Light-aging-resistant preparation process and application of wood material

Abstract

The invention discloses a wood material light-aging-resistant preparation process and application thereof. The wood material light-aging-resistant preparation process comprises the following steps that 1, a wood material is soaked in a mixed solution of peroxyformic acid, NaOH, sodium sulfite and NaHCO3; 2, the treated wood material is dried at the room temperature till the water content is lower than 9%, the lignin removal rate is 80%-100%, and after the process, the wood material is in a loose fiber bundle state and is called as micro / cm cellulose; and step 3, soaking the cellulose with micro / centimeter in phenolic resin glue, and then carrying out hot pressing to obtain the photoaging-resistant cellulose plate. According to the application, the cellulose plate is used as a surface plate to cover an outdoor material for shading. A wood material is subjected to delignification treatment to a higher degree, then cellulose and hemicellulose subjected to delignification treatment are subjected to gluing and hot pressing again, the cellulose veneer with good light resistance is formed, and the cellulose veneer is firm, reliable, not prone to falling apart and capable of providing good light shading performance.

Description

Technical Field

[0001] The invention relates to the technical field of light aging resistant materials, in particular to a light aging resistant preparation process of a wood material and application thereof. Background Art

[0002] Wood materials are mainly composed of cellulose, hemicellulose and lignin, and the three major components absorb ultraviolet light to a certain extent. Lignin can absorb 80-95% of the ultraviolet light irradiated to the surface of the material because it contains a large number of active groups and aromatic structures. At the same time, the chemical bond energy of lignin is relatively low and it is easy to be selectively photodegraded. Therefore, under the action of ultraviolet light, the secondary alcohol hydroxyl, carboxyl, aromatic and phenolic groups on the surface lignin of the wood material are easy to form free radicals. The continuous generation of free radicals causes the lignin on the surface of the wood material to be selectively photodegraded, thereby causing the wood material to age due to lignin. For this reason, the publication number CN115781842A discloses a method for preparing a light-resistant wood material and its application in outdoor materials. The scheme is to delignify the wood surface board to obtain a delignified veneer; then the delignified veneer is glued and placed on the surface of the wood inner board, and finally pressed to obtain a light-resistant wood material. Although the scheme discloses the inspiration of sampling delignified veneer as a wood surface board for light resistance, the scheme adopts a mixture of sodium sulfite solution and sodium hydroxide solution for delignification, and the degree of delignification is low, which can only reach about 10-60%. The unremoved lignin in the wood material is similar to the role of adhesive, which will glue cellulose and hemicellulose together, so that the wood material still presents a plate-like structure. Therefore, the scheme is to directly apply glue to the delignified veneer after the delignification process and then hot press it onto the wood core board to form a light-resistant aging material. However, the applicant's experiments have found that this kind of delignified veneer will still be degraded outdoors due to the residual lignin, causing the cellulose and hemicellulose to crack and peel quickly, causing the delignified veneer to fall apart, and ultraviolet light will still penetrate into the wood core board, causing the entire material to age faster. Summary of the invention

[0003] The purpose of the present invention is to provide a preparation process and application of wood material resistant to light aging. The present invention performs a high degree of delignification on the wood material, and then re-glue and hot-press the delignified cellulose and hemicellulose to form a cellulose veneer with good light resistance. The cellulose veneer is firm and reliable, not easy to fall apart, and can provide good light-shielding properties.

[0004] The technical solution of the present invention is a process for preparing wood materials resistant to light aging, comprising the following steps:

[0005] Step 1: soak the wood material in a mixed solution of peroxyformic acid, NaOH, sodium sulfite and NaHCO3 at 20-105°C for 2-24 hours;

[0006] Step 2: Dry the treated wood material at room temperature for 24-48 hours until the moisture content is less than 9% and the lignin removal rate is 80%-100%. After this process, the wood material is in a loose fiber bundle state, which is called micro / cm cellulose;

[0007] Step 3: The micro / cm cellulose is soaked in phenolic resin glue, and then hot-pressed to obtain a light-resistant cellulose board.

[0008] In the above-mentioned process for preparing wood materials resistant to light aging, in step 1, the concentration of NaOH is 3 mol / L, the concentration of sodium sulfite is 1 mol / L, and the concentration of NaHCO3 is 1 mol / L.

[0009] In the aforementioned process for preparing wood materials resistant to light aging, in step 1, the volume ratio of peroxyformic acid, NaOH, sodium sulfite and NaHCO3 is 1:1:1:1.

[0010] In the aforementioned light aging resistant preparation process for wood materials, in step 1, the ambient temperature is 20-40° C. and the treatment time is 8-16 hours.

[0011] In the aforementioned light aging resistant preparation process for wood materials, in step 3, the amount of phenolic resin glue applied is 10-18% of the mass of micro / cm cellulose.

[0012] In the aforementioned process for preparing wood materials resistant to light aging, in step 3, the hot pressing temperature is 140-150 degrees Celsius, and the hot pressing time is 1 mm / minute.

[0013] The aforementioned light aging resistant preparation process for wood materials is applied to use cellulose boards as surface boards to cover outdoor materials for shading.

[0014] In the aforementioned application, the outdoor material includes a wood core board or a bamboo core board, and the cellulose board covers the surface of the wood core board or the bamboo core board.

[0015] In the above application, the cellulose board is sliced ​​to form a cellulose veneer, the bottom surface of the cellulose veneer is glued and covered on the surface of a wood core board or a bamboo core board, and then hot-pressed to obtain a light-resistant composite material.

[0016] In the above application, the glue amount applied to the bottom surface of the cellulose veneer is 14-20% of the total weight of the cellulose veneer and the wood core board or bamboo core board; the hot pressing temperature is 140-150 degrees Celsius, and the hot pressing time is 1mm / minute.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention utilizes a mixed solution of peroxyformic acid, NaOH, sodium sulfite and NaHCO3 to treat wood materials, removes lignin, a component that is easily photodegraded, and has a high degree of delignification, with a removal rate of 80-100%. After this process, the wood material is in a loose fiber bundle state, which is called micro / cm cellulose. Therefore, the present invention uses a glue-applying method to polymerize the cellulose again, and then obtains a cellulose board that is resistant to light aging through hot pressing. The cellulose board obtained by the present invention has a lower lignin content than conventional delignified boards, and the cellulose and hemicellulose are glued together by an adhesive, so that even if the remaining lignin is degraded, the cellulose board will not fall apart, and the integrity of the cellulose board is guaranteed by combining the hot pressing process. In addition, the present application uses a weather-resistant adhesive (phenolic resin glue) to glue the micro / cm cellulose and glue the cellulose veneer to the wood core board. Since the weather-resistant adhesive itself has good opacity and good adhesive strength, the overall material has good stability after gluing. In the present invention, the strong oxidizing property of peroxyformic acid starts the degradation process of lignin, the alkaline environment provided by NaOH promotes the dissolution of lignin and the decomposition of peroxyformic acid, and enhances the delignification ability; sodium sulfite protects cellulose and hemicellulose and assists in the removal of lignin; NaHCO3 adjusts the pH of the solution to create a stable environment for other components to play a role. They cooperate with each other to achieve efficient delignification treatment of wood materials, so that the lignin removal rate in the wood materials reaches 80%-100%, and micro / cm cellulose in the state of loose fiber bundles is obtained, laying a foundation for the subsequent preparation of light-resistant cellulose boards. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the XPS analysis of the cellulose board and common wood material obtained in Example 4;

[0020] Figure 2 The photographs of fresh and 320-hour photo-aged EHL are shown;

[0021] Figure 3 The elemental analysis of fresh and 320 h photoaging EHL is shown;

[0022] Figure 4 The L*, a*, and b* parameter values ​​of EHL during photoaging are shown with error bars;

[0023] Figure 5 A comparison of the EHLΔE changes with and without water spray during the exposure period is shown;

