A low-temperature desizing water-based sizing agent for quartz fiber, a preparation method and application thereof

Abstract

The application belongs to the technical field of inorganic fiber sizing agent, and discloses a water-based sizing agent for quartz fiber with low-temperature desizing and a preparation method and application thereof. According to the water-based sizing agent, the total mass of the water-based sizing agent is 100%, and the water-based sizing agent is composed of the following components: modified water-soluble polyester 2%-8%, polyvinyl alcohol 0.5%-5%, softening agent 0.5%-3%, surfactant 0.05%-0.5%, and the rest is water. The water-based sizing agent can reduce the damage of quartz fiber yarn in the friction process, and can be desized in a low-temperature and low-concentration alkaline aqueous solution, thereby reducing the adverse effect of desizing treatment on the breaking strength of quartz fiber yarn. The application uses water as a dispersion medium, and no volatile organic solvent is added in the preparation process of the water-based sizing agent.

Description

Technical Field

[0001] This invention belongs to the field of inorganic fiber sizing agent technology, specifically relating to a water-based sizing agent for quartz fiber that can be desized at low temperatures, its preparation method, and its application. Background Technology

[0002] Quartz fiber is a high-performance inorganic fiber made of high-purity silica. It possesses excellent properties such as low dielectric constant, low dielectric loss, high temperature resistance, and corrosion resistance, and is widely used in fields such as microwave-transparent composite materials, high-frequency electronic substrates, and aerospace structural materials. During the yarn guiding, drafting, warping, and weaving processes of quartz fiber, sizing is typically required to overcome the problems of monofilament slippage and breakage caused by the smooth surface and weak cohesion of the fibers. Existing technologies often use starch, polyvinyl alcohol (PVA), or their compound systems as the main film-forming substances. A protective sizing film is formed on the fiber surface through impregnation, pressing, and drying processes to improve the fiber bundle's cohesion and resistance to abrasion damage. In subsequent processes, a high-temperature heat treatment at 400-600℃ is commonly used to remove the surface organic sizing film. This high temperature causes the organic components such as starch or PVA to undergo thermal decomposition, burning, or carbonization, thereby achieving desizing.

[0003] However, in existing technologies, for brittle silica-oxygen inorganic fibers such as quartz fibers, desizing methods relying on high-temperature heat treatment often struggle to balance fiber strength integrity with thorough desizing. Higher desizing temperatures or longer heat treatment times can easily induce or exacerbate micro-defects on the fiber surface, leading to irreversible declines in fiber or fabric strength. Simultaneously, organic sizing agents may produce carbonized residues or ash during high-temperature decomposition, causing uneven desizing and consequently affecting subsequent fiber opening and composite material interface quality. Existing sizing systems still struggle to achieve an ideal balance between providing effective weaving protection and achieving low-damage, low-temperature desizing.

[0004] Based on the above problems, it is necessary to develop an aqueous sizing agent suitable for quartz fiber yarn, which can form a uniform, continuous and resilient protective film on the fiber surface during the weaving stage, thereby improving the bundle properties, abrasion resistance and breaking strength of quartz fiber yarn. At the same time, the film can absorb water and swell, loosen the interface and peel off in a low-temperature weak alkaline water bath, thus achieving effective desizing and avoiding damage to quartz fibers caused by traditional high-temperature desizing. Summary of the Invention

[0005] The purpose of this invention is to provide a water-based sizing agent for quartz fibers that can be desized at low temperatures. This agent can form a continuous sizing film on the surface of quartz fiber yarn, reducing frictional damage to the fiber yarn during yarn guiding, warping and weaving processes, and can be desized in low-temperature, low-concentration alkaline aqueous solutions.

[0006] Another object of the present invention is to provide a method for preparing the aqueous sizing agent, a method for preparing sized quartz fiber yarn using the aqueous sizing agent, and a method for desizing the sized quartz fiber yarn.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] The first aspect of this invention provides an aqueous sizing agent for quartz fibers that can be desized at low temperatures, comprising, based on 100% of the total mass of the aqueous sizing agent: Modified water-soluble polyester 2%–8%; Polyvinyl alcohol 0.5%–5%; Softener 0.5%–3%; Surfactant 0.05%–0.5%; The remainder is water.

[0009] The modified water-soluble polyester is prepared by esterification and polycondensation of terephthalic acid, ethane-1,2-diol, sodium isophthalate-5-sulfonate and lactate-containing modified siloxane diol.

[0010] Based on the total mass of the synthetic raw materials for the modified water-soluble polyester being 100%, the mass percentage of each synthetic raw material is as follows: The mass percentage of terephthalic acid is 52%–58%. The mass percentage of ethane-1,2-diol is 28%–32%. The mass percentage of sodium isophthalic acid-5-sulfonate is 8%–12%. The mass percentage of lactate-modified siloxane diols is 2%–8%. Furthermore, the sum of the mass percentages of the aforementioned synthetic raw materials is 100%.

[0011] The total mass of the above-mentioned raw materials does not include catalysts, heat stabilizers, and other trace process aids used in the reaction. The lactate-modified siloxane diol is prepared by ring-opening polymerization of α,ω-dihydroxypropyl polydimethylsiloxane with a number average molecular weight of 2000 and lactide at a molar ratio of 1:5.

