Process for preparing silicate functionalized engineered wood articles with improved properties

Abstract

The invention relates to a process for manufacturing a flame-retardant gluing engineering wood product. The process includes providing an engineered wood part treated by immersion with a metal silicate solution, exposing the metal silicate treated engineered wood part to an adhesive, and bonding a plurality of units of the metal silicate treated engineered wood together by the adhesive to form a flame retardant glued engineered wood article. The present invention also relates to flame retardant glued engineered wood articles prepared by the processes described herein.

Description

[0001] This application claims priority to U.S. Provisional Application No. 63,428,257, filed on November 28, 2022, and the entire contents of that application are incorporated herein by reference. Technical Field

[0002] The present invention generally relates to the field of flame retardant glued engineered wood products. Background Art

[0003] Wood is a building material that has been used for thousands of years. Joining multiple pieces of wood together and attaching wood to other materials is important. This connection can be accomplished mechanically, using nails, screws, or fastening plates. More recently, the use of wood glue or adhesives has become increasingly common. For example, wood glue can be applied to the wood and then the joint secured until adhesion to the wood is established and the glue has fully cured.

[0004] Typical approaches to improving the adhesion, durability, or cure rate of glues or adhesives involve formulating or reformulating the glue or adhesive itself by changing its ingredients and other additives. For example, additives can be added to the glue to roughen or treat the wood surface to improve the mechanical interlocking between the wood. Another approach is to create a chemical bond or a more chemically compatible interface between the wood substrate and the adhesive. For example, in the case of moisture-curing or epoxy adhesives, the use of catalysts on the surface can enhance adhesion or increase the reaction rate.

[0005] Sodium silicate has been used to catalyze faster curing reactions for some glues commonly used for wood bonding. For example, Liu et al., “PVA wood adhesive modified with sodium silicate cross-linked copolymers” (2012), published at the 2012 International Conference on Biobased Materials Science and Engineering (BMSE), and Liu et al., “Study on the effects of organic additives and inorganic fillers on the properties of polyvinyl alcohol-modified sodium silicate wood adhesives” (2015), published in BioResources, 10(1):1528-42, describe the effects of adding sodium silicate to polyvinyl alcohol to form a wood adhesive on the curing time of the glue, as well as the adhesive strength and water resistance of the glue. However, the references do not address the effects of sodium silicate impregnation on the flame retardant properties of the treated wood.

[0006] U.S. Patent No. 8,323,449 discloses the addition of sodium silicate to polyphenol adhesives, a common glue used in composite materials such as plywood, as part of an extender formulation intended to reduce the amount of adhesive required. The patent also discloses that the adhesive needs to be reformulated to include polyhydric alcohols to improve the shelf life and increase the working time of the glue, as simply adding sodium silicate to phenolic or melamine urea-formaldehyde adhesives results in rapid gelation. However, the patent does not address the treatment of wood impregnated with sodium silicate, the interaction of sodium silicate with the treated wood, or the effect of silicate impregnation on the flame retardant properties of the treated wood.

[0007] Silicate binders have also been used alone as inorganic binders. For example, U.S. Patent No. 3,663,355 discloses the use of sodium silicate as an inorganic binder layer for bonding wood boards. However, this patent does not address the impregnation treatment of wood with sodium silicate or the interaction of sodium silicate or the binder with silicate-treated wood; nor does the patent discuss any flame retardant properties of the wood.

[0008] All of the aforementioned references and patents involve adding sodium silicate directly to an adhesive or using sodium silicate itself as an adhesive layer. None of them disclose treating engineered wood parts by impregnation with a metal silicate and then bonding the silicate-treated engineered wood parts with an adhesive, nor the benefits associated with such a process, let alone the unique benefits of such a process for improving the mechanical and flame retardant properties of the glued silicate-treated engineered wood.

[0009] Sodium silicate has been used to impregnate wood products. U.S. Patent No. 6,827,984 and U.S. Patent No. 6,303,234 disclose impregnation of porous combustible materials (e.g., wood) to improve fire resistance. However, in both patents, the wood products are already assembled, and the glue (if any) used is located between the wood veneers, wood chips, flakes, or particles and has been fully cured before the wood products are treated with sodium silicate impregnation. As a result, the glue (if any) between the wood is unable to react effectively with the silicate, and the mechanical properties of the adhesive and interface are easily damaged and / or degraded.

[0010] Therefore, there remains a need to develop wood products with improved bonding efficiency to wood adhesives, improved stability of wood adhesives, and improved flame retardancy of wood adhesives and wood, while providing enhanced mechanical properties to the wood adhesives and wood. The present invention addresses this need. Summary of the Invention

[0011] The disclosure herein describes a wood product and a process for achieving such a wood product, which improves the bonding efficiency of wood adhesives by impregnating wood with metal silicates (e.g., sodium silicate), and then exhibits faster and stronger curing with the wood adhesive. This silicate-impregnated wood achieves improvements to the adhesive without requiring a long time to reformulate the wood adhesive, nor does it affect the adhesive's pot life and handling characteristics because the co-reactants (i.e., the wood adhesive and the metal silicate) are separately contained in the wood. The adhesive is not modified before contacting silicate-treated wood during the manufacturing process. This process can also limit the reaction between the adhesive and the metal silicate to the adhesive-wood interface, which increases the modulus and shortens the curing time, while the portion of the adhesive not in contact with the wood maintains its original properties. The combination of a higher modulus on the adhesive's top surface and a lower modulus on the inner surface can provide ductility and strength that cannot be achieved in a homogeneous material (e.g., simply using a metal silicate as an adhesive or adding the metal silicate to the adhesive to form a reformulated adhesive). Silicates also improve the physical properties of the wood itself, most notably the fire resistance of the resulting wood products, a property that further enhances the performance of the adhesive.

[0012] The present invention also provides a method for converting a conventional engineered wood manufacturing line to one that is capable of impregnating silicate wood prior to adhesive bonding as part of the manufacturing process.

[0013] Therefore, one aspect of the present invention relates to a process for producing a flame retardant glued engineered wood product. The process comprises:

[0014] Providing engineered wood components treated by impregnation with a metal silicate solution,

[0015] exposing the metal silicate treated engineered wood component to the adhesive, and

[0016] Multiple units of metal silicate-treated engineered wood components are bonded together by an adhesive to form a flame-retardant glued engineered wood product.

[0017] Another aspect of the present invention relates to a process for modifying an engineered wood production line to produce flame-retardant glued engineered wood products. The process comprises providing an engineered wood production line comprising the following steps:

[0018] forming engineered wood components,

[0019] optionally drying the engineered wood component,

[0020] exposing the engineered wood component to an adhesive, and

[0021] The multiple units of the engineered wood component are bonded together by adhesive.

[0022] The process further includes incorporating into the engineered wood production line the step of treating the engineered wood component by impregnation with a metal silicate solution prior to the step of exposing the engineered wood component to the adhesive.

[0023] In some embodiments, the exposing step forms a layer of adhesive on the surface of the metal silicate-treated engineered wood component.

[0024] In some embodiments, the reaction between the binder and the metal silicate provides one or more of the following:

[0025] (i) Improve the bonding efficiency between wood and adhesive through faster and stronger curing,

[0026] (ii) improving the flame retardancy of the adhesive by infusing the adhesive with metal silicates embedded in the wood,

[0027] (iii) improving the stability of the adhesive by minimizing adhesive degradation caused by fungi, algae, yeasts, lichens and / or bacteria,

[0028] (iv) improving mechanical properties by hardening the adhesive, and

[0029] (v) Improved mechanical properties through mechanical interlocking of the adhesive and wood by metal silicates embedded in the wood.

[0030] In some embodiments, bonding of multiple units of sodium silicate-treated engineered wood components forms a wood-adhesive interface where the reaction between the adhesive and the metal silicate is limited to the wood-adhesive interface, providing improved ductility and strength due to a combination of higher modulus at the surface where the adhesive reacts with the metal silicate and lower modulus at the interior of the adhesive where it does not react with the metal silicate.

[0031] In some embodiments, the metal silicate is sodium silicate, potassium silicate, lithium silicate, iron silicate, or a mixture thereof. In some embodiments, the metal silicate is sodium silicate, potassium silicate, lithium silicate, or a mixture thereof, forming a solution having about 2-40 wt% solids. In some embodiments, the metal silicate-treated engineered wood component contains about 5-25 wt% silicate solids.

[0032] In some embodiments, impregnation is performed by applying vacuum and / or pressure. In some embodiments, vacuum and / or pressure are applied in batches. Alternatively, vacuum and / or pressure are applied continuously, for example, by applying pressure on one side of the wood and vacuum on the other side. In some embodiments, the apparatus for applying vacuum pressure includes an additional recovery line for supplying the metal silicate solution to the vacuum side.

[0033] In some embodiments, the process further comprises drying the metal silicate-treated engineered wood component to a moisture level of 19% or less prior to the exposing step.

[0034] In some embodiments, the process further comprises at least partially curing the adhesive and / or metal silicate in the treated wood. In some embodiments, the at least partial curing occurs before the exposing and / or bonding steps. In some embodiments, the at least partial curing occurs after the exposing and / or bonding steps.

[0035] In some embodiments, the metal silicate-treated wood component is uncured prior to the exposing and / or bonding steps.

[0036] In some embodiments, curing is at least partially performed by heating.

[0037] In some embodiments, the curing is at least partially performed by a curing agent. In some embodiments, the curing agent is selected from the group consisting of: a protic acid, an inorganic acid, a Lewis acid, a metal salt, carbon dioxide, an organic molecule, an additive, and a polyvalent Lewis acid salt.

[0038] In some embodiments, the process further comprises applying pressure after at least partially curing and / or bonding. In some embodiments, the pressure is applied by mechanical clamping or rolling. In some embodiments, the pressure is increased to above atmospheric pressure.

[0039] In some embodiments, impregnation is performed by applying pressure alone. In some embodiments, pressure is applied by mechanical clamping or rolling. In some embodiments, the pressure is increased to above atmospheric pressure.

[0040] In some embodiments, the adhesive is animal glue, phenol / polyphenol / resorcinol formaldehyde, lignin-phenol-formaldehyde, urea-formaldehyde, melamine formaldehyde, melamine urea-formaldehyde, polyurethane, epoxy resin, polyvinyl alcohol, polyvinyl acetate, cyanoacrylate, casein, aliphatic resin, or contact adhesive.

[0041] In some embodiments, the engineered wood component is plywood, lumber, veneer, oriented strand board, wood chips, flakes or wood chips, particles or sawdust.

[0042] Another aspect of the present invention relates to a flame retardant glued engineered wood product, which is prepared by the process described in any of the above aspects and embodiments of the present invention.

[0043] Another aspect of the present invention relates to the use of the flame retardant glued engineered wood product described in any of the above aspects and embodiments of the present invention in the construction, furniture or appliance manufacturing, structural timber, plywood, oriented strand board, particle board or wood composite material manufacturing and development processes.

[0044] In some embodiments, there is provided a use of the flame-retardant glued engineered wood product described in any of the above aspects and embodiments of the present invention in a building connection material.

