Phosphogypsum-based interior wall latex paint, preparation method and application thereof

Abstract

The present application relates to the technical field of building coatings, and particularly relates to a phosphogypsum-based interior wall latex paint as well as a preparation method and application thereof. The latex paint comprises: modified phosphogypsum filler 25-45 parts, styrene-acrylic emulsion 30-50 parts, titanium white powder 10-20 parts, calcined kaolin 3-10 parts, film-forming aid 0.5-2 parts, dispersant 0.3-1 part, wetting agent 0.1-0.5 part, defoaming agent 0.2-0.6 part, thickening agent 0.3-1.2 part, pH regulator 0.05-0.2 part, anti-corrosion and anti-mildew agent 0.1-0.4 part, and water 15-30 parts. The present application improves the interfacial compatibility between the phosphogypsum filler and the styrene-acrylic emulsion by sequentially performing calcination treatment and ball milling treatment on the phosphogypsum and performing three-step composite modification of titanium ester coupling agent, silane coupling agent and stearic acid, realizes high-content utilization of the phosphogypsum in the interior wall latex paint, and endows the coating film with good scrub resistance and adhesion.

Description

Technical Field

[0001] This invention relates to the field of architectural coatings technology, and in particular to a phosphogypsum-based interior wall latex paint, its preparation method, and its application. Background Technology

[0002] Phosphogypsum is a major industrial byproduct of wet-process phosphoric acid production, generating approximately 4-5 tons of phosphogypsum for every ton of phosphoric acid produced. The stockpiling of large quantities of phosphogypsum not only occupies valuable land resources, but its soluble phosphorus, soluble fluorine, and organic matter impurities are also released through rainwater leaching, impacting soil and aquatic environments.

[0003] Currently, the comprehensive utilization of phosphogypsum mainly includes cement retarder, gypsum blocks, and roadbed filler. In addition, in the coating field, there are public reports of using phosphogypsum as a filler in interior wall coatings. However, the existing technology still has the following shortcomings: (1) The compatibility between phosphogypsum and organic film-forming resins is poor. Phosphogypsum filler has strong hydrophilicity, while the film-forming resins commonly used in interior wall latex paints are mostly organic polymers. The interface properties of the two are significantly different, which makes it difficult for the filler to be evenly dispersed in the coating system, and it is easy to agglomerate and settle, affecting the storage stability and construction smoothness of the coating. (2) The soluble phosphorus, soluble fluorine and other impurities remaining in phosphogypsum may slowly precipitate after the coating film is formed, which has an adverse effect on the long-term durability and decorative effect of the coating film. (3) The amount of phosphogypsum filler added in the existing technology is generally low, and the absorption capacity of phosphogypsum is limited.

[0004] Therefore, exploring more effective ways to utilize phosphogypsum in the field of interior wall coatings is of great significance. Summary of the Invention

[0005] The purpose of this invention is to address the problems of poor compatibility between fillers and resins, low utilization rate of phosphogypsum, and the need to improve the overall performance of coatings in existing phosphogypsum-based interior wall latex paints, and to provide a phosphogypsum-based interior wall latex paint, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides a phosphogypsum-based interior wall latex paint, comprising the following components in parts by weight: The ingredients are: 25-45 parts modified phosphogypsum filler, 30-50 parts styrene-acrylic emulsion, 10-20 parts titanium dioxide, 3-10 parts calcined kaolin, 0.5-2 parts film-forming aid, 0.3-1 part dispersant, 0.1-0.5 parts wetting agent, 0.2-0.6 parts defoamer, 0.3-1.2 parts thickener, 0.05-0.2 parts pH adjuster, 0.1-0.4 parts preservative and mildew inhibitor, and 15-30 parts water. The preparation method of the modified phosphogypsum filler includes the following steps: (1) The phosphogypsum was calcined and ball-milled in sequence to obtain gypsum powder; (2) Heat the gypsum powder to 40-60℃, add titanate coupling agent for the first mixing, then add silane coupling agent for the second mixing, and finally add stearic acid for the third mixing to obtain modified phosphogypsum filler.

[0007] In some optional embodiments, in step (1), the heating rate of the calcination treatment is 5-10℃ / min, the target temperature is 600-800℃, and the holding time is 60-120min; after the calcination treatment is completed, it is naturally cooled to room temperature and then ball milling is performed; the ball milling speed is 300-500r / min and the time is 1-3h.

[0008] In some optional embodiments, in step (2), the mass ratio of the gypsum powder, titanate coupling agent, silane coupling agent and stearic acid is 100:(1.5-3):(0.5-1.5):(0.5-1); the stirring speeds of the first mixing, the second mixing and the third mixing are 200-400 r / min respectively; the time for the first mixing is 10-20 min, the time for the second mixing is 10-20 min, and the time for the third mixing is 5-10 min.

[0009] In some optional embodiments, the film-forming aid includes at least one of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and propylene glycol phenyl ether; the dispersant is a sodium polycarboxylate dispersant; and the wetting agent includes at least one of alkylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether.

[0010] In some optional embodiments, the defoamer includes at least one of mineral oil defoamer and polyether-modified silicone defoamer; the thickener includes at least one of hydroxyethyl cellulose, alkali-swellable acrylic thickener, and polyurethane associative thickener.

[0011] In some optional embodiments, the pH adjuster is 2-amino-2-methyl-1-propanol; and the preservative and antifungal agent is an isothiazolinone compound.

[0012] This invention also provides a method for preparing a phosphogypsum-based interior wall latex paint, comprising the following steps: S1. Mix water, dispersant, wetting agent, first-part defoamer, pH adjuster, titanium dioxide, calcined kaolin and modified phosphogypsum filler to obtain pigment slurry; S2. Mix the pigment paste, styrene-acrylic emulsion, film-forming aid, remaining defoamer, preservative and mildew inhibitor and thickener to obtain the phosphogypsum-based interior wall latex paint.

[0013] In some alternative embodiments, in S2, after mixing, the material is filtered through an 80-120 mesh sieve to obtain phosphogypsum-based interior wall latex paint.

[0014] In some optional embodiments, the mass ratio of the first portion of defoamer in S1 to the remaining defoamer in S2 is (0.5-1.5):(0.5-1.5).

[0015] In some optional embodiments, in S1, the mixing includes: weighing water according to the ratio, adding it to a dispersion tank, and sequentially adding a dispersant, wetting agent, first-part defoamer, and pH adjuster at a stirring speed of 200-400 r / min, stirring for 5-10 min until uniformly mixed; then, slowly adding titanium dioxide, calcined kaolin, and modified phosphogypsum filler at a stirring speed of 200-400 r / min, increasing the speed to 800-1200 r / min after the addition is complete, and dispersing at high speed for 20-40 min to obtain a uniform pigment slurry; transferring the pigment slurry to a sand mill and grinding it to a fineness ≤50 μm.

[0016] In some optional embodiments, in S2, the mixing includes: transferring the ground pigment slurry into a paint mixing tank, adding styrene-acrylic emulsion at a stirring speed of 300-500 r / min, and stirring for 10-15 min; then, sequentially adding film-forming aid, remaining defoamer and preservative and mildew inhibitor, and continuing to stir for 10-15 min; finally, slowly adding thickener and continuing to stir for 15-20 min.

[0017] The present invention also provides the application of the aforementioned phosphogypsum-based interior wall latex paint in building interior wall decoration.

[0018] A schematic diagram of the preparation process of the modified phosphogypsum filler in this invention is shown below. Figure 1 As shown.

