A strong adhesive for bamboo board and its preparation method

Abstract

The application discloses a preparation method of a bamboo board adhesive with high adhesion, and the preparation steps comprise the following steps: (1) preparing a one-step synthesis product; (2) preparing a two-step synthesis product; (3) preparing a cross-linking product; (4) mixing the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide and water to form a mixture, heating, stirring, then adding the cross-linking product and a formaldehyde solution, heating again after the feeding is completed, keeping warm and stirring, and stirring to room temperature in an ice bath, adjusting the pH, and obtaining the bamboo board adhesive. The bamboo board adhesive prepared by the method has high bonding strength, shows good adhesion, and further improves the durability of the bamboo board product.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bamboo-wood adhesive, in particular to a strong-bonding bamboo board adhesive and a preparation method thereof. BACKGROUND

[0002] According to the traditional classification concept of bamboo-wood artificial board, the currently produced bamboo-wood artificial board mainly includes: bamboo plywood (including bamboo woven plywood, bamboo curtain plywood, etc.), bamboo particle board (including bamboo shaving board and bamboo fiber board), bamboo large piece / directional shaving board and bamboo strip integrated board, bamboo / wood composite plywood and bamboo / wood composite floor, and bamboo-based veneered board covered with resin impregnated paper, wood veneer and other veneer materials. Therefore, the adhesive has a wide application in the bamboo-wood processing industry. The adhesive for bamboo-wood artificial board is mainly composed of traditional phenolic and urea-formaldehyde synthetic resin, wherein the phenolic resin is a common phenolic adhesive, which is generally obtained by polycondensation of phenolic compounds such as phenol, m-diphenol, cresol, bisphenol A and aldehyde compounds such as formaldehyde, paraformaldehyde, furfural and glyoxal. The phenolic resin is one of the commonly used adhesives for wood veneer products due to its excellent strength, water resistance and thermal stability. SUMMARY

[0003] To this end, the present application provides a preparation method of a strong-bonding bamboo board adhesive, and the preparation steps include:

[0004] (1) a pyridine solution of tannic acid is configured, the pyridine solution of tannic acid is heated to 30±3℃ in a water bath for insulation, then methyl tetrahydrophthalic anhydride is added to the solution under stirring, after the completion of feeding, the solution is continuously stirred at 30±3℃ for 1h or more, then heated to 90±3℃, and the solution is continuously stirred at 90±3℃ for 40h or more, then naturally cooled to room temperature, an excess of diethyl ether is added for precipitation, the precipitate is collected by solid-liquid separation, the precipitate is dried, and a one-step synthesis product is obtained;

[0005] (2) apigenin is added to tert-amyl alcohol, and the solution is heated to 60±2℃ in a water bath for insulation, and stirred at constant temperature for 2h or more, and condensed reflux during the insulation process; then methyl laurate and immobilized lipase are added to the solution under stirring, after the completion of feeding, the solution is continuously stirred at 60±2℃ for 20h or more, and the solution is air-cooled to room temperature after stirring, and a two-step synthesis product is obtained;

[0006] (3) an epichlorohydrin solution of protocatechuic acid is configured, the epichlorohydrin solution of protocatechuic acid is heated to 95±5℃ in an oil bath for insulation, then dodecyltrimethylammonium chloride is added to the solution under stirring, after the completion of feeding, the solution is continuously stirred at 95±5℃ for 20min or more, then sodium hydroxide solution is added dropwise to the solution under stirring, after the completion of dropwise addition, the solution is continuously stirred at 95±5℃ for 3h or more, then the solution is naturally cooled to room temperature, the pH of the solution is adjusted to neutral with dilute hydrochloric acid, and water and epichlorohydrin are removed by rotary evaporation, and a crosslinking product is obtained;

[0007] (4) mixing the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide and water to form a mixture, heating the mixture to 96±2℃, then constant temperature stirring the mixture for 2-3h, condensing reflux during the constant temperature process; after the stirring is completed, it is naturally cooled to 40±2℃, then the cross-linking product and formaldehyde solution are added under stirring, after the feeding is completed, it is heated to 85±2℃, constant temperature stirring for 1h or more, after the stirring is completed, ice bath stirring is used to reduce the temperature to room temperature, sulfuric acid is added to adjust the pH to 7.5-8, and the bamboo board adhesive is obtained.

