Method for producing a film web
The invention relates to a method for producing a film web during which an initial film web made of thermoplastic polymer material with a polyethylene matrix, in which 1 to 70 parts by weight of polypropylene, with regard to 100 parts by weight of polyethylene matrix, are contained, is, after being heated, guided through a cooled roll gap ( 7, 8 ), whereby the initial film web is heated only until the polymer matrix material melts but not to a temperature at which the polypropylene melts.
1. A process for the production of a film web suitable for use as a hygienic film, comprising the steps of:
a) warming a starting film web of thermoplastic polymer material comprising a polyethylene matrix containing 1 to 70 parts by weight of polypropylene, based on 100 parts by weight of polyethylene matrix, to a temperature above the molten state of the polyethylene matrix, but below the molten state of the polypropylene to form a partially molten film web; wherein said starting film web is warmed by one or more heating rolls;
b) passing the partially molten film web through a cooled roll nip, thereby forming the film web suitable for use as a hygiene film.
2. The process according to claim 1 , characterized in that a starting film web containing 5 to 45 parts by weight of polypropylene, based on 100 parts by weight of polyethylene matrix, is used.
3. The process according to claim 2 , characterized in that a starting film web containing 10 to 40 parts by weight of polypropylene, based on 100 parts by weight of polyethylene matrix, is used.
4. The process according to claim 1 , characterized in that a starting film web containing a polyethylene matrix of 60% by weight of LDPE and 40% by weight of LLDPE is used.
5. The process according to claim 3 , characterized in that a starting film web containing a polyethylene matrix of 60% by weight of LDPE and 40% by weight of LLDPE-octene with an amount of octene of 5 to 10% by weight, and an amount of 30 parts by weight of propylene ethylene copolymer containing 3 to 12% by weight of ethylene as comonomer, based on 100 parts by weight of polyethylene matrix, is used.
6. The process according to claim 1 , wherein the starting film web of thermoplastic polymer material consists essentially of the polyethylene matrix and 1 to 70 parts by weight of the polypropylene, based on 100 parts by weight of the polyethylene matrix, wherein the polypropylene is a homopolymer or a copolymer of propylene and a second olefin.
7. The process according to claim 6 , wherein the polypropylene is a copolymer of propylene and ethylene.
8. The process according to claim 1 , characterized in that a starting film web having a thickness of from 10 to 30 μm is used.
9. The process according to claim 1 , characterized in that heating rolls having reduced adhesion tendency to the film web with molten polyethylene matrix are used.
10. The process according to claim 1 , characterized in that a starting film web which has been subjected during production to transverse stretching is used.
11. The process according to claim 1 , characterized in that a film web having a thickness of from about 15 μm to about 20 μm is produced.
12. The process of claim 1 , wherein the partially molten film web is cooled in the roll nip to a temperature below the crystalline melting point of the polyethylene matrix.
13. The process of claim 1 , wherein the starting film web is warmed to a temperature not higher than 10 to 15° C. below the crystalline melting point of the polypropylene.
14. A film web obtained by a process according to claim 1 .
15. The film web according to claim 14 , having a thickness in the range of from 15 to 20 μm.