Tie-Layer Adhesives for Styrene Polymers Thermoforming
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Solution Overview
Problem
Existing multi-layer structures face challenges in effectively bonding dissimilar resin layers, particularly between styrene polymer and barrier resin layers, leading to reduced adhesion during thermoforming processes.
Innovation Solution
Adhesive compositions comprising 40-70% ethylene-C4-8 α-olefin copolymer, 2.5-25% polyethylene resin grafted with ethylenically unsaturated carboxylic acid, and 20-50% styrene-isoprene-styrene and styrene-butadiene-styrene triblock copolymers, with a weight ratio of SIS to SBS ranging from 5:1 to 1:5, are used to enhance adhesion in multi-layer constructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional tie-layer adhesives comprising unmodified and functionalized polyolefins and styrenic polymers are used, then basic adhesion is achieved, but adhesion to styrene polymer layers deteriorates particularly after thermoforming
Solution Approach 1:
The patent applies composite materials by formulating a tie-layer adhesive that combines three distinct polymer components: polyethylene (provides flexibility and processability), functionalized polyethylene (provides chemical bonding capability through grafted carboxylic acid groups), and styrene-isoprene-styrene triblock copolymer (provides adhesion to styrene layers through styrene end blocks). This composite formulation creates synergistic effects where each component contributes specific properties that collectively achieve both strong initial adhesion and retained adhesion after thermoforming, resolving the technical contradiction between adhesion strength and adhesion reliability.
Solution Approach 2:
The patent applies parameter changes by optimizing the weight percentages of each adhesive component (polyethylene: 40-70%, functionalized polyethylene: 2.5-25%, SIS triblock copolymer: 20-50%) and the graft level of carboxylic acid on the functionalized polyethylene (0.5-5.0%). These parameter optimizations ensure sufficient flexibility and bonding capability while maintaining adhesion strength through thermoforming, directly addressing the contradiction between adhesion strength and adhesion retention.
2Strength
If styrene polymer layers are used to provide structural integrity and moldability, then structural performance is improved, but bonding to dissimilar barrier resin layers becomes difficult
Solution Approach 1:
The patent applies the intermediary principle by using the tie-layer adhesive as a mediator between the styrene polymer layer (providing structural integrity) and the barrier resin layer (EVOH or polyamide). The adhesive's functionalized polyethylene component with grafted carboxylic acid groups chemically bonds to the barrier layer, while the SIS triblock copolymer's styrene end blocks adhere to the styrene layer. This intermediary adhesive layer enables reliable bonding between dissimilar materials without compromising the structural performance of the styrene layer.
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
The adhesive blends significantly improve adhesion to styrenic resin layers and retain a higher percentage of adhesion after thermoforming, demonstrating improved performance in multi-layer films and sheets used for thermoformed applications.
Implementation Method 1
polyethylene resin grafted with an ethylenically unsaturated carboxylic acid or acid derivative
Implementation Method 2
functionalized polyethylene and a styrenic polymer present at a weight ratio from 5:1 to 1:5
Implementation Method 3
adhesive compositions which provide significantly improved adhesion to styrenic resins
Implementation Method 4
styrene-isoprene-styrene and styrene-butadiene-styrene triblock copolymers present at a weight ratio from 5:1 to 1:5
Data Source
AI summary
Adhesive compositions for styrene polymers are provided. The adhesives are suitable for use as tie-layers in multi-layer films and sheets and comprise a polyolefin base resin, a functionalized polyolefin and a combination of styrene triblock copolymers.