PU (polyurethane) matte white finish applied to melamine board and preparation method of PU matte white finish

Abstract

The invention relates to the field of high-adhesion finishing paint, in particular to PU (polyurethane) matte white finishing paint applied to a melamine board and a preparation method of the PU matte white finishing paint. The PU matte white finish applied to the melamine board comprises a main agent, a curing agent and a diluent, the mass ratio of the main agent to the curing agent to the diluent is 1: (0.1-0.3): (0.5-0.8); the main agent is prepared from acrylic resin, a dispersing agent, a defoaming agent, pigment, filler, matting powder, an auxiliary agent, a flatting agent, a viscosity reducer, corn fiber, lotus leaf powder, coconut fiber and a coupling agent. Compared with the prior art, the adhesive force of the PU matte white finish on a melamine board can be enhanced, the PU matte white finish can be well attached under the condition that polishing is not in place or even polishing is not conducted, and therefore a good surface effect is provided, and the PU matte white finish has high yellowing resistance and high toughness.

Description

Technical Field

[0001] The present application relates to the field of high-adhesion topcoats, and more specifically, to a PU matte white topcoat applied to melamine boards and a preparation method thereof. Background Art

[0002] In the furniture decoration industry, melamine sheets are widely used due to their low cost, good processing performance, wear resistance and scratch resistance. For furniture products with relatively low product positioning, they are often made by directly splicing melamine sheets, and their surfaces are no longer decorated with additional paint to maintain their original texture and color. However, as consumers' requirements for furniture quality and aesthetics increase, furniture products with higher product positioning often require fine coating treatment to give the furniture surface a more delicate, smooth and textured appearance.

[0003] Melamine board is different from solid wood or medium-density fiberboard. The surface of melamine board has a certain hardness and density. If the surface is not worn out by grinding, the paint film is not easy to adhere to the board tightly, resulting in the phenomenon of surface paint falling off. This not only affects the aesthetics of the furniture, but also shortens the service life of the furniture. If grinding is performed, the process not only increases the production cost, but also prolongs the production cycle and reduces the production efficiency. In addition, excessive grinding may also destroy the original structure of the surface of the melamine board, affecting its overall performance and durability.

[0004] Therefore, there is room for improvement. Summary of the invention

[0005] In order to enhance the adhesion of PU matte white topcoat on melamine board so that it can adhere well even without inadequate polishing or even without polishing, thereby providing a better surface effect, the present application provides a PU matte white topcoat for melamine board and a preparation method thereof.

[0006] In the first aspect, the present application provides a PU matte white topcoat applied to melamine board, which adopts the following technical solution: A PU matte white topcoat applied to melamine board, comprising a main agent, a curing agent, and a diluent; according to the mass ratio, the main agent: curing agent: diluent = 1: (0.1-0.3): (0.5-0.8); The main agent includes the following components in percentage by mass: acrylic resin, 1-1.5% dispersant, 0.1-0.5% defoamer, 25-30% pigment, 5-10% filler, 1-5% matting powder, 0.01-5% additive, 0.1-0.5% leveling agent, 5-10% viscosity reducer, 1-5% corn fiber, 0.5-2% lotus leaf powder, 0.1-1% coconut shell fiber, and 0.1-1% coupling agent.

[0007] The amount of thinner used is not necessarily the better. If too much thinner is added, the solid content of the paint will be reduced, making the coating thinner after drying, thereby weakening the bonding force between the coating and the substrate. It will also cause the paint to become too thin, affecting its coating effect and adhesion.

[0008] This application can effectively reduce the viscosity of the coating, enhance fluidity, and make the topcoat easier to apply by limiting the dosage of the main agent, curing agent, and diluent. Under this limitation, the application performance of the coating can be improved, so that the coating can better wet and penetrate the surface of the substrate, which helps to form a closer bond between the coating and the substrate, thereby improving the adhesion of the coating.

[0009] By adopting the above technical scheme, with the cooperation of corn fiber, lotus leaf powder and coconut shell fiber, corn fiber and coconut shell fiber are interwoven to form a network, and lotus leaf powder is mixed into the interwoven network to form a special structure, which is well dispersed inside the PU matte white paint.

