Wood fiber reinforced material, preparation method therefor and use thereof, and chemical modification method

Abstract

The present invention provides a wood fiber reinforced material, comprising compressed wood cell walls; the diameter of the wood fiber reinforced material is 0.2-0.8 mm; and the density of the wood fiber reinforced material is 0.9-1.8 g / cm3. Compared with the existing technology, the wood fiber reinforced material provided by the present invention has an excellent mechanical reinforcement effect, a composite material obtained by compounding said material with a resin significantly exhibits the texture, color, and feel of a brushed wood panel, combining aesthetics and high performance. Furthermore, said material has excellent long-term dynamic mechanical properties, being able to withstand 1 million cycles without significant performance degradation under fatigue test conditions of 90 MPa maximum stress and 5 Hz frequency. In addition, the wood fiber reinforced composite material has excellent flame retardant properties, being capable of reaching the flame retardant level of self-extinguishing after removal from fire without adding any flame retardant. Furthermore, the wood fiber reinforced material has excellent resistance to ultraviolet aging and damp-heat aging.

Description

A wood fiber reinforced material, its preparation method and application and chemical modification method

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on February 6, 2024, with application number 2024101716440 and invention name “A wood fiber reinforced material, its preparation method and application”, parts of which are incorporated by reference into this application. Technical Field

[0002] The present invention belongs to the technical field of reinforcing materials, and in particular relates to a wood fiber reinforced material, a preparation method thereof, and an application and chemical modification method thereof. Background Art

[0003] As a reinforcing material, high-performance fiber is compounded with resin to form composite structural parts. It has the characteristics of light weight and high strength, which can achieve lightweight structure. Therefore, it is widely used in automobiles, aerospace, rail transportation, ships, construction, sports equipment, wind power, consumer electronics, home decoration, leisure and entertainment, etc.

[0004] Reinforcement fibers primarily include organic and inorganic fibers. Organic fibers are primarily derived from fossil fuels and undergo high temperature and high pressure to densely arrange carbon chains, resulting in excellent mechanical properties. These materials include carbon fiber, aramid fiber, and ultra-high molecular weight polyethylene fiber. Inorganic fibers primarily include glass fiber and basalt fiber. These fibers are obtained by melting inorganic materials at high temperatures and then drawing them into wire. Compared to organic fibers, these fibers have a higher density and, therefore, a lower lightweighting effect.

[0005] However, the preparation methods of the above-mentioned organic synthetic fibers and inorganic fibers require a lot of energy consumption, which is often accompanied by the emission of large amounts of waste gas and waste liquid. At the same time, since the materials cannot be decomposed in the environment, they need to be recycled to avoid soil or ocean pollution.

[0006] Plant fiber, a naturally formed fiber material through photosynthesis, is sustainable throughout its life cycle. Using plant fiber as a product material can easily achieve zero carbon emissions, or even negative carbon emissions due to the carbon sequestration properties of plant fiber itself. However, most plant fibers do not possess the mechanical properties required for reinforcing materials without special treatment. Therefore, only a very small number of plant fibers have been successfully commercialized for use in composite materials, primarily hemp fibers. Hemp fiber has excellent mechanical properties, but after molding, it has a grayish-yellow appearance and texture, lacking the premium feel of wood products. In addition, hemp fiber has average long-term dynamic mechanical properties, poor creep resistance and fatigue resistance, and is not suitable for use in structural parts subjected to long-term stress. Plant fibers also include some products that are directly used after extracting cellulose from plants such as straw, or further artificially synthesized into lignin fibers. However, these methods involve chemical extraction and synthesis, which have certain barriers to entry, and cellulose monofilaments have disadvantages such as high moisture absorption. The above reasons have restricted the market size of plant fibers in the field of composite material reinforcement fibers. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a wood fiber reinforced material with excellent mechanical strengthening effect, a preparation method thereof, and an application and chemical modification method thereof.

[0008] The present invention provides a wood fiber reinforced material, comprising compressed wood cell walls; the diameter of the wood fiber reinforced material is 0.2 to 0.8 mm; the density of the wood fiber reinforced material is 0.9 to 1.8 g / cm 3 ; The density of the wood fiber reinforced material is 1.64 to 3.6 times that of the wood raw material.

[0009] Preferably, the tensile strength at break of the wood fiber reinforced material is 200 to 800 MPa; and the Young's modulus of the wood fiber reinforced material is 15 to 60 GPa.

[0010] Preferably, the wood fiber reinforcement material is a continuous filament; a single strand of the continuous filament comprises a single twisted wire; and the cross-section of the wire is circular or approximately circular.

[0011] Preferably, the surface and interior of the wood fiber reinforced material have a microscopic layered corrugated structure; the inclination of the layered corrugated structure to the axial direction of the wood fiber reinforced material is 5° to 40°.

[0012] Preferably, the proportion of natural wood in the wood fiber reinforcement material is 99.95 to 99.993 wt.%.

[0013] The present invention also provides a method for preparing a wood fiber reinforced material, comprising the following steps:

[0014] S1) chemically modifying the narrow straight-grain veneer to obtain modified veneer;

[0015] S2) splicing the modified veneers to obtain continuous veneers;

[0016] S3) continuously twisting to obtain a wood yarn;

[0017] S4) drawing the wood strands into a dense form to obtain a wood fiber reinforced material.

[0018] Preferably, the thickness of the narrow straight-grain veneer is 0.1 to 0.5 mm; the width of the narrow straight-grain veneer is 0.5 to 8 mm;

[0019] and / or, the angle between the grain and the edge of the narrow straight-grain veneer is less than 10°;

[0020] Within a length of 20 cm, the number of burrs larger than 1 mm on the edge of the narrow straight-grain veneer is less than or equal to 10, and the length without burrs is greater than 5 mm and the width is greater than 0.3 mm.

[0021] Preferably, the chemical modification in step S1) is carried out in a closed high-pressure system; the temperature of the chemical modification is 100-150° C.; the pressure of the chemical modification is 0.07-1 MPa; the time of the chemical modification is 2-12 hours; and the heating rate of the chemical modification is 0.5-5° C. / min;

[0022] Alternatively, the chemical modification is carried out under normal pressure; the time of the chemical modification is 24 to 72 hours; the temperature of the chemical modification is 100° C., the boiling temperature of water; the heating rate of the chemical modification is 0.5 to 5° C. / min;

[0023] And / or, after chemical modification, the reaction solution is cooled to obtain modified veneer; the cooling rate is 1-10°C / min; the cooling includes water cooling or air cooling.

[0024] Preferably, the chemically modified solution in step S1) comprises an alkaline substance and a sulfonating agent;

[0025] The pH value of the modified liquid is 12 to 14;

[0026] The concentration of the alkaline substance in the modified solution is 0.01 to 5 kg / L;

[0027] The alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate;

[0028] The concentration of the sulfonating agent in the modified solution is 0.01 to 5 kg / L;

[0029] The sulfonating agent in the modified liquid is selected from one or more of sulfite, chlorosulfonic acid, hydroxymethylsulfonate, sulfuryl chloride and aminosulfonic acid;

[0030] And / or, the material ratio of the narrow straight grain veneer to the chemically modified modifying liquid is 4.6 to 184 cm 3 : 1L.

[0031] Preferably, the mass of the modified veneer is reduced by 35-60% compared to that of the narrow straight-grain veneer.

[0032] Preferably, the splicing in step S2) is performed by glue;

[0033] The proportion of natural wood in the continuous veneer is 99.95 to 99.993 wt.%.

[0034] Preferably, the twisting linear speed in step S3) is 0.5-5 m / min;

[0035] And / or, the twist of the wooden thread is 80 to 300 twists per meter.

[0036] Preferably, after twisting in step S3), an extrusion densification process is performed to obtain wood yarn;

[0037] The extrusion densification treatment includes a first extrusion densification treatment or includes a first extrusion densification treatment and a second extrusion densification treatment;

[0038] The area of ​​the mold used in the first extrusion densification treatment is 30% to 60% of the cross-sectional area of ​​the modified veneer;

[0039] The area of ​​the die used in the second extrusion densification treatment is 40% to 80% of the area of ​​the die used in the first extrusion densification treatment.

[0040] Preferably, the second extrusion densification treatment is performed under the condition of mold heating; the temperature of the mold heating is 60°C to 250°C.

[0041] Preferably, the wire drawing and densification linear speed in step S4) is 0.2-5 m / min;

[0042] And / or, the temperature of the die for wire drawing and densification is 60°C to 250°C.

[0043] Preferably, the wire drawing densification in step S4) is multi-stage wire drawing die densification; the number of stages of the multi-stage wire drawing die densification is 2 to 15; the outlet diameter of the wire drawing die used for the multi-stage wire drawing die densification is successively reduced by 0 to 0.1 mm.

[0044] Preferably, the outlet diameter of the first-stage drawing die to the n-stage drawing die of the multi-stage drawing die decreases by 0.01 to 0.1 mm, and the outlet diameter of the n+1-stage drawing die to the last-stage drawing die decreases by 0 to 0.03 mm; n is an integer greater than or equal to 1 / 3 to 2 / 3 of the number of stages.

[0045] Preferably, the step S4) further comprises a keratinization treatment; the keratinization treatment comprises a hydration treatment and a dehydration treatment;

[0046] The water filling treatment makes the moisture content 60 to 120 wt %;

[0047] The dehydration treatment makes the water content 2-20 wt%.

[0048] Preferably, the keratinization treatment is carried out during the wire drawing and densification process, and the keratinization dehydration treatment is carried out through a die used for wire drawing and densification.

[0049] Preferably, the keratinization treatment is multiple keratinization treatments; the wire drawing densification is multi-stage wire drawing die densification;

[0050] The number of multiple keratinization treatments is 1 to 5 times;

[0051] The multi-stage wire drawing die has a density level of 2 to 15.

[0052] The present invention also provides a wood fiber cloth reinforcement material, comprising the above-mentioned wood fiber reinforcement material.

[0053] The present invention also provides a polymer resin composite material, comprising the above-mentioned wood fiber reinforced material and / or the above-mentioned wood fiber cloth reinforced material.

[0054] The present invention provides a wood fiber reinforced material, comprising compressed wood cell walls; the diameter of the wood fiber reinforced material is 0.2 to 0.8 mm; the density of the wood fiber reinforced material is 0.9 to 1.8 g / cm 3 Compared with the prior art, the wood fiber reinforced material provided by the present invention has a very excellent mechanical reinforcement effect. The composite material obtained by compounding it with resin has the significant texture, color and texture of a brushed wood panel, taking into account both aesthetics and high performance. At the same time, it has excellent long-term dynamic mechanical properties. Under the fatigue test conditions of 90MPa maximum stress and 5Hz frequency, it can reach 1 million cycles without significant performance degradation. In addition, the wood fiber reinforced composite material has excellent flame retardant properties and can achieve a flame retardant grade of self-extinguishing when away from fire without adding any flame retardants. In addition, the wood fiber reinforced material has excellent resistance to ultraviolet aging and resistance to wet heat aging. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG1 is a schematic diagram of the preparation process of the wood fiber reinforced material provided by the present invention;

[0056] FIG2 is a schematic structural diagram of a material frame for a vertical reactor provided by the present invention;

[0057] FIG3 is a schematic structural diagram of a vertical reactor provided by the present invention and installed in a multi-layer material frame;

[0058] FIG4 is a schematic structural diagram of a material frame for a horizontal reactor provided by the present invention;

[0059] FIG5 is a schematic structural diagram of a horizontal reactor provided by the present invention and installed in a multi-layer material frame;

[0060] FIG6 is a schematic structural diagram of a vertical reactor loaded with multiple material bags provided by the present invention;

[0061] FIG7 is a schematic structural diagram of the twisting device used in the present invention;

[0062] FIG8 is a schematic diagram of the structure of the device with a humidifying box that can operate two twisting devices at the same time used in the present invention;

[0063] FIG9 is a schematic structural diagram of the wire drawing and densification equipment used in the present invention;

[0064] FIG10 is a schematic structural diagram of different wood fiber cloth reinforcement materials provided by the present invention;

[0065] FIG11 is a schematic structural diagram of a polymer resin composite material with unidirectional distribution of wood fiber reinforcement provided by the present invention;

[0066] FIG12 is a schematic diagram of the preparation process of the polymer resin composite material provided by the present invention;

[0067] FIG13 is a photograph of the straight-grained veneer (left), wood strands (center), and wood fiber reinforcement (right) used in Example 1 of the present invention;

[0068] FIG14 is a scanning electron microscope image of the wood fiber reinforced material obtained in Example 1 of the present invention;

[0069] FIG15 is a photograph of the wood fiber reinforced material obtained in Example 1 of the present invention;

[0070] FIG16 is a graph showing tensile stress-strain curves of the wood fiber reinforced material and the wood fiber reinforced epoxy resin-based composite material obtained in Example 1 of the present invention;

[0071] FIG17 is a photograph of the wood fiber cloth reinforcement material obtained in Example 2 of the present invention;

[0072] FIG18 is a flat-lay photograph of the wood fiber cloth reinforcement material obtained in Example 2 of the present invention;

[0073] FIG19 is a photograph of the winding of the wood fiber cloth reinforcement material obtained in Example 2 of the present invention;

[0074] FIG20 is a photograph of the wood fiber reinforced epoxy resin-based composite material obtained in Example 3 of the present invention;

[0075] FIG21 is a photograph of the wood fiber reinforced epoxy resin-based composite material obtained in Example 3 of the present invention;

[0076] FIG22 is a graph showing the vibration damping performance of the wood fiber reinforced epoxy resin-based composite material obtained in Example 3 of the present invention;

[0077] FIG23 is a graph showing the fatigue cycle test results of the wood fiber reinforced epoxy resin-based composite material obtained in Example 3 of the present invention;

[0078] FIG24 is a photograph of the appearance changes of the wood fiber reinforced epoxy resin-based composite material obtained in Example 3 of the present invention after the hygrothermal aging performance test; the left side shows the sample before the test, and the right side shows the sample after the test;

[0079] FIG25 is a photograph showing the appearance changes of the wood fiber-reinforced epoxy resin-based composite material obtained in Example 3 of the present invention after natural outdoor weathering performance testing; the left side shows the sample before the test, and the right side shows the sample after the test;

[0080] FIG26 is a graph showing the flame retardancy of the wood fiber reinforced epoxy resin composite material obtained in Example 3 of the present invention; the left side shows the sample under flame, and the right side shows the sample after the flame is removed;

[0081] FIG27 is a microscope image of different narrow straight-grain veneers in Examples 4-5 of the present invention and Comparative Examples 1-3. DETAILED DESCRIPTION

[0082] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0083] The present invention provides a wood fiber reinforced material, comprising compressed wood cell walls; the diameter of the wood fiber reinforced material is 0.2 to 0.8 mm; the density of the wood fiber reinforced material is 0.9 to 1.8 g / cm 3 .

[0084] According to the present invention, the entire wood fiber reinforced material is composed of tightly compressed wood cell walls, which are obtained by chemically modifying, twisting and drawing straight-grained wood veneer; the diameter of the wood fiber reinforced material is preferably 0.3-0.6 mm, more preferably 0.4-0.5 mm; the density of the wood fiber reinforced material is preferably 0.9-1.8 g / cm 3 .

[0085] The density of the wood fiber reinforced material provided by the present invention is 1.64 to 3.6 times that of the raw straight-grain veneer; with the same length, the weight of the wood fiber reinforced material provided by the present invention is 35% to 55% lighter than that of the raw straight-grain veneer.

[0086] According to the present invention, the cross-sectional area of ​​the wood fiber reinforced material is preferably 0.0314 to 0.5024 mm 2 The present invention has no particular limitation on the shape of the cross section of the wood fiber reinforced material. In the present invention, the cross section is preferably circular or elliptical close to a circular shape.

