Preparation method of high light fastness discoloring type softwood base plate

Abstract

This invention relates to the field of engineered wood processing technology, specifically to a method for preparing a high-resistance photochromic cork-based board, comprising the following steps: S1. Preparation of a modifier; S2. Preparation of a modified adhesive; S3. Preparation of the board. This invention significantly improves the photochromic resistance of cork-based boards by adding a photochromic modifier to the adhesive used for the cork-based board, and the operation is simple. The added modifier does not change the original color of the cork-based board and has no effect on subsequent processing, such as dyeing and finishing.

Description

Technical Field

[0001] This invention relates to the field of wood-based panel processing technology, specifically a method for preparing a high-light-resistant cork-based panel. Background Technology

[0002] Cork, harvested from the outer bark of cork trees, is characterized by its softness and good elasticity. While its most common use is as cork stoppers, its natural texture, feel, and environmental friendliness have led to promising prospects in the decoration industry in recent years. By mixing leftover cork granules with adhesives and molding them, various boards can be produced; these cork-based boards can be used for flooring, wall panels, protective panels, and interior panels, effectively increasing their added value. However, the main chemical components of cork are cork resin, lignin, cellulose, hemicellulose, extractives, and ash, with cork resin and lignin comprising a high proportion. This makes cork-based boards more susceptible to photochromic changes compared to natural wood boards, thus limiting their applications. Therefore, developing highly photochromic-resistant cork-based boards is of significant importance.

[0003] One way to improve the lightfastness of cork-based boards is to print new color patterns onto the surface using high-color-fastness dyes and then apply a weather-resistant coating to enhance their lightfastness. For example, Lu Zhihua et al. (China Wood-based Panels, 2021) used a flatbed UV inkjet printer to print cork flooring, achieving an actual lightfastness of grade 4 or higher. Another method involves applying a weather-resistant decorative layer to the surface of the cork-based board. For instance, Song Zhuwan (CN201611061951.5) applied a pre-treated fiber layer to the cork layer to improve its lightfastness. Guo Anru et al. (CN201810425192.9) formed a flexible styrene-butadiene-styrene block copolymer / epoxy resin hydrophobic layer on the surface of cork composite materials, preventing discoloration, peeling, and flaking in humid environments. However, these methods all alter the natural color of the cork material to some extent and cannot be used to produce color-changing cork-based boards. Therefore, it is essential to prepare a cork-based board with high resistance to light-changing color while retaining the natural color of cork. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a cork-based board with high photochromic resistance. This method involves adding a multi-site polymer adhesive / organic antioxidant—a nano-titanium dioxide intercalated hydrotalcite organic-inorganic composite modifier—to an elastic polyurethane adhesive, which is then combined with cork particles. During bonding, the adhesive simultaneously coats the surface of the cork particles, forming a photochromic layer, thereby improving the photochromic resistance of the cork-based board. This manufacturing method is simple; simply adding a modifier to the adhesive is sufficient to improve the overall photochromic resistance of the board.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing a cork-based board with high lightfastness and colorfastness includes the following preparation steps:

[0007] S1. Preparation of modifier: Mix 1-3 parts of multi-site polymer, 0.05-1 parts of organic antioxidant, and 0.03-0.08 parts of nano titanium dioxide evenly at room temperature, then add 1-2 parts of hydrotalcite powder and grind, then centrifuge and wash with anhydrous ethanol to obtain the modifier.

[0008] S2. Preparation of modified adhesive: Add the modifier to 12-18 parts of elastic polyurethane adhesive and stir evenly. Add 0.05-0.1 parts of acetone to reduce the viscosity of the reaction system to obtain the modified adhesive.

[0009] S3. Preparation of the board: Mix 80-85 parts of cork granules and the modified adhesive obtained in step S2 in a mixer until uniform, then add to a mold and press at room temperature for 24-48 hours, with the pressure controlled at 0.1-0.2 MPa. Maintain the pressure and heat to 120-140℃ for 5-10 minutes to obtain a cork-based board with high lightfastness and colorfastness.

