A rigid-flexible controllable high-strength formaldehyde-free artificial board and a preparation method thereof

Abstract

The present application relates to a kind of rigid-flexible controllable high-strength formaldehyde-free artificial board and its preparation method, belong to artificial board manufacturing field and timber processing field.The artificial board includes plant short fiber, polymer long fiber and adhesive, adhesive is applied on the surface of plant short fiber;Semi-interlocking physical entanglement three-dimensional grid is constructed using plant short fiber and polymer long fiber, high-strength formaldehyde-free artificial board is prepared by high-temperature thermal plasticization and low-temperature cooling setting.Preparation method includes (1) high-speed airflow depolymerization fiber bundle process, (2) semi-interlocking physical entanglement three-dimensional grid construction process and (3) continuous segmented forming process.When the thickness of artificial board is ≤3mm, the board has flexibility, and when the thickness of artificial board is ≥3mm, the board has rigidity.The present application breaks through the problem of rigidity of traditional artificial board, and is conducive to promoting the application of artificial board in the field of curved surface in decoration.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of rigid and flexible controllable high-strength formaldehyde-free artificial board and its preparation method, a new type of rigid and flexible controllable, high mechanical property, formaldehyde-free artificial board is prepared, specifically relates to the preparation method for using plant fiber and polymer fiber to construct semi-interlocking physical entanglement grid, and then hot-pressing preparation environment-friendly formaldehyde-free artificial board, belongs to the field of artificial board manufacturing and wood processing field. BACKGROUND

[0002] Formaldehyde-free board refers to the board made by applying "formaldehyde-free adhesive or not applying adhesive" and not adding other additives containing formaldehyde components in the production process of board. Formaldehyde-free artificial board has great market potential in indoor decoration, furniture and custom home. The formaldehyde-free adhesive on the market includes polyurethane, soy protein, plant starch, polyvinyl acetate and polyacrylate. However, the market share of formaldehyde-free fiber is not high.

[0003] The main factors restricting the production of formaldehyde-free artificial board are as follows: first, the price problem. Formaldehyde-free adhesive is more expensive than traditional formaldehyde adhesive, and the hot-pressing factor of formaldehyde-free adhesive production is small or the production efficiency is reduced, so the price of formaldehyde-free product is naturally higher than that of formaldehyde-containing product. Second, the production process problem. The performance of formaldehyde-free adhesive is different from that of traditional urea-formaldehyde resin adhesive and phenol-formaldehyde resin adhesive, so the production of formaldehyde-free board means to reform the equipment, and there are many difficulties in the production technology, so there are not many manufacturers who have mastered mature formaldehyde-free manufacturing technology. Based on the above reasons, the artificial board industry urgently needs to develop new preparation process to solve the manufacturing problem of formaldehyde-free board.

[0004] In addition, the current artificial board products (including fiberboard, particle board, plywood, blockboard, etc.) are mainly concentrated in flat plate applications and cannot be applied to curved surface field, which seriously mismatches the current personalized decoration market. Thermoplastic resin adhesive is a kind of adhesive made of thermoplastic resin. Its mechanism is to soften and melt when heated, and to harden and have certain strength after cooling to achieve the purpose of bonding. It has the characteristics of environmental protection and formaldehyde-free, and also has certain flexibility, which is very suitable for developing rigid and flexible controllable formaldehyde-free artificial board.

[0005] Therefore, it is of great significance to develop rigid and flexible controllable artificial board to improve the market share of this type of board. SUMMARY

[0006] Therefore, in order to solve the problems of formaldehyde-free artificial board adhesive and the flexibility of artificial board, expand the market share of artificial board and improve the added value of artificial board, the present application provides a kind of rigid and flexible controllable high-strength formaldehyde-free artificial board and its preparation method.

[0007] The present invention adopts the following technical solution:

[0008] A high-strength, formaldehyde-free engineered wood product with controllable rigidity and flexibility comprises short plant fibers, long polymer fibers, and an adhesive. The short plant fibers are a mixture of one or more plant fibers selected from wood fiber, bamboo fiber, and hemp fiber, with a fiber length of less than 0.5 mm. The long polymer fibers are a mixture of one or more polymer fibers selected from polyethylene fiber, polypropylene fiber, polyurethane fiber, and polyamide fiber, with a fiber length of 2-10 mm. The adhesive is a mixture of one or more of urea-formaldehyde resin, melamine resin, phenolic resin, isocyanate, epoxy resin, ethylene-vinyl acetate, and vinyl acetate resin. The adhesive is applied to the surface of the short plant fibers at a dosage of ≥0% and ≤15 wt.%. A semi-interlocking, physically entangled three-dimensional mesh is constructed using the short plant fibers and long polymer fibers, and the high-strength, formaldehyde-free engineered wood product is prepared through high-temperature thermoplasticization and low-temperature cooling and shaping.

