KR20060133579A - Improved thermoplastic polyolefin alloys and process for their preparation - Google Patents

Abstract

A thermoplastic polyolefin alloy having high (notched) Izod impact strength and process for its preparation are disclosed. The alloys of this invention comprises of a polypropylene block copolymer as a base polymer, an elastomer, a compatibilizer and optionally a natural filler and is prepared by melt blending a twin-screw extruder (or Buss-co- kneader) the above ingredients. The polyolefin alloys of this invention exhibit very high (notched) Izod impact strength of 60 to 90 kg. cm/cm, flexural modulus of 6,000 to 8,000 kg/ cm2, tensile strength at yield of 150 to 200 kg/cm2, and heat deflection temperature of 60 to 70 °C with 4. 6 kgf stress. The alloys also possess melt flow index of 2-5 g /10 min. when tested according to ASTM D1238 and allow injection molding, compression molding, thermoforming and other conventional techniques to be applied for making end products that demand high impact strength.

Description

Improved thermoplastic polyolefin alloys and process for their preparation

The present invention relates to an improved thermoplastic polyolefin alloy. In particular, the present invention relates to a compatabilized polypropylene copolymer blend prepared by melt blending in a co-rotating twin-screw extruder (or Buss-cokneader). The compatible blends of the present invention exhibit very high notched Izod impact strenth at normal concentrations of elastomers and suitable compatibilizers in the presence / absence of natural fillers. The present invention also relates to a process for producing improved thermoplastic polyolefin alloys.

Polymer blends have grown significantly commercially over the past 2-3 years, at least 2-5% ahead of existing polymer growth. Commercial polymer blends are designed or selected to have some degree of compatibility between the components to increase their resistance to delamination and ductility loss. Compatibility is the ability of polymer components to coexist as a molecularly miscible blend or a morphologically istinct phase but interfacially stable blend without the tendency of delamination. Means.

To date, the commercialization of highly immiscible commercial polymer pairs has been a technical challenge for polymer blend technicians in the industry. However, in recent years, graft or block copolymer-based compatibilizers or other interfacial agents that effectively reduce the interfacial tension between components can be used to stabilize morphologies that are detrimental to processing effects, yet at a useful level. Significant advances have been made in achieving ductility and resistance to delamination. Interfacial compatibilization in commercial polymer blends is generally achieved through reactive extrusion, where block or graft copolymer compatibilizers occur in situ at the interface during melt blending. .

Many commercial polymer blends often include elastomers to improve the impact strength of the blend under conditions of stress concentration. Elastomer dispersions are closely included in the matrix phase, in the dispersed polymer phase, or in both phases, depending on the blend's requirements and breaking behavior. The overwhelming factor in determining the impact strength of an immiscible or partially immiscible blend is the degree and efficiency of the interfacial compatibilization inherent in or designed into the blend system. If the interfacial adhesion or compatibility is poor, toughness will not be improved with the elastomer dispersion alone. Combining high levels of (notched) Izod impact strength with moderate stiffness has been a major focus of this invention.

