Optical crystal wafer polishing without wax pad and its production process

Abstract

The application discloses an optical crystal wafer polishing wax-free pad capable of preventing crystal fragments and a production process thereof, and belongs to the technical field of optical crystal processing. The optical crystal wafer polishing wax-free pad capable of preventing crystal fragments comprises, from bottom to top, a substrate layer, a buffer layer and a surface layer, the surface layer is made of composite superfine fibers in a non-woven manner, and is subjected to surface modification to form a fabric, and the buffer layer is made of polyurethane foam. The application solves the problem of fracture of the existing crystal wafer in the polishing process. The optical crystal wafer polishing wax-free pad capable of preventing crystal fragments and the production process thereof are provided, the substrate layer is made of polyurethane as a main component, the strength and durability of the pad are provided, the buffer layer is made of polyurethane foam, stress concentration is avoided, the surface layer forms a micro-suede structure, good polishing effect can be provided, and no scratches or residues are left on the surface of the crystal wafer.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical crystal processing, in particular to an optical crystal wafer polishing wax-free pad and its production process for preventing the occurrence of crystal fragments. BACKGROUND

[0002] In the traditional optical crystal wafer polishing process, the use of wax-containing polishing pads can easily cause wax residues on the surface of the crystal wafer, affecting subsequent processing and optical performance. In addition, polishing pads with too high hardness can increase the risk of crystal wafer breakage during polishing. Therefore, developing a new type of wax-free polishing pad that can both improve polishing efficiency and reduce the breakage rate of crystal wafers is an urgent problem in the current field of optical crystal processing. SUMMARY

[0003] The purpose of the present application is to provide an optical crystal wafer polishing wax-free pad and its production process for preventing the occurrence of crystal fragments. By using polyurethane as the main component of the base layer, the strength and durability of the pad are provided. The buffer layer uses polyurethane foam to avoid stress concentration. The surface layer forms a micro-suede structure, which can provide good polishing effect without leaving scratches or residues on the surface of the crystal wafer, solving the problems raised in the background technology.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme: an optical crystal wafer polishing wax-free pad for preventing the occurrence of crystal fragments, comprising a base layer, a buffer layer and a surface layer connected in turn from bottom to top, the surface layer is made of a composite ultra-fine fiber fabric formed by non-woven method and surface modification, the composite fiber material includes the following raw materials by weight: polyester fiber 12-18 parts, polyacrylonitrile fiber 10-12 parts and soybean protein fiber 5-12 parts, and the buffer layer is made of polyurethane foam.

[0005] Preferably, the polyester fiber, polyacrylonitrile fiber and soybean protein fiber are all island-type ultra-fine fibers with a diameter less than 1 micron.

[0006] Preferably, the preparation method of the surface layer is as follows:

[0007] The polyester fiber, polyacrylonitrile fiber and soybean protein fiber are formed into a uniform distribution of fiber web by air laying. The fiber web is sent into a hydroentangling machine, and the fiber web is impacted by high-pressure water flow to make the fibers entangle with each other. After hydroentangling, the fiber web is dried to remove moisture, and then heated by a hot calender. The heating temperature of the hot calender is 170-185℃. The polyester fiber softens and forms bonding points with the polyacrylonitrile fiber and soybean protein fiber, which melt to form a fabric with a thickness of 0.2-0.6mm and a grammage of 100-130gsm. Finally, the fabric is surface modified.

[0008] Preferably, the surface modification of the fabric comprises the following steps: preparing a softener containing surfactants, immersing the fabric in the softener, ensuring the fabric absorbs the softener, using a mangle to squeeze out the excess liquid, immersing and squeezing for two to three times, controlling the amount of residual liquid on the fabric to be 80%-120% when the fabric is taken out of the last bath, sending the fabric into a dryer, baking at 100°C-120°C for 2-4 minutes to evaporate the water on the fabric and fix the softener, and cooling the fabric immediately after it comes out of the dryer.

[0009] Preferably, the softener is prepared as follows: heating deionized water to 60°C, slowly adding fatty alcohol polyoxyethylene ether, stirring until completely dissolved, adding quaternary ammonium salt, stirring until dissolved, adjusting the pH to 7.5-8, the content of fatty alcohol polyoxyethylene ether being 3-5%, and the content of quaternary ammonium salt being 2-4%.

