Multi-layer Polyolefin Films for High Draw Ratio Orientation
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Solution Overview
Problem
Conventional machine direction oriented polyethylene films face limitations in achieving significant downgauging while maintaining desirable mechanical properties such as tear strength and stiffness, often resulting in weakened tear strength and fibrillation due to high draw ratios.
Innovation Solution
A uniaxially oriented film comprising a polyolefin plastomer, single-site catalyzed linear low density polyethylene, and Ziegler-Natta catalyzed ultra low density polyethylene, with specific density and melt index ranges, and an inner layer, oriented in the machine direction at a draw ratio of 4:1 to 10:1, achieving high 2% secant modulus and limited tear strength drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If machine direction oriented films are stretched at high draw ratios to achieve down gauging, then film thickness is reduced and stiffness is improved, but tear strength in the machine direction deteriorates and fibrillation occurs
Solution Approach 1:
The patent applies local quality by creating a multi-layer film structure where different layers have different properties. Specifically, the film comprises a first layer and a second layer with different polymer compositions and crystallinities, allowing each layer to contribute differently to the overall performance - one layer provides stiffness through high orientation while the other maintains tear strength through appropriate molecular weight and composition
Solution Approach 2:
The patent uses composite materials by combining different polyolefin polymers in a multi-layer structure. The first layer contains a polyolefin plastomer with specific density and melt index ranges, while the second layer contains a different polyolefin with distinct properties. This composite structure enables the film to achieve both high stiffness and maintained tear strength that cannot be obtained with a single polymer
2Volume of moving object
If machine direction oriented films are stretched at high draw ratios to achieve down gauging, then film thickness is reduced, but fibrillation occurs in the machine direction
Solution Approach 1:
The patent applies local quality by creating a multi-layer film structure where different layers have different properties. Specifically, the film comprises a first layer and a second layer with different polymer compositions and crystallinities, allowing each layer to contribute differently to the overall performance - one layer provides stiffness through high orientation while the other maintains tear strength through appropriate molecular weight and composition
Solution Approach 2:
The patent uses composite materials by combining different polyolefin polymers in a multi-layer structure. The first layer contains a polyolefin plastomer with specific density and melt index ranges, while the second layer contains a different polyolefin with distinct properties. This composite structure enables the film to achieve both high stiffness and maintained tear strength that cannot be obtained with a single polymer
3Quantity of substance
If film gauge is reduced to achieve thinner films, then material usage is reduced and cost is lowered, but toughness and tear strength are sacrificed
Solution Approach 1:
The patent applies parameter changes by precisely controlling the density and melt index parameters of the polyolefin polymers used in each layer. The first layer uses a polyolefin plastomer with density of 0.865 to 0.908 g/cm³ and I2 melt index of 0.5 to 6.0 g/10 minutes, while the second layer uses a polyolefin with different parameters. These parameter specifications enable the production of thinner films with maintained mechanical properties
Solution Approach 2:
The patent uses composite materials by combining different polyolefin polymers in a multi-layer structure. The first layer contains a polyolefin plastomer with specific density and melt index ranges, while the second layer contains a different polyolefin with distinct properties. This composite structure enables the film to achieve both high stiffness and maintained tear strength that cannot be obtained with a single polymer
Data Source
AI summary
The present invention provides uniaxially oriented films and packages formed from such films. In one aspect, a uniaxially oriented film comprises (a) a first layer comprising a polyolefin plastomer having a density of 0.865 to 0.908 g/cm3 and a melt index (I2) of 0.5-6 g/10 minutes, and at least one of a single-site catalyzed linear low density polyethylene having a density of 0.912 g/cm3 to 0.935 g/cm3 and a melt index (I2) of 0.5 to 6 g/10 minutes, or a Ziegler-Natta catalyzed ultra low density polyethylene having a density of 0.880 g/cm3 to 0.912 g/cm3, a melt index (I2) of 0.5 to 6 g/10 minutes, and a MWD of 6.0 or less; (b) a second layer comprising a Ziegler-Natta catalyzed ultra low density polyethylene having a density of 0.880 g/cm3 to 0.912 g/cm3, a melt index (I2) of 0.5 to 6 g/10 minutes, and a MWD of 6.0 or less; and (c) at least one inner layer between the first layer and the second layer comprising at least one polyolefin. The film is oriented in the machine direction at a draw ratio of between 4:1 and 10:1, and can exhibit a machine direction 2% secant modulus of 85,000 psi or more when measured as per ASTM D882.