Formaldehyde-free composite board for cabinet and preparation method of formaldehyde-free composite board

Abstract

The invention discloses a formaldehyde-free composite board for a cabinet and a preparation method of the formaldehyde-free composite board, and relates to the technical field of artificial board manufacturing. The preparation method of the formaldehyde-free composite board for the cabinet comprises the following steps: mixing high amylose with a choline chloride / urea deep eutectic solution, stirring, adding concentrated hydrochloric acid for reaction, adjusting the pH value, and adding ammonium persulfate to obtain pretreated oxidized starch; methacrylic acid dehydrated glyceride is added into the pretreated oxidized starch for a grafting reaction, then modified polyvinyl alcohol is added for blending, sodium metaphosphate is added for crosslinking, finally, heating and curing are conducted, modified titanium dioxide nanoparticles are added, and the formaldehyde-free starch adhesive is obtained. The wood shavings and the formaldehyde-free starch adhesive are mixed, and a core material is obtained; and arranging the core material between the formaldehyde-free veneers, and carrying out hot press molding to obtain the formaldehyde-free composite board. The formaldehyde-free composite board for the cabinet has excellent mechanical strength, bonding performance and water resistance.

Description

Technical Field

[0001] This invention relates to the field of engineered wood products manufacturing technology, specifically to a formaldehyde-free composite board for cabinets and its preparation method. Background Technology

[0002] Among all home furnishing products, kitchen cabinets occupy a large portion of the living space. Kitchen cabinets, wardrobes, TV cabinets, balcony cabinets, etc., all require the use of engineered wood products. As consumers' living standards improve, their demands for the environmental friendliness and health of their home's cabinetry are also increasing, leading to a growing market demand for formaldehyde-free engineered wood products. Formaldehyde-free engineered wood products can be categorized into formaldehyde-free MDF, formaldehyde-free particleboard, and formaldehyde-free veneered particleboard, among others. Formaldehyde-free particleboard, in particular, is widely used in furniture manufacturing due to its low price, stable structure, and good processing performance.

[0003] Particleboard is made through processes such as particle preparation, drying and sorting, gluing, laying, pre-pressing, and hot pressing. Particleboard has an extremely high surface flatness, clear and realistic texture, uniform density, and minimal thickness error. Traditionally, formaldehyde-based adhesives, such as urea-formaldehyde resin, are the mainstream choice in particleboard production. These adhesives have low curing temperatures and produce good bonding effects on particleboard made from various plant materials such as wheat straw and rice husks. However, it is undeniable that these aldehyde-based adhesives release excessive amounts of formaldehyde. During the production and use of particleboard, the continuous release of formaldehyde can cause significant harm to the human body. Long-term exposure to environments containing high concentrations of formaldehyde can severely damage human health, such as irritating the respiratory tract, triggering allergic reactions, weakening the immune system, and even increasing the risk of cancer. Therefore, there is an urgent need for technological innovation to improve the environmental performance and quality of products to meet market demands.

[0004] Currently, in the application of formaldehyde-free adhesives in particleboard production, polyurethane adhesives, soybean protein adhesives, and molecular diisocyanate (MDI) adhesives are typical examples. However, each has its limitations. Polyurethane adhesives have a fast curing speed, but poor adhesion. Soybean protein adhesives have poor bonding strength and water resistance, while MDI adhesives themselves have poor water resistance, causing the boards to absorb water and swell. Therefore, developing a new type of tackifying and water-resistant adhesive is of great significance for improving the performance of formaldehyde-free particleboard. Summary of the Invention

[0005] The purpose of this invention is to provide a formaldehyde-free composite board for kitchen cabinets and its preparation method, thereby solving the following technical problems: Existing formaldehyde-free composite boards used in kitchen cabinets suffer from problems such as insufficient water resistance, low bonding strength, and limited storage stability.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing a formaldehyde-free composite board for kitchen cabinets, characterized by comprising at least the following steps: High amylose starch was mixed with a choline chloride / urea deep eutectic solution, stirred, and then concentrated hydrochloric acid was added to react. After adjusting the pH, ammonium persulfate was added to obtain pretreated oxidized starch. Dehydrated glyceryl methacrylate was added to the pretreated oxidized starch for grafting reaction, followed by the addition of modified polyvinyl alcohol for blending, then the addition of sodium metaphosphate for crosslinking, and finally the mixture was heated and matured and modified titanium dioxide nanoparticles were added to obtain an aldehyde-free starch adhesive. Wood shavings and formaldehyde-free starch adhesive are mixed to obtain the core material; The core material is placed between the formaldehyde-free veneer and hot-pressed to obtain a formaldehyde-free composite board.

