Three-Polymer Hot Melt Adhesive for Aging-Stable Bonding
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Solution Overview
Problem
There is a need for olefin-based hot melt adhesive compositions with improved machinability and initial bonding performance that is maintained upon aging, particularly in disposable absorbent articles such as diapers and adult incontinence products.
Innovation Solution
A hot melt adhesive composition comprising a blend of hydrogenated styrenic block copolymer, propylene polymer, ethylene polymer, tackifying agent, and plasticizer, with specific weight percentages and viscosities tailored to enhance bonding performance and machinability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional olefin-based hot melt adhesive compositions are used, then basic bonding function is provided, but machinability is poor and initial bonding performance degrades upon aging
Solution Approach 1:
The patent uses a composite material system consisting of a tri-block copolymer (styrene-ethylene/butylene-styrene) combined with propylene polymer and ethylene polymer. This composite approach allows the adhesive to achieve both improved machinability through the propylene/ethylene components and maintained bonding performance through the styrenic block copolymer, resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The patent optimizes specific parameters including the styrene content (10-45% by weight), butylene content in the mid-block (>50% by weight), and Brookfield viscosity (>15,000 cP at 120°C). These parameter changes enable the adhesive to achieve the desired balance between machinability and bonding performance stability over time.
2Strength
If adhesive composition is formulated for high bonding strength, then initial bonding performance is improved, but viscosity becomes too high for proper machinability
Solution Approach 1:
The patent carefully controls the Brookfield viscosity parameter to be greater than 15,000 cP at 120°C, which provides sufficient bonding strength while maintaining acceptable machinability. This parameter optimization resolves the contradiction between strength and ease of operation.
Solution Approach 2:
The tri-block copolymer blend system allows the adhesive to achieve high bonding strength through the styrenic blocks while the propylene and ethylene components maintain appropriate viscosity characteristics for machinability, thus resolving the contradiction between strength and ease of operation.
3Reliability
If adhesive formulation is simplified, then manufacturing cost is reduced, but bonding performance deteriorates upon aging
Solution Approach 1:
The patent employs a composite material system with three specific polymer components (styrenic block copolymer, propylene polymer, ethylene polymer) in optimized proportions. This composite formulation achieves superior aged bonding performance while maintaining reasonable composition complexity, resolving the contradiction between reliability and device complexity.
Data Source
AI summary
This invention is directed to hot melt adhesive compositions useful for forming disposable absorbent articles that include a three polymer blend, have excellent initial bonding performance, and maintain bonding upon aging.