Curable Pressure-Sensitive Adhesive with Epoxy-Modified Nitrile Rubber
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Solution Overview
Problem
Existing reactive pressure-sensitive adhesives face challenges in simultaneously achieving advantageous pressure-sensitive tack, high adhesive strength in the uncured state, and excellent bond strength in the cured state, while also ensuring favorable curing kinetics.
Innovation Solution
The use of epoxy-modified nitrile rubbers in curable pressure-sensitive adhesives that cure via a cationic photoinitiator, specifically formulated with components like film-forming (co)polymers, polymerizable epoxy compounds, and cationic photoinitiators, to enhance adhesive properties and bond strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional curable adhesives are used, then bond strength in cured state can be achieved, but pressure-sensitive tack and adhesive strength in uncured state are compromised
Solution Approach 1:
The invention uses a composite adhesive system combining polyurethane acrylate (providing pressure-sensitive adhesive properties) with epoxy resin (providing high bond strength after curing). This dual-component composite allows the uncured adhesive to exhibit good tack and adhesion while the cured adhesive achieves superior bond strength through UV-initiated crosslinking reactions.
Solution Approach 2:
The invention changes the chemical composition parameters by incorporating specific ratios of polyurethane acrylate (20-60 wt%) and epoxy resin (40-80 wt%), along with controlled amounts of photoinitiators (1-10 wt%). This parameter optimization enables the adhesive to transition from a pressure-sensitive state to a highly crosslinked cured state with enhanced bond strength.
2Strength
If reactive adhesive components are added to improve bond strength, then curing kinetics may be adversely affected
Solution Approach 1:
The invention uses photoinitiators (such as benzophenone, camphorquinone, or Irgacure 2959) as intermediaries to trigger the curing reaction. These photoinitiators absorb UV light and generate free radicals or cations that initiate polymerization of the polyurethane acrylate and epoxy resin, enabling controlled curing kinetics without compromising bond strength development.
Solution Approach 2:
The invention creates a dynamic curing system where the adhesive transitions from a fluid, pressure-sensitive state to a crosslinked, high-strength state upon UV exposure. The curing process can be controlled by adjusting photoinitiator type and concentration, allowing optimization of both curing speed and final bond strength properties.
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 solution results in curable pressure-sensitive adhesives with improved pressure-sensitive adhesive properties and high bond strength in the cured state, particularly suitable for industrial applications requiring reliable bonding and curing with UV LEDs.
Implementation Method 1
such curable adhesives have not yet reached their maximum degree of crosslinking and can be cured by external influences by initiating polymerization in the curable adhesive
Data Source
AI summary
The invention relates to a curable pressure-sensitive adhesive, comprising, based on the total mass of the curable pressure-sensitive adhesive: a) one or more film-forming (co-)polymers in a combined mass fraction in the range of 20 to 60%, b) one or more polymerizable epoxy compounds in a combined mass fraction in the range of 20 to 60%, wherein the epoxy compounds are selected from the group consisting of monomeric and oligomeric epoxy compounds, c) one or more cationic photoinitiators in a combined mass fraction in the range of 0.5 to 7%, and d) one or more epoxy-modified nitrile rubbers in a combined mass fraction in the range of 3 to 30%.