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

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

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

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

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

[0013] Further, in the step (4), the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, water, the cross-linking product and the formaldehyde solution are 20-24 parts, 12-16 parts, 50 parts of phenol, 15-18 parts of sodium hydroxide, 50-60 parts of water, 10-15 parts of cross-linking product and 100-120 parts of formaldehyde solution by weight fraction, and the formaldehyde solution is a 37% mass percentage formaldehyde aqueous solution.

[0014] The bamboo board adhesive prepared by the method has high bonding strength, which is significantly higher than 0.7 MPa required by the standard, and exhibits good adhesion, and the durability of the bamboo board product is further improved. As can be seen from the comparison between Example 3 and the various comparative examples, by adding the one-step synthesis product, the two-step synthesis product and the crosslinking product prepared by the method to the components of the traditional phenolic resin adhesive, the bonding strength of the adhesive can be significantly optimized. This is mainly because tannic acid contains a large number of phenolic hydroxyl groups, and the phenolic hydroxyl groups of tannic acid are modified by methyl tetrahydrophthalic anhydride in the present application 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, the connection strength of the components in the phenolic resin can be improved, thereby improving the strength and adhesion of the adhesive as a whole. Then ester exchange is carried out with apiose and methyl laurate to form a macromolecule containing acyl groups, which forms an interpenetrating network structure with the phenolic resin and the above-mentioned hyperbranched polymer to improve the adhesion; finally, by adding the crosslinking product, the crosslinking density of the molecules in the resin is improved by using the epoxy groups in the crosslinking product, thereby improving the overall bonding strength of the adhesive. DETAILED DESCRIPTION

[0015] The present application will be further described below in conjunction with examples.

[0016] Example 1

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

[0018] (1) prepare a pyridine solution of tannic acid, wherein the concentration of tannic acid in the pyridine solution is 3 g / 100 mL, and the solvent is pyridine; heat the pyridine solution of tannic acid to 30℃ in a water bath for insulation, then add methyl tetrahydrophthalic anhydride to the solution under stirring, the mass ratio of methyl tetrahydrophthalic anhydride to the volume of the pyridine solution of tannic acid is methyl tetrahydrophthalic anhydride: pyridine solution of tannic acid = 32 g: 100 mL; after the addition is completed, continue to stir at 30℃ for 1 h, then heat to 90℃, and stir at 90℃ for 40 h, then naturally cool to room temperature, add excess diethyl ether for precipitation, collect the precipitate by solid-liquid separation, and dry the precipitate at 60℃ for 2 h to obtain a one-step synthesis product;

[0019] (2) adding apigenin into t-amyl alcohol, the amount of apigenin added into t-amyl alcohol is 8g:1L, water bath heating to 60℃, constant temperature stirring for 2h, condensing reflux during the constant temperature process; then adding methyl laurate and immobilized lipase into the solution under stirring, the mass ratio of methyl laurate, immobilized lipase and apigenin is methyl laurate: immobilized lipase: apigenin = 50g:2g:8g; the immobilized lipase is Lipozyme 435 enzyme; after the completion of feeding, continue constant temperature stirring at 60℃ for 20h, air cooling to room temperature after stirring, obtaining the two-step synthesis product;

[0020] (3) configuring epichlorohydrin solution of protocatechuic acid, the concentration of protocatechuic acid in the epichlorohydrin solution of protocatechuic acid is 4g / 100mL, and the solvent is epichlorohydrin; oil bath heating the epichlorohydrin solution of protocatechuic acid to 95℃, then adding dodecyltrimethylammonium chloride into the solution under stirring, after the completion of feeding, continue constant temperature stirring of the solution at 95℃ for 20min, then adding sodium hydroxide solution into the solution under stirring, the volume ratio of dodecyltrimethylammonium chloride, sodium hydroxide solution and 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 solute in the sodium hydroxide solution is 20%, and the solvent is water; after the completion of dropwise addition, continue constant temperature stirring of the solution at 95℃ for 3h, then naturally cooling to room temperature, adjusting the pH of the solution to neutral with dilute hydrochloric acid, the mass percentage of solute in the dilute hydrochloric acid is 5%; removing water and epichlorohydrin by rotary evaporation, obtaining the crosslinking product;

[0021] (4) mixing the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide and water to form a mixture, heating the mixture to 96℃, then constant temperature stirring the mixture for 2h, condensing reflux during the constant temperature process; after the completion of stirring, naturally cooling to 40℃, then adding the crosslinking product and formaldehyde solution under stirring, the used one-step synthesis product, two-step synthesis product, phenol, sodium hydroxide, water, the crosslinking product and formaldehyde solution are as follows: one-step synthesis product 20 parts, two-step synthesis product 12 parts, phenol 50 parts, sodium hydroxide 15 parts, water 50 parts, crosslinking product 10 parts, formaldehyde solution 100 parts, the formaldehyde solution is formaldehyde aqueous solution with a mass percentage of 37% of solute; after the completion of feeding, heating to 85℃ again, constant temperature stirring for 1h, ice bath stirring to reduce the temperature to room temperature after the completion of stirring, adding sulfuric acid (the mass percentage of solute is 20%, and the solvent is water) to adjust the pH to 7.5, obtaining the bamboo board adhesive.

[0022] Example 2

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

[0024] (1) A pyridine solution of tannic acid is configured, wherein the concentration of tannic acid in the pyridine solution is 3 g / 100 mL, and the solvent is pyridine; the pyridine solution of tannic acid is heated to 30°C in a water bath for preservation, and then methyltetrahydrophthalic anhydride is added to the solution under stirring, wherein the mass ratio of methyltetrahydrophthalic anhydride to the pyridine solution of tannic acid is 34 g:100 mL; after the addition is completed, constant temperature stirring at 30°C is continued for 1 h, and then heating to 90°C is performed, constant temperature stirring at 90°C is continued for 40 h, and then natural cooling to room temperature is performed; an excess of diethyl ether is added for precipitation, the precipitate is collected by solid-liquid separation, the precipitate is dried at 60°C for 2 h, and a one-step synthesis product is obtained;

[0025] (2) Apigenin is added to tert-amyl alcohol, and the amount of apigenin added to tert-amyl alcohol is in the ratio of apigenin:tert-amyl alcohol=9 g:1 L; water bath heating to 60°C is performed, and constant temperature stirring for 2 h is performed, with condensation reflux during the preservation process; then methyl laurate and immobilized lipase are added to the solution under stirring, wherein the mass ratio of methyl laurate to immobilized lipase to apigenin is 53 g:2 g:9 g; the immobilized lipase is Lipozyme 435 enzyme; after the addition is completed, constant temperature stirring at 60°C is continued for 20 h, and then air cooling to room temperature is performed after the stirring is completed, and a two-step synthesis product is obtained;

[0026] (3) An epichlorohydrin solution of protocatechuic acid is configured, wherein the concentration of protocatechuic acid in the epichlorohydrin solution is 5 g / 100 mL, and the solvent is epichlorohydrin; the epichlorohydrin solution of protocatechuic acid is heated to 95°C in an oil bath for preservation, then dodecyltrimethylammonium chloride is added to the solution under stirring, after the addition is completed, constant temperature stirring of the solution at 95°C is continued for 20 min, then sodium hydroxide solution is added dropwise to the solution under stirring, wherein the volume ratio of dodecyltrimethylammonium chloride to sodium hydroxide solution to the epichlorohydrin solution of protocatechuic acid is 2 g:5 mL:100 mL, and the mass percentage of solute in the sodium hydroxide solution is 20%, and the solvent is water; after the dropwise addition is completed, constant temperature stirring of the solution at 95°C is continued for 3 h, then natural cooling to room temperature is performed, the pH of the solution is adjusted to neutral with dilute hydrochloric acid, and the mass percentage of solute in the dilute hydrochloric acid is 5%; water and epichlorohydrin are removed by rotary evaporation, and a crosslinked product is obtained;

[0027] (4) mixing the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide and water to form a mixture, heating the mixture to 96℃, then constant temperature stirring the mixture for 2h, condensing reflux during constant temperature process; after stirring, natural cooling to 40℃, then adding the cross-linking product and formaldehyde solution under stirring, the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, water, the cross-linking product and formaldehyde solution are 22 parts, 14 parts, 50 parts, 16 parts, 55 parts, 12 parts, 110 parts by weight fraction respectively, the formaldehyde solution is 37% formaldehyde aqueous solution; after adding, heating to 85℃, constant temperature stirring for 1h, ice bath stirring to room temperature after stirring, adding sulfuric acid (20% solute, water as solvent) to adjust pH to 7.5, obtaining the bamboo board adhesive.

