High-strength veneered plywood and method for producing the same

Abstract

The application relates to the technical field of environment-friendly and decorative materials, in particular to a high-strength veneered plywood and a preparation method thereof, which comprises the following steps: splitting and defibrating bamboo to obtain a fiberized bamboo veneer; gluing and drying the fiberized bamboo veneer; gluing two surfaces of a plywood blank, and directionally laying the glued fiberized bamboo veneer on the upper and lower surfaces of the plywood blank; and obtaining a bamboo fiber veneered plywood through hot pressing molding. The bamboo, which is rich in sources, is used as a veneering raw material, the cost is low, the splitting and defibrating method is simple, the fiberized bamboo veneer has high flatness, and the directional arrangement on the upper and lower surfaces of the plywood blank can greatly improve the mechanical properties of the plywood. In addition, the density of the recombined blank is uniform, the surface is smooth, and the plywood with excellent appearance quality can be obtained by directly pasting a melamine impregnated paper and other film paper materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental protection and decoration materials, and particularly relates to a high-strength veneered plywood and a preparation method thereof. BACKGROUND

[0002] The impregnated film paper veneered plywood is a kind of artificial board developed in China in recent years, also known as ecological board. It is obtained by using plywood as base material and then veneering with three-polymer impregnated paper. Among all the veneered artificial boards in China, the impregnated film veneered artificial board accounts for about 60%, which is mainly used in furniture decoration, packaging and other industries. When used as an outer wall panel of a wall, it can not only protect and decorate, but also has heat insulation performance. When used outdoors, it can replace general wood and reduce problems caused by long-term sunlight irradiation, rain erosion, and fungus and insect corrosion.

[0003] Since the veneering process of the impregnated film paper has a high requirement on the flatness of the artificial board, a layer of wood veneer, ultra-thin fiberboard, particle board or the like is generally needed to be added to the surface of the plywood in the production process to adjust the surface flatness of the base layer and the density difference of the board, and then veneering is performed. For example, the prior art CN111360952A discloses a particle veneered plywood and a preparation method thereof. Single boards are glued and assembled, and a core layer plywood is obtained after pressing. The core layer plywood is uniformly paved with glued particles on the upper and lower surfaces, and a particle veneered plywood is obtained after pressing. The prior art CN110385753A discloses an environmentally friendly technology wood veneer veneered plywood and a preparation method thereof. After sanding the upper and lower surfaces of the plywood, the technology wood veneer is veneered with the plywood in room temperature. The adhesive used in the veneering has no formaldehyde and has a formaldehyde purification function. The prior art CN101164742A discloses a production process of a veneered plywood for a container bottom plate. Dry single boards are glued and assembled with phenolic resin as adhesive, and a plywood is obtained after hot pressing. After thickness setting, sanding, edge sawing and repairing, the surface of the plywood is coated with a liquid resin and then hot pressed.

[0004] However, the existing plywood is generally directly made of multiple thin wood boards, and has low strength. Adding a layer of thin wood veneer or ultra-thin fiberboard to the surface of the plywood will further reduce the strength of the plywood, which is easy to be damaged due to collision during transportation, and reduces the practicability of the plywood and is inconvenient to use. Therefore, finding a method of plywood production process that can make the surface of the plywood flat and improve the strength of the plywood is a difficult problem to be solved in the field of artificial boards at present. SUMMARY

[0005] The present application aims to provide a high-strength veneered plywood and a preparation method thereof to solve the problems in the background art, and has the advantages of high strength and veneer, solves the problem of low strength of the existing veneered plywood, which is easy to be damaged due to collision during transportation, and is inconvenient for users to use.

[0006] To achieve the above-mentioned purpose, the present application provides a preparation method of a veneered plywood, comprising:

[0007] S1, splitting and defibrating bamboo to obtain fibrous bamboo veneer;

[0008] S2, gluing and drying the fibrous bamboo veneer;

[0009] S3, gluing the plywood blank on both sides, and orienting and laying the fibrous bamboo veneer on the upper and lower surfaces of the plywood blank after gluing, and obtaining a bamboo fiber veneered plywood by hot pressing.

