A silicasol-based fire-retardant coating and a preparation method thereof

Abstract

The present application relates to the technical field of silica sol coating, and particularly relates to a silica sol-based flame-retardant coating and a preparation method thereof. The preparation method comprises the following steps: S1: tetraethyl orthosilicate and 3-glycidyloxypropyltriethoxysilane are subjected to hydrolysis and polycondensation to obtain an epoxy-modified silica sol; S2: DOPO is reacted with maleic anhydride to obtain carboxyl-modified DOPO; S3: the epoxy-modified silica sol, glycidyl methacrylate, monoglycidyl ether-terminated polydimethylsiloxane and the carboxyl-modified DOPO are subjected to esterification to obtain a DOPO-modified silica sol containing an unsaturated double bond; and S4: the DOPO-modified silica sol containing the unsaturated double bond is subjected to polymerization with an acrylate monomer to obtain a polyacrylate / DOPO-modified silica sol, i.e. the silica sol-based flame-retardant coating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silica sol coating, in particular to a silica sol-based flame-retardant coating and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for wood materials in the field of construction and home furnishing, the fire hazard caused by the flammability of wood materials is increasingly prominent. Wood combustion produces a large amount of heat, smoke and toxic gases. High temperature accelerates the spread of fire, smoke greatly reduces the visibility of the fire scene, and toxic gases can even cause suffocation and death of personnel. Therefore, in order to eliminate this potential fire hazard, wood materials need to be treated with flame retardant to improve their fire safety.

[0003] At present, a common method for flame-retardant treatment of wood materials is to coat a layer of flame-retardant layer, such as a silica sol layer, on the surface of the wood materials. Although the silica sol layer has good flame-retardant effect, it also has defects such as high brittleness, poor adhesion and poor water resistance, which to some extent limit its application.

[0004] Therefore, it is of great significance to provide a silica sol-based flame-retardant coating and a preparation method thereof. SUMMARY

[0005] The present application aims to provide a silica sol-based flame-retardant coating and a preparation method thereof to solve the problems in the background art.

[0006] In order to solve the above technical problems, the present application provides the following technical solutions:

[0007] A preparation method of a silica sol-based flame-retardant coating, comprising the following steps:

[0008] S1: hydrolytic polycondensation of tetraethyl orthosilicate and 3-glycidyloxypropyltriethoxysilane to obtain an epoxy-modified silica sol;

[0009] S2: reaction of DOPO and maleic anhydride to obtain a carboxyl-modified DOPO;

[0010] S3: esterification reaction of the epoxy-modified silica sol, glycidyl methacrylate, monoglycidyl ether-terminated polydimethylsiloxane and the carboxyl-modified DOPO to obtain a DOPO-modified silica sol containing unsaturated double bonds;

[0011] S4: initiation of polymerization of the DOPO-modified silica sol containing unsaturated double bonds and an acrylate monomer to obtain a polyacrylate / DOPO-modified silica sol, i.e. a silica sol-based flame-retardant coating.

[0012] Further, the preparation method of the silica sol-based flame-retardant coating comprises the following steps, specifically:

[0013] S1: tetraethyl orthosilicate, 3-glycidyloxypropyltriethoxysilane, ethanol, hydrochloric acid, deionized water are added into a reaction container, stirred and heated to 60-80 DEG C, stirred for 6-12 hours, the reaction is completed, and an epoxy-modified silica sol is obtained;

[0014] S2: under nitrogen protection, DOPO and toluene are added into a reaction container, stirred and mixed uniformly, then maleic anhydride is added, stirred and heated to 90-100 DEG C, stirred for 6-12 hours, the reaction is completed, and a carboxyl-modified DOPO is obtained after separation and purification;

[0015] S3: under nitrogen protection, the carboxyl-modified DOPO is added into the epoxy-modified silica sol, stirred and mixed uniformly, then 3,5-diisopropylsalicylic acid chromium is added, stirred and heated to 70-80 DEG C, stirred for 2-6 hours; then monoglycidyl ether-terminated polydimethylsiloxane is added, continued to heat and stir for 1-3 hours; finally, glycidyl methacrylate and a polymerization inhibitor are added, continued to stir for 2-4 hours, the reaction is completed, and a DOPO-modified silica sol containing unsaturated double bonds is obtained after separation and purification;

[0016] S4: under nitrogen protection, the DOPO-modified silica sol containing unsaturated double bonds, an acrylic ester monomer, an alkylphenol polyoxyethylene ether and deionized water are added into a reaction container, pre-emulsified by stirring, then heated to 70-80 DEG C, and an aqueous solution of ammonium persulfate is added dropwise for 1-2 hours, continued to stir for 4-8 hours after the dropwise addition is completed, the reaction is completed, ammonia water is added to adjust the pH to neutral, and a polyacrylate / DOPO-modified silica sol, i.e. a silica sol-based flame-retardant coating, is obtained after separation and purification.

