UV-Crosslinkable Pressure-Sensitive Adhesive with High Molecular Weight Copolymer
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Solution Overview
Problem
Pressure-sensitive adhesive compositions containing tackifiers face challenges in maintaining cohesive strength and shear holding power due to the attenuation of ultraviolet radiation and reaction of tackifiers with crosslinking species, leading to decreased adhesive performance.
Innovation Solution
A crosslinkable composition comprising two different (meth)acrylate copolymers and a tackifier, where one copolymer has a high molecular weight and a high number of UV crosslinkable groups, allowing for the formation of crosslinks upon exposure to ultraviolet radiation, even in the presence of substantial tackifier amounts, thereby enhancing cohesive strength and shear holding power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If tackifiers are added to pressure-sensitive adhesive compositions, then tack and adhesion are improved, but cohesive strength and shear holding power decrease due to attenuation of ultraviolet radiation and reaction of tackifiers with crosslinking species
Solution Approach 1:
The patent changes the molecular weight parameter of the (meth)acrylate copolymer to be greater than 100,000 Daltons, which fundamentally alters the adhesive's behavior. This high molecular weight provides inherent cohesive strength that is not compromised by the presence of tackifiers, resolving the contradiction between improving tack/adhesion and maintaining cohesive strength
Solution Approach 2:
The patent creates a composite adhesive system combining high molecular weight (meth)acrylate copolymer with UV crosslinkable groups and tackifiers. This composite structure allows the different components to perform their respective functions: the high molecular weight polymer provides cohesive strength, the UV crosslinkable groups enable crosslinking for enhanced strength, and the tackifiers provide tack and adhesion without compromising the overall performance
2Strength
If high levels of tackifiers are used to enhance adhesion, then tack and surface energy are improved, but UV radiation attenuation increases, reducing crosslinking efficiency
Solution Approach 1:
The patent changes the molecular weight parameter of the (meth)acrylate copolymer to be greater than 100,000 Daltons, which fundamentally alters the adhesive's behavior. This high molecular weight provides inherent cohesive strength that is not compromised by the presence of tackifiers, resolving the contradiction between improving tack/adhesion and maintaining cohesive strength
Solution Approach 2:
The patent creates a composite adhesive system combining high molecular weight (meth)acrylate copolymer with UV crosslinkable groups and tackifiers. This composite structure allows the different components to perform their respective functions: the high molecular weight polymer provides cohesive strength, the UV crosslinkable groups enable crosslinking for enhanced strength, and the tackifiers provide tack and adhesion without compromising the overall performance
3Strength
If UV crosslinkable groups are incorporated into (meth)acrylate copolymers to enable crosslinking, then cohesive strength is improved, but device complexity and formulation difficulty increase
Solution Approach 1:
The patent changes the molecular weight parameter of the (meth)acrylate copolymer to be greater than 100,000 Daltons, which fundamentally alters the adhesive's behavior. This high molecular weight provides inherent cohesive strength that is not compromised by the presence of tackifiers, resolving the contradiction between improving tack/adhesion and maintaining cohesive strength
Solution Approach 2:
The patent creates a composite adhesive system combining high molecular weight (meth)acrylate copolymer with UV crosslinkable groups and tackifiers. This composite structure allows the different components to perform their respective functions: the high molecular weight polymer provides cohesive strength, the UV crosslinkable groups enable crosslinking for enhanced strength, and the tackifiers provide tack and adhesion without compromising the overall performance
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 enables the creation of pressure-sensitive adhesives with improved cohesive strength and shear holding performance, even with high tackifier levels, by effectively crosslinking the adhesive composition under UV exposure, resulting in enhanced adhesive properties.
Implementation Method 1
At least one of the (meth)acrylate copolymers contains pendant aromatic groups that upon exposure to ultraviolet radiation result in the formation of crosslinks within the polymeric material
Data Source
AI summary
Crosslinkable compositions, crosslinked compositions, articles containing these compositions, and methods of making the articles are provided. The crosslinkable compositions, which include two (meth)acrylate copolymers plus a tackifier, are used to form the crosslinked compositions upon exposure to ultraviolet radiation. The crosslinked compositions can function as pressure-sensitive adhesives. The crosslinkable compositions are well suited for use with hot melt processing methods.