DIELS ALDER GRAFT COPOLYMERS

Abstract: A graft polymer obtained by effecting a Diels Alder reaction between a glassy copolymer having repeating units derived from N-(benzocyclobutenyl)maleimide and an elastomer having repeating units derived from a non-conjugated diene.

Description: This invention relates to novel graft polymers. More specifically, this invention relates to the formation of graft polymers between glassy polymers and elastomeric polymers using thermally initiated Diels-Alder chemistry. In one of its more specific aspects, this invention pertains to the incorporation of N-(benzocyclobutenyl) maleimide into a glassy polymer followed by the reaction of the maleimide containing glassy polymer with an elastomer having pendant carbon-carbon double bonds via Diels-Alder chemistry. The resulting graft polymers exhibit excellent impact strength properties upon molding. US-A-3489822 discloses grafted terpolymers comprising a rubbery component which is obtained by polymerising a resin-forming monomer or monomers in the presence of a rubbery copolymer resulting from the copolymerisation of two or more α-olefins and optionally a minor proportion of a diolefin. Methods for making the rubbery copolymers are well known and are disclosed for example in US 3000866, US 3000 867 and US 2933480. According to this invention, there is provided a graft polymer represented by formula (I): wherein R represents hydrogen or alkyl; R¹ represents phenyl, alkyl substituted phenyl, chloro or bromo substituted phenyl, CO₂H, CO₂CH₃, CO₂CH₂CH₃, or C≡N; X represents O, NH, NCH₃, NCH₂CH₃, NC(CH₃)₃, NC₆H₅, N-(p-Br)C₆H₄, N-(p-CH₃)C₆H₄, N-[p-C(CH₃)₃]C₆H₄, or N-(p-CH₃O)C₆H₄; the mole percent of the total recurring units designated by subscripts a + b + d equals 100 with a + d being a number from 95 to 99.5, b being a number from 0.5 to 5, and d being a number from 0 to 45, with the proviso that if the recurring unit designated by subscript d is present, it is directly substituted for a portion of the recurring unit designated by the subscript a; the mole percent of the total recurring units designated by subscripts w + y + z equals 100, with w being a number from 30 to 55, y being a number from 44.9 to 55, and z being a number of from 0.1 to 15; and, wherein at least 1 percent of the recurring units designated by the subscript b and at least 1 percent of the recurring units designated by the subscript z have been reacted to form a graft structure. Also according to this invention there is provided a method of producing the graft polymer represented by formula (I) above, comprising reacting a first and a second polymer at a reaction temperature equal to or greater than 250°C., said first copolymer being represented by the following formula (IV): wherein R, R¹, X, a, b, and d are as defined above; and said second copolymer is represented by the following formula (V): wherein w, y, and z are as defined above. According to this invention there is also provided a graft polymer represented by formula (II): wherein: R represents hydrogen or alkyl; R¹ represents phenyl, alkyl substituted phenyl, chloro or bromo substituted phenyl, CO₂H, CO₂CH₃, CO₂CH₂CH₃, or C≡N; X represents O, NH, NCH₃, NCH₂CH₃, NC(CH₃)₃, NC₆H₅, N-(p-Br)C₆H₄, N-(p-CH₃)C₆H₄, N-[p-C(CH₃)₃]C₆H₄, or N-(p-CH₃O)C₆H₄; the mole percent of the total recurring units designated by subscripts a + b + d equals 100 with a being a number from about 95 to about 99.5, b being a number from about 0.5 to about 5, and d being a number from 0 to about 45, with the proviso that if the recurring unit designated by subscript d is present, it is directly substituted for the recurring unit designated by the subscript a; the mole percent of the total recurring units designated by subscripts w + y + z equals 100, with w being a number from about 30 to about 55, y being a number from about 44.9 to about 55, and z being a number of from about 0.1 to about 15; and wherein at least 1 percent of the recurring units designated by the subscript b and at least 1 percent of the recurring units designated by the subscript z have been reacted to form a graft structure. Also according to this invention there is provided a method of producing the graft polymer represented by formula (II) above comprising reacting a first and a second polymer at a reaction temperature equal to or greater than 250°C., said first copolymer being represented by the following formula (IV): wherein R, R¹, X, a, b, and d are as defined above; and said second copolymer is represented by the following formula (VI): wherein w, y, and z are as defined above. According to this invention there is also provided a graft polymer represented by formula (III): wherein: R represents hydrogen or alkyl; R¹ represents phenyl, alkyl substituted phenyl, chloro or bromo substituted phenyl, CO₂H, CO₂CH₃, CO₂CH₂CH₃, or C≡N; X represents O, NH, NCH₃, NCH₂CH₃, NC(CH₃)₃, NC₆H₅, N-(p-Br)C₆H₄, N-(p-CH₃)C₆H₄, N-[p-C(CH₃)₃]C₆H₄, or N-(p-CH₃O)C₆H₄; the mole percent of the total recurring units designated by subscripts a + b + d equals 100 with a being a number from about 95 to about 99.5, b being a number from about 0.5 to about 5, and d being a number from 0 to about 45, with the proviso that if the recurring unit designated by subscript d is present, it is directly substituted for the recurring unit designated by the subscript a; the mole percent of the total recurring units designated by subscripts w + y + z equals 100, with w being a number from about 30 to about 55, y being a number from about 44.9 to about 55, and z being a number of from about 0.1 to about 15; and wherein at least 1 percent of the recurring units designated by the subscript b and at least 1 percent of the recurring units designated by the subscript z have been reacted to form a graft structure. Also according to this invention there is provided a method of producing the graft polymer represented by formula (III) above comprising reacting a first and a second polymer at a reaction temperature equal to or greater than 250°C., said first copolymer being represented by the following formula (IV): wherein R, R¹, X, a, b, and d are as defined above; and said second copolymer is represented by the following formula (VII): wherein w, y, and z are as defined above. According to this invention, there is also provided a moldable composition comprising a graft copolymer having the formulae (I), (II), or (III). The chemistry involved in forming the graft polymers of this invention is illustrated below: Examples of glassy polymers into which the N-(benzocyclobutenyl)maleimide monomer can be incorporated are vinyl aromatic homopolymers and copolymers such as polystyrene, poly(p-methylstyrene), poly(t-butylstyrene), styrene/maleic anhydride copolymers, styrene/N-arylmaleimide copolymers, styrene/N-alkylmaleimide copolymers, styrene/maleimide copolymers, styrene/methyl methacrylate copolymers, styrene/acrylonitrile copolymers, and styrene/(meth)acrylic acid copolymers, as well as poly(alkyl acrylate) homopolymers and copolymers such as poly(methyl methacrylate), methyl methacrylate/N-arylmaleimide copolymers, methyl methacrylate/N-alkylmaleimide copolymers and methyl methacrylate/maleic anhydride copolymers. The number average molecular weight of the glassy polymers suitable for use to produce the graft polymers of this invention should be from about 100,000 to about 300,000. Examples of elastomers having pendant unsaturation are ethylene/propylene/non-conjugated diene terpolymers where the non-conjugated diene is selected from 1,4-hexadiene, dicyclopentadiene, methylene norbornene and the like. The number average molecular weight of the elastomers suitable for use to produce the graft polymers of this invention should be from about 50,000 to about 250,000. The glassy polymers used to produce the graft polymers of this invention contain from 0.5 to 5 mol percent of the N-(benzocyclobutenyl)maleimide monomer. The elastomer used to produce the graft polymers of this invention contains from 1 to 15 mol percent of the non-conjugated diene. The reaction between the glassy polymer and the elastomer to form the graft copolymers of this invention is generally effected by exposing a mixture thereof to a temperature of at least 250°C and for a period of time of from 2 to 20 minutes. The mass is thereafter cooled and the graft copolymers recovered. The graft polymers of this invention are well suited for molding using any conventional molding/extrusion method suitable for thermoplastics. In general, molding is effected by pressure molding at a pressure in the mold in the range of 136 to 540 kg/cm² (2000-8000 psi), a temperature in the range 180°C to 270°C and a residence time of 2 to 8 minutes. The molded articles produced from the graft polymers of this invention are characterised by significantly improved impact characteristics. In the formulation of a final molding