GLASS FIBER, GLASS FIBER MANUFACTURING METHOD, AND GLASS

Abstract

To provide a glass fiber having a low spinning temperature and a low liquidus temperature, a large difference between the liquidus temperature and the spinning temperature, and excellent alkali resistance, and a manufacturing method therefor. A glass fiber contains, as a glass composition, in mass % in terms of oxide, from 50% to 70% of SiO.sub.2, from 10% to 20% of Na.sub.2O, from 0% to 5.5% of TiO.sub.2, and from 10% to 30% of ZrO.sub.2.

Claims

1: A glass fiber comprising, as a glass composition, in mass % in terms of oxide, from 50% to 70% of SiO.sub.2, from 10% to 20% of Na.sub.2O, from 0% to 5.5% of TiO.sub.2, and from 10% to 30% of ZrO.sub.2.

2: The glass fiber according to claim 1, further comprising, as a glass composition, in mass % in terms of oxide, from 0.001% to 0.1% of Y.sub.2O.sub.3.

3: The glass fiber according to claim 1, further comprising, as a glass composition, in mass % in terms of oxide, from 0.001% to 1% of HfO.sub.2.

4: The glass fiber according to claim 1, comprising, as a glass composition, in mass % in terms of oxide, from 57.1% to 64.8% of SiO.sub.2, from 0% to 0.3% of Al.sub.2O.sub.3, from 1.71% to 10% of CaO, from 12% to 20% of Na.sub.2O, from 0% to 6% of K.sub.2O, from 0% to 5% of TiO.sub.2, and from 15.1% to 18.5% of ZrO.sub.2.

5: The glass fiber according to claim 1, wherein as a glass composition, Y.sub.2O.sub.3/ZrO.sub.2 is 0.0005 or more in mass ratio in terms of oxide.

6: The glass fiber according to claim 1, wherein as a glass composition, Na.sub.2O/ZrO.sub.2 is from 0.4 to 1.3 in mass ratio in terms of oxide.

7: The glass fiber according to claim 1, wherein as a glass composition, K.sub.2O/CaO is 15 or less in mass ratio in terms of oxide.

8: The glass fiber according to claim 1, wherein as a glass composition, K.sub.2O/ZrO.sub.2 is 0.5 or less in mass ratio in terms of oxide.

9: The glass fiber according to claim 1, wherein as a glass composition, (Na.sub.2O+K.sub.2O)/(CaO+MgO) is 1.5 or more in mass ratio in terms of oxide.

10: The glass fiber according to claim 1, wherein as a glass composition, (Na.sub.2O+K.sub.2O+CaO)/Al.sub.2O.sub.3 is 80 or more in mass ratio in terms of oxide.

11: The glass fiber according to claim 1, wherein a spinning temperature Tx is 1350 C. or lower.

12: The glass fiber according to claim 1, wherein a temperature difference Txy between a spinning temperature Tx and a liquidus temperature Ty is 15 C. or more.

13: The glass fiber according to claim 1, wherein a liquidus temperature Ty is 1250 C. or lower.

14: The glass fiber according to claim 1, wherein when a glass corresponding to a specific gravity crushed and classified to a particle size of from 300 m to 500 m is immersed in 100 ml of a 10 mass % NaOH aqueous solution at 80 C. for 168 hours, a mass loss rate of the glass is less than 4.5%.

15: A glass fiber manufacturing method comprising: melting a mixed raw material batch in a glass melting furnace, continuously drawing the obtained molten glass out of a bushing, and forming the drawn-out glass into a fiber shape, to obtain the glass fiber according to claim 1.

16: A glass comprising, as a glass composition, in mass % in terms of oxide, from 50% to 70% of SiO.sub.2, from 10% to 20% of Na.sub.2O, from 0% to 5.5% of TiO.sub.2, and from 10% to 30% of ZrO.sub.2.

Description

DESCRIPTION OF EMBODIMENTS

[0028] A glass fiber according to the present invention contains, as a glass composition, in mass % in terms of oxide, from 50% to 70% of SiO.sub.2, from 10% to 20% of Na.sub.2O, from 0% to 5.5% of TiO.sub.2, and from 10% to 30% of ZrO.sub.2. The reasons why the glass composition is limited as described above are shown below. Note that, in the description regarding the content of each component below, % means mass % unless otherwise specified.

[0029] SiO.sub.2 is a main component that forms a network frame of a glass. It is also a component that improves the mechanical strength of the glass and the acid resistance of the glass. When the content of SiO.sub.2 is too small, the mechanical strength decreases and the elastic modulus decreases, making it difficult to obtain sufficient strength. In addition, the acid resistance of the glass decreases. Therefore, the lower limit of the content of SiO.sub.2 is preferably 50% or more, 51% or more, 52% or more, 53% or more, 54% or more, 55% or more, 56% or more, 57% or more, more than 57%, 57.1% or more, 57.5% or more, 57.8% or more, 58% or more, 58.5% or more, 58.6% or more, 58.7% or more, 58.8% or more, 58.9% or more, 59% or more, 59.1% or more, 59.2% or more, 59.3% or more, 59.4% or more, and particularly preferably 59.5% or more. On the other hand, when the content of SiO.sub.2 is too large, the viscosity of the molten glass becomes too high, making it difficult to maintain a homogeneous molten state, and as a result, it may become difficult to adjust the diameter of the glass fiber. In addition, when the viscosity is high, the energy required to melt the glass increases, a spinning temperature Tx also increases, the damage to a noble metal bushing increases, the frequency of replacement increases, and the production cost increases. Therefore, the upper limit of the content of SiO.sub.2 is preferably 70% or less, 69% or less, 68% or less, 67% or less, 66% or less, 65.5% or less, 65.3% or less, 65% or less, 64.9% or less, 64.8% or less, 64.7% or less, 64.6% or less, 64.5% or less, 64% or less, 63.5% or less, 63.4% or less, 63.3% or less, 63.2% or less, 63.1% or less, 63% or less, less than 63%, 62.9% or less, 62.8% or less, and particularly preferably 62.7% or less.

[0030] Na.sub.2O is a component that improves the meltability and the formability of the glass by decreasing the viscosity of the glass. When the content of Na.sub.2O is too small, the viscosity of the glass increases and the energy required to melt the glass increases. In addition, the damage to a noble metal bushing increases, the frequency of replacement increases, and the production cost increases. Therefore, the lower limit of the content of Na.sub.2O is preferably 10% or more, 11% or more, 12% or more, 12.1% or more, 12.2% or more, 12.3% or more, 12.4% or more, 12.5% or more, 12.6% or more, 12.7% or more, 12.8% or more, 12.9% or more, 13% or more, more than 13%, 13.1% or more, 13.2% or more, 13.3% or more, 13.4% or more, 13.5% or more, and particularly preferably 13.6% or more. On the other hand, when the content of Na.sub.2O is too large, the initial phase in which CaO, Na.sub.2O, K.sub.2O, and the like are dissolved in zircon (ZrSiO.sub.4) tends to precipitate, the liquidus temperature of the glass increases, the difference between the spinning temperature and the liquidus temperature becomes small, and the productivity decreases. In addition, the water resistance of the glass decreases. Therefore, the upper limit of the content of Na.sub.2O is preferably 20% or less, 19% or less, 18.5% or less, 18% or less, 17.5% or less, 17% or less, 16.9% or less, 16.8% or less, 16.7% or less, 16.5% or less, 16.4% or less, 16.3% or less, 16.2% or less, 16.1% or less, 16% or less, 15.9% or less, 15.8% or less, 15.7% or less, 15.6% or less, 15.5% or less, 15.4% or less, 15.3% or less, 15.2% or less, 15.1% or less, 15% or less, 14.9% or less, 14.8% or less, 14.7% or less, 14.6% or less, 14.5% or less, 14.4% or less, 14.3% or less, and particularly preferably 14.2% or less.

