Water-resistant, crack-resistant, formaldehyde-free multi-layer composite board and its manufacturing process

Abstract

The present invention relates to the technical field of composite panels, specifically a water-resistant, crack-resistant, formaldehyde-free multilayer composite panel and its manufacturing process, comprising the following process steps: taking five layers of log slices, applying an adhesive to the upper surfaces thereof, and overlapping to form a composite panel; laying facing paper on the upper surface of the composite panel and pressing; applying a surface varnish to the surface of the facing paper, UV curing, forming a surface varnish layer, and obtaining a composite panel; the surface varnish comprises the following components by weight: 20 to 60 parts of branched modified polyurethane, 10 to 30 parts of modified polysulfide, 2 to 3 parts of photoinitiator, and 1 part of auxiliary agent. The present invention uses a mixture of branched modified polyurethane and modified polysulfide as the resin material of the surface varnish, resulting in a surface varnish having high activity and low viscosity, and UV curing to form a three-dimensional network cross-linked structure, which helps to reduce the curing shrinkage of the surface varnish layer and improves the adhesion, hardness, water resistance, tensile strength, impact resistance, and other properties.

Description

Technical Field

[0001] The present invention relates to the technical field of composite boards, in particular to a water-resistant, crack-resistant and formaldehyde-free multi-layer composite board and a manufacturing process thereof. Background Art

[0002] With the continuous development of the coatings industry, people are increasingly aware of energy conservation, environmental protection, and health. UV-curable coatings have seen rapid growth due to their "5E" advantages: high efficiency, environmental protection, energy conservation, cost-effectiveness, and wide adaptability. UV-curable coatings utilize ultraviolet light to excite photoinitiators, triggering polymerization and cross-linking reactions between the photosensitive resin and monomer molecules acting as reactive diluents in the coating, thereby hardening the paint film. This chemical drying process is achieved through the formation of chemical bonds. UV-curable coatings have rapidly developed and gained widespread application due to their low VOC emissions, fast cure speed, and ability to be applied to heat-sensitive substrates (plastics, paper, and wood). Among existing UV-curable coatings, polyurethane coatings are widely used, but their water resistance is poor. Furthermore, UV-curable coatings often contain diluents, which can significantly shrink after curing, affecting the hardness and mechanical properties of the coating film. Furthermore, in composite wood panels, the moisture content of the wood can fluctuate significantly due to temperature differences between indoor and outdoor, as well as dry and cold weather. This can disrupt the wood's internal fiber structure, affect product stability, and cause water seepage and cracking in wooden furniture finishes. Therefore, we propose a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board and a manufacturing process thereof. Summary of the Invention

[0003] The object of the present invention is to provide a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board and a manufacturing process thereof, so as to solve the problems raised in the above-mentioned background technology.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: a water-resistant, crack-proof and formaldehyde-free multi-layer composite board, comprising log slices, an adhesive layer, facing paper and a surface paint layer;

[0005] The number of layers of the log slices is five, the facing paper is located on the upper surface of the uppermost layer of log slices, and the surface paint layer is provided on the upper surface of the facing paper;

[0006] The facing paper, the top layer of log slices and two adjacent layers of log slices are bonded together by adhesive to form an adhesive layer.

[0007] Furthermore, the thickness of the composite board is 18 to 22 mm.

[0008] Furthermore, the log slices are Australian pine boards, and the thickness of a layer of log slices is 3.5 to 5.5 mm.

[0009] Furthermore, the adhesive layer is made of Huntsman MDI adhesive with a thickness of 0.03 to 0.05 mm.

[0010] Furthermore, the facing paper is from Schattdecor of Germany, with a specification of 100-120g / m2.

[0011] Furthermore, the surface paint layer is formed by UV curing of the surface paint and has a thickness of 0.05 to 0.10 mm.

[0012] In the above technical solution, the log slices are placed in a ventilated and cool place to dry for three months before use, which can effectively prevent the deformation and cracking of the wood and enhance the comprehensive performance of the composite board.

