Lignin-based DA bond semi-interpenetrating network polymer for wood surface and preparation method thereof

Abstract

The invention discloses a preparation method of a lignin-based DA bond semi-interpenetrating network polymer for a wood surface. The lignin-based DA bond semi-interpenetrating network polymer comprises the following raw materials: lignin, furfuryl glycidyl ether (FGE), trimethylamine hydrochloride, bisphenol A diglycidyl ether (DGEBA), furfuryl alcohol (FA), bismaleimide (BMI), triethylamine (TEA) and tetrahydrofuran (THF). Lignin is used as a part of raw material, furyl is grafted in lignin by FGE in an alkaline environment to prepare furyl modified lignin, the furyl modified lignin and BMI are subjected to a DA reaction to prepare a cross-linked polymer with self-repairing performance, in order to effectively improve the fluidity of the polymer, a furyl grafted epoxy monomer is prepared by FA and DGEBA at the same time, and the cross-linked polymer with self-repairing performance is prepared. A linear self-repairing polymer with better fluidity is prepared through a DA reaction with BMI, the linear self-repairing polymer and the BMI are combined in proportion to form a semi-interpenetrating network structure, and the semi-interpenetrating network polymer with better performance is formed and used for wood microcrack self-repairing.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and specifically, to a polymer capable of self-repairing scratches generated during the daily use of wood products and fine cracks caused by wood cracking, and a preparation method thereof. Background Art

[0002] Green, low-carbon, and environmental protection have become the focus of attention in the whole society. Wood is light in weight, high in strength, beautiful in appearance, and low in processing energy consumption. It is the only renewable, recyclable, and naturally degradable green material and biological resource among the four major materials in the world today (steel, cement, wood, and plastic). However, at the same time, as a natural material, wood itself has many uncontrollable material properties, which lead to the occurrence of cracks, scratches and other damages in the living scenario. The structure of self-repairing materials can completely self-repair after being externally damaged, and the wound will heal automatically or under certain conditions. This is a hot research direction recently. The emergence of self-repairing coatings makes it highly possible to make up for the existing defects of wood at present. The practical application of self-repairing material coatings on the wood surface urgently needs to be developed. Summary of the Invention

[0003] The purpose of the present invention is to address the problem that wooden furniture materials will inevitably come into contact with various objects during use and generate fine cracks on the surface that affect the appearance of the product, and in many cases, the generated cracks are irreversible, thus reducing the service life of the product. A lignin-based DA bond semi-interpenetrating network polymer for the wood surface is provided, which can self-repair cracks after damage, restore the coating to its original state, effectively improve the service life of wood products and their coatings, and thus reduce the use of wood materials.

[0004] To achieve the above technical purpose, the technical solution adopted by the present invention is as follows:

[0005] A lignin-based DA bond semi-interpenetrating network polymer for the wood surface, comprising the following raw materials in parts by weight:

[0006] 45-55 parts by weight of lignin, 2.5-3.6 parts by weight of KOH (potassium hydroxide), 7-12 parts by weight of FGE (furfuryl glycidyl ether), 1.5-3.5 parts by weight of trimethylamine hydrochloride, 8-11.5 parts by weight of DGEBA (bisphenol A diglycidyl ether), 3.5-5.5 parts by weight of FA (furfuryl alcohol), 16-23 parts by weight of BMI (bismaleimide), 0.25-0.45 parts by weight of TEA (triethylamine), 175-185 parts by weight of THF (tetrahydrofuran), 100 parts by weight of distilled water.

[0007] As a further improved and preferred solution of the present invention, it comprises the following raw materials in parts by weight:

[0008] 47-53 parts by weight of lignin, 2.7-3.5 parts by weight of KOH, 8-11 parts by weight of FGE, 1.7-3.2 parts by weight of trimethylamine hydrochloride, 8.5-11 parts by weight of DGEBA, 3.7-5.3 parts by weight of FA, 17-22 parts by weight of BMI, 0.27-0.43 parts by weight of TEA, 180 parts by weight of THF, and 100 parts by weight of distilled water.

