JPH07133401A - Thermoplastic resin composition for refrigerator - Google Patents

Abstract

PURPOSE:To obtain a thermoplastic resin composition useful as an interior material of a refrigerator, etc., having a high environmental stress cracking resistance to a substitute for fluorocarbon and a high molding property. CONSTITUTION:A mixture of 100wt.pt. of a following rubber containing styrene base resin with 0.1-100wt.pt. of an acrylic rubber. (a) The above rubber containing styrene base resin is composed of 5-50wt.% of a graft copolymer [G]and 50-95wt.% of a matrix resin [M], (b) where G is a graft copolymer of two or more monomers containing a conjugated diene base rubber [B], an unsaturated nitrile monomer (N) and an aromatic vinyl monomer (St) and contains 20-36wt.% of N and 65-80wt.% of St, (c) and where M is copolymer of more than two monomers containing 35-65wt.% of N and 50-65wt.% of St, and (d) the above rubber containing styrene base resin contains in total 2-40wt.% of B, 20-50wt.% of N and 10-78wt.% of St.

Description

Detailed Description of the Invention

[0001]

The present invention is composed of a specific rubber-containing styrene resin and acrylic rubber, and has improved environmental stress crack resistance and molding processability, and is suitable as an interior material for electric refrigerators. It relates to a thermoplastic resin composition used.

[0002]

AB representing rubber-containing styrene resin
S resin is widely used as a general-purpose resin with excellent properties such as rigidity, impact resistance, chemical resistance, and moldability in household electrical appliances and other applications, but depending on the application, environmental stress crack resistance May be required to improve. For example ABS
Resin is used as an interior material of an electric refrigerator, and the wall of such an electric refrigerator is a urethane foam as a heat insulating material in a space surrounded by an exterior material such as a steel plate and an interior material made of ABS resin. Is used as the foaming agent, and fluorocarbon, that is, chlorofluorocarbon, is generally used as a foaming agent when a urethane foam is manufactured.

However, in the interior material of the electric refrigerator made of the ABS resin plate thus manufactured, cracks may occur due to the environmental stress cracking phenomenon. It is considered that the cause is that CFC used as a foaming agent for urethane, together with the tensile stress applied to the interior material at the time of molding or use, causes environmental stress crack fracture.

By the way, it has been pointed out that certain CFCs such as CFC11 currently used as a foaming agent are suspected as a substance causing the greenhouse effect of the global environment or a substance causing the destruction of the ozone layer. It is planned and the use of alternative CFCs with less potential for environmental damage is planned. However, Freon 141b or Freon 1 which is an alternative Freon to be used as a foaming agent.
23 has a greater effect on the environmental stress crack fracture of the ABS resin than CFC 11. Therefore, CFC 11 is used as the interior material of an electric refrigerator manufactured using CFC 141b or CFC 123 as a foaming agent. The environmental stress crack fracture phenomenon is more likely to occur than when used.

For the purpose of preventing environmental stress crack destruction due to CFCs, the thickness of the ABS resin plate constituting the interior material of the electric refrigerator is increased, or a polyethylene film layer is interposed at the interface between the ABS resin plate and the urethane foam. However, since it is inferior in economic efficiency, it is desired to develop an ABS resin having improved environmental stress crack resistance against alternative CFCs.

In order to improve the environmental stress crack resistance of the ABS resin, the molecular weight of the AS (acrylonitrile-styrene) resin which constitutes the resin component of the ABS resin is increased.
Methods for increasing the composition ratio of acrylonitrile, which is a polar monomer that constitutes S resin, or copolymerizing a polar monomer other than acrylonitrile with AS resin are known, but these methods are the molding processing of ABS resin. In addition to the deterioration of the properties, the effect of improving the environmental stress crack resistance is insufficient.

As a method for improving the environmental stress crack resistance of rubber-containing styrene resin such as ABS resin, the present inventors have already proposed a thermoplastic resin composition comprising a rubber-containing styrene resin and a specific acrylic rubber. (Japanese Patent Publication Sho 63-22
222, JP-B-63-28445, JP-B-63-28460, JP-B-63-54303, JP-B2-1857, and JP-B-3-52783.
Japanese Patent Publication No. 3-54984). However, these inventions did not optimize the improvement of the environmental stress crack resistance against the alternative CFCs. Further, no means has been proposed for achieving both improved environmental stress crack resistance against alternative CFCs and good moldability, and there was a problem in practical use in electric refrigerators and the like.

