High-temperature-resistant masking paper and preparation process thereof

Abstract

The invention provides high-temperature-resistant textured paper and a preparation process thereof, and belongs to the technical field of textured paper. The preparation process comprises the following steps: preparing the raw paper; preparing a gum dipping solution; and impregnating the raw paper. The preparation method comprises the following steps: by taking p-vinylbenzoic acid and 2-vinylpyridine as functional monomers, mixing the p-vinylbenzoic acid and 2-vinylpyridine with styrene, butadiene and tert-dodecanethiol, adding the mixture into an emulsifier solution, emulsifying to prepare a pre-emulsion, then carrying out copolymerization under the initiation of potassium persulfate to prepare modified styrene-butadiene latex, and introducing carboxyl to form a strong hydrogen bond, so as to obtain the modified styrene-butadiene latex. According to the modified styrene-butadiene latex, the action force between molecular chains is remarkably enhanced, polar nitrogen atoms of pyridine rings and polar groups in adjacent molecular chains can form dipole interaction, the binding force between molecules is enhanced, and then the thermal stability of the styrene-butadiene latex is improved. The high temperature resistance of the prepared masking paper can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of masking papers, and in particular to a high-temperature resistant masking paper and a preparation process thereof. Background Art

[0002] Masking paper, a common industrial paper, is widely used in applications such as automotive painting, electronic component painting, circuit board mounting, and architectural decoration. The masking paper production process involves pulping and papermaking the fiber and additives into base paper. An adhesive is typically applied to the paper. The adhesive's high bonding power and viscosity bond the fibers and pulp particles together, enhancing the paper's strength and hardness while also improving its water resistance and durability, slowing down its aging process and making it more durable.

[0003] In automobile production, masking tape is mainly used to accurately cover non-painted areas such as windows, lights, and decorative strips. It usually needs to withstand high-temperature paint baking environments to avoid paint surface contamination due to high-temperature softening, residual glue or tearing, so as to ensure clear boundaries and no penetration. However, the currently commonly used adhesive system is mainly based on styrene-butadiene latex, whose main component is styrene-butadiene copolymer. The molecular chain contains a large number of carbon-carbon double bonds brought by butadiene units. Under high temperature conditions, it is easily attacked by oxidants such as oxygen in the air, triggering free radical chain oxidation reactions, thereby aging and failure, causing the paper to become brittle, break, and the adhesive to fall off.

[0004] Therefore, it is necessary to propose a high-temperature resistant masking paper and a preparation process thereof to be suitable for high-temperature spray painting environments. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a high-temperature resistant masking paper and a preparation process thereof.

[0006] A preparation process of high-temperature resistant masking paper comprises the following steps: S1: Preparation of base paper Bleached hardwood pulp, bleached softwood pulp, polyester fiber, aramid, wet strength agent, softener and defoamer are mixed to make pulp, and then formed into base paper wet paper web by paper machine, and then sent to the pressing section, and after being pressed and wrinkled, it is dried to obtain base paper; S2: Preparation of dipping solution The modified styrene-butadiene rubber latex and the surface-modified nano-silica are stirred and mixed uniformly to obtain a dipping solution; S3: Base paper impregnation The base paper is placed in the dipping solution, both sides are dipped in glue, and after drying, a high temperature resistant masking paper is obtained; The raw material composition of the base paper is as follows: 10-20 parts of bleached hardwood pulp, 40-50 parts of bleached softwood pulp, 10-30 parts of polyester fiber, 10-30 parts of aramid fiber, 1-3 parts of wet strength agent, 1-2 parts of softener and 1-3 parts of defoaming agent. Wherein, the wet strength agent is any one of polyamide epichlorohydrin resin and polyphenylene ether; The softener is a silicone softener; The defoaming agent is a non-silicone defoaming agent.

[0007] Further, the preparation steps of the modified styrene-butadiene latex are as follows: A1: Add octylphenol polyoxyethylene ether, sodium lauryl sulfate, and sodium bicarbonate to deionized water, stir at 50-60°C until completely dissolved, and cool to obtain an emulsifier solution; A2: Styrene, butadiene, p-vinylbenzoic acid, 2-vinylpyridine, and tert-dodecyl mercaptan are mixed uniformly, and then added to the emulsifier solution while stirring to obtain a pre-emulsion; A3: Add 1 / 2 of a 5% by mass potassium persulfate solution to the pre-emulsion. Under nitrogen, keep the mixture at 75-85°C for 1-2 hours. Then add the remaining potassium persulfate solution and continue the reaction for 5-6 hours. When the temperature drops to 50°C, introduce nitrogen to remove residual monomers. Adjust the pH to 8.5-9 with 10% sodium hydroxide solution, filter, and distill under reduced pressure to a solid content of 40-50% to obtain a modified styrene-butadiene latex.

[0008] Furthermore, the preparation steps of surface modified nano-silica are as follows: B1: Add nano-silica to anhydrous ethanol at a ratio of 1g: (20-30)mL, ultrasonically disperse for 20-30min, then add silane coupling agent KH-550, stir evenly, heat and stir under reflux at 70-80℃ for 3-4h, then centrifuge, wash and vacuum dry to obtain amino-silica; B2: Disperse the above-mentioned amino-silica in N,N-dimethylformamide at a ratio of 1g: (30-40)mL, ultrasonically treat for 20-30min, then add modified lignin, and heat and stir at 95-105℃ for 6-8h. After cooling, centrifuge, wash, vacuum dry and grind to obtain surface-modified nano-silica.

[0009] Furthermore, the preparation steps of modified lignin are as follows: C1: Add alkali lignin to N,N-dimethylformamide at a ratio of 1g: (10-20)mL, heat and stir at 50-60℃ until completely dissolved to obtain alkali lignin solution; C2: Add glycerophosphodiester and p-toluenesulfonic acid to the above alkaline lignin solution at a ratio of 1 g: (0.1-0.2) g: (15-25) mL, and heat at 110-120°C for 4-5 hours to obtain an intermediate reaction solution; C3: When the intermediate reaction liquid is cooled to 70-80°C, triethylenetetramine is added and the reaction is continued for 5-6 hours. After cooling, a precipitate is added and the solid is collected by filtration, washed with deionized water and vacuum dried to obtain modified lignin.

[0010] Furthermore, the raw material composition of the modified styrene-butadiene latex includes, by mass: 40-45 parts of styrene, 40-45 parts of butadiene, 5-8 parts of p-vinylbenzoic acid, 5-10 parts of 2-vinylpyridine, 0.2-0.4 parts of tert-dodecyl mercaptan, 1-1.5 parts of octylphenol polyoxyethylene ether, 0.5-1 parts of sodium lauryl sulfate, 0.3-0.5 parts of sodium bicarbonate, 0.4-0.6 parts of potassium persulfate and 130-150 parts of deionized water.

[0011] Furthermore, the mass ratio of triethylenetetramine to glycerophosphodiester is 1:(1.6-1.8).

[0012] Furthermore, the mass ratio of the silane coupling agent KH-550 to the nano-silica is 1:(3.3-3.5).

[0013] Furthermore, the mass ratio of the modified lignin to the amino-silica is (2-2.6):1.

[0014] Furthermore, the dipping solution is prepared by mixing modified styrene-butadiene rubber latex and surface-modified nano-silica in a mass ratio of (8-10):1.

[0015] Furthermore, a high-temperature resistant masking paper is prepared by the preparation process of a high-temperature resistant masking paper described in any one of the above.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: 1. In the present invention, p-vinylbenzoic acid and 2-vinylpyridine are used as functional monomers, the two are mixed with styrene, butadiene and tert-dodecyl mercaptan and added into an emulsifier solution for emulsification to prepare a pre-emulsion, and then copolymerized under the initiation of potassium persulfate to prepare a modified styrene-butadiene latex. On the one hand, since the benzene ring in p-vinylbenzoic acid and the pyridine ring in 2-vinylpyridine are both rigid aromatic structures, the rigidity of the molecular chain can be significantly increased after being introduced into the styrene-butadiene latex, and the conjugated π electron system of the aromatic ring can increase the energy barrier of the chain segment movement, thereby The glass transition temperature and thermal decomposition temperature of styrene butadiene latex. On the other hand, p-vinyl benzoic acid introduces carboxyl groups into styrene butadiene latex. The carboxyl groups can form strong hydrogen bonds, which significantly enhance the interaction force between molecular chains and make it less likely for chain slip to occur at high temperatures. The polar nitrogen atoms of the pyridine ring in 2-vinyl pyridine can form dipole interactions with the polar groups in the adjacent molecular chains, enhance the intermolecular binding force, and thus improve the thermal stability of styrene butadiene latex. Therefore, after the base paper is impregnated with the modified styrene butadiene latex, the high temperature resistance of the resulting masking paper can be effectively improved.