[0010] Preferably, the preparation of multisite polymers includes the following steps:

[0011] S11. Dissolve polyethyleneimine with a molecular weight of 1000-10000 in water to prepare a polyethyleneimine aqueous solution with a mass fraction of 50-60%;

[0012] S12. Add 10-15% by weight of a polybasic organic acid in the form of a polyethyleneimine aqueous solution, and stir at 40-60℃ for 8-10 min to obtain a multi-site polymer.

[0013] Preferably, the stirring speed in steps S2 and S3 is 300-500 r / min and the time is 10-15 min.

[0014] Preferably, the polybasic organic acid is one or more of trihydroxymethylpropane acid, tricarboxymethylmethane acid, and 3-carboxy-3-hydroxyglutaric acid.

[0015] Preferably, the elastic polyurethane adhesive is a two-component polyurethane adhesive composed of component A and component B, wherein component A is the main agent, which is a polyurethane prepolymer containing terminal isocyanate groups, accounting for 65-70% of the mass fraction of the elastic polyurethane adhesive, and component B is a curing agent, which is a polyester polyol, accounting for 30-35% of the mass fraction of the elastic polyurethane adhesive.

[0016] Preferably, the organic antioxidant is a hindered phenolic antioxidant.

[0017] Preferably, the average particle size of nano-titanium dioxide is 20-100 nm.

[0018] Preferably, the preparation of hydrotalcite includes the following steps:

[0019] S21. Slowly add 1-2 parts of aluminum nitrate aqueous solution with a mass fraction of 60-70%, 2-4 parts of magnesium nitrate aqueous solution with a mass fraction of 60-70%, 1-2 parts of sodium hydroxide aqueous solution with a mass fraction of 60-70%, and 3-7 parts of sodium carbonate aqueous solution with a mass fraction of 60-70% together to obtain a slurry.

[0020] S22. The obtained slurry is immediately transferred to an autoclave, aged at 90-100℃, centrifuged, washed several times with anhydrous ethanol, dried at 80-100℃, and pulverized through an 80-mesh sieve to obtain hydrotalcite.

[0021] Preferably, the cork particles have a particle size of 10-100 mesh.

[0022] Preferably, in step S1, the grinding process is carried out in a planetary ball mill at a speed of 800-1000 r / min for 1-2 hours.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. This invention uses multi-site polymers as reactive centers to chemically graft antioxidants and nano-titanium dioxide to form an organic-inorganic hybrid system, which synergistically improves photochromic resistance. Furthermore, the effective components are intercalated into the interior of the hydrotalcite through the interlayer adsorption properties of the hydrotalcite, thus preparing an easily stored solid modifier.

[0025] 2. The modifier prepared by this invention has good compatibility with polyurethane adhesives, with no precipitation, agglomeration, demulsification, or other phenomena. It does not change the curing characteristics of the adhesive and has no effect on the bonding strength of the board.

[0026] 3. This invention significantly improves the lightfastness of cork-based boards by adding a lightfastness modifier to the adhesive, and the process is simple. The added modifier does not change the original color of the cork-based board and has no impact on subsequent processing, such as dyeing and finishing. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the preparation process of the high lightfastness cork-based board of the present invention.

[0028] Figure 2 This is a flowchart illustrating the preparation process of the multi-site polymer of the present invention;

[0029] Figure 3 This is a flowchart illustrating the preparation process of the hydrotalcite of this invention. Detailed Implementation

[0030] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] Please see Figure 1-3 The present invention provides a technical solution:

[0032] Example 1

[0033] A type of cork-based board with high lightfastness and colorfastness:

[0034] S101. Preparation of modifier: 20g of multi-site polymer, 0.8g of hindered phenolic antioxidant 1010 and 0.3g of nano titanium dioxide are mixed evenly at room temperature. Then, 20g of hydrotalcite powder is added and the mixture is ground in a planetary ball mill at 800r / min for 1h. After centrifugation and washing with anhydrous ethanol, the modifier can be obtained.

[0035] S102. Preparation of modified adhesive: Add the modifier to 120g of elastic polyurethane adhesive and stir at 300r / min for 10min. Add 0.5g of acetone to reduce the viscosity of the reaction system to obtain the modified adhesive.

[0036] S103. Preparation of the board: 800g of cork granules and the modified adhesive obtained in step S102 are stirred in a mixer at a speed of 300r / min for 10min. Then, the mixture is added to a mold and pressed at room temperature for 24h, with the pressure controlled at 0.1MPa. After that, the pressure is maintained and heated to 120℃ for 5min to obtain a cork-based board with high lightfastness and colorfastness.

[0037] In this embodiment, the preparation of the multisite polymer includes the following steps:

[0038] S10111. Dissolve polyethyleneimine in water to prepare a 50% (w / w) polyethyleneimine aqueous solution;

[0039] S10112. Add trihydroxymethylpropaneic acid, which is 10% of the weight of polyethyleneimine aqueous solution, and stir at 40°C for 10 min to prepare a multi-site polymer;

[0040] The preparation of hydrotalcite includes the following steps:

[0041] S10121. Slowly add 1 part of 60% aluminum nitrate aqueous solution, 2 parts of 60% magnesium nitrate aqueous solution, 1 part of 60% sodium hydroxide aqueous solution, and 3 parts of 60% sodium carbonate aqueous solution together to obtain a slurry.

[0042] S10122. The obtained slurry was immediately transferred to an autoclave, aged at 90°C, centrifuged, washed several times with anhydrous ethanol, dried at 80°C, and pulverized through an 80-mesh sieve to obtain hydrotalcite.

[0043] Example 2

[0044] A type of cork-based board with high lightfastness and colorfastness:

[0045] S201. Preparation of modifier: 10g of multi-site polymer, 10g of hindered phenolic antioxidant 1076 and 0.5g of nano titanium dioxide are mixed evenly at room temperature. Then, 10g of hydrotalcite powder is added and the mixture is ground in a planetary ball mill at 1000r / min for 2h. After centrifugation and washing with anhydrous ethanol, the modifier can be obtained.

[0046] S202. Preparation of modified adhesive: Add the modifier to 150g of elastic polyurethane adhesive and stir at 500r / min for 15min. Add 1g of acetone to reduce the viscosity of the reaction system to obtain the modified adhesive.

[0047] S203. Preparation of the board: 830g of cork granules and the modified adhesive obtained in step S202 are stirred in a mixer at a speed of 500r / min for 15min. Then, the mixture is added to a mold and pressed at room temperature for 48h, with the pressure controlled at 0.2MPa. After that, the pressure is maintained and heated to 140℃ for 10min to obtain a cork-based board with high lightfastness and colorfastness.

[0048] In this embodiment, the preparation of the multisite polymer includes the following steps:

[0049] S20111. Dissolve polyethyleneimine in water to prepare a 60% (w / w) polyethyleneimine aqueous solution;

[0050] S20112. Add tricarboxymethylmethane acid at a mass of 15% of the polyethyleneimine aqueous solution, and stir at 60°C for 10 min to obtain a multi-site polymer;

[0051] The preparation of hydrotalcite includes the following steps:

[0052] S20121. Slowly add 2 parts of 70% aluminum nitrate aqueous solution, 4 parts of 70% magnesium nitrate aqueous solution, 2 parts of 70% sodium hydroxide aqueous solution, and 7 parts of 70% sodium carbonate aqueous solution together to obtain a slurry.

[0053] S20122. The obtained slurry was immediately transferred to an autoclave, aged at 100°C, centrifuged, washed several times with anhydrous ethanol, dried at 100°C, and pulverized through an 80-mesh sieve to obtain hydrotalcite.

[0054] Example 3

[0055] A type of cork-based board with high lightfastness and colorfastness:

[0056] S301. Preparation of modifier: 30g of multi-site polymer, 0.8g of hindered phenolic antioxidant 1010 and 0.8g of nano titanium dioxide are mixed evenly at room temperature. Then, 20g of hydrotalcite powder is added and the mixture is ground in a planetary ball mill at a speed of 900r / min for 1.5h. After centrifugation and washing with anhydrous ethanol, the modifier can be obtained.

