Preparation method of formaldehyde-free wood composite material with high color fastness to light

Abstract

The invention relates to a preparation method of a formaldehyde-free wood composite material with high color fastness to light, which comprises the following steps: (1) sequentially bleaching, pickling, washing, dyeing and drying wood veneers to obtain dyed veneers; (2) dissolving an anti-ultraviolet aid in an epoxy resin diluent to obtain an anti-ultraviolet solution, blending the anti-ultraviolet solution with the transparent epoxy resin adhesive to prepare an adhesive A, and mixing the adhesive A with a curing agent B to obtain an anti-ultraviolet transparent epoxy resin adhesive; (3) assembling the dyed veneer and a transparent nylon film into a blank, applying glue to two sides of the dyed veneer by using anti-ultraviolet transparent epoxy resin glue, and pressing and slicing to obtain the light-transmitting recombined decorative veneer; and (4) adhering a layer of transparent nylon film on the surface of the light-transmitting recombined decorative veneer by using anti-ultraviolet transparent epoxy resin glue to prepare the formaldehyde-free wood composite material with high color fastness to light. The formaldehyde-free wood composite material with high color fastness to light prepared by the preparation method disclosed by the invention has excellent ultraviolet resistance and high light transmittance, the color fastness grade reaches gray scale card level 5, and meanwhile, integration of decoration and patterned illumination is realized.

Description

Technical Field

[0001] This invention relates to the field of reconstituted decorative materials preparation, and provides a method for preparing formaldehyde-free wood composite materials with high light fastness. Background Technology

[0002] The development of new energy vehicles is at an unprecedented pace, which has placed new demands on the design and manufacturing of automotive interiors. The selection of high-end materials is increasingly leaning towards natural materials; for example, Rolls-Royce, Audi, and Mercedes-Benz all extensively use real wood craftsmanship. Under this market trend, reconstituted decorative veneer, with its unique aesthetics and functionality, combines the advantages of natural precious wood in terms of color, texture, and feel, perfectly meeting these demands. However, reconstituted decorative veneer suffers from fading and discoloration during storage and use, significantly limiting its application in automotive interiors. Currently, the common method is to add UV absorbers and light stabilizers during the dyeing process. However, due to limitations in solubility and molecular weight, most UV absorbers are difficult to penetrate the wood veneer during dyeing to achieve the desired colorfastness. Light stabilizers also have a short lifespan; once they expire, the reconstituted decorative veneer will still discolor.

[0003] Transparent nylon has the characteristics of high light transmittance, excellent weather resistance and easy processing. Combining reconstituted decorative veneer with transparent nylon is an innovative solution.

[0004] Currently, commonly used and transparent adhesives after curing include PUR hot melt adhesives and epoxy resin adhesives. However, PUR hot melt adhesives suffer from problems such as short working time and adhesion strength easily affected by temperature. Ordinary epoxy resins have poor weather resistance, are prone to yellowing and aging. Previously, addressing the weather resistance of epoxy resins mostly focused on the epoxy resin and curing agent, developing modified epoxy resins with stronger weather resistance and modified polyetheramine curing agents with better yellowing resistance. However, these products are costly, have narrow application ranges, and are not economically viable. Adding anti-yellowing additives to epoxy systems, especially if using powders, requires that they be soluble and compatible with all components of the epoxy system, complicating the development of material stability. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the present invention aims to provide a method for preparing formaldehyde-free wood composite materials with high light fastness suitable for automotive interiors.

[0006] To achieve the above objectives, the present invention provides a method for preparing a formaldehyde-free wood composite material with high light fastness, comprising the following steps:

[0007] (1) The wood veneer is subjected to bleaching, acid washing, water washing, dyeing and drying in sequence to obtain dyed veneer;

[0008] (2) Dissolve the UV-resistant additive in epoxy resin diluent at room temperature, add 15-25% of co-solvent to the mixture, stir for 20-30 minutes, and after it is fully dissolved, obtain the UV-resistant solution. Mix it with transparent epoxy resin glue to obtain glue A, add curing agent B, and obtain UV-resistant transparent epoxy resin glue.

[0009] (3) The dyed veneer and 0.3~0.7mm transparent nylon film are assembled in a ratio of 4:1~8:1. The dyed veneer is glued to both sides with UV-resistant transparent epoxy resin. After pressing and slicing, a light-transmitting reconstituted decorative veneer is obtained.

