A modified low-boron low-fluorine alkali-free glass fiber composition and a method for preparing the same

Abstract

The application belongs to the technical field of alkali-free glass fiber, and particularly relates to a modified low-boron and low-fluorine alkali-free glass fiber composition and a preparation method thereof. The modified low-boron and low-fluorine alkali-free glass fiber composition comprises the following components: SiO2, Al2O3, B2O3, CaO, MgO, Fe2O3, TiO2, F2, R2O, X2O3, Li2O and ZnO, wherein R2O is a mixture of K2O and Na2O, and X2O3 is a mixture of La2O3 and Y2O3. The application provides the modified low-boron and low-fluorine alkali-free glass fiber composition and the preparation method thereof. Through the introduction of rare earth elements and the synergistic effect of Li2O and B2O3 components, the problems of high viscosity, high crystallization risk and narrow temperature window of the existing low-boron and low-fluorine glass fiber are effectively solved while the content of boron and fluorine is greatly reduced, and the elastic modulus, breaking strength and water resistance of the glass fiber are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of alkali-free glass fiber technology, specifically relating to a modified low-boron, low-fluorine alkali-free glass fiber composition and its preparation method. Background Technology

[0002] Alkali-free glass fiber (also known as E-glass fiber) is an aluminoborosilicate glass fiber with an alkali metal oxide (R2O) content of less than 0.8%. Alkali-free glass possesses high strength and good chemical stability, and is primarily used in composite materials and electrical insulation applications.

[0003] The preparation of traditional alkali-free glass fiber compositions heavily relies on boron and fluorine raw materials. B2O3, as the core network-forming oxide, not only effectively improves glass melting performance and reduces high-temperature viscosity but also enhances the formability and overall mechanical properties of glass fibers. Fluorides, on the other hand, are highly efficient fluxing and clarifying agents, significantly lowering the glass melting point, promoting bubble escape from the melt, and improving the uniformity of the glass melt. However, this traditional formulation system suffers from several industry pain points: Firstly, traditional alkali-free glass has a high boron and fluorine content, and boron-containing raw materials are mainly imported, resulting in relatively high costs. Secondly, boron and fluorine raw materials are highly volatile during high-temperature glass melting, with large amounts of boron and fluorides escaping with the flue gas. This not only reduces raw material utilization and further increases production costs but also corrodes furnace equipment. Furthermore, the released boron and fluorine pollutants damage the atmosphere, water bodies, and other ecological environments. Therefore, low-boron, low-fluorine alkali-free glass fiber compositions are a key research focus in the glass fiber field.

[0004] CN103172268A discloses a low-boron, low-softening-point E-glass fiber, its preparation method, and its applications. By mass percentage, it contains: 54.2-55.3% SiO2, 14.2-15.2% Al2O3, 22.8-24.3% CaO, 2.2-2.8% MgO, 0.5-0.8% Na2O and K2O, 2.0-3.0% B2O3, with the balance being Fe2O3. By reducing the amount of boron-calcium silicate, it reduces reliance on imported raw materials, and lowers the softening point and melting temperature to reduce energy consumption. The product mainly meets the corrosion resistance and insulation performance requirements of yarn used in high-pressure oil pipelines. However, its boron content reduction is limited, and its glass elastic modulus, tensile strength, and water resistance are relatively weak, making it unsuitable for the needs of high-end electronics and high-end composite materials.

[0005] CN105217962A discloses a low-boron, fluorine-free glass fiber composition, comprising, by mass percentage: 49-59% SiO2, 13-23% Al2O3, 15-25% CaO, 2.75% MgO, 0.5% B2O3, and 0.27% Fe2O3, with the balance being unavoidable impurities. Its core feature is the use of calcined alumina to replace traditional pyrophyllite as the Al2O3 source, combined with an electric fluxing process. This addresses the problems of high viscosity, severe crystallization, pyrophyllite shortage, and poor heat permeability caused by excessive iron content in traditional low-boron, fluorine-free glass, reducing total iron content, decreasing SO2 emissions, extending furnace life, increasing fiber yield, and alleviating raw material supply pressure. While the use of calcined alumina to replace pyrophyllite alleviates the pyrophyllite shortage to some extent, calcining alumina requires higher melting temperatures, resulting in high energy consumption.

