Glass fiber and method for producing the same

Abstract

The present invention relates to glass fibers and a method for producing the same. The glass fibers of the present invention are suitable for preventing breakage, and are suitable for long-term stable production, with a β-OH of 0.02 mm ‑1 or less and below 0.55 mm ‑1 The SO3 content is preferably higher than 0 ppm and 70 ppm or less on a mass basis. It is preferable that the glass fibers substantially do not contain As and Sb. SO3 can be supplied to the glass raw material as an alkali metal or alkaline earth metal sulfate or the like.

Description

[0001] This application is a divisional application of PCT application (PCT / JP2018 / 036571) with application number: 201880091909.9, application date: September 28, 2018, and invention name: "Glass fiber and method for manufacturing the same". Technical Field

[0002] The present invention relates to glass fibers. The glass fibers of the present invention can be obtained by a production method comprising the following steps: forming a glass melt from a glass raw material; and spinning glass fibers from the glass melt. Background Art

[0003] Glass fiber is spun from molten glass using a forming device called a bushing. The bushing has numerous spinnerets (also called spinnerets) at its base, and at least the portion that comes into contact with the molten glass is made of a precious metal such as platinum or a platinum alloy. Molten glass flows from a furnace through the bushing and is discharged as numerous filaments. These filaments are then coated with a sizing agent and bundled and wound into single or multiple strands.

[0004] Unexpected severing of single filaments hinders the stable production of glass fibers. It is known that filament breakage is related to foreign matter such as devitrified materials in the glass melt, and fluctuations in the meniscus formed near the spinneret as the glass melt is discharged from the spinneret, but the causes are not fully understood. Since completely preventing accidental filament breakage is difficult in practice, some manufacturing technologies have been proposed that assume filament breakage is a prerequisite. One example is a technology that instantly detects filament breakage through image processing (Patent Document 1).

[0005] In the field of glass fiber technology, bubbles are considered a factor in the formation of hollow fibers. Small bubbles remaining in the glass melt remain in the glass fiber in an elongated state along the discharge direction of the glass melt, reducing the strength and other properties of the glass fiber.

[0006] Patent Document 2 discloses a glass fiber whose SO₃ content is kept below 50 ppm by mass to prevent the incorporation of hollow fibers. The SO₃ in the glass fiber originates from sulfates intentionally added to the glass raw materials as a fining agent or present as small amounts of impurities. Patent Document 2 points out that an excessively high SO₃ content increases bubbles remaining in the glass melt, which contribute to the formation of hollow fibers.

[0007] Patent Document 2 also discloses that β-OH should be controlled to 0.55 to 0.65 mm -1 β-OH is an indicator of the amount of water contained in glass. In Patent Document 2, β-OH is kept at 0.55 mm -1As described above, the viscosity of the glass melt is reduced to promote clarification and prevent the formation of hollow fibers.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-105657

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 2011-68549 Summary of the Invention

[0012] In order to achieve stable production of glass fibers, it is necessary to prevent fiber breakage as much as possible. The present invention aims to provide a glass fiber that is suitable for stable production while avoiding fiber breakage.

[0013] As a result of intensive research, the present inventors have discovered that the frequency of fiber breakage can be reduced by controlling the β-OH content within a specific range.

[0014] The present invention provides β-OH of 0.02mm -1 Above and below 0.55mm -1 of glass fiber.

[0015] The glass fiber of the present invention is suitable for mass production due to stable continuous long-term operation. DETAILED DESCRIPTION

[0016] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment. Hereinafter, all percentages indicating the content of glass components are by mass, and all ppm are by mass. Furthermore, the phrase "substantially free of" a component means that the content of that component is less than 0.1% by mass, preferably less than 0.08% by mass, and more preferably less than 0.05% by mass.