[0012] The statement in this specification that "the molar ratio of α,ω-dihydroxypropyl polydimethylsiloxane to lactide is 1:5" refers to the addition of 5 mol of lactide for every 1 mol of α,ω-dihydroxypropyl polydimethylsiloxane. Since 1 mol of lactide forms two lactic acid structural units after ring-opening, and assuming these units are evenly distributed across both ends of the polydimethylsiloxane, the theoretical average number of lactic acid structural units at each end is approximately 5. This theoretical average is calculated based on the feed amount and does not indicate that every product molecule has the exact same number of lactic acid structural units.

[0013] Preferably, the degree of alcoholysis of the polyvinyl alcohol PVA0588 is 87% to 89%, and the average degree of polymerization is 550 to 650.

[0014] Preferably, the softener includes one of polyethylene glycol-2000 (PEG-2000), polyethylene glycol-4000 (PEG-4000), and polyethylene glycol-6000 (PEG-6000).

[0015] Preferably, the surfactant includes one of fatty alcohol polyoxyethylene ether (AEO-9), Tween-80, and carboxymethyl cellulose (CMC).

[0016] A second aspect of the present invention provides a method for preparing the above-mentioned aqueous sizing agent for quartz fibers that can be desized at low temperatures, comprising the following steps: Step 1: Weigh the following raw materials according to the total weight percentage: 2%-8% modified water-soluble polyester, 0.5%-5% polyvinyl alcohol, 0.5%-3% softener, 0.05%-0.5% surfactant, and the balance is water; Step 2: Add the modified water-soluble polyester to water and stir at a constant temperature of 85-100℃ until there are no insoluble particles visible to the naked eye in the system, thus obtaining a modified water-soluble polyester solution. Step 3: Add polyvinyl alcohol to water and stir at a constant temperature of 85-100℃ until there are no insoluble particles visible to the naked eye in the system, thus obtaining a polyvinyl alcohol solution. Step 4: Mix the modified water-soluble polyester solution obtained in Step 2 with the polyvinyl alcohol solution obtained in Step 3 to obtain a mixture of main film-forming components; Step 5: Add softener and surfactant to the main film-forming component mixture obtained in Step 4, and stir for 10-30 minutes; Step 6: After cooling the reaction system from Step 5 to room temperature, continue stirring for 20-60 minutes, let it stand to remove bubbles, and you will get the water-based sizing agent for quartz fiber that can be desized at low temperatures.

[0017] Preferably, the preparation method of the modified water-soluble polyester includes the following steps: Terephthalic acid, ethane-1,2-diol and sodium isophthalate-5-sulfonate were added to a reactor and esterification was carried out in the presence of a catalyst and under nitrogen protection. When the actual water output reaches 50% to 70% of the theoretical water output, add a lactate-modified siloxane diol to continue the esterification reaction. After the esterification reaction is completed, the reaction system is heated to 230-255°C, and the absolute pressure of the reaction system is gradually reduced to 50-300 Pa to carry out the polycondensation reaction. After the reaction is completed, the material is discharged, cooled, pelletized and dried to obtain the modified water-soluble polyester.

[0018] Preferably, the preparation method of the lactate-modified siloxane diol includes the following steps: α,ω-dihydroxypropyl polydimethylsiloxane with a number average molecular weight of 2000 and lactide were added to a reactor at a molar ratio of 1:5. Stannous octoate was added, and the reaction was carried out at 130-150°C for 4-8 hours under nitrogen protection. After the reaction was completed, the mixture was subjected to reduced pressure treatment at 110-130°C and an absolute pressure not exceeding 300 Pa for 0.5-2 hours to obtain the lactate-modified siloxane diol.

[0019] The third aspect of the present invention provides the application of the above-mentioned aqueous sizing agent for quartz fibers that can be desized at low temperatures in the sizing treatment of quartz fiber yarn and quartz fiber fabric.

[0020] When the water-based sizing agent is used for sizing quartz fiber yarn, the water-based sizing agent is added to the sizing tank of the sizing equipment, and the raw quartz fiber yarn is continuously passed through the sizing tank so that the water-based sizing agent wets the quartz fiber yarn bundle; then the wetted quartz fiber yarn is passed through the sizing roller to remove excess sizing liquid and control the sizing rate; then the sizing quartz fiber yarn is dried and wound to obtain sized quartz fiber yarn.

[0021] Preferably, the temperature of the sizing tank is 10-30℃, the running speed of the quartz fiber yarn is 5-7m / min, the drying temperature is 80-120℃, and the sizing rate is 2.8%-3.2%.

[0022] The sizing rate is calculated according to the following formula: Sizing rate = (Oven-dry weight of sized yarn - Oven-dry weight of original yarn) / Oven-dry weight of original yarn × 100%.

[0023] The fourth aspect of the present invention provides a method for desizing sized quartz fiber yarn products, wherein the sized quartz fiber yarn products are placed in an alkaline aqueous solution at 50-95°C with an alkaline substance mass fraction of 0.05%-0.50% for 5-90 minutes, followed by washing and drying.

