Polymer compositions

Abstract: A polymer composition comprising a thermoplastic polycar­ bonate and a terpolymer of recurring units of a monovinyl aromatic monomer, recurring units of a maleimide monomer and recurring units of an α, β ethylenically unsaturated cyclic anhy­ dride monomer.

Description: This invention relates to polymer compositions. More specifically, this invention relates to a polymer composition comprising a thermoplastic polycarbonate and a terpolymer of recurring units of a monovinyl aromatic monomer, recurring units of a maleimide monomer and recurring units of an α,β ethylenically unsaturated cyclic anhydride monomer. In one of its more specific aspects, this invention pertains to a polymer alloy comprising a thermoplastic polycarbonate and a terpolymer which contains not more than 30 total weight percent of a maleimide monomer and α,β-ethylenically unsaturated cyclic anhydride monomer with the balance being a monovinyl aromatic monomer. The incompatibility of polymers with one another is well established. Coming up with a workable combination of polymers is still as much luck and art as it is science. In the past, the terms "polymer alloy" and "polymer blend" or "polyblend" were used interchangeably. Technically, however, and as used herein, the term "polymer alloy" means a combination of polymers which are fully compatible with one another. And, as used herein, the term "polyblend" means a combination of polymers which are partially compatible, that is, the polymers exhibit partial miscibility with each other. DE―A―2811749 discloses compatible polymer compositions comprising 90―10% w. of a polycarbonate and 10―90% w. of a copolymer of for example styrene and maleimide grafted on a rubber. This invention provides a workable combination of polymers, which polymers are fully compatible with one another thus forming, quite unexpectedly, a polymer alloy. According to this invention there is provided a polymer composition comprising in weight percent, from 1 to 99 of a thermoplastic polycarbonate based on bis-(hydroxyaryl) alkanes and from 99 to 1 of a random terpolymer of 70 to 90 % by weight of recurring units of styrene, 2 to 24 % by weight of recurring units of N-phenylmaleimide and 2 to 24 % by weight of recurring units of maleic anhydride the total of the weight % of each of the three components of the tercopolymer adding up to 100. Polycarbonates suitable to produce the polymer compositions of this invention are homopolycarbonates based on bisphenols having the following general formula: wherein each R separately represents hydrogen, a C₁ to C₄ alkyl group, chlorine, or bromine and wherein X represents a direct bond C₁ to C₈ alkylene. Bisphenols having the above general formula include: 2,2-bis(4-hydroxyphenyl)-propane; 2,2-bis-(3-chloro-4-hydroxyphenyl)-propane; 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)propane; 2,4-bis-(3,5-dimethyl-4-hydroxylphenyl)-2-methylbutane. Particularly suitable for use in the practice of this invention is 2,2-bis-(4-hydroxyphenyl)-propane. The terpolymers suitable for use in this invention are random terpolymers desirably having peak number average molecular weights within the range of from 50,000 to 300,000, preferably 150,000 to 250,000. They can be prepared by a free radical polymerization in solution, or in bulk. Preferably, the terpolymers will be prepared by continuous bulk polymerization. To further enhance the impact strength properties of the polymer alloys of this invention, the terpolymers can be chemically grafted to a rubber or mixture of rubbers during the synthesis of the terpolymer. As the rubber, use can be made for example, of any conjugated diene homopolymer or copolymer with a styrenic monomer. The rubber contained in the resultant rubber-modified terpolymer will normally be present in an amount up to 25 parts per 100 parts by weight of the terpolymer. Methods for chemically grafting polymers to rubbers are well known. Following Example V teaches a method for the preparation of a styrene/N-phenyl maleimide/maleic anhydride terpolymer chemically grafted to a styrene/butadiene copolymer rubber using a continuous stirred tank reactor process. The polymer compositions of this invention may be prepared using any suitable method of blending. Preferably, they are prepared by melt mixing at a temperature above the softening points of the polymers using any conventional high shear melt mixing apparatus, including twin screw extruders, single screw extruders, and the like. The extrudate can be chopped into pellets and molded using any conventional method of molding including: injection molding, roto-molding and the like. The word "molding" is meant to encompass all sheet and profile extrusion processes. Example I This example demonstrates the preparation of a styrene/N-phenylmaleimide/maleic anhydride terpolymer containing a total of 28.1 weight percent N-phenylmaleimide and maleic anhydride, using a continuous stirred tank reactor process. The resulting terpolymer is suitable for