Powder coating gypsum board with scratch resistance and preparation method thereof

Abstract

The invention provides a powder coating gypsum board with scratch resistance and a preparation method thereof, and belongs to the technical field of paints.The preparation method comprises the following steps that modified polyester, modified glass beads, polytetrafluoroethylene, barium sulfate, titanium dioxide, a flatting agent and a curing agent are mixed and stirred, melt extrusion is conducted, tabletting is conducted after cooling, smashing, grinding and sieving are conducted, and the powder coating gypsum board is obtained. Powder coating is obtained; and sanding and dedusting the surface of the gypsum board substrate, electrostatically spraying the powder coating onto the surface of the substrate, heating, curing and cooling to obtain the gypsum board. Wherein the modified polyester is prepared from polyester, a reinforcing agent and 3-glycidyl ether oxypropyl triethoxy silane. The powder coating gypsum board prepared by the invention has excellent scratch resistance, impact resistance and wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and particularly relates to a powder-coated gypsum board with scratch-resistant properties and its preparation method. Background Technology

[0002] Powder coatings, an environmentally friendly coating technology developed in the 20th century, have gradually replaced some traditional solvent-based coatings and are widely used in the industrial field due to their advantages such as air dispersion, zero VOC emissions, high material utilization, good weather resistance, and low material and labor costs. Their core advantage lies in the direct adhesion of solid powder to the substrate surface through electrostatic spraying or fluidized bed dip coating processes, followed by high-temperature curing to form a dense coating, significantly reducing resource waste and environmental pollution, achieving a shift from "end-of-pipe treatment" to "source replacement." However, the limitations of powder coatings are also becoming apparent. For example, their curing temperature is relatively high, resulting in poor compatibility with heat-sensitive substrates; uneven electrostatic adsorption on the coating surface can lead to defects in edge and corner coverage; and the cured coating is difficult to repair, requiring complete recoating if scratches or damage occur. Gypsum board, a commonly used material for building decoration and partitions, possesses lightweight, fire-resistant, and sound-insulating properties, but its surface hardness is low, making it susceptible to mechanical scratches. Traditional coatings still suffer from insufficient wear resistance and poor durability, and the application process is complex, requiring puttying and painting. Therefore, by developing powder coatings specifically for gypsum board, we can leverage the environmental advantages of powder coatings while also overcoming their limitations in application on complex substrates.

[0003] Currently, powder coating preparation methods for gypsum board are mainly divided into three categories: electrostatic spraying, which uses high-voltage electrostatics to adsorb powder coating onto the surface of gypsum board; however, the porous structure of gypsum board easily leads to uneven powder coating penetration, making it difficult to control the coating thickness; and the electrostatic field has limited coverage of irregular surfaces, easily resulting in missed areas or accumulation at corners, affecting the decorative effect and scratch resistance. Fluidized bed immersion coating, which directly immerses gypsum board in fluidized powder coating and cures it at high temperature, can form a thicker coating, but the poor thermal stability of gypsum board makes it prone to internal moisture evaporation at high temperatures, leading to coating cracking or substrate deformation, and the process has high energy consumption. Pretreatment composite coating method, which first coats the gypsum board surface with a primer to enhance adhesion, and then sprays the powder coating; however, the primer and powder have insufficient compatibility, easily causing interface delamination, and the multi-layer coating process is complex, significantly increasing costs. In addition, existing methods generally rely on epoxy or polyester as film-forming substances, which can improve adhesion, but their balance between hardness and flexibility is poor, making it difficult to achieve high scratch resistance on the brittle substrate of gypsum board. Some studies have attempted to add wear-resistant fillers, but uneven dispersion of the fillers can lead to a rough coating surface, which in turn increases the risk of scratches.

[0004] To address the aforementioned issues, attempts have been made to improve the coating by modifying resins, optimizing filler systems, and adjusting curing processes. Introducing acrylic or polyurethane-modified epoxy resins enhances coating hardness and flexibility, but the modification process is complex, and high-temperature curing can still cause internal stress cracking in the gypsum board. Adding nano-silica or silicon carbide enhances wear resistance, but nanoparticles tend to agglomerate, affecting coating uniformity; simultaneously, excessive filler reduces powder flowability and spraying efficiency. Segmented heating or infrared-assisted curing reduces thermal shock, but equipment costs are high, and precise control of the thermal expansion matching between the gypsum board and the coating is difficult. While these improvements have yielded breakthroughs in local performance, a contradiction remains regarding overall scratch resistance, heat resistance, and application compatibility: high-hardness coatings are prone to brittleness, while flexible coatings lack sufficient wear resistance; and the porosity of the gypsum board surface is difficult to balance with the required powder adhesion. Therefore, a new powder coating system is urgently needed that, through improved component formulation and process design, simultaneously enhances comprehensive performance such as scratch resistance and impact resistance to meet the high requirements of gypsum board in architectural decoration. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing powder-coated gypsum board with scratch-resistant properties. By using specific modified polyester, modified glass microspheres, polytetrafluoroethylene and other raw materials to make a powder coating specifically for gypsum board, the interaction of the components gives the powder-coated gypsum board excellent scratch resistance, impact resistance and wear resistance.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing powder-coated gypsum board with scratch-resistant properties, comprising the following steps:

[0008] 70-90 parts by weight of modified polyester, 5-15 parts by weight of modified glass microspheres, 10-20 parts by weight of polytetrafluoroethylene, 15-20 parts by weight of barium sulfate, 10-15 parts by weight of titanium dioxide, 1-3 parts by weight of leveling agent, and 3-6 parts by weight of curing agent are added to a mixer and mixed and stirred at 65-75℃ and 150-250 r / min for 5-15 min. The mixture is then transferred to a screw extruder and melt-extruded at 130-140℃ and 300-400 r / min. After cooling, the mixture is pressed into sheets, crushed, ground, and passed through a 270-400 mesh sieve to obtain a powder coating.

[0009] The surface of the gypsum board substrate is sanded and dust-removed to remove dust and impurities. Then, the powder coating is electrostatically sprayed onto the substrate surface and baked at 175-185℃ for 10-20 minutes to cure into a film with a coating thickness of 70-90μm. After cooling, the powder-coated gypsum board with scratch resistance is obtained.

[0010] Preferably, the leveling agent is one or a mixture of two or more of the following: leveling agent GLP588, leveling agent GLP788, and leveling agent GLP599.

[0011] Furthermore, the leveling agent is leveling agent GLP588.

[0012] Preferably, the curing agent is one or a mixture of two or more of isophthalic anhydride, phthalic anhydride, and adipate dihydrazide.

[0013] Preferably, the curing agent is isophthalic acid hydrazide.

[0014] Preferably, the method for preparing the modified polyester includes the following steps:

[0015] Trimethylolpropane, 1,16-hexadecanediol, 1,5-pentanediol, and a catalyst were added to a sealed reactor and heated. An isocyanate mixture was added dropwise, and the reaction was maintained at this temperature. Azelaic acid and N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide were added to the reactor, and the temperature was raised and maintained. Trimeric trioxide was then added to continue the reaction, followed by the addition of an antioxidant. The mixture was cooled and granulated to obtain a polyester. The polyester was mixed evenly with propylene glycol methyl ether acetate, and then a reinforcing agent and 3-glycidyl etheroxypropyltriethoxysilane were added. The mixture was ultrasonically treated, then ball-milled, distilled under reduced pressure, and dried to obtain the modified polyester.

[0016] This invention utilizes a modified polyester prepared by the aforementioned method, which, in conjunction with modified glass microspheres and polytetrafluoroethylene (PTFE), significantly improves the scratch resistance, impact resistance, and abrasion resistance of powder-coated gypsum boards. In the preparation of the modified polyester, firstly, the introduction of the isocyanate mixture forms a rigid urethane bond network. The high reactivity of diphenylmethane-4,4'-diisocyanate and the compliant segments of hexamethylene diisocyanate work together to enhance the coating's hardness and chemical resistance while preventing excessive embrittlement. Trimethylolpropane, as a triol, reacts with isocyanates to construct a three-dimensional cross-linked structure, significantly improving the cohesive strength and impact toughness of the molecular chains. The long-chain structure of 1,16-hexadecanediol imparts flexibility to the molecular chains, buffering external impact energy, while the moderate chain length of 1,5-pentanediol further optimizes the balance between rigidity and flexibility, reducing the risk of brittle fracture. Next, azelaic acid undergoes polycondensation with polyols to form rigid ester bonds, enhancing the regularity and ordered arrangement of the molecular chains and improving scratch resistance. The tetrahydroxy structure of N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide forms a multi-point anchored three-dimensional network through crosslinking with trimellitic anhydride, significantly improving impact resistance, while its flexible side chains maintain the material's toughness. The trifunctionality of trimellitic anhydride maximizes the crosslinking density, forming a dense molecular structure that effectively resists external deformation and frictional damage. Simultaneously, antioxidants delay oxidative degradation, ensuring long-term performance stability. During the modification stage, propylene glycol methyl ether acetate serves as a solvent to promote uniform dispersion of the components. High-strength, high-hardness silicon carbide and high-lubricity, high-temperature-resistant boron nitride form a reinforcing agent, directly improving surface hardness and wear resistance through a physical filler effect. It also assists boron nitride in reducing the coefficient of friction and minimizing scratch formation. 3-glycidyl etheroxypropyltriethoxysilane forms a chemically bonded interface through the reaction of epoxy groups with hydroxyl / carboxyl groups in the polyester. Simultaneously, after alkoxy hydrolysis, it combines with hydroxyl groups on the filler surface, significantly improving the compatibility between the filler and the matrix, avoiding stress concentration caused by agglomeration, and thus uniformly transmitting external forces. This multi-layered functional synergy allows the coating to maintain flexibility while simultaneously achieving significant improvements in scratch resistance, impact resistance, and wear resistance through the combined effects of a rigid crosslinking network, filler reinforcement, and interface optimization.

[0017] Preferably, the weight ratio of the mixture of trimethylolpropane, 1,16-hexadecanediol, 1,5-pentanediol, catalyst, and isocyanate is 10-20:5-15:30-40:0.2-0.5:50-70.

[0018] Preferably, the weight ratio of azelaic acid, N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide, trimellitic anhydride, and antioxidant is 10-20:3-7:10-20:0.3-0.5.

[0019] Preferably, the weight ratio of trimethylolpropane to azelaic acid is 10-20:10-20.

[0020] Preferably, the weight ratio of the polyester, reinforcing agent, and 3-glycidyl etheroxypropyltriethoxysilane is 25-35:10-15:3-7.

[0021] Preferably, the method for preparing the modified polyester includes the following steps:

[0022] Add 10-20 parts by weight of trimethylolpropane, 5-15 parts by weight of 1,16-hexadecanediol, 30-40 parts by weight of 1,5-pentanediol, and 0.2-0.5 parts by weight of catalyst to a sealed reactor, heat to 130-140°C, and dropwise add 50-70 parts by weight of isocyanate mixture over 1-2 hours. After the addition is complete, maintain the temperature for 1-2 hours. Add 10-20 parts by weight of azelaic acid and 3-7 parts by weight of N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide to the reactor, raise the temperature to 225-235°C, and maintain the temperature for 2-4 hours. Then, 10-20 parts by weight of trimellitic anhydride are added and the reaction continues for 4-6 hours. Then, 0.3-0.5 parts by weight of antioxidant are added and the reaction continues for 0.5-1.5 hours. After cooling, the mixture is granulated to obtain polyester. 25-35 parts by weight of polyester are mixed evenly with 30-50 parts by weight of propylene glycol methyl ether acetate. Then, 10-15 parts by weight of reinforcing agent and 3-7 parts by weight of 3-glycidyl ether oxypropyltriethoxysilane are added and ultrasonically treated for 30-50 minutes. Then, the mixture is ball-milled for 2-4 hours. After the treatment, the solvent is removed by vacuum distillation and the mixture is dried to obtain the modified polyester.

[0023] Preferably, the isocyanate mixture consists of diphenylmethane-4,4'-diisocyanate and hexamethylene diisocyanate.

[0024] Further, the isocyanate mixture is composed of 30-40 parts by weight of diphenylmethane-4,4'-diisocyanate and 20-30 parts by weight of hexamethylene diisocyanate.

[0025] Preferably, the catalyst is one or a mixture of two or more of dibutyltin dilaurate, bismuth isooctanoate, and tetrabutyl titanate.

[0026] Preferably, the antioxidant is composed of antioxidant 1010 and antioxidant 168, and the weight ratio of antioxidant 1010 to antioxidant 168 is 1-3:1.

[0027] Preferably, the acid value of the polyester is 25-35 mg KOH / g.

[0028] Preferably, the reinforcing agent is composed of silicon carbide and boron nitride, wherein the weight ratio of silicon carbide to boron nitride is 1.5-2:1.

[0029] The silicon carbide has an average particle size of 8-15 μm, and the boron nitride has an average particle size of 1-3 μm.

[0030] Preferably, the frequency of the ultrasound is 30-40kHz and the power is 150-250W.

[0031] Preferably, the rotational speed of the ball mill is 400-600 r / min.

[0032] Preferably, the modified glass microspheres are obtained by surface modification of hollow glass microspheres after alkali treatment with 3-glycidyl etheroxypropyltriethoxysilane.

[0033] Preferably, the method for preparing the modified glass microspheres includes the following steps:

[0034] Hollow glass microspheres were mixed evenly with sodium hydroxide aqueous solution, heated and stirred, cooled, filtered, washed with water, and dried to obtain alkali-treated glass microspheres; 3-glycidyl etheroxypropyltriethoxysilane was mixed evenly with ethanol aqueous solution, the pH was adjusted to acidic, and then the alkali-treated glass microspheres were added for ultrasonic treatment, filtered, and dried to obtain modified glass microspheres.

[0035] This invention also incorporates modified glass microspheres prepared by the above method. Through synergistic surface chemical treatment and physical structure, the scratch resistance and wear resistance of powder-coated gypsum board are further improved. Specifically, alkali treatment etches the surface of the hollow glass microspheres, removing surface impurities and introducing a large number of hydroxyl active groups, increasing surface roughness and reactive sites, providing a high-bonding-energy interface for subsequent grafting of 3-glycidyl etheroxypropyltriethoxysilane. After hydrolysis, the alkoxy groups of 3-glycidyl etheroxypropyltriethoxysilane dehydrate and condense with the hydroxyl groups on the glass microsphere surface to form stable silicon-oxygen bonds, while the epoxy groups react with the hydroxyl / carboxyl groups in the modified polyester to construct a chemically bonded interface. This significantly improves the compatibility and interfacial bonding strength between the filler and the polymer matrix, avoiding early failure caused by interfacial stress concentration. The modified spherical structure of glass microspheres creates a micro-bearing effect in the coating. When subjected to external friction, their smooth surface reduces the direct shear force from contact with hard objects, disperses local pressure, and lowers the probability of scratches. Simultaneously, the hollow structure imparts low density and high rigidity, reducing coating weight while providing compressive support and inhibiting microcrack propagation. Furthermore, the low surface energy of PTFE further reduces the coefficient of friction, while the rigid spheres of the glass microspheres physically prevent PTFE migration or aggregation, forming a stable and uniform friction-reducing network. Together with the reinforcing agent in the modified polyester, these components construct a multi-scale damage-resistant system. The rigid filler provides intrinsic strength, while the dynamic slippage effect of the glass microspheres and the lubrication of PTFE jointly inhibit plastic deformation and wear debris shedding caused by external forces, thereby further improving scratch resistance and wear resistance.

