Glass compositions and glass articles using the glass compositions

Abstract

This invention relates to glass compositions and glass articles using the glass compositions. The invention provides a glass composition suitable for glass fibers, etc., which does not require large amounts of rare earth raw materials, can be manufactured using general glass manufacturing equipment, and has a high Young's modulus and high crack resistance. The glass composition of this invention, expressed in mol%, contains SiO2: 50%–65%, Al2O3: 7.5%–26%, MgO: 15%–30%, CaO: 0–8%, B2O3: 0–3%, Li2O: 0–3%, Na2O: 0–0.2%, with a total MgO and CaO content of 18 mol%–35 mol%, and the Al2O3 / (MgO+CaO) value being less than 1.

Description

[0001] This application is a divisional application, which targets the Chinese national application number 201780092528.8 and the international application number PCT / JP2017 / 036810, filed on October 11, 2017, entered into China on December 25, 2019, and is entitled "Glass Composition and Glass Article Using the Glass Composition". Technical Field

[0002] This invention relates to glass compositions suitable for glass fibers, etc., and more specifically, to glass compositions suitable for rubber-reinforced yarns, glass fiber articles such as glass fiber nonwoven fabrics, granular glass articles used as fillers, etc.; and glass articles made of the glass compositions. Background Technology

[0003] Rubber reinforcing threads are used as reinforcing materials for rubber products subjected to repeated bending stress. These threads are embedded in rubber products such as rubber belts and tires to suppress the reduction in elongation and strength, contributing to improved dimensional stability and extended fatigue life. Known fibers used to constitute rubber reinforcing threads include aramid fibers, carbon fibers, polyester fibers, and glass fibers.

[0004] Patent Document 1 discloses a glass fiber composed of a glass composition with a high elastic modulus, suitable for use as a rubber-reinforced fiber. Most glass compositions used in practice have a Young's modulus (tensile modulus) of 90 GPa or less, but the glass composition in Patent Document 1 has a Young's modulus exceeding 100 GPa. This glass composition, expressed as a percentage by weight, contains 10% to 40% SiO2, 10% to 30% Al2O3, and 20% to 60% Y2O3 + La2O3 as essential components.

[0005] Patent Document 2 discloses a glass composition, expressed as a percentage by weight, comprising 60%–70% SiO2, 17%–27% Al2O3, 7%–17% MgO, and 0.1%–1.0% transition metal oxides. Examples of transition metal oxides include Fe2O3, TiO2, and CeO2. According to Patent Document 2, the only permitted components in the glass composition other than those described above are fluorine and sulfurous acid components, which have a clarifying effect, with a maximum permitted percentage by weight of 0.5%.

[0006] Patent Document 3 discloses glass fibers using oxynitride glass in order to provide high-strength glass fibers. Oxynitride glass is an oxide glass in which oxygen atoms are partially replaced by nitrogen atoms. The glass fibers in Patent Document 3 contain nitrides such as silicon nitride in a proportion exceeding 10% by weight.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2006 / 057405

[0010] Patent Document 2: Japanese Patent Application Publication No. 11-21147

[0011] Patent Document 3: Japanese Patent Publication No. 7-29815 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] The glass composition disclosed in Patent Document 1 has a high Young's modulus, but requires more than 20% by weight of Y₂O₃ and / or La₂O₃. Therefore, its manufacture requires a considerable amount of rare earth raw materials, increasing manufacturing costs. Furthermore, because it contains more than 20% by weight of rare earth oxides, the glass composition is relatively heavy.

[0014] According to the inventors' research, the elastic modulus of the glass fiber disclosed in Patent Document 2 is actually lower than that required for some glass fiber products, such as rubber-reinforced yarn. This is believed to be because the SiO2 content in the glass composition is too high. In the specific composition examples disclosed in Patent Document 2 (SiO2: 64.6% by weight or more; Tables 1 and 2), the SiO2 content, converted to molar percentage, is in the range of over 65%.

[0015] The oxynitride glass disclosed in Patent Document 3 requires melting the glass raw material in a nitrogen atmosphere. Furthermore, the inner wall of the furnace used to melt the raw material for the oxynitride glass cannot use platinum-based materials commonly used for glass melting; special materials are required.

