Low temperature curing formaldehyde removal powder coating for MDF and its application process

Abstract

A low-temperature curing formaldehyde removal powder coating for MDF and its application process, the components of the powder coating are in percentage by weight, powder 1: low-temperature curing polyester 25-40%; epoxy resin 25-40%; leveling agent 0.5-1.5%; brightener 0.5-1.5%; degassing agent 0.3-0.8%; defoaming agent 0.5-1.5%; adhesion promoter 0.3-1.5%; electric field enhancer 0.3-5%; sanding agent 0.3-1.5%, organic bentonite 0.1-1.5%; filler 5-40%; pigment 0.1-20%; other additives 0.1-0.5%; powder 2: low-temperature curing additive 0.2-1.5%; formaldehyde removal functional material 1-10%, by adjusting the formula and a certain process, a continuous and dense, defect-free paint film is formed on the surface of MDF, and the paint film has the purposes of removing formaldehyde, decomposing organic matter and purifying indoor air.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, and in particular to a low-temperature curing formaldehyde-removing powder coating for MDF and its application process. Background Technology

[0002] Since the 1970s, powder coatings and painting have gained attention from the global coatings and painting industry for their 4E coating products, which are characterized by high production efficiency, excellent film performance, eco-friendliness, and economy.

[0003] Traditionally, the surfaces of everyday wood, including engineered wood products, are protected and decorated with paint. However, with increasing environmental awareness, since the 1990s, some have begun experimenting with using environmentally friendly powder coatings on medium-density fiberboard (MDF). Powder coatings have been used on wood for over two decades, but their development has been slow due to certain limitations. However, given the significant environmental advantages of powder coatings, once the constraints of production, preparation, and coating technologies are overcome, their application in wood will experience rapid growth. Based on this, lower curing temperatures and shorter curing times will be the inevitable trend in the future.

[0004] Meanwhile, regarding indoor environmental issues, due to the rapid development of the real estate industry in recent years and the increasing luxury of interior decoration, the pollution from interior decoration and furniture boards is receiving more and more attention. More and more people are choosing high-grade environmentally friendly paints and furniture. While this significantly reduces the concentration of pollution in the indoor environment, the combined effect of various environmentally friendly materials should not be underestimated. Formaldehyde pollution, in particular, is continuously released. A large amount of adhesive is used in various types of boards for bonding; as the saying goes, "no formaldehyde, no adhesive." The amount of adhesive used in engineered wood products is very large. The main component of this adhesive is urea-formaldehyde resin, whose two main components are formaldehyde and urea. The formaldehyde content exceeds 50%. In fact, for the strength of boards, the higher the formaldehyde content in urea-formaldehyde resin, the better the strength. Conversely, if too little formaldehyde is added, it will affect the condensation reaction of the raw materials, greatly reducing the adhesiveness. As the temperature rises, the release of formaldehyde increases. Indoor air quality is receiving increasing attention from the government. The latest GB / T 18883-2022 "Indoor Air Quality Standard" has changed the formaldehyde emission limit from 0.10 mg / m³ to 0.08 mg / m³ and the benzene limit from 0.11 mg / m³ to 0.03 mg / m³. Based on this, it is urgent to reduce the release of harmful substances from indoor materials in all aspects.

[0005] Most existing powder coatings are cured at high temperatures (above 180℃) to form a film. Even powder coatings used in MDF often suffer from low curing degree, pinholes in the paint film, poor edge coverage, low adhesion, and non-dense paint film. This causes the continuous release of harmful substances (formaldehyde, TVOC, etc.) from the internal MDF after heating. There is an urgent need for a powder coating and its process that can cure well at lower temperatures and solve the problem of harmful substance release. This would greatly solve the problem of indoor air pollution. Summary of the Invention

[0006] This invention provides a low-temperature curing formaldehyde-removing powder coating for MDF and its application process to solve the above-mentioned problems. The powder coating provided by this method can be cured at a low temperature of 130℃, possesses a certain formaldehyde removal capability, and achieves the purpose of purifying indoor air.