[0028] Example 3

[0029] A preparation method of a strong adhesive bamboo board adhesive, the preparation steps comprising:

[0030] (1) configuring a pyridine solution of tannic acid, the concentration of tannic acid in the pyridine solution of tannic acid is 4g / 100mL, and the solvent is pyridine; heating the pyridine solution of tannic acid to 30℃ in water bath, then adding methyl tetrahydrophthalic anhydride to the solution under stirring, the mass ratio of methyl tetrahydrophthalic anhydride to the volume of the pyridine solution of tannic acid is methyl tetrahydrophthalic anhydride: pyridine solution of tannic acid = 34g: 100mL; after adding, continuing constant temperature stirring at 30℃ for 1h, then heating to 90℃, constant temperature stirring at 90℃ for 40h, then natural cooling to room temperature, adding excess ethyl ether for precipitation, collecting the precipitate after solid-liquid separation, drying the precipitate at 60℃ for 2h, obtaining the one-step synthesis product;

[0031] (2) adding apioside to tert-amyl alcohol, the mass ratio of apioside to tert-amyl alcohol is apioside: tert-amyl alcohol = 9g: 1L, water bath heating to 60℃, constant temperature stirring for 2h, condensing reflux during constant temperature process; then adding methyl laurate and immobilized lipase to the solution under stirring, the mass ratio of methyl laurate to immobilized lipase to apioside is methyl laurate: immobilized lipase: apioside = 56g: 3g: 9g; the immobilized lipase is Lipozyme435 enzyme; after adding, continuing constant temperature stirring at 60℃ for 20h, air cooling to room temperature after stirring, obtaining the two-step synthesis product;

[0032] (3) configuring an epichlorohydrin solution of protocatechuic acid, wherein the concentration of protocatechuic acid in the epichlorohydrin solution of protocatechuic acid is 5 g / 100 mL, and the solvent is epichlorohydrin; heating the epichlorohydrin solution of protocatechuic acid to 95℃ in an oil bath, then adding dodecyltrimethylammonium chloride to the solution under stirring, continuing to stir the solution at 95℃ for 20 min after the addition is completed, then adding a sodium hydroxide solution dropwise to the solution under stirring, wherein the volume ratio of dodecyltrimethylammonium chloride, the sodium hydroxide solution, and the epichlorohydrin solution of protocatechuic acid is dodecyltrimethylammonium chloride: sodium hydroxide solution: epichlorohydrin solution of protocatechuic acid = 3 g: 6 mL: 100 mL, wherein the mass percentage of the solute in the sodium hydroxide solution is 20%, and the solvent is water; continuing to stir the solution at 95℃ for 3 h after the dropwise addition is completed, then naturally cooling to room temperature, adjusting the pH of the solution to neutral with dilute hydrochloric acid, wherein the mass percentage of the solute in the dilute hydrochloric acid is 5%; removing water and epichlorohydrin by rotary evaporation to obtain a crosslinking product;

[0033] (4) mixing the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, and water to form a mixture, heating the mixture to 96℃, then stirring the mixture at constant temperature for 2 h, and condensing backflow during the constant temperature process; naturally cooling to 40℃ after the stirring is completed, then adding the crosslinking product and a formaldehyde solution under stirring, wherein the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, water, the crosslinking product, and the formaldehyde solution are used in a weight fraction of one-step synthesis product 22 parts, two-step synthesis product 14 parts, phenol 50 parts, sodium hydroxide 17 parts, water 55 parts, crosslinking product 14 parts, and formaldehyde solution 120 parts, and the formaldehyde solution is a formaldehyde aqueous solution with a solute mass percentage of 37%; heating to 85℃ after the addition is completed, stirring at constant temperature for 1 h, ice-bath stirring to reduce the temperature to room temperature after the stirring is completed, and adding sulfuric acid (solute mass percentage 20%, solvent water) 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) configuration of tannic acid pyridine solution, the tannic acid pyridine solution, the concentration of tannic acid is 4g / 100mL, the solvent is pyridine; the tannic acid pyridine solution is heated to 30℃ in water bath, then methyl tetrahydrophthalic anhydride is added to the solution under stirring, the mass ratio of methyl tetrahydrophthalic anhydride to tannic acid pyridine solution is methyl tetrahydrophthalic anhydride: tannic acid pyridine solution = 36g: 100mL; after the completion of feeding, continue to stir at 30℃ for 1h, then heat to 90℃, stir at 90℃ for 40h, then cool to room temperature naturally, add excess ether for precipitation, collect the precipitate after solid-liquid separation, dry the precipitate at 60℃ for 2h, obtain the one-step synthesis product;

