JPH06192345A - Core-shell polymer, unsaturated polyester resin composition containing the same and its molded product - Google Patents

Abstract

PURPOSE:To obtain the subject polymer comprising a specific constitution, useful as a contraction-reducing agent for unsaturated polyester resins and giving unsaturated polyester resin molded products excellent in moldability, transparency and surface luster. CONSTITUTION:The objective polymer comprises (A) 50-90wt.% of a core layer formed of the crosslinked polymer obtained from monomers containing >=50wt.% of an aromatic vinyl (preferably styrene) and (B) 50-10wt.% of a shell layer formed of the polymer obtained from monomers containing >=50wt.% of methyl methacrylate, and has a refractive index of 1.52-1.58. This polymer is produced by emulsion-polymerizing 80-99.5wt.% of an aromatic vinyl, 0-20wt.% of a copolymerizable vinylic monomer, 0.1-1wt.% of divinyl benzene as a crosslinkable monomer and 0-1wt.% of a graft polymer for the formation of the layer A, and subsequently emulsion-polymerizing 80-95wt.% of methyl methacrylate, 0-2wt.% of a crosslinkable monomer and 0-2wt.% of a graft monomer for the formation of the shell layer B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core / shell polymer, an unsaturated polyester resin composition containing the same, and a molded article thereof, and more specifically, a core / shell polymer useful as a low shrinkage agent for unsaturated polyester resins, It relates to an unsaturated polyester resin composition containing such a core-shell polymer as a low-shrinking agent, having improved moldability, and giving a molded article excellent in transparency and gloss.

[0002]

BACKGROUND OF THE INVENTION Unsaturated polyester resins are generally composed mainly of unsaturated polyester and vinyl monomers, and have been widely used as molding materials for various resin molded products. Molding of such an unsaturated polyester resin generally utilizes a so-called curing reaction in which the vinyl monomer is copolymerized with an unsaturated group in the unsaturated polyester to form a network. When curing and molding the saturated polyester resin, usually 6 to 8%
It is known that the volume contraction of Such volume shrinkage not only impairs the dimensional accuracy and appearance of the obtained molded product, but also when the unsaturated polyester resin is combined with a fibrous, granular, or other form of reinforcing material, the resin and its The stress remains at the interface with such a reinforcing material, and the desired strength cannot be obtained.

Therefore, in order to prevent such shrinkage at the time of molding, it has been widely practiced to add and mix a low-shrinking agent composed of a thermoplastic resin or crosslinked polymer particles into an unsaturated polyester resin. . Such a low-shrinking agent, when the compatibility with the unsaturated polyester resin is poor,
A large amount of energy and time are required to mix and disperse the low-shrinking agent in the resin, and the low-shrinking agent is separated even after the mixing, so that mold stains and molded product surface defects are likely to occur. Therefore, a low-shrinking agent that can be easily dispersed in a resin and has good dispersion stability is desired. Furthermore, even when molding at high temperature in a short time,
Moldability is also one of the important properties required of the unsaturated polyester resin composition so that a molded product free from molding defects can be obtained.

Unsaturated polyester resins have hitherto been used for the production of various molded articles. For example, when used as a marble-like molded article for bathtubs, kitchen counters, vanities, etc., Appearance with excellent transparency and gloss is required. Japanese Patent Publication No. 62-64858 discloses a sheet molding compound (SMC) containing glass powder and crosslinked polystyrene particles as a low-shrinking agent. According to this molding material, it is possible to obtain a molded article having excellent transparency and a uniform hue, but the crosslinked polystyrene particles have poor dispersibility in the unsaturated polyester resin, and the transparency and Further improvement is desired in the moldability at high temperature. Also, "Reinforced Plastics" Vol. 38, No. 2, No. 4
The page shows a low shrinkage bulk for transparent artificial marble containing a core / shell polymer having a particle size of 100 nm or less as a low shrinkage agent.
A molding compound (BMC) has been proposed, but even in this case, the moldability is inferior and there is room for further improvement in the surface gloss of the molded product.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems in unsaturated polyester resins, and as a result, the core layer and the shell layer each are a polymer of a monomer having a predetermined composition. Further, by having a crosslinked structure in the core layer, it can be easily dispersed in the unsaturated polyester resin as a low shrinkage agent,
Not only is it effective for lowering the shrinkage of the unsaturated polyester resin at the time of curing, but the unsaturated polyester resin composition containing such a core / shell polymer can be used to form cracks or the like even at high temperature for a short time. The present invention has been accomplished by finding that a molded product having improved moldability without causing defects and having excellent transparency and surface gloss can be provided.