[0007] As a further aspect of the present invention: the amylose content of the high amylose is 40-70 wt%, the mass ratio of choline chloride to urea in the choline chloride / urea deep eutectic solution is 1-1.5:1, and the mass ratio of the high amylose to the choline chloride / urea deep eutectic solution is 1:10-100.

[0008] As a further aspect of the present invention: the concentration of the concentrated hydrochloric acid is 36-38 wt%, and the mass ratio of the high amylose starch, the concentrated hydrochloric acid and the ammonium persulfate is 100:3-5:2-3.

[0009] As a further aspect of the present invention, the method for preparing the modified polyvinyl alcohol includes at least the following preparation steps: Polyvinyl alcohol and water were mixed, glyoxal was added and the pH was adjusted to 1. After observing the sticky string phenomenon, the pH was adjusted to 7-7.5, and then ammonium persulfate was added. After the reaction, modified polyvinyl alcohol was obtained.

[0010] As a further aspect of the present invention: the mass ratio of glyoxal to polyvinyl alcohol is 0.05-0.2:1, and the mass ratio of ammonium persulfate to polyvinyl alcohol is 0.003-0.01:1.

[0011] As a further aspect of the present invention: the mass ratio of the high amylose starch, the dehydrated glyceryl methacrylate, the modified polyvinyl alcohol, the sodium metaphosphate and the modified titanium dioxide nanoparticles is 20:3-5:5-7:2-4:0.8-1.6.

[0012] As a further aspect of the present invention, the preparation method of the modified titanium dioxide nanoparticles includes the following steps: Titanium dioxide nanoparticles were dispersed in anhydrous ethanol, γ-methacryloxypropyltrimethoxysilane was added, and the mixture was stirred, filtered, washed and dried to obtain alkylated modified nano-titanium dioxide powder. The alkylated modified nano-titanium dioxide powder and sodium dodecyl sulfate were dispersed in distilled water, heated, and then an aqueous solution of ammonium persulfate was added. butyl acrylate was added dropwise, and after the reaction, calcium chloride solution was added to precipitate the mixture. The precipitate was then filtered, washed, dried, and extracted using a Soxhlet extract to obtain modified titanium dioxide nanoparticles.

[0013] As a further aspect of the present invention: the mass ratio of the titanium dioxide nanoparticles to the γ-methacryloyloxypropyltrimethoxysilane is 1:0.5-1, and the mass ratio of the alkylated modified nano-titanium dioxide powder, the sodium dodecyl sulfate, the ammonium persulfate, and the n-butyl acrylate is 10:0.8-1.2:0.06-0.15:12-18.

[0014] As a further aspect of the present invention: the mass ratio of the wood shavings to the formaldehyde-free starch adhesive is 100:8-16, and the formaldehyde-free finish is at least one of formaldehyde-free impregnated paper, formaldehyde-free PVC film, or formaldehyde-free melamine decorative panel.

[0015] A formaldehyde-free composite board for kitchen cabinets is prepared by any one of the above-described methods for preparing formaldehyde-free composite boards for kitchen cabinets.

[0016] The beneficial effects of this invention are: The formaldehyde-free composite board for cabinets prepared in this invention is a formaldehyde-free particleboard. The particleboard core material is prepared using a formaldehyde-free starch adhesive, which is then bonded to a formaldehyde-free finish to create the formaldehyde-free composite board for cabinets. The formaldehyde-free starch adhesive prepared in this invention uses high-amylose starch as the starch matrix, and dehydrated glyceryl methacrylate is grafted onto the starch molecular chains, introducing flexible polymer branches and active epoxy groups. Through covalent cross-linking of the epoxy groups with the hydroxyl groups of wood cellulose, the bonding strength is greatly improved. Further addition of modified polyvinyl alcohol for blending, and the addition of sodium metaphosphate for cross-linking, allows the epoxy groups of dehydrated glyceryl methacrylate to cross-link with the hydroxyl groups of starch. Combined with the secondary cross-linking of sodium metaphosphate, a three-dimensional network structure is formed, significantly improving the adhesive strength. Furthermore, the cross-linking network formed by sodium metaphosphate, polyvinyl alcohol, and starch hydroxyl groups, along with the hydrophobic effect of the grafted dehydrated glyceryl methacrylate chains, jointly constructs a dense hydrophobic system, effectively blocking water molecule intrusion. The introduction of modified titanium dioxide nanoparticles further provides photocatalytic bactericidal and antifungal functions. The adhesive prepared by this invention can form a strong bond with wood shavings and the decorative layer, making the board less prone to cracking and blistering under the cold and heat cycles and humidity changes experienced in the cabinet environment. It has excellent dimensional stability, which improves the durability of the prepared formaldehyde-free composite board. Moreover, there is no formaldehyde added from the adhesive to the decorative layer, which fundamentally eliminates formaldehyde release.

[0017] The modified polyvinyl alcohol prepared in this invention, through controlled glyoxal dosage and reaction conditions, as well as moderate chain-splitting degradation by ammonium persulfate, allows glyoxal to react with the hydroxyl groups of polyvinyl alcohol, forming a localized, controllable cross-linked network. This avoids excessive gelation and significantly improves the initial tack, water resistance, and cohesive strength of the polyvinyl alcohol after film formation, ensuring good flowability and processability, facilitating subsequent uniform blending with starch adhesives. This invention, by introducing dehydrated glyceryl methacrylate grafting and modified polyvinyl alcohol into high-amylose starch, significantly improves the flowability and initial tack of the adhesive, making it more suitable for particleboard sizing processes. The modified molecular structure is stable, less prone to retrogradation and aging, and has a significantly extended shelf life.

[0018] In this invention, the starch substrate is selected as high amylose content starch. High amylose corn starch adhesive has stronger water resistance and better flowability. Pre-oxidation and activation are performed before starch grafting. Activation disrupts the crystalline regions of the starch, making the subsequent grafting reaction more uniform. Subsequent acid hydrolysis and oxidation reactions introduce carboxyl and aldehyde groups onto the starch molecular chains. These functional groups not only improve hydrophilicity but also serve as active sites for subsequent reactions with dehydrated glycerol methacrylate and modified polyvinyl alcohol. In this invention, starch is mixed with a choline chloride / urea deep eutectic solvent and ultrasonically treated to activate the starch, thereby controlling the aggregation state and molecular weight distribution of the starch macromolecular chains. This allows the amylose molecular chains to form uniformly dispersed nanoscale aggregates. The deep eutectic solution can form new hydrogen bonds with the hydroxyl groups in the starch molecules. On the one hand, this disrupts the starch's own hydrogen bond network, making the starch plasticized and dissolving, facilitating processing. On the other hand, the formation of new hydrogen bonds reduces the exposed hydroxyl groups in the starch molecules, preventing water intrusion. This results in adhesives prepared from high amylose having stronger shear strength and water resistance. The starch pretreatment oxidation method provided in this invention significantly improves the grafting efficiency, crosslinking density, water resistance, and storage stability of the final adhesive.

[0019] In this invention, surface-modified titanium dioxide nanoparticles are synthesized by grafting n-butyl acrylate onto the surface of alkylated modified nano-titanium dioxide via free radical-initiated polymerization. These modified titanium dioxide nanoparticles are introduced during the starch curing stage, and the surface grafting with n-butyl acrylate ensures uniform dispersion in the adhesive, forming a physical barrier and further improving water resistance. The uniform dispersion of titanium dioxide nanoparticles in the adhesive layer provides a nano-reinforcing effect, effectively transferring and dispersing stress, improving the bonding strength and storage stability of the formaldehyde-free starch adhesive, and enhancing the static bending strength, elastic modulus, and internal bond strength of the composite board. Furthermore, the photocatalytic activity of the nano-titanium dioxide can inhibit mold growth, improving the mold resistance of the composite board. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: The preparation method of modified titanium dioxide nanoparticles includes the following steps: 10g of dried nano-titanium dioxide particles were dispersed in 50ml of anhydrous ethanol, and then dispersed by high-speed shearing for 5min. 7g of γ-methacryloxypropyltrimethoxysilane was added to the dispersion, and the mixture was ultrasonicated (30kHz) for 15min. The mixture was then placed in a water bath and stirred under magnetic stirring at 50℃ for 2h. After filtration, the mixture was washed 4 times with ethanol and dried in an oven at 50℃ for 24h to obtain alkylated modified nano-titanium dioxide powder. 10g of the alkylated modified nano-titanium dioxide powder and 1g of sodium dodecyl sulfate were dispersed in distilled water, and the dispersion was treated with ultrasound (30 kHz) for 10 min. 0.1g of ammonium persulfate was added to the dispersion in a water bath at 70°C, and 15g of n-butyl acrylate was slowly added dropwise over 2 h. After the addition was complete, the mixture was kept at 70°C for another 30 min. Finally, the mixture was precipitated with a 5wt% CaCl2 aqueous solution, filtered, and washed four times with ethanol. After freeze-drying and Soxhlet extraction (acetone, 70°C, 48 h), modified titanium dioxide nanoparticles were obtained.

[0022] Example 2: The preparation method of modified polyvinyl alcohol includes the following steps: 6 g of polyvinyl alcohol 1788 (PVA) and 54 mL of excess water were added to a three-necked flask equipped with a spherical condenser, a stirrer, and a constant pressure funnel. The mixture was then heated to 95 °C and stirred for 2 h. After cooling to 60 °C, 0.6 g of glyoxal was added, and the pH was adjusted to 1. Stringing was observed, and the pH was adjusted to 7. Then, 0.5% (based on the mass of PVA) of ammonium persulfate was added, and the reaction was carried out for 30 min to obtain modified polyvinyl alcohol.

[0023] Example 3: The preparation method of choline chloride / urea deep eutectic solution includes the following steps: Weigh out 279.3g of choline chloride with a concentration of 139.63g / mol and 240g of urea with a concentration of 60.03g / mol, mix them together, seal the mixture with plastic wrap, place the beaker in an 85℃ constant temperature water bath, and stir continuously for 20 minutes at a speed of 150rpm until a transparent and stable solution is formed, thus obtaining a choline chloride / urea deep eutectic solution.

[0024] Example 4: A method for preparing a formaldehyde-free composite board for kitchen cabinets includes the following steps: 10g of high amylose G50 was added to 500g of the choline chloride / urea deep eutectic solution prepared in Example 3, and placed in a 50℃ constant temperature water bath. The mixture was stirred continuously for 1 hour at a speed of 200 rpm until the solution in the cup was free of starch particles and became translucent. 0.4mL of concentrated hydrochloric acid was added, and the mixture was kept at 50℃ for 2 hours. Then, NaOH solution was added to adjust the pH to 5.5-6, and 0.25g of ammonium persulfate was added. The mixture was reacted for 1 hour to obtain pretreated oxidized starch. 2 mL of dehydrated glyceryl methacrylate was added to the pretreated oxidized starch and reacted for 1.5 h. Then, 3 g of modified polyvinyl alcohol prepared in Example 2 was added to continue the reaction. After mixing and stirring for 1-1.5 h, 1 g of sodium metaphosphate was added for crosslinking for 30 min. Then, the temperature was raised to 80 °C and 0.5 g of modified titanium dioxide nanoparticles prepared in Example 1 were added and kept for 30 min to obtain formaldehyde-free starch adhesive. Place 100g of poplar wood shavings in an oven to dry, then spray 10g of the above-mentioned formaldehyde-free starch adhesive into the shavings using a glue gun, stir evenly, and obtain the core material. Formaldehyde-free impregnated paper is placed on the upper and lower surfaces of the core material, placed in a mold, spread evenly, and then hot-pressed and cured using a hot-pressing process at a platen temperature of 150℃ and a pressure of 5MPa to obtain a formaldehyde-free composite board for cabinets.

[0025] Compared with Example 4, Example 5 only replaces high amylose G50 with high amylose G70 by mass during the preparation process of Example 4. The other components and preparation methods are completely the same as those of Example 4.

[0026] Compared with Example 4, Example 6 only increased the mass of the modified titanium dioxide nanoparticles prepared in Example 1 to 0.7g during the preparation process of Example 4. The other components and preparation methods are completely the same as those in Example 4.

[0027] Example 7 A method for preparing a formaldehyde-free composite board for kitchen cabinets includes the following steps: 10g of high amylose G50 was added to 500g of the choline chloride / urea deep eutectic solution prepared in Example 3, and placed in a 50℃ constant temperature water bath. The mixture was stirred continuously for 1 hour at a speed of 200 rpm until the solution in the cup was free of starch particles and became translucent. 0.4mL of concentrated hydrochloric acid was added, and the mixture was kept at 50℃ for 2 hours. Then, NaOH solution was added to adjust the pH to 5.5-6, and 0.25g of ammonium persulfate was added. The mixture was reacted for 1 hour to obtain pretreated oxidized starch. 2.5 mL of dehydrated glyceryl methacrylate was added to the pretreated oxidized starch and reacted for 1.5 h. Then, 2.5 g of modified polyvinyl alcohol prepared in Example 2 was added to continue the reaction. After mixing and stirring for 1-1.5 h, 2 g of sodium metaphosphate was added for crosslinking for 30 min. Then, the temperature was raised to 80 °C and 0.5 g of modified titanium dioxide nanoparticles prepared in Example 1 was added and kept for 30 min to obtain formaldehyde-free starch adhesive. Place 100g of poplar wood shavings in an oven to dry, then spray 10g of the above-mentioned formaldehyde-free starch adhesive into the shavings using a glue gun, stir evenly, and obtain the core material. Formaldehyde-free impregnated paper is placed on the upper and lower surfaces of the core material, placed in a mold, spread evenly, and then hot-pressed and cured using a hot-pressing process at a platen temperature of 150℃ and a pressure of 5MPa to obtain a formaldehyde-free composite board for cabinets.

[0028] Comparative Example 1: A method for preparing a formaldehyde-free composite board for kitchen cabinets includes the following steps: 10g of high amylose G50 was added to 30mL of distilled water and stirred at 50℃ for 1h. 2mL of dehydrated glyceryl methacrylate was added and reacted for 1.5h. Then, 3g of modified polyvinyl alcohol prepared in Example 2 was added to continue the reaction. After mixing and stirring for 1-1.5h, 2.5g of sodium metaphosphate was added for crosslinking for 30min. Subsequently, the temperature was raised to 80℃ and 0.5g of modified titanium dioxide nanoparticles prepared in Example 1 were added and kept for 30min to obtain an aldehyde-free starch adhesive. Place 100g of poplar wood shavings in an oven to dry, then spray 10g of the above-mentioned formaldehyde-free starch adhesive into the shavings using a glue gun, stir evenly, and obtain the core material. Formaldehyde-free impregnated paper is placed on the upper and lower surfaces of the core material, placed in a mold, spread evenly, and then hot-pressed and cured using a hot-pressing process at a platen temperature of 150℃ and a pressure of 5MPa to obtain a formaldehyde-free composite board for cabinets.

[0029] Comparative Example 2: A method for preparing a formaldehyde-free composite board for kitchen cabinets includes the following steps: 10g of high amylose G50 was added to 500g of the choline chloride / urea deep eutectic solution prepared in Example 3, and placed in a 50℃ constant temperature water bath. The mixture was stirred continuously for 1 hour at a speed of 200 rpm until the solution in the cup was free of starch particles and became translucent. 0.4mL of concentrated hydrochloric acid was added, and the mixture was kept at 50℃ for 2 hours. Then, NaOH solution was added to adjust the pH to 5.5-6, and 0.25g of ammonium persulfate was added. The mixture was reacted for 1 hour to obtain pretreated oxidized starch. 2 mL of dehydrated glyceryl methacrylate was added to the pretreated oxidized starch. After reacting for 1.5 h, the temperature was raised to 80 °C and 0.5 g of modified titanium dioxide nanoparticles prepared in Example 1 were added and kept for 30 min to obtain an aldehyde-free starch adhesive. Place 100g of poplar wood shavings in an oven to dry, then spray 10g of the above-mentioned formaldehyde-free starch adhesive into the shavings using a glue gun, stir evenly, and obtain the core material. Formaldehyde-free impregnated paper is placed on the upper and lower surfaces of the core material, placed in a mold, spread evenly, and then hot-pressed and cured using a hot-pressing process at a platen temperature of 150℃ and a pressure of 5MPa to obtain a formaldehyde-free composite board for cabinets.

[0030] Compared with Example 4, Comparative Example 3 only replaced the high amylose G50 added in Example 4 with waxy corn starch Waxy (amylose content 3.2%). The remaining components and preparation methods were completely the same as in Example 4.

[0031] Compared with Example 4, Comparative Example 4 is identical to Example 4 except that modified titanium dioxide nanoparticles are not introduced in the step of preparing the formaldehyde-free starch adhesive in Example 4.

[0032] Performance testing Adhesion strength test: The formaldehyde-free composite boards for cabinets obtained in Examples 4-7 and Comparative Examples 1-4 were dried at room temperature for 48 hours to prepare composite board test specimens. The mechanical properties of the formaldehyde-free composite boards were tested using WAY-300B from Jinan Yongce Industrial Equipment Co., Ltd. The adhesive strength of the dry board of the formaldehyde-free composite board was measured according to the Chinese national standard (GB / T 17657-2022). The sample size was 100×25mm (length×width), the loading speed was 5mm / min, the test distance between the two clamps was 40mm, and at least 5 samples were taken for each test. The average value was taken. The specimens were pre-soaked in water at 63±3℃ for 3 hours and then air-dried at room temperature for 10 minutes to obtain the adhesive strength of the wet board. The test results are shown in Table 1. Surface thermal cycling resistance test: According to the Chinese national standard GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels", the specimen (150±2) mm × (150±2) mm was fixed on a metal frame and placed in a forced-air drying oven at a temperature of (63±2)℃. The placement direction of the specimen was consistent with the air convection mode of the drying oven. The heat treatment was carried out for (120±10) min. The specimen was then removed and immediately placed in a low-temperature test chamber at (-20±3)℃ for (120±10) min. After two cycles of this treatment, the specimen was removed and allowed to reach room temperature. Under natural light conditions, the surface of the specimen was observed from multiple angles. The presence of cracks or blistering indicated failure. The observation results were recorded. The test results are shown in Table 1. Water resistance test: The formaldehyde-free composite boards for cabinets obtained in Examples 4-7 and Comparative Examples 1-4 were immersed in distilled water at 30°C for 2 hours, then removed and dried. The boards were then dried in an oven at 50°C for 1 hour to obtain specimens that had been immersed for 2 hours. The shear strength of the specimens was tested, and the degree of shear strength decay was used to characterize the water resistance. The test results are shown in Table 1. Mechanical property testing: Referring to GB / T 17657-2013, the static bending strength (MOR) and modulus of elasticity (MOE) of the formaldehyde-free composite board were tested using a universal testing machine. The loading speed was 5 mm / min, and the results are expressed as the average value of 5 samples. The test results are shown in Table 1. Table 1: Statistical Table of Performance Test Data of Formaldehyde-Free Composite Boards in Examples 4-7 and Comparative Examples 1-4

[0033] As shown in Table 1, the formaldehyde-free composite board for cabinets prepared by this invention exhibits excellent mechanical strength, bonding performance, and water resistance. In Comparative Example 1, the pretreatment steps of starch activation, acid hydrolysis, and oxidation were omitted, resulting in insufficient grafting efficiency and crosslinking density of the prepared formaldehyde-free starch adhesive, leading to significant deterioration in various properties. In Comparative Example 2, the absence of modified polyvinyl alcohol resulted in a significant decrease in the bonding strength and water resistance of the prepared formaldehyde-free starch adhesive. In Comparative Example 3, the use of waxy starch with low linear content prevented the formation of a strong and tough gel network, resulting in poor performance of the prepared formaldehyde-free composite board. In Comparative Example 4, the absence of modified titanium dioxide nanoparticles led to a significant decrease in the water resistance of the prepared formaldehyde-free composite board, while other properties showed a slight decline, but the difference was not substantial.

