JPS6330956B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a low-shrinkage unsaturated polyester resin composition that exhibits excellent low-shrinkage properties when cured at room temperature. Generally, cured molded products of unsaturated polyester resins are made by hand using an organic peroxide such as benzoyl peroxide or methyl ethyl ketone peroxide as a polymerization catalyst and, if necessary, an organic metal salt such as cobalt naphthenate or cobalt octenoate as a polymerization accelerator. Contact pressure molding methods such as the lay-up method, cold press methods that utilize the reaction heat generated during curing of unsaturated polyester resin using a relatively low-pressure press or press-in machine, resin injection methods, resin mortar, resin concrete, etc. It is obtained by a room-temperature molding method, or a heat molding method using a molding composition such as a sheet molding compound (SMC) or a bulk molding compound (BMC). However, unsaturated polyester resin has a large curing shrinkage of about 5 to 12% by volume, and no matter which of the above molding methods is used, various defects such as strength reduction, cracks, warping, and surface stains occur due to curing shrinkage. was unavoidable. As a method of reducing the curing shrinkage of the above-mentioned unsaturated polyester resin, a method has been used in which a thermoplastic resin such as polystyrene, polymethyl methacrylate, polyvinyl acetate, etc. is blended with the unsaturated polyester resin, and these methods have a certain degree of effectiveness. It is known that it is possible to develop a low contraction effect. However, fundamentally important drawbacks remain. That is, in order for a general thermoplastic resin to exhibit its effect as a low-shrinkage agent that reduces curing shrinkage of unsaturated polyester resins, it is necessary that the molding temperature be quite high during curing molding. For this reason, there is no effective low-shrinkage agent for molding methods other than hot molding. Furthermore, general thermoplastic resins have poor dispersion stability in unsaturated polyester resins, causing embossment from unsaturated polyester resin moldings during the curing stage, resulting in roughness and roughness on the surface of the cured product.
The field and range of use of this resin is limited due to poor curing, non-uniform curing shrinkage, reduced strength, etc. The inventors of the present invention made intensive efforts to solve the above-mentioned drawbacks, and as a result, a block copolymer mixture consisting of vinyl acetate and styrene segments, with an acid group bonded to one of the segments, was used as an unsaturated polyester resin. He discovered that if added during curing, the cured product of unsaturated polyester resin could exhibit an excellent low shrinkage effect, and this patent application was published in 1983.
The application was filed under No. 48769 (Japanese Unexamined Patent Publication No. 164114/1983). However, although this invention was sufficient in heat forming, room temperature curing was still insufficient. The present inventors conducted research to provide a block copolymer mixture that can be stably dispersed in an unsaturated polyester resin and exhibit sufficient low shrinkage effects even when cured at room temperature. The non-aqueous dispersion resin composition containing this block copolymer mixture has a high blocking efficiency of 70 to 90% by weight and exhibits extremely excellent dispersion stability. The present invention was completed based on the knowledge that a composition blended with a saturated polyester resin has particularly excellent effects on low shrinkage when cured at room temperature. That is, the present invention comprises (A); 20 to 70% by weight of an unsaturated polyester (B); 30 to 70% by weight of a monomer copolymerizable with the unsaturated polyester (A); (C); defined below. Consisting of 2 to 20% by weight of a block copolymer mixture, the above
(B) the monomer and (C) the block copolymer mixture is in a non-aqueous dispersion state, and the unsaturated polyester (A),
This is a low shrinkage unsaturated polyester resin composition in which a mixture of a monomer (B) and a block copolymer mixture (C) is in a non-aqueous dispersion state. The above block copolymer mixture has the general formula [In the formula, R ₁ represents an alkylene group or substituted alkylene group having 1 to 18 carbon atoms, a cycloalkylene group or substituted cycloalkylene group having 3 to 15 carbon atoms, a phenylene group or a substituted phenylene group,
R ₂ is an alkylene group or substituted alkylene group having 2 to 10 carbon atoms,

