JPH09216978A - Transparent styrene resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber-modified styrene resin composition excellent in the balance among strength, transparency and moldability. SOLUTION: This composition is a rubber-modified styrene resin composition wherein the continuous phase is a styrene copolymer (A) comprising 30-80wt.% styrene monomer component and 70-20wt.% at least either (meth)acrylic acid or an alkyl ester thereof and the disperse phase is a rubbery polymer (B) comprising 10-60wt.% styrene polymer and 90-40wt.% butadiene polymer in a weight ratio (A/B) of 98/2 to 70/30. The total weight of low-molecular-weight compounds having a weight-average molecular weight (in terms of polystyrene) as measured by gel permeation chromatography is 2.0% or below.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber-modified styrene resin composition having excellent transparency. More specifically, a styrene polymer comprising a styrene monomer component and at least one (meth) acrylic acid or its alkyl ester monomer component, and a rubbery polymer comprising a styrene polymer and a butadiene polymer. A rubber-modified styrenic resin composition consisting of, characterized in that the total amount of low-molecular-weight compounds having a specific molecular weight or less therein is a specific amount or less, and a rubber-modified rubber having excellent balance of strength, transparency and moldability. The present invention relates to a styrene resin composition. Further, the present invention provides a rubber-modified styrene-based resin composition which does not cause a decrease in transparency and a decrease in productivity due to a sweating phenomenon during molding and has an excellent balance of strength, transparency and moldability.

The rubber-modified styrenic resin composition of the present invention can be used as a material for molded articles such as food containers, household articles, packaging articles and electric appliances.

[0003]

BACKGROUND OF THE INVENTION Since styrene resins are excellent in strength, transparency and moldability, they have been widely used as molding materials for food containers, packaging products, household products, electric appliances and the like. In the market in recent years, high quality and low cost resins have been demanded, and even in the styrene resin field,
High-quality resins with excellent balance of strength, transparency, and moldability are required. So far, styrene-based resins having high strength include styrene-based polymers containing a rubber-like elastic material as dispersed particles, so-called impact-resistant styrene-based resins, but these resins are cloudy and opaque, and thus have a high transparency. There was a problem that it could not be used in the required fields.

To satisfy the strength and the transparency of the styrene resin at the same time, a method of blending polystyrene with a styrene-butadiene block copolymer is used, but the improvement of the strength is insufficient. However, it is necessary to further increase the amount of the styrene-butadiene block copolymer in order to sufficiently improve the strength. However, although this method improves the strength, it does not satisfy the market in terms of transparency and moldability.

In order to supplement the moldability, for example, there is a styrene resin to which a plasticizer such as mineral oil is added. However, during molding, bleeding out causes a sweating phenomenon, resulting in deterioration of transparency of the molded product and production. However, there is a problem that it causes deterioration of sex. Also, to improve moldability,
Japanese Examined Patent Publication No. 62-25701 discloses a method of blending a styrene-based monomer and a second monomer, for example, a copolymer of butyl acrylate and a styrene-butadiene copolymer. However, although this method certainly improves the strength, it has a problem in moldability and heat resistance because the glass transition temperature of the obtained resin is low.

Further, in JP-A-62-169812, in the presence of a styrene-butadiene block copolymer,
A method of polymerizing styrene, butyl acrylate and methyl methacrylate is disclosed. Although the resin obtained by this method is improved in strength and moldability, there is a problem that a sweating phenomenon due to bleed-out occurs at the time of molding, resulting in a marked decrease in transparency and productivity.

Further, in Japanese Examined Patent Publication No. 2-48005, as a method for imparting a balance between strength and transparency without adding a rubber component to a styrene resin, a styrene-methyl methacrylate copolymer having a low residual amount is left in the copolymer. A method is disclosed in which the total amount of the molecular weight compound is set to a specific amount or less. However, this method improves the transparency considerably as compared with the case where the rubber component is not contained, but the strength is not the one satisfying the market.