[0010] It uses abundant bamboo as a veneer raw material, has low cost, and the splitting and defibrating method is simple. The fibrous bamboo veneer obtained has high flatness, and the oriented arrangement on the upper and lower surfaces of the plywood blank can greatly improve the mechanical properties of the plywood. In addition, the density of the reconstituted blank is uniform, and the surface is smooth, which is beneficial to the subsequent direct bonding of melamine impregnated paper and other film paper materials to obtain a plywood with excellent appearance quality.

[0011] Further, the splitting and defibrating includes forming point and / or line segment cracks on the bamboo green and bamboo yellow surfaces, and simultaneously removing the wax layer and siliceous layer of the bamboo green and bamboo yellow surfaces to obtain the fibrous bamboo veneer. For example, a splitting and defibrating device as shown in Figure 1 The device includes two extrusion rollers with a certain gap therebetween, a plurality of point-shaped defibrating teeth distributed on the surface of one extrusion roller, and a plurality of line segment-shaped defibrating teeth distributed on the surface of the other extrusion roller. The defibrating teeth are discontinuously arranged along the circumferential and axial directions of the extrusion rollers. The height of the point-shaped defibrating teeth is 0.5-0.8 times the thickness of the bamboo wall, the cross-sectional diameter is 1-10 mm, and the spacing is 1-10 mm. The length of the line segment-shaped defibrating teeth is 10-50 mm, and the spacing is 5-25 mm. The main material is split into two semicircular bamboo tubes, and then sent between the two extrusion rollers. The two extrusion rollers are driven at different speeds to split and defibrate the bamboo.

[0012] Further, the diameter of a single bamboo fiber of the fibrous bamboo veneer is 0.01-5 mm, preferably 0.1-2 mm. Splitting and defibrating the main material into a fibrous structure can improve flatness and increase specific surface area, which facilitates the absorption of adhesive and improves bonding strength.

[0013] And / or, the laying thickness of the fibrous bamboo veneer is 2.0-4.0 mm.

[0014] And / or, the thickness of the bamboo fiber veneer plywood is 1.0-2.0mm. After hot pressing, the overall thickness is thinned.

[0015] Further, the temperature of hot pressing is 120-150℃, the time is 50-70s / mm, and the pressure is 2.5-3.5MPa.

[0016] Further, the bamboo material is selected from one or more of Phyllostachys edulis, Dendrocalamus giganteus, Dendrocalamus latiflorus and Dendrocalamus strictus;

[0017] And / or, the moisture content of the fiberized bamboo veneer after drying is 8%-12%.

[0018] Further, the adhesive used for gluing the fiberized bamboo veneer is selected from one or more of diphenylmethane diisocyanate adhesive, urea-formaldehyde resin adhesive and phenol-formaldehyde resin adhesive; preferably, the gluing is carried out by the dipping method;

[0019] The adhesive used for gluing the fiberized bamboo veneer is selected from one or more of melamine modified urea-formaldehyde resin adhesive, isocyanate adhesive, epoxy resin adhesive and phenol-formaldehyde resin.

[0020] Further, the preparation method further comprises: chemically dissociating the bamboo material to obtain a fibrous product and a powdery product; separately gluing the fibrous product and the powdery product, and then compounding the glued fibrous product and the glued powdery product with the glued fiberized bamboo veneer, and then directionally laying on the upper and lower surfaces of the plywood blank to obtain the bamboo fiber veneer plywood through hot pressing. The present application dissociates the organization structure of the bamboo material through chemical reaction, wherein the powdery product is mainly parenchyma tissue, and the remaining vascular bundles and the like are basically not affected in the longitudinal direction and still exist in the form of fibrous structure, i.e. the fibrous product. The diameter of the dissociated fibrous product is 0.01-0.15mm, and the particle size of the powdery product is 0.01-0.1mm. The compounding of the fibrous product and the powdery product with the fiberized bamboo veneer can further improve the strength and flatness of the veneerable plywood, and the controllability of the structure is higher. The mass ratio of the fiberized bamboo veneer, the fibrous product and the powdery product is 4:1:3-4:3:1, i.e. the mass ratio of the fibrous product to the powdery product is 1:3-3:1, and the mass ratio of the fiberized bamboo veneer to the sum of the fibrous product and the powdery product is 4:(2-4).

[0021] Further, the chemical dissociation comprises: immersing the bamboo material in a solution composed of peroxide and small molecule acid for chemical dissociation, then neutralizing with an alkali solution and washing with water, and finally separating and drying the product to obtain the fibrous product and the powdery product; the flexibility of the dissociated fibrous product is improved, which is more conducive to processing and forming; and the powdery product can fill in the fiber gap to further improve the strength.

[0022] Preferably, the peroxide comprises hydrogen peroxide; and / or, the small molecule acid comprises formic acid;

[0023] Preferably, the time of chemical dissociation is 4-20h;

[0024] Preferably, the mass fraction of the alkaline solution is 0.1-2%, preferably sodium hydroxide solution.

[0025] Further, the solution is prepared by hydrogen peroxide with a mass fraction of 20-40% and formic acid; and / or, the solution comprises hydrogen peroxide and formic acid with a molar ratio of (0.5-2):1;

[0026] Preferably, 0.1-2wt% of sulfuric acid is further added to the solution;

[0027] In some specific embodiments, the fibrous product is impregnated with sizing agent, and then arranged directionally together with the sized fiberized bamboo veneer to form a bamboo fiber board; the powdery product is sprayed with sizing agent, and then hot-pressed after being compounded with the bamboo fiber board, and then directionally laid on the upper and lower surfaces of the plywood blank to obtain a bamboo fiber veneer plywood by hot-pressing. Alternatively, the fibrous product and the sized fiberized bamboo veneer are directionally laid on the upper and lower surfaces of the plywood blank, and then the powdery product sprayed with sizing agent is filled between the fiberized bamboo veneers, and preferably hot-pressed to obtain a bamboo fiber veneer plywood.

[0028] To achieve the above-mentioned purposes, the application further provides a veneerable plywood prepared by any one of the above preparation methods.

[0029] The beneficial effects of the application are as follows:

[0030] 1. The veneerable plywood provided by the application uses abundant bamboo as the veneer raw material, has low cost, and the splitting and defibrating method is simple. The fiberized bamboo veneer obtained has high flatness, and the directional arrangement on the upper and lower surfaces of the plywood blank can greatly improve the mechanical properties of the plywood. In addition, the density of the reconstituted blank is uniform, and the surface is smooth, which is beneficial to the subsequent direct bonding of melamine impregnated paper and other film paper materials to obtain a plywood with excellent appearance quality.

[0031] 2. The application further improves the strength and flatness of the plywood by compounding the fiberized bamboo veneer obtained by mechanical splitting and defibrating with the fibrous product and the powdery product obtained by chemical dissociation. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and the ordinary skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0033] Figure 1 It is an optional dissection and defibration principle schematic diagram of the present application. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the ordinary skilled in the art without any creative effort belong to the protection scope of the present application.

[0035] Embodiment 1

[0036] A preparation method of a veneered plywood, comprising:

[0037] S1, dissection and defibration of bamboo to obtain a fiberized bamboo veneer with a diameter of 1mm;

[0038] S2, impregnation and glue application drying of the fiberized bamboo veneer; the adhesive is a phenolic resin adhesive.

[0039] S3, glue application on both sides of the plywood blank, directional laying of the fiberized bamboo veneer after glue application on the upper and lower surfaces of the plywood blank, and hot pressing to obtain a bamboo fiber veneered plywood.

[0040] The temperature of hot pressing is 140℃, the time is 60s / mm, and the pressure is 3MPa.

[0041] The laying thickness of the fiberized bamboo veneer is 3mm, and the thickness of the bamboo fiber veneered plywood is 1.5mm.

[0042] Embodiment 2

[0043] A preparation method of a veneered plywood, comprising:

[0044] S1, dissection and defibration of bamboo to obtain a fiberized bamboo veneer with a diameter of 2mm;

[0045] S2, impregnation and glue application drying of the fiberized bamboo veneer; the adhesive is a urea-formaldehyde resin adhesive.

[0046] S3, gluing on both sides of the plywood blank, and orientally laying the glued fibrid bamboo veneer on the upper and lower surfaces of the plywood blank to obtain a bamboo fiber veneer plywood through hot-pressing.

[0047] The temperature of the hot-pressing is 120℃, the time is 70s / mm, and the pressure is 3.5MPa.

[0048] The laying thickness of the fibrid bamboo veneer is 4mm, and the thickness of the bamboo fiber veneer plywood is 2mm.

[0049] Example 3

[0050] A method for preparing a veneerable plywood comprises:

[0051] S1, splitting and defibrating bamboo to obtain fibrid bamboo veneer with a diameter of 1mm;

[0052] S2, impregnating, gluing and drying the fibrid bamboo veneer; the adhesive is a phenolic resin adhesive.

[0053] The bamboo cylinder is immersed in a solution of peroxyformic acid at 60℃ for 14h, then neutralized with a 1wt% sodium hydroxide solution, and washed several times with deionized water to remove chemicals. The separated fibrous product and the powdery product are obtained by shaking, and the treated product is dried at room temperature for a period of time. The diameter of the fibrous product is 0.06mm, and the particle size of the powdery product is 0.04mm.

[0054] The solution of peroxyformic acid is synthesized from 30% hydrogen peroxide and formic acid at a molar ratio of 1:1.

[0055] The powdery product of bamboo is sprayed with glue, and the fibrous product is impregnated with glue.

[0056] The adhesive for gluing is an isocyanate adhesive.

[0057] S3, gluing on both sides of the plywood blank, and orientally laying the glued fibrid bamboo veneer, the fibrous product and the powdery product on the upper and lower surfaces of the plywood blank to obtain a bamboo fiber veneer plywood through hot-pressing.

[0058] The mass ratio of the fibrid bamboo veneer, the fibrous product and the powdery product is 4:3:1.

[0059] The temperature of the hot-pressing is 150℃, the time is 60s / mm, and the pressure is 3.5MPa.

[0060] The laying thickness of the fibrid bamboo veneer (including the fibrous product and the powdery product) is 3mm, and the thickness of the bamboo fiber veneer plywood is 1.5mm.

[0061] Example 4

[0062] A method for preparing a veneered plywood, comprising:

[0063] S1, splitting and defibrating bamboo to obtain a fibrous bamboo veneer with a diameter of 0.5 mm;

[0064] S2, impregnating and applying glue to the fibrous bamboo veneer and drying; the adhesive is a phenolic resin adhesive.

[0065] The bamboo cylinder was immersed in a solution of peroxyformic acid at 60°C for 16 h, then neutralized with a 2wt% sodium hydroxide solution, and washed several times with deionized water to remove chemicals. The separated fibrous product and the powdered product were obtained by shaking, and the treated product was dried at room temperature for a period of time. The diameter of the fibrous product was 0.1 mm, and the particle size of the powdered product was 0.06 mm.

[0066] The peroxyformic acid solution was synthesized from 40% hydrogen peroxide and formic acid at a molar ratio of 2:1. The sulfuric acid content was 1wt%.

[0067] The powdered bamboo product was sprayed with glue, and the fibrous product was impregnated with glue.

[0068] The adhesive used for gluing was a melamine-modified urea-formaldehyde resin adhesive.

[0069] S3, applying glue to both sides of the plywood blank, and orienting and laying the fibrous bamboo veneer, the fibrous product, and the powdered product on the upper and lower surfaces of the plywood blank after gluing, and hot pressing to obtain a bamboo fiber veneered plywood.

[0070] The mass ratio of the fibrous bamboo veneer, the fibrous product, and the powdered product was 4:2:1.

[0071] The hot pressing temperature was 150°C, the time was 60s / mm, and the pressure was 2.5MPa.

[0072] The laying thickness of the fibrous bamboo veneer (including the fibrous product and the powdered product) was 2mm, and the thickness of the bamboo fiber veneered plywood was 1mm.

[0073] Comparative Example 1

[0074] A method for preparing a veneered plywood, comprising the following steps:

[0075] (1) cutting the bamboo cylinder into flat bamboo pieces, and then compounding them into bamboo boards;

[0076] (2) applying glue to both sides of the plywood blank, and then hot pressing it with two compounded bamboo boards to obtain a bamboo cell reorganized veneered high-strength plywood. The pressing temperature was 130°C, the time was 60s / mm, and the pressure was 2MPa.

[0077] Performance test

[0078] The static bending strength and elastic modulus of the material were tested according to GB / T 17657-2013. The results are shown in Table 1.

[0079] Table 1 Performance test results of Examples 1-4 and Comparative Example 1

[0080] Class Static strength / MPa Elastic modulus / MPa Example 1 49.3 4020 Example 2 48.6 3940 Example 3 56.3 4860 Example 4 54.7 4550 Comparative Example 1 39.7 2790

[0081] As can be seen from Examples 1 and 2 in Table 1, compared with the bamboo chips of Comparative Example 1, the fiberized bamboo veneer obtained by splitting and loosening according to the present application can improve the static bending strength and elastic modulus. As can be seen from Examples 3 and 4, after being compounded with the fibrous product and the powdery product obtained by chemical dissociation, the static bending strength and elastic modulus are further improved.

[0082] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a surface-finishable plywood, characterized in that, include: S1. The bamboo is split and decomposed to obtain fibrous bamboo veneer; S2. Apply glue to the fiberized bamboo veneer and dry it; S3. The bamboo material is immersed in a solution composed of peroxide and small molecule acid for chemical dissociation, then neutralized with an alkaline solution and washed with water. Finally, the product is separated and dried to obtain fibrous product and powder product. S4. The fibrous product and the glued fiberized bamboo veneer are laid together in an orientation on the upper and lower surfaces of the plywood blank. Then, the powdered product after spraying and gluing is filled between the fiberized bamboo veneers. Finally, the plywood is hot-pressed to obtain bamboo fiber veneer plywood. The chemical dissociation involves immersing the bamboo in a solution composed of peroxide and small molecule acid for chemical dissociation, then neutralizing it with an alkaline solution and washing it with water, and finally separating and drying the product to obtain fibrous product and powder product. The peroxide is hydrogen peroxide, and the small molecule acid is formic acid; The chemical dissociation time is 4-20 hours; The alkaline solution is a sodium hydroxide solution with a mass fraction of 0.1-2%.

2. The method for preparing the surface-decorative plywood according to claim 1, characterized in that, The splitting and thinning process includes: forming dot-shaped and / or line-shaped cracks on the green and yellow sides of the bamboo, while removing the waxy and siliceous layers on the green and yellow sides of the bamboo to obtain fibrous bamboo veneer.

3. The method for preparing the surface-decorative plywood according to claim 2, characterized in that, The diameter of a single bamboo fiber in the fibrous bamboo veneer is 0.01-5mm.

4. The method for preparing the surface-decorative plywood according to claim 3, characterized in that, The diameter of a single bamboo fiber in the fibrous bamboo veneer is 0.1-2 mm; The thickness of the fiberized bamboo veneer is 2.0-4.0 mm; The thickness of the bamboo fiber veneer plywood is 1.0-2.0 mm.

5. The method for preparing the surface-decorative plywood according to claim 1, characterized in that, The hot pressing temperature is 120-150℃, the time is 50-70s / mm, and the pressure is 2.5-3.5MPa.

6. The method for preparing the surfaced plywood according to any one of claims 1-5, characterized in that, The bamboo material is selected from one or more of the following: moso bamboo, Ci bamboo, giant dragon bamboo, and Nan bamboo; The moisture content of the dried fibrous bamboo veneer is 8%-12%.

7. The method for preparing the surfaced plywood according to any one of claims 1-5, characterized in that, The adhesive used for applying the fibrous bamboo veneer is selected from one or more of the following: diphenylmethane diisocyanate adhesive, urea-formaldehyde resin adhesive, phenolic resin adhesive, melamine-modified urea-formaldehyde resin adhesive, isocyanate adhesive, and epoxy resin adhesive.

8. The method for preparing the surface-decorative plywood according to claim 7, characterized in that, The fibrous bamboo veneer is applied using the impregnation method.

9. The method for preparing the surface-decorative plywood according to claim 1, characterized in that, The solution is prepared by mixing hydrogen peroxide and formic acid with a mass fraction of 20-40%; the solution includes hydrogen peroxide and formic acid in a molar ratio of (0.5-2):

1.

10. The method for preparing the surface-decorative plywood according to claim 9, characterized in that, The solution also contains 0.1-2 wt% sulfuric acid.

11. The method for preparing the surface-decorative plywood according to claim 10, characterized in that, The fibrous product has a diameter of 0.01-0.15 mm, and the powdered product has a particle size of 0.01-0.10 mm.

12. A type of surface-decorative plywood, characterized in that, It is prepared by any one of the preparation methods according to claims 1-11.

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