JPH047391B2 - - 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 produced by hand-laying 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 UP method, cold press methods and resin injection methods that use the reaction heat generated during curing of unsaturated polyester resin using a relatively low-pressure press or press-in machine, resin mortar, resin concrete, etc. It is obtained by a cold molding method or a hot 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 curing shrinkage of the above-mentioned unsaturated polyester resins, a method of blending thermoplastic resins such as polystyrene, polymethyl methacrylate, polyvinyl acetate, etc. with unsaturated polyester resins has been used, and these methods have been used to some extent. It is known that it is possible to exhibit a low shrinkage 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, roughening of the surface of the cured product, poor curing, and poor curing shrinkage. The field and range of use of this resin is restricted due to uniformity, reduced strength, etc. As a result of intensive research in order to solve the above-mentioned drawbacks, the present inventors have developed a block copolymer mixture consisting of vinyl acetate and styrene segments, with an acid group bonded to one of the segments, to an unsaturated polyester resin. The inventor discovered that if added during curing, the unsaturated polyester resin cured product could exhibit an excellent low shrinkage effect, and this was patented in 1983.
-48769 (Japanese Unexamined Patent Publication No. 57-164114).
However, although this invention was sufficient for heat molding, it was still insufficient for room temperature curing. The present inventors have stably dispersed in unsaturated polyester resin,
Moreover, as a result of research to provide a block copolymer mixture that can exhibit a sufficient low shrinkage effect even when cured at room temperature, the block copolymer mixture described below has a high block efficiency of 70 to 90% by weight when obtained. Moreover, a non-aqueous dispersion resin composition containing this block copolymer mixture exhibits extremely excellent dispersion stability, and furthermore, a composition prepared by blending the above block copolymer mixture with an unsaturated polyester resin is particularly curable at room temperature. The present invention was completed based on the knowledge that it has an excellent effect on low shrinkage. 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. It consists of 2 to 20% by weight of a 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) and the monomer This is a low shrinkage unsaturated polyester resin composition in which a mixture of (B) and block copolymer mixture (C) is in a non-aqueous dispersion state. What is the above 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, or a phenylene group or a substituted phenylene group,
R ₂ represents an ethylene group, an acetylene group or a phenylene group. n=2-40. ] Using polymer peroxide represented by as a polymerization initiator, either one of the monomers defined in (a) and (b) below (hereinafter referred to as monomer (a) and monomer (b), respectively) ) or a mixture of monomers (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 mixture of
This is a block copolymer obtained by block copolymerization. (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); Number of carbon atoms in acrylic acid or methacrylic acid 1~
A monomer or monomer mixture consisting of 70 to 100% by weight of the alkyl ester of No. 4 and 30 to 0% by weight of a monomer copolymerizable therewith. The unsaturated polyester (A) used in the present invention is α,β- Manufactured from 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, neopentyl glycol, hexylene glycol,
Hydrogenated bisphenol A, 2,2'-di(4-hydroxypropoxyphenyl)pueropan, 2,
These include 2'-di(4-hydroxyethoxyphenyl)propane, ethylene oxide, and propylene oxide. Monomer (B) copolymerizable with unsaturated polyester (A)
For example, alkenyl aromatic monomers such as styrene, α-methylstyrene, and 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 polymer having peroxy bonds in the molecule 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 can be taken out from the reaction system. It is also possible to carry out block copolymerization subsequently. In addition, the amount of polymer peroxide used is based on 100 parts by weight of the monomer (a) or monomer (b).
Appropriate values are 0.1 to 10 parts by weight, a polymerization temperature of 40 to 140°C, and a polymerization time of 2 to 15 hours. The polymeric peroxide used in the production of the block copolymer mixture (c) in the present invention can be obtained by reacting a dihydroperoxide and a dibasic acid chloride in the presence of a base using a conventional method for producing peroxyesters. It can be easily manufactured by Specifically, the polymeric peroxide represented by the general formula () in the present invention is, for example, (In all of the above, n=2 to 40.) etc. Examples of monomers copolymerizable with the styrene monomer used to produce the block copolymer mixture (c) of the present invention include acrylic acid, acrylic esters, methacrylic acid, methacrylic esters, and styrene derivatives. , acrylonitrile, methacrylnitrile, derivatives of fumaric acid or maleic acid, vinyl ketone, vinylpyridine, butadiene, etc., and the amount used is limited to 30% by weight or less in the monomer mixture with styrene monomer. be done. If it exceeds 30% by weight, the performance of the finally synthesized block copolymer mixture (c) will be adversely affected, and the unsaturated polyester resin composition containing the block copolymer mixture (c) will be adversely affected. If the cured product is cured, the surface of the cured product will lack gloss and the pigment colorability will be more poor. Examples of monomers copolymerizable with alkyl esters of acrylic acid or methacrylic acid having 1 to 4 carbon atoms include alkyl esters of acrylic acid or methacrylic acid having 5 to 18 carbon atoms, acrylic acid, methacrylic acid, methacryl nitrile, Examples include styrene and styrene derivatives, and the amount used thereof 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, the final synthesized block copolymer mixture
When curing an unsaturated polyester resin composition containing the block copolymer mixture (C), the block copolymer mixture (C) adversely affects the properties of (c). Embossing is observed, and uneven curing shrinkage occurs. The ratio of monomer (a) and monomer (c) used to produce the block copolymer mixture (c) is 10 to 90 parts by weight of monomer (a). Quantity (b) is 90-10
Parts by weight are preferred. If it is outside this range, when an unsaturated polyester resin composition is made, the unsaturated polyester and the block copolymer mixture (C) will tend to separate into layers before or during curing, resulting in defects in the composition of the cured product. This is not preferable because it will lead to homogenization. In the present invention, the blending amount of the block copolymer mixture (C) 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 or a resin concrete composition, which is 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 the specific block copolymer mixture (C) is stably dispersed microscopically for an extremely long time; It has the feature that a sufficient curing temperature is not necessarily required for the product to exhibit a low shrinkage effect. 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, regardless of the conventional molding method that employs room-temperature curing. Furthermore, it is a matter of course that the low shrinkage effect of the composition will further increase if accompanied by a sufficient curing temperature, and if the thermoforming method used as a molding composition for SMC, BMC, etc., the composition will have extremely large dimensions. It can provide precision, strength, gloss, surface smoothness, etc. Hereinafter, the present invention will be explained in detail with reference to 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 [Formula] (n≒ 9.72) In a glass reactor equipped with a thermometer and a stirrer, 2.
178 parts of 5-dimethylhexane-2,5-dihydroperoxide, 190 parts of pyridine and methylene chloride
1000 copies were made. Furthermore, the contents of this glass reactor were stirred while maintaining the temperature at 0 to 5°C.
To this contents was added 183 parts of adipate chloride via addition funnel over a period of 30 minutes. After the dropwise addition, the contents of the glass reactor were heated for 2 hours while maintaining the temperature at 0 to 5℃.
Stirring was continued for an hour to complete the reaction. The reaction product was washed with dilute hydrochloric acid to remove residual pyridine, then washed with water, and methylene chloride was distilled off under reduced pressure at 20° C. or lower to obtain 254 parts of a viscous liquid. The amount of active oxygen in the obtained viscous liquid was determined by the usual iodometry method and was found to be 10.9%. From the characteristic absorption wavelength in the infrared absorption spectrum and the τ value and intensity of the nuclear magnetic resonance spectrum of this viscous liquid, it was confirmed that it was a peroxyester type polymeric peroxide consisting of the following structural units. The average molecular weight of this polymer peroxide is
When measured by the VPO method, it was 2800. 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.
0.5 parts of polymeric peroxide (hereinafter abbreviated as P/PO) obtained in Reference Example 1 to 10 parts (abbreviated as P/PO)
and the solution obtained by dissolving 1 part. After replacing the air in the reactor with nitrogen gas, while stirring
Polymerization was initiated by heating to 105°C. After polymerizing for 1.5 hours while maintaining the temperature at 105°C, 90 parts of styrene (hereinafter abbreviated as ST) was added. Then the temperature
The temperature was raised to 115°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 [Production 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 in the same manner as in Reference Example 2, except that 2.5 parts of a solution of 2.5 parts of ST was used and 50 parts of ST were 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 96 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.
I got the department. 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 was dissolved, 95 parts of a block copolymer mixture was obtained in the same manner as in 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 [Manufacture 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, 94 parts of a block copolymer mixture was obtained according to Reference Example 2 except that 10 parts of ST was used. 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
50 copies

