Ultralow-temperature curing powder coating composition, preparation method and facing treatment method for gypsum board by using ultralow-temperature curing powder coating composition

Abstract

The invention discloses an ultralow-temperature curing powder coating composition, a preparation method and a facing treatment method for a gypsum board, and belongs to the technical field of powder coating preparation, and the ultralow-temperature curing powder coating composition comprises the following raw materials in parts by mass: 30-35 parts of carboxyl-terminated saturated polyester resin, 20-30 parts of unsaturated acrylic resin, 1-3 parts of a curing agent, 1-3 parts of a curing agent, 1-3 parts of a curing agent and 1-3 parts of a curing agent. The coating is prepared from the following components in parts by weight: 5 to 10 parts of curing agent, 1 to 5 parts of catalyst, 0.1 to 0.5 part of degassing agent, 0 to 0.5 part of antioxidant, 0.3 to 1.0 part of flatting agent, 0 to 2.0 parts of polymerization inhibitor, and 27.1 to 32.2 parts of pigment and filler. The low-temperature curing powder coating disclosed by the invention can be directly sprayed on heat-sensitive base materials such as wood, gypsum boards and plastic products, and the curing temperature of the powder is lower than 100 DEG C. After the powder coating is cured for 10-30 minutes at the temperature of 95-110 DEG C, a coating obtained after the powder coating is cured is tested, the curing degree of the coating can reach 80% or above, and a coating film is good in mechanical performance and excellent in chemical resistance, aging resistance and salt spray resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of powder coating preparation and the technical field of gypsum board surface treatment process, and specifically relates to a process method for preparing an ultra-low temperature curing powder coating and its treatment of gypsum board surface. Background Technique

[0002] There are many types of powder coatings, and the types of resins, cross-linking agents, and curing accelerators in each system are different.

[0003] For example, in the acid / hydroxyl system, a polyester capped with carboxylic acid is used as the film-forming substance. Due to the nature of the esterification reaction and the need to remove water to obtain a high conversion rate, the lowest low-temperature curing temperature can only reach 150°C. In the hydroxyl / isocyanate system, due to the limitation of the deblocking temperature of the blocked isocyanate, the lowest curing temperature of the system is generally about 140°C.

[0004] For another example, Patent CN112266683A adjusts the formula and process together to reduce the curing temperature to 110°C, and the coating can maintain basic mechanical properties. However, this scheme has poor weather resistance and limited application scenarios. The powder coating prepared by the method disclosed in Patent CN118562344A is cured at 110°C for 5 minutes and then cured by a 3KW ultraviolet mercury lamp for 15 seconds. The coating is cured through the synergistic effect of the two means. This scheme has high requirements for existing curing equipment, requires the manufacturer to add an ultraviolet mercury lamp curing production line, has a large equipment investment, poor economic applicability, and the ultraviolet mercury lamp has insufficient penetration for thick coatings (such as 50-100μm) or coatings with high pigment content (such as black and white), which easily leads to incomplete deep curing. In addition, this scheme is not applicable to application scenarios with complex-shaped substrates or high requirements for long-term outdoor weather resistance.

[0005] None of the above-mentioned schemes can reduce the coating curing temperature below 110°C through formula adjustment, which limits the use of powder coatings on heat-sensitive substrates such as wood-based panels, gypsum boards, calcium silicate boards, engineering plastics, and composite materials, and seriously restricts the development of powder coatings.

[0006] Traditional gypsum board materials have the following defects in building partitions and ceiling applications: Due to the lack of a decorative finish layer, additional secondary processing such as applying putty and painting latex paint is required, resulting in an extended construction period, increased labor costs, and pollution problems caused by the release of volatile organic compounds (VOCs). This process defect restricts the process of building industrialization and the requirements of green construction, and there is an urgent need for a new technical solution to solve the above problems.

[0007] As a type of green and environmentally friendly coating, powder coatings hardly release VOCs during the construction and curing processes. However, the curing temperature of conventional powder coatings is too high, generally requiring above 150 °C to achieve effective curing. After testing, most gypsum boards will show obvious deformation when exposed to a temperature environment above 110 °C for 30 minutes. Therefore, powder coatings are rarely used in the surface treatment of gypsum boards. Summary of the Invention

[0008] In view of the above problems existing in the existing powder coatings and gypsum boards, the present invention provides a process method for preparing a super-low temperature curing powder coating and its surface treatment of gypsum boards, which reduces the curing temperature of the powder coating to below 110 °C, with a minimum curing temperature of 95 °C. The cured powder coating can maintain good mechanical properties, chemical resistance, aging resistance, and salt spray resistance. This enables the powder coating to be sprayed on heat-sensitive substrates such as wood-based panels, gypsum boards, calcium silicate boards, engineering plastics, and composite materials.

[0009] To achieve the above objectives, the present invention is realized through the following technical solutions: A super-low temperature curing powder coating composition, which comprises the following raw materials by weight: carboxyl-terminated saturated polyester resin: 30 parts to 35 parts, unsaturated acrylic resin: 20 parts to 30 parts, curing agent: 5 parts to 10 parts, catalyst: 1 part to 5 parts, degassing agent: 0.1 part to 0.5 part, antioxidant: 0 part to 0.5 part, leveling agent: 0.3 part to 1.0 part, inhibitor: 0 part to 2.0 parts, sanding agent: 0 to 1 part, pigments and fillers: 10 parts to 40 parts.

[0010] As a preferred embodiment, the acid value of the carboxyl-terminated saturated polyester resin is 30 - 40 mg KOH / g, the softening point is 55 - 65 °C, and the viscosity is 1500 - 3000 mPa.s @ 200 °C.

[0011] As a preferred embodiment, the unsaturated acrylic resin is selected from unsaturated polyurethane acrylate resin with a carbon-carbon double bond equivalent of 400 g / q, a softening point of 40 - 45 °C, and a viscosity of 2500 - 4000 mPa.s @ 200 °C; or unsaturated epoxy acrylate resin with a carbon-carbon double bond equivalent of 600 g / q, a softening point of 35 - 40 °C, and a viscosity of 2000 - 4000 mPa.s @ 200 °C.

[0012] As a preferred embodiment, the curing agent is isocyanuric acid trisglycidyl ester; the catalyst is selected from onium salt compounds, metal salts, imidazoles, organotin compounds, or quaternary ammonium salts.

[0013] As a preferred embodiment, the antioxidant is at least one of hindered amine types and phosphite types; the leveling agent is an acrylate type, fluorocarbon type, dendritic polymer, or silicone type leveling agent.

[0014] Preferably, the inhibitor is a saturated polyester resin with an acid value of 50 - 55 mg KOH / g, a softening point of 55 - 65 °C, and a viscosity of 700 - 1000 mPa·s at 200 °C.

[0015] A method for preparing the ultra-low temperature curable powder coating composition as described above, which comprises the following steps: Weigh the raw materials, premix the raw materials, and then carry out melt extrusion at a temperature not exceeding 80 °C to obtain a molten material. Press the molten material into tablets and cool to obtain tablet materials. Crush the tablet materials, then grind and screen them to obtain the ultra-low temperature curable powder coating composition.

[0016] A method for finishing a gypsum board using the ultra-low temperature curable powder coating composition as described above, which comprises the following steps: Roll coat the gypsum board with a UV conductive adhesive and then cure it with ultraviolet light to enhance the conductivity of the gypsum board. After grinding the gypsum board roll-coated with the UV conductive adhesive, electrostatically spray the ultra-low temperature curable powder coating composition and cure it at 95 - 110 °C.

[0017] Preferably, the curing method is hot air curing or infrared curing; the gypsum board is a gypsum board without a finished surface effect.