[0016] To provide high-strength glass fibers, glass compositions with high elastic modulus, specifically Young's modulus, are suitable. However, the practical strength of glass fibers is affected by the formation of microcracks and the resulting failure due to their elongation. The strength against microcracks is influenced not only by Young's modulus but also significantly by the crack resistance load. Therefore, to obtain high-strength glass fibers, it is desirable to use glass compositions that possess both high Young's modulus and high crack resistance load. Furthermore, in recent years, there has been a demand for even higher strength in granular glass used as a filler in reinforcing masterbatches such as plastics.

[0017] In view of the above, the object of the present invention is to provide a glass composition that does not require a large amount of rare earth raw materials, and has a high Young's modulus and high crack resistance within the range of compositions that can be manufactured using general glass manufacturing equipment.

[0018] Methods for solving problems

[0019] This invention provides a glass composition comprising, in mole percent:

[0020]

[0021] The combined content of MgO and CaO ranges from 18 mol% to 35 mol%.

[0022] The molar ratio calculated using Al2O3 / (MgO+CaO) is less than 1.

[0023] The effects of the invention

[0024] According to the present invention, a glass composition can be provided that does not require a large amount of rare earth raw materials, and has a high Young's modulus and high crack resistance within the range of compositions that can be manufactured using general glass manufacturing equipment. Attached Figure Description

[0025] Figure 1 This is a diagram showing an example of the structure of a toothed rubber strip having a rubber reinforcing thread as a glass fiber article of the present invention. Detailed Implementation

[0026] The present invention will now be described in detail, but this description does not limit the invention to specific embodiments. Hereinafter, unless otherwise stated, all percentages of the glass component content are mol%. Furthermore, "substantially does not contain" a component means that the content of that component is 0.1 mol% or less, preferably less than 0.08 mol%, more preferably less than 0.05 mol%. Additionally, "granular" means granules with a maximum diameter of 5 mm or less, preferably 3 mm or less, more preferably 1 mm or less.

[0027] [Components of the glass composition]

[0028] (SiO2)

[0029] SiO2 is a component that forms the glass framework, and its content is set in the range of 50% to 65%. The SiO2 content is preferably 52% or more, more preferably 53% or more, particularly preferably 54% or more, and can be 56% or more, and further preferably 57% or more, depending on the situation. When the SiO2 content is too high, the Young's modulus may sometimes decrease. Therefore, the SiO2 content is preferably 62% or less, more preferably 61% or less, particularly preferably 60% or less, and can be 59% or less, and further preferably 58% or less, depending on the situation.

[0030] It should be noted that the SiO2 content in the glass composition disclosed in Patent Document 2, in a manner that allows for the calculation of the molar basis composition, exceeds 65%.

[0031] (Al2O3)

[0032] Al2O3 contributes to maintaining the heat resistance and water resistance of the glass composition, and is also a component that affects devitrification temperature and viscosity. The content of Al2O3 is set in the range of 7.5% to 26%. The content of Al2O3 is preferably 9% or more, more preferably 10% or more, particularly preferably 11% or more, and can be 12% or more, and more preferably 14% or more, depending on the situation. When the content of Al2O3 is too high, the liquidus temperature rises significantly, which may cause inconvenience in manufacturing. Therefore, the content of Al2O3 is preferably 24% or less, more preferably 22% or less, and can be 20% or less, and more preferably 19% or less, depending on the situation.

[0033] In particular, for mass production considerations, the devitrification temperature of the glass composition is preferably sufficiently low compared to the liquidus temperature. The content of Al₂O₃ suitable for sufficiently lowering the devitrification temperature compared to the liquidus temperature is 11%–15%, further 11%–14%, and particularly 11.5%–13.5%. As will be described later, appropriate amounts of Li₂O and / or B₂O₃ can be added to sufficiently lower the devitrification temperature compared to the liquidus temperature.

[0034] The suitable Al2O3 content for significantly increasing crack resistance is 15%–26%, further 16%–22%, and particularly 17%–21%.

[0035] (MgO)

[0036] MgO contributes to increasing Young's modulus and also affects devitrification temperature and viscosity. The MgO content is set in the range of 15% to 30%. Preferably, the MgO content is 17% or more, more preferably 18% or more, particularly preferably 20% or more, and depending on the situation, it can be 21% or more, and further, 22% or more. When the MgO content is too high, the liquidus temperature may sometimes rise significantly. Therefore, the MgO content is preferably 29% or less, and depending on the situation, it can be 28% or less, and further, 27% or less.