[0031] TiO.sub.2 can improve the water resistance of the glass and can lower the melting temperature of the glass, and the viscosity and the spinning temperature Tx of the glass, thereby maintaining good productivity. On the other hand, when the content of TiO.sub.2 is too large, the alkali resistance of the glass tends to decrease, and TiO.sub.2-based devitrified crystals tend to be generated in the molten glass, which may cause clogging of nozzles of the bushing during glass fiber forming. Therefore, the content of TiO.sub.2 is preferably from 0% to 5.5%, from 0% to 5.4%, from 0% to 5.3%, from 0% to 5.2%, from 0% to 5.1%, from 0% to 5%, from 0% to less than 5%, from 0% to 4%, from 0% to 3%, from 0% to 2%, from 0% to 1%, and particularly preferably from 0.01% to less than 1%.

[0032] ZrO.sub.2 is a component that improves the alkali resistance, the acid resistance, and the water resistance of the glass. When the content of ZrO.sub.2 is too small, the alkali resistance decreases, and it is impossible to achieve the durability required for GRC. Therefore, the lower limit of the content of ZrO.sub.2 is preferably 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, 14.5% or more, 14.8% or more, 15% or more, 15.1% or more, 15.2% or more, 15.3% or more, 15.4% or more, 15.5% or more, 15.6% or more, 15.7% or more, 15.8% or more, 15.9% or more, 16% or more, 16.1% or more, 16.2% or more, 16.3% or more, 16.4% or more, and particularly preferably 16.5% or more. On the other hand, when the content of ZrO.sub.2 is too large, a liquidus temperature Ty of the glass increases, a temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty becomes small, and the productivity decreases. Therefore, the upper limit of the content of ZrO.sub.2 is preferably 30% or less, 29% or less, 28% or less, 27% or less, 26% or less, 25% or less, 24% or less, 23% or less, 22% or less, 21% or less, 20% or less, 19% or less, 18.9% or less, 18.8% or less, 18.7% or less, 18.6% or less, 18.5% or less, 18.4% or less, 18.3% or less, 18.2% or less, 18.1% or less, 18% or less, less than 18%, and particularly preferably 17.9% or less.

[0033] In addition, the glass fiber according to the present invention may contain components other than the above components (SiO.sub.2, Na.sub.2O, TiO.sub.2, and ZrO.sub.2).

[0034] Y.sub.2O.sub.3 is a component that improves the alkali resistance, the acid resistance, the water resistance, and the mechanical strength of the glass. When the content of Y.sub.2O.sub.3 is too small, the alkali resistance decreases and it is difficult to obtain sufficient alkali resistance. Therefore, the lower limit of the content of Y.sub.2O.sub.3 is preferably 0.001% or more, 0.002% or more, 0.003% or more, 0.004% or more, 0.005% or more, 0.006% or more, 0.007% or more, 0.008% or more, 0.009% or more, 0.01% or more, 0.015% or more, 0.02% or more, 0.025% or more, 0.026% or more, 0.027% or more, 0.028% or more, 0.029% or more, and particularly preferably 0.03% or more. On the other hand, when the content of Y.sub.2O.sub.3 is too large, it forms yttria-stabilized zirconia with ZrO.sub.2, the liquidus temperature Ty increases, the temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty becomes small, and the productivity decreases. In addition, since the raw material cost is high, the production cost increases. Therefore, the upper limit of the content of Y.sub.2O.sub.3 is preferably 0.1% or less, less than 0.1%, 0.09% or less, 0.08% or less, 0.07% or less, 0.06% or less, 0.05% or less, and particularly preferably less than 0.05%.

[0035] HfO.sub.2 is a component that improves the alkali resistance, the acid resistance, the water resistance, and the mechanical strength of the glass. When the content of HfO.sub.2 is too small, the alkali resistance decreases and it is difficult to obtain sufficient alkali resistance. Therefore, the lower limit of the content of HfO.sub.2 is preferably 0.001% or more, 0.002% or more, 0.003% or more, 0.004% or more, 0.005% or more, 0.006% or more, 0.007% or more, 0.008% or more, 0.009% or more, 0.01% or more, 0.015% or more, 0.02% or more, 0.025% or more, 0.026% or more, 0.027% or more, 0.028% or more, 0.029% or more, and particularly preferably 0.03% or more. On the other hand, when the content of HfO.sub.2 is too large, crystals containing Hf precipitate, the glass tends to devitrify, and the productivity decreases. In addition, since the raw material cost is high, the production cost increases. Therefore, the upper limit of the content of HfO.sub.2 is preferably 1% or less, less than 1%, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, and particularly preferably less than 0.5%.

[0036] Al.sub.2O.sub.3 is a component that improves the chemical durability and the mechanical strength of the glass. On the other hand, Al.sub.2O.sub.3 is also a component that increases the viscosity of the glass. When the content of Al.sub.2O.sub.3 is too large, devitrified crystals of mullite (3Al.sub.2O.sub.3.Math.2SiO.sub.2) whose main component is Al.sub.2O.sub.3 tend to be generated in the molten glass, the viscosity of the molten glass becomes too high, making it difficult to maintain a homogeneous molten state, and as a result, the dimensional accuracy of the diameter of the glass fiber tends to decrease. In addition, the energy required to melt the glass increases, the spinning temperature Tx also increases, the damage to a noble metal bushing increases, the frequency of replacement increases, and the production cost increases. Therefore, the content of Al.sub.2O.sub.3 is preferably from 0% to 3%, from 0% to 2%, from 0% to 1.5%, from 0% to 1%, from 0% to 0.8%, from 0% to 0.7%, from 0% to 0.6%, from 0% to 0.5%, from 0% to 0.4%, from 0% to 0.3%, from 0% to 0.2%, and particularly preferably from 0.01% to 0.2%.

[0037] CaO is a component that lowers the spinning temperature Tx during glass fiber forming and that improves the alkali resistance. When the content of CaO is too small, it is difficult to obtain the above effects. Therefore, the lower limit of the content of CaO is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more, 1% or more, 1.1% or more, 1.2% or more, 1.3% or more, 1.4% or more, 1.5% or more, 1.6% or more, 1.7% or more, more than 1.7%, 1.71% or more, 1.75% or more, 1.8% or more, 1.9% or more, 2% or more, 2.1% or more, 2.2% or more, 2.3% or more, 2.4% or more, 2.5% or more, 2.6% or more, 2.7% or more, 2.8% or more, 2.9% or more, 3% or more, 3.2% or more, 3.4% or more, 3.5% or more, 3.6% or more, 3.8% or more, 4% or more, 4.2% or more, 4.4% or more, 4.5% or more, 4.6% or more, 4.8% or more, 4.9% or more, 5% or more, 5.1% or more, 5.2% or more, 5.3% or more, 5.4% or more, 5.5% or more, 5.6% or more, and particularly preferably more than 5.6%. On the other hand, since Ca ions have large electric field strength, when the content of CaO is too large, zircon in which Ca is dissolved tends to precipitate as the initial phase, so that the liquidus temperature Ty of the glass increases, the temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty becomes small, and the productivity decreases. Therefore, the upper limit of the content of CaO is preferably 10% or less, 9% or less, 8% or less, 7.5% or less, 7.4% or less, 7.3% or less, 7.2% or less, 7.1% or less, 7% or less, 6.9% or less, 6.8% or less, 6.7% or less, 6.6% or less, 6.5% or less, and particularly preferably less than 6.5%.

