JPWO2016103875A1 - Fiber sizing agent - Google Patents

Abstract

An acrylic resin (a) having a glass transition temperature in the range of −20 to 40 ° C. is a fiber sizing agent containing an aqueous resin dispersion (A) dispersed in an aqueous medium, and the acrylic resin (a The fiber sizing agent is provided with an average particle diameter of 0.5 to 5 μm. This fiber sizing agent has excellent fiber sizing properties, does not cause fiber bundle unwinding or fluffing in the weaving process, weaving, yarn breakage, etc., and has low discoloration after heat treatment at high temperatures, Excellent in properties. For this reason, the fiber bundle focused by the fiber sizing agent of the present invention can be suitably used as a reinforcing material for molded products for various applications including automobile and aircraft members, home appliance parts and wind power generation members. it can.

Description

  The present invention relates to a fiber sizing agent that can be used for fiber sizing.

  Conventionally, fiber reinforced plastics including a matrix resin and a fiber material have been used as automobile members, aircraft members, and the like that are required to have high strength and excellent durability. As the matrix resin, for example, nylon, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and the like are used. Many are used.

  On the other hand, the fiber material such as carbon fiber and glass fiber contained in the fiber reinforced plastic is used as a fiber bundle that is generally bundled to about several thousand to several tens of thousands by a fiber sizing agent from the viewpoint of imparting high strength. There are many. As such a fiber sizing agent, a glass fiber sizing agent containing a (meth) acrylic acid ester polymer has been proposed (see, for example, Patent Document 1).

  However, the fiber sizing agent described in Patent Document 1 may cause unraveling, fluffing, and yarn breakage of the fiber bundle in the winding or weaving process of the fiber bundle that is bundled using the fiber sizing agent. In some cases, the productivity of the bundled fiber bundles and the productivity of the finally obtained molded product are significantly reduced.

  Accordingly, there has been a demand for a fiber sizing agent that is excellent in fiber sizing properties and that can provide a molded product that can be used even in parts that require high heat resistance.

JP 2003-261359 A

  The problem to be solved by the present invention is to provide a fiber sizing agent having excellent fiber sizing properties and heat resistance.

  As a result of intensive studies to solve the above problems, the present inventors have obtained a resin dispersion in which an acrylic resin (a) having a glass transition temperature in the range of −20 to 40 ° C. is dispersed in an aqueous medium ( A fiber sizing agent containing A) and having an average particle diameter of acrylic resin (a) in the range of 0.5 to 5 μm was found to be excellent in fiber sizing property and heat resistance, and the present invention was completed.

  That is, the present invention is a fiber sizing agent containing an aqueous resin dispersion (A) in which an acrylic resin (a) having a glass transition temperature in the range of −20 to 40 ° C. is dispersed in an aqueous medium. An average particle diameter of the acrylic resin (a) is in the range of 0.5 to 5 μm.

  Since the fiber sizing agent of the present invention is excellent in fiber sizing property and heat resistance, a molded product obtained using a fiber bundle and a matrix resin bundled using the fiber sizing agent of the present invention is, for example, an automobile or aircraft. It can be used in various applications including members, parts of home appliances and wind power generation members.

  The fiber sizing agent of the present invention is a fiber sizing agent containing an aqueous resin dispersion (A) in which an acrylic resin (a) having a glass transition temperature in the range of −20 to 40 ° C. is dispersed in an aqueous medium. And the average particle diameter of the said acrylic resin (a) is the range of 0.5-5 micrometers.

  First, the acrylic resin (a) will be described. The acrylic resin (a) has a glass transition temperature in the range of -20 to 40 ° C. However, since the fiber sizing property of the fiber sizing agent is further improved, the range of -10 to 30 ° C is preferable, and 0 to 20 A range of ° C is more preferred.

