Ultraviolet-yellowing-resistant delignification veneer and preparation method thereof

Abstract

The invention discloses a delignification veneer resistant to ultraviolet yellowing and a preparation method of the delignification veneer. The method comprises the following steps that firstly, a veneer is immersed in an alkaline sodium sulfite solution, vacuum treatment is conducted, then boiling is conducted, an alkaline delignification veneer is prepared, and residual chemical reagents on the delignification veneer are washed away through deionized water; and secondly, cooking the cleaned alkali delignification veneer by using an acidic sodium chlorite solution until the sample becomes white to obtain an acid-alkali combined treated delignification veneer, cleaning the delignification veneer by using deionized water, and freeze-drying the sample to obtain the ultraviolet yellowing resistant delignification veneer. According to the delignification veneer resistant to ultraviolet yellowing and the preparation method of the delignification veneer, the wood delignification efficiency can be improved, and the ultraviolet yellowing resistance of the wood veneer is remarkably improved. The ultraviolet-resistant delignification veneer disclosed by the invention can be widely applied to the fields of reconstituted decorative materials, dyed veneers, novel composite materials and the like, and is particularly suitable for occasions with relatively high requirements on light resistance and attractiveness.

Description

Technical Field

[0001] The invention relates to a delignified veneer resistant to ultraviolet yellowing and a preparation method thereof, belonging to the technical field of wood modification and functional materials. Background Art

[0002] As a natural and renewable material, wood has good mechanical properties and beautiful appearance. It is widely used in construction, furniture, decoration, cultural relics restoration and other functional materials. However, components in wood, such as lignin, are prone to photodegradation under ultraviolet light, producing yellow or brown degradation products, resulting in obvious yellowing on the wood surface. Especially when exposed to outdoor environment or strong ultraviolet light for a long time, the yellowing problem of wood is more significant, which not only affects the appearance of wood, but also reduces its long-term stability and durability, thus limiting the application of wood in high-end decoration and functional materials.

[0003] In order to solve this problem, delignification treatment has become a common method to improve the appearance of wood and enhance its resistance to UV yellowing. Delignification can effectively remove the lignin component in wood, reduce the yellowing tendency of wood, and enhance the optical properties of wood. However, existing delignification treatment methods still face some technical challenges. Although these methods can remove a certain amount of lignin, the treated wood will still turn yellow under ultraviolet light, and its resistance to UV yellowing is limited, making it difficult to meet the requirements of high-end wood products for color stability and durability. Therefore, the development of a delignification treatment method that can effectively remove lignin and improve the resistance to UV yellowing of wood has become a technical problem that needs to be solved urgently in the field of wood modification.

[0004] In view of the above problems, the present invention proposes a UV-yellowing-resistant delignified veneer and a preparation method thereof. By adopting an acid-base combined treatment method, the color stability and yellowing resistance of wood under ultraviolet light can be significantly improved. This technology can not only effectively reduce the yellowing phenomenon caused by ultraviolet light, but also broaden the application scope of wood in the fields of reconstituted decorative materials, dyed veneer and new composite materials, and has important application prospects and market value. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a delignified veneer resistant to ultraviolet yellowing and a preparation method thereof, which can effectively reduce the yellowing phenomenon caused by ultraviolet light and improve its weather resistance and long-term use stability.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A transparent wood material resistant to ultraviolet yellowing and a preparation method thereof, comprising the following steps: firstly, immersing a veneer in an alkaline sodium sulfite solution for vacuum impregnation and then boiling it to prepare alkali delignified balsa wood, and then washing it with deionized water; secondly, boiling the alkali delignified balsa wood with an acidic sodium chlorite solution to obtain delignified balsa wood treated with acid and alkali, and then freeze-drying the sample after washing to obtain a delignified veneer material resistant to ultraviolet yellowing.

[0008] The method is characterized in that: the wood is first subjected to alkaline delignification treatment, in which the concentration of sodium hydroxide is 1.5-3 mol / L and the concentration of sodium sulfite is 0.2-0.4 mol / L in the alkaline sodium sulfite solution; vacuum impregnation treatment is first performed, with a vacuum degree of -0.01-0.1 MPa for 30-60 min; boiling is then continued for 2-3 h; the alkali delignified light wood is repeatedly washed with deionized water to remove residual chemicals; then acidic delignification treatment is performed, with a sodium chlorite concentration of 1-3 wt%, a pH value of about 4-5, and a solution temperature of 75-90°C, and the sample is boiled until it turns white for about 2-3 h, and then washed with deionized water and freeze-dried for storage.

[0009] Beneficial effects of the present invention: The present invention effectively removes lignin through a combined acid-base treatment method, significantly improving the resistance of wood to UV yellowing, allowing it to maintain a stable color under long-term UV irradiation and reduce yellowing. The treated delignified veneer has a uniform color and beautiful appearance, and can maintain a natural tone for a long time, and is particularly suitable for high-end decoration and artistic wood products. In addition, the delignification treatment enhances the light transmittance of the wood, providing the possibility for high value-added applications such as transparent wood and optical functional materials. The process of the present invention is optimized, the light aging resistance of the wood is improved, and its application range in high-end furniture, architectural decoration and functional composite materials is broadened. DETAILED DESCRIPTION

[0010] The present invention is further described in detail below in conjunction with implementation examples. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

[0011] Example 1

[0012] The 2mm balsa wood veneer was immersed in an alkaline sodium sulfite solution, wherein the sodium hydroxide concentration was 2.5mol / L and the sodium sulfite concentration was 0.4mol / L, and vacuum treatment was performed, the vacuum treatment time was 30min, and the vacuum degree was -0.1Mpa, and then the reactor was boiled, the mixed solution in the reactor was kept boiling, and the mixed solution in the reactor was kept boiling for 2h to obtain alkali-treated delignified balsa wood, and the alkali-treated delignified wood was repeatedly cleaned with deionized water; secondly, it was boiled with an acidic sodium chlorite solution, wherein the sodium chlorite concentration was 1wt%, and the pH value was adjusted to about 4.6 with glacial acetic acid, and the solution was kept boiled at 80℃ until the sample color turned white, the time was about 2h, and then it was repeatedly cleaned with deionized water, and the freeze-dried sample was obtained to obtain delignified balsa wood treated with acid and alkali. UV light (wavelength 365nm) was irradiated for 12h, and the color difference changed by 3.62 compared with the blank sample.

[0013] Example 2

[0014] 3mm birch veneer was immersed in an alkaline sodium sulfite solution, wherein the sodium hydroxide concentration was 2.0mol / L and the sodium sulfite concentration was 0.6mol / L, and vacuum treatment was performed, the vacuum treatment time was 45min, and the vacuum degree was -0.1Mpa, and then the reactor was boiled, the mixed solution in the reactor was kept boiling, and the mixed solution in the reactor was kept boiling for 3h, and the alkali-treated delignified birch veneer was obtained, and the alkali-treated delignified veneer was repeatedly cleaned with deionized water; secondly, it was boiled with an acidic sodium chlorite solution, wherein the sodium chlorite concentration was 1wt%, and the pH value was adjusted to about 4.6 with glacial acetic acid, and the solution was kept boiled at 80℃ until the sample color turned white, the time was about 2h, and then it was repeatedly cleaned with deionized water, and the freeze-dried sample was obtained to obtain the delignified birch veneer treated with acid and alkali. UV lamp (wavelength 365nm) was irradiated for 12h, and the color difference changed by 3.08 compared with the blank sample.

[0015] Example 3

[0016] 3mm poplar veneer was immersed in alkaline sodium sulfite solution, wherein the concentration of sodium hydroxide was 1.5mol / L and the concentration of sodium sulfite was 0.4mol / L, and vacuum treatment was performed, the vacuum treatment time was 45min, and the vacuum degree was -0.1Mpa, and then the reactor was boiled, the mixed solution in the reactor was kept boiling, and the mixed solution in the reactor was kept boiling for 3h, and the alkali-treated delignified birch veneer was obtained, and the alkali-treated delignified veneer was repeatedly cleaned with deionized water; secondly, it was boiled with acidic sodium chlorite solution, wherein the concentration of sodium chlorite was 2wt%, and the pH value was adjusted to about 5.0 with glacial acetic acid, and the solution was kept boiled at 75℃ until the sample color turned white, the time was about 3h, and then it was repeatedly cleaned with deionized water, and the freeze-dried sample was obtained to obtain the delignified poplar veneer treated with acid and alkali. UV lamp (wavelength 365nm) was irradiated for 12h, and the color difference changed by 2.35 compared with the blank sample.

[0017] 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 UV-resistant delignified veneer and a preparation method thereof, characterized in that: The method comprises the following steps: firstly, immersing a veneer in an alkaline sodium sulfite solution, first subjecting it to vacuum treatment, then boiling it to prepare an alkaline delignified veneer, and washing the alkaline delignified veneer with deionized water to wash away residual chemical reagents; secondly, using an acidic sodium chlorite solution to steam the cleaned alkaline delignified veneer until the sample turns white to obtain a delignified veneer treated with acid and alkali combined treatment, and then washing it with deionized water and freeze-drying the sample to obtain a UV-resistant yellowing delignified veneer.

2. The ultraviolet yellowing resistant delignified veneer and the preparation method thereof according to claim 1, characterized in that: The wood can be balsa wood, poplar, birch, white sycamore, etc., with a thickness of 0.5mm to 3mm.

3. The ultraviolet yellowing resistant delignified veneer and the preparation method thereof according to claim 1, characterized in that: In the alkaline sodium sulfite solution, the concentration of sodium hydroxide is 1.5-3 mol / L, and the concentration of sodium sulfite is 0.2-0.6 mol / L.

4. The ultraviolet yellowing resistant delignified veneer and the preparation method thereof according to claim 1, characterized in that: The vacuum treatment time of the single board treatment is 30 to 60 minutes, and the vacuum degree is -0.01 to -0.1 MPa.

5. The ultraviolet yellowing resistant delignified veneer and the preparation method thereof according to claim 1, characterized in that: When the veneer is treated with alkali, the mixed solution is kept boiling for 2 to 3 hours.

6. The ultraviolet yellowing resistant delignified veneer and the preparation method thereof according to claim 1, characterized in that: Acidic sodium chlorite solution, sodium chlorite concentration is 1-3wt%, pH value is about 4-5.

7. The ultraviolet yellowing resistant delignified veneer and the preparation method thereof according to claim 1, characterized in that: During the single plate acid treatment, the mixed solution temperature is maintained at 75-90°C until the sample is boiled and turns white, which lasts for about 2-3 hours.

8. A UV-resistant delignified veneer, characterized in that: The veneer is prepared by the method for preparing a UV yellowing resistant delignified veneer as described in any one of claims 1 to 7.