[0009] The plant short fibers have a moisture content of less than 15 wt.%, and the fiber length is preferably 0.1-0.4 mm, and the fiber diameter is 50-200 μm.

[0010] The amount of adhesive applied to the plant short fibers is 0.1 wt.%-15 wt.%, preferably 1 wt.%-15 wt.%, and more preferably 5 wt.%-12 wt.%.

[0011] The length of the polymer slender fibers is preferably 3-8 mm, most preferably 5-6 mm, and the diameter of the fibers is 5-50 μm, preferably 10-50 μm.

[0012] The plant short fibers account for more than 30% of the total mass of all fibers, preferably 80%-40%, and most preferably 75%-60%.

[0013] A method for preparing a high-strength, formaldehyde-free engineered wood product with controllable rigidity and flexibility includes the following steps:

[0014] (1) High-speed airflow depolymerization fiber bundle process: High-speed airflow is used to disperse the bundled plant short fibers and polymer long fibers, so that they remain loose and suspended in the air, thereby eliminating the fiber agglomeration phenomenon. Then, the two dispersed fibers are stirred and mixed evenly by comb-shaped roller rotation technology. An adhesive is applied to the surface of the plant short fibers, and the amount of adhesive is greater than or equal to 0% and less than or equal to 15 wt.%.

[0015] (2) Construction of a semi-interlocked physical entanglement three-dimensional grid: Using negative pressure sedimentation technology, the two mixed fibers floating in the air are settled down to form a loose grid; at this time, the slender polymer fibers run through the entire grid to form a physically entangled three-dimensional grid, locking the short plant fibers in the grid pores to form a semi-interlocked state.

[0016] (3) Continuous segmented molding process: The loose mesh is fed into a continuous hot-press-cold-press integrated equipment, and high-strength artificial board is prepared by high-temperature thermoplasticization and low-temperature cooling and shaping.

[0017] In step (1), the high-speed airflow refers to an airflow speed of 20L / min-500L / min, preferably 20L / min-200L / min, and most preferably 30L / min-150L / min.

[0018] The plant short fibers are a mixture of one or more plant fibers selected from wood fiber, bamboo fiber and hemp fiber. The moisture content of the plant fibers is less than 15 wt.%, and the length of the fibers is less than 0.5 mm, preferably 0.1-0.4 mm, and the diameter of the fibers is 50-200 μm.

[0019] The plant fibers are coated with an adhesive, which can be one or a mixture of two or more of urea-formaldehyde resin, melamine resin, phenolic resin, isocyanate, epoxy resin, ethylene-vinyl acetate, and vinyl acetate resin in any proportion. The amount of adhesive applied to the plant fibers is 0.1 wt.%-15 wt.%, preferably 1 wt.%-15 wt.%, and more preferably 5 wt.%-12 wt.%.

[0020] The polymer slender fibers are one or a mixture of two or more polymer fibers such as polyethylene fibers, polypropylene fibers, polyurethane fibers and polyamide fibers, and the length of the fibers is 2-10 mm, preferably 3-8 mm, most preferably 5-6 mm, and the diameter of the fibers is 5-50 μm, preferably 10-50 μm.

[0021] Of the two fibers, plant fiber accounts for more than 30% of the total mass of the two fibers, preferably 80%-40%, and most preferably 75%-60%.

[0022] The aforementioned de-agglomeration of fibers refers to using high-speed airflow to dissolve the electrostatic forces between fibers, allowing the fibers to disperse evenly and float in the air.

[0023] Furthermore, before use, the plant fibers need to be softened by an alkaline solution. The alkaline solution is one or a mixture of two or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide solutions. The concentration (mass fraction) of the alkaline solution is 5-15%, preferably 5-10%, and more preferably 8%. The treatment temperature is 30-80℃, preferably 40-60℃. The treatment time is 1-5 hours, preferably 2-4 hours.

