DE3019068A1 - METHOD FOR PRODUCING MOLDED PARTS FROM THERMOPLASTIC DISPERSIONS AND WOOD PARTICLES - Google Patents

Abstract

The process is used for the production of mouldings in the furniture, construction and light industry. It comprises using thermoplastic dispersions to produce stable and re-shapeable mouldings without a post-curing time which have thin walls, are stable and are versatile. This is achieved by spraying the wood particles with an aqueous, plasticiser-free, finely disperse dispersion of terpolymers based on acrylates or on acrylate-styrene copolymers or on homopolymers of polyvinyl acetate. The pourable mixture is subsequently pre-consolidated to give rough nonwovens and assembled in one or more layers under pressure and heat to give the moulding.

Description

Title of the invention

Process for the production of molded parts from thermoplastic dispersions and wood particles Field of application of the invention The invention relates to a method for the production of molded parts from thermoplastic dispersions and wood particles for the furniture, construction and light industries.

Characteristics of the known technical solutions There are many technical ones Solutions known, the process for the production of press plates or molded parts made of wood particles with the addition of binders. These differ in each case in the selection of the material components or

Binders, the way in which the components are incorporated and mixed in and in the shaping of the finished parts.

It is i.a. a process known that the powdery or fibrous Thermoplastic insert describes. Additional work steps are necessary here to produce a processable wood particle-thermoplastic mixture.

So is z. B. a granulation technology or a mixing in the Melt with subsequent crushing required to form an aggregated particulate Wood-thermoplastic mixture to obtain (CH-PS 570869). The alternating Compression and decompression in the extruder as well as the removal of the resulting gas-water mixture has a disadvantageous effect due to the effort involved (DE-OS 2245871).

Furthermore, a method is known in which the necessary drying of the wood particle material before mixing as well as a comminution of the thermoplastic Starting material too finely divided - often powdery - thermoplastic matrix than Disadvantages are to be mentioned (DE-OS 2206829).

The known use of condensation resins - thermosetting resins - in turn brings with it the disadvantages that a post-curing time (when using of phenolic resin) or conditioning time (when using melamine or urea-formaldehyde resins) after the hot pressing of the wood particle material is necessary. Also be the surfaces of the pressed parts are subsequently ground after hot pressing, in order to To obtain a homogeneous, scratch-resistant and, if possible, closed surface. at The use of xondensation resins is also a subsequent deformation or relief formation made of panel materials not possible for special applications (US 3649297, US 3627864, US 3793125, AT 295119) Objective of the invention The objective of the invention is', a variably shaped, thin-walled, but stable and versatile Thermoplastic wood particle molded part to be produced efficiently.

Statement of the essence of the invention The invention is the task based, with little technological effort and using suitable thermoplastic dispersions, which are added to the wood particles, stable and post-formable molded parts, their Surface finish is smooth and firm without producing post-curing time.

According to the invention the object is achieved in that the wood particles, preferably wood fibers, with an aqueous, plasticizer-free, finely dispersed, terpolymer Dispersion based on acrylic acid ester or acrylic acid ester-styrene copolymer or with an aqueous, plasticizer-free, finely divided monopolymer dispersion of the polyvinyl acetate are sprayed. The resulting pourable mixture is then pre-compressed into coarse nonwovens and placed in the press under pressure and heat formed into a molded part. The fleeces are produced in one or more layers, where homopolymer dispersion of polyvinyl acetate or acrylic acid ester or Acrylic acid ester-styrene copolymer corresponding to that placed on the respective layer Requirement can be added differently. For special applications the wood particle-thermoplastic mixture of the middle layer of a multi-layer fleece a thermosetting resin added. The molded part is formed either directly or as well through subsequent reshaping of the panel material at the end user.

The production of these thin-walled thermoplastic wood particle moldings experience has shown that it is possible using a simple technology. The thermoplastic dispersions are advantageously ready for processing in the delivery state, meanwhile other thermoplastic material must first be processed and shredded accordingly got to. It is permitted to spray the wood particles with the aqueous thermoplastic dispersion a good dosage, an intimate and all-round wetting and mixing of both Components, which eliminates the problem of segregation that would otherwise have to be taken into account. That has a favorable effect on the characteristic values and the surface appearance of the shaped bodies the end.

The present invention also has the cost-reducing advantage that the wood particles to be pressed do not have to be dried again. A Another advantage results from the fact that grinding of the molded part surfaces in contrast to the use of condensation resins can be omitted because when using of thermoplastic dispersions a good, smooth, firm and closed one even without grinding surface is achieved. It is also advantageous that as plates Manufactured parts under simultaneous exposure to heat and pressure from the end user are post-deformable for its special purpose, the deformability depends on the thermoplastic content. With a higher proportion of thermoplastics, heavily deformed Objects are produced as they were previously only made of press plates by joining them together individual parts could be manufactured. The known usage does not apply Post-curing time necessary for condensation resins through several days of stacking. To After cooling down, the molded parts can be processed or used immediately. Ever Depending on the claim in use, the thermoplastic component in the surface can be opposite of the middle class or used depending on the type.

EXEMPLARY EMBODIMENTS The invention is based on the following examples to be explained in more detail.

Example 1 3000 g of wood fibers are mixed with 2000 g of an aqueous dispersion of an acrylic acid ester-styrene copolymer (solids content on 'atro-Plast 40%) bedUst and the pourable mixture in a filter system to form a coarse fleece sheet or sprinkled to form a shaped body (moisture content 3 ... 7%; solids content on absolutely dry wood 25 ... 30%). After the fleece has been transported, the desired Part formed in a direct process. Press conditions: specific press pressure 2.5 ... 5 Mea, temperature 170 ... 200 C. Adjustable raw density range: 600 ... 1000 kg / m-.

If no surface effect is intended, then silicone release film is used -used as a supplement during the pressing process. If necessary, ~ all Process molded parts in the same way as conventional wood-based materials.

Example 2 3000 g of wood fibers are produced using an aqueous terpolymer Dispersion based on acrylic acid ester (solids content on atro Plast 43%) is analogous Example 1 treated.

Example 3 3000 g of wood fibers are obtained using an aqueous hompolymer dispersion of the polyvinyl acetate (pesticide content on atro Plast 55 0 treated analogously to Example 1).

Example 4 Production of the sprayable, free-flowing wood particle-thermoplastic mixtures and nonwovens in a known manner analogous to Examples 2 and 3. Before moving into the Press takes place the layering of three individual fleeces.

Composition of the outer layer nonwovens analogous to Example 2, composition of the middle fleece as in Example 3. The mass of the middle layer is 1 ... 6 times the mass of a top layer fleece.

Press conditions analogous to Example 1.

Example 5 Production of the sprayable, free-flowing wood particle-thermoplastic mixtures and nonwovens in a known manner analogous to Example 4, with that for the central nonwoven proposed wood fiber-thermoplastic mixture analogous to Examples 1 to 3 in addition heat-curable resin sprayed on from 0.5 to 30 percent by weight based on the total mass will. Further treatment as in Example 4.

Example 6 Production of the sprayable, pourable wood particle-thermoplastic mixture and nonwoven in a known manner analogous to Examples 1 to 4 '. In the press a transportable fibreboard blank produced. Press conditions analogous to the example 1 using spacer strips (5 ... 8 mm) O This fibreboard blank is after renewed plasticization (heating to 17c..180 C) in the preheated press tool profiled to the desired molded fiber part in the post-deformation process. Press conditions of the post-forming see example lo for the following examples 1 to 6 molded parts produced result in the following listed average Properties: Gross density (kWm) 690 1000 Flexural strength (MPa) 37 - 41 42 E'-module (MPa) 1900 1800 - 2500 Thickness swelling (%) 15 - 18 15 - 18 Thickness (mm) 4 3.2 Summary The invention relates to a method for producing molded parts from thermoplastic dispersions and wood particles for the furniture, construction and light industries0 is the object of the invention es, Uhermoplast wood particle moldings with positive and efficient properties to manufacture.

The object of the invention is to use suitable Thermoplastic dispersions to produce stable and post-formable molded parts without post-curing time, which are thin-walled, stable and versatile.

According to the invention the object is achieved in that the wood particles with an aqueous, plasticizer-free, finely divided, terpolymeric dispersion based on acrylic acid ester or aaryl acid ester-styrene copolymer or with a Homopolymer dispersion of the polyvinyl acetate are sprayed. The pourable Mixture is then pre-compressed into coarse fleeces and placed in the press Pressure and heat formed on the molded part

Claims (5)

Invention claim 9 process for the production of molded parts Thermoplastic dispersions and wood particles, characterized in that the wood particles, preferably wood fibers with an aqueous, plasticizer-free, finely dispersed, terpolymer Dispersion based on acrylic acid ester or acrylic acid ester-styrene copolymer or with an aqueous, plasticizer-free, finely dispersed homopolymer dispersion of the polyvinyl acetate, pre-compressed into coarse fleeces and in a press be formed into a molded part in one or more layers under pressure and heat. 2o method according to item 1, characterized in that the solids content of the thermoplastic dispersions 39 ... 57% and the solids content based on absolutely dry wood particles 10 ... 40%. 3. The method according to points 1. and 2., characterized in that the thermoplastic dispersions according to the requirements placed on each layer different ~ be added. 40 The method according to points 1. to 3., characterized in that for special applications for the wood particle-thermoplastic mixture of the middle layer a thermosetting resin is added to the fleece. 5. The method according to items 1. to 3., characterized in that the Production of the molded part directly or by subsequent reshaping of the panel material takes place at the end user.