A kind of full cellulose colloid adhesive and its preparation method and bonding method

Abstract

A full-cellulose colloidal adhesive and a preparation method and a bonding method thereof, which belong to the field of adhesives. The present invention aims to solve the problems that the existing adhesives synthesized with cellulose as the matrix do not have water resistance, and the existing biomass adhesives have the disadvantages of high viscosity and low solid content. The full-cellulose colloidal adhesive is prepared from biomass cellulose, dilute sulfuric acid and distilled water; the preparation method: 1. weighing; 2. pyrolysis; 3. adding dilute sulfuric acid to the partially pyrolyzed and depolymerized intermediate cellulose for reaction; 4. continuing the reaction, and then adding the weighed distilled water for reaction; the bonding method: ① preparing a composite slab or a slab after gluing; ② hot pressing and curing. The present invention is used for full-cellulose colloidal adhesives and their preparation and bonding.

Description

Technical Field

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

[0002] Adhesives are an important part of the modern industrial field and play an irreplaceable and important role in all walks of life. However, traditional adhesives are synthesized from organic chemical raw materials, which are not only harmful to the environment and human body, but also non-degradable and recyclable, and the preparation cost is high. At the same time, the existing biomass adhesives have the disadvantages of high viscosity and low solid content. Biomass adhesives are adhesives prepared by modifying or synthesizing with other materials with natural renewable biomass as the main raw material. Because biomass resources have the advantages of wide sources, low cost, renewable and degradable and recyclable, biomass adhesives have always been at the forefront of research in the field of adhesives, and are also a hot spot and key point of research. Cellulose, as the most abundant biomass resource in nature, is also the most abundant organic polymer compound in nature. Because it has a large number of reactive groups, it provides it with the potential for various chemical modifications and wide applications. However, adhesives currently made from cellulose as the main raw material are generally not water-resistant due to the strong hydrophilicity of cellulose itself. Cellulose needs to be synthesized or modified with other chemical raw materials to make it water-resistant, but this will also significantly increase its cost and make it lose its biodegradability, recycling and environmental friendliness. This is the key point and difficulty to be broken through in the high-value utilization of cellulose, and it is also the research bottleneck for the large-scale application of cellulose in the field of adhesives.

[0003] At the same time, most of the adhesives currently used for artificial boards will have formaldehyde volatilization pollution and volatile organic pollutants, which will cause irreversible damage to the environment and human body. Especially when it comes to cost issues, low-cost adhesives used for artificial boards are generally traditional "trialdehyde glues" with a large amount of formaldehyde. These materials will release a large amount of free formaldehyde during production, transportation, storage and use, and can exist in the surrounding environment for a long time, causing pollution and damage to the environment and human body. In addition, traditional organic chemical raw materials also have the disadvantages of being difficult to degrade and recycle and non-renewable.

[0004] Therefore, if cellulose can break through the research bottleneck and can truly replace traditional adhesives in the field of adhesives, it will be a great progress for industrial production and scientific and technological development, and the economic and social benefits it generates are very considerable. Therefore, it is hoped that cellulose can be used as the only raw material to prepare a high-performance adhesive. Cellulose has a unique aggregated structure and rich chemical functional groups, which creates conditions for its research and application in various fields. Although the large number of hydroxyl groups (-OH) contained in the cellulose molecular chain can provide higher reactivity and a large number of binding sites, its strong hydrophilicity will combine with water molecules to form hydrogen bonds and also form a hydrogen bond network with the water molecules around it, thereby absorbing moisture. This makes the adhesive synthesized with cellulose as the matrix almost water-resistant, so that cellulose, the most abundant renewable resource in nature, cannot be effectively utilized in the field of adhesives. Summary of the invention

[0005] The present invention aims to solve the problems that the existing adhesives synthesized with cellulose as the matrix do not have water resistance and the existing biomass adhesives have the disadvantages of high viscosity and low solid content, and further provides a full cellulose colloid adhesive and a preparation method and a bonding method thereof.

[0006] A full cellulose colloid adhesive is prepared from 2 to 10 parts of biomass cellulose, 4 to 12 parts of dilute sulfuric acid and 80 to 90 parts of distilled water by mass.

[0007] A method for preparing a full cellulose colloid adhesive is carried out according to the following steps:

[0008] 1. Weigh 2 to 10 parts of biomass cellulose, 4 to 12 parts of dilute sulfuric acid and 80 to 90 parts of distilled water by mass;

[0009] 2. Heating the weighed biomass cellulose to 150°C to 220°C, pyrolyzing it for 2h to 5h at a temperature of 150°C to 220°C, and then cooling it with ice water to obtain partially pyrolyzed and depolymerized intermediate cellulose;

[0010] 3. Add the weighed dilute sulfuric acid to the partially thermally decomposed intermediate cellulose, react for 1 h to 6 h at a temperature of 160°C to 200°C with stirring, and cool to room temperature to obtain a light-colored uniform liquid phase glue system;

[0011] 4. Place the light-colored uniform liquid adhesive system at a temperature of 40°C to 100°C, continue to react for 2h to 8h, then add weighed distilled water, react for 1h to 6h at a temperature of 40°C to 100°C with stirring to obtain a full cellulose colloidal adhesive.

[0012] A bonding method of a full cellulose colloid adhesive is carried out according to the following steps:

[0013] ① Single-sided coating amount is 160g / m 2 ~220g / m 2 , coating the whole cellulose colloid adhesive on the surface of the biomass unit, and then stacking them to obtain a composite slab;

[0014] Or according to the glue application amount of 20kg / m 3 ~25kg / m 3 , spraying the full cellulose colloid adhesive onto the fibers or wood chips, and then pre-pressing to obtain a sizing blank;

[0015] ② The composite slab or the slab after gluing is cured by hot pressing, and finally closed and aged at room temperature, thereby completing the bonding method of the all-cellulose colloid adhesive.

[0016] The beneficial effects of the present invention are:

[0017] (1) Wide sources of raw materials: Renewable biomass cellulose is the only raw material for preparing adhesives. Cellulose is the most abundant biomass resource in nature and the most abundant organic polymer compound in nature. It has a wide range of sources and is easy to prepare. At the same time, it also has a large number of reactive groups, which provides it with the potential for various chemical modifications and wide applications.

[0018] (2) Low cost of raw materials required for preparation: Cellulose is used as the only raw material for preparing adhesives. Cellulose is widely available and inexpensive. It is an excellent raw material that is low-cost, non-toxic and easy to prepare.

[0019] (3) Green, environmentally friendly, renewable, biodegradable and recyclable: The only raw material, cellulose, is completely obtained from green plants and is a renewable green sustainable resource. The prepared adhesive uses water as a solvent and the raw material is only a single cellulose. As a water-based adhesive, it does not contain any formaldehyde or volatile organic pollutants, thus avoiding harm to the environment and human body as well as the use and discharge of large amounts of organic chemical raw materials.

[0020] (4) The preparation process is simple and easy to obtain: the two-step pyrolysis and acidification method is used to prepare the product, without other complicated steps and strict preparation conditions, and no other curing agent needs to be added during the bonding and curing process of the adhesive, which not only saves the production and preparation costs, but also simplifies the steps during the production and manufacturing. At the same time, this is also conducive to the further industrial production and application of the adhesive in the present invention.

[0021] (5) The all-cellulose colloid adhesive achieves high performance of boiling water resistance: The adhesive of the present invention has excellent comprehensive performance and is comparable to the currently popular urea-formaldehyde resin adhesive, phenolic resin adhesive and melamine formaldehyde adhesive on the market. The bonding strength can meet the Chinese national standard for indoor panels and the U.S. national standard for indoor panels. It is a new type of environmentally friendly biomass adhesive with excellent performance and broad application prospects.

[0022] (6) Excellent properties of high solid content and low viscosity: The adhesive of the present invention overcomes the disadvantages of high viscosity and low solid content of traditional biomass adhesives, and achieves breakthroughs in ultra-low viscosity and high solid content. This makes it have great advantages and appeal in the application of various board materials such as plywood, particleboard and fiberboard.

[0023] Instruction Manual

[0024] Figure 1 The flowchart of the preparation of the intermediate cellulose by partial pyrolysis and depolymerization in step 2 of the present invention includes: (1) a source of renewable cellulose raw materials; (2) biomass cellulose; (3) a crucible; (4) a constant temperature drying oven; (5) a distribution and agglomeration diagram of the intermediate cellulose by partial pyrolysis and depolymerization; and (6) a schematic diagram of a single cellulose molecule in the intermediate cellulose by partial pyrolysis and depolymerization.

[0025] Figure 2 The preparation of the full cellulose colloid adhesive and plywood in steps three and four of the present invention comprises: (1) preparing raw materials; (2) forming a sulfuric acid environment reaction system; (3) heating reaction; (4) continuing reaction in a constant temperature drying oven; (5) continuing heating reaction with deionized water; and (6) preparing plywood.

[0026] Figure 3 The macrostructure of the bonding interface of plywood sample 1 prepared in Example 1;

[0027] Figure 4 The microstructure of the bonding interface of plywood sample 1 prepared in Example 1. DETAILED DESCRIPTION

[0028] Specific implementation method The first implementation method is a full cellulose colloid adhesive, which is prepared from 2 to 10 parts of biomass cellulose, 4 to 12 parts of dilute sulfuric acid and 80 to 90 parts of distilled water by weight.

[0029] This embodiment can directly use biomass cellulose as a super water-resistant adhesive through simple reactions and conversions. It can form a dense cross-linked network structure after hot pressing and curing, and rely on the electrostatic interaction between the internal interfaces, the interaction between hydrogen bonds, and the covalent bond force in the network structure to enable it to have high-strength mechanical properties and water resistance, and even boiling water resistance.

[0030] This embodiment uses renewable, low-cost biomass cellulose as the only raw material to prepare high-performance boiling water-resistant adhesives, achieving high-value utilization of cellulose and technological breakthroughs in the adhesive field. This adhesive can produce plywood products with excellent performance under relatively low heat and pressure conditions, making it a great potential to replace traditional wood adhesives in different market segments. At the same time, it can reduce the use of chemical raw materials, which is of great significance for protecting the environment and human health, and can also actively promote the realization of carbon neutrality goals.

[0031] This implementation method can achieve high performance of the adhesive while maintaining the advantages of high activity of cellulose raw materials and the characteristics of biomass itself as much as possible. An intermediate state of active cellulose is explored, and it is trapped and protected in a special structure that can continue the secondary cross-linking condensation reaction after hot pressing and heating. The simple two-step method can directly use cellulose as a wood adhesive after simple treatment to obtain high-strength mechanical properties and boiling water resistance. It paves the way for degradable, recyclable, low-cost, high-performance environmentally friendly adhesives, and also truly realizes the high-value utilization of biomass cellulose.

[0032] The beneficial effects of this embodiment are:

[0033] (1) Wide sources of raw materials: Renewable biomass cellulose is the only raw material for preparing adhesives. Cellulose is the most abundant biomass resource in nature and the most abundant organic polymer compound in nature. It has a wide range of sources and is easy to prepare. At the same time, it also has a large number of reactive groups, which provides it with the potential for various chemical modifications and wide applications.

[0034] (2) Low cost of raw materials required for preparation: Cellulose is used as the only raw material for preparing adhesives. Cellulose is widely available and inexpensive. It is an excellent raw material that is low-cost, non-toxic and easy to prepare.

[0035] (3) Green, environmentally friendly, renewable, biodegradable and recyclable: The only raw material, cellulose, is completely obtained from green plants and is a renewable green sustainable resource. The prepared adhesive uses water as a solvent and the raw material is only a single cellulose. As a water-based adhesive, it does not contain any formaldehyde or volatile organic pollutants, thus avoiding harm to the environment and human body as well as the use and discharge of large amounts of organic chemical raw materials.

[0036] (4) The preparation process is simple and easy to obtain: the two-step pyrolysis and acidification method is used to prepare the product, without other complicated steps and strict preparation conditions, and no other curing agent needs to be added during the bonding and curing process of the adhesive, which not only saves the production and preparation costs, but also simplifies the steps during the production and manufacturing. At the same time, this is also conducive to the further industrial production and application of the adhesive in the present invention.

[0037] (5) The all-cellulose colloid adhesive achieves high performance of boiling water resistance: The adhesive of the present invention has excellent comprehensive performance and is comparable to the currently popular urea-formaldehyde resin adhesive, phenolic resin adhesive and melamine formaldehyde adhesive on the market. The bonding strength can meet the Chinese national standard for indoor panels and the U.S. national standard for indoor panels. It is a new type of environmentally friendly biomass adhesive with excellent performance and broad application prospects.

[0038] (6) Excellent properties of high solid content and low viscosity: The adhesive of the present invention overcomes the disadvantages of high viscosity and low solid content of traditional biomass adhesives, and achieves breakthroughs in ultra-low viscosity and high solid content. This makes it have great advantages and appeal in the application of various board materials such as plywood, particleboard and fiberboard.

[0039] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that: the biomass cellulose is microcrystalline cellulose or pulp cellulose; the particle size of the biomass cellulose is 20 μm to 50 μm, and the molecular weight is 80,000 to 150,000. Others are the same as specific embodiment 1.

[0040] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the mass percentage of the dilute sulfuric acid is 1% to 10%. The rest is the same as specific implementation method 1 or 2.

[0041] Specific embodiment 4: This embodiment is a method for preparing a full cellulose colloid adhesive, which is carried out according to the following steps:

[0042] 1. Weigh 2 to 10 parts of biomass cellulose, 4 to 12 parts of dilute sulfuric acid and 80 to 90 parts of distilled water by mass;

[0043] 2. Heating the weighed biomass cellulose to 150°C to 220°C, pyrolyzing it for 2h to 5h at a temperature of 150°C to 220°C, and then cooling it with ice water to obtain partially pyrolyzed and depolymerized intermediate cellulose;

[0044] 3. Add the weighed dilute sulfuric acid to the partially thermally decomposed intermediate cellulose, react for 1 h to 6 h at a temperature of 160°C to 200°C with stirring, and cool to room temperature to obtain a light-colored uniform liquid phase glue system;

[0045] 4. Place the light-colored uniform liquid adhesive system at a temperature of 40°C to 100°C, continue to react for 2h to 8h, then add weighed distilled water, react for 1h to 6h at a temperature of 40°C to 100°C with stirring to obtain a full cellulose colloidal adhesive.

[0046] Figure 1 This is a flow chart of the preparation of the intermediate cellulose by partial pyrolysis and depolymerization in step 2 of this specific embodiment, (1) the source of renewable cellulose raw materials, (2) biomass cellulose, (3) crucible, (4) constant temperature drying oven, (5) distribution and aggregation diagram of the intermediate cellulose by partial pyrolysis and depolymerization, (6) schematic diagram of individual cellulose molecules in the intermediate cellulose by partial pyrolysis and depolymerization. Figure 1 As shown in the embodiment, the biomass cellulose extracted from renewable biomass is used as raw material for selective partial pyrolysis and depolymerization. The biomass cellulose raw material is weighed, evenly spread in a ceramic crucible, and then placed in a closed constant temperature blast drying oven for pyrolysis and depolymerization. After the pyrolysis and depolymerization treatment here, partially pyrolyzed and depolymerized intermediate cellulose can be obtained.

[0047] Figure 2 In the preparation of steps 3 and 4 of this specific embodiment, the whole cellulose colloid adhesive and plywood are as follows: (1) raw material preparation, (2) sulfuric acid environment reaction system, (3) heating reaction, (4) constant temperature drying oven to continue reaction, (5) deionized water to continue heating reaction, and (6) preparation of plywood. Figure 2 As shown in , an appropriate volume of dilute sulfuric acid is added to the partially thermally decomposed intermediate cellulose, and the reaction is stirred at a certain temperature. After the reaction is completed, it is placed in a forced air drying oven to continue to react at a certain temperature. Finally, a certain amount of deionized water is added, and the reaction is magnetically stirred at an appropriate temperature to obtain a full cellulose colloidal adhesive.

[0048] Specific implementation mode 5: This implementation mode is different from specific implementation mode 4 in that: in step 2, ice water with a temperature of 0°C to 5°C is used to cool down to room temperature. The rest is the same as specific implementation mode 4.

[0049] Specific implementation method 6: This implementation method is different from specific implementation method 4 or 5 in that the stirring speed in step 3 is 150 rpm to 260 rpm, and the stirring speed in step 4 is 260 rpm to 360 rpm. The rest is the same as specific implementation method 4 or 5.

[0050] Specific embodiment 7: This embodiment is a bonding method of a full cellulose colloid adhesive, which is characterized by being carried out according to the following steps:

[0051] ① Single-sided coating amount is 160g / m 2 ~220g / m2 , coating the whole cellulose colloid adhesive on the surface of the biomass unit, and then stacking them to obtain a composite slab;

[0052] Or according to the glue application amount of 20kg / m 3 ~25kg / m 3 , spraying the full cellulose colloid adhesive onto the fibers or wood chips, and then pre-pressing to obtain a sizing blank;

[0053] ② The composite slab or the slab after gluing is cured by hot pressing, and finally closed and aged at room temperature, thereby completing the bonding method of the all-cellulose colloid adhesive.

[0054] Specific embodiment eight: This embodiment differs from specific embodiment seven in that: the biomass unit described in step ① is a biomass single board, a biomass plywood or a biomass lattice structure board; the fiber described in step ① is wood fiber or bamboo fiber; the shavings described in step ① are wood shavings board or bamboo shavings; and step ② obtains plywood, fiberboard or shavings board. The rest is the same as specific embodiment seven.

[0055] Specific embodiment 9: This embodiment is different from specific embodiment 7 or 8 in that the pre-pressing in step ① is performed at room temperature and a pressure of 0.9 MPa to 1.5 MPa for 12 to 24 hours. The rest is the same as specific embodiment 7 or 8.

[0056] Specific embodiment 10: This embodiment is different from specific embodiments 7 to 9 in that: when the plywood is obtained in step ②, the hot pressing curing is specifically performed under the conditions of 0.9MPa to 3.0MPa and 120℃ to 160℃, and the hot pressing is performed for 1min to 4min per 1mm thickness; when the fiberboard is obtained in step ②, the hot pressing curing is specifically performed under the conditions of 3MPa to 9MPa and 160℃ to 230℃, and the hot pressing is performed for 1min to 3min per 1mm thickness; when the particleboard is obtained in step ②, the hot pressing curing is specifically performed under the conditions of 3MPa to 9MPa and 160℃ to 230℃, and the hot pressing is performed for 1min to 3min per 1mm thickness. The rest is the same as specific embodiments 7 to 9.

[0057] The following examples are used to verify the beneficial effects of the present invention:

[0058] Embodiment 1:

[0059] A method for preparing a full cellulose colloid adhesive is carried out according to the following steps:

[0060] 1. Weigh 8 parts of biomass cellulose, 10 parts of dilute sulfuric acid and 90 parts of distilled water by mass;

[0061] The biomass cellulose is microcrystalline cellulose; the particle size of the biomass cellulose is 20 μm to 50 μm, and the molecular weight is 80,000 to 150,000;

[0062] The mass percentage of the dilute sulfuric acid is 1%;

[0063] 2. The weighed biomass cellulose was heated to 160°C, and pyrolyzed at 160°C for 2 hours, and then cooled to room temperature with ice water at 0°C to obtain partially pyrolyzed and depolymerized intermediate cellulose;

[0064] 3. Add the weighed dilute sulfuric acid to the partially thermally decomposed intermediate cellulose, and react for 2 hours at a temperature of 180°C and a stirring speed of 250 rpm, and cool to room temperature to obtain a light-colored uniform liquid phase glue system;

[0065] 4. Place the light-colored uniform liquid adhesive system at a temperature of 63°C and continue to react for 2 hours. Then add the weighed distilled water and continue to react for 4 hours at a temperature of 40°C and a stirring speed of 330 rpm to obtain a full cellulose colloidal adhesive.

[0066] Example 2: This example is different from Example 1 in that the pyrolysis step 2 is performed for 3 hours. The rest is the same as Example 1.

[0067] Example 3: This example is different from Example 1 in that the pyrolysis in step 2 is performed for 4 hours. The rest is the same as Example 1.

[0068] Example 4: This example is different from Example 1 in that the pyrolysis in step 2 is performed for 5 hours. The rest is the same as Example 1.

[0069] Example 5: This example is different from Example 1 in that: Step 2 is pyrolyzed for 3 hours; Step 3 is reacted for 1 hour. Other aspects are the same as Example 1.

[0070] Example 6: This example is different from Example 1 in that: Step 2 is pyrolyzed for 3 hours; Step 3 is reacted for 3 hours. Other aspects are the same as Example 1.

[0071] Example 7: This example is different from Example 1 in that: Step 2 is pyrolyzed for 3 hours; Step 3 is reacted for 4 hours. Other aspects are the same as Example 1.

[0072] Comparative Experiment 1: The difference between this comparative experiment and Example 1 is that: Step 2 is eliminated; Step 3 is to add the weighed dilute sulfuric acid to the weighed biomass cellulose. The rest is the same as Example 1.

[0073] Comparative Experiment 2: The difference between this comparative experiment and Example 1 is that in step 1, 10 parts of dilute sulfuric acid are replaced by 10 parts of dilute hydrochloric acid; the mass percentage of the dilute hydrochloric acid is 1%; and step 2 is pyrolyzed for 3 hours. The rest is the same as Example 1.

[0074] Example 1: A bonding method of a full cellulose colloid adhesive prepared in Example 2 is carried out according to the following steps:

[0075] ① Place the peeled poplar veneer at room temperature to cure until the moisture content is 10%, and the coating amount on one side is 180g / m 2 , applying the full cellulose colloid adhesive prepared in Example 2 to the surface of the poplar veneer, and stacking three layers in a manner such that the grains are perpendicular to each other to obtain a composite slab;

[0076] ② Under the conditions of a pressure of 0.9 MPa and a temperature of 120°C, the composite slab was hot pressed for 3 minutes, and finally closed and aged at room temperature for 6 hours to obtain a plywood (sample 1), thus completing the bonding method of the all-cellulose colloid adhesive.

[0077] Example 2: This example is different from Example 1 in that the poplar veneer in step ① is replaced with a beech veneer, and plywood (sample 2) is obtained in step ②. The rest is the same as Example 1.

[0078] Example 3: This example is different from Example 1 in that the poplar veneer in step ① is replaced with eucalyptus veneer, and plywood (sample 3) is obtained in step ②. The rest is the same as Example 1.

[0079] Example 4: This example is different from Example 1 in that the poplar veneer in step ① is replaced with a pine veneer, and plywood (sample 4) is obtained in step ②. The rest is the same as Example 1.

[0080] Example 5: This example is different from Example 1 in that the adhesive prepared in Example 2 is replaced by the full cellulose colloid adhesive prepared in Examples 1, 3 to 7 and Comparative Experiments 1 to 2 to obtain poplar plywood. Others are the same as Example 1.

[0081] Comparative Experiment 1: The difference between this comparative experiment and Example 1 is that: in step ①, the all-cellulose colloid adhesive prepared in Example 2 is replaced by the all-cellulose colloid adhesive prepared in Comparative Experiment 1; and in step ②, a plywood (sample 5) is obtained. The rest is the same as Example 1.

[0082] Comparative Experiment 2: The difference between this comparative experiment and Example 1 is that: in step ①, the all-cellulose colloid adhesive prepared in Example 2 is replaced by the all-cellulose colloid adhesive prepared in Comparative Experiment 2; and in step ②, a plywood (sample 6) is obtained. The rest is the same as Example 1.

[0083] Example 5: A bonding method of a full cellulose colloid adhesive prepared in Example 2 is carried out according to the following steps:

[0084] ①First, place the poplar fiber in a high-speed mixer and stir it. The moisture content of the poplar fiber is 0.76%. The glue application amount is 25kg / m 3 , spraying the full cellulose colloid adhesive onto the poplar wood fiber, the moisture content of the poplar wood fiber after sizing is 2.78%, and then pre-pressing for 12 hours at room temperature and a pressure of 1.3 MPa to obtain a slab after sizing;

[0085] ② Under the conditions of a pressure of 5 MPa and a temperature of 180°C, the slab after gluing was hot pressed for 7 minutes, and finally closed and aged at room temperature for 6 hours to obtain a poplar fiberboard (sample 7);

[0086] The size of the poplar fiberboard is 35cm×35cm×4mm.

[0087] Example 6: A bonding method of a full cellulose colloid adhesive prepared in Example 2 is carried out according to the following steps:

[0088] ①Put the cut poplar wood shavings in a drying oven at 80℃ and dry them to a moisture content of 5%. Apply glue at a rate of 25kg / m 3 , spraying the full cellulose colloid adhesive onto the poplar wood shavings, and then assembling the shavings by laying the upper and lower surface layers with fine shavings and the middle layer with coarse shavings, and then pre-pressing for 12 hours at room temperature and a pressure of 1.3 MPa to obtain the slab after gluing;

[0089] ② Under the conditions of a pressure of 5 MPa and a temperature of 180°C, the slab after gluing was hot pressed for 7 minutes, and finally closed and aged at room temperature for 6 hours to obtain a poplar particleboard (sample 8);

[0090] The thickness of the fine wood shavings on the upper and lower surface layers is 8mm-12mm, and the thickness of the coarse wood shavings on the middle layer is 15mm-18mm; the size of the coarse wood shavings is: length 15mm-45mm, width 3mm-10mm, thickness 0.4mm-0.7mm; the size of the fine wood shavings is: length 3mm-15mm, width 0.5mm-1.5mm, thickness 0.2mm-0.4mm;

[0091] The size of the poplar wood particle board is 35cm×35cm×4mm.

[0092] (I) The following tests are performed on the full cellulose colloid adhesive:

[0093] (1) pH value test: The test is based on the requirements of the national standard GBT14074-2006, and the pH value is accurately measured using pH.

[0094] (2) Solid content test: The test is carried out in accordance with the requirements of the national standard GBT14074-2006. The solid content is measured after treatment in an electric constant temperature blast drying oven (DCG-9070 model), and the required data is recorded.

[0095] (3) Viscosity test: The adhesive solution was treated to eliminate bubbles, the test temperature was room temperature, and the test volume was about 200 mL. The test was carried out in accordance with GB / T2794-1995 standard, and a rotational viscometer (Shanghai Pingxuan Scientific Instrument Co., Ltd., NDJ-79) was used for viscosity testing.

[0096] (ii) The following tests are conducted on the plywood:

[0097] The test specimens are prepared according to the national standard GB / T17657-2013. The wood grain direction of the core board between the glue layers to be measured should be perpendicular to the length direction of the test specimens. The groove width and depth of the test specimens shall be carried out in accordance with the dimensions and requirements shown in the diagrams drawn according to the national standard.

[0098] Dry shear strength: According to GB / T17657-2013 standard, the prepared standard specimens were stored in a desiccator for 2 days and tested using a universal mechanical testing machine (RGT-20). The mechanical sensor value was 5Kn and the test tensile speed was 5mm / min.

[0099] 63℃ water boiling wet shear strength: According to GB / T17657-2013 standard, the prepared standard specimens were boiled in 63℃ water for 3 hours and then immediately subjected to tensile shear test.

[0100] Determination of boiling water shear strength performance: According to GB / T17657-2013 standard, the prepared standard specimen is boiled in 100℃ boiling water for 3h, and then placed in an electric constant temperature blast drying oven (DCG-9070 model) for constant temperature drying for 20±3h, and then placed in a dryer to cool to (23±2)℃. After boiling the specimen in boiling water for 3h, take it out and immediately put it into a container of distilled water at (23±2)℃. After the liquid level exceeds the specimen and cools for 15min, the tensile shear strength test is immediately carried out.

[0101] (III) The following tests are conducted on poplar fiberboard to poplar particleboard:

[0102] Static bending strength test: The specimen is prepared and tested according to GB / T17657-2013 standard. The size of the specimen is 150mm×50mm, and the span is 100mm. The force sensor value is 50KN, and the loading speed during the test is 5mm / min.

[0103] Internal bonding strength test: The specimen is prepared and tested according to GB / T17657-2013 standard. The size of the specimen is 50mm×50mm. The adhesive used between the specimen and the fixture is hot melt adhesive. According to GB / T17657-2013 standard, the prepared bonding specimen is placed in a balanced treatment room with a temperature of (20±2)℃ and a relative humidity of (65±5)%. After the specimen is taken out of the balanced treatment room, the test should be completed within 1 hour. The mechanical sensor value is 50KN, and the tensile rate during the test is 5mm / min.

[0104] 24h water absorption thickness expansion rate test: The specimens are prepared and tested according to GB / T17657-2013 standard. The size of the specimens is 50×50mm. The water source used in the experimental test is tap water with a water pH value of 7±1 and a test temperature of 20±1℃. The specimens to be tested are immersed in a water tank. The temperature is kept constant during the test. The surface of the test specimen is perpendicular to the water surface. The distance between the specimens and between the specimens and the bottom and wall of the water tank is at least 15mm. The upper part of the specimen is (25±5)mm below the water surface.

[0105] (IV) Characterization of bonding interface structure:

[0106] The macrostructure and microstructure of the plywood bonding interface were characterized and analyzed respectively. The microstructure was observed and studied using an optical microscope (LEICA DM 1000LED).

[0107] Table 1 pH value, solid content, viscosity test and shear strength of the full cellulose colloid adhesive prepared in Example

[0108]

[0109]

[0110] Table 2. Plywood tensile shear strength of various panels

[0111]

[0112] The national standards in the table refer to dry strength, 63°C water boiling wet strength and 100°C boiling water resistance strength, all of which are ≥0.7.

[0113] It can be seen from Table 2 that the tensile shear strength of the prepared plywood can fully pass the boiling water resistance test of the relevant national standards, and meets the requirements of the latest ordinary plywood standard GB / T 9846-2015 indoor plywood, which is a high-performance adhesive that can withstand boiling water.

[0114] Table 3 Properties of fiberboard and particleboard

[0115]

[0116] As shown in Table 3, the static bending strength, internal bonding strength and 24h water absorption expansion rate of the prepared fiberboard and particleboard can fully pass the test of relevant national standards, meet the requirements of standard GB / T 17657-2013 indoor wood-based panels, and are a high-performance adhesive that can be used in many applications and is resistant to boiling water.