[0017] Further, the molar ratio of the tetraethyl orthosilicate and the 3-glycidyloxypropyltriethoxysilane is 4:1.

[0018] Further, the molar ratio of the ethanol, deionized water, hydrochloric acid and n(Si) is 4:4:0.002:1; wherein the hydrochloric acid is a 0.1 mol / L hydrochloric acid solution.

[0019] Further, the molar ratio of the DOPO and the maleic anhydride is (1-1.05):1.

[0020] Further, the amount of the toluene added is 3 times the total mass of the DOPO and the maleic anhydride.

[0021] Further, the unsaturated double bond-containing DOPO modified silica sol is prepared by using the raw material components in the amount of, by weight fraction, 20 parts of epoxy group modified silica sol, 6-8 parts of carboxyl modified DOPO, 1.4-2.6 parts of monoglycidyl ether terminated polydimethylsiloxane, 8 parts of glycidyl methacrylate, 0.3-0.5 parts of 3,5-diisopropyl salicylic acid chromium, and 0.02-0.03 parts of polymerization inhibitor.

[0022] Further, the polymerization inhibitor is phenothiazine; since the epoxy group and the carboxyl group reaction requires 3,5-diisopropyl salicylic acid chromium as a catalyst, if a conventional hydroquinone, p-hydroxyanisole and other polymerization inhibitors are used, oxidation side reactions will occur, and then the reactivity of the subsequent glycidyl methacrylate is reduced, the grafting amount is insufficient, thereby affecting the performance of the prepared polyacrylate / DOPO modified silica sol; therefore, the polymerization inhibitor is preferably phenothiazine.

[0023] Further, the unsaturated double bond-containing DOPO modified silica sol is prepared by using the raw material components in the amount of, by weight fraction, 20 parts of epoxy group modified silica sol, 6-8 parts of carboxyl modified DOPO, 1.4-2.6 parts of monoglycidyl ether terminated polydimethylsiloxane, 8 parts of glycidyl methacrylate, 0.3-0.5 parts of 3,5-diisopropyl salicylic acid chromium, and 0.02-0.03 parts of polymerization inhibitor.

[0024] Further, the unsaturated double bond-containing DOPO modified silica sol is prepared by using the raw material components in the amount of, by weight fraction, 20 parts of epoxy group modified silica sol, 6-8 parts of carboxyl modified DOPO, 1.4-2.6 parts of monoglycidyl ether terminated polydimethylsiloxane, 8 parts of glycidyl methacrylate, 0.3-0.5 parts of 3,5-diisopropyl salicylic acid chromium, and 0.02-0.03 parts of polymerization inhibitor.

[0025] Further, the unsaturated double bond-containing DOPO modified silica sol is prepared by using the raw material components in the amount of, by weight fraction, 20 parts of epoxy group modified silica sol, 6-8 parts of carboxyl modified DOPO, 1.4-2.6 parts of monoglycidyl ether terminated polydimethylsiloxane, 8 parts of glycidyl methacrylate, 0.3-0.5 parts of 3,5-diisopropyl salicylic acid chromium, and 0.02-0.03 parts of polymerization inhibitor.

[0026] Further, the unsaturated double bond-containing DOPO modified silica sol is prepared by using the raw material components in the amount of, by weight fraction, 20 parts of epoxy group modified silica sol, 6-8 parts of carboxyl modified DOPO, 1.4-2.6 parts of monoglycidyl ether terminated polydimethylsiloxane, 8 parts of glycidyl methacrylate, 0.3-0.5 parts of 3,5-diisopropyl salicylic acid chromium, and 0.02-0.03 parts of polymerization inhibitor.

[0027] In the present application, first, tetraethyl orthosilicate and 3-glycidyl ether oxypropyl triethoxysilane are hydrolyzed and polycondensed to obtain an epoxy group modified silica sol containing an epoxy group; then, P-H of DOPO reacts with the double bond of maleic anhydride to obtain carboxyl modified DOPO containing a carboxyl group; then, the carboxyl group of the carboxyl modified DOPO is first esterified and grafted with the epoxy group of the epoxy group modified silica sol, and the carboxyl modified DOPO is used as a bridge, and then monoglycidyl ether terminated polydimethylsiloxane, glycidyl methacrylate and another carboxyl group of the carboxyl modified DOPO are added in sequence to esterify and graft, thereby preparing an unsaturated double bond-containing DOPO modified silica sol; finally, the unsaturated double bond-containing DOPO modified silica sol is initiated to polymerize with an acrylate monomer to prepare a polyacrylate / DOPO modified silica sol.

[0028] In the preparation process of the DOPO modified silica sol containing unsaturated double bond in the application, monoglycidyl ether terminated polydimethylsiloxane and glycidyl methacrylate are selected to participate in the reaction. The amount of monoglycidyl ether terminated polydimethylsiloxane should not be too much. On the one hand, it is considered from the cost, and on the other hand, too much polydimethylsiloxane segment content will cause the drying speed of the coating to slow down, even sticky and other problems, thereby affecting the quality and service life of the coating. The amount of glycidyl methacrylate is excessive, which is to fully react the -COOH of the reactant, and then graft enough polyacrylate segment on the DOPO modified silica sol containing unsaturated double bond.

