JP2651491B2 - High gloss impact resistant styrenic resin composition - Google Patents

Description

The present invention relates to a novel high gloss impact-resistant styrene resin composition. More specifically, the present invention
The present invention relates to a styrene-based resin composition which is suitable as a material for OA equipment, home appliances, sheets and the like, has a high impact strength, and has excellent gloss and rigidity, and has an excellent balance of physical properties.

[Prior art] Conventionally, in order to improve the impact resistance of a styrene resin,
By blending a rubber-like polymer with polystyrene, or by polymerizing styrene in the presence of a rubber-like polymer, styrene is partially graft-polymerized to the rubber-like polymer, and the rest of styrene becomes polystyrene. Industrially, a so-called rubber-modified polystyrene resin composition is substantially mixed with a rubbery polymer / styrene graft copolymer and polystyrene.

In such a rubber-modified polystyrene resin composition, the rubber-like polymer is usually dispersed in the styrene-based polymer in the form of particles, and the size of the particles and the impact resistance, rigidity, and gloss are close to each other. Having a relationship is well known. That is, the rigidity and gloss are better as the rubber-like polymer particles are smaller, but on the other hand, the impact resistance decreases in proportion to the smaller rubber-like polymer particles,
Below a certain limit, the effect of improving impact resistance is substantially lost.

In a conventional rubber-modified polystyrene resin composition,
In order to obtain the desired impact resistance, the rubbery polymer is dispersed in the polystyrene resin phase as particles having a particle diameter of 1 μm or more, usually in the range of 1 to 10 μm. However, there is a problem that the use of the apparatus cannot be avoided.

Therefore, recently, in order to improve the balance between impact resistance and gloss and rigidity, rubber-like polymers are dispersed in a styrene resin phase in two types, small particles and large particles having different particle sizes. Further, various rubber-modified styrene resin compositions have been proposed. For example, a composition in which small particles have a particle size of 0.5 to 1.5 μm and large particles have a particle size of 4 to 6 μm (Japanese Patent Laid-Open No. 59-1519), a small particle having a particle size of 0.5 to 1.0 μm, A composition in which particles have a particle size of 2.0 to 3.0 μm (US Pat. No. 4,214,056), and a composition in which small particles have a particle size of 0.5 to 1.0 μm and large particles have a particle size of 2 to 3 μm (US Pat. No. 4,146,589).

However, in these compositions, the size of the small particles is in the range of 0.5 to 1.5 μm, and the gloss cannot be said to be sufficient. Also, the particle size of the small particles is 0.1 to 0.6
A polystyrene resin composition having a size of 0.7 μm and large particles of 0.7 to 2.0 μm has been proposed (Japanese Patent Application Laid-Open No. 63-112646). ,
Impact resistance is not always satisfactory.

Further, a composition in which the small particles have a particle size of 0.05 to 0.5 μm and the large particles have a particle size of 2 to 10 μm (JP-A-46-41467) and the small particles have a particle size of 0.2 to 0.6 μm, A composition having large particles having a particle size of 2 to 8 μm (U.S. Pat. No. 4,493,922) is disclosed. However, in the former composition, since the small particles do not have a single occlusion structure, the balance between gloss and impact resistance is not sufficient, and in the latter composition, the microstructure of the rubber polymer particles is not controlled at all. Therefore, the balance between gloss and impact resistance is not always sufficient.

[Problems to be Solved by the Invention] The present invention overcomes the disadvantages of the conventional rubber-modified styrenic resin composition, has high impact strength, and has excellent gloss and rigidity. The purpose of the present invention is to provide a styrene-based resin composition having an excellent balance.

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to develop a styrene-based resin composition having an excellent balance of physical properties such as impact resistance, gloss, and rigidity. And a rubber-like polymer in a specific ratio, and found that a composition in which the rubber-like polymer has a specific dispersion form and microstructure can meet the above-mentioned object, and based on this finding, the present invention Was completed.

