MXPA99001883A - Improvement of thermal stability of sterile acrylate copolymers replaced in position a - Google Patents

Abstract

The thermal stability of alpha-substituted acrylate graft copolymers can be improved by: (a) making a graft copolymer containing a backbone of a propylene polymer material having graft polymerized to these monomers comprising: (1) an acrylic acid substituted by 1-3 C alkyl, and (ii) an acrylic ester substituted with 1-3 C alkyl, wherein the total amount of the polymerized monomers is from about 20% to about 240 parts per hundred parts of the propylene polymer material, and the amount of (i) is from about 1 to about 20%, based on the total weight of the monomers, and (b) removing any grafting monomer that does not react from the resulting propylene polymer material decomposing any initiator that does not react, and deactivating any residual free radical in the material

Description

IMPROVEMENT OF THERMAL STABILITY OF ALLOY GRAFT COPOLYMERS REPLACED IN THE ALPHA POSITION FIELD OF THE INVENTION This invention relates to a process for preparing graft copolymers of a polymeric propylene material and a polymerizable, substituted alpha acrylate monomer.

BACKGROUND OF THE INVENTION Substituted alpha polymers such as methacrylates, methacrylonitriles and α-methylstyrene are thermally unstable and are known to depolymerize their monomers corresponding to temperatures greater than 230 ° C. Above 300 ° C, poly (methyl methacrylate) (PMMA) rapidly depolymerizes at high conversions (> 95%). The normal extrusion and molding temperatures for these polymers are 200 ° -290 ° C. The significant depolymerization to the respective monomers will occur in this temperature range, affecting the safety of the operation, as well as the properties of the product. Polymethacrylates, and in particular PMMA, are alpha-substituted polymers most widely used in commercial applications. To expand the range of applications for these polymers it is important to improve their thermal stability.

In the manufacture of graft copolymers containing a main chain of a propylene polymer material, to which the poly (methyl methacrylate) is grafted, small amounts of the non-methacrylate monomers such as methyl acrylate, butyl acrylate and styrene by the common ones are copolymerized with methyl methacrylate to improve the thermal stability, since the polymers of these monomers are much more stable to heat and undergo degradation at relatively higher temperatures. However, the addition of these monomers affects the mechanical properties of the graft copolymers as well as the molecular weight and efficiency of the graft. As reported by Nishimoto et al., Polymer 32, 1275 (1991), methacrylate monomers have been used with methyl methacrylate to improve compatibility with other functional polymers such as polycarbonates, but the authors conclude that these did not improve thermal stability. Thus, there is a need for a method for increasing the thermal stability of the graft copolymers including the polymerized substituted alpha acrylates, as compared to those obtainable with the non-methacrylate comonomers currently used for this purpose.

SUMMARY OF THE INVENTION The method of this invention for improving the thermal stability of alpha substituted acrylate graft copolymers consists of: (a) preparing a graft copolymer containing a main chain of propylene polymer material having polymerized by grafting to the same, monomers containing: (i) an acrylic acid substituted with alkyl of 1-3 C, and (ii) an acrylic acid substituted with alkyl of 1-3 C, wherein the total amount of the polymerized monomers is from about 20 to about 240 parts per hundred parts of the propylene polymer material, and the amount of (i) is about 1% to about 20%, based on the total weight of the monomers, and (b) removing any of the graft monomers that do not react from the resulting grafted propylene polymer material, decomposing any unreacted initiator, and deactivating any residual free radical in the material. The copolymerization of a small amount of an acrylic acid substituted with 1-3C alkyl with the substituted alpha acrylate during the preparation of the graft copolymers of propylene polymer materials significantly increases the thermal stability of the copolymer of graft. The mechanical properties at room temperature and the molecular weight of the graft copolymer, and the efficiency of graft formation is not adversely affected.