[0008]

As described above, when the rubber-containing styrene resin resin is used for electric refrigerators and the like, improvement of environmental stress crack resistance against alternative CFCs and improvement of good moldability are desired. ing. The purpose of the present invention is to
It is an object of the present invention to solve these problems and form a rubber-containing styrene-based resin suitable for applications such as electric refrigerators, which is economically superior.

[0009]

The present invention is a thermoplastic resin composition comprising a rubber-containing styrene resin and an acrylic rubber, which are controlled in a specific composition range, and is excellent in environmental stress crack resistance against alternative CFCs. At the same time, it is based on the finding that it has good moldability. That is, the present invention is a thermoplastic resin composition for an electric refrigerator, which is obtained by mixing 100 parts by weight of a rubber-containing styrene resin having the following characteristics and 0.1 to 100 parts by weight of acrylic rubber. The rubber-containing styrene resin used was composed of (a) 5 to 50% by weight of the graft copolymer [G] and 50 to 95% by weight of the matrix resin [M], and (b) the graft copolymer [G] was conjugated. A copolymer obtained by graft-copolymerizing a graft branch [GM], which is a copolymer of two or more monomers containing an unsaturated nitrile monomer and an aromatic vinyl monomer, with a diene rubber [B]. The graft branch [GM] is composed of 20 to 35% by weight of an unsaturated nitrile monomer and 65 of an aromatic vinyl monomer.
Is a copolymer of two or more kinds of monomers containing 80 to 80% by weight, and (c) the matrix resin [M] comprises 35 to 50% by weight of an unsaturated nitrile monomer and 50 to 50% of an aromatic vinyl monomer. 6
It is a copolymer of two or more kinds of monomers containing 5% by weight, and (d) the conjugated diene rubber [B] component in the rubber-containing styrene resin is 2 to 40% by weight, and the unsaturated nitrile component is 20 to 50% by weight and aromatic vinyl component 10 to 78
It is characterized by containing wt%.

The present invention is also the thermoplastic resin composition for electric refrigerators, wherein the rubber-containing styrene resin is an ABS resin.

The present invention is also the thermoplastic resin composition for electric refrigerators, wherein the acrylic resin has a glass transition temperature of 20 ° C. or lower.

The present invention is also a thermoplastic resin composition for electric refrigerators, wherein 0.01 to 10 parts by weight of silicone oil is added to 100 parts by weight of these thermoplastic resin compositions.

The rubber-containing styrene resin used in the thermoplastic resin composition of the present invention contains a conjugated diene rubber component [B], an unsaturated nitrile component and an aromatic vinyl component. The rubber [B] is a homopolymer or copolymer of a conjugated diene monomer such as butadiene, isoprene or chloroprene, and the unsaturated nitrile component is a polymer of an unsaturated nitrile monomer such as acrylonitrile or methacrylonitrile. The aromatic vinyl component means that it is a polymer of a styrene-based monomer such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, bromostyrene.

The rubber-containing styrenic resin of the present invention is
It is composed of a graft copolymer [G] and a matrix resin [M], and the graft copolymer [G] is two or more kinds containing an unsaturated nitrile monomer and an aromatic vinyl monomer in a conjugated diene rubber [B]. Is a copolymer obtained by graft-copolymerizing a graft branch [GM] composed of a copolymer of the above monomer, and the matrix resin [M] is an unsaturated nitrile monomer having a composition different from that of the graft branch [GM]. It is a copolymer of two or more monomers including an aromatic vinyl monomer.