[0024] In step (2), the negative pressure settling refers to using an air extraction method to draw the two uniformly mixed fibers from the air onto the porous mesh plate. The air extraction speed is 1L / min-50L / min, and the preferred air extraction speed is 5L / min-15L / min.

[0025] The aforementioned semi-interlocking physical entanglement three-dimensional mesh refers to the polymer slender fibers intertwined with each other without undergoing a chemical reaction, forming a network structure; while the plant slender short fibers are locked in the mesh pores in the form of fillers, and cannot intertwine with each other, thus forming a semi-interlocking structure.

[0026] In step (3), the continuous (segmented) hot-press-cold-press integrated equipment refers to the hot-press equipment where the first half is a high-temperature stage and the second half is a low-temperature stage; the high temperature refers to a temperature between 100-250℃, a pressure of 1-5MPa, and a hot-pressing time of 0.5-20 minutes; the low temperature refers to a temperature between room temperature (25℃) and 80℃, a pressure of 10-15MPa, and a cold-pressing time of 0.5-10 minutes.

[0027] When the polymer fiber is polyurethane fiber, the preferred temperature is 120-170℃; when the polymer fiber is polypropylene fiber, polyethylene fiber, or polyamide fiber, the preferred temperature is 150-250℃; regardless of the type of polymer fiber used, the preferred low temperature is room temperature - 60℃, and the most preferred temperature is room temperature - 30℃.

[0028] The resulting engineered wood product exhibits controllable rigidity and flexibility. When the thickness of the engineered wood product is ≤3mm, it exhibits flexibility; when the thickness is ≥3mm, it exhibits rigidity.

[0029] The beneficial effects of this invention are:

[0030] (1) This invention discloses a method for manufacturing a high-strength engineered wood panel with controllable rigidity and flexibility. It proposes for the first time a combination of high-speed airflow depolymerization and negative pressure settling technology to create a semi-interlocking, physically entangled three-dimensional mesh of polymer fibers and plant fibers. After hot pressing, the mesh is cured by cooling with thermoplastic resin to achieve an adhesive effect, thus enabling the use of thermoplastic resin as an adhesive in the preparation of engineered wood panels. When manufacturing flexible panels, an alkaline solution can also be used for treatment, which can soften the plant fibers and further facilitate the control of the panel's flexibility.

[0031] (2) Polymer fibers are used as adhesives, and the adhesive can be applied during the fiber blending and laying process without the need for a special subsequent adhesive application process. The operation is simple, the process is simple, and the cost is low. In addition, this type of adhesive also has formaldehyde-free and environmentally friendly characteristics.

[0032] (3) Based on the difference in the flexibility of polymer fibers, fibers with different hardness can be selected or the two can be mixed in different proportions and then blended with plant fibers to prepare a semi-interlocked physical entangled grid. After hot pressing, the rigidity and flexibility can be controlled, which breaks through the problem of rigidity of traditional artificial boards and is beneficial to the application of curved surfaces of artificial boards.

[0033] (4) This invention fiberizes polymers and then blends them with plant fibers to prepare a semi-interlocked physical entanglement three-dimensional mesh, thereby realizing the preparation of high-content plant fiber boards and overcoming the problem that high-content plant fibers and polymer resins cannot be blended to prepare new materials. Attached Figure Description

[0034] Figure 1-1 and Figure 1-2 This is a schematic diagram of the artificial board in Embodiment 1 of the present invention;

[0035] Figure 2 This is a schematic diagram of the artificial board in Embodiment 2 of the present invention;

[0036] Figure 3 This is a schematic diagram of the artificial board in Embodiment 3 of the present invention;

[0037] Figure 4 This is a schematic diagram of the artificial board in Embodiment 4 of the present invention;

[0038] Figure 5 This is a schematic diagram of the artificial board in Embodiment 5 of the present invention. Detailed Implementation

[0039] The principles and specific steps of the present invention will be described in detail and completely below with reference to embodiments of the present invention. However, the described embodiments are only a part of the present invention, not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention, through simple repetition without creative effort, are within the scope of protection of the present invention.

[0040] A high-strength, formaldehyde-free engineered wood product with controllable rigidity and flexibility is made from raw materials such as plant short fibers, polymer long fibers, and adhesives. The adhesive is applied to the surface of the plant short fibers, and a semi-interlocking physical entanglement three-dimensional mesh is constructed using plant short fibers and polymer long fibers. The high-strength, formaldehyde-free engineered wood product is prepared by high-temperature thermoplasticization and low-temperature cooling and shaping.