[0017] 2. In the present invention, after dissolving the alkali lignin, glycerophosphodiester is added and reacted under the catalysis of p-toluenesulfonic acid to cause the phosphate group of glycerophosphodiester to react with the hydroxyl group of lignin to undergo esterification reaction, and then triethylenetetramine is added to react to cause the amino group of triethylenetetramine to react with the phosphate group of glycerophosphodiester and the carboxyl group of lignin to introduce nitrogen to obtain modified lignin, and finally the modified lignin is reacted with the amino group on the surface of the aminated silica to form a covalent bond, and the modified lignin is grafted onto the surface of the nano-silica. After modification, it can not only improve the dispersibility of nano-silica in modified styrene-butadiene latex, thereby further improving the high-temperature resistance of the masking paper, but also the phosphorus element contained in the glycerol phosphate diester introduced in the modified lignin will decompose when heated to produce acidic substances such as phosphoric acid and metaphosphoric acid, which will promote the dehydration and carbonization of cellulose in the masking paper fiber to form a dense carbon layer. The nitrogen element introduced by triethylenetetramine will decompose when burned to produce non-combustible gases such as ammonia and nitrogen, which will inhibit the spread of flames, thereby improving the flame retardant properties of the masking paper and reducing the risk of fire. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable one skilled in the relevant art to make and use the present disclosure.

[0019] Figure 1 This is a flow chart of the preparation process of the high-temperature resistant masking paper used in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following describes in detail a high-temperature resistant masking paper and a preparation process thereof provided by the present invention in conjunction with the accompanying drawings and specific embodiments.

[0021] Example 1 A preparation process of high temperature resistant masking paper, such as Figure 1 As shown, the following steps are included: (1) Preparation of modified styrene-butadiene latex: Octylphenol polyoxyethylene ether, sodium lauryl sulfate and sodium bicarbonate were added to deionized water and stirred at 50 ° C until completely dissolved. After cooling, an emulsifier solution was obtained. Styrene, butadiene, p-vinyl benzoic acid, 2-vinyl pyridine and tert-dodecyl mercaptan were then mixed evenly and added to the emulsifier solution while stirring to obtain a pre-emulsion. Then, 1 / 2 of a 5% potassium persulfate solution by mass was added to the pre-emulsion. Under the protection of nitrogen, the mixture was kept warm at 75 ° C for 1 hour, and the remaining potassium persulfate solution was added. The reaction was continued for 5 hours and the temperature was cooled. When the temperature reaches 50° C., nitrogen is introduced to remove residual monomers, and then the pH is adjusted to 8.5 with a 10% sodium hydroxide solution. The mixture is filtered and distilled under reduced pressure until the solid content is 40%, thereby obtaining a modified styrene-butadiene latex, wherein the raw material composition of the modified styrene-butadiene latex comprises, by weight, 40 parts of styrene, 40 parts of butadiene, 5 parts of p-vinylbenzoic acid, 5 parts of 2-vinylpyridine, 0.2 parts of tert-dodecyl mercaptan, 1 part of octylphenol polyoxyethylene ether, 0.5 parts of sodium lauryl sulfate, 0.3 parts of sodium bicarbonate, 0.4 parts of potassium persulfate and 130 parts of deionized water; (2) Preparation of modified lignin: Alkali lignin was added to N,N-dimethylformamide at a ratio of 1 g:10 mL, heated and stirred at 50° C. until completely dissolved to obtain an alkali lignin solution, and then glycerophosphodiester and p-toluenesulfonic acid were added to the alkali lignin solution at a ratio of 1 g:0.1 g:15 mL, and the mixture was kept warm at 110° C. for 4 hours to obtain an intermediate reaction liquid. When the intermediate reaction liquid was cooled to 70° C., triethylenetetramine was added, and the reaction was continued at this temperature for 5 hours. After cooling, a precipitate was added and the solid was collected by filtration, washed with deionized water, and vacuum dried to obtain modified lignin, wherein the mass ratio of triethylenetetramine to glycerophosphodiester was 1:1.6; (3) Preparation of surface-modified nano-silica: Nano-silica was added to anhydrous ethanol at a ratio of 1 g: 20 mL, ultrasonically dispersed for 20 minutes, and then a silane coupling agent KH-550 was added. After stirring evenly, the mixture was heated at 70°C with stirring and reflux for 3 hours, and then centrifuged, washed, and vacuum-dried to obtain amino-silica, wherein the mass ratio of the silane coupling agent KH-550 to the nano-silica was 1:3.3. Aminated silica was then dispersed in N,N-dimethylformamide at a ratio of 1 g: 30 mL, ultrasonically treated for 20 minutes, and then modified lignin was added. The mixture was heated at 95°C with stirring for 6 hours, cooled, centrifuged, washed, vacuum-dried, and ground to obtain surface-modified nano-silica, wherein the mass ratio of the modified lignin to the amino-silica was 2:1. S1: Preparation of base paper 10 parts by weight of bleached hardwood pulp, 40 parts by weight of bleached softwood pulp, 10 parts by weight of polyester fiber, 10 parts by weight of aramid, 1 part by weight of a wet strength agent, 1 part by weight of a silicone softener, and 1 part by weight of a non-silicon defoamer are mixed to prepare pulp, and after being pulped by a paper machine to form a base paper wet paper web, the wet paper web is sent to a press section, pressed and wrinkled, and then dried to obtain base paper; S2: Preparation of dipping solution The modified styrene-butadiene rubber latex and the surface-modified nano-silica are stirred and mixed uniformly in a mass ratio of 8:1 to obtain a dipping solution; S3: Base paper impregnation The base paper is placed in the above-mentioned impregnation solution, impregnated on both sides, and dried to obtain a high-temperature resistant masking paper.

