Composite modified anhydrous calcium sulfate whisker as well as preparation method and application thereof

Abstract

The invention provides a composite modified anhydrous calcium sulfate whisker and a preparation method and application thereof.The preparation method of the composite modified anhydrous calcium sulfate whisker comprises the following steps that anhydrous calcium sulfate whisker and a solution containing a first modifier are mixed for a first reaction, and first modified whisker is obtained after filtering and washing; the first modifier comprises alginic acid and / or alginate; mixing the first modified whisker with a solution containing a second modifier for second reaction, and filtering and washing to obtain the composite modified anhydrous calcium sulfate whisker, the second modifier comprises alkyl fatty acid and / or alkyl fatty acid salt. Through the synergistic effect of the two modifiers, the hydrophobicity and the interface bonding force of the calcium sulfate whisker are remarkably improved, and the compatibility of the calcium sulfate whisker in an organic composite material is improved. The prepared composite modified anhydrous calcium sulfate whisker can be used as a novel modified filler, and can effectively improve the strength, glossiness and other indexes of an emulsion paint system.

Description

Technical Field

[0001] This invention relates to the field of inorganic material surface modification technology, specifically to a composite modified anhydrous calcium sulfate whisker, its preparation method, and its application. Background Technology

[0002] Anhydrous calcium sulfate whiskers are an inorganic fibrous material extracted from industrial gypsum solid waste. They possess a uniform cross-section, a smooth and stable surface structure, and excellent mechanical properties. Their aspect ratio is typically greater than 50, a characteristic that gives them a significant advantage in reinforcing materials. As an inorganic whisker material, calcium sulfate whiskers exhibit high strength, modulus, excellent high-temperature resistance, and non-toxicity, making them widely applicable in various fields. Specifically, calcium sulfate whiskers can be used as reinforcing agents or functional fillers in resins, coatings, papermaking, friction materials, building materials, sealing materials, insulation materials, and flame-retardant materials to improve the mechanical properties, thermal stability, and corrosion resistance of the added materials.

[0003] However, due to the strong polarity and hydrophilic-oleophobic properties of anhydrous calcium sulfate whiskers, their composite compatibility is poor when mixed with organic matrices as fillers. This makes it difficult to achieve efficient bonding at the two-phase interface, thus failing to fully leverage the reinforcing effect of anhydrous calcium sulfate whiskers on composite materials. Therefore, it is necessary to modify the surface of anhydrous calcium sulfate whiskers to improve their composite compatibility with organic matrices. Patent CN106497142A proposes a method for preparing modified calcium sulfate whisker paper filling material. This patent uses a wet chemical coating modification technique, employing phosphoric acid and magnesium chloride as modifiers under specific conditions to modify the surface of calcium sulfate whiskers. The modified calcium sulfate whiskers can replace 20%~35% of papermaking raw materials and significantly improve whisker retention and paper strength properties. Patent CN120025604A introduces substances that can react with rubber onto the surface of calcium sulfate whiskers by using tetraethyl orthosilicate and titanate coupling agents as modifiers, thereby enhancing the bonding force between the whiskers and the rubber and promoting the synergistic effect of the rubber system, thus providing a sustainable solution for high-performance rubber composite materials.

[0004] Currently, the modification of calcium sulfate whiskers mainly employs wet modification techniques, aiming to inhibit the solubility of calcium sulfate whiskers in water and enhance their oleophilic properties by changing the type of modifying agents. However, existing modification methods still suffer from unsatisfactory modification effects, complex processes, and difficulty in industrial-scale production. Therefore, a method is needed to modify anhydrous calcium sulfate whiskers to effectively improve their compatibility with organic materials and enhance their application performance in composite materials. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a composite modified anhydrous calcium sulfate whiskers, its preparation method and application, aiming to solve the technical problems of poor lipophilic modification effect and complex process in the existing wet modification technology of calcium sulfate whiskers.

[0006] In a first aspect, the present invention provides a method for preparing composite modified anhydrous calcium sulfate whiskers, comprising the following steps: Anhydrous calcium sulfate whiskers were mixed with a solution containing a first modifier to carry out a first reaction, filtered, and washed to obtain the first modified whiskers; the first modifier included alginate and / or alginate. The first modified whisker was mixed with a solution containing a second modifier to carry out a second reaction. After filtration and washing, composite modified anhydrous calcium sulfate whiskers were obtained. The second modifier included alkyl fatty acids and / or alkyl fatty acid salts.