[0007] The technical solution adopted in this invention:

[0008] A low-temperature curing formaldehyde-removing powder coating for MDF, wherein the powder coating components are expressed as a percentage by weight, and the powder includes powder 1 and powder 2.

[0009] Powder 1: Low-temperature curing polyester 25-40%; epoxy resin 25-40%; leveling agent 0.5-1.5%; gloss enhancer 0.5-1.5%; degassing agent 0.3-0.8%; defoamer 0.5-1.5%; adhesion promoter 0.3-1.5%; electrostatic agent 0.3-5%; texture agent 0.3-1.5%; organic bentonite 0.1-1.5%; filler 5-40%; pigment 0.1-20%; other additives 0.1-0.5%.

[0010] Powder 2: Low-temperature curing aid 0.2-1.5%; formaldehyde removal functional material 1-10%.

[0011] The low-temperature curing polyester is a carboxyl-terminated polyester that is cured by infrared light at 120-160 degrees Celsius, preferably a highly reactive carboxyl-terminated polyester resin for 50 / 50 mixed powder coatings.

[0012] The epoxy resin is a bisphenol A type epoxy resin, preferably an epoxy resin with an epoxy equivalent of 700-900 and high viscosity.

[0013] The leveling agent is one or two of the following: acrylate homopolymer, acrylate copolymer, silicone-modified acrylate polymer, and polysiloxane.

[0014] The brightening agent is one of the acrylate copolymers.

[0015] The brightening agent is a copolymer of butyl acrylate and methyl methacrylate.

[0016] The degassing agent is benzoin or modified benzoin.

[0017] The defoamer is at least one of modified polyether defoamer, esterified defoamer, higher alcohol defoamer, and modified amide defoamer.

[0018] The adhesion promoter is at least one of coupling agents and polymers containing amino active groups.

[0019] The charge enhancer is at least one of quaternary ammonium salts, quaternized imidazoles, and polar long-chain lipids.

[0020] The texture agent is at least one of amide-modified fluorocarbon compound and polyamide-modified special vinylidene fluoride.

[0021] The organic bentonite mentioned is one of montmorillonite and montmorillonite modification.

[0022] The filler is at least one of barium sulfate, calcium carbonate, and silicon dioxide.

[0023] The pigment is at least one of titanium dioxide, carbon black, iron oxide red, iron oxide yellow, iron oxide black, and ultramarine.

[0024] The low-temperature curing aid is at least one of 2-methylimidazolium, 2-phenylimidazoline, cycloamidinium, and benzyltriethylammonium chloride.

[0025] The formaldehyde-removing functional materials include at least one or a compound product of formaldehyde-removing powder, diatomaceous earth, photocatalyst powder, and formaldehyde scavenger.

[0026] An application process for a low-temperature curing formaldehyde-removing powder coating for MDF, comprising the following steps:

[0027] ①According to the formula content, low-temperature curing polyester, epoxy resin, leveling agent, gloss enhancer, degassing agent, defoamer, adhesion promoter, electrostatic agent, texture agent, organic bentonite, filler, pigment and other additives are fully premixed and pre-crushed to obtain primary powder 1;

[0028] ② After dispersing and mixing formaldehyde scavenger, diatomaceous earth, photocatalyst and low temperature curing agent in a certain proportion, powder 2 is obtained. Powder 2 is added to powder 1 and extruded in a twin-screw extruder. The powder is then tableted, crushed and sieved to obtain powder with a particle size D50 of 25-35μm.

[0029] ③ Pre-treat MDF, control the moisture content of MDF to be between 5% and 10%, and preheat it at a temperature between 100℃ and 120℃ for 5 to 10 minutes.

