Preparation method of silicon-aluminum modified barium sulfate and application of silicon-aluminum modified barium sulfate in coating

Abstract

The invention relates to a preparation method of silicon-aluminum modified barium sulfate, which comprises the following steps: adding a sodium silicate solution into barium sulfate slurry for silicon coating, adding an aluminum sulfate solution for aluminum coating, washing to remove sulfate radicals, carrying out solid-liquid separation, and drying a solid-phase substance to obtain the silicon-aluminum modified barium sulfate. Wherein the weight of sodium silicate is 0.5%-1% of the weight of barium sulfate in terms of silicon dioxide, the weight of aluminum sulfate is 2%-3% of the weight of barium sulfate in terms of aluminum oxide, the silicon-aluminum modified barium sulfate prepared by the preparation method is narrow in particle size distribution, and the glossiness of the silicon-aluminum modified barium sulfate is higher than that of similar products by using a resin test; the coating has excellent dispersity and high glossiness, the color separation function of the coating can be improved, titanium dioxide is replaced to achieve high shielding performance, the weather resistance of the coated product is also improved, and the coating can be used in high-end coatings represented by automobile paints.

Description

Technical Field

[0001] The present invention belongs to the technical field of coating compositions, and particularly relates to a preparation method of silicon-aluminum modified barium sulfate and its application in coatings. Background Art

[0002] Barium sulfate has the advantages of strong chemical inertness, good stability, acid and alkali resistance, moderate hardness, high specific gravity, high whiteness, and the ability to absorb harmful rays, and is widely used in various coating industries.

[0003] With the development of technology, in high-end coating fields such as automotive paints, higher standards are required for the gloss, color, transparency, hiding power, weather resistance, etc. of the paint surface. Ordinary barium sulfate is difficult to meet the requirements of its application performance. It is necessary to modify the surface of barium sulfate to improve its dispersibility and affinity and reduce the oil absorption value.

[0004] CN103819937A discloses an aluminum-silicon coated barium sulfate and its preparation method, which uses an alkaline system silicon-aluminum hydrolysis growth process to prepare the coated barium sulfate. A fixed-concentration barium sulfate emulsion is mixed with a fixed-concentration coating mixture (sodium silicate and sodium aluminate mixed solution) in a certain volume ratio, and then through a series of processes such as heating, cooling, stirring, filtering, hot washing, and drying, the surface modification of barium sulfate is completed, and finally the finished product of aluminum-silicon coated barium sulfate is produced.

[0005] CN117304712A discloses a preparation method of modified barium sulfate powder, modified barium sulfate powder and its application. The pre-prepared barium hydroxy sulfate is first subjected to an esterification reaction to obtain an intermediate, and then the intermediate is slurried. By adding a sodium silicate solution first and then a sodium aluminate solution, modified barium sulfate with silicon-aluminum coating is obtained.

[0006] Among them, for the aluminum-silicon coated barium sulfate produced by the preparation method of CN103819937A, its gloss is still difficult to meet the performance requirements of some special coatings (such as high-grade car paint, etc.). Moreover, the process of mixing the coating mixture with the barium sulfate emulsion for coating is likely to result in poor coating effect of barium sulfate, unstable particle size distribution, and low yield. In addition, its preparation method emulsifies the barium sulfate slurry and requires steps such as sealed steam heating and hot washing, with cumbersome steps and low efficiency.

[0007] Although the preparation method of CN117304712A uses a coating process of silicon first and then aluminum to prepare modified barium sulfate, due to the need to prepare barium hydroxy sulfate and intermediate before coating, there is also the problem of cumbersome and complex steps. Summary of the Invention

[0008] In order to overcome the disadvantages of the above-mentioned prior art, the purpose of the present invention is to provide a preparation method of silicon-aluminum modified barium sulfate and its application in coatings, so as to solve the problems of cumbersome process steps and low efficiency in the prior art, and further solve the deficiencies of the existing modified barium sulfate in at least one aspect such as gloss, color, transparency, hiding power, weather resistance, etc.

[0009] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0010] A preparation method of silicon-aluminum modified barium sulfate, comprising the following steps:

[0011] Step 1, adding a sodium silicate solution to the barium sulfate slurry. Calculated as silicon dioxide, the weight of sodium silicate is 0.5% - 1% of the weight of barium sulfate. Subsequently, standing and aging are carried out for silicon coating, specifically growing uniformly on the surface of barium sulfate in the form of silicic acid to form a silicic acid coating layer. At this time, a silicon-coated barium sulfate slurry is obtained.

[0012] Step 2, adding an aluminum sulfate solution to the silicon-coated barium sulfate slurry. Calculated as aluminum oxide, the weight of aluminum sulfate is 2% - 3% of the weight of barium sulfate. Subsequently, standing and aging are carried out for aluminum coating, specifically growing uniformly on the surface of the silicic acid coating layer of barium sulfate in the form of aluminum hydroxide to form an aluminum hydroxide coating layer. At this time, a silicon-aluminum-coated barium sulfate slurry is obtained.

[0013] Step 3, washing the silicon-aluminum-coated barium sulfate slurry to remove sulfate radicals therein.

[0014] Step 4, performing solid-liquid separation on the silicon-aluminum-coated barium sulfate slurry from which sulfate radicals have been removed by means such as filtration, and drying the solid phase material to obtain silicon-aluminum modified barium sulfate.

