Artificial wood product and method for producing the same

Abstract

A compressed solid monolithic form of a wood product, comprising a plurality of natural wood pieces bound together by a crosslinked thermoplastic binder that has been crosslinked during processing, wherein the wood product maintains its compressed solid shape at high temperatures, and wherein the crosslinked thermoplastic binder has a glass transition temperature that is equal to or lower than the normal use temperature of the wood product.

Description

[0001] This application is a divisional application of patent application No. 201680043322.1 filed on July 22, 2016, entitled "Artificial Wood Products and Methods for Preparing Them".

[0002] Priority documents

[0003] This application claims priority to Australian Provisional Patent Application No. 2015902938, filed on July 23, 2015, entitled “MANUFACTURED WOOD PRODUCTS AND METHODS OF PRODUCTION”, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0004] This invention relates to engineered wood products. In one particular form, this invention relates to engineered wood flooring products. Background Technology

[0005] For many years, natural timber has been used in structures and buildings. However, in recent years, increased demand for timber, especially hardwoods and exotic species, has led to more widespread deforestation and unrestricted logging, reducing the supply of natural timber and having adverse environmental impacts.

[0006] For these reasons, attention has shifted to composite or engineered wood products made from recycled, inexpensive, and / or more readily available wood. Many of these newer wood products are suitable for buildings and structures when they are not visible (i.e., for “interior surface” applications), such as structural panels, beams, or veneers in buildings. Engineered wood products designed for exterior surface applications (such as flooring or wall panels) are more difficult to manufacture because the product’s physical properties (hardness, durability, etc.) and aesthetic appearance must be suited to the end use. In these products, the natural look and texture of the wood grain is a major draw.

[0007] In the flooring industry, certain types of hardwood are often more popular and preferred than others due to their natural hardness, density, and visual appeal. Preferred hardwoods for flooring include red eucalyptus, red oak, beech, and blue gum. Unfortunately, a considerable amount of waste wood is generated when processing logs into flooring products and from plantations currently used for sustainable timber. For this reason, attention has turned to engineered wood products for flooring applications and related uses. Recently, attention has shifted to using inferior wood species to create aesthetically pleasing engineered wood products, such as flooring. For example, U.S. Patent 8,268,430 discloses a method for manufacturing engineered wood products with a natural wood grain appearance using inferior or discarded natural wood chips. Engineered wood products formed in this way can have an aesthetically pleasing appearance, but in some cases, physical properties such as modulus of elasticity (“MOE”) and modulus of rupture (“MOR”) may be undesirable. U.S. Patent No. 20100178451 discloses a method for preparing engineered wood products using bamboo. These products are known as "wood fiber woven bamboo flooring" and possess many desirable physical properties. For example, engineered wood products are much harder than those made from other wood species, making them ideal for flooring applications.

[0008] As is known from existing technology, the physical properties of many known artificial wood products are significantly affected by the type of wood used.

[0009] Artificial wood products are typically prepared by: providing multiple strips, chips, fibers, or shavings of wood; covering or impregnating the strips, chips, fibers, or shavings with an adhesive; optionally drying the adhesive (depending on the adhesive); arranging the strips, chips, fibers, or shavings in a mold or feeding them into a continuous system; applying pressure; and curing the resin. Adhesives commonly used in this process include urea-formaldehyde resin, phenolic resin, melamine-formaldehyde resin, methylene diphenyl diisocyanate resin, and polyurethane resin. However, many of these resins present challenges. A significant drawback of urea-formaldehyde, phenolic, and melamine-formaldehyde resins is the slow release of formaldehyde into the surrounding environment from products formed from these materials. These emissions are commonly referred to as volatile organic compounds (VOCs). Due to the environmental, health, and regulatory concerns associated with formaldehyde emissions from wood products, alternative resins are needed. Recent legislation has banned or severely restricted the use of formaldehyde in some countries or states. Phenolic resins have been used to prepare artificial wood products for many years, and it has become apparent that the resin yellows over time, negatively impacting the appearance of the product. Furthermore, in practice, the quality of products formed using these resins can be adversely affected by incomplete monomer curing / conversion during product manufacturing. Urea-formaldehyde resins are not waterproof, which causes problems in many flooring applications. Methylene diphenyl diisocyanate and polyurethane resins are formaldehyde-free and generally waterproof, but they are quite expensive to use and have other drawbacks: they are highly reactive, making curing difficult to control, and the physical properties of engineered wood products made using these resins are highly dependent on the moisture content of the wood being treated.

[0010] US Patent No. 20020074095 discloses a method for preparing wood-based particleboard by bonding wood fibers using a crosslinkable adhesive. Wood fibers are prepared by crushing wood particles, and the resulting fibers are mixed with approximately 15% by weight of an adhesive and compacted to form a particleboard product. However, the resulting particleboard product is a composite particleboard and does not possess any of the natural appearance and texture of the wood chips from which it is formed. Furthermore, the physical properties of the particleboard product are a combination of the physical properties of the wood fibers used and the physical properties of the adhesive used. In other words, the adhesive used significantly contributes to both the physical and aesthetic properties of the product.

[0011] Current methods for producing engineered wood products are often highly dependent on the moisture content of the wood being processed. Variations in the initial moisture content of the wood can be easily addressed by drying the wood chips to a low, predetermined moisture content. However, this is an energy- and labor-intensive method, which fundamentally limits the commercial feasibility of manufacturing these products in many jurisdictions and for many potentially ideal wood species. Variations in moisture content during the various stages of preparation can also lead to warping of the finished product. Therefore, the types of adhesives explored to date present fundamental problems with the manufacturability of these products, and this has so far limited the broader development of known manufacturing methods.

[0012] Therefore, new methods are needed to manufacture wood products that improve manufacturing feasibility. Optionally or additionally, new methods are needed to manufacture wood products that impart advantageous physical properties to the final product. Optionally or additionally, new methods for manufacturing wood products are needed that result in artificial wood products with the natural appearance and texture of wood grain. Optionally or additionally, new methods for manufacturing wood products are needed that are more environmentally friendly or economically sustainable than existing methods. Optionally or additionally, there is a need to provide resins and / or methods for preparing artificial wood products that overcome one or more difficulties associated with known resins. Summary of the Invention

[0013] In a first aspect, this document discloses a compacted, monolithic engineered wood product comprising a plurality of natural wood chips bonded together by a crosslinked thermoplastic adhesive that has been crosslinked during processing, wherein the engineered wood product retains its compacted shape at a high temperature, and wherein the crosslinked thermoplastic adhesive has a glass transition temperature equal to or lower than the normal use temperature of the engineered wood product.

[0014] In the second aspect, this article discloses a compressed, monolithic engineered wood product comprising multiple natural wood chips bonded together by a cross-linked thermoplastic adhesive that has been cross-linked during processing, wherein the veneer shape of each assembled wood chip after compression differs from the veneer shape of each assembled wood chip before compression.

[0015] In a third aspect, the present invention discloses a method for preparing artificial wood products, comprising:

[0016] - Offers multiple natural wood chips with a basic balance of moisture content;

[0017] - Apply a thermoplastic adhesive comprising a thermoplastic resin and a crosslinking agent to the wood chip to form an adhesive-coated wood chip;

[0018] - Optionally, the adhesive-coated wood chips are heated to form heated adhesive-coated wood chips;

[0019] - Assemble the adhesive-coated wood chips in the desired configuration to form an assembled adhesive-coated wood chip assembly;

[0020] - The assembled adhesive-coated wood chips are compressed in a press under pressure for a sufficient time to force out trapped air and mechanically deform the assembled adhesive-coated wood chips so that adjacent wood chips conform to each other in shape.

[0021] - During the compression step, the thermoplastic adhesive is crosslinked to at least a critical crosslinking amount to form at least partially cured artificial wood products, wherein the critical crosslinking amount is sufficient to allow the at least partially cured artificial wood products to substantially maintain their compressed form and to prevent the wood chips from expanding and returning to their initial state when the pressure is released during the compression step.

[0022] - Remove the at least partially cured artificial wood product from the press; and

[0023] - Optionally, the partially cured artificial wood product may be further cured to provide an artificial wood product with a substantially balanced moisture content.

[0024] In the fourth aspect, this article discloses artificial wood products formed by the method of the third aspect.

[0025] In some implementations, the engineered wood product is selected from the group consisting of engineered wood panels, wood composite panels, fiberboard, oriented strand board, particleboard, and flooring.

[0026] In some implementations, artificial wood products are suitable for exterior surface applications and have the desired physical properties and aesthetic appearance suitable for the end use.

[0027] In some embodiments, the crosslinked thermoplastic adhesive in the artificial wood product has a glass transition temperature of less than about 70 degrees Celsius, less than about 50 degrees Celsius, less than about 40 degrees Celsius, less than about 30 degrees Celsius, or less than about 20 degrees Celsius. In some specific embodiments, the crosslinked thermoplastic adhesive in the artificial wood product has a glass transition temperature of about -30 degrees Celsius to about 25 degrees Celsius. In some specific embodiments, the crosslinked thermoplastic adhesive in the artificial wood product has a glass transition temperature below room temperature.