[0037] (2) add apigenin to tert-amyl alcohol, the amount of apigenin added to tert-amyl alcohol is apigenin: tert-amyl alcohol = 10g: 1L, heat to 60℃ in water bath, constant temperature stirring for 2h, condense backflow during incubation; then add methyl laurate and immobilized lipase to the solution under stirring, the mass ratio of methyl laurate to immobilized lipase to apigenin is methyl laurate: immobilized lipase: apigenin = 60g: 3g: 10g; the immobilized lipase is Lipozyme435 enzyme; after the completion of feeding, continue to stir at 60℃ for 20h, cool to room temperature after stirring, obtain the two-step synthesis product;

[0038] (3) configuration of protocatechuic acid epichlorohydrin solution, the concentration of protocatechuic acid in the protocatechuic acid epichlorohydrin solution is 6g / 100mL, the solvent is epichlorohydrin; the protocatechuic acid epichlorohydrin solution is heated to 95℃ in oil bath, then dodecyltrimethylammonium chloride is added to the solution under stirring, after the completion of feeding, continue to stir the solution at 95℃ for 20min, then add sodium hydroxide solution to the solution dropwise under stirring, the volume ratio of dodecyltrimethylammonium chloride to sodium hydroxide solution to protocatechuic acid epichlorohydrin solution is dodecyltrimethylammonium chloride: sodium hydroxide solution: protocatechuic acid epichlorohydrin solution = 3g: 6mL: 100mL, wherein the mass percentage of solute in the sodium hydroxide solution is 20%, the solvent is water; after the completion of dropwise addition, continue to stir the solution at 95℃ for 3h, then cool to room temperature naturally, adjust the pH of the solution to neutral with dilute hydrochloric acid, the mass percentage of solute in the dilute hydrochloric acid is 5%; remove water and epichlorohydrin by rotary evaporation, obtain the crosslinked product;

[0039] (4) mixing the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide and water to form a mixture, heating the mixture to 96℃, then constant temperature stirring the mixture for 2h, constant temperature process condensing reflux; after stirring, natural cooling to 40℃, then adding the cross-linking product and formaldehyde solution under stirring, the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, water, the cross-linking product and formaldehyde solution are 24 parts, 16 parts, 50 parts, 18 parts, 60 parts, 15 parts, 120 parts by weight fraction respectively, the formaldehyde solution is a 37% formaldehyde aqueous solution; after adding, heating to 85℃, constant temperature stirring for 1h, after stirring, ice bath stirring to room temperature, adding sulfuric acid (20% solute, water as solvent) to adjust pH to 7.5, obtaining the bamboo board adhesive.

[0040] Comparative Example 1

[0041] A preparation method of a comparative bamboo board adhesive, the preparation steps comprising:

[0042] (1) adding apigenin into t-amyl alcohol, the amount of apigenin added into t-amyl alcohol is apigenin:t-amyl alcohol = 9g:1L, water bath heating to 60℃, constant temperature stirring for 2h, constant temperature process condensing reflux; then adding methyl laurate and immobilized lipase into the solution under stirring, the mass ratio of methyl laurate and immobilized lipase to apigenin is methyl laurate: immobilized lipase: apigenin = 56g:3g:9g; the immobilized lipase is Lipozyme 435 enzyme; after adding, continuing constant temperature stirring at 60℃ for 20h, after stirring, air cooling to room temperature, obtaining the synthesis product of the comparative example;

