A method for producing engineered wood using bleaching, brightening, and yellowing resistance technologies

Abstract

The present invention relates to a method for producing engineered wood using bleaching, whitening, and yellowing resistance technologies, belonging to the technical field of wood processing. The method for producing yellowing-resistant engineered wood according to the present invention includes steps such as normal sodium silicate bleaching, bleach bleaching, and brightener whitening. The yellowing-resistant engineered wood obtained by this method can maintain the whitening effect for a long time and effectively avoid the problem of fading and yellowing of engineered wood veneers.

Description

Technical Field

[0001] The present invention belongs to the technical field of wood processing and relates to a method for producing engineered wood using bleaching, whitening, and yellowing resistance technologies. Background Art

[0002] Natural wood veneer is the most primitive and commonly used raw material in the current wood veneer market and is mainly used in the surface veneering process of indoor wooden furniture. Natural wood veneer is obtained from natural tree species and has a good sense of comfort and natural fragrance.

[0003] Engineered wood veneer is a new type of decorative material with more superior performance, which is produced from ordinary wood (fast-growing wood) as raw material and uses the principle of bionics to carry out various modification and physical-chemical treatments on ordinary wood and fast-growing wood.

[0004] Engineered wood veneer corrects the natural defects of raw wood, makes up for the performance defects of raw wood veneer, and has richer and more diverse textures and colors. Therefore, the application of engineered wood veneer is becoming more and more extensive. Moreover, economically developed regions such as the European Union have always used engineered wood veneer as the veneer material for furniture.

[0005] The diversification of engineered wood veneer not only enriches the color imagination space of consumers, improves the use value of wood veneer, but also can be customized according to customer needs, endowing more texture to home products, and is known as "derived from nature, better than nature". Engineered wood veneer has unique textures and colors, showing a sense of fashion and texture, and is widely used in modern luxury products, meeting the diversified needs of furniture design, and fully reflecting the beauty of color and texture of engineered wood veneer. Engineered wood veneer has good practicability and applicability, and also meets the needs of different consumers in terms of appearance, which is also an important reason for its market recognition.

[0006] The essence of wood veneer dyeing is the reshaping of its color, including a series of operations such as "fading" treatment, preparing dyes, and allowing the dyes to fully penetrate into the wood veneer. Due to the difference in its production process, there are also some defects in engineered wood veneer, such as color difference, blackheads, cracking, white edges, etc. The most concerned problem is the "color change" problem. Due to the influence of the natural environment, under the irradiation of sunlight ultraviolet rays, the color development system of engineered wood veneer is damaged, resulting in color changes such as fading and yellowing. Summary of the Invention

[0007] The main object of the present invention is a method for preparing yellowing-resistant engineered wood. This method uses bleaching and whitening technologies to obtain yellowing-resistant engineered wood, and the obtained engineered wood veneer can maintain the whitening effect for a long time.

[0008] The present invention adopts the following technical solutions to achieve the above object:

[0009] A method for producing engineered wood using bleaching, whitening, and yellowing resistance technologies, comprising the following steps:

[0010] (1) Sodium silicate mixed solution bleaching: Add hydrogen peroxide, sodium silicate, and sodium hydroxide to soft water, mix evenly to obtain a sodium silicate mixed solution; maintain the temperature of the sodium silicate mixed solution at 50 - 55 °C and the pH value at 9 - 11; place the original color veneer in the sodium silicate mixed solution, bleach for 5 - 6 hours, take it out and place it in an acid pickling tank for acid pickling for 0.5 - 1.5 hours; place the acid - pickled veneer in a soft water tank for water washing for 0.5 - 1.5 hours to obtain the first - level bleached veneer;

[0011] Among them, the acid used in the acid pickling step is one or more of phosphoric acid and acetic acid.

[0012] (2) Bleaching agent bleaching: Add hydrogen peroxide and a bleaching agent to soft water, mix evenly to obtain a bleaching agent solution; maintain the temperature of the bleaching agent solution at 75 - 80 °C and the pH at 9 - 11; place the first - level bleached veneer in the bleaching agent solution, bleach for 6 - 8 hours, take it out and place it in an acid pickling tank for acid pickling for 0.5 - 1.5 hours; place the acid - pickled veneer in a soft water tank for water washing for 0.5 - 1.5 hours to obtain the second - level bleached veneer;

[0013] (3) Whitening agent whitening: Place the whitening agent in water at 90 - 95 °C, dissolve it, maintain the pH at 7 - 8 to obtain a whitening agent solution; place the second - level bleached veneer in the whitening agent solution, heat for 1 - 2 hours, take it out and dry it to obtain the yellowing - resistant engineered wood veneer.

