Bamboo board adhesive with high cohesiveness and preparation method of bamboo board adhesive

Abstract

The invention discloses a preparation method of a bamboo board adhesive with high cohesiveness. The preparation method comprises the following steps: (1) preparing a one-step synthetic product; (2) preparing a two-step synthetic product; (3) preparing a cross-linked product; and (4) mixing the one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide and water to form a mixture, heating and stirring, then adding the cross-linked product and a formaldehyde solution, heating and stirring in a heat preservation manner after charging is completed, stirring in an ice bath after stirring is completed, cooling to normal temperature, and adjusting the pH value to obtain the bamboo board adhesive. The bamboo board adhesive prepared by the method disclosed by the invention has relatively high bonding strength and good cohesiveness, and further improves the durability of a bamboo board product.

Description

Technical Field

[0001] The invention relates to the technical field of bamboo-wood adhesives, and in particular to a bamboo board adhesive with strong adhesion and a preparation method thereof. Background Art

[0002] According to the classification concept of traditional bamboo-wood panels, the bamboo-wood panels currently produced mainly include: bamboo plywood (including bamboo woven plywood, bamboo curtain plywood, etc.), bamboo particle board (including bamboo particle board and bamboo fiberboard), bamboo large piece / oriented strand board and bamboo strip integrated board, bamboo / wood composite plywood and bamboo / wood composite flooring, bamboo-based veneer covered with resin-impregnated paper, wood veneer and other veneer materials. Therefore, adhesives are widely used in the bamboo and wood processing industry. The adhesives for bamboo-wood panels are mainly traditional phenolic and urea-formaldehyde synthetic resins, among which phenolic resin is a common phenolic adhesive, which is generally formed by condensation of phenolic compounds such as phenol, meta-diphenol, cresol, bisphenol A and aldehyde compounds such as formaldehyde, polyformaldehyde, furfural, and glyoxal. Phenolic resin is one of the commonly used adhesives for wood panel products due to its excellent strength, water resistance and thermal stability. Summary of the invention

[0003] To this end, the present invention provides a method for preparing a bamboo board adhesive with strong adhesion, the preparation steps comprising:

[0004] (1) preparing a pyridine solution of tannic acid, heating the pyridine solution of tannic acid in a water bath to 30±3° C., then adding methyltetrahydrophthalic anhydride to the solution under stirring, continuing to stir at a constant temperature of 30±3° C. for more than 1 hour after the addition is completed, then heating to 90±3° C., stirring at a constant temperature of 90±3° C. for more than 40 hours, then naturally cooling to room temperature, adding excess ether for precipitation, collecting the precipitate by solid-liquid separation, and drying the precipitate to obtain a one-step synthetic product;

[0005] (2) adding apigenin to tert-amyl alcohol, heating to 60±2° C. in a water bath, stirring at a constant temperature for more than 2 hours, and condensing and refluxing during the heat preservation process; then adding methyl laurate and immobilized lipase to the solution under stirring, and continuing to stir at a constant temperature of 60±2° C. for more than 20 hours after the addition is completed, and air cooling to room temperature after the stirring is completed to obtain a two-step synthetic product;

[0006] (3) preparing a protocatechuic acid epichlorohydrin solution, heating the protocatechuic acid epichlorohydrin solution in an oil bath to 95±5° C. for insulation, then adding dodecyltrimethylammonium chloride to the solution under stirring, and continuing to stir the solution at a constant temperature of 95±5° C. for more than 20 minutes after the addition is completed, and then dropping sodium hydroxide solution into the solution under stirring, and continuing to stir the solution at a constant temperature of 95±5° C. for more than 3 hours after the dropwise addition is completed, and then naturally cooling to room temperature, adjusting the pH of the solution to neutral with dilute hydrochloric acid, and removing water and epichlorohydrin by rotary evaporation to obtain a cross-linked product;

[0007] (4) The one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide and water are mixed to form a mixture, the mixture is heated to 96±2° C., and then the mixture is stirred at a constant temperature for 2-3 hours, and condensed and refluxed during the constant temperature process; after the stirring is completed, it is naturally cooled to 40±2° C., and then the cross-linked product and formaldehyde solution are added under stirring. After the addition is completed, it is heated to 85±2° C. and stirred at this temperature for more than 1 hour. After the stirring is completed, the mixture is cooled to room temperature by stirring in an ice bath, and sulfuric acid is added to adjust the pH to 7.5-8 to obtain the bamboo board adhesive.

[0008] Furthermore, in the step (1), the concentration of tannic acid in the pyridine solution of tannic acid is 3-4 g / 100 mL, and the solvent is pyridine; the volume ratio of the added mass of methyltetrahydrophthalic anhydride to the pyridine solution of tannic acid is methyltetrahydrophthalic anhydride: pyridine solution of tannic acid = 32-36 g: 100 mL.

[0009] Furthermore, in the step (2), apigenin is added to tert-amyl alcohol in a ratio of apigenin:tert-amyl alcohol=8-10 g:1 L, and the added mass ratio of methyl laurate and immobilized lipase to the added mass ratio of apigenin is methyl laurate:immobilized lipase:apigenin=50-60 g:2-3 g:8-10 g.