[0010] The nano wax crystals on the surface of lotus leaf powder act as a natural barrier, which can effectively scatter and absorb ultraviolet rays, reduce the impact of ultraviolet rays on PU white paint, and thus delay the yellowing process caused by light aging and improve the yellowing resistance. At the same time, the natural antioxidant components in corn fiber and coconut shell fiber produce a good synergistic effect in PU white paint, jointly resisting the invasion of oxidation reactions and further maintaining the color and gloss of the paint film. The stable and special structure formed by the three interweaving can effectively prevent the PU matte white paint from deformation or cracking due to external forces or environmental factors, enhance the toughness of the PU matte white paint, and reduce the risk of yellowing caused by structural damage.

[0011] In addition, the fiber network formed by the interweaving of corn fiber and coconut shell fiber greatly increases the roughness of the paint film surface, allowing more mechanical bite force to form between the paint film and the substrate, just like countless small hooks tightly grasping the substrate, improving adhesion. At the same time, the special structure reacts chemically with the functional groups in the PU white topcoat to form a chemical bond. The strength of this chemical bond far exceeds that of a simple physical bond, making the connection between the paint film and the substrate more secure.

[0012] The hydrophobic property of lotus leaf powder can also effectively prevent moisture from penetrating into the interface between the paint film and the substrate, keeping the interface dry and clean, providing additional protection for adhesion. Some tiny lotus leaf powder will be able to penetrate into the tiny pores of the substrate, forming a closer bond with the substrate, further enhancing adhesion.

[0013] Preferably, the diluent includes butyl ester, xylene, and PMA.

[0014] Preferably, the diluent is butyl ester, xylene, and PMA; in terms of the mass percentage of the diluent, xylene is 20-30%, and PMA is 20-25%.

[0015] By adopting the above technical solution, the type and amount of the thinner added to the topcoat are further optimized, which can not only effectively adjust the viscosity of the topcoat, improve the leveling property, and make the coating more uniform and smooth, but also promote the drying of the topcoat to a certain extent and shorten the construction period. The specially selected thinner can better blend with the resin and other components in the topcoat to form a tighter structure, thereby improving the adhesion of the topcoat to a certain extent and ensuring a firm bond between the coating and the substrate.

[0016] Preferably, the curing agent includes isocyanate and butyl ester.

[0017] Preferably, the curing agent is hexamethylene diisocyanate-based polyisocyanate and butyl ester; according to the mass percentage of the curing agent, the hexamethylene diisocyanate-based polyisocyanate is 35-40%.

[0018] By adopting the above technical solution, the type of isocyanate is further limited, and butyl ester is added to the curing agent to reduce the viscosity of the curing agent as much as possible.

[0019] As a low-viscosity, solvent-free aliphatic polyisocyanate, hexamethylene diisocyanate-based polyisocyanate has excellent chemical resistance and weather resistance. Hexamethylene diisocyanate-based polyisocyanate can chemically react with the main agent to form a cross-linked structure, thereby significantly improving the hardness, wear resistance and corrosion resistance of the coating.

[0020] Butyl ester can reduce the viscosity of the coating, improve fluidity, and make the coating easier to apply. Butyl ester can also promote better fusion of the main agent and hexamethylene diisocyanate-based polyisocyanate to form a tighter structure, thereby improving the adhesion of the coating to a certain extent. The addition of butyl ester can also promote the curing process of the coating, allowing the coating to reach its optimal performance faster.

[0021] Preferably, the filler comprises a mixture of one or more of talc, calcium carbonate, kaolin and barium sulfate.

[0022] Preferably, the filler is talcum powder of 4500-5500 mesh.

[0023] The quality of melamine boards varies, and some boards have tiny holes on their surfaces. It is difficult to fill the tiny holes with general topcoats without powder fillers. By adopting the above technical solution, talcum powder with a mesh size of 4500-5500 is further preferred, which can provide a better filling effect while ensuring the fineness of the paint film.

