JP5500841B2 - Shrinkage inhibitor - Google Patents

Description

The present invention relates to a shrinkage control agent. More particularly, the present invention relates to a shrinkage-suppressing agent used to reduce the polymerization shrinkage upon unsaturated polyester resins derived from a monomer mixture containing a diallyl phthalate.

For example, it is known to use an unsaturated polyester resin as a molding material in artificial marble. This molded body material becomes a molded body made of an insoluble and infusible cured product by curing the unsaturated polyester resin constituting it in a mold by heating or crosslinking at room temperature (three-dimensionalization).
It is known that when an unsaturated polyester resin is cured, shrinkage of 6 to 10% by volume occurs in the molded body. If this shrinkage is left untreated, sink marks, dents, cracks and other deformations are likely to occur in the molded body. In order to suppress these deformations, it has been proposed to include a fibrous reinforcing material in the molded body. Although the deformation is suppressed to some extent by this inclusion, there is a problem that the reinforcing material is raised on the surface, resulting in a decrease in appearance, a decrease in paintability due to the occurrence of pinholes, and a decrease in dimensional stability.

Therefore, it has been proposed to use a general thermoplastic resin such as polystyrene, polyvinyl acetate, polymethyl methacrylate, polyethylene or the like as a shrinkage inhibitor for the molded body material. Among these, since polystyrene is relatively inexpensive, it is frequently used in the field (for example, JP 2000-63648 A: Patent Document 1).
By the way, from the viewpoint of suppressing shrinkage, the resin for shrinkage inhibitor is required to be mixed as uniformly as possible with the unsaturated polyester resin in the molded body material. Therefore, a solvent capable of dissolving the shrinkage inhibitor resin is necessary. Moreover, the crosslinking agent for bridge | crosslinking unsaturated polyester resin is required in a molded object material, and an ethylenically unsaturated monomer is used normally. In the above publication, various ethylenically unsaturated monomers are described, and among them, styrene serves as both a solvent and an ethylenically unsaturated monomer, and thus is suitably used in this field. It is also used in the examples of the above publication.

JP 2000-63648 A

  Since the styrene in the molding material has a problem that styrene is volatilized by volatilization by heat in the manufacturing process of the molding and emits a styrene odor to the surroundings, it is desired to reduce the styrene odor. In addition, from the problem of reducing VOC (volatile organic compounds) in recent years, it is desired to reduce the residual amount of styrene in the molded body. However, since styrene serves as a crosslinking agent for unsaturated polyester resins, it cannot simply be reduced and must be replaced with other ethylenically unsaturated monomers. In the above publication, there is no example other than styrene, and no consideration is given to the solubility of the resin for shrinkage inhibitor and the crosslinkability of the unsaturated polyester resin when other ethylenically unsaturated monomers are used.

If the inventors of the present invention use diallyl phthalate instead of styrene as the ethylenically unsaturated monomer, the styrene odor can be reduced and the residual amount of styrene in the molded product can be greatly reduced. It was found that it can be reduced. However, since diallyl phthalate is difficult to dissolve a known resin for shrinkage inhibitor, the inventors of the present invention, as a result of diligent investigation, found that the type and amount of monomer from which the resin for shrinkage inhibitor is derived, the resin By specifying the weight average molecular weight, it was surprisingly found that the resin can be dissolved in the ethylenically unsaturated monomer and that a desired shrinkage inhibiting function can be imparted to the molded article.
Thus, according to the present invention, a monomer comprising 50 to 80% by weight of a monofunctional styrene monomer and 50 to 20% by weight of an acrylic acid monomer selected from ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate. derived from a body mixture, the weight average molecular weight der Ru styrene 50,000 to 500,000 - the acrylic resin particles, shrinkage control agents during curing of the molding material containing diallyl phthalate and unsaturated polyester resin is provided.