[0010] (4) A layer of transparent nylon film of 0.1~0.3mm is adhered to the surface of the light-transmitting reconstituted decorative veneer with UV-resistant transparent epoxy resin adhesive, and cold-pressed for 10-15h to obtain a formaldehyde-free wood composite material with high light fastness suitable for automotive interiors.

[0011] Preferably, the bleaching solution contains the following components by mass fraction: 20-35% hydrogen peroxide, 10-20% sodium hydroxide, 5-10% sodium silicate, 1-5% magnesium sulfate, and 45-55% water. Further, the specific mass fraction of hydrogen peroxide can be 20%, 22.5%, 25%, 27.5%, 30%, 32.5%, or 35%; the specific mass fraction of sodium hydroxide can be 10%, 12.5%, 15%, 17.5%, or 20%; the specific mass fraction of sodium silicate can be 5%, 6%, 7%, 8%, 9%, or 10%; the specific mass fraction of magnesium sulfate can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%; and the specific mass fraction of water can be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, or 55%.

[0012] Preferably, the ratio of the wood veneer to the bleach is 0.5:10 to 1:10, and more preferably 0.5:10, 0.6:10, 0.7:10, 0.8:10, 0.9:10 or 1:10.

[0013] Preferably, the bleaching temperature is 65~70℃, specifically 65℃, 66℃, 67℃, 68℃, 69℃ or 70℃; the time is 3~6h, specifically 3h, 4h, 5h or 6h.

[0014] In the wood bleaching process, the anions in the hydrogen peroxide solution react with the chromogenic groups (such as carbonyl groups and carbon-carbon double bonds) in the veneer through a redox reaction. By cleaving the side chain structure of these groups, the color-developing properties are eliminated, thus preventing subsequent discoloration. Excessive bleaching time can damage the wood's cellulose structure. Controlling the bleaching time within the range of 3-6 hours ensures both effective bleaching and maximizes the preservation of the veneer's mechanical strength and lifespan.

[0015] Preferably, the pickling reagent is a phosphoric acid solution or an acetic acid solution; further, the pickling reagent is preferably an acetic acid solution; the pH value of the pickling reagent is 5-6; the pickling temperature is room temperature, and the time is 20-30 min, specifically 20 min, 22.5 min, 25 min, 27.5 min, or 30 min.

[0016] Preferably, the water washing temperature is room temperature and the time is 10-20 minutes; further, the water washing time is preferably 10 minutes, 12.5 minutes, 15 minutes, 17.5 minutes or 20 minutes.

[0017] The acid washing step can effectively neutralize residual alkaline substances and decompose unconsumed peroxides; the water washing process can remove oxygen-containing free radicals and other soluble byproducts generated during bleaching, reducing the interference of residual oxidants on subsequent dyeing processes.

[0018] Preferably, the dye includes one or more of yellow, red, blue, and purple dyes; the yellow dye is further preferably Acid Golden Yellow G; the red dye is further preferably Acid Red 18; the blue dye is further preferably Acid Blue 193; and the purple dye is further preferably Acid Violet 43. In this invention, the concentration of yellow dye in the dyeing solution is preferably... The concentrations of red dye, blue dye, and purple dye are preferably 0.03~5 g / L.

[0019] Preferably, the dyeing temperature is 90~98℃ and the dyeing time is 4~8h. More specifically, the dyeing temperature is preferably 90℃, 92℃, 94℃, 95℃, 96℃ or 98℃, and the dyeing time is preferably 4h, 5h, 6h, 7h or 8h.

[0020] Preferably, the drying temperature is 80-90℃ and the time is 3-10 minutes. More specifically, the drying temperature is preferably 80℃, 82℃, 85℃, 87℃, or 90℃; and the drying time is preferably 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes. This invention does not specifically limit the drying parameters, as long as the moisture content of the final high-colorfastness reconstituted decorative veneer is 8-14%.

[0021] Preferably, the UV-resistant additive includes one or more of the following: UV absorbers and light stabilizers that are easily soluble in epoxy resin diluents and are colorless and transparent after dissolution. Specifically, it may be one or more of the following substances: benzotriazole UV absorbers, formamidin UV absorbers, light stabilizer 292, etc.

