Preparation method and bonding method of biomass adhesive for bonding wood at room temperature without pressure

Abstract

The invention discloses a preparation method of a biomass adhesive for bonding wood at room temperature without pressure and a bonding method of the biomass adhesive, and belongs to the field of wood processing. The problems that an existing biomass adhesive is large in viscosity, low in bonding strength, poor in water resistance and complex in process are solved. The method comprises the following steps: 1, treating the surface of a veneer to remove part of lignin and hemicellulose; secondly, the pretreated veneer is soaked in a cellulose solvent system to be completely dissolved; the bonding method comprises the following steps: coating the biomass adhesive for bonding the wood at room temperature without pressure on a to-be-bonded surface of the wood, then butting, dipping in water at room temperature, and finally drying at room temperature, thereby completing the bonding method. The preparation method is used for preparing and bonding the biomass adhesive for bonding the wood at room temperature without pressure.

Description

Technical Field

[0001] The invention belongs to the field of wood processing. Background Art

[0002] In recent years, with the global attention paid to the protection of forest resources, the production of artificial board products is an effective way to solve the difficulties of the wood processing industry. Artificial boards are made of wood or non-wood plant fibers as the main raw materials, processed into various material units, with or without adhesives and other additives, assembled and glued to form boards or shaped products, mainly including plywood, particleboard, fiberboard and its surface decorative boards and other products. Adhesives play a vital role in the production process of artificial boards. Through the hot pressing and curing of adhesives, the scraps of the wood processing industry (small-diameter wood, shavings, sawdust, etc.) can be prepared into artificial boards that can be used for furniture manufacturing and interior decoration. This is one of the effective ways to improve the comprehensive utilization rate of wood.

[0003] At present, most of the traditional adhesives used in the wood-based panel industry are synthetic resin adhesives, among which urea-formaldehyde resin, phenol-formaldehyde resin and melamine formaldehyde resin (hereinafter referred to as trialdehyde resin) are the most widely used. When using traditional adhesives, the following factors often need to be considered: (1) Process: The adhesive bonding process is complex, generally requiring hot pressing or cold pressing and other processes, which consumes a lot of energy; (2) Environmental protection: The raw materials of synthetic resin adhesives are mostly petrochemical resources, which are harmful to the ecological environment and are non-renewable; (3) Health: Taking the most commonly used urea-formaldehyde resin adhesive in production as an example, formaldehyde gas will be released during use. Formaldehyde is highly toxic and can cause cancer and teratogenesis. Therefore, biomass adhesives came into being. Common biomass-based adhesives mainly include lignin adhesives, cellulose adhesives, tannin adhesives, soy protein adhesives, etc. Biomass-based adhesives have the characteristics of low cost, low formaldehyde emission, and excellent bonding performance. The application of biomass-based adhesives in the wood-based panel industry is conducive to promoting the green and healthy development of the wood-based panel industry. Although biomass-based adhesives have huge market application prospects, the existing biomass adhesives have high viscosity, poor adhesion and water resistance, complex preparation process, and require hot pressing or cold pressing molding, which consumes a lot of energy. Therefore, a new type of biomass adhesive is developed to achieve room temperature and pressure-free bonding of wood. Summary of the invention

[0004] The present invention aims to solve the problems of existing biomass adhesives such as high viscosity, low bonding strength, poor water resistance and complex process, and further provide a preparation method of a biomass adhesive for bonding wood under pressure at room temperature and a bonding method thereof.

[0005] A method for preparing a biomass adhesive for bonding wood at room temperature without pressure is carried out according to the following steps:

[0006] 1. Raw material pretreatment:

[0007] Treating the surface of the wood chips to remove part of the lignin and hemicellulose, then washing and drying the wood chips to obtain pretreated wood chips;

[0008] 2. Dissolution of wood components:

[0009] The pretreated wood chips are immersed in a cellulose solvent system to be completely dissolved, thereby obtaining a biomass adhesive for bonding wood at room temperature without pressure.

