Methods, compositions and blends for forming articles having improved environmental stress crack resistance

Rzeczpospolitej Polskiej (21) Application number: 378332 (22) Application date: 16.01.2004 (86) Date and number of the international application:

04/16/2004, PCT / AU04 / 000060 (87) International application publication number and date:

2004-07-29, WO04 / 062896 (11) 211431 (13) B1 (51) Int.Cl.

B29D 23/20 (2006.01) B29C 45/00 (2006.01) C08L 101/12 (2006.01) (54)

A method of producing flexible thin-walled products

<td>(30) Priority: 2003-01-16, AU, 2003900292 2003-03-24, AU, 2003901342 2003-04-24, AU, 2003901952</td><td>(73) The right holder of the patent: Jacobs Ian Orde Michael, Mt. Eliza, AU</td>

<td>(43) Application was announced: March 20, 2006 BUP 06/06</td><td>(72) Inventor (s): IAN ORDE MICHAEL JACOBS, Mt. Eliza, AU</td>

<td>(45) The grant of the patent was announced: May 31, 2012 WUP 05/12</td><td>(74) Representative: item. stalemate. Leokadia Płotczyk</td>

PL 211 431 B1

Description of the invention

The present invention relates to a method for producing flexible, thin-walled articles such as tubes and the like, providing an improvement in environmental stress cracking strength (ESCR) and other properties by aging the article after forming its final shape.

Thin-walled tubular containers such as those used in the cosmetics industry are currently mainly produced by a combination of extrusion and cutting to size of a tube body, injection molding of a head and shoulders, and welding the body to the head and shoulders. Low melt index polyethylene (MFI) (generally less than 2) is a preferred polymer for making tubes because it generally provides the feel and flexibility properties required by customers and is workable. in the extrusion process. In addition, low MFI low density polyethylene (LDPE) provides sufficient product strength and sufficient barrier properties to make it suitable for most articles currently packaged in tubes. In cases where the barrier properties of polyethylene are not suitable for specific applications, films made of medium density polyethylene (MDPE), high density polyethylene (HDPE), polypropylene (PP) and multi-layer polymer are commonly used. As the tube body is extruded, low MFI polymers with inherently good ESCR can be used in their manufacture. In addition, being a relatively low shear process, the extrusion-molding process introduces a minimum stress and molecular orientation of the polymer molecules into the tube body during manufacture. The use of polymers, with an inherently good ESCR, the relative lack of molecular orientation in extruded and extrusion / blow molded tubes, and the relatively low pressures and processing rates inherent in the extrusion process result in the extruded tubes having a low stress and inherently good ESCR . Consequently, the relaxation of stress in extruded tubes through aging is a minimum value for the great majority of tube applications and types.

Although injection molding of flexible, thin-walled articles such as tubes has been proposed prior to new technology development techniques disclosed in PCT / AU98 / 00255 (Patent 255) incorporated herein by reference, it has not previously been possible to injection mold such articles that had relatively long, thin sections while not being very susceptible to damage during commercial or practical use. The main problems with polymers as applied to injection molded tubes are that the injection molding process of a cylindrical or other tube shape requires the polymer to simultaneously have a high MFI value which allows it to flow down a long, narrow, curved path defined by the shape of the tube without the use of excessive injection pressures, and at the same time still had sufficiently good mechanical properties, capable of withstanding the handling of the tube and providing resistance to the effects of stress cracking for many products that will be packaged therein. Tube injection molding requires that the polymer / polymer blend have flow properties capable of producing molded parts with a radius and length-to-thickness ratio of 100, and often much higher. Generally, the polymer or polymer blends are required to have an MFI greater than 10, preferably greater than 20, more preferably greater than 30, and often greater than 50. It is well known that the physical properties of polymers, especially ESCR, decrease significantly with increasing MFI, so the inherent ESCR properties of polymer / polymer blends, with the MFI values ​​required for injection molded tubes, are significantly and inherently inferior to these properties for tubes obtained by extrusion. To further aggravate the problem, forcing the polymer to flow in a mold of this size introduces severe stresses to the polymer, whereby in an article produced these stresses are "frozen" when the polymer is rapidly cooled below its crystallization temperature before these stresses can be obtained. to discharge. These stresses cause the tube to have surprisingly different and inferior properties to other products formed from the same polymers under less stringent molding conditions.

Subsequent stresses are applied to the injection molded tubes as they are filled with product and then crimped and sealed - most commonly by heat sealing or ultrasonic welding. This process involves folding the "open" end of the tube back over itself through an angle of up to 180 ° C to form a fold at the edge of the gasket. This fold is formed

The direction of the flow of the polymer during molding, which direction is shown as the direction in which the molded article shows the greatest weakness. This "folded and sealed" area, in which the tube is desired to be deformed in order to seal, is an area of ​​the injection molded tube that is particularly susceptible to stress and bending cracking. Likewise, the tube body is permanently distorted and thus additionally and permanently stressed due to the crimping / sealing process, as can be readily seen from the distorted shape of the crimped and sealed tube compared to the shape of an untreated tube. These stresses, especially those induced by permanent deformation of the article after crimping and sealing, but also those that arise from the application of pressure and bending to the tube during normal use, cause significant deterioration of the ESCR and other physical properties of the polymers.

From which an injection molded article is made, the consequent necessity of using polymers that exhibit exceptionally good ESCR and other physical properties when forming the desired articles. Such polymers / polymer blends can have many disadvantages over other polymers / polymer blends such as their higher cost, the need for longer cooling periods (and therefore longer cycle times), to show more stiffness, i.e., less "feel", the need for more intensive or expensive mixing of ingredients, etc.

The following examples show the extremely high stresses that are introduced into the tubes during their manufacture by an injection molding process as opposed to extrusion.

Tubes measuring 120 x 35 mm were injection molded using a DuPont 2020T polymer, a polymer with an MFI = 1.1, commonly used in the commercial manufacture of extruded tubes, and which DuPont describes as "particularly suitable for injection molded closures and extruded piping systems. where flexibility and maximum environmental stress cracking are required ”. Injection molded tubes were made with great difficulty and the process itself required very high injection pressures and temperatures to simply fill the mold with 2020T polymer. During each molding, significant core shift / bend was noted, caused without any doubt by the extremely high injection pressures that were required. In addition, it was noted that the tubes showed an almost complete lack of resistance to bending in the flow direction of the material, with significant fracture already causing the tube to be squeezed by hand less than 5 times. Environmental stress cracking of the same tubes was tested using an ESCR test as described herein and it was found that despite the claims that "maximum resistance" to environmental stress cracking was found to be totally unsuitable for forming thin wall tubes by injection molding. This is in direct contrast to what is known as the "favorite polymer" for tubes made by an extrusion process. The dramatic deterioration in the properties of the 2020T polymer during injection molding is almost exclusively due to the extremely high level of molded and oriented stresses, compared to those found in tubes extruded from the same material.

In another illustration of the very high level of forming stress inherent in injection molded tubes, 150 x 50 mm tubes were molded from Dowlex 2517 polymer, which was LLDPE with an MFI of 25. In the Dowlex LLDPE brochure, Dow reports that LLDPE polymers have substantially better ESCR properties than the equivalent but high pressure LDPE. To illustrate the difference, Dow states in this brochure that, in one comparative test, Dowlex LLDPE high-flowability polymer exhibits an ESCR in oil approximately 80 times higher than the ESCR obtained with high-pressure LDPE, with similar density and MFI (5,700 hours in oil). compared to 70 hours). The brochure further states that LLDPE polymer has an ESCR of approximately 10 times higher than LDPE when immersed in a 10% Teric solution at 50 ° C (225 hours versus 26 hours). However, in contrast to these observations, we have found that when these polymers are formed into thin-walled tubes and the ESCR then tested using the ESCR test as described herein, both the Dow Dowlex LLDPE 2517 polymer and the Kemcor LD 8153 polymer (high pressure LDPE with similar MFI and similar density) performed poorly in 10% Teric N9 solution at 50 ° C, and both failed within 20 minutes and the ESCR was on the order of 600 times lower than indicated in the brochure. The exceptional degradation in ESCR level of both polymers when molded by injection molding into tubes is almost exclusively the result of the high level of molded and oriented stresses in injection molded tubes.

PL 211 431 B1

As an indicator of the degree of strain increase in the area of ​​the tube that is folded and sealed relative to the unsealed (i.e. open) tube, the deformation in the area obtained after sealing was calculated by the formula:

Deformation in polymer = fold radius / square of strip thickness

Assuming a nominal radius for a flat polymer strip of 1 meter in length and a strip thickness of 0.5 mm (typical wall thickness in a tube), the deformation of unsealed polymer is 0.00025. After sealing, the radius of the strip at the edge of the gasket is in the order of 0.65 mm, resulting in a calculated deformation of 0.385. In other words, sealing the tube increases the deformation in the polymer by more than 1600 times as compared to the deformation in the unsealed tube. For extruded tubes, with their polymer inherently higher ESCR and much lower stresses in the molding treatment, this increase in strain raises several problems in terms of ESCR and / or tear strength level. That is, aging articles prepared using these polymers in conjunction with an extrusion process is not likely to result in an apparent and / or commercially valuable improvement in the ESCR and tear strength of the article. However, the applicant has found that when injection-molded thin-walled flexible articles with their much higher molding and oriented stresses using polymers, with a lower ESCR in nature, and thus having a higher inherent bendability and deterioration of ESCR, it is due to the process due to the process. aging can make a significant difference for both the ESCR and / or the tear strength of the article. Such an improvement may mean the difference between functionality and non-functionality of a product from the point of view of its commercial purpose.

The present invention relates to a process for the production of thin-walled flexible articles, wherein a blend of (a) at least one polymer and (b) at least one high melt flow compatible polymer having an MFI greater than 100 is formed into a flexible article. thin-walled by injection.

Preferably the high melt flow compatible polymer has an MFI greater than 100, more preferably the high melt flow compatible polymer has an MFI greater than 300.

In a preferred embodiment, at least one of components (a) and (b) is a metallocene or similar catalyst system polymer, more preferably both components (a) and (b) are propylene and / or ethylene polymer or copolymer.

Preferably, component (a) is present in an amount ranging from 40 to 99.9% by weight of the blend, the total weight of which is equal to the sum of components (a) and (b), and which forms a continuous or co-continuous phase in the blend.

In a preferred embodiment, the polymer (a) and / or (b) is polypropylene, having varying tactics throughout its structure.

Preferably both components (a) and (b) have an MFI greater than 100.

A preferred embodiment further employs an aging of thin-walled injection molded articles.

Preferably, the blend further comprises (c) nanoparticles dispersed therein.

Preferably, the content of extractable substances in the compositions according to the invention and the compacts obtained therefrom is preferably less than or equal to 2.0% by weight, more preferably less than or equal to 1.6% by weight, most preferably less than or equal to 1.4% by weight, which is measured by ASTM D-5227.

In a preferred embodiment, the at least one polymer has a higher crystallinity than that of the at least one compatible polymer.

We have now found that aging a flexible, injection molded thin walled article exactly before, during, or after the article is filled and deformed to the final desired shape significantly improves the ESCR and many other physical properties of the article such as polymer flow tear resistance. as measured using the Gullwing test method (ASTM D-1004). These improvements are most noticeable in areas of the product that have been subjected to additional stresses applied thereto, such as that occur as a result of any deformation of the product during and after sealing, or as a result of a load applied to it during, for example, stacking. The added benefit of aging according to this

According to the invention, by increasing their ESCR etc., polymers / polymer blends can be used to produce flexible thin-walled articles, which flexible, thin-walled articles, if not subjected to aging, would be of marginal importance or would be unsuitable. for packing strictly defined products. During the aging process of the article, if it is heated or otherwise treated to sufficiently soften, and / or in cases where the article is sufficiently supported to prevent undesirable deformation, the polymer may melt and the article may take a new shape due to application of appropriate forces exerted by various types of devices.

