JPH05330884A - Unsaturated polyester resin composition for scagliola - Google Patents

Abstract

PURPOSE:To obtain a molded product of scagliola having high transparency without generating cracks by molding under heating. CONSTITUTION:This unsatd. polyester resin compsn. for scagliola consists essentially of 100 pts.wt. unsatd. polyester resin, an inorg. filler, a curing agent, and 3-30 pts.wt. three-dimensional copolymer based on styrene, methyl methacrylate, butyl acrylate and a crosslinkable monomer and having 0.5-10% crosslinking density and 1.50-1.57 refractive index.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an unsaturated polyester resin composition for artificial marble, and more specifically to an unsaturated polyester resin composition for artificial marble which can give a highly transparent artificial marble molded product without molding cracks. Regarding things.

[0002]

2. Description of the Related Art In recent years, with the trend toward higher quality, the use of artificial marble has become active in housing-related products such as bathtubs, kitchen counters, vanities and tables. This is due to the fact that mining of natural marble is limited and the price is high. In addition, artificial marble based on unsaturated polyester resin can be formed into complicated shapes in a relatively short time and has various characteristics. This is because it has advantages such as the ability to manufacture artificial marble. However, unsaturated polyester resins show a large shrinkage upon curing, and this causes cracks in the molded product, so various means for dealing with this have been put into practical use.

In order to solve the problem of cracks, the toughness of the unsaturated polyester resin, which reduces the reactivity of the unsaturated polyester resin from the material side and suppresses rapid shrinkage, increases the elongation of the molded product. Or a thermoplastic resin is added as a shrinkage reducing agent to reduce shrinkage. However, among these methods, in the method of lowering the reactivity of the unsaturated polyester resin or toughening it, the boiling resistance and the heat resistance are lowered, which causes a problem that the commercial value is greatly impaired. .. Further, the method of incorporating the shrinkage reducing agent causes a fundamental problem that the transparency is impaired.

On the other hand, the manufacturing method of artificial marble using unsaturated polyester resin includes (1) normal temperature casting method, (2) heating casting method, and (3) heating with a molding material such as BMC (bulk molding compound). There is a pressure molding method. The room temperature casting method has an advantage that cracks are less likely to occur during molding, but has a drawback that the molding time is long and the productivity is very poor. Although the heat-casting method can improve the productivity, it has a drawback that cracks increase and the defective rate increases. In addition, although the heat and pressure molding method is very excellent in mass productivity, it is said that the transparency of the marble is greatly impaired because a large amount of a filler is mixed to prevent cracks or a shrinkage reducing agent is mixed. There's a problem.

Among the crack prevention measures, the following are specific examples of the method of incorporating the shrinkage reducing agent. In Japanese Patent Laid-Open No. 63-128057, a polystyrene polymer is used as a low-shrinking agent in combination with a specific unsaturated polyester resin, and heat-press molding is performed to obtain a semitransparent artificial material having no cracks or distortions. It is disclosed that a marble molding is obtained. Also, JP-A-6
Japanese Patent Laid-Open No. 3-56555 discloses a method for producing a semitransparent artificial marble having no cracks by thermoforming an unsaturated polyester resin molding material containing a three-dimensional styrene polymer as a low-contracting agent. There is. However, the idea of causing the polystyrene polymer used in the former method to function as a shrinkage-reducing agent is that droplets of this polymer such as styrene expand due to heat generated during curing, which reduces cure shrinkage. Since it is a thing, it is unavoidable that a void is left in the final cured product and a considerable opacification phenomenon occurs, and as a result, it is not possible to obtain an artificial marble molded product having the deep transparency of natural marble. I can't do it at all. Also, when the latter three-dimensional styrene polymer, which is a low-contraction agent, is used, voids do not remain in the cured product, so the transparency of the molded product is not greatly impaired, but it is Since the rates are not close to each other, it is still difficult to obtain a molded article having high transparency. Furthermore, since the effect of preventing shrinkage is low, cracks may occur depending on the molding temperature during heat molding and the shape of the molded product. Further, since any of the low-contraction agents have poor compatibility with the unsaturated polyester resin, they are raised on the surface during the curing process. in this way,
With regard to low-shrinking agents, anti-shrinkage ability and transparency holding ability are incompatible with each other, and low-shrinking agents with high anti-shrinkage ability have a high degree of obstructing transparency, and conversely low shrinkage that does not significantly impair transparency The fact is that the agent lacks the ability to prevent shrinkage.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an unsaturated polyester resin composition for artificial marble, which can give a highly transparent artificial marble molded product without cracking during heat molding. Especially.

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above, and a composition comprising an unsaturated polyester resin, an inorganic filler and a curing agent is crosslinked with styrene, methyl methacrylate and butyl acrylate. A specific amount of a three-dimensional copolymer having a specific crosslink density and refractive index based on a polymerizable monomer,
The resin composition blended as a low-shrinking agent has completed the present invention by finding the fact that a highly transparent artificial marble molded article can be provided without cracking during heat molding. is there.

That is, according to the present invention, (a) unsaturated polyester resin, (b) inorganic filler, (c) curing agent and (d) three-dimensional copolymer are used as substantial constituents, and three-dimensional co-polymer The united product is a copolymer based on styrene, methyl methacrylate, butyl acrylate and a crosslinkable monomer, and the three-dimensional copolymer has a crosslink density of 0.5 to 10% and a refractive index of 1.50.
The present invention relates to an unsaturated polyester resin composition for artificial marble in which the amount is 3 to 1.57, and the copolymer is 3 to 30 parts by weight based on 100 parts by weight of the unsaturated polyester resin.

The unsaturated polyester resin in the present invention is a product obtained by diluting an unsaturated polyester with an ethylenically unsaturated monomer copolymerizable with the unsaturated polyester. Any of the monomers can be used, but for the purpose of producing a molded product with an emphasis on boiling resistance, isophthalic acid or terephthalic acid, neopentyl glycol, bisphenol A alkylene oxide adduct or hydrogen is used. Of unsaturated polyester mainly composed of bisphenol A
It is preferable to select an ethylenically unsaturated monomer containing styrene as a main component.

As the inorganic filler, various glass powders, glass beads, glass fibers, glass fiber powders, aluminum hydroxide, barium sulfate and the like are preferable in consideration of the approximation to the refractive index of the unsaturated polyester resin, but the refractive index Considering the appropriateness, price, appearance of molded articles, boiling resistance, etc., borosilicate glass powder or aluminum hydroxide treated with a silane coupling agent having a refractive index of 1.50 to 1.57 is most preferable. .. Further, the compounding amount of the inorganic filler is not particularly limited, but a practically preferable compounding amount is 50 with respect to 100 parts by weight of the unsaturated polyester resin.
To 300 parts by weight, more preferably 100 to 250 parts by weight. When the compounding amount is less than 50 parts by weight, cracks are likely to occur during molding, and when the compounding amount exceeds 300 parts by weight, the viscosity of the molding material becomes too high, the workability is remarkably deteriorated, and the finally obtained molding is obtained. The transparency of the product also deteriorates.

Examples of the curing agent include azobis compounds such as azobisisobutyronitrile, methyl ethyl ketone peroxide, bis (p-tert-butylcyclohexyl) peroxydicarbonate, tert-butylperoxy-2-ethylhexanoate and tert. -Hexylperoxy-2-ethylhexanoate, benzoyl peroxide, tert-butyl peroxybenzoate, lauroyl peroxide, dicumyl peroxide, cumene hydroperoxide, and other organic peroxides commonly used for curing unsaturated polyester resins. Cobalt naphthenate, if necessary,
As a curing accelerator, metal soaps such as cobalt octenoate, quaternary ammonium salts such as dimethylbenzylammonium chloride, β-diketones such as acetylacetone, amines such as dimethylaniline, N-ethylmetatoluidine and triethanolamine are used as curing accelerators. Can be used together. The types and amounts of these curing agents and curing accelerators are appropriately selected depending on the desired molding temperature and molding time.