[0010] Furthermore, the immobilized lipase is Lipozyme435 enzyme.

[0011] Furthermore, in the step (3), the concentration of protocatechuic acid in the epichlorohydrin solution of protocatechuic acid is 4-6 g / 100 mL, and the solvent is epichlorohydrin; the volume ratio of the added amount of the dodecyltrimethylammonium chloride and the sodium hydroxide solution to the epichlorohydrin solution of protocatechuic acid is dodecyltrimethylammonium chloride: sodium hydroxide solution: epichlorohydrin solution of protocatechuic acid = 2-3 g: 5-6 mL: 100 mL, wherein the mass percentage of the solute in the sodium hydroxide solution is 20%, and the solvent is water.

[0012] Furthermore, in the step (3), the mass percentage of the solute in the dilute hydrochloric acid is 5%.

[0013] Furthermore, in step (4), the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, water, the cross-linked product and the formaldehyde solution are calculated in parts by weight as follows: 20 to 24 parts of the one-step synthesis product, 12 to 16 parts of the two-step synthesis product, 50 parts of phenol, 15 to 18 parts of sodium hydroxide, 50 to 60 parts of water, 10 to 15 parts of the cross-linked product, and 100 to 120 parts of the formaldehyde solution, wherein the formaldehyde solution is a formaldehyde aqueous solution with a solute mass percentage of 37%.

[0014] The beneficial effects of the present invention are: the bamboo board adhesive prepared by the method of the present invention has a high bonding strength, which is significantly higher than the 0.7MPa required by the standard, shows good adhesion, and further improves the durability of the bamboo board product. By comparing Example 3 of the present invention and each comparative example, it can be seen that by adding the one-step synthetic product, the two-step synthetic product and the cross-linked product prepared by the method of the present invention to the components of the traditional phenolic resin adhesive, the bonding strength of the adhesive can be significantly optimized. This is mainly due to: tannic acid contains a large number of phenolic hydroxyl groups. The present invention first modifies the phenolic hydroxyl groups of tannic acid by methyltetrahydrophthalic anhydride to obtain a hyperbranched polymer containing more long-chain fatty chain segments. On the one hand, the long-chain fatty chain segments can disperse stress during the stress process, improve the toughness and strength of the subsequent phenolic resin, and on the other hand, can improve the connection strength of each component in the phenolic resin, thereby improving the strength and viscosity of the adhesive as a whole. Then, apigenin and methyl laurate are ester-exchanged to form macromolecules containing acyl groups, which form an interpenetrating network structure with the phenolic resin and the above-mentioned hyperbranched polymer to improve the adhesion; finally, by adding a cross-linked product and utilizing the epoxy group in the cross-linked product, the cross-linking density of the molecules in the resin is increased, thereby improving the overall adhesion strength of the adhesive. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the embodiments.

[0016] Example 1

[0017] A method for preparing a bamboo board adhesive with strong adhesion, the preparation steps comprising:

[0018] (1) preparing a tannic acid pyridine solution, wherein the concentration of tannic acid in the tannic acid pyridine solution is 3 g / 100 mL, and the solvent is pyridine; heating the tannic acid pyridine solution to 30° C. in a water bath and keeping the temperature, then adding methyltetrahydrophthalic anhydride to the solution under stirring, wherein the volume ratio of the added mass of methyltetrahydrophthalic anhydride to the tannic acid pyridine solution is methyltetrahydrophthalic anhydride: tannic acid pyridine solution = 32 g: 100 mL; after the addition is completed, stirring is continued at a constant temperature of 30° C. for 1 hour, then heating to 90° C., stirring at a constant temperature of 90° C. for 40 hours, then naturally cooling to room temperature, adding excess ether for precipitation, collecting the precipitate by solid-liquid separation, and drying the precipitate at 60° C. for 2 hours to obtain a one-step synthetic product;

[0019] (2) adding apigenin to tert-amyl alcohol, the mass ratio of apigenin to tert-amyl alcohol is apigenin: tert-amyl alcohol = 8 g: 1 L, heating to 60° C. in a water bath, stirring at a constant temperature for 2 hours, and condensing and refluxing during the heat preservation process; then adding methyl laurate and immobilized lipase to the solution under stirring, the mass ratio of the added methyl laurate and immobilized lipase to the added apigenin is methyl laurate: immobilized lipase: apigenin = 50 g: 2 g: 8 g; the immobilized lipase is Lipozyme435 enzyme; after the addition is completed, stirring is continued at a constant temperature of 60° C. for 20 hours, and after the stirring is completed, air cooling is performed to room temperature to obtain a two-step synthesis product;

