A method for preparing an ultra-low formaldehyde-releasing wood-based reconstituted material

Abstract

The application discloses a preparation method of super-low formaldehyde release wood-based recombined material, and the wood-based recombined material prepared has a thickness of 15-25 mm, a density of 0.9-1.2 g / cm3, a static bending strength of 120-150 MPa, an elastic modulus of 15000-17000 MPa, a water absorption thickness expansion rate of 2-4.5%, and a formaldehyde release amount of 0.1-0.4 mg / L. The modified bamboo fiber is inserted into the surface cracks of the defibrated veneer, and a low formaldehyde release urea-formaldehyde resin adhesive is used to realize stable bonding and curing between the defibrated veneers, so that the super-low formaldehyde release wood-based recombined material is prepared, the formaldehyde release amount is greatly reduced, and the mechanical properties and durability of the wood-based recombined material are remarkably improved. Compared with the prior art, the application still maintains the high mechanical properties of the wood-based recombined material while ensuring the super-low formaldehyde release, and exhibits obvious superiority and practicability.

Description

Technical Field

[0001] This invention relates to the field of reconstituted wood technology, and in particular to a method for preparing ultra-low formaldehyde release wood-based reconstituted materials. Background Technology

[0002] China holds a significant position in furniture manufacturing and export, with wooden furniture accounting for over 30% of total furniture production, making it the leading producer. With the booming development of the furniture industry, consumer demand for wooden furniture is increasingly strong. However, my country's timber resources are relatively scarce; therefore, the planting of fast-growing artificial timber has become an effective means to alleviate the supply-demand imbalance. Although fast-growing artificial forests grow rapidly, they suffer from defects such as poor dimensional stability, high stress, and susceptibility to cracking. To fully utilize the natural characteristics of wood raw materials, the industry has proposed developing an innovative product similar to natural wood—reconstituted wood—while maintaining the original fiber orientation and basic properties of the wood.

[0003] Reconstituted wood products possess superior performance. Compared to natural wood, they are virtually non-bending, non-cracking, and non-twisting. They exhibit uniform texture, excellent rigidity, high dimensional stability, and adjustable density. Furthermore, the dimensions and cross-sectional shape of reconstituted wood can be customized to specific applications. Their significant economic advantages lie in the elimination of waste and value loss associated with natural wood processing, achieving a wood utilization rate of up to 80%.

[0004] Currently, the production of reconstituted wood mainly relies on urea-formaldehyde resin adhesives to bond and cure veneers. However, this process generates high levels of formaldehyde, posing a serious threat to human health. Although using non-formaldehyde adhesives, such as biomass-based adhesives, may solve the formaldehyde release problem, these adhesives often face challenges such as insufficient bond strength and high cost.

[0005] Therefore, it is necessary to provide a method for preparing ultra-low formaldehyde release wood-based reconstituted materials to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a method for preparing ultra-low formaldehyde release wood-based reconstituted wood.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing ultra-low formaldehyde release wood-based reconstituted timber, comprising the following steps:

[0008] S1. The logs are rotary-cut into veneers with a thickness of 4 to 12 mm, and then processed by a debonding machine to form debonded veneers with linear cracks distributed along the longitudinal direction of the wood fibers on the surface.

[0009] S2. Use urea-formaldehyde resin modifier to modify bamboo fiber, and then mix the modified bamboo fiber evenly into urea-formaldehyde resin adhesive.

[0010] S3. Use a cage to fix the loosened veneer and vertically place it into a dipping tank containing urea-formaldehyde resin adhesive mixed with modified bamboo fiber for adhesive application.

[0011] S4. Dry the veneer after gluing, and then lay it up into a veneer with several layers to ensure that the fiber direction of adjacent veneer layers is perpendicular to each other.

[0012] S5. The slabs formed after paving and assembly are subjected to hot pressing, curing and edge trimming to prepare ultra-low formaldehyde emission wood-based reconstituted timber.

[0013] In a preferred embodiment of the present invention, the thickness of the slitting veneer is 0.5 to 1.0 mm, and the tooth gap of the slitting machine is controlled at 0.1 to 0.3 mm.

