Medium-density fiberboard coated with flame-retardant UV paint and preparation method of medium-density fiberboard

Abstract

The invention belongs to the technical field of special boards, and discloses a medium-density board coated with flame-retardant UV paint and a preparation method thereof.The medium-density board coated with the flame-retardant UV paint comprises a medium-density board body and the UV paint coated on the surface of the medium-density board body; the UV paint comprises the following raw materials in parts by weight: 85-110 parts of modified polyurethane emulsion, 10-25 parts of composite filler, 5-8 parts of a modified additive, 1-3 parts of a photoinitiator, 4-6 parts of a dispersant, 0.5-2 parts of a defoaming agent, 0.5-2 parts of a flatting agent and 10-20 parts of water, the modified polyurethane emulsion is adopted as a film forming substance, a paint film has excellent physical properties such as hardness, gloss and the like, and by adding the composite filler, the UV paint can be applied to the field of photocuring. And by adding the modified additive, the aging resistance and flame retardance of the material are improved, so that the medium-density board coated with the UV paint has good heat resistance and flame retardance, and the risk of combustion caused by over-high local temperature during use of the electronic circuit base plate can be effectively avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of special boards, and in particular relates to a medium density board coated with flame retardant UV paint and a preparation method thereof. Background Art

[0002] Medium density fiberboard is a kind of man-made board made by mechanically separating and chemically treating wood or plant fibers, adding adhesives and waterproofing agents, and then forming them at high temperature and high pressure. The structure of medium density fiberboard is more uniform than that of natural wood, and it also avoids problems such as decay and insect infestation. At the same time, it has low expansion and contraction and is easy to process. In recent years, the pads of circuit boards in the electronics industry have gradually adopted density fiberboard. During the drilling process of printed circuit boards, the pads are placed under the circuit boards and in direct contact with the workbench of the drilling machine. They are auxiliary board-shaped materials used to protect the processed boards and drilling machines and improve the drilling quality. In order to improve the appearance and performance of medium density fiberboard, UV paint is usually applied on the surface of medium density fiberboard. UV paint is a light-curing paint. When ultraviolet light is irradiated on the light-curing paint, the photoinitiator in the paint is excited and decomposed to generate free radicals. The active free radicals hit the double bonds in the paint and react to form growth chains. This reaction continues to extend, breaking the double bonds in the active diluent and the oligomer, and cross-linking to form a film.

[0003] UV paint has the characteristics of high curing speed, low energy consumption, low environmental pollution and high performance, but it still has some disadvantages: uneven curing, low degree of crosslinking, and the cured film generally has the disadvantages of wide mechanical transformation range and easy stress cracking. In addition, due to the inhibition of oxygen, the wear resistance of the surface is poor, and inorganic materials need to be added for modification. However, the compatibility of inorganic materials with coatings is poor, and corresponding additives need to be added to avoid affecting the stability and leveling properties of the coating. In addition, since medium-density fiberboard is made of wood fiber and adhesive pressed together, it is a flammable material. In the process of manufacturing printed circuit boards in the electronics industry, it is necessary to use a hot press to perform high-temperature and high-pressure heat treatment. Therefore, the requirements for the heat resistance and flame retardancy of medium-density fiberboard are getting higher and higher to avoid the risk of combustion caused by excessive local temperature during the use of electronic circuit pads. Summary of the invention

