JP2001329024A - Shrink control agent, molding resin composition, and moldings - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shrink control agent which is low in cost and in viscosity, does not cause scumming, etc., is excellent in shrink control properties, and can realize good gloss and colorability; a molding resin composition containing the same; and moldings obtained by molding the composition. SOLUTION: A styrene-monomer-containing polymerizable monomer component and a cross-linker in a charge ratio by wt. of the monomer component to the cross-linker of (100/0.001)-(100/0.2) are subjected to bulk polymerization so that the conversion at the completion of the reaction is 20-60%, giving a styrene-monomer-soluble shrink control agent. The agent and a fibrous reinforcement are compounded into an unsaturated polyester resin to give a molding resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-shrinkage agent, a molding resin composition and a molded article, and more particularly to a low-shrinkage agent suitably used as a low-shrinkage agent for unsaturated polyester resin. The present invention relates to a molding resin composition contained therein and a molded product obtained by molding the molding resin composition.

[0002]

2. Description of the Related Art Conventionally, SM has been used as an FRP molding material.
C (sheet molding compound), TMC (thick molding compound), BMC (bulk molding compound) and the like are well known.
Such an FRP molding material is a compound containing an unsaturated polyester resin dissolved in a styrene monomer or the like, a curing catalyst, a release agent, a filler, a thickener, a polymerization inhibitor, a glass fiber, and the like. Therefore, usually, it is thickened and made into a sheet shape or a raw bread shape, and this is
By compression molding or injection molding, various molded articles such as a bathtub, a waterproof pan, a bathtub with a washing place, and a ceiling panel are obtained.

[0003] Further, in such an FRP molding material, polystyrene, polyvinyl acetate, polymethyl methacrylate, SBS rubber,
It is known to incorporate a low shrinkage agent such as gel styrene.

[0004] Among the low-shrinking agents, polystyrene, which is most commonly used for the purpose of colored molded products, has low compatibility with unsaturated polyester resins, and has low compatibility with SMC, TMC,
When the BMC or the like is separated during storage, a so-called scumming is formed on the surface of the molded product at the time of molding, which causes a problem that its appearance is impaired.

[0005] Further, polyvinyl acetate or polymethyl methacrylate is not suitable for a molded article requiring a good appearance such as a bathtub, for example, because the molded article becomes whitish as a whole. Further, the SBS rubber has a disadvantage that the viscosity of the compound becomes high and the impregnation of the glass fiber cannot be performed well.

On the other hand, gel styrene, which has recently been used as a low-shrinkage agent, can exhibit good gloss and coloring without causing scumming or the like on the surface of the obtained molded article. JP-B-51-1276, JP-B-63-61344, JP-A-7-29
No. 2231).

[0007]

However, gel styrene is not so good in low shrinkage, and cracks occur during molding or wrinkles occur on the surface of the obtained molded product. There is a limit, and in order to obtain gel styrene, styrene monomer and cross-linking agent are subjected to suspension polymerization or emulsion polymerization in water, water is decanted, gel is dried, and then swelled in styrene monomer. In order to facilitate the production, it is necessary to sieve the powder into very small powdery ones. Therefore, there is a problem that the manufacturing process is complicated, the production efficiency is low, and the cost is high. Further, gel styrene does not completely dissolve in the styrene monomer, and therefore has a disadvantage that the compound viscosity increases.

The present invention has been made in view of such circumstances, and aims at low cost, low viscosity, no scumming, excellent low shrinkage,
Capable of expressing good gloss and coloring properties,
An object of the present invention is to provide a low-shrinkage agent, a molding resin composition containing the low-shrinkage agent, and a molded product obtained by molding the molding resin composition.

[0009]

Means for Solving the Problems To achieve the above object, the low shrinkage agent of the present invention is obtained by reacting a polymerizable monomer containing a styrene monomer with a cross-linking agent. It is characterized by being soluble in the monomer.

The low shrinkage agent has a charge ratio of the polymerizable monomer to the crosslinking agent of from 0.001 to 0.2 part by weight of the crosslinking agent to 100 parts by weight of the polymerizable monomer. The conversion is preferably in the range of 20 to 6 at the end of the reaction.
It is preferably 0%, and more preferably, the reaction is performed by bulk polymerization.