[0006] CN120573956A discloses a low-boron, high-performance, alkali-free glass fiber composition, comprising 52-60% SiO2, 11-15% Al2O3, 2-6% B2O3, 18-25% CaO, 1-3% MgO, 0.1-0.6% Fe2O3, 0.1-2.5% TiO2, 0.3-0.6% F2, 0.05-0.75% K2O, 0.05-0.75% Na2O, and 0.1-3% XO, wherein XO is Fe. One or more of O, SeO2, BeO, La2O3, and CeO2; while reducing the boron content, it ensures melting and molding stability, optimizes light transmittance and dielectric constant through component adjustment, and the product is suitable for large-scale production in tank furnaces; however, the reduction in boron content in this composition is limited, and in order to maintain the stability of the product under alkali-free conditions, a relatively high boron and fluorine content is still required, and in order to improve the elastic modulus of glass fiber, multiple rare elements need to be added, making it impossible to simultaneously achieve low boron and low fluorine content and excellent glass fiber performance.

[0007] Although the boron content has been reduced in existing technologies, glass performance and melting conditions still need further optimization. Furthermore, with the significant reduction in boron and fluorine content, the high-temperature viscosity of the glass melt increases significantly, leading to poor melt flow during the glass melting process. This results in insufficient melting and uneven mixing of raw materials, making glass products prone to defects such as bubbles and stones, thus reducing product yield. Simultaneously, the reduced boron and fluorine content significantly narrows the glass's temperature window (the difference between the forming temperature and the crystallization temperature). The probability of crystallization increases significantly throughout the melting, heat preservation, and fiber drawing processes. Once crystallization occurs, it directly leads to a sharp increase in the difficulty of glass fiber drawing, a higher breakage rate, and a significant decrease in production efficiency, even making continuous industrial production impossible. Moreover, existing low-boron and low-fluorine formulations, while reducing boron and fluorine content, struggle to maintain the core performance of glass fibers. While some formulations achieve a reduction in boron and fluorine content and basic optimization of melting and forming performance, key performance characteristics such as the elastic modulus, tensile strength, and water resistance of glass fibers are reduced to varying degrees, failing to meet the high-performance requirements of downstream high-end composite materials and electronic information fields. Summary of the Invention

[0008] To overcome the aforementioned defects in the existing technology, this invention provides a modified low-boron, low-fluorine, alkali-free glass fiber composition and its preparation method. By introducing rare earth elements to synergistically work with Li2O and B2O3 components, the boron and fluorine content is significantly reduced, while effectively solving the problems of high viscosity, high crystallization risk, and narrow temperature window of existing low-boron, low-fluorine glass fibers. This significantly improves the elastic modulus, breaking strength, and water resistance of the glass fiber.

[0009] The modified low-boron, low-fluorine, alkali-free glass fiber composition of the present invention comprises the following components in weight percentage: SiO2: 52.0-62.0%, Al2O3: 14.0-17.0%, B2O3: 0.1-3.0%, CaO: 20-23%, MgO: 0.5-3%, Fe2O3: 0.1-0.3%, TiO2: 0.1-1.5%, F2: 0.05-0.1%, R2O: 0.1-0.8%, X2O3: 0.2-1.0%, Li2O: 0.2-0.8%, ZnO: 0.1-2.0%; wherein: R2O is a mixture of K2O and Na2O; X2O3 is a mixture of La2O3 and Y2O3.

[0010] Preferably, the mass ratio of K2O to Na2O in the R2O is 1:(0.3-0.5).

[0011] Preferably, the mass percentage of X2O3 is 0.25-0.8%, and the mass ratio of La2O3 to Y2O3 is 1:(0.55-1.5).

[0012] Preferably, the mass ratio of X2O3, Li2O and B2O3 is (0.1-4):(0.05-4):1.

[0013] Preferably, the mass ratio of CaO to MgO is (8-12):1.

[0014] Preferably, the mass percentage of B2O3 is 0.2-2.5%.

[0015] Preferably, the TiO2 mass percentage is 0.2-1.4% and the ZnO mass percentage is 0.25-1.9%.

[0016] Preferably, the raw materials used are pyrophyllite, dolomite, borocalcite, limestone, rare earth mineral raw materials, zinc oxide, lithium oxide, titanium dioxide, fluorite, and recycled glass powder.

[0017] Preferably, the raw materials used are kaolin, pyrophyllite, dolomite, borocalcite, quicklime, rare earth mineral raw materials, zinc oxide, lithium oxide, titanium dioxide, fluorite, and recycled glass powder.

