Sizing agent for quartz glass fibers, quartz glass fiber, quartz glass yarn, and quartz glass cloth

Abstract

Provided are a sizing agent for quartz glass fibers capable of suppressing charging of quartz glass fibers, and suppressing generation of fluff in a production process for quartz glass fibers and a weaving process for a quartz glass cloth, a quartz glass fiber or a quartz glass yarn having applied thereonto the sizing agent, a quartz glass cloth, a prepreg for a printed circuit board, and a product using the quartz glass fiber. The sizing agent for quartz glass fibers includes an aqueous solution containing: a cationic vinyl acetate copolymer emulsion in which a cationic vinyl acetate copolymer having a weight average molecular weight of from 5,000 to 500,000 is dispersed in water; and starch, in which emulsion particles of the cationic vinyl acetate copolymer emulsion have a 50% diameter on a volume basis of from 0.1 m to 5 m.

Claims

1. A quartz glass fiber, which has applied thereonto a sizing agent, said sizing agent comprising an aqueous solution containing: a cationic vinyl acetate copolymer emulsion in which a cationic vinyl acetate copolymer having a weight average molecular weight of from 5,000 to 500,000 is dispersed in water; and starch, wherein emulsion particles of the cationic vinyl acetate copolymer emulsion have a 50% diameter on a volume basis of from 0.1 m to 5 m.

2. A quartz glass fiber product, comprising the quartz glass fiber of claim 1.

3. A quartz glass yarn, which has applied thereonto a sizing agent, said sizing agent comprising an aqueous solution containing: a cationic vinyl acetate copolymer emulsion in which a cationic vinyl acetate copolymer having a weight average molecular weight of from 5,000 to 500,000 is dispersed in water; and starch, wherein emulsion particles of the cationic vinyl acetate copolymer emulsion have a 50% diameter on a volume basis of from 0.1 m to 5 m.

4. A quartz glass yarn according to claim 3, wherein the quartz glass yarn is formed of quartz glass fibers formed of quartz glass filaments each having a diameter of from 3 m to 8 m.

5. A quartz glass yarn according to claim 3, wherein the quartz glass yarn has a charge potential of from +1.5 kV to 1.0 kV.

6. A quartz glass yarn according to claim 3, wherein the quartz glass yarn has a pulling resistance of from 0.1 cN to 50 cN.

7. A quartz glass cloth, comprising the quartz glass yarn according to claim 3.

8. A prepreg for a printed circuit board, comprising the quartz glass cloth of claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view for illustrating a method of measuring pulling resistance of a glass yarn in Examples.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(2) Embodiments of the present invention are described below, but these embodiments are described as examples, and hence it is understood that various modifications may be made thereto without departing from the technical spirit of the present invention.

(3) The term cationic vinyl acetate copolymer emulsion refers to an emulsion in which a vinyl acetate copolymer having a positively charged moiety in its molecular structure is dispersed in a liquid, and may be produced by, for example, a known method described below. Water is suitable as the liquid.

(4) That is, the cationic vinyl acetate copolymer emulsion is obtained by emulsion polymerization or the like of a vinyl acetate monomer and a polyvinyl alcohol cationized with a compound having a cationic group, such as 3-chloro-2-hydroxypropyltrimethylammonium chloride, 3-chloroethyltrimethylammonium chloride, 3-chloropropyltrimethylammonium chloride, 2-acryloxyethyltrimethylammonium chloride, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, or glycidyltrimethylammonium chloride. For example, an azo-based catalyst and a peroxide are given as a catalyst to be used in the copolymerization.

(5) In the copolymerization, other copolymerizable monomers, such as ethylene, propylene, vinyl chloride, vinylpyrrolidone, an ester, maleic acid, and itaconic acid, may be copolymerized as long as the effects of the present invention are not impaired.

(6) The cationic vinyl acetate copolymer emulsion to be used in the present invention is not particularly limited as long as the cationic vinyl acetate copolymer has a weight average molecular weight of from 5,000 to 500,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion have a 50% diameter on a volume basis of from 0.1 m to 5 m. The cationic vinyl acetate copolymer has a weight average molecular weight of preferably from 50,000 to 500,000, more preferably from 80,000 to 500,000. Meanwhile, the emulsion particles of the cationic vinyl acetate copolymer emulsion have a 50% diameter on a volume basis of preferably from 0.1 m to 2 m, more preferably from 0.1 m to 1 m.

(7) When the weight average molecular weight of the cationic vinyl acetate copolymer is less than 5,000, a glass yarn bundling property lowers, and hence fluff is liable to be generated. When the weight average molecular weight of the cationic vinyl acetate copolymer is more than 500,000, a glass yarn becomes harder, and glass filaments are broken particularly at the intersection of warp and weft of a glass cloth at the time of weaving, with the result that the fluff cannot be suppressed. In addition, when the 50% diameter on a volume basis of the emulsion particles of the cationic vinyl acetate copolymer emulsion is less than 0.1 m, the emulsion particles are trapped in gaps of starch molecules coexisting in a sizing agent for quartz glass fibers, and hence an antistatic effect exhibited by the cationic vinyl acetate copolymer is not obtained sufficiently, with the result that the fluff cannot be suppressed. Meanwhile, when the 50% diameter on a volume basis of the emulsion particles of the cationic vinyl acetate copolymer emulsion is more than 5 m, the chemical stability of the cationic vinyl acetate copolymer emulsion lowers, and hence uniform application of the emulsion onto quartz glass fibers becomes difficult, with the result that fluff cannot be suppressed.

(8) The blending ratio of the cationic vinyl acetate copolymer emulsion in the sizing agent is not particularly limited, but is, for example, from 0.01 wt % to 20 wt %, preferably from 0.01 wt % to 10 wt %, more preferably from 0.1 wt % to 5 wt % in terms of a solid content with respect to 100 wt % of the total amount of the sizing agent for quartz glass fibers. When the blending ratio is less than 0.01 wt %, a sufficient coating cannot be formed on the glass fibers, and hence the antistatic effect is not obtained sufficiently. When the blending ratio is more than 20 wt %, further improvement in the antistatic effect cannot be expected, and further, a desizing property lowers.

(9) Starch to be used in the present invention is not particularly limited, but, for example, corn starch, tapioca starch, wheat starch, potato starch, rice starch, and the like may be used. The starch may be subjected to processing, such as etherification, esterification, grafting, or crosslinking.

(10) The blending ratio of the starch in the sizing agent is not particularly limited, but is, for example, from 0.1 wt % to 20 wt %, preferably from 0.1 wt % to 10 wt %, more preferably from 0.1 wt % to 5 wt % with respect to 100 wt % of the total amount of the sizing agent for quartz glass fibers. When the blending ratio is less than 0.1 wt %, a sufficient coating cannot be formed on the glass fibers. When the blending ratio is more than 20 wt %, the desizing property lowers.

(11) In addition to the cationic vinyl acetate copolymer emulsion and the starch described above, the sizing agent for quartz glass fibers of the present invention may contain other components the effects of the present invention are not impaired. Examples of the other components include a lubricant, an emulsifier, a cationic softener, an antistatic agent, a silane coupling agent, and an antiseptic. In addition, an alcohol, such as methanol, ethanol, or isopropanol, or any other organic solvent may be added in a small amount to the sizing agent for quartz glass fibers of the present invention.

(12) It is suitable that the lubricant be added for the purpose of enhancing the slip property of the glass fibers. It is suitable that the emulsifier be added for the purpose of dispersing the lubricant in water. It is suitable that the cationic softener be added for the purpose of softening the glass fibers. It is suitable that the silane coupling agent be added for the purpose of increasing the strength of the glass fibers. It is suitable that the antiseptic be added for the purpose of suppressing generation of mold on the starch.

(13) A quartz glass fiber of the present invention has applied thereonto the sizing agent for quartz glass fibers formed of an aqueous solution containing: the cationic vinyl acetate copolymer emulsion in which the cationic vinyl acetate copolymer having a weight average molecular weight of from 5,000 to 500,000 is dispersed in water; and the starch, in which the emulsion particles of the cationic vinyl acetate copolymer emulsion have a 50% diameter on a volume basis of from 0.1 m to 5 m. With this, the charge potential and pulling resistance of the quartz glass fiber can be kept within ranges of from +1.5 kV to 1.0 kV and from 0.1 cN to 50 cN, respectively. As a result, a quartz glass cloth with a small amount of fluff can be obtained.

