JPH07119347B2 - Styrene resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rubber-modified styrene-based resin composition having excellent heat resistance, impact resistance, and releasability, which is preferably used in the fields of home appliances and OA.

[Prior Art] In order to improve the heat resistance of a styrene resin, a method of copolymerizing styrene with a comonomer such as α-methylstyrene, maleic anhydride, or methacrylic acid is generally used. However, the obtained copolymer is expensive because of the high cost of the comonomer, and has problems such as low fluidity and high hygroscopicity, which limits its use.

A rubber-modified styrene resin composition having heat resistance, impact resistance, and releasability, which contains a rubber-like polymer as dispersed particles in an aromatic monovinyl polymer, is disclosed in JP-A 1-247446. However, there is a problem that the molecular weight of the aromatic monovinyl polymer is small and the heat resistance is not sufficient.

[Problems to be Solved by the Invention] An object of the present invention is to provide a rubber-modified styrene-based resin composition having an excellent balance of heat resistance, impact resistance, and releasability, which solves the above problems. It is a thing.

[Means for Solving the Problems] As a result of intensive studies conducted by the present inventors to solve the above-mentioned problems, as a result of containing a specific rubber-like polymer in a matrix polystyrene resin having a specific molecular weight, The above object is achieved by a styrene-based resin composition obtained by adding a specific amount of a specific release agent to a rubber-modified styrene-based resin in which the total amount of dimers and styrene trimers and the total amount of residual volatile components are less than specific amounts. Based on this finding, the present invention has been completed.

That is, the present invention relates to 4.0-8.0% by weight of a particulate rubbery polymer having a particle size of 1.0 to 4.0 μm in a matrix polystyrene resin having a molecular weight of 16 × 10 ^{4 to} 24 × 10 ⁴ and a styrene dimer. 500 with respect to the rubber-modified styrene resin (A) and the composition obtained by polymerizing styrene containing a styrene trimer in a total amount of 0.5% by weight or less and residual volatile components in a total amount of 500 ppm or less with a rubber-like polymer. ~ 3000ppm of one or more compounds selected from saturated higher aliphatic carboxylic acids and their metal salts, 50% by weight of compounds having a melting point of 100 ° C or less
The present invention provides a styrene resin composition comprising the following release agent (B).

The rubber-modified styrenic resin (A) in the present invention is obtained by polymerizing styrene and a rubber-like polymer, and is a method commonly used in the production of conventional rubber-modified styrenic resins, for example, an emulsion polymerization method or a block-like method. It can be produced by any method such as a polymerization method, a bulk-suspension polymerization method, and a suspension polymerization method, but in the present invention, from the economically advantageous point, the bulk-suspension polymerization method or the continuous bulk method is used. A production method by a polymerization method is selected.

Next, an example of the method for producing the rubber-modified styrene resin of the present invention will be described. First, the rubber-like polymer is added to a mixed solution containing styrene and other copolymerizable monomer used as desired, and dissolved at a temperature of about 20 to 70 ° C., and then the solution is stirred. Through a devolatilization component step of separating the solid component and the volatile components such as unreacted monomer and solvent from the final stage of the polymerization by feeding the mixture into one or more, preferably two or more polymerization vessels, The desired resin is obtained.

In this method, the first stage polymerization vessel is fed with a rubber-like polymer dissolved in a monomer, and the monomer and a polymerization initiator or a chain transfer agent used as desired are It may be fed to the polymerization vessel at any stage.

In this polymerization method, examples of the polymerization initiator used as desired include t-butyl hydroperoxide,
Di-t-butyl peroxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide,
1,1-bis (t-butylperoxy) cyclohexane,
2,5-Dimethyl-2,5-di (t-butylperoxy) hexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,2-bis (4,4- Organic peroxides such as di-t-butylperoxycyclohexane) propanone, azobisisobutyronitrile, azobis-2,
Examples thereof include azo compounds such as 4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, and azobiscyanovaleric acid. These can be used alone or in admixture of two or more, but those with a half-life temperature temperature (10 hours) of 100 ° C or less
It is preferable to mix and use those having a temperature of not less than ° C.

Examples of the chain transfer agent used as desired include mercaptans such as n-dodecyl mercaptan and t-dodecyl mercaptan, α-methylstyrene dimer, 1-phenyl-butene-2-fluorene, terpinol, and chloroform. Is mentioned.

The styrene resin as the matrix component obtained by polymerizing the styrene monomer is a copolymer of a styrene homopolymer or a monomer copolymerizable with styrene, and as the copolymerizable monomer, For example, α-methylstyrene, vinyltoluene, vinylethylbenzene, vinylxylene, p-
aromatic monovinyl compounds such as t-butylstyrene, α-methyl-p-methylstyrene and vinylnaphthalene,
Acrylonitrile, methyl methacrylate, methyl acrylate, methacrylic acid, acrylic acid, maleic anhydride,
Examples thereof include phenylmaleimide. 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 the total monomers containing styrene. Used in proportion.