[0017] [β-OH]

[0018] According to the inventors' research, one cause of wire breakage is the generation of oxygen gas due to the reboiling of the glass melt in contact with the leak plate. The OH groups in the glass melt come into contact with the precious metals, such as platinum, that make up the leak plate and are reduced, generating hydrogen (H2). Because hydrogen can pass through the precious metal barrier, some of the generated hydrogen is released outside the furnace. Consequently, the excess residual oxygen atoms in the glass melt generate oxygen (O2), which in turn causes new bubbles to form in the glass melt, or the growth of tiny bubbles composed of SO2 and other substances contained in the glass melt.

[0019] In Patent Document 2, in order to suppress the formation of hollow fibers, minute bubbles are removed, and for this purpose, β-OH is set to 0.55 mm.-1 However, from the perspective of suppressing reboiling, it is appropriate to limit the β-OH, an indicator of the amount of water contained in the glass, to a lower level. Specifically, the β-OH of the glass fiber should be adjusted to less than 0.55 mm -1 The preferred β-OH is 0.53 mm -1 Below, more preferably below 0.5mm -1 , especially preferably less than 0.48 mm -1 .

[0020] Too low β-OH makes it difficult to clarify the glass melt. Therefore, the β-OH of glass fiber is set at 0.02mm -1 Above. The preferred β-OH is 0.1 mm -1 More than, more preferably 0.3mm -1 Above, more preferably 0.35mm -1 Above, particularly preferably 0.4 mm -1 above.

[0021] β-OH can be controlled by adjusting the moisture content of the glass raw materials and the moisture content of the furnace atmosphere where the glass raw materials are melted. Glass fibers produced under typical manufacturing conditions often have β-OH levels exceeding the preferred range described above. Therefore, it is recommended to reduce β-OH by, for example: i) selecting glass raw materials with low moisture content; ii) performing a pretreatment to dry the glass raw materials; or iii) blowing an inert gas such as nitrogen into the glass melt.

[0022] [SO3]

[0023] SO₃ in glass fibers comes from sulfates in the glass raw materials and sulfur in the melting fuel. Sulfates act as fining agents, generating SO₂ bubbles in the glass melt. While SO₂ bubbles themselves can contribute to hollow fiber formation, it's difficult to conclude that SO₂ bubbles alone are the direct cause of fiber breakage. In fact, according to the inventors' experience, fiber breakage is more frequent in glass compositions with relatively low SO₃ content than in glass compositions with relatively high SO₃ content.

[0024] However, the bubbles of SO2 contained in the glass melt affect the ease of breakage. Therefore, the content of SO3 remaining in the glass fiber is preferably 75 ppm or less, more preferably 70 ppm or less, and particularly preferably 68 ppm or less. On the other hand, in order to obtain the refining effect from the sulfate, the content of SO3 is preferably set in the range of more than 0 ppm. More preferably, the content of SO3 is 5 ppm or more, 20 ppm or more, further preferably 25 ppm or more, and particularly preferably 30 ppm or more. The content of SO3 can also be more than 50 ppm, for example, 55 ppm or more, and further can be 60 ppm or more.

[0025] [As and Sb]

[0026] In the production of glass fibers, as in the production of other glass products, it is desirable to avoid the use of oxides of As and Sb as fining agents, which have high environmental load. In the preferred embodiment of the present application, the glass fiber is substantially free of As and Sb. In this case, in order to obtain the refining effect from the sulfate, the content of SO3 in the glass fiber is preferably in the range of more than 0 ppm, for example, more than 0 ppm and 75 ppm or less, and more specifically, 20 to 75 ppm.

[0027] [The diameter of the glass fiber]

[0028] The diameter of the glass fiber of the present application can be 15 μm or less, further preferably 10 μm or less, and particularly preferably 5 μm or less. The present application is particularly suitable for applications to glass fibers having a fine diameter, for which stable continuous production is relatively difficult. In a rope for rubber reinforcement having a bundle of glass fibers bundled, the use of glass fibers having a finer diameter makes the bundle relatively soft and easy to bend. Therefore, glass fibers having a finer diameter can increase the flexural strength of the rope. In addition, if compared at the same strength, the cross-sectional area of the rope can be reduced. The lower limit of the diameter of the glass fiber is not particularly limited, and for example, can be 2 μm or 3 μm. However, the glass fiber of the present application can also be applied to glass fibers having a fiber diameter of more than 15 μm, and further can be applied to glass fibers having a fiber diameter of up to 20 μm or more.