  The glass transition temperature in the present invention is measured by a method based on JIS K7121 using a differential scanning calorimeter “DSC Q-100” (manufactured by TA Instrument). Specifically, a polymer from which the solvent was completely removed by vacuum suction was measured for a change in calorie at a rate of temperature increase of 20 ° C./min in a range of −100 ° C. to + 200 ° C. The point at which the straight line equidistant in the vertical axis direction intersects with the curve of the stepwise change portion of the glass transition was defined as the glass transition temperature.

  The acrylic resin (a) preferably has a weight average molecular weight in the range of 5,000 to 150,000 because the heat resistance is further improved. The range of 10,000 to 100,000. Particularly preferred are those having a weight average molecular weight of In addition, the said weight average molecular weight points out the value measured using gel permeation chromatography (GPC).

  The acrylic resin (a) can be produced, for example, by radical polymerization by heating a polymerizable monomer in an organic solvent at a temperature of 50 to 150 ° C. in the presence of a polymerization initiator.

  Examples of the polymerizable monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and t-butyl (meth). ) Acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, and other alkyl (meth) acrylates; 2-hydroxyethyl (meth) acrylate , 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (meth) acrylate having a hydroxyl group such as 2-hydroxybutyl (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylate Relate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, (meth) acrylate having an amino group such as N, N-diethylaminopropyl (meth) acrylate; polyethylene glycol (meta ) Acrylate, methoxypolyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, polybutylene glycol (meth) acrylate, methoxypolybutylene glycol (meth) acrylate and other (alkoxy) polyalkylene glycols Unsaturated monocarboxylic acids such as (meth) acrylate; (meth) acrylic acid and crotonic acid; itaconic acid (anhydride), maleic acid (anhydride), fumaric acid, etc. Unsaturated dicarboxylic acid; vinyl monomers such as styrene, α-methylstyrene, paramethylstyrene, chloromethylstyrene, vinyl acetate; tetrahydrofurfuryl (meth) acrylate, benzyl (meth) acrylate, glycidyl (meth) acrylate, etc. Is mentioned. These polymerizable monomers can be used alone or in combination of two or more.

  Among these polymerizable monomers, since the particle stability is further improved, (alkoxy) polyalkylene glycol (meth) acrylate is used in the range of 1 to 10% by mass in the total polymerizable monomers. Is preferred.

  Examples of the organic solvent include aromatic solvents such as toluene and xylene; alicyclic solvents such as cyclohexanone; ester solvents such as normal butyl acetate and ethyl acetate; isobutanol, normal butanol, isopropyl alcohol, sorbitol, propylene Solvents having a hydroxyl group such as glycol monomethyl ether acetate; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone can be used. These solvents can be used alone or in combination of two or more.

  Examples of the polymerization initiator include azo compounds such as 2,2′-azobis (isobutyronitrile), 2,2′-azobis (2-methylbutyronitrile), azobiscyanovaleric acid; tert-butylperoxy Organic peroxides such as pivalate, tert-butylperoxybenzoate, tert-butylperoxy-2-ethylhexanoate, di-tert-butyl peroxide, cumene hydroperoxide, benzoyl peroxide, tert-butyl hydroperoxide Oxides; inorganic peroxides such as hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate and the like. These polymer initiators can be used alone or in combination of two or more. Moreover, it is preferable to use the said polymerization initiator within the range of 0.1-10 mass% with respect to the sum total of the monomer used as the raw material of the said acrylic resin (A).

  Examples of the aqueous medium include water, an organic solvent miscible with water, and a mixture thereof. Examples of the organic solvent miscible with water include alcohols such as methanol, ethanol, n-propanol and isopropanol; ketones such as acetone and methyl ethyl ketone; polyalkylene glycols such as ethylene glycol, diethylene glycol and propylene glycol; alkyl ethers of polyalkylene glycols And lactams such as N-methyl-2-pyrrolidone. In the present invention, only water may be used, a mixture of water and an organic solvent miscible with water may be used, or only an organic solvent miscible with water may be used. From the viewpoint of safety and load on the environment, water alone or a mixture of water and an organic solvent miscible with water is preferable, and it is particularly preferable to use only water.

