JP3067297B2 - Unsaturated polyester resin composition - Google Patents

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, and more particularly to an unsaturated polyester resin composition capable of providing a molded article having no molding cracks and high transparency.

[0002]

2. Description of the Related Art In recent years, artificial marble has been increasingly employed in housing-related products such as bathtubs, kitchen counters, vanities, and tables as the trend toward higher-grade products has increased. This is because natural marble has a limit in mining and its price is high.In particular, artificial marble based on unsaturated polyester resin can be formed into a complex shape in a relatively short time. This is because it has advantages such as the ability to manufacture artificial marble having various characteristics by responding to the composition. However, the unsaturated polyester resin shows a large shrinkage upon curing, which causes cracks in the molded product. Various means have been put to practical use to cope with this.

In order to solve the problem of cracks, from the viewpoint of the material, the reactivity of the unsaturated polyester resin is reduced to suppress abrupt shrinkage, and the elongation of a molded article is increased by using a toughened unsaturated polyester resin. Or a method of blending a thermoplastic resin as a low-shrinking agent to reduce shrinkage. However, among these methods, the method of lowering the reactivity of the unsaturated polyester resin or increasing the toughness causes a decrease in boiling resistance or heat resistance, and causes a problem such as a great loss in commercial value. . In addition, the method of adding a low-shrinking agent has a fundamental problem that transparency, which is a characteristic of marble, is impaired.

On the other hand, the method of producing artificial marble using an unsaturated polyester resin includes (1) a cold casting method, (2) a hot casting method, and (3) a heating method using a molding material such as BMC (bulk molding compound). There is a pressure molding method. The room-temperature casting method has the advantage of less occurrence of cracks during molding, but has the disadvantage that the molding time is long and the productivity is very poor. Although the productivity is improved in the hot casting method, cracks are frequently generated and the defective rate is increased. In addition, although the heat and pressure molding method is very excellent in mass productivity, the transparency of marble is greatly impaired because a large amount of filler is blended to prevent cracks and a low shrinkage agent is blended. There's a problem.

[0005] Among the measures for preventing cracks, the following is a specific example of a method of blending a low-shrinking agent. JP-A-63-128057 discloses that a polystyrene-based polymer is used in combination with a specific unsaturated polyester resin as a low-shrinkage agent, and is molded under heat and pressure to obtain a translucent film without cracks or distortion. It is disclosed that an artificial marble molded product can be obtained. Also, JP-A-63-
No. 56555 discloses a method for producing a crack-free translucent artificial marble by heating and molding an unsaturated polyester resin molding material containing a three-dimensional styrene polymer as a low-shrinking agent. However, when the polystyrene-based polymer used in the former method is used as a low-shrinking agent, the idea is that droplets of the polymer, such as styrene, expand due to heat generated during curing, which reduces curing shrinkage. Therefore, it is inevitable that a void remains in the final cured product and a considerable opacity phenomenon occurs.As a result, it is impossible to obtain an artificial marble molded article having the deep transparency of natural marble. I couldn't do it at all. When the latter three-dimensional styrene polymer is used as a low-shrinkage agent, the transparency of the molded article is not greatly impaired because no void is left in the cured product, but the unsaturated polyester resin is used. Because of the poor compatibility, the dispersion state in the unsaturated polyester resin became uneven, and it was also difficult to obtain a molded article having high transparency. Further, since the shrinkage preventing effect is low, cracks may be generated depending on the molding temperature during heat molding and the shape of the molded product. As described above, regarding the low-shrinking agent, the anti-shrinkage effect and the transparency retention ratio are in an incompatible relationship, and the low-shrinkage agent having a high anti-shrinkage effect has a high degree of inhibiting transparency, and conversely increases the transparency. The fact is that a low-shrinkage agent that does not impair is insufficient in the effect of preventing shrinkage.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an unsaturated polyester resin composition capable of giving a molded article having high transparency without generating cracks during heat molding.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been proposed in view of the above. An unsaturated polyester resin comprises a vinyl polymer part in which one segment is crosslinked and the other segment comprising the unsaturated polyester resin. A composition in which a block copolymer, which is an uncrosslinked vinyl polymer portion having compatibility with a resin, is blended as a low-shrinking agent, and cracks occur during heat molding when having a specific blending ratio and characteristics described below. Without finding the fact that a molded article having high transparency can be obtained without using the present invention, the present invention has been completed.