[0022] Example 2 A preparation process of high temperature resistant masking paper, such as Figure 1 As shown, the following steps are included: (1) Preparation of modified styrene-butadiene latex: Octylphenol polyoxyethylene ether, sodium lauryl sulfate and sodium bicarbonate were added to deionized water and stirred at 55 ° C until completely dissolved. After cooling, an emulsifier solution was obtained. Styrene, butadiene, p-vinyl benzoic acid, 2-vinyl pyridine and tert-dodecyl mercaptan were then mixed evenly and added to the emulsifier solution while stirring to obtain a pre-emulsion. Then, 1 / 2 of a 5% potassium persulfate solution by mass was added to the pre-emulsion. Under the protection of nitrogen, the mixture was kept warm at 80 ° C for 1.5 h, and the remaining potassium persulfate solution was added. The reaction was continued for 5.5 h. After the temperature was cooled to 5 At 0°C, nitrogen was introduced to remove residual monomers, and then the pH was adjusted to 8.8 with a 10% sodium hydroxide solution. The mixture was filtered and distilled under reduced pressure until the solid content was 45%, thereby obtaining a modified styrene-butadiene latex, wherein the raw material composition of the modified styrene-butadiene latex includes, by mass, 48 ​​parts of styrene, 48 parts of butadiene, 6.5 parts of p-vinylbenzoic acid, 7.5 parts of 2-vinylpyridine, 0.3 parts of tert-dodecyl mercaptan, 1.25 parts of octylphenol polyoxyethylene ether, 0.75 parts of sodium lauryl sulfate, 0.4 parts of sodium bicarbonate, 0.5 parts of potassium persulfate and 140 parts of deionized water; (2) Preparation of modified lignin: Alkali lignin was added to N,N-dimethylformamide at a ratio of 1 g:15 mL, and heated at 55° C. with stirring until completely dissolved to obtain an alkali lignin solution. Then, glycerophosphodiester and p-toluenesulfonic acid were added to the alkali lignin solution at a ratio of 1 g:0.15 g:20 mL, and the mixture was kept warm at 115° C. for 4.5 hours to obtain an intermediate reaction solution. When the intermediate reaction solution was cooled to 75° C., triethylenetetramine was added, and the mixture was kept warm for 5.5 hours. After cooling, a precipitate was added and the solid was collected by filtration, washed with deionized water, and vacuum dried to obtain modified lignin, wherein the mass ratio of triethylenetetramine to glycerophosphodiester was 1:1.7. (3) Preparation of surface-modified nano-silica: Nano-silica was added to anhydrous ethanol at a ratio of 1 g: 25 mL, ultrasonically dispersed for 25 minutes, and then silane coupling agent KH-550 was added. After stirring evenly, the mixture was heated at 75°C with stirring and reflux for 3.5 hours, and then centrifuged, washed, and vacuum-dried to obtain amino-silica, wherein the mass ratio of silane coupling agent KH-550 to nano-silica was 1:3.4. Aminated silica was then dispersed in N,N-dimethylformamide at a ratio of 1 g: 35 mL, ultrasonically treated for 25 minutes, and then modified lignin was added. The mixture was heated at 100°C with stirring for 7 hours, cooled, centrifuged, washed, vacuum-dried, and ground to obtain surface-modified nano-silica, wherein the mass ratio of modified lignin to amino-silica was 2.3:1. S1: Preparation of base paper 15 parts by weight of bleached hardwood pulp, 45 parts by weight of bleached softwood pulp, 20 parts by weight of polyester fiber, 20 parts by weight of aramid fiber, 2 parts by weight of a wet strength agent, 1.5 parts by weight of a silicone softener, and 2 parts by weight of a non-silicon defoaming agent are mixed to prepare pulp, and the pulp is formed into a base paper wet paper web by a paper machine, and then the wet paper web is sent to a press section, pressed and wrinkled, and then dried to obtain base paper; S2: Preparation of dipping solution The modified styrene-butadiene rubber latex and the surface-modified nano-silica were stirred and mixed uniformly in a mass ratio of 9:1 to obtain a dipping solution; S3: Base paper impregnation The base paper is placed in the above-mentioned impregnation solution, impregnated on both sides, and dried to obtain a high-temperature resistant masking paper.