[0030] ④ Use an electrostatic spray gun to evenly spray powder onto all surfaces of the MDF;

[0031] ⑤ Place the coated MDF board in an infrared oven at 130℃ and bake for 5-10 minutes;

[0032] ⑥ Remove and let stand until it reaches room temperature.

[0033] The beneficial effects of the present invention are as follows: By adjusting the formula and using certain processes, the present invention enables powder coatings to form a continuous, dense, and defect-free paint film on the surface of MDF under infrared light conditions at 130℃. This paint film has the purpose of removing formaldehyde, decomposing organic matter, and purifying indoor air. Detailed Implementation

[0034] This invention adapts the powder coating formula to meet the requirements of MDF construction process by rationally adjusting the powder coating formula, so that the powder coating can be cured at a lower temperature and can also achieve the purpose of removing formaldehyde and purifying indoor air.

[0035] Low-temperature curing polyester and epoxy resin are well known to those skilled in the art. In the powder coating of this invention, they mainly play the role of film-forming substances. However, the problem lies in how to select a suitable low-temperature curing polyester and epoxy resin. If a low-temperature curing polyester and ordinary epoxy resin are selected at will, it will result in low strength, excessively high curing temperature and excessively long curing time, low degree of curing after film formation, low adhesion of the final paint film, and poor board surface.

[0036] A low-temperature curing formaldehyde-removing powder coating for MDF, wherein the powder coating components are expressed as a percentage by weight, and the powder includes powder 1 and powder 2.

[0037] Powder 1: Low-temperature curing polyester 25-40%; epoxy resin 25-40%; leveling agent 0.5-1.5%; gloss enhancer 0.5-1.5%; degassing agent 0.3-0.8%; defoamer 0.5-1.5%; adhesion promoter 0.3-1.5%; electrostatic agent 0.3-5%; texture agent 0.3-1.5%; organic bentonite 0.1-1.5%; filler 5-40%; pigment 0.1-20%; other additives 0.1-0.5%.

[0038] Powder 2: Low-temperature curing aid 0.2-1.5%; formaldehyde removal functional material 1-10%.

[0039] The low-temperature curing polyester is a carboxyl-terminated polyester that is cured by infrared light at 120-160 degrees Celsius, preferably a highly reactive carboxyl-terminated polyester resin for 50 / 50 mixed powder coatings.

[0040] The epoxy resin is a bisphenol A type epoxy resin, preferably an epoxy resin with an epoxy equivalent of 700-900 and high viscosity.

[0041] The leveling agent is one or two of the following: acrylate homopolymer, acrylate copolymer, silicone-modified acrylate polymer, and polysiloxane.

[0042] The brightening agent is one of the acrylate copolymers.

[0043] The brightening agent is a copolymer of butyl acrylate and methyl methacrylate.

[0044] The degassing agent is benzoin or modified benzoin.

[0045] The defoamer is at least one of modified polyether defoamer, esterified defoamer, higher alcohol defoamer, and modified amide defoamer.

[0046] The adhesion promoter is at least one of coupling agents and polymers containing amino active groups.

[0047] The charge enhancer is at least one of quaternary ammonium salts, quaternized imidazoles, and polar long-chain lipids.

[0048] The texture agent is at least one of amide-modified fluorocarbon compound and polyamide-modified special vinylidene fluoride.

[0049] The organic bentonite mentioned is one of montmorillonite and montmorillonite modification.

[0050] The filler is at least one of barium sulfate, calcium carbonate, and silicon dioxide.

[0051] The pigment is at least one of titanium dioxide, carbon black, iron oxide red, iron oxide yellow, iron oxide black, and ultramarine.

[0052] The low-temperature curing aid is at least one of 2-methylimidazolium, 2-phenylimidazoline, cycloamidinium, and benzyltriethylammonium chloride.

[0053] The formaldehyde-removing functional materials include at least one or a compound product of formaldehyde-removing powder, diatomaceous earth, photocatalyst powder, and formaldehyde scavenger.

