JP2011116589A - Acrylic resin composition for glass fiber sizing agent, glass fiber sizing agent, its production method, and glass fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic resin composition having excellent sizing property, which when used as a reinforcing agent for a thermoplastic resin, particularly a polyamide resin, avoids deterioration of physical properties even when a metal salt is added to a sizing agent-containing molding formulation, and which can give a fiber-reinforced resin molded product having good mechanical characteristics, particularly tensile characteristics. <P>SOLUTION: The acrylic resin composition for a glass fiber sizing agent contains as an essential component a copolymer having a weight-average molecular weight of 5,000-150,000 obtained by radical copolymerization of a polymerizable monomer mixture comprising a (meth)acrylic ester and maleic acid (anhydride), wherein a weight ratio of the (meth)acrylic ester (a) to the maleic acid (anhydride) (m) [(a)/(m)] in the polymerizable monomer mixture is 7/3 to 3/7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an acrylic resin composition for glass fiber sizing agent suitable for a glass fiber sizing agent including chopped strands, rovings, yarns, and the like, and a glass containing the acrylic resin composition for glass fiber sizing agent Fiber sizing agent, glass fiber with glass fiber sizing agent coated on the surface

In general, glass fibers are formed by drawing molten glass from a number of nozzles provided at the bottom of a platinum bushing. After a sizing agent is applied to the surface of each glass fiber (filament), several hundred to several Thousands are bundled into one strand. In addition, the glass fiber reinforced thermoplastic resin composition is obtained by cutting the strand obtained as described above into a predetermined length, or winding the strand once and then drawing out and cutting it into a predetermined length into a glass chopped strand. Then, this is kneaded with a thermoplastic matrix resin while heating, and then molded into a predetermined shape by various molding methods.
Conventionally, for the purpose of improving the mechanical properties of glass fiber reinforced thermoplastic resin (FRTP), various glass fiber sizing agents have been proposed which are coated on the surface of glass fiber and give suitable adhesion to the thermoplastic resin. . For example, a glass fiber sizing agent containing a polyurethane resin synthesized from an isocyanate and a polyol is generally known.
Under such circumstances, a glass fiber sizing agent using an acrylic copolymer resin has been widely studied for the purpose of improving the hue and mechanical strength of a molded product. However, these resins, particularly when used as a reinforcing agent for polyamide resins, have good water resistance strength, but the tensile strength and impact strength of the molded product are insufficient, and there are problems of strength reduction and coloring over time. On the other hand, an acrylic resin-based composition mainly composed of a polymerizable dibasic acid and acrylic acid has been proposed, but this technique aims at improving heat resistance especially during compounding of a molded product containing a sizing agent. When a metal salt is added, there is a problem that a problem of a decrease in mechanical strength occurs.

JP2008-138026

  The problem to be solved by the present invention is that the sizing property is excellent, and when used as a reinforcing agent for a thermoplastic resin, particularly a polyamide resin, even if a metal salt enters the molding compound containing the sizing agent, the physical properties are deteriorated. It is another object of the present invention to provide an acrylic resin composition capable of providing a fiber-reinforced resin molded article having good mechanical properties, particularly tensile properties of a molded product.

  The present inventor is an acrylic resin obtained by copolymerizing a polymerizable monomer composed of (anhydrous) maleic acid and (meth) acrylic ester, and a resin having no carboxyl group derived from acrylic acid in the acrylic resin. It has been found that an acrylic resin composition as an essential component solves this problem.

That is, the present invention uses, as an essential component, a copolymer having a weight average molecular weight of 5,000 to 150,000 obtained by radical copolymerization of a polymerizable monomer mixture comprising (meth) acrylic acid ester and (anhydrous) maleic acid. An acrylic resin composition for glass fiber sizing agent, wherein the weight ratio of (meth) acrylic acid ester (a) and (anhydrous) maleic acid (m) in the polymerizable monomer mixture [(a) / (M)] is 7/3 to 3/7, an acrylic resin composition for glass fiber sizing agent, a glass fiber sizing agent containing the acrylic resin composition for glass fiber sizing agent, and glass A glass fiber having a surface coated with a fiber sizing agent is provided.
(A) H ₂ C = CXHCOOR ¹
(Here, X represents a hydrogen atom or a methyl group, and R ¹ represents a linear or branched alkyl group having 1 to 4 carbon atoms.)