That is, the present invention provides (a) an unsaturated polyester resin and (b) a crosslinked vinyl polymer segment (a) and an uncrosslinked polymer segment (b) having compatibility with the unsaturated polyester resin. And an AB type block copolymer consisting essentially of: (a)
Has a crosslink density of 0.01 to 10%, a weight ratio of the segment (a) to the segment (b) is 98: 2 to 50:50, and AB is relative to 100 parts by weight of the unsaturated polyester resin.
The mold block copolymer relates to an unsaturated polyester resin composition contained in 3 to 30 parts by weight.

The unsaturated polyester resin in the present invention is obtained by diluting an unsaturated polyester with an ethylenically unsaturated monomer copolymerizable with the unsaturated polyester. Any of the monomers can be used. A in the present invention
The A segment of the B-type block copolymer is a crosslinked vinyl polymer portion. The crosslinked vinyl polymer portion is composed of, for example, a styrene-based, acrylic-based, maleate-based, vinyl acetate-based polymer crosslinked with a crosslinkable monomer, and a copolymer thereof.

Examples of the vinyl monomer crosslinked by the crosslinkable monomer include styrene, α-methylstyrene, t-butylstyrene, substituted styrene such as vinyltoluene, methyl (meth) acrylate, and (meth) acrylic acid. ethyl,
Propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, oleyl (meth) acrylate, ( (Meth) acrylates such as cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, glycidyl (meth) acrylate, dimethyl maleate, ethyl maleate, diethyl maleate, butyl maleate Monofunctional or diester maleates such as dibutyl maleate, octyl maleate, dioctyl maleate, glycidyl maleate, and diglycidyl maleate; and monofunctional vinyl monomers such as vinyl acetate. Alternatively, two or more are selected.

Examples of the crosslinking monomer include divinylbenzene derivatives such as divinylbenzene and divinyltoluene; alkylene glycol di (meth) acrylate derivatives such as ethylene glycol dimethacrylate and ethylene glycol diacrylate; trimethylolpropane trimethacrylate; Examples thereof include polyfunctional vinyl monomers having two or more polymerizable double bonds in one molecule such as methacrylate, diallyl phthalate, vinyl acrylate, vinyl crotonate, and the like. Selected from more than one species.

The crosslinked density of the crosslinked vinyl polymer portion is 0.01 to 10%, more preferably 0.1 to 10%.
~ 5%. When the crosslink density is less than 0.01%,
The solubility of the AB type block copolymer to the ethylenically unsaturated monomer which is a constituent component of the unsaturated polyester resin is increased, and the unsaturated polyester resin obtained by blending the AB type block copolymer is obtained. The transparency of a molded article produced from the composition tends to be deteriorated. On the other hand, if it exceeds 10%, the AB type block copolymer is less likely to swell with the ethylenically unsaturated monomer, so that the effect of preventing the AB type block copolymer from shrinking is reduced. When an unsaturated polyester resin composition obtained by blending an AB block copolymer is formed, cracks are likely to occur. The term "crosslink density" as used herein refers to the weight% of the crosslinkable monomer relative to the vinyl monomer to be crosslinked.

