A medium-density fiberboard coated with flame-retardant UV paint and a preparation method thereof

Abstract

The present invention belongs to the technical field of special plates, and discloses a medium density fiberboard coated with flame-retardant UV paint and a preparation method thereof. The medium density fiberboard coated with flame-retardant UV paint comprises a medium density fiberboard and UV paint coated on the surface of the medium density fiberboard. 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. Using the modified polyurethane emulsion as a film-forming substance, the paint film has excellent physical properties such as hardness and gloss. By adding the composite filler, the paint film hardness and wear resistance of the material are further improved. Adding the modified additive improves the aging resistance and flame retardant properties of the material. Furthermore, the medium density fiberboard coated with UV paint has good heat resistance and flame retardant properties, and can effectively avoid the risk of combustion caused by excessive local temperature during the use of electronic circuit pads.

Description

Technical Field

[0001] The present invention belongs to the technical field of special plates, and particularly relates to a medium density fiberboard coated with flame-retardant UV paint and a preparation method thereof. Background Art

[0002] Medium density fiberboard is a kind of artificial board made by mechanically separating and chemically treating wood or plant fibers, adding adhesives, water repellents, etc., and then forming under high temperature and high pressure. The structure of medium density fiberboard is more uniform than natural wood, and problems such as decay and insect damage are also avoided. At the same time, it has small expansion and contraction and is convenient for processing. In recent years, density fiberboard has gradually been used as the backing plate for circuit boards in the electronics industry. During the drilling process of printed circuit boards, it is placed under the circuit board and directly contacts the drilling machine workbench, and is an auxiliary plate-shaped material used to protect the plate to be processed and the drilling machine and improve the drilling quality. And in order to improve the appearance and performance of medium density fiberboard, UV paint is usually coated on the surface of medium density fiberboard. UV paint is a photocurable coating. When ultraviolet light irradiates the photocurable coating, the photoinitiator in the coating is excited and decomposed to generate free radicals. The active free radicals hit the double bonds in the coating and react to form a growing chain. This reaction continues to extend, causing the double bonds in the active diluent and oligomer to break and crosslink to form a film.

[0003] UV paint has the characteristics of high curing speed, low energy consumption, small environmental pollution, high performance, etc., but it still has some disadvantages: uneven curing, low crosslinking degree, and the cured film generally has disadvantages such as a relatively wide mechanical transition range and easy stress cracking. In addition, due to the oxygen inhibition polymerization effect, the surface wear resistance is poor, and inorganic materials need to be added for modification. However, the compatibility between inorganic materials and the coating is poor, and corresponding additives need to be added to avoid affecting the performance of the coating such as stability and leveling property. In addition, since medium density fiberboard is made by pressing wood fibers and adhesives, it belongs to a flammable material. During the manufacturing process of electronic industry printed circuit boards, it is necessary to use a hot press to perform high-temperature and high-pressure heat treatment on it. 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 backing plates. Summary of the Invention

[0004] To solve the deficiencies mentioned in the above background art, 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 uses 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 hardness and wear resistance of the material's paint film are further improved. Adding modified additives improves the aging resistance and flame retardancy of the material. The medium density fiberboard coated with UV paint has good heat resistance and flame retardancy, and can effectively avoid the risk of combustion caused by excessive local temperature during the use of electronic circuit backing plates.

[0005] The object of the present invention can be achieved by the following technical solutions:

[0006] A medium-density fiberboard coated with a flame-retardant UV paint, comprising a medium-density fiberboard and a UV paint coated on the surface of the medium-density fiberboard. The UV paint comprises the following raw materials in parts by weight: 85-110 parts of a modified polyurethane emulsion, 10-25 parts of a 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 an antifoaming agent, 0.5-2 parts of a leveling agent, and 10-20 parts of water;

[0007] 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 coating nano-aluminum hydroxide on the surface of silica after being coated with polydopamine. The modified additive is a triazine derivative containing benzophenone and DOPO groups.

