Lignin-based adhesive and preparation method thereof

Abstract

The invention provides a lignin-based adhesive and a preparation method thereof, and relates to the field of adhesives. The method is used for wood bonding and production of shaving boards, laminated boards, fiberboards and the like and comprises the following steps of 1, room-temperature degreasing, specifically, materials are placed at the degreasing position, extraction is carried out according to the volume ratio of the materials to benzene-ethanol being 2: 1, then drying treatment is carried out, 2, grinding is carried out, specifically, dried wood powder is ground for a long time, cell structures of wood are destroyed, and the wood is obtained. 3, extracting and concentrating: extracting for multiple times by using dioxane and water according to a ratio of 9: 1, and then concentrating the extracting solution, and 4, obtaining crude lignin: drying the treated material to obtain crude lignin accounting for 50-70% of the lignin in the raw material. By using the path trend mechanism and the erasing mechanism, the added aluminum sulfate belongs to multivalent metal salt, so that the water resistance of the lignin-based adhesive can be improved, the lignin-based adhesive is more practical, and the application range is wider.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and particularly to a lignin-based adhesive and a preparation method thereof. Background Art

[0002] As time goes on, as an important source of industrial raw materials at the present stage, petroleum, coal, etc. are showing a decreasing trend, which poses a severe challenge to future industrial production. However, people's requirements for greenness will not decrease accordingly. With the rapid development of the economy, products such as wooden furniture and floors have entered thousands of households, which puts higher requirements on the environmental protection performance of wood materials, and wood adhesives are the most important among them.

[0003] When the applicant applied for the present invention, after retrieval, it was found that a Chinese patent disclosed a "lignin-based formaldehyde-free adhesive and a preparation method thereof", and its application number was "201610482289.4". This patent mainly synthesizes the lignin-based formaldehyde-free adhesive without using formaldehyde as a raw material, greatly reducing the formaldehyde release amount of the artificial board pressed with the adhesive of the present invention, which is beneficial to the environment and human health. The lignin-based formaldehyde-free adhesive uses glutaraldehyde as a cross-linking agent, which can form a tight cross-linked structure between polyvinyl alcohol and lignin, enhancing the bonding strength of the artificial board pressed with the adhesive of the present invention. However, this invention did not innovate in the water resistance of the lignin-based formaldehyde-free adhesive. Therefore, the present invention focuses on the water resistance of the lignin-based formaldehyde-free adhesive and solves the problem of insufficient water resistance of the lignin-based formaldehyde-free adhesive. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] Aiming at the deficiencies of the prior art, the present invention provides a lignin-based adhesive and a preparation method thereof, which solves the problem of insufficient water resistance of the lignin-based formaldehyde-free adhesive.

[0006] (2) Technical Solutions

[0007] To achieve the above object, the present invention is realized through the following technical solutions: A lignin-based adhesive and a preparation method thereof, including the following steps:

[0008] Step 1: Degreasing at room temperature: Place the material at the degreasing location, extract it with a volume ratio of the material to benzene-ethanol of 2:1, and then perform a drying treatment;

[0009] Step 2: Grinding: Grind the dried wood powder for a long time to destroy the cell structure of the wood;

[0010] Step 3: Extraction and concentration: Extract it multiple times with a ratio of dioxane to water of 9:1, and then concentrate the extract;

[0011] Step 4: Obtain crude lignin: Dry the treated material to obtain crude lignin accounting for 50%-70% of the lignin in the raw material;

[0012] Step 5: Oil bath: Enzymatically hydrolyze the lignin, then weigh the dried enzymatically hydrolyzed lignin and mix it with an acidic dioxane and water mixture. After shaking and mixing evenly, carry out reflux and extraction under a nitrogen atmosphere;

[0013] Step 6: Filter and neutralize: Let the product obtained in Step 5 stand and filter, wash it with a dioxane and water mixture, collect the filtrate, and then concentrate it;

[0014] Step 7: Inject acid: Inject a large amount of acidic deionized water into the concentrated solution to precipitate lignin;

[0015] Step 8: Clean: Wash and dry the precipitated lignin to obtain lignin;

[0016] Step 9: Mix and make glue: Add aluminum sulfate to the lignin, and co-condense the lignin with phenol formaldehyde or mix it with phenolic resin to make glue. Directly mix it with phenolic (PF) resin to make glue, and after ultrafiltration, mix it with PF to make Kraeex glue, and use it in combination with PF resin after hydroxymethylation modification.