[0045] Another aspect of the present invention relates to the use of the flame retardant glued engineered wood product described in any of the above aspects and embodiments of the present invention for increasing adhesion to a polymeric material. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a flow chart showing an exemplary process for making a flame retardant glued engineered wood product with improved fire resistance and mechanical properties.

[0047] Figure 2 Exemplary wood morphologies and representative wood structures used in the processes described herein are listed.

[0048] Figures 3A-3C is an exemplary embodiment of the process of the present invention ( Figure 3C ) and the process for treating glued wood products with silicate impregnation ( Figure 3A ) and the use of modified wood adhesives in the manufacture of glued wood products ( Figure 3B ), where Figure 3B In

[15] , modified wood adhesives were reformulated by adding additives such as silicates directly to conventional wood adhesives.

[0049] Figure 4 is a diagram of a typical plywood manufacturing process using wood glue / adhesives.

[0050] Figure 5 is a schematic diagram showing the manufacturing process of plywood containing silicate-treated veneer.

[0051] Figure 6 is a schematic diagram showing the in-line silicate treatment of veneer in the plywood manufacturing process.

[0052] Figure 7 is a schematic diagram showing a plywood manufacturing process that incorporates silicate treatment of veneer and further incorporates the addition of additives (eg, curing agent) and drying. DETAILED DESCRIPTION

[0053] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In the specification and claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0054] The embodiments of the present invention and its various features and advantages are explained more fully with reference to the non-limiting embodiments and examples illustrated and described in the following description of the examples. In order to avoid obscuring the invention, descriptions of well-known components and technologies are omitted. The examples used herein are merely intended to facilitate an understanding of how the invention can be practiced and to further enable those of ordinary skill in the art to practice the invention. Therefore, the examples and embodiments described herein should not be construed as limiting the scope of the invention as defined by the claims.

[0055] This disclosure describes materials and processes for making wood products that improve the interaction of wood with commonly used wood glues by treating the wood without adding to the glue formula and without the need to reformulate the glue. This process not only improves the adhesion and mechanical strength of the wood-adhesive-wood interface, but also enhances flame retardancy and environmental performance.

[0056] In this process, wood is treated by immersing it in a metal silicate solution (e.g., by soaking the wood, coating the wood, or using an aqueous solution of the metal silicate via vacuum pressure impregnation) to interact with the adhesive molecules used to make engineered wood composites during the manufacture of engineered wood products, resulting in silicate-functionalized engineered wood. The silicate-treated wood exhibits faster and stronger glue cure, and the silicate treatment also improves the physical properties of the wood itself. Also described is a process and design modification to a conventional engineered wood production line to infuse the wood with metal silicate in an in-line process during the manufacture of engineered wood products, prior to bonding the treated wood with an adhesive.

[0057] Silicate functionalization process and its effect on the wood-adhesive-wood interface

[0058] One aspect of the present invention relates to a process for producing a flame-retardant glued engineered wood product. The process comprises:

[0059] Providing engineered wood components treated by impregnation with a metal silicate solution,

[0060] exposing the metal silicate treated engineered wood component to the adhesive, and

[0061] Multiple units of metal silicate-treated engineered wood components are bonded together by an adhesive to form a flame-retardant glued engineered wood product.

[0062] Another aspect of the present invention relates to a process for modifying an engineered wood production line to produce flame-retardant glued engineered wood products. The process comprises providing an engineered wood production line comprising the following steps:

[0063] forming engineered wood components,

[0064] optionally drying the engineered wood component,

[0065] exposing the engineered wood component to an adhesive, and

[0066] The multiple units of the engineered wood component are bonded together by adhesive.

[0067] The process further includes incorporating into the engineered wood production line the step of treating the engineered wood component by impregnation with a metal silicate solution prior to the step of exposing the engineered wood component to the adhesive.

[0068] Materials and process conditions

[0069] In the processes described herein, a wood component (e.g., an engineered wood component) is provided. Any wood type suitable for gluing can be used in the processes described herein. The wood typically used is engineered wood. Wood in any wood form can be used, including but not limited to veneer, solid / continuous (e.g., lumber, plywood, solid wood components), assembled solid (e.g., cross-laminated timber), laminated / assembled laminated (e.g., plywood), wood chips (e.g., particle board), wood chips and strips (e.g., oriented strand board), particles (e.g., particle board), or sawdust (e.g., polymer filler, adhesive filler, wood filler, etc.). For example, see Figure 2 Examples of engineered wood include wood substrates (e.g., plywood, oriented strand board, fiberboard, particle board), structural composite lumber (e.g., laminated veneer lumber, parallel strand lumber, laminated strand lumber, I-beams), and dimension lumber (cross-laminated timber, glue-laminated timber, dowel-laminated timber, nail-laminated timber).

[0070] In some embodiments, the wood component used is early-stage wood and / or porous wood. In some embodiments, the wood component used is blue-stain wood. Without being limited by theory, the use of early-stage wood and / or porous wood, as well as the use of blue-stain wood, can increase the silicate concentration in the wood product. In some embodiments, the wood component used is hardwood. In some embodiments, the wood component used is softwood. Without being limited by theory, the use of hardwood or softwood can affect the degree of silicate impregnation and the ultimate properties of the silicate-treated wood. In some embodiments, the engineered wood component is a plywood veneer. In some embodiments, the engineered wood component is OSB or particle board.

[0071] Prior to exposing the wood parts to the adhesive, the wood parts are impregnated with an aqueous solution of a metal silicate. Suitable metal silicates include, but are not limited to, sodium silicate, potassium silicate, lithium silicate, iron silicate, or mixtures thereof. In some embodiments, the metal silicate is sodium silicate, potassium silicate, lithium silicate, iron silicate, or mixtures thereof. In some embodiments, the metal silicate is sodium silicate, potassium silicate, lithium silicate, or mixtures thereof. In some embodiments, the metal silicate forms a solution having about 2-40 wt% solids, for example, about 2-35 wt%, about 2-30 wt%, about 2-25 wt%, about 2-20 wt%, about 2-15 wt%, about 2-10 wt%, about 2-5 wt%, about 5-40 wt%, about 5-35 wt%, about 5-30 wt%, about 5-25 wt%, about 5-20 wt%, about 5-15 wt%, about 5-10 wt%, about 10-40 wt% solids. %, about 10-35 wt %, about 10-30 wt %, about 10-25 wt %, about 10-20 wt %, about 10-15 wt %, about 15-40 wt %, about 15-35 wt %, about 15-30 wt %, about 15-20 wt %, about 20-40 wt %, about 20-35 wt %, about 20-30 wt %, about 25-40 wt %, about 25-35 wt %, or about 30-40 wt % solids (i.e., dissolved metal silicate). In one embodiment, the metal silicate-treated engineered wood component contains about 5-25 wt % silicate solids.

[0072] In some embodiments, the metal silicate (e.g., sodium silicate) comprises a mixture of different silicates having different moduli (i.e., ratio of silicon dioxide to sodium oxide). In some embodiments, the metal silicate comprises a mixture of silicates having different counterions. In some embodiments, the metal silicate comprises a mixture of silicates having both different moduli and different counterions.

[0073] In some embodiments, the metal silicate solution (eg, sodium silicate) further comprises ingredients such as borates, boric acid, surfactants, multivalent salts (eg, calcium, magnesium, aluminum, and zinc salts).

[0074] The metal silicate can be impregnated in a variety of ways. The metal silicate solution can be applied to the wood by an immersion bath. The wood can be immersed in the metal silicate solution with or without vacuum or pressure assistance. For example, the metal silicate can be incorporated into the interstices and / or surface of the wood by immersing the wood parts in a static or agitated solution without vacuum or pressure assistance, exposing the wood parts to a solution of a metal silicate (e.g., sodium silicate). Alternatively, the metal silicate can be incorporated into the interstices and / or surface of the wood by immersing the wood parts in a static or agitated solution with vacuum and / or pressure assistance, exposing the wood parts to a solution of a metal silicate (e.g., sodium silicate).

[0075] The metal silicate solution can be applied to the wood by surface coating. For example, the wood component can be exposed to the metal silicate (e.g., sodium silicate) solution by coating the wood surface with or without a subsequent pressure step or repeated / additional applications.

[0076] In some embodiments, impregnation is performed by applying vacuum and / or pressure. In some embodiments, vacuum and / or pressure are applied in batches. In some embodiments, vacuum and / or pressure are applied continuously, for example, by applying pressure on one side of the wood and vacuum on the other side of the wood. In some embodiments, the apparatus for applying vacuum pressure includes an additional recovery line for supplying the metal silicate solution to the vacuum side.

[0077] In some embodiments, the impregnation is performed at a temperature of about 25°C to about 100°C (eg, from about 30°C to about 80°C, or from about 35°C to about 70°C).

[0078] In some embodiments, the impregnation is performed by applying pressure alone. In some embodiments, the pressure is applied by mechanical clamping or rolling. In some embodiments, the pressure is increased to above atmospheric pressure. Typically, the pressure applied ranges from 5 to 200 psi, for example, from 10 to 200 psi, from 50 to 190 psi, from 100 to 190 psi, from 120 to 190 psi, from 100 to 150 psi, or from 110 to 120 psi.

[0079] The soaking can be carried out for about 10 minutes to about 24 hours, for example, about 10 minutes to about 12 hours, about 10 minutes to about 6 hours, about 10 minutes to about 4 hours, about 10 minutes to about 2 hours, about 10 minutes to about 60 minutes, about 30 minutes to about 6 hours, about 30 minutes to about 4 hours, about 30 minutes to about 2 hours, or about 30 minutes to about 60 minutes.

[0080] More details regarding suitable metal silicate types and suitable impregnation conditions can be found in U.S. Patent No. 6,827,984, U.S. Patent No. 6,303,234, and International Patent Application WO 2021 / 113705, the entire contents of which are incorporated herein by reference.

[0081] The process may include an optional drying step, during which the wood can be analyzed for silicate concentration by XRF and can be used with adhesive at this point, or cut, planed, or stranded as needed to achieve different morphologies. This drying step can be performed using ambient air or heat (e.g., oven-drying). The silicate-treated wood parts can be dried to remove excess moisture, but are generally allowed to maintain a moisture content of about 19% or less. In some embodiments, the process further includes a drying step prior to exposing the engineered wood parts to the adhesive.

[0082] The process may further include at least partially curing or completely curing the metal silicate embedded in the wood by physical or chemical means. Curing the silicate refers to reducing the water solubility of the metal silicate (e.g., sodium silicate) deposited from the aqueous solution, rendering the silicate embedded in the wood insoluble. Curing improves the water resistance of the metal silicate (e.g., sodium silicate) impregnation, and applying silica particles to the treated wood surface further improves the wood's performance in a flame environment.

[0083] Without being limited by theory, the use of metal silicates (eg, sodium silicate) may also enhance the cure of the adhesive when combined with silicate-impregnated wood.

[0084] Curing of the metal silicate and / or binder can be achieved by using an energy source (e.g., heating), providing an acid source (e.g., a mineral acid, a protic acid or a Lewis acid (e.g., HCl, acetic acid, citric acid, phosphoric acid, boric acid, carbonic acid, etc.), a metal salt (e.g., calcium chloride, magnesium chloride, aluminum sulfate, etc.), carbon dioxide, an organic molecule, or an additive. Curing can also be achieved by adding a polyvalent Lewis acid salt. Other curing agents can be found in U.S. Patent No. 9,415,526 and U.S. Patent No. 3,974,318, the entire contents of which are incorporated herein by reference.

[0085] In some embodiments, the metal silicate (eg, sodium silicate) impregnated wood is at least partially cured or fully cured by heating or using any of the curing techniques described above.

[0086] The curing temperature may range from about 25°C to about 100°C, for example, from about 30°C to about 80°C, or from about 35°C to about 70°C.

[0087] Curing or other post-treatment can be performed for about 10 minutes to about 24 hours, for example, about 10 minutes to about 12 hours, about 10 minutes to about 6 hours, about 10 minutes to about 4 hours, about 10 minutes to about 2 hours, about 10 minutes to about 60 minutes, about 30 minutes to about 6 hours, about 30 minutes to about 4 hours, about 30 minutes to about 2 hours, or about 30 minutes to about 60 minutes.

[0088] Additional curing may be performed before or after the exposing and / or bonding steps. In some embodiments, the at least partial curing occurs before the exposing and / or bonding steps. In some embodiments, the at least partial curing occurs after the exposing and / or bonding steps. In some embodiments, the metal silicate-treated wood component is cured both before and after the exposing and / or bonding steps.

[0089] In some embodiments, the metal silicate-treated wood component is uncured prior to the exposing and / or bonding steps.

[0090] After the at least partially curing step, and / or after the bonding step, pressure can be applied. In certain embodiments, pressure is applied by mechanical clamping or rolling. In certain embodiments, pressure is increased to more than atmospheric pressure. Usually, the pressure range applied is 5 to 200 psi, for example, from 10 to 200 psi, from 50 to 190 psi, from 100 to 190 psi, from 120 to 190 psi, from 100 to 150 psi or from 110 to 120 psi.

[0091] The bonding of the silicate-treated wood components is then completed by applying wood glue / adhesive and securing the joint until glue-wood adhesion has developed and the glue has fully cured.

[0092] Bonding can be accomplished by applying pressure until the adhesive cures into a solid structure.

[0093] Suitable adhesives for process described herein include any wood glue known to those of ordinary skill in the art. Exemplary wood glue includes, but is not limited to: animal glue (for example, hoof glue, leather glue etc.), phenol / polyphenol / resorcinol formaldehyde, lignin-phenol-formaldehyde, urea-formaldehyde, melamine formaldehyde, melamine urea-formaldehyde, polyurethane, epoxy resin, polyvinyl alcohol, polyvinyl acetate, cyanoacrylate, casein, aliphatic resin or contact adhesive. Wood glue can also include inorganic wood glue, for example, based on magnesium oxychloride (for example, magnesium oxychloride cement-based inorganic adhesive), lead oxide (for example, red lead), sulphur and various metal phosphates (for example, aluminum phosphate inorganic adhesive). In one embodiment, adhesive is PVA.

[0094] More details on additional suitable wood adhesives and techniques for wood bonding via these wood adhesives can be found in Pizzi et al., Advanced wood adhesives technology, Marcel Dekker GmbH, New York, 1994, U.S. Pat. No. 10,100,232; a review article on the adhesion of silicate coatings can be found in Yona et al., Coatings, 11:61-76 (2021), all of which are incorporated herein by reference in their entirety.

[0095] During processing, other additives may be added, such as plasticizers, surfactants, accelerators (e.g., sodium bicarbonate), initiators, or primers. These further reactions can further enhance the wood's strength, provide a better substrate for adhesives, and impart improved flame retardancy, insect resistance, and antifungal / bacterial properties. Each of these additional treatments may impart different pH, hardness, solubility, and properties to the silicate precipitate with adhesives and wood products.

[0096] Additional Examples of Exemplary Processes

[0097] Figure 1 An exemplary process for producing a flame-retardant glued engineered wood product with improved fire resistance and mechanical properties is presented. Figure 1 Each step or component shown in the is assigned a reference number, and the following table provides a corresponding description of each step or component.

[0098]

[0099]

[0100] The following table is Figure 1 A more detailed description is provided for each step / component identified in .

[0101]

[0102]

[0103] Mechanisms and benefits of the process

[0104] The present invention describes the use of silicate-modified wood in the manufacture of glued engineered wood products (e.g., plywood, particleboard, oriented strand board (OSB), and particle board). The process described herein differs from using metal silicates (e.g., sodium silicate) as wood glue or reformulating wood glue by adding metal silicates to wood glue (e.g., adding metal silicates as additives to wood glue). The process described herein also differs from simply treating glued wood products with silicate impregnation. Glued engineered wood products prepared by the process described herein modify the wood by incorporating a metal silicate impregnation and then bonding the treated wood pieces together with conventional wood adhesives.

[0105] The inventors surprisingly discovered that glued engineered wood products prepared using the process described herein exhibit properties similar to or even superior to those of engineered wood glued using reformulated glues containing metal silicates. Furthermore, the process described herein enhances the properties of the engineered wood composite and the wood / adhesive interface. Modifying the wood with a metal silicate impregnant further enhances the fire resistance of the adhesive in glued engineered wood. Without being limited by theory, this result may be explained by the fact that, since combustion initiates from the exterior surface, silicates embedded in the wood can slow combustion. Furthermore, the wood / glue interface incorporates silicates into the glue, further enhancing its flame retardancy.

[0106] Without being limited by theory, in the process described herein, when exposed to the adhesive, the metal silicates (e.g., sodium silicate) in the wood may react with the adhesive and harden the adhesive, thereby causing the adhesive to harden faster than wood that has not been treated with silicates. This reaction can not only improve mechanical properties (e.g., by producing a higher modulus bond at the wood-adhesive interface), but can also further enhance water and moisture resistance, as well as flame retardancy, by reducing the flow and dripping properties of the adhesive (particularly in the wood-adhesive bond area). In addition, because the metal silicates (e.g., sodium silicate) are embedded in the wood structure, the mechanical interlocking of the adhesive with the wood can be improved by embedding a harder adhesive / silicate composite material in the pores of the wood. The latter result cannot be achieved when simply adding silicates to wood adhesives.

[0107] In some embodiments, the reaction between the adhesive and the metal silicate improves the bonding efficiency between the wood and the adhesive by faster and stronger curing. In some embodiments, the reaction between the adhesive and the metal silicate improves the flame retardancy of the adhesive by injecting the metal silicate embedded in the wood into the adhesive. In some embodiments, the reaction between the adhesive and the metal silicate improves the stability of the adhesive by minimizing the degradation of the adhesive caused by fungi, algae, yeast, lichens and / or bacteria. In some embodiments, the reaction between the adhesive and the metal silicate improves the mechanical properties by hardening the adhesive. In some embodiments, the reaction between the adhesive and the metal silicate improves the mechanical properties by mechanically interlocking the adhesive and the wood via the metal silicate embedded in the wood.

[0108] In some embodiments, the adhesive applied to silicate-treated wood reacts only at the surface, resulting in various benefits for the resulting wood product. First, the adhesive rapidly adheres and cures at the wood surface, increasing its modulus, while the remaining bulk of the adhesive remains unaffected, curing more slowly and maintaining a lower modulus. This allows the adhesive's inner layer to maintain its working properties longer, creating a hard surface within a soft inner layer, a property that improves impact properties. This property depends on the thickness of the adhesive layer and the hard / soft thickness ratio.

[0109] Compared with other processes, the process described in this paper brings unique benefits such as Figures 3A-3C shown.

[0110] Figure 3A The process of treating glued wood products with silicate impregnation is shown. Figure 3A In this process, individual wooden elements are pressed together using wood adhesive to form a board. The finished board is then pressure-treated with a silicate solution to achieve fire resistance. While fire resistance can be achieved through this process, the mechanical properties of the adhesive and the wood-adhesive-wood interface may be susceptible to damage and / or degradation.

[0111] Figure 3B A process for manufacturing glued wood products by using a modified wood adhesive that is reformulated by adding additives such as silicates directly to conventional wood adhesives is shown. Figure 3B In the past, modified wood adhesives were used to press individual wood elements together to form panels. This approach yields improved mechanical properties. However, because the combustion process initiates from the outer surface of the panel, while the required fire protection is from the outside in, the silicates contained in the adhesive between the wood elements and within the panel offer no protection against flames originating from the outside, thus sacrificing fire resistance.

[0112] Figure 3C An exemplary embodiment of a process for making a glued engineered wood product as described herein is shown. Figure 3C In this approach, individual wood elements are treated by impregnation with a solution of a metal silicate (e.g., sodium silicate). The silicate-treated wood elements are then pressed together with a wood adhesive to form a board. In this case, the silicates embedded in the wood can interact at the adhesive-wood interface: the adhesive interacts with the silicates, which helps build mechanical properties, such as stiffening the adhesive; the mechanical interlocking of the adhesive with the wood is improved by embedding a stiffer adhesive / silicate composite within the pores of the wood, forming a bond at the adhesive-wood interface without damaging the wood-adhesive-wood interface. Furthermore, the silicates embedded in the wood can provide fire protection from the outside in, slowing combustion; and the wood-adhesive interface can also infuse the adhesive with silicates, further improving its fire resistance.

[0113] In addition to the benefits discussed above, the process described herein eliminates the need to reformulate wood adhesives using commercial adhesives, thereby preventing the short pot life of the reformulated adhesives that results from adding metal silicates (e.g., sodium silicate) directly to the adhesive. This latter benefit is important for construction sites and other high-throughput manufacturing locations because the process described herein ensures the pot life of the adhesive, thereby keeping the adhesive fluid before contact with the wood and reducing the time required for the adhesive to set. Thus, the process described herein facilitates both the use of the adhesive and the time required to secure the joint.

[0114] Transformation

[0115] like Figure 4 The diagram below presents a typical plywood manufacturing process as a prototype for the manufacture of glued wood products. See the diagram in the U.S. Environmental Protection Agency's Air Emission Factors / AP-42, 5th Edition, Volume 1, Chapter 10, "Wood Products Industry," Section 10.5, "Plywood Manufacturing" (1995), which is incorporated herein by reference in its entirety. The process can be simplified to the steps of forming the veneer, drying, gluing, and pressing.

[0116] This typical process can be modified to produce glued silicate-treated veneer by treating the veneer in a separate silicate treatment step, or by forming the veneer from silicate-treated logs and then using them directly in the process. Figure 5 shown.

[0117] Alternatively, the veneer can be treated using an in-line silicate treatment (e.g., by pressure treatment) after the veneer has been formed. This in-line silicate treatment can be achieved by a standard vacuum pressure impregnation step, drying the veneer, followed by pressure vacuum impregnation, or by applying pressure to the veneer alone (e.g., by mechanical pressure or increased pressure above atmospheric pressure) to embed the silicate into the wood veneer. The treated veneer can then be dried, exposed to glue, and pressed into a final product, such as Figure 6 shown.

[0118] Furthermore, further chemical treatments can be added to the manufacturing process, such as curing the silicate by adding curing agents such as protic acids or Lewis acid metal salts, adding additives to adjust the final pH, or adding other additives (e.g., antifungals, pesticides, or pigments). Figure 7 shown.

[0119] More details about traditional engineered wood production lines and ways to modify or convert traditional engineered wood manufacturing lines can be found in PCT / US2023 / 025457, filed on June 15, 2023, the entire contents of which are incorporated herein by reference.

[0120] Another aspect of the present invention relates to a flame retardant glued engineered wood product prepared by the process described in any of the above aspects of the present invention.

[0121] All of the above descriptions and all of the embodiments discussed in the above aspects relating to the process of manufacturing flame-retardant glued engineered wood products and in the above aspects relating to modifying an engineered wood production line to manufacture flame-retardant glued engineered wood products are applicable to this aspect of the present invention relating to flame-retardant glued engineered wood products.

[0122] The improved wood can be used in any application where glued wood is currently used. For example, suitable applications for flame-retardant glued engineered wood products include, but are not limited to, construction, furniture or appliance manufacturing, structural wood (such as cross-laminated timber or other engineered wood), plywood, oriented strand board, particle board, or wood composite material manufacturing and development processes.

[0123] In some embodiments, the flame-retardant glued engineered wood products produced by the processes described herein can be used as construction joint materials.

[0124] In some embodiments, the flame-retardant glued engineered wood products prepared by the processes described herein can be used to increase adhesion to polymeric materials.

[0125] Example

[0126] The following examples are for illustrative purposes only and are not intended to limit the scope of protection of the present invention in any way.

[0127] Example 1. Laboratory treatment of wood chips / strips to determine silicate impregnation:

[0128] Longer wood strips or chips were prepared using an electric planer (DeWalt thickness planer). OSB wood strips were obtained. These wood strips were soaked in a 10 wt% sodium silicate solution.

[0129] Exemplary treatment recipe:

[0130] Sodium silicate 7.1%

[0131] Sodium hydroxide 2.5%

[0132] Protonic acid (boric acid) 0.4%

[0133] Water 90%

[0134] The wood strips were soaked at 45°C for 30 minutes and 60 minutes, respectively, then rinsed with water and dried in an oven.

[0135] The treated wood strips were tested using X-ray fluorescence spectroscopy (XRF) to determine the percentage of silicate in the silicate treated wood strips. The results are shown in the table below.

[0136]

[0137] As shown in the table, the silicate-impregnated wood strips contained approximately 5.4-6.0% silicate under both treatment conditions (30 minutes and 60 minutes).

[0138] Example 2. Pressure treatment and flame testing of wood chips / strips with silicate impregnation:

[0139] During the treatment process, the wood chips are placed in a wire basket that contains the wood chips. The wood chips are then treated according to the following process:

[0140] ●Pretreatment: Maintain under vacuum of -20 to 30 mmHg for 5-30 minutes.

[0141] ●Processing formula and conditions:

[0142] ○Processing formula:

[0143] Sodium silicate 41.5%

[0144] ■Protonic acid (boric acid) 0.4%

[0145] ■Protonic acid (acetic acid) 0.4%

[0146] Water 57.7%

[0147] ○Conditions for processing wood chips in reactor:

[0148] ■Processing solution temperature range is 35℃ to 70℃

[0149] ■ Pressure range is 120 to 190 psi

[0150] ■Processing time = 30 to 120 minutes

[0151] After the above silicate impregnation treatment and after removing the treatment formulation from the reactor,

[0152] ■Maintain vacuum at -20 to 30 mmHg for 5 to 30 minutes

[0153] ■ Carbon dioxide treatment for 30 to 120 minutes

[0154] The chips were then allowed to air dry for 3 days and then oven dried at 80°C.

[0155] XRF was then used to measure silicate content. The silicate content of the treated chips was also compared to that of untreated chips. The chips tested included untreated chips / strips (Sample 1), chips or strips treated through all the above steps (Sample 2), and chips / strips treated through the above pretreatment and treatment steps, then rinsed with room temperature water and dried in an oven (Sample 3). The silicate content results for the various chip samples are shown in the table below.

[0156] The sample wood chips (Sample Nos. 1-3) were then exposed to a burn test to determine their resistance to flame spread. The test was conducted using a hand-held propane torch, with the samples placed in a metal pan. The flame was held 7 inches from the sample, and the burn test was conducted for 30 and 60 seconds. The samples were weighed before and after the burn, and the weight loss was recorded. The burn test results for the various wood chip samples are shown in the table below.

[0157]

[0158] As shown in the table above, after burning for 60 and 30 seconds, the weight loss of the treated wood chips for both treated samples was approximately 11% and 12% lower than the weight loss of the untreated wood chips. In addition, after the flame was extinguished, the treated wood chips extinguished quickly, while the untreated wood chips continued to burn for 60 seconds.

[0159] Example 3: Laboratory flame testing of adhesive mixed with sawdust and silicate-treated sawdust

[0160] Sawdust from wood was treated using the process described in Example 2, except that a higher level of silicate was obtained (ie, 23% [Si]). The control sawdust was untreated sawdust.

[0161] An equal volume of each sawdust sample (silicate-treated sawdust and untreated sawdust control) was added to a 2-inch radius pool of liquid binder and the sawdust was mixed in by stirring.

[0162] The silicate-treated sawdust formed a sticky solid within three minutes and quickly became touchable, while the control sawdust took 48 hours to dry completely.

[0163] The sawdust samples were then exposed to a flame test to determine their resistance to flame spread. The test was conducted using a handheld propane torch, with the samples clamped in a bench vise and exposed to the flame for 10 seconds. The flame was held 7 inches from the sample. While the control samples burned for 30 and 60 seconds, the treated samples extinguished within 2-3 seconds. It was also noted that the treated samples retained their heat longer without reigniting or dripping.

Claims

1. A process for producing a flame-retardant glued engineered wood product, comprising: providing an engineered wood component treated by impregnation with a metal silicate solution, exposing the metal silicate treated engineered wood component to an adhesive, and Multiple units of the metal silicate-treated engineered wood component are bonded together by the adhesive to form a flame-retardant glued engineered wood product.

2. A process for modifying an engineered wood production line to produce flame-retardant glued engineered wood products, comprising: Provide an engineered wood production line with the following operating steps: forming engineered wood components, optionally drying the engineered wood component, exposing the engineered wood component to an adhesive, and bonding together a plurality of units of the engineered wood component via the adhesive; as well as Prior to the step of exposing the engineered wood component to an adhesive, a step of treating the engineered wood component by impregnation with a metal silicate solution is incorporated into the engineered wood production line.

3. The process according to claim 1 or 2, wherein The exposing step forms a layer of adhesive on the surface of the metal silicate-treated engineered wood component.

4. The process according to claim 1 or 2, wherein The reaction between the binder and the metal silicate provides one or more of the following: (i) Improve the bonding efficiency between wood and adhesive through faster and stronger curing, (ii) improving the flame retardancy of the adhesive by infusing the metal silicate embedded in the wood into the adhesive, (iii) improving the stability of the adhesive by minimizing degradation of the adhesive by fungi, algae, yeasts, lichens and / or bacteria, (iv) improving mechanical properties by hardening the adhesive, and (v) The adhesive and wood are mechanically interlocked by the metal silicate embedded in the wood, thereby improving mechanical properties.

5. The process according to claim 1 or 2, wherein The bonding of multiple units of the sodium silicate-treated engineered wood component forms a wood-adhesive interface, and wherein the reaction between the adhesive and the metal silicate is limited to the wood-adhesive interface, provides improved ductility and strength due to a combination of a higher modulus at the surface where the adhesive reacts with the metal silicate and a lower modulus at the interior of the adhesive where it does not react with the metal silicate.

6. The process according to claim 1 or 2, wherein The metal silicate is sodium silicate, potassium silicate, lithium silicate, iron silicate or a mixture thereof.

7. The process according to claim 6, wherein The metal silicate is sodium silicate, potassium silicate, lithium silicate, or a mixture thereof, forming a solution having about 2-40 wt% solids.

8. The process according to claim 7, wherein The metal silicate-treated engineered wood component contains about 5-25 wt% silicate solids.

9. The process according to claim 1 or 2, wherein Impregnation is performed by applying vacuum and / or pressure.

10. The process according to claim 9, wherein The vacuum and / or pressure is applied in a batch manner.

11. The process according to claim 9, wherein The vacuum and / or pressure are applied in a continuous manner by applying pressure on one side of the wood and vacuum on the other side of the wood.

12. The process according to claim 11, wherein The means for applying vacuum pressure comprises an additional recovery line for supplying the metal silicate solution on the vacuum side.

13. The process according to claim 1 or 2, further comprising: Prior to the exposing step, the metal silicate-treated engineered wood component is dried to a moisture level of 19% or less.

14. The process according to claim 1 or 2, further comprising: The binder and / or metal silicate in the treated wood is at least partially cured.

15. The process according to claim 14, wherein Said at least partial curing occurs before said exposing and / or bonding steps.

16. The process of claim 14, wherein The at least partial curing occurs after the exposing and / or bonding steps.

17. The process according to claim 1 or 2, wherein Prior to said exposing and / or said bonding steps, said metal silicate treated wood component is uncured.

18. The process of claim 16, wherein The at least partial curing is performed by heating.

19. The process of claim 16, wherein: The at least partial curing is performed by a curing agent.

20. The process of claim 19, wherein The curing agent is selected from the group consisting of protic acids, inorganic acids, Lewis acids, metal salts, carbon dioxide, organic molecules, additives, and multivalent counterions.

21. The process of claim 1, 2 or 14, further comprising: Pressure is applied after said at least partially curing step and / or said bonding step.

22. The process of claim 1 or 2, wherein The impregnation is performed by impregnation with applied pressure alone.

23. The process according to claim 21 or 22, wherein The pressure is applied by mechanical clamping or rolling.

24. The process of claim 21 or 22, wherein The pressure is increased to above atmospheric pressure.

25. The process of claim 1 or 2, wherein The adhesive is animal glue, phenol / polyphenol / resorcinol formaldehyde, lignin-phenol-formaldehyde, urea formaldehyde, melamine formaldehyde, melamine urea formaldehyde, polyurethane, epoxy resin, polyvinyl alcohol, polyvinyl acetate, cyanoacrylate, casein, aliphatic resin or contact adhesive.

26. The process of claim 1 or 2, wherein The engineered wood component is plywood, lumber, veneer, oriented strand board, wood chips, flakes or wood chips, pellets or sawdust.

27. A flame retardant glued engineered wood product produced by the process according to any one of claims 1 to 26.

28. The flame retardant glued engineered wood product of claim 27 is used in construction, furniture or appliance manufacturing, structural timber manufacturing, plywood, oriented strand board, particle board, or wood composite material manufacturing and development processes.

29. Use of the flame retardant glued engineered wood product according to claim 27 as a construction connection material.

30. Use of the flame retardant glued engineered wood product according to claim 27 for increasing adhesion to polymeric materials.

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