[0034] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0035] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for preparing a formaldehyde-free composite board for kitchen cabinets, characterized in that, At least the following steps are included: High amylose starch was mixed with a choline chloride / urea deep eutectic solution, stirred, and then concentrated hydrochloric acid was added to react. After adjusting the pH, ammonium persulfate was added to obtain pretreated oxidized starch. Dehydrated glyceryl methacrylate was added to the pretreated oxidized starch for grafting reaction, followed by the addition of modified polyvinyl alcohol for blending, then the addition of sodium metaphosphate for crosslinking, and finally the mixture was heated and matured and modified titanium dioxide nanoparticles were added to obtain an aldehyde-free starch adhesive. Wood shavings and formaldehyde-free starch adhesive are mixed to obtain the core material; The core material is placed between the formaldehyde-free veneer and hot-pressed to obtain a formaldehyde-free composite board.

2. The method for preparing a formaldehyde-free composite board for kitchen cabinets according to claim 1, characterized in that, The amylose content of the high amylose is 40-70 wt%, the mass ratio of choline chloride to urea in the choline chloride / urea deep eutectic solution is 1-1.5:1, and the mass ratio of the high amylose to the choline chloride / urea deep eutectic solution is 1:10-100.

3. The method for preparing a formaldehyde-free composite board for kitchen cabinets according to claim 1, characterized in that, The concentration of the concentrated hydrochloric acid is 36-38 wt%, and the mass ratio of the high amylose, the concentrated hydrochloric acid, and the ammonium persulfate is 100:3-5:2-3.

4. The method for preparing a formaldehyde-free composite board for kitchen cabinets according to claim 1, characterized in that, The method for preparing the modified polyvinyl alcohol includes at least the following preparation steps: Polyvinyl alcohol and water were mixed, glyoxal was added and the pH was adjusted to 1. After observing the sticky string phenomenon, the pH was adjusted to 7-7.5, and then ammonium persulfate was added. After the reaction, modified polyvinyl alcohol was obtained.

5. The method for preparing a formaldehyde-free composite board for kitchen cabinets according to claim 4, characterized in that, The mass ratio of glyoxal to polyvinyl alcohol is 0.05-0.2:1, and the mass ratio of ammonium persulfate to polyvinyl alcohol is 0.003-0.01:

1.

6. The method for preparing a formaldehyde-free composite board for kitchen cabinets according to claim 1, characterized in that, The mass ratio of the high amylose starch, the dehydrated glyceryl methacrylate, the modified polyvinyl alcohol, the sodium metaphosphate, and the modified titanium dioxide nanoparticles is 20:3-5:5-7:2-4:0.8-1.

6.

7. The method for preparing a formaldehyde-free composite board for kitchen cabinets according to claim 1, characterized in that, The preparation method of the modified titanium dioxide nanoparticles includes the following steps: Titanium dioxide nanoparticles were dispersed in anhydrous ethanol, γ-methacryloxypropyltrimethoxysilane was added, and the mixture was stirred, filtered, washed and dried to obtain alkylated modified nano-titanium dioxide powder. The alkylated modified nano-titanium dioxide powder and sodium dodecyl sulfate were dispersed in distilled water, heated, and then an aqueous solution of ammonium persulfate was added. butyl acrylate was added dropwise, and after the reaction, calcium chloride solution was added to precipitate the mixture. The precipitate was then filtered, washed, dried, and extracted using a Soxhlet extract to obtain modified titanium dioxide nanoparticles.

8. The method for preparing a formaldehyde-free composite board for kitchen cabinets according to claim 7, characterized in that, The mass ratio of the titanium dioxide nanoparticles to the γ-methacryloyloxypropyltrimethoxysilane is 1:0.5-1, and the mass ratio of the alkylated modified nano-titanium dioxide powder, the sodium dodecyl sulfate, the ammonium persulfate, and the n-butyl acrylate is 10:0.8-1.2:0.06-0.15:12-18.

9. The method for preparing a formaldehyde-free composite board for kitchen cabinets according to claim 1, characterized in that, The mass ratio of the wood shavings to the formaldehyde-free starch adhesive is 100:8-16, and the formaldehyde-free finish is at least one of formaldehyde-free impregnated paper, formaldehyde-free PVC film, or formaldehyde-free melamine decorative panel.

10. A formaldehyde-free composite board for kitchen cabinets, characterized in that, It is prepared by the method for preparing formaldehyde-free composite board for cabinets as described in any one of claims 1-9.

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