Brief description of the drawings Figure 1 is a graph of the temperature (° C) against the percent of the original weight of the sample and the weight loss is observed during the thermogravimetric analysis and, therefore, the thermal stability of the graft copolymers containing a main chain of the propylene homopolymer, to which the poly (methyl methacrylate), a methyl methacrylate / methyl acrylate (MeAc) copolymer, and methacrylate copolymers were grafted of methyl / methacrylic acid (MAA) containing different amounts of methacrylic acid. Figure 2 is a graph of the temperature (° C) against the percent of the original weight of the sample and the weight loss is observed during the thermogravimetric analysis and, therefore, the thermal stability of the graft copolymers containing a main chain of propylene homopolymer to which poly (methyl methacrylate), methyl methacrylate / methacrylic acid (MAA) copolymer, a methyl methacrylate / methyl acrylate (MeAc) copolymer, and methacrylate copolymers were grafted of methyl / acrylic acid (AA) containing different amounts of acrylic acid. In both figures, polypropylene with a sufficiently broad molecular weight distribution was added to the graft copolymers to adjust the effective addition level to 50 parts of the polymerized monomers per 100 parts of polypropylene.

ILED DESCRIPTION OF THE INVENTION The first step in the process of this invention for improving the thermal stability of substituted alpha acrylate graft copolymers is to make a graft copolymer containing a backbone of a propylene polymer material having graft polymerized the same monomers consisting of (i) an acrylic acid substituted with alkyl of 1-3 C, and (ii) an ester of an acrylic acid substituted with alkyl of 1-3. The propylene polymer material that is used as the main chain of the graft copolymer can be: (a) a crystalline propylene homopolymer having an isotactic index greater than 80, preferably about 85 to about 99; (b) a crystalline copolymer of propylene and an olefin selected from the group consisting of ethylene and alpha-olefin of 4-10 C, with the proviso that, when the olefin is ethylene, the maximum content of polymerized ethylene is 10% by weight, preferably about 4%, and when the olefin is an alpha-olefin of 4-10 C, the maximum content thereof is 20%, preferably about 16% by weight, the copolymer having an isotactic index greater than 85; (c) a crystalline terylene polymer of propylene and two olefins selected from the group consisting of ethylene and alpha-olefins of 4-8 C, with the proviso that the maximum content of polymerized 4-8 C alpha-olefin is 20% by weight, preferably about 16%, and, when the ethylene is one of the olefins, the maximum content of polymerized ethylene is 5% by weight, preferably about 4%, the terpolymer having an isotactic index greater than 85; (d) an olefin polymer composition consisting of: (i) about 10% to about 60% by weight, preferably about 15% to about 55% of a crystalline propylene homopolymer having an isotactic index greater than 80, preferably about 85 to about 98, or a crystalline copolymer selected from the group consists of: (a) propylene and ethylene, (b) propylene, ethylene and an alpha olefin of 4-8 C, and (c) propylene and an alpha olefin of 4-8 C, the copolymer having a higher propylene content than 85% by weight, preferably about 90% to about 99%, and an isotactic index greater than 85; (ii) about 5% to about 25%, preferably about 5% to about 20% of an ethylene-propylene copolymer or an alpha-olefin of 4-8 C, which is insoluble in xylene at room temperature, and (iii) ) about 30% to about 70%, preferably about 20 to about 65% of an elastomeric copolymer selected from the group consisting of: (a) ethylene and propylene, (b) ethylene, propylene and an alpha olefin of 4-8 C , and (c) ethylene and a 4-8 C alpha olefin, the copolymer optionally containing about 0.5% to about 10% of a diene, and containing less than 70% by weight, preferably about 10% to about 60% of more preferably about 12% to about 55% ethylene and being soluble in xylene at room temperature, and with an intrinsic viscosity of about 1.5 to about 4.0 dl / g, wherein the total amount of? i) and (iii) / based on the total composition of the olefin polymer, is about 50% to about 90%, the weight ratio (ii) / (iii) is less than 0.4, preference 0.1 to 0.3, and the composition is prepared by polymerization in at least 2 stages, and has a flexural modulus of less than 150 MPa; or (e) a thermoplastic olefin containing: (i) about 10% to about 60%, preferably about 20% to about 50% of a crystalline propylene homopolymer having an isotactic index greater than 80, or a selected crystalline copolymer of the group consisting of: (a) ethylene and propylene, (b) ethylene, propylene and an alpha olefin of 4-8 C, and (c) ethylene and an alpha-olefin of 4-8 C, the copolymer having a content of propylene greater than 85 and an isotactic index greater than 85; (ii) about 20% to about 60%, preferably about 30% to about 50% of an amorphous copolymer selected from the group consisting of: (a) ethylene and propylene, (b) ethylene, propylene and an alpha olefin of 4 -8 C, and (c) ethylene and an alpha-olefin of 4-8 C, the copolymer optionally containing about 0.5% to about 10% of a diene, and containing less than 70% ethylene and being soluble in xylene at temperature ambient; Y (iii) about 3% to about 40%, preferably about 10% to about 20% of an ethylene-propylene copolymer or a 4-8 C alpha-olefin that is insoluble in xylene at room temperature, wherein the composition it has a flexural modulus greater than 150, but less than 1200 MPa, about 200 to about 1100 MPa, more preferably about 200 to about 1000 MPa. The room temperature is ~ 25 ° C. Alpha-defines of 4-8 C useful in the preparation of (d) and (e) include, for example, butene-1; pentene-1; exeno-1; 4-methylpentene-1, and octene-1. The diene, when present, is usually a butadiene; 1,4-hexadiene; 1, 5-hexadiene or ethylidenebornene.