[0038] K.sub.2O is a component that improves the meltability and the formability of the glass by decreasing the viscosity of the glass. On the other hand, when the content of K.sub.2O is too large, the water resistance of the glass decreases. In addition, the raw material batch easily absorbs moisture, and an aggregate of raw material powders tends to be formed. When an aggregate of raw material powders is formed, the solubility of the raw material batch deteriorates, and undissolved zirconia tends to remain in the product glass. Therefore, the content of K.sub.2O is preferably from 0% to 10%, from 0% to 9%, from 0% to 8%, from 0% to 7%, from 0% to 6%, from 0% to 5%, from 0% to 4.5%, from 0% to 4%, from 0% to 3.5%, from 0% to 3%, from 0% to 2.5%, from 0% to 2%, from 0% to 1.5%, from 0% to 1.4%, from 0% to 1.3%, from 0% to 1.2%, from 0% to 1.1%, from 0% to 1%, from 0% to 0.9%, from 0% to 0.8%, from 0% to 0.7%, from 0% to 0.6%, from 0% to 0.5%, from 0% to 0.4%, from 0% to 0.3%, from 0% to less than 0.3%, from 0.001% to less than 0.3%, from 0.001% to 0.25%, and particularly preferably from 0.001% to 0.2%.

[0039] MgO is a component that decreases the viscosity of the glass and that improves the elastic modulus of the glass. On the other hand, when the content of MgO is too large, crystals tend to be generated, which may cause clogging of the nozzles of the bushing during glass fiber forming. Therefore, the content of MgO is preferably from 0% to 1.5%, from 0% to 1.4%, from 0% to 1.3%, from 0% to 1.2%, from 0% to 1.1%, and particularly preferably from 0% to 1%.

[0040] P.sub.2O.sub.5 is a component that lowers the liquidus temperature Ty. When the content of P.sub.2O.sub.5 is too small, it is difficult to obtain the above effect. Therefore, the lower limit of the content of P.sub.2O.sub.5 is preferably 0.01% or more, 0.015% or more, and particularly preferably 0.02% or more. On the other hand, when the content of P.sub.2O.sub.5 is too large, the alkali resistance tends to decrease. Therefore, the upper limit of the content of P.sub.2O.sub.5 is preferably 0.2% or less, 0.1% or less, 0.07% or less, and particularly preferably 0.05% or less.

[0041] Li.sub.2O is a component that decreases the viscosity of the glass and that improves the meltability and the formability. However, since Li.sub.2O has a high raw material cost, the production cost increases. Therefore, the content of Li.sub.2O is preferably from 0% to 1%, from 0% to 0.9%, from 0% to 0.8%, from 0% to 0.7%, from 0% to 0.6%, from 0% to 0.5%, from 0% to 0.4%, from 0% to 0.3%, from 0% to 0.2%, from 0% to 0.15%, and particularly preferably from 0% to less than 0.15%.

[0042] Fe.sub.2O.sub.3 is a component that lowers the liquidus temperature Ty. When the content of Fe.sub.2O.sub.3 is too small, it is difficult to obtain the above effect. Therefore, the lower limit of the content of Fe.sub.2O.sub.3 is preferably 0.0001% or more, 0.0002% or more, 0.0003% or more, 0.0004% or more, 0.0005% or more, 0.0006% or more, and particularly preferably 0.001% or more. On the other hand, when the content of Fe.sub.2O.sub.3 is too large, undissolved Fe.sub.2O.sub.3 tends to remain in the product glass, and un-preferred crystals tend to be generated, which may cause clogging of the nozzles of the bushing during glass fiber forming. Therefore, the upper limit of the content of Fe.sub.2O.sub.3 is preferably 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, and particularly preferably 0.1% or less.

[0043] SO.sub.3 is a component that improves the fining property during glass melting. When the content of SO.sub.3 is too small, it is difficult to obtain the above effect. Therefore, the lower limit of the content of SO.sub.3 is preferably 0.0001% or more, 0.0002% or more, 0.0003% or more, 0.0004% or more, 0.0005% or more, 0.0006% or more, and particularly preferably 0.001% or more. On the other hand, when the content of SO.sub.3 is too large, a large amount of bubbles are generated in the glass melt, and bubbles are generated during glass fiber forming, leading to cutting of the glass fiber, resulting in a decrease in productivity. Therefore, the upper limit of the content of SO.sub.3 is preferably 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, and particularly preferably 0.1% or less.

[0044] The glass fiber according to the present invention can maintain high alkali resistance and productivity in a more preferred manner by controlling Y.sub.2O.sub.3/ZrO.sub.2. When Y.sub.2O.sub.3/ZrO.sub.2 is too small, the alkali resistance decreases, the liquidus temperature Ty of the glass increases, the temperature difference Txy between the spinning temperature and the liquidus temperature becomes small, and the productivity decreases. Therefore, the lower limit of Y.sub.2O.sub.3/ZrO.sub.2 is preferably 0.0005 or more, 0.001 or more, 0.0011 or more, 0.0012 or more, 0.0013 or more, 0.0014 or more, 0.0015 or more, more than 0.0015, 0.0016 or more, 0.0017 or more, 0.0018 or more, and particularly preferably more than 0.0018. On the other hand, when Y.sub.2O.sub.3/ZrO.sub.2 is too large, Y.sub.2O.sub.3 forms yttria-stabilized zirconia with ZrO.sub.2, the liquidus temperature Ty increases, the temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty becomes small, and the productivity decreases. Therefore, the upper limit of Y.sub.2O.sub.3/ZrO.sub.2 is preferably 1 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, 0.1 or less, and particularly preferably less than 0.1.

[0045] The glass fiber according to the present invention can maintain high alkali resistance and productivity in a more preferred manner by controlling Na.sub.2O/ZrO.sub.2. When Na.sub.2O/ZrO.sub.2 is too large or too small, the alkali resistance of the glass decreases, the liquidus temperature Ty increases, the temperature difference Txy between the spinning temperature and the liquidus temperature becomes small, and the productivity decreases. Therefore, the lower limit of Na.sub.2O/ZrO.sub.2 is preferably 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, and particularly preferably 0.8 or more. The upper limit of Na.sub.2O/ZrO.sub.2 is preferably 1.3 or less, 1.25 or less, 1.2 or less, 1.15 or less, 1.14 or less, 1.13 or less, 1.12 or less, 1.11 or less, and particularly preferably 1.1 or less.