In the AB type block copolymer of the present invention, the B segment is an uncrosslinked vinyl polymer portion having compatibility with the unsaturated polyester resin. The term "compatible" as used herein includes not only a completely compatible state but also a semi-compatible state, and means a state that does not show rapid laminar separation when blended with an unsaturated polyester resin. Examples of the vinyl monomer constituting the uncrosslinked vinyl polymer portion compatible with the unsaturated polyester resin include vinyl acetate, methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) Propyl acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, oleyl (meth) acrylate, (meth) acryl (Meth) acrylates such as cyclohexyl acid, phenyl (meth) acrylate, benzyl (meth) acrylate, glycidyl (meth) acrylate, dimethyl fumarate, diethyl fumarate,
Diisopropyl fumarate, dibutyl fumarate, dicyclohexyl fumarate, di (2-ethylhexyl) fumarate
And the like, and one or more of these groups are selected, but it is preferable that the diester is appropriately selected depending on the type of the unsaturated polyester resin to be used.

In the AB block copolymer in the resin composition of the present invention, the ratio of the A segment is 50 to 9
8% by weight, the proportion of the B segment is 50 to 2% by weight, more preferably the proportion of the A segment is 70 to 95% by weight, and the proportion of the B segment is 30 to 5% by weight. A
When the proportion of the segment is less than 50% by weight, that is, the proportion of the B segment exceeds 50% by weight, the molding produced from the unsaturated polyester resin composition obtained by blending the AB type block copolymer. The transparency of the product tends to deteriorate. When the proportion of the A segment exceeds 98% by weight, that is, when the proportion of the B segment is less than 2% by weight, the effect of preventing the AB type block copolymer from shrinking decreases, and When an unsaturated polyester resin composition obtained by blending a mold block copolymer is molded, cracks are likely to occur.

The amount of the AB type block copolymer in the composition of the present invention is in the range of 3 to 30 parts by weight, more preferably 5 to 30 parts by weight, based on 100 parts by weight of the unsaturated polyester resin.
-15 parts by weight. If less than 3 parts by weight,
When the unsaturated polyester resin composition of the present invention is easily formed with cracks when it is molded, and when it exceeds 30 parts by weight, the viscosity of the unsaturated polyester resin composition becomes too high, the workability is remarkably poor, and practical use is difficult. It becomes difficult to use.

The AB block copolymer in the composition of the present invention is prepared by using a monomer or a mixture of monomers constituting the A and B segments and using a polymeric peroxide as a polymerization initiator (JP-A-53-149918). No.)
Can be produced by a known production process (described in Japanese Patent Publication No. 60-3327). However, the monomer or monomer mixture constituting the B segment is used in the first-stage polymerization reaction, and the monomer or monomer mixture constituting the A segment and the crosslinkable monomer are used in the second-stage polymerization reaction. It is preferred to use a body. And the polymer generated by the first-stage polymerization reaction of the monomer or the monomer mixture constituting the B segment,
It has a peroxy bond in the molecule, and is taken out of the reaction system as an intermediate and used as a raw material for the next block copolymer production using a monomer or a monomer mixture constituting the A segment and a crosslinkable monomer. Alternatively, block copolymerization can be carried out without taking out from the reaction system.

As the production means, any polymerization method such as a bulk polymerization method, a suspension polymerization method, and an emulsion polymerization method can be mentioned, but the suspension polymerization method is most preferable industrially. At this time, as the suspending agent, partially saponified polyvinyl alcohol, sodium polyacrylate, sodium polymethacrylate, hydrophilic organic polymers such as carboxymethyl cellulose, tribasic calcium phosphate, barium sulfate, hardly soluble inorganic salts such as calcium carbonate and the like. Commonly used, but not limited to these. When a poorly soluble inorganic salt is used, it is preferable to use an anionic surfactant in combination. Examples of the anionic surfactant include sodium alkylbenzene sulfonate, sodium α-olefin sulfonate, sodium alkyl sulfonate and the like.
It is preferable that the types and amounts of these suspending agents and anionic surfactants are appropriately selected according to the particle size of the final polymer to be aimed.

The polymeric peroxide which can be used in the production of the AB block copolymer in the present invention is, for example, a compound represented by the following formulas (1), (2) and (3).

Embedded image

Embedded image

Embedded image And the like.