[0020] (3) preparing a protocatechuic acid epichlorohydrin solution, wherein the protocatechuic acid concentration in the protocatechuic acid epichlorohydrin solution is 4 g / 100 mL and the solvent is epichlorohydrin; heating the protocatechuic acid epichlorohydrin solution to 95° C. in an oil bath and then adding dodecyltrimethylammonium chloride to the solution under stirring, and continuing to stir the solution at a constant temperature of 95° C. for 20 minutes after the addition is completed, and then adding sodium hydroxide solution dropwise to the solution under stirring, and the dodecyltrimethylammonium chloride and sodium hydroxide solution are added. The volume ratio of the amount of protocatechuic acid to the epichlorohydrin solution of protocatechuic acid is dodecyltrimethylammonium chloride: sodium hydroxide solution: epichlorohydrin solution of protocatechuic acid = 2g: 5mL: 100mL, wherein the mass percentage of the solute in the sodium hydroxide solution is 20%, and the solvent is water; after the dropwise addition is completed, the solution is continuously stirred at a constant temperature of 95°C for 3h, then naturally cooled to room temperature, and the pH of the solution is adjusted to neutral with dilute hydrochloric acid, wherein the mass percentage of the solute in the dilute hydrochloric acid is 5%; water and epichlorohydrin are removed by rotary evaporation to obtain a cross-linked product;

[0021] (4) The one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide and water are mixed to form a mixture, the mixture is heated to 96° C., and then the mixture is stirred at a constant temperature for 2 hours, and condensed and refluxed during the constant temperature process; after the stirring is completed, the mixture is naturally cooled to 40° C., and then the cross-linked product and formaldehyde solution are added under stirring, and the one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide, water, the cross-linked product and formaldehyde solution used are calculated by weight: 20 parts of the one-step synthetic product, 12 parts of the two-step synthetic product, 50 parts of phenol, 15 parts of sodium hydroxide, 50 parts of water, 10 parts of the cross-linked product, and 100 parts of the formaldehyde solution, wherein the formaldehyde solution is a formaldehyde aqueous solution with a solute mass percentage of 37%; after the addition is completed, the mixture is heated to 85° C. and stirred at this temperature for 1 hour. After the stirring is completed, the mixture is cooled to room temperature by stirring in an ice bath, and sulfuric acid (the solute mass percentage is 20%, and the solvent is water) is added to adjust the pH to 7.5 to obtain the bamboo board adhesive.

[0022] Example 2

[0023] A method for preparing a bamboo board adhesive with strong adhesion, the preparation steps comprising:

[0024] (1) preparing a tannic acid pyridine solution, wherein the concentration of tannic acid in the tannic acid pyridine solution is 3 g / 100 mL, and the solvent is pyridine; heating the tannic acid pyridine solution to 30° C. in a water bath and keeping the temperature, then adding methyltetrahydrophthalic anhydride to the solution under stirring, wherein the volume ratio of the added mass of methyltetrahydrophthalic anhydride to the tannic acid pyridine solution is methyltetrahydrophthalic anhydride: tannic acid pyridine solution = 34 g: 100 mL; after the addition is completed, stirring is continued at a constant temperature of 30° C. for 1 hour, then heating to 90° C., stirring at a constant temperature of 90° C. for 40 hours, then naturally cooling to room temperature, adding excess ether for precipitation, collecting the precipitate by solid-liquid separation, and drying the precipitate at 60° C. for 2 hours to obtain a one-step synthetic product;

[0025] (2) adding apigenin to tert-amyl alcohol, the mass ratio of apigenin to tert-amyl alcohol is apigenin:tert-amyl alcohol=9g:1L, heating to 60°C in a water bath, stirring at constant temperature for 2h, and condensing and refluxing during the heat preservation process; then adding methyl laurate and immobilized lipase to the solution under stirring, the mass ratio of the added methyl laurate and immobilized lipase to the added apigenin is methyl laurate:immobilized lipase:apigenin=53g:2g:9g; the immobilized lipase is Lipozyme435 enzyme; after the addition is completed, stirring is continued at 60°C for 20h, and after the stirring is completed, air cooling is performed to room temperature to obtain a two-step synthesis product;

[0026] (3) preparing a protocatechuic acid epichlorohydrin solution, wherein the protocatechuic acid concentration in the protocatechuic acid epichlorohydrin solution is 5 g / 100 mL and the solvent is epichlorohydrin; heating the protocatechuic acid epichlorohydrin solution to 95° C. in an oil bath and then adding dodecyltrimethylammonium chloride to the solution under stirring, and continuing to stir the solution at a constant temperature of 95° C. for 20 minutes after the addition is completed, and then dropping a sodium hydroxide solution into the solution under stirring, and adding the dodecyltrimethylammonium chloride and sodium hydroxide solution. The volume ratio of the amount of protocatechuic acid to the epichlorohydrin solution of protocatechuic acid is dodecyltrimethylammonium chloride: sodium hydroxide solution: epichlorohydrin solution of protocatechuic acid = 2g: 5mL: 100mL, wherein the mass percentage of the solute in the sodium hydroxide solution is 20%, and the solvent is water; after the dropwise addition is completed, the solution is continuously stirred at a constant temperature of 95°C for 3h, then naturally cooled to room temperature, and the pH of the solution is adjusted to neutral with dilute hydrochloric acid, wherein the mass percentage of the solute in the dilute hydrochloric acid is 5%; water and epichlorohydrin are removed by rotary evaporation to obtain a cross-linked product;

[0027] (4) The one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide and water are mixed to form a mixture, the mixture is heated to 96° C., and then the mixture is stirred at a constant temperature for 2 hours, and condensed and refluxed during the constant temperature process; after the stirring is completed, the mixture is naturally cooled to 40° C., and then the cross-linked product and formaldehyde solution are added under stirring, and the one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide, water, the cross-linked product and formaldehyde solution used are calculated by weight: 22 parts of the one-step synthetic product, 14 parts of the two-step synthetic product, 50 parts of phenol, 16 parts of sodium hydroxide, 55 parts of water, 12 parts of the cross-linked product, and 110 parts of the formaldehyde solution, wherein the formaldehyde solution is a formaldehyde aqueous solution with a solute mass percentage of 37%; after the addition is completed, the mixture is heated to 85° C. and stirred at this temperature for 1 hour. After the stirring is completed, the mixture is cooled to room temperature by stirring in an ice bath, and sulfuric acid (the solute mass percentage is 20%, and the solvent is water) is added to adjust the pH to 7.5 to obtain the bamboo board adhesive.

[0028] Example 3

[0029] A method for preparing a bamboo board adhesive with strong adhesion, the preparation steps comprising:

[0030] (1) preparing a tannic acid pyridine solution, wherein the concentration of tannic acid in the tannic acid pyridine solution is 4 g / 100 mL, and the solvent is pyridine; heating the tannic acid pyridine solution to 30° C. in a water bath and keeping the temperature, then adding methyltetrahydrophthalic anhydride to the solution under stirring, wherein the volume ratio of the added mass of methyltetrahydrophthalic anhydride to the tannic acid pyridine solution is methyltetrahydrophthalic anhydride: tannic acid pyridine solution = 34 g: 100 mL; after the addition is completed, stirring is continued at a constant temperature of 30° C. for 1 hour, then heating to 90° C., stirring at a constant temperature of 90° C. for 40 hours, then naturally cooling to room temperature, adding excess ether for precipitation, collecting the precipitate by solid-liquid separation, and drying the precipitate at 60° C. for 2 hours to obtain a one-step synthetic product;

[0031] (2) adding apigenin to tert-amyl alcohol, the mass ratio of apigenin to tert-amyl alcohol is apigenin:tert-amyl alcohol=9g:1L, heating to 60°C in a water bath, stirring at constant temperature for 2h, and condensing and refluxing during the heat preservation process; then adding methyl laurate and immobilized lipase to the solution under stirring, the mass ratio of the added methyl laurate and immobilized lipase to the added apigenin is methyl laurate:immobilized lipase:apigenin=56g:3g:9g; the immobilized lipase is Lipozyme435 enzyme; after the addition is completed, stirring is continued at 60°C for 20h, and after the stirring is completed, air cooling is performed to room temperature to obtain a two-step synthesis product;

[0032] (3) preparing a protocatechuic acid epichlorohydrin solution, wherein the protocatechuic acid concentration in the protocatechuic acid epichlorohydrin solution is 5 g / 100 mL and the solvent is epichlorohydrin; heating the protocatechuic acid epichlorohydrin solution to 95° C. in an oil bath and then adding dodecyltrimethylammonium chloride to the solution under stirring, and continuing to stir the solution at a constant temperature of 95° C. for 20 minutes after the addition is completed, and then dropping a sodium hydroxide solution into the solution under stirring, and adding the dodecyltrimethylammonium chloride and sodium hydroxide solution. The volume ratio of the amount of protocatechuic acid to the epichlorohydrin solution of protocatechuic acid is dodecyltrimethylammonium chloride: sodium hydroxide solution: epichlorohydrin solution of protocatechuic acid = 3g: 6mL: 100mL, wherein the mass percentage of the solute in the sodium hydroxide solution is 20%, and the solvent is water; after the dropwise addition is completed, the solution is continuously stirred at a constant temperature of 95°C for 3h, then naturally cooled to room temperature, and the pH of the solution is adjusted to neutral with dilute hydrochloric acid, wherein the mass percentage of the solute in the dilute hydrochloric acid is 5%; water and epichlorohydrin are removed by rotary evaporation to obtain a cross-linked product;

[0033] (4) The one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide and water are mixed to form a mixture, the mixture is heated to 96° C., and then the mixture is stirred at a constant temperature for 2 hours, and condensed and refluxed during the constant temperature process; after the stirring is completed, the mixture is naturally cooled to 40° C., and then the cross-linked product and formaldehyde solution are added under stirring, and the one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide, water, the cross-linked product and formaldehyde solution used are calculated by weight: 22 parts of the one-step synthetic product, 14 parts of the two-step synthetic product, 50 parts of phenol, 17 parts of sodium hydroxide, 55 parts of water, 14 parts of the cross-linked product, and 120 parts of the formaldehyde solution, wherein the formaldehyde solution is a formaldehyde aqueous solution with a solute mass percentage of 37%; after the addition is completed, the mixture is heated to 85° C. and stirred at this temperature for 1 hour. After the stirring is completed, the mixture is cooled to room temperature by stirring in an ice bath, and sulfuric acid (the solute mass percentage is 20%, and the solvent is water) is added to adjust the pH to 7.5 to obtain the bamboo board adhesive.