[0041] The method for preparing a high-strength engineered wood panel with controllable rigidity and flexibility according to the present invention includes the following steps:

[0042] (1) High-speed airflow depolymerization fiber bundle process: High-speed airflow is used to disperse the bundled plant short fibers and polymer long fibers, so that they remain loose and suspended in the air, thereby eliminating the fiber agglomeration phenomenon. Then, the two dispersed fibers are stirred and mixed evenly by the comb-shaped roller rotation technology. Adhesive can be applied to the surface of the plant short fibers as needed, and the amount of adhesive applied is greater than or equal to 0% and less than or equal to 15%.

[0043] The aforementioned short plant fibers are one or a mixture of several plant fibers selected from wood fiber, bamboo fiber, and hemp fiber. The moisture content of the plant fibers is below 15 wt.%, and the fiber length is less than 0.5 mm, preferably 0.1-0.4 mm. The diameter of the short plant fibers is 50-200 μm. An adhesive is applied to the plant fibers; the adhesive can be one or a mixture of urea-formaldehyde resin, melamine resin, phenolic resin, isocyanate, epoxy resin, ethylene-vinyl acetate, and vinyl acetate resin.

[0044] The polymer slender fibers are one or a mixture of several polymer fibers such as polyethylene fiber, polypropylene fiber, polyurethane fiber, and polyamide fiber, and the fiber length is 2-10 mm, preferably 3-8 mm, and most preferably 5-6 mm. The diameter of the polymer slender fibers is 5-50 μm, preferably 5-40 μm.

[0045] Of the two fibers, plant fiber accounts for ≥30% of the total mass fraction of the two fibers, preferably ≥80% and ≥40% of the total mass fraction of the two fibers, and most preferably ≥75% and ≥60% of the total mass fraction of the two fibers.

[0046] Furthermore, the flexible board material and plant fibers also need to be softened by an alkaline solution. The alkaline solution refers to one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide, with a mass fraction of 5-15% and a concentration of 5-10%, more preferably 8%. The treatment temperature is 30-80℃, preferably 40-60℃, and the treatment time is 1-5 hours, preferably 2-4 hours.

[0047] High-speed airflow refers to airflow speeds of 20L / min to 500L / min, preferably 20L / min to 200L / min, and most preferably 30L / min to 150L / min.

[0048] The aforementioned de-agglomeration of fibers refers to using high-speed airflow to dissolve the electrostatic forces between fibers, allowing the fibers to disperse evenly and float in the air. The high-speed airflow eliminates electrostatic forces, van der Waals forces, and intermolecular forces, thus separating the fibers.

[0049] (2) Construction of a semi-interlocked physically entangled three-dimensional mesh: Using negative pressure sedimentation technology, the two kinds of mixed fibers floating in the air are settled to form a loose mesh. At this time, the slender polymer fibers run through the entire mesh to form a physically entangled three-dimensional mesh, locking the short plant fibers in the mesh pores to form a semi-interlocked state.

[0050] The negative pressure settling refers to using an air extraction method to draw the two uniformly mixed fibers from the air onto a porous mesh plate. The air extraction speed is 1L / min-50L / min, and the preferred air extraction speed is 5L / min-15L / min.

[0051] The semi-interlocked physical entanglement mesh refers to the polymer long fibers entangled with each other without undergoing a chemical reaction, forming a network structure; while the plant short fibers are locked in the mesh pores in the form of fillers, and cannot entangle with each other, thus forming a semi-interlocked structure.

[0052] Physically entangled interlocking meshes, utilizing a dual programming strategy of orthogonal supramolecular heterogeneous networks, can achieve permanent shape control of materials during gradual deformation, thereby enabling complex shape changes with higher degrees of freedom. The fabrication of flexible fiberboards based on meshes and strategies results in dual-network entanglement.

[0053] (3) Continuous segmented molding process: segmented hot pressing method: thermoplasticization and cooling molding. Loose mesh is fed into a continuous hot-press-cold-press integrated equipment, and high-strength artificial board is prepared by high-temperature thermoplasticization and low-temperature cooling molding.