[0037] The content of MgO suitable for sufficiently lowering the devitrification temperature compared to the liquidus temperature is 18%–30%, and further 20%–28%.

[0038] The appropriate MgO content for significantly increasing crack resistance is 17%–30%, further 18%–26%, and particularly 22%–26%.

[0039] (CaO)

[0040] CaO helps maintain water resistance and the like, and is an optional component that affects the devitrification temperature, viscosity, etc. The content of CaO is set in the range of 0 to 8%. Considering the aspect of reducing the liquid phase temperature, it is preferred to add an appropriate amount of CaO. Therefore, it is preferred to add CaO (content exceeding 0%), and its content is preferably 0.1% or more, more preferably 0.12% or more, and may be 2% or more, further may be 3% or more according to circumstances. Among them, too much CaO sometimes reduces the Young's modulus. Therefore, the content of CaO is preferably 7% or less, more preferably 5% or less. The content of CaO that is particularly suitable for improving the Young's modulus and crack resistance load is less than 1%.

[0041] <Total of MgO and CaO>

[0042] The total content of MgO and CaO is set in the range of 18% to 35%, preferably set in the range of 20% to 30%.

[0043] <(Al2O3) / (MgO + CaO)>

[0044] The molar ratio of Al2O3 to the total content of MgO and CaO is set to be less than 1. Thereby, it is easy to balance a high Young's modulus and a not-too-high liquid phase temperature. The molar ratio Al2O3 / (MgO + CaO) is preferably 0.3 to 0.9, particularly preferably 0.35 to 0.85, and may be 0.4 to 0.7, further may be 0.4 to 0.6 according to circumstances. Among them, the molar ratio Al2O3 / (MgO + CaO) that is particularly suitable for improving the crack resistance load is 0.7 or more and less than 1, further 0.7 or more and 0.9 or less, especially 0.8 or more and 0.9 or less.

[0045] (B2O3)

[0046] B2O3 is an optional component that affects properties such as the devitrification temperature and viscosity while forming the glass skeleton. The content of B2O3 is set in the range of 0 to 3%. The addition of a trace amount of B2O3 sometimes helps to reduce the devitrification temperature. Therefore, it is preferred to add B2O3 (content exceeding 0%), and its content is preferably 0.1% or more, particularly preferably 0.3% or more, and may be 0.5% or more, further may be 0.7% or more according to circumstances. Among them, too much B2O3 sometimes reduces the Young's modulus. The content of B2O3 is preferably 2.5% or less, more preferably 2% or less, particularly preferably 1.8% or less, and may be 1.6% or less, further may be 1.5% or less according to circumstances. An example of the preferred range of the content of B2O3 is 0.1% to 1.6%.

[0047] (Li2O)

[0048] Li2O is a component that modifies the glass skeleton and is any component that affects properties such as liquidus temperature, devitrification temperature, and viscosity. The content of Li2O is set within the range of 0 to 3%. Adding Li2O within this range has the effect of reducing the devitrification temperature. Therefore, it is preferable to add Li2O (content exceeding 0%), and its content is preferably 0.1% or more, more preferably 0.2% or more, particularly preferably 0.3% or more, and may be 0.5% or more, further may be 0.7% or more depending on circumstances. When the content of Li2O is too high, the Young's modulus may sometimes decrease. Therefore, the content of Li2O is preferably 2.5% or less, more preferably 2% or less, particularly preferably 1.8% or less, and may be 1.6% or less, further may be 1.5% or less depending on circumstances. An example of the preferred range of the content of Li2O is 0.2% to 2.5% and is a range higher than the content of Na2O.

[0049] <Coexistence of B2O3 and Li2O>

[0050] If B2O3 and Li2O coexist (B2O3 > 0%, Li2O > 0%), it is easy to appropriately adjust the liquidus temperature and devitrification temperature of the glass. The total content of B2O3 and Li2O is preferably 0.1% or more, more preferably exceeding 0.5%, particularly preferably 0.7% or more, and may be 1% or more depending on circumstances. In addition, the total is preferably 5.5% or less, more preferably 5% or less, particularly preferably 4%, and may be 3.5% or less depending on circumstances.