While the proposed theory imposes certain limitations, it is believed that the rapid cooling of the polymer during the injection molding step, from the molten state to a temperature below the solidification temperature of the polymer, causes various stresses and strains "stored" in the solidified piece, and that successive stresses are introduced, as a result of product deformation caused by the sealing process. These stresses make the article more susceptible to attack by stress fracture inducing agents and to physical bending and thus failure. This, in particular, takes place in the period immediately after filling and sealing when, due to molding deformation resulting from sealing, the stresses within the molded part are of the highest value (they are at a level that "weakens" and dissipates over an extended period of time) and the stress fracture agent is in direct contact with the article and can "attack high stress areas during the period after filling and sealing, causing failure." It is believed that by aging the polymer, stresses are reduced before the stress crack inducers are able to "attack" the stressed polymer, causing failure. If the stresses are not released immediately, it is believed that for many formulations containing the polymer, the stress crack agent is capable of causing damage to the article before "normal" polymer relaxation reduces the susceptibility of the article to failure.

The degree of stress during forming, and hence the degree of reduction, ESCR and the characteristics of other properties may vary somewhat from part to part and over time. Thus, it is difficult to reliably and accurately compensate for the variation in the reduction in ESCR between the compacts while abandoning an aging treatment. Another complication is caused by the gradual reduction of stress over time, along with the fact that the level of stress reduction will depend on the conditions (primarily time and temperature) in which the articles are stored before and after filling and sealing. It is not possible to accurately and consistently predict how long this may take for all tubes made of a particular polymer-based formulation to make them usable by reducing intrinsic stress. For this reason, inter alia, to minimize the possibility of commercial damage due to inadequate ESCR and the nature of other properties, polymers with proven, exceptionally good ESCR values ​​now generally need to be used when under tension. This requirement has many potentially negative aspects, particularly in areas such as potentially higher polymer cost / unit, increased cycle times and less than ideal "feel" and flexibility. It is therefore advantageous for the stresses in the forming process to be released before they begin to substantially adversely affect the commercial functionality of the thin walled article.

It has been found that while stresses induced during molding in an injection molded article are released to a greater or lesser degree, before a product capable of producing a stress crack into the article will have sufficient time to contact the polymer under tension to cause or to initiate a fracture, then flexible, thin-walled injection molded articles can be produced with increased ESCR and other improved properties. Moreover, it has been found that aging of articles allows a much wider variety of polymers and their blends to be used to make commercially viable flexible, thin-walled articles than is possible without the aging operation.

If there is a significant amount of time between forming and filling operations with sealing (for example, if the product is formed in one location, packaged and then shipped elsewhere for filling and sealing) and it is desirable to age the casting before shipping the product - most conveniently immediately after molding - this is by aging the molding operation and you can still achieve many of the benefits of aging thoroughly before, during and / or after deformation of the product. The benefits of doing so may not be as clear as those

These may be obtained by aging after deformation of the article, but may nevertheless, depending on the nature of the polymer and the molding conditions, deserve attention.

The benefits that can be obtained by aging after the forming operation but before filling are most noticeable in those areas of the casting that are subjected to at least additional stress after crimping and sealing. These areas are most often those that are relatively large distances from the "pinch" and "seal" areas - for example, areas that are relatively close to the head and shoulders of the tube. We have found that the areas of the part that were aged were allowed to cool (if the aging process raised the temperature of the part above its temperature prior to aging) and then subjected to significant deformation such as occurs in and around the sealed area during the crimping and sealing operations. may show a dramatically reduced ESCR characteristics, in relation to the same, significantly deformed areas in equivalent moldings, but not aged. This is illustrated by the ESCR test as described herein in which three sets of polymer blend strips taken from the same area of ​​the compacts were subjected to the subject ESCR test. One set of straps was aged after clasping with staples, the second set was not aged, and a third set of straps was aged before clasping with staples. The ESCR scores were as follows:

• Only 4% of the belts, sealed with buckles, were damaged within 190 hours • 25% of the non-aged belts were damaged within 190 hours • Almost all belts (94%), aged before buckling, were damaged within just 3.5 hours.

As shown by the above results, aging the tubes when they are in a stressed state greatly improves their ESCR, as compared to non-aged tubes, while aging the tubes under tension and then stressing them causes a drastic reduction in ESCR.

Aging is generally defined as the process of removing or reducing distortion and stresses in thermoplastics. This is often achieved by heating the substance to be aged and then allowing it to gradually cool down. Of the two successful methods often used to age thermoplastics, one is a method that removes the thermoplastics from a heat source and the other is a method that causes the heat from a heat source to diminish. Both methods are often used for aging bulk items as they require heating inside and outside of thermoplastics. Heating with the first method is carried out in lehrs, and the second method is carried out in furnaces. As additional methods for aging bulk thermoplastic objects, there can be mentioned those that use infrared radiation. Thermal aging is often the preferred method of aging because simple tooling and techniques are widely available and this step is inexpensive. In other embodiments, aging may be accomplished by applying pressure, compression, or stretching for a short period of time.

We are currently seeing a growing interest in reducing the stresses and strains of thermoplastics without using bulk aging techniques such as those described above. For this reason, a surface aging method that surprisingly and simultaneously protects the physical and chemical properties of the thermoplastics may be used to reduce distortion in thermoplastics. Surface aging is defined as heating the outer layer of the thermoplastic, the thickness of which is no more than half the thickness of the area to be aged, such as 0.25 mm for an article with a wall thickness of 0.5 mm. Moreover, there is no limitation on the heat source used in this surface aging other than that it does not heat the outer thermoplastic layer and the inner thermoplastic part to the same temperature, the inner part being defined as any part of the thermoplastic, not containing the outer layer as previously defined. Thus, heat can reach the inner part; however, after surface aging of the outer coating layer, the inner part is cooler than the outer layer. Therefore, aging throughout the mass of the object becomes impossible. Surface aging is especially effective in improving the ESCR of the thin-walled flexible article when the surface that is being aged is the surface that will come into contact with the stress crack agent.

PL 211 431 B1

The inner wall of a tube or other container, preferably the outer wall of a tube or other container, is an example of a surface against which surface aging is particularly effective. This is because an aged inner wall of a tube or other container turns out to be a stress fracture factor and its surface has a reduced stress and thus an improved ESCR, relative to the non-aged inner wall, thereby reducing the likelihood that the stress fracture factor will be a stress fracture factor. capable of initiating a stress fracture that could possibly damage the tube or container. If the outer surface of the tube or container is an aged surface, the stress fracture factor will be able to initiate a fracture in the non-aged inner surface with which it is in direct contact, thereby potentially weakening the tube or container. Aging of the inner surface of a tube or other container can be accomplished by blowing hot air on the surface in question, bringing the source of radiant heat a short distance to the inner surface, or by other suitable method well known to those skilled in the art.

Aging the injection molded thin walled article can be made easier by one or more methods selected from a great number of possible. For example, the aging step may consist of exposing the plastic material of the article to various types of electromagnetic radiation, such as infrared, ultraviolet, and microwave radiation. Alternatively, acoustic energy, supersonic and / or ultrasound, electric energy, electron arc, electron beam, plasma (e.g. halo, glow discharge, etc.), steam, heated gas (e.g. hot air), magnetic fields, radiation may be used. ionizing, lasers, radio frequency and direct contact with heated or vibrating surfaces. Preferably, the aging operation is performed by applying heat to the plastic material immediately before, during or immediately after the body is adapted to the shaped product form.

The aging process may be performed in situ by filling the article with a medium having a temperature high enough to facilitate aging of the article by transferring heat from the medium to the article itself. In this case, the heating medium may be placed before, during or immediately after deformation (if any) of the article. Due to the thin-walled nature of the article, the temperature of the areas of the articles which are in contact with, or are relatively close to, the medium may reach a level close to or equal to the temperature of the medium itself. For example, while a well-defined area of ​​the article to be sealed should preferably not be in contact with the medium as soon as the medium is introduced into the article, the temperature of the area to be sealed will tend to be at the temperature level of the medium. While this temperature is sufficient to initiate aging, it will cause partial or complete aging of areas of the article, including the area of ​​the article being sealed. The in situ temperature of the aging medium is preferably higher than 18 ° C, more preferably higher than 22 ° C, even more preferably higher than 25 ° C, even more preferably higher than 30 ° C and most preferably higher than 30 ° C. 35 ° C.

Alternative aging processes using heat include immersing the article in, or passing it through a bath, oven, or other device containing or capable of directing the article into, or exposing the article to, a heating liquid or gas or other aging agent. For example, the articles may be immersed in a hot water bath for a period of time sufficient to warm them to the required temperature. The precise residence time in the hot water bath can depend on many factors, such as the shape and / or thickness of the articles and whether the water bath is stationary or vigorously agitated, and whether the size of the bath causes fluctuations in most articles. bath temperature, and other factors. This method of aging is especially useful in cases where there is a need for the contents containing the articles to also be heated above a specific temperature, such as when distilling from the retort of certain food products. The articles can then be removed from the water bath, dried, and cooled to ambient temperature.

In other embodiments, radiant heating such as infrared heating is used. One advantage of radiant heating, especially infrared, is the speed of such heating that can be practiced. Yet another advantage is that a separate drying step can be eliminated.

PL 211 431 B1

When the aging agent is one or more types of electromagnetic radiation, the article containing the polymer should be irradiated for a period of time at least sufficient to absorb sufficient energy to relieve stress from the polymer before stress cracking occurs therein. The irradiation is performed at one or more frequency ranges which are absorbed by the polymer and which are effective in relieving stress without causing little or no softening or flow of the polymer induced by heat. As electromagnetic radiation, infrared, visible, ultraviolet, microwave, radio, laser and other types of electromagnetic radiation are used.

The aging treatment may, depending on the type of plastic and the type of product, be carried out before, during or after the deformation of the product. If the aging process is performed prior to deformation of the article, it is preferable that the aging process still affects the polymer during the deformation process. For example, if heat is used to perform the aging and the heat source is removed or significantly reduced in power prior to deformation of the article, the plastic material should still be hot enough during and after the deformation process to allow aging of the deformed article. Another method of aging with heat is to store the final, packaged product in heated or naturally hot storage areas where the temperature is continuously or intermittently increased or allowed to increase to 22 ° C or more, more preferably 25 ° C, or higher, even more preferably 27 ° C or higher, even more preferably 30 ° C or higher, and most preferably 35 ° C or higher, for a sufficiently long time, to cause aging of the article or part thereof, as measured by an increase in ESCR and / or Gullwing tear strength in the direction of polymer flow, compared to the non-aged article or part thereof.

In order to obtain satisfactory results, it is not necessary to age the entire product. If desired, the aging process may be applied to one or more areas of the article where aging has been determined to produce particularly satisfactory results, such as those areas in the injection molded article that are most susceptible to ESCR or other mechanical damage. Partial aging of an article can be achieved, for example, by aging some parts of the article with infrared radiation while protecting other parts of the article from this radiation. In the case of a tube, areas that can be satisfactorily and selectively aged include the pinched / sealed and adjacent area and other areas of the tube that deform and are consequently exposed to additional and unusual stresses as a result of the crimping / sealing process. .

Moreover, aging may take place in one or more stages. For example, part of the article may first be aged by filling it with, for example, a hot, fluid medium. This will age mainly those areas of the article which are in contact with and / or close to the hot liquid medium. When the article is a tube, the primary aging process will primarily age the body of the tube, although if the medium is hot enough and a sufficient period of time is provided, other areas of the tube, such as the area to be crimped / sealed, may also age. Following the preconditioning operation, the tube may then, in a separate operation, be crimped and sealed at the open end, thereby aging the portion of the tube.