[0007] Secondly, the present invention provides a composite modified anhydrous calcium sulfate whisker, which is prepared by the preparation method described in the first aspect.

[0008] Thirdly, the present invention provides a latex paint whose raw materials include the composite modified anhydrous calcium sulfate whiskers described in the second aspect.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a composite modified anhydrous calcium sulfate whiskers, which are modified in two steps using alginic acid (or its salt) and alkyl carboxylic acids (or their salts). Alginic acid (or its salt) forms a hydroxyl-rich calcium alginate activation layer on the whisker surface through chemical complexation, providing more active sites for the subsequent chemisorption of alkyl carboxylic acids (or their salts). After composite modification, the long alkyl chains are oriented outwards and exposed on the outermost layer, forming a dense hydrophobic surface, improving the hydrophobicity of the whiskers and enhancing the compatibility between the anhydrous calcium sulfate whiskers and the organic matrix. The composite modified anhydrous calcium sulfate whiskers obtained by this invention can be used as a novel modified filler in the preparation of reinforced latex paints. They exhibit good compatibility in latex paint systems, not only improving the elongation at break of the latex paint film but also effectively reducing the gloss of the film, significantly improving the performance and application effect of the latex paint. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the process flow for the preparation method of composite modified anhydrous calcium sulfate whiskers in Example 1 of the present invention. Detailed Implementation

[0011] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0012] To address the technical problems of poor lipophilic modification effect and complex process in existing wet modification techniques for calcium sulfate whiskers, this invention provides a composite modified anhydrous calcium sulfate whisker, its preparation method, and its application. The composite action of alginate (or its salt) and alkyl fatty acids (or their salts) alters the surface polarity of the calcium sulfate whiskers, significantly improving their hydrophobicity and interfacial bonding, thereby enhancing their compatibility and reinforcing effect in organic composite materials.

[0013] In a first aspect, embodiments of the present invention provide a method for preparing composite modified anhydrous calcium sulfate whiskers, comprising the following steps: Anhydrous calcium sulfate whiskers were mixed with a solution containing a first modifier to carry out a first reaction, filtered, and washed to obtain the first modified whiskers; the first modifier included alginate and / or alginate. The first modified whisker was mixed with a solution containing a second modifier to carry out a second reaction. After filtration and washing, composite modified anhydrous calcium sulfate whiskers were obtained. The second modifier included alkyl fatty acids and / or alkyl fatty acid salts.

[0014] In the technical solution of this invention embodiment, alginate (or its salt) forms a hydroxyl-rich calcium alginate activation layer on the surface of calcium sulfate whiskers through chemical complexation. This activation layer provides more active sites for the subsequent chemisorption of alkyl carboxylic acids (or their salts), promoting the hydrogen bond adsorption between functional groups in alkyl fatty acid molecules and the whisker surface. After composite modification, the long alkyl chains are oriented outward and exposed on the outermost layer, forming a dense hydrophobic surface, thereby significantly inhibiting the penetration and dissolution of water molecules, significantly reducing the solubility of anhydrous calcium sulfate whiskers in water, and enhancing the compatibility between anhydrous calcium sulfate whiskers and the organic matrix.

[0015] Furthermore, in some embodiments, the pH of the solution containing the first modifier is 4-10; the mass ratio of the first modifier to anhydrous calcium sulfate is (0.1-0.5):1; and the mass concentration of the first modifier is 1-50 g / L.

[0016] Furthermore, in some embodiments, the temperature of the first reaction is 50~80°C; the time of the first reaction is 20~60 min.

[0017] Furthermore, in some embodiments, the alginate includes at least one of sodium alginate, potassium alginate, and ammonium alginate.

[0018] Furthermore, in some embodiments, the pH of the solution containing the second modifier is 4-10; the mass ratio of the second modifier to anhydrous calcium sulfate is (0.1-0.5):1; and the mass concentration of the second modifier is 1-50 g / L.

[0019] Furthermore, in some embodiments, the temperature of the second reaction is 50~80°C; the time of the second reaction is 20~60 min.