[0028] In some embodiments, the artificial wood product contains less than 15% (by weight), less than 10% (by weight), or less than 6% (by weight) of adhesive.

[0029] In some implementations, the thickness of the wood chips is less than a critical thickness at which the mechanical properties of the wood chips themselves cannot overcome the adhesive force between the wood and the adhesive and / or the cohesive strength of the adhesive when the wood chips are expanded, resulting in structural delamination.

[0030] In some embodiments, the wood chips have a maximum thickness of about 0.1 mm to about 10 mm. For example, the wood chips may have a maximum thickness of about 10 mm, about 8 mm, about 6 mm, about 5 mm, about 4 mm, about 3 mm, about 2 mm, about 1 mm, about 0.5 mm, about 0.3 mm, or about 0.1 mm. In some embodiments, the wood chips have a maximum thickness of about 2 mm to about 10 mm.

[0031] In some embodiments, the wood used for the natural wood chips is selected from the group consisting of eucalyptus, pine, red maple, white maple, Queensland maple, ash, aspen, walnut, oak, mahogany, birch, mahogany, ebony, cherry, Oregonwood, poplar, and herbaceous woods, such as bamboo. The wood used for the natural wood chips can be a combination of two or more of these species.

[0032] In some implementations, the wood is pine.

[0033] In some implementations, the wood is eucalyptus.

[0034] In some implementations, the wood chips are derived from low-value timber.

[0035] In some implementations, for pine, the equilibrium moisture content of the multiple natural wood chips is from about 5% to about 15% (by weight).

[0036] In some implementations, for hardwood species, the equilibrium moisture content of multiple natural wood chips is from about 8% to about 12%.

[0037] In some implementations, the thermoplastic resin is polyethylene ester.

[0038] In some embodiments, the thermoplastic resin is polyvinyl acetate or a copolymer thereof or a hydrolyzed form thereof.

[0039] In some embodiments, the crosslinking agent is a catalyst or reactant selected from the group consisting of N-hydroxymethylacrylamide, borax, aluminum zirconium carbonate, aluminum chloride, magnesium chloride, p-toluenesulfonic acid, acetaldehyde, formaldehyde, urea-formaldehyde, melamine-formaldehyde, trimethylol melamine, copper ammonium complex, chromium complex, organotitanate, dichromate, polyaldehyde, butyraldehyde, chloroformate, urea, isocyanate, and zirconium ammonium carbonate. Optionally, the thermoplastic adhesive is crosslinked by ethoxylation, propoxylation, cyanoethylation, exposure to gamma rays, or electron beam crosslinking.

[0040] In some embodiments, the crosslinking agent is aluminum chloride. In other embodiments, the crosslinking agent is p-toluenesulfonic acid.

[0041] In some embodiments, the thermoplastic adhesive comprising a thermoplastic resin and a crosslinking agent is a water-based emulsion.

[0042] In some implementations, thermoplastic adhesives are applied to the wood chips by hand, brush, spray, roller, machine, dipping and / or curtain / extrusion coating.

[0043] Thermoplastic resin and crosslinking agent can be applied to wood chips together (i.e., simultaneously) or separately.

[0044] In some embodiments, the adhesive includes one or more additives selected from the group consisting of expansion control agents, bactericides, insecticides, colorants, UV stabilizers, fillers, extenders, refractories, flame retardants, fibers, etc.

[0045] In some implementations, the wood can be treated before the adhesive is applied to obtain different properties. For example, the color of the wood can be changed by heat treatment, staining agents or dyes, and / or additives selected from the group consisting of expansion control agents, fungicides, insecticides, colorants, UV stabilizers, fillers, extenders, refractories, flame retardants, fibers, etc. can be applied to the wood before the adhesive is applied.

[0046] In some embodiments, the adhesive-coated wood chips are heated to dry the adhesive and maintain a substantially balanced moisture content in the adhesive-coated wood chips.

[0047] In some implementations, the wood chips coated with adhesive are preheated before they are assembled and compressed in the desired configuration.

[0048] In some embodiments, the adhesive-coated wood chips are heated to a temperature of about 50°C to about 200°C.

[0049] In some embodiments, the adhesive-coated wood chips are heated for a period of about 1 minute to about 40 minutes.

[0050] In some embodiments, dried wood chips coated with adhesive are assembled in a mold.

[0051] In some implementations, the assembled wood chips are subjected to pressures of approximately 4 to 20 MPa during the compression step.

[0052] In some embodiments, the assembled wood chips are heated to a temperature of about 70°C to about 150°C or maintained at a temperature of about 70°C to about 150°C during the compression step.

[0053] In some implementations, the compression step takes approximately 5 minutes to approximately 90 minutes.

[0054] In some embodiments where the wood chips assembled during the compression step are heated, the at least partially cured artificial wood product is released from the mold while still warm.

[0055] In some implementations, multiple natural wood chips are mechanically deformed during processing so that adjacent wood chips conform to each other in shape.

[0056] In some implementations, the veneer shape of each assembled wood chip after compression is different from the veneer shape of each assembled wood chip before compression.

[0057] In some implementations, partially cured artificial wood products undergo additional curing steps to provide the artificial wood product. Attached Figure Description

[0058] Embodiments of the invention will be discussed with reference to the accompanying drawings, in which:

[0059] Figure 1 Visual results obtained by using wood chips in different orientations in a mold are shown;

[0060] Figure 2 Showing the dimensions of blocks used in artificial wood products;

[0061] Figure 3 The DMA measurement curves of the storage modulus of overnight-dried Aquadhere films and Aquadhere + glyoxal films are shown. The figure shows that Aquadhere softens once it passes its glass transition point, indicating that it is not cross-linked, and it flows readily once the temperature is above 50°C. The addition of the cross-linking agent (glyoxal) increases the storage modulus above the Tg temperature, thus indicating that it is cross-linked.

[0062] Figure 4 The DMA measurement curves for the storage modulus of the TB3 film are shown. This figure illustrates that the TB3 binder with glyoxal (TB3GX) crosslinks above 50°C (the storage modulus increases during the second temperature scan), resulting in higher stiffness at temperatures above the glass transition temperature (20°C) in subsequent temperature scans.

[0063] Figure 5 Showing with Figure 4 The DMA measurement curve of the storage modulus of the TB3 film is compared to the curve shown for TB3 (TB3GX) with glyoxal. This figure shows a greater increase in the storage modulus of TB3GX above 50°C (increase in storage modulus during the temperature scan), indicating a higher crosslinking content in TB3GX.

[0064] Figure 6 The DMA measurement curves for the storage modulus of TB3 films, TB3 with glutaraldehyde (TB3GA) films, and TB3 with glyoxal (TB3GX) films are shown. Figure 4 and Figure 5 The figure shows a comparison of the three different compositions, each exhibiting a curing process occurring at different temperatures, indicated by the increase in storage modulus with increasing temperature.

[0065] Figure 7 The different orientations of the wood chips in the molds used in the embodiments are shown; and

[0066] Figure 8 The curves showing the density and hardness of pine blocks manufactured using various processing conditions illustrate the range of achievable physical properties. Detailed Implementation

[0067] This invention is the result of the inventors' research on resins suitable for the preparation of artificial wood products and provides a new method to overcome the problems associated with existing methods. In particular, the inventors have discovered that certain thermoplastic adhesives, when applied to wood fibers or veneers, can deform under pressure and subsequently crosslink under pressure exceeding a critical crosslinking level, and optionally, be heated to produce products with properties similar to those of raw wood. Under these conditions, artificial wood products can be prepared that have a density substantially similar to or greater than that of raw wood and (i) release upon pressure release or heating and (ii) substantially retain their integrity after boiling for three hours. Thermoplastic adhesives that do not crosslink beyond the critical level (i) do not retain their compressed form and (ii) fail such a boiling test, and as a result of the boiling test, typically lead to an expanded structure similar to the initial wood chips.

[0068] The use of adhesives described in this paper enables the compression of wood chips into a dense, solid sheet with physical integrity within an economical timeframe. In other words, the solid sheet can be compressed and cured into its final shape within an economical timeframe, and ideally, it can be released from compression without loss of its structural form while still hot (if heated). This combination of input materials, adhesives, moisture content, heat, and pressure is what makes this product possible.

[0069] These findings provide new methods for the economical processing of wood shreds, wood veneers, wood particles, wood strips, wood chips, wood fibers, or wood flakes (collectively referred to herein as "wood chips") into re-cured wood products. In particular, thermoplastic adhesives that crosslink above a critical level during processing allow:

[0070] • Wood chips are pressed under pressure into a single block coated with adhesive, and optionally, heated until at least a critical amount of crosslinking is achieved, at which point the pressure can be released and the block can be cooled or heated further without additional periods of pressure and without significant deformation, or the wood chips expand and return to their initial state before pressure is applied; and

[0071] • A composite of adhesive and wood chips is continuously extruded into a die to provide a desired shape maintained by a thermoplastic adhesive, which is then crosslinked under pressure beyond a critical level to maintain the shape after the pressure is removed.