[0024] In a second aspect, the present application provides a method for preparing a PU matte white topcoat applied to a melamine board, using the following technical solution: A method for preparing a PU matte white topcoat applied to a melamine board comprises the following steps: Step 1: Prepare the main agent: Step 1a: Stir the acrylic resin, dispersant and defoamer at 750-850 r / min for 5-20 min; Step 1b: Continue to add pigments and fillers, and stir at 1100-1300 r / min for 15-40 min; Step 1c: Continue to add the remaining raw materials and stir at 900-1100 r / min for 5-15 min to obtain the main agent; Step 2: Mix the main agent, curing agent and diluent until they are uniform to obtain the PU matte white topcoat for use on the melamine board.

[0025] Preferably, the corn fiber, lotus leaf powder, coconut shell fiber and coupling agent are stirred and mixed at 2000-2500 r / min for 10-20 min, and then allowed to stand for 1-2 h to obtain a mixture; the mixture is added in step 1c and mixed with the remaining raw materials.

[0026] By adopting the above technical solution and mixing various raw materials in a specific order, the various raw materials can be more fully matched, thereby further improving the adhesion effect of the PU matte white paint and the melamine board, and improving the yellowing resistance of the PU matte white paint.

[0027] In summary, this application has the following beneficial effects: 1. Through the combination of corn fiber, coconut shell fiber and lotus leaf powder, an interwoven network with a special structure is formed inside the PU matte white paint. The nano wax crystals on the surface of lotus leaf powder can effectively scatter and absorb ultraviolet rays, thereby significantly reducing the impact of ultraviolet rays on the paint film and delaying the yellowing process caused by light aging. At the same time, the natural antioxidant ingredients in corn fiber and coconut shell fiber can work synergistically to resist the invasion of oxidation reactions, further maintaining the color and gloss of the paint film. This unique formula combination enables the PU matte white paint to maintain its original appearance during long-term use and prolong its service life.

[0028] 2. The stable and special structure formed by the interweaving of corn fiber and coconut shell fiber can not only effectively prevent the PU matte white topcoat from deformation or cracking due to external forces or environmental factors, but also greatly enhance the toughness of the paint film. At the same time, this interwoven structure increases the roughness of the paint film surface, allowing more mechanical bite force to be formed between the paint film and the substrate, thereby improving adhesion. It can also effectively prevent moisture from penetrating into the interface between the paint film and the substrate, keeping the interface dry and clean, and providing additional protection for adhesion. This enhanced toughness and adhesion enable the PU matte white topcoat to maintain stability and durability in a variety of complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a test diagram of the PU matte white topcoat applied to the melamine board of Example 1 in Test 1. DETAILED DESCRIPTION

[0030] The present application is further described in detail below with reference to the accompanying drawings and embodiments.

[0031] The raw materials used in the following examples and comparative examples are all commercially available products. Example

[0032] Example 1 A PU matte white topcoat applied to a melamine board comprises a main agent, a curing agent and a diluent; the mass ratio of the main agent, the curing agent and the diluent is 1:0.2:0.6.

[0033] The main agent includes the following components: acrylic resin, dispersant, defoamer, pigment, filler, matting powder, additive, leveling agent, viscosity reducer, corn fiber, lotus leaf powder, coconut shell fiber and coupling agent.

[0034] The specific content of each component of the main agent is shown in Table 1, in mass percentage.

[0035] In this embodiment, the solid content of the main agent is 61±1%.

[0036] The acrylic resin is AC1164A low-hydroxy acrylic resin purchased from Guangdong Di Ai Sheng Tong De Resin Co., Ltd.

[0037] The dispersant was 4010 dispersant purchased from Efcona Polymer Co., Ltd.

[0038] The defoaming agent was 5300 defoaming agent purchased from Haiming Si Deqian Chemical Co., Ltd.

[0039] The pigment is titanium dioxide.

[0040] The filler is 5000 mesh talc.

[0041] The matting powder was 915 matting powder purchased from Qingyuan Xinhui Chemical Co., Ltd.