[0024] Preferably, the alkaline substance is selected from at least one of sodium hydroxide, sodium carbonate, and sodium bicarbonate.

[0025] Preferably, the sized quartz fiber yarn is placed in an aqueous solution of sodium hydroxide at 80°C with a mass fraction of 0.20% for 30 minutes, then washed with water until the pH of the final washing solution is 6.5-7.5, and then dried.

[0026] The advantages and beneficial effects of this invention are as follows: 1. This invention uses lactate-modified siloxane diols as reactive raw materials to participate in the esterification and polycondensation reactions of water-soluble polyesters. Compared with directly adding lactate-modified siloxane diols during the sizing agent preparation stage, this reactive introduction method is beneficial to improving the distribution stability of silicon-containing structures and lactate structures in the film-forming resin.

[0027] 2. Without being constrained by theoretical limitations, it is believed that the hydrophilic groups introduced by sodium isophthalic acid-5-sulfonate facilitate the penetration of water and alkaline media into the slurry membrane; the siloxane structure improves the flexibility of the slurry membrane and its spreadability on the quartz fiber surface; and the lactate structure exhibits a certain degree of hydrolytic sensitivity in weakly alkaline aqueous solutions. The combined effect of these structures enables the resulting slurry membrane to achieve both the friction protection performance during the sizing stage and the water bath removal performance during the desizing stage.

[0028] 3. This invention uses water as the dispersion medium, eliminating the need to add volatile organic solvents during the sizing agent preparation process. The use of a low-temperature, weakly alkaline water bath for desizing also reduces the adverse effects of high-temperature heat treatment on the breaking strength of the quartz fiber yarn. Attached Figure Description

[0029] Figure 1 The image shows a comparison of the 1H NMR spectra of the raw material α,ω-dihydroxypropyl polydimethylsiloxane and the lactate-modified siloxane diol prepared in Example 1. The solid line represents the 1H NMR spectrum of the raw material α,ω-dihydroxypropyl polydimethylsiloxane, and the dotted line represents the 1H NMR spectrum of the lactate-modified siloxane diol. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Unless otherwise stated, all percentage contents in the embodiments are mass percentages.

[0031] Example 1: Optimal Formulation System A water-based sizing agent for quartz fiber that can be desized at low temperatures, with a total mass of 100% water-based sizing agent, has the following formula: 4% WPET-SiL (modified water-soluble polyester), 2% PVA0588 (polyvinyl alcohol), 1% polyethylene glycol-6000, 0.15% fatty alcohol polyoxyethylene ether, and the balance being deionized water.

[0032] The degree of alcoholysis of PVA0588 is 88%, and the average degree of polymerization is 550-650.

[0033] The preparation method of the aqueous sizing agent is as follows: (1) Preparation of lactate-modified siloxane diols 200.0 g of α,ω-dihydroxypropyl polydimethylsiloxane with a number average molecular weight of 2000 and 72.1 g of lactide were weighed and added to a dried reaction vessel. The amount of lactide added was measured according to 5 mol of lactide for every 1 mol of α,ω-dihydroxypropyl polydimethylsiloxane.

[0034] Nitrogen gas was introduced into the reactor and a vacuum was created. This process was repeated three times to reduce the oxygen and moisture content in the reaction system. Then, 0.14 g of stannous octoate was added as a catalyst. Under nitrogen protection, the reaction system was heated to 140 °C and stirred for 6 hours to allow lactide to undergo ring-opening polymerization initiated by the terminal hydroxyl groups of α,ω-dihydroxypropyl polydimethylsiloxane.

[0035] After the reaction was completed, the reaction system was cooled to 120°C and subjected to reduced pressure treatment for 1 hour under an absolute pressure not exceeding 200 Pa to remove unreacted lactide and low molecular weight substances, thereby obtaining lactate-modified siloxane diol.

[0036] Based on the feed rate, 5 mol of lactide is added for every 1 mol of α,ω-dihydroxypropyl polydimethylsiloxane. Since 1 mol of lactide forms two lactic acid structural units after ring opening, and assuming these units are evenly distributed across both ends of the polydimethylsiloxane, the theoretical average number of lactic acid structural units at each end is approximately 5. This theoretical average is calculated based on the feed rate and does not indicate that every product molecule has the exact same number of lactic acid structural units.

[0037] (2) Preparation of WPET-SiL Based on a total mass of 1000g of WPET-SiL synthesis raw materials, weigh out 550.0g of terephthalic acid, 300.0g of ethane-1,2-diol, 100.0g of sodium isophthalic acid-5-sulfonate and 50.0g of the above-mentioned lactate-modified siloxane diol.

[0038] First, terephthalic acid, ethane-1,2-diol and sodium isophthalate-5-sulfonate are added to a polyester reactor equipped with a stirrer, a distillation column, a condenser and a vacuum interface. At the same time, 0.28g of tetrabutyl titanate is added as a catalyst and 0.11g of triphenyl phosphite is added as a heat stabilizer.