[0072] In particular, the inventors have discovered that cross-linked thermoplastic resins impart desirable physical properties to products, such as mechanical stability, high density levels, and high hardness levels. Furthermore, the properties of the resin or the manufacturing method can be adjusted to alter the physical properties of the artificial wood product, thereby achieving certain final properties by regulating the resin and / or processing parameters. Additionally, the adhesives used can be transparent, meaning that the texture and color in the artificial wood product are the same as the original wood chips, resulting in an artificial wood product with a more realistic or natural appearance.

[0073] Therefore, the present invention provides a new method to overcome the fundamental problems associated with existing technical methods.

[0074] This article discloses a method for preparing artificial wood products, including:

[0075] - Offers multiple natural wood chips with a basic balance of moisture content;

[0076] - Apply a thermoplastic adhesive comprising a thermoplastic resin and a crosslinking agent to the wood chip to form an adhesive-coated wood chip;

[0077] - Optionally, the adhesive-coated wood chips are heated to form heated adhesive-coated wood chips;

[0078] - Assemble the adhesive-coated wood chips in the desired configuration to form an assembled adhesive-coated wood chip assembly;

[0079] - The assembled adhesive-coated wood chips are compressed in a press under pressure for a sufficient time to force out trapped air and mechanically deform the assembled adhesive-coated wood chips so that adjacent wood chips conform to each other in shape.

[0080] - During the compression step, the thermoplastic adhesive is crosslinked to at least a critical crosslinking amount to form at least partially cured artificial wood products, wherein the critical crosslinking amount is sufficient to allow the at least partially cured artificial wood products to substantially retain their compressed form and to prevent the wood chips from expanding and returning to their initial state when the pressure is released during the compression step.

[0081] - Remove the at least partially cured artificial wood product from the press; and

[0082] - Optionally, the partially cured artificial wood product may be further cured to provide an artificial wood product with a substantially balanced moisture content.

[0083] The disclosed method provides an alternative to known methods. Typically, known engineered wood products, such as particleboard, MDF, etc., use thermosetting adhesives that rely on crosslinking reactions of liquid reactants. In these products, liquid monomers are added to wood or bamboo fibers and compressed and heated under certain conditions to polymerize the monomers and convert the liquid monomers into a solid thermosetting adhesive. To achieve this, numerous chemical reactions must be carried out, requiring high temperatures, long durations, and avoiding side reactions to achieve the expected or desired end product. In contrast, the method described herein uses a thermoplastic adhesive, which is already a polymer, and then crosslinks it during the method to form a three-dimensional network. This method requires fewer chemical reactions, thus providing a more robust processing window. It also has the advantage of being able to use water-based emulsion polymer systems, which are easy to handle, have long shelf lives, low toxicity and low VOCs, and can adhere wood chips before crosslinking. The further crosslinking during this method imparts more compression set to the adhesive, allowing the engineered wood product to be released from the hot mold, and also giving the engineered wood product greater thermal stability during further processing and use.

[0084] The use of crosslinkable thermoplastic adhesives allows for the rapid achievement of desired properties by crosslinking the adhesive during the compression step. Thermoplastic adhesives also offer speed advantages due to the lower conversion rate required to reach the gel point, relatively lower crosslinking density requiring less crosslinking agent thus protecting the wood, lower energy requirements, better reaction control, a wider process window, and faster processing times. Furthermore, known formaldehyde-based resins react rapidly at temperatures but involve complex chemical processes and cannot cure effectively if not heated properly (e.g., due to the thickness of the product to be heated). Varying moisture contents in the wood chips to be treated can also lead to different properties within and between blocks. This method minimizes these problems. By using lower temperatures during processing, the presence of water in the wood is less of a concern, and this allows for greater water retention in the wood during the method. In the method described herein, a near (i.e., “basic”) equilibrium moisture level is maintained in the wood throughout the process. For example, for pine, the equilibrium moisture content of multiple natural wood chips can be from about 5% to about 15% (by weight), or for hardwood species, it can be from about 8% to about 10%. Therefore, the equilibrium moisture content of multiple natural wood chips can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15% (by weight). Existing methods require engineered wood products to be dried after manufacturing or otherwise stabilized at an equilibrium moisture content after manufacturing, otherwise the product will become cupped, warped, or twisted when cut. This is often an energy- or time-intensive step. However, in the method of this paper, the moisture content of the wood chips is generally maintained throughout the process, resulting in less waiting time at the end of the method before the product can be cut. Therefore, matching the moisture content of the wood to the final application environment reduces twisting and warping, and reduces the need for aging to stabilize the manufactured product before further processing. The lower drying requirements due to the use of less energy make it cheaper to operate.

[0085] As used herein, the term “about” when used in conjunction with numerical values ​​indicates that the actual value may be ±20%, ±19%, ±18%, ±17%, ±16%, ±15%, ±14%, ±13%, ±12%, ±11%, ±10%, ±9%, ±8%, ±7%, ±6%, ±5%, ±4%, ±3%, ±2%, or ±1%.

[0086] As used herein, the term "artificial wood product" is intended to refer to man-made or machine-made wood products, such as engineered wood panels, wood-based composite panels, fiberboard, oriented strand board (OSB), or any other similar workpiece containing wood-based material. The materials and methods described herein are particularly suitable for use as flooring in residential or commercial buildings, and further discussion herein relates to flooring and its manufacturing methods. However, it will be understood that any such discussion is not intended to limit the scope of the invention to that particular application, and a variety of alternative applications for artificial wood products can be conceived, such as in furniture, wall panels, structural components, railway sleepers, bridge decks, columns and railings, or any application where the physical and / or aesthetic properties of the wood product are important. In some embodiments, the artificial wood product is suitable for exterior surface applications and has desired physical properties and aesthetic appearance suitable for the end use.

[0087] In some embodiments, the artificial wood product comprises multiple natural wood chips that have been compressed and bonded together by a cross-linked thermoplastic adhesive. In these embodiments, the artificial wood product is a substantially monolithic structure.

[0088] Multiple natural wood chips undergo mechanical deformation during processing, causing adjacent chips to conform to each other's shapes. Furthermore, the veneer shape of each assembled wood chip after compression differs from the veneer shape of each assembled wood chip before compression. The veneer shape can be determined by examining the "end grain" of the blocks in the engineered wood product. Therefore, this paper provides engineered wood products in the form of compressed monolithic sheets comprising multiple natural wood chips bonded together by a cross-linked thermoplastic adhesive that has been cross-linked during processing, wherein the veneer shape of each assembled wood chip after compression differs from the veneer shape of each assembled wood chip before compression.

[0089] As used herein, the term "wood chip" includes wood filaments, wood veneer, wood particles, wood strips, wood chips, wood fibers, or wood flakes. The inventors have discovered that wood chips must be less than a critical thickness because thick wood chips, constructed with the same adhesive in a thick laminate, cannot pass tests such as the boiling test. Without being theoretically limited, it is suggested that if wood chips are too thick, their own mechanical properties can compromise the adhesive strength between the wood and the adhesive and / or the cohesive strength of the adhesive, and cause structural delamination when the wood chips are swelled (e.g., upon exposure to moisture / humidity).

[0090] The wood chips may have a thickness, with a minimum of about 0.1 mm, about 0.3 mm, about 0.5 mm, about 1 mm, about 2 mm, or about 3 mm, and a maximum of about 10 mm, about 8 mm, about 6 mm, about 5 mm, about 4 mm, about 3 mm, or about 2 mm. The wood chips may have any suitable dimensions in a plan view. In some embodiments, the length of the wood chip in the fiber direction is the product length, preferably substantially aligned with the fiber direction, and the transverse direction is any dimension that facilitates further processing into boards or manufacturability for a particular application. In other words, the artificial wood product may be a woven product of wood fibers in which the fiber / wood filament length is the product length, and the transverse direction may be a continuous sheet assembled into a mold in various ways, or it may be slices, or it may be cut or crushed wood filaments.

[0091] There are no particular limitations on the wood used for natural wood chips; it can be any hardwood, softwood, or “herbaceous wood,” such as bamboo or palm. Therefore, as used herein, the term “natural wood chips” is intended to include, within its scope, herbaceous woods, such as bamboo and palm, which are known for their use in the manufacture of engineered wood products. Suitable woods include, but are not limited to, eucalyptus, pine, red maple, white maple, Queensland maple, ash, aspen, walnut, oak, mahogany, birch, mahogany, ebony, cherry, Oregonwood, poplar, etc. Herbaceous woods such as bamboo and palm may also be used. In some specific embodiments, the wood is pine, such as radiata pine, bunya pine, Caribbean pine (Southern Pine), Corsican pine, Montreal cypress, Kenning pine, kauri, slash pine (Southern Pine), South European pine, western yellow pine, and slash pine (Southern Pine). In certain other specific embodiments, the wood is eucalyptus, such as red eucalyptus, blue eucalyptus, black eucalyptus, blue-leaved stringybark, brown mallet, Dunns white eucalyptus, flooded eucalyptus, Gympie messmate, red eucalyptus, kauri wood, eucalyptus serrata, river red eucalyptus, silver-topped stringybark, spotted eucalyptus, and tallowwood. In some embodiments, the wood is selected from the group consisting of pine, red maple, red oak, ash, aspen, or blue eucalyptus. The final engineered wood product may contain more than one species or type of wood.

