A solvent-free waterproof acrylic coating and preparation method thereof

Abstract

The invention discloses a solvent-free waterproof acrylic coating and a preparation method thereof, and relates to the technical field of coating preparation. A solution of sodium methyl silicate or the like is used as a raw material, and a silicone resin micropowder slurry with a solid content of 55 to 65 wt% is prepared through methods such as seed preparation, precipitation, aging, and modification and removal of hydroxyl groups. The prepared silicone resin micropowder slurry is mixed with auxiliary agents such as a high-elastic acrylic emulsion, a defoamer, and a mildewproof agent to form a solvent-free waterproof acrylic coating. The preparation method of the invention is simple, and the resin micropowder slurry is directly used for coating preparation, thereby eliminating the steps of drying, crushing, and grinding of traditional fillers, and the preparation cycle is shorter and the cost is lower while retaining the compatibility and activity of the fillers.

Description

Technical Field

[0001] The invention relates to the technical field of coating preparation, and in particular to a solvent-free waterproof acrylic coating and a preparation method thereof. Background Art

[0002] Waterproof coatings are applied to the surface of buildings. Through the volatilization of solvents or water or the chemical reaction of the two components, a thin film is formed to isolate the surface of the building from water, thereby playing a waterproof and sealing role. The waterproof film formed by the waterproof coating after curing has certain elongation, elasticity, crack resistance, impermeability and weather resistance, and can play a waterproof, anti-seepage and protective role. Waterproof coatings have good temperature adaptability, simple operation, easy repair and maintenance, and are essential materials for indoor and outdoor decoration.

[0003] Waterproof coatings mainly include polyurethane coatings and acrylic coatings. Acrylic coatings are generally made by mixing acrylic lactic acid, fillers and other additives. However, the fillers in the prior art usually adopt the steps of drying, crushing and grinding, which is relatively cumbersome. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a solvent-free waterproof acrylic coating and a preparation method thereof.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing a solvent-free waterproof acrylic coating comprises the following steps:

[0007] S1: adding the organic silicate solution and the hydrochloric acid solution into deionized water, controlling the temperature at 50-60°C, maintaining the reaction pH value at 2-3, and ripening for 20-60 minutes to obtain a resin micropowder seed solution;

[0008] S2: adding sodium methyl silicate solution and hydrochloric acid solution to the resin micropowder seed solution obtained in step S1 at 50-60° C., maintaining the reaction pH at 2-3, raising the temperature to 80-90° C., and keeping the temperature to mature to obtain a white slurry;

[0009] S3: filter the white powder slurry in step S2 to obtain an acid filter cake, disperse the acid filter cake into a fine slurry at high speed, add a silane coupling agent hydrolyzate to the fine slurry, heat and stabilize at 80-90° C., maintain for 1-3 hours, and obtain a mixed slurry;

[0010] S4: collecting the mixed slurry in step S3 by pressure filtration, and washing the filter cake with water until it becomes neutral to obtain a neutral filter cake;

[0011] S5: Disperse the neutral filter cake obtained in step S4 into a fine concentrated slurry, add the fine concentrated slurry into the acrylic emulsion and mix, add a defoamer and a mildew preventer at the same time, mix well, and obtain an acrylic paint.

[0012] Preferably, the organic silicate solution comprises a mixture of one or more of sodium methyl silicate, potassium methyl silicate, high boiling sodium silicate and high boiling potassium silicate, and its effective solid content (excluding Na2O etc.) is 15-20wt%.

[0013] Preferably, in step S3, the silane coupling agent hydrolyzate is one or more of KH550, KH560, KH570, KH590 and A171, and its added amount is 1-3wt% of the powder slurry solids in the fine slurry.

[0014] Preferably, in step S5, the mass ratio of the acrylic emulsion to the fine concentrated slurry is 1:1 to 0.5.

[0015] Preferably, in step S5, the defoaming agent is NXZ, and the added amount is 0.2-0.5 wt % of the acrylic emulsion.

[0016] Preferably, in step S5, the mildew preventer is LFM, and the added amount is 0.1-0.3 wt % of the acrylic emulsion.

[0017] Preferably, in step S1, the solid content of the resin micro-powder seed solution is 0.8-1.2 wt%.

[0018] Preferably, in step S2, the solid content of the white slurry is 4-6 wt%.

