Preparation method of EVA waterproof coating

Abstract

The application relates to the technical field of paint, and discloses a preparation method of EVA waterproof paint, in which montmorillonite is activated and reacted with toluene diisocyanate to obtain isocyanate modified montmorillonite. EVA is hydrolyzed under the catalysis of potassium hydroxide to obtain hydroxylated EVA. An epoxy group trisiloxane intermediate is reacted with terephthalic acid under the ring-opening esterification of benzyl triethyl ammonium chloride to obtain p-hydroxy trisiloxane benzoate. The p-hydroxy trisiloxane benzoate, the hydroxylated EVA, the isocyanate modified montmorillonite and toluene diisocyanate are crosslinked under the catalysis of stannous octoate, then a defoaming agent and a dispersing agent are added, and stirring is carried out until uniformity, so that the EVA waterproof paint is obtained. The prepared EVA waterproof paint has good mechanical properties and waterproof performance.

Description

[0001] This application is a divisional application of application filed on January 20, 2024, with application number 202510086452.4 and invention title "A method for preparing EVA waterproof coating". Technical Field

[0002] This invention relates to the field of coating technology, specifically to a method for preparing an EVA waterproof coating. Background Technology

[0003] Water, chloride ions, and other harmful ions can penetrate concrete and other porous materials through pores, affecting their durability and increasing maintenance costs. Therefore, waterproof coatings are needed to apply to material surfaces, providing waterproofing and wear resistance to extend their lifespan. Consequently, the research and development of new waterproof coatings is a current focus for researchers.

[0004] EVA is an ethylene-vinyl acetate copolymer material with excellent elasticity, flexibility, insulation, and chemical resistance, and is widely used in wires and cables, films, adhesives, coatings, and other fields. Montmorillonite is a silicate mineral with a layer of alumina octahedrons sandwiched between two layers of silicon-oxygen tetrahedra and a negatively charged surface, exhibiting good dispersibility and impact resistance. For example, patent application publication number CN113930169B discloses a heat-resistant EVA film and its preparation method. The film prepared by this invention has good tensile strength, tear strength, and good resistance to damp heat, but its waterproof performance is poor. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a method for preparing EVA waterproof coating, wherein the prepared EVA waterproof coating has good mechanical properties and waterproof properties.

[0006] The technical solution of this invention is:

[0007] A method for preparing an EVA waterproof coating, the method being as follows:

[0008] (1) The epoxy trisiloxane intermediate, terephthalic acid, and benzyl triethylammonium chloride were placed in 1,2-dichloroethane and reacted at 75-90℃ for 2.5-4h. After cooling to room temperature, the mixture was filtered under reduced pressure, recrystallized, and dried to obtain p-hydroxytrisiloxane benzoate.

[0009] (2) Place p-hydroxytrisiloxane benzoate, hydroxylated EVA, isocyanate-modified montmorillonite, stannous octoate, and tetrahydrofuran solvent in a flask, stir evenly, add toluene diisocyanate, heat to 60-70℃, react for 2-4 hours, cool to room temperature, add water, remove tetrahydrofuran by vacuum distillation, add defoamer and dispersant, stir evenly, and obtain EVA waterproof coating.

[0010] Furthermore, in step (1), the mass ratio of the epoxy trisiloxane intermediate to terephthalic acid is 1:0.2-0.3.

[0011] Furthermore, in step (1), the amount of benzyltriethylammonium chloride used is 1-1.5% of the total mass of the epoxytrisiloxane intermediate and terephthalic acid.

[0012] Furthermore, in step (2), the mass ratio of p-hydroxytrisiloxane benzoate, hydroxylated EVA, isocyanate-modified montmorillonite, stannous octoate, and toluene diisocyanate is 5-30:100:0.5-8:0.02-0.12:3-20.

[0013] Furthermore, the preparation method of hydroxylated EVA in step (2) is as follows:

[0014] (3) Place EVA in toluene solution, add potassium hydroxide isopropanol solution at 50-70℃, stir for 5-8h, precipitate with ethanol, filter, wash with ethanol, and dry to obtain hydroxylated EVA.

[0015] Furthermore, in step (3), the mass ratio of EVA to potassium hydroxide is 100:5-7.