[0092] Advantageously, wood chips can be derived from low-value timber, such as sawmill waste, ball mill waste, and plantation waste including initial thinning. However, it is also understandable that wood chips can be derived from high-value timber (if desired).

[0093] The size and quality of the wood used to form wood chips can vary significantly. If desired, any suitable equipment can be used to break the wood into chips of the desired size. In some embodiments, wood chips are formed by rolling up a continuous sheet of veneer and then crushing it. In other examples, the wood chips can be cut strips, multiple smaller rolls of veneer, or crushed wood fibers.

[0094] Advantageously, natural wood chips have the appearance of natural wood, and engineered wood products are suitable for applications where the texture of wood products is displayed and aesthetically pleasing.

[0095] As discussed above, by using crosslinked thermoplastic adhesives, the moisture content of the wood chips does not need to be precisely controlled or controlled to very low levels, and a range of values ​​can be used, allowing for a wider process window compared to the use of moisture-sensitive adhesives (e.g., isocyanate-based materials). Depending on the type of wood used, the moisture content of the wood chips can be from about 5% to about 20%. For example, hardwoods may have an initial moisture content of 6-7%. Pine chips may have an initial moisture content of 10-12%. Typically, the initial wood chips have a set moisture content (e.g., 12%). The optimal moisture content of the wood chips can be a function of the desired moisture content in the final product, the type of wood used, and / or the adhesive used, and can be determined empirically. If the moisture content of the wood chips is too low, the chips will absorb too much moisture from the adhesive and impair the physical properties of the product. Conversely, if the moisture content of the wood chips is too high, the adhesive will not be effective. Optionally, the initial wood chips can be dried to the desired moisture content before the adhesive is applied. For example, drying can be carried out by air drying or by heating with suitable heating equipment (e.g., an infrared heater or an oven that supplies hot air). The inventors have discovered that the method using crosslinked thermoplastic adhesives can have a higher moisture content than other possible adhesives, and this can advantageously promote the deformation of the wood chips during the compaction stage to produce excellent engineered wood products.

[0096] Thermoplastic adhesives can be applied to wood chips by hand, brush, spray, roller, dip, machine, and / or curtain coating. Known spraying, dipping, and spin coating methods can be used. In some embodiments, the thermoplastic adhesive is sprayed onto the wood chips. Thermoplastic adhesives can be delivered as an aqueous emulsion, in a solvent, or by extrusion of a hot melt. Thermoplastic resins and crosslinking agents can be applied to the wood chips together (i.e., simultaneously) or separately.

[0097] Adhesives are crosslinkable thermoplastic resins. As used herein, the term "thermoplastic" is used to indicate its glass transition temperature (Tg). g The above becomes soft, malleable, or fluid and in its T g The following polymers become solid.

[0098] Therefore, this article also provides engineered wood products in the form of compressed monolithic materials, comprising a plurality of natural wood chips bonded together by cross-linked thermoplastic adhesives that have been cross-linked during processing, wherein the engineered wood product maintains its compressed shape at high temperatures, and wherein the cross-linked thermoplastic adhesives have a glass transition temperature equal to or lower than the normal use temperature of the engineered wood product.

[0099] A wide variety of thermoplastic resins are known, and the use of any one or more known thermoplastic resins can be conceived, provided that the adhesive can crosslink during processing and the TT of the adhesive in the artificial wood product is suitable. g The temperature should be equal to or lower than the normal operating temperature of the artificial wood product, for example, below room temperature. The physical properties of the adhesive can be pre-selected to have a T value below 70°C, 50°C, 40°C, 30°C, or 20°C. g In some embodiments, the adhesive has a T0 of -30 degrees Celsius to about 25 degrees Celsius. g This makes the adhesive "rubber-like" at room temperature. The advantage of an adhesive having a rubber-like consistency at room temperature is that it can undergo post-curing at low temperatures (i.e., curing after the product has been removed from the press and cooled). Conversely, adhesives with a higher Tg... g The adhesive is glassy at room temperature and requires a post-curing heat step, increasing the cost and complexity of the method. Rubber-like adhesives are also more accepting of additives (such as dyes) than glassy adhesives at room temperature. Unexpectedly, the inventors have discovered T g Thermoplastics that are below the normal operating temperature of wood products (and therefore rubbery) are very effective and offer significant advantages in the final product, contrary to the commonly held view that adhesives should be glassy at normal operating temperatures, which is the case for products such as medium-density fiberboard (MDF), high-density fiberboard (HDF), plywood, laminated veneer lumber (LVL), and particleboard.

[0100] In some embodiments, the thermoplastic resin is polyethylene ester. Polyvinyl ester is formed from vinyl acetate and its copolymers. For example, the inventors have found that polyvinyl acetate (“PVA”) is suitable. As used herein, the terms “polyvinyl acetate” and “PVA” are used to encompass hydrolyzed forms of PVA within their scope, including various levels of hydrolyzed forms to form poly(vinyl alcohol) copolymers. Other vinyl acetate-based polymers that may be used include poly(vinyl acetate)-co-butyl maleate-co-isoborneol acrylate, poly(vinyl acetate) cyanomethyl diphenyl dithiocarbamate, poly(vinyl cinnamate), poly(vinyl acetate), and poly(vinyl stearate), as well as copolymers or terpolymers thereof (including polymers made from acrylates and methacrylates).

[0101] Commercial adhesives III (Franklin International, Columbus, Ohio, USA) and similar adhesives from Sika, Selleys and Bostik are suitable thermoplastic adhesives.

[0102] As discussed above, thermoplastic resins are crosslinked during processing (including the curing stage and post-curing). Specifically, thermoplastic resin materials (such as PVA) are crosslinked using a suitable reactive crosslinking agent. The inventors have found that artificial wood products formed using uncrosslinked thermoplastic adhesives exhibit poorer physical properties compared to those formed using thermoplastic adhesives in combination with crosslinking agents. For example, artificial wood products formed from wood chips below a critical thickness using PVA adhesives without crosslinking agents fail the 3-hour boiling test, while those formed using PVA and crosslinking agents perform well in the same test. PVA adhesives with insufficiently cured or crosslinked crosslinking agents also fail the 3-hour boiling test. Therefore, crosslinking of thermoplastics above a critical level imparts the desired physical properties to artificial wood products.

[0103] In some embodiments, the crosslinking agent is a catalyst or reactant selected from the group consisting of N-hydroxymethylacrylamide, aluminum zirconium carbonate, aluminum chloride, borax, magnesium chloride, p-toluenesulfonic acid, acetaldehyde, formaldehyde, urea-formaldehyde, melamine-formaldehyde, trimethylol melamine, copper ammonium complexes, chromium complexes, organotitanates, dichromates, polyaldehydes, butyraldehyde, chloroformates, urea, isocyanates, and zirconium ammonium carbonate. Thermoplastic adhesives can also be crosslinked by ethoxylation, propoxylation, cyanoethylation, exposure to gamma rays, or electron beam crosslinking. If desired, thermoplastic resins can be manufactured to react with specific crosslinking agents. As used herein, the term "crosslinking" is used broadly to encompass both covalent crosslinking bonds and ionic crosslinking bonds (i.e., complexation).

[0104] In some embodiments, the crosslinking agent is aluminum chloride. In other embodiments, the crosslinking agent is p-toluenesulfonic acid.

[0105] Other crosslinking agents that can be used are dialdehydes. Dialdehydes may have the general formula OHC-R-CHO, where R is a bond or a divalent organic group (such as an aliphatic, alicyclic, aromatic, or heterocyclic group). In some embodiments, R is a divalent aliphatic hydrocarbon group having 1 to 12 carbon atoms. Glyoxal (R = bond), malondialdehyde (R = CH2), succinal (R = CH2CH2), and glutaraldehyde (i.e., R = CH2CH2CH2) are suitable dialdehydes. In some embodiments, the crosslinking agent is glyoxal. In other embodiments, the crosslinking agent is glutaraldehyde.

[0106] The crosslinking agent can be used in amounts from 0.1% to 20% by weight.

[0107] As discussed earlier, thermoplastic adhesives crosslink at a level exceeding the critical crosslinking threshold. The "critical crosslinking threshold" is achieved when the product maintains its compressed shape at high temperatures. In other words, and not theoretically, the wood chips in engineered wood products are prone to expand back to their initial shape, but crosslinking provides the adhesive with sufficient mechanical reinforcement to withstand the internal stresses generated by the wood chips.

[0108] Thermoplastic adhesives can be crosslinked (or “cured”) at any suitable stage during the formation of artificial wood products. Suitablely, at least some crosslinking occurs when the wood chips are compressed in a compression step during the formation of the artificial wood product. As described in more detail later, the adhesive-coated wood chips are typically compressed in a mold under conditions where the thermoplastic adhesive is at least partially cured to form a partially cured artificial wood product, which can then be further cured to provide the artificial wood product. While crosslinking agents can be added at any stage of the manufacturing process, it is beneficial to contact the wood chips with the thermoplastic adhesive and crosslinking agent before assembling them in the mold to ensure that the amount of crosslinking is relatively uniformly distributed in the final product.