[0015] The present invention strictly limits the amounts of sodium silicate and aluminum sulfate required for uniformly coating a layer of silicic acid on the surface of barium sulfate particles and then uniformly coating a layer of aluminum hydroxide on the surface of the silicic acid coating layer, and obtains a finished silicon-aluminum modified barium sulfate with smaller particle size and better coating effect, which helps to achieve good dispersibility and gloss. At the same time, the concentration of silicon ions in the sodium silicate solution configured in the present invention is 0.9 - 1 mol / L, and the concentration of aluminum ions in the aluminum sulfate solution is 0.9 - 1 mol / L, which is greatly improved compared with the prior art, and can also improve the coating effect to a certain extent and improve the product gloss.

[0016] In one embodiment, in the barium sulfate slurry used in step 1 of the present invention, the weight content of barium sulfate is preferably 17% - 25%, the particle size of barium sulfate is preferably 0.120 μm - 0.150 μm, and barium sulfate can be prepared by adding barium carbonate to sulfuric acid. Using barium carbonate that meets the requirements (first-class product standard of GB / T 1614 - 2021), a barium sulfate slurry that can be directly coated is prepared. Specifically, based on the dry basis (BaSO4), the weight content of the prepared barium sulfate can reach more than 97.5%. Correspondingly, in the silicon-aluminum modified barium sulfate obtained in step 4, the particle size of the silicon-aluminum modified barium sulfate is 0.10 μm - 0.30 μm, the whiteness ≥ 98%, the typical particle size is 0.269 μm, the whiteness is 98.5, and also by weight, the barium sulfate content ranges from 92% - 98%, typically 93.1%.

[0017] In one embodiment, in step 1 of the present invention, during the process, the system temperature is maintained at 60°C - 80°C, the pH is 9 - 10, and the static aging time is about 2 h - 3 h. Under these process conditions, silicon coating can be better achieved. Further, when the pH value is 9.5, it is easier to create an alkaline environment suitable for silicon-aluminum coating with the corresponding concentration of coating solution in the technical solution of the present invention, and it is easier to form a dense oxide film, which can ultimately improve the gloss of the product.

[0018] Correspondingly, in step 1, the barium sulfate can be slurried to obtain a barium sulfate slurry, and the temperature and pH of the barium sulfate slurry can be adjusted to the system temperature and pH, and the sodium silicate solution can be added in a dropping manner. For example, the barium sulfate slurry with the aforementioned weight content of 17% - 25% can be kept warm in a water bath while stirring, the temperature is controlled at 60°C - 80°C, and during this period, the pH is adjusted to 9 - 10 with a 20% by weight sodium hydroxide solution, and then the sodium silicate solution is slowly added dropwise to the barium sulfate slurry.

[0019] In one embodiment, in step 2 of the present invention, during the process, the system temperature is maintained at 60°C - 80°C, the pH is 7 - 8, and the static aging time is about 2 h - 3 h. Under these process conditions, aluminum coating can be better achieved. Compared with the prior art, the pH value during the single aluminum coating in the present invention is higher. On the one hand, it is beneficial to wash off the excess water-soluble salts in the later stage, and on the other hand, good dispersion performance is ensured through the high pH, improving the gloss.

[0020] In one embodiment, in steps 1 and 2 of the present invention, the above system temperature is maintained by a water bath method, and the pH of the system can be adjusted by adding an alkali (such as NaOH), and the system is continuously stirred at a rotation speed of 100 r / min - 120 r / min. By way of example, in each step, it is preferably that the temperature is constant and the pH is constant.

[0021] In one embodiment, for step 3, the specific implementation method of the water washing in the present invention is as follows:

[0022] (1) Rinse the silicon-aluminum-coated barium sulfate slurry with water;

[0023] (2) Detect with barium chloride solution and wash with water until there is no sulfate in the silicon-aluminum-coated barium sulfate slurry.

[0024] In one embodiment, for the step 4 of drying, the conditions are 100 °C to 110 °C and 6 h to 8 h.

[0025] The silicon-aluminum modified barium sulfate obtained by the preparation method of silicon-aluminum modified barium sulfate of the present invention can be used as a functional component in coatings due to its good gloss and dispersibility, etc., especially for high-end coatings represented by automotive paints. Typical functional components can be, for example, high-gloss functional fillers, powder functional fillers or pigment pastes, etc.

[0026] In one embodiment, in addition to the silicon-aluminum modified barium sulfate, the coating may further include components such as film-forming substances, additives, solvents, etc.

[0027] Exemplarily, the film-forming substances include but are not limited to one or several of alkyd resins, epoxy resins, polyurethane resins, linseed oil, tung oil, acrylic latex or polyvinyl chloride latex, the additives include but are not limited to one or several of defoamers, leveling agents, dispersants or thickeners, and the solvents include but are not limited to aqueous solvents, oil-based solvents or organic solvents. When in use, the corresponding film-forming substances, additives and solvents can be selected and added according to the target use.

[0028] Compared with the prior art CN117304712A, the present invention does not need to prepare barium hydroxy sulfate and esterification reaction intermediates, but directly uses the barium sulfate slurry as the coating object. Compared with the prior art CN103819937A, the present invention adopts a coating process of silicon first and then aluminum, and does not need to emulsify the barium sulfate slurry. Therefore, the present invention reduces the process steps, thereby improving the preparation efficiency, saving resource input, and on this basis, combined with the selection of the concentration of the coating agent, improving the coating effect and increasing the yield of good products.

[0029] Moreover, compared with the prior art CN117304712A and CN103819937A which use sodium aluminate solution, the present invention uses aluminum sulfate solution for aluminum coating, which can make the free barium in the solution react with sulfate to generate barium sulfate to increase the barium sulfate content and avoid the generation of heavy metal soluble barium. And the pH value after aluminum coating is 7 - 8, which can be controlled to wash away the excess water-soluble salts during water washing, improve the dispersibility of the finished product and enhance the gloss.