The rubber-containing styrenic resin of the present invention comprises a graft copolymer [G] constituting a dispersed phase and a matrix resin [M] constituting a continuous phase. In order to realize such a form, To the presence of the conjugated diene rubber [B] latex produced by emulsion polymerization, the necessary amounts of two or more monomers including unsaturated nitrile monomer and aromatic vinyl monomer are added and emulsion radical polymerization is performed. The method is generally carried out industrially. It is also known to add a separately produced matrix resin to the rubber-containing styrene resin obtained by such a production method. The rubber-containing styrene resin of the present invention can be manufactured by such a method, but the manufacturing method is not particularly limited.

The rubber-containing styrene resin used industrially is a conjugated diene rubber [B], a graft branch [GM] for the purpose of improving properties such as rigidity, heat resistance, impact resistance and molding processability. Alternatively, during the production of the matrix resin [M], it is generally carried out that a monomer other than the above-mentioned monomer is added to the above-mentioned monomers shown as the monomers constituting these polymers and copolymerized. If necessary, these techniques can be applied to the present invention as well. Examples of such a monomer include (meth) acrylic acid, methyl (meth) acrylate, and (meth) acrylic acid. (Meth) acrylate monomers such as ethyl, butyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate Maleimide, N- butyl maleimide, N- cyclohexyl maleimide, maleimide monomers such as N- phenyl maleimide, and (meth) acrylamides, maleic anhydride and the like.

The rubber-containing styrenic resin of the present invention is
(A) Containing 5 to 50% by weight of the graft copolymer [G] and 50 to 95% by weight of the matrix resin [M], and (b) the graft copolymer [G] is unsaturated in the conjugated diene rubber [B]. It is a copolymer obtained by graft-copolymerizing a graft branch [GM] composed of a copolymer of two or more kinds of monomers including a nitrile monomer and an aromatic vinyl monomer, and the graft branch [GM] is unsaturated. It is a copolymer of two or more kinds of monomers containing 20 to 35% by weight of a nitrile monomer and 65 to 80% by weight of an aromatic vinyl monomer, and (c) the matrix resin [M] is an unsaturated nitrile. It is a copolymer of two or more kinds of monomers containing 35 to 50% by weight of a monomer and 50 to 65% by weight of an aromatic vinyl monomer, and (d) a conjugated diene rubber in a rubber-containing styrene resin. Component [B] is 2 to 40% by weight, unsaturated nitrile component is 20 to 50% by weight. And the aromatic vinyl component 10-7
It is characterized by containing 8% by weight.

These requirements are conditions for the thermoplastic resin composition for an electric refrigerator of the present invention to have practically preferable environmental stress crack resistance and moldability. In order to improve the environmental stress crack resistance of the rubber-containing styrenic resin against the CFC substitute, for example, as described in JP-A-5-155949, the composition ratio of the unsaturated nitrile component constituting the ABS resin or the like is increased. However, as the composition ratio of the unsaturated nitrile component increases, the melt viscosity of the resin increases, and industrially unfavorable molding processability decreases.
However, the inventors of the present invention have found that in the rubber-containing styrene resin, when the composition ratio of the unsaturated nitrile component constituting the ABS resin or the like is increased, the unsaturated nitrile component of the graft branch [GM] is lowered. By suppressing and increasing the unsaturated nitrile component of the matrix resin [M],
A thermoplastic resin composition having high environmental stress crack resistance and good moldability can be obtained. That is, the rubber-containing styrene resin of the present invention is inferior in environmental stress crack resistance when the unsaturated nitrile component is less than 20% by weight, and inferior in moldability when it exceeds 50% by weight. Further, if the unsaturated nitrile monomer of the graft branch [GM] constituting the graft copolymer of the rubber-containing styrene resin of the present invention exceeds 35% by weight, moldability becomes poor. If the unsaturated nitrile monomer of the matrix resin [M] is less than 35% by weight, the resistance to environmental stress cracking is poor, and 5
If it exceeds 0% by weight, the moldability is poor.

In order to produce a rubber-containing styrene resin in which the composition of the graft branch [GM] and the matrix resin [M] are different, unsaturated nitrile monomer and aromatic group which are polymerized in the presence of the diene rubber [B] are used. There is a method of sequentially changing the composition ratio of vinyl monomers, a method of blending a rubber-containing styrene resin with a matrix resin having a different composition, but the manufacturing method is not limited.

