A method for preparing an environmentally friendly fiber board by using laccase and microbial treatment

Abstract

The present invention discloses a method for preparing an environmentally friendly fiber board by using laccase and microorganisms. First, attapulgite powder, hexametaphosphate calcium, and a silane coupling agent are added to water and mixed. Then, after heating and reacting, filtration is carried out to obtain precipitate A. Peracrylate, potassium persulfate, and sodium bicarbonate are added to water. Then, after drying and pulverizing precipitate A, it is added. Then, after heating and reacting and filtering again, precipitate B is obtained. After washing precipitate B, vacuum drying and pulverizing are carried out to obtain modified attapulgite powder. Laccase, white rot fungus, and modified attapulgite powder are added to water and stirred and mixed. Then, lignin is added and mixed evenly. Then, after reacting and treating at 60-70 °C, epoxy resin is added and the reaction continues to obtain an adhesive. Wood fibers and the adhesive are mixed and sized, then dried and paved to obtain a board blank, and then the board blank is hot-pressed to obtain an environmentally friendly fiber board. The present invention solves the problems of uneven mechanical strength and large differences in dimensional stability existing in environmentally friendly fiber boards.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection fiberboards, and particularly relates to a method for preparing environmental protection fiberboards by using laccase and microorganisms. Background Art

[0002] Lignin mainly contains elements C, H, O, and N, and is widely distributed in plant cell walls, middle lamellae, and secondary walls. The main function of lignin in plants is "adhesion", forming a stable cross-linked system together with cellulose and hemicellulose, constituting the main structure of the plant skeleton, and playing a role in bearing the self-weight of plants and resisting external forces. However, due to the complex molecular structure of lignin and the influence of its various functional groups, the processing and utilization of lignin are hindered. Researchers at home and abroad have treated and modified lignin by physical, chemical, and biological methods to achieve the modification of the structure and function of lignin, and used it in fields such as surfactants, dye dispersants, synthetic tanning agents, activated carbon, carbon fibers, wood ceramics, and lignin-synthetic polymer blends.

[0003] Laccase (Laccases, Lac) is a polyphenol oxidase that can degrade lignin, and it is widely present in fungi, plants, and some insects. Laccase can catalyze lignin to produce phenoxy radicals, and further cross-linking reactions between the radicals produce a complex sugar complex, which can bond lignin, cellulose, and hemicellulose together to achieve gluing. Therefore, laccase can be used to catalyze the oxidation of lignin to prepare adhesives and be used in the production of new environmental protection artificial fiber materials. During the production process, no toxic chemical raw materials such as formaldehyde need to be added, and there is no problem of release of toxic gases and harmful substances. However, there are still technical problems such as uneven mechanical strength and large differences in dimensional stability in environmental protection wood fiber products manufactured using bio-enzyme activation technology. Summary of the Invention

[0004] Aiming at the above deficiencies, the present invention discloses a method for preparing environmental protection fiberboards by using laccase and microorganisms, which solves the problems of uneven mechanical strength and large differences in dimensional stability existing in environmental protection fiberboards.

[0005] The present invention is realized by adopting the following technical scheme:

[0006] A method for preparing environmental protection fiberboards by using laccase and microorganisms, which comprises the following steps:

[0007] (1)Weigh attapulgite powder and calcium hexametaphosphate according to the mass ratio of attapulgite powder, calcium hexametaphosphate and water being (8 - 10):(0.2 - 0.3):100, add them to water and mix evenly. Then add a silane coupling agent, where the mass ratio of the silane coupling agent to attapulgite powder is (0.01 - 0.03):1. Then add acetic acid to adjust the pH to 5.0 - 6.0, and then heat to 75 - 85 °C and react at a constant temperature for 1 - 2 h. Then naturally cool to room temperature, and then filter to obtain precipitate A. Weigh acrylate, potassium persulfate, sodium bicarbonate and water according to the mass ratio of (8 - 10):(0.2 - 0.3):(0.5 - 0.8):100, add acrylate, potassium persulfate and sodium bicarbonate to water and mix evenly to obtain a mixed solution. Then dry and crush precipitate A and add it to the mixed solution, where the mass ratio of precipitate A to acrylate is 1:(8 - 10). Then stir and mix for 10 - 15 min, then continue to stir and heat to 55 - 65 °C and react at a constant temperature for 1 - 2 h. Then filter to obtain precipitate B, wash precipitate B with ethanol 2 - 3 times, and then vacuum dry and crush to obtain modified attapulgite powder;