[0017] Preferably, place the material in a degreasing area, extract it with a volume ratio of material to benzene-ethanol of 2:1, and then carry out a drying treatment to preliminarily process the raw material for subsequent operations.

[0018] Preferably, place the dried wood powder in a vibrating ball mill and grind it for 48 hours or more to destroy the cell structure of the wood. Thorough grinding can improve the extraction rate of lignin, increase output, and reduce cost consumption.

[0019] Preferably, extract it multiple times with dioxane and water in a ratio of 9:1 for 48 hours or more. Then add a small amount of benzene to the extract to precipitate the sugar-containing substances in the extract, and then filter. Then concentrate the filtrate using a rotary evaporator to remove the impurities inside the solution for subsequent operations.

[0020] Preferably, dry the treated material, control the drying temperature at 40 degrees to obtain crude lignin accounting for 50%-70% of the lignin in the raw material, preliminarily obtain crude lignin, and then carry out subsequent operations. Operating step by step is conducive to large-scale production.

[0021] Preferably, the lignin is enzymatically hydrolyzed, and then the dried enzymatically hydrolyzed lignin is weighed and mixed with an acidic dioxane and water mixture. After shaking and mixing evenly, it is refluxed and extracted in a nitrogen atmosphere at 80-90 °C for two hours to refine the crude lignin and improve the quality of the lignin.

[0022] Preferably, the product obtained in the previous step is allowed to stand and filtered, washed with a dioxane and water mixture, the filtrate is collected, and then concentrated to remove some residues in the solution, ensuring the quality of the lignin.

[0023] Preferably, a large amount of acidic deionized water with a pH of 2 is injected into the concentrated solution to precipitate the lignin, further optimizing the lignin and improving the quality of the final lignin.

[0024] Preferably, the precipitated lignin is washed and dried, and finally washed with n-hexane to further optimize the lignin and improve the quality of the final lignin.

[0025] Preferably, aluminum sulfate is added to the lignin, and the lignin is co-condensed with phenol formaldehyde or mixed with phenolic resin to make glue. It is directly mixed with phenolic (PF) resin to make glue, mixed with PF after ultrafiltration to make Kraeex glue, and used in combination with PF resin after hydroxymethylation modification, increasing the water resistance of the lignin-based adhesive and improving the quality of the lignin-based adhesive.

[0026] Working principle: Place the material at the degreasing position, extract it with the volume ratio of the material to benzene-ethanol being 2:1, and then conduct drying treatment. Place the dried wood powder in a vibrating ball mill and grind it for 48 hours or more to destroy the cell structure of the wood. Extract it multiple times with dioxane and water in a ratio of 9:1, and the extraction time is 48 hours or more. Then add a small amount of benzene to the extract to precipitate the sugar-containing substances in the extract, and then filter. Then concentrate the filtrate using a rotary evaporator. Dry the treated material, control the drying temperature at 40 degrees, and crude lignin accounting for 50%-70% of the lignin in the raw material can be obtained. Enzymatically hydrolyze the lignin, and then weigh the dried enzymatically hydrolyzed lignin and a mixed solution of acidic dioxane and water. After shaking and mixing evenly, carry out nitrogen atmosphere reflux and extraction for two hours in an environment of 80-90 degrees. Let the product obtained in the previous step stand and filter, wash it with a mixed solution of dioxane and water, collect the filtrate, and then concentrate it. Inject a large amount of acidic deionized water with a pH of 2 into the concentrated solution to precipitate lignin. Wash and dry the precipitated lignin, and finally wash it with n-hexane. Add aluminum sulfate to the lignin, and conduct co-condensation of lignin with phenol formaldehyde or mix it with phenolic resin to make glue. Directly mix it with phenolic (PF) resin to make glue, and after ultrafiltration, mix it with PF to make Kraeex glue. After hydroxymethylation modification, it can be used in combination with PF resin.