[0014] In a preferred embodiment of the present invention, the preparation of the modified bamboo fiber includes the following steps:

[0015] S21. Mix urea-formaldehyde resin modifier with water in a ratio of 1:2 to 3 to obtain urea-formaldehyde resin modified solution;

[0016] S22. Add bamboo fiber to urea-formaldehyde resin modified solution and let stand for 30-45 minutes;

[0017] S23. Remove the bamboo fibers and allow them to dry naturally to obtain modified bamboo fibers.

[0018] In a preferred embodiment of the present invention, the urea-formaldehyde resin adhesive is a low-formaldehyde-release urea-formaldehyde resin adhesive.

[0019] In a preferred embodiment of the present invention, in step S2, the modified bamboo fiber and urea-formaldehyde resin adhesive are first divided into several equal parts, then alternately placed into a mixing tank, and finally stirred and mixed.

[0020] In a preferred embodiment of the present invention, in step S3, the sparse panels are arranged in the same way in the cage, and there is a gap between adjacent sparse panels.

[0021] In a preferred embodiment of the present invention, in step S3, the urea-formaldehyde resin adhesive mixed with modified bamboo fibers is in a flowing state, and the flow direction is towards the front or back of the veneer.

[0022] In a preferred embodiment of the present invention, the flow rate of the urea-formaldehyde resin adhesive mixed with modified bamboo fibers is 0.5 to 1 m / min.

[0023] In a preferred embodiment of the present invention, in step S3, the impregnation time is 15-25 minutes, and then the product is removed and drained for 4-10 minutes until the adhesive no longer drips.

[0024] In a preferred embodiment of the present invention, in step S4, a blower is used to thoroughly blow air onto the front and back of the loosened veneer before laying the preform.

[0025] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0026] (1) This invention provides a method for preparing ultra-low formaldehyde emission wood-based reconstituted timber. Modified bamboo fibers are interlaced within the surface cracks of the veneer, and a low-formaldehyde-emission urea-formaldehyde resin adhesive is used to achieve stable bonding and curing between the veneers, resulting in ultra-low formaldehyde emission wood-based reconstituted timber. This method not only significantly reduces formaldehyde emission but also significantly improves the mechanical properties and durability of the wood-based reconstituted timber. Compared to existing technologies, this invention maintains high mechanical properties of the wood-based reconstituted timber while ensuring ultra-low formaldehyde emission, demonstrating significant superiority and practicality.

[0027] (2) In this invention, a urea-formaldehyde resin modifier is used to modify bamboo fibers and is inserted into the cracks on the surface of the veneer. It is used in conjunction with a low-formaldehyde-release urea-formaldehyde resin adhesive to prepare an ultra-low formaldehyde-release wood composite. The urea-formaldehyde resin modifier reacts with the hydroxyl groups on the surface of the bamboo fibers to form a chemical structure that can absorb and fix formaldehyde. After the low-formaldehyde-release urea-formaldehyde resin adhesive is cured, some of the formaldehyde components will be absorbed by the modified bamboo fibers, further reducing the content of free formaldehyde in the product.

[0028] (3) In this invention, bamboo fibers are interspersed in the cracks on the surface of the veneer. After gluing, laying and hot pressing, a stable mechanical anchoring effect is formed between the bamboo fibers and adjacent or even interlayered veneers. This structure increases the connection strength between adjacent and interlayered veneers, improves the mechanical properties and durability of wood-based reconstituted timber, and brings a new technological breakthrough to the wood processing industry.

[0029] (4) In this invention, modified bamboo fibers are uniformly mixed into urea-formaldehyde resin adhesive, and then the veneer is applied using a hanging cage method. Simultaneously, in the impregnation tank, the urea-formaldehyde resin adhesive mixed with modified bamboo fibers is in a flowing state, with the flow direction towards the front or back of the veneer. As the flowing adhesive carrying the modified bamboo fibers passes over the veneer, some adhesive remains on the veneer surface, while the rest penetrates into the cracks on the veneer surface. This process design achieves effective penetration of bamboo fibers into the surface of the veneer, thus avoiding the problem of bamboo fibers being unable to enter the cracks on the veneer surface. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart of a preferred embodiment of the present invention for preparing ultra-low formaldehyde release wood-based reconstituted timber;

