A method for manufacturing formaldehyde-free fire-resistant engineered wood panels

Abstract

This invention discloses a method for manufacturing formaldehyde-free fire-resistant engineered wood panels, comprising the following steps: S1, collecting pre-cut bamboo, cleaning and drying it; S2, crushing the dried bamboo into granules and homogenizing it to make the particle size distribution more uniform; S3, subjecting the homogenized bamboo granules to acid-alkali treatment to reduce the molecular weight of lignin and hemicellulose in the bamboo granules; S4, subjecting the acid-alkali pretreated bamboo granules to a gradually increasing high-temperature treatment, causing the fiber macromolecules in the bamboo granules to react at high temperature and form a trapezoidal structure of a multi-conjugated system; S5, cooling the high-temperature treated bamboo granules to room temperature and adding formaldehyde-free adhesive as a binder; S6, pressing the bonded bamboo granules into panels using a pressing molding process, and performing necessary finishing and polishing. This invention uses bamboo as raw material and, through a specific processing technology, manufactures an environmentally friendly and fire-resistant engineered wood panel.

Description

Technical Field

[0001] This invention relates to the field of engineered wood panel manufacturing technology, and more particularly to a method for manufacturing a formaldehyde-free fire-resistant engineered wood panel. Background Technology

[0002] With societal development and increasing environmental awareness, people's demand for home safety is constantly rising, leading to stricter requirements for engineered wood products. Traditional engineered wood product manufacturing often uses adhesives containing harmful substances such as formaldehyde, posing a potential threat to human health and polluting the environment. Furthermore, the wood used in traditional engineered wood products exacerbates deforestation and has significant shortcomings in fire resistance. In the event of a fire, these boards are easily ignited, accelerating the spread of flames and posing a serious threat to people's lives and property.

[0003] Currently, many raw materials have been tested as materials for engineered wood products, but effective methods to improve their fire resistance are lacking. Existing fire-resistant board manufacturing processes typically improve fire resistance by adding refractory materials or performing special treatments. However, these methods often suffer from high production costs, complex processes, and severe environmental pollution. Furthermore, fire-resistant boards produced using these methods often fail to meet formaldehyde-free environmental requirements, limiting their competitiveness in the market.

[0004] Therefore, a new solution is needed to address the above problems. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides a method for manufacturing formaldehyde-free fire-resistant engineered wood panels.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for manufacturing formaldehyde-free fire-resistant engineered wood panels, comprising the following steps:

[0007] S1. Raw material selection and processing: Collect the bamboo after preliminary cutting, and then clean and dry it;

[0008] S2. Crushing and homogenization: The dried bamboo is crushed into granules and homogenized to make the particle size distribution of the bamboo particles more uniform.

[0009] S3. Acid and alkali pretreatment: Acid and alkali treatment is performed on homogenized bamboo particles to reduce the molecular weight of lignin and hemicellulose in the bamboo particles.

[0010] S4. High-temperature treatment: The bamboo particles after acid and alkali pretreatment are subjected to a high-temperature treatment with gradually increasing temperature, so that the fiber macromolecules in the bamboo particles react at high temperature to form a ladder structure of multiple conjugated system.

[0011] S5. Cooling and Adding Formaldehyde-Free Adhesive: Cool the bamboo particles after high-temperature treatment to room temperature and add formaldehyde-free adhesive as a binder.

[0012] S6. Pressing and post-processing: The bonded bamboo particles are pressed into boards through the pressing process, and necessary trimming and polishing are carried out.

[0013] In a preferred embodiment of the present invention, in step S1, the length of the bamboo material after initial segmentation is 0.6-1.2m.

[0014] In a preferred embodiment of the present invention, during the drying process of bamboo in step S1, the moisture content of the bamboo is controlled to be between 6% and 10%.

[0015] In a preferred embodiment of the present invention, in step S2, at least one of a hammer crusher, a shear crusher, and a disc crusher is used for the crushing of bamboo, and the diameter of the crushed bamboo particles is 8-28 mm; a high-pressure homogenizer is used for the homogenization of bamboo.