[0042] The additives are anti-settling agent and adhesion promoter. The anti-settling agent is 8800 polyamide wax anti-settling slurry purchased from Guangzhou Huaxia Additive Chemical Co., Ltd. The adhesion promoter is 6040 adhesion promoter purchased from Dow Corning.

[0043] The leveling agent is BYK333.

[0044] The viscosity reducer is butyl ester.

[0045] Corn fiber was commercially available from Hubei Xinghengye Technology Co., Ltd.

[0046] The lotus leaf powder is homemade, and the specific preparation method is: select fresh lotus leaves, dry them with hot air until the moisture content is 5%; then grind and sieve them in a grinder to obtain lotus leaf powder with a particle size of 5μm.

[0047] Coconut shell fiber was commercially available from Shandong Lvhe Composite Materials Co., Ltd.

[0048] The coupling agent is silane coupling agent, KH-560.

[0049] The curing agent is hexamethylene diisocyanate-based polyisocyanate and butyl ester. According to the mass percentage of the curing agent, the hexamethylene diisocyanate-based polyisocyanate is 38% and the butyl ester is 62%.

[0050] In this embodiment, the solid content of the curing agent is 37±0.5%.

[0051] The diluents are butyl ester, xylene and PMA. According to the mass percentage of the diluents, xylene is 25%, PMA is 22% and butyl ester is 53%.

[0052] This embodiment also provides a method for preparing a PU matte white topcoat applied to a melamine board, comprising the following steps: Step 1: Prepare the main agent: Step 1a: corn fiber, lotus leaf powder, coconut shell fiber and coupling agent were mixed, and then stirred at 2300 r / min for 15 min.

[0053] The mixture was then mixed and allowed to stand for 1.5 h to obtain a mixture for later use.

[0054] Step 1b: Add acrylic resin, dispersant and defoamer into a container and stir at 800 r / min for 10 minutes.

[0055] Step 1c: Continue to add pigment and filler into the container and stir at 1200r / min for 30min.

[0056] Step 1d: Continue to add the remaining raw materials into the container, stir at 1000 r / min for 10 min to obtain the main agent.

[0057] Step 2: Prepare a curing agent: Mix hexamethylene diisocyanate-based polyisocyanate and butyl ester, stir until uniform, and obtain a curing agent for standby use.

[0058] Step 3: Prepare diluent: mix butyl ester, xylene and PMA, stir until uniform, and obtain diluent for standby use.

[0059] Step 4: Mix the main agent, curing agent and diluent according to the mass ratio, stir until uniform, and obtain the PU matte white topcoat for melamine board.

[0060] The fineness of the PU matte white topcoat applied to the melamine board is 25μm.

[0061] When applied on melamine board, the board surface is smooth without particles and feels smooth.

[0062] Example 2 A PU matte white topcoat applied to a melamine board, which is different from Example 1 in that: The mass ratio of the main agent, curing agent and diluent is 1:0.1:0.5.

[0063] In the main agent, the content of each component is different, and the filler is 4500 mesh talc powder. The specific content is shown in Table 1.

[0064] In the curing agent, the isocyanate is isophorone diisocyanate. According to the mass percentage of the curing agent, the isophorone diisocyanate is 35% and the butyl ester is 65%.

[0065] In the diluent, according to the mass percentage of the diluent, xylene is 20%, PMA is 20%, and butyl ester is 60%.

[0066] A method for preparing a PU matte white topcoat applied to a melamine board, which is different from Example 1 in that some parameters are different, specifically comprising the following steps: Step 1: Prepare the main agent: Step 1a: corn fiber, lotus leaf powder, coconut shell fiber and coupling agent are mixed, and then stirred at 2000r / min for 20min.

[0067] The mixture was then mixed and allowed to stand for 1 h to obtain a mixture for later use.

[0068] Step 1b: Add acrylic resin, dispersant and defoamer into a container and stir at 750 r / min for 20 minutes.

[0069] Step 1c: Continue to add pigment and filler into the container and stir at 1100r / min for 40min.

[0070] Step 1d: Continue to add the remaining raw materials into the container and stir at 900 r / min for 15 min to obtain the main agent.

