Preparation process of green bamboo material expansion board and bamboo board

Abstract

The application relates to the technical field of bamboo boards, and discloses a preparation process of a bamboo board with green bamboo and the bamboo board. The process comprises the following steps: carbonizing treatment is carried out on bamboo with green bamboo by heating the bamboo to 170-180 DEG C to obtain first bamboo; the obtained primary bamboo is immersed in a treatment liquid at 50-60 DEG C and is subjected to ultrasonic treatment, is cleaned and dried to obtain second bamboo; a surface modifier is sprayed on the surface of the bamboo layer of the second bamboo, and heat treatment is carried out to obtain third bamboo which is subjected to surface grafting treatment; the surface modifier comprises a silane coupling agent containing an unsaturated double bond and a silane coupling agent containing an amino group; after a primer is coated on the surface of the third bamboo, heat curing is carried out, and the primer contains an active group which can react with a group introduced in the step. The bamboo board can keep good mildew-proof and corrosion-proof characteristics, and can also keep good adhesion with varnish.

Description

Technical Field

[0001] This application relates to the technical field of bamboo boards, and in particular to a process for preparing a bamboo unfolded board with green bamboo and the bamboo board itself. Background Technology

[0002] Bamboo unfolded panels, as a renewable and environmentally friendly material, are widely used in the construction, furniture, and decoration fields when made by hot pressing bamboo unfolded panels. The existing process for making bamboo unfolded panels includes: first, longitudinally splitting the cut bamboo tubes into arc-shaped bamboo strips; then softening the bamboo through heating methods such as saturated steam or microwaves; next, removing the green and yellow parts; then flattening the bamboo strips under pressure once or continuously in stages to obtain a bamboo unfolded panel; finally, the bamboo panel is prepared through steps such as gluing, hot pressing, edge trimming, and applying a clear varnish layer.

[0003] The outer green layer of bamboo, containing dense waxes and silicates, forms a natural protective layer, giving bamboo planks excellent anti-mildew properties. However, its extremely low surface energy affects the adhesion of varnishes. Traditional processes typically remove this green layer through physical planing or sanding, which not only reduces bamboo utilization by 30-40% but also damages the natural beauty of the bamboo's grain.

[0004] In existing technologies, although attempts have been made to improve the surface of bamboo by simple cleaning or alkali treatment, the effects are limited. It is impossible to achieve a long-term and firm bond with high-performance varnish while preserving the complete bamboo layer, which limits the application of bamboo in high value-added products. Summary of the Invention

[0005] In one aspect, this application provides a process for preparing bamboo with bamboo green leaves.

[0006] The technical solution adopted in this application is as follows: A process for preparing a bamboo unfolded board with a greenish tinge includes the following steps: (1) The bamboo with bamboo green is heated to 170-180℃ for carbonization treatment to obtain the first bamboo material; (2) The obtained primary bamboo material is immersed in a treatment solution at 50-60℃ and ultrasonically treated, rinsed clean and dried to obtain the second bamboo material; the second bamboo material includes the following components by mass percentage: sodium dodecylbenzene sulfonate 1.5-3.0wt%, fatty alcohol polyoxyethylene ether 1-2wt%, isopropanol 8-10wt%, sodium citrate 0.2-0.5wt%, and the balance is deionized water. The pH of the treatment solution is adjusted to 8.5-9.0. (3) A surface modifier is sprayed onto the surface of the second bamboo layer and heat-treated to obtain a third bamboo with surface grafting treatment; the surface modifier includes silane coupling agents containing unsaturated double bonds and silane coupling agents containing amino groups. (4) After applying a primer to the surface of the third bamboo material, heat curing is performed. The primer contains active groups that can react with the groups introduced in step (3).

[0007] By adopting the above technical solution, the bamboo is first carbonized to moderately degrade the hemicellulose, significantly reducing the bamboo's hygroscopicity and improving its dimensional stability. This process also removes most of the moisture from the bamboo, giving it better anti-mildew and anti-corrosion effects and increasing the surface roughness of the bamboo green layer. A treatment solution is used to dissolve and peel off some waxy components from the bamboo green layer surface, facilitating subsequent surface modification. Furthermore, unsaturated double bonds and amino groups are introduced into the bamboo green layer surface through grafting. After applying the primer, a chemical bond-based connection is formed between the primer and the bamboo green layer, combined with mechanical anchoring. This allows the primer to stably adhere to the bamboo green layer, while the varnish adheres to it. This results in good adhesion between the bamboo unfolded board and the varnish while retaining the bamboo green layer.

[0008] In some embodiments of this application, in the carbonization process of step (1), the temperature is first raised to 110-120℃ and held for 10-15 minutes, then raised to 140-145℃ and held for 15-20 minutes, and then raised to 170-180℃ and held for 8-10 minutes.

[0009] By adopting the above technical solution, the first stage begins the degradation of hemicellulose, followed by a second stage of heating. Under these conditions, it is beneficial to control the release rate of volatile components. Then, carbonization is carried out at the target temperature. Through the carbonization process, dimensional stability is improved and a certain physical anchoring point is provided by increasing the micro-roughness.

[0010] In some embodiments of this application, in step (2), the treatment liquid further contains 0.5-0.8 wt% tetraethoxysilane.

[0011] By adopting the above technical solution, tetraethoxysilane is hydrolyzed to form silica sol, which further crosslinks to enhance the density and hardness of the silane layer.

[0012] In some embodiments of this application, in step (3), the surface modifier comprises the following components by mass percentage: 2-3 wt% methacryloyloxysilane coupling agent, 1-2 wt% aminosilane coupling agent, and the balance being a mixture of ethanol and water; the pH of the surface modifier is adjusted to 4.0-4.5 before use.

[0013] By adopting the above technical solution, the coupling agent of the corresponding mass fraction can better perform surface modification. The methacryloyloxysilane coupling agent can be selected from one of 3-methacryloyloxypropylmethyldiethoxysilane, 3-acryloyloxypropyltrimethoxysilane, or 3-methacryloyloxypropyltrimethoxysilane. The aminosilane coupling agent can be selected from one of 3-aminopropylmethyldimethoxysilane or 3-aminopropylmethyldiethoxysilane.

[0014] In some embodiments of this application, in step (3), after the surface modifier is sprayed onto the surface of the second bamboo material, it is kept under vacuum for more than 2 minutes, and then placed in an environment of 80°C for 30-35 minutes and in an environment of 120°C for 45-50 minutes.

[0015] By adopting the above technical solution, in a vacuum environment, the solution can be promoted to penetrate deep into the microtexture, and then in a thermal environment, the reaction of the groups can be promoted, so that the coupling agent is grafted onto the surface of the bamboo.

[0016] In some embodiments of this application, the primer comprises component A and component B. Component A comprises, by mass fraction, 30-40 wt% bisphenol A epoxy resin, 15-20 wt% hydroxyl acrylic resin, 15-18 wt% polyester polyol, 1-2 wt% nano-fumed silica, 0.2-0.3 wt% leveling agent, 0.2-0.3 wt% defoamer, and the balance being propylene glycol methyl ether acetate. Component B comprises, by mass fraction, 70-80 wt% isocyanate trimer, 0.05-0.1 wt% dibutyltin dilaurate, and the balance being butyl acetate.

[0017] By adopting the above technical solution, the cyclooxygenated groups in component A can react with the amino groups on the surface of the bamboo green layer through ring-opening reaction, and the isocyanate groups in component B can react simultaneously with the amino groups on the surface of the bamboo green layer, the hydroxyl groups in component A, and the cyano groups on the surface of the bamboo green layer, thereby forming an interpenetrating polymer network primer layer, which is connected to the bamboo green layer through chemical bonds and other means, and has a good adhesion effect.

[0018] In some embodiments of this application, the leveling agent is selected from polyether-modified polydimethylsiloxane.

[0019] In some embodiments of this application, the defoamer is selected from BYK-066N.

[0020] In some embodiments of this application, in step (4) thermosetting, the material is first pre-cured at 50-60°C for 5-10 min, and then cured at 90-100°C for 20-25 min.

[0021] Secondly, this application provides a bamboo board.

[0022] A bamboo board is prepared by the unfolded board obtained through the above-described preparation process.

[0023] By adopting the above technical solution, the bamboo board prepared can retain the original anti-corrosion and anti-mildew effects of bamboo. In the presence of the bamboo green layer, it can also give the bamboo board a better aesthetic and artistic feel. The primer layer is connected to the bamboo green layer through chemical bonds, and the primer layer can be connected to the varnish layer with high adhesion, thereby improving the stability of the varnish layer.