The acrylic rubber of the present invention is a homo- or copolymer of a (meth) acrylic acid ester type monomer.
Monomers to be copolymerized include ethylene, propylene, 1-butene, isobutylene, in addition to the above-mentioned unsaturated nitrile monomer, aromatic vinyl monomer, maleimide-based monomer, (meth) acrylamide and maleic anhydride. Examples include olefin monomers such as 2-butene and fatty acid vinyl monomers such as vinyl acetate.

The present inventors have previously proposed a graft-polymerized acrylic rubber for the purpose of improving the compatibility between the acrylic rubber and the rubber-containing styrene resin (Japanese Patent Publication No. 63-
28445, Japanese Patent Publication No. 63-28460),
The acrylic rubber of the present invention may be the acrylic rubber having a graft branch disclosed in the publication.

The acrylic rubber of the present invention preferably has a glass transition temperature of 20 ° C. or lower. Glass transition temperature is 2
When it exceeds 0 ° C, the environmental stress crack resistance of the thermoplastic resin composition is insufficient. When the acrylic rubber has graft branches, the glass transition temperature of the acrylic rubber means the glass transition temperature of the trunk polymer that does not contain graft branches.

The present inventors have also found that when a small amount of silicone oil is added to the thermoplastic resin composition of the present invention, a remarkable effect of improving impact resistance is recognized. The effective addition amount is 0.01 to 100 parts by weight of a thermoplastic resin composition composed of a rubber-containing styrene resin and acrylic rubber.
It is in the range of 10 parts by weight. Although the mechanism of impact resistance improvement is unknown, improvement of impact resistance by adding silicone oil is effective in achieving both high rigidity and high impact resistance required for interior materials of electric refrigerators. The molecular weight and structure of the silicone oil are not particularly limited, and polydimethylsiloxane having a polymerization degree of 10 to 100,000 or the like can be used.

The thermoplastic resin composition of the present invention can be obtained by mixing a rubber-containing styrene resin and acrylic rubber, but the production method is arbitrary. For example, when both the rubber-containing styrene resin and the acrylic rubber are produced by emulsion polymerization, the obtained polymer latex can be mixed according to the method described in JP-B-63-22222. The acrylic rubber composition preliminarily mixed in the emulsified state according to the method described in JP-B-3-52783 can also be melt-kneaded with a rubber-containing styrene resin separately. In addition, a method of mixing an acrylic rubber latex with a rubber-containing styrene resin solid is also possible by utilizing the method disclosed in Japanese Patent Publication No. 59-15942. When the rubber-containing styrene resin and the acrylic rubber are both solid, they can be melt-mixed by a melt-mixing device such as a screw extruder or a Banbury mixer.

The thermoplastic resin composition of the present invention comprises 100 parts by weight of a rubber-containing styrene resin and 0.1 to 10 acrylic rubber.
Although the amount is 0 parts by weight, if the content of acrylic rubber is less than 0.1 parts by weight, the environmental stress crack resistance of the obtained thermoplastic resin composition is insufficient, and if it exceeds 100 parts by weight, it is effective. Is not only saturated, but also the thermoplastic resin composition is deteriorated in properties such as heat resistance, rigidity and gloss, which is not preferable.
When the acrylic rubber has a graft branch, the content of the acrylic rubber means the content of the trunk polymer containing no graft branch.

The thermoplastic resin composition of the present invention has impact resistance,
It can be used as a mixture with other polymer materials for the purpose of improving properties such as heat resistance, rigidity and flame retardancy. Such polymer materials are SBR (styrene-butadiene rubber), E
Elastomers such as PR (ethylene-propylene rubber) and NBR (acrylonitrile-butadiene rubber), polyolefins such as polyethylene and polypropylene, nylon 6, nylon 66, nylon 610, nylon 612,
Examples include polyamides such as nylon 11 and nylon 12, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polycarbonates, acrylic resins, polyvinyl chloride and the like.

[0027]

The present invention will be described in more detail with reference to Examples and Comparative Examples. The parts and% in the examples are shown by weight.