[0030] The silicon-aluminum modified barium sulfate prepared by the present invention has a narrow product particle size distribution. When tested with resin, its glossiness is higher than that of similar products. It has excellent dispersibility and high glossiness, can improve the function of preventing color separation in coatings, replace titanium dioxide to achieve high hiding power, and the weather resistance of the product is also improved after coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of the preparation method of the silicon-aluminum modified barium sulfate of the present invention.

[0032] Figure 2 is the particle size of the silicon-aluminum modified barium sulfate obtained in Example 1 of the present invention. The abscissa is the particle size in μm, and the ordinate is the differential distribution in %.

[0033] Figure 3 is the particle size of the silicon-aluminum modified barium sulfate obtained in Example 2 of the present invention. The abscissa is the particle size in μm, and the ordinate is the differential distribution in %.

[0034] Figure 4 is the particle size of the silicon-aluminum modified barium sulfate obtained in Example 3 of the present invention. The abscissa is the particle size in μm, and the ordinate is the differential distribution in %. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The following will describe in detail the embodiments of the present invention with reference to the drawings and examples.

[0036] As mentioned above, in the prior art, CN117304712A prepared silicon-aluminum modified barium sulfate by first silicon and then aluminum, with secondary coating. However, it relies on the intermediate obtained from barium hydroxy sulfate and esterification reaction, so the process is complex and cumbersome. Therefore, the present invention optimizes the pretreatment process of barium sulfate and controls the dosage of raw materials, so as to directly prepare silicon-aluminum modified barium sulfate from barium sulfate slurry as the raw material, thus reducing the two steps of preparing barium hydroxy sulfate and preparing the coating intermediate by esterification reaction in patent CN117304712A, greatly reducing the process procedures, reducing the preparation difficulty, and controlling the preparation cost.

[0037] The following are several embodiments of the present invention.

[0038] Example 1

[0039] Reference Figure 1 , the preparation method of the silicon-aluminum modified barium sulfate in this example includes the following steps:

[0040] Step 1, pretreatment of barium sulfate.

[0041] Place a slurry of barium sulfate with a weight content of 25% (produced by Shaanxi Fuhua Chemical Co., Ltd., D50 is 0.15 μm, production batch number CP - 20240729006) in a 65°C water bath and stir at a speed of 120 r / min. During this period, adjust the pH value of the barium sulfate slurry to 9 with a 20% NaOH solution by weight.

[0042] Step 2, silicon coating.

[0043] Slowly add sodium silicate solution to the barium sulfate slurry obtained in Step 1 according to the ratio of the weight of silicon dioxide to the weight of barium sulfate being 0.5%. Continue to stir in a 65°C water bath at a speed of 120 r / min. During this period, maintain the pH value of the mixed system at 9 by adding a 20% NaOH solution by weight. After the addition is complete, let it stand and age for 2 hours to allow the growth of silica evenly on the surface of barium sulfate, obtaining a silicon-coated barium sulfate slurry.

[0044] Step 3, aluminum coating.

[0045] Slowly add aluminum sulfate solution to the silicon-coated barium sulfate slurry obtained in Step 2 according to the ratio of aluminum oxide to the weight of barium sulfate being 2%. Continue to stir in a 65°C water bath at a speed of 120 r / min. During this period, adjust the pH value of the mixed system to 7 by adding a 20% NaOH solution by weight. After the addition is complete, let it stand and age for 2 hours to allow the growth of aluminum hydroxide evenly on the surface of barium sulfate, obtaining a silicon-aluminum-coated barium sulfate slurry.

[0046] Step 4, post-treatment.

[0047] Wash the silicon-aluminum-coated barium sulfate slurry obtained in Step 3, and use barium chloride solution to detect the sulfate ion concentration in the silicon-aluminum-coated barium sulfate slurry until there is no sulfate ion in the slurry. Then, perform filtration to separate the solid and liquid. Take the solid substance obtained after filtration and dry it at 105°C for 6 hours, and then crush it to obtain silicon-aluminum-modified barium sulfate.

[0048] Use a laser particle size analyzer to detect the particle size of the prepared silicon-aluminum-modified barium sulfate. The results are as Figure 2 shown. The D10 of this silicon-aluminum-modified barium sulfate is 0.065 μm, D25 is 0.088 μm, D50 is 0.125 μm, D75 is 0.178 μm, D90 is 0.246 μm, D97 is 0.458 μm, D(3,2) is 0.119 μm, D(4,3) is 0.156 μm, Span is 1.445, the volume specific surface area (m 2 / cm 3 ) is 50.566, and the weight specific surface area (m 2The weight (kg) was 50566.460, the weighted residual (%) was 4.548, and D90 - D10 = 0.181, indicating that the particle size distribution of the silicon-aluminum modified barium sulfate obtained in this example was narrow and the particle size distribution was stable.

[0049] Example 2

[0050] Reference Figure 1 , the preparation method of the silicon-aluminum modified barium sulfate in this example includes the following steps:

[0051] Step 1, pretreatment of barium sulfate.

[0052] A slurry of barium sulfate with a weight content of 17% (produced by Shaanxi Fuhua Chemical Co., Ltd., D50 is 0.15 μm, production batch number CP - 20240729006) was placed in an 80°C water bath and stirred at a speed of 120 r / min. During this period, the pH value of the barium sulfate slurry was adjusted to 9 with a 20% NaOH solution by weight concentration.