[0009] In order to achieve the above technical purpose, another technical solution adopted by the present invention is:

[0010] A method for preparing a lignin-based DA bond semi-interpenetrating network polymer for wood surface comprises the following steps:

[0011] (1) Lignin and KOH were dissolved in water, and the water was removed by freeze drying to obtain freeze-dried alkaline lignin.

[0012] (2) The freeze-dried alkaline lignin was uniformly mixed with furfuryl glycidyl ether (FGE), heated and kept at a constant temperature, and then cooled to room temperature.

[0013] (3) Add the treated mixture and trimethylamine hydrochloride into an appropriate amount of tetrahydrofuran (THF) and stir thoroughly until completely dissolved.

[0014] (4) The treated solution is passed through a silica gel column to remove the generated KCl and excess trimethylamine hydrochloride, the excess solvent is evaporated and the product is precipitated in n-hexane to remove unreacted furfuryl glycidyl ether (FGE), and the product is washed with n-hexane to obtain furanyl grafted modified lignin.

[0015] (5) Add bisphenol A diglycidyl ether (DGEBA) and furfuryl alcohol (FA) into a beaker, use tetrahydrofuran (THF) as a solvent, add triethylamine (TEA) as a catalyst, heat the mixture to a constant temperature and stir, and react at this temperature for a period of time. The solution is viscous and clear, and the product is a viscous liquid, namely, a furan-functionalized epoxy resin (FFR).

[0016] (6) The product FFR and modified lignin are added into a beaker, and bismaleimide (BMI) is added, and an appropriate amount of tetrahydrofuran (THF) is added as a solvent and stirred for a period of time after heating to form a semi-interpenetrating network polymer.

[0017] As a further improved technical solution of the present invention, in step (1), lignin and KOH are mixed in a ratio of 100:7 and freeze-dried alkaline lignin is obtained by freeze-drying.

[0018] As a further improved technical solution of the present invention, in step (2), freeze-dried alkaline lignin and FGE are mixed in a ratio of 1:1, heated to 110 °C and maintained for 12 h, and then cooled to room temperature.

[0019] As a further improved technical solution of the present invention, in step (3), the mass of trimethylamine hydrochloride is less than the mass of KOH but greater than half of the mass of KOH.

[0020] As a further improved technical solution of the present invention, in step (5), the mass ratio of DGEBA to FA is 111:50, and the mass of the catalyst triethylamine is 8% of that of FA. The mixture is heated to 65 °C and kept at a constant temperature with stirring, maintained and reacted for 5 h until the solution presents a viscous and clear state to obtain furan-functionalized epoxy resin (FFR).

[0021] As a further improved technical solution of the present invention, in step (6), the mass of the modified lignin is 4 - 5 times the mass of FA, and BMI 4 - 5 times the mass of FA is added. The mixture is heated to 50 °C in THF, kept stirring and reacted for 40 min to obtain a semi-interpenetrating network polymer.

[0022] The present invention also provides a method for using the semi-interpenetrating network polymer. The semi-interpenetrating network polymer is coated on the wood surface by brushing, and a coating is formed after drying and curing. The drying and curing temperature is 60 °C, and the drying and curing time is 6 h.

[0023] The beneficial effects of the present invention are as follows:

[0024] Lignin, one of the natural polymers existing in wood and one of the three major components in wood, has a high content and renewable resources. However, due to some reasons, its utilization is not sufficient at the present stage. Lignin and its derivatives have inherent self-healing ability. Due to the rich hydroxyl and aldehyde groups in its structure, it has natural hydrogen bonds and can become a promising choice for developing long-term self-healing polymer systems. The present invention uses lignin as part of the raw materials, grafts furan groups onto natural lignin by using FGE to prepare furan-modified lignin, uses DA reaction to prepare self-healing cross-linked polymers, and composes a self-healing material with a semi-interpenetrating network structure (semi-IPN) with a linear self-healing polymer prepared by epoxy modification for the self-healing of wood surface coatings. This patent enables the coating to have self-healing performance, can effectively extend the service life of wood products, and the coating can be recycled under certain conditions. At the same time, the coating raw materials are green, environmentally friendly, and renewable, reducing the coating preparation cost.