[Formula] (In the formula, R ₃ represents a hydrogen atom or a methyl group, R ₄ represents an alkylene group having 2 to 10 carbon atoms or a substituted alkylene group, and m = 1 to 13
It is. ),

【formula】 or

[Formula] is shown, and n=2 to 20. ] Using polymer peroxide as a polymerization initiator, the following (a) and (b)
Either one of the monomers defined in (hereinafter referred to as monomer (a) and monomer (b)) (hereinafter referred to as monomer (b)) is polymerized (first polymerization reaction), and A block copolymer (a) obtained by obtaining a polymer having a peroxy bond, and then block copolymerizing this polymer with a monomer or a mixture of monomers not used in the first polymerization reaction; Monomer or monomer mixture (b) consisting of 70 to 100% by weight of a styrene monomer and 30 to 0% by weight of a monomer copolymerizable with the same; acrylic acid or methacrylic acid having 1 to 4 carbon atoms
A monomer or monomer mixture consisting of 70 to 100% by weight of an alkyl ester of and 30 to 0% by weight of a monomer copolymerizable with the unsaturated polyester used in the present invention is α,
Manufactured from β-unsaturated dibasic acids, saturated dibasic acids and glycols. Here, the α,β unsaturated dibasic acid is, for example, maleic anhydride, maleic acid, fumaric acid, mesaconic acid, tetraconic acid, itaconic acid, chlorinated maleic acid, or alkyl esters thereof. Examples of the saturated dibasic acid include phthalic anhydride, phthalic acid, isophthalic acid, tetraphthalic acid, tetrahydrophthalic acid, halogenated phthalic anhydride, adipic acid, succinic acid, sebacic acid, and alkyl esters thereof. Examples of glycols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neobentyl glycol, hexylene glycol, hydrogenated bisphenol A, and 2,2'-di(4-hydroxyproboxyphenyl). Propane, 2,2'-di(4-hydroxyethoxyphenyl)propane,
Ethylene oxide, propylene oxide, etc. Examples of the monomer (B) copolymerizable with unsaturated polyester include styrene, α-methylstyrene,
Alkenyl aromatic monomers such as t-butylstyrene, alkyl esters of acrylic acid and methacrylic acid, and the like are used, with styrene being particularly preferred. In addition, the block copolymer mixture (C) is polymerized using a polymeric peroxide represented by the general formula () by a conventional bulk polymerization method, suspension polymerization method, emulsion polymerization method, solution polymerization method, etc. By doing so, it can be easily manufactured. In this case, the copolymer mixture having peroxy bonds in the molecules produced by the first polymerization reaction can be taken out from the reaction system as an intermediate and used as a raw material for the next block copolymer mixture, or it can be taken out from the reaction system. It is also possible to carry out block copolymerization subsequently. Further, the amount of polymeric peroxide used is 0.1 to 10 parts per 100 parts of monomer A or monomer B, the polymerization temperature is 40 to 90 DEG C., and the polymerization time is 2 to 15 hours. The polymeric peroxide used in the production of the block copolymer mixture in the present invention is produced by reacting a dibasic acid chloride having an ester bond in the molecule with sodium peroxide, using the usual method for producing diacyl peroxide. Easy to manufacture. Specifically, the polymeric peroxide represented by the general formula () in the present invention is, for example, (In all of the above, n=2 to 20.) etc. Examples of monomers copolymerizable with the styrene monomer used to produce the block copolymer mixture of the present invention include acrylic acid, acrylic esters, methacrylic acid, methacrylic esters, styrene derivatives, and acrylonitrile. , methacrylnitrile, derivatives of fumaric acid or maleic acid, vinyl ketone, vinylpyridine, butadiene, etc., and the amount used thereof is limited to 30% by weight or less in the monomer mixture with styrene. If it exceeds 30% by weight, the performance of the finally synthesized block copolymer mixture will be adversely affected, and if an unsaturated polyester resin composition containing the block copolymer mixture is cured, the cured product will be affected. The surface becomes insufficiently glossy, and pigment coloring properties become insufficient. Examples of monomers copolymerizable with C1-C4 alkyl esters of acrylic acid or methacrylic acid include C5-18 alkyl esters of acrylic acid or methacrylic acid, acrylic acid, methacrylic acid, methacryl nitrile, Examples include styrene and styrene derivatives, and the amount thereof used is limited to 30% by weight or less in the monomer mixture consisting of an alkyl ester of acrylic acid or methacrylic acid having 1 to 4 carbon atoms. If it exceeds 30% by weight, it will adversely affect the performance of the finally synthesized block copolymer mixture, and the unsaturated polyester resin composition containing the block copolymer mixture will be difficult to cure. During curing, embossment of the block copolymer mixture is observed, resulting in non-uniform curing shrinkage. The ratio of monomer (a) and monomer (b) used to produce the block copolymer mixture (C) is such that monomer (a) is 10 to 90 parts by weight. Quantity (b) is 90-10