Further, the present invention relates to such a low-shrinkage agent,
It includes a molding resin composition containing an unsaturated polyester resin and a reinforcing fiber, and further includes a molded article obtained by molding such a molding resin composition.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The low shrinkage agent of the present invention can be obtained by reacting a polymerizable monomer containing a styrene monomer with a crosslinking agent.

The polymerizable monomer is a compound having one polymerizable ethylenically unsaturated double bond in one molecule and is capable of copolymerizing with a styrene monomer and these styrene monomers and a crosslinking agent. It may contain a vinyl monomer. Such vinyl monomers include, for example,
Examples include acrylates such as vinyl acetate, acrylic acid and methyl acrylate, methacrylates such as methyl methacrylate, acrylonitrile, and acrylamide. These vinyl monomers may be used alone or in combination of two or more. The amount of such a vinyl monomer charged is appropriately selected depending on the purpose and use of the obtained molded article.
About 30% by weight based on 100 parts by weight of styrene monomer
Up to the extent is practically preferable.

The crosslinking agent is a compound having two or more polymerizable ethylenically unsaturated double bonds in one molecule, for example, divinylbenzene derivatives such as divinylbenzene and divinyltoluene, for example, ethylene Examples thereof include polyacrylate derivatives such as glycol dimethacrylate, ethylene glycol diacrylate, and trimethylolpropane trimethacrylate, and, for example, diallyl derivatives such as diallyl phthalate. These crosslinking agents may be used alone, or two or more of them may be used in combination. The amount of such a cross-linking agent is 0.001 to 0.2 part by weight, preferably 0.003 to 0.15 part by weight, based on 100 parts by weight of the polymerizable monomer.
If the charged amount of the cross-linking agent is less than this, there is a case where there is no great difference from the linear polystyrene, and the gloss and the colorability may be reduced. If the charged amount is larger than this, gelation may occur during the reaction.

The reaction between the polymerizable monomer and the crosslinking agent is not particularly limited. For example, a styrene monomer and, if necessary, a vinyl monomer, a crosslinking agent and a polymerization initiator are charged and reacted by bulk polymerization (bulk polymerization). I just need. According to the bulk polymerization, the production process is simple, the production efficiency is good, and the production can be performed at low cost as compared with the suspension polymerization or the emulsion polymerization.

The polymerization initiator is a compound that generates a radical for initiating radical polymerization of these monomers, and is not particularly limited. Examples thereof include benzoyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide, and the like. t-butyl peroxy-2
-Ethylhexanoate, t-butylperoxyoctoate, t-butylperoxybenzoate, cumenehydroperoxide, cyclohexanone peroxide, dicumyl peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate, , 1,
Organic peroxides such as 3,3-tetramethylbutylperoxy-2-ethylhexanoate, for example, 2,2'-
Azobisisobutyronitrile, 2-phenylazo-2,
Examples include azo compounds such as 4-dimethyl-4-methoxyvaleronitrile. These polymerization initiators may be used alone or in combination of two or more. The amount of the polymerization initiator to be charged is not particularly limited.

In this reaction, if necessary,
In order to adjust the average molecular weight of the polymer, it is preferable to add a chain transfer agent. Although it does not specifically limit as a chain transfer agent, For example, a thiol compound, (alpha) -methylstyrene dimer, carbon tetrachloride etc. are mentioned. Among these chain transfer agents, a thiol compound is preferably used because the polymerization reaction of the monomer can be controlled very easily. Such thiol compounds include, for example, t
-Butyl mercaptan, n-octyl mercaptan, n
Alkyl mercaptans such as -dodecyl mercaptan, t-dodecyl mercaptan, for example thiophenol,
Aromatic mercaptans such as thionaphthol, for example, thioglycolic acid such as thioglycolic acid, octyl thioglycolate, ethylene glycol thioglycolate, trimethylolpropane tris- (thioglycolate), pentaerythritol tetrakis- (thioglycolate) And alkyl esters thereof, for example, β-mercaptopropionic acid, octyl β-mercaptopropionate, 1,4-butanediol di (β-thiopropionate), trimethylolpropane tris- (β-thiopropionate), Pentaerythritol tetrakis- (β
Thiopropionate) and its alkyl esters. These chain transfer agents may be used alone or in combination of two or more. The amount of the chain transfer agent is appropriately selected depending on the amount of the cross-linking agent, the type of the chain transfer agent, and the like.
0.1 to 15 parts by weight.