[0004] In order to solve the deficiencies mentioned in the above-mentioned background technology, the purpose of the present invention is to provide a medium-density fiberboard coated with flame-retardant UV paint and a preparation method thereof. The UV paint coated on the medium-density fiberboard adopts modified polyurethane emulsion as the film-forming substance. The paint film has excellent physical properties such as hardness and gloss. By adding composite fillers, the paint film hardness and wear resistance of the material are further improved. The addition of modified additives improves the aging resistance and flame retardant properties of the material. The medium-density fiberboard coated with UV paint has good heat resistance and flame retardant properties, which can effectively avoid the risk of combustion caused by excessive local temperature during the use of electronic circuit pads.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A medium density board coated with flame retardant UV paint, comprising a medium density board and a UV paint coated on the surface of the medium density board, wherein the UV paint comprises the following raw materials in parts by weight: 85-110 parts of modified polyurethane emulsion, 10-25 parts of composite filler, 5-8 parts of modified additive, 1-3 parts of photoinitiator, 4-6 parts of dispersant, 0.5-2 parts of defoamer, 0.5-2 parts of leveling agent, and 10-20 parts of water; The modified polyurethane emulsion is an epoxy resin-modified castor oil-based water-based polyurethane emulsion, the composite filler is a strawberry-like core-shell structure formed by white carbon black coated with polydopamine and loaded with nano-aluminum hydroxide on the surface, and the modified additive is a triazine derivative containing benzophenone and DOPO groups.

[0006] Furthermore, the photoinitiator is photoinitiator 2959 or photoinitiator 1173, the dispersant is dispersant BYK-190 or dispersant TEGO 750W, the defoamer is defoamer BYK-093, and the leveling agent is leveling agent BFK-2700W.

[0007] Further, the preparation method of the modified polyurethane emulsion comprises the following steps: A. Add toluene diisocyanate, polyether diol, castor oil and dibutyltin dilaurate into a four-necked flask equipped with an electric stirrer, a thermometer and a reflux condenser, and react at 80°C until the R value reaches 2.8; B. Then, dimethylol propionic acid and trimethylol propane were added in sequence to react, and then the reaction temperature was lowered to 70° C., epoxy resin E-44, pentaerythritol triacrylate and hydroxyethyl methacrylate were added for end-capping, and the reaction was terminated when the R value reached 1.5; C. Cool to below 50°C, add measured triethylamine for neutralization, react for 50 minutes, and finally add deionized water for emulsification for 2 hours under high-speed stirring to obtain epoxy resin-modified castor oil-based waterborne polyurethane emulsion.

[0008] Furthermore, in step A, the molar ratio of monomers of toluene diisocyanate, polyether diol and castor oil is 10:8:3.2.

[0009] Furthermore, in step B, dimethylolpropionic acid accounts for 4-6% of the total mass of the monomers toluene diisocyanate, polyether diol and castor oil, trimethylolpropane accounts for 1.5-2% of the total mass of the monomers toluene diisocyanate, polyether diol and castor oil, and the molar ratio of epoxy resin E-44, pentaerythritol triacrylate and hydroxyethyl methacrylate used for end-capping is 1:1:2.

[0010] Furthermore, the preparation method of the composite filler comprises the following steps: a. Disperse white carbon black powder in a Tris buffer solution, add dopamine hydrochloride after ultrasonic dispersion, continue ultrasonic treatment for 10-15 minutes, then stir and react at room temperature for 24 hours, centrifuge, wash and dry to obtain white carbon black with polydopamine coated on the surface; b. Add nano aluminum hydroxide to an ethanol aqueous solution, disperse by ultrasonication to obtain a nano aluminum hydroxide dispersion, then add 3-aminopropyltrimethoxysilane to the nano aluminum hydroxide dispersion, stir and heat to 80°C for reaction for 3-5 hours, centrifuge, wash, filter and dry to obtain silane-modified nano aluminum hydroxide; c. Add the white carbon black with surface coated with polydopamine obtained in step a to N,N-dimethylformamide and ultrasonically treat it for 20 to 30 minutes to form a uniform suspension, then add the silane-modified nano aluminum hydroxide obtained in step b to the above suspension, ultrasonically treat it again for 20 to 30 minutes, then heat it to 110° C., stir and react for 4 to 6 hours, centrifuge, wash, filter and dry the product to obtain a composite filler.

[0011] Furthermore, in step c, the mass ratio of the white carbon black with the surface coated with polydopamine to the silane-modified nano aluminum hydroxide is 4-6:1.

[0012] Further, the preparation method of the modified additive comprises the following steps: (1) 2,4-dichloro-1,3,5-triazine, 2,4-dihydroxybenzophenone and p-hydroxybenzaldehyde were dissolved in acetone respectively, sodium carbonate was added to the 2,4-dichloro-1,3,5-triazine solution under nitrogen atmosphere, 2,4-dihydroxybenzophenone solution was slowly added after stirring, and the reaction was carried out in an ice bath for 2-4 hours after the addition was completed. The p-hydroxybenzaldehyde solution was added to the reaction system, and the temperature was slowly raised to 40-50°C, and the reaction was continued for 2-4 hours. After the reaction was completed, the reaction was cooled to room temperature, filtered under reduced pressure, and washed with ethanol, distilled water and ethanol in turn, and dried to obtain product A; (2) Add DOPO to 1,2-dichloroethane, stir and heat to 85°C. After DOPO is completely dissolved, slowly add product A and keep the system temperature at 85°C for reflux reaction for 4-6 hours. After the reaction is completed, reduce the pressure and filter, then wash with 1,2-dichloroethane 3-5 times to remove excess DOPO. After washing, dry it to obtain a modified additive.

[0013] Furthermore, the molar ratio of 2,4-dichloro-1,3,5-triazine, 2,4-dihydroxybenzophenone, p-hydroxybenzaldehyde and DOPO is 1:1:1:1.

[0014] A method for preparing a medium density fiberboard coated with a flame retardant UV paint comprises the following steps: S1. The logs are peeled and cut into small pieces. The wood chips are then put into a digester and softened with steam to partially dissolve the lignin. The cooked wood chips are then sent to a pulper and ground into fine fibers by a high-speed rotating grinding disc. S2. Evenly mix the ground fiber and adhesive, spread the mixed fiber on the pre-pressing machine, perform preliminary compaction to form a slab, send the pre-pressed slab to the laying machine, spread the fiber evenly on the conveyor belt through the laying head to form a continuous slab layer, send the laid slab to the hot press, and hot press at 180℃~220℃ to fully combine the fiber and adhesive to form a dense board; S3. After the hot-pressed board is taken out of the hot press, it is naturally cooled to room temperature. The surface of the density board is initially sanded with a sander to remove the burrs on the surface, and then fine sandpaper is used for fine sanding to make the surface smoother and flatter. Finally, the board is cut into medium-density boards of standard specifications; S4. Evenly mix the modified polyurethane emulsion, composite filler, modified additive, photoinitiator, dispersant, defoamer, leveling agent and water to prepare UV paint, then evenly apply the UV paint on the surface of the medium-density fiberboard, dry at 45°C for 24 hours, and then expose it under ultraviolet light. After the paint film is completely cured, the medium-density fiberboard coated with flame-retardant UV paint is obtained.