[0013] A process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board, comprising the following steps:

[0014] Take five layers of log slices, apply adhesive on the upper surface, and overlap to form a composite board; lay facing paper on the upper surface of the composite board and press it;

[0015] The surface paint is applied to the surface of the facing paper and UV cured to form a surface paint layer to obtain a composite board.

[0016] Furthermore, the pressing process is 0.03 to 0.05 MPa.

[0017] Furthermore, the surface paint is obtained by mixing branched modified polyurethane, modified polysulfide, photoinitiator and additives.

[0018] Furthermore, the surface paint comprises the following components by mass: 20 to 60 parts of branched modified polyurethane, 10 to 30 parts of modified polysulfide, 2 to 3 parts of photoinitiator benzophenone (PB), and 1 part of auxiliary agent triethylamine.

[0019] Furthermore, the branched modified polyurethane is prepared by the following process:

[0020] Mix a polyhydroxy compound and N,N-dimethylformamide, add isophorone diisocyanate and dibutyltin dilaurate, and react at 25-30°C for 12 hours under nitrogen atmosphere; add hydroxyethyl acrylate, hydroxyethyl methacrylate, and p-hydroxyanisole, raise the temperature to 70-80°C and react for 4 hours; concentrate, precipitate in anhydrous ether, rotary evaporate, and vacuum dry to obtain a branched modified polyurethane.

[0021] Furthermore, the ratio of the polyhydroxy compound to N,N-dimethylformamide is 10 g / 100 mL.

[0022] Furthermore, the branched modified polyurethane includes the following components by mass: 100 to 116 parts of polyhydroxy compound, 55 to 60 parts of isophorone diisocyanate, 0.2 to 0.3 parts of dibutyltin dilaurate, 32.7 to 34.8 parts of hydroxyethyl acrylate, 40.7 to 42.2 parts of hydroxyethyl methacrylate, and 0.4 to 0.5 parts of p-hydroxyanisole.

[0023] Further, the polyol is prepared by the following process:

[0024] Mix cyanuric chloride, acetone and deionized water, stir and adjust the system temperature to 0-5°C, slowly add piperazine and sodium hydroxide solution within 2 hours, and react for 100-150 minutes; heat to 35-40°C, add diethanolamine, and react for 100-150 minutes; evaporate the acetone, add aminobenzenethiol and sodium hydroxide solution, and continue to react for 6-8 hours; vacuum filter, wash with acetone, wash with water, and dry to constant weight to obtain a polyhydroxy compound.

[0025] Furthermore, the polyol comprises the following components by mass: 18.4 parts of cyanuric chloride, 4.3-4.4 parts of piperazine, 5.3-5.4 parts of diethanolamine, and 6.2-6.4 parts of aminobenzenethiol;

[0026] The ratio of cyanuric chloride, acetone and deionized water is 37g:175mL:70mL;

[0027] The concentration of sodium hydroxide solution is 0.2M;

[0028] Before use, aminobenzenethiol was protected by 1-nitro-2,4-dibenzylmercaptan.

[0029] Furthermore, the modified polysulfide is prepared by the following process:

[0030] Trimethylolpropane tris(3-mercaptopropionate) and N,N-dimethylformamide are mixed, and 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate, glycidyl methacrylate, and a catalyst are added under nitrogen atmosphere, and the mixture is reacted at 30-35°C for 5-6 hours; the mixture is concentrated, precipitated, and dried to obtain a modified polysulfide.

[0031] Furthermore, the ratio of trimethylolpropane tris(3-mercaptopropionate) to N,N-dimethylformamide is 25 g / 100 mL;

[0032] The modified polysulfide comprises the following components by weight: 4.0 parts of trimethylolpropane tris(3-mercaptopropionate), 1.6-3.2 parts of 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate, 1.4-3.0 parts of glycidyl methacrylate, and 0.03-0.04 parts of a catalyst;

[0033] The catalyst is 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).