These polymeric peroxides are represented by AB
The amount used as a polymerization initiator for producing the mold block copolymer is 0.1 to 1 with respect to 100 parts by weight of the monomer or monomer mixture constituting the B segment.
It is preferably 0 parts by weight. The polymerization temperature of the above-mentioned polymerization is 40 to 80 ° C. for the first-stage polymerization reaction and 60 to 100 ° C. for the second-stage polymerization reaction, and the polymerization temperature in the first-stage polymerization reaction is the second-stage polymerization reaction. It is preferably lower than the polymerization temperature in the reaction. Furthermore, the method of charging the monomer or monomer mixture constituting the A segment or the B segment includes batch charging, split charging, continuous charging, and the like, and is not particularly limited. It is preferable that it is appropriately selected. The polymerization time varies depending on the type of the monomer used and the amount used, but it is preferable that both the first-stage polymerization reaction and the second-stage polymerization reaction be in the range of 1 to 10 hours.

Incidentally, when the AB type block copolymer is produced, a homopolymer of each monomer or an arbitrary copolymer or a three-dimensional copolymer of a monomer mixture may be by-produced. When used as a low-shrinkage agent for the unsaturated polyester resin in the invention, it can be used as it is without any particular purification. At this time, the production conditions and the like are selected so that the gel fraction of the AB block copolymer in the acetone solvent is 50 to 98% by weight, more preferably 70 to 95% by weight. When the gel fraction is out of this range, the balance between the shrinkage preventing effect and the transparency retention ratio tends to deteriorate. The gel fraction referred to here indicates a value measured as follows. That is, 5 g of the polymer is precisely weighed in a 100 ml Erlenmeyer flask, 100 ml of acetone is added, and the mixture is left at room temperature for 24 hours. This was applied to Toyo Filter Paper No. The filter paper 2 (manufactured by Toyo Roshi Kaisha Co., Ltd.) is absolutely dried, weighed precisely, and filtered at normal pressure. Next, the gel content remaining on the filter paper was
Wash twice and dry in an oven at 80 ° C. for 1 hour. The dried gel is stored in a desiccator, cooled to room temperature, and then precisely weighed. Then, the gel fraction is calculated based on the percentage of the amount of sampled gel / the amount of sample.

In order to obtain the unsaturated polyester resin composition of the present invention using the AB type block copolymer produced as described above, the AB type block copolymer is obtained by mixing the unsaturated polyester resin with the unsaturated polyester resin. It is necessary to uniformly disperse and swell inside. Therefore, when obtaining the unsaturated polyester resin composition of the present invention, the fine powder AB type block copolymer may be directly blended with the unsaturated polyester resin and sufficiently mixed and dispersed. The AB-type block copolymer of the above may be gel-swelled sufficiently with an ethylenically unsaturated monomer such as styrene in advance, and blended with the unsaturated polyester resin. The fine powder type AB block copolymer can be obtained by a method based on the above-mentioned polymerization method or a fine or granular polymer obtained by ordinary suspension polymerization or bulk polymerization by mechanical means. It can be obtained by crushing.

The unsaturated polyester resin composition of the present invention may be an azo compound such as azobisisobutyronitrile, tert-butyl perbenzoate, tert-butyl peroctoate, benzoyl peroxide, methyl ethyl ketone peroxide, bis (p -Tert
-Butylcyclohexyl) peroxydicarbonate,
Lauroyl peroxide, dicumyl peroxide,
Organic peroxides such as cumene hydroperoxide, etc., using a curing agent generally used for curing unsaturated polyester resins, and metal soaps such as cobalt naphthenate and cobalt octenoate, dimethylbenzylammonium chloride, etc., if necessary. Quaternary ammonium salts, β-diketones such as acetylacetone, and amines such as dimethylaniline, N-ethylmethtoluidine, triethanolamine and the like can be used as a curing accelerator and used as such for various applications. it can. The types and amounts of these curing agents and curing accelerators are appropriately selected depending on the molding temperature and molding time.