The three-dimensional copolymer in the present invention is a copolymer based on the three components of styrene, methyl methacrylate and butyl acrylate and a crosslinkable monomer. The ratio of styrene, methyl methacrylate and butyl acrylate constituting the copolymer is 10 to 90% by weight and 10 respectively.
It is desirable that the content is ˜90 wt%, 5˜50 wt% (however, the total of the three components is 100 wt%). Generally, the curing reaction of an unsaturated polyester resin is accompanied by a polarity change in the system during the curing process. Therefore, unless it is a low-contracting agent that can always maintain compatibility with the unsaturated polyester resin whose polarity changes with time, it may cause protrusion to the surface or phase separation during the curing process. The former causes deterioration of the surface property of the molded product, and the latter causes deterioration of the transparency of the molded product. The three components are a limited combination of monomers constituting a three-dimensional copolymer that can always maintain compatibility with the unsaturated polyester resin in the curing process,
Finally, it becomes possible to obtain a molded product having excellent surface properties and transparency.

When the unsaturated polyester resin composition of the present invention is used as a molding material such as BMC, the three-dimensional copolymer is further allowed to contain acrylic acid or methacrylic acid as a constituent, so that the molding material The stability of the three-dimensional copolymer in the inside can be improved, and the surface appearance of the artificial marble molded product can be further enhanced. The composition ratio of acrylic acid or methacrylic acid is 1 to 5 in the total weight of the constituent components excluding the crosslinkable monomer of the three-dimensional copolymer, considering the suitability of thickening agent such as BMC for the thickening agent described later. It is preferably in the weight%.

Examples of the crosslinkable monomer include divinylbenzene, divinyltoluene and other divinylbenzene derivatives, ethylene glycol dimethacrylate, ethylene glycol diacrylate and other alkylene glycol di (meth) acrylate derivatives, trimethylolpropane trimethacrylate and methacryl. Examples thereof include allyl acid, diallyl phthalate, vinyl acrylate, vinyl crotonate, and other polyfunctional vinyl monomers having two or more polymerizable double bonds in one molecule. Although selected from two or more, allyl methacrylate or trimethylolpropane trimethacrylate is particularly suitable from the viewpoint of performance as a shrinkage reducing agent for the three-dimensional copolymer.

The crosslink density of the three-dimensional copolymer is 0.5-10.
%, And more preferably 1 to 5%. When the cross-linking density is less than 0.5%, the content of the three-dimensional copolymer dissolved in the ethylenically unsaturated monomer, which is a constituent of the unsaturated polyester resin, becomes large, and the three-dimensional copolymer is blended. The transparency of the artificial marble molded article produced from the unsaturated polyester resin composition thus obtained tends to deteriorate. On the other hand, if it exceeds 10%, the three-dimensional copolymer becomes difficult to swell with the ethylenically unsaturated monomer, and the shrinkage-preventing ability of the three-dimensional copolymer is reduced. When an artificial marble is molded from the unsaturated polyester resin composition obtained by blending, cracks are likely to occur. The term "crosslinking density" as used herein means the weight% of the crosslinkable monomer constituting the three-dimensional copolymer with respect to the constituent components excluding the crosslinkable monomer.

The three-dimensional copolymer has a refractive index of 1.50 to 1.50.
It is 1.57. Regarding the refractive index, for example,
Brand Wrap, E. H. Imagat, "Polymer Handbook" (Willie Interscience Publishing), III Edition, VI Chapter 453-457 (1989)
Shows the refractive index of various polymers. The above-mentioned refractive index is a value calculated according to the copolymerization composition ratio of a three-dimensional copolymer consisting of styrene, methyl methacrylate, butyl acrylate and a crosslinkable monomer. For example, polystyrene, polymethyl methacrylate, polybutyl acrylate, and polyallyl methacrylate all have a refractive index of 1.
59, 1.49, 1.47 and 1.52, so 2
The refractive index of a three-dimensional copolymer based on 5 wt% styrene, 59 wt% methyl methacrylate, 16 wt% butyl acrylate and 1 wt% allyl methacrylate has a refractive index of 1.51.
Becomes The refractive index of the three-dimensional copolymer is 1.50 to 1.57.
When it is out of the range, the transparency of the finally obtained molded product deteriorates.

The blending amount of the three-dimensional copolymer is in the range of 3 to 30 parts by weight with respect to 100 parts by weight of the unsaturated polyester resin,
It is more preferably in the range of 5 to 15 parts by weight. When it is less than 3 parts by weight, cracks are apt to occur when an artificial marble is molded from the unsaturated polyester resin composition obtained by blending the three-dimensional copolymer, and when it exceeds 30 parts by weight, The viscosity of the unsaturated polyester resin composition becomes too high, resulting in poor workability and difficulty in practical use.

