Thermoplastic polymer composition

Abstract: A thermoplastic polymer composition contains: (a) 10 to 95 parts by weight of a block copolymer comprised of at least two polymer segments comprising mainly a vinyl aromatic hydrocarbon and at least one polymer segment composed mainly a conjugated diene, in which block copolymer: (i) the content of the vinyl aromatic hydrocarbon is more than 60% by weight and less than 95% by weight; (ii) the ratio of the vinyl aromatic hydrocarbon present in the block copolymer as the vinyl aromatic hydrocarbon polymer block to the total vinyl aromatic hydrocarbons present in the block copolymer is more than 75% by wieght and up to 98% by weight; and (iii) the ratio of the weight average molecular weight to the number average molecular weight of the vinyl aromatic hydrocarbon polymer block in the block copolymer is 1.2 to 2.0 and (b) 5 to 90% by weight of polyphenylene ether, and, optionally, (c) 3 to 400 parts by weight, based on 100 parts by weight of the total weight of said components (a) and (b), of a styrenic polymer.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic polymer composition which is superior in transparency, impact resistance, surface hardness, heat resistance, and gloss and with little warping. 2. Description of the Related Art Block copolymers comprised of conjugated dienes and vinyl aromatic hydrocarbons are superior in transparency when the content of the vinyl aromatic hydrocarbons is relatively high and provide a thermoplastic resin with better impact resistance than polystyrene. Accordingly, these block copolymers have increasingly been used in recent years in the fields of food packaging, sundry goods for daily use, toys, home appliance components, and the like. However, these block copolymers have the defect of being poorer than other plastics in their surface hardness and heat resistance. On the other hand, polyphenylene ether resins are superior in dimensional stability, electrical characteristics, resistance to heat deformation under high loads, waterproofness, and the like and are therefore widely used in industry. However, such polyphenylene ether resins have the defect of being inferior in impact resistance and processability during molding. Therefore, various attempts have been made to blend the two with the object of taking advantage of the respective merits of block copolymers comprised of conjugated dienes and vinyl aromatic hydrocarbons and polyphenylene ether resins and to compensate for their mutual defects. For example, Japanese Unexamined Patent Publication (Kokai) No. 48-62851 (i.e., DE-A-2255930) and Japanese Unexamined Patent Publication (Kokai) No. 51-129450 (i.e., GB-A-1532455) disclose normally rigid thermoplastic compositions comprised of (a) polyphenylene ether resins, (b) A-B-A' type elastomer block copolymers wherein the central block B has a molecular weight which is larger than the combined molecular weights of the end blocks A and A', and (c) styrene homopolymers or random copolymers. Further, Japanese Unexamined Patent Publication (Kokai) No. 52-125560 (i.e., GB-A-1522458) discloses a thermoplastic molding composition comprised of a homogeneous mixture of (i) a polyphenylene ether resin, (ii) a styrene resin, and (iii) a radial tereblock copolymer. Further, Japanese Unexamined Patent Publication (Kokai) No. 58-176240 discloses a thermoplastic resin composition comprised primarily of 1 to 20 parts by weight of a block copolymer comprised of 10 to 60 parts by weight of a vinyl aromatic compound and 40 to 90 parts by weight of a conjugated diene, based on 100 parts by weight of a modified polyphenylene oxide resin. However, the block copolymers used in these compositions are block copolymers having a content of the vinyl aromatic compounds of 60% by weight or less and these compositions are inferior in transparency, surface hardness, heat resistance, and gloss. On the other hand, Japanese Examined Patent Publication (Kokoku) No. 54-27025 (i.e., U.S. Patent No. 3639508) discloses a thermoplastic composition containing (A) 1 to 45% by weight of a polyarylene oxide and (B) 99 to 55% by weight of a block copolymer having 10 to 90% by weight of at least one type of monovinyl aromatic block. It describes a composition using a block copolymer with a content of the vinyl aromatic compound of 80% by weight. However, the composition has the problems of being inferior in impact resistance and susceptible to the occurrence of microcracks when bent. Further, Japanese Unexamined Patent Publication (Kokai) No. 61-223054 and Japanese Unexamined Patent Publication (Kokai) No. 62-70448 disclose impact resistant polyphenylene ether resin compositions containing (a) polyphenylene ether resins, (b) A-B-A' type block copolymers wherein the block B has a molecular weight that is smaller than the combined molecular weights of the blocks A and A'), and (c) an elastomer. However, these compositions have the problem that, while being superior in impact resistance, they are inferior in transparency and surface hardness. Further, Japanese Unexamined Patent Publication (Kokai) No. 50-71742 (i.e., GB-A-1477706), Japanese Unexamined Patent Publication (Kokai) No. 53-94540 (i.e., GB-A-1559052) and Japanese Unexamined Patent Publication (Kokai) No. 56-95949 (i.e., U.S. Patent No. 4309514) disclose compositions comprised of (a) polyphenylene ether resins, (b) styrene resins, and (c) hydrogenated block copolymers. However, the block copolymers used in these compositions have a content of the vinyl aromatic hydrocarbons of 60% by weight or less and are thus inferior in transparency, surface hardness, heat resistance, and gloss. Further, EP-A-0 048 397 discloses a thermoplastic molding composition comprising a polyphenylene ether and a block copolymer consisting of 60 to 80 weight% of a monovinyl aromatic compound and 40 to 20 weight% of a conjugated diene having 4 to 8 carbon atoms. The composition is reported to have improved processability resulting in shaped bodies having good transparency. SUMMARY OF THE INVENTION Accordingly, the objects of the present invention are to eliminate the above-mentioned disadvantages of the prior art and to provide a thermoplastic polymer composition which is superior in transparency, impact resistance, surface hardness, heat resistance (or resistance to heat deformation), and gloss and with little warping. Other objects and advantages of the present invention will be apparent from the following description. In accordance with the present invention, there is provided a thermoplastic polymer composition comprising: (a) 10 to 95 % by weight of a block copolymer which comprises at least two polymer segments composed mainly of a vinyl aromatic hydrocarbon and at least one polymer segment composed mainly of a conjugated diene, in which block copolymer: (i) the content of the vinyl aromatic hydrocarbon is more than 60% by weight and not more than 95% by weight based on the weight of the block copolymer; (ii) the ratio of the vinyl aromatic hydrocarbon present, as a vinyl aromatic hydrocarbon polymer block, in the block copolymer to the total vinyl aromatic hydrocarbons present in the block copolymer is more than 75% by weight and up to 98% by weight, based on the weight of the block copolymer, and (iii) the ratio of the weight average molecular weight to the number average molecular weight of the vinyl aromatic hydrocarbon polymer block in the block copolymer is 1.2 to 2.0 and (b) 5 to 90% by weight of a polyphenylene ether having a stabilizing end group. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail hereinbelow. The block copolymer of the component (a) used in the present invention comprises at least two polymer segments composed mainly of vinyl aromatic hydrocarbons and at least one polymer segment composed mainly of conjugated dienes. The content of the vinyl aromatic hydrocarbon, based on the weight of the block copolymer is over 60% by weight and 95% by weight or less, preferably from 65 to 90% by weight. When the content of the vinyl aromatic hydrocarbon is 60% by weight or less, the surface hardness, heat resistance, and gloss are inferior and when the content is more than 95% by weight, the impact resistance is inferior, and thus these contents are not preferred. Further, in the present invention, the polymer segment composed mainly of vinyl aromatic hydrocarbons means a polymer segment having 50% by weight or more of a vinyl aromatic hydrocarbon, preferably 70% by weight or more. It is a segment comprised of a copolymer block of a vinyl aromatic hydrocarbon and a conjugated diene and a homopolymer block of a vinyl aromatic hydrocarbons or a segment composed of a homopolymer block of a vinyl aromatic hydrocarbon. Further, the polymer segment composed mainly of a conjugated diene means a polymer segment having a content of a conjugated diene based on the weight of the block copolymer of more than 50% by weight, preferably 70% by weight or more. It is a segment composed of a copolymer block of a conjugated diene and a vinyl aromatic hydrocarbon and/or a homopolymer block of a conjugated diene. The vinyl aromatic hydrocarbons copolymerized in the copolymer blocks in these segments may be uniformly distributed or may be distributed in a tapered form. Further, said copolymer blocks may have a plurality of coexisting portions with vinyl aromatic hydrocarbons uniformly distributed and/or portions with them distributed in a tapered form. The block copolymer of the component (a) used in the present invention has a ratio of the vinyl aromatic hydrocarbons present in the said block copolymer as the vinyl aromatic hydrocarbon polymer block to the total vinyl aromatic hydrocarbons contained in the block copolymer (hereinbelow, referred to as the block ratio of the vinyl aromatic hydrocarbons) of more than 75% by weight and up to 98% by weight, preferably from 77 to 96% by weight, more preferably 80 to 95% by weight. When the block ratio of the vinyl aromatic hydrocarbons is 75% by weight or less, the surface hardness and heat resistance are inferior and when over 98% by weight, the impact resistance is inferior, and thus, these block ratios are not preferred. The block ratio of the vinyl aromatic hydrocarbons may be determined by the method for oxidation decomposition of copolymers using osmium tetraoxide as a catalyst and using di-tertiary-butyl hydroperoxide (for example, the method disclosed by L. M. Kolthoff et al., J. Polymer Sci., 1, 429 (1946)). After the block copolymer is decomposed by oxidation by the above-mentioned method, a large amount of methanol is added to the decomposition product to obtain the vinyl aromatic hydrocarbon polymer component (in general, having a number average molecular weight of about 1000 or more, preferably about 3000 to 1,000,000, more preferably about 5000 to 1,000,000), the amount of which is divided by the amount of the total vinyl aromatic hydrocarbons contained in the block copolymer, whereby it is possible to determine the block ratio of the vinyl aromatic hydrocarbons. Further, the block copolymer of the component (a) used in the present invention has a ratio of the weight average molecular weight (hereinafter referred to as the M w) to the number average molecular weight (hereinafter referred to as the M n) of the vinyl aromatic hydrocarbon polymer block in the block copolymer of, 1.2 to 2.0, preferably in the range of 1.3 to 1.8. When the ratio of M w/ M n is less than 1.2, the impact resistance is inferior and when more than 2.0, anistrophy in molding occurs causing the problem of warping of the molded product. The M w/ M n of the vinyl aromatic hydrocarbon polymer block in the block copolymer bay be determined in the following manner: Specifically, the vinyl aromatic hydrocarbon polymer component obtained by oxidation decomposition of the block copolymer by the above-mentioned method may be determined by gel permeation chromatograph (GPC) and calculated in accordance with a usual method (for example, the method disclosed in "Chromatography 〈Basics〉, published by Kodansha). The calibration curve used in the GPC may be prepared using standard polystyrene commercially available for GPC use. The block copolymer which is especially preferable as the block copolymers of the component (a) used in the present invention is the block copolymer having a glass transition temperature (Tg) of the polymer segment composed principally of vinyl aromatic hydrocarbons of 65 to 98°C, preferably 75 to 96°C. When a block copolymer having a Tg in this range is used, a composition is obtained with little occurrence of microcracks as seen when bending the composition. Further, the Tg used herein defines the temperature found from the point of inflection of the dynamic modulus of elasticity (E') in the measurement of the dynamic elastoviscosity or the temperature found from the point of inflection of the temperature change in a differential scanning calorimeter (DSC). The dynamic elastoviscosity may be measured using, for example, a Rheovibron (Model DDV-3) made by Toyo Baldwin. The block copolymer of the component (a) used in the present invention may be a block copolymer with a polymer structure represented by the general formula: (A-B) n+1 , A(B-A) n , B(A-B) n wherein, A is a polymer block comprising mainly a vinyl aromatic hydrocarbon and B is a polymer block comprising mainly a conjugated diene. The boundary between the A block and B block does not necessarily have to be clearly differentiated. Further, n is an integer of 1 or more, preferably an integer of 1 to 5, or the general formula: wherein, A and B are the same as mentioned above, X is, for example, a residual group of silicon tetrachloride, tin