[0022] Preferably, the epoxy resin diluent includes one or more of a non-reactive diluent and a mixture of reactive diluents, specifically one or more of substances such as ethyl acetate, dibutyl phthalate, butyl glycidyl ether, and butanediol diglycidyl ether.

[0023] Preferably, the UV-resistant additive and the diluent are dissolved in a mass ratio of 1:5 to 1:10, specifically preferably 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10.

[0024] Preferably, the co-solvent is one or more of a colorless and transparent fatty acid glycerides that are miscible with ethyl acetate and accelerate the dissolution of UV-resistant additives. The amount of co-solvent added is 15-25%, specifically 15%, 17%, 20%, 22%, or 25%. The stirring time is 20-30 minutes, specifically 20 minutes, 22 minutes, 25 minutes, 27 minutes, or 30 minutes, until complete dissolution is achieved.

[0025] Preferably, 5-25% of an anti-UV solution is added to a transparent epoxy resin adhesive to obtain adhesive A, and 20-25% of a curing agent B is added to obtain an anti-UV transparent epoxy resin adhesive with a viscosity of 700-4000 mPa·s. The preferred proportions of the anti-UV solution are 5%, 7%, 10%, 12%, 15%, 17%, 20%, 22%, or 25%. Preferably, the amount of curing agent B added is 20-25% of adhesive A, specifically 20%, 21%, 22%, 23%, 24%, and 25%.

[0026] Preferably, the curing agent B is one or more of the following: aliphatic amine curing agent 593, alicyclic amine curing agent, etc., which are colorless and transparent and can cure rapidly at room temperature.

[0027] This invention dissolves an anti-UV additive in an epoxy resin diluent, and then mixes this with a transparent epoxy resin to impart UV resistance to the transparent epoxy resin adhesive. Compared with developing modified epoxy resins with stronger weather resistance and modified polyetheramine curing agents with better yellowing resistance, this method reduces the technical problems and processes of resin and curing agent modification, lowers product costs, and has a wide range of applications. Compared with directly using powder, it reduces the complexity of research on the compatibility and stability of additives with epoxy resin, and the dispersion is also more uniform.

[0028] The use of UV-resistant transparent epoxy resin in this invention has three advantages. First, it is formaldehyde-free and environmentally friendly, making it greener and healthier than traditional urea-based adhesives. Second, the transparency of the epoxy resin ensures that the color and texture of the reconstituted decorative veneer remain clearly visible even after a transparent nylon film is adhered to its surface. Third, the UV-resistant transparent epoxy resin adhesive layer provides UV protection, improving the colorfastness of the reconstituted decorative material.

[0029] Preferably, the transparent nylon film used in this invention can be from brands such as TROGAMIDCX9704NC, GrilamidTR90, or TF1206.

[0030] Preferably, the dyed veneer and the 0.3-0.7mm transparent nylon film are assembled in a ratio of 4:1 to 8:1, and the transparent nylon film is preferably 0.3mm, 0.4mm, 0.5mm, 0.6mm or 0.7mm; the assembly ratio is preferably 4:1, 5:1, 6:1, 7:1 or 8:1.

[0031] Preferably, the amount of adhesive applied when bonding the dyed veneer and the transparent nylon film is 120~150g / m². 2 Specifically, the preferred value is 120g / m 2 130g / m 2 140g / m 2 150g / m 2 The unit pressure of the press is 1.8~2.5MPa, preferably 1.8MPa, 1.9MPa, 2.0MPa, 2.1MPa, 2.2MPa, 2.3MPa, 2.4MPa or 2.5MPa; the pressure holding time is 2~5 days, specifically 2 days, 3 days, 4 days or 5 days.

[0032] Preferably, the amount of adhesive applied when bonding the translucent reconstituted decorative veneer and the transparent nylon film is 130~160g / m². 2 Specifically, the preferred value is 130g / m 2 135g / m 2 140g / m 2 145g / m 2 150g / m 2155g / m 2 and 160g / m 2 The unit pressure of the pressing is 1.8~2.5MPa, preferably 1.8MPa, 1.9MPa, 2.0MPa, 2.1MPa, 2.2MPa, 2.3MPa, 2.4MPa or 2.5MPa; the pressing time is 10~15h, specifically 10h, 11h, 12h, 13h, 14h or 15h.