(14) As a method of allowing the sizing agent for quartz glass fibers of the present invention to adhere to the quartz glass fibers, a known method may be adopted. Examples of such method include an immersion method, a method involving using a roller-type or belt-type applicator, and a spray method.

(15) A quartz glass cloth of the present invention preferably includes a glass yarn of the present invention, and is more preferably formed only of the glass yarn of the present invention, because the charge potential and pulling resistance of the glass yarn can be kept within ranges of from +1.5 kV to 1.0 kV and from 0.1 cN to 50 cN, respectively, with the result that the fluff can be effectively suppressed.

(16) The weave construction, weave density, and the like of the quartz glass cloth of the present invention are not particularly limited, but examples of the weave construction include a plain weave, a satin weave, a basket weave, and a twill weave. In addition, the weave density is, for example, from 10 yarns/25 mm to 1.50 yarns/25 mm.

(17) A weaving method for the quartz glass cloth of the present invention is not particularly limited, but examples of the method include a method involving using an air jet loom, a method involving using a water jet loom, a method involving using a rapier loom, and a method involving using a shuttle loom. Of those, a method involving using an air jet loom is suitable from the viewpoints of productivity and the dimensional stability of the glass cloth.

(18) The quartz glass cloth of the present invention may be subjected to washing with water, desizing through heating, or opening treatment, as required.

EXAMPLES

(19) The present invention is hereinafter described in more detail with Examples, but it is needless to say that Examples are only illustrative and not intended to be interpreted in a limited way.

(20) Measurement and evaluation in the following Examples, Comparative Examples, and Reference Example were performed by the following methods.

(21) 1. Weight Average Molecular Weight of Vinyl Acetate Copolymer

(22) A vinyl acetate copolymer was dissolved in tetrahydrofuran, and a soluble component was collected. Next, the weight average molecular weight of the soluble component in terms of polystyrene was measured with a size exclusion chromatography Shodex GPC-104 manufactured by Showa Denko K.K.

(23) 2. 50% Diameter on Volume Basis (D50) of Emulsion Particles of Vinyl Acetate Copolymer Emulsion

(24) The 50% diameter on a volume basis of emulsion particles of a vinyl acetate copolymer emulsion was measured with a laser diffraction/scattering particle size distribution analyzer LA-950V2 manufactured by Horiba, Ltd. The refractive indices of a vinyl acetate copolymer and water serving as a solvent were set to 1.460 and 1.333, respectively. The 50% diameter on a volume basis refers to a 50% cumulative particle diameter in a particle diameter distribution on a volume basis represented as a cumulative distribution.

(25) 3. Charge Potential of Glass Yarn

(26) An electrostatic measuring instrument STATIRON DX-01 manufactured by Shishido Electrostatic, Ltd. was placed at a distance of 5 cm from an outermost glass yarn wound around a bobbin, and the charge potential of the glass yarn was continuously measured while the glass yarn was jetted at an air pressure of 0.1 MPa. The measurement time was set to 1 minute, and an average charge potential was calculated.

(27) 4. Pulling Resistance of Glass Yarn (Slip Property)

(28) In a device as illustrated in FIG. 1, a glass yarn 1 was pulled from a bobbin at a winding speed of 20 m/min with a winder 4, and the pulling resistance (slip property) of the glass yarn was measured with an online tension meter 3 while a load was applied to the glass yarn 1 with tension washers 2. Four tension washers each having a weight of 3.5 g were used. The measurement time was set to 1 minute, and an average pulling resistance was calculated.

(29) 5. Thickness of Glass Cloth

(30) The thickness of the glass cloth was measured by a method described in the JIS R3420 201.3 7.10.1A method.