The type of the rubber-like polymer is not particularly limited, and those conventionally used for rubber-modified styrenic resins such as natural rubber, polybutadiene rubber, polyisoprene rubber,
A synthetic rubber such as a styrene-butadiene copolymer rubber, a styrene-isoprene copolymer rubber, a butyl rubber, an ethylene-propylene copolymer rubber, or a graft copolymer rubber of these rubbers and styrene is used.

The amount of the rubber-like polymer in the rubber-modified styrenic resin obtained as described above can be calculated from the concentration of the charged rubber and the final conversion rate of the resin. The particle size of the rubber-like polymer is determined as follows as the area average particle size (diameter) (Ds) of the rubber-like polymer. That is, pellets of rubber-modified styrenic resin having a small orientation were treated with a 3 wt% osmium tetroxide aqueous solution and thinned with an ultramicrotome, and a transmission electron microscope image of this was obtained.
Approximate the diameter (D) in the major axis direction of the rubber-like polymer particles on the image
The area average particle diameter (diameter) (Ds) of the rubber-like polymer is obtained by measuring 1000 particles and determining the area average value according to the following formula.

(N is the number of rubber-like polymer particles having a diameter D.) It is necessary that the content of the rubber-like polymer is 4.0 to 8.0% by weight. If it is less than 4.0% by weight, impact resistance is lowered, and 8.0% by weight.
If it exceeds, heat resistance will decrease. The preferred range is 4.0-7.5
% By weight. The rubber-like polymer has a particle size of 1.0 to 4.0 μm.
If it is less than 1.0 μm, the impact resistance is lowered, and if it exceeds 4.0 μm, the impact resistance and the heat resistance are lowered. The preferred range is 1.2 to 3.6 μm.

Next, the molecular weight of the matrix polystyrene resin is determined as follows. That is, after the rubber-modified styrene resin was dissolved in methyl ethyl ketone, it was centrifuged to remove the gel component, and the supernatant containing the matrix component was dried. Then, a 0.2 wt% solution of the matrix component was prepared using tetrahydrofuran as a solvent, and a weight average molecular weight (Mw) was used using GPC150C manufactured by Waters Co.
Was calculated in terms of polystyrene. The molecular weight of the matrix polystyrene resin is required to be in the range of 16 × 10 ^{4 to} 24 × 10 ⁴ , and if it is less than 16 × 10 ⁴ , impact resistance and heat resistance will decrease, and if it exceeds 24 × 10 ^4. Liquidity decreases. The preferred range is 17 × 10 ⁴ to 23 × 10 ⁴ .

Further, in the rubber-modified styrene resin of the present invention, the total amount of styrene dimer and trimer in the resin needs to be 0.5% by weight or less. If this total amount exceeds 0.5% by weight, the heat resistance decreases. A preferred range is 0.4% by weight or less. Further, the rubber-modified styrene resin of the present invention requires that the total amount of residual volatile components in the resin is 500 ppm or less. If this total amount exceeds 500 ppm, the heat resistance decreases.
The preferred range is 400 ppm or less. The residual volatile components include styrene, isopropylbenzene, n-propylbenzene, ethylbenzene and the solvent used for the polymerization.

The total amount of the above-mentioned styrene dimer and trimer and the total amount of residual volatile components were determined by using a gas chromatography GC-3BF manufactured by Shimadzu Corporation.

Next, as the saturated higher aliphatic carboxylic acid used as the component (B), a linear saturated monocarboxylic acid having about 12 to 42 carbon atoms is used. For example, lauric acid (44 ℃), myristic acid (54 ℃), palmitic acid (63 ℃), stearic acid (70 ℃), behenic acid (81 ℃), montanic acid (89 ℃)
And so on. Examples of the metal of these metal salts include lithium, sodium, potassium, magnesium, calcium, aluminum and zinc. Typical metal salts of higher aliphatic carboxylic acids include magnesium stearate (132 ° C) and stearin. Aluminum oxide (103
℃), calcium stearate (180 ℃), zinc stearate (140 ℃) and the like (parentheses represent the melting point).

In the composition of the present invention, the release agent (B) is composed of one or more compounds selected from the saturated higher fatty acids and their metal salts, and the compound having a melting point of 100 ° C. or less is 50% by weight or less. It is necessary. If the content of the compound having a melting point of 100 ° C. or less exceeds 50% by weight, the heat resistance will decrease. Further, the amount of the release agent needs to be 500 to 3000 ppn with respect to the composition. If it is less than 500 ppm, the releasability will decrease, and 3000 ppm
If it exceeds, heat resistance will decrease. The preferred range is 1000-25
It is 00 ppm.

The method of adding the release agent is not particularly limited and may be obtained by adding it to a styrene solution in which rubber, which is a raw material of a rubber-modified styrene resin, is dissolved, or by adding it to a polymerization step or a devolatilizing component step. It may be added to any of the resin pellets.