[0053] Step 2, silicon coating.

[0054] According to the ratio that the weight of silicon dioxide is 1% of the weight of barium sulfate, the sodium silicate solution was slowly added dropwise to the barium sulfate slurry obtained in Step 1, and continuous stirring was carried out at a speed of 120 r / min in an 80°C water bath. During this period, the pH value of the mixed system was maintained at 9 by adding a 20% NaOH solution by weight concentration. After the addition was completed, it was left to stand and age for 2 hours to enable the uniform growth of silicic acid on the surface of barium sulfate, obtaining a silicon-coated barium sulfate slurry.

[0055] Step 3, aluminum coating.

[0056] According to the ratio that aluminum oxide is 3% of the weight of barium sulfate, the aluminum sulfate solution was slowly added dropwise to the silicon-coated barium sulfate slurry obtained in Step 2, and continuous stirring was carried out at a speed of 120 r / min in an 80°C water bath. During this period, the pH value of the mixed system was adjusted to 7 by adding a 20% NaOH solution by weight concentration. After the addition was completed, it was left to stand and age for 2 hours to enable the uniform growth of aluminum hydroxide on the surface of barium sulfate, obtaining a silicon-aluminum-coated barium sulfate slurry.

[0057] Step 4, post-treatment.

[0058] The silicon-aluminum-coated barium sulfate slurry obtained in Step 3 was washed with water, and the sulfate ion concentration in the silicon-aluminum-coated barium sulfate slurry was detected using barium chloride solution until there was no sulfate ion in the slurry. Subsequently, filtration was carried out to separate the solid and liquid. The solid substance obtained after filtration was dried at 105°C for 6 hours and pulverized to obtain silicon-aluminum modified barium sulfate.

[0059] The particle size of the prepared silicon-aluminum modified barium sulfate was detected using a laser particle size analyzer, and the results are as Figure 3As shown, the D10 of the silicon-aluminum modified barium sulfate is 0.067 μm, D25 is 0.091 μm, D50 is 0.132 μm, D75 is 0.195 μm, D90 is 0.298 μm, D97 is 0.570 μm, D(3,2) is 0.125 μm, D(4,3) is 0.175 μm, Span is 1.744, the volume specific surface area (m 2 / cm 3 ) is 47.967, the weight specific surface area (m 2 / kg) is 47966.653, the weighted residual (%) is 4.039, D90 - D10 = 0.231, indicating that the particle size distribution of the silicon-aluminum modified barium sulfate obtained by this method is narrow and the particle size distribution is stable.

[0060] Example 3

[0061] Reference Figure 1 , the preparation method of the silicon-aluminum modified barium sulfate in this example includes the following steps:

[0062] Step 1, pretreatment of barium sulfate.

[0063] The slurry of fine precipitated barium sulfate with a weight content of 25% (produced by Shaanxi Fuhua Chemical Co., Ltd., D50 is 0.75 μm, production batch number CP-20240729002) is placed in a 65°C water bath and stirred at a speed of 120 r / min. During this period, the pH value of the barium sulfate slurry is adjusted to 9 with a 20% NaOH solution by weight. Here, fine precipitation means that the particle size of barium sulfate is about 0.69 μm, and compared with the barium sulfate in Example 1 and Example 2, its product particle size is larger.

[0064] Step 2, silicon coating.

[0065] According to the ratio that the weight of silicon dioxide is 0.5% of the weight of barium sulfate, the sodium silicate solution is slowly added dropwise to the barium sulfate slurry obtained in Step 1, and the mixture is continuously stirred at a speed of 120 r / min in a 65°C water bath. During this period, the pH value of the mixed system is maintained at 9 by adding a 20% NaOH solution by weight. After the addition is completed, it is left to stand and age for 2 hours to allow the growth of silica evenly on the surface of barium sulfate, obtaining a silicon-coated barium sulfate slurry.

[0066] Step 3, aluminum coating.

[0067] According to the ratio that aluminum oxide is 2% of the weight of barium sulfate, slowly drop the aluminum sulfate solution into the barium sulfate slurry coated with silicon obtained in Step 2, and continue to stir continuously in a water bath at 65°C at a rotation speed of 120 r / min. During this period, adjust the pH value of the mixed system to 7 by adding a NaOH solution with a weight concentration of 20%. After the dropping is completed, let it stand and age for 2 hours to enable aluminum hydroxide to grow uniformly on the surface of barium sulfate, obtaining a barium sulfate slurry coated with silicon and aluminum.

[0068] Step 4, post-treatment.

[0069] Wash the barium sulfate slurry coated with silicon and aluminum obtained in Step 3, and use barium chloride solution to detect the sulfate ion concentration in the barium sulfate slurry coated with silicon and aluminum until there is no sulfate ion in the slurry. Then carry out filtration to separate the solid and liquid. Take the solid substance obtained after filtration, dry it at 105°C for 6 hours, and pulverize it to obtain silicon and aluminum modified barium sulfate.

[0070] Use a laser particle size analyzer to detect the particle size of the prepared silicon and aluminum modified barium sulfate, and the results are as Figure 4 shown. The D10 of this silicon and aluminum modified barium sulfate is 0.108 μm, D25 is 0.227 μm, D50 is 0.690 μm, D75 is 1.336 μm, D90 is 2.220 μm, D97 is 3.216 μm, D(3,2) is 0.319 μm, D(4,3) is 0.955 μm, Span is 3.062, the volume specific surface area (m 2 / cm 3 ) is 18.830, the weight specific surface area (m 2 / kg) is 18829.898, the weighted residual (%) is 2.021, and D90 - D10 = 2.112. Since the particle size of the fine precipitated barium sulfate is larger than that of the barium sulfate in Example 1 and Example 2, the particle size distribution of the obtained silicon and aluminum modified barium sulfate is relatively wide.

