LU500652B1

LU500652B1 - Manufacturing Method of High-stability Formaldehyde-free Plywood

Info

Publication number: LU500652B1
Application number: LU500652A
Authority: LU
Inventors: Xiaoju Hua; Yundan Dong; Luyao Xiong; Hui Huang; Qian Zhang; Lei He; Fengwen Sun
Original assignee: Jiangxi Acad Of Forestry; Univ Nanjing Forestry
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2022-03-15

Abstract

A manufacturing method of high-stability formaldehyde-free indoor plywood, which comprises the following process steps: 1) drying the veneer; 2) coating or spraying a surface modifier on the surface of the veneer, and drying until a film is formed on the surface of the veneer; 3) arranging the veneers, assembling the veneers according to requirements, and laying a hot melt adhesive film with the same size as that of the veneers between every two layers of veneers; 4) sending the slab into a hot press for hot pressing, gluing and forming; reducing the temperature after hot pressing, and then discharging the slab; 5) storing the slab at normal temperature, and making the final product by machining of size and post-forming. The method has the advantages that hot melt adhesive film is used to replace the traditional formaldehyde adhesive, so that there is no formaldehyde or other harmful substances in the product.

Description

DESCRIPTION 7500652 Manufacturing Method of High-stability Formaldehyde-free Plywood

TECHNICAL FIELD The invention relates to a manufacturing method of formaldehyde-free indoor plywood which has advantages of excellent waterproofness and dimensional stability and does not release harmful substances, and belongs to the technical fields of wood science and engineering technology and decorative building materials.

BACKGROUND With the decrease of natural hardwood resources, plantation fast-growing wood is increasingly used in the production of various plywood boards due to its rapid growth and large reserves. However, due to the short growth cycle, fast-growing wood has some natural defects, such as soft texture, low strength, low hardness and poor dimensional stability; moreover, in the production process of plywood and other products, urea-formaldehyde resin or melamine modified urea-formaldehyde resin is generally used as adhesive, which inevitably has the problem of releasing formaldehyde, seriously affecting the quality of living environment and endangering human physical and mental health and life safety.

SUMMARY The invention provides a manufacturing method of high-stability formaldehyde-free plywood, which aims to overcome the problems of poor water resistance, warping deformation, releasing formaldehyde and the like, which exist in products such as plywood and multi-layer laminated wood flooring for indoor decoration at present. Through the combination of hydrophobic treatment of veneer surface and hot melt adhesive film bonding technology, it provides environment friendly plywood with excellent dimensional stability and waterproof performance, which does not release formaldehyde and any other harmful substances.

According to the technical scheme of the invention, the manufacturing method of the formaldehyde-free indoor plywood comprises the following process steps: 1) drying the veneer until the water content is 8%-14%;

2) coating or spraying a surface modifier on the surface of the dried veneer with 500652 the dosage of 10-50 g/m”, and air-drying or low-temperature drying until a film is formed on the surface of the veneer; 3) arranging the veneer after surface treatment, assembling the veneer according to the slab structure requirements of plywood or floor substrate, and laying a hot melt adhesive with the same size as that of the veneer between two layers of veneers; 4) sending the slab into a hot press for hot pressing, gluing and forming, wherein the process of hot pressing and gluing is as follows: the hot pressing temperature is 130-160°C, the unit pressure is 0.1-0.6 MPa, and the hot pressing time is 30-60 s/mm; after hot pressing, reducing temperature to below 100°C, and then discharging the slab; 5) storing the hot-pressed slab for more than 24 hours at normal temperature, and making the final product by machining of size and post-forming.

The method has the advantages that the hot melt adhesive film is used to replace the traditional formaldehyde adhesive, so that there is no formaldehyde or other harmful substances in the product, thereby saving the gluing process, improving the production environment and increasing the production efficiency; moreover, the surface of the veneer is modified by environment friendly organosilicon waterproofing agent, which increased the hardness of the veneer surface and formed hydrophobic film, greatly improved the bonding strength between the hot melt adhesive film and the veneer, and improved the waterproof property and dimensional stability of the product.