[0025] The present invention uses lignin as part of the raw material, adopts DA bonds as the self-repairing mechanism, and uses a semi-interpenetrating network structure to strengthen the material itself. It is a lignin-based DA bond semi-interpenetrating network polymer for wood surface and a preparation method thereof, which is used to self-repair scratches generated during daily use and small cracks caused by wood cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are further described below according to the accompanying drawings:

[0028] Embodiment 1:

[0029] like Figure 1 As shown, this embodiment provides a method for preparing a lignin-based DA bond semi-interpenetrating network polymer for wood surface, comprising the following steps:

[0030] (1) 47 g of lignin and 3.5 g of KOH were dissolved in water, and the water was removed by freeze drying to obtain freeze-dried alkaline lignin.

[0031] (2) 9.44 g of freeze-dried alkaline lignin was uniformly mixed with 10 g of FGE and heated to 110°C and kept at that temperature for 12 h, and then cooled to room temperature.

[0032] (3) Add the treated mixture and 3.1 g of trimethylamine hydrochloride into 50 ml of THF and stir thoroughly until completely dissolved.

[0033] (4) The treated solution is passed through a silica gel column to remove the generated KCl and excess trimethylamine hydrochloride, the excess solvent is evaporated and the product is precipitated in n-hexane to remove the unreacted FGE, and the product is washed with n-hexane to obtain furanyl grafted modified lignin.

[0034] (5) 9 g of DGEBA and 5 g of FA were added to a beaker, 50 ml of THF was used as a solvent, and 0.4 g of TEA was added as a catalyst. The mixture was heated to a constant temperature and stirred, and reacted at this temperature for 5 h. The solution was viscous and clear, and the product was a viscous liquid, namely, a furan-functionalized epoxy resin (FFR).

[0035] (6) Add 14 g FFR and 18.79 g modified lignin into a beaker, add 22 g BMI, and add an appropriate amount of 100 ml THF as a solvent. After heating and stirring for a period of time, a self-healing polymer with a semi-interpenetrating network structure (semi-interpenetrating network polymer) is formed. The semi-interpenetrating network structure is applied to the wood surface by a brush coating method, and dried and cured at 60 ° C for 6 hours to form a coating.

[0036] Example 2:

[0037] (1) Dissolve 53 g of lignin and 2.7 g of KOH in water, remove the water by freeze-drying method to obtain freeze-dried alkaline lignin.

[0038] (2) Uniformly mix 10.4 g of freeze-dried alkaline lignin and 9 g of FGE, heat to 110 °C and keep the temperature constant for 12 h, then cool to room temperature.

[0039] (3) Add the treated mixture and 2 g of trimethylamine hydrochloride to 50 ml of THF, stir well until completely dissolved.

[0040] (4) Remove the generated KCl and excess trimethylamine hydrochloride from the treated solution through a silica gel column, evaporate the excess solvent, precipitate the product in n-hexane, remove the unreacted FGE, and wash the product with n-hexane to obtain furan group grafted modified lignin.

[0041] (5) Add 9 g of DGEBA and 4 g of FA to a beaker, use 50 ml of THF as a solvent, and add 0.3 g of TEA as a catalyst. Heat and stir the mixture constantly, and react at this temperature for 5 h. The solution shows a viscous and clear state, and the obtained product is a viscous liquid, namely furan group functionalized epoxy resin (FFR).