[0023] Example 3 A preparation process of high temperature resistant masking paper, such as Figure 1 As shown, the following steps are included: (1) Preparation of modified styrene-butadiene latex: Octylphenol polyoxyethylene ether, sodium lauryl sulfate and sodium bicarbonate were added to deionized water and stirred at 60 ° C until completely dissolved. After cooling, an emulsifier solution was obtained. Subsequently, styrene, butadiene, p-vinyl benzoic acid, 2-vinyl pyridine and tert-dodecyl mercaptan were mixed evenly and then added to the emulsifier solution while stirring to obtain a pre-emulsion. Then, 1 / 2 of a 5% potassium persulfate solution by mass was added to the pre-emulsion. Under the protection of nitrogen, the mixture was kept warm at 85 ° C for 2 hours, and the remaining potassium persulfate solution was added. The reaction was continued for 6 hours. When the temperature reaches 50° C., nitrogen is introduced to remove residual monomers, and then the pH is adjusted to 9 with a 10% sodium hydroxide solution. The mixture is filtered and distilled under reduced pressure until the solid content is 50%, thereby obtaining a modified styrene-butadiene latex, wherein the raw material composition of the modified styrene-butadiene latex comprises, by weight, 45 parts of styrene, 45 parts of butadiene, 8 parts of p-vinylbenzoic acid, 10 parts of 2-vinylpyridine, 0.4 parts of tert-dodecyl mercaptan, 1.5 parts of octylphenol polyoxyethylene ether, 1 part of sodium lauryl sulfate, 0.5 parts of sodium bicarbonate, 0.6 parts of potassium persulfate, and 150 parts of deionized water; (2) Preparation of modified lignin: Alkali lignin was added to N,N-dimethylformamide at a ratio of 1 g:20 mL, heated and stirred at 60° C. until completely dissolved to obtain an alkali lignin solution, and then glycerophosphodiester and p-toluenesulfonic acid were added to the alkali lignin solution at a ratio of 1 g:0.2 g:25 mL, and the mixture was kept warm at 120° C. for 5 hours to obtain an intermediate reaction liquid. When the intermediate reaction liquid was cooled to 80° C., triethylenetetramine was added, and the reaction was continued for 6 hours. After cooling, a precipitate was added and the solid was collected by filtration, washed with deionized water, and vacuum dried to obtain modified lignin, wherein the mass ratio of triethylenetetramine to glycerophosphodiester was 1:1.8; (3) Preparation of surface-modified nano-silica: Nano-silica was added to anhydrous ethanol at a ratio of 1 g:30 mL, ultrasonically dispersed for 30 minutes, and then a silane coupling agent KH-550 was added. After stirring evenly, the mixture was heated at 80°C with stirring and reflux for 4 hours, and then centrifuged, washed, and vacuum-dried to obtain amino-silica, wherein the mass ratio of the silane coupling agent KH-550 to the nano-silica was 1:3.5. Aminated silica was then dispersed in N,N-dimethylformamide at a ratio of 1 g:40 mL, ultrasonically treated for 30 minutes, and then modified lignin was added. The mixture was heated at 105°C with stirring for 8 hours, cooled, centrifuged, washed, vacuum-dried, and ground to obtain surface-modified nano-silica, wherein the mass ratio of the modified lignin to the amino-silica was 2.6:1. S1: Preparation of base paper 20 parts by weight of bleached hardwood pulp, 50 parts by weight of bleached softwood pulp, 30 parts by weight of polyester fiber, 30 parts by weight of aramid fiber, 3 parts by weight of a wet strength agent, 2 parts by weight of a silicone softener, and 3 parts by weight of a non-silicon defoaming agent are mixed to prepare pulp, and after being pulped by a paper machine to form a base paper wet paper web, the wet paper web is sent to a press section, pressed and wrinkled, and then dried to obtain base paper; S2: Preparation of dipping solution The modified styrene-butadiene rubber latex and the surface-modified nano-silica were stirred and mixed uniformly in a mass ratio of 10:1 to obtain a dipping solution; S3: Base paper impregnation The base paper is placed in the above-mentioned impregnation solution, impregnated on both sides, and dried to obtain a high-temperature resistant masking paper.