[0117] Figure 3 The macrostructure of the bonding interface of plywood sample 1 prepared in Example 1; Figure 4 The microstructure of the bonding interface of plywood sample 1 prepared in Example 1; as can be seen from the figure, the glue lines between the bonding interfaces are clear and obvious. First, the macroscopic bonding interface of the plywood ( Figure 3 ) is flat and smooth and the glue line is tight and uniform, which is a direct reflection of the excellent adhesive performance of the all-cellulose colloid adhesive prepared in Example 1. At the same time, in the microscopic image of the bonding interface ( Figure 4 ), it can be clearly observed that the glue liquid evenly and deeply penetrates between the bonding interfaces, and the penetration effect is excellent, which enables a strong mechanical interlocking ability to be formed between the bonding interfaces, thereby significantly enhancing the bonding performance (mechanical properties) of the plywood prepared by the all-cellulose colloid adhesive. In addition, the bonding effect between the interfaces is also very excellent, and the interface bonding is continuous and tight without any cracks, which is also a strong proof of the excellent bonding performance of the adhesive prepared in this embodiment.

Claims

1. A full cellulose colloid adhesive, characterized in that It is prepared from 2 to 10 parts of biomass cellulose, 4 to 12 parts of dilute sulfuric acid and 80 to 90 parts of distilled water by weight. The biomass cellulose is microcrystalline cellulose or pulp cellulose; the particle size of the biomass cellulose is 20 μm to 50 μm, and the molecular weight is 80,000 to 150,000; The mass percentage of the dilute sulfuric acid is 1% to 10%; The above-mentioned full cellulose colloid adhesive is prepared according to the following steps:

1. Weigh 2 to 10 parts of biomass cellulose, 4 to 12 parts of dilute sulfuric acid and 80 to 90 parts of distilled water by mass; 2. Heating the weighed biomass cellulose to 150°C~220°C, pyrolyzing it at 150°C~220°C for 2h~5h, and then cooling it with ice water to obtain partially pyrolyzed and depolymerized intermediate cellulose; 3. Add the weighed dilute sulfuric acid to the partially thermally decomposed intermediate cellulose, react for 1h~6h at a temperature of 160℃~200℃ and under stirring conditions, cool to room temperature to obtain a light-colored uniform liquid phase glue system; 4. Place the light-colored uniform liquid adhesive system at a temperature of 40°C~100°C, continue to react for 2h~8h, then add weighed distilled water, react for 1h~6h at a temperature of 40°C~100°C with stirring to obtain a full cellulose colloidal adhesive.

2. A full cellulose colloid adhesive according to claim 1, characterized in that In step 2, ice water at a temperature of 0°C to 5°C is used to cool the mixture to room temperature.

3. A full cellulose colloid adhesive according to claim 1, characterized in that The stirring speed described in step 3 is 150rpm~260rpm; the stirring speed described in step 4 is 260rpm~360rpm.

4. A bonding method using the full cellulose colloid adhesive according to claim 1, characterized in that It is carried out in the following steps: ① Single-sided coating amount is 160g / m 2 ~220g / m 2 , coating the whole cellulose colloid adhesive on the surface of the biomass unit, and then stacking them to obtain a composite slab; Or according to the glue application amount of 20kg / m 3 ~25kg / m 3 , spraying the full cellulose colloid adhesive onto the fibers or wood chips, and then pre-pressing to obtain a sizing blank; ② The composite slab or the slab after gluing is cured by hot pressing, and finally closed and aged at room temperature, thereby completing the bonding method of the all-cellulose colloid adhesive.

5. A bonding method of a full cellulose colloid adhesive according to claim 4, characterized in that The biomass unit described in step ① is a biomass single board, a biomass plywood or a biomass lattice structure board; the fiber described in step ① is wood fiber or bamboo fiber; the shavings described in step ① are wood particleboard or bamboo shavings; and step ② obtains plywood, fiberboard or particleboard.

6. A bonding method of a full cellulose colloid adhesive according to claim 4, characterized in that The pre-pressing in step ① is specifically performed at room temperature and a pressure of 0.9 MPa to 1.5 MPa for 12 h to 24 h.

7. A bonding method of a full cellulose colloid adhesive according to claim 6, characterized in that When the plywood is obtained in step ②, the hot pressing curing is specifically carried out under the conditions of a pressure of 0.9MPa~3.0MPa and a temperature of 120℃~160℃, and the hot pressing is performed for 1min~4min per 1mm thickness; when the fiberboard is obtained in step ②, the hot pressing curing is specifically carried out under the conditions of a pressure of 3MPa~9MPa and a temperature of 160℃~230℃, and the hot pressing is performed for 1min~3min per 1mm thickness; when the particleboard is obtained in step ②, the hot pressing curing is specifically carried out under the conditions of a pressure of 3MPa~9MPa and a temperature of 160℃~230℃, and the hot pressing is performed for 1min~3min per 1mm thickness.

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