[0016] In a preferred embodiment of the present invention, in step S3, during the acid-base treatment of bamboo particles, the bamboo particles are first soaked in an acidic solution for 30-60 minutes at a temperature of 40-60°C, and the pH value during the soaking process is controlled to be 2.5-4.0; then the bamboo particles are rinsed with an alkaline solution to neutralize the solution to neutral.

[0017] In a preferred embodiment of the present invention, in step S4, the bamboo particles are subjected to high-temperature treatment using a reaction vessel, including the following steps:

[0018] S41. Oxidation: Bamboo particles are fed into a reaction vessel, thoroughly mixed with oxygen, and heated to 300-400℃ for 4-6 hours. This allows the cellulose to undergo an oxidation reaction in a high-temperature and oxygen-rich environment, forming oxygen-containing functional groups such as carboxyl and aldehyde groups.

[0019] S42. Cycling: The reactor is heated to 400-500℃ for 2-3 hours to induce cyclization between the generated oxygen-containing functional groups, forming a cyclic structure.

[0020] S43, Dehydrogenation: Heat the reactor to 500-600℃, add a metal oxidant as a catalyst, and continue for 2-4 hours to increase the conjugated system in the molecular chain of bamboo particles.

[0021] S44. Carbonization: The reactor is heated to 600-800℃ for 4-8 hours to carbonize the cellulose molecules of the bamboo particles, forming an ordered trapezoidal structure.

[0022] In a preferred embodiment of the present invention, in step S5, the type of formaldehyde-free adhesive is at least one of MDI adhesive, starch-based formaldehyde-free adhesive, and soybean bio-based formaldehyde-free adhesive.

[0023] In a preferred embodiment of the present invention, in step S5, the moisture content of the mixed adhesive is <12%.

[0024] In a preferred embodiment of the present invention, in step S6, the sheet metal is pressed and formed using a hot press at a temperature of 100-150°C, a pressure of 1.5-2.5 MPa, and a pressing time of 30-50 min.

[0025] In a preferred embodiment of the present invention, in step S6, the surface of the pressed sheet is ground and polished, and then coated with a layer of environmentally friendly varnish.

[0026] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0027] (1) This invention provides a method for manufacturing a formaldehyde-free fire-resistant engineered wood panel. The method uses bamboo as raw material and a specific processing technology to manufacture an engineered wood panel that is both environmentally friendly and fire-resistant. The engineered wood panel has excellent environmental protection and fire resistance properties and is suitable for furniture, construction and other fields. It is of great significance for promoting the green development of the engineered wood panel industry and improving product performance.

[0028] (2) The present invention provides a method for manufacturing a formaldehyde-free fire-resistant engineered wood panel, which uses bamboo as raw material, making full use of the renewable and fast-growing characteristics of bamboo, reducing the dependence on forest resources; at the same time, formaldehyde-free glue is used as an adhesive, avoiding the release of harmful substances such as formaldehyde in traditional engineered wood panels, which meets environmental protection requirements.

[0029] (3) The present invention provides a method for manufacturing a formaldehyde-free fire-resistant engineered wood panel. Through a high-temperature treatment with gradually increasing temperature, the fiber macromolecules in the bamboo particles undergo a series of chemical reactions, ultimately forming a stable multi-conjugated trapezoidal structure, which makes the panel more stable at high temperatures, less prone to combustion, and significantly improves the fire resistance of the engineered wood panel.