composition, it is possible, and and frequently desirable, to include other ingredients such as extenders, processing aids, pigments, anti-oxidants, stabilizers, mold release agents, for their conventionally employed purpose. Fillers in amounts sufficient to impart reinforcement or property modification can also be added, such as silica, calcium carbonate, talc, mica, processed mineral fibers, titanium dioxide, potassium titanate and titanate whiskers, carbon fibers, aramid fibers, glass flakes, glass spheres, chopped glass fibers, and their mixtures. In the following examples, which serve to demonstrate the invention, the evaluation of material properties was performed based on the following ASTM standard tests: Notched Izod (D-256) and DTUL (deflection temperature under load, 3.175 mm at 1821.6 KPa (1/8" at 264 psi) (D-648). Gardner falling weight index (GFWI) was established using a 31.75 mm (1-1/4") diameter orifice and a 3.6 kg 12.7 mm (8 pound 1/2") diameter weight. Glass transition temperature was determined by differential scanning colorimetry (DSC). EXAMPLE 1 This example serves to demonstrate the preparation of a styrene/N-(benzocyclobutenyl)maleimide copolymer. A baffled 2-liter resin kettle was equipped with a mechanical stirrer, pressure equalizing addition funnel and nitrogen purge. The resin kettle was charged with 700 grams of styrene monomer. The pressure equalizing addition funnel was charged with a solution containing 185 grams of styrene monomer, 13.5 grams of N-(benzocyclobutenyl)maleimide monomer, and 1.21 grams of VAZO® 88 free radical initiator (E. I. DuPont Company). The reactor was heated to 110°C. and the contents of the addition funnel were metered in at a rate of 4 milliliters/minute. The reaction was stopped at 44% solids (396 grams) and the polymer was recovered by precipitation into methanol. The nitrogen content of the copolymer was 0.27 weight percent which corresponds to 3.8 weight percent N-(benzocyclobutenyl)maleimide incorporation. The glass transition temperature of the copolymer was 114°C. The number average molecular weight of the copolymer as measured by gel permeation chromatography was 147,900. EXAMPLE 2 This example serves to demonstrate the thermally activated grafting reaction between the styrene/N-(benzocyclobutenyl)maleimide copolymer produced in Example 1 and an ethylene/propylene/1,4-hexadiene elastomer. As shown in following Table 1, six moldable compositions (Compositions A-F) were prepared. Composition B is a Diels-Alder graft polymer of this invention. Compositions A, C, D, E, and F are control compositions. The two components employed in each of Compositions A-F were physically mixed and extruded into pellets in a counterrotating twin screw extruder at 260°C. The resulting pellets were separately molded into test specimens for physical property evaluation. Physical properties were as shown in following Table 1. The above data illustrate the superior impact properties of Composition B, a graft polymer according to this invention.

Claims: Claims for the following Contracting States : BE, DE, FR, GB, IT, NL A graft copolymer comprising (i) a first polymer chain formed of the repeating units : wherein in each repeating unit of structure a, R represents hydrogen or alkyl and R¹ represents phenyl, alkyl substituted phenyl, chloro or bromo substituted phenyl, CO₂H, CO₂CH₃, CO₂CH₂CH₃, or C≡N; and in each repeating unit d, X represents O, NH, NCH₃ NCH₂CH₃, NC(CH₃)₃, NC₆H₅, N-(p-Br)C₆H₄, N-(p-CH₃)C₆H₄, N-[p-C(CH₃)₃]C₆H₄, or N-(p-CH₃O)C₆H₄; and wherein the number of units a and the number of units d in the polymer chain together form from 95 to 99.5 mol % of the total number of units a + b + d , the number of units b in the polymer chain form from 0.5 to 5 mol % of the total number of units a + b + d , and if the recurring unit d is present, it is directly substituted for the recurring unit a and is present in an amount of up to 45 mol %, based on the total number of units a + b + d; and (ii) a second polymer chain formed of the repeating units: where - Z - is selected from the group consisting of: there being in the polymer chain from 30 to 55 mol % of units w, from 44.9 to 55 mol % of units y, and from 0.1 to 15 mol % of units z, each based on the total number of units w, y and z in the polymer chain; and, wherein at least 1 percent of the recurring units b and at least 1 percent of the recurring units z have been reacted whereby to form