JPH0613583B2 - Method for producing copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a copolymer suitable for providing a thermoplastic resin composition having excellent environmental stress crack resistance and improved layered peeling property. It relates to a manufacturing method.

[Conventional technology]

When the rubber-containing styrene resin is brought into contact with a chemical under stress, a crack is generated, and in a remarkable case, a phenomenon of breaking is observed. This phenomenon is called environmental stress crack phenomenon,
As is well known, it is remarkably observed in chemicals such as alcohols, carboxylic acids, esters, alkanes and alkenes, which have low solubility in resins.

The environmental stress cracking phenomenon is such that even when no external force is applied to the resin molded product, the distortion during molding that remains inside the molded product
Since it is generated by being opened by contact with a chemical, it greatly limits the use of the rubber-containing styrene resin.

The rubber component content and the resin component molecular weight are known as factors that affect the environmental stress crackability of rubber-containing styrenic resins. Increase the rubber component content or increase the resin component molecular weight. The higher the value, the better the environmental stress crackability, but the hardening was not practically sufficient.

Recently, the present inventors have found that the environmental stress cracking property of the rubber-containing styrene-based resin is dramatically improved by mixing the acrylic acid ester-based polymer with the rubber-containing styrene-based resin (special feature: (Kaisho 58-179257).

However, although the composition of the invention has a remarkable effect of improving the environmental stress cracking property, a mica-like layered delamination phenomenon may be observed in an injection-molded product, and improvement has been required. The layered delamination phenomenon is remarkable in a molded product injection-molded under a high shear rate condition, and is remarkable in the vicinity of the gate.

The layered peeling phenomenon occurs when the acrylic acid ester polymer particles dispersed in the rubber-containing styrene resin undergoes flat deformation due to shear stress during injection molding. For the purpose of preventing the flat deformation of the acrylic acid ester-based polymer particles, it is effective to copolymerize polyfunctional vinyl monomer resistance during the polymerization of the acrylic acid ester-based polymer.

[Problems to be solved by the invention]

However, for example, an acrylic acid ester-based polymer obtained by copolymerizing a polyfunctional vinyl monomer such as divinylbenzene and ethylene glycol dimethacrylate has a high gel content although the layered peeling phenomenon is improved. However, the effect of improving the environmental stress cracking resistance of the rubber-containing styrene resin is insufficient. Therefore, by using a polyfunctional vinyl monomer and a chain transfer agent in combination to produce an acrylate polymer having a low gel content and a branched structure, the layered delamination phenomenon and environmental stress resistance can be improved. It is possible to balance the crackability, but the effect was unsatisfactory in practice.

It is an object of the present invention to provide a method for producing a copolymer, in which the above-mentioned drawbacks of the prior art are improved.

[Means for solving problems]

Briefly describing the present invention, the present invention relates to a method for producing a copolymer, which comprises a monoacrylic acid ester monomer 10
0 parts by weight, or monoacrylic acid ester monomer 50
100 parts by weight of a mixture containing at least 50% by weight and a copolymerizable monomer selected from styrene monomers, nitrile monomers and monomethacrylic acid ester monomers, and the nitrile monomer is less than 30% by weight And the following general formula I: [Wherein R ₁ and R ₂ are H or CH ₃ groups, and X is — (CH ₂ ) ₁ (CH
R ³ ) _m (CR ⁴ R ⁵ ) _n -group (1, m and n are each an integer of 0 or more, and 1 + m + n is an integer of 5 or more, R ³ , R
⁴ and R ⁵ are an alkyl group, an aryl group, an alkoxyl group or a hydroxyl group) and / or (X and y are each integer of 0 or more, ^{R 6} and _{R 7} is H or CH ₃ group, Y is -O -, - S -, - SO
₂ -, - CH ₂ -, shows an alkylidene group or an alkylene group). ] A long-chain bifunctional monomer represented by 0.0
1 to 10 parts by weight are copolymerized in an emulsified state, the solubility parameter is 8.4 to 9.8 (Cal / CC) ^1/2 , the glass transition temperature is 20 ° C. or lower, and the gel content is 70 parts by weight. % Or less copolymer is obtained.

The mixture of the copolymer according to the method of the present invention (hereinafter referred to as an acrylic acid ester-based polymer) and the rubber-containing styrene-based resin has excellent resistance to environmental stress cracking, and is unlikely to exhibit the layered peeling phenomenon.

Examples of the monoacrylic ester monomer used as a raw material in the method for producing an acrylic ester-based polymer according to the present invention include methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate, octyl acrylate, hydroxyethyl acrylate, Methoxyethyl acrylate, phenyl acrylate, glycidyl acrylate and the like can be mentioned.

Styrene-based monomers that can be copolymerized with monoacrylic acid ester monomers include styrene, α-methylstyrene, and t-butylstyrene, and nitrile monomers include acrylonitrile and methacrylonitrile. Examples of the ester monomer include methyl methacrylate, butyl methacrylate, glycidyl methacrylate and the like, and the monoacrylic acid ester is contained in an amount of 50% by weight or more in the monoacrylic acid ester monomer and the copolymerizable monomer mixture thereof. Keep the nitrile monomer below 30% by weight.

Further, examples of the long-chain bifunctional monomer represented by the general formula I include [general formula I] [Wherein R ¹ and R ² are H or CH ₃ groups, and X is — (CH ₂ ) ₁ (CH
R ³ ) _m (CR ⁴ R ⁵ ) _n -group (1, m and n are each an integer of 0 or more, and 1 + m + n is an integer of 5 or more, R ³ , R
⁴ and R ⁵ are an alkyl group, an aryl group, an alkoxyl group or a hydroxyl group) and / or (X and y are each an integer of 0 or more, R ⁶ and R ⁷ are H or CH ³ groups, Y is -o-, -s-, -SO _2- , -CH _2- , alkylidene group or Is an alkylene group). ] A specific example of X is And the like. Specific examples of the compound represented by the general formula I include And so on.

These long-chain bifunctional monomers may be used alone or in combination of two or more.

The long-chain bifunctional monomer is used in an amount of 0.01 to 10 parts by weight, preferably 0.01 to 7 parts by weight, based on 10.0 parts by weight of the monomer to be copolymerized as described above. However, if this amount is less than 0.01 parts by weight, the effect of improving the layered peelability is poor, while if it is 10 parts by weight, the effect is saturated.

Further, in the production method of the present invention, it is essential to copolymerize the long-chain bifunctional monomer, but in addition to the long-chain bifunctional monomer, other polyfunctional vinyl monomer is added. A small amount may be copolymerized. Examples of polyfunctional vinyl monomers that can be used are divinylbenzene, ethylene glycol dimethacrylate, 1,3-butylene glycol methacrylate, 1,4-butylene glycol dimethacrylate, propylene glycol dimethacrylate, triallyl cyanurate, isocyanuric acid. Triallyl acid, trimethylolpropane trimethacrylate, allyl acrylate, allyl methacrylate, vinyl acrylate, vinyl methacrylate and the like can be mentioned.

The acrylic acid ester-based polymer according to the present invention has a viscosity of 8.4 to 9.8.
It is necessary to have a solubility parameter of (cal / cc) _1/2 , and a more preferable numerical range is 8.6 to 9.6 (cal / cc) _1/2 . As used herein, the solubility parameter refers to a polymer handbook (Polymer) edited by J. Brandrup and EHImmergut, published by John Wiley End Sons, Inc. in 1975, New York City.
Handbook) 2nd edition, pages N-337 to N359, using the solubility parameter values, the solubility parameter δ _T of the copolymer is defined as the individual vinyl monomers constituting the copolymer composed of m kinds of vinyl monomers. It is calculated from the solubility parameter δ _n of the homopolymer of the polymer and its weight fraction W _{n according} to the following formula II.