[0018] The preparation of glass fibers using the above-mentioned modified low-boron, low-fluorine, alkali-free glass fiber composition includes the following steps: S1: Mix the required raw materials in proportion for 2-6 minutes to obtain the mixture; S2: The mixture is delivered to the kiln hopper using a pneumatic conveying tank, and then the mixture is added to the kiln using a feeding machine; S3: Melt the mixture at 1430-1500℃ under an atmosphere with a residual oxygen concentration of 1.5-5 Vol% to obtain a clear and homogeneous glass melt; S4: Homogeneous molten glass flows through the furnace passage to the baffle plate, maintaining the baffle plate temperature at 1200-1250℃, and is drawn into wire to obtain modified low-boron, low-fluorine, alkali-free glass fiber.

[0019] In this invention, pyrophyllite is the main aluminosilicate raw material, primarily incorporating SiO2 and Al2O3. SiO2 serves as the main body of the glass network skeleton, providing the fibers with chemical stability, mechanical strength, and water resistance. Its content is controlled between 52.0% and 62.0%, ensuring network integrity without excessively increasing the melting temperature. The Al2O3 content is 14.0% to 17.0%, which improves the glass's softening point, elastic modulus, and acid resistance. Together with SiO2, it forms a stable three-dimensional network structure, suppressing the tendency for crystallization. Furthermore, compared to clay minerals such as kaolin, pyrophyllite contains lower levels of iron and alkali metal impurities. Its layered structure is also more prone to deagglomeration during melting, which is beneficial for the homogenization of the molten glass.

[0020] CaO can drastically reduce the high-temperature viscosity of glass, accelerate the melting and clarification process, and improve the mechanical strength of fibers; MgO improves the water resistance of glass, lowers the liquidus temperature to inhibit crystallization, and shortens the solidification time of the glass melt. By controlling the mass ratio of CaO to 20-23% and MgO to 0.5-3%, and the CaO / MgO ratio to between 8-12, it is possible to prevent excessive Ca from causing easy crystallization, excessive thermal expansion, and poor water resistance, and excessive Mg from causing increased melt viscosity, melting difficulties, and increased fiber breakage rate.

[0021] This invention significantly reduces the boron content in traditional alkali-free glass fibers by 5-10%, aiming to reduce environmental pollution caused by boron volatilization, extend furnace life, and reduce costs. However, a small amount of B2O3 is retained to maintain its partial modification effect on the glass network. The reason is that if the B2O3 content is too low, it cannot effectively inhibit crystallization and reduce glass viscosity, while if it is too high, it will lead to increased costs. Therefore, in order to ensure the performance of glass fibers with low boron content, the rare earth element lanthanum is used as a good crystal nucleation inhibitor, and the mass percentage of B2O3 can be further reduced to 0.1-3.0%.

[0022] TiO2, as an intermediate component of the glass network, can fill the gaps in the silicon-aluminum network, optimize the internal structure of the glass, and significantly improve the high-temperature structural stability, acid and alkali corrosion resistance, and anti-aging ability of glass fibers. At the same time, it can gently regulate the temperature gradient of glass viscosity and broaden the process window for fiber drawing. The content of TiO2 is limited to 0.1-1.5%, preferably 0.3-1.2%, to avoid insufficient modification effect due to too low content, and excessive content to induce high-temperature crystallization of glass and abnormal increase in viscosity, resulting in unstable fiber drawing and increased fiber breakage.

[0023] A small amount of fluoride ions can significantly reduce the high-temperature melting viscosity of glass, promote the rising and expulsion of bubbles, and improve the clarification and homogenization effect of the glass melt. This invention controls the fluoride content to 0.05-0.1%, achieving a low-fluoride and environmentally friendly formula. This formula not only plays a role in melting and clarification, but also avoids the large-scale volatilization of fluoride from corroding the refractory materials of the kiln and polluting the flue gas environment. At the same time, it prevents excessive fluoride from damaging the dense structure of the glass, causing a decrease in fiber water resistance and a reduction in mechanical strength.

