Methods to produce stretchable products
The invention provides methods for producing flexible, stretchable, and/or elastic products comprised principally of material such as natural elastomers and other synthetic polymers. The method for producing stretchable products by spraying product material over a workpiece former, and method for creating perforated products by spraying product material over fibres in an upright position. The invention provides methods for making double sided fibre coating of the product and, or to at least coating the product surface on the side facing the wall without the need for removing the product from the wall.
1. A method for producing a stretchable workpiece, said method comprising the steps of:
(a) coating a surface of a wall with a wetting agent;
(b) applying a first layer of loose fibres onto at least a portion of the surface of the wetting agent coated wall, in a manner that the loose fibres are anchored in said wetting agent and held by it at substantially upright position relative to the wall surface, the fibres partially covered by the wetting agent, to produce at least a partially fibre-coated surface; and
(c) spraying a liquid product material onto the uncovered top of said substantially upright standing fibres to form a product material layer on the fibre-coated surface and produce a stretchable workpiece comprising a porous or micro-porous web of partially connected droplets of product material having fibres partially embedded thereto, wherein the workpiece has an inner surface and an outer surface and the fibres are attached to the inner surface of the workpiece facing the wall and wherein said spraying of liquid product material is carried out by controlling spray intensity, droplet size, or surface tension of the product material.
2. The method according to claim 1 , further comprising spraying the product material in more than one step so as to control product material layer porosity.
3. The method according to claim 1 or 2 , wherein step (a) comprises applying the wetting agent at a predetermined thickness and viscosity range.
4. The method according to claim 1 , wherein the wetting agent is a gel.
5. The method according to claim 1 , 2 , 3 or 4 , further comprising the step of applying a second layer of loose fibres onto the outer surface of the product material layer, wherein the product material layer is uncured or partially uncured, to produce a stretchable workpiece comprising a porous or micro-porous web of partially connected droplets of product material having fibres partially embedded thereto, wherein the workpiece has an inner surface and an outer surface and the fibres are attached to the inner surface and to the outer surface of the workpiece.
6. The method according to claim 1 , wherein the loose fibres are applied electrostatically.
7. The method according to claim 1 , further comprising the step of allowing the product material layer to dry or cure.
8. The method according to claim 1 or 2 , further comprising the step of drying or evaporating the solvent in the wetting agent during drying or curing of the product layer so that little or no wetting agent residue remains on the first layer of the fibres.
9. The method according to claim 1 or 2 , wherein the product material layer has different thicknesses at different areas.
10. The method according to claim 1 or 2 , wherein the product material layer has the same thickness at different areas.
11. The method according to claim 1 , wherein the wall is flat.
12. The method according to claim 11 , wherein the wall is a flat conveyor belt.
13. The method according to claim 12 , wherein the wall is an embossed conveyor belt, complex shaped conveyor belt, perforated conveyor belt, or combination thereof.
14. The method according to claim 1 , wherein the wall is a workpiece former.
15. The method according to claim 14 , wherein the workpiece former comprises a complex shape to which the workpiece substantially conforms.
16. The method according to claim 1 , wherein the wall comprises a plurality of perforations.
17. The method according to claim 16 , wherein the spraying is carried out such that at least no substantial product material layer forms over the perforations.
18. The method according to claim 1 wherein the fibres are made of natural or synthetic materials.
19. The method according to claim 18 , wherein the fibres are lightweight cotton fibres, viscose fibres or a combination of the two.
20. The method according to claim 1 , wherein the liquid product material comprises a natural or artificial elastomer.
21. The method according to claim 20 , wherein the natural elastomer comprises natural latex rubber.
22. The method according to claim 20 , wherein the artificial elastomer comprises polyurethane.
23. The method according to claim 5 , wherein the loose fibres are applied electrostatically.
24. The method according to claim 5 , further comprising the step of allowing the product material layer to dry.
25. The method according to claim 5 wherein the fibres are made of natural or synthetic materials.
26. The method according to claim 5 , further comprising the step of drying or evaporating the solvent in the wetting agent during drying or curing of the product layer so that little or no wetting agent residue remains on the first layer of the fibers.