dt><dd> 0,00 0,9597 100 </dd></dl>

<dl><dt>P / Al = 0.3 </dt><dd> 1,80 0,9567 36 </dd></dl>

<dl><dt>P / Al = 0.3 </dt><dd> 3,65 0,9538 42 </dd></dl>

<dl><dt>P / Al = 0.4 </dt><dd> 0,00 0,9610 100 </dd></dl>

<dl><dt>P / Al = 0.4 </dt><dd> 4,00 0,9544 49 </dd></dl>

<dl><dt>Chrome / silica</dt><dd /></dl>

<dl><dt> 0,00 </dt><dd> 0,965 100 </dd></dl>

<dl><dt> 1,00 </dt><dd> 0,952 104 </dd></dl>

<dl><dt> 2,00 </dt><dd> 0,943 100 </dd></dl>

<dl><dt> 3,00 </dt><dd> 0,938 96 </dd></dl>

<dl><dt> 4,00 </dt><dd> 0,934 106 </dd></dl>

As Table 8 and Figures 4 and 5 illustrate, the decrease in the density of chromium / aluminophosphate catalyst systems is negligible as 1-hexene is added, which is illustrative of the low activity of the catalyst system. Even with amounts greater than 1-hexene, that is, up to 4 percent of the diluent, the

5 Density decrease is still minimal. As depicted in Table 8 and Figures 4 and 5, the production of copolymers using typical chromium / aluminophosphate catalyst systems is problematic at best and certainly cannot produce copolymers with densities of approximately 0.955 g / cc and less. .

EXAMPLES OF THE INVENTION AM

The following examples illustrate the processes of the present invention and their effectiveness on the polymerization process 10 and the resulting polymer.

Examples AM demonstrate the effectiveness of the methods of the present invention. These examples, listed in Table 9, were prepared in the 0.09 m3 (23 gallon) loop reactor described above using the chromium / aluminophosphate catalyst systems (referred to as AlPO4 in the table) that have a P / Al molar ratio of 0.2, which were subsequently impregnated with 2% and 2.64% fluoride, as indicated (present in an effective amount

fifteen of ammonium bifluoride). The catalyst systems were activated at a temperature of l000 ° F (538 ° C) and 1100 ° F (594 ° C) as indicated, and ran with 0 to 2 ppm of TEB cocatalyst, as indicated in the table.

As shown in Table 9, the AM examples have HLMI values ​​at desired processing intervals of 5 to 10 g / 10 minutes, densities ranging from 0.945-0.951 g / cc, and ESCR PENT values ​​ranging from more than 1950 hours to more than 2091 hours. In all cases the ESCR PENT tests stopped as

twenty the time approached 2000 hours, not due to the failures of the sample, but in order to release the test station for another job. The high ESCR PENT values ​​associated with the AM examples were obtained without excessively low HLMI values ​​and relatively high densities, in one case at a density of 0.9516 g / cc. In addition, as shown in Table 9, the HM examples have weighted average molecular weight distributions (Mw / Mn) ranging from 98 to 108, well above the comparative examples.

25 Carbon monoxide reduction can optionally be used in accordance with the methods of the present invention to improve the incorporation of 1-hexene. The effects that carbon monoxide reduction can have on the resulting polymer can be seen in examples F and G. Although the HLMI values ​​of examples F and G are lower than the desired range, as shown in Table 9, the copolymers were produced in accordance with the present invention, even in the absence of carbon monoxide reduction.

30 TABLE 9

<dl><dt>ESCR PENT values ​​for selected pipe resins values </dt><dd /></dl>

<dl><dt>Run da </dt><dd>Catalyst system Fluoride level (% by weight of F) Activation temperature (ºC) CO reduction (371ºC) Cocatali zador (Conc ppm) HL MI (g / 1.0 min) Densid ad (g / cc) ESC R (2.5 4 Mpa) Mw (x10 00) Mn (x100 0) Mw / Mn </dd></dl>

<dl><dt>TO </dt><dd>Cr / ALPO4 = 0.2 two% 537 No TEB (2.05) 7.53 0.9505 &gt; 19 50 </dd></dl>

