Rheology-modified grafts and adhesive blends
Rheologically-modified functionalized polyolefins and tie-layer adhesive blends formulated therewith which exhibit improved adhesion in multi-layer barrier films are provided. Multi-layer barrier shrink films having improved adhesion are also disclosed.
1 . A rheologically-modified functionalized polyolefin comprising an ethylene polymer having a density from 0.85 to 0.965 g/cm 3 grafted with 0.25 to 5 weight percent maleic anhydride and having a relaxation time from 0.12 second to 0.001 second.
2 . The rheologically-modified functionalized polyolefin of claim 1 wherein the ethylene polymer is selected from the group consisting of high density polyethylene, linear low density polyethylene and ethylene-C 4-8 α-olefin plastomers.
3 . The rheologically-modified functionalized polyolefin of claim 1 grafted with 0.5 to 4 weight percent maleic anhydride.
4 . The rheologically-modified functionalized polyolefin of claim 3 having a relaxation time from 0.10 second to 0.04 second and melt index from 2 to 30 g/10 min.
5 . The rheologically-modified functionalized polyolefin of claim 4 wherein the ethylene polymer is selected from the group consisting of high density polyethylene, linear low density polyethylene and ethylene-C 4-8 α-olefin plastomers.
6 . A tie-layer adhesive composition comprising an ethylene homopolymer or ethylene-C 4-8 α-olefin copolymer base resin having a melt index from 0.01 to 50 g/10 min and 2.5 to 30 weight percent, based on the total weight of the composition, rheologically-modified functionalized polyolefin comprising an ethylene polymer having a density from 0.85 to 0.965 g/cm 3 grafted with 0.25 to 5 weight percent maleic anhydride and having a relaxation time from 0.12 second to 0.001 second.
7 . The tie-layer adhesive composition of claim 6 wherein the base resin is selected from the group consisting of low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene and very low density polyethylene and constitutes from 70 to 97.5 weight percent of the composition.
8 . The tie-layer adhesive composition of claim 6 wherein the base resin is linear low density polyethylene.
9 . The tie-layer adhesive composition of claim 8 wherein the linear low density polyethylene is an ethylene copolymer having a network structure containing hard and soft rubber phases.
10 . The tie-layer adhesive composition of claim 6 wherein the rheologically-modified functionalized polyolefin is an ethylene polymer selected from the group consisting of high density polyethylene, linear low density polyethylene and ethylene-C 4-8 α-olefin plastomers.
11 . The tie-layer adhesive composition of claim 7 comprising 80 to 95 weight percent base resin and 5 to 20 weight percent rheologically-modified functionalized polyolefin.
12 . The tie-layer adhesive composition of claim 7 comprising 20 to 85 weight percent, based on the total weight of the composition, base resin, 5 to 20 weight percent, based on the total weight of the composition, rheologically-modified functionalized polyolefin and 5 to 65 weight percent, based on the total weight of the composition, elastomeric or low crystalline component.
13 . The tie-layer adhesive composition of claim 12 wherein the elastomeric or low crystalline component is selected from the group consisting of ethylene-vinyl acetate copolymers, ethylene-alkyl acrylate copolymers, ethylene-α-olefin copolymers and terpolymers, plastomers and propylene polymer elastomers.
14 . The tie-layer adhesive composition of claim 13 comprising 25 to 75 weight percent, based on the total weight of the composition, base resin, 10 to 15 weight percent, based on the total weight of the composition, rheologically-modified functionalized polyolefin and 10 to 60 weight percent, based on the total weight of the composition, low crystallinity or elastomeric component.
15 . A multi-layer barrier film comprising a barrier resin layer and polyolefin resin layer adhesively bonded thereto utilizing a tie-layer adhesive composition comprising an ethylene homopolymer or ethylene-C 4-8 α-olefin base resin having a melt index from 0.01 to 50 g/10 min. and 2.5 to 30 weight present, based on the weight of the total composition, rheologically-modified functionalized polyolefin comprising an ethylene polymer having a density from 0.85 to 0.965 g/cm 3 grafted with 0.25 to 5 weight percent maleic anhydride and having a relaxation time from 0.12 second to 0.001 second.
16 . The multi-layer barrier film of claim 15 wherein the barrier resin is a polyamide or ethylene-vinyl alcohol copolymer and the polyolefin resin is selected from the group consisting of low density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid or ester copolymer and ethylene-methacrylic acid or ester copolymer.
17 . The multi-layer barrier film of claim 16 wherein the tie-layer adhesive composition is comprised of 80 to 95 weight percent, based on the total weight of the composition, base resin selected from the group consisting of low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene and very low density polyethylene and 5 to 20 weight percent, based on the total weight of the composition, rheologically-modified ethylene polymer selected from the group consisting of high density polyethylene, linear low density polyethylene and ethylene-C 4-8 α-olefin plastomers grafted with 0.5 to 4 weight percent maleic anhydride.
18 . The multi-layer barrier film of claim 16 wherein the tie-layer adhesive composition is comprised of 25 to 75 weight percent, based on the total weight of the composition, base resin selected from the group consisting of low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene and very low density polyethylene, 10 to 15 weight percent, based on the total weight of the composition, rheologically-modified ethylene polymer selected from the group consisting of high density polyethylene, linear low density polyethylene and ethylene-C 4-8 α-olefin plastomers grafted with 0.5 to 4 weight percent maleic anhydride, and 10 to 60 weight percent, based on the total weight of the composition, elastomeric or low crystallinity component selected from the group consisting of ethylene-vinyl acetate copolymers, ethylene-alkyl acrylate copolymers, ethylene-α-olefin copolymers and terpolymers, plastomers and propylene polymer elastomers.
19 . The multi-layer barrier film of claim 15 which is oriented.
20 . The multi-layer barrier film of claim 15 which is oriented and irradiated.