Since the styrene-acrylic resin particles for shrinkage inhibitors of the present invention have good solubility in diallyl phthalate contained in the molded body material, styrene contained in the conventional molded body material can be replaced with diallyl phthalate. . Therefore, the styrene odor at the time of shaping | molding which was a subject in the case of using styrene, and VOC which arises from the obtained molded object can be reduced. Further, diallyl phthalate can be easily prepared as a molded material because it is thermally stable.
The resin constituting the styrene-acrylic resin particles for shrinkage inhibitor has a glass transition temperature in a specific range, a diallyl phthalate solution in a specific viscosity range, and a diallyl phthalate solution has a specific solubility. Thus, the solubility in diallyl phthalate can be improved, VOC can be further reduced, and the styrene odor can be suppressed. In addition, the handling property of the mixture at the time of shaping | molding can be improved because the styrene-acrylic-type resin particle for shrinkage | contraction inhibitors has a specific average particle diameter.

(Styrene-acrylic resin particles for shrinkage inhibitors)
The styrene-acrylic resin particles for shrinkage inhibitor of the present invention are used for suppressing shrinkage of a molded product obtained by curing a molded material containing diallyl phthalate and an unsaturated polyester resin. It consists of copolymer resin derived from the monomer mixture which consists only of an acid type monomer.

  Acrylic monomers include acrylic acid and derivatives of acrylic acid, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, acrylic acid Nonyl, decyl acrylate, undecyl acrylate, dodecyl acrylate, glycidyl acrylate, methoxyethyl acrylate, propoxyethyl acrylate, butoxyethyl acrylate, methoxydiethylene glycol acrylate, ethoxydiethylene glycol acrylate, methoxyethylene glycol acrylate, acrylic Acid butoxytriethylene glycol, methoxydipropylene glycol acrylate, phenoxyethyl acrylate, phenoxydiethylene acrylate , Phenoxytetraethylene glycol acrylate, benzyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, N-vinyl-2-pyrrolidone acrylate, Examples include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, 2-hydroxy-3-phenyloxypropyl acrylate, glycidyl acrylate, acrylonitrile, acrylamide, N-methylol acrylamide, diacetone acrylamide, and the like. Among these, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and the like are preferable from the viewpoint of adjusting the glass transition temperature of the polymer.

Examples of the styrene monomer include styrene derivatives such as α-methylstyrene, vinyltoluene, and pt-butylstyrene in addition to styrene.
The proportions of styrene monomer and acrylic acid monomer are 50 to 80% by weight and 50 to 20% by weight. When the styrene monomer is 50 to 80% by weight, the solubility in diallyl phthalate is increased. A more preferable use ratio of the styrene monomer is 65 to 75% by weight.

Next, the styrene-acrylic resin particles for shrinkage inhibitor have a weight average molecular weight of 50,000 to 500,000. When the weight average molecular weight is less than 50,000, the solubility of the styrene-acrylic resin particles for shrinkage inhibitor in diallyl phthalate is improved, but it adheres to the kneader during kneading with the unsaturated polyester resin, etc. Since there are many adhesions and handling property is bad, workability | operativity worsens. If it is larger than 500,000, the solubility in diallyl phthalate decreases, so that the dissolution time becomes longer and the workability becomes worse. Moreover, the viscosity of the diallyl phthalate solution containing the styrene-acrylic resin particles for the shrinkage inhibitor is increased, resulting in poor workability.
The styrene-acrylic resin particles for shrinkage inhibitor may contain other components such as a colorant, a reinforcing fiber, an antioxidant, and an antistatic agent as long as the effects thereof are not impaired.

The resin constituting the styrene-acrylic resin particles for the shrinkage inhibitor preferably has a glass transition temperature of 40 to 80 ° C. When the glass transition temperature is lower than 40 ° C., the heat resistance may be insufficient. If it is higher than 80 ° C, the solubility may be insufficient. A more preferable glass transition temperature is 55 to 75 ° C.
Further, when 10 parts by weight of the styrene-acrylic resin particles for shrinkage inhibitor is dissolved in 60 parts by weight of diallyl phthalate, it is preferable to give it to a solution having a viscosity of 80 poise or less from the viewpoint of improving workability. A more preferred viscosity is 60 poise or less.
Furthermore, when 30 parts by weight of the styrene-acrylic resin particles for shrinkage inhibitor are stirred with 100 parts by weight of diallyl phthalate at 65 to 80 ° C., it is dissolved within 80 minutes from the viewpoint of improving workability. preferable.