[0006]

The core-shell polymer according to the present invention comprises a core layer comprising a cross-linked polymer of a monomer containing 50% by weight or more of aromatic vinyl and a monolayer containing 50% by weight or more of methyl methacrylate. And a shell layer made of a polymer, having a refractive index in the range of 1.52 to 1.58, and the core layer in the range of 50 to 90% by weight.

Further, the unsaturated polyester resin composition according to the present invention contains the above core / shell polymer as a low-shrinking agent, and the refractive index of the core / shell polymer is a cured product of the above unsaturated polyester resin. The refractive index is within the range of ± 0.02. The core-shell polymer according to the present invention can be obtained by a continuous multi-stage seed emulsion polymerization method in which the polymer of the previous stage is sequentially coated with the polymer of the latter stage. In the multi-stage seed emulsion polymerization method, a seed latex is usually prepared by emulsion polymerization by adding monomers all at once, and then seed polymerization is carried out in the presence of this seed latex to form core particles. Of the core-shell polymer is obtained by repeating the seed polymerization in the presence of the core latex. The seed latex can be obtained, for example, by collectively adding monomers according to the required characteristics and emulsion-polymerizing the monomers. As the monomer, styrene, methyl methacrylate, ethyl acrylate, or a mixture thereof is usually often used.

Thus, when the core / shell polymer is produced by emulsion polymerization, an anionic surfactant such as sodium dodecylbenzene sulfonate or sodium lauryl sulfate, polyisocyanate or the like is used as an emulsifier according to a conventional method in the polymerization. Oxyethylene nonylphenyl ether, nonionic surfactants such as sorbitan monolaurate, or using a cationic surfactant such as octadecylamine acetate, potassium persulfate as a polymerization initiator, peroxides such as cumene peroxide, An azo compound such as 2,2′-azobis (2-amidinopropane) hydrochloride can be used.

Hereinafter, for the sake of simplicity, the first stage seed emulsion polymerization for obtaining the core latex and the second stage seed emulsion polymerization in the presence of such core latex are carried out to form the shell layer. The production of the core-shell polymer according to the present invention will be described by taking a two-stage seed emulsion polymerization method as an example. The first stage polymerization is 50% by weight of aromatic vinyl monomer.
Polymerization is performed by polymerizing a monomer containing the above and a crosslinkable monomer to form a core layer made of a crosslinked polymer. here,
Specific examples of the aromatic vinyl monomer include, for example, styrene-based monomers such as styrene, α-methylstyrene and chlorostyrene, alkylvinylbenzene such as vinyltoluene and ethylvinylbenzene, and polycyclic aromatics such as vinylnaphthalene. Group vinyl compounds may be mentioned. These aromatic vinyl monomers may be used alone or in combination of two or more. Particularly, in the present invention, as the aromatic vinyl monomer, a styrene-based monomer is preferable, and among them, styrene is preferably used.

The monomer used in the first-stage polymerization may contain a vinyl monomer having a copolymerizability therewith, in addition to the aromatic vinyl. Examples of vinyl monomers having copolymerizability with aromatic vinyl include aliphatic conjugated dienes having 4 to 6 carbon atoms such as butadiene, isoprene, and chloroprene, such as ethyl acrylate, propyl acrylate, and butyl acrylate. (Meth) acrylic acid alkyl ester having an alkyl group having 1 to 10 carbon atoms such as cyclohexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate and butyl methacrylate, vinyl cyanide such as acrylonitrile and methacrylonitrile, and vinylidene cyanide. Can be mentioned.

In order for the core-shell polymer according to the present invention to be useful as a low shrinkage agent for unsaturated polyester resins, the core layer needs to be crosslinked. To construct the core layer from the crosslinked polymer in this way,
A core layer made of a crosslinked polymer is formed by copolymerizing the above-mentioned monomer with a polyfunctional monomer having copolymerizability, that is, a crosslinkable monomer.

The combined use of a crosslinkable monomer in the production of core / shell polymers is described, for example, in US Pat.
It is already well known as described in 96,202. That is, the crosslinkable monomer refers to a polyfunctional monomer having two or more addition-polymerizable (ethylenic) unsaturated bonds in the molecule and having substantially the same reactivity. Such a crosslinkable monomer partially brings about a three-dimensional network structure, that is, a crosslinked polymer structure, in the polymer forming the core layer.

Examples of such crosslinkable monomers include aromatic divinyl monomers such as divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, hexanediol diacrylate, hexanediol dimethacrylate, Examples of alkane polyol polyacrylates such as oligoethylene glycol diacrylate, oligoethylene glycol dimethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, etc. However, divinylbenzene is particularly preferably used.

The amount of the crosslinkable monomer used in the polymerization for forming the core layer is closely related to the reduction of the shrinkage of the resulting core-shell polymer when used as the shrinkage reducing agent of the unsaturated polyester resin. In general, 0.01 to 5% by weight, preferably 0.05 to 2% by weight, and most preferably 0.1 to 5% by weight of the amount of the monomer used for forming the core layer.
It is in the range of 1% by weight.