[0010] Preferably, the soybean protein fiber is prepared as follows: extracting protein from soybeans and dissolving the purified soybean protein in water to form a uniform solution at a dissolution temperature of 50°C-60°C, dispersing the nanoparticles in water using ultrasonic waves to form a stable suspension, the ultrasonic time being 30-90 minutes, slowly adding the dispersed nanoparticle suspension to the soybean protein solution while stirring, stirring the mixed solution at room temperature for 1-3 hours, removing any undispersed particles or impurities from the solution by passing it through a filter, and using a bi- fluid spinning technique in which the soybean protein nanoparticle composite solution is the island phase and polylactic acid (PLA) is the sea phase, the two phases being extruded through a special spinneret to form an island-in-sea structure, the extruded fiber being solidified in a coagulation bath, the fiber being removed from the coagulation bath and washed multiple times to remove residual solvent and coagulation bath components, and then being dried to form the soybean protein fiber.

[0011] Preferably, the amount of nanoparticles added is 2%-4% of the soybean protein solution, the nanoparticles including silicon dioxide and aluminum oxide, and the nanoparticles being surface-modified using a coupling agent before use, as follows: selecting a silane coupling agent to be dissolved in an alcohol solvent to form a solution with a concentration of about 0.5%-5%, adding water to the coupling agent solution in an amount of 5% of the mass of the coupling agent, dispersing the nanoparticles in ethanol, breaking the aggregation state of the particles by ultrasonic treatment to form a stable suspension, adding the suspension to the activated silane coupling agent solution to ensure that the nanoparticles are in full contact with the coupling agent, stirring the mixture for 4-5 hours, separating the modified nanoparticles by centrifugation and washing them with an alcohol solvent several times to remove unreacted coupling agent and other byproducts, and drying the modified nanoparticles in a vacuum drying oven to remove residual solvent.

[0012] Preferably, the base layer is made of the following raw materials by weight: 25-40 parts of toluene diisocyanate, 50-70 parts of polyether polyol, 0.1-1 part of amine catalyst, 0.1-1 part of foaming agent, 1-2 parts of surfactant, 1-2 parts of flame retardant, and 1-2 parts of stabilizer.

[0013] Preferably, the buffer layer comprises at least a three-layer structure, and the pore diameter of the three-layer structure decreases layer by layer from the base layer to the surface layer. The buffer layer comprises the following raw materials by weight: 45-55 parts of toluene diisocyanate, 40-60 parts of polyether polyol, 3-8 parts of carbon fiber, 0.1-1 part of amine catalyst, 0.1-1 part of foaming agent, 1-2 parts of surfactant, 1-2 parts of flame retardant, and 1-2 parts of stabilizer.

[0014] Another technical problem to be solved by the present application is to provide a production process of a wax-free polishing pad for optical crystal wafers to prevent the occurrence of crystal fragments, comprising the following steps:

[0015] Step one, preparing the base layer: uniformly premixing polyether polyol, amine catalyst, foaming agent, surfactant, flame retardant, and stabilizer in a stirrer, adding toluene diisocyanate into the premixed polyol mixture, rapidly stirring, immediately pouring the mixed material into a mold, foaming and solidifying the material in the mold, and taking out the prepared base layer after the foam is completely solidified;

[0016] Step two, preparing the buffer layer: uniformly premixing polyether polyol, amine catalyst, carbon fiber, foaming agent, surfactant, flame retardant, and stabilizer in a stirrer, adding toluene diisocyanate into the premixed polyol mixture, rapidly stirring, positioning and spraying the mixed material through a mold onto the base layer, foaming and solidifying the material in the mold, and disassembling the mold after the foam is completely solidified to form the buffer layer;