[0018] Preferably, the gypsum board is a paper-faced gypsum board.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The ultra-low temperature curing powder coating of the present invention can be directly sprayed on heat-sensitive substrates such as wood-based panels, gypsum boards, calcium silicate boards, engineering plastics, and composite materials, and the curing temperature of the powder is lower than 110°C. The powder coating is cured by infrared at 95-110°C for 4-5 minutes or by hot air at 95-110°C for 15-30 minutes. After testing the cured coating of the powder coating, the curing degree can reach more than 80%. The mechanical properties of the coating film are good, and the stain resistance, aging resistance, and salt spray resistance are excellent. On the premise of ensuring the coating performance, it can be cured at low temperature, saving energy consumption, enabling the powder coating to be applied to heat-sensitive substrates, and broadening the application field of the powder coating. After the gypsum board is surface-treated with the above ultra-low temperature curing powder coating, it has higher moisture-proof and waterproof performance, hardness, and yellowing resistance than traditional products, which not only extends the storage life and service life of the gypsum board, but also expands the application scenarios of the gypsum board material. At the same time, it enhances the surface finish effect of the gypsum board, expands its application scenarios, and avoids the VOC emission problem caused by subsequent latex paint. After the decoration is completed, the owner can move in immediately, reducing the waiting cost of the owner, making the gypsum board more popular among end-users, and further expanding the application scenarios. Detailed Embodiments

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] Unless otherwise specified, the raw materials used in the present invention are all commercially available products.

[0022] I. Embodiment 1 This embodiment provides a preparation method for an ultra-low temperature curing powder coating composition, which specifically includes the following steps: Step 1. Weigh the raw materials: Weigh and mix the raw materials evenly: malonic acid ester-based carboxyl-terminated saturated polyester resin: 30 parts, unsaturated acrylic resin: 30 parts, curing agent: 5 parts, catalyst: 5 parts, degassing agent: 0.1 part, antioxidant: 0.5 part, leveling agent: 0.3 part, inhibitor: 2.0 parts, pigments and fillers: 27.1 parts; The above raw materials are all commercially available products; among them, the acid value of the malonic ester-based carboxyl-terminated saturated polyester resin is 30-40 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 2000-3000 mPa·s @ 200 °C; the unsaturated acrylic resin is selected as an unsaturated polyurethane acrylate resin, the carbon-carbon double bond equivalent is 400 g / q, the softening point is 40-45 °C, and the viscosity is 2500-4000 mPa·s @ 200 °C; the curing agent is triglycidyl isocyanurate, and the product of Huangshan Huahui Technology Company is used in this example; the catalyst is an onium salt compound, a metal salt, an imidazole, an organotin or a quaternary ammonium salt, preferably a quaternary ammonium carboxylate, and dodecyltrimethylammonium formate is used in this example; the degassing agent is a low-temperature degassing agent, and Tianwo PowderAdd ® D700 is used in this example; the antioxidant is a hindered amine, a phosphite and a compound antioxidant, and the synergistic effect of hindered amines and phosphites is used in this example; the leveling agent is an acrylate, a fluorocarbon, a dendritic polymer or a silicone leveling agent, and an acrylate leveling agent is preferably used in this example; the inhibitor is a saturated polyester, the acid value of the resin is 50-55 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 700-1000 mPa·s @ 200 °C; Step 2: Use a twin-screw extruder to melt-extrude the pre-mixed raw materials, and set the extrusion temperature not higher than 80 °C; Step 3: Use a cold roll and a tablet press to press and cool the extruded molten material; Step 4: Crush the cooled sheet material, and then grind and screen it to obtain an ultra-low temperature curing powder coating.

[0023] II. Example 2 This example provides a preparation method of an ultra-low temperature curing powder coating composition, which specifically includes the following steps: Step 1: Weigh the raw materials and mix them evenly: 35 parts of malonic ester-based carboxyl-terminated saturated polyester resin, 20 parts of unsaturated acrylic resin, 10 parts of curing agent, 1 part of catalyst, 0.5 part of degassing agent, 0.5 part of antioxidant, 0.5 part of leveling agent, 1 part of inhibitor, 0.5 part of sanding agent. Pigments and fillers: 31 parts; The above raw materials are all commercially available products; among them, the acid value of the malonic ester-based carboxyl-terminated saturated polyester resin is 30-40 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 2000-3000 mPa·s @ 200 °C; the unsaturated acrylic resin is an unsaturated polyurethane acrylate resin, the carbon-carbon double bond equivalent is 400 g / q, the softening point is 40-45 °C, and the viscosity is 2500-4000 mPa·s @ 200 °C; for the triglycidyl isocyanurate, the product of Huangshan Huahui Technology Co., Ltd. is preferably used in this example; the catalyst is an onium salt compound, a metal salt, an imidazole, an organotin or a quaternary ammonium salt, and a carboxylic acid quaternary ammonium salt is preferred, and dodecyltrimethylammonium formate is preferably used in this example; the degassing agent is a low-temperature degassing agent, and Tianwo PowderAdd ® D700 is preferably used in this example; the antioxidant is a hindered amine, a phosphite and a compound antioxidant, and a compound antioxidant is preferably used in this example; the leveling agent is an acrylate, a fluorocarbon, a dendritic polymer or a silicone leveling agent, and an acrylate leveling agent is preferably used in this example; the inhibitor is a saturated polyester, the acid value of the resin is 50-55 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 700-1000 mPa·s @ 200 °C; the sand pattern agent is bentonite or a modified polyvinylidene fluoride polymer, and a modified polyvinylidene fluoride polymer is preferably used in this example; Step 2: Use a twin-screw extruder to melt-extrude the pre-mixed raw materials, and set the extrusion temperature not higher than 80 °C; Step 3: Use a cold roll and a tablet press to press and cool the extruded molten material; Step 4: Crush the cooled sheet material, and then grind and screen it to obtain an ultra-low temperature curable powder coating.

[0024] III. Example 3 This example provides a preparation method of an ultra-low temperature curable powder coating composition, which specifically includes the following steps: Step 1: Weigh the raw materials: 30 parts of malonic ester-based carboxyl-terminated saturated polyester resin, 25 parts of unsaturated acrylic resin, 5 parts of curing agent, 4 parts of catalyst, 0.5 part of degassing agent, 0.3 part of antioxidant, 1.0 part of leveling agent, 2 parts of inhibitor, 32.2 parts of pigments and fillers; Among them, the above raw materials are all commercially available products; among them, the acid value of the malonic ester-terminated carboxyl saturated polyester resin is 30-40 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 2000-3000 mPa·s @ 200 °C; the unsaturated acrylic resin is selected as an unsaturated epoxy acrylic resin, the carbon-carbon double bond equivalent is 600 g / q, the softening point is 35-40 °C, and the viscosity is 2000-4000 mPa·s @ 200 °C; for the triglycidyl isocyanurate, the product of Huangshan Huahui Technology Co., Ltd. is preferably used in this example; the catalyst is an onium salt compound, a metal salt, an imidazole, an organotin or a quaternary ammonium salt, and a carboxylic acid quaternary ammonium salt is preferred. In this example, dodecyltrimethylammonium formate is preferably used; the degassing agent is a low-temperature degassing agent, and Tianwo PowderAdd ® D700 is preferably used in this example; the antioxidant is a hindered amine, a phosphite and a compound antioxidant, and a compound antioxidant is preferably used in this example; the leveling agent is an acrylate, a fluorocarbon, a dendritic polymer or a silicone leveling agent, and a dendritic polymer is preferably used in this example; the inhibitor is a saturated polyester, the acid value of the resin is 50-55 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 700-1000 mPa·s @ 200 °C; Step 2: Use a twin-screw extruder to melt-extrude the pre-mixed raw materials, and set the extrusion temperature not higher than 80 °C; Step 3: Use a cold roll and a tablet press to press and cool the extruded molten material; Step 4: Crush the cooled sheet material, and then grind and screen it to obtain an ultra-low temperature curable powder coating.

[0025] IV. Example 4 This example provides a preparation method of an ultra-low temperature curable powder coating composition, which specifically includes the following steps: Step 1: Weigh the raw materials: 30 parts of malonic ester-terminated carboxyl saturated polyester resin, 25 parts of unsaturated acrylic resin, 5 parts of curing agent, 4 parts of catalyst, 0.5 part of degassing agent, 0.3 part of antioxidant, 1.0 part of leveling agent, 2 parts of inhibitor, 1 part of sanding agent, 31.2 parts of pigment and filler; Among them, the above raw materials are all commercially available products; among them, the acid value of the malonic ester-based carboxyl-terminated saturated polyester resin is 30-40 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 2000-3000 mPa·s @ 200 °C; the unsaturated acrylic resin is selected as an unsaturated epoxy acrylate resin, the carbon-carbon double bond equivalent is 600 g / q, the softening point is 35-40 °C, and the viscosity is 2000-4000 mPa·s @ 200 °C; for the triglycidyl isocyanurate, the product of Huangshan Huahui Technology Co., Ltd. is preferably used in this embodiment; the catalyst is an onium salt compound, a metal salt, an imidazole, an organotin or a quaternary ammonium salt, and a carboxylic acid quaternary ammonium salt is preferred, and dodecyltrimethylammonium formate is preferably used in this embodiment; the degassing agent is a low-temperature degassing agent, and Tianwo PowderAdd ® D700 is preferably used in this embodiment; the antioxidant is a hindered amine, a phosphite and a compound antioxidant, and a compound antioxidant is preferably used in this embodiment; the leveling agent is an acrylate, a fluorocarbon, a dendritic polymer or a silicone leveling agent, and a fluorocarbon type is preferably used in this embodiment; the inhibitor is a saturated polyester, the acid value of the resin is 50-55 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 700-1000 mPa·s @ 200 °C. The sanding agent is bentonite or a modified polyvinylidene fluoride polymer, and bentonite is preferably used in this embodiment; Step 2: Use a twin-screw extruder to melt-extrude the pre-mixed raw materials, and set the extrusion temperature not higher than 80 °C; Step 3: Use a cold roll and a tablet press to press and cool the extruded molten material; Step 4: Crush the cooled sheet material, and then grind and screen it to obtain an ultra-low temperature curing powder coating.

[0026] V. Example 5 This embodiment provides a preparation method of an ultra-low temperature curing powder coating composition, which specifically includes the following steps: Step 1: Weigh the raw materials: 30 parts of malonic ester-based carboxyl-terminated saturated polyester resin, 25 parts of unsaturated acrylic resin, 5 parts of curing agent, 4 parts of catalyst, 0.5 part of degassing agent, 0.3 part of antioxidant, 1.0 part of leveling agent, 0 part of inhibitor, 34.2 parts of pigment and filler; Among them, the above raw materials are all commercially available products; among them, the acid value of the malonic ester-based carboxyl-terminated saturated polyester resin is 30-40 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 2000-3000 mPa·s @ 200 °C; the unsaturated acrylic resin is selected as an unsaturated epoxy acrylate resin, the carbon-carbon double bond equivalent is 600 g / q, the softening point is 35-40 °C, and the viscosity is 2000-4000 mPa·s @ 200 °C; for the triglycidyl isocyanurate, the product of Huangshan Huahui Technology Co., Ltd. is preferably used in this example; the catalyst is an onium salt compound, a metal salt, an imidazole, an organotin or a quaternary ammonium salt, and imidazoles are preferred. 2-phenylimidazole is preferably used in this example; the degassing agent is a low-temperature degassing agent, and Tianwo PowderAdd® D700 is preferably used in this example; the antioxidant is a hindered amine, a phosphite and a compound antioxidant, and hindered amines are preferred in this example; the leveling agent is an acrylate, a fluorocarbon, a dendritic polymer or a silicone leveling agent, and a silicone leveling agent is preferably used in this example; Step 2: Use a twin-screw extruder to melt-extrude the pre-mixed raw materials, and set the extrusion temperature not higher than 80 °C; Step 3: Use a cold roll and a tablet press to press and cool the extruded molten material; Step 4: Crush the cooled sheet material, and then grind and screen it to obtain an ultra-low temperature curable powder coating.

[0027] Six, Example 6 This example provides a preparation method of an ultra-low temperature curable powder coating composition, which specifically includes the following steps: Step 1: Weigh the raw materials and mix them evenly: 35 parts of malonic ester-based carboxyl-terminated saturated polyester resin, 25 parts of unsaturated acrylic resin, 10 parts of curing agent, 4 parts of catalyst, 0.5 part of degassing agent, 0.5 part of antioxidant, 0.5 part of leveling agent, 2 parts of inhibitor, 22.5 parts of pigment and filler; The above raw materials are all commercially available products; among them, the acid value of the malonic ester-terminated carboxyl saturated polyester resin is 30-40 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 2000-3000 mPa·s @ 200 °C; the unsaturated acrylic resin is selected as an unsaturated polyurethane acrylate resin, the carbon-carbon double bond equivalent is 400 g / q, the softening point is 40-45 °C, and the viscosity is 2500-4000 mPa·s @ 200 °C; the triglycidyl isocyanurate, in this embodiment, the product of Huangshan Huahui Technology Co., Ltd. is preferably selected; the catalyst is an onium salt compound, a metal salt, an imidazole, an organotin or a quaternary ammonium salt, preferably an organotin, and in this embodiment, dibutyltin dilaurate is preferably selected; the degassing agent is a low-temperature degassing agent, and in this embodiment, Tianwo PowderAdd ® D700 is preferably selected; the antioxidant is a hindered amine, a phosphite and a compound antioxidant, and in this embodiment, a compound antioxidant is preferably selected; the leveling agent is an acrylate, a fluorocarbon, a dendritic polymer or a silicone leveling agent, and in this embodiment, an acrylate leveling agent is preferably selected; the inhibitor is a saturated polyester, the acid value of the resin is 50-55 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 700-1000 mPa·s @ 200 °C; Step 2: Use a twin-screw extruder to melt-extrude the pre-mixed raw materials, and set the extrusion temperature not higher than 80 °C; Step 3: Use a cold roll and a tablet press to press and cool the extruded molten material; Step 4: Crush the cooled sheet material, and then grind and screen it to obtain an ultra-low temperature curing powder coating.

[0028] VII. Example 7 This embodiment provides a preparation method of an ultra-low temperature curing powder coating composition, which specifically includes the following steps: Step 1: Weigh the raw materials: 30 parts of malonic ester-terminated carboxyl saturated polyester resin, 25 parts of unsaturated polyurethane acrylate resin, 5 parts of curing agent, 4 parts of catalyst, 0.5 part of degassing agent, 0.3 part of antioxidant, 1.0 part of leveling agent, 0 part of inhibitor, 33.2 parts of pigment and filler; The above raw materials are all commercially available products; among them, the acid value of the malonic ester-based carboxyl-terminated saturated polyester resin is 30-40 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 2000-3000 mPa·s at 200 °C; the unsaturated acrylic resin is an unsaturated polyurethane acrylate resin, the carbon-carbon double bond equivalent is 400 g / q, the softening point is 40-45 °C, and the viscosity is 2500-4000 mPa·s at 200 °C; for the triglycidyl isocyanurate, the product of Huangshan Huahui Technology Co., Ltd. is preferably used in this example; the catalyst is an onium salt compound, a metal salt, an imidazole, an organotin or a quaternary ammonium salt, and organotin is preferably used, and dibutyltin dilaurate is preferably used in this example; the degassing agent is a low-temperature degassing agent, and Tianwo PowderAdd ® D700 is preferably used in this example; the antioxidant is a hindered amine, a phosphite and a compound antioxidant, and phosphite is preferably used in this example; the leveling agent is an acrylate, a fluorocarbon, a dendritic polymer or a silicone leveling agent, and an acrylate leveling agent is preferably used in this example; the inhibitor is a saturated polyester, the acid value of the resin is 50-55 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 700-1000 mPa·s at 200 °C; Step 2: Use a twin-screw extruder to melt-extrude the pre-mixed raw materials, and set the extrusion temperature not higher than 80 °C; Step 3: Use a cold roll and a tablet press to press and cool the extruded molten material; Step 4: Crush the cooled sheet material, and then grind and screen it to obtain an ultra-low temperature curable powder coating.

[0029] VIII. Example 8 This example provides a preparation method of an ultra-low temperature curable powder coating composition, which specifically includes the following steps: Step 1: Weigh the raw materials: 30 parts of malonic ester-based carboxyl-terminated saturated polyester resin, 25 parts of unsaturated polyurethane acrylate resin, 10 parts of curing agent, 4 parts of catalyst, 0.5 part of degassing agent, 0.3 part of antioxidant, 1.0 part of leveling agent, 0 part of inhibitor, 23.2 parts of pigment and filler; The above raw materials are all commercially available products; among them, the acid value of the malonic ester-based carboxyl-terminated saturated polyester resin is 30-40 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 2000-3000 mPa·s @ 200 °C; the unsaturated acrylic resin is an unsaturated polyurethane acrylate resin, the carbon-carbon double bond equivalent is 400 g / q, the softening point is 40-45 °C, and the viscosity is 2500-4000 mPa·s @ 200 °C; for the triglycidyl isocyanurate, the product of Huangshan Huahui Technology Co., Ltd. is preferably used in this embodiment; the catalyst is an onium salt compound, a metal salt, an imidazole, an organotin or a quaternary ammonium salt, preferably an organotin, and dibutyltin dilaurate is preferably used in this embodiment; the degassing agent is a low-temperature degassing agent, and Tianwo PowderAdd ® D700 is preferably used in this embodiment; the antioxidant is a hindered amine, a phosphite and a compound antioxidant, and a phosphite is preferably used in this embodiment; the leveling agent is an acrylate, a fluorocarbon, a dendritic polymer or a silicone leveling agent, and an acrylate leveling agent is preferably used in this embodiment; the inhibitor is a saturated polyester, the acid value of the resin is 50-55 mg KOH / g, the softening point is 55-65 °C, and the viscosity is 700-1000 mPa·s @ 200 °C; Step 2: Use a twin-screw extruder to melt and extrude the pre-mixed raw materials, and set the extrusion temperature not higher than 80 °C; Step 3: Use a cold roll and a tablet press to press and cool the extruded molten material; Step 4: Crush the cooled sheet material, and then grind and screen it to obtain an ultra-low temperature curing powder coating.

[0030] IX. Comparative Example 1 The difference between this comparative example and Example 1 is only that the carboxyl-terminated saturated polyester resin is replaced with a common low-temperature curing polyester, such as GH-1157 of Zhejiang Guanghua Technology Co., Ltd.

[0031] The powder coatings prepared in Examples 1-8 and Comparative Example 1 were tested according to the detection items of general weather-resistant topcoats for outdoor use, and the results are shown in Tables 1 and 2.

[0032]

[0033]

[0034] The carboxyl-terminated saturated polyester used in the present invention is different from the common low-temperature curing polyester. When it reacts with the unsaturated resin under the action of a catalyst, after the catalyst melts and releases at 95 °C, it can catalyze the Michael addition reaction of the main resin at a low temperature, so that the prepared powder coating cures at 95 °C - 110 °C.

[0035] The low-temperature curing powder coating of the present invention can be directly sprayed on heat-sensitive substrates such as wood, gypsum board, and plastic products, and the curing temperature of the powder is lower than 100°C. After the powder coating is cured at 95°C to 110°C for 10 minutes to 30 minutes, the cured coating of the powder coating is tested, and the curing degree can reach more than 80%. The mechanical properties of the coating film are good, and the anti-aging and salt spray resistance properties are excellent. On the premise of ensuring the coating performance, it can be cured at low temperature, saving energy consumption, enabling the powder coating to be applied to heat-sensitive substrates, and broadening the application field of the powder coating.