[0029] Compared with the prior art, the application has the following beneficial effects: the polyacrylate / DOPO modified silica sol prepared by the application contains polydimethylsiloxane segment, DOPO structure and polyacrylate segment. The polydimethylsiloxane segment has the following effects: (1) effectively improves the flexibility of the cured silica sol and reduces its brittleness; (2) can improve the waterproof performance of the subsequent coating layer, avoid water vapor from entering the silica sol coating layer, and thus cause the attenuation of its adhesion, flame retardance and other properties; (3) can also promote the film formation of the coating, making the coating layer more uniform. The DOPO structure can further improve the flame retardance of the coating. The polyacrylate segment has the following effects: (1) can further improve the flexibility of the coating layer; (2) can effectively improve the adhesion of the coating; (3) can also improve the curing speed of the silica sol-based flame retardant coating; (4) the monomers polymerized by the polyacrylate segment contain acrylonitrile and styrene, acrylonitrile contains nitrogen element, which can synergistically enhance the flame retardance with DOPO, and the benzene ring in styrene helps to form carbon, which can also promote the flame retardance to a certain extent.

[0030] In summary, the application comprehensively prepares a silica sol-based flame retardant coating with fast curing speed, and excellent water resistance, flexibility, adhesion and flame retardance after curing. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0032] It should be noted that the following parts are by weight, and the purchase of all raw materials involved in the application has no special restrictions, including:

[0033] In the following examples, tetraethyl orthosilicate, purity ≥ 99%; 3-glycidyloxypropyltriethoxysilane, purity ≥ 97%; glycidyl methacrylate, purity ≥ 97%; monoglycidyl ether terminated polydimethylsiloxane, CAS No. 157723-26-7, average molecular weight 5000, item No. 480290; phenothiazine, purity ≥ 98%; acrylic acid, purity ≥ 99%; methyl methacrylate, purity ≥ 99%; acrylonitrile, purity ≥ 99%; styrene, purity ≥ 99%; all purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0034] DOPO, purity ≥ 99.5%, purchased from Hubei Yongkong Technology Co., Ltd.;

[0035] 3,5-diisopropyl chromium salicylate, purity ≥ 98%, purchased from Xi'an Lanhe Auxiliary Factory; the rest of the raw materials are commercially available;

[0036] 50 g per weight part;

[0037] Preparation in advance: acrylic acid, methyl methacrylate, acrylonitrile, and styrene are mixed in a mass ratio of 1.5:1:1.5:1.5 to obtain an acrylate monomer.

[0038] Example 1: A preparation method of a silicon sol-based flame-retardant coating

[0039] S1: 20 parts (about 4.8 mol) of tetraethyl orthosilicate, 6.682 parts (about 1.2 mol) of 3-glycidyloxypropyltriethoxysilane, ethanol, hydrochloric acid, and deionized water are added to a reaction container, stirred and heated to 60-80°C, stirred and reacted for 6-12 h, and the reaction is stopped. Epoxy-modified silica sol is obtained;

[0040] Among them, the molar ratio relationship of ethanol, deionized water, hydrochloric acid and n(Si) is 4:4:0.002:1;

[0041] S2: Under the protection of nitrogen, 12 parts (2.776 mol) of DOPO and 52.332 parts of toluene are added to a reaction container, stirred and mixed uniformly, then 5.444 parts (2.776 mol) of maleic anhydride is added, stirred and heated to 95°C, stirred and reacted for 8 h, and the reaction is stopped. After vacuum distillation, washing and drying, carboxyl-modified DOPO is obtained;

[0042] S3: Under the protection of nitrogen, 7 parts of carboxyl-modified DOPO were added to 20 parts of epoxy-modified silica sol, and stirred and mixed uniformly. Then, 0.4 parts of 3, 5-diisopropyl salicylic acid chromium were added thereto, and stirred and heated to 75°C. Stirring reaction was carried out for 4 h. Then, 2 parts of monoglycidyl ether-terminated polydimethylsiloxane were added thereto, and stirring reaction was continuously carried out for 2 h. Finally, 8 parts of glycidyl methacrylate and 0.025 parts of phenothiazine were added thereto, and stirring reaction was continuously carried out for 3 h. After reaction was completed, dialysis, and reduced-pressure distillation were carried out, to obtain DOPO-modified silica sol containing unsaturated double bonds;

[0043] S4: Under the protection of nitrogen, 30 parts of DOPO-modified silica sol containing unsaturated double bonds, 10 parts of acrylic ester monomer, 0.2 parts of alkyl phenol polyoxyethylene ether, and 48 parts of deionized water were added to a reaction container, and stirred for 40 min for pre-emulsification. Then, stirring was carried out while heating to 75°C. Ammonium persulfate aqueous solution (0.2 parts of ammonium persulfate was dissolved in 2 parts of deionized water to prepare) was added dropwise thereto, and dropwise addition was carried out for 1.5 h. After dropwise addition was completed, stirring reaction was continuously carried out for 6 h. After reaction was completed, 10 wt% ammonia water was added to adjust pH to neutral. After filtration and blending, polyacrylate / DOPO-modified silica sol with a solid content of 45 wt% was obtained, that is, a silica sol-based flame-retardant coating.