[0029] The diameter of the glass fiber of the present application can have a deviation of ±3 μm or less, and further ±2 μm or less. The present application is also suitable for reduction of the deviation of the diameter of the glass fiber. A glass fiber having a large deviation in diameter and an uneven diameter is likely to have a stress due to waviness of the outer shape, and the flexural strength is reduced. Therefore, the deviation of the diameter of the glass fiber is preferably as small as possible. Here, the deviation of the diameter of the glass fiber is determined by the difference between the simple average and the maximum value (indicated by +) and the difference between the simple average and the minimum value (indicated by -), which are measured at 50 points at random. Also, the diameter of the glass fiber can be determined from the simple average.

[0030] [Length of the glass fiber]

[0031] The length of the glass fiber of the present application is not particularly limited, but from the viewpoint of productivity, for example, it is 2 m or more, and preferably 5 km or more.

[0032] [Roundness of the glass fiber]

[0033] The cross section of the glass fiber of the present application is, for example, substantially circular, and the roundness thereof can be 0.7 or more. Here, the roundness is a value defined by (4πS / L 2 ) when the cross-sectional area of the glass fiber is S and the circumference of the cross section is L. The cross section having a value of 1 is a perfect circle. The roundness can be measured using, for example, a scanning electron microscope. At this time, it is convenient if an image processing software such as Image J by Wayne Rasband is used.

[0034] [Preferred embodiment]

[0035] By controlling SO3 and β-OH in the above-mentioned preferred ranges, respectively, both the refining effect from the sulfate and the continuous production of the glass fiber substantially free of As and Sb, which can inhibit the breakage of the glass fiber, can be achieved. In a preferred embodiment of the present application, the content of SO3 is higher than 0 ppm and 75 ppm or less, and particularly preferably 20 to 75 ppm, and β-OH is 0.1 mm -1 or more and lower than 0.55 mm -1 , and particularly preferably 0.3 mm -1 or more and lower than 0.55 mm -1 . However, in the present application, as another embodiment, there is included a glass fiber in which the content of SO3 is higher than 75 ppm and 100 ppm or less, and particularly higher than 75 ppm and 85 ppm or less, and β-OH is 0.1 mm -1 or more and lower than 0.3 mm -1 . These embodiments can also be the glass fiber substantially free of As and Sb. In addition, the diameter of the glass fiber of these embodiments can also be 15 μm or less.

[0036] [Glass composition]

[0037] The glass fiber of the present application, for example, has the following glass composition A. The glass composition can also contain components other than the following. Among the components other than the following, for example, SO3 is contained.

[0038] SiO2: 45 to 80%

[0039] Al2O3: 0 to 40%

[0040] B2O3: 0 to 30%

[0041] MgO: 0 to 30%

[0042] CaO: 0 to 30%

[0043] SrO: 0 to 30%

[0044] Li2O: 0 to 4.5%

[0045] Na2O: 0 to 5%

[0046] K2O: 0 to 5%

[0047] A preferable example of the glass composition A is a glass composition B in which the content of SiO2 is 45 to 70%, the content of Al2O3 is 15 to 40%, and the total of the contents of MgO, CaO, and SrO expressed in mass% is 0 to 30%.

[0048] In the glass compositions A and B, the content of SiO2 can also be 50 to 80% each.

[0049] Another preferable example of the glass composition A is a glass composition C in which the content of SiO2 is 52 to 66%, the content of Al2O3 is 12 to 26%, the content of B2O3 is 0 to 4%, the content of MgO is 5 to 19%, the content of CaO is 0 to 16%, and the content of Na2O is 0 to 2%.