[0054] Other additives include, for example, modified polyethylene wax-based anti-scratch additives, which effectively increase the smoothness of the coating surface and reduce friction, thereby providing anti-scratch properties; modified PTFE wax-based hardening additives, which improve the wear resistance of the coating; modified thermoplastic resin-based toughening additives, which effectively improve the flexibility and bending resistance of the paint film; and halogen-containing compound organics or other types of flame retardants, which can slow down the burning rate.

[0055] Example 1

[0056] A low-temperature curing formaldehyde-removing powder coating for MDF, wherein the powder coating components are expressed as a percentage by weight, and the powder includes powder 1 and powder 2.

[0057] Powder 1: 30% low-temperature curing polyester (Zhanxin Resin 1545-6); 30% epoxy resin (Anhui Meijia E-12); 0.8% leveling agent; 0.8% gloss enhancer; 0.4% degassing agent; 0.5% defoamer; 0.5% adhesion promoter; 0.3% electrostatic agent; 1% texture agent; 0.8% organic bentonite; 31.6% filler; 0.6% pigment; 0.2% other additives.

[0058] Powder 2: Low-temperature curing aid 0.5%; formaldehyde removal functional material 2%.

[0059] Example 2

[0060] A low-temperature curing formaldehyde-removing powder coating for MDF, wherein the powder coating components are expressed as a percentage by weight, and the powder includes powder 1 and powder 2.

[0061] Powder 1: 35% low-temperature curing polyester (Zhanxin Resin 1545-6); 35% epoxy resin (Anhui Meijia E-12); 0.8% leveling agent; 0.8% gloss enhancer; 0.4% degassing agent; 0.5% defoamer; 1% adhesion promoter; 0.3% electrostatic agent; 1.5% texture agent; 1% organic bentonite; 12.2% filler; 5% pigment; 0.3% other additives.

[0062] Powder 2: Low-temperature curing aid 1.2%; Formaldehyde removal functional material 5%.

[0063] Example 3

[0064] A low-temperature curing formaldehyde-removing powder coating for MDF, wherein the powder coating components are expressed as a percentage by weight, and the powder includes powder 1 and powder 2.

[0065] Powder 1: 40% low-temperature curing polyester (Zhanxin Resin 1545-6); 40% epoxy resin (Anhui Meijia E-12); 0.8% leveling agent; 0.8% gloss enhancer; 0.4% degassing agent; 0.5% defoamer; 1% adhesion promoter; 0.3% electrostatic agent; 1.5% texture agent; 1% organic bentonite; 6.6% filler; 3% pigment; 0.3% other additives.

[0066] Powder 2: Low-temperature curing aid 0.8%; formaldehyde removal functional material 3%.

[0067] The application processes of Examples 1-3 are basically the same, the difference being the different formulation ratios used. The application process steps used in Examples 1-3 are as follows:

[0068] An application process for a low-temperature curing formaldehyde-removing powder coating for MDF, comprising the following steps:

[0069] ① Prepare the powder according to the formula content of powder 1, premix it thoroughly, and then pulverize it to obtain primary powder 1;

[0070] ② After dispersing and mixing formaldehyde scavenger, diatomaceous earth, photocatalyst and low temperature curing agent in a certain proportion, add primary powder 1, extrude in a twin-screw extruder, press into tablets, crush and sieve to obtain powder with particle size D50 of 25-35μm;

[0071] ③ Pre-treat the MDF, controlling the moisture content of the MDF to be between 5% and 10%, and preheat it at a temperature of 110℃ for 10 minutes.

[0072] ④ Use an electrostatic spray gun to evenly spray powder onto all surfaces of the MDF;

[0073] ⑤ Place the coated MDF board in an infrared oven at 130 degrees Celsius and bake for 10 minutes;

[0074] ⑥ Remove and let stand until it reaches room temperature.