[0019] A solvent-free waterproof acrylic paint is prepared by any of the above preparation methods.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the preparation method of the present invention is simple, and the resin micropowder concentrate is directly used for coating preparation, eliminating the steps of traditional filler drying, crushing and grinding. The preparation cycle is shorter and the cost is lower while retaining the compatibility and activity of the filler. At the same time, when preparing the coating, only the fine concentrate slurry needs to be added to the acrylic emulsion, and then other additives are added, and the process of adding solvent for preparation is omitted, which is more convenient and time-saving. DETAILED DESCRIPTION

[0021] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0022] Example 1

[0023] S1: Deionized water is pumped into the reactor A, stirring is started, the water temperature is controlled at 50°C by circulating water, a mixed solution of sodium methyl silicate and potassium methyl silicate with a solid content of 15wt% (mass ratio is 1:1) and a hydrochloric acid solution (15wt%) are simultaneously pumped into the reactor A, and the reaction pH is controlled to be maintained at 2. After the feeding is completed, the mixture is kept at 50°C and stirred for 30 minutes, and the feeding amount is controlled to obtain a resin micropowder seed solution with a solid content of 0.8wt%;

[0024] S2: Pump the resin powder seed solution in S1 into the reactor B, start stirring, and pump a mixed solution of sodium methyl silicate and potassium methyl silicate with a solid content of 15wt% (mass ratio of 1:1) and a hydrochloric acid solution (15wt%) into the reactor B at 50°C, and control the reaction pH to maintain at 2. After the feeding is completed, heat to 80°C, keep warm and mature for 30 minutes, and control the feeding amount to obtain a white powder slurry with a solid content of 4wt%;

[0025] S3: The white powder obtained in S2 is collected by filter press, and the acid filter cake is placed in a pulper to be dispersed into a fine slurry at high speed. The slurry is pumped into the reactor C, and 1wt% of silane coupling agent hydrolyzate KH550 is added to the slurry under stirring, and the temperature is raised and stabilized at 80°C for 1 hour;

[0026] S4: The slurry is filtered and collected by a filter press, and washed with clean water until it is neutral, and excess water is squeezed out to keep the solid content of the filter cake at 55wt%;

[0027] S5: The neutral filter cake is placed in a pulper and dispersed again into a fine thick slurry, and the high elastic acrylic emulsion and the thick slurry are mixed in a ratio of 1wt%:1wt%, and 0.2wt% of the defoamer NXZ and 0.1wt% of the mildewproof agent LFM based on the mass of the high elastic acrylic emulsion are added, and the mixture is evenly mixed to obtain a waterproof acrylic coating.

[0028] Example 2

[0029] S1: Deionized water is pumped into the reactor A, stirring is started, the water temperature is controlled at 52°C by circulating water, a mixed solution of sodium methyl silicate and high boiling sodium silicate (mass ratio is 1:1) with a solid content of 16wt% and a hydrochloric acid solution (15wt%) are pumped into the reactor A at the same time, and the reaction pH is controlled to be maintained at 2.5. After the feeding is completed, the mixture is kept at 50°C and stirred for 40 minutes, and the feeding amount is controlled to obtain a resin micropowder seed solution with a solid content of 1.0wt%;

[0030] S2: Pump the resin powder seed solution in S1 into the reactor B, start stirring, and pump a mixed solution of sodium methyl silicate and high boiling sodium silicate (mass ratio is 1:1) with a solid content of 16wt% and a hydrochloric acid solution (15wt%) into the reactor B at 52°C, and control the reaction pH to maintain at 2.5. After the feeding is completed, heat to 83°C, keep warm and mature for 30 minutes, and control the feeding amount to obtain a white powder slurry with a solid content of 5wt%;

[0031] S3: Use a filter press to collect the powder slurry obtained in S2, place the acid filter cake in a pulper and disperse it into a fine slurry at high speed, pump the slurry into the reactor C, add 1.5wt% of the powder solid silane coupling agent hydrolyzate KH560 to the slurry under stirring, raise the temperature and stabilize it at 85°C for 1.5h;

[0032] S4: The slurry is filtered and collected by a filter press, and washed with clean water until it is neutral, and excess water is squeezed out to keep the solid content of the filter cake at 56wt%;

[0033] S5: The neutral filter cake is placed in a pulper and dispersed again into a fine thick slurry, and the high elastic acrylic emulsion and the thick slurry are mixed in a ratio of 1wt%:0.8wt%, and 0.3wt% of the defoamer NXZ and 0.15wt% of the mildewproof agent LFM based on the mass of the high elastic acrylic emulsion are added, and the mixture is evenly mixed to obtain a waterproof acrylic coating.