Further, in the present invention, if necessary,
In forming the core layer, a grafting monomer may be used together with the above-mentioned crosslinking monomer. The combined use of grafting monomers in the production of core / shell polymers is already well known, as described, for example, in US Pat. No. 4,096,202. This grafting monomer is a polyfunctional monomer having two or more addition-polymerizable (ethylenic) unsaturated bonds in the molecule, but at least one of them having a reactivity different from the rest. Refers to the body. Such a grafting monomer leaves ethylenic unsaturation at or near the surface of the core layer after the core layer is formed, and is polymerized on the surface of the core layer after the formation of the core layer to form a shell layer. When the shell layer is formed, the ethylenically unsaturated bond left on the surface of the core layer or in the vicinity thereof participates in the polymerization for forming the shell layer, and at least a part of the shell layer chemically reacts with the core layer. Will be combined with.

Examples of such grafting monomers include allyl acrylate, allyl methacrylate, diallyl malate, diallyl fumarate, diallyl itaconate, allyl acid malate (half ester), allyl acid fumarate (half ester), A typical example is an ethylenically unsaturated carboxylic acid allyl ester such as allyl acid itaconate (half ester).

According to the present invention, the grafting monomer is 5% by weight or less, preferably 2% by weight or less, and particularly preferably 1% by weight or less in the monomer used for forming the core layer. Used in a range. In particular, according to the invention,
The core / shell polymer is aromatic vinyl 50-99.99.
% By weight, vinyl monomer copolymerizable therewith 0-4.99
By polymerizing a monomer mixture consisting of 0.01% by weight of the crosslinking monomer, 0.01 to 5% by weight of the crosslinkable monomer, and 0 to 5% by weight of the grafting monomer, the refractive index is higher than that of the shell layer described later. It is preferred to form the core layer polymer.

Particularly, according to a preferred embodiment of the core-shell polymer according to the present invention, the core layer is made of aromatic vinyl 80.
~ 99.5% by weight, vinyl monomer copolymerizable therewith 0 ~
It is formed by polymerizing a monomer mixture consisting of 20% by weight, 0.1 to 1% by weight of a crosslinkable monomer and 0 to 1% by weight of a grafting monomer. The second-stage polymerization is a polymerization for forming a shell layer in the core / shell polymer, and is a polymerization for forming a shell layer made of a polymer of a monomer containing 50% by weight or more of methyl methacrylate.

Also in this second-stage polymerization, a vinyl monomer having copolymerizability can be used together with methyl methacrylate. As the vinyl monomer copolymerizable with this methyl methacrylate, the aromatic vinyl exemplified as a monomer that can be used in the first-stage polymerization, particularly a styrene-based monomer, and an alkyl group having 1 to 10 carbon atoms
Acrylic acid alkyl ester, methacrylic acid alkyl ester excluding methyl methacrylate, vinyl cyanide, vinylidene cyanide, conjugated diene, and α, β-unsaturated carboxylic acid such as acrylic acid and methacrylic acid, and an alkyl group. A hydroxyalkyl acrylate or hydroxyalkyl methacrylate having 1 to 10 carbon atoms, for example, α such as hydroxyethyl methacrylate,
Examples thereof include hydroxyalkyl esters of β-unsaturated carboxylic acids.

Also in the second-stage polymerization, as in the case of the first-stage polymerization, the above-mentioned crosslinking monomer or grafting monomer can be used. The cross-linking monomer and the grafting monomer are used in the range of 5% by weight or less, preferably 2% by weight or less, and particularly preferably 1% by weight or less in the monomers used for forming the shell layer. To be

Therefore, in a preferred embodiment according to the invention, in the second stage polymerization for the formation of the shell layer, the shell layer is 80-95% by weight of methyl methacrylate, copolymerizable therewith as described above. Vinyl monomer 2
It is formed by copolymerizing a monomer mixture consisting of 0 to 5% by weight, a crosslinkable monomer of 0 to 5% by weight, and a grafting monomer of 0 to 5% by weight.

According to a particularly preferred embodiment, in the second stage polymerization for the formation of the shell layer, the shell layer comprises 80 to 95% by weight of methyl methacrylate, styrene, methacrylic acid, hydroxyethyl methacrylate or a mixture thereof 20. 5% by weight, 0-2% by weight of the crosslinkable monomer, and 0-2% by weight of the grafting monomer to form a copolymer.

Such a shell layer has a lower refractive index than the above-mentioned core layer, and the core / shell polymer is 1.
It has a refractive index in the range of 52 to 1.58, and thus, when the refractive index of the cured product of the unsaturated polyester resin to be the matrix is n, it is in the range of n ± 0.02 and is a low shrinkage agent. When used, an unsaturated polyester resin cured product having excellent transparency can be provided.