[0046] The glass fiber according to the present invention can maintain high alkali resistance and productivity in a more preferred manner by controlling K.sub.2O/CaO. When K.sub.2O/CaO is too large, the liquidus temperature Ty increases, the temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty becomes small, and the productivity decreases. Therefore, K.sub.2O/CaO is preferably 15 or less, 14 or less, 13.6 or less, and particularly preferably 13.5 or less. Note that, the lower limit of K.sub.2O/CaO is not particularly limited, and is realistically 0.0001 or more.

[0047] The glass fiber according to the present invention can maintain high alkali resistance and productivity in a more preferred manner by controlling K.sub.2O/ZrO.sub.2. When K.sub.2O/ZrO.sub.2 is too large, the liquidus temperature Ty increases, the temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty becomes small, and the productivity decreases. Therefore, K.sub.2O/ZrO.sub.2 is preferably 0.5 or less, 0.4 or less, 0.35 or less, less than 0.35, 0.34 or less, 0.33 or less, 0.32 or less, 0.31 or less, 0.3 or less, 0.29 or less, 0.28 or less, 0.27 or less, 0.26 or less, 0.25 or less, 0.24 or less, 0.23 or less, 0.22 or less, 0.21 or less, and particularly preferably 0.2 or less. Note that, the lower limit of K.sub.2O/ZrO.sub.2 is not particularly limited, and is realistically 0.0001 or more.

[0048] The glass fiber according to the present invention can have a reduced raw material cost and maintain high productivity in a more preferred manner by controlling (Na.sub.2O+K.sub.2O)/(CaO+MgO). When (Na.sub.2O+K.sub.2O)/(CaO+MgO) is too small, the liquidus temperature Ty of the glass increases, the temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty becomes small, and the productivity decreases. Therefore, (Na.sub.2O+K.sub.2O)/(CaO+MgO) is preferably 1.5 or more, 1.6 or more, 1.7 or more, 1.75 or more, 1.8 or more, 1.9 or more, 2 or more, more than 2, 2.1 or more, 2.11 or more, 2.12 or more, 2.13 or more, 2.14 or more, 2.15 or more, 2.16 or more, 2.17 or more, 2.18 or more, 2.19 or more, 2.2 or more, 2.25 or more, 2.3 or more, and particularly preferably more than 2.3. Note that, the upper limit of (Na.sub.2O+K.sub.2O)/(CaO+MgO) is not particularly limited, and is realistically 1000 or less.

[0049] The glass fiber according to the present invention can maintain the alkali resistance and high productivity in a more preferred manner by controlling (Na.sub.2O+K.sub.2O+CaO)/Al.sub.2O.sub.3. When (Na.sub.2O+K.sub.2O+CaO)/Al.sub.2O.sub.3 is too small, the alkali resistance decreases, the spinning temperature Tx of the glass increases, and the productivity decreases. Therefore, (Na.sub.2O+K.sub.2O+CaO)/Al.sub.2O.sub.3 is preferably 80 or more, 90 or more, 100 or more, 105 or more, 110 or more, 120 or more, 125 or more, 126 or more, 127 or more, 128 or more, 129 or more, 130 or more, 131 or more, 132 or more, 133 or more, 134 or more, 135 or more, 136 or more, 137 or more, 138 or more, 139 or more, more than 139, and particularly preferably 140 or more. Note that, the upper limit of (Na.sub.2O+K.sub.2O+CaO)/Al.sub.2O.sub.3 is not particularly limited, and is realistically 5000 or less.

[0050] In addition, the glass fiber according to the present invention may contain trace components other than the above components (SiO.sub.2, Al.sub.2O.sub.3, CaO, Na.sub.2O, TiO.sub.2, ZrO.sub.2, HfO.sub.2, Y.sub.2O.sub.3, K.sub.2O, MgO, P.sub.2O.sub.5, Li.sub.2O, Fe.sub.2O.sub.3, and SO.sub.3). However, it is preferable to adjust the composition such that the total content of the above components is 97% or more, 98% or more, 98.5% or more, and particularly preferably 99% or more. When the total content of these components is less than 97%, problems tend to occur that the alkali resistance, the acid resistance, and the water resistance may be decreased due to mixing of different components and the characteristics of the product deteriorate, or the temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty becomes small and the productivity decreases.

[0051] As components other than the above components, trace components such as H.sub.2, CO.sub.2, CO, H.sub.2O, He, Ne, Ar, or N.sub.2 may be contained up to 0.1% each. In addition, up to 500 ppm of noble metal elements such as Pt, Rh, and Au may be added to the glass.

[0052] MoO.sub.3 is a component that can be mixed in from raw materials, members for melting, and the like, and when it is contained in too much, crystals containing Mo precipitate, the glass tends to devitrify, and the productivity decreases. The content of MoO.sub.3 is preferably 1000 ppm or less, 900 ppm or less, 800 ppm or less, 700 ppm or less, 600 ppm or less, 500 ppm or less, 400 ppm or less, 300 ppm or less, 200 ppm or less, and particularly preferably 100 ppm or less. On the other hand, since removal of MoO.sub.3 contained in raw materials as impurities increases the raw material cost, the lower limit of the content of MoO.sub.3 is preferably 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 2 ppm or more, 3 ppm or more, 4 ppm or more, and particularly preferably 5 ppm or more.

[0053] Further, in order to improve the alkali resistance and the liquidus temperature Ty, B.sub.2O.sub.3, SrO, BaO, ZnO, Cr.sub.2O.sub.3, Sb.sub.2O.sub.3, MnO, SnO.sub.2, CeO.sub.2, Cl.sub.2, La.sub.2O.sub.3, WO.sub.3, and Nb.sub.2O.sub.5 may be contained in a total amount of 2% or less, 1.5% or less, 1.2% or less, 1.1% or less, and particularly preferably 1% or less. Note that, from the viewpoint of environmental load, it is preferable not to contain large amounts of Cr.sub.2O.sub.3 and B.sub.2O.sub.3 in terms of composition design. The content of Cr.sub.2O.sub.3 is preferably less than 1%, less than 0.5%, less than 0.3%, and particularly preferably less than 0.1%, and the content of B.sub.2O.sub.3 is preferably less than 1%, less than 0.5%, less than 0.3%, and particularly preferably less than 0.2%.

[0054] Next, the characteristics of the glass fiber according to the present invention will be described.

[0055] In the glass fiber according to the present invention, the spinning temperature Tx is preferably 1350 C. or lower, 1340 C. or lower, 1330 C. or lower, 1320 C. or lower, 1310 C. or lower, 1300 C. or lower, 1290 C. or lower, and particularly preferably 1280 C. or lower. When the spinning temperature Tx is too high, since it is necessary to perform spinning at a high temperature, the damage to the noble metal bushing increases, the frequency of replacement increases, and the production cost increases. Note that, the lower limit of the spinning temperature Tx is not particularly limited, and is realistically 1100 C. or higher.

[0056] In the glass fiber according to the present invention, the temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty is preferably 15 C. or more, 20 C. or more, 30 C. or more, 40 C. or more, 50 C. or more, 60 C. or more, 70 C. or more, 80 C. or more, 90 C. or more, 100 C. or more, and particularly preferably 110 C. or more. When the temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty is too small, the productivity decreases. Note that, the upper limit of Txy is not particularly limited, and is realistically 250 C. or less.