[0020] In the technical solution of this invention embodiment, the environment and temperature of the modification reaction both have a certain impact on the modification effect. When the pH is acidic, the ionization of stearic acid is inhibited to a certain extent, affecting the adsorption of stearate anions; under neutral to weakly alkaline conditions (pH=7~10), stearic acid is fully ionized, which is conducive to chemical bonding. As the reaction temperature increases, the thermal motion of stearic acid molecules is enhanced, making it easier for them to diffuse to the whisker surface.

[0021] Furthermore, in some embodiments, the alkyl fatty acid includes any one of stearic acid, oleic acid, lauric acid, and dodecylbenzenesulfonic acid; the alkyl fatty acid salt includes any one of sodium stearate, sodium oleate, sodium laurate, and sodium dodecylbenzenesulfonate; the alkyl fatty acid is more preferably stearic acid; and the alkyl fatty acid salt is more preferably sodium stearate.

[0022] Secondly, embodiments of the present invention provide a composite modified anhydrous calcium sulfate whisker, which is prepared by the preparation method described in the first aspect.

[0023] Thirdly, embodiments of the present invention provide a latex paint, the raw materials of which include the composite modified anhydrous calcium sulfate whiskers described in the second aspect.

[0024] In the technical solution of this invention embodiment, composite modified anhydrous calcium sulfate whiskers can be used as a new type of modified filler. After adding composite modified anhydrous calcium sulfate whiskers to latex paint, the strength, gloss and other indicators of the latex paint film can be effectively improved.

[0025] Furthermore, in some embodiments, the raw materials for preparing latex paint include the following components by weight: 10-20 parts deionized water, 1-2 parts thickener, 0.5-2 parts dispersant, 0.2-1 parts wetting agent, 0.2-1 parts defoamer, 0.2-1 parts pH adjuster, 0.2-1 parts preservative, 20-25 parts titanium dioxide, 5-10 parts heavy calcium carbonate, 5-15 parts composite modified anhydrous calcium sulfate whiskers, 30-40 parts styrene-acrylic emulsion, 1-2 parts co-solvent, and 2-5 parts film-forming aid.

[0026] Furthermore, in some embodiments, the dispersant includes polycarboxylate superdispersants; the defoamer includes metal soap defoamers; the thickener includes acrylate polymer thickeners and associative polyurethane thickeners; the cosolvent includes propylene glycol; and the pH adjuster includes organic alcohol amine compounds.

[0027] The following are some specific embodiments. It should be noted that 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. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0028] In the following embodiments of the present invention, the properties of each raw material are as follows: Anhydrous calcium sulfate whiskers: aspect ratio 40~60, purity above 96%, water content less than 1.5%; Sodium alginate: light yellow powder, purity above 99.5%, moisture content less than 0.1%; Sodium stearate: colorless or white crystals, purity above 99.5%, water content less than 0.1%.

[0029] Example 1 Reference Figure 1 The schematic diagram shown illustrates a method for preparing composite modified anhydrous calcium sulfate whiskers. The specific steps are as follows: (1) Accurately weigh 1.0g of sodium alginate and dissolve it in 100mL of deionized water (pH about 7.5). Add 5g of anhydrous calcium sulfate whiskers, stir thoroughly at 70℃ for 40min, filter, rinse three times with deionized water and dry to obtain sodium alginate modified whiskers. (2) Accurately weigh 1.5g of sodium stearate and dissolve it in 100ml of anhydrous ethanol. After adjusting the pH value to 7 with Na2CO3 / HCl solution, add sodium alginate-modified whiskers and stir at 60℃ for 30min. Filter the mixture, rinse it three times with anhydrous ethanol, and dry it to obtain composite modified anhydrous calcium sulfate whiskers.

[0030] Example 2 A method for preparing composite modified anhydrous calcium sulfate whiskers, the specific steps of which are as follows: (1) Accurately weigh 1.0g of sodium alginate and dissolve it in 100mL of deionized water (pH about 7.5). Add 5g of anhydrous calcium sulfate whiskers, stir thoroughly at 70℃ for 40min, filter, rinse three times with deionized water and dry to obtain sodium alginate modified whiskers. (2) Accurately weigh 1.5g of sodium stearate and dissolve it in 100ml of anhydrous ethanol. After adjusting the pH value to 5.0 with Na2CO3 / HCl solution, add sodium alginate-modified whiskers and stir at 60℃ for 30min. Filter the mixture, rinse it three times with anhydrous ethanol, and dry it to obtain composite modified anhydrous calcium sulfate whiskers.