[0036] Furthermore, the preparation method of the modified glass microspheres includes the following steps:

[0037] Mix 3-8 parts by weight of hollow glass microspheres with 90-100 parts by weight of 30-40 wt% sodium hydroxide aqueous solution, stir at 70-75℃ and 100-200 r / min for 80-100 min, cool, filter, wash with water until neutral, and dry to obtain alkali-treated glass microspheres; mix 0.4-0.6 parts by weight of 3-glycidyl etheroxypropyltriethoxysilane with 40-50 parts by weight of 80-90 wt% ethanol aqueous solution, adjust the pH to 5-6, then add 4-6 parts by weight of alkali-treated glass microspheres, sonicate for 40-60 min, filter, and dry to obtain modified glass microspheres.

[0038] Preferably, the frequency of the ultrasound is 30-40kHz and the power is 150-250W.

[0039] Preferably, the gypsum board substrate used in this invention is a commercially available gypsum board substrate or is prepared using the following methods.

[0040] Preferably, the gypsum board substrate is made of calcined gypsum powder, borate, lignin, foaming agent and water.

[0041] Furthermore, the method for preparing the gypsum board substrate includes the following steps:

[0042] Mix 70-150 parts by weight of calcined gypsum powder, 0.1-0.8 parts by weight of borate, and 0.5-2 parts by weight of lignin evenly to obtain a solid powder; mix 0.1-0.5 parts by weight of foaming agent with 50-100 parts by weight of water evenly, then foam the mixture through a foaming system and feed it into a mixer. Add the solid powder to the mixer and stir thoroughly to obtain a uniform slurry; after extrusion molding, solidification, cutting, and drying, obtain a gypsum board substrate.

[0043] Preferably, the borate is borax.

[0044] Preferably, the foaming agent is sodium dodecyl sulfate.

[0045] Preferably, the gypsum board substrate has a length of 0.1-3050 mm, a width of 0.1-1220 mm, and a thickness of 5-15 mm.

[0046] Furthermore, the gypsum board substrate has a length of 3000mm, a width of 1200mm, and a thickness of 12mm.

[0047] This invention also provides a powder coating with scratch-resistant properties specifically for gypsum board, comprising the following raw materials:

[0048] 70-90 parts by weight of modified polyester, 5-15 parts by weight of modified glass microspheres, 10-20 parts by weight of polytetrafluoroethylene, 15-20 parts by weight of barium sulfate, 10-15 parts by weight of titanium dioxide, 1-3 parts by weight of leveling agent, and 3-6 parts by weight of curing agent.

[0049] The present invention also provides a powder-coated gypsum board with scratch-resistant properties, which is prepared by the above method.

[0050] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0051] 1. This invention provides a powder-coated gypsum board with scratch-resistant properties and its preparation method. A powder coating specifically for gypsum board is prepared by using a self-made modified polyester, modified glass microspheres, polytetrafluoroethylene, and other raw materials. The modified polyester is composed of polyester, a reinforcing agent, and 3-glycidyl etheroxypropyltriethoxysilane. The modified glass microspheres are obtained by surface modification of hollow glass microspheres after alkali treatment with 3-glycidyl etheroxypropyltriethoxysilane. The interaction of these components further improves the scratch resistance, impact resistance, and abrasion resistance of the powder-coated gypsum board.

[0052] 2. The modified polyester prepared by this invention comprises an isocyanate mixture that enhances the hardness and chemical resistance of the coating while preventing excessive embrittlement; the reaction of trimethylolpropane with isocyanate constructs a three-dimensional cross-linked structure, significantly improving the cohesive strength and impact toughness of the molecular chain; the long-chain structure of 1,16-hexadecanediol imparts flexibility to the molecular chain, buffering the impact energy of external forces, while the medium chain length of 1,5-pentanediol further optimizes the balance between rigidity and flexibility, reducing the risk of brittle fracture; azelaic acid and polyol condense to form rigid ester bonds, improving the regularity and orderly arrangement of the molecular chain, and enhancing scratch resistance; the tetrahydroxy structure of N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide forms a multi-point anchored three-dimensional network through cross-linking reaction with trimellitic anhydride, significantly improving impact resistance, while its flexible side chains maintain the toughness of the material; silicon carbide and boron nitride constitute a reinforcing agent, which directly improves surface hardness and wear resistance through physical filler effect, and assists the lubricity of boron nitride to reduce the coefficient of friction and reduce scratch formation.

[0053] 3. This invention also incorporates modified glass microspheres. The spherical structure of the modified glass microspheres creates a micro-bearing effect in the coating. When subjected to external friction, their smooth surface reduces the direct shear force from contact with hard objects, disperses local pressure, and lowers the probability of scratches. The hollow structure imparts low density and high rigidity, reducing the weight of the coating while providing compressive support and inhibiting the propagation of microcracks. The low surface energy of polytetrafluoroethylene (PTFE) further reduces the coefficient of friction, while the rigid spheres of the glass microspheres physically prevent PTFE from migrating or agglomerating, forming a stable and uniform friction-reducing network. Together with the reinforcing agent in the modified polyester, they construct a multi-scale damage-resistant system. The rigid filler provides intrinsic strength, while the dynamic slippage effect of the glass microspheres and the lubrication effect of PTFE jointly inhibit plastic deformation and wear debris shedding caused by external forces, thereby further improving scratch resistance and wear resistance. Detailed Implementation

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] The following are some of the raw materials used in the examples and comparative examples:

[0056] The polytetrafluoroethylene was purchased from Shandong Huafu Chemical Co., Ltd., with the grade 4S01-A and an average particle size of 180μm.