The abbreviations used in Tables 1 to 7 of Examples and Comparative Examples are as follows. PB: polybutadiene SBR: styrene-butadiene rubber AN: acrylonitrile SM: styrene nBA: n-butyl acrylate MMA: methyl methacrylate AMA: allyl methacrylate

Examples and Comparative Examples Using the ABS resin of Table 1, the AS resin of Table 2 and the acrylic rubbers of Tables 3 and 4, Table 5 (characteristics of ABS resin constituting the thermoplastic resin composition), Table 6 ( The composition and physical properties of the thermoplastic resin composition) and the formulations shown in Table 7 (composition and physical properties of the thermoplastic resin composition) were compounded and melt-kneaded at about 240 ° C to obtain a thermoplastic resin composition. The examples are shown in Experiment Nos. 1 to 18 of Tables 6 and 7, and the comparative examples are shown in Experiment Nos. 19 to 24 of Table 7. As is clear from Tables 6 and 7, the thermoplastic resin composition of the present invention is excellent in environmental stress crack resistance against Freon 141b and has good moldability.

The ABS resin, acrylic rubber and thermoplastic resin composition used in Examples and Comparative Examples were manufactured as follows. (1) Manufacturing method of ABS resin Polybutadiene latex or polybutadiene latex and styrene-butadiene rubber (styrene content 25
%) Ion-exchanged water, an emulsifier, and a reducing agent containing ferrous sulfate were added to a stainless steel reactor containing a mixture of latex, and acrylonitrile, styrene, cumene hydroperoxide were added while maintaining the temperature at 50 ° C under a nitrogen atmosphere. Emulsion graft polymerization was carried out by continuously applying a mixture of oxide and n-dodecyl mercaptan for 5 hours. After the temperature was properly adjusted, the temperature was raised to 70 ° C. and the temperature was maintained for 2 hours to complete the polymerization. The characteristics of the obtained ABS resin are shown in Table 1.

(2) Method for producing acrylic rubber A stainless steel reactor was charged with ion-exchanged water, an emulsifier and potassium sulphate, and the (meth) acrylic acid shown in Table 3 was maintained while maintaining the temperature at 70 ° C. under a nitrogen atmosphere. The ester monomer mixture was continuously subjected to emulsion polymerization for 7 hours, and emulsion polymerization was completed by holding the mixture at 70 ° C. for 2 hours to obtain an acrylic rubber. The characteristics of the obtained acrylic rubber are shown in Table 3.

(3) Graft Polymerization of Acrylonitrile and Styrene onto Acrylic Rubber A stainless steel reactor charged with acrylic rubber latex of sample number c1, c3 or c4 in Table 3 is a reducing agent containing ion-exchanged water and ferrous sulfate. Was added and the temperature was maintained at 50 ° C. under a nitrogen atmosphere. Emulsion graft polymerization was carried out by continuously and appropriately applying a mixture of acrylonitrile, styrene, n-dodecyl mercaptan and cumene hydroperoxide and an aqueous emulsifier solution. After the temperature was appropriately adjusted, the temperature was raised to 70 ° C. and the temperature was maintained for 2 hours to complete the polymerization. The characteristics of the obtained graft polymer are summarized in Table 4.

(4) Method for producing thermoplastic resin composition The ABS resin latex of Table 1 and the acrylic rubber latex of Table 3 or Table 4 are mixed in a latex state, and a suspension of the antioxidant is added. Dilute sulfuric acid was poured at about 90 ° C. to deposit a latex. The obtained slurry was dehydrated and dried to obtain a polymer powder. The polymer powder thus obtained and the AS resin powder shown in Table 2 were mixed with a Henschel mixer, and silicone oil (SH200 manufactured by Toray Industries, Inc.) was further mixed if necessary, and then a twin-screw extruder was used. Melt-kneading was performed at about 240 ° C. to obtain thermoplastic resin compositions having the compositions shown in Tables 6 and 7. The obtained thermoplastic resin composition was shaped into a required shape and the physical properties were evaluated, and the results are summarized in Tables 6 and 7. The ABS resins constituting the thermoplastic resin compositions in Table 6 and Table 7 are A in Table 1.
It is a mixture of BS resin and AS resin of Table 2 and has the composition described in Table 5.

