JPS6351460B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber-modified styrenic resin composition with improved impact resistance. More specifically, the present invention relates to a rubber-modified styrenic resin composition containing an organic polysiloxane and having a specific structure. Several methods are known for improving the impact resistance of rubber-modified thermoplastic resin compositions, such as increasing the amount of rubbery polymer in the resin composition, and increasing the amount of polymer forming a continuous phase in the resin composition. Examples include a method of adding a substance that increases the molecular weight of the material and improves impact resistance. On the other hand, virtually
For the purpose of improving the impact resistance of rubber-modified thermoplastic resins such as ABS resins, several methods have been proposed so far that include the addition of organosilicon compounds as one of the requirements. For example, Special Public Interest Publication No. 49-29947
describes a composition in which an organosilicon compound is added together with a fatty acid metal salt to a blend of an emulsion polymerized ABS resin and an AS resin with a specific structure, and in JP-A-53-124561, liquid paraffin and polysiloxane are added to a solution polymerized ABS resin solution. JP-A-55-3494 describes a method of adding polysiloxane and a specific stearic acid derivative to ABS resin in combination; No. 31896 discloses a composition in which a silicourethane derivative is added to an ABS resin. However, the methods described in Japanese Patent Publication No. 49-29947 and Japanese Patent Application Laid-open No. 55-3494 have the limitation that specific additives such as fatty acid metal salts and stearic acid derivatives must be added to the ABS resin in combination with organosilicon compounds. Furthermore, since these additives generally have a subtle influence on the molding processability, particularly mold releasability, appearance of molded products, etc. of the resin composition, it is desirable that the above-mentioned restrictions do not apply. The method described in JP-A-53-124561 has the limitation of adopting a solution polymerization method, which is not economically advantageous in terms of polymer recovery and purification compared to bulk polymerization or suspension polymerization. The effect of improving impact resistance is also not sufficient. Furthermore, the method described in JP-A-55-31896 has the limitation that an organic silicon compound with a special structure such as a silicourethane derivative must be used as an additive for improving impact resistance. As described above, the conventional state of the art related to the addition of organosilicon compounds for the purpose of improving impact resistance is quite limited and insufficient, and is not necessarily sufficient for improving impact resistance. Ta. In recent years, there has been an increasing demand for cost reduction in the field of rubber-modified thermoplastic resins, especially in application fields that require relatively high rigidity and high impact resistance. It is hoped that the emergence of For example, costs for mechanical parts and housings for light electrical products are being reduced by thinning resin products, and higher impact resistance than before is required. The present inventors have conducted intensive research with the aim of providing a rubber-modified thermoplastic resin composition with excellent impact resistance free from the above-mentioned limitations, and have developed a rubber-modified styrenic resin composition having a specific resin structure. The present invention was completed by discovering that by adding a specific organosilicon compound, that is, an organopolysiloxane, a product can be freed from the above-mentioned limitations and has excellent high rigidity and high impact resistance. That is, the present invention provides a rubber-modified styrenic resin composition comprising a homopolymer or copolymer of a styrenic monomer in which a rubbery polymer constitutes soft component particles and is dispersed therein. 70% by weight or more of the aggregate is polybutadiene in which the 1.2 vinyl bond structure is in the range of 15 mol % or more and 30 mol or less, (b) the average particle size of the soft component particles is in the range of 0.5 to 2.5 μ, (c) A rubber-modified styrenic resin composition containing 0.002 to 0.2% by weight of organic polysiloxane as silicon content. Constituent element (a) of the present invention is 70% by weight of the rubbery polymer.
The above means that the 1/2 vinyl bond structure is 15 mol% or more30
It is polybutadiene (hereinafter referred to as high vinyl PBR) with a molecular weight of less than 15% by mole, and other rubbery polymers such as polybutadiene with a 1.2 vinyl bond structure of less than 15 mol% (low vinyl PBR), 1.
When polybutadiene, styrene-butadiene copolymer rubber (SBR), nitrile rubber, etc. in which the divinyl bond structure exceeds 30 mol % is used, the effect of improving impact resistance is small. The reason for this is not clear, but in the case of polybutadiene in which the 1/2 vinyl bond structure exceeds 30%, the 1/2 vinyl bonds are likely to cause crosslinking, resulting in excessive crosslinking of the soft component particles, resulting in improved impact resistance. It is assumed that the effect will be smaller. However, other rubbery polymers other than Hi-Vinyl PBR may be used in combination without impeding the purpose of the present invention, and the amount used is 30% or less of the total amount of rubbery polymers used. The above-mentioned Hi-vinyl PBR can be produced by a known production method, for example, by polymerizing 1,3-butadiene using a catalyst containing an organolithium compound. An example of the above-mentioned rubber is the product name Asaprene 700X (manufactured by Asahi Kasei Corporation). The solution viscosity of the above Hi-Vinyl PBR (the viscosity of a 5% styrene solution at 30°C) is not a limitation of the present invention, but the solution viscosity of the rubbery polymer is a factor that has a large effect on the average particle size of the soft component particles. If the solution viscosity is too large, it will be difficult to adjust the average particle size of the soft component particles within the range of the present invention, so it is preferably in the range of 30 to 200 CST. Constituent requirement (b) of the present invention is that the average particle size of the soft component particles is in the range of 0.5 to 2.5 μ, and the 0.5 μ
When the soft component particles have an average particle diameter of less than 2.5 μm or more than 2.5 μm, the effect of improving impact resistance is small. The average particle diameter referred to here is calculated by taking a transmission electron micrograph of the resin composition using an ultra-thin section method, measuring the particle diameter of 200 to 500 soft component particles in the photograph, and using the following formula. be. Average particle size = ΣniDi ² /ΣniDi (where ni is the number of soft component particles with particle size Di) The average particle size of the soft component particles depends on the molecular weight of the rubbery polymer used, the solution viscosity, and the amount of the molecular weight modifier. , the stirring intensity during polymerization, the molecular weight of the polymer produced by polymerization, etc., and by changing these, the particle size can be adjusted to the desired size. Constituent feature (c) of the present invention is that the composition contains an organic polysiloxane in an amount of 0.002 to 0.2% by weight as silicon content. What is organic polysiloxane? General formula (R ₁ and R ₂ represent an alkyl group, an aryl group, or an aralkyl group) A homopolymer-type organic polysiloxane consisting of one type of structural unit and a combination of two or more types of structural units. Any of random type, block type, and graft type copolymerized organic polysiloxanes may be used. Further, these organic polysiloxanes may be organic polysiloxanes in which some of the organic groups are substituted with hydroxyl groups, alkoxy groups, hydroxyalkyl groups, or polyhydroxyalkylene groups. These organic polysiloxanes can also be used as a mixture of two or more. Examples of these organic polysiloxanes include dimethylpolysiloxane, methylphenylpolysiloxane, and diphenylpolysiloxane. Although the viscosity of the above organic polysiloxane is not limited to the present invention, the viscosity is 10% at 30°C.
Preferably in the range ~100000CST,
Anything less than 10CST has high volatility, so adding it will cause poor appearance when molded.On the other hand, if it has a high viscosity of more than 100,000CST, it will be difficult to mix uniformly into the resin composition. will arise. The amount of organic polysiloxane added is required to be 0.005 to 0.2% by weight as a silicon content, preferably in the range of 0.02 to 0.1% by weight. Then
If the amount added is less than 0.005% by weight, the effect of improving impact resistance will be poor, and if the amount added is more than 0.2% by weight, the effect of improving impact resistance will reach a plateau, but other properties such as hardness, tensile strength, and heat resistance will decrease. do. The method of adding the organic polysiloxane is not particularly limited, and it can be added at each stage of manufacturing the rubber-modified styrenic resin composition, for example, adding it to the monomer to be polymerized, or adding it at an intermediate stage in the polymerization process. Any of the following methods can be adopted: a method of adding in the extrusion process, a method of adding directly in the molding process, etc. In addition, when adding in a process after the extrusion process,
It is also possible to dilute the organic polysiloxane with a resin of the same quality as the resin composition with which it is premixed and add it in the form of pellets that are easy to handle. However, the preferred method of addition is to add it to the monomers to be polymerized or to add it during the extrusion process. In addition, the amount of the rubbery polymer constituting the soft component particles in the resin composition of the present invention depends on the resin composition.
A range of 1 to 15 parts by weight per 100 parts by weight is desirable. If the amount of the rubbery polymer is less than 1 part by weight, the impact resistance will not be sufficiently developed, and therefore the impact resistance improvement effect of the present invention will be small. Furthermore, if the amount of the rubbery polymer exceeds 15 parts by weight, the impact resistance improvement effect reaches a plateau, and an effective improvement effect cannot be expected, and it is difficult to manufacture economically advantageously. Become. The amount of the rubbery polymer used is particularly preferably in the range of 2 to 10 parts by weight. The styrenic resin constituting the rubber-modified styrenic resin composition of the present invention is a homopolymer or copolymer of styrene monomers. Styrenic monomers include, for example, styrene, α-alkylstyrene, nuclear-substituted mono- or dialkylstyrene,
One or more types of nuclear-substituted mono- or dichlorostyrene, nuclear-substituted mono- or dibromostyrene, etc. are used. Preferred are homopolymers of styrene monomers, copolymers of styrene and α-methylstyrene, and copolymers of styrene and nuclear-substituted mono- or dibromostyrene, and particularly preferred are styrene homopolymers. The resin composition of the present invention can be produced by various known methods such as blending, emulsion polymerization, bulk polymerization, suspension polymerization, etc., but preferably in the presence of a rubbery polymer. A bulk polymerization method or a bulk one-suspension two-stage polymerization method in which a styrenic monomer is polymerized is applied, and for example, a production method as described below is adopted. That is, after dissolving Hyvinyl PBR in styrene at 60 to 80°C, bulk polymerization is performed at 90 to 120°C with stirring until the polymerization rate of styrene reaches 10 to 40%.
This process is called prepolymerization, and during this process, the rubbery polymer dissolved in styrene separates and precipitates due to the polymerization of styrene, and is dispersed in the form of particles in the styrene solution of polystyrene under the action of stirring. do. In the main polymerization step that follows the prepolymerization step, bulk polymerization may be continued, or suspension polymerization may be performed by suspending the polymer in an aqueous phase containing a suspending agent such as calcium phosphate. Polymerization is usually carried out until the polymerization rate is substantially 100%, but if the polymerization rate is low, e.g. 60-80%.
It may be recovered by an operation such as performing polymerization until the end of the reaction and distilling off unreacted styrene. The polymer obtained as described above is pelletized by an extrusion process when all polymerization steps are carried out by bulk polymerization, and the bead-shaped polymer slurry obtained when all polymerization steps are carried out by suspension polymerization is After washing, dehydration, and drying, it is usually pelletized in an extrusion process or used as is for molding. Various additives such as chain transfer agents, polymerization initiators, plasticizers, antioxidants, lubricants, colorants, etc. that are commonly used in polymerization and extrusion steps can be used. Moreover, the resin composition of the present invention can be used as a conventional substantially compatible resin composition, especially a non-rubber modified resin composition,
For example, it can be used by blending it with general polystyrene or AS resin in any proportion. The rubber-modified styrenic resin composition in which the rubbery polymer specified in the present invention constitutes soft component particles and is dispersed therein can be obtained by adding an organosilicon compound to the previously known rubber-modified thermoplastic resin. This method significantly improves the impact resistance of molded products, especially the impact strength evaluated by Izot impact, without being subject to any special restrictions on the manufacturing method and additives used in combination. The present invention will be specifically described below with reference to Examples. Example 1 Hyvinyl PBR (Asahi Kasei Co., Ltd.: trade name Asaprene 700X, 1/2 vinyl bond 19 mol%) 7.5 kg, styrene 92.5 kg, and t-dodecyl mercaptan 0.07 kg were charged into a polymerization tank with an internal volume of 120 and equipped with a stirrer, and stirred. After heating at 65°C for 5 hours to make a homogeneous solution, prepolymerization was performed at 115°C for 5 hours. The polymerization rate of styrene in this case was about 30%. Prepare the following aqueous phase in a polymerization tank with an internal volume of 300 mm and equipped with a stirrer, add 150 kg of water, 3 kg of tribasic calcium phosphate, and suspend the polymerization solution obtained in the above prepolymerization.
