A method for preparing a modified silica sol and its use in waterborne uv coatings

Abstract

The application discloses a preparation method of modified silica sol and application of the modified silica sol in water-based UV paint, and the preparation method comprises the following steps: 1) mixing silica sol with cation exchange resin, so that the pH of the mixed solution is 1-7; 2) adding a silane coupling agent and an aqueous solution of inorganic salt into the mixed solution in step 1) drop by drop, so that the silane coupling agent is bonded to the surface of the silica sol; 3) adding an anion exchange resin into the reaction solution in step 2), so that the pH value of the reaction system is 2-12, and then filtering, so that the silane coupling agent modified silica sol is obtained. When the silane coupling agent modified silica sol is used in the water-based UV paint, the adhesion of the UV paint on a PVC substrate and the iodine alcohol resistance of the UV paint can be obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of modified silica sol, more particularly, to a preparation method of silica sol modified by silane coupling agent and its application in water-based UV coating. BACKGROUND

[0002] Silica sol is an inorganic nanometer material with excellent performance, which is a colloidal solution of amorphous silica particles uniformly dispersed in water or organic solvent, and is an inorganic polymer material with extremely wide application. It has a large number of applications in the fields of chemical mechanical polishing (CMP), textile industry, investment casting, ceramics, coating and papermaking. The silica colloid has a large number of silicon hydroxyl groups, which have very good affinity to water-based systems. However, the compatibility of silica sol with organic monomers is poor. The silica sol with single composition and structure cannot meet the application in some special fields. With the bridging effect of silane coupling agent between inorganic and organic materials, the silica sol modified by silane coupling agent can make up for the defects of ordinary silica sol and expand its application range.

[0003] The most commonly used method for modifying silica sol by silane in the industry is to add an appropriate amount of silane to the acidic silica sol and stir to hydrolyze. The main defect of this method is that the amount of silane actually bonded to the sol colloid is small, which cannot achieve the purpose of organic modification. Further optimized process is to adjust the pH value of the system and increase the condensation of silane hydrolysis product. This method also has the risk of silane self-gelation, and the stability is not enough. SUMMARY

[0004] In one aspect, the present application provides a preparation method of modified silica sol, which comprises the following steps:

[0005] 1) mixing silica sol with cation exchange resin to make the pH of the mixed solution 1-7;

[0006] 2) adding silane coupling agent and aqueous solution of inorganic salt to the mixed solution of step 1) to bond the silane coupling agent to the surface of the silica sol;

[0007] 3) adding anion exchange resin to the reaction solution of step 2) to make the pH value of the reaction system 2-12, and filtering to obtain silica sol modified by silane coupling agent.

[0008] In another preferred embodiment, the pH of the silica sol is 8-12, and the particle size is 5-100 nm.

[0009] In another preferred embodiment, the solid content of the silica sol is 5-40%.

[0010] In another preferred embodiment, the silane coupling agent is selected from an alkyl group substituted alkoxy silane, an unsaturated double bond containing alkoxy silane, an epoxy group containing alkoxy silane, an amino group containing alkoxy silane, or a combination thereof.

[0011] In another preferred embodiment, the alkyl group substituted alkoxy silane is selected from methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, or a combination thereof.

[0012] In another preferred embodiment, the unsaturated double bond containing alkoxy silane is selected from vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, or a combination thereof.

[0013] In another preferred embodiment, the epoxy group containing alkoxy silane is selected from γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0014] In another preferred embodiment, the amino group containing alkoxy silane is selected from aminopropyltrimethoxysilane, aminopropyltriethoxysilane, or a combination thereof.

[0015] In another preferred embodiment, the cation exchange resin is selected from a styrene-divinylbenzene copolymer having sulfonic acid groups (-SO3H) or carboxylic acid groups (-COOH).

[0016] In another preferred embodiment, the inorganic salt is selected from sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, or a combination thereof.