Further, in the present invention, a monomer containing a functional group having reactivity during the curing reaction process of the unsaturated polyester resin is used in forming the shell layer, and such a monomer component is used in the shell layer. The inclusion is very useful for increasing the adhesive strength between the core / shell polymer and the matrix. Examples of such a monomer include an epoxy group-containing monomer copolymerizable with methyl methacrylate, and the above-mentioned grafting monomer used for polymerization for forming the core layer.

Examples of the epoxy group-containing monomer include glycidyl methacrylate, glycidyl acrylate, and allyl glycidyl ether, and glycidyl methacrylate is particularly preferably used. The preferred amount of these epoxy-containing monomers used is in the range of 20% by weight or less, and particularly preferably 10% by weight or less, of the monomers for forming the shell layer.

It is also possible to use a monomer which enhances the compatibility with the unsaturated polyester resin in the formation of the shell layer and to have such a monomer component in the shell layer. It is very useful for improving the dispersibility of the core / shell polymer. Examples of such a monomer include a carboxyl group-containing monomer copolymerizable with methyl methacrylate, a hydroxyl group-containing monomer, and a vinyl ester monomer.

Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and citraconic acid, with methacrylic acid being particularly preferred. Examples of the hydroxyl group-containing monomer include hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, and the like, and hydroxyethyl methacrylate is particularly preferably used.

In the present invention, the amount of the above-mentioned carboxyl group-containing monomer and hydroxyl group-containing monomer used is preferably 20% by weight or less, preferably 10% by weight of the monomer for forming the shell layer. % Or less.
Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl chloroacetate and the like, and vinyl acetate is particularly preferably used. The amount of these vinyl ester monomers used is also preferably 20% by weight or less of the monomers for forming the shell layer, preferably 1%.
It is in the range of 0% by weight or less.

In the core-shell polymer according to the present invention, the core layer is 50 to 90% by weight, and the shell layer is 50 to 1%.
It is in the range of 0% by weight, and preferably the core layer is 60-8.
0% by weight, and the shell layer is in the range of 40 to 20% by weight.
In the core / shell polymer, when the core layer is less than 50% by weight, the molded article obtained by curing and molding the unsaturated polyester resin composition containing such a core / shell polymer is impaired in transparency, while %, The core-shell polymer has low dispersibility in the unsaturated polyester resin.

In the present invention, the shell layer may be formed as a continuous layer or a plurality of layers whose refractive index decreases from the center toward the surface. Furthermore, when the core-shell polymer according to the present invention is used as a low-shrinking agent for unsaturated polyester resins, the average particle size of the core-shell polymer is preferably in the range of 100 to 800 nm. When the average particle diameter of the core / shell polymer exceeds 800 nm, the transparency of the resulting molded product of the unsaturated polyester resin composition may be decreased, while when it is smaller than 100 nm, the intended purpose is originally intended. This is because the effect of low shrinkage at the time of curing the unsaturated polyester resin by the core / shell polymer may not be sufficiently obtained.

As described above, the core-shell polymer having such an average particle diameter can be obtained by the multistage seed emulsion polymerization method. That is, such a core-shell polymer is advantageously prepared by producing a latex by the already known multi-stage seed emulsion polymerization method, and freeze-thawing or salting it out to form a polymer particle in a reaction system. It can be obtained as a powder by separating the product from the product, centrifugal dehydration and drying. As mentioned above, spray drying with a spray dryer is also a suitable method for removing the core-shell polymer from the latex.

The core-shell polymer thus obtained can be added as a low-shrinking agent as a low-shrinking agent and mixed at the time of preparation of the unsaturated polyester resin composition, in order to improve workability. It can also be used as a stable dispersion in which a vinyl monomer used in the unsaturated polyester resin in advance, typically, styrene, is dispersed.

The unsaturated polyester resin composition according to the present invention contains an unsaturated polyester, a copolymerizable vinyl monomer copolymerizable therewith, and a low-shrinking agent composed of the core-shell polymer as described above, Usually, such a resin mixture is mixed with an inhibitor, a polymerization initiator, a filler, a release agent, a pigment, a thickener, etc. and used as a resin paste. Such a resin paste is usually used by impregnating it with a fiber reinforcement.

The unsaturated polyester may be one that has been widely used conventionally, and is usually produced by condensation of an α, β-olefin unsaturated dicarboxylic acid and a divalent glycol. In addition, in the production of such an unsaturated polyester, in addition to the two components of the above α, β-olefinic unsaturated dicarboxylic acid and a divalent glycol, a saturated dicarboxylic acid, an aromatic dicarboxylic acid, and a carboxylic acid Dicyclopentadiene which reacts can be used together.

