Polyurethane Adhesive Hydrogen Bonding Heat Seal Strength
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Solution Overview
Problem
Conventional two-component polyurethane-based laminating adhesives often exhibit suboptimal bond strength and heat seal strength after heat treatment, which is a limitation in various laminating applications such as food packaging.
Innovation Solution
A two-component polyurethane adhesive composition comprising an aromatic polyisocyