POLY(VINYL CHLORIDE) COMPOSITIONS

Abstract: A composition comprising an intimate admixture of (a) 50 to 98 parts by weight of a vinyl chloride polymer having an inherent viscosity of at least 0.4 and (b) 50 to 2 parts by weight of a random addition tetrapolymer containing the following monomers combined in the polymer structure in the following weight percentages: where (a) plus (b) total 100 parts by weight, and the total parts by weight of combined indene plus α-methyl styrene plus styrene in the tetrapolymer (b) is 38 - 70 parts by weight.

Description: This invention relates to poly(vinyl chloride) plastic molding compositions having improved working and performance characteristics, including a higher melt index and a higher heat distortion temperature (HDT). Poly(vinyl chloride) resins are well known to be useful to mold many end products such as bottles, film, sheet, pipe, structural moldings. However, the normal poly(vinyl chloride) resin compositions used to make rigid end products have too low a heat distortion temperature for use in applications under heat and load because the shape of the product will become distorted when approaching the heat distortion temperature. For instance, it would be desirable to have poly(vinyl chloride) compositions in the form of pipe and bottles that will stand a higher temperature in service than the standard poly(vinyl chloride) resins having a normal 65 to 70 or 71°C heat distortion temperature. It would, moreover, be desirable to have poly(vinyl chloride) molding compositions having a higher melt index than the standard commercial resins in order to improve their processability in shaping and forming operations. It is an object of the present invention to provide rigid poly(vinyl chloride) compositions having improved properties, including a higher heat distortion temperature and a higher melt index, as well as good or improved flexural modulus and tensile strength, among other mechanical properties. Other objects, as well as aspects, features and advantages of the present invention, will become apparent from a study of specification, including the examples and the claims. The objects numerated above, and other objects, are realized according to the present invention by providing a composition or blend of a vinyl chloride polymer and certain random tetrapolymers containing indene as one of the monomers. The vinyl chloride resin of the blend of the invention can be a homopolymer of vinyl chloride or a copolymer of vinyl chloride with a minor portion of one or more monomers copolymerizable with vinyl chloride. In such copolymers vinyl chloride comprises on a weight basis at least about 80 (preferably at least 90) percent of the copolymer and the copolymerizable monomer comprises up to about 20 (preferably up to about 10) percent. A wide variety of copolymerizable monomers may be used to prepare such vinyl chloride copolymers. These include vinylidene chloride; vinyl acetate and vinyl stearate; acrylic and methacrylic acid esters; olefins such as ethylene, propylene, isobutylene and the like; vinyl alkyl ethers such as vinyl isobutyl ether, vinyl lauryl ether, and vinyl cetyl ether; acrylic acid and methacrylic acid; acrylonitrile and methacrylonitrile; diethyl fumarate; maleic anhydride; dimethyl itaconate; styrene, N-vinyl carbazole; N-vinyl pyrrolidone; or mixtures thereof. Methods for the preparation of vinyl chloride polymers are well known in the art and reported in the literature. See for example Kirk-Othmer , Encyclopedia of Chemical Technology , Third Edition, Interscience Publishers, Volume 23, pages 886-936, (Copyright 1983). Vinyl chloride polymers are available from a number of commercial suppliers. For preparing blends of this invention for use in injection molding operations, the vinyl chloride polymer usually has an inherent viscosity (as measured at a concentration of 0.5 gram per 100 grams of cyclohexanone at 25°C) in the range of .40 to about .70 and more usually in the range of about 0.50 to 0.70. Blends of such injection molding grade poly(vinyl chloride) homopolymer with our tetrapolymers are particularly useful. Blends of the tetrapolymers with extrusion grade vinyl chloride polymers are also very useful, and the extrusion grade vinyl chloride polymers used in such blends generally have viscosities in the inherent viscosity range from over 0.70 to 1.2, measured on the same basis. The present blends usually use a vinyl chloride polymer having an inherent viscosity of 0.54 to 1. The random tetrapolymers used in the blends of the present invention are polymers that are the result of addition polymerization of the monomers acrylonitrile, methyl methacrylate, α-methylstyrene and/or styrene, and indene. These random tetrapolymers usually have a relatively low inherent viscosity. As will be seen, this low viscosity is itself an advantage. As used herein inherent viscosity is in deciliters per gram of polymer composition. According to the present invention there is provided a composition comprising an intimate admixture of (a) 50 to 98 parts by weight of a vinyl chloride polymer having an inherent viscosity of at least 0.4 and (b) 50 to 2 parts by weight of a random addition tetrapolymer containing the following monomers combined in the polymer structure in the following weight percentages: where (a) plus (b) total 100 parts by weight, and the total parts by weight of combined indene plus α-methyl styrene plus styrene in the tetrapolymer (b) is 38 - 70 parts by weight, usually 45-60 parts. The compositions of this invention can include