Specific examples of the above α, β-olefinic unsaturated dicarboxylic acid include maleic acid, fumaric acid, itaconic acid, citraconic acid and the like, and anhydrides of these dicarboxylic acids. Specific examples of the saturated dicarboxylic acid that may be used in combination with these α, β-olefinic unsaturated dicarboxylic acids include, for example, adipic acid, sebacic acid, succinic acid, gluconic acid, phthalic anhydride, o-phthalic acid and isophthalic acid. Acid, terephthalic acid, tetrahydrophthalic acid, tetrachlorophthalic acid and the like can be mentioned.

As the glycol, for example, alkanediol, oxaalkanediol, bisphenol A or a diol obtained by adding an alkylene oxide such as ethylene oxide or propylene oxide to bisphenol A or the like, or a hydrogenated product thereof can be used. In addition to such glycol, monool or trivalent triol can be used.

Specific examples of alkanediols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol,
Examples include 1,5-pentanediol, 1,6-hexanediol, cyclohexanediol and the like. Examples of the oxaalkane diol include dioxyethylene glycol and trioxyethylene glycol. Examples of monohydric or trihydric alcohols that may be used in combination with these glycols include octyl alcohol, oleyl alcohol, and trimethylpropane.

The unsaturated polyester is usually composed of a dicarboxylic acid component such as those mentioned above and a glycol (if necessary, 1
Monohydric or trihydric alcohol) under heating to remove the by-produced water and proceed with the condensation reaction. In the present invention, the unsaturated polyester has an average molecular weight of 800 to 4000 and an acid value of 20 to 60.
Those within the range are preferably used.

In the present invention, a monovalent copolymerizable vinyl monomer is used as the vinyl monomer copolymerizable with the unsaturated polyester. Examples of such monovalent vinyl monomers include aromatic vinyl monomers such as styrene, p-chlorostyrene, and vinyltoluene, acrylic acid, methyl acrylate, methacrylic acid,
Examples thereof include acrylic monomers such as methyl methacrylate and acrylonitrile. This copolymerizable vinyl monomer is usually blended as a diluent for unsaturated polyester to form an unsaturated polyester resin. It can also be added separately from the unsaturated polyester diluent.

In the present invention, a polyvalent copolymerizable compound may be used in combination with the above monovalent copolymerizable vinyl monomer, if necessary. Examples of such polyvalent copolymerizable compounds include, for example, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, propylene glycol dimethacrylate, dipropylene glycol dimethacrylate, 1,4-butanediol dimethacrylate. Methacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate,
Ethylene glycol diacrylate, 1,3-propanediol diacrylate, 1,4-butanediol diacrylate, neopentyl glycol diacrylate, 1,6
Examples thereof include hexanediol diacrylate, trimethylolpropane dimethacrylate, glycerin dimethacrylate, pentaerythritol dimethacrylate, and trimethylolpropane diacrylate, which are dimethacrylates and diacrylates of alkane polyols having 2 to 12 carbon atoms.

Further, for example, trimethylolpropane trimethacrylate, glycerin trimethacrylate, pentaerythritol trimethacrylate, glycerin triacrylate, pentaerythritol triacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexamethacrylate, pentaerythritol tetraacrylate, dipentaerythritol. Examples thereof include polymethacrylates and polyacrylates of alkane polyols having 3 to 12 carbon atoms such as hexaacrylate.

In the unsaturated polyester resin composition according to the present invention, the inhibitors include PBQ (parabenzoquinone), MTBHQ (methyl-t-butylhydroquinone), BHT (3,5-di-t-butyl-4-hydroxy). Toluene, that is, 2,6-di-t-butyl-4-methylphenol), HQ (hydroquinone), TBC (t-butylcatechol), and other well-known substances are used.

In the present invention, an unsaturated polyester,
The resin mixture comprising a copolymerizable vinyl monomer copolymerizable therewith and the above-mentioned low-shrinking agent is usually 20 to 90% by weight of the unsaturated polyester and the copolymerizable vinyl monomer 20.
.About.70 wt% and low shrinkage agent 1 to 30 wt%. In the unsaturated polyester resin composition according to the present invention, t-butylperoxybenzoate (T
BPB), t-butyl peroxyoctoate (TBP
O), 2,5-dimethyl-2,5-di (benzoylperoxy) cyclohexane (DDBPH), t-amylperoxy octoate (TAPO), t-butyl isopropyl carbonate (TBIPC), etc. Among the materials, one kind or two or more kinds are used, appropriately selected according to the desired curing rate. Such an initiator is usually used in an amount of 0.3 to 4 parts by weight based on 100 parts by weight of the resin mixture.