[0036] X. Example 9 This example provides a surface treatment method for gypsum board, which specifically includes the following steps: After roller-coating the UV conductive adhesive on the gypsum board without surface finish effect, it is cured with ultraviolet light to enhance the conductivity of the gypsum board; After grinding the gypsum board roller-coated with the UV conductive adhesive, electrostatically spray the ultra-low temperature curing powder coating composition prepared in Example 1, and infrared cure it at 95 to 110°C for 4 to 5 minutes.

[0037] The above examples are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements on some of the technical features; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An ultra-low temperature curing powder coating composition, characterized in that: The invention comprises the following raw materials in parts by weight: 30 to 35 parts of carboxyl-terminated saturated polyester resin, 20 to 30 parts of unsaturated acrylic resin, 5 to 10 parts of curing agent, 1 to 5 parts of catalyst, 0.1 to 0.5 parts of degassing agent, 0 to 0.5 parts of antioxidant, 0.3 to 1.0 parts of leveling agent, 0 to 2.0 parts of inhibitor, 0 to 1 parts of sand grain agent, and 10 to 40 parts of pigment and filler; the acid value of the carboxyl-terminated saturated polyester resin is 30 to 40 mgKOH / g, the softening point is 55 to 65°C, and the viscosity is 1500 to 3000 mPa.s@ 200°C; the carboxyl-terminated saturated polyester resin is a malonic acid ester carboxyl-terminated saturated polyester resin.

2. The ultra-low temperature curing powder coating composition according to claim 1, characterized in that: The unsaturated acrylic resin is selected from unsaturated polyurethane acrylic resin, with a carbon-carbon double bond equivalent of 400g / q, a softening point of 40-45°C, and a viscosity of 2500-4000 mPa.s@ 200°C; or unsaturated epoxy acrylic resin, with a carbon-carbon double bond equivalent of 600g / q, a softening point of 35-40°C, and a viscosity of 2000-4000 mPa.s@ 200°C.

3. The ultra-low temperature curing powder coating composition according to claim 1, characterized in that: The curing agent is triglycidyl isocyanurate; the catalyst is uranium salt compounds, metal salts, imidazoles, organic tin or quaternary ammonium salts.

4. The ultra-low temperature curing powder coating composition according to claim 1, characterized in that: The antioxidant is at least one of hindered amines and phosphites; the leveling agent is an acrylate, fluorocarbon, dendritic polymer or silicone leveling agent.

5. The ultra-low temperature curing powder coating composition according to claim 1, characterized in that: The polymerization inhibitor is a saturated polyester resin with an acid value of 50-55 mg KOH / g, a softening point of 55-65°C, and a viscosity of 700-1000 mPa.s@ 200°C.

6. A method for preparing the ultra-low temperature curing powder coating composition according to claim 1, characterized in that: The steps include: Weighing raw materials, premixing the raw materials, and then melt-extruding at a temperature not exceeding 80° C. to obtain a molten material; The molten material is sheeted and cooled to obtain sheet material; The flakes are crushed, then ground and sieved to obtain an ultra-low temperature curing powder coating composition.

7. A method for finishing gypsum board using the ultra-low temperature curing powder coating composition according to claim 1, characterized in that: The steps include: After the gypsum board is roller-coated with UV conductive adhesive, it is cured with ultraviolet light to enhance the conductivity of the gypsum board; After the gypsum board coated with the UV conductive adhesive by roller is polished, the ultra-low temperature curing powder coating composition is electrostatically sprayed on it and cured at 95-110°C.

8. The method for finishing a gypsum board according to claim 7, characterized in that: The curing method is hot air curing or infrared curing; the gypsum board is a gypsum board without a finishing effect.

9. The method for finishing a gypsum board according to claim 8, characterized in that: The gypsum board is a paper-faced gypsum board.

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