The extent of the required aging of a specific product can be determined experimentally; it may vary depending on the degree / severity of the detrimental effect of the product packaged in the article on the article and the type of plastic material used to form the article and the molding conditions used to manufacture the article and the desired properties of the article after processing. Particularly harmful products (i.e. with high stress crack potential) can advantageously be packaged into products which have been aged more intensively than the same product intended for a less harmful product. Likewise, articles with higher stress levels due to, for example, their shape, their manufacturing conditions and / or the magnitude of the additional stresses exerted on them through filling, crimping and sealing, etc., may benefit from more extensive aging than would otherwise be expected. that's the place otherwise.

Moreover, it is noted here that there is no limitation as to the heat sources used, due to the molecular arrangement of thermoplastics. Therefore, the heat source and the thermoplastic can

It may be mobile, the heat source may move while the thermoplastic remains stationary, or vice versa.

As soon as the product is heated to the temperature within the required limits, the product may be cooled or, if appropriate, allowed to cool. Various cooling techniques may similarly be used in the cooling step. Dry cooling techniques are particularly suitable for use in the invention. For example, articles can be cooled to room temperature using forced gas convection cooling. Alternatively, the articles may be allowed to cool naturally, that is, without the use of cooling accelerators. The air may be at room temperature or, if desired, it may be cooled in order to shorten the duration of the cooling steps. In yet another embodiment, ultrasonic heating may be used in place of radiant heating. In still other variants, heating with forced hot gas convection may be used.

The products can be introduced into an oven or other heating zones using various combinations of radiant and convection heating.

The type of plastic material for a thin-walled article is not particularly limited as long as it is capable of being molded by injection molding a flexible, thin-walled article. Indeed, preferred forms of the plastic material are set forth below in accordance with further aspects of the invention.

Australian Patent Specification PCT AU98 / 00255 states that it is generally possible to obtain by injection molding flexible, thin-walled products having relatively long, thin-walled segments, by selecting polymers used in the injection molding process, characterized by a failure-free time of longer than 10 hours as tested according to the following ESCR testing procedure:

i) a plurality of strips (preferably 6 or more) of a polymer or blend of polymers, incorporated at any point in the molding processing, intended for the final article having cross-sectional dimensions - a thickness of 0.65 mm and a width of 10 mm, are injection molded, high shear, long flow conditions, the same as or similar to the conditions that are intended to be used in the manufacture of a flexible, thin-walled article;

(ii) the tapes are folded back over onto themselves and sewn together 3 mm from the fold;

iii) the bent tapes are immersed in a solution of a stress crack inducer such as ethoxylated nonylphenol, for example a 10% solution of Teric N9 (nonylphenol ethoxylated with 9 moles of ethylene oxide) from Orica Australia Pty Ltd) and allowed to maintain a temperature of 50 ° C; and (iv) the straps are inspected for signs of breakage, with any signs of breakage being the failure; and

(v) time to failure is the time after which 50% of the straps show signs of failure.

The ESCR test, described above, is designed to simulate stresses exerted on the area of ​​the tube that is crimped and sealed after the crimping and sealing operation has been performed, being that area of ​​the crimped and sealed tube that is particularly susceptible to bending and ESCR failure. The need for this special test arose because "standard" ESCR tests such as ASTM D-1693 are completely unsuitable for determining the ESCR of polymers when they are formed into flexible, thin-walled moldings and then crimped and sealed - a fact clearly demonstrated by comparing the ESCR results obtained with Dupont 2020T and Dowlex 2517 polymers using the "standard" ESCR test and the test mentioned above.

In general, for a polymer blend suitable for the manufacture of flexible, thin-walled articles, the ESCR, checked according to the above procedure, should be greater than 10 hours. Preferably the ESCR of the polymer blend is greater than 100 hours, more preferably greater than 200 hours, and most preferably greater than 360 hours. Where the thin-walled product is a tube or other container used to package a mixture such as a moisturizer or shampoo, which may be quite aggressive to the thin-walled product and deteriorate its properties over time, choose a polymer blend having an ESCR of sufficiently high in such a way that the thin-walled product formed from this mixture would be able to withstand the hardships of use, despite possible deterioration of properties, caused by the aggressive nature of the materials inside the thin-walled product.

PL 211 431 B1

Where a thin-walled product is used to pack a relatively inert material, one can settle for a lower ESCR.

The ESCR test as defined above can be performed using a wide variety of stress crack agents. A preferred stress crack inducer is Teric N9, a 9 molar nonylphenol ethoxylate, available from Orica Australia Pty Ltd. Other nonylphenol ethoxylates can also be advantageously used. Other stress crack agents may be used and may be selected depending on the desired end use; these are, for example, mineral oils, cationic surfactants, solvents, and other agents that will be readily apparent to those skilled in the art.

The ESCR test as described above is performed under forming conditions that are the same as or similar to those used in the manufacture of the thin-walled articles. For example, where one intends to produce a thin walled article using melt oscillation introducing molding, it is preferable to perform ESCR tests on plaques made from compacts prepared using melt oscillation methods. Likewise, the molding conditions that are intended to be employed in forming thin-walled articles, such as injection rate, injection pressure, melting point, temperature of the mold core and cavities, etc., are preferably used for the production of the moldings used in the ESCR test.

The suitability of a polymer or blend for use in the present invention, and potentially beneficial effects thereof, can be determined by performing the ESCR test as described above, but preferably with the following additions and modifications:

• Prepare two sets of 6 or more strips for ESCR testing • After folding and sewing two sets of strips, subject one set of strips to the proposed aging treatment (for example, at a temperature elevated to 50 ° C for 30 minutes), allow the strips to cool to 22 ° C and keep at this temperature for 2 hours • Place two sets of strips in the stress crack medium as previously described for the ESCR test

The potential benefit of the present invention can be assessed by comparing the ESCR and / or Gullwing tear strength results for a polymer tested with and without aging while under tension. The present invention is particularly suitable and useful for thin-walled articles where the difference in time to failure, as measured by the ESCR test as described herein, between the aged and the untreated strips of the polymer blend used to make the failure. of the product is more than 5 hours, preferably more than 10 hours, more preferably more than 20 hours, even more preferably more, more than 30 hours, more preferably more than 50 hours, even more preferably more than 100 hours and most preferably more than 350 hours.

Alternatively, the suitability of a polymer or polymer blend for use in the present invention can be determined by comparing the Gullwing tear strength (measured in the direction of the polymer flow) for aged and untreated strips cut from compact parts such as can be used in an ESCR test. the strips are of dimensions suitable for the performance of the test. Aged strips preferably have a tear strength of more than 5% greater than that of non-aged strips. Preferably, this strength is more than 10% greater, more preferably more than 15% greater, and most preferably more than 20% greater. The tear strength of an injection molded, flexible, thin-walled article is particularly important when the article is made of polymers that tend to break or tear with relative ease, such as polypropylene. This tendency to crack or break is often exacerbated when polymers are formed into articles that are, by the very nature of the molding process, tooling design and molding conditions, highly oriented. The Gullwing Tear Test is particularly useful for assessing the suitability of polypropylene-based polymers and blends thereof (including those cited above), among other polymers, for the manufacture of injection molded flexible thin wall articles, as such polymers and their blends can pass the ESCR test well. but because of their poor tear strength, they are still unsuitable for making commercially useful injection molded flexible, thin-walled products. As mentioned above, aging such

By making the articles according to the present invention, the tear strength of the articles can be increased to a level where the article becomes commercially viable.

The benefit of the present invention is illustrated by the following example. From a formulation containing 25% Profax SC973 (PP, MFI = 100, from Basell), 34% Engage 8401 (mPE, MFI = 30, from Dupont - Dow) and 41% WSG 189 (LDPE, MFI = 100, with from Qenos), cylindrical tubes 165 mm in length and 0.5 mm in thickness were formed using molding conditions to introduce maximum stress into the molded tubes. The ESCR values ​​of both aged and unaged strips cut from the tubes were determined using the ESCR method described herein. As a result of the measurement, more than 60% of the unaged strips taken from the unaged tubes showed worse ESCR results within 2 hours, while no damage was noticed in the strips taken from the tubes aged by heating the stitched strips for 30 minutes. at 50 ° C, cool to 22 ° C and condition at 22 ° C for 2 hours. In addition, 94% of the unaged strips, compared to only 22% of the aged strips, showed damage after 360 hours. This is evidence that the use of the present invention significantly improves the ESCR of injection molded flexible thin walled articles and allows the use of many blends of polymers that may not have an adequate ESCR when inspected according to the method described herein and which are intended for use in manufacturing. commercially valuable, flexible, thin-walled products.

The advantages of the present invention are most noticeable in flexible, thin-walled articles having a thin section, the thickness of which is less than 1 mm, and where the thin section is substantially continuous for more than 50 mm, in the direction of flow of the molten polymer blend in the mold preferably greater than 90mm in the flow direction of the molten polymer blend in the mold, and most preferably greater than 100mm. towards the flow of the molten polymer blend in the mold.

Blends containing isotactic polypropylene and ethylene-propylene copolymers in which ethylene constitutes from 4% to 35% by weight, both components having isotactic propylene chains long enough to crystallize, are described in WO 00/01766. Such blends are suitable for making flexible tubes and other containers that are subjected to heating by methods such as hot-filling the product that the container should contain and / or treating the filled container with heat using methods such as retort distillation. The blends corresponding to the above description contain 1% to 95% by weight of isotactic polypropylene and an ethylene-propylene copolymer wherein the propylene content is more than 65% by weight of the weight of the copolymer, and preferably more than 80% by weight of the weight of the copolymer. copolymer.

Blends of various polypropylene polymers and polymers of compounds from the range of α-olefins, such as ethylene, propylene or butene, may also be particularly useful in the manufacture of flexible tubes and other containers that are heated by methods such as hot-filling with the product that the container should be filled with. contain and / or treat the filled container with heat, using methods such as retort distillation. The mixtures corresponding to the above descriptions include: as component (a) at least one isotactic, syndiotactic or atactic polypropylene homopolymer or an α-olefin copolymer, preferably a copolymer of one or more α-olefins containing from 2 to 20 carbon atoms per molecule, more preferably a copolymer of one or more α-olefins containing from 2 to 8 carbon atoms per molecule, prepared with a wide variety of catalysts such as a metallocene or similar catalysts, and as component (b) at least one ethylene copolymer, propylene and / or butene, preferably a copolymer of an α-olefin such as ethylene, propylene or butene having 2 to 20 carbon atoms per molecule, more preferably an α-olefin copolymer such as ethylene containing 2 to 8 carbon atoms per molecule prepared with a wide variety of catalysts such as metallocene or similar catalysts and characterized by super-random distribution of the copolymer within and between the molecular chains of the polymer. The blends contain from 1 to 99% of component (a) and from 99 to 1% of component (b), preferably from 30 to 99% of component (a) and from 70 to 1% of component (b), even more preferably from 45 to 99 % of component (a) and 55 to 1% of component (b), even more preferably 55 to 99% of component (a) and 45 to 1% of component (b), and most preferably 60 to 99% of component (a) ) and from 40 to 1% of component (b).

As noted in PCT / AU98 / 00255, AU 200020674 A1, AU 72146-99, and Australian Patent Nos. 2002200093 and 2002100211, all of which are incorporated herein by reference, mixing at least one compatible agent with each at least one polymer often results in a significant increase in ESCR. Such

The incorporation of a compatible agent also often improves the Gullwing tear test performance of the blend. Such at least one compatible agent is preferably a polymer (also referred to herein as "compatible polymer") which, when mixed with at least one polymer, produces blends having properties that, when used to form flexible, thin-walled articles. such as flexible injection molded tubes, are superior to those of the starting components or pure polymers. This phenomenon is advantageously used in the development of blends suitable for the injection molding of flexible, thin-walled articles according to the invention.

The particular category of compatible agents, as stated by the applicant, is primarily useful in blends for the production of flexible, thin-walled articles by injection molding. These are compatible polymers with a high melt flow rate. It has been found that blends containing such compatible agents are particularly useful in the process described above in relation to the invention, and may also be useful in processes that do not employ the above-described aging step of the molded article.