<dl><dt>B </dt><dd>Cr / ALPO4 two% 537 No TEB 7.77 0.9491 &gt; 19 </dd></dl>

<dl><dt>=0,2 </dt><dd> (1,32) 57 </dd></dl>

<dl><dt>C </dt><dd>Cr / ALPO4 = 0.2 two% 537 No TEB (1.16) 4.14 0.9484 &gt; 19 66 </dd></dl>

<dl><dt>D </dt><dd>Cr / ALPO4 = 0.2 two% 593 No TEB (1.5) 10.8 2 0.9496 &gt; 20 35 </dd></dl>

<dl><dt>AND </dt><dd>Cr / ALPO4 = 0.2 two% 593 No TEB (1.77) 9.13 0.9455 &gt; 20 91 </dd></dl>

<dl><dt>F </dt><dd>Cr / ALPO4 = 0.2 two% 593 Yes 4.37 0.9481 &gt; 15 62 </dd></dl>

<dl><dt>G </dt><dd>Cr / ALPO4 = 0.2 two% 593 Yes 2.68 0.9456 &gt; 20 06 </dd></dl>

<dl><dt>H </dt><dd>Cr / ALPO4 = 0.2 2.64% 593 No TEB (1) 4.8 0.9494 &gt; 20 00 718 6900 104 </dd></dl>

<dl><dt>I </dt><dd>Cr / ALPO4 = 0.2 2.64% 593 No TEB (1) 6.0 0.9496 &gt; 20 00 679 6900 98 </dd></dl>

<dl><dt>J </dt><dd>Cr / ALPO4 = 0.2 2.64% 593 No TEB (1) 7.9 0.9512 &gt; 20 00 714 6800 105 </dd></dl>

<dl><dt>K </dt><dd>Cr / ALPO4 = 0.2 2.64% 593 No TEB (1) 5.3 0.9492 &gt; 20 00 740 6900 107 </dd></dl>

<dl><dt>L </dt><dd>Cr / ALPO4 = 0.2 2.64% 593 No TEB (1) 6.2 0.9507 &gt; 20 00 702 6500 108 </dd></dl>

<dl><dt>M </dt><dd>Cr / ALPO4 = 0.2 2.64% 593 No TEB (1) 7.5 0.9516 &gt; 20 00 724 6900 105 </dd></dl>

<dl><dt>C10</dt><dd> 963 Magnapor e 649 No 10.3 1 0.9443 64 173, 45 17.85 9.72 </dd></dl>

<dl><dt>C11</dt><dd> 964 Magnapor e 649 No TEB (2.05) 11.2 8 0.9457 194 234, 95 10.25 22.92 </dd></dl>

<dl><dt>C12</dt><dd> 963 Magnapor e 537 Yes TEB (3.12) 5.21 0.9495 113 </dd></dl>

<dl><dt>C13</dt><dd> 963 Magnapor e 649 Yes TEB (0.8) 10.5 2 0.9436 51 </dd></dl>

<dl><dt>C14</dt><dd> 963 Magnapor e 537 No TEB (6) 8.4 0.9511 250 554 8200 68 </dd></dl>

<dl><dt>C15</dt><dd> 963 Magnapor e 537 No TEB (6) 4.7 0.9504 374 564 8200 69 </dd></dl>

<dl><dt>C16</dt><dd> 963 Magnapor e 537 No TEB (6) 4.3 0.9507 281 571 7700 74 </dd></dl>

<dl><dt>C17</dt><dd> 965 Sylopore 593 No TEB (1.75) 3.91 0.9486 52 </dd></dl>

<dl><dt>C18</dt><dd> 969 MS 593 No TEB 12.3 0.9435 356 254, 12.81 19.9 </dd></dl>

<dl><dt>(2,15)</dt><dd> 7 94 </dd></dl>

<dl><dt>C19</dt><dd> Cr / ALPO4 = 0.3 593 Yes TEB (1) 21.4 4 0.9463 17 257, 14 8.99 28.59 </dd></dl>

<dl><dt>C20</dt><dd> Cr / ALPO4 = 0.3 593 Yes TEB (1) 15.5 4 0.9507 37 </dd></dl>

<dl><dt>C21</dt><dd> Cr / ALPO4 = 0.6 593 Yes 13.2 5 0.9432 143 259, 02 11.03 23.48 </dd></dl>