[0018] Bulk polymerization of the polymerizable monomer and the cross-linking agent is, more specifically, a styrene monomer,
If necessary, a vinyl monomer, a crosslinking agent, a polymerization initiator, and a chain transfer agent, if necessary, may be simultaneously charged, and then the mixture may be heated as it is. Alternatively, only a styrene monomer and, if necessary, a vinyl monomer, may be charged. The agent and, if necessary, the chain transfer agent may be charged as they are, or may be dissolved in a small amount of a styrene monomer in advance and divided over a certain period of time. further,
A styrene monomer, if necessary, a vinyl monomer, a cross-linking agent and a chain transfer agent are charged, and after heating, the polymerization initiator is allowed to be charged as it is or dissolved in a small amount of styrene monomer in advance and divided over a certain period of time. Good. The heating temperature of this bulk polymerization is not particularly limited, but is usually 40 to 150 ° C., preferably 60 to 150 ° C.
0 ° C.

Then, after heating, the conversion is 20 to
It is preferable to terminate the polymerization reaction when it reaches 60%, preferably 30 to 50%. By terminating the polymerization reaction halfway without completing it, a partially three-dimensionally reduced styrene polymer low shrinkage agent that is completely solubilized in the styrene monomer can be easily obtained. If the conversion rate is lower than this, the production of the polymer is small and the low shrinkage may decrease, and if it is higher than this, the viscosity becomes too high and the handleability is reduced, and in extreme cases, the gel is In some cases. Thus, the low-shrinkage agent can be obtained as a solution of a polymerizable monomer containing a styrene monomer. The conversion is determined as a non-volatile content (solid content).

At the end of the reaction, a stabilizer is preferably added in order to improve the storage stability. Examples of such a stabilizer include polyhydric phenols such as hydroquinone, tolyl hydroquinone, monotertiary butyl hydroquinone, and tertiary butyl catechol, for example, quinones such as parabenzoquinone and naphthoquinone, and ditertiary butyl hydroxytoluene. Hindered phenols and the like. Such stabilizers are typically 50-1000 to low shrinkage agents.
It is added in the range of ppm.

The low-shrinkage agent of the present invention thus obtained has a low viscosity because it is substantially solubilized in a styrene monomer and can be produced by bulk polymerization. As compared with the case of manufacturing by emulsion polymerization or emulsion polymerization, washing, drying and sieving are not required, the manufacturing process is simple, the production efficiency is good, and the manufacturing can be performed at low cost.

Such a low-shrinkage agent is blended with an unsaturated polyester resin and a reinforcing fiber to prepare a compound, thereby preparing an FRP molding material such as SMC, TMC and BMC, that is, a resin composition for molding. The molded article molded with such a molding resin composition does not cause scumming or the like on its surface and exhibits good gloss and coloring.

As the unsaturated polyester resin, α, β
And those obtained by polycondensation of an acid component such as an unsaturated dibasic acid or an acid anhydride thereof and an aromatic saturated dibasic acid or an acid anhydride thereof with a glycol component such as glycols. In addition, depending on the purpose and use, there are those in which an aliphatic or alicyclic saturated dibasic acid is blended as an acid component, and, in addition, those in which unsaturated polyester is vinyl-modified at the end, and epoxy. A vinyl ester resin in which the terminal of the skeleton is vinyl-modified is also included.

Examples of the α, β-unsaturated dibasic acid or its anhydride include maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, chlormaleic acid and esters thereof.

Examples of the aromatic saturated dibasic acid or its acid anhydride include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, nitrophthalic acid, tetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride,
Examples include halogenated phthalic anhydride and esters thereof.

Examples of the aliphatic or alicyclic saturated dibasic acid include oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, glutaric acid, hexahydrophthalic anhydride and esters thereof. Can be

These acid components may be used alone or in combination of two or more.

Examples of the glycols include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, and 2-methylpropane.
1,3-diol, neopentyl glycol, triethylene glycol, tetraethylene glycol, 1,5-
Pentanediol, 1,6-hexanediol, bisphenol A, hydrogenated bisphenol A, ethylene glycol carbonate, 2,2-di- (4-hydroxypropoxydiphenyl) propane, and the like.

These glycol components may be used alone or in combination of two or more. Also,
In addition, as the glycol component, an alkylene oxide such as ethylene oxide and propylene oxide can be similarly used, and a polycondensate such as polyethylene terephthalate can be used as a part of the acid component and the glycol component.