Further, in the present invention, together with the initiator,
A curing accelerator can also be used in combination. Examples of the curing accelerator include organic metal compounds such as cobalt, copper and manganese, such as octoate, naphthenate and acetylacetonate. These may be used alone or as a mixture. These curing accelerators are usually 20 to 200 p based on 100 parts by weight of the resin mixture.
Used in the pm range.

Further, the unsaturated polyester resin according to the present invention may be blended with a filler, a release agent, a pigment, a thickener and the like, if necessary. As the filler, calcium carbonate, aluminum hydroxide, talc, silica, clay, glass powder, glass balloon and the like are used. Examples of the release agent include metal soaps such as zinc stearate and calcium stearate, fluorine-based organic compounds, and phosphoric acid-based compounds. As a pigment,
Titanium oxide, carbon black, rouge, phthalocyanine blue, etc. are used. Further, examples of the thickener include oxides and hydroxides of magnesium, calcium and the like.

As the fiber reinforcing material, glass fiber is generally used. Preferably, for example, a diameter of about 8-20
Glass fibers having a length of 1 μm and a length of 1 to 50 mm are used. In addition, as the fiber reinforcing material, for example, organic or inorganic fibers such as carbon fiber, aramid fiber, and vinylon fiber can be used. Such a fiber reinforcement is usually blended in the range of about 3 to 40% by weight with respect to the total amount of the unsaturated polyester resin composition.

The unsaturated polyester resin composition according to the present invention is kneaded and impregnated with these components by a conventional means to give an SMC (sheet molding compound), TMC (sick molding compound) or the like. Sheet or BMC (bulk
It can be a bulk molding material such as molding compound), but when using a thickener,
The mixture is kneaded, impregnated, and then aged at a predetermined temperature for a predetermined time and then subjected to molding.

A molded article made of the unsaturated polyester resin composition according to the present invention is heated and pressed at a predetermined temperature and a predetermined pressure with a compression molding machine or an injection molding machine, using the unsaturated polyester resin composition. Can be obtained by For example, pressure 10-120 kgf / cm ² , temperature 80-
A molded product can be obtained by curing at 160 ° C.

[0049]

The core / shell polymer according to the present invention is
A core layer made of a cross-linked polymer of monomers containing 50% by weight or more of aromatic vinyl, and 50% by weight of methyl methacrylate.
It has a shell layer made of a polymer of monomers containing the above, 1.
The core layer has a refractive index in the range of 52 to 1.58 and has a refractive index of 50.
˜90% by weight.

When such a core-shell polymer is used as a low-shrinking agent for unsaturated polyester resin, the core-shell polymer can be easily dispersed in the unsaturated polyester resin, and further, a low-shrinking agent containing such a low-shrinking agent is used. The saturated polyester resin composition does not cause molding defects such as cracks even when molded at high temperature for a short time, has improved moldability, and thus provides an unsaturated polyester resin molded article excellent in transparency and surface gloss. Obtainable.

[0051]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following, all "parts" indicate parts by weight. The abbreviations used below are as shown below. Abbreviations Methyl Methacrylate: MMA Styrene: St Allyl Methacrylate: AlMA Divinylbenzene ^*) : DVB Methacrylic Acid: MAA 2-Hydroxyethyl Methacrylate HEMA Deionized Water: DIW Dioctyl Sulfosuccinate Sodium Salt: SSS Sodium Persulfate: SPS Sodium Bicarbonate: SHC *) consists of 58% by weight of divinylbenzene and 42% by weight of aromatic vinyl monomer.

Method for Measuring Physical Properties of Core / Shell Polymer The particle size of the core / shell polymer was measured by a laser particle size analysis system LPA-3000 manufactured by Otsuka Electronics Co., Ltd. The refractive index of the core / shell polymer is 0.3 mm obtained by hot pressing the core / shell polymer.
Sheet was measured with an Abbe refractometer.

Example 1 (Production of core-shell polymer as low shrinkage agent A) DIW was placed in a 2 liter polymerization vessel equipped with a reflux condenser.
560 g, 2% SSS aqueous solution 10 g and 1% SHC aqueous solution 40 g were charged, and the mixture was stirred at 75 ° C. under a nitrogen stream.
The temperature was raised to. To this, 40 g of MMA was added and dispersed for 10 minutes, and then 80 g of a 2% SPS aqueous solution was added to initiate seed emulsion polymerization. Subsequently, 1030.2 g of a first-stage monomer emulsion having the following composition was continuously fed for 3 hours.

First-stage monomer emulsion St 656.5 g DVB 3.5 g 2% SSS aqueous solution 290.0 g SHS 1% aqueous solution 40.0 g DIW 40.0 g The internal temperature was raised to 90 ° C., and after aging for 1 hour, Then, the temperature was cooled to 70 ° C. to start the second-stage polymerization. That is, 2% SPS
20 g of the aqueous solution was added, and further 420 g of the second-stage monomer emulsion having the following composition was fed over 60 minutes.