[0042] (6) Add 13 g of the product FFR and 18.9 g of modified lignin to a beaker, add 20 g of BMI, and add 100 ml of THF as a solvent. After heating, stir for a period of time to form a self-healing polymer with a semi-interpenetrating network structure. Coat it on the wood surface by brushing method and dry and cure at 60 °C for 6 h to form a coating.

[0043] Example 3:

[0044] (1) Dissolve 52 g of lignin and 3 g of KOH in water, remove the water by freeze-drying method to obtain freeze-dried alkaline lignin.

[0045] (2) Uniformly mix 10.3 g of freeze-dried alkaline lignin and 8 g of FGE, heat to 110 °C and keep the temperature constant for 12 h, then cool to room temperature.

[0046] (3) Add the treated mixture and 1.7 g of trimethylamine hydrochloride to 50 ml of THF, stir well until completely dissolved.

[0047] (4) The treated solution is passed through a silica gel column to remove the generated KCl and excess trimethylamine hydrochloride, the excess solvent is evaporated and the product is precipitated in n-hexane to remove the unreacted FGE, and the product is washed with n-hexane to obtain furanyl grafted modified lignin.

[0048] (5) 8.5 g of DGEBA and 4.7 g of FA were added to a beaker, 50 ml of THF was used as a solvent, and 0.3 g of TEA was added as a catalyst. The mixture was heated to a constant temperature and stirred, and reacted at this temperature for 5 h. The solution was viscous and clear, and the product was a viscous liquid, namely, a furan-functionalized epoxy resin (FFR).

[0049] (6) Add 13.2 g FFR and 17.74 g modified lignin into a beaker, add 21.8 g BMI, and add 100 ml THF as a solvent. Stir for a period of time after heating to form a self-healing polymer with a semi-interpenetrating network structure. Apply it on the wood surface by brush coating, dry and cure at 60 °C for 6 h to form a coating.

[0050] Embodiment 4:

[0051] (1) 48.5 g of lignin and 2.8 g of KOH were dissolved in water, and the water was removed by freeze drying to obtain freeze-dried alkaline lignin.

[0052] (2) 9.6 g of freeze-dried alkaline lignin was uniformly mixed with 11 g of FGE and heated to 110°C and kept at that temperature for 12 h, and then cooled to room temperature.

[0053] (3) Add the treated mixture and 2.7 g of trimethylamine hydrochloride into 50 ml of THF and stir thoroughly until completely dissolved.

[0054] (4) The treated solution is passed through a silica gel column to remove the generated KCl and excess trimethylamine hydrochloride, the excess solvent is evaporated and the product is precipitated in n-hexane to remove the unreacted FGE, and the product is washed with n-hexane to obtain furanyl grafted modified lignin.

[0055] (5) 11 g of DGEBA and 4.7 g of FA were added to a beaker, 50 ml of THF was used as a solvent, and 0.3 g of TEA was added as a catalyst. The mixture was heated to a constant temperature and stirred, and reacted at this temperature for 5 h. The solution was viscous and clear, and the product was a viscous liquid, namely, a furan-functionalized epoxy resin (FFR).

[0056] (6) Add 15.7 g FFR and 20.08 g modified lignin into a beaker, add 19 g BMI, and add 100 ml THF as a solvent. After heating and stirring for a period of time, a self-healing polymer with a semi-interpenetrating network structure is formed. The self-healing polymer is coated on the wood surface by a brush coating method and dried and cured at 60 °C for 6 h to form a coating.

[0057] Embodiment 5:

[0058] (1) 52.5 g of lignin and 3.2 g of KOH were dissolved in water, and the water was removed by freeze drying to obtain freeze-dried alkaline lignin.

[0059] (2) 10.4 g of freeze-dried alkaline lignin was uniformly mixed with 10.6 g of FGE and heated to 110°C and kept at that temperature for 12 h, and then cooled to room temperature.

[0060] (3) Add the treated mixture and 2.2 g of trimethylamine hydrochloride into 50 ml of THF and stir thoroughly until completely dissolved.