That is, the present invention relates to (A) a styrene-based polymer 70 to 92
% By weight and (B) 30 to 8% by weight of a rubbery polymer, wherein the rubbery polymer is (a)
Has a single occlusion structure and has an area average particle size
0.1 to 0.7 μm small particles and (b) large particles having a salami structure and having an area average particle diameter of 2.4 to 5 μm dispersed in a styrene polymer, and the weight ratio of the small particles to the large particles But
In the range of 70:30 to 99: 1, the gel amount is 1.1 to 4.0 weight ratio with respect to the rubbery polymer, and the swelling index is 5 to 20.
It is intended to provide a styrenic resin composition characterized by the following.

 Hereinafter, the present invention will be described in detail.

The styrene-based polymer as the component (A) in the composition of the present invention is a styrene homopolymer or a copolymer of a monomer copolymerizable with styrene, and examples of the copolymerizable monomer include: Aromatic monovinyl compounds such as α-methylstyrene, vinyltoluene, vinylethylbenzene, vinylxylene, pt-butylstyrene, α-methyl-p-methylstyrene, vinylnaphthalene, acrylonitrile, methyl methacrylate, methyl acrylate, methacryl Acids, acrylic acid, maleic anhydride, phenylmaleimide and the like can be mentioned. 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, the type of the rubbery polymer as the component (B) is not particularly limited, and those conventionally used in rubber-modified styrene resin compositions, for example, natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene Synthetic rubbers such as copolymer rubber, styrene-isoprene copolymer rubber, butyl rubber, and ethylene-propylene copolymer rubber, or graft copolymer rubbers of these rubbers and styrene are used.

In the styrenic resin composition of the present invention, the rubbery polymer as the component (B) has (a) a single occlusion structure and an area average particle diameter of 0.1 to 0.7 μm, preferably
It has small particles of 0.2 to 0.6 μm and (b) a salami structure and has an area average particle diameter of 2.4 to 5 μm, preferably 2.4 to 4.6 μm.
It is necessary that the particles are dispersed in the styrene-based polymer of the component (A) as large particles of μm. If the area average particle diameter of the small particle portion is less than 0.1 μm, the impact resistance is not sufficient, and if it exceeds 0.7 μm, the gloss tends to decrease. Also, the small particles need to have a single occlusion structure, thereby providing a good balance between gloss and impact resistance. The single occlusion structure refers to a structure in which the core is a styrene-based polymer and the shell is a rubber-like polymer. On the other hand, if the area average particle diameter of the large particle portion is less than 2.4 μm, the impact resistance is not sufficient, and if it exceeds 5 μm, the gloss tends to decrease. Also, these large particles need to have a salami structure,
Thereby, the balance between gloss and impact resistance is improved.
The salami structure means a structure in which styrene-based polymer particles are scattered in a rubber elastic phase.

In the composition of the present invention, the ratio of the small particles to the large particles must be in the range of 70:30 to 99: 1, preferably 73:27 to 97: 3 by weight. If the amount of the large particles is less than the above range, the impact strength may decrease, and if the amount is large, the gloss tends to decrease.

Further, in the composition of the present invention, the rubber-like polymer particles need to have a specific microstructure. That is, the gel amount needs to be in the range of 1.1 to 4.0 weight ratio, preferably 1.4 to 3.6 weight ratio with respect to the rubbery polymer, and its swelling index is 5 to 20, preferably 7 to 18. Must be in range. If the gel amount is less than 1.1 weight ratio, the impact resistance is not sufficient, and if it exceeds 4.0 weight ratio, the gloss may decrease. If the swelling index is outside the above range, the impact strength tends to decrease.

In the composition of the present invention, the styrenic polymer of the component (A) and the rubbery polymer of the component (B) are each 70%.
-92% by weight and 30-8% by weight, preferably 72-90% by weight
And 28 to 10% by weight.
If the content of the rubbery polymer is less than 8% by weight, the effect of improving the impact resistance is not sufficiently exhibited, and if it exceeds 30% by weight, the gloss and the fluidity tend to decrease.

The styrene-based resin composition of the present invention is a rubber-modified styrene-based polymer containing a small-particle rubber-like polymer and a rubber-modified styrene-based polymer containing a large-particle rubber-like polymer, separately prepared. It may be prepared by blending with an extruder or the like, or may be prepared by allowing a small particle rubber-like polymer and a large particle rubber-like polymer to exist in the course of polymerization of a styrene-based polymer.

The method for producing the rubber-modified styrenic polymer is not particularly limited, and a conventionally used method such as an emulsion polymerization method, a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or a bulk-suspension two-stage polymerization method And the like.

