The invention relates to a composite material, made from a microfilament nonwoven fabric having masses per unit area of 50 to 200 g/m2, which is bonded with a thermoplastic synthetic material directly, using an injection-molding process.
Paneling parts for automobile interiors are known from the document EP 0 968 806, whereby a microfiber nonwoven fabric is placed into a mold and bonded to a thermoplastic synthetic material by an injection-molding process. Such injection-molding or “direct injection molding” (DIM) processes permit efficient production of paneling parts in the automobile interior sector. The microfiber nonwoven fabric is preferably made from polyester fibers that function as a binding layer for a decorative layer that is applied subsequently.
In the course of ever greater requirements in the automobile industry, new demands are being made on the suppliers. For example, the paneling parts used in the interior of the automobile are supposed to demonstrate attractive optical and sensory properties of the decor. The parts are supposed to be capable of recycling, to possess a very high level of resistance to color fading, especially under the effects of black-panel temperatures, a low tendency to become dirty, a high level of friction wear resistance, moisture resistance, fire resistance, cleanability, a low tendency or no tendency to emit gases, and low costs. Furthermore, efficient, cost-effective production methods for the production of the paneling parts are aimed at.
The invention has set itself the task of indicating a composite material, as well as a method for its production, that take into account the stated requirements.
According to the present invention, the task is accomplished by a composite material that is made from a microfilament nonwoven fabric having a mass per unit area of 50 to 200 g/m2, the nonwoven fabric being made from melt-spun, drawn multi-component endless filaments having a titer of 1.5 to 5 dtex and directly laid up to form a fibrous web, and the multi-component endless filaments, optionally after prebonding, being split up to at least 80% to form micro-endless filaments having a titer of 0.1-1.2 dtex, and bonded, and then bonded to a thermoplastic synthetic material using an injection-molding process. The composite material demonstrates a high level of specific fiber surface at a comparatively low mass per unit area, as well as high opacity. The fineness of the filaments permits good printability and embossability, and thereby decorative structuring of the nonwoven fabric used for the production of the composite material according to the invention. In this connection, the thermoplastic synthetic material does not impregnate the nonwoven fabric.
Preferably, the composite material is one in which the nonwoven fabric is made from melt-spun, aerodynamically stretched multi-component endless filaments having a titer of 1.5 to 3 dtex and directly laid up to form a fibrous web, and the multi-component endless filaments are split up to at least 80% to form micro-endless filaments having a titer of 0.1 to 0.3 dtex, and bonded. The composite material demonstrates an isotropic filament distribution in the web, making further processing relatively independent of the machine running direction and thereby very advantageous for material utilization.
Preferably, the composite material is one in which the multi-component endless filament is a bicomponent endless filament made from two incompatible polymers, particularly a polyester and a polyamide. Such a bicomponent endless filament demonstrates good splittability into micro-endless filaments and results in an advantageous ratio of strength to mass per unit area. At the same time, the composite material according to the invention is very easy to clean and wipe down, because of the polymers used and their filament structure, and demonstrates a high level of wear resistance, i.e. it is easy to take care of.
Preferably, the composite material is one in which the multi-component endless filaments have a cross-section having an orange-like multi-segment structure, also called a “pie” structure, the segments alternately containing one of the two incompatible polymers in each case. In addition to this orange-like multi-segment structure of the multi-component endless filaments, a “side-by-side” (s/s) segment arrangement of the incompatible polymers in the multi-component endless filaments is also possible, which arrangement is preferably used for the production of crimped filaments. Such segment arrangements of the incompatible polymers in the multi-component endless filament have proven to be very easy to split. The nonwoven fabric used for the production of the composite material according to the invention possesses a good deep drawing capacity, or deformability, which is expressed in the average strength values at a high expansion capacity and comparatively low modulus values.
Preferably, the composite material is furthermore one in which at least one of the incompatible polymers forming the multi-component endless filament contains an additive, such as color pigments, permanently acting anti-statics, flame retarding agents and/or additives that influence the hydrophobic properties, in amounts up to 10 percent by weight. Static charges can be reduced or prevented with the additives, and the lightfastness of the surfaces visible in the automobile interior on exposure to a high black-panel temperature can be improved. Using overdyed products, values for lightfastness under black-panel temperatures of ≧6 have been achieved, determined according to DIN EN 20105-A02.
The method according to the invention, for the production of a composite material, is made up of the steps that multi-component endless filaments are spun from the melt, stretched, and directly laid up to form a web, that prebonding takes place, and that the nonwoven fabric is bonded using high-pressure fluid jets, and, at the same time, split into micro-endless filaments having a titer of 0.1 to 1.2 dtex, and bonded to a thermoplastic synthetic material by an injection-molding process. The composite material obtained in this way can be produced in very short cycle times. The cycle times can be reduced from approximately 50 to 2 to 5 seconds, as compared with known composite components.
It is advantageous that the method for the production of the composite material is carried out in such a manner that the multi-component endless filaments are bonded and split in that the nonwoven fabric, which has been prebonded if necessary, is impacted at least once on each side with high-pressure water jets, and placed into an injection-molding mold after a drying process, and backed with a thermoplastic synthetic material by injection-molding. As a result, the composite material demonstrates a good surface and a degree of splitting of the multi-component endless filaments >80%.
Advantageously, the nonwoven fabric used in the composite material according to the invention is subjected to spot calandering in order to increase its friction wear resistance. For this purpose, the split and bonded nonwoven fabric is passed through heated rollers, at least one of which has elevations that result in melt-bonding of the filaments to one another at certain points.
Because of its properties, such as good printability, a high level of friction wear resistance, as well as its good lightfastness under black-panel temperatures, and its haptic properties, the nonwoven fabric used for producing the composite material according to the invention is suited for the production of door, pillar, and/or trunk linings, rear window shelves, car roof linings, dashboards, as well as wheel house liners.