The propylene polymer materials (d) and (e) can be prepared by polymerization in at least two stages, wherein in the first stage the propylene, propylene and ethylene; propylene and an alpha-olefin, or propylene, ethylene and an alpha-olefin are polymerized to form the component (i) of (d) or (e), and in the following steps the mixtures of ethylene and propylene, ethylene and the alpha-olefin or ethylene, propylene and the alpha-olefin, and optionally a diene, are polymerized to form the components (ii) and (iii) of (d) or (e).

The polymerization can be carried out in liquid phase, gas phase or liquid-gas phase using separate reactors, all of which can be done batchwise or continuously. For example, it is possible to carry out the polymerization of component (i) using liquid propylene as a diluent, and the polymerization of components (ii) and (iii) in the gas phase, without intermediary steps except for the partial degassing of propylene. The preferred method is all in the gas phase. The preparation of the propylene polymer material (d) is described in greater detail in U.S. Patent Nos. 5,212,246 and 5,409,992, the preparation of which is incorporated herein by reference. The preparation of the propylene polymer material (e) is described in greater detail in U.S. Patent Nos. 5,302,454 and 5,409,992, the preparation of which is incorporated herein by reference. Propylene homopolymer is the preferred propylene polymer backbone material. One of the monomers that is polymerized by grafting onto the main chain of the propylene polymer material is an acrylic acid substituted with alkyl of 1-3 C. Methacrylic acid is the preferred substituted acrylic acid. The amount of substituted acrylic acid is about 1% to about 20%, preferably about 1% to about 10%, and most preferably about 1% to about 5%, based on the total weight of the monomers. Acrylic acid is not effective at similar concentrations (see Figure 2). The other monomers that are polymerized by grafting onto the main chain of the propylene polymer material is an ester of an acrylic acid substituted by alkyl of 1-3 C. Methacrylic acid is the preferred substituted acrylic acid. Suitable esters include, for example, methyl, ethyl, butyl, benzyl, phenylethyl, phenoxyethyl, epoxy propyl, and hydroxypropyl esters. Esters of 1-4 C alkanols are preferred. Methyl methacrylate is the most preferred. The total amount of the polymerizable monomers is about 20 to about 240 parts, preferably about 30 to about 95 parts, per hundred parts of the propylene polymer material. The graft copolymer can be prepared according to any of the different methods. One of these methods includes forming the active sites for grafting onto the propylene polymer material by treatment with a peroxide or other chemical compound that is a free radical polymerization initiator, or by irradiation with high energy ionizing radiation. Free radicals produced in the polymer as a result of chemical or radiation treatment form active sites for grafting on the polymer and initiate the polymerization of the monomers at these sites. Graft copolymers produced by peroxide-initiated grafting methods are preferred. During graft polymerization, the monomers are also polymerized to form a certain amount of free or ungrafted polymer or copolymer. The morphology of the graft copolymer is such that the propylene polymer material is the continuous phase or matrix, and the polymerized monomers, both grafted and non-grafted, are a dispersed phase. The last step of the process of this invention is to remove any unreacted graft monomer from the resulting grafted propylene polymer material, decomposing any unreacted initiator and deactivating any residual free radical in the material.