Next, an example of a preferred method for producing the resin composition of the present invention by the bulk-suspension two-stage polymerization method will be described. First, styrene or a mixture of a monomer copolymerizable with styrene is mixed with a rubber-like polymer. Add coalescence and heat to dissolve as needed. This dissolution is preferably performed as uniformly as possible.

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

Next, the prepolymerized solution is suspended in an aqueous phase using tribasic calcium phosphate, polyvinyl alcohol or the like as a suspending agent, and suspension polymerization (main polymerization) is usually performed until the degree of polymerization approaches 100%. If necessary, after this main polymerization step,
Further heating may be continued. Examples of the molecular weight regulator include α-methylstyrene dimer, n-dodecylmercaptan, t-dodecylmercaptan, 1-phenylbutene-2-fluorene, dipentene, mercaptans such as chloroform, terpenes, and halogen compounds. Can be.

Further, as a polymerization initiator used as desired,
For example, peroxyketals such as 1,1-bis (t-butylperoxy) cyclohexane and 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, dicumyl peroxide, di-t-butyl peroxide, 2,
Dialkyl peroxides such as 5-dimethyl-2,5-di (t-butylperoxy) hexane, dialperoxides such as benzoyl peroxide and m-toluoyl peroxide; peroxydicarbonates such as dimyristyl peroxydicarbonate; Organic peroxides such as peroxyesters such as butylperoxyisopropyl carbonate, ketone peroxides such as cyclohexanone peroxide, and hydroperoxides such as p-menthahydroperoxide can be exemplified.

The particle size, particle size distribution, and particle structure of the rubber-like polymer can be controlled by controlling the number of rotations of the stirring and the amount of the molecular weight modifier used, and the amount of gel and the swelling index are determined by 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 ordinary means, the bead-like reactant is taken out, dried, and then pelletized according to a conventional method to obtain the styrene resin composition of the present invention. Can be

The styrenic resin composition of the present invention, if desired, various commonly used additives such as stearic acid,
Lubricant such as behenic acid, zinc stearate, calcium stearate, magnesium stearate, ethylene bis stearamide, organic polysiloxane, mineral oil, or 2,6-di-t-butyl-4-methylphenol, stearyl- β- (3,5-di-t-butyl-4
Hindered phenols such as -hydroxyphenyl) propionate, triethylene glycol-bis-3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate and tri (2,4-di-t-butylphenyl) ) Phosphites, phosphorus-based antioxidants such as 4,4'-butylidenebis (3-methyl-6-t-butylphenyl-di-tridecyl) phosphite, other ultraviolet absorbers, flame retardants, antistatic agents, Molding agents, plasticizers, dyes, pigments, various fillers, and the like can be added. Further, other polymers, for example, polyphenylene ether and the like can be blended.

The styrene-based resin composition of the present invention thus obtained has an excellent balance of physical properties such as impact resistance, gloss, and rigidity, and is suitably used as a material for OA equipment, home electric appliances, sheets, and the like.

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

 The properties of the composition were determined by the following method.

(1) Gel amount and swelling index Sample Wc (g) was dissolved in toluene,
After centrifugation for minutes, the supernatant was decanted to determine the amount of swollen insoluble components Ws (g), and then the swollen insoluble components were vacuum-dried at 60 ° C. for 24 hours to obtain a dry insoluble component Wg.
(G) is obtained.

Gel amount (wt%) = (Wg / Wc) x 100 Swelling index = Ws / Wg (2) Structure of rubber-like polymer particles, area average particle diameter After staining a sample with osmic acid, photograph with a transmission electron microscope And the structure of the rubber-like polymer particles was confirmed. Further, the particle diameter was measured for 1000 particles, and the area average particle diameter Ds was calculated according to the following equation.

(N is the number of rubber-like polymer particles having a particle diameter D) (3) Izod impact value It was determined in accordance with JIS K-7110 (notched at 23 ° C).

(4) Gloss The gloss was determined in accordance with JIS K-7105.

(5) Flexural modulus was determined in accordance with ASTM D-790.

(6) Melt index [MI] Determined in accordance with JSO R-1133.

