A modified block copolymer

Abstract: A modified block copolymer comprising a radial base block copolymer of at least two monovinyl substituted aromatic hydrocarbon polymer blocks (A) and at least one olefin compound polymer block (B) composed mainly of a conjugated diene compound which polymer block (B) has its conjugated diene compound moiety hydrogenated to have an ethylenic unsaturation degree not exceeding 20 %, said radial base block copolymer having a monovinyl substituted aromatic hydrocarbon content of 5 to 95 % by weight, said conjugated diene compound moiety of said polymer block (B) having a vinyl content of 25 to 65 % in terms of the vinyl content prior to the hydrogenation of said conjugated diene compound moiety; and at least one molecular unit grafted to said radial base block copolymer, said molecular unit containing at least one member selected from a dicarboxylic acid group and groups derived therefrom.

Description: The present invention relates to a modified block copolymer having excellent properties, particularly with respect to the impact resistance, adhesion, paint adhesion, weatherability, resistance to heat aging, transparency and gloss and heat resistance, abrasion resistance, compression set resistance, adhesion, transparency, oil resistance, weatherability and resistance to heat aging. Recently, thermoplastic resins such as polyamides, thermoplastic polyesters, thermoplastic polyurethanes, polyoxymethylene resins, polycarbonate resins, polysulfone resins, nitrile resins, polyphenylene ether resins and polyarylene sulfide resins have been widely used for mechanical parts and electrical parts for which excellent mechanical characteristics, high heat resistance and good durability are required. Weight reduction of the body of an automobile has been promoted to decrease fuel expenses as one of the energy-saving measures, and thermoplastic resins have attracted attentions as light-weight materials for automobile parts which have excellent mechanical characteristics and durability. However, these thermoplastic resins have some defects and fail to sufficiently satisfy requirements demanded in their application fields. For example, polyoxymethylene resins and nitrile resins are advantageous in that they have very high tensile strength, flexural strength and flexural modulus, they can provide very tough molded articles and they are excellent in solvent resistance, but these resins are inferior in paint adhesion and they cannot advantageously be used as automotive exterior and interior trims or as exterior decorative materials of household electrical appliances. Polycarbonate resins have a very high mechanical strength and their impact strength is very high, but these resins are defective in that the paint adhesion is relatively poor. Furthermore, polyamides, thermoplastic polyesters, polysulfone resins, polyphenylene ether resins and polyarylene sulfide resins have a good heat resistance and a high mechanical strength, but they are defective in that the impact resistance is poor. Block copolymers comprising a monovinyl substituted aromatic hydrocarbon and a conjugated diene compound, especially styrene-butadiene block copolymers, are polymeric materials which have recently attracted attention . Characteristic properties of these block copolymers differ according to the content of the monovinyl substituted aromatic hydrocarbon. More specifically, a block copolymer having a relatively low content of the monovinyl substituted aromatic hydrocarbon, even though it is unvulcanized, has a good elasticity at room temperature and shows rubbery characteristics. On the other hand, a block copolymer having a relatively high content of the monovinyl substituted aromatic hydrocarbon is excellent in transparency and impact resistance and shows resinous characteristics. Moreover, a block copolymer comprising a monovinyl substituted aromatic hydrocarbon and a conjugated diene compound shows at high temperatures flow characteristics similar to those of a thermoplastic resin, and this block copolymer is advantageous in that the block copolymer can easily be molded by an ordinary extruder or injection molding machine. However, the above-mentioned block copolymers are fatally defective in that the weatherability and resistance to thermal deterioration are poor, and therefore, they have been used in the fields where such properties are not required. Furthermore, shoes prepared from these block copolymers are inferior to clogs prepared from a vinyl chloride polymer or the like in abrasion resistance and resistance to compression set. Accordingly, improvements of characteristics for over-coming these disadvantages have been desired. In order to improve the weatherability and resistance to heat aging of the above-mentioned block copolymers, hydrogenating the conjugated diene compound polymer block in the block copolymers have been proposed in Canadian Patent No. 815,575 and U.S. Patent No. 3,431,323. Although the weatherability or resistance to heat aging is improved to some extent according to this method, the hydrogenated block copolymer is defective in that the adhesion to other materials such as other plastics, metals, glass and woven fabrics is drastically degraded. As means for eliminating this defect, U.S. Patent No. 3,792,124 discloses a method in which an ionically crosslinked product comprising ethylene and an α,β-ethylenically unsaturated carboxylic acid is incorporated into the hydrogenated block copolymer. However a composition prepared by the method desclosed in U.S. Patent No. 3,792,124 does not have an satisfactorily improved adhesion to other materials, and the composition is defective in that peeling is readily caused in the bonded surface under high humidity conditions or when immersed in water. As is apparent from the foregoing description, although block copolymers comprising a monovinyl substituted aromatic hydrocarbon and a conjugated diene compound have various excellent properties, they cannot be materials sufficiently satisfying requirements demanded in the fields where they are actually used. It is therefore the object of the present invention to provide a rubbery or leather-like modified block copolymer which is excellent in heat resistance, abrasion resistance, resistance to compression set, adhesion, weatherability, resistance to heat aging, transparency and oil resistance and which may be used as an additive to a thermoplastic polymer. DISCLOSURE OF THE PRESENT INVENTION The present inventors have made extensive and intensive researches on polymer compositions comprising different polymers with a view to improving the compatibility between the different polymers and developing excellent polymer compositions retaining characteristics of the respective polymers. As a result, the present inventors have found that a modified block copolymer comprising a base block copolymer having at least two monovinyl substituted aromatic hydrocarbon polymer blocks and at least one olefin compound polymer block having an ethylenic unsaturation degree not exceeding 20 % and at least one molecular unit containing a dicarboxylic acid group and/or a group derived therefrom, which is grafted to said base block copolymer, has a good compatibility with thermoplastic polymers such as polar group-containing polar thermoplastic polymers, polyoxymethylenes, or polycarbonates and that a modified block copolymer composition comprising this modified block copolymer and a thermoplastic polymer is excellent over conventional compositions in mechanical characteristics and has very excellent weatherability and resistance to heat aging. The present invention has been made based on such novel findings. More specifically, in accordance with the present invention, there is provided a modified block copolymer comprising a radial base block copolymer of at least two monovinyl substituted aromatic hydrocarbon polymer blocks (A) and at least one olefin compound polymer block (B) composed mainly of a conjugated diene compound which polymer block (B) has its conjugated diene compound moiety hydrogenated to have an ethylenic unsaturation degree not exceeding 20 %, said radial base block copolymer having a monovinyl substituted aromatic hydrocarbon content of 5 to 95 % by weight, said conjugated diene compound moiety of said polymer block (B) having a vinyl content of 25 to 65 % in terms of the vinyl content prior to the hydrogenation of said conjugated diene compound moiety; and at least one molecular unit grafted to said radial base block copolymer, said molecular unit containing at least one member selected from a dicarboxylic acid group and groups derived therefrom. The olefin compound polymer block is preferably a polymer block in which at least one olefin compound selected from mono-olefins such as ethylene, propylene, 1-butene and isobutylene, conjugated diolefins such as butadiene, isoprene and 1,3-pentadiene and non-conjugated diolefins such as 1,4-hexadiene, norbornene and norbornene derivatives is homopolymerized or copolymerized, and the ethylenic unsaturation degree of this block does not exceed 20%. The term "ethylenic unsaturation degree" as used herein is intended to mean the percent of the number of the monomer units having an unsaturated bond relative to the number of all the monomer units constituting the olefin compound polymer block. Accordinly, the term "ethylenic unsaturation degree not exceeding 20%" as used herein is intended to mean that the percent of the number of the monomer units having an unsaturated bond relative to the number of all the monomer units constituting the olefin compound polymer block does not exceed 20%. It is preferred that the ethylenic unsaturation degree of the olefin compound polymer block be not more than 15%. If the olefin compound polymer block has an ethylenic unsaturation degree exceeding 20%, the weatherability and resistance to thermal deterioration of a composition obtained with this block copolymer are degraded, and no good results can be obtained. Accordingly, if a diolefin such as mentioned above is used as the constituent monomer of the olefin compound polymer block, it is necessary that the ethylenic unsaturation degree should be reduced by hydrogenation or the like to such an extent that the ethylenic unsaturation degree of the olefin compound polymer block does not exceed 20%, preferably not more than 15%. A monovinyl substituted aromatic hydrocarbon may be random-copolymerized to the olefin compound polymer block. As the base block copolymer, there may be mentioned a hydrogenation product of a block copolymer of a monovinyl substituted aromatic hydrocarbon and a conjugated diene compound, and a block copolymer of a monovinyl substituted aromatic hydrocarbon and a mono-olefin. The modified block copolymer according to the present invention is one prepared by addition-reacting the above-mentioned base block copolymer with at least one modifier selected from unsaturated dicarboxylic acids and derivatives thereof. The modified block copolymer of the present invention which is most preferred is a modified block copolymer obtained by selectively hydrogenating a block copolymer (hereinafter referred to as "precursory block copolymer") comprising at least two monovinyl substituted aromatic hydrocarbon polymer blocks and at least one polymer block composed mainly of a conjugated diene compound. In the polymer block composed mainly of a conjugated diene compound, it is preferred that the monovinyl substituted aromatic hydrocarbon/conjugated diene compound weight ratio be in the range of from 0/100 to 50/50, particularly from 0/100 to 30/70. In the case where the conjugated diene compound is copolymerized with the monovinyl substituted aromatic hydrocarbon in this polymer block, the distribution of the monovinyl substituted aromatic hydrocarbon may be a random distribution, a tapering distribution (the monomer content increases or decreases along the molecule chain), a partial block form distribution or any combination thereof. In the precursory block copolymer of the present invention, a portion of a copolymer of the monovinyl substituted aromatic hydrocarbon and the conjugated diene compound having a monovinyl substituted aromatic hydrocarbon content higher than 50% by weight may be present in the transitional portion between the monovinyl substituted aromatic hydrocarbon polymer block and the polymer block composed mainly of the conjugated diene compound. In the present invention, this copolymer portion is included in the polymer block composed mainly of the conjugated diene compound. In the precursory block copolymer, the monovinyl substituted aromatic hydrocarbon content is 5 to 95% by weight, preferably 10 to 90% by weight, more preferably 15 to 85% by weight. When the monovinyl substituted aromatic hydrocarbon content is not more than 60% by weight, preferably not more than 55% by weight, the precursory block copolymer has characteristics as a thermoplastic elastomer, and when the monovinyl substituted aromatic hydrocarbon content is more than 60%, preferably more than 70%, the precursory block copolymer has characteristics as a resinous polymer. At least one member selected from styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, dimethylstyrene and p-tert-butylstyrene is preferably used as the monovinyl substituted aromatic hydrocarbon constituting the precursory block copolymer, and styrene is particularly preferred. At least one member selected from butadiene, isoprene and 1,3-pentadiene is preferably used as the conjugated diene compound, and butadiene and/or isoprene is particularly preferred. The number average molecular weight of the precursory block copolymer is 20,000 to 500,000, preferably 40,000 to 300,000. It is preferred that the ratio of the weight average molecular weight relative to the number average molecular weight be in the range of from 1.05 to 10. The weight average molecular weight can be measured by the ultra-centrifugal method and the number average molecular weight can be measured by the osmotic pressure method. In the precursory polymer block, it is preferred that the vinyl content of the conjugated diene portion be 25 to 65%, particularly 35 to 55%. This modified block copolymer shows rubbery elasticity. The vinyl content of the precursory block copolymer can be measured by means of a nuclear magnetic resonance apparatus. In the precursory block copolymer the at least two monovinyl substituted aromatic hydrocarbon polymer blocks may have the same structure, or they may be different in monomer content, monomer distribution in the molecule chain, molecular weight of the block and linking manner of the conjugated diene portion. As the method for preparing the precursory block copolymer, there may be mentioned methods disclosed in British Patent No. 895 980, British Patent No. 1 130 770, U.S. Patent No. 3 281 383, Japanese Patent Application Publication No. 2423/1973 and U.S. Patent No. 3 639 517. According to each of these methods, the monovinyl substituted aromatic hydrocarbon is block-copolymerized with the conjugated diene compound in a hydrocarbon solvent using as an anion polymerization initiator an organic lithium compound or the like and if necessary using as a vinyl modifier an ether compound such as diethyl ether or tetrahydrofuran, a tertiary amine such as triethyl amine or N,N,N',N'-tetramethylethylene diamine or a Lewis base such as a phosphine compound, e.g., hexamethylphosphamide, and as a coupling agent a polyfunctional compound such as silicon tetrachloride or epoxidized soy bean oil. A block copolymer having a branched or radial structure can be obtained. In the present invention, a block copolymer prepared according to any of the foregoing polymerization methods can be used. Not only one precursory block copolymer but also a mixture of two or more precursory block copolymers may be used. The base block copolymer can be obtained by hydrogenating the above-mentioned precursory block copolymer according to a known method, for example, the method disclosed in British Patent No. 1,020,720. It is requisite that at least 80%, preferably at least 85%, of the monomer units having an aliphatic double bond in the polymer block composed mainly of the conjugated diene compound in the precursory block copolymer should be hydrogenated. In other words, it is requisite that the ethylenic unsaturation degree of the olefin compound polymer block 3 formed by conversion of the polymer block composed mainly of the conjugated diene compound by hydrogenation should not exceed 20%, preferably not exceed 15%. As pointed out hereinbefore, if the ethylenic unsaturation degree of the olefin compound polymer block exceeds 20%, the weatherability or resistance to thermal deterioration of a composition obtained therefrom is degraded and no good results can be obtained. From the standpoint of mechanical characteristics, it is preferred that the degree of hydrogenation of the monomer units containing aromatic double bonds derived from the monovinyl substituted aromatic hydrocarbon in the monovinyl substituted aromatic hydrocarbon polymer block and the monovinyl substituted aromatic hydrocarbon copolymerized according to need to the polymer block composed mainly of the conjugated diene compound be not more than 20%. The ethylenic unsaturation degree of the olefin compound polymer block can be measured by instrumental analysis using an infrared spectrophotometer (IR) or a nuclear magnetic resonance apparatus (NMR) or by titration analysis such as iodine titration. The base block copolymer is then modified by addition reaction with at least one modifier selected from unsaturated dicarboxylic acids and derivatives thereof, whereby a modified block copolymer is obtained. As the unsaturated dicarboxylic acid or its derivative which is used as the modifier, there may be mentioned, or example, maleic acid, maleic anhydride, maleic acid esters, maleic acid amides, maleic acid imides, fumaric acid, fumaric-acid esters, fumaric acid amides, fumaric acid imides, itaconic acid, itaconic anhydride, itaconic acid esters, itaconic acid amides, itaconic acid imides, halogenated maleic acid, halogenated maleic anhydride, halogenated maleic acid esters, halogenated maleic acid amides, halogenated maleic acid imides, cis-4-cyclohexene-1,2-dicarboxylic acid, cis-4-cyclohexene-1,2-dicarboxylic anhydride, cis-4-cyclohexene-1,2-dicarboxylic acid esters, cis-4-cyclohexene-1,2-dicarboxylic acid amides, cis-4-cyclohexene-1,2-dicarboxylic acid imides, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic anhydride, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid esters, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid amide, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid imide. These modifiers may be used alone or in combination thereof. Among these modifiers maleic anhydride is particularly preferred. The modified block copolymer is obtained by grafting the above-mentioned modifier onto the base block polymer in a solution state or molten state in the presence or absence of a radical initiator. The method for preparing the modified block copolymer is not particularly critical in the present invention. However, a method providing a modified block copolymer containing an undesirable component such as gel or a modified block copolymer having an extremely high melt viscosity and degrading the processability of the composition is not preferred. For example, there is preferably adopted a method in which the base block copolymer is reacted with the above-mentioned modifier in the presence of a radical initiator in, for example, an extruder. The amount of the molecular unit containing a carboxylic acid group or a group derived therefrom, which is contained in the modified block copolymer, that is, the amount of the unsaturated dicarboxylic acid or its derivative grafted onto the base block copolymer, is 0.05 to 30 parts by weight, preferably 0.1 to 20 parts by weight, more preferably 0.3 to 10 parts by weight, per 100 parts by weight of the base block copolymer, as the mean value in the entire modified block copolymer used in the present invention. When this amount of the molecular unit containing a carboxylic acid group or a group derived therefrom is smaller than 0.05 part by weight, no significant modification effect can be obtained over the unmodified block copolymer, and even if this amount exceeds 30 parts by weight, no substantial increase of the modification effect can be attained. The content of the molecular unit containing a dicarboxylic acid group or a group derived therefrom in the modified block copolymer can be easily determined by infrared spectrophotometry or titration. In the present invention, the modified block copolymer may be an ionically crosslinked modified block copolymer. This ionically crosslinked modified block copolymer is obtained by crosslinking the above-mentioned modified block copolymer through at least one member selected from monovalent, divalent and trivalent metal ions. Namely, the crosslinked modified block copolymer is prepared by reacting the modified block copolymer with at least one crosslinking agent selected from monovalent, divalent and trivalent metal compounds. In the ionically crosslinked modified block copolymer, the carboxylic acid group and/or the group derived therefrom of the modified block copolymer is ionized by addition of the above-mentioned crosslinking agent. The degree of ionization can be adjusted according to the amount of the crosslinking compound employed, and the degree of ionization can be determined by, for example, an infrared spectrophotometer. The crosslinking agent is added in such an amount that a carboxylic acid group and/or a group derived therefrom, which is contained in the modified block copolymer, is partially or completely ionized. The ionization reaction is advanced substantially quantitatively, but in some case, in order to obtain the desirable degree of ionization, it is necessary to add the crosslinking agent in excess of the stoichiometrical amount. In order to obtain the ionically crosslinked modified block copolymer effectively, it is preferred that the ratio of the mole number of the metal compound relative to the total mole number of the carboxylic acid group and the group derived therefrom, contained in the modified block copolymer be in the range of from 0.1 to 3.0. At least one member selected from compounds of metals of the Groups I, II and III of the Periodic Table is preferably used as the crosslinking agent to be added to the modified block copolymer for formation of the ionically crosslinked modified block copolymer. More specifically at least one member selected from lithium compounds, sodium compounds, potassium compounds, magnesium compounds, calcium compounds, zinc compounds and aluminum compounds is preferably used. It is preferred that these compounds are hydroxides, alcoholates or carboxylic acid salts. As the method for obtaining the ionically crosslinked modified block copolymer, there may be mentioned a method in which the crosslinking agent is added to the melt of the modified block copolymer, a method in which the modified block copolymer is dissolved in an appropriate solvent, for example, an organic solvent such as toluene, benzene or tetrahydrofuran and the crosslinking agent is added to the solution to effect the crosslinking reaction, and a method in which the crosslinking agent is added to a latex of the modified block copolymer. Any of these methods can be used for formation of the ionically crosslinked modified block copolymer to be used in the present invention. The ionically crosslinked modified block copolymer which is used in the present invention is thermoplastic, and processable at high temperatures, and the ionic crosslinkage is a reversible crosslinkage. These characteristic properties are not possessed by block copolymers obtained through irreversible crosslinkage such as sulfur crosslinkage, peroxide crosslinkage or irradiation crosslinkage. From the standpoint of mechanical characteristics it is preferred that the monovinyl substituted aromatic hydrocarbon content of the base block copolymer of the modified block copolymer composition of the present invention be 5 to 95 % by weight. When the modified block copolymer is required to have a rubber elasticity, it is preferred that the monovinyl substituted aromatic hydrocarbon content of the base block copolymer be 5 to 60 % by weight. On the other hand, when the modified block copolymer is required to have resinous characteristics, it is preferred that the monovinyl substituted aromatic hydrocarbon content of the base block copolymer is over 60 % by weight up to 95 % inclusive by weight. As pointed out hereinbefore, the modified block copolymer of the present invention can be used to produce a resinous composition, a rubbery composition or a leather-like composition according to the ratio of the thermoplastic polymer contained in the composition. The modified block copolymer of the present invention may be blended with a polar thermoplastic polymer containing at least one polar functional group, with polyoxy methylene, polycarbonates, modified polycarbonates, polysulfone, modified polysulfone, nitrile polymers, polyphenylene ethers, modified polyphenylene ethers, polyarylene sulfides and modified polyarylene sulfides in order to improve the properties of the obtained copolymer composition. Reinforcers, fillers, antioxidants, ultraviolet absorbers, coloring agents, pigments, lubricants, flame retardents, foaming agents and other additives may be added to this modified block copolymer composition. Specific examples of the additives which can be added to the composition are described in "Handbood of Additive Chemicals to Rubbers and Plastics" published by Rubber Digest Co., Ltd., Japan in 1974. The modified block copolymer of the present invention may be added to the above defined polymers by mixing the components by means of a mixing device appropriately selected according to the mixing ratio of the components from various mixing devices such as a single screw extruder, a multiple screw extruder, a mixing roll, a Banbury mixer and a kneader. It is preferred that the mixing be carried out in the molten state. Moreover, the blending can be performed according to a method in which the respective components are dissolved in an organic solvent such as toluene, benzene or tetrahydrofuran and the solvent is removed from the resulting mixture by heating. PREFERRED EMBODIMENTS OF THE INVENTION The present invention will now be described in more detail with reference to the following Examples. In the Examples, the number average molecular weights of polymers were determined according to the osmotic pressure method and the weight average molecular weights were determined according to the ultra-centrifugal method. Furthermore, the melt index values referred to in the Examples are those determined according to the method of ASTM D-1238. (1) Preparation of Unmodified Block Copolymers: Unmodified block copolymers shown in Table 1 were prepared by subjecting butadiene and styrene to anionic block copolymerization in n-hexane or cyclohexane as a solvent by using n-butyl lithium as a polymerization catalyst and tetrahydrofuran as a vinyl content adjusting agent. For example, an unmodified block copolymer A-1 was prepared by performing polymerization according to the following procedures. To an n-hexane solution containing 13 parts by weight of butadiene (butadiene concentration, 20% by weight) were added 0.1 part by weight of n-butyl lithium and 5 parts by weight of tetrahydrofuran, and polymerization was carried out at about 60°C for 1 hour. After substantial completion of the polymerization of butadiene, an n-hexane solution containing 20 parts by weight of styrene (styrene concentration, 20% by weight) was added to the resulting reaction mixture and polymerization was carried out at about 60°C for 1 hour. After substantial completion of the polymerization of styrene, an n-hexane solution containing 47 parts by weight of butadiene ( butadiene concentration, 20% by weight) was added to the resulting reaction mixture and polymerization was carried out at about 60°C for 1 hour. After substantial completion of the polymerization of butadiene, an n-hexane solution containing 20 parts by weight of styrene (styrene concentration, 20% by weight) was added to the resulting reaction mixture and polymerization was carried out at about 60°C for 1 hour to obtain the unmodified block copolymer A-1. When unmodified block copolymers A-4 and A-5 were prepared, silicon tetrachloride was used as a coupling agent. 2,6-Di-tert-butyl-4-methylphenol (hereinafter often referred to as "BHT") was added as a stabilizer to each of the unmodified block copolymers shown in Table 1. magnetic resonance apparatus. (2) Preparation of Hydrogenated Block Copolymers: The unmodified block copolymer shown in Table 1 was put in an n-hexane/cyclohexane mixed solvent or a cyclohexane solvent, and hydrogenation was carried out at 50°C under a hydrogen pressure of 7 Kg/cm² for 5 hours using cobalt naphthenate and triethyl aluminum as catalysts, whereby there was obtained a selectively hydrogenated block copolymer in which about 90% of double bonds of the butadiene block were hydrogenated but benzene rings of the styrene block were scarcely hydrogenated. The metals of the catalyst residue were removed by washing with an aqueous solution of hydrochloric acid and methanol. The hydrogenated block copolymers obtained by thus hydrogenating the unmodified block copolymers A-1 through A-6 shown in Table 1 are designated as hydrogenated block copolymers B-1 through B-6, respectively. (3) Preparation of Modified Hydrogenated Block Copolymers: To 100 parts by weight of the so-obtained hydrogenated block copolymer was added 1 to 5 parts by weight of maleic anhydride so that a desired amount of maleic anhydride as added to the hydrogenated block copolymer, and 0.1 part by weight of Perhexa 25B [the trade name of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane manufactured and sold by Nippon Yushi K.K., Japan] was added to the mixture, and the mixture was homogeneously blended and supplied to a single screw extruder having a diameter of 20 mm [length/diameter ratio (hereinafter often referred to as "L/D") = 24]. The maleinization reaction was carried out at a cylinder temperature of 250°C to prepare a modified copolymer. Unreacted maleic anhydride was removed from the modified hydrogenated block copolymer by heating under reduced pressure, and BHT was added as a stabilizer in an amount of 0.5 part by weight per 100 parts by weight of the modified copolymer. Thus, modified hydrogenated block copolymers shown in Table 2 were prepared. The analysis values of the obtained modified hydrogenated block copolymer are shown in Table 2. The modified hydrogenated block copolymers obtained by hydrogenating and modifying the unmodified block copolymers A-1, A-2, A-4, A-5 and A-6 shown in Table 1 are designated as modified hydrogenated block copolymers C-1, C-2, C-5, C-6 and C-7, respectively. The modified hydrogenated block copolymers obtained by hydrogenating the unmodified block copolymer A-3 and modifying the hydrogenated block copolymer so that the amounts of maleic anhydride grafted onto the hydrogenated block copolymer were 1.2% by weight and 0.7% by weight are designated as modified hydrogenated block copolymers C-3 and C-4, respectively. (4) Preparation of Modified Unhydrogenated Block Copolymers: Modified unhydrogenated block copolymers D-1, D-2, and D-3 were prepared by grafting maleic anhydride onto the unmodified block copolymers A-2, A-3 and A-3 according to the following procedures. To 100 parts by weight of the unmodified block copolymer was added 2 to 5 parts by weight of maleic anhydride so that a desired amount of maleic anhydride was grafted onto the unmodified block copolymer, and 0.3 part by weight of BHT and 0.2 part by weight of phenothiazine were added to the mixture. The mixture was homogeneously blended using a mixer. The mixture was supplied to a single extruder having a diameter of 20 mm (L/D = 24) and the maleinization reaction was carried out at a cylinder temperature of 250°C to prepare a modified copolymer. Unreacted maleic anhydride was removed from the obtained modified copolymer by drying under reduced pressure. Then, 0.5 part by weight of BHT was added to 100 parts by weight of the modified copolymer. Thus, modified unhydrogenated block copolymers shown in Table 3 were prepared. The analysis values of the obtained modified unhydrogenated polymers are shown in Table 3. Modified Unhydrogenated Block Copolymer Polymer before Modification Amount of Maleic Anhydride Grafted onto Unmodified Block Copolymer (% by weight) D-1 A-2 1.8 D-2 A-3 0.7 D-3 A-5 1.2 (5) Preparation of Ionically Crosslinked Modified Block Copolymer: Ionically crosslinked modified block copolymers E-1 through E-4 were obtained according to a recipe shown in Table 4. When the ionic crosslinking was carried out in a solvent, the solvent was removed by heating after the crosslinking reaction. By the infrared spectrum, it was confirmed that the acid anhydride groups in the samples E-1 through E-4 were ionized. In the following examples which show the use of the modified block copolymers of the present invention as a blending component in the production of a polymer composition are described in more detail. In these examples the modified block copolymers according to the invention are indicated as component (b) and the other polymers as component (a). Examples 1 and 2 and Comparative Examples 1 and 2 A resinous composition was obtained by mixing 80 parts by weight of nylon 6 (number average molecular weight: 18,000) as the polar thermoplastic polymer with 20 parts by weight of the modified hydrogenated block copolymer C-1 shown in Table 2 by means of a screw type extruder having a diameter of 30 mm (twin, L/D = 28). Another resinous composition was obtained in the same manner as described above except that the modified block copolymer C-2 was used instead of the modified hydrogenated block copolymer C-1. For comparison, a comparative resinous composition was obtained