Process for abrasion-resistant needle-punched composite
A process for making abrasion-resistant composites is disclosed. The process comprises the steps of providing a fibrous sheet containing a high density of relatively short staple fibers having a decitex under 6.6; needle-punching the staple layer and applying an adhesive containing layer; followed by the application of heat and pressure to the composite to form a thin consolidated and abrasion-resistant back-face layer on the composite. Preferably, the adhesive layer is penetrated by the needled fibers during the needling step and the product is shrunk in area by 20-50% before the consolidation step. Also optionally, the consolidated layer is abraded or perforated to create micro-pores that are permeable to gases and capable of containing liquids under low-to-moderate pressures.
1. A process for forming an abrasion-resistant composite comprising the steps of:
a. providing at least one fibrous layer, wherein a portion of the fibrous layer comprises staple fibers of about 6.6 decitex or less;
b. providing a first layer of adhesive to the fibrous layer, wherein the melting point of the staple fibers is higher than the melting point of the resin;
c. needle-punching each said at least one fibrous layer through said first layer of adhesive by driving a plurality of said staple fibers through said first layer of adhesive so that the driven staple fibers are held within the adhesive layer in substantially the normal position; and
d. applying heat and pressure to the composite from the side opposite to the needle entries to form an abrasion resistant consolidated back-face layer of comprising adhesive and the driven staple fibers, by melting the adhesive and enveloping the driven staple fibers with the molten adhesive;
wherein the count of said fiber ends is at least about 2,000/cm 2 and the density of needle-punching penetrations is greater than about 40 penetrations/cm 2 , and the Wyzenbeek abrasion resistance of the abrasion resistant consolidated back-face layer is higher than about 2,000 cycles using 80-grit abrasive paper.
2. The process of claim 1 further comprising the step of shrinking the composite by at least 20% in at least one direction.
3. The process of claim 2 , wherein the fibrous layer is shrunk.
4. The process of claim 1 , wherein step (b) comprises providing a second adhesive layer.
5. The process of claim 4 , further comprising the step of shrinking the second adhesive layer by at least 20% in at least one direction.
6. The process of claim 1 , wherein additional adhesive is applied to the back side of the composite before step (d).
7. The process of claim 1 , further comprising the step of limiting the penetration of adhesive into the fibrous layer to less than about 0.5 mm.
8. The process of claim 1 , wherein each fibrous layer is needle-punched before the next fibrous layer is provided and needle-punched.
9. The process of claim 1 further comprising the step of abrading at least a portion of the consolidated back-face layer.
10. The process of claim 9 , wherein the abrading step comprises a sanding step.
11. The process of claim 1 further comprising the step of forming micro-pores on the consolidated back-face layer.
12. The process of claim 1 further comprising the step of providing at least one additional layer between the fibrous layer and the adhesive.
13. The process of claim 12 , wherein said at least one additional layer comprises higher denier staple fibers, continuous filament fibers, bonded nonwoven, woven or knit fabrics, flat or textured yams, re-enforcing scrims, thermal insulators, fire-retardant materials, anti-bacterial materials, gas or odor-absorbing materials or cushioning layers.
14. The process of claim 1 , wherein said staple fibers provide an accumulated count of at least 3,000 ends/cm 2 .
15. The process of claim 2 , wherein the composite is shrunk by at least about 40%.
16. The process of claim 1 further comprising the step of embossing the composite at an elevated temperature to produce a textured surface.
17. The process of claim 4 , wherein the adhesive layer comprises a polyethylene film.
18. The process of claim 1 , wherein step (c) occurs before step (b).
19. The process of claim 1 , wherein the melting temperature of the stable fibers is about 10° C. to about 30° C. higher than the melting point of the resin.
20. The process of claim 2 , wherein after the shrinking step the composite is needle-punched further before the applying heat and pressure step.
21. The process of claim 20 , wherein additional staple fibers are added before the additional needle-punching step.
22. The process of claim 20 , wherein additional adhesive is added to the composite before the additional needle-punching step.
23. The process of claim 1 , further comprising the step of limiting the penetration of adhesive into the fibrous layer to between about 0.2 mm and about 1.0 mm.
24. The process of claim 1 , wherein in step (a) the at least one fibrous layer comprises staple fibers of about 3.3 decitex or less.
25. The process of claim 24 , wherein in step (a) the at least one fibrous layer comprises staple fibers of about 1.0 decitex or less.
26. The process of claim 1 , wherein in step (d) the count of the fiber ends is about 20,000/cm 2 or less.
27. The process of claim 1 , wherein in step (d) the count of the fiber ends is about 16,000/cm 2 or less.
28. The process of claim 1 , wherein in step (d) the density of needle-punching penetrations is greater than about 90 penetrations/cm 2 .
29. The process of claim 28 , wherein in step (d) the density of needle-punching penetrations is greater than about 180 penetrations/cm 2 .
30. The process of claim 29 , wherein in step (d) the density of needle-punching penetrations is less than about 300 penetrations/cm 2 .
31. The process of claim 1 , wherein in step (d) the Wyzenbeek abrasion resistance is greater than 3,000 cycles.
32. The process of claim 31 , wherein in step (d) the Wyzenbeek abrasion resistance is greater than 5,000 cycles.