[0043] (2) configuring an epoxy chloropropane solution of protocatechuic acid, in which the concentration of protocatechuic acid is 5 g / 100 mL and the solvent is epoxy chloropropane; heating the epoxy chloropropane solution of protocatechuic acid to 95℃ in an oil bath, then adding dodecyltrimethylammonium chloride to the solution under stirring, continuing to stir the solution at 95℃ for 20 min after the completion of the addition, then adding sodium hydroxide solution to the solution dropwise under stirring, the volume ratio of dodecyltrimethylammonium chloride, sodium hydroxide solution and the epoxy chloropropane solution of protocatechuic acid being dodecyltrimethylammonium chloride: sodium hydroxide solution: epoxy chloropropane solution of protocatechuic acid = 3 g: 6 mL: 100 mL, wherein the mass percentage of solute in the sodium hydroxide solution is 20% and the solvent is water; continuing to stir the solution at 95℃ for 3 h after the completion of the dropwise addition, then naturally cooling to room temperature, adjusting the pH of the solution to neutral with dilute hydrochloric acid, the mass percentage of solute in the dilute hydrochloric acid being 5%; removing water and epoxy chloropropane by rotary evaporation to obtain a cross-linking product;

[0044] (3) mixing the synthetic product, phenol, sodium hydroxide and water to form a mixture, heating the mixture to 96℃, then stirring the mixture at constant temperature for 2 h, condensing and refluxing in the process of constant temperature; naturally cooling to 40℃ after the completion of the stirring, then adding the cross-linking product and formaldehyde solution under stirring, the synthetic product, phenol, sodium hydroxide, water, the cross-linking product and formaldehyde solution used being 14 parts of synthetic product, 50 parts of phenol, 17 parts of sodium hydroxide, 55 parts of water, 14 parts of cross-linking product and 120 parts of formaldehyde solution, the formaldehyde solution being a formaldehyde aqueous solution with a solute mass percentage of 37%; heating to 85℃ again after the completion of the addition, stirring at constant temperature for 1 h, ice-bath stirring to reduce the temperature to room temperature after the completion of the stirring, adjusting the pH to 7.5 by adding sulfuric acid (solute mass percentage 20%, solvent water) to obtain the bamboo board adhesive of the present comparative example.

[0045] Comparative Example 2

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

[0047] (1) prepare a pyridine solution of tannic acid, wherein the concentration of tannic acid is 4 g / 100 mL and the solvent is pyridine; heat the pyridine solution of tannic acid to 30°C in a water bath, then add methyltetrahydrophthalic anhydride to the solution under stirring, wherein the mass ratio of methyltetrahydrophthalic anhydride to the pyridine solution of tannic acid is 34 g:100 mL; after the addition is completed, continue to stir at 30°C for 1 h, then heat to 90°C, and stir at 90°C for 40 h, then naturally cool to room temperature, add excess diethyl ether to precipitate, collect the precipitate by solid-liquid separation, and dry the precipitate at 60°C for 2 h to obtain a one-step synthesis product;

[0048] (2) prepare an epichlorohydrin solution of protocatechuic acid, wherein the concentration of protocatechuic acid is 5 g / 100 mL and the solvent is epichlorohydrin; heat the epichlorohydrin solution of protocatechuic acid to 95°C in an oil bath, then add dodecyltrimethylammonium chloride to the solution under stirring, continue to stir the solution at 95°C for 20 min after the addition is completed, then add a sodium hydroxide solution dropwise to the solution under stirring, wherein the volume ratio of dodecyltrimethylammonium chloride, the sodium hydroxide solution, and the epichlorohydrin solution of protocatechuic acid is 3 g:6 mL:100 mL, and the mass percentage of the solute in the sodium hydroxide solution is 20% and the solvent is water; after the dropwise addition is completed, continue to stir the solution at 95°C for 3 h, then naturally cool to room temperature, adjust the pH of the solution to neutral with dilute hydrochloric acid, and the mass percentage of the solute in the dilute hydrochloric acid is 5%; remove water and epichlorohydrin by rotary evaporation to obtain a crosslinking product;

[0049] (3) mix the one-step synthesis product, phenol, sodium hydroxide, and water to form a mixture, heat the mixture to 96°C, then stir the mixture at a constant temperature for 2 h, and condense and reflux during the constant temperature process; after the stirring is completed, naturally cool to 40°C, then add the crosslinking product and a formaldehyde solution under stirring, and the weight fractions of the one-step synthesis product, phenol, sodium hydroxide, water, the crosslinking product, and the formaldehyde solution are as follows: 22 parts of the one-step synthesis product, 50 parts of phenol, 17 parts of sodium hydroxide, 55 parts of water, 14 parts of the crosslinking product, and 120 parts of the formaldehyde solution, and the formaldehyde solution is a 37% formaldehyde aqueous solution; after the addition is completed, heat to 85°C again, and stir at a constant temperature for 1 h, then cool to room temperature by ice bath stirring, adjust the pH to 7.5 by adding sulfuric acid (20% solute, water solvent) to obtain the bamboo board adhesive of the present comparative example.