[0027] (III) Beneficial effects

[0028] The present invention provides a lignin-based adhesive and its preparation method. It has the following beneficial effects:

[0029] 1. When making glue by mixing with lignin, the methyl phenolic resin has better chemical affinity with lignin in terms of structure. Especially in the initial stage of the reaction, it contains a large amount of hydroxymethyl groups, and its cross-linking copolymerization reaction activity with lignin is better. Based on the mixing principle, the phenolic resin with the most suitable performance should be selected to match with lignin.

[0030] 2. The added aluminum sulfate belongs to a polyvalent metal salt, which can improve the water resistance of the lignin-based adhesive, making the lignin-based adhesive more practical and having a wider applicable range.

[0031] 3. Place the wood powder in a vibrating ball and grind it for no less than 48 hours to destroy the cell structure of the wood, increase the output of lignin, and reduce the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the preparation process of a lignin-based adhesive and its preparation method proposed by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] Example 1:

[0035] As Figure 1 shown, the embodiments of the present invention provide a lignin-based adhesive and a preparation method thereof, including the following steps:

[0036] Step 1: Degreasing at room temperature: Place the material at the degreasing location, extract it with a volume ratio of the material to benzene-ethanol of 2:1, and then perform a drying treatment;

[0037] Step 2: Grinding: Grind the dried wood powder for a long time to destroy the cell structure of the wood;

[0038] Step 3: Extraction and concentration: Extract multiple times with dioxane and water in a ratio of 9:1, and then concentrate the extract;

[0039] Step 4: Obtaining crude lignin: Dry the treated material to obtain crude lignin accounting for 50%-70% of the lignin in the raw material;

[0040] Step 5: Oil bath: Enzymatically hydrolyze the lignin, then weigh the dried enzymatically hydrolyzed lignin and mix it evenly with an acidic mixture of dioxane and water, and then perform reflux and extraction under a nitrogen atmosphere;

[0041] Step 6: Filtration and neutralization: Let the product obtained in Step 5 stand for filtration, wash it with a mixture of dioxane and water, collect the filtrate, and then concentrate it;

[0042] Step 7: Acid injection: Inject a large amount of acidic deionized water into the concentrated solution to precipitate lignin;

[0043] Step 8: Cleaning: Wash and dry the precipitated lignin to obtain lignin;

[0044] Step 9: Mixing and glue making: Add aluminum sulfate to the lignin, and co-condense the lignin with phenol formaldehyde or mix it with phenolic resin to make glue. Directly mix it with phenolic (PF) resin to make glue, mix it with PF after ultrafiltration to make Kraeex glue, and use it in combination with PF resin after hydroxymethylation modification.

[0045] Example 2:

[0046] The differences between this embodiment and the first embodiment are as follows: The material is placed at the degreasing position, and extraction is carried out with the volume ratio of the material to benzene-ethanol being 2:1, and then drying treatment is carried out. The dried wood powder is placed in a vibrating ball mill and ground for 48 hours or more to destroy the cell structure of the wood. It is extracted multiple times with dioxane and water in a ratio of 9:1, and the extraction time is 48 hours or more. Then, a small amount of benzene is added to the extract to precipitate the sugar-containing substances in the extract, and then filtration is carried out. The filtrate is then concentrated using a rotary evaporator. The treated material is dried, and the drying temperature is controlled at 40 °C to obtain crude lignin accounting for 50%-70% of the lignin in the raw material. The lignin is enzymatically hydrolyzed, and then the dried enzymatically hydrolyzed lignin and a mixed solution of acidic dioxane and water are weighed. After shaking and mixing evenly, nitrogen atmosphere reflux and extraction are carried out in an environment of 80-90 °C for two hours. The product obtained in the previous step is allowed to stand and filtered, washed with a mixed solution of dioxane and water, and the filtrate is collected and then concentrated. A large amount of acidic deionized water with a pH of 2 is injected into the concentrated solution to precipitate lignin. The precipitated lignin is washed and dried, and finally washed with n-hexane. Aluminum sulfate is added to the lignin, and the lignin is co-condensed with phenol formaldehyde or mixed with phenolic resin to make glue. It is directly mixed with phenolic (PF) resin to make glue, and after ultrafiltration, it is mixed with PF to make Kraeex glue, and after hydroxymethylation modification, it is used in combination with PF resin.