[0008] (2)Weigh laccase and white rot fungus according to the mass ratio of laccase, white rot fungus and water being (2 - 5):(1 - 3):100, add them to water and mix evenly to obtain a composite bacterial solution. Then add the modified attapulgite powder obtained in step (1) and stir and mix at a speed of 50 - 100 r / min for 10 - 15 min, where the mass ratio of the modified attapulgite powder to the composite bacterial solution is (1 - 2):10. Then add lignin and mix evenly, where the mass ratio of lignin to the modified attapulgite powder is (2 - 3):1. Then react and treat at 60 - 70 °C for 8 - 16 h, and then add epoxy resin and react at 65 - 75 °C for 1 - 2 h to obtain an adhesive, where the mass ratio of lignin to epoxy resin is (2 - 5):1;

[0009] (3)Take wood fibers and mix them with the adhesive obtained in step (2), where the mass ratio of the wood fibers to the adhesive is 10:(1 - 1.2). Dry the wood fibers after mixing with the adhesive until the moisture content is 8 - 10%, and then perform paving to obtain a board blank. Then hot press the board blank to obtain an environmentally friendly fiber board.

[0010] The lignin is one or more of alkali lignin, acetic acid lignin, sulfate lignin and papermaking black liquor lignin. The wood fibers are obtained by crushing, cooking and softening, hot grinding, and drying one or more of straw, pine wood, and eucalyptus wood.

[0011] Further, in step (1), the particle size of the attapulgite powder is 100 - 120 mesh.

[0012] Further, in step (1), the precipitate A is dried, pulverized, sieved through a 200-300 mesh sieve, and then added to the mixed solution.

[0013] Further, in step (1), the silane coupling agent is an amino silane coupling agent; the acrylate is any one or a combination of two of methyl acrylate and ethyl acrylate.

[0014] Further, in step (1), after the precipitate A is dried and pulverized, it is added to the mixed solution, and then stirred and mixed at a speed of 100-300 r / min for 10-15 min.

[0015] Further, in step (3), the wood fibers after sizing are dried at a temperature of 60-80 °C until the moisture content is 8-10%.

[0016] Further, in step (3), the temperature of the hot pressing is 160-240 °C, the hot pressing time is 3-5 min, and the hot pressing pressure is 1-7 MPa.

[0017] The present technical solution has the following beneficial effects compared with the prior art:

[0018] 1. In the present invention, acrylate and attapulgite powder are mixed and crosslinked to obtain modified attapulgite powder. The modified attapulgite powder has better hydrophobicity, reducing its solubility in water. Then, laccase and white rot fungi are mixed to prepare a composite bacterial solution, and the modified attapulgite powder is added to adsorb laccase and white rot fungi. Then, lignin is added, so that lignin interacts with laccase and white rot fungi to generate phenoxy radicals, and further crosslinking reactions occur between the radicals to produce a complex sugar complex. This complex can bond lignin, cellulose, and hemicellulose together to achieve gluing, thus acting as an adhesive. The attapulgite powder modified with acrylate can promote the dispersion of lignin, improve the contact between laccase and white rot fungi and lignin, and promote their interaction. At the same time, the modified attapulgite powder adsorbs and immobilizes laccase, improving the stability and heat resistance of laccase, enabling laccase to act on lignin at a higher temperature condition, and the higher temperature can improve the reaction efficiency and shorten the production time. The white rot fungi adsorbed by the modified attapulgite powder can degrade and soften lignin, synergistically act with laccase, promote the degradation of lignin to produce phenoxy radicals and further crosslink to obtain a sugar complex with adhesive properties. In addition, adding a certain amount of attapulgite powder as a filler to the fiberboard can improve the fire resistance and mechanical properties of the fiberboard.