[0017] Step three, preparing the surface layer: forming a fabric by using non-woven composite ultra-fine fibers and performing surface modification to prepare the surface layer, bonding the prepared surface layer and the prepared buffer layer by using an isocyanate-based adhesive, and performing post-processing such as cutting and polishing to prepare the wax-free pad.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] The optical crystal wafer polishing wax-free pad for preventing crystal fragments and the production process thereof are provided, the wax-free pad is composed of three layers of composite materials, the base layer uses polyurethane as the main component to provide the strength and durability of the pad, the buffer layer uses polyurethane foam, the microporous structure of which can effectively absorb the impact force in the polishing process to avoid stress concentration, the surface layer is made of polyester fiber, polyacrylonitrile fiber and soybean protein fiber in a non-woven way to form a fabric and is surface modified to form a micro-suede structure, which can provide good polishing effect without leaving scratches or residues on the surface of the crystal wafer, the polyester fiber has good strength, wear resistance and wrinkle resistance, the polyacrylonitrile fiber has good heat resistance and chemical stability, and the soybean protein fiber is added with nanoparticles to improve the high-temperature resistance of the soybean protein fiber while retaining the softness and air permeability of the soybean protein fiber, thereby preventing the occurrence of crystal fragments and adapting to higher working temperature. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The structure diagram of the optical crystal wafer polishing wax-free pad for preventing crystal fragments is shown.

[0021] In the figure: 1, base layer; 2, buffer layer; 3, surface layer. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] Embodiment one:

[0024] In order to solve the problem that the use of polishing pads containing wax in the conventional optical crystal wafer polishing process easily leads to the residue of wax on the surface of the crystal wafer, affecting the subsequent processing and optical performance, and the polishing pad with too high hardness increases the risk of fracture of the crystal wafer in the polishing process, please refer to Figure 1 The technical solutions are provided in the embodiment as follows:

[0025] The optical crystal wafer polishing wax-free pad for preventing crystal fragments comprises a base layer 1, a buffer layer 2 and a surface layer 3 connected in sequence from bottom to top, the surface layer 3 is made of composite ultra-fine fibers in a non-woven way to form a fabric and is surface modified, the composite fiber material comprises the following raw materials by weight: 12 parts of polyester fiber, 10 parts of polyacrylonitrile fiber and 6 parts of soybean protein fiber, and the buffer layer 2 is made of polyurethane foam.

[0026] The polyester fiber, the polyacrylonitrile fiber and the soybean protein fiber are all island type ultrafine fibers, and the diameters are less than 1 micron.

[0027] The preparation method of the surface layer 3 is as follows:

[0028] The polyester fiber, the polyacrylonitrile fiber and the soybean protein fiber are all island type ultrafine fibers, and the diameters are less than 1 micron.

[0029] The surface modification of the fabric specifically includes the following steps: configuring a softener containing a surfactant, fully immersing the fabric in the softener, ensuring that the fabric fully absorbs the softener, using a mangle to squeeze out the excess liquid, two to three times of immersion and squeezing operations, and controlling the amount of residual liquid on the fabric to be 80% when the last squeezing treatment bath is performed, sending the fabric into a drying machine, baking at 120°C for 2 minutes to evaporate the water on the fabric and fix the softener, and immediately cooling the fabric after it comes out of the drying machine to avoid fabric damage caused by excessive drying.

[0030] The configuration method of the softener is as follows: heating the deionized water to 60°C, slowly adding the fatty alcohol polyoxyethylene ether, stirring until completely dissolved, adding the quaternary ammonium salt, also stirring until dissolved, adjusting the pH to 7.5, the content of the fatty alcohol polyoxyethylene ether is 3%, the fatty alcohol polyoxyethylene ether is suitable for various fibers and can provide good softness and washing stability, the content of the quaternary ammonium salt is 2%, the quaternary ammonium salt is suitable for most synthetic fibers and part of protein fibers, and can significantly improve the softness and antistatic performance of the fabric.

[0031] The soybean protein fiber is prepared as follows: protein is extracted from soybean, and the purified soybean protein is dissolved in water to form a uniform solution, the dissolving temperature is 50°C, the nanoparticles are dispersed in water using ultrasonic wave to form a stable suspension, the ultrasonic time can be 45 minutes, the dispersed nanoparticle suspension is slowly added to the soybean protein solution while stirring to ensure uniform distribution, the mixed solution is stirred at room temperature for 2 hours, the mixed solution is filtered through a filter to remove any undispersed particles or impurities to ensure smooth spinning process, a bi- fluid spinning technology is used, in which the soybean protein nanoparticle composite solution is used as the island phase, and polylactic acid (PLA) is used as the sea phase, the two phases are extruded through a special spinneret to form an island-in-sea structure, the extruded fiber is solidified in a coagulation bath, the fiber is taken out of the coagulation bath and washed multiple times to remove residual solvent and coagulation bath components, and then dried to obtain the soybean protein fiber.

