Method for improving color fastness of recombined decorative veneer and high-color-fastness recombined decorative veneer

Abstract

The invention belongs to the technical field of wood dyeing, and provides a method for improving the color fastness of a recombined decorative veneer and the high-color-fastness recombined decorative veneer. The method comprises the following steps that wood veneers are sequentially subjected to bleaching, acid pickling, water washing and drying treatment, and dried veneers are obtained; irradiating the dried veneer by using an ultraviolet lamp or sunlight to obtain a light-treated veneer; and sequentially dyeing and drying the light-treated veneer. According to the method, ultraviolet light or sunlight is utilized to irradiate the bleached dry veneer, chemical bonds of residual lignin, extracts and other substances in the bleached veneer are damaged by the ultraviolet light to form phenolic hydroxyl groups, double bonds, carbonyl groups and other free radicals, and the unsaturated groups change in color under the action of the ultraviolet light; the color change and color fading caused by the influence of illumination and the like after the wood veneer is dyed are avoided. In addition, the bleaching time of the wood veneer is shortened by 1-1.5 h, damage to the structure of the wood veneer is reduced, and the service life of the recombined decoration material is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of wood dyeing, and provides a method for improving the color fastness of a reconstructed decorative veneer and a reconstructed decorative veneer with high color fastness. Background Art

[0002] Reconstructed decorative materials are made of common tree species wood as raw materials, processed into veneers through rotary cutting (or slicing), and then processed through bleaching, dyeing, slicing and other processes. They have the advantages of color, texture and texture of natural precious wood, and reduce the consumption of precious tree species wood. Since reconstructed decorative materials completely retain the natural properties of natural wood such as heat insulation, insulation, temperature regulation and humidity regulation, they are widely used in interior decoration. However, with the continuous improvement of consumption level and demand, the requirements for color fastness of reconstructed decorative materials are also increasing.

[0003] Affected by the natural environment, the color system of reconstructed decorative materials is destroyed in an environment of light, high temperature, and humidity, which will lead to fading, discoloration, and other phenomena. At present, the commonly used method is to improve the color fastness of reconstructed decorative materials by adding ultraviolet absorbers and light stabilizers. After absorbing light energy, ultraviolet absorbers can effectively dissipate the energy generated by radiation, thereby reducing and eliminating the impact of ultraviolet rays on reconstructed decorative materials; however, due to the solubility and molecular weight of ultraviolet absorbers, most ultraviolet absorbers are difficult to immerse into wood veneers during the dyeing process to achieve the effect of improving the color fastness of reconstructed decorative materials. Light stabilizers will generate a particularly stable nitrogen oxide free radical in the environment of light and oxygen. This free radical can react with the highly active free radicals that are oxidized and decomposed in the reconstructed decorative materials, and it will be converted into a relatively stable compound; but light stabilizers have a lifespan, and when they expire, the reconstructed decorative materials will still change color. Therefore, how to effectively improve the color fastness of reconstructed decorative materials is a problem that needs to be solved urgently in this field. Summary of the invention

[0004] In view of this, in order to improve the problem of easy fading and discoloration of existing reconstructed decorative materials, the present invention provides a method for improving the color fastness of reconstructed decorative veneers, comprising the following steps:

[0005] (1) sequentially bleaching, pickling, washing and drying the wood veneer to obtain a dried veneer;

[0006] (2) irradiating the dried veneer with ultraviolet light or sunlight to obtain a light-treated veneer; the energy density of the irradiation is 1400 to 5400 mJ / cm 2 , specifically 1400mJ / cm 2 、1800mJ / cm 2 、2000mJ / cm 2 、2200mJ / cm 2 、2600mJ / cm2 、2800mJ / cm 2 、3000mJ / cm 2 、3200mJ / cm 2 、3600mJ / cm 2 、3800mJ / cm 2 、4000mJ / cm 2 、4200mJ / cm 2 、4600mJ / cm 2 、4800mJ / cm 2 、5000mJ / cm 2 、5200mJ / cm 2 or 5400mJ / cm 2 .

