JPH0689204B2 - Styrene resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a novel styrene-based resin composition. More specifically, the present invention provides a high impact strength suitable as a material for OA equipment parts and sliding materials. The present invention also relates to a styrene resin composition having excellent balance of physical properties such as having excellent gloss and slidability.

[Prior Art] Styrene-based resins are used as materials for keyboard parts such as reels for video tapes, personal computers and touch-tone phones. However, when used as these materials, good slidability in addition to impact resistance is required. It

It is known that it is effective to contain a polyorganosiloxane in the styrene resin in order to impart the sliding property to the styrene resin. For example, a composition containing a polyorganosiloxane having self-lubricating property is known. Manufacturing method (Japanese Patent Publication No. 52-43863, Japanese Patent Publication No. 63-15287)
Also disclosed are styrenic resin compositions containing polyorganosiloxane (JP-A-60-217254).

However, since the rubber-modified styrene resin used for these styrene resins has a salami structure, the styrene resin obtained by mixing polyorganosiloxane with this resin has improved slidability and impact resistance. However, there was a drawback that the gloss was low. Therefore, there is a problem in that it cannot be escaped from the limitation of use.

[Problems to be Solved by the Invention] The present invention overcomes the drawbacks of such conventional styrene resin compositions, has high impact strength, and has excellent physical properties such as excellent gloss and slidability. It was made for the purpose of providing an excellent styrene resin composition.

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies in order to develop a styrene resin composition having an excellent balance of physical properties such as impact resistance, gloss, and slidability, and as a result, rubber modification It was found that the use of a rubber-modified styrenic resin composition having an occlusion structure in a dispersed rubber form as the styrene-based resin composition can meet the above-mentioned object, and the present invention has been completed based on this finding.

That is, the present invention relates to (a) 100 parts by weight of a rubber-modified styrenic resin composition comprising a styrenic polymer and a rubbery polymer, and (b) a polydimethylsiloxane or polydimethylsiloxane having a viscosity at 25 ° C. of 500 to 100,000 centistokes. A composition comprising 1 to 3.5 parts by weight of methylphenylsiloxane,
Further, the rubber-like polymer in the component (a) is a styrene-butadiene block copolymer rubber alone or a styrene-butadiene block copolymer rubber and polybutadiene in which polybutadiene rubber is blended in a proportion of 40% by weight or less. It is a mixture with rubber and has an area average particle size (diameter) of 0.4 to 0.6 μm, and the dispersed rubber form is one rubber particle in which the core is a styrene polymer and the shell is a rubbery polymer. 70% of the occlusion structure that contains 5 or less inclusion occlusions, and at least 50% or more of them contains 1 inclusion occlusion.
The present invention provides a styrene resin composition having the above.

Hereinafter, the present invention will be described in detail.

The rubber-modified styrene resin composition of the component (a) in the styrene resin composition of the present invention is required to have an occlusion structure in the dispersed rubber form.

If the dispersed rubber form does not have an occlusion structure, it will be inferior in impact resistance and gloss.

Here, the occlusion structure means that in one rubber particle,
A structure in which the core is a styrenic polymer and the shell contains 5 or less inclusion occlusions made of a rubbery polymer, and at least 50% or more of the inclusion occlusions are 1 inclusion occlusion.

In the present invention, the occlusion structure as described above is used.
% Or more, and particles such as salami structure
If 30% or more is mixed, good gloss may not be obtained.

The rubber-modified styrene-based resin composition as the component (a) comprises a styrene-based polymer and a rubber-like polymer.

The styrene-based polymer may be a styrene homopolymer or a copolymer of styrene and a monomer copolymerizable with styrene. Examples of the copolymerizable monomer include α-methylstyrene, vinyltoluene, vinylethylbenzene, vinylxylene, pt-butylstyrene and α.
-Aromatic monovinyl compounds such as -methyl-p-methylstyrene, bromostyrene, chlorostyrene, and vinylnaphthalene, acrylonitrile, methyl methacrylate, methyl acrylate, methacrylic acid, acrylic acid, maleic anhydride, and phenylmaleimide. it can.
These monomers may be used alone or in combination of two or more, but usually 50% by weight or less, preferably 40% by weight or less based on all monomers containing styrene. Used in proportion.

On the other hand, as the rubber-like polymer, a styrene-butadiene block copolymer rubber alone or a styrene-butadiene block copolymer in which a polybutadiene rubber is blended in a proportion of 40% by weight or less, preferably 35% by weight or less. A mixture of rubber and polybutadiene rubber is used.

As the styrene-butadiene block copolymer rubber, the molecular weight is in the range of 50,000 to 500,000, and the content of the polymer block formed of styrenes is 10 to 60.
Those in the range of wt% are particularly preferable. This molecular weight
If it is less than 50,000, the impact resistance is not sufficient, 500,
If it exceeds 000, the fluidity at the time of molding will decrease,
Not preferable. Further, if the content of the polymer block formed by styrenes is less than 10% by weight, the gloss is poor,
If it exceeds 60% by weight, the impact resistance tends to decrease. In addition, a polybutadiene rubber having a molecular weight of about 50,000 to 1,000,000 may be appropriately mixed and used with the styrene-butadiene block copolymer rubber.

The molecular weight of this rubber-like polymer is the weight average molecular weight in terms of polystyrene by GPC.

The rubber-like polymer has an occlusion structure and has an area average particle diameter (diameter) of 0.4 to 0.6 μm, and a ratio of the area average particle diameter to the number average particle diameter (diameter) is 1.0 to 2.5, preferably 1.0. It is preferable that the particles having a particle size of about 1.8 are dispersed in the styrene-based polymer as the component (a).

If the area average particle size is less than 0.4 μm, the impact resistance is not sufficient, and if it exceeds 0.6 μm, the gloss tends to decrease. Further, the area average particle diameter is 2.
If it exceeds 5, the gloss tends to decrease.

The styrene-based polymer and the rubber-like polymer are preferably contained in the proportions of 70 to 92% by weight and 30 to 8% by weight, respectively, preferably 72 to 90% by weight and 28 to 10% by weight. is there. If the content of the rubber-like polymer is less than 8% by weight, the impact resistance improving effect tends to be insufficiently exerted, resulting in 30% by weight.
If it exceeds, gloss and fluidity tend to decrease.

The rubber-modified styrenic resin composition as the component (a) can be produced by blending a styrenic polymer and a rubber-like polymer, but is copolymerized with styrene or styrene in the presence of the rubber-like polymer. It is preferably prepared by polymerizing with possible monomers.

Next, one example of a preferred method for producing the resin composition of the present invention by the bulk-suspension two-step polymerization method will be described. First, styrene or a mixture of styrene and a monomer copolymerizable with styrene,
A rubbery polymer is added and heated as necessary to dissolve. It is preferable that this dissolution be performed as uniformly as possible.

Next, to this solution, a molecular weight regulator (chain transfer agent) such as alkyl mercaptan and a polymerization initiator such as an organic peroxide used as necessary are added, while heating to a temperature of about 70 to 150 ° C., Preliminary polymerization by bulk polymerization is carried out with stirring until the degree of polymerization reaches 10 to 60%. In this prepolymerization step, the rubbery polymer is dispersed into particles by stirring.

Then, the prepolymerized solution is suspended in an aqueous phase using tricalcium phosphate or polyvinyl alcohol as a suspending agent,
Usually, suspension polymerization (main polymerization) until the degree of polymerization approaches 100%.
I do. If necessary, heating may be further continued after this main polymerization step.

Examples of the molecular weight modifier include mercaptans such as α-methylstyrene dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, 1-phenylbutene-2-fluorene, dipentene and chloroform, terpenes, halogen compounds and the like. You can

Examples of the polymerization initiator used as desired include peroxy compounds such as 1,1-bis (t-butylperoxy) cyclohexane and 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane. Ketals, dicumyl peroxide, di-t-butyl peroxide, 2,5
-Dialkyl peroxides such as dimethyl-2,5-di (t-butylperoxy) hexane, benzoyl peroxide, diallyl peroxides such as m-toluoyl peroxide, dimyristyl peroxydicarbonates, t-butylperoxyisopropyl carbonate, etc. Examples thereof include peroxyesters such as peroxydicarbonate, ketone peroxides such as cyclohexanone peroxide, and organic peroxides such as hydroperoxides such as p-menthane hydroperoxide.

The particle size, particle size distribution, and particle structure of the rubber-like polymer can be controlled by the stirring rotation speed and the amount of the molecular weight modifier used, and the gel amount and the swelling index are the type and amount of the catalyst, It can be controlled by the reaction temperature, reaction time and the like.

Next, the slurry thus obtained is treated by an ordinary means to take out a bead-like reaction product, which is dried and then pelletized according to a conventional method to form a rubber-modified styrene having a dispersed rubber form having an occlusion structure. A system polymer is obtained.

The molecular weight of the matrix portion of the rubber-modified styrenic resin composition thus obtained is advantageously in the range of 100,000 to 300,000, preferably 130,000 to 280,000. If the molecular weight is less than 100,000, the impact resistance is poor, and 300,000
If it exceeds, the fluidity during molding becomes insufficient.

In the present invention, as the component (b), the viscosity at 25 ° C is
500 to 100,000 centistokes of polydimethylsiloxane or polymethylphenylsiloxane is used.

The polydimethylsiloxane or polymethylphenylsiloxane used in the present invention has a viscosity of 500 to 100,0 at 25 ° C.
It should be 00 centistokes, but is preferably in the range 800-80,000 centistokes. If the viscosity is less than 500 centistokes, the object of the present invention cannot be sufficiently achieved, and if it exceeds 100,000, it becomes extremely difficult to uniformly disperse it in the composition.

The content ratio of the component (a) and the component (b) in the styrene resin composition of the present invention is in the range of 1 to 3.5 parts by weight of the component (b) with respect to 100 parts by weight of the component (a). If the amount of the component (b) is less than 1 part by weight, the slidability is insufficient, and if it exceeds 3.5 parts by weight, the whiteness of the molded product is remarkable, the appearance is apt to be impaired, the gloss is lowered, and there is a problem in coloring. May occur.

The styrenic resin composition of the present invention can be obtained by blending these components in predetermined amounts, and the production method may be according to a conventional method. For example, each component is premixed by a mixer such as a Henschel mixer, a tumbler blender, and a kneader, and then kneaded by an extruder, or melt-kneaded by a heating roll and a Banbury mixer.

Further, it can also be produced by preparing a master pellet having a high concentration of the component (b) from the component (a) and the component (b) and mixing the master pellet with the component (a). Further, it can be produced by adding the component (b) during the polymerization of the component (a).

The styrene-based resin composition, if desired, various additives usually used, for example, stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, lubricants such as ethylene bis stearamide, and the like, Mineral oil, or 2,6-di-t-
Butyl-4-methylphenol, stearin-β- (3,
5-di-t-butyl-4-hydroxyphenyl) propionate, triethylene glycol-bis-3- (3-
t-Butyl-4-hydroxy-5-methylphenyl) propionate and other hindered phenols and tri (2,
4-di-t-butylphenyl) phosphite, 4,4'-butylidene bis (3-methyl-6-t-butylphenyl-
It is possible to add phosphorus-based antioxidants such as di-tridecyl) phosphite, other ultraviolet absorbers, antistatic agents, release agents, plasticizers, flame retardants, stabilizers, dyes, pigments, and various fillers. it can. In addition, other polymers such as polystyrene and polyphenylene ether may be added.

[Examples] Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Production Example 1 In an autoclave with a squid-type stirring blade having an internal capacity of 5,
Styrene-butadiene block copolymer with a molecular weight of 230,000 and a styrene content of 40 wt% (BL6533 manufactured by Bayer) 527
g, polybutadiene (BR15HB made by Ube Industries, molecular weight 55
10,000) 132 g, styrene 3000 g and n- as a chain transfer agent
Add 1 g of dodecyl mercaptan and stir at 400 rpm.
The bulk polymerization reaction was carried out at 130 ° C. for 4 hours.

Then, in an autoclave with an internal volume 10 squid-type stirring blade, the reaction mixture 3000 g, water 3000 g, polyvinyl alcohol 10 as a suspension stabilizer, benzoyl peroxide 6 g and dicumyl peroxide 3 g as a polymerization initiator, and at 300 rpm. While stirring, the temperature was raised from 80 ° C. to 140 ° C. at a heating rate of 30 ° C./hr, and the reaction was continued for another 4 hours at that temperature to obtain beads of the rubber-modified polystyrene composition.

The beads were pelletized by a single screw extruder at 220 ° C.
When the obtained pellets were analyzed by an electron microscope, they had an occlusion structure in which the area average particle diameter was 0.50 μm and the ratio of the area average particle diameter to the number average particle diameter was 2.2. In addition, the physical properties of the molded product are 96% gloss and Izod impact strength.
It was 14.8 kg / cm / cm. This copolymer had a rubbery polymer content of 18% and a molecular weight of 210,000.

Production Example 2 In Production Example 1, the rotation speed of the stirring blade in the bulk polymerization was
The same procedure as in Production Example 1 was performed except that the speed was set to 500 rpm.

The obtained rubber-modified polystyrene composition has an area average particle size.
It has 90% of occlusion structure of 0.41μm and the ratio of area average particle diameter to number average particle diameter is 2.1, and gloss is 9
9%, Izod impact strength was 10.6kg · cm / cm. This copolymer had a rubbery polymer content of 18% and a molecular weight of 21,500.

Example 1 100 parts by weight of the rubber-modified polystyrene composition obtained in Production Example 1 and 2.5 parts by weight of polydimethylsiloxane (SH-200 oil manufactured by Toray Silicone Co., Ltd.) having a viscosity of 10,000 centistokes at 25 ° C. were preblended. The blended product was melt-kneaded with a single screw extruder at a cylinder temperature of 220 ° C. and injection-molded to prepare a test piece. The physical properties of this test piece are shown in Table 1.

Example 2 In Example 1, the blending amount of polydimethylsiloxane was changed.
The same procedure as in Example 1 was repeated except that the amount was changed to 1.0 part by weight. The physical properties of the obtained test pieces are shown in Table 1.

Example 3 In Example 1, the rubber-modified polystyrene composition obtained in Production Example 2 was used in place of the rubber-modified polystyrene composition obtained in Production Example 1, and the viscosity at 25 ° C. was 10,000 centistokes. 25 ° C instead of dimethylsiloxane
Viscosity of 5,000 centistokes polymethylphenylsiloxane (SH-700 oil manufactured by Toray Silicone)
Example 1 was repeated except that 3.5 parts by weight was used. The physical properties of the obtained test pieces are shown in Table 1.

Comparative Example 1 In Example 1, polydimethylsiloxane having a viscosity of 100 centistokes at 25 ° C. (KF-96ST manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of polydimethylsiloxane having a viscosity of 10,000 centistokes at 25 ° C. of 2.5. The same procedure as in Example 1 was repeated except that the parts by weight were used.

Comparative Example 2 In Example 1, the blending amount of polydimethylsiloxane was changed.
The same procedure as in Example 1 was repeated except that the amount was changed to 0.3 part by weight.

The physical properties of Comparative Examples 1 and 2 are shown in Table 1.

The physical properties of the test pieces were measured by the following methods.

Gloss: Complies with JIS K-7105.

Izod impact strength: Complies with JIS K-7110 (23 ° C notched).

Sliding property: A cylindrical test piece with an outer diameter of 26 mm, an inner diameter of 20 mm, and a height of 15 mm is molded, and a polyorganosiloxane-free product is separately added to 50 mm ² × 3 mm.
Mold into a disc. One end of the cylindrically shaped product of the test piece is brought into contact with the disc surface, and a pressure load of 0.
When the cylinder-shaped product is rotated at a constant rotation speed of 5 kg · f, the rotation speed at which the test piece and the cylinder do not fuse for 30 minutes from the melting limit rotation speed and the time until the fusion The number was used as an index of slidability.

[Effects of the Invention] The styrene resin composition of the present invention has characteristics that the dispersed rubber form has an occlusion structure, so that the impact strength is high, and that the styrene resin composition has excellent gloss and slidability and is excellent in physical property balance. There is.

Claims (1)

[Claims] (1) 100 parts by weight of a rubber-modified styrenic resin composition comprising (a) a styrenic polymer and a rubbery polymer, and (b) a polydimethylsiloxane or poly having a viscosity at 25 ° C of 500 to 100,000 centistokes. A composition comprising 1 to 3.5 parts by weight of methylphenylsiloxane, wherein the rubber-like polymer in the component (a) is a styrene-butadiene block copolymer rubber alone or a polybutadiene rubber of 40% by weight or less. It is a mixture of styrene-butadiene block copolymer rubber and polybutadiene rubber blended in a ratio, the area average particle diameter (diameter) is 0.4 to 0.6 μm, and the dispersed rubber form is one rubber particle. Contains 5 or less inclusion occlusions in which the core is a styrenic polymer and the shell is a rubbery polymer, and at least one of them is included. 70% of the occlusion structure where 50% or more has one inclusion occlusion
A styrene resin composition having the above.