Low Haze TPU Elastomer Using Cyclohexanedimethanol Chain Extenders
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Solution Overview
Problem
Thermoplastic polyurethane (TPU) elastomers based on 1,4-butanediol often exhibit significant haze or loss of optical clarity, especially in thicker parts, which is undesirable for applications requiring both mechanical properties and transparency.
Innovation Solution
A TPU elastomer formulation using a chain extender mixture comprising at least 60 mole-% of an acyclic diol or diamine with a molecular weight up to 400, combined with a mixture of cyclohexanedimethanol isomers, including 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol, to improve optical clarity and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If 1,4-butanediol is used as the chain extender in TPU elastomers, then good mechanical properties and reasonable cost are achieved, but significant haze or loss of optical clarity occurs especially in thicker parts
Solution Approach 1:
The patent changes the chemical composition parameters of the chain extender by incorporating cyclohexanedimethanol (CHDM) isomers (1,3- and 1,4-) into the chain extender mixture. This chemical parameter change resolves the contradiction by maintaining the mechanical properties needed for manufacturing while eliminating the haze formation that degrades optical clarity in thicker parts.
Solution Approach 2:
The patent creates a composite chain extender system by combining multiple components: acyclic diols/diamines (providing mechanical properties) with cyclohexanedimethanol isomers (providing optical clarity). This composite approach allows the TPU elastomer to simultaneously achieve good mechanical performance and excellent optical clarity even in thicker sections.
2Strength
If the thickness of the TPU part is increased, then mechanical strength and durability are improved, but haze increases and optical clarity is lost
Solution Approach 1:
The patent modifies the chemical structure parameters of the chain extender by incorporating cyclic CHDM structures with specific molecular weights and configurations. This parameter change allows the material to maintain mechanical strength in thicker sections while preventing the light scattering that causes haze, thereby resolving the thickness-related optical degradation.
3Reliability
If TPU elastomer is made with conventional chain extenders, then good abrasion resistance and permeability are achieved, but haze significantly reduces optical clarity
Solution Approach 1:
The patent develops a composite chain extender formulation that combines conventional acyclic diols (which provide abrasion resistance and permeability) with cyclohexanedimethanol isomers (which eliminate haze). This composite material approach maintains the reliable mechanical performance needed for footwear applications while achieving the optical clarity required for aesthetic and functional purposes.
Data Source
AI summary
The present invention is a low haze thermoplastic polyurethane (TPU) prepared from a chain extender mixture that includes an acyclic diol and a mixture of 1,3- and 1,4-cyclohexanedimethanol. The TPU elastomers exhibit good optical clarity, particularly when formed into relatively thick injection molded parts.