JPH05170839A - Rubber-modified styrene resin composition - Google Patents

Abstract

PURPOSE:To provide the title compsn. excellent in the balance between flowability and impact strength. CONSTITUTION:The title compsn. has a rubberlike polymer content of 4-12wt.%, a reduced viscosity [etasp/c] of an arom. monovinyl polymer in the resin phase of 0.6-0.8, a methanol-sol. content of 8wt.% or lower, and a plasticizer content of 6wt.% or lower and satisfies the formula: [W]<=--66X[etasp/c(g/dl)]+63 (wherein [W] is a proportion of the part of the monovinyl polymer having a mol.wt. of 50,000 or lower). The compsn. is excellent in the balance between flowability and impact strength and suitable for preparing a molding of a complicated shape by high-speed injection molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber-modified styrenic resin composition having an excellent balance between fluidity and impact strength.

[0002]

2. Description of the Related Art Rubber-modified styrenic resins are widely used in various fields because of their excellent moldability, and particularly in the field of housing materials with complicated shapes such as home electric appliances and 0A equipment. Then, in recent years, development of a rubber-modified styrene resin composition excellent in high-speed injection moldability has been demanded. Therefore, some studies have been conducted to improve the flowability of this type of rubber-modified styrene resin composition.
For example, in order to improve impact strength, a method in which a rubber component such as polybutadiene is added at a specific ratio during the polymerization of styrene and mineral oil is added (JP-A-60-192755), Set the intrinsic viscosity (molecular weight) of the styrene polymer in the resin phase to a certain low range,
A method of adjusting the blending amount of mineral oil, lubricant, unreacted monomer content, etc. to a certain specific range (JP-A-1-247,
No. 446) has been proposed.

However, in the former invention, although the effect of improving the fluidity is remarkable, there is a problem that the heat resistance is lowered and oil oozes out on the surface of the molded product. Further, in the latter invention, although the balance between the physical properties of fluidity and heat resistance is excellent, it is necessary to lower the intrinsic viscosity (molecular weight) to a certain low range, so that the impact resistance is significantly lowered. There were problems and these methods still had room for improvement. As described above, the impact strength and the fluidity are mutually contradictory performances in that the performance of one of them is deteriorated when the performance of the other is deteriorated, and it is difficult to improve both of them in the past. Was thought to be.

In view of this point, the inventors of the present invention have conducted extensive studies to develop a rubber-modified styrenic resin having an excellent balance of physical properties such as fluidity and impact resistance. Molecular weight 5 in group monovinyl polymer
By controlling the content of the low molecular weight polymer of 50,000 or less within a certain range depending on the reduced viscosity of this resin phase,
The inventors have found that the balance between impact strength and fluidity can be significantly improved, and completed the present invention. Therefore, an object of the present invention is to solve the above-mentioned conventional problems and to provide a rubber-modified styrene resin composition having an excellent balance of physical properties of fluidity and impact resistance.

[0005]

That is, the present invention relates to a rubber-modified styrene resin composition containing a rubber-like polymer as dispersed particles, wherein (a) the rubber-like polymer content is 4 to 12% by weight. And (b) the reduced viscosity [η _{sp / c} ] of the aromatic monovinyl polymer of the resin phase is in the range of 0.6 to 0.8, and the content of the (c) methanol-soluble component is 8% or less. And (d) the content of the plasticizer is 6% or less, (e)
Percentage of a polymer having a molecular weight of 50,000 or less in the methanol insoluble matter of the aromatic monovinyl polymer in the resin phase [W
(%)] And the reduced viscosity [η _{sp / c} (dl / g)] are in the range of [W] ≦ −66 × [η _{sp / c} ] +63, which is a rubber-modified styrene resin composition.

The present invention will be described in detail below. The present invention is a rubber-modified styrenic resin composition containing a rubber-like polymer as dispersed particles, basically, the rubber-like polymer is dissolved in an aromatic monovinyl-based monomer and stirred under bulk polymerization conditions. However, after it is made into dispersed rubber particles, it is continuously polymerized by either a bulk polymerization method or a suspension polymerization method. In the present invention, the above conditions (a) to (e) may be satisfied. is necessary.