  Furthermore, the styrene-acrylic resin particles for shrinkage inhibitor are preferably composed of particles having an average particle diameter of 0.1 to 0.8 mm. When it is smaller than 0.1 mm, the styrene-acrylic resin particles for the shrinkage inhibitor may be sparged due to the fine particle size when dissolved in diallyl phthalate, which may increase the dissolution time. Moreover, workability may be reduced due to generation of dust. When it is larger than 0.8 mm, it may take time to dissolve in diallyl phthalate. A more preferable average particle diameter is 0.15 to 0.65 mm.

(Method for producing styrene-acrylic resin particles for shrinkage inhibitor)
The production method of the styrene-acrylic resin particles for the shrinkage inhibitor is not particularly limited, and can be produced by a known method such as bulk polymerization or suspension polymerization. Of these, suspension polymerization is preferred because styrene-acrylic resin particles for shrinkage inhibitor having a uniform average particle diameter can be easily obtained.
Suspension polymerization is a method in which a monomer mixture and optionally other components are dispersed in an aqueous medium to form oil droplets and the oil droplets are polymerized. For polymerization of the monomer mixture, a polymerization initiator may be used as necessary.

  The polymerization initiator is not particularly limited, and oil-soluble organic peroxides, azo compounds and the like can be used. Examples of the organic peroxide include benzoyl peroxide, lauroyl peroxide, orthomethoxybenzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, t-butyl hydroperoxide and the like. It is done. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2 ′-(2,3-dimethylbutyronitrile), 2,2′-azobis (2,3,3-trimethylbutyronitrile), 2,2′-azobis (2-isopropylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2- (carbamoylazo) isobutyronitrile, 4,4′-azobis (4-cyanovaleric acid), dimethyl-2,2 ′ -Azobisisobutyrate etc. are mentioned. Of these polymerization initiators, benzoyl peroxide, lauroyl peroxide, 2,2'-azobisisobutyronitrile, and 2,2'-azobis (2,4-dimethylvaleronitrile) are preferable.

  The usage-amount of a polymerization initiator can be suitably set according to polymerization conditions, such as the kind, the polymerizability of a monomer, and polymerization temperature. For example, it is preferably used in the range of 0.01 to 2 parts by weight with respect to 100 parts by weight of the monomer mixture. When the amount used is less than 0.01 parts by weight, the polymerization time may be long. On the other hand, when the amount used exceeds 2 parts by weight, an effect commensurate with the amount used cannot be expected.

The aqueous medium is not particularly limited, and examples thereof include water or a mixed medium of water and a water-soluble organic solvent (for example, a lower alcohol such as methanol or ethanol). The aqueous medium is preferably used in the range of 100 to 400 parts by weight and more preferably in the range of 120 to 200 parts by weight with respect to 100 parts by weight of the monomer mixture.
In addition, an inorganic suspension stabilizer may be included in the aqueous medium in order to stabilize the oil droplets suspended in the aqueous medium. As inorganic suspension stabilizers, calcium phosphates such as tricalcium phosphate and hydroxyapatite, phosphates such as magnesium pyrophosphate, poorly water-soluble such as titanium oxide, calcium hydroxide, calcium carbonate, calcium sulfate, colloidal silica An inorganic compound etc. are mentioned. Of these, magnesium pyrophosphate and colloidal silica are preferred. The inorganic suspension stabilizer is preferably used in the range of 0.2 to 15 parts by weight with respect to 100 parts by weight of the monomer mixture.

A surfactant may be added to the aqueous medium. As the surfactant, any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant can be used.
Examples of the anionic surfactant include higher fatty acids such as sodium oleate, alkyl sulfate salts such as sodium lauryl sulfate and sodium α-olefin sulfonate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and dialkyl. Examples include sulfosuccinate and alkyl phosphate ester salts.
Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and quaternary ammonium salts such as lauryltrimethylammonium chloride.