There have been some innovations in this field and many patents have been granted. U. S. Patent No. 5,030, 694 (1991) to Kelly, J.M. discloses a blend of ethylene-propylene copolymers with some organic peroxides and EPDM with significant melt flow, impact strength and flexural modulus properties. EP Patent 132,968 (1985), issued to Mitsui Petrochemical Industries Ltd., provides excellent rigidity as a blend of ethylene-propylene copolymers and random ethylene-α-olefin copolymer rubbers containing natural fillers such as talc. Disclosed are blends that provide excellent impact properties as well as) properties. Nissan Motor Co. Ltd. And Mitsubishi Petrochemical Co. GB 2,246,358 (1992), issued to Ltd., discloses blends with good flow, impact and bending properties as blends of ethylene-propylene copolymers, EPR and talc. Nippon Petrochemicals Co. Ltd. And EP 435,247 (1991), issued to Nippon Oil and Fats, are blends of polypropylene and multi-phase propylene-vinyl monomer graft copolymers that provide blends that provide excellent impact resistance as well as good formability and heat resistance. To start. German Patent DE 3,520,151 (1986) to Dynamic Nobel, AG discloses blends having a high impact resistance and good weather resistance properties as blends of partially crystalline EP polymers, polypropylene homo or copolymers and polyethylenes comprising organic peroxides. do. Japanese Patent JP 04,258,652 (1992) to Mitsui Toatsu Chemicals Inc. discloses a blend that exhibits high impact strength and transparency as a syndiotactic PP and ethylene-propylene copolymer blend. It is disclosed in Japanese Patent JP 04,96,947 (1992) to Mitsui Toatsu Kagaku, K.K, that similar properties are exhibited by blending a propylene polymer containing an aromatic phosphorus metal salt and a thermoplastic elastomer. JP 03,252,436 (1991) to Tonen Chemical Corporation and Toyota Motor Corporation discloses blends that exhibit excellent heat and impact resistance properties as blends of ethylene-propylene block copolymers, EPR, amorphous nylon and modified PP. Idemitsu Petrochemical Co. Japanese Patent JP 03,168,233 (1991) issued to Ltd. discloses a blend exhibiting improved impact strength and weather resistance as a blend of PP and elastomer. Japan Synthetic Rubber Co. Ltd. has received Japanese Patent JP 02,191,656 (1990) for their blends exhibiting significant impact resistance as blends of thermoplastics, rubbers, crosslinking monomers and other additives. The company has received another Japanese Patent JP 02,49,043 (1990) for their polyolefin blends having resistance properties. In the case of nonpolyolefin materials, innovations have also been made regarding high impact materials. Idemitsu Petrochemical Co. Ltd. And Nippon Zeon Co. EP 297,517 (1989) to Ltd. discloses blends which exhibit excellent low temperature impact and solvent resistance properties as blends of graft copolymers obtained from polycarbonates and vinyl / polyfunctional vinyl monomers. US Patent No. 4,673,722 (1987) to General Motors discloses a blend that provides significant impact strength as a blend of nylon and polyurea.

In all the above patents, impact resistance is most important. As industrialization progresses and new and innovative machines are developed, the demand for high impact materials is increasing because of the increasing application of high impact materials in some devices. The present invention has been completed to meet the need for cost-efficient polyolefin blends with moderate stiffness and heat deflection temperatures but with very high impact strength. This blend disclosed in the present invention can be used in some applications, for example molded luggage, furniture, body panels and automotive parts.

One object of the present invention is to provide a compatible blend of polypropylene block copolymers and EPDM or EPR and to improve miscibility by using suitable compatibilizers.

Another object of the present invention is to provide a compatible polyolefin blend or alloy using a twin-screw extruder or Buss-cokneader.

Another object of the present invention is an alloy of polypropylene copolymer, EPDM or EPR with suitable compatibilizers and other additives, for example very large (notched) Izod impact strength of 60-90 kg.cm/cm, 6000- Provides alloys that exhibit flexural modulus of 8,000 kg / cm ² , heat deflection temperatures of 60-70 ° C., and which injection molding, compression molding, thermoforming and other conventional techniques can be applied to produce final products. It is.

It is a further object of the present invention to provide a process for the production of cost effective polyolefin alloys which is suitable for producing final products which exhibit very high (notched) Izod impact strength with moderate bending modulus.

The present invention provides a process for the preparation of polypropylene copolymer alloys with or without EPDM or EPR and suitable compatibilizers and fillers, melt blending all together or in separate batches in a co-rotating twin-screw extruder or Buss-cokneader. And a process for maintaining the extruder temperature in the range of 125-240 ° C. and the screw rotational speed in the range of 50-100 rpm.

In one embodiment of the invention, the polypropylene copolymer has been tested at 1-4 g / 10 min. When tested at 230 ° C./2.16 kg load (according to ASTM D 1238). Melt flow index in the range; And EPDM having a specific gravity of 0.86-0.90 and an ethylene content in the range of 55-65% by weight and a Mooney viscosity in the range of 36-77 [ML (1 + 4) 125 ° C.]; Or EPR.

In one embodiment of the invention, the alloy comprises polypropylene copolymer as the dominant phase in a concentration range of 50-95% by weight.

