Polyolefin Laminate Adhesion via Low Density Polyethylene Blend
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Solution Overview
Problem
Propylene-α-olefin copolymers used in film applications suffer from low flexibility and stickiness at high temperatures, leading to processing issues such as wrinkles and poor optical quality during metallization, which are partially addressed by slip agents but result in reduced surface tension and organoleptic issues.
Innovation Solution
A polyolefin resin composition comprising a blend of 90-99.7wt% of a copolymer with 80-98wt% propylene and 2-20wt% α-olefin units, combined with 0.3-10wt% of polyethylene with a density of 870-920 kg/m³, adhered to a base layer, improving adhesion and film quality while maintaining surface tension for printing and metallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If slip agents are added to propylene-α-olefin copolymers to reduce stickiness during processing, then the risk of polymer sticking to rollers is reduced, but the surface tension of the film is reduced making printing or adhesion onto metallized surface much more difficult
Solution Approach 1:
The invention changes the chemical composition parameters of the copolymer by controlling comonomer content (2-20wt% α-olefin) and propylene content (80-98wt%) to achieve the right balance between flexibility and surface tension retention, eliminating the need for slip agents
Solution Approach 2:
The invention removes (extracts) the slip agents from the system entirely by designing a copolymer composition that inherently provides sufficient flexibility and processability without requiring external slip agents, thus preserving surface tension for good adhesion
2Ease of operation
If high density polyethylene (density ≥ 940 kg/m³) is used in the blend to improve flexibility and reduce stickiness, then processing issues are reduced, but metal film adhesion and organoleptic properties deteriorate
Solution Approach 1:
The invention changes the density parameter of the polyethylene component from ≥940 kg/m³ (high density) to 870-920 kg/m³ (lower density), which provides better flexibility and metal film adhesion while maintaining processability
Solution Approach 2:
The invention creates a composite resin composition blending propylene-α-olefin copolymer with lower density polyethylene (870-920 kg/m³) in specific ratios (90-99.7wt% copolymer, 0.3-10wt% polyethylene) to achieve synergistic effects of flexibility and adhesion
Data Source
Figure 1
AI summary
A laminate is disclosed comprising a polyolefin layer of a composition comprising a blend of 90-99.7wt% of a copolymer of propylene and at least one a-olefin, and 0.3-10wt% of a polyethylene having a density of 940 kg/m3 or less, adhered to a base layer comprising a propylene homopolymer or a copolymer of propylene and up to 5wt% of C2-C10 alpha- olefin units other than propylene. The laminate may optionally be metallised.