Examples of zwitterionic surfactants include lauryl dimethylamine oxide.
Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, oxy Examples include ethylene-oxypropylene block polymers. You may use the said surfactant individually or in combination of 2 or more types. When a poorly water-soluble phosphate is used as the inorganic suspension stabilizer, alkyl sulfate ester salt, sodium alkylbenzene sulfonate, and sodium α-olefin sulfonate are preferable.
The amount of the surfactant used is appropriately adjusted according to the average particle size of the styrene-acrylic resin particles for shrinkage inhibitor, and is generally used in the range of 0.001 to 0.1% by weight in the aqueous medium. It is preferable.

The polymerization temperature is preferably 70 to 100 ° C, more preferably 75 to 90 ° C. The polymerization time is preferably 2 to 20 hours, more preferably 3 to 15 hours.
It is preferable to take the process of reducing an unreacted monomer following the said polymerization process. The temperature in the step of reducing the unreacted monomer is preferably 100 to 130 ° C, and more preferably 105 to 125 ° C. The time for the step of reducing the unreacted monomer is preferably 1 to 5 hours, and more preferably 1.5 to 3.5 hours.
In addition, the polymerization is usually performed with stirring to such an extent that the oil droplets of the monomer mixture are not destroyed. Examples of the stirring condition include a condition in which the peripheral speed of the stirring blade is defined at 150 to 400 rpm.
The obtained styrene-acrylic resin particles for shrinkage inhibitor can be isolated from an aqueous medium by undergoing steps such as suction filtration, centrifugal dehydration, centrifugal separation, pressure dehydration, water washing, and drying.

(Molded body material)
The molded body material in which the styrene-acrylic resin particles for shrinkage inhibitor of the present invention are used is a raw material for molded bodies such as decorative sheets such as headlamp reflectors, breakers, connectors, printed boards, and wall materials. . The molded body material contains at least styrene-acrylic resin particles for shrinkage inhibitor, diallyl phthalate, and unsaturated polyester resin.
It is preferable that the usage-amount of the styrene-acrylic-type resin particle for shrinkage | contraction inhibitors to a molded object material is 5-50 weight part with respect to 100 weight part of total amounts of diallyl phthalate and unsaturated polyester resin. If it is less than 5 parts by weight, the suppression of shrinkage of the unsaturated polyester resin during molding may be insufficient. When the amount is more than 50 parts by weight, the viscosity is increased, and workability during blending may be deteriorated.

Examples of the unsaturated polyester resin include a polymer of an acid component and an alcohol component. The acid component includes unsaturated dibasic acids such as maleic acid, fumaric acid, itaconic acid and mesaconic acid or their anhydrides, isophthalic acid, terephthalic acid, phthalic anhydride, succinic acid, adipic acid, sebacic acid and other polybasic acids. Examples include acids. On the other hand, examples of the alcohol component include diols such as ethylene glycol, diethylene glycol, propylene glycol, dipyropylene glycol, butanediol, and neopentyl glycol, and triols such as trimethylolpropane.
The unsaturated polyester resin (solid ester resin) preferably has a number average molecular weight of 1500 to 4000. When the weight average molecular weight is in this range, good physical properties of the molded article can be obtained. A more preferable range of the number average molecular weight is 2000 to 3000.

The amount of diallyl phthalate used is preferably in the range of 5 to 25% by weight in the molded body material. If it is less than 5% by weight, the viscosity of the molded body material becomes too high, so that it may be a material for the papasa material. On the other hand, when the amount is more than 25% by weight, the viscosity of the molded product becomes too low, the stickiness becomes severe, and the workability may be deteriorated. A more preferable use amount is in the range of 10 to 20% by weight.
In addition, the composition may include fillers such as glass fiber, calcium carbonate, and alumina, thickeners such as aluminum hydroxide, magnesium oxide, magnesium hydroxide, and calcium oxide, and various organic peroxides as necessary. A curing catalyst, a release agent such as stearic acid, and various colorants such as dyes and pigments may be added.