[0034] Furthermore, the process conditions of UV curing are: high-voltage UV light irradiation for 15 to 45 seconds, and a wavelength of 300 to 400 nm.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] In the above technical solution, in an acetone and deionized water system, sodium hydroxide is used as an acid-binding agent to react and condense the chlorine in cyanuric chloride with the amino groups in piperazine, diethanolamine, and aminobenzenethiol to obtain a polyhydroxy compound with a triazine structure as a core to form a branched structure; the triazine structure is used as a polyol to react with diisocyanate, and hydroxyethyl acrylate, hydroxyethyl methacrylate, and p-hydroxyanisole are added to prepare a polyurethane acrylate having a double bond and a thiol group (protecting group), which is recorded as a branched modified polyurethane. The introduction of the triazine and piperazine structures can effectively improve the adhesion, stability, water resistance, and heat resistance of the surface paint layer, and as a rigid skeleton, simultaneously improve the mechanical properties of the surface paint layer.

[0037] In a dry nitrogen and N,N-dimethylformamide solvent system, a catalyst causes the mercapto group in trimethylolpropane tris(3-mercaptopropionate) to react with the double bonds in 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate and glycidyl methacrylate to obtain a thioether, which can improve the toughness of the prepared surface paint layer and form a branched structure, recorded as a modified polythioether. The epoxy-terminated structure facilitates the subsequent UV curing of the surface paint; the introduction of fluorine element can improve the hardness and water resistance of the prepared surface paint layer.

[0038] Branched modified polyurethane and modified polysulfide are mixed as the resin material of the surface paint. Both are branched molecules with reduced entanglement between molecular chains and a large number of active terminal functional groups, which reduces the viscosity of the surface paint, reduces the use of diluents, reduces toxicity, avoids a decrease in curing rate, an increase in the shrinkage of the surface paint layer, and a decrease in adhesion, hardness, water resistance, tensile strength, impact resistance and other properties.

[0039] The thiol protective agent in the branched modified polyurethane leaves under UV light, exposing the thiol group; under the action of photoinitiators and additives, it reacts and cross-links with double bonds and epoxy groups in modified polysulfide to form a three-dimensional network cross-linked structure. The number of double bonds is reduced, which can effectively improve the toughness of the surface paint layer and improve its adhesion; the sufficient content of photosensitive groups helps to improve the hardness of the surface paint layer; the internal cavity formed by the three-dimensional cross-linked structure can effectively reduce the internal stress of the surface paint layer and reduce its curing shrinkage, further improving the hardness, tensile strength, impact resistance and other comprehensive properties of the surface paint layer, and achieving water resistance and crack resistance of the composite board; and no formaldehyde is added in the composite board material system, which is safer and more environmentally friendly. DETAILED DESCRIPTION

[0040] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] In the following specific embodiments,

[0042] The log slices are Australian pine boards, with a thickness of 4.0mm per layer. They are placed in a ventilated and cool place to air for three months before use. The adhesive layer uses Huntsman MDI glue, with a single layer coating thickness of 0.05mm. The facing paper is from Schattdecor of Germany, with a specification of 100g / ㎡.

[0043] Thiol protection process of aminobenzenethiol:

[0044] Mix 0.10 mol of 1-nitro-2,4-dibenzyl mercaptan, 35 mL of deionized water, and 65 mL of ethanol, add 0.12 mol of thiourea, 5 mL of 36% concentrated hydrochloric acid, and 5 mL of 30% hydrogen peroxide at 2°C, and react for 5 h; add 0.01 mol of aminobenzenethiol and react for 8 h; extract, concentrate under reduced pressure, and dry;

[0045] The following “parts” are all parts by mass.

[0046] Example 1: A process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board, comprising the following steps:

[0047] Step (1) preparing the surface paint:

[0048] 1.1. Preparation of polyols:

[0049] Cyanuric chloride, acetone and deionized water were mixed, stirred and the system temperature was adjusted to 0°C, piperazine and sodium hydroxide solution were slowly added within 2 hours, and the reaction was carried out for 150 minutes; the temperature was raised to 35°C, diethanolamine was added, and the reaction was carried out for 150 minutes; the acetone was evaporated, aminobenzenethiol and sodium hydroxide solution were added, and the reaction was continued for 6 hours; vacuum filtration was carried out, the mixture was washed with acetone and water, and dried to constant weight to obtain a polyol; the polyol comprised the following components by weight: 18.4 parts of cyanuric chloride, 4.3 parts of piperazine, 5.3 parts of diethanolamine, and 6.4 parts of aminobenzenethiol; the ratio of cyanuric chloride, acetone and deionized water was 37 g:175 mL:70 mL; the concentration of the sodium hydroxide solution was 0.2 M;