The three-dimensional copolymer of the present invention comprises benzoyl peroxide, lauroyl peroxide, tert-butylperoxy-2-ethylhexanoate, ditert-butyl peroxide, acetyl peroxide, tert-butylperoxybenzoate as the constituents. Organic peroxides such as cumene hydroperoxide, azobis compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile, inorganic peroxides such as ammonium persulfate, sodium persulfate, potassium persulfate and hydrogen peroxide It can be produced by radical polymerization using a radical polymerization initiator. As the radical polymerization initiator, those having a 10-hour half-life temperature of 50 to 130 ° C. as exemplified above are preferable, and the amount thereof is 0.1 to the total weight of all the constituent components of the three-dimensional copolymer. ~ 5
It is preferably in the weight%.

As a production means, a bulk polymerization method, a suspension polymerization method,
Although any polymerization method such as an emulsion polymerization method can be mentioned,
From the industrial viewpoint, the suspension polymerization method is most preferable. At this time, as the suspending agent, partially saponified polyvinyl alcohol, sodium polyacrylate, sodium polymethacrylate, hydrophilic organic polymers such as carboxymethyl cellulose, and slightly soluble inorganic salts such as tricalcium phosphate, barium sulfate, and calcium carbonate are used. Commonly used, but not limited to. When using a difficult inorganic salt,
It is preferable to use an anionic surfactant together. Examples of the anionic surfactant include sodium alkylbenzene sulfonate, sodium α-olefin sulfonate, sodium alkyl sulfonate, and the like. The types and amounts of these suspending agents and anionic surfactants are preferably selected appropriately depending on the particle size of the final polymer to be produced.

In order to prepare the unsaturated polyester resin composition for artificial marble of the present invention by blending the three-dimensional copolymer, the three-dimensional copolymer is uniformly dispersed and swollen in the unsaturated polyester resin. It is necessary. Therefore, a fine powdery three-dimensional copolymer may be directly blended with the unsaturated polyester resin and sufficiently mixed and dispersed, or a granular or lumpy three-dimensional copolymer may be previously mixed with an ethylenic monomer such as styrene. A gelled product which is sufficiently swollen with a saturated monomer may be blended with the unsaturated polyester resin. Further, as a method for producing a fine powdery three-dimensional copolymer, even by a method by adjusting the polymerization method, a granular or lumpy polymer obtained by usual suspension polymerization or bulk polymerization is finely pulverized by mechanical means. The method to do is also good.

In the case of producing a colored artificial marble molded product, an organic or inorganic dye or pigment is used to embody a pattern having a marble-like appearance, whereby a product having a higher commercial value can be obtained. .. Further, when the unsaturated polyester resin composition of the present invention is used as a molding material such as BMC, an oxide of an alkaline earth metal such as magnesium oxide, calcium oxide, magnesium hydroxide or calcium hydroxide is used as a thickener or Hydroxides, internal release agents such as zinc stearate, calcium stearate, stearic acid, etc., reinforcing materials such as glass fibers, inorganic fibers such as carbon fibers, aramid fibers, polyester fibers, organic fibers such as vinylon fibers, metal fibers. It is also possible to appropriately blend the above.

Molding of the unsaturated polyester resin composition of the present invention is carried out by introducing the unsaturated polyester resin composition into a preheated mold. A heat and pressure molding method in which a molding material such as BMC is introduced into the mold and then pressure is applied may be used. That is, the heat molding method includes heat pressure molding. The molding temperature is preferably in the range of 60 to 150 ° C. If the temperature is too low, it takes a long time to mold, which leads to deterioration of productivity.
If it is too high, the molded product may be burnt and yellow, or the molded product may swell. The molding pressure is not applied or in the range of 140 kg / cm ² or less, and the unsaturated polyester resin composition is sandwiched between upper and lower molds for molding. As the mold, a plywood mold, a resin mold, an electroforming mold, and various metal molds can be used. The molding method may be, for example, a casting method, a compression molding method, an injection molding method, a transfer molding method, an injection molding method or an extrusion molding method.

