Wood structural material and method for producing the same

Abstract

The present application provides a kind of wood structure material and its preparation method.The method comprises: the rotary cut veneer is pretreated, and the pretreatment product is obtained;The pretreatment product is subjected to wet heat setting treatment;Select the dynamic elastic modulus as 9000MPa or more as wet heat setting product;First wet heat setting product is selected to be impregnated in resin solution and dried, and dry product is obtained;The dry product is subjected to compression densification, and dense veneer is obtained;Second wet heat setting product is selected, and at least one surface of second wet heat setting product has first adhesive;The dense veneer and the second wet heat setting product with first adhesive are subjected to assembly hot pressing, and first forming body is obtained;Optionally, third wet heat setting product is selected, and the second wet heat setting product with first adhesive is subjected to assembly hot pressing, and second forming body is obtained;In the presence of second adhesive, two first forming bodies are selected, and second forming body or sawn timber is subjected to cold pressing, and wood structure material is obtained.

Description

Technical Field

[0001] This invention relates to a wood structural material and its preparation method, specifically to a high-strength wood structural material made of ultra-thick veneer and its preparation method, belonging to the field of wood application. Background Technology

[0002] With the depletion of global forest resources, high-quality, large-diameter logs are becoming increasingly scarce, leading to a sharp decline in natural timber production. The high-value utilization of fast-growing timber from plantations has become an important way to alleviate the supply-demand imbalance in my country's timber industry. Due to its short growth cycle, most fast-growing timber is juvenile, exhibiting problems such as loose texture, low density, susceptibility to cracking, and low strength. Therefore, the application range of fast-growing timber is limited. It is typically used as a raw material for engineered wood products such as fiberboard, particleboard, plywood, and other engineered wood products, indirectly used in households and other sectors, or as a raw material for papermaking and construction templates. Although domestic and international scholars have developed corresponding processing and technologies to modify and functionalize fast-growing timber, such as composite processing, consolidation, softening, plasticizing, color treatment, anti-corrosion, and flame retardancy, thereby broadening its application areas, its use in building structures remains challenging.

[0003] Cross-laminated timber (CLT) is an engineered wood product made by orthogonally bonding at least three layers of sized sawn timber together with adhesive. It possesses excellent physical and mechanical properties, high stability, and is not prone to cracking or deformation, making it widely used in timber-frame construction in Europe and North America. However, CLT has strict requirements for raw materials; it must be graded solid sawn timber. Internationally, large-diameter timber is generally used, while my country's current plantation forests have relatively small diameters, resulting in low yields. Thick veneers can utilize small-diameter, fast-growing timber and can replace standard sawn timber in the manufacture of engineered structural materials similar to CLT.

[0004] Because plantation timber is currently relatively soft, rotary-cut thick veneers cannot meet the requirements of structural timber. Currently, thick veneers are only used to manufacture core boards for decorative purposes. Furthermore, the manufacture of large-format wood-based composite materials using wood veneers typically employs a hot-pressing process. If a hot-pressing process is used to manufacture structural timber of a certain thickness using thick veneers, the heat transfer of the interlayer will be affected, thus impacting the curing of the adhesive.

[0005] Reference 1 discloses a solid wood composite board made of ultra-thick veneer, comprising two outer surface layers and a core layer therebetween, with adhesive between the veneer layers; the core layer is composed of ultra-thick veneer with a thickness of 6mm-12mm, and the surface layer is composed of veneer with a thickness of 0.2mm-1.5mm. However, this solid wood composite board can only be used indoors and cannot be used for load-bearing or building construction.

[0006] Reference 2 discloses a method for producing high-performance laminated veneer sheets with high elastic modulus, high dimensional stability, high wear resistance, and low variability. The sheets are categorized into high and low grades, or high, medium, and low grades, based on their dynamic elastic modulus (MOE). This laminated veneer material uses graded thin veneers as raw materials and achieves high compression ratios to manufacture engineering structural materials. However, even with grading, thick veneers cannot achieve high compression ratios and still cannot solve the problem of their inherently soft material properties.

