Glass fiber production method
Provided is a method for producing glass fiber, capable of stably performing the spinning of glass fibers without mixing of red crystals in glass fibers. When glass fibers are formed by discharging, from a nozzle tip, a molten glass obtained by melting glass raw materials mixed so as to give a glass composition including, when melted, in relation to the total amount thereof, SiO 2 in a range from 57.0 to 62.0% by mass, Al 2 O 3 in a range from 15.0 to 20.0% by mass, MgO in a range from 7.5 to 12.0% by mass, and CaO in a range from 9.0 to 16.5% by mass, and having a total content of SiO 2 , Al 2 O 3 , MgO and CaO of 98.0% by mass or more, the glass composition includes B 2 O 3 , Li 2 O, or B 2 O 3 and Li 2 O as an additive or additives capable of suppressing the generation of red crystals.
1. A method for producing glass fiber, when glass fibers are formed by discharging, from a nozzle tip, a molten glass obtained by melting glass raw materials mixed so as to give a glass composition comprising, when melted, in relation to the total amount thereof, SiO 2 in a range from 57.0 to 58.8% by mass, Al 2 O 3 in a range from 18.0 to 20.0% by mass, MgO in a range from 7.5 to 12.0% by mass, and CaO in a range from 9.0 to 12.5% by mass, and having a total content of SiO 2 , Al 2 O 3 , MgO and CaO of 98.0% by mass or more, the glass composition comprises B 2 O 3 , or a combination of B 2 O 3 and Li 2 O, as an additive or additives capable of suppressing generation of red crystals,
wherein a ratio of the product between a content of the additive or additives capable of suppressing generation of red crystals (% by mass) and the content (% by mass) of CaO to the content (% by mass) of Al 2 O 3 is in a range from 0.25 to 1.00.
2. The method for producing glass fiber according to claim 1 , wherein the glass fibers each have a modified cross sectional shape in which a ratio (major axis/minor axis) of the major axis to the minor axis of the cross sectional shape falls within a range from 2.0 to 6.0.
3. The method for producing glass fiber according to claim 1 , wherein the glass fibers each have a modified cross sectional shape in which a fiber diameter defined as a diameter when a cross-sectional area is converted to a perfect circle, falls within a range from 10 to 30 μm.
4. The method for producing glass fiber according to claim 1 , wherein the glass fibers have perfect circular cross sections, and fiber diameters falling within a range of 3 μm or more to less than 10 μm.
5. The method for producing glass fiber according to claim 1 , wherein the glass raw materials mixed so as to give the glass composition are melted by using a melting furnace in which a portion in contact with the molten glass is formed of bricks containing chromium oxide.
6. The method for producing glass fiber according to claim 1 , wherein the glass composition comprises B 2 O 3 as the additive capable of suppressing the generation of red crystals, in a content of 0.5 to 1.5% by mass in relation to the total amount of the glass composition.
7. The method for producing glass fiber according to claim 1 , wherein the glass composition comprises B 2 O 3 and Li 2 O as the additives capable of suppressing the generation of red crystals, in a content of 0.5 to 1.5% by mass in relation to the total amount of the glass composition.
8. The method for producing glass fiber according to claim 1 , wherein in the glass composition, an 1000-poise temperature thereof is a temperature falling within a range from 1300 to 1370° C., a liquid phase temperature thereof is a temperature falling within a range from 1200 to 1270° C., and a working temperature range thereof is 50° C. or higher.
9. The method for producing glass fiber according to claim 1 , wherein the glass fibers each have a modified cross sectional shape in which a ratio (major axis/minor axis) of the major axis to the minor axis of the cross sectional shape falls within a range from 2.0 to 6.0, and a fiber diameter defined as a diameter when a cross-sectional area is converted to a perfect circle, falls within a range from 10 to 30 μm.
10. The method for producing glass fiber according to claim 1 , wherein the glass composition comprises CaO in a range of 10.3 to 12.5% by mass.
11. The method for producing glass fiber according to claim 1 , wherein the glass composition comprises MgO in a range of 8.8 to 12.0% by mass.