[0051] From the aspect of improving properties, it is advantageous to add B2O3 and Li2O in an appropriate ratio. The molar ratio represented by B2O3 / Li2O is preferably 0.2 to 5, more preferably 0.4 to 2.5, particularly preferably 0.5 to 2, and preferably within the range of 0.8 to 1.25 depending on circumstances.

[0052] (Na2O)

[0053] Similar to Li2O, Na2O is any component that affects properties such as liquidus temperature, devitrification temperature, and viscosity. However, compared with Li2O, it has a greater effect on reducing the Young's modulus, so its content is set within the range of 0 to 0.2%. It is preferably substantially free of Na2O, but for the clarification of the glass melt, it is preferably limited to 0.2%, more preferably limited to 0.15%, and for example, it is preferably added within the range of exceeding 0% and less than 0.1%.

[0054] <Total of the components described above>

[0055] The total content of the seven components described above (SiO2, Al2O3, MgO, CaO, B2O3, Li2O, and Na2O) is preferably 95% or more, more preferably 97% or more, particularly preferably 98% or more, especially preferably 99% or more, and may be 99.5%, more preferably over 99.9%, or even 100%, depending on the circumstances. In an embodiment where the total content of the seven components is 100%, in other words, the glass composition consists only of SiO2, Al2O3, MgO, CaO, B2O3, Li2O, and Na2O.

[0056] <Additional ingredients>

[0057] As additional ingredients beyond the seven ingredients described above, the following ingredients can be cited as examples. However, the additional ingredients are not limited to these, and the representation of their content is also illustrative.

[0058] (K2O)

[0059] Like Li2O, K2O is any component that affects properties such as liquidus temperature, devitrification temperature, and viscosity, thus promoting the clarification of the glass melt. However, compared with Na2O, it has a greater effect on reducing Young's modulus, so its content is preferably set in the range of 0 to 0.1%, more preferably 0 to 0.05%, and particularly preferably 0 to 0.03%.

[0060] (SrO)

[0061] SrO can affect properties such as liquidus temperature, devitrification temperature, and viscosity. However, adding SrO can sometimes decrease Young's modulus. Furthermore, excessive SrO can sometimes hinder the homogeneity of the glass melt. Therefore, the SrO content is preferably set in the range of 0-5%. The SrO content is preferably 3% or less, more preferably 1% or less, particularly preferably 0.5% or less, and especially preferably 0.1% or less. Additionally, the total SrO content with CaO is preferably set to 8% or less, more preferably 6% or less, and especially preferably 5% or less.

[0062] (BaO)

[0063] BaO can affect properties such as liquidus temperature, devitrification temperature, and viscosity. However, the addition of BaO can sometimes significantly reduce Young's modulus. Furthermore, BaO is an environmentally unfriendly and hazardous component. Therefore, it is preferable to avoid adding BaO.

[0064] (Transition metal oxides, etc.)

[0065] 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 Group 12 elements, is also permitted as an additional component. These oxides are preferably excluded substantially, but sometimes they inevitably mix in as impurities from raw material sources or manufacturing equipment. In addition, depending on the type of oxide, their trace additions sometimes function as clarifying agents, etc. The total content of oxides of elements from Groups 3 to 12 is preferably 3% or less, more preferably 1% or less, particularly preferably 0.5% or less, and may be limited to 0.1% or less if necessary. The content of each transition metal oxide is preferably 0.5% or less, particularly preferably 0.3% or less, and especially preferably 0.1% or less.

[0066] In this specification, the content of oxides of transition elements present in the glass composition with multiple valences is calculated by converting them into the oxide with the highest oxidation state of that metal. For example, iron oxide is usually present in the glass composition as Fe2O3 or FeO. Therefore, iron oxide present as FeO is converted into Fe2O3, and the content of iron oxide is calculated by adding the iron oxide present as Fe2O3 (conventionally expressed as "T-Fe2O3").

[0067] (Other ingredients)

[0068] Examples of additional components besides those mentioned above include SnO2, Sb2O3, Sb2O5, SO3, Cl, and F. These components can function as clarifying agents. Additionally, Ga2O3 and P2O5 can be examples of other additional components. The content of each of the SnO2 to P2O5 components shown in this column is preferably 0.5% or less, particularly preferably 0.3% or less, and especially preferably 0.1% or less.

[0069] <Examples of preferred methods for glass compositions>

[0070] In one embodiment of the invention, the glass composition substantially does not contain oxides of rare earth elements. In another embodiment of the invention, the glass composition contains 0-0.5% T-Fe₂O₃ and substantially does not contain oxides of divalent metals other than MgO, CaO, and FeO. In yet another embodiment of the invention, the glass composition substantially does not contain alkali metal oxides other than Li₂O and Na₂O. In yet another embodiment of the invention, the glass composition substantially does not contain TiO₂ and ZrO₂. In yet another embodiment of the invention, the nitride content of the glass composition is 10% by weight or less, and preferably substantially does not contain nitrides.

[0071] In one embodiment of the invention, the total content of the aforementioned seven components (SiO2, Al2O3, MgO, CaO, B2O3, Li2O, and Na2O) and the additional five components (K2O, SrO, TiO2, ZrO2, and T-Fe2O3) in the glass composition is 99% or more, further 99.5% or more, particularly 99.9% or more, especially 99.95% or more, and depending on the case, 100%. In this embodiment, the content of the additional five components is: K2O: 0-0.05%, SrO: 0-5%, TiO2: 0-0.1%, ZrO2: 0-0.1%, and T-Fe2O3: 0-0.5%.

[0072] In one embodiment of the invention, the total content of the aforementioned seven components (SiO2, Al2O3, MgO, CaO, B2O3, Li2O, and Na2O) and the three additional components (K2O, TiO2, and T-Fe2O3) in the glass composition is 99% or more, further 99.5% or more, particularly 99.9% or more, especially 99.95% or more, and depending on the case, 100%. In this embodiment, the content of the three additional components is K2O: 0 to 0.05%, TiO2: 0 to 0.1%, and T-Fe2O3: 0 to 0.5%.

[0073] In one embodiment of the present invention, the glass composition comprises:

[0074]

[0075] The molar ratio calculated using Al2O3 / (MgO+CaO) is 0.3–0.5.

[0076] The combined content of MgO and CaO in this glass composition ranges from 18% to 35%. This embodiment is particularly suitable for adjusting the devitrification temperature to a preferred range in relation to the liquidus temperature, etc.

[0077] In one embodiment of the present invention, the glass composition comprises:

[0078]

[0079]

[0080] The molar ratio calculated using Al2O3 / (MgO+CaO) is 0.5 or more and less than 1, preferably 0.7 to 0.9. The total content of MgO and CaO in this glass composition is in the range of 18% to 35%. This embodiment is particularly suitable for increasing crack resistance.

[0081] [Properties of the Glass Composition]

[0082] (proportion)

[0083] In one embodiment of the present invention, the specific gravity of the glass composition is 3.0 or less, preferably 2.8 or less, and more preferably 2.7 or less. The lower limit of the specific gravity is not particularly limited and can be 2.5 or more. The glass composition disclosed in Patent Document 1, which contains a considerable amount of rare earth elements, has a specific gravity exceeding 3.

[0084] (Young's modulus)

[0085] In one embodiment of the invention, the Young's modulus of the glass composition is 98 GPa or more, preferably 100 GPa or more. There is no particular limitation on the upper limit of the Young's modulus; it can be 110 GPa or less, and more preferably 105 GPa or less. The method for determining the Young's modulus is described in the Examples section. Glass compositions with high Young's modulus are suitable for providing glass fibers with low deformation under tensile stress.

[0086] (Crack resistance load)

[0087] In one embodiment of the invention, the crack resistance of the glass composition is 300g or more, preferably 400g or more, and more preferably 500g or more. Surprisingly, according to one embodiment of the invention, glass compositions with particularly high crack resistance, such as 900g or more, further 1000g or more, and especially 1200g or more, can also be provided. The upper limit of the crack resistance is not particularly limited and can be 2000g or less. The method for measuring the crack resistance is described in the Examples section. Glass compositions with high crack resistance are suitable for providing glass fibers with high strength against tensile or bending stresses.

[0088] In another embodiment of the invention, the glass composition has a crack resistance load in the range of 300g to 550g and a devitrification temperature TL of 1250°C to 1350°C. This composition is suitable for the mass production of high-strength glass fibers.