0.1 kg of 2.5 dimethyl-2.5 di-t-butyl peroxyhexane was added and main polymerization was carried out at 110°C for 7 hours. After the obtained polymer particles were washed, separated, and dried, a predetermined amount of organic polysiloxane master pellets prepared separately were added, pelletized using a 40 m/mφ extruder, and test pieces were formed by injection molding. Impact resistance and tensile strength were measured using injection molded test pieces according to ASTM D-256 and
Measured according to ASTMD-638. The average particle diameter of the soft component particles was measured and calculated from the above-mentioned electron micrograph of the ultrathin section of the pellet. The organic polysiloxane master pellet is dimethylpolysiloxane (Toray Industries, Inc.: trade name, Toray Silicon SH-
200, 10000CS, Si content approximately 38%) and GP polystyrene (Mitsui Toatsu Chemical Co., Ltd.: trade name, Toporex
525-51) to produce 10% master pellets using a twin screw extruder. Examples 2 and 3 Molded pieces were made in the same manner as in Example 1, except that the type and amount of rubbery polymer, amount of styrene, and amount of dimethylpolysiloxane added were changed as shown below. and tensile strength were measured. In addition, in accordance with changes in the type and amount of the rubbery polymer used, the stirring rotation speed in the prepolymerization step was changed in order to adjust the average particle diameter of the soft component particles to the target value.

[Table] Note that the amount of high vinyl PBR in the rubbery polymer of Example 2 is 80% by weight. Example 4 At the start of the prepolymerization process, dimethylpolysiloxane (Toray Industries, Inc.: trade name, Toray Silicon SH-200,
Polymer particles were produced in the same manner as in Example 1, except that 1000CS (Si content approximately 38%) was added to give a silicon content of 0.05%, and extrusion molded without adding master pellets. The molded pieces were prepared and their impact resistance and tensile strength were measured. Comparative Example 1 A molded piece was prepared in the same manner as in Example 1 except that extrusion was carried out without adding master pellets, and the impact resistance and tensile strength were measured. Comparative Example 2 Rubber-like polymer is made of low vinyl PBR (Asahi Kasei Co., Ltd.:
Product name, diene NF35A, 1/2 bond 10.2%) 7.5
A molded piece was prepared in the same manner as in Example 1 except that the weight was changed to kg, and the impact resistance and tensile strength were measured. Comparative Examples 3 to 5 Molded pieces were prepared in the same manner as in Example 2, except that the type and amount of rubbery polymer used were changed as shown in Table 1, and impact resistance and tensile strength were measured. Here, in Comparative Example 3, the Hi-vinyl PBR content with respect to the total rubber-like polymer was 50%, which is outside the scope of the present invention. In Comparative Examples 4 and 5, the average particle size of the soft component particles is outside the scope of the present invention. Note that the stirring rotation speed in the prepolymerization step was changed in the same manner as in Examples 2 and 3 in accordance with changes in the type and amount of the rubbery polymer used. The measurement results of Examples 1 to 4 and Comparative Examples 1 to 5 are summarized in Table 1.

【table】

Claims (1)

[Scope of Claims] 1. A rubber-modified styrenic resin composition comprising a homopolymer or copolymer of a styrenic monomer in which a rubbery polymer is dispersed in the form of soft component particles, comprising: (a) the rubber; 70% by weight or more of the shaped polymer is polybutadiene in which the 1,2-vinyl bond structure is in the range of 15 mol% or more and 30 mol% or less, and (b) the average particle size of the soft component particles is in the range of 0.5 to 2.5μ. (c) A rubber-modified styrenic resin composition characterized in that the composition contains 0.002 to 0.2% by weight of organic polysiloxane as silicon content. 2. The composition according to claim 1, wherein the rubber-modified styrenic resin composition is produced by a continuous bulk polymerization method or a bulk-suspension two-stage polymerization method in the presence of a rubbery polymer.