[0024] In summary, this application includes at least one of the following beneficial effects: 1. In this application, after carbonization and treatment with a processing liquid, unsaturated double bonds and amino groups are grafted onto the surface of the bamboo green layer. The epoxy groups, hydroxyl groups, and isocyanate groups contained in the primer component can react with the amino groups, unsaturated double bonds introduced on the bamboo green surface, and the hydroxyl groups of the bamboo itself to form a covalent bond connection structure, thereby making the primer stably connected to the bamboo green layer. After the primer layer is cured, it forms an ideal substrate that can also form a certain interpenetration and physical entanglement structure with the varnish, resulting in good adhesion. 2. After the carbonized bamboo unfolded board of this application is coated with varnish, the surface has a bamboo green layer, a primer layer and a varnish layer. The physical properties of bamboo and varnish are very different, such as shrinkage rate. The primer acts as a transition layer. When the bamboo undergoes dimensional changes due to temperature and humidity changes, this transition layer with a certain toughness can absorb and disperse stress, avoiding direct stress transmission and damage to the brittle topcoat layer or fragile interface. Detailed Implementation

[0025] The following provides a further detailed description of this application.

[0026] The bamboo raw material in this application is prepared by longitudinally splitting the cut bamboo tubes into arc-shaped bamboo strips, then softening the bamboo by microwave heating, removing the yellowing, and then continuously flattening it step by step to obtain bamboo raw material with bamboo green. Example 1

[0027] This embodiment discloses a process for preparing a bamboo unfolded board with bamboo green covering, including the following steps: (1) Place the bamboo raw material with bamboo green in a carbonization furnace, first heat it to 120℃ and keep it for 10 minutes, then heat it to 145℃ and keep it for 15 minutes, then heat it to 180℃ and keep it for 10 minutes to obtain the first bamboo material. (2) The first bamboo material was immersed in a treatment solution at 60°C and ultrasonically treated (power 300W, frequency 28kHz) for 5 minutes, rinsed clean and dried to obtain the second bamboo material. The treatment solution included the following components by mass percentage: sodium dodecylbenzene sulfonate 1.5wt%, fatty alcohol polyoxyethylene ether 1wt%, isopropanol 8wt%, sodium citrate 0.2wt%, and the balance was deionized water. The pH of the treatment solution was adjusted to 8.5 with triethanolamine. Through the combination of sodium dodecylbenzene sulfonate and fatty alcohol polyoxyethylene ether, a microemulsion was formed, which could effectively penetrate and encapsulate the wax, thereby removing some waxy materials on the surface of the bamboo green layer. Isopropanol, as a co-solvent and penetrant, better promoted the dissolution and peeling of the bamboo green layer surface. (3) A surface modifier is sprayed onto the surface of the second bamboo layer and kept under a vacuum of -0.09 MPa for 3 min. Then, it is successively placed in an environment of 80℃ for 30 min and an environment of 120℃ for 50 min to obtain a third bamboo with surface grafting treatment. The surface modifier includes silane coupling agents containing unsaturated double bonds and silane coupling agents containing amino groups. The unsaturated double-bond silane coupling agent is selected from 3-methacryloyloxypropyltrimethoxysilane, and the aminosilane coupling agent is selected from 3-aminopropylmethyldimethoxysilane; the surface modifier comprises the following components by mass percentage: 2 wt% methacryloyloxysilane coupling agent, 1 wt% aminosilane coupling agent, and the balance being a mixture of ethanol and water (volume ratio of 8:2); the pH of the surface modifier is adjusted to 4.5 using glacial acetic acid; After applying a primer to the surface of the third bamboo material, pre-cur it at 50°C for 10 minutes, and then cure it at 100°C for 25 minutes. The primer comprises component A and component B. The first two components are mixed evenly. Component A, by mass fraction, comprises 30wt% bisphenol A epoxy resin (epoxy equivalent 185-190), 20wt% hydroxyl acrylic resin (hydroxyl value 100-110mgKOH / g), 18wt% polyester polyol (molecular weight 2000), 1wt% nano-fumed silica, 0.2wt% leveling agent (selected from polyether modified polydimethylsiloxane), 0.3wt% defoamer (BYK-066N), and the balance being propylene glycol methyl ether acetate. Component B, by mass fraction, comprises 80wt% isocyanate trimer (TDI), 0.05wt% dibutyltin dilaurate, and the balance being butyl acetate. Example 2