The polycondensation reaction between the acid component and the glycol component is not particularly limited, and the acid component and the glycol component may be subjected to a condensation reaction in substantially equimolar amounts under known conditions. .

The unsaturated polyester resin thus obtained is usually used by dissolving 30 to 80 parts by weight of the unsaturated polyester resin in 70 to 20 parts by weight of the styrene monomer. In addition, depending on the purpose and use, it is not limited to the styrene monomer, and may be used by dissolving it in another α, β-unsaturated monomer. Examples of such α, β-unsaturated monomers include vinyl toluene, α-methylstyrene, chlorostyrene, dichlorostyrene, vinylnaphthalene, ethyl vinyl ether, methyl vinyl ketone, methyl acrylate, ethyl acrylate, methyl methacrylate And vinyl compounds such as acrylonitrile and methacrylonitrile, and allyl compounds such as diallyl phthalate, diallyl fumarate, diallyl succinate and triallyl cyanurate. These styrene monomers and α, β-unsaturated monomers may be used alone or in combination of two or more.

In the above description, the styrene monomer and the styrene monomer or styrene are practically the same compound, although they are distinguished literally according to the application.

Then, a monomer solution of such an unsaturated polyester resin (a solution in which the unsaturated polyester resin is dissolved in a styrene monomer and / or an α, β-unsaturated monomer) and a low shrinkage The mixing ratio with the agent is preferably in the range of 5 to 40 parts by weight of the low shrinkage agent with respect to 60 to 95 parts by weight of the monomer solution of the unsaturated polyester resin.

The reinforcing fibers are not particularly restricted but include, for example, glass fibers, carbon fibers, aramid fibers and polyvinyl alcohol fibers.
Glass fibers. Such a reinforcing fiber may be appropriately used in a known shape such as a chopped strand depending on its purpose and use. In addition, the amount is not particularly limited, and may be appropriately added according to the required strength.
It is preferable that the ratio of the reinforcing fiber in the weight part is 10 to 60 parts by weight, more preferably 15 to 40 parts by weight.

The molding resin composition thus prepared may further contain known additives such as a curing catalyst, a release agent, a filler, a thickener, and a polymerization inhibitor. You may mix.

Examples of the curing catalyst include ketone peroxides, peroxydicarbonates, hydroperoxides, diacyl peroxides, peroxyketals, dialkyl peroxides, peroxyesters and the like. . These curing catalysts may be used alone or in combination of two or more as appropriate. Further, 0.1 to 100 parts by weight of the total amount of the unsaturated polyester resin monomer solution and the low shrinkage agent, 0.1 to
It is preferable to use 10 parts by weight, more preferably 0.5 to 5 parts by weight.

Examples of the release agent include zinc stearate and calcium stearate. These release agents may be used alone or in combination of two or more. In addition, 1 part by weight based on a total of 100 parts by weight of the monomer solution of the unsaturated polyester resin and the low shrinkage agent is used.
It is preferably used in the range of 10 to 10 parts by weight, more preferably 2 to 5 parts by weight.

Examples of the filler include inorganic fillers such as silica sand, calcium carbonate, talc, and clay, and organic fillers such as wood powder, polyethylene powder, and pulverized products of various FRP molded products. These fillers
They may be used alone or in combination of two or more. Further, 50 to 300 parts by weight based on a total of 100 parts by weight of the monomer solution of the unsaturated polyester resin and the low shrinkage agent
It is preferably used in an amount of 100 parts by weight, more preferably 100 to 200 parts by weight.

Examples of the thickener include magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide and the like. These fillers may be used alone or in combination of two or more. Further, it is preferably used in an amount of 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, based on 100 parts by weight of the total of the monomer solution of the unsaturated polyester resin and the low shrinkage agent.

Examples of the polymerization inhibitor include p-benzoquinone, naphthoquinone, tolquinone, hydroquinone,
Mono-t-butylhydroquinone, dibutylhydroxytoluene and the like can be mentioned. These polymerization inhibitors may be used alone or in combination of two or more. Further, it is preferably used in an amount of 2 parts by weight or less, more preferably 1 part by weight or less, based on 100 parts by weight of the total of the unsaturated polyester resin monomer solution and the low shrinkage agent.