[0032] The amount of nanoparticles added is 2% of the soybean protein solution, and the nanoparticles include silicon dioxide and aluminum oxide. In order to improve the compatibility of the nanoparticles with the soybean protein, the nanoparticles can be surface modified. A coupling agent such as a silane coupling agent is used for treatment. The modified nanoparticles can be better dispersed in the protein solution and form a more stable combination with the protein. Before use, the nanoparticles are surface modified using a coupling agent as follows: a silane coupling agent is selected and dissolved in an alcohol solvent to form a solution with a concentration of about 0.5%, water is added to the coupling agent solution in an amount of 5% of the mass of the coupling agent, the presence of water promotes the hydrolysis reaction of the coupling agent to form active end groups, which can more easily react with the hydroxyl (-OH) groups on the surface of the nanoparticles, the nanoparticles are dispersed in ethanol, and ultrasonic treatment is used to break the aggregation state of the particles to form a stable suspension, the suspension is added to the activated silane coupling agent solution to ensure that the nanoparticles are in sufficient contact with the coupling agent, the mixture is stirred for 4 hours to promote the chemical reaction between the coupling agent and the surface of the nanoparticles, the modified nanoparticles are separated by centrifugation and washed with an alcohol solvent several times to remove unreacted coupling agent and other byproducts, and the modified nanoparticles are dried in a vacuum drying oven to remove residual solvent.

[0033] The base layer 1 is made of the following raw materials by weight: toluene diisocyanate 25 parts, polyether polyol 55 parts, amine catalyst 0.2 parts, foaming agent 0.5 parts, surfactant 1 part, flame retardant 1 part, stabilizer 1 part.

[0034] The buffer layer 2 comprises at least a three-layer structure, the three-layer structure has a pore size gradually decreasing from the base layer 1 to the surface layer 3, can disperse stress on different scales, and reduce local stress concentration. The buffer layer 2 comprises the following raw materials by weight: 45 parts of toluene diisocyanate, 45 parts of polyether polyol, 5 parts of carbon fiber, 0.5 part of amine catalyst, 0.5 part of foaming agent, 1 part of surfactant, 1 part of flame retardant, and 1 part of stabilizer. The addition of carbon fiber can improve the overall strength and rigidity of the foam and reduce stress concentration.

[0035] In order to better show the production process of the optical crystal wafer polishing wax-free pad for preventing crystal fragments, the embodiment proposes a production process of the optical crystal wafer polishing wax-free pad for preventing crystal fragments, which comprises the following steps:

[0036] Step one, preparing the base layer 1: uniformly premix polyether polyol, amine catalyst, foaming agent, surfactant, flame retardant, and stabilizer in a stirrer. This stage is usually carried out at room temperature to ensure that all ingredients are fully mixed. Then, toluene diisocyanate is added to the premixed polyol mixture and stirred quickly. This step needs to be completed in a short time to avoid premature gelation or foaming. The mixed material is immediately poured into a mold. At this time, the foaming agent begins to decompose to generate gas, which promotes the expansion and solidification of the mixture. The material foams and solidifies in the mold. After the foam is completely solidified, the prepared base layer 1 is taken out of the mold.

[0037] Step two, preparing the buffer layer 2: uniformly premix polyether polyol, amine catalyst, carbon fiber, foaming agent, surfactant, flame retardant, and stabilizer in a stirrer. Then, toluene diisocyanate is added to the premixed polyol mixture and stirred quickly. The mixed material is sprayed onto the base layer 1 through mold positioning. The material foams and solidifies in the mold. After the foam is completely solidified, the mold is disassembled to form the buffer layer 2.

[0038] Step three, preparing the surface layer 3: composite ultra-fine fibers are formed into a fabric by non-woven method and surface modification to prepare the surface layer 3. The surface layer 3 is bonded to the prepared buffer layer 2 using an isocyanate-based adhesive. Post-processing such as cutting and polishing is performed to prepare the wax-free pad.

[0039] Example two:

[0040] The optical crystal wafer polishing wax-free pad for preventing crystal fragments comprises a base layer 1, a buffer layer 2, and a surface layer 3 connected in sequence from bottom to top. The surface layer 3 is made of composite ultra-fine fibers formed into a fabric by non-woven method and surface modification. The composite fiber material comprises the following raw materials by weight: 12 parts of polyester fiber, 10 parts of polyacrylonitrile fiber, and 8 parts of soybean protein fiber. The buffer layer 2 is made of polyurethane foam.

[0041] The base layer 1 is made of the following raw materials by weight: toluene diisocyanate 25 parts, polyether polyol 55 parts, amine catalyst 0.2 parts, foaming agent 0.5 parts, surfactant 1 part, flame retardant 1 part, stabilizer 1 part.

[0042] The buffer layer 2 includes at least a three-layer structure, the three-layer structure has a pore size gradually decreasing from the base layer 1 to the surface layer 3, and the buffer layer 2 includes the following raw materials by weight: toluene diisocyanate 45 parts, polyether polyol 45 parts, carbon fiber 5 parts, amine catalyst 0.5 parts, foaming agent 0.5 parts, surfactant 1 part, flame retardant 1 part, stabilizer 1 part.

[0043] The optical crystal sheet polishing wax-free pad is prepared by the same method as in Example 1.

[0044] Example Three:

[0045] The optical crystal sheet polishing wax-free pad for preventing crystal fragments includes, from bottom to top, a base layer 1, a buffer layer 2, and a surface layer 3, the surface layer 3 is made of composite ultra-fine fibers by forming a fabric in a non-woven manner and surface modification, the composite fiber material includes the following raw materials by weight: polyester fiber 12 parts, polyacrylonitrile fiber 10 parts, and soybean protein fiber 12 parts, and the buffer layer 2 is made of polyurethane foam.

[0046] The base layer 1 is made of the following raw materials by weight: toluene diisocyanate 25 parts, polyether polyol 55 parts, amine catalyst 0.2 parts, foaming agent 0.5 parts, surfactant 1 part, flame retardant 1 part, stabilizer 1 part.

[0047] The buffer layer 2 includes at least a three-layer structure, the three-layer structure has a pore size gradually decreasing from the base layer 1 to the surface layer 3, and the buffer layer 2 includes the following raw materials by weight: toluene diisocyanate 45 parts, polyether polyol 45 parts, carbon fiber 5 parts, amine catalyst 0.5 parts, foaming agent 0.5 parts, surfactant 1 part, flame retardant 1 part, stabilizer 1 part.

[0048] The optical crystal sheet polishing wax-free pad is prepared by the same method as in Example 1.

[0049] Comparative Example One:

[0050] The optical crystal sheet polishing wax-free pad for preventing crystal fragments includes, from bottom to top, a base layer 1, a buffer layer 2, and a surface layer 3, the surface layer 3 is made of composite ultra-fine fibers by forming a fabric in a non-woven manner and surface modification, the composite fiber material includes the following raw materials by weight: polyester fiber 12 parts and polyacrylonitrile fiber 10 parts, and the buffer layer 2 is made of polyurethane foam.

[0051] The base layer 1 is made of the following raw materials in parts by weight: toluene diisocyanate 25 parts, polyether polyol 55 parts, amine catalyst 0.2 parts, foaming agent 0.5 parts, surfactant 1 part, flame retardant 1 part, stabilizer 1 part.

[0052] The buffer layer 2 comprises at least a three-layer structure, the three-layer structure has a pore diameter gradually decreasing from the base layer 1 to the surface layer 3, and the buffer layer 2 comprises the following raw materials in parts by weight: toluene diisocyanate 45 parts, polyether polyol 45 parts, carbon fiber 5 parts, amine catalyst 0.5 parts, foaming agent 0.5 parts, surfactant 1 part, flame retardant 1 part, stabilizer 1 part.

[0053] The optical crystal wafer polishing wax-free pad is prepared by the same method as in Example 1.

[0054] The prepared optical crystal wafer polishing wax-free pad is detected, and the following data is obtained:

[0055]

[0056]

[0057] As can be seen from the above table, the wax-free pads prepared in Examples 1 to 3 all have higher elastic recovery rate, adsorption force and maximum working temperature than those of Comparative Example 1, which shows that the addition of soybean protein fiber can affect the elastic recovery rate, adsorption force and maximum working temperature of the wax-free pad. The wax-free pad prepared in the examples has lower hardness than the wax-free pad in Comparative Example 1.

[0058] In summary, the optical crystal wafer polishing wax-free pad and its production process for preventing the occurrence of crystal fragments are provided. The wax-free pad is composed of three layers of composite material. The base layer 1 uses polyurethane as the main component to provide the strength and durability of the pad. The buffer layer 2 uses polyurethane foam, which has a microporous structure that can effectively absorb the impact force during polishing to avoid stress concentration. The surface layer 3 uses polyester fiber, polyacrylonitrile fiber and soybean protein fiber to form a fabric in a non-woven manner and is surface modified to form a micro-suede structure, which can provide good polishing effect without leaving scratches or residues on the crystal wafer surface. The polyester fiber has good strength, wear resistance and wrinkle resistance. The polyacrylonitrile fiber has good heat resistance and chemical stability. The soybean protein fiber is added with nanoparticles to improve the high-temperature resistance of the soybean protein fiber while retaining its softness and breathability, thereby preventing the occurrence of crystal fragments and adapting to higher working temperatures.

[0059] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting; it is not intended to exclude myriad other embodiments of the present application that other inventors can develop based on the same general inventive concepts embodied by the described embodiments. That is, although the present application is described in terms of particular embodiments and illustrative figures, it should be apparent that the scope of the present application is not limited to these specific embodiments.

[0060] While the embodiments of the application have been shown and described herein, it will be understood by those of ordinary skill in the art that various changes, modifications, alternatives, and variations can be made to the embodiments without departing from the spirit and scope of the application, which is defined by the claims and their equivalents.

Claims

1. A wax-free pad for polishing an optical crystal sheet to prevent crystal fragments, comprising a base layer (1), a buffer layer (2) and a surface layer (3) connected in sequence from bottom to top, characterized in that: The surface layer (3) is made of composite ultrafine fibers formed into a fabric in a non-woven manner and subjected to surface modification. The composite fiber material comprises the following raw materials in parts by weight: 12-18 parts of polyester fiber, 10-12 parts of polyacrylonitrile fiber, and 5-12 parts of soybean protein fiber. The buffer layer (2) is made of polyurethane foam.

2. The wax-free pad for polishing an optical crystal sheet to prevent crystal fragmentation according to claim 1, wherein: The polyester fiber, polyacrylonitrile fiber and soybean protein fiber are all island-type ultrafine fibers with a diameter of less than 1 micron.

3. The wax-free pad for polishing an optical crystal sheet to prevent crystal fragmentation according to claim 2, wherein: The preparation method of the surface layer (3) is as follows: Polyester fiber, polyacrylonitrile fiber and soy protein fiber are air-laid to form a uniformly distributed fiber web. The fiber web is then fed into a hydroentanglement machine, where high-pressure water jets impact the fiber web, causing the fibers to entangle with each other. After hydroentanglement, the fiber web is dried to remove moisture, and then heated by hot pressing rollers at a temperature of 170°C-185°C. The ester fiber softens and forms bonding points, which melt with the polyacrylonitrile fiber and soy protein fiber to form a fabric with a thickness of 0.2 mm-0.6 mm and a grammage of 100 gsm-130 gsm. Finally, the fabric is surface modified.

4. The wax-free pad for polishing an optical crystal sheet to prevent crystal fragmentation according to claim 3, wherein: The surface modification of the fabric specifically includes the following steps: preparing a softener containing a surfactant, completely immersing the fabric in the softener to ensure that the fabric fully absorbs the softener, using a padder to squeeze out excess liquid, and performing the immersion and squeezing operation two to three times. When squeezing out the bath for the last time, the residual liquid on the fabric is controlled to be 80%-120%, and the fabric is sent to the dryer and baked at 100℃-120℃ for 2-4 minutes to evaporate the moisture on the fabric and fix the softener at the same time. After the fabric comes out of the dryer, it should be cooled immediately.

5. The wax-free pad for polishing an optical crystal sheet to prevent crystal fragmentation according to claim 4, characterized in that: The softener is prepared as follows: deionized water is heated to 60° C., fatty alcohol polyoxyethylene ether is slowly added, and stirred until completely dissolved. A quaternary ammonium salt is added and stirred until dissolved. The pH is adjusted to 7.5-8, the content of fatty alcohol polyoxyethylene ether is 3-5%, and the content of quaternary ammonium salt is 2-4%.

6. The wax-free pad for polishing an optical crystal sheet to prevent crystal fragmentation according to claim 1, wherein: The preparation method of the soybean protein fiber is as follows: protein is extracted from soybeans, and purified soybean protein is dissolved in water to form a uniform solution at a dissolution temperature of 50°C-60°C; nanoparticles are dispersed in water using ultrasound to form a stable suspension; the ultrasound time is 30-90 minutes; the dispersed nanoparticle suspension is slowly added to the soybean protein solution while stirring; the mixture is stirred at room temperature for 1-3 hours; the mixed solution is passed through a filter to remove any undispersed particles or impurities; a dual-fluid spinning technology is used, in which a soybean protein nanocomposite solution is used as an island phase and polylactic acid (PL) is used as a sea phase; the two phases are extruded through a specific spinneret to form an island-in-sea structure; the extruded fibers are solidified in a coagulation bath; the fibers are taken out of the coagulation bath, washed multiple times to remove residual solvent and coagulation bath components, and then dried to prepare the soybean protein fibers.

7. The wax-free pad for polishing an optical crystal sheet to prevent crystal fragmentation according to claim 6, characterized in that: The nanoparticles are added in an amount of 2%-4% of a soy protein solution. The nanoparticles include silicon dioxide and aluminum oxide. Before use, the nanoparticles are surface-modified using a coupling agent. The method is as follows: a silane coupling agent is dissolved in an alcohol solvent to form a solution with a concentration of 0.5%-5%, water with a mass fraction of 5% of the coupling agent is added to the coupling agent solution, the nanoparticles are dispersed in ethanol, and ultrasonic treatment is performed to destroy the aggregation state of the particles to form a stable suspension. The suspension is added to an activated silane coupling agent solution to ensure that the nanoparticles are in full contact with the coupling agent. The mixture is stirred for 4-5 hours, the modified nanoparticles are separated by centrifugation, and washed several times with an alcohol solvent to remove unreacted coupling agent and other by-products. The modified nanoparticles are dried in a vacuum drying oven to remove residual solvent.

8. The wax-free pad for polishing an optical crystal sheet to prevent crystal fragmentation according to claim 1, wherein: The base layer (1) is made of the following raw materials in parts by weight: 25-40 parts of toluene diisocyanate, 50-70 parts of polyether polyol, 0.1-1 part of amine catalyst, 0.1-1 part of foaming agent, 1-2 parts of surfactant, 1-2 parts of flame retardant, and 1-2 parts of stabilizer.

9. The wax-free pad for polishing an optical crystal sheet to prevent crystal fragmentation according to claim 1, wherein: The buffer layer (2) comprises at least a three-layer structure, wherein the pore size of the three-layer structure decreases layer by layer from the base layer (1) to the surface layer (3), and the buffer layer (2) comprises the following raw materials in parts by weight: 45-55 parts of toluene diisocyanate, 40-60 parts of polyether polyol, 3-8 parts of carbon fiber, 0.1-1 part of amine catalyst, 0.1-1 part of foaming agent, 1-2 parts of surfactant, 1-2 parts of flame retardant, and 1-2 parts of stabilizer.

10. A process for producing a wax-free pad for polishing an optical crystal sheet to prevent crystal fragmentation as claimed in claim 9, characterized in that: The following steps are involved: Step 1, preparing the base layer (1): premixing the polyether polyol, amine catalyst, foaming agent, surfactant, flame retardant and stabilizer in a blender, adding toluene diisocyanate to the premixed polyol mixture, stirring rapidly, and immediately pouring the mixed material into a mold. The material foams and solidifies in the mold. After the foam is completely solidified, the prepared base layer (1) is taken out from the mold; Step 2, preparing the buffer layer (2): premixing the polyether polyol, amine catalyst, carbon fiber, foaming agent, surfactant, flame retardant and stabilizer in a blender, adding toluene diisocyanate to the premixed polyol mixture, stirring rapidly, and spraying the mixed material onto the base layer (1) through a mold. The material foams and solidifies in the mold. After the foam is completely solidified, the mold is disassembled to form the buffer layer (2); Step 3, preparing the surface layer (3): forming the composite ultrafine fibers into a fabric in a non-woven manner, and performing surface modification to prepare the prepared surface layer (3), bonding the prepared surface layer (3) to the prepared buffer layer (2) using an isocyanate-based adhesive, and performing post-processing such as cutting and polishing to prepare a wax-free pad.

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