  According to the acrylic resin composition for a glass fiber sizing agent of the present invention, when considered as a reinforcing agent for a conventional polyamide resin, there is no deterioration in physical properties even when a metal salt is added to the sizing agent, and good glass fiber sizing. It is possible to provide an acrylic resin composition that can provide a fiber-reinforced resin molded product having excellent properties and good mechanical properties, particularly tensile properties of a molded product.

  The acrylic resin composition (A) for glass fiber sizing agent of the present invention is a (meth) acrylic acid ester, particularly preferably a (meth) acrylic acid ester represented by the following general formula (a) and (anhydrous) maleic acid. An acrylic resin obtained by radical polymerization of an acid polymerizable monomer with a radical initiator in the presence of the solvent (c) is an essential component. A part or all of the acrylic resin composition may be neutralized with the basic compound (b) and may be in the form of an aqueous dispersion in which the acrylic resin composition is dispersed in water. Further, a solvent obtained by removing the water dispersion may be used.

(A) H ₂ C = CXHCOOR ¹
(Here, X represents a hydrogen atom or a methyl group, and R ¹ represents a linear or branched alkyl group having 1 to 4 carbon atoms.)

  The aqueous dispersion has an average particle diameter in the range of 500 nm or less for reasons such as film-forming properties, glass fiber wettability, glass fiber bundling, and mechanical strength of FRTP using this glass fiber as a reinforcing agent. It is preferable that The average particle diameter here refers to the average particle diameter on a volume basis measured by a dynamic light scattering method.

  The aqueous resin is preferably contained in an amount of 10 to 70% by weight based on the total amount of the aqueous resin dispersion of the present invention for reasons of resin storage stability and resin coating suitability.

The acrylic resin composition of the present application will be described.
First, the (meth) acrylic acid ester (a) will be described.
Examples of the (meth) acrylic acid ester (a) include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, -n-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, There are methacrylic acid-n-propyl, isopropyl methacrylate, methacrylic acid-n-butyl, isobutyl methacrylate, and the like, but in view of the balance between glass sizing properties and mechanical strength, methacrylic acid-n-butyl is particularly preferable.

  For (anhydrous) maleic acid (m)

Next, the basic compound (b) will be described.
Examples of the basic compound (b) include ammonia, organic amines such as triethylamine, dimethylethanolamine, pyridine and morpholine, alkanolamines such as monoethanolamine, and metal bases including Na, K, Li, Ca and the like. Compounds and the like.
The neutralization rate with the basic compound depends on the solid content acid value of the modified polyolefin, but is preferably 100% or more in consideration of the resin stability after dispersion.

  As the organic solvent (c), organic solvents such as esters, aromatics, ketones, alcohols and the like can be used. In consideration of radical polymerization temperature or solvent removal, ester solvents, alcohol solvents, n-Butyl acetate, -n-ethyl acetate, isobutanol, -n-butanol and isopropyl alcohol are preferred.

  Moreover, as said acrylic resin composition (A), as above-mentioned, from the reason of mechanical strength provision of FRTP (Fiber Reinforced ThermoPlastics) which used the fiber fiber converging property and this glass fiber as a reinforcing agent, it is 5000- It is preferable to use one having a weight average molecular weight of 150,000. In addition, the said weight average molecular weight points out the value measured using gel permeation chromatography (GPC). (It means FRTP (Fiber Reinforced ThermoPlastics) fiber reinforced thermoplastic resin).

  Furthermore, the maleic anhydride content in the maleic anhydride / (meth) acrylic acid ester mixture of the acrylic resin composition (A) includes the glass fiber bundling properties and the mechanical properties of the substrate using the same. Considering the balance of strength, the content is desirably 30 to 70% by weight.

  The acid value of the solid content of the acrylic resin composition is preferably 440 to 690 mgKOH / g in consideration of 340 to 800 mgKOH / g, constraining property of glass fiber, and durability (water resistance) of the molded product. It is good to be.