In another embodiment of the invention, the alloy is a propylene-ethylene / butylene-styrene block copolymer (SEBS), styrene-acrylonitrile copolymer (SAN) and polypropylene copolymer grafted with maleic anhydride (PPBC- g-MAH) and a compatibilizer in a concentration range of 5-30% by weight selected from the group of two ionomers.

In another embodiment of the invention, the alloy is also a natural filler selected from the group consisting of calcium carbonate, talc, mica, with a preferred particle size in the range of 10-30 microns and a suitable adhesion promoting surface treated natural Fillers are included in a concentration range of 0-10% by weight.

In another embodiment of the invention, the alloy is tested according to ASTM D 1238 2-5 g / 10 min. Melt flow index of the range.

In another embodiment of the invention, the alloy cuts an injection molded 3.2 mm thick sample (cut at the central portion of a tensile bar of type-I described in ASTM D638) according to ASTM D 256. Izod impact strength (notched sample) in the range of 60-90 kg.cm/cm when tested with, and 50-70 kg.cm/cm when tested with a 6.4 mm thick sample.

In another embodiment of the invention, the alloy exhibits a flexural modulus of 6,000-8,000 kg / cm ² when tested according to ASTM D 790.

In another embodiment of the present invention, the alloy exhibits tensile strength in the range of 150-200 kg / cm ² when tested according to ASTM D 638 using injection molded specimens.

In another embodiment of the invention, the alloy has a heat deflection temperature of 60-70 ° C. when tested at 4.6 kg and 45-55 ° C. when tested at 18.2 kgf stress to stress in accordance with ASTM D 648. Indicates.

Polyolefin polymers or propylene ethylene block copolymers (PPBC) are the preferred matrix materials for completing the present invention. This is obtained in the form of granules soon after the addition of the appropriate stabilizer and antioxidant. This granule is preferably dried at 80 ± 5 ° C. for 2 hours in an oven equipped with an air circulation system. Elastomers, preferably in granule form, ie ethylene propylene copolymer rubber (EPR) or ethylene-propylene-diene monomer (EPDM), are also separately dried in an air circulation oven for two hours in the preferred temperature range of 80 ± 5 ° C. do.

In the group of two ionomers of styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-acrylonitrile copolymer (SAN) and polypropylene copolymer (PPBC-g-MAH) grafted with maleic anhydride The selected compatibilizer is also dried at the same temperature as above for the same time. Similarly, as a natural filler selected from the group of talc, mica and calcium carbonate, the natural filler, preferably in the particle size range of 10-30 microns, is dried at the same temperature for the same time as above.

The purpose of melt blending by means of twin-screw extruders or Buss-cokneaders with specially designed screw profiles is to break the elastomer into fine particles as much as possible and to distribute them uniformly in the matrix of the polypropylene block copolymer. As closely related to the presence of suitable compatibilizers, alloys are obtained that exhibit the desired mechanical properties, in particular improved impact strength.

Dried PPBC, elastomer, compatibilizer, filler present or absent and other ingredients are tumble-mixed together in the following composition: 50-59% PPBC, 5-50% EPR / EPDM, 5-30% by weight of compatibilizer (s), 0-10% by weight filler, initiator, sulfur and other additives such as glycerin monostearate, Tinuvin-770, Tinuvin-327, B-blend-225 and Chimmasorb, Tinuvin-622 Each combination of benzophenone 0.01-0-10 phr. This tumble mixed dry mixture is extruded in a co-rotating twin-screw extruder (or Buss-cokneader) with the desired screw profile as follows: temperature range 125-240 ° C., screw speed 50-100 rpm, residence time 0.5-5.0 minute. This extrudate is immersed in cold circulating water and broken into granules 3-4 mm long.

The extruded granules are dried and then injection molded into ASTM standard test pieces to evaluate various performance characteristics such as tensile strength, flexural modulus, notched Izod impact strength and heat deflection temperature. Injection molding is a computer-controlled system with four heating zones operating in the range of 130-230 ° C, injection pressure (in 6 steps) 60-100kg / cm ² , injection time (in 6 steps) 2-6 seconds It is carried out using an injection molding machine. Screw speed (applied in two stages) is 90-105 rpm. The standard specimens thus obtained are used to test the various mechanical properties of the alloys (mentioned above) according to the ASTM standard test methods.