[0017] In another preferred embodiment, the anion exchange resin is selected from a styrene-divinylbenzene copolymer having quaternary ammonium groups [-N(CH3)3OH] or tertiary ammonium groups [-N(CH3)2].

[0018] In another more preferred embodiment, in step 1), the cation exchange resin is used in an amount of 0.1-0.9:1, more preferably 0.3-0.8:1, by mass ratio to the silica sol.

[0019] In another more preferred embodiment, step 1) is stirred at 40-70°C for 0.5-2h, more preferably 45-60°C for 0.5-1.5h.

[0020] In another more preferred embodiment, in step 2), the silane coupling agent is used in an amount of 0.008-0.1:1, more preferably 0.01-0.08:1, by mass ratio to the silica sol.

[0021] In another more preferred embodiment, in step 2), the inorganic salt is used in an amount of 0.0001-0.01:1, more preferably 0.0005-0.08:1, by mass ratio to the silica sol.

[0022] In another more preferred embodiment, step 2) is carried out at 35-65°C for 4-7h, more preferably at 45-60°C for 5-6h.

[0023] In another more preferred embodiment, in step 2), the stirring rate is 10-200rpm.

[0024] In another more preferred embodiment, in step 3), the amount of anion exchange resin is 0.1-0.6:1, more preferably 0.1-0.4:1, by mass ratio of the anion exchange resin to the silica sol.

[0025] In another more preferred embodiment, step 3) is carried out at 10-40°C for 4-7h.

[0026] Another aspect of the present application provides the use of the silica sol prepared by the above method in preparing a water-based UV coating, which is used for roll coating on a PVC substrate.

[0027] Another aspect of the present application provides a water-based UV coating containing the silica sol prepared by the above method.

[0028] In another more preferred embodiment, the raw materials for preparing the water-based UV coating include the following components by weight:

[0029]

[0030] In another more preferred embodiment, the raw materials for preparing the water-based UV coating include the following components by weight:

[0031]

[0032]

[0033] The present application also provides a method for preparing the above water-based UV coating, which comprises the following steps:

[0034] (1) placing the water-based UV resin into a dispersion barrel, and stirring by a stirrer

[0035] (2) slowly adding the modified silica sol, water, co-solvent, initiator, and wetting agent, and continuously stirring for 20-40min to mix uniformly;

[0036] (3) slowly adding the thickening agent, and adjusting the viscosity of the coating according to different coating processes

[0037] (4) filtering by using a 200-mesh filter bag to complete the preparation of the water-based UV coating. DETAILED DESCRIPTION

[0038] The present application inventors have found through in-depth research that the coordination of silica dioxide in the alkaline silica sol with inorganic salts through ion exchange resins can solve the modification of alkaline silica sol to the desired functional group silane modified silica sol at one time, and the functional groups on the surface of the customized silica sol can be prepared through this technology.

[0039] The preparation method of the modified silica sol provided by the present application comprises the following steps:

[0040] 1) mixing the silica sol with cation exchange resin to make the pH of the mixed solution 1-7;

[0041] 2) adding a silane coupling agent and an aqueous solution of inorganic salt to the mixed solution of step 1);

[0042] 3) adding an anion exchange resin to the reaction solution of step 2), continuously stirring at 10-40°C, making the pH of the reaction system 2-12, and filtering to obtain the silane coupling agent modified silica sol.

[0043] In the preparation method of the modified silica sol of the present application, the silica sol used is alkaline, and the pH is 8-12. In some specific embodiments, the pH of the silica sol is 8-10, 8-9, 9-10, 10-11, etc. In some specific embodiments, the particle size of the silica sol used is 5-100 nm. In some more preferred specific embodiments, the particle size of the silica sol used is 20-30 nm, 40-50 nm, 50-60 nm, 60-80 nm, 70-90 nm, 80-100 nm, etc. In some specific embodiments, the solid content in the silica sol used is 5-40%. In some more preferred specific embodiments, the solid content in the silica sol used is 15-20%, 20-25%, 20-30%, 30-40%, etc.

