Multi-Layer Acrylic PSA Structure for Tack and Shear Balance
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Solution Overview
Problem
Existing pressure sensitive adhesives (PSAs) with acrylic polymers face challenges in achieving both good tack adhesion and shear resistance, particularly when used on polyolefin substrates, and there is a need to address the migration of tackifiers between layers, which reduces adhesion.
Innovation Solution
A multi-layer PSA structure is developed, where the top layer contains a high level of acrylic polymer with a tackifier and the underlying layer has a lower level of acrylic polymer with specific molecular weight and glass transition temperature, minimizing tackifier migration and maintaining adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a tackifier compound is added to the PSA to increase tack adhesion, then tack adhesion is improved, but shear resistance is reduced
Solution Approach 1:
The invention divides the PSA into multiple layers with different compositions. The top layer contains tackifier for high tack adhesion, while the bottom layer has lower tackifier content for shear resistance. This segmentation allows each layer to optimize its function without compromising the other property.
Solution Approach 2:
Different regions of the PSA are given different compositions tailored to their specific functions. The top layer (in contact with substrate) has high tackifier concentration for immediate bonding, while the bottom layer has reduced tackifier for structural integrity and shear resistance.
2Force
If the top layer contains a high level of tackifier to maximize tack adhesion, then tack adhesion is improved, but tackifier migration to other layers occurs, reducing adhesion performance
Solution Approach 1:
The PSA is segmented into layers with a gradient in tackifier concentration. The bottom layer acts as a barrier with lower tackifier content, preventing migration while the top layer maintains high tackifier for adhesion.
Solution Approach 2:
The composition varies locally across the layers. The top layer is optimized for tack adhesion with high tackifier, while the bottom layer is optimized for stability and migration resistance with lower tackifier content.
Data Source
Figure 1~2
AI summary
Provided is a pressure sensitive adhesive article comprising (a) a substrate (Sa) (b) in contact with the substrate (Sa), a layer (Lb) of a pressure sensitive composition (Cb) that comprises one or more acrylic polymer (POLb) having Tg of 20°C or lower, and (c) in contact with the layer (Lb), a layer (Lc) that comprises, (i) one or more acrylic polymer (POLc1) having Tg of 20°C or lower, and (ii) one or more acrylic tackifier polymer having Tg of -10°C or higher. Also provided are a method of making the pressure sensitive adhesive article and a bonded article made by using the pressure sensitive adhesive article.