[0057] In the glass fiber according to the present invention, the liquidus temperature Ty is preferably 1250 C. or lower, 1240 C. or lower, 1230 C. or lower, 1220 C. or lower, 1210 C. or lower, 1200 C. or lower, 1190 C. or lower, 1185 C. or lower, and particularly preferably 1180 C. or lower. When the liquidus temperature is too high, the productivity decreases. Note that, the lower limit of the liquidus temperature Ty is not particularly limited, and is realistically 900 C. or higher.

[0058] In the glass fiber according to the present invention, when a glass corresponding to a specific gravity crushed and classified to a particle size of from 300 m to 500 m is immersed in 100 ml of a 10 mass % NaOH aqueous solution at 80 C. for 168 hours, the mass loss rate of the glass is preferably less than 4.5%, 4.3% or less, 4.2% or less, 4% or less, 3.9% or less, 3.8% or less, 3.7% or less, 3.6% or less, 3.5% or less, and particularly preferably 3.4% or less. When the mass loss rate of the glass due to an alkali resistance test is high, the alkali resistance of the glass decreases, and the reliability as a reinforcing material for composite materials such as a calcium silicate board and GRC decreases.

[0059] Next, a glass fiber manufacturing method according to the present invention will be described using a direct melt method (DM method) as an example. However, the present invention is not limited to the method described below, and for example, it is also possible to employ a so-called indirect forming method (MM method: marble melt method) in which a fiber glass material formed into a marble shape is remelted using a bushing device and subjected to spinning. Note that this method is suitable for low-volume and high-mix production.

[0060] First, a glass raw material batch mixed to have the above composition (and characteristics) is charged into a glass melting furnace, vitrified, melted, and homogenized. Note that the melting temperature is preferably about 1400 C. to 1600 C.

[0061] Subsequently, the molten glass is formed into a glass fiber.

[0062] In some embodiments, the molten glass is supplied to a bushing, and the molten glass supplied to the bushing is continuously drawn in filaments out of a number of bushing nozzles provided at the bottom surface of the bushing. Various treatment agents are applied to the monofilaments drawn out in this manner, and a glass strand is obtained by bundling the monofilaments in predetermined numbers. Note that, the glass fiber according to the present invention includes not only the above glass strand, but also a short fiber such as glass wool formed by a centrifugation method, or the like, and monofilaments before bundled into the glass stand.

[0063] The glass fiber according to the present invention thus formed is processed into a chopped strand, a yarn, a roving, and the like, and is used for various applications. Note that, the chopped strand is obtained by cutting a glass fiber (strand) in which glass monofilaments are bundled to a predetermined length. The yarn is a twist of a strand. The roving is a combination of a plurality of strands and winding the same into a cylindrical shape.

Example 1

[0064] Hereinafter, the present invention will be described in detail based on Examples. Tables 1 to 7 show Examples of glasses constituting the glass fiber according to the present invention (Sample Nos. 1 to 38 and Nos. 40 to 68) and Comparative Example (Sample No. 39), respectively.

TABLE-US-00001 TABLE 1 mass % No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 No. 9 No. 10 SiO.sub.2 64.8 64.5 63.3 62.4 61.5 60.9 60.0 58.8 60.4 60.3 Na.sub.2O 15.4 15.3 15.4 15.4 15.2 15.4 15.3 15.3 15.4 15.3 TiO.sub.2 0.0 1.8 1.7 0.0 5.0 1.7 0.0 0.0 0.0 0.0 ZrO.sub.2 17.6 17.4 17.5 17.6 17.3 17.5 17.6 17.3 17.6 17.5 Y.sub.2O.sub.3 0.037 0.036 0.036 0.037 0.036 0.036 0.036 0.036 0.036 0.036 HfO.sub.2 0.34 0.34 0.34 0.34 0.33 0.34 0.34 0.34 0.34 0.34 Al.sub.2O.sub.3 0.15 0.15 0.16 0.15 0.15 0.15 0.15 0.15 0.15 0.15 CaO 1.2 0.0 1.2 3.5 0.0 3.5 3.4 3.4 4.3 4.0 K.sub.2O 0.330 0.270 0.260 0.260 0.260 0.260 2.850 4.292 1.529 2.001 MgO 0.013 0.007 0.014 0.032 0.005 0.032 0.032 0.033 0.039 0.038 P.sub.2O.sub.5 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 Li.sub.2O 0.09 0.09 0.09 0.09 0.09 0.09 0.10 0.10 0.10 0.09 Fe.sub.2O.sub.3 0.030 0.030 0.030 0.031 0.030 0.031 0.031 0.031 0.031 0.031 SO.sub.3 0.071 0.062 0.068 0.076 0.066 0.075 0.077 0.078 0.078 0.078 MoO.sub.3 (ppm) 7.9 8.3 8.6 6.9 7.5 7.2 7.1 7.1 7.1 7.5 Y.sub.2O.sub.3/ZrO.sub.2 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 0.0020 0.0021 0.0020 0.0021 Na.sub.2O/ZrO.sub.2 0.88 0.88 0.88 0.87 0.88 0.88 0.87 0.88 0.88 0.87 K.sub.2O/CaO 0.2845 13.5000 0.2241 0.0741 8.6667 0.0747 0.8285 1.2471 0.3533 0.4963 K.sub.2O/ZrO.sub.2 0.0188 0.0155 0.0149 0.0148 0.0150 0.0149 0.1619 0.2478 0.0870 0.1142 (Na.sub.2O + K.sub.2O)/(CaO + MgO) 13.41 576.67 13.34 4.42 441.71 4.46 5.23 5.64 3.88 4.25 (Na.sub.2O + K.sub.2O + CaO)/Al.sub.2O.sub.3 113 104 105 128 103 128 144 154 142 142 Tx ( C.) 1348 1350 1323 1304 1309 1280 1272 1253 1270 1272 Ty ( C.) 1145 1136 1159 1195 1143 1206 1216 1235 1214 1214 Txy ( C.) 203 214 164 109 166 74 56 18 56 58 Mass loss rate (mass %) 3.1 3.5 3.3 2.8 4.0 3.1 3.0 2.6 2.9 2.6

