JPWO2016093212A1 - Glass composition for glass fiber, glass fiber and method for producing glass fiber - Google Patents

Abstract

Provided is an alkali-resistant glass composition for glass fibers, which has high productivity because the difference between the spinning temperature and the liquidus temperature of the glass is large, and is less susceptible to devitrification due to composition change. As a glass composition, it is the mass% of oxide conversion, SiO250-65%, Al2O30-5%, CaO0.3-10%, Na2O10-20%, K2O0.6-5%, TiO27.3-10% And ZrO 217 to 20%.

Description

  The present invention relates to a glass composition for glass fibers having excellent corrosion resistance. In particular, it relates to a glass composition for glass fiber that is suitable as a reinforcing material such as calcium silicate board and GRC (glass fiber reinforced concrete), and as a material that requires corrosion resistance such as a battery separator and an asbestos substitute, and has excellent productivity. It is.

Conventionally, as a reinforcing material of GRC, a SiO ₂ —ZrO ₂ —R ₂ O (R is Li, Na, K) -based ZrO ₂ -containing alkali-resistant glass fiber as described in Patent Document 1 has been used. Yes.

  This glass fiber is also used as a corrosion-resistant material such as a reinforcing material for a calcium silicate plate and a battery separator.

  GRC is a building that is molded into a plate shape by spraying a mixture of glass fiber cut to a predetermined length and cement, aggregate, admixture, water, etc. into the mold using a spray gun or the like. It is a structural material for use. Glass fibers used for GRC are required to have sufficient strength even in decades in concrete.

The glass fiber as described above, for example, is obtained by continuously molding and spinning molten glass using a noble metal bushing device to obtain a fiber shape. The bushing structure has a container shape for retaining molten glass, and a number of nozzles are arranged in the vertical direction at the bottom. Glass fiber is molded by drawing molten glass adjusted to a temperature in the vicinity of the spinning temperature (the temperature at which the viscosity of the glass is approximately 10 ³ dPa · s, also called the molding temperature) from the nozzle at the bottom of the bushing. .

Japanese Patent Publication No.49-40126 WO2014 / 065321

From the viewpoint of improving alkali resistance, as described in Patent Document 1, it is effective to contain a large amount of ZrO ₂ in the glass composition. However, if a large amount of ZrO ₂ is contained, the spinning temperature of the glass is reduced. It will be high. When the spinning temperature of glass is high, glass melting at a high temperature is required, so that the noble metal bushing device is severely damaged, and the replacement frequency increases, resulting in an increase in production cost. Further, when ZrO ₂ is contained in a large amount, the liquidus temperature rises and the difference between the spinning temperature and the liquidus temperature tends to be small. When the difference between the spinning temperature and the liquidus temperature is small, there is a problem that the glass tends to be devitrified at the nozzle at the bottom of the bushing and continuous production is difficult.

Patent Document 2 reduces the ZrO ₂ content and contains a certain amount of TiO ₂ and K ₂ O, thereby achieving a spinning temperature of 1280 ° C. or lower and a difference between the liquid phase temperature and the spinning temperature of 80 ° C. or higher. The glass composition made public. However, considering continuous production in a glass melting kiln, it is preferable that there is little change in devitrification (difference between liquidus temperature and spinning temperature) even if the glass composition changes somewhat. However, the glass composition disclosed in Patent Document 2 does not consider such a point.

  The present invention has been made in view of the above circumstances, and since the difference between the spinning temperature and the liquidus temperature of the glass is large, the productivity is good and the devitrification property is not easily changed by a composition change. The object is to provide a glass composition.

  As a result of intensive studies, the present inventors have found that the above problem can be solved by strictly defining the glass composition, and propose the present invention.

That is, glass composition for glass fiber of the present invention has a glass composition, in weight percent oxide _{equivalent, SiO 2 50~65%, Al 2} O 3 0~5%, CaO 0.3~10%, Na _It contains 10 to 20% ₂ O, 0.6 to 5% K ₂ O, 7.3 to 10% TiO ₂ , and 17 to 20% ZrO ₂ .

  By having the above-mentioned configuration, the glass composition for glass fiber is excellent in alkali resistance, has a glass spinning temperature and a liquidus temperature of 100 ° C. or higher, and devitrification hardly changes due to a composition change. Can do.

In the present invention, preferably contains 0 to 0.2% _Li 2 O in weight percent on the oxide basis.