[0054] A continuous segmented hot pressing equipment refers to a hot pressing equipment where the first half is a high-temperature stage and the second half is a low-temperature stage. The high-temperature stage is defined as a temperature between 100-250℃. When the polymer fiber is polyurethane fiber, the preferred temperature is 120-170℃, and the hot pressing time is 0.5-20 minutes. When the polymer fiber is polypropylene fiber, polyethylene fiber, or polyamide fiber, the preferred temperature is 150-250℃, and the hot pressing time is 0.5-20 minutes. The low-temperature stage is defined as a temperature between room temperature and 80℃. Regardless of the type of polymer fiber used, the preferred low-temperature stage is room temperature -60℃, and the most preferred is room temperature -30℃, with a cold pressing time of 0.5-10 minutes.

[0055] Polymer fibers are fibers made from flexible resins such as polyurethane, which gives the engineered wood panels flexibility. Polymer fibers used are fibers made from rigid resins such as polypropylene and polyethylene. When the thickness of the engineered wood panel is ≤3mm, the panel is flexible; when the thickness of the engineered wood panel is ≥3mm, the panel is rigid, thus achieving a controllable stiffness and flexibility.

[0056] Example 1

[0057] Poplar fiber and polypropylene fiber were selected as raw materials. The length of the poplar fiber was less than 0.5 mm and the diameter of the poplar fiber was 80-120 μm. A phenolic resin adhesive was applied to the surface of the poplar fiber with an application rate of 5 wt.%. The polypropylene fiber was 5 mm in size and had a diameter of 35-45 μm.

[0058] The mass ratio of poplar fiber to polypropylene fiber is 70:30. A high-speed airflow (50 L / min) disperses the clumps of short, fine poplar fibers and long, fine polypropylene fibers, keeping them loose and suspended in the air. A comb-shaped rotating paddle is used to stir and mix the two types of fibers evenly. The mixed material is then fed into a negative pressure press, where negative pressure settling technology helps the two types of fibers float in the air to settle. The air extraction speed is 10 L / min, forming a semi-interlocking physically entangled mesh. Finally, the loose mesh is conveyed to a hot-press-cold-press integrated equipment, where it is thermoplasticized in a high-temperature press at 170°C (1 MPa) for 3 minutes. The plasticized slab is then fed into a low-pressure press at room temperature (25°C) and 11 MPa for 3 minutes. After cooling and shaping, the slab is 3 mm thick and relatively hard, yielding a product as shown in the image. Figure 1-1 and Figure 1-2 The high-rigidity, high-strength engineered wood panel shown is an example.

[0059] Example 2

[0060] Poplar fiber and polypropylene fiber were selected as raw materials. The poplar fiber size was less than 0.5 mm, and the diameter was 140-160 μm. The poplar fiber was soaked in an 8% sodium hydroxide solution for 3 hours at 80℃, and then dried. A urea-formaldehyde resin adhesive was applied to the surface of the poplar fiber at a dosage of 5 wt.%. The polypropylene fiber size was 5 mm, and the diameter was 25-35 μm.

[0061] Poplar fiber and polypropylene fiber were mixed in a 70:30 mass ratio. A high-speed airflow (100 L / min) dispersed the clumps of short, fine wood fibers and long, fine polypropylene fibers, keeping them loose and suspended in the air. A comb-like rotating paddle was used to stir and mix the two types of fibers evenly. The mixture was then fed into a negative pressure press, where negative pressure settling technology was used to settle the two types of fibers floating in the air. The air extraction speed was 5 L / min, forming a semi-interlocked physical entanglement mesh. Finally, the loose mesh was conveyed to a hot-press-cold-press integrated equipment. It was thermoplasticized in a high-temperature press at 170°C with a pressure of 1 MPa for 3 minutes. The plasticized board was then fed into a low-temperature press at room temperature (25°C) with a pressure of 11 MPa for 3 minutes. After cooling and shaping, the thickness of the engineered wood board was 1 mm. The board was relatively soft, resulting in a product as shown in the image. Figure 2 The example shown is a flexible, high-strength engineered wood panel.

[0062] Example 3

[0063] Poplar fiber and polyurethane fiber were selected as raw materials. The poplar fiber size was less than 0.5 mm, and the diameter was 50-60 μm. The poplar fiber was soaked in a 5% sodium hydroxide solution for 3 hours at 80℃, and then dried. An isocyanate adhesive was applied to the surface of the poplar fiber at a dosage of 6 wt.%. The polyurethane fiber size was 6 mm, and the diameter was 30-40 μm.