[0007] (3) The light-treated veneer is dyed and dried in sequence to obtain a reconstructed decorative veneer with high color fastness.

[0008] Preferably, the bleaching liquid contains the following components in mass fractions: 20-30% hydrogen peroxide, 15-20% sodium hydroxide, 5-10% sodium silicate, 1-3% magnesium sulfate, and 40-50% water; the bath ratio of the wood veneer and the bleaching liquid is 0.5:10-1:10, and specifically preferably 0.5:10, 0.6:10, 0.7:10, 0.8:10, 0.9:10 or 1:10. Furthermore, in the bleaching solution, the mass fraction of hydrogen peroxide is 25-27.5%, specifically 20%, 22.5%, 25%, 27.5% or 30%; the mass fraction of sodium hydroxide is 16-17%, specifically 15%, 16%, 17%, 18%, 19% or 20%; the mass fraction of sodium silicate is 6-9%, specifically 5%, 6%, 7%, 8%, 9% or 10%; the mass fraction of magnesium sulfate is 1.5-2.5%, specifically 1%, 1.5%, 2%, 2.5% or 3%; the mass fraction of water is 45-48%, specifically 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50%.

[0009] Preferably, the bleaching temperature is 60-70°C, specifically preferably 60°C, 62°C, 64°C, 65°C, 66°C, 68°C or 70°C; the bleaching time is 4-6h, specifically preferably 4h, 5h, 5.5h or 6h.

[0010] In the present invention, the anions of hydrogen peroxide in the bleaching solution react with the chromophoric groups such as carbonyl groups and double bonds in the wood veneer to break the side chains, so as to avoid the subsequent discoloration problem of these chromophoric groups; a long bleaching time will damage the structure of the wood veneer, and controlling the bleaching time to 4 to 6 hours can reduce the structural damage to the wood veneer and extend the service life of the wood veneer.

[0011] 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 minutes, specifically 20 minutes, 25 minutes or 30 minutes.

[0012] Preferably, the water washing temperature is room temperature, and the time is 5 to 15 minutes; further, the water washing time is preferably 5 minutes, 10 minutes or 15 minutes.

[0013] Acid washing and water washing of the bleached wood veneer can remove most of the peroxides remaining in the wood veneer and the oxygen-containing free radicals generated during the bleaching process, reducing the impact of the residual peroxides on the dyeing and color fastness of the wood veneer.

[0014] Preferably, the drying treatment temperature is 85-95°C, and the time is 4-10 min. Further, the drying treatment temperature is preferably 85°C, 90°C or 95°C; the drying treatment time is preferably 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min. In the present invention, the drying treatment is preferably carried out in a dryer.

[0015] Preferably, the wavelength of the ultraviolet lamp is 320-400 nm.

[0016] After drying, the wood veneer still contains lignin and extracts. The energy of ultraviolet rays can destroy the chemical bonds of lignin and extracts to form active free radicals, such as phenolic hydroxyl groups, aromatic skeletons, double bonds and carbonyl groups. At the same time, hemicellulose also contains oxygen-containing free radicals such as carbonyl groups. These colored unsaturated compounds will further form new aromatic and other phenoxy free radicals under the action of ultraviolet rays. The phenoxy free radicals are converted into quinone structures, causing color changes on the wood surface.

[0017] The present invention utilizes ultraviolet light or sunlight to irradiate the dried veneer, and uses ultraviolet light to destroy the chemical bonds of the remaining lignin and extracts in the wood veneer in advance to form free radicals such as phenolic hydroxyl, double bonds and carbonyl. These unsaturated groups, including the carbonyl contained in hemicellulose, change color in advance under the action of ultraviolet light, thereby avoiding discoloration and fading caused by light after the wood veneer is dyed.

[0018] The present invention induces active free radicals in the bleached veneer in advance that will change color under light conditions. Compared with the traditional addition of additives such as light absorbers and free radical scavengers, the present invention avoids the problem of decreased color fastness after the life of the additives, eliminates the problems of local discoloration and fading of the veneer caused by uneven distribution of the additives, and significantly improves the color fastness of the wood veneer.