(Molded body)
A molded body is obtained by subjecting the molded body material to a curing treatment.
The molded body can be molded by, for example, a method in which a predetermined mold is filled with the molded body material and the mold is heated and pressurized. Examples of the molding conditions include a molding temperature of 130 to 180 ° C., a molding time of 3 to 30 minutes, and a molding pressure of 30 to 100 kg / cm ² .
The shape of a molded object is not specifically limited, It can determine suitably according to a use application.

Hereinafter, although an example is given and explained further, the present invention is not limited by these examples.
(Measurement of weight average molecular weight)
The weight average molecular weight is measured using gel permeation chromatography (GPC). The measuring method is as follows. In addition, a weight average molecular weight means a polystyrene (PS) conversion weight average molecular weight.
Measuring device: GPC HLC-8020 manufactured by Tosoh Corporation
Guard column: TOSOH TSK guard column HHR (S) x 1 (7.5 mm ID x 7.5 cm)
Column: TOSOH TSK-GEL GMHHR-H (S) × 3 (7.8 mm ID × 30 cm)
Measurement conditions: column temperature (40 ° C.), mobile phase (primary THF / 45 ° C.),
S. PUMP / R. PUMP flow rate (0.8 / 0.5 mL / min), RI temperature (35 ° C.),
INLET temperature (35 ° C), measurement time (55 min), detector (UV254 nm, RI)
Measurement method: 50 mg of a sample is allowed to stand overnight in 10 mL primary THF (mobile phase) and dissolved, and filtered through a 0.45 μm or 0.20 μm filter.
Standard polystyrene for calibration curve: manufactured by Showa Denko KK, trade name “shodex”, weight average molecular weight: 1030000, manufactured by Tosoh Corporation, weight average molecular weight: 5480000, 3840000, 355000, 102000, 37900, 9100, 2630, 495

(Measurement of average particle size)
About 50 g of a sample was sieved using a low-tap type sieve shaker (manufactured by Iida Seisakusho Co., Ltd.) with a sieve opening of 4.00 mm, an opening of 3.35 mm, an opening of 2.80 mm, an opening of 2.36 mm, and an opening 2.00 mm, opening 1.70 mm, opening 1.40 mm, opening 1.18 mm, opening 1.00 mm, opening 0.85 mm, opening 0.71 mm, opening 0.60 mm, opening 0. JIS standard sieve with 50mm, 0.425mm opening, 0.355mm opening, 0.300mm opening, 0.250mm opening, 0.212mm opening, 0.180mm opening, 0.150mm opening for 10 minutes Classification is performed, the sample weight on the sieve net is measured, and based on the cumulative weight distribution curve obtained from the result, the particle diameter (median diameter) at which the cumulative weight is 50% is defined as the average particle diameter.

(Measurement of residual styrene content)
A measurement sample is prepared by adding 25 ml of carbon disulfide and 1 ml of an internal standard solution to 1 g of resin particles and leaving it to stand for 12 hours or more. The internal standard solution is prepared by adding 0.1 ml of toluene to 75 ml of carbon disulfide. Using this measurement sample, a styrene chart was obtained from a gas chromatograph (CG-7A manufactured by Shimadzu Corp.) under the following conditions, and the styrene weight was calculated from the chart based on a styrene calibration curve measured in advance. The amount of residual styrene contained in the resin particles is obtained from the obtained styrene weight.
Column packing: Liquid phase PEG-20M
Carrier: Chromasorb W
Detector: FID
Carrier gas: Nitrogen Column temperature: 105 ° C

(Measurement of glass transition temperature)
Using a differential thermothermal gravimetric simultaneous measurement device (TG / DTA6200 manufactured by Seiko Instruments Inc.), a sample consisting of 15 mg in an air atmosphere, a temperature range of 30 to 200 ° C., and a temperature rising rate of 7.5 ° C./min Then, the glass transition temperature is measured. The obtained low temperature side inflection point is defined as the glass transition temperature.

