Alkoxysilacycloalkanes, their preparation and use in the polymerisation of olefin

IS 2 158 201 T3

DESCRIPTION

Alkoxysilacycloalkanes, their preparation process and their use for olefin polymerization.

The invention relates to alkoxysilacycloalkanes, their preparation process and their use as electron donors in the polymerization or copolymerization processes of olefins, such as propylene or ethylene.

A polyolefin, which has too high a degree of heptane solubility, can have a tendency to stick, being therefore difficult to transport and, for this reason, it is poorly adapted to industrial applications. Furthermore, in the field of food, the presence of solubles in a polyolefin destined to come into contact with food is considered undesirable. For these reasons, for example, isotaoctic polypropylene preferably has an index of insolubility in heptane (represented by HI of the expression "insoluble heptane") greater than 80% by weight.

Patent application EP 665 243 describes the use of certain silanes as electron donors in olefin polymerization.

Patent application EP 250229 describes that the use of certain silanes during the polymerization of olefins makes it possible to reduce the degree of hexane solubility of the polyolefin obtained.

The article by R. West, Journal of the American Society (1954) 76, 6012 describes a mode for the preparation of 1,1-dimethoxysilacyclohexane. This preparation involves numerous stages and goes through the formation of a chlorosilacycloalkane that is particularly delicate to handle and easily degradable.

The process of the present invention is particularly simple, it involves readily accessible and relatively stable raw materials, and it does not involve chlorosilacycloalkane. The stability of the products used limits the risks of secondary reactions, which goes in the direction of greater purity of the finally prepared products.

The presence of alkoxysilacycloalkanes in the polymerization or copolymerization medium of at least one olefin, translates into a noticeable increase in polyolefin productivity and in a noticeable increase in the HI of said polyolefin. Furthermore, alkoxysilacycloalkane plays a protective role of morphology in polymerization or copolymerization processes in suspension and in the gas phase. This means that, for these so-called heterogeneous processes, the polymer or copolymer formed is a better morphological replicate of the starting solid catalyst component if an alkoxysilacycloalkane is introduced into the polymerization or copolymerization medium as an external electron donor.

The process according to the invention comprises the reaction step between a dimagnesium alkylene dibromide of the form Br-Mg-A-Mg-Br in which A is a bivalent alkylene radical, optionally substituted, for example by an alkyl radical comprising, by For example, from 1 to 6 carbon atoms, comprising the aforementioned alkylene radical, excluding the or the possible substituents, from 4 to 7 carbon atoms, and a tetraalkoxysilane of the formula (OR¹) (OR²) (OR³) (OR⁴) If in which R¹, R², R³ and R⁴, they can be identical or different and represent hydrocarbon radicals, saturated and / or unsaturated, linear or branched, which can comprise a ring.

Preferably, the radicals R¹, R², R³ yR⁴ they are alkyl radicals comprising 1 to 6 carbon atoms.

The reaction can be carried out in a solvent, which preferably has a Lewis base character such as ethers. The solvent can be, for example, diethyl ether.

The amount of inert solvent used can be, for example, such that, assuming that the reaction yield is equal to 100%, the alkoxysilacycloalkane formed is in a concentration between 0.05 and 2 moles / liter.

The reaction can be carried out, for example, between 0 and 50 ° C for 10 minutes to 12 hours, if necessary under pressure if the volatility of the species used requires it, taking into account the chosen temperature. The reaction is generally exotothermic, so it is preferable to contact the dibromide

ES 2 158 201 T3 and tetraalkoxysilane progressively and under stirring in order to maintain control of the temperature of the medium. The reaction leads to the formation of at least one alkoxysilacycloalkane of formula, OX

So

OY (I) in which X and Y represent groupings that are part of the group of radicals R¹, R², R³ and R⁴ and in which A retains the previously given meaning. The alkoxysilacycloalkane cycle therefore comprises a silicon atom and a number of carbon atoms equal to the number of carbon atoms that the alkylene radical A comprised, excluding any substituents of said radical.

The alkoxysilacycloalkanes, in which A is an alkylene radical comprising at least one alkyl substituent, also constitute an object of the present invention.

By way of example, Table 1 below mentions some alkoxysilacycloalkanes that can be prepared according to the process of the invention by reacting tetramethoxysilane with a dimagnesium alkylene dibromide, depending on the nature of the bivalent alkylene radical A comprised in dimagnesium alkylene dibromide .