Example 1 In an autoclave having an internal volume of 5, 704 g of SB block copolymer [ZLS-01 manufactured by Zeon Corporation] and 3,000 g of styrene
Then, 1 g of n-dodecyl mercaptan as a chain transfer agent was added, and the mixture was reacted at 130 ° C. for 4 hours while stirring at 300 rpm to obtain a prepolymer (I).

On the other hand, polybutadiene [NF35AS] 40 manufactured by Asahi Kasei Corporation
Using 9 g, a prepolymer (II) was obtained in the same manner as described above.

Beads were synthesized from the prepolymers (I) and (II) under the same conditions as those of the suspension polymerization shown below, and the respective rubber structures were determined to be single occlusion of Ds0.4 μm and Ds3 by an electron microscope. It was confirmed that it had a salami structure of 0.2 μm.

Next, 2550 g of the prepolymer (I), 450 g of the prepolymer (II), 3000 g of water, 10 g of polyvinyl alcohol as a suspension stabilizer, 6 g of benzoyl peroxide as a polymerization initiator, and 6 g of dicumyl Add peroxide 3g, stirring at 500rpm, 80 ℃ ~ 30 ℃ / h
The temperature was raised to 140 ° C. at a temperature raising rate of r, and the reaction was further performed at that temperature for 4 hours to obtain beads of a rubber-modified polystyrene composition.

As a result of observing the beads with an electron microscope, it was confirmed that the rubbery polymer was dispersed as small particles having a single occlusion structure of Ds0.4 μm and large particles having a salami structure of Ds3.2 μm.

Next, the beads of the obtained composition were pelletized by a single screw extruder at 220 ° C., and then molded.

 Table 4 shows the properties of the composition.

Examples 2 to 5 and Comparative Examples 1 to 6 A rubber-modified polystyrene composition was obtained in the same manner as in Example 1, except that the polymerization conditions shown in Table 1 were used. The characteristics are shown in Table 4.

Example 6 The prepolymer (I) obtained in Example 1 and the prepolymer (II) obtained in Example 5 were subjected to suspension polymerization in the same manner as in Example 1 to obtain a rubber-modified polystyrene. Beads were obtained.

Next, 2850 g of beads obtained from the prepolymer (I) and 150 g of beads obtained from the prepolymer (II) were blended, and the composition was pelletized by a single screw extruder at 220 ° C., followed by molding. Was done. Table 4 shows the properties of the composition.

Example 7, Comparative Examples 7 and 8 In the same manner as in Example 6, as shown in Table 2, beads from the prepolymer (I) and beads from the prepolymer (II) were obtained, and then they were obtained. After blending and pelletizing the composition, molding was performed. Table 4 shows the properties of the composition.

Examples 8 and 9, Comparative Examples 9 and 10 In the suspension polymerization in Example 1, a rubber-modified polystyrene composition was prepared in the same manner as in Example 1 except that the polymerization initiator used was changed as shown in Table 3. I got The characteristics are shown in Table 4.

Example 11 The rubber-modified polystyrene composition beads obtained in Example 1 were mixed with 0.2% by weight of polydimethylsiloxane,
After pelletizing with a single screw extruder at 20 ° C., molding was performed.

 Table 4 shows the properties of the composition.

[Effect of the Invention] The high gloss impact styrenic resin composition of the present invention is characterized in that the rubber-like polymer has a characteristic particle diameter having a single occlusion structure and a large particle having a characteristic particle diameter having a salami structure. Dispersed in the styrenic polymer phase at a predetermined ratio,
In addition, since it has a specific microstructure, it has characteristics such as high impact strength, excellent gloss and rigidity, and excellent balance of physical properties.

Claims (1)

(57) [Claims] 1. A styrenic resin composition comprising (A) 70 to 92% by weight of a styrenic polymer and (B) 30 to 8% by weight of a rubbery polymer, wherein the rubbery polymer comprises (a) Has an occlusion structure, and has an area average particle size of 0.1 to 0.7
μm small particles and (b) large particles having a salami structure and having an area average particle diameter of 2.4 to 5 μm are dispersed in the styrene polymer, and the weight ratio of the small particles to the large particles is 70:30. A styrene resin composition having a gel amount of 1.1 to 4.0 by weight based on the rubber-like polymer and a swelling index of 5 to 20.