[0014] Furthermore, in step (1), the concentration of hydrogen peroxide is 27.5%, the addition amount of hydrogen peroxide is 10% of the mass of soft water; the addition amount of sodium silicate is 0.15% of the mass of soft water; the addition amount of sodium hydroxide is 0.075% of the mass of soft water.

[0015] In step (2), the concentration of hydrogen peroxide is 27.5%, the addition amount of hydrogen peroxide is 10% of the mass of soft water; the addition amount of the bleaching agent is 1.5% of the mass of soft water.

[0016] In step (3), the addition amount of the whitening agent is 0.2 - 0.5% of the mass of soft water.

[0017] Even further, the bleaching agent comprises the following components in weight ratio: 30 - 45 parts of sodium salicylate, 25 - 40 parts of sodium silicate, 20 - 25 parts of acetic acid, 8 - 10 parts of borate ester;

[0018] The whitening agent contains the following components in weight ratio: 40 - 55 parts of fluorescent whitening agent CXT, 15 - 20 parts of 6,7 - dimethoxycoumarin, 10 - 15 parts of isostearyl isostearate.

[0019] The present invention has the following beneficial effects:

[0020] 1. In the preparation method of the present invention, sodium silicate is first used for bleaching to slightly bleach and decolorize the original color veneer. The red silk threads and red lines in the original color veneer can be bleached and faded. During the bleaching process, a relatively low temperature can play a good protective role for the veneer.

[0021] 2. The present invention further screens the components and ratios of the bleaching agent. The compounded bleaching agent can bleach and fade the blue-stained veneer and black silk veneer at a relatively high temperature, and the whiteness can reach Class 2 - 4. In this way, the natural defects on the veneer of the science and technology wood are reduced, the veneer is fully utilized, and the utilization rate is improved; at the same time, according to the different whitenesses of the bleached veneer, products of various colors can be developed, making the products diversified and suitable for simply preparing light and medium-colored products.

[0022] 3. In the preparation method of the present invention, a step of whitening the bleached veneer with a whitening agent is added, and the components and ratios of the whitening agent are screened, so that the effect of the compounded whitening agent is enhanced. The veneer whitened with the whitening agent can be made into a bleached product without dyeing directly. The whitening process is completed at a relatively high temperature, which can improve the fastness of the whitened veneer. After drying, the whitened veneer is redder than the simply bleached veneer, which can effectively solve the problem of the veneer turning blue in the subsequent preparation process of the bleached veneer.

[0023] 4. In the bleaching agent of the present invention, sodium salicylate, sodium silicate, and acetic acid act synergistically to effectively bleach the veneer, eliminate black spots or stripes, and have good bleaching performance and uniform bleaching. The addition of borate can play a good protective role for the wood fibers in the veneer, reducing the damage of the bleaching agent to the internal fibers of the wood, which is beneficial to the subsequent processing procedures of the bleached veneer; in the whitening agent, a fluorescent whitening agent and 6,7-dimethoxycoumarin act synergistically to whiten the bleached veneer, and the whitening effect is good. Isostearyl isostearate is used as a stabilizer, which is equivalent to adding a protective film on the surface of the whitened veneer, which can prevent the whitened veneer from fading and yellowing during the subsequent process or storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Appendix Figure 1 : Color comparison between the original color veneer and the veneer bleached with sodium silicate solution in Example 1;

[0025] Appendix Figure 2 : Color comparison between the original color veneer and the veneer bleached with the bleaching agent and whitened with the whitening agent in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will be further illustrated below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, various equivalent modifications made by those skilled in the art fall within the scope protected by the claims of this application.

[0027] Example 1 Preparation of Yellowing-resistant Technology Wood

[0028] Bleaching with sodium silicate mixed solution: Add soft water into a 20-ton vat, add hydrogen peroxide with a concentration of 27.5% (the addition amount is 5% of the mass of the soft water), sodium silicate (the addition amount is 0.15% of the mass of the soft water), and sodium hydroxide (the addition amount is 0.075% of the mass of the soft water) into the soft water, mix evenly to obtain a sodium silicate mixed solution; keep the temperature of the sodium silicate mixed solution at 50 °C and the pH value at 11; place the original color veneer in the sodium silicate mixed solution, bleach for 6 hours, take it out and place it in an acid pickling vat for acid pickling with phosphoric acid for 1.5 hours; the acid-pickled veneer is placed in a soft water vat for water washing for 0.5 hours to obtain a first-level bleached veneer;

[0029] Bleaching with bleach: Add soft water into a 20-ton vat, add hydrogen peroxide with a concentration of 27.5% (the addition amount is 10% of the mass of the soft water), bleach (the addition amount is 1.5% of the mass of the soft water, and the bleach contains 45 parts of sodium salicylate, 25 parts of sodium silicate, 25 parts of acetic acid, and 8 parts of borate ester) into the soft water, mix evenly to obtain a bleach solution; keep the temperature of the bleach solution at 75 °C and the pH at 11; place the first-level bleached veneer in the bleach solution, bleach for 8 hours, sample and compare the whiteness according to the bleaching time. After the whiteness reaches the standard, take out the veneer and place it in an acid pickling vat for acid pickling for 1.5 hours; the acid-pickled veneer is placed in a soft water vat for water washing for 0.5 hours to obtain a second-level bleached veneer;

[0030] Whitening with whitening agent: Add soft water into the vat and boil it to 95 °C; weigh 0.5% of the mass of the soft water of the whitening agent (containing 40 parts of fluorescent whitening agent CXT, 20 parts of 6,7-dimethoxycoumarin, and 10 parts of isostearyl isostearate), dissolve the weighed whitening agent in boiling water, pour it into the vat, mix evenly, and keep the pH at 8 to obtain a whitening agent solution; place the second-level bleached veneer in the whitening agent solution, heat and boil for 1 hour, take out the veneer after boiling and dry it to obtain the yellowing-resistant technology wood veneer.

[0031] Example 2 Preparation of Yellowing-resistant Technology Wood

[0032] Sodium silicate mixed solution bleaching: Add soft water into a 20-ton vat, add hydrogen peroxide with a concentration of 27.5% (the addition amount is 5% of the mass of the soft water), sodium silicate (the addition amount is 0.15% of the mass of the soft water), and sodium hydroxide (the addition amount is 0.075% of the mass of the soft water) to the soft water, mix evenly to obtain a sodium silicate mixed solution; keep the temperature of the sodium silicate mixed solution at 55 °C and the pH value at 9; place the original color veneer in the sodium silicate mixed solution, bleach for 5 hours, take it out and place it in an acid pickling vat for pickling with acetic acid for 0.5 hours; the pickled veneer is placed in a soft water vat for water washing for 1.5 hours to obtain first-grade bleached veneer;

[0033] Bleaching agent bleaching: Add soft water into a 20-ton vat, add hydrogen peroxide with a concentration of 27.5% (the addition amount is 10% of the mass of the soft water) and a bleaching agent (the addition amount is 1.5% of the mass of the soft water, and the bleaching agent contains 30 parts of sodium salicylate, 40 parts of sodium silicate, 20 parts of acetic acid, and 10 parts of borate ester) to the soft water, mix evenly to obtain a bleaching agent solution; keep the temperature of the bleaching agent solution at 80 °C and the pH at 9; place the first-grade bleached veneer in the bleaching agent solution, bleach for 6 hours, sample and compare the whiteness according to the bleaching time, after the whiteness reaches, take out the veneer and place it in an acid pickling vat for pickling for 0.5 hours; the pickled veneer is placed in a soft water vat for water washing for 1.5 hours to obtain second-grade bleached veneer;

[0034] Whitening agent whitening: Add soft water into the vat and boil it to 90 °C; weigh a whitening agent (containing 55 parts of fluorescent whitening agent CXT, 15 parts of 6,7-dimethoxycoumarin, and 15 parts of isostearyl isostearate) accounting for 0.2% of the mass of the soft water, dissolve the weighed whitening agent in boiling water, pour it into the vat, mix evenly, and keep the pH at 7 to obtain a whitening agent solution; place the second-grade bleached veneer in the whitening agent solution, heat and boil for 2 hours, take out the boiled veneer and dry it to obtain the yellowing-resistant technology wood veneer.

[0035] Preparation of technology wood for Comparative Example 1

[0036] Sodium silicate mixed solution bleaching: Add soft water into a 20-ton vat, add hydrogen peroxide with a concentration of 27.5% (the addition amount is 5% of the mass of the soft water), sodium silicate (the addition amount is 0.15% of the mass of the soft water), and sodium hydroxide (the addition amount is 0.075% of the mass of the soft water) to the soft water, mix evenly to obtain a sodium silicate mixed solution; keep the temperature of the sodium silicate mixed solution at 50 °C and the pH value at 11; place the original color veneer in the sodium silicate mixed solution, bleach for 6 hours, take it out and place it in an acid pickling vat for pickling with phosphoric acid for 1.5 hours; the pickled veneer is placed in a soft water vat for water washing for 0.5 hours to obtain first-grade bleached veneer;

[0037] Bleaching with bleach: Add soft water into a 20-ton vat, add hydrogen peroxide with a concentration of 27.5% (the addition amount is 10% of the mass of the soft water) and bleach (the addition amount is 1.5% of the mass of the soft water, and the bleach contains 45 parts of sodium salicylate, 25 parts of sodium silicate, 20 parts of anhydrous sodium sulfate, and 15 parts of magnesium sulfate) into the soft water, mix evenly to obtain a bleach solution; keep the temperature of the bleach solution at 75 °C and the pH at 11; place the first-grade bleached veneer in the bleach solution and bleach for 8 hours. Take samples according to the bleaching time to compare the whiteness of the bleach. After the whiteness is reached, take out the veneer and place it in an acid pickling vat for acid pickling for 1.5 hours; place the acid-pickled veneer in a soft water vat for water washing for 0.5 hours to obtain a second-grade bleached veneer.