[0015] Beneficial effects of the present invention: The UV paint coated on the density board of the present invention adopts modified polyurethane emulsion as the film-forming substance, and uses epoxy resin to react with waterborne polyurethane, and both epoxy groups and hydroxyl groups can participate in the reaction, which greatly improves the crosslinking degree and branching degree of the waterborne polyurethane, so that the paint film has excellent physical properties such as hardness and gloss, and the paint film hardness and wear resistance of the material are improved by adding composite fillers, and the aging resistance and flame retardant properties of the material are improved by adding modified additives. The composite filler is a strawberry-like core-shell structure formed by surface-loading nano aluminum hydroxide after white carbon black is coated with polydopamine. The polydopamine coating improves the compatibility of white carbon black with the polymer, so that it can be evenly dispersed, thereby better exerting its reinforcing effect on the paint film. At the same time, the surface-loaded nano aluminum hydroxide is an excellent inorganic flame retardant, which can achieve the purpose of synergistic flame retardancy with the modified additive, thereby improving the flame retardant properties of the paint film. The modified additive of the present invention reacts two active chlorine atoms on 2,4-dichloro-1,3,5-triazine with the hydroxyl groups of 2,4-dihydroxybenzophenone and p-hydroxybenzaldehyde respectively, and then reacts with DOPO through the aldehyde group to obtain a triazine derivative containing benzophenone and DOPO groups. The benzophenone structure has an anti-ultraviolet function, which can prevent the paint film from aging and yellowing and causing the paint film to deteriorate in performance. The DOPO group and the triazine ring provide abundant P elements and N elements, which can be decomposed under high temperature conditions to produce phosphate esters and gases, promote the dehydration and carbonization of the polymer, and form a carbonaceous protective layer at the same time. The non-combustible gas produced by the decomposition also has a good gas-phase flame retardant effect. The medium-density board coated with UV paint has good heat-resistant and flame-retardant properties, and can effectively avoid the risk of combustion caused by excessive local temperature during the use of the electronic circuit pad. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a SEM image of the composite filler prepared in Example 2 of the present invention; Figure 2 This is the Fourier infrared spectrum of the modified additive prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Example 1 A modified polyurethane acrylate emulsion, wherein the modified polyurethane acrylate emulsion is an epoxy resin-modified castor oil-based water-based polyurethane emulsion, and the preparation method thereof comprises the following steps: A. Add 0.15 mol toluene diisocyanate, 0.12 mol polyether diol 400, 0.05 mol castor oil and 0.5 g dibutyltin dilaurate into a four-necked flask equipped with an electric stirrer, a thermometer and a reflux condenser, and react at 80° C. until the R value reaches 2.8; B. Then, 5.6 g of dimethylol propionic acid and 1.8 g of trimethylol propane were added in sequence to react, and then the reaction temperature was lowered to 70° C., 0.02 mol of epoxy resin E-44, 0.02 mol of pentaerythritol triacrylate and 0.04 mol of hydroxyethyl methacrylate were added for end-capping, and the reaction was terminated when the R value reached 1.5; C. Cool to below 50°C, add measured triethylamine for neutralization, react for 50 minutes, and finally add a certain amount of deionized water under high-speed stirring for emulsification for 2 hours to obtain epoxy resin modified castor oil-based waterborne polyurethane emulsion.

[0020] Example 2 A composite filler having a strawberry-like core-shell structure formed by coating white carbon black with polydopamine and then loading nano-aluminum hydroxide on the surface, wherein the preparation method comprises the following steps: a. Disperse 2.5 g of white carbon black powder in 30 ml of Tris buffer solution, add 12.2 g of dopamine hydrochloride after ultrasonic dispersion, continue ultrasonic treatment for 12 min, then stir and react at room temperature for 24 h, centrifuge, wash and dry to obtain white carbon black with polydopamine coated on the surface; b. Add 3.1 g of nano aluminum hydroxide into 20 ml of 95% vol ethanol aqueous solution, and disperse by ultrasonication to obtain a nano aluminum hydroxide dispersion. Then, add 5.8 g of 3-aminopropyltrimethoxysilane into the nano aluminum hydroxide dispersion, and heat to 80° C. with stirring for 4 seconds. Centrifugally wash, filter, and dry to obtain silane-modified nano aluminum hydroxide. c. Add 5.5 g of the white carbon black with surface coated with polydopamine obtained in step a to 30 ml of N,N-dimethylformamide and ultrasonically treat it for 25 minutes to form a uniform suspension, then add 1.2 g of the silane-modified nano aluminum hydroxide obtained in step b to the above suspension, ultrasonically treat it again for 25 minutes, then heat to 110° C., stir and react for 5 hours, centrifuge, wash, filter and dry the product to obtain the composite filler.

[0021] The SEM images of white carbon black before and after modification are as follows: Figure 1As shown, the surface of the modified composite filler is loaded with granular nano-aluminum hydroxide, forming a unique strawberry-like structure.