[0033] Preferably, a layer of transparent nylon film with a thickness of 0.1~0.3mm is adhered to the surface of the translucent reconstituted decorative veneer with transparent epoxy resin adhesive. The thickness is specifically preferably 0.1mm, 0.12mm, 0.15mm, 0.17mm, 0.2mm, 0.22mm, 0.25mm, 0.27mm or 0.3mm.

[0034] This invention utilizes a transparent nylon film, with a composite structure (veneer:nylon film layer ratio of 4:1 to 8:1) that imparts a light transmittance of over 80% to certain areas of the material. This allows for patterned designs of wood grain and translucent areas, catering to the intelligent lighting needs of automotive interiors. By precisely controlling the layer ratio of stained veneer to transparent nylon film, patterns with varying light transmittance can be flexibly customized. Under the reflection of light, the natural wood grain and translucent areas complement each other, presenting a unique light and shadow art effect and bringing more creative possibilities to automotive interior design. Furthermore, the transparent nylon film adhered to the surface of the translucent reconstituted decorative veneer enhances its colorfastness due to UV resistance, while also protecting the surface from scratches, stains, and other damage.

[0035] In this invention, a transparent nylon film and a UV-resistant transparent epoxy resin layer provide dual protection to improve color fastness. Compared to conventional methods that involve adding composite regulators to the dye bath and using stabilizers for color fixation and lightfastness treatment after dyeing, this invention simplifies the dyeing process by eliminating the need for adding auxiliaries and lightfastness curing. Furthermore, the dual UV barrier formed by the UV-resistant epoxy resin layer and the transparent nylon film is more uniform, has a wider coverage, and provides better results than adding auxiliaries during the dyeing process.

[0036] The present invention provides a formaldehyde-free wood composite material with high color fastness obtained by the above technical solution, wherein the light fastness of the high color fastness wood composite material is greater than or equal to level 5 of the gray scale.

[0037] Beneficial effects:

[0038] In this invention, a dual UV barrier—a transparent nylon film and a UV-resistant transparent epoxy resin layer—is formed on the surface of the reconstituted decorative veneer to improve color fastness. Compared to traditional methods that add UV absorbers and free radical scavengers, this invention eliminates the need for additives and light-curing treatments during the dyeing process, simplifying the dyeing process. Furthermore, the dual UV barrier formed by the UV-resistant epoxy resin layer and the transparent nylon film is more uniform and denser in coverage than adding additives during the dyeing process, eliminating problems such as localized discoloration and fading of the veneer caused by uneven application of additives, and significantly improving the color fastness of the reconstituted decorative veneer.

[0039] This invention improves the color fastness of reconstituted decorative veneers while the preform structure (veneer: nylon film = 4:1~8:1 layer ratio) gives the material a local light transmittance of more than 80%, realizing the integration of decoration and patterned lighting; in addition, it uses UV-resistant transparent epoxy resin adhesive, which is formaldehyde-free and environmentally friendly, and is greener and healthier than traditional urea adhesive.

[0040] The formaldehyde-free, high-colorfastness wood composite material obtained by the method of the present invention has a light fastness greater than or equal to grade 5 on the gray scale.

[0041] This technology, through a transparent nylon film-UV-resistant epoxy resin laminated composite system, improves the light fastness of wood composite materials to level 5 under the premise of formaldehyde-free and environmentally friendly manufacturing. Simultaneously, the high-transmittance preform structure integrates decorative and functional lighting, and the simplified process avoids the need for dyeing auxiliaries, providing key technical support for the high-end development of automotive interiors. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of timber pressing, where 1-1 is dyed veneer, 1-2 is transparent nylon film, and 1-3 is UV-resistant transparent epoxy resin adhesive layer; Figure 2 This diagram illustrates the preparation of a formaldehyde-free wood composite material with high lightfastness. 1-2 is a transparent nylon film, 1-3 is a UV-resistant transparent epoxy resin adhesive layer, and 1-4 is a light-transmitting reconstituted decorative veneer. Detailed Implementation

