Low-temperature curing powder coating and preparation method thereof

Abstract

The invention discloses a low-temperature curing powder coating and a preparation method thereof, relates to the technical field of environment-friendly powder coatings, and aims to solve the problem that the existing powder coating cannot meet the coating requirements of diversified substrates. The invention discloses a water-based paint which is composed of 600g of polyester resin, 45g of triglycidyl isocyanurate, 25g of auxiliaries, 25g of low-temperature curing agent, 25g of pigment and 280g of filler, the polyester resin is low-temperature active polyester resin, and the auxiliaries comprise a flatting agent, a defoaming agent and a stabilizer. The powder coating has the advantages that the applicable base material range of the powder coating is greatly expanded, safe coating of heat-sensitive plastics and flammable materials is achieved, energy consumption is remarkably reduced, and the bottleneck of base material application limitation and high energy consumption is broken through.

Description

Technical Field

[0001] The present invention relates to the technical field of environmentally friendly powder coatings, and more particularly to a low-temperature curing powder coating and a preparation method thereof. Background Art

[0002] In the field of modern industrial coatings, powder coatings are widely used due to their environmental friendliness, high efficiency, and excellent coating performance. However, the curing temperature of traditional powder coatings is usually controlled at 180-200°C, which severely limits the choice of substrate.

[0003] Plastics with low heat deformation temperatures, such as polypropylene and polyethylene, can significantly deform or even melt in a curing environment of 180-200°C, rendering the finished product useless. Furthermore, flammable materials like wood and paper pose a risk of combustion at high temperatures, making them impossible to coat with traditional powder coatings. This significantly hinders the application of powder coatings in areas such as automotive interiors, appliance housings, and packaging materials, hindering their ability to meet the coating needs of diverse substrates. Furthermore, high-temperature curing increases coating energy consumption. To address this issue, we propose a low-temperature curing powder coating and its preparation method. Summary of the Invention

[0004] The object of the present invention is to provide a low-temperature curing powder coating and a preparation method thereof, aiming to solve the problem that existing powder coatings cannot meet the coating requirements of diversified substrates.

[0005] To solve the above technical problems, the present invention provides the following technical solution: a low-temperature curing powder coating, which, per 1000 g, consists of 600 g of polyester resin, 45 g of triglycidyl isocyanurate, 25 g of additives, 25 g of low-temperature curing agent, 25 g of pigment and 280 g of filler, wherein the polyester resin is a low-temperature active polyester resin, and the additives include a leveling agent, a defoaming agent and a stabilizer.

[0006] Preferably, the polyester resin has an acid value of 25-35 mgKOH / g, a glass transition temperature of 45-55°C, contains hydroxyl and carboxyl active groups in the molecular chain, and is prepared by a condensation reaction of a dibasic acid and a diol under the action of a catalyst, wherein the dibasic acid includes terephthalic acid, isophthalic acid and adipic acid in a molar ratio of 3:2:1, and the diol includes ethylene glycol, propylene glycol and neopentyl glycol in a molar ratio of 2:1:1.5.

[0007] Preferably, the leveling agent in the auxiliary agent is a composite of a polyether-modified silicone leveling agent and a graphene dispersion having a graphene content of 5-10 wt%, wherein the ratio of the polyether-modified silicone leveling agent to the graphene dispersion is 4:1, the defoaming agent is a polysiloxane defoaming agent or a mineral oil defoaming agent, and the stabilizer is a hindered phenol stabilizer or a phosphite stabilizer, and the ratio of the leveling agent, defoaming agent and stabilizer is 4:2:4.

[0008] Preferably, the low-temperature curing agent is a compound containing an imidazole structure or a blocked isocyanate, which can rapidly undergo a curing reaction with a low-temperature reactive polyester resin and triglycidyl isocyanurate at 140°C.

[0009] Preferably, the filler is one or more of calcium carbonate with a particle size of 10-15 μm, barium sulfate with a particle size of 10-15 μm, or talc with a particle size of 10-20 μm.

[0010] Preferably, the pigment is one or more combinations of titanium dioxide, carbon black or organic pigments, and its particle size is ≤5 μm.