[0050] The glass composition C can also be a glass composition D in which the content of SiO2 is 55 to 60%, the content of MgO is 5 to 16%, and the total of the contents of Li2O, Na2O, and K2O expressed in mass% is 0 to 2%.

[0051] The glass composition C can also be a glass composition E in which the content of Al2O3 is 19 to 26%, the content of B2O3 is 0 to 2%, the content of MgO is 9 to 19%, the content of CaO is 0 to 10%, the content of Li2O is 0 to 0.5%, the content of Na2O is 0 to 1.5%, and the content of K2O is 0 to 0.5%.

[0052] Another preferred example of glass composition A may be glass composition F having a SiO content of 45 to 78%, an AlO content of 0 to 18%, a BO content of 14 to 30%, a MgO content of 0 to 6%, a CaO content of 0 to 8%, a NaO content of 0 to 5% (preferably 0 to 1.5%), and a KO content of 0 to 1.5%. In glass composition F, the SiO content may be 50 to 80%.

[0053] Glass compositions A to F may be glass compositions that do not substantially contain divalent metal oxides other than MgO and CaO.

[0054] [Glass composition components]

[0055] (SiO2)

[0056] SiO2 is a component that forms the glass skeleton, and its content is set in the range of 45 to 80%, for example. Preferably, the content of SiO2 is 50% or more, more preferably 52% or more, further preferably 53% or more, particularly preferably 54% or more, and depending on the circumstances, it can also be 56% or more, further 57% or more. Preferably, the content of SiO2 is 73% or less, more preferably less than 70%, particularly preferably 68% or less, and depending on the circumstances, it can also be 66% or less, further 63% or less, and particularly preferably 62% or less.

[0057] (Al2O3)

[0058] Al2O3 helps maintain the heat resistance and water resistance of glass fiber, and is also a component that affects the devitrification temperature, viscosity, etc. The content of Al2O3 is set in the range of 0 to 40%, for example. The content of Al2O3 is preferably 10% or more, more preferably 12% or more, particularly preferably 15% or more, and depending on the circumstances, it can also be 17% or more, and further 19% or more. If the content of Al2O3 is too high, the liquidus temperature rises significantly, causing inconvenience in manufacturing. Therefore, the content of Al2O3 is preferably 30% or less, more preferably 26% or less, further preferably 25% or less, and depending on the circumstances, it can also be 22% or less, and further 20% or less.

[0059] (B2O3)

[0060] B2O3 forms the skeleton of glass and is an arbitrary component that affects properties such as devitrification temperature and viscosity. The content of B2O3 is set in the range of 0 to 30%, for example. The addition of a small amount of B2O3 helps to lower the devitrification temperature. Therefore, it is preferred to add B2O3 (content higher than 0%), and its content is preferably 0.1% or more, particularly preferably 0.5% or more, and depending on the circumstances, it can also be 1% or more, and further 1.5% or more. The content of B2O3 is preferably 2.5% or less, more preferably 2.2% or less, particularly preferably 2% or less, and depending on the circumstances, it can also be 1.8% or less, and further 1.6% or less. However, B2O3 can also be contained in an amount of about 14 to 30%, for example.

[0061] (MgO)

[0062] MgO is also a component that affects the devitrification temperature, viscosity, etc. The MgO content is set, for example, in the range of 0 to 30%. The MgO content is preferably 5% or more, more preferably 9% or more, particularly preferably 12% or more, and may be 15% or more depending on the situation. If the MgO content is too high, the liquidus temperature rises significantly. Therefore, the MgO content may be 28% or less, further 20% or less, and may be 19% or less, further 18% or less depending on the situation. However, the MgO content may be limited to the range of 0 to 6%, for example.

[0063] (CaO)

[0064] CaO contributes to the maintenance of water resistance, etc., and is an arbitrary component that affects the devitrification temperature, viscosity, etc. The content of CaO is set, for example, in the range of 0 to 30%. The addition of an appropriate amount of CaO lowers the liquidus temperature, and is preferred from this point of view. Therefore, it is preferred to add CaO (with a content higher than 0%), and its content is preferably 0.1% or more, more preferably 0.2% or more, and depending on the circumstances, it can also be 1% or more, and further 3% or more. The content of CaO is preferably 16% or less, more preferably 10% or less, and depending on the circumstances, it can also be 8% or less, further 5% or less, and particularly preferably less than 1%.