[0087] The present invention does not specifically limit the length of the wood fiber-reinforced material; the wood fiber-reinforced material can be continuous fibers of any length. In a specific embodiment provided by the present invention, the wood fiber-reinforced material is a continuous filament. Since the length of the straight-grained veneer used to prepare the wood fiber-reinforced material is limited, continuous fibers of any length can be prepared through a splicing process; the splicing preferably uses glue. More specifically, the proportion of natural wood in the wood fiber-reinforced material provided by the present invention is 99.95% to 99.993% by weight. Therefore, the wood fiber-reinforced material provided by the present invention is derived from sustainable biomass raw materials formed through photosynthesis in nature. The processing process is low-energy and environmentally friendly. At the end of its life cycle, it can be naturally degraded in landfill, achieving low carbon emissions throughout its life cycle, or even zero carbon and negative carbon emissions.

[0088] The wood fiber reinforced material provided by the present invention is a coarse fiber with large gaps between the fibers, which allows polymer resin to easily enter the gaps between the fibers. Composite material structures with relatively small defects can be easily prepared using various molding processes, and defects such as bubbles are not likely to appear in composite material structures containing wood fiber reinforced materials.

[0089] The wood fiber reinforced material provided by the present invention preferably comprises a single twisted wire, more preferably comprises a single twisted continuous filament; the number of twists within 1 meter of the wood fiber reinforced material is preferably 80 to 300, more preferably 100 to 220, and even more preferably 120 to 200.

[0090] The wood fiber-reinforced material provided by the present invention has a microscopic layered corrugated structure on its surface and interior. Specifically, the layered corrugated structure is preferably inclined at an angle of 5° to 40°, more preferably 10° to 40°, and even more preferably 15° to 30° relative to the axial direction of the wood fiber-reinforced material. The wood fiber-reinforced material provided by the present invention is a self-twisted yarn. The layered corrugated structure is neatly arranged along the twist direction, exhibiting a regularly arranged furrow pattern. This layered corrugated structure increases the surface roughness and surface area of ​​the wood fiber-reinforced material, allowing the polymer resin to penetrate into the corrugations on the surface of the wood fiber-reinforced material when used as a reinforcement material to prepare a polymer resin composite material, thereby improving the bonding between the wood fiber-reinforced material and the polymer resin.

[0091] The wood fiber reinforced material provided by the present invention has a very excellent mechanical reinforcement effect; the tensile fracture strength of the wood fiber reinforced material is preferably 200 to 800 MPa, more preferably 400 to 800 MPa; the tensile fracture strength of the wood fiber reinforced material is 3.3 to 16 times the tensile fracture strength of the raw material straight-grain veneer; the Young's modulus of the wood fiber reinforced material is preferably 15 to 60 GPa, more preferably 25 to 60 GPa; the Young's modulus of the wood fiber reinforced material is 4.16 to 10 times the Young's modulus of the raw material straight-grain veneer.

[0092] The present invention also provides a method for preparing the above-mentioned wood fiber reinforced material, comprising the following steps: S1) chemically modifying narrow straight-grain veneer to obtain modified veneer; S2) splicing the modified veneer to obtain continuous veneer; S3) twisting the continuous veneer to obtain wood strands; S3) drawing the wood strands to obtain wood fiber reinforced material.

[0093] Referring to FIG1 , FIG1 is a schematic diagram of the preparation process of the wood fiber reinforced material provided by the present invention.

[0094] The present invention has no particular limitation on the sources of all raw materials, and any commercially available raw materials may be used.

[0095] In the present invention, the narrow straight-grain veneer can be any straight-grain veneer known to those skilled in the art, without particular limitation. Examples include, but are not limited to, walnut, oak, basswood, rosewood, ebony, teak, rosewood, catalpa, ebony, cherry, cork, poplar, beech, cedarwood, pine, maple, and ash. The narrow straight-grain veneer is natural, avoiding the environmental risks of artificial engineered wood that incorporates excessive amounts of polymers and can cause structural separation during subsequent chemical reactions. Natural veneer is environmentally friendly, with cellulose, hemicellulose, and lignin cross-linked within the naturally formed structure, maintaining structural integrity during subsequent chemical reactions. The thickness of the narrow straight-grain veneer is preferably 0.1 to 0.5 mm, more preferably 0.1 to 0.3 mm. This thickness makes narrow straight-grain veneer easier to process, and the resulting wood fiber fabric reinforcement is thinner, providing better paving during composite molding. The smaller the width of the narrow straight-grain veneer, the finer the diameter of the wood fiber produced, the thinner the thickness of the wood fiber cloth reinforcement material, and the better the paving properties in the composite material molding process. However, a small width will also reduce the tensile load of the material. In specific process flows, such as the densification process of wire drawing, it is easy for the tensile load on the material to be higher than its own breaking load, resulting in material breakage and affecting process stability. In addition, since the subsequent splicing-twisting-densification process is a linear process, the line speed is fixed in the process. Therefore, at the same length, materials with a small width will lead to reduced process capacity and increased process costs. Therefore, considering all factors, the width of the narrow straight-grain veneer is preferably 0.5 to 8 mm, and more preferably 1 to 4 mm.

[0096] In the present invention, only narrow straight-grained veneer that meets the above-mentioned thickness and width can be finally formed into a fibrous linear shape, meeting the feasibility of the wire drawing densification process; if the cross-sectional area of ​​the narrow straight-grained veneer is too large, it cannot be processed into a filamentous / fibrous / linear shape, and therefore is not suitable for the wire drawing densification process. The wire drawing densification process is a process that applies uniform stress 360° from the outside to the center of the material to achieve the effect of diameter reduction. Unlike the intermittent hot pressing process, the wire drawing densification process is a continuous process, which also means that the time for each area of ​​the material to be subjected to the external force is very short. In order to achieve the effect of diameter reduction in a short time, the diameter of the material must be small enough so that the straight-line distance for the external stress to be transmitted from the force point to the center of the circle is short and the compression efficiency is relatively high. Therefore, if the width and thickness of the narrow straight-grained veneer do not meet the above conditions, it is not processable by the wire drawing densification process.

[0097] The angle between the grain and the edge of the narrow straight-grain veneer is preferably less than or equal to 10°, more preferably less than or equal to 6°, and even more preferably less than or equal to 5°. If the angle between the grain and the edge is too large, the wood fiber reinforced material finally prepared will not be able to fully utilize the advantages of the anisotropy of wood, and the mechanical properties will be relatively poor. On the other hand, since the narrow straight-grain veneer is relatively long, a large angle between the grain and the edge will result in many grain end points on the edge of a single straight-grain veneer. These grain end points are prone to stress concentration, which has a negative impact on process stability. Therefore, in order to improve the mechanical properties of the final product and increase process stability at the same time, it is necessary to minimize the angle between the grain and the edge of the narrow straight-grain veneer.

[0098] The narrow straight-grain veneer should minimize edge burrs, as these are a material defect that significantly impacts process stability. In the present invention, the narrow straight-grain veneer should preferably have fewer than 10 burrs > 1 mm within any 20 cm length, and no burrs should be greater than 5 mm in length and greater than 0.3 mm in width.

[0099] In the present invention, the narrow straight-grain veneer surface is preferably free of obvious defects, including but not limited to grain defects, insect bites, knots, burrs, decay, notches, and cracks. These defects can easily cause stress concentration, leading to material breakage during subsequent processing and compromising process stability. Straight-grain veneer should have relatively high fiber parallelism. This is because wood is a highly anisotropic material with the best mechanical properties along the fiber orientation. Therefore, relatively high fiber parallelism ensures that the wood fiber reinforcement material with generally high mechanical properties is produced during the process.

[0100] In the present invention, the narrow straight-grained veneer can be commercially available or homemade, as long as it meets the above requirements. Specifically, the narrow straight-grained veneer can be obtained by slicing the straight-grained veneer; the thickness of the straight-grained veneer is the same as that of the narrow straight-grained veneer; the present invention has no special restrictions on the length and width of the straight-grained veneer, as long as it is the maximum length and width that can be produced by the wood species during its slicing process. In the present invention, the length of the straight-grained veneer is preferably 1 to 15 meters, and the width is preferably 5 to 50 cm. The slicing method is a method well known to those skilled in the art and is not particularly limited. In the present invention, a conventional veneer shearing machine can be used to automatically slice the straight-grained veneer; the straight-grained veneer can be sliced ​​individually or stacked before slicing to improve process efficiency; the number of stacks can be determined by the specifications of the equipment and is generally 20 to 300 sheets. Because the target product of the slice process is narrow straight-grain veneer, the edges of the stacked straight-grain veneers must be highly aligned. One or more trimming steps must be performed to ensure alignment of all the stacked straight-grain veneers. This ensures consistent narrow straight-grain veneer width after sliced ​​veneer. The standard deviation and range of width after sliced ​​veneer production should be as small as possible to ensure consistency. In this invention, the standard deviation within a batch is required to be <0.1mm, and the range is required to be <0.4mm.

[0101] The narrow straight-grain veneer is chemically modified to obtain modified veneer; the pH value of the chemically modified modification liquid is preferably 12-14; the chemically modified modification liquid preferably comprises an alkaline substance, a sulfonating agent and water; the alkaline substance is an alkaline substance well known to those skilled in the art and is not particularly limited. In the present invention, it preferably comprises but is not limited to one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate; the concentration of the alkaline substance in the modification liquid is preferably 0.01-5 kg / L, more preferably 0.05-3 kg / L, and even more preferably 0.1-2 kg / L; in some embodiments provided by the present invention, the concentration of the alkaline substance in the modification liquid is specifically 0.1 kg / L, 0.05 kg / L or 0.145 kg / L; The sulfonating agent is any sulfonating agent well known to those skilled in the art and is not particularly limited. In the present invention, it preferably includes but is not limited to one or more of sulfite, chlorosulfonic acid, hydroxymethylsulfonate, sulfuryl chloride and aminosulfonic acid; the sulfite is preferably sodium sulfite; the concentration of the sulfonating agent in the modifying solution is preferably 0.01 to 5 kg / L, more preferably 0.01 to 3 kg / L, and even more preferably 0.01 to 1 kg / L; in some embodiments provided by the present invention, the concentration of the sulfonating agent in the modifying solution is specifically 0.05 kg / L, 0.075 kg / L or 0.072 kg / L; the concentration of the sulfonating agent in the modifying solution can be increased accordingly as the volume of the reaction solution increases, thereby compensating for the reduced mass transfer caused by the increase in the scale of the chemical reaction. The volume of the modified liquid can be any volume, depending on the production requirements and the specifications of the reactor equipment, including but not limited to 500mL, 2L, 4L, 20L, 100L, 500L, 1000L, 2000L, 5000L, 8000L, 10000L, etc.; the material ratio of the narrow straight-grained veneer to the chemically modified modified liquid is preferably 4.6 to 184cm 3 :1L. The higher the material ratio, the higher the single reaction output, so it is generally necessary to increase the material ratio of the reaction as much as possible, but it is also necessary to comprehensively consider the difficulty of mass transfer and the problem of excessive accumulation of materials in the kettle. During the reaction process, the alkaline substance will react with the lignin, hemicellulose and cellulose in the straight-grained veneer. Taking the alkaline substance as sodium hydroxide and the sulfonating agent as sodium sulfite as an example, hemicellulose may react with sodium hydroxide to form sodium hemicellulose (as shown in Reaction Formula 1), and lignin may react with sodium hydroxide and sodium sulfite to form sodium lignin sulfonate (as shown in Reaction Formula 2 and Reaction Formula 3). The by-products of these reactions will separate from the straight-grained veneer structure and dissolve or suspend in the reaction solution. If the material ratio is too high, it will make it difficult for the reaction by-products to be evenly dispersed in the system, which will lead to a decrease in the reaction rate in local areas, resulting in a decrease in the uniformity of the properties of the straight-grained veneer after the reaction, affecting the stability of subsequent processes and the performance of the final product. In addition, the problem of excessive accumulation of materials in the kettle will also increase the friction between the straight-grained veneer during the reaction or the friction with the structure inside the kettle, thereby causing damage to the straight-grained veneer.

[0102] For the reaction below 100L, because the reaction scale is smaller, the mass transfer and heat transfer in the system is easier, and the narrow straight-grained veneer quantity is also less. The narrow straight-grained veneer can be put into the reactor together, or it can be pre-layered or bagged and put into the reactor. For the reaction above 100L, because the reaction scale is larger, the mass transfer and heat transfer rate in the system is reduced, and the narrow straight-grained veneer quantity is larger, so it is necessary to pre-layer the narrow straight-grained veneer or bagged and put into the reactor. Pre-layering and bagging can maximize the utilization of the reactor internal space, and the narrow straight-grained veneer is evenly arranged in the reactor everywhere. In addition, by this partitioning, the narrow straight-grained veneer in a single area can also be controlled to a certain number, reducing the straight-grained veneer damage problem caused by mutual friction. In the present invention, the narrow veneer can be pre-layered with a material frame stacked up and down, referring to Figures 2 and 3, Figure 2 is a structural representation of a material frame for a vertical reactor, and Figure 3 is a structural representation of a vertical reactor equipped with a multi-layer material frame, wherein 1 is a vertical reactor, 2 is a stirring device, and 3 is a material frame. The material frame has a hole structure and further has a porous structure; the diameter of the hole ranges from 3 to 5 mm, and the overall hole density is 4×10 5 ~3.5×10 5 pcs / m 3 The material frame is provided with a partition, which divides the material frame into a plurality of compartments, and the width of adjacent compartments increases from the center of the material frame to the side wall of the material frame from the inside to the outside; the thickness of the partition is 1 to 5 mm, more preferably 3 mm; the partition has a hole structure; the diameter of the hole ranges from 3 to 5 mm, and the overall hole density is 4×10 5 ~3.5×10 5 pcs / m 3 ; The material frame is preferably a cylindrical material frame; the number of the partitions is multiple; multiple partitions are arranged in concentric circles within the frame.

[0103] In the present invention, a horizontally stacked material frame can also be used to pre-layer the narrow veneer. See Figures 4 and 5. Figure 4 is a schematic diagram of the structure of the material frame for a horizontal reactor provided by the present invention, and Figure 5 is a schematic diagram of the structure of a horizontal reactor equipped with a multi-layer material frame. The multi-layer material frame is a horizontally stacked material frame; the material frame and the material bag have a pore structure. The diameter of the pore structure ranges from 3 to 5 mm; the overall pore density of the material frame and the material bag is 6.8×10 5 ~5.0×10 5 pcs / m 3The material frame is provided with a partition, which divides the material frame into a plurality of compartments. Adjacent compartments have equal widths. The thickness of the partition is 1 to 5 mm. The partition has a hole structure. The material frame is a rectangular parallelepiped material frame. There are multiple partitions, which are arranged in parallel in the material frame.

[0104] The material frame needs to be designed with a porous structure to allow substances to migrate freely in and out of the material frame. The pore size should be as large as possible, but it cannot allow the straight-grain veneer to pass through. This can effectively separate the narrow straight-grain veneer without affecting mass transfer. The material frame needs to be designed to be close to the inner diameter of the reactor. This way, the stacked multi-layer material frame can maximize the use of the reactor space. The material frame needs to be made of alkali-resistant and heat-resistant materials.

[0105] Alternatively, stacking bags can be used to pre-bag straight-grain veneer. See Figure 6, which shows a schematic diagram of a vertical reactor loaded with multiple bags. Figure 1 represents the vertical reactor, and 2 represents the bags. The bags are made of porous fabric to allow for free movement of materials in and out of the bag. The pores are designed to be as large as possible, but not enough to allow narrow-grain veneer to pass through. This allows for effective bagging without compromising mass transfer. The bags are relatively flexible, allowing them to be stacked to maximize the use of the reactor space. The bags should be made of a material that is both alkali-resistant and heat-resistant.