[0011] A method for preparing a low-temperature curing powder coating, which is used to prepare any of the low-temperature curing powder coatings described above, and comprises the following steps:

[0012] S1. Weigh the materials: 600 g of polyester resin, 45 g of triglycidyl isocyanurate, 25 g of additive, 25 g of low-temperature curing agent, 25 g of pigment and 280 g of filler, and then mix the materials;

[0013] S2, melt extrusion, feed the mixed material into a twin-screw extruder, control the extrusion temperature between 90-120 ° C, extrude the material into strips or sheets, and then cool;

[0014] S3, crushing and classifying, using an air classifying mill or a micro powder mill to crush the cooled extruded material to an average particle size of 30-50 μm, and then sieving and classifying to remove coarse particles to obtain a finished powder coating;

[0015] S4. Screen and package the finished powder, test the fineness and color of the finished powder, bag and seal the qualified products, and store them in a dry place away from light.

[0016] Preferably, in the above step S1, the weighed materials are mixed by a high-speed mixer, and the mixing time is dry mixing at room temperature for 10-15 minutes to ensure that the materials are evenly mixed.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention uses a low-temperature active polyester resin and a low-temperature curing agent to reduce the curing temperature to 140°C, allowing the smooth coating of heat-sensitive plastics such as polypropylene and polyethylene and flammable materials such as wood and paper. This greatly expands the scope of applicable substrates for powder coatings, achieving safe coating of heat-sensitive plastics and flammable materials while significantly reducing energy consumption, breaking through the limitations of substrate application and the bottleneck of high energy consumption.

[0019] 2. The present invention selects a low-temperature active polyester resin with an acid value of 25-35 mgKOH / g and a glass transition temperature of 45-55°C, and combines it with a specific ratio of additives system to ensure that the powder coating can still maintain good dispersibility and stability in an environment of 30-40°C, effectively avoiding the particle adhesion and agglomeration phenomenon caused by temperature increase during storage, and ensuring the reliability of coating transportation and storage.

[0020] 3. The polyether-modified silicone leveling agent in the additive of the present invention is compounded with 5-10wt% graphene dispersion in a ratio of 4:1, which can optimize the uniformity of the surface tension of the coating and reduce defects such as shrinkage cavities and orange peel. The polysiloxane or mineral oil defoamer can eliminate bubbles generated during the curing process and improve the density of the coating. The hindered phenol or phosphite stabilizer can inhibit photo-oxidative aging and extend the service life of the coating. At the same time, the hydroxyl and carboxyl active groups of the low-temperature active polyester resin form a three-dimensional cross-linked network with triglycidyl isocyanurate, which improves the hardness, wear resistance and salt spray resistance of the coating.

[0021] 4. The filler in the present invention is a composition of calcium carbonate, barium sulfate or talc with a particle size of 10-20 μm, and the pigment particle size is ≤5 μm, so that the coating has good dispersibility and fluidity, which is convenient for construction and spraying. The low-temperature curing process shortens the curing time and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic flow diagram of the preparation method of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0024] Example 1

[0025] A low-temperature curing powder coating, which, based on 1000g, consists of 600g of polyester resin, 45g of triglycidyl isocyanurate, 25g of additives, 25g of low-temperature curing agent, 25g of pigment and 280g of filler, wherein the polyester resin is a low-temperature active polyester resin, and the additives include a leveling agent, a defoaming agent and a stabilizer.

[0026] Furthermore, the polyester resin has an acid value of 25 mgKOH / g and a glass transition temperature of 45°C. The molecular chain contains hydroxyl and carboxyl active groups. It is prepared by a condensation reaction of a dibasic acid and a diol under the action of a catalyst, wherein the dibasic acid includes terephthalic acid, isophthalic acid and adipic acid in a molar ratio of 3:2:1, and the diol includes ethylene glycol, propylene glycol and neopentyl glycol in a molar ratio of 2:1:1.5.

[0027] Furthermore, the leveling agent in the auxiliary agent is a composite of a polyether-modified silicone leveling agent and a graphene dispersion having a graphene content of 5 wt%, wherein the ratio of the polyether-modified silicone leveling agent to the graphene dispersion is 4:1, the defoaming agent is a polysiloxane defoaming agent, and the stabilizer is a hindered phenol stabilizer, and the ratio of the leveling agent, defoaming agent and stabilizer is 4:2:4.