[0050] 1.2. Preparation of branched modified polyurethane:

[0051] A polyol and N,N-dimethylformamide are mixed, isophorone diisocyanate and dibutyltin dilaurate are added, and the mixture is reacted at 25°C for 12 hours under a nitrogen atmosphere; hydroxyethyl acrylate, hydroxyethyl methacrylate, and p-hydroxyanisole are added, and the mixture is heated to 70°C and reacted for 4 hours; the mixture is concentrated, precipitated in anhydrous ether, rotary evaporated, and vacuum dried to obtain a branched modified polyurethane; the ratio of the polyol to N,N-dimethylformamide is 10 g / 100 mL; the branched modified polyurethane comprises the following components by mass: 100 parts of the polyol, 55 parts of isophorone diisocyanate, 0.2 parts of dibutyltin dilaurate, 32.7 parts of hydroxyethyl acrylate, 40.7 parts of hydroxyethyl methacrylate, and 0.4 parts of p-hydroxyanisole;

[0052] 1.3. Preparation of modified polysulfide:

[0053] Trimethylolpropane tris(3-mercaptopropionate) and N,N-dimethylformamide were mixed, and 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate, glycidyl methacrylate, and a catalyst were added under nitrogen atmosphere, and the mixture was reacted at 30°C for 5 hours; the mixture was concentrated, precipitated, and dried to obtain a modified polysulfide; the ratio of trimethylolpropane tris(3-mercaptopropionate) to N,N-dimethylformamide was 25 g / 100 mL; the modified polysulfide comprised the following components by weight: 4.0 parts of trimethylolpropane tris(3-mercaptopropionate), 1.6 parts of 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate, 1.4 parts of glycidyl methacrylate, and 0.03 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a catalyst;

[0054] 1.4. Preparation of surface paint:

[0055] 60 parts of branched modified polyurethane, 10 parts of modified polysulfide, 2 parts of photoinitiator benzophenone (PB), and 1 part of auxiliary agent triethylamine were mixed to obtain a surface paint;

[0056] Step (2) Preparation of composite board:

[0057] Take five layers of log slices, apply adhesive on the upper surface, and stack them to form a composite board; lay facing paper on the upper surface of the composite board and press at 0.03MPa for 60s;

[0058] The surface paint is applied to the surface of the facing paper with a coating thickness of 0.05 mm and UV curing is performed under the following process conditions: high-pressure UV light irradiation for 15 seconds with a wavelength of 365 nm to form a surface paint layer and obtain a composite board.

[0059] Example 2: A process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board, comprising the following steps:

[0060] Step (1) preparing the surface paint:

[0061] 1.1. Preparation of polyols:

[0062] Cyanuric chloride, acetone and deionized water were mixed, stirred and the system temperature was adjusted to 2°C, piperazine and sodium hydroxide solution were slowly added within 2 hours, and the reaction was carried out for 120 minutes; the temperature was raised to 37°C, diethanolamine was added, and the reaction was carried out for 120 minutes; the acetone was evaporated, aminobenzenethiol and sodium hydroxide solution were added, and the reaction was continued for 7 hours; vacuum filtration was carried out, the mixture was washed with acetone and water, and dried to constant weight to obtain a polyol; the polyol comprised the following components by weight: 18.4 parts of cyanuric chloride, 4.35 parts of piperazine, 5.35 parts of diethanolamine, and 6.3 parts of aminobenzenethiol; the ratio of cyanuric chloride, acetone and deionized water was 37g:175mL:70mL; the concentration of the sodium hydroxide solution was 0.2M;

[0063] 1.2. Preparation of branched modified polyurethane:

[0064] A polyol and N,N-dimethylformamide were mixed, isophorone diisocyanate and dibutyltin dilaurate were added, and the mixture was reacted at 27°C for 12 hours under a nitrogen atmosphere; hydroxyethyl acrylate, hydroxyethyl methacrylate, and p-hydroxyanisole were added, and the temperature was raised to 75°C for 4 hours; the mixture was concentrated, precipitated in anhydrous ether, rotary evaporated, and vacuum dried to obtain a branched modified polyurethane; the ratio of the polyol to N,N-dimethylformamide was 10 g / 100 mL; the branched modified polyurethane comprised the following components by mass: 108 parts of the polyol, 57 parts of isophorone diisocyanate, 0.25 parts of dibutyltin dilaurate, 33.7 parts of hydroxyethyl acrylate, 41.5 parts of hydroxyethyl methacrylate, and 0.45 parts of p-hydroxyanisole;

[0065] 1.3. Preparation of modified polysulfide:

[0066] Trimethylolpropane tris(3-mercaptopropionate) and N,N-dimethylformamide were mixed, and 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate, glycidyl methacrylate, and a catalyst were added under nitrogen atmosphere, and the mixture was reacted at 32°C for 5.5 hours; the mixture was concentrated, precipitated, and dried to obtain a modified polysulfide; the ratio of trimethylolpropane tris(3-mercaptopropionate) to N,N-dimethylformamide was 25 g / 100 mL; the modified polysulfide comprised the following components by weight: 4.0 parts of trimethylolpropane tris(3-mercaptopropionate), 2.4 parts of 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate, 2.2 parts of glycidyl methacrylate, and 0.035 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a catalyst;

[0067] 1.4. Preparation of surface paint:

[0068] 60 parts of branched modified polyurethane, 20 parts of modified polysulfide, 2.5 parts of photoinitiator benzophenone (PB), and 1 part of auxiliary agent triethylamine were mixed to obtain a surface paint;

[0069] Step (2) Preparation of composite board:

[0070] Take five layers of log slices, apply adhesive on the upper surface, and stack them to form a composite board; lay facing paper on the upper surface of the composite board and press at 0.04MPa for 60s;

[0071] The surface paint is applied to the surface of the facing paper with a coating thickness of 0.08 mm and UV curing is performed under the following process conditions: high-pressure UV light irradiation for 30 seconds with a wavelength of 365 nm to form a surface paint layer and obtain a composite board.

[0072] Example 3: A process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board, comprising the following steps:

[0073] Step (1) preparing the surface paint:

[0074] 1.1. Preparation of polyols:

[0075] Cyanuric chloride, acetone and deionized water were mixed, stirred and the system temperature was adjusted to 5°C, piperazine and sodium hydroxide solution were slowly added within 2 hours, and the reaction was carried out for 150 minutes; the temperature was raised to 40°C, diethanolamine was added, and the reaction was carried out for 100 minutes; the acetone was evaporated, aminobenzenethiol and sodium hydroxide solution were added, and the reaction was continued for 8 hours; vacuum filtration was carried out, the mixture was washed with acetone and water, and dried to constant weight to obtain a polyol; the polyol comprised the following components by weight: 18.4 parts of cyanuric chloride, 4.4 parts of piperazine, 5.4 parts of diethanolamine, and 6.4 parts of aminobenzenethiol; the ratio of cyanuric chloride, acetone and deionized water was 37g:175mL:70mL; the concentration of the sodium hydroxide solution was 0.2M;

[0076] 1.2. Preparation of branched modified polyurethane:

[0077] A polyol and N,N-dimethylformamide were mixed, isophorone diisocyanate and dibutyltin dilaurate were added, and the mixture was reacted at 30°C for 12 hours under a nitrogen atmosphere; hydroxyethyl acrylate, hydroxyethyl methacrylate, and p-hydroxyanisole were added, and the temperature was raised to 80°C for 4 hours; the mixture was concentrated, precipitated in anhydrous ether, rotary evaporated, and vacuum dried to obtain a branched modified polyurethane; the ratio of the polyol to N,N-dimethylformamide was 10 g / 100 mL; the branched modified polyurethane comprised the following components by mass: 116 parts of the polyol, 60 parts of isophorone diisocyanate, 0.3 parts of dibutyltin dilaurate, 34.8 parts of hydroxyethyl acrylate, 42.2 parts of hydroxyethyl methacrylate, and 0.5 parts of p-hydroxyanisole;

[0078] 1.3. Preparation of modified polysulfide:

[0079] Trimethylolpropane tris(3-mercaptopropionate) and N,N-dimethylformamide were mixed, and 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate, glycidyl methacrylate, and a catalyst were added under nitrogen atmosphere, and the mixture was reacted at 35°C for 6 hours; the mixture was concentrated, precipitated, and dried to obtain a modified polysulfide; the ratio of trimethylolpropane tris(3-mercaptopropionate) to N,N-dimethylformamide was 25 g / 100 mL; the modified polysulfide comprised the following components by weight: 4.0 parts of trimethylolpropane tris(3-mercaptopropionate), 3.2 parts of 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate, 3.0 parts of glycidyl methacrylate, and 0.04 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a catalyst;

[0080] 1.4. Preparation of surface paint:

[0081] 60 parts of branched modified polyurethane, 30 parts of modified polysulfide, 3 parts of photoinitiator benzophenone (PB), and 1 part of auxiliary agent triethylamine were mixed to obtain a surface paint;

[0082] Step (2) Preparation of composite board:

[0083] Take five layers of log slices, apply adhesive on the upper surface, and stack them to form a composite board; lay facing paper on the upper surface of the composite board and press at 0.05MPa for 60s;

[0084] The surface paint is applied to the surface of the facing paper with a coating thickness of 0.10 mm and UV curing is performed under the following process conditions: high-pressure UV light irradiation for 45 seconds with a wavelength of 365 nm to form a surface paint layer and obtain a composite board.

[0085] Comparative Example 1: A process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board, comprising the following process steps:

[0086] Step (1) preparing the surface paint:

[0087] 1.1. Pentaerythritol triacrylate is used as the polyol:

[0088] 1.2. Preparation of branched modified polyurethane:

[0089] A polyol and N,N-dimethylformamide were mixed, isophorone diisocyanate and dibutyltin dilaurate were added, and the mixture was reacted at 25°C for 12 hours under a nitrogen atmosphere; hydroxyethyl acrylate, hydroxyethyl methacrylate, and p-hydroxyanisole were added, and the temperature was raised to 70°C for 4 hours; the mixture was concentrated, precipitated in anhydrous ether, rotary evaporated, and vacuum dried to obtain a branched modified polyurethane; the ratio of the polyol to N,N-dimethylformamide was 10 g / 100 mL; the branched modified polyurethane comprised the following components by mass: 16 parts of the polyol, 55 parts of isophorone diisocyanate, 0.2 parts of dibutyltin dilaurate, 32.7 parts of hydroxyethyl acrylate, 40.7 parts of hydroxyethyl methacrylate, and 0.4 parts of p-hydroxyanisole;

[0090] Steps 1.3-1.4 and (2) are the same as in Example 1 to obtain a composite board.

[0091] Comparative Example 2: A process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board, comprising the following process steps:

[0092] Step (1) preparing the surface paint:

[0093] 1.1. Preparation of branched modified polyurethane:

[0094] Pentaerythritol triacrylate and N,N-dimethylformamide were mixed, isophorone diisocyanate and dibutyltin dilaurate were added, and the mixture was reacted at 25°C for 12 hours under a nitrogen atmosphere; hydroxyethyl acrylate, hydroxyethyl methacrylate, and p-hydroxyanisole were added, and the temperature was raised to 70°C for 4 hours; the mixture was concentrated, precipitated in anhydrous ether, rotary evaporated, and vacuum dried to obtain a branched modified polyurethane; the ratio of pentaerythritol triacrylate to N,N-dimethylformamide was 10 g / 100 mL; the branched modified polyurethane comprised the following components by mass: 16 parts of pentaerythritol triacrylate, 55 parts of isophorone diisocyanate, 0.2 parts of dibutyltin dilaurate, 32.7 parts of hydroxyethyl acrylate, 40.7 parts of hydroxyethyl methacrylate, and 0.4 parts of p-hydroxyanisole;