The preparation of the graft copolymers by contacting the propylene polymer with a free radical polymerization initiator, such as an organic peroxide, and a vinyl monomer is described in more detail in US 5,140,074, the preparation of which is incorporated in US Pat. the present as a reference. The preparation of the graft copolymers by irradiating an olefin polymer and then treating with a vinyl monomer is described in greater detail in US 5,411,994, the preparation of which is incorporated herein by reference.

The compositions containing the graft copolymers of this invention can be easily modified by shock by the addition of one or more rubber components selected from the group consisting of: (i) an olefin copolymer rubber (ii) a hydrocarbon block copolymer monoalkenyl aromatic-conjugated diene, and (iii) a core-sheath rubber. Any of these rubber components may have acid or anhydride functionality or may be free of these functional groups. The preferred rubber components are (i) and (ii), alone or in combination. Suitable olefin copolymer rubbers include, for example, saturated olefin copolymer rubbers [sic] such as ethylene / propylene monomer rubbers.

(EPM), ethylene / octene-1 and ethylene / butene-1 rubbers, and unsaturated olefin terpolymer rubbers such as ethylene / propylene / diene monomer (EPDM) rubbers. Preferred olefin copolymer rubbers are ethylene / propylene, ethylene / butene-1 and ethylene / octene-1 copolymers. The monoalkenyl aromatic hydrocarbon-conjugated diene hydrocarbon block copolymer can be a thermoplastic elastomer of an AB (or diblock) structure, a linear ABA (or triblock) structure, the radial type (AB) r., Where n = 3-B 30% , or a combination of these types of structures, wherein each block A is a monoalkenyl aromatic hydrocarbon polymer block, and each block B is a unsaturated rubber block. The different grades of copolymers of this type are commercially available. The grades differ in structure, molecular weight of the intermediate and extreme blocks, and the ratio of the monoalkenyl aromatic hydrocarbon to rubber. The block copolymer can also be hydrogenated. The monomers of the common monoalkenyl aromatic hydrocarbons are styrene, linear or branched alkyl styrenes, 1-4 C, substituted by a ring, and vinyl toluene. Styrene is preferred. Suitable conjugated dienes include, for example, butadiene and isoprene. Preferred block copolymers are hydrogenated styrene / ethylene butene styrene copolymers. The weight average molecular weight Mw of the block copolymers will generally be in the range of about 45,000 to about 260,000 g / mol, the average molecular weights in the range of about 50,000 to about 125,000 g / mol being preferred to these producing compositions that They have a better balance of shock resistance and rigidity. Also, although it is possible to use block copolymers having unsaturated as well as saturated rubber blocks, copolymers having saturated rubber blocks are preferred, also on the basis of the impact / stiffness balance of the compositions containing them. The The weight ratio of the monoalkenyl aromatic hydrocarbon to conjugated diene rubber in the block copolymer is in the range of about 5/95 to about 50/50, preferably about 10/90 to about 40/60. The core-sheath rubber components comprise small particles of the cross-linked rubber phase surrounded by a compatibilizing shell, typically a vitreous polymer or copolymer. The nucleus is usually a diene rubber such as butadiene or isoprene, or an acrylate. The sheath is usually a polymer of 2 or more monomers selected from styrene, methyl methacrylate and acrylonitrile. Particularly preferred core-sheath rubbers have an acrylate core. Suitable resilience modifiers include, for example, the ethylene / octene-1 Engage 8100,8150, and 8200 copolymers, commercially available from DuPont Dow Elastomers; ethylene / propylene EPM 306P random copolymer, available commercially from Miles Inc., Polysar Rubber Division; the triblock styrene / ethylene-butene / styrene copolymer Kraton G 1652, commercially available from Shell Chemical Company; the ethylene / butene-1 Exact copolymers, commercially available from Exxon Chemical, Company and the heterophasic polyolefins KS080 and KS350, commercially available from Montell USA Inc.