[0034] Example 4

[0035] A method for preparing a bamboo board adhesive with strong adhesion, the preparation steps comprising:

[0036] (1) preparing a tannic acid pyridine solution, wherein the concentration of tannic acid in the tannic acid pyridine solution is 4 g / 100 mL, and the solvent is pyridine; heating the tannic acid pyridine solution to 30° C. in a water bath and keeping the temperature, then adding methyltetrahydrophthalic anhydride to the solution under stirring, wherein the volume ratio of the added mass of methyltetrahydrophthalic anhydride to the tannic acid pyridine solution is methyltetrahydrophthalic anhydride: tannic acid pyridine solution = 36 g: 100 mL; after the addition is completed, stirring is continued at a constant temperature of 30° C. for 1 hour, then heating to 90° C., stirring at a constant temperature of 90° C. for 40 hours, then naturally cooling to room temperature, adding excess ether for precipitation, collecting the precipitate by solid-liquid separation, and drying the precipitate at 60° C. for 2 hours to obtain a one-step synthetic product;

[0037] (2) adding apigenin to tert-amyl alcohol, the mass ratio of apigenin to tert-amyl alcohol is apigenin: tert-amyl alcohol = 10 g: 1 L, heating to 60° C. in a water bath, stirring at a constant temperature for 2 hours, and condensing and refluxing during the heat preservation process; then adding methyl laurate and immobilized lipase to the solution under stirring, the mass ratio of the added methyl laurate and immobilized lipase to the added apigenin is methyl laurate: immobilized lipase: apigenin = 60 g: 3 g: 10 g; the immobilized lipase is Lipozyme 435 enzyme; after the addition is completed, stirring is continued at a constant temperature of 60° C. for 20 hours, and after the stirring is completed, air cooling is performed to room temperature to obtain a two-step synthesis product;

[0038] (3) preparing a protocatechuic acid epichlorohydrin solution, wherein the protocatechuic acid concentration in the protocatechuic acid epichlorohydrin solution is 6 g / 100 mL and the solvent is epichlorohydrin; heating the protocatechuic acid epichlorohydrin solution to 95° C. in an oil bath and then adding dodecyltrimethylammonium chloride to the solution under stirring, and continuing to stir the solution at a constant temperature of 95° C. for 20 minutes after the addition is completed, and then adding sodium hydroxide solution dropwise to the solution under stirring, and the dodecyltrimethylammonium chloride and sodium hydroxide solution are added. The volume ratio of the amount of protocatechuic acid to the epichlorohydrin solution of protocatechuic acid is dodecyltrimethylammonium chloride: sodium hydroxide solution: epichlorohydrin solution of protocatechuic acid = 3g: 6mL: 100mL, wherein the mass percentage of the solute in the sodium hydroxide solution is 20%, and the solvent is water; after the dropwise addition is completed, the solution is continuously stirred at a constant temperature of 95°C for 3h, then naturally cooled to room temperature, and the pH of the solution is adjusted to neutral with dilute hydrochloric acid, wherein the mass percentage of the solute in the dilute hydrochloric acid is 5%; water and epichlorohydrin are removed by rotary evaporation to obtain a cross-linked product;

[0039] (4) The one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide and water are mixed to form a mixture, the mixture is heated to 96° C., and then the mixture is stirred at a constant temperature for 2 hours, and condensed and refluxed during the constant temperature process; after the stirring is completed, the mixture is naturally cooled to 40° C., and then the cross-linked product and formaldehyde solution are added under stirring, and the one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide, water, the cross-linked product and formaldehyde solution used are calculated by weight: 24 parts of the one-step synthetic product, 16 parts of the two-step synthetic product, 50 parts of phenol, 18 parts of sodium hydroxide, 60 parts of water, 15 parts of the cross-linked product, and 120 parts of the formaldehyde solution, wherein the formaldehyde solution is a formaldehyde aqueous solution with a solute mass percentage of 37%; after the addition is completed, the mixture is heated to 85° C. and stirred at this temperature for 1 hour. After the stirring is completed, the mixture is cooled to room temperature by stirring in an ice bath, and sulfuric acid (the solute mass percentage is 20%, and the solvent is water) is added to adjust the pH to 7.5 to obtain the bamboo board adhesive.

[0040] Comparative Example 1

[0041] A method for preparing a bamboo board adhesive as a comparison, the preparation steps comprising:

[0042] (1) adding apigenin to tert-amyl alcohol, the mass ratio of apigenin to tert-amyl alcohol is apigenin:tert-amyl alcohol=9g:1L, heating to 60°C in a water bath, stirring at constant temperature for 2h, and condensing and refluxing during the heat preservation process; then adding methyl laurate and immobilized lipase to the solution under stirring, the mass ratio of the added methyl laurate and immobilized lipase to the added apigenin is methyl laurate:immobilized lipase:apigenin=56g:3g:9g; the immobilized lipase is Lipozyme435 enzyme; after the addition is completed, stirring is continued at 60°C for 20h, and after the stirring is completed, air cooling is performed to room temperature to obtain the synthetic product of this comparative example;