[0039] After purging the air from the reactor with nitrogen, the mixture is stirred and heated to 210°C under nitrogen protection for 3 hours for esterification. The water produced in the reaction is then discharged through a water separator. When the actual water output reaches 60% of the theoretical output, lactate-modified siloxane diol is added to the reactor, and the reaction is continued at this temperature for another hour.

[0040] The reaction system was then heated to 245°C, and the absolute pressure of the reaction system was gradually reduced to 100–200 Pa for 2 hours of polycondensation. After the reaction was completed, nitrogen gas was introduced to restore atmospheric pressure, the molten product was discharged, cooled, pelletized, and vacuum dried at 70°C until the moisture content was less than 0.1%, thus obtaining modified water-soluble polyester (WPET-SiL).

[0041] The obtained WPET-SiL is a pale yellow to light yellow particle that can form a homogeneous aqueous system after being stirred in water at 85–100°C.

[0042] Figure 1 The figure shows a comparison of the 1H NMR spectra of the raw material α,ω-dihydroxypropyl polydimethylsiloxane and the lactate-modified siloxane diol prepared in Example 1. The solid line represents the 1H NMR spectrum of the raw material α,ω-dihydroxypropyl polydimethylsiloxane, and the dotted line represents the 1H NMR spectrum of the lactate-modified siloxane diol. As can be seen from the figure, both the raw material α,ω-dihydroxypropyl polydimethylsiloxane and the lactate-modified siloxane diol exhibit the characteristic signal of Si-CH3 protons at δ 0.08 ppm, indicating that the polydimethylsiloxane chain segment is retained in the reaction product. Compared with the raw material α,ω-dihydroxypropyl polydimethylsiloxane, the reaction product exhibits the characteristic signal of methyl protons in the lactate structure at δ 1.58 ppm and the characteristic signal of methylene protons in the lactate structure at δ 5.15 ppm. The above-mentioned 1H NMR results indicate that, under the reaction conditions of this embodiment, lactide undergoes a ring-opening reaction, and a lactate structure is introduced into the siloxane diol. The resulting reaction product contains both polydimethylsiloxane segments and a lactate structure.

[0043] (3) Preparation of water-based sizing agent Weigh out WPET-SiL, PVA0588, polyethylene glycol-6000, fatty alcohol polyoxyethylene ether, and deionized water according to the above formula.

[0044] WPET-SiL was added to a portion of deionized water and stirred at a constant temperature of 90°C until no insoluble particles were visible to the naked eye, thus obtaining a WPET-SiL solution.

[0045] PVA0588 was added to the remaining deionized water and stirred at a constant temperature of 90°C until no insoluble particles were visible to the naked eye, thus obtaining a PVA solution.

[0046] The WPET-SiL solution and PVA solution were mixed and stirred at 90°C for 30 min to obtain the main film-forming component mixture.

[0047] Add polyethylene glycol-6000 to the mixture of main film-forming components and stir for 20 minutes, then add fatty alcohol polyoxyethylene ether and stir for 20 minutes.

[0048] After cooling the obtained system to room temperature, continue stirring for 50 minutes, let it stand to remove bubbles, and obtain the water-based sizing agent.

[0049] The prepared water-based sizing agent is subjected to sizing treatment as follows: The prepared water-based sizing agent is added to the sizing tank of the sizing machine, and the temperature of the sizing tank is controlled at 20℃. The unsized 150tex quartz fiber yarn is continuously passed through the sizing tank at a speed of 6m / min under the action of the traction device, so that the water-based sizing agent is soaked and attached to the surface of the quartz fiber yarn bundle.

[0050] The impregnated quartz fiber yarn is then passed through a sizing roller to remove excess sizing liquid, and the sizing rate is controlled to 3.0% ± 0.2% by adjusting the pressure of the sizing roller. The sizing quartz fiber yarn is then dried in a 100℃ oven and finally wound into a cylinder by a traction winding device to obtain sized quartz fiber yarn.

[0051] The prepared sized quartz fiber yarn is desized using the following method: The sized quartz fiber yarn was treated in a 0.20% NaOH aqueous solution at 80℃ for 30 minutes. After treatment, the yarn was washed with water until the pH of the final wash solution was 6.5–7.5, and then dried.

[0052] Example 2: Low-content lactate-modified siloxane diol system The only difference between this embodiment and Example 1 is the ratio of raw materials used in the synthesis of WPET-SiL.

[0053] Based on a total mass of 1000g of WPET-SiL synthesis raw materials, weigh out 580.0g of terephthalic acid, 300.0g of ethane-1,2-diol, 100.0g of sodium isophthalic acid-5-sulfonate, and 20.0g of the lactate-modified siloxane diol prepared in Example 1.

[0054] Except for the differences mentioned above, the preparation method of WPET-SiL, the formulation of the aqueous sizing agent, the preparation method of the aqueous sizing agent, the sizing treatment method, and the desizing treatment method are all the same as in Example 1.

[0055] Example 3: High-content lactate-modified siloxane diol system The only difference between this embodiment and Example 1 is the ratio of raw materials used in the synthesis of WPET-SiL.