[0109] The physical properties of the adhesive can be pre-selected to have a Tg below room temperature, making it "rubber-like" at the normal operating temperature of the product.

[0110] Crosslinked thermoplastic adhesives can contain additives to impart advantageous properties to engineered wood products. Suitable additives include, but are not limited to, swelling control agents, bactericides, insecticides, colorants, UV stabilizers, fillers, extenders, refractories, flame retardants, fibers, etc. Additives can be incorporated into the thermoplastic adhesive before being applied to the wood chips. This results in a simple manufacturing method for introducing additives into engineered wood products. The additives can optionally be designed to migrate from the adhesive to the wood chips during processing.

[0111] Additives can also be added directly to the wood chips before adhesive coating, allowing them to penetrate the chips and provide protection throughout the veneer and ultimately the entire product. This can have the advantage of being able to use some of the agents at lower levels than are currently possible in wood products.

[0112] Additives can also be applied after the wood chips are coated with adhesive, thereby incorporating the additives into the adhesive, but without affecting the stability, shelf life, or properties (such as viscosity) of the adhesive before the wood chips are coated.

[0113] Suitable additives include lignin and tannin. In fact, the inventors have discovered that adding lignin and / or tannin as additives along with a dialdehyde crosslinking agent results in reduced expansion of engineered wood products (compared to products without added lignin and / or tannin) and greater resistance to outdoor weathering.

[0114] Suitable fungicides comprise any chemical substance that kills, destroys, inhibits, or inactivates fungi to prevent their growth. Fungicides can be synthetic or biosynthetic and can contain both organic and inorganic compounds. Fungicides can be solid (e.g., powder), liquid, or combinations thereof. See, for example, *Concise Chemical and Technical Dictionary*, Fourth Enlarged edition, Bennett, Chemical Publishing Company, NY, NY (1986); and *McGraw-Hill Concise Encyclopedia of Science & Technology*, Fourth Edition, Parker, McGraw-Hill, NY, NY (1998). Examples of suitable fungicides include formic acid, acetic acid, propionic acid, nonanoic acid, decanoic acid, copper ammonium acetate (CAA), copper naphthenates, and combinations thereof.

[0115] Pesticides can be any chemical, but are preferably chemicals that have been approved by the relevant regulatory government agency. Examples of suitable pesticides include copper-containing pesticides, such as ammonium copper carbonate. In some embodiments, pesticides can be used for the mitigation, control, or elimination of termites.

[0116] Suitable UV stabilizers include benzophenone, triazole, salicylates, formamide, and benzoates, which are known UV stabilizers. The following materials are suitable: Sanduvor VSU: 2-ethyl-2-ethoxyaniline (trademarked by Sandoz), Tinuvin 144 and 770: hindered amine light stabilizers (trademarked as HALS by Ciba Geigy), Irgastab. 2002: Nickel phosphate (Ciba-Geigy trademark), 2,2'-dihydroxybenzophenone, 2,2,4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-diethoxybenzophenone, 2,2'-dihydroxy-4,4'-dipropoxybenzophenone, 2,2'-dihydroxy-4,4'-dibutoxybenzophenone, 2,2'-dihydroxy-4-methoxy-4'-ethoxybenzophenone, 2,2'-dihydroxy-4-methoxy-4'-propoxybenzophenone, 2-hydroxy-4, 4',5'-Trimethoxybenzophenone, 2-hydroxy-4-ethoxy-4'-methylbenzophenone, 2-hydroxy-4-ethoxy-4'-ethylbenzophenone, 2-hydroxy-4-ethoxy-4'-propylbenzophenone, 2-hydroxy-4-ethoxy-4'-methoxybenzophenone, 2-hydroxy-4,4-diethoxybenzophenone, 2-hydroxy-4-ethoxy-4'-propoxybenzophenone, 2-hydroxy-4-ethoxy-4'-butoxybenzophenone, 2-hydroxy-4-ethoxy-4'-chlorobenzophenone, 2-hydroxy-4-ethoxy-4-bromobenzophenone, 2-(2 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-methyl-5'-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-5'-cyclohexylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-dimethylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-butylphenyl)-5-chlorobenzotriazole and 2-(2'-hydroxy-3'-ditert-butylphenyl)benzotriazole, 2,2'-dihydroxy-4-methoxy-4'-butoxybenzophenone, 2,2'-dihydroxy- 4-Ethoxy-4'-propoxybenzophenone, 2,3'-dihydroxy-4,4'-dimethoxybenzophenone, 2,3'-dihydroxy-4-methoxy-4'-butoxybenzophenone, 2,3'-dihydroxy-4,4,5'-trimethoxybenzophenone, 2-hydroxy-4,4,5'-trimethoxybenzophenone, 2-hydroxy-4,4,6'-tributoxybenzophenone, 2-hydroxy-4-ethoxy-2,4'-dibutylbenzophenone, 2-hydroxy-4-propoxy-4,6'-dichlorobenzophenone, 2-hydroxy-4-propoxy-4',6'-dibromobenzophenone, 2,4-Dihydroxybenzophenone, 2-Hydroxy-4-methoxybenzophenone, 2-Hydroxy-4-ethoxybenzophenone, 2-Hydroxy-4-propoxybenzophenone, 2-Hydroxy-4-butoxybenzophenone, 2-Hydroxy-4-methoxy-4'-methylbenzophenone, 2-Hydroxy-4-methoxy-4'-propylbenzophenone, 2-Hydroxy-4-methoxy-4'-butylbenzophenone, 2-Hydroxy-4-methoxy-4'-tert-butylbenzophenone 2-Hydroxy-4-methoxy-4'-chlorobenzophenone, 2-hydroxy-4-methoxy-2'-chlorobenzophenone, 2-hydroxy-4-methoxy-4'-bromobenzophenone, 2-hydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4,4'-dimethoxy-3-methylbenzophenone, 2-hydroxy-4,4'-dimethoxy-3-methylbenzophenone, 2-hydroxy-4,4'-2'-ethylbenzophenone, and 2-hydroxyacetophenone.

[0117] Nanoparticles (such as ZnO) can also be used as UV absorbers and protectants in adhesives. Unbound by theory, these nanoparticles offer the advantage of absorbing potentially damaging ultraviolet light while remaining transparent in the visible light region of the spectrum, thus not affecting the color or appearance of engineered wood products. Other nanoparticles include, but are not limited to, TiO2.

[0118] Suitable fillers comprise substances added to adhesives to improve their performance, strength, or other qualities. For example, fillers can be fibers to increase the compressive and / or adhesive strength of the adhesive, and thus improve the compressive and / or adhesive strength of the final engineered wood product. Fibers can be glass fibers, carbon fibers, cellulose fibers, cellulose nanotubes, carbon microfibers, carbon nanofibers, carbon microtubes, carbon nanotubes, etc.

[0119] Expanded ceramic particles can be added to adhesives to impart flame-retardant properties to engineered wood products. Hydrated metal silicates, borax, calcium borate, magnesium borate, and zinc borate are suitable materials for this purpose.

[0120] Metal hydrates that release water upon heating, halogenated flame retardants, char-forming additives, and low-melting-point glass can be added to adhesives to impart fire-resistant properties to artificial wood products.

[0121] The adhesive-coated wood chips are then returned to approximately their equilibrium moisture content. If necessary, the adhesive-coated wood chips can be dried using any suitable method, including air drying or heating. Heating can be provided via hot air, microwave, radio frequency, or infrared methods, which affect the time required for heating, and then the moisture or solvent is removed to the desired level.

[0122] The adhesive-coated wood chips can be heated before being assembled in the desired configuration, or alternatively, heating is not required during the compression step to initiate crosslinking of the thermoplastic adhesive. In some embodiments, the adhesive-coated wood chips are heated to the molding temperature before being placed in a mold, thereby eliminating the need for heating during molding and limiting thermal conductivity by the integral material being manufactured. Advantageously, in addition to accelerating the curing process, eliminating the need for additional heating during molding speeds up the process because heat contributes to the uniformity of the wood chips in the mold, and this has the additional advantage of reducing processing time in the press, as the low thermal conductivity of wood does not limit the heating of the entire block. The temperature at which the adhesive-coated wood chips are heated is ideally low enough to prevent or minimize crosslinking of the adhesive before compression. In some embodiments, the adhesive-coated wood chips are heated to a temperature of about 50°C to about 200°C, for example, about 50°C to about 100°C. In some specific embodiments, the adhesive-coated wood chips are heated to a temperature of about 75°C. This step results in at least partial drying of the adhesive and heating of the individual adhesive-coated wood chips. By heating the adhesive-coated wood chips before assembling them into the mold, the heat required for the compression step is not solely provided by the mold. In this way, the thickness of the wood chips assembled in the mold is not as critical as when the only heat source during the compression phase is an external heat source. This means the compression phase can proceed more quickly and requires less time to heat the innermost wood chips in the mold to the desired temperature.