Parts by weight are preferred. If outside this range, when an unsaturated polyester resin composition is made, the unsaturated polyester and block copolymer mixture tend to separate into layers before or during curing, resulting in non-uniformity of the composition of the cured product. I don't like this because it invites people. In the present invention, the blending amount of the block copolymer mixture is 2 to 2 to
20% by weight is required. If the amount is less than 2% by weight, the shrinkage reduction effect will not occur. Also
If it exceeds 20% by weight, the expansion during curing will be too large and the mechanical strength of the cured molded product will decrease. The unsaturated polyester resin composition having the composition detailed above can be used as it is for various purposes, but it can also be used as a fine powder (e.g. calcium carbonate,
It is also effective as a resin mortar composition and a resin concrete composition, which are made by appropriately blending inorganic or organic fine powders such as talc, clay, and wood powder, and aggregates (for example, inorganic granular materials such as sand, gravel, and crushed stone). Can be used. These compositions do not form a resin-rich layer even after being left for several days, and remain fine powders.
Not only does it have excellent storage stability with little aggregate settling, but it also maintains dimensional accuracy under room temperature curing conditions of 10°C to 30°C for 10 minutes to 10 hours if cured according to conventionally known procedures. A cured molded product with excellent compositional homogeneity can be obtained. That is, the low shrinkage unsaturated polyester resin composition of the present invention is a composition that maintains a non-aqueous dispersion state in which a specific block copolymer mixture is stably dispersed microscopically for an extremely long time, and the composition has a low shrinkage property. It has the feature that it does not necessarily require a sufficient curing temperature to exhibit its effects. Due to this feature, it has become possible to obtain molded products with higher strength, superior dimensional accuracy, surface gloss, etc. compared to conventional molded products using any of the conventional molding methods that employ room-temperature curing. In addition, it is a matter of course that the low shrinkage effect of the composition becomes even greater as the curing temperature increases, and therefore, by employing a thermoforming method as a molding composition for SMC, BMC, etc., extremely high dimensional accuracy, It can provide strength, gloss, surface smoothness, etc. Hereinafter, the present invention will be explained in detail using Reference Examples, Examples, and Comparative Examples. In each example, parts and % indicate parts by weight and % by weight unless otherwise specified. Reference example 1 [Manufacture of polymeric peroxide] Production of 183 parts of adipic acid chloride and 75 parts of triethylene glycol were charged into a glass reactor equipped with a thermometer and a stirrer. The contents of the glass reactor are heated to a temperature of 20~
30℃, under stirring while maintaining pressure at 40-50mmHg.
The reaction was carried out for 60 minutes to obtain 220 parts of triethylene glycol bis(adipoyl chloride) as a colorless viscous liquid. Next, a glass reactor equipped with a thermometer, a stirrer, and a dropping funnel was charged with an aqueous sodium peroxide solution prepared in advance with 30 parts of a 50% hydrogen peroxide solution and 832 parts of a 5% aqueous sodium hydroxide solution. Furthermore, while stirring the contents of this glass reactor and maintaining the temperature at 0 to 5°C, triethylene glycol bis(adipoyl chloride 176) obtained in the previous reaction was added to the contents.
of the mixture was added using an addition funnel. After the dropwise addition was completed, stirring was continued for 30 minutes while maintaining the temperature of the obtained reaction composition at 0 to 5°C to complete the reaction. A solid precipitate formed from the reaction product was separated, washed twice with water, and then dried under vacuum to obtain 140 parts of a white solid. Dissolve this white solid in 360 parts of chloroform and
It was purified by pouring it into 1600 parts of methanol and recrystallizing it. This product was separated to obtain 108 parts of a white solid.
The purified reaction product was analyzed for purity, molecular weight, decomposition temperature, infrared absorption spectroscopy, and nuclear magnetic resonance spectroscopy by iodine measurement, and the following results were obtained. The molecular weight was measured by VPO (manufactured by Hitachi, Ltd., vapor pressure equilibrium method molecular weight measuring device model 115). Purity by iodine measurement method 99.7% Decomposition temperature 90℃ Molecular weight 2140 (n≒5.3) Infrared absorption spectrum 1725cm ^-1 (C=O bond of ester group) 1780cm ^-1 and 1805cm ^-1 (C=0 bond of diacyl group) 875cm ^-1 (O-O bond) Nuclear magnetic resonance spectrum τ: 8.24 (8H,