[0044] Example 2: A preparation method of a silica sol-based flame-retardant coating

[0045] S1: 20 parts (about 4.8 mol) of tetraethyl orthosilicate, 6.682 parts (about 1.2 mol) of 3-glycidyl ether oxypropyl triethoxysilane, ethanol, hydrochloric acid, and deionized water were added to a reaction container, and stirring was carried out while heating to 60-80°C. Stirring reaction was carried out for 6-12 h. After reaction was completed, epoxy-modified silica sol was obtained.

[0046] The molar ratio relationship of ethanol, deionized water, hydrochloric acid, and n(Si) was 4:4:0.002:1.

[0047] S2: Under the protection of nitrogen, 12 parts (2.776 mol) of DOPO and 52.332 parts of toluene were added to a reaction container, and stirred and mixed uniformly. Then, 5.444 parts (2.776 mol) of maleic anhydride were added thereto, and stirring was carried out while heating to 95°C. Stirring reaction was carried out for 8 h. After reaction was completed, reduced-pressure distillation, washing, and drying were carried out, to obtain carboxyl-modified DOPO.

[0048] S3: Under the protection of nitrogen, 6 parts of carboxyl-modified DOPO were added to 20 parts of epoxy-modified silica sol, stirred and mixed uniformly, then 0.4 parts of 3,5-diisopropyl salicylic acid chromium was added, stirred and heated to 75℃, and stirred and reacted for 4h; then 1.4 parts of monoglycidyl ether-terminated polydimethylsiloxane was added, and the stirring and reaction was continued for 2h; finally, 8 parts of glycidyl methacrylate and 0.025 parts of phenothiazine were added, and the stirring and reaction was continued for 3h, the reaction was stopped, and the unsaturated double bond-containing DOPO-modified silica sol was obtained by dialysis and reduced pressure distillation;

[0049] S4: Under the protection of nitrogen, 30 parts of unsaturated double bond-containing DOPO-modified silica sol, 10 parts of acrylic ester monomer, 0.2 parts of alkyl phenol polyoxyethylene ether, and 50 parts of deionized water were added to a reaction container, stirred for 40min, pre-emulsified, then stirred and heated to 75℃, and then ammonium persulfate aqueous solution (0.2 parts of ammonium persulfate was dissolved in 2 parts of deionized water to prepare) was added dropwise, the dropping was completed in 1.5h, and the stirring and reaction was continued for 6h, the reaction was stopped, 10wt% ammonia water was added to adjust the pH to neutral, and the polyacrylate / DOPO-modified silica sol with a solid content of 45wt% was obtained by filtration and blending, that is, the silica sol-based flame-retardant coating.

[0050] Example 3: A preparation method of a silica sol-based flame-retardant coating

[0051] S1: 20 parts (about 4.8 mol) of tetraethyl orthosilicate, 6.682 parts (about 1.2 mol) of 3-glycidyl ether propyl triethoxysilane, ethanol, hydrochloric acid, and deionized water were added to a reaction container, stirred and heated to 60~80℃, and stirred and reacted for 6~12h, and the reaction was stopped to obtain an epoxy-modified silica sol;

[0052] The molar ratio relationship of ethanol, deionized water, hydrochloric acid, and n(Si) is 4:4:0.002:1;

[0053] S2: Under the protection of nitrogen, 12 parts (2.776 mol) of DOPO and 52.332 parts of toluene were added to a reaction container, stirred and mixed uniformly, then 5.444 parts (2.776 mol) of maleic anhydride was added, stirred and heated to 95℃, and stirred and reacted for 8h, and the reaction was stopped, and the carboxyl-modified DOPO was obtained by reduced pressure distillation, washing, and drying;

[0054] S3: Under the protection of nitrogen, 8 parts of carboxyl-modified DOPO were added to 20 parts of epoxy-modified silica sol, and stirred and mixed uniformly. Then 0.4 parts of 3,5-diisopropyl salicylic acid chromium were added, and stirred and heated to 75°C. Stirring and reaction were continued for 4 hours. Then 2.6 parts of monoglycidyl ether-terminated polydimethylsiloxane were added, and stirring and reaction were continued for 2 hours. Finally, 8 parts of glycidyl methacrylate and 0.025 parts of phenothiazine were added, and stirring and reaction were continued for 3 hours. After reaction, dialysis and vacuum distillation were performed to obtain the DOPO-modified silica sol containing unsaturated double bonds;