[0050] Comparative Example 3

[0051] A preparation method of a contrastive bamboo board adhesive, the preparation steps comprising:

[0052] (1) configure a pyridine solution of tannic acid, wherein the concentration of tannic acid in the pyridine solution is 4 g / 100 mL, and the solvent is pyridine; heat the pyridine solution of tannic acid to 30°C in a water bath, then add methyltetrahydrophthalic anhydride to the solution under stirring, the mass ratio of methyltetrahydrophthalic anhydride to the volume of the pyridine solution of tannic acid is methyltetrahydrophthalic anhydride: pyridine solution of tannic acid = 34 g: 100 mL; after the addition is completed, continue to stir at 30°C for 1 h, then heat to 90°C, and stir at 90°C for 40 h, then naturally cool to room temperature, add excess diethyl ether for precipitation, collect the precipitate after solid-liquid separation, and dry the precipitate at 60°C for 2 h to obtain a one-step synthesis product;

[0053] (2) add apigenin to tert-amyl alcohol, the amount of apigenin added to tert-amyl alcohol is apigenin: tert-amyl alcohol = 9 g: 1 L, heat to 60°C in a water bath, and stir at constant temperature for 2 h, and condense backflow during the constant temperature process; then add methyl laurate and immobilized lipase to the solution under stirring, the mass ratio of methyl laurate to immobilized lipase to apigenin is methyl laurate: immobilized lipase: apigenin = 56 g: 3 g: 9 g; the immobilized lipase is Lipozyme 435 enzyme; after the addition is completed, continue to stir at constant temperature at 60°C for 20 h, and cool to room temperature after stirring is completed to obtain a two-step synthesis product;

[0054] (3) mix the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, and water to form a mixture, heat the mixture to 96°C, then stir the mixture at constant temperature for 2 h, and condense backflow during the constant temperature process; after stirring is completed, naturally cool to 40°C, then add formaldehyde solution under stirring, the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, water, and formaldehyde solution are used in a weight fraction of one-step synthesis product 22 parts, two-step synthesis product 14 parts, phenol 50 parts, sodium hydroxide 17 parts, water 55 parts, and formaldehyde solution 120 parts, the formaldehyde solution is a 37% mass percentage formaldehyde aqueous solution; after the addition is completed, heat to 85°C again, stir at constant temperature for 1 h, then stir to cool to room temperature in an ice bath, add sulfuric acid (20% mass percentage of solute, water as solvent) to adjust the pH to 7.5 to obtain the bamboo board adhesive of the present contrastive example.

[0055] Example 5

[0056] Test the bonding strength of the adhesives prepared by the methods of the above examples and comparative examples according to the requirements of the standard GB / T14074-2017, and the sizing amount is 150 g / m 2After gluing, hot-pressing is carried out by using a hot press for 6 min, the hot-pressing pressure is set to 1.2 MPa, the temperature is set to 145 DEG C, after hot-pressing, normal temperature standing is carried out for 24 h, then the gluing strength is tested again, each group of samples is tested for 3 times, the average value is taken as the gluing strength value of the group, and the result is shown in Table 1.

[0057] As shown in Table 1, the bamboo board adhesive prepared by the method of the application has higher gluing strength, which is significantly higher than 0.7 MPa required by the standard, and exhibits good adhesion, and further improves the durability of the bamboo board product. As compared with Example 3 and each comparative example of the application, it can be seen that by adding the one-step synthesis product, the two-step synthesis product and the crosslinking product prepared by the method of the application into the components of the traditional phenolic resin adhesive, the gluing strength of the adhesive can be significantly optimized. This is mainly because: tannic acid contains a large number of phenolic hydroxyl groups, the phenolic hydroxyl groups of tannic acid are modified by methyl tetrahydrophthalic anhydride in the application, and a hyperbranched polymer containing more long-chain fatty chain segments is obtained, which can improve the toughness and strength of the subsequent phenolic resin on the one hand, and can improve the connection strength of each component in the phenolic resin on the other hand, thereby improving the strength and adhesion of the whole adhesive. Then ester exchange is carried out by using apiose and methyl laurate to form a macromolecule containing acyl groups, which forms an interpenetrating network structure with the phenolic resin and the above-mentioned hyperbranched polymer, thereby improving the adhesion; finally, by adding the crosslinking product, the crosslinking density of the molecules in the resin is improved by using the epoxy groups in the crosslinking product, thereby improving the overall adhesion strength of the adhesive.