【formula】) τ: 7.56 (8H,

[Formula]) τ: 6.28 (8H, - CH ₂ CH ₂ OCH ₂ -) τ: 5.72 (4H,

[Formula]) From these results, it was confirmed that the purified reaction product was a polymeric peroxide having the following general formula. Reference Example 2 [Manufacture of block copolymer mixture-1] In a glass reactor equipped with a thermometer, a stirrer, and a condenser, 300 parts of a 1.0% polyvinyl alcohol aqueous solution and methyl methacrylate (hereinafter MMA) were placed in advance.
It is abbreviated as ) 10 parts of the polymeric peroxide obtained in Reference Example 1 (hereinafter abbreviated as P/PO).
A solution obtained by dissolving 0.5 part was added.
After replacing the air in the reactor with nitrogen gas, the reactor was heated to 65° C. with stirring to initiate polymerization. Temperature 65℃
After polymerizing for 1.5 hours while maintaining the same temperature, 90 parts of styrene (hereinafter abbreviated as ST) was added. Then, the temperature was raised to 75°C and polymerization was continued for 12 hours. After the polymerization was completed by cooling to room temperature, the polymer was separated, thoroughly washed with water, and then dried under vacuum to obtain 97 parts of a white granular block copolymer mixture. Reference Example 3 [Manufacture of block copolymer mixture-2] P/PO obtained in Reference Example 1 was added to 50 parts of MMA in advance.
A block copolymer mixture 97 was prepared according to Reference Example 2 except that 2.5 parts of ST was dissolved in the solution and 50 parts of ST was used.
I got the department. Reference Example 4 [Manufacture of block copolymer mixture-3] P/PO obtained in Reference Example 1 was added to 90 parts of MMA in advance.
A block copolymer mixture was prepared according to Reference Example 2 except that 4.5 parts of ST was dissolved in the solution and 10 parts of ST was used.
Obtained 96 copies. Reference Example 5 [Manufacture of block copolymer mixture-4] P/PO obtained in Reference Example 1 was added to 10 parts of MMA in advance.
After polymerizing a solution in which 0.5 part of ST was dissolved, 95 parts of a block copolymer mixture was obtained according to Reference Example 2, except that a mixture of 63 parts of ST and 27 parts of methacrylic acid (hereinafter abbreviated as MA) was used. Reference Example 6 [Production of Block Copolymer Mixture-5) A solution prepared by dissolving 6 parts of P/PO obtained in Reference Example 1 in 63 parts of MMA and 27 parts of acrylic acid (hereinafter abbreviated as AA) in advance was polymerized. After that, the block copolymer mixture was prepared according to Reference Example 2 except that ST10 was used.
Obtained 94 copies. Reference Example 7 [Manufacture of block copolymer mixture-6] After polymerizing a solution in which 4.5 parts of P/PO obtained in Reference Example 1 was dissolved in 35 parts of MMA and 15 parts of AA, 35 parts of ST and 15 parts of MA were added. Reference example 2 except for use
93 parts of a block copolymer mixture was obtained. Reference example 8 [Manufacture of block copolymer mixture-7] Butyl acrylate (hereinafter abbreviated as BA) in advance
Reference Example 2 except that a solution in which 1 part of P/PO obtained in Reference Example 1 was dissolved in 50 parts, and 50 parts of ST were used.
96 parts of a block copolymer mixture was obtained. Next, 2.0 g of each of the block copolymer mixtures obtained in Reference Examples 2 to 8 was weighed and extracted using a Soxhlet extractor, first with cyclohexane for 24 hours and then with acetonitrile for 24 hours. The amount of weight loss due to cyclohexane and acetonitrile extraction is defined as the content of polystyrene (hereinafter abbreviated as PST), polymethyl methacrylate (hereinafter abbreviated as PMMA) or polybutyl acrylate (hereinafter abbreviated as PBA), and the extracted residue is % was defined as the content of the block copolymer. The results are shown in Table 1.