use to produce polymer alloys of this invention. Into a mixing vessel were added, with stirring, 224 g of N-phenylmaleimide, 224 g of maleic anhydride and 2329.6 g of styrene. The resulting solution was filtered to eliminate maleic acid and insoluble impurities. To the filtered solution were added, with stirring, 22.4 g of a polybutadiene rubber designated Diene® 55 commercially available from Firestone Synthetic Rubber and Latex Co.; 2.24 g of a mixture of alkylated aryl phosphites designated Polygard® HR antioxidant commercially available from Uniroyal Chemical, division of Uniroyal, Inc., and 2.2 g of benzoyl peroxide. Although optional, the addition of from 0.5 to about 1 percent of a rubber e.g. Diene® 55 polybutadiene, has been found to increase the solubility of the terpolymer in styrene. The resulting solution was charged to the top of a continuous stirred tank reactor at a reaction temperature of about 90°C and a reactor pressure of about 8.2 bar (120 psi). The polymerization product was withdrawn from the reactor bottom at a conversion of about 45 weight percent. The polymerization product, a styrene/N-phenylmaleimide/maleic anhydride terpolymer, was diluted with styrene monomer, recovered by precipitation in methanol and dried. The recovered terpolymer was analyzed and found to contain about 16.1 weight percent N-phenylmaleimide and about 12 weight percent maleic anhydride with the balance being styrene. The glass transition temperature of the terpolymer was found to be 154.5°C as measured by differential scanning calorimetry (DSC). Example II (Comparative) This example demonstrates the preparation of a styrene/N-phenylmaleimide/maleic anhydride terpolymer containing a total of 30.5 weight percent N-phenylmaleimide and maleic anhydride using a semi-batch process. The resulting terpolymer is suitable for use to produce polyblends. A solution of 124.4 g N-phenylmaleimide and 1746 g of styrene was prepared and filtered to eliminate insoluble impurities. The resulting solution was then transferred into a one gallon stirred reactor and heated to 100°C under a nitrogen atmosphere. Into the closed reactor were charged 1.8 g of Polygard® HR antioxidant and 0.5 g benzoyl peroxide to start the polymerization. In a separate mixing vessel, a solution of 166.6 g of maleic anhydride and 760 g of styrene was previously prepared and filtered. The resulting solution was charged continuously to the one gallon reactor containing the polymerizing N-phenylmaleimide-styrene solution. The continuous addition of the maleic anhydride-styrene solution took 40 minutes after which the polymerization was terminated by adding 0.49 g hydroquinone into the reactor. The polymerization product, a styrene/N-phenylmaleimide/maleic anhydride terpolymer was diluted with styrene monomer, recovered by precipitation in methanol and dried. The recovered terpolymer was analyzed and found to contain 11.1 weight percent N-phenylmaleimide, 19.4 weight percent maleic anhydride with the balance being styrene. The glass transition temperature of the terpolymer was found to be 163.5°C (very narrow) by DSC. Example III (Comparative) This example demonstrates the preparation of a styrene/N-phenylmaleimide/maleic anhydride terpolymer containing a total of 32 weight percent N-phenylmaleimide and maleic anhydride. The terpolymer is suitable for use to produce polyblends. The same amounts of ingredients and substantially the same procedure of Example II was used. The resulting terpolymer was analyzed and found to contain 13.6 weight percent N-phenylmaleimide, and 18.4 weight percent maleic anhydride with the balance being styrene. The glass transition temperature of the terpolymer was found to be 160°C (narrow) by DSC. Example IV (Comparative) This example demonstrates the preparation of a styrene/N-phenylmaleimide/maleic anhydride terpolymer containing a total of 40.8 weight percent N-phenylmaleimide and maleic anhydride using a batch process. The terpolymer is suitable for use to produce polyblends. Into a mixing vessel were added, with stirring, 224 g N-phenylmaleimide, 156.8 g maleic anhydride and about 2396.8 g of styrene. The resulting solution was filtered to eliminate maleic acid and insoluble impurities. To the filtered solution were added, with stirring, 2.4 g Diene® 55 polybutadiene, 2.2 g Polygard® HR antioxidant and 0.22 g benzoyl peroxide. The resulting solution was charged to a one gallon reactor under a nitrogen atmosphere. The reactor temperature was heated to 90°C and the polymerization reaction was allowed to proceed for 50 minutes. The polymerization reaction was terminated by the addition of 0.5 g hydroquinone. The polymerization product a styrene/N-phenylmaleimide/maleic anhydride terpolymer was diluted with styrene monomer, recovered by precipitation in methanol and dried. The resulting terpolymer was analyzed and found to contain 24.7 weight percent N-phenylmaleimide and 16.1 weight percent maleic anhydride with the balance being styrene. The glass transition temperature of the