[0016] Furthermore, the preparation method of isocyanate-modified montmorillonite in step (2) is as follows:

[0017] (4) Under nitrogen protection, activated montmorillonite and toluene diisocyanate were placed in toluene solvent and stirred and dispersed for 20-40 min. The mixture was heated to react, cooled to room temperature, filtered, washed, and dried under vacuum to obtain isocyanate modified montmorillonite.

[0018] Furthermore, in step (4), the mass ratio of activated montmorillonite to toluene diisocyanate is 1:0.2-0.5.

[0019] Furthermore, in step (4), the heating reaction time is 60-100 min and the temperature is 70-90℃.

[0020] The beneficial technical effects of this invention are:

[0021] Activated montmorillonite reacts with toluene diisocyanate to obtain isocyanate-modified montmorillonite. EVA is hydrolyzed under potassium hydroxide catalysis to obtain hydroxylated EVA. An epoxy-based trisiloxane intermediate reacts with terephthalic acid under ring-opening esterification with benzyltriethylammonium chloride to obtain p-hydroxytrisiloxane benzoate. p-hydroxytrisiloxane benzoate, hydroxylated EVA, isocyanate-modified montmorillonite, and toluene diisocyanate are crosslinked under stannous octoate catalysis. Defoamer and dispersant are then added and stirred until homogeneous to obtain an EVA waterproof coating.

[0022] The coating prepared by this invention possesses a large cross-linked network structure, exhibiting high density and low surface tension. Distributed on the material surface, it prevents water molecules and other ions from penetrating the material's interior, thus providing excellent waterproofing. Furthermore, upon impact, the large network structure can absorb a significant amount of impact force, transferring the force to the material, reducing stress concentration, delaying the fracture process, and improving the material's mechanical properties. In addition, the siloxane structure can generate a cross-linked structure through hydrolysis and gelation, further restricting water molecule penetration and enhancing the material's waterproofing performance. The montmorillonite used in this invention possesses good mechanical properties, but its surface contains active groups such as hydroxyl groups. Surface modification is first performed to reduce surface free energy, and then it is used as a reactant in a chemical reaction, which is then applied to the EVA waterproof coating, improving the coating's mechanical properties. The EVA waterproof coating prepared by this invention exhibits excellent mechanical and waterproofing properties. Attached Figure Description

[0023] Figure 1 This is the preparation route for p-hydroxytrisiloxane benzoate. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] Preparation method of epoxy-based trisiloxane intermediate: 1,1,1,3,5,5,5-heptamethyltrisiloxane and allyl glycidyl ether in a molar ratio of 1:1.05 were placed in an isopropanol solution. Under a nitrogen atmosphere, an alcoholic solution of chloroplatinic acid was added to the solution. The reaction was carried out at 90°C for 5 h. The solvent was evaporated, and low-boiling substances were removed under vacuum at 85°C and 60 kPa for 30 min. The solution was then cooled to room temperature to obtain the epoxy-based trisiloxane intermediate.

[0026] Preparation method of activated montmorillonite: Under a nitrogen atmosphere, montmorillonite is placed in a flask and activated at 250℃ for 2 hours to obtain activated montmorillonite.

[0027] Example 1

[0028] (1) Under nitrogen protection, 60g of activated montmorillonite and 15g of toluene diisocyanate were placed in toluene solvent and stirred and dispersed for 30min. The temperature was raised to 80℃ and reacted for 80min. The mixture was then cooled to room temperature, filtered, washed, and dried under vacuum to obtain isocyanate modified montmorillonite.

[0029] (2) Place 80g of EVA in toluene solution and add 5g of potassium hydroxide to isopropanol solution. Stir to dissolve and mix the two solutions. Stir and react at 60℃ for 7h. Precipitate with ethanol, filter, wash with ethanol, and dry to obtain hydroxylated EVA.

[0030] (3) 12g of epoxytrisiloxane intermediate, 3 terephthalic acid and 0.2g of benzyltriethylammonium chloride were placed in 1,2-dichloroethane and reacted at 80°C for 4h. After cooling to room temperature, the mixture was filtered under reduced pressure, recrystallized and dried to obtain p-hydroxytrisiloxane benzoate.

[0031] (4) Place 10g of p-hydroxytrisiloxane benzoate, 200g of hydroxylated EVA, 1g of isocyanate-modified montmorillonite, 0.1g of stannous octoate, and tetrahydrofuran solvent in a flask, stir evenly, and add 20g of toluene diisocyanate. Heat to 65°C and react for 4h. Cool to room temperature, add water, remove tetrahydrofuran by vacuum distillation, add 1.5g of defoamer BKY-141 and 0.8g of titanate dispersant NXH-1242, stir evenly, and obtain EVA waterproof coating.

[0032] Example 2

[0033] (1) Under nitrogen protection, 60g of activated montmorillonite and 20g of toluene diisocyanate were placed in toluene solvent and stirred and dispersed for 30min. The temperature was raised to 90℃ and reacted for 100min. The mixture was cooled to room temperature, filtered, washed, and dried under vacuum to obtain isocyanate modified montmorillonite.

[0034] (2) Place 80g of EVA in toluene solution and add 5.6g of potassium hydroxide to isopropanol solution. Stir to dissolve and mix the two solutions. Stir and react at 50°C for 7h. Precipitate with ethanol, filter, wash with ethanol, and dry to obtain hydroxylated EVA.

[0035] (3) 12g of epoxytrisiloxane intermediate, 3.5% terephthalic acid and 0.23g of benzyltriethylammonium chloride were placed in 1,2-dichloroethane and reacted at 90°C for 3h. After cooling to room temperature, the mixture was filtered under reduced pressure, recrystallized and dried to obtain p-hydroxytrisiloxane benzoate.

[0036] (4) Place 26g of p-hydroxytrisiloxane benzoate, 200g of hydroxylated EVA, 6g of isocyanate-modified montmorillonite, 0.24g of stannous octoate, and tetrahydrofuran solvent in a flask, stir evenly, and add 25g of toluene diisocyanate. Heat to 70°C and react for 3h. Cool to room temperature, add water, remove tetrahydrofuran by vacuum distillation, add 1.5g of defoamer BKY-141 and 0.8g of titanate dispersant NXH-1242, stir evenly, and obtain EVA waterproof coating.

[0037] Example 3

[0038] (1) Under nitrogen protection, 60g of activated montmorillonite and 20g of toluene diisocyanate were placed in toluene solvent and stirred and dispersed for 20min. The temperature was raised to 80℃ and reacted for 70min. The mixture was then cooled to room temperature, filtered, washed, and dried under vacuum to obtain isocyanate modified montmorillonite.

[0039] (2) Place 80g of EVA in toluene solution and add 5g of potassium hydroxide to isopropanol solution. Stir to dissolve and mix the two solutions. Stir and react at 60℃ for 6h. Precipitate with ethanol, filter, wash with ethanol, and dry to obtain hydroxylated EVA.

[0040] (3) 12g of epoxytrisiloxane intermediate, 3.5% terephthalic acid and 0.15g of benzyltriethylammonium chloride were placed in 1,2-dichloroethane and reacted at 80°C for 3h. After cooling to room temperature, the mixture was filtered under reduced pressure, recrystallized and dried to obtain p-hydroxytrisiloxane benzoate.

[0041] (4) 42g of p-hydroxytrisiloxane benzoate, 200g of hydroxylated EVA, 11g of isocyanate-modified montmorillonite, 0.15g of stannous octoate, and tetrahydrofuran solvent were placed in a flask, stirred evenly, and 20g of toluene diisocyanate was added. The temperature was raised to 65°C and reacted for 4h. The temperature was lowered to room temperature, water was added, and tetrahydrofuran was removed by vacuum distillation. 1.5g of defoamer BKY-141 and 0.8g of titanate dispersant NXH-1242 were added and stirred evenly to obtain EVA waterproof coating.

[0042] Example 4

[0043] (1) Under nitrogen protection, 60g of activated montmorillonite and 20g of toluene diisocyanate were placed in toluene solvent and stirred and dispersed for 30min. The temperature was raised to 80℃ and reacted for 80min. The mixture was then cooled to room temperature, filtered, washed, and dried under vacuum to obtain isocyanate modified montmorillonite.

[0044] (2) Place 80g of EVA in toluene solution and add 5.6g of potassium hydroxide to isopropanol solution. Stir to dissolve and mix the two solutions. Stir and react at 60℃ for 7h. Precipitate with ethanol, filter, wash with ethanol, and dry to obtain hydroxylated EVA.

