Method for manufacturing hybrid plywood and hybrid plywood

Abstract

In a method for manufacturing hybrid plywood, in which, according to an exemplary embodiment of the invention, the large surfaces of a wood-based board (1) are bonded to the surfaces of a facing layer (2), at the beginning, during the operation of preparing the facing layer material, a selection of birch veneers is carried out, during which birch veneers having a thickness of 1.5 mm are selected, maintaining surface rectangularity and having a length allowance of 5 cm and a width allowance of 5 cm relative to the expected final board dimensions. The prepared veneers are brought to a moisture content in the range of from 3% to 6%. A wood-based construction board (MFP) is used as the wood-based board (1). As the facing layer (2), two sheets of birch veneer are applied in a crosswise arrangement to each large surface of the wood-based board (1). Adhesive in an amount of 170 g / m2 is applied on both sides, by means of glue rollers, to the surfaces of the birch veneers placed inside the stack forming the hybrid plywood, and the prepared stack is transported to a cold press, where it is compressed for 11 min under a pressure of 20 MPa, after which the stack is transported to a hot press and pressed there at a temperature of 127°C and a pressure of 15 MPa for 8 min.

Description

[0001] Method for Manufacturing Hybrid Plywood and Hybrid Plywood The subject matter of the invention is a method for manufacturing hybrid plywood and hybrid plywood.

[0002] From the description of the invention according to Republic of Korea patent No. KR101821568B1, a known solution is a method for manufacturing hybrid plywood comprising the following steps: preparing a flooring material made of medium-density fiberboard MDF (Medium Density Fiberboard), applying a first adhesive to one side of the flooring material, wherein the first adhesive is produced by incorporating at least an acrylic emulsion resin, a melamine resin, and graphite. The adhesive is activated under a pressure from 3 to 5 kg / cm2for 10 to 30 minutes, followed by drying at room temperature for 100 to 140 minutes, and then a second adhesive is applied to a printing layer. According to this invention, hybrid plywood is also manufactured by pressing a high-density fiberboard HDF (High Density Fiberboard) of a specified thickness at high temperature and high pressure, thereby reducing structural deformation caused by humidity or temperature.

[0003] From the description of the invention according to Republic of Korea patent No. KR102286560B1, a solution is known in the form of hybrid plywood consisting of a core in the form of a wood-based medium-density fiberboard MDF, the large surfaces of which are bonded with an adhesive to the surfaces of a facing layer constituting a thermosetting decorative board, HPL, or laminate. Formaldehyde is commonly used in the production of resins applied in adhesives used in the manufacture of laminated boards. Formaldehyde, however, is one of the most well-known indoor pollutants in new houses or houses furnished with new furniture. This organic compound, although occurring naturally in relatively low amounts, may be hazardous andeven carcinogenic at high levels. For this reason, wooden elements, including all types of boards (also laminated boards), must meet strict formaldehyde standards and therefore should be provided with an appropriate hygienic certificate confirming compliance with these standards.

[0004] The aim of the present invention is to provide a construction board in the form of hybrid plywood characterized by reduced manufacturing costs compared to construction boards and having technical and performance parameters not inferior thereto, in particular expressed by high physical and mechanical properties.

[0005] The aim of the present invention is to provide a construction board with reduced formaldehyde emissions, which may find wider application, for example, in the furniture industry.

[0006] The aim of the invention is to provide a method for manufacturing a construction board in the form of hybrid plywood characterized by resistance to separation of the surface adhesive layer, deformation, shrinkage, and dimensional changes.

[0007] The essence of the method for manufacturing hybrid plywood, wherein according to the invention the large surfaces of a wood-based board are bonded to the surfaces of a facing layer by applying an adhesive thereto, followed by applying pressure by means of a press, and after curing of the applied adhesive, the previously provided machining allowances of the plywood are cut off, is characterized in that during the operation of preparing the facing material, a selection of deciduous or coniferous veneers (preferably birch veneers) is carried out, during which veneers having a thickness of from 0.8 mm to 4 mm are selected, maintaining surface rectangularity and having a length allowance of from 4.7 cm to 5.2 cm and a width allowance of from 4.7 cm to 5.2 cm relative to the expected final board dimensions, afterwhich the prepared veneers are brought to a moisture content of from 3% to 6%, while a wood-based construction board (MFP) is used as the wood-based board, and as the facing layer at least two veneer sheets are applied in a crosswise arrangement to each large surface of the wood-based board. Moreover, adhesive is applied on both sides to the surfaces of the veneers placed inside the stack forming the hybrid plywood, in an amount of from 160 g / m2to 180 g / m2. The prepared stack is transported to a cold press, where it is compressed for a period of from 10 min to 11 min under a pressure of from 18 MPa to 22 MPa, after which the stack is transported to a hot press and pressed there at a temperature of from 125°C to 129°C and a pressure of from 14 MPa to 16 MPa for a period of from 7 to 10 min.

[0008] The essence of the structure of hybrid plywood, which according to the invention comprises a core in the form of a wood-based board, the large surfaces of which are bonded with an adhesive to the surfaces of a facing layer, is characterized in that the core is a wood-based construction board (MFP), while the facing layer comprises at least four sheets of deciduous or coniferous veneer (preferably birch veneer) having a thickness of from 0.8 mm to 4 mm, oriented in a crosswise arrangement, with at least two veneer sheets on each large surface of the wood-based construction board.

[0009] A beneficial effect of the invention is the possibility of producing a construction board in the form of hybrid plywood characterized by reduced manufacturing costs compared to construction boards and having technical and performance parameters not inferior thereto, in particular expressed by high physical and mechanical properties.

[0010] A beneficial effect of the invention is reduced formaldehyde emission enabling wider application, for example, in the furniture industry, achieved due to the specific arrangement of the veneers.A beneficial effect of the invention is a construction of a construction board in the form of hybrid plywood characterized by high resistance to separation of the surface adhesive layer, deformation, shrinkage, and dimensional changes, as well as high technical and performance parameters, in particular expressed by physical and mechanical properties. Due to the fact that the plywood according to the invention is very rigid and cohesive, it is ideally suited for the construction of frame furniture as well as upholstered furniture components, while its resistance to loads and bending allows its use in demanding structures such as, for example, floor or roof sheathing.

[0011] The method according to the invention will be explained in more detail by means of an exemplary embodiment illustrated in the drawing, in which Fig. 1 schematically shows a fragment of a crosssection of the plywood. The plywood according to the invention will be explained in more detail by means of its exemplary embodiment illustrated in the drawing, in which Fig. 1 schematically shows a fragment of a cross-section of the plywood, while Fig. 2 illustrates the level of strength parameters of the plywood according to the invention compared with the strength parameters of boards known from the prior art.

[0012] Example 1

[0013] In the method for manufacturing hybrid plywood, wherein according to the exemplary embodiment of the invention the large surfaces of the wood-based board 1 are bonded to the surfaces of the facing layer 2, at the beginning, during the operation of preparing the facing material, a selection of birch veneers is carried out, during which birch veneers having a thickness of 1.5 mm are selected, maintaining surface rectangularity and having a length allowance of 5 cm and a width allowance of 5 cm relative to the expected final boarddimensions. The prepared veneers are brought to a moisture content in the range of from 3% to 6%. A wood-based construction board (MFP) is used as the wood-based board 1. As the facing layer 2, two sheets of birch veneer are applied in a crosswise arrangement to each large surface of the wood-based board 1. Adhesive is applied on both sides, by means of glue rollers, to the surfaces of the birch veneers placed inside the stack forming the hybrid plywood, in an amount of 170 g / m2, and the prepared stack is transported to a cold press, where it is compressed for 11 min under a pressure of 20 MPa, after which the stack is transported to a hot press and pressed there at a temperature of 127°C and a pressure of 15 MPa for 8 min. In the method according to the invention, veneers obtained from both deciduous and coniferous wood may be used.

[0014] Example 2

[0015] Hybrid plywood, according to an exemplary embodiment of the invention, comprises a core in the form of a wood-based board 1, the large surfaces of which are bonded with an adhesive to the surfaces of a facing layer 2. The core is a wood-based construction board (MFP) 1, while the facing layer 2 comprises four sheets of birch veneer having a thickness of from 1.3 mm to 1.7 mm, oriented as two birch veneer sheets in a crosswise arrangement on each large surface of the woodbased construction board 1. In the plywood according to the invention, the veneers may be obtained from both deciduous and coniferous wood.

[0016] The hybrid plywood has very good quality parameters, in particular longitudinal / transverse elasticity, obtained due to the specific orientation of the veneers, wherein on each surface of the wood-based board the first two veneers should be arranged in a crosswise configuration, which guarantees the overall quality of the plywood.

Claims

Claims1. A method for manufacturing hybrid plywood, in which the large surfaces of a wood-based board are bonded to the surfaces of a facing layer by applying an adhesive thereto, followed by applying pressure thereto by means of a press, and after curing of the applied adhesive, the previously provided machining allowances of the plywood are cut off, characterized in that, during the operation of preparing the facing layer material (2), a selection of birch veneers is carried out, during which birch veneers having a thickness of from 0.8 mm to 4 mm are selected, maintaining surface rectangularity and having a length allowance of from 4.7 cm to 5.2 cm and a width allowance of from 4.7 cm to 5.2 cm relative to the expected final board dimensions, after which the prepared veneers are brought to a moisture content of from 3% to 6%, while a wood-based construction board (MFP) is used as the wood-based board (1), and wherein, as the facing layer, two sheets of birch veneer are applied in a crosswise arrangement to each large surface of the wood-based board (1), moreover, adhesive is applied on both sides to the surfaces of the birch veneers placed inside the stack forming the hybrid plywood, in an amount of from 160 g / m2to 180 g / m2, and the prepared stack is transported to a cold press, where it is compressed for a period of from 10 to 11 min under a pressure of from 18 MPa to 22 MPa, after which the stack is transported to a hot press and pressed there at a temperature of from 125°C to 129°C and a pressure of from 14 MPa to 16 MPa for a period of from 7 to 10 min.

2. Hybrid plywood comprising a core in the form of a wood-based board, the large surfaces of which are bonded with an adhesive to the surfaces of a facing layer, characterized in that the core is a woodbased construction board (1) (MFP), while the facing layer (2) comprises at least four veneer sheets having a thickness of from 0.8mm to 4 mm, oriented in a crosswise arrangement, with at least two veneer sheets on each large surface of the wood-based construction board (1).

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