[0019] 2. The lignin product obtained by treating with laccase and white-rot fungi is mixed and copolymerized with epoxy resin in the present invention to obtain a composite adhesive, which further improves the gluing performance of the adhesive. Moreover, the compatibility between components is good, which is beneficial to sizing on wood fibers, can be evenly coated on the surface of wood fibers, and can be evenly heated during the subsequent hot pressing process to obtain a better curing effect. Detailed implementation mode

[0020] The present invention is further illustrated by the following examples, but it is not limited to the present invention. The specific experimental conditions and methods not specified in the following examples are usually conventional means well-known to those skilled in the art.

[0021] Example 1: A method for preparing an environmentally friendly fiber board by treating with laccase and microorganisms, which comprises the following steps:

[0022] (1) According to the mass ratio of attapulgite powder, calcium hexametaphosphate and water of 9:0.25:100, weigh attapulgite powder and calcium hexametaphosphate and add them to water to mix evenly. Then add a silane coupling agent, and the mass ratio of the silane coupling agent to attapulgite powder is 0.02:1. Then add acetic acid to adjust the pH to 5.5, and then heat to 80 °C and react at a constant temperature for 1.5 h. Then cool naturally to room temperature, and then filter to obtain precipitate A. According to the mass ratio of acrylate, potassium persulfate, sodium bicarbonate and water of 9:0.25:0.6:100, weigh acrylate, potassium persulfate and sodium bicarbonate and add them to water to mix evenly to obtain a mixed solution. Then add precipitate A after drying, crushing and passing through a 250-mesh sieve to the mixed solution, and the mass ratio of precipitate A to acrylate is 1:9. Then stir and mix at a speed of 200 r / min for 12 min, then continue to stir and heat to 60 °C and react at a constant temperature for 1.5 h, and then filter to obtain precipitate B. Wash precipitate B with ethanol twice, and then vacuum dry and crush to obtain modified attapulgite powder. The particle size of the attapulgite powder is 110 mesh. The silane coupling agent is an amino silane coupling agent. The acrylate is ethyl acrylate.

[0023] (2) According to the mass ratio of laccase, white-rot fungi and water of 3.5:2:100, weigh laccase and white-rot fungi and add them to water to mix evenly to obtain a composite bacterial solution. Then add the modified attapulgite powder obtained in step (1) and stir and mix at a speed of 80 r / min for 12 min. The mass ratio of the modified attapulgite powder to the composite bacterial solution is 1.2:10. Then add lignin and mix evenly. The mass ratio of lignin to the modified attapulgite powder is 2.2:1. Then react and treat at 65 °C for 10 h, and then add epoxy resin and react at 70 °C for 1.5 h to obtain an adhesive. The mass ratio of lignin to epoxy resin is 3.5:1.

[0024] (3) Take wood fibers and mix them with the adhesive obtained in step (2). The mass ratio of the wood fibers to the adhesive is 10:1.1. Dry the wood fibers after mixing with the adhesive at a temperature of 65°C until the moisture content is 9%, then perform paving to obtain a board blank, and then hot press the board blank to obtain an environmentally friendly fiber board. The temperature of the hot pressing is 200°C, the hot pressing time is 4 minutes, and the hot pressing pressure is 3 MPa.

[0025] Example 2: A method for preparing an environmentally friendly fiber board by using laccase and microbial treatment, which comprises the following steps:

[0026] (1) According to the mass ratio of attapulgite powder, hexametaphosphate and water of 8:0.2:100, weigh attapulgite powder and hexametaphosphate and add them to water and mix evenly. Then add a silane coupling agent. The mass ratio of the silane coupling agent to the attapulgite powder is 0.01:1. Then add acetic acid to adjust the pH to 5.0, then heat to 75°C and react at a constant temperature for 1 hour. Then naturally cool to room temperature, and then filter to obtain precipitate A. According to the mass ratio of acrylate, potassium persulfate, sodium bicarbonate and water of 8:0.2:0.5:100, weigh acrylate, potassium persulfate and sodium bicarbonate and add them to water and mix evenly to obtain a mixed solution. Then add the dried and pulverized precipitate A passed through a 200-mesh sieve to the mixed solution. The mass ratio of the precipitate A to the acrylate is 1:8. Then stir and mix at a speed of 100 r / min for 10 minutes. Then continue to stir and heat to 55°C and react at a constant temperature for 1 hour. Then filter to obtain precipitate B, wash precipitate B twice with ethanol, and then vacuum dry and pulverize to obtain modified attapulgite powder. The particle size of the attapulgite powder is 100 mesh. The silane coupling agent is an amino silane coupling agent. The acrylate is a combination of methyl acrylate and ethyl acrylate.