<dl><dt>C22</dt><dd> Cr / ALPO4 = 0.6 593 Yes 12.5 7 0.9440 166 170, 6 9.5 17.95 </dd></dl>

* Weighted average molecular weight (Mw), numerical average molecular weight (Mn), and polydispersion

(Mw / Mn) was determined by the SEG method (not coupled with FTIR)

COMPARATIVE EXAMPLES C10-C18

It was also shown in Table 9 that similar resins for pipe were obtained under similar conditions, but using conventional catalyst systems. It is indicated that example C10, made with a Magnapore chromium / silica-titanium catalyst system produced a much lower density than desired and the ESCR PENT value was excessively low compared to the examples of the invention described above. While example C10 did not employ a triethylboro cocatalyst, known to extend the molecular weight distribution of the chromium / silica-titanium catalyst systems, examples C11-C16 employed a triethylboro cocatalyst. However, even with the addition of TEB, it can be seen in Table 9 that the ESCR PENT value improved, but the results are still lower compared to the examples of the invention. Also, in examples C12, and C14-C16, the benefits that can be obtained by using a lower activation temperature can be observed, in this case 537 ° C (1000 ° F) instead of 649 ° C (1200 ° F). While examples C12, C14-C16 produced high densities, ESCR PENT values ​​were poor compared to the examples of the invention.

Also, example C17 used a triethylboro cocatalyst with a lower porosity chromium / silica-titanium catalyst system, but again the ESCR PENT value was very low, even at an excessively low HLMI of 3.9 g / 10 minutes. Even when a chromium / silica catalyst system of the chromium / silicatitanium catalyst system was used as shown in example 10, the benefits were minimal. While the ESCR PENT value for the chromium / silica catalyst system was higher than that of the other chromium / silica-titanium catalyst systems, it was still very low compared to the examples of the invention.

COMPARATIVE EXAMPLES C19-C22

The low ESCR PENT values ​​of Examples C19-C22 show that no chromium / aluminophosphate catalyst system can be used, only those described in accordance with the present invention. In these examples, the chromium / aluminophosphate catalyst systems were obtained as described above, and were run according to the same conditions used in the examples of the invention AM, but the P / Al molar ratio varied. In examples C19 and C20, the molar ratio of P / Al rose to 0.3, only slightly higher than the molar ratio of 0.2 used in the AM examples. As shown in examples C21 and C22, the molar ratio of P / Al increased to 0.6, but again gave low ESCR PENT values, even at the low level of unacceptable density obtained. As the data in Table 9 demonstrate, the ESCR PENT value suffered considerably when the molar ratio of P / Al increased much more than 0.2. However, lower levels of P / Al molar ratios may also be unacceptable, since the activity of the catalyst system decreases substantially.

Example 15

This example illustrates the effect of fluoride on the catalyst systems used in accordance with the present invention. It is generally known that fluoride improves the activity of catalyst systems containing alumina, but its effects on density have not been previously known. In this example, chromium / aluminophosphate catalyst systems were obtained as described above, but were impregnated with different amounts of fluoride. Two molar ratios of P / Al, one high (P / Al = 0.6), and one low (P / Al = 0.2) were selected to illustrate the effects of fluorination on density. The catalyst systems were activated at 1200 ° F (649 ° C) and the polymers were produced in the 0.09 m3 (23 gallon) loop reactor described above using approximately 1 ppm of triethylboro cocatalyst (TEB). The results are described in the following Table 10.

TABLE 10

<dl><dt>Effect of fluoride on the polymer indicated by the density of the polymer at the P / Al molar ratios of 0.2 and 0.6 </dt><dd /></dl>

<dl><dt>Percent fluoride added </dt><dd>Polymer density P / Al = 0.2 P / Al = 0.6 </dd></dl>

