CS227298B1 - Method of manufacturing construction elements from wood and reactoplasts - Google Patents

Description

The present invention provides a process for the manufacture of wood components and thermosetting plastics with a finished surface.

There are currently known methods of using cured wood veneers as surface veneers. The disadvantages of the known processes are that thermochemical curing of veneers in one step at temperatures of 80 to 120 ° C is highly demanding in terms of occupational safety and in terms of control and regulation of the curing process of veneer and other materials. Completely curing to conversions close to K = 100% results in polymer increments on the surface of the veneer and gluing of veneer materials at the points of contact with each other during curing. In-situ polymerization of thermosetting plastics occurs mainly in the area of high conversions due to the so-called " Tromsdorf effect or gel effect for excessive exothermic heat generation, with exothermic peak temperatures often in the region of 170-180 ° C. Complete hardened wood veneer materials are brittle and deteriorate when pressed into planar or molded parts, resulting in low production balance. The gluing of wood veneers by known methods and conventional urea-formaldehyde and phenol-formaldehyde adhesives used in the wood and furniture industry achieves low bond strengths and it is therefore necessary to use special adhesives adjusted with melamine or resorcinol, which is one of the main causes of preventing plastics. veneer in production.

The aforementioned disadvantages are largely eliminated by the method of manufacturing wood components and thermosetting plastics, which is based on the fact that veneers impregnated with a solution of thermosetting plastics in an organic solvent with a viscosity of the impregnating agent in the range of 2 to 30 mPa. s are pre-cured to a polymer conversion of 35 to 90%, a solvent content of 5 to 25%, and the impregnated veneer is cured after application of the adhesive to the pre-cured veneer during molding at temperatures of 100 to 190 ^° C. Embossing presses with embossing can also be used for pressing.

The method of manufacturing the components according to the invention is advantageous in that it makes it possible to produce components with a finished surface without treatment with paints. There is no formation of inlay during pre-hardening of the thermosetting plastics, and the pre-hardened veneers are flexible during compression. They do not lose by cracking when pressed onto the central layer of the component 227298 ca. When gluing it is possible to use commonly used adhesives in the wood and furniture industry. Compared to hitherto known processes for manufacturing components which are not refined with a precured thermosetting material, the leakage of the adhesive used for bonding the surface veneers to the central part of the component is substantially reduced. By the described production method, it is possible to reduce the consumption of glue and to reduce the leakage of formaldehyde from the internal parts of the boards or glued joints.

In order to carry out the described process for the manufacture of components, it is most advantageous to use as known impregnating agents commercially known solutions of thermosetting plastics for the modification of wood in organic solvents, for practical reasons, in particular for impregnation to be carried out in technologically acceptable times. up to 30 mPa. with. Examples of impregnation of veneers with thermosetting solutions are vacuum-pressure impregnation at a vacuum value of 200 to 600 torr for 50 min, at a subsequent pressure of 0.5 to 0.6 MPa for 150 min. Upon completion of pressurization, it is preferred to use a vacuum to remove excess impregnating agent with parameters ranging from 300 to 500 torr for 60 to 120 min. depending on the desired polymer retention in veneers and the type of wood used. In addition to the commonly used impregnating agents, epoxy resin solutions having a non-volatile component content of 25 to 45% by weight, with an epoxy group content of 0.15 to 0.30 equivalents of epoxy groups in 100 g of dry resin, can be advantageously used. Polyalkylene polyamines having an amine number of 1400 to 1700 mg KOH / g are preferably used as hardener. The pre-curing of the impregnated veneers can be carried out at the operating temperature in this case. During precuring, the veneers are folded or suspended so as to prevent their contact and sticking together, especially at the beginning of the precuring. Pre-curing is carried out for 1 to 5 days according to the depth of the veneer used until the solvent content has dropped to 5 to 25%.

Example 1

Koto veneers (Ptarygota macrocarpaj of three thicknesses of 0.5, 0.8 and 1.1 mm, 40 x 100 cm format, are evacuated for 30 minutes at a vacuum of 400 torr. Then, a 40 wt. parts of epoxy resin, with an epoxy group concentration of 0.25 equivalents / 100 g, 2.7 parts by weight of a polyalkylene amine catalyst, and

39.5 wt. parts of a solvent mixture of toluene, xylene, ethyl acetate and methanol. A pressure of 0.8 MPa is then applied for 150 min. After the impregnating agent has been drained and its excess evacuated, the veneers are spread on racks at an operating temperature in the range of 19-25 ° C for 2 days. In this case, an average conversion of 88% is achieved and the solvent content in veneers varies between 15 and 22%. Subsequently, 150 g / m ^{2 of} urea-formaldehyde adhesive is applied to the veneers and the pre-cured veneers are pressed onto the main and side surfaces of the central parts of the components while simultaneously veneering the veneers at a temperature of 140 ° C for 1 to 3 min. used veneer. After hardening, the components are treated exclusively by mechanical treatment, grinding and polishing with a dry polishing belt.

Example 2

A method of manufacturing components using other thermosetting plastics is to impregnate veneers or thin blanks with an impregnating system based on water-emulsifiable polyester resins. Styrene is used as the solvent in this case. The viscosity of the impregnating agent at the operating temperature is 3 to 15 mPa. with. A 1: 2 mixture of dibenzoyl peroxide and tert-butyl perbenzoate is used as the catalyst at a total concentration in the impregnating agent of 0.7 to 1.1%. Pre-curing is carried out at a temperature of 90 ° C for 1 to 2.5 hours, depending on the dimensions of the wood material used, so as to achieve a polymer conversion in the range of 35 to 60 ° / o. The degree of polymerization is selected according to the particular operating conditions depending on the time between the pre-curing and subsequent adhesive application and the veneer hardening on the component by pressing. The pressing and curing temperatures are in the range 100 to 190 ° C, preferably 140 to 160 ° C.

A particular and particularly preferred way of carrying out the described process is to impregnate thin veneers and micro veneers. In this method, veneers, e.g. 0.2 to 0.7 mm thick impregnate with a thermosetting solution, which is then pre-dried and partially cured so that the veneer surface is no longer sticky and adhesive can be applied to the veneer and then pressed onto the central part of the component. A great advantage in this case is that the in-situ pre-cured thermosetting plastics material in the wood structure represents a barrier layer against adhesive leakage. This fact substantially extends the possibilities of using micro veneers and thin veneers. After the second hardening step, the thermosetting plastic has the function of an internal paint in situ and thus the surface treatment of the veneered part or at least a part thereof can be achieved by mechanical surface treatment. A further advantage of this method applied to thin veneers and micro-veneers is that the repair of the surface of furniture, tiles, ceilings, doors, furniture of electrical equipment and other products can be achieved by fine mechanical processing, regrinding or polishing. This is very important for thin veneers and micro veneers. Such a method is not possible with a coating.

The described method of manufacturing components can be used for the production of wall coverings, interior ceilings, partition walls, especially in wooden buildings, furniture, plywood and molded products, flooring materials such as sandwich wood-plastic materials, floor panels, mosaic parquet, veneer inlays and the like. This method can also be used to change the color shade of wood by coloring impregnation systems with known dyes soluble in the impregnating liquid, mainly from the technology class of fat soluble dyes. The present method can be used wherever it is necessary to eliminate the classical methods of surface treatment with paints and to reduce the labor intensity of the surface treatment and the related sanitary and fire risks. Due to the increased plasticity and toughness of the pre-hardened veneers modified, in particular, with epoxy and polyester thermosetting plastics, this method can be used to press and harden the veneers with relief presses and produce such embossed construction that is especially interior.

Claims (2)

SUBJECT 1. A process for the manufacture of wood components and thermosetting plastics whose surface is veneered with thermosetting modified veneers such as epoxy, polyester, alkyd or polyurethane resins, characterized in that veneers of a thickness of 0.2 to 10 mm impregnated with a solution of thermosetting plastics in organic solvent with a viscosity of the impregnating agent in the range of 2 to 30 mPa. s are pre-cured for the conversion of polymer 35 to 35 INVENTION It 90%, for a solvent content of 5 to 25% and the impregnated veneer hardening is carried out after the adhesive has been applied to the precured veneers during the molding of the component at temperatures of 100 to 190 ° C. 2. A process for the production of wood and thermosetting plastics components according to claim 1, characterized in that relief stamping presses are used for the hardening and pressing of the veneers onto the construction thatch.