TABLE 1

<td>Nature of A</td><td>Alkoxysylacycloalkane formed</td>

<td>tetramethylene</td><td>1,1-dimethoxysilacyclopentane</td>

<td>1-methyltetramethylene</td><td>1,1-dimethoxy-2-methylsilacyclopentane</td>

<td>1-ethyltetramethylene</td><td>1,1-dimethoxy-2-ethylsilacyclopentane</td>

<td>1-n-propyltetramethylene</td><td>1,1-dimethoxy-2-n-propylsilacyclopentane</td>

<td>1-isopropyltetramethylene</td><td>1,1-dimethoxy-2-isopropylsilacyclopentane</td>

<td>1-n-butyltetramethylene</td><td>1,1-dimethoxy-2-n-butylsilacyclopentane</td>

<td>pentamethylene</td><td>1,1-dimethoxysilacyclohexane</td>

<td>1-methylpentamethylene</td><td>1,1-dimethoxy-2-methylsilacyclohexane</td>

<td>1-ethylpentamethylene</td><td>1,1-dimethoxy-2-ethylsilacyclohexane</td>

<td>1-n-propylpentamethylene</td><td>1,1-dimethoxy-2-n-propylsilacyclohexane</td>

<td>1-isopropylpentamethylene</td><td>1,1-dimethoxy-2-isopropylsilacyclohexane</td>

<td>1-n-butylpentamethylene</td><td>1,1-dimethoxy-2-n-butylsilacyclohexane</td>

<td>2,3-dimethyltetramethylene</td><td>1,1-dimethoxy-3,4-dimethylsilacyclopentane</td>

<td>1,4-dimethyltetramethylene</td><td>1,1-dimethoxy-2,5-dimethylsilacyclopentane</td>

<td>hexamethylene</td><td>1,1-dimethoxysilacycloheptane</td>

The reaction also generates the formation of BrMgOZ in which Z is a radical that is part of the group of radicals R¹, R², R³ and R⁴. This BrMgOZ, considered as a by-product in the scope of the present invention, is generally solid and can be removed, in this case, for example by filtration. After evaporation of any solvent used and any excess reagents, the alkoxysilacycloalkane can be purified by distillation, preferably under reduced pressure, for example between 1 and 1.10³ mbars.

IS 2 158 201 T3

Dimagnesium alkylene dibromide of the formula Br-Mg-A-Mg-Br can be prepared, for example, by reaction between a dibromoalkane of the formula Br-A-Br and magnesium in the presence of a solvent, for example an other such as diethyl ether, for example For example, between 0 and 50 ° C, if necessary under pressure without the volatility of the species used, you need it, taking into account the chosen temperature.

The alkoxysilacycloalkanes that can be obtained by the process according to the invention can serve as electron donors in polymerization or copolymerization of at least one olefin. For example, the silacycloalkane can be introduced into the interior of a solid catalytic component of the Ziegler-Natta type and play the role of internal electron donor.

It is also possible to use it as an external electron donor in a polymerization or copolymerization medium of at least one olefin in order to reduce the degree of solubility of the finely prepared polymer or copolymer in hexane.

For this last application (external electron donor), it is preferable to use an alkoxysilacycloalkane of formula (I) in which X and Y represent methyl radicals.

Preferably, the alkoxysilacycloalkane comprises at least one alpha-alkyl substituent with respect to the silicon atom. Particularly high HI values ​​are obtained when the alkyl substituent comprises at least 2 carbon atoms. An excellent compromise between the properties (very high HI and generally high productivity) is obtained when the alkyl substituent comprises 2 or 3 carbon atoms, as is the case of 1,1-dimethoxy-2-ethylsilacyclopentane, 1,1-dimethoxy-2- npropylsilacyclopentane, 1,1-dimethoxy-2-isopropylsilacyclopentane, 1,1-dimethoxy-2-ethylsilacyclohexane, 1,1-dimethoxy-2-n-propylsilacyclohexane, 1,1-dimethoxy-2-isopropylsilacyclohexane.

Generally, the alkoxysilacycloalkane is introduced at the rate of 1.10^-4 up to 0.2 mmol per mole of olefin to be polymerized or copolymerized. If the alkoxysilacycloalkane has been prepared in the presence of a solvent with a low Lewis character, it is recommended to remove the latter before the polymerization or copolymerization stage since it may have an undesirable influence on the structure of the polymers formed. . On the contrary, the alkoxysilacycloalkane can be introduced in the presence, for example, of an aliphatic, alicholic or aromatic hydrocarbon solvent without manifest baosic character in the Lewis sense, such as hexane, cyclohexane or toluene.

Generally, a solid catalyst component, comprising a transition metal, is introduced into the polymerization or copolymerization medium.

