Multilayer Cast Films Reducing Blocking via Narrow MWD Copolymer

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Solution Overview

Problem

Multilayer cast films used in packaging exhibit high blocking tendencies, which hinder the packaging process due to strong adherence of adjacent film surfaces, compromising optical, mechanical, and frictional properties.

Innovation Solution

Incorporating a core layer with a narrow molecular weight distribution ethylene/α-olefin copolymer and inner and outer layers of low density polyethylene homopolymers, characterized by specific melt indices and densities, to reduce blocking forces while maintaining optical and mechanical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional multilayer cast films are used with broader molecular weight distribution copolymers, then mechanical strength and optical properties can be maintained, but blocking tendency increases significantly

Engineering Contradiction:

Improveoptical and mechanical propertiesVSAvoidblocking tendency

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by controlling the molecular weight distribution of the ethylene/α-olefin copolymer through specific catalytic polymerization processes. By adjusting polymerization parameters to achieve a narrow molecular weight distribution (low polydispersity index), the film exhibits reduced blocking tendency while maintaining mechanical strength and optical clarity. This parameter optimization resolves the contradiction between reliability and blocking behavior.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials by creating a multilayer structure where an ethylene/α-olefin copolymer layer is combined with polyethylene layers. The specific copolymer composition with controlled molecular weight distribution acts as a blocking reduction agent within the composite film structure, achieving low blocking properties while the combination of materials maintains overall mechanical and optical performance.

Inventive Principle:

Principle #40Composite materials

2Productivity

If film blocking is reduced through material modification, then packaging process speed improves, but film structure complexity increases

Engineering Contradiction:

Improvepackaging process speedVSAvoidfilm structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

Rather than adding complex multilayer structures or additives, the patent achieves reduced blocking by optimizing the molecular weight distribution parameter of the copolymer. This single parameter change enables faster packaging processes while avoiding increased structural complexity, as the modification occurs at the molecular level within existing layer structures.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10899113B2Multilayer cast films with reduced blocking and methods of making same

Publication Date: 2021.01.26 CHEVRON PHILLIPS CHEMICAL COMPANY LP

AI summary

Multilayer cast films with an ethylene/α-olefin copolymer core layer, and inner and outer layers containing low density polyethylene homopolymers, and multilayer cast films with an ethylene polymer core layer, and inner and outer layers containing ethylene/α-olefin copolymers, are described. These cast films have a reduced tendency to block, and are useful in various food packaging applications.