[0056] Based on a total mass of 1000g of WPET-SiL synthesis raw materials, weigh out 520.0g of terephthalic acid, 300.0g of ethane-1,2-diol, 100.0g of sodium isophthalic acid-5-sulfonate, and 80.0g of the lactate-modified siloxane diol prepared in Example 1.

[0057] Except for the differences mentioned above, the preparation method of WPET-SiL, the formulation of the aqueous sizing agent, the preparation method of the aqueous sizing agent, the sizing treatment method, and the desizing treatment method are all the same as in Example 1.

[0058] Example 4: Low-content water-based sizing agent formulation system A water-based sizing agent for quartz fiber that can be desized in a low-temperature weak alkaline water bath, with a formula based on 100% of the total mass of the water-based sizing agent: 2% WPET-SiL obtained in Example 1, 0.5% PVA0588, 0.5% polyethylene glycol-2000, 0.05% fatty alcohol polyoxyethylene ether, and the balance being deionized water.

[0059] The preparation method, sizing treatment method, and desizing treatment method of the water-based sizing agent are the same as those in Example 1.

[0060] Example 5: High-content water-based sizing agent formulation system A water-based sizing agent for quartz fiber that can be desized in a low-temperature weak alkaline water bath, with a total mass of 100% water-based sizing agent, has the following formula: 8% WPET-SiL obtained in Example 1, 5% PVA0588, 3% polyethylene glycol-6000, 0.5% Tween-800, and the balance being deionized water.

[0061] The preparation method, sizing treatment method, and desizing treatment method of the water-based sizing agent are the same as those in Example 1.

[0062] Comparative Example 1: Ordinary water-soluble polyester system The difference between this comparative example and Example 1 is that a common water-soluble polyester without the introduction of lactate-modified siloxane diol is used instead of WPET-SiL in Example 1.

[0063] Based on a total mass of 1000g of common water-soluble polyester synthetic raw materials, terephthalic acid, ethane-1,2-diol, and sodium isophthalate-5-sulfonate (excluding lactate-modified siloxane diol) from Example 1 were normalized according to their original mass ratios, and 578.9g of terephthalic acid, 315.8g of ethane-1,2-diol, and 105.3g of sodium isophthalate-5-sulfonate were weighed.

[0064] The above raw materials were added to a polyester reactor equipped with a stirrer, a fractionating column, a condenser, and a vacuum interface. 0.28 g of tetrabutyl titanate and 0.11 g of triphenyl phosphite were added. Under nitrogen protection, the temperature was raised to 210°C for esterification. Subsequently, the reaction system was heated to 245°C, and the absolute pressure of the reaction system was gradually reduced to 100–200 Pa for polycondensation reaction for 2 hours. After the reaction, the material was discharged, cooled, pelletized, and vacuum dried at 70°C to obtain ordinary water-soluble polyester.

[0065] According to the aqueous sizing agent formulation of Example 1, WPET-SiL was replaced by the same mass of ordinary water-soluble polyester. The content of other components, the preparation method of the aqueous sizing agent, the sizing treatment method and the desizing treatment method were the same as in Example 1.

[0066] Comparative Example 2: Ordinary water-soluble polyester and added lactate-modified siloxane diol system This comparative example uses the ordinary water-soluble polyester obtained in Comparative Example 1, and adds the lactate-containing modified siloxane diol obtained in Example 1 during the preparation stage of the water-based sizing agent.

[0067] Based on a total mass of 100% water-based sizing agent, the formulation of this comparative example is as follows: 3.80% ordinary water-soluble polyester, 0.20% lactate-modified siloxane diol, 2.00% PVA0588, 1.00% polyethylene glycol-6000, 0.15% fatty alcohol polyoxyethylene ether, and the balance being deionized water.

[0068] The total mass percentage of ordinary water-soluble polyester and lactate-modified siloxane diol is 4.00%, which is the same as the amount of WPET-SiL added in Example 1; the amount of lactate-modified siloxane diol added is calculated based on its proportion of 5% of the total mass of WPET-SiL synthetic raw materials in Example 1.

[0069] During preparation, ordinary water-soluble polyester is first added to a portion of deionized water and stirred at 90°C until no insoluble particles are visible to the naked eye in the system; PVA0588 is then added to the remaining deionized water and stirred at 90°C until no insoluble particles are visible to the naked eye in the system.

[0070] After mixing the two solutions, lactate-modified siloxane diol, polyethylene glycol-6000, and fatty alcohol polyoxyethylene ether were added sequentially, stirring for 20 minutes after each addition. The resulting system was cooled to room temperature and stirred for another 50 minutes, then allowed to stand to remove bubbles, yielding the water-based sizing agent of this comparative example.

[0071] The sizing and desizing methods are the same as in Example 1.

[0072] Comparative Example 3: Traditional high-hydrolyzability PVA system The difference between this comparative example and Example 1 is that WPET-SiL is not added, and PVA1799 is used as the main film-forming component.

[0073] Based on a total mass of 100% water-based sizing agent, the formulation of this comparative example is: 6% PVA1799, 1% polyethylene glycol-6000, 0.15% fatty alcohol polyoxyethylene ether, and the balance being deionized water.

