JPH0827235A - Rubber-modified styrene-based resin composition - Google Patents

Abstract

PURPOSE:To obtain a rubber-modified polystyrene excellent in the balance of physical properties such as gloss, impact resistance, etc. CONSTITUTION:In this rubber-modified styrene-based resin composition, a rubber- based polymer is dispersed in particle-like state and the amount of a styrene- based polymer contained in the dispersed rubber particles is in the range of 26 to 60 volume% based on total amount of the resin composition and the average particle diameter of the dispersed rubber particle is in the range of 0.3-2.0mum.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rubber-modified styrene resin composition having an excellent quality balance. More specifically, the present invention relates to a rubber-modified styrene-based resin composition having excellent surface gloss and excellent impact strength and excellent quality balance.

[0002]

2. Description of the Related Art At present, in order to improve the impact resistance of styrene resin, a large amount of rubber-modified styrenic resin containing a rubber-like polymer as dispersed particles in the resin is manufactured, and it is used for housings of printers and TVs. Widely used in the fields of light electrical equipment, office supplies, packaging, and sundries.

In recent years, the field of demand for such products has expanded, and the demand for physical properties better than before, in particular the balance between impact resistance and surface gloss, is increasing.

Conventionally, in order to improve impact resistance, a method of increasing the particle size of dispersed rubber particles or increasing the content of a rubber-like polymer is known. However, these methods conversely reduce the surface gloss. As described above, since impact resistance and surface gloss are controlled by contradictory factors, a rubber-modified styrenic resin excellent in quality balance that maintains high impact resistance and has excellent surface gloss. It was very difficult to get.

A method is disclosed which requires limiting the properties of the rubbery polymer used as one method for improving the gloss performance. For example, Japanese Examined Japanese Patent Sho 61-50488
JP-A-59-20334 and JP-A-60-203618 disclose a method which requires that the properties of the rubber-like polymer used, such as solution viscosity, microstructure and branched structure, are limited. JPA
No. 62-178458 and JP-A No. 4-100810 disclose a method which requires the use of a rubber-like polymer composed of high molecular weight polybutadiene and low molecular weight polybutadiene.
However, if you examine these methods in detail,
Although it is certainly improved as compared with the conventional method, there was a problem that the balance between surface gloss and impact resistance was not yet practically satisfactory.

As another method, there is disclosed a method in which a styrene-butadiene block copolymer rubber having a strong affinity with an aromatic vinyl resin is used as a rubber-like polymer. For example, Japanese Patent Publication Nos. 42-17492 and 48-185
94, Japanese Examined Patent Publication No. 1-33485, JP-A-63-78317, JP-A-63
No. 165413, there is a method of using a styrene-butadiene block copolymer rubber alone, and in JP-A-4-88006, a rubber-like polymer is used as a rubber-like polymer and a low molecular weight styrene-butadiene block copolymer rubber. Although methods of mixing and using a styrene-butadiene block copolymer rubber having a molecular weight are respectively disclosed, the gloss of the resin obtained by any of the methods is improved, but the impact resistance is lowered, and moreover, as a rubber component. There is a problem in that it is necessary to use a large amount of a costly rubber called styrene-butadiene copolymer.

[0007] Further, as another method, JP-A-62-28021
Japanese Patent Laid-Open No. 4-209614 discloses a method in which a styrene-butadiene copolymer rubber and a polybutadiene rubber are mixed and used. However, in any of these cases, the impact resistance of the resulting resin was insufficient because of the small proportion of polybutadiene rubber used.

[0008]

In recent years, there has been a trend to switch from high-grade resins to inexpensive styrene resins in response to demands from the market for cost reduction of raw materials. Against this background, simultaneous improvement of impact resistance and gloss of rubber-modified styrenic resin is strongly desired.

[0009]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventor has found that the average particle diameter of the dispersed rubber particles in the styrene resin composition and the styrene-based weight contained in the dispersed rubber particles. By limiting the amount of coalescence to a specific range, the rubber-modified styrene resin composition of the present invention having high surface gloss without impairing impact resistance has been completed.