Other tests such as melt flow index, crystallization kinetics (using a differential scanning calorimeter) and filler content (using a thermogravimetric analyzer) are performed using the dry granules of the alloy. Dispersions and fillers of elastomers are observed using polarized light microscopy using thin microtome sections cut from injection molded flexural bars.

Rubber toughening is the most commonly used technique for improving the impact strength of polymers. In impact-modified materials, the composition, their miscibility, and the morphology of each component affect the deformation and fracture mechanisms of the blend. The particle size of the elastomer, its dispersion and adhesion with the matrix (if required by the use of a suitable compatibilizer) are also important factors in determining the toughness of the blend.

In the case of PPBC blends with EPDM / EPR, elastomers have been found to reduce the crystallinity of PPBC and significantly affect the destruction mechanism. Crazing and shear yielding, the mechanisms involved in plastic deformation in rigid polymers, have all been found to work simultaneously in these blends. These two mechanisms do not exclude each other and both operate simultaneously under certain conditions. They have been found to be responsible for toughening the matrix material PPBC.

The invention will now be described in more detail by the following examples. Its purpose is merely to illustrate the invention and not to limit the scope of the invention.

Example 1

Dry granules of 60% by weight of polypropylene copolymer were dried EPDM at a concentration of 20% by weight, 5% by weight of a preferred preferred compatibilizer styrene-acrylonitrile copolymer (SAN), PPBC (PPBC-g-grafted with maleic anhydride). MAH) 5% by weight and natural filler, preferably 10% by weight of talc. All of these ingredients were thoroughly tumble mixed. This dried mixture was extruded in an extruder (or Buss-cokneader) with co-rotating twin-screws with the desired screw profile for the purpose of intimately mixing the components. The extruder was operated at a temperature range of 125-240 ° C. and a screw rotation speed of 50-100 rpm. Extruded strand (referred to as Alloy-A) was immersed in a bucket of cold circulating water. This strand was then dried and granulated.

Standard ASTM test pieces were prepared by injection molding the dry granules of alloy-A using a FRK-85, Knockner-Windsor injection molding machine, applying the molding conditions given in Table 1 below.

Conventional Injection Molding Conditions for Making ASTM Specimen of Polyolefin Alloys number Processing parameters unit The usual value One Injection pressure kg / cm ² 60-100 2 Injection speed mm / sec 7-12 3 Holding temperature ℃ 130-230 4 Injection time sec. 2-6 5 Cooling time sec. 30-90 6 Screw speed rpm. 90-105

The performance characteristics of the alloy injection molded under the above conditions are shown in Table 2 below. For each performance reported here, at least six specimens were tested and their average value calculated.

Typical Performance of Alloy-A number characteristic unit ASTM Alloy-A One Melt flow index g / 10min. D 1238 4.2 2 The tensile strength kg / cm ² D 638 167 3 Tensile Modulus kg / cm ²  D 638 8,958 4 Bending strength kg / cm ² D 790 206 5 Flexural modulus kg / cm ²  D 790 8,134 6 Notched Izod Impact Strength 3.2 mm thick specimens * 6.4 mm thick specimens kg.cm/cm D 256  62 55 7 Heat deflection temperature at 4.6 kgf stress at 18.2 kgf stress ℃ D 648  75 50

(* The central part of the test piece of the injection molded ASTM standard tensile test piece was used)

Example 2

72 wt% moisture free granules of polypropylene copolymer were dried in a 23 wt% dry elastomer, preferably EPR and dried compatibilizer, preferably styrene-ethylene / butylene-styrene block copolymer (SEBS). ) 5% by weight. All of these components were tumble mixed thoroughly and then extruded under the same extruder and same conditions as described in Example 1 above. This extrudate (called Alloy-B) was granulated and standard ASTM test pieces were prepared under the same conditions using the same injection molding machine described in the above examples. The performance of the alloy-B is shown in Table 3 below.