Resilience modifiers, if present, are used in an amount of about 2% to about 30%, preferably about 5% to about 15% by weight, based on the total weight of the composition. The composition may also contain a propylene polymer material with broad molecular weight distribution (mw / Mn) (BM D PP) the BMWD PP has a m, .. / M. from about 5 to about 60, preferably from about 5 to about 40; a melt flow rate of about 0.5 to about 50, preferably about 1 to about 30 g / 10 min, and insoluble in xylene at 25 ° C greater than or equal to 94%, preferably greater than or equal to 96% , and more preferably greater than or equal to 98%. The propylene polymer material having a broad molecular weight distribution can be a propylene homopolymer or a modified propylene homopolymer in its ethylene / propylene rubber resilience, wherein the propylene homopolymer has a broad molecular weight distribution. The BMWD PP can be prepared by sequential polymerization in at least two stages, in the presence of a Ziegler-Natta catalyst with active magnesium halide support. The polymerization process occurs in separate and consecutive stages, and in each stage the Polymerization is carried out in the presence of a polymer and the catalyst coming from the previous stage. The polymerization process can be carried out in a batch mode or in a continuous mode according to the known techniques, operating in liquid phase in the presence or absence of an inert diluent, or a gas phase, or a liquid-gas phase, preferably in the gas phase. The preparation of the BMWD PP is described in greater detail in US Pat. No. 5,286,791, the preparation of which is incorporated herein by reference. The BMW DB, if present, is used in an amount of about 5% to about 90%, preferably about 10% to about 70%, based on the total weight of the composition. Other additives such as fillers and reinforcing agents, for example, carbon black and glass fibers, as well as inorganic powders such as calcium carbonate, talc and mica; pigments, slip agents; waxes; oils; Antiblock agents and antioxidants may also be present. The test methods used to evaluate the molded samples were: Izod Resilience Value ASTM D-256A Tensile Strength ASTM D-638-89 Flexibility Module ASTM D-790-86 Flexural strength ASTM D-790-86 Elongation to deformation ASTM D-638-89 Elongation to break ASTM D-638-89 Strength in ASTM D-638-89 line welding Resistance retained determined by dividing it in the line of welding resistance in the welding line between the tensile strength and multiplying by 100. ASTM D-6 deformation temperature 8 per heat ASTM D-1238 flow velocity cast, 230 ° C, 3.8 kg The porosity of the propylene homopolymer used as the main chain polymer in the manufacture of the graft copolymers is measured as described in Winslow, N.M. and Shapiro, J.J., "An Instrument for the Measurement of Pore-Size Distribution by Mercury Penetration" ASTM Bull., TP 39-44 (Feb. 1959), and Rootare, H.M. "Review of Mercury Porosi ertry "225-252 (In Hirshhom, J. S. and Roll, K. H. Eds., Advanced Experimental Techniques in Powder Metallurgy, Plenum Press, New York, 1970). In this specification, all parts and percentages are by weight at m < .ios that is indicated otherwise.

EXAMPLE 1 This example demonstrates the thermal stability of a graft copolymer containing a main chain of the propylene homopolymer, to which the copolymers methyl methacrylate / methacrylic acid (MMA / MAA) with different amounts of methacrylic acid was grafted. The results were compared with the thermal stability of a graft copolymer containing a backbone of the propylene homopolymer to which poly (methyl methacrylate) or a methyl methacrylate / methyl acrylate copolymer (MMA / MeAc) was grafted. In this and the following examples the propylene homopolymer used as the main chain polymer had the following properties: spherical shape, melt flow rate (MFR) of 9 g / 10 min, a porosity of 0.45 cmVg and a weighted average molecular weight (Mw) of 17,000.

