Patent Application
20240217867
The present invention relates to the technical field of glass fibers, and in particular to a low thermal expansion coefficient glass fiber.
The application of glass fibers has more and more extensive prospects, but the high thermal expansion coefficients of most glass series at present limit their demands in high-precision parts such as electronic printed circuit boards (PCB) and automobile industry. The thermal expansion coefficient is an important thermal property of glass fibers and depends to a large extent on the chemical composition of the glass fibers.
Among the common glass fiber series, the expansion coefficient of S series glass is about 4.0×10−6/° C., and the expansion coefficient of D series glass is about 3.5×10−6/° C. The expansion coefficients of S series glass and D series glass are large, which cannot meet the demands of high-precision parts.
The expansion coefficient of T series glass is low, but the content of SiO2 and Al2O3 in T series glass is very high (≥89%), which causes the temperature of T series glass at 1000 Poise to exceed 1460° C., and the difference between the temperature of 1000 Poise and the liquidus temperature (operating temperature range) is very small, so the T series glass is very difficult to process and low in fiber forming rate and is not suitable for industrial application.
Chinese patent CN103347831A discloses a glass composition with a low thermal expansion coefficient and a glass fiber prepared therefrom. The expansion coefficient of the glass composition is 3.0-3.6×10−6/° C., but its fiber forming temperature (about 1365-1400° C.) and crystallization upper limit temperature (about 1320-1370° C.) are high, and its elastic modulus is 89-90 GPa. Although the expansion coefficient of the glass fiber disclosed in the invention patent is decreased, it is still not enough to meet higher demands. In addition, the elastic modulus of the glass fiber is relatively low, and its fiber forming temperature and crystallization upper limit temperature are still relatively high.
Therefore, for higher demands, further decreasing the expansion coefficient of glass fibers while maintaining sufficient elastic modulus is an urgent problem to be solved.
In order to make up for the deficiencies of the prior art and solve the problems in the prior art that the expansion coefficients of glass fibers are not low enough, production is difficult, and mechanical properties such as elastic modulus cannot meet the requirements at the same time, the present invention provides a low thermal expansion coefficient glass fiber. In the present invention, SiO2, Al2O3, and MgO are the main ternary system. In the system, the contents of SiO2 and Al2O3 are controlled, B2O3, ZnO, TiO2, ZrO2, HfO2, and Li2O are added, and CaO, K2O, and Na2O are definitely not added. Because ZnO and TiO2, ZrO2, and HfO2 have a coordination complementarity effect between network bodies in the glass formation process, when the contents of ZnO, TiO2, ZrO2, and HfO2 and the ratio of ZnO/(TiO2+ZrO2+HfO2) are within certain ranges, synergistic effects can be achieved, the thermal expansion coefficient can be significantly decreased, and meanwhile the elastic modulus can be guaranteed to be more than 93 GPa.
The technical solution of the present invention is as follows:
A low thermal expansion coefficient glass fiber is characterized by being composed of the following ingredients in percentage by weight:
other inevitable impurities balance,
where,
As a preferred solution, the low thermal expansion coefficient glass fiber is composed of the following ingredients in percentage by weight:
≤0.3%
other inevitable impurities balance.
As a preferred solution, the sum of the contents of ZnO, TiO2, ZrO2 and HfO2 is 2.0-8.0%.
As a further preferred solution, ZnO/(TiO2+ZrO2+HfO2) is 0.5-1.1.
As a preferred solution, the sum of the contents of SiO2 and B2O3 is greater than or equal to 61%.
As a preferred solution, the sum of the contents of SiO2 and Al2O3 is less than or equal to 80%. When the sum of the contents of SiO2 and Al2O3 is too high, the clarification temperature and the processing difficulty will be increased.
As a preferred solution, the glass fiber has an expansion coefficient of between 2.77×10−6/° C. and 2.98×10−6/° C.
As a preferred solution, the glass fiber has a fiber forming temperature of between 1330° C. and 1365° C.
As a preferred solution, the glass fiber has a crystallization upper limit temperature of between 1280° C. and 1325° C.
As a preferred solution, the glass fiber has an elastic modulus of more than 93 GPa.
Each ingredient of the glass fiber of the present invention is described as follows:
SiO2 is the basic ingredient that forms glass grids, and is also the largest proportion of element in the low expansion glass composition, because the Si—O bond is large in bonding force and stable, and has a very small expansion coefficient, which may reach the order of 10−7. Besides, the Si—O bond can also effectively improve the mechanical strength, chemical stability and thermal stability of glass, but has a high melting temperature and fiber forming difficulty, and only an appropriate content can provide the best performance. In the glass fiber system of the present invention, the content of SiO2 is within a range of 55-63%, preferably 57-62%.
B2O3 has a relatively low expansion coefficient and good fluxing property. B2O3 exists as a boron-oxygen triangle under high-temperature melting conditions, which can reduce the high-temperature viscosity of glass, thereby reducing the clarification temperature of the glass. In a low-temperature glassy state, B2O3 can tend to form a boron-silicon tetrahedron, which enables the structure to be more compact to decrease the expansion coefficient of glass. The replacement of SiO2 with an appropriate amount of B2O3 can decrease the thermal expansion coefficient, and can also reduce the viscosity of glass, reduce the clarification temperature and guarantee the melting of glass with a low bubble rate. However, boron oxide is prone to the phase separation of molten glass and easy to volatilize, and the volatiles corrode refractory materials. The content of B2O3 in the present invention is determined to be 2.0-9.0%, a more preferable range being 3.0-7.0%.
Al2O3 is a network intermediate. By introducing a small amount of Al3+, non-bridging oxygen can be captured to form an aluminum-oxygen tetrahedron into a silicon-oxygen network, which makes the glass structure tend to be compact, decreases the expansion coefficient, and improves the elastic modulus. However, the aluminum-oxygen tetrahedron [AlO4] has a larger volume and a looser structure than the silicon-oxygen tetrahedron, so the higher Al2O3 content increases the expansion coefficient. Therefore, the content of Al2O3 introduced into the glass fiber system of the present invention is 17.5-25.0%, a more preferable range being 18.5-23.0%.
MgO is a network modifier oxide with a low expansion coefficient and a relatively small ionic radius, which is more conducive to the formation of a compacter glass network structure, decreasing the expansion coefficient of glass and improving glass modulus. However, if the MgO content is too high, the crystallization upper limit temperature and the crystallization rate will increase significantly. Therefore, the MgO content of the glass fiber system in the present invention is within a range of 9.0-16.5%, preferably 9.5-13.0%.
ZnO not only has a low expansion coefficient in glass, but also may serve as a flux. The appropriate addition may effectively improve the melting and clarifying of the glass composition. The higher the content of ZnO in a certain range is, the smaller the expansion coefficient is. Zn has two coordination states, which may be a zinc-oxygen tetrahedron [ZnO4] participating in network construction, or a zinc-oxygen octahedron [ZnO6] outside the network. In the presence of less ZnO, the added ZnO captures “free oxygen” in the system and then its coordination number becomes 4 to participate in the formation of the network, so that the structure of the glass is strengthened, the degree of connection of the network is improved, and the stability is increased, which can decrease the expansion coefficient of the glass. When the amount of ZnO added exceeds a certain value, with the increase of ZnO content, the free oxygen content in the glass decreases, and the ratio of [ZnO4]/[ZnO6] decreases, which destroys the network structure of the glass and reduce the stability of the glass, thereby increasing the expansion coefficient. Therefore, the content of ZnO in the present invention is within a range of 0.1-4.5%, more preferably 1.5-4.0%.
TiO2 is an intermediate oxide, and in the glass system of the present invention, most of TiO2 contained enters the network structure as titanium oxide tetrahedrons [TiO4], and an extremely small part of the TiO2 is outside the structure as [TiO6] octahedrons. [TiO4] in the network absorbs sufficient free oxygen and plays a part in repairing a broken network. Zr4+ is high in bond strength and coordination, and in the glass system of the present invention, ZrO2 has a cubic [ZrO8] structure, which is a network outer body. Hf and Zr are in a same subgroup and adjacent periods in the periodic table of elements, and Hf4+ has a larger ionic radius than Zr4+ and has an [Hf8] cubic structure in the glass system of the present invention. Zr4+ and Hf4+ with high bond strength and high coordination are in voids of the network, which gathers surrounding Si—O and B—O networks and reduces the expansion coefficient of the network. Because TiO2 itself has a coloring ability, the content of TiO2 in the present invention is determined to be 0.1-4.0%, a more preferable range being 0.5-2.0%, and a usage amount thereof may be reduced as much as possible in a field of materials having requirements on colors, and ZrO2 or HfO2 may be used to substitute for TiO2. The content of ZrO2 is limited to 0.1-3.0%, a preferable range being 0.3-2.0%. The content of HfO2 is limited to 0.1-2.0%, preferably 0.2-1.5%.
Li2O: Li+ is not an inert gas type ion and plays a role of “accumulation” in the structure. When Li+ replaces K+ and Na+, the chemical stability of glass can be improved. Li+ has high-temperature fluxing and glass melting accelerating effects. When the content of Li+ is too high, the accumulation effect is too strong, which causes the phase separation of glass. In the glass system of the present invention, the main function of adding Li2O is to reduce the clarification temperature, forming temperature and crystallization upper limit temperature of the glass. The content of Li2O in the present invention is within a range of 0.1-2.0%, preferably 0.5-2.0%.