[0043] (2) preparing a protocatechuic acid epichlorohydrin solution, wherein the protocatechuic acid concentration in the protocatechuic acid epichlorohydrin solution is 5 g / 100 mL and the solvent is epichlorohydrin; heating the protocatechuic acid epichlorohydrin solution to 95° C. in an oil bath and then adding dodecyltrimethylammonium chloride to the solution under stirring, and continuing to stir the solution at a constant temperature of 95° C. for 20 minutes after the addition is completed, and then adding sodium hydroxide solution dropwise to the solution under stirring, and the dodecyltrimethylammonium chloride and sodium hydroxide solution are added. The volume ratio of the amount of protocatechuic acid to the epichlorohydrin solution of protocatechuic acid is dodecyltrimethylammonium chloride: sodium hydroxide solution: epichlorohydrin solution of protocatechuic acid = 3g: 6mL: 100mL, wherein the mass percentage of the solute in the sodium hydroxide solution is 20%, and the solvent is water; after the dropwise addition is completed, the solution is continuously stirred at a constant temperature of 95°C for 3h, then naturally cooled to room temperature, and the pH of the solution is adjusted to neutral with dilute hydrochloric acid, wherein the mass percentage of the solute in the dilute hydrochloric acid is 5%; water and epichlorohydrin are removed by rotary evaporation to obtain a cross-linked product;

[0044] (3) The synthetic product, phenol, sodium hydroxide and water are mixed to form a mixture, the mixture is heated to 96° C., and then the mixture is stirred at a constant temperature for 2 hours, and condensation reflux is performed during the constant temperature process; after the stirring is completed, the mixture is naturally cooled to 40° C., and then the cross-linked product and formaldehyde solution are added under stirring, and the synthetic product, phenol, sodium hydroxide, water, the cross-linked product and formaldehyde solution used are calculated in parts by weight: 14 parts of synthetic product, 50 parts of phenol, 17 parts of sodium hydroxide, 55 parts of water, 14 parts of cross-linked product, and 120 parts of formaldehyde solution, wherein the formaldehyde solution is a formaldehyde aqueous solution with a solute mass percentage of 37%; after the addition is completed, the mixture is heated to 85° C. and stirred at this temperature for 1 hour. After the stirring is completed, the mixture is cooled to room temperature by stirring in an ice bath, and sulfuric acid (the solute mass percentage is 20%, and the solvent is water) is added to adjust the pH to 7.5 to obtain the bamboo board adhesive of this comparative example.

[0045] Comparative Example 2

[0046] A method for preparing a bamboo board adhesive for comparison, the preparation steps comprising:

[0047] (1) preparing a tannic acid pyridine solution, wherein the concentration of tannic acid in the tannic acid pyridine solution is 4 g / 100 mL, and the solvent is pyridine; heating the tannic acid pyridine solution to 30° C. in a water bath and keeping the temperature, then adding methyltetrahydrophthalic anhydride to the solution under stirring, wherein the volume ratio of the added mass of methyltetrahydrophthalic anhydride to the tannic acid pyridine solution is methyltetrahydrophthalic anhydride: tannic acid pyridine solution = 34 g: 100 mL; after the addition is completed, stirring is continued at a constant temperature of 30° C. for 1 hour, then heating to 90° C., stirring at a constant temperature of 90° C. for 40 hours, then naturally cooling to room temperature, adding excess ether for precipitation, collecting the precipitate by solid-liquid separation, and drying the precipitate at 60° C. for 2 hours to obtain a one-step synthetic product;

[0048] (2) preparing a protocatechuic acid epichlorohydrin solution, wherein the protocatechuic acid concentration in the protocatechuic acid epichlorohydrin solution is 5 g / 100 mL and the solvent is epichlorohydrin; heating the protocatechuic acid epichlorohydrin solution to 95° C. in an oil bath and then adding dodecyltrimethylammonium chloride to the solution under stirring, and continuing to stir the solution at a constant temperature of 95° C. for 20 minutes after the addition is completed, and then adding sodium hydroxide solution dropwise to the solution under stirring, and the dodecyltrimethylammonium chloride and sodium hydroxide solution are added. The volume ratio of the amount of protocatechuic acid to the epichlorohydrin solution of protocatechuic acid is dodecyltrimethylammonium chloride: sodium hydroxide solution: epichlorohydrin solution of protocatechuic acid = 3g: 6mL: 100mL, wherein the mass percentage of the solute in the sodium hydroxide solution is 20%, and the solvent is water; after the dropwise addition is completed, the solution is continuously stirred at a constant temperature of 95°C for 3h, then naturally cooled to room temperature, and the pH of the solution is adjusted to neutral with dilute hydrochloric acid, wherein the mass percentage of the solute in the dilute hydrochloric acid is 5%; water and epichlorohydrin are removed by rotary evaporation to obtain a cross-linked product;

[0049] (3) The one-step synthetic product, phenol, sodium hydroxide and water are mixed to form a mixture, the mixture is heated to 96° C., and then the mixture is stirred at a constant temperature for 2 hours, and condensation reflux is performed during the constant temperature process; after the stirring is completed, the mixture is naturally cooled to 40° C., and then the cross-linked product and formaldehyde solution are added under stirring, and the one-step synthetic product, phenol, sodium hydroxide, water, the cross-linked product and formaldehyde solution used are calculated by weight: 22 parts of one-step synthetic product, 50 parts of phenol, 17 parts of sodium hydroxide, 55 parts of water, 14 parts of cross-linked product, and 120 parts of formaldehyde solution, wherein the formaldehyde solution is a formaldehyde aqueous solution with a solute mass percentage of 37%; after the addition is completed, the mixture is heated to 85° C. and stirred at this temperature for 1 hour. After the stirring is completed, the mixture is cooled to room temperature by stirring in an ice bath, and sulfuric acid (the solute mass percentage is 20%, and the solvent is water) is added to adjust the pH to 7.5 to obtain the bamboo board adhesive of this comparative example.