[0030] (4) The method for manufacturing formaldehyde-free artificial fire-resistant board disclosed in this invention combines crushing and homogenization treatment with acid and alkali treatment, which improves the fineness of bamboo particles, accelerates the reaction rate, removes excess lignin and some hemicellulose from bamboo particles, thereby further improving the rate and effect of subsequent high-temperature treatment, which is conducive to improving the quality of the product. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart of a preferred embodiment of the present invention; Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0035] like Figure 1 As shown, a method for manufacturing a formaldehyde-free fire-resistant engineered wood panel includes the following steps:

[0036] S1. Raw material selection and processing: Collect the bamboo after preliminary cutting, wherein the length of the bamboo after preliminary cutting is 0.6-1.2m, preferably 0.8-1.0m; then, carry out cleaning and drying treatment, wherein the moisture content of the bamboo is controlled at 6%-10% when drying the bamboo.

[0037] S2. Crushing and Homogenization: The dried bamboo is crushed into granules and homogenized to make the particle size distribution of the bamboo particles more uniform. For the crushing of bamboo, at least one of hammer crusher, shear crusher, and disc crusher is used, preferably shear crusher. For the homogenization of bamboo, a high-pressure homogenizer is used.

[0038] S3. Acid-base pretreatment: The homogenized bamboo particles are subjected to acid-base treatment to reduce the molecular weight of lignin and hemicellulose in the bamboo particles. In the acid-base treatment process, the bamboo particles are first soaked in an acidic solution for 30-60 minutes at a temperature of 40-60℃, and the pH value is controlled at 2.5-4.0 during the soaking process. Then, the bamboo particles are rinsed with an alkaline solution to neutralize the solution to neutral.

[0039] S4. High-temperature treatment: The bamboo particles after acid and alkali pretreatment are subjected to a high-temperature treatment with gradually increasing temperature, so that the fiber macromolecules in the bamboo particles react at high temperature to form a trapezoidal structure of a multi-conjugated system.

[0040] S5. Cooling and Addition of Formaldehyde-Free Adhesive: Cool the bamboo particles after high-temperature treatment to room temperature and add formaldehyde-free adhesive as a binder; wherein, the type of formaldehyde-free adhesive is at least one of MDI adhesive, starch-based formaldehyde-free adhesive, and soybean bio-based formaldehyde-free adhesive, preferably MDI adhesive; wherein, the moisture content of the mixture after mixing the adhesive is <12%.

[0041] S6. Pressing and Post-processing: The bonded bamboo particles are pressed into boards through a pressing process. The pressing of the boards is carried out using a hot press at a temperature of 100-150℃, a pressure of 1.5-2.5MPa, and a pressing time of 30-50min. Necessary finishing and polishing are then performed. After polishing, the surface of the pressed boards is coated with a layer of environmentally friendly varnish.

[0042] In this embodiment, in step S4, the bamboo particles are subjected to high-temperature treatment using a reaction vessel, including the following steps:

[0043] S41. Oxidation: Bamboo particles are fed into a reaction vessel, thoroughly mixed with oxygen, and heated to 300-400℃ for 4-6 hours. This allows the cellulose to undergo an oxidation reaction in a high-temperature and oxygen-rich environment, forming oxygen-containing functional groups such as carboxyl and aldehyde groups.

[0044] S42. Cycling: The reactor is heated to 400-500℃ for 2-3 hours to induce cyclization between the generated oxygen-containing functional groups, forming a cyclic structure.

[0045] S43, Dehydrogenation: Heat the reactor to 500-600℃, add a metal oxidant as a catalyst, and continue for 2-4 hours to increase the conjugated system in the molecular chain of bamboo particles.

[0046] S44. Carbonization: The reactor is heated to 600-800℃ for 4-8 hours to carbonize the cellulose molecules of the bamboo particles, forming an ordered trapezoidal structure.

[0047] In steps S1 and S2, the present invention selects bamboo as the raw material for the board. First, bamboo is collected, preferably fresh bamboo strips, because the fibers in fresh bamboo strips have not been damaged by long-term drying and aging, maintaining the original high fiber quality of bamboo. Therefore, its strength and toughness are better than that of aged dried bamboo. In addition, the moderate moisture content makes it easier to cut, crush and shape during processing, making it a good material. Then, the bamboo is initially divided. The purpose of this step is to cut the bamboo into bamboo strips of similar size to facilitate subsequent crushing and processing.

