Multilayer Blown Films for Shrink Labels
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Solution Overview
Problem
Existing multilayer blown film technologies face challenges in achieving desirable shrink characteristics, such as high machine direction (MD) shrink and controlled cross-direction (CD) shrink, without the need for expensive and complex orientation processes like tenter frame, double bubble, or machine direction orientation (MDO).
Innovation Solution
The development of multilayer blown films comprising a core layer and outer/inner layers made from specific polymers, such as ethylene polymers and conjugated diene monovinylarene block copolymers, which are coextruded using a standard blown film process without additional orientation steps, achieving a MD:CD shrink ratio of 4:1 to 30:1 and MD shrink greater than 60% with CD shrink ranging from 0% to 15%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard blown film process is used without orientation processes, then production cost and process complexity are reduced, but shrink characteristics (MD shrink and CD shrink control) are insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the molecular weight distribution parameters of the polymer material. Specifically, it uses a polymer with a weight average molecular weight to number average molecular weight ratio (Mw/Mn) between 2.0 and 10.0, and a melt flow ratio (HLMI/MI) between 20 and 100. These parameter changes enable the material to achieve desirable shrink characteristics through standard blown film extrusion without requiring additional orientation processes, thus resolving the contradiction between manufacturing simplicity and shrink performance.
2Manufacturing precision
If tenter frame or MDO processes are used to achieve high MD shrink, then shrink characteristics are improved, but device complexity and production cost increase
Solution Approach 1:
The patent applies the extraction principle by removing the need for complex orientation processes such as tenter frame or machine direction orientation (MDO) equipment. Instead of using these elaborate external systems, the invention extracts the essential shrink-inducing function and embeds it directly into the polymer material's molecular structure through controlled molecular weight distribution. This allows high MD shrink (greater than 60%) to be achieved through standard blown film extrusion alone, eliminating the need for additional orientation equipment and processes.
3Manufacturing precision
If multilayer structure with specific polymers is used, then shrink ratio control (MD:CD ratio 4:1 to 30:1) is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the molecular weight distribution parameters of the polymer used in the multilayer structure. By controlling the Mw/Mn ratio between 2.0 and 10.0 and the HLMI/MI ratio between 20 and 100, the material inherently provides the desired anisotropic shrink behavior (MD:CD ratio of 4:1 to 30:1). This parameter optimization allows the multilayer coextrusion process to achieve precise shrink ratio control without requiring complex process control systems or additional equipment, as the shrink characteristics are built into the material itself.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the production of films with enhanced shrink properties and optical characteristics like low haze and high gloss, while eliminating the need for costly and complex orientation processes, thereby reducing production costs and complexity.
Implementation Method 1
These multilayer blown films can have a MD:CD shrink ratio in a range from about 4:1 to about 30:1 at 150° C.
Data Source
AI summary
The present invention discloses multilayer blown films for shrink label and related applications. These multilayer blown films can comprise a core layer containing an ethylene polymer, and inner and outer layers containing conjugated diene monovinylarene block copolymers.