[0055] S4: Under the protection of nitrogen, 30 parts of the DOPO-modified silica sol containing unsaturated double bonds, 10 parts of acrylate monomer, 0.2 parts of alkylphenol polyoxyethylene ether, and 48 parts of deionized water were added into a reaction container, and stirred for 40 minutes for pre-emulsification. Then, stirring and heating were continued until the temperature reached 75°C. An aqueous solution of ammonium persulfate (0.2 parts of ammonium persulfate was dissolved in 2 parts of deionized water to prepare) was added dropwise for 1.5 hours. After the dropwise addition was completed, stirring and reaction were continued for 6 hours. After reaction, 10 wt% of ammonia water was added to adjust the pH to neutral. After filtration and blending, a polyacrylate / DOPO-modified silica sol with a solid content of 45 wt% was obtained, i.e., a silica sol-based flame-retardant coating.

[0056] The following comparative examples 1-5 were based on example 1 and were set up for control experiments, and the details were as follows:

[0057] Comparative example 1: Comparative example 1 was based on example 1, and the tetraethyl orthosilicate hydrolysis and polycondensation were adjusted to obtain a silica sol-based flame-retardant coating. Specifically, a preparation method of a silica sol-based flame-retardant coating was as follows:

[0058] S1: 25 parts (about 6 mol) of tetraethyl orthosilicate, ethanol, hydrochloric acid, and deionized water were added into a reaction container, and stirring and heating were continued until the temperature reached 60-80°C. Stirring and reaction were continued for 6-12 hours. After reaction, blending was performed, and a silica sol with a solid content of 45% was obtained, which was used as a silica sol-based flame-retardant coating.

[0059] Among them, the molar ratio relationship of ethanol, deionized water, hydrochloric acid, and n(Si) was 4:4:0.002:1.

[0060] Comparative example 2: Comparative example 2 was based on example 1, and the carboxyl-modified DOPO was not prepared, and other processes remained unchanged. Specifically, a preparation method of a silica sol-based flame-retardant coating was as follows:

[0061] S1: 20 parts (about 4.8 mol) of tetraethyl orthosilicate, 6.682 parts (about 1.2 mol) of 3-glycidyl ether propyl triethoxysilane, ethanol, hydrochloric acid, and deionized water were added into a reaction container, and stirring and heating were continued until the temperature reached 60-80°C. Stirring and reaction were continued for 6-12 hours. After reaction, an epoxy-modified silica sol was obtained.

[0062] wherein the molar ratio relationship of ethanol, deionized water, hydrochloric acid and n(Si) is 4:4:0.002:1;

[0063] S2: 7 parts of succinic anhydride were added to 20 parts of epoxy-modified silica sol under nitrogen protection, and stirred and mixed uniformly, then 0.4 parts of 3,5-diisopropyl salicylic acid chromium was added, and stirred and heated to 75℃, and stirred and reacted for 4h; 2 parts of monoglycidyl ether-terminated polydimethylsiloxane was then added, and the temperature was kept and stirred and reacted for 2h; finally, 8 parts of glycidyl methacrylate and 0.025 parts of phenothiazine were added, and the stirring was continued for 3h, and the reaction was ended, and dialysis, vacuum distillation were performed to obtain the DOPO-modified silica sol containing unsaturated double bonds;

[0064] S3: 30 parts of the DOPO-modified silica sol containing unsaturated double bonds, 10 parts of acrylate monomer, 0.2 parts of alkylphenol polyoxyethylene ether and 48 parts of deionized water were added into a reaction container under nitrogen protection, and stirred for 40min for pre-emulsification, then stirred and heated to 75℃, and an aqueous solution of ammonium persulfate (0.2 parts of ammonium persulfate was dissolved in 2 parts of deionized water to prepare) was added dropwise, the dropping was performed for 1.5h, after the dropping was completed, the stirring was continued for 6h for reaction, the reaction was ended, 10wt% ammonia water was added to adjust the pH to neutral, and filtration and blending were performed to obtain a polyacrylate / DOPO-modified silica sol with a solid content of 45wt%, i.e. a silica sol-based flame-retardant coating.

[0065] Comparative Example 3: Comparative Example 3 was based on Example 1, and the adjustment was that no monoglycidyl ether-terminated polydimethylsiloxane was added in S3, and other processes remained unchanged, and the specific process was as follows: a method for preparing a silica sol-based flame-retardant coating:

[0066] S1: 20 parts (about 4.8 mol) of tetraethyl orthosilicate, 6.682 parts (about 1.2 mol) of 3-glycidyl ether oxypropyl triethoxysilane, ethanol, hydrochloric acid and deionized water were added into a reaction container, and stirred and heated to 60-80℃, and stirred and reacted for 6-12h, and the reaction was ended to obtain an epoxy-modified silica sol;

[0067] wherein the molar ratio relationship of ethanol, deionized water, hydrochloric acid and n(Si) is 4:4:0.002:1;