When the unsaturated polyester resin composition of the present invention is used for producing artificial marble, a filler is generally used in combination. Fillers include aluminum hydroxide, glassy powder, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, kaolin, talc, clay,
Examples include asbestos, silica, colloidal silica, mica, gypsum, alumina, antimony trioxide, porcelain powder, metal powder, wood powder, synthetic resin powder, etc. From the standpoint of obtaining, aluminum hydroxide or a vitreous powder that is similar to the refractive index of the unsaturated polyester resin is most preferred. The amount of the filler is not particularly limited, but is preferably based on 100 parts by weight of the unsaturated polyester and the total weight of the ethylenically unsaturated monomer copolymerizable therewith. 50 to 300 parts by weight, more preferably 1
It can be blended in the range of 00 to 250 parts by weight. 5
If the amount is less than 0 parts by weight, cracks are easily formed during molding. If the amount exceeds 300 parts by weight, the viscosity of the molding material becomes too high, the workability is remarkably deteriorated, and the transparency of the finally obtained molded article is reduced. Also gets worse.

When coloring a molded article, commercially available organic or inorganic dyes or pigments can be used, and by embodying a pattern having a marble appearance, a product having a higher commercial value can be obtained. it can. Further, when the unsaturated polyester resin composition of the present invention is used as a molding material such as BMC, magnesium oxide, calcium oxide, magnesium hydroxide, an oxide of an alkaline earth metal such as calcium hydroxide or the like as a thickener. The hydroxide may be appropriately blended with zinc stearate, calcium stearate, stearic acid and the like as an internal release agent.

The molding of the unsaturated polyester resin composition of the present invention is carried out, for example, by introducing the above unsaturated polyester resin composition into a preheated mold. Alternatively, a heat and pressure molding method in which a molding material such as BMC is introduced into a mold and then pressurized may be used. The heat molding method in the present invention includes heat and pressure molding. Molding temperature is 60-150 ° C
Is preferable. If the temperature is too low, it takes a long time for molding, leading to a decrease in productivity. If the temperature is too high, the molded product may burn and yellow, or the molded product may blister. The molding pressure is no pressure or 140kg / c
m ² or less, and is molded by sandwiching the unsaturated polyester resin composition in upper and lower molds. The molding pressure is also selected depending on the material of the mold. That is, the pressure is low in a plywood or resin mold, and high pressure molding is possible in a steel plate mold. The molding method is, for example, a casting method, a compression molding method,
Any of injection molding, transfer molding, injection molding, and extrusion molding may be used.

[0026]

With respect to the block copolymer contained in the unsaturated polyester resin composition of the present invention, one of the segments is an uncrosslinked vinyl polymer portion having compatibility with the unsaturated polyester resin. Since the dispersed state in the unsaturated polyester resin composition is uniform and the other segment is a crosslinked vinyl polymer portion, no phase separation occurs during curing, and finally the unsaturated polyester A highly transparent molded article can be obtained from the resin composition. For the effect of preventing shrinkage,
In order to have both a crosslinked vinyl polymer portion and an uncrosslinked vinyl polymer portion in the block copolymer, the crosslinked vinyl polymer such as polystyrene and the crosslinked polymer such as a three-dimensional styrene polymer are used. It has an intermediate performance with that of the molded vinyl polymer, which greatly contributes to prevention of cracks during heat molding.

[0027]

As described above, the use of the unsaturated polyester resin composition containing the special block copolymer of the present invention makes it possible to prevent shrinkage and maintain transparency, which were difficult to achieve conventionally. The performance can be exhibited in a well-balanced manner, and a molded article having high transparency can be obtained without cracks being generated by heat molding.