[0071] Step 2: Prepare a curing agent: Mix hexamethylene diisocyanate-based polyisocyanate and butyl ester, stir until uniform, and obtain a curing agent for standby use.

[0072] Step 3: Prepare diluent: mix butyl ester, xylene and PMA, stir until uniform, and obtain diluent for standby use.

[0073] Step 4: Mix the main agent, curing agent and diluent according to the mass ratio, stir until uniform, and obtain the PU matte white topcoat for melamine board.

[0074] Example 3 A PU matte white topcoat applied to a melamine board, which is different from Example 1 in that: The mass ratio of the main agent, curing agent and diluent is 1:0.3:0.8.

[0075] In the main agent, the content of each component is different, and the filler is talcum powder with a mesh size of 5500. The specific content is shown in Table 1.

[0076] In the curing agent, according to the mass percentage of the curing agent, the hexamethylene diisocyanate-based polyisocyanate is 40% and the butyl ester is 60%.

[0077] In the diluent, according to the mass percentage of the diluent, xylene is 30%, PMA is 25%, and butyl ester is 45%.

[0078] A method for preparing a PU matte white topcoat applied to a melamine board, which is different from Example 1 in that some parameters are different, specifically comprising the following steps: Step 1: Prepare the main agent: Step 1a: corn fiber, lotus leaf powder, coconut shell fiber and coupling agent were mixed, and then stirred at 2500 r / min for 10 min.

[0079] The mixture was then mixed and allowed to stand for 2 h to obtain a mixture for later use.

[0080] Step 1b: Add acrylic resin, dispersant and defoamer into a container and stir at 850 r / min for 5 minutes.

[0081] Step 1c: Continue to add pigment and filler into the container and stir at 1300r / min for 15min.

[0082] Step 1d: Continue to add the remaining raw materials into the container, stir at 1100 r / min for 5 minutes to obtain the main agent.

[0083] Step 2: Prepare a curing agent: Mix hexamethylene diisocyanate-based polyisocyanate and butyl ester, stir until uniform, and obtain a curing agent for standby use.

[0084] Step 3: Prepare diluent: mix butyl ester, xylene and PMA, stir until uniform, and obtain diluent for standby use.

[0085] Step 4: Mix the main agent, curing agent and diluent according to the mass ratio, stir until uniform, and obtain the PU matte white topcoat for melamine board.

[0086] Table 1 Example 4 A PU matte white topcoat applied to melamine board is different from Example 1 in that the curing agent is hexamethylene diisocyanate-based polyisocyanate, that is, butyl ester is omitted.

[0087] Example 5 A PU matte white topcoat applied to melamine board is different from Example 1 in that: in the diluent, according to the mass percentage of the diluent, xylene is 60%, PMA is 10%, and butyl ester is 30%.

[0088] Example 6 A PU matte white topcoat applied to melamine board, which is different from Example 1 in that the diluent is butyl ester, that is, xylene and PMA are omitted.

[0089] Example 7 A method for preparing a PU matte white topcoat applied to a melamine board, which is different from that of Example 1 in that the advance preparation of the mixture is omitted.

[0090] Specifically, the following steps are included: Step 1: Prepare the main agent: Step 1a: Add acrylic resin, dispersant and defoamer into a container and stir at 800 r / min for 10 minutes.

[0091] Step 1b: Continue to add pigment and filler into the container and stir at 1200r / min for 30min.

[0092] Step 1c: Continue to add the remaining raw materials into the container, stir at 1000 r / min for 10 minutes to obtain the main agent.

[0093] Step 2: Prepare a curing agent: Mix hexamethylene diisocyanate-based polyisocyanate and butyl ester, stir until uniform, and obtain a curing agent for standby use.

[0094] Step 3: Prepare diluent: mix butyl ester, xylene and PMA, stir until uniform, and obtain diluent for standby use.

[0095] Step 4: Mix the main agent, curing agent and diluent according to the mass ratio, stir until uniform, and obtain the PU matte white topcoat for melamine board.

[0096] Comparative Example Comparative Example 1 A PU matte white topcoat applied to a melamine board, which is different from Example 1 in that corn fiber is replaced by bamboo fiber.