[0065] (SrO)

[0066] SrO is also an optional component that affects properties such as liquidus temperature, devitrification temperature, and viscosity. The SrO content is, for example, set within a range of 0 to 30%. However, excessive SrO impairs the homogeneity of the glass melt. Therefore, the SrO content is preferably set within a range of 0 to 5%. The SrO content is preferably 3% or less, more preferably 1% or less, particularly preferably 0.5% or less, and even more preferably 0.1% or less.

[0067] (BaO)

[0068] BaO is also an optional component that affects properties such as liquidus temperature, devitrification temperature, and viscosity. However, BaO is a component that has a large environmental and operational burden. Therefore, it is preferably substantially free of BaO.

[0069] <Total of MgO and CaO>

[0070] The total content of MgO and CaO is preferably set to 15 to 30%, more preferably 18 to 30%, and particularly preferably 20 to 30%.

[0071] <Total of MgO, CaO, and SrO>

[0072] The total content of MgO, CaO, and SrO is, for example, 0 to 30%, and preferably is set within the range of 15 to 30%.

[0073] (Li2O)

[0074] Li2O is a component that modifies the skeleton of glass and is an arbitrary component that affects properties such as liquidus temperature, devitrification temperature, and viscosity. The content of Li2O is set, for example, in the range of 0 to 4.5%. The addition of Li2O in this range is effective in lowering the devitrification temperature. Therefore, it is preferred to add Li2O (content higher than 0%), and its content is preferably 0.1% or more, more preferably 0.2% or more, particularly preferably 0.3% or more, and depending on the circumstances, it can also be 0.5% or more, and further 0.7% or more. The content of Li2O is preferably 2.5% or less, more preferably 2% or less, particularly preferably 1.8% or less, and depending on the circumstances, it can also be 1.6% or less, and further 1.5% or less. An example of a preferred range of the content of Li2O is 0.2 to 2.5%, which is in a range higher than the content of Na2O.

[0075] (Na2O)

[0076] Like Li2O, Na2O is an optional component that affects properties such as liquidus temperature, devitrification temperature, and viscosity. The Na2O content is, for example, set within a range of 0 to 5%. The Na2O content is preferably 0.05% or greater, more preferably 0.1% or greater, and may be 1% or greater depending on the circumstances. The Na2O content is preferably 2% or less, more preferably 1.5% or less, and particularly preferably 1.2% or less.

[0077] (K2O)

[0078] Like Li2O, K2O is an optional component that affects properties such as liquidus temperature, devitrification temperature, and viscosity, and plays a role in promoting clarification of the glass melt. The K2O content is, for example, set within a range of 0 to 5%. The K2O content may be 0.05% or higher, and further 0.1% or higher. The K2O content is preferably 2.5% or lower, more preferably 2% or lower, particularly preferably 1.5% or lower, and particularly preferably 1.2% or lower. Depending on the circumstances, it may be 1.0% or lower, further 0.5% or lower, and particularly 0.3% or lower.

[0079] <Total of Li2O, Na2O, and K2O>

[0080] The combined content of Li₂O, Na₂O, and K₂O is preferably set to 0-5%, more preferably 0-3%, and particularly preferably 0-2%. However, the presence of trace amounts of Li₂O, Na₂O, and K₂O has the effect of reducing the viscosity of the glass melt. Taking this into account, the combined content of Li₂O, Na₂O, and K₂O may be set to 0.1% or more, further 0.3% or more, and particularly 0.5% or more.

[0081] (Transition metal oxides, etc.)

