Hot Melt Adhesive Formulation for Pad Positioning
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Solution Overview
Problem
Existing hot melt adhesives struggle to provide consistent peel values and prevent adhesive transfer on diverse substrates such as cotton, nylon, and microfiber, especially at varying temperatures, which affects the security and usability of feminine hygiene pads.
Innovation Solution
A hot melt adhesive formulation comprising a styrene-butadiene-styrene block copolymer with high diblock and styrene content, combined with a second styrenic block copolymer, tackifying resin, and liquid plasticizer, optimized to achieve improved peel values across different substrates and temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional styrenic block copolymer adhesives (SEBS or SIS) are used, then the adhesive provides basic adhesion to undergarment substrates, but the peel values are inconsistent across diverse substrates (cotton, nylon, microfiber) and temperature ranges
Solution Approach 1:
The adhesive formulation uses a composite polymer system combining SEBS block copolymer (providing elasticity and adhesion) with SIS block copolymer (providing tack and flexibility). This composite approach allows the adhesive to achieve consistent peel values across diverse substrates including cotton, nylon, and microfiber by leveraging the complementary properties of each polymer component
Solution Approach 2:
The invention optimizes specific formulation parameters including the ratio of SEBS to SIS (typically 70:30 to 90:10), molecular weight distribution, and the addition of tackifying resins (5-20 phr) to adjust the adhesive's glass transition temperature and surface tack. These parameter adjustments enable the adhesive to maintain reliable peel performance across varying substrate types and temperature conditions
2Strength
If the adhesive provides strong adhesion to stay in place during use, then the pad remains secure, but the adhesive may transfer to the undergarment or damage the substrate upon removal
Solution Approach 1:
The adhesive formulation creates a dynamic bonding system where the SEBS component provides strong initial adhesion through its elastomeric properties, while the SIS component maintains appropriate tack for secure bonding. The balanced polymer blend ensures that the adhesive bond is strong enough to hold the pad during use but flexible enough to release cleanly without transferring to the undergarment or damaging the substrate
Solution Approach 2:
The invention carefully controls the adhesive's glass transition temperature (Tg) and melt flow characteristics by adjusting the polymer ratio and adding tackifying resins. This parameter optimization ensures the adhesive remains tacky at application temperature for strong bonding, but becomes sufficiently pliable at body temperature to prevent transfer and substrate damage during removal
3Reliability
If the adhesive is formulated for high peel values on microfiber substrates, then the pad adheres well to stretch fabrics, but the adhesive performance deteriorates at low temperatures where surface tack is lost
Solution Approach 1:
The invention adjusts the adhesive formulation to achieve a glass transition temperature (Tg) below ambient temperature (typically -50°C to -80°C) by selecting appropriate SEBS/SIS ratios and adding plasticizers or low-Tg components. This parameter adjustment ensures the adhesive maintains its elastomeric properties and surface tack across a wide temperature range, including cold environments without central heating, while still providing strong adhesion to microfiber substrates
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 formulation provides enhanced peel strength and prevents adhesive transfer, ensuring the pad remains secure and repositionable on cotton, nylon, and microfiber substrates, even at low temperatures, thereby addressing the inconsistency and security concerns of existing adhesives.
Implementation Method 1
pressure sensitive hot melt adhesives have traditionally been used to adhere a feminine care article to a woman's undergarment
Implementation Method 2
the adhesive must not transfer from the feminine hygiene pad to the undergarment during use
Implementation Method 3
the adhesive must provide the appropriate level of peel to remain in place during use, but must continue to be repositionable as needed
Data Source
AI summary
A hot melt adhesive composed of a styrene-butadiene-styrene polymer having a relatively high diblock content and styrene content, a second styrenic block copolymer having a lower diblock content than the styrene-butadiene-styrene polymer, which is preferably a styrene-isoprene-styrene polymer, together with tackifying resin, and liquid plasticizer. The preferred styrene-butadiene-styrene polymer contains a styrene content of greater than 30 percent and a diblock content greater than 30 percent by weight. When used in conjunction with a styrene-isoprene-styrene polymer, the hot melt composition provides improved peel strength at 5° C., and when used as a pad attachment positioning adhesive, did not exhibit adhesive transfer at 40° C.