Therefore, according to the invention, a method of producing flexible, thin-walled articles has been developed by forming a blend containing (a) at least one polymer and (b) at least one compatible polymer, with a high melt flow rate, having a higher MFI, than 100, by injection.

The compatible high melt flow rate polymer has an MFI greater than 100, preferably greater than 200, more preferably greater than 300, and may have an MFI greater than 500, even greater than 1000, and even more. greater than 1500. One or more or more of the polymer components or both components (a) and (b) are preferably prepared with a metallocene catalyst or a similar catalyst system.

In the polymer blend, component (a) is preferably about 40 to about 99.9% by weight of the total weight of components (a) and (b) and forms the continuous or co-continuous phase of the blend. The polymer blend is generally prepared by mixing components (a) and (b) under high shear or otherwise suitable for homogeneous blending, for example in parallel or series-connected reactors producing, in each of them, one or more blend components a) and / or b). An example of a suitable mixing device may be a device such as a twin screw extruder. Another way to obtain a homogeneous blend will be apparent to those skilled in the art.

The polymer blend may be prepared by extruding some or all of the components of the polymer blend, and the resulting product is chopped and used in the injection molding process of the present invention. Alternatively, the polymer blend may be provided as ingredients and mixed prior to and during the melting of the polymer blend in the present process.

The high melt flow compatible polymer may be selected from the group of compounds such as ethylene vinyl acetate, ethylene vinyl alcohol, plasticized polyvinyl acetate, and polyvinyl alcohol; polyolefins substituted with an alkyl carboxyl group; organic acid anhydride copolymers; epoxy group-containing copolymers; chlorinated polyethylene; ethylene-propylene-butylene copolymers etc .; ultra-low-density, ultra-low-density, medium-high-density polyethylene and its copolymers; polypropylene, polybutylene and their copolymers; polyester ethers; polyether esters (such as DuPont's Hytrel rank); acrylonitrile methacrylate copolymers; block copolymers having styrene as end blocks; half esters; amine and alkoxysilomethane grafted polyethylenes; vinyl addition polymers; styrene butadiene block copolymers; acid grafted polyolefins; vinylpyrrolidine grafted polyolefins; block copolymers of dihydric monomers; unsaturated propylene grafted esters; modified polyolefins containing amide, epoxy, hydroxyl or acyloxy functionalities with 2 to 6 carbon atoms per molecule; other polymeric compatible agents suitable for use with polyolefins; molecules coated with any of the above compounds; and mixtures thereof. In the above compatible polymers, functional groups are generally incorporated into a modified polyolefin as part of an unsaturated monomer that is either copolymerized with the olefinic monomer or grafted onto the polyolefin to form a modified polyolefin. Mention may be made here of ethylene and / or propylene ethyl and / or methyl acrylates and resins which are copolymers of ethylene acrylic acid and methacrylic acid with ethylene.

PL 211 431 B1

Blends of compatible polymers such as a neutralized ionomer such as Surlyn (ex Dupont) and EEA and / or EMA and / or EMAA are also possible. For example, a partially neutralized low MFI ionomer such as Surlyn 9970 (MFI = 14) can be combined with a high MFI EMA such as Nucrel 599 (ex Dupont) (MFI = 500) to give a blend of compatible polymers with a higher MFI than would be obtainable for Surlyn alone, while still retaining the beneficial properties of pure Surlyn. It will be appreciated by those skilled in the art that the above example is just one possibility chosen from a very wide variety of compatible polymer combinations falling within the scope of the present invention.

Alkyl carboxyl-substituted polyolefins include those substituted polyolefins in which the carboxyl groups are derived from acids, esters, anhydrides, and their salts. Carboxylic acid salts include neutralized carboxylic acids and are often referred to as ionomers (e.g., Surlyn). Typical acids, anhydrides and esters include methacrylic acid, acrylic acid, methacrylic acid, ethacrylic acid, glisidyl maleate, 2-hydroxyacrylate, diethyl maleate, maleic anhydride, maleic acid, esters of dicarboxylic acids, etc. As preferred examples, unsaturated copolymers can be mentioned. carboxylic acids, ethylene series derivatives such as methacrylic acid and acrylic acid with polyethylene and their salts. As copolymers of organic acid anhydrides, there may be mentioned copolymers of maleic anhydride and copolymers of anhydrides containing an aromatic ring.

Poly-2-oxazoline compounds and fluoroelastomers are also suitable as a high melt flow compatible agent. It is preferred to include 1-40%, most preferably 2-20% of the poly-2-oxazoline compounds. These compatible polymers improve the adhesion of the polyethylene blend to a variety of substrates which may make them suitable for printing or labeling. The homogeneously blendable compatible polymer is an α-olefin copolymer as the substrate grafted with an amount of an aromatic polymer containing a monovinylidene group. Preferably, the α-olefin copolymer as substrate is a terpolymer, i.e. the polymerization product of three monomers, such as ethylene, propylene and an uncoupled diolefin. Various aromatic and aliphatic olefin copolymers are particularly useful as compatible and high MFI compatible agents. Among this group, as examples of copolymers, especially useful for the production of flexible, thin-walled products, one can mention block copolymers of the composition styrene - butadiene-1,4 butylene - styrene (SBBSA copolymers), copolymers of the composition styrene - butadiene - styrene (SBS copolymers) and copolymers composed of styrene - ethylene - butylene - styrene (SEBS copolymers).

The high melt flow compatible polymer according to the second aspect of the present invention is a compatible polymer or is a component of a mixture wherein at least one compatible polymer generally has an MFI greater than 100, preferably greater than 200, more preferably greater than 300 and potentially more than 500 or more than 1000, and even more than 1500. Unless otherwise stated, the MFI is measured according to ASTM D 1238 (condition 190 ° C / 2.16 kg). Unless otherwise stated, the MFI of polymers in which propylene is more than 50% by weight of the polymer is measured according to ASTM D 1238, at 230 ° C / 2.16 kg condition. Preferably, as the high melt flow compatible polymer of the present invention, a polypropylene homopolymer, a block or random polypropylene co- or terpolymer or a mixture thereof is used in which the propylene-based polymer component has an MFI value (as measured by ASTM D 1238 using condition 230 ° C, 2.16 kg), equal to 100 g / min or more, often more than 200, sometimes more than 300, and even more than 1500. Preferably, an isotactic or syndiotactic polypropylene is used as the propylene-based polymer component as a homopolymer or copolymer having an MFI within the ranges specified above. Preferably, the propylene-based polymer component will have a MWD ranging from 1.8 to 4.0 and a narrow component composition distribution that is characteristic of metallocene or similar catalyzed propylene-based polymers. However, propylene-based polymers, such as those cited in US Patent No. 6,476,173, and incorporated herein by reference, and having MWD values ​​as high as 20, will often give good results. Polymers such as those set out above are conveniently prepared using a stereospecific metallocene catalyst system. Random blended ethylene / propylene / vinyl aromatic polymers such as ethylene / propylene / styrene blended polymers can also be used as compatible and / or compatible polymer

PL 211 431 B1 with the high melt flow rate of the present invention. Polymers with similar technical conditions to those described above but having MFI values ​​of less than 100 are also useful as compatible polymers according to the present invention.

A wide range of compatible high melt flow polymers based on polypropylene, especially when blended with low molecular weight plastomers, and substantially linear polyethylenes, metallocene branched long chain polyethylenes, and copolymers of the aforementioned ethylene polymers as polymer, make it possible to produce blends suitable for for use in a method in accordance with the present invention. Many monomers have been copolymerized with propylene to give propylene copolymers for use as compatible polymers. Many of these copolymers with high MFI levels are suitable as polymer or compatible polymers for use in the present invention.

As high MFI polypropylenes suitable as the high melt flow compatible polymer for use in the process of the present invention, isotactic, syndiotactic and atactic polypropylene and blends thereof with different MFI values, densities and crystallinity which provide the desired properties in the present invention can be mentioned. products formed by the method of the present invention. Polypropylenes which are particularly useful as the high melt flow compatible polymer may include propylene homopolymers or copolymers with one or more α-olefins selected from the group of compounds such as ethylene or linear or branched α-olefins containing from 4 to 20 carbon atoms in the molecule, preferably ethylene or α-olefins, containing from 4 to 8 carbon atoms per molecule, more preferably ethylene, butene-1, hexene-1,4-methylpentene-1,3-methylpentene-1, 3,5,5-trimethylhexene-1, and octene-1, even more preferably ethylene or butene-1 or hexene or octene, even more preferably ethylene or butene-1 or hexene or octene, and optionally, small amounts of non-conjugated diolefins, preferably diolefins having from 6 to 20 carbon atoms per molecule. In one embodiment, the α-olefin may contain ring structures that are fully saturated, such that the α-olefin as a monomer does not contain a ring portion with optional olefinic unsaturated or optional aromatic structures. The α-olefins are preferably mono-olefins. These propylene copolymers, with the comonomer levels prescribed in the range, are preferably obtained by polymerizing the corresponding olefins, in the presence of supported or unsupported metallocene catalyst systems or the like.

When the propylene-based compatible polymer either comprises a single copolymer or consists of several copolymers, such copolymers preferably include propylene as the main monomer and an alpha-olefin other than propylene as the comonomer. The propylene content is generally 70 mole% or more, often 80 mole% or more, very often 90 mole% or more, and sometimes 98 mole% or more.

A number of ethylene copolymers are also suitable for the high melt flow compatible polymers in the process of the present invention. For example, single site catalysed polymers such as metallocene catalyzed polyethylene and ethylene may be mentioned.

The polymer blends preferably include (a) at least one polymer with an MFI greater than 10, preferably greater than 20, more preferably greater than 30, and even more preferably greater than 50, said polymer preferably being a homopolymer or an α-olefin copolymer such as ethylene or propylene or butene, preferably produced with a metallocene or the like catalyst, and having a narrowly distributed component composition, that is, the content of the fractional comonomer from particle to particle will be similar; and (b), at least one high melt flow compatible polymer, preferably a homopolymer or copolymer of an α-olefin such as ethylene or propylene or butene, having a melt flow rate greater than 100 and preferably prepared with a catalyst metallocene or the like. All references made in this description to metallocene catalysts will also apply to other catalysts (e.g. single-site and constrained geometry catalysts) capable of producing polymers having properties the same or similar to those exhibited by metallocene-produced polymers ( e.g. with a narrow or wide MWD, with a narrow range of component composition distribution). Such blends may optionally contain additives well known to those skilled in the art and may contain, inter alia, additives that reduce the rate of transmission of water vapor and / or oxygen through the polymers in which these media are contained. For example, as described

In WO / 02/074854, incorporated herein by reference, the addition of 0.5% to 3% of a hydrogenated low molecular weight aliphatic resin such as poly (dicyclopentadiene) can reduce the transmission of normally occurring wet vapor, and sometimes the rate at which oxygen moves through the blend and its products.

The polyethylene as used herein may be a homopolymer or copolymer, and includes ethylene plastomers. VLDPE, LLDPE, LDPE and HDPE. The term "ethylene plastomers" as used herein refers to the class of ethylene-based copolymers having a density less than about 33%.

0.915 g / cm³ (lower down to about 0.865 g / cm³). Ethylene plastomers have ethylene crystallinity, which is between plastics (ie linear low and very low density polyethylenes) and elastomers of α-olefins with ethylene. VLDPE is a very low density polyethylene₃ usually in the range of 0.90 to 0.915 g / cm³. LLDPE is a linear low density polyethylene,₃ which is usually from 0.915 to 0.930 g / cm³. LDPE is a low-density polyethylene that usually₃ ranges from 0.915 to 0.930 g / cm³. HDPE is a high density polyethylene that is typically 0.930 to 0.970 g / cm³.