[0034] Example 3

[0035] S1: Deionized water was pumped into the reactor A, stirring was started, the water temperature was controlled at 55°C by circulating water, a mixed solution of sodium methyl silicate and high-boiling potassium silicate (mass ratio of 1:1) with a solid content of 17wt% and a hydrochloric acid solution (15wt%) were simultaneously pumped into the reactor A, and the reaction pH was controlled to be maintained at 2.5. After the feeding was completed, the mixture was kept warm at 50°C and stirred for 45min, and the feeding amount was controlled to obtain a seed solution with a solid content of 1.1wt%;

[0036] S2: Pump the resin powder seed solution in S1 into the reactor B, start stirring, and pump a mixed solution of sodium methyl silicate and high-boiling potassium silicate (mass ratio of 1:1) with a solid content of 17wt% and a hydrochloric acid solution (15wt%) into the reactor B at 58°C, and control the reaction pH to maintain at 2. After the feeding is completed, heat to 85°C, keep warm and mature for 30 minutes, and control the feeding amount to obtain a white powder slurry with a solid content of 4.5wt%;

[0037] S3: Use a filter press to collect the powder slurry obtained in S2, place the acid filter cake in a pulper and disperse it into a fine slurry at high speed, pump the slurry into the reactor C, add 2wt% of the powder slurry solid silane coupling agent hydrolyzate KH570 to the slurry under stirring, raise the temperature and stabilize it at 87°C for 2h;

[0038] S4: The slurry is filtered and collected by a filter press, and washed with clean water until it is neutral, and excess water is squeezed out to keep the solid content of the filter cake at 58wt%;

[0039] S5: placing the neutral filter cake in a pulper and dispersing it again into a fine thick slurry, mixing the high elastic acrylic emulsion and the thick slurry in a ratio of 1wt%:0.7wt%, adding 0.4wt% of the defoamer NXZ and 0.2wt% of the mildew preventer LFM based on the mass of the high elastic acrylic emulsion, and mixing evenly to obtain a waterproof acrylic coating;

[0040] Example 4

[0041] Deionized water was pumped into the reactor A, stirring was started, the water temperature was controlled at 57°C by circulating water, a mixed solution of potassium methyl silicate and high-boiling sodium silicate (mass ratio of 1:1) with a solid content of 18wt% and a hydrochloric acid solution (15wt%) were pumped into the reactor A at the same time, the reaction pH was controlled to be maintained at 2.8, after the feeding was completed, the mixture was kept at 50°C for stirring and aging for 35min, and the feeding amount was controlled to obtain a seed solution with a solid content of 1.2wt%;

[0042] S2: Pump the resin powder seed solution in S1 into reactor B, start stirring, and pump a mixed solution of potassium methyl silicate and high-boiling sodium silicate (mass ratio of 1:1) with a solid content of 18wt% and a hydrochloric acid solution (15wt%) into reactor B at 60°C, and control the reaction pH to maintain at 2.7. After the feeding is completed, heat to 85°C, keep warm and mature for 30 minutes, and control the feeding amount to obtain a white powder slurry with a solid content of 5wt%;

[0043] S3: Use a filter press to collect the powder slurry obtained in S2, place the acid filter cake in a pulper and disperse it into a fine slurry at high speed, pump the slurry into the reactor C, add 2.5wt% of the silane coupling agent hydrolyzate KH590 to the slurry under stirring, raise the temperature and stabilize it at 87°C for 2.5h;

[0044] S4: The slurry is filtered and collected by a filter press, and washed with clean water until it is neutral, and excess water is squeezed out to keep the solid content of the filter cake at 58wt%;

[0045] S5: placing the neutral filter cake in a pulper and dispersing it again into a fine thick slurry, mixing the high elastic acrylic emulsion and the thick slurry in a ratio of 1wt%:0.6wt%, adding 0.5wt% of the defoamer NXZ and 0.25wt% of the mildew preventer LFM based on the mass of the high elastic acrylic emulsion, and mixing evenly to obtain a waterproof acrylic coating;

[0046] Example 5

[0047] S1: Deionized water was pumped into the reactor A, stirring was started, the water temperature was controlled at 60°C by circulating water, a mixed solution of potassium methyl silicate and high-boiling potassium silicate (mass ratio of 1:1) with a solid content of 19wt% and a hydrochloric acid solution (15wt%) were simultaneously pumped into the reactor A, and the reaction pH was controlled to be maintained at 3. After the feeding was completed, the mixture was kept at 50°C for 60min with stirring, and the feeding amount was controlled to obtain a seed solution with a solid content of 1.2wt%;

[0048] S2: Pump the resin powder seed solution in S1 into the reactor B, start stirring, and pump a mixed solution of potassium methyl silicate and high-boiling potassium silicate (mass ratio of 1:1) with a solid content of 19wt% and a hydrochloric acid solution (15wt%) into the reactor B at 60°C, and control the reaction pH to maintain at 3. After the feeding is completed, heat to 90°C, keep warm and mature for 30 minutes, and control the feeding amount to obtain a white slurry with a solid content of 6wt%;

[0049] S3: The powder slurry obtained in S2 is collected by filter press, and the acid filter cake is placed in a pulper and dispersed into a fine slurry at high speed. The slurry is pumped into the reactor C, and the silane coupling agent hydrolyzate A171 in an amount of 3 wt% of the powder slurry solid is added to the slurry under stirring, and the temperature is raised and stabilized at 90°C for 3 hours;

[0050] S4: The slurry is filtered and collected by a filter press, and washed with clean water until it is neutral, and excess water is squeezed out to keep the solid content of the filter cake at 60wt%;

[0051] S5: placing the neutral filter cake in a pulper and dispersing it again into a fine thick slurry, mixing the high elastic acrylic emulsion and the thick slurry in a ratio of 1wt%:0.5wt%, adding 0.5wt% of the defoamer NXZ based on the mass of the high elastic acrylic emulsion and 0.3wt% of the mildew preventer LFM based on the mass of the high elastic acrylic emulsion, and mixing evenly to obtain a waterproof acrylic coating;

[0052] Comparative Example 1

[0053] The ratio is the same as that of Example 1, except that the liquid-solid content of the resin micropowder in S1 is 0.4 wt %.

[0054] Comparative Example 2

[0055] The ratio is the same as that of Example 1, except that the feed amount in S2 is controlled so that the solid content of the slurry is 8 wt %.

[0056] Comparative Example 3

[0057] The ratio is the same as that of Example 1, except that calcium carbonate with a solid content of 55 wt % is used as filler powder and mixed with high-elastic acrylic acid.

[0058] The coatings of the above embodiments and comparative examples were subjected to performance test experiments, and the results are as follows:

[0059] 1. Coating water absorption test

[0060] Cut the dried waterproof coating film into squares, weigh m0, and then put it into water and immerse it for 24 hours. After taking it out, wipe the surface moisture and weigh m1 again to calculate the water absorption rate Q. Q = (m0-m1) / m0×100%.

[0061] 2. Coating contact angle test

[0062] Place the treated paint film horizontally on the drip table, start the corresponding software, and after debugging, slowly rotate the knob to make water droplets appear at the bottom of the capillary, and stop when the water droplets slightly shake, like dripping but not dripping. Then raise the drip table, and when the coating film and the water droplets are about to contact, slowly raise it so that the surface of the coating film and the water droplets are lightly tangent to each other. When the image of the water droplets on the screen is still, freeze the image, take the two points on the edge of the contact between the water droplet and the coating film and the highest point on the image, and get the contact angle.

[0063] 3. Coating impermeability test

[0064] The test was carried out with reference to the water-impermeability test of GB-T 16777-2008. The test results are shown in Table 1.