[0058] Table 1

[0059] Test group Gluing 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 solutions provided by the application are described in detail above, and for the general technical personnel in the art, the specific implementation manners and application ranges will be changed according to the idea of the embodiments of the application, and according to the above, the content of the specification should not be understood as a limitation of the application.

Claims

1. A method for preparing a strong adhesive for a bamboo board, characterized by, The preparation steps include: (1) configuring a pyridine solution of tannic acid, heating the pyridine solution of tannic acid to 30±3°C in a water bath, then adding methyl tetrahydrophthalic anhydride to the solution under stirring, continuing to stir the solution at 30±3°C for 1h or more after the addition is completed, then heating to 90±3°C, stirring the solution at 90±3°C for 40h or more, then naturally cooling to room temperature, adding excess ether to precipitate, collecting the precipitate by solid-liquid separation, drying the precipitate, and obtaining a one-step synthesis product; (2) adding apiose to tert-amyl alcohol, heating to 60±2°C in a water bath, and stirring at constant temperature for 2h or more, with condensation reflux during the incubation; then adding methyl laurate and immobilized lipase to the solution under stirring, continuing to stir the solution at 60±2°C for 20h or more after the addition is completed, and cooling to room temperature after stirring, to obtain a two-step synthesis product; (3) configuring an epichlorohydrin solution of protocatechuic acid, heating the epichlorohydrin solution of protocatechuic acid to 95±5°C in an oil bath, then adding dodecyltrimethylammonium chloride to the solution under stirring, continuing to stir the solution at 95±5°C for 20min or more after the addition is completed, then adding sodium hydroxide solution to the solution dropwise under stirring, continuing to stir the solution at 95±5°C for 3h or more after the dropwise addition is completed, 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-linking product; (4) mixing the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, and water to form a mixture, heating the mixture to 96±2°C, then stirring the mixture at constant temperature for 2-3h, with condensation reflux during the incubation; after the stirring is completed, naturally cooling to 40±2°C, then adding the cross-linking product and formaldehyde solution under stirring, the one-step synthesis product, the two-step synthesis product, phenol, sodium hydroxide, water, the cross-linking product, and formaldehyde solution being in a weight ratio of: one-step synthesis product 20-24 parts, two-step synthesis product 12-16 parts, phenol 50 parts, sodium hydroxide 15-18 parts, water 50-60 parts, cross-linking product 10-15 parts, and formaldehyde solution 100-120 parts, the formaldehyde solution being a 37% formaldehyde aqueous solution; after the addition is completed, heating to 85±2°C, incubating and stirring for 1h or more, ice-bath stirring to reduce the temperature to room temperature after the stirring is completed, adjusting the pH to 7.5-8 with sulfuric acid, and obtaining the bamboo board adhesive.

2. The method of claim 1, wherein the adhesive for the bamboo board has a high bonding strength. In the step (1), the concentration of tannic acid in the pyridine solution of tannic acid is 3-4g / 100mL, and the solvent is pyridine; the mass ratio of methyl tetrahydrophthalic anhydride to the pyridine solution of tannic acid is methyl tetrahydrophthalic anhydride: pyridine solution of tannic acid = 32-36g: 100mL.

3. The method of claim 1, wherein the adhesive for the bamboo board has a high bonding strength. In the step (2), the amount ratio of apiose to tert-amyl alcohol is apiose: tert-amyl alcohol = 8-10g: 1L, and the mass ratio of methyl laurate and immobilized lipase to apiose is methyl laurate: immobilized lipase: apiose = 50-60g: 2-3g: 8-10g.

4. The method of claim 3, wherein the adhesive for the bamboo board has a high bonding strength. The immobilized lipase is Lipozyme 435 enzyme.

5. The method of claim 1, wherein the adhesive for the bamboo board has a high bonding strength. 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 adding amount of dodecyltrimethylammonium chloride and 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 solute in the sodium hydroxide solution is 20%, and the solvent is water.

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