Low Basis Weight Substrate Adhesive Bonding
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Solution Overview
Problem
Conventional hot-melt adhesives, including low application temperature adhesives, face issues with thermal damage to substrates, adhesive bleed-through in low basis weight substrates, and unsuitable shear viscosity across varying manufacturing process conditions, leading to cosmetic defects and reduced bond strength.
Innovation Solution
A disposable absorbent article using a low basis weight substrate and a low application temperature adhesive with specific shear viscosity characteristics, formulated with block copolymers, waxes, tackifying resins, and plasticizing oils, applied using a slot-coater type adhesive applicator to maintain consistent adhesive flow and prevent contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional hot-melt adhesives are applied at high temperatures (above 130°C), then adhesive strength and bond strength are improved, but thermal damage to the substrate occurs
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition of the adhesive system. It uses a two-component adhesive system consisting of a carboxyl-terminated polybutadiene (CTPB) and a polyfunctional isocyanate crosslinking agent. The chemical reaction between these components creates a crosslinked network that provides strong adhesion at lower temperatures (below 130°C), eliminating thermal damage while maintaining bond strength. This transforms the adhesive from a temperature-dependent physical bond to a chemically crosslinked bond.
2Object-affected harmful factors
If low application temperature adhesives are used (below 130°C), then thermal damage to substrate is reduced, but adhesive bleed-through occurs in low basis weight substrates
Solution Approach 1:
The patent employs composite materials by creating a crosslinked adhesive network through the chemical reaction between CTPB and polyfunctional isocyanate. This composite adhesive system combines the low-temperature application benefits with enhanced viscosity and cohesion properties that prevent bleed-through. The crosslinked structure provides a balanced formulation that adheres well to low basis weight substrates without penetrating through them.
3Ease of manufacture
If conventional hot-melt adhesives are used, then ease of manufacture is improved, but unsuitable shear viscosity across varying process conditions occurs
Solution Approach 1:
The patent applies dynamics by formulating an adhesive system that adapts its viscosity characteristics to varying shear rates and process conditions. The crosslinked polyurethane network provides shear-thinning behavior and maintains appropriate flow properties during application, then develops full strength upon curing. This dynamic response ensures reliable performance across different manufacturing speeds and application methods.
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 solution provides a disposable absorbent article with improved adhesive bond strength, reduced bleed-through, and suitable shear viscosity across a range of process conditions, minimizing thermal damage and contamination, while maintaining cost-effectiveness and consumer benefits.
Implementation Method 1
it is known that an increase in shear rate (e.g., due to a corresponding increase in the pressure applied to the adhesive in the adhesive applicator) may cause a phenomenon in certain fluids known as shear thinning (i.e., a decrease in shear viscosity)
Implementation Method 2
Conventional hot-melt adhesives are typically liquefied, for example, using a hot-melt tank and subsequently transported via a pump to the point of application
Data Source
AI summary
A disposable absorbent article that includes a first and second substrate, a portion of which is joined together with a hot-melt adhesive applied at a temperature of less than 130° C. At least one of the first second substrates has a basis weight of less than 15 grams per square meter. The adhesive provides suitable bond strength on low basis weight substrates and allows for flexible processing conditions.