Propylene-Styrene Hot Melt Adhesive for Elastic Attachment
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Solution Overview
Problem
Existing hot melt adhesives used in disposable absorbent articles, such as diapers and adult incontinence products, face challenges with shear properties, odor, and thermal stability, particularly in elastic attachment and core stabilization applications.
Innovation Solution
A hot melt adhesive composition comprising a propylene-based polymer with a molecular weight of no greater than 75,000 and a hydrogenated styrene block copolymer with a styrene content of no greater than 20%, combined with a polydispersity index of less than 5, and a Melt Flow of no greater than 25 g/10 min, which includes no more than 18% by weight plasticizer, providing improved static peel and creep resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing hot melt adhesives are used for elastic attachment, then bonding is achieved, but shear properties are insufficient and creep resistance is poor
Solution Approach 1:
The patent uses a composite adhesive system combining a propylene-based polymer (first polymer) with a styrene block copolymer (second polymer). This composite formulation leverages the complementary properties of each polymer: the propylene-based polymer provides baseline adhesion and flexibility, while the styrene block copolymer enhances shear strength and creep resistance. The synergistic interaction between these two polymers creates an adhesive composition that simultaneously achieves both improved shear properties and creep resistance.
Solution Approach 2:
The patent optimizes specific parameters of the adhesive composition including the molecular weight of the propylene-based polymer (no greater than 75,000), the styrene content of the block copolymer (no greater than 20%), and the plasticizer content (no greater than 18% by weight). By precisely controlling these parameters, the adhesive achieves optimal balance between shear strength and creep resistance, resolving the technical contradiction through parameter optimization.
2Object-affected harmful factors
If existing hot melt adhesives are used, then bonding is achieved, but odor is excessive
Solution Approach 1:
The patent selects specific polymers with controlled chemical compositions and molecular weights that inherently produce lower odor during application and curing. The propylene-based polymer with Mw ≤ 75,000 and the styrene block copolymer with styrene content ≤ 20% are chosen not only for performance but also for their favorable odor characteristics. Additionally, limiting plasticizer content to ≤ 18% by weight further reduces odor generation, as plasticizers are a common source of volatile organic compounds in hot melt adhesives.
3Stability of the object's composition
If existing hot melt adhesives are used, then bonding is achieved, but thermal stability is insufficient
Solution Approach 1:
The composite adhesive system provides enhanced thermal stability through the synergistic combination of polymers with complementary thermal properties. The propylene-based polymer offers good thermal resistance, while the styrene block copolymer contributes to overall thermal stability. This composite structure maintains adhesive performance across a broader temperature range compared to single-polymer systems, enabling stable bonding during high-temperature processing and application.
Solution Approach 2:
The patent optimizes the molecular weight of the propylene-based polymer (no greater than 75,000) and limits plasticizer content (no greater than 18% by weight) to enhance thermal stability. Lower molecular weight polymers generally exhibit better thermal stability and reduced volatility, while controlled plasticizer levels prevent excessive softening at elevated temperatures, thereby expanding the usable processing temperature range.
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 superior shear properties, low odor, and excellent thermal stability, resulting in enhanced bonding performance, including increased static peel and reduced creep, making it suitable for elastic attachment and core stabilization in disposable absorbent articles.
Implementation Method 1
the adhesive composition bonds the elastic material to the first substrate
Data Source
AI summary
The invention relates to a hot melt adhesive composition comprising: a first polymer that is propylene-based and has a Mw of no greater than about 75,000 and a polydispersity index of less than about 5 and;a second polymer that is a hydrogenated styrene block copolymer with a styrene content of no greater than about 20%, and a Melt Flow when tested according to ASTM 1238 (230°C, 5kg) of no greater than about 25 g/10 min; wherein the adhesive composition contains between 10% by weight and 18% by weight plasticizer.