Hydrogenated diene copolymer-containing resin composition and process for producing the same

Abstract: A hydrogenated diene copolymer resin composition comprising (A) 5-70% by weight of a hydrogenated diene copolymer which is a hydrogenation product of a random copolymer of at least one conjugated diene and 3-50% by weight of an alkenyl aromatic compound having a number average molecular weight of 5,000-1,000,000 and a molecular weight distribution (Mw/Mn) of 10 or less, the vinyl content in the diene portion of the random copolymer being 10-90%, at least 70% of the olefinic unsaturation of the random copolymer being hydrogenated, and (B) 95-30% by weight of at least one resin selected from the group consisting of a polypropylene resin, a polyphenylene ether resin and an alkenyl aromatic compound polymer resin. The hydrogenated diene copolymer (A) can be used in combina­ tion with (B) a polyphenylene ether resin and (C) at least one member selected from the group consisting of a poly­ amide and a thermoplastic polyester in such a proportion that the amount of (A) is 1-50 parts by weight, the amount of (B) is 10-89 parts by weight and the amount of (C) is 10-89 parts by weight. The above composition has improved impact resistance and improved gloss and appearance of molded article.

Description: This invention relates to a hydrogenated diene copolymer-containing resin composition having improved impact resistance and improved gloss and appearance of molded article, and a process for producing the composition. Propylene resin is used in a large amount in the interior and exterior trim of automobile, particularly bumper of automobile, and the like in view of its moldability, price and the like. However, it is inferior in impact resistance at low temperatures and coating strength, and therefore, it is blended with a modifier such as an ethylene-propylene copolymer rubber or the like (see, for example, Japanese Patent Application Kokoku No. 37-8,483 and 36-150,432). Also, in order to enhance the impact resistance at low temperatures of polypropylene resin, the amount of the ethylene-propylene copolymer rubber added is increased or a high molecular weight ethylene-propylene copolymer rubber is added to the polypropylene resin. However, when the amount of ethylene-propylene copolymer rubber added is increased, the stiffness is lowered, and when a high molecular weight ethylene-propylene copolymer rubber is added to prevent the stiffness from being lowered, the dispersibility of the rubber becomes low and the surface gloss is also lowered. Because of recent needs such as low fuel economy rating, fashion, personality and the like, the bumper of automobile has been changed in shape and large-sized. Therefore, the physical properties which a bumper material is required to have have been diversified. One of the required physical properties is directed to flexibilization in view of safety. Heretofore, for the flexibilization of a polypropylene resin composition, it has been proposed to increase the amount of the ethylene-propylene copolymer rubber added or add a plasticizer such as a mineral oil or the like. However, when the amount of ethylene-propylene copolymer rubber added is increased, there is a problem that the moldability of the composition becomes inferior, in other words, the surface of a molded article becomes sticky. Also, when a plasticizer such as a mineral oil or the like is added, the flexibilization can be achieved but there is a problem that the mineral oil oozes out to the surface of molded article. As mentioned above, the addition of a modifier such as ethylene-propylene copolymer rubber or the like to a polypropylene resin has been known; however, the improvement obtained thereby is still insufficient. In addition, such a modifier as ethylene-propylene copolymer rubber or the like is insufficient to meet the diversification of the required physical properties. Moreover, thermoplastic resin such as polyphenylene ether resin, polystyrene resin and the like are unsatisfactory in impact resistance, and the fields of use thereof are limited. In order to remedy the above disadvantage, a styrene-butadiene random copolymer, a styrene-butadiene block copolymer or a polybutadiene or the like has been incorporated into and dispersed in such thermoplastic resins by a mechanical method. However, in the method of dispersing a rubbery polymer in a resin by a mechanical method, a mere brittle mixture is obtained when the two have no affinity to each other. When the affinity is good, the impact resistance can be improved; however, the other mechanical characteristics of the resin cannot be sufficiently improved. In addition, the surface gloss of molded article therefrom is not satisfactory, and in the molded article, molecules are highly oriented, so that the molded article is greatly different in impact resistance depending upon places. Therefore, the appearance of the molded article becomes bad. Furthermore, the resin modified by such a rubbery polymer is inferior in weather resistance and resistance to heat deterioration. A method of blending a styrene-butadiene block copolymer with the resin can be used; however, molded articles of the resulting blend tend to have pearl-like gloss on their surface. Polyphenylene ether resins have excellent mechanical properties, electrical properties and heat resistance, and are good in dimension stability, so that attention is paid thereto as a resin suitable for uses in a wide field. However, the resins are inferior in moldability. In order to improve the moldability of a polyphenylene ether resin, Japanese Patent Application Kokoku No. 45-997 proposes blending a polyamide therewith and Japanese Patent Application Kokoku No. 51-21,664 proposes blending a thermoplastic polyester therewith. However, the polyphenylene ether resin is very poor in compatibility with the polyamide and thermoplastic polyester, and the resulting resin composition is inferior in mechanical characteristics, and molded articles obtained by injection-molding the resin composition are very low in impact resistance. In order to improve the compatibility between the polyphenylene ether resin and the polyamide resin, Japanese Patent Application Kohyo No. 61-502,195 and Japanese Patent Application Kokai No. 57-36,150 propose using a polycarboxylic acid; Japanese Patent Application Kokai No. 57-36,150 further proposes using a styrene-maleic acid anhydride copolymer; Japanese Patent Application Kokoku No. 60-11,966 proposes adding an unsaturated compound having a specific functional group in the step of melt-mixing; Japanese Patent Application Kokai No. 61-204,262 proposes modifying a polyphenylene ether with an acid anhydride group; Japanese Patent Application Kokai No. 62-129,348 proposes using an ethylene-α-olefin copolymer modified with a specific functional group and a styrene resin; Japanese Patent Application Kokai No. 62-127,339 proposes using a styrene-butadiene-styrene block copolymer as a rubber and Japanese Patent Application Kokai No. 62-81,449 proposes using a partially hydrogenated styrene-butadiene-styrene block copolymer as a rubber. However, when a styrene-butadiene-styrene block copolymer or a partially hydrogenated styrene-butadiene-styrene block copolymer is blended as a rubber with a polyphenylene ether-polyamide composition or a partially hydrogenated styrene-butadiene-styrene block copolymer is used as proposed in the above publications, the heat resistance and the surface appearance of molded article are inferior and the heat resistance, particularly heat distortion. Moreover, the addition of a rubber-modified polystyrene is known as a method of improving the impact resistance and processability of a polyphenylene ether. However, the rubber-modified polystyrene is usually obtained by dissolving a styrene monomer in a rubbery polymer and then subjecting the resulting solution to bulk-suspension polymerization. Therefore, it is necessary to limit the amount of the rubbery polymer used in order to conduct the phase transfer favorably, and the rubbery polymer is usually used in a proportion of about 10% by weight of the weight of the rubber-modified polystyrene. A composition consisting of a rubber-modified polystyrene and a polyphenylene ether in such a proportion is insufficient in impact resistance and, in some cases, the corner parts or thin wall portions of a molded article are cracked when the molded article is taken out of a mold in the molding step. For the purpose of improving the impact resistance, the addition of a styrene-butadiene-styrene block copolymer or a hydrogenated styrene-butadiene-styrene block copolymer to the composition consisting of a polyphenylene ether and a rubber-modified polystyrene has been proposed; however, the use of such a rubber results in deterioration of heat resistance and generation of pearl-like gloss. As a result, the appearance of a molded article becomes bad. The present inventors have made extensive study to solve the above-mentioned problems, and have found that the problems can be solved by incorporating a specific hydrogenated diene copolymer into polypropyiene resin. An object of this invention is to provide a hydrogenated diene copolymer-containing resin composition which has improved processability, surface gloss, coatability and impact resistance and can meet various requirements concerning physical properties. Another object of this invention is to provide a process for producing such a hydrogenated diene copolymer-containing resin composition. Other objects and advantages of this invention will become apparent from the following description. According to this invention, there is provided a hydrogenated diene copolymer-containing resin composition comprising (A) 5-70% by weight of a hydrogenated diene copolymer which is a hydrogenation product of a random copolymer of at least one conjugated diene and 3-50% by weight of an alkenyl aromatic compound having a number average molecular weight of 5,000-1,000,000 and a molecular weight distribution (Mw/Mn) of 10 or less, the vinyl content in the diene portion of the copolymer being 10-90%, at least 70% of the olefinic unsaturation of the random copolymer being hydrogenated, and (B) 95-30% by weight of polypropylene resin. This invention further provides a process for producing the above hydrogenated diene copolymer-containing resin composition, which comprises melt-mixing (A) 50-80% by weight of a hydrogenated diene copolymer which is a hydrogenation product of a random copolymer of at least one conjugated diene and 3-50% by weight of an alkenyl aromatic compound having an average molecular weight of 5,000-1,000,000 and a molecular weight distribution (Mw/Mn) of 10 or less, the vinyl content in the diene portion of the copolymer being 10-90%, at least 70% of the olefinic unsaturation of the random copolymer being hydrogenated, and (B) 50-20% by weight of a polypropylene resin, and further melt-mixing the resulting mixture in the form of pellets or a block with the same resin (B). The random copolymer of at least one conjugated diene and 3-50% by weight of an alkenyl aromatic compound (hereinafter referred to as the random copolymer) which is the starting material of the hydrogenation product (A) used in this invention can be obtained by anionic living polymerization of the monomers in a hydrocarbon solvent with an organolithium initiator. The random copolymer can be converted into a branched polymer by adding a tri- or more functional coupling agent just before the completion of the anionic living polymerisation and subjecting the random copolymer to coupling reaction. The conjugated diene monomers used in the random copolymer includes, for example, 1,3-butadiene, isoprene, 1,3-pentadiene, 2,2'-dimethylbutadiene and 3-ethylbutadiene. Preferred are 1,3-butadiene, isoprene and 1,3-pentadiene, and 1,3-butadiene is more preferable. Also, the alkenyl aromatic compound includes styrene, α-methylstyrene, p-methylstyrene, p-ethylstyrene and vinylnaphthalene. Styrene, p-methylstyrene and p-ethylstyrene are preferable, and styrene is more preferable. The organolithium initiator may be n-butyl-lithium, sec-butyllithium or tert-butyllithium. In the polymerization, hexane, heptane, methylcyclohexane, cyclohexane, benzene, toluene, xylene, 2-methylbutene-1, 2-methylbutene-2 may be used as the hydrocarbon solvent in the polymerization. The control of the vinyl content such as 1,2-content, 3,4-content may be effected by using an ether, a tertiary amine compound, and an alkali metal (sodium, potassium), an alkoxide, a