The monomers were grafted onto the polypropylene backbone at a grafting temperature of 115 ° C using the peroxide-initiated graft polymerization process described above. 95 parts by weight of the monomers were added per 100 parts of the polypropylene. Lupersol PMS 50% t-butylperoxy-2-ethyl hexanoate in mineral spirits, commercially available from Elf Atochem, was used as the peroxide initiator. The monomers were fed at a rate of 1 pcc / min. HE I use a molar monomer to initiator ratio of 120. After the grafting reaction was complete the temperature was raised to 140 ° C for 2 hours under a nitrogen purge. The percent conversion of monomer to polymer was 97.2-57.7 for the MMA / MAA copolymers and 99.7 for the MMA / MeAc copolymer. The graft copolymer (68.4% by weight) was then mixed with 31.6% by weight of a polypropylene with broad molecular weight distribution (BMWD PP) with a polydispersity index of 7.4, an MFR of 1 g / 10 min, and soluble in xylene at room temperature of 1.5%, available commercially from Montell USA Inc., the MBWD PP was added to adjust the effective addition level to 50 parts of the polymerized monomer (s) per 100 parts of the polypropylene. The samples were composed on an intercooler Leistritz LSM double coil extruder, 34 mm co-rotator. Each sample was extruded as pellets at a barrel temperature of 210 ° C, a propeller speed of 300 rpm and a waste rate of 20 lb / hr. The stabilizer package used was 0.1% by weight of calcium stearate and 0.25% by weight of antioxidant Irganox B215. The antioxidant Irganox B215 is a mixture of one part antioxidant Irganox 1010 tetrakis [methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)] methane, and two parts antioxidant Irgafos 168 tris ^ 2,4-di t -butylphenyl) phosphite, both commercially available from CIBA Specialty Chemicals Corporation. The thermal stability of the granulated samples was assessed by thermogravimetric analysis (TGA) using the Perkin-Elmer TGA-7 analyzer. Approximately 10 mg of the sample were screened at 10 ° C / min under nitrogen at 30 ° C to 900 ° C and the weight loss was monitored. The region of interest lies between 200 ° C and 350 ° C, where poly (methyl methacrylate) tends to lose weight by depolymerization. The results are shown in Table 1 and Figure 1.

The data shows that graft copolymers having different levels of methacrylic acid are more stable at a given temperature than graft copolymers prepared with 100% MMA or MMA / MeAc (4.4%).

Example 2 This example demonstrates the physical properties of a graft copolymer containing a propylene homopolymer backbone, to which it was grafted with methyl methacrylate / methacrylic acid copolymer with different amounts of methacrylic acid. The results were compared to a control consisting of a graft copolymer containing a propylene homopolymer as the main chain polymer, to which a MMA / MeAc copolymer containing 4.4% methyl acrylate was grafted. The graft copolymers were prepared as described in Example 1. The graft copolymer (38.6% by weight) was then mixed with 42.9% by weight of the MBWD PP described in Example 1 to adjust the level of effective addition to 30 ppc. of polymerized monomers per 100 parts of polypropylene. The Engage 8150 ethylene / octene elastomer containing 25% octene, commercially available from DuPont-Dow Elastomer (14.55% by weight), was added to the samples. The black pigment Ampac ^ t 19472, a the commercial disposition of Ampace Corporation was also added in an amount of 2.91% by weight. The stabilizer package used was 0.05% Pationic 1240 modified calcium salt of lactic acid, available commercially from Pateo Polymer Additives Division, American Ingredients Company; 0.20% Irganox EC 20 FF stabilizer, Irganox 1010 antioxidant and one part of Irgafox 12 stabilizer, which is 2, 2 ', 2"-nitrile triethyl-tris [3, 3', 5 ', 5' -tetra-t- butyl-1, 1 '-biphenyl-2, 2'-diyl] phosphite, both commercially available from CIBA Specialty Chemicals Corporation; 0.30% antioxidant Tinuvin 328 2- (2-hydroxy-3,5-di-t- amylphenyl) -2H-benzotriazole, commercially available from CIBA Specialty Chemical Corporation, 0.24% antioxidant Tinuvin 770 bis (2, 2,6,6-tetramethyl-4-piperidinyl) cebacate, available commercially from CIBA Specialty Chemical Corporation, and 0.24% antioxidant Chimmasorb 119, commercially available from CIBA Specialty Chemical Corporation.The samples were composited in a Werner &Pfleiderer ZSK twin-screw extruder between 40mm co-rotator mixer. sample was extruded as granules at a barrel temperature of 210 ° C, and a propeller speed of 490 rpm and a waste rate of 17 0 lb / h. The composite samples were dried at 80 ° C for at least 4 hours before molding to remove the humed - .. d superficial. Test bars of 1 inch x 1/8 inch were used for all measurements of physical properties. The test bars were produced on a 5 oz. Battenfeld injection molding machine at a barrel temperature of 450 ° F and a mold temperature of 130 ° F. The results of the property assessments for each sample are given in Table 2.