units of the structure: where Q is selected from depending on the nature of z. A method of forming a graft copolymer as claimed in claim 1 comprising heating together at a temperature equal to or greater than 250°C (a) a first polymer comprising a polymer chain formed of the repeating units: and (b) a second polymer comprising a polymer chain formed of the repeating units wherein R, R¹, X and Z and the number of units a, b, d, w, y and z are as defined in claim 1 to effect Diels Alder reaction between repeating units of the structure b in the first polymer and repeating units of the structure z in the second polymer A method of obtaining a graft copolymer comprising effecting Diels Alder reaction between (i) at least 1% of the repeating units derived from N-(benzocyclobutenyl)maleimide of a glassy copolymer containing from 0,5 to 5 mol % of repeating units derived from said N-(benzocyclobutenyl)maleimide and (ii) at least 1% of the repeating units derived from the non-conjugated diene of an elastomer having pendant unsaturation containing from 1 to 15 mol % of repeating units derived from a non-conjugated diene. A moldable composition comprising a graft polymer as claimed in Claim 1. A method of producing a molded composition comprising molding a composition as claimed in claim 4, optionally in contact with a filler. A method of producing a molded composition comprising (a) producing a graft polymer according to the method claimed in claim 2 or claim 3 and (b) molding the resulting graft copolymer, optionally in contact with a filler. Claims for the following Contracting State : ES A method of obtaining a graft copolymer comprising effecting Diels Alder reaction between (i) at least 1% of the repeating units derived from N-(benzocyclobutenyl) maleimide of a glassy copolymer containing from 0.5 to 5 mol % of repeating units derived from said N-(benzocyclobutenyl) maleimide and (ii) at least 1% of the repeating units derived from the non-conjugated diene of an elastomer having pendant unsaturation containing from 1 to 15 mol% of repeating units derived from a non-conjugated diene. A method of forming a graft copolymer as claimed in claim 1, comprising heating together at a temperature of at least 250°C (a) a first polymer comprising a polymer chain formed of the repeating units: wherein in each repeating unit of structure A, R represents hydrogen or alkyl and R¹ represents phenyl, alkyl substituted phenyl, chloro or bromo substituted phenyl, CO₂H, CO₂CH₃, CO₂CH₂CH₃, or C≡N; and in each repeating unit D, X represents O, NH, NCH₃, NCH₂CH₃, NC(CH₃)₃, NC₆H₅, N-(p-Br)C₆H₄, N-(p-CH₃)C₆H₄, N-[p-C(CH₃)₃]C₆H₄, or N-(p-CH₃O)C₆H₄; and wherein the number of units A and the number of units D in the polymer chain together form from 95 to 99.5 mol % of the total number of units A + B + D , the number of units B in the polymer chain form from 0.5 to 5 mol % of the total number of units A + B + D , and if the recurring unit D is present, it is directly substituted for the recurring unit A and is present in an amount of up to 45 mol %, based on the total number of units A + B + D ; and (b) a second polymer comprising a polymer chain formed of the repeating units: where - Z - is selected from the group consisting of: there being in the polymer chain from 30 to 55 mol % of units W, from 44.9 to 55 mol % of units Y, and from 0.1 to 15 mol % of units Z, each based on the total number of units W, Y and Z in the polymer chain, to effect Diels Alder reaction between repeating units of the structure B in the first polymer and repeating units of the structure Z in the second polymer. A method of producing a molded composition comprising (a) producing a graft polymer according to the method claimed in claim 1 or claim 2 and (b) molding the resulting graft copolymer, optionally in contact with a filler. A method of obtaining a molded article comprising molding a graft copolymer comprising (i) a first polymer chain formed of the repeating units: wherein in each repeating unit of structure A, R represents hydrogen or alkyl and R¹ represents phenyl, alkyl substituted phenyl, chloro or bromo substituted phenyl, CO₂H, CO₂CH₃, CO₂CH₂CH₃, or C≡N; and in each repeating unit D, X represents O, NH, NCH₃, NCH₂CH₃, NC(CH₃)₃, NC₆H₅, N-(p-Br)C₆H₄, N-(p-CH₃)C₆H₄, N-[p-C(CH₃)₃]C₆H₄, or N-(p-CH₃O)C₆H₄; and wherein the number of units A and the number of units D in the polymer chain together form from 95 to 99.5 mol % of the total