[0007] Therefore, researching a wood-based structural material and its preparation method to solve the problem that rotary-cut thick veneers from fast-growing plantations cannot be directly used to manufacture structural timber has become an urgent technical issue.

[0008] References:

[0009] Reference 1: CN101524859A

[0010] Reference 2: CN103433983A Summary of the Invention

[0011] The problem the invention aims to solve

[0012] In view of the technical problems existing in the prior art, the purpose of this invention is to provide a wood structural material and its preparation method, so as to solve the problem that thick veneer rotary-cut from fast-growing plantation timber cannot be directly used to manufacture structural materials.

[0013] Solution for solving the problem

[0014] This invention provides a method for preparing a wood-based structural material, comprising the following steps:

[0015] Pre-treating the rotary-cut veneer yields a pre-treated product;

[0016] The pretreated product is subjected to a wet heat setting treatment; and the dynamic elastic modulus of the pretreated product after wet heat setting is detected. The product with a dynamic elastic modulus of 9000 MPa or higher is selected as the wet heat set product.

[0017] At least one first heat-set product is selected, impregnated in a resin solution, and then dried to obtain a dried product;

[0018] The dried product is compressed and compacted to obtain compacted veneer;

[0019] A second heat-set product is selected, and at least one surface of the second heat-set product is covered with a first adhesive;

[0020] The solidified veneer is hot-pressed with a second heat-cured product containing a first adhesive, with the solidified veneer located on the surface, to obtain a first molded body;

[0021] Optionally, a third heat-cured product is selected and hot-pressed with a second heat-cured product containing a first adhesive to obtain a second molded body;

[0022] In the presence of a second adhesive, two of the first molded bodies are cold-pressed with a second molded body or sawn timber to obtain a wood structural material; wherein...

[0023] The second molded body or the sawn timber is located between the two first molded bodies, and the dense veneers in the first molded bodies are all located away from the second molded body or the sawn timber.

[0024] According to the preparation method of the present invention, the thickness of the rotary-cut veneer is 6-20 mm; and / or the moisture content of the pretreated product is 20-40%.

[0025] According to the preparation method of the present invention, the temperature of the heat setting treatment is 140-210℃; the pressure of the heat setting treatment is 0.5-2.5MPa; and the time of the heat setting treatment is 30-90min.

[0026] According to the preparation method of the present invention, the resin solution contains 10%-30% resin by mass; preferably, the resin comprises one or more of epoxy resin, phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin, and furfuryl alcohol resin; and / or

[0027] The moisture content of the dried product is 10%-15%.

[0028] According to the preparation method of the present invention, the compression rate of the compression densification is 10-50%, the compression densification temperature is 100-200℃, and the compression densification time is 10-60 min.

[0029] According to the preparation method of the present invention, the amount of the first adhesive is 150-350 g / m³. 2 ; and / or

[0030] The hot pressing compression rate is 1%-10%, the hot pressing temperature is 100-170℃, and the hot pressing time is 0.5-3 min / mm; and / or

[0031] The thickness of the first molded body is no more than 35 mm.

[0032] According to the preparation method of the present invention, the second adhesive comprises one or both of polyurethane and white glue; and / or

[0033] The amount of the second adhesive used is 80-180 g / m².2 .

[0034] According to the preparation method of the present invention, the thickness of the second molded body or the sawn timber is not greater than 35 mm.

[0035] According to the preparation method of the present invention, the pressure of the cold pressing is 1-2 MPa, the cold pressing time is 60-240 min, and the cold pressing temperature is 0-40℃.

[0036] The present invention also provides a wood-based structural material, which is prepared by the preparation method described in the present invention.

[0037] The effects of the invention

[0038] The wood-based structural material prepared by the method of the present invention has high static bending strength, high elastic modulus, and high shear strength, and can be used in building structures.

[0039] The preparation method of the present invention involves dividing the thick veneer into grades and impregnating the main stress-bearing surfaces with resin to densify them, while the core layer, which is subject to less stress, is made of a second molded body or sawn timber. The static bending strength of the material is improved through surface reinforcement and reasonable structural design.

[0040] The preparation method of the present invention can improve the preparation efficiency and bonding quality of materials by combining hot and cold pressing. Attached Figure Description

[0041] Figure 1 A schematic diagram of the structure of a first molded body according to the present invention is shown;

[0042] Figure 2 A schematic diagram of another first molded body of the present invention is shown;

[0043] Figure 3 A schematic diagram of the structure of a second molded body according to the present invention is shown;

[0044] Figure 4 A structural schematic diagram of a wood-based structural material according to the present invention is shown;

[0045] Figure 5 A structural schematic diagram of another wood-based structural material according to the present invention is shown;

[0046] Figure 6 A structural schematic diagram of another wood-based structural material of the present invention is shown. Detailed Implementation

[0047] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0048] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0049] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0050] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0051] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0052] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0053] In this instruction manual, when "room temperature" or "room temperature" is used, the temperature can be between 10-40℃.

[0054] This invention first provides a method for preparing a wood-based structural material, which includes the following steps:

[0055] Pre-treating the rotary-cut veneer yields a pre-treated product;

[0056] The pretreated product is subjected to a wet heat setting treatment; and the dynamic elastic modulus of the pretreated product after wet heat setting is detected. The product with a dynamic elastic modulus of 9000 MPa or higher is selected as the wet heat set product.

[0057] The first wet heat-set product was selected, impregnated in a resin solution, and then dried to obtain the dried product;

[0058] The dried product is compressed and compacted to obtain compacted veneer;

[0059] A second heat-set product is selected, and at least one surface of the second heat-set product is covered with a first adhesive;

[0060] The solidified veneer is hot-pressed with a second heat-cured product containing a first adhesive, with the solidified veneer located on the surface, to obtain a first molded body;

[0061] Optionally, a third heat-cured product is selected and hot-pressed with a second heat-cured product containing a first adhesive to obtain a second molded body;

[0062] In the presence of a second adhesive, two of the first molded bodies are cold-pressed with a second molded body or sawn timber to obtain a wood structural material; wherein...

[0063] The second molded body or the sawn timber is located between the two first molded bodies, and the dense veneer in both the first and second molded bodies is located away from the second molded body or the sawn timber.

[0064] In this invention, the thick veneer is derived from one or more of poplar, eucalyptus, fir, larch, radiata pine, and Masson pine.

[0065] The first, second, and third moist heat-set products described in this invention all belong to the category of moist heat-set products. For better distinction, they are referred to as the first, second, and third moist heat-set products. Furthermore, in this invention, the first moist heat-set product is generally one moist heat-set product; the second and third moist heat-set products are not limited to one, but are generally greater than or equal to one, for example: one, three, five, seven, etc.

[0066] The preparation method of this invention involves grading thick veneers and impregnating the veneers on the main stress-bearing surfaces with resin to achieve densification, while the core layer, which experiences less stress, is prepared using a second molded body or sawn timber. Surface reinforcement and a rational structural design improve the static bending strength of the material. Furthermore, the preparation method of this invention combines hot and cold pressing, which improves the material preparation efficiency and bonding quality.

[0067] In some specific implementations, the rotary-cut veneer of the present invention is an ultra-thick veneer, that is, a thick veneer of wood rotary-cut from logs. Specifically, the thickness of the rotary-cut veneer is 6-20mm, for example: 8mm, 10mm, 12mm, 15mm, 18mm, etc. The present invention solves the problem that thick rotary-cut veneers of fast-growing plantation timber cannot be directly used to manufacture structural materials by using high-strength wood structural materials made from ultra-thick veneers.