[0050] Comparative Example 3

[0051] A method for preparing a bamboo board adhesive as a comparison, the preparation steps comprising:

[0052] (1) preparing a tannic acid pyridine solution, wherein the concentration of tannic acid in the tannic acid pyridine solution is 4 g / 100 mL, and the solvent is pyridine; heating the tannic acid pyridine solution to 30° C. in a water bath and keeping the temperature, then adding methyltetrahydrophthalic anhydride to the solution under stirring, wherein the volume ratio of the added mass of methyltetrahydrophthalic anhydride to the tannic acid pyridine solution is methyltetrahydrophthalic anhydride: tannic acid pyridine solution = 34 g: 100 mL; after the addition is completed, stirring is continued at a constant temperature of 30° C. for 1 hour, then heating to 90° C., stirring at a constant temperature of 90° C. for 40 hours, then naturally cooling to room temperature, adding excess ether for precipitation, collecting the precipitate by solid-liquid separation, and drying the precipitate at 60° C. for 2 hours to obtain a one-step synthetic product;

[0053] (2) adding apigenin to tert-amyl alcohol, the mass ratio of apigenin to tert-amyl alcohol is apigenin:tert-amyl alcohol=9g:1L, heating to 60°C in a water bath, stirring at constant temperature for 2h, and condensing and refluxing during the heat preservation process; then adding methyl laurate and immobilized lipase to the solution under stirring, the mass ratio of the added methyl laurate and immobilized lipase to the added apigenin is methyl laurate:immobilized lipase:apigenin=56g:3g:9g; the immobilized lipase is Lipozyme435 enzyme; after the addition is completed, stirring is continued at 60°C for 20h, and after the stirring is completed, air cooling is performed to room temperature to obtain a two-step synthesis product;

[0054] (3) The one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide and water are mixed to form a mixture, the mixture is heated to 96° C., and then the mixture is stirred at a constant temperature for 2 hours, and condensation reflux is performed during the constant temperature process; after the stirring is completed, the mixture is naturally cooled to 40° C., and then a formaldehyde solution is added under stirring, wherein the one-step synthetic product, the two-step synthetic product, phenol, sodium hydroxide, water and formaldehyde solution used are calculated in parts by weight as follows: 22 parts of the one-step synthetic product, 14 parts of the two-step synthetic product, 50 parts of phenol, 17 parts of sodium hydroxide, 55 parts of water, and 120 parts of formaldehyde solution, wherein the formaldehyde solution is a formaldehyde aqueous solution with a solute mass percentage of 37%; after the addition is completed, the mixture is heated to 85° C., stirred at this temperature for 1 hour, cooled to room temperature by stirring in an ice bath after the stirring is completed, sulfuric acid (the solute mass percentage is 20%, and the solvent is water) is added to adjust the pH to 7.5, and the bamboo board adhesive of this comparative example is obtained.

[0055] Example 5

[0056] The bonding strength of the adhesives prepared by the methods described in the above embodiments and comparative examples was tested according to the requirements of standard GB / T14074-2017, and the amount of adhesive applied was 150 g / m 2After gluing, the samples were hot pressed for 6 minutes with a hot press. The hot pressing pressure was set to 1.2 MPa and the temperature was set to 145°C. After hot pressing, they were left to stand at room temperature for 24 hours and then the bonding strength was tested. Each group of samples was tested 3 times and the average value was taken as the bonding strength value of the group. The results are shown in Table 1.

[0057] As shown in Table 1, the bamboo board adhesive prepared by the method of the present invention has a higher bonding strength, which is significantly higher than the 0.7MPa required by the standard, showing good adhesion, and further improving the durability of the bamboo board product. By comparing Example 3 of the present invention and each comparative example, it can be seen that by adding the one-step synthesis product, the two-step synthesis product and the cross-linked product prepared by the method of the present invention to the components of the traditional phenolic resin adhesive, the bonding strength of the adhesive can be significantly optimized. This is mainly due to: tannic acid contains a large amount of phenolic hydroxyl groups, and the present invention first modifies the phenolic hydroxyl groups of tannic acid by methyltetrahydrophthalic anhydride to obtain a hyperbranched polymer containing more long-chain fatty chain segments, on the one hand, the long-chain fatty chain segments can disperse stress during the force-bearing process, improve the toughness and strength of the subsequent phenolic resin, and on the other hand, can improve the connection strength of each component in the phenolic resin, thereby improving the strength and viscosity of the adhesive as a whole. Then, apigenin and methyl laurate are ester-exchanged to form macromolecules containing acyl groups, which form an interpenetrating network structure with the phenolic resin and the above-mentioned hyperbranched polymer to improve the adhesion; finally, by adding a cross-linked product and utilizing the epoxy group in the cross-linked product, the cross-linking density of the molecules in the resin is increased, thereby improving the overall adhesion strength of the adhesive.