The transition metal can be chosen from the elements of groups 3b, 4b, 5b, 6b, 7b, 8, of the lantoanides, of the actonides, of the periodic classification of the elements, such as those defined in the Handbook of Chemistry and Physics, seventy-first edition, 1980-1981. These transition metals are preferably chosen from titanium, vanadium, hafnium, zirconium or chromium.

The solid catalytic component can be of the Ziegler-Natta type and can be, for example, in the form of a complex comprising at least the elements Mg, Ti and Cl, titanium being in the form of Ti chloride.^IV and / or You^III. The solid component may comprise an electron donor or acceptor. A catalytic component of the Ziegler-Natta type is usually the result of the combination of at least one titanium compound, a magnesium compound, chlorine and, eventually, an aluminum compound and / or an electron donor or acceptor as well as any other compound that can be used in this type of component.

The titanium compound is usually chosen from among the chlorinated compounds of titanium of the formula Ti- (OR ') xCl4-x in which R' represents an aliphatic or aromatic hydrocarbon radical, containing 1 to 14 carbon atoms, or represents COR⁵ representing R⁵ an aliphatic or aromatic hydrocarbon radical containing 1 to 14 carbon atoms, and x represents an integer nuomer ranging from 0 to 3.

The magnesium compound is usually chosen from the compounds of the formula Mg (OR⁶) nCl2-n, where R⁶ represents hydrogen or a linear or colic hydrocarbon radical and n represents an integer number ranging from 0 to 2.

The chlorine present in the Ziegler-Natta type component can come directly from the titanium halide and / or the magnesium halide. It can also come from a separate chlorinating agent such as hydrochloric acid or an organic halide such as butyl chloride.

IS 2 158 201 T3

Depending on the nature of the transition metal included in the solid catalyst component, it may be necessary to add to the polymerization medium a catalyst capable of activating the transition metal of the solid component. If the transition metal is titanium, the catalyst can be chosen from the orgaonic derivatives of aluminum.

This orgaonic derivative of aluminum can be a derivative of formula R⁷R⁸R⁹Al, in which R⁷, R⁸yR⁹ They can be identical or different, each representing either a hydrogen atom, a halogen atom, or an alkyl group containing from 1 to 20 carbon atoms, representing at least one of the R moieties.⁷, R⁸ oR⁹ an alkyl group. As an example of a suitable compound, mention may be made of ethylaluminum dichloride or dibromide or dihydride, isobutylaluminum dichloride or dibromide or dihydride, diethylaluminum chloride or bromide or hydride, din-propylaluminum chloride or bromide or hydride, diisobutylaluminum chloride or bromide or hydride. In preference to the aforementioned compounds, a trialkylaluminum such as tri-n-hexylaluminum, triisobutylaluminum, trimethylaluminum or triethylaluminum is used.

The cocatalyst can also be an aluminoxane. This aluminoxane can be linear, of the formula

R

R -^[Hello]n + 2

R2Al-O- (Al-O) n -AlR2, or cyclic formula where R represents an alkyl radical comprising from 1 to 6 carbon atoms, n being an integer number ranging from 2 to 40, preferably from 10 to 20. The aluminoxane can comprise R groupings of a different nature. Preferably, all R groups represent methyl groupings. On the other hand, cocatalyst is also understood to mean mixtures of the aforementioned compounds.

The amounts of cocatalyst used must be sufficient to activate the transition metal.

Generally, when an orgaonic derivative of aluminum is used as a cocatalyst, an amount is introduced such that the atomic ratio between the aluminum, contributed by the cocatalyst, on the transition metal (s) to be activated, ranges from 0.5 to 10,000 and preferably 1 to 1,000.

The polymerization or copolymerization process can be carried out in suspension, in solution, in gas phase or in bulk.

A mass polymerization process consists of carrying out a polymerization in at least one of the olefins to be polymerized, kept in a liquid or hypercrotic state.

The processes of polymerization in solution or in suspension consist of carrying out a polymerization in solution or in suspension in an inert medium and, mainly, in an aliphatic hydrocarbon.

For a solution polymerization process, for example, a hydrocarbon containing 8 to 12 carbon atoms or a mixture of these hydrocarbons can be used. For a suspension polymerization process, for example n-heptane, n-hexane, isohexane, isopentane or isobutane can be used.

The operating conditions for these polymerization processes in bulk, in solution, in suspension or in the gas phase are those that are usually proposed for similar cases using conventional catalytic systems of the Ziegler-Natta type supported or not.