[0089] (Relationship between high-temperature viscosity and devitrification temperature)

[0090] In one embodiment of the present invention, the devitrification temperature TL of the glass composition is at least 20°C lower than the temperature T2 at which the logarithm (logη) of the liquid phase viscosity η (in dPa·s) of the molten glass composition reaches 2, preferably at least 30°C lower, more preferably at least 50°C lower, and particularly preferably at least 100°C lower. Furthermore, in another embodiment of the present invention, the devitrification temperature TL of the glass composition is higher than the temperature T3 at which the logarithm (logη) of the liquid phase viscosity η of the molten glass composition reaches 3, but lower than T2.5 based on the same definition. Methods for measuring the devitrification temperature TL and the liquid phase viscosity η are described in the Examples section.

[0091] In one embodiment of the present invention, the devitrification temperature TL is 1450°C or less, preferably 1400°C or less, more preferably 1380°C or less, and particularly preferably 1350°C or less.

[0092] [Glass fiber]

[0093] The glass composition described above is suitable for use as glass fiber. In another respect, the present invention provides glass fiber composed of the glass composition of the present invention. The glass fiber can be either long glass fiber or short glass fiber. Long glass fiber is manufactured by allowing molten glass of controlled viscosity to flow from a nozzle and then winding it using a winding machine. This continuous fiber is cut to an appropriate length during use. Short glass fiber is manufactured by blowing away molten glass using high-pressure air, centrifugal force, or the like. Short glass fiber has a cotton-like morphology and is therefore sometimes referred to as glass wool.

[0094] [Fiberglass Products]

[0095] The long and short glass fibers of the present invention can be further processed into various glass fiber products for use. As for glass fiber products where high Young's modulus and crack resistance are particularly desirable, rubber-reinforced yarns are an example. Rubber-reinforced yarns consist of bundles of multiple long glass fibers (called filaments). Each bundle typically consists of 100 to 2000, or 200 to 600, glass filaments. Most bundles are used to coat with a coating layer that improves adhesion to rubber. The processing liquid and method for forming the coating layer have been described in detail in documents such as Patent Document 1, and therefore will not be described here.

[0096] Other glass fiber products that exemplify the characteristics of glass fibers, such as high Young's modulus and high crack resistance, include glass fiber nonwoven fabrics. Glass fiber nonwoven fabrics are nonwoven fabrics composed of glass fibers; one example is cellophane, which is made by papermaking from tiny short glass fibers. Generally, high strength is expected in glass fiber nonwoven fabrics. In particular, high porosity is often required in applications such as reinforcing materials for electrolyte membranes in fuel cells and separators in electrochemical devices, such as secondary batteries. Therefore, there is a particular expectation for improving the strength of glass fibers in these applications.

[0097] From another perspective, the present invention provides glass fiber articles comprising the glass fibers of the present invention. As described above, preferred examples of glass fiber articles include rubber-reinforced yarns having bundles of long glass fibers and glass fiber nonwoven fabrics comprising short glass fibers.

[0098] [Glassy Granular Products]

[0099] The glass compositions described above are suitable not only for use as glass fibers but also for use as granular glass, particularly glass flakes. Glass flakes are flake-shaped glass with dimensions, for example, an average thickness of 2 μm to 5 μm and an average grain size of 10 μm to 4000 μm (especially 10 μm to 1000 μm). Glass flakes are mass-produced by forming molten glass using methods such as blow molding and rotational molding. Granular glass, represented by glass flakes, is sometimes used as a filler mixed into the base material to improve its strength. A representative base material is plastic. In particular, the miniaturization of plastic parts in recent years has demanded further improvements in the dimensional stability and strength of the parts. Therefore, for granular glass used as a filler, it is desirable to use glass compositions with high Young's modulus and high crack resistance. The shape of granular glass is typically flake-shaped, but there are no restrictions on its shape as long as it is equivalent to "granular" (maximum diameter less than 5 mm).

[0100] Figure 1 The diagram shows an example of a rubber strip containing rubber reinforcing threads. The rubber strip 1 has a so-called toothed strip shape and includes a base rubber 3 and two or more rubber reinforcing threads 2 embedded within the base rubber 3. The rubber reinforcing threads 2 are arranged parallel to each other along the length direction of the rubber strip 1, in other words, along a direction orthogonal to the strip width direction transverse to the protrusions 4, which are called "teeth". Toothed cloth 5 is adhered to the surface of the rubber strip 1 where the protrusions 4 are formed, for purposes such as suppressing wear.