[0032] Figure 2 This is a flowchart of a preferred embodiment of the preparation method of modified bamboo fiber according to the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0035] like Figure 1 As shown, this invention provides a method for preparing ultra-low formaldehyde release wood-based reconstituted timber, comprising the following steps:

[0036] S1. The logs are rotary-cut into veneers with a thickness of 4 to 12 mm, and then processed by a de-fibering machine to form de-fibered veneers with linear cracks distributed longitudinally along the wood fibers on the surface; the thickness of the de-fibered veneers is 0.5 to 1.0 mm, and the tooth gap of the de-fibering machine is controlled at 0.1 to 0.3 mm.

[0037] S2. Use urea-formaldehyde resin modifier to modify bamboo fibers, and then mix the modified bamboo fibers evenly into urea-formaldehyde resin adhesive.

[0038] S3. Use a cage to fix the loosened veneer and vertically place it into a dipping tank containing urea-formaldehyde resin adhesive mixed with modified bamboo fiber for adhesive application.

[0039] S4. Dry the veneer after gluing, and then lay it up into a veneer with several layers to ensure that the fiber direction of adjacent veneer layers is perpendicular to each other.

[0040] S5. The slabs formed after paving and assembly are subjected to hot pressing, curing and edge trimming to prepare ultra-low formaldehyde emission wood-based reconstituted timber.

[0041] In step S1, after the log veneer is prepared into veneer, it needs to be dried. The drying methods include, but are not limited to, hot air drying, microwave drying and vacuum drying. Microwave drying is preferred because it is fast and the drying effect is uniform. The moisture content of the dried veneer is 8% to 10%.

[0042] The linear cracks on the surface of the veneer are parallel to each other and evenly distributed, which increases the flexibility and workability of the veneer and maintains the basic planar structure.

[0043] like Figure 2 As shown, the preparation of modified bamboo fiber includes the following steps:

[0044] S21. A urea-formaldehyde resin modifier is mixed with water in a ratio of 1:2 to 3 to obtain a urea-formaldehyde resin modified solution; the solution is then subjected to ultrasonic treatment to ensure uniform mixing. The urea-formaldehyde resin modifier is at least one of bismuth nitrate, bismuth oxychloride, and tin dioxide.

[0045] S22. Add bamboo fibers to a urea-formaldehyde resin modified solution and let stand for 30-45 minutes; the diameter of the bamboo fibers is between 50 and 120 μm, and they are made into cotton-like short fibers with a length of 80-450 μm.

[0046] S23. Take out the bamboo fiber and allow it to dry naturally to obtain modified bamboo fiber; the degree of drying is until there is no obvious moisture on the surface of the bamboo fiber.

[0047] The urea-formaldehyde resin adhesive used in this embodiment is a low-formaldehyde-release urea-formaldehyde resin adhesive.

[0048] This low-formaldehyde-emission urea-formaldehyde resin adhesive comprises urea-formaldehyde resin obtained by reacting formaldehyde with urea, a urea-formaldehyde resin modifier, nanocellulose, and the additive polyvinyl alcohol. The free formaldehyde content in this low-formaldehyde-emission urea-formaldehyde resin adhesive is <0.6%. The urea-formaldehyde resin modifier is one or more of bismuth nitrate, bismuth oxychloride, tin dioxide, and zinc sulfide. This low-formaldehyde-emission urea-formaldehyde resin adhesive is existing technology and can effectively reduce the formaldehyde emission of finished wood-based reconstituted timber products.

[0049] In step S2, the modified bamboo fiber and urea-formaldehyde resin adhesive are first divided into several equal portions, then alternately placed into a mixing tank, and finally stirred and mixed.

[0050] It is worth noting that the modified bamboo fibers are evenly laid out to avoid accumulation. Using this method to premix the modified bamboo fibers with urea-formaldehyde resin adhesive can improve the mixing effect and efficiency, and reduce the problems of uneven structure and distribution of the modified bamboo fibers.

[0051] In step S3, the sparse panels are arranged in the same way in the cage, and there is a gap between adjacent sparse panels.

[0052] All the veneers are fixed vertically, and the orientation of the veneers is consistent. A gap of at least 10mm is left between adjacent veneers to allow urea-formaldehyde resin adhesive to pass through and maintain a certain flow state, thereby increasing the permeability of the urea-formaldehyde resin adhesive.

[0053] In step S3, the urea-formaldehyde resin adhesive mixed with modified bamboo fibers is in a flowing state, and the flow direction is towards the front or back of the veneer; the flow rate of the urea-formaldehyde resin adhesive mixed with modified bamboo fibers is 0.5 to 1 m / min.

[0054] It is worth noting that the impregnation tank is set up at an inlet, with the upper part being the inlet for adding urea-formaldehyde resin adhesive mixed with modified bamboo fibers and the lower part being the outlet. The cage is placed in the middle of the impregnation tank. The inclined impregnation tank setting enables the directional flow of urea-formaldehyde resin adhesive mixed with modified bamboo fibers.

[0055] In step S3, the soaking time is 15-25 minutes, and then the product is removed and drained for 4-10 minutes until the adhesive stops dripping.

[0056] When the flowing adhesive carrying modified bamboo fibers passes through the veneer, some of the adhesive remains on the veneer surface, while the rest penetrates into the cracks on the veneer surface. This process design achieves effective penetration of bamboo fibers into the veneer surface, thus avoiding the problem of bamboo fibers being unable to enter the cracks on the veneer surface.

[0057] In step S4, the veneer after gluing is dried to a moisture content of 10% to 12%. The drying method includes, but is not limited to, hot air drying, microwave drying, and vacuum drying, with microwave drying being preferred.

[0058] In step S4, before laying the preform, a blower is used to thoroughly blow air onto the front and back of the loosened veneer.

[0059] The purpose of using low wind speed is to stand up the ends of the modified bamboo fibers interspersed in the cracks of the veneer, so that they can enter the cracks of adjacent or even interlayered veneers in the subsequent paving assembly. After hot pressing, they can form a stable mechanical anchoring effect with adjacent or even interlayered veneers. This anchoring effect is formed through the connection between the modified bamboo fibers and between the modified bamboo fibers and the veneer.

[0060] In step S5, the hot pressing is carried out in stages to achieve curing. The hot pressing temperature is maintained between 130 and 140°C, and the initial hot pressing pressure is set to 2 to 3 MPa. After hot pressing for 2 to 3 minutes, the pressure is increased to 8 to 10 MPa and held for 6 to 9 minutes to complete the hot pressing.

[0061] In step S5, the curing process involves placing the heat-pressed and cured wood-based reconstituted timber in a curing room with relatively stable temperature and humidity. The preferred temperature is 30–40°C, and the humidity is controlled at 50%–70%. This allows the chemical reaction in the adhesive to continue until complete curing, thereby ensuring the structural stability and mechanical properties of the reconstituted wood.

[0062] The trimming in step S5 refers to using a circular saw or band saw to remove irregular parts of the edges of the wood-based reconstituted timber, such as excess adhesive, burrs, or uneven edges, in order to obtain neat and smooth edges.

[0063] The wood-based reconstituted timber prepared using the above-mentioned method for producing ultra-low formaldehyde release wood has a thickness of 15–25 mm and a density of 0.9–1.2 g / cm³. 3 The static bending strength is 120-150 MPa, the elastic modulus is 15000-17000 MPa, the water absorption thickness swelling rate is 2-4.5%, and the formaldehyde release is 0.1-0.4 mg / L.

[0064] Example 1

[0065] Based on the above-mentioned method for preparing ultra-low formaldehyde emission wood-based reconstituted timber, eucalyptus trees from Guangxi, aged ten years and with a diameter at breast height of 100-200 mm, were used. The eucalyptus was rotary-cut into 4 mm thick veneers and then placed in a debonding machine to produce debonded veneers with a thickness of 0.7 mm. The tooth gap of the debonding machine was controlled at 0.2 mm. Microwave drying was then used to control the moisture content of the debonded veneers to 10%.

[0066] Bismuth oxychloride and water were mixed in a 1:2 ratio by ultrasonic treatment to obtain a urea-formaldehyde resin modification solution. Then, bamboo fibers were added to the urea-formaldehyde resin modification solution and left to stand for 45 minutes. After that, the fibers were taken out and dried until there was no obvious moisture on the surface.

[0067] The modified bamboo fiber and the low-formaldehyde-release urea-formaldehyde resin adhesive were divided into 12 equal parts and alternately placed into a mixing tank. Finally, they were mechanically stirred and mixed.

[0068] Use a hanging cage to fix the veneer, leaving a 15mm gap between the veneers. A urea-formaldehyde resin adhesive mixed with modified bamboo fibers flows towards the front of the veneer at a rate controlled at 0.6m / min. Immerse for 20 minutes, then remove and drain until the adhesive no longer drips.

[0069] Microwave drying was used to control the moisture content of the veneer after gluing to 11%, followed by thorough air blowing treatment on both the front and back sides of the veneer. Finally, the veneer was laid into 17.2mm thick boards.

[0070] Hot pressing of the board: The hot pressing temperature is 135℃, the initial hot pressing pressure is 3MPa, and after hot pressing for 3 minutes, the pressure is increased to 9MPa and held for 8 minutes to complete the hot pressing. Then, it is cured for 5 days to prepare wood-based reconstituted timber with a thickness of 15.4mm.

[0071] Example 2

[0072] Based on Example 1, eucalyptus wood was rotary-cut into 4mm thick veneers and then placed in a delaminating machine to prepare delaminating veneers with a thickness of 1.0mm. The delaminating veneers were then laid into 24.6mm thick boards and then hot-pressed and cured to obtain wood-based reconstituted timber with a thickness of 22.3mm.

[0073] Example 3

[0074] Based on Example 1, bismuth oxychloride and water were mixed in a 1:3 ratio by ultrasonic treatment to obtain a urea-formaldehyde resin modification solution, which was then used to prepare modified bamboo fibers. The resulting wood-based reconstituted wood had a thickness of 15.3 mm.

[0075] Comparative Example 1

[0076] Based on Example 1, eucalyptus wood was rotary-cut into 4mm thick veneers and then placed in a delaminating machine to prepare delaminating veneers with a thickness of 2.0mm. The delaminating veneers were then laid into 17.4mm thick boards and prepared into 15.7mm thick wood-based reconstituted timber through hot pressing and curing.

[0077] Comparative Example 2

[0078] Based on Example 1, without modifying the bamboo fiber, a wood-based reconstituted material with a thickness of 15.4 mm was prepared using conventional urea-formaldehyde resin adhesive.

[0079] Comparative Example 3

[0080] Based on Example 1, modified bamboo fibers were evenly sprinkled on the surface of the veneer, and the hanging cage gluing method was still used. The adhesive did not flow, and a wood-based reconstituted wood with a thickness of 15.4 mm was prepared.

[0081] Mechanical properties and formaldehyde emission levels were tested on the wood-based reconstituted wood samples prepared in Examples 1, 2, and 3, as well as Comparative Examples 1, 2, and 3. For mechanical property verification, GB / T 17657-1999 standard was followed. For formaldehyde emission determination, the desiccator method (sections 4.12.1 to 4.12.6) of GB / T 17657-1999 standard was used. The results are shown in Table 1.

[0082]

[0083]

[0084] Table 1. Test results of wood-based reconstituted materials

[0085] The tests above show that the mechanical properties of Examples 1, 2, and 3 are close to or even meet the technical requirements for high-performance reconstituted wood, and the formaldehyde emission is also at an ultra-low level, meeting the national standard requirement of E0 grade <0.5mg / L. Comparative Example 1 has a thicker veneer and fewer layers, resulting in fewer modified bamboo fibers interspersed in the surface cracks of the veneer, leading to insufficient anchor points and poorer mechanical properties in the prepared wood-based reconstituted wood. Comparative Example 2 did not modify the bamboo fibers and used conventional urea-formaldehyde resin adhesives; the resulting wood-based reconstituted wood had a high formaldehyde emission, failing to meet current environmental protection standards. In contrast, in Comparative Example 3, modified bamboo fibers were sprinkled onto the surface of the reconstituted veneer and then applied using a hanging cage method. The modified bamboo fibers could not effectively penetrate into the cracks on the surface of the reconstituted veneer and could not form an effective mechanical anchoring effect, resulting in poor mechanical properties. This is because most of the modified bamboo fibers remained on the surface of the reconstituted veneer and fell off after gluing and drying. Therefore, the presence of modified bamboo fibers in the wood-based reconstituted material was relatively small, resulting in less absorption of free formaldehyde and poor environmental performance.

[0086] This invention provides a method for preparing ultra-low formaldehyde emission wood-based reconstituted timber. Modified bamboo fibers are interlaced within surface cracks of the veneer, and a low-formaldehyde-emission urea-formaldehyde resin adhesive is used to achieve stable bonding and curing between the veneers, resulting in ultra-low formaldehyde emission wood-based reconstituted timber. This method not only significantly reduces formaldehyde release but also substantially improves the mechanical properties and durability of the wood-based reconstituted timber. Compared to existing technologies, this invention maintains high mechanical properties while ensuring ultra-low formaldehyde emission, demonstrating significant superiority and practicality.

[0087] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing an ultra-low formaldehyde-releasing wood-based reconstituted material, characterized by, It comprises the following steps: S1, the log is rotary cut into veneer with thickness of 4-12mm, and is treated by defibrator to form defibrated veneer with linear cracks distributed along the longitudinal direction of wood fibers on the surface; S2, the bamboo fiber is modified by using urea-formaldehyde resin modifier, and then the modified bamboo fiber is uniformly mixed into urea-formaldehyde resin adhesive; The preparation of the modified bamboo fiber comprises the following steps: S21, urea-formaldehyde resin modifier and water are mixed in a ratio of 1:2-3 to obtain urea-formaldehyde resin modification solution; S22, the bamboo fiber is added to the urea-formaldehyde resin modification solution and left for 30-45min; S23, the bamboo fiber is taken out and naturally dried to obtain modified bamboo fiber; S3, the defibrated veneer is fixed by a hanging cage and vertically placed in a glue dipping tank containing low formaldehyde release urea-formaldehyde resin adhesive mixed with modified bamboo fiber for gluing operation; S4, the defibrated veneer after gluing is dried, and then is laid up to form a plurality of layered board blanks, and the fiber directions of adjacent veneer layers are perpendicular to each other; S5, the board blank formed after laying up is treated by hot pressing, aging and edge cutting to obtain ultra-low formaldehyde release wood reconstituted material; In the S3, the defibrated veneer is placed in the hanging cage in the same way, and a gap is left between adjacent defibrated veneers; the low formaldehyde release urea-formaldehyde resin adhesive mixed with modified bamboo fiber is in a flowing state, and the flowing direction is towards the front or back surface of the defibrated veneer.

2. A process for the preparation of ultra-low formaldehyde releasing wood-based reconstituted material according to claim 1, characterized in that: The thickness of the defibrated veneer is 0.5-1.0mm, and the tooth gap of the defibrator is controlled at 0.1-0.3mm.

3. A process for the preparation of ultra-low formaldehyde releasing wood-based reconstituted material according to claim 1, characterized in that: In the S2, the modified bamboo fiber and urea-formaldehyde resin adhesive are first respectively divided into several parts, then are alternately put into a mixing barrel, and finally are stirred and mixed.

4. A process for the preparation of ultra-low formaldehyde releasing wood-based reconstituted material according to claim 1, characterized in that: The flow rate of the urea-formaldehyde resin adhesive mixed with modified bamboo fiber is 0.5-1m / min.

5. A process for the preparation of ultra-low formaldehyde releasing wood-based reconstituted material according to claim 1, characterized in that: In the S3, the dipping time is 15-25min, and then the defibrated veneer is taken out and drained for 4-10min until the glue solution no longer drips.

6. A process for the preparation of ultra-low formaldehyde releasing wood-based reconstituted material according to claim 1, characterized in that: In the S4, before laying up, the front and back surfaces of the defibrated veneer are fully blown by a blower.

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