[0044] In the preparation method of the modified silica sol of the present application, the role of the cation exchange resin is to exchange the cations in the silica sol, reducing the content of metal ions in the system. The cation exchange resin that can be used in the present application includes but is not limited to styrene-divinylbenzene copolymer with sulfonic acid group (-SO3H) or carboxylic acid group (-COOH).

[0045] In the preparation method of the modified silica sol of the present application, the silane coupling agent is bonded to the surface of the silica sol through hydrolytic polycondensation, and the surface is increased with special organic groups, and the surface of the sol is changed from mainly hydroxyl groups. The silane coupling agent that can be used in the present application includes but is not limited to alkyl-substituted alkoxy silane (such as methyl trimethoxysilane, methyl triethoxysilane, ethyl triethoxysilane, propyl trimethoxysilane), unsaturated double bond-containing alkoxy silane (such as vinyl trimethoxysilane, vinyl triethoxysilane, γ-methacryloyloxy propyl trimethoxysilane), epoxy group-containing alkoxy silane (such as γ-(2,3-epoxypropoxy) propyl trimethoxysilane), amino group-containing alkoxy silane (such as aminopropyl trimethoxysilane, aminopropyl triethoxysilane).

[0046] In the preparation method of the modified silica sol of the present application, the inorganic salt functions to slowly increase the content of cations in the reaction system as the reaction proceeds, and to control the bonding speed of the silane and the surface hydroxyl groups of the silica sol. In comparison with the step of directly modifying with the modifier without adding the inorganic salt, in the preparation method of the modified silica sol of the present application, as the inorganic salt is introduced into the whole reaction system, the pH of the system can be slowly changed from acidic to weakly alkaline as the reaction proceeds, and the defects of difficulty in bonding the silane hydrolysate to the surface of the silica sol under acidic conditions and easy polycondensation gelation of the silane hydrolysate under alkaline conditions are avoided. The inorganic salt that can be used in the present application includes but is not limited to sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate.

[0047] In the preparation method of the modified silica sol of the present application, the anion exchange resin functions to ion-exchange the anions introduced by the inorganic salt. The anion exchange resin that can be used in the present application includes but is not limited to styrene-divinyl benzene copolymer with quaternary ammonium group [-N(CH3)3OH] or tertiary ammonium group [-N(CH3)2].

[0048] In step (1) of the preparation method of the modified silica sol of the present application, the amount of the cation exchange resin is not particularly limited, as long as the pH of the silica sol is adjusted to 1-7, and more preferably, the mass ratio of the silica sol to the dehydrated cation exchange resin is 1:0.30-0.80, for example, 1:0.4, 1:0.5, 1:0.55, 1:0.6, 1:0.7, etc. The reaction temperature is not particularly limited, and is preferably 20-70°C, and more preferably 45-60°C, for example, 45°C, 48°C, 50°C, 55°C, 58°C, 60°C, etc.

[0049] In step 2) of the preparation method, the silane coupling agent is preferably used in a mass ratio of 0.008-0.1:1, more preferably 0.01-0.08:1, to the alkaline silica sol, for example, 0.01:1, 0.015:1, 0.01:1, 0.27:1, etc. The amount of inorganic salt is not particularly limited, and more preferably, the mass ratio of the inorganic salt to the alkaline silica sol is 0.0001-0.01:1, more preferably 0.0005-0.08:1, for example, 0.0014:1, 0.0012:1, 0.0014:1, 0.0015:1, 0.002:1, etc. The concentration of the aqueous solution of the inorganic salt is also not particularly limited, and preferably, the concentration of the aqueous solution of the inorganic salt is 0.5-1.5 mol / L, for example, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L.