[0045] (3) 12g of epoxytrisiloxane intermediate, 3 terephthalic acid and 0.2g of benzyltriethylammonium chloride were placed in 1,2-dichloroethane and reacted at 80°C for 3h. After cooling to room temperature, the mixture was filtered under reduced pressure, recrystallized and dried to obtain p-hydroxytrisiloxane benzoate.

[0046] (4) Place 60g of p-hydroxytrisiloxane benzoate, 200g of hydroxylated EVA, 16g of isocyanate-modified montmorillonite, 0.24g of stannous octoate, and tetrahydrofuran solvent in a flask, stir evenly, and add 30g of toluene diisocyanate. Heat to 65°C and react for 3h. Cool to room temperature, add water, remove tetrahydrofuran by vacuum distillation, add 1.5g of defoamer BKY-141 and 0.8g of titanate dispersant NXH-1242, stir evenly, and obtain EVA waterproof coating.

[0047] Comparative Example 1

[0048] (1) Place 80g of EVA in toluene solution and add 5g of potassium hydroxide to isopropanol solution. Stir to dissolve and mix the two solutions. Stir and react at 60℃ for 7h. Precipitate with ethanol, filter, wash with ethanol, and dry to obtain hydroxylated EVA.

[0049] (2) 12g of epoxytrisiloxane intermediate, 3 terephthalic acid and 0.2g of benzyltriethylammonium chloride were placed in 1,2-dichloroethane and reacted at 80°C for 4h. After cooling to room temperature, the mixture was filtered under reduced pressure, recrystallized and dried to obtain p-hydroxytrisiloxane benzoate.

[0050] (3) Place 10g of p-hydroxytrisiloxane benzoate, 200g of hydroxylated EVA, 0.1g of stannous octoate and tetrahydrofuran solvent in a flask, stir evenly and add 20g of toluene diisocyanate, heat to 65℃ and react for 4h, cool to room temperature, add water and remove tetrahydrofuran by vacuum distillation, add 1.5g of defoamer BKY-141 and 0.8g of titanate dispersant NXH-1242, stir evenly to obtain EVA waterproof coating.

[0051] Comparative Example 2

[0052] (1) Under nitrogen protection, 60g of activated montmorillonite and 15g of toluene diisocyanate were placed in toluene solvent and stirred and dispersed for 30min. The temperature was raised to 80℃ and reacted for 80min. The mixture was then cooled to room temperature, filtered, washed, and dried under vacuum to obtain isocyanate modified montmorillonite.

[0053] (2) Place 200g of hydroxylated EVA, 1g of isocyanate-modified montmorillonite, 0.1g of stannous octoate and tetrahydrofuran solvent in a flask, stir evenly and add 20g of toluene diisocyanate, heat to 65℃ and react for 4h, cool to room temperature, add water and remove tetrahydrofuran by vacuum distillation, add 1.5g of defoamer BKY-141 and 0.8g of titanate dispersant NXH-1242, stir evenly to obtain EVA waterproof coating.

[0054] The prepared waterproof coating was applied to a polytetrafluoroethylene (PTFE) sheet to form a 1.5 mm thick film. The film was cured for one week under standard test conditions, and its performance was then tested. The standard test conditions were a temperature of 23 ± 2℃ and a relative humidity of (50 ± 10)%.

[0055] The mechanical properties of the samples were tested using an electronic tensile testing machine.

[0056]

[0057] Example 3 exhibits higher tensile strength and elongation at break, at 11.60 MPa and 124.1%, respectively. Comparative Example 1 shows the lowest tensile strength and elongation at break. This is because montmorillonite was added to Examples 1-5 and Comparative Example 2. Montmorillonite has good mechanical properties, and since Examples 1-5 and Comparative Examples 1-2 both contain excellent cross-linked network structures, they can transfer the impact force received by the material when subjected to impact, thereby enhancing the mechanical properties of the coating.

[0058] The water resistance of the coating was tested in accordance with GB / T 16777-2008 "Test Methods for Waterproof Coatings for Buildings" and GB / T1733-1993 "Determination of Water Resistance of Paint Films".