[Formula] (n≒12.5) A solution in which a part of P/PO is dissolved, and
96 parts of a block copolymer mixture was obtained according to Reference Example 2 except that 50 parts of ST was used. 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 [Production of Comparative Block Copolymer Mixture-1] A 1.0% polyvinyl alcohol aqueous solution 300ml was placed in a glass reactor equipped with a thermometer, a stirrer, and a 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 100°C with stirring to initiate polymerization. Temperature the contents of the reactor
After polymerizing for 3 hours while maintaining at 100℃, ST90
A mixture of 1 part and 10 parts of MA was added. Then the temperature
The temperature was raised to 115°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 [Production of Comparative Block Copolymer Mixture-2] P/PO obtained in Reference Example 1 was added to 50 parts of VAC in advance.
Use a solution containing 2.5 parts, then add 50 parts of ST.
98 parts of a block copolymer mixture was obtained in accordance with Reference Example 10, except that 1.5 parts of MA was used in the mixture. 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 103,000 in ST to a concentration of 30% to make a solution. Comparative low-shrinkage agent (a) And so. (b) PMMA having a molecular weight of approximately 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 (b). The block copolymer mixtures obtained in Reference Examples 2 to 8, 10, and 11 were used in the following examples as dispersions in which the block copolymer mixtures were dispersed in ST at a concentration of 30%. Example 1 [Low shrinkage effect of unsaturated polyester resin composition at room temperature and in a water bath system] The ST dispersion of the block copolymer mixture obtained in Reference Example 2 and the UPR obtained in Reference Example 9 were polymerized using a polymerization catalyst. The mixture was mixed in the presence of Permec N (manufactured by NOF Corporation, trade name of methyl ethyl ketone peroxide) and cobalt naphthenate, a polymerization accelerator.
Next, inject this into a glass tube of known volume,
The cured product was left standing in a water bath at 20°C, 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 large, and no temperature increase was observed. Ta. 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 conducted according to Example 1 using each of the block copolymer mixtures obtained in Reference Examples 2 to 8. The results are shown in Table 3.