[0027] (2) According to the mass ratio of laccase, white rot fungus and water of 2:1:100, weigh laccase and white rot fungus and add them to water and mix evenly to obtain a composite bacterial solution. Then add the modified attapulgite powder obtained in step (1) and stir and mix at a speed of 50 r / min for 10 minutes. The mass ratio of the modified attapulgite powder to the composite bacterial solution is 1:10. Then add lignin and mix evenly. The mass ratio of the lignin to the modified attapulgite powder is 2:1. Then react and treat at 60°C for 8 hours. Then add epoxy resin and react at 65°C for 1 hour to obtain an adhesive. The mass ratio of the lignin to the epoxy resin is 2:1.

[0028] (3) Take wood fibers and mix them with the adhesive obtained in step (2). The mass ratio of the wood fibers to the adhesive is 10:1. Dry the wood fibers after mixing with the adhesive at a temperature of 60°C until the moisture content is 8%, then perform paving to obtain a board blank, and then perform hot pressing on the board blank to obtain an environmentally friendly fiber board. The temperature of the hot pressing is 160°C, the hot pressing time is 3 minutes, and the hot pressing pressure is 1 MPa.

[0029] Example 3: A method for preparing an environmentally friendly fiber board by using laccase and microbial treatment, which includes the following steps:

[0030] (1) Weigh attapulgite powder and calcium hexametaphosphate according to the mass ratio of attapulgite powder, calcium hexametaphosphate and water of 9.5:0.28:100, add them to water and mix evenly. Then add a silane coupling agent. The mass ratio of the silane coupling agent to the attapulgite powder is 0.02:1. Then add acetic acid to adjust the pH to 5.5, then heat to 82°C and react at a constant temperature for 1.5 h. Then naturally cool to room temperature, and then filter to obtain precipitate A. Weigh acrylate, potassium persulfate, sodium bicarbonate and water according to the mass ratio of 8.5:0.26:0.75:100, add acrylate, potassium persulfate and sodium bicarbonate to water and mix evenly to obtain a mixed solution. Then dry and crush precipitate A through a 250-mesh sieve and add it to the mixed solution. The mass ratio of precipitate A to acrylate is 1:9.5. Then stir and mix at a speed of 200 r / min for 12 min. Then continue to stir and heat to 58°C and react at a constant temperature for 1.5 h. Then filter to obtain precipitate B, wash precipitate B with ethanol 3 times, and then vacuum dry and crush to obtain modified attapulgite powder. The particle size of the attapulgite powder is 100 mesh. The silane coupling agent is an amino silane coupling agent. The acrylate is methyl acrylate.

[0031] (2) Weigh laccase and white rot fungi according to the mass ratio of laccase, white rot fungi and water of 4:2.2:100, add them to water and mix evenly to obtain a composite bacterial solution. Then add the modified attapulgite powder obtained in step (1) and stir and mix at a speed of 80 r / min for 12 min. The mass ratio of the modified attapulgite powder to the composite bacterial solution is 1.2:10. Then add lignin and mix evenly. The mass ratio of lignin to the modified attapulgite powder is 2.5:1. Then react and treat at 68°C for 12 h. Then add epoxy resin and react at 70°C for 1.5 h to obtain an adhesive. The mass ratio of lignin to epoxy resin is 4:1.