[0023]

The three-dimensional copolymer, which is a constituent component of the unsaturated polyester resin composition of the present invention, does not cause phase separation during curing because the specific monomer component is a three-dimensionalized copolymer. Furthermore, since it has a refractive index in a specific range that is close to the refractive index of the unsaturated polyester resin, it becomes possible to finally obtain an artificial marble molded article with high transparency from the unsaturated polyester resin composition. Further, by setting the cross-linking density of the three-dimensional copolymer within a specific range, it is possible to control the degree of swelling by the ethylenically unsaturated monomer that is a constituent component of the unsaturated polyester resin. It is closely related to the shrinkage prevention ability of the coalescence and greatly contributes to the prevention of cracks during heat molding.

[0024]

As described above, the use of the unsaturated polyester resin composition containing the specific three-dimensional copolymer of the present invention makes it possible to prevent shrinkage and transparency, which have been difficult to achieve in the past. It is possible to obtain a highly transparent artificial marble molded product which has a holding ability and does not generate cracks due to heat molding.

[0025]

EXAMPLES The present invention will be described in more detail with reference to Reference Examples, Examples and Comparative Examples. In these examples, parts and% represent parts by weight and% by weight, respectively, unless otherwise specified.

[Production Example of Three-Dimensional Copolymer of the Present Invention] Reference Example 1 150 parts of water and 1.5 parts of sodium dodecylbenzenesulfonate in a glass reactor equipped with a thermometer, a nitrogen introducing tube, a stirrer and a condenser. And 150 parts of a 10% aqueous solution of tricalcium phosphate were charged. Next, 0.3 part of benzoyl peroxide (hereinafter abbreviated as BPO) is 25 parts of styrene (hereinafter abbreviated as St), 59 parts of methyl methacrylate (hereinafter abbreviated as MMA), and butyl acrylate (hereinafter B).
16 parts and allyl methacrylate (hereinafter referred to as A)
It was dissolved in a mixture of 1 part (abbreviated as MA) and charged into the reactor. While introducing nitrogen into the reactor, polymerization was carried out at 80 ° C. for 3 hours with stirring, and then at 90 ° C. for 30 minutes. After cooling to room temperature, the obtained polymer was washed with 1000 g of 5% hydrochloric acid, subsequently with water, filtered off, and vacuum dried to obtain 92 parts of a white fine powder polymer having an average particle diameter of 39 μm. The results are shown in Table 1.

Reference Examples 2 to 5 A three-dimensional copolymer was produced in the same manner as in Reference Example 1 except that the charged amounts of St, MMA, BA and AMA were changed as shown in Table 1. A polymer was obtained. The results are shown in Table 1. Reference Example 6 Same as Reference Example 1 except that methacrylic acid (hereinafter abbreviated as MAA) was used in addition to St, MMA, BA, and AMA, and the charged amount was changed as shown in Table 1. To produce a three-dimensional copolymer to obtain a white fine powdery polymer. The results are shown in Table 1. Reference Example 7 In Reference Example 1, instead of AMA, trimethylolpropane trimethacrylate (hereinafter abbreviated as TMPT).
A three-dimensional copolymer was produced in the same manner as in Reference Example 1 except that was used to obtain a white fine powdery polymer. The results are shown in Table 1.

[Production Example of Three-Dimensional Copolymer Deviated from the Claims of the Present Invention] Reference Examples 8 to 11 Reference Example 1 except that the amounts of St, MMA, BA and AMA charged were changed as shown in Table 1. A three-dimensional copolymer was produced in the same manner as in, to obtain a white fine powdery polymer. The results are shown in Table 1. In Reference Examples 8 and 9, the refractive index of the three-dimensional copolymer and Reference Examples 10 and 11, respectively, deviate from the claims of the present invention with respect to the constituent ratio of the crosslinkable monomer, that is, the crosslink density. ..

[0029]

[Table 1]

Reference Example 12 [Preparation of a shrinkage reducing agent for comparison] (A) St solution of polySt PolySt (DIALEX HF-77) manufactured by Mitsubishi Monsanto Kasei Co., Ltd. was used so that the solid content was 30%. Was dissolved in St to give a low-contracting agent for comparison (A). (B) Three-dimensional St polymer According to the method described in Example 1 of JP-B-51-1276, 100 parts of St and 1 part of DVB are used to obtain an average particle size of 2
An 8-μm three-dimensional St polymer was obtained and used as a comparative low-contracting agent (B).