[0047] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A lignin-based adhesive and its preparation method, characterized in that, It includes the following steps: Step 1: Degreasing at room temperature: Place the material at the degreasing location, extract it with a volume ratio of the material to benzene-ethanol of 2:1, and then conduct a drying treatment; Step 2: Grinding: Grind the dried wood powder for a long time to destroy the cell structure of the wood; Step 3: Extraction and concentration: Extract multiple times with a ratio of dioxane to water of 9:1, and then concentrate the extract; Step 4: Obtain crude lignin: Dry the treated material to obtain crude lignin accounting for 50%-70% of the lignin in the raw material; Step 5: Oil bath: Enzymatically hydrolyze the lignin, then weigh the dried enzymatically hydrolyzed lignin and mix it with an acidic mixture of dioxane and water, shake and mix evenly, and then conduct nitrogen atmosphere reflux and extraction; Step 6: Filtration and neutralization: Let the product obtained in Step 5 stand for filtration, wash it with a mixture of dioxane and water, collect the filtrate, and then concentrate it; Step 7: Inject acid: Inject a large amount of acidic deionized water into the concentrated solution to precipitate lignin; Step 8: Cleaning: Wash and dry the precipitated lignin to obtain lignin; Step 9: Mixing and making glue: Add aluminum sulfate to the lignin, and co-condense the lignin with phenol formaldehyde or mix it with phenolic resin to make glue. Directly mix it with phenolic (PF) resin to make glue, after ultrafiltration, mix it with PF to make Kraeex glue, and use it in combination with PF resin after hydroxymethylation modification.

2. The lignin-based adhesive and its preparation method according to claim 1, characterized in that: The step of placing the material at the degreasing location, extracting it with a volume ratio of the material to benzene-ethanol of 2:1, and then conducting a drying treatment.

3. A lignin-based adhesive and its preparation method according to claim 1, characterized in that: The step of placing the dried wood powder in a vibrating ball mill and grinding it for 48 hours or more to destroy the cell structure of the wood.

4. A lignin-based adhesive and its preparation method according to claim 1, characterized in that: The step of extracting multiple times with a ratio of dioxane to water of 9:1, with the extraction time being 48 hours or more, then adding a small amount of benzene to the extract to precipitate the sugar-containing substances in the extract, then filtering, and then concentrating the filtrate using a rotary evaporator.

5. The lignin-based adhesive and its preparation method according to claim 1, characterized in that: The step of drying the treated material, controlling the drying temperature at 40 degrees, to obtain crude lignin accounting for 50%-70% of the lignin in the raw material.

6. The lignin-based adhesive and its preparation method according to claim 1, characterized in that: The step of enzymatically hydrolyzing the lignin, then weighing the dried enzymatically hydrolyzed lignin and mixing it with an acidic mixture of dioxane and water, shaking and mixing evenly, and conducting nitrogen atmosphere reflux and extraction for two hours in an environment of 80-90 degrees.

7. A lignin-based adhesive and its preparation method according to claim 1, characterized in that: The step of letting the product obtained in the previous step stand for filtration, washing it with a mixture of dioxane and water, collecting the filtrate, and then concentrating it.

8. A lignin-based adhesive and its preparation method according to claim 1, characterized in that: The step of injecting a large amount of acidic deionized water with a pH of 2 into the concentrated solution to precipitate lignin.

9. The lignin-based adhesive and its preparation method according to claim 1, characterized in that: The step of washing and drying the precipitated lignin, and finally washing it with n-hexane.

10. A lignin-based adhesive and its preparation method according to claim 1, characterized in that: The step of adding aluminum sulfate to the lignin, and co-condensing the lignin with phenol formaldehyde or mixing it with phenolic resin to make glue. Directly mix it with phenolic (PF) resin to make glue, after ultrafiltration, mix it with PF to make Kraeex glue, and use it in combination with PF resin after hydroxymethylation modification.

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