Example 1
In 2000 g of water in an autoclave having an internal volume of 5 L, 7.2 g of magnesium pyrophosphate and 0.47 g of alkylbenzene sulfonate (Neogen SL-200 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were added and dispersed as a suspension stabilizer. Into this, 1200 g of styrene (St) prepared in advance, 400 g of butyl acrylate (BA), and 12.9 g of benzoyl peroxide (NIPPER BW manufactured by NOF Corporation, 74.2% pure) as a polymerization initiator are dissolved. The mixed solution was added. Next, the mixture was heated to 85 ° C., polymerized at 85 ° C. for 5 hours while stirring at 170 rpm, and then reacted at 110 ° C. for 3 hours to reduce unreacted monomers. The particles obtained here were treated with hydrochloric acid, washed and filtered, and then dried to obtain resin particles. The obtained resin particles had a weight average molecular weight of 110,000, a residual styrene monomer amount of 0.2%, an average particle diameter of 0.3 mm, and a glass transition temperature of 61 ° C.

(Example 2)
Resin particles were obtained in the same manner as in Example 1 except that 6.9 g of benzoyl peroxide was used and the reaction time at 85 ° C. was 9 hours. The obtained resin particles had a weight average molecular weight of 190,000, a residual styrene monomer amount of 0.3%, an average particle diameter of 0.3 mm, and a glass transition temperature of 61 ° C.
(Example 3)
Resin particles were obtained in the same manner as in Example 1 except that 4.7 g of benzoyl peroxide was used and the reaction time at 85 ° C. was 12 hours. The obtained resin particles had a weight average molecular weight of 260000, a residual styrene monomer amount of 0.7%, an average particle diameter of 0.3 mm, and a glass transition temperature of 60 ° C.
(Example 4)
Resin particles were obtained in the same manner as in Example 1 except that 28.0 g of benzoyl peroxide was used. The obtained resin particles had a weight average molecular weight of 56,000, a residual styrene monomer amount of 0.2%, an average particle diameter of 0.4 mm, and a glass transition temperature of 60 ° C.

(Comparative Example 1)
In 2000 g of water in an autoclave having an internal volume of 5 L, 5.0 g of magnesium pyrophosphate and 0.1 g of sodium dodecylbenzenesulfonate were added and dispersed as a suspension stabilizer. To this was added a premixed mixture of 1500 g of styrene, 500 g of butyl acrylate, and 3.0 g of t-butyl peroxyisopropyl carbonate as an initiator. Next, resin particles were obtained in the same manner as in Example 1 except that the polymerization was carried out at 80 ° C. for 20 hours, followed by reaction at 110 ° C. for 4 hours as an unreacted monomer reduction step. The obtained resin particles had a weight average molecular weight of 1,000,000, a residual styrene monomer amount of 0.6%, an average particle diameter of 0.7 mm, and a glass transition temperature of 61 ° C.

(Comparative Example 2)
Resin in the same manner as in Example 1 except that 1600 g of styrene is used instead of the monomer mixture of styrene and butyl acrylate, 28.0 g of benzoyl peroxide is used, and the stirring speed during polymerization is 150 rpm. Particles were obtained. The obtained resin particles had a weight average molecular weight of 57,000, a residual styrene monomer amount of 0.2%, an average particle diameter of 0.6 mm, and a glass transition temperature of 100 ° C.
(Comparative Example 3)
Resin particles in the same manner as in Example 1 except that 1600 g of styrene was used instead of the monomer mixture of styrene and butyl acrylate, 4.3 g of benzoyl peroxide was used, and polymerization was performed at 85 ° C. for 10 hours. Got. The obtained resin particles had a weight average molecular weight of 340000, a residual styrene monomer amount of 0.2%, an average particle diameter of 0.3 mm, and a glass transition temperature of 105 ° C.
Table 1 shows the blending ratio of the monomers used in the production of the styrene-acrylic resin particles for shrinkage inhibitors of Examples and Comparative Examples, the weight average molecular weight (Mw), average particle diameter and glass transition temperature of the resin particles. .