[0008]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention A rubber-modified styrene resin composition which solves the above-mentioned problems in the prior art and has an excellent balance of strength, transparency and moldability is provided.

[0009]

[Means for Solving the Problems] (Meth) acrylic acid or its alkyl ester monomer is introduced as a monomer copolymerizable with a styrene monomer, and a polymer composed of these monomers is continuously phased. In the rubber-modified styrenic resin composition having a rubbery polymer as a dispersed phase, by limiting the total amount of low molecular weight compounds having a specific molecular weight or less therein to a specific amount or less, strength, transparency, and moldability of It was found that a rubber-modified styrene resin composition having an excellent balance can be obtained, and the present invention has been completed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention is a rubber-modified styrene resin composition, wherein the continuous phase comprises 30 to 80% by weight of a styrene monomer component and at least one (meth).
Acrylic acid or its alkyl ester monomer component 70
Is a styrenic copolymer (A) composed of 20 to 60% by weight, and a dispersed phase is a rubbery polymer (B) composed of 20 to 60% by weight of a styrene polymer and 80 to 40% by weight of a butadiene polymer, The weight ratio of (A) and (B) is 98/2 to 7
0/30, wherein the total amount of low molecular weight compounds having a polystyrene-reduced weight average molecular weight of 500 or less by gel permeation chromatography of 500 or less in the composition is 2.0% or less, and a transparent rubber-modified styrene. -Based resin composition.

The second embodiment is a transparent rubber-modified styrene resin composition, wherein the dispersed rubber-like particles in the composition have an average particle diameter of 0.2 to 0.8 μm.

In the third embodiment, the rubber-modified resin composition according to the first or second embodiment is characterized in that the volume fraction of dispersed rubber-like particles in the entire rubber-modified resin composition is 0.2 to 0.6. A styrene resin composition is provided.

Hereinafter, the present invention will be described in detail.

Styrene-based copolymer (A) used in the present invention
Is a multi-component copolymer comprising a styrene monomer and at least one (meth) acrylic acid or its alkyl ester monomer.

Although styrene is generally used as the styrene-based monomer, o-methylstyrene, p-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, p-ethylstyrene, p-t. It is possible to use a nuclear alkyl-substituted styrene such as butyl styrene, an α-nuclear alkyl-substituted styrene such as α-methylstyrene, α-methyl-p-methylstyrene, a halogenated styrene such as o-chlorostyrene or p-chlorostyrene. it can. Preferred styrene-based monomers include styrene, α-methylstyrene and p-methylstyrene, with styrene being particularly preferred. These styrenic monomers may be used alone or in combination of two or more.

As the (meth) acrylic acid or its alkyl ester monomer, methyl methacrylate is generally used, but acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, methacrylic acid, methacrylic acid are used. Ethyl, n-butyl methacrylate, etc. can also be used.
You may use these monomers individually or in mixture of 2 or more types.

The ratio of the styrene-based monomer component to the (meth) acrylic acid or its alkyl ester monomer component is 30 to 80% by weight of the styrene-based monomer component, (meth).
Acrylic acid or its alkyl ester monomer component 70
˜20% by weight, preferably styrene-based monomer component 35
60% by weight, 65 to 40% by weight of (meth) acrylic acid or its alkyl ester monomer component. When the content of the styrene-based monomer component is 30% by weight or less, it does not satisfy the market in terms of cost, and when it exceeds 80% by weight, the strength of the styrene-based resin composition decreases.

As the low molecular weight compound having a polystyrene-reduced weight average molecular weight of 500 or less by gel permeation chromatography according to the present invention, each monomer,
Examples thereof include dimers, trimers, oligomer components, polymerization solvents, and plasticizers such as mineral oil.

The total amount of these low molecular weight compounds is 2.0%
Hereafter, it is preferably 1.0% or less.

The total amount of styrene-based monomer and (meth) acrylic acid ester monomer remaining in the resin of the present invention is
It is preferably 0.1% by weight or less. 0.1% by weight
If it exceeds, it is not preferable in terms of food hygiene.