[Table] Reference Example 9 [Production of unsaturated polyester resin] 812 parts of fumaric acid, 498 parts of isophthalic acid, 396 parts of propylene glycol, and neopentyl glycol
Synthesize unsaturated polyester (acid value: 30, hereinafter abbreviated as UP) by esterifying 542 parts using the usual method, diluting the obtained UP with ST and adjusting the ST concentration to 35% of the total. An unsaturated polyester resin (hereinafter abbreviated as UPR) was obtained. Reference Example 10 [Manufacture of block copolymer mixture for comparison-1] 1.0% polyvinyl alcohol aqueous solution 300 ml was placed in a glass reactor equipped with a thermometer, stirrer, and condenser.
and vinyl acetate (hereinafter abbreviated as VAc) in advance.
A solution obtained by dissolving 0.5 part of P.PO obtained in Reference Example 1 was added to 10 parts. After replacing the air in the reactor with nitrogen gas, the reactor was heated to 60° C. with stirring to initiate polymerization. Bring the contents of the reactor to a temperature of 60℃
After polymerizing for 3 hours while maintaining
A mixture of 10 parts MA was added. Then, the temperature was raised to 75°C and polymerization was continued for 7 hours. After the polymerization was completed by cooling to room temperature, the polymer was separated, thoroughly washed with water, and then vacuum dried to obtain 103 parts of a white granular block copolymer mixture. Reference Example 11 [Manufacture of Comparative Block Copolymer Mixture-2] Add P/PO obtained in Reference Example 1 to 50 parts of VA (50 parts) in advance.
Use a solution containing 2.5 parts, then add 50 parts of ST.
98 parts of a block copolymer mixture was obtained according to Reference Example 10 except that a mixture with 1.5 parts of MA was used. Next, 2.0 g of each of the block copolymer mixtures obtained in Reference Examples 10 to 11 was weighed and extracted using a Soxhlet extractor, first with methanol for 24 hours and then with cyclohexane for 24 hours. The weight loss due to methanol and cyclohexane extraction was defined as the content of polyvinyl acetate (hereinafter abbreviated as PVAc) and PST, respectively, and the extraction residue was defined as the content of the block copolymer. The results are shown in Table 2.