The data shows that all graft copolymers containing methacrylic acid as one of the grafted monomers have properties similar to those of the control.

EXAMPLE 3 This example shows the effect of using methacrylic acid as one of the grafted monomers on the molecular properties and the efficiency of the graft formation of a graft copolymer containing a main chain of the propylene homopolymer to which a methacrylate copolymer was grafted of methyl / methacrylic acid. The results were compared with the properties of a graft copolymer containing a main chain wall of propylene homopolymer, to which poly (methyl methacrylate) or a MMA / MeAc copolymer (4.4%) was grafted.

The graft copolymers were prepared as described in Example 1. The numerical and weighted average molecular weights, the soluble MMA copolymer (XSRT) and the efficiency of the graft formation were measured using a Bio-Rad FTS-7 infrared spectrometer. and a Perkin-Elmer gel permeation chromatography (GPC) at room temperature with a refractive index detector and a mobile phase of tetrahydrofuran. It was found that the grafts of the MMA / MAA copolymer were only sparingly soluble in xylene, the solvent normally used for the measurements in the XSRT, even though only 1% of MAA was present in the poly (methyl methacrylate). Therefore, cycloheptanone was chosen as the solvent. The total amount of monomers, which is necessary for the calculation of The efficiency of the graft formation was measured by infrared analysis of the Fourier transforms, assuming that the polymer is 100% poly (methyl methacrylate). It was expected that this assumption would incur a minimal error for copolymers containing less than 5% MAA. The results are given in Table 3. In Table 3, the total ppc refers to the total amount of the monomers per 100 parts of the propylene homopolymer. M "and Mr? are the weighted average and number average molecular weights, respectively, of the polymerized monomers that are not grafts of the polypropylene backbone.

The data show that the addition of MAA does not affect the molecular weight of ungrafted polymerized monomers, or the efficiency of graft formation to the same extent as occurs with methyl acrylate. Higher values for molecular weight and efficiency of graft formation are preferred. Other features, advantages and embodiments of the invention described herein will be more apparent to those who exercise ordinary skills after reading the above description. In this regard, although the specific embodiments of the invention have been described in considerable detail, variations and modifications to these embodiments can be made without departing from the spirit and scope of the invention as described and claimed.

Claims (13)

1. A process for improving the thermal stability of alpha substituted acrylate graft copolymers consisting of: (a) preparing a graft copolymer containing a main chain of propylene polymer material having polymerized by grafting thereto, monomers containing: ( i) an acrylic acid substituted with alkyl of 1-3 C, and (ii) an acrylic acid substituted with alkyl of 1-3 C, wherein the total amount of the polymerized monomers is from about 20 to about 240 parts per hundred parts of the propylene polymer material, and the amount of (i) is from about 1% to about 20%, based on the total weight of the monomers, and (b) removing any unreacted graft monomer from the material resulting grafted propylene polymer, decompose any initiator that does not react, and deactivate any of the residual free radicals in the material.

