Polyvinylaromatic-Polydiene Adhesives With Reactive Resin Curing
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Solution Overview
Problem
Existing polyvinylaromatic-polydiene block copolymer-based pressure sensitive adhesives (PSAs) struggle to achieve an excellent balance between high thermal shear strength and good peel adhesion, particularly in applications requiring temperatures above their glass transition point.
Innovation Solution
A formulation comprising 25 to 45 wt% of polyvinylaromatic-polydiene block copolymer with specific molar mass and block structure, 33 to 55 wt% of tackifier resin with defined softening temperature, and 13 to 30 wt% of reactive resin with specific Hansen parameter, along with a cationic curing initiator, to enhance thermal shear strength and peel adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyvinylaromatic-polydiene block copolymer-based PSAs are used to achieve good peel adhesion and cohesion, then peel adhesion is improved, but thermal shear strength deteriorates when glass transition temperature is reached
Solution Approach 1:
The patent changes the chemical composition parameters by introducing reactive resin components (epoxides, polyisocyanates, polyesters, or carboxylic acids) that can form crosslinked networks. These compositional changes enable the adhesive to maintain strength at elevated temperatures by creating a three-dimensional crosslinked structure that prevents polymer chain mobility even above glass transition temperature
Solution Approach 2:
The patent creates a composite adhesive system combining polyvinylaromatic-polydiene block copolymer with reactive resin components. This composite formulation integrates the adhesive properties of the block copolymer with the thermal stability and crosslinking capability of the reactive resins, achieving both good peel adhesion and high thermal shear strength
2Temperature
If physical crosslinking through block separation is used to achieve thermal shear strength below glass transition temperature, then thermal shear strength is improved, but cohesion deteriorates when glass transition temperature is reached
Solution Approach 1:
The patent performs preliminary chemical crosslinking through reactive resin components before the adhesive is subjected to high temperature conditions. This pre-established crosslinked network structure provides ongoing structural support and maintains cohesion even when the glass transition temperature is reached and physical crosslinks become ineffective
Solution Approach 2:
The patent transforms the crosslinking mechanism from purely physical (reversible) to chemical (irreversible) by incorporating reactive resin components that form permanent crosslinks. This parameter change in crosslinking nature enables the adhesive to maintain its structural integrity and cohesion at temperatures above the glass transition point
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 formulation achieves a thermal shear strength of at least 150°C and peel adhesion of at least 4 N/cm, providing a superior balance of properties for self-adhesive tapes.
Implementation Method 1
contain at least one kind of a cationic curable reactive resin which on curing produces an enhancement of the thermal shear strength
Implementation Method 2
polyvinylaromatic-rich regions are formed which, in temperature ranges below their glass transition temperature, serve as crosslinking points
Data Source
AI summary
The invention relates to polyvinal aromate-polydiene-block copolymer-based adhesive compounds that contain at least one type of a cationically curable reactive resin and that result, when cured, in improved thermal shear strength. The invention further relates to adhesive strips that contain at least one layer of such an adhesive compound, and a method of production.