tetrachloride, polyepoxide such as epoxidized soybean oil, polyhalogenated hydrocarbons, carboxylic acid ester, polyvinyl compounds, or other coupling agents or a residual group of a polyfunctional organic lithium compound or other initiator, m and n are integers of 1 or more, preferably m is an integer of 1 to 10 and n is an integer of 1 to 5. The block copolymer used in the present invention may be any mixture of block copolymers expressed by the above-mentioned general formulae. Examples of the vinyl aromatic hydrocarbon used in the method of the present invention are styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinyl anthracene. Of these styrene is generally used. These may be used alone or any mixtures thereof. Examples of the conjugated dienes used in the present invention are diolefins such as 1,3-butadiene, 2-methyl-1,3-butadiene (i.e., isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene. Of these 1,3-butadiene and isoprene are most preferably used. These may be used alone or mixture thereof. The block copolymer used in the present invention may be obtained by polymerization in a hydrocarbon solvent using an organic lithium compound as an initiator. Examples of the hydrocarbon solvent usable in the present invention are butane, pentane, hexane, isopentane, heptane, octane, isooctane, and other aliphatic hydrocarbons; cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, and other alicyclic hydrocarbons; benzene, toluene, ethylbenzene, xylene, and other aromatic hydrocarbons. The organic lithium compound usable in the present invention, is an organic lithium compound with one or more lithium atoms bonded in the molecule and may be, for example, ethyl lithium, n-propyl lithium, isopropyllithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, hexamethylene dilithium, butadienyl dilithium, isoprenyl dilithium. In the block copolymer of the component (a) used in the present invention, the number average molecular weight of the segment A is 5,000 to 500,000, preferably 70,000 to 300,000, while the number average molecular weight of the segment B is 1,000 to 400,000, preferably 3,000 to 300,000. Further, the number average molecular weight of the block copolymer as a whole is 10,000 to 1,000,000, preferably 30,000 to 500,000. The block copolymer used in the present invention may be a block copolymer having a polar group-containing atomic group at least at one polymer chain end of the block copolymer (hereinafter abbreviated as an end-modified block copolymer). The polar group-containing atomic group mentioned here means an atomic group containing at least one kind of atom selected from nitrogen, oxygen, silicon, phosphorus, sulfur, or tin. Specifically, mention may be made of an atomic group containing at least one type of polar group selected from the carboxyl group, carbonyl group, thiocarbonyl group, acid halide group, acid anhydride group, carboxlic acid group, thiocarboxylic acid group, aldehyde group, thioaldehyde group, carboxylic acid ester group, amide group, sulfonic acid group, sulfonic acid ester group, phosphoric acid group, phosphoric acid ester group, amino group, imino group, nitrile group, pyridyl group, quinoline group, epoxy group, thioepoxy group, sulfide group, isocyanate group, isothiocyanate group, silicon halide group, alkoxy silicon group, tin halide group, alkyl tin group, phenyl tin group or the like. More specifically, use may be made of the end modified block copolymer described in EP-A-245504 In the present invention, it is possible to use hydrogenated block copolymer of the afore-mentioned block copolymer or end-modified block copolymer. Examples of the catalyst usable for the hydrogenation reaction are (1) supported or carried type heterogeneous catalysts wherein Ni, Pt, Pd, Ru, or other metals are carried in carbon, silica, alumina, diatomaceous earth, or other support and (2) so-called Ziegler catalysts using Ni, Co, Fe, Cr, or other organic acid salts or acetylacetone salts and organic aluminum or other reducing agents or so-called organic complex catalysts or other homogeneous catalysts such as Ru, Rh, or other organic metal compounds. The specific methods disclosed in, for example, Japanese Examined Patent Publication (Kokoku) No.42-8704 (i.e., DE-A-1222260), Japanese Examined Patent Publication (Kokoku) No. 43-6636 (i.e., U.S. Patent No. 3333024), or Japanese Unexamined Patent Publication (Kokai) No. 59-133203 (i.e., U.S. Patent No. 4501857) and Japanese Unexamined Patent Publication (Kokai) No. 60-220147 (i.e., U.S. Patent No. 4673714) can be used in the present invention. According to these methods, hydrogen is added in an inert medium in the presence of a hydrogenation catalyst to obtain a hydrogenated product and synthesize a hydrogenated polymer for use in the present invention. The hydrogenated ratio of the aliphatic double bond based on the conjugated diene compound in the polymer may be controlled to any desired value by, for example, adjusting the reaction temperature, the reaction time, the amount of hydrogen supply, the amount of the catalyst, etc. For example, when trying to improve the resistance to heat deterioration while maintaining the properties of the nonhydrogenated polymer, it is recommended to hydrogenate the aliphatic double bonds, based on the conjugated dienes, by 3% to less than 80%, preferably from 5% to less than 75%, more preferably from 10 to 45%. When trying to improve the resistance to heat deterioration and the weather resistance, it is preferably to hydrogenate to 80% or more, preferably 90% or more. In this case, there are no particular limitations to the hydrogenated ratio of the aromatic double bonds based on the vinyl aromatic compounds copolymerized with the polymer block A comprising mainly the vinyl aromatic compounds and, in accordance with need, the polymer block B comprising mainly the conjugated dienes, but it is preferable to make the hydrogenated ratio 20% or less. The amount of the nonhydrogenated aliphatic double bonds contained in said hydrogenated block copolymers can be easily determined by, for example, an infrared spectrometer, a nuclear magnetic resonance apparatus and the like. Next, the stabilized polyphenylene ether of component (b) of the thermoplastic polymer composition used in the present invention may be a homopolymer comprising repeating units expressed by the general formula: wherein, at least one of R₁ and R₂ is a linear chain or primary or secondary branch chain C₁ - C₄ alkyl group, aryl group, halogen atom, or hydrogen atom, and R₁ and R₂ may be the same or different; a copolymer comprised of repeating units expressed by the above-mentioned general formula (I) and the repeating units expressed by the general formula: wherein, R₃ , R₄ , R₅ , and R₆ may be the same or mutally different and represent each a linear chain or primary or secondary branch