[0064] The mass ratio of poplar fiber to polyurethane fiber is 70:30. A high-speed airflow (100 L / min) disperses the clumps of short, fine wood fibers and long, fine polyurethane fibers, keeping them loose and suspended in the air. A comb-shaped rotating paddle is used to stir and mix the two types of fibers evenly. The mixed material is then fed into a negative pressure press, where negative pressure settling technology helps the two types of fibers float in the air to settle. The air extraction speed is 20 L / min, forming a semi-interlocked physical entangled mesh. Finally, the loose mesh is conveyed to a hot-press-cold-press integrated equipment. It is thermoplasticized in a high-temperature press at 120°C with a pressure of 1 MPa for 3 minutes. The plasticized board is then fed into a low-temperature press at room temperature (25°C) with a pressure of 11 MPa for 2 minutes. After cooling and shaping, the thickness of the engineered wood board is 2 mm. The board is relatively soft, resulting in a product as shown in the image. Figure 3 The example shown is a flexible, high-strength engineered wood panel.

[0065] Example 4

[0066] Poplar fiber and polyurethane fiber were selected as raw materials. The poplar fiber size was less than 0.5 mm, and the diameter was 110-130 μm. The poplar fiber was soaked in a 5% sodium hydroxide solution for 1 hour at 50℃, and then dried. An isocyanate adhesive was applied to the surface of the poplar fiber at a dosage of 5%. The polyurethane fiber size was 6 mm, and the diameter was 35-45 μm.

[0067] The mass ratio of sizing poplar wood fiber to polyurethane fiber is 70:30. A high-speed airflow (100 L / min) disperses the clumps of short wood fibers and long polyurethane fibers, keeping them loose and suspended in the air. A comb-shaped rotating paddle is used to stir and mix the two types of fibers evenly. The mixed material is then fed into a negative pressure press, where negative pressure settling technology settles the two types of mixed fibers floating in the air. The air extraction speed is 40 L / min, forming a semi-interlocked physical entanglement mesh. Finally, the loose mesh is conveyed to a hot-press-cold-press integrated equipment. It is thermoplasticized in a high-temperature press at 120°C with a pressure of 1 MPa for 3 minutes. The plasticized board is then fed into a low-pressure press at room temperature (25°C) with a pressure of 11 MPa for 2 minutes. After cooling and shaping, the thickness of the engineered wood board is 5 mm. The board is relatively soft, resulting in a product as shown in the image. Figure 4 The example shown is a flexible, high-strength engineered wood panel.

[0068] Example 5

[0069] Bamboo fiber and polyethylene fiber were selected as raw materials. The size of the bamboo fiber was less than 0.5 mm, and the diameter of the bamboo fiber was 110-130 μm. The size of the polyethylene fiber was 8 mm, and the diameter of the polyethylene fiber was 25-35 μm.

[0070] A 10% urea-formaldehyde resin is applied to the surface of bamboo fiber. The mass ratio of the sizing bamboo fiber to polyethylene fiber is 60:40. A high-speed airflow (100 L / min) disperses the clumps of short bamboo fiber and long polyethylene fiber, keeping them loose and suspended in the air. A comb-shaped rotating paddle is used to stir and mix the two types of fibers evenly. The mixed material is then fed into a negative pressure press, where negative pressure settling technology settles the two types of mixed fibers floating in the air. The air extraction speed is 35 L / min, forming a semi-interlocking physical entanglement mesh. Finally, the loose mesh is conveyed to a hot-press-cold-press integrated equipment. It is thermoplasticized in a high-temperature press at 140℃, with a press pressure of 1 MPa and a hot-pressing time of 3 minutes. The plasticized board is then fed into a low-pressure press at room temperature (25℃), with a press pressure of 11 MPa and a cold-pressing time of 1 minute. After cooling and shaping, the thickness of the artificial board is 3 mm, and the board texture is hard.Figure 5 The rigid, high-strength engineered wood panel shown is an example.

[0071] To demonstrate the beneficial effects of this invention, the high-strength engineered wood panels obtained in the above embodiments were tested for properties such as bending radius, board thickness, and bending strength. The test results are shown in Table 1. It can be seen that the product of this invention possesses controllable rigidity and flexibility, giving the fiberboard high added value.

