Molding resin to form continuous structures
A molding apparatus includes a movable molding surface with molding cavities, a pressure shoe with a stationary outer surface that defines in cooperation with the molding surface a pressure zone, and a resin source configured to introduce molten resin into the pressure zone to be forced into the molding cavities by pressure in the pressure zone. The molding surface is movable with respect to the pressure shoe to introduce molding cavities to the pressure zone to be filled with resin while the outer surface of the pressure shoe and the molding surface define in between an entrance gap of decreasing width upstream of the pressure zone. The outer surface of the pressure shoe is spaced from the molding surface in the pressure zone to define a minimum gap at which the outer surface of the pressure shoe has a slope parallel to the molding surface. The pressure shoe is adapted to be held in a flexed condition against resin in the pressure zone while forcing resin into the cavities, with the outer surface of the pressure shoe curved upstream of the pressure zone.
1. A method of molding resin, the method comprising:
introducing resin to a pressure zone defined between a movable molding surface and a reaction surface, the molding surface defining an array of molding cavities extending from a periphery of the molding surface;
forcing the resin into the molding cavities to mold resin projections extending from a resin base; and then
stripping the resin from the molding surface;
wherein the resin is introduced under conditions that cause a bead of the resin to form between the molding surface and the reaction surface just upstream of the pressure zone, and to rotate toward the molding surface, from which rotating resin bead resin is steadily drawn into the pressure zone by operation of the moving molding surface.
2. The method of claim 1 , wherein the resin is molten as introduced.
3. The method of claim 1 , wherein rotation of the bead of resin is caused by a velocity gradient within the resin between the molding surface and the reaction surface.
4. The method of claim 1 , wherein the bead of resin has an outer surface exposed to atmospheric pressure.
5. The method of claim 1 , wherein the reaction surface is stationary.
6. The method of claim 5 , wherein the reaction surface comprises a pressure shoe.
7. The method of claim 6 , wherein the pressure shoe comprises a cantilevered compliant blade with one end fixed and a second end flexed under pressure in the pressure zone.
8. The method of claim 1 , wherein the bead is of an asymmetric shape.
9. The method of claim 1 , wherein the resin is introduced by being dropped as a molten resin stream into a nip formed between the molding surface and the reaction surface, and wherein the resin stream curves toward the molding surface as it nears the nip.
10. The method of claim 1 , further comprising introducing a substrate to an exposed surface of the resin base before the resin is stripped from the molding surface.
11. The method of claim 10 , wherein the substrate is introduced under conditions that cause the substrate to become permanently laminated to the base.
12. The method of claim 10 , wherein the substrate is introduced under conditions that cause the substrate to become at least partially melted by heat from the base.
13. The method of claim 1 , wherein the resin base has a substantially uniform thickness of less than 0.075 millimeters.
14. The method of claim 1 , wherein the reaction surface comprises multiple reaction surface portions spaced along a width of the molding surface and defining respective pressure zones with the molding surface.
15. The method of claim 14 , wherein introducing the resin comprises introducing separate streams of resin, with each stream of resin introduced to a respective one of the pressure zones.
16. The method of claim 1 , wherein the resin is forced into the cavities in the pressure zone.
17. The method of claim 1 , wherein the resin is forced into the cavities in a pressure nip formed between the molding surface and a pressure roll downstream of the pressure zone.
18. The method of claim 1 , wherein the projections comprise discrete loop-engageable fastener elements.
19. The method of claim 1 , wherein the movable molding surface comprises a mold roll.
20. A method of molding resin, the method comprising:
introducing resin to a pressure zone defined between a movable molding surface and a reaction surface, the molding surface defining an array of molding cavities extending from a periphery of the molding surface;
forcing the resin into the molding cavities to mold resin projections extending from a resin base; and then
stripping the resin from the molding surface;
wherein the resin is introduced under conditions that cause a bead of the resin to form under atmospheric pressure between the molding surface and the reaction surface just upstream of the pressure zone, while the movable molding surface is driven to create a velocity gradient within the resin between the molding surface and the reaction surface.
21. The method of claim 20 , wherein the resin is molten as introduced.
22. The method of claim 20 , wherein the reaction surface is stationary.
23. The method of claim 20 , further comprising introducing a substrate to an exposed surface of the resin base before the resin is stripped from the molding surface.
24. The method of claim 20 , wherein the projections comprise discrete loop-engageable fastener elements.
25. The method of claim 20 , wherein the movable molding surface comprises a mold roll.