In the present invention, Na ₂ O + K ₂ O is preferably 10 to 20%. Here, “Na ₂ O + K ₂ O” means the total content of Na ₂ O and K ₂ O.

  If the said structure is employ | adopted, the viscosity of glass can be reduced and the glass composition for glass fibers excellent in a meltability and a moldability can be obtained.

In the present invention, the spinning temperature is preferably 1280 ° C. or lower. In the present invention, the “spinning temperature” means a temperature at which the glass has a viscosity of 10 ³ dPa · s.

  By adopting the above configuration, fiberization can be performed at a low temperature, so that the service life of fiberization equipment such as bushings can be extended, and the production cost can be reduced.

  In the present invention, the difference between the spinning temperature and the liquidus temperature is preferably 105 ° C. or higher.

  If the said structure is employ | adopted, since spinning becomes easy, the glass composition for glass fibers excellent in productivity can be obtained effectively.

  In the present invention, when the specific gravity × 2 weight of glass classified to a particle size of 300 to 500 μm is immersed in 100 ml of 10 mass% NaOH aqueous solution at 80 ° C. for 16 hours, the weight reduction rate of the glass is 3% or less. Preferably there is.

  If the said structure is employ | adopted, it will become easy to obtain highly reliable glass fiber as a reinforcing material of composite materials, such as a calcium silicate board and GRC.

  In the present invention, when the specific gravity × 2 weight of glass classified to a particle size of 300 to 500 μm is immersed in 100 ml of 10 mass% HCl aqueous solution at 80 ° C. for 16 hours, the weight reduction rate of the glass is 3% or less. Preferably there is.

  If the said structure is employ | adopted, it will become easy to obtain highly reliable glass fiber as corrosion-resistant materials, such as a battery separator.

  The glass fiber of this invention consists of said glass composition for glass fibers, It is characterized by the above-mentioned.

Process for producing a glass fiber of the present invention has a glass composition, in weight percent oxide _{equivalent, SiO 2 50~65%, Al 2} O 3 0~5%, CaO 0.3~10%, Na 2 O 10 _{~20%, K 2 O 0.6~5%} , TiO 2 7.3~10%, the raw batch which is prepared to have a glass containing ZrO 2 17 to 20% was melted in a glass melting furnace, the molten Glass is continuously drawn from the bushing and formed into a fiber shape.

  Hereinafter, the glass composition for glass fiber of the embodiment of the present invention will be described. First, the effect | action of the component which comprises the glass of this invention and the reason which prescribed | regulated the content as mentioned above are demonstrated. In addition, in description of the containing range of each component,% display points out the mass%.

SiO ₂ is a main component that forms a glass skeleton structure. Moreover, it is a component which improves the acid resistance of glass. The content of SiO ₂ is 50 to 65%, preferably 55 to 60%, more preferably 57 to 60%. When the content of SiO ₂ is too small, the mechanical strength of the glass tends to decrease. Moreover, the acid resistance of glass falls. When the content of SiO ₂ is too large, the energy increases required to melt the glass viscosity of the glass becomes high. Further, the noble metal bushing is severely damaged, the replacement frequency is increased, and the production cost is increased. Moreover, the alkali resistance of glass falls.

Al ₂ O ₃ is a component that increases the chemical durability and mechanical strength of glass. On the other hand, Al ₂ O ₃ is also a component that increases the viscosity of the glass. The content of Al ₂ O ₃ is 0 to 5%, preferably 0 to 3%, more preferably 0 to 1%. Al viscosity of the glass when the content is too large the ₂ O ₃ becomes energy increases required for melting the glass is high.

  CaO is a component that lowers the viscosity of the glass. The content of CaO is 0.3 to 10%, preferably 0.3 to 5%, more preferably 0.3 to 4%, and still more preferably 0.3 to 3%. If the content of CaO is too small, it is difficult to obtain the above effect. If the content of CaO is too large, crystals composed of Zr, Si, Na, and Ca are likely to precipitate in the glass, the liquidus temperature of the glass is increased, and the difference between the spinning temperature and the liquidus temperature is reduced, resulting in productivity. Decreases.