Typical performance of alloy-B number characteristic unit ASTM Alloy-B One Melt flow index g / 10min. D 1238 2.34 2 The tensile strength kg / cm ² D 638 160 3 Tensile Modulus kg / cm ²  D 638 7,964 4 Bending strength kg / cm ² D 790 170 5 Flexural modulus kg / cm ²  D 790 6,800 6 Notched Izod Impact Strength 3.2 mm thick specimens * 6.4 mm thick specimens kg.cm/cm D 256  73 69 7 Heat deflection temperature at 4.6 kgf stress at 18.2 kgf stress ℃ D 648  65 48

(* The central part of the test piece of the injection molded ASTM standard tensile test piece was used)

Example 3

45% by weight of polypropylene copolymer, 45% by weight of PPBC (PPBC-g-MAH) grafted with maleic anhydride, and 10% by weight of elastomer, preferably EPDM, were all weighed and dried. All components were then thoroughly mixed and then extruded under the same extruder and the same extrusion conditions. This extrudate (referred to as Alloy-C) was granulated and a standard ASTM test piece was injection molded as described in the examples above. The performance of the alloy-C is shown in Table 4 below.

Typical performance of alloy-C number characteristic unit ASTM Alloy-C One Melt flow index g / 10min. D 1238 7.2 2 The tensile strength kg / cm ² D 638 165 3 Tensile Modulus kg / cm ²  D 638 7,758 4 Bending strength kg / cm ² D 790 180 5 Flexural modulus kg / cm ²  D 790 6,489 6 Notched Izod Impact Strength 3.2 mm thick specimens * 6.4 mm thick specimens kg.cm/cm D 256  76 63 7 Heat deflection temperature at 4.6 kgf stress at 18.2 kgf stress ℃ D 648  67 50

(* The central part of the test piece of the injection molded ASTM standard tensile test piece was used)

The present invention relates to an improved thermoplastic polyolefin alloy. In particular, the present invention relates to compatible polypropylene copolymer blends prepared by melt blending in a co-rotating twin-screw extruder (or Buss-cokneader). The compatible blends of the present invention exhibit very high notched Izod impact strenth at normal concentrations of elastomers and suitable compatibilizers in the presence / absence of natural fillers. The present invention also relates to a process for producing improved thermoplastic polyolefin alloys.

Claims (36)