For example, for a suspension or solution polymerization process, it can be operated at temperatures ranging up to 250 ° C and under pressures ranging from atmospheric pressure to 250 bars. In the case of a polymerization process in liquid propylene medium, the temperatures can go up to the chromic temperature and the pressures can be between atmospheric pressure and chromic pressure. For a mass polymerization process, which leads to polyethylenes or copolymers in ethylene, it can be operated at temperatures between 1.30 C and 350 C and under pressures ranging from 200 to 3,500 bars.

A gas phase polymerization process can be carried out by means of any reactor that allows gas phase polymerization and, in particular, in a stirred bed and / or fluidized bed reactor.

IS 2 158 201 T3

The conditions for carrying out the polymerization in the gas phase, mainly temperature, pressure, injection of the olefin or olefins into the reactor with stirred bed and / or with fluidized bed, temperature control and polymerization pressure, are similar. to those of the prior art processes for the gas phase polymerization of olefins. Generally, it operates at a temperature lower than the melting point Tf of the polymer or prepolymer to be synthesized and, more particularly, between + 20 ° C and (Tf-5) ° C, and under a pressure such that the olefin or olefins are essentially in the vapor phase.

Solution, suspension, bulk, or gas phase polymerization processes can involve a chain transfer agent in order to control the melt index of the polymer to be produced. As chain transfer agent, hydrogen can be used, which is introduced in an amount that can go up to 90% and which is preferably between 0.01 and one% by moles of the olefin and hydrogen combined fed to the reactor.

Olefins which can be used for polymerization or copolymerization are, for example, olefins comprising 2 to 20 carbon atoms and, in particular, alpha-olefins of this group. As olefin, mention may be made of ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-octene, 1-hexene, 3-methyl-1-pentene, 3-methyl-1 -butene, 1-decene, 1-tetradecene, or their mixtures.

The polymerization or copolymerization process according to the invention is particularly adapted to reduce the degree of solubility of polymers or copolymers in heptane when the polymerization or copolymerization medium comprises an olefin having at least 3 carbon atoms. Therefore, this process is particularly suited for the polymerization or copolymerization of propylene.

In the following examples, the degree of insolubility in heptane (represented by "HI") has been measured by extracting the polymer from the soluble fraction by boiling heptane for 2 hours in a Kumagawa type apparatus.

Examples 1 to 15

a) Preparation of dimagnesium alkyl dibromides

After purging with argon, 0.2 moles of dibromoalkane of the Br-A-Br formula are added to a 500 ml glass flask, equipped with a water cooler, with a thermometer and with a mechanical stirring system, in It forms a solution in 200 ml of anhydrous diethyl ether, over 0.46 moles of magnesium, and this preparation is left under stirring for 6 hours at room temperature. The preparation is then transferred to an addition vial.

b) Preparation of dimethoxysilacycloalkanes

They are added to a 1.5-liter glass flask, equipped with a mechanical stirring system, with a water cooler, with the addition ampoule, containing the preparation made in a), after purging with argon, the preparation carried out in a) over the course of 2 hours on 0.18 mol of tetramethoxysilane in the form of a solution in 400 ml of diethyl ether at room temperature. Heat is released and a precipitate forms. When the addition is complete, the mixture is stirred for 30 minutes, then refluxed for 4 hours. The mixture is then cooled to room temperature, the solid being removed by filtration and washed with ether, always under an argon atmosphere. The other is removed on the rotary evaporator at approximately 25 ° C under a pressure of 30 millibars. The residue contains a dimethoxysilacycloalkane of formula

OCH₃

A Yes (II) ^xoch₃

Table 2 gives the boiling points (Eb), under pressure P, of the molecules made, as a function of the nature of the bivalent radicals A used.

c) Polymerizations in liquid propylene

After purging the reactor with nitrogen, they are introduced into an 8-liter stainless steel reactor, equipped with a stirring system and with a temperature regulation, in this order: 2.5 Nl of hydrogen,

ES 2 158 201 T3 liters of liquid propylene, 30 mmol of triethylaluminum in the form of a solution in hexane with 1.5 mol / liter and then a dimethoxysilacycloalkane as prepared in b), in the form of a solution in hexane with 0 , 2 moles per liter, in order to respect an Al / Si molar ratio indicated in table 2. After stirring for 10 minutes at room temperature, 40 mg of a solid catalyst component prepared as in example 12 of US patent 5,212,132 are introduced. Still under stirring, the temperature of the reactor is then brought to 70 ° C in the course of 10 minutes, it is kept at this temperature for one hour, and the reactor is then cooled and decompressed. Table 2 indicates the results.

Example 16 (comparative)

Propylene is polymerized under conditions equivalent to those described in c) of the previous examples, except that no alkoxysilacycloalkane is introduced into the polymerization medium. Table 2 indicates the results.

TABLE 2

<td></td><td colspan="4">Preparation of alkoxysilacycloalkanes</td>

<td>Ex. No.</td><td>Nature of A</td><td>Nature of the dimethoxysila-cycloalkane obtained</td><td>Eb. (° C)</td><td>P (mbar)</td>

<td> 1</td><td>tetramethylene</td><td>1,1-dimethoxysila-cyclopentane</td><td> 63</td><td> 40</td>

<td> 2</td><td>1-methyltetramethylene</td><td>1,1-dimethoxy-2-methylsilacyclo-pentane</td><td> 80</td><td> 33</td>

<td> 3</td><td>1-ethyltetramethylene</td><td>1,1-dimethoxy-2-ethylsilacyclo-pentane</td><td> 92</td><td> 40</td>

<td> 4</td><td>1-n-propyltetramethylene</td><td>1,1-dimethoxy-2-n-propylsila-cyclopentane</td><td> 104</td><td> 40</td>

<td> 5</td><td>1-isopropyltetramethylene</td><td>1,1-dimethoxy-2-isopropylsila-cyclopentane</td><td> 95-100</td><td> 1,3</td>

<td> 6</td><td>1-n-butyltetramethylene</td><td>1,1-dimethoxy-2-n-butylsila-cyclopentane</td><td> 49-51</td><td> 5,3</td>

<td> 7</td><td>pentamethylene</td><td>1,1-dimethoxysilacyclohexane</td><td> 171</td><td> 1.013</td>

<td> 8</td><td>1-methylpentamethylene</td><td>1,1-dimethoxy-2-methylsilacylohexane</td><td> 75-78</td><td> 40</td>

<td> 9</td><td>1-ethylpentamethylene</td><td>1,1-dimethoxy-2-ethylsilacyclo-hexane</td><td> 102-105</td><td> 40</td>

<td> 10</td><td>1-n-propylpentamethylene</td><td>1,1-dimethoxy-2-n-propylsila-cyclohexane</td><td> 88-90</td><td> 10,7</td>

<td> 11</td><td>1-isopropylpentamethylene</td><td>1,1-dimethoxy-2-isopropylsila-cyclohexane</td><td> 110-115</td><td> 40</td>

<td> 12</td><td>1-n-butylpentamethylene</td><td>1,1-dimethoxy-2-n-butylsila-cyclohexane</td><td> 60-62</td><td> 4</td>

<td> 13</td><td>2,3-dimethyltetramethylene</td><td>1,1-dimethoxy-3,4-dimethylsila-cyclopentane</td><td> 68-71</td><td> 40</td>

<td> 14</td><td>1,4-dimethyltetramethylene</td><td>1,1-dimethoxy-2,5-dimethylsila-cyclopentane</td><td> 70</td><td> 40</td>

<td> 15</td><td>hexamethylene</td><td>1,1-dimethoxysilacycloheptane</td><td> 80</td><td> 40</td>

<td>16 (comp.)</td><td> -</td><td> -</td><td></td><td></td>

IS 2 158 201 T3

TABLE 2 (Continued)

<td></td><td colspan="3">Polymerization</td>

<td>Ex. No.</td><td>Al / Si</td><td>Productivity⁽g^/g⁾</td><td>HI (% in weigh)</td>

<td> 1</td><td> 10</td><td> 8.100</td><td> 61,7</td>

<td> 2</td><td> 10</td><td> 20.640</td><td> 91,3</td>

<td> 3</td><td> 10</td><td> 30.240</td><td> 96,2</td>

<td> 4</td><td> 10</td><td> 24.300</td><td> 95,1</td>

<td> 5</td><td> 23</td><td> 36.800</td><td> 94,1</td>

<td> 6</td><td> 10</td><td> 27.600</td><td> 94,5</td>

<td> 7</td><td> 10</td><td> 10.400</td><td> 82,3</td>

<td> 8</td><td> 20</td><td> 35.100</td><td> 96,4</td>

<td> 9</td><td> 20</td><td> 42.780</td><td> 97,9</td>

<td> 10</td><td> 20</td><td> 34.200</td><td> 96,8</td>

<td> 11</td><td> 20</td><td> 29.800</td><td> 96,5</td>

<td> 12</td><td></td><td></td><td></td>

<td> 13</td><td> 10</td><td> 17.600</td><td> 89,3</td>

<td> 14</td><td> 10</td><td> 27.700</td><td> 96</td>

<td> 15</td><td></td><td></td><td></td>

<td>16 (comp.)</td><td></td><td> 7.400</td><td> 60</td>