For example, the solubility parameters for polybutyl acrylate and ethyl polyacrylate are 8.8 (cal / cc) ^1/2 and 9, respectively.
Assuming 4 (cal / cc) ^1/2 , the solubility parameter of a copolymer composed of 70% by weight of polybutyl acrylate and 30% by weight of polyethyl acrylate is calculated to be 9.0 (cal / cc) ^1/2 .

The solubility parameter of the acrylate polymer is
If it is less than 8.4 or exceeds 9.8, the composition obtained by mixing with the rubber-containing styrene resin has low environmental stress crack resistance, which is not preferable.

The acrylic acid ester polymer according to the present invention needs to have a glass transition temperature of 20 ° C. or lower, preferably 10 ° C. or lower. If the glass transition temperature exceeds 20 ° C., the environmental stress crack resistance of the composition obtained by mixing with the rubber-containing styrene resin becomes low, which is not preferable.

Further, the acrylic acid ester-based polymer according to the present invention needs to have a gel content of 70% by weight or less. The gel content referred to in the present specification means that 1.0 g of the polymer was precisely weighed, put in a basket made of 400-mesh stainless steel wire net, immersed in 100 g of toluene, and left at 5 ° C. for 24 hours. After that, the basket was pulled up, and the weight (g) of the polymer insoluble matter after air-drying at room temperature was measured, and the value was calculated according to the following formula III.

[(Weight of polymer insoluble matter) / 1] × 100 (%) [II
I] Gel content of acrylate polymer is 70% by weight
If it exceeds, the environmental stress crack resistance of the resin obtained by mixing with the rubber-containing styrene resin becomes low, which is not preferable.

The polymerization method in the present invention is not particularly limited,
The production by the emulsion polymerization method is industrially most advantageous, and a known technique regarding the emulsion polymerization method can be arbitrarily applied.

The acrylic ester-based polymer obtained by the present invention,
To mix with the rubber-containing styrenic resin, a known mixing technique is applied, and both components in an emulsified state, a particle state, or a molten state are blended and melt-kneaded to easily obtain an intended mixture. You can When the acrylic acid ester-based polymer is produced by an emulsion polymerization method, the polymer latex is blended with a rubber-containing styrene-based polymer in an emulsified state, a particle state or a molten state, and a dehydration step or a dehydration step is performed. At the same time, melt kneading can be performed. Examples of the melt-kneading device include a Banbury mixer, an intensive mixer, a mixed extruder, a cokneader, an extruder, and a roll. Also, JP-A-56-1316
The manufacturing method disclosed in Japanese Patent Publication No. 56 can also be applied.

The rubber-containing styrene resin referred to in the present invention refers to a group of composite thermoplastic resins composed of a rubber component, a resin component, and a covalently bonded product of the rubber component and the resin component. Polystyrene, ABS (acrylonitrile-butane-styrene) resin, heat resistant ABS
(Acrylonitrile-butadiene-styrene-α-methylstyrene) resin, AAS (acrylonitrile-acrylic ester-styrene) resin, AES (acrylonitrile-EPDM-styrene) resin, MBAS (methyl methacrylate-butadiene-acrylonitrile-styrene) resin, etc. is there.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to these examples. In addition, all parts and% described in each example are based on weight.

Example 1 and Comparative Example 1 An aqueous solution containing 150 parts of pure water, 2 parts of sodium dodecylbenzenesulfonate and 0.05 parts of potassium persulfate was heated to 70 ° C. with stirring, and the monomer mixture liquid shown in Table 1 was used. 100 parts were continuously added in 4 hours. Further, the mixture was stirred at 70 ° C. for 2 hours to complete the polymerization.

Table 2 shows the properties of the obtained acrylic acid ester-based polymer.

The long-chain bifunctional monomer used in Table 1 is as follows.

Moreover, each physical property value was calculated | required by the following method.

(1) Glass transition temperature Acrylic ester-based polymer latex was poured into an aqueous solution of calcium chloride to dry a solid, which was measured using a 910 differential scanning calorimeter and 990 thermal analyzer, which are DuPont type measuring instruments. did.