(Experimental example)
The styrene-acrylic resin particles for shrinkage inhibitors obtained in Examples and Comparative Examples were evaluated by the following methods.
(1) Solubility 30 parts by weight of styrene-acrylic resin particles for shrinkage inhibitor and 100 parts by weight of diallyl phthalate (Daiso Dup Monomer) are placed in a 300 ml flask and heated to 70 ° C. while stirring at 85 rpm. The solubility of the styrene-acrylic resin particles for shrinkage inhibitor after maintaining stirring at 70 ° C. for 80 minutes is determined as follows.
○: completely dissolved and the solution is transparent.
X: Not sufficiently dissolved, and styrene-acrylic resin particles for shrinkage inhibitor remain.

(2) Viscosity A measurement sample is prepared by completely dissolving 10 g of styrene-acrylic resin particles for shrinkage inhibitor in 60 g of diallyl phthalate (Daimon Co., Ltd., DUP monomer) at room temperature (about 25 ° C.). Viscosity is measured using a B-type viscometer (B8H type manufactured by Tokimec Co., Ltd.) and a rotor (No. 5), a measurement sample is set at a predetermined position of the viscometer, and rotated at 20 rpm and 10 rpm. The viscosity is obtained by reading the scale when is stable and comparing the scale value against the calculation table. When the viscosity is 80 P or less, the evaluation is “good”, and when the viscosity is greater than 80 P, “X” is given.

(3) Appearance of molded body 10.5 parts by weight of unsaturated polyester resin (8524 manufactured by Nippon Iupika), 4.5 parts by weight of styrene-acrylic resin particles for shrinkage inhibitors of Examples and Comparative Examples, diallyl phthalate (Daiso) 15 parts by weight of a dapp monomer manufactured by the company, 0.45 parts by weight of t-butyl perbenzoate as a curing agent, and 71 parts by weight of other additives (glass fiber, release agent, etc.) were kneaded in a kneader for 20 minutes. Next, the kneaded product was aged (still) at 40 ° C. for 24 hours, then molded with a mold at 155 ° C., and taken out from the mold to obtain a molded body.
The surface state of the obtained molded body was visually determined based on the following criteria.
○: The surface is smooth and glossy, and there is no color unevenness.
Δ: Surface gloss or color unevenness is observed.
X: There is no gloss on the surface and uneven color is also observed.
The evaluation results are shown in Table 2.

From Table 2, the following can be understood.
(About the ratio of styrene monomer and acrylic acid monomer)
In the examples within the range of 50 to 80% by weight of the styrene monomer and 50 to 20% by weight of the acrylic monomer, both the viewpoints of solubility and appearance are superior to those of Comparative Examples 2 and 3 outside the range. .
(About weight average molecular weight)
The Example in the range whose weight average molecular weight is 50000-500000 is excellent from the viewpoint of viscosity evaluation compared with the comparative example 1 outside a range.

Claims (5)

  Derived from a monomer mixture consisting of 50 to 80% by weight of monofunctional styrene monomer and 50 to 20% by weight of acrylic acid monomer selected from ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate, and 50,000 The shrinkage | contraction inhibitor at the time of hardening of the molded object material which consists of diallyl phthalate and unsaturated polyester resin which consists of a styrene-acrylic-type resin particle which is a weight average molecular weight of -500,000. The styrene - acrylic resin particles, shrinkage control agent according to claim 1 which is particles of resin having a glass transition temperature of 40 to 80 ° C..   The shrinkage inhibitor according to claim 1 or 2, wherein the styrene-acrylic resin particles provide a solution having a viscosity of 80 P or less when 10 parts by weight thereof is dissolved in 60 parts by weight of diallyl phthalate.   The shrinkage according to any one of claims 1 to 3, wherein the styrene-acrylic resin particles dissolve within 80 minutes when 30 parts by weight of the styrene-acrylic resin particles are stirred with 100 parts by weight of diallyl phthalate at 65 to 80 ° C. Inhibitor.   The shrinkage inhibitor according to any one of claims 1 to 4, wherein the styrene-acrylic resin particles are particles having an average particle diameter of 0.1 to 0.8 mm.