in the same manner as described above except that the unmodified block copolymer A-1 shown in Table 1 was used instead of the modified hydrogenated block copolymer C-1 or C-2. Another comparative resinous composition was obtained in the same manner as described above except that the unmodified block copolymer A-3 was used instead of the modified hydrogenated copolymer C-1 or C-2 or the unmodified block copolymer A-1. Test pieces were prepared of the so-obtained resinous compositions by injection molding, and the physical properties of the test pieces were measured. The obtained results are shown in Table 5. As will be readily understood from the results shown in Table 5, the compositions obtained with the modified block copolymers of the present invention are excellent in compatibility and have a highly improved impact resistance over the comparative compositions. Example 3 and Comparative Example 3 A rubbery composition was obtained by kneading 30 parts by weight of nylon 6 (number average molecular weight : 18,000) as a polar thermoplastic polymer with 70 parts by weight of the modified hydrogenated block copolymer C-1 shown in Table 2 for 10 minutes by means of a Brabender Plastograph. Test pieces were prepared of the obtained composition by compression molding, and the physical properties were determined. For comparison, a comparative rubbery composition was obtained in the same manner as described above except that the unmodified block copolymer A-1 shown in Table 1 was used instead of the modified hydrogenated block copolymer C-1, and test pieces were prepared of the composition and the physical properties were determined. The obtained results are shown in Table 6. As will be readily understood from the results shown in Table 6, the composition comprising the modified hydrogenated block copolymer of the present invention and nylon 6 is highly improved in compatibility over the comparative composition, as is proved by the values of the transparency. Moreover, the composition has high tensile strength and modulus and is improved in heat resistance represented by the tensile strength at a high temperature. Furthermore, the composition is characterized by a highly improved weatherability. Examples 4 and 5 and Comparative Examples 4 and 5 Resinous compositions were prepared in the same manner as in Examples 1 and 2 and Comparative Examples 1 and 2 except that nylon 66 (number average molecular weight : 20,000) was used instead of nylon 6. In the same manner as in Examples 1 and 2 end Comparative Examples 1 and 2, test pieces were prepared of the obtained compositions and the physical properties were determined. The obtained results are shown in Table 7. Examples 6 and 7 and Comparative Examples 6 and 7 A resinous composition was obtained by mixing 80 parts by weight of PBT 1041 (the trade name for polybutylene terephthalate manufactured and sold by Toray Industries Inc., Japan) as a polar thermoplastic polymer with 20 parts by weight of the modified hydrogenated block copolymer C-1 shown in Table 2 by means of a screw type extruder having diameter of 30 mm (twin, L/D = 28). Another resinous composition was obtained in the same manner as described above except that the modified hydrogenated block copolymer C-3 was used instead of the modified hydrogenated block copolymer C-1. For comparison, a comparative resinous composition was obtained in the same manner as described above except that the unmodified block copolymer A-1 shown in Table 1 was used instead of the modified hydrogenated block copolymer C-1 or C-3. Another comparative resinous composition was obtained in the same manner as described above except that the unmodified block copolymer A-3 was used instead of the modified hydrogenated block copolymer C-1 or C-3 or the unmodified block copolymer A-1. Test pieces were prepared of the so-obtained compositions by injection molding, and the physical properties thereof were measured. The obtained results are shown in Table 8. Example 8 and Comparative Example 8 A polyester prepared from ethylene glycol (diol component), terephthalic acid (dicarboxylic acid component) and isophthalic acid (dicarboxylic acid component) and having a softening point of 195°C and an intrinsic viscosity of 0.75 (as measured at 35°C in o-chlorophenol) was used as a polar thermoplastic polymer. A rubbery composition was obtained by mixing 20 parts by weight of the above-mentioned polyester as a polar thermoplastic polymer with 80 parts by weight of the modified hydrogenated block copolymer C-1 shown in Table 2 by using a screw type extruder having a diameter of 30 mm (twin L/D = 28). For comparison, a comparative rubbery composition was prepared in the same manner as described above except that the unmodified block copolymer A-1 shown in Table 1 was used instead of the modified hydrogenated block copolymer C-1. Test pieces were prepared of the so-obtained compositions by compression molding, and the physical properties thereof were determined. The obtained results are shown in Table 9. As will be readily understood from the results shown in Table 9, the composition of Example 8 comprising the modified hydrogenated block copolymer and the polyester is excellent over the composition of Comparative Example 8 comprising the unmodified block copolymer and the polyester in mechanical properties such as the tensile strength and 300% modulus, the oil resistance and the heat resistance represented by the tensile strength retention at 50°C, and the modified block copolymer of the present invention is a very valuable material. Examples 9 through 11 and Comparative Examples 9 and 10 A resinous composition was obtained by mixing and kneading EVAL EP-E [the trade name for an ethylene-vinyl alcohol copolymer, obtained by saponifying an ethylene-vinyl acetate copolymer, manufactured and sold by Kuraray Co., Ltd., Japan] with the modified hydrogenated block copolymer C-1 shown in Table 2 at a mixing ratio shown in Table 10 by means of a mixing roller. Another resinous composition was obtained by mixing and kneading 75 parts by weight of EVAL EP-E with 25 parts by weight of the modified hydrogenated block copolymer C-3 by means of a mixing roller. A comparative resinous composition was obtained by mixing and kneading 75 parts by weight of EVAL EP-E with 25 parts by weight of the unmodified block copolymer A-1 shown in Table 1 by means of a mixing roll. Another comparative resinous composition was obtained in the same manner as described above except that the unmodified block copolymer A-3 shown in Table 1 was used instead of the unmodified block copolymer A-1. Test pieces were prepared of the so-obtained compositions by compression molding, and the physical properties thereof were determined. The obtained results are shown in Table 10. Furthermore, the adhesion of each composition to high density polyethylene was determined. The obtained results are also shown in Table 10. As will be readily understood from the results snown in Table 10, the composition of Example 9 comprising the modified hydrogenated block copolymer has a tensile strength (yield point) substantially comparable to that of the composition of Ccmparative Example 9 comprising the corresponding unmodified block copolymer, but the notched Izod impact strength of the composition of Example 9 is extremely improved over that of the comparative composition. When the samples of the compositions of Example 9 and Comparative Example 9 were observed by a phase contrast microscope, it was found that in the sample of Example 9, the modified block copolymer is uniformly dispersed in the form of particles having a size of about 0.5 to about 2 µ in the matrix of the ethylene-vinyl alcohol copolymer, whereas in the sample of Comparative Example 9, unmodified block copolymer particles having a size of about 5 to about 10 µ or larger are dispersed. Accordingly, it has been confirmed that there is a distinct difference of the compatibility between the two samples. Furthermore it has been confirmed that the composition containing the modified block copolymer of the present invention has an improved adhesion to polyethylene. Examples 12 and 13 and Comparative Examples 11 and 12 Each composition shown in Table 11 was prepared by using a mixing roller. Test pieces were prepared of the obtained composition by compression molding. The physical properties thereof were determined. The obtained results are shown in Table 11. As will be readily understood from the results shown in Table 11, the modulus of the composition is highly improved and the oil resistance is remarkably improved by addition of a small amount of the ethylene-vinyl alcohol copolymer. Moreover, the adhesion to polyethylene is improved with respect to the composition of the present invention. Examples 14 through 16 and Comparative Examples 13 through 15 Compositions containing a modified block copolymer of the present invention and comparative compositions were obtained by mixing Paraplene P-22 SM (the trade name for a thermoplastic polyurethane manufactured and sold by Nippon Polyurethane Co., Ltd., Japan) as a polar thermoplastic polymer according to the recipe shown in Table 12 by means of a Brabender Plastograph. Each of the obtained compositions was press-bonded at 180°C to a polyvinyl chloride sheet or a high density polyethylene sheet and the peeling strength was measured according to JIS K-6854. The obtained results are shown in Table 12. As will be readily understood from the results shown in Table 12, the composition obtained with the modified block copolymer of the present invention has excellent adhesion characteristics to polyvinyl chloride and polyethylene sheets within a broad mixing ratio. In contrast, the adhesiveness of the comparative composition is inferior to that of the corresponding composition of the present invention. Examples 17 and 18 and Comparative Examples 16 through 21 Compositions were prepared by mixing block copolymers shown in Table 15 with the same nylon 66 as used in Examples 4 and 5 or the same EVAL EP-E as used in Examples 9 through 11, and the Izod impact strength was measured and the weatherability test and the heat aging resistance test were carried out. It was confirmed that the compositions of the present invention are excellent in impact resistance, weatherability and resistance to heat aging. Example 19 and Comparative Example 22 A modified hydrogenated block copolymer C-1' having maleic anhydride grafted onto the hydrogenated block copolymer in an mount of 4.1% by weight was prepared in the same manner as adopted for the production of the modified hydrogenated block copolymer C-1 except that 7 parts by weight of maleic anhydride was incorporated into 100 parts by weight of the hydrogenated block copolymer B-1 (obtained by hydrogenating the unmodified block copolymer A-1 shown in Table 1). A modified ethylene-propylene copolymer rubber G-1 was prepared in the same manner as described above except that JSR EP57P (the trade name of an ethylene-propylene copolymer rubber manufactured and sold by Nippon Gosei Gomu K.K., Japan) was used instead of the hydrogenated block copolymer B-1. The amount of maleic anhydride grafted was 3.0% by weight. A resinous composition was obtained by mixing 20 parts by weight of the so-obtained modified hydrogenated block copolymer C-1' with 80 parts by weight of the same nylon-66 as used in Examples 4 and 5 by means of a screw type extruder having a diameter of 30 mm (twin, L/D = 28). A comparative resinous composition was obtained in the same manner as described above except that the modified ethylene-propylene copolymer rubber G-1 as prepared above was used instead of the modified hydrogenated block copolymer C-1'. Test pieces were prepared of the obtained compositions by injection molding, and the physical properties thereof were determined. Furthermore, test pieces having a thickness of 0.5 mm were prepared of the compositions, and the transparency was measured. The obtained results are shown in Table 16. From the results shown in Table 16, it is apparent that the composition of the present invention is excellent in transparency and impact resistance. Examples 20 through 25 and Comparative Examples 23 through 26 Compositions comprising Surlyn A-1706 (the trade name of a partially metal-crosslinked ethylene-acrylic acid copolymer available from Du Pont Co., U.S.A.) as the component (a) were prepared by mixing according to the recipe shown in Table 15 by means of rollers. The physical properties of the test pieces prepared from these compositions by compression molding are shown in Table 15. As will be readily understood from the results shown in Table 15, the composition of the present invention is improved over the comparative compositions in tensile strength and oil resistance. Incidentally, in Examples 20 through 25, it was confirmed by an infrared spectrophotometer that the acid anhydride groups in the modified block copolymer participated in the ionic crosslinking. Then, the adhesion of each composition to an aluminum plate was examined. It was found that the compositions containing the modified block copolymer of the present invention are excellent over the comparative compositions in adhesive properties, and have a good adhesion even after immersion in water, and this is a great characteristic not possessed by the comparative compositions. Examples 26 through 31 and Comparative Examples 27 through 30 Compositions comprising Copolene QD-400 (the trade name of a partially metal-crosslinked ethylene-acrylic acid copolymer manufactured and sold by Asahi Dow Co., Japan) as the components (a) were obtained by mixing according to the recipe shown in Table 18 by means of mixing rolls. The physical properties of the test pieces prepared of the obtained compositions by compression molding are shown in Table 18. Then, tine adhesion of each composition to nylon (undrawn sheet of nylon 6) was examined. The obtained results are shown in Table 16. From the results shown in Table 16, it is apparent that the compositions of the present invention are excellent over the comparative compositions in tensile strength and adhesiveness. Examples 32 through 41 and Comparative Examples 30 through 41 Compositions comprising a thermoplastic polymer and a block copolymer, as shown in Table 17, were prepared. More specifically, 100 parts by weight of a thermoplastic polymer was sufficiently mixed with 10 parts by weight of a block copolymer by a Henschel mixer, and tine mixture was pelletized by a screw type extruder having a diameter of 40 mm (single, L/D = 28). A flat plate having a size of 120 mm x 120 mm x 3 mm was prepared from the pelletized composition by injection molding. The obtained flat plate was degreased with methyl alcohol, spray-coated with Acryca B160 (the trade name of an acrylic resin paint available from Kawakami Toryo K.K. Japan), and naturally dried. In case of the composition comprising a polyoxymethylene or nitrile resin as the thermoplastic polymer, the plate was, instead of being degreased with methyl alcohol, immersed in a 0.1 N hydrochloric acid solution for 30 seconds and spray-washed with water. Each resulting plate was subjected to the paint adhesion test The obtained results are shown in Table 17 . As is apparent from the results shown in Table 17, the compositions of the present invention are excellent in paint adhesion. Examples 42 through 45 and Comparative Examples 42 through 53 Compositions comprising a thermoplastic polymer and a block copolymer, shown in Table 18, were prepared in the following manner. Namely, 100 parts by weight of a thermoplastic polymer was mixed with 50 parts by weight of a block copolymer by a screw type extruder having a diameter of 40 mm ( single L/D=28) and the mixture was pelletized. Test pieces were prepared of the pelletized composition by injection molding. The Izod impact strength and gloss thereof were measured and the weatherability and heat aging tests were carried out. The obtained results are shown in Table 18. In Table 18, there are also shown the values of the gloss measured for the test pieces of the composition comprising the ionic crosslinking product E-3 of the modified block copolymer C-6, which was used as a block copolymer. From the results shown in Table 18, it is seen that the compositions containing the modified block copolymer of the present invention are excellent in weatherability and heat aging resistance as expressed in strength retention. Examples 46 through 49 and Comparative Examples 54 through 57 Compositions containing the modified block copolymer of the present invention and comparative compositions were prepared according to the recipes shown in Table 19 by using a screw type extruder having a diameter of 40 mm ( single, L/D = 28 ). Test pieces were prepared of the obtained compositions by injection molding, and the Izod impact strength thereof was measured. The obtained results are shown in Table 19. From the results shown in Table 19, it is seen that the composition containing the modified block copolymer of the present invention is excellent in impact resistance. Incidentally, polystyrene