[0024] Figure 6Thermogravimetric and DTG analysis of lignin fresh and after 320 h of photoaging are shown;

[0025] Figure 7 The 3D infrared spectra of the pyrolysis products at a heating rate of 10 °C / min are shown;

[0026] Figure 8 FTIR spectra of lignin pyrolysis products of fresh and aged lignin are shown. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0028] Embodiment 1: A process for preparing a wood material resistant to light aging, comprising the following steps:

[0029] Step 1: using a mixed solution of peroxyformic acid, 3 mol / L NaOH, 1 mol / L sodium sulfite and 1 mol / L NaHCO3 with a volume ratio of 1:1:1:1 to soak the wood material in an environment of 25°C for 24 hours;

[0030] Step 2: Dry the treated wood material at room temperature for 24-48 hours until the moisture content is less than 9%, at which point the lignin removal rate is 87%. After this process, the wood material is in a loose fiber bundle state, which is called micro / cm cellulose;

[0031] Step 3: The micro / cm cellulose is soaked in phenolic resin glue, the amount of phenolic resin glue applied is 13% of the mass of the micro / cm cellulose, and then hot-pressed (hot-pressing temperature is 140-150 degrees Celsius, hot-pressing time is 1mm / minute) to obtain a light-resistant cellulose board with a thickness of 1.5-3cm.

[0032] Embodiment 2: A process for preparing a wood material resistant to light aging, comprising the following steps:

[0033] Step 1: using a mixed solution of peroxyformic acid, 3 mol / L NaOH, 1 mol / L sodium sulfite and 1 mol / L NaHCO3 with a volume ratio of 1:1:1:1 to soak the wood material in an environment of 35°C for 18 hours;

[0034] Step 2: Dry the treated wood material at room temperature for 24-48 hours until the moisture content is less than 9%, at which point the lignin removal rate is 90%. After this process, the wood material is in a loose fiber bundle state, which is called micro / cm cellulose;

[0035] Step 3: The micro / cm cellulose is soaked in phenolic resin glue, the amount of phenolic resin glue applied is 14% of the mass of the micro / cm cellulose, and then hot-pressed (hot-pressing temperature is 140-150 degrees Celsius, hot-pressing time is 1mm / minute) to obtain a light-resistant cellulose board with a thickness of 1.5-3cm.

[0036] Embodiment 3: A process for preparing a wood material resistant to light aging, comprising the following steps:

[0037] Step 1: using a mixed solution of peroxyformic acid, 3 mol / L NaOH, 1 mol / L sodium sulfite and 1 mol / L NaHCO3 with a volume ratio of 1:1:1:1 to soak the wood material in an environment of 55°C for 16 hours;

[0038] Step 2: Dry the treated wood material at room temperature for 24-48 hours until the moisture content is less than 9%, at which point the lignin removal rate is 95%. After this process, the wood material is in a loose fiber bundle state, which is called micro / cm cellulose;

[0039] Step 3: The micro / cm cellulose is soaked in phenolic resin glue, the amount of phenolic resin glue applied is 15% of the mass of the micro / cm cellulose, and then hot-pressed (hot-pressing temperature is 140-150 degrees Celsius, hot-pressing time is 1mm / minute) to obtain a light-resistant cellulose board with a thickness of 1.5-3cm.

[0040] Embodiment 4: A process for preparing a wood material resistant to light aging, comprising the following steps:

[0041] Step 1: using a mixed solution of peroxyformic acid, 3 mol / L NaOH, 1 mol / L sodium sulfite and 1 mol / L NaHCO3 with a volume ratio of 1:1:1:1 to soak the wood material in an environment of 65°C for 14 hours;

[0042] Step 2: Dry the treated wood material at room temperature for 24-48 hours until the moisture content is less than 9%, at which point the lignin removal rate is 99%. After this process, the wood material is in a loose fiber bundle state, which is called micro / cm cellulose;

[0043] Step 3: The micro / cm cellulose is soaked in phenolic resin glue, the amount of phenolic resin glue applied is 16% of the mass of the micro / cm cellulose, and then hot-pressed (hot-pressing temperature is 140-150 degrees Celsius, hot-pressing time is 1mm / minute) to obtain a light-resistant cellulose board with a thickness of 1.5-3cm.