chain C₁ - C₄ alkyl groups, aryl groups, halogen atoms, hydrogen atoms, except that R₃ and R₄ are not simultaneously a hydrogen atom, a graft copolymer formed by graft polymerization of styrene with the homopolymer or copolymer. Typical examples of the homopolymers of the polyphenylene ether may be poly(2,6-dimethyl-1,4-phenylene)ether, poly(2-methyl-6-ethyl-1,4-phenylene)ether, poly(2,6-diethyl-1,4-phenylene)ether, poly(2-ethyl-6-n-propyl-1,4-phenylene)ether, poly(2,6-di-n-propyl-1,4-phenylene)ether, poly(2-methyl-6-n-butyl-1,4-phenylene)ether, poly(2-ethyl-6-isopropyl-1,4-phenylene)ether, poly(2-methyl-6-chloro-1,4-phenylene)ether, poly(2-methyl-6-hydroxyethyl-1,4-phenylene)ether, poly(2-methyl-6 chloroethyl-1,4-phenylene)ether, and other similar homopolymers. The polyphenylene ether copolymer may include a polyphenylene ether copolymers composed principally of a polyphenylene ether structure obtained by copolymerization with o-cresol or 2,3,6-trimethylphenol or other alkyl substituted phenols expressed by the general formula: wherein, R₃ , R₄ , R₅ , and R₆ are each the same as defined above. The number average degree (n) of polymerization of the polyphenylene ether is selected from the range of 50 to 500, preferably 75 to 250. With a number average degree of polymerization of less than 50, the resultant compositions are remarkably reduced in impact strength and other physical properties and are not suited for practical use. Further when more than 500, the resultant compositions are inferior in processability and easily gel and are thus not preferable. The polyphenylene ether used in the present invention may be a modified polyphenylene ether formed by addition and/or graft polymerization of a radical polymerizable vinyl compound with the above-mentioned homopolymers or copolymers. The vinyl compound may be the afore-mentioned vinyl aromatic hydrocarbons and their halogen substituents, acrylic acid esters, methacrylic acid esters, and other unsaturated monocarboxylic acid esters, acrylic acid amides, methacrylic acid amides, and other unsaturated carboxylic acid amides, maleic acid, fumaric acid, itaconic acid, and other unsaturated dicarboxylic acids, or acid anhydrides of these unsaturated dicarboxylic acids, esters amides, imides, acrylonitriles, methacrylonitriles and other nitrile monomers. As the polyphenylene ether of component (b) used in the present invention has a stabilizing end group, the polymer composition having a light color or the molded article therefrom having a light color can be preferably obtained. Typical examples of the end groups of the polyphenylene ether having a stabilizing end group are represented by the general formula (IV): wherein, R₁ to R₅ are independently hydrogen, an alkyl group, substituted alkyl group, halogen group, aryl group, or substituted aryl group, R₆ to R₉ are independently hydrogen, an alkyl group, substituted alkyl group, alkenyl group, substituted alkenyl group, halogen group, aryl group substituted aryl group, alkoxyl group, N-lactam group, carboxylic acid group, carboxylic acid anhydride group, carboxylic acid ester group, carboxylic acid amide group, nitrile group, acyloxyl group, or acyl group. Note that R₆ and R₇ and R₈ and R₉ may be independently bonded to form spirocyclic structure rings. The above-mentioned stabilizing end group may preferably include such groups in which the average number of the end group is 0.01 or more, based on 100 phenylene ether units. The polyphenylene ether cyclized with the above-mentioned end structure, namely 6-chroman skeleton is extremely suitable for providing a composition with an extremely high degree of stability during molding, resistant to thermal oxidation, and clear or light color. In the stabilized polyphenylene ether used in the present invention, it is preferably that there be contained an average of 0.01 or more cyclic end groups having the general formula (IV) with respect to 100 phenylene ether units constituting the resin. In the case of the resin used as an engineering plastic, of which average molecular weight is about 10,000 to 30,000, it is preferable that the cyclic end groups be present in an amount of an average 0.15 or more with respect to 100 phenylene ether units. More preferably, they are present in an amount of an average 0.2 or more. There is no particular upper limit of the amount of the cyclic end groups in that it is a case of the more the better in terms of the resistance to deterioration by thermal oxidation. Further, a resin in which all of its end groups are of the structure of the general formula (IV) is also extremely stable as a resin. The stabilized polyphenylene ether resin used in the present invention may be produced as follows: That is, the polyphenylene ether polymer having end group having the general formula (V): wherein, R₁ to R₅ are each the same as defined in the formula (IV) and R₁₀ and R₁₁ are independently hydrogen, an alkyl group, or a substituted alkyl group, but are not simultaneously hydrogen, may be heated to a temperature over the glass transition temperature of the polyphenylene ether polymer with a compound having a carbon-carbon double bond (hereinafter referred to as an unsaturated compound) having the general formula (VI) wherein, R₆ to R₉ are each in the absence of the same as those defined in formula (IV) in the absence of a radical initiator so as to produce the stabilized polyphenylene ether resin of the present invention. A polyphenylene ether having such end groups (V) may be obtained by oxidative coupling polymerization or copolymerization of a phenol compound having at least one benzyl position hydrogen at an ortho-position of a hydroxyl group (i.e., a phenol compound including the above-mentioned structure (I)) in the presence of a catalyst containing a primary or secondary amine for example, U.S. Patent No. 4,788,277). Further, as specific examples of the unsaturated compound (VI), mention may be made of styrene, α-methylstyrene, chlorostyrene, methylstyrene, stilbene, cinnamic alcohol, benzal acetone, ethyl cinnamate, nitrile cinnamate, 4-vinylpyridine and 2-vinyl-3,5-diamino-(s)-triazine. In the present invention, it is possible to use a polymer of the above-mentioned vinyl aromatic hydrocarbons or a copolymer with the above-mentioned vinyl aromatic hydrocarbons and a copolymerizable vinyl compound (hereinafter, referred to as the component (c). As the copolymerizable monomer, use may be made of the above-mentioned vinyl compounds. The (co)polymer preferable as the component (c) may be a styrenic polymer such as polystyrene styrene-α-methylstyrene copolymer, acrylonitrile-styrene copolymer, styrene-ester methacrylate copolymer and styrene-anhydrous maleic acid copolymer. These may be used alone or in any mixture thereof. The (co)polymers are effective in further improving the surface strength and rigidity