Acrylic Adhesive Side Chain Crystallinity for Clean Removal
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Solution Overview
Problem
Conventional pressure-sensitive adhesives (PSAs) fail to maintain sufficient shear holding strength while allowing clean removal from delicate surfaces without causing damage, leading to undesirable consequences such as delamination or tearing of surfaces in multipack applications.
Innovation Solution
Acrylic adhesives derived from the reaction product of an acrylic acid ester with an alkyl group of 5 to 10 carbon atoms and a nonpolar acrylic monomer, exhibiting side chain crystallinity and a solubility parameter of less than 9.2, which provide a balance of low peel adhesion, high tack, and high shear strength, enabling clean removal from delicate surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional pressure-sensitive adhesives are used to bind packages in multipacks, then sufficient shear holding strength is achieved, but the adhesive causes delamination or tearing of delicate surfaces upon removal
Solution Approach 1:
The patent modifies the chemical composition parameters of the acrylic adhesive by incorporating specific monomers (acrylic acid ester with 5-10 carbon atoms and nonpolar acrylic monomer with solubility <9.2) and controlling the polymer structure to achieve side chain crystallinity. This parameter change in composition and structure enables the adhesive to provide sufficient shear holding strength while allowing clean removal from delicate surfaces without causing delamination or tearing.
Solution Approach 2:
The patent creates a composite adhesive system by combining multiple monomer components (acrylic acid ester and nonpolar acrylic monomer) with specific properties. This composite material approach allows the adhesive to exhibit both strong bonding characteristics and clean removal properties, resolving the contradiction between shear holding strength and surface integrity upon removal.
2Strength
If acrylic adhesives with high shear strength are formulated, then sufficient bond strength is achieved, but peel adhesion becomes too high causing permanent bonding and damage upon removal
Solution Approach 1:
The patent applies local quality by creating side chain crystallinity within the polymer structure. This localized structural feature provides strong shear resistance in the bulk adhesive while the overall adhesive formulation maintains lower peel adhesion. The side chain crystallinity acts as a localized reinforcement that doesn't uniformly increase adhesion in all directions, allowing high shear strength without proportionally high peel adhesion.
Solution Approach 2:
The patent changes the solubility parameter of the nonpolar acrylic monomer to less than 9.2 and controls the alkyl group size (5-10 carbon atoms) in the acrylic acid ester. These parameter changes create an adhesive with balanced properties where shear strength is enhanced through crystallinity while peel adhesion remains at manageable levels, preventing permanent bonding.
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 acrylic adhesives achieve a balance of adhesive properties that allow for strong bonding and subsequent clean removal from delicate surfaces, preventing damage during the separation of multipack components.
Implementation Method 1
The acrylic adhesive exhibits side chain crystallinity as indicated by fusion enthalpy of at least 2.5 J/g. Side chain crystallinity modifies the performance of the adhesive in certain applications due to the reduced segmental mobility of these side chains that limit adhesion build up over extended application time.
Data Source
AI summary
An acrylic adhesive derived from the reaction product of (i) an acrylic acid ester of monohydric alcohol having an alkyl group of 5 to 10 carbon atoms; and (ii) a nonpolar acrylic monomer having a solubility of less than 9.2 as measured with the Fedors method using a homopolymer of the nonpolar acrylic monomer. The acrylic adhesive possesses performance characteristics that enable the adhesive to function in certain embodiments as a pressure-sensitive adhesive for applications involving articles that are sensitive to delamination or tearing upon removal of the adhesive from the article.