[0019] This invention utilizes a three-step method—high-temperature calcination, ball milling, and composite modification—to deeply process phosphogypsum, achieving a systematic improvement in the performance of phosphogypsum fillers. The technical principle is as follows: (1) Calcination treatment Phosphogypsum raw materials contain impurities such as soluble phosphorus, soluble fluorine, organic matter, and iron and magnesium oxides. Under high-temperature calcination conditions of 600-800℃, the calcium sulfate dihydrate in phosphogypsum first dehydrates to form calcium sulfate hemihydrate, and then to form chemically stable and water-insoluble type II anhydrous calcium sulfate. Within this temperature range, organic matter is fully oxidized and decomposed, soluble phosphorus is converted into insoluble calcium pyrophosphate salt, and soluble fluorine is converted into insoluble calcium fluoride or calcium fluorophosphate, thereby effectively passivating the activity of impurities. In addition, the calcination process can also generate microcracks and active sites on the surface of phosphogypsum particles, which is beneficial for the subsequent chemical bonding of coupling agents to their surface.

[0020] (2) Composite modification Titanate coupling agents contain alkoxy groups in their molecular structure, which can chemically bond with the active hydroxyl groups on the surface of phosphogypsum, forming an organic coating layer on the phosphogypsum surface. Silane coupling agents similarly increase the density of organic groups on the phosphogypsum surface through a condensation reaction between their alkoxy groups and the active hydroxyl groups on the phosphogypsum surface. The long-chain alkyl groups of stearic acid form a hydrophobic layer on the phosphogypsum surface through physical adsorption and chemical bonding. These three modifiers work in a synergistic sequence of "first chemical bonding and anchoring, then organic group expansion, and finally hydrophobic coating," transforming the surface of the phosphogypsum filler from hydrophilic to hydrophobic, thereby significantly improving its interfacial compatibility with styrene-acrylic emulsions and its dispersion stability in latex paint systems.

[0021] (3) Synergistic reinforcement of fillers Modified phosphogypsum filler and calcined kaolin form a filler gradation structure in latex paint systems. Modified phosphogypsum has high hardness and rigidity, which can improve the abrasion resistance and scratch resistance of the coating film; calcined kaolin has a lamellar structure, which can improve the density and hiding power of the coating film. The synergistic effect of the two significantly improves the scrub resistance of the coating film.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention modifies phosphogypsum by combining titanate coupling agent, silane coupling agent and stearic acid, which significantly improves the interfacial compatibility between the modified phosphogypsum filler and styrene-acrylic emulsion, thereby allowing 25-45 parts by weight of modified phosphogypsum filler to be added to interior wall latex paint, thus realizing high dosage utilization of phosphogypsum in interior wall latex paint.

[0023] (2) Modified phosphogypsum filler has high hardness and rigidity, and calcined kaolin has a flaky structure. The two form a filler gradation structure in the latex paint system, which plays a synergistic reinforcing role and effectively improves the scrub resistance of the coating film.

[0024] (3) The present invention uses titanate coupling agent, silane coupling agent and stearic acid to perform composite modification treatment on phosphogypsum, so that the surface of phosphogypsum filler changes from hydrophilic to hydrophobic, which improves the interfacial compatibility between filler and styrene-acrylic emulsion, thereby enhancing the bonding force between coating film and substrate.

[0025] (4) This invention makes extensive use of industrial by-product phosphogypsum, reducing the mining of natural mineral fillers. At the same time, after the phosphogypsum is calcined at a high temperature of 600-800℃, the activity of impurities such as soluble phosphorus and soluble fluorine is passivated, reducing the risk of them slowly precipitating during the use of coatings.

[0026] (5) The latex paint of the present invention exhibits good performance in terms of container state, workability, coating appearance, drying time, contrast ratio, alkali resistance and other performance indicators, and can meet the requirements of use in the field of interior wall decoration. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the preparation process of the modified phosphogypsum filler in this invention; Figure 2 These are comparative graphs showing the scrub resistance of phosphogypsum-based interior wall latex paints in Examples 1-3 and Comparative Examples 1-3 of this invention. Figure 3 This is a comparison diagram of the adhesion of phosphogypsum-based interior wall latex paints in Examples 1-3 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0028] The following embodiments are provided to better understand the present invention and are not limited to the described embodiments. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0029] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0030] In the following embodiments and comparative examples of the present invention, the calcium sulfate dihydrate content in phosphogypsum is 86-92%, the free water content is ≤10%, and the pH value is 3.5-5.

[0031] Example 1 This embodiment provides a method for preparing phosphogypsum-based interior wall latex paint, including the following steps: (1) Preparation of modified phosphogypsum filler The phosphogypsum was placed in a muffle furnace and heated to 700°C at a heating rate of 8°C / min, held at that temperature for 90 min, and then allowed to cool naturally to room temperature. It was then placed in a planetary ball mill and ball-milled at 400 r / min for 2 h to obtain a median particle size D. 50 The gypsum powder is 8μm in size.

[0032] Plaster powder was placed in a high-speed mixer and heated to 50°C. At a stirring speed of 300 r / min, 2% titanate coupling agent (NDZ-101) by weight of plaster powder was added and mixed for 15 min. Then, 1% water by weight of plaster powder was sprayed in and stirred for another 3 min. Next, 1% silane coupling agent (KH-570) by weight of plaster powder was added and mixed for 15 min. Finally, 0.8% stearic acid by weight of plaster powder was added and mixed for 8 min. The product was then discharged to obtain modified phosphogypsum filler.

[0033] (2) Preparation of phosphogypsum-based interior wall latex paint Weigh each component according to the following parts by mass: 35 parts modified phosphogypsum filler, 40 parts styrene-acrylic emulsion (solid content 48%, glass transition temperature 20℃), 15 parts titanium dioxide (rutile type), 6 parts calcined kaolin, 1.2 parts film-forming aid (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), 0.6 parts dispersant (sodium polycarboxylate dispersant, Dispersant-5040), 0.3 parts wetting agent (octylphenol polyoxyethylene ether), 0.4 parts defoamer (polyether modified silicone defoamer, BYK-024), 0.8 parts thickener (hydroxyethyl cellulose), 0.1 parts pH adjuster (2-amino-2-methyl-1-propanol), 0.2 parts preservative and mildew inhibitor (isothiazolinone compound, benzisothiazolinone), and 22 parts water.

[0034] Weigh water according to the ratio and add it to the dispersion tank. Add the dispersant, wetting agent, first part of the defoamer (0.2 parts), and pH adjuster in sequence at a stirring speed of 300 r / min, and stir for 8 min until the mixture is uniform. Then, slowly add titanium dioxide, calcined kaolin, and modified phosphogypsum filler at a stirring speed of 300 r / min. After the addition is complete, increase the speed to 1000 r / min and disperse at high speed for 30 min to obtain a uniform pigment slurry. Transfer the pigment slurry to a sand mill and grind it to a fineness of ≤50 μm.

[0035] The ground pigment slurry was transferred into a paint mixing tank. Styrene-acrylic emulsion was added at a stirring speed of 400 r / min and stirred for 12 min. Then, film-forming aid, remaining defoamer (0.2 parts), and preservative and mildew inhibitor were added in sequence and stirred for another 12 min. Finally, thickener was slowly added and stirred for another 18 min until uniform. The mixture was then filtered through a 100-mesh sieve to obtain phosphogypsum-based interior wall latex paint.

[0036] Example 2 This embodiment provides a method for preparing phosphogypsum-based interior wall latex paint, including the following steps: (1) Preparation of modified phosphogypsum filler The phosphogypsum was placed in a muffle furnace and heated to 800°C at a heating rate of 10°C / min, held at that temperature for 60 min, and then allowed to cool naturally to room temperature. It was then placed in a planetary ball mill and ball-milled at 500 r / min for 1.5 h to obtain a median particle size D. 50 It is a 10μm gypsum powder.