[0082] Oxides of transition elements (Groups 3 to 11 of the periodic table), known as transition metal oxides, are also permitted as additional components. Examples of transition metal oxides include TiO2, ZrO2, Fe2O3, Y2O3, La2O3, and CeO2. ZnO, an oxide of an element from Group 12, is also permitted as an additional component. While it is desirable to generally exclude these oxides, they may inevitably be introduced as impurities from raw materials or manufacturing equipment. Depending on the type of oxide, trace amounts may be added to act as clarifiers, etc. The total content of oxides of elements from Groups 3 to 12 is preferably 3% or less, more preferably 1% or less, and particularly preferably 0.5% or less. If necessary, it may be limited to 0.1% or less. The content of each transition metal oxide is preferably 0.5% or less, particularly preferably 0.3% or less, and even more preferably 0.1% or less. Glass compositions containing CeO2 exhibit low devitrification temperatures.

[0083] In this specification, the content of transition element oxides present in glass compositions at multiple valences is calculated by converting them to the oxide with the highest oxidation number for that metal. For example, iron oxide is typically present in glass compositions as Fe₂O₃ or FeO. Therefore, the iron oxide present as FeO is converted to Fe₂O₃ and combined with the iron oxide present as Fe₂O₃ to calculate the iron oxide content (usually expressed as "T-Fe₂O₃").

[0084] (Other ingredients)

[0085] Examples of additional components other than those listed above include Cl and F. Other examples of additional components include SnO₂, Ga₂O₃, and P₂O₅. The content of each of the components listed here, from Cl to P₂O₅, is also preferably 0.5% or less, particularly preferably 0.3% or less, and even more preferably 0.1% or less. It is preferred that Cl and F are substantially absent. However, glass compositions containing F exhibit low devitrification temperatures.

[0086] As and Sb oxides such as As2O5, Sb2O3, and Sb2O5 function as clarifiers but have a large environmental impact. Therefore, the glass composition of the glass fiber is preferably adjusted so as to substantially not contain these oxides.

[0087] [Method for producing glass fiber]

[0088] The glass fibers described above can preferably be produced by a method comprising the following steps: forming a glass melt from a glass raw material containing a sulfate; and spinning glass fibers from the glass melt. As the sulfate, sulfates of alkali metals or alkaline earth metals can be used.

[0089] The sulfate preferably contains at least one selected from lithium sulfate, sodium sulfate, and potassium sulfate.

[0090] In the above-mentioned production method, the glass raw materials may be melted to form a glass melt, but the glass melt may not be solidified before being used for spinning. This method is called a direct melting method. Alternatively, the above-mentioned production method may include the following steps: solidifying the molten glass raw materials to obtain a solidified product; and melting the solidified product to form a glass melt. Since the solidified product, which serves as the intermediate raw material, is called a glass ball, this method is known as a glass ball melt method.

[0091] [Glass fiber forms and products using glass fiber]

[0092] One form of the glass fiber of the present invention is a long glass fiber. The length of the long glass fiber can be 2 meters or longer, or 5 kilometers or longer, but from the perspective of weight, it is preferably 300 kilometers or shorter. From another aspect, the present invention provides a rubber reinforcing rope having a wiring harness, which is formed by bundling the long glass fibers of the present invention. From another aspect, the present invention provides a rubber product reinforced by the rubber reinforcing rope of the present invention. Examples of rubber products include rubber belts, rubber tires, and rubber tubes. An example of a rubber belt is a transmission belt. Examples of transmission belts include interlocking transmission belts and friction transmission belts. An example of an interlocking transmission belt is a toothed belt represented by a timing belt for an automobile. Examples of friction transmission belts include flat belts, round belts, V-belts, and multi-V belts. The rubber tire is typically an automobile tire or a bicycle tire. The rubber reinforcing rope and rubber product of the present invention can be obtained using known manufacturing methods, except that the long glass fibers of the present invention are used.

[0093] From another aspect, the present invention provides a yarn obtained by twisting a plurality of bundles of long glass fibers of the present invention. In addition, the present invention also provides a fabric, particularly a cloth and a tape, using the yarn of the present invention as warp and / or weft yarn.

[0094] One form of the glass fiber of the present invention is short glass fiber. From another aspect, the present invention provides a glass fiber nonwoven fabric containing the short glass fiber of the present invention. The glass fiber nonwoven fabric of the present invention can be produced using known production methods, except for the use of the short glass fiber of the present invention.

[0095] From another aspect, the present invention provides a laminate containing the glass short fibers and / or cloth of the present invention and a resin material, in particular a laminate for printed circuit boards and a laminate for integrated circuits. In addition, it also provides a glass fiber reinforced thermosetting plastic product (GFRP) and a glass fiber reinforced thermoplastic plastic product (GFRTP) containing the glass fibers of the present invention.

[0096] Example

[0097] Hereinafter, the present invention will be described in more detail with reference to examples.

[0098] Glass raw materials were prepared to obtain glass fibers having the glass composition shown in Table 1. These raw materials were melted in a glass melting furnace and continuously produced using a drain plate mounted at the bottom of the furnace. The above-described methods i) to iii) were preferably applied, or not applied, to alter the β-OH content of the obtained glass fibers. Furthermore, sodium sulfate (glauber's salt) was used as part of the glass raw materials. The diameter of the obtained glass fibers was in the range of 10 to 12 μm.

[0099] Each glass fiber was spun for 20 minutes. If no fiber breakage occurred during this period, it was judged as "good", and if fiber breakage occurred, it was judged as "poor". In addition, as the frequency of fiber breakage, considering actual production, each glass fiber was spun 10 times at a high spinning speed of about 500 m / min (winding speed of the glass fiber). In addition, the spinning speed was adjusted around 500 m / min so that the diameter of the glass fiber would be the above-mentioned value. At this time, it was judged as successful when the fiber could be spun without breakage for more than 10 minutes, A for more than 9 times, B for 7 to 8 times, C for 4 to 6 times, D for 1 to 3 times, and E for 0 times. In addition, the temperature of the spun glass melt (spinning temperature) was adjusted to a temperature near the value shown in Table 1 at which the viscosity of the glass melt was.

[0100] β-OH is measured as follows. A glass melt extracted from a flow channel near a bushing in a glass melting furnace is solidified and slowly cooled to obtain a glass block. A glass plate with a thickness (t) of 1 mm is cut from the glass block and measured using FT-IR at a reference wavelength of 3846 cm. -1 Transmittance T1 (%) and OH group absorption wavelength 3600cm -1 Substituting t(1mm), T1 and T2 into the formula: (1 / t)log(T1 / T2), we can get the value of β-OH (unit: mm -1 ).

[0101] The content of SO3 is measured according to the same method as in Patent Document 2. That is, 1 g of the powdered sample is weighed in a platinum crucible, mixed with 2 g of Na2CO3, and then mixed with 1 g of Na2CO3, and alkali-melted in an electric furnace set at 950°C for 20 minutes. Thereafter, the contents of the platinum crucible are taken out in warm water (ultrapure water) and soaked at 80°C. Thereafter, the mixture is filtered with 5 types of C filter paper and the volume is adjusted to 100 ml. 20 ml of the liquid is measured, stirred with 30 ml of ion exchange resin for 10 minutes, filtered with 5 types of A filter paper, and the volume is adjusted to 100 ml. The content of the SO3 component is confirmed by measuring with an ion chromatograph.

[0102] The above measurement results are shown in Tables 1 and 2. Furthermore, when the deviation in the diameter of the glass fiber obtained was calculated according to the above definition, the values ​​in each example were all within ±1.5 μm. Furthermore, in the expression of the SO3 content, "<20" means that it is higher than 0 ppm and lower than 20 ppm.

[0103]

Table 1

[0104]

[0105]

Table 2

[0106]

Claims

1. A glass fiber, wherein Contains expressed in mass % SiO2: 45%~80% Al2O3: 0%~40% B2O3: 0%~30% MgO: 0%~30% CaO: 0%~30% SrO: 0%~30% Li2O: 0%~4.5% Na2O: 0%~5% K2O: 0%~5%, The SO3 content is less than 75 ppm on a mass basis. β-OH is 0.02mm -1 Above and below 0.55mm -1 . The glass fiber according to claim 1 , which has a diameter of 15 μm or less.