That is, according to the present invention, in a rubber-modified styrenic resin composition in which a rubber-like polymer is dispersed in the form of particles, the amount of the styrene-based polymer contained in the dispersed rubber particles is in the entire resin composition. On the other hand, the rubber-modified styrene resin composition is characterized in that it is in the range of 26 to 60% by volume, and the average particle diameter of the dispersed rubber particles is in the range of 0.3 to 2.0 μm.

In order to achieve the object of the present invention, as described above, the average particle diameter of the dispersed rubber particles in the styrene resin composition and the amount of the styrene polymer contained in the dispersed rubber particles are in a specific range. The lack of any one of these requirements does not achieve the object of the present invention.

Each requirement will be described in more detail below.

The average particle diameter of the dispersed rubber particles contained in the rubber-modified styrene resin composition of the present invention is 0.3 to 2.0 μm.
, Preferably 0.3 to 1.5 μm. When the average particle size is less than 0.3 μm, the impact resistance is lowered, and when the average particle size is larger than 2.0 μm, the surface gloss is lowered.

The amount of the styrene polymer contained in the dispersed rubber particles needs to be in the range of 26 to 60% by volume based on the total resin composition. If the amount of the styrenic polymer contained in the dispersed rubber particles is less than 26% by volume, the impact resistance will decrease, and if it is more than 60% by volume, the surface gloss will decrease. Further, particularly when the average particle size of the dispersed rubber particles is 0.3 to 0.5 μm, the amount of the styrene-based polymer contained in the dispersed rubber particles is 26 to 60% by volume, and the average particle size of the dispersed rubber particles is Is 0.5 to 1.0 μm, the amount of the styrene polymer contained in the dispersed rubber particles is 28 to 60% by volume, and the average particle size of the dispersed rubber particles is 1.0 to 1.5 μm. The amount of the styrene polymer contained in the dispersed rubber particles is preferably 30 to 60% by volume.

The amount of styrene-based polymer contained in the dispersed rubber particles in the present invention was determined by the following procedure.
First, a rubber-modified styrenic resin is stained with osmium tetroxide, an ultrathin section is created and a transmission electron micrograph is taken with a field of view of 1000 or more dispersed rubber particles, and the area of the dispersed rubber particle phase in the photograph ( X) and the area of the matrix polystyrene phase
(Y) is obtained using an image processing device. Separately, the volume (Z% by weight) of only the polybutadiene component in the charged rubber-like polymer is calculated. Finally, these results
The amount of the styrene-based polymer contained in the dispersed rubber particles was calculated by calculation according to the formula of X / (X + Y) × 100−Z.

The average particle size is taken by taking a transmission electron microscope photograph in the same manner as described above to obtain dispersed rubber particles in the photograph.
It is obtained by measuring the particle size of 1000 particles. The average particle size is calculated by the following formula.

[0017]

[Equation 1]

(Here, n _i is the number of dispersed rubber particles having a particle diameter D _i ).

The structure of the dispersed rubber particles is preferably a cellular structure or a mixed structure of a cellular structure and a capsule structure. Especially the average particle size of dispersed rubber particles is 0.3
When the particle size is ˜0.5 μm, the number of rubber particles having a cellular structure is preferably 50% or more of the total number of rubber particles. If the number of rubber particles having a cellular structure is less than 50% of the total number of rubber particles, the impact resistance will decrease.

The rubber-modified styrenic resin of the present invention is a bulk-suspension two-stage polymerization method in which a rubber-like polymer is dissolved in an aromatic monovinyl monomer, and then bulk polymerization is followed by suspension polymerization.
Alternatively, it is produced by a bulk polymerization method.

At the time of polymerization, a molecular weight regulator such as α-methylstyrene dimer, mercaptans, terpenes and halogen compounds, a solvent, a polymerization initiator and the like can be added. The amount of the molecular weight regulator added is based on the composition.
It is preferably 10% by weight or less, and when it exceeds 10% by weight, the molecular weight is remarkably reduced and the impact resistance becomes insufficient. As a solvent,
Aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, aliphatic hydrocarbons, and dialkyl ketones may be used alone or as a mixture of two or more kinds. The amount of solvent used is
0 to 50% by weight, based on the composition, is preferred. If it exceeds 50% by weight, the polymerization rate is remarkably reduced, and the energy for recovering the solvent is increased, resulting in poor economy.

