Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
  • C08L33/04—Homopolymers or copolymers of esters
  • C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
  • C08L33/10—Homopolymers or copolymers of methacrylic acid esters
  • C08L33/12—Homopolymers or copolymers of methyl methacrylate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/01—Hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/10—Homopolymers or copolymers of propene
  • C08L23/12—Polypropene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L25/00—Compositions of, homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Compositions of derivatives of such polymers
  • C08L25/02—Homopolymers or copolymers of hydrocarbons
  • C08L25/04—Homopolymers or copolymers of styrene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L51/06—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/26—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers modified by chemical after-treatment
  • C08L2023/40—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers modified by chemical after-treatment by reaction with compounds changing molecular weight
  • C08L2023/42—Depolymerisation, vis-breaking or degradation
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/08—Copolymers of ethene
  • C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms
  • C08L23/0815—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms with aliphatic 1-olefins containing one carbon-to-carbon double bond
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L91/00—Compositions of oils, fats or waxes; Compositions of derivatives thereof

Definitions

• This invention relates to a process for making thermally stable polymers, including graft copolymers comprising a backbone of a propylene polymer material.
• polymers that are substituted at the alpha-carbon atom such as poly(methacrylates), poly(methacrylonitriles) and poly(alpha-methylstyrene).
• poly(methacrylates) and particularly poly(methyl methacrylate) (PMMA) are the most widely used in commercial applications.
• PMMA poly(methyl methacrylate)
• Copolymerization with a minor amount of non-methacrylate monomer such as methyl acrylate, ethyl acrylate, butyl acrylate or styrene is often required to improve stability for processing in commercial applications.
• PMMA could depolymerize readily at high conversion (>95%) above 300°C.
• copolymerization affects the mechanical and molecular properties of PMMA. Depolymerization during processing also raises safety and health concerns due to monomer exposure, and odor associated with the monomer. The free monomer in the polymer can also lead to surface irregularities called splay, as well as odor in the finished product.
• 6,04-6,273 describes a method for increasing the thermal stability of alpha-substituted acrylate graft copolymers by grafting to the backbone of propylene polymer material monomers comprising (a) an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl grqup and (b) an ester of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group.
• International Patent Publication WO 00/08078 describes a method for increasing the thermal stability of acrylic-grafted propylene polymers by graft polymerizing in the presence of a 4-vinyl-substituted 5-12 C cyclic 1-alkene, which acts as an end-capping agent.
• Polymers that are unsubstituted in the alpha-position such as polyethylene, polypropylene, polystyrene, and polyacrylonitrile, generally degrade by random scission at temperatures higher than those at which depolymerization of alpha-substituted polymers takes place, resulting in rapid loss of molecular weight and mechanical properties. In the presence of oxygen, degradation can also proceed via formation of hydroperoxide species, causing further decomposition.
• U.S. 5,914,194 discloses vinylidene chloride compositions having enhanced thermal stability and a decreased tendency to degrade while being extruded by using certain fatty acid derivatives, particularly fatty acid derivatives of castor oil, as a stabilizer in amounts up to about 4. )% by w ight, along with up to about 2 weight percent of a plasticizer.
• Use of at least one ali ⁇ latic unsaturated compound, e.g., soybean oil or safflower oil, to stabilize polyolefin compositions against radiation-induced degradation is disclosed in U.S. 6,017,986.
• the process of this invention for improving the thermal stability of polymers comprises blending, before melt processing, (1) a polymer selected from the group consisting of (a) olefin polymers, (b) polymers of vinyl-substituted aromatic compounds, (c) polymers of acrylic esters selected from the group consisting of (i) an ester of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group, and (ii) a combination of (i) and at least one monomer capable of being polymerized by free radicals, and (d) graft copolymers comprising a backbone of a.