[0048] In steps S1 and S2, before crushing the bamboo strips, the present invention also cleans them to remove surface impurities; then, they are dried, preferably by microwave drying, which is characterized by high efficiency and uniform heating during drying and curing, ensuring that every part of the bamboo reaches the same temperature and degree of dryness; during the drying process, the bamboo needs to be turned over constantly to help remove moisture, thereby controlling the moisture content of the bamboo at 6%-10%, preferably 8%, which helps to accelerate the efficiency of subsequent high-temperature treatment; then, the bamboo is crushed into uniformly distributed bamboo particles by a shear crusher and a high-pressure homogenizer, which increases the contact area of ​​the reactants for a series of subsequent chemical reactions.

[0049] In step S3, bamboo contains not only cellulose but also lignin and hemicellulose. These components differ in chemical composition, fiber morphology, and crystallinity. To avoid these components causing different reaction rates, product structures, and performance changes in various parts of the bamboo during thermochemical treatment, resulting in poor final stability, it is necessary to pre-treat the bamboo. Step S3 preferably uses acid-base treatment. Acid and base treatment can change the chemical structure of each component in the bamboo, such as removing some lignin and reducing the molecular weight of hemicellulose, so that these components have more similar reactivity in subsequent thermochemical treatment.

[0050] In step S4, when the fiber macromolecules in bamboo are subjected to high temperatures, a series of chemical reactions occur, including oxidation, cyclization, dehydrogenation, and carbonization. These reactions lead to significant changes in the structure of the fiber macromolecules, ultimately forming a special multi-conjugated ladder structure. Specifically, the multi-conjugated ladder structure refers to a stable structure formed by multiple conjugated systems (i.e., systems containing alternating single and double bonds) connected to each other. In this structure, the fiber macromolecules form a ladder-shaped main chain structure through reactions such as oxidation and cyclization, which contains a large number of conjugated double bonds. The presence of these conjugated double bonds makes the entire structure very stable and can effectively resist the erosion of high temperatures and oxidation.

[0051] The trapezoidal structure formed in step S4 is characterized by high thermal and chemical stability, and can maintain structural integrity at high temperatures. Therefore, when fiber macromolecules undergo reactions such as oxidation, cyclization, dehydrogenation and carbonization, the trapezoidal structure of the multi-conjugated system formed can significantly improve the fire resistance of the engineered wood panel.

[0052] The reactor in step S4 is preferably a stainless steel reactor, which has good high temperature resistance and corrosion resistance; the metal oxidant in the dehydrogenation reaction is preferably alumina.

[0053] In step S5, the bamboo particles with the trapezoidal structure that have formed a multi-conjugated system are cooled to room temperature, and then formaldehyde-free adhesive is added. The formaldehyde-free adhesive is preferably MDI adhesive, that is, isocyanate adhesive, which not only has excellent bonding performance, quickly and effectively bonding the bamboo particles together firmly, providing excellent bonding effect, ensuring the structural strength and stability of the product, but also has no formaldehyde, low volatility, and excellent environmental performance.

[0054] In step S6, bamboo granules and formaldehyde-free adhesive are added to the mold together and pressed into shape using a hot press. This not only tightly presses the bamboo granules into a board, but also accelerates the curing of the formaldehyde-free adhesive by relying on high temperature, which helps to improve production efficiency.

[0055] In step S6, polishing is required to improve the smoothness and aesthetics of the cured board surface. Mechanical methods, such as grinding or polishing machines, are preferred for polishing. After polishing, an environmentally friendly varnish is applied to protect the board surface and improve its durability. This varnish has multiple functions, including high adhesion, waterproofing, dustproofing, corrosion resistance, and slip resistance. It is also formaldehyde-free and environmentally friendly, posing no harm to human health or the environment.

[0056] Example 1

[0057] Step 1: Collect the pre-cut bamboo, which should be 0.8-1.0m in length. Then, clean and dry the bamboo, controlling the moisture content to 8%.

