Process for producing film and sheet materials from thermoplastic materials having hot tack by the blown film process and the film and sheet materials thereby obtained

Abstract

Thermoplastic materials which have hot tack and which are incapable of being independently processed by the blown film process due to the tack they show in hot state and especially in the as extruded state are processed to film and sheet by the blown film process by extruding and inflating in a manner known per se an at least two-ply tubular film or sheet of thermoplastic material, the inner ply being formed by a tack-free thermoplastic material and the outer ply superposed thereon being formed by said hot-tacky thermoplastic material; slitting the double-ply tubing for storage and after flattening at least at one edge, and arranging the film web, preferably with winding-up, together with the web of tack-free material in such a manner that one web having hot tack alternates with one tack-free web. The multi-ply film and sheet materials produced by the process are comprised by the invention. .Iadd.

What is claimed is: .[.1. A process for production of film of hot-tacky thermoplastic material by the blown film process, which material is tacky to the extent that in production thereof by the blown film process, wherein a tube of the material is independently extruded, the extruded tube is inflated and thereafter flattened with squeeze rollers so that walls of the tubing are superimposed, the superimposed walls become bonded together, with comprises extruding two tubes, one outside the other to produce a two ply tube comprising an inner ply and an outer ply, inflating the two ply tube, and thereafter flattening the two ply tube with squeeze rollers, and removing the flattened two ply tube from the squeeze rollers, the outer ply being said hot-tacky thermoplastic material, and the inner ply being a tack-free thermoplastic material..]. .[.2. A process according to claim 1, and slitting the flattened two ply tube, and winding the split two ply tube into a roll wherein hot-tacky and tack-free turns alternate..]. .[.3. A process according to claim 1, wherein said tack-free thermoplastic material is a polyolefin..]. .[.4. A process according to claim 3, wherein the polyolefin is polyethylene or polypropylene..]. 
     
        .[.    A process according to claim 1, which comprises extruding a third tube to produce a three-ply tube comprising an inner ply, intermediate ply and an outer ply, in which the inner ply is said ply of tack-free thermoplastic material, the intermediate ply is said ply of hot-tacky material and the outer ply is a hot-tacky thermoplastic material different from the intermediate layer or a tack-free thermoplastic material..]. .[.6. A process according to claim 1, in which the softening temperature of the tack-free material is not substantially in excess of the softening temperature of said hot-tacky thermoplastic material..]. .[.7. A process according to claim 6, wherein said tack-free material has a softening temperature which is about 10° to 80° C. lower than that of the hot-tacky material..]. .[.8. A process according to claim 6, wherein said tack-free material has a softening temperature which is about 10° to 40° C. lower than that of the hot-tacky material..]. 
     
     
        .[.9.  A process according to claim 1, which comprises extruding the hot-tacky material to form film having a thickness of about 10 to 300 microns while operating, within the following ratios of film thicknesses of the hot-tacky material to tack-free material: hot-tacky material about 50 to 100 microns/tack-free material having about the same film thickness:   hot-tacky material less tha 50 microns/tack-free material having greater film thickness;   hot-tacky material in excess of 100 microns/tack-free material having not more than the same or lower film thickness..]. .[.10. A process according to claim 1, which comprises extruding the hot-tacky material to form film having a thickness of about 10 to 300 microns while operating, within the following ratios of film thicknesses of the hot-tacky material to tack-free material:   hot-tacky material about 50 to 100 microns/tack-free material having about the same film thickness;   hot-tacky material less than 50 microns/tack-free material having a greater film thickness in a ratio oif 1:1.5 to 1:2.5;   hot-tacky material in excess of 100 microns/tack-free material having a lower thickness in a ratio of 1:0.8 to 1:0.6..]. .[.11. A process according to claim 5, the inner ply and the outer ply having thicknesses   
     
     
        not exceeding about 100 microns..]. .[.12.  A process according to claim 5, the inner ply and outer ply having thicknesses of 20 to 50 microns..]. .[.13. A process according to claim 5, wherein the intermediate ply and the outer ply are undetachably bonded together..]. .[.14. A process according to claim 1, wherein a blowing agent is incorporated in the hot-tacky material prior to extrusion..]. .[.15. A process according to claim 1, which comprises extruding a third tube to produce a three-ply tube comprising an inner ply, intermediate ply and an outer ply in which the inner ply is said ply of tack-free thermoplastic material, the intermediate ply is said ply of hot-tacky material and the outer ply is a thermoplastic material having a blowing agent incorporated therein and is undetachably bonded to the intermediate ply..]. .[.16. A process according to claim 1, wherein the hot-tacky material has a softening temperature of up to 280° C..]. .[.17. A process according to claim 1, wherein the hot-tacky material has a softening temperature of up to 220° C..]. 
     
     
        .[.18.  A process according to claim 1, wherein the tack free thermoplastic material does not substantially adhere to the hot-tacky thermoplastic material and the inner ply of tack free thermoplastic material is a release ply which can be detached from the outer ply of hot-tacky thermoplastic material, the outer ply, after detachment from the 
     
     
        inner ply being a self-supporting film..]. .Iadd.19.  A process for production of film of hot-tacky thermoplastic material by the blown film process, which hot-tacky material is selected from the group consisting of polyurethanes and copolyamides, having a softening temperature higher than tacky saran up to 280° C.; being extrudable at temperatures of 180° C. and higher; and which is tacky to the extent that in production thereof by the blown film process, wherein a tube of the material is independently extruded, the extruded tube inflated and thereafter flattened with squeeze rollers so that walls of the tubing are superimposed, the superimposed walls become bonded together; said process comprising the steps of extruding two tubes, one outside the other to produce a two ply tube having an inner ply and an outer ply; inflating the two ply tube, and thereafter flattening the two ply tube from the squeeze rollers, the inner ply being a tack-free thermoplastic material having a softening temperature which is about 10° C. to 80° C. lower than that of the hot-tacky material; slitting the flattened two ply tube; and winding the split two ply tube into a roll wherein hot-tacky and tack-free turns alternate..Iaddend. .Iadd.20. A process for production of film of hot-tacky polyurethane or copolyamide thermoplastic material by the blown film process,   said hot-tacky material having a softening temperature higher than tacky saran up to 280° C., being extrudable at temperatures of 180° C. and higher, and being tacky to the extent that in production thereof by the blown film process, wherein a tube of the material is independently extruded, the extruded tube inflated and thereafter flattened with squeeze rollers so that walls of the tubing are superimposed, the superimposed walls become bonded together;   said process comprising the steps of extruding two tubes, one outside the other, to produce a two ply tube having an inner ply of tack-free thermoplastic material with a softening temperature of about 10° to 80° C. lower than that of the hot-tacky material, and an outer ply of said hot-tacky thermoplastic material, the hot-tacky material being extruded to a thickness of about 10 to 300 microns and the ratio of hot-tacky material to tack-free material being defined as follows:   when the hot-tacky material is about 50 to 100 microns, the tack-free material is about the same film thickness:   when the hot-tacky material is less than 50 microns, the tack-free material has greater film thickness:   when the hot-tacky material is in excess of 100 microns, the tack-free material has not more than the same or lower film thickness;   inflating the two ply tube, thereafter flattening the inflated two ply tube with squeeze rollers; and removing the flattened two ply tube from the   
     
     
        squeeze rollers..Iaddend. .Iadd.21.  The process of claim 20 wherein the ratio of materials is defined as follows: when the hot-tacky material is about 50 to 100 microns the tack-free material is about the same film thickness;   when the hot-tacky material is less than 50 microns the tack-free material has a greater film thickness in a ratio of 1:1.5 to 1:2.5;   when the hot-tacky material is in excess of 100 microns the tack-free material has a lower thickness in a ratio of 1:0.8 to 1:0.6..Iaddend.   
     
     
        .Iadd.22.  A process for production of film of hot-tacky thermoplastic material by the blown film process, which hot-tacky material is selected from the group consisting of polyurethanes and copolyamides having a softening temperature higher than tacky saran up to 280° C.; being extrudable at temperatures of 180° C. and higher; and is tacky to the extent that in production thereof by the blown film process, wherein a tube of the material is independently extruded, the extruded tube is inflated and thereafter flattened with squeeze rollers so that walls of the tubing are superimposed, the superimposed walls become bonded together; said process comprising the steps of extruding two tubes, one outside the other to produce a two ply tube having an inner ply of tack-free thermoplastic material and an outer ply of said hot-tacky thermoplastic material, the tack free thermoplastic material having a softening temperature of about 10° C. to 80° C. lower than that of the hot-tacky material; the hot-tacky material being extruded to a thickness of about 10 to 300 microns and the ratio of hot-tacky material to tack-free material being defined as follows:   when the hot-tacky material is about 50 to 100 microns, the tack-free material is about the same film thickness;   when the hot-tacky material is less than 50 microns, the tack-free material has greater film thickness;   when the hot-tacky material is in excess of 100 microns, the tack-free material has about the same or less film thickness;   inflating the two ply tube, and thereafter flattening the two ply tube with squeeze rollers; and removing the flattened two ply tube from the squeeze   
     
     
        rollers..Iaddend. .Iadd.23.  The process of claim 19 wherein the hot-tacky material has a softening temperature higher than tacky saran and up to 220° C. and the inner ply of tack-free thermoplastic material has a softening temperature which is 10° C. to 40° C. lower than that of the hot-tacky material..Iaddend.