[0071] Example 4

[0072] Reference Figure 1 , the preparation method of the silicon and aluminum modified barium sulfate in this example includes the following steps:

[0073] Step 1, barium sulfate pretreatment.

[0074] Place the barium sulfate slurry with a weight content of 20% (produced by Shaanxi Fuhua Chemical Co., Ltd., D50 is 0.15 μm, production batch number CP - 20240729006) in an 80°C water bath, stir at a rotation speed of 120 r / min, and adjust the pH value of the barium sulfate slurry to 10 with a NaOH solution with a weight concentration of 20% during this period.

[0075] Step 2, silicon coating.

[0076] According to the ratio that the weight of silicon dioxide is 0.6% of the weight of barium sulfate, the sodium silicate solution was slowly added dropwise to the barium sulfate slurry obtained in Step 1, and continuous stirring was carried out in a water bath at 80 °C at a rotation speed of 120 r / min. During this period, the pH value of the mixed system was maintained at 10 by adding a NaOH solution with a weight concentration of 20%. After the addition was completed, it was left to stand and age for 2 hours to enable the uniform growth of silica on the surface of barium sulfate, obtaining a silica-coated barium sulfate slurry.

[0077] Step 3, aluminum coating.

[0078] According to the ratio that aluminum oxide is 2.5% of the weight of barium sulfate, the aluminum sulfate solution was slowly added dropwise to the silica-coated barium sulfate slurry obtained in Step 2, and continuous stirring was carried out in a water bath at 60 °C at a rotation speed of 120 r / min. During this period, the pH value of the mixed system was adjusted to 8 by adding a NaOH solution with a weight concentration of 20%. After the addition was completed, it was left to stand and age for 2 hours to enable the uniform growth of aluminum hydroxide on the surface of barium sulfate, obtaining a silica-aluminum-coated barium sulfate slurry.

[0079] Step 4, post-treatment.

[0080] The silica-aluminum-coated barium sulfate slurry obtained in Step 3 was washed with water, and the sulfate ion concentration in the silica-aluminum-coated barium sulfate slurry was detected using a barium chloride solution until no sulfate ions remained in the slurry. Subsequently, filtration was carried out to separate the solid and liquid. The solid substance obtained after filtration was dried at 110 °C for 6 hours and then pulverized to obtain silica-aluminum-modified barium sulfate.

[0081] Example 5

[0082] Reference Figure 1 , the preparation method of the silica-aluminum-modified barium sulfate in this example includes the following steps:

[0083] Step 1, barium sulfate pretreatment.

[0084] A slurry of barium sulfate with a weight content of 18% (produced by Shaanxi Fuhua Chemical Co., Ltd., D50 is 0.15 μm, production batch number CP-20240729006) was placed in a water bath at 60 °C and stirred at a rotation speed of 100 r / min. During this period, the pH value of the barium sulfate slurry was adjusted to 9.5 using a NaOH solution with a weight concentration of 20%.

[0085] Step 2, silica coating.

[0086] According to the proportion that the weight of silicon dioxide is 0.65% of the weight of barium sulfate, slowly drop the sodium silicate solution into the barium sulfate slurry obtained in Step 1, and continuously stir at a rotation speed of 110 r / min in a 60°C water bath. During this period, maintain the pH value of the mixed system at 9.5 by adding a 20% (by weight) NaOH solution. After the dropping is completed, let it stand and age for about 3 hours to allow the growth of silica evenly on the surface of barium sulfate, obtaining a silica-coated barium sulfate slurry.

[0087] Step 3, aluminum coating.

[0088] According to the proportion that aluminum oxide is 2.8% of the weight of barium sulfate, slowly drop the aluminum sulfate solution into the silica-coated barium sulfate slurry obtained in Step 2, and continuously stir at a rotation speed of 120 r / min in an 80°C water bath. During this period, adjust the pH value of the mixed system to 7.5 by adding a 20% (by weight) NaOH solution. After the dropping is completed, let it stand and age for about 3 hours to allow the growth of aluminum hydroxide evenly on the surface of barium sulfate, obtaining a silica-aluminum-coated barium sulfate slurry.

[0089] Step 4, post-treatment.

[0090] Wash the silica-aluminum-coated barium sulfate slurry obtained in Step 3, and use barium chloride solution to detect the sulfate ion concentration in the silica-aluminum-coated barium sulfate slurry until there is no sulfate ion in the slurry. Then carry out filtration to separate the solid and liquid. Take the solid substance obtained after filtration, dry it at 100°C for 8 hours, and pulverize it to obtain silica-aluminum-modified barium sulfate.

[0091] Comparative Example 1

[0092] The difference from Example 2 is that in Step 2, the weight ratio range of silicon dioxide to barium sulfate is between 0.5% and 1% defined in the present invention, but different from Example 2, and in Step 3, the weight ratio range of aluminum oxide to barium sulfate is not between 2% and 3% defined in the present invention. Specifically as follows:

[0093] Step 1, barium sulfate pretreatment.

[0094] It is the same as the pretreatment steps and parameters of Example 2.

[0095] Step 2, silica coating.

[0096] The weight of silicon dioxide is 0.5% of the weight of barium sulfate, and the other steps and parameters are the same as those of Example 2.