[0101] Example

[0102] The present invention will be described in more detail below through examples.

[0103] Glass raw materials were blended according to the compositions shown in Tables 1 and 2, and melted in an electric furnace maintained at 1500°C–1600°C for 4 hours. During melting, the glass was stirred repeatedly using a quartz glass stirring rod to ensure homogeneity. The molten glass was then poured into a stainless steel frame to form plate-shaped glass. These plate-shaped glass plates were held at their respective glass transition temperatures +20°C–50°C for at least 2 hours, and then allowed to cool naturally to room temperature for approximately 8 hours. This slow cooling process yielded the sample glass for testing. The following properties were measured using the sample glass thus obtained.

[0104] (density)

[0105] For small pieces of sample glass, the density was determined using the Archimedes method with water as the impregnation solution.

[0106] (Young's modulus)

[0107] The Young's modulus was measured by the ultrasonic pulse method described in Japanese Industrial Standard (JIS) R 1602-1995. Each test piece was a cuboid with dimensions of 5 mm×25 mm×35 mm. Additionally, the measurement was carried out at room temperature in the atmosphere. The device used was a 25DLPlus type manufactured by Panametrics.

[0108] It should be noted that for glass fibers and bulk glass composed of the same glass composition, it is generally known that glass fibers have a relatively low elastic modulus. It is considered that this is because when formed from a glass melt, the glass fibers are cooled more quickly. However, there is a positive correlation between the elastic modulus of glass fibers and the elastic modulus of bulk glass (the elastic modulus measured by the above JIS), so it is appropriate to use the measured values based on the above JIS to evaluate the properties of glass fibers or the glass composition used as glass fibers. Regarding granular glass, it is also reasonable to select an appropriate glass composition by referring to the evaluation results of the elastic modulus of bulk glass. The same applies to the crack resistance load described in the next paragraph.

[0109] (Crack resistance load)

[0110] The crack resistance load was measured by a test of pressing a Vickers indenter onto the surface of a mirror-polished specimen glass. The device used was a Vickers hardness tester manufactured by Akashi Seisakusho. The specimen glass was processed into a plate shape with parallel planes. Additionally, the plane for pressing the indenter was polished into a mirror surface using a suspension of cerium oxide abrasive. The Vickers indenter was pressed onto this mirror-polished surface for 15 seconds, and after unloading for 5 minutes, it was measured whether cracks occurred starting from the vertices in the square indentations remaining on the surface of the specimen glass. Regarding whether cracks occurred, it was judged by observing with a microscope assembled in the Vickers hardness tester. The magnification of the microscope was 100 times. This measurement was carried out 10 times, and the number of vertices where cracks occurred was divided by the total number of vertices 40 measured to calculate the crack occurrence probability P. Regarding the above measurement, the load was changed in the order of 50 g, 100 g, 200 g, 300 g, 500 g, 1000 g, 2000 g, and repeated until P = 100% was reached to obtain the crack occurrence probability P at each load. In this way, two adjacent loads WH and WL straddling P = 50% and the crack occurrence probabilities PH and PL at this time (PH < 50% < PL) were obtained. Taking the load and the crack occurrence probability as the horizontal axis and the vertical axis respectively, a straight line passing through the two points (WH, PH) and (WL, PL) was plotted, and the load at P = 50% was taken as the crack resistance load.

[0111] (Devitrification temperature TL)

[0112] The glass sample was crushed and passed through a sieve with a mesh size of 2.380 mm. Glass particles remaining on a sieve with a mesh size of 1.000 mm were collected. These glass particles were immersed in ethanol, ultrasonically cleaned, and then dried in a constant temperature bath. 30 g to 32 g of these glass particles were placed in a platinum boat with a width of 12 mm, a length of 200 mm, and a depth of 10 mm to form a generally uniform thickness, serving as the test sample. The platinum boat was kept in an electric furnace (temperature gradient furnace) with a temperature gradient of 950 °C to 1550 °C for 2 hours. The highest temperature at which the crystalline phase (devitrification) distributed in the test sample was observed was evaluated as the liquidus temperature (TL).