[0058] Step 2, Crushing and Homogenization: Using a shear crusher and a high-pressure homogenizer, the bamboo is crushed into bamboo particles with a diameter of 18mm and then homogenized.

[0059] Step 3, acid-base pretreatment: Soak the bamboo particles in a 0.1 mol / L dilute sulfuric acid solution for 45 minutes at a temperature of 55℃, and control the pH value to 3.0 during the soaking process; then rinse the bamboo particles with a 0.1 mol / L NaOH solution to neutralize the entire solution to neutral.

[0060] Step 4, High-temperature treatment: The bamboo particles after acid and alkali pretreatment are subjected to a high-temperature treatment with gradually increasing temperature, so that the fiber macromolecules in the bamboo particles react at high temperature to form a ladder structure of multiple conjugated system.

[0061] Specifically, bamboo particles are first fed into a reactor and thoroughly mixed with oxygen, then heated to 350°C for 5 hours; the reactor is then heated to 450°C for 2 hours; the reactor is then heated to 500°C, alumina is added as a catalyst, and the process is repeated for 2 hours; finally, the reactor is heated to 800°C for 6 hours.

[0062] Step 5, Cooling and Adding Formaldehyde-Free Adhesive: Cool the bamboo particles after high-temperature treatment to room temperature and add MDI adhesive as a binder; control the moisture content of the mixture after mixing the adhesive to 10.8%.

[0063] Step 6, Pressing and Post-processing: Use a hot press to press the bonded bamboo particles into a board at a temperature of 130℃, a pressure of 2.0MPa, and a hot pressing time of 45min, to prepare a sample with a size of 2000*1000*8mm.

[0064] Example 2

[0065] Based on Example 1, the difference in the preparation process is that: in step 1, the moisture content of the bamboo is controlled at 8%; in step 3, the bamboo is acid-soaked for 45 minutes at a temperature of 55°C and a pH value of 2.5.

[0066] Example 3

[0067] Based on Example 1, the difference in the preparation process is that: in step 1, the moisture content of the bamboo is controlled at 8%; in step 3, the bamboo is acid-soaked for 45 minutes at a temperature of 55°C and a pH value of 4.0.

[0068] Comparative Example 1

[0069] Based on Example 1, the difference in the preparation process is that: before the bamboo particles are crushed and homogenized, they are not dried, and then no acid or alkali treatment is performed. Instead, they are directly subjected to high-temperature treatment and pressed to obtain a sample.

[0070] Comparative Example 2

[0071] Based on Example 1, the difference in the preparation process is that the acid-base treatment in step 3 and the high-temperature treatment in step 4 are not performed. After the bamboo is cleaned, dried and crushed, it is directly pressed to obtain the sample.

[0072] The samples prepared in the above embodiments and comparative examples were sampled and tested, and the results of their fire resistance test are shown in Table 1.

[0073]

[0074]

[0075] Table 1. Fire resistance test results of bamboo samples

[0076] Based on the GB / T 17657-1999 standard, as can be seen from Table 1, Examples 1, 2 and 3 all meet the requirements of Class A non-combustible materials, while Comparative Example 1, which has not undergone acid and alkali treatment, belongs to Class B flame-retardant materials, and Comparative Example 2, which has not undergone high-temperature treatment, belongs to Class C combustible materials.

[0077] It is worth noting that the pH values ​​used for acid and alkali treatment differed in Examples 1, 2, and 3. The fire resistance of the engineered wood product was best when the pH value was 3.0. However, the fire resistance decreased when the pH value was too high or too low. This is because a pH value that is too low will cause excessive decomposition of bamboo fibers, destroying their original structural integrity, while a pH value that is too high will not effectively remove impurities or activate the fiber surface. Both of these situations will result in a loose structure of the board and reduce its fire resistance. Based on the planning and solving method, the optimal pH value for acid and alkali treatment was predicted to be 3.0.

[0078] Therefore, it can be concluded that the method for manufacturing formaldehyde-free fire-resistant engineered wood panels provided by the present invention can significantly improve the fire resistance of engineered wood panels through high-temperature treatment with gradual heating; and the crushing homogenization and acid-alkali treatment in the present invention can further improve the fire resistance of engineered wood panels.

[0079] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for manufacturing a formaldehyde-free fire resistant wood-based panel, characterized in that, The method comprises the following steps: S1, raw material selection and processing: collecting the preliminarily cut bamboo, and performing cleaning and drying treatment; S2, crushing and homogenization: crushing the dried bamboo into granules, and performing homogenization treatment to make the particle size distribution of the bamboo granules more uniform; S3, acid-base pretreatment: performing acid-base treatment on the homogenized bamboo granules to reduce the molecular weight of lignin and hemicellulose in the bamboo granules; during the acid-base treatment of the bamboo granules, the bamboo granules are first soaked in an acidic solution for 30-60 min at a temperature of 40-60℃, and the PH value during the soaking process is controlled to be 2.5-4.0; then the bamboo granules are washed with an alkaline solution, and the solution is neutralized to neutral; S4, high-temperature treatment: performing high-temperature treatment on the bamboo granules after acid-base pretreatment by gradually increasing the temperature, so that the fiber macromolecules in the bamboo granules react at high temperature to form a ladder structure of a multi-conjugated system; using a reaction kettle to perform high-temperature treatment on the bamboo granules, comprising the following steps: S41, oxidation: sending the bamboo granules into the reaction kettle, fully mixing with oxygen, heating to 300-400℃, and maintaining for 4-6h, so that the cellulose reacts in the high-temperature and oxygen environment to form oxygen-containing functional groups such as carboxyl and aldehyde groups; S42, cyclization: increasing the temperature of the reaction kettle to 400-500℃, and maintaining for 2-3h, so that the generated oxygen-containing functional groups react to form a ring structure; S43, dehydrogenation: increasing the temperature of the reaction kettle to 500-600℃, adding a metal oxidant as a catalyst, and maintaining for 2-4h, so that the conjugated system in the molecular chain of the bamboo granules is increased; S44, carbonization: increasing the temperature of the reaction kettle to 600-800℃, and maintaining for 4-8h, so that the cellulose molecules of the bamboo granules are carbonized to form an ordered ladder structure; S5, cooling and formaldehyde-free glue addition: cooling the bamboo granules after high-temperature treatment to room temperature, and adding formaldehyde-free glue as an adhesive; S6, pressing and post-processing: pressing the bonded bamboo granules into a board through a pressing process, and performing trimming and polishing.

2. A method of manufacturing a formaldehyde-free fire resistant wood-based panel according to claim 1, characterized in that: In the S1, the length of the preliminarily cut bamboo is 0.6-1.2m.

3. A method of manufacturing a formaldehyde-free fire resistant wood-based panel according to claim 1, characterized in that: In the S1, when the bamboo is subjected to drying treatment, the moisture content of the bamboo is controlled to be 6%-10%.

4. The method of claim 1, wherein: In the S2, for the crushing treatment of the bamboo, at least one of a hammer crusher, a shearing crusher, and a disc crusher is used; for the homogenization treatment of the bamboo, a high-pressure homogenizer is used.

5. The method of claim 1, wherein: In the S5, the type of the formaldehyde-free glue is at least one of MDI glue, starch-based formaldehyde-free glue, and soybean bio-based formaldehyde-free glue.

6. The method of claim 1, wherein: In the S5, the moisture content of the mixture after mixing the adhesive is <12%.

7. The method of claim 1, wherein: In the S6, the pressing of the board is performed using a hot press at a temperature of 100-150℃, a pressure of 1.5-2.5MPa, and a hot pressing time of 30-50min.

8. The method of claim 1, wherein: In the S6, after polishing and polishing the surface of the pressed board, a layer of environmentally friendly varnish is brushed.

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