Further, the total amount of oligomer components having a polystyrene-equivalent weight average molecular weight of 500 or less produced by gel permeation chromatography produced from styrene-based monomers and (meth) acrylic acid ester monomers is 0.7% by weight or less. Is. If it exceeds 0.7% by weight, it causes a sweating phenomenon during sheet molding, resulting in a decrease in transparency and productivity. Further, it has a function of lowering the strength, which is not preferable.

The rubbery polymer (B) used in the present invention includes 10 to 60% by weight of a styrene polymer and 90 to 40% by weight of a butadiene polymer, preferably 20 to 50% by weight of a styrene polymer and butadiene. Polymer 80-50% by weight
It should consist of

The content of butadiene in the rubber-like polymer is 40
If less than 10% by weight, Izod impact strength is poor,
If it exceeds, the transparency is poor.

The butadiene polymer contained in the rubbery polymer (B) has a content of 1,4-cis bonds of about 9
High cis polybutadiene having a content of 5% or more, middle cis polybutadiene having a content of 1,4-cis bonds of about 90 to 94%, low cis polybutadiene having a content of 1,4-cis bonds of about 38% or less, etc. It can be appropriately selected from known ones.

The ratio of the rubber-like polymer to the styrene polymer (A) consisting of the styrene monomer component and the (meth) acrylic acid or its alkyl ester monomer component is 2
-30% by weight, preferably 5-20% by weight. When the amount of the rubber-like polymer is less than 2% by weight, the effect of improving the strength is hardly seen, and when it exceeds 30% by weight,
Moldability and transparency of the rubber-modified styrene-based resin composition will decrease.

The dispersed rubber-like particles in the present invention have an average particle diameter of 0.2 to 0.8 μm, and more preferably 0.3 to.
It is 0.7 μm. If the average particle size is less than 0.2 μm, the strength will decrease, and if it exceeds 0.8 μm, the transparency will decrease.

The average particle size as used in the present invention is a transmission electron microscope photograph of a rubber-modified styrenic resin composition dyed with osmium acid using an ultrathin section method, and a circle of 1000 dispersed rubber-like particles is taken. It is a value calculated by measuring the converted particle size and using the following formula.

[0028]

[Equation 1] As a method for controlling the average particle size of the dispersed rubber-like particles,
It can be appropriately selected from known methods such as a method of changing the temperature and stirring speed during the polymerization, a method of adding an initiator or a chain transfer agent during the polymerization, and a method of changing the structure, molecular weight or viscosity of the rubber-like polymer to be used.

Further, in the present invention, the volume fraction of dispersed rubber-like particles in the whole rubber-modified styrene resin composition is in the range of 0.2 to 0.6, preferably 0.3 to 0.5. is required. When the volume fraction is less than 0.2, strength such as impact resistance is lowered, and when it exceeds 0.6, transparency is lowered.

The volume fraction of the dispersed rubber-like particles in the present invention is a transmission electron microscope photograph taken by the same method as described above, and the area (X) of the dispersed rubber-like particle phase in the photograph and the continuous phase ( Y) is obtained by using an image processing device, and is obtained according to the formula of X / (X + Y).

For the rubber-modified styrenic resin composition of the present invention, a known polymerization method can be appropriately selected, but in order to reduce the formation of low molecular weight compounds, avoid thermal polymerization and use an initiator. Is preferred.