[0019] Preferably, the dye used for dyeing includes one or more of yellow dye, red dye, blue dye and purple dye; the yellow dye is more preferably acid yellow 42; the red dye is more preferably acid red 37, the blue dye is more preferably acid blue 90, and the purple dye is more preferably acid purple 48. In the present invention, in the dye solution used for dyeing, the concentration of the yellow dye is preferably 0.01 to 6 g / L, the concentration of the red dye is preferably 0.01 to 6 g / L, the concentration of the blue dye is preferably 0.01 to 6 g / L, and the concentration of the purple dye is preferably 0.01 to 6 g / L.

[0020] Preferably, the dyeing temperature is 90-98°C, and the dyeing time is 3-8h. Further, the dyeing temperature is preferably 90°C, 92°C, 94°C, 95°C, 96°C or 98°C, and the dyeing time is preferably 3h, 4h, 5h, 6h, 7h or 8h.

[0021] The present invention does not impose any specific limitation on the drying parameters, as long as the moisture content of the final high color fastness reconstructed decorative veneer is ensured to be 8-12%.

[0022] The present invention combines bleaching and ultraviolet irradiation. Compared with the conventional method for improving color fastness, the veneer needs to be immersed in an aqueous solution of a nitroxide free radical compound, an acetic anhydride solution, a Bianstone powder particle, etc. for pretreatment before dyeing, a composite regulator is added to the dye solution, and a light stabilizer is used for color fixation and light resistance treatment after dyeing. The present invention does not need to perform steps such as pretreatment, adding auxiliary agents, and light resistance curing treatment during the dyeing process, thereby simplifying the dyeing process and reducing the consumption of auxiliary agents, steam, electric energy, etc.

[0023] The present invention provides a high color fastness reconstructed decorative veneer prepared by the above technical solution, wherein the water content of the high color fastness reconstructed decorative veneer is 8-12%, and the light fastness is greater than or equal to grayscale card level 4.

[0024] The high color fastness reconstructed decorative veneer of the present invention improves color fastness while requiring little change in the dyeing formula, and is easy to operate in the actual production process.

[0025] Beneficial effects:

[0026] The method of the present invention induces active free radicals in the bleached wood veneer in advance that will change color under the action of ultraviolet rays. Compared with the traditional addition of additives such as light absorbers and free radical scavengers, the method avoids the problem of decreased color fastness after the life of the additives expires, eliminates the problems of local discoloration and fading of the veneer caused by uneven distribution of the additives, and significantly improves the color fastness of the veneer.

[0027] Compared with the conventional method for improving color fastness, the wood veneer needs to be pretreated by immersing it in an aqueous solution of nitroxide free radical compounds, an acetic anhydride solution, Bianstone powder particles, etc. before dyeing, a composite regulator is added to the dye solution, and a light stabilizer is used to perform color fixation and light resistance treatment after dyeing. The method of the present invention does not require the steps of pretreatment, adding auxiliary agents, and light resistance curing treatment during the dyeing process, thereby simplifying the dyeing process and reducing the consumption of auxiliary agents, steam, electric energy, etc.

[0028] The light color fastness of the high color fastness wood veneer obtained by the method of the present invention is greater than or equal to gray card level 4.

[0029] The method of the present invention improves color fastness while requiring little change to the dye solution formula, and is convenient to operate in the actual production process.

[0030] The method of the invention reduces the bleaching time, can reduce the damage to the wood veneer structure, and prolongs the service life of the reconstructed decorative material. DETAILED DESCRIPTION

[0031] The method for improving the color fastness of the reconstructed decorative veneer and the high color fastness reconstructed decorative veneer provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0032] Example 1

[0033] (1) The wood veneer is immersed in a bleaching solution (comprising the following components by mass fraction: 30% hydrogen peroxide, 15% sodium hydroxide, 9% sodium silicate, 1% magnesium sulfate, and 45% water) at a bath ratio of 1:10, bleached at 60°C for 5 hours, taken out, pickled in an acetic acid solution with a pH value of 6 for 20 minutes, taken out, washed with water for 10 minutes, and dried in a dryer at a temperature of 85°C for 4 minutes to obtain a dried veneer.