[0074] During preparation, PVA1799 was added to deionized water and stirred at 90°C until no insoluble particles were visible to the naked eye in the system; polyethylene glycol-6000 and fatty alcohol polyoxyethylene ether were added and stirred evenly; after cooling to room temperature, stirring was continued for 50 minutes, and the mixture was allowed to stand to remove bubbles, thus obtaining the water-based sizing agent of this comparative example.

[0075] The sizing and desizing methods are the same as in Example 1.

[0076] Comparative Example 4: Hydroxyl-containing polydimethylsiloxane-modified water-soluble polyester system The difference between this comparative example and Example 1 is that α,ω-bishydroxypropyl polydimethylsiloxane is used as the modifying raw material to replace the lactate-modified siloxane diol in Example 1 in the esterification and polycondensation reactions of the water-soluble polyester.

[0077] The number-average molecular weight of the α,ω-bishydroxypropyl polydimethylsiloxane is 2000.

[0078] Based on a total mass of 1000g of modified water-soluble polyester synthetic raw materials, weigh out 50.0g of α,ω-dihydroxypropyl polydimethylsiloxane, 550.0g of terephthalic acid, 300.0g of ethane-1,2-diol and 100.0g of sodium isophthalate-5-sulfonate.

[0079] Except for replacing the lactate-containing modified siloxane diol with α,ω-dihydroxypropyl polydimethylsiloxane, the preparation method of the modified water-soluble polyester, the formulation of the water-based sizing agent, the preparation method of the water-based sizing agent, the sizing treatment method, and the desizing treatment method are all the same as in Example 1.

[0080] Comparative Example 5: High-Temperature Heat Treatment Desizing This comparative example uses the sized quartz fiber yarn obtained in Example 1, but instead of using a low-temperature weak alkaline water bath for desizing, it undergoes high-temperature heat treatment for desizing.

[0081] The sized quartz fiber yarn obtained in Example 1 was placed in a muffle furnace and heated to 500°C at a heating rate of 5°C / min. The temperature was held for 30 minutes and then cooled to room temperature with the furnace to obtain the quartz fiber yarn after high-temperature heat treatment and desizing.

[0082] Performance testing The average coefficient of friction, the rate of retention of breaking strength after friction, the desizing rate, and the rate of retention of breaking strength relative to the original yarn after desizing were tested on the samples obtained from the examples and comparative examples.

[0083] Unless otherwise specified, 10 valid parallel specimens are tested in each group, and the arithmetic mean is calculated. Invalid tests due to specimen slippage, clamp breakage, or abnormal equipment recording are not included in the statistics, and data deletion is not based on test results that are too high or too low.

[0084] 1. Average friction coefficient test The friction and wear tester was used for testing. During the test, the quartz fiber yarn was fixed to the lower clamp, and the upper stainless steel friction component was in 90° orthogonal contact with the quartz fiber yarn. The normal load was 0.3 N, the reciprocating frequency was 3 Hz, the stroke was 4 mm, and the friction time was 600 s.

[0085] The friction coefficients within the effective friction phase were recorded, and the arithmetic mean of the friction coefficients within the effective friction phase was used as the average friction coefficient. All samples were compared using the same equipment, friction components, and test conditions.

[0086] 2. Fracture strength retention rate test Using a single yarn strength tester, the breaking strength of sized yarn before friction, sized yarn after friction, raw yarn, and desized yarn were measured under the same clamping and tensile conditions.

[0087] The rate of retention of fracture strength after friction is calculated according to the following formula: The rate of retention of breaking strength after friction = breaking strength of sized yarn after friction / breaking strength of sized yarn before friction × 100%.

[0088] The rate of retention of breaking strength relative to the original yarn after desizing is calculated according to the following formula: The rate of retention of the breaking strength of the yarn after desizing = breaking strength of the yarn after desizing / breaking strength of the yarn after desizing × 100%.

[0089] 3. Low-temperature weak alkaline water bath desizing rate test The dry weight m0 of the raw yarn and the dry weight m1 of the sized yarn in the same batch were measured separately.

[0090] The sized quartz fiber yarn was treated in a 0.20% NaOH aqueous solution at 80℃ for 30 minutes. After treatment, the yarn was washed with water until the pH of the final washing solution was 6.5–7.5. The sample was then dried to constant weight, and the dry weight (m2) of the desized yarn was measured.

[0091] The desizing rate in a low-temperature, weakly alkaline water bath is calculated using the following formula: Desizing rate = (m1 - m2) / (m1 - m0) × 100%.

[0092] Where m0 is the dry weight of the original yarn with the same length as the sized yarn, m1 is the dry weight of the sized yarn before desizing, and m2 is the dry weight of the yarn after desizing, washing, and drying to constant weight.

[0093] 4. High-temperature heat treatment desizing rate test The high-temperature heat treatment desizing rate was only used in Comparative Example 5.

[0094] The dry weight m0 of the raw yarn and the dry weight m1 of the sized yarn were measured separately. The sized quartz fiber yarn was placed in a muffle furnace and heated to 500℃ at a heating rate of 5℃ / min, held at that temperature for 30 min, and then cooled to room temperature with the furnace. The yarn after high-temperature heat treatment was dried and weighed, and the dry weight m3 of the yarn after high-temperature heat treatment was measured.