[0032] (3) Take the wood fiber and mix it with the adhesive obtained in step (2). The mass ratio of the wood fiber to the adhesive is 10:1.15. Dry the wood fiber after mixing the adhesive at a temperature of 70 °C until the moisture content is 8.5%. Then, perform paving to obtain a board blank, and then perform hot pressing on the board blank to obtain an environmentally friendly fiber board. The temperature of the hot pressing is 180 °C, the hot pressing time is 3.5 min, and the hot pressing pressure is 6 MPa.

[0033] Example 4: A method for preparing an environmentally friendly fiber board by using laccase and microbial treatment, which includes the following steps:

[0034] (1) According to the mass ratio of attapulgite powder, hexametaphosphate and water of 10:0.3:100, weigh attapulgite powder and hexametaphosphate and add them to water and mix evenly. Then, add a silane coupling agent. The mass ratio of the silane coupling agent to the attapulgite powder is 0.03:1. Then, add acetic acid to adjust the pH to 6.0. Then, heat to 85 °C and react at a constant temperature for 2 h. Then, naturally cool to room temperature, and then filter to obtain precipitate A. According to the mass ratio of acrylate, potassium persulfate, sodium bicarbonate and water of 10:0.3:0.8:100, weigh acrylate, potassium persulfate and sodium bicarbonate and add them to water and mix evenly to obtain a mixed solution. Then, dry and crush precipitate A through a 300-mesh sieve and add it to the mixed solution. The mass ratio of precipitate A to acrylate is 1:10. Then, stir and mix at a speed of 300 r / min for 15 min. Then, continue to stir and heat to 65 °C and react at a constant temperature for 2 h. Then, filter to obtain precipitate B. Wash precipitate B with ethanol 3 times. Then, perform vacuum drying and crushing to obtain modified attapulgite powder. The particle size of the attapulgite powder is 120 mesh. The silane coupling agent is an amino silane coupling agent. The acrylate is methyl acrylate.

[0035] (2) According to the mass ratio of laccase, white rot fungus and water of 5:3:100, weigh laccase and white rot fungus and add them to water and mix evenly to obtain a composite bacterial solution. Then, add the modified attapulgite powder obtained in step (1) and stir and mix at a speed of 100 r / min for 15 min. The mass ratio of the modified attapulgite powder to the composite bacterial solution is 2:10. Then, add lignin and mix evenly. The mass ratio of lignin to the modified attapulgite powder is 3:1. Then, react and treat at 70 °C for 16 h. Then, add epoxy resin and react at 75 °C for 2 h to obtain an adhesive. The mass ratio of lignin to epoxy resin is 5:1.

[0036] (3) Take wood fibers and mix them with the adhesive obtained in step (2). The mass ratio of the wood fibers to the adhesive is 10:1.2. Dry the mixed wood fibers at a temperature of 80 °C until the moisture content is 10%. Then, perform paving to obtain a board blank, and then perform hot pressing on the board blank to obtain an environmentally friendly fiber board. The temperature of the hot pressing is 240 °C, the hot pressing time is 5 minutes, and the hot pressing pressure is 7 MPa.

[0037] Comparative Example 1: The difference between the method for preparing an environmentally friendly fiber board by using laccase and microorganisms described in this comparative example and the method described in Example 1 is only that step (1) is omitted, and modified attapulgite powder is not added in step (2). Instead, laccase, white rot fungus, and water are directly mixed and then lignin is added for treatment.

[0038] Comparative Example 2: The difference between the method for preparing an environmentally friendly fiber board by using laccase and microorganisms described in this comparative example and the method described in Example 1 is only that step (1) is omitted without modifying the attapulgite powder. At the same time, in step (2), laccase, white rot fungus, and water are directly mixed, and then attapulgite powder and lignin are added for treatment.

[0039] Comparative Example 3: The difference between the method for preparing an environmentally friendly fiber board by using laccase and microorganisms described in this comparative example and the method described in Example 1 is only that white rot fungus is not used in step (2).

[0040] Experimental Example: Prepare fiber boards according to the methods described in Examples 1 to 4 and Comparative Examples 1 to 3. Then, perform performance testing on the obtained fiber boards according to the national standard for medium density fiber boards in GB / T 11718-2021. The specific results are shown in Table 1.