[0068] This invention first pre-treats the rotary-cut veneer to obtain a pre-treated product. Specifically, the pre-treatment is not particularly limited, as long as the moisture content of the pre-treated product is 20-40%, such as 22%, 25%, 28%, 30%, 32%, 35%, 38%, etc. Specifically, in this invention, the rotary-cut veneer can be steamed and then naturally air-dried to obtain a pre-treated product with a moisture content of 20-40%.

[0069] Furthermore, the pretreated product is subjected to a hygrothermal setting treatment; and the dynamic elastic modulus of the pretreated product after hygrothermal setting is tested. A dynamic elastic modulus of 9000 MPa or higher is selected as the hygrothermal-set product. When a dynamic elastic modulus of 9000 MPa or higher is used as the hygrothermal-set product, the resulting wood-based structural material exhibits excellent overall mechanical properties.

[0070] In some specific implementations, the temperature of the moist heat setting treatment is 140-210℃, for example: 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, etc.; the pressure of the moist heat setting treatment is 0.5-2.5MPa, for example: 0.8MPa, 1MPa, 1.2MPa, 1.5MPa, 1.8MPa, 2MPa, 2.2MPa, etc.; the time of the moist heat setting treatment is 30-90min, for example: 40min, 50min, 60min, 70min, 80min, etc. Through moist heat setting treatment, the pretreated product can be shaped and flattened.

[0071] Furthermore, the first heat-set product is selected and impregnated in a resin solution before drying to obtain a dried product. By impregnating the first heat-set product in a resin solution, the present invention can fill the pores such as vessels and cell cavities in the wood with resin, thereby increasing the wood density and improving its mechanical properties.

[0072] In some specific embodiments, the resin solution contains 10%-30% resin by mass, for example: 12%, 15%, 18%, 20%, 22%, 25%, 28%, etc.; preferably, the resin includes one or more combinations selected from epoxy resin, phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin, and furfuryl alcohol resin. Preferably, the dried product has a moisture content of 10%-15%, for example: 11%, 12%, 13%, 14%, etc.

[0073] Furthermore, the dried product is compressed and densified to obtain a densified veneer. The inventors of this invention have discovered that through compression and densification treatment, the internal porosity of the veneer can be further reduced, the veneer density can be increased, and the mechanical properties of the veneer can be improved.

[0074] In some specific implementations, the compression rate of the compaction process is 10-50%, for example: 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc.; the temperature of the compaction process is 100-200℃, for example: 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, etc.; and the time of the compaction process is 10-60 minutes, for example: 20 minutes, 30 minutes, 40 minutes, 50 minutes, etc.

[0075] Furthermore, the densified veneer is hot-pressed with a second wet heat-cured product containing a first adhesive, with the densified veneer located on the surface, to obtain a first molded body.

[0076] In some specific implementations, the amount of the first adhesive used is 150-350 g / m². 2 170g / m 2 200g / m 2 220g / m 2 250g / m 2 280g / m 2 300g / m 2 320g / m 2 Generally, the first adhesive of this invention can be a hot-press adhesive, which has high hot-pressing efficiency when the thickness of the pressed material is small, and can achieve curing in a short time. Specifically, in this invention, the first adhesive is selected from one or more combinations of isocyanate, phenolic resin, urea-formaldehyde resin, and melamine-formaldehyde resin.

[0077] Specifically, the compression rate of the hot pressing is 1%-10%, for example: 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc.; the hot pressing temperature is 100-170℃, for example: 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, etc.; the hot pressing time is 0.5-3min / mm, for example: 0.7min / mm, 1min / mm, 1.2min / mm, 1.5min / mm, 1.8min / mm, 2min / mm, 2.2min / mm, 2.5min / mm, 2.8min / mm, etc.

[0078] Furthermore, in this invention, the thickness of the first molded body is no more than 35 mm.

[0079] Optionally, a third heat-set product is selected and hot-pressed with a second heat-set product containing a first adhesive to obtain a second molded body. Specifically, the compression rate of the hot pressing is 1%-10%, for example: 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc.; the hot pressing temperature is 100-170℃, for example: 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, etc.; the hot pressing time is 0.5-3 min / mm, for example: 0.7 min / mm, 1 min / mm, 1.2 min / mm, 1.5 min / mm, 1.8 min / mm, 2 min / mm, 2.2 min / mm, 2.5 min / mm, 2.8 min / mm, etc.

[0080] In this invention, the assembly method of the first and second molded bodies is not particularly limited, and can be performed as needed. Specifically, the wood grain between the veneers can be approximately parallel (e.g., Figure 2 As shown), it can also be roughly vertical (as shown). Figure 1 (As shown). That is, the present invention can produce wood structural materials by using a parallel grain assembly method or by using a cross-grain assembly method.

[0081] Finally, in the presence of the second adhesive, two first molded bodies are selected and cold-pressed with the second molded body or sawn timber to obtain a wood structural material; wherein, the second molded body is located between the two first molded bodies, and the densified veneers in the first molded bodies are all located away from the second molded body or the sawn timber. In this invention, the second adhesive can be a cold-pressing adhesive. When the pressed thickness is large, the influence of thickness on heat transfer can be disregarded, and it can be cured at room temperature, although the curing time is longer compared to that of the first adhesive.

[0082] In some specific embodiments, the second adhesive comprises one or both of polyurethane and white glue. Specifically, the amount of the second adhesive used is 80-180 g / m³. 2 90g / m 2 100g / m 2 110g / m 2 120g / m 2 130g / m 2 140g / m 2 150g / m 2 160g / m 2 170g / m 2 wait.

[0083] Specifically, the thickness of the second molded body or the sawn timber is no greater than 35 mm. In this invention, the performance of the second molded body and the sawn timber is inferior to that of the first molded body, and therefore it can be used as a neutral layer that is essentially unaffected by stress. The present invention does not impose a particular limitation on the number of the second molded body and / or the sawn timber; it can be set as needed, generally one, three, five, etc.

[0084] In some specific implementations, the cold pressing pressure is 1-2 MPa, for example: 1.2 MPa, 1.5 MPa, 1.8 MPa, etc.; the cold pressing time is 60-240 min, for example: 80 min, 100 min, 120 min, 150 min, 180 min, 200 min, 220 min, etc.; the cold pressing temperature is 0-40℃, for example: 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, etc.

[0085] Furthermore, the present invention also provides a wood-based structural material, which is prepared by the preparation method described in the present invention.

[0086] Example

[0087] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0088] Example 1

[0089] 1) Rotary cut radiata pine logs into 8mm thick veneers, steam them, and then air-dry them until the moisture content reaches 30%.

[0090] 2) Perform a wet heat setting treatment on rotary-cut radial thick veneer; wherein the wet heat setting treatment temperature is 170℃, the wet heat setting treatment pressure is 1MPa, and the wet heat setting treatment time is 60min.

[0091] 3) Based on the dynamic modulus of elasticity (MOE) of each flattened thick veneer (detected by resonance method using a dynamic modulus of elasticity measuring instrument), the veneers are divided into two grades: high (≥9000MPa) and low (<9000MPa). The high-grade thick veneers are selected as the wet heat setting products.

[0092] 4) A heat-set product is impregnated with a resin solution and then dried to obtain a dried product. The resin used is phenolic resin, and the resin solution used for impregnation contains 20% phenolic resin by mass; the dried product has a moisture content of 10%.

[0093] 5) The dried product is compressed and densified to obtain densified veneers. The compression and densification process is as follows: the compression rate is 10%, the compression and densification temperature is 160℃, and the compression and densification time is 30 minutes.

[0094] 6) Take another 4 heat-set products and coat their surfaces with phenolic resin adhesive. The coating amount of phenolic resin adhesive is 150 g / m². 2 Single-sided coating. A solidified veneer is placed on the surface and hot-pressed with four other layers of veneers coated with adhesive to obtain a first molded body with a thickness of 35mm and a solid surface layer. Figure 2 (As shown). The hot-pressing compression rate is 5%, the hot-pressing temperature is 150℃, and the hot-pressing time is 1 min / mm. The veneer arrangement is such that the wood grain between the veneers is approximately parallel.

[0095] 7) Five heat-set products were coated with phenolic resin and then hot-pressed to obtain a second molded body with a thickness of 35 mm. Figure 3 (As shown). The coating amount of the phenolic resin adhesive is 150 g / m². 2 Single-sided coating. The hot-pressing compression rate is 8%, the hot-pressing temperature is 150℃, and the hot-pressing time is 1 min / mm. The assembly form is such that the wood grain between the veneers is approximately perpendicular.

[0096] 8) Coat the surfaces of the first molded body and the second molded body with polyurethane adhesive. The surface of the solidified veneer of the first molded body is not coated with adhesive. The coating amount of polyurethane adhesive is 100 g / m². 2 Double-sided coating.

[0097] 9) Two first molded bodies are used as upper and lower layers, wherein the dense veneer in the first molded body is located away from the second molded body, and the second molded body serves as the core layer. Then, a cold-pressing process is performed to obtain a wood structural material with a thickness of 105 mm, as detailed below. Figure 4 As shown. The preform structure of the wood structural material is an orthogonal preform structure consisting of a first molded body and a second molded body. The cold pressing pressure is 1 MPa, the cold pressing time is 120 min, and the cold pressing temperature is 25℃.

[0098] Example 2

[0099] 1) Rotary cut radiata pine logs into 8mm thick veneers, steam them, and then air-dry them until the moisture content reaches 30%.

[0100] 2) Perform a wet heat setting treatment on rotary-cut radial thick veneer; wherein the wet heat setting treatment temperature is 170℃, the wet heat setting treatment pressure is 1.8MPa, and the wet heat setting treatment time is 30min.

[0101] 3) Based on the dynamic modulus of elasticity (MOE) of each flattened thick veneer (detected by resonance method using a dynamic modulus of elasticity measuring instrument), the veneers are divided into two grades: high (≥9000MPa) and low (<9000MPa). The high-grade thick veneers are selected as the wet heat setting products.

[0102] 4) A heat-set product is impregnated with a resin solution and then dried to obtain a dried product. The resin used is phenolic resin, and the resin solution used for impregnation contains 20% phenolic resin by mass; the dried product has a moisture content of 10%.

[0103] 5) The dried product is compressed and densified to obtain densified veneers. The compression and densification process is as follows: the compression rate is 10%, the compression and densification temperature is 160℃, and the compression and densification time is 30 minutes.

[0104] 6) Take another 4 heat-set products and coat their surfaces with phenolic resin adhesive. The coating amount of phenolic resin adhesive is 150 g / m². 2 Single-sided coating. A solidified veneer is placed on the surface and hot-pressed with four other layers of veneers coated with adhesive to obtain a first molded body with a thickness of 35mm and a solid surface layer. Figure 2 (As shown). The hot-pressing compression rate is 5%, the hot-pressing temperature is 150℃, and the hot-pressing time is 1 min / mm. The veneer arrangement is such that the wood grain between the veneers is approximately parallel.

[0105] 7) Apply polyurethane adhesive to the surface of the first molded body and the 35mm thick sawn timber. The surface of the solidified veneer of the first molded body is not coated with adhesive. The amount of polyurethane adhesive applied is 150g / m². 2 Double-sided coating.

[0106] 8) Two first-molded bodies are used as upper and lower layers, wherein the dense veneer in the first-molded body is located away from the second-molded body, and the sawn timber is the core layer. Then, a cold-pressing process is performed to obtain a wood structural material with a thickness of 105 mm, as detailed below. Figure 5 As shown. The preform structure of the wood structural material consists of a first molded body and a second molded body arranged in parallel. The cold pressing pressure is 1 MPa, the cold pressing time is 60 min, and the cold pressing temperature is 25℃.

[0107] Example 3

[0108] 1) Rotary cut radiata pine logs into 8mm thick veneers, steam them, and then air-dry them until the moisture content reaches 30%.

[0109] 2) Perform a wet heat setting treatment on the rotary-cut radial thick veneer; wherein the wet heat setting treatment temperature is 150℃, the wet heat setting treatment pressure is 1MPa, and the wet heat setting treatment time is 60min.

[0110] 3) Based on the dynamic modulus of elasticity (MOE) of each flattened thick veneer (detected by resonance method using a dynamic modulus of elasticity measuring instrument), the veneers are divided into two grades: high (≥9000MPa) and low (<9000MPa). The high-grade thick veneers are selected as the wet heat setting products.

[0111] 4) A heat-set product is impregnated with a resin solution and then dried to obtain a dried product. The resin used is phenolic resin, and the resin solution used for impregnation contains 10% phenolic resin by mass; the dried product has a moisture content of 10%.

[0112] 5) The dried product is compressed and densified to obtain densified veneers. The compression and densification process is as follows: the compression rate is 8%, the compression and densification temperature is 140℃, and the compression and densification time is 30 minutes.

[0113] 6) Take another 4 heat-set products and coat their surfaces with phenolic resin adhesive. The coating amount of phenolic resin adhesive is 180 g / m². 2 Single-sided coating. A solidified veneer is placed on the surface and hot-pressed with four other layers of veneers coated with adhesive to obtain a first molded body with a thickness of 35mm and a solid surface layer. Figure 1 (As shown). The hot-pressing compression rate is 10%, the hot-pressing temperature is 150℃, and the hot-pressing time is 1 min / mm. The veneer arrangement is such that the wood grain between the veneers is approximately perpendicular.

[0114] 7) Five heat-set products were coated with phenolic resin and then hot-pressed to obtain a second molded body with a thickness of 35 mm. The coating amount of phenolic resin adhesive was 150 g / m². 2 Single-sided coating. The hot-pressing compression rate is 8%, the hot-pressing temperature is 150℃, and the hot-pressing time is 1 min / mm. The assembly form is such that the wood grain between the veneers is approximately perpendicular.

[0115] 8) Coat the surfaces of the first molded body and the second molded body with polyurethane adhesive. The surface of the solidified veneer of the first molded body is not coated with adhesive. The coating amount of polyurethane adhesive is 100 g / m². 2 Double-sided coating.

[0116] 9) Two first molded bodies are used as upper and lower layers, wherein the dense veneer in the first molded body is located away from the second molded body, and the second molded body serves as the core layer. Then, a cold-pressing process is performed to obtain a wood structural material with a thickness of 105 mm, as detailed below. Figure 6 As shown. The preform structure of the wood structural material is an orthogonal preform structure consisting of a first molded body and a second molded body. The cold pressing pressure is 1 MPa, the cold pressing time is 120 min, and the cold pressing temperature is 25℃.

[0117] Comparative Example

[0118] 1) Rotary cut radiata pine logs into 8mm thick veneers, steam them, and then air-dry them until the moisture content reaches 30%.

[0119] 2) The rotary-cut radial thick veneer is subjected to a wet heat setting treatment to obtain a wet heat set product; wherein, the wet heat setting treatment temperature is 170℃, the wet heat setting treatment pressure is 1MPa, and the wet heat setting treatment time is 60min.

[0120] 3) Coat the surface of the heat-set product with phenolic resin adhesive at a coating amount of 150 g / m². 2 Single-sided coating.

[0121] Five layers of a heat-set product coated with adhesive were assembled and hot-pressed to obtain a molded body with a thickness of 35 mm. The hot-pressing conditions were: a compression rate of 10%, a hot-pressing temperature of 150°C, and a hot-pressing time of 1 min / mm. The assembly pattern was such that the wood grain between the veneers was approximately parallel or perpendicular.

[0122] 4) Apply polyurethane adhesive to the surface of the molded body. For molded bodies where the wood grain of the veneers is approximately parallel, no adhesive is applied to the surface. The application amount is 100g / m². 2 Double-sided coating.

[0123] 5) Two molded bodies with roughly parallel wood grains are used as the upper and lower layers, and another molded body with roughly perpendicular wood grains between the veneers is used as the core layer. Both are then cold-pressed to obtain a wood-based composite material with a thickness of 105 mm. The cold-pressing pressure is 1 MPa, the cold-pressing time is 120 min, and the cold-pressing temperature is 25℃.

[0124] Performance testing

[0125] The static bending strength and modulus of elasticity of the material were tested according to GB / T 17657-2013. The results are shown in Table 1.

[0126] Table 1

[0127] Example 1 60.43 13924 Example 2 58.27 13328 Example 3 50.36 12237 Comparative Example 1 28.64 10753

[0128] As can be seen from Examples 1 and 3 in Table 1, compared with the wood-based composite material of Comparative Example 1, the first molded body of the present invention, with a dense surface layer, can improve the static bending strength and modulus of elasticity. As can be seen from Example 2, using the second molded body or sawn timber for the core layer of the wood-based composite material has little effect on its static bending strength and modulus of elasticity.

[0129] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0130] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a wood-based structural material, characterized in that, Includes the following steps: The rotary-cut veneer is pretreated to obtain a pretreated product, wherein the moisture content of the pretreated product is 20-40% and the thickness of the rotary-cut veneer is 6-20mm. The pretreated product is subjected to a wet heat setting treatment; and the dynamic elastic modulus of the pretreated product after wet heat setting is detected. The product with a dynamic elastic modulus of 9000 MPa or higher is selected as the wet heat set product. The first wet heat-set product was selected, impregnated in a resin solution, and then dried to obtain the dried product; The dried product is compressed and compacted to obtain compacted veneers. The compression rate of the compression and compaction is 10-50%, the temperature of the compression and compaction is 100-200℃, and the time of the compression and compaction is 10-60 min. A second heat-set product is selected, and at least one surface of the second heat-set product is covered with a first adhesive; The solidified veneer is hot-pressed with a second heat-cured product containing a first adhesive, with the solidified veneer located on the surface, to obtain a first molded body; A third heat-cured product is selected and hot-pressed with a second heat-cured product containing a first adhesive to obtain a second molded body. In the presence of a second adhesive, two of the first molded bodies are cold-pressed with a second molded body or sawn timber to obtain a wood structural material; wherein... The second molded body or the sawn timber is located between the two first molded bodies, and the dense veneers in the first molded bodies are all located away from the second molded body or the sawn timber; The first adhesive is used in an amount of 150-350 g / m 2 ; The hot pressing compression rate is 1%-10%, the hot pressing temperature is 100-170℃, and the hot pressing time is 0.5-3 min / mm; The thickness of the first molded body is no more than 35 mm.

2. The preparation method according to claim 1, characterized in that, The temperature of the heat setting treatment is 140-210℃; the pressure of the heat setting treatment is 0.5-2.5MPa; and the time of the heat setting treatment is 30-90min.

3. The preparation method according to claim 1 or 2, characterized in that, The resin solution contains 10%-30% resin by mass. The moisture content of the dried product is 10%-15%.

4. The preparation method according to claim 3, characterized in that, The resin includes one or more of epoxy resin, phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin, and furfuryl alcohol resin.

5. The preparation method according to claim 1 or 2, characterized in that, The second adhesive includes one or both of polyurethane and white glue; The second adhesive is used in an amount of 80-180 g / m 2 .

6. The preparation method according to claim 1 or 2, characterized in that, The thickness of the second molded body or the sawn timber is no more than 35 mm.

7. The preparation method according to claim 1 or 2, characterized in that, The cold pressing pressure is 1-2 MPa, the cold pressing time is 60-240 min, and the cold pressing temperature is 0-40℃.

8. A wood-based structural material, which is prepared by the preparation method according to any one of claims 1-7.

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