Three-Polymer Hotmelt Composition for Blobbing-Free Slot Coating
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Solution Overview
Problem
Existing hotmelt adhesives used in disposable absorbent articles face challenges in high-speed slot coating processes due to material accretion ('blobbing') at the nozzle, leading to line stops and consumer-noticeable defects, particularly when bonding nonwoven substrates, and often require costly tackifiers.
Innovation Solution
A hotmelt composition comprising three polymers with distinct peak molecular weights: a first propylene-ethylene copolymer below 40,000 g/mol, a second above 40,000 g/mol, and a third between 70,000 g/mol and 700,000 g/mol, minimizing tackifier use and preventing blobbing during high-speed slot coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional hotmelt adhesives are used in high-speed slot coating, then bonding of nonwoven substrates is achieved, but material accretion (blobbing) occurs at the nozzle causing line stops and defects
Solution Approach 1:
The patent applies parameter changes by carefully controlling the molecular weight distribution of polyethylene components in the hotmelt adhesive. Specifically, it limits very high molecular weight polyethylene ( VHMP E) to 5-20 wt% and includes medium molecular weight polyethylene (MMWPE) in controlled amounts, creating an optimized molecular weight profile that prevents nozzle accretion while maintaining bonding performance at high speeds
Solution Approach 2:
The patent creates a composite hotmelt adhesive system combining multiple polyethylene components with different molecular weights (VHMP E, MMWPE, and conventional HMWPE) in specific proportions. This composite approach leverages the complementary properties of each component: VHMP E provides initial tack and bonding speed, MMWPE prevents accretion, and HMWPE ensures bond strength, achieving both high productivity and reliability
2Strength
If formulated hotmelt adhesives with tackifiers are used, then bonding performance is improved, but cost increases and formulation complexity increases
Solution Approach 1:
The patent extracts and eliminates tackifiers and other conventional adhesive additives from the hotmelt formulation. Instead of using a complex multi-component system with tackifiers, plasticizers, and waxes, it relies solely on optimized polyethylene polymer components, simplifying the formulation while maintaining or improving bond strength through controlled molecular weight distribution
Solution Approach 2:
The patent changes the fundamental parameter of adhesive chemistry from a complex formulated system requiring multiple additives to a simplified polymer blend system. By optimizing the molecular weight parameters of polyethylene components and their relative proportions, it achieves effective bonding without tackifiers, reducing formulation complexity from multiple chemical components to a controlled polymer mixture
Data Source
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AI summary
A hotmelt composition comprises at least three co-polymers having different peak molecular weight. The hotmelt composition may be formulated with little or no tackifiers. The hotmelt can be used in absorbent articles such as diapers comprising two substrates at least partially attached by the hotmelt composition. The hotmelt provides especially good nonwoven-nonwoven bond and nonwoven-film bond.