S-I/B-S Block Copolymer Hot Melt Adhesive Creep Resistance
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Solution Overview
Problem
Current hot melt adhesives lack effective bonding properties for certain substrates and applications, particularly in elastic attachment and laminate construction, requiring adhesives with controllable viscosity, long open time, and high creep resistance to maintain mechanical integrity under stress.
Innovation Solution
A hot melt adhesive composition using polystyrene-(polyisoprene-co-butadiene)-polystyrene block copolymers with a styrene content of at least 25 wt% and a diblock percentage of less than 25%, combined with a second thermoplastic elastomer, tackifying resin, and optional additives like wax and liquid plasticizer, to provide enhanced cohesive strength and creep performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hot melt adhesives are used for elastic attachment applications, then the adhesive can be applied to substrates, but the adhesive lacks sufficient creep resistance to prevent elastic materials from moving or detaching under stress
Solution Approach 1:
The patent uses a composite adhesive formulation combining S-I/B-S block copolymer with specific diblock content (less than 25%), tackifying resin, and plasticizer. This composite material approach allows the adhesive to simultaneously achieve high creep resistance and bond strength by leveraging the complementary properties of each component: the block copolymer provides elasticity and creep resistance, while the tackifying resin enhances initial bonding strength.
2Strength
If hot melt adhesive is applied to bond substrates, then the adhesive can join materials together, but the adhesive layer lacks sufficient mechanical integrity to maintain bond strength under stress
Solution Approach 1:
The patent optimizes specific parameters of the S-I/B-S block copolymer, namely the diblock percentage (less than 25%) and styrene content (at least 25%), to achieve the desired balance between mechanical integrity and bond stability. By precisely controlling these compositional parameters, the adhesive maintains its structural integrity under stress while ensuring reliable, stable bonding performance in elastic attachment applications.
3Adaptability or versatility
If a single adhesive is used for both lamination and elastic bonding, then the adhesive formulation becomes more versatile, but the adhesive cannot simultaneously optimize properties for both construction and elastic attachment applications
Solution Approach 1:
The patent develops a multi-functional adhesive based on S-I/B-S block copolymer that can perform both lamination and elastic attachment functions. The specific formulation with controlled diblock content (less than 25%) provides the dual capability: sufficient viscosity control for lamination applications and adequate creep resistance for elastic bonding, making a single adhesive suitable for multiple functions that previously required separate adhesive systems.
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 adhesive composition exhibits excellent bond strength and creep performance, making it suitable for elastic attachment and laminate applications, such as in disposable absorbent garments, with improved mechanical integrity and flexibility.
Implementation Method 1
The block copolymers have an endblock styrene content of at least 25 wt % and a diblock percentage of less than 25 %. The mid-block is formed by randomly polymerized isoprene and butadiene.
Implementation Method 2
These compositions are described as pressure sensitive adhesive compositions for adhesive tapes or sheets or for use as sealants
Implementation Method 3
to bond elastic materials to substrates, a different adhesive which exhibits high creep resistance to ensure that the elastic, when under stress, does not move relative to the surfaces of the substrates
Data Source
AI summary
Hot melt adhesive compositions containing a polystyrene-polyisoprene/polybutadiene-polystyrene block copolymer and its use in the manufacture of disposable absorbent articles. The adhesive comprises a thermoplastic polystyrene-polyisoprene/polybutadiene- polystyrene block copolymer having a styrene content of at least 25 wt % and a diblock percentage of less than 30 %, a second thermoplastic block copolymer and a tackifier.