of the compositions. Further, in the present invention, it is possible to mix in a rubber-modified vinyl aromatic hydrocarbon polymer (hereinafter referred to as component (d)). The rubber-modified vinyl aromatic hydrocarbon polymer may be obtained by polymerization of the above-mentioned vinyl aromatic hydrocarbon or a mixture of a monomer copolymerizable therewith and an elastomer. As the method of polymerization, suspension polymerization, emulsion polymerization, mass polymerization and mass-suspension polymerization may be used. Examples of the monomers copolymerizable with the vinyl aromatic hydrocarbon, may be α-methylstyrene, acrylonitrile, acrylic acid ester, methacrylic acid ester, anhydrous maleic acid, and other of the above-mentioned vinyl compounds. Further, examples of the elastomers usable in the present invention may be natural rubber, synthetic isoprene rubber, butadiene rubber, styrene-butadiene rubber, high styrene rubber, polybutadiene rubber, chloroprene rubber, polybutene rubber, rubbery ethylene-propylene copolymers, rubbery butadiene-acrylonitrile copolymers, butyl rubber, various nitrile rubbers, rubbery ethylene-vinyl acetate copolymers, rubbery ethylene acrylic acid ester copolymers, rubbery atactic polypropylene resins, rubbery ethylene-acrylic acid ionomer and the like. These elastomers are dissolved in the monomer in general in an amount of 2 to 70 parts by weight, based on 100 parts by weight of the vinyl aromatic hydrocarbons or monomers copolymerizable with the same, more generally 3 to 50 parts by weight or are supplied to the mass polymerization, mass-suspension polymerization and emulsion polymerization in a latex form. Examples of the particularly preferable rubber modified polymers usable in the present invention may be impact resistant rubber-modified styrene polymers, acrylonitrile butadiene-styrene copolymers, acrylic acid ester-butadiene-styrene copolymers, methacrylic acid ester-butadiene styrene copolymers, impact resistant rubber modified styrene anhydrous maleic acid copolymers. These may be used alone or in any mixture thereof. In the present invention, the weight ratio of the mixture of the component (a) to the component (b) is 10 to 95% by weight of component (a), preferably 20 to 85% by weight, more preferably 30 to 80% by weight. When the component (a) is less than 10% by weight, the impact resistance and processability are inferior and when more than 95% by weight, the heat resistance and surface hardness are inferior, and thus, these weight percentages are not preferred. The particularly preferable weight ratio of mixture is 35 to 75% by weight of the component (a). In this range, the operation and effect of giving a composition having an impact resistance which is superior to the impact resistance strength of the component (a) and the component (b) alone, were found to be totally unexpected. Further, in the present invention, it is possible to mix in the above-mentioned component (c) in an amount of up to 500 parts by weight, preferably 3 to 400 parts by weight, more preferably 5 to 300 parts by weight, based on 100 parts by weight of the composition comprised of the component (a) and the component (b). The component (c) can be used to improve the processability.When the amount of the component (c) formulated is more than 500 parts by weight, the impact resistance and heat resistance fall, and thus this amount is not preferred. Further, in the present invention, it is possible to mix in the above-mentioned component (d), in an amount of up to 500 parts by weight, preferably 3 to 400 parts by weight, more preferably 5 to 300 parts by weight, with respect to 100 parts by weight of the composition comprised of the component (a) and the component (b), so as to improve the impact resistance. When the amount of the component (d) formulated is more than 500 parts by weight, the heat resistance falls, so that this is not preferred. Further, when desiring to obtain a composition with a good transparency, it is recommended that the amount of the component (d) formulated be 50 parts by weight or less, preferably 25 parts by weight or less. It is possible to formulate about 50 parts by weight or less, based on 100 parts of the components (a) and (b), of other thermoplastic resins or rubbery polymers into the thermoplastic polymer composition of the present invention. Examples of the thermoplastic resins, usable in he present invention may be polyethylene, copolymers of ethylene containing 50 percent or more ethylene, copolymers of this with other copolymerizable monomers, polypropylene, copolymers of propylene, containing 50 percent or more propylene, copolymers of this with other copolymerizable monomers, polybutene resins, polyvinyl chloride resins, polyvinyl acetate resins, their hydrolyzed products, polyacrylate resins, acrylonitrile resins, polyamide resins, polyester resins, polyphenylene sulfide resins, polyacetal resins, polycarbonate resins, polysulfone resins, thermoplastic polyurethane resins, polybutadiene resins, polyacrylate resins, fluorine resins, polyoxybenzoyl resins, polyimide resins, etc. Further, as the rubbery polymers, mention may be made of polybutadiene, polyisoprene, styrene-butadiene copolymers, butadiene-acrylonitrile copolymers, ethylene-propylene copolymers, ethylene-propylene copolymers, ethylene-propylene-diene copolymers, silicone rubber, epichlorohydrin rubber, acryl rubber, and ethylene-vinyl acetate copolymers. The thermoplastic polymer composition of the present invention may, optionally, include any conventional additives. The types of the additives are not particularly limited and may be any generally used for formulation with plastics. Examples of the additives may be glass fiber, glass beads, silica, calcium carbonate, talc, and other inorganic reinforcers, organic fibers, coumarone-indene resins, and other organic reinforcers, organic peroxides, inorganic peroxides, and other cross-linking agents, titanium white, carbon black, iron oxide, and other pigments, dyes, flame retardants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, other thickeners or mixtures of the same. The thermoplastic polymer composition of the present invention may be produced by any of the conventionally known methods. For example, use may be made of the melt kneading method using open rolls, intensive mixers, internal mixers, cokneaders, twin rotor equipped continuous kneaders, extruders, and other general mixers, the method of dissolving or dispersing and mixing the components in a solvent, then heating to remove the solvent. Examples of the components of data processing equipment according to the present invention are components of word processors, facsimiles, copiers, printers, typewriters, office computers, personal computers, minicomputers, and other data recording and processing equipment and also