<dl><dt>0,00%</dt><dd> 0,9582 0,9647 </dd></dl>

<dl><dt>0,34%</dt><dd> 0.9573 n / a </dd></dl>

<dl><dt>0,67%</dt><dd> 0,9565 0,9625 </dd></dl>

<dl><dt>1,34%</dt><dd> 0,9547 0,9605 </dd></dl>

<dl><dt>2,01%</dt><dd> 0,9538 0,9600 </dd></dl>

<dl><dt>2,68%</dt><dd> 0.9539 n / a </dd></dl>

As the data in Table 10 demonstrate, as fluoride was added to the catalyst systems, it was observed that the natural density of the polymers decreased. As shown in Table 10, most of the effect

5 on density occurred with the addition of 2 percent NH4HF2 (1.34% F), but small decreases in density were visualized with increased fluoride percentages, in both P / Al molar ratios of 0.2 and 0 6. Natural density reduction is very useful for chromium / aluminophosphate catalyst systems because, as indicated above, chromium / aluminophosphate catalyst systems tend to be poisoned with the 1-hexene comonomer that would ordinarily be used to reduce density .

10 However, as shown in the following Table 11, the addition of too much fluoride can be harmful.

TABLE 11

<dl><dt>Effect of fluoride on the activity of the catalyst system </dt><dd /></dl>

<dl><dt>%F </dt><dd>Grams of the charged catalyst system (g cat) Grams of the polymer obtained (g pol) Time (min) Activity pol / g cat / h) </dd></dl>

<dl><dt>0,00%</dt><dd> 0,06 138,3 60,0 2305 </dd></dl>

<dl><dt>2,68%</dt><dd> 0,0487 132,5 53,3 3063 </dd></dl>

<dl><dt>4,00%</dt><dd> 0,0376 73,0 61,2 1903 </dd></dl>

<dl><dt>4,00%</dt><dd> 0,0950 213,0 62,5 2152 </dd></dl>

<dl><dt>4,00%</dt><dd> 0,0686 132 60,5 1908 </dd></dl>

The data in Table 11 were obtained from polymers manufactured using the laboratory reactor with 8 ppm of

fifteen TEB cocatalyst, under the conditions described above. Chromium / aluminophosphate catalyst systems were obtained as described above with a P / Al molar ratio of 0.2 and at an activation temperature of 1100 ° F (593 ° C), except that the level of ammonium bifluoride varied. As indicated in Table 11, although fluoride initially potentiated the activity of the catalyst system, 6 percent NH4HF2 (4% F) seemed to impair the activity of the catalyst system. While the precise optimum level of fluoride will vary somewhat with the temperature of

twenty activation, surface area and other factors, etc., it would appear that the optimum level should be in the general range of 4 percent NH4HF2 (1.34-2.68% F) or the equivalent of this from another source of fluoride.

Example 16

This example illustrates the preferred use of the cocatalyst (s) in the present invention. Because the low molar ratios of P / Al and the low activation temperatures are preferable in the 25 chromium / aluminophosphate catalyst systems for better polymer properties, the catalyst systems naturally exhibit

low activity, especially if you add 1-hexene to obtain copolymers. Consequently, the use of cocatalyst (s) to improve the activity of the catalyst system is particularly effective for chromium / aluminophosphate catalyst systems. Preferably, according to the methods of the present invention, a cocatalyst (s) is present in the reactor in a concentration in the range of 0.3 to 10 ppm. In this example, aluminophosphate catalyst systems were prepared according to the procedure described above at a temperature of 1200 ° F (649 ° C) and used with various catalysts as indicated in the following Table 12. The effect of Cocatalyst on the activity of the catalyst system.

TABLE 12

<dl><dt>Cocatalyst Effect </dt><dd /></dl>

<dl><dt>Cocatalyst </dt><dd>Concentration (ppm) Activity (g pol / g cat / h) </dd></dl>