[0057] The method for preparing the modified glass microspheres includes the following steps:

[0058] Five parts by weight of hollow glass microspheres were mixed evenly with 95 parts by weight of 32 wt% sodium hydroxide aqueous solution, stirred at 72℃ and 150 r / min for 90 min, cooled to room temperature, filtered, washed with water until neutral, and dried to obtain alkali-treated glass microspheres; 0.5 parts by weight of 3-glycidyl etheroxypropyltriethoxysilane were mixed evenly with 45 parts by weight of 85 wt% ethanol aqueous solution, the pH was adjusted to 5.5, and then 5 parts by weight of alkali-treated glass microspheres were added, and ultrasonic treatment was carried out for 50 min at a frequency of 35 kHz and a power of 200 W, filtered, and dried to obtain modified glass microspheres.

[0059] The hollow glass microspheres were purchased from Wenzhou Weizhen New Materials Co., Ltd., model number 7015, with an average particle size of 65μm and a density of 0.15g / cm³. 3 .

[0060] The commercially available polyester was purchased from Anhui Shenjian New Material Co., Ltd., model SJ4B, with an acid value of 30 mg KOH / g.

[0061] The method for preparing the gypsum board substrate includes the following steps:

[0062] 100 parts by weight of calcined gypsum powder, 0.5 parts by weight of borate, and 1.5 parts by weight of lignin are mixed evenly to obtain a solid powder. 0.3 parts by weight of foaming agent and 80 parts by weight of water are mixed evenly. Sodium dodecyl sulfate is used as the foaming agent. The mixture is then foamed through a foaming system and fed into a mixer. The solid powder is then added to the mixer and stirred thoroughly to obtain a uniform slurry. The slurry is then leveled, solidified, cut, and dried to obtain a gypsum board substrate with a length of 3000 mm, a width of 1200 mm, and a thickness of 12 mm.

[0063] Example 1

[0064] This embodiment provides a method for preparing powder-coated gypsum board with scratch-resistant properties, including the following steps:

[0065] 80 parts by weight of modified polyester, 10 parts by weight of modified glass microspheres, 15 parts by weight of polytetrafluoroethylene, 18 parts by weight of barium sulfate, 12 parts by weight of titanium dioxide, 2 parts by weight of leveling agent, and 5 parts by weight of curing agent were added to a mixer and stirred at 70℃ and 200 r / min for 10 min. The mixture was then transferred to a screw extruder and melt-extruded at 135℃ and 350 r / min. After cooling to room temperature, the mixture was pressed into sheets, pulverized, ground, and passed through a 325-mesh sieve to obtain a powder coating. The leveling agent was GLP588, and the curing agent was isophthalamide hydrazide.

[0066] The surface of the gypsum board substrate is sanded and dust-removed to remove dust and impurities. Then, the powder coating is electrostatically sprayed onto the substrate surface, baked at 180°C for 12 minutes to cure into a film with a coating thickness of 80μm, and cooled to room temperature to obtain the powder-coated gypsum board with scratch-resistant properties.

[0067] The method for preparing the modified polyester includes the following steps:

[0068] 35 parts by weight of diphenylmethane-4,4'-diisocyanate and 25 parts by weight of hexamethylene diisocyanate were mixed evenly to obtain an isocyanate mixture. 15 parts by weight of trimethylolpropane, 10 parts by weight of 1,16-hexadecanediol, 35 parts by weight of 1,5-pentanediol, and 0.3 parts by weight of dibutyltin dilaurate catalyst were added to a sealed reactor and heated to 135°C. 60 parts by weight of the isocyanate mixture were added dropwise over 1.5 hours, and the reaction was maintained at this temperature for 1.5 hours after the addition was complete. 15 parts by weight of azelaic acid and 5 parts by weight of N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide were then added to the reactor, and the temperature was raised to 230°C and maintained. The mixture was reacted at room temperature for 3 hours, then 15 parts by weight of trimellitic anhydride were added and the reaction continued for 5 hours. Next, 0.4 parts by weight of antioxidant were added, and the reaction continued for 1 hour. After cooling to room temperature, the mixture was granulated to obtain polyester with an acid value of 30 mg KOH / g. 30 parts by weight of polyester were mixed evenly with 40 parts by weight of propylene glycol methyl ether acetate, then 12 parts by weight of reinforcing agent and 5 parts by weight of 3-glycidyl etheroxypropyltriethoxysilane were added and ultrasonically treated for 40 minutes at a frequency of 35 kHz and a power of 200 W. The mixture was then ball-milled for 3 hours at a speed of 500 r / min. After the treatment, the solvent was removed by vacuum distillation, and the mixture was dried to obtain the modified polyester. The antioxidant consisted of antioxidant 1010 and antioxidant 168 in a weight ratio of 1.5:1, and the reinforcing agent consisted of silicon carbide and boron nitride in a weight ratio of 1.6:1. The average particle size of the silicon carbide was 10 μm, and the average particle size of the boron nitride was 2 μm.