[0008] Furthermore, the photoinitiator is photoinitiator 2959 or photoinitiator 1173, the dispersant is dispersant BYK-190 or dispersant TEGO 750W, the antifoaming agent is antifoaming agent BYK-093, and the leveling agent is leveling agent BFK-2700W.

[0009] Furthermore, the preparation method of the modified polyurethane emulsion comprises the following steps:

[0010] 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;

[0011] B. Subsequently, add dimethylolpropionic acid and trimethylolpropane in sequence for reaction, then lower the reaction temperature to 70 °C, add epoxy resin E-44, pentaerythritol triacrylate, and 2-hydroxyethyl methacrylate for capping, and end the reaction when the R value reaches 1.5;

[0012] C. Cool to below 50 °C, add a measured amount of triethylamine for neutralization, react for 50 min, and finally add deionized water for emulsification under high-speed stirring for 2 h to obtain an epoxy resin-modified castor oil-based waterborne polyurethane emulsion.

[0013] Furthermore, in step A, the molar ratio of the monomers toluene diisocyanate, polyether diol, and castor oil is 10:8:3.2.

[0014] Furthermore, in step B, dimethylolpropionic acid is 4-6% of the total mass of the monomers toluene diisocyanate, polyether diol, and castor oil, trimethylolpropane is 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 2-hydroxyethyl methacrylate used for capping is 1:1:2.

[0015] Furthermore, the preparation method of the composite filler comprises the following steps:

[0016] a. Disperse the silica white powder in Tris buffer solution, add dopamine hydrochloride after ultrasonic dispersion, continue ultrasonic treatment for 10 - 15 min, then place it at room temperature and stir for reaction for 24 h, centrifuge, wash and dry to obtain silica white coated with polydopamine on the surface;

[0017] b. Add nano aluminum hydroxide into the ethanol - aqueous solution, ultrasonic disperse to obtain a nano aluminum hydroxide dispersion, then add 3 - aminopropyltrimethoxysilane into the nano aluminum hydroxide dispersion, stir and heat to 80 °C for reaction for 3 - 5 h, centrifuge, wash, filter and then dry to obtain silane - modified nano aluminum hydroxide;

[0018] c. Add the silica white coated with polydopamine obtained in step a into N,N - dimethylformamide and ultrasonic treat for 20 - 30 min to form a uniform suspension, then add the silane - modified nano aluminum hydroxide obtained in step b into the above suspension, ultrasonic treat again for 20 - 30 min, then heat to 110 °C, stir and react for 4 - 6 h, centrifuge, wash, filter the product and then dry to obtain the composite filler.

[0019] Furthermore, the mass ratio of the silica white coated with polydopamine to the silane - modified nano aluminum hydroxide in step c is 4 - 6:1.

[0020] Furthermore, the preparation method of the modified additive comprises the following steps:

[0021] (1) Dissolve 2,4 - dichloro - 1,3,5 - triazine, 2,4 - dihydroxybenzophenone and p - hydroxybenzaldehyde in acetone respectively. Add sodium carbonate into the 2,4 - dichloro - 1,3,5 - triazine solution under a nitrogen atmosphere, stir evenly and then slowly add the 2,4 - dihydroxybenzophenone solution. After dropping is completed, react in an ice bath for 2 - 4 h. Add the p - hydroxybenzaldehyde solution into the reaction system, slowly raise the temperature to 40 - 50 °C, continue to react for 2 - 4 h. After the reaction is completed, cool to room temperature, carry out vacuum filtration and wash successively with ethanol, distilled water and ethanol, then dry by baking to obtain product A;

[0022] (2) Add DOPO into 1,2 - dichloroethane, stir and heat to 85 °C. After DOPO is completely dissolved, slowly add product A, keep the system temperature at 85 °C and reflux for reaction for 4 - 6 h. After the reaction is completed, carry out vacuum filtration, then wash with 1,2 - dichloroethane for 3 - 5 times to remove the excessive DOPO. After washing is completed, dry by baking to obtain the modified additive.

[0023] Furthermore, the molar ratio of 2,4 - dichloro - 1,3,5 - triazine, 2,4 - dihydroxybenzophenone, p - hydroxybenzaldehyde and DOPO is 1:1:1:1.