[0097] Comparative Example 2 A PU matte white topcoat applied to a melamine board, which is different from Example 1 in that the lotus leaf powder is replaced by calcium carbonate.

[0098] Comparative Example 3 A PU matte white topcoat applied to a melamine board, which is different from Example 1 in that coconut shell fiber is replaced by hydroxyethyl cellulose.

[0099] Comparative Example 4 A PU matte white topcoat applied to a melamine board, which is different from Example 1 in that corn fiber, lotus leaf powder and coconut shell fiber are omitted.

[0100] Performance testing 1. Adhesion test: The PU matte white topcoat applied to melamine board of Examples 1-7 and Comparative Examples 1-4 was tested with reference to GB / T 9286-1998 "Scratch test for paint and varnish films", and the test results are recorded in Table 2.

[0101] The substrate is an unpolished melamine board. The PU matte white topcoat applied to the melamine board is sprayed on the substrate, and the paint film thickness is maintained at 15±2μm. After being placed at room temperature (air-conditioned constant temperature room 25±2℃) for 96 hours, a test board is obtained.

[0102] The test results of Example 1 refer to Figure 1 2. Yellowing resistance test: GB / T 9761-2008 “Visual colorimetry of paints and varnishes” was used to test the PU matte white topcoat applied to melamine boards in Examples 1-7 and Comparative Examples 1-4.

[0103] Taking Example 1 as an example, the remaining groups were processed and tested using the same method.

[0104] The reference standard plate is: the PU matte white topcoat applied to the melamine board in Example 1 is sprayed on the substrate, the paint film thickness is maintained at 15±2 μm, and the reference standard plate is obtained after being placed at room temperature (air-conditioned constant temperature room 25±2° C.) for 96 hours.

[0105] The test board is: first spray the PU matte white topcoat applied to the melamine board of Example 1 on the substrate, keep the paint film thickness at 15±2μm, place it at room temperature (air-conditioned constant temperature room 25±2℃) for 96 hours, and then place it at 60±3℃ and irradiance 0.68W / m 2 The test plate was exposed to continuous light for 168 hours under the conditions of 340°C and UVA-340, and then taken out to obtain the test plate.

[0106] The substrate is unpolished melamine board.

[0107] Compare the test plate with the reference standard plate under natural daylight conditions and record the color difference level in Table 2.

[0108] 3. Impact strength test: With reference to GB / T 1732-2020 “Determination of impact resistance of paint film”, the PU matte white topcoat applied to melamine board of Examples 1-7 and Comparative Examples 1-4 was tested, and the maximum height was recorded in Table 2.

[0109] The substrate is an unpolished melamine board. The PU matte white topcoat applied to the melamine board is sprayed on the substrate, and the paint film thickness is maintained at 15±2μm. After being placed at room temperature (air-conditioned constant temperature room 25±2℃) for 96 hours, a test board is obtained.

[0110] Table 2 Category Adhesion testing Yellowing resistance test Impact strength test (cm) Example 1 0 0 48 Example 2 1 1 46 Example 3 1 1 45 Example 4 1 1 42 Example 5 1 0 44 Example 6 1 1 41 Example 7 1 1 41 Comparative Example 1 2 2 32 Comparative Example 2 1 2 34 Comparative Example 3 2 3 35 Comparative Example 4 2 4 27 Comparative Example 4 is based on Example 1, but corn fiber, lotus leaf powder and coconut shell fiber are omitted. Since Comparative Example 4 still maintains a well-coordinated system of main agent, curing agent and diluent, the adhesion is still within a fair range. However, compared with Example 1, the adhesion rating of Comparative Example 4 still has a relatively obvious decline. In the yellowing resistance test of Comparative Example 4, the color difference between the reference standard plate and the test plate is quite different, indicating that the yellowing resistance of Comparative Example 4 is not good.