[Table] Comparative Examples 1 to 8 Tests were conducted according to Example 1 except that the comparative low shrinkage agent prepared in Reference Example 12 was used, and the results are shown in Table 4. Comparative Examples 9 to 12 Tests were conducted in accordance with Example 1, except that the ST dispersion of the comparative block copolymer mixture prepared in Reference Examples 10 and 11 was used, and the results are shown in Table 5.

【table】

【table】

[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 parts.
ST dispersion liquid made by dispersing ST in such a manner that %
with a lab mixer (high shear mixer).
After mixing for 20 minutes, 1.0 part of Permec N and 0.3 part of cobalt naphthenate were added and mixed, followed by 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, 100 parts of calcium carbonate (weight ratio: 1) were added and mixed to obtain a resin mortar composition. This composition was cured at room temperature for 2 hours,
After 7 days of curing, the surface condition was observed and the low shrinkage effect was measured. 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 0.006%. Comparative Example 13 Block copolymer mixture ST in Example 15
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 dispersion. 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 the block copolymer mixture obtained in Reference Example 2 were mixed at a concentration of 30 parts.
ST dispersion liquid made by dispersing ST in such a manner that %
After mixing for 20 minutes with a lab mixer, 1.0 part of Permec 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 horizontal
The resin concrete was poured into a mold of 100 mm x 50 mm in height, 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 comparative 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
A resin concrete was obtained which was tested according to Example 16, except that no ST dispersion was added. The surface was in poor condition with cracks and scratches. The results are shown in Table 6.

【table】

[Table] Indicates a defective condition due to generation or separation of the low shrinkage agent.
As is clear from comparing the above examples and comparative examples, when the block copolymer mixture used in the present invention is used as a low shrinkage agent in the same amount,
It was observed that the volume shrinkage rate was lower than that of conventional low shrinkage agents. 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 much superior to the product of the comparative example in terms of surface condition and linear shrinkage rate. 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); consisting of 2 to 20% by weight of a block copolymer mixture defined;
The mixture of the monomer (B) and the block copolymer mixture (C) is in a non-aqueous dispersion state, and the mixture of the unsaturated polyester (A), the monomer (B) and the block copolymer mixture (C) is A low shrinkage unsaturated polyester resin composition, the mixture of which 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, or a phenylene group or a substituted phenylene group,
R ₂ represents an ethylene group, an acetylene group or a phenylene group. n=2-40. ] Using the polymer peroxide represented by )
Alternatively, a mixture of monomers is polymerized (first polymerization reaction) to obtain a polymer having a peroxy bond in the molecule, and then this polymer is combined with the monomer or monomers not used in the first polymerization reaction. A block copolymer obtained by block copolymerizing a mixture. (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); Number of carbon atoms in acrylic acid or methacrylic acid 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.