[0031] Example 3 A method for preparing composite modified anhydrous calcium sulfate whiskers, the specific steps of which are as follows: (1) Accurately weigh 1.0g of sodium alginate and dissolve it in 100mL of deionized water (pH about 7.5). Add 5g of anhydrous calcium sulfate whiskers, stir thoroughly at 70℃ for 40min, filter, rinse three times with deionized water and dry to obtain sodium alginate modified whiskers. (2) Accurately weigh 1.5g of sodium stearate and dissolve it in 100ml of anhydrous ethanol. After adjusting the pH value to 9.0 with Na2CO3 / HCl solution, add sodium alginate-modified whiskers and stir at 80℃ for 30min. Filter the mixture, rinse it three times with anhydrous ethanol, and dry it to obtain composite modified anhydrous calcium sulfate whiskers.

[0032] Example 4 A method for preparing composite modified anhydrous calcium sulfate whiskers, the specific steps of which are as follows: (1) Accurately weigh 1.0g of sodium alginate and dissolve it in 100mL of deionized water. Add 5g of anhydrous calcium sulfate whiskers, stir thoroughly at 70℃ for 40min, filter, rinse three times with deionized water and dry to obtain sodium alginate modified whiskers. (2) Accurately measure 1.5g of sodium oleate and dissolve it in 100ml of anhydrous ethanol for hydrolysis. Adjust the pH value to about 7 using Na2CO3 / HCl solution, add sodium alginate to modify the whiskers, stir at 60℃ for 30min, filter, rinse three times with anhydrous ethanol and dry to obtain modified anhydrous calcium sulfate whiskers.

[0033] Example 5 A method for preparing composite modified anhydrous calcium sulfate whiskers, the specific steps of which are as follows: (1) Accurately weigh 1.0 g of sodium alginate and dissolve it in 100 mL of deionized water. Add 5 g of anhydrous calcium sulfate whiskers, stir thoroughly at 60 °C for 20 min, filter, rinse three times with deionized water and dry to obtain sodium alginate modified whiskers. (2) Accurately weigh 1.5g of lauric acid and dissolve it in 100mL of anhydrous ethanol. After adjusting the pH value to 5.0 with Na2CO3 / HCl solution, add sodium alginate modified whiskers, stir at 60℃ for 30min, filter, rinse three times with anhydrous ethanol, and dry to obtain modified anhydrous calcium sulfate whiskers.

[0034] Example 6 A method for preparing composite modified anhydrous calcium sulfate whiskers, the specific steps of which are as follows: (1) Accurately weigh 1.0g of sodium alginate and dissolve it in 100mL of deionized water. Add 5g of anhydrous calcium sulfate whiskers, stir thoroughly at 70℃ for 40min, filter, rinse three times with deionized water and dry to obtain sodium alginate modified whiskers. (2) Accurately weigh 1.5g of sodium lauryl sulfate and dissolve it in 100mL of anhydrous ethanol. After adjusting the pH value to 9.0 with Na2CO3 / HCl solution, add sodium alginate-modified whiskers, stir at 80℃ for 30min, filter, rinse three times with anhydrous ethanol, and dry to obtain modified anhydrous calcium sulfate whiskers.

[0035] Comparative Example 1 A method for preparing modified calcium sulfate whiskers, the specific steps of which are as follows: (1) Accurately weigh 1.0g of sodium phosphate and dissolve it in 100mL of deionized water. Add 5g of anhydrous calcium sulfate whiskers, stir thoroughly at 60℃ for 20min, filter, rinse three times with deionized water and dry to obtain sodium phosphate modified whiskers. (2) Accurately weigh 1.5g of sodium stearate and dissolve it in 100mL of anhydrous ethanol. After adjusting the pH value to 7 with Na2CO3 / HCl solution, add sodium phosphate modified whiskers, stir at 60℃ for 30min, filter, rinse three times with anhydrous ethanol, and dry to obtain modified anhydrous calcium sulfate whiskers.

