High speed method of making plastic film and nonwoven laminates
View Patent ↗Laminates of thermoplastic films and nonwoven fibrous webs are made at high speeds on the order of about 700 fpm to about 1200 fpm. Bond strengths of film and nonwoven laminates are effectively controlled to make breathable laminates at high speeds. Air cooling devices cause the air to flow substantially parallel to the extruded plastic web during drawdown and provide a plurality of cooling air vortices to effectively cool the web. Film gauge control is also achieved by the method.
1. A high speed method of making a laminate of a nonwoven fibrous sheet and a microporous thermoplastic film comprising
melt blending a thermoplastic polymer and filler particles to form a thermoplastic polymer composition,
extruding a web of said molten thermoplastic composition from a slot die through a cooling zone into a nip of rollers to form a film at a speed greater than about 700 fpm,
employing a first and a second cooling device which are offset on opposite sides of said web between said slot die and said nip of rollers,
each said cooling device for directing a stream of cooling gas to flow through said zone substantially parallel to the surface of said web to cool the web and form the film without draw resonance,
each cooling device for enhancing the cooling effectiveness of said cooling gas by creating a plurality of vortices of said gas as the stream moves through said zone to cool the web, and
introducing a nonwoven fibrous sheet into said nip of rollers and controlling the temperature and compressive force between the fibrous sheet and the film at the nip to bond the surface of the fibrous sheet to the film and to form a laminated sheet having bond strength between the film and the fibrous sheet of about 100 to about 600 grams/inch as measured at room temperature.
2. The method of claim 1 wherein said bond strengths are about 200 grams/inch to about 500 grams/inch.
3. The method of claim 1 comprising the further step of applying a stretching force to the laminate at said speed to provide a microporous laminate.
4. The method of claim 3 wherein the stretching force is an incremental stretching force applied across the laminated sheet to provide a cloth-like microporous laminate having a web to film bond strength of about 100 to about 200 grams/inch.
5. The method of claim 1 wherein said laminate is formed at a speed of greater than about 700 fpm to about 1200 fpm.
6. The method of claim 1 wherein the composition comprises
(a) about 30% to about 45% by weight of a linear low density polyethylene,
(b) about 1% to about 10% by weight of a low density polyethylene,
(c) about 40% to about 60% by weight calcium carbonate filler particles.
7. The method of claim 6 wherein said melt blended composition consists essentially of about 41% by weight linear low density polyethylene, about 5% by weight low density polyethylene, about 45% by weight calcium carbonate filler particles, and about 5% by weight high density polyethylene.
8. The method of claim 7 wherein said melt blended composition further comprises about 3% by weight titanium dioxide and about 1% by weight antioxidant/processing aid.
9. The method of claim 1 wherein said nip of rollers comprises a metal embossing roller and a rubber roller and the compressive force between said rollers is controlled to form an embossed film.
10. The method of claim 1 wherein the melt blended composition comprises a thermoplastic polymer containing a dispersed phase of particles selected from the group consisting of an inorganic filler and an organic material.
11. The method of claim 1 wherein said fibrous sheet comprises polyolefin fibers.
12. The method of claim 1 wherein said fibers are selected from the group consisting of polypropylene, polyethylene, polyesters, cellulose, rayon, nylon, and blends or coextrusions of two or more of such fibers.
13. The method of claim 1 wherein the fibrous sheet has a weight from about 5 to about 70 gms/yd 2 and the microporous film has a thickness on the order of about 0.25 to about 10 mils.
14. The method of claim 13 wherein said fibrous sheet is formed from staple fibers or filaments.
15. The method of claim 3 wherein said incremental stretching step is conducted at ambient temperature.
16. The method of claim 3 wherein said incremental stretching step is conducted at elevated temperature.
17. The method of claim 1 wherein said thermoplastic composition is a polymer selected from the group consisting of polyethylene, polypropylene, and copolymers thereof.
18. The method of claim 1 wherein said thermoplastic composition is an elastomeric polymer.
19. The method of claim 18 wherein said elastomeric polymer is selected from the group consisting of poly(ethylene-butene), poly(ethylene-hexene), poly(ethylene-octene), poly(ethylene-propylene), poly(styrene-butadiene-styrene), poly(styrene-isoprene-styrene), poly(styrene-ethylene-butylene-styrene), poly(ester-ether), poly(ether-amide), poly(ethylene-vinylacetate), poly(ethylene-methylacrylate), poly(ethylene-acrylic acid), poly(ethylene butylacrylate), polyurethane, poly(ethylene-propylene-diene), and ethylene-propylene rubber.
20. A high speed method of making a laminate of a microporous thermoplastic film and nonwoven fibrous sheet comprising
melt blending a composition of
(a) about 30% to about 45% by weight of a linear low density polyethylene,
(b) about 1% to about 10% by weight of a low density polyethylene,
(c) about 40% to about 60% by weight calcium carbonate filler particles,
extruding a web of said melt blended composition through a cooling zone into a nip of rollers to form a film at a speed on the order of at least about 700 fpm to about 1200 fpm,
employing a first and a second cooling device which are offset on opposite sides of said web between said slot die and said nip of rollers,
each said cooling device for directing a stream of cooling gas to flow through said zone substantially parallel to the surface of said web to cool the web and form the film without draw resonance,
each said cooling device for enhancing the cooling effectiveness of said cooling gas by creating a plurality of vortices of said gas as the stream moves through said zone to cool the web,
introducing a nonwoven fibrous sheet into the nip,
controlling the temperature and compressive force between the fibrous sheet and the film at the nip to bond the surface of the fibrous sheet to form a laminated sheet having a bond strength between the film and the fibrous sheet of about 200 to about 500 grams/inch at about room temperature.
applying an incremental stretching force to said laminated sheet at said speed along lines substantially and uniformly across said laminated sheet and throughout its depth to provide a microporous laminate having a fibrous sheet to film bond strength of about 100 to about 200 grams/inch.
21. The method of claim 20 wherein said melt composition further contains high density polyethylene and titanium dioxide.
22. The method of claim 21 wherein the high density polyethylene is contained in an amount of 5% by weight and the titanium dioxide is contained in an amount of about 3% by weight.
23. The method of claim 20 wherein said linear low density polyethylene is selected from the group consisting of poly(ethylene-butene), poly(ethylene-hexene), poly(ethyiene-octene), poly(ethylene-propylene), poly(styrene-butadiene-styrene), poly(styrene-isoprene-styrene), poly(styrene-ethylene-butylene-styrene), poly(ester-ether), poly(ether-amide), poly(ethylene-vinylacetate), poly(ethylene-methylacrylate), poly(ethylene-acrylic acid), poly(ethylene butylacrylate), polyurethane, poly(ethylene-propylene-diene), and ethylene-propylene rubber.
24. The method of claim 20 wherein said fibers are selected from the group consisting of polypropylene, polyethylene, polyesters, cellulose, rayon, nylon, and blends of coextrusions of two or more such fibers.
25. The method of claim 24 wherein the fibrous sheet has a weight of from about 5 to about 70 grams/yd 2 and the microporous film has a thickness on the order of about 0.25 to about 10 mils.
26. The method of claim 20 wherein said incremental stretching step is conducted at ambient temperature.
27. The method of claim 20 wherein said incremental stretching step is conducted at an elevated temperature.