  As a method for obtaining the aqueous resin dispersion (A) by dispersing the acrylic resin (a) in an aqueous medium, various dispersion methods can be used. However, since particle stability is further improved, an emulsifier is used. The method of dispersing is preferred.

  As a method of dispersing using the emulsifier, for example, the acrylic resin (a), the emulsifier, and water are supplied into a static mixer to obtain a pre-emulsified mixture, and then emulsified and dispersed with an ultrasonic homogenizer. If necessary, a method for removing the solvent may be mentioned.

  Moreover, the method etc. which carry out emulsification dispersion | distribution, supplying water to the mixture of the said acrylic resin (a) and an emulsifier, and remove solvent as needed are also mentioned.

  Examples of the emulsifier include nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polyoxypropylene condensate, alkyl sulfate ester salt, alkylbenzene sulfonate, polyoxyethylene alkyl ether sulfate. Anionic emulsifiers such as ester salts and polyoxyethylene alkylphenyl ether sulfate esters, and cationic emulsifiers such as quaternary ammonium salts. Among these, nonionic emulsifiers are preferable because particle stability is improved, and polyoxyethylene polyoxypropylene condensates are particularly preferable. These emulsifiers can be used alone or in combination of two or more.

  In the fiber sizing agent of the present invention, the average particle diameter of the acrylic resin (a) is in the range of 0.5 to 5 μm. However, since the fiber sizing property is further improved, 0.8 to 4.5 μm. Is preferable, and the range of 1.2 to 4 μm is more preferable.

  The average particle diameter in the present invention refers to a value obtained by laser diffraction particle size distribution measurement (“WingSALDII” manufactured by Shimadzu Corporation).

  The fiber sizing agent of the present invention contains the aqueous resin dispersion (A). However, since the mechanical strength of the obtained molded article is improved, it is preferable to contain a silane coupling agent, Among them, it is particularly preferable to contain γ-aminopropyltriethoxysilane, γ-ureidopropyltriethoxysilane, and γ-aminopropyltriethoxysilane. In addition, these silane coupling agents can be used alone or in combination of two or more.

  The fiber sizing agent of the present invention can contain components such as a binder such as urethane resin, acrylic resin, and epoxy resin, a lubricant, and an antistatic agent as long as the effects of the present invention are not impaired.

  The fiber treated with the fiber sizing agent of the present invention is used as a reinforcing agent for matrix resins such as polyolefin resin, polycarbonate resin, polyamide resin, polyester resin, polyphenylene sulfide resin, and is particularly preferably used for polyamide resin.

  Next, the present invention will be specifically described with reference to examples and comparative examples.

[Measurement of glass transition temperature]
A differential scanning calorimeter “DSC Q-100” (manufactured by TA Instrument) was used, and the measurement was performed by a method in accordance with JIS K7121. The polymer from which the solvent was completely removed by vacuum suction was measured for the change in calorie at a rate of temperature increase of 20 ° C./min in the range of −100 ° C. to + 200 ° C. The point at which the straight line that is equidistant and the curve of the stepwise change portion of the glass transition intersect was defined as the glass transition temperature.