[0028] Furthermore, the low-temperature curing agent is a compound containing an imidazole structure, which can quickly undergo a curing reaction with a low-temperature active polyester resin and triglycidyl isocyanurate at 140°C.

[0029] Furthermore, the filler is one of calcium carbonate with a particle size of 10-15 μm, barium sulfate with a particle size of 10-15 μm, or talc with a particle size of 10-20 μm.

[0030] Furthermore, the pigment is one or more combinations of titanium dioxide, carbon black or organic pigments, and its particle size is ≤5 μm.

[0031] A method for preparing a low-temperature curing powder coating, which is used to prepare any of the low-temperature curing powder coatings described above, and comprises the following steps:

[0032] S1. Weigh the materials: 600 g of polyester resin, 45 g of triglycidyl isocyanurate, 25 g of additive, 25 g of low-temperature curing agent, 25 g of pigment and 280 g of filler, and then mix the materials;

[0033] S2, melt extrusion, feed the mixed material into a twin-screw extruder, control the extrusion temperature between 90 ° C, extrude the material into strips, and then cool;

[0034] S3, crushing and classifying, using an air classifying mill to crush the cooled extruded material to an average particle size of 30 μm, and then sieving and classifying to remove coarse particles, thereby obtaining a finished powder coating;

[0035] S4. Screen and package the finished powder, test the fineness and color of the finished powder, bag and seal the qualified products, and store them in a dry place away from light.

[0036] Furthermore, in the above step S1, the weighed materials are mixed by a high-speed mixer, and the mixing time is dry mixing at room temperature for 10 minutes to ensure that the materials are evenly mixed.

[0037] Example 2

[0038] A low-temperature curing powder coating, which, based on 1000g, consists of 600g of polyester resin, 45g of triglycidyl isocyanurate, 25g of additives, 25g of low-temperature curing agent, 25g of pigment and 280g of filler, wherein the polyester resin is a low-temperature active polyester resin, and the additives include a leveling agent, a defoaming agent and a stabilizer.

[0039] Furthermore, the polyester resin has an acid value of 35 mgKOH / g and a glass transition temperature of 55°C. The molecular chain contains hydroxyl and carboxyl active groups. It is prepared by a condensation reaction between a dibasic acid and a diol under the action of a catalyst, wherein the dibasic acid includes terephthalic acid, isophthalic acid and adipic acid in a molar ratio of 3:2:1, and the diol includes ethylene glycol, propylene glycol and neopentyl glycol in a molar ratio of 2:1:1.5.

[0040] Furthermore, the leveling agent in the auxiliary agent is a composite of a polyether-modified silicone leveling agent and a graphene dispersion having a graphene content of 10 wt%, wherein the ratio of the polyether-modified silicone leveling agent to the graphene dispersion is 4:1, the defoaming agent is a mineral oil defoaming agent, and the stabilizer is a phosphite stabilizer. The ratio of the leveling agent, defoaming agent and stabilizer is 4:2:4.

[0041] Furthermore, the low-temperature curing agent is a blocked isocyanate, which can rapidly undergo a curing reaction with the low-temperature reactive polyester resin and triglycidyl isocyanurate at 140°C.

[0042] Furthermore, the filler is a combination of calcium carbonate with a particle size of 10-15 μm, barium sulfate with a particle size of 10-15 μm, or talc with a particle size of 10-20 μm.

[0043] Furthermore, the pigment is one or more combinations of titanium dioxide, carbon black or organic pigments, and its particle size is ≤5 μm.