TABLE-US-00002 TABLE 2 mass % No. 11 No. 12 No. 13 No. 14 No. 15 No. 16 No. 17 No. 18 No. 19 No. 20 SiO.sub.2 60.4 59.6 59.0 62.0 61.5 61.1 60.6 61.0 59.7 60.7 Na.sub.2O 15.5 15.4 15.3 15.9 16.3 16.8 17.3 15.8 15.8 16.9 TiO.sub.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.2 2.4 0.0 ZrO.sub.2 17.5 17.5 17.5 17.6 17.6 17.6 17.5 17.5 17.7 17.7 Y.sub.2O.sub.3 0.036 0.037 0.036 0.037 0.037 0.037 0.037 0.037 0.037 0.037 HfO.sub.2 0.34 0.34 0.34 0.34 0.34 0.34 0.34 0.34 0.34 0.34 Al.sub.2O.sub.3 0.15 0.15 0.15 0.16 0.15 0.15 0.15 0.15 0.15 0.15 CaO 4.6 3.4 3.4 3.4 3.5 3.4 3.5 3.4 3.4 3.7 K.sub.2O 1.160 2.849 2.852 0.290 0.280 0.280 0.280 0.270 0.270 0.270 MgO 0.045 0.550 1.097 0.033 0.032 0.031 0.031 0.030 0.030 0.030 P.sub.2O.sub.5 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 Li.sub.2O 0.09 0.00 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 Fe.sub.2O.sub.3 0.031 0.031 0.031 0.031 0.031 0.031 0.031 0.031 0.031 0.031 SO.sub.3 0.078 0.079 0.081 0.079 0.078 0.080 0.080 0.092 0.092 0.091 MoO.sub.3 (ppm) 7.2 7.9 7.4 8.3 8.3 8.1 8.2 8.0 7.8 7.9 Y.sub.2O.sub.3/ZrO.sub.2 0.0021 0.0021 0.0020 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 Na.sub.2O/ZrO.sub.2 0.89 0.88 0.87 0.90 0.93 0.95 0.99 0.90 0.89 0.96 K.sub.2O/CaO 0.2516 0.8285 0.8314 0.0841 0.0812 0.0812 0.0812 0.0796 0.0799 0.0738 K.sub.2O/ZrO.sub.2 0.0663 0.1629 0.1626 0.0165 0.0159 0.0159 0.0160 0.0154 0.0153 0.0153 (Na.sub.2O + K.sub.2O)/(CaO + MgO) 3.58 4.57 4.00 4.65 4.76 4.91 5.05 4.70 4.71 4.65 (Na.sub.2O + K.sub.2O + CaO)/Al.sub.2O.sub.3 142 145 144 123 134 137 140 130 130 139 Tx ( C.) 1269 1269 1290 1288 1280 1269 1281 1265 1271 1271 Ty ( C.) 1217 1230 1176 1193 1205 1219 1184 1179 1217 1220 Txy ( C.) 52 39 114 95 75 50 97 86 54 51 Mass loss rate (mass %) 2.4 2.5 2.5 2.5 2.5 2.6 2.7 2.7 2.5 2.7

TABLE-US-00003 TABLE 3 mass % No. 21 No. 22 No. 23 No. 24 No. 25 No. 26 No. 27 No. 28 No. 29 No. 30 SiO.sub.2 60.6 60.5 60.6 60.7 60.7 60.4 61.5 60.7 60.4 60.4 Na.sub.2O 16.9 16.3 16.4 17.5 16.8 15.7 15.3 15.8 15.8 16.3 TiO.sub.2 0.0 0.0 0.0 0.0 0.0 1.8 0.0 0.0 0.0 0.0 ZrO.sub.2 17.6 17.7 17.7 17.7 17.6 17.6 17.7 17.8 17.6 17.6 Y.sub.2O.sub.3 0.037 0.037 0.037 0.037 0.037 0.037 0.037 0.037 0.037 0.037 HfO.sub.2 0.34 0.34 0.34 0.34 0.34 0.34 0.34 0.34 0.34 0.34 Al.sub.2O.sub.3 0.15 0.16 0.15 0.17 0.17 0.17 0.17 0.17 0.17 0.16 CaO 3.5 3.6 4.0 3.3 4.0 3.4 4.4 4.6 3.6 3.3 K.sub.2O 0.540 1.080 0.539 0.000 0.000 0.270 0.270 0.270 1.759 1.619 MgO 0.030 0.032 0.034 0.030 0.035 0.032 0.039 0.041 0.033 0.032 P.sub.2O.sub.5 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 Li.sub.2O 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 Fe.sub.2O.sub.3 0.032 0.032 0.033 0.033 0.032 0.033 0.033 0.032 0.032 0.032 SO.sub.3 0.092 0.091 0.091 0.092 0.092 0.090 0.091 0.091 0.090 0.092 MoO.sub.3 (ppm) 7.5 7.8 7.8 7.9 7.6 7.5 7.6 8.2 8.0 7.4 Y.sub.2O.sub.3/ZrO.sub.2 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 Na.sub.2O/ZrO.sub.2 0.96 0.92 0.93 0.99 0.96 0.89 0.86 0.89 0.90 0.93 K.sub.2O/CaO 0.1547 0.2959 0.1353 0.0000 0.0000 0.0796 0.0612 0.0590 0.4835 0.4880 K.sub.2O/ZrO.sub.2 0.0307 0.0611 0.0305 0.0000 0.0000 0.0153 0.0153 0.0152 0.1000 0.0920 (Na.sub.2O + K.sub.2O)/(CaO + MgO) 4.95 4.72 4.21 5.19 4.17 4.67 3.50 3.48 4.78 5.35 (Na.sub.2O + K.sub.2O + CaO)/Al.sub.2O.sub.3 140 131 140 123 122 114 118 121 125 133 Tx ( C.) 1271 1271 1269 1271 1273 1287 1273 1273 1271 1271 Ty ( C.) 1203 1213 1216 1205 1185 1192 1223 1203 1214 1201 Txy ( C.) 68 58 53 66 88 95 50 70 57 70 Mass loss rate (mass %) 2.6 2.5 2.7 2.5 2.6 2.3 2.3 2.3 2.5 2.5

TABLE-US-00004 TABLE 4 mass % No. 31 No. 32 No. 33 No. 34 No. 35 No. 36 No. 37 No. 38 No. 39 No. 40 SiO.sub.2 60.3 61.6 61.8 61.3 61.5 61.8 61.1 59.7 58.8 61.3 Na.sub.2O 16.0 15.1 15.4 15.8 15.9 15.9 15.7 15.4 14.7 15.5 TiO.sub.2 0.0 0.0 0.0 1.2 1.2 1.2 1.2 4.4 5.8 1.2 ZrO.sub.2 17.6 17.7 17.7 17.3 16.9 16.5 17.4 17.6 16.5 17.5 Y.sub.2O.sub.3 0.036 0.037 0.037 0.036 0.036 0.035 0.033 0 0 0.036 HfO.sub.2 0.34 0.34 0.34 0.28 0.31 0.38 0.44 0.25 0.00 0.33 Al.sub.2O.sub.3 0.18 0.17 0.18 0.17 0.16 0.16 0.16 0.17 0.20 0.12 CaO 3.5 3.3 3.4 3.4 3.4 3.4 3.4 1.9 3.8 3.4 K.sub.2O 1.750 1.548 0.899 0.260 0.260 0.260 0.256 0.270 0.000 0.300 MgO 0.032 0.031 0.033 0.029 0.030 0.030 0.029 0.019 0 0.024 P.sub.2O.sub.5 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0 0.027 Li.sub.2O 0.09 0.09 0.10 0.10 0.10 0.10 0.10 0.09 0.09 0.00 Fe.sub.2O.sub.3 0.032 0.033 0.032 0.031 0.031 0.030 0.031 0.030 0.040 0.033 SO.sub.3 0.091 0.092 0.091 0.090 0.087 0.086 0.088 0.085 0.070 0.004 MoO.sub.3 (ppm) 7.8 7.4 7.9 7.7 7.9 8.1 7.9 7.8 0.0 7.5 Y.sub.2O.sub.3/ZrO.sub.2 0.0020 0.0021 0.0021 0.0021 0.0021 0.0021 0.0019 0.0021 0.0000 0.0021 Na.sub.2O/ZrO.sub.2 0.91 0.85 0.87 0.91 0.94 0.96 0.90 0.87 0.89 0.884 K.sub.2O/CaO 0.5029 0.4755 0.2639 0.0772 0.0769 0.0765 0.0760 0.1399 0.0000 0.0888 K.sub.2O/ZrO.sub.2 0.0994 0.0876 0.0508 0.0150 0.0154 0.0158 0.0147 0.0153 0.0000 0.0171 (Na.sub.2O + K.sub.2O)/(CaO + MgO) 5.05 5.06 4.73 4.72 4.74 4.71 4.71 8.04 3.87 4.64 (Na.sub.2O + K.sub.2O + CaO)/Al.sub.2O.sub.3 118 117 110 114 122 122 123 104 93 160 Tx ( C.) 1296 1296 1277 1276 1276 1274 1273 1307 1250 1288 Ty ( C.) 1165 1171 1183 1175 1162 1147 1146 1143 1126 1188 Txy ( C.) 131 125 94 101 114 127 127 164 124 100 Mass loss rate (mass %) 2.5 2.5 2.8 2.9 2.9 3.2 3.4 4.2 4.5 2.6