  In addition, the acrylic resin composition is in a state where the polymerization is completed in the solvent (c), and the carboxylic acid is (partially) neutralized by the neutralizing agent (b), and then water-dispersed by adding water. Is possible. Furthermore, it is also possible to remove the solvent from the aqueous dispersion by distillation under reduced pressure.

  The glass fiber sizing agent of the present invention is a mixture of the acrylic resin composition for glass fiber sizing agent with an additive described later.

  When the glass fiber sizing agent of the present invention contains a silane coupling agent, particularly γ-aminopropyltriethoxysilane, γ-ureidopropyltriethoxysilane, γ-aminopropyltriethoxysilane, etc. The bond strength with the polyolefin resin formed on the surface is increased, and the mechanical strength of the polyolefin FRTP is improved, which is preferable.

  Further, the glass fiber sizing agent of the present invention contains components such as a binder such as urethane resin, acrylic resin, and epoxy resin, lubricant, antistatic agent, etc., in addition to the above-described components, as long as the effects of the present invention are not impaired. Can be added. Moreover, the glass fiber reinforced thermoplastic resin of this invention can contain glass fiber in 5 to 65 mass%.

  Glass fiber treated with a glass fiber sizing agent using the acrylic water-soluble resin composition of the present invention is used as a reinforcing agent for matrix resins such as polyolefin resin, polycarbonate resin, polyamide resin, polyester resin, and in particular, polyamide resin. Is preferably used.

  Hereinafter, the present invention will be described in detail based on examples. In addition, parts and% indicate parts by weight and% by weight, respectively, unless otherwise specified.

Example 1
A four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen blowing tube was charged with 95 parts by weight of n-butyl acetate and heated to 120 ° C., and then 98 parts by weight of maleic anhydride and methacrylic acid-n— 147 parts by weight of butyl, 75 parts by weight of -n-butyl acetate, 1.6 parts by weight of perbutyl D (ditertiary butyl hydroperoxide: manufactured by Nippon Oil & Fats Co., Ltd.), perbutyl Z (tertiary butyl peroxybenzoate: Japanese oil and fat ( Co., Ltd.) 3.0 parts by weight of the dissolved mixture was added dropwise over 2 hours and reacted at 120 to 125 ° C. Thereafter, after holding at 120 ° C. for 120 minutes, the temperature was lowered to 90 ° C., 137 parts by weight of 25% aqueous solution and 600 parts by weight of ion-exchanged water were added, and neutralization and water dissolution were performed. Under reduced pressure at 90 ° C. (0.080 to 0.095 MPa), solvent removal (about 60 minutes) and cooling were performed, the nonvolatile content was about 23% by weight, pH 7.6, viscosity 580 mPa · s, weight average molecular weight 7.0. Ten thousand aqueous acrylic resin compositions were obtained.

  First, as a film-forming component, a sizing agent (aqueous dispersion) was prepared by using 3.0% by weight of the above aqueous acrylic resin composition as a solid content and 0.5% by weight of γ-aminopropyltriethoxysilane as a solid content. ) And was uniformly applied to the surface of a fiber having a diameter of 13 μm. After converging the fibers, the fibers were cut to a length of 3 mm and dried to prepare chopped strands.

  The chopped strand was kneaded while heating at 270 ° C. with 30% by weight of the chopped strand, 69.5% by weight of polyamide 66 (nylon 66) resin, 0.5% by weight of magnesium oxide, and pelletized by a known method. An FRTP molded product was prepared by injection molding the pellet. Subsequently, the obtained FRTP molded product was evaluated by the following test method, and the obtained results are shown in Table 1.

Evaluation Method of Convergence and Mechanical Strength Convergence: Convergence of the chopped strand is 50 g of the prepared chopped strand and 100 g of polyamide 66 resin put into a 1 L volume tumbler and mixed for 10 minutes. The generated fluff was collected and evaluated by measuring its mass. The evaluation results in the table depend on the following criteria.
○ ・ ・ ・ less than 0.15g △ ・ ・ ・ 0.15-1.5g × ・ ・ ・ 1.5g or more

Mechanical strength: Measured based on the tensile strength (ASTM D638) of the FRTP molded product obtained above. The evaluation results in the table depend on the following criteria.
○ ・ ・ ・ 90MPa or more △ ・ ・ ・ 70 ~ 90MPa × ・ ・ ・ 70MPa or less