However, the document PCT / AU98 / 00255 states that "a wide range of polypropylene-based polymers with a very wide range of MFI (from 1 to 200), densities and crystallinity provide blends suitable for use in the process of the present invention". of the invention ", no particular advantages are mentioned therein of introducing at least one compatible polymer of any kind, including polypropylene polymers, with high MFI values, and furthermore, no examples of compatible polymers with an MFI greater than 100 are given therein.

The compatible polymer largely forms the dispersed or co-continuous phase in the blends of the present invention. It has now been found, surprisingly, that incorporating at least one high melt flow compatible polymer into formulations for producing a flexible, thin walled article often has a number of significant advantages over the use of the same compatible polymer (s). but with a low MFI value. It has also been found that unless the molecular weight of the at least one compatible polymer falls below a value beyond which its ability to improve ESCR and / or tear strength in the flow direction of the polymer is lost in the molded blend, incorporation into the blend of compatible polymers with a high MFI value, there are many significant advantages over incorporating the same compatible polymer but with a low MFI value. For example, a high melt flow compatible polymer often increases the deformability and overall MFI of the overall blend, thereby improving its flow properties. Also, since there is usually an inverse relationship between the MFI and some physical properties of polymers, it is often found that polymer properties such as flexural modulus and hardness decrease with increasing MFI. If necessary, for example due to cost, ESCR efficiency, etc., use as a specific compatible polymer a polymer but with a low MFI value (i.e. from the group of polymers with an MFI &lt;100) having a flexural modulus too high, in relation to the required purpose and which causes the moldings to be too dense, then replacement with a chemically similar or (identical compatible polymer with high MFI, all compatible polymer with an MFI &lt;100 or part of it in the blend allows blends to be produced and used with a much higher MFI than were previously available, while reducing the negative impact on properties such as "feel" and higher flexural modulus that would normally accompany a compatible polymer with a lower MFI value. Depending on the desired properties of the molded article, the high melt flow compatible polymer may either be used as the only compatible polymer in the blend or may be blended with compatible polymers having other MFIs which may be either high or low MFI compatible polymers. Depending on the desired properties of the molded article, the compatible high melt flow rate polymer may either be used as the only compatible polymer in the blend or it may be blended with compatible polymers having a different MFI which may be compatible polymers having either high, low or high melt flow rates. or low MFI.

Without wishing to be bound by theory, it is believed that the interaction between the polymer and the compatible polymer, especially the high melt flow compatible polymer, creates regions within the molded articles which can be considered "joints". These "joints" appear to absorb or dissipate stresses in articles made of a blend of polymers. Presence

These "joints", scattered throughout the article, appear to absorb or dissipate stresses within the article that would otherwise degrade the physical properties. It is believed that the benefits obtained by using the at least one high melt flow compatible polymer are primarily (due to more efficient dispersion in at least one compatible polymer compared to lower MFI variations of the same compatible polymer, and, that they allow the formation of more particles of the dispersed phase with smaller dimensions, compared to those achievable with low MFI varieties of the same polymer. In general, the higher the MFI of the compatible polymer, the smaller the particle size it can form, although there is a level of MFI (and therefore MW) beyond which further reduction of the MW will not further reduce the particle size of the high melt flow compatible polymer. . The smaller particle size of the dispersed phase, in turn, increases the total surface area for a given weight percent compatible polymer content, thus allowing more junctions and areas to interact between the polymer and the dispersed phase (i.e., compatible polymer) in the blend. The effect of reducing the particle size of the compatible polymer on the number of compatible polymer molecules in the blend can be illustrated by the statement that for a given percentage by weight of compatible polymer in the blend, reducing the particle size by half (e.g., by halving the particle radius) of the compatible polymer increases the number of compatible polymer eight times and the total surface area of ​​the compatible polymer twice. Thus, halving the compatible polymer particle radius increases the number of stress-relieving "joints" inside the compact eight-fold and the surface area of ​​the compatible polymer-polymer interaction doubled. Both of these enhancements have the potential effect of improving compact properties such as ESCR and tear strength.

Again, without wishing to be bound by theory, we believe that the increase in the number of molecules and the surface area of ​​the compatible polymer in the discontinuous phase is one of the key reasons for many of the improvements in properties (e.g. ESCR, tear strength) according to the invention. The improvement in ESCR etc., obtained by introducing compatible polymers with a high MFI, often allows the percentage of compatible polymer in the blend to be reduced while still having an acceptable level of ESCR etc. This can be advantageous, for example where it is desired to reduce the amount of compatible polymer on the blend. based on polypropylene in the blend to reduce the flexural modulus of the blend in question.

Alternatively, and using the same example, maintaining the percentage of compatible high melt flow polypropylene causes a significant increase in the number of disperse phase particles, relative to the equivalent amount of low MFI polypropylene, which in turn increases the overall ESCR of the blend. This improvement in ESCR, in turn, allows the use of polymers with a higher MFI, thereby improving the processing characteristics of the blend, while maintaining an acceptable ESCR level.

Without wishing to be bound by theory, we believe that the interfacial stress between the two non-miscible polymers decreases as the molecular weight decreases, just as with increasing MFI of the dispersed phase, the compatibility between the polymers increases until they become miscible. For each type of compatible polymer, there will be an upper limit to how high its MFI can be (i.e., how low its molecular weight will be) before it begins to unacceptable degradation in the performance of a particular blend intended for a particular application. This upper limit will vary depending upon the characteristics of the particular compatible polymer (e.g. PP homopolymer or copolymer, ionomer, etc.), the characteristics of any other compatible polymers in the blend, and the characteristics and interaction of the polymer (s) and the end use of the molded article ( for example, what is going to be packed into the article), and can be determined experimentally. For some applications, slight degradation of certain characteristics of a particular blend from the incorporation of one or more compatible polymers with a high MFI, compared to the same blend with the same compatible polymer but with a low MFI, can be accepted in order to obtain the benefits of improving others properties of the mixture resulting from their introduction. Again, the limit that the upper MFI value of the high melt compatible polymer can reach, as well as the incorporation level achievable before the blend performance is lowered to an unacceptable level can be determined experimentally.

PL 211 431 B1

The high melt flow compatible polymer can be made directly in the reactor using suitable catalysts (including metallocene catalysts or the like) and process conditions. The high melt flow polymer can also be produced by "breaking" the lower MFI of the same type of polymers caused by a variety of peroxides or other molecular chain fractionating polymers known to those skilled in the art. For example, a polypropylene homopolymer or copolymer with an MFI of 50 can be converted into a polypropylene homopolymer or copolymer with a high MFI (equal to, for example, 300, 500, 1000 or 1500) by breaking it. The disintegration required to produce the high melt flow compatible polymer having a well-defined MFI value can be performed prior to introducing the high melt flow compatible polymer into the polymer, thereby producing the high melt flow compatible polymer ready for blending.

Alternatively, the high melt flow compatible polymer can be prepared in situ in the blend by incorporating it into the blend and / or coating the compatible polymer with an appropriate amount and type of disintegrant capable of breaking the polymer to the required MFI, adding the combination thus obtained with the composition : compatible polymer / disintegrant to one or more other components of the blend, and subjecting the resulting blend to conditions (usually at a sufficiently high temperature) to allow the disintegrant to reduce the MW (molecular weight) of the compatible polymer to a level that will allow the compatible polymer to provide the required MFI value. In the latter method of obtaining a high melt flow compatible polymer, determine the effect, if any, of the disintegrant into other blend components during processing (i.e. determine any unintentional breakdown or crosslinking of other blend components with a disintegrant), and, if it is necessary to adjust the composition of the blend so as to improve the overall properties of the blend as a result. Another method of making blends containing the high melt compatible polymer as a dispersed phase within the continuous or co-continuous polymer phase is to produce a blend comprising the high melt compatible polymer and the polymer in a reactor. This can be done in a number of ways well known to those skilled in the art. For example, the high melt flow compatible polymer and polymer can be made in a single reactor in the presence of suitable catalysts. Alternatively, they may be produced in two or more reactors, connected in parallel or in series, or one polymerized component may be finally added to the reactor in which the other component is produced.

High tensile strength, flexibility and tear strength can be mentioned as some of the advantageous properties of the final blend which is molded. The extractable substances in the blends and compacts obtained therefrom is preferably less than 2.0% by weight or equal to this number, more preferably less than 1.6% by weight or equal to this number. most preferably less than 1.4% by weight or equal to that as measured by ASTM D-5227.

Similar to the function of the compatible agents described in Australian application PCT / A-U98 / 00255, the high melt flow compatible polymer is used in an amount at least sufficient to improve environmental stress cracking strength and / or tear resistance, was measured by a Gullwing peel test on a blend of polymers. The high melt flow compatible polymer may also be used in amounts greater than those required to make the polymer blend compatible to improve the viscosity characteristics of the subject blend of polymers so as to optimize the molding characteristics of the subject blend of polymers and / or the overall properties of the molded product such as softness and flexibility. Typically, the high melt flow compatible polymer is used in an amount ranging from about 2 to about 40% by weight of the total composition of the polymer blend, although lower or higher amounts may be used in some polymer blends. The optimal amount for a particular blend composition will depend on the properties required and can be determined experimentally. Moreover, it has been found that the inclusion of a higher percentage of the high melt flow compatible polymer than is needed to improve the environmental stress cracking strength of the polymer blend will often also improve the properties of the polymer blend such as tear strength and impact resistance. barrier properties, chemical resistance, "feel" of the treatment and the product.

PL 211 431 B1

For example, incorporating a greater than required amount of a compatible high melt flow polypropylene-based polymer to improve the environmental stress cracking strength of the polyethylene-based polymer blend to a desired level can improve chemical resistance and overall barrier properties. , and lowering the rate of transmission of water vapor and water through the polymer blend compared to polymer blends, containing the minimum amount of high melt flow compatible polypropylene based polymer required to improve environmental stress cracking strength alone. The properties of such blends, containing the high melt flow compatible polymer, can be further modified by selecting the appropriate grades of the high melt flow compatible polymer and / or polymer components to achieve the desired end properties. For example, where it is desired to have a polymer blend of relatively high percentage polypropylene based polymers, blend properties such as "feel", "softness", impact resistance (especially low temperature impact resistance), stretch to the breaking strength, tear strength and / or distillability of such a blend can be significantly modified, using a relatively low percentage of low flexural modulus polymers as components of the polyethylene-based blend. As examples of suitable low flex modulus polyethylene-based polymers, mention may be made of low flexural modulus plastomers such as the Engage 8401 plastomer from DuPont-Dow and some of the propylene-α-olefin copolymers such as Tafiner XR from Mitsui. It has further been found that the inclusion of a greater than the required percentage of the high melt flow compatible polymer may allow the incorporation of a greater percentage of other polymers than would otherwise be in accordance with the present invention. Thus, the use of a high melt flow compatible polymer in such amounts may allow the incorporation of greater than otherwise possible amounts of such advantageous, substantially incompatible other polymers such as nylons and EVOH while maintaining improvements in properties such as tear strength and impact resistance, barrier properties, chemical resistance and the "feel" of the product.

The polymer blend containing the high melt flow compatible polymer may also incorporate a variety of other additives. Examples of such additives are further polymers, glidants, anti-sticking agents, pigments, dyes, fillers, antioxidants, plasticizers, UV protectants, viscosity modifying polymers, additives (some of which are themselves polymers), capable of reacting with, or absorbing harmful chemicals such as oxygen and other polymers released during molding, and melt resistance modifiers, among others. In addition, compatibility agents may be added to the blends that improve various properties of the blends such as strength at the weld point (seams), compatibility between the polymer and the high melt flow compatible polymer, particle size reduction of the disperse phase, ESCR, tear strength, e.t.c. The above-mentioned and other suitable additives may be added to one or more components of the polymer blend or to the polymer blend as a whole, prior to molding, to modify its properties to suit specific applications or to achieve specific effects in the final product. In cases where the polymer itself serves as one or more additives, for example in some oxygen scavenging systems, the subject polymer may be a polymer or a compatible polymer in the polymer blend. The non-polymeric additives can be compatible polymers from the polymer blend.