[0024] Lanthanum ions, with their larger radius, primarily enter the interstitial network, enhancing the glass's elastic modulus, chemical stability, and fracture strength through an accumulation effect, thus compensating for the decline in mechanical properties caused by low boron content. Yttrium ions, with their smaller radius, are better able to regulate high-temperature viscosity, inhibit crystallization, and improve dielectric properties. The combination of lanthanum and yttrium compensates for the insufficient structural strength of low-boron glass. Simultaneously, yttrium accumulates on the surface during glass corrosion, forming a dense alteration layer together with zinc. This alteration layer is a crucial barrier against further water erosion. As the yttrium content increases, the bonding force between the alteration layer and the glass matrix significantly strengthens. This enhanced bonding makes the alteration layer less prone to peeling off during use, thus providing continuous protection.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The modified low-boron, low-fluorine, alkali-free glass fiber composition of the present invention reduces the boron and fluorine content while introducing rare earth elements. By controlling the mass ratio of rare earth elements to Li2O and B2O3, the stability of the glass fiber composition under melting and forming conditions and the performance of its products are guaranteed. At the same time, the introduction of rare earth elements can improve the elastic modulus, fracture strength, and water resistance of glass products, inhibit glass crystallization, and reduce high-temperature viscosity.

[0026] (2) The modified low-boron, low-fluorine, alkali-free glass fiber composition of the present invention reduces the use of boron and fluorine raw materials, reduces the volatilization of boron-containing substances during the melting process, and helps to reduce environmental protection costs.

[0027] (3) The preparation method of the modified low boron, low fluorine and alkali-free glass fiber of the present invention is simple. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to embodiments and comparative examples.

[0029] In the following examples and comparative examples, the modified low-boron, low-fluorine, alkali-free glass fiber was prepared according to the formulation of the modified low-boron, low-fluorine, alkali-free glass fiber composition, including the following steps: S1: Calculate the required mass of each raw material based on the content of each component in the modified low-boron, low-fluorine, alkali-free glass fiber composition, use the raw material batching system to batch the raw materials according to the set ratio, mix and stir the raw materials for 4 minutes to obtain the mixture; S2: The mixture is delivered to the kiln hopper using a pneumatic conveying tank, and then the mixture is added to the kiln using a feeding machine; S3: The mixture is heated from room temperature to 1450°C in an atmosphere with a residual oxygen concentration of 3 Vol% to obtain a clear and homogeneous glass melt; S4: Homogeneous molten glass flows through the furnace passage to the baffle plate, maintaining the baffle plate temperature at 1225℃, and is drawn into wire to obtain modified low-boron, low-fluorine, alkali-free glass fiber.

[0030] Examples 1-3 The formulations of the modified low-boron, low-fluorine, alkali-free glass fiber compositions of Examples 1-3 are shown in Table 1 below. Impurities are inevitably introduced, and the balance in the composition is the amount of impurities introduced.

[0031] Table 1 Raw material formula table for the embodiment

[0032] Comparative Examples 1-6 The formulations of the modified low-boron, low-fluorine, alkali-free glass fiber compositions of Comparative Examples 1-6 are shown in Table 2 below. Impurities are inevitably introduced, and the balance in the composition is the amount of impurities introduced.

[0033] Table 2 Comparative Example Raw Material Formulation Table

[0034] Glass fibers were prepared according to the formulations described in the examples and comparative examples, and the performance of the prepared products was tested. The test results are shown in Table 3. The elastic modulus of the glass fiber is referenced to standard GB / T 37780-2019; the tensile strength is referenced to standard GB / T 7690.3-2013; and the alkali leaching amount is referenced to GB / T33832-2017, specifically the mass change caused by component leaching after the sample is soaked in water.

[0035] Table 3 Product Performance Test Results

[0036] As shown in the table above, compared with Comparative Example 1, excess TiO2 in Examples 1-3 increases the glass melting temperature and decreases the fracture strength. This is because excess TiO2... 4+ This leads to the breaking of bridging oxygen bonds such as Si–O–Si, generating non-bridging oxygen, significantly reducing the number of bridging oxygens, causing the three-dimensional network to depolymerize and collapse, and reducing mechanical properties.

[0037] Compared with Comparative Example 2, in Examples 1-3, excessive Li2O leads to a decrease in the amount of alkali precipitation, elastic modulus and tensile strength of glass fibers. The main reason is that when there is excess, the amount of free oxygen increases, the number of non-bridging oxygen increases, the three-dimensional network depolymerizes and loosens, resulting in microcracks on the glass surface, which in turn reduces alkali resistance and mechanical properties.

[0038] Compared with Comparative Example 3, in Examples 1-3, an excess of ZnO leads to a lower alkali precipitation in the glass fiber, but a significantly higher melting temperature, increasing the difficulty of glass melting. At the same time, the glass fracture strength and elastic modulus decrease. The main reason is that when there is an excess of ZnO, the free oxygen in the system is insufficient to support its existence as a tetracoordinate, which breaks the bridging oxygen bonds of the silicon-oxygen backbone, causing the network structure to change from a dense state to a loose state, thus affecting the glass strength.