TABLE-US-00005 TABLE 5 mass % No. 41 No. 42 No. 43 No. 44 No. 45 No. 46 No. 47 No. 48 No. 49 No. 50 SiO.sub.2 60.2 60.3 60.6 60.9 60.1 60.3 59.9 62.17 62.2 62.3 Na.sub.2O 15.1 15.2 15.2 15.3 15.1 15.1 14.9 14.1 14.5 13.6 TiO.sub.2 4.4 3.5 1.8 0.0 3.5 1.1 0.0 0.4 0.0 0.1 ZrO.sub.2 17.6 17.6 17.7 17.8 17.5 17.6 17.4 16.9 16.9 17.4 Y.sub.2O.sub.3 0.036 0.036 0.036 0.036 0.036 0.036 0.036 0.035 0.036 0.098 HfO.sub.2 0.33 0.33 0.33 0.33 0.33 0.33 0.33 0.29 0.33 0.38 Al.sub.2O.sub.3 0.12 0.12 0.12 0.12 0.12 0.12 0.13 0.12 0.13 0.03 CaO 1.9 2.5 3.8 5.0 1.9 1.9 1.9 5.7 5.7 6.1 K.sub.2O 0.300 0.280 0.280 0.270 1.260 3.296 5.279 0.042 0.069 0.003 MgO 0.016 0.020 0.026 0.035 0.016 0.019 0.020 0.04 0.038 0.045 P.sub.2O.sub.5 0.03098 0.02898 0.02802 0.02601 0.029 0.02597 0.02399 0.035 0.028 0.011 Li.sub.2O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe.sub.2O.sub.3 0.032 0.032 0.032 0.033 0.032 0.031 0.031 0.051 0.033 0.004 SO.sub.3 0.007 0.082 0.084 0.081 0.084 0.087 0.084 0.087 0.080 0.103 MoO.sub.3 (ppm) 7.8 8.4 7.2 7.6 7.8 7.7 7.6 7.9 7.9 8.1 Y.sub.2O.sub.3/ZrO.sub.2 0.0020 0.0020 0.0020 0.0020 0.0021 0.0020 0.0021 0.0021 0.0021 0.0056 Na.sub.2O/ZrO.sub.2 0.858 0.864 0.859 0.860 0.863 0.858 0.856 0.837 0.858 0.779 K.sub.2O/CaO 0.1587 0.1120 0.0747 0.0538 0.6632 1.7277 2.7937 0.0074 0.0122 0.0005 K.sub.2O/ZrO.sub.2 0.0170 0.0159 0.0158 0.0152 0.0720 0.1875 0.3034 0.0025 0.0041 0.0002 (Na.sub.2O + K.sub.2O)/ 8.08 6.14 4.10 3.08 8.54 9.54 10.57 2.48 2.56 2.19 (CaO + MgO) (Na.sub.2O + 144 150 160 172 152 169 170 166 156 757 K.sub.2O + CaO)/ Al.sub.2O.sub.3 Tx ( C.) 1284 1285 1283 1283 1288 1290 1283 1291 1288 1305 Ty ( C.) 1132 1166 1190 1212 1142 1196 1214 1149 1171 1159 Txy ( C.) 152 119 93 71 146 94 69 142 117 146 Mass loss 3.4 3.3 2.7 2.3 3.3 2.9 2.8 2.7 2.5 2.3 rate (mass %)

TABLE-US-00006 TABLE 6 mass % No. 51 No. 52 No. 53 No. 54 No. 55 No. 56 No. 57 No. 58 No. 59 No. 60 SiO.sub.2 62.3 59.3 62.3 62.3 61.1 61.4 61.7 61.8 61.8 61.4 Na.sub.2O 13.5 14.7 13.9 12.5 13.8 13.9 14.0 13.8 14.0 14.1 TiO.sub.2 0.1 2.3 0.1 0.1 1.5 1.0 0.8 0.9 0.7 0.7 ZrO.sub.2 17.3 17.0 17.1 17.3 16.9 17.0 17.0 17.0 17.0 17.1 Y.sub.2O.sub.3 0.037 0.037 0.036 0.037 0.036 0.036 0.036 0.036 0.036 0.036 HfO.sub.2 0.33 0.33 0.33 0.33 0.33 0.33 0.33 0.33 0.33 0.33 Al.sub.2O.sub.3 0.13 0.12 0.13 0.13 0.12 0.13 0.13 0.14 0.13 0.13 CaO 6.1 3.4 5.8 7.1 5.7 5.6 5.8 5.7 5.7 5.9 K.sub.2O 0.004 2.570 0.012 0.006 0.250 0.390 0.039 0.040 0.038 0.040 MgO 0.034 0.021 0.034 0.039 0.045 0.043 0.046 0.044 0.044 0.045 P.sub.2O.sub.5 0.029 0.032 0.03001 0.031 0.04108 0.03902 0.03897 0.039 0.039 0.039 Li.sub.2O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe.sub.2O.sub.3 0.033 0.032 0.033 0.034 0.033 0.035 0.033 0.033 0.033 0.033 SO.sub.3 0.076 0.079 0.076 0.074 0.077 0.077 0.078 0.073 0.077 0.075 MoO.sub.3 (ppm) 7.9 7.9 7.9 7.8 7.8 7.9 7.7 8.0 7.6 8.0 Y.sub.2O.sub.3/ZrO.sub.2 0.0021 0.0022 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 0.0021 Na.sub.2O/ZrO.sub.2 0.780 0.865 0.813 0.723 0.817 0.818 0.824 0.812 0.824 0.825 K.sub.2O/CaO 0.0007 0.7471 0.0021 0.0008 0.0437 0.0699 0.0067 0.0070 0.0067 0.0068 K.sub.2O/ZrO.sub.2 0.0002 0.1512 0.0007 0.0003 0.0148 0.0229 0.0023 0.0024 0.0022 0.0023 (Na.sub.2O + K.sub.2O)/ 2.20 4.99 2.37 1.75 2.44 2.54 2.39 2.40 2.45 2.39 (CaO + MgO) (Na.sub.2O + K.sub.2O + 151 173 152 151 165 153 153 140 152 154 CaO)/Al.sub.2O.sub.3 Tx ( C.) 1305 1266 1300 1304 1278 1288 1288 1290 1291 1285 Ty ( C.) 1164 1194 1162 1188 1171 1159 1156 1149 1167 1173 Txy ( C.) 141 72 138 116 107 129 132 141 124 112 Mass loss 2.1 3.0 2.4 2.1 2.8 2.6 2.5 2.7 2.6 2.7 rate (mass %)