[0068] S2: 12 parts (2.776 mol) of DOPO and 52.332 parts of toluene were added into a reaction container under nitrogen protection, and stirred and mixed uniformly, then 5.444 parts (2.776 mol) of maleic anhydride was added, and stirred and heated to 95℃, and stirred and reacted for 8h, and the reaction was ended, and vacuum distillation, washing and drying were performed to obtain carboxyl-modified DOPO;

[0069] S3: 7 parts of carboxyl-modified DOPO were added to 20 parts of epoxy-modified silica sol under nitrogen protection, and stirred and mixed uniformly, then 0.4 parts of 3, 5-diisopropyl salicylic acid chromium was added, and stirred and heated to 75°C, and stirred and reacted for 4h; then 8 parts of glycidyl methacrylate and 0.025 parts of phenothiazine were added, and the stirring and reaction was continued for 3h, and the reaction was ended, and the unsaturated double bond-containing DOPO-modified silica sol was obtained by dialysis and reduced pressure distillation;

[0070] S4: 30 parts of the unsaturated double bond-containing DOPO-modified silica sol, 20 parts of the acrylate monomer, 0.3 parts of the alkyl phenol polyoxyethylene ether, and 48 parts of deionized water were added to a reaction container under nitrogen protection, and stirred for 40min for pre-emulsification, then stirred and heated to 75°C, and an aqueous ammonium persulfate solution (0.3 parts of ammonium persulfate was dissolved in 2 parts of deionized water to prepare) was added dropwise, and the dropping was continued for 1.5h, and after the dropping was completed, the stirring and reaction was continued for 6h, and the reaction was ended, and 10wt% ammonia water was added to adjust the pH to neutral, and the polyacrylate / DOPO-modified silica sol with a solid content of 45wt% was obtained by filtration and blending, that is, the silica sol-based flame-retardant coating.

[0071] Comparative Example 4: Comparative Example 4 was based on Example 1, and the amount of the monoglycidyl ether-terminated polydimethylsiloxane in S3 was increased, and other processes remained unchanged, and the specific process was as follows: a method for preparing a silica sol-based flame-retardant coating:

[0072] S1: 20 parts (about 4.8mol) of tetraethyl orthosilicate, 6.682 parts (about 1.2mol) of 3-glycidyl ether oxypropyl triethoxysilane, ethanol, hydrochloric acid, and deionized water were added to a reaction container, and stirred and heated to 60-80°C, and stirred and reacted for 6-12h, and the reaction was ended to obtain an epoxy-modified silica sol;

[0073] The molar ratio relationship of the ethanol, deionized water, hydrochloric acid, and n(Si) was 4:4:0.002:1;

[0074] S2: 12 parts (2.776mol) of DOPO and 52.332 parts of toluene were added to a reaction container under nitrogen protection, and stirred and mixed uniformly, then 5.444 parts (2.776mol) of maleic anhydride was added, and stirred and heated to 95°C, and stirred and reacted for 8h, and the reaction was ended, and the carboxyl-modified DOPO was obtained by reduced pressure distillation, washing, and drying;

[0075] S3: 7 parts of carboxyl-modified DOPO were added to 20 parts of epoxy-modified silica sol under nitrogen protection, and stirred and mixed uniformly, then 0.4 parts of 3,5-diisopropyl salicylic acid chromium was added thereto, and stirred and heated to 75°C, and stirred and reacted for 4 h; then 4 parts of monoglycidyl ether-terminated polydimethylsiloxane was added thereto, and continued to be stirred and reacted for 2 h; finally, 8 parts of glycidyl methacrylate and 0.025 parts of phenothiazine were added thereto, and continued to be stirred and reacted for 3 h, and the reaction was ended, and the unsaturated double bond-containing DOPO-modified silica sol was obtained through dialysis and reduced-pressure distillation;

[0076] S4: 30 parts of the unsaturated double bond-containing DOPO-modified silica sol, 10 parts of an acrylate monomer, 0.2 parts of an alkyl phenol polyoxyethylene ether, and 48 parts of deionized water were added into a reaction container under nitrogen protection, and stirred for 40 min for pre-emulsification, then stirred and heated to 75°C, and an ammonium persulfate aqueous solution (0.2 parts of ammonium persulfate was dissolved in 2 parts of deionized water to prepare) was added dropwise thereto for 1.5 h, and after the dropwise addition was completed, the stirring and reaction were continued for 6 h, and the reaction was ended, 10 wt% of ammonia water was added to adjust the pH to neutral, and the polyacrylate / DOPO-modified silica sol with a solid content of 45 wt% was obtained through filtration and blending, that is, the silica sol-based flame-retardant coating.