Example 2
A four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen blowing tube was charged with 95 parts by weight of n-butyl acetate and heated to 120 ° C., and 75 parts by weight of maleic anhydride and methacrylic acid-n— 170 parts by weight of butyl, 75 parts by weight of n-butyl acetate, 1.6 parts by weight of perbutyl D (ditertiary butyl hydroperoxide: manufactured by Nippon Oil & Fats Co., Ltd.), perbutyl Z (tertiary butyl peroxybenzoate: Japanese oil and fat ( Co., Ltd.) 3.0 parts by weight of the dissolved mixture was added dropwise over 2 hours and reacted at 120 to 125 ° C. Thereafter, after holding at 120 ° C. for 120 minutes, the temperature was lowered to 90 ° C., and 105 parts by weight of 25% water and 630 parts by weight of ion-exchanged water were added to neutralize and dissolve in water. Under reduced pressure at 90 ° C. (0.080 to 0.095 MPa), solvent removal (about 60 minutes) and cooling were performed, the nonvolatile content was about 22% by weight, pH 7.7, viscosity 650 mPa · s, weight average molecular weight 6.5. Ten thousand aqueous acrylic resin compositions were obtained. The production of chopped strands and FRTP molded products and various evaluations were the same as in Example 1. The obtained results are shown in Table 1.

Example 3
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 95 parts by weight of -n-butylacetate and heated to 120 ° C. To this, 170 parts by weight of maleic anhydride, methacrylic acid-n- 75 parts by weight of butyl, 75 parts by weight of -n-butyl acetate, 1.6 parts by weight of perbutyl D (ditertiary butyl hydroperoxide: manufactured by Nippon Oil & Fats Co., Ltd.), perbutyl Z (tertiary butyl peroxybenzoate: Japanese oil and fat ( Co., Ltd.) 3.0 parts by weight of the dissolved mixture was added dropwise over 2 hours and reacted at 120 to 125 ° C. After holding at 120 ° C. for 120 minutes, the temperature was lowered to 90 ° C., and 240 parts by weight of 25% water and 500 parts by weight of ion-exchanged water were added for neutralization and water dissolution. Under reduced pressure at 90 ° C. (0.080 to 0.095 MPa), solvent removal (about 60 minutes) and cooling were performed, the nonvolatile content was about 21% by weight, pH 7.4, viscosity 850 mPa · s, weight average molecular weight 6.5. Ten thousand aqueous acrylic resin compositions were obtained.
The production of chopped strands and FRTP molded products was the same as in Example 1.

Example 4
A four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen blowing tube was charged with 95 parts by weight of n-butyl acetate and heated to 120 ° C., and then 98 parts by weight of maleic anhydride and methacrylic acid-n— 147 parts by weight of butyl, 75 parts by weight of n-butyl acetate, 3.2 parts by weight of perbutyl D (ditertiary butyl hydroperoxide: manufactured by Nippon Oil & Fats Co., Ltd.), perbutyl Z (tertiary butyl peroxybenzoate: Japanese oil and fat ( 12.0 parts by weight of the dissolved mixture was added dropwise over 2 hours and reacted at 120 to 125 ° C. Thereafter, after holding at 120 ° C. for 120 minutes, the temperature was lowered to 90 ° C., 137 parts by weight of 25% aqueous solution and 600 parts by weight of ion-exchanged water were added, and neutralization and water dissolution were performed. Under reduced pressure at 90 ° C. (0.080 to 0.095 MPa), solvent removal (about 60 minutes) and cooling were performed, the nonvolatile content was about 25% by weight, pH 7.6, viscosity 230 mPa · s, weight average molecular weight 0.7. Ten thousand aqueous acrylic resin compositions were obtained. The production of chopped strands and FRTP molded products and various evaluations were the same as in Example 1. The obtained results are shown in Table 1.