[0024] Comparative Example 1 The difference between this comparative example 1 and example 1 is that p-vinylbenzoic acid and 2-vinylpyridine are removed in step (1), and the other conditions remain unchanged.

[0025] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that step (2) is removed and the modified lignin in step (3) is removed.

[0026] Test Case Test 1: The tensile strength at 200° C. of the masking papers prepared in Examples 1-3 and Comparative Examples 1-2 was tested. The results are shown in Table 1.

[0027] Table 1: Masking paper tensile strength test results

[0028] As shown in Table 1, in Comparative Example 1, after the styrene butadiene latex was not modified with p-vinylbenzoic acid and 2-vinylpyridine, the 200°C tensile strength of the masking paper prepared was lower than that of Example 1. This shows that by using p-vinylbenzoic acid and 2-vinylpyridine as functional monomers, mixing the two with styrene, butadiene and tert-dodecyl mercaptan, and adding them to an emulsifier solution for emulsification to prepare a pre-emulsion, and then copolymerizing them under the initiation of potassium persulfate to prepare a modified styrene butadiene latex, and then impregnating the base paper with the modified styrene butadiene latex, the high temperature resistance of the masking paper prepared can be effectively improved; In addition, in Comparative Example 2, after the nano-silica was not modified by modified lignin, the 200°C tensile strength of the masking paper obtained was also lower than that of Example 1. This shows that by reacting the modified lignin with the amino groups on the surface of the amino-silica to form a covalent bond, the modified lignin was grafted onto the surface of the nano-silica. After modification, the dispersibility of the nano-silica in the modified styrene-butadiene latex can be improved, thereby further improving the high temperature resistance of the masking paper.

[0029] Test 2: The limiting oxygen index of the masking papers prepared in Examples 1-3 and Comparative Example 2 was tested. The results are shown in Table 2.

[0030] Table 2: Masking paper limiting oxygen index test results

[0031] As shown in Table 2, in Comparative Example 2, after the nano-silica is not modified with modified lignin, the limiting oxygen index of the masking paper prepared is lower than that of Example 1. This shows that after the nano-silica is modified with modified lignin, the flame retardant properties of the masking paper can be effectively improved and the fire risk can be reduced.

[0032] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A preparation process for high temperature resistant masking paper, characterized in that: The steps include: S1: Preparation of base paper Bleached hardwood pulp, bleached softwood pulp, polyester fiber, aramid, wet strength agent, softener and defoamer are mixed to make pulp, and then formed into base paper wet paper web by paper machine, and then sent to the pressing section, and after being pressed and wrinkled, it is dried to obtain base paper; S2: Preparation of dipping solution The modified styrene-butadiene rubber latex and the surface-modified nano-silica are stirred and mixed uniformly to obtain a dipping solution; S3: Base paper impregnation The base paper is placed in the dipping solution, both sides are dipped in glue, and after drying, a high temperature resistant masking paper is obtained; The raw material composition of the base paper is as follows: 10-20 parts of bleached hardwood pulp, 40-50 parts of bleached softwood pulp, 10-30 parts of polyester fiber, 10-30 parts of aramid fiber, 1-3 parts of wet strength agent, 1-2 parts of softener and 1-3 parts of defoaming agent. Wherein, the wet strength agent is any one of polyamide epichlorohydrin resin and polyphenylene ether; The softener is a silicone softener; The defoamer is a non-silicone defoamer.