containers and/or container parts for holding audio and visual recording magnetic tape, IC's, and other data recording and processing media, magnetic cards, IC cards, and other data recording and processing cards. Typical examples of molded articles used as components for data equipment are as follows: examples of molded articles for components of word processors are the external housing, control panel, keytops, switches, lever holders, sensor holders, paper guides, plachire holders, sliders, chassises, viewing windows, sound covers, protective covers, and other covers. As the shaped articles used for components of facsimiles, mention may be made of external housings, switches and buttons, panels, chassises, spencer guides, receiver frames, transmitter frames, recording paper boxes, viewing windows, sound covers, protective covers, and other covers. As the shaped articles used for the components for copiers, mention may be made of top covers, front-back and right-left control covers, paper holding covers, internal covers, front covers, operating surface covers, sound covers, protective covers, and other covers, display panels, and buttons, control panels, flanges for photosensitive media, cleaner housings, containers and bottles for recovery of developers, boxes for developer, handles, attachment and release levers, toner box covers, lens housings, light shielding plates, mirror holding plates, static insulators, shields, paper containers, paper container covers, paper guides, copy receivers, chutes, frames. Examples of the molded articles used for printer components are upper and lower external housings, display panels, cassette housings, cassette covers, cassette guides, paper covers, paper guides, hammer covers, lock lever knobs, select levers, platen knobs, carriages, carriage bases, printer bodies, viewing windows, sound covers, protective covers, and other covers. Examples of the molded articles used for typewriter components are knob caps, knobs, platen gears, carriage stop pins, paper ball levers, flat cables, adjusting levers, paper guides, hammer covers, lock lever knobs, correction levers, tape guides, ribbon holding plates, wheel guides, ribbon motor frames, ribbon winding shafts, daisy protectors, carriage transfer devices, runfeed gears, hood housings, sound covers, protective covers, switch box covers, and other covers, brand badges, model badges, paper guides, indicators, top covers, sun covers, eraser tables, check connector covers, control panels, key tops, viewing windows. Example of the molded articles used for office computer components, mention may be made of covers for key component housings, printer covers, CRT covers, protective covers, and other covers, gate guide plates, louvers, KB cases, fans, and viewing windows. Examples of the molded articles used for components for personal computers and minicomputers are key component housing covers, CRT covers, memory device housing covers, protective covers, and other covers, keyboard cases, fans, terminal boards, floppy insertion ports, knobs, relays, holders, connectors, and viewing windows. Among the above-mentioned equipment components, the particularly suitable molded articles according to the present invention are sound covers, protective covers, and other covers, viewing windows, paper containers, paper container covers, paper receivers, guides, frames, magnetic tape containers, IC containers, and other molded articles for which transparency is required. As the methods for obtaining the molded articles of data equipment components of the present invention from the above-mentioned thermoplastic polymer compositions, any of the conventionally known mixing methods may be used, e.g., injection molding, extrusion, blow molding, calendering, lamination, vacuum molding, compressed air molding, foam molding, film making may be used. The thermoplastic polymer compositions of the present invention may be used for various applications making use of their superior transparency, impact resistance, surface hardness, heat resistance and gloss, and optionally clear or light color. The compositions of the present invention may be molded and processes by extrusion, injection molding, hollow molding, and the like to form sheets, films, foam, and other various shaped injection molded products, hollow molded products, press molded products and vacuum molded products. For use for food packaging, components for home electric appliances, auto parts, industrial products and toys. In particular, due to the little warping of the compositions of the present invention when injection molded, they are suited for injection molding of flat molded articles, molded articles with many flat portions, and large sized molded articles. EXAMPLES The present invention will now be further illustrated by, but is by no means limited to, the following Examples. Comparative Examples 1 to 8 A styrene-butadiene block copolymer with a polymer structure represented by the general formula A₁-B-A₂ was produced in cyclohexane using n-butyl lithium as a catalyst. In the manufacture of the block copolymer, the Mw/Mn was adjusted by changing the ratio of the amount of the styrene used for the portion A₁ and the amount of the styrene used for the portion A₂. The block ratio of the styrene was adjusted by changing the ratio simultaneously with the continuous supply to the polymerization vessel of the mixed monomer of styrene and butadiene as the monomer of the portion B. Further, the melt flow index (MI (G)) was adjusted by changing the amount of the n-butyl lithium. The resultant block copolymer was pelletized by the extruder, then melted and kneaded with polyphenylene ether and polystyrene in a twin screw extruder. After this, use was made of an IS-80A (142 g (5 oz) injection molding machine) made by Toshiba Kikai K.K. to injection mold the same at 250°C into a flat plate of a thickness of 3 mm. The physical properties of the resultant injection molded products are shown in Table 1. The warping was ranked as follows based on the differences in mold shrinkage rates: Up to 0.2% o ○ (Excellent) Over 0.2% and up to 0.4% o (Good) Over 0.4% and up to 0.6% ▵ (Fair) Over 0.6% x (Poor) Further, for the mold shrinkage rate in the direction perpendicular to the direction of flow, the mold shrinkage rate of the side opposite to the gate side was measured. Comparative Examples 9 to 13 The same method as in Comparative Example 1 was used to prepare a styrene-butadiene block copolymer with a polymer structure expressed by the general formula A₁-B-A₂. The same mixing with polyphenylene ether and polystyrene and molding were performed as in Example 1. The physical properties of the resultant injection molded articles are shown in Table 2. Comparative Examples 14 to 18 A block copolymer with a polymer structure expressed by the general formula B₁-A₁-B₂-A₂-A₁-B₁-A₂-B₂-A₃ and (A₁-B₁)₄X (wherein X indicates a residual group of SiCl₄) was prepared by the same method as in comparative Example 1. The mixing with polyphenylene ether and polystyrene and the molding were performed in the same way as Example 1 too. The physical properties of the resultant injection molded articles are shown in Table 3. Comparative Example 19 A 100 parts by weight amount of the block copolymer composition of Comparative Example 1, 3 parts by weight of antimony trioxide, 30 parts by weight of decabromotetralin, and 35 parts by weight of glass fiber were melted and kneaded together to prepare a test piece for measurement of physical properties. Reference Examples Compositions were prepared by replacing the polystyrene in the composition of Comparative Example 1 with styrene-methylmethacrylate copolymer, impact resistant rubber modified styrene copolymer (HIPS)(Polystyrene 475S manufactured by Asahi Kasei Kogyo), acrylonitrilebutadiene-styrene copolymer (ABS) (JSR-35 manufactured by Nihon Synthetic Rubber), and methyl methacrylate-butadiene-styrene copolymer (MBS) (Kane e su B-28 manufactured by Kanegafuchi Kagaku K.K.). The resultant compositions were all superior in impact resistance, surface hardness, and heat resistance. Examples 1 to 5 and Comparative Examples 20 and 21 The methods of Comparative Examples 1 to 5 and Examples 17 and 18 were used, respectively, except that a polyphenylene ether having a stabilized end group was used as the polyphenylene ether. The polyphenylene ether used was prepared by oxidative coupling polymerization of the starting polyphenylene ether with 2,6-xylenol in the presence of dibutyl amine according to the method disclosed in U.S. Patent No. 4788277. The viscosity of the resultant polyphenylene ether was 0.545 and the glass transition temperature was about 208°C. As a result of a ¹H nuclear magnetic resonance spectrum, it was confirmed that 0.32 of the end groups expressed by the formula were present, based on 100 of the main repeating units: Further, the amount of the free phenolic hydroxyl groups was confirmed to be 0.34 per 100 of the above-mentioned main repeating units. A 10 parts by weight amount of styrene were added to 100 parts by weight of the polyphenylene ether and the two blended homogeneously by a Henschel mixer. The mixture was then melted and kneaded by a twin screw extruder with a screw diameter of 30 mm (PCM-30 made by Ikegai Tekko K.K.) at a temperature of 300°C and passed through a water vessel for pelletization. The pellets thus obtained were analyzed by a ¹H nuclear magnetic resonance spectrum. As a result, it was confirmed from the 5.02 ppm signal area value that 0.25 of the end groups having the formula: were present, based on 100 of the main repeating units. Further, the amount of the free phenolic hydroxyl groups was confirmed to be 0.45 per 100 of the above-mentioned main repeating units. Further, the number average molecular weight determined by GPC was 24,500 and the viscosity was 0.547. The polyphenylene ether thus obtained (hereinafter, referred to as the polyphenylene ether resin A) the block copolymer, and conventional polystyrene were melted and kneaded in a twin screw extruder. Thereafter, use was made of an IS-80A (142 g (5 oz) injection molding machine) made by Toshiba Kikai to injection mold the same at 250°C into a flat plate of a thickness of 3 mm. The physical properties of the resultant injection molded products are shown in Table 5. The polyphenylene ether B in Table 5 does not have the stabilized end group. The block copolymer compositions having a stabilized end group gives molded articles which are superior in impact resistance, pencil hardness, and heat resistance and clear color. Comparative Example 21 The styrene-butadiene block copolymer with a polymer structure having the general formula A₁-B-A₂ was produced in cyclohexane using n-butyl lithium as a catalyst. Thereafter, the block copolymer was hydrogenated using the Ti hydrogenation catalyst disclosed in Japanese Unexamined Patent Publication (Kokai) No. 59-133203 (i.e., U.S. Patent No. 4501857) to prepare a hydrogenated block copolymer with about 99% hydrogenated ratio of the aliphatic double bonds of the butadiene portion. Next, the resultant hydrogenated block copolymer was melted and kneaded with polyphenylene ether and polystyrene in a twin screw extruder. The physical properties of the resultant composition are shown in Table 4. Block copolymer Example 11 Styrene content (wt%) 75 Block ratio of styrene (%) 90 Vinyl bond content of butadiene portion (%) 30 Polystyrene block M w/ M n 1.4 Hydrogenated block copolymer Hydrogenated ratio (%) 99 MI (G) (g/10 min) 10 Formulation ratio (parts by weight) Block copolymer 68 Polyphenylene ether 32 Polystyrene 14 Dart impact strength (kg-cm) 75 Pencil hardness F Haze (%) 3 Heat deformation temperature (°C) 90 Microcracking o Warping of molded article o Example 6 In Comparative Example 21 only the polyphenylene ether was replaced with a polyphenylene ether having a stabilizing end group. The physical properties of the resultant composition are shown in Table 6. As is clear from the results shown in Table 6, even when the hydrogenated block copolymer is used, the use of the polyphenylene ether having a stabilizing end group gives clear or light color to the resultant composition. Example 6 Comparative Example 21 Block copolymer before hydrogenation Styrene content (wt%) 75 75 Block ratio of styrene (%) 90 90 Content of vinyl bond of butadiene portion (%) 30 30 M w/ M n of polystyrene block 1.4 1.4 Block copolymer after hydrogenation Hydrogenated ratio (%) 99 99 MI (G) (g/10 min) 10 10 Formulation ratio (wt.parts) Block copolymer 68 68 Polyphenylene ether (A) 32 (B) 32 Polystyrene 14 14 Dart impact strength (kg-cm) 77 75 Pencil hardness F F Haze (%) 3 3 Heat deformation temperature (°C) 90 90 Microcracking o o Warping of molded article o o Lightness *L 82 65 Examples 7 to 11 and Comparative Examples 22 to 30 In Comparative Example 1, the polystyrene used as the component (C) was removed from the polymer composition and the polymer composition shown in Table 7 was prepared in the same manner as in Comparative Example 1. The polyphenylene ethers A and B used are the same as those used in the Examples 1 to 5 and Comparative Examples 20 and 21. The resultant polymer compositions were injection molded and the physical properties were evaluated. The results are shown in Table 7. As is clear from the results shown in Table 7, the present polymer compositions composed of the two components, i.e., the block copolymer (a) and the polyphenylene ether (b) exhibited the excellent transparency, impact strength, heat resistance, and surface hardness. Furthermore, when the polyphenylene ether having a stabilizing end group, the resultant composition is excellent in the lightness in color.