TABLE-US-00007 TABLE 7 mass % No. 61 No. 62 No. 63 No. 64 No. 65 No. 66 No. 67 No. 68 SiO.sub.2 61.6 61.8 62.2 61.6 61.8 62.0 61.8 61.8 Na.sub.2O 14.2 14.2 14.1 14.1 14.1 14.1 13.8 13.7 TiO.sub.2 0.9 0.7 0.4 0.4 0.4 0.5 0.9 0.9 ZrO.sub.2 17.0 17.0 16.6 17.0 17.0 17.1 17.0 17.0 Y.sub.2O.sub.3 0.036 0.036 0.033 0.034 0.034 0.034 0.034 0.034 HfO.sub.2 0.33 0.33 0.33 0.33 0.33 0.31 0.33 0.33 Al.sub.2O.sub.3 0.12 0.13 0.13 0.15 0.13 0.13 0.13 0.13 CaO 5.6 5.6 5.9 6.1 5.9 5.6 5.8 5.9 K.sub.2O 0.039 0.039 0.038 0.040 0.039 0.038 0.004 0.004 MgO 0.043 0.043 0.044 0.031 0.030 0.029 0.030 0.030 P.sub.2O.sub.5 0.03899 0.03798 0.03503 0.02802 0.02802 0.02801 0.02801 0.0280 Li.sub.2O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe.sub.2O.sub.3 0.033 0.033 0.030 0.032 0.031 0.031 0.031 0.031 SO.sub.3 0.078 0.077 0.076 0.078 0.078 0.079 0.078 0.078 MoO.sub.3 (ppm) 7.9 7.8 7.6 7.8 8.2 7.6 7.9 7.9 Y.sub.2O.sub.3/ZrO.sub.2 0.0021 0.0021 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 Na.sub.2O/ZrO.sub.2 0.835 0.835 0.849 0.829 0.829 0.825 0.812 0.806 K.sub.2O/CaO 0.0070 0.0070 0.0065 0.0066 0.0066 0.0067 0.0007 0.0007 K.sub.2O/ZrO.sub.2 0.0023 0.0023 0.0023 0.0024 0.0023 0.0022 0.0002 0.0002 (Na.sub.2O + K.sub.2O)/ 2.53 2.53 2.39 2.31 2.39 2.50 2.38 2.33 (CaO + MgO) (Na.sub.2O + K.sub.2O + 165 153 154 135 154 152 150 150 CaO)/Al.sub.2O.sub.3 Tx ( C.) 1287 1289 1290 1286 1289 1294 1290 1291 Ty ( C.) 1169 1165 1160 1170 1161 1166 1148 1155 Txy ( C.) 118 124 130 116 128 128 142 136 Mass loss 2.5 2.5 2.6 2.3 2.5 2.4 2.5 2.4 rate (mass %)

[0065] Each sample in the tables was prepared as follows.

[0066] First, various glass raw materials such as natural raw materials and chemical raw materials were weighed and mixed so as to have the glass composition shown in the tables, and a raw material batch was prepared. Next, this raw material batch was charged into a platinum-rhodium alloy crucible, and then heated in an indirect heating electric furnace at 1550 C. for 5 hours to obtain a molten glass. Note that, in order to obtain a homogeneous molten glass, the molten glass was stirred a plurality of times using a heat-resistant stirring bar. Subsequently, the obtained molten glass was poured into a refractory mold to form a sheet-shaped glass, which was then subjected to an annealing treatment (heating for 30 minutes at a temperature 30 C. to 50 C. higher than the temperature at 10.sup.13 dPa.Math.s, and then lowering the temperature at a rate of 3 C./min from the annealing point to the strain point) in an annealing furnace. For each sample obtained, the spinning temperature Tx, the liquidus temperature Ty, and the alkali resistance were measured.

[0067] The spinning temperature Tx at which the viscosity of the molten glass corresponded to 10.sup.3 dPa.Math.s was calculated by interpolation of a viscosity curve obtained based on a plurality of measurements of each viscosity measured based on a platinum sphere pull up method after the formed glass is charged into an alumina crucible, reheated, and heated to a molten state.

[0068] For the liquidus temperature Ty, a platinum container was filled with a glass powder that passed through a standard sieve 30-mesh sieve (300 m) and remained on a 50-mesh sieve (300 m) to have an appropriate bulk density, and the sample was charged into an indirect heating type temperature gradient furnace with a maximum temperature of 1320 C., left standing, and heat-treated in an air atmosphere for 16 hours. Thereafter, the platinum container containing the glass sample was taken out, and the glass sample was removed from the platinum container. The glass sample was allowed to cool to room temperature, then the location where crystals started to precipitate was confirmed using a polarizing microscope, and the crystal precipitation temperature was calculated based on a temperature gradient in the indirect heating furnace.

[0069] The temperature difference Txy between the spinning temperature Tx and the liquidus temperature Ty was calculated by (spinning temperature Tx)(liquidus temperature Ty).

[0070] The alkali resistance was measured as follows. First, the above sheet-shaped glass sample was crushed, and a glass having a particle size of from 300 m to 500 m in diameter was precisely weighed by the specific gravity, and then immersed in 100 ml of a 10 mass % NaOH solution and shaken at 80 C. for 168 hours. Thereafter, the mass loss rate of the glass sample was measured. The smaller this value is, the better the alkali resistance is.

[0071] As is clear from Tables 1 to 7, in Sample Nos. 1 to 38 and Nos. 40 to 68, which are Examples, the spinning temperature Tx of the glass is 1350 C. or lower, the liquidus temperature Ty is 1235 C. or lower, and the temperature difference Txy between the spinning temperature Tx of the glass and the liquidus temperature Ty is 18 C. or more, and the productivity is excellent. Further, the mass loss rate, which is an indicator of the alkali resistance, is less than 4.5% in all cases.

[0072] In contrast, in sample No. 39, which is Comparative Example, the mass loss rate, which is an indicator of the alkali resistance, is 4.5%, and the alkali resistance is low.

Example 2

[0073] Next, raw material batches mixed to have the glass compositions of Sample Nos. 1 to 38 and Nos. 40 to 68 described in Tables 1 to 7 were each charged into a glass melting furnace, and melted and homogenized at 1400 C. to 1600 C. Subsequently, the obtained molten glass was supplied to a bushing and continuously drawn in filaments out of bushing nozzles provided at the bottom surface. A treatment agent was applied to the monofilaments thus obtained, and 2,000 to 4,000 of the monofilaments were bundled into a glass strand.

INDUSTRIAL APPLICABILITY

[0074] The glass fiber according to the present invention is suitable not only as a reinforcing material for GRC but also as a reinforcing material for a calcium silicate board, a corrosion-resistant material such as a battery separator.