[0028]

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 AB Type Block Copolymer Having Characteristics Included in Unsaturated Polyester Resin Composition of the Present Invention] Reference Example 1 Glass provided with thermometer, nitrogen inlet tube, stirrer, and condenser The reactor was charged with 150 parts of water, 1.5 parts of sodium dodecylbenzenesulfonate and 150 parts of a 10% aqueous solution of tribasic calcium phosphate. next

Embedded image Is dispersed in the aqueous solution for 1 hour at room temperature, 10 parts of vinyl acetate (hereinafter abbreviated as VAc) is charged, and nitrogen is introduced into the reactor. 60 ° C. while stirring
For 2 hours (first stage polymerization reaction). Thereafter, the mixture was cooled to room temperature, a mixture of 90 parts of styrene (hereinafter abbreviated as St) and 0.9 part of divinylbenzene (hereinafter abbreviated as DVB) was added to the reactor, and an impregnation operation was performed at room temperature for 1 hour. 7 hours at 80 ° C. with stirring, followed by 30 hours at 90 ° C.
Polymerization (second stage polymerization reaction) was carried out for one minute. After cooling to room temperature, the obtained polymer was washed with 1000 g of 5% hydrochloric acid, then with water, separated by filtration, dried in vacuo, and dried under vacuum with an average particle size of 27 μm.
As a result, 92 parts of a white fine powder polymer having a segment crosslink density of about 1% were obtained. Using a part of the polymer thus obtained, the gel fraction in an acetone solvent was determined.
%Met. Table 1 shows the results.

Reference Examples 2 to 7 AB in the same manner as in Reference Example 1 except that the charged amounts of P.PO, VAc, St and DVB were changed as shown in Table 1.
A mold block copolymer was produced, and a polymer in the form of a white fine powder was obtained. The gel fraction of these polymers was determined in the same manner as in Reference Example 1. Table 1 shows the results. Reference Example 8 An AB type block copolymer was produced in the same manner as in Reference Example 1 except that methyl methacrylate (hereinafter abbreviated as MMA) was used in place of VAc in Reference Example 1, and a white fine powder was obtained. Was obtained. The gel fraction of this polymer was determined in the same manner as in Reference Example 1. Table 1 shows the results.

Reference Example 9 An AB block copolymer was produced in the same manner as in Reference Example 1 except that MMA was used in place of St, and a white fine powdery polymer was obtained. . The gel fraction of this polymer was determined in the same manner as in Reference Example 1. Table 1 shows the results. [Production Example of AB Type Block Copolymer Having Unsuitable Properties Included in Unsaturated Polyester Resin Composition of the Present Invention] Reference Examples 10 to 13 The charge amounts of P.PO, VAc, St and DVB were determined. AB in the same manner as in Reference Example 1 except for changing as shown in Table 1.
A mold block copolymer was produced, and a polymer in the form of a white fine powder was obtained. The gel fraction of these polymers was determined in the same manner as in Reference Example 1. Table 1 shows the results. Production Example 1
In Examples 0 and 11, the crosslink density of the A segment is different from that in Production Examples 12 and 13, and the composition ratios of the A segment and the B segment deviate from the scope of the present invention.

[0032]

[Table 1]

Reference Example 14 [Preparation of Comparative Low Shrinkage Agent] (A) PolySt PolySt (Dialex HF-77) manufactured by Mitsubishi Monsanto Kasei Co., Ltd. was converted to St so as to have a solid content of 30%. It melt | dissolved and was set as the comparative low contraction agent (A). (B) Three-dimensional St polymer According to the method described in Example 1 of JP-B-51-1276, the crosslink density is 1 using 100 parts of St and 1 part of DVB.
% Of a three-dimensional St polymer, and a low-shrinking agent for comparison (B)
And (C) Poly VAc S of acid group-containing poly VAc manufactured by Union Carbide Co., Ltd.
A t40% solution (Bakelite LP-40A) was prepared with St so that the solid content was 30%, and used as a comparative low-shrinkage agent (C).