[0065] Table 1 Performance test results of embodiments and comparative examples

[0066] Water absorption (%) Water contact angle (°) Waterproofness (0.3Mpa, 30min) Example 1 1.28 84.87 impermeable Example 2 1.02 86.81 impermeable Example 3 1.13 84.36 impermeable Example 4 1.79 78.68 impermeable Example 5 1.92 76.63 impermeable Comparative Example 1 4.63 42.15 impermeable Comparative Example 2 4.06 41.23 impermeable Comparative Example 3 10.21 29.24 impermeable

[0067] The preparation methods of Examples 1 to 5 are basically the same. Within the range of preparation conditions, uniformly dispersed waterproof acrylic coatings can be obtained by dispersing and mixing. The slurry is essentially a silicone resin micropowder slurry, which becomes hydrophobic as the coating loses water naturally. The addition of a coupling agent can effectively reduce the proportion of hydrophilic hydroxyl groups in the slurry to enhance its hydrophobicity. Therefore, the proportion of coupling agent added to the slurry, as well as the matching ratio of high elastic acrylic emulsion and concentrated slurry, will affect the waterproof effect. The higher the proportion of coupling agent added and the higher the proportion of slurry when matching, the better the waterproof effect.

[0068] The difference between Comparative Examples 1 and 2 and Example 1 is that the solid content of the seed solution is low or the feed amount is increased, which will easily produce large-sized particles in the process of preparing the white slurry, causing certain difficulties in the subsequent slurry dispersion work. In addition, the particles in the slurry become coarser, and the particle size of the particles is partially uneven when the coating is made, resulting in a decrease in the density of the coating film, making the coating film more susceptible to water seepage, a smaller contact angle, and a deviation in waterproof performance.

[0069] The difference between Comparative Example 3 and Example 1 is that the waterproof effect of calcium carbonate itself is very limited. Even if the ratio is the same as that of Example 1, the waterproof effect is still biased.

[0070] Under the premise that no conflict occurs, those skilled in the art may freely combine and superimpose the above-mentioned additional technical features.

[0071] The above-mentioned embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all these changes and deformations should fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a solvent-free waterproof acrylic coating, characterized in that: The following steps are involved: S1: Add the organic silicate solution and the hydrochloric acid solution into deionized water, control the temperature at 50-60°C, maintain the reaction pH at 2-3, and ripen for 20-60 minutes to obtain the resin micro powder seed solution; In step S1, the solid content of the resin micropowder seed solution is 0.8-1.2wt%; S2: adding sodium methyl silicate solution and hydrochloric acid solution to the resin micropowder seed solution obtained in step S1 at 50-60° C., maintaining the reaction pH at 2-3, raising the temperature to 80-90° C., and keeping the temperature to mature to obtain a white slurry; The solid content of the white slurry is 4-6wt%; S3: filter the white powder slurry in step S2 to obtain an acid filter cake, disperse the acid filter cake into a fine slurry at high speed, add a silane coupling agent hydrolyzate to the fine slurry, heat and stabilize at 80-90° C., maintain for 1-3 h, and obtain a mixed slurry; S4: collecting the mixed slurry in step S3 by pressure filtration, and washing the filter cake with water until it becomes neutral to obtain a neutral filter cake; S5: Disperse the neutral filter cake obtained in step S4 into a fine concentrated slurry, add the fine concentrated slurry into the acrylic emulsion and mix, add a defoamer and a mildew preventer at the same time, mix well, and obtain an acrylic paint.

2. The method for preparing a solvent-free waterproof acrylic coating according to claim 1, characterized in that: In step S1, the organic silicate solution includes one or more mixtures of sodium methyl silicate, potassium methyl silicate, high boiling sodium silicate, and high boiling potassium silicate, and its effective solid content is 15-20 wt%.

3. The method for preparing a solvent-free waterproof acrylic coating according to claim 1, characterized in that: In step S3, the silane coupling agent hydrolyzate is one or more of KH550, KH560, KH570, KH590 and A171, and the amount added is 1-3wt% of the powder slurry solids in the fine slurry.

4. The method for preparing a solvent-free waterproof acrylic coating according to claim 1, characterized in that: In step S5, the mass ratio of the acrylic emulsion to the fine thick slurry is 1:1-0.

5.

5. The method for preparing a solvent-free waterproof acrylic coating according to claim 1, characterized in that: In step S5, the amount of the defoamer added is 0.2-0.5wt% of the acrylic emulsion.

6. The method for preparing a solvent-free waterproof acrylic coating according to claim 1, characterized in that: In step S5, the amount of the antifungal agent added is 0.1-0.3 wt % of the acrylic emulsion.

7. A solvent-free waterproof acrylic coating, characterized in that: The method is prepared by any one of claims 1 to 6.