[0028] The process steps in this embodiment are the same as those in Embodiment 1. The difference is that in step (2), the treatment liquid includes the following components by mass percentage: sodium dodecylbenzenesulfonate 3.0wt%, fatty alcohol polyoxyethylene ether 2wt%, isopropanol 10wt%, sodium citrate 0.5wt%, and the balance is deionized water. The pH of the treatment liquid is adjusted to 8.5 with triethanolamine. Example 3

[0029] The process steps in this embodiment are the same as those in Embodiment 1. The difference is that in step (3), the surface modifier includes the following components by mass percentage: 3 wt% methacryloyloxysilane coupling agent, 2 wt% aminosilane coupling agent, and the balance being a mixture of ethanol and water (volume ratio of 8:2); the pH of the surface modifier is adjusted to 4.5 using glacial acetic acid. Example 4

[0030] The process steps in this embodiment are the same as those in Embodiment 1. The difference is that in step (3), the treatment liquid also includes 0.7 wt% tetraethoxysilane. Example 5

[0031] The process steps in this embodiment are the same as those in embodiment 4. The difference is that in step (4), the primer includes component A and component B. Component A includes, by mass fraction, 40wt% bisphenol A epoxy resin (epoxy equivalent 185-190), 15wt% hydroxyl acrylic resin (hydroxyl value 100-110mgKOH / g), 15wt% polyester polyol (molecular weight 2000), 2wt% nano-fumed silica, 0.3wt% leveling agent (selected from polyether modified polydimethylsiloxane), 0.2wt% defoamer (BYK-066N), and the balance is propylene glycol methyl ether acetate. Component B includes, by mass fraction, 70wt% isocyanate trimer (TDI), 0.08wt% dibutyltin dilaurate, and the balance is butyl acetate.

[0032] Comparative Example 1 The process steps of this comparative example are the same as those of Example 1, except that the bamboo was not carbonized in step (1).

[0033] Comparative Example 2 The process steps of this comparative example are the same as those of Example 1, except that the bamboo was not treated in step (2).

[0034] Comparative Example 3 The process steps of this comparative example are the same as those of Example 1, except that only the carbonization treatment in step (1) is performed.

[0035] Comparative Example 4 The process steps of this comparative example are the same as those of Example 1, except that the primer coating treatment in step (4) was not performed.

[0036] Performance testing Within one hour of the bamboo unfolded board curing, a commercially available two-component PU topcoat containing isocyanate groups (-NCO) and hydroxyl groups (-OH) was applied to the surface of the bamboo unfolded board to a thickness of 50 μm and cured. Then, according to ASTM D4541 standard, a 20 mm diameter aluminum ingot was glued to the coated surface with special adhesive. After the adhesive was completely cured, the coating was cut along the edge of the ingot to the substrate to isolate the test area. Then, the ingot was pulled out at a uniform speed perpendicular to the surface with a tester until the coating was detached. The maximum tensile force value was recorded as the adhesion. The sample was alternately stored in an environment of 10℃ and 60℃ for 2 hours, 200 times, and then the adhesion was tested again. The rate of decrease in adhesion was measured as follows: decrease rate = (original adhesion - adhesion after cycle) / original adhesion * 100%. The lower the decrease rate, the better the cycle resistance.

[0037] The test results of Examples 1-5 and Comparative Examples 1-4 are shown in the table below.

[0038] Example 1 3.51 1.98 Example 2 3.83 1.75 Example 3 3.92 1.72 Example 4 3.72 1.69 Example 5 4.01 1.53 Comparative Example 1 2.62 3.41 Comparative Example 2 1.63 9.85 Comparative Example 3 0.56 20.12 Comparative Example 4 3.18 3.01 In this application, carbonization and treatment with a processing solution facilitate the grafting of unsaturated double bonds and amino groups onto the surface of the bamboo veneer layer. The epoxy groups, hydroxyl groups, and isocyanate groups contained in the primer components can react with the amino groups and unsaturated double bonds introduced onto the bamboo veneer surface, as well as the hydroxyl groups of the bamboo itself, to form a covalent bond structure, thereby ensuring that the primer is stably attached to the bamboo veneer layer. The primer layer forms an ideal substrate. Common varnishes (such as PU, epoxy, and acrylic) also contain similar groups or groups that can interact with the primer, forming a certain degree of interpenetration and physical entanglement with the primer, resulting in good adhesion. Furthermore, the primer layer has a certain degree of deformability, acting as a transition layer between the bamboo veneer layer and the varnish layer, and maintaining good adhesion even after thermal cycling.