[Preparation of Unsaturated Polyester Resin Composition and Preparation of Artificial Marble Molded Article] Example 1 100 parts of unsaturated polyester resin (manufactured by Nippon Yupica Co., Ltd., trade name: Yupica 6424, Tele system), Reference Example 1 5 parts of the three-dimensional copolymer obtained in Step 5, 0.5 parts of bis (p-tert-butylcyclohexyl) peroxydicarbonate (manufactured by NOF CORPORATION, trade name: Perloyl TCP), t
ert-hexyl peroxy-2-ethylhexanoate (manufactured by NOF CORPORATION, trade name: Perhexyl O)
5 parts and 200 parts of borosilicate glass powder (manufactured by Nippon Fellow Co., Ltd., trade name: M-50S) were sufficiently stirred and mixed with a mixer to prepare the unsaturated polyester resin composition of the present invention.
After gently degassing the above composition with a vacuum pump, 1
00x100x5mm mold and 150x80x200
mm, and a thickness of 10 mm was poured into an FRP mold having a bath shape and cured in a thermostatic bath at 80 ° C. to prepare two types of artificial marble molded products. A molded product obtained from the mold is called a molded product A, and a molded product obtained from the FRP mold is called a molded product B. Table 2 shows the compounding composition and the obtained evaluation results.

The measurement of the volumetric shrinkage of the cured product and the evaluation of the molded product were carried out as follows. Volumetric shrinkage of cured product The specific gravity of the above composition is measured using a pycnometer. Then, this was poured into a test tube having a volume of about 20 ml, the upper part of the test tube was tightly plugged, and then allowed to stand in an oil bath at 80 ° C. to proceed with curing. After the curing is completed, the cured product is taken out from the test tube, and the specific gravity of the cured product is measured by a solid densitometer (S manufactured by Shimadzu Corporation).
GM-SH200 _-11 ) and the volumetric shrinkage of the cured product was determined by the following formula. Volume contraction rate (%) = (1- (specific gravity of resin composition / specific gravity of cured product)) × 100 cracks The presence or absence of cracks generated in two types of molded products was visually determined. Total Light Transmittance According to JIS-K7105 (method for testing optical properties of plastics), the total light transmittance of the molded product A was measured using a direct-reading haze meter manufactured by Toyo Seiki Seisaku-sho, Ltd. Transparency A printed matter was placed under the molded product A, and it was judged whether or not the font was visible from the upper part of the molded product. A: The font can be confirmed, and the font can be read. ○: The font can be confirmed, but the font cannot be read. X: The font cannot be confirmed.

Examples 2 to 9 Using the three-dimensional copolymers obtained in Reference Examples 1 to 7, artificial marble moldings were produced according to Example 1 with the blending composition shown in Table 2. Then, the molded product was evaluated according to Example 1, and the results are shown in Table 2.

[0034]

[Table 2]

Comparative Examples 1 to 4 Using the three-dimensional copolymers obtained in Reference Examples 8 to 11, artificial marble moldings were prepared according to Example 1 with the compounding compositions shown in Table 3. Then, the molded product was evaluated according to Example 1, and the results are shown in Table 3.

[0036]

[Table 3]

Comparative Examples 5 to 7 The comparative shrinkage reducing agents (A) and (B) obtained in Reference Example 12 were used in place of the three-dimensional copolymer, and the composition was shown in Table 4 to give an example. An artificial marble molded product was produced according to 1. Then, the molded product is evaluated according to Example 1,
The results are shown in Table 4.

Comparative Example 8 An artificial marble molded article was produced in the same manner as in Example 1 except that the three-dimensional copolymer was not used. The molded product was evaluated according to Example 1, and the results are shown in Table 4.