[0022] Example 3 A modified additive is a triazine derivative containing benzophenone and DOPO groups, and its molecular structure is as follows: ; The preparation method comprises the following steps: (1) Dissolve 0.05 mol 2,4-dichloro-1,3,5-triazine, 0.05 mol 2,4-dihydroxybenzophenone and 0.05 mol p-hydroxybenzaldehyde in 50 ml acetone respectively. Add 0.5 g sodium carbonate to the 2,4-dichloro-1,3,5-triazine solution under nitrogen atmosphere. Stir evenly and then slowly add 2,4-dihydroxybenzophenone solution. After the addition is complete, react in an ice bath for 3 h. Add p-hydroxybenzaldehyde solution to the reaction system, slowly raise the temperature to 45 °C, and continue to react for 3 h. After the reaction is completed, cool to room temperature, filter under reduced pressure, wash with ethanol, distilled water and ethanol in turn, and dry to obtain product A. (2) Add 0.05 mol DOPO to 20 ml 1,2-dichloroethane, stir and heat to 85 °C. After DOPO is completely dissolved, slowly add product A, maintain the system temperature at 85 °C, and reflux for 5 h. After the reaction is completed, reduce the pressure and filter, then wash with 1,2-dichloroethane 3 to 5 times to remove excess DOPO. After washing, dry it to obtain a modified additive.

[0023] The prepared modified additive is subjected to infrared spectroscopy analysis to obtain the Fourier infrared spectrum of the modified additive as shown in Figure 2 As shown, at 1523 cm -1 The characteristic peak of the triazine ring is at 750cm -1 、810cm -1 、850cm -1 The characteristic peak of benzene ring is 1054cm -1 The characteristic peak of PO bond of DOPO group is 1680cm -1 The peak at the center is the characteristic peak of the C=O bond of benzophenone, indicating that the triazine derivative containing benzophenone and DOPO groups was successfully synthesized.

[0024] Example 4 A medium density fiberboard coated with flame retardant UV paint comprises a medium density fiberboard and a UV paint coated on the surface of the medium density fiberboard, wherein the UV paint comprises the following raw materials in parts by weight: 85 parts of modified polyurethane emulsion, 25 parts of composite filler, 5 parts of modified additive, 3 parts of photoinitiator 1173, 4 parts of dispersant BYK-190, 2 parts of defoamer BYK-093, 0.5 parts of leveling agent BFK-2700W, and 20 parts of water; the modified polyurethane emulsion is prepared in Example 1, the composite filler is prepared in Example 2, and the modified additive is prepared in Example 3.

[0025] The method for preparing the medium density fiberboard coated with flame retardant UV paint comprises the following steps: S1. The logs are peeled and cut into small pieces. The wood chips are then put into a digester and softened with steam to partially dissolve the lignin. The cooked wood chips are then sent to a pulper and ground into fine fibers by a high-speed rotating grinding disc. S2. Evenly mix the ground fiber and adhesive, spread the mixed fiber on the pre-pressing machine, perform preliminary compaction to form a slab with a certain thickness, send the pre-pressed slab to the laying machine, and evenly spread the fiber on the conveyor belt through the laying head to form a continuous slab layer, and send the laid slab to the hot press machine, and hot press at 180℃~220℃ to fully combine the fiber and adhesive to form a dense board; S3. After the hot-pressed board is taken out of the hot press, it is naturally cooled to room temperature. The surface of the density board is initially sanded with a sander to remove the burrs on the surface, and then fine sandpaper is used for fine sanding to make the surface smoother and flatter. Finally, the board is cut into medium-density boards of standard specifications; S4. Evenly mix the modified polyurethane emulsion, composite filler, modified additive, photoinitiator, dispersant, defoamer, leveling agent and water to prepare UV paint, then evenly apply the UV paint on the surface of the medium-density fiberboard, dry at 45°C for 24 hours, and then expose it under ultraviolet light. After the paint film is completely cured, the medium-density fiberboard coated with flame-retardant UV paint is obtained.

[0026] Example 5 A medium density fiberboard coated with flame retardant UV paint comprises a medium density fiberboard and a UV paint coated on the surface of the medium density fiberboard, wherein the UV paint comprises the following raw materials in parts by weight: 110 parts of modified polyurethane emulsion, 10 parts of composite filler, 8 parts of modified additive, 1 part of photoinitiator 1173, 6 parts of dispersant TEGO 750W, 0.5 parts of defoamer BYK-093, 2 parts of leveling agent BFK-2700W, and 10 parts of water; the modified polyurethane emulsion is prepared in Example 1, the composite filler is prepared in Example 2, and the modified additive is prepared in Example 3.