[0057] S302. Preparation of modified adhesive: Add the modifier to 180g of elastic polyurethane adhesive and stir at 400r / min for 12min. Add 0.5g of acetone to reduce the viscosity of the reaction system to obtain the modified adhesive.

[0058] S303. Preparation of the board: 800g of cork granules and the modified adhesive obtained in step S302 are stirred in a mixer at a speed of 400r / min for 13min. Then, the mixture is added to a mold and pressed at room temperature for 36h with the pressure controlled at 0.1MPa. After that, the pressure is maintained and heated to 130℃ for 7min to obtain a cork-based board with high lightfastness and colorfastness.

[0059] In this embodiment, the preparation of the multisite polymer includes the following steps:

[0060] S30111. Dissolve polyethyleneimine in water to prepare a 55% (w / w) polyethyleneimine aqueous solution;

[0061] S30112. Add 3-carboxy-3-hydroxyglutaric acid at a mass of 12% of the polyethyleneimine aqueous solution, and stir at 50°C for 9 min to obtain a multi-site polymer;

[0062] The preparation of hydrotalcite includes the following steps:

[0063] S30121. Slowly add 2 parts of 65% aluminum nitrate aqueous solution, 3 parts of 65% magnesium nitrate aqueous solution, 1 part of 65% sodium hydroxide aqueous solution, and 5 parts of 65% sodium carbonate aqueous solution together to obtain a slurry.

[0064] S30122. The obtained slurry was immediately transferred to an autoclave, aged at 95°C, centrifuged, washed several times with anhydrous ethanol, dried at 90°C, and pulverized through an 80-mesh sieve to obtain hydrotalcite.

[0065] Comparative Example 1

[0066] The only difference between Comparative Example 1 and Example 1 is that this Comparative Example does not contain multi-site polymers, organic antioxidants, nano-titanium dioxide, and hydrotalcite.

[0067] Comparative Example 2

[0068] The only difference between Comparative Example 2 and Example 1 is that this comparative example does not contain multi-site polymers, organic antioxidants, or nano-titanium dioxide.

[0069] Comparative Example 3

[0070] The only difference between Comparative Example 3 and Example 1 is that no multi-site polymer was added to this Comparative Example.

[0071] Comparative Example 4

[0072] The only difference between Comparative Example 4 and Example 1 is that no organic antioxidants were added to this comparative example.

[0073] Comparative Example 5

[0074] The only difference between Comparative Example 5 and Example 1 is that nano-titanium dioxide is not added to this comparative example.

[0075] Performance testing:

[0076] Comparative Example 1, compared to Example 1, did not contain the multi-site polymer, organic antioxidant, nano-titanium dioxide, or hydrotalcite. Comparative Example 2, compared to Example 1, did not contain the multi-site polymer, organic antioxidant, or nano-titanium dioxide. Comparative Example 3, compared to Example 1, did not contain the multi-site polymer. Comparative Example 4, compared to Example 1, did not contain the organic antioxidant. Comparative Example 5, compared to Example 1, did not contain nano-titanium dioxide. The modified adhesives obtained from Examples 1-3 and Comparative Examples 1-5 were tested for appearance, solid content, and viscosity. The resulting cork-based boards were tested according to the national standard GB / T 17657-2022 for water absorption thickness swelling rate, tensile strength, and light fastness. The results are shown in Tables 1 and 2 below.

[0077] Table 1 Properties of Modified Adhesives

[0078]

[0079] Table 2 Comparison of properties of cork-based boards

[0080]

[0081] As can be seen from the results in Table 1, the appearance, solid content and viscosity of Examples 1-3 after the addition of the modifier were basically unchanged compared with the pure adhesive Comparative Example 1. However, Comparative Examples 2 and 3 without the addition of the multi-site polymer both showed sedimentation and demulsification, and were unusable. The performance of Comparative Examples 4 and 5 was also basically the same as that of the pure adhesive Comparative Example 1.