[0075] The design of the comparative example determines the role of the key components. The comparative example 1 is basically the same as the example 1, except that the amount of low-temperature curing polyester and epoxy resin used in the powder is reduced to 20%, while the other amounts are used within the range.

[0076] Comparative Example 2 was designed. Comparative Example 2 was basically the same as Example 1, except that the amount of low-temperature curing polyester and epoxy resin used in the powder was reduced to 45%, while the other amounts were used within the range.

[0077] Comparative Example 3 was designed and is basically the same as Example 1, except that no low-temperature curing agent was added to the powder, and other dosages were used within the specified range.

[0078] Comparative Example 4 was designed and is basically the same as Example 1, except that no formaldehyde-removing functional material was added to the powder.

[0079] Comparative Example 5 was designed and was basically the same as Example 1, except that formaldehyde-removing functional material was added to the powder at 0.5%.

[0080] Comparative Example 6 was designed and was basically the same as Example 1, except that 20% of the formaldehyde-removing functional material was added to the powder.

[0081] Comparative Example 7 was designed. Comparative Example 7 is basically the same as Example 1, except that a non-low-temperature curing ordinary polyester was selected.

[0082] Comparative Example 8 was designed and is basically the same as Example 1, except that the MDF preheating temperature is 50°C.

[0083] Comparative Example 9 was designed and is basically the same as Example 1, except that the baking time after spraying is 3 minutes.

[0084] Comparative Example 10 was designed and was basically the same as Example 1, except that it was baked in a non-infrared oven at 130°C after spraying.

[0085] The powder coating products obtained in Examples 1-3 and Comparative Examples 1-10 were subjected to performance tests. The coating film thickness was controlled between 50-70 μm. The testing methods were based on some methods in HG / T 2006-2006 Thermosetting Powder Coatings and JC / 2177-2013 Diatom Mud Decorative Wall Materials. The test results are shown in Table 1 below.

[0086] Table 1

[0087]

[0088] As shown in Table 1, the performance test results of Examples 1-3 all meet the corresponding technical requirements, and the performance of Examples 1-3 is better than that of the comparative example. The paint film surface is good, and while meeting the requirements for impact, toughness and other properties, it is excellent in terms of formaldehyde purification performance.

[0089] In Comparative Example 1, too little resin was added, which prevented the formation of a continuous paint film that coated pigments and fillers, resulting in powdering and a lack of mechanical properties.

[0090] Comparative Example 2 has less resin and less film-forming material in the paint film, resulting in poor overall performance of the paint film, with defects such as pinholes on the surface and poor coverage of edges and corners.

[0091] Comparing Example 1 with Comparative Examples 1 and 2, it was found that a certain resin content is necessary to obtain a good paint film that meets other properties such as impact resistance and toughness.

[0092] Comparative Example 3 did not contain a low-temperature curing agent, resulting in poor curing at 130℃ and poor mechanical properties.

[0093] Comparative Example 4 did not contain any formaldehyde removal materials, so it could not achieve formaldehyde purification capabilities.

[0094] Comparative Example 5 contained too few formaldehyde-removing functional materials, resulting in weak formaldehyde purification capabilities.

[0095] Comparative Example 6 had too much formaldehyde-removing functional material added, resulting in poor paint film appearance and poor mechanical properties.

[0096] Comparing Example 1 and Comparative Examples 4-6, it was found that a certain proportion of formaldehyde-removing functional materials is necessary; too little or too much will not meet the overall requirements.

[0097] Comparative Example 7 used a non-low-temperature curing polyester, which did not reach the reaction temperature at 130℃, and thus could not obtain a continuous paint film.

[0098] In Comparative Example 8, the MDF preheating temperature was 50℃, which made it difficult to apply powder and resulted in poor charge-carrying capacity, thus failing to produce a paint film that met the requirements.

[0099] In Comparative Example 9, the baking time was insufficient, the degree of curing was inadequate, and the performance was poor.

[0100] Comparative Example 10, due to the use of a non-infrared oven, could not form a fully cured paint film.

