WO2021101493A1

WO2021101493A1 - Plywood and method for manufacturing same

Info

Publication number: WO2021101493A1
Application number: PCT/UA2020/000025
Authority: WO
Inventors: Виктор Григорьевич МАТВИЕНКО; Анатолий Григорьевич МАТВИЕНКО
Original assignee: Виктор Григорьевич МАТВИЕНКО; Анатолий Григорьевич МАТВИЕНКО
Priority date: 2019-11-20
Filing date: 2020-03-13
Publication date: 2021-05-27

Abstract

The group of inventions relates to the woodworking industry, more particularly to the technology for manufacturing plywood from veneer by hot-pressing an assembly of veneer with an adhesive layer between sheets of the veneer. The technical problem: improving the quality of plywood and a method for manufacturing same by improving the physical and mechanical properties, the water resistance and the environmental friendliness of the plywood; simplifying the manufacturing technology and providing environmentally safe production. The essence of the invention consists in that the plywood comprises veneer sheets which are connected by an adhesive layer, where film-type polymers: polyethene or polypropene are used as the adhesive layer. The method for manufacturing plywood comprises hot-pressing an assembly of veneer with an adhesive layer between sheets of the veneer, in which film-type polymers: polyethene or polypropene are used as the adhesive layer, where the film-type polymer has a thickness of 10 - 200 μm, wherein the hot-pressing is carried out for 0.3 – 2.5 min per 1 mm of thickness of the plywood, at a pressure of 0.5 – 7.5 MPa and a temperature of 115 – 215°C.

Description

PLYWOOD AND METHOD OF ITS PRODUCTION

IPC (2020.01): B 27 D 1/04; B27G 11/00

FIELD OF TECHNOLOGY

The group of inventions relates to the woodworking industry, in particular, to the production of plywood by hot pressing a veneer assembly with an adhesive layer between veneer sheets, and can be used in the production of plywood, and plywood - in construction, furniture industry, etc.

PRIOR ART

For the production of environmentally friendly plywood, protein or casein adhesives are traditionally used as glue (Mikhailtska G.S., Panov V.V. Kjie ^' i for gluing wood. - Levt: Athena, 2002. - 179 p.). However, plywood based on them does not have the required water resistance and mechanical strength. Currently, up to 90% of waterproof plywood is made with adhesives containing phenol-formaldehyde resins, which are hazardous to the environment and human health. The closest in properties to the claimed plywood is plywood containing veneer sheets glued together with phenol-formaldehyde resin of the resol type SFZh-3013. (AS USSR N 1402427, MKI V 27 D 1/04, 1988).

A significant drawback of such plywood and its production technology is the emission of toxic phenol and formaldehyde, which are carcinogenic and belong to the second class of hazard substances (highly hazardous substances). The maximum permissible concentration of phenol and formaldehyde in the air is 0.3 mg / m3. Plywood emits formaldehyde during operation, which significantly narrows the scope of this board material. In addition, the value of the parameter The "ultimate bending strength" of plywood based on phenol-formaldehyde resins is no more than 70-75 MPa, which in some cases is insufficient.

A known method of manufacturing plywood, which contains veneer sheets glued together with phenol-formaldehyde resin of the resole type SFZh-3011 (Kondratyev VP and other Waterproof adhesives in the woodworking industry. M .: Forest Industry, 1988, S. 50).

The product made in this way is harmful to the environment, human health and has insufficiently high physical and mechanical properties.

To reduce the toxicity of plywood, phenol-formaldehyde resins with additives that reduce the emission of formaldehyde and phenol are used as an adhesive.

Closest to the claimed method of manufacturing plywood is a method of manufacturing plywood (RF patent N ° 2440890, IPC B27D1 / 04, 2012), in which an adhesive composition based on phenol-formaldehyde resin brand SFZh-3013 contains a modifier - an extract of the bark of coniferous trees.

The disadvantages of this method of making plywood are the complication of the production process, the impossibility of standardizing the active components of the extract, which does not significantly reduce the toxicity of plywood. At the same time, the disadvantages inherent in all methods of producing plywood using resin solutions are not eliminated: the need to apply liquid glue and its increased consumption, drying of the veneer assembly and its preliminary cold pressing, a significant decrease in the volume of veneer assembly during pressing ("pressing"), scrap due to "Bubbling" of plywood caused by water vapor pressure, limited pot life of the adhesive.

In this regard, it is urgent to improve the method of making plywood, which will allow combining high strength and water resistance of the product with its environmental friendliness. DISCLOSURE OF THE INVENTION

Technical task: improving the quality of plywood and improving the method of its manufacture by improving the physical and mechanical properties, water resistance, environmental friendliness of plywood; simplification of the technology of its manufacture and ensuring the environmental safety of production.

The problem is solved by the proposed plywood containing veneer sheets connected by an adhesive layer, in which film polymers are used as an adhesive layer: polyethylene or polypropylene with a thickness of 10-200 microns, and on the front sides of the plywood, a film laminating polymer layer is additionally applied, identical to the polymer that used as an adhesive layer, while the film laminating polymer layer has a thickness of 30 - 300 microns.

Also, the problem is solved by the proposed method of hot pressing a veneer assembly with an adhesive layer between veneer sheets, in which film polymers are used as an adhesive layer: polyethylene or polypropylene, where the film polymer has a thickness of 10-200 microns, while hot pressing is carried out for 0, 3 - 2.5 minutes per 1 mm of plywood thickness, at a pressure of 0.5 - 7.5 MPa and a temperature of 115 - 215 ° C.

The essential features of the group of inventions in common with the prototype are:

- use of an adhesive layer to join veneer sheets;

- the use of hot pressing to form plywood.

An essential feature that distinguishes a group of inventions:

- use as an adhesive layer of film polymers: polyethylene or polypropylene.

There is a causal relationship between the essential feature that distinguishes the group of inventions and the technical result. Since polyethylene and polypropylene film polymers do not emit harmful substances, their environmental friendliness is beyond doubt. They are highly water resistant. In addition, these molten polymers have high adhesion to the wood surface. Therefore, the use of film polymers that do not contain formaldehyde instead of liquid thermosetting resins (phenolic and urea-formaldehyde) makes it possible to eliminate the toxicity of the product and obtain plywood with high physical and mechanical properties and high water resistance, simplify the process of obtaining plywood and make it environmentally friendly.

The advantages of the proposed group of inventions:

1. High mechanical strength of plywood.

2. Water resistance of the adhesive joint and its elasticity.

3. Ecological cleanliness of production and its product.

4. Ease of application and uniform distribution of the adhesive film.

5. Absence of the stage of drying the veneer assembly before hot pressing.

6. Significant reduction in glue consumption and its share in the cost of plywood.

7. Small pressing of plywood in the manufacturing process.

8. Possibility of precise variation of the thickness of the adhesive layer.

9. No scrap due to plywood “bubbling” caused by water vapor pressure.

10. Permanent readiness of the film adhesive for use and its unlimited shelf life. BEST MODE FOR CARRYING OUT THE INVENTION The essence of the group of inventions is illustrated by examples.

Example 1. An assembly of 7 veneer layers is made. A polypropylene film with a thickness of 50 microns is placed between the veneer sheets. The assembly is hot pressed at a pressure of 2.5 MPa and a temperature of 195 ° C for 7 min (0.8 min / mm). Then the plate is kept in a cold press at a pressure of 2.5 MPa for 1.5 minutes. The density of the obtained material a is 652 kg / m, the ultimate bending strength is 140 MPa, the ultimate shear strength after soaking in water for 24 hours is 2.1 MPa. Other experiments were carried out in a similar way, the results of which are shown in the table. All plywood samples contain formaldehyde <0.1 mg / m3 hour.

Table. Properties of seven-layer plywood and parameters of the technological process of its production (PE - polyethylene, PP - polypropylene)

Example 2. An assembly of 7 veneer layers is made. A polypropylene film with a thickness of 50 microns is placed between the veneer sheets. The faces of the veneer assembly are covered with a polypropylene film with a thickness of 150 microns, and the veneer assembly itself is located between sheets of aluminum foil or between polished sheets of stainless steel. The assembly is hot pressed at a pressure of 2.5 MPa and a temperature of 195 ° C for 7 min (0.8 min / mm). Then the plate is kept in a cold press at a pressure of 2.5 MPa for 1.5 minutes. The density of the obtained material is 662 kg / m, the ultimate bending strength is 142 MPa, the ultimate shear strength after soaking in water for 24 hours is 2.0 MPa.

INDUSTRIAL APPLICABILITY

As follows from the above data, environmentally friendly plywood obtained in accordance with the claimed group of inventions has high strength and high water resistance. The quantitative parameters of the plywood manufacturing process given in this group of inventions are determined experimentally for strong and water-resistant boards.

If the thickness of the adhesive film is less than 10 microns, then the mechanical strength of the material is significantly reduced. It is impractical to increase the thickness of the adhesive film more than 200 microns due to the fact that the mechanical properties of plywood slightly improve with an increase in the consumption of glue.

At a pressing pressure below 0.5 MPa, the mechanical strength of the board material significantly decreases, and at a pressure above 7.5 MPa, the pressing of plywood significantly increases and the technological process of its manufacture becomes more complicated. The pressing temperature below 115 ° C does not make it possible to obtain a strong adhesive bond, and heating above 215 ° C negatively affects the strength of the veneer wood. Decrease pressing time below 0.3 min / mm leads to a decrease in the strength of the plates, and an increase in the time of more than 2.5 min / mm is impractical due to a significant decrease in the productivity of the equipment while the strength of the plates remains unchanged.

Thus, the implementation of the proposed group of inventions makes it possible to obtain plywood by hot pressing, which uniquely combines environmental friendliness, high mechanical strength and water resistance. This simplifies the production process and increases its environmental friendliness, significantly reduces the consumption of glue and pressing of plywood, eliminates the defect that occurs due to the "bubbling" of plywood due to the release of water vapor during pressing.

Claims

CLAIM

1. Plywood containing veneer sheets connected by an adhesive layer, characterized in that film polymers are used as the adhesive layer: polyethylene or polypropylene, where the film polymer has a thickness of 10-200 microns.

2. Plywood according to claim 1, characterized in that the front sides of the plywood additionally have a film laminating polymer layer identical to the polymer used as an adhesive layer, wherein the film laminating polymer layer has a thickness of 30 - 300 μm.

3. A method of making plywood by hot pressing a veneer assembly with an adhesive layer between veneer sheets, characterized in that film polymers are used as an adhesive layer: polyethylene or polypropylene, where the film polymer has a thickness of 10-200 microns, while hot pressing is carried out for 0.3 - 2.5 min per 1 mm of plywood thickness, at a pressure of 0.5 - 7.5 MPa and a temperature of 115 - 215 ° C.