Block Copolymer Adhesive Composition Tack Viscosity Balance
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Solution Overview
Problem
Conventional adhesive compositions based on vinyl aromatic monomer-conjugated diene monomer block copolymers, such as SBS and SIS, face challenges in achieving a balance between viscous adhesion performance and melt viscosity, as well as coatability and tack strength.
Innovation Solution
A block copolymer composition comprising two types of block copolymers with specific structures, weight average molecular weights, and vinyl aromatic monomer unit content, combined with a tackifier and softener, to enhance the balance between viscous adhesion and melt viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional vinyl aromatic monomer-conjugated diene monomer block copolymers (SBS, SIS) are used as base polymer for adhesive compositions, then viscous adhesion characteristics such as tack strength are achieved, but melt viscosity is high and coatability is insufficient
Solution Approach 1:
The patent segments the adhesive composition into multiple block copolymer components with different molecular weights and structures. Specifically, it uses a combination of high molecular weight block copolymer (providing tack strength) and low molecular weight block copolymer (providing low melt viscosity and coatability), thereby resolving the contradiction between adhesion strength and ease of application
Solution Approach 2:
The patent changes the molecular weight parameter of the block copolymer components. By selecting block copolymers with weight average molecular weights in specific ranges (e.g., 50,000-200,000 for high MW component and 10,000-50,000 for low MW component) and controlling their compositional ratios, the patent optimizes both tack strength and melt viscosity to achieve balanced performance
2Strength
If block copolymer composition is optimized for viscous adhesion performance, then tack strength is improved, but melt viscosity increases and coatability deteriorates
Solution Approach 1:
The patent creates a composite adhesive system by combining multiple block copolymer components with different molecular weights and structures. This composite approach allows the high molecular weight component to provide tack strength while the low molecular weight component provides low melt viscosity, achieving both strong adhesion and good coatability simultaneously
3Strength
If adhesive composition uses higher molecular weight block copolymer to improve tack strength, then viscous adhesion characteristics are enhanced, but melt viscosity increases and processing becomes difficult
Solution Approach 1:
The patent divides the block copolymer system into segments with different molecular weights. The high molecular weight segment (50,000-200,000) provides the necessary tack strength, while the low molecular weight segment (10,000-50,000) ensures low melt viscosity and easy processing, thereby resolving the contradiction between adhesion performance and manufacturability
Data Source
AI summary
A block copolymer composition including: 10% by mass or more and 90% by mass or less of a component (a), and 10% by mass or more and 90% by mass or less of a component (b), wherein the component (a) is a block copolymer containing a polymer block (A) primarily including a vinyl aromatic monomer unit and a polymer block (B) primarily including a conjugated diene monomer unit, wherein the block copolymer has a weight average molecular weight of 30,000 or higher and 150,000 or lower; and the component (b) is a block copolymer containing a polymer block (A) primarily including a vinyl aromatic monomer unit and a polymer block (B) primarily including a conjugated diene monomer unit.