[0101] In summary, this invention integrates various requirements to obtain a low-temperature curing formaldehyde-removing powder coating for MDF. Through a specific process, the MDF board achieves continuous formaldehyde removal and air purification, greatly solving the problem of indoor air pollution.

[0102] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made in accordance with the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A low-temperature curing formaldehyde-removing powder coating for MDF, wherein the components of the powder coating, by weight percentage, are characterized in that... The powder coating comprises powder 1 and powder 2; Powder 1: Low-temperature curing polyester 25-40%; epoxy resin 25-40%; leveling agent 0.5-1.5%; gloss enhancer 0.5-1.5%; degassing agent 0.3-0.8%; defoamer 0.5-1.5%; adhesion promoter 0.3-1.5%; electrostatic agent 0.3-5%; texture agent 0.3-1.5%; organic bentonite 0.1-1.5%; filler 5-40%; pigment 0.1-20%; other additives 0.1-0.5%. Powder 2: Low-temperature curing agent 0.2-1.5%; Formaldehyde removal functional material 1-10%; The degassing agent is benzoin or modified benzoin; The defoamer is at least one of modified polyether defoamer, higher alcohol defoamer, and modified amide defoamer; The adhesion promoter is a coupling agent; The charge enhancer is at least one of quaternary ammonium salts, quaternized imidazoles, and polar long-chain lipids; The low-temperature curing aid is at least one of 2-methylimidazolium, 2-phenylimidazoline, cycloamidinium, and benzyltriethylammonium chloride; The formaldehyde-removing functional materials mentioned above include a compound product of diatomaceous earth, photocatalyst powder, and formaldehyde scavenger; The low-temperature curing polyester is a carboxyl-terminated polyester that is cured by infrared light at 120-160 degrees Celsius. The application process for low-temperature curing formaldehyde-removing powder coatings used in MDF includes the following steps: ①According to the formula content, low-temperature curing polyester, epoxy resin, leveling agent, gloss enhancer, degassing agent, defoamer, adhesion promoter, electrostatic agent, texture agent, organic bentonite, filler, pigment and other additives are fully premixed and pre-crushed to obtain primary powder 1; ② After dispersing and mixing formaldehyde scavenger, diatomaceous earth, photocatalyst powder and low-temperature curing agent in a certain proportion, powder 2 is obtained. It is added to powder 1, extruded in a twin-screw extruder, tableted, crushed and sieved to obtain powder with a particle size D50 of 25-35μm. ③ Pre-treat MDF, control the moisture content of MDF to be between 5% and 10%, and preheat it at a temperature between 100℃ and 120℃ for 5 to 10 minutes. ④ Use an electrostatic spray gun to evenly spray powder onto all surfaces of the MDF; ⑤ Place the coated MDF board in an infrared oven at 130℃ and bake for 5-10 minutes; ⑥ Remove and let stand until it reaches room temperature.

2. The low-temperature curing formaldehyde-removing powder coating for MDF according to claim 1, characterized in that, The leveling agent is one or two of the following: acrylate homopolymer, acrylate copolymer, silicone-modified acrylate polymer, and polysiloxane; The brightening agent is one of the acrylate copolymers.

3. The low-temperature curing formaldehyde-removing powder coating for MDF according to claim 2, characterized in that, The brightening agent is a copolymer of butyl acrylate and methyl methacrylate.

4. The low-temperature curing formaldehyde-removing powder coating for MDF according to claim 1, characterized in that, The texture agent is an amide-modified fluorocarbon compound; The organic bentonite is one of montmorillonite and montmorillonite modification, and the filler is at least one of barium sulfate, calcium carbonate and silicon dioxide.

5. The low-temperature curing formaldehyde-removing powder coating for MDF according to claim 1, characterized in that, The pigment is at least one of titanium dioxide, carbon black, iron oxide red, iron oxide yellow, iron oxide black, and ultramarine.

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