[0036] Comparative Example 2 A method for preparing modified calcium sulfate whiskers, the specific steps of which are as follows: (1) Accurately weigh 1.0 g of polyglycerol ester and dissolve it in 100 mL of deionized water. Add 5 g of anhydrous calcium sulfate whiskers, stir thoroughly at 60 °C for 20 min, filter, rinse three times with deionized water and dry to obtain polyglycerol ester modified whiskers. (2) Accurately weigh 1.5g of sodium stearate and dissolve it in 100mL of anhydrous ethanol. After adjusting the pH value to 5.0 with Na2CO3 / HCl solution, add polyglycerol ester modified whiskers, stir at 60℃ for 30min, filter, rinse three times with anhydrous ethanol, and dry to obtain modified anhydrous calcium sulfate whiskers.

[0037] Comparative Example 3 A method for preparing modified calcium sulfate whiskers, the specific steps of which are as follows: (1) Accurately weigh 1.0 g of dodecyl glycoside and dissolve it in 100 mL of deionized water. Add 5 g of anhydrous calcium sulfate whiskers, stir thoroughly at 70 °C for 40 min, filter, rinse three times with deionized water and dry to obtain dodecyl glycoside modified whiskers. (2) Accurately weigh 1.5g of sodium stearate and dissolve it in 100mL of anhydrous ethanol. After adjusting the pH value to 9.0 with Na2CO3 / HCl solution, add dodecyl glycoside modified whiskers, stir at 80℃ for 30min, filter, rinse three times with anhydrous ethanol, and dry to obtain modified anhydrous calcium sulfate whiskers.

[0038] Comparative Example 4 A method for preparing modified calcium sulfate whiskers, the specific steps of which are as follows: Accurately weigh 1.5g of sodium stearate and dissolve it in 100mL of anhydrous ethanol. Add 5g of anhydrous calcium sulfate whiskers, stir thoroughly at 60℃ for 30min, filter, rinse three times with deionized water, and dry to obtain modified sodium stearate whiskers, which are modified anhydrous calcium sulfate whiskers.

[0039] Performance testing: 1. Contact Angle Test The contact angle of the modified calcium sulfate whiskers obtained in each embodiment and comparative example was tested, and the results are shown in Table 1 below.

[0040] Table 1

[0041] The results showed that after modification with alginate and alkylcarboxylic acid, the contact angle of anhydrous calcium sulfate whiskers increased significantly, indicating a significant improvement in hydrophobicity. Under neutral to weakly alkaline pH conditions, stearic acid was fully ionized, which was more conducive to chemical bonding; as the reaction temperature increased, the thermal motion of stearic acid molecules was enhanced, making it easier to diffuse to the whisker surface, further improving hydrophobicity.

[0042] 2. Performance testing when applied to latex paint The modified calcium sulfate whiskers obtained in Examples 1-6 and Comparative Examples 1-4 were applied to the preparation of latex paint; the preparation method of the latex paint is as follows: Mix 20 parts deionized water with 0.4 parts thickener and stir at 300 rpm for 5 minutes until evenly dispersed. Then add 0.5 parts dispersant, 0.2 parts wetting agent, 0.2 parts defoamer, 0.2 parts pH adjuster, and 0.2 parts preservative and stir at 800 rpm for 10 minutes. Add 22 parts titanium dioxide, 5 parts heavy calcium carbonate, and 10 parts modified anhydrous calcium sulfate whiskers and stir at 1200 rpm for 15 minutes. Finally, add 0.3 parts defoamer, 1.5 parts cosolvent, 2 parts film-forming aid, 38 parts styrene-acrylic emulsion, and 1.5 parts thickener. The latex paint was obtained by stirring at 500 rpm for 10 min. The thickener consisted of an acrylate polymer thickener and an associative polyurethane thickener; the dispersant was a polycarboxylate superdispersant 5040; the wetting agent was an ethylene oxide-propylene oxide block copolymer; the defoamer was a metal soap defoamer; the pH adjuster was an organic alcohol amine compound (2-amino-2-methyl-1-propanol); the preservative was 2-benzimidazole carbamate; the titanium dioxide was rutile titanium dioxide; the heavy calcium carbonate had a size of 7.5~14 μm; the co-solvent was propylene glycol; and the film-forming aid was alcohol ester 12.