[0106] The reactor can be vertical or horizontal, and any heating method can be used, as long as the temperature accuracy within the system can be controlled within ±10°C. For large-volume reactors, additional stirring, solution reflux, overall reactor rotation, and external circulation pumps can be used to improve mass transfer. In the present invention, there are two options for the reaction temperature and pressure of the chemical modification: one is to heat to the boiling state of water at normal pressure, but this method requires an additional condensation reflux module, and the reaction energy consumption will increase a lot. In addition, the reaction time at normal pressure is 24 to 72 hours to ensure that the reaction is complete; in some embodiments provided by the present invention, the reaction time at normal pressure can be specifically 48 hours; another option is to heat to a temperature exceeding the boiling point of water in a closed high-pressure system, preferably 100 to 150°C, more preferably 110 to 150°C, more preferably 120 to 130°C, and most preferably 125°C, to form the entire system into a high-pressure system, so that there is no need to add a condensation reflux module, and the reaction time can be reduced to 2 to 12 hours for the reaction to be complete, more preferably 3 to 10 hours, more preferably 4 to 8 hours, and most preferably 5 to 8 hours, which can greatly reduce the energy consumption of the reaction and reduce the process cost of the chemical reaction. The optimal reaction temperature depends on the wood species and the scale of the reactor. Different wood species will have slightly different temperature windows due to different chemical components. Generally, the larger the scale of the reactor, the higher the reaction temperature is to compensate for the reduction in mass transfer and heat transfer. Generally, the higher the reaction temperature, the faster the reaction rate. However, since cellulose will be gradually hydrolyzed starting at 150°C, and the mechanical properties of cellulose are relatively high and need to be retained as much as possible, the reaction temperature needs to be set below 150°C. In some embodiments provided by the present invention, the temperature of the chemical modification in the closed high-pressure system is specifically 125°C, 116°C or 130°C; in some embodiments provided by the present invention, the time of the chemical modification in the closed high-pressure system is specifically 6h, 8h or 6.5h; when the chemical modification is carried out in a closed high-pressure system, the pressure of the chemical modification is preferably 0.07~1MPa; the present invention has no special restrictions on the heating rate of the chemical modification. The specific chemical modification can be carried out under normal pressure or in a closed high-pressure system at a heating rate of 0.2~5°C / min, more preferably 0.5~5°C / min. In some embodiments provided herein, the heating rate can be 3°C / min, 2.5°C / min, 5°C / min, 2°C / min, 0.5°C / min, or 0.2°C / min. Once the system temperature reaches and stabilizes at the target temperature, the reaction is maintained at the target temperature for 2-12 hours in a closed high-pressure system, or for 24-72 hours under normal pressure, before cooling. Because the modified straight-grain veneer reforms its intermolecular hydrogen bonds and begins crystallization during cooling, the cooling method significantly affects the final performance.If the cooling rate is too fast, the molecular chains of the modified straight-grained veneer will be fixed prematurely, the intermolecular forces will not be fully established, the crystallinity will be low and the crystal particles will be large, all of which will have a negative impact on the performance. Therefore, in the present invention, after the chemical modification is completed, it is preferred to heat exchange the reaction liquid with the external environment at room temperature and slowly cool it down. This cooling method can promote the establishment of intermolecular forces and obtain crystals with high crystallinity and large grain size. Specifically, the cooling method includes water cooling or air cooling; the cooling rate is preferably 0.2 to 10°C / min, more preferably 1 to 10°C / min; in some embodiments provided by the present invention, the cooling rate is specifically 0.2°C / min, 1°C / min, 0.5°C / min, 2°C / min or 3°C / min.

[0107] After cooling to room temperature and atmospheric pressure, the modified veneer is preferably washed and dried. Specifically, the reactor is opened and the modified veneer is removed, or the material frame or bag containing the modified veneer is removed. The resulting material is then placed in water for washing, or the entire material frame or bag containing the material is placed in water for washing. Washing removes residual chemicals on the surface and simultaneously converts any sodium cellulose that may have formed during the reaction back into cellulose, thereby maintaining the natural chemical composition of the wood. Multiple rounds of washing can be performed depending on the material. After cleaning, the material is dried to obtain the modified veneer. The material can be dried naturally or placed in an oven for accelerated drying. The mass of the modified veneer is preferably reduced by 35-60% compared to that of straight-grained veneer. In some specific embodiments provided by the present invention, the mass of the modified veneer is reduced by 45%, 48.2%, 39.6%, 40.5%, 40.7%, 45.2%, 45.6%, 45.1%, 49.6%, 46.1%, 45.3%, 48.8%, 46.2% or 44.1% compared to that of straight-grained veneer.

[0108] In a specific embodiment provided by the present invention, the chemical modification method is specifically as follows: in a closed environment, the veneer is heated in a modifying liquid to a target temperature above the boiling temperature of the modifying liquid at normal pressure, and after staying at the target temperature for a certain period of time, the temperature is then cooled to below the boiling temperature of the modifying liquid at normal pressure to obtain the modified veneer; high pressure can be formed by heating the veneer to above the boiling temperature of the modifying liquid at normal pressure in the closed environment. The target temperature retention time is greater than or equal to 0h; the modifying liquid includes an alkaline substance, a sulfonating agent and water; the modifying liquid is the same as described above and will not be repeated here; the target temperature is preferably 100-150°C; optionally, the target temperature is 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or a range between any two of the above values; the pressure after reaching the target temperature is preferably 0.07-1.9MPa; optionally, the pressure after reaching the target temperature is 0.07MPa, 0.1MPa, 0.3MPa, 0.5MPa, 0.8MPa, 1MPa, 1.3MPa, 1.5MPa, 1.8MPa, 1.9MPa or a range between any two of the above values The dwell time at the target temperature is preferably 0 to 12 hours; optionally, the dwell time after reaching the target temperature is 0 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, or a range between any two of the above values; the cooling method preferably includes water cooling or air cooling; the cooling rate is preferably 0.2 to 10°C / min; optionally, the cooling rate is 0.2°C / min, 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or a range between any two of the above values. During the chemical modification process, the mass of the veneer decreases by 35 to 60%, resulting in a large number of voids in the microstructure. These voids give the modified veneer excellent plastic deformation ability, making it easy to be compressed to a smaller size under external force. At the same time, the quality decreases because a large amount of lignin and hemicellulose in the veneer are removed, so the proportion of cellulose in the overall composition increases. Since cellulose has the best mechanical properties among the three major components of veneer, this adjustment in proportion allows the material to have the potential to be enhanced. The plastic deformation ability of wood that has not undergone any modification is relatively poor. If you want to make the wood that has not undergone any modification undergo significant plastic deformation, it generally requires 2 to 24 hours of steam heating and humidification treatment to achieve sufficient softening effect. The wire drawing densification process is a continuous process, which also means that each area of ​​the material is subjected to external forces for a very short time. In order to achieve the effect of diameter reduction in a short period of time, the material needs to have very good plastic deformation ability, which is something that unmodified wood does not have.Therefore, without the chemical modification process, the wood is not processable by the wire drawing densification process.

[0109] The waste liquid from chemical modification is a brown strong alkaline waste liquid. Taking the waste liquid from a certain chemical modification as an example, the waste liquid component analysis and comparison with GB8978 and DB 31 / 199-2018 Shanghai Comprehensive Wastewater Discharge Standard showed that the waste liquid mainly had a high pH value (13.6) and a high COD value (6.96×10 3 mg / L). Among them, the high pH value is due to the residual alkaline substances in the waste liquid. The high COD value comes from the by-products produced after wood modification, including but not limited to lignin sulfonate, lignin hydrolysis secondary products (vanillin) and a small amount of other organic components. The problem of high pH value can be treated by acid-base neutralization method, reduced to a neutral value, and meet the discharge standard. The treatment methods of COD are mainly divided into physical adsorption and chemical oxidation decomposition. Among them, physical adsorption mainly uses porous activated carbon, macroporous resin, and bentonite for adsorption treatment. This method can greatly reduce the COD value. For example, after using porous activated carbon for adsorption on a certain occasion, the COD value of the waste liquid was reduced to 7.79×10 -3mg / L. The problem with this method is that the activated carbon after adsorption cannot be reused and needs to be treated as hazardous waste among solid wastes. The most common treatment method of chemical oxidation in industrial applications is biochemical degradation-evaporation crystallization-oxidation treatment. A wastewater treatment method in which the waste liquid is placed in a microbial fermentation tank for microbial oxidation treatment, relying on microbial enzymes to oxidize or reduce organic molecules, destroying their unsaturated bonds and chromophores, thereby achieving the treatment purpose. Due to the limited degradation capacity of organisms, the waste liquid after biochemical treatment may not meet the discharge standards of discharge or secondary sewage treatment plants. Therefore, the waste liquid after this method requires a subsequent crystallization-oxidation process. During the treatment of saline industrial wastewater, it enters a low-temperature, multi-effect concentration and crystallization unit. After three to six evaporation and condensation cycles, it is separated into desalinated water (which may contain trace amounts of low-boiling-point organic matter) and concentrated crystal slurry wastewater. Inorganic salts and some organic matter can be crystallized and separated, then incinerated to form inorganic salt waste residue. Non-crystallizable organic matter concentrate wastewater can be treated using a drum evaporator, resulting in a solid waste residue that is incinerated. Desalinated water can be returned to the production system for reuse as a replacement for softened water. However, this method requires high equipment and construction costs and is generally used by bulk chemical manufacturers. Wet oxidation / supercritical oxidation is also a widely applicable treatment method. Wet (catalytic) oxidation uses oxygen or air as an oxidant (with the addition of a catalyst) at high temperatures (150-350°C), high pressures (0.5-20 MPa), and a catalyst to (catalytically) oxidize dissolved or suspended organic matter or reduced inorganic matter in the water, thereby removing pollutants. In addition, electrocatalytic oxidation is also a popular treatment method due to its small footprint and relatively clean, environmentally friendly nature. Electrochemical (catalytic) oxidation technology degrades organic matter directly through anodic reactions or by generating oxidants such as hydroxyl radicals (˙OH) and ozone. Electrochemical (catalytic) oxidation includes two-dimensional and three-dimensional electrode systems. Three-dimensional electrode systems are currently highly regarded due to their micro-field electrolysis. Three-dimensional electrodes are constructed by placing granular or other debris-like working electrode materials between the electrodes of a traditional two-dimensional electrolytic cell. The surface of the material is charged, creating a third electrode where electrochemical reactions can occur. Compared to two-dimensional flat electrodes, three-dimensional electrodes have a larger surface area, increasing the cell's aspect ratio and enabling higher current intensities at lower current densities. The small interparticle spacing allows for faster mass transfer and high spatiotemporal conversion efficiency, resulting in high current efficiency and superior treatment results. Three-dimensional electrodes can be used to treat difficult-to-degrade organic wastewaters such as domestic sewage, pesticide, dye, pharmaceutical, and phenol-containing wastewater, as well as metal ions and landfill leachate. For example, once the electrochemical (catalytic) oxidation technology was used on the wastewater, the COD value was reduced to 1.47×10 -3mg / L, meeting the discharge standards. Currently, the most preferred method is to first neutralize the wastewater with acid and alkali, followed by electrochemical (catalytic) oxidation technology. After comparison with GB8978 and DB 31 / 199-2018 Shanghai Comprehensive Wastewater Discharge Standards, all indicators of the wastewater meet the discharge standards.

[0110] Since narrow straight-grained veneer is a discontinuous strand, subsequent processing can lead to discontinuous processes, making large-scale production impossible. This is a significant issue with plant fibers. Since plant growth is inherently limited in height, plant fibers are inherently discontinuous fibers before undergoing specialized processing. Therefore, in the present invention, the modified veneer is spliced ​​to produce a continuous veneer. This splicing method is preferably bonding. By splicing two pieces of modified veneer together using end-to-end bonding, and repeating this process, a continuous veneer of any length can be obtained. The splicing is preferably performed using glue. The most crucial step in the splicing process is gluing one end of one piece of modified veneer and then bonding it to the end of another piece of modified veneer. The glue material must exhibit excellent adhesion to wood, and the glue can be cured by various methods, including room temperature, heat, UV, and moisture curing. For process efficiency, a glue with an initial curing time of less than 10 seconds is preferred. After initial curing, the glue exhibits a certain degree of adhesion, and can subsequently be fully cured at room temperature. After complete curing, the tensile breaking load at the splicing needs to be able to reach at least 10N. In addition, considering that the subsequent process involves thermal processing, the glue is preferably a thermoplastic polymer material, so that it can soften and easily deform after being heated to a certain temperature, so that the subsequent process is less likely to cause the problem of material jamming in the splicing area. In the present invention, specifically, the material of the glue can be common thermoplastic wood glues such as polyvinyl acetate, polyacrylate, polyurethane, polyether, polyamide, etc., or it can be any glue material that meets the above requirements. The amount of glue used in the splicing should be as small as possible, so as to reduce the problem of material jamming caused by excessive material in the splicing area in the subsequent process. In the present invention, the proportion of natural wood in the continuously modified veneer is preferably 99.95~99.993wt.%, and the rest is glue. Since the amount of glue accounts for a very low proportion, the glue at the splicing will not affect the overall appearance.

[0111] In addition, if a certain proportion of material is not removed in advance in the splicing area, the splicing area will definitely have twice the amount of wood plus glue. Such a splicing area will have significantly more material than the non-splicing area and will be significantly larger in size, which will have a relatively large impact on the stability of the subsequent process. Therefore, it is recommended to remove a certain proportion of material from both ends of the splicing area before splicing. For the splicing method provided by the present invention, the best way to remove material is beveling, which can ensure that there is residual material in the splicing area in the length direction. Beveling can remove half of the material at each end of the splicing, so that there will be no significant problems of excessive material and oversize. In order to facilitate material removal, the ends can be simply ironed before material removal.

[0112] Continuous veneer is untwisted, with a rectangular cross-section. Since the subsequent densification process involves circumferential compression, the material's cross-section must be as close to circular as possible. Therefore, it is continuously twisted to produce wood strands. After twisting, the material's cross-section is circular or nearly circular, such as elliptical, with a very small diameter and a very high aspect ratio. Therefore, the resulting wood strands can be classified as fibers. The twisting speed is preferably 0.5-5 m / min, more preferably 1-3 m / min, and even more preferably 1.5-2 m / min. Faster speeds increase productivity, but may lead to decreased process stability. Slower speeds improve process stability, but reduce productivity. Therefore, the process speed should be adjusted based on the material's actual process performance. The twist of the wood strands is preferably 80-300 twists / m, more preferably 100-220 twists / m, and even more preferably 120-200 twists / m. In some embodiments provided by the present invention, the twist of the wood thread is specifically 80 twists / m, 300 twists / m, 220 twists / m, 180 twists / m or 150 twists / m; by twisting, a wire with uniform size and a cross-section that is slightly circular can be obtained. The twisting can be performed by methods well known to those skilled in the art without any special restrictions. In the present invention, the device disclosed in the Chinese patent publication number CN219449997U is preferably used for twisting, which can realize continuous twisting production of continuous veneer to obtain continuous wood thread. See Figure 7, which is a structural schematic diagram of the twisting device, wherein 1 is a reel, 2 is an equipment frame, 3 is a mold for improving the gripping structure, 4 is a lifting device 1, 5 is a heatable mold, 6 is a lifting device 2, and 7 is a winding roller. During this process, each device can process one modified veneer at the same time, but the control panel can control multiple twisting devices at the same time. At the same time, since the twisting device occupies a small area, multiple twisting devices can be arranged horizontally or vertically in the same operating area to improve the utilization rate of the production area. See Figure 8, which is a schematic diagram of the equipment structure with a humidifying box that can run two twisting devices at the same time, where 1 is a humidifying box, 2 is an equipment frame, 3 is a lifting device 1, 4 is a heatable mold, 5 is a lifting device 2, and 6 is a winding roller. In addition, since the material needs to have a certain degree of softness in order to be easily twisted, the material can be humidified to a certain extent before twisting or during twisting to increase its softness, depending on the shape of the material. The method of humidification is a method well known to those skilled in the art and is not particularly limited. In the present invention, it can be water immersion, water mist spraying, etc., preferably, the continuous veneer is placed in a humidification box before twisting. However, this process needs to control the humidification so that it cannot be excessive, otherwise the material strength will be too low and breakage will occur during the process. In the present invention, preferably, the humidification treatment is to make the moisture content of the continuous veneer preferably 30-50%, more preferably 35-45%, and even more preferably 40%.