[0039]

[Table 4]

[Preparation of BMC molding material and artificial marble molding] Example 10 Unsaturated polyester resin (Dainippon Ink and Chemicals, Inc.)
Manufactured, product name: Polylite PS-266) 100 parts, three-dimensional copolymer 20 parts obtained in Reference Example 6, tert-butyl peroxybenzoate (manufactured by NOF Corporation, table product name: perbutyl Z) 1 part, 200 parts of borosilicate glass powder (manufactured by Nippon Fellow Co., Ltd., trade name: M-50S) and 4 parts of zinc stearate (manufactured by NOF CORPORATION, trade name: Zinc Ste) were kneaded for 15 minutes with a Banbury kneader. 1 part of magnesium oxide (Kyowa Chemical Industry Co., Ltd., trade name: Kyowamag # 40F) was added, and the mixture was further kneaded for 3 minutes and then aged at 40 ° C. for 24 hours to obtain a BMC molding material.
The above molding material was heated to 140 ° C. and heated to 1000 × 300.
Placed in a mold of × 10mm, molding pressure 50kg / cm
^2. Heat and pressure molding was performed under the condition that the molding time was 9 minutes. As a result, an artificial marble molded article having a high total transparency of 25% and a high transparency and a high specular gloss of 60% and a surface gloss of 90% was obtained. The linear shrinkage of the obtained molded product was 0.09%, and no cracks or warpage were found in the molded product.

The molded products were evaluated as follows. Total light transmittance According to JIS-K7105 (Plastic optical property test method), the total light transmittance of the molded product was measured using a direct-reading haze meter manufactured by Toyo Seiki Seisakusho. 60-degree specular glossiness The 60-degree specular glossiness of the molded product was measured using a gloss meter manufactured by Toyo Seiki Seisakusho KK according to JIS-K7105 (method for testing optical properties of plastics). Linear shrinkage The linear shrinkage of the molded product was measured by the following formula. Linear shrinkage rate (%) = ((longitudinal mold size-molded product size) / longitudinal mold size) x 100

Comparative Example 9 BMC molding was carried out in the same manner as in Example 10 except that 30 parts of the comparative shrinkage reducing agent (A) obtained in Reference Example 12 was used in place of the three-dimensional copolymer in Example 10. A material was prepared, and using this molding material, an artificial marble molded article was produced according to the conditions described in Example 10. When the molded product was evaluated according to Example 10, the total light transmittance was 8%.
The result shows that the transparency is low, and the surface gloss is 60% and the surface glossiness is 45%. It was presumed that the surface gloss of the molded product was poor because the low-shrinking agent was poor in stability in the molding material, and thus it was projected on the surface during aging or curing. The linear shrinkage of the obtained molded product was 0.12%, and cracking or warpage of the molded product was not observed.

Comparative Example 10 BMC molding was carried out in the same manner as in Example 10 except that the same amount of the comparative shrinkage reducing agent (B) obtained in Reference Example 12 was used in place of the three-dimensional copolymer. A material was prepared, and using this molding material, an artificial marble molded article was produced according to the conditions described in Example 10. When the molded product was evaluated according to Example 10, the total light transmittance was 12%.
The result shows that the transparency is low and the specular gloss of 60 degrees is 62% and the surface gloss is slightly low. Further, although no crack was observed in the molded product, the linear shrinkage ratio of the obtained molded product was 0.20%, which was inferior to the dimensional stability. When the above examples and comparative examples are compared, the three-dimensional copolymer having a specific crosslinking density and refractive index based on the specified three-component monomer and the crosslinkable monomer in the present invention is an unsaturated polyester resin. It is clear that when used as a low-shrinking agent, a highly transparent artificial marble molded product can be obtained without cracking due to the low shrinkage ratio during heat molding.

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Claims (2)

[Claims] 1. (a) unsaturated polyester resin and (b)
An inorganic filler, (c) a curing agent, and (d) a three-dimensional copolymer are essentially constituent components, and the three-dimensional copolymer is based on styrene, methyl methacrylate, butyl acrylate, and a crosslinkable monomer. It is a copolymer, and the three-dimensional copolymer has a cross-linking density of 0.5 to 10% and a refractive index of 1.50 to 1.57, and the copolymer is added to 100 parts by weight of the unsaturated polyester resin. On the other hand, the unsaturated polyester resin composition for artificial marble is 3 to 30 parts by weight. 2. The three-dimensional copolymer is a copolymer based on styrene, methyl methacrylate, butyl acrylate, acrylic acid or methacrylic acid and a crosslinkable monomer.
The unsaturated polyester resin composition for artificial marble as described above.