• a polymer selected from the group consisting of (a) olefin polymers, (b) polymers of vinyl-substituted aromatic compounds, (c) polymers of acrylic esters selected from the group consisting of (i) an ester of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group, and (ii) a combination of (
• propylene polymer material having graft polymerized thereto a monomer selected from the group consisting of (i) an ester of an acrylic acid substituted at the alpha- carbon atom by a 1-3 C alkyl group, and (ii) a combination of (i) and at least one monomer capable Of being polymerized by free radicals, and (2) about 0.1% to about 5%, based on the weight of the polymer, of at least one aliphatic compound having at least one site of unsaturation, the compound having a molecular weight of at least 200 and an iodine number of at least 10.
• composition comprising (1) a polymer selected from the group consisting of (a) polymers of vinyl-substituted aromatic compounds, (b) polymers of acrylic esters selected from the group consisting of (i) an ester of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group, and (ii) a combination of (i) and at least one monomer capable of being polymerized by free radicals, and (c) graft copolymers comprising a backbone of a propylene polymer material having graft polymerized thereto a monomer selected ffrom the group consisting of (i) an ester of an acrylic acid substituted at the alpha- carbon atom by a 1-3 C alkyl group, and (ii) a combination of (i) and at least one monomer capable of being polymerized by free radicals, and (2) about 0.1% to about 5%, based on the weight of the polymer, of at least one aliphatic compound having at least one site of
• the aliphatic unsaturated compound retards degradation of the polymer during melt processing.
• the improvement in thermal stability of the polymer is indicated by a lower melt flow rate (MF ), a shifting of the weight loss vs temperature curve generated by thermogravimetric analysis (TGA), towards higher temperatures, and/or lowering of the amount of the residual monomer in pelletized samples.
• MF melt flow rate
• TGA thermogravimetric analysis
• Figure 1 is a plot of temperature (°C) against the % of the original weight of the grafted polymer and shows the weight loss during TGA and therefore the thermal stability of (1) a graft copclymer comprising a. backbone of propylene homopolymer, to which was grafted poly(methyl methacrylate-co-methyl acrylate) without the unsaturated additive, (2) a graft copolymer comprising a backbone of propylene homopolymer, to which was grafted a copolymer of methyl methacrylate and methyl acrylate, blended with 5% soybean oil, and (3) a graft copolymer comprising a backbone of propylene homopolymer, to which was grafted a copolymer of methyl methacrylate and 5% methacrylic acid, blended with 5% soybean oil.
• a graft copclymer comprising a. backbone of propylene homopolymer, to which was grafted poly(methyl methacrylate
• Figure 2 shows the effect of various oils (2.5 wt. %) on the residual methyl methacrylate concentration (ppm), the % reduction in residual methyl methacrylate, and the MFR of ja graft cjopolymer comprising a backbone of propylene homopolymer, to which was grafted poly(methyl methacrylate-co-methyl acrylate).
• Figure 3 shows the effect of various oils (2.5 wt. %) on the residual methyl methacrylate concentration (ppm), the % reduction in residual methyl methacrylate, and the MFR of ja graft copolymer comprising a backbone of propylene homopolymer, to which was grafted a copolymer of methyl methacrylate and 10% methacrylic acid.
• the process of this invention for improving the thermal stability of polymers comprises blending, before melt processing, (1) a polymer selected from the group consisting of (a) olefin polymers, (b) polymers of vinyl-substituted aromatic compounds, (c) polymers of acrylic esters selected from the group consisting of (i) an ester of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group, and (ii) a combination of (i) and at least one monomer capable of being polymerized by free radicals, and (d) graft copolymers comprising a backbone of a propylene polymer material having graft polymerized thereto a monomer selected from th group consisting of (i) an ester of an acrylic acid substituted at the alpha- carbon atom by a 1-3 C alkyl group, and (ii) a combination of (i) and at least one monomer capable of being polymerized by free radicals, and (2) about 0.1% to about 5%,
• I weight of the polymer of at least one aliphatic compound having at least one site of unsaturation, the compound having a molecular weight of at least 200 and an iodine number of at least 10, preferably at least 25.
• Suitable olefin polymers that can be used in the process of this invention include, for example, polyethylene and polypropylene.
• Suitable polymers of vinyl-substituted aromatic compounds include, for example, polymers of styrene, alpha-methylstyrene, para-methylstyrene, and other ring-substituted styrenes.
• th ester is an ester of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group.
• Methacrylic acid is the preferred substituted acrylic acid.
• Suitable esters include, for example, the methyl, ethyl, butyl, benzyl, phenylethyl, epoxypropyl, and hydroxypropyl esters. Esters of 1-4 C alkanols are preferred. Methyl methacrylate is most preferred.
• the acrylic ester is a combination of (i) an ester of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group and (ii) at least one monomer capable of being polymerized by free radicals
• Typical substituent groups can be alkyl, hydroxyalkyl, aryl, and halo.
• the vinyl monomer will be a member of one of the following classes: (1) vinyl-substituted aromatic, heterocyclic, or alicyclic compounds, including styrene, vinylnap ithalenej vinylpyridine, vinylpyrrolidone, vinylcarbazole, and homologs thereof, e.g., alpha- and para-riethylstyrene, methylchlorostyrene, p-tert-butylstyrene, methylvinylpyridine, and eth lvinylpyridine; (2) vinyl esters of aromatic and saturated aliphatic carboxylic acids, including vinyl formate, vinyl acetate, vinyl chloroacetate, vinyl cyanoacetate, vinyl propionate, and vinyl benzoate; and (3) unsaturated aliphatic nitriles and carboxylic acids and their derivatives, including acrylonitrile; methacrylomtrile; acrylamide; methacrylamide, and acrylic acid; acrylate esters, such
• Olefin polymers polymers of vinyl-substituted aromatic compounds, and polymers of acrylic esters are all commercially available.
• the propylene polymer material that is used as the backbone of the graft copolymer can be:
• thermoplastic olefin comprising:
• Propylene polymer materials (d) and (e) can be prepared by polymerization in at least two stag'es, where 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 component (i) of (d) or (e), and in the following stages 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 components (ii) and (iii) of (d) or (e).
• the polymerization can be conducted in liquid phase, gas phase, or liquid-gas phase using separate actors, all of which can be done either by batch or continuously.
• the preparation of propylene polymer material (d) is described in more detail in U.S.
• Patents 5,212,246 and 5,409,992 which are incorporated herein by reference.
• the preparation of propylene polymer material (e) is described in more detail in U.S. Patents 5,302,454 and 5,409,992, which are incorporated herein by reference.
• Propylene homopolymer is the preferred propylene polymer backbone material.
• the monomers that can be graft polymerized onto the backbone of propylene polymer material are selected from the group consisting of (i) an ester of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group, and (ii) a combination of (i) and at least one monome:: capable of being polymerized by free radicals.
• One of the monomers that can be graft polymerized onto the backbone of propylene polymer material is an ester !of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group.
• Methacrylic acid is the preferred substituted acrylic acid.
• Suitable esters include, for example, the methyl, ethyl, benzyl, phenylethyl, phenoxyethyl, epoxypropyl, and hydroxypropyl esters. Esters of 1-4 C alkanols are preferred. Methyl methacrylate is most preferred.
• the monomer capable of being polymerized by free radicals can be any of the monomeric vinyl compounds described previously in connection with the polymers of acrylic esters.
• the preferred combination of an ester of a substituted acrylic acid and a monomer i capable of being polymerized by free radicals is a combination of methyl methacrylate and methyl, ethyl, or butyl acrylate; a combination of methyl methacrylate and styrene, or a combination of methyl methacrylate and methacrylic acid.
• the total amount of polymerized monomers used to make the graft copolymer 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 made according to any one of various methods. One of these methods involves forming active grafting sites on 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. The free radicals produced in the polymer as a result of the chemical or irradiation treatment form active grafting sites on the polymer and initiate the polymerization of the monomers at these sites.
• the monomers also polymerize 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 or matrix phase, and the polymerized monomers, both grafted and ungrafted, are a dispersed phase.
• the last step of the process for making the graft copolymers is removing any unreacted grafting monomer from the resulting grafted propylene polymer material, decomposing any unreacted initiator, and deactivating any residual free radicals in the material.!
• 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 U.S. 5,140,074, which is incorporated herein by reference.
• a free radical polymerization initiator such as an organic peroxide and a vinyl monomer
• Preparation of graft copolymers by irradiating an olefin polymer and then treating with a vinyl monomer is described in more detail in U.S. 5,411,994, which is incorporated herein by reference.
• the degree of retardation of polymer degradation was found to depend on the degree of unsaturation of the unsaturated aliphatic compound and its concentration in the formulation.
• the degree of unsaturation is indicated by the iodine number of the unsaturated compound.
• a minimum amount of unsaturation (iodine number of 10) is required.
• a compound having multiple unsaturation sites will typically be more effective than a compound having a single unsaturation site.
• the molecular weight of the unsaturated aliphatic compound is typically at least 200, and preferably at least 350, to avoid volatility problems during extrusion of the polymer.
• Suitable unsaturated aliphatic compounds include, for example, fatty oils, squalene, polybutadiene, a tertiary amine having at least one aliphatic, unsaturated substituent derived from a fatty acid, oleamide, calcium oleate, erucyl erucamide, and glycerol monooleate. Many of these compounds are commercially available.
• the fatty oils are composed largely of glycerides of the fatty acids, chiefly oleic, palmitic, stearic, and linoleic acids, although they are typically described in terms of their fatty acid content.
• the presence of free acid in edible oils such as safflower oil is undesirable.
• sush oils are refined to ensure that there is little or no free acid present.
• S oybean oil, safflower oil, and linseed oil are particularly preferred fatty oils for use in the practice of this invention.
• Soybean oil is a drying oil extracted from soybeans and has an iodine vilue of 1123-140.
• Safflower oil is a drying oil extracted from safflower (carthamus) seed and has an iodine number of about 145.
• Linseed oil is a drying oil extracted from flaxseed 'and has an iodine value of about 180.
• the oils are readily available and less expensive than adding antioxidants to the polymers or adding comonomers in the case of substituted acrylic acid esters.
• Squalene is an aliphatic hydrocarbon having six unconjugated double bonds, has an iodine number of about 310, a molecular weight of 423, and is found in shark liver oil.
• the polybutadiene can have significant unsaturation (e.g., an iodine value of about 470) and can contain a variety of cis- and trans-unsaturation.
• unsaturation e.g., an iodine value of about 470
• trans-unsaturation e.g., a polybutadiene containing 70% 1,2-vinyl double bonds, 20%
• Suitable aliphatic, unsaturated amine compounds include oleamide and erucyl erucamice, in addition to tertiary amines having at least one aliphatic, unsaturated substituent derived from a fatty acid.
• An example of such a tertiary amine includes a commercially available mixture of compounds having two methyl groups and a mixture of substituents derived from fatty acids comprising about 22% saturated C 16 and C 18 , 53% oleic acid, 22% linoleic acid and 3%> linolenic acid. The mixture has a calculated iodine value of 86.
• the improvement in the thermal stability of a given polymer can be confirmed by lower MFR, shifting of weight loss vs temperature curves towards higher temperatures using TGA and/or lowering of the amount of residual monomer in the pelletized samples.
• compositions comprising (1) a polymer selected from the group consisting of (a) polymers of vinyl-substituted aromatic compounds, i (b) polymers of acrylic esters selected from the group consisting of (i) an ester of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group, and (ii) a combination of (i) and at least one monomer capable of being polymerized by free radicals, and (c) graft copoly ers comprising a backbone of a propylene polymer material having graft polymerized thereto a monomer selected from the group consisting of (i) an ester of an acrylic acid substituted at the alpha-carbon atom by a 1-3 C alkyl group, and (ii) a combination of (i) and at least one monomer capable of being polymerized by free radicals, and (2) about 0.1% to about 5%, based on the weight of the polymer, of at least one aliphatic compound having at
• the polymer components and the unsaturated aliphatic compounds are the same as those described above in relation to the process for improving the thermal stability of the polymers.
• the compositions of this invention can easily be impact-modified by the addition of one or more rubber components selected from the group consisting of (i) an olefin copolymer rubber, (ii) a monoalkenyl aromatic hydrocarbon-conjugated diene block copolymer, and (iii) a core-shell rubber. Any of these rubber components can have acid or anhydride functionality or can be free of these functional groups.
• the preferred rubber components are (i) and (ii), either alone or in combination.
• Suitable olefin copolymer rubbers include, for example, saturated olefin copolymer rubbers such as 1 ethylene/propylene monomer rubbers (EPM), ethylene/octene-1, and
• ethylene/butene-1 rubbers and unsaturated olefin terpolymer rubbers such as ethylene/propylene/diene monomer rubbers (EPDM).
• the preferred olefin copolymer rubbers are ethylene/propylene, ethylene/butene-1, and ethylene/octene-1 copolymers.
• Various grades of copolymers of this type are commercially available. The grades differ in structure, molecular weight of the mid and end blocks, ⁇ nd ratio of monoalkenyl aromatic hydrocarbon to rubber.
• the block copolymer can also be hydrogenated.
• Typical monoalkenyl aromatic hydrocarbon monomers are styrene, ring-substituted 1-4 C linear or branched alkyl styrenes, and vinyltoluene. Styrene is preferred. Suitable conjugated dienes inplude, for example, butadiene and isoprene. Preferred block copolymers are hydrogenated styrene/ethylene-butene/styrene triblock copolymers.
• the weight average molecular weight M w of the block copolymers generally will be in the range of about 45,000 to about 260,000 g/mole, average molecular weights in the range of about 50,000 to about 125,000 g/mole being preferred because they produce compositions having the best balance of impact strength and stiffness. Also, while block copolymers having unsaturated as well as saturated rubber blocks can be used, copolymers having saturated rubber blocks are preferred, also on the basis of the impact/stiffness balance of the compositions containing them.
• the weight ratio of 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 !l0/90 to about 40/60.
• the core-shell rubber components comprise small particles of crosslinked rubber phase surrounde , by a compatibilizing shell, normally a glassy polymer or copolymer.
• the core is typically a diene rubber such as butadiene or isoprene, or an acrylate.
• the shell is typically a polymer of two or more monomers selected from styrene, methyl methacrylate, and acrylonitrile. Particularly preferred core-shell rubbers have an acrylate core.
• Suitable impact modifiers include, for example, Engage 8100, 8150, and 8200 ethylene/octene-1 copolymers, commercially available from DuPont Dow Elastomers; EPM
• the propylene polymer material having a broad molecular weight distribution can be a homopolymer of propylene or an ethylene/propylene rubber impact-modified homopolymer of propylene, 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 supported on magnesium halide in active form.
• the polymer zation process occurs in separate and consecutive stages, and in each stage polymerization takes place in the presence of the polymer and the catalyst coming from the precedin lg stage.
• the polymerization process can be carried out in a batch or in a continuous mode accordin lg; to known techniques, operating in liquid phase in the presence or not of an inert diluent, or in gas phase, or liquid-gas phase, preferably in gas phase.
• the preparation of the BMWD PP is described in more detail in U.S. Patent 5,286,791, which is incorporated herein by reference.
• the BMWD PP 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.
• Either one or both of the rubber component and the BMWD PP can be added to the composition.
• the polymer compositions can also include other additives that are conventionally employed in the art, such as pigments, slip agents, waxes, antiblocking agents, and antioxidants.
• the melt flow rate of the graft copolymers is measured according to ASTM 1238 at 230°C and 3.8 kg!
• the melt! flow rate of propylene polymers is measured according to ASTM 1238 at 230°C and 2.16 kg.
• the porosity of the propylene homopolymer used as the backbone polymer in the manufacture of the graft copolymers is measured as described in Winslow, N. M. and Shapiro,! J. I., "An Instrument for the Measurement of Pore-Size Distribution by Mercury Penetration," ASTM Bull., TP 49, 39-44 (Feb. 1959), and Rootare, H. M., "Review of Mercury Porosimetry," 225-252 (In Hirshhom, J. S. and Roll, K. H., Eds., Advanced Experimental Techniques in Powder Metallurgy, Plenum Press, New York, 1970).
• Isotactic index is defined as the xylene insouble fraction.
• the weight percent of olefin polymer soluble in xylene at room temperature is determined by dissolving 2.5 g of the polymer in 250 ml of xylene in a vessel equipped with a stirrer, that is heated at 135°C with agitation for 20 minutes. The solution is cooled to 25°C while continuing the agitation, and then left to stand without agitation for 30 minutes so that the solids can settle. The solids are filtered wi ith filter paper, the remaining solution is evaporated by treating it with a nitrogen stream, and the solid residue is vacuum dried at 80°C until a constant weight is reached.
• the percent by weight of polymer insoluble in xylene at room temperature is the isotactic index of the polymer.
• the value obtained in this manner corresponds substantially to the isotactic index determined via extraction with boiling n-heptane, which by definition constitutes the isotactic index of the polymer.
• PI Polydispersity index
• MMA Residual i methyl methacrylate
• Example 1 This example describes the effect of soybean oil on the thermal stability of a graft copolymer comprising a propylene homopolymer backbone, to which was grafted a methyl methacrylate copolymer.
• the graft copolymers are designated as PP-g-(MMA-co-MeAc) and PP-g-(MMA-co-MAA) in Table 1.
• the propylene homopolymer used as the backbone polymer! had the following properties: spherical form, a MFR of 9 g/10 min, a porosity of 0.45 cm 3 /g and a M w of 170,000.
• the monomers were fed at a rate of 1 pph/min.
• the temperature was raised to 140°C for 2 hours under a nitrogen purge.
• the soybean oil was added to the graft copolymer and a broad molecular weight distribution propylene homopolymer (BMWD PP), and the mixture was allowed to stand overnight. Calcium stearate and the Irganox B-225 antioxidant were then added.
• the BMWD PP was added to adjust the effective add level to 50 parts of polymerized monomers per hundred parts of propylene homopolymer. It had a polydispersity index of 7.4, a MFR of
• Irganox B-225 antioxidant is a blend of 1 part Irganox 1010 antioxidant and 1 part Irgafos 168 tris(2,4-di-t-butylphenyl) phosphite antioxidant, commercially available from Ciba Specialty Chemicals Corporation. All
• the blends were homogenized prior to compounding to disperse the oil, either by hand shaking or tumble blending, and then extruded on a Leistritz 34 mm twin screw extruder at 230°C at a feed rate of 20 lb/hr and a screw speed of 300 rpm.
• the thermal stability of the pelletized samples was assessed by TGA using a Perkin- Elmer T3A-7 analyzer. About 7.5 mg of sample was scanned at 10°C/min in nitrogen from
• Graft copolymers comprising a backbone of propylene homopolymer, to which were i grafted (MMA-co-MeAc) and (MM-co-MAA) were prepared as described in Example 1, except that 10% MAA was used instead of 5%.
• the components of the compositions were combinqd as described in Example 1.
• the same BMWD PP was used as in Example 1 and was added to adj ust the effective add level to 50 parts of polymerized monomers per hundred parts of ropyler.e homopolymer.
• I i calcium stearate, and the antioxidant are shown in Table 3.
• the BMWD PP and the antioxidant are the same as in Example 1. All amounts are given in weight per cent unless otherwise noted.
• Residual MMA reduction was realized at 0.5, 1.0, and 1.5% oil.
• the MFRs were also lower than the respective control samples without the oil.
• Ihis example demonstrates the effectiveness of various oils in controlling the degradation of graft copolymers comprising a propylene homopolymer backbone, to which were grafted two different methyl methacrylate copolymers.
• the oils selected and their iodine numbers are given in Table 4.
• the effect of these oils on the MFR and the residual MMA concentration are represented in Figures 2 and 3.
• the graft copolymer tested in Figure 2 had a backbone of propylene homopolymer to which was grafted a methyl methacrylate/methyl acrylate copolymer, wherein the amount of methyl acrylate was 4.4%> of the total monomers.
• the graft copolymer tested in Figure 3 had a backbone of propylene homopolymer, to which was grafted ja methyl methacrylate/me hacrylic acid copolymer, wherein the amount of methacrylic acid was 5% of the total monomers.