(31) 6. Fluff Number of Glass Cloth

(32) Five areas of 3 mm square were visually observed with an optical microscope while sidelight was radiated to the glass cloth, and the number of bright points was counted. The total number of bright points was adopted as the fluff number, and the case where the fluff number was five or less was regarded as acceptable.

Example 1

(33) A sizing agent for quartz glass fibers containing: 0.5 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 100,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 0.6 m; 1.25 wt % of hydroxypropyl ether starch serving as first starch; 1.25 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.5 wt % of beef tallow serving as a lubricant, 0.11 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.25 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.05 wt % of octyldimethylethyl ammonium ethylsulfate serving as an antistatic agent, 0.1 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared.

(34) A quartz glass material was loaded in burner flame, and the above-mentioned sizing agent for quartz glass fibers was applied thereonto while the material was extended. Thus, a quartz glass strand formed of 50 quartz glass filaments each having a diameter of 3.5 m was produced. Next, the resultant quartz glass strand was twisted 0.2 times per 25 mm, to produce a quartz glass yarn. The quartz glass yarn was used for the measurement of the charge potential and pulling resistance of a quartz glass yarn.

(35) The resultant quartz glass yarn was set to an air jet loom, and a plain weave quartz glass cloth having a warp density of 95 yarns/25 mm and a weft density of 95 yarns/25 mm was obtained through weaving. The quartz glass cloth was used for the measurement of the thickness and fluff number of a quartz glass cloth. The results are shown in Table 1.

Example 2

(36) A sizing agent for quartz glass fibers containing: 0.5 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 6,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 0.4 m; 1.25 wt % of hydroxypropyl ether starch serving as first starch; 1.25 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.5 wt % of beef tallow serving as a lubricant, 0.11 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.25 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.05 wt % of octyldimethylethyl ammonium ethylsulfate serving as an antistatic agent, 0.1 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. A quartz glass cloth was obtained in the same manner as in Example 1 except for the foregoing. The results are shown in Table 1.

Example 3

(37) A sizing agent for quartz glass fibers containing: 1 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 350,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 1 m; 1.45 wt % of hydroxypropyl ether starch serving as first starch; 1.05 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.5 wt % of sesame oil serving as a lubricant, 0.11 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.25 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.29 wt % of stearyltrimethylammonium chloride serving as an antistatic agent, 0.1 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared.

(38) A quartz glass material was loaded in burner flame, and the above-mentioned sizing agent for quartz glass fibers was applied thereonto while the material was extended. Thus, a quartz glass strand formed of 50 quartz glass filaments each having a diameter of 4 m was produced. Next, the resultant quartz glass strand was twisted 0.2 times per 25 mm, to produce a quartz glass yarn. The quartz glass yarn was used for the measurement of the charge potential and pulling resistance of a quartz glass yarn.

(39) The resultant quartz glass yarn was set to an air jet loom, and a plain weave quartz glass cloth having a warp density of 95 yarns/25 mm and a weft density of 95 yarns/25 mm was obtained through weaving. The quartz glass cloth was used for the measurement of the thickness and fluff number of a quartz glass cloth. The results are shown in Table 1.

Example 4

(40) A sizing agent for quartz glass fibers containing: 1 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 10,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 0.2 m; 1.45 wt % of hydroxypropyl ether starch serving as first starch; 1.05 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.5 wt % of sesame oil serving as a lubricant, 0.11 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.25 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.29 wt % of stearyltrimethylammonium chloride serving as an antistatic agent, 0.1 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. A quartz glass cloth was obtained in the same manner as in Example 3 except for the foregoing. The results are shown in Table 2.

Example 5

(41) A sizing agent for quartz glass fibers containing: 1 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 200,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 2 m; 1.45 wt % of hydroxypropyl ether starch serving as first starch; 1.05 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.5 wt % of sesame oil serving as a lubricant, 0.11 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.25 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.1 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. An antistatic agent was not added to the sizing agent for quartz glass fibers. A quartz glass cloth was obtained in the same manner as in Example 3 except for the foregoing. The results are shown in Table 2.