[0050] In step 2), the stirring rate is not particularly limited, and preferably, the stirring rate is 10-200 rpm. The reaction temperature is not particularly limited, and preferably, the reaction temperature is 30-60°C, more preferably 35-60°C, for example, 35°C, 45°C, 55°C, etc. The reaction time is not particularly limited, and preferably, the reaction time is 4-7 hours, more preferably 5-6 hours, for example, 5 hours, 6 hours or 7 hours.

[0051] In step 3), the amount of the anion exchange resin is preferably in a mass ratio of 0.1-0.6:1, more preferably 0.1-0.4:1, to the silica sol, for example, 0.2:1, 0.25:1, 0.3:1, 0.35:1,

[0052] The water-based UV coating described in the present application is an environmentally friendly coating that combines the respective advantages of traditional UV coatings and water-based coatings; water is used as a diluent, which greatly reduces the emission of volatile organic compounds (VOCs). Under the irradiation of ultraviolet light, the photoinitiator absorbs the radiant energy of ultraviolet light and splits into free radicals, initiating the polymerization, crosslinking and grafting reactions of the prepolymer. The coating can be rapidly cured in a short time under ultraviolet irradiation, greatly improving the production efficiency and facilitating continuous production.

[0053] Compared with the prior art, the present application has the following advantages:

[0054] The preparation method of the modified silica sol of the present application makes the hydrolysis rate of the silane coupling agent controllable due to the addition of the inorganic salt, so that the silane coupling agent will not undergo gelation reaction during the bonding process with the silica sol.

[0055] The water-based UV coating prepared from the modified silica sol prepared by the preparation method of the modified silica sol of the present application has significantly increased adhesion and iodine alcohol resistance after being roll-coated on a PVC substrate.

[0056] The application will be further described in connection with specific examples. The specific examples are implemented on the premise of the technical scheme of the application, and detailed implementation modes and operation processes are given. It should be understood that these examples are only used to illustrate the application and not to limit the scope of the application. The experimental methods in the following examples are generally carried out under conventional conditions. Unless otherwise specified, the proportions and percentages are by weight.

[0057] Example 1

[0058] 1) 1 kg of basic silica sol with an average particle size of 12 nm, a solid content of 30%, and a pH of 11 and 500 g of strongly acidic cation exchange resin (such as Zhengguang resin ZGC151) were added into a reaction container, and the temperature was raised to 50°C for 1 h of continuous stirring;

[0059] 2) 20 g of methyltrimethoxysilane and 20 ml of 1 mol / L NaCl solution were respectively added into the reaction container using a peristaltic pump at a rate of 10 ml / h, and after the addition was completed, 5 h of continuous stirring was carried out;

[0060] 3) The reaction solution was cooled to 30°C, 200 g of anion exchange resin (such as Zhengguang resin ZGA351) was added into the reaction container, and the stirring was continued, the dynamic change of the pH value of the system was detected using a pH meter, and when the pH value of the system was 7, the stirring was stopped, and filtration was carried out, and the liquid obtained by filtration was neutral methyltrimethoxysilane modified silica sol (pH = 7).

[0061] Example 2

[0062] 1) 1 kg of basic silica sol with an average particle size of 20 nm, a solid content of 30%, and a pH of 10 and 400 g of strongly acidic cation exchange resin (such as Zhengguang resin ZGC151) were added into a reaction container, and the temperature was raised to 45°C for 1.5 h of continuous stirring;

[0063] 2) 10 g of a mixture of vinyltrimethoxysilane and methyltrimethoxysilane and 20 ml of 1 mol / L KCl solution were respectively added into the reaction container using a peristaltic pump at a rate of 5 ml / h, and after the addition was completed, 5 h of continuous stirring was carried out at 45°C;

[0064] 3) The temperature was lowered to 30°C, 150 g of anion exchange resin (such as Zhengguang resin ZGA351) was added into the reaction container, and the stirring was continued, the dynamic change of the pH value of the system was detected using a pH meter, and when the pH of the system was 7, the filtration was carried out, and the liquid obtained by filtration was neutral silica sol modified by neutral vinyltrimethoxysilane and methyltrimethoxysilane (pH = 7).