[0043] The following detailed description, in conjunction with embodiments, illustrates the method for improving the color fastness of reconstituted decorative veneer and the high color fastness wood composite material of the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] (1) Immerse veneer 1-1 in bleaching solution (containing the following components by mass fraction: hydrogen peroxide 32.5%, sodium hydroxide 12.5%, sodium silicate 8%, magnesium sulfate 2%, water 45%), with a bath ratio of 1:10, and bleach at 65℃ for 4 hours. Then remove it. Then acid wash in acetic acid solution with pH 6 for 30 minutes and take it out, and wash it with water for 20 minutes. After washing, dye the veneer in dye solution at 90℃ for 4 hours. The dye solution includes Acid Golden Yellow G (0.03 g / L), Acid Red 18 (0.04 g / L), Acid Blue 193 (0.09 g / L) and water. After dyeing, dry the veneer until the moisture content is 10%.

[0046] (2) Mix UV absorber UV-329 and ethyl acetate at a mass ratio of 1:6, add 20% fatty acid glycerides, stir for 25 min to fully dissolve to obtain UV-resistant solution, add 20% UV-resistant solution to transparent epoxy resin glue E-44 to prepare glue A, add 20% fatty amine curing agent 593 to obtain UV-resistant transparent epoxy resin glue.

[0047] (3) Please refer to Figure 1 The dried dyed veneer 1-1 and 0.4mm thick TF1206 nylon film 1-2 were assembled in a ratio of 6:1, and then coated with UV-resistant transparent epoxy resin 1-3 at a coating amount of 120g / m³. 2 The unit pressure is 2.0MPa, and after holding the pressure for 3 days, it is planed to obtain a light-transmitting reconstituted decorative veneer.

[0048] (4) Please refer to Figure 2 A 0.1mm thick TF1206 nylon film 1-2 is attached to the surface of the translucent reconstituted decorative veneer 1-4 using UV-resistant transparent epoxy resin adhesive 1-3, with an adhesive application rate of 130g / m². 2 A high color fastness wood composite material suitable for automotive interiors was obtained by cold pressing at a unit pressure of 2.0 MPa for 12 hours.

[0049] Example 2

[0050] (1) Immerse the wood veneer in a bleaching solution (containing the following components by mass fraction: 30% hydrogen peroxide, A solution of 12.5% ​​sodium hydroxide, 5% sodium silicate, 2.5% magnesium sulfate, and 50% water (liquid ratio 0.9:10) was used for bleaching at 67℃ for 5 hours. The veneers were then acid-washed in an acetic acid solution at pH 6 for 25 minutes, followed by a 15-minute wash with water. The washed veneers were then dyed in a dye bath at 95℃ for 5 hours. The dye bath consisted of Acid Golden G (0.18 g / L), Acid Red 18 (0.08 g / L), Acid Blue 193 (0.20 g / L), and water. After dyeing, the veneers were dried until the moisture content was 8%.

[0051] (2) Mix UV absorber UV-329 and ethyl acetate at a mass ratio of 1:6, add 20% fatty acid glycerides, stir for 25 min to fully dissolve to obtain UV-resistant solution, add 20% UV-resistant solution to transparent epoxy resin glue E-44 to prepare glue A, add 20% fatty amine curing agent 593 to obtain UV-resistant transparent epoxy resin glue.

[0052] (3) The dried dyed veneer and 0.4 mm thick TF1206 nylon film were assembled in a ratio of 5:1, and then coated with UV-resistant transparent epoxy resin at a coating amount of 120 g / m. 2 The unit pressure is 2.0MPa, and after holding the pressure for 3 days, it is planed to obtain a light-transmitting reconstituted decorative veneer.

[0053] (4) Apply a 0.15mm thick TF1206 nylon film to the surface of the translucent reconstituted decorative veneer using UV-resistant transparent epoxy resin adhesive, with an adhesive application rate of 140g / m². 2 A high color fastness wood composite material suitable for automotive interiors was obtained by cold pressing at a unit pressure of 2.0 MPa for 12 hours.

[0054] Example 3

[0055] (1) Immerse the wood veneer in a bleach solution (containing the following components by mass fraction: 25% hydrogen peroxide, A solution of 17% sodium hydroxide, 6% sodium silicate, 3% magnesium sulfate, and 50% water (liquid ratio 0.8:10) was used. The veneer was bleached at 70℃ for 6 hours and then removed. It was then acid-washed in an acetic acid solution with pH 6 for 20 minutes, followed by a 20-minute water wash. The washed veneer was then dyed in a dye bath at 98℃ for 6 hours. The dye bath consisted of Acid Golden G (1.85 g / L), Acid Red 18 (1.15 g / L), Acid Blue 193 (2.35 g / L), and water. After dyeing, the veneer was dried until the moisture content was 10%.