[0038] Brightening with brightener: Add soft water into the vat and boil it to 95 °C; weigh 0.5% of the fluorescent brightener based on the mass of the soft water, dissolve the weighed brightener in boiling water, pour it into the vat, mix evenly, and keep the pH at 8 to obtain a brightener solution; place the second-grade bleached veneer in the brightener solution, heat and boil for 1 hour, take out the boiled veneer and dry it to obtain the yellowing-resistant technology wood veneer.

[0039] Yellowing-resistant performance test

[0040] Use UVA(340) as the light source, cover the upper half of the technology wood obtained in Example 1, Example 2, and Comparative Example 1, place it in a fluorescent ultraviolet aging machine with a temperature of 60 ± 3 °C, an irradiance of 0.64 W / m2 and dry, and keep continuous light for 240 h throughout the process. After the light exposure, take out each technology wood and compare it with the upper half that has not been exposed to light, and use a color difference meter to measure the color change. The smaller the measured value, the better the yellowing resistance.

[0041] Table 1 Test results of yellowing-resistant performance of each technology wood

[0042] Test item Example 1 Example 2 Comparative example 1 △E* 0.3 0.6 1.3

[0043] In the present invention, the components in the bleach of the present invention act synergistically. First, the veneer is bleached to eliminate black spots or stripes, and it can also play a good protective role for the wood fibers in the veneer, reducing the damage of the bleach to the internal fibers of the wood; the components in the brightener act synergistically to brighten the bleached veneer and add a protective film on the surface of the brightened veneer, which can prevent the brightened veneer from fading and yellowing during subsequent processes or storage. The bleach and brightener in Comparative Document 1 are different from those of the present invention, and the veneer prepared therefrom has poor yellowing resistance and obvious yellowing after light exposure.

Claims

1. A method for producing engineered wood using bleaching, whitening, and yellowing resistance technologies, comprising the following steps: Step (1) Bleaching with sodium silicate mixed solution: Add hydrogen peroxide, sodium silicate, and sodium hydroxide to soft water, mix evenly to obtain a sodium silicate mixed solution; maintain the temperature of the sodium silicate mixed solution at 50 - 55 °C and the pH value at 9 - 11; place the raw veneer in the sodium silicate mixed solution, bleach for 5 - 6 hours, take it out and place it in an acid pickling tank for acid pickling for 0.5 - 1.5 hours; place the acid - pickled veneer in a soft water tank for water washing for 0.5 - 1.5 hours to obtain the first - grade bleached veneer; Step (2) Bleaching with bleach: Add hydrogen peroxide and bleach to soft water, mix evenly to obtain a bleach solution; maintain the temperature of the bleach solution at 75 - 80 °C and the pH at 9 - 11; place the first - grade bleached veneer in the bleach solution, bleach for 6 - 8 hours, take it out and place it in an acid pickling tank for acid pickling for 0.5 - 1.5 hours; place the acid - pickled veneer in a soft water tank for water washing for 0.5 - 1.5 hours to obtain the second - grade bleached veneer; The bleach comprises the following components in weight ratio: 30 - 45 parts of sodium salicylate, 25 - 40 parts of sodium silicate, 20 - 25 parts of acetic acid, and 8 - 10 parts of boric acid ester; Step (3) Whitening with whitening agent: Place the whitening agent in soft water at 90 - 95 °C, dissolve it, and maintain the pH at 7 - 8 to obtain a whitening agent solution; place the second - grade bleached veneer in the whitening agent solution, heat for 1 - 2 hours, take it out and dry it to obtain the yellowing - resistant engineered wood veneer; The whitening agent contains the following components in weight ratio: 40 - 55 parts of fluorescent whitening agent CXT, 15 - 20 parts of 6,7 - dimethoxycoumarin, and 10 - 15 parts of isostearyl isostearate.

2. The method according to claim 1, characterized in that, In step (1), the concentration of hydrogen peroxide is 27.5%, and the addition amount of hydrogen peroxide is 10% of the mass of soft water; the addition amount of sodium silicate is 0.15% of the mass of soft water; the addition amount of sodium hydroxide is 0.075% of the mass of soft water.

3. The method according to claim 1, characterized in that, In step (2), the concentration of hydrogen peroxide is 27.5%, and the addition amount of hydrogen peroxide is 10% of the mass of soft water; the addition amount of bleach is 1.5% of the mass of soft water.

4. The method according to claim 1, wherein In step (3), the addition amount of the whitening agent is 0.2 - 0.5% of the mass of soft water.

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