[Measurement of weight average molecular weight]
Measuring device: High-speed GPC device (“HLC-8220GPC” manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series.
"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 “TSKgel G2000” (7.8 mm ID × 30 cm) × 1 detector: RI (differential refractometer)
Column temperature: 40 ° C
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 mL / min Injection amount: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4 mass%)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

[Measurement of average particle size]
Measuring device: Laser diffraction particle size distribution measurement (“WingSALDII” manufactured by Shimadzu Corporation)
Measurement method: The refractive index was set as follows.
Urethane resin: 1.7-0.2i
Acrylic resin: 1.6-0.1i

(Example 1: Production and evaluation of fiber sizing agent (1))
In a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser, 50 parts by mass of n-butyl acrylate, 47 parts by mass of methyl methacrylate, and methoxypolyethylene glycol methacrylate (“NK Ester M-manufactured by Shin-Nakamura Chemical Co., Ltd.) 230G ") 3 parts by mass were charged, and a monomer premix (1) uniformly mixed was obtained.
Separately, a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 1 part by mass of an azo initiator (“V-59” manufactured by Wako Pure Chemical Industries, Ltd.) and 15 parts by mass of toluene, and a catalyst solution. (1) was obtained.
Next, 85.5 parts by mass of toluene was charged into a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen blowing tube, and the temperature was raised to 80 ° C. while stirring in a nitrogen atmosphere. Subsequently, the monomer premix (1) and the catalyst solution (1) obtained above were each dropped in parallel with a dropping funnel over 3 hours to carry out polymerization. After completion of dropping, the mixture was further maintained at 80 ° C. for 3 hours, and then cooled to room temperature to obtain a solution of acrylic resin (a-1) having a nonvolatile content of 50%.
202 parts by mass of the acrylic resin (a-1) solution and 140.7 parts by mass of an aqueous solution containing 10.1 parts by mass of a polyoxyethylene polyoxypropylene condensate (number average molecular weight of about 16,000) Resin (a-1) solution / Polyoxyethylene polyoxypropylene condensate aqueous solution) = (202 parts by mass / 140.7 parts by mass) The flow rate ratio is 202 ml / 140.7 parts by mass. Then, the mixture is introduced into an ultrasonic homogenizer (“Sonator BT type” manufactured by Sonic Corporation, using a 0.003 inch ² orifice) at a pressure of 120 Kgf / cm 2 while applying back pressure, and emulsified and dispersed. It was. The obtained water dispersion was desolvated under reduced pressure at 40 ° C. (0.080 to 0.095 MPa) over about 6 hours, then cooled, and a fiber sizing agent having a nonvolatile content of 45% and an average particle size of 1.5 μm ( 1) was obtained. The acrylic resin (a-1) had a glass transition temperature of 3 ° C. and a weight average molecular weight of 30,000.

[Evaluation of heat resistance (thermal discoloration)]
The fiber sizing agent (1) obtained above is flowed to a base material having a frame at the four corners of the A4 size PP base material, dried at room temperature for 24 hours, and further dried at 150 ° C. for 5 minutes. Got. Furthermore, the appearance after heat-treating this film at 200 ° C. for 1 hour was measured with a spectrocolorimeter (“CM-3500d” manufactured by Konica Minolta Co., Ltd.) and evaluated by the Δb value. The lower the Δb value, the smaller the thermal discoloration.

[Evaluation of fiber convergence]
2.2 parts by mass of the fiber sizing agent (1) obtained above (1 part by mass as a solid content), 0.1 part by mass of γ-aminopropyltriethoxysilane, and 97.7 parts by mass of ion-exchanged water were mixed. Then, it was uniformly applied to the surface of the glass fiber having a diameter of 13 μm with respect to the fiber mass by 1%. After concentrating the fibers, the fibers were cut to a length of 3 mm and dried to prepare chopped strands (1). 50 g of this chopped strand (1) and 100 g of polyamide 66 resin were put into a 1 L volume tumbler and mixed for 10 minutes, and then the generated fluff was collected and its mass was measured and evaluated according to the following criteria.
○: Less than 0.15 g Δ: 0.15 g or more and less than 1.5 g ×: 1.5 g or more