The rubber-modified styrenic resin composition of the present invention contains various additives that are usually used as desired, for example, a lubricant such as ethylene bisstearamide or an organic polysiloxane,
Mineral oil and the like, and as antioxidants, for example, hindered phenols, hindered bisphenols,
Hindered trisphenols, etc., for example, 2,6
-Di-t-butyl-4-methylphenol, stearyl-β- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, triethylene glycol-bis-
3- (3-t-butyl-4-hydroxy-6-methylphenyl) propionate, etc., or phosphorus compounds such as tri (2,4-di-t-butylphenyl) phosphite, 4,4′-butylidene -Bis- (3-methyl-6
-T-Butylphenyl-di-tridecyl) phosphite and the like can be added. Further, if necessary, stabilizers, dyes, pigments, fillers, lubricants, plasticizers, antistatic agents and the like can be added.

Further, the styrene resin composition of the present invention, if desired,
General-purpose polystyrene (GPPS) and other polymers such as polyphenylene ether and ABS can also be blended.

[Examples] Hereinafter, the present invention will be described based on Examples, but the present invention is not limited thereto. The methods for measuring physical properties are shown below.

(1) Melt index (MI) Measured according to JIS-K-7210.

(2) Izod impact strength Measured according to JIS-K-7110 (23 ° C, notched).

(3) Ball pressure temperature Put the test piece in a constant temperature bath, apply a static load of 20N for 1 hour using a steel ball with a diameter of 5 mm, remove the steel ball, and immediately remove it in water at 25 ° C ± 5 ° C. The temperature at which the diameter of the dented hole is 2 mm (0.209 mm when converted to depth) when cooled for 30 minutes and measured.

(4) Releasability A complicated molded product with many ribs and bosses was injection-molded at a molding temperature of 220 ° C., and the appearance of the molded product was evaluated according to the following ranks.

⊚: No scratches or whitening.

◯: Some scratches and whitening.

Δ: There are considerable scratches and whitening.

X: There are scratches, whitening, and cracks.

Example 1 A mixture having the following composition was continuously fed to a first polymerization tank having a volume of 23 l at a feed rate of 20 l per hour.

Rubbery polymer: NF35AS (polybutadiene manufactured by Asahi Kasei Corporation)
5.2 wt% Styrene 89.8 wt% Ethylbenzene 5.0 wt% n-Dodecyl mercaptan 200 ppm 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane 300 ppm 2,5-Dimethyl-2,5-di (t- Butylperoxy) hexane 100 ppm The temperature of the first polymerization tank was 115 ° C, and the rotation speed was 150 rpm.

Then, the solution was sequentially fed to a second polymerization tank having a capacity of 33 l and a third polymerization tank having a capacity of 33 l. Temperature and rotation speed are 137 ℃, 50rpm, 160, respectively
It was 20 ° C. at 20 ° C. The addition rate at the outlet of the third polymerization tank is 8
It was 5% by weight.

Further, volatile components were removed in a vacuum chamber heated to a temperature of 230 to 280 ° C to obtain pellet-shaped rubber-modified styrene resin. The following operating conditions are shown in Table 1.

2500 ppm of calcium stearate was added to the pellets and kneaded with an extruder. Table 2 shows the composition and physical properties of the obtained resin composition and the resin structure of the rubber-modified styrene resin.

Examples 2 to 4 In Example 1, the operating conditions were changed as shown in Table 1 and the release agent composition was changed as shown in Table 2. Table 2 shows the physical properties of the obtained resin composition and the resin structure of the rubber-modified styrene resin.

Comparative Examples 1 to 5 In Example 1, the operating conditions were changed as shown in Table 1 and the release agent composition was changed as shown in Table 2. Table 2 shows the physical properties of the obtained resin composition and the resin structure of the rubber-modified styrene resin.

[Effects of the Invention] According to the present invention, a styrene resin composition having an excellent balance of heat resistance, impact resistance and releasability, and particularly excellent heat resistance can be obtained.

Therefore, the styrenic resin composition of the present invention can be used for home appliances and OA.
It is preferably used as a material in the field and its industrial value is extremely large.

Claims (1)

[Claims] 1. A matrix polystyrene resin having a molecular weight of 16 × 10 ^{4 to} 24 × 10 ⁴ containing 4.0 to 8.0% by weight of a particulate rubbery polymer having a particle size of 1.0 to 4.0 μm, a styrene dimer and styrene. A rubber-modified styrenic resin (A) obtained by polymerizing styrene containing a trimer in a total amount of 0.5% by weight or less and a residual volatile component in a total amount of 500 ppm or less and a rubber-like polymer, and a composition of 500 to A release agent (B) comprising 3000 ppm of a saturated higher aliphatic carboxylic acid and one or more compounds selected from their metal salts, and 50% by weight or less of a compound having a melting point of 100 ° C or less. A styrene-based resin composition comprising: