LWRT MATERIAL WITH OUTER LAYER THAT WILL NOT ADHERE TO PRESS MOLDS, AND AUTOMOTIVE COMPONENT MADE OF SUCH LWRT MATERIAL

Abstract

An LWRT material having a core layer that includes thermoplastically bound structural fibers, and having at least one outer layer that likewise includes thermoplastically bound structural fibers, the outer layer also having bicomponent fibers as structural binder fibers, each of which has a fiber core made of a fiber core material with a predetermined fiber core melting or fiber core softening temperature, and a sheath surrounding the fiber core radially and made of a thermoplastic sheath material with a predetermined sheath melting or sheath softening temperature, the sheath melting or sheath softening temperature being lower than the fiber core melting or fiber core softening temperature, and the sheaths of the bicomponent fibers contributing to the thermoplastic binding of fibers in the outer layer.

Claims

1-13. (canceled)

14. An LWRT material having a core layer that comprises thermoplastically bound core structural fibers, and having at least one outer layer that comprises thermoplastically bound outer layer structural fibers, the at least one outer layer further comprises bicomponent fibers as structural binder fibers, the structural binder fibers having a fiber core made of a fiber core material with a predetermined fiber core melting or fiber core softening temperature, and a sheath surrounding the fiber core radially and made of a thermoplastic sheath material with a predetermined sheath melting or sheath softening temperature, the sheath melting or sheath softening temperature being lower than the fiber core melting or fiber core softening temperature, and the sheaths of the bicomponent fibers contributing to the thermoplastic binding of fibers in the at least one outer layer.

15. The LWRT material according to claim 14, wherein the fiber core material includes polyester.

16. The LWRT material according to claim 14, wherein the fiber core material is selected from the group consisting of a polyester, a polyethylene terephthalate, a polyacrylonitrile, an oxidized polyacrylonitrile, a cellulose, a viscose, a polyetheretherketone, a polystyrene, a glass, a quartz, a stone, a silica, and a metal.

17. The LWRT material according to claim 14, wherein the thermoplastically bound core structural fibers are formed from the same material as the thermoplastically bound outer layer structural fibers.

18. The LWRT material according to claim 14, wherein the sheath material is selected from the group consisting of a polyolefin, a polyamide and a polylactate.

19. The LWRT material according to claim 14, wherein the at least one outer layer has no thermoplastic binder material matrix.

20. The LWRT material according to claim 14, wherein the fibers of the at least one outer layer are thermoplastically bound solely by the sheaths of the structural binder fibers that are fused together.

21. The LWRT material according to claim 14, wherein no less than 10% by weight of a fiber weight contained in the at least one outer layer is the structural binder fibers.

22. The LWRT material according to claim 21, wherein no more than 60% by weight of the fiber weight contained in the at least one outer layer is the structural binder fibers.

23. The LWRT material according to claim 14, wherein no more than 60% by weight of a fiber weight contained in the at least one outer layer is the structural binder fibers.

24. The LWRT material according to claim 23, wherein no more than 50% by weight of the fiber weight contained in the at least one outer layer is the structural binder fibers.

25. The LWRT material according to claim 14, wherein the at least one outer layer has a weight per unit area of less than 400 g/m.sup.2.

26. The LWRT material according to claim 14, wherein the weight per unit area is less than 300 g/m.sup.2.

27. The LWRT material according to claim 14, wherein the at least one outer layer includes two outer layers, one provided on each side of the core layer.

28. The LWRT material according to claim 14, wherein the thermoplastically bound core structural fibers includes at least one of glass fibers, mineral fibers and plastic fibers made of a plastic that has a higher melting or softening temperature than that of a matrix material, bound in a porous thermoplastic matrix.

29. The LWRT material according to claim 14, further including an intermediate layer provided between the core layer and the at least one outer layer.

30. The LWRT material according to claim 29, wherein the intermediate layer includes at least one of a tangled fiber web, a film, a thermoplastic and a polyolefin.

31. An automotive component, in particular a shielding component, such as an underbody shield or fender skirt, comprising an LWRT material according to claim 14.

32. The automotive component according to claim 31, wherein one of the at least one outer layer forms an outwardly exposed surface of the automotive component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail and illustrated in the accompanying drawings which forms a part hereof and wherein:

[0041] FIG. 1 is a rough schematic cross-sectional view of an LWRT material embodied according to the invention; and

[0042] FIG. 2 is a cross-sectional view of a bicomponent structural binder fiber, as is used in the outer layers of the LWRT material of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0043] Referring now to the drawings wherein the showings are for the purpose of illustrating preferred and alternative embodiments of the invention only and not for the purpose of limiting the same, FIG. 1 shows an LWRT material according to the invention, depicted only roughly schematically in cross-section, that is labeled overall as 10. LWRT material 10 comprises a central core layer 12, a first outer layer 14 and a second outer layer 16. An intermediate layer 18, for example in the form of a polypropylene film, is provided between first outer layer 14 and core layer 12.

[0044] Core layer 12 is composed of a tangled web of structural fibers 20, bound to one another by a thermoplastic matrix 24. Core layer 12 is porous and is partially compacted in the finished state; the degree of compaction of the core layer may be different in situ, for example, core layer 12 may be more densely compressed in some areas than in others due to the formation of swage lines, etc. in the LWRT material 10.

[0045] The thermoplastic matrix 24 of core layer 12, in which polypropylene is preferably used as the matrix material, has been formed from a fiber mixture containing the thermally stable structural fibers 20 and polypropylene binder fibers, which are no longer present in the processing state shown in FIG. 1.

[0046] During processing, the LWRT material 10 has been heated to a temperature at which the binder material, in this case: polypropylene, is molten, so that the fiber structure of the initially present binder fibers is lost, but the structural fibers 20 remain dimensionally stable.

[0047] Core layer 12 can have a weight per unit area of 400 to 1200 g/m.sup.2, depending on the intended use of the component produced from LWRT material 10.

[0048] Outer layers 14 and 16, the outer surfaces 14a and 16b of which can form the outer surfaces of LWRT material 10 overall, are substantially identical in structure; the following description will therefore refer only to first outer layer 14, but will apply to both outer layers 14 and 16.

[0049] Outer layer 14 contains bicomponent fibers 26 as structural binder fibers 26, as a constituent element. These are contained in the fiber mixture of the outer layer in a proportion of 10% to 50% by weight or 10% to 60% by weight.

[0050] Structural binder fibers 26 are formed from two components, as illustrated schematically in the cross-sectional diagram of FIG. 2.

[0051] Structural binder fiber 26 has a central fiber core 28 made of a fiber core material that remains dimensionally stable at temperatures at which the material of the sheath 30, which completely surrounds fiber core 28 in the circumferential direction and extends together with fiber core 28 in the longitudinal direction of the fiber, is molten.

[0052] The same material may be used as the sheath material for forming sheath 30 of structural binder fibers 26 as is used for forming matrix 24 of core layer 12, in this case: polypropylene. Fiber core 28 can be made of any material that melts at higher temperatures, but is preferably a polyester, such as polyethylene terephthalate.

[0053] In addition to structural binder fibers 26, outer layer 14 comprises other conventional fibers, such as single-component fibers 32, which may be identical to the structural fibers 20 of core layer 12, which may in turn be additionally or alternatively made of the same material from which the fiber cores 28 of structural binder fibers 26 are made. Moreover, the additional fibers 32 may be made of viscose and/or oxidized polyacrylonitrile and/or polyethylene terephthalate, to impart excellent stone impact resistance to outer layer 14 (and to outer layer 16).

[0054] The percentage by weight of conventional fibers 32, which are not structural binder fibers 26 in the outer layer, plus the percentage by weight of structural binder fibers 26 makes up 100% of the total fiber weight of outer layer 14.

[0055] Between outer layer 14 and core layer 12, an intermediate layer 18 may be provided, made of polypropylene, for example, so that intermediate layer 18 is compatible with the matrix material of matrix 24 in core layer 12 and with the sheath material of sheaths 30 of structural binder fibers 26, thereby facilitating the binding of layers 12, 18 and 14 to one another. Intermediate layer 18 may be made of any material, however. If necessary, it may be bonded to core layer 12 and/or to outer layer 14 by the additional provision of adhesion promoting materials.

[0056] Solely by way of example, no intermediate layer is provided here between core layer 12 and second outer layer 16, although an intermediate layer could also be provided there.

[0057] Because the selected materials are advantageously compatible: the material of matrix 24 on one hand and the sheath material of sheaths 30 of structural binder fibers 26 on the other hand, a bond can also be produced directly between core layer 12 and outer layer 16.

[0058] Since the above-mentioned compacting of core layer 12 is generally performed on the finished LWRT material 10, the compacting of outer layers 14 and 16 is the same as described above for core layer 12.

[0059] Outer layers 14 and/or 16 have a weight per unit area ranging from 180 to 400 g/m.sup.2, depending on the intended application.

[0060] Since the sheath 30 of a structural binder fiber 26 retains its sheath structure even after being heated to above the melting point, no sheath material or only an insignificant amount of sheath material escapes through outer surface 14a during processing of the LWRT material 10, and as a result, the tendency of the exposed surface 14a of outer layer 14 to adhere to machining tools, in particular contact heating tools, is low to extremely low. LWRT material 10 can therefore be implemented without the otherwise customary provision of protective fleeces on the exposed outer surfaces 14a and 16b of LWRT material 10. The above description relating to surface 14a also applies to the likewise exposed outer surface 16b of LWRT material 10.

[0061] While considerable emphasis has been placed on the preferred embodiments of the invention illustrated and described herein, it will be appreciated that other embodiments, and equivalences thereof, can be made and that many changes can be made in the preferred embodiments without departing from the principles of the invention. Furthermore, the embodiments described above can be combined to form yet other embodiments of the invention of this application. Accordingly, it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.