Examples of the initiator include ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylhexanone peroxide, 1,1-bis (t-butylperoxy) cyclohexane, and n. -Butyl-4,4-
Peroxyketals such as bis (t-butylperoxy) valerate, cumene hydroperoxide, diisopropylbenzene peroxide, hydroperoxides such as 2,5-dimethylhexane-2,5-dihydroperoxide, t- Butyl cumyl peroxide, α, α′-bis (t-butylperoxy-m-isopropyl) benzene, 2,5-dimethylhexane, 2,
Dialkyl peroxides such as 5-di (t-butylperoxy) hexyne-3, decanoyl peroxide,
Diacyl peroxides such as lauroyl peroxide, benzoyl peroxide and 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-azobis (2-methylbutyronitrile), 1,
There are azo compounds such as 1′-azobis (cyclohexane-1-carbonitrile), and these can be used alone or as a mixture of two or more kinds. Also,
The method of adding these polymerization initiators is not particularly limited, and a method of batch charging at the beginning of polymerization, a method of dividing and adding in several times from the beginning of the polymerization to the latter half of the polymerization, or the two methods are used at the same time. You can also
In order to reduce the low molecular weight components, it is better to use an initiator.

In the present invention, a chain transfer agent or a solvent may be optionally used during the polymerization. Examples of the chain transfer agent include terpinolene, α-methylstyrene dimer, n-dodecyl mercaptan and t-dodecyl mercaptan. Examples of the solvent include aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, aliphatic hydrocarbons, dialkyl group ketones, and a mixture of two or more kinds. The amount of the solvent used is 0.2 to 20% by weight. 0.2
If it is less than 20% by weight, the fluidity is lowered, and if it exceeds 20% by weight, the proportion of the resin remaining in the resin is increased, which causes a sweating phenomenon, and the transparency and the productivity are lowered. Further, the polymerization rate is remarkably lowered, and the energy for recovering the solvent is increased, resulting in poor economic efficiency.

Furthermore, the composition of the present invention may contain a lubricant such as zinc stearate, calcium stearate, or ethylene bisstearylamide, a phenolic or phosphorus antioxidant, an ultraviolet absorber, a colorant, etc., if necessary. It may contain an additive.

[0035]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.
Moreover, the following methods were used for measuring the physical properties and the like in Examples and Comparative Examples. The results are shown in Tables 1 and 2. (1) The weight average molecular weight is G manufactured by Shimadzu Corporation by the GPC method.
It measured using PC (LC-6A) and the Showa Denko KK-made GPC column (KF-806L, 3 series).
(2) The volume average particle diameter of the rubber particles is obtained by taking a photograph of a rubber-modified styrene resin composition by the ultrathin section method using a transmission electron microscope and measuring the particle diameter of 1000 rubber-like polymer particles. , (Formula I). (3) For DuPont impact strength, A4 size test pieces are cut from the sheet. Mass from height 50 cm 0.05 to 0.3
The weight of kg was dropped and measured. (4) The haze was measured according to ASTM D1003 by preparing a test piece having a thickness of 2 mm with an injection molding machine. (5) The melt flow rate was measured according to ASTM D1238. In the examples given below, the internal volume 2 equipped with a stirrer
A rubber-modified styrene-based resin composition was produced using a polymerization device in which two 0 L reactors were connected in series and then a twin-screw extruder equipped with a devolatilization device was connected. (Example 1) 34.6 parts by weight of styrene, 55.4 parts by weight of methyl methacrylate, and 5% at a styrene content of 25% by weight.
Styrene solution styrene-butadiene block copolymer having a viscosity of 15 centipoise (Tufden 2 manufactured by Asahi Kasei Corporation)
003) A solution prepared by adding a raw material solution of 6.5 parts by weight, 0.02 parts by weight of t-butylperoxybenzoate, 2.48 parts by weight of ethylbenzene, and 1.0 part by weight of mineral oil was charged into a reactor at 120 ° C., 140 ° C. Polymerization is carried out at ℃. An electron micrograph of the obtained rubber-modified styrenic resin was taken to measure the average particle size of dispersed rubber particles in the resin. Further, the monomer composition of the obtained rubber-modified styrene resin matrix was determined using an NMR analyzer. (Examples 2 and 3) Other than changing the rotation speed of the stirrer,
The same operation as in Example 1 is performed. (Example 4) 34.2 parts by weight of styrene, 54.8 parts by weight of methyl methacrylate, 5% at a styrene content of 25% by weight.
Styrene solution styrene-butadiene block copolymer having a viscosity of 15 centipoise (Tufden 2 manufactured by Asahi Kasei Corporation)
003) A solution containing a raw material solution consisting of 6.2 parts by weight, 0.02 parts by weight of t-butylperoxybenzoate, 3.48 parts by weight of ethylbenzene and 1.3 parts by weight of mineral oil was charged into a reactor at 130 ° C. and 155 Polymerization is carried out at ℃. An electron micrograph of the obtained rubber-modified styrenic resin was taken to measure the average particle size of dispersed rubber particles in the resin. Further, the monomer composition of the matrix of the obtained rubber-modified styrene resin was analyzed using an NMR analyzer. (Examples 5 and 6) Other than changing the rotation speed of the stirrer,
The same operation as in Example 1 is performed.

