Low Temperature Hot Melt Adhesive for Elastic Substrates
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Solution Overview
Problem
Hot melt adhesives used in the diaper industry face challenges in applying elastic components at low temperatures to avoid damaging heat-sensitive substrates and to reduce energy costs, while maintaining high bond strength and creep resistance, as existing solutions either compromise on cohesion or are not practical for industrial application.
Innovation Solution
A hot melt adhesive composition using styrene block copolymers with high softening point mid-block tackifying resins and low to medium softening point aromatic tackifying resins, applied at temperatures below 150°C, achieving low viscosity and high bond retention with mechanical and thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hot melt adhesive is applied at high temperature (≥150°C), then good bond strength and cohesion are achieved, but heat-sensitive substrates are damaged and energy consumption increases
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive system by incorporating specific plasticizers (glycol benzoates, polyether polyols) in controlled amounts (5-35% and 0-20% respectively) along with styrene block copolymers and tackifying resins. This compositional parameter change enables the adhesive to achieve adequate bond strength at lower application temperatures (100-150°C), thereby preventing substrate damage while maintaining bonding performance.
Solution Approach 2:
The patent creates a composite adhesive system combining multiple material components: styrene block copolymers (providing elastic properties and adhesion), midblock and endblock tackifying resins (providing cohesion and tack), and specific plasticizers (improving processability and lowering application temperature). This composite material approach allows the adhesive to function effectively at reduced temperatures without sacrificing bond strength.
2Reliability
If hot melt adhesive is applied at high temperature, then proper wet-out and adhesion are achieved, but energy cost increases and safety hazards arise
Solution Approach 1:
The patent modifies the rheological and thermal parameters of the adhesive by incorporating plasticizers that lower the glass transition temperature and melting point of the system. This parameter change enables the adhesive to achieve proper wet-out and adhesion at lower temperatures (100-150°C), reducing energy consumption while maintaining reliable bonding performance.
3Temperature
If adhesive viscosity is reduced to enable low temperature application, then application temperature is lowered, but cohesion and bond retention are compromised
Solution Approach 1:
The patent employs a composite formulation where styrene block copolymers provide the base adhesive matrix, midblock tackifying resins (with softening point ≥110°C) provide cohesion and high-temperature stability, and plasticizers provide low-temperature processability. This composite structure allows the adhesive to maintain adequate viscosity for cohesion while remaining applicible at lower temperatures.
Solution Approach 2:
The patent assigns different functional qualities to different components: the styrene block copolymer provides adhesion to substrates, the midblock tackifying resin provides internal cohesion and structural integrity, and the plasticizer provides low-temperature flow characteristics. This local quality differentiation allows the overall system to achieve both low application temperature and maintained cohesion.
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 allows for effective elastic attachment in diaper structures with bond retention exceeding 60% after two days and 50% after one week at elevated temperatures, while being processed at lower temperatures to prevent substrate damage and reduce energy consumption.
Implementation Method 1
hot melt adhesive composition... applied at temperatures below 150°C
Implementation Method 2
the viscosity of the composition is equal to or less than about 20,000 mPa·s at 120°C
Implementation Method 3
bond retention exceeding 60% after two days and 50% after one week... initial bond resistance
Data Source
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AI summary
A hot melt adhesive composition, comprising a blend of components including about 10% to about 40% by weight of an elastomeric block copolymer, preferably styrene-isoprene-styrene (SIS) or styrene-butadiene-styrene (SBS), about 15% to about 70% by weight of a first midblock tackifying resin having a softening point of at least about 110°C and having an aromatic content of at least about 1.5% by weight; about 0 to 55% of second midblock tackifying resin, about 5% to about 35% by weight of a plasticizer; and about 0% to about 20% by weight of an end block resin having a softening point lower than 125°C; wherein the components total 100% by weight of the composition, the viscosity of the composition is equal to or less than about 20,000 mPa.s at 12O°C, and is applied at a temperature lower that 150°C and initial bond retention of the composition on elastic strands is at least about 60%. Also, the elastic modulus G' of the composition is higher than about 5000 Pa, the vicous modules G" is higher than about 50 Pa, and the tan delta value is between about 0.5 and about 60. Laminates, especially those used in disposable soft goods, and methods of making such laminates are also described. The adhesive composition and/or laminate may be used in making a variety of end products such as a disposable diaper, a sanitary napkin, a bed pad, a bandage, a surgical drape, a tape, a label, a plastic sheet, a nonwoven sheet, a paper sheet, a cardboard, a book, a filter, or a package.