[0010] A method for bonding wood with a biomass adhesive at room temperature without pressure, which is carried out according to the following steps:

[0011] The double-sided glue application amount is 1.2g / m 2 ~2.0g / m 2 , apply the biomass adhesive for bonding wood under pressure at room temperature to the surface of the wood to be bonded, then butt the coated surfaces to obtain the bonded parts, immerse the bonded parts in water at room temperature for 20 minutes to 60 minutes, and finally dry them at room temperature to complete the bonding method.

[0012] The beneficial effects of the present invention are:

[0013] The biomass adhesive for bonding wood at room temperature without pressure of the present invention has the advantages of wide sources of raw materials and low cost. Compared with the existing biomass adhesive, it has higher bonding strength, simple preparation and bonding process, excellent water resistance and ultra-long validity period. The specific advantages are as follows:

[0014] (1) Utilization: The present invention dissolves cellulose, lignin and hemicellulose to form a biomass adhesive, which greatly improves the utilization rate of raw materials and promotes the utilization of wood. At the same time, the biomass adhesive prepared by the present invention has a low viscosity, and the viscosity can be further regulated by controlling the quality of the added veneer, thereby achieving controllable bonding of wood of different sizes.

[0015] (2) Process flow: The preparation method of the present invention is simple, and the bonding process does not require hot pressing or cold pressing molding processes, and the bonding process can be completed at room temperature without pressure. The bonding process is fast and low in energy consumption, which conforms to the ecological concept of green environmental protection. The bonding process does not require the use of special equipment, is not limited to specific wood species and wood orientation, does not rely on the bonding site environment, can bond large panels, and is expected to be mass-produced.

[0016] (3) Adhesive properties: The adhesive strength of the product obtained by the present invention is high, and the adhesive strength of the product after bonding can reach the national standard GB / T 17657-2022 "Test methods for physical and chemical properties of artificial boards and veneer artificial boards", which meets the performance requirements of national Class I plywood. The present invention has good water resistance, heat resistance and cold resistance, greatly expanding the use environment of biomass adhesives and promoting the use of biomass adhesives in tropical high-humidity areas and cold-zone low-temperature areas.

[0017] (4) Safety in use: In the preparation and bonding process of the present invention, the chemical components used have been basically removed and will not cause harm to human health in daily use.

[0018] Instruction Manual

[0019] Figure 1 This is an appearance diagram of the biomass adhesive for bonding wood at room temperature without pressure prepared in Example 1;

[0020] Figure 2 This is a graph showing the determination and analysis of carbohydrates and lignin in the biomass adhesive for bonding wood at room temperature without pressure, prepared in step 1 of Example 1;

[0021] Figure 3 Viscosity analysis of the biomass adhesive for bonding wood at room temperature without pressure prepared in Example 1;

[0022] Figure 4 This is a bonding performance analysis diagram of the adhesive member in Example 2;

[0023] Figure 5 This is an analysis chart of the shelf life of the biomass adhesive for bonding wood at room temperature without pressure prepared in Example 1;

[0024] Figure 6 This is a graph analyzing the heat resistance and cold resistance of the adhesive in Example 2;

[0025] Figure 7 This is a bonding performance analysis diagram of the adhesive member in Example 3;

[0026] Figure 8 This is an analysis diagram of the bonding performance of the adhesive in Example 4. DETAILED DESCRIPTION

[0027] Specific implementation method 1: This implementation method is a method for preparing a biomass adhesive for bonding wood at room temperature without pressure, which is carried out according to the following steps:

[0028] 1. Raw material pretreatment:

[0029] Treating the surface of the wood chips to remove part of the lignin and hemicellulose, then washing and drying the wood chips to obtain pretreated wood chips;

[0030] 2. Dissolution of wood components:

[0031] The pretreated wood chips are immersed in a cellulose solvent system to be completely dissolved, thereby obtaining a biomass adhesive for bonding wood at room temperature without pressure.

[0032] The purpose of the raw material pretreatment in step 1 of this specific implementation method is to partially remove lignin and hemicellulose so that more cellulose chains are exposed on the wood surface.

[0033] The purpose of the cleaning step in this specific implementation method is to remove the chemical reagents infiltrated in the wood chips.

[0034] The biomass adhesive obtained in step 2 of this specific embodiment has a yellow-brown, clear and transparent liquid appearance. The purpose of step 2 is to dissolve cellulose, lignin and hemicellulose.

[0035] The beneficial effects of this embodiment are:

[0036] The biomass adhesive for bonding wood at room temperature without pressure in this embodiment has the advantages of a wide range of raw material sources and low cost. Compared with existing biomass adhesives, it has higher bonding strength, simple preparation and bonding processes, excellent water resistance and ultra-long validity period. The specific advantages are as follows:

[0037] (1) Utilization: This embodiment dissolves cellulose, lignin and hemicellulose to form a biomass adhesive, which greatly improves the utilization rate of raw materials and promotes the utilization of wood. At the same time, the biomass adhesive prepared in this embodiment has a low viscosity, and the viscosity can be further controlled by controlling the mass of the added veneer to achieve controllable bonding of wood of different sizes.

[0038] (2) Process flow: The preparation method of this embodiment is simple, and the bonding process does not require hot pressing or cold pressing molding processes, and the bonding process can be completed at room temperature without pressure. The bonding process is fast and low in energy consumption, which conforms to the ecological concept of green environmental protection. The bonding process does not require the use of special equipment, is not limited to specific wood species and wood orientation, does not rely on the bonding site environment, can bond large panels, and is expected to be mass-produced.

[0039] (3) Adhesive performance: The adhesive strength of the product obtained by bonding in this embodiment is high, and the adhesive strength of the product after bonding can reach the national standard GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneer wood-based panels", which meets the performance requirements of national Class I plywood. This embodiment has good water resistance, heat resistance and cold resistance, greatly expanding the use environment of biomass adhesives and promoting the use of biomass adhesives in tropical high-humidity areas and cold-zone low-temperature areas.

[0040] (4) Safety in use: In the preparation and bonding process of this embodiment, the chemical components used have been basically removed and will not cause harm to human health in daily use.

[0041] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the thickness of the thin wood slices in step 1 is 0.2 mm to 2.0 mm. The rest is the same as the specific implementation method 1.

[0042] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that: in step 1, the veneer is immersed in a hydrogen peroxide / glacial acetic acid mixture at a temperature of 120°C to 140°C for 0.5h to 2h to remove part of the lignin and hemicellulose; the mass ratio of the veneer to the hydrogen peroxide / glacial acetic acid mixture in step 1 is 1:(40-60). Others are the same as specific embodiment 1 or 2.

[0043] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the hydrogen peroxide / glacial acetic acid mixture is prepared by adding glacial acetic acid to 20% to 40% by mass of hydrogen peroxide until the pH value reaches 3 to 4.5. Other aspects are the same as specific embodiments 1 to 3.

[0044] Specific embodiment 5: This embodiment is different from specific embodiments 1 to 4 in that: the cleaning described in step 1 is specifically carried out according to the following steps: immersing in a mixture of anhydrous ethanol / water for 0.5h to 1.5h at room temperature, then taking out and replacing the mixture of anhydrous ethanol / water, and repeating the immersion 3 to 5 times; the volume ratio of anhydrous ethanol to water in the mixture of anhydrous ethanol / water is 1:(1 to 2); the drying described in step 1 is specifically drying at a temperature of 30°C to 50°C for 10h to 14h. The rest is the same as specific embodiments 1 to 4.

[0045] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that the mass ratio of the pretreated veneer to the cellulose solvent system in step 2 is 1:(20-50). Other aspects are the same as specific embodiments 1 to 5.

[0046] Specific embodiment 7: This embodiment is different from Specific embodiments 1 to 6 in that: the cellulose solvent system described in step 2 is one or a combination of dimethylacetamide / lithium chloride mixed solution, 1-ethyl-3-methylimidazolium chloride solution and sodium hydroxide / thiourea mixed solution; the mass percentage of lithium chloride in the dimethylacetamide / lithium chloride mixed solution is 6% to 10%. Others are the same as Specific embodiments 1 to 6.

[0047] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that: in step 2, the pretreated veneer is immersed in a cellulose solvent system at room temperature for 20 hours to 24 hours to completely dissolve. The rest is the same as specific embodiments 1 to 7.

[0048] Specific embodiment 9: This embodiment is a method for bonding wood with a biomass adhesive at room temperature without pressure, which is carried out according to the following steps:

[0049] The double-sided glue application amount is 1.2g / m 2 ~2.0g / m 2 , apply the biomass adhesive for bonding wood under pressure at room temperature to the surface of the wood to be bonded, then butt the coated surfaces to obtain the bonded parts, immerse the bonded parts in water at room temperature for 20 minutes to 60 minutes, and finally dry them at room temperature to complete the bonding method.

[0050] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that the wood is balsa wood, basswood, poplar or birch, and the wood is wood along the growth direction of the wood or wood perpendicular to the growth direction of the wood. The rest is the same as specific embodiment 9.

[0051] The following examples are used to verify the beneficial effects of the present invention:

[0052] Embodiment 1:

[0053] A method for preparing a biomass adhesive for bonding wood at room temperature without pressure is carried out according to the following steps:

[0054] 1. Raw material pretreatment:

[0055] The veneer is immersed in a hydrogen peroxide / glacial acetic acid mixture at a temperature of 130° C. for 1 hour to remove part of the lignin and hemicellulose, and then washed and dried to obtain pretreated veneer;

[0056] The veneer has a thickness of 0.5 mm and is made of basswood along the growth direction;

[0057] The mass ratio of the veneer to the hydrogen peroxide / glacial acetic acid mixture is 1:50;

[0058] The hydrogen peroxide / glacial acetic acid mixture is specifically prepared by adding glacial acetic acid to 30% by mass hydrogen peroxide until the pH value reaches 4.0;

[0059] 2. Dissolution of wood components:

[0060] At room temperature, the pretreated veneer is immersed in a dimethylacetamide / lithium chloride mixed solution for 24 hours to completely dissolve, thereby obtaining a biomass adhesive for bonding wood at room temperature without pressure.

[0061] The mass ratio of the pretreated veneer to the dimethylacetamide / lithium chloride mixed solution is 1:25; the mass percentage of lithium chloride in the dimethylacetamide / lithium chloride mixed solution is 8%.

[0062] The cleaning described in step one is specifically carried out according to the following steps: immersing in a mixture of anhydrous ethanol / water at room temperature for 1 hour, then taking out and replacing the mixture of anhydrous ethanol / water, and repeating the immersion 4 times; the volume ratio of anhydrous ethanol to water in the anhydrous ethanol / water mixture is 1:1; the drying described in step one is specifically carried out at a temperature of 40°C for 12 hours.

[0063] Embodiment 2:

[0064] The bonding method of the biomass adhesive for bonding wood at room temperature without pressure prepared in Example 1 is carried out according to the following steps:

[0065] The double-sided glue application amount is 1.6g / m 2 , apply the biomass adhesive for bonding wood at room temperature without pressure on the wood surface to be bonded, then butt the coated surfaces together with an overlap area of ​​25 mm×25 mm to obtain a bonded part, immerse the bonded part in water at room temperature for 30 minutes, and finally dry it at room temperature for 24 hours to obtain a bonded part;

[0066] The wood is a basswood veneer with a size of 100mm×25mm×3mm; and the wood is the wood along the growth direction of the wood.

[0067] Embodiment 3: This embodiment is different from Embodiment 2 in that the wood material is a balsa wood veneer with a size of 100 mm×25 mm×3 mm. The rest is the same as Embodiment 2.

[0068] Embodiment 4: This embodiment is different from Embodiment 2 in that: the wood is a 100mm×25mm×3mm basswood veneer; the wood is perpendicular to the growth direction. The rest is the same as Embodiment 2.

[0069] Figure 1 This is an appearance picture of the biomass adhesive for bonding wood at room temperature without pressure prepared in Example 1; as can be seen from the figure, the biomass adhesive is yellow-brown, clear and transparent.

[0070] Figure 2This is a determination and analysis diagram of carbohydrates and lignin in the biomass adhesive for bonding wood at room temperature without pressure prepared in step 1 of Example 1; since the pretreated veneer contains 94.5wt.% cellulose, 3.2wt.% lignin and 2wt.% hemicellulose, and the pretreated veneer is completely dissolved in a dimethylacetamide / lithium chloride mixed solution in step 2, it can be determined that the contents of cellulose, lignin and hemicellulose in the biomass adhesive are also 94.5wt.% cellulose, 3.2wt.% lignin and 2wt.% hemicellulose.

[0071] Figure 3 This is the viscosity analysis of the biomass adhesive for bonding wood at room temperature without pressure prepared in Example 1; as can be seen from the figure, the viscosity of the biomass adhesive gradually decreases with the increase of shear rate, which is consistent with the shear thinning characteristics, and at a shear rate of 100 / s, the viscosity is 54.3Pa.s.

[0072] Plywood bonding strength test is carried out according to the national standard GB / T-9846-2015 "Ordinary Plywood"; Figure 4 This is an analysis diagram of the bonding performance of the adhesive in Example 2; it can be seen from the figure that the maximum tensile force that the adhesive can withstand is 886.88N; the bonding strength of the adhesive is 1.42MPa; and the elastic modulus of the adhesive is 240.10MPa. It meets the national standard GB / T 17657-2022 "Test methods for physical and chemical properties of artificial boards and veneer artificial boards", and meets the national performance requirements for Class I artificial boards.

[0073] The biomass adhesive for bonding wood at room temperature without pressure prepared in Example 1 was stored at room temperature, normal pressure and a humidity of 30% to 50% for 7 months, and then bonded according to the steps of Example 2, and the plywood bonding strength test was performed according to the national standard GB / T-9846-2015 "Ordinary Plywood"; Figure 5 This is a shelf life analysis chart of the biomass adhesive for bonding wood at room temperature without pressure prepared in Example 1; as can be seen from the figure, after the adhesive is stored for 7 months and then bonded, the bonded part can still withstand a maximum tensile force of 606.76N; the bonding strength of the bonded part is 0.99MPa, which meets the national standard GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Artificial Boards and Faced Artificial Boards", meets the national Class I performance requirements for artificial boards, and has an ultra-long shelf life.

[0074] Plywood bonding strength test is carried out according to the national standard GB / T-9846-2015 "Ordinary Plywood"; Figure 6This is an analysis chart of the heat resistance and cold resistance of the adhesive in Example 2; it can be seen from the figure that when the adhesive is placed in an environment of -30°C for 2 hours, the maximum tensile force that the adhesive can withstand is 825.40N, and the bonding strength of the adhesive is 1.32MPa; when the adhesive is placed in an environment of room temperature for 2 hours, the maximum tensile force that the adhesive can withstand is 841.06N, and the bonding strength of the adhesive is 1.35MPa; when the adhesive is placed in an environment of 100°C for 2 hours, the maximum tensile force that the adhesive can withstand is 826.83N, and the bonding strength of the adhesive is 1.29MPa; under the three environments, the bonding performance of the adhesive can meet the national standard GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels", meet the national Class I performance requirements for wood-based panels, and have a wide range of applicable temperatures.

[0075] Plywood bonding strength test is carried out according to the national standard GB / T-9846-2015 "Ordinary Plywood"; Figure 7 The figure is an analysis diagram of the bonding performance of the adhesive in Example 3; it can be seen from the figure that the maximum tensile force that the adhesive can withstand is 320.09N; the bonding strength of the adhesive is 0.51MPa. After the test, the adhesive has wood cracks.