[0069] Example 2

[0070] This embodiment provides a method for preparing powder-coated gypsum board with scratch-resistant properties, including the following steps:

[0071] 70 parts by weight of modified polyester, 5 parts by weight of modified glass microspheres, 10 parts by weight of polytetrafluoroethylene, 15 parts by weight of barium sulfate, 10 parts by weight of titanium dioxide, 1 part by weight of leveling agent, and 3 parts by weight of curing agent were added to a mixer and stirred at 65°C and 250 r / min for 15 min. The mixture was then transferred to a screw extruder and melt-extruded at 130°C and 400 r / min. After cooling to room temperature, the mixture was pressed into sheets, pulverized, ground, and passed through a 270-mesh sieve to obtain a powder coating. The leveling agent was GLP588, and the curing agent was isophthalamide hydrazide.

[0072] The surface of the gypsum board substrate is sanded and dust-removed to remove dust and impurities. Then, the powder coating is electrostatically sprayed onto the substrate surface, baked at 175°C for 20 minutes to cure into a film with a coating thickness of 70 μm, and cooled to room temperature to obtain the powder-coated gypsum board with scratch resistance.

[0073] The preparation method of the modified polyester is the same as that in Example 1.

[0074] Example 3

[0075] This embodiment provides a method for preparing powder-coated gypsum board with scratch-resistant properties, including the following steps:

[0076] 90 parts by weight of modified polyester, 15 parts by weight of modified glass microspheres, 20 parts by weight of polytetrafluoroethylene, 20 parts by weight of barium sulfate, 15 parts by weight of titanium dioxide, 3 parts by weight of leveling agent, and 6 parts by weight of curing agent were added to a mixer and stirred at 75°C and 150 r / min for 5 min. The mixture was then transferred to a screw extruder and melt-extruded at 140°C and 300 r / min. After cooling to room temperature, the mixture was pressed into sheets, pulverized, ground, and passed through a 400-mesh sieve to obtain a powder coating. The leveling agent was GLP588, and the curing agent was isophthalamide hydrazide.

[0077] The surface of the gypsum board substrate is sanded and dust-removed to remove dust and impurities. Then, the powder coating is electrostatically sprayed onto the substrate surface, baked at 185°C for 10 minutes to cure into a film with a coating thickness of 90μm, and cooled to room temperature to obtain the powder-coated gypsum board with scratch resistance.

[0078] The preparation method of the modified polyester is the same as that in Example 1.

[0079] Comparative Example 1

[0080] The difference between this comparative example and Example 1 is that the preparation method of the modified polyester is different, as follows: The preparation method of the modified polyester includes the following steps:

[0081] 35 parts by weight of diphenylmethane-4,4'-diisocyanate and 25 parts by weight of hexamethylene diisocyanate were mixed evenly to obtain an isocyanate mixture. 25 parts by weight of 1,16-hexadecanediol, 35 parts by weight of 1,5-pentanediol, and 0.3 parts by weight of dibutyltin dilaurate catalyst were added to a sealed reactor and heated to 135°C. 60 parts by weight of the isocyanate mixture were added dropwise over 1.5 hours, and the reaction was maintained at this temperature for 1.5 hours after the addition was complete. 15 parts by weight of azelaic acid and 5 parts by weight of N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide were added to the reactor, and the temperature was raised to 230°C. The reaction was maintained at a constant temperature for 3 hours, then 15 parts by weight of trimellitic anhydride were added and the reaction continued for 5 hours. Next, 0.4 parts by weight of antioxidant were added, and the reaction continued for 1 hour. The mixture was cooled to room temperature and granulated to obtain polyester. 30 parts by weight of polyester and 40 parts by weight of propylene glycol methyl ether acetate were mixed evenly, then 12 parts by weight of reinforcing agent and 5 parts by weight of 3-glycidyl etheroxypropyltriethoxysilane were added and ultrasonically treated for 40 minutes at a frequency of 35 kHz and a power of 200 W. The mixture was then ball-milled for 3 hours at a speed of 500 r / min. After the treatment, the solvent was removed by vacuum distillation, and the mixture was dried to obtain the modified polyester. The antioxidant consisted of antioxidant 1010 and antioxidant 168 in a weight ratio of 1.5:1, and the reinforcing agent consisted of silicon carbide and boron nitride in a weight ratio of 1.6:1. The average particle size of the silicon carbide was 10 μm, and the average particle size of the boron nitride was 2 μm.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Example 1 is that the preparation method of the modified polyester is different, as follows: The preparation method of the modified polyester includes the following steps:

[0084] 35 parts by weight of diphenylmethane-4,4'-diisocyanate and 25 parts by weight of hexamethylene diisocyanate were mixed evenly to obtain an isocyanate mixture. 25 parts by weight of trimethylolpropane, 35 parts by weight of 1,5-pentanediol, and 0.3 parts by weight of dibutyltin dilaurate catalyst were added to a sealed reactor and heated to 135°C. 60 parts by weight of the isocyanate mixture were added dropwise over 1.5 hours, and the reaction was maintained at this temperature for 1.5 hours after the addition was complete. 15 parts by weight of azelaic acid and 5 parts by weight of N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide were added to the reactor, and the temperature was raised to 230°C and maintained. The reaction was carried out for 3 hours, then 15 parts by weight of trimellitic anhydride were added and the reaction was continued for 5 hours. Next, 0.4 parts by weight of antioxidant were added and the reaction was continued for 1 hour. After cooling to room temperature, the mixture was granulated to obtain polyester. 30 parts by weight of polyester and 40 parts by weight of propylene glycol methyl ether acetate were mixed evenly, then 12 parts by weight of reinforcing agent and 5 parts by weight of 3-glycidyl etheroxypropyltriethoxysilane were added and ultrasonically treated for 40 minutes at a frequency of 35 kHz and a power of 200 W. The mixture was then ball-milled for 3 hours at a speed of 500 r / min. After the treatment, the solvent was removed by vacuum distillation, and the mixture was dried to obtain the modified polyester. The antioxidant consisted of antioxidant 1010 and antioxidant 168 in a weight ratio of 1.5:1, and the reinforcing agent consisted of silicon carbide and boron nitride in a weight ratio of 1.6:1. The average particle size of the silicon carbide was 10 μm, and the average particle size of the boron nitride was 2 μm.

[0085] Comparative Example 3

[0086] The difference between this comparative example and Example 1 is that the preparation method of the modified polyester is different, as follows: The preparation method of the modified polyester includes the following steps:

[0087] 35 parts by weight of diphenylmethane-4,4'-diisocyanate and 25 parts by weight of hexamethylene diisocyanate were mixed evenly to obtain an isocyanate mixture. 15 parts by weight of trimethylolpropane, 10 parts by weight of 1,16-hexadecanediol, 35 parts by weight of 1,5-pentanediol, and 0.3 parts by weight of dibutyltin dilaurate catalyst were added to a sealed reactor and heated to 135°C. 60 parts by weight of the isocyanate mixture were added dropwise over 1.5 hours, and the reaction was maintained at this temperature for 1.5 hours after the addition was complete. 5 parts by weight of N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide were added to the reactor, and the temperature was raised to 230°C. The reaction was carried out at ℃ for 3 hours, then 15 parts by weight of trimellitic anhydride were added and the reaction continued for 5 hours. Then 0.4 parts by weight of antioxidant were added and the reaction continued for 1 hour. After cooling to room temperature, the mixture was granulated to obtain polyester. 30 parts by weight of polyester and 40 parts by weight of propylene glycol methyl ether acetate were mixed evenly, then 12 parts by weight of reinforcing agent and 5 parts by weight of 3-glycidyl etheroxypropyltriethoxysilane were added and ultrasonically treated for 40 minutes at a frequency of 35 kHz and a power of 200 W. The mixture was then ball-milled for 3 hours at a speed of 500 r / min. After the treatment, the solvent was removed by vacuum distillation, and the mixture was dried to obtain the modified polyester. The antioxidant consisted of antioxidant 1010 and antioxidant 168 in a weight ratio of 1.5:1, and the reinforcing agent consisted of silicon carbide and boron nitride in a weight ratio of 1.6:1. The average particle size of the silicon carbide was 10 μm, and the average particle size of the boron nitride was 2 μm.

[0088] Comparative Example 4

[0089] The difference between this comparative example and Example 1 is that the modified polyester is replaced with polyester, specifically as follows: The preparation method of the polyester includes the following steps:

[0090] 35 parts by weight of diphenylmethane-4,4'-diisocyanate and 25 parts by weight of hexamethylene diisocyanate were mixed evenly to obtain an isocyanate mixture. 15 parts by weight of trimethylolpropane, 10 parts by weight of 1,16-hexadecanediol, 35 parts by weight of 1,5-pentanediol, and 0.3 parts by weight of dibutyltin dilaurate catalyst were added to a sealed reactor and heated to 135°C. 60 parts by weight of the isocyanate mixture were added dropwise over 1.5 hours, and the reaction was maintained at this temperature for 1.5 hours after the addition was complete. 15 parts by weight of azelaic acid and 5 parts by weight of N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide were added to the reactor, and the temperature was raised to 230°C and maintained for 3 hours. Then, 15 parts by weight of trimellitic anhydride were added and the reaction continued for 5 hours. Finally, 0.4 parts by weight of antioxidant were added and the reaction continued for 1 hour. The mixture was cooled to room temperature and granulated to obtain a polyester with an acid value of 30 mg KOH / g. The antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 1.5:1.

[0091] Comparative Example 5

[0092] The difference between this comparative example and Example 1 is that the modified polyester is replaced with commercially available polyester.

[0093] Comparative Example 6

[0094] The difference between this comparative example and Example 1 is that the modified glass microspheres are replaced with hollow glass microspheres.

[0095] Performance testing

[0096] The powder-coated gypsum boards with scratch-resistant properties prepared in Examples 1-3 and Comparative Examples 1-6 were subjected to performance tests to assess the scratch resistance, impact resistance, and abrasion resistance of the coating film on the gypsum board surface. Impact resistance was tested according to the method in National Standard GB / T 1732-2020. Abrasion resistance was tested according to the method in National Standard GB / T 23988-2009; the higher the abrasion resistance (the more sand required to abrade a unit of coating), the better the abrasion resistance. Scratch resistance was tested on the coating surface using a coating scratch tester. The results are shown in Table 1.