[Table] Reference Example 12 [Preparation of comparative low shrinkage agent] (a) Dissolve PVAc with a molecular weight of approximately 103000 in ST to a concentration of 30%, make a solution, and prepare a comparative low shrinkage agent (a ). (b) PMMA with a molecular weight of about 500,000 was dissolved in ST to a concentration of 30% to form a solution, which was used as a comparative low-shrinkage agent (b). (c) PST Styron 666 manufactured by Asahi Dow Industries Co., Ltd. was dissolved in ST to a concentration of 30% to form a solution, which was used as a comparative low shrinkage agent (c). (d) ST-MMA random copolymer A random copolymer with a weight ratio of ST(50)/MMA(50) with a molecular weight of approximately 500,000, whose concentration is
It was dissolved in ST to a concentration of 30% and made into a solution, which was used as a comparative low shrinkage agent (d). The block copolymer mixtures obtained in Reference Examples 2 to 8, 10, and 11 were prepared as dispersions in ST so that the concentration was 30%, and used in the following examples. did. Example 1 [Low shrinkage effect of unsaturated polyester resin composition in water bath system at room temperature] The block copolymer mixture obtained in Reference Example 2
The ST dispersion and the UPR obtained in Reference Example 9 were mixed in the presence of a polymerization medium Permec N (manufactured by NOF Corporation, trade name of methyl ethyl ketone peroxide) and a polymerization catalyst cobalt naphthenate. Next, this was poured into a glass tube with a known volume and left to stand in a 20°C water bath, and the volumetric shrinkage rate of the cured product was determined using the following formula. Volume shrinkage rate (%) Volume before curing - Volume after curing / Volume before curing x 100 The temperature change of the composition injected into the glass tube during the injection to curing stage was measured, but the heat removal effect by the water bath was measured. was large, and no temperature rise was observed. The results are shown in Table 3. Examples 2 to 14 [Low shrinkage effect of unsaturated polyester resin compositions at room temperature and in a water bath system] Tests were carried out according to Example 1 except that the respective block copolymer mixtures obtained in Reference Examples 3 to 8 were used. The results are shown in Table 3.

[Table] Shows the amount added to the weight.
Comparative Examples 1 to 8 Tests were conducted according to Example 1 except that the comparative low yield agent prepared in Reference Example 12 was used, and the results are shown in Table 4. Comparative Examples 9 to 12 Tests were conducted according to Example 1 except that the comparative block copolymer mixtures prepared in Reference Examples 10 and 11 were used, and the results are shown in Table 5.

【table】

[Table] Adhesion properties: completely separated into two layers.

[Table] Example 15 [Low shrinkage effect in resin mortar composition, etc.] 80 parts of UPR obtained in Reference Example 9 and the block copolymer mixture obtained in Reference Example 2 were mixed at a concentration of 30%.
Mix 20 parts of ST dispersion with 20 parts of ST dispersion in a lab mixer (high shear mixer) so that
After mixing, 1.0 part of Parmeck N and 0.3 parts of cobalt naphthenate are added and mixed, and a mixture of aggregate and filler (2 parts of silica sand No. 3, 1 part of silica sand No. 4, 1 part of silica sand No. 7, calcium carbonate) is mixed. (weight ratio of 1)
100 parts were added and mixed to obtain a resin mortar composition. This composition was cured at room temperature for 2 hours, and the surface condition was observed after 7 days of curing to measure the low shrinkage effect. As a result, the cured product showed no cracks or deformation, and the surface condition was good. The linear shrinkage rate at this time is
It was 0.005%. Comparative Example 13 A test was conducted according to Example 15, except that the comparative low shrinkage agent (c) of Reference Example 12 was used instead of the block copolymer ST dispersion in Example 15. As a result, the surface of the cured product had tackiness due to the separation of PST, and it was impossible to measure the shrinkage rate. Example 16 [Low shrinkage effect in resin concrete composition, etc.] 80 parts of UPR obtained in Reference Example 9 and a block copolymer mixture obtained in Reference Example 2 were mixed at a concentration of 30%.
After mixing 20 parts of ST dispersion with ST in a lab mixer for 20 minutes,
1.0 part of N and 0.3 part of cobalt naphthenate were added and mixed. Next, 100 parts of calcium carbonate and 300 parts of river sand (maximum particle size: 5 mm) were mixed to obtain a resin concrete composition. This composition is 1000mm long x 100mm wide
The resin concrete was poured into a mold of mm x height 50 mm, cured at room temperature for 2 hours, and cured for 7 days to obtain resin concrete with a good surface condition. The results are shown in Table 6. Examples 17 to 22 [Low shrinkage effect in resin concrete compositions] Tests were conducted according to Example 16 except that the block copolymer mixtures obtained in Reference Examples 3 to 8 were used, and resins with good surface conditions were tested. Got concrete. The results are shown in Table 6. Comparative Examples 14 to 17 Tests were conducted according to Example 16 except that the comparative low shrinkage agents (a) to (d) of Reference Example 12 were used, but the surface tackiness, which was thought to be due to the embossment of the low shrinkage agents, was Admitted. The results are shown in Table 6. Comparative Examples 18-19 A test was conducted in accordance with Example 16, except that the block copolymer mixtures obtained in Reference Examples 10 and 11 were used, and resin concrete with a good surface condition was obtained. The results are shown in Table 6. Comparative Example 20 In Example 16, the block copolymer mixture
Resin concrete was obtained according to Example 16 except that the ST dispersion was not added. The surface was in poor condition with cracks and scratches.
The results are shown in Table 6.