[0065] Example 3

[0066] 1) 1 kg of basic silica sol with an average particle size of 30 nm, a solid content of 40%, and a pH of 10 and 600 g of strongly acidic cation exchange resin (such as ZGC151 resin) were added into a reaction vessel, and the temperature was raised to 55°C for stirring for 1 h;

[0067] 2) 15 g of a mixture of aminopropyltrimethoxysilane and methyltrimethoxysilane and 30 ml of a 1 mol / L NaCl solution were added into the reaction vessel at a rate of 5 ml / h using a peristaltic pump, respectively, and after the addition was completed, the temperature was maintained at 55°C for stirring for 6 h;

[0068] 3) The reaction solution was cooled to 15°C, 250 g of anion exchange resin (such as ZGA351 resin) was added into the reaction vessel, and the stirring was continued, the dynamic change of the pH value of the system was detected using a pH meter, and when the pH of the system was 5, filtration was performed, and the liquid obtained by filtration was an acidic silica sol modified by aminopropyltrimethoxysilane and methyltrimethoxysilane (pH = 5).

[0069] Example 4

[0070] 1) 1 kg of basic silica sol with an average particle size of 20 nm, a solid content of 20%, and a pH of 10 and 550 g of strongly acidic cation exchange resin (such as ZGC151 resin) were added into a reaction vessel, and the temperature was raised to 60°C for stirring for 0.5 h;

[0071] 2) 13 g of a mixture of γ-glycidoxypropyltrimethoxysilane and methyltrimethoxysilane and 25 ml of a 1 mol / L NaCl solution were added into the reaction vessel at a rate of 5 ml / h using a peristaltic pump, respectively, and after the addition was completed, the temperature was maintained at 35°C for stirring for 5 h;

[0072] 3) The reaction solution was cooled to 20°C, 200 g of anion exchange resin (such as ZGA351 resin) was added into the reaction vessel, and the stirring was continued, the dynamic change of the pH value of the system was detected using a pH meter, and when the pH of the system was 5, filtration was performed, and the liquid obtained by filtration was an acidic silica sol modified by γ-glycidoxypropyltrimethoxysilane and methyltrimethoxysilane (pH = 5).

[0073] Comparative Example 1

[0074] The preparation method of the modified silica sol of the present comparative example is different from that of Example 3 in that no NaCl aqueous solution is added. The specific steps are as follows:

[0075] 1) 1 kg of basic silica sol with an average particle size of 30 nm, a solid content of 40%, and a pH of 10 and 600 g of strongly acidic cation exchange resin (such as ZGC151 resin) were added into a reaction vessel, and the temperature was raised to 55°C for stirring for 1 h;

[0076] 2) 15 g of aminopropyltrimethoxysilane and 12 g of methyltrimethoxysilane were mixed and added dropwise into the reaction vessel at a rate of 5 ml / h using a peristaltic pump, after the dropwise addition was completed, 55°C continuous stirring for 6 h;

[0077] 3) The reaction solution was cooled to 15°C, 250 g of anion exchange resin (such as Zhengguang resin ZGA351) was added into the reaction vessel, and stirring was continued, the dynamic change of the pH value of the system was detected using a pH meter, when the pH of the system was 5, filtration was carried out, and the liquid obtained by filtration was an acidic silicasol modified by acidic aminopropyltrimethoxysilane and methyltrimethoxysilane (pH = 5).