[0097] Table 1: Test Results of Various Performance Aspects of Powder Coated Gypsum Board

[0098] Impact resistance (kg·cm) Abrasion resistance (L / μm) Scratch resistance Example 1 40.25 3.72 No scratches Example 2 39.03 3.65 No scratches Example 3 39.80 3.69 No scratches Comparative Example 1 33.71 3.13 Minor scratches Comparative Example 2 34.95 3.25 Minor scratches Comparative Example 3 38.30 3.30 Minor scratches Comparative Example 4 37.56 2.58 Obvious scratches Comparative Example 5 31.05 1.96 Obvious scratches Comparative Example 6 38.02 3.01 Obvious scratches

[0099] The test results above show that the powder-coated gypsum boards with scratch-resistant properties prepared in Examples 1-3 have excellent scratch resistance, impact resistance, and abrasion resistance. In particular, the powder-coated gypsum board prepared in Example 1 exhibits the most outstanding comprehensive performance. This is because the present invention significantly improves the scratch resistance, impact resistance, and abrasion resistance of the powder-coated gypsum board through the synergistic effect of specific modified polyester, modified glass microspheres, and polytetrafluoroethylene. Compared with Example 1, Comparative Examples 1-3 did not use the specific self-made polyester, the polyester in Comparative Example 4 was not modified, commercially available polyester was used in Comparative Example 5, and the glass microspheres in Comparative Example 6 were not surface-modified. The test results show that these modifications led to a decrease in the comprehensive performance of the prepared powder-coated gypsum boards. These experimental results further demonstrate the importance of the technical solutions corresponding to Examples 1-3 of the present invention for their technical effects.

[0100] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing powder-coated gypsum board with scratch-resistant properties, characterized in that, Includes the following steps: 70-90 parts by weight of modified polyester, 5-15 parts by weight of modified glass microspheres, 10-20 parts by weight of polytetrafluoroethylene, 15-20 parts by weight of barium sulfate, 10-15 parts by weight of titanium dioxide, 1-3 parts by weight of leveling agent and 3-6 parts by weight of curing agent are mixed and stirred, melted and extruded, cooled and pressed into sheets, crushed, ground and sieved to obtain powder coating; the surface of gypsum board substrate is sanded and dusted, the powder coating is electrostatically sprayed onto the surface of the substrate, heated and cured, and cooled to obtain the final product.

2. The method for preparing powder-coated gypsum board with scratch-resistant properties according to claim 1, characterized in that, The method for preparing the modified polyester includes the following steps: Trimethylolpropane, 1,16-hexadecanediol, 1,5-pentanediol, and a catalyst were added to a sealed reactor and heated. An isocyanate mixture was added dropwise, and the reaction was maintained at this temperature. Azelaic acid and N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide were added to the reactor, and the temperature was raised and maintained. Trimeric trioxide was then added to continue the reaction, followed by the addition of an antioxidant. The mixture was cooled and granulated to obtain polyester. The polyester was then mixed evenly with propylene glycol methyl ether acetate, and a reinforcing agent and 3-glycidyl etheroxypropyltriethoxysilane were added. The mixture was ultrasonically treated, then ball-milled, distilled under reduced pressure, and dried to obtain modified polyester.

3. The method for preparing powder-coated gypsum board with scratch-resistant properties according to claim 2, characterized in that, The weight ratio of the mixture of trimethylolpropane, 1,16-hexadecanediol, 1,5-pentanediol, catalyst, and isocyanate is 10-20:5-15:30-40:0.2-0.5:50-70; the weight ratio of azelaic acid, N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide, trimellitic anhydride, and antioxidant is 10-20:3-7:10-20:0.3-0.5; and the weight ratio of polyester, reinforcing agent, and 3-glycidyl etheroxypropyltriethoxysilane is 25-35:10-15:3-7.

4. The method for preparing powder-coated gypsum board with scratch-resistant properties according to claim 2, characterized in that, The isocyanate mixture consists of diphenylmethane-4,4'-diisocyanate and hexamethylene diisocyanate.

5. The method for preparing powder-coated gypsum board with scratch-resistant properties according to claim 2, characterized in that, The catalyst is one or a mixture of two or more of dibutyltin dilaurate, bismuth isooctanoate, and tetrabutyl titanate.

6. The method for preparing powder-coated gypsum board with scratch-resistant properties according to claim 2, characterized in that, The antioxidant is composed of antioxidant 1010 and antioxidant 168.

7. The method for preparing powder-coated gypsum board with scratch-resistant properties according to claim 2, characterized in that, The reinforcing agent is composed of silicon carbide and boron nitride.

8. The method for preparing powder-coated gypsum board with scratch-resistant properties according to claim 1, characterized in that, The modified glass microspheres are made by surface modification of hollow glass microspheres after alkali treatment with 3-glycidyl etheroxypropyltriethoxysilane.

9. The method for preparing powder-coated gypsum board with scratch-resistant properties according to claim 1, characterized in that, The leveling agent is one or a mixture of two or more of the leveling agents GLP588, GLP788, and GLP599; the curing agent is one or a mixture of two or more of the isophthalohydrazide, phthalic anhydride, and adipate dihydrazide.

10. A powder-coated gypsum board with scratch-resistant properties, characterized in that, Prepared by the method according to any one of claims 1-9.