[0041] Table 1 Performance testing results of fiber boards

[0042]

[0043] It can be seen from the above data that the internal bond strength of the fiber board obtained by the method of the present invention has been significantly improved, and there are also certain improvements in waterproof and mechanical properties. Moreover, the present invention does not use formaldehyde-containing adhesives, and there are no problems of toxic gas and harmful substance release.

[0044] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing an environment-friendly fiber board by using laccase and microorganisms, characterized in that: It includes the following steps: (1) According to the mass ratio of attapulgite powder, calcium hexametaphosphate and water being (8-10):(0.2-0.3):100, weigh attapulgite powder and calcium hexametaphosphate, add them to water and mix evenly. Then add a silane coupling agent, and the mass ratio of the silane coupling agent to attapulgite powder is (0.01-0.03):

1. Then add acetic acid to adjust the pH to 5.0-6.0, and then heat to 75-85 °C and react at a constant temperature for 1-2 h. Then naturally cool to room temperature, and then filter to obtain precipitate A; According to the mass ratio of acrylate, potassium persulfate, sodium bicarbonate and water being (8-10):(0.2-0.3):(0.5-0.8):100, weigh acrylate, potassium persulfate and sodium bicarbonate, add them to water and mix evenly to obtain a mixed solution. Then dry and crush precipitate A and add it to the mixed solution. The mass ratio of precipitate A to acrylate is 1:(8-10). Then stir and mix for 10-15 min, and then continue to stir and heat to 55-65 °C and react at a constant temperature for 1-2 h. Then filter to obtain precipitate B, wash precipitate B with ethanol 2-3 times, and then vacuum dry and crush to obtain modified attapulgite powder; (2) According to the mass ratio of laccase, white rot fungus and water being (2-5):(1-3):100, weigh laccase and white rot fungus, add them to water and mix evenly to obtain a composite bacterial solution. Then add the modified attapulgite powder obtained in step (1) and stir and mix at a speed of 50-100 r / min for 10-15 min. The mass ratio of the modified attapulgite powder to the composite bacterial solution is (1-2):

10. Then add lignin and mix evenly. The mass ratio of lignin to the modified attapulgite powder is (2-3):

1. Then react and treat at 60-70 °C for 8-16 h, and then add epoxy resin and react at 65-75 °C for 1-2 h to obtain an adhesive. The mass ratio of lignin to epoxy resin is (2-5):1; (3) Take wood fibers and mix them with the adhesive obtained in step (2). The mass ratio of the wood fibers to the adhesive is 10:(1-1.2). Dry the glued wood fibers until the moisture content is 8-10%, and then perform paving to obtain a board blank. Then hot press the board blank to obtain an environment-friendly fiber board.

2. The method for preparing an environment-friendly fiber board by using laccase and microorganisms according to claim 1, characterized in that: In step (1), the particle size of the attapulgite powder is 100-120 mesh.

3. The method for preparing an environment-friendly fiber board by using laccase and microorganisms according to claim 1, characterized in that: In step (1), precipitate A is dried, crushed, passed through a 200-300 mesh sieve and then added to the mixed solution.

4. The method for preparing an environment-friendly fiber board by using laccase and microorganisms according to claim 1, characterized in that: In step (1), the silane coupling agent is an amino silane coupling agent; the acrylate is any one or a combination of two of methyl acrylate and ethyl acrylate.

5. The method for preparing an environment-friendly fiber board by using laccase and microorganisms according to claim 1, characterized in that: In step (1), the precipitate A is then dried and pulverized and added to the mixed solution, and then stirred and mixed at a speed of 100-300 r / min for 10-15 min.

6. The method for preparing an environment-friendly fiber board by using laccase and microorganisms according to claim 1, characterized in that: In step (3), the glued wood fibers are dried at a temperature of 60-80 °C until the moisture content is 8-10%.

7. The method for preparing an environment-friendly fiber board by using laccase and microorganisms according to claim 1, characterized in that: In step (3), the temperature of the hot pressing is 160-240 °C, the hot pressing time is 3-5 min, and the hot pressing pressure is 1-7 MPa.

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