Example 6

(42) A sizing agent for quartz glass fibers containing: 1 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 470,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 4 m; 1.5 wt % of hydroxypropyl ether starch serving as first starch; 1.5 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.6 wt % of beef tallow serving as a lubricant, 0.14 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.3 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.34 wt % of distearyldimethylammonium chloride serving as an antistatic agent, 0.12 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared.

(43) A quartz glass material was loaded in burner flame, and the above-mentioned sizing agent for quartz glass fibers was applied thereonto while the material was extended. Thus, a quartz glass strand formed of 200 quartz glass filaments each having a diameter of 7 m was produced. Next, the resultant quartz glass strand was twisted 0.6 times per 25 mm, to produce a quartz glass yarn. The quartz glass yarn was used for the measurement of the charge potential and pulling resistance of a quartz glass yarn.

(44) The resultant quartz glass yarn was set to an air jet loom, and a plain weave quartz glass cloth having a warp density of 65 yarns/25 mm and a weft density of 65 yarns/25 mm was obtained through weaving. The quartz glass cloth was used for the measurement of the thickness and fluff number of a quartz glass cloth. The results are shown in Table 2.

Example 7

(45) A sizing agent for quartz glass fibers containing: 1 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 60,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 0.5 m; 1.5 wt % of hydroxypropyl ether starch serving as first starch; 1.5 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.6 wt % of beef tallow serving as a lubricant, 0.14 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.3 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.34 wt % of distearyldimethylammonium chloride serving as an antistatic agent, 0.12 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. A quartz glass cloth was obtained in the same manner as in Example 6 except for the foregoing. The results are shown in Table 3.

Example 8

(46) A sizing agent for quartz glass fibers containing: 1 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 60,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 0.5 m; 1.5 wt % of hydroxypropyl ether starch serving as first starch; 1.5 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.6 wt % of beef tallow serving as a lubricant, 0.14 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.3 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.12 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. An antistatic agent was not added to the sizing agent for quartz glass fibers. A quartz glass cloth was obtained in the same manner as in Example 6 except for the foregoing. The results are shown in Table 3.

Example 9

(47) A sizing agent for quartz glass fibers containing: 0.5 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 150,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 0.2 m; 1.5 wt % of hydroxypropyl ether starch serving as first starch; 1.5 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.6 wt % of beef tallow serving as a lubricant, 0.14 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.3 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.34 wt % of distearyldimethylammonium chloride serving as an antistatic agent, 0.12 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. A quartz glass cloth was obtained in the same manner as in Example 6 except for the foregoing. The results are shown in Table 3.

Comparative Example 1

(48) A sizing agent for quartz glass fibers containing: 1 wt % of a non-ionic vinyl acetate copolymer emulsion in terms of a solid content in which a non-ionic vinyl acetate copolymer had a weight average molecular weight of 350,000 and emulsion particles of the non-ionic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 1 m; 1.45 wt % of hydroxypropyl ether starch serving as first starch; 1.05 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.5 wt % of sesame oil serving as a lubricant, 0.11 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.25 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.29 wt % of stearyltrimethylammonium chloride serving as an antistatic agent, 0.1 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. A quartz glass cloth was obtained in the same manner as in Example 3 except for the foregoing. The results are shown in Table 4.

Comparative Example 2

(49) A sizing agent for quartz glass fibers containing: 1 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 3,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 1 m; 1.45 wt % of hydroxypropyl ether starch serving as first starch; 1.05 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.5 wt % of sesame oil serving as a lubricant, 0.11 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.25 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.29 wt % of stearyltrimethylammonium chloride serving as an antistatic agent, 0.1 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. A quartz glass cloth was obtained in the same manner as in Example 3 except for the foregoing. The results are shown in Table 4.

Comparative Example 3

(50) A sizing agent for quartz glass fibers containing: 1 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 600,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 1 m; 1.45 wt % of hydroxypropyl ether starch serving as first starch; 1.05 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.5 wt % of sesame oil serving as a lubricant, 0.11 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.25 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.29 wt % of stearyltrimethylammonium chloride serving as an antistatic agent, 0.1 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. A quartz glass cloth was obtained in the same manner as in Example 3 except for the foregoing. The results are shown in Table 4.