(Comparative Example 1) Styrene 32.6 parts by weight, methyl methacrylate 52.1 parts by weight, styrene content 25
Styrene-butadiene block copolymer having a 5% styrene solution viscosity of 15 centipoise by weight (Asahi Kasei Corporation)
Manufactured by Tafden 2003), 6.5 parts by weight, 5.6 parts by weight of ethylbenzene and 3.2 parts by weight of mineral oil were added to the reactor, and a solution was charged into the reactor at 130 ° C. for 15 days.
Polymerization is carried out at 5 ° C. An electron micrograph of the obtained rubber-modified styrenic resin was taken to measure the average particle size of dispersed rubber particles in the resin. Further, the monomer composition of the matrix of the obtained rubber-modified styrene resin was analyzed using an NMR analyzer. (Comparative Example 2) The same operation as in Example 1 is performed except that the rotation speed of the stirrer is changed. (Comparative Example 3) Styrene 34.
6.2 parts by weight of 2 parts by weight, 54.8 parts by weight of methyl methacrylate, a styrene content of 25% by weight, and a styrene-butadiene block copolymer having a 5% styrene solution viscosity of 15 centipoise (Tufden 2003, manufactured by Asahi Kasei Corporation). Part, 3.5 parts by weight of ethylbenzene and 1.3 parts by weight of mineral oil were added to the raw material solution and charged into the reactor.
The same operation as in Example 1 is performed except that the polymerization is performed at 0 ° C. and 155 ° C. (Comparative Example 4) The same operation as in Comparative Example 3 is performed except that the rotation speed of the stirrer is changed. Comparative Example 5 The same operation as in Example 1 was performed except that the amount of the styrene-butadiene block copolymer was 3.0 parts by weight.

[0037]

[Table 1]

[0038]

The rubber-modified styrenic resin composition of the present invention reduces the transparency due to a sweating phenomenon at the time of molding by keeping the total amount of the low molecular weight compounds remaining in the rubber composition to a specific amount or less. Strength that does not reduce productivity,
A rubber-modified styrene-based resin composition having an excellent balance of transparency and moldability can be obtained.

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Claims (3)

[Claims] 1. A rubber-modified styrene resin composition comprising:
A continuous phase is a styrene copolymer (A) comprising 30 to 80% by weight of a styrene monomer component and 70 to 20% by weight of at least one (meth) acrylic acid or its alkyl ester monomer component, Disperse phase is styrene polymer 10
To 60% by weight and 90 to 40% by weight of butadiene polymer, which is a rubber-like polymer (B), and the weight ratio of (A) and (B) is 98/2 to 70/30. A transparent rubber-modified styrene-based resin composition, characterized in that the total amount of low molecular weight compounds having a polystyrene-equivalent weight average molecular weight of 500 or less as determined by gel permeation chromatography is 2.0% or less. 2. The average particle size of the dispersed rubber-like particles is 0.2 to.
The rubber-modified styrene resin composition according to claim 1, which has a thickness of 0.8 μm. 3. The rubber-modified styrenic resin composition according to claim 1, wherein the volume ratio of the dispersed rubber-like particles to the entire rubber-modified resin composition is 0.2 to 0.6.