Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-06-13
2003-09-30
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S242000, C156S212000, C156S214000
Reexamination Certificate
active
06627029
ABSTRACT:
The present invention relates to a process for producing a three-dimensional molding from a layered composite material comprising a thermoplastic polymer backing, an intermediate layer arranged thereupon and a heat-cured layer applied to the intermediate layer.
The layered composite materials known hitherto are used in particular in the furniture industry and in the household equipment industry and essentially consist of a backing layer made from wood or from wood fibres or from individual sheets of paper press-molded with additional resin, to which decorative layers, and also other heat-cured layers, known as overlays, are applied using heat and pressure. The decorative layers used here frequently have a woodgrain, metallic or marble pattern. In many cases the decorative layers are used together with the heat-cured layers applied thereto, in the form of laminates.
However, a disadvantage of layered composite materials of this type is that they are to some extent susceptible to moisture penetrating into the core layer from the edges, since both wood and wood fibres, and also individual sheets of paper, tend to swell when exposed to moisture. In addition, layered composite materials of this type are relatively difficult to shape.
For a wide variety of industrial applications, for example in the automotive and electrical industries, there is a need for surface materials which firstly have compressive strength and are scratch resistant and secondly have comparatively high heat resistance, and which moreover can readily be produced with decorative effects.
Surface materials used for a long time in furniture production have two or more layers, including a backing layer, a decorative layer and a heat-cured layer applied thereto. These layers, with the aid of other bonded layers, for example made from paper or from adhesive films, give a decorative layered composite material. However, a layered composite material of this type is very complicated to produce, frequently has a high formaldehyde content, and has disadvantageous swelling behavior.
DE-A 1 97 22 339 discloses a layered composite material which comprises a backing layer made from polypropylene, a decorative layer arranged thereupon and a heat-cured layer applied to the decorative layer. The earlier application DE-A 19 858 173 moreover describes a layered composite material made from a backing layer of various other thermoplastic polymers, for example certain styrene copolymers or polyoxymethylene or, respectively, polybutylene terephthalate, and also a decorative layer applied thereto and a heat-cured layer lying thereupon. Examples of features of layered composite materials of this type with a backing layer made from thermoplastic polymers are, when compared with conventional layered composite materials with backing layers made from wood, wood fibers or paper: high heat and moisture-resistance, better mechanical strength and easier processing. However, a degree of stiffness and brittleness in the individual polymeric layers means that the layered composite materials known from DE-A 19 722 339 and DE-A 19 858 173 still have certain disadvantages in processing and shaping, in particular in three-dimensional shaping to give components for the automotive sector, the household sector or the electrical sector, especially when three-dimensional moldings are being produced. For three-dimensional shaping, high flexibility and easy processability of the molding are particularly important.
It is an object of the present invention to overcome the disadvantages described and develop a process which produces a three-dimensional molding from a layered composite material, is simple to carry out, gives moldings with any desired design and can be carried out without excessive use of resources in a cost-effective manner in conventional molding systems. A further object is that the novel process should also allow the production of three-dimensional moldings which are not susceptible to chemically, mechanically or thermally induced damage and have high scratch resistance and compressive strength.
We have found that this object is achieved by developing a new process to produce a three-dimensional molding from a layered composite material. The layered composite material here has a thermoplastic polymer backing, an intermediate layer arranged thereupon and a heat-cured layer applied to the intermediate layer, and the process comprises bonding the intermediate layer and the heat-cured layer applied thereto to the backing by heat treatment in a molding system and also giving these a three-dimensional shape prior to or during the heat treatment in the molding system.
In the layered composite material produced by the novel process it is also possible for both sides of the backing made from the thermoplastic polymer to have an intermediate layer arranged thereupon and a heat-cured layer applied to the intermediate layer, giving a sandwich structure with the backing in the middle.
There is also a modification of the novel process in which the layered composite material also has, between the intermediate layer and the heat-cured layer, a decorative layer which has been arranged upon the intermediate layer and which, together with the intermediate layer and the heat-cured layer, is bonded to the backing by heat treatment in a molding system and moreover is given a three-dimensional shape prior to or during heat treatment in the molding system.
Based on the total weight of the backing, the material of the backing may comprise from 1 to 60% by weight, preferably from 5 to 50% by weight, particularly preferably from 10 to 40% by weight, of reinforcing fillers, such as barium sulfate, magnesium hydroxide or talc with an average particle size of from 0.1 to 10 &mgr;m, measured to DIN 66 115, wood, flax, chalk, glass fibers, coated glass fibers, long or short glass fibers, glass beads or mixtures of these. The material of the backing may also comprise the usual additives, such as stabilisers to protect against the action of light, UV radiation or heat, pigments, carbon blacks, lubricants, flame retardants, blowing agents and the like, in the amounts which are usual and required.
Examples of thermoplastic polymers which may form the backing are polypropylene, polyethylene, polyvinylchloride, polysulfones, polyetherketones, polyesters, polycycloolefins, polyacrylates and polymethacrylates, polyamides, polycarbonate, polyurethane, polyacetals, such as polyoxymethylene, polybutylene terephthalates and polystyrenes. Both homopolymers and copolymers of these thermoplastic polymers may be used here. The backing preferably also comprises, besides the reinforcing fillers, polypropylene, polyoxymethylene, polybutylene terephthalate or polystyrene, in particular styrene copolymers with subordinate proportions of one or more comonomers, such as butadiene, &agr;-methylstyrene, acrylonitrile, vinylcarbazole, or else esters of acrylic, methacrylic or itaconic acid. The backing used in the novel process may also comprise recycled materials made from these thermoplastic polymers.
For the purposes of the present invention, polyoxymethylenes are homo- or copolymers of aldehydes, for example of formaldehyde, or of cyclic acetals, containing recurring carbon-oxygen bonds in their molecule and having a melt flow rate (MFR) to ISO 1133 of from 5 to 40 g/10 min, in particular from 5 to 30 g/10 min, at 230° C. with a load of 2.16 kg.
The polybutylene terephthalate preferably used is a higher-molecular-weight esterification product of terephthalic acid and butylene glycol with a melt flow rate (MFR) to ISO 1133 of from 5 to 50 g/10 min., in particular from 5 to 30 g/10 min, at 230° C. with a load of 2.16 kg.
Possible styrene copolymers are in particular copolymers having up to 45% by weight, preferably up to 20% by weight, of copolymerized acrylonitrile. Copolymers of this type made from styrene and acrylonitrile (SAN) have a melt flow rate (MFR) to ISO 1133 of from 1 to 25 g/10 min, in particular from 4 to 20 g/10 min, at 230° C. with a load of 2.16 kg.
Other styrene copolymers whose
Klemm Klaus
Müller Klaus
Aftergut Jeff H.
Basell Polyolefine GmbH
Keil & Weinkauf
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