[0037] Plaster powder was placed in a high-speed mixer and heated to 60°C. At a stirring speed of 350 r / min, 2.5% titanate coupling agent (NDZ-201) by weight of plaster powder was added and mixed for 12 min. Then, 1% water by weight of plaster powder was sprayed in and stirred for another 3 min. Next, 1.2% silane coupling agent (KH-560) by weight of plaster powder was added and mixed for 12 min. Finally, 0.6% stearic acid by weight of plaster powder was added and mixed for 6 min. The product was then discharged to obtain modified phosphogypsum filler.

[0038] (2) Preparation of phosphogypsum-based interior wall latex paint Weigh each component according to the following parts by mass: 45 parts modified phosphogypsum filler, 35 parts styrene-acrylic emulsion (solid content 45%, glass transition temperature 25℃), 12 parts titanium dioxide (rutile type), 4 parts calcined kaolin, 1.5 parts film-forming aid (propylene glycol phenyl ether), 0.8 parts dispersant (sodium polycarboxylate dispersant, HS-5040), 0.4 parts wetting agent (alkylphenol polyoxyethylene ether), 0.5 parts defoamer (mineral oil defoamer, BYK-035), 0.6 parts thickener (alkali-swellable acrylic thickener, TT-615), 0.15 parts pH adjuster (2-amino-2-methyl-1-propanol), 0.3 parts preservative and mildew inhibitor (isothiazolinone compound, methylisothiazolinone), and 25 parts water.

[0039] Weigh water according to the formula and add it to the dispersion tank. Add the dispersant, wetting agent, first part of the defoamer (0.25 parts), and pH adjuster in sequence at a stirring speed of 400 r / min. Stir for 10 min until the mixture is uniform. Then, slowly add titanium dioxide, calcined kaolin, and modified phosphogypsum filler at a stirring speed of 400 r / min. After the addition is complete, increase the speed to 1200 r / min and disperse at high speed for 20 min to obtain a uniform pigment slurry. Transfer the pigment slurry to a sand mill and grind it to a fineness of ≤50 μm.

[0040] The ground pigment slurry was transferred into a paint mixing tank. Styrene-acrylic emulsion was added at a stirring speed of 500 r / min and stirred for 10 min. Then, film-forming aid, remaining defoamer (0.25 parts), and anti-corrosion and anti-mildew agent were added in sequence and stirred for another 10 min. Finally, thickener was slowly added and stirred for another 20 min until uniform. The mixture was filtered through an 80-mesh sieve to obtain phosphogypsum-based interior wall latex paint.

[0041] Example 3 This embodiment provides a method for preparing phosphogypsum-based interior wall latex paint, including the following steps: (1) Preparation of modified phosphogypsum filler The phosphogypsum was placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min, held at that temperature for 120 min, and then allowed to cool naturally to room temperature. It was then placed in a planetary ball mill and ball-milled at 300 r / min for 3 h to obtain a median particle size D. 50 The gypsum powder is 6μm in size.

[0042] Plaster powder was placed in a high-speed mixer and heated to 45°C. At a stirring speed of 250 r / min, 1.8% (by weight of the plaster powder) of titanate coupling agent (bis(dioctyloxypyrophosphate) ethylene titanate) was added and mixed for 18 min. Then, 1% (by weight of the plaster powder) of water was sprayed in and mixing continued for 3 min. Next, 0.8% (by weight of the plaster powder) of silane coupling agent (KH-550) was added and mixed for 18 min. Finally, 1% (by weight of the plaster powder) of stearic acid was added and mixed for 10 min. The mixture was then discharged to obtain modified phosphogypsum filler.

[0043] (2) Preparation of phosphogypsum-based interior wall latex paint Weigh each component according to the following parts by mass: 25 parts modified phosphogypsum filler, 48 parts styrene-acrylic emulsion (50% solid content, glass transition temperature 15℃), 18 parts titanium dioxide (rutile type), 8 parts calcined kaolin, 1 part film-forming aid (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), 0.5 parts dispersant (sodium polycarboxylate dispersant, Dispex® AA 4140), 0.2 parts wetting agent (octylphenol polyoxyethylene ether), 0.3 parts defoamer (polyether modified silicone defoamer, Tego Foamex 810), 1 part thickener (polyurethane associative thickener, RM-8W), 0.08 parts pH adjuster (2-amino-2-methyl-1-propanol), 0.15 parts preservative and mildew inhibitor (isothiazolinone compound, chloromethylisothiazolinone), and 18 parts water.

[0044] Weigh water according to the formula and add it to the dispersion tank. Add the dispersant, wetting agent, first part of the defoamer (0.15 parts), and pH adjuster in sequence at a stirring speed of 200 r / min, and stir for 5 min until the mixture is uniform. Then, slowly add titanium dioxide, calcined kaolin, and modified phosphogypsum filler at a stirring speed of 200 r / min. After the addition is complete, increase the speed to 800 r / min and disperse at high speed for 40 min to obtain a uniform pigment slurry. Transfer the pigment slurry to a sand mill and grind it to a fineness of ≤50 μm.

[0045] The ground pigment slurry was transferred into a paint mixing tank. Styrene-acrylic emulsion was added at a stirring speed of 300 r / min and stirred for 15 min. Then, film-forming aid, remaining defoamer (0.15 parts), and preservative and mildew inhibitor were added in sequence and stirred for another 15 min. Finally, thickener was slowly added and stirred for another 15 min until uniform. The mixture was then filtered through a 120-mesh sieve to obtain phosphogypsum-based interior wall latex paint.

[0046] Comparative Example 1 The only difference between this comparative example and Example 1 is that the "modified phosphogypsum filler" is replaced with gypsum powder that has not been modified by coupling agent and stearic acid, i.e., the "median particle size D" in Example 1. 50 "8μm gypsum powder".

[0047] Comparative Example 2 The only difference between this comparative example and Example 1 is that the "modified phosphogypsum filler" is replaced with gypsum powder that has only been modified with a titanate coupling agent. Specifically, the "median particle size D" in Example 1 is replaced with... 50 Plaster powder with a thickness of 8μm was placed in a high-speed mixer, heated to 50℃, and stirred at a speed of 300r / min. 2% of the mass of the plaster powder was added as a titanate coupling agent (NDZ-101). The mixture was stirred for 15min and then discharged.

[0048] Comparative Example 3 The only difference between this comparative example and Example 1 is that the addition of "calcined kaolin" is omitted and replaced with an equal mass of "modified phosphogypsum filler", that is, the number of parts of modified phosphogypsum filler is 41 parts.

[0049] Experimental Example 1 The phosphogypsum-based interior wall latex paints prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests. The specific test items and methods are as follows. The test panel preparation methods for each test item were performed according to the relevant testing method standards. Asbestos-free fiber cement flat plates were used as the substrate. Before application, the substrate was placed at (23±2)℃ and (50±5)% relative humidity for at least 24 hours.

[0050] (1) State in the container Open the container, stir with a spatula, and visually inspect whether there are any lumps and the mixture is homogeneous.

[0051] (2) Constructability Apply the sample to the surface of the test plate with a brush and observe whether there are no obstacles when applying the two coats.

[0052] (3) Coating appearance After the construction test, the test panels were cured at (23±2)℃ and (50±5)% relative humidity for 24 hours, and the coating was visually observed to see if it was normal.

[0053] (4) Drying time The test was conducted using the filter paper method as specified in GB / T 1728-2020 "Determination of Drying Time of Paint Film and Putty Film". At (23±2)℃ and (50±5)% relative humidity, the sample was coated onto a test plate. After a specified time, a slow-drying qualitative filter paper (15mm×15mm) was placed on the coating surface and gently pressed. The time at which the filter paper no longer adhered was taken as the surface drying time.

[0054] (5) Contrast ratio The hiding power of paints and varnishes was determined according to the method specified in GB / T 23981.1-2019 "Determination of hiding power of paints and varnishes - Part 1: Determination of contrast ratio of white and light-colored paints". The sample was prepared with a coating coverage of 20 μm. 2 / L was applied to black and white cardstock and dried at (23±2)℃ for 24h. The reflectance of the coating on the black and white substrates was measured using a reflectometer (wavelength 457nm) and the ratio of the two was calculated, which is the contrast ratio.

[0055] (6) Alkali resistance The test was conducted according to the method specified in GB / T 9265-2009 "Determination of Alkali Resistance of Architectural Coatings". The coating test panel was immersed in a saturated calcium hydroxide solution (pH value ≥ 12) at (23±2)℃ for 24 hours. After rinsing with water, the coating was visually observed for any abnormal phenomena such as blistering, peeling, or discoloration.

[0056] (7) Washability The test was conducted according to the method specified in GB / T 9266-2009 "Determination of Scrub Resistance of Architectural Coatings". The sample was coated onto an asbestos-free fiber cement plate and cured under standard conditions for 7 days. Then, it was placed in a scrub resistance tester and subjected to reciprocating friction on the coating surface under a load of 450g using a scrubbing medium (0.5% detergent solution, pH 9.5-11). The stroke was 300mm, and the scrubbing frequency was 37 times / min. The number of scrubbing cycles required for the coating to show signs of exposure to the substrate was recorded.

[0057] (8) Adhesion The test was conducted according to the method specified in GB / T 9286-2021 "Cross-cut Test for Paints and Varnishes". A cross-cut knife was used to cut the coating onto the substrate in a right-angled grid pattern (1 mm spacing). Adhesive tape (adhesion strength (10±1) N / 25 mm) was then applied and removed. The grade was determined based on the proportion of coating area removed. Grade 0: Completely smooth cut edges with no peeling; Grade 1: Minor coating peeling at the intersection of cuts, but the peeling area does not exceed 5%; Grade 2: Peeling area greater than 5% but not exceeding 15%; Grade 3: Peeling area greater than 15% but not exceeding 35%.

[0058] The performance test results are shown in Table 1. Additionally, a comparison chart of the scrub resistance of the phosphogypsum-based interior wall latex paints in Examples 1-3 and Comparative Examples 1-3 is presented, as shown below. Figure 2 As shown; a comparison diagram of the adhesion of phosphogypsum-based interior wall latex paints in Examples 1-3 and Comparative Examples 1-3, as shown. Figure 3 As shown.

[0059] Table 1 Performance Test Results

[0060] As can be seen from the above results, all performance indicators of Examples 1-3 meet the standard requirements, with a washability of over 2000 cycles and an adhesion grade of 0-1. The washability of Comparative Examples 1-3 are 850, 1450, and 1650 cycles, respectively, and the adhesion grades are 3, 2, and 2, respectively, all of which are worse than those of the Examples.

[0061] Experiment Example 2 The phosphogypsum-based interior wall latex paints prepared in Examples 1-3 were tested for harmful substances. The content of volatile organic compounds (VOCs) was determined according to the method specified in Appendix A of GB 18582-2020; the content of free formaldehyde was determined according to the method specified in GB / T 23993-2009 "Determination of Formaldehyde Content in Waterborne Coatings - Acetylacetone Spectrophotometric Method"; the total content of benzene series compounds (benzene, toluene, ethylbenzene, xylene) was determined according to the method specified in Appendix B of GB 18582-2020; and the content of soluble heavy metals (lead, cadmium, chromium, mercury) was determined according to the method specified in Appendix C of GB 18582-2020.

[0062] The results of the hazardous substance test are shown in Table 2.

[0063] Table 2 Hazardous Substance Detection Results

[0064] As can be seen from Table 2, the phosphogypsum-based interior wall latex paint prepared by this invention has good environmental performance.