A wide variety of polymers can be used as the polymer in blends containing the high melt flow compatible polymer. These polymers include homopolymers and copolymers of olefins, preferably homopolymers and copolymers of ethylene or propylene or butene with α- or β-olefins having from 3 to 20 carbon atoms per molecule, and / or polyenes, preferably α- or β-olefins, containing from 3 to 8 carbon atoms per molecule, such polymers having densities ranging from very low to high (this range is from 0.85 to 0.97 g / cm³). Also suitable for use in the present invention are vinyl end group ethylene, propylene and butene copolymers and ethylene, propylene and butene copolymers containing more than 50% ethylene, propylene or butene which are copolymerized with comonomers such as acrylates methyl, ethyl acrylates, acrylic acid, methacrylic acid and other polar comonomers, ionomers, ABA styrene-ethylene / butene-styrene copolymers, styrene, Halogen or alkyl substituted styrenes or other aromatic vinylidene monomers and / or one or more aliphatic

Or hindered cycloaliphatic vinylidene monomers, tetrafluoroethylene, vinylbenzocyclobutane, and naphthenes (e.g., cyclopentene, cyclohexene and cyclooctene). These polymers can be made by a wide variety of methods, including high and low pressure processes, with many types of catalysts such as Ziegler-Natta and metallocenes, and have molecular structures ranging from linear to highly branched to highly branched. thus LDPE, MDPE and HDPE belong to this group. Particularly suitable for use in the present invention are plastomers, "substantially linear" and branched polyethylenes or polypropylenes, copolymers of propylene and ethylene or one or more α-olefins, terpolymers of ethylene, propylene and one or more α-olefins (of which, for example, include (mention Catalloy polymers ex Montell) and polymers and copolymers prepared using metallocene or similar catalysts and which are characterized by super random distribution of the copolymers. Propylene random copolymers are suitable for the production of flexible, thin-walled compacts, especially when improved optical clarity is required. As other polymers suitable for use in the present invention, mention may be made of polylactic acid-containing polymers, other suitable biodegradable polymers and polyketones, ethylene-carbon monoxide (ECO) copolymers, ethylene-propylene-carbon monoxide (EPCO) polymers, linearly alternating copolymers ECOs such as those disclosed in U.S. Serial No. 08/009198, and the disclosure of which is incorporated herein by reference, reused polyethylene (for example, high-density reused polyethylene, recovered from consumer used bottles).

As illustrated in Japanese Patent Nos. 07316356, 07316355 and 07330982, which are incorporated herein by reference, blends of crystalline PP, in combination with ethylene / styrene / α-olefin elastomers, can be used as a polymer for the production of elastic, thin-walled products.

Also suitable for use as polymers are linear or branched isotactic polymers, especially polypropylene and polybutene homopolymers or random copolymers, having a structure in which their tacticity varies from 25 to 60% (mmmm) concentration after five days. This tacticity variation is due to the statistical distribution of stereoscopic errors in the polymer chains. Such polymers are described, inter alia, in WO 01/27169 (P&amp;G), WO / 99/52955 (Rieger) and WO 99/52950, ​​and (Rieger), which are hereby incorporated by reference. The term "stereoscopic error" refers to a stereoscopic sequence, mostly but not exclusively characterized by a [mrrm] pentade that has been incorporated into a polymer in which different pentads (e.g., [mmmm] (isotactic) or [mrmr] (syndiotactic) characterize the polymer . These stereoscopic errors alter the characteristics of the polymer - for example, isotactic polypropylene (PP) with stereoscopic errors tends to have more elastomeric properties than the same polymer but without stereoscopic errors. The term "tacticity" is a measure of the order of the order of repeating configuration units in the backbone and / or side chains of a polymer molecule.

Also suitable for use in the present invention are linear or branched isotactic polymers having any or rather regular order of isotactic and atactic blocks within the polymer molecules, such as those described in WO 99/29749 (ExxonMobil), incorporated herein as reference. WO / 99/2949 describes a branched polyolefin having crystalline side chains and an amorphous backbone where at least 90% by mole of the side chains are isotactic or syndiotactic polypropylene and at least 80% by mole of the backbone is atactic polypropylene. .

The polymers with reduced tacticity as described above may find particular use in blends as at least one compatible polymer in blends where at least one polymer is a polymer such as crystalline or semi-crystalline PP. This will be especially the case where the polymer (s) in question have a relatively low flexural modulus because it acts to reduce the flexural modulus of the blend with crystalline or semi-crystalline polypropylene as the at least one polymer and increase the tensile strength. tear, flexural modulus and impact resistance, compounds.

Recent advances in polypropylene polymerization technology are applicable to injection molded, flexible, thin-walled moldings. One such technological advancement is the ability to produce very pliable, soft and flexible polypropylene polymers with a lower percentage in the ethylene copolymer and essentially devoid of a diene. These polymers have limited crystallinity due to the close proximity of the isotactic propylene units and do

A relatively low melting point. They are generally devoid of any significant intermolecular heterogeneity in tacticity and comonomer composition, and are substantially diene-free. They are also devoid of any significant heterogeneity in the intramolecular component distribution. The ethylene copolymer contains from a lower limit of 5% by weight ethylene derived units to an upper limit of 25% by weight ethylene derived units. Within these limits, these copolymers are weakly crystalline, as measured by Differential Scanning Calorimetry (DSC), and are extremely soft while still retaining considerable tensile strength and elasticity. Such polymers are described in US Patent No. 6,525,157 (ExxonMobil).

Recent advances in technology have made it possible to synthesize partially atactic, partially isotactic polypropylene polymers that possess elastomeric properties. In these components, each molecule is believed to consist of parts that are isotactic and therefore crystallizable, while other parts of the same polypropylene molecule are atactic and therefore amorphous. Such polymers are suitable for injection molded flexible thin walled moldings, either as at least one polymer or at least one compatible polymer in blends, in combination with other polymers such as polyethylenes, polypropylenes and / or their copolymers with α-olefins. . Examples of such propylene homopolymers with different levels of isotacticity in different parts of the molecule are found in, inter alia, U.S. Patent No. 5,594,080 (Waymouth), Journal American Chemical Society (1995), Vol. 117, page 11586, and Journal American Chemical Society ( 1997), Vol. 119, page 3635.

Particularly when polymers such as those described in the P&amp;G, Rieger, Waymouth and ExxonMobil patents are incorporated into blends having an MFI greater than 10, preferably greater than 20, more preferably greater than 30, and most preferably greater, than 50, and even more preferably the polymers themselves have an MFI greater than 10, preferably greater than 20, more preferably greater than 30, and most preferably greater than 50, they may then be used either as the sole polymer or as a compatible polymer or high melt flow compatible polymer, and may have either narrow or wide molecular weight distribution H. Polymers as described above are often particularly suitable for the production of flexible, thin-walled articles as compared to the higher tacticity of the equivalent polymers, because their relatively lower tacticity causes these polymers to have a reduced stiffness and increase their flexibility and elasticity. When the polymer (s) are used as the compatible polymer or the high melt flow compatible polymer, it is preferred, though not necessary, to be used in conjunction with at least one polymer made of the same monomer (s) as the compatible polymer or a high melt flow compatible polymer as this results in greater compatibility / durability between the polymer (s), and allows easier disposal of injection molded, flexible, thin-walled products made of such blends. For example, if a polypropylene homopolymer or copolymer with a tacticity ranging from 25 to 60% pentads (mmmm) is used as the polymer, it can be blended with a higher tacticity polypropylene homopolymer or copolymer to form a blend suitable for use in flexible applications. , thin-walled products. Alternatively, these polymers can be used in conjunction with other polymers to form blends that are suitable for the manufacture of flexible injection molded thin walled articles. For example, these polymers can be blended with polyethylenes and copolymers of various types, including LDPE, MDPE, and HDPE, which in turn can be made using a variety of production methods, catalysts, and copolymers as described in Australian application PCT / AU98 / 00255 and in this application. The polyethylene is preferably produced using metallocene catalysts or the like.

In many of the blends suitable for the present invention, it is preferred to incorporate at least two polymers, at least one of these polymers having a higher crystallinity, and preferably a higher MFI, than at least one other polymer. It is preferred, though not essential, that the higher crystallinity polymer has a crystallinity that is at least 5% greater, and preferably 10% or more greater than the crystallinity of the at least one other polymer. The high crystallinity polymer can be made by a variety of methods, with a large number of catalysts such as metallocene, Ziegler-Natta and limited geometry catalysts at hand, or it can be produced by a free radical reaction. It may be linear, substantially linear or branched in structure. In blends where a high crystallinity polymer is incorporated together with at least one lower crystallinity polymer (which is preferably

Metallocene-prepared polymer), better ESCR results are often obtained when the polymer with high crystallinity has a broad MWD (molecular weight distribution). A polymer with a broad MWD (i.e., multimodal) and high crystallinity, can be produced by a number of different methods. They include:

1) Thorough mixing of two or more polymers with different MFI values ​​in a suitable mixing device,

2) Manufacture of bimodal or multimodal polymers using "tandem" reactors; and

3) Production of bimodal or multimodal polymers in a single reactor, using appropriate catalysts.

We have found that plastomers, substantially linear polyethylenes, branched polyethylenes obtained by metallocene, and copolymers of the aforementioned ethylene polymers, mixed polymers of α-olefins such as propylene and polymers, and mixed polymers of propylene obtained by metallocene are preferred polymers that can be used in the present invention for the production of thin-walled products, and particularly for the production of flexible, thin-walled products. A key feature of plastomers, substantially linear polyethylenes, branched polyethylenes, obtained using metallocene, and copolymers of the aforementioned ethylene polymers, mixed polymers of α-olefins such as propylene, and polymers and mixed polymers of propylene obtained using metallocene, is their composition distribution, that is means the uniformity of comonomer distribution within and among the polymer molecules. Another advantage of such catalysts is that the degree of molecular branching within and between the polymer molecules obtained with these catalysts is more uniform than that which can be obtained using conventional catalysts. For example, using conventional Ziegler-Natta type catalysts, copolymers are generally obtained having a much broader component composition distribution - and in the case of copolymers, the comonomer distribution in the polymers thus obtained will vary greatly among the polymer molecules, and will also be less. randomly distributed within a given molecule. In addition, the degree of branching of the long chain is more constant between particles prepared with metallocene catalysts or the like than with particles prepared with Ziegler-Natta catalysts or the like.

These polymers may advantageously have a molecular weight distribution, on a Mw / Mn ratio, that is from 1.5 to 30, preferably from 1.8 to 10 and more preferably from 2 to 4. Generally, a plastomer, substantially linear or branched ethylene polymers or propylene are homopolymers of ethylene or propylene and mixed polymers of ethylene and / or propylene, at least one α-olefin copolymer having from 3 to 20 carbon atoms per molecule is particularly preferred. The term "mixed polymer" as used herein means a copolymer or terpolymer or the like. That is, at least one other comonomer is copolymerized with ethylene or propylene to form a mixed polymer containing an α-olefin.