[0077] Comparative Example 5: Comparative Example 5 was based on Example 1, and the adjustment was that in S3, the polymerization inhibitor was selected to be hydroquinone, and the other processes remained unchanged, and the specific process was as follows: a method for preparing a silica sol-based flame-retardant coating:

[0078] S1: 20 parts (about 4.8 mol) of tetraethyl orthosilicate, 6.682 parts (about 1.2 mol) of 3-glycidyloxypropyltriethoxysilane, ethanol, hydrochloric acid, and deionized water were added into a reaction container, and stirred and heated to 60-80°C, and stirred and reacted for 6-12 h, and the reaction was ended to obtain an epoxy-modified silica sol;

[0079] The molar ratio relationship of the ethanol, deionized water, hydrochloric acid, and n(Si) was 4:4:0.002:1;

[0080] S2: 12 parts (2.776 mol) of DOPO and 52.332 parts of toluene were added into a reaction container under nitrogen protection, and stirred and mixed uniformly, then 5.444 parts (2.776 mol) of maleic anhydride was added thereto, and stirred and heated to 95°C, and stirred and reacted for 8 h, and the reaction was ended, and the carboxyl-modified DOPO was obtained through reduced-pressure distillation, washing, and drying;

[0081] S3: Under the protection of nitrogen, 7 parts of carboxyl-modified DOPO were added to 20 parts of epoxy-modified silica sol, stirred and mixed uniformly, then 0.4 parts of 3,5-diisopropyl salicylic acid chromium was added, stirred and heated to 75°C, and reacted for 4h; then 2 parts of monoglycidyl ether-terminated polydimethylsiloxane was added, and the reaction was continued for 2h; finally, 8 parts of glycidyl methacrylate and 0.025 parts of hydroquinone were added, and the reaction was continued for 3h, then the reaction was stopped, and the unsaturated double bond-containing DOPO-modified silica sol was obtained by dialysis and vacuum distillation;

[0082] S4: Under the protection of nitrogen, 30 parts of unsaturated double bond-containing DOPO-modified silica sol, 10 parts of acrylic monomer, 0.2 parts of alkyl phenol polyoxyethylene ether, and 48 parts of deionized water were added to a reaction vessel, stirred for 40min, pre-emulsified, then stirred and heated to 75°C, and then ammonium persulfate aqueous solution (0.2 parts of ammonium persulfate dissolved in 2 parts of deionized water) was added dropwise, the dropping was completed in 1.5h, and the reaction was continued for 6h, then the reaction was stopped, 10wt% ammonia water was added to adjust the pH to neutral, and the polyacrylate / DOPO-modified silica sol with a solid content of 45wt% was obtained by filtration and blending, i.e. the silica sol-based flame-retardant coating.

[0083] Performance test: The silica sol-based flame-retardant coatings prepared in Examples 1-3 and Comparative Examples 1-5 were respectively coated on the surface of a 20cm×20cm×1cm wood board using a 40μm wire bar coater, and the following related performance tests were carried out:

[0084] (1) The surface dry time was tested according to the standard of GB / T 1728-2020 at a temperature of 23°C and a relative humidity of 50%, and then the subsequent performance test was carried out. The wood board obtained after the surface dry of the silica sol-based flame-retardant coating was called "coated wood board";

[0085] (2) The adhesion performance test was carried out according to the standard of GB / T 4893.4-2023 at a temperature of 23°C and a relative humidity of 50%. Six parallel cutting lines were cut on the surface of the coated wood board along the horizontal and vertical directions using a grid knife, and then the surface appearance of each cross-cut area was observed and rated according to the area of the falling-off;

[0086] (3) The water resistance test was carried out according to the standard of GB / T 1733-1993 at a temperature of 23°C. Two-thirds of the coated wood board was immersed in water, and after 24h, it was taken out and observed whether there were phenomena such as bubbling, wrinkling, and falling-off on the surface;

[0087] (4) Flame retardant performance test: according to GB / T 16172-2007 and ISO 5660-1:2015 standards, at a temperature of 23 DEG C, 50% relative humidity, using a cone calorimeter to detect the flame retardant smoke suppression performance of the coated wood board, and the radiant power is 50 kW / m 2 .

[0088] The data results of the above test items are shown in Table 1 as follows:

[0089] Table 1

[0090] Sample Surface dry time (min) Adhesion rating (scale) Surface condition Ignition time (s) Heat release rate peak (Kw / m 2 )]]> Peak smoke release rate (m 2 / s) Example 1 47 0 No significant change 68 73.2 0.015 Example 2 43 0 No significant change 59 81.4 0.019 Example 3 56 0 No significant change 75 69.2 0.013 Comparative Example 1 156 5 Shedding 12 226.3 0.068 Comparative Example 2 49 0 No significant change 36 168.6 0.048 Comparative Example 3 55 2 Roughening 48 104.5 0.028 Comparative Example 4 84 0 No significant change 41 117.4 0.033 Comparative Example 5 73 1 Blistering 60 77.7 0.018

[0091] Result analysis: comparing the data results of the examples and the comparative examples in Table 1, it can be seen that the silicon sol-based flame retardant coating prepared by the present application has fast curing speed and excellent comprehensive performance of the coating layer after curing.