Comparative Example 4

(51) A sizing agent for quartz glass fibers containing: 1 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 350,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 0.05 m; 1.45 wt % of hydroxypropyl ether starch serving as first starch; 1.05 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.5 wt % of sesame oil serving as a lubricant, 0.11 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.25 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.29 wt % of stearyltrimethylammonium chloride serving as an antistatic agent, 0.1 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. A quartz glass cloth was obtained in the same manner as in Example 3 except for the foregoing. The results are shown in Table 5.

Comparative Example 5

(52) A sizing agent for quartz glass fibers containing: 1 wt % of a cationic vinyl acetate copolymer emulsion in terms of a solid content in which a cationic vinyl acetate copolymer had a weight average molecular weight of 350,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of 10 m; 1.45 wt % of hydroxypropyl ether starch serving as first starch; 1.05 wt % of hydroxypropyl crosslinked starch serving as second starch; and as other components, 0.5 wt % of sesame oil serving as a lubricant, 0.11 wt % of a polyoxyethylene alkyl ether serving as an emulsifier, 0.25 wt % of an acetate of a condensation product of polyethylene pentamine with stearic acid serving as a cationic softener, 0.29 wt % of stearyltrimethylammonium chloride serving as an antistatic agent, 0.1 wt % of N-2-(aminoethyl)-3-aminopropylmethoxysilane serving as a silane coupling agent, and 0.01 wt % of an antiseptic, with the balance being water, was prepared. A quartz glass cloth was obtained in the same manner as in Example 3 except for the foregoing. The results are shown in Table 5.

Reference Example

(53) The sizing agent for quartz glass fibers of Comparative Example 1 was prepared. An E-glass cloth was obtained in the same manner as in Example 3 except that the sizing agent was applied onto an E-glass yarn formed of E-glass filaments each having a diameter of 4 m. The results are shown in Table 5.

(54) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Kind of vinyl acetate copolymer Cationic Cationic Cationic Weight average molecular weight 100,000 6,000 350,000 of vinyl acetate copolymer 50% diameter on volume basis of m 0.6 0.4 1 emulsion particles of vinyl acetate copolymer emulsion Diameter of glass filament m 3.5 3.5 4 Number of glass filaments filaments 50 50 50 Charge potential of glass yarn kV +0.4 +0.5 +0.2 Pulling resistance of glass yarn cN 13 18 15 Thickness of glass cloth mm 0.011 0.011 0.014 Fluff number of glass cloth pieces 0 2 0 Total evaluation

(55) TABLE-US-00002 TABLE 2 Example 4 Example 5 Example 6 Kind of vinyl acetate copolymer Cationic Cationic Cationic Weight average molecular weight 10,000 200,000 470,000 of vinyl acetate copolymer 50% diameter on volume basis of m 0.2 2 4 emulsion particles of vinyl acetate copolymer emulsion Diameter of glass filament m 4 4 7 Number of glass filaments filaments 50 50 200 Charge potential of glass yarn kV +0.2 0.4 0.5 Pulling resistance of glass yarn cN 22 13 20 Thickness of glass cloth mm 0.014 0.014 0.095 Fluff number of glass cloth pieces 2 1 5 Total evaluation

(56) TABLE-US-00003 TABLE 3 Example 7 Example 8 Example 9 Kind of vinyl acetate copolymer Cationic Cationic Cationic Weight average molecular weight 60,000 60,000 150,000 of vinyl acetate copolymer 50% diameter on volume basis of m 0.5 0.5 0.2 emulsion particles of vinyl acetate copolymer emulsion Diameter of glass filament m 7 7 7 Number of glass filaments filaments 200 200 200 Charge potential of glass yarn kV +0.2 0.4 +0.1 Pulling resistance of glass yarn cN 14 18 11 Thickness of glass cloth mm 0.095 0.095 0.095 Fluff number of glass cloth pieces 2 4 1 Total evaluation

