Bio-based moisture-proof antibacterial wood plywood and preparation method thereof

Abstract

The invention discloses bio-based moisture-proof and antibacterial wood plywood and a preparation method thereof, and belongs to the technical field of plywood. The preparation method comprises the following steps: stirring 8-15 parts of polyvinyl alcohol, 1-3 parts of an auxiliary agent and 90-100 parts of deionized water at 90-100 DEG C for 2-4 hours, and cooling to obtain a premixed solution; stirring 1-2 parts of copper salt and 12-16 parts of phosphoric acid to obtain a phosphoric acid solution of copper; mixing the premixed solution, a phosphoric acid solution of copper, 0.01-0.1 part of a defoaming agent, 1-2 parts of a thickening agent, 20-30 parts of flour and 25-35 parts of polyisocyanate to obtain an adhesive; the surface of the single board is coated with an adhesive, then the single board is laid into a board blank, pre-pressing and hot-pressing are conducted, and the wood plywood is obtained. The assistant endows the adhesive with excellent antibacterial property and water resistance; the bonding strength and the bonding water resistance of the adhesive are improved through the interaction among the premixed liquid containing the auxiliaries, the flour and the polyisocyanate, and the bio-based wood plywood is more dampproof and antibacterial through the combined action of the raw materials such as the thickening agent.

Description

Technical Field

[0001] The present invention belongs to the technical field of plywood, and specifically, relates to a bio-based moisture-proof and antibacterial wood plywood and a preparation method thereof. Background Art

[0002] Plywood is a sheet material made of three or more layers formed by veneering wood segments into veneers or planing wood blocks into thin woods and then gluing them with adhesives. Usually, an odd number of veneer layers are used, and the fiber directions of adjacent veneer layers are glued perpendicular to each other. Plywood is one of the commonly used materials for furniture and is one of the three major types of wood-based panels. It can also be used as a building material for airplanes, ships, trains, cars, buildings, and packaging boxes. A group of veneers is usually assembled and glued with the grain directions of adjacent layers perpendicular to each other. Usually, the surface veneer and the inner veneer are symmetrically arranged on both sides of the core layer or the board core. The board blank formed by arranging the veneers coated with glue in a crisscross pattern along the grain direction is pressed under heating or non-heating conditions. The number of layers is generally odd, and a few are even. The physical and mechanical properties in the longitudinal and transverse directions have relatively small differences. Commonly used types of plywood include three-ply boards and five-ply boards. Plywood can improve the utilization rate of wood and is a major way to save wood.

[0003] Wood plywood is made by gluing multiple thin wood slices with glue. Although its structural strength is high, it will absorb water and expand in a humid environment, resulting in deformation or damage of the board. At the same time, it will also breed miscellaneous bacteria, leading to mildew, which poses a great threat to human health. In addition, most of the existing wood plywood uses formaldehyde-based adhesives. The biggest problem with this adhesive is that it will release formaldehyde, which is extremely harmful to the human body. With the economic development and social progress, people's awareness of environmental protection and health has been significantly improved, and people are more pursuing bio-based wood plywood that does not cause harm to the human body. Therefore, researching and producing a bio-based moisture-proof and antibacterial wood plywood is an urgent problem to be solved in the current plywood field. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a bio-based moisture-proof and antibacterial wood plywood and a preparation method thereof.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A preparation method of a bio-based moisture-proof and antibacterial wood plywood includes the following steps:

[0007] (1) Stir 8 - 15 parts by weight of polyvinyl alcohol, 1 - 3 parts of auxiliary agent, and 90 - 100 parts of deionized water evenly, heat up to 90 - 100 °C and continue stirring for 2 - 4 h, then cool to room temperature to obtain a premixed solution; Stir 1 - 2 parts of copper salt and 12 - 16 parts of phosphoric acid evenly to obtain a copper phosphoric acid solution; Mix the premixed solution, the copper phosphoric acid solution, 0.01 - 0.1 part of defoaming agent, 1 - 2 parts of thickening agent, 20 - 30 parts of flour, and 25 - 35 parts of polyisocyanate evenly to obtain an adhesive;

[0008] (2) Use a roller coater to coat the adhesive on the surface of the veneer, then lay the veneers longitudinally and crosswise in the direction of the wood grain to form a board blank, and pre - press and then hot - press the obtained board blank to obtain a wood plywood.

[0009] Further, the auxiliary agent is prepared through the following steps:

[0010] S1. Under nitrogen protection, add D - glucosamine, triethylamine, and ethanol into a three - necked flask, stir to dissolve, then slowly add 3 - chloro - 1,2 - propanediol. After adding, heat up to 60 °C and stir for 3 h. After the reaction is completed, cool to room temperature, perform reduced - pressure distillation, and purify by column chromatography (select a mixed solvent of chloroform and methanol as the eluent, and the volume ratio of chloroform to methanol is 19:1), then perform reduced - pressure distillation to obtain intermediate 1; The dosage ratio of D - glucosamine, 3 - chloro - 1,2 - propanediol, triethylamine, and ethanol is 28 g:12 mL:24 mL:200 mL;

[0011] Triethylamine is used as an acid - binding agent, controlling the molar ratio of D - glucosamine to 3 - chloro - 1,2 - propanediol to be 1.05 - 1.1:1. The - NH2 of D - glucosamine undergoes a nucleophilic substitution reaction with the - Cl of 3 - chloro - 1,2 - propanediol, and the reaction process is as follows:

[0012]

[0013] S2. Under nitrogen protection, add intermediate 1, triethylamine, and toluene into a three - necked flask, stir to dissolve, then slowly add bromotetradecane. After adding, heat up to 70 °C and stir for 3 h. After the reaction is completed, cool to room temperature, perform reduced - pressure distillation, and purify by column chromatography (select a mixed solvent of chloroform and acetone as the eluent, and the volume ratio of chloroform to acetone is 17:3), then perform reduced - pressure distillation to obtain intermediate 2; The dosage ratio of intermediate 1, bromotetradecane, triethylamine, and toluene is 25 g:27 mL:15 mL:200 mL;

[0014] Triethylamine is used as an acid - binding agent, controlling the molar ratio of intermediate 1 to bromotetradecane to be 1.05 - 1.1:1. The - NH - of intermediate 1 undergoes a nucleophilic substitution reaction with the - Br of bromotetradecane, and the reaction process is as follows:

[0015]

[0016] S3. Nitrogen was used to blow-dry the three-necked flask for 30 min to expel the air and moisture inside the flask. Subsequently, intermediate 2, pyridine, and toluene were added. After stirring and dissolving, 3-chloropropyltriethoxysilane was slowly added under nitrogen protection. After the addition was completed, the temperature was raised to 70 °C and stirred for reaction for 4 h. After the reaction ended, it was cooled to room temperature, and then subjected to vacuum distillation and column chromatography purification (the eluent was a mixed solvent of benzene and ethyl acetate, and the volume ratio of benzene to ethyl acetate was 1:1). After vacuum distillation, the auxiliary agent was obtained. The dosage ratio of intermediate 2, 3-chloropropyltriethoxysilane, pyridine, and toluene was 27 g:16 mL:5.5 mL:200 mL.

[0017] Pyridine was used as an acid-binding agent to control the molar ratio of intermediate 2 to 3-chloropropyltriethoxysilane to be 1:1.1 - 1.15. The tertiary amine of intermediate 2 underwent a nucleophilic substitution reaction with the -Cl of 3-chloropropyltriethoxysilane. The reaction process is shown as follows:

[0018]

[0019] The auxiliary agent contains an organosilicon quaternary ammonium salt structure. The organosilicon quaternary ammonium salt structure has good bactericidal effects on Staphylococcus aureus and Escherichia coli. This is because the cations in the organosilicon quaternary ammonium salt structure are adsorbed on the negatively charged bacteria through electrostatic force and hydrogen bonds, and hydrophobic binding occurs between the surfactant and proteins. The organosilicon quaternary ammonium salt causes a chamber resistance effect in bacteria. At the same time, the interaction between the surfactant molecules and proteins changes the permeability of the membrane in bacteria, thereby changing the cell structure and causing the cells to rupture, resulting in the death of bacteria. The antibacterial property of the quaternary ammonium salt is also related to the alkyl chain length of the quaternary ammonium salt. When the number of carbon atoms in the alkyl chain of the quaternary ammonium salt is 14, the antibacterial property of the quaternary ammonium salt antibacterial agent is the strongest. Therefore, the long carbon chain (14 carbons) enhances the antibacterial property of the auxiliary agent. Therefore, adding the auxiliary agent into the adhesive and then preparing the wood plywood has excellent antibacterial effects, is not easy to breed miscellaneous bacteria, is not easy to mildew, and the service life is greatly increased.

[0020] The auxiliary agent of the present invention contains silane oxy groups, which will hydrolyze in water to generate Si-OH and -Si-O-Si- chains. Therefore, when the adhesive dries, the -Si-O-Si- chains will migrate to the surface of the adhesive. The silicon atom is at the center of the tetrahedron in the compound. According to the tetrahedron structure, two ethyl groups are perpendicular to the plane where silicon is connected to two adjacent oxygen atoms. In addition, the Si-O bond length is relatively long, so that the five hydrogens on the two non-polar ethyl groups are like an opened umbrella, making the adhesive have good hydrophobicity. Furthermore, the adhesive of the present invention is not easy to absorb water and swell in a humid environment, can effectively prevent the deformation or damage of the wood plywood, enhances the water resistance of the wood plywood, and the service life is also greatly increased.

[0021] The auxiliary agent also contains abundant hydroxyl groups, which can form hydrogen bond interactions with the hydroxyl groups in polyvinyl alcohol. This not only increases the stability and dispersion degree of the auxiliary agent, but also increases the crosslinking degree of the premix. In addition, the hydroxyl groups of Si-OH in the auxiliary agent can form chemical bonds with the hydroxyl groups in flour, and the hydroxyl groups in the premix, the hydroxyl groups and amino groups in flour can all react chemically with the isocyanate groups in polyisocyanate. This further increases the stability and dispersion degree of the auxiliary agent and the crosslinking degree of the adhesive, so that the adhesive of the present invention has excellent and stable gluing strength and adhesive water resistance. The wood-based plywood of the present invention is also more antibacterial, mildew-proof and water-resistant, and its service life is greatly increased.

[0022] Further, the copper salt is one or more of copper phosphate, copper sulfate and copper nitrate.

[0023] Further, the defoaming agent is one or more of silicone defoaming agents.

[0024] Further, the thickening agent is one or more of carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose and xanthan gum.

[0025] Further, the polyisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate and polyphenyl polymethylene polyisocyanate.

[0026] Further, the veneer is one of poplar, walnut, pine and fir.

[0027] The present invention also discloses a bio-based moisture-proof and antibacterial wood-based plywood, which is prepared according to the preparation method of the above-mentioned bio-based moisture-proof and antibacterial wood-based plywood.

[0028] Advantages of the present invention:

[0029] (1) The wood-based plywood prepared by the present invention is a bio-based wood-based plywood that does not cause harm to the human body.

[0030] (2) The auxiliary agent containing abundant hydroxyl groups and the structure of organosilicon quaternary ammonium salt endows the adhesive with a high crosslinking degree and excellent antibacterial and water resistance; the interaction between the premix containing the auxiliary agent, flour and polyisocyanate increases the gluing strength and adhesive water resistance of the adhesive. Together with the co-action of raw materials such as thickening agent, the wood-based plywood of the present invention is more moisture-proof and antibacterial, and its service life is greatly increased. Specific embodiments

[0031] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] Example 1, Preparation of an auxiliary agent, the specific steps are as follows:

[0033] S1. Under nitrogen protection, 28 g of D-glucosamine, 24 mL of triethylamine and 200 mL of ethanol are added into a 500 mL three-necked flask, stirred and dissolved, and then 12 mL of 3-chloro-1,2-propanediol is slowly added. After the addition is completed, the temperature is raised to 60 °C and stirred for reaction for 3 h. After the reaction is completed, it is cooled to room temperature, distilled under reduced pressure, and purified by column chromatography (the eluent is a mixed solvent of chloroform and methanol, and the volume ratio of chloroform to methanol is 19:1), and distilled under reduced pressure to obtain Intermediate 1;

[0034] S2. Under nitrogen protection, 25 g of Intermediate 1, 15 mL of triethylamine and 200 mL of toluene are added into a 500 mL three-necked flask, stirred and dissolved, and then 27 mL of tetradecyl bromide is slowly added. After the addition is completed, the temperature is raised to 70 °C and stirred for reaction for 3 h. After the reaction is completed, it is cooled to room temperature, distilled under reduced pressure, and purified by column chromatography (the eluent is a mixed solvent of chloroform and acetone, and the volume ratio of chloroform to acetone is 17:3), and distilled under reduced pressure to obtain Intermediate 2;

[0035] S3. The 500 mL dry three-necked flask is purged with nitrogen for 30 min to remove the air and moisture in the flask. Then, 27 g of Intermediate 2, 5.5 mL of pyridine and 200 mL of toluene are added, stirred and dissolved, and then 16 mL of 3-chloropropyltriethoxysilane is slowly added under nitrogen protection. After the addition is completed, the temperature is raised to 70 °C and stirred for reaction for 4 h. After the reaction is completed, it is cooled to room temperature, distilled under reduced pressure, and purified by column chromatography (the eluent is a mixed solvent of benzene and ethyl acetate, and the volume ratio of benzene to ethyl acetate is 1:1), and distilled under reduced pressure to obtain the auxiliary agent.

[0036] Example 2, Preparation of wood plywood, the specific steps are as follows:

[0037] (1) According to parts by weight, 8 parts of polyvinyl alcohol, 1 part of the auxiliary agent prepared in Example 1 and 90 parts of deionized water are stirred evenly, heated to 90 °C and stirred for another 4 h, and cooled to room temperature to obtain a premixed solution; 1 part of copper nitrate and 12 parts of phosphoric acid are stirred evenly to obtain a copper phosphoric acid solution; the premixed solution, the copper phosphoric acid solution, 0.01 part of defoamer BYK-024, 1 part of carboxymethyl cellulose, 20 parts of flour and 25 parts of toluene diisocyanate are mixed evenly to obtain an adhesive;

[0038] (2) Use a roll coater to coat the adhesive on the surface of the veneer (poplar), with a single-sided sizing amount of 180 g / m 2 , then lay the veneers crosswise and lengthwise along the grain direction to form a board blank. First, pre-press the obtained board blank at 0.5 MPa for 60 min, and then hot-press it at 120 °C with a hot-pressing factor of 1.4 min / mm to obtain the wood-based plywood.

[0039] Example 3. Preparation of wood-based plywood. The specific steps are as follows:

[0040] (1) Stir 15 parts of polyvinyl alcohol, 3 parts of the auxiliary agent prepared in Example 1, and 100 parts of deionized water evenly by weight, heat up to 100 °C and continue stirring for 2 h, then cool to room temperature to obtain a premixed solution; Stir 1 part of copper sulfate, 1 part of copper nitrate, and 16 parts of phosphoric acid evenly to obtain a copper phosphoric acid solution; Mix the premixed solution, the copper phosphoric acid solution, 0.05 part of defoamer BYK-022, 0.05 part of defoamer BYK-024, 1 part of hydroxyethyl cellulose, 1 part of hydroxypropyl methylcellulose, 30 parts of flour, and 35 parts of diphenylmethane diisocyanate evenly to obtain the adhesive;

[0041] (2) Use a roll coater to coat the adhesive on the surface of the veneer (fir), with a single-sided sizing amount of 200 g / m 2 , then lay the veneers crosswise and lengthwise along the grain direction to form a board blank. First, pre-press the obtained board blank at 1.5 MPa for 20 min, and then hot-press it at 130 °C with a hot-pressing factor of 1.5 min / mm to obtain the wood-based plywood.

[0042] Example 4. Preparation of wood-based plywood. The specific steps are as follows:

[0043] (1) Stir 12 parts of polyvinyl alcohol, 2.5 parts of the auxiliary agent prepared in Example 1, and 95 parts of deionized water evenly by weight, heat up to 95 °C and continue stirring for 3 h, then cool to room temperature to obtain a premixed solution; Stir 1.5 parts of copper phosphate and 14 parts of phosphoric acid evenly to obtain a copper phosphoric acid solution; Mix the premixed solution, the copper phosphoric acid solution, 0.08 part of defoamer BYK-028, 1 part of carboxymethyl cellulose, 0.5 part of xanthan gum, 28 parts of flour, and 30 parts of polyphenyl polymethylene polyisocyanate evenly to obtain the adhesive;

[0044] (2) Use a roll coater to coat the adhesive on the surface of the veneer (pine), with a single-sided sizing amount of 190 g / m 2 , then lay the veneers crosswise and lengthwise along the grain direction to form a board blank. First, pre-press the obtained board blank at 1.1 MPa for 40 min, and then hot-press it at 125 °C with a hot-pressing factor of 1.45 min / mm to obtain the wood-based plywood.

[0045] Comparative Example 1. Preparation of wood-based plywood. The specific steps are as follows:

[0046] Keep the remaining steps unchanged, only remove the auxiliary agent in step (1) of Example 2 to prepare the wood plywood.

[0047] Comparative Example 2, prepare wood plywood, the specific steps are as follows:

[0048] Keep the remaining steps unchanged, only replace the auxiliary agent in step (1) of Example 2 with 1 part of tetradecyltrimethylammonium chloride to prepare the wood plywood.

[0049] Performance test

[0050] Place the wood plywood obtained by hot pressing Examples 2-4 and Comparative Examples 1-2 at room temperature for 8 h, and determine the formaldehyde release amount according to GB18580-2017 "Indoor Decorative and Refurbishment Materials - Formaldehyde Release Amount in Wood-Based Panels and Their Products"; determine the bonding strength according to GB / T 17657-2013 "Test Methods for Physical and Chemical Properties of Wood-Based Panels and Decorated Wood-Based Panels"; place the wood plywood obtained by hot pressing Examples 2-4 and Comparative Examples 1-2 at room temperature for 8 h, then immerse them in hot water at (63±3)°C for 3 h, cool at room temperature for 10 min, and then test the change rate of the bonding strength according to GB / T 17657-2013. The test results of all items are shown in Table 1 below:

[0051] Table 1

[0052] Test Items Formaldehyde Emission (mg / L) Gluing Strength (MPa) Rate of Change in Gluing Strength (%) Example 2 0.02 1.33 -6.5 Example 3 0.01 1.35 -6.1 Example 4 0.01 1.39 -5.6 Comparative Example 1 0.03 1.01 -9.3 Comparative Example 2 0.02 1.02 -9.1

[0053] It can be seen from the test results in Table 1 above that the wood plywood prepared in Examples 2-4 of the present invention has lower formaldehyde release amount, stronger bonding strength and water resistance.

[0054] Antibacterial property test: Add 20 mL of agar medium (prepare the agar solution by adding 3.2 g of nutrient agar to every 100 mL of deionized water, shake well and sterilize in an autoclave, wait until the temperature in the autoclave drops to 60°C, take out and set aside) and 0.1 mL of Escherichia coli suspension (Escherichia coli 35218: from the China Center for Type Culture Collection, 6×10 5 CFU / mL) into a sterile petri dish, after shaking evenly, add 70 mL of 0.01 mol / L phosphate buffer solution, place the wood plywood prepared in Examples 2-4 and Comparative Example 2 at room temperature for 8 h, cut them into thin slices with a diameter of 5 mm and add them to the petri dish, place each group of petri dishes in a constant temperature and humidity (temperature is 37°C, relative humidity is greater than 90%) incubator, culture at 37°C for 24 h and 30 days, and then calculate the antibacterial rate. The test results are shown in Table 2 below:

[0055] Table 2

[0056]

[0057] As can be seen from the results in Table 2 above, the wood plywood prepared in Examples 2-4 of the present invention has more excellent and stable antibacterial properties.

[0058] In the description of the specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0059] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the specific embodiments described or use similar methods to replace them. As long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A preparation method of a bio-based moisture-proof and antibacterial wood-based plywood, characterized in that, It includes the following steps: (1) Stir 8 - 15 parts by weight of polyvinyl alcohol, 1 - 3 parts of an auxiliary agent, and 90 - 100 parts of deionized water evenly, heat up to 90 - 100 °C and stir for 2 - 4 h, then cool to room temperature to obtain a premixed solution; Stir 1 - 2 parts of a copper salt and 12 - 16 parts of phosphoric acid evenly to obtain a copper phosphoric acid solution; Mix the premixed solution, the copper phosphoric acid solution, 0.01 - 0.1 part of an antifoaming agent, 1 - 2 parts of a thickening agent, 20 - 30 parts of flour, and 25 - 35 parts of polyisocyanate evenly to obtain an adhesive; (2) Use a roller coater to coat the adhesive on the surface of the veneer, then lay the veneers longitudinally and cross - longitudinally in the direction of the wood grain to form a board blank, pre - press and then hot - press the board blank to obtain a wood - based plywood; Among them, the auxiliary agent is prepared through the following steps: S1. Under nitrogen protection, add D - glucosamine, triethylamine, and ethanol into a flask, stir, add 3 - chloro - 1,2 - propanediol, heat up to 60 °C and react for 3 h, cool to room temperature, carry out vacuum distillation, purify by column chromatography, and then carry out vacuum distillation to obtain intermediate 1; The dosage ratio of D - glucosamine, 3 - chloro - 1,2 - propanediol, triethylamine, and ethanol is 28 g:12 mL:24 mL:200 mL; S2. Under nitrogen protection, add intermediate 1, triethylamine, and toluene into a flask, stir, add bromotetradecane, heat up to 70 °C and react for 3 h, after the reaction ends, cool to room temperature, carry out vacuum distillation, purify by column chromatography, and then carry out vacuum distillation to obtain intermediate 2; The dosage ratio of intermediate 1, bromotetradecane, triethylamine, and toluene is 25 g:27 mL:15 mL:200 mL; S3. After blowing nitrogen into the flask, add intermediate 2, pyridine, and toluene, stir, add 3 - chloropropyltriethoxysilane, heat up to 70 °C and react for 4 h, cool to room temperature, carry out vacuum distillation, purify by column chromatography, and then carry out vacuum distillation to obtain the auxiliary agent; The dosage ratio of intermediate 2, 3 - chloropropyltriethoxysilane, pyridine, and toluene is 27 g:16 mL:5.5 mL:200 mL.

2. The preparation method of a bio-based moisture-proof and antibacterial wood-based plywood according to claim 1, characterized in that, The copper salt is one or more of copper phosphate, copper sulfate, and copper nitrate.

3. The preparation method of a bio-based moisture-proof and antibacterial wood-based plywood according to claim 1, characterized in that, The antifoaming agent is one or more of silicone antifoaming agents.

4. The preparation method of a bio-based moisture-proof and antibacterial wood-based plywood according to claim 1, characterized in that, The thickening agent is one or more of carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and xanthan gum.

5. The preparation method of a bio-based moisture-proof and antibacterial wood-based plywood according to claim 1, characterized in that, The polyisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, and polyphenyl polymethylene polyisocyanate.

6. The preparation method of a bio-based moisture-proof and antibacterial wood-based plywood according to claim 1, characterized in that, The veneer is one of poplar, walnut, pine, and fir.

7. A bio-based moisture-proof and antibacterial wood-based plywood, characterized in that, It is prepared by the preparation method of a bio - based moisture - proof and antibacterial wood - based plywood according to any one of claims 1 - 6.

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