Low shrink tension film
View Patent ↗A low shrink tension packaging film contains a first polymer that is an ethylene-unsaturated carboxylic acid copolymer and a second polymer containing one or more copolymers selected from an ethylene-vinyl acetate copolymer and an ethylene-acrylate copolymer. A molar ratio of a specific structural unit of the first polymer to a specific structural unit of the second polymer is in a specific range, such that the low shrink tension packaging film has excellent optical and mechanical properties and a significantly low tension applied when being shrunk by heat.
1 . A polymer composition for a low shrink tension packaging film, comprising:
a first polymer that is an ethylene-unsaturated carboxylic acid copolymer, wherein the ethylene-unsaturated carboxylic acid copolymer is an ethylene-acrylic acid copolymer, an ethylene-(meth)acrylic acid copolymer, or a combination thereof; and
a second polymer containing one or more copolymers selected from an ethylene-vinyl acetate copolymer and an ethylene-acrylate copolymer,
wherein a molar ratio of an unsaturated carboxylic acid structural unit of the first polymer to a hydrogen bonding functional group of the second polymer is 1:1 to 12,
wherein a ratio of a melt index (190° C./2.16 kg, ASTM D1238) of the first polymer to a melt index (190° C./2.16 kg, ASTM D1238) of the second polymer is 1:1 to 9, and wherein a shrink force of the film ranges from 59% to 77%.
2 . The polymer composition of claim 1 , wherein a content of the unsaturated carboxylic acid structural unit of the first polymer is 1 to 10 mol %.
3 . The polymer composition of claim 2 , wherein a content of the hydrogen bonding functional group of the second polymer is 2.5 mol % or more.
4 . The polymer composition of claim 1 , wherein the first polymer is contained in an amount of 55 to 90 wt %, and the second polymer is contained in an amount of 10 to 45 wt %.
5 . The polymer composition of claim 1 , further comprising a third polymer that is a polyolefin elastomer copolymer.
6 . The polymer composition of claim 5 , wherein the first polymer is contained in an amount of 30 to 70 wt %, the second polymer is contained in an amount of 10 to 40 wt %, and the third polymer is contained in an amount of 15 to 50 wt %.
7 . The polymer composition of claim 1 , wherein the ethylene-acrylate copolymer is an ethylene-(C1-C8) alkyl acrylate copolymer.
8 . The polymer composition of claim 1 , wherein the second polymer contains the ethylene-acrylate copolymer.
9 . A packaging film formed of the polymer composition of claim 1 .
10 . The packaging film of claim 9 , wherein an average thickness of the packaging film is 10 to 500 μm.
11 . The packaging film of claim 10 , a light transmittance of the packaging film when being irradiated with light having a wavelength of 550 nm at a film thickness of 50 μm is 55% or more.
12 . The packaging film of claim 9 , wherein a shrinkage rate of the packaging film after being maintained at 120° C. for 30 seconds is 80% or less.
13 . The packaging film of claim 9 , wherein the packaging film is produced by:
a mixing step of blending the first polymer and the second polymer to prepare a polymer composition for a low shrink tension packaging film; and
an extrusion step of extruding and molding the polymer composition for a low shrink tension packaging film to produce a packaging film.
14 . The packaging film of claim 13 , wherein in the mixing step, the blending is dry blending performed at a relative humidity of 70 to 100%.