[0027] The preparation method of the above-mentioned medium density fiberboard coated with flame retardant UV paint is the same as that of Example 4.

[0028] Example 6 A medium density fiberboard coated with flame retardant UV paint comprises a medium density fiberboard and a UV paint coated on the surface of the medium density fiberboard, wherein the UV paint comprises the following raw materials in parts by weight: 98 parts of modified polyurethane emulsion, 15 parts of composite filler, 6 parts of modified additive, 2 parts of photoinitiator 2959, 5 parts of dispersant BYK-190, 1.2 parts of defoamer BYK-093, 1.5 parts of leveling agent BFK-2700W, and 15 parts of water; the modified polyurethane emulsion is prepared in Example 1, the composite filler is prepared in Example 2, and the modified additive is prepared in Example 3.

[0029] The preparation method of the above-mentioned medium density fiberboard coated with flame retardant UV paint is the same as that of Example 4.

[0030] Comparative Example 1 A medium density fiberboard coated with flame retardant UV paint comprises a medium density fiberboard and a UV paint coated on the surface of the medium density fiberboard, wherein the UV paint comprises the following raw materials in parts by weight: 98 parts of modified polyurethane emulsion, 15 parts of white carbon black, 6 parts of modified additives, 2 parts of photoinitiator 2959, 5 parts of dispersant BYK-190, 1.2 parts of defoamer BYK-093, 1.5 parts of leveling agent BFK-2700W, and 15 parts of water; the modified polyurethane emulsion is prepared in Example 1, and the modified additive is prepared in Example 3.

[0031] The preparation method of the above-mentioned medium density fiberboard coated with flame retardant UV paint is the same as that of Example 4.

[0032] Comparative Example 2 A medium density fiberboard coated with flame retardant UV paint comprises a medium density fiberboard and a UV paint coated on the surface of the medium density fiberboard, wherein the UV paint comprises the following raw materials in parts by weight: 98 parts of modified polyurethane emulsion, 15 parts of composite filler, 2 parts of photoinitiator 2959, 5 parts of dispersant BYK-190, 1.2 parts of defoamer BYK-093, 1.5 parts of leveling agent BFK-2700W, and 15 parts of water; the modified polyurethane emulsion is prepared in Example 1, and the composite filler is prepared in Example 2.

[0033] The preparation method of the above-mentioned medium density fiberboard coated with flame retardant UV paint is the same as that of Example 4.

[0034] Performance Testing 1. Paint film physical properties test The UV paint prepared in Examples 4 to 6 and Comparative Examples 1 to 2 was coated on a medium-density board and dried at 45° C. for 24 hours, then directly exposed to ultraviolet light for curing, and then the pencil hardness of the paint film was determined according to GBT 6739-2022, the impact resistance of the paint film was determined according to GB / T1732-2020, the adhesion of the paint film was determined according to GB / T 9286-2021, and the abrasion resistance of the paint film was tested according to GB / T 1768-2006, and the data were shown in Table 1 below.

[0035] Table 1 Physical properties test of UV paint film in Examples 4 to 6 and Comparative Examples 1 to 2 ; It can be seen from the data in Table 1 that in Comparative Example 1, unmodified silica was used to replace the composite filler, and the hardness, impact resistance and wear resistance of the paint film decreased slightly. The possible reason is that the unmodified silica has poor compatibility with the polymer matrix, and uneven dispersion in the emulsion leads to agglomeration, thereby affecting the above-mentioned properties of the paint film.

[0036] 2. Aging resistance and flame retardant performance test The UV paint coated medium density boards prepared in Examples 4 to 6 and Comparative Examples 1 to 2 were placed on and dried at 45°C for 24 hours, then directly exposed to UV light for curing, and then subjected to artificial weathering aging tests in accordance with GB / T1865-2009, and evaluated in accordance with GB / T1766-2008, and the vertical burning (UL94) grade was tested in accordance with ASTM3801 standard, and the data obtained were shown in Table 2 below.