[0043] The latex paints prepared using the modified calcium sulfate whiskers obtained in Examples 1-6 and Comparative Examples 1-4 were tested. The test items and test methods are as follows: (1) 60° gloss: Refer to GB / T 9754 Method for determining 60° gloss in the determination of 20°, 60° and 85° specular gloss of paint and varnish films without metallic pigments in 2007. (2) Settlement assessment: Refer to GB / T 6753.3 Tests were conducted in 1986; (3) Container condition, workability, coating appearance, alkali resistance, water resistance, drying time, and elongation at break: tests were conducted in accordance with JG / T 172-2014 Elastic Building Coatings; The test results are shown in Tables 2-1 and 2-2 below.

[0044] Table 2-1

[0045] Table 2-2

[0046] The test results above show that the latex paint prepared by the composite modified anhydrous calcium sulfate whiskers provided in this embodiment of the invention has excellent performance. Adding the modified anhydrous calcium sulfate whiskers as a filler to the latex paint results in good compatibility with the organic matrix, significantly improving the elasticity and strength properties of the latex paint while effectively reducing its gloss.

[0047] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method for preparing composite modified anhydrous calcium sulfate whiskers, characterized in that, Includes the following steps: Anhydrous calcium sulfate whiskers were mixed with a solution containing a first modifier to carry out a first reaction, filtered, and washed to obtain the first modified whiskers; the first modifier included alginate and / or alginate. The first modified whisker is mixed with a solution containing a second modifier to carry out a second reaction, filtered, and washed to obtain the composite modified anhydrous calcium sulfate whisker; the second modifier includes alkyl fatty acids and / or alkyl fatty acid salts.

2. The method for preparing composite modified anhydrous calcium sulfate whiskers according to claim 1, characterized in that, The pH of the solution containing the first modifier is 4-10; And / or, the mass ratio of the first modifier to anhydrous calcium sulfate is (0.1~0.5):1; And / or, the mass concentration of the first modifier is 1~50 g / L.

3. The method for preparing composite modified anhydrous calcium sulfate whiskers according to claim 1, characterized in that, The temperature of the first reaction is 50~80℃, and the reaction time is 20~60min.

4. The method for preparing composite modified anhydrous calcium sulfate whiskers according to claim 1, characterized in that, The alginate includes at least one of sodium alginate, potassium alginate, and ammonium alginate.

5. The method for preparing composite modified anhydrous calcium sulfate whiskers according to claim 1, characterized in that, The pH of the solution containing the second modifier is 4-10; And / or, the mass ratio of the second modifier to anhydrous calcium sulfate is (0.1~0.5):1; And / or, the mass concentration of the second modifier is 1~50 g / L.

6. The method for preparing composite modified anhydrous calcium sulfate whiskers according to claim 1, characterized in that, The temperature of the second reaction is 50~80℃, and the reaction time is 20~60min.

7. The method for preparing composite modified anhydrous calcium sulfate whiskers according to claim 1, characterized in that, The alkyl fatty acid includes any one of stearic acid, oleic acid, lauric acid, and dodecylbenzenesulfonic acid; the alkyl fatty acid salt includes any one of sodium stearate, sodium oleate, sodium laurate, and sodium dodecylbenzenesulfonate.

8. A composite modified anhydrous calcium sulfate whisker, characterized in that, It is prepared by the method for preparing composite modified anhydrous calcium sulfate whiskers according to any one of claims 1 to 7.

9. A latex paint, characterized in that, The raw materials for preparation include the composite modified anhydrous calcium sulfate whiskers as described in claim 8.

10. The latex paint according to claim 9, characterized in that, The raw materials for preparing the latex paint include the following components by weight: 10-20 parts deionized water, 1-2 parts thickener, 0.5-2 parts dispersant, 0.2-1 parts wetting agent, 0.2-1 parts defoamer, 0.2-1 parts pH adjuster, 0.2-1 parts preservative, 20-25 parts titanium dioxide, 5-10 parts heavy calcium carbonate, 5-15 parts composite modified anhydrous calcium sulfate whiskers, 30-40 parts styrene-acrylic emulsion, 1-2 parts co-solvent, and 2-5 parts film-forming aid.

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