Claims: A thermoplastic polymer composition comprising : (a) 10 to 95 % by weight of a block copolymer which comprises at least two polymer segments comprising mainly a vinyl aromatic hydrocarbon and at least one polymer segment comprising mainly a conjugated diene, in which block copolymer: (i) the content of the vinyl aromatic hydrocarbon is more than 60% by weight and not more than 95% by weight; (ii) the ratio of the vinyl aromatic hydrocarbon present, as a vinyl aromatic hydrocarbon polymer block, in the block copolymer to the total vinyl aromatic hydrocarbons contained in the block copolymer is more than 75% by weight and up to 98% by weight; and (iii) the ratio of the weight average molecular weight to the number average molecular weight of the vinyl aromatic hydrocarbon polymer block in the block copolymer is 1.2 to 2.0 and (b) 5 to 90% by weight of polyphenylene ether having a stabilizing end group. A thermoplastic polymer composition as claimed in claim 1, wherein said stabilizing end group has the following structure (IV) : wherein R₁ to R₅ are independently hydrogen, an alkyl group, substituted alkyl group, a halogen group, an aryl group, or a substituted aryl group, R₆ to R₉ are independently hydrogen, an alkyl group, substituted alkyl group, alkenyl group, substituted alkenyl group, halogen group, aryl group, substituted aryl group, alkoxyl group, N-lactam group, carboxylic acid group, carboxylic acid anhydride group, carboxylic acid ester group, carboxylic acid amide group, nitrile group, acyloxyl group, or acyl group, provided that R₆ and R₇, R₈ and R₉ may be independently bonded to form spirocyclic structure rings and an average number of the end group is 0.01 or more, based on 100 phenylene ether units. A thermoplastic polymer composition as claimed in claim 1 or 2, wherein the average molecular weight of the polyphenylene ether is 10,000 to 30,000 and the average number of the end group based on 100 phenylene ether units is 0.15 or more. A thermoplastic polymer composition as claimed in claim 1 to 3, wherein the content of the vinyl aromatic hydrocarbon in the block copolymer (a) is 65 to 90% by weight and the ratio of the vinyl aromatic hydrocarbons present, as a vinyl aromatic hydrocarbon polymer block, in the block copolymer to the total vinyl aromatic hydrocarbon present in the block copolymer (a) is 77 to 96% by weight. A thermoplastic polymer composition as claimed in claim 1 to 4, wherein the ratio of the weight average molecular weight to the number average molecular weight of the vinyl aromatic hydrocarbon polymer block in the copolymer is 1.3 to 1.8. A thermoplastic polymer composition as claimed in claim 1 to 5, wherein the block copolymer (a) has a glass transition temperature of the polymer segment comprising mainly vinyl aromatic hydrocarbon of 65 to 98°C. A thermoplastic polymer composition as claimed in any one of claims 1 to 6, wherein the vinyl aromatic hydrocarbon is at least one compound selected from the group consisting of styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, and vinyl anthracene. A thermoplastic polymer composition as claimed in any one of claims 1 to 7, wherein the conjugated diene is at least one compound selected from the group consisting of 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. A thermoplastic polymer composition as claimed in any one of claims 1 to 8, wherein said polyphenylene ether is at least one polymer selected from the group consisting of: a homopolymer of the repeating unit (I); wherein, at least one of R₁ and R₂ is a linear chain or a primary or secondary branch chain C₁ - C₄ alkyl group, aryl group , halogen atom, or hydrogen atom, and R₁ and R₂ may be the same or different; a copolymer comprised of the repeating unit (I) and the repeating unit (II) wherein R₃, R₄, R₅, and R₆ may be the same or mutally different and represent each a linear chain or a primary or secondary branched chain C₁ - C₄ alkyl group, aryl group , halogen atom, hydrogen atom, except that R₃ and R₄ are never simultaneously hydrogen atoms; and a graft copolymer formed by graft polymerization of styrene with the homopolymer or copolymer. A thermoplastic polymer composition as claimed in any one of claims 1 to 9, further comprising 3 to 400 parts by weight, based on 100 parts by weight of the total weight of said components (a) and (b), of a styrenic polymer (c). A thermoplastic polymer composition as claimed in claim 10, wherein said styrenic polymer is at least one polymer selected from the group consisting of polystyrenes, styrene-α-methyl styrene copolymers, acrylonitrile-styrene copolymers, styrene-methacrylic acid ester copolymers, and styrene-maleic anhydride copolymers. A thermoplastic polymer composition as claimed in any one of claims 1 to 11, wherein 3% or more of the aliphatic double bond derived from the conjugated diene is hydrogenated in said block copolymer. A molded article for a component of a data processing equipment comprised of the thermoplastic polymer composition according to any one of claims 1 to 12.

Inventors: HATTORI YASUO, HOSHI SUSUMU, NAGANO HARUHISA, SHIRAKI TOSHINORI, HATTORI, YASUO, HOSHI, SUSUMU, NAGANO, HARUHISA, SHIRAKI, TOSHINORI
Applicants: ASAHI CHEMICAL IND, ASAHI KASEI KOGYO KABUSHIKI KAISHA
Application year: 1989
Main classification: C08L53
IPC codes: C08L53, C08L71