[0061] (4) The treated solution is passed through a silica gel column to remove the generated KCl and excess trimethylamine hydrochloride, the excess solvent is evaporated and the product is precipitated in n-hexane to remove the unreacted FGE, and the product is washed with n-hexane to obtain furanyl grafted modified lignin.

[0062] (5) 10.53 g of DGEBA and 3.7 g of FA were added to a beaker, 50 ml of THF was used as a solvent, and 0.27 g of TEA was added as a catalyst. The mixture was heated to a constant temperature and stirred, and reacted at this temperature for 5 h. The solution was viscous and clear, and the product was a viscous liquid, namely, a furan-functionalized epoxy resin (FFR).

[0063] (6) Add 14.23 g FFR and 20.69 g modified lignin into a beaker, add 17 g BMI, and add 100 ml THF as a solvent. After heating and stirring for a period of time, a self-healing polymer with a semi-interpenetrating network structure is formed. The self-healing polymer is coated on the wood surface by a brush coating method and dried and cured at 60 °C for 6 h to form a coating.

[0064] Embodiment 6:

[0065] (1) 49 g of lignin and 3.4 g of KOH were dissolved in water, and the water was removed by freeze drying to obtain freeze-dried alkaline lignin.

[0066] (2) 9.8 g of freeze-dried alkaline lignin was uniformly mixed with 8.7 g of FGE and heated to 110°C and kept at that temperature for 12 h, and then cooled to room temperature.

[0067] (3) Add the treated mixture and 2.57 g of trimethylamine hydrochloride into 50 ml of THF and stir thoroughly until completely dissolved.

[0068] (4) The treated solution is passed through a silica gel column to remove the generated KCl and excess trimethylamine hydrochloride, the excess solvent is evaporated and the product is precipitated in n-hexane to remove the unreacted FGE, and the product is washed with n-hexane to obtain furanyl grafted modified lignin.

[0069] (5) 8.6 g of DGEBA and 5.3 g of FA were added to a beaker, 50 ml of THF was used as a solvent, and 0.43 g of TEA was added as a catalyst. The mixture was heated to a constant temperature and stirred, and reacted at this temperature for 5 h. The solution was viscous and clear, and the product was a viscous liquid, namely, a furan-functionalized epoxy resin (FFR).

[0070] (6) Add 13.9 g FFR and 17.86 g modified lignin into a beaker, add 22 g BMI, and add 100 ml THF as a solvent. After heating and stirring for a period of time, a self-healing polymer with a semi-interpenetrating network structure is formed. The self-healing polymer is coated on the wood surface by a brush coating method and dried and cured at 60 °C for 6 h to form a coating.

[0071] Embodiment 7:

[0072] (1) 49.24 g of lignin and 3.45 g of KOH were dissolved in water, and the water was removed by freeze drying to obtain freeze-dried alkaline lignin.

[0073] (2) 9.8 g of freeze-dried alkaline lignin was uniformly mixed with 9.85 g of FGE and heated to 110°C and kept at that temperature for 12 h, and then cooled to room temperature.

[0074] (3) Add the treated mixture and 3.2 g of trimethylamine hydrochloride into 50 ml of THF and stir thoroughly until completely dissolved.

[0075] (4) The treated solution is passed through a silica gel column to remove the generated KCl and excess trimethylamine hydrochloride, the excess solvent is evaporated and the product is precipitated in n-hexane to remove the unreacted FGE, and the product is washed with n-hexane to obtain furanyl grafted modified lignin.

[0076] (5) 10.83 g of DGEBA and 4.92 g of FA were added to a beaker, 50 ml of THF was used as a solvent, and 0.39 g of TEA was added as a catalyst. The mixture was heated to a constant temperature and stirred, and reacted at this temperature for 5 h. The solution was viscous and clear, and the product was a viscous liquid, namely, a furan-functionalized epoxy resin (FFR).