[Table] Indicates a defective condition.
As is clear from a comparison of the above Examples and Comparative Examples, the cured product of cold-molded unsaturated polyester obtained by the present invention has a larger volume than that of conventional cold-molded polyester when the same amount of low-shrinkage agent is used. It was observed that the shrinkage rate was low. In addition, when resin concrete was produced using the product of the present invention and the product of the comparative example, and the resulting products were compared, the product of the present invention was significantly superior in surface condition and linear shrinkage rate compared to the product of the comparative example. It was recognized that there was.

Claims (1)

[Claims] 1 (A); 20 to 70% by weight of unsaturated polyester (B); 30 to 70% by weight of a monomer copolymerizable with the unsaturated polyester (A); and (C); 2 to 20% by weight of the defined block copolymer mixture, the mixture of the monomer (B) and the block copolymer mixture (C) is in a non-aqueous dispersion state, and the unsaturated polyester (A), Monomer (B) and block copolymer mixture (C)
A low shrinkage unsaturated polyester resin composition in which a mixture of is in a non-aqueous dispersion state. Block copolymer mixture; general formula [In the formula, R ₁ represents an alkylene group or substituted alkylene group having 1 to 18 carbon atoms, a cycloalkylene group or substituted cycloalkylene group having 3 to 15 carbon atoms, a phenylene group or a substituted phenylene group,
R ₂ is an alkylene group or substituted alkylene group having 2 to 10 carbon atoms, [Formula] (wherein, R ₃ is a hydrogen atom or a methyl group, and R ₄ is a carbon number 2
-10 alkylene groups or substituted alkylene groups, m=1-13. ),
[Formula] or [Formula], and n = 2 to 20. ] using polymeric peroxide represented by as a polymerization initiator, any one of the monomers or a mixture of monomers defined in (a) and (b) below (hereinafter referred to as monomer (a) and monomer, respectively) (referred to as polymer (b)) (first polymerization reaction) to obtain a polymer having a peroxy bond in the molecule, and then this polymer and a monomer or monomers not used in the first polymerization reaction. A block copolymer obtained by block copolymerizing a mixture of (a); Monomer or monomer mixture consisting of 70 to 100% by weight of a styrene monomer and 30 to 0% by weight of a monomer copolymerizable with the same (b); Carbon of acrylic acid or methacrylic acid Numbers 1-4
A monomer or monomer mixture comprising 70 to 100% by weight of an alkyl ester of and 30 to 0% by weight of a monomer copolymerizable therewith.