[0095] The desizing rate after high-temperature heat treatment is calculated using the following formula: High-temperature heat treatment desizing rate = (m1 - m3) / (m1 - m0) × 100%.

[0096] Performance test results Table 1. Performance test results of quartz fiber yarns with different sizing agent systems and after desizing treatment.

[0097] As shown in Table 1, the average coefficient of friction of the unsized quartz fiber yarn is 0.038. Under the specified reciprocating friction conditions, the unsized yarn exhibited significant fiber bundle loosening and monofilament breakage, and no effective tensile strength test value was obtained after friction, indicating that the unsized quartz fiber yarn has poor resistance to friction damage.

[0098] The average coefficient of friction of the sized quartz fiber yarns obtained in Examples 1-5 was 0.012-0.021, the breaking strength retention rate after friction was 80.6%-89.4%, the desizing rate in a low-temperature weak alkaline water bath was 92.6%-95.8%, and the relative breaking strength retention rate of the original yarn after desizing was 98.2%-99.3%. These results indicate that, under the formulation, sizing conditions, and testing conditions used in the embodiments of this invention, the aqueous sizing agent can reduce the average coefficient of friction of the quartz fiber yarn and achieve a high removal rate of the sizing film in an 80°C, 0.20% (w / w) NaOH aqueous solution.

[0099] The average coefficient of friction in Example 1 was 0.013, the breaking strength retention rate after friction was 88.6%, the low-temperature weak alkaline water bath desizing rate was 95.2%, and the breaking strength retention rate relative to the original yarn after desizing was 99.1%, indicating that the formulation of Example 1 can take into account both friction protection performance and low-temperature weak alkaline water bath desizing performance.

[0100] Comparative Example 1 used a common water-soluble polyester without the introduction of lactate-modified siloxane diols. Compared with Example 1, Comparative Example 1 had a higher average coefficient of friction and a lower retention rate of breaking strength after friction, but still exhibited a certain desizing rate in a low-temperature weak alkaline water bath. This indicates that the common water-soluble polyester containing sodium sulfonate groups can provide a certain degree of hydrophilicity, but its friction protection performance is lower than that of the WPET-SiL system used in Example 1.

[0101] Comparative Example 2 involved the physical compounding of ordinary water-soluble polyester with lactate-modified siloxane diol. Compared to Example 1, Comparative Example 2 showed a decrease in average friction coefficient, post-friction breaking strength retention rate, and low-temperature weak alkaline water bath desizing rate. This indicates that, under the experimental conditions, using lactate-modified siloxane diol as a reactive raw material in the synthesis of water-soluble polyester yields better overall results than physical compounding during the preparation stage of the water-based sizing agent.

[0102] Comparative Example 3 used PVA1799 as the main film-forming component, and its low-temperature weak alkaline water bath desizing rate was 80.5%, lower than that of Example 1. The relative breaking strength retention rate of the original yarn after desizing in Comparative Example 3 was 104.2%. Because the desizing rate of Comparative Example 3 was low, there may still be a significant amount of residual sizing material on the yarn surface after desizing. This residual sizing material may enhance the bundle aggregation effect of the fibers, making the yarn breaking strength appear higher than it actually is. Therefore, the result of 104.2% cannot be interpreted as an increase in the intrinsic strength of the quartz fiber after desizing, nor can this value alone be used to conclude that its desizing effect is superior to that of Example 1.

[0103] Comparative Example 4 used α,ω-dihydroxypropyl polydimethylsiloxane-modified water-soluble polyester without a lactate structure. Its average coefficient of friction and post-friction breaking strength retention rate were similar to those of Example 1, but its low-temperature weak alkaline water bath desizing rate was 87.4%, lower than that of Example 1. This indicates that while introducing only the polydimethylsiloxane structure is beneficial for friction protection, it is not conducive to achieving the same low-temperature weak alkaline water bath desizing effect as Example 1.

[0104] Table 2 Comparison of the performance of low-temperature weak alkaline water bath desizing in Example 1 and high-temperature heat treatment desizing in Comparative Example 5

[0105] As shown in Table 2, when the sized quartz fiber yarn obtained in Example 1 was desized using a low-temperature weak alkaline water bath, the desizing rate was 95.2%, and the relative breaking strength retention rate of the original yarn after desizing was 99.1%. When desizing was performed using a high-temperature heat treatment at 500℃, the desizing rate was 96.8%, but the relative breaking strength retention rate of the original yarn after desizing decreased to 91.6%.

[0106] Under the conditions of this experiment, both desizing methods can remove most of the slurry, but the loss of fracture strength caused by high-temperature heat treatment is significantly higher than that caused by low-temperature weak alkaline water bath desizing.

[0107] Based on the above results, under the formulation and testing conditions of the embodiments of the present invention, using lactate-modified siloxane diols as reactive raw materials for the synthesis of water-soluble polyesters is beneficial to ensure that the resulting water-based sizing agent has both the friction protection properties of quartz fiber yarn and the low-temperature weak alkaline water bath desizing properties.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Equivalent substitutions, simple modifications, or improvements made by those skilled in the art without departing from the concept of the present invention should all fall within the scope of protection of the present invention.