Na ₂ O and K ₂ O, which are alkali metal oxides, are components that lower the viscosity of the glass and increase the meltability and moldability. On the other hand, the alkali metal oxide is a component that reduces the water resistance of the glass if contained in a large amount. The total content of Na ₂ O and K ₂ O (Na ₂ O + K ₂ O) is 10 to 20%, preferably 10 to 18%, more preferably 12 to 18%, still more preferably 16.1 to 17%. It is. When Na 2 O _{+ K} 2 the amount of _O is too small, the energy increases required to melt the glass viscosity of the glass becomes high. Further, the noble metal bushing is severely damaged, the replacement frequency is increased, and the production cost is increased. When Na ₂ O + _{K 2} the amount of O is too large, the water resistance of the glass decreases.

Na ₂ O is a component that increases the meltability and moldability of glass by reducing the viscosity of the glass. The content of Na ₂ O is 10 to 20%, preferably 10 to 18%, more preferably 12 to 18%, and most preferably 12 to 15.6%. When the Na 2 _O content is too small, the energy increases required to melt the glass viscosity of the glass becomes high. Further, the noble metal bushing is severely damaged, the replacement frequency is increased, and the production cost is increased. When the content of Na 2 _O is too large high liquidus temperature of the glass, the difference between the spinning temperature and the liquidus temperature becomes productivity is reduced smaller. Moreover, the water resistance of the glass decreases.

K ₂ O is a component that improves the meltability and moldability of the glass by reducing the viscosity of the glass. In addition, it has a function of lowering the liquidus temperature, and has a great effect of reducing fluctuations in devitrification due to composition changes. The content of K ₂ O is 0.6 to 5%, preferably 0.6 to 3%, more preferably 0.6 to 2%, still more preferably 0.8 to 2%, and most preferably 1.0 to 2.0%. If the content of K ₂ O is too small, devitrification changes rapidly due to a composition change, which is not preferable. When the content of K 2 _O is too large water resistance of glass decreases. In addition, the batch raw material easily absorbs moisture, and an aggregate (so-called “dama”) of the raw material powder is easily formed. If aggregates of the raw material powder are formed, the solubility of the batch raw material deteriorates, and undissolved zirconia tends to remain in the product glass, which is not preferable.

In addition to Na ₂ O and _{K 2} O, the glass composition for glass fiber of the present invention may contain Li ₂ O. Li ₂ O is a component that significantly lowers the liquidus temperature by adding a small amount, increases the difference between the spinning temperature and the liquidus temperature, and improves the productivity. The content of Li ₂ O is preferably 0 to 0.2%. However, since Li ₂ O has a high raw material cost, if the content of Li ₂ O is too large, the manufacturing cost increases. Furthermore, with the recent increase in demand for lithium batteries, there is a growing concern that the supply of lithium raw materials will be short-circuited. Therefore Li 2 _O lithium material can not be secured required for production and the content is too much, there is a concern that is necessary measures such as reducing the production. Thus from the point of view of cost and supply, it is preferred not to contain Li 2 _O. Here, “not containing Li ₂ O” means that Li ₂ O is not actively contained as a glass composition, and does not exclude inevitable impurities. More specifically, it means that the content including impurities is 0.01% by mass or less. Employing the above configuration makes it easy to avoid problems such as anxiety of raw material supply and soaring raw material costs.

TiO ₂ is a component that improves the water resistance and alkali resistance of glass, lowers the spinning temperature, and greatly reduces the liquidus temperature. The content of TiO ₂ is 7.3 to 10%, preferably 7.3 to 8.5%, more preferably 7.3 to 8.0%. When the content of TiO ₂ is too small, water resistance and alkali resistance of the glass decreases. In addition, the spinning temperature rises and the production cost increases. When the content of TiO ₂ is too large, the liquidus temperature becomes easier crystals precipitated comprising TiO ₂ rises dramatically in the glass. As a result, the difference between the spinning temperature and the liquidus temperature is reduced and the productivity is lowered.

ZrO ₂ is a component that improves the alkali resistance, acid resistance, and water resistance of the glass. The content of ZrO ₂ is 17 to 20%, preferably 17.2 to 20%, more preferably 17.2 to 19.5%, still more preferably 17.2 to 18.5%, and most preferably 17.5. ~ 18.0%. When the content of ZrO ₂ is too small, the alkali resistance is decreased, can not be realized and the durability required for GRC. When the content of ZrO ₂ is too large, the liquidus temperature of the glass becomes high, the difference between the spinning temperature and the liquidus temperature becomes small, and the productivity is lowered.

In recent years, with the increase in demand for lithium batteries, there is a growing concern that the supply of lithium raw materials will be short-circuited. The demand for lithium batteries is expected to increase due to the popularization of electric vehicles and the increase in renewable energy. Furthermore, Li ₂ O has a high raw material cost. Therefore, it is preferable that the glass composition for glass fiber of the present invention does not contain Li ₂ O in terms of composition design.