First, as the aromatic monovinyl monomer used in the present invention, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4
-Dimethylstyrene, ethylstyrene, p-tert-
Nuclear alkyl-substituted styrene such as butyl styrene and α such as α-methyl styrene and α-methyl-p-methyl styrene
-Alkyl-substituted styrene and the like. These aromatic monovinyl monomers may be used alone or in combination of two or more. It is also possible to copolymerize a monomer other than the aromatic monovinyl-based monomer in combination, and specific examples of the copolymerizable monomer include vinyl ethylbenzene, vinyl xylene and vinyl naphthalene. Such as aromatic monovinyl compounds, methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, acrylonitrile, methacrylonitrile, methacrylic acid, acrylic acid,
Examples thereof include maleic anhydride, phenylmaleimide, and halogen-containing vinyl monomers. Also in this case, as for the copolymerizable monomer, only one kind thereof may be used, or two or more kinds thereof may be used in combination, but the amount thereof is not limited to the total amount of all monomers. On the other hand, it is usually used in an amount of 40% by weight or less, preferably 30% by weight or less.

The rubber-like polymer used in the present invention includes polybutadiene, styrene-butadiene copolymer,
Examples thereof include polyisoprene, butadiene-isoprene copolymer, and natural rubber. The polybutadiene may be low cis polybutadiene or high cis polybutadiene. The styrene-butadiene copolymer may be a random type having a styrene content of 5 to 50% by weight or a block type. And these rubber-like polymers may use only 1 type and may be used in combination of 2 or more types, but as content of the rubber-like polymer in a resin composition, it is 4-12. %, Preferably 5 to 11% by weight. If the amount of the rubber-like polymer used is 4% by weight or less, the impact resistance is insufficient, and if it exceeds 12% by weight, the fluidity of the resin composition is impaired and the polymerization system becomes highly viscous during production. However, it is not preferable because operating problems are likely to occur. The rubber-like polymer is contained as dispersed particles in a styrene resin, and the average rubber particle size is usually 1
It is preferably in the range of ˜5 μm, preferably 1 to 3 μm.

Next, in the rubber-modified styrene resin composition of the present invention, the reduced viscosity [η _{sp / c} ] of the aromatic monovinyl polymer of the resin phase is 0.6 to 0.8 dl / g, preferably It is in the range of 0.60 to 0.76. If the value of this reduced viscosity [η _{sp / c} ] is less than 0.6 dl / g, the impact resistance such as Izod impact strength will decrease, and conversely, the value of this reduced viscosity [η _{sp / c} ] will be 0.8 dl. / G is not preferable because the fluidity of the resin composition deteriorates. In addition,
The reduced viscosity of this resin phase [η _{sp / c} ] is measured by dissolving the rubber-modified styrene resin composition in methyl ethyl ketone,
Then, the gel phase containing the rubbery polymer was separated by centrifugation, the polymer solution of the supernatant was reprecipitated with methanol, the methanol-insoluble matter was filtered out, and the dried one was dissolved in toluene (concentration: 0). 0.4g / 100m
l) and measure according to a conventional method at 30 ° C. using an Ubbelohde viscometer.