(Example 2: Production and evaluation of fiber sizing agent (2))
First, in the same manner as in Example (1), a solution of acrylic resin (a-1) having a nonvolatile content of 50% by mass was added to a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen blowing tube. Obtained.
Next, 3 parts by mass of a styrenated phenol surfactant (“NF-08” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is added to 202 parts by mass of the acrylic resin (a-1) solution, and then stirred. 132 parts by mass of ion-exchanged water was added dropwise over 1 hour to carry out emulsification dispersion. Thereafter, an aqueous solution of 101.6 parts by mass containing 7.1 parts by mass of a polyoxyethylene polyoxypropylene condensate (number average molecular weight of about 16,000) was added, and this was reduced in pressure at 60 ° C. (0.080 to 0.095 MPa). Then, after removing the solvent over about 6 hours, the mixture was cooled to obtain a fiber sizing agent (2) having a nonvolatile content of 45% by mass and an average particle size of 2.5 μm.

  In place of the fiber sizing agent (1) of Example 1 and using the fiber sizing agent (2), the heat resistance (thermochromic property) and the fiber sizing property were evaluated in the same manner as in Example 1.

(Comparative Example 1: Production and evaluation of fiber sizing agent (R-1))
A four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 71.1 parts by mass of polypropylene glycol (OH number: 112) and 1 part by mass of dimethylolpropionic acid, and after sufficient stirring and mixing, isophorone diisocyanate. 27.9 parts by mass was added, and the reaction was continued at 80 ° C. until NCO% reached 3.9%, followed by cooling to obtain urethane resin (1).
The urethane resin (1) and an aqueous solution containing triethylamine, polyoxyethylene nonylphenyl ether (HLB: 14) and ion-exchanged water were mixed with urethane resin (1) / (triethylamine / polyoxyethylene nonylphenyl ether (HLB: 14). ) / Ion-exchanged water) = 100 / (0.72 / 6.0 / 93.4) The flow rate ratio of parts by mass is supplied into the static mixer with each metering pump to obtain a pre-emulsified mixed solution, and then mixed. The solution was introduced into an ultrasonic homogenizer (“Sonator BT type” manufactured by Sonic Corporation, using a 0.003 inch ² orifice) at a pressure of 120 kgf / cm 2 while applying back pressure, and emulsified and dispersed. The obtained aqueous resin was mixed with 19.9 parts by mass of a 20% by mass anhydrous piperazine aqueous solution to cause a chain extension reaction, and then diluted with ion-exchanged water to have a non-volatile content of 45% by mass and an average particle size of 0.6 μm. Fiber sizing agent (R-1) was obtained.

  In place of the fiber sizing agent (1) of Example 1, the fiber sizing agent (R-1) was used, and the heat resistance (thermochromic property) and the fiber sizing property were evaluated in the same manner as in Example 1. .

(Comparative Example 2: Production and evaluation of fiber sizing agent (R-2))
In a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser, 55.9 parts by mass of ion-exchanged water and polyoxyethylene alkyl ether diluted to 10% by mass (“NL-” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 15 parts by weight of “180” aqueous solution was charged and mixed uniformly.Next, 50 parts by weight of n-butyl acrylate, 47 parts by weight of methyl methacrylate and methoxypolyethylene glycol methacrylate (“NK” manufactured by Shin-Nakamura Chemical Co., Ltd.) were added while stirring. Ester M-230G ") 3 parts by mass was added to obtain an emulsified dispersion (1).
Separately, an aqueous catalyst solution (1) was obtained by diluting 1 part by mass of ammonium persulfate (manufactured by Kishida Chemical Co., Ltd.) with 15 parts by mass of water in a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser.
Next, 45.9 parts by mass of ion-exchanged water was charged into a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, and the temperature was raised to 80 ° C. while stirring in a nitrogen atmosphere. Subsequently, the emulsion dispersion (1) and the aqueous catalyst solution (1) obtained above were dropped in parallel with a dropping funnel over 3 hours, and emulsion polymerization was performed. After completion of dropping, the mixture was further maintained at a temperature of 80 ° C. for 3 hours, and then cooled to room temperature to obtain a fiber sizing agent (R-2) having a nonvolatile content of 45 mass% and an average particle size of 0.2 μm. The glass transition temperature of the obtained acrylic resin was 3 ° C.

  In place of the fiber sizing agent (1) of Example 1, the fiber sizing agent (R-2) was used, and the heat resistance (thermochromic property) and fiber sizing property were evaluated in the same manner as in Example 1. .

(Comparative Example 3: Production and evaluation of fiber sizing agent (R-3))
In a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser, 20.6 parts by mass of n-butyl acrylate, 77.5 parts by mass of methyl methacrylate, and methoxypolyethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd. “ NK ester M-230G ") 3 parts by mass were charged, and a monomer premix (2) uniformly mixed was obtained.
Separately, a catalyst solution (1) was obtained in the same manner as in Example 1.
Next, 86 parts by mass of toluene was charged into a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen blowing tube, and the temperature was raised to 80 ° C. while stirring in a nitrogen atmosphere. Subsequently, the monomer premix (2) and the catalyst solution (1) obtained above were each dropped in parallel with a dropping funnel over 3 hours to carry out polymerization. After completion of dropping, the mixture was further maintained at 80 ° C. for 3 hours, and then cooled to room temperature to obtain a solution of acrylic resin (Ra-1) having a nonvolatile content of 50% by mass.
A solution of the acrylic resin (RA-1) and 141.5 parts by mass of an aqueous solution containing 10.1 parts by mass of a polyoxyethylene polyoxypropylene condensate (number average molecular weight of about 16,000) (acrylic resin (RA -1) solution / polyoxyethylene polyoxypropylene condensate aqueous solution) = (202 parts by mass / 141.5 parts by mass) at a flow rate ratio, each of the metering pumps supplied into a static mixer to obtain a pre-emulsified mixture. Thereafter, the mixture was introduced into an ultrasonic homogenizer (“Sonator BT type” manufactured by Sonic Corporation, using a 0.003 inch ² orifice) at a pressure of 120 kgf / cm 2 while applying back pressure, and emulsified and dispersed. The obtained aqueous dispersion was desolvated under reduced pressure at 40 ° C. (0.080 to 0.095 MPa) for about 6 hours, then cooled, and a fiber sizing agent having a nonvolatile content of 45% by mass and an average particle size of 1.2 μm. (R-3) was obtained. The glass transition temperature of the acrylic resin (Ra-1) was 50 ° C.

  In place of the fiber sizing agent (1) of Example 1, the fiber sizing agent (R-3) was used, and the heat resistance (thermochromic property) and the fiber sizing property were evaluated in the same manner as in Example 1. .

  Table 1 shows the evaluation of the fiber sizing agent obtained in Examples 1-2 and Comparative Examples 1-3.

  It was confirmed that the fiber sizing agents of Examples 1 and 2 which are the fiber sizing agents of the present invention are excellent in heat resistance and fiber sizing properties.

  On the other hand, although the comparative example 1 is an example using a urethane resin as a resin component, it was confirmed that it was inferior in heat resistance.

  Comparative Example 2 is an example in which the average particle size is 0.2 μm which is smaller than 0.5 μm which is the lower limit of the present invention, but it was confirmed that the fiber focusing property is inferior.

  Although the comparative example 3 is an example whose glass transition temperature of acrylic resin is 50 degreeC higher than 40 degreeC which is the upper limit of this invention, it was confirmed that it is inferior to fiber convergence.

Claims (2)

  An acrylic resin (a) having a glass transition temperature in the range of −20 to 40 ° C. is a fiber sizing agent containing an aqueous resin dispersion (A) dispersed in an aqueous medium, and the acrylic resin (a ) In the range of 0.5 to 5 μm.   The fiber sizing agent according to claim 1, wherein the resin dispersion (A) is one in which the acrylic resin (a) is dispersed in an aqueous medium by an emulsifier.