[0113] According to the present invention, after twisting, it is preferably also subjected to an extrusion densification treatment to obtain wood strands; the size and shape of the wood strands can be made more uniform by extrusion densification; the parameters of extrusion densification can be adjusted according to the size and shape of the material; the present invention has no special restrictions on the number of extrusion densifications, which can be selected according to actual needs, and can be one or more times; in the present invention, specifically, the extrusion densification preferably includes a first extrusion densification treatment (i.e., the number of extrusion densification treatments is 1 time) or includes a first extrusion densification treatment and a second extrusion densification treatment (i.e., the number of extrusion densification treatments is 2 times); the area of ​​the mold used for the first extrusion densification treatment is preferably 30-60% of the cross-sectional area of ​​the modified veneer, more preferably 35-55%, further preferably 40-50%, and most preferably 40-45%; the first extrusion densification is mainly to provide a holding force for twisting; the area of ​​the mold used for the second extrusion densification treatment is preferably 40-80% of the area of ​​the mold used for the first extrusion densification treatment, more preferably 45-75%, further preferably 50-70%, further preferably 55-65%, and most preferably is 60-65%; through the second extrusion densification, the size and shape of the twisted veneer can be made more uniform; in the present invention, the extrusion densification is preferably carried out after twisting by passing the twisted material through one or more dies; in order to facilitate the entry of the material, the die is preferably larger at the inlet, which is convenient for the material to enter the die without constraint, and the outlet of the die is the die opening of the above-mentioned specific area to achieve the purpose of extrusion densification; since the second extrusion densification will produce a certain extrusion force on the material, the die can be heated to above the glass transition temperature of the wood to increase the permeability of the wood, so in the present invention, the second extrusion densification treatment is preferably carried out under the condition of mold heating; since the glass transition temperature of wood varies greatly depending on the wood species and moisture content, in the present invention, the temperature of the second extrusion densification die heating is preferably 60-250°C, more preferably 100-250°C, more preferably 100-200°C, and most preferably 150°C; in some embodiments provided by the present invention, the temperature of the second pressurization densification can specifically be 150°C. Since the primary purpose of the first extrusion densification is to provide a certain grip for the modified veneer during the twisting process, the material and overall shape of the die used for the first extrusion densification are not very demanding. The die used for the second extrusion densification is preferably a wire drawing die used in metal drawing processes, as this die has a high internal smoothness and a low coefficient of friction. Metal wire drawing dies have a smoothly tapered die hole with a circular cross-section. Materials include, but are not limited to, tungsten steel, stainless steel, diamond, artificial polycrystalline, copper, and the like.

[0114] The wood wire is subjected to wire drawing to densify; the wire drawing process is a conventional processing process for materials such as metal wire, glass fiber, and basalt wire. A linear material with a diameter larger than the inner diameter of the wire drawing die is forced through the die under the action of an external force, so that the cross section of the material is compressed to a size equal to or slightly smaller than the inner diameter of the wire drawing die. The wire drawing process has relatively high requirements on the plastic deformability and fracture strength of the material. Some metal wires can be drawn at room temperature. Glass fiber and basalt wire need to be melted before being drawn. At a specific processing temperature, if the material requires an external force exceeding its fracture strength to obtain the corresponding plastic deformation, it cannot be processed by the wire drawing densification process. Since wood is not in a molten state and linear wood will break during the wire drawing process, the wire drawing process is generally not suitable for wood processing. However, the present invention obtains a wood strand suitable for wire drawing through the previous process for the following reasons: (1) During the chemical modification process, the mass of the modified veneer decreases by 35-60%, so a large number of voids are generated in the microstructure. These voids make the modified veneer have good plastic deformation ability and can be easily compressed to a smaller size under external force; (2) The mass reduction is related to the large amount of lignin and hemicellulose removed from the modified veneer, and the cellulose with good mechanical properties does not undergo significant hydrolysis. Therefore, in terms of the overall composition, the proportion of cellulose after chemical modification is greatly increased, which also means that the material does not have a significant decrease in mechanical properties due to the mass reduction. On the contrary, the increase in the proportion of cellulose gives the material the potential for enhancement; (3) The wire drawing process is a continuous processing process. During the splicing process, the wood changes from a discontinuous short material state to a continuous long material state, which also makes the material processable for continuous processing; (4) The wire drawing process is a circumferential compression process, which requires the cross-sectional shape of the wire to be circular or close to circular, so that the material can be compressed and densified by uniform force at 360°. During the twisting process, the veneer is prepared into continuous wood strands with a circular or nearly circular cross-section that can be compressed circumferentially. During the drawing process, since the voids in the microstructure are compressed and the wood strands obtain a good orientation force along the direction of force, the density and mechanical properties of the continuous wood strands are significantly improved, reaching the mechanical property range of the reinforced material, and a wood fiber reinforced material is obtained. During the drawing densification process, the continuous wood strands pass through the drawing die under the action of traction. The inlet diameter of the drawing die is larger than the diameter of the wood strands to facilitate their entry. During the process, the diameter is gradually reduced to a value smaller than the diameter of the continuous wood strands, thereby exerting an extrusion force on them, and they eventually leave the drawing die from the outlet. The material passes through a combination of dies with gradually decreasing outlet diameters to achieve a gradually densified effect, and ultimately a wood fiber reinforced material with excellent mechanical properties is prepared.See Figure 9, which is a structural diagram of the wire drawing densification equipment, wherein 1 is a wire drawing densification die, 2 is a transverse motor, 3 is a fiber breakage sensor, 4 is a control output motor, 5 is an output platform, 6 is an output reel, 7 is a transverse platform, 8 is a die loading platform, 9 is an input reel, 10 is an active slide rail, 11 is a driven slide rail, 12 is a control input motor, and 13 is an input platform. The wire drawing densification die is preferably a wire drawing die commonly used in metal wire drawing process, which has high internal smoothness and low friction coefficient. The metal wire drawing die has a die hole with a tapered smooth transition, and the cross section of the die hole is circular. Its material includes but is not limited to tungsten steel, stainless steel, diamond, artificial polycrystalline, copper, etc. The hardness of these molds is relatively high, and they can be used in the wire drawing process of wood wire for a long time, and the update frequency is low. In the present invention, the wire drawing densification is preferably multi-stage wire drawing die densification; the number of stages of the multi-stage wire drawing die densification is preferably 2 to 15, more preferably 3 to 15, more preferably 5 to 12, and most preferably 7 to 10; the outlet diameter of the wire drawing die used for the multi-stage wire drawing die densification is preferably reduced by 0 to 0.1 mm, more preferably by 0 to 0.08 mm, more preferably by 0 to 0.05 mm, and most preferably by 0 to 0.035 mm; specifically, the outlet diameter of the first-stage wire drawing die to the n-stage wire drawing die of the multi-stage wire drawing die densification is preferably reduced by 0.01 to 0.1 mm. mm, more preferably, it is reduced by 0.01 to 0.08 mm, more preferably by 0.01 to 0.05 mm, more preferably by 0.01 to 0.035 mm, and most preferably by 0.015 to 0.035; the outlet diameter of the n+1th stage drawing die to the outlet diameter of the last stage drawing die is preferably reduced by 0 to 0.03 mm; n is an integer greater than or equal to 1 / 3 to 2 / 3 of the number of stages; in the present invention, the size of the reduction in outlet diameter of adjacent drawing dies can be the same or different, and there are no special restrictions. The selection of the drawing die combination needs to comprehensively consider the process efficiency and product performance. In the process of wire drawing and densification, the material will be subjected to external traction and friction resistance when passing through the die. The external traction force needs to be greater than the friction force so that the material will continue to pass through the die. However, the size of the die cannot be too small. According to the calculation formula of sliding friction, the friction force of the material is linearly positively correlated with the extrusion force. Excessive extrusion pressure will lead to excessive friction. In order for the material to continue to pass through the die, the external traction force needs to be increased. Once the external traction force exceeds the tensile strength of the material, the material will break. In the early stages of wire drawing and densification, due to the presence of many voids in the microstructure of the wood thread, its densification is relatively easy, and the difference in the outlet diameter of two consecutive dies can be large. However, when the wire drawing is densified to a certain extent, most of the microstructural voids of the wood thread are squeezed and filled with material, and the subsequent densification process becomes increasingly difficult. Therefore, the diameter of each die needs to be reduced more and more slowly, and it is even possible to repeatedly pass through the same aperture die.In a specific embodiment of the present invention, for narrow straight-grain veneer with a cross-sectional size of 4mm x 0.23mm, the preferred die outlet diameter combinations for wire drawing densification are 0.535mm, 0.50mm, 0.475mm, 0.46mm, 0.45mm, 0.445mm, 0.44mm, 0.435mm, and 0.435mm. Using these wire drawing densification die combinations, a wood fiber-reinforced material with a diameter of 0.43mm can be produced. This material is 15.8% the size of the raw material and 3.48 times the density (due to a 45% reduction in wood mass), resulting in a significant densification effect. In another specific embodiment provided by the present invention, the narrow straight-grained veneer with a cross-sectional size of 4mm×0.23mm, the preferred combination of the die outlet diameters for wire drawing and densification is 0.72mm, 0.69mm and 0.68mm; In another specific embodiment provided by the present invention, the narrow straight-grained veneer with a cross-sectional size of 4mm×0.23mm, the preferred combination of the die outlet diameters for wire drawing and densification is 0.82mm, 0.79mm and 0.78mm; In another specific embodiment provided by the present invention, the narrow straight-grained veneer with a cross-sectional size of 4mm×0.23mm, the preferred combination of the die outlet diameters for wire drawing and densification is 0.54mm, 0.51mm and 0.50mm; In another specific embodiment provided by the present invention, the narrow straight-grained veneer with a cross-sectional size of 4mm×0.2 For narrow straight-grain veneer with a cross-section of 3mm, the preferred combination of die outlet diameters for wire drawing and densification is 0.49mm, 0.46mm and 0.44mm; in another specific embodiment provided by the present invention, for narrow straight-grain veneer with a cross-section size of 4mm×0.23mm, the preferred combination of die outlet diameters for wire drawing and densification is 0.62mm, 0.60mm and 0.59mm; in another specific embodiment provided by the present invention, for narrow straight-grain veneer with a cross-section size of 4mm×0.23mm, the preferred combination of die outlet diameters for wire drawing and densification is 0.76mm, 0.74mm and 0.73mm; in the present invention, a wire drawing and densification device can be loaded with only one die, or multiple dies can be connected in series to improve process efficiency, depending on how much total traction force is required when the material passes through these die combinations. The dense wire drawing process can make the microstructure of wood fiber reinforced materials highly dense. After a carbonized layer is formed on the surface during the combustion process, the highly dense internal structure prevents the diffusion of oxygen, allowing the material to achieve high flame retardant properties of self-extinguishing when away from fire without the need to add flame retardants.

[0115] In the present invention, densification by drawing can be performed under heating conditions, specifically, heating to above the glass transition temperature of the wood to increase the permeability of the wood strands. Because the glass transition temperature of wood strands can vary significantly depending on the wood species and moisture content, the densification temperature is preferably between 60°C and 250°C.

[0116] In the present invention, the linear speed for wire drawing density is preferably 0.2-5 m / min; specifically, the linear speed for wire drawing density depends on the magnitude of the friction resistance when the material passes through a specific wire drawing die. When the resistance encountered when passing through the wire drawing die is small, the process stability is relatively high, and the linear speed can be set to 1.5-5 m / min; when the resistance encountered when passing through the wire drawing die is large, the process stability is relatively low, and the linear speed can be set to 0.2-1.5 m / min. The smaller the linear speed, the higher the process stability, but it will reduce the production capacity of this process.

[0117] Densification through drawing can achieve mechanical densification of continuous wood strands. In addition to mechanical densification, veneer can also achieve self-densification through a microstructural hydration-dehydration process, a process known as keratinization. This process occurs because the chemically modified wood microstructure contains numerous voids that are easily filled with water. Furthermore, since cellulose is the dominant component in the continuous veneer, its chemical structure contains numerous hydroxyl groups, making it a hydrophilic material, which facilitates the entry of water molecules into the microstructural voids. During this hydration process, the voids between the cellulose microfibrils expand significantly. During the subsequent drying process, water is removed from these voids, which disappear due to capillary forces. The distance between the cellulose microfibrils is rapidly shortened, and hydrogen bonds between the microfibrils are re-established. This structural contraction and chemical bonding creates a self-densification effect. While the self-densification effect of keratinization is weaker than mechanical densification achieved through external forces and orientation, keratinization is a largely spontaneous process with low energy consumption. Therefore, in the present invention, it is preferred to also include keratinization treatment as an auxiliary process to further improve the densification effect; the keratinization treatment includes water filling treatment and dehydration treatment; the water filling treatment can be achieved by the following methods: 1) immersing the entire body in water; 2) exposing the entire body to a high humidity environment; 3) continuously passing through a water tank at a fixed linear speed; 4) continuously passing through a high humidity environment at a fixed linear speed. Method 1) and method 2) are only applicable to the case where the length of the wooden thread on the unit coil is relatively short. Once the wooden thread on the unit coil has a certain length, the use of method 1) and method 2) will result in a relatively large difference in the amount of water filling between the wooden thread on the outside of the coil that is in direct contact with water and the wooden thread on the inside of the coil, which will ultimately result in a difference in the degree of keratinization, which will have a negative impact on the stability of material performance; although method 4) can achieve the effect of stable keratinization, it takes a longer time to achieve the same water filling effect in a high humidity environment compared to the scheme of immersing in water; therefore, method 3) is preferably used in the present invention to ensure that the material obtains the same water filling effect in a short time; the water filling treatment preferably makes the moisture content 60-120wt.%; too low a moisture content will result in an insignificant keratinization effect after dehydration, and too high a moisture content will cause the material to be too soft and easy to break under the action of external force; the dehydration treatment can be achieved by the following methods: 1) natural drying as a whole; 2) accelerated drying as a whole; 3) passing through the accelerated drying zone at a fixed speed; 4) completing dehydration by heating the drawing die during the drawing densification process.However, the above-mentioned dehydration treatment methods 1) and 2) are also only applicable to the case where the length of the wood thread on the unit coil is relatively short. Once the wood thread on the unit coil has a certain length, the use of methods 1) and 2) will result in a relatively large difference in the dehydration rate of the wood thread material on the outside of the coil and the wood thread material on the inside of the coil, which will ultimately produce a difference in the degree of keratinization, which has a negative impact on the stability of the material performance; although the dehydration treatment method 3) can achieve the effect of stable keratinization, it requires additional drying equipment compared to method 4); therefore, in the present invention, the dehydration treatment method 4) is preferably used to achieve the effect of uniform dehydration without adding additional equipment. The dehydration treatment preferably makes the moisture content 2 to 20wt.%; the material can complete the keratinization process when the moisture content is below 20wt.%.