Further, in the present invention, the molecular weight of the aromatic monovinyl polymer in the resin phase is 5 in the methanol insoluble matter.
The ratio [W (%)] occupied by a polymer of 20,000 or less is
It is controlled within a specific range depending on the reduced viscosity of the resin phase. Generally, the ratio [W (%)] occupied by a polymer having a molecular weight of 50,000 or less is the reduced viscosity of the resin phase [η _{sp / c} ].
The higher (corresponding to the average molecular weight), the smaller the amount, and conversely, the lower the reduced viscosity [η _{sp / c} ], the larger the amount. Then, as a result of various studies by the present inventors, a molecular weight of 50,000 was obtained.
The ratio [W (%)] occupied by the following polymers and the reduced viscosity [η
By satisfying the relationship of _{sp / c} (dl / g)] [W] ≦ −66 × [η _{sp / c} ] +63, the balance between impact strength and fluidity can be significantly improved. That is, in the present invention, it is necessary to reduce the ratio [W (%)] occupied by a polymer having a molecular weight of 50,000 or less to the value of the above formula or less according to the reduced viscosity of the resin phase. If exceeded, impact strength per unit content of rubber (kgf · cm /
cm ² ) is significantly reduced. The molecular weight is measured by gel permeation chromatography (GPC) according to a conventional method.

Further, in the present invention, the content of the methanol-soluble component is preferably 8% or less, particularly preferably 6% or less. Examples of the methanol-soluble component include liquid paraffin or a plasticizer such as fatty acid esterified product such as octyl palmylate and glycerin diaceto-monolaurate, and a low molecular weight oligomer. If the content of the methanol-soluble component exceeds 8%, the heat resistance of the resin composition is greatly reduced, which is not preferable. Further, in the present invention, the content of the plasticizer is preferably 6% or less, particularly preferably 5% or less. 6% plasticizer content
When it exceeds the above range, the heat resistance of the resin composition is extremely lowered, which is not preferable.

In addition, in the present invention, it is desirable that the lubricant contains 0.1% or more of a higher fatty acid, a metal salt of a higher fatty acid, an amidation product or the like as a lubricant. Examples of the higher fatty acid include stearic acid, and examples of the amidation product of the higher fatty acid include ethylenebisstearylamide. Furthermore, examples of metal salts of higher fatty acids include zinc stearate and calcium stearate.

The rubber-modified styrenic resin composition of the present invention can be produced by polymerizing an aromatic monovinyl polymer by a bulk polymerization method, a bulk suspension polymerization method or the like in the presence of a rubbery polymer. Here, the polymerization conditions are not particularly limited, but if necessary, a solvent such as ethylbenzene or toluene is used, and benzoyl peroxide, ter
Usually, an organic peroxide such as t-butyl-hydroperoxide or dicumyl peroxide is used as a polymerization initiator in an amount of 7
It is preferable to polymerize under heating at 0 to 200 ° C. In addition, in this polymerization, in order to control the molecular weight, it is effective to use a molecular weight regulator (chain transfer agent) such as mercaptans or α-methylstyrene dimer.

Particularly in the present invention, the operational factors effective for obtaining the reduced viscosity [η _{sp / c} ] of the specified aromatic monovinyl polymer in the resin phase are the polymerization temperature and the molecular weight modifier in each reactor. Is added, the amount of peroxide added, the amount of solvent added, etc. By appropriately adjusting these, those having desirable physical properties can be obtained. Also, the molecular weight is 5
As a method of decreasing the proportion [W (%)] occupied by a polymer of 20,000 or less to a specific value or less according to the reduced viscosity of the resin phase, when a plurality of reactors are used, It is possible to set the polymerization conditions so that the reduced viscosities (molecular weights) of the polymers produced by the polymerization reaction are as similar as possible. The polymerization rate of styrene is about 60 to 90.
The polymerization operation is continued until the polymerization reaction is completed by weight% or substantially. After completion of the polymerization operation, in order to remove the unreacted styrene monomer, low molecular weight oligomer, solvent and the like in the polymerization solution containing the produced polymer, treatment is carried out with a known heating and depressurizing removal device.