(2) Solubility Parameter The solubility parameter value [unit is (cal / cc) ^1/2 ] of each polymer used for calculating the solubility parameter in each example is as follows.

Butyl polyacrylate; 8.8 Polyethyl acrylate; 9.4 Polymethylmethacrylate; 9.5 Polyacrylonitrile; 12.5 Polystyrene; 9.1 (3) Gel content Obtained by pouring acrylic acid ester-based polymer latex into calcium chloride aqueous solution The solid was dried. 1.0g
Was accurately weighed, processed as previously described, measured and calculated according to equation III.

Application Example 1 and Reference Example 1 80 parts of ABS resin latex (as polymer) consisting of 50% of polybutadiene, 15% of acrylonitrile and 35% of styrene, and 20 parts of polymer latex of acrylic acid ester polymer shown in Table 1 (as polymer) are latex. After mixing in the state, adding calcium chloride aqueous solution, then at 95 ℃
The mixture was agitated and the resulting precipitate was filtered to recover a polymer. After drying the obtained mixture, 40 parts of the mixture was mixed with 60 parts of acrylonitrile-styrene copolymer resin (acrylonitrile content 30%) powder, 4,4′-isopropylidene-bis [monophenyl-di-alkyl ( C
_{12 ~C 15)} phosphite] [Adeka Argus Chemical Co., Ltd., were mixed in a mark (MARK) 1500] 0.3 parts of a Henschel mixer, Ltd. center Machinery Co., Ltd. V
It was supplied to C-40 (vented single-screw extruder) to obtain pellets.

A molded product was produced using the obtained pellets and the physical properties were evaluated. The results are shown in Experiment Nos. 1 to 24 in Table 3.

The measured physical properties of each example were obtained by the following methods.

(1) Tensile yield point …… ASTM D-638 (2) Izod impact strength …… ASTM D-256 (3) Chemical resistance (environmental stress crack resistance) ASTM D-638 Type I dumbbell with 50 mm deflection The time required to reach breakage when given, fixed to a jig, coated with ethylene glycol monoethyl ether, and allowed to stand at a temperature of 23 ° C. is expressed in minutes. > 300 in the table indicates that the material does not break after 300 minutes.

(4) Layered Peelability A 50 × 20 × 2 mm plate-shaped molded product having a gate of 5 × 3 × 1 mm was molded using a 5-ounce injection molding machine. In Application Example 2 and Reference Example 2 (Experiment Nos. 25 to 32) described below, the resin temperature was 240 ° C., in Application Example 1 and Reference Example 1, the resin temperature was 200 ° C., the injection speed was 90 mm / sec, and the mold temperature was 40.
℃ was made.

The layered peeling property of the gate portion of the molded product was evaluated as follows in comparison with a standard sample.

A: No peeling at all B: Peeling slightly C: Peeling considerably D: Peeling significantly Numbers 1 to 18 are application examples, and numbers 19 to 24 are reference examples. As is clear from the reference example, when the glass transition temperature, gel content, and solubility parameter of the acrylic acid ester-based polymer deviate from the scope of the present invention, environmental stress crack resistance is inferior, and a long-chain bifunctional monomer is used. When the amount of the body used is insufficient, the occurrence of a layered delamination phenomenon is observed.

Application Example 2 and Reference Example 2 The ABS resin latex and the acrylate polymer latex used in Application Example 1 were acrylonitrile-α.
-Methylstyrene copolymer (24% acrylonitrile)
After mixing with a latex in a latex state, an aqueous solution of calcium chloride was added, and the mixture was stirred at 110 ° C. The resulting precipitate is filtered to collect the polymer, and after drying,
The stabilizer used in Application Example 1 was added to 100 parts of the mixture.
3 parts were mixed and supplied to VC-40 manufactured by Chuo Kikai Seisakusho Co., Ltd. to obtain pellets.

A molded product was produced using the obtained pellets and physical properties were evaluated. The results are shown in Table 4.

All parts in the table indicate the number of parts as a polymer.

When an acrylonitrile-α-methylstyrene copolymer is used as the matrix resin, the melt viscosity of the resin is high and the resin is subjected to high shear stress at the time of injection molding. Therefore, an acrylic ester that does not copolymerize a long-chain bifunctional monomer is used. When the polymer is used, a remarkable delamination phenomenon is observed (Table 4, experiment numbers 30 and 31). However, almost no peeling phenomenon was observed in the acrylic acid ester-based polymer according to the present invention, and the effect of the present invention is clearly shown (Table 4).
Experiment number 25-29).

Example 2 120 parts of pure water and 2 parts of sodium dodecylbenzenesulfonate were charged into an autoclave and stirred while stirring at 65
The temperature was raised to ° C. Next, 0.005 parts of ferrous sulfate heptahydrate,
0.01 parts of tetrasodium ethylenediaminetetraacetate tetrahydrate,
An aqueous solution prepared by dissolving 0.3 part of sodium formaldehyde sulfoxylate in 10 parts of pure water was added.

Further, 20% of a monomer mixture liquid consisting of 70 parts of n-butyl acrylate, 30 parts of methyl methacrylate, 1.00 part of HD, and 0.5 part of ethylene glycol dimethacrylate was added to the autoclave to obtain 2.5 parts of 0.2% potassium persulfate aqueous solution. Was added to initiate polymerization.

Simultaneously with the start of the polymerization, the remaining amount of the monomer mixture solution was continuously added over 4 hours. Simultaneously with the start of polymerization, an aqueous solution prepared by dissolving 0.05 part of potassium persulfate in 20 parts of pure water was continuously added over 6 hours. After the addition of the aqueous potassium persulfate solution was completed, the contents of the autoclave were cooled to complete the polymerization.

The properties of the obtained acrylic acid ester polymer B-25 were a glass transition temperature of -18 ° C and a gel content of 0.16%.

Although B-25 has the same monomer composition as B-20, the gel content is significantly different. That is,
The gel content of the acrylic acid ester-based polymer, which is one of the essential requirements of the present invention, is not uniquely determined by the type and / or addition amount of the polyfunctional monomer.

Application Example 3 Using B-25, a composition pellet was prepared by treating in the same manner as in Application Example 1, and the physical properties were evaluated. As a result, the tensile yield point 410 was obtained.
kg / cm ² , Izod impact strength 28 kgcm / cm, chemical resistance>
The layered peelability A was obtained after 300 minutes, which satisfied the object of the present invention.

〔The invention's effect〕

As described above, the polymer obtained by the production method of the present invention, by mixing with the thermoplastic resin, the layered peeling phenomenon of the molded article is less likely to be expressed, and the effect of excellent environmental stress crack resistance The effect is remarkable.

Claims (1)

[Claims] 1. A monoacrylic acid ester monomer 100 parts by weight, or a monoacrylic acid ester monomer 50% by weight.
100 parts by weight of a mixture containing a copolymerizable monomer selected from the above and a styrene monomer, a nitrile monomer, and a monomethacrylic acid ester monomer, and the nitrile monomer is less than 30% by weight, The following general formula I: [Wherein R ¹ and R ² are H or CH ₃ groups, and X is — (CH ₂ ) ₁ (CH
R ³ ) _m (CR ⁴ R ⁵ ) _n -group (1, m and n are each an integer of 0 or more, and 1 + m + n is an integer of 5 or more, R ³ , R
⁴ and R ⁵ are an alkyl group, an aryl group, an alkoxyl group or a hydroxyl group) and / or (X and y are each integer of 0 or more, ^{R 6} and _{R 7} is H or CH ₃ group, Y is -O -, - S -, - SO 2 -, -
CH _2- , alkylidene group or alkylene group)
Indicates. ] The long-chain bifunctional monomer represented by 0.01-1
0 part by weight is copolymerized in an emulsified state, the solubility parameter is 8.4 to 9.8 (Cal / CC) ^1/2 , the glass transition temperature is 20 ° C or lower, and the gel content is 70% by weight or lower. A method for producing a copolymer, wherein the polymer is