Claims

1. A water-based sizing agent for quartz fibers that can be desized at low temperatures, characterized in that, Based on 100% of the total mass of the water-based sizing agent, the components include: Modified water-soluble polyester 2%-8%; Polyvinyl alcohol 0.5%-5%; Softener 0.5%-3%; Surfactant 0.05%-0.5%; The remainder is water; The modified water-soluble polyester is prepared by esterification and polycondensation reaction of terephthalic acid, ethane-1,2-diol, sodium isophthalate-5-sulfonate and lactate-containing modified siloxane diol. Based on the total mass of the synthetic raw materials for the modified water-soluble polyester being 100%, the mass percentage of each synthetic raw material is as follows: 52%-58% terephthalic acid; Ethane-1,2-diol 28%-32%; Sodium isophthalic acid-5-sulfonate 8%-12%; Contains 2%-8% lactate-modified siloxane diols; Furthermore, the sum of the mass percentages of the above-mentioned synthetic raw materials is 100%; The lactate-modified siloxane diol is prepared by ring-opening polymerization of α,ω-dihydroxypropyl polydimethylsiloxane with a number average molecular weight of 2000 and lactide in a molar ratio of 1:

5.

2. The aqueous sizing agent for quartz fiber capable of low-temperature desizing according to claim 1, characterized in that: The polyvinyl alcohol is PVA0588, with a degree of alcoholysis of 87% to 89% and an average degree of polymerization of 550 to 650.

3. The aqueous sizing agent for quartz fiber capable of low-temperature desizing according to claim 1, characterized in that: The softener includes one of polyethylene glycol-2000, polyethylene glycol-4000, and polyethylene glycol-6000.

4. The aqueous sizing agent for quartz fiber capable of low-temperature desizing according to claim 1, characterized in that: The surfactant includes one of fatty alcohol polyoxyethylene ether, Tween-80, and carboxymethyl cellulose.

5. A method for preparing a low-temperature desizing aqueous sizing agent for quartz fibers according to any one of claims 1-4, characterized in that: Includes the following steps: Step 1: Weigh the following raw materials according to the total weight percentage: 2%-8% modified water-soluble polyester, 0.5%-5% polyvinyl alcohol, 0.5%-3% softener, 0.05%-0.5% surfactant, and the balance is water; Step 2: Add the modified water-soluble polyester to water and stir at a constant temperature of 85-100℃ until there are no insoluble particles visible to the naked eye in the system, thus obtaining a modified water-soluble polyester solution. Step 3: Add polyvinyl alcohol to water and stir at a constant temperature of 85-100℃ until there are no insoluble particles visible to the naked eye in the system, thus obtaining a polyvinyl alcohol solution. Step 4: Mix the modified water-soluble polyester solution obtained in Step 2 with the polyvinyl alcohol solution obtained in Step 3 to obtain a mixture of main film-forming components; Step 5: Add softener and surfactant to the main film-forming component mixture obtained in Step 4, and stir for 10-30 min respectively; Step 6: After cooling the reaction system from Step 5 to room temperature, continue stirring for 20-60 minutes, let it stand to remove bubbles, and you will get the water-based sizing agent for quartz fiber that can be desized at low temperatures.

6. The preparation method according to claim 5, characterized in that, The modified water-soluble polyester is prepared by the following method: Terephthalic acid, ethane-1,2-diol and sodium isophthalate-5-sulfonate were esterified in the presence of a catalyst. When the actual water output reaches 50%-70% of the theoretical output, add a lactate-modified siloxane diol to continue the esterification reaction. After the esterification reaction is completed, a polycondensation reaction is carried out at 230-255℃ and an absolute pressure of 50-300Pa to obtain the modified water-soluble polyester.

7. The preparation method according to claim 6, characterized in that, The lactate-modified siloxane diol is prepared by the following method: α,ω-dihydroxypropyl polydimethylsiloxane with a number average molecular weight of 2000 and lactide were added to a reactor at a molar ratio of 1:

5. Stannous octoate was added, and the reaction was carried out at 130-150°C for 4-8 hours under nitrogen protection. After the reaction was completed, the mixture was subjected to reduced pressure treatment at 110-130°C and an absolute pressure not exceeding 300 Pa for 0.5-2 hours to obtain the lactate-modified siloxane diol.

8. A sized quartz fiber yarn product, characterized in that, The sizing agent described in any one of claims 1-4 is used to sizing, pressing, and drying quartz fiber yarn, and the sizing rate of the sized quartz fiber yarn product is 2.8%-3.2%.

9. A method for desizing the sized quartz fiber yarn product as described in claim 8, characterized in that, The sized quartz fiber yarn product is placed in an alkaline aqueous solution at a temperature of 50-95°C and an alkaline substance mass fraction of 0.05%-0.50% for 5-90 minutes, followed by washing and drying; the alkaline substance is selected from at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

10. The application of an aqueous sizing agent as described in any one of claims 1-4 in the sizing treatment of quartz fiber yarn and quartz fiber fabric.

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