[0097] Step 3, aluminum coating.

[0098] Aluminum oxide is 3.5% of the weight of barium sulfate, and the other steps and parameters are the same as those of Example 2.

[0099] Step 4, post-treatment.

[0100] The steps and parameters are the same as those in the post-treatment of Example 2.

[0101] Comparative Example 2

[0102] The difference from Example 1 is that aluminum coating is carried out first and then silicon coating. Specifically as follows:

[0103] Step 1, Barium sulfate pretreatment.

[0104] The steps and parameters are the same as those in the pretreatment of Example 1.

[0105] Step 2, Aluminum coating.

[0106] According to the proportion that aluminum oxide is 2% of the weight of barium sulfate, the aluminum sulfate solution is slowly dropped into the barium sulfate slurry obtained in Step 1, and the mixture is continuously stirred at a speed of 120 r / min in a 65°C water bath. During this period, the pH value of the mixed system is adjusted to 7 by adding a 20% (by weight) NaOH solution. After the dropping is completed, it is left standing for aging for 2 hours to enable aluminum hydroxide to grow uniformly on the surface of barium sulfate, obtaining an aluminum-coated barium sulfate slurry.

[0107] Step 3, Silicon coating.

[0108] According to the proportion that silicon dioxide is 0.5% of the weight of barium sulfate, the sodium silicate solution is slowly dropped into the aluminum-coated barium sulfate slurry obtained in Step 2, and the mixture is continuously stirred at a speed of 120 r / min in a 65°C water bath. During this period, the pH value of the mixed system is maintained at 9 by adding a 20% (by weight) NaOH solution. After the dropping is completed, it is left standing for aging for 2 hours to enable silicic acid to grow uniformly on the surface of barium sulfate, obtaining an aluminum-silicon-coated barium sulfate slurry.

[0109] Step 4, Post-treatment.

[0110] Wash the aluminum-silicon-coated barium sulfate slurry obtained in Step 3, detect the sulfate ion concentration in the aluminum-silicon-coated barium sulfate slurry using barium chloride solution until there is no sulfate ion in the slurry, and then perform filtration to separate the solid and liquid. Take the solid substance obtained after filtration, dry it at 100°C for 6 hours, and pulverize it to obtain silicon-aluminum modified barium sulfate.

[0111] Comparative Example 3

[0112] The difference from Example 1 is that silicon and aluminum are coated simultaneously. Specifically as follows:

[0113] Step 1, Barium sulfate pretreatment.

[0114] The steps and parameters are the same as those in the pretreatment of Example 1.

[0115] Step 2, Simultaneously carry out silicon-aluminum coating.

[0116] According to the proportion that aluminum oxide is 2% of the weight of barium sulfate and the proportion that silicon dioxide is 0.5% of the weight of barium sulfate, mix the aluminum sulfate solution and sodium silicate solution and slowly drop them into the barium sulfate slurry obtained in Step 1. Continue to stir continuously in a 65°C water bath at a speed of 120 r / min. During this period, adjust the pH value of the mixed system to 7 by adding a 20% NaOH solution by weight. After the dropping is completed, let it stand and age for 2 hours to enable the coating agent to grow evenly on the surface of barium sulfate, and obtain a silicon-aluminum-coated barium sulfate slurry.

[0117] Step 3, post-treatment.

[0118] Wash the silicon-aluminum-coated barium sulfate slurry obtained in Step 2, detect the sulfate ion concentration in the silicon-aluminum-coated barium sulfate slurry using barium chloride solution until there is no sulfate ion in the slurry, and then perform filtration to separate the solid and liquid. Take the solid substance obtained after filtration and dry it at 105°C for 6 hours, and then crush it to obtain modified barium sulfate coated with both silicon and aluminum.

[0119] As other embodiments of the present invention, barium sulfate can be prepared by reacting barium carbonate with sulfuric acid. By controlling the process conditions, barium sulfate particles with a particle size of 0.120 μm to 0.150 μm can be obtained. This barium sulfate with a small particle size has better dispersion performance and gloss after being coated with silicon and aluminum.

[0120] Perform performance evaluation on the products obtained in the above-mentioned examples and comparative examples, including:

[0121] 1. Detect the barium sulfate content, whiteness, particle size, oil absorption, silicon ion content, and aluminum ion content of the modified barium sulfate prepared in each example and comparative example. Use a laser particle size analyzer to detect the particle size and a gloss meter to detect the gloss. The detection results are shown in Table 1.

[0122] Table 1 Detection results of each example and comparative example

[0123] Test Items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Barium Sulfate Content, wt% 97.38 95.52 97.13 89.16 97.21 96.53 Whiteness 98.2 98 98.1 98 98 98 Particle Size (D50), μm 0.125 0.132 0.690 0.130 0.131 0.132 Oil Absorption 17.1 18 20 18 20 21 Silicon Ion Content, wt% 0.468 0.519 0.404 0.484 0.401 0.412 Aluminum Ion Content, wt% 0.60 1.01 0.504 2.10 0.70 0.63 Gloss (60°C), % 189.3 189.7 188.2 187.1 166.37 156.23