[0082] As shown in Table 2, Examples 1-3 showed no effect on the 24-hour water absorption thickness swelling rate and tensile strength of Comparative Example 1 compared to the pure adhesive. Their lightfastness reached grade 5, while Comparative Example 1 only reached grade 2 on the gray scale. Comparative Examples 4 and 5, lacking the organic-inorganic synergistic lightfastness characteristic, only showed a slight improvement in lightfastness, reaching grade 3. This indicates that the prepared modifier has good compatibility with the polyurethane adhesive, exhibiting no precipitation, agglomeration, or demulsification, and does not alter the adhesive's curing characteristics, thus having no impact on the bonding strength of the boards.

[0083] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-light-resistance cork-based board, characterized in that, The preparation steps include the following: S1. Preparation of modifier: Mix 1-3 parts of multi-site polymer, 0.05-1 parts of organic antioxidant, and 0.03-0.08 parts of nano titanium dioxide evenly at room temperature, then add 1-2 parts of hydrotalcite powder and grind, then centrifuge and wash with anhydrous ethanol to obtain the modifier. S2. Preparation of modified adhesive: Add the modifier to 12-18 parts of elastic polyurethane adhesive and stir evenly. Add 0.05-0.1 parts of acetone to reduce the viscosity of the reaction system to obtain the modified adhesive. S3. Preparation of the board: Mix 80-85 parts of cork granules and the modified adhesive obtained in step S2 in a mixer until uniform, then add to a mold and press at room temperature for 24-48 hours, with the pressure controlled at 0.1-0.2 MPa. Maintain the pressure and heat to 120-140℃ for 5-10 minutes to obtain a cork-based board with high light-diffusing resistance. The preparation of the multisite polymer includes the following steps: S11. Dissolve polyethyleneimine with a molecular weight of 1000-10000 in water to prepare a polyethyleneimine aqueous solution with a mass fraction of 50-60%. S12. Add 10-15% by weight of poly(ethyleneimine) aqueous solution of a poly(organic) acid, and stir at 40-60℃ for 8-10 min to obtain a multi-site polymer. The elastic polyurethane adhesive is a two-component polyurethane adhesive composed of component A and component B. Component A is the main agent, which is a polyurethane prepolymer containing terminal isocyanate groups, accounting for 65-70% of the mass fraction of the elastic polyurethane adhesive. Component B is a curing agent, which is a polyester polyol, accounting for 30-35% of the mass fraction of the elastic polyurethane adhesive. The preparation of the hydrotalcite includes the following steps: S21. Slowly add 1-2 parts of aluminum nitrate aqueous solution with a mass fraction of 60-70%, 2-4 parts of magnesium nitrate aqueous solution with a mass fraction of 60-70%, 1-2 parts of sodium hydroxide aqueous solution with a mass fraction of 60-70%, and 3-7 parts of sodium carbonate aqueous solution with a mass fraction of 60-70% together to obtain a slurry. S22. The obtained slurry is immediately transferred to an autoclave, aged at 90-100℃, centrifuged, washed several times with anhydrous ethanol, dried at 80-100℃, and pulverized through an 80-mesh sieve to obtain hydrotalcite.

2. The method for preparing a high-light-resistance cork-based board according to claim 1, characterized in that, The polybasic organic acid is one or more of trihydroxymethylpropane acid, tricarboxymethylmethane acid, and 3-carboxy-3-hydroxyglutaric acid.

3. The method for preparing a high-light-resistance cork-based board according to claim 1, characterized in that, In steps S2 and S3, the stirring speed is 300-500 r / min and the time is 10-15 min.

4. The method for preparing a high-light-resistance cork-based board according to claim 1, characterized in that, The organic antioxidant is a hindered phenolic antioxidant.

5. The method for preparing a high-light-resistance cork-based board according to claim 1, characterized in that, The average particle size of the nano-titanium dioxide is 20-100 nm.

6. The method for preparing a high-light-resistance cork-based board according to claim 1, characterized in that, The cork particles have a particle size of 10-100 mesh.

7. The method for preparing a high-light-resistance cork-based board according to claim 1, characterized in that, In step S1, the grinding process is carried out in a planetary ball mill at a speed of 800-1000 r / min for 1-2 hours.

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