[0072] Table 1 Mechanical properties of various composite materials of the present invention compared with traditional formaldehyde-free fiberboard or particleboard

[0073]

[0074]

[0075] This invention utilizes the cooling and curing of polymer resin to achieve bonding, thereby producing high-strength engineered wood panels with controllable rigidity and flexibility. A combination of "high-speed airflow depolymerization" and "negative pressure settling" techniques is employed to create a semi-interlocking, physically entangled three-dimensional mesh from polymer fibers and plant fibers. This three-dimensional mesh is then manufactured into the engineered wood panel through a "continuous segmented molding" process. Depending on the flexibility of the polymer fibers, fibers of varying hardness can be selected, or they can be mixed in different proportions and blended with plant fibers to prepare the semi-interlocking, physically entangled mesh. After hot pressing, controllable rigidity and flexibility can be achieved. If the polymer fibers are made from flexible resins such as polyurethane, the engineered wood panel will have flexibility; if the polymer fibers used are made from rigid resins such as polypropylene and polyethylene, the panel will be flexible when the thickness is ≤3mm, and rigid when the thickness is ≥3mm. This invention overcomes the rigidity problem of traditional engineered wood panels, which is beneficial for promoting the application of engineered wood panels in curved surfaces in decoration and renovation.

Claims

1. A high-strength, formaldehyde-free engineered wood product with controllable rigidity and flexibility, characterized in that: The product comprises short plant fibers, long polymer fibers, and an adhesive. The short plant fibers are one or a mixture of two or more of wood fibers, bamboo fibers, and hemp fibers, and the fiber length is less than 0.5 mm. The long polymer fibers are one or a mixture of two or more of polyethylene fibers, polypropylene fibers, polyurethane fibers, and polyamide fibers, and the fiber length is 2-10 mm. The adhesive is one or a mixture of two or more of urea-formaldehyde resin, melamine resin, phenolic resin, isocyanate, epoxy resin, ethylene-vinyl acetate, and vinyl acetate. The adhesive is applied to the surface of the short plant fibers at a dosage greater than 0% and less than or equal to 15 wt.%. A semi-interlocking, physically entangled three-dimensional mesh is constructed using short plant fibers and long polymer fibers, and a high-strength formaldehyde-free engineered wood panel is prepared by high-temperature thermoplasticization and low-temperature cooling and shaping. The method for preparing the high-strength, formaldehyde-free engineered wood panel with controllable rigidity and flexibility includes the following steps: (1) High-speed airflow depolymerization of fiber bundles: High-speed airflow is used to disperse the bundled plant short fibers and polymer long fibers, keeping them loose and suspended in the air, thereby breaking the fiber agglomeration. Then, the dispersed fibers are stirred and mixed evenly using a comb-shaped roller rotation technique; the airflow velocity of the high-speed airflow is 20L / min-500L / min; an adhesive is applied to the surface of the plant short fibers, with an adhesive application amount greater than 0% and less than or equal to 15wt.%. (2) Construction of a semi-interlocked physical entanglement three-dimensional grid: Using negative pressure sedimentation technology, the two mixed fibers floating in the air are settled down to form a loose grid; at this time, the slender polymer fibers run through the entire grid to form a physically entangled three-dimensional grid, locking the short plant fibers in the grid pores to form a semi-interlocked state. The negative pressure sedimentation method involves using air extraction to draw the two uniformly mixed fibers from the air onto a porous mesh plate at a speed of 1L / min to 50L / min. The semi-interlocking physical entanglement three-dimensional mesh refers to the polymer filaments intertwining with each other without chemical reaction, forming a network structure. Meanwhile, the plant filaments are locked in the mesh pores as fillers, preventing them from intertwining and thus forming a semi-interlocking structure. (3) Continuous segmented molding process: The loose mesh is fed into a continuous hot-press-cold-press integrated equipment, and high-strength artificial board is prepared by high-temperature thermoplasticization and low-temperature cooling and shaping.

2. The high-strength, formaldehyde-free engineered wood panel with controllable rigidity and flexibility according to claim 1, characterized in that: The plant short fibers have a moisture content of less than 15 wt.%, a fiber length of 0.1-0.4 mm, and a fiber diameter of 50-200 μm; the amount of adhesive applied to the plant short fibers is 0.1 wt.%-15 wt.%; the polymer long fibers have a length of 3-8 mm and a fiber diameter of 5-50 μm; the plant short fibers account for more than 30% of the total mass of all fibers.

3. The method for preparing a high-strength, formaldehyde-free engineered wood panel with controllable rigidity and flexibility according to claim 1 or 2, comprising the following steps: (1) High-speed airflow depolymerization of fiber bundles: High-speed airflow is used to disperse the bundled plant short fibers and polymer long fibers, keeping them loose and suspended in the air, thereby breaking the fiber agglomeration. Then, the dispersed two types of fibers are stirred and mixed evenly by a comb-shaped roller rotation technique. An adhesive is applied to the surface of the plant short fibers, with an adhesive amount greater than 0% and less than or equal to 15 wt.%. The plant short fibers are one or a mixture of two or more of wood fibers, bamboo fibers, and hemp fibers, and the fiber length is less than 0.5 mm; the polymer long fibers are one or a mixture of two or more of polyethylene fibers, polypropylene fibers, polyurethane fibers, and polyamide fibers, and the fiber length is 2-10 mm; the adhesive is one or a mixture of two or more of urea-formaldehyde resin, melamine resin, phenolic resin, isocyanate, epoxy resin, ethylene-vinyl acetate, and vinyl acetate. (2) Construction of a semi-interlocked physical entanglement three-dimensional grid: The two mixed fibers floating in the air are settled by using negative pressure sedimentation technology to form a loose grid; at this time, the slender polymer fibers run through the entire grid to form a physical entanglement three-dimensional grid, locking the short plant fibers in the grid pores to form a semi-interlocked state; (3) Continuous segmented molding process: The loose mesh is fed into a continuous hot-press-cold-press integrated equipment, and high-strength artificial board is prepared by high-temperature thermoplasticization and low-temperature cooling and shaping.

4. The method for preparing high-strength formaldehyde-free engineered wood panels with controllable rigidity and flexibility according to claim 3, characterized in that: The airflow velocity of the high-speed airflow is 20L / min to 500L / min.

5. The method for preparing high-strength formaldehyde-free engineered wood panels with controllable rigidity and flexibility according to claim 3, characterized in that: The plant short fibers have a moisture content of less than 15 wt.%, a fiber length of 0.1-0.4 mm, and a fiber diameter of 50-200 μm; the sizing amount of the plant short fibers is 0.1 wt.%-15 wt.%; the polymer long fibers have a length of 3-8 mm and a fiber diameter of 5-50 μm; the plant fibers account for more than 30% of the total mass of the two types of fibers.

6. The method for preparing high-strength formaldehyde-free engineered wood panels with controllable rigidity and flexibility according to claim 5, characterized in that: Before use, the plant fibers are softened by an alkaline solution, which is a mixture of one or more of sodium hydroxide, potassium hydroxide and calcium hydroxide solutions. The concentration of the alkaline solution is 5-15 wt.%, the treatment temperature is 30-80℃, and the treatment time is 1-5 hours.

7. The method for preparing high-strength formaldehyde-free engineered wood panels with controllable rigidity and flexibility according to claim 3, characterized in that: The negative pressure sedimentation is achieved by using air extraction to draw the two uniformly mixed fibers from the air onto a porous mesh plate at a speed of 1L / min to 50L / min. The semi-interlocking physical entanglement three-dimensional mesh refers to the polymer slender fibers intertwining with each other without chemical reaction, forming a network structure. Meanwhile, the plant slender fibers are locked in the mesh pores as fillers, preventing them from intertwining with each other, thus forming a semi-interlocking structure.

8. The method for preparing high-strength formaldehyde-free engineered wood panels with controllable rigidity and flexibility according to claim 3, characterized in that: The continuous hot-pressing-cold-pressing integrated equipment refers to a hot-pressing equipment where the first half is a high-temperature stage and the second half is a low-temperature stage; the high temperature refers to a temperature between 100-250℃, a pressure of 1-5MPa, and a hot-pressing time of 0.5-20 minutes; the low temperature refers to a temperature between 25℃-80℃, a pressure of 10-15MPa, and a cold-pressing time of 0.5-10 minutes.

9. The method for preparing high-strength formaldehyde-free engineered wood panels with controllable rigidity and flexibility according to claim 8, characterized in that: When the polymer fiber is polyurethane fiber, the temperature is 120-170℃; when the polymer fiber is polypropylene fiber, polyethylene fiber, or polyamide fiber, the temperature is 150-250℃; the low temperature refers to a temperature of room temperature - 60℃.

10. The method for preparing high-strength formaldehyde-free engineered wood panels with controllable rigidity and flexibility according to claim 3, characterized in that: The resulting engineered wood products have controllable rigidity and flexibility. When the thickness of the engineered wood product is less than 3mm, the product is flexible; when the thickness of the engineered wood product is greater than or equal to 3mm, the product is rigid.

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