[0034] (2) Use ultraviolet light (wavelength 320-400nm) to irradiate the dried veneer with an energy density of 1800mJ / cm 2 , and obtain a light-processed single board.

[0035] (3) Dyeing the light-treated veneer in a dye solution at a temperature of 90° C. for 4 hours, and then drying to a moisture content of 8% to obtain a reconstructed decorative veneer with high color fastness; the dye solution includes acid yellow 42 (0.02 g / L), acid red 37 (0.03 g / L), acid blue 90 (0.08 g / L) and water.

[0036] Example 2

[0037] (1) The wood veneer is immersed in a bleaching solution (comprising the following components by mass fraction: 27.5% hydrogen peroxide, 16% sodium hydroxide, 7% sodium silicate, 1.5% magnesium sulfate, and 48% water) at a bath ratio of 1:10, bleached at 65°C for 5.5 hours, then taken out, pickled in an acetic acid solution with a pH value of 6 for 25 minutes, taken out, washed with water for 10 minutes, and dried in a dryer at a temperature of 90°C for 5 minutes to obtain a dried veneer.

[0038] (2) Use ultraviolet light (wavelength 320-400nm) to irradiate the dried veneer with an energy density of 3600mJ / cm 2 , and obtain a light-processed single board.

[0039] (3) Dyeing the light-treated veneer in a dye solution at a temperature of 95° C. for 5 hours, and then drying to a moisture content of 10% to obtain a reconstructed decorative veneer with high color fastness; the dye solution includes acid yellow 42 (0.19 g / L), acid red 37 (0.09 g / L), acid blue 90 (0.20 g / L) and water.

[0040] Example 3

[0041] (1) The wood veneer is immersed in a bleaching solution (comprising the following components by mass fraction: 25% hydrogen peroxide, 17% sodium hydroxide, 6% sodium silicate, 2% magnesium sulfate, and 50% water) at a bath ratio of 1:10, bleached at 70°C for 6 hours, taken out, pickled in an acetic acid solution with a pH value of 6 for 30 minutes, taken out, washed with water for 15 minutes, and dried in a dryer at a temperature of 95°C for 6 minutes to obtain a dried veneer.

[0042] (2) Use ultraviolet light (wavelength 320-400nm) to irradiate the dried veneer with an energy density of 5400mJ / cm 2 , and obtain a light-processed single board.

[0043] (3) Dyeing the light-treated veneer in a dye solution at a temperature of 95° C. for 6 hours, and then drying to a moisture content of 12% to obtain a reconstructed decorative veneer with high color fastness; the dye solution includes acid yellow 42 (1.82 g / L), acid red 37 (1.05 g / L), acid blue 90 (2.55 g / L) and water.

[0044] Comparative Example 1

[0045] The difference from Example 1 is that step (2) is omitted, that is, no ultraviolet light irradiation is performed.

[0046] Comparative Example 2

[0047] The difference from Example 2 is that step (2) is omitted, that is, no ultraviolet light irradiation is performed.

[0048] Comparative Example 3

[0049] The difference from Example 3 is that step (2) is omitted, that is, no ultraviolet light irradiation is performed.

[0050] Example 4

[0051] The difference from Example 1 is that the bleaching time is 4 h and the irradiation energy density is 1400 mJ / cm 2 .

[0052] Example 5

[0053] The difference from Example 2 is that the bleaching time is 4.5 h and the irradiation energy density is 2800 mJ / cm 2 .

[0054] Example 6

[0055] The difference from Example 3 is that the bleaching time is 4.5 h and the irradiation energy density is 4200 mJ / cm 2 .

[0056] The samples obtained in the embodiment and the comparative example were tested for light fastness according to GB / T 28999-2012 "Reconstructed Decorative Veneer", and the samples obtained in the embodiment and the comparative example were tested for color difference according to GB / T250-2008. The results are shown in Tables 1 and 2.

[0057] Table 1 Performance test results of samples obtained from Examples 1 to 3 and Comparative Examples 1 to 3

[0058] project Color fastness / grade Color difference value Dyeing rate (%) Example 1 5 0.17 30 Example 2 4.5 0.92 32 Example 3 4 1.84 28 Comparative Example 1 3.5 2.25 23 Comparative Example 2 3.5 2.56 22 Comparative Example 3 3 3.24 20

[0059] As can be seen from Table 1, compared with the untreated veneer, the dried veneer is irradiated with ultraviolet light to induce the color change of the color-changing group in advance, so that the color fastness of the obtained recombinant decorative veneer is improved by 1 to 1.5 levels. The color fastness of the sample is compared with the corresponding color difference value in the standard, and the test results of the color fastness and the color difference value are consistent; and the dyeing rate of the recombinant decorative veneer prepared by the present invention is significantly better than that of the recombinant decorative veneer obtained in the comparative example.

[0060] Table 2 Performance test results of samples obtained in Examples 4 to 6

[0061] project Color difference value Color fastness / grade Example 4 0.15 5 Example 5 0.84 4.5 Example 6 1.63 4

[0062] The final color of the dried veneer after ultraviolet irradiation will always be yellowish. From Table 2 about Examples 1 to 3 and Examples 4 to 6, it can be seen that reducing the bleaching time by 1 to 1.5 hours can reduce the energy density required to make the final color of the bleached veneer close to the same, and the color fastness level that the dyed veneer can finally achieve remains unchanged. In summary, the present invention irradiates the dried veneer with ultraviolet light or light treatment to induce the color change of the color-changing group in advance, which can improve the color fastness of the reconstructed decorative material by 1 to 1.5 levels, and the dyeing rate is also improved. In addition, the bleaching time of the wood veneer can be reduced by 1 to 1.5 hours, which reduces the damage to the structure of the wood veneer and prolongs the service life of the high color fastness reconstructed decorative veneer.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for improving the color fastness of a reconstructed decorative veneer, characterized in that: The following steps are involved: The wood veneer is sequentially bleached, pickled, washed and dried to obtain a dried veneer; The dried veneer is irradiated with ultraviolet light or sunlight to obtain a light-treated veneer; the energy density of the irradiation is 1400 to 5400 mJ / cm 2 ; The light-treated veneer is dyed and dried in sequence to obtain a reconstructed decorative veneer with high color fastness.

2. The method according to claim 1, characterized in that The bleaching liquid contains the following components in mass fraction: 20-30% hydrogen peroxide, 15-20% sodium hydroxide, 5-10% sodium silicate, 1-3% magnesium sulfate and 40-50% water.

3. The method according to claim 2, characterized in that The bath ratio of the wood veneer and the bleaching liquid is 0.5:10 to 1:

10.

4. The method according to claim 1, 2 or 3, characterized in that: The bleaching temperature is 60-70° C. and the bleaching time is 4-6 hours.

5. The method according to claim 1, characterized in that The pickling reagent is a phosphoric acid solution or an acetic acid solution; the pH value of the pickling reagent is 5 to 6; the pickling temperature is room temperature, and the pickling time is 20 to 30 minutes.

6. The method according to claim 1, characterized in that The water washing temperature is room temperature and the washing time is 5 to 15 minutes.

7. The method according to claim 1, characterized in that The drying process is carried out at a temperature of 85 to 95° C. and for a time of 4 to 10 minutes.

8. The method according to claim 1, characterized in that The wavelength of the ultraviolet lamp is 320-400nm.

9. The method according to claim 1, characterized in that: The dye used for dyeing includes one or more of yellow dye, red dye, blue dye and purple dye; The dyeing temperature is 90-98° C. and the dyeing time is 3-8 hours.

10. The high color fastness reconstructed decorative veneer prepared by the method according to any one of claims 1 to 9, characterized in that: The water content of the high color fastness reconstructed decorative veneer is 8-12%.