[0092] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the present application has been described in detail with reference to the foregoing examples, for those skilled in the art, it still can be modified to the technical solutions recorded in the foregoing examples, or equivalent replacement of some technical features. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a silica sol-based flame-retardant coating, characterized in that: Includes the following steps: S1: Tetraethyl orthosilicate and 3-glycidyl etheroxypropyltriethoxysilane are hydrolyzed and polycondensed to obtain epoxy-modified... Silica sol; S2: DOPO reacts with maleic anhydride to obtain carboxyl-modified DOPO; S3: Epoxy-modified silica sol, glycidyl methacrylate, monoglycidyl ether-terminated polydimethylsiloxane and carboxyl-modified DOPO undergo esterification reaction to obtain DOPO-modified silica sol containing unsaturated double bonds. S4: DOPO-modified silica sol containing unsaturated double bonds is polymerized with acrylate monomers to obtain polyacrylate / DOPO-modified silica sol, i.e. silica sol-based flame retardant coating. In S3, the amounts of the raw material components required for preparing the DOPO-modified silica sol containing unsaturated double bonds are, by weight, 20 parts of epoxy-modified silica sol, 6-8 parts of carboxyl-modified DOPO, 1.4-2.6 parts of monoglycidyl ether-terminated polydimethylsiloxane, 8 parts of glycidyl methacrylate, 0.3-0.5 parts of chromium 3,5-diisopropylsalicylate, and 0.02-0.03 parts of polymerization inhibitor; wherein the polymerization inhibitor is phenothiazine.

2. The method for preparing a silica sol-based flame-retardant coating according to claim 1, characterized in that: The steps include the following: S1: Tetraethyl orthosilicate, 3-glycidyl etheroxypropyltriethoxysilane, ethanol, hydrochloric acid, and deionized water are added to a reaction vessel, stirred and heated to 60-80℃, and stirred for 6-12 hours to complete the reaction and obtain epoxy-modified silica sol. S2: Under nitrogen protection, DOPO and toluene are added to the reaction vessel and stirred until homogeneous. Maleic anhydride is then added, and the mixture is stirred and heated to 90-100℃ for 6-12 hours. The reaction is then terminated, and the carboxyl-modified DOPO is obtained after separation and purification. S3: Under nitrogen protection, carboxyl-modified DOPO was added to epoxy-modified silica sol and stirred until homogeneous. Then, chromium 3,5-diisopropylsalicylate was added, and the mixture was stirred and heated to 70-80°C for 2-6 hours. Next, monoglycidyl ether-terminated polydimethylsiloxane was added, and the mixture was stirred and kept at the same temperature for 1-3 hours. Finally, glycidyl methacrylate and a polymerization inhibitor were added, and the mixture was stirred and kept for 2-4 hours. The reaction was then stopped, and the product was separated and purified to obtain DOPO-modified silica sol containing unsaturated double bonds. S4: Under nitrogen protection, DOPO-modified silica sol containing unsaturated double bonds, acrylate monomers, alkylphenol polyoxyethylene ethers, and deionized water are added to a reaction vessel and stirred for pre-emulsification. Then, the mixture is stirred and heated to 70-80°C, and ammonium persulfate aqueous solution is added dropwise over 1-2 hours. After the addition is complete, the reaction is stirred for another 4-8 hours. The reaction is then stopped, and ammonia is added to adjust the pH to neutral. After separation and purification, polyacrylate / DOPO-modified silica sol is obtained, which is a silica sol-based flame retardant coating.

3. The method for preparing a silica sol-based flame-retardant coating according to claim 2, characterized in that: In S1, the molar ratio of tetraethyl orthosilicate and 3-glycidyl etheroxypropyltriethoxysilane is 4:1; The molar ratio of ethanol, deionized water, hydrochloric acid and n(Si) is 4:4:0.002:1; wherein the hydrochloric acid is a 0.1 mol / L hydrochloric acid solution.

4. The method for preparing a silica sol-based flame-retardant coating according to claim 2, characterized in that: In S2, the molar ratio of DOPO and maleic anhydride is (1~1.05):1; The amount of toluene added is three times the total mass of DOPO and maleic anhydride.

5. The method for preparing a silica sol-based flame-retardant coating according to claim 2, characterized in that: In S4, the amount of raw material components required for the preparation of the polyacrylate / DOPO modified silica sol, by weight, is as follows: 30 parts of DOPO modified silica sol containing unsaturated double bonds, 8-12 parts of acrylate monomer, 0.1-0.3 parts of alkylphenol polyoxyethylene ether, 0.1-0.3 parts of ammonium persulfate, and 50 parts of deionized water.

6. The method for preparing a silica sol-based flame-retardant coating according to claim 5, characterized in that: The acrylate monomer is obtained by mixing acrylic acid, methyl methacrylate, acrylonitrile and styrene in a mass ratio of (1~2):1:(1~2):(1~2).

7. The polyacrylate / DOPO modified silica sol prepared by the method for preparing a silica sol-based flame-retardant coating according to any one of claims 1 to 6, characterized in that: The solid content of the polyacrylate / DOPO modified silica sol is 40~50wt%.