[0124] As can be seen from Table 1, firstly, the coating sequence of aluminum and silicon affects the gloss of modified barium sulfate. Compared with the methods of modifying barium sulfate by coating aluminum first and then silicon (Comparative Example 2) and coating silicon and aluminum simultaneously (Comparative Example 3), the gloss of the modified barium sulfate obtained by the method of coating silicon first and then aluminum (Examples 1 to 3, Comparative Example 1) is significantly improved. Secondly, the smaller the particle size of the barium sulfate raw material, the higher the gloss of the modified barium sulfate. By selecting different barium sulfate raw materials (Examples 1 and 3) and modifying them by coating silicon first and then aluminum, the smaller the particle size of the barium sulfate raw material, the higher the gloss of the obtained modified barium sulfate. And the influence of the coating sequence on the gloss is much greater than that of the particle size of the barium sulfate raw material on the gloss. Finally, the addition amount of aluminum ions affects the gloss of modified barium sulfate. By selecting the same barium sulfate raw material and the same modification method of coating silicon first and then aluminum, with different addition amounts of aluminum ions, the gloss of the obtained modified barium sulfate is significantly different. And when aluminum oxide is 2% - 3% of the weight of barium sulfate, the gloss of the obtained modified barium sulfate is higher. The above results show that when silica is 0.5% - 1% of the weight of barium sulfate, and at the same time aluminum oxide is 2% - 3% of the weight of barium sulfate, coating silicon first and then aluminum can obtain a modified barium sulfate product with significantly improved gloss, and the modified barium sulfate has a high barium sulfate content, high whiteness, narrow and stable particle size distribution.

[0125] 2. Detect the viscosity, fineness and gloss of the silicon-aluminum modified barium sulfate prepared in Example 2 above and the existing barium sulfate to further evaluate the properties of the barium sulfate prepared by the method of the present invention. The detection results are shown in Table 2.

[0126] Table 2 Detection Results of Examples and Existing Barium Sulfate

[0127]

[0128] As can be seen from Table 2, the gloss of the silicon-aluminum modified barium sulfate obtained by the method of the present invention is close to that of silicon-aluminum modified barium sulfate B-30, and the gloss after modification is significantly improved compared with that before modification (the fine precipitated barium sulfate in Example 3, the barium sulfate in Examples 1 and 2), indicating that the barium sulfate modified by the method of the present invention has high gloss.

[0129] Based on the properties of the silicon-aluminum modified barium sulfate obtained by the present invention, which has good gloss and dispersion performance, it can be applied in high-end coatings represented by automotive paints, specifically to replace the existing barium sulfate, and the film-forming substances, additives, solvents and other components in the coatings can continue to use the existing reagents.

[0130] Specifically, in one embodiment, 40% of a dispersion resin, 40% of the silicon-aluminum modified barium sulfate of the present invention, and 20% of a xylene solvent are mixed by weight, where the silicon-aluminum modified barium sulfate serves as a filler. High-speed grinding and dispersion are carried out at different speeds with and without a dispersant (the addition amount is 0.3% of the weight of the mixed system). The grinding conditions are as follows: a high-speed disperser, at room temperature, maintaining for 20 min at a speed of 1500 RPM, and then maintaining for 20 min at a speed of 2000 RPM. The weight ratio of the slurry to zirconia beads is 1:1, and the dispersion performance is shown in Table 3.

[0131] Table 3 Dispersion Detection Results

[0132] Grinding Conditions Without Dispersant With Dispersant (0.3wt%) 1500 revolutions for 20 minutes 20.0μm 15.0μm 2000 revolutions for 20 minutes 15.0μm 10.0μm

[0133] The silicon-aluminum modified barium sulfate of the present invention is used in a high-gloss coating, and its preparation method is as follows: First, acrylic resin, titanium dioxide, silicon-aluminum modified barium sulfate, a dispersant, an antifoaming agent, a leveling agent, and xylene are mixed and then dispersed at high speed for 15 - 20 minutes. Then, a leveling agent is added, and after medium-speed dispersion for 5 minutes, filtration is carried out to obtain the product.

[0134] The embodiments of the present invention provide two formulations, namely Formulation A and Formulation B, as shown in Table 4 below.

[0135] Table 4 Components of High-Gloss Coating Formulation A and Formulation B

[0136] Raw Material Name Formulation A (wt%) Formulation B (wt%) Acrylic Resin 54.5 54.5 Defoamer 0.1 0.1 Dispersant 0.2 0.2 Leveling Agent 0.2 0.2 Titanium Dioxide 30 20 Silicon-Aluminum Modified Barium Sulfate / 10 Xylene 15 15

[0137] The product condition performance is as shown in Table 5 below.

[0138] Table 5 Performance of High-Gloss Coating Formulation A and Formulation B

[0139]

[0140] It can be seen from Tables 3, 4, and 5 above that the silicon-aluminum modified barium sulfate of the present invention can make the dispersion of the coating more uniform, thereby improving the color rendering efficiency. Also, thus, within an appropriate range, the silicon-aluminum modified barium sulfate can replace part of the pigment components without affecting the color concentration and hiding power of the pure color paste and color paint, and when adjusting the color, it can also improve the color concentration of the color paint to a certain extent.

[0141] Meanwhile, after adding the silicon-aluminum modified barium sulfate to the system, the gloss of the paint film is improved, it is easier to level, the bubbles are reduced, and the smoothness is also improved to a certain extent. Based on the easy-dispersing property of the silicon-aluminum modified barium sulfate, it can be dispersed at high speed by selecting a suitable dispersant. Finally, the silicon-aluminum modified barium sulfate in the coating is not easy to precipitate, the gloss of the paint film of the coating will not decrease, and at the same time, the silicon-aluminum modified barium sulfate also has a certain anti-floating color and blooming effect.