[0078] Comparative Example 2

[0079] The preparation method of the modified silicasol of the present comparative example is different from that of Example 4 in that no NaCl aqueous solution is added. The specific steps are as follows:

[0080] 1) 1 kg of basic silicasol with an average particle size of 20 nm, a solid content of 20%, and a pH of 10, and 550 g of strong acidic cation exchange resin (such as Zhengguang resin ZGC151) were added into the reaction vessel, and the temperature was raised to 60°C for continuous stirring for 0.5 h;

[0081] 2) 13 g of γ-glycidoxypropyltrimethoxysilane and 10 g of methyltrimethoxysilane were mixed and added dropwise into the reaction vessel at a rate of 5 ml / h using a peristaltic pump, after the dropwise addition was completed, 35°C continuous stirring for 5 h;

[0082] 3) The reaction solution was cooled to 20°C, 200 g of anion exchange resin (such as Zhengguang resin ZGA351) was added into the reaction vessel, and stirring was continued, the dynamic change of the pH value of the system was detected using a pH meter, when the pH of the system was 5, filtration was carried out, and the liquid obtained by filtration was an acidic silicasol modified by acidic γ-glycidoxypropyltrimethoxysilane and methyltrimethoxysilane (pH = 5).

[0083] Comparative Example 3

[0084] The preparation method of the modified silicasol of the present comparative example is different from that of Example 3 in that the basic silicasol itself is a basic system, and the silane reagent is directly added for reaction. The specific steps are as follows:

[0085] 1) 1 kg of basic silicasol with an average particle size of 30 nm, a solid content of 40%, and a pH of 10 was added into the reaction vessel, and the temperature was raised to 55°C for continuous stirring for 1 h;

[0086] 2) 15 g of aminopropyltrimethoxysilane and 12 g of methyltrimethoxysilane were mixed and added dropwise into the reaction vessel at a rate of 5 ml / h each using a peristaltic pump. After the dropwise addition was completed, stirring was continued at 55°C for 6 h;

[0087] 3) The reaction solution was cooled to 15°C, and filtration was performed. The liquid obtained by the filtration was the basic aminopropyltrimethoxysilane and methyltrimethoxysilane-modified basic silica sol.

[0088] The color and state of the final collected product after the reaction of the examples and comparative examples were as follows:

[0089]

[0090] As can be seen from the results of the collected product of the examples and comparative examples, the direct addition of a silane reagent under basic conditions cannot bond functional groups to the surface of the silica sol particles. The silane is directly condensed and gelled to produce flocculation under basic conditions.

[0091] The unmodified silica sol (the silica sol used in Example 3, a basic silica sol having an average particle size of 30 nm, a solid content of 40%, and a pH of 10), the modified silica sols of Examples 1 to 4, and the modified silica sols of Comparative Examples 1 and 2 were used to prepare water-based UV coatings, and these water-based UV coatings were applied to a PVC substrate.

[0092] The water-based UV coatings were prepared using the above unmodified silica sol or the above modified silica sol, wherein the raw materials for preparing the water-based UV coatings included the following components in parts by weight:

[0093]

[0094] The method for preparing the coating base formulation included the following steps:

[0095] (1) The resin was placed in a dispersion barrel, and a stirrer was stirred

[0096] (2) The unmodified silica sol or the modified silica sol, water, a cosolvent, an initiator, and a wetting agent were slowly added, and stirring was continued for 20 to 40 min, and the mixture was uniformly mixed;

[0097] (3) A thickening agent was slowly added, and the viscosity of the coating was adjusted according to different coating processes

[0098] (4) A 200-mesh filter bag was used for filtration, and the preparation of the water-based UV coating was completed.

[0099] Application Example 1

[0100] This application example used an unmodified silica sol (a basic silica sol having an average particle size of 30 nm, a solid content of 40%, and a pH of 10) to prepare a water-based UV coating.

[0101] Application Example 2

[0102] The modified silica sol prepared in Example 1 was used to prepare a waterborne UV coating.

[0103] Application Example 3

[0104] The modified silica sol prepared in Example 2 was used to prepare a waterborne UV coating.