[0039] Application examples The bamboo unfolded board prepared in Example 1 was assembled and hot-pressed at 1.2-1.8 MPa and 120-125℃ using phenolic resin adhesive. Then, it was coated with PU varnish and cured to obtain a bamboo board.

[0040] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A process for preparing a bamboo unfolded board with green inclusions, characterized in that: Includes the following steps: (1) The bamboo with bamboo green is heated to 170-180℃ for carbonization treatment to obtain the first bamboo material; (2) The obtained primary bamboo material is immersed in a treatment solution at 50-60℃ and ultrasonically treated, rinsed clean and dried to obtain the second bamboo material; the second bamboo material includes the following components by mass percentage: sodium dodecylbenzene sulfonate 1.5-3.0wt%, fatty alcohol polyoxyethylene ether 1-2wt%, isopropanol 8-10wt%, sodium citrate 0.2-0.5wt%, and the balance is deionized water. The pH of the treatment solution is adjusted to 8.5-9.

0. (3) A surface modifier is sprayed onto the surface of the second bamboo layer and heat-treated to obtain a third bamboo with surface grafting treatment; the surface modifier includes silane coupling agents containing unsaturated double bonds and silane coupling agents containing amino groups. (4) After applying a primer to the surface of the third bamboo material, heat curing is performed. The primer contains active groups that can react with the groups introduced in step (3).

2. The process for preparing a green bamboo unwinding board according to claim 1, characterized in that: In the carbonization process of step (1), the temperature is first raised to 110-120℃ and held for 10-15 minutes, then raised to 140-145℃ and held for 15-20 minutes, and then raised to 170-180℃ and held for 8-10 minutes.

3. The process for preparing a green bamboo unwinding board according to claim 2, characterized in that: In step (2), the treatment solution also contains 0.5-0.8 wt% tetraethoxysilane.

4. The process for preparing a green bamboo unwinding board according to claim 3, characterized in that: In step (3), the surface modifier comprises the following components by mass percentage: 2-3 wt% methacryloyloxysilane coupling agent, 1-2 wt% aminosilane coupling agent, and the balance being a mixture of ethanol and water; the pH of the surface modifier is adjusted to 4.0-4.5 before use.

5. The process for preparing a green bamboo unwinding board according to claim 4, characterized in that: In step (3), after the surface modifier is sprayed onto the surface of the second bamboo material, it is kept under vacuum for more than 2 minutes, and then placed in an environment of 80°C for 30-35 minutes and in an environment of 120°C for 45-50 minutes.

6. The process for preparing a green bamboo unwinding board according to claim 1, characterized in that: The primer comprises component A and component B. Component A, by mass fraction, comprises 30-40 wt% bisphenol A epoxy resin, 15-20 wt% hydroxyl acrylic resin, 15-18 wt% polyester polyol, 1-2 wt% nano-fumed silica, 0.2-0.3 wt% leveling agent, 0.2-0.3 wt% defoamer, and the balance being propylene glycol methyl ether acetate. Component B, by mass fraction, comprises 70-80 wt% isocyanate trimer, 0.05-0.1 wt% dibutyltin dilaurate, and the balance being butyl acetate.

7. The process for preparing a bamboo unfolded board with green inclusions according to claim 6, characterized in that: The leveling agent is selected from polyether-modified polydimethylsiloxane.

8. A process for preparing a green bamboo unwinding board according to claim 7, characterized in that: The defoamer is selected from BYK-066N.

9. The process for preparing a green bamboo unwinding board according to claim 6, characterized in that: In step (4) heat curing, the product is first pre-cured at 50-60℃ for 5-10 minutes, and then cured at 90-100℃ for 20-25 minutes.

10. A bamboo board, characterized by: The unfolded board is prepared by the bamboo unfolding board preparation process according to any one of claims 1-9.