Second stage monomer emulsion MMA 293.4 g St 6.6 g 1% SSS aqueous solution 60.0 g 1% SHC aqueous solution 20.0 g DIW 40.0 g The internal temperature was raised to 90 ° C. and aged for 1 hour. Then, the mixture was cooled to 40 ° C. or lower and filtered through a 300-mesh stainless wire mesh to obtain a latex of core-shell polymer having a solid content of 45.7% and a weight average particle diameter of 385 nm. This latex was spray-dried at an inlet temperature of 140 ° C. and an outlet temperature of 70 ° C. to obtain a low shrinkage agent A having a particle diameter of 50 to 100 μm.

Examples 2 to 5 (Production of Core / Shell Polymer as Low Shrinking Agents B to E) Emulsion polymerization and spray drying were carried out in the same manner as in Example 1 with the charging compositions shown in Tables 1 and 2. Low shrinkage agent B,
C, D and E were obtained.

Example 6 (Production of core-shell polymer as low shrinkage agent F) DIW was placed in a 2 liter capacity polymerization vessel equipped with a reflux condenser.
193 g, 2% SSS aqueous solution 2.7 g and 1% SHC aqueous solution 13.3 g were charged, and the mixture was stirred under a nitrogen stream to 70
The temperature was raised to ° C. To this, 3.3 g of MMA was added and dispersed over 10 minutes, and then 25 g of a 2% SPS aqueous solution was added to initiate seed emulsion polymerization. Subsequently, the internal temperature was raised to 90 ° C., 47.3 g of a 2% SPS aqueous solution was added,
1463.9 g of the first-stage monomer emulsion having the following composition
Was continuously fed for 6 hours.

First-stage monomer emulsion St 656.5 g DVB 3.5 g MMA 36.7 g 1% SSS aqueous solution 580.0 g 1% SHC aqueous solution 40.0 g DIW 147.0 g Keeping the internal temperature at 90 ° C., 1 After aging for a period of time, it was cooled to 80 ° C. to start the second stage polymerization. That is, 2% SPS
20 g of the aqueous solution was added, and further 440 g of the second-stage monomer emulsion having the following composition was fed over 2 hours.

Second-stage monomer emulsion MMA 263.4 g St 6.6 g MAA 30.0 g 1% SSS aqueous solution 120.0 g 1% SHC aqueous solution 20.0 g The internal temperature was raised to 90 ° C. and aged for 1 hour. Then, the mixture was cooled to 40 ° C. or lower and filtered through a 300-mesh stainless steel wire net to obtain a latex of core-shell polymer having a solid content of 44.9% and a weight average particle diameter of 650 nm. This latex was spray-dried at an inlet temperature of 140 ° C and an outlet temperature of 70 ° C to obtain a low-shrinking agent F having a particle size of 50 to 100 µm.

Examples 7 and 8 (Production of core / shell polymer as low-shrinking agents G and H) Emulsion polymerization and spray drying were carried out in the same manner as in Example 6 with the charging compositions shown in Tables 1 and 2. As a result, low shrinkage agents G and H were obtained.

[0061]

[Table 1]

[0062]

[Table 2]

Example 9 (Production of unsaturated polyester resin composition) Based on the formulation shown in Table 3, the unsaturated polyester resin composition (1) was prepared.
Was manufactured. As the unsaturated polyester resin, Polymer 6317 manufactured by Takeda Pharmaceutical Co., Ltd., M as an inhibitor
TBHQ, BIC- manufactured by Kayaku Akzo Co., Ltd. as a curing agent
75, glass powder M-60S manufactured by Nippon Fellow Co., Ltd. as a filler, zinc stearate as a release agent,
Magnesium oxide was used as the thickening agent, and the unsaturated polyester resin used in the formulation was mixed with 10% of titanium oxide. The glass chop used for BMC manufactured by Nippon Sheet Glass Co., Ltd. was used. The refractive index of the cured product of Polymer 6317 was 1.55561.

BMC was produced as an example of the resin composition.
First, raw materials other than the thickener and the low-shrinking agent were kneaded with a general-purpose kneader for 5 minutes, and then the low-shrinking agent was added and kneaded until the low-shrinking agent was uniformly dispersed. The time required for uniform dispersion was measured. The results are shown in Table 4. Add a thickener, knead for 2 minutes, and finally add glass chops.
After kneading for a minute, a resin composition was obtained. Glass chop
5% was used based on the weight of the total resin composition. The obtained resin composition was aged at 40 ° C. for 72 hours, and used for molding after the PV value at 25 ° C. became 60 or less.