[0015]

The present invention will be described in more detail based on the following examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

Example 1 As a polymerization apparatus, one 10-liter complete mixing tank type reactor (first reactor), three 18-liter piston flow type reactors (second to fourth reactors), An apparatus in which two devolatilization units were connected in series and combined was used.
Styrene monomer 80 parts by weight, ethylbenzene 20 parts by weight, polybutadiene rubber 7 parts by weight, ditertiary butyl-peroxycyclohexane (PO) 0.05
Parts by weight and tertiary decyl mercaptan (TD
A mixed solution of M) with 0.02 part by weight was used as a raw material and continuously supplied to the polymerization apparatus from the first reactor at 8 liter / hr. A part of the polymerization liquid was sampled at the outlet of each reactor,
The reduced viscosity of the resin phase was measured, and the reaction temperature was adjusted so that the reduced viscosity at the outlet of each reactor was in the range of 0.75 to 0.77. The polymerization conversion rate of styrene at the end of the polymerization was 89%. This polymerization liquid is continuously charged into a devolatilization device to remove volatile components such as unreacted monomers and solvents, and then a plasticizer is added and kneaded, and pelletized to obtain a rubber-modified styrene resin composition. It was Polymerization conditions in each reactor at this time are shown in Table 1, and measurement results of physical properties of the obtained resin composition are shown in Table 2.

Examples 2 to 5 and Comparative Examples 1 to 4 The rubber-modified styrene resin composition was the same as in Example 1 except that the composition ratio of the mixed solution used in Example 1 and the polymerization conditions in each reactor were variously changed. Manufactured. Polymerization conditions in each reactor at this time are shown in Table 1, and measurement results of physical properties of the obtained resin composition are shown in Table 2. In addition, regarding the results of the above Examples and Comparative Examples, the reduced viscosity (dl / g) and the impact strength [(Izod-
1) / rubber content], the fluidity [MFR
(G / 10 min)] and Izod impact strength (kgf · c
m / cm ² ) and the reduced viscosity (dl
/ G) and low molecular weight component content [W (%)]. The reduced viscosity is an index of the average molecular weight, and the smaller the value, the smaller the average molecular weight. Also,
(Izod-1) / rubber content is the Izod impact strength per unit rubber content, and (Izod-1) is defined as I with a rubber content of 0% (that is, GP polystyrene).
This is because the zod is about 1.

[0018]

[Table 1]

[0019]

[Table 2]

In Example 4 and Comparative Example 2, the rubber content was low, and in Comparative Example 2, the rubber content was 3.3%, and even if the MFR was good, the Izod strength was as low as 3.1. It is not practical. In addition, Example 5 and Comparative Example 3 show the case where the amount of the plasticizer added is larger than those of the other examples, and Comparative Example 3 shows that if the amount of the plasticizer added is too large, the heat resistance is greatly reduced. ..

[0021]

The rubber-modified styrenic resin composition of the present invention has an excellent balance of physical properties such as fluidity and impact strength, and is used as a material for manufacturing home electric appliances, automobile parts, OA equipment, etc. As is the best.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between reduced viscosity (dl / g) and impact strength [(Izod-1) / rubber content].

FIG. 2 shows liquidity [MFR (g / 10 mi
n]] and Izod impact strength (kgf · cm / cm ² ).

FIG. 3 is a graph showing a relationship between reduced viscosity (dl / g) and low molecular weight component content [W (%)].

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[Procedure amendment]

[Submission date] February 26, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (2)

[Claims] 1. A rubber-modified styrene-based resin composition containing a rubber-like polymer as dispersed particles, wherein (a) the content of the rubber-like polymer is 4 to 12% by weight, and (b) the fragrance of the resin phase. The reduced viscosity [η _{sp / c} ] of the group I monovinyl polymer is 0.
6 to 0.8, (c) the content of the methanol-soluble component is 8% or less, (d) the content of the plasticizer is 6% or less, and (e) the aromatic of the resin phase. The proportion [W (%)] of the polymer having a molecular weight of 50,000 or less in the methanol-insoluble matter of the monovinyl polymer and the reduced viscosity [η _{sp / c} (dl /
g)] is in the range of [W] ≦ −66 × [η _{sp / c} ] +63, the rubber-modified styrene resin composition. 2. The rubber-modified styrenic resin composition according to claim 1, wherein the plasticizer is liquid paraffin or an esterified product of a fatty acid.