[0123] The adhesive-coated wood chips can be heated for a period of approximately 1 minute to approximately 40 minutes, such as 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, 35 minutes, 36 minutes, 37 minutes, 38 minutes, 39 minutes, or 40 minutes. In some embodiments, the adhesive-coated wood chips can be heated for a period of approximately 10 minutes to approximately 12 minutes.

[0124] The wood chips coated with adhesive are then assembled before compression. The adhesive-coated wood chips can be assembled into a mold onto the press table or a plastic peeling plate. In some embodiments, the wood chips are assembled in a mold. The wood chips are typically aligned within the mold. The mold can be any suitable shape, such as square or rectangular, flat or slightly curved to provide a pre-formed monolithic material. The advantage of the method described herein is that the mold can be shaped (e.g., bent) to provide a shaped artificial wood product. For example, thin artificial wood products can be used for decorative purposes on furniture or motor vehicles, and the mold can be suitably shaped and can include surface features (e.g., dents, pawls, etc.) that can be transferred to the artificial wood product.

[0125] The height of the assembled wood chips can be less than, greater than, or substantially the same as the height of the mold. Typically, the pressing step compacts and compresses the assembled wood chips together, resulting in a material with a smaller cross-section than unpressed assembled wood chips.

[0126] The wood chips are typically aligned within a mold. In some implementations, the length of the wood chips along the fiber direction is substantially the same as the length of the mold. The orientation of the wood chips relative to the bottom of the mold can be used to create different visual effects in the final engineered wood product, such as... Figure 1 As shown. For example, a wood chip positioned parallel to the bottom of the mold will produce an artificial wood product with the appearance of the topmost wood chip. A wood chip typically positioned perpendicular to the bottom of the mold will produce an artificial wood product with a striped appearance. A wood chip positioned at an angle relative to the bottom of the mold will produce an artificial wood product with a more pronounced wood grain appearance. Different wood species or different colors of wood chips can also be used to provide the desired effect in the artificial wood product. Advantageously, the method described herein allows for a wide range of different orientations of wood chips without substantially affecting the physical properties of the artificial wood product.

[0127] Once the adhesive-coated wood chips are assembled, pressure is applied to compress the assembled chips to secure them. A suitable press can be used to apply the compression. Any suitable pressure device and / or apparatus can be used to apply pressure to the assembled adhesive-coated wood chips. The pressure forces trapped air out of the assembled adhesive-coated wood chips, creates molecular contact between the wood surfaces, and forces the adhesive to penetrate the wood structure for more effective mechanical bonding. In other words, the adhesive reacts with itself and the wood chips during the compression step. Furthermore, the wood chips undergo mechanical deformation during the compression step, resulting in adjacent chips conforming to each other's shape and interlocking with each other at least to some extent, thereby increasing the product's stiffness and durability. The assembled adhesive-coated wood chips can withstand pressures of approximately 0-100 MPa. In some embodiments, the assembled adhesive-coated wood chips are subjected to pressures of approximately 4 to 20 MPa, for example, approximately 6-10 MPa.

[0128] As discussed above, wood chips coated with adhesive can be heated before assembly, and this heating provides certain processing advantages. However, it is also conceivable that the wood chips may be heated during the compression step, optionally or additionally. For example, heated molds may be used.

[0129] The thermoplastic adhesive is crosslinked to form an artificial wood product that is at least partially cured. Crosslinking can be initiated by heating during the compression step, or it can be initiated at room temperature during the compression step, depending on the thermoplastic resin and crosslinking agent used. During this stage, the assembled wood chips covered with adhesive can be maintained at a temperature of about 70°C to about 150°C. This heat transfer facilitates effective curing of the adhesive. The compression step takes about 5 minutes to about 90 minutes. In some embodiments, the compression step takes about 20 minutes.

[0130] Crosslinking and compression steps can provide fully cured or partially cured engineered wood products. The term "at least partially cured engineered wood product" encompasses both partially cured and fully cured products within its scope.

[0131] If the wood chips coated with adhesive are heated before or during the compression step, the partially cured engineered wood product can be cooled before release, or released while still warm. In the latter case, processing advantages can be obtained by removing the partially cured engineered wood product while it is still warm. Specifically, for products made with phenolic resins, the product must be cooled before being released from the mold because the resin is formed from monomers / prepolymers, which means a longer curing time and the product is prone to splitting if it is released hot from the mold. Less energy and time are required if the partially cured engineered wood product can be removed from the mold while still warm.

[0132] In some implementations, partially cured engineered wood products can undergo an additional curing step to provide the final product. This additional curing can be carried out at temperatures up to 140°C for up to 4 hours, if necessary.

[0133] After processing, engineered wood products are made from a single piece of wood with virtually no voids or gaps within the product. Depending on processing conditions and wood species, the density can range from 0.6 to 1.2, and the corresponding hardness is from 0.4 to 3.0 (using a modified Janka hardness test with a 5mm ball; see [link to relevant documentation]). Figure 8 The modulus of elasticity (MOE) and modulus of rupture (MOR) of blocks or portions cut from blocks (where the wood fibers within the veneer have the same length as the test sample) are similar to those of conventional sheets of the same wood species (see Table 1). Importantly, engineered wood products possess similar mechanical properties and visual appeal to the wood used to manufacture them, and are quite different from existing engineered wood products.

[0134] Table 1 - Modulus of Elasticity (MOE) and Modulus of Rupture (MOR)

[0135] sample <![CDATA[Density (g / cm 3 )]]> Hardness (Janka, 5mm) MOE (MPa) MOR (MPa) Particleboard (chipboard) 0.54 0.67 2,500 18 Medium-density fiberboard (MDF) 0.71 0.94 2,400 27 plywood 0.65 0.77 6350 66 Sydney blue gum (seasonal timber) 0.85-1.15 1.7-2.0 18,000 140 Sydney Blue Eucalyptus Blocks 0.85-1.1 1.5-1.9 14,500 158 Blackwood (seasonal timber) 0.9-1.2 1.7-2.0 19,000 144 Black base wood blocks 0.85-1.2 1.6–2.0 14,000 196 Pine (seasonal timber) 0.5-0.75 0.6-0.8 13,000 90 pine wood blocks 0.75-1.2 0.7-2.2 8,500 90 Red willow seasonal timber 0.985 1.99

[0136] In some embodiments, the artificial wood product contains less than about 15% (by weight), such as less than about 10% (by weight) or less than about 6% (by weight).

[0137] This article also provides artificial wood products formed by the methods described herein.

[0138] Example

[0139] Test - Expansion of the manufactured wooden block in boiling water

[0140] The boiling test is a stringent test used to screen the durability of adhesives. The boiling test is conducted for 3 hours in tap water at 100-105°C (mild boiling). Then, the blocks are dried at room temperature for 2-3 days before measurement.

[0141] By analyzing the x, z, and y dimensions of the block ( Figure 2 Perform initial and final measurements and use the following equation to calculate the expansion percentage to analyze the results:

[0142]

[0143] This allows for the calculation of the expansion percentage in each direction, but due to the orientation of the single plate, the expansion in the y and z dimensions are the only results showing significant changes.

[0144] Test - Modified Janka Hardness Test

[0145] Hardness was measured using the Janka hardness test method (based on ASTM D1037) with a 5mm ball, and the average of five measurements was taken from the largest facet of the block. Clearly, hardness is related to the density of the block.

[0146] Test-Dynamic Mechanical Analysis (DMA)

[0147] The thermomechanical properties of the adhesive were tested on a dry adhesive film using a TA Instruments Q800 DM in stretch mode at a heating rate of 3°C / min.

[0148] Testing - Modulus of Elasticity (MOE) and Modulus of Rupture (MOR)

[0149] According to ASTM D1037-06a, MOE and MOR are tested in three-point bending mode using an Instron tensile testing machine with a typical span of 90 mm.

[0150] Unless otherwise stated, the results of all sample tests are shown in Table 2.

[0151] Example 1 - Preparation of artificial wood products using Sydney blue gum wood and cross-linking adhesives

[0152] Sydney blue gum veneer sheets with a thickness between 2mm and 3mm and a substantially balanced moisture content are cut into individual sheets suitable for molds and coated with a thermoplastic adhesive emulsion (Franklin Titebond 3 plus 10-15% (by weight) water, hereinafter “TB3”) applied by brushing. The adhesive can also be applied by roller coating, spraying, or dipping. The sheets are then dried until the adhesive becomes substantially transparent, then placed in a metal mold and compressed. The adhesive is cured at 80-100°C under a load of 8-12T for approximately 30 minutes. After the molding time, the mold and the manufactured wood block are removed from pressure and allowed to cool to ambient temperature. The block does not change shape or deform upon removal from the mold.

[0153] The block was cut into test pieces, one of which was boiled in water for 3 hours. The other piece was tested for hardness using a modified Janka hardness tester with a 5mm steel indenter ball. The test results are shown in Table 2.

[0154] Example 2 - Experimental preparation of artificial wood products using non-crosslinking adhesives

[0155] Blocks of artificial wood products were prepared using the method described in Example 1, but Selleys Aquadhere was used as the adhesive, which is a non-crosslinked PVA adhesive.

[0156] This example demonstrates that using uncrosslinked adhesives cannot adequately bond the veneer sheets and leads to block failure during testing. Figure 3 ).

[0157] Examples 3 to 5 - Experimental preparation of artificial wood products using low-level crosslinking adhesives

[0158] Blocks of artificial wood products were prepared using the method described in Example 1, but Selleys Aquadhere+ was used as an adhesive (Example 3), Bostik AVXL+ as an adhesive (Example 4), and Henkel F8 as an adhesive (Example 5), all of which are low-level crosslinked PVA adhesives.

[0159] These examples demonstrate that low-level crosslinking adhesives do not produce the desired results.

[0160] Examples 6 to 8 - Preparation of artificial wood products using other crosslinking adhesives

[0161] Blocks of artificial wood products were prepared using the method described in Example 1, but Henkel DLAU7 (a cross-linked PVA adhesive) was used as the adhesive (Example 6), Henkel KL325 (a cross-linked PVA adhesive) was used as the adhesive (Example 7), and Henkel UK5400 (a cross-linked polyurethane emulsion adhesive) was used as the adhesive (Example 8).

[0162] These examples demonstrate that adhesives exhibiting sufficient levels of bonding and crosslinking do indeed produce blocks of engineered wood products that pass the boiling test.

[0163] Example 9 - Preparation of artificial wood products using another crosslinking additive (glyoxal)

[0164] Blocks of the artificial wood product were manufactured using the method described in Example 1, but 2.5% glyoxal was added to the TB3 adhesive as an additional crosslinking agent. The pressing time was extended to 40 minutes to ensure that any reaction occurred.

[0165] This example demonstrates that using crosslinking additives in commercial adhesives produces satisfactory blocks of engineered wood products, and that expansion properties (after boiling test) are improved. Figure 4-6 ).

[0166] Example 10 - Preparation of artificial wood products using another crosslinking additive (glutaraldehyde)

[0167] Blocks of the artificial wood product were manufactured using the method described in Example 1, but 2.5% glutaraldehyde was added to the TB3 adhesive as an additional crosslinking agent. The pressing time was extended to 40 minutes to ensure that any reaction was completed.

[0168] This example demonstrates that using crosslinking additives in commercial adhesives produces satisfactory blocks of engineered wood products, and that expansion properties (after boiling test) are improved. Figure 6 ).

[0169] Example 11 - Preparation of artificial wood products using alternative wood species (pine)

[0170] Blocks of artificial wood products are manufactured using the method described in Example 1, but using Radiata pine veneer.

[0171] This example demonstrates that a satisfactory artificial wood product can be prepared using an alternative wood species (in this case, softwood).

[0172] Example 12 - Preparation of artificial wood products using alternative wood species (pine) with non-crosslinking adhesives

[0173] Blocks of artificial wood products are manufactured using the method described in Example 2, but using Radiata pine veneer.

[0174] This example demonstrates that using uncrosslinked adhesives cannot adequately bond veneers and causes block failure during testing.

[0175] Example 13 - Preparation of artificial wood products using alternative wood species (pine) with crosslinking adhesive

[0176] Blocks of artificial wood products are manufactured using the method described in Example 7, but using Radiata pine veneer.

[0177] This embodiment demonstrates that when using cross-linked PVA-based adhesives, it is possible to use alternative wood species (in this case, softwood) to manufacture blocks of satisfactory artificial wood products.

[0178] Example 14 - Preparation of artificial wood products using alternative wood species (blue gum) with crosslinking additives

[0179] Blocks of the artificial wood product were prepared using the method described in Example 11, but with the adhesive Henkel KL442. The sheets in the block did not adhere, and the block split upon removal from the mold.

[0180] This example demonstrates that not all adhesives can be used to form a monolithic material that retains its compacted shape.

[0181] Example 15 - Preparation of artificial wood products using alternative wood species (pine) with crosslinking additives

[0182] Blocks of artificial wood products were manufactured using the method described in Example 11, but with 5% by weight of glyoxal added to the adhesive and a pressing time of 20 minutes.

[0183] This example demonstrates that using a crosslinking additive (glyoxal) in a commercially available pack of adhesive produces a satisfactory block of engineered wood product with improved expansion properties (after a boiling test).

[0184] Example 16 - Preparation of engineered wood products using alternative wood species (pine) with crosslinking additives and longer pressurization time

[0185] Blocks of artificial wood products were manufactured using the method in Example 15, but with a longer curing time (40 minutes) in the press.

[0186] This example demonstrates that using a crosslinking additive (glyoxal) in a commercially available pack of adhesive produces a satisfactory block of engineered wood product with improved expansion properties (after a boiling test).

[0187] Example 17 - Preparation of artificial wood products using alternative wood species (pine) with crosslinking additives, longer pressure time, and post-heat treatment.

[0188] Blocks of artificial wood products were manufactured using the method in Example 16, but then postheated in an oven at 120°C for 2 hours.

[0189] This example demonstrates that the artificial wood product blocks prepared using this method are stable at high temperatures.

[0190] Example 18 - Preparation of artificial wood products using alternative wood species (bamboo)

[0191] Blocks of artificial wood products are manufactured using the method in Example 1, but bamboo filaments are used instead of wood veneer.

[0192] Examples 19-23 - Preparation of artificial wood products using alternative wood species

[0193] Blocks of artificial wood products were manufactured using the method described in Example 5, but veneers of blackwood (Example 19), red maple (Example 20), Tasmanian oak (Example 21), giant eucalyptus (Example 22), and aspen (Example 23) were used.

[0194] Examples 18 to 23 demonstrate that this method can be used to manufacture blocks of artificial wood products from various wood species, which retain their shape after molding and a 3-hour water boiling test. These blocks possess mechanical properties similar to typical hardwoods.

[0195] Example 24 - Experimental Preparation of Artificial Wood Products with Excessively Thick Venes

[0196] Blocks of artificial wood products were manufactured using the method described in Example 1, but thick slices of black base wood, approximately 10 mm thick, were cut from the board. The resulting blocks of artificial wood products were of poor quality, with many gaps, and therefore did not form a solid structure.

[0197] Example 25 - Preparation of artificial wood products without heating during the pressing stage

[0198] Blocks of artificial wood products were manufactured using the method in Example 1, but the press was not heated.

[0199] This indicates that blocks of artificial wood products can be manufactured by curing wood blocks containing room temperature curing adhesives at ambient temperature.

[0200] Examples 26 and 27 - Preparation of artificial wood products using cold release from a press

[0201] According to the method in Example 1, blocks of artificial wood products are manufactured using blue gum veneer (Example 26) or giant eucalyptus (Example 27). In these examples, the blocks are cooled to <40°C in a mold using a water cooling system in a hot press.

[0202] These examples demonstrate that higher density and hardness can be achieved by changing processing conditions. Furthermore, the range of density and hardness properties achievable by changing processing conditions for blocks made from pine veneer is described in [the following section / section / etc.]. Figure 8 As shown in the image.

[0203] Example 28 - Trial preparation of engineered wood products with veneer of high moisture content

[0204] The block is manufactured according to the method in Example 11, but excess moisture from the veneer sheets is not dried before molding. When removed from the mold, the block is still moist and soft, and the veneer sheets do not stick together.

[0205] This embodiment demonstrates that a very high moisture content is undesirable.

[0206] Example 29 - Preparation of artificial wood products by post-heat treatment after heat release

[0207] The block was manufactured using the method described in Example 1, but using giant eucalyptus wood, and then post-heated in an oven at 140°C for 2 hours. The block retained its solid shape.

[0208] Examples 30-35 - Preparation of artificial wood products using different orientations of veneers

[0209] like Figure 7 As shown, veneers can be oriented in different ways within the mold. Using the method in Example 1, blocks are manufactured in the mold using veneers with various orientations. Example 1 is as follows... Figure 7 C is oriented, as in Examples 30 and 31. Figure 7 A is oriented, as in Examples 32 and 34. Figure 7 E is used for orientation, as in Example 33. Figure 7 D is used for orientation, as in Example 35. Figure 7 F is used for orientation.

[0210] These examples demonstrate that while the visual appearance on a flat top surface or a cut surface along the length of the block is strongly affected, the mechanical properties (density and hardness) are essentially unaffected by the orientation of the veneer (Table 3).

[0211] Table 2 - Physical and mechanical properties of blocks of artificial wood products prepared according to the examples (Ex# indicates example number).

[0212]

[0213]

[0214] Note: "Material retention" means maintaining the compressed shape of the whole material after removal from the mold; "cooking test" means maintaining the shape essentially during 3 hours of water cooking without significant decomposition or cracking; MOE is the modulus of elasticity, and MOR is the modulus of rupture.

[0215] Table 3 - Effects of Orientation Changes in Wood Veneer in the Mold on Hardness and Density (Ex# refers to the example number)

[0216]

[0217] Throughout the specification and the subsequent claims, unless the context otherwise requires, the words “comprising” and “including”, as well as variations thereof, shall be understood to include integers or groups of integers, but not exclude any other integers or groups of integers.

[0218] Any reference to prior art in this specification is not, and should not be construed as, any form of implied acceptance that such prior art is part of common general knowledge.

[0219] Those skilled in the art will understand that the use of this invention is not limited to the specific applications described. The invention, in its preferred embodiments, is also not limited to the specific elements and / or features described or narrated herein. It is understood that the invention is not limited to the disclosed embodiments, but many rearrangements, modifications, and substitutions are possible without departing from the scope of the invention as set forth and defined by the appended claims.

Claims

1. A compacted, monolithic artificial wood product having similar mechanical properties and visual appeal to the wood used to manufacture it, the artificial wood product comprising a plurality of natural wood fibers or veneers bonded together by a crosslinked thermoplastic adhesive that has been crosslinked during processing, wherein the crosslinked thermoplastic adhesive has been applied to the wood fibers or veneers before assembly into a mold, and comprising: (i) an aqueous polymer emulsion and (ii) a crosslinking agent, the crosslinking agent being a catalyst or reactant selected from the group consisting of N-hydroxymethylacrylamide, borax, aluminum zirconium carbonate, aluminum chloride, magnesium chloride, p-toluenesulfonic acid, acetaldehyde, formaldehyde, urea-formaldehyde, melamine-formaldehyde, trimethylol melamine, copper ammonium complex, chromium complex, organotitanate, dichromate, polyaldehyde, butyraldehyde, chloroformate, urea, isocyanate, and zirconium ammonium carbonate, wherein the artificial wood product maintains its compacted shape at a high temperature, and wherein the crosslinked thermoplastic adhesive has a glass transition temperature of less than 70 degrees Celsius.

2. The artificial wood product according to claim 1, wherein the crosslinked thermoplastic adhesive in the artificial wood product has a glass transition temperature of less than 50 degrees Celsius.

3. The artificial wood product according to claim 1, wherein the crosslinked thermoplastic adhesive in the artificial wood product has a glass transition temperature of less than 30 degrees Celsius.

4. The artificial wood product according to claim 1, wherein the crosslinked thermoplastic adhesive in the artificial wood product has a glass transition temperature of less than 20 degrees Celsius.

5. The artificial wood product according to claim 1, wherein the crosslinked thermoplastic adhesive has a glass transition temperature below room temperature.

6. The artificial wood product according to any one of claims 1 to 5, wherein the plurality of wood fibers or wood veneers are mechanically deformed during processing such that adjacent wood fibers or wood veneers are identical in shape to each other.

7. The artificial wood product according to any one of claims 1 to 5, wherein the artificial wood product comprises less than 15% by weight of cross-linked thermoplastic adhesive.

8. The artificial wood product according to any one of claims 1 to 5, wherein the artificial wood product comprises less than 10% by weight of cross-linked thermoplastic adhesive.

9. The artificial wood product according to any one of claims 1 to 5, wherein the artificial wood product comprises less than 6% by weight of crosslinked thermoplastic adhesive.

10. The artificial wood product according to any one of claims 1 to 5, wherein the veneer shape of each assembled wood filament or wood veneer after compression is different from the veneer shape of each assembled wood filament or wood veneer before compression.

11. The artificial wood product according to any one of claims 1 to 5, wherein the wood used for the wood fibers or wood veneer is selected from the group consisting of eucalyptus, pine, red maple, Queensland maple, ash, aspen, walnut, oak, mahogany, birch, mahogany, ebony, cherry, Oregon wood, fir, rubberwood, teak, paulownia, poplar, and grasses.

12. The artificial wood product according to any one of claims 1 to 5, wherein the artificial wood product comprises one or more additives.

13. A method for preparing artificial wood products, comprising: - Offer multiple wood fibers or veneers with a basic balance of moisture content; - Apply a thermoplastic adhesive containing a thermoplastic resin and a crosslinking agent to the wood filaments or wood veneer to form a wood filaments or wood veneer coated with a thermoplastic adhesive; - Heating the wood filaments or veneer coated with thermoplastic adhesive to form heated wood filaments or veneer coated with thermoplastic adhesive; - Assemble the wood velvet or wood veneer coated with thermoplastic adhesive in the desired configuration to form an assembled wood velvet or wood veneer coated with thermoplastic adhesive. - The assembled wood filaments or veneers coated with thermoplastic adhesive are compressed in a press under pressure for a time sufficient to press and compress the assembled wood filaments or veneers to force out trapped air and mechanically deform the assembled wood filaments or veneers coated with thermoplastic adhesive, so that adjacent wood filaments or veneers conform to each other in shape. - During the compression step, the thermoplastic adhesive is crosslinked to at least a critical crosslinking amount to form at least partially cured artificial wood products, wherein the crosslinked thermoplastic adhesive in the artificial wood products has a glass transition temperature of less than 70 degrees Celsius, and wherein the critical crosslinking amount is sufficient to allow the at least partially cured artificial wood products to substantially maintain their compressed form and to prevent the wood fibers or wood veneers from expanding under release pressure and returning to their initial state during the compression step. - Remove the at least partially cured artificial wood product from the press; and - Further cure the at least partially cured artificial wood product to provide an artificial wood product with a substantially balanced moisture content.

14. The method of claim 13, wherein the thermoplastic adhesive comprises one or more additives.

15. The method of claim 13, wherein one or more additives are applied to the wood fibers or wood veneer prior to coating the thermoplastic adhesive.

16. The method according to any one of claims 13 to 15, wherein the wood fibers or veneer coated with the thermoplastic adhesive are heated to dry the thermoplastic adhesive and to maintain a substantially balanced moisture content in the wood fibers or veneer coated with the thermoplastic adhesive.

17. The method according to any one of claims 13 to 15, wherein the wood fibers or veneers coated with thermoplastic adhesive are preheated before being assembled and compressed in the desired configuration.

18. The method of claim 17, wherein the wood filaments or wood veneer coated with the thermoplastic adhesive are heated to a temperature of up to 200°C.

19. The method of claim 18, wherein the wood filaments or veneer coated with the thermoplastic adhesive are heated for a period of 1 minute to 40 minutes.

20. The method according to any one of claims 13 to 15, wherein the plurality of wood fibers or wood veneers are mechanically deformed during the compression step such that adjacent wood fibers or wood veneers are shaped to match each other.

21. The method according to any one of claims 13 to 15, wherein the veneer shape of each assembled wood filament or wood veneer after compression is different from the veneer shape of each assembled wood filament or wood veneer before compression.

22. The method according to any one of claims 13 to 15, wherein the crosslinked thermoplastic adhesive comprises: (i) an aqueous polymer emulsion and (ii) a crosslinking agent, said crosslinking agent being a catalyst or reactant selected from the group consisting of N-hydroxymethylacrylamide, borax, aluminum zirconium carbonate, aluminum chloride, magnesium chloride, p-toluenesulfonic acid, acetaldehyde, formaldehyde, urea-formaldehyde, melamine-formaldehyde, trimethylol melamine, copper ammonium complex, chromium complex, organotitanate, dichromate, polyaldehyde, butyraldehyde, chloroformate, urea, isocyanate and zirconium ammonium carbonate.

23. The method according to any one of claims 13 to 15, wherein the wood filaments or wood veneers coated with thermoplastic adhesive are assembled in a mold in the desired configuration.

24. The method according to any one of claims 13 to 15, wherein the assembled wood fibers or wood veneer are compressed under a pressure of 4 to 20 MPa.

25. The method according to any one of claims 13 to 15, wherein the crosslinking is initiated by heating during the compression step.

26. The method of claim 25, wherein, During the compression step, the assembled wood fibers or veneers are kept at a temperature of up to 150°C.

27. The method of claim 25, wherein the compression step takes 5 to 90 minutes.

28. The method according to claim 27, wherein, At least partially cured artificial wood products are released from the mold while still warm.

29. The method according to any one of claims 13 to 15, wherein the at least partially cured artificial wood product undergoes an additional curing step to provide the artificial wood product.

30. The method according to any one of claims 13 to 15, wherein the wood fibers or wood veneer have a maximum thickness of 0.1 mm to 10 mm.

31. The method of claim 24, wherein the wood used for the wood fibers or wood veneer is selected from the group consisting of eucalyptus, pine, red maple, Queensland maple, ash, aspen, walnut, oak, mahogany, birch, mahogany, ebony, cherry, Oregonwood, fir, rubberwood, teak, paulownia, poplar, and grasses.

32. The method according to any one of claims 13 to 15, comprising assembling the wood filaments or wood veneer coated with thermoplastic adhesive or dried wood filaments or wood veneer coated with thermoplastic adhesive in a configuration such that the length of the wood filaments or wood veneer in the fiber direction is the same as the length of the artificial wood product to form an assembled wood filaments or wood veneer.

33. An artificial wood product formed by the method according to any one of claims 13 to 32.

Images