Thermoplastic polyolefin alloy comprising a polypropylene block copolymer, an elastomer and a compatibilizer and having a large (notched) Izod impact strength as a base polymer. The Izod of claim 1 wherein the alloy is tested on notched specimens of 3.2 mm thickness in accordance with ASTM D 256 test method using standard injection molded specimens. A polyolefin alloy characterized by exhibiting impact strength (notched sample). 3. The polyolefin alloy of claim 1 or 2, wherein the polypropylene block copolymer is a block copolymer of propylene and ethylene. The polyolefin of claim 1, wherein the elastomer is selected from terpolymers made from ethylene propylene diene monomer (EPDM) / ethylene propylene copolymer rubber (EPR). Alloy. 5. The compatibilizer according to claim 1, wherein the compatibilizer is grafted with styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-acrylonitrile copolymer (SAN) and maleic anhydride. A polyolefin alloy characterized in that it is selected from the group of two different ionomers of polypropylene block copolymer (PPBC-g-MAH). The polyolefin alloy according to any one of claims 1 to 5, wherein the polypropylene block copolymer is present in an amount of 50 to 95% by weight of the alloy. The polyolefin alloy according to any one of claims 1 to 6, wherein the elastomer is present in a concentration range of 5 to 50% by weight. The polyolefin alloy according to any one of claims 1 to 7, wherein the compatibilizer is present in an amount of 5 to 30% by weight. The polyolefin alloy according to any one of claims 1 to 8, further comprising a natural filler. 10. The polyolefin alloy of claim 9, wherein said natural filler is selected from the group consisting of mica, talc and calcium carbonate. The polyolefin alloy according to claim 9 or 10, wherein the filler is present in a concentration range of 0-10% by weight. 50 to 59 weight percent of a base polymer selected from block copolymers of propylene and ethylene (PPBC); 5-50% by weight of an elastomer comprising a terpolymer prepared from ethylene propylene diene monomer (EPDM) / ethylene propylene copolymer rubber (EPR); With two different ionomers of styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-acrylonitrile copolymer (SAN) and polypropylene block copolymer (PPBC-g-MAH) grafted with maleic anhydride 5 to 30% by weight of a compatibilizer selected from the group consisting of; And 0-10% by weight of a natural filler selected from the group consisting of mica, talc and calcium carbonate and having a large (notched) Izod impact strength. 13. The thermoplastic polyolefin alloy according to claim 12, wherein the thermoplastic polyolefin alloy exhibits two to three endothermic peaks in the range of 90-167 ° C when heated in a differential scanning calorimeter at a uniform heating rate of 10 ° C / min. In a nitrogen atmosphere. The exotherm according to claim 12, which is exothermic in a temperature range of 115-25 ° C. when heated to 200 ° C. in a differential scanning calorimeter at a uniform heating rate of 10 ° C./min. In a nitrogen atmosphere, isothermally maintained for 3 minutes, and then cooled. A thermoplastic polyolefin alloy having a major peak and having a minor peak having a total ΔH value in the range of 113 to 125 ° C. and a value in the range of 55 to 75 J / g. The polyolefin alloy of claim 12, wherein the alloy has a melt flow index in the range of 2-5 g / 10 min. When tested according to ASTM D 1238 standard test method using dry granules. The polyolefin alloy of claim 12, wherein the alloy has a tensile strength in the range of 150 to 200 kg / cm ² when tested according to ASTM D 638 standard test method using injection molded specimens. The polyolefin alloy of claim 12, wherein the alloy has a tensile modulus in the range of 7,000 to 8,000 kg / cm ² when tested according to ASTM D 638 standard test method using injection molded specimens. The polyolefin alloy of claim 12, wherein the alloy has a flexural strength in the range of 160 to 200 kg / cm ² when tested according to ASTM D 790 standard test method using injection molded specimens. . The polyolefin alloy of claim 12, wherein the alloy has a flexural modulus in the range of 6,000 to 8,000 kg / cm ² when tested according to ASTM D 790 standard test method using injection molded specimens. . 13. The polyolefin of claim 12 wherein the alloy has a heat deflection temperature in the range of 60-70 ° C. at 4.6 kgf stress when tested according to ASTM D 648 standard test method using injection molded specimens. Alloy. The polyolefin alloy of claim 12, wherein the alloy has a heat deflection temperature in the range of 45-55 ° C. at 18.2 kgf stress when tested according to ASTM D 648 standard test method using injection molded specimens. A method of making a thermoplastic polyolefin alloy having a large (notch) izod impact strength comprising melt blending a polypropylene block copolymer, terpolymer and compatibilizer in the presence or absence of a filler. 23. The method of claim 22, wherein the melt blending is carried out in a twin screw extruder or Buss cokneader. The method of claim 22 wherein the polypropylene block copolymer is a block copolymer of propylene and ethylene. The preparation according to any of claims 22 to 24, wherein the elastomer is selected from terpolymers made from ethylene propylene diene monomer (EPDM) / ethylene propylene copolymer rubber (EPR). Way. 26. The compatibilizer according to any one of claims 22 to 25, wherein the compatibilizer is grafted with styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-acrylonitrile copolymer (SAN) and maleic anhydride. A process characterized in that the polypropylene block copolymer (PPBC-g-MAH) is selected from the group of two different ionomers. 27. A process according to any one of claims 22 to 26 wherein the polypropylene block copolymer is present in an amount of from 50 to 95% by weight of the alloy. 28. The method according to any one of claims 22 to 27, wherein the elastomer is present in a concentration range of 5 to 50% by weight. 29. The method of any one of claims 22 to 28, wherein the compatibilizer is present in an amount of 5 to 30 weight percent. 30. The method of any one of claims 22-29, further comprising a natural filler. 31. The method of claim 30, wherein said natural filler is selected from the group consisting of mica, talc and calcium carbonate. 32. The method of claim 31 wherein the filler is present in a concentration range of 0-10% by weight. 33. The method of any one of claims 23 to 32, wherein the extruder temperature is maintained in the range of 125 to 240 ° C. 34. A method according to any one of claims 23 to 33, wherein the twin-screw extruder / Buss co-kneader is operated with a screw rotating at a speed of 50-100 rpm. 35. The method of any one of claims 22 to 34, wherein the melt blending is performed with a residence time of 0.5 to 5.0 min. 22. An article made of the polyolefin alloy according to any one of claims 1 to 21.