[0095] 1.2. Preparation of modified polysulfide:

[0096] Trimethylolpropane tris(3-mercaptopropionate) and N,N-dimethylformamide were mixed, glycidyl methacrylate and a catalyst were added under nitrogen atmosphere, and the mixture was reacted at 30°C for 5 hours; the mixture was concentrated, precipitated, and dried to obtain a modified polysulfide; the ratio of trimethylolpropane tris(3-mercaptopropionate) to N,N-dimethylformamide was 25 g / 100 mL; the modified polysulfide comprised the following components by weight: 4.0 parts of trimethylolpropane tris(3-mercaptopropionate), 3.0 parts of glycidyl methacrylate, and 0.03 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a catalyst;

[0097] 1.3. Preparation of surface paint:

[0098] 60 parts of branched modified polyurethane, 10 parts of modified polysulfide, 2 parts of photoinitiator benzophenone (PB), and 1 part of auxiliary agent triethylamine were mixed to obtain a surface paint;

[0099] Step (2) is the same as in Example 1 to obtain a composite board.

[0100] Comparative Example 3: A process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board, comprising the following process steps:

[0101] Step (1) preparing the surface paint:

[0102] 1.1. Preparation of branched modified polyurethane:

[0103] Pentaerythritol triacrylate and N,N-dimethylformamide were mixed, isophorone diisocyanate and dibutyltin dilaurate were added, and the mixture was reacted at 25°C for 12 hours under a nitrogen atmosphere; hydroxyethyl acrylate, hydroxyethyl methacrylate, and p-hydroxyanisole were added, and the temperature was raised to 70°C for 4 hours; the mixture was concentrated, precipitated in anhydrous ether, rotary evaporated, and vacuum dried to obtain a branched modified polyurethane; the ratio of pentaerythritol triacrylate to N,N-dimethylformamide was 10 g / 100 mL; the branched modified polyurethane comprised the following components by mass: 16 parts of pentaerythritol triacrylate, 55 parts of isophorone diisocyanate, 0.2 parts of dibutyltin dilaurate, 32.7 parts of hydroxyethyl acrylate, 40.7 parts of hydroxyethyl methacrylate, and 0.4 parts of p-hydroxyanisole;

[0104] 1.2. Preparation of surface paint:

[0105] 60 parts of branched modified polyurethane, 2 parts of trimethylolpropane tris(3-mercaptopropionate), 2 parts of photoinitiator benzophenone (PB), and 1 part of auxiliary agent triethylamine were mixed to obtain a surface paint;

[0106] Step (2) is the same as in Example 1 to obtain a composite board.

[0107] Experiment: Take the composite boards obtained in Examples 1-3 and Comparative Examples 1-3 to prepare samples, test their properties and record the test results:

[0108] Hardness test: Using GB / T 6739 as reference standard, use pencil hardness tester to test the pencil hardness of surface paint layer in composite board;

[0109] Adhesion test: Based on GB / T9286 as the reference standard, a paint film adhesion tester is used to test the adhesion of the surface paint layer of the composite board;

[0110] Impact strength test: Based on GB / T 1732 as the reference standard, an impact tester is used to test the impact strength of the surface paint layer of the composite board.

[0111] Tensile strength test: Use a tensile testing machine to test the tensile strength of the surface paint layer of the composite board at a tensile rate of 5 mm / min and a test temperature of 25°C;

[0112] Water resistance test: A video optical contact angle meter is used to detect the water contact angle of the surface paint layer of the composite board for testing.

[0113]

[0114] According to the data in the above table, we can clearly draw the following conclusions:

[0115] The composite plates obtained in Examples 1-3 were compared with the composite plates obtained in Comparative Examples 1-3. The test results show that:

[0116] Compared with the comparative example, the composite panels obtained in Examples 1-3 have surface paint layers with higher hardness, adhesion grade, tensile strength, impact strength and contact angle data, which fully demonstrates that the invention achieves improvements in the hardness, adhesion, mechanical properties and water resistance of the surface paint layers of the composite panels, and improves the water resistance and crack resistance of the composite panels.