[Preparation of Unsaturated Polyester Resin Composition and Preparation of Artificial Marble Molded Product] Example 1 100 parts of unsaturated polyester resin (trade name: Yupica 6424, manufactured by Nippon Yupika Co., Ltd.), Reference Example 1 5 parts of the AB block copolymer obtained in 1), 1 part of tert-butyl peroctoate (trade name: Perbutyl O, manufactured by NOF Corporation) and glassy powder (Nippon Fellow Co., Ltd.)
(Trade name: M-10S) was sufficiently stirred and mixed with a mixer to prepare an unsaturated polyester resin composition. After gently degassing the above composition with a vacuum pump, 10
0x100x5tmm mold and 150x80x200
It was poured into a FRP mold having a bathtub shape of 10 mm in thickness and 10 mm in thickness, and was cured in a constant temperature bath at 80 ° C. to produce two types of artificial marble products. The molded product obtained from the mold is referred to as molded product A, and the molded product obtained from the FRP mold is referred to as molded product B. Table 2 shows the composition and the evaluation results obtained.

The evaluation was performed as follows. Volume shrinkage The specific gravity of the composition is measured using a pycnometer.
Then, the mixture was poured into a test tube having a volume of about 20 ml, the upper portion of the test tube was sealed, and the mixture was allowed to stand in an oil bath at 80 ° C. to advance curing. After completion of curing, removed the cured product from the test tube, the specific gravity of the cured product was measured by solid hydrometer (Shimadzu Corp. SGM-SH200 _-11), the volume shrinkage of the cured product by the following formula I asked. Volume shrinkage (%) = (1− (specific gravity of resin composition / specific gravity of cured product)) × 100 cracks The presence or absence of cracks generated in the two types of molded articles was visually determined. Total light transmittance The total light transmittance of the molded product A was measured using a direct-reading haze meter manufactured by Toyo Seiki Seisaku-Sho, Ltd. in accordance with JIS-K7105 (Test method for optical properties of plastics). Transparency The printed matter was placed under the molded article A, and it was determined whether or not the font was visible from above the molded article. A: The font can be confirmed and the font can be read. ：: The font can be confirmed, but the font cannot be read. ×: The font cannot be confirmed.

Examples 2 to 12 Using the AB type block copolymers obtained in Reference Examples 1 to 9, artificial marble molded articles were prepared according to the composition shown in Table 2 according to Example 1. . Then, evaluation was performed according to Example 1, and the results are shown in Table 2.

[0037]

[Table 2]

Comparative Examples 1-4 Using the AB block copolymers obtained in Reference Examples 10-13, artificial marble molded articles were produced according to the composition shown in Table 3 in accordance with Example 1. . Then, evaluation was performed according to Example 1. The results are shown in Table 3.

[0039]

[Table 3]

Comparative Examples 5 to 8 The composition shown in Table 4 was obtained by using the comparative low-shrinkage agents (A) to (C) obtained in Reference Example 14 in place of the AB block copolymer. According to Example 1, an artificial marble molded product was produced. Then, evaluation was performed according to Example 1, and the results are shown in Table 4.

COMPARATIVE EXAMPLE 9 An artificial marble molded product was produced in the same manner as in Example 1 except that the AB block copolymer was not used. Then, evaluation was performed according to Example 1, and the results are shown in Table 4.

[0042]

[Table 4]

As is clear from the comparison between the above Examples and Comparative Examples, when the specific block copolymer of the present invention was used as a low-shrinking agent, cracks were generated due to a small shrinkage during heat molding. A molded article having high transparency was obtained without generation.

Claims (1)

(57) [Claims] (1) An unsaturated polyester resin and (B)
An AB type block copolymer comprising a crosslinked vinyl polymer segment (a) and an uncrosslinked polymer segment (b) compatible with the unsaturated polyester resin as a substantially main component, The crosslink density of (a) is 0.1.
The weight ratio of the segment (a) to the segment (b) is 98: 2 to 50:50, and the AB block copolymer is 3 to 30 with respect to 100 parts by weight of the unsaturated polyester resin. An unsaturated polyester resin composition contained in parts by weight.