Example 5
A four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen blowing tube was charged with 95 parts by weight of n-butyl acetate and heated to 110 ° C., and 98 parts by weight of maleic anhydride and methacrylic acid-n— 147 parts by weight of butyl, 75 parts by weight of acetic acid-n-butyl, 0.8 parts by weight of perbutyl D (ditertiary butyl hydroperoxide: manufactured by Nippon Oil & Fats Co., Ltd.), perbutyl Z (tertiary butyl peroxybenzoate: Japanese oil and fat ( Co., Ltd.) 1.5 parts by weight of the dissolved mixture was added dropwise over 2 hours and reacted at 110 to 115 ° C. Thereafter, after holding at 120 ° C. for 120 minutes, the temperature was lowered to 90 ° C., 137 parts by weight of 25% aqueous solution and 600 parts by weight of ion-exchanged water were added, and neutralization and water dissolution were performed. Under reduced pressure at 90 ° C. (0.080 to 0.095 MPa), solvent removal (about 60 minutes) and cooling were performed, the nonvolatile content was about 20% by weight, pH 7.6, viscosity 1230 mPa · s, weight average molecular weight 12.7. Ten thousand aqueous acrylic resin compositions were obtained. The production of chopped strands and FRTP molded products and various evaluations were the same as in Example 1. The obtained results are shown in Table 1.

Comparative Example 1
Preparation of monomer premix 50 parts by weight of ion-exchanged water, 43.2 parts by weight of itaconic acid, 90 parts by weight of 80% acrylic acid were uniformly dissolved, 90 parts by weight of 25% aqueous solution was added, and methyl acrylate 28.8 A part by weight was added to prepare a monomer premix.
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 120 parts by weight of ion-exchanged water and heated to 70 ° C. while blowing nitrogen. Thereafter, 4 parts of 10% aqueous solution of ammonium persulfate (APS) was added, and then 302 parts by weight of monomer premix and 76 parts by weight of 10% aqueous solution of ammonium persulfate were dropped in parallel for 3 hours, and then held at the same temperature for 3 hours. The mixture was cooled to obtain an aqueous acrylic resin composition having a nonvolatile content of about 30% by weight, a pH of 6.5, and a viscosity of 350 mPa · s. The production of chopped strands and FRTP molded products and various evaluations were the same as in Example 1. The obtained results are shown in Table 2.

Comparative Example 2
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen blowing tube was charged with 95 parts by weight of n-butyl acetate and heated to 120 ° C., to which 60 parts by weight of maleic anhydride, methacrylic acid-n— 185 parts by weight of butyl, 75 parts by weight of n-butyl acetate, 1.6 parts by weight of perbutyl D (ditertiary butyl hydroperoxide: manufactured by Nippon Oil & Fats Co., Ltd.), perbutyl Z (tertiary butyl peroxybenzoate: Japanese oil and fat ( Co., Ltd.) 3.0 parts by weight of the dissolved mixture was added dropwise over 2 hours and reacted at 120 to 125 ° C. After holding at 120 ° C. for 120 minutes, the temperature was lowered to 90 ° C., and 84 parts by weight of 25% water and 680 parts by weight of ion-exchanged water were added for neutralization and water dissolution. Under reduced pressure at 90 ° C. (0.080 to 0.095 MPa), solvent removal (about 60 minutes) and cooling were performed, the nonvolatile content was about 22% by weight, pH 7.4, viscosity 280 mPa · s, weight average molecular weight 6.5. Ten thousand aqueous acrylic resin compositions were obtained. The production of chopped strands and FRTP molded products and various evaluations were the same as in Example 1. The obtained results are shown in Table 2.

Comparative Example 3
A four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen blowing tube was charged with 95 parts by weight of n-butyl acetate and heated to 120 ° C., to which 190 parts by weight of maleic anhydride, methacrylic acid-n— 55 parts by weight of butyl, 75 parts by weight of n-butyl acetate, 1.6 parts by weight of perbutyl D (ditertiary butyl hydroperoxide: manufactured by Nippon Oil & Fats Co., Ltd.), perbutyl Z (tertiary butyl peroxybenzoate: Japanese oil and fat ( Co., Ltd.) 3.0 parts by weight of the dissolved mixture was added dropwise over 2 hours and reacted at 120 to 125 ° C. Thereafter, after holding at 120 ° C. for 120 minutes, the temperature was lowered to 90 ° C., 268 parts by weight of 25% aqueous solution and 500 parts by weight of ion-exchanged water were added, and neutralization and water dissolution were performed. Under reduced pressure at 90 ° C. (0.080 to 0.095 MPa), solvent removal (about 60 minutes) and cooling were performed, the nonvolatile content was about 20% by weight, pH 7.3, viscosity 1120 mPa · s, weight average molecular weight 6.5. Ten thousand aqueous acrylic resin compositions were obtained. The production of chopped strands and FRTP molded products and various evaluations were the same as in Example 1. The obtained results are shown in Table 2.