[0105] Application Example 4

[0106] The modified silica sol prepared in Example 3 was used to prepare a waterborne UV coating.

[0107] Application Example 5

[0108] The modified silica sol prepared in Example 4 was used to prepare a waterborne UV coating.

[0109] Application Example 6

[0110] The modified silica sol prepared in Comparative Example 1 was used to prepare a waterborne UV coating.

[0111] Application Example 7

[0112] The modified silica sol prepared in Comparative Example 2 was used to prepare a waterborne UV coating.

[0113] Application Example 8

[0114] The above waterborne UV coating was coated on a PVC substrate according to the following process:

[0115] (1) Provide a PVC substrate;

[0116] (2) The waterborne UV coating of Application Examples 1-7 was roll-coated on the PVC substrate;

[0117] (3) 60°C, baking for 10 min, then UV curing (medium pressure mercury lamp, 80-100 mW / cm 2 , 300-500 mJ / cm 2 ).

[0118] The performance of the waterborne UV coatings of Application Examples 1-7 on the PVC substrate was characterized. The hardness measurement standard was GB / T 6739-2022 Paint and Varnish - Determination of Film Hardness by Pencil Method, the adhesion measurement standard was GB / T 9286-2021 Paint and Varnish - Crosshatch Test, and the iodine resistance standard was: internal inspection index (drop a drop of iodine on the surface of the test sample, cover with a cover glass to the top of the iodine, stand for 10 min, then remove the cover glass and use 50% alcohol to scrub, observe the depth of the remaining yellow marks as the basis for evaluation. The results are shown in Table 1 below.

[0119] Table 1

[0120]

[0121]

[0122] As can be seen from Table 1, the modified silica sol prepared in Examples 1-4 and Comparative Examples 1-2 can significantly improve the hardness, adhesion and iodine alcohol resistance of the water-based UV coating when used in the water-based UV coating.

[0123] The preparation method of the modified silica sol of the present application increases the number of silane bonds on the surface of the silica sol particles, thereby forming chemical bonds in the water-based UV coating system through chemical reaction between the surface functional groups of the modified silica sol and the organic groups in the coating, thereby enhancing the bonding force between the coating and the substrate. This chemical bonding not only improves the adhesion of the coating, but also makes the coating more dense, effectively preventing the intrusion of external substances such as water and oxygen, thereby prolonging the service life of the coating. At the same time, the addition of the silica sol can also significantly improve the hardness and wear resistance of the coating, making it more durable.

[0124] The above is only a preferred embodiment of the present application, and is not intended to limit the scope of the present application. The above embodiment of the present application can also be variously changed. Any simple, equivalent changes and modifications made in accordance with the content of the claims and description of the present application shall fall within the scope of protection of the present patent. The present application is not described in detail, and all conventional technical contents are included.

Claims

1. A method for preparing a modified silica sol, characterized by, The preparation method comprises the following steps: 1) mixing the silica sol with the cation exchange resin to make the pH of the mixed solution 1-7; 2) adding a silane coupling agent and an aqueous solution of an inorganic salt to the mixed solution of step 1) dropwise, so that the silane coupling agent is bonded to the surface of the silica sol; 3) adding an anion exchange resin to the reaction solution of step 2) so that the pH of the reaction system is 2-12, and filtering to obtain the silane coupling agent modified silica sol; The silica sol has a pH of 8-12 and a particle size of 5-100 nm, The silica sol has a solid content of 5-40%, The silane coupling agent is selected from alkyl-substituted alkoxysilane, unsaturated double bond-containing alkoxysilane, epoxy group-containing alkoxysilane, amino group-containing alkoxysilane, or a combination thereof; The cation exchange resin is selected from a styrene-divinylbenzene copolymer having a sulfonic acid group (-SO3H) or a carboxylic acid group (-COOH), The inorganic salt is selected from sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, or a combination thereof, The anion exchange resin is selected from a styrene-divinylbenzene copolymer having a quaternary ammonium group [-N(CH3)3OH] or a tertiary ammonium group [-N(CH3)2]; Step 1) has one or more of the following characteristics: (i) the mass ratio of silica sol to dehydrated cation exchange resin is 1:0.1-0.9; (ii) stirring at 40-70°C for 0.5-2h; Step 2) has one or more of the following characteristics: (i) the amount of silane coupling agent is 0.008-0.1:1 of the mass ratio of the silane coupling agent to the silica sol, (ii) the amount of inorganic salt is 0.0001-0.01:1 of the mass ratio of the inorganic salt to the silica sol, (iii) continuous stirring at 35-65°C for 4-7h, (iv) the concentration of the aqueous solution of the inorganic salt is 0.2-5.0 mol / L, (v) the stirring rate is 10-200rpm.