[0059]

[0060] Examples 1-5 and Comparative Example 1 are all waterproof, but Comparative Example 2 is permeable to water. The water resistance of Examples 1-5 is that there is no peeling or blistering, which is qualified. This is because siloxane structures are contained in Examples 1-5 and Comparative Example 1, which can generate cross-linked structures through hydrolysis and gelation, restricting the entry of water molecules and enhancing the waterproof performance of the material. Moreover, the structure prepared in the present invention has a low surface energy and also has good hydrophobic and waterproof properties. Therefore, the waterproof effect of Comparative Example 2 is the worst.

[0061] The present application has been described in detail above in conjunction with specific embodiments and exemplary examples, but these descriptions should not be construed as limitations on the present application. Those skilled in the art understand that without departing from the spirit and scope of the present application, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present application, and these all fall within the scope of the present application. The protection scope of the present application is subject to the appended claims.

Claims

1. A method for preparing an EVA waterproof coating, characterized in that: The preparation method includes the following steps: (1) 1,1,1,3,5,5,5-heptamethyltrisiloxane and allyl glycidyl ether in a molar ratio of 1:1.05 were placed in an isopropanol solution. An alcoholic solution of chloroplatinic acid was added to the solution under a nitrogen atmosphere. The reaction was carried out at 90°C for 5 h. The solvent was evaporated. Low-boiling substances were removed under vacuum at 85°C and 60 kPa for 30 min. The solution was cooled to room temperature to obtain an epoxytrisiloxane intermediate. (2) The epoxy trisiloxane intermediate, terephthalic acid, and benzyl triethylammonium chloride were placed in 1,2-dichloroethane and reacted at 75-90℃ for 2.5-4h. After cooling to room temperature, the mixture was filtered under reduced pressure, recrystallized, and dried to obtain p-hydroxytrisiloxane benzoate. (3) Place p-hydroxytrisiloxane benzoate, hydroxylated EVA, isocyanate-modified montmorillonite, stannous octoate, and tetrahydrofuran solvent in a flask, stir evenly, add toluene diisocyanate, heat to 60-70℃, react for 2-4 hours, cool to room temperature, add water, remove tetrahydrofuran by vacuum distillation, add defoamer and dispersant, stir evenly, and obtain EVA waterproof coating; The preparation method of hydroxylated EVA in step (3) is as follows: EVA was placed in a toluene solution, and an isopropanol solution of potassium hydroxide was added at 50-70℃. The mixture was stirred and reacted for 5-8 hours. Ethanol was used to precipitate the precipitate, which was then filtered, washed with ethanol, and dried to obtain hydroxylated EVA. The preparation method of isocyanate-modified montmorillonite in step (3) is as follows: Under nitrogen protection, activated montmorillonite and toluene diisocyanate were placed in toluene solvent and stirred and dispersed for 20-40 min. The mixture was heated to react, cooled to room temperature, filtered, washed, and dried under vacuum to obtain isocyanate-modified montmorillonite.

2. The method for preparing the EVA waterproof coating according to claim 1, characterized in that: In step (2), the mass ratio of epoxytrisiloxane intermediate to terephthalic acid is 1:0.2-0.

3.

3. The method for preparing the EVA waterproof coating according to claim 1, characterized in that: In step (2), the amount of benzyltriethylammonium chloride used is 1-1.5% of the total mass of the epoxytrisiloxane intermediate and terephthalic acid.

4. The method for preparing the EVA waterproof coating according to claim 1, characterized in that: In step (3), the mass ratio of p-hydroxytrisiloxane benzoate, hydroxylated EVA, isocyanate-modified montmorillonite, stannous octoate, and toluene diisocyanate is 5-30:100:0.5-8:0.02-0.12:3-20.

5. The method for preparing the EVA waterproof coating according to claim 1, characterized in that: In step (3), the mass ratio of EVA to potassium hydroxide is 100:5-7.

6. The method for preparing the EVA waterproof coating according to claim 1, characterized in that: In step (3), the mass ratio of activated montmorillonite to toluene diisocyanate is 1:0.2-0.

5.

7. The method for preparing the EVA waterproof coating according to claim 1, characterized in that: In step (3), the heating reaction time is 60-100 min and the temperature is 70-90℃.

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