[0044] Embodiment 5: A process for preparing a wood material resistant to light aging, comprising the following steps:

[0045] Step 1: using a mixed solution of peroxyformic acid, 3 mol / L NaOH, 1 mol / L sodium sulfite and 1 mol / L NaHCO3 with a volume ratio of 1:1:1:1 to soak the wood material in an environment of 85°C for 10 hours;

[0046] Step 2: Dry the treated wood material at room temperature for 24-48 hours until the moisture content is less than 9%, at which point the lignin removal rate is 98%. After this process, the wood material is in a loose fiber bundle state, which is called micro / cm cellulose;

[0047] Step 3: The micro / cm cellulose is soaked in phenolic resin glue, the amount of phenolic resin glue applied is 17% of the mass of the micro / cm cellulose, and then hot-pressed (hot-pressing temperature is 140-150 degrees Celsius, hot-pressing time is 1mm / minute) to obtain a light-resistant cellulose board with a thickness of 1.5-3cm.

[0048] Embodiment 6: A process for preparing a wood material resistant to light aging, comprising the following steps:

[0049] Step 1: using a mixed solution of peroxyformic acid, 3 mol / L NaOH, 1 mol / L sodium sulfite and 1 mol / L NaHCO3 with a volume ratio of 1:1:1:1 to soak the wood material in an environment of 100° C. for 10 hours;

[0050] Step 2: Dry the treated wood material at room temperature for 24-48 hours until the moisture content is less than 9%, at which point the lignin removal rate is 96%. After this process, the wood material is in a loose fiber bundle state, which is called micro / cm cellulose;

[0051] Step 3: The micro / cm cellulose is soaked in phenolic resin glue, the amount of phenolic resin glue applied is 16% of the mass of the micro / cm cellulose, and then hot-pressed (hot-pressing temperature is 140-150 degrees Celsius, hot-pressing time is 1mm / minute) to obtain a light-resistant cellulose board with a thickness of 1.5-3cm.

[0052] Example 7: Based on the cellulose board prepared in Example 4, the cellulose board is sliced ​​to obtain a cellulose veneer with a length, width and height of 25mm×20mm×3mm, and then the bottom surface of the cellulose veneer is glued and covered on the surface of a 25mm×20mm×5mm wooden core board, and the amount of glue applied is 16% of the total weight of the cellulose veneer and the wooden core board; then, the hot pressing temperature is 140-150 degrees Celsius, and the hot pressing time is 1mm / minute to obtain a 25mm×20mm×5mm light-resistant composite material.

[0053] Example 8: Based on the cellulose board prepared in Example 4, the cellulose board is sliced ​​to obtain a cellulose veneer with a length, width and height of 25mm×20mm×3mm, and then the bottom surface of the cellulose veneer is glued and covered on the surface of a 25mm×20mm×5mm bamboo core board, and the amount of glue applied is 16% of the total weight of the cellulose veneer and the bamboo core board; then, the hot pressing temperature is 140-150 degrees Celsius, and the hot pressing time is 1mm / minute to obtain a 25mm×20mm×5mm light-resistant composite material.

[0054] Example 9: Based on the cellulose board prepared in Example 4, the cellulose board is sliced ​​to obtain a cellulose veneer with a length, width and height of 25mm×20mm×3mm, and then the bottom surface of the cellulose veneer is glued and covered on the surface of a 25mm×20mm×5mm wooden core board. After the bottom surface of the wooden core board is glued, it is covered on the surface of a 25mm×20mm×5mm wooden bottom board. The amount of glue applied is 20% of the total weight of the cellulose veneer, the wooden core board and the wooden bottom board. Then, at a hot pressing temperature of 140-150 degrees Celsius and a hot pressing time of 1mm / minute, a light-resistant composite material of 25mm×20mm×10mm is obtained.