2. The method of claim 1, wherein the modified silica sol is prepared by the steps of: The alkyl-substituted alkoxysilane is selected from methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, or a combination thereof, The unsaturated double bond-containing alkoxysilane is selected from vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, or a combination thereof, The epoxy group-containing alkoxysilane is selected from γ-(2,3-epoxypropoxy)propyltrimethoxysilane, The amino group-containing alkoxysilane is selected from aminopropyltrimethoxysilane, aminopropyltriethoxysilane, or a combination thereof.

3. The method of claim 1, wherein the modified silica sol is prepared by the steps of: Step 1) has one or more of the following characteristics: (i) the mass ratio of silica sol to dehydrated cation exchange resin is 0.3-0.8:1; (ii) stirring at 45-60°C for 0.5-1.5h.

4. The method of claim 1, wherein the modified silica sol is prepared by the steps of: Step 2) has one or more of the following characteristics: (i) the amount of silane coupling agent is 0.01-0.08:1 of the mass ratio of the silane coupling agent to the silica sol, (ii) the amount of inorganic salt is 0.0005-0.08:1 of the mass ratio of the inorganic salt to the silica sol, (iii) continuous stirring at 45-60°C for 5-6h, (iv) the concentration of the aqueous solution of the inorganic salt is 0.5-1.5 mol / L, (v) the stirring rate is 10-200 rpm.

5. Use of the modified silica sol obtained by the preparation method of any one of claims 1-4 in the preparation of an aqueous UV coating for roll coating on a PVC substrate.

6. An aqueous UV coating comprising the silane coupling agent modified silica sol obtained by the preparation method of any one of claims 1-4.

7. The aqueous UV coating according to claim 6, characterized in that Raw materials for preparing the aqueous UV coating include the following components by weight: aqueous UV resin 100 parts wetting agent 0.1-0.5 parts initiator 0.5-4 parts thickening agent 0.2-2 parts co-solvent 5-20 parts water 20-50 parts silane coupling agent modified silica sol 15-40 parts.

8. The aqueous UV coating according to claim 7, characterized in that Raw materials for preparing the aqueous UV coating include the following components by weight: resin ETERCURE DR-W493 100 parts, wetting agent tego KL 245 0.1-0.5 parts, MBF initiator 0.0.25-2.0 parts, TPO initiator 0.25-2.0 parts, isopropyl alcohol 5-20 parts, water 20-50 parts, thickening agent RHEOLATE 350D 0.2-2.0 parts, silane coupling agent modified silica sol 15-40 parts.

9. The method of producing the aqueous UV coating according to claim 7, characterized in that The preparation method includes the following steps: (1) Place the aqueous UV resin into a dispersion bucket and stir with a stirrer (2) Slowly add the silane coupling agent modified silica sol, water, co-solvent, initiator, and wetting agent, and continue stirring for 20-40 min to mix evenly; (3) Slowly add the thickening agent, and adjust the viscosity of the coating according to different coating processes (4) Filter using a 200-mesh filter bag to complete the preparation of the aqueous UV coating.

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