[0065]

[Table 3]

[0066]

[Table 4]

Examples 10 to 16 (Production of unsaturated polyester resin composition) In Example 7, instead of the low shrinkage agent A, low shrinkage agents B, C, D, E,
Unsaturated polyester resin compositions (2), (3), (4), (5), (6), using F, G and H, respectively.
(7) and (8) were obtained. Table 4 shows the time required to uniformly disperse the low shrinkage agent.

Comparative Examples 1 and 2 (Production of low shrinkage agent) Low shrinkage agents I and J as shown in Table 5
Was manufactured. The low shrinkage agent F is a core-shell polymer having a refractive index lower than 1.52, and the low shrinkage agent G is a single-layer crosslinked polymer having no shell.

[0069]

[Table 5]

Comparative Examples 3 to 6 (Production of Unsaturated Polyester Resin Composition) In Example 6, instead of the low shrinkage agent A, low shrinkage agents I and J, cross-linked polystyrene SGP-70C manufactured by Soken Chemical Industry Co., Ltd. (Particle size 5
-30 μm cross-linked polystyrene particles) and Nippon Paint Co., Ltd. Microgel P-5001 (particle diameter 50 nm)
Crosslinked polymer particles containing styrene as a main component), and an unsaturated polyester resin composition (9),
(10), (11) and (12) were obtained. Table 4 shows the time required to uniformly disperse the low shrinkage agent.

Next, using the unsaturated polyester resin compositions of the above (1) to (12), a 300 mm square molded plate having a thickness of 8 mm was compression molded, and the physical properties thereof were compared. Molding pressure is 1
The molding temperature was 00 kgf / cm ² , the molding temperature was 140 ° C., and the molding time was 8 minutes. Table 6 shows the physical properties of the molded product. The shrinkage ratio was determined from the ratio of the size of the molded 300 mm square molded plate at room temperature to the size of the mold used for molding. The gloss was measured using a gloss meter IG-310 manufactured by Horiba, Ltd., and the light transmittance was measured using a turbidimeter 300A manufactured by Nippon Denshoku Co., Ltd., respectively.

Further, in order to examine the formability of BMC, FIG.
Also, the miniature bathtub shown in FIG. 2 was molded and examined for the presence of molding defects such as cracks. Molding temperature is 145/1
40 ℃ (core / cavity), molding pressure is 100kgf /
cm ² , and the molding time was 10 minutes. The thickness of the apron and the bottom part is 10 mm, and the thickness of the side part is 8 mm.

[0073]

[Table 6]

[Brief description of drawings]

FIG. 1 is a plan view of a miniature bathtub formed by preparing an unsaturated polyester resin composition containing a core-shell polymer according to the present invention as a low-shrinking agent and examining the moldability of BMC prepared using the same. (Dimension unit is m
m).

FIG. 2 is a front view of the miniature bathtub.

Claims (7)

[Claims] 1. A core layer made of a cross-linked polymer of a monomer containing 50 wt% or more of aromatic vinyl, and a shell layer made of a polymer of a monomer containing 50 wt% or more of methyl methacrylate. A core-shell polymer having a refractive index in the range of 1.52 to 1.58 and the core layer in the range of 50 to 90% by weight. 2. 50% by weight or more of styrene and 0.
A core layer made of a cross-linked polymer of a monomer containing 01 to 5% by weight, and a shell layer made of a polymer of a monomer containing 50% by weight or more of methyl methacrylate. The core-shell polymer according to claim 1, which is in the range of 80% by weight. 3. The core-shell polymer according to claim 1, wherein the particle diameter is in the range of 100 to 800 nm. 4. An unsaturated polyester resin composition containing an unsaturated polyester resin and a core / shell polymer as a low-shrinking agent, wherein the core / shell polymer contains 50% by weight or more of aromatic vinyl. And a shell layer made of a monomer polymer containing 50% by weight or more of methyl methacrylate.
The core layer has a refractive index in the range of 1.58 and has a refractive index of 50 to 90.
In the range of wt%, the refractive index of the core / shell polymer is ± of the refractive index of the cured product of the unsaturated polyester resin.
An unsaturated polyester resin composition characterized by being in the range of 0.02. 5. A core layer comprising a cross-linked polymer of a monomer comprising a core-shell polymer containing 50% by weight or more of styrene and 0.01 to 5% by weight of a crosslinkable monomer, and 50% by weight of methyl methacrylate. The unsaturated polyester resin composition according to claim 4, wherein the unsaturated polyester resin composition has a shell layer made of a polymer of the above-mentioned monomers, and the core layer is in a range of 60 to 80% by weight. 6. The average particle diameter of the core-shell polymer is 10.
5. The range is 0 to 800 nm.
Or the unsaturated polyester resin composition according to item 5. 7. A molded product obtained by curing and molding the unsaturated polyester resin composition according to claim 4.