other ingredients, such as impact modifiers, thermal stabilizers, processing aids, fillers, lubricants, pigments, flame retardants, reinforcing fibers, smoke retardants, antioxidants, and the like. The compositions of this invention can also contain fillers Examples are calcium carbonate, wollastonite, silicates such as talc, acicular calcium silicate, titanium dioxide, potassium titanate, and glass flakes. Amounts of such fillers of up to about 50 parts per 100 parts of the combined vinyl chloride polymer plus the random tetrapolymer. In the foregoing compositions of the invention the more usual composition ranges for the tetrapolymer component are It is an advantage of our tetrapolymers that they are low molecular weight polymers. This automatically results from the influence of the monomer, indene, on the course of the polymerization; thus indene seems to act as an automatic chain transfer agent. As a result, the polymers used in making the blends of the invention have an inherent viscosity of 0.08 to 0.4, usually 0.1 to 0.36 deciliters per gram. Because of this characteristic of the tetrapolymers, their blends with vinyl chloride polymers result in a polymer blend having not only a higher HDT than the vinyl chloride polymer, but also a much higher melt index. The blends of the invention thus not only greatly increase the HDT but also are much more easily mechanically worked because of the high melt index. In the tetrapolymer compositions forming the additive component of our invention, we have found that the indene and the α-methylstyrene and/or the styrene are the main components increasing the HDT, while the polar compounds, acrylonitrile and methylacrylate contribute to compatibility with the vinyl chloride polymer, thus helping to maintain other physical mechanical properties. One reason that acrylonitrile alone cannot be used to supply the needed polarity is that too much acrylonitrile also makes the tetrapolymer less compatible with the vinyl chloride polymer. The reason that indene alone cannot be used as the HDT modifier component is that when the indene content of the additive polymer becomes too high, the polymer tends to become much less compatible with the vinyl chloride polymer, and the use of some α-methylstyrene alleviates this problem, although the reason is not well understood. Properties reported in this application were determined by the procedures of the following ASTM designations: Also, when inherent viscosity was determined for the tetrapolymers, it was for a solution of 0.2 grams of the polymer in 100 cc of dimethylformamide and was measured at 25°C. The following examples of the compositions of the invention are merely illustrative and are not to be considered limiting. In the examples unless otherwise stated, the PVC used in the blends was an injection grade PVC having an inherent viscosity of 0.68 deciliters/gm. for a 0.5 weight percent solution in cyclohexanone, and when stabilized with 3 parts by weight of Thermolite 813 per 100 parts of PVC, the PVC had a tensile strength of 58,607 kPa (8,500 psi), and HDT of 70°*, a flexural strength of 85,498 kPa (12,400 psi), a flexural modulus of 2,964,850 kPa (430,000 psi), a notched Izod of 0.0546 Nm/cm² (0.26 ft-lbs/sq. in.), and a melt index of 0.6 grams/10 minutes. In the examples, Thermolite 813 is di-n-octyltin maleate polymer sold by M & T Chemicals Inc. having the formula ((C₈H₁₇)₂SnCH₂O₄) n having a melting point of 90°C and specific gravity of 0.6. It is a commonly used thermal stabilizer. EXAMPLE A A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 20 parts of Acrylonitrile, 5 parts of methyl methacrylate, 4 parts of α-methylstyrene, and 47.5 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring; then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 10 parts of methyl methacrylate, 10 parts of α-methylstyrene and 2.5 parts of indene was added continually into the reactor over a period of 12 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered, and dried in a vacuum oven for 24 hours at 60°C. A powdery tetrapolymer was obtained in a 40% yield. The composition of the polymer was 15 acrylonitrile, 19 methyl methacrylate, 41 α-methylstyrene and 25 indene as determined by C¹³ NMR. The inherent viscosity was 0.132. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties. The HDT was 81°C, the melt index was 5.5g./10 min, the tensile strength was 63,434 kPa (9,200 psi), the flexural strength was 51,023 kPa (7,400 psi) and the flexural modulus 3,033,800 kPa (440,000 psi). The melt index of a blend made with 65 parts of PVC and 35 parts of the tetrapolymer was 10.6g./10 min. and the HDT was 82.5°C. EXAMPLE B A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 25 parts of Acrylonitrile, 5 parts of methyl methacrylate, 10 parts of α-methylstyrene, and 45 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring; then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 5 parts of methyl methacrylate and 10 parts of α-methylstyrene was added continually into the reactor over a period of 12 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered, and dried in a vacuum oven for 24 hours at 60°C. A powdery tetrapolymer was obtained in a 30.6% yield. The composition of the polymer was 26 acrylonitrile, 14 methyl methacrylate, 38 α-methylstyrene and 21 indene as determined by C¹³ NMR. The inherent viscosity was 0.186. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with mixing a brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties. The HDT was 79°C, the melt index was 4.2g./10 min, the tensile strength was 66,192 kPa (9,600 psi), the flexural strength was 75,155 kPa (10,900 psi) and the flexural modulus 3,447,500 kPa (500,000 psi). EXAMPLE C A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 30 parts of Acrylonitrile, and 40 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring; then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 15 parts of methyl methacrylate and 15 parts of α-methylstyrene was added continually into the reactor over a period of 12 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered, and dried in a vacuum oven for 24 hours at 60°C. A powdery tetrapolymer was obtained in a 49% yield. The composition of the polymer was 26 acrylonitrile, 15 methyl methacrylate, 21 α-methylstyrene and 38 indene as determined by C¹³ NMR. The inherent viscosity was 0.213. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties. The HDT was 78°C, the melt index was 2.5g./10 min, the tensile strength was 66,881 kPa (9,700 psi), the flexural strength was 82,740 kPa (12,000 psi) and the flexural modulus 3,240,650 kPa (470,000 psi). EXAMPLE D A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 30 parts of Acrylonitrile and 30 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring; then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 10 parts of methyl methacrylate and 30 parts of α-methylstyrene was added continually into the reactor over a period of 12 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered, and dried in a vacuum oven for 24 hours at 60°C. A powdery tetrapolymer was obtained in a 54% yield. The composition of the polymer was 24 acrylonitrile, 6 methyl methacrylate, 42 α-methylstyrene and 28 indene as determined by C¹³ NMR. The inherent viscosity was 0.215. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties. The HDT was 75°C, the melt index was 3.1g./10 min, the tensile strength was 62,744 kPa (9,100 psi), the flexural strength was 72,397 kPa (10,500 psi) and the flexural modulus 2,964,850 kPa (430,000 psi). When a composition was made with 35 percent of the tetrapolymer the HDT was 77°C, the melt index was 4.7g./10 min., the tensile strength was 48,265 kPa (7000 psi), the flexural strength was 64,123 kPa (9,300 psi) and the flexural modulus was 3,102,750 kPa (450,000 psi). EXAMPLE E A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 30 parts of Acrylonitrile and 40 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring; then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 15 parts of methyl methacrylate and 15 parts of α-methylstyrene was added continually into the reactor over a period of 12 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered, and dried in a vacuum oven for 24 hours at 60°C. A powdery tetrapolymer was obtained in a 51% yield. The composition of the polymer in weight percent was 25 acrylonitrile, 16 methyl methacrylate, 28 α-methylstyrene and 31 indene as determined by C¹³ NMR. The inherent viscosity was 0.210. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties, as noted below: Results: The HDT was 74°C, the melt index was 2.7, the tensile strength was 60,676 kPa (8,800 psi), the flexural strength was 76,534 kPa (11,100 psi) and the flexural modulus 3,240,650 kPa (470,000 psi). When a composition was made with 35 percent of the tetrapolymer the HDT was 79°C, the melt index was 4.0 g./10 min., the tensile strength was 57,918 kPa (8400 psi), the flexural strength was 57,228 kPa (8,300 psi) and the flexural modulus was 3,378,550 kPa (490,000 psi). EXAMPLE F A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 25 parts of Acrylonitrile and 40 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 70°c with stirring; then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 20 parts of methyl methacrylate, 10 parts of α-methylstyrene and 5 parts of indene was added continually into the reactor over a period of 12 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered, and dried in a vacuum oven for 24 hours at 60°C. A powdery tetrapolymer was obtained in a 40% yield. The composition of the polymer in weight percent was 22 acrylonitrile, 23 methyl methacrylate, 20 α-methylstyrene and 36 indene as determined by C¹³ NMR. The inherent viscosity was 0.166. 35 parts by weight of the tetrapolymer was mixed with 65 parts of injection grade PVC and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties, as noted below: The HDT was 82°C, the melt index was 6.7, the tensile strength was 53,091 kPa (7,700 psi), the flexural strength was 36,543 kPa (5,300 psi) and the flexural modulus 3,102,750 kPa (450,000 psi). EXAMPLE G A tetrapolymer was made by emulsion polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 200 parts by weight of distilled water, 2.5 parts of Sodium lauryl sulfate, 1.0 part of Na₃PO₄·12H₂O, 18 parts of acrylonitrile, 12 parts of methyl methacrylate, 8 parts of α-methylstyrene, 25 parts of indene and 0.7 parts of Na₂S₂O₈ were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held at 75°C for 1 hour with stirring; then a monomer mixture comprising 7 parts of acrylonitrile, 8 parts of methyl methacrylate and 22 parts of α-methylstyrene was incrementally added in portions into the reactor once every hour over a period of 5 hours through a syringe pump. At the third hour an additional 0.3 parts of Na₂S₂O₈ was added into the reactor for maintaining the reaction rate. The resulting mixture was allowed to react for 1.5 more hours more after the incremental additions. After completion of the reaction, the polymer was recovered through freeze coagulation of the latex. The polymer was filtered, and was then stirred with excess methanol overnight to remove residual monomers. The polymer was filtered again and dried in a vacuum oven for 24 hours at 60°C. A powdery tetrapolymer was obtain in an 88 percent yield. Its composition, as determined by gas chromatograph analysis of redsidual monomers and the yield, was 25 acrylonitrile, 21 methyl methacrylate, 33 α-methylstyrene and 21 indene, all in weight percent. The inherent viscosity was 0.230. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties, as noted below: The HDT of the blend was 81.5°C, the tensile strength was 60,676 kPa (8,800 psi), the flexural strength was 98,598 kPa (14,300 psi) and the flexural modulus 3,171,700 kPa (460,000 psi). The melt index of the blend was 5.1 g./10 min. EXAMPLE H A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 25 parts of Acrylonitrile, 10 parts of methyl methacrylate and 45 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring; then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 10 parts of methyl methacrylate and 10 parts of styrene is added continually into the reactor over a period of 12 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered and dried in avacuum oven for 24 hrs at 60°C. A powdery tetrapolymer was obtained in a 43 percent yield. The composition of the polymer in weight percent was 25 acrylonitrile, 28 methyl methacrylate, 7 styrene and 40 indene as determined by C¹³ NMR. The inherent viscosity was 0.152. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 deciliters/gm) and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties, as noted below: The HDT was 76°C, the melt index was 3.3, the tensile strength was 60,676 kPa (8,800 psi), the flexural strength was 86,877 kPa (12,600 psi) and the flexural modulus 3,171,700 kPa (460,000 psi). When a mixture was prepared having 35 weight percent of the tetrapolymer, the HDT was 79.5, the melt index was 8.0, the tensile strength was 55,160 kPa (8,000 psi), the flexural strength was 59,297 kPa (8,600 psi), and the flexural modulus was 3,033,800 kPa (440,000 psi). EXAMPLE I A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 25 parts of Acrylonitrile, 5 parts of methyl methacrylate, 2 of styrene and 45 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring; then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 5 parts of methyl methacrylate and 18 parts of styrene was added continually into the reactor over a period of 12 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered and dried in a vacuum oven for 24 hrs at 60°C. A powdery tetrapolymer was obtained in a 50 percent yield. The composition of the polymer in weight percent was 30 acrylonitrile, 13 methyl methacrylate, 22 styrene and 35 indene as determined by C¹³ NMR. The inherent viscosity was 0.175. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 deciliters/gm) and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties, as noted below: The HDT was 74.5°C, the melt index was 3.0, the tensile strength was 68,950 kPa (10,000 psi), the flexural strength was 71,708 kPa (10,400 psi) and the flexural modulus 3,102,750 kPa (450,000 psi). When a mixture was prepared having 35 weight percent of the tetrapolymer, the HDT was 77.5°C, the melt index was 7.0, the tensil strength was 59,297 kPa (8,600 psi), the flexural strength was 71,018 kPa (10,300 psi), and the flexural modulus was 3,309,600 kPa (480,000 psi). EXAMPLE J A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 20 parts of Acrylonitrile and 40 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring. Then 20 parts of MMA was added at a constant rate with a syringe pump over a period of 8.5 hours and using another syringe pump 20 parts of styrene was added at a constant rate over a period of 11 hours. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered and dried in a vaccum oven for 24 hrs at 60°C. A powdery tetrapolymer was obtained in a 50 percent yield. The composition of the polymer in weight percent was 22 acrylonitrile, 24 methyl methacrylate, 23 styrene and 31 indene as determined by C¹³ NMR. The inherent viscosity was 0.194. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 deciliters/gm) and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties, as noted below: The HDT was 77°C, the melt index was 4.1, the tensile strength was 64,813 kPa (9,400 psi), the flexural strength was 75,845 kPa (11,000 psi) and the flexural modulus 3,102,750 kPa (450,000 psi). EXAMPLE K A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 20 parts of Acrylonitrile and 40 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring. Then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 10 parts of methyl methacrylate, and 30 parts of styrene was added continually into the reactor over a period of 12 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered and dried in a vaccum oven for 24 hrs at 60°C. A powdery tetrapolymer was obtained in a 51 percent yield. The composition of the polymer in weight percent was 25 acrylonitrile, 15 methyl methacrylate, 35 styrene, and 25 indene, as determined by C¹³ NMR. The inherent viscosity was 0.184. 35 parts by weight of the tetrapolymer was mixed with 65 parts of injection grade PVC (inherent viscosity 0.68 deciliters/gm) and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties, as noted below: The HDT was 75.5°C, the melt index was 11.2, the tensile strength was 51,712 kPa (7,500 psi), the flexural strength was 57,918 kPa (8,400 psi) and the flexural modulus 3,033,800 kPa (440,000 psi). EXAMPLE L A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 20 parts of Acrylonitrile, 5 parts of of methyl methacrylate and 30 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring. Then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 25 parts of methyl methacrylate, and 20 parts of styrene was added continually into the reactor over a period of 12 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. Aftler completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered and dried in a vacuum oven for 24 hrs at 60°C. A powdery tetrapolymer was obtained in a 54 percent yield. The composition of the polymer in weight percent was 20 acrylonitrile, 29 methyl methacrylate, 14 styrene and 37 indene as determined by C¹³ NMR. The inherent viscosity was 0.226. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 deciliters/gm) and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties, as noted below: The HDT was 78°C, the melt index was 4.3, the tensile strength was 66,192 kPa (9,600 psi), the flexural strength was 77,913 kPa (11,300 psi) and the flexural modulus 3,102,750 kPa (450,000 psi). When a mixture was prepared having 35 weight percent of the tetrapolymer, the HDT was 79.5°C, the melt index was 7.3, the tensile strength was 62,744 kPa (9,100 psi), the flexural strength was 62,744 kPa (9,100 psi), and the flexural modulus was 3,171,700 kPa (460,000 psi). EXAMPLE M A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 100 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in 100 parts of water), 0.4 parts of the catalyst, 20 parts of Acrylonitrile, 7.5 parts of of methyl methacrylate and 40 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 0.5 hours at 100°C with stirring. Then a monomer mixture comprising 0.2 parts of the catalyst, 22.5 parts of methyl methacrylate, and 10 parts of styrene was added continually into the reactor over a period of 10 hours. The polymer was allowed to settle and the water decanted. Thereafter the polymer was washed with methanol, filtered and dried. Conversion was 69 percent to the tetrapolymer having a composition in weight percent of 21 acrylonitrile, 40 methyl methacrylate, 9 styrene and 29 indene as determined by C¹³ MMR. Its inherent viscosity was 0.154. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 deciliters/gm) and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties, as noted below: The HDT was 75.5°C, the melt index was 4.5, the tensile strength was 66,881 kPa (9,700 psi), the flexural strength was 86,877 kPa (12,600 psi) and the flexural modulus 3,240,650 kPa (470,000 psi). EXAMPLE N A tetrapolymer was made by emulsion polymerization according to the following recipe in which amounts are shown in weight parts per 100 total parts of the monomers. A 1-liter, 3-necked flask was fitted with a Teflon-bladed stirrer, a thermometer, a reflux condenser, a septum and a nitrogen inlet at the top of the condenser. The nitrogen line was fitted with a T and a water bubbler to maintain a constant, slight positive nitrogen pressure in the reactor. The reactor (3-necked flask) was suspended in a glycerol heating bath maintained at a constant temperature. A syringe metering pump was used to meter in part of the monomer during the polymerization. The flask was charged with the water, emulsifier, and monomers and bubbled with a strong nitrogen stream to remove oxygen. The neck opening was capped with a rubber septum and the flask was heated. The flask contents were maintained under a nitrogen atmosphere and stirred at about 200 rmp. When the flask contents reached 65°C, 4 ml of a 10 percent solution of sodium persulfate was injected into the reactor. The reaction temperature remained constant at 65°C throughout the reaction time. After the reaction had progressed for 1 hour, the metering pump was turned on. The metering pump contained the quantity of monomer shown in the recipe. The monomer was metered into the reactor during a 13 hour period at a constant rate. During the polymerization, the other 10 ml of catalyst (10 percent Na₂S₂O₈) was injected into the reactor in two equal portions; 3 ml at 4.25 hours and 3 ml at 7.75 hours. At the end of the monomer metering period, the temperature and stirring was maintained for 8.75 additional hours. Then the polymer latex was allowed to cool. A total solids determination on the latex indicated a conversion of 80.4 percent. C¹³ NMR indicated a polymer composition of 21 percent acrylonitrile, 40 percent methyl methacrylate, 17 percent α-methylstyrene and 22 percent indene, all in weight percent. The cooled latex was filtered through cheesecloth, collecting 3.5 parts by weight (when dried) of a finely-divided prefloc (powder when dried). After coogulation the polymer was later collected on a filter by vacuum filtration. The polymer particles were flushed with water then with methanol to remove water and monomer from the particle surfaces. The polymer particles were then stirred in some methanol and again filtered. The powder was then allowed to stand in methanol overnight to further soak out monomer. After again filtering and air drying, the polymer was dried overnight in a vacuum oven at 80°C. The product had the appearance of glistening, white sugary-type powder. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 diciliters/gm) and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties. The results were as noted below: The HDT was 80°C, the tensile strength was 67,571 kPa (9,800 psi), the flexural strength was 62,744 kPa (9,100 psi) and the flexural modulus 3,102,750 kPa (450,000 psi). The inherent viscosity of the tetrapolymer (0.2 percent solution in DMF at 25°C) was 0.205. EXAMPLE O A tetrapolymer was made by emulsion polymerization according to the following recipe in a 10 gallon, stainless steel reactor equipped with a heating jacket, and a stirrer. The reactor was charged with the ingredients listed under initial charge in the recipe above, except for the persulfate catalyst. The reactor was buttoned down and the oxygen removed by alternately applying a vacuum and nitrogen pressure three times. The reactor was then pressure tested with nitrogen at 50 psi. The stirrer was set at 150 ft/min tip speed, and heat applied. At 75°C, 500 g of 10 percent solution of the persulfate catalyst was added. Total solids were taken at intervals to follow the conversion; After the first hour 5 incremental additions of the added monomers were made each hour. During the polymerization, the other 600g of catalyst (10 percent Na₂S₂O₈) was injected into the reactor in two equal portions; 300g at 2.5 hours and 300 g at 4.5 hours. At the end of the monomer addition period, the temperature and stirring was maintained for 1 additional hour. Then the polymer latex was allowed to cool. A gas chromatographic analysis of the unreacted monomers indicated a conversion of 88 percent, a polymer composition of 25 percent acrylonitrile, 21 percent methyl methacrylate, 33 percent α-methylstyrene and 21 percent indene. The cooled latex was filtered through cheesecloth. The cooled latex was freeze coagulated, filtered and the polymer collected on a filter by vacuum filtration. The polymer particles were flushed with water then with methanol to remove water and monomer from the particle surfaces. The polymer particles were then stirred in some methanol and again filtered. The powder was then allowed to stand in methanol overnight to further soak out monomer. After again filtering and air drying, the polymer was dried overnight in a vacuum oven at 80°C. The product had the appearance of glistening, white sugary-type powder. The inherent viscosity of the tetrapolymer was 0.256. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 deciliters/gm) and 3 parts Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties, as noted below: The HDT was 81°C, the melt index was 6.0, the tensile strength was 64,123 kPa (9,300 psi), the flexural strength was 98,598 kPa (14,300 psi), and the flexural modulus was 3,171,700 kPa (460,000 psi). EXAMPLE P A tetrapolymer was made by emulsion polymerization according to the following recipe in which amounts are shown in parts by weight. A 1-liter, 3-necked flask was fitted with a Teflon-bladed stirrer, a thermometer, a reflux condenser, a septum and a nitrogen inlet at the top of the condenser. The nitrogen line was fitted with a T and a water bubbler to maintain a constant, slight positive nitrogen pressure in the reactor. The reactor (3-necked flask) was suspended in a glycerol heating bath maintained at a constant temperature. A syringe metering pump was used to meter in part of the monomer during the polymerization. The flask was charged with the water, emulsifier, and monomers and bubbled with a strong nitrogen stream to remove oxygen. The neck opening was capped with a rubber septum and the flask was heated. The flask contents were maintained under a nitrogen atmosphere and stirred at about 200 rpm. When the flask contents reached 75°C, 10 ml of a 10 percent solution of sodium persulfate was injected into the reactor. The reaction temperature remained constant at 75°C throughout the reaction time. After the reaction had progressed for 0.5 hour, the metering pump was turned on. The metering pump contained the quantity of monomer shown in the recipe. The monomer was metered into the reactor during a 5 hour period at a constant rate. After 2.5 hours polymerization, 5 ml of catalyst (10 percent Na₂S₂O₈) was injected into the reactor, and 5 ml after 4.5 hours. At the end of the monomer metering period, the temperature and stirring was maintained for 1.0 additional hour. Then the polymer latex was allowed to cool. A total solids determination on the latex indicated a conversion of 87 percent. A gas chromatographic analysis of the unreacted monomers indicated a conversion of 89 percent, a polymer composition of 25 percent acrylonitrile, 21 percent methyl methacrylate, 33 percent α-methylstyrene and 21 percent indene. The cooled latex was filtered through cheesecloth, collecting 3.5 parts by weight (when dried) of a finely-divided prefloc (powder when dried). The polymer latex was freeze coagulated and later collected on a filter by vacuum filtration. The polymer particles were flushed with water then with methanol to remove water and monomer from the particle surfaces. The polymer particles were then stirred in some methanol and again filtered. The powder was then allowed to stand in methanol overnight to further soak out monomer. After again filtering and air drying, the polymer was dried overnight in a vacuum oven at 80°C. The product had the appearance of glistening, white sugary-type powder. The inherent viscosity of the tetrapolymer was 0.227. Analysis of the polymer by gas chromatography (polymer dissolved in THF) showed that it contained about 0.21 percent indene monomer and no other monomers. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 deciliters/gm) and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties. The results were as noted below: The HDT was 78°C, the melt index was 3.3, the tensile strength was 67,571 kPa (9,800 psi), the flexural strength was 64,123 kPa (9,300 psi) and the flexural modulus 2,723,525 kPa (395,000 psi). EXAMPLE Q A tetrapolymer was made by emulsion polymerization according to the following recipe in which amounts are shown in weight parts per 100 total parts of the monomers. Sodium lauryl sulfate, the sodium phosphate and triton 770 were dissolved in water and charged to the reactor fitted with a cooling condenser. The reactor contents were placed under a nitrogen atmosphere. The reactor was charged with a monomer mixture consisting of 20 phm acrylonitrile, 15 phm methyl methacrylate, 10 phm α-methylstyrene and 25 phm indene. The contents of the reactor were heated to 75°C and agitated with a mechanical stirrer. Polymerization was initiated by adding 0.8 phm Na₂S₂O₈. A monomer mixture consisting of 5 phm acrylonitrile, 5 phm methyl methacrylate and 20 phm α-methylstyrene was introduced in measurements starting at 1 hour after the beginning of polymerization. The exact amounts were as following: In addition, 0.3 phm and 0.2 phm of additional Na₂S₂O₈ were added at 3 hours and 5 hours, respectively. After 7 hours the polymerization reached a monomer conversion of 87 percent as determined by the solids measurements. Its inherent viscosity was 0.206. Its composition in weight percent was 23 acrylonitrile, 29 methyl methacrylate, 32 α-methylstyrene and 16 indene, as measured by C¹³ NMR. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 diciliters/gm) and 3parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties. The results were as noted below: The HDT was 81°C, the melt index was 3.1, the tensile strength was 67,571 kPa (9,800 psi), the flexural strength was 56,539 kPa (8,200 psi) and the flexural modulus was 3,171,700 kPa (460,000 psi). EXAMPLE R A tetrapolymer was made by emulsion polymerization according to the following recipe in which amounts are shown in weight parts per 100 total parts of the monomers. Sodium lauryl sulfate and the sodium phosphate were dissolved in water and charged to the reactor fitted with a cooling condenser. The reactor contents were placed under a nitrogen atmosphere. The reactor was charged with a monomer mixture consisting of 20 phm acrylonitrile, 15 phm methyl methacrylate, 10 phm α-methylstyrene and 25 phm indene. The contents of the reactor were heated to 75°C and agitated with a mechanical stirrer. Polymerization was initiated by adding 0.7 phm Na₂S₂O₈. A monomer mixture consisting of 5 phm acrylonitrile, 5 phm methyl methacrylate and 20 phm α-methylstyrene was introduced in measurements starting at 1 hour after the beginning of polymerization. The exact amounts were as following: In addition, 0.3 phm and 0.2 phm of additional Na₂S₂O₈ was added at 3 hours and 5 hrs, respectively. After 6 hours the polymerization reached a monomer conversion of 88.7 percent as determined by the solids measurements. Its inherent viscosity was 0.228. Its composition in weight percent was 25 acrylonitrile, 21 methyl methacrylate, 35 α-methylstyrene and 20 indene, as measured by gas chromatography analysis of the residual monomers. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 diciliters/gm) and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties. The results were as noted below: The HDT was 77.5°C, the melt index was 3.9, the tensile strength was 65,502 kPa (9,500 psi), the flexural strength was 85,773 kPa (12,440 psi) and the flexural modulus was 3,240,650 kPa (470,000 psi). EXAMPLE S A tetrapolymer was made by emulsion polymerization according to the following recipe in which amounts are shown in weight parts per 100 total parts of the monomers. Sodium lauryl sulfate and the sodium phosphate were dissolved in water and charged to the reactor fitted with a cooling condenser. The reactor contents were placed under a nitrogen atmosphere. The reactor was charged with a monomer mixture consisting of 17 phm acrylonitrile, 11 phm methyl methacrylate, 10 phm α-methylstyrene and 25 phm indene. The contents of the reactor were heated to 75°C and agitated with a mechanical stirrer. Polymerization was initiated by adding 0.7 phm Na₂S₂O₈. A monomer mixture consisting of 8 phm acrylonitrile, 9 phm methyl methacrylate and 20 phm α-methylstyrene was introduced in measurements starting at 1 hour after the beginning of polymerization. The exact amounts were as following: In addition, 0.3 phm and 0.2 phm of additional Na₂S₂O₈ was added at 3 hours and 5 hours, respectively. After 7 hours the polymerization reached a monomer conversion of 88 percent as determined by the solids measurements. Its inherent viscosity was 0.224. Its composition in weight percent was 25 acrylonitrile, 21 methyl methacrylate, 36 α-methylstyrene and 18 indene, as measured by gas chromatography analysis of the residual monomers. 25 parts by weight of the tetrapolymer was mixed with 75 parts of injection grade PVC (inherent viscosity 0.68 diciliters/gm) and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties as noted below: The HDT was 79.5°C, the melt index was 2.9, the tensile strength was 68,260 kPa (9,900 psi), the flexural strength was 98,598 kPa (14,300 psi) and the flexural modulus was 2,964,850 kPa (430,000 psi). In the following example the poly(vinyl chloride) used was a commercial extrusion grade PVC having an inherent viscosity of 0.93 deciliters/gram for a 0.2 weight percent solution in cyclohexanone measured at 25°C. When compounded with 3 parts of Thermolite 813 per 100 weight parts of PVC, the stabilized PVC had an HDT of 72°C, a tensile strength of 68,950 kPa (10,000 psi), a flexural strength of 94,461 kPa (13,700 psi) and a flexural modulus of 3,171,700 kPa (460,000 psi). Its melt index was not measurable. EXAMPLE T A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 20 parts of Acrylonitrile, 10 parts of methyl methacrylate, 10 parts of α-methylstyrene, and 40 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring; then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 10 parts of methyl methacrylate and 10 parts of α-methylstyrene was added continually into the reactor over a period of 10 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered, and dried in a vacuum oven for 24 hours at 60°C. A powdery tetrapolymer was obtained. The composition of the polymer was 23 acrylonitrile, 20 methyl methacrylate, 34 α-methylstyrene and 22 indene as determined by C¹³ NMR. The inherent viscosity was 0.172. 25 parts by weight of the tetrapolymer was mixed with 75 parts of extrusion grade PVC and 3 parts of Thermolite 813 by a blender. The mixture was kneaded for 5 minutes with mixing a brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. A resin plaque thus prepared was tested for HDT, which was 80°C, melt index, tensile strength and other physical properties. The HDT was 80°C, the melt index was 0.12/10 min, the tensile strength was 77,913 kPa (11,300 psi), the flexural strength was 112,388 kPa (16,300 psi) and the flexural modulus 3,516,450 kPa (510,000 psi). In the following example the poly(vinyl chloride) used was a commerical extrusion grade PVC having an inherent viscosity of 0.93, and when compounded with 3 weight parts the diisooctyl ester of dibutyltin dimercaptoacetic acid, (C₈H₁₇SCH₂COO)₂Sn(C₄H₉)₂, thermal stabilizer and 1 part of oxidized ethylene homopolymer lubricant per 100 parts of PVC, the stabilized PVC had an HDT of 67°C, a tensile strength of 64,813 kPa (9,400 psi), a flexural strength of 91,014 kPa (13,200 psi), and a flexural modulus of 2,964,850 kPa (430,000 psi). Its melt index was not measurable. Example U A tetrapolymer was made by suspension polymerization according to the following recipe. Amounts are in weight parts per 100 parts of total monomers. 150 parts by weight of distilled water, 0.2 parts of HEC (which has been dissolved in water), 0.2 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 20 parts of Acrylonitrile, 15 parts of methyl methacrylate, 2 parts of styrene, and 40 parts of indene were charged into a reactor provided with a stirrer. The reactor was purged with nitrogen, and was kept under nitrogen pressure. The temperature of the reactor was held for 5 minutes at 65°C with stirring; then a monomer mixture comprising 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile), 15 parts of methyl methacrylate and 8 parts of styrene was added continually into the reactor over a period of 8 hours through a syringe pump. The resulting mixture was further allowed to react for 6 more hours. After completion of the reaction, the polymer obtained was dissolved into acetone, and reprecipitated in excess methanol. The polymer was filtered, and dried in a vacuum oven for 24 hours at 60°C. A powdery tetrapolymer was obtained. The composition of the polymer was 19 acrylonitrile, 41 methyl methacrylate, 16 styrene and 23 indene as determined by C¹³ NMR. The inherent viscosity was 0.215. 25 parts by weight of the tetrapolymer was mixed with 75 parts of extrusion grade PVC and 3 parts of the diisooctyl ester of di-n-butyltin dimercaptoacetic acid as thermostabilizer and 1 part of oxidized ethylene homopolymer as lubricant by a blender. The mixture was kneaded for 5 minutes with a mixing brabender having a surface temperature of 190°C. The resulting blend was press formed at 190°C into a sheet, then a plaque. Each resin plaque thus prepared was tested for HDT, melt index, tensile strength and other physical properties. The HDT was 74.5°C, the melt index was 0.64/10 min, the tensile strength was 66,881 kPa (9,700 psi), the flexural strength was 83,429 kPa (12,100 psi) and the flexural modulus 3,240,650 kPa (470,000 psi). As will be evident to those skilled in the art, various modifications of this invention can be made or followed in the light of the foregoing disclosure and discussion without departing from the spirit and scope of the disclosure or from the scope of the claims.

Claims: A composition comprising an intimate admixture of (a) 50 to 98 parts by weight of a vinyl chloride polymer having an inherent viscosity of at least 0.4 and (b) 50 to 2 parts by weight of a random addition tetrapolymer containing the following monomers combined in the polymer structure in the following weight percentages: said tetrapolymer having an inherent viscosity of 0.08 to 0.4 deciliters per gram, where (a) plus (b) total 100 parts by weight, and the total parts by weight of combined indene plus α-methyl styrene plus styrene in the tetrapolymer (b) is 38 - 70 parts by weight. A composition comprising an intimate admixture of (a) 50 to 98 parts by weight of a vinyl chloride polymer having an inherent viscosity of at least 0.4 and (b) 50 to 2 parts by weight of a random addition tetrapolymer containing the following monomers combined in the polymer structure in the following weight percentages: said tetrapolymer having an inherent viscosity of 0.08 to 0.4 deciliters per gram, where (a) plus (b) total 100 parts by weight, and the total parts by weight of combined indene plus α-methyl styrene plus styrene in the tetrapolymer (b) is 45 - 60 parts by weight.

Inventors: DEWITT, ELMER JOHN, LI, GEORGE S., WU, MUYEN MICHAEL
Applicants: THE STANDARD OIL COMPANY
Application year: 1986
Main classification: C08L27
IPC codes: C08L25, C08L37, C08L45, C08L27, C08L33