[0055] Comparative Example 1: The wooden surface board is delignified to obtain a delignified veneer; the delignification treatment is to remove the air in the wooden surface board by vacuuming, and then prepare 6 times the concentration of 0.4 mol / L sodium sulfite solution and 4 times the concentration of 4 mol / L sodium hydroxide solution according to the volume of the wooden surface board, place the wooden surface board in a mixed solution of sodium sulfite solution and sodium hydroxide solution, and then immerse it at 65°C for 2 hours, take it out after immersion, wash it with deionized water, and then repeat the above immersion process 3 times. After testing, the lignin removal rate in the wood material is 60%.

[0056] Comparative Example 2: The wood surface board is subjected to delignification treatment to obtain a delignified veneer; the delignification treatment is to remove the air in the wood surface board by vacuuming, and then prepare 5 times the volume of the wood surface board with a concentration of 0.5 mol / L sodium sulfite solution and 5 times the concentration of 2.5 mol / L sodium hydroxide solution, and place the wood surface board in a mixed solution of the sodium sulfite solution and the sodium hydroxide solution, and then immerse it at 60°C for 1.5 hours, take it out after immersion and wash it with deionized water, and then repeat the above immersion process 3 times. After testing, the lignin removal rate in the wood material is 55%.

[0057] Furthermore, a comparative study was conducted on the cellulose board obtained in Example 4 and ordinary wood materials. Table 1 shows the chromaticity parameters and total color difference of the light-resistant wood materials and the control samples before and after light aging:

[0058]

[0059] Table 1

[0060] It can be seen from Table 1 that after accelerated aging, the color stability of the light aging-resistant wood material of the present invention is significantly improved. In addition, XPS analysis was performed on the cellulose board and ordinary wood material obtained in Example 4. Figure 1 The results show that after accelerated light aging, the chemical structure stability of the light resistant material of Example 4 is significantly improved compared with the ordinary wood of the control group. The C1 (CC and CH bonds) of the control group decreased significantly from 68.9% to 61%, while C2 (CO bond), C3 (C=O bond) and C4 (OC=O bond) increased significantly, increasing by 5.7%, 82.8% and 48.7% respectively. Compared with the control group, the chemical structure stability of the light resistant material of Example 4 is significantly enhanced. After aging, C1 only decreased from 54.28 to 54.26%, C2 showed a slight decrease, and C3 and C4 showed a slight increase.

[0061] Furthermore, in order to prove that lignin is a material that is easily photodegraded in wood materials, the present invention extracted enzymatic hydrolysis lignin (EHL) whose structure is closest to natural lignin, and used a xenon lamp aging box to simulate an outdoor photodegradation environment to study the chemical degradation process of lignin during photodegradation. The present invention conducted experiments on fresh lignin (EHL) and lignin after photoaging. Figure 2 The photos of fresh and 320 hours of light-aged EHL are shown. In the figure, the letter n in EHL-nm is the amount of water applied, and the water applied amounts of 0, 3 and 6 are 0, 0.46 g / g and 0.90 g / g, respectively; m is the accelerated aging time, and 0, 200 and 320 are the accelerated aging times of 0, 200 and 320 h, respectively. Figure 3 The elemental analysis of fresh and 320 h photoaging EHL is shown; Figure 3 The results showed that the C and H contents of photoaged EHLs showed a decreasing trend, while the N content showed an increasing trend, compared with fresh EHLs. Figure 4 Shown are the L*, a*, and b* parameter values ​​of EHL during photoaging with error bars. Figure 5 A comparison of the EHL ΔE changes with and without water spray during exposure is shown, with the maximum ΔE value for EHL-3-320 being 5.46 ± 0.23 (mean ± SD). Figure 6 Thermogravimetric and DTG analyses of fresh and 320 h photo-aged lignin are shown. Figure 7 The 3D infrared spectra of the pyrolysis products at a heating rate of 10 °C / min are shown. Figure 8 FTIR spectra of fresh and aged lignin pyrolysis products are shown ( Figure 8The curves in each figure are 35°C-700°C from bottom to top).

[0062] The above results discuss the physical and chemical evolution of lignin during the photodegradation process, and also prove that lignin is the most photodegradable component in wood materials and the main contributor to the photodegradation of wood materials. Therefore, the present invention uses a mixed solution of peroxyformic acid, NaOH, etc. to remove the easily photodegradable component lignin, and the degree of delignification is high, and the removal rate can reach 80-100%, and at the same time, it produces a light stability enhancement effect on functional groups with low chemical bond energy such as CO in cellulose and hemicellulose. After the present invention removes lignin, the wood material is in a loose fiber bundle state, which is called micro / cm cellulose. Therefore, the present invention uses a sizing method to polymerize cellulose again, and then obtains a cellulose board resistant to light aging through hot pressing. The cellulose board obtained by the present invention has a lower lignin content than the conventional delignified board, and the cellulose and hemicellulose are glued by an adhesive, so even if the residual lignin is degraded, the problem of the cellulose board falling apart will not occur, and the integrity of the cellulose board is guaranteed by combining the hot pressing process. In addition, the present invention adopts a phenolic resin adhesive, which has strong light aging resistance. Therefore, through a series of combinations, the composite material prepared by the present invention has extremely high light aging resistance.

Claims

1. A process for preparing wood materials resistant to light aging, characterized in that: The steps include: Step 1: soak the wood material in a mixed solution of peroxyformic acid, NaOH, sodium sulfite and NaHCO3 at 20-105°C for 2-24 hours; Step 2: Dry the treated wood material at room temperature for 24-48 hours until the moisture content is less than 9% and the lignin removal rate is 80%-100%. After this process, the wood material is in a loose fiber bundle state, which is called micro / cm cellulose; Step 3: The micro / cm cellulose is soaked in phenolic resin glue, and then hot-pressed to obtain a light-resistant cellulose board.

2. The process for preparing wood material resistant to light aging according to claim 1, characterized in that: In step 1, the concentration of NaOH is 3 mol / L, the concentration of sodium sulfite is 1 mol / L, and the concentration of NaHCO3 is 1 mol / L.

3. The process for preparing wood material resistant to light aging according to claim 2, characterized in that: In step 1, the volume ratio of peroxyformic acid, NaOH, sodium sulfite and NaHCO3 is 1:1:1:

1.

4. The process for preparing wood material resistant to light aging according to claim 1, characterized in that: In step 1, the ambient temperature is 20-40° C. and the treatment time is 8-16 hours.

5. The process for preparing wood material resistant to light aging according to claim 1, characterized in that: In step 3, the amount of phenolic resin glue applied is 10-18% of the mass of micro / cm cellulose.

6. The process for preparing wood material resistant to light aging according to claim 1, characterized in that: In step 3, the hot pressing temperature is 140-150 degrees Celsius, and the hot pressing time is 1 mm / minute.

7. Application of the light aging resistant preparation process for wood materials according to any one of claims 1 to 6, characterized in that: Cellulose sheets are used as surface panels for outdoor cladding to block out sunlight.

8. The use according to claim 7, characterized in that: The outdoor material comprises a wood core board or a bamboo core board, and the cellulose board covers the surface of the wood core board or the bamboo core board.

9. The use according to claim 7, characterized in that: The cellulose board is sliced ​​to form a cellulose veneer, and the bottom surface of the cellulose veneer is glued and covered on the surface of a wood core board or a bamboo core board, and then hot-pressed to obtain a light-resistant composite material.

10. The use according to claim 9, characterized in that: The glue application amount on the bottom surface of the cellulose veneer is 14-20% of the total weight of the cellulose veneer and the wood core board or bamboo core board; the hot pressing temperature is 140-150 degrees Celsius, and the hot pressing time is 1mm / minute.

Images