terpolymer was found to be 191.5°C (broad) by DSC. Example V This example demonstrates the preparation of a styrene/N-phenylmaleimide/maleic anhydride terpolymer chemically grafted to a rubber using a continuous stirred tank reactor process. Into a mixing vessel is added, with stirring, 239.4 g of N-phenylmaleimide, 138.6 g of maleic anhydride and 2119.6 g of styrene. The resulting solution is filtered to eliminate maleic acid and insoluble impurities. To the filtered solution is added, with stirring, 302.4 g of a butadiene-styrene copolymer rubber designated Stereon® 720 Rubber commercially available from Firestone Synthetic Rubber and Latex Co. (Stereon® 720 Rubber contains 10 wt% bound styrene); 2.5 g of a mixture of alkylated aryl phosphites designated Polygard® HR antioxidant commercially available from Uniroyal Chemical, division of Uniroyal, Inc., and about 0.6 g of benzoyl peroxide. The resulting solution is charged to the top of a continuous stirred tank reactor at a reaction temperature of about 100°C and a reactor pressure of about 11 bar (160 psi). The polymerization product is withdrawn from the reactor bottom at a conversion of about 45―50 weight percent. The polymerization product, a styrene/N-phenylmaleimide/maleic anhydride terpolymer chemically grafted to rubber is diluted with styrene monomer, recovered by precipitation in methanol and dried. Example VI This example demonstrates the preparation of a polymer alloy of this invention from polycarbonate and the styrene/N-phenylmaleimide/maleic anhydride terpolymer produced in Example I. 591.2 g of 2,2-bis(4-hydroxyphenyl)propane polycarbonate designated Merlon® M―50 commercially available from Mobay Chemical Corporation were melt compounded at 249°C (480°F) with about 483.7 g of the styrene/N-phenylmaleimide/maleic anhydride terpolymer produced in Example I. Test specimens were injection molded for physical property testing. Table I below sets forth the property values obtained. Example VII (Comparative) This example demonstrates the preparation of a polyblend from polycarbonate and the styrene/N-phenylmaleimide/maleic anhydride terpolymer produced in Example II. 789.5 g of Merlon® M―50 polycarbonate were melt compounded at about 260°C (500°F) with 646 g of the styrene/N-phenylmaleimide/maleic anhydride terpolymer produced in Example II. Test specimens were injection molded for physical property testing. Table I below sets forth the property values obtained. Example VIII (Comparative) This example demonstrates the preparation of a polyblend of this invention from polycarbonate and the styrene/N-phenylmaleimide/maleic anhydride terpolymer produced in Example III. 783.7 g of Merlon® M―50 polycarbonate were melt compounded at about 260°C (500°F) with 522.5 g of the styrene/N-phenylmaleimide/maleic anhydride terpolymer produced in Example III. Test specimens were injection molded for physical property testing. Table I below sets forth the property values obtained. Example IX (Comparative) This example demonstrates the preparation of a polyblend from polycarbonate and the styrene/N-phenylmaleimide/maleic anhydride terpolymer produced in Example IV. 607 g of Merlon® M―50 polycarbonate were melt compounded with 496.7 g of the styrene/N-phenylmaleimide/maleic anhydride terpolymer produced in Example IV. Test specimens were injection molded for physical property testing. Table I below sets forth the property values obtained.

Claims: A polymer composition comprising polycarbonate and a copolymer of monovinyl aromatic monomer and maleimide monomer, characterised in that said composition is a polymer alloy wherein the polycarbonate and the copolymer are fully compatible with one another and comprises in weight percent, from 1 to 99 of thermoplastic polycarbonate based on bis-(hydroxyaryl) alkane and from 99 to 1 of a random terpolymer of 70 to 90% by weight of recurring units of styrene, 2 to 24% by weight of recurring units of N-phenyl maleimide, and 2 to 24% by weight of recurring units of maleic anhydride, the total of the weight % of the three components of the tercopolymer adding up to 100. A polymer composition as claimed in claim 1 characterised in that said bis-(hydroxyaryl)alkane has the following general formula: wherein each R separately represents hydrogen, a C₁ to C₄ alkyl group, chlorine or bromine and wherein X represents a direct C₁ to C₄ alkylene. A polymer composition as claimed in claim 2 characterised in that said bis(-hydroxyaryl) alkane is 2,2-bis-(4-hydroxyphenyl)-propane. The polymer composition of any one of claims 1 to 3 in which said terpolymer has a number average peak molecular weight within the range of from 50,000 to 300,000 preferably from 150,000 to 250,000. The polymer composition of any one of claims 1 to 4 in which said terpolymer is chemically grafted to a rubber.

Inventors: LE-KHAC BI, LE-KHAC, BI
Applicants: ARCO CHEM TECH, ARCO CHEMICAL TECHNOLOGY, L.P.
Application year: 1984
Main classification: C08L69
IPC codes: C08L51, C08L33, C08L69, C08L35, C08L21, C08L7, C08L25