Multilayer Pressure-Sensitive Adhesive Assembly with Low VOC
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Solution Overview
Problem
Current pressure-sensitive adhesives face challenges in providing robust and cost-effective multilayer assemblies with reduced VOC levels while maintaining excellent adhesion characteristics, particularly on low and medium surface energy substrates, and they often suffer from cohesive strength issues and excessive flow, especially in hotmelt processes.
Innovation Solution
A multilayer pressure-sensitive adhesive assembly comprising a polymeric foam layer and a first pressure-sensitive adhesive layer, where the polymeric foam includes a multi-arm block copolymer, a polymeric plasticizer, and a hydrocarbon tackifier with low VOC levels, and the adhesive layer comprises a linear block copolymer, a (meth)acrylate copolymer, and optional multi-arm or diblock copolymers, all processed through melt co-extrusion to enhance cohesion and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If acrylate-based pressure sensitive adhesives are used to reduce VOC levels, then VOC emissions are reduced, but cohesive strength decreases and excessive flow occurs
Solution Approach 1:
The patent employs a composite adhesive system combining acrylate-based PSA with a polymeric foam layer containing rubber particles and functional additives. This composite structure allows the acrylate layer to provide low VOC characteristics while the foam layer with rubber particles (polymerized conjugated diene or hydrogenated derivatives) and coupling agents contributes cohesive strength and flow control, resolving the contradiction between VOC reduction and mechanical performance
Solution Approach 2:
The patent modifies the chemical composition parameters of the adhesive system by incorporating specific rubber particles with controlled glass transition temperatures, molecular weights, and functional group contents. The coupling agent concentration and type are also parameterized to optimize the balance between VOC emissions and cohesive strength, enabling the system to achieve both low VOC and adequate mechanical properties
2Strength
If pressure sensitive adhesives are formulated for high cohesive strength at elevated temperatures, then shear holding capability improves, but adhesion to low surface energy substrates deteriorates
Solution Approach 1:
The patent creates different functional zones within the adhesive assembly: the acrylate-based PSA layer provides optimized adhesion to low surface energy substrates through its chemical composition and tackifier selection, while the polymeric foam layer with rubber particles provides enhanced cohesive strength and high-temperature shear holding. Each layer is locally optimized for its specific function, resolving the contradiction between adhesion and cohesion
Solution Approach 2:
The multilayer composite structure combines materials with complementary properties: the acrylate PSA layer addresses substrate adhesion requirements while the foam layer with rubber particles addresses cohesive strength and temperature resistance requirements, allowing both adhesion to LSE substrates and high-temperature shear holding to be achieved simultaneously
3Productivity
If multilayer pressure sensitive adhesive assemblies are manufactured by hotmelt process, then manufacturing efficiency improves, but processability deteriorates due to excessive flow
Solution Approach 1:
The patent carefully controls the molecular weight, glass transition temperature, and functional group content of the rubber particles and coupling agents to modify the viscosity-temperature relationship of the adhesive system. This parameter optimization allows the material to maintain adequate viscosity during hotmelt processing (preventing excessive flow) while still enabling efficient manufacturing through the hotmelt process
Data Source
AI summary
The present disclosure relates to a multilayer pressure sensitive adhesive assembly comprising a polymeric foam layer and a first pressure sensitive adhesive layer adjacent to the polymeric foam layer, wherein the polymeric foam comprises: a) a multi-arm block copolymer having the formula Qn-Y, wherein: (i) Q represents an arm of the multi-arm block copolymer and each arm independently has the formula G-R, (ii) n represents the number of arms and is a whole number of at least 3, and (iii) Y is the residue of a multifunctional coupling agent, wherein each R is a rubbery block comprising a polymerized conjugated diene, a hydrogenated derivative of a polymerized conjugated diene, or combinations thereof; and each G is a glassy block comprising a polymerized monovinyl aromatic monomer; b) a polymeric plasticizer having a weight average molecular weight Mw of at least 10.000 g/mol; c) at least one hydrocarbon tackifier, wherein the hydrocarbon tackifier(s) have a Volatile Organic Compound (VOC) value of less than 1000 ppm, when measured by thermogravimetric analysis according to the weight loss test methods described in the experimental section; and d) optionally, a linear block copolymer having the formula L - (G)m, wherein L is a rubbery block comprising a polymerized olefin, a polymerized conjugated diene, a hydrogenated derivative of a polymerized conjugated diene, or any combinations thereof; and wherein m is 1 or 2; and wherein the first pressure sensitive adhesive comprises: a) a linear block copolymer having the formula M - (G)p, wherein M is a rubbery block comprising a polymerized olefin, a polymerized conjugated diene, a hydrogenated derivative of a polymerized conjugated diene, or any combinations thereof; and wherein p is 1 or 2; b) at least one second hydrocarbon tackifier; c) a (meth)acrylate copolymer having a Tg higher than 25°C and a weight average molecular weight (Mw) comprised between 1000 and 100.000 Daltons, and comprising: (i) (meth)acrylic acid ester monomer units having a Tg higher than 25°C when homopolymerized; and (ii) optionally, monofunctional ethylenically unsaturated comonomer units; d) optionally, a multi-arm block copolymer having the formula Sq-Z, wherein: (i) S represents an arm of the multi-arm block copolymer and each arm independently has the formula G-N, (ii) q represents the number of arms and is a whole number of at least 3, and (iii) Z is the residue of a multifunctional coupling agent, wherein each N is a rubbery block comprising a polymerized conjugated diene, a hydrogenated derivative of a polymerized conjugated diene, or combinations thereof; and e) optionally, a diblock copolymer having the formula T - (G), wherein T is a rubbery block comprising a polymerized olefin, a polymerized conjugated diene, a hydrogenated derivative of a polymerized conjugated diene, or any combinations thereof. The present disclosure also relates to a method of manufacturing such a multilayer pressure sensitive adhesive assembly and uses thereof.