DD145079A1 - METHOD FOR PRODUCING MOLDED PARTS FROM THERMOPLASTIC DISPERSIONS AND WOOD PARTICLES - Google Patents

Abstract

The invention relates to a process for the production of molded parts from thermoplastic dispersions and wood particles for the furniture, construction and light industry. The aim of the invention is to produce thermoplastic wood particle moldings with positive properties and rational. The object of the invention is to produce stable and deformable molded parts without Nachhaertezeit using suitable thermoplastic dispersions, which are thin-walled, stable and versatile. According to the invention, the object is achieved in that the wood particles are sprayed with an aqueous, plasticizer-free, finely dispersed, terpolymeric dispersions based on acrylic acid ester or acrylic ester-styrene copolymer or with a homopolymer dispersion of the polyvinyl acetate. The pourable mixture is then precompressed to coarse nonwovens and formed in the press under pressure and heat to the molding.

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 process for the production of molded parts from thermoplastic dispersions and wood particles for the furniture, construction and light industries.

Characteristic of the known technical solutions

Many technical solutions are known, which include processes for the production of press plates or moldings from wood particles with the addition of binders. These differ in each case in the selection of Werkst off components or binders, the nature of the introduction and mixing of the components and in the shape of the 'finished parts.

It is ua. a method is known which describes the powdery or fibrous thermoplastic insert. Additional operations are needed to make a workable wood particle-thermoplastic blend *

For example, Ze B * granule technology or melt blending with subsequent comminution is required to form an aggregated particulate wood-thermoplastic blend

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to receive (CH-PS 570869) · The alternate compression and decompression in the extruder and the withdrawal of the resulting gas-water mixture has a disadvantageous effect due to the expense (DE-OS 2245871) «Furthermore, a method is known in which the necessary Drying of the wood particle material prior to mixing and comminution dea thermoplastic starting material to finely divided - often called powdery thermoplastic matrix as disadvantages are (DE-OS 2206829) ·

The well-known use of condensation resins - thermosetting resins - in turn brings with it the disadvantages that a Nachhärtezeit (when using phenolic resin) bzwo conditioning time (when using melamine or * urea-formaldehyde resins) after hot pressing of the wood particle material is necessary the surfaces of the pressed parts are subsequently ground after hot pressing in order to obtain a homogeneous, scratch-resistant and preferably closed surface. When condensation resins are used, subsequent deformation or relief formation from board materials is not possible for special applications (US Pat. No. 3,649,297, US Pat. No. 3,627,864, US Pat. No. 3,793,125, US Pat. AT 295119).

Object of the invention

The aim of the invention is to produce a variably shaped, thin-walled, but stable and versatile applicable thermoplastic wood particle molding rational.

Explanation of the essence of the invention

The invention is based on the object, with little technological effort and using suitable thermoplastic dispersions which are added to the wood particles, stable and deformable moldings whose surface texture is smooth and firm to produce without post-curing.

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Erf indungs according to the object is achieved in that the wood particles, preferably wood fibers, with an aqueous, plasticizer-free, finely dispersed, terpolymeric dispersion based on acrylic ester or acrylic ester-styrene copolymer or with an aqueous, plasticizer-free, finely dispersed monopolymer dispersion of polyvinyl acetate The freewheeling mixture obtained is then precompressed to coarse nonwovens and formed in the press under pressure and heat to form the molded article. The nonwovens are produced in one or more layers, with homopolymer dispersion of the polyvinyl acetate or acrylic ester or acrylic ester-styrene copolymer correspondingly the request made to each layer is different. For special applications, a heat-curable resin is added to the wood particle / thermoplastic mixture of the middle layer of a multilayer nonwoven. The shaping of the shaped part takes place directly or else by subsequent deformation of the board material by the end user.

The preparation of these thin-walled thermoplastic wood particle moldings is possible according to a simple technology. The thermoplastic dispersions are advantageously ready to be processed while other thermoplastic material has to be processed and comminuted accordingly. The spraying of the wood particles with the aqueous thermoplastic dispersion allows a good dosage, an intimate one and all-round wetting and mixing of both components, which eliminates the problem of segregation which otherwise would have to be considered · This has a favorable effect on the characteristic properties and the surface appearance of the shaped bodies.

The present invention further has the cost-reducing advantage that the wood particles to be compressed need not be dried again. "A further advantage results from the fact that grinding of the molding surfaces can be omitted in contrast to the use of condensation resins, as when using thermoplastic dispersions without grinding a good, smooth, firm and closed surface

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is reached. A further advantage is that manufactured as plates parts under the simultaneous action of heat and pressure from the end user for his specific application are deformable, the deformability of the thermoplastic part depends · At higher thermoplastic content and highly deformed objects can be produced, as they have been from press plates previously only It is no longer necessary to cure individual parts after the use of condensation resins. After cooling, the molded parts can be processed or used immediately. Depending on the utility value, the thermoplastic content in the surface can be increased in relation to the middle layer or used depending on the type ·

embodiments

The invention will be explained in more detail in the following examples.

example 1

3000 g of wood fibers are sprayed with 2000 g of an aqueous dispersion of an acrylic ester-styrene copolymer (pesticide content on atro plastic 40 %) and the free-flowing mixture is spread in a felter plant to a coarse non-woven plate or to a shaped body (moisture 3 ··· 7%). Solid content on dry wood 25o ·· 30 %) · After transport of the web, the desired molding is formed in a direct process in the pressing tool of the press. · Pressing conditions: specific pressing pressure 2.5. ».5 I-IPa, temperature 170 ·· .200 ° C _e Adjustable gross density range: 600 ·., 1000 kg / m \

If no surface effect is provided, then. Silicone release film used as a supplement during the pressing process · If still necessary, all shaped parts can be processed like usual wood-based materials.

Example 2

3000 g of wood fibers are treated "analogously to Example 1 when using an aqueous, terpolymeric dispersion based on acrylic acid ester (pesticide content on atro plastic 43 %) .

Example 3

3OOO g of wood fibers are treated analogously to Example 1 when an aqueous homopolymer dispersion of polyvinyl acetate (solids content on atro plastic 55 %) is used.

Example 4

Production of the Coasted Wood-Particle-Thermoplastic Mixtures and Nonwovens in a Known Way Analogous to Examples 2 and 3o Prior to entering the press, the stratification of three individual webs takes place «

Composition of the Top Layer Nonwovens Analogous to Example 2, Composition of the Medium Nonwoven Analogous to Example 3 The mass of the middle layer is 10 times the mass of a cover layer nonwoven fabric Preßbedingungen analog Example 1

Example 5

Production of the wettable wood particle-thermoplastic mixtures and nonwovens in a known manner analogously to Example 4j wherein the intended for the nonwoven wood fiber thermoplastic mixture analogous to Example 1 to 3 in addition a thermosetting resin of 0.5 ··· 30 weight percent based on the Total mass is sprayed on · Further treatment analogous to Example 4

Example 6

Production of the low-rise pourable wood particle-thermoplastic mixture and fleece in a manner known per Example 1 to 4 · A transportable fiber board blank is produced in the press · Pressing conditions analogous to Example 1 using spacer strips (5 o ·· 8 mm) ·

This fiberboard blank is after further plasticizing (heating to 170 ··· 180 ⁰ C) profiled in the preheated press tool to the corresponding desired fiber molded part in the Hachverformungsprozeß. Prepress conditions for press conditions see Example 1

For the molded parts produced according to Examples 1 to 6, the average properties listed below result;

Bulk density (kg / m ³ )

690 1000

Flexural strength (MPa) Modulus of elasticity (MPa) Thickness swelling Thickness (mm)

37 - 41 42 1900 1800 - 2500 15 - 18 15-18 4 3.2

Claims (5)

Erfindungsanapruch 1 · A process for the production of standard parts from thermoplastic dispersions and wood particles, characterized in that the Rolzpartikeln, preferably wood fibers, with an aqueous, plasticizer-free, finely dispersed terpolymeren dispersion based on acrylic acid ester or acrylic ester-styrene copolymer or with an aqueous, plasticizer-free, sprayed finely dispersed homopolymer dispersion of polyvinyl acetate, precompacted to coarse nonwovens and formed in a press or one or more layers under pressure and heat to the molding · 2 · Method according to item 1, characterized in that the content of the pesticides of the thermoplastic dispersions 39 ··· is 57 % and the pesticide content relative to atro-wood particles 10 10, 40 % . 3. The method according to item 1 · and 2 ·, characterized in that the thermoplastic dispersions are added differently according to the requirements imposed on the respective layer. 4. The method according to point 1 · to 3 · »characterized» that for special applications, the wood particle-thermoplastic mixture of the middle layer of the nonwoven mixed with a thermosetting resin 7 / ird. 5 «Procedure according to points 1 to 3 ·» characterized by? that the production of the Pormteils takes place directly or by subsequent deformation de3 plate material at the end user ·