• Both graft copolymers were prepared as described in Example 1. In each case 2.5%> of the oil was used.
• oils having a higher degree of unsaturation i.e., a higher iodine number, were more effective in retarding the degradation of the poly(methyl methacrylate) (PMMA) in tbe graft copolymer.
• This example shows the effect of soybean oil on the stability of polystyrene as determined by TGA.
• the polystyrene had a M w of 280,000 and is commercially available from Aldrich Chemical Company.
• the polystyrene was first ground and then mixed with 2.5% soybean oil.
• the data from the weight loss/temperature curve obtained by TGA are given in Table 5.
• This example shows the effect of soybean oil on the degradation of alpha- methylstyrene, which is less thermally stable than polystyrene because of substitution by the methyl group in the alpha position of the phenyl ring.
• the poly(alpha-methylstyrene) had a
• This example shows the effect of soybean oil on the degradation of a graft copolymer having a backbone of propylene homopolymer, to which polystyrene was graft polymerized
• graft polymerization process Eighty-five parts by weight of styrene were added per 100 parts of propylene homopolymer.
• the monomer was fed at 1.0 pph/min, and a monomer to initiator molar ratio of 105 was used.
• the weight loss/temperature data from TGA are numerically represented in Table 8.
• soybean oil resulted in a drop in MFR from 64 to 28.8 dg/min without stabilizer and from 70 to 18.8 dg/min with stabilizer.
• weight loss vs temperature curve from TGA shifted towards higher temperatures.
• This example shows the effect of soybean oil on the thermal stability of propylene homopolymer (PP) using TGA.
• the propylene homopolymer used as the backbone polymer in Example 1 was mixed with 2.5% soybean oil.
• Propylene homopolymer without oil was used as a control and the temperatures at which polymer weight loss occurred were compared.
• This example shows the effect of soybean oil on the thermal stability of poly(methyl methacrylate) (PMMA) using TGA.
• the poly(methyl methacrylate) was Plexiglas VS, commercially available from Rohm & Haas, having a M w of 82,700.
• the amounts of each component, the MFR, the amount of residual MMA by GPC, and the % reduction in residual MMA are given in Table 10. All amounts are given in weight % unless otherwise noted.
• the weight loss/temperature data from TGA are numerically represented in Table 11.
• the graft copolymer consisted of a propylene homopolymer backbone to which was grafted a MMA/MeAc copolymer and was prepared as described in Example 1.
• the components of the compositions were combined as described in Example 1.
• the BMWD PP was the same as in Example 1 and was added to adjust the effective add level to 70 parts of polymerized monomers per hundred parts of propylene homopolymer.
• the amounts of graft copolyr ⁇ er, BMWD PP, rubber, UN stabilizer masterbatch, and soybean oil are given in Table 12. All ⁇ mounts in Table 12 are in parts by weight unless otherwise noted.
• the rubber component was Engage 8150 polyolefin elastomer and is a copolymer of ethylene and octene containing 25% octene, commercially available from Du Pont-Dow Elastomers.
• the UN stabilizer masterbatch contained 0.05% by weight Pationic 1240 modified calcium salt derived from lactic acid, commercially available from Patco Polymer Additives Division, American Ingredients Company; 0.10% Irganox 1010 antioxidant; 0.10 % Irgafos 12 phosphite antioxidant; 0.30% Tinuvin 328 antioxidant, which is 2-(2-hydroxy-3,5- di-tert-amylphenyl-2H-benzotriazole; 0.25% Tinuvin 770 antioxidant, which is bis(2,2,6,6- tetramethyl-4-piperidinyl) sebacate, and 0.25% Chimassorb 119 antioxidant, all commercially available from Ciba Specialty Chemicals Corporation.
• the samples were homogenized prior to compounding to disperse the oil and then compounded on a 40 mm co-rotating, intermeshing Werner-Pfleiderer twin screw extruder at a temperature of 210°-270°C, 475-500 RPM, and a through-put rate of 110-170 lb/hr. Each sample was extruded as pellets.

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