DESCRIPTION OF THE INVENTION The manufacturing method of formaldehyde-free indoor plywood is characterized by comprising the following process steps: 1) drying the veneer until the water content is 8%-14%; 2) coating or spraying a surface modifier on the surface of the dried veneer with the dosage of 10-50 g/m”, and air-drying or low-temperature drying until a film is formed on the surface of the veneer;

3) arranging the veneer after surface treatment, assembling the veneer according 500652 to the requirements of the slab structure of plywood, and laying a hot melt adhesive with the same size as that of the veneer between two layers of veneers; 4) sending the slab into a hot press for hot pressing, gluing and forming, wherein the process of hot pressing and gluing is as follows: the hot pressing temperature is 130-160°C, the unit pressure is 0.1-0.6 MPa, and the hot pressing time is 30-60 s/mm; after hot pressing, reducing temperature to below 100°C, and then discharging the slab; 5) storing the hot-pressed slab for more than 24 hours at normal temperature, and making the final product by machining of size and post-forming.

The surface modifier in the step 2) refers to one of film-forming water glass, sodium methyl silicate or octyl triethoxysilane waterproofing agent.

The hot melt adhesive film in the step 3) is one of TPU, EVA, PA, PO (EAA) or PES adhesive film, and the thickness of the adhesive film is controlled within 0.1-0.25 mm.

Example 1 Putting 2.0 mm thick poplar veneer into a drying oven, drying at 50°C for 20 min, and then taking out, next, spraying octyl triethoxysilane waterproof agent on the glued surface of the veneer with amount of 20 g/m? and placing in the air for 24 h; placing a PES hot melt adhesive film with a thickness of 0.2 mm between every two layers of the dried veneer to form a 7-layer slab, next, putting the slab into a hot press with a hot pressing temperature of 140°C, a unit pressure of 0.5 MPa and a hot pressing time of 5 min, and then discharging the slab after reducing the temperature to 90°C.

Sawing the plywood pressed by the above method into 75 mm*75 mm specimens, putting into water at 63°C for soaking 3 hours, and then drying at 63°C for 3 hours after taking out. There is no glue opening in each glue layer.

Example 2 Putting 2.0 mm thick poplar veneer into a drying oven, drying at 50°C for 20 min, and then taking out, next, coating the veneer with water glass waterproof agent with modulus of 3.0 and baume degree of 40 with the coating amount of 50 g/m°, and 500652 then taking out, putting into a drying box for drying at 50°C for 1 h; placing a PO hot melt adhesive film with a thickness of 0.25 mm between every two layers of the dried veneer to form a 7-layer slab, next, putting the slab into a hot press with a hot pressing temperature of 150°C, a unit pressure of 0.5 MPa and a hot pressing time of 6 min, and then discharging the slab after reducing the temperature to 90°C.

Sawing the plywood pressed by the above method into 75 mm*75 mm specimens, putting into water at 63°C for soaking 3 hours, and then drying at 63°C for 3 hours after taking out. There is no glue opening in each glue layer; moreover, the slope rate of stripped veneer is over 80%.

Claims

1. A manufacturing method of formaldehyde-free glued indoor plywood is characterized by comprising the following steps: 1) drying the veneer until the water content is 8%-14%; 2) coating or spraying a surface modifier on the surface of the dried veneer with the dosage of 10-50 g/m”, and air-drying or low-temperature drying until a film is formed on the surface of the veneer; 3) arranging the veneer after surface treatment, assembling the veneer according to the requirements of the slab structure of plywood, and laying a hot melt adhesive with the same size as that of the veneer between two layers of veneers; 4) sending the slab into a hot press for hot pressing, gluing and forming, wherein the process of hot pressing and gluing is as follows: the hot pressing temperature is 130-160°C, the unit pressure is 0.1-0.6 MPa, and the hot pressing time is 30-60 s/mm; after hot pressing, reducing temperature to below 100°C, and then discharging the slab; 5) storing the hot-pressed slab for more than 24 hours at normal temperature, and making the final product by machining of size and post-forming.

2. The manufacturing method of formaldehyde-free glued indoor plywood according to claim 1 is characterized in that the surface modifier in the step 2) refers to one of film-forming water glass, sodium methyl silicate or octyl triethoxysilane waterproofing agent.

3. The manufacturing method of formaldehyde-free glued indoor plywood according to claim 1 is characterized in that the hot melt adhesive film in the step 3) is one of TPU, EVA, PA, PO (EAA) or PES adhesive film, and the thickness of the adhesive film is controlled within 0.1-0.25 mm.