2. The process of claim 1, wherein the propylene polymer material is selected from: (a) a crystalline propylene homopolymer having an isotactic index greater than 80; (b) a crystalline copolymer of propylene and an olefin selected from the group consisting of ethylene and alpha-defines of 4-10 C, with the proviso that, when the olefin is ethylene, the maximum content of polymerized ethylene is 10% by weight. weight, and when the olefin is an alpha-olefin of 4-10 C, the maximum polymerized content thereof is 20% by weight, the copolymer having an isotactic index greater than 85; (c) a propylene crystalline terpolymer and two defines selected from the group consisting of ethylene and alpha-olefins of 4-8 C, provided that the maximum polymerized 4-8 C alpha-olefin content is 20 % by weight, and, when ethylene is one of the olefins, the maximum content of polymerized ethylene is 5% by weight, the terpolymer having an isotactic index greater than 85; (d) an olefin polymer composition consisting of: (i) about 10% to about 60% by weight, of a crystalline propylene homopolymer having an isotactic index greater than 80, or a crystalline copolymer selected from the group consisting of in: (a) propylene and ethylene, (b) propylene, ethylene and an alpha olefin of 4-8 C, and (c) propylene and an alpha olefin of 4-8 C, the copolymer having a propylene content greater than 85% by weight, and a higher isotactic index than 85; (ii) about 5% to about 25%, of an ethylene-propylene copolymer or an alpha-olefin of 4-8 C, which is insoluble in xylene at room temperature, and (iii) about 30% to about 70%, of an elastomeric copolymer selected from the group consisting of: (a) ethylene and propylene, (b) ethylene, propylene and an alpha olefin of 4-8 C, and (c) ethylene and an alpha olefin of 4-8 C, containing the copolymer optionally about 0.5% to about 10% of a diene, and containing less than 70% by weight, of ethylene and being soluble in xylene at room temperature, and with an intrinsic viscosity of about 1.5 to about 4.0 dl / g, in where the total amount of (ii) and (iii), based on the total composition of the olefin polymer, is approximately 50% to about 90%, the weight ratio (ii) / (iii) is less than 0.4, preferably 0.1 to 0.3, and the composition is prepared by polymerization in at least 2 stages, and has a lower flexural modulus than 150 MPa; or (e) a thermoplastic olefin containing: (i) about 10% to about 60%, of a homopolymer d? crystalline propylene that has a isotactic index greater than 80, or a crystalline copolymer selected from the group consisting of: (a) ethylene and propylene, (b) ethylene, propylene and an alpha-olefin of 4-8 C, and (c) ethylene and an alpha-olefin of 4-8 C, the copolymer having a propylene content greater than 85% and an isotactic index greater than 85; (ii) about 20% to about 60%, of an amorphous copolymer selected from the group consisting of: (a) ethylene and propylene, (b) ethylene, propylene and an alpha olefin of 4-8 C, and (c) ethylene and an alpha-olefin of 4-8 C, the copolymer optionally containing about 0.5% to about 10% of a diene, and containing less than 70% ethylene and being soluble in xylene at room temperature; and (iii) about 3% to about 40%, of an ethylene-propylene copolymer or a 4-8 C alpha-olefin that is insoluble in xylene at room temperature, wherein the composition has a flexural modulus greater than 150. , but less than 1200 MPa.

3. The process of claim 1, wherein the propylene polymer material is a propylene homopolymer.

4. The process of claim 1. wherein the substituted acrylic acid is methacrylic acid.

5. The process of claim 4, wherein the ester of the substituted acrylic acid is an ester of an alkanol of 1-4 C.

6. The process of claim 5, wherein the ester is methyl methacrylate.

The process of claim 1, wherein the amount of (a) (i) is from about 1% to about 5%.

8. The product prepared by the process of claim 1.

9. A composition consisting of the product of claim 8, and about 2% to about 30% based on the total weight of the composition, of one or more components of rubber selected from the group consisting of (a) an olefin copolymer rubber, (b) a monoalkenyl aromatic conjugated diene hydrocarbon block copolymer, and (c) a core-sheath rubber.

10. The composition of claim 9 which further contains about 5% to about 90%, based on the total weight of the composition, of a broad molecular weight distribution propylene polymer material having an Mw / Mn of about 5 to about 60 and a melt flow rate of from about 0.5 to about 50 g / 10 min.

11. The product produced by the process of claim 6.

12. A composition consisting of the product of claim 11 and about 2% to about 30%, based on the total weight of the composition, of one or more rubber components selected from the group consisting of: (a) a copolymer rubber of olefin (b) a monoalkenyl aromatic hydrocarbon-conjugated diene hydrocarbon block copolymer, and (c) a core-sheath rubber. The composition of claim 12 which further contains from about 5% to about 90%, based on the total weight of the composition, of a broad molecular weight distribution propylene polymer material having an Mw / Mn of about 5. at about 60 and a melt flow rate of about 0.05 to about 50 g / 10 min.