[0024] A preparation method of medium density fiberboard coated with flame-retardant UV paint, comprising the following steps:

[0025] S1. Peel the log and cut it into small pieces, then put the wood chips into a steamer and soften them with steam to dissolve part of the lignin. After steaming, the wood chips are sent into a refiner, and the wood chips are ground into fine fibers by a high-speed rotating grinding disc;

[0026] S2. Mix the ground fibers evenly with an adhesive, spread the mixed fibers on a pre-press for preliminary compaction to form a board blank. Send the pre-pressed board blank into a batching machine, and evenly spread the fibers on the conveyor belt through a batching head to form a continuous board blank layer. Send the batched board blank into a hot press, and hot press at 180°C to 220°C to make the fibers and the adhesive fully combine to form a dense board;

[0027] S3. After the hot-pressed board is taken out of the hot press, it is naturally cooled to room temperature. Use a sander to perform preliminary sanding on the surface of the medium density fiberboard to remove the burrs on the surface, and then use fine sandpaper for fine sanding to make the surface smoother and flatter. Finally, cut the board into medium density fiberboard of standard specifications;

[0028] S4. Mix modified polyurethane emulsion, composite filler, modified additive, photoinitiator, dispersant, defoamer, leveling agent and water evenly to prepare UV paint, then evenly coat the UV paint on the surface of the medium density fiberboard, dry at 45°C for 24h, and then expose it under an ultraviolet lamp. After the paint film is completely cured, a medium density fiberboard coated with flame-retardant UV paint is obtained.

[0029] The beneficial effects of the present invention:

[0030] In the medium-density fiberboard coated with UV paint of the present invention, a modified polyurethane emulsion is used as the film-forming substance. By using epoxy resin for waterborne polyurethane, both epoxy groups and hydroxyl groups can participate in the reaction, greatly improving the crosslinking degree and branching degree of waterborne polyurethane, so that the paint film has excellent physical properties such as hardness and gloss. By adding composite fillers, the hardness and wear resistance of the paint film of the material are improved, and by adding modified additives, the aging resistance and flame retardancy of the material are improved. The composite filler is a strawberry-like core-shell structure formed by loading nano-aluminum hydroxide on the surface of silica after being coated with polydopamine. By coating with polydopamine, the compatibility between silica and the polymer is improved, enabling it to be evenly dispersed, thus better exerting its reinforcing effect on the paint film. At the same time, the nano-aluminum hydroxide loaded on the surface is an excellent inorganic flame retardant, which can cooperate with the modified additive to achieve the purpose of synergistic flame retardancy, thereby improving the flame retardancy of the paint film. The modified additive of the present invention reacts with the hydroxyl groups of 2,4-dihydroxybenzophenone and p-hydroxybenzaldehyde respectively through two active chlorine atoms on 2,4-dichloro-1,3,5-triazine, and then reacts with DOPO through the aldehyde group to obtain a triazine derivative containing benzophenone and DOPO groups. The benzophenone structure therein has an ultraviolet resistance function, which can prevent the decline of the paint film performance caused by the aging and yellowing of the paint film. The DOPO group and the triazine ring provide abundant P and N elements, which can decompose to produce phosphate esters and gases at high temperatures, promote the dehydration and carbonization of the polymer, and at the same time form a carbonaceous protective layer. The non-combustible gases decomposed also have a good gas-phase flame retardancy effect. The medium-density fiberboard coated with UV paint has good heat resistance and flame retardancy, and can effectively avoid the risk of combustion caused by excessive local temperature during the use of electronic circuit pads. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 SEM diagram of the composite filler prepared in Example 2 of the present invention;

[0033] Figure 2 Fourier infrared spectrum of the modified additive prepared in Example 3 of the present invention. Detailed Embodiments

[0034] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] Example 1

[0036] A modified polyurethane acrylate emulsion, the modified polyurethane acrylate emulsion is an epoxy resin modified castor oil-based waterborne polyurethane emulsion, and its preparation method includes the following steps:

[0037] A. Add 0.15 mol of toluene diisocyanate, 0.12 mol of polyether diol 400, 0.05 mol of castor oil, and 0.5 g of 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;

[0038] B. Subsequently, add 5.6 g of dimethylolpropionic acid and 1.8 g of trimethylolpropane in sequence for reaction, then lower the reaction temperature to 70 °C, add 0.02 mol of epoxy resin E-44, 0.02 mol of pentaerythritol triacrylate, and 0.04 mol of 2-hydroxyethyl methacrylate for capping, and end the reaction when the R value reaches 1.5;

[0039] C. Cool to below 50 °C, add a measured amount of triethylamine for neutralization, react for 50 min, and finally add a certain amount of deionized water for emulsification under high-speed stirring for 2 h to obtain an epoxy resin modified castor oil-based waterborne polyurethane emulsion.

[0040] Example 2

[0041] A composite filler, a strawberry-like core-shell structure formed by coating silica with polydopamine and then loading nano-aluminum hydroxide on the surface, and its preparation method includes the following steps:

[0042] a. Disperse 2.5 g of silica powder in 30 ml of Tris buffer solution, add 12.2 g of hydrochloric acid dopamine after ultrasonic dispersion, continue ultrasonic treatment for 12 min, and then place it at room temperature for stirring reaction for 24 h, centrifuge, wash, and dry to obtain silica coated with polydopamine on the surface;

[0043] b. Add 3.1 g of nano-aluminum hydroxide into 20 ml of 95% vol ethanol aqueous solution, ultrasonically disperse to obtain a nano-aluminum hydroxide dispersion, then add 5.8 g of 3-aminopropyltrimethoxysilane into the nano-aluminum hydroxide dispersion, stir and heat to 80 °C for reaction for 4 h, centrifuge, wash, filter, and dry to obtain silane-modified nano-aluminum hydroxide;

[0044] c. Add 5.5 g of the surface-coated polydopamine silica white carbon black obtained in step a to 30 ml of N,N-dimethylformamide, and ultrasonically treat for 25 min to form a uniform suspension. Then add 1.2 g of the silane-modified nanoaluminum hydroxide obtained in step b to the above suspension, ultrasonically treat again for 25 min, then heat to 110 °C, stir and react for 5 h. After the product is centrifuged, washed, filtered and dried, the composite filler is obtained.

[0045] The SEM images of the silica white carbon black before and after modification are as Figure 1 shown. The surface of the composite filler obtained after modification is loaded with granular nanoaluminum hydroxide, forming a unique strawberry-like structure.

[0046] Example 3

[0047] A modified additive is a triazine derivative containing benzophenone and DOPO groups, and its molecular structure is as follows:

[0048] ;

[0049] Its preparation method includes the following steps:

[0050] (1) Dissolve 0.05 mol of 2,4-dichloro-1,3,5-triazine, 0.05 mo of 2,4-dihydroxybenzophenone and 0.05 mo of p-hydroxybenzaldehyde in 50 ml of acetone respectively. Under a nitrogen atmosphere, add 0.5 g of sodium carbonate to the 2,4-dichloro-1,3,5-triazine solution, stir evenly and then slowly add the 2,4-dihydroxybenzophenone solution. After the addition is completed, react in an ice bath for 3 h. Add the p-hydroxybenzaldehyde solution to the reaction system, slowly heat to 45 °C, and continue to react for 3 h. After the reaction is completed, cool to room temperature, filter under reduced pressure and wash successively with ethanol, distilled water and ethanol, and dry by baking to obtain product A;

[0051] (2) Add 0.05 mol of DOPO to 20 ml of 1,2-dichloroethane, stir and heat to 85 °C. After DOPO is completely dissolved, slowly add product A, keep the system temperature at 85 °C, and reflux and react for 5 h. After the reaction is completed, filter under reduced pressure, and wash with 1,2-dichloroethane 3 - 5 times to remove the excess DOPO. After the washing is completed, dry by baking to obtain the modified additive.

[0052] The prepared modified additive was subjected to infrared spectroscopy analysis, and the Fourier infrared spectrum of the modified additive is as Figure 2 shown. At 1523 cm -1 is the characteristic peak of the triazine ring, and at 750 cm -1 , 810 cm -1 , 850 cm -1 are the characteristic peaks of the benzene ring, and at 1054 cm-1 The peak at 1680 cm -1 is the characteristic peak of the P-O bond of the DOPO group, and the peak at 1680 cm

[0053] Example 4

[0054] A medium-density fiberboard coated with a flame-retardant UV paint, comprising a medium-density fiberboard and a UV paint coated on the surface of the medium-density fiberboard. The UV paint comprises the following raw materials in parts by weight: 85 parts of a modified polyurethane emulsion, 25 parts of a composite filler, 5 parts of a modified additive, 3 parts of a photoinitiator 1173, 4 parts of a dispersant BYK-190, 2 parts of an antifoaming agent BYK-093, 0.5 part of a 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.

[0055] The preparation method of the above-mentioned medium-density fiberboard coated with a flame-retardant UV paint comprises the following steps:

[0056] S1. Peel the logs and cut them into small pieces, then put the wood chips into a steamer and soften them with steam to dissolve part of the lignin. After steaming, the wood chips are sent into a refiner and ground into fine fibers by a high-speed rotating grinding disc.

[0057] S2. Mix the ground fibers evenly with an adhesive, spread the mixed fibers on a pre-presser and perform preliminary compaction to form a board blank with a certain thickness. Send the pre-pressed board blank into a spreader, and evenly spread the fibers on a conveyor belt through a spreading head to form a continuous board blank layer. Send the spread board blank into a hot press and hot press at 180°C to 220°C to fully combine the fibers and the adhesive to form a dense board.

[0058] S3. After the hot-pressed board is taken out of the hot press, it is naturally cooled to room temperature. Use a sander to perform preliminary sanding on the surface of the medium-density fiberboard to remove the burrs on the surface, and then use fine sandpaper for fine sanding to make the surface smoother and flatter. Finally, cut the board into medium-density fiberboards of standard specifications.

[0059] S4. Mix the modified polyurethane emulsion, the composite filler, the modified additive, the photoinitiator, the dispersant, the antifoaming agent, the leveling agent and water evenly to prepare a UV paint, then evenly coat the UV paint on the surface of the medium-density fiberboard, dry it at 45°C for 24 h, and then expose it under an ultraviolet lamp. After the paint film is completely cured, the medium-density fiberboard coated with a flame-retardant UV paint is obtained.

[0060] Example 5

[0061] A medium-density fiberboard coated with a flame-retardant UV paint, comprising a medium-density fiberboard and a UV paint coated on the surface of the medium-density fiberboard. The UV paint comprises the following raw materials in parts by weight: 110 parts of a modified polyurethane emulsion, 10 parts of a composite filler, 8 parts of a modified additive, 1 part of photoinitiator 1173, 6 parts of dispersant TEGO 750W, 0.5 part 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.

[0062] The preparation method of the above medium-density fiberboard coated with a flame-retardant UV paint is the same as that in Example 4.

[0063] Example 6

[0064] A medium-density fiberboard coated with a flame-retardant UV paint, comprising a medium-density fiberboard and a UV paint coated on the surface of the medium-density fiberboard. The UV paint comprises the following raw materials in parts by weight: 98 parts of a modified polyurethane emulsion, 15 parts of a composite filler, 6 parts of a 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.

[0065] The preparation method of the above medium-density fiberboard coated with a flame-retardant UV paint is the same as that in Example 4.

[0066] Comparative Example 1

[0067] A medium-density fiberboard coated with a flame-retardant UV paint, comprising a medium-density fiberboard and a UV paint coated on the surface of the medium-density fiberboard. The UV paint comprises the following raw materials in parts by weight: 98 parts of a modified polyurethane emulsion, 15 parts of silica, 6 parts of a 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, and the modified additive is prepared in Example 3.

[0068] The preparation method of the above medium-density fiberboard coated with a flame-retardant UV paint is the same as that in Example 4.

[0069] Comparative Example 2

[0070] A medium-density fiberboard coated with a flame-retardant UV paint, comprising a medium-density fiberboard and a UV paint coated on the surface of the medium-density fiberboard. The UV paint comprises the following raw materials in parts by weight: 98 parts of a modified polyurethane emulsion, 15 parts of a composite filler, 2 parts of a photoinitiator 2959, 5 parts of a dispersant BYK-190, 1.2 parts of an antifoaming agent BYK-093, 1.5 parts of a 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.

[0071] The preparation method of the above medium-density fiberboard coated with a flame-retardant UV paint is the same as that in Example 4.

[0072] Performance Testing

[0073] I. Physical Property Testing of the Paint Film

[0074] The UV paints prepared in Examples 4 to 6 and Comparative Examples 1 to 2 were coated on medium-density fiberboards and dried at 45°C for 24 h, and then directly exposed to ultraviolet light for curing. Then, the pencil hardness of the paint film was measured according to GBT 6739-2022, the impact resistance of the paint film was measured according to GB / T1732-2020, the adhesion of the paint film was measured according to GB / T 9286-2021, and the abrasion resistance of the paint film was tested according to GB / T 1768-2006. The data obtained are shown in Table 1 below.

[0075] Table 1 Physical Property Testing of the UV Paint Films in Examples 4 to 6 and Comparative Examples 1 to 2

[0076] ;

[0077] 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 abrasion resistance of the paint film decreased slightly. The possible reason is that the compatibility between unmodified silica and the polymer matrix is poor, and it agglomerates due to uneven dispersion in the emulsion, thus affecting the above properties of the paint film.

[0078] II. Aging Resistance and Flame Retardancy Testing

[0079] The UV paints prepared in Examples 4 to 6 and Comparative Examples 1 to 2 were coated on medium-density fiberboards and dried at 45°C for 24 h, and then directly exposed to ultraviolet light for curing. Then, artificial weathering aging testing was carried out according to the provisions of GB / T1865-2009 and evaluated according to GB / T1766-2008. At the same time, the vertical burning (UL94) grade was tested according to the ASTM3801 standard. The data obtained are shown in Table 2 below.

[0080] Table 2 Test Results of Aging Resistance and Flame Retardancy of the UV Paint Films in Examples 4 to 6 and Comparative Examples 1 to 2

[0081] ;

[0082] As can be seen from the data in Table 2, in Comparative Example 2, no modified additive was added, and the paint film showed obvious blistering and peeling after artificial weathering, and severe chalking. Its weather resistance was significantly lower than that of other groups, and its flame retardancy was also poorer than that of other groups, indicating that the modification had 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 lower than that of Examples 4 to 6. This is because the nano-aluminum hydroxide loaded on the surface of silica is an inorganic flame retardant, which can also play a flame retardant role, so that the medium-density fiberboard coated with UV paint has good heat-resistant and flame retardant properties, effectively avoiding the risk of combustion caused by excessive local temperature during the use of the electronic circuit backing plate.

[0083] In the description of this specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do 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.

[0084] 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 by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A medium density fiberboard coated with a flame-retardant UV paint, characterized in that, It includes medium density fiberboard and UV paint coated on the surface of the medium density fiberboard. 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 coating silica with polydopamine and then loading nano - aluminum hydroxide on the surface. 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, wherein The photoinitiator is photoinitiator 2959 or photoinitiator 1173. The dispersant is dispersant BYK - 190 or dispersant TEGO 750W. The defoamer is defoamer BYK - 093. The leveling agent is leveling agent BFK - 2700W.

3. The medium density fiberboard coated with flame-retardant UV paint according to claim 1, wherein, 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. Subsequently, add dimethylolpropionic acid and trimethylolpropane in sequence for reaction, then lower the reaction temperature to 70°C, add epoxy resin E - 44, pentaerythritol triacrylate and 2 - hydroxyethyl methacrylate for capping, and end the reaction when the R value reaches 1.5; C. Cool to below 50°C, add a measured amount of triethylamine for neutralization, react for 50 min, and finally add deionized water for emulsification under high - speed stirring for 2 h to obtain the 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 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, wherein In step B, dimethylolpropionic acid is 4 - 6% of the total mass of the monomers toluene diisocyanate, polyether diol and castor oil, trimethylolpropane is 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 2 - hydroxyethyl methacrylate used for 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 silica powder in Tris buffer solution, add dopamine hydrochloride after ultrasonic dispersion, continue ultrasonic treatment for 10 - 15 min, then place it at room temperature and stir for reaction for 24 h, and centrifuge, wash and dry to obtain silica coated with polydopamine on the surface; b. Add nano - aluminum hydroxide into an ethanol - water solution, ultrasonically disperse to obtain a nano - aluminum hydroxide dispersion, then add 3 - aminopropyltrimethoxysilane into the nano - aluminum hydroxide dispersion, stir and heat to 80°C for reaction for 3 - 5 h, centrifuge, wash, filter and dry to obtain silane - modified nano - aluminum hydroxide; c. Add the silica white coated with polydopamine obtained in step a into N,N-dimethylformamide and ultrasonically treat it for 20 - 30 min to form a uniform suspension. Then add the silane-modified nano-aluminum hydroxide obtained in step b into the above suspension, ultrasonically treat it again for 20 - 30 min, then heat it to 110 °C and stir and react for 4 - 6 h. After the product is centrifuged, washed, filtered and dried, the composite filler is obtained.

7. The medium density fiberboard coated with the flame-retardant UV paint according to claim 6, wherein In step c, the mass ratio of the silica white 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 includes the following steps: (1) Dissolve 2,4-dichloro-1,3,5-triazine, 2,4-dihydroxybenzophenone and p-hydroxybenzaldehyde in acetone respectively. Under a nitrogen atmosphere, add sodium carbonate to the 2,4-dichloro-1,3,5-triazine solution, stir evenly and then slowly add the 2,4-dihydroxybenzophenone solution. After the dropping is completed, react in an ice bath for 2 - 4 h. Add the p-hydroxybenzaldehyde solution to the reaction system, slowly raise the temperature to 40 - 50 °C and continue to react for 2 - 4 h. After the reaction is completed, cool to room temperature, carry out vacuum filtration and wash successively with ethanol, distilled water and ethanol, and dry by baking to obtain product A; (2) Add DOPO into 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 and reflux and react for 4 - 6 h. After the reaction is completed, carry out vacuum filtration, and then wash with 1,2-dichloroethane for 3 - 5 times to remove the excessive DOPO. After the washing is completed, dry by baking to obtain the modified additive.

9. The medium density fiberboard coated with the flame-retardant UV paint according to claim 8, characterized in that, The molar ratio of 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 according to any one of claims 1 to 9, characterized in that, It includes the following steps: S1. Peel the log and cut it into small pieces, then put the wood chips into a steamer and carry out softening treatment with steam to dissolve part of the lignin. The steamed wood chips are sent into a refiner and ground into fine fibers by a high-speed rotating grinding disc; S2. Mix the ground fibers and the adhesive evenly, spread the mixed fibers on a pre-presser and carry out preliminary compaction to form a slab. Send the pre-pressed slab into a layer former, and evenly spread the fibers on a conveyor belt through a laying head to form a continuous slab layer. Send the laid slab into a hot press and hot press at 180 °C - 220 °C to make the fibers and the adhesive fully combine to form a dense board; S3. After the hot-pressed board is taken out of the hot press, naturally cool it to room temperature. Use a sander to carry out preliminary sanding on the surface of the density board to remove the burrs on the surface, and then use fine sandpaper for fine sanding to make the surface smoother and flatter. Finally, cut the board into medium density fiberboards of standard specifications; S4. Mix the modified polyurethane emulsion, the composite filler, the modified additive, the photoinitiator, the dispersant, the defoamer, the leveling agent and water evenly to prepare the UV paint. Then evenly coat the UV paint on the surface of the medium density fiberboard, dry it at 45 °C for 24 h, and then expose it under an ultraviolet lamp. After the paint film is completely cured, the medium density fiberboard coated with the flame-retardant UV paint is obtained.

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