having a weight average molecular weight of about 220,000 was used in Example 48 and Comparative Example 56. Examples 50 and 51 and Comparative Examples 58 and 59 The unmodified block copolymer A-5 was hydrogenated according to the same method as adopted for production of the hydrogenated block copolymers B-1 through 3-6 to obtain two hydrogenated block copolymers having hydrogenation degrees of about 86% and about 60% ,respectively. The hydrogenated block copolymers were modified according to the same method as adopted for production of the modified hydrogenated block copolymer C-6 to obtain modified hydrogenated block copolymers C-6' and C-6" having a hydrogenation degree different from that of C-6. Compositions comprising the modified hydrogenated block copolymer C-6, the obtained modified hydrogenated block copolymer C-6′ or C-6″ or the modified unhydrogenated block copolymer D-3 were obtained according to the recipe shown in Table 22 by using a screw type extruder having a diameter of 40 mm (single, L/D = 28). Test pieces were prepared of the obtained compositions by injection molding, and the weatherability and heat aging tests were carried out. The obtained results are shown in Table 20. From the results shown in Table 20, it is seen that when a modified block copolymer prepared from a block copolymer having a hydrogenation degree lower than 80% (an ethylenic unsaturation degree exceeding 20%) is used, the weatherability and resistance to heat aging are degraded. Examples 52 and 53 Compositions containing a glass fiber were prepared according to the recipe shown in Table 21 by using a screw type extruder having a diameter of 30 mm (twin, L/D = 28). Test pieces were prepared of the obtained compositions by injection molding, and the Izod impact strength was measured. The obtained results are shown in Table 21. Examples 54 through 61 and Comparative Examples 60 through 66 Compositions of the present invention and comparative compositions comprising a block copolymer and a thermoplastic polymer, shown in Table 22, were prepared according to the recipe shown below by using a screw type extruder having a diameter of 30 mm (twin, L/D = 23) for kneading. Test pieces of the obtained compositions were prepared by molding, and the tensile strength, abrasion resistance and compression permanent strain thereof were determined. The obtained results are shown in Table 22. From the results shown in Table 22, it is seen that the composition containing the modified block copolymer of the present invention is excellent over the comparative composition comprising an unmodified block copolymer in tensile strength, abrasion resistance and resistance to compression permanent strain. According to the method described in the Note *10 under Table 6, the weatherability test was carried out. It was found that the test pieces of the compositions of Examples 54 through 61 , after the weatherability test, substantially retained the characteristics and rubbery elasticity, while with respect to the test pieces of the compositions of Comparative Examples 62 through 68, the elongation retention at the tensile test was lower than 30% and the rubbery elasticity was lost, showing considerable deterioration. Examples 62 and 63 and Comparative Example 67 Compositions comprising Surlyn A-1706 (the trade name of a partially metal-crosslinked ethylene-acrylic acid copolymer available from Du Pont Co., U.S.A.) as the component (a) were prepared according to the recipe shown in Table 23 by using mixing rolls. Test pieces of the obtained compositions were prepared by compression molding and the Izod impact strength thereof was measured to obtain results shown in Table 25, from which it is seen that the compositions of the present invention have an excellent Izod impact strength. Examples 64 through 66 and Comparative Examples 68 through 72 Compositions comprising a modified block copolymer and Evaflex 150 (the trade name of an ethylene-vinyl acetate copolymer available from Mitsui Polychemical Co., Ltd., Japan), as shown in Table 26, were prepared by using a screw type extruder having a diameter of 40 mm (single, L/D = 28 ), and these compositions were tested with respect to the adhesiveness to an aluminum plate. The obtained results are shown in Table 24. The modified hydrogenated block copolymer C-8 shown in Table 26 was prepared in the following manner. A block copolymer of the S-B-S type having a styrene content of 20% by weight, a number average molecular weight of about 100,000 and a vinyl content in the butadiene block of about 35% was hydrogenated to obtain a hydrogenated block copolymer B-7 (having a hydrogenation degree of about 90%). The obtained copolymer B-7 was modified with maleic anhydride to obtain a modified hydrogenated block copolymer C-8 (the amount of maleic anhydride grafted onto the hydrogenated block copolymer was 0.25% by weight). Example 67 The hydrogenated block copolymer B-1 was supplied into a screw type extruder having a diameter of 30 mm (twin, L/D = 28), and simultaneously, 0.1 part by weight of Perhexa 25B [the trade name of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane available from Nippon Yushi K.K., Japan] and 35 parts by weight of maleic anhydride, per 100 parts by weight of the hydrogenated block copolymer B-1, were supplied through the side supply inlet provided on the cylinder portion of the extruder. The maleinization reaction was carried out at a cylinder temperature of 250°C. The obtained block copolymer (C-9) was treated and analyzed in the same manner as described hereinbefore. It was found that the amount of maleic anhydride grafted onto the hydrogenated block copolymer was 18.5% by weight. Compositions were prepared in the same manner as described in Examples 32 through 45 except that the copolymer C-9 was used as the modified hydrogenated block copolymer, and the physical properties of the compositions were examined. It was found that this composition is excellent in paint adhesion, impact resistance, gloss, weatherability and resistance to heat aging as well as the compositions obtained in Examples 32 through 45.

Claims: A modified block copolymer comprising: a radial base block copolymer of at least two monovinyl substituted aromatic hydrocarbon polymer blocks (A) and at least one olefin compound polymer block (B) composed mainly of a conjugated diene compound which polymer block (B) has its conjugated diene compound moiety hydrogenated to have an ethylenic unsaturation degree not exceeding 20 %, said radial base block copolymer having a monovinyl substituted aromatic hydrocarbon content of 5 to 95 % by weight, said conjugated diene compound moiety of said polymer block (B) having a vinyl content of 25 to 65 % in terms of the vinyl content prior to the hydrogenation of said conjugated diene compound moiety; and at least one molecular unit grafted to said radial base block copolymer, said molecular unit containing at least one member selected from a dicarboxylic acid group and groups derived therefrom. The modified block copolymer according to claim 1, which is one obtained by the reaction of a radial base block copolymer of at least two monovinyl substituted aromatic hydrocarbon polymer blocks and at least one olefin compound polymer block composed mainly of a conjugated diene compound which olefin compound polymer block has its conjugated diene compound moiety hydrogenated to have an ethylenic unsaturation degree not exceeding 20 %, said radial base block copolymer having a monovinyl substituted aromatic hydrocarbon content of 5 to 95 % by weight, said conjugated diene compound moiety of said olefin compound polymer block having a vinyl content of 25 to 65 % in terms of the vinyl content before the hydrogenation of said conjugated diene compound moiety, with at least one modifying agent selected from the group consisting of unsaturated dicarboxylic acids and derivatives thereof. The modified block copolymer according to claim 2, wherein said radial base block copolymer is one obtained by selectively hydrogenating a radial precursory block copolymer comprising at least two monovinyl substituted aromatic hydrocarbon polymer blocks and at least one polymer block composed mainly of a conjugated diene compound, said radial precursory block copolymer having a vinyl content of 25 to 65 %, wherein said selective hydrogenation is performed at the conjugated diene compound moiety of said polymer block to the extent that the ethylenic unsaturation degree of the polymer block composed mainly of the conjugated diene compound is 20 % or