[0076] Plywood bonding strength test is carried out according to the national standard GB / T-9846-2015 "Ordinary Plywood"; Figure 8 The figure is an analysis diagram of the bonding performance of the adhesive in Example 4; it can be seen from the figure that the maximum tensile force that the adhesive can withstand is 178.34 N. After the test, the adhesive was broken.

Claims

1. A method for preparing a biomass adhesive for bonding wood at room temperature without pressure, characterized in that It is carried out in the following steps:

1. Raw material pretreatment: Treating the surface of the wood chips to remove part of the lignin and hemicellulose, then washing and drying the wood chips to obtain pretreated wood chips; 2. Dissolution of wood components: The pretreated wood chips are immersed in a cellulose solvent system to be completely dissolved, thereby obtaining a biomass adhesive for bonding wood at room temperature without pressure.

2. The method for preparing a biomass adhesive for bonding wood at room temperature without pressure according to claim 1, characterized in that The thickness of the veneer described in step 1 is 0.2 mm to 2.0 mm.

3. The method for preparing a biomass adhesive for bonding wood at room temperature without pressure according to claim 1, characterized in that In step 1, the veneer is immersed in a hydrogen peroxide / glacial acetic acid mixture, and treated for 0.5h to 2h at a temperature of 120° C. to 140° C. to remove part of the lignin and hemicellulose; the mass ratio of the veneer to the hydrogen peroxide / glacial acetic acid mixture in step 1 is 1:(40-60).

4. The method for preparing a biomass adhesive for bonding wood at room temperature without pressure according to claim 3, characterized in that The hydrogen peroxide / glacial acetic acid mixed solution is specifically prepared by adding glacial acetic acid into 20% to 40% by mass of hydrogen peroxide until the pH value is 3 to 4.

5.

5. The method for preparing a biomass adhesive for bonding wood at room temperature without pressure according to claim 1, characterized in that The cleaning described in step one is specifically carried out according to the following steps: immersing in a mixture of anhydrous ethanol / water for 0.5h to 1.5h at room temperature, then taking out and replacing the mixture of anhydrous ethanol / water, and repeating the immersion 3 to 5 times; the volume ratio of anhydrous ethanol to water in the anhydrous ethanol / water mixture is 1:(1 to 2); the drying described in step one is specifically carried out at a temperature of 30°C to 50°C for 10h to 14h.

6. The method for preparing a biomass adhesive for bonding wood at room temperature without pressure according to claim 1, characterized in that The mass ratio of the pretreated veneer chips to the cellulose solvent system described in step 2 is 1:(20-50).

7. The method for preparing a biomass adhesive for bonding wood at room temperature without pressure according to claim 1, characterized in that The cellulose solvent system described in step 2 is one of dimethylacetamide / lithium chloride mixed solution, 1-ethyl-3-methylimidazolium chloride solution and sodium hydroxide / thiourea mixed solution or a combination thereof; the mass percentage of lithium chloride in the dimethylacetamide / lithium chloride mixed solution is 6% to 10%.

8. The method for preparing a biomass adhesive for bonding wood at room temperature without pressure according to claim 1, characterized in that In step 2, the pretreated veneer is immersed in a cellulose solvent system at room temperature for 20 hours to 24 hours to completely dissolve.

9. A method for bonding wood with a biomass adhesive at room temperature without pressure as prepared in claim 1, characterized in that It is carried out in the following steps: The double-sided glue application amount is 1.2g / m 2 ~2.0g / m 2 , apply the biomass adhesive for bonding wood under pressure at room temperature to the surface of the wood to be bonded, then butt the coated surfaces to obtain the bonded parts, immerse the bonded parts in water at room temperature for 20 minutes to 60 minutes, and finally dry them at room temperature to complete the bonding method.

10. The method for bonding wood with a biomass adhesive at room temperature without pressure according to claim 9, characterized in that The wood is balsa wood, basswood, poplar or birch; the wood is wood along the growth direction of the wood or wood perpendicular to the growth direction of the wood.

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