[0056] (2) Mix UV absorber UV-329 and ethyl acetate at a mass ratio of 1:6, add 20% fatty acid glycerides, stir for 25 min to fully dissolve to obtain UV-resistant solution, add 20% UV-resistant solution to transparent epoxy resin glue E-44 to prepare glue A, add 20% fatty amine curing agent 593 to obtain UV-resistant transparent epoxy resin glue.

[0057] (3) The dried dyed veneer and 0.4 mm thick TF1206 nylon film were assembled in a ratio of 4:1, and then coated with UV-resistant transparent epoxy resin at a coating amount of 120 g / m. 2 The unit pressure is 2.0MPa, and after holding the pressure for 3 days, it is planed to obtain a light-transmitting reconstituted decorative veneer.

[0058] (4) Apply a 0.2mm thick TF1206 nylon film to the surface of the translucent reconstituted decorative veneer using UV-resistant transparent epoxy resin adhesive, with an adhesive application rate of 150g / m². 2 A high color fastness wood composite material suitable for automotive interiors was obtained by cold pressing at a unit pressure of 2.0 MPa for 12 hours.

[0059] Comparative Example 1

[0060] The difference from Example 1 is that step (4) is omitted, that is, the transparent nylon film is not adhered to the surface of the translucent reconstituted decorative veneer with UV-resistant transparent epoxy resin adhesive.

[0061] Comparative Example 2

[0062] The difference from Example 2 is that step (4) is omitted, that is, the transparent nylon film is not adhered to the surface of the translucent reconstituted decorative veneer with anti-ultraviolet transparent epoxy resin adhesive.

[0063] Comparative Example 3

[0064] The difference from Example 3 is that step (4) is omitted, that is, the transparent nylon film is not adhered to the surface of the translucent reconstituted decorative veneer with anti-ultraviolet transparent epoxy resin adhesive.

[0065] Comparative Example 4

[0066] The difference from Example 1 is that the thickness of the TF1206 nylon film adhered to the surface of the light-transmitting reconstituted decorative material in step (4) is 0.08 mm.

[0067] Comparative Example 5

[0068] The difference from Example 1 is that the thickness of the TF1206 nylon film adhered to the surface of the light-transmitting reconstituted decorative material in step (4) is 0.06 mm.

[0069] Comparative Example 6

[0070] The difference from Example 1 is that the thickness of the TF1206 nylon film adhered to the surface of the light-transmitting reconstituted decorative material in step (4) is 0.04 mm.

[0071] Comparative Example 7

[0072] The difference from Example 1 is that: in step (4), the amount of UV-resistant transparent epoxy resin adhesive used to adhere the TF1206 nylon film to the surface of the translucent reconstituted decorative material is 120 g / m. 2 .

[0073] Comparative Example 8

[0074] The difference from Example 1 is that: in step (4), the amount of UV-resistant transparent epoxy resin adhesive used to adhere the TF1206 nylon film to the surface of the translucent reconstituted decorative material is 110 g / m. 2 .

[0075] Comparative Example 9

[0076] The difference from Example 1 is that: in step (4), the amount of UV-resistant transparent epoxy resin adhesive used to adhere the TF1206 nylon film to the surface of the translucent reconstituted decorative material is 100g / m². 2 .

[0077] According to GB / T28999-2012 "Reconstituted Decorative Veneers", the lightfastness and formaldehyde emission of the samples obtained in the examples and comparative examples were tested. The lightfastness test was terminated when the color change of the blue wool standard (grade 2) reached grade 4 on the gray card. The color difference values ​​of the samples obtained in the examples and comparative examples were compared according to GB / T250-2008.

[0078] Table 1. Performance test results of samples obtained from Examples 1-3 and Comparative Examples 1-3 test Colorfastness (grade) Color difference value <![CDATA[Formaldehyde emission (mg / m 3 )]]> Example 1 5 0.12 0.005 Example 2 5 0.14 0.004 Example 3 5 0.18 0.006 Comparative Example 1 3 3.56 0.004 Comparative Example 2 4 1.82 0.005 Comparative Example 3 3.5 2.31 0.007

[0079] Table 2 shows the performance test results of the samples obtained from Comparative Examples 4-9. test Colorfastness (grade) Color difference value <![CDATA[Formaldehyde emission (mg / m 3 )]]> Comparative Example 4 4 1.84 0.003 Comparative Example 5 4 1.96 0.006 Comparative Example 6 3.5 2.17 0.004 Comparative Example 7 4 1.90 0.004 Comparative Example 8 4 1.98 0.003 Comparative Example 9 3.5 2.25 0.007

[0080] This invention discloses a dual-barrier structure of transparent nylon film and UV-resistant transparent epoxy resin adhesive. In Examples 1-3, when the complete dual-barrier structure (nylon film ≥ 0.1 mm + adhesive application rate ≥ 130 g / m²) is used, the material's lightfastness consistently reaches grade 5 (ΔE ≤ 0.18). However, in Comparative Examples 1-3, lacking the physical barrier of the nylon film, even with the same adhesive application rate, the colorfastness drops to grade 3-4 (ΔE ≤ 3.56). This order-of-magnitude performance difference demonstrates that a single chemical barrier cannot meet the high standards required for automotive interior materials, necessitating the construction of a composite protective system.

[0081] Experimental data revealed significant nonlinear characteristics: when the nylon film thickness decreased from 0.1 mm (Example 1) to 0.08 mm (Comparative Example 4), the colorfastness grade underwent a qualitative change (from grade 5 to grade 4), indicating that 0.1 mm is the critical threshold for the physical barrier to take effect. Similarly, an application rate below 130 g / m² (Comparative Example 7) resulted in a 1-grade decrease in colorfastness, and this attenuation confirms that there is a minimum application rate requirement for the chemical barrier.

[0082] Spectroscopic analysis revealed that the working mechanism of the complete dual-barrier system involves the nylon film first blocking over 90% of the high-energy ultraviolet band (280-320nm), while residual ultraviolet light is absorbed by benzotriazole additives in the epoxy adhesive layer. This gradient attenuation mode achieves a total ultraviolet blocking rate of over 99.5%, while the maximum blocking rate of a single barrier does not exceed 85%. Molecular dynamics simulations show that when the film thickness or adhesive application is insufficient, ultraviolet photons concentrate and penetrate in weak areas of the barrier, generating a hotspot effect. This is the microscopic mechanism by which the breakage of the synergistic chain leads to a sharp drop in performance. This technical solution achieves synergistic protection by precisely controlling the synergistic ratio of two key parameters: film thickness ≥0.1mm and adhesive application rate ≥130g / m².

[0083] In summary, this invention uses UV-resistant transparent epoxy resin adhesive to adhere a transparent nylon film to the surface of reconstituted decorative veneer, improving the color fastness of the reconstituted decorative veneer by 1-2 grades. Furthermore, the UV resistance of the wood composite material is positively correlated with the thickness of the transparent nylon film and the amount of UV-resistant transparent epoxy resin adhesive applied, with both synergistically improving the color fastness of the wood composite material. In addition, while improving the color fastness of the reconstituted decorative veneer, the preform structure (veneer:nylon film = 4:1~8:1 layer ratio) imparts a local light transmittance of over 80% to the material, achieving integration of decoration and patterned lighting. Secondly, the use of UV-resistant transparent epoxy resin adhesive is formaldehyde-free and environmentally friendly, making it greener and healthier than traditional urea adhesives.

[0084] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention is not limited to these specific embodiments. Several improvements and modifications can be made without departing from the principles of the invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing a formaldehyde-free wood-based composite material with high lightfastness, characterized in that, The preparation method includes the following steps: (1) The wood veneer is subjected to bleaching, acid washing, water washing, dyeing and drying in sequence to obtain dyed veneer (1-1). (2) Dissolve the UV-resistant additive in epoxy resin diluent at room temperature, add 15-25% of the co-solvent to the mixture, stir for 20-30 minutes, and after it is fully dissolved, obtain the UV-resistant solution. Mix it with transparent epoxy resin glue to obtain glue A, add curing agent B, and obtain UV-resistant transparent epoxy resin glue. (3) The dyed veneer (1-1) and 0.3~0.7mm transparent nylon film (1-2) are assembled in a layer ratio of 4:1~8:

1. The dyed veneer is coated on both sides with UV-resistant transparent epoxy resin glue (1-3), and after pressing and slicing, a light-transmitting reconstituted decorative veneer (1-4) is obtained. (4) Apply a layer of 0.1~0.3mm transparent nylon film (1-2) to the surface of the translucent reconstituted decorative veneer (1-4) with UV-resistant transparent epoxy resin adhesive (1-3), with an adhesive application rate of 130g / m². 2 ~160g / m 2 After cold pressing for 10-15 hours, a formaldehyde-free wood composite material with high light fastness is obtained, suitable for automotive interiors.

2. The method for preparing a formaldehyde-free wood composite material with high lightfastness according to claim 1, characterized in that, The bleaching solution contains the following components by mass fraction: 20-35% hydrogen peroxide, 10-20% sodium hydroxide, 5-10% sodium silicate, 1-5% magnesium sulfate, and 45-55% water; the ratio of the wood veneer to the bleaching solution is 0.5:10-1:10, the bleaching temperature is 65-70℃, and the bleaching time is 3-6 hours.

3. The method for preparing a formaldehyde-free wood composite material with high lightfastness according to claim 1, characterized in that, The acid washing reagent is a phosphoric acid or acetic acid solution with a pH of 5-6. The acid washing temperature is room temperature and the time is 20-30 minutes. The water washing temperature is room temperature and the water washing time is 10-20 minutes.

4. The method for preparing a formaldehyde-free wood composite material with high lightfastness according to claim 1, characterized in that, The dyes used for single-layer dyeing include one or more of yellow, red, blue, and purple dyes, and the dyeing temperature is 90-98℃ for 4-8 hours; the drying temperature is 80-90℃ for 3-10 minutes.

5. The method for preparing a formaldehyde-free wood composite material with high lightfastness according to claim 1, characterized in that, The UV-resistant additives include one or more of benzotriazole UV absorbers, formamidin UV absorbers, and light stabilizer 292.

6. The method for preparing a formaldehyde-free wood composite material with high lightfastness according to claim 1, characterized in that, The epoxy resin diluent includes one or more of the following: ethyl acetate, dibutyl phthalate, butyl glycidyl ether, and butylene glycol diglycidyl ether.

7. The method for preparing a formaldehyde-free wood composite material with high lightfastness according to claim 1, characterized in that, The UV-resistant additive and epoxy resin diluent are mixed in a mass ratio of 1:5 to 1:

10. 15-25% of a co-solvent is added to the mixture, and the mixture is stirred for 20-30 minutes until fully dissolved to obtain a UV-resistant solution. 5-25% of the UV-resistant solution is added to a transparent epoxy resin adhesive to obtain adhesive A. 20-25% of curing agent B is added to obtain a UV-resistant transparent epoxy resin adhesive with a viscosity of 700-4000 mPa·s.

8. The method for preparing a formaldehyde-free wood composite material with high lightfastness according to claim 1, characterized in that, The cosolvent is a fatty acid glyceride; the transparent epoxy resin adhesive is E-44; and the curing agent is a fatty amine curing agent 593 and / or a cycloaliphatic amine curing agent. According to claim 1, the method for preparing a formaldehyde-free wood composite material with high lightfastness is characterized in that the amount of adhesive applied when bonding the dyed veneer and the transparent nylon film is 120 g / m². 2 ~150g / m 2 The unit pressure for pressing is 1.8~2.5MPa, and the timber is kept under pressure for 2-5 days.

9. The method for preparing a formaldehyde-free wood composite material with high lightfastness according to claim 1, characterized in that, The amount of adhesive applied when bonding the dyed veneer and the transparent nylon film is 120g / m². 2 ~150g / m 2 The unit pressure for pressing is 1.8~2.5MPa, and the timber is kept under pressure for 2-5 days.

10. The method for preparing a formaldehyde-free wood composite material with high lightfastness according to claim 1, characterized in that, The amount of adhesive applied when bonding the translucent reconstituted decorative veneer and the transparent nylon film is 130g / m². 2 ~160g / m 2 The unit pressure for pressing is 1.8~2.5MPa, and the pressing time is 10-15h.

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