[0111] According to the test data in Table 2, the PU matte white topcoat of Examples 1-7 sprayed on the unpolished melamine board has a higher adhesion level than that of Comparative Example 4. The reference standard board of Examples 1-7 and the test board have no visible difference or very slight or just visible difference in color difference level, and have significantly better yellowing resistance than Comparative Example 4. The impact strength of Examples 1-7 is 41-48cm, which is much greater than 27cm of Comparative Example 4. It can be seen that Examples 1-7 have higher impact strength than Comparative Example 4.

[0112] This shows that the PU matte white paint spray provided in this application can indeed have the effects of high adhesion, high yellowing resistance and high toughness at the same time.

[0113] Comparative Examples 1-3 are based on Example 1, but any of the corn fiber, lotus leaf powder and coconut shell fiber is omitted, and the obtained PU matte white topcoat has a large gap in adhesion, yellowing resistance and impact strength compared with Example 1. It shows that if the special combination of corn fiber, lotus leaf powder and coconut shell fiber is destroyed, a special structure cannot be generated to play a synergistic role.

[0114] Example 4 is based on Example 1, but the combination of curing agents is changed; Examples 5-6 are based on Example 1, but the proportion of diluents or the selection of diluents are changed. Example 7 is based on Example 1, but the preparation of the mixture in advance is omitted. Although the performance of Examples 4-7 is still better than that of Comparative Example 4, there is a slight gap between them and Example 1. It shows that further limiting the curing agent, diluent and preparation method can effectively enhance the performance of PU matte white topcoat.

[0115] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed. However, as long as it is within the scope of the claims of the present application, it shall be protected by the patent law.

Claims

1. A PU matte white topcoat applied to melamine board, characterized in that: Including main agent, curing agent and diluent; according to the mass ratio, main agent: curing agent: diluent = 1: (0.1-0.3): (0.5-0.8); The main agent includes the following components in percentage by mass: acrylic resin, 1-1.5% dispersant, 0.1-0.5% defoamer, 25-30% pigment, 5-10% filler, 1-5% matting powder, 0.01-5% additive, 0.1-0.5% leveling agent, 5-10% viscosity reducer, 1-5% corn fiber, 0.5-2% lotus leaf powder, 0.1-1% coconut shell fiber, and 0.1-1% coupling agent.

2. The PU matte white topcoat for melamine board according to claim 1, characterized in that: The diluent includes butyl ester, xylene, and PMA.

3. The PU matte white topcoat for melamine board according to claim 2, characterized in that: The diluents are butyl ester, xylene and PMA; according to the mass percentage of the diluents, xylene is 20-30% and PMA is 20-25%.

4. The PU matte white topcoat for melamine board according to claim 1, characterized in that: The curing agent includes isocyanate and butyl ester.

5. The PU matte white topcoat for melamine board according to claim 4, characterized in that: The curing agent is hexamethylene diisocyanate-based polyisocyanate and butyl ester; according to the mass percentage of the curing agent, the hexamethylene diisocyanate-based polyisocyanate is 35-40%.

6. The PU matte white topcoat for melamine board according to claim 1, characterized in that: The filler includes a mixture of one or more of talc, calcium carbonate, kaolin and barium sulfate.

7. The PU matte white topcoat for melamine board according to claim 6, characterized in that: The filler is talcum powder of 4500-5500 mesh.

8. A method for preparing the PU matte white topcoat applied to melamine board according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Prepare the main agent: Step 1a: Stir the acrylic resin, dispersant and defoamer at 750-850 r / min for 5-20 min; Step 1b: Continue to add pigments and fillers, and stir at 1100-1300 r / min for 15-40 min; Step 1c: Continue to add the remaining raw materials and stir at 900-1100 r / min for 5-15 min to obtain the main agent; Step 2: Mix the main agent, curing agent and diluent until they are uniform to obtain the PU matte white topcoat for use on the melamine board.

9. The method for preparing the PU matte white topcoat applied to melamine board according to claim 8, characterized in that: The corn fiber, lotus leaf powder, coconut shell fiber and coupling agent are stirred and mixed at 2000-2500 r / min for 10-20 min, and then allowed to stand for 1-2 h to obtain a mixture; the mixture is added in step 1c and mixed with the remaining raw materials.

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