When the polymer is a plastomer, an essentially linear or branched polymer in which the content of propylene or butene is more than 50% by weight of that polymer, the MFI of the α-olefin copolymer with propylene or butene may be higher than is usually acceptable for flexible, thin-walled, molded injection molding of articles where the polymer consists of α-olefins containing ethylene. This is because propylene and butene containing α-olefins generally have better ESCR properties in nature, with the same MFI, compared to most ethylene containing α-olefins. Thus, many α-olefins containing propylene and butene, especially those obtained with metallocene catalysts or the like, may have elevated MFI values, even greater than 200, and yet when used as at least one polymer and / or at least one compatible polymer, can still produce satisfactory, flexible, thin-walled articles with good ESCR. The optimal MFI value for a particular α-olefin polymer, containing propylene or butene, can be determined experimentally by any person skilled in the art. However, it will preferably be more than 30, more preferably more than 50, and generally more than 100 and possibly more than 150. As α-olefins suitable for copolymerization with propylene or butene to produce propylene or butene containing α-olefins suitable for use in the present invention, there may be mentioned α-olefins having from about 2 to about 20 carbon atoms per molecule, preferably from about 3 to about 16 carbon atoms per molecule, most preferably from about 2 to about 8 carbon atoms per molecule. Illustrative examples of such α-olefins include, but are not limited to, ethylene, propylene, butene-1, pentene-V 1,4-methylpentene-1, hexene-1, octene-1, dodecene-1 and the like similar. Polyene comonomers, equivalent 22

Not to be copolymerized with propylene or butene to obtain the propylene or butene copolymers useful in the present invention generally have about 3 to 20 carbon atoms per molecule, preferably about 4 to about 20 carbon atoms per molecule, most preferably about 4 to about 15 carbon atoms per molecule. In one embodiment, the polyene is a diene having about 3 to about 20 carbon atoms per molecule, and it may be a straight chain, branched, hydrocarbon diene, or it may be a cyclic diene. A preferred diene is a nonconjugated diene. As examples of alpha-olefins with ethylene or propylene as plastomers suitable for use in the present invention, there may be mentioned, without intending to be limited only thereto, copolymers having the composition: propylene or butene (1-butene, propylene or butene). hexene-1, propylene or butene / octene-1, and propylene or butene / ethylene.

As examples of terpolymers useful as propylene or butene-containing plastomers in the present invention, mention may be made of, without wishing to be limited only thereto, the terpolymers of the composition: ethylene / propylene or 1,4-butene / hexadiene and propylene or butene / octene-1. / hexadiene-1,4. Copolymers of propylene or butene with other α-olefins containing from 2 to 8 carbon atoms in the molecule that are particularly useful in the present invention are copolymers containing propylene or butene and ethylene as necessary components (monomeric units) and copolymers of propylene or butene with ethylene and at least one useable alpha-olefin having 4 to 8 carbon atoms, such as butene-1, 3-methylbutene-1, pentene-1, 4-methylpentene-1, hexene-1, and octene-1. In addition, the copolymer may contain as comonomer 0.5 to 10% by weight of a non-conjugated diene such as 1,4,5-methyl-hexadiene-1,5, octadiene-1,4, cyclohexadiene, cyclooctadiene, dicyclopentadiene, 5-ethylidene norbornene-2, or 2-isopropenyl norbornene-5. Preferably these copolymers are prepared using metallocene catalysts or the like. The percentage of ethylene and / or other α-olefins copolymerized with propylene or butene to obtain polymers useful in the present invention can vary widely, depending on the desired properties of compacts made from blends composed of these materials. In general, the more the copolymer polymerized with propylene or butene contains, by percentage, ethylene and / or α-olefin, the lower the flexural modulus of the resulting polymer and the more flexible compacts in which the polymers in question are polymer blends will be obtained. .

U.S. Patent No. 6,355,736, hereby incorporated by reference, describes a propylene block copolymer consisting of (A) a random copolymer of propylene with an α-olefin, with a propylene content of 99.4 to 99.9% by mole, and (B) a random copolymer of propylene with an α-olefin, having a propylene content of 35 to 60 mole%. There are also described compositions of the propylene block copolymer where the content of the propylene-α-olefin random copolymer (B) is from 22 to 40% by weight, based on the total weight of the propylene block copolymer. Such propylene block copolymers are suitable for use in the present invention as a polymer component and / or high melt flow compatible polymer.

US Patent No. 6,458,901, incorporated herein by reference, teaches propylene copolymers suitable for use as the polymeric component and / or compatible high melt polymer suitable for use in the present invention. The propylene copolymers described therein contain propylene, at least one olefin selected from the group of olefins having 2 to 20 carbon atoms per molecule, in addition to propylene, and a cyclic olefin, and are characterized in that the total number of carbon atoms in the monomers, in addition to the cyclic olefin, is , at least 7. Incorporation of cyclic olefins into polymers containing propylene, at least one olefin selected from the group of olefins having 2 to 20 carbon atoms in the molecule, in addition to propylene, results in an improvement in the heat resistance of the obtained polymer. The propylene copolymer preferably comprises 0.01 to 20 mole%, more preferably 0.05 to 15 mole%, particularly preferably 0.1 to 10 mole%, most preferably 0.15 to 5 mole%, of the cyclic olefin. When the propylene copolymer of the present invention contains ethylene (an olefin having two carbon atoms in the molecule), the ethylene content is preferably 80 mole% or less, more preferably 70 mole% or less, particularly preferably 60 mole% or less. , most preferably 50 mole% or less from the standpoint of improving the flexibility of the thermoplastic resin blend.

The Short Chain Side Chain Distribution Index (SCBDI) is defined as the weight percentage of molecules with 15% of the average total molar comonomer content present in them. SCBDI of propylene polymers, useful for the present invention

The ratio is preferably greater than approximately 30%, more preferably greater than 50%, with values ​​of 70% or greater being also obtainable.

When a copolymer is described by a certain percentage of a particular monomer in its composition, for example a propylene-ethylene copolymer of which ethylene is 5%, this means, unless otherwise stated, that the copolymer consists of 5% by weight of units derived from of ethylene, calculated to the sum of the masses of propylene and the units derived from ethylene, which in this specific case is 100%.

MWD (molecular weight distribution) is, unless otherwise stated, the ratio of weight average molecular weight to number average molecular weight, i.e. Mw / Mn.

"Crystallizable" (for example, as used in the phrase "propylene-ethylene copolymer with crystallizable isotactic sequences of propylene") means, unless otherwise stated, that a particular polymer or blend generally has crystallizable sequences of a particular type (e.g., isotactic propylene), which can be identified by the heat of fusion characterization of the individual crystallizable sequences, as highlighted in the DSC analysis.

The blends that take advantage of the benefits of adding a high melt flow compatible polymer to the polymer are clearly illustrated by the following examples:

Example 1

A blend of the composition SC973-Engage 8401-WSM 168 in a ratio of 25: 37.5: 37.5 was injection molded into a tube and the ESCR was examined. SC973 is the compatible polymer in this formulation and is a 100 MFI polypropylene obtained from Basell. This formulation showed a degree of ESCR damage of ± 30% after 360 hours.

Example 2

A blend of Atofina 3960-Engage 8401-WSM 168 in a ratio of 25: 37.5: 37.5 was injection molded into a tube and the ESCR was examined. Atofina 3960 is a compatible polymer in this preparation and it is a polypropylene with MFI = 350, obtained from Atofina. This formulation showed 0% ESCR damage after 360 hours and significantly improved clarity compared to the comparative formulation.

The only difference between the formulations of Examples 1 and 2 is the replacement of a compatible polymer with an approximately chemically equivalent compatible polymer, a compatible polymer, high melt flow, with the key difference being that the high melt flow compatible polymer has a much higher MFI. with respect to a compatible polymer. The significant improvement in the ESCR score is due to the much higher MFI (corresponding to a much lower molecular weight) of the compatible polymer, with a high melt flow rate, compared to the compatible polymer.

It will be appreciated that the percentages of the different types of blend components shown in these examples may vary depending upon the required properties of the compacts produced therefrom, and that the range of these percentages for the different types of blend ingredients will provide satisfactory compacts. can be determined experimentally.

Example 3

70% propylene / butene copolymer, with 15% butene content, MFI = 50 and MWD &lt;4, and made with metallocene / single site catalyst.

30% Exact 4038, an ethylene / butene copolymer, MFI = 125, density 0.885, from ExxonMobil.

This example illustrates the incorporation of a metallocene-obtained polyethylene with a high MFI as a compatible polymer which is suitable for making thin-walled flexible articles into a propylento-olelin copolymer.

Example 4

70% propylene / octene copolymer, with an octene content of 20%, MFI = 30 and MWD &lt;4, and made with a metallocene / single site catalyst.

30% Fina 3960, a polypropylene homopolymer with MFI = 350, from Atofina.

This example illustrates the incorporation of a high MFI polypropylene polypropylene into a propylene / octene α-olefin copolymer as a compatible polymer that is suitable for making thin-walled flexible articles.

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Example 5

70% substantially linear propylene / ethylene copolymer, with an ethylene content of 25%, MFI = 50, and MWD &lt;4, and made with metallocene / single site catalysts.

30% Fina 3960, a polypropylene homopolymer with MFI = 350, from Atofina.

This example illustrates the incorporation of a high MFI polypropylene α-olefin copolymer in a substantially linear propylene / ethylene copolymer as a compatible polymer which is suitable for making thin wall flexible articles.

Example 6

80% propylene / butene copolymer as plastomer, with 30% butene content, MFI = 70 and MWD &lt;4, and made with metallocene / single site catalyst.

10% isotactic or syndiotactic polypropylene homopolymer, MFI = 50, made by metallocene / single site catalyst.

10% Fina 3960, a polypropylene homopolymer with an MFI = 350 from Atofina.

This example illustrates the incorporation into an α-olefin copolymer of propylene / butene plastomer, high MFI polypropylene and low MFI polypropylene compatible polymer which is suitable for making thin wall flexible articles.

Example 7

90% propylene / butene copolymer, with 30% butene content, MFI = 70 and MWD &lt;4, and made with metallocene / single site catalyst.

10% polyethylene, MFI = 500, or an α-olefin-ethylene copolymer made with a metallocene catalyst.

This example illustrates the incorporation of a high MFI polyethylene or an α-olefin ethylene copolymer as the compatible polymer in combination with an α-olefin copolymer of propylene / butene. The percentage of α-olefin in the copolymer may vary from 0.5% to 49%, depending on the end use requirements.

Example 8

90% propylene / butene copolymer, with 30% butene content, MFI = 150 and MWD &lt;4, and made with metallocene / single site catalyst.

10% polyethylene, MFI = 500, preferably metallocene catalyst / single site.

This example illustrates the incorporation of a high MFI polyethylene as the compatible polymer in combination with a high MFI polypropylene as the compatible polymer.

Example 9

40% propylene / butene copolymer with a density of 0.86 and reduced isotacticity and an MFI = 14 such as Vistamaxx 1120 (ex ExxonMobil).

60% Fina 3960, a polypropylene homopolymer with MFI = 350, from Atofina.

This example illustrates the incorporation of a tactically modified and reduced isotactic polypropylene polymer with a high MFI and high crystallinity into a propylene / ethylene copolymer that is suitable for the production of thin-walled flexible articles.

Example 10

30% propylene / butene copolymer, MFI = 14, density 0.86 and tacticity altered, such as Vistamaxx 1120.

30% isotactic or syndiotactic polypropylene random copolymer, with MFI = 50, and

40% Fina 3960, a polypropylene homopolymer, MFI = 350, from Atofina.

This example illustrates the incorporation of a high MFI polypropylene and a low MFI propylene / ethylene copolymer having a statistical distribution of stereoscopic errors together with a random polypropylene copolymer. This blend is suitable for making thin-walled, flexible articles and has improved clarity and a lower stress whitening tendency due to the inclusion of a random copolymer instead of some polypropylene homopolymer.

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Example 11

35% propylene / butene copolymer, stereoscopic errors, having MFI = 300, density = 0.86 and flexural modulus (secant 1%) of approximately 13 MPa

65% random polypropylene copolymer with MFI = 100

This example illustrates the incorporation of a propylene / ethylene copolymer with a very high MFI with stereoscopic errors into a readily available grade of prior art polypropylene random copolymer to obtain a blend with a relatively high MFI suitable for making thin wall flexible articles.