[0118] In the present invention, the keratinization treatment is preferably multiple keratinization treatments; the process of multiple keratinization treatments is preferably 1 to 5 times, more preferably 2 to 5 times, and even more preferably 3 to 4 times; the keratinization treatment can be used as a pretreatment step of the overall wire drawing densification process before wire drawing densification, or can be integrated between two wire drawing densification steps during wire drawing densification, or can be performed after wire drawing densification is completed, and there are no special restrictions; the keratinization treatment is preferably performed during wire drawing densification, more preferably as a pretreatment step before wire drawing densification and during wire drawing densification, so that the keratinization treatment and wire drawing densification are staggered, the material can maximize the use of self-densification and external mechanical densification, and the wire drawing densification can also be reduced by keratinization treatment. Specifically, in a specific embodiment provided by the present invention, a water filling treatment of the first keratinization treatment is first performed, and then a dehydration treatment of the first keratinization treatment is performed using the 1 to a levels of the multi-stage drawing die densification, and then a water filling treatment of the second keratinization treatment is performed, and then a+1 to b levels of the multi-stage drawing die densification are used to perform a dehydration treatment of the second keratinization treatment. When the number of keratinization treatments is equal to 2, the multi-stage drawing die densification is continued. When the number of keratinization treatments is greater than 2, the above steps are repeated until the multi-stage drawing die densification is continued after the keratinization treatment is completed, or until the multi-stage drawing film is densified. The specific number can be determined according to the number of keratinization treatments, the number of multi-stage drawing die densification levels and the degree of dehydration treatment of each keratinization treatment; The a is preferably an integer greater than or equal to 1, more preferably an integer of 1 to 5, more preferably an integer of 1 to 4, more preferably an integer of 1 to 3, and most preferably an integer of 1 or 2; when a is equal to 1, the dehydration treatment can be completed by heating a die of the multi-stage drawing die density, and when a is an integer greater than 1, the dehydration treatment is completed by heating multiple die of the multi-stage drawing die density; the b is an integer greater than or equal to a+1, and the specific difference between b and a+1 can be an integer of 0 to 5, more specifically the difference between b and a+1 can be an integer of 0 to 4; specifically, in a specific embodiment provided by the present invention, the 1 to c levels of the multi-stage drawing die density are first performed, and then the first keratinization treatment is performed, and then the c+ of the multi-stage drawing die density is used to perform the water filling treatment. The first keratinization treatment is carried out at levels 1 to d, followed by a water filling treatment for the second keratinization treatment, and then the second keratinization treatment is carried out at levels d+1 to e of the multi-stage wire drawing die densification. When the number of keratinization treatments is equal to 2, the multi-stage wire drawing die densification is continued. When the number of keratinization treatments is greater than 2, the above steps are repeated until the multi-stage wire drawing die densification is continued after the keratinization treatment is completed, or until the multi-stage wire drawing film densification is completed. The specific number can be determined according to the number of keratinization treatments, the number of multi-stage wire drawing die densification levels and the degree of dehydration treatment of each keratinization treatment; the c is preferably an integer greater than or equal to 1, more preferably an integer of 1 to 5, more preferably an integer of 1 to 4, more preferably an integer of 1 to 3, and most preferably an integer of 1 or 2;The d is an integer greater than or equal to c+1, and the specific difference between d and c+1 can be an integer of 0 to 5, and more specifically, the difference between d and c+1 can be an integer of 0 to 4; when the difference between d and c+1 is equal to 0, the dehydration treatment can be completed by heating a single die of the multi-stage drawing die; when the difference between d and c+1 is an integer greater than or equal to 1, the dehydration treatment is completed by heating multiple die of the multi-stage drawing die; similarly, e is an integer greater than or equal to d+1, and the specific difference between e and d+1 can be an integer of 0 to 5, and more specifically, the difference between e and d+1 can be an integer of 0 to 4. Specifically, in some specific embodiments provided by the present invention, with a narrow straight-grained veneer having a cross-sectional size of 4mm×0.23mm, the preferred drawing densification die and keratinization process combination is as follows: a first keratinization water-filled treatment, a die with a 0.535mm outlet diameter, a second keratinization water-filled treatment, a die with a 0.50mm outlet diameter, a die with a 0.46mm outlet diameter, a third keratinization water-filled treatment, a die with a 0.45mm outlet diameter, a die with a 0.44mm outlet diameter, a die with a 0.435mm outlet diameter, and a die with a 0.435mm outlet diameter. By sequentially combining these drawing dies, a wood strand reinforcement material with a diameter of 0.43mm can be prepared, which is 15.8% of the raw material and 3.48 times the density of the raw material (due to a 45% decrease in the quality of the wood), with a significant densification effect. Compared to a drawing densification process without keratinization, keratinization can reduce the number of drawing dies, because keratinization can produce a self-densification effect, replacing part of the external mechanical densification work. ;

[0119] In a specific embodiment provided by the present invention, the water filling treatment in the keratinization treatment is preferably carried out by placing in a high temperature and high humidity environment and / or placing in a high humidity environment; the humidity of the high temperature and high humidity environment is preferably 90-98% RH, more preferably 95-98% RH; the temperature of the high temperature and high humidity environment is preferably 80-100°C; the placement time in the high temperature and high humidity environment is preferably 30-90 min; the humidity of the high humidity environment is preferably 90-98% RH, more preferably 90-95% RH; the placement time in the high humidity environment is preferably 0.5-12 h.

[0120] In order to improve the efficiency of the water filling treatment in the keratinization treatment, in a specific embodiment provided by the present invention, when the number of the keratinization treatment is 1, the water filling treatment is performed by first placing it in a high temperature and high humidity environment and then placing it in a high humidity environment; when the number of the keratinization treatment is multiple times, the water filling treatment of the first keratinization treatment is preferably performed by first placing it in a high temperature and high humidity environment and then placing it in a high humidity environment, and the water filling treatments of the remaining keratinization treatments are performed by placing it in a high humidity environment.

[0121] The wood fiber reinforced material provided by the present invention has a very excellent mechanical reinforcement effect. The composite material obtained by compounding it with a resin has the significant texture, color and texture of a brushed wood panel, combining aesthetics with high performance. At the same time, it has excellent long-term dynamic mechanical properties. Under fatigue test conditions of a maximum stress of 90 MPa and a frequency of 5 Hz, it can reach 1 million cycles without significant performance degradation. In addition, the wood fiber reinforced composite material has excellent flame retardant properties and can achieve a flame retardant grade of self-extinguishing when away from fire without adding any flame retardants. In addition, the wood fiber reinforced material has excellent resistance to ultraviolet aging and resistance to wet heat aging.

[0122] The present invention also provides a wood fiber cloth reinforcement material, comprising the above-mentioned wood fiber reinforcement material.

[0123] The present invention does not impose any particular restrictions on the type of wood fiber cloth reinforcement material, including but not limited to plain cloth, twill cloth, satin cloth, unidirectional cloth, etc. prepared by weaving; or fiber-reinforced biaxial fabric or multiaxial fabric prepared by composite warp knitting equipment; see Figure 10, Figure 10 is a schematic structural diagram of different wood fiber cloth reinforcement materials, Figure 10 shows plain weave on the left and biaxial warp knitting on the right.

[0124] The wood fiber reinforcement material provided by the present invention is a continuous long fiber, which can be obtained by a conventional cloth weaving process to obtain a wood fiber cloth reinforcement material.

[0125] In the present invention, the wood fiber cloth reinforcement material can be formed solely from the wood fiber reinforcement material or from the wood fiber reinforcement material and other yarns, without particular limitation. In a specific embodiment provided by the present invention, the wood fiber cloth reinforcement material is a unidirectional cloth, and the wood fiber reinforcement material can serve as either the warp or the weft of the unidirectional cloth, without particular limitation. Preferably, fine yarn is used in the direction of the non-wood fiber reinforcement material. The yarn diameter is preferably 0.02 to 0.2 mm. The yarn is preferably a thin yarn that is relatively transparent in appearance, so that the wood fiber cloth reinforcement material is essentially visible only from the wood fiber reinforcement material. Thus, the polymer resin composite material formed by the wood fiber cloth reinforcement material and the polymer resin has a brushed wood grain texture, without other non-wood materials, and is more similar to a wooden product. Similarly, the yarn used for knitting is preferably 0.02 to 0.2 mm in diameter and relatively transparent in appearance, so that the unidirectional cloth produced in this way essentially only has the wood fiber reinforcement material visible from the outside.

[0126] In the present invention, the thickness of the wood fiber cloth reinforcement material is determined by the size and stacking relationship of the wood fiber reinforcement material or the wood fiber reinforcement material and the yarn. Preferably, the thickness of the wood fiber cloth reinforcement material is 0.2 to 1.8 mm. The present invention has no special restrictions on the length and width of the wood fiber cloth reinforcement material, which depends on the specifications of the weaving or knitting equipment.

[0127] The present invention also provides a polymer resin composite material, comprising the above-mentioned wood fiber reinforcement material and / or the above-mentioned wood fiber cloth reinforcement material; preferably, it also includes a polymer resin; the polymer resin is a polymer resin well known to those skilled in the art, and there is no special limitation. In the present invention, it preferably includes but is not limited to one or more thermosetting resins such as epoxy resin, unsaturated polyester, polyimide, phenolic resin, polyurethane, bismaleimide resin and thermoplastic resins such as PP, PET, PP, etc.

[0128] When the polymer resin composite material includes a wood fiber reinforced material, the wood fiber reinforced material is preferably regularly distributed in the polymer resin composite material, more preferably unidirectionally regularly distributed, as shown in FIG11 , which is a schematic structural diagram of a polymer resin composite material in which the wood fiber reinforced material is unidirectionally distributed, wherein 1 is a polymer resin and 2 is a wood fiber reinforced composite material.

[0129] Because wood fiber reinforcements are coarse fibers, it's easy to create composite materials with a relatively high volume fraction of reinforcement. For example, under conventional RTM processes, the volume fraction of the wood fiber reinforcement and / or wood fiber cloth reinforcement in the polymer resin composite is preferably 50-75%. This results in the polymer resin composite being both strong and lightweight, with an appearance reminiscent of the texture, color, and feel of brushed wood.

[0130] Because wood fiber reinforcements are primarily composed of cellulose, which contains numerous hydroxyl groups in its chemical structure, they can form hydrogen bonds with the molecular structures of resins such as epoxy resins, phenolic resins, polyurethanes, and unsaturated polyesters. Therefore, wood fiber reinforcements and / or wood fiber cloth reinforcements exhibit excellent bonding with these polymer resins, resulting in polymer resin composites with excellent mechanical properties. The polymer resin composites provided by the present invention preferably have a tensile strength at break of 150 to 750 MPa, and a Young's modulus of 10 to 52 GPa.

[0131] The polymer resin composite material provided by the present invention also has excellent long-term dynamic mechanical properties and can achieve 1 million cycles without significant performance degradation under fatigue test conditions of 90 MPa maximum stress and 5 Hz frequency.

[0132] The polymer resin composite material provided by the present invention has excellent flame retardancy and can achieve a flame retardancy level of self-extinguishing when away from fire without adding any flame retardants. In addition, the polymer resin composite material also has excellent resistance to ultraviolet aging and wet heat aging.

[0133] The polymer resin composite material provided by the present invention is obtained by composite molding wood fiber reinforcement material and / or wood fiber cloth reinforcement material with polymer resin. Referring to FIG12 , FIG12 is a schematic diagram of the preparation process of the polymer resin composite material provided by the present invention.

[0134] In the present invention, the composite molding method is not particularly limited and includes, but is not limited to, one or more of hand lay-up, compression molding, filament winding, pultrusion, spray molding, wet vacuum bagging, vacuum infusion molding, and RTM molding. Because wood fiber reinforced materials are coarse fibers with relatively large pores, polymer resins can easily penetrate the gaps between the fibers. Using various molding processes, composite structural parts with minimal defects can be easily produced, and defects such as bubbles are less likely to occur in wood fiber reinforced composite structural parts.

[0135] In order to further improve the convenience of composite molding, it is preferred to pre-impregnate the wood fiber reinforced material and / or the wood fiber cloth reinforced material and then composite molded with the polymer resin; the prepreg used for the pre-impregnation includes but is not limited to one or more thermosetting prepregs such as epoxy resin and phenolic resin and thermoplastic prepregs such as PP, PET, PP.

[0136] To further illustrate the present invention, the following embodiments provide a wood fiber reinforced material, a preparation method thereof, an application thereof, and a method for chemical modification thereof.

[0137] The reagents used in the following examples are all commercially available.

[0138] Example 1

[0139] 1) Slice

[0140] The raw material is a thin veneer of basswood straight grain, with a thickness of 0.23mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to grain defects, insect bites, knots, burrs, decay, gaps, cracks, etc.

[0141] The veneer is automatically sliced ​​using a conventional veneer shear, with the stacking quantity reaching 80 sheets. Since the target product of the slicing process is straight-grained veneer, the edges of the stacked veneers must be highly aligned, and one or more trimming passes must be performed first to ensure that all the edges of the stacked veneers are aligned. This ensures that the subsequent slicing produces straight-grained veneers of uniform width.

[0142] The width of straight-grain veneer after slicing is 4mm. The angle between the grain and the edge after slicing is 2-5°. Burrs on the edges of straight-grain veneer after slicing should be minimized. Within any 20cm length, the number of burrs > 1mm should be less than or equal to 10, and no burrs should be longer than 5mm and wider than 0.3mm.

[0143] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0144] 2) Chemical modification

[0145] First, a reaction solution with a total volume of 100L was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 100g / L sodium hydroxide and 50g / L sodium sulfite, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 50ml / L. The reactor was heated to 125°C at a rate of 3°C / min, creating a high-pressure state within the system. After maintaining the target temperature and pressure for 5 hours, the temperature was lowered at a rate of 0.2°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 45% weight reduction.

[0146] 3) Splicing

[0147] Cut half of the material at each end of the modified straight-grain veneer to be spliced ​​at a 45° angle, glue one end with conventional wood PVA glue, and then keep the two ends bonded at 70°C for 30 seconds to obtain a modified straight-grain veneer with a length of 5m. Repeat the above steps until a continuous modified veneer with a length of 500m is obtained.

[0148] 4) Twisting

[0149] The continuous modified veneer obtained in step 3) was twisted at a relative humidity of 85-90% RH, a line speed of 1.5 m / min, and a twist of 200 t / m. Two dies were added during the twisting process. The first die had an exit diameter of 0.7 mm and provided only gripping force. The second die (stainless steel) had an exit diameter of 0.55 mm and was heated to 150°C. This allowed the continuous wood fibers to have a more uniform size and shape, resulting in a wood strand.

[0150] 5) Dense drawing

[0151] The twisted veneer is continuously passed through a tungsten steel drawing die with an outlet diameter of 0.53 mm (temperature 220°C) at a linear speed of 1 m / min, and then the obtained sample is placed in a high temperature and high humidity (100°C, 98% RH) steam environment for treatment for 60 minutes. After completion, the sample is transferred to a closed humidity-controlled environmental box (humidity 90-95% RH) for state adjustment for 3 hours; after the state adjustment is completed, the sample is continuously passed through a tungsten steel drawing die with an outlet diameter of 0.50 mm (temperature 220°C) at a linear speed of 0.8 m / min, and after completion, it is continuously passed through a tungsten steel drawing die with an outlet diameter of 0.48 mm (temperature 220°C) in a closed humidity-controlled environmental box (humidity 90-95% RH) for state adjustment for 3 hours, and then continuously passed through a tungsten steel drawing die with an outlet diameter of 0.48 mm (temperature 220°C) at a linear speed of 0.8 m / min to finally obtain a wood fiber reinforced material.

[0152] See FIG13 , which is a photograph of the straight-grained veneer (left), wood strands (middle), and wood fiber reinforcement (right) used in Example 1, with a large background grid of 1 mm.

[0153] The wood fiber reinforced material obtained in Example 1 was tested using an electron scanning microscope, and the obtained scanning electron microscope image is shown in FIG14 .

[0154] FIG15 is a photograph of the wood strand reinforcement material obtained in Example 1.

[0155] The density of the wood fiber reinforced material obtained in Example 1 was measured using a balance and a vernier caliper, and the density was found to be 1.45 g / cm 3 .

[0156] The tensile properties of the wood fiber reinforced material obtained in Example 1 were tested using a universal mechanical testing machine. The two ends of the test sample were glued between two larger pieces of cardboard using wood glue to increase the clamping force at both ends. The two ends were clamped in the upper and lower clamps. The sample gauge length was 50 mm, the tensile rate was 5 mm / min, and the load cell was 50 kg. The specimen was stretched until it broke, and the tensile properties were recorded. The tensile stress-strain curve is shown in Figure 16; the tensile fracture strength was 624 MPa and the Young's modulus was 38 GPa.

[0157] Example 2

[0158] Transparent nylon thread with a diameter of 0.1 mm was used as the warp yarn, and the wood reinforcement material obtained in Example 1 was used as the weft yarn. The warp and weft density was set to 36×200 on a rapier loom, and a gram weight of about 600 g / m was obtained. 2 Wood cord fabric reinforcement.

[0159] FIG17 is a photograph of the wood strand cloth reinforcement material obtained in Example 2.

[0160] FIG18 is a flat-lay photograph of the wood strand cloth reinforcement material obtained in Example 2.

[0161] FIG19 is a photograph of the winding of the wood yarn cloth reinforcement material obtained in Example 2.

[0162] Example 3

[0163] The wood fiber cloth reinforcement material obtained in Example 2 was molded with an epoxy resin (Sicomin GP56 + Cardolite 2401, the pure resin had a tensile strength of 67 MPa and a Young's modulus of 3.3 GPa after curing) using a vacuum-assisted resin transfer molding (VARTM) process, wherein the volume percentage of the wood fiber cloth reinforcement material was 60%, to obtain a wood fiber-reinforced epoxy resin-based composite material.

[0164] See Figures 20 and 21, which are photos of the wood fiber reinforced epoxy resin-based composite material obtained in Example 3.

[0165] The tensile properties of the wood fiber-reinforced epoxy resin-based composite material obtained in Example 3 were tested using a universal mechanical testing machine. The two ends of the test sample were glued between two large pieces of cardboard using wood glue to increase the clamping force at both ends. Each end was clamped to an upper and lower clamp. The sample had a gauge length of 50 mm, a tensile rate of 5 mm / min, and a load cell of 50 kg. The specimen was stretched until it broke, and the tensile properties were recorded. The tensile stress-strain curve is shown in Figure 16.

[0166] The vibration damping performance of the wood fiber reinforced epoxy resin-based composite material was tested using a dynamic mechanical analyzer. A single cantilever beam deformation mode was used, with a frequency of 1 Hz and a fixed deformation of 0.01%. The vibration damping performance diagram is shown in Figure 22. The green color is the wood fiber reinforced epoxy resin-based composite material obtained in Example 3, and the others are common fiber reinforced composite materials, pure epoxy resin and aluminum alloy (vibration damping is an intrinsic property of the partial material, and the vibration damping of the same material system is basically the same). Among them, the preparation method of the fiber reinforced composite material is the same as that in Example 3, except that the reinforcing material is different. As can be seen from Figure 22, the loss factor of the wood fiber reinforced epoxy resin-based composite material obtained in Example 3 is 2.4%, and the shock absorption effect is good.

[0167] The polymer composite material obtained in Example 3 was subjected to fatigue cycle testing according to ASTM D3479 using an electro-hydraulic servo fatigue testing machine (Model: SDS100). The test waveform was sinusoidal, with a frequency of 5 Hz, a stress ratio R = 0.1, a maximum stress of 90 MPa, and a maximum cycle of 1 million cycles. The test environment was 20.5-22.5°C and a relative humidity of 40-45%. The fatigue cycle test results are shown in FIG23 .

[0168] The wet heat aging performance of the wood fiber-reinforced epoxy resin composite material obtained in Example 3 was tested according to ASTM D5229 at a temperature of 50°C and a relative humidity of 90% for 1000 hours, equivalent to five years of environmental exposure in Shanghai. The average tensile strength at break of the wood fiber-reinforced epoxy resin composite material remained unchanged before and after the test, while the average Young's modulus decreased by 16%. Photos of the appearance changes are shown in Figure 24, with the left image showing the pre-aging test and the right image showing the post-aging test.

[0169] The natural outdoor weathering performance of the wood fiber reinforced epoxy resin composite material obtained in Example 3 was tested according to ASTM G154. The test process simulated day and night. During the simulated day, 340nm ultraviolet light with a light intensity of 0.55W / m 2 , lasting 3.8 hours. During the simulated darkness phase, the black box environment was dark, with no light, and 38°C water was sprayed on the test sample surface for 1 hour. This cycle of day and night was repeated until the test period reached 1000 hours. The average tensile strength at break of the wood fiber-reinforced epoxy resin composite increased by 5% and the average Young's modulus increased by 25% before and after the test. Photos of the appearance changes are shown in Figure 25, with the left image showing before and after the aging test and the right image showing after.

[0170] The flame retardancy of the wood fiber reinforced epoxy resin composite material obtained in Example 3 was tested, and the flame retardancy test diagram was shown in FIG26 , wherein the left side shows the ignition process, which lasts for 15 seconds, and the right side shows the phenomenon 5 seconds after leaving the fire.

[0171] The processes of steps 2) chemical modification, 3) splicing, 4) twisting, and 5) densification by drawing in Examples 4 to 10 are the same as those in Example 1. Only the process and parameters of step 1) slicing are changed.

[0172] Example 4

[0173] The raw material is a thin veneer of basswood straight grain, with a thickness of 0.23mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to grain defects, insect bites, knots, burrs, decay, gaps, cracks, etc.

[0174] We used a purely manual method to slice and slice to obtain the exact angle between the grain and the edge, thereby testing the effect of this parameter on processing performance and mechanical properties. The method is as follows: Use a marker to draw a cutting range with a 2° angle to the grain and a width of 4mm, then cut with a utility knife.

[0175] The edge burrs of straight-grained veneer after slicing should be avoided as much as possible. Within any 20cm length, the number of burrs > 1mm is less than or equal to 10, and the length of no burrs is > 5mm and the width is > 0.3mm.

[0176] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0177] Example 5

[0178] The raw material is a thin veneer of basswood straight grain, with a thickness of 0.23mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to grain defects, insect bites, knots, burrs, decay, gaps, cracks, etc.

[0179] We used a purely manual method to slice and slice to obtain the exact angle between the grain and the edge, thereby testing the effect of this parameter on processing performance and mechanical properties. The method is as follows: Use a marker to draw a cutting range with a 4° angle to the grain and a width of 4mm, then cut with a utility knife.

[0180] The edge burrs of straight-grained veneer after slicing should be avoided as much as possible. Within any 20cm length, the number of burrs > 1mm is less than or equal to 10, and the length of no burrs is > 5mm and the width is > 0.3mm.

[0181] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0182] Comparative Example 1

[0183] The raw material is a thin veneer of basswood straight grain, with a thickness of 0.23mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to grain defects, insect bites, knots, burrs, decay, gaps, cracks, etc.

[0184] We used a purely manual method to slice and slice to obtain the exact angle between the grain and the edge, thereby testing the effect of this parameter on processing performance and mechanical properties. The method is as follows: Use a marker to draw a cutting range with a 20° angle to the grain and a width of 4mm, then cut with a utility knife.

[0185] The edge burrs of straight-grained veneer after slicing should be avoided as much as possible. Within any 20cm length, the number of burrs > 1mm is less than or equal to 10, and the length of no burrs is > 5mm and the width is > 0.3mm.

[0186] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0187] Comparative Example 2

[0188] The raw material is a thin veneer of basswood straight grain, with a thickness of 0.23mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to grain defects, insect bites, knots, burrs, decay, gaps, cracks, etc.

[0189] We used a purely manual method to slice and slice to obtain the exact angle between the grain and the edge, thereby testing the effect of this parameter on processing performance and mechanical properties. The method is as follows: Use a marker to draw a cutting range with a 49° angle to the grain and a width of 4mm, then cut with a utility knife.

[0190] The edge burrs of straight-grained veneer after slicing should be avoided as much as possible. Within any 20cm length, the number of burrs > 1mm is less than or equal to 10, and the length of no burrs is > 5mm and the width is > 0.3mm.

[0191] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0192] Comparative Example 3

[0193] The raw material is a thin veneer of basswood straight grain, with a thickness of 0.23mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to grain defects, insect bites, knots, burrs, decay, gaps, cracks, etc.

[0194] We used a purely manual method to slice and slice to obtain the exact angle between the grain and the edge, thereby testing the effect of this parameter on processing performance and mechanical properties. The method is as follows: Use a marker to draw a cutting range with a 61° angle to the grain and a width of 4mm, then cut with a utility knife.

[0195] The edge burrs of straight-grained veneer after slicing should be avoided as much as possible. Within any 20cm length, the number of burrs > 1mm is less than or equal to 10, and the length of no burrs is > 5mm and the width is > 0.3mm.

[0196] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0197] Microscope images of the narrow straight-grain veneers obtained in Examples 4-5 and Comparative Examples 1-3 are shown in FIG27 , which illustrate the textures and edge angles of the different narrow straight-grain veneers in Examples 4-5 and Comparative Examples 1-3.

[0198] The test results of the processing properties and tensile properties of the wood fiber reinforced materials obtained in Examples 4 to 5 and Comparative Examples 1 to 3 are shown in Table 1.

[0199] Table 1 Test results of processing properties and tensile properties of wood fiber reinforced materials in Examples 4 to 5 and Comparative Examples 1 to 3

[0200] Example 6

[0201] The raw material is maple straight-grain veneer with a thickness of 0.23mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to grain defects, insect-eaten spots, knots, burrs, decay, gaps, cracks, etc.

[0202] The veneer is automatically sliced ​​using a conventional veneer shear, with the stacking quantity reaching 80 sheets. Since the target product of the slicing process is straight-grained veneer, the edges of the stacked veneers must be highly aligned, and one or more trimming passes must be performed first to ensure that all the edges of the stacked veneers are aligned. This ensures that the subsequent slicing produces straight-grained veneers of uniform width.

[0203] The width of straight-grain veneer after slicing is 4mm. The angle between the grain and the edge after slicing is 2-5°. Burrs on the edges of straight-grain veneer after slicing should be minimized. Within any 20cm length, the number of burrs > 1mm should be less than or equal to 10, and no burrs should be longer than 5mm and wider than 0.3mm.

[0204] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0205] The remaining steps are the same as those in Example 1.

[0206] The average tensile strength at break of the wood fiber reinforced material obtained was 290 MPa, and the average Young's modulus was 29 GPa.

[0207] Example 7

[0208] The raw material is oak straight-grain veneer with a thickness of 0.23mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to grain defects, insect-eaten spots, knots, burrs, decay, gaps, cracks, etc.

[0209] The veneer is automatically sliced ​​using a conventional veneer shear, with the stacking quantity reaching 80 sheets. Since the target product of the slicing process is straight-grained veneer, the edges of the stacked veneers must be highly aligned, and one or more trimming passes must be performed first to ensure that all the edges of the stacked veneers are aligned. This ensures that the subsequent slicing produces straight-grained veneers of uniform width.

[0210] The width of straight-grain veneer after slicing is 4mm. The angle between the grain and the edge after slicing is 2-5°. Burrs on the edges of straight-grain veneer after slicing should be minimized. Within any 20cm length, the number of burrs > 1mm should be less than or equal to 10, and no burrs should be longer than 5mm and wider than 0.3mm.

[0211] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0212] The remaining steps are the same as those in Example 1.

[0213] The average tensile strength of the wood fiber reinforced material obtained is 253 MPa, and the average Young's modulus is 22 GPa.

[0214] Example 8

[0215] The raw material is a thin veneer of basswood straight grain, with a thickness of 0.23mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to grain defects, insect bites, knots, burrs, decay, gaps, cracks, etc.

[0216] The veneer is automatically sliced ​​using a conventional veneer shear, with the stacking quantity reaching 80 sheets. Since the target product of the slicing process is straight-grained veneer, the edges of the stacked veneers must be highly aligned, and one or more trimming passes must be performed first to ensure that all the edges of the stacked veneers are aligned. This ensures that the subsequent slicing produces straight-grained veneers of uniform width.

[0217] The width of straight-grain veneer after slicing is 2mm. The angle between the grain and the edge after slicing is 2-5°. Burrs on the edges of straight-grain veneer after slicing should be minimized. Within any 20cm length, the number of burrs > 1mm should be less than or equal to 10, and no burrs should be longer than 5mm and wider than 0.3mm.

[0218] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0219] The parameters of the subsequent process of Example 8 are the same as those of Example 1, except for the outlet diameter of the die used in the twisting and wire drawing densification processes. The specific parameters are as follows:

[0220] The outlet diameter of the first twisting die is 0.5 mm, and the outlet diameter of the second twisting die is 0.43 mm.

[0221] The outlet diameter of the first die for dense drawing is 0.375mm, the outlet diameter of the second die is 0.35mm, and the outlet diameter of the third die is 0.34mm.

[0222] The diameter of the wood fiber reinforced material finally obtained was 0.33 mm, and other properties were similar to those of Example 1.

[0223] Example 9

[0224] The raw material is a thin veneer of basswood straight grain, with a thickness of 0.23mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to grain defects, insect bites, knots, burrs, decay, gaps, cracks, etc.

[0225] The veneer is automatically sliced ​​using a conventional veneer shear, with the stacking quantity reaching 80 sheets. Since the target product of the slicing process is straight-grained veneer, the edges of the stacked veneers must be highly aligned, and one or more trimming passes must be performed first to ensure that all the edges of the stacked veneers are aligned. This ensures that the subsequent slicing produces straight-grained veneers of uniform width.

[0226] The width of straight-grain veneer after slicing is 6mm. The angle between the grain and the edge after slicing is 2-5°. Burrs on the edges of straight-grain veneer after slicing should be minimized. Within any 20cm length, the number of burrs > 1mm should be less than or equal to 10, and no burrs should be longer than 5mm and wider than 0.3mm.

[0227] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0228] The parameters of the subsequent process of Example 9 are the same as those of Example 1, except for the outlet diameter of the die used in the twisting and wire drawing densification processes. The specific parameters are as follows:

[0229] The outlet diameter of the first twisting die is 0.87 mm, and the outlet diameter of the second twisting die is 0.75 mm.

[0230] The outlet diameter of the first die for dense drawing is 0.7 mm, the outlet diameter of the second die is 0.62 mm, and the outlet diameter of the third die is 0.59 mm.

[0231] The diameter of the wood fiber reinforced material finally obtained was 0.57 mm, and other properties were similar to those of Example 1.

[0232] Example 10

[0233] The raw material is thin veneer of basswood straight grain, with a thickness of 0.35mm, a length of 2.5m and a width of 15cm. The surface of the veneer has no obvious defects, including but not limited to texture defects, insect bites, knots, burrs, decay, gaps, cracks, etc.

[0234] The veneer is automatically sliced ​​using a conventional veneer shear, with the stacking quantity reaching 80 sheets. Since the target product of the slicing process is straight-grained veneer, the edges of the stacked veneers must be highly aligned, and one or more trimming passes must be performed first to ensure that all the edges of the stacked veneers are aligned. This ensures that the subsequent slicing produces straight-grained veneers of uniform width.

[0235] The width of straight-grain veneer after slicing is 4mm. The angle between the grain and the edge after slicing is 2-5°. Burrs on the edges of straight-grain veneer after slicing should be minimized. Within any 20cm length, the number of burrs > 1mm should be less than or equal to 10, and no burrs should be longer than 5mm and wider than 0.3mm.

[0236] The standard deviation and range of the width after slicing should be as small as possible. The standard deviation of the same batch should be <0.1mm and the range should be <0.4mm.

[0237] The parameters of the subsequent process of Example 10 are the same as those of Example 1, except for the outlet diameter of the die used in the twisting and wire drawing densification processes. The specific parameters are as follows:

[0238] The outlet diameter of the first twisting die is 0.86 mm, and the outlet diameter of the second twisting die is 0.68 mm.

[0239] The outlet diameter of the first die for dense drawing is 0.64mm, the outlet diameter of the second die is 0.61mm, and the outlet diameter of the third die is 0.59mm.

[0240] The diameter of the wood fiber reinforced material finally obtained was 0.57 mm, and other properties were similar to those of Example 1.

[0241] The steps 1) slicing, 3) splicing, 4) twisting, and 5) densification in Examples 11 to 23 are the same as those in Example 1. Only the process and parameters of step 2) chemical modification are changed.