phenoxide or a sulfonate. The polymerization may be batchwise or continuously effected usually at a temperature of 0-120°C for a period of 10 minutes to 3 hours. The coupling agent is a tri- or more functional coupling agent such as tetrachlorosilane, butyltrichlorosilane, tetrachlorotin, butyltrichlorotin, tetrachlorogermanium, bis(trichlorosilyl)ethane, epoxidized linseed oil, tolylene diisocyanate or 1,2,4-benzene triisocyanate. The hydrogenated diene copolymer (A) is obtained by hydrogenating the thus obtained random copolymer. In the hydrogenated diene copolymer (A) used in this invention, the hydrogenation percentage of the olefinic unsaturation is at least 70%, preferably at least 80%. When the hydrogenation percentage is less than 70%, the weather resistance and heat resistance of the polymer cannot be sufficiently improved, and hence, the uses thereof are limited. The hydrogenation is effected by dissolving the above random copolymer in a hydrocarbon solvent and subjecting the resulting solution to a temperature of 20-150°C and a hydrogenation pressure of 1-100 kg/cm² in the presence of a hydrogenation catalyst. As the hydrogenation catalyst, there is used a catalyst in which a noble metal such as palladium, ruthenium or platinum is supported on silica, carbon or diatomaceous earth; a complex catalyst of rhodium, ruthenium or platinum; a catalyst consisting of an organic carboxylic acid salt with cobalt or nickel and an organoaluminum or organolithium; a hydrogenation catalyst consisting of a combination of a titanium compound such as dicyclopentadienyltitanium dichloride, dicyclopentadienyldiphenyltitanium, dichlopentadienyltitaniumditolyl or dicyclopentadienyltitaniumdibenzyl with a reducing organometallic compound comprising lithium, aluminum or magnesium;. The vinyl content in the conjugated diene portion of the random copolymer which is the starting material for the hydrogenated diene copolymer (A) and the alkenyl aromatic compound content of the random copolymer are important factors for improving the physical properties of the hydrogenated diene copolymer-containing resin composition. The state of the conjugated diene bound in the random copolymer is a factor for improving mainly the stiffness and flexibility of the hydrogenated diene copolymer-containing resin composition and the alkenyl aromatic compound content is a factor for improving the stiffness and impact resistance in good balance. When stress is put on the improvement of the stiffness of the resin composition of this invention, the hydrogenated diene copolymer (A) is preferably derived from a random copolymer having a vinyl content falling in the region lower than the line indicated by the interrelation equation x = y + 50 in which x represents the vinyl content in the conjugated diene and 10 ≦ x ≦ 65, preferably 15 ≦ x ≦ 65 and y represents the alkenyl aromatic compound content and 3 ≦ y ≦ 50, preferably 3 ≦ y ≦ 40, more preferably 5 ≦ y ≦ 35, and a hydrogenated diene copolymer-containing resin composition consisting of 5-70% by weight of the (A) component and 95-30% by weight of the (B) component has the characteristics that the stiffness is high and the impact resistance at low temperatures is high. When the vinyl content of the random copolymer used for this purpose is less than 10%, the hydrogenated diene copolymer-containing resin composition of this invention has only a small effect on improving the impact resistance at low temperatures. When the vinyl content x exceeds the interrelation line of x = y + 50 , the stiffness is lowered. The increase of the alkenyl aromatic compound content is effective for enhancing the stiffness; however, when it exceeds 50% by weight, the effect on improving the impact resistance at low temperatures is lowered. Also, when the alkenyl aromatic compound content y is less than 3% by weight, the coating strength is lowered and the stiffness becomes insufficient. On the other hand, when stress is put on the improvement of flexibility in the composition of this invention, the hydrogenated diene copolymer (A) is preferably derived from a random copolymer having a vinyl content higher than the line indicated by the interrelation equation x = y + 50 in which x represents the vinyl content and 50 ≦ x ≦ 90, preferably 60 ≦ x ≦ 85 and y represents the alkenyl aromatic compound content and 3 ≦ y ≦ 20, and a hydrogenated diene copolymer-containing resin composition consisting of 5-70% by weight of the (A) component and 95-30% by weight of the (B) component is excellent in flexibility and flowability. When the vinyl content x of the random copolymer used for this purpose is lower than the line indicated by the interrelation equation x = y + 50 , the effect on flexibility becomes small. When the vinyl content x exceeds 90%, the impact resistance at low temperatures is deteriorated. When the alkenyl aromatic compound content y is more than 20% by weight, the flexibility and impact resistance at low temperatures becomes insufficient. Thus, the hydrogenated diene copolymer used in this invention has contradictory characteristics which depend upon balance between the vinyl content and the alkenyl aromatic compound content, and can respond widely to quality improvement of a thermoplastic resin. In common with these uses, the molecular weight Mn of the random copolymer is 5,000 to 1,000,000, preferably 30,000 to 300,000. When it is less than 5,000, the hydrogenated diene copolymer used in this invention does not become rubbery but liquid, and the expected sufficient improvement of the stiffness and impact resistance at low temperatures cannot be achieved. When it exceeds 1,000,000, the flowability becomes too low, and the dispersion of the hydrogenated diene copolymer in the final composition becomes low and the surface gloss is deteriorated. Also, the molecular weight distribution (Mw/Mn) is 10 or less, preferably 6 or less. When it exceeds 10, the flowability is deteriorated and the surface gloss is lowered. Moreover, surface stickiness due to low molecular weight is caused. The polypropylene resin used in this invention is not critical; however, it may be a homopolymer of propylene obtained by homopolymerizing propylene with a transition metal catalyst called Ziegler-Natta catalyst or a propylene-ethylene or α-olefin copolymer obtained by copolymerising propylene and a small amount of ethylene or an α-olefin having 4 to 12 carbon atoms. When the above polypropylene resin is the copolymer, the proportion of ethylene or α-olefin in the copolymer is usually 3-25% by weight and the copolymer may be either random or block copolymer. The melt flow index of the polypropylene resin is preferably 0.3-100 g/10 min (230°C), more preferably 2-70 g/10 min (230°C). The above polypropylene resins may be used alone or in combination of two or more. The hydrogenated diene copolymer-containing resin composition of this invention can be produced from (A) the hydrogenated diene copolymer and (B) a polypropylene resin by a conventional method. For example, the hydrogenated diene copolymer (A) is melt-mixed with the resin (B) using an extruder, kneader-blender, Banbury blender or the like. In this case, the melt-mixing is conducted so that the temperature becomes finally 170°C or higher. Though the mixing method is not critical, the resin composition of this invention can be obtained by mixing the hydrogenated diene copolymer (A) with the resin (B) so that the final proportion of the (A) component to the (B) component falls within the range of this invention. A better method is a method comprising melt-mixing 50-80% by weight of the hydrogenated diene copolymer (A) with 50-20% by weight of the resin (B) and then further melt-mixing the resulting mixture in the form of pellets or a block with the same at least one resin as above. According to this method, a molded article excellent in impact resistance, surface gloss and appearance can be obtained, and the handling of the hydrogenated diene copolymer (A) can be improved. That is, the blocking of the hydrogenated diene copolymer (A) can be completely prevented and the subsequent processing becomes easy. The hydrogenated diene copolymer-containing resin composition may further comprise conventional additives such as antioxidant, heat stabilizer, ultraviolet absorber, carbon black, coloring agent and the like. Moreover, it may also comprise a filler such as calcium carbonate, kaolin, talc, asbestos, glass fiber or the like, and a rubber and/or a resin such as ethylene-propylene random copolymer, olefin (co)polymer rubber (for example, butyl rubber), low density polyethylene resin, high density polyethylene resin, polystyrene resin, acrylonitrile-butadiene-styrene resin, acrylonitrile-butadiene-styrene copolymer resin, ethylene-vinyl acetate copolymer resin or its hydrogenation product or polybutadiene rubber. For softening the resin, a mineral oil, a liquid or low molecular weight olefin (co)polymer may be incorporated into the composition. The hydrogenated diene copolymer-containing resin composition can be formed into various molded articles by injection molding, sheet-extrusion, vacuum forming, profile extrusion or expansion molding. The molded articles obtained by the above molding method can be used in exterior or interior trim material of automobile, electric or electronic parts and housings utilizing the excellent properties of the molded articles. The resin composition of this invention is excellent in gloss of molded article, appearance of molded article, impact resistance and weather resistance, and therefore, has a very great value in industry. In particular, the resin composition comprising the hydrogenated diene copolymer (A) and the polypropylene resin as the (B) component is superior in processability, surface gloss, coatability and impact resistance to conventional resin composition consisting of polypropylene and ethylene-propylene rubber used in industry, and when the molecular characteristics of the hydrogenated diene copolymer contained therein is controlled to an appropriate region, not only a polypropylene resin composition having a high stiffness but also a very soft polypropylene resin composition can be obtained. Such characteristics cannot be imparted by known polypropylene resin-moldifiers such as ethylene-propylene rubber, hydrogenated block copolymer and the like. This invention is described more specifically below referring to Examples. However, this invention should not be interpreted as being restricted to the Examples. In the following Examples, the unit PHR is used to mean parts by weight per 100 parts by weight of polymer. Reference Example 1 Preparation of hydrogenated diene copolymers Into a 5-liter autoclave were charged 2,500 g of cyclohexane, 75 g of styrene and 425 g of 1,3-butadiene, all of which had been degassed and dehydrated. To the mixture were added 1.5 g of tetrahydrofuran and 0.35 g of n-butyllithium. The resulting mixture was subjected to temperature-elevating polymerization wherein the polymerization temperature was elevated from 30°C to 80°C. When the conversion reached approximately 100%, 0.13 g of SiCl₄ was added to the reaction mixture. Then, 2,6-di-tert-butylcatechol was added, and the resulting mixture was subjected to steam stripping to remove the solvent and dried by a hot roll at 120°C to obtain a polymer. The styrene-butadiene random copolymer had a vinyl content of 18%, a styrene content of 15% by weight and a tri- or more-branched polymer content of 42% by weight. When analyzed by GPC, the random copolymer had a number-average molecular weight of 160,000 and a Mw/Mn of 1.7. The random copolymer was charged into a 3-liter autoclave to prepare a 15% cyclohexane solution thereof. The autoclave inside was purged with nitrogen, and thereto was added a catalyst solution of nickel naphthenate : n-butyllithium : tetrahydrofuran = 1 : 8 : 20 (molar ratio), which had been prepared in a different vessel, at a proportion of 1 mole (in terms of nickel) per 2,000 moles of the olefin portion of the copolymer. Then, hydrogen was introduced into the reaction system, and hydrogenation reaction was effected at 70°C. In the reaction, the hydrogenation percentage was controlled based on the amount of hydrogen absorbed and consumed. Thereafter, the hydrogen in the reaction system was replaced by nitrogen, and 1 PHR of 2,6-di-tert-butylcresol was added as an antioxidant. Catalyst removal and coagulation were effected, followed by drying according to a conventional method. The resulting hydrogenated diene copolymer (Sample No. 1-1) had a hydrogenation percentage of 85%. Various random copolymers were prepared in the same manner as above, except that the type and amount of alkenyl aromatic compound used, the amount of n-butyllithium used and the amount of tetrahydrofuran used were varied as shown in Table I-1. At that time, the coupling reaction was effected using no SiCl₄ or SiCl₄ in different amounts. The random copolymers were subjected to the same hydrogenation reaction as above. The resulting hydrogenated diene copolymers (Sample Nos. 1-2 to 1-13) are shown in Table I-1. Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-6 1,890 g of one of the hydrogenated diene copolymer Sample Nos. 1-1 to 1-7 shown in Table 1-1 and 810 g of a polypropylene resin (Noblen BC-2 manufactured by Mitsubishi Petrochemical Co., Ltd.) were melt-kneaded using a 4-liter test Banbury mixer. Each of the kneaded materials obtained was formed into pellets using a 50-mm full-flighted single screw type extruder. In this pelletization, each of the hydrogenated diene copolymer Sample Nos. 1-1 to 1-7 used could be formed into pellets having no adhesivity. (These pellets are hereinafter referred to as master pellets.) The master pellets and an additional amount of the polypropylene resin (Noblen BC-2 manufactured by Mitsubishi Petrochemical Co., Ltd.) were melt-kneaded using a 4-liter Banbury mixer so that the final ratio of the hydrogenated diene copolymer (A) and the polypropylene resin (B) became 25/75 by weight, to obtain resin compositions to this invention. Each of the resin compositions was pelletized by a pelletizer. The resulting pellets were subjected to injection molding by a 6.5-ounce injection molding machine (6.5-ounce in-line screw type manufactured by Nihon Seiko K.K.) to obtain test pieces. The conditions of injection molding were as follows: Injection pressure Primary pressure 500 kg/cm² Secondary pressure 400 kg/cm² Injection time 15 seconds in total under the primary pressure and the secondary pressure Molding temperature 240°C Cooling time 40 sec The test pieces were measured for physical properties according to the following test methods to obtain the results shown in Table I-2: (1) Melt flow rate (MFR) (yardstick for processability) Measured at 230°C under a load of 2.16 kg in accordance with JIS K 7210. (2) Izod impact strength Measured in accordance with JIS K 7110. (3) Flexural modulus (MF) (yardstick of stiffness) Measured in accordance with JIS K 7203. (4) Surface gloss (GL) Measured in accordance with JIS K 7105. (5) Bonding strength of film (yardstick of coatability) A sheet of 2 mm in thickness obtained by injection molding was degreased with ethanol and then surface-treated with trichloroethane vapor. The resulting sheet was coated firstly with a primer (RB291H manufactured by Nihon Bee Chemical K.K.) and then with a polyurethane type coating (R263 manufactured by the same firm) in a total film thickness (as dried) of about 50 µm. The coated sheet was dried to cure the film. Then, the adhesion strength between the sheet and the film was measured by subjecting the film to 180° peeling at a drawing speed of 30 mm/min. For comparison, each of the hydrogenated diene copolymer Sample Nos. 1-12 and 1-13 shown in Table I-1, an ethylene-propylene copolymer I (EP02P manufactured by Japan Synthetic Rubber Co., Ltd.), an ethylene-propylene copolymer II (EP07P manufactured by Japan Synthetic Rubber Co., Ltd.), an ethylene-1-butene copolymer (Tafmer A4085 manufactured by Mitsui Petrochemical Industries, Ltd.) and a hydrogenated butadiene-styrene-butadiene triblock copolymer (Kraton G1650 manufactured by Shell Chemical) was subjected to the same treatments (melt-kneading with polypropylene resin via master pellets) as for the hydrogenated diene copolymer Sample Nos. 1-1 to 1-7 in Examples 1-1 to 1-7 to obtain resin compositions. (In each composition, the ratio of the copolymer and the polypropylene resin was 25/75 by weight.) Each resin composition was pelletized and injection molded in the same manner as in Examples 1-1 to 1-7, to obtain test pieces. The test pieces were measured for physical properties to obtain the results shown in Table I-2. As is clear from Table 1-2, the compositions of Examples 1-1 to 1-7 according to this invention, each using a hydrogenated diene copolymer falling in a lower vinyl content region than the line indicated by the interrelation equation, x = y + 50 in which x is a vinyl content (%) in the copolymer and 10 ≦ x ≦ 65 and y is an alkenyl aromatic compound content (%) in the copolymer and 3 ≦ y ≦ 50, are superior in processability, Izod impact strength at low temperatures, flexural modulus, surface gloss and film strength. In contrast, the composition of Comparative Example 1-1 using a hydrogenated diene copolymer containing no alkenyl aromatic compound is inferior in film strength, and the composition of Comparative Example 1-2 using a hydrogenated diene copolymer containing an alkenyl aromatic compound in a large amount (55% by weight) is inferior in Izod impact strength. Both the compounds of Comparative Examples 1-3 and 1-4 each using an ethylene-propylene copolymer are inferior in Izod impact strength at a very low temperature (-40°C) and flexural modulus. The composition of Comparative Example 1-5 using an ethylene-1-butene copolymer is inferior in Izod impact strength at low temperatures. The composition of Comparative Example 1-6 using a butadiene-styrene-butadiene triblock copolymer has a relatively good balance in Izod impact strength at low temperatures and flexural modulus but is inferior in surface gloss. Thus, the compositions of Examples 1-1 to 1-7 are highly evaluated in respects of Izod impact strength, flexural modulus, surface gloss and film strength and accordingly possess balanced properties. Examples 1-8 to 1-14 and Comparative Examples 1-7 to 1-10 In the same manner as in Examples 1-1 to 1-7, master pellets were prepared using each of the hydrogenated diene copolymer Sample Nos. 1-8 to 1-11 shown in Table I-1. The master pellets had no adhesivity. The master pellets and the same polypropylene resin as used in Examples 1-1 to 1-7 were subjected to the same treatment as in Examples 1-1 to 1-7, to obtain resin compositions of Examples 1-8 to 1-11 according to this invention. For comparison, the ethylene-propylene copolymer I used in Comparative Example 1-1 was melt-kneaded with the same polypropylene resin at weight ratios of 20/80, 30/70, 40/60 and 50/50 to obtain resin compositions of Comparative Examples 1-7 to 1-10, respectively. Each composition was subjected to the same treatment as in Examples 1-1 to 1-7 to prepare test pieces and then measured for physical properties. The results obtained are shown in Table I-3. As is clear from Table I-3, the compositions of Examples 1-8 to 1-11 according to this invention, each using a hydrogenated diene copolymer falling within the higher vinyl content region than the line indicated by the interrelation equation, x = y + 50 in which x is a vinyl content (%) in the copolymer and 50 ≦ x ≦ 90 and y is an alkyl aromatic compound content (%) in the copolymer and y ≦ 20, are superior in processability, Izod impact strength at low temperatures and surface gloss. These compositions, as compared with the compositions of Comparative Examples 1-3 to 1-6 containing the same amount of the same polypropylene resin, have improved flexibility and significantly improved low temperature impact resistance. Meanwhile, the compositions of Comparative Examples 1-8 to 1-10 give low flexural modulus when the proportion of ethylene-propylene copolymer in the composition is made high, but has very low flowability and accordingly inferior processability. In Examples 1-12 to 1-14, the blending ratios of the components (A) and (B) were changed, but each composition clearly exhibits the meritorious effects of this invention. Reference Example 2 Preparation of hydrogenated diene copolymers (1) Into a 5-liter autoclave were charged 2,500 g of cyclohexane, 150 g of styrene and 350 g of 1,3-butadiene, all of which had been degassed and dehydrated. Thereto were added 2.5 g of tetrahydrofuran and 0.34 g of n-butyllithium. The resulting mixture was subjected to temperature-elevating polymerization wherein the polymerization temperature was elevated from 30°C to 80°C. When the conversion reached approximately 100%, 0.14 g of SiCl₄ was added to the reaction mixture. Then, 2,6-di-tert-butyl catechol was added, and the resulting mixture was subjected to steam stripping to remove the solvent and dried by a hot roll at 120°C to obtain a polymer. The thus obtained styrene-butadiene copolymer had a vinyl content of 30%, a styrene content (Bd-ST) of 30% by weight and a tri- or more-branched polymer content of 56% by weight. When analyzed by GPC, the copolymer had a number-average molecular weight of 32,000 and a Mw/Mn of 1.5. (2) The conjugated diene copolymer obtained in (1) above was charged into a 3-liter autoclave to prepare a 15% cyclohexane solution thereof. The autoclave inside was purged with nitrogen, and to the solution was added a catalyst solution of nickel naphthenate : n-butyllithium : tetrahydrofuran = 1 : 8 : 20 (molar ratio) which had been prepared in a different vessel, at a proportion of 1 mole (in terms of nickel) per 2,000 moles of the olefin portion of the copolymer. Then, hydrogen was introduced into the reaction system, and hydrogenation reaction was effected at 70°C. In the reaction, the hydrogenation percentage was controlled based on the amount of hydrogen absorbed and consumed. Thereafter, the hydrogen in the reaction system was replaced by nitrogen, and 1 PHR of 2,6-di-tert-butyl-p-cresol was added as an antioxidant. Catalyst removal and coagulation were repeated, followed by drying according to a conventional method, to obtain a hydrogenated diene copolymer (Sample No. 2-1) having a hydrogenation percentage of 90%. Sample Nos. 2-2 to 2-13 were obtained in the same manner. Incidentally, Sample Nos. 2-1 to 2-8 are components (A) falling within the range of this invention, and Sample Nos. 2-9 to 2-13 are outside the range of this invention. Examples 2-1 to 2-11 (not falling within the invention) Compositions were prepared according to the compounding recipes shown in Table II-1. From each of the compositions were prepared test pieces for evaluation, using an injection machine. The test pieces were evaluated for physical properties to obtain the results shown in Table II-1. The physical properties of each thermoplastic resin composition were measured in accordance with the following test methods: (1) Izod impact strength (1/4 in., notched) Measured in accordance with ASTM D 256 on a molded article prepared by molding the resin by an 8-ounce injection machine (cylinder temperature = 200°C). (2) Tensile strength Measured in accordance with ASTM D 638 on a molded article prepared by molding the resin by an 8-ounce injection machine (cylinder temperature = 200°C). (3) Gloss Gloss at 45° reflection was measured in accordance with ASTM D 523 on a molded article prepared by molding the resin by an 8-ounce injection machine (cylinder temperature = 200°C). (4) Weather resistance A sample was exposed for 1,000 hours in a sunshine weathermeter (WEL-6XS-DC manufactured by Suga Shikenki K.K.) using a carbon arc as a light source, and then measured for Izod impact strength. Test conditions Black panel temperature: 63 ± 3°C Chamber inside humidity: 60 ± 5% R.H. Rainfall cycle: 18 minutes every two hours Carbon exchange cycle: 60 hours Izod impact strength: ASTM D 256 (Sectional area: 1/8 in. x 1/2 in.) Comparative Examples 2-1 to 2-5 Compositions were prepared according to the compounding recipes shown in Table 2-1. Test pieces were prepared from each composition in the same manner as in Examples 2-1 to 2-11 and evaluated in accordance with the same test methods as used in Examples 2-1 to 2-11. The evaluation results are shown in Table II-1. Reference Example 3 Preparation of hydrogenated diene copolymers (1) Preparation of Sample No. 3-1 (i) Into a 5-liter autoclave were charged 2,500 g of cyclohexane, 150 g of styrene and 350 g of 1,3-butadiene, all of which had been degassed and dehydrated. Thereto were added 2.5 g of tetrahydrofuran and 0.34 g of n-butyllithium. The resulting mixture was subjected to temperature-elevating polymerization wherein the polymerization temperature was elevated from 30°C to 80°C. When the conversion reached approximately 100%, 0.14 g of SiCl₄ was added to the reaction mixture. Then, 2,6-di-tert-butylcatechol was added, and the resulting mixture was subjected to steam stripping to remove the solvent and dried by a hot roll at 120°C to obtain a polymer. The thus obtained styrene-butadiene copolymer had a vinyl content of 30%, a styrene content of 30% by weight and a tri- or more-branched polymer content of 56% by weight. When analyzed by GPC, the copolymer had a molecular weight distribution (Mw/Mn) of 1.5. (ii) The conjugated diene copolymer obtained in (i) above was charged into a 3-liter autoclave to prepare a 15% cyclohexane solution thereof. The autoclave inside was purged with nitrogen, and a catalyst solution of nickel naphthenate : n-butyllithium : tetrahydrofuran = 1 : 8 : 20 (molar ratio) which had been prepared in a different vessel was added in a proportion of 1 mole (in terms of nickel) per 2,000 moles of the olefin portion of the copolymer. Then, hydrogen was introduced into the reaction system, and hydrogenation reaction was effected at 70°C. In the reaction, the hydrogenation percentage was controlled based on the amount of hydrogen absorbed and consumed. Thereafter, the hydrogen in the reaction system was replaced by nitrogen, and 1 PHR of 2,6-di-tert-butyl-p-cresol was added as an antioxidant. Catalyst removal and coagulation were repeated, followed by drying according to a conventional method, to obtain a hydrogenated diene copolymer (Sample No. 3-1) having a hydrogenation percentage of 95%. (2) Preparation of Sample No. 3-2 The same procedure as in Reference Example 3-(1)-(i) was repeated, except that no coupling reaction was effected, to obtain a styrene-butadiene copolymer having a vinyl content of 30% and a styrene content of 30% by weight. The copolymer was subjected to the same treatment as in Reference Example 3-(1)-(ii) to obtain a hydrogenated diene copolymer (Sample No. 3-2) having a hydrogenation percentage of 98%. (3) Preparation of Sample Nos. 3-3 to 3-5 Hydrogenated diene copolymers (Sample Nos. 3-3 to 3-5) were obtained in the same manner. All of these hydrogenated diene copolymers (Sample Nos. 3-1 to 3-5) are shown in Table III-1. Analytical methods The styrene content was obtained from a calibration curve prepared by an infrared method based on the absorption by phenyl group at 679 cm⁻¹. The vinyl content was obtained by an infrared method (Morrero method). The molecular weight, molecular weight distribution (Mw/Mn) and coupling efficiency were obtained by gel permeation chromatography (GPC). The hydrogenation percentage was calculated from the spectrum decrease in the unsaturation portion in a H-NMR spectrum (100 MHz) obtained at a 15% concentration using ethylene tetrachloride as a solvent. Examples 3-1 to 3-17 (not falling within the invention) [Compositions containing an optional polyamide resin] Polyphenylene ether resins as the component (B) were prepared as follows: (1) Polymer B-1 (polyphenylene ether) This polymer was obtained by subjecting 2,6-xylenol to oxidation coupling polymerization. Polymer B-1 had an intrinsic viscosity [η] of 0.4 dl/g as measured at 30°C in chloroform. (2) Polymer B-2 (polyphenylene ether) This polymer was obtained by subjecting a mixture of 2,6-xylenol and 2,3,6-trimethylphenol = 90/10 (molar ratio) to oxidation coupling polymerization. Polymer B-2 had an intrinsic viscosity [η] of 0.40 dl/g as measured under the same conditions as above. (3) Polymer B-3 (maleic anhydride-modified polyphenylene ether) 100 parts by weight of polymer B-1, 2 parts by weight of maleic anhydride and 1.0 part by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane were dry blended at room temperature. The blend was melt-kneaded using a vented twin-screw extruder in which the screws were rotated in the same direction at a cylinder temperature of 280°C at 150 rpm and then pelletized to obtain pellets of maleic anhydride-modified polyphenylene ether. The following polyamides were used as the component (C): (1) Polymer C-1: Nylon 6 (Amylan CM1017 manufactured by TORAY INDUSTRIES CO., LTD.) (2) Polymer C-2: Nylon 6 (Amylan CM1007 manufactured by TORAY INDUSTRIES CO., LTD.) (3) Polymer C-3: Nylon 6,6 (Amylan CM3006 manufactured by TORAY INDUSTRIES CO., LTD.) (4) Polymer C-4: Nylon 4,6 manufactured by DSM. (5) Polymer C-5: PBT Duranex XD499 manufactured by Polyplastics K.K. (6) Polymer C-6: PET RY523 manufactured by Nihon Unipet K.K. Components (A), (B), (C) and maleic anhydride were mixed according to the compounding receipt shown in Table III-2. The first stage components and the second stage component in Table III-2 indicate that in the extrusion and kneading step, the first stage components were added at the first stage and the second stage component was added in the middle of extruder. Each mixture was pelletized using a twin screw extruder (PCM-45 manufactured by Ikegai Corp.) at 300 rpm. Each of the resulting thermoplastic resin compositions in the pellet form was thoroughly dried in a dehumidifying drier and then subjected to injection molding by an injection machine to prepare test pieces. The test pieces were evaluated for impact resistance, heat resistance and surface appearance of molded article in accordance with the following test methods to obtain the results shown in Table III-2: Impact resistance Measured in accordance with ASTM D 256 (thickness: 1/4 in., notched). Heat resistance (amount of sag when heated) A test piece of 1/8 in. x 1/2 in. x 5 in. was fixed leaving a 10-cm length free and kept horizontally. The test piece was allowed to stand in a constant temperature chamber at 180°C or 190°C for 1 hour. Then, the amount (mm) of sag of the end was measured. Surface appearance of molded article A plate having a weld portion was prepared, and the weld portion was visually checked according to the following criterion: ○ : It is difficult to detect the weld portion and the appearance of the weld portion is good. ▵ : The weld portion is somewhat detectable. x : It is easy to detect the weld portion and the appearance of the weld portion is no good. Examples 3-18 and 3-19 and Comparative Examples 3-5 and 3-6 [Composition containing a polyphenylene ether resin as the component (B)] Polymer B-4 A modified polyphenylene ether resin obtained by melt-mixing 40% by weight of Polymer B-1 (obtained by subjecting 2,6-xylenol to oxidation coupling polymerization) and 60% by weight of a polystyrene (Toporex 500-51 manufactured by Mitsui Toatsu Chemicals, Inc.).