[0117] Compared with Example 1, pentaerythritol triacrylate is used as the polyhydroxy compound in Comparative Example 1; based on Comparative Example 1, the preparation components of the modified polysulfide in Comparative Example 2 are different; based on Comparative Example 1, trimethylolpropane tris(3-mercaptopropionate) is used to replace the modified polysulfide in Comparative Example 3; the composite boards obtained in Comparative Examples 1-3 have a surface paint layer with higher hardness, adhesion grade, tensile strength, impact strength and decreased contact angle data. It can be seen that the setting of the surface paint components and the preparation process thereof in the present invention can promote the improvement of the hardness, adhesion performance, mechanical properties and water resistance of the surface paint layer, and help to improve the water resistance and crack resistance of the composite board.

[0118] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprise," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0119] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board, characterized by: The process steps include: Take five layers of log slices, apply adhesive on the upper surface, and overlap to form a composite board; lay facing paper on the upper surface of the composite board and press it; Applying a surface paint on the surface of the facing paper and UV curing to form a surface paint layer to obtain a composite board; The surface paint comprises the following components by mass: 20 to 60 parts of branched modified polyurethane, 10 to 30 parts of modified polysulfide, 2 to 3 parts of photoinitiator, and 1 part of auxiliary agent; The branched modified polyurethane is prepared by the following process: Mix a polyol and N,N-dimethylformamide, add isophorone diisocyanate and dibutyltin dilaurate, and react at 25-30°C for 12 hours under nitrogen atmosphere; add hydroxyethyl acrylate, hydroxyethyl methacrylate, and p-hydroxyanisole, raise the temperature to 70-80°C, and react for 4 hours to obtain a branched modified polyurethane; The polyol is prepared by the following process: Mix cyanuric chloride, acetone and deionized water, stir and adjust the system temperature to 0-5°C, slowly add piperazine and sodium hydroxide solution within 2 hours, and react for 100-150 minutes; heat to 35-40°C, add diethanolamine, and react for 100-150 minutes; evaporate the acetone, add aminobenzenethiol and sodium hydroxide solution, and continue to react for 6-8 hours to obtain a polyhydroxy compound; The modified polysulfide is prepared by the following process: Trimethylolpropane tris(3-mercaptopropionate) and N,N-dimethylformamide are mixed, and under the protection of nitrogen atmosphere, 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate, glycidyl methacrylate and a catalyst are added, and the mixture is reacted at a temperature of 30-35°C for 5-6 hours to obtain a modified polysulfide.

2. The process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board according to claim 1, characterized in that: The branched modified polyurethane comprises the following components by mass: 100-116 parts of polyhydroxy compound, 55-60 parts of isophorone diisocyanate, 0.2-0.3 parts of dibutyltin dilaurate, 32.7-34.8 parts of hydroxyethyl acrylate, 40.7-42.2 parts of hydroxyethyl methacrylate, and 0.4-0.5 parts of p-hydroxyanisole.

3. The process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board according to claim 1, characterized in that: The polyhydroxy compound includes the following components by mass: 18.4 parts of cyanuric chloride, 4.3-4.4 parts of piperazine, 5.3-5.4 parts of diethanolamine, and 6.2-6.4 parts of aminobenzenethiol.

4. The process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board according to claim 1, characterized in that: The modified polysulfide comprises the following components by weight: 4.0 parts of trimethylolpropane tris(3-mercaptopropionate), 1.6-3.2 parts of 2,2,3,3,3-pentafluoro-2-fluoropropyl acrylate, 1.4-3.0 parts of glycidyl methacrylate, and 0.03-0.04 parts of a catalyst.

5. The process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board according to claim 1, characterized in that: The process conditions of UV curing are: high-pressure UV light irradiation for 15 to 45 seconds and a wavelength of 300 to 400 nm.

6. The process for producing a water-resistant, crack-resistant, formaldehyde-free multi-layer composite board according to claim 1, characterized in that: The thickness of the composite board is 18 to 22 mm.

7. A water-resistant, crack-resistant, formaldehyde-free multi-layer composite board produced according to the production process according to any one of claims 1 to 6.

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