[0044] A method for preparing a low-temperature curing powder coating, which is used to prepare any of the low-temperature curing powder coatings described above, and comprises the following steps:

[0045] S1. Weigh the materials: 600 g of polyester resin, 45 g of triglycidyl isocyanurate, 25 g of additive, 25 g of low-temperature curing agent, 25 g of pigment and 280 g of filler, and then mix the materials;

[0046] S2, melt extrusion, feeding the mixed material into a twin-screw extruder, controlling the extrusion temperature between 120°C, extruding the material into sheets, and then cooling;

[0047] S3, crushing and classifying, using a micro powder mill to crush the cooled extruded material to an average particle size of 50 μm, and then sieving and classifying to remove coarse particles, thereby obtaining a finished powder coating;

[0048] S4. Screen and package the finished powder, test the fineness and color of the finished powder, bag and seal the qualified products, and store them in a dry place away from light.

[0049] Furthermore, in the above step S1, the weighed materials are mixed by a high-speed mixer, and the mixing time is dry mixing at room temperature for 15 minutes to ensure that the materials are evenly mixed.

[0050] The embodiments disclosed in the present invention are preferred embodiments, but are not limited to them. Ordinary technicians in this field can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. As long as they do not deviate from the spirit of the present invention, they are all within the scope of protection of the present invention.

Claims

1. A low temperature curing powder coating, characterized in that: The powder coating is composed of 600g of polyester resin, 45g of triglycidyl isocyanurate, 25g of additives, 25g of low-temperature curing agent, 25g of pigment and 280g of filler based on 1000g of the powder coating, wherein the polyester resin is a low-temperature active polyester resin, and the additives include a leveling agent, a defoaming agent and a stabilizer.

2. A low temperature curing powder coating according to claim 1, characterized in that: The polyester resin has an acid value of 25-35 mgKOH / g and a glass transition temperature of 45-55°C. The molecular chain contains hydroxyl and carboxyl active groups. The polyester resin is prepared by a condensation reaction between a dibasic acid and a diol under the action of a catalyst, wherein the dibasic acid includes terephthalic acid, isophthalic acid and adipic acid in a molar ratio of 3:2:1, and the diol includes ethylene glycol, propylene glycol and neopentyl glycol in a molar ratio of 2:1:1.

5.

3. A low temperature curing powder coating according to claim 1, characterized in that: The leveling agent in the auxiliary agent is a composite of a polyether-modified silicone leveling agent and a graphene dispersion having a graphene content of 5-10 wt%, wherein the ratio of the polyether-modified silicone leveling agent to the graphene dispersion is 4:1, the defoaming agent is a polysiloxane defoaming agent or a mineral oil defoaming agent, and the stabilizer is a hindered phenol stabilizer or a phosphite stabilizer. The ratio of the leveling agent, defoaming agent and stabilizer is 4:2:

4.

4. A low temperature curing powder coating according to claim 1, characterized in that: The low-temperature curing agent is a compound containing an imidazole structure or a blocked isocyanate, which can quickly undergo a curing reaction with a low-temperature active polyester resin and triglycidyl isocyanurate at 140°C.

5. The low temperature curing powder coating according to claim 1, characterized in that: The filler is one or more of calcium carbonate with a particle size of 10-15 μm, barium sulfate with a particle size of 10-15 μm, or talc with a particle size of 10-20 μm.

6. The low temperature curing powder coating according to claim 1, characterized in that: The pigment is one or more combinations of titanium dioxide, carbon black or organic pigments, and its particle size is ≤5 μm.

7. A method for preparing a low-temperature curing powder coating, the method being used to prepare a low-temperature curing powder coating according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: S1. Weigh the materials: 600 g of polyester resin, 45 g of triglycidyl isocyanurate, 25 g of additive, 25 g of low-temperature curing agent, 25 g of pigment and 280 g of filler, and then mix the materials; S2, melt extrusion, feed the mixed material into a twin-screw extruder, control the extrusion temperature between 90-120 ° C, extrude the material into strips or sheets, and then cool; S3, crushing and classifying, using an air classifying mill or a micro powder mill to crush the cooled extruded material to an average particle size of 30-50 μm, and then sieving and classifying to remove coarse particles to obtain a finished powder coating; S4. Screen and package the finished powder, test the fineness and color of the finished powder, bag and seal the qualified products, and store them in a dry place away from light.

8. The method for preparing a low-temperature curing powder coating according to claim 7, characterized in that: In the above step S1, the weighed materials are mixed by a high-speed mixer for 10-15 minutes at room temperature to ensure that the materials are evenly mixed.

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