Example 12

35% propylene / butene copolymer, stereoscopic errors, having MFI = 300, density = 0.86 and flexural modulus (secant 1%) of approximately 13 MPa

40% random polypropylene copolymer with MFI = 100 25% polypropylene copolymer with MFI = 100 such as SC973 from Basell

This example illustrates the incorporation of a propylene / ethylene copolymer, with a very high MFI, with stereoscopic errors, into a readily available grade of prior art polypropylene random copolymer and a readily available grade of prior art polypropylene copolymer to obtain a blend of relatively high MFI, suitable for the production of thin-walled, flexible products.

With reference to the above description, an improvement in the production of highly branched polyolefins has made it possible to produce star, comb, nano-gel and other polymers. These polymers are distinguished by a multitude of polyolefin arms linked to a polymeric backbone to provide a highly branched structure where the properties of the highly branched structure can be conveniently adjusted depending on the intended use of the polymer. The choice of the particular reactive polymeric backbone and / or the method of its preparation is governed by the branched structure, be it star, comb, nano-gel polymers or structural combinations thereof. This allows the production of polymers having a relatively low viscosity compared to their linear counterparts with the same absolute molecular weight. The types of these polymers, and the blends prepared therefrom, may be particularly suitable for the production of injection-molded, flexible, thin-walled moldings. The rheological behavior of these polymers in controlled branching shows surprising and useful features. These polymers often have a zero shear viscosity which is higher than that of linear polymers of the same molecular weight. They show a rapid decrease in viscosity with shear rate (a high degree of shear reduction in viscosity of non-Newtonian liquids) and a stable modulus that is at least two times lower than that of the prior art linear and branched polymers. The latter feature is particularly surprising since ethylene polymers of different types exhibit substantially the same stable modulus. This was believed to be inherent in the type of monomer and not dependent on the structure of the polymer. The lower stable modulus means that the comb and similar polymers are much less entangled than linear, thus giving them such a low viscosity for their molecular weight. The utility of these properties of these polymers lies in the fact that they have a very low viscosity at their molecular weights under melt processing conditions, and therefore can be processed much more easily than the polymers of the prior art. Even when added in relatively small amounts to conventional blends suitable for injection molded flexible thin walled moldings, they can greatly improve the processability of the blend. U.S. Patent Nos. 6,355,757 and 6,084,030, inter alia, describe the preparation of polymers as set forth above.

The copolymers of the above and similar inventions find use in blends suitable for the preparation of injection molded flexible thin walled moldings, these blends containing the branched copolymer of the inventions with a very large spread (e.g. 0.1 to 99.9% by weight). ), but most often in the range of 1 to 5%. Depending on the properties of the particular highly branched polymer of the above inventions and the desired properties of the individual formulation, the subject polymer may be used as a component of at least one polymer or at least one compatible polymer forming part of a blend for use in the present invention. Depending on their properties, they can also be regarded as additives rather than components of the polymer part of the present invention.

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Recent catalyst and process development has enabled the production of a wide variety of polypropylene homopolymers and copolymers with properties that make them particularly useful for the manufacture of injection molded flexible thin wall articles. Among these useful polymers are elastomeric homopolymers and polypropylene copolymers, polymers produced by varying the tacticity of the polymer in various ways and the ability to produce alpha-olefin polypropylene copolymers with a low flexural modulus with relatively low percentages of alpha-olefins in the copolymers.

Examples of one of the latter developments are linear or branched isotactic polymers, especially polypropylene and polybutene homopolymers or random copolymers, which have a structure in which their tacticity varies from 25 to 60% pentads [mmmm]. This change in tacticity is due to the statistical distribution of stereoscopic errors in the polymer chains. Such polymers are described, inter alia, in WO 01/27169 (P&amp;G), WO 99/52955 (Rieger) and WO 99/52950 (Rieger). Likewise, propylene / ethylene copolymers of the type disclosed in US Patent No. 6,525,157 (ExxonMobil) are suitable for use in injection molding flexible, thin-walled moldings. It is worth noting that α-olefins containing propylene, in which the number of carbon atoms in the α-olefin molecule&gt; 4, show particular utility value for packaging, requiring better resistance to cold plastic deformation, compared to α-olefins containing propylene, in which the number of carbon atoms in the α-olefin molecule is &lt;4.

When the at least one polymer in the blend is a linear, substantially linear or branched polymer in which propylene or butene comprises more than 50% by weight of the polymer, the MFI of the at least one homopolymer or α-olefin copolymer may be higher than is generally acceptable when ethylene-containing α-olefins form at least one polymer, because propylene and butene containing homopolymers or α-olefins are generally better in nature, ESCR properties at the same MFI, compared to most ethylene-containing α-olefins. Thus, some propylene and butene-containing homopolymers or copolymers of α-olefins, especially those obtained with metallocene or the like catalysts, may have MFI values ​​even greater than 150, and even when used as at least one polymer, they can be used to obtain acceptable injection molded flexible thin walled moldings with good ESCR. The optimal MFI for a particular propylene or butene-containing α-olefin homopolymer or copolymer as at least one polymer can be determined experimentally, but will be preferably&gt; 30, more preferably&gt; 50 and, depending on the characteristics of the particular polypropylene or polybutene homopolymer or copolymer The α-olefin can even more preferably be&gt; 100 and most preferably&gt; 150. As α-olefins, suitable for copolymerization with propylene or butene to produce α-olefins, containing propylene or butene, suitable for injection-molded flexible, thin-walled moldings, there may be mentioned α-olefins having from about 2 to about 20 carbon atoms per molecule , preferably from about 2 to about 16 carbon atoms per molecule, and most preferably from about 2 to about 8 carbon atoms per molecule. Furthermore, the copolymer may contain as comonomer 0.5 to 10% by weight of an unconjugated diene such as 1,4-hexadiene, 5-methylhexadiene-1,5, octadiene-1,4, cyclohexadiene, cyclooctadiene, dicyclopentadiene, 5-ethylidene norbornene. -2,5-butylidene-norbornene-2, or 2-isopropenyl-norbornene-5. Preferably these copolymers are prepared using metallocene catalysts or the like. The percentages of ethylene and / or other α-olefins copolymerized with propylene or butene to obtain polymers suitable for injection molded flexible, thin-walled moldings can vary widely, depending on the required properties of moldings prepared from blends consisting of these materials. In general, the higher the percentage of ethylene and / or other α-olefin in the copolymer obtained by polymerization with propylene or butene, the lower the bending modulus of the resulting polymer and the more flexible the moldings obtained therefrom, in which the polymers in question are at least one polymer in the blend.

Blends which are intended for recovery and which contain a dispersed phase with a higher crystallinity and a continuous phase with a lower crystallinity, such as those described below, are suitable for the production of injection-molded flexible, thin-walled compacts. The dimensions of the individual domains of the dispersed phase in these blends are preferably very small. The components of the blend are also compatible to the extent that no adaptation agent is needed to achieve and maintain this fine morphology. One of the components is the polymer as it is

A predominantly stereospecific polypropylene, preferably isotactic polypropylene. This is a higher crystallinity component (XPP). The second component is a copolymer of propylene and at least one α-olefin having two, or 4 to 20 carbon atoms per molecule, preferably ethylene. This is a less crystalline component (SXPP). In the copolymer, propylene is preferably polymerized substantially stereospecifically. Preferably the copolymer has a substantially uniform distribution of the constituent composition, preferably as a result of polymerization with a metallocene catalyst. Most preferably, the subject XPP is an ethylene propylene copolymer, for example a semi-crystalline ethylene propylene elastomer.

It has been found that mixing at least one XPP and at least one SXPP results in a favorable (processing performance, still providing a blend having reduced flexural modulus and increased tensile strength, increased elongation, recovery and greater overall hardness. The third polymeric component, which is another α-olefin propylene (SXPP2) crystallizable copolymer, has a crystallinity which is between that of XP and that of SXPP. One type of blend comprising polypropylene suitable for injection molded flexible thin wall moldings is crystalline, isotactic or syndiotactic polypropylene (XPP) mixed with a semi-crystalline α-olefin polypropylene copolymer (SXPP) having the same tacticity as XPP, preferably copolymer XPP ethylene with propylene, containing 4% by weight, up to 35% by weight, of an α-olefin, preferably ethylene, and optionally a second copolymer of an α-olefin with propylene, with a crystallinity intermediate between that of XPP and SXPP and of similar tacticity. These mixtures have a heterophasic morphology. It is believed that this stereoregularity adjustment increases the compatibility of the components and results in better adhesion in the region of interaction of domains of polymers of different crystallinity in the composition of the polymer blend. Narrow intermolecular and intramolecular constituent distribution in the copolymer is preferred but not essential. These and similar blends may be particularly suitable for making injection molded flexible thin walled moldings and other containers that are heated by methods such as hot-filling the container with the product that the container should contain and / or heat treating the filled container using methods. such as retort distillation. The composition of the blend may vary widely, depending on the purpose of its use, and may contain 1% to 95% by weight of XPP and SXPP, with more than 65% by weight propylene content, preferably more than 80% by weight. % by weight of the propylene content.

Polypropylene-based at least one polymer blends having a low flex modulus are particularly useful for injection molded flexible thin walled moldings. Below are some general formulations capable of producing suitable blends containing low flexural polypropylene.

Type 1 preparation

1. 8-25% crystalline PP or PP copolymer, most preferably 12-18%. If it is a copolymer, it should contain at least 85% by weight of PP, preferably more than 90%.

2. 75% -92%, most preferably 82-88%, of two elastomeric polymers. Polymer a) and Polymer b): Polymer a) having 15-32% α-olefin, preferably 25-30%, optionally containing 0.5-5% diene and Polymer b) having 32-45% α-olefin preferably 35-40%, optionally containing 0.5-5% of a diene. The weight ratio of polymer a) to polymer b) is 1: 5 to 5: 1.

The above blend may be produced sequentially by either polymerization or mixing. The preferred α-olefin is ethylene. Depending on the required properties, the above blends can be used in combination with EPR (ethylene / propylene copolymers), ethylene / propylene / diene (EPDM) terpolymers, a polymer composed of ethylento-olelin with 4-12 carbon atoms per molecule (e.g. ethylene / octane such as Engage). Such elastomeric polymers may constitute 5% -80% by weight of the blend weight.

Preparation type 2:

1) 10-60% crystalline propylene homopolymer or copolymer

2) 10-40% propylene / ethylene copolymer, xylene insoluble (i.e. with low ethylene content in copolymer) and

PL 211 431 B1

3) 30-60% ethylene / propylene copolymer, soluble in xylene at room temperature (i.e. high ethylene content in copolymer)

The above blend may be produced sequentially by either polymerization or mixing.

Preparation type 3:

1) 70-98% crystalline polypropylene homopolymer or copolymer

2) 2-30% some xylene soluble propylene / ethylene copolymer (i.e. a copolymer with a relatively low ethylene content)

This blend has a relatively high flexural modulus due to the relatively high% crystalline copolymer content and the relatively low α-olefin content in the polypropylene copolymer, and can be produced sequentially by polymerization or blending.

Other types of formulations are obtained by easily blending many different types of polypropylene as at least one of the polymers as mentioned above, preferably polypropylene homopolymers with different tactics and α-olefin-polypropylene copolymers with different tactics and different levels of α-olefin content. , with at least one of compatible polymers of various types, especially polyethylene homopolymers, metallocene and polypropylene of different tactics and α-olefin-polypropylene copolymers with different tactics and different levels of α-olefin content, having a lower flexural modulus than polypropylene as at least one polymer to be used in a particular blend.

In addition to their use in blends containing polypropylene, HD / MD / LDPE blends with copolymers containing polyethylene which can act as "binder molecules", for example, low density metallocene polyethylene, can also be improved by using techniques to strengthen the spheroidal boundary. This enables the binding molecules to reach a concentration at the crystal boundary, which effectively increases the number of binding molecules at the crystal interface, resulting in an increase in the ESCR of the blend.

It will be appreciated by those skilled in the art that the percentages of ingredients in the various blend types shown in the above examples may vary depending upon the properties of the compact required, and that the range of percentages for the various blend types that will produce satisfactory compacts may be determined. experimentally.