[0039] Compared with Comparative Example 4, in Examples 1-3, excessive Y2O3 leads to a decrease in the elastic modulus and tensile strength of glass fibers. The main reason is that when excessive Y2O3 is added, its structural effect is reversed, forcing the generation of non-bridging oxygen, which leads to network depolymerization, a looser structure, and affects the strength of glass fibers.

[0040] Compared with Comparative Example 5, in Examples 1-3, excessive La2O3 leads to a decrease in the elastic modulus and tensile strength of glass fibers. The main reason is that the addition of excessive La2O3 results in an excess of free oxygen in the system, which causes the silicon-oxygen skeleton to be cut off on a large scale, generating a large amount of non-bridging oxygen, which reduces the degree of polymerization of the glass and leads to a decrease in elastic modulus and strength.

[0041] Compared with Comparative Example 6, Examples 1-3 show that adding appropriate amounts of TiO2, Li2O, ZnO, Y2O3, and La2O3 to glass can effectively improve the elastic modulus, alkali precipitation, melting temperature, and fracture strength of glass fibers.

Claims

1. A modified low-boron, low-fluorine, alkali-free glass fiber composition, characterized in that, The composition includes the following components by mass percentage: SiO2: 52.0-62.0%, Al2O3: 14.0-17.0%, B2O3: 0.1-3.0%, CaO: 20-23%, MgO: 0.5-3%, Fe2O3: 0.1-0.3%, TiO2: 0.1-1.5%, F2: 0.05-0.1%, R2O: 0.1-0.8%, X2O3: 0.2-1.0%, Li2O: 0.2-0.8%, ZnO: 0.1-2.0%; wherein: R2O is a mixture of K2O and Na2O; X2O3 is a mixture of La2O3 and Y2O3, with a mass ratio of La2O3 to Y2O3 of 1:(0.55-1.5).

2. The modified low-boron, low-fluorine, alkali-free glass fiber composition according to claim 1, characterized in that, The mass ratio of K2O to Na2O in the R2O is 1:(0.3-0.5).

3. The modified low-boron, low-fluorine, alkali-free glass fiber composition according to claim 1, characterized in that, The mass percentage of X2O3 is 0.25-0.8%.

4. The modified low-boron, low-fluorine, alkali-free glass fiber composition according to claim 1, characterized in that, The mass ratio of X2O3, Li2O and B2O3 is (0.1-4):(0.05-4):

1.

5. The modified low-boron, low-fluorine, alkali-free glass fiber composition according to claim 1, characterized in that, The mass ratio of CaO to MgO is (8-12):

1.

6. The modified low-boron, low-fluorine, alkali-free glass fiber composition according to claim 1, characterized in that, The mass percentage of B2O3 is 0.2-2.5%.

7. The modified low-boron, low-fluorine, alkali-free glass fiber composition according to claim 1, characterized in that, The mass percentage of TiO2 is 0.2-1.4%; the mass percentage of ZnO is 0.25-1.9%.

8. The modified low-boron, low-fluorine, alkali-free glass fiber composition according to claim 1, characterized in that, The raw materials used are pyrophyllite, dolomite, borocalcite, limestone, rare earth minerals, zinc oxide, titanium dioxide, lithium oxide, fluorite, and recycled glass powder.

9. The modified low-boron, low-fluorine, alkali-free glass fiber composition according to claim 1, characterized in that, The raw materials used are kaolin, pyrophyllite, dolomite, borocalcite, quicklime, rare earth mineral raw materials, zinc oxide, titanium dioxide, lithium oxide, fluorite, and recycled glass powder.

10. A method for preparing the modified low-boron, low-fluorine, alkali-free glass fiber composition according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Mix the required raw materials in proportion for 2-6 minutes to obtain the mixture; S2: The mixture is delivered to the kiln hopper using a pneumatic conveying tank, and then the mixture is added to the kiln using a feeding machine; S3: Melt the mixture in an atmosphere with a residual oxygen concentration of 1.5-5 Vol% by raising the temperature from room temperature to 1430-1500℃ to obtain a clear and homogeneous glass melt; S4: Homogeneous molten glass flows through the furnace passage to the baffle plate, maintaining the baffle plate temperature at 1200-1250℃, and is drawn into wire to obtain modified low-boron, low-fluorine, alkali-free glass fiber.

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