[0242] Example 11

[0243] First, a reaction solution with a total volume of 20L was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 100g / L sodium hydroxide and 50g / L sodium sulfite, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 10.8ml / L. The reactor was heated to 125°C at a rate of 3°C / min, creating a high-pressure state within the system. After maintaining the target temperature and pressure for 6 hours, the temperature was lowered at a rate of 0.2°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 48.2% weight reduction.

[0244] Example 12

[0245] First, a reaction solution with a total volume of 20L was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 100g / L sodium hydroxide and 50g / L sodium sulfite, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 10.8ml / L. The reactor was heated to 116°C at a rate of 2.5°C / min, creating a high-pressure state within the system. After maintaining the target temperature and pressure for 6 hours, the temperature was lowered at a rate of 1.0°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 39.6% weight reduction.

[0246] Example 13

[0247] First, a reaction solution with a total volume of 20L was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 50g / L sodium hydroxide and 50g / L sodium sulfite, and the pH of the reaction solution was 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 5.4ml / L. The reactor was heated to 116°C at a heating rate of 5°C / min, creating a high-pressure state within the entire system. After maintaining the target temperature and pressure for 6 hours, the temperature was lowered at a rate of 0.5°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 40.5% weight reduction.

[0248] Example 14

[0249] First, a reaction solution with a total volume of 20L was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 100g / L sodium hydroxide and 50g / L sodium sulfite, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 10.8ml / L. The reactor was heated to 116°C at a rate of 2°C / min, creating a high-pressure state within the system. After maintaining the target temperature and pressure for 8 hours, the temperature was lowered at a rate of 0.5°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 40.7% weight reduction.

[0250] Example 15

[0251] First, a reaction solution with a total volume of 20L was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 100g / L sodium hydroxide and 50g / L sodium sulfite, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 32.4ml / L. The reactor was heated to 125°C at a rate of 0.5°C / min, creating a high-pressure state within the system. After maintaining the target temperature and pressure for 6 hours, the temperature was lowered at a rate of 2°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 45.2% weight reduction.

[0252] Example 16

[0253] First, a reaction solution with a total volume of 20L was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 100g / L sodium hydroxide and 75g / L sodium sulfite, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 54ml / L. The reactor was heated to 125°C at a rate of 0.2°C / min, creating a high-pressure state within the system. After maintaining the target temperature and pressure for 6 hours, the temperature was lowered at a rate of 1°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 45.6% weight reduction.

[0254] Example 17

[0255] First, a reaction solution with a total volume of 100 L was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 100 g / L sodium hydroxide and 50 g / L sodium sulfite, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 21.6 mL / L. The reactor was heated to 125°C at a rate of 1.5°C / min, creating a high-pressure state within the system. After maintaining the target temperature and pressure for 6 hours, the temperature was lowered at a rate of 1°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 45.1% weight reduction.

[0256] Example 18

[0257] First, a reaction solution with a total volume of 100L was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 100g / L sodium hydroxide and 50g / L sodium sulfite, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 54ml / L. The reactor was heated to 125°C at a heating rate of 3°C / min, creating a high-pressure state within the entire system. After maintaining the target temperature and pressure for 6.5 hours, the temperature was lowered at a rate of 1°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 49.6% weight reduction.

[0258] Example 19

[0259] First, a reaction solution with a total volume of 3 L was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 100 g / L sodium hydroxide and 50 g / L sodium sulfite, and the pH of the reaction solution was 14. The reaction solution and straight-grained veneer were then placed in a round-bottom flask at a material ratio of 9 mL / L. The solution was heated in an oil bath for approximately 1 hour until the solution reached a boiling state of approximately 105°C. Reflux was then initiated to bring the entire internal system to atmospheric pressure, which was maintained for 48 hours. The solution was then cooled to room temperature over approximately 2 hours. The round-bottom flask was then opened and the modified straight-grained veneer was removed. The modified straight-grained veneer was then washed with water and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 46.1% weight reduction.

[0260] Example 20

[0261] First, a reaction solution with a total volume of 180 ml was prepared. Sodium hydroxide and sodium sulfite were dissolved in water to a concentration of 100 g / L sodium hydroxide and 25 g / L sodium sulfite, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a 500 ml hydrothermal reactor at a material ratio of 21 ml / L. The reaction mixture was heated to a target temperature of 130°C over approximately one hour and then maintained at this temperature and pressure for six hours, maintaining the entire internal system under high pressure. After cooling to room temperature over two hours, the 500 ml hydrothermal reactor was opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 45.3% weight reduction.

[0262] Example 21

[0263] First, a reaction solution with a total volume of 100L was prepared. Potassium hydroxide and sodium sulfite were dissolved in water to a concentration of 145g / L potassium hydroxide and 50g / L sodium sulfite, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 54ml / L. The reactor was heated to 125°C at a rate of 3°C / min, creating a high-pressure state within the system. After maintaining the target temperature and pressure for 6.5 hours, the temperature was lowered at a rate of 1°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 48.8% weight reduction.

[0264] Example 22

[0265] First, a reaction solution with a total volume of 100 L was prepared. Sodium hydroxide and sodium hydroxymethanesulfonate were dissolved in water to a concentration of 100 g / L sodium hydroxide and 84 g / L sodium hydroxymethanesulfonate, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 54 mL / L. The reactor was heated to 125°C at a rate of 3°C / min, creating a high-pressure state within the reactor. After maintaining the target temperature and pressure for 6 hours, the temperature was lowered at a rate of 3°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 46.2% weight reduction.

[0266] Example 23

[0267] First, a reaction solution with a total volume of 100 L was prepared. Sodium hydroxide and sodium hydroxymethanesulfonate were dissolved in water to a concentration of 100 g / L sodium hydroxide and 72 g / L sodium hydroxymethanesulfonate, with a pH of 14. The reaction solution and straight-grained veneer were then placed in a reactor at a material ratio of 54 mL / L. The reactor was heated to 125°C at a rate of 3°C / min, creating a high-pressure state within the reactor. After maintaining the target temperature and pressure for 6 hours, the temperature was lowered at a rate of 3°C / min to ambient temperature and pressure. The reactor was then opened, the modified straight-grained veneer removed, washed, and dried to complete the chemical modification process. The resulting modified straight-grained veneer had a 44.1% weight reduction.

[0268] The properties of the wood fiber reinforced materials obtained in Examples 11 to 23 were tested, and the results are shown in Table 2.

[0269] Table 2 Performance test results of wood fiber reinforced materials in Examples 11 to 23

[0270] The processes of steps 1) slicing, 2) chemical modification, and 3) splicing in Examples 24-29 were the same as those in Example 1. However, the process and parameters of step 4) twisting were changed, resulting in changes in the dimensions of the wood strands. Consequently, the exit diameter of the die for the dense drawing process in step 5) was also changed.

[0271] Example 24

[0272] The continuous modified veneer obtained in step 3) was twisted in an ambient relative humidity of 85-90% RH, at a line speed of 1.5 m / min and a twist of 80 t / m. Two dies were added during the twisting process. The first die had an exit diameter of 0.82 mm and provided only gripping force. The second die (stainless steel) had an exit diameter of 0.78 mm and was heated to 150°C. This allowed the continuous wood fibers to have a more uniform size and shape, resulting in a wood strand.

[0273] The outlet diameter of the first die for dense drawing is 0.72mm, the outlet diameter of the second die is 0.69mm, and the outlet diameter of the third die is 0.68mm.

[0274] The density and diameter of the wood fiber reinforced material obtained in Example 1 were measured using a balance and a vernier caliper, and the density was found to be 0.93 g / cm 3 , with a diameter of 0.65mm.

[0275] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 354 MPa and Young's modulus was 16 GPa.

[0276] Example 25

[0277] The continuous modified veneer obtained in step 3) was twisted at a relative humidity of 85-90% RH, a line speed of 1.5 m / min, and a twist of 300 t / m. Two dies were added during the twisting process. The first die had an exit diameter of 0.89 mm and provided only gripping force. The second die (stainless steel) had an exit diameter of 0.84 mm and was heated to 150°C. This allowed the continuous wood fibers to have a more uniform size and shape, resulting in a wood strand.

[0278] The outlet diameter of the first die for dense drawing is 0.82mm, the outlet diameter of the second die is 0.79mm, and the outlet diameter of the third die is 0.78mm.

[0279] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.75 g / cm 3 , with a diameter of 0.76mm.

[0280] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 339 MPa and Young's modulus was 43 GPa.

[0281] Example 26

[0282] The continuous modified veneer obtained in step 3) was twisted in an ambient relative humidity of 85-90% RH, at a line speed of 1.5 m / min and a twist of 220 t / m. Two dies were added during twisting. The first die had an exit diameter of 0.71 mm and provided only gripping force. The second die (stainless steel) had an exit diameter of 0.57 mm and was heated to 150°C. This achieved more uniform size and shape of the continuous wood fibers, resulting in a wood strand.

[0283] The outlet diameter of the first die for dense drawing is 0.54mm, the outlet diameter of the second die is 0.51mm, and the outlet diameter of the third die is 0.50mm.

[0284] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.45 g / cm 3 , with a diameter of 0.49mm.

[0285] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 439 MPa and Young's modulus was 51 GPa.

[0286] Example 27

[0287] The continuous modified veneer obtained in step 3) was twisted in an ambient relative humidity of 85-90% RH, at a line speed of 1.5 m / min and a twist of 180 t / m. Two dies were added during twisting. The first die had an exit diameter of 0.67 mm and provided only gripping force. The second die (stainless steel) had an exit diameter of 0.51 mm and was heated to 150°C. This allowed the continuous wood fibers to have a more uniform size and shape, resulting in a wood strand.

[0288] The outlet diameter of the first die for dense drawing is 0.49 mm, the outlet diameter of the second die is 0.46 mm, and the outlet diameter of the third die is 0.44 mm.

[0289] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.17 g / cm 3 , with a diameter of 0.43mm.

[0290] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 419 MPa and Young's modulus was 39 GPa.

[0291] Example 28

[0292] The continuous modified veneer obtained in step 3) was twisted in an ambient relative humidity of 85-90% RH, at a line speed of 1.5 m / min and a twist of 150 t / m. Two dies were added during twisting. The first die had an exit diameter of 0.77 mm and provided only gripping force. The second die (stainless steel) had an exit diameter of 0.66 mm and was heated to 150°C. This achieved more uniform size and shape of the continuous wood fibers, resulting in a wood strand.

[0293] The outlet diameter of the first die for dense drawing is 0.62mm, the outlet diameter of the second die is 0.60mm, and the outlet diameter of the third die is 0.59mm.

[0294] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.13 g / cm 3 , with a diameter of 0.57mm.

[0295] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 371 MPa and Young's modulus was 32 GPa.

[0296] Example 29

[0297] The continuous modified veneer obtained in step 3) was twisted in an ambient relative humidity of 85-90% RH, at a line speed of 1.5 m / min and a twist of 150 t / m. Two dies were added during the twisting process. The first die had an exit diameter of 0.86 mm and provided only gripping force. The second die (stainless steel) had an exit diameter of 0.79 mm and was heated to 150°C. This achieved more uniform size and shape of the continuous wood fibers, resulting in a wood strand.

[0298] The outlet diameter of the first die for dense drawing is 0.76mm, the outlet diameter of the second die is 0.74mm, and the outlet diameter of the third die is 0.73mm.

[0299] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 0.98 g / cm 3 , with a diameter of 0.71mm.

[0300] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 227 MPa and Young's modulus was 21 GPa.

[0301] The properties of the wood fiber reinforced materials obtained in Examples 24 to 29 are shown in Table 3.

[0302] Table 3 Performance test results of wood fiber reinforced materials in Examples 24 to 29

[0303] The processes of steps 1) slicing, 2) chemical modification, 3) splicing, and 4) twisting in Examples 30 to 36 are the same as those in Example 1. Only the process and parameters of step 5) densification are changed.

[0304] Example 30

[0305] The twisted veneer was continuously passed through a tungsten steel wire drawing die with an outlet diameter of 0.65 mm (temperature 60°C) at a linear speed of 0.5 m / min, and then the obtained sample was placed in a high temperature and high humidity (100°C, 98% RH) steam environment for 90 minutes. After completion, the sample was transferred to a closed humidity-controlled environmental box (humidity 90-95% RH) for state adjustment for 12 hours to make the moisture content of the sample reach 120 wt%; the sample after state adjustment was continuously passed through a tungsten steel wire drawing die with an outlet diameter of 0.65 mm (temperature 60°C) at a linear speed of 0.5 m / min. After passing through tungsten steel wire drawing dies with outlet diameters of 0.64mm, 0.63mm, 0.62mm, 0.61mm, and 0.60mm (temperature 100°C), the moisture content of the wood line is tested to be lower than 20%; after completion, it is conditioned in a closed humidity-controlled environmental chamber (humidity 90-95% RH) for 3 hours, and then continuously passed through tungsten steel wire drawing dies with outlet diameters of 0.59mm, 0.58mm, 0.56mm, 0.54mm, and 0.52mm at a linear speed of 0.8m / min (temperature 120 ℃), the moisture content of the wood line is tested to be less than 10%; after completion, it is conditioned in a closed humidity-controlled environmental box (humidity 90-95% RH) for 2 hours, and then continuously passes through tungsten steel drawing dies with outlet diameters of 0.51mm, 0.50mm, etc. (temperature 120 ℃) ​​at a linear speed of 1.5m / min, and the moisture content of the wood line is tested to be less than 8%; after completion, it is conditioned in a closed humidity-controlled environmental box (humidity 90-95% RH) for 1 hour, and then at a linear speed of 3m / min The linear speed continuously passes through tungsten steel drawing dies with outlet diameters of 0.49mm, 0.48mm, etc. (temperature 150°C), and the moisture content of the wood line is tested to be lower than 5% after passing. After completion, the state is adjusted for 0.5h in a closed humidity-controlled environmental box (humidity 90-95% RH), and then the linear speed is continuously passed through tungsten steel drawing dies with outlet diameters of 0.47mm, 0.46mm, etc. (temperature 250°C) at a linear speed of 5m / min. The moisture content of the wood line is tested to be lower than 2% after passing, and finally a wood fiber reinforced material is obtained.

[0306] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.68 g / cm 3 , with a diameter of 0.44mm.

[0307] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 581 MPa and Young's modulus was 51 GPa.

[0308] Example 31

[0309] The twisted veneer is continuously passed through a tungsten steel drawing die with an outlet diameter of 0.65 mm (temperature 120°C) at a linear speed of 5 m / min, and then the obtained sample is placed in a high temperature and high humidity (100°C, 98% RH) steam environment for treatment for 90 minutes. After completion, the sample is transferred to a closed humidity-controlled environmental box (humidity 90-95% RH) for state adjustment for 12 hours to make the moisture content of the sample reach 120wt.%; the sample after state adjustment is continuously passed through tungsten steel drawing dies with outlet diameters of 0.60 mm, 0.58 mm, 0.56 mm, etc. (temperature 220°C) at a linear speed of 0.2 m / min. After passing the test, the moisture content of the wood wire is tested to be less than 8%; finally, a wood fiber reinforced material is obtained.

[0310] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.17 g / cm 3 , with a diameter of 0.55mm.

[0311] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 336 MPa and Young's modulus was 21 GPa.

[0312] Example 32

[0313] The twisted veneer is continuously passed through a tungsten steel drawing die with an outlet diameter of 0.56 mm and 0.53 mm (temperature 180°C) at a linear speed of 1.2 m / min, and then the obtained sample is placed in a high temperature and high humidity (100°C, 98% RH) steam environment for treatment for 30 minutes. After completion, the sample is transferred to a closed humidity-controlled environmental box (humidity 90-95% RH) for state adjustment for 3 hours to make the moisture content of the sample reach 60 wt.%; the sample after state adjustment is continuously passed through a tungsten steel drawing die with an outlet diameter of 0.52 mm and 0.50 mm (temperature 250°C) at a linear speed of 0.6 m / min, and the moisture content of the wood wire tested after passing is less than 2%; finally, a wood fiber reinforced material is obtained.

[0314] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.33 g / cm 3 , with a diameter of 0.51mm.

[0315] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 431 MPa and Young's modulus was 32 GPa.

[0316] Example 33

[0317] The twisted veneer is continuously passed through a tungsten steel drawing die with an outlet diameter of 0.50 mm (temperature 180°C) at a linear speed of 0.8 m / min, and then the obtained sample is placed in a high temperature and high humidity (100°C, 98% RH) steam environment for treatment for 30 minutes. After completion, the sample is transferred to a closed humidity-controlled environmental box (humidity 90-95% RH) for state adjustment for 12 hours to make the moisture content of the sample reach 80wt%; the sample after state adjustment is passed through a tungsten steel drawing die with an outlet diameter of 0.48 mm (temperature 220°C) at a linear speed of 0.4 m / min, and the moisture content of the wood wire tested after passing is less than 10%; finally, a wood fiber reinforced material is obtained.

[0318] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.38 g / cm 3 , with a diameter of 0.47mm.

[0319] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 509 MPa and Young's modulus was 52 GPa.

[0320] Example 34

[0321] The twisted veneer is continuously passed through a tungsten steel drawing die with an outlet diameter of 0.56 mm (temperature 120°C) at a linear speed of 3 m / min, and the obtained sample is then placed in a high temperature and high humidity (100°C, 98% RH) steam environment for treatment for 30 minutes. After completion, the sample is transferred to a closed humidity-controlled environmental box (humidity 90-95% RH) for state adjustment for 12 hours to make the moisture content of the sample reach 90wt.%; the sample after state adjustment is continuously passed through tungsten steel drawing dies with outlet diameters of 0.53 mm, 0.52 mm, etc. (temperature 150°C) at a linear speed of 0.6 m / min, and the moisture content of the wood line after passing the test is less than 15%; after completion, the sample is state adjusted in a closed humidity-controlled environmental box (humidity 90-95% RH) for 6 hours, and then passed through a tungsten steel drawing die with an outlet diameter of 0.50 mm (temperature 200°C) at a linear speed of 0.8 m / min, and the moisture content of the wood line after passing the test is less than 5%; finally, a wood fiber reinforced material is obtained.

[0322] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.29 g / cm 3 , with a diameter of 0.49mm.

[0323] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 383 MPa and Young's modulus was 38 GPa.

[0324] Example 35

[0325] The twisted veneer is continuously passed through a tungsten steel wire drawing die with an outlet diameter of 0.56 mm (temperature 120°C) at a linear speed of 1.5 m / min, and then the obtained sample is placed in a high temperature and high humidity (100°C, 98% RH) steam environment for treatment for 60 minutes. After completion, the sample is transferred to a closed humidity-controlled environmental box (humidity 90-95% RH) for state adjustment for 9 hours to make the moisture content of the sample reach 100wt.%; the sample after state adjustment is continuously passed through tungsten steel wire drawing dies with outlet diameters of 0.54 mm, 0.52 mm, etc. (temperature 150°C) at a linear speed of 1.2 m / min, and the moisture content of the sample after passing through the wire is 100 wt.%. The moisture content test is lower than 15%; after completion, it is conditioned in a closed humidity-controlled environmental box (humidity 90-95% RH) for 3 hours, and then passes through a tungsten steel drawing die with an outlet diameter of 0.50mm and 0.49mm (temperature 180°C) at a linear speed of 1.0m / min, and the moisture content test of the wood line after passing is lower than 10%; after completion, it is conditioned in a closed humidity-controlled environmental box (humidity 90-95% RH) for 1 hour, and then passes through a tungsten steel drawing die with an outlet diameter of 0.47mm (temperature 220°C) at a linear speed of 0.8m / min, and the moisture content test of the wood line after passing is lower than 5%; finally, a wood fiber reinforced material is obtained.

[0326] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.49 g / cm 3 , with a diameter of 0.48mm.

[0327] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 493 MPa and Young's modulus was 47 GPa.

[0328] Example 36

[0329] The twisted veneer is continuously passed through a tungsten steel drawing die with an outlet diameter of 0.60 mm (temperature 100°C) at a linear speed of 1.5 m / min, and the obtained sample is then placed in a high temperature and high humidity (100°C, 98% RH) steam environment for 60 minutes. After completion, the sample is transferred to a closed humidity-controlled environmental box (humidity 90-95% RH) for state adjustment for 12 hours to make the moisture content of the sample reach 120 wt.%; after the state adjustment, the sample is continuously passed through tungsten steel drawing dies with outlet diameters of 0.58 mm, 0.56 mm, 0.54 mm, etc. (temperature 120°C) at a linear speed of 1.2 m / min. After passing the test, the moisture content of the wood line is less than 15%; after completion, the sample is state adjusted for 9 hours in a closed humidity-controlled environmental box (humidity 90-95% RH). , and then passed through tungsten steel drawing dies with outlet diameters of 0.54mm and 0.52mm (temperature 150°C) at a linear speed of 1.0m / min, and the moisture content of the wood line was tested to be less than 10%; after completion, it was conditioned in a closed humidity-controlled environmental box (humidity 90-95% RH) for 6 hours, and then passed through a tungsten steel drawing die with an outlet diameter of 0.50mm (temperature 180°C) at a linear speed of 0.8m / min, and the moisture content of the wood line was tested to be less than 5%; after completion, it was conditioned in a closed humidity-controlled environmental box (humidity 90-95% RH) for 6 hours, and then passed through a tungsten steel drawing die with an outlet diameter of 0.47mm (temperature 180°C) at a linear speed of 0.6m / min, and the moisture content of the wood line was tested to be less than 2%, and finally a wood fiber reinforced material was obtained.

[0330] The density and diameter of the obtained wood fiber reinforced material were tested using a balance and a vernier caliper, and the density was found to be 1.51 g / cm 3 , with a diameter of 0.46mm.

[0331] The mechanical properties of the obtained wood fiber reinforced material were tested, and the results showed that its tensile strength at break was 542 MPa and Young's modulus was 53 GPa.

[0332] The properties of the wood fiber reinforced materials obtained in Examples 30 to 36 are shown in Table 4.

[0333] Table 4 Performance test results of wood fiber reinforced materials in Examples 30 to 36

[0334] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A wood fiber reinforced material, characterized in that: The wood fiber reinforced material comprises compressed wood cell walls; the diameter of the wood fiber reinforced material is 0.2 to 0.8 mm; the density of the wood fiber reinforced material is 0.9 to 1.8 g / cm 3 ; The density of the wood fiber reinforced material is 1.64 to 3.6 times that of the wood raw material.

2. The wood fiber reinforced material according to claim 1, characterized in that The tensile strength of the wood fiber reinforced material is 200-800 MPa; the Young's modulus of the wood fiber reinforced material is 15-60 GPa.

3. The wood fiber reinforced material according to claim 1, characterized in that The wood fiber reinforcement material is a continuous filament; a single strand of the continuous filament comprises a single twisted wire; and the cross section of the wire is circular or approximately circular.

4. The wood fiber reinforced material according to claim 1, characterized in that The surface and interior of the wood fiber reinforced material have a microscopic layered wrinkle structure; the inclination of the layered wrinkle structure to the axial direction of the wood fiber reinforced material is 5° to 40°.

5. The wood fiber reinforced material according to claim 1, characterized in that The ratio of natural wood in the wood fiber reinforcement material is 99.95 to 99.993 wt.%.

6. A method for preparing a wood fiber reinforced material, characterized in that: The following steps are involved: S1) chemically modifying the narrow straight-grain veneer to obtain modified veneer; S2) splicing the modified veneers to obtain continuous veneers; S3) twisting the continuous veneer to obtain wood yarn; S4) drawing the wood strands into a dense form to obtain a wood fiber reinforced material.

7. The preparation method according to claim 6, characterized in that The thickness of the narrow straight-grain veneer is 0.1 to 0.5 mm; the width of the narrow straight-grain veneer is 0.5 to 8 mm; and / or, The angle between the grain and the edge of the narrow straight-grain veneer is less than 10°; Within a length of 20 cm, the number of burrs larger than 1 mm on the edge of the narrow straight-grain veneer is less than or equal to 10, and the length without burrs is greater than 5 mm and the width is greater than 0.3 mm.

8. The preparation method according to claim 6, characterized in that The chemical modification in step S1) is carried out in a closed high-pressure system; the temperature of the chemical modification is 100-150°C; the pressure of the chemical modification is 0.07-1 MPa; the time of the chemical modification is 2-12 hours; and the heating rate of the chemical modification is 0.5-5°C / min; Alternatively, the chemical modification is carried out under normal pressure; the time of the chemical modification is 24 to 72 hours; the temperature of the chemical modification is 100° C., the boiling temperature of water; the heating rate of the chemical modification is 0.5 to 5° C. / min; And / or, after chemical modification, the reaction solution is cooled to obtain modified veneer; the cooling rate is 1-10°C / min; the cooling includes water cooling or air cooling.

9. The preparation method according to claim 6, characterized in that The chemically modified modification liquid in step S1) includes an alkaline substance and a sulfonating agent; The pH value of the modified liquid is 12 to 14; The concentration of the alkaline substance in the modified solution is 0.01 to 5 kg / L; The alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate; The concentration of the sulfonating agent in the modified solution is 0.01 to 5 kg / L; The sulfonating agent in the modified liquid is selected from one or more of sulfite, chlorosulfonic acid, hydroxymethylsulfonate, sulfuryl chloride and aminosulfonic acid; and / or, the material ratio of the narrow straight grain veneer to the chemically modified modifying liquid is 4.6 to 184 cm 3 : 1L.

10. The preparation method according to claim 6, characterized in that The weight of the modified veneer is reduced by 35-60% compared with that of narrow straight-grain veneer.

11. The preparation method according to claim 6, characterized in that The splicing in step S2) is performed by glue; The proportion of natural wood in the continuous veneer is 99.95 to 99.993 wt.%.

12. The preparation method according to claim 6, characterized in that The twisting linear speed in step S3) is 0.5-5 m / min; And / or, the twist of the wooden thread is 80 to 300 twists per meter.

13. The preparation method according to claim 6, characterized in that After twisting in step S3), performing extrusion and densification treatment to obtain wood yarn; The extrusion densification treatment includes a first extrusion densification treatment or includes a first extrusion densification treatment and a second extrusion densification treatment; The area of the mold used in the first extrusion densification treatment is 30% to 60% of the cross-sectional area of the modified veneer; The area of the die used in the second extrusion densification treatment is 40% to 80% of the area of the die used in the first extrusion densification treatment.

14. The preparation method according to claim 13, characterized in that The second extrusion densification treatment is performed under the condition of mold heating; the temperature of the mold heating is 60°C to 250°C.

15. The preparation method according to claim 6, characterized in that The linear speed of the wire drawing process in step S4) is 0.2 to 5 m / min; And / or, the temperature of the die for wire drawing and densification is 60°C to 250°C.

16. The preparation method according to claim 6, characterized in that The wire drawing densification in step S4) is multi-stage wire drawing die densification; the number of stages of the multi-stage wire drawing die densification is 2 to 15; the outlet diameter of the wire drawing die used for the multi-stage wire drawing die densification is reduced by 0 to 0.1 mm in sequence.

17. The preparation method according to claim 16, characterized in that The outlet diameter of the dense first-stage wire drawing die of the multi-stage wire drawing die decreases by 0.01 to 0.1 mm to the outlet diameter of the n-stage wire drawing die, and the outlet diameter of the n+1-stage wire drawing die decreases by 0 to 0.03 mm to the outlet diameter of the last-stage wire drawing die; n is an integer greater than or equal to 1 / 3 to 2 / 3 of the number of stages.

18. The preparation method according to claim 6, characterized in that: The step S4) further includes a keratinization treatment; the keratinization treatment includes a hydration treatment and a dehydration treatment; The water filling treatment makes the moisture content 60 to 120 wt %; The dehydration treatment makes the water content 2-20 wt%.

19. The preparation method according to claim 18, characterized in that The keratinization treatment is carried out during the wire drawing and densification process, and the keratinization dehydration treatment is carried out through the die used for wire drawing and densification.

20. The preparation method according to claim 19, characterized in that The keratinization treatment is multiple keratinization treatments; the wire drawing densification is multi-stage wire drawing die densification; The number of multiple keratinization treatments is 1 to 5 times; The multi-stage wire drawing die has a density level of 2 to 15.

21. A wood fiber cloth reinforcement material, characterized in that: The invention comprises the wood fiber reinforced material according to any one of claims 1 to 5 or the wood fiber reinforced material prepared by the preparation method according to any one of claims 6 to 20.

22. A polymer resin composite material, characterized in that: The invention comprises the wood fiber reinforced material according to any one of claims 1 to 5 or the wood fiber reinforced material prepared by the preparation method according to any one of claims 6 to 20 and / or the wood fiber cloth reinforced material according to claim 21.

23. A method for chemical modification, characterized in that: The following steps are involved: In a closed environment, the veneer is heated in a modification liquid to a target temperature above the normal pressure boiling temperature of the modification liquid, and after staying at the target temperature for a certain period of time, the temperature is then lowered to below the normal pressure boiling temperature of the modification liquid to obtain the modified veneer; The high pressure can be formed by heating the modified liquid in the closed environment to a temperature above the normal pressure boiling temperature; The target temperature stay time is greater than or equal to 0h; The modifying liquid comprises an alkaline substance, a sulfonating agent and water.

24. The method according to claim 23, wherein The pH value of the modified liquid is 12 to 14; and / or, the concentration of the alkaline substance in the modified solution is 0.01 to 5 kg / L; And / or, the alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate; and / or, the concentration of the sulfonating agent in the modified solution is 0.01 to 5 kg / L; and / or, the sulfonating agent is selected from one or more of sulfite, chlorosulfonic acid, hydroxymethylsulfonate, sulfuryl chloride and aminosulfonic acid; And / or, the material ratio of the veneer to the modified liquid is 4.6 to 184 cm 3 : 1L.

25. The method according to claim 23, characterized in that The target temperature is 100-150°C; and / or, the pressure after reaching the target temperature is 0.07 to 1.9 MPa; And / or, the time of staying at the target temperature is 0 to 12 hours.

26. The method according to claim 23, wherein The cooling method includes water cooling or air cooling; And / or, the cooling rate is 0.2-10°C / min.

27. The method according to claim 23, characterized in that The weight of the modified veneer is reduced by 35% to 60% compared with the veneer raw material.

28. A vertical reactor, characterized in that: A multi-layer material frame or a material bag is provided in the vertical reactor; the multi-layer material frame is a material frame stacked up and down; the material frame and the material bag have a hole structure.

29. The vertical reactor according to claim 28, characterized in that: The material frame has a porous structure; And / or, the material bag is made of porous fabric; And / or, the diameter of the pores ranges from 3 to 5 mm, and the overall pore density is 4×10 5 ~3.5×10 5 pcs / m 3 ; And / or, a partition is provided in the material frame; the partition divides the material frame into multiple intervals, and the width of adjacent intervals increases from the center of the material frame to the side wall of the material frame from the inside to the outside; the thickness of the partition is 1 to 5 mm; the partition has a hole structure.

30. A horizontal reactor, characterized in that: A multi-layer material frame or material bag is arranged in the horizontal reactor; the multi-layer material frame is a horizontally stacked material frame; the material frame and the material bag have a hole structure.

31. The horizontal reactor according to claim 30, characterized in that: The diameter of the hole structure is in the range of 3 to 5 mm; the overall hole density of the material frame and the material bag is 6.8×10 5 ~5.0×10 5 pcs / m 3 ; And / or, a partition is provided in the material frame; the partition divides the material frame into a plurality of compartments; the widths of adjacent compartments are equal; the thickness of the partition is 1 to 5 mm; and the partition has a hole structure.

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