less. The modified block copolymer according to claim 3, wherein said radial precursory block copolymer has a number average molecular weight of 20,000 to 500,000. The modified block copolymer according to claim 2, wherein said modifying agent is selected from the group consisting of maleic acid, maleic anhydride, maleic acid esters, maleic acid amides, maleic acid imides, fumaric acid, fumaric acid esters, fumaric acid amides, fumaric acid imides, itaconic acid, itaconic anhydride, itaconic acid esters, itaconic acid amides, itaconic acid imides, halogenated maleic acid, halogenated maleic anhydride, halogenated maleic acid esters, halogenated maleic acid amides, halogenated maleic acid imides, cis-4-cyclohexene-1,2-dicarboxylic acid, cis-4-cyclohexene-1,2-dicarboxylic anhydride, cis-4-cyclohexene-1,2-dicarboxylic acid esters, cis-4-cyclohexene-1,2-dicarboxylic acid amides, cis-4-cyclohexene-1,2-dicarboxylic acid imides, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic anhydride, endo-cis-bicyclo(2,2,1 )-5heptene-2,3-dicarboxylic acid esters, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid amides, and endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid imides. The modified block copolymer according to any one of claims 1 to 5, wherein said molecular unit is grafted to said radial base block copolymer in an amount of 0.05 to 30 parts by weight, per 100 parts by weight of said radial base block copolymer. The modified block copolymer according to any one of claims 1 to 5, wherein the monovinyl substituted aromatic hydrocarbon content of said radial base block copolymer is 5 to 60 % inclusive by weight. The modified block copolymer according to any one of claims 1 to 5, wherein the monovinyl substituted aromatic hydrocarbon content of said radial base block copolymer is over 60 % by weight up to 95 % inclusive by weight. The modified block copolymer according to any one of claims 1 to 5, which is ionically crosslinked through at least one metal ion selected from the group consisting of monovalent, divalent and trivalent metal ions to form an ionically crosslinked modified block copolymer. The modified block copolymer according to claim 9, wherein the ionical crosslinking of said modified block copolymer through said metal ion is effected using at least one crosslinking agent selected from compounds of said metals in a ratio of 0.1 to 3.0 in terms of a molar ratio of the metal of said crosslinking agent relative to said member selected from a dicarboxylic acid group and groups derived therefrom which member is contained in said modified block copolymer. The modified block copolymer according to claim 9, wherein said metal ion is at least one member selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, zinc and aluminum ions. The modified block copolymer according to claim 9, wherein said molecular unit is grafted to said radial base block copolymer in an amount of 0.05 to 30 parts by weight, per 100 parts by weight of said radial base block copolymer. The modified block copolymer according to claim 9, wherein the monovinyl substituted aromatic hydrocarbon content of said radial base block copolymer is 5 to 60 % inclusive by weight. The modified block copolymer according to claim 9, wherein the monovinyl substituted aromatic hydrocarbon content of said radial base block copolymer is over 60 % by weight up to 95 % inclusive by weight. A process for producing a modified block copolymer, which comprises reacting a radial base block copolymer of at least two monovinyl substituted aromatic hydrocarbon polymer blocks and at least one olefin compound polymer block composed mainly of a conjugated diene compound which olefin compound polymer block has its conjugated diene compound moiety hydrogenated to have an ethylenic unsaturation degree not exceeding 20 %, said radial base block copolymer having a monovinyl substituted aromatic hydrocarbon content of 5 to 95 % by weight, said conjugated diene compound moiety of said olefin compound polymer block having a vinyl content of 25 to 65 % in terms of the vinyl content before the hydrogenation of said conjugated diene compound moiety, with at least one modifying agent selected from the group consisting of unsaturated dircarboxylic acids and derivatives thereof in the presence or absence of a radical initiator so that at least one molecular unit containing at least one member selected from a dicarboxylic acid group and groups derived therefrom is grafted to said radial base block copolymer. The process according to claim 15, wherein said radial base block copolymer is one obtained by selectively hydrogenating a radial precursory block copolymer comprising at least two monovinyl substituted aromatic hydrocarbon polymer blocks and at least one polymer block composed mainly of a conjugated diene compound, said radial precursory block copolymer having a vinyl content of 25 to 65 %, wherein said selective hydrogenation is performed at the conjugated diene compound moiety of said polymer block to the extent that the ethylenic unsaturation degree of the polymer block composed mainly of the conjugated diene compound is 20 % or less. The process according to claim 16, wherein the said radial precursory block copolymer has a number average molecular weight of 20,000 to 500,000. The process according to claim 15, wherein said modifying agent is selected from the group consisting of maleic acid, maleic anhydride, maleic acid esters, maleic acid amides, maleic acid imides, fumaric acid, fumaric acid esters, fumaric acid amides, fumaric acid imides, itaconic acid, itaconic anhydride, itaconic acid esters, itaconic acid amides, itaconic acid imides, halogenated maleic acid, halogenated maleic anhydride, halogenated maleic acid esters, halogenated maleic acid amides, halogenated maleic acid imides, cis-4-cyclohexene-1,2-dicarboxylic acid, cis-4-cyclohexene-1,2-dicarboxylic anhydride, cis-4-cyclohexene-1,2-dicarboxylic acid esters, cis-4-cyclohexene-1,2-dicarboxylic acid amides, cis-4-cyclohexene-1,2-dicarboxylic acid imides, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic anhydride, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid esters, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid amides, and endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid imides. The process according to any one of claims 15 to 18, wherein said molecular unit is grafted to said radial base block copolymer in an amount of 0.05 to 30 parts by weight, per 100 parts by weight of said radial base block copolymer. The process according to any one of claims 15 to 18, wherein the monovinyl substituted aromatic hydrocarbon content of said radial base block copolymer is 5 to 60 % inclusive by weight. The process according to any one of claims 15 to 18, wherein the monovinyl substituted aromatic hydrocarbon content of said radial base block copolymer is over 60 % by weight up to 95 % inclusive by weight. The process according to any one of claims 15 to 18, which further comprises crosslinking said modified block copolymer with at least one crosslinking agent selected from metal compounds, wherein the metal is selected from the group consisting of monovalent, divalent and trivalent metals to form an ionically crosslinked modified block copolymer. The process according to claim 22, wherein said crosslinking agent is employed in a ratio of 0.1 to 3.0 in terms of a molar ratio of the metal of said crosslinking agent relative to said member selected from a dicarboxylic acid group and groups derived therefrom which member is contained in said modified block copolymer. The process according to claim 22, wherein the metal is selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, zinc and aluminum. The process according to claim 22, wherein said molecular unit is grafted to said radial base block copolymer in an amount of 0.05 to 30 parts by weight, per 100 parts by weight of said radial base block copolymer. The process according to claim 22, wherein the monovinyl substituted aromatic hydrocarbon content of said radial base block copolymer is 5 to 60 % inclusive by weight. The process according to claim 22, wherein the monovinyl substituted aromatic hydrocarbon content of said radial base block copolymer is over 60 % by weight up to 95 % inclusive by weight.

Inventors: HAYANO FUSAKAZU, MORITA HIDEO, SHIRAKI TOSHINORI, HAYANO, FUSAKAZU, MORITA, HIDEO, SHIRAKI, TOSHINORI
Applicants: ASAHI CHEMICAL IND, ASAHI KASEI KOGYO KABUSHIKI KAISHA
Application year: 1982
Main classification: C08F287
IPC codes: C08L77, C08F287, C08L51, C08F8