[0065] In summary, this invention provides a phosphogypsum-based interior wall latex paint, its preparation method, and its application. This latex paint significantly improves the interfacial compatibility between phosphogypsum filler and styrene-acrylic emulsion through a three-step composite modification process involving calcination, ball milling, and the application of titanate coupling agent, silane coupling agent, and stearic acid. This achieves high utilization of phosphogypsum in the interior wall latex paint and imparts excellent scrub resistance and adhesion to the coating film. Furthermore, this invention fully utilizes industrial by-product phosphogypsum, reducing the mining of natural mineral fillers and offering significant environmental benefits. The preparation process of this invention is mature and controllable, suitable for industrial production, and has broad application prospects.

[0066] Finally, it should be noted that the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A phosphogypsum-based interior wall latex paint, characterized in that, The components include the following parts by mass: The ingredients are: 25-45 parts modified phosphogypsum filler, 30-50 parts styrene-acrylic emulsion, 10-20 parts titanium dioxide, 3-10 parts calcined kaolin, 0.5-2 parts film-forming aid, 0.3-1 part dispersant, 0.1-0.5 parts wetting agent, 0.2-0.6 parts defoamer, 0.3-1.2 parts thickener, 0.05-0.2 parts pH adjuster, 0.1-0.4 parts preservative and mildew inhibitor, and 15-30 parts water. The preparation method of the modified phosphogypsum filler includes the following steps: (1) The phosphogypsum was calcined and ball-milled in sequence to obtain gypsum powder; (2) Heat the gypsum powder to 40-60℃, add titanate coupling agent for the first mixing, then add silane coupling agent for the second mixing, and finally add stearic acid for the third mixing to obtain modified phosphogypsum filler.

2. The phosphogypsum-based interior wall latex paint according to claim 1, characterized in that, In step (1), the heating rate of the calcination treatment is 5-10℃ / min, the target temperature is 600-800℃, and the holding time is 60-120min; the rotation speed of the ball milling treatment is 300-500r / min, and the time is 1-3h.

3. The phosphogypsum-based interior wall latex paint according to claim 1, characterized in that, In step (2), the mass ratio of the gypsum powder, titanate coupling agent, silane coupling agent and stearic acid is 100:(1.5-3):(0.5-1.5):(0.5-1); the stirring speeds of the first mixing, the second mixing and the third mixing are 200-400 r / min respectively; the time for the first mixing is 10-20 min, the time for the second mixing is 10-20 min, and the time for the third mixing is 5-10 min.

4. The phosphogypsum-based interior wall latex paint according to claim 1, characterized in that, The film-forming aid includes at least one of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and propylene glycol phenyl ether; the dispersant is a sodium polycarboxylate dispersant; and the wetting agent includes at least one of alkylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether.

5. The phosphogypsum-based interior wall latex paint according to claim 1, characterized in that, The defoamer includes at least one of mineral oil defoamer and polyether-modified silicone defoamer; the thickener includes at least one of hydroxyethyl cellulose, alkali-swellable acrylic thickener, and polyurethane associative thickener.

6. The phosphogypsum-based interior wall latex paint according to claim 1, characterized in that, The pH adjuster is 2-amino-2-methyl-1-propanol; the preservative and antifungal agent is an isothiazolinone compound.

7. A method for preparing a phosphogypsum-based interior wall latex paint as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Mix water, dispersant, wetting agent, first-part defoamer, pH adjuster, titanium dioxide, calcined kaolin and modified phosphogypsum filler to obtain pigment slurry; S2. Mix the pigment paste, styrene-acrylic emulsion, film-forming aid, remaining defoamer, preservative and mildew inhibitor and thickener to obtain the phosphogypsum-based interior wall latex paint.

8. The preparation method according to claim 7, characterized in that, In S2, after mixing, the mixture is filtered through an 80-120 mesh sieve to obtain phosphogypsum-based interior wall latex paint.

9. The preparation method according to claim 7, characterized in that, The mass ratio of the first part of the defoamer in S1 to the remaining defoamer in S2 is (0.5-1.5):(0.5-1.5).

10. The application of the phosphogypsum-based interior wall latex paint according to any one of claims 1-6 in the decoration of building interior walls.

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