[0058] Table 1

[0059] Experimental Group Bonding strength (MPa) Example 1 2.62 Example 2 2.73 Example 3 2.79 Example 4 2.76 Comparative Example 1 1.91 Comparative Example 2 1.80 Comparative Example 3 1.58

[0060] The technical solution provided by the present invention is introduced in detail above. For those skilled in the art, according to the concept of the embodiments of the present invention, there may be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a bamboo board adhesive with strong adhesion, characterized in that: The preparation steps include: (1) preparing a pyridine solution of tannic acid, heating the pyridine solution of tannic acid in a water bath to 30±3° C., then adding methyltetrahydrophthalic anhydride to the solution under stirring, continuing to stir at a constant temperature of 30±3° C. for more than 1 hour after the addition is completed, then heating to 90±3° C., stirring at a constant temperature of 90±3° C. for more than 40 hours, then naturally cooling to room temperature, adding excess ether for precipitation, collecting the precipitate by solid-liquid separation, and drying the precipitate to obtain a one-step synthetic product; (2) adding apigenin to tert-amyl alcohol, heating to 60±2° C. in a water bath, stirring at a constant temperature for more than 2 hours, and condensing and refluxing during the heat preservation process; then adding methyl laurate and immobilized lipase to the solution under stirring, and continuing to stir at a constant temperature of 60±2° C. for more than 20 hours after the addition is completed, and air cooling to room temperature after the stirring is completed to obtain a two-step synthetic product; (3) preparing a protocatechuic acid epichlorohydrin solution, heating the protocatechuic acid epichlorohydrin solution in an oil bath to 95±5° C. for insulation, then adding dodecyltrimethylammonium chloride to the solution under stirring, and continuing to stir the solution at a constant temperature of 95±5° C. for more than 20 minutes after the addition is completed, and then dropping sodium hydroxide solution into the solution under stirring, and continuing to stir the solution at a constant temperature of 95±5° C. for more than 3 hours after the dropwise addition is completed, and then naturally cooling to room temperature, adjusting the pH of the solution to neutral with dilute hydrochloric acid, and removing water and epichlorohydrin by rotary evaporation to obtain a cross-linked product; (4) The one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide and water are mixed to form a mixture, the mixture is heated to 96±2° C., and then the mixture is stirred at a constant temperature for 2-3 hours, and condensed and refluxed during the constant temperature process; after the stirring is completed, it is naturally cooled to 40±2° C., and then the cross-linked product and formaldehyde solution are added under stirring. After the addition is completed, it is heated to 85±2° C. and stirred at this temperature for more than 1 hour. After the stirring is completed, the mixture is cooled to room temperature by stirring in an ice bath, and sulfuric acid is added to adjust the pH to 7.5-8 to obtain the bamboo board adhesive.

2. The method for preparing a bamboo board adhesive with strong adhesion according to claim 1, characterized in that: In the step (1), the concentration of tannic acid in the pyridine solution of tannic acid is 3-4 g / 100 mL, and the solvent is pyridine; the volume ratio of the added mass of methyltetrahydrophthalic anhydride to the pyridine solution of tannic acid is methyltetrahydrophthalic anhydride: pyridine solution of tannic acid = 32-36 g: 100 mL.

3. The method for preparing a bamboo board adhesive with strong adhesion according to claim 1, characterized in that: In the step (2), apigenin is added to tert-amyl alcohol in a ratio of apigenin:tert-amyl alcohol=8-10 g:1 L, and the added mass ratio of methyl laurate and immobilized lipase to the added mass ratio of apigenin is methyl laurate:immobilized lipase:apigenin=50-60 g:2-3 g:8-10 g.

4. The method for preparing a bamboo board adhesive with strong adhesion according to claim 3, characterized in that: The immobilized lipase is Lipozyme435 enzyme.

5. The method for preparing a bamboo board adhesive with strong adhesion according to claim 1, characterized in that: In the step (3), the concentration of protocatechuic acid in the epichlorohydrin solution of protocatechuic acid is 4-6 g / 100 mL, and the solvent is epichlorohydrin; the volume ratio of the added amount of the dodecyltrimethylammonium chloride and the sodium hydroxide solution to the epichlorohydrin solution of protocatechuic acid is dodecyltrimethylammonium chloride: sodium hydroxide solution: epichlorohydrin solution of protocatechuic acid = 2-3 g: 5-6 mL: 100 mL, wherein the mass percentage of the solute in the sodium hydroxide solution is 20%, and the solvent is water.

6. The method for preparing a bamboo board adhesive with strong adhesion according to claim 1, characterized in that: In the step (3), the mass percentage of the solute in the dilute hydrochloric acid is 5%.

7. The method for preparing a bamboo board adhesive with strong adhesion according to claim 1, characterized in that: In the step (4), the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, water, the cross-linked product and the formaldehyde solution are calculated in parts by weight as follows: 20 to 24 parts of the one-step synthesis product, 12 to 16 parts of the two-step synthesis product, 50 parts of phenol, 15 to 18 parts of sodium hydroxide, 50 to 60 parts of water, 10 to 15 parts of the cross-linked product, and 100 to 120 parts of the formaldehyde solution, wherein the formaldehyde solution is a formaldehyde aqueous solution with a solute mass percentage of 37%.