The preparation of the molding resin composition is not particularly limited, and the unsaturated polyester resin, reinforcing fiber, low-shrinking agent and other additives may be blended by a known method. Other components except for the reinforcing fibers may be prepared in advance as a compound, and this compound may be impregnated into the reinforcing fibers.

The molding resin composition of the present invention may be molded by a known molding method such as compression molding or injection molding.

[0043]

The present invention will be described more specifically with reference to the following Examples and Comparative Examples, but the present invention is not limited to the Examples and Comparative Examples. The “parts” shown below are defined on a weight basis unless otherwise specified.

Production Example 1 In a reactor equipped with a thermometer, a cooler, a nitrogen gas inlet tube and a stirrer, 100 parts of styrene monomer, 0.05 parts of divinylbenzene, 0.5 parts of t-dodecyl mercaptan, 0.5 parts of azobis After charging 0.25 parts of isobutyronitrile, the inside of the reactor was replaced with nitrogen gas, the temperature was raised to 80 ° C. while stirring, and the reaction was carried out for 5 hours. When the conversion reaches 35%, 0.01 part of mono-tert-butylhydroquinone is added to the reaction solution, and at the same time, the reaction is stopped by introducing air into the reaction system to thereby obtain a viscosity of 1500 mPa.・
s of the low-shrinking agent A was obtained.

Production Example 2 98 parts of styrene monomer and 2 parts of methacrylic acid were used instead of 100 parts of styrene monomer, and the conversion was 36%.
Except that the reaction was stopped at the time when became, a low shrinkage agent B having a viscosity of 1700 mPa · s was obtained by the same operation as in Production Example 1.
I got

Production Example 3 Production Example 3 was repeated except that 0.05 parts of trimethylolpropane trimethacrylate was used instead of 0.05 parts of divinylbenzene, and the reaction was stopped when the conversion reached 35%. By the same operation, a low-shrinkage agent C having a viscosity of 1500 mPa · s was obtained.

Production Example 4 In place of 0.25 parts of azobisisobutyronitrile, Percure WO (trade name, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, Nippon Yushi ( Co., Ltd., active ingredient content 50%) using 0.5 parts,
Except that the reaction was stopped when the conversion reached 36%, the same operation as in Production Example 1 was carried out, and the viscosity was 1,520 mPa.
・ S low shrinkage agent D was obtained.

Production Example 5 Production Example 1 was repeated except that 0.5 parts of n-dodecyl mercaptan was used instead of 0.5 parts of t-dodecyl mercaptan, and the reaction was stopped when the conversion reached 35%. By the same operation as described above, a low-shrinkage agent E having a viscosity of 1510 mPa · s was obtained.

Production Example 6 First, 100 parts of a styrene monomer was charged into a reactor, and the temperature was raised to 80 ° C. while stirring. Then, 0.05 parts of divinylbenzene, 0.5 part of t-dodecyl mercaptan and 0.5 part of styrene were added to a small amount of styrene. Production Example 1 Except that a solution in which 0.25 part of azobisisobutyronitrile was dissolved was added dropwise over 3 hours, the reaction was further performed for 3 hours, and the reaction was stopped when the conversion reached 37%. By the same operation as described above, the viscosity is 150
A low shrinkage agent F of 0 mPa · s was obtained.

Production Example 7 100 parts of styrene monomer, 0.05 of divinylbenzene
Part, t-dodecylmercaptan 0.5 part was first charged into a reactor, and the temperature was raised to 80 ° C. while stirring. Then, a solution obtained by dissolving 0.25 part of azobisisobutyronitrile in a small amount of styrene was added to 3 parts. The viscosity was 1480 m by the same operation as in Production Example 1 except that the reaction was stopped at the time when the conversion reached 36%, and the reaction was continued for 3 hours.
A low shrinkage agent G of Pa · s was obtained.

Production Example 8 100 parts of styrene monomer, 0.25 of divinylbenzene
Part, t-dodecyl mercaptan 0.5 part, azobisisobutyronitrile 0.25 part, and the reaction was stopped when the conversion reached 36%, by the same operation as in Production Example 1. , Low-shrinkage agent H having a viscosity of 2000 mPa · s
I got

Production Example 9 100 parts of styrene monomer, 0.00 of divinylbenzene
05 parts, 0.5 part of t-dodecyl mercaptan, and 0.25 part of azobisisobutyronitrile were charged, and the conversion was 36.
%, And the same operation as in Production Example 1 was carried out, except that the reaction was stopped at the time of the reaction, to obtain a low-shrinkage agent I having a viscosity of 1400 mPa · s.