The glass fiber system of the present invention does not contain CaO, K2O, and Na2O, because the above three elements have an obvious tendency to increase the expansion coefficient, where CaO is a network modifier, and Ca2+ has the effects of polarizing bridge oxygen and weakening Si—O bonding, which increases the expansion coefficient. K2O and Na2O are common alkali metal oxides in glass, and mainly play a role of breaking the network (Si—O bond) in the structure, which also increase the expansion coefficient. Therefore, the addition of ingredients containing CaO, K2O, and Na2O is prohibited in the present invention.
The two ingredients SiO2 and B2O3 guarantee the basic network structure of the glass, and both have the characteristic of low expansion coefficient, so in the present invention, SiO2+B2O3≥59.0, and more preferably SiO2+B2O3≥61%.
In the present invention, SiO2, Al2O3, and MgO are the main ternary system. In the system, the contents of SiO2 and Al2O3 are controlled, B2O3, ZnO, TiO2, ZrO2, HfO2, and Li2O are added, and CaO, K2O, and Na2O are definitely not added. Experiments show that the addition of ZnO, TiO2, ZrO2, and HfO2 to the glass system of the present invention achieves better effects than the use of one or two of them; and when the contents of ZnO, TiO2, ZrO2, and HfO2 and the ratio range of ZnO/(TiO2+ZrO2+HfO2) are reasonably controlled and the content ranges of other ingredients are optimized, the expansion coefficient of the glass fiber in the present invention is significantly reduced, and the elastic modulus can be guaranteed to be more than 93 GPa at the same time. The inventor believes that ZnO and TiO2, ZrO2 and HfO2 should have a coordination complementarity effect between network bodies in the glass formation process; when the contents of ZnO, TiO2, ZrO2, and H/O2 and the ratio of ZnO/(TiO2+ZrO2+HfO2) are reasonably controlled within certain ranges, synergistic effects can be achieved, and the thermal expansion coefficient can be significantly decreased; and when the contents and the ratio are out of the aforementioned ranges, the thermal expansion coefficient of the glass system in the present invention is decreased relatively little.
The beneficial effects of the present invention are as follows:
The technical solutions in the embodiments of the present invention will be clearly and completely described below. The embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative efforts shall fall within the protection scope of the present invention.
A production process for a low thermal expansion coefficient glass fiber includes the following steps:
The present invention uses the raw materials having different particle sizes, which on the one hand reduces the crushing and grinding costs of the raw materials, and on the other hand, facilitates the discharge of bubbles generated during the melting process of the raw materials, is beneficial to the clarifying of molten glass, and decreases the hollow rate of the fiber. The bubbles in the molten glass can be easily discharged.
The present invention uses the all-electric melting furnace, which increases the melting temperature, improves the utilization of energy, reduces exhaust emission, and reduces the strict requirements for the furnace. Because boron oxide is easily volatilized at a high temperature, the all-electric melting furnace is more suitable for the characteristic of high boron oxide content in the glass system of the present invention.
Table 2 shows examples of low thermal expansion coefficient glass fibers in the present invention. Table 3 shows compositions of glass fibers in comparative examples.
When the comprehensive properties of the glass fibers in the examples and comparative examples are verified, the following parameters are selected:
The property parameters of glass fibers in examples and comparative examples are shown in Table 4.
According to Table 4,
According to the above experimental results, the inventor believes that ZnO and TiO2, ZrO2 and HfO2 have a very significant impact on the expansion coefficient of the glass fiber, because the ZnO and TiO2, ZrO2 and HfO2 have a coordination complementarity effect between network bodies in the glass formation process; therefore, when the contents of ZnO, TiO2, ZrO2, and HfO2 and the ratio of ZnO/(TiO2+ZrO2+HfO2) are reasonably controlled within certain ranges, synergistic effects can be achieved, and the thermal expansion coefficient can be decreased; however, when the contents and the ratio are out of certain ranges, the effect to decrease the thermal expansion coefficient of the glass fiber is relatively little.
According to the low expansion coefficient glass fiber of the present invention, CaO, K2O, and Na2O ingredients are not added, but B2O3, ZnO, TiO2, ZrO2, and HfO2 are simultaneously added, and the proportion of each element is optimized, significantly decreasing the expansion coefficient of the glass fiber in the present invention. The elastic modulus is as high as 93 GPa or more. Therefore, the low expansion coefficient glass fiber meets the requirements of high-precision parts. The low expansion coefficient glass fiber has a forming temperature (lg3.0) of 1330-1365° C., a crystallization upper limit temperature of 1280-1325° C., and a low crystallization rate. The difference between the drawing forming temperature and the crystallization upper limit temperature is ΔT>43° C., which meets the requirements of the drawing process and can achieve scale production.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202110010617.1 | Jan 2021 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2021/142138 | 12/28/2021 | WO |