[0077] (6) Add 15.75 g of product FFR and 19.01 g of modified lignin to a beaker, then add 18.12 g of BMI, and add 100 ml of THF as a solvent. Stir for a period of time after heating to form a self-healing polymer with a semi-interpenetrating network structure. Coat it on the wood surface using the brush coating method and dry and cure it at 60 °C for 6 h to form a coating.

[0078] Performance test:

[0079] For the coating films of Examples 1-7, then according to GB / T 4893.6-2013, use a gloss meter to test the gloss of the coating film; according to GB / T 4893.8-2013, use the abrasion resistance measurement method to test the abrasion resistance of the coating film; according to GB / T 4893.9-2013, use a coating impact tester to test the impact resistance of the coating film; according to GB / T 21866-2008, test the antibacterial property of the coating film; use a scratch experiment to test the self-healing rate of the coating film and compare it with a pure epoxy resin paint surface (control), and the test results are shown in Table 1 below.

[0080] In the experiment of modifying lignin and synthesizing a DA bond semi-interpenetrating network polymer to coat on the wood surface in the present invention, the coating can have gloss, abrasion resistance, impact resistance and self-healing ability. The semi-interpenetrating network polymer of the present invention is coated on the surface of basswood boards (100 mm × 100 mm × 12 mm). According to the national standard GB / T 4893.6-2013, the gloss of the coating film is detected as high gloss. According to the national standard GB / T 4893.8-2013, the abrasion resistance of the coating film is detected as grade 1 (abrasion rotation speed 5000 revolutions). According to the national standard GB / T 4893.9-2013, the impact resistance is detected as grade 2. For the self-healing rate test of the coating film, use an 8 × 19 mm single-sided blade to scratch the surface of the experimental sample, immediately observe and mark the scratch width under a microscope as H0, and observe the scratch width again under a microscope five days later as H1. The calculation formula for the self-healing rate is H = (H0 - H1) / H0·100%.

[0081] Table 1 shows the test results:

[0082]

[0083] The present invention uses lignin as a partial raw material, grafts furyl groups onto lignin by FGE under an alkaline environment to prepare furyl-modified lignin, and conducts a DA reaction with BMI to prepare a cross-linked polymer with self-healing properties. In order to effectively improve the fluidity of the polymer, at the same time, a furyl-grafted epoxy monomer is prepared by using FA and DGEBA, and a linear self-healing polymer with better fluidity is prepared by conducting a DA reaction with BMI. The two are combined in proportion to form a semi-interpenetrating network structure, forming a polymer with better performance, which is used for self-healing of scratches in daily use of wood products and self-healing of microcracks caused by wood cracking in part.

[0084] The protection scope of the present invention includes but is not limited to the above embodiments. The protection scope of the present invention is subject to the claims, and any substitutions, deformations, and improvements that are easily conceivable by those skilled in the art to this technology fall within the protection scope of the present invention.

Claims

1. Lignin-based DA bond semi-interpenetrating network polymer for wood surface, characterized in that It comprises raw materials in the following parts by weight: 45 - 55 parts by weight of lignin, 2.5 - 3.6 parts by weight of KOH, 7 - 12 parts by weight of furfuryl glycidyl ether (FGE), 1.5 - 3.5 parts by weight of trimethylamine hydrochloride, 8 - 11.5 parts by weight of bisphenol A diglycidyl ether (DGEBA), 3.5 - 5.5 parts by weight of furfuryl alcohol (FA), 16 - 23 parts by weight of bismaleimide (BMI), 0.25 - 0.45 parts by weight of triethylamine (TEA), 175 - 185 parts by weight of tetrahydrofuran (THF), 100 parts by weight of distilled water.