Production Example 10 Styrene monomer 100 parts, divinylbenzene 0.05
Parts, 0.5 parts of t-dodecyl mercaptan and 0.25 parts of azobisisobutyronitrile were charged and reacted for 3 hours.
The reaction was terminated when the conversion reached 18%.
By the same operation as in Production Example 1, the viscosity was 1000 mPa ·
s of low shrinkage agent J was obtained.

Production Example 11 100 parts of styrene monomer, 0.05 of divinylbenzene
Production Example 1 except that 0.5 part of t-dodecylmercaptan and 0.25 part of azobisisobutyronitrile were charged, reacted for 15 hours, and terminated when the conversion reached 63%. By the same operation as described above, the viscosity becomes 4000 mP
As a low shrinkage agent K was obtained.

Example 1 75 parts of Polymerl 6619 (trade name, composition: neopentyl glycol / isophthalic acid resin, manufactured by Takeda Pharmaceutical Co., Ltd.) as an unsaturated polyester resin, low-shrinkage agent A25
Part, 150 parts of calcium carbonate (average particle size: 2 μ), 5 parts of zinc stearate, t-butyl peroxybenzoate 1
Parts, parabenzoquinone 0.01 parts, ivory toner 5 parts, magnesium oxide (trade name: Kyowa Mag # 4)
0.8 part of Kyowa Chemical Co., Ltd.) was sufficiently mixed and kneaded to prepare a compound.

The compound was impregnated into a chopped strand having a fiber length of 25 mm using a known TMC manufacturing apparatus, covered with a polypropylene film, further covered with a polyester film, and aged at a temperature of 40 ° C. for 24 hours. And TMC as a molding resin composition
I got The mixing ratio of the chopped strand is T
The content was 25% by weight of the entire MC. Using the thus obtained TMC having a thickness of 6.0 mm, a molding temperature of 140 was used.
A bathtub with a washing place was compression-molded under a molding condition of ℃ and a molding pressure per projection unit area of 9.8 MPa.

Example 2 As an unsaturated polyester resin, polymer No. 6619 was used.
(Trade name, manufactured by Takeda Pharmaceutical Co., Ltd.) 92 parts instead of 75 parts of Polymerl 6619 (trade name, manufactured by Takeda Pharmaceutical Co., Ltd.)
A bathtub with a washing place was formed under the same conditions as in Example 1 except that 8 parts of the low-shrinkage agent A was used instead of 25 parts of the low-shrinkage agent A.

Example 3 As an unsaturated polyester resin, POLYMER 6619 was used.
Instead of 75 parts (trade name, manufactured by Takeda Pharmaceutical Co., Ltd.) 65, Polymerl 6619 (trade name, manufactured by Takeda Pharmaceutical Co., Ltd.)
A bathtub with a washing place was formed under the same conditions as in Example 1 except that 35 parts of the low-shrinkage agent A was used instead of 25 parts of the low-shrinkage agent A.

Example 4 A bathtub with a washing place was formed under the same conditions as in Example 1 except that 25 parts of the low-shrinkage agent B was used instead of 25 parts of the low-shrinkage agent A.

Example 5 A bathtub with a washing place was formed under the same conditions as in Example 1 except that 25 parts of the low-shrinkage agent C was used instead of 25 parts of the low-shrinkage agent A.

Example 6 A bath tub with a washing place was formed under the same conditions as in Example 1 except that 25 parts of the low-shrinkage agent A was used instead of 25 parts of the low-shrinkage agent A.

Example 7 A bathtub with a washing place was formed under the same conditions as in Example 1 except that 25 parts of the low-shrinkage agent A was used instead of 25 parts of the low-shrinkage agent A.

Example 8 A bath tub with a washing place was formed under the same conditions as in Example 1 except that 25 parts of the low-shrinkage agent F was used instead of 25 parts of the low-shrinkage agent A.

Example 9 A bathtub with a washing place was formed under the same conditions as in Example 1 except that 25 parts of the low-shrinkage agent A was used instead of 25 parts of the low-shrinkage agent A.

Example 10 A bathtub with a washing place was formed under the same conditions as in Example 1 except that 25 parts of the low-shrinkage agent A was used instead of 25 parts of the low-shrinkage agent A.