3. The glass fiber according to claim 2, wherein The SO 3 content is higher than 0 ppm and lower than 75 ppm on a mass basis, and As and Sb are substantially not contained.

4. The glass fiber according to claim 3, wherein The SO3 content is 20 ppm to 75 ppm on a mass basis, and the β-OH content is 0.3 mm -1 Above and below 0.55mm -1 .

5. The glass fiber according to claim 1, wherein The SO 3 content is higher than 0 ppm and lower than 75 ppm on a mass basis, and As and Sb are substantially not contained.

6. The glass fiber according to claim 5, wherein The SO3 content is 20 ppm to 75 ppm on a mass basis, and the β-OH content is 0.3 mm -1 Above and below 0.55mm -1 .

7. The glass fiber according to any one of claims 1 to 6, wherein The SO3 content is 20ppm to 70ppm based on mass, and the β-OH content is 0.35 mm -1 ~0.53mm -1 .

8. The glass fiber according to any one of claims 1 to 6, wherein The diameter is less than 10μm.

9. The glass fiber according to any one of claims 1 to 6, wherein The diameter variation is 3 μm or less.

10. The glass fiber according to claim 1, wherein The SiO2 content expressed in mass % is 50% to 80%.

11. The glass fiber according to claim 1, wherein The content of SiO2 expressed in mass % is 45% to 70%, the content of Al2O3 is 15% to 40%, and the total content of MgO, CaO and SrO expressed in mass % is 0% to 30%.

12. The glass fiber according to claim 11, wherein The SiO2 content expressed in mass % is 50 to 70%.

13. The glass fiber according to claim 12, wherein Expressed in mass %, the SiO2 content is 52% to 66%, the Al2O3 content is 12% to 26%, the B2O3 content is 0% to 4%, the MgO content is 5% to 19%, the CaO content is 0% to 16%, and the Na2O content is 0% to 2%.

14. The glass fiber according to claim 13, wherein The SiO2 content expressed in mass % is 55% to 60%, the MgO content is 5% to 16%, and the total content expressed in mass % of Li2O, Na2O, and K2O is 0% to 2%.

15. The glass fiber according to claim 13, wherein Expressed in mass %, the Al2O3 content is 19% to 26%, the B2O3 content is 0% to 2%, the MgO content is 9% to 19%, the CaO content is 0% to 10%, the Li2O content is 0% to 0.5%, the Na2O content is 0% to 1.5%, and the K2O content is 0% to 0.5%.

16. The glass fiber according to claim 1, wherein Expressed in mass %, the SiO2 content is 45% to 78%, the Al2O3 content is 0% to 18%, the B2O3 content is 14% to 30%, the MgO content is 0% to 6%, the CaO content is 0% to 8%, the Na2O content is 0% to 5%, and the K2O content is 0% to 1.5%.

17. The glass fiber according to claim 16, wherein The SiO2 content expressed in mass % is 50% to 78%.

18. The glass fiber according to any one of claims 11 to 17, wherein It contains substantially no divalent metal oxides other than MgO and CaO.

19. The glass fiber according to any one of claims 1 to 6, which is a long glass fiber.

20. The glass fiber according to any one of claims 1 to 6, which is a glass short fiber.

21. A rubber reinforcing rope comprising a bundle of the long glass fibers according to claim 19.

22. A rubber product reinforced with the rubber reinforcing cord according to claim 21.

23. A glass fiber nonwoven fabric comprising the glass short fibers according to claim 20.

24. A method for producing a glass fiber, the method being a method for producing the glass fiber according to any one of claims 1 to 18, comprising: a step of forming a glass melt from a glass raw material containing sulfate; a step of spinning glass fibers from the glass melt, The sulfate contains sulfate of an alkali metal or an alkaline earth metal.

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