Hot Melt Adhesive Composition Stabilizing Polymer Phases
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Solution Overview
Problem
Hot melt adhesive compositions face challenges in combining different polymers due to incompatibility, phase separation, and maintaining adhesion at room and cold temperatures, especially when using ethylene vinyl acetate and styrene block copolymers with synthetic waxes.
Innovation Solution
A hot melt adhesive composition comprising an ethylene alpha-olefin copolymer, styrene block copolymer, tackifying agent, and a third polymer such as ethylene vinyl acetate or ethylene n-butyl acrylate, combined with synthetic wax, which ensures homogeneity, fast set time, and strong adhesive bonds at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different types of polymers (ethylene vinyl acetate and styrene block copolymers) are combined in hot melt adhesive composition, then adhesive performance is improved, but phase separation occurs upon aging
Solution Approach 1:
The patent introduces a compatibilizer (block copolymer with specific structure) as an intermediary substance that mediates between ethylene vinyl acetate and styrene block copolymer phases. This compatibilizer contains both ethylene and styrene blocks, allowing it to interface with both polymer phases and prevent phase separation, thus maintaining compositional stability while preserving the adhesive performance benefits of combining different polymers
Solution Approach 2:
The patent creates a multi-component composite adhesive system comprising ethylene vinyl acetate, styrene block copolymer, and a specifically designed block copolymer compatibilizer. This composite formulation leverages the complementary strengths of different polymer types while using the compatibilizer to ensure long-term stability and prevent phase separation during aging
2Reliability
If synthetic waxes are added to hot melt adhesive composition, then bonding properties are improved, but compatibility problems occur with styrene block copolymers and ethylene vinyl acetate
Solution Approach 1:
The block copolymer compatibilizer also serves as a mediator between synthetic waxes and the polymer matrix. The compatibilizer's specific structure allows it to interface with synthetic wax components while maintaining compatibility with both styrene block copolymers and ethylene vinyl acetate, thereby enabling the inclusion of synthetic waxes for improved bonding properties without causing compatibility issues
3Productivity
If fast set time is achieved for high speed packaging operations, then productivity is improved, but adhesion at room temperature may be compromised
Solution Approach 1:
The patent carefully adjusts the compositional parameters and ratios of the polymer components to achieve optimal balance between set time and adhesion. By modifying the proportions of ethylene vinyl acetate, styrene block copolymer, and compatibilizer, the formulation achieves fast set time for high-speed packaging operations while maintaining sufficient adhesion strength at room temperature
Data Source
AI summary
A hot melt adhesive composition that includes a first ethylene alpha-olefin copolymer having a density of no greater than 0.90 grams per cubic centimeter, a second styrene block copolymer, tackifying agent, synthetic wax having a melting point of at least 70 °C and a heat of fusion of at least 200 Joules/gram, and a third polymer selected from the group consisting of ethylene-polar comonomer copolymer derived from at least 90 mole % ethylene and no greater than 10 mole % co-monomer, propylene-alpha-olefin copolymer derived from at least 8 mole % co-monomer, exhibiting a heat of fusion of from at least 5 J/g to no greater than 60 J/g, and having a polydispersity index of no greater than 10, and propylene homopolymer exhibiting a heat of fusion of from at least 5 J/g to no greater than 60 J/g.