<dl><dt>None </dt><dd> 1725 </dd></dl>

<dl><dt>BEt3 </dt><dd> 4 3920 </dd></dl>

<dl><dt>BEt3 </dt><dd> 8 4400 </dd></dl>

<dl><dt>BEt3 </dt><dd> 16 1930 </dd></dl>

<dl><dt>BBu3 </dt><dd> 4 5590 </dd></dl>

<dl><dt>BBu3 </dt><dd> 8 6264 </dd></dl>

<dl><dt>BBu3 </dt><dd> 16 5735 </dd></dl>

<dl><dt>BBu3 </dt><dd> 24 1055 </dd></dl>

<dl><dt>BPh3 </dt><dd> 8 1290 </dd></dl>

<dl><dt>AlEt3 </dt><dd> 4 1885 </dd></dl>

<dl><dt>AlEt3 </dt><dd> 8 1720 </dd></dl>

<dl><dt>AlEt3 + BEt3 </dt><dd>4 &amp; 4 6855 </dd></dl>

<dl><dt>ZnEt2 </dt><dd> 8 1945 </dd></dl>

<dl><dt>AlEt2Cl</dt><dd> 4 1790 </dd></dl>

<dl><dt>AlEt2Cl</dt><dd> 8 1450 </dd></dl>

<dl><dt>AlEt2Cl</dt><dd> 8 1065 </dd></dl>

<dl><dt>MgBu2 </dt><dd> 8 1670 </dd></dl>

<dl><dt>LiBu</dt><dd> 4 1540 </dd></dl>

<dl><dt>LiBu</dt><dd> 8 1280 </dd></dl>

<dl><dt>AlEt2Oet </dt><dd> 8 1210 </dd></dl>

<dl><dt>BEtCl2</dt><dd> 8 505 </dd></dl>

<dl><dt>NaBPh4</dt><dd> 4 850 </dd></dl>

<dl><dt>NaBPh4 </dt><dd> 8 2130 </dd></dl>

<dl><dt>Cocatalyst </dt><dd>Concentration (ppm) Activity (g pol / g cat / h) </dd></dl>

<dl><dt>NaBPh4</dt><dd> 32 260 </dd></dl>

<dl><dt>LiBBu4</dt><dd> 4 1957 </dd></dl>

<dl><dt>SbBu3</dt><dd> 16 685 </dd></dl>

<dl><dt>SbPh3 </dt><dd> 16 1730 </dd></dl>

<dl><dt>Sn2Bu6</dt><dd> 15 2090 </dd></dl>

<dl><dt>Et3SiOAlEt2 </dt><dd> 8 3125 </dd></dl>

<dl><dt>GeBu4</dt><dd> 16 0 </dd></dl>

<dl><dt>Ph3SiOBEt2</dt><dd> 16 0 </dd></dl>

<dl><dt>Et = Ethyl; Bu = Butyl; Ph = phenyl</dt><dd /></dl>

As the data in Table 12 demonstrate, the trialkylboro compounds as cocatalyst were effective in their effect on the activity of the catalyst system as well as the trialkylsiloxyaluminium compounds. The combinations of triethylboro and triethylaluminum compounds were also effective on system activity.

5 catalyst. In some cases, the combination of triethylboro and triethylaluminum compounds as cocatalyst (s) exhibited greater activity of the catalyst system than each compound alone.

Example 17

This example illustrates the molecular weight distribution of polymers produced in accordance with the present invention. To obtain this distribution, a chromium / aluminophosphate catalyst system was prepared with a ratio

10 P / Al molar of 0.2 and 4 weight percent ammonium bifluoride by the method described above and activated at 1100 ° F (649 ° C). Triethylboro was used as cocatalyst at 2.1 ppm. The resulting polymer was produced in the 23.1 gallon (87.1 liter) loop reactor as described above and had an HLMI of 6.75 g / 10 minutes and a density of 0.9485 g / cc. An analysis of the branching profile of this polymer that exhibits the distribution of branching and molecular weight is shown in Figure 6.

fifteen Typically, chromium-based catalyst systems tend to incorporate comonomers in the low molecular weight portion of the distribution. This may not be convenient since desirable properties can be found in the distributions that contain branching in the larger chains, since these can serve as binding molecules between the crystals. Figure 6, as well as Figures 1 and 2, demonstrate that the catalyst systems of the present invention produce polymers where branching tends to favor the extreme weight

twenty high molecular, which is where the higher ESCR PENT values ​​can be found. Also, Figure 6 and Figures 1 and 2 demonstrate the extremely wide molecular weight distribution of the polymers produced in accordance with the present invention. The weighted average molecular weight (Mw) was 759,000 while the number average molecular weight (Mn) was 4310, which gives a polydispersion amplitude (Mw / Mn) of 176.3, determined by the method of determining SEG-branching branches. FTIR