The glass composition for glass fiber of the present invention may comprise the above-mentioned component _{(SiO 2, Al 2 O 3} , CaO, Na 2 O, K 2 O, TiO 2 and ZrO ₂₎ other than the component. However, it is desirable to adjust the composition so that the total content of the above components is 98% or more, particularly 99% or more. The reason for this is that when the total amount of these components is less than 98%, the alkali resistance, acid resistance, and water resistance are lowered due to unintentional mixing of different components, and the product characteristics are lowered, and the spinning temperature and liquid phase are decreased. Inconveniences such as a decrease in temperature and a decrease in productivity are likely to occur.

As components other than the above-described components, for example, trace components such as H ₂ , CO ₂ , CO, H ₂ O, He, Ne, Ar, and N ₂ may be contained up to 0.1%. Moreover, you may add noble metal elements, such as Pt, Rh, Au, to 500 ppm in glass.

Furthermore, in order to improve alkali resistance, acid resistance, water resistance and liquidus temperature, B ₂ O ₃ , MgO, SrO, BaO, ZnO, Fe ₂ O ₃ , P ₂ O ₅ , Cr ₂ O ₃ , Sb ₂ O ₃ , SO ₃ , MnO, SnO ₂ , CeO ₂ , Cl ₂ , La ₂ O ₃ , WO ₃ , Nb ₂ O ₅ , Y ₂ O _{3 and the} like may be contained up to 2% in total.

  The glass composition for glass fiber according to the present invention has a reduced weight of glass when immersed in 100 ml of a 10% by weight NaOH aqueous solution at 80 ° C. for 16 hours with a glass having a specific gravity of 2 weights classified to a particle size of 300 to 500 μm. The rate is preferably 3% or less, particularly 1% or less, and more preferably 0.8% or less. When the weight reduction rate of the glass by this alkali resistance test is higher than 3%, the alkali resistance of the glass is lowered, and the reliability as a reinforcing material of a composite material such as a calcium silicate plate or GRC is lowered.

  The glass composition for glass fiber according to the present invention has a reduced weight of glass when a specific gravity × 2 weight of glass classified to a particle size of 300 to 500 μm is immersed in 100 ml of 10 mass% HCl aqueous solution at 80 ° C. for 16 hours. The rate is preferably 3% or less, particularly 1% or less, and more preferably 0.5% or less. When the weight reduction rate of the glass by this acid resistance test is higher than 3%, the acid resistance of the glass is lowered, and the reliability as a corrosion resistant material such as a battery separator is lowered.

  The glass composition for glass fiber of the present invention preferably has an alkali elution amount of 0.40 mg or less, particularly 0.35 mg or less, more preferably 0.30 mg or less. When the amount of alkali elution is larger than 0.40 mg, the alkali component is eluted from the glass during the autoclave treatment, and the glass tends to deteriorate.

  The glass composition for glass fibers of the present invention preferably has a spinning temperature of 1280 ° C. or lower, particularly 1260 ° C. or lower. When the spinning temperature is higher than 1280 ° C., it is necessary to perform spinning at a high temperature, so that the noble metal bushing is severely damaged, the replacement frequency is increased, and the production cost is increased.

  In the glass composition for glass fibers of the present invention, the difference between the spinning temperature and the liquidus temperature is preferably 100 ° C. or higher, particularly 105 ° C. or higher. If the difference between the spinning temperature and the liquidus temperature is small, the productivity decreases.

The glass composition for glass fiber of the present invention is preferably 23 ° C. or lower when the devitrification change amount with respect to composition variation obtained by the following evaluation is evaluated. First, for the composition to be evaluated, the difference (ΔT) between the spinning temperature and the liquidus temperature is determined. Next, for the composition in which the content of SiO ₂ , Al ₂ O ₃ , Na ₂ O and ZrO ₂ was fixed to a constant value and 0.3 mass% of CaO was replaced with K ₂ O, the difference between the spinning temperature and the liquidus temperature The absolute value (| ΔT−ΔTck |) of the amount of change in is obtained. Similarly, the absolute value (| ΔT−ΔTkt |) of the difference in the difference between the spinning temperature and the liquid phase temperature before and after substitution when 0.3% by mass of K ₂ O is substituted with TiO ₂ , 0.3 of CaO The absolute value (| ΔT−ΔTct |) of the change amount of the difference between the spinning temperature and the liquid phase temperature before and after the substitution when the mass% is substituted with TiO ₂ is obtained. Among the | ΔT−ΔTck |, | ΔT−ΔTkt | and | ΔT−ΔTct | determined in this way, the value having the largest amount of change is adopted, and this value is referred to as “amount of change in devitrification with respect to composition variation”. Call it. If this value is too large, it becomes difficult to perform stable spinning in actual production.

  Next, the method for producing the glass fiber of the present invention will be described by taking the direct melt method (DM method) as an example. The present invention is not limited to the following method. For example, a so-called indirect molding method (MM method: marble melt method) in which a glass fiber material molded into a marble shape is remelted and spun using a bushing apparatus is employed. You can also. This method is suitable for small-lot, multi-product production.

First, in% by weight in terms of _{oxide, SiO 2 50~65%, Al 2} O 3 0~5%, CaO 0.3~10%, Na 2 O 10~20%, K 2 O 0.6~5% , TiO ₂ 7.3 to 10%, ZrO ₂ 17 to 20% to prepare a glass raw material so as to contain. Glass cullet may be used for a part or all of the glass raw material. The reason why the content of each component is as described above is as described above, and the description is omitted here.

  Subsequently, the prepared glass raw material batch is put into a glass melting furnace, vitrified, melted and homogenized. The melting temperature is preferably about 1400 to 1600 ° C.

  Subsequently, molten glass is spun and formed into glass fibers. More specifically, molten glass is supplied to the bushing. The molten glass supplied to the bushing is continuously drawn out in filament form from a number of bushing nozzles provided on the bottom surface. Various processing agents are applied to the monofilaments drawn in this way, and glass fibers are obtained by focusing each monofilament.

  The glass fiber of the present invention thus formed is processed into chopped strands, yarns, rovings, etc. and used for various applications.

  The chopped strand is obtained by cutting glass fibers (strands) obtained by focusing glass monofilaments into a predetermined length. A yarn is a twisted strand. Roving is a combination of a plurality of strands wound in a cylindrical shape.

Hereinafter, based on an Example, this invention is demonstrated in detail.
Table 1 shows examples (samples Nos. 1 to 7) of the present invention, and Table 2 shows comparative examples (samples Nos. 8 to 10).

  Each sample in the table was prepared as follows.

First, various glass raw materials, such as a natural raw material and a chemical raw material, were weighed and mixed so that it might become the glass composition in a table | surface, and the glass batch was produced. Next, after putting this glass batch into a crucible made of platinum rhodium alloy, it was heated in an indirect heating electric furnace at 1550 ° C. for 5 hours to obtain a molten glass. In order to obtain a homogeneous molten glass, the molten glass was stirred a plurality of times using a heat-resistant stirring rod during heating. Subsequently, the molten glass obtained was poured into a refractory mold to form a plate-like glass, and then annealed in a slow cooling furnace (heated at a temperature 30 to 50 ° C. higher than the temperature at 10 ¹³ dPa · s for 30 minutes) Then, the temperature range from the annealing point to the strain point was lowered at 1 ° C./min). About each obtained sample, alkali resistance, acid resistance, the amount of alkali elution, spinning temperature, and liquidus temperature were measured.

  The alkali resistance was measured as follows. First, the above plate glass sample is pulverized, a glass having a particle size of 300 to 500 μm is precisely weighed by a specific gravity × 2 weight, and subsequently immersed in 100 ml of 10% by mass NaOH solution at 80 ° C. for 16 hours. Shake on the conditions. Thereafter, the weight reduction rate of the glass sample was measured. The smaller this value, the better the alkali resistance.

  The acid resistance was measured as follows. First, the above plate glass sample is pulverized, a glass having a particle size of 300 to 500 μm is precisely weighed by a specific gravity × 2 weight, and subsequently immersed in 100 ml of 10% by mass HCl solution at 80 ° C. for 16 hours. Shake on the conditions. Thereafter, the weight reduction rate of the glass sample was measured. The smaller this value, the better the acid resistance.

  The alkali elution amount was measured by a method based on JIS R3502 (1995). The smaller this value, the better the water resistance.