[0142] According to the above basic properties, generally speaking, by adding barium sulfate modified with silicon and aluminum at a weight ratio of 10%, the performance of the paint film can be effectively improved, mainly by improving the gloss, leveling property, defoaming property, etc. of the paint film. At the same time, it also helps to improve the mechanical strength of the paint film, slightly improve the smoothness and color concentration of the color paste, and can reduce the sedimentation of pigments in the paint.

[0143] From the perspective of cost, if barium sulfate modified with silicon and aluminum is used to replace part of the pigments, the cost of the paint can be greatly reduced.

[0144] Therefore, the main uses of the barium sulfate modified with silicon and aluminum in the present invention in paints include high-gloss functional fillers, powder functional fillers and pigment pastes.

[0145] When used as a high-gloss functional filler, compared with traditional fillers such as calcium carbonate, talcum powder, alumina, and ordinary barium sulfate, the barium sulfate modified with silicon and aluminum has extremely little influence on the gloss of the paint film, and its weather resistance, acid and alkali resistance, easy dispersibility and non-precipitation property are even incomparable to other traditional fillers. Adding barium sulfate modified with silicon and aluminum at a total weight of 20% as a filler in the ink can enhance the ink skeleton while ensuring that the gloss of the ink does not decrease and the hiding power remains unchanged. When adding barium sulfate modified with silicon and aluminum at a total weight of 10-20% as a filler in the automotive primer, the gloss of the paint film will not decrease, and the gloss can still reach more than 90%, which can achieve the same gloss as the topcoat.

[0146] When used as a powder functional filler, the barium sulfate modified with silicon and aluminum has a small oil absorption, good leveling, high gloss, good hiding power and good weather resistance. It can not only replace part of the titanium dioxide without reducing the hiding power, but also significantly improve the leveling of the paint film, especially suitable for high-gloss thin-film powder coatings.

[0147] When used as a pigment paste, the barium sulfate modified with silicon and aluminum can replace 10% by weight of titanium dioxide in the titanium white paste (for example, originally 60 parts by weight of titanium dioxide were required, now 54 parts by weight of titanium dioxide are added, and 6 parts by weight of barium sulfate modified with silicon and aluminum are added). Among organic pigments, the effect of applying the barium sulfate modified with silicon and aluminum of the present invention is the best for phthalocyanine blue and phthalocyanine green, and it can be applied in black pigment pastes.

Claims

1. A preparation method of silicon-aluminum modified barium sulfate, characterized in that, It includes the following steps: Step 1: Add a sodium silicate solution to the barium sulfate slurry. Based on silicon dioxide, the weight of sodium silicate is 0.5% - 1% of the weight of barium sulfate. Then, let it stand for aging to carry out silicon coating to obtain a silicon-coated barium sulfate slurry; Step 2: Add an aluminum sulfate solution to the silicon-coated barium sulfate slurry. Based on aluminum oxide, the weight of aluminum sulfate is 2% - 3% of the weight of barium sulfate. Then, let it stand for aging to carry out aluminum coating to obtain a silicon-aluminum-coated barium sulfate slurry; Step 3: Wash the silicon-aluminum-coated barium sulfate slurry to remove sulfate radicals therein; Step 4: Carry out solid-liquid separation on the silicon-aluminum-coated barium sulfate slurry after removing sulfate radicals, and dry the solid substance to obtain silicon-aluminum-modified barium sulfate.

2. The preparation method of the silicon-aluminum modified barium sulfate according to claim 1, characterized in that, By weight, in the barium sulfate slurry in Step 1, the content of barium sulfate is 17% - 25%; in the silicon-aluminum-modified barium sulfate obtained in Step 4, the content of barium sulfate is 92% - 98%, and the whiteness of the silicon-aluminum-modified barium sulfate ≥ 98%.

3. The preparation method of the silicon-aluminum modified barium sulfate according to claim 1, characterized in that, In Step 1, keep the system temperature at 60°C - 80°C and the pH at 9 - 10 during the process; in Step 2, keep the system temperature at 60°C - 80°C and the pH at 7 - 8 during the process. The standing and aging time for both Step 1 and Step 2 is 2h - 3h.

4. The preparation method of the silicon-aluminum modified barium sulfate according to claim 3, characterized in that, In Step 1, prepare a barium sulfate slurry by slurrying barium sulfate, and adjust the temperature and pH of the barium sulfate slurry to the system temperature and pH, and add the sodium silicate solution in a dropping manner.

5. The preparation method of the silicon-aluminum modified barium sulfate according to claim 1, characterized in that, In Step 1 and Step 2, maintain the temperature of the system through a water bath, adjust the pH of the system by adding an alkali, and continuously stir the system at a rotation speed of 100r / min - 120r / min.

6. The preparation method of the silicon-aluminum modified barium sulfate according to claim 1, characterized in that, In Step 4, the drying conditions are 100°C - 110°C for 6h - 8h.

7. Application of the silicon-aluminum-modified barium sulfate obtained by the preparation method of the silicon-aluminum-modified barium sulfate according to any one of claims 1 to 6 as a functional component in a coating.

8. The application according to claim 7, wherein The coating includes a film-forming substance, an additive, a solvent, and the silicon-aluminum-modified barium sulfate.

9. The application according to claim 8, wherein The film-forming substance is one or more of alkyd resin, epoxy resin, polyurethane resin, linseed oil, tung oil, acrylic latex, or polyvinyl chloride latex. The additive is one or more of an antifoaming agent, a leveling agent, a dispersant, or a thickening agent. The solvent is an aqueous solvent, an oil-based solvent, or an organic solvent.

10. The application according to claim 7, characterized in that, The functional component is a high-gloss functional filler, a powder functional filler, or a pigment paste.

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