Siloxane Release Coatings for Adhesion and Low Force
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Solution Overview
Problem
Existing adhesive coatings face challenges in achieving both low release forces and high adhesion to carrier materials, particularly on smooth substrates, with existing siloxane-based compositions either having unsatisfactory adhesion or increased release forces over time.
Innovation Solution
Compositions comprising a combination of siloxanes with ethylenically unsaturated, radically polymerizable groups and hydrocarbons with 2 to 6 such groups, which allow for optimal adhesion and release characteristics by adjusting the modification density and structure, enabling effective adhesion on smooth surfaces while maintaining low release forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If terminally (meth)acrylate-modified organopolysiloxanes with sufficiently large siloxane chains are used, then release forces remain low, but adhesion to carrier material becomes unsatisfactory
Solution Approach 1:
The patent applies local quality by differentiating between terminal and lateral modifications of the siloxane chain. Terminal modifications provide the release properties, while lateral modifications provide the adhesion properties. This allows different parts of the same polymer molecule to have different functions, resolving the contradiction between low release force and high adhesion.
Solution Approach 2:
The patent creates a composite structure within the polysiloxane molecule itself, combining siloxane units with both terminal (meth)acrylate groups and lateral polar groups. This molecular-level composite material simultaneously provides the release characteristics from the siloxane chain and the adhesion characteristics from the lateral polar groups.
2Strength
If higher density of modification with polar and/or reactive groups is achieved by shortening siloxane chains, then adhesion to substrate improves, but release force increases unsatisfactorily and cost increases
Solution Approach 1:
The patent resolves this contradiction by placing polar and reactive groups laterally along the siloxane chain rather than terminally. This lateral positioning allows high density of polar groups for adhesion without shortening the chain, thereby maintaining the low release force property that depends on chain length.
3Strength
If laterally (meth)acrylate-modified organosiloxanes are used to vary modification density, then adhesion can be improved, but uncrosslinked acrylate groups increase release forces over time
Solution Approach 1:
The patent changes the chemical nature of the lateral groups from purely (meth)acrylate to a combination of polar groups and reactive groups. This parameter change allows the lateral groups to provide adhesion through polarity while the reactive groups participate in crosslinking to prevent follow-on reactions with adhesives that would increase release forces.
Solution Approach 2:
The patent converts the potential harm of reactive groups (which could cause follow-on reactions) into a benefit by ensuring they fully crosslink during curing. The crosslinked structure then prevents the harmful follow-on reactions with adhesive materials, stabilizing the release force over time.
4Strength
If purely organic coating materials are admixed to (meth)acrylate-modified organopolysiloxanes, then adhesion to many substrates improves, but low release forces and long stability are critically impaired
Solution Approach 1:
The patent eliminates the need for admixing purely organic materials by incorporating both adhesion-providing polar groups and release-providing siloxane chain structures into a single integrated polysiloxane molecule. This local differentiation within the molecule achieves both adhesion and low release force without the negative effects of mixtures.
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 described compositions achieve excellent adhesion and low release forces, even on smooth substrates, with stable release force over time, improving upon the limitations of prior art by using a specific combination of components that balance reactivity and polymerization efficiency.
Implementation Method 1
The curing is accomplished in particular through UV radiation (following addition of known photoinitiators) or by electron beams
Implementation Method 2
compositions comprising at least one siloxane which has ethylenically unsaturated, radically polymerizable groups, and also comprising at least one hydrocarbon which has 2 to 6 ethylenically unsaturated, radically polymerizable groups
Implementation Method 3
attain good adhesion of the coating to the carrier material
Data Source
AI summary
A composition contains at least one siloxane having ethylenically unsaturated, radically-polymerizable groups, and at least one hydrocarbon having 2 to 6 ethylenically-unsaturated, radically-polymerizable groups, and can be used as a release coating, said composition allowing a good degree of release behavior from adhesive compounds while at the same time also achieving a high level of adhesion of the coating to the carrier material.