The thermoplastic resin composition thus obtained was evaluated as follows. (1) Tensile yield point ...... JIS K 687
1 (2) Izod impact strength ...... JIS K 687
1 (3) Melt flow rate ...... JIS K 721
Compliant with 0 (Temperature 220 ℃, Load 10kg)

(4) Resistance to environmental stress cracking JIS K 7113 type test pieces were given a deflection of 50 mm and fixed to a jig and left at 23 ° C. in an atmosphere of Freon 141b for 24 hours, and then at a temperature of −30. JIS at ℃
A tensile test was conducted according to K 6871 to determine the tensile elongation at break, and the results were evaluated as follows. Evaluation C does not endure practical use such as interior materials for electric refrigerators. Evaluation criteria A: Tensile elongation at break 15% or more B: Tensile elongation at break 10 or more and less than 15% C: Tensile elongation at break less than 10%

(5) Molding processability Using a single screw extruder equipped with a T-type die, the temperature is about 240 ° C.
Was extruded to prepare a thermoplastic resin composition plate having a width of 40 cm and a thickness of 2 mm. After preheating the obtained resin plate at 80 ° C., the temperature of the resin plate is controlled to 160 ° C. by using a plug assist type compressed air vacuum forming machine,
Length 246 mm with satin pattern on the bottom, width 165 m
A lidless box-shaped molded product having a size of m and a depth of 30 mm was obtained. The appearance of the obtained molded product, in particular, the reproduced state of the pattern on the bottom surface was visually observed to evaluate A to C. Evaluation C does not endure practical use such as interior materials for electric refrigerators. Evaluation Criteria A: The pattern on the bottom is clearly transferred, and the ridges and corners of the box are also acute. B: The pattern on the bottom is slightly unclear, and the ridges and corners of the box are slightly obtuse. C: The pattern on the bottom is extremely unclear, and the ridges and corners of the box are obtuse.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4]

[0041]

[Table 5]

[0042]

[Table 6]

[0043]

[Table 7]

[0044]

INDUSTRIAL APPLICABILITY As described above, in the thermoplastic resin composition of the present invention, the occurrence of the environmental stress cracking phenomenon due to the CFC substitute is suppressed, and moreover, the molding processability is excellent and the electric refrigerator It is suitable for applications such as interior materials.

Claims (4)

[Claims] 1. A thermoplastic resin composition for an electric refrigerator comprising 100 parts by weight of a rubber-containing styrene resin having the following characteristics and 0.1-100 parts by weight of an acrylic rubber,
The rubber-containing styrene resin is (a) 5 to 50% by weight of the graft copolymer [G] and 50 to 50% of the matrix resin [M].
95% by weight, and (b) the graft copolymer [G] is a conjugated diene rubber [B] having a copolymerization weight of two or more monomers including an unsaturated nitrile monomer and an aromatic vinyl monomer. The graft branch [GM] is a copolymer obtained by graft-copolymerizing the graft branch [GM], and the graft branch [GM] is an unsaturated nitrile monomer 2
0 to 35% by weight and aromatic vinyl monomer 65 to 80% by weight
(C) matrix resin [M] is a copolymer of two or more monomers containing
A conjugated diene rubber [B] which is a copolymer of two or more monomers containing 0 wt% and 50 to 65 wt% of an aromatic vinyl monomer, and (d) a rubber-containing styrene resin. It is characterized in that the component comprises 2 to 40% by weight, the unsaturated nitrile component comprises 20 to 50% by weight, and the aromatic vinyl component comprises 10 to 78% by weight. 2. The thermoplastic resin composition for an electric refrigerator according to claim 1, wherein the rubber-containing styrene resin is an ABS (acrylonitrile-butadiene-styrene) resin. 3. The glass transition temperature of acrylic rubber is 20 ° C.
The thermoplastic resin composition for an electric refrigerator according to claim 1, wherein: 4. A thermoplastic resin composition for an electric refrigerator, which is obtained by adding 0.01 to 10 parts by weight of silicone oil to 100 parts by weight of the thermoplastic resin composition according to claim 1, claim 2 or claim 3.