Example 11 A bathtub with a washing place was formed under the same conditions as in Example 1 except that 25 parts of the low-shrinkage agent A was used instead of 25 parts of the low-shrinkage agent A.

Example 12 A bathtub with a washing place was formed under the same conditions as in Example 1 except that 25 parts of the low-shrinkage agent A was used instead of 25 parts of the low-shrinkage agent A.

Example 13 A bathtub with a washing place was formed under the same conditions as in Example 1 except that 25 parts of the low-shrinkage agent A was used instead of 25 parts of the low-shrinkage agent A.

Comparative Example 1 A polystyrene solution (viscosity: 2800 mPa · s, solid content: 35% by weight) obtained by removing the crosslinking agent and heating only styrene and the polymerization initiator instead of 25 parts of the low-shrinkage agent A 25 A bathtub with a washing place was formed under the same conditions as in Example 1 except that the part was used.

Comparative Example 2 A commercially available gel styrene (trade name: SGP-70C, manufactured by Soken Chemical Co., Ltd.) swelled in styrene instead of 25 parts of low-shrinkage agent A (gel styrene / styrene = 30/7)
A bathtub with a washing place was formed under the same conditions as in Example 1 except that 25 parts (0 weight ratio) was used.

Evaluation The shrinkage ratio during molding in Examples 1 to 13 and Comparative Examples 1 and 2 was calculated as (mold size−molded product size) / mold size ×
100 (%), and observing the appearance of the molded article of the obtained bathtub with a washing place, scumming, gloss,
The presence or absence of wrinkles and cracks was examined. Table 2 shows the results. Table 1 also shows the properties of the low-shrinkage agents A to K obtained in Production Examples 1 to 11.

[0072]

[Table 1]

[0073]

[Table 2]

[0074]

As described above, since the low-shrinkage agent of the present invention is soluble in styrene monomer, it has a low viscosity, has no scumming, and exhibits good gloss and coloring. Can be done.

Further, since it can be produced by bulk polymerization, it does not require washing, drying and sieving as compared with the case of production by suspension polymerization or emulsion polymerization, and the production process is simple and the production efficiency is good. It can be manufactured at low cost.

A molded article molded from the resin composition for molding containing such a low shrinkage agent is free from scumming in appearance, has a low shrinkage rate, and has good gloss and coloring properties. And an excellent appearance can be exhibited.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 25/04 C08L 25/04 67/06 67/06 // B29K 67:00 B29K 67:00 105: 06 105: 06 105: 24 105: 24 (72) Inventor Noriyuki Moriyama 18F, Tsubota Oshinya, Kashiwara-cho, Hikami-gun, Hyogo Prefecture F-term (in reference) 4F072 AA02 AA04 AA07 AB04 AB06 AB09 AB10 AB22 AD05 AD38 AE02 AE06 AE11 AE12 AE13 AG02 AG03 AG04 AH21 AK05 AK14 AL01 AL06 4F204 AA13 AA41 AB01 AB03 AB19 AB25 AH49 EA03 EB01 EF02 4J002 BC02X BE023 CF22W CL063 DA016 DL006 FA043 FA046 FD010 ABFD FD013 FD016 FD0130 FD016 AB24 AB25 BA04 BA05 BA07 BA13 BA22 BA29 CA12 CA19 CA36 CA38 CB03 CC02 CD02 4J100 AB02P AB16Q AG04R AG71Q AJ02R AL03R AL62Q AL63Q AM02R AM15R CA04 CA05 FA18

Claims (6)

[Claims] 1. A low-shrinking agent obtained by reacting a polymerizable monomer containing a styrene monomer with a crosslinking agent and being soluble in the styrene monomer. 2. The charge ratio between the polymerizable monomer and the crosslinking agent is as follows:
0.00100 parts by weight of the polymerizable monomer, the crosslinking agent is 0.00
The low shrinkage agent according to claim 1, wherein the amount is in the range of 1 to 0.2 parts by weight. 3. The low shrinkage agent according to claim 1, wherein the conversion at the end of the reaction is 20 to 60%. 4. The low-shrinkage agent according to claim 1, wherein the reaction is carried out by bulk polymerization. 5. A molding resin composition comprising the low-shrinkage agent according to claim 1, an unsaturated polyester resin, and a reinforcing fiber. 6. A molded article obtained by molding the molding resin composition according to claim 5. Description: