Oriented Film Produced In-Process for Use in the Stretch Film Market
Pre-stretched films may be used to increase the rate at which loads can be wrapped and to minimize the exertion required when using conventional stretch films. However, pre-stretched films must generally be stretched in a separate step and stored for several days in order for cling to fully develop. The present disclosure describes compositions, devices, systems, and methods for producing film that eliminate the stretching and storage steps. In particular, the present disclosure relates to the use of selected resins and an angled die to increase the level of orientation in the film as it is formed, thus eliminating the need to stretch the film in a separate step. The present disclosure also relates to the use of a cling agent which eliminates the storage time traditionally required to develop the film's cling properties.
1 . An oriented film produced in-process that mimics the properties of pre-stretched handheld film.
2 . The oriented film according to claim 1 , wherein the oriented film is comprised of a linear low density polyethylene (LLDPE) copolymer resin.
3 . The oriented film according to claim 2 , wherein the LLDPE copolymer resin is blended with other resins chosen from the group consisting of polyethylenes, polyethylene copolymers, and polypropylene copolymers.
4 . The oriented film according to claim 1 , wherein the oriented film is comprised of a majority layer and a plurality of minority layers, the oriented film having a total film thickness.
5 . The oriented film according to claim 4 , wherein the majority layer is comprised of a LLDPE copolymer resin.
6 . The oriented film according to claim 4 , wherein the minority layers are comprised of resins chosen from the group consisting of polyethylene, polyethylene copolymers, and polypropylene copolymers.
7 . The oriented film according to claim 4 , wherein the minority layers have a thickness ranging from 0 to 49 percent of the total film thickness.
8 . The oriented film according to claim 7 , wherein the minority layers have a thickness of approximately 16 percent of the total film thickness.
9 . The oriented film according to claim 6 , wherein the resins comprising the minority layers have a melt index ranging from 0.5 to 12.
10 . The oriented film according to claim 9 , wherein the resins comprising the minority layers have a melt index ranging from 3 to 5.
11 . The oriented film according to claim 6 , wherein the resins comprising the minority layers have a density ranging from 0.850 to 0.969.
12 . The oriented film according to claim 11 , wherein the resins comprising the minority layers have a density of approximately 0.917.
13 . The oriented film according to claim 5 , wherein the majority layer is comprised of a higher alpha-olefin LLDPE resin.
14 . The oriented film according to claim 5 , wherein the resin comprising the majority layer has a melt index ranging from 0.5 to 4.
15 . The oriented film according to claim 14 , wherein the resin comprising the majority layer has a melt index ranging from 0.8 to 1.2.
16 . The oriented film according to claim 5 , wherein the resin comprising the majority layer has a density ranging from 0.900 to 0.960.
17 . The oriented film according to claim 16 , wherein the resin comprising the majority layer has a density of approximately 0.920.
18 . An oriented film produced in-process that contains a cling agent comprised of a polybutene polymer, the oriented film having a total film structure.
19 . The oriented film according to claim 18 , wherein the polybutene polymer has a Saybolt Universal Viscosity of 14,900 SUS at 99° C. and a number average molecular weight of 2,060.
20 . The oriented film according to claim 18 , wherein the cling agent is incorporated into the film at an incorporation rate.
21 . The oriented film according to claim 20 , wherein the incorporation rate varies from 0 to 25 percent of the total film structure on a weight-to-weight basis.
22 . The oriented film according to claim 21 , wherein the incorporation rate is approximately 0.6 percent of the total film structure on a weight-to-weight basis.
23 . An oriented film produced in-process that contains a non-migratory cling agent incorporated into one or more layers of the film.
24 . The oriented film according to claim 23 , wherein the non-migratory cling agent is incorporated into the layers of the oriented film at an incorporation rate.
25 . The oriented film according to claim 24 , wherein the incorporation rate varies from 0 to 25 percent of the total film structure on a weight-to-weight basis.
26 . The oriented film according to claim 25 , wherein the incorporation rate is approximately 1 percent of the total film structure on a weight-to-weight basis.
27 . An apparatus for producing oriented film, the apparatus comprising:
an extruder that receives a resin and melts the resin to a selected temperature that allows the resin to melt; and
an angled die that delivers a layer of melted resin from the extruder onto a casting roll to produce a film.
28 . The apparatus according to claim 27 , wherein the angled die has an intercept angle that is less than 90°.