[0037] Table 2 Test results of aging resistance and flame retardancy of UV paint films in Examples 4 to 6 and Comparative Examples 1 to 2 ; From the data in Table 2, it can be seen that in Comparative Example 2, no modifying additives were added, and the paint film had obvious blistering and peeling after artificial weathering, and severe powdering, and the weather resistance was significantly lower than that of other groups, and the flame retardant performance was also worse than that of other groups, indicating that the modification played a good anti-aging and flame retardant effect. In Comparative Example 1, no composite filler was added, and the flame retardant effect of the paint film was also reduced compared with Examples 4 to 6. This is because the nano aluminum hydroxide loaded on the surface of white carbon black is an inorganic flame retardant, which can also play a flame retardant effect, so that the medium density board coated with UV paint has good heat resistance and flame retardant properties, which can effectively avoid the risk of combustion caused by excessive local temperature during the use of electronic circuit pads.

[0038] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0039] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A medium density fiberboard coated with flame retardant UV paint, characterized in that: It comprises a medium density board and a UV paint coated on the surface of the medium density board, wherein the UV paint comprises the following raw materials in parts by weight: 85-110 parts of modified polyurethane emulsion, 10-25 parts of composite filler, 5-8 parts of modified additive, 1-3 parts of photoinitiator, 4-6 parts of dispersant, 0.5-2 parts of defoamer, 0.5-2 parts of leveling agent, and 10-20 parts of water; The modified polyurethane emulsion is an epoxy resin modified castor oil-based waterborne polyurethane emulsion, the composite filler is a strawberry-like core-shell structure formed by white carbon black coated with polydopamine and loaded with nano-aluminum hydroxide on the surface, and the modified additive is a triazine derivative containing benzophenone and DOPO groups.

2. The medium density fiberboard coated with flame retardant UV paint according to claim 1, characterized in that: The photoinitiator is photoinitiator 2959 or photoinitiator 1173, the dispersant is dispersant BYK-190 or dispersant TEGO 750W, the defoamer is defoamer BYK-093, and the leveling agent is leveling agent BFK-2700W.

3. The medium density fiberboard coated with flame retardant UV paint according to claim 1, characterized in that: The preparation method of the modified polyurethane emulsion comprises the following steps: A. Add toluene diisocyanate, polyether diol, castor oil and dibutyltin dilaurate into a four-necked flask equipped with an electric stirrer, a thermometer and a reflux condenser, and react at 80°C until the R value reaches 2.8; B. Then, dimethylol propionic acid and trimethylol propane were added in sequence to react, and then the reaction temperature was lowered to 70° C., epoxy resin E-44, pentaerythritol triacrylate and hydroxyethyl methacrylate were added for end-capping, and the reaction was terminated when the R value reached 1.5; C. Cool to below 50°C, add measured triethylamine for neutralization, react for 50 minutes, and finally add deionized water for emulsification for 2 hours under high-speed stirring to obtain epoxy resin-modified castor oil-based waterborne polyurethane emulsion.

4. The medium density fiberboard coated with flame retardant UV paint according to claim 3, characterized in that: In the step A, the molar ratio of the monomers toluene diisocyanate, polyether diol and castor oil is 10:8:3.

2.

5. The medium density fiberboard coated with flame retardant UV paint according to claim 3, characterized in that: In the step B, the dimethylolpropionic acid accounts for 4-6% of the total mass of the monomers toluene diisocyanate, polyether diol and castor oil, the trimethylolpropane accounts for 1.5-2% of the total mass of the monomers toluene diisocyanate, polyether diol and castor oil, and the molar ratio of the epoxy resin E-44, pentaerythritol triacrylate and hydroxyethyl methacrylate used for end-capping is 1:1:

2.

6. The medium density fiberboard coated with flame retardant UV paint according to claim 1, characterized in that: The preparation method of the composite filler comprises the following steps: a. Disperse white carbon black powder in a Tris buffer solution, add dopamine hydrochloride after ultrasonic dispersion, continue ultrasonic treatment for 10-15 minutes, then stir and react at room temperature for 24 hours, centrifuge, wash and dry to obtain white carbon black with polydopamine coated on the surface; b. Add nano aluminum hydroxide to an ethanol aqueous solution, disperse by ultrasonication to obtain a nano aluminum hydroxide dispersion, then add 3-aminopropyltrimethoxysilane to the nano aluminum hydroxide dispersion, stir and heat to 80°C for reaction for 3-5 hours, centrifuge, wash, filter and dry to obtain silane-modified nano aluminum hydroxide; c. Add the white carbon black with polydopamine coated on the surface obtained in step a to N,N-dimethylformamide and ultrasonically treat it for 20 to 30 minutes to form a uniform suspension, then add the silane-modified nano aluminum hydroxide obtained in step b to the above suspension, ultrasonically treat it again for 20 to 30 minutes, then heat it to 110° C., stir and react for 4 to 6 hours, centrifuge, wash, filter and dry the product to obtain the composite filler.

7. The medium density fiberboard coated with flame retardant UV paint according to claim 6, characterized in that: In the step c, the mass ratio of the white carbon black with the surface coated with polydopamine to the silane-modified nano aluminum hydroxide is 4-6:

1.

8. The medium density fiberboard coated with flame retardant UV paint according to claim 1, characterized in that: The preparation method of the modified additive comprises the following steps: (1) 2,4-dichloro-1,3,5-triazine, 2,4-dihydroxybenzophenone and p-hydroxybenzaldehyde were dissolved in acetone respectively, sodium carbonate was added to the 2,4-dichloro-1,3,5-triazine solution under nitrogen atmosphere, 2,4-dihydroxybenzophenone solution was slowly added after stirring evenly, ice bath was reacted for 2-4 hours after the addition was completed, p-hydroxybenzaldehyde solution was added to the reaction system, the temperature was slowly raised to 40-50°C, the reaction was continued for 2-4 hours, after the reaction was completed, the reaction was cooled to room temperature, the product A was filtered under reduced pressure, washed with ethanol, distilled water and ethanol in turn, and dried to obtain product A; (2) Add DOPO to 1,2-dichloroethane, stir and heat to 85°C. After DOPO is completely dissolved, slowly add product A and keep the system temperature at 85°C for reflux reaction for 4-6 hours. After the reaction is completed, reduce the pressure and filter, then wash with 1,2-dichloroethane 3-5 times to remove excess DOPO. After washing, dry it to obtain a modified additive.

9. The medium density fiberboard coated with flame retardant UV paint according to claim 8, characterized in that: The molar ratio of the 2,4-dichloro-1,3,5-triazine, 2,4-dihydroxybenzophenone, p-hydroxybenzaldehyde and DOPO is 1:1:1:

1.

10. A method for preparing a medium density fiberboard coated with a flame retardant UV paint as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: S1. The logs are peeled and cut into small pieces. The wood chips are then put into a digester and softened with steam to partially dissolve the lignin. The cooked wood chips are then sent to a pulper and ground into fine fibers by a high-speed rotating grinding disc. S2. Evenly mix the ground fiber and adhesive, spread the mixed fiber on the pre-pressing machine, perform preliminary compaction to form a slab, send the pre-pressed slab to the laying machine, spread the fiber evenly on the conveyor belt through the laying head to form a continuous slab layer, send the laid slab to the hot press, and hot press at 180℃~220℃ to fully combine the fiber and adhesive to form a dense board; S3. After the hot-pressed board is taken out of the hot press, it is naturally cooled to room temperature. The surface of the density board is initially sanded with a sander to remove the burrs on the surface, and then fine sandpaper is used for fine sanding to make the surface smoother and flatter. Finally, the board is cut into medium-density boards of standard specifications; S4. Evenly mix the modified polyurethane emulsion, composite filler, modified additive, photoinitiator, dispersant, defoamer, leveling agent and water to prepare UV paint, then evenly apply the UV paint on the surface of the medium-density fiberboard, dry at 45°C for 24 hours, and then expose it under ultraviolet light. After the paint film is completely cured, the medium-density fiberboard coated with flame-retardant UV paint is obtained.

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