The spinning temperature was measured as follows. First, a plate-like glass sample was crushed to an appropriate size and put into an alumina crucible so as to prevent air bubbles from being involved. Subsequently, the alumina crucible was heated to bring the sample into a molten state, and the viscosity of the glass at a plurality of temperatures was determined by a platinum ball pulling method. Thereafter, a viscosity curve was created from the obtained plurality of measured values, and the temperature at which 10 ³ dPa · s was obtained was calculated by interpolation.

  The liquid phase temperature was measured as follows. First, a plate-like glass sample was pulverized and filled in a fire-resistant container with an appropriate bulk density in a state adjusted to have a particle size in the range of 300 to 500 μm. Subsequently, the refractory container was placed in an indirect heating type temperature gradient furnace having a maximum temperature set to 1250 ° C. and left to stand for 16 hours in an air atmosphere. Then, the test body was taken out from the temperature gradient furnace together with the refractory container, cooled to room temperature, and then the liquid phase temperature was specified by a polarizing microscope.

  The difference between the spinning temperature and the liquidus temperature was calculated from both values.

The amount of change in devitrification with respect to composition variation was evaluated as follows. First _{SiO 2, Al 2 O 3,} Na 2 O, the content of ZrO ₂ is fixed to a constant value, and the measurement sample a of 0.3 mass% was replaced by _{K 2} O of CaO, the _{K 2} O 0. 3% by weight and the measurement sample b was replaced by TiO _2, were respectively prepared measurement sample c was substituted for 0.3 weight% of CaO in TiO _2. Next, for each measurement sample, the absolute value (° C.) of the amount of change in the difference between the spinning temperature and the liquid phase temperature before and after substitution was determined. Of the absolute values thus determined, the largest value was defined as the amount of change in devitrification with respect to composition variation.

  GRC durability was evaluated as follows. First, using a spray gun, a mixture of glass fiber and mortar was sprayed into a wooden frame and formed into a plate shape. The sample on the 14th day of the material age was immersed in warm water at 70 ° C., a three-point bending test was performed on the sample on the 10th day after the immersion, and the bending strength (Modulus of rupture) was measured. The evaluation of the bending strength was conducted using sample No. The case where it became 10 or more was marked with ◯, and the others were marked with ×.

  The glass fiber produced using the glass composition for glass fiber of the present invention is suitable as a corrosion-resistant material such as a reinforcing material for a calcium silicate plate and a battery separator.

Claims (10)

As a glass composition, in weight percent oxide _{equivalent, SiO 2 50~65%, Al 2} O 3 0~5%, CaO 0.3~10%, Na 2 O 10~20%, K 2 O 0.6 _~5%, TiO 2 _7.3~10%, glass fiber glass composition characterized by containing ZrO 2 17 to 20%.
The glass composition for glass fibers according to claim 1, further comprising 0 to 0.2% of Li ₂ O in terms of mass% in terms of oxide. Na ₂ O + _{K 2} O is a glass fiber glass composition according to claim 1 or 2, characterized in that 10 to 20%.   The glass composition for glass fibers according to any one of claims 1 to 3, wherein the spinning temperature is 1280 ° C or lower.   The glass composition for glass fibers according to any one of claims 1 to 4, wherein the difference between the spinning temperature and the liquidus temperature is 105 ° C or higher.   The glass composition for glass fibers according to any one of claims 1 to 5, wherein an alkali elution amount according to JIS R3502 is 0.40 mg or less.
The glass has a weight reduction rate of 3% or less when immersed in 100 ml of a 10% by weight NaOH aqueous solution at 80 ° C. for 16 hours in a glass having a specific gravity of 2 weight classified to a particle size of 300 to 500 μm. The glass composition for glass fibers according to any one of claims 1 to 6.
The glass has a weight reduction rate of 3% or less when immersed in 100 ml of a 10% by weight HCl aqueous solution at 80 ° C. for 16 hours in a glass having a specific gravity of 2 weight classified to a particle size of 300 to 500 μm. The glass composition for glass fibers according to any one of claims 1 to 7.   A glass fiber comprising the glass composition for glass fiber according to any one of claims 1 to 8. As a glass composition, in weight percent oxide _{equivalent, SiO 2 50~65%, Al 2} O 3 0~5%, CaO 0.3~10%, Na 2 O 10~20%, K 2 O 0.6 ~ 5%, TiO ₂ 7.3 to 10%, ZrO ₂ 17 to 20% Glass raw material batch was melted in a glass melting furnace, and the molten glass was drawn continuously from the bushing to form a fiber A method for producing glass fiber, characterized in that it is formed into a glass.