Claims: A hydrogenated diene copolymer resin composition comprising (A) 5-70% by weight of a hydrogenated diene copolymer which is a hydrogenation product of a random copolymer of at least one conjugated diene and 3-50% by weight of an alkenyl aromatic compound having a number average molecular weight of 5,000-1,000,000 and a molecular weight distribution (Mw/Mn) of 10 or less, the vinyl content in the diene portion of the random copolymer being 10-90%, at least 70% of the olefinic unsaturation of the random copolymer being hydrogenated, and (B) 95-30% by weight of a polypropylene resin. The hydrogenated diene copolymer resin composition according to Claim 1, wherein at least 80% of the olefinic unsaturation of the random copolymer is hydrogenated. The hydrogenated diene copolymer resin composition according to Claim 1, wherein the random copolymer has a number average molecular weight of 30,000 to 300,000. The hydrogenated diene copolymer resin composition according to Claim 1, wherein the random copolymer has a molecular weight distribution (Mw/Mn) of 6 or less. The hydrogenated diene copolymer resin composition according to Claim 1, wherein the conjugated diene of the random copolymer is selected from the group consisting of 1,3-butadiene, isoprene, 1,3-pentadiene, 2,2′-dimethylbutadiene and 3-ethylbutadiene. The hydrogenated diene copolymer resin composition according to Claim 1, wherein the conjugated diene of the random copolymer is selected from the group consisting of 1,3-butadiene, isoprene and 1,3-pentadiene. The hydrogenated diene copolymer resin composition according to Claim 1, wherein the conjugated diene of the random copolymer is 1,3-butadiene. The hydrogenated diene copolymer resin composition according to Claim 1, wherein the alkenyl aromatic compound of the random copolymer is selected from the group consisting of styrene, α-methylstyrene, p-methylstyrene, p-ethylstyrene and vinylnaphthalene. The hydrogenated diene copolymer resin composition according to Claim 1, wherein the alkenyl aromatic compound of the random copolymer is selected from the group consisting of styrene, p-methylstyrene and p-ethylstyrene. The hydrogenated diene copolymer resin composition according to Claim 1, wherein the alkenyl aromatic compound of the random copolymer is styrene. The hydrogenated diene copolymer resin composition according to Claim 1, wherein the random copolymer is of 1,3-butadiene and styrene. The hydrogenated diene copolymer resin composition according to Claim 1, wherein the (B) component is polypropylene resin. The hydrogenated diene copolymer resin composition according to Claim 12, wherein the polypropylene resin has a melt flow index of 0.3-100 g/10 min at 230°C. The hydrogenated diene copolymer resin composition according to Claim 12, wherein the polypropylene resin is at least one member selected from the group consisting of homopolymer of propylene and copolymers of propylene and an α-olefin having 4 to 12 carbon atoms. A process for producing a hydrogenated diene copolymer resin composition of Claim 1, which comprises melt-mixing (A) 50-80% by weight of a hydrogenated diene copolymer which is a hydrogenation product of a random copolymer of at least one conjugated diene and 3-50% by weight of an alkenyl aromatic compound having a number average molecular weight of 5,000-1,000,000 at a molecular weight distribution (Mw/Mn) of 10 or less, the vinyl content in the diene portion of the random copolymer being 10-90%, at least 70% of the olefinic unsaturation of the random copolymer being hydrogenated, and (B) 50-20% by weight of a polypropylene resin, and further melt-mixing the resulting mixture in the form of pellets or a block with the same at least one resin as above.

Inventors: GOSHIMA KUNIO, HASEGAWA MINORU, KIMURA SHINICHI, MAEDA MINORU, MAKINO KENYA, MAWATARI MASAAKI, SHIBATA TOORU, TAKEUCHI MIKIO, TAKEUCHI YASUO, TERAMOTO TOSHIO, GOSHIMA, KUNIO, HASEGAWA, MINORU, KIMURA, SHINICHI, MAEDA, MINORU, MAKINO, KENYA, MAWATARI, MASAAKI, SHIBATA, TOORU, TAKEUCHI, MIKIO, TAKEUCHI, YASUO, TERAMOTO, TOSHIO
Applicants: JAPAN SYNTHETIC RUBBER CO LTD, JAPAN SYNTHETIC RUBBER CO., LTD.
Application year: 1989
Main classification: C08L9
IPC codes: C08L15, C08L71, C08L77, C08L25, C08L21, C08L67, C08L47, C08L23, C08J3, C08L37