number of units A + B + D , the number of units B in the polymer chain form from 0.5 to 5 mol % of the total number of units A + B + D , and if the recurring unit D is present, it is directly substituted for the recurring unit A and is present in an amount of up to 45 mol %, based on the total number of units A + B + D ; and (ii) a second polymer chain formed of the repeating units: where - Z - is selected from the group consisting of: there being in the polymer chain from 30 to 55 mol % of units W, from 44.9 to 55 mol % of units Y, and from 0.1 to 15 mol % of units Z, each based on the total number of units W, Y and Z in the polymer chain; and, wherein at least 1 percent of the recurring units B and at least 1 percent of the recurring units Z have been reacted whereby to form units of the structure: where Q is selected from depending on the nature of Z. A method of obtaining a molded article comprising molding a a graft polymer represented by formula (I): wherein R represents hydrogen or alkyl; R¹ represents phenyl, alkyl substituted phenyl, chloro or bromo substituted phenyl, CO₂H, CO₂CH₃, CO₂CH₂CH₃, or C≡N; X represents O, NH, NCH₃, NCH₂CH₃, NC(CH₃)₃, NC₆H₅, N-(p-Br)C₆H₄, N-(p-CH₃)C₆H₄, N-[p-C(CH₃)₃]C₆H₄, or N-(p-CH₃O)C₆H₄; the mole percent of the total recurring units designated by subscripts a + b + d equals 100 with a being a number from 95 to 99.5, b being a number from 0.5 to 5, and d being a number from 0 to 45, with the proviso that if the recurring unit designated by subscript d is present, it is directly substituted for the recurring unit designated by the subscript a; the mole percent of the total recurring units designated by subscripts w + y + z equals 100, with w being a number from 30 to 55, y being a number from 44.9 to 55, and z being a number of from 0.1 to 15; and, wherein at least 1 percent of the recurring units designated by the subscript b and at least 1 percent of the recurring units designated by the subscript z have been reacted to form a graft structure. A method of obtaining a molded article comprising molding graft polymer represented by formula (II): wherein: R represents hydrogen or alkyl; R¹ represents phenyl, alkyl substituted phenyl, chloro or bromo substituted phenyl, CO₂H, CO₂CH₃, CO₂CH₂CH₃, or C≡N; X represents O, NH, NCH₃, NCH₂CH₃, NC(CH₃)₃, NC₆H₅, N-(p-Br)C₆H₄, N-(p-CH₃)C₆H₄, N-[p-C(CH₃)₃]C₆H₄, or N-(p-CH₃O)C₆H₄; the mole percent of the total recurring units designated by subscripts a + b + d equals 100 with a being a number from 95 to 99.5, b being a number from 0.5 to 5, and d being a number from 0 to 45, with the proviso that if the recurring unit designated by subscript d is present, it is directly substituted for the recurring unit designated by the subscript a; the mole percent of the total recurring units designated by subscripts w + y + z equals 100, with w being a number from 30 to 55, y being a number from 44.9 to 55, and z being a number of from 0.1 to 15; and wherein at least 1 percent of the recurring units designated by the subscript b and at least 1 percent of the recurring units designated by the subscript z have been reacted to form a graft structure. A method of obtaining a molded article comprising molding a graft polymer represented by formula (III): wherein: R represents hydrogen or alkyl; R¹ represents phenyl, alkyl substituted phenyl, chloro or bromo substituted phenyl, CO₂H, CO₂CH₃, CO₂CH₂CH₃, or C≡N; X represents O, NH, NCH₃, NCH₂CH₃, NC(CH₃)₃, NC₆H₅, N-(p-Br)C₆H₄, N-(p-CH₃)C₆H₄, N-[p-C(CH₃)₃]C₆H₄, or N-(p-CH₃O)C₆H₄; the mole percent of the total recurring units designated by subscripts a + b + d equals 100 with a being a number from 95 to 99.5, b being a number from 0.5 to 5, and d being a number from 0 to 45, with the proviso that if the recurring unit designated by subscript d is present, it is directly substituted for the recurring unit designated by the subscript a; the mole percent of the total recurring units designated by subscripts w + y + z equals 100, with w being a number from 30 to 55, y being a number from 44.9 to 55, and z being a number of from 0.1 to 15; and wherein at least 1 percent of the recurring units designated by the subscript b and at least 1 percent of the recurring units designated by the subscript z have been reacted to form a graft structure.

Inventors: DEAN, BARRY D.
Applicants: ARCO CHEMICAL TECHNOLOGY, L.P.
Application year: 1987
Main classification: C08G81
IPC codes: C08G81, C08F291