(57) TABLE-US-00004 TABLE 4 Comparative Comparative Comparative Example 1 Example 2 Example 3 Kind of vinyl acetate copolymer Non-ionic Cationic Cationic Weight average molecular weight 350,000 3,000 600,000 of vinyl acetate copolymer 50% diameter on volume basis of m 1 1 1 emulsion particles of vinyl acetate copolymer emulsion Diameter of glass filament m 4 4 4 Number of glass filaments filaments 50 50 50 Charge potential of glass yarn kV 5.3 0.9 0.1 Pulling resistance of glass yarn cN 65 37 18 Thickness of glass cloth mm 0.014 0.014 0.014 Fluff number of glass cloth pieces 25 17 13 Total evaluation x x x

(58) TABLE-US-00005 TABLE 5 Comparative Comparative Reference Example 4 Example 5 Example Kind of vinyl acetate copolymer Cationic Cationic Non-ionic Weight average molecular weight 350,000 350,000 350,000 of vinyl acetate copolymer 50% diameter on volume basis of m 0.05 10 1 emulsion particles of vinyl acetate copolymer emulsion Diameter of glass filament m 4 4 4 Number of glass filaments filaments 50 50 50 Charge potential of glass yarn kV 4.9 5.8 0.2 Pulling resistance of glass yarn cN 69 81 14 Thickness of glass cloth mm 0.014 0.014 0.014 Fluff number of glass cloth pieces 19 22 2 Total evaluation x x

(59) The charge potential and pulling resistance of each of the quartz glass yarns obtained in Examples 1 to 9 fell within ranges of from +1.5 kV to 1.0 kV and from 0.1 cN to 50 cN, respectively, because the quartz glass yarns each had applied thereonto the sizing agent for quartz glass fibers containing: a cationic vinyl acetate copolymer emulsion in which a cationic vinyl acetate copolymer had a weight average molecular weight of from 5,000 to 500,000 and emulsion particles of the cationic vinyl acetate copolymer emulsion had a 50% diameter on a volume basis of from 0.1 m to 5 m; and starch. In addition, in the quartz glass cloths obtained by weaving the quartz glass yarns, charging was sufficiently suppressed, and hence high-quality quartz glass cloths with an extremely small amount of fluff were able to be obtained.

(60) Meanwhile, the glass yarn having applied thereonto the sizing agent for quartz glass fibers of Comparative Example 1 using the non-ionic vinyl acetate copolymer emulsion was highly negatively charged, and hence a yarn bundling force lowered, with the result that a large amount of fluff was generated during the weaving. The sizing agent for quartz glass fibers of Comparative Example 2, in which the cationic vinyl acetate copolymer had a small weight average molecular weight, had a poor bonding force between the quartz glass filaments, and hence a bundling property lowered, with the result that a large amount of fluff was generated during the weaving. The sizing agent for quartz glass fibers of Comparative Example 3, in which the cationic vinyl acetate copolymer had a large weight average molecular weight, provided a hard yarn, and hence the glass filaments were broken particularly at an intersection portion of warp and weft of the quartz glass cloth, and the quartz glass cloth was partly broken. In the sizing agent for quartz glass fibers of Comparative Example 4, in which the emulsion particles of the cationic vinyl acetate copolymer emulsion had a small 50% diameter on a volume basis, it is considered that the emulsion particles were trapped in gaps of coexisting starch molecules, and an antistatic effect was not able to be exhibited sufficiently. Therefore, the generation of static electricity was not able to be suppressed during the weaving, with the result that a large amount of fluff was generated. The sizing agent for quartz glass fibers of Comparative Example 5, in which the emulsion particles of the cationic vinyl acetate copolymer emulsion had a large 50% diameter on a volume basis, was not able to be uniformly applied onto the glass fibers owing to low stability of the cationic vinyl acetate copolymer emulsion. Therefore, local unevenness of the sizing agent for quartz glass fibers occurred, and a sufficient antistatic effect was not able to be obtained. In Reference Example, in which the sizing agent for quartz glass fibers used in Comparative Example 1 was applied onto the E-glass yarn, the amount of fluff generated was small in spite of the use of the non-ionic vinyl acetate copolymer emulsion, because E-glass was less liable to be charged as compared to quartz glass.

(61) 1: yarn, 2: tension washers, 3: tension meter, 4: winder.