[0113] (T2, T2.5, T3)

[0114] T2, T2.5, and T3 were measured as follows: For the sample glass, the viscosity at each temperature was measured at 25°C intervals using the platinum ball pulling method, and the intermediate viscosity was calculated using the Fulcher equation.

[0115] The aforementioned properties were measured for each of the obtained samples. The results are shown in Tables 1 and 2. As can be seen from the examples, glass compositions with moderate specific gravity, high Young's modulus, and high crack resistance were obtained.

[0116]

[0117] Table 2

[0118]

[0119] RO = (MgO + CaO); the content of the components is expressed in mol% and the unit of TL to T2 is ℃.

Claims

1. A glass composition comprising, in mole percent: SiO2 53%~62% Al2O3 7.5%~15% MgO 18%~30% CaO 0-8% B2O30~1.5% Li2O 0.2%~2.5% Na2O 0~0.2% Y2O3 0~0.1% La2O30~0.1%, The content of Li2O is higher than that of Na2O. The combined content of MgO and CaO ranges from 18 mol% to 35 mol%. The combined content of B2O3 and Li2O is less than 3.5 mol%. The molar ratio calculated using Al2O3 / (MgO+CaO) is less than 1. The total content of SiO2, Al2O3, MgO, CaO, B2O3, Li2O and Na2O is 95 mol% or more.

2. A glass composition comprising, in mole percent: SiO2 53%~62% Al2O3 7.5%~15% MgO 18%~30% CaO 0-8% B2O3 0~1.5% Li2O 0.2%~2.5% Na2O 0~0.2% Y2O3 0~0.1% La2O3 0~0.1% The content of Li2O is higher than that of Na2O. The combined content of MgO and CaO ranges from 18 mol% to 35 mol%. The combined content of B2O3 and Li2O is less than 3.5 mol%. The molar ratio calculated using Al2O3 / (MgO+CaO) is less than 1. The total content of SiO2, Al2O3, MgO, CaO, B2O3, Li2O, Na2O, K2O, SrO, TiO2, ZrO2, and T-Fe2O3 is 99 mol% or more. in, The contents of K2O to T-Fe2O3, expressed in mole percent, are as follows: K2O: 0-0.05%, SrO: 0-5%, TiO2: 0-0.1%, ZrO2: 0-0.1%, T-Fe2O3: 0-0.5%.

3. The glass composition according to claim 1 or 2, wherein, The Young's modulus, as determined by the ultrasonic pulse method described in JIS R1602-1995, is above 98 GPa.

4. The glass composition according to claim 1 or 2, wherein, The content of B2O3 is greater than 0 mol% and less than 1.5 mol%.

5. The glass composition according to claim 1 or 2, wherein, The SiO2 content is 56 mol% to 60 mol%.

6. The glass composition according to claim 1 or 2, wherein, The glass composition contains 0 to 0.5 mol% T-Fe2O3 and substantially contains no oxides of divalent metals other than MgO, CaO and FeO.

7. The glass composition according to claim 1 or 2, wherein, Apart from Li₂O and Na₂O, it does not actually contain alkali metal oxides.

8. The glass composition according to claim 1 or 2, wherein, The glass composition does not substantially contain TiO2 and ZrO2.

9. The glass composition according to claim 1 or 2, wherein, The glass composition comprises, expressed in mol% as: SiO2 53%~60% Al2O3 11%~15% MgO 18%~30% CaO 0-5% B2O3 0.2%~1.5% Li2O 0.5%~2.5% Na2O 0~0.2%, The molar ratio calculated using Al2O3 / (MgO+CaO) is 0.3–0.

5.

10. The glass composition according to claim 1 or 2, wherein, The CaO content ranges from 0.1 mol% to 8 mol%.

11. The glass composition according to claim 1 or 2, wherein, The SiO2 content is 56 mol% to 62 mol%.

12. A glass fiber comprising any one of the glass compositions according to claims 1 to 11.

13. A rubber-reinforced thread comprising a bundle of glass long fibers as described in claim 12.

14. A short glass fiber comprising the glass composition according to any one of claims 1 to 11.

15. A glass fiber nonwoven fabric comprising the glass short fibers of claim 14.

16. A granular glass comprising the glass composition according to any one of claims 1 to 11.

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