2. The lignin-based DA bond semi-interpenetrating network polymer for wood surfaces according to claim 1, characterized in that, It comprises raw materials in the following parts by weight: 47 - 53 parts by weight of lignin, 2.7 - 3.5 parts by weight of KOH, 8 - 11 parts by weight of FGE, 1.7 - 3.2 parts by weight of trimethylamine hydrochloride, 8.5 - 11 parts by weight of DGEBA, 3.7 - 5.3 parts by weight of FA, 17 - 22 parts by weight of BMI, 0.27 - 0.43 parts by weight of TEA, 180 parts by weight of THF, 100 parts by weight of distilled water.

3. A preparation method of a lignin-based DA bond semi-interpenetrating network polymer for wood surface, characterized in that, It includes the following steps: (1) Dissolve lignin and KOH in water, remove the water by freeze-drying method to obtain freeze-dried alkaline lignin; (2) Uniformly mix the freeze-dried alkaline lignin and furfuryl glycidyl ether (FGE), heat and keep at a constant temperature, then cool to room temperature; (3) Add the treated mixture and trimethylamine hydrochloride into an appropriate amount of tetrahydrofuran (THF), and stir well until completely dissolved; (4) Pass the treated solution through a silica gel column to remove the generated KCl and excessive trimethylamine hydrochloride, evaporate the excess, precipitate the product in n-hexane, remove the unreacted furfuryl glycidyl ether (FGE), and wash the product with n-hexane to obtain furan group grafted modified lignin; (5) Add bisphenol A diglycidyl ether (DGEBA) and furfuryl alcohol (FA) into a beaker, use tetrahydrofuran (THF) as a solvent, and add triethylamine (TEA) as a catalyst, heat the mixture to a constant temperature and stir. React for a period of time until the solution shows a viscous and clear state to obtain the product, a viscous liquid, i.e., furan group functionalized epoxy resin (FFR). (6) Add the product FFR and the modified lignin into a beaker, add bismaleimide (BMI), and add an appropriate amount of tetrahydrofuran (THF) as a solvent, heat and stir for a period of time to form a semi-interpenetrating network polymer.

4. The preparation method of the lignin-based DA bond semi-interpenetrating network polymer for wood surface according to claim 3, characterized in that, In step (1), lignin and KOH are mixed in a weight ratio of 100:7 and the freeze-dried alkaline lignin is obtained by the freeze-drying method.

5. The preparation method of the lignin-based DA bond semi-interpenetrating network polymer for wood surface according to claim 3, characterized in that, In step (2), the freeze-dried alkaline lignin and FGE are mixed in a weight ratio of 1:1, heated to 110 °C and kept for 12 h, then cooled to room temperature.

6. The preparation method of the lignin-based DA bond semi-interpenetrating network polymer for wood surface according to claim 3, characterized in that, In step (3), the mass of trimethylamine hydrochloride is less than the mass of KOH but greater than half of the mass of KOH.

7. The preparation method of the lignin-based DA bond semi-interpenetrating network polymer for the wood surface according to claim 3, characterized in that, In step (5), the mass ratio of DGEBA to FA is 111:50, the mass of the catalyst triethylamine (TEA) is 8% of FA, and the mixture is heated to 65 °C and kept at a constant temperature and stirred, and the reaction is maintained for 5 h until the solution shows a viscous and clear state to obtain furan group functionalized epoxy resin (FFR).

8. The preparation method of the lignin-based DA-bonded semi-interpenetrating network polymer for wood surface according to claim 3, characterized in that, In step (6), the mass of the modified lignin is 4-5 times that of the FA, and BMI 4-5 times the mass of the FA is added. The mixture is heated to 50 °C in THF and kept stirring for 40 min for reaction to obtain a semi-interpenetrating network polymer.

9. Method for using the semi-interpenetrating network polymer prepared by the preparation method according to claim 3, characterized in that: The semi-interpenetrating network polymer is coated on the wood surface by the brushing method, and a coating is formed after drying and curing.

10. The usage method according to claim 9, characterized in that, The drying and curing temperature is 60 °C and the time is 6 h.

Images