As the polymerization initiator, ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide and methylcyclohexanone peroxide, 1,1-bis (t-butylperoxy) -3,3 3,5-trimethylcyclohexane,
1,1-bis (t-butylperoxy) cyclohexane,
Peroxyketals such as n-butyl-4,4-bis (t-butylperoxy) valerate, cumene hydroperoxide, diisopropylbenzene peroxide,
Hydroperoxides such as 2,5-dimethylhexane-2,5-dihydroperoxide, t-butylcumyl peroxide, α, α′-bis (t-butylperoxy-m-isopropyl) benzene, 2, 5-dimethyl-
Dialkyl peroxides such as 2,5-di (t-butylperoxy) hexyne-3, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, diacyl peroxides such as 2,4-dichlorobenzoyl peroxide, Peroxycarbonates such as bis (t-butylcyclohexyl) peroxydicarbonate, t-butylperoxybenzoate, 2,5-
Organic peroxides such as peroxyesters such as dimethyl-2,5-di (benzoylperoxy) hexane and 2,2-
There are azo compounds such as azobis (2-methylbutyronitrile) and 1,1′-azobis (cyclohexane-1-carbonitrile), which can be used alone or as a mixture of two or more kinds. Also, as the addition amount,
0 to 10% by weight relative to the composition is preferred. When the amount added exceeds 10% by weight, it becomes difficult to control the polymerization rate.

Further, during the bulk polymerization reaction, it is usually preferable to effectively stir until the polymerization rate of the aromatic monovinyl monomer reaches about 25%, but it is preferable to moderate the stirring thereafter. .

The rubbery polymer may be Co-based, Ni-based, in a polymerization solvent such as benzene, toluene, hexane or heptane.
Cis produced using a Ti-based Ziegler-type catalyst, cis-1,4 bond content of 90% or more, or cis produced using a Li-based alkyllithium catalyst.
It can be used together with low cis polybutadiene having a 1,4 bond content of 35 to 40%. Further, it is desirable to use a mixture of styrene-butadiene copolymers with the above polybutadiene. However, in this case, the amount of the styrene-butadiene copolymer used is preferably 50% by weight or less of the rubber-like polymer. If the amount of the styrene-butadiene copolymer used exceeds 50% by weight, the raw material cost becomes large and the economical efficiency becomes poor, which is not desirable. Further, in any of the above cases, the content of polybutadiene component in the rubber-modified styrene resin composition is preferably 4 to 8% by weight. When the content of polybutadiene component is less than 4% by weight, impact resistance is lowered, and when the content of polybutadiene component is more than 8% by weight, surface gloss is lowered.

Styrene is generally used as the aromatic monovinyl monomer, but o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, etc. Α-Alkyl-substituted styrenes such as nuclear alkyl-substituted styrene, α-methylstyrene, α-methyl-p-methylstyrene, and the like can also be used. In addition, the aromatic monovinyl monomer may include, if necessary, for example, a (meth) acrylic acid ester such as methyl methacrylate, ethyl acrylate, and butyl acrylate, (meth) acrylic acid, maleic anhydride, acrylonitrile, and the like. The polymerizable monomer may be added within the range where the economical efficiency is not deteriorated.

The composition of the present invention contains, if necessary, a lubricant such as zinc stearate, calcium stearate, or ethylene bisstearylamide, a plasticizer such as mineral oil, a phenol-based or phosphorus-based antioxidant, and an ultraviolet absorber. It may contain additives such as agents, flame retardants, antistatic agents, fillers, colorants, and dimethyl silicone oil.

[0027]

The rubber-modified styrenic resin composition of the present invention has an average particle size of dispersed rubber particles and an amount of styrene-based polymer contained in the dispersed rubber particles within a specific range. It is possible to obtain a molded product having high impact resistance and high surface gloss and having an excellent quality balance without using a large amount of expensive rubber components.

[0028]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. Moreover, each physical property value was measured by the following measuring methods.

(1) Izod impact strength: measured according to JIS K-6871 (2) Surface gloss: measured according to JIS Z-8741.

Example 1 In a complete mixing tank reactor having an internal volume of 10 liters, 6636 g of styrene monomer, 254 g of high cis polybutadiene (BR1220SG manufactured by Nippon Zeon Co., Ltd.), and a styrene-butadiene copolymer having a styrene content of 40% by weight. (Asaprene 670A manufactured by Asahi Kasei Corp.) and 500 g of ethylbenzene were charged, and after nitrogen substitution, polymerization was carried out at a stirring speed of 100 rpm to a polymerization rate of 25%, and the reaction solution was transferred into a tubular reactor equipped with a stirrer and polymerized at a stirring speed of 20 rpm. Polymerization up to 60%. Then, transfer the reaction solution into another tubular reactor with a stirrer, stirring speed 10 rpm
The polymerization rate was 95%. The reaction solution was taken out from the tubular reactor and the unreacted monomer was removed under reduced pressure of 200 ° C. and 10 mmHg to obtain a rubber-modified styrene resin composition. The obtained rubber-modified styrene resin composition was injection-molded to prepare a test piece, and Izod impact strength and surface gloss were measured.
Further, electron micrographs were taken to measure the average particle diameter of the dispersed rubber particles and the amount of styrene polymer contained in the dispersed rubber particles. The results of these measurements are summarized in Table 1.

Example 2 In a complete mixing tank type reactor having an internal volume of 10 liters, 6636 g of styrene monomer, 244 g of high-cis polybutadiene (UBEPOL-Z022 manufactured by Ube Industries, Ltd.), and styrene content of 40% by weight.
120 g of styrene-butadiene copolymer (Asaprene 670A manufactured by Asahi Kasei Co., Ltd.) and 500 g of ethylbenzene were charged, and after nitrogen substitution, polymerization was carried out at a stirring speed of 80 rpm to a polymerization rate of 25%, and the reaction solution was placed in a tubular reactor with a stirrer. Transfer,
Polymerization was carried out at a stirring rate of 20 rpm to a polymerization rate of 60%. After that, transfer the reaction solution into another tubular reactor with a stirrer, and stir speed
Polymerization was carried out at 10 rpm to a polymerization rate of 95%, and a rubber-modified styrene resin composition was obtained in the same manner as in Example 1. When the resin composition was evaluated, the results shown in Table 1 were obtained.

Example 3 A complete mixing tank reactor having an internal volume of 10 liters had a stirring speed of 80.
A rubber-modified styrene resin composition was obtained in the same manner as in Example 1 except that the speed was rpm. When the resin composition was evaluated, the results shown in Table 1 were obtained.

Example 4 A complete mixing tank reactor having an internal volume of 10 liters was charged with 6636 g of styrene monomer and 532 g of Rhocis polybutadiene (BR1242ST manufactured by Nippon Zeon Co., Ltd.), and after nitrogen substitution, the polymerization rate was 90 rpm. After polymerizing to 25%, the reaction solution was transferred into a tubular reactor equipped with a stirrer and polymerized to a polymerization rate of 95% at a stirring speed of 10 rpm, and a rubber-modified styrene resin composition was obtained in the same manner as in Example 1. When the resin composition was evaluated, the results shown in Table 1 were obtained.

Example 5 In a complete mixing tank type reactor having an internal volume of 10 liters, 6636 g of styrene monomer, 355 g of high cis polybutadiene (BR01 manufactured by Nippon Synthetic Rubber Co., Ltd.), and a styrene-butadiene copolymer weight having a styrene content of 40% by weight. Combined (Asaprene 67 manufactured by Asahi Kasei Corporation)
(0A) 177 g and 500 g of ethylbenzene were charged, and after nitrogen substitution, polymerization was carried out at a stirring rate of 80 rpm to a polymerization rate of 25%, and the reaction solution was transferred into a tubular reactor equipped with a stirrer and the stirring rate was 10%.
Polymerization was carried out at a rpm of 95% to obtain a rubber-modified styrene resin composition in the same manner as in Example 1. When the resin composition was evaluated, the results shown in Table 1 were obtained.

Comparative Example 1 The same as Example 1 except that low cis polybutadiene (Diene 35XN manufactured by Asahi Kasei Co., Ltd.) was used as the rubber-like polymer instead of the mixture of high cis polybutadiene and styrene-butadiene copolymer. To obtain a rubber-modified styrene resin composition. When the resin composition was evaluated, the results shown in Table 1 were obtained.

Comparative Example 2 As a rubber-like polymer, high cis polybutadiene (BR1220SL manufactured by Nippon Zeon Co., Ltd.) was used instead of a mixture of 254 g of high cis polybutadiene and 110 g of styrene-butadiene copolymer having a styrene content of 40% by weight. 364 g was used and 1,1-di-t-butylperoxy- was used as a polymerization initiator.
A rubber-modified styrene resin composition was obtained in the same manner as in Example 1 except that 2 g of 3,3,5-trimethylcyclohexane was used. When the resin composition was evaluated, the results shown in Table 1 were obtained.

Comparative Example 3 A complete mixing tank type reactor having an internal volume of 10 liters was charged with 6636 g of styrene monomer and 364 g of low cis polybutadiene (BR1241ST manufactured by Nippon Zeon Co., Ltd.), and after substitution with nitrogen, the polymerization rate was 90 rpm. Polymerization was performed up to 40%, and the reaction solution was transferred into a tubular reactor equipped with a stirrer and polymerized to a polymerization rate of 95% at a stirring speed of 10 rpm, and a rubber-modified styrene resin composition was obtained in the same manner as in Example 1. When the resin composition was evaluated, the results shown in Table 1 were obtained.

Comparative Example 4 A complete mixing tank reactor having an internal volume of 10 liters was charged with 6636 g of styrene monomer and 364 g of high cis polybutadiene (BR1220SU manufactured by Nippon Zeon Co., Ltd.), and after nitrogen substitution, the polymerization rate was 70 rpm. Polymerization was performed up to 40%, and the reaction solution was transferred into a tubular reactor equipped with a stirrer and polymerized to a polymerization rate of 95% at a stirring speed of 10 rpm, and a rubber-modified styrene resin composition was obtained in the same manner as in Example 1. When the resin composition was evaluated, the results shown in Table 1 were obtained.

Comparative Example 5 A complete mixing tank reactor having an internal volume of 10 liters was charged with 6636 g of styrene monomer and 364 g of high-cis polybutadiene (UBEPOL-Z022 manufactured by Ube Industries, Ltd.), and after nitrogen substitution, the stirring speed was 60 rpm. Polymerization was carried out to a polymerization rate of 50%, and the reaction solution was transferred into a tubular reactor equipped with a stirrer and polymerized to a polymerization rate of 95% at a stirring speed of 10 rpm, and a rubber-modified styrene resin composition was obtained in the same manner as in Example 1. When the resin composition was evaluated, the results shown in Table 1 were obtained.

[0040]

[Table 1]

Claims (5)

[Claims] 1. A rubber-modified styrene-based resin composition in which a rubber-like polymer is dispersed in particles, wherein the amount of styrene-based polymer contained in the dispersed rubber particles is 26 to 60 with respect to the entire resin composition. A rubber-modified styrenic resin composition characterized in that it is in the range of volume% and the average particle diameter of the dispersed rubber particles is in the range of 0.3 to 2.0 μm. 2. A rubber-modified styrene-based resin composition in which a rubber-like polymer is dispersed in the form of particles, wherein the amount of styrene-based polymer contained in the dispersed rubber particles is 26 to 60 with respect to the entire resin composition. A rubber-modified styrenic resin composition, characterized in that it is in the range of volume% and the average particle diameter of the dispersed rubber particles is in the range of 0.3 to 0.5 μm. 3. A rubber-modified styrene-based resin composition in which a rubber-like polymer is dispersed in particles, wherein the amount of styrene-based polymer contained in the dispersed rubber particles is 28 to 60 with respect to the entire resin composition. A rubber-modified styrenic resin composition characterized in that it is in the range of volume% and the average particle diameter of the dispersed rubber particles is in the range of 0.5 to 1.0 μm. 4. A rubber-modified styrene-based resin composition in which a rubber-like polymer is dispersed in a particulate form, wherein the amount of styrene-based polymer contained in the dispersed rubber particles is 30 to 60 relative to the entire resin composition. A rubber-modified styrenic resin composition characterized in that it is in the range of volume% and the average particle size of the dispersed rubber particles is in the range of 1.0 to 1.5 μm. 5. The rubber-modified styrene-based resin composition according to claim 2, wherein the number of rubber particles having a cellular structure among the dispersed rubber particles is 50% or more of the total number of rubber particles.