Comparative Example 4
A four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen blowing tube was charged with 95 parts by weight of n-butyl acetate and heated to 120 ° C., and then 98 parts by weight of maleic anhydride and methacrylic acid-n— 147 parts by weight of butyl, 75 parts by weight of n-butyl acetate, 6.4 parts by weight of perbutyl D (ditertiary butyl hydroperoxide: manufactured by Nippon Oil & Fats Co., Ltd.), perbutyl Z (tertiary butyl peroxybenzoate: Japanese oil and fat ( 20.0 parts by weight of the dissolved mixture was added dropwise over 2 hours and reacted at 120 to 125 ° C. Thereafter, after holding at 120 ° C. for 120 minutes, the temperature was lowered to 90 ° C., 137 parts by weight of 25% aqueous solution and 600 g of ion-exchanged water were added to neutralize and dissolve in water. Under reduced pressure at 90 ° C. (0.080 to 0.095 MPa), solvent removal (about 60 minutes) and cooling were performed, the nonvolatile content was about 28% by weight, pH 7.6, viscosity 45 mPa · s, weight average molecular weight 0.3. Ten thousand aqueous acrylic resin compositions were obtained.
The production of chopped strands and FRTP molded products was the same as in Example 1.

Comparative Example 5
A four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen blowing tube was charged with 95 parts by weight of n-butyl acetate and heated to 110 ° C., and 98 parts by weight of maleic anhydride and methacrylic acid-n— 147 parts by weight of butyl, 75 parts by weight of n-butyl acetate, 0.4 parts by weight of perbutyl D (ditertiary butyl hydroperoxide: manufactured by Nippon Oil & Fats Co., Ltd.), perbutyl Z (tertiary butyl peroxybenzoate: Japanese oil and fat ( Co., Ltd.) 0.7 part by weight of the dissolved mixture was added dropwise over 2 hours and reacted at 110 to 115 ° C. Thereafter, after holding at 120 ° C. for 120 minutes, the temperature was lowered to 90 ° C., 137 parts by weight of 25% aqueous solution and 600 parts by weight of ion-exchanged water were added, and neutralization and water dissolution were performed. Under reduced pressure at 90 ° C. (0.080 to 0.095 MPa), solvent removal (about 60 minutes) and cooling were performed, and the nonvolatile content was about 18% by weight, pH 7.6, viscosity 930 mPa · s, weight average molecular weight 16.9. Ten thousand aqueous acrylic resin compositions were obtained. The production of chopped strands and FRTP molded products and various evaluations were the same as in Example 1. The obtained results are shown in Table 2.

Claims (5)

Acrylic for glass fiber sizing agent comprising as essential component a copolymer having a weight average molecular weight of 5000 to 150,000 obtained by radical copolymerization of a polymerizable monomer mixture comprising (meth) acrylic acid ester and (anhydrous) maleic acid. The weight ratio [(a) / (m)] of (meth) acrylic acid ester (a) and (maleic anhydride) (m) in the polymerizable monomer mixture is 7 An acrylic resin composition for a glass fiber sizing agent, characterized in that it is / 3 to 3/7. The acrylic resin composition (A) for glass fiber sizing agent according to claim 1, wherein the (meth) acrylic acid ester is represented by the following general formula (a).
H ₂ C = CXHCOOR ¹ (a)
(Here, X represents a hydrogen atom or a methyl group, and R ¹ represents an alkyl group having 1 to 4 carbon atoms.) An acrylic resin composition for glass fiber sizing agents, wherein the acrylic resin composition for glass fiber sizing agents according to claim 1 or 2 is neutralized with a basic compound (b) and then dispersed in water. A glass fiber sizing agent comprising the acrylic resin composition for glass fiber sizing agent according to claim 1, 2 or 3. A glass fiber having a surface coated with the glass fiber sizing agent according to claim 4.