2. The process for preparing a high temperature resistant masking paper according to claim 1, characterized in that: The preparation steps of modified styrene-butadiene latex are as follows: A1: Add octylphenol polyoxyethylene ether, sodium lauryl sulfate, and sodium bicarbonate to deionized water, stir at 50-60°C until completely dissolved, and cool to obtain an emulsifier solution; A2: Styrene, butadiene, p-vinylbenzoic acid, 2-vinylpyridine, and tert-dodecyl mercaptan are mixed uniformly, and then added to the emulsifier solution while stirring to obtain a pre-emulsion; A3: Add 1 / 2 of a 5% by mass potassium persulfate solution to the pre-emulsion. Under nitrogen, keep the mixture at 75-85°C for 1-2 hours. Then add the remaining potassium persulfate solution and continue the reaction for 5-6 hours. When the temperature drops to 50°C, introduce nitrogen to remove residual monomers. Adjust the pH to 8.5-9 with 10% sodium hydroxide solution, filter, and distill under reduced pressure to a solid content of 40-50% to obtain a modified styrene-butadiene latex.

3. The process for preparing a high temperature resistant masking paper according to claim 2, characterized in that: The preparation steps of surface modified nano-silica are as follows: B1: Add nano-silica to anhydrous ethanol at a ratio of 1g: (20-30)mL, ultrasonically disperse for 20-30min, then add silane coupling agent KH-550, stir evenly, heat and stir under reflux at 70-80℃ for 3-4h, then centrifuge, wash and vacuum dry to obtain amino-silica; B2: Disperse the above-mentioned amino-silica in N,N-dimethylformamide at a ratio of 1g: (30-40)mL, ultrasonically treat for 20-30min, then add modified lignin, and heat and stir at 95-105℃ for 6-8h. After cooling, centrifuge, wash, vacuum dry and grind to obtain surface-modified nano-silica.

4. The process for preparing a high temperature resistant masking paper according to claim 3, characterized in that: The preparation steps of modified lignin are as follows: C1: Add alkali lignin to N,N-dimethylformamide at a ratio of 1g: (10-20)mL, heat and stir at 50-60℃ until completely dissolved to obtain alkali lignin solution; C2: Add glycerophosphodiester and p-toluenesulfonic acid to the above alkaline lignin solution at a ratio of 1 g: (0.1-0.2) g: (15-25) mL, and heat at 110-120°C for 4-5 hours to obtain an intermediate reaction solution; C3: When the intermediate reaction liquid is cooled to 70-80°C, triethylenetetramine is added and the reaction is continued for 5-6 hours. After cooling, a precipitate is added and the solid is collected by filtration, washed with deionized water and vacuum dried to obtain modified lignin.

5. The process for preparing a high temperature resistant masking paper according to claim 2, characterized in that: The raw material composition of the modified styrene-butadiene latex includes, by mass, 40-45 parts of styrene, 40-45 parts of butadiene, 5-8 parts of p-vinylbenzoic acid, 5-10 parts of 2-vinylpyridine, 0.2-0.4 parts of tert-dodecyl mercaptan, 1-1.5 parts of octylphenol polyoxyethylene ether, 0.5-1 parts of sodium lauryl sulfate, 0.3-0.5 parts of sodium bicarbonate, 0.4-0.6 parts of potassium persulfate and 130-150 parts of deionized water.

6. The process for preparing a high temperature resistant masking paper according to claim 4, characterized in that: The mass ratio of triethylenetetramine to glycerophosphodiester is 1:(1.6-1.8).

7. The process for preparing a high temperature resistant masking paper according to claim 3, characterized in that: The mass ratio of silane coupling agent KH-550 to nano-silica is 1: (3.3-3.5).

8. The process for preparing a high temperature resistant masking paper according to claim 3, characterized in that: The mass ratio of modified lignin to amino silica is (2-2.6):

1.

9. The process for preparing a high temperature resistant masking paper according to claim 1, characterized in that: The dipping solution is prepared by mixing modified styrene-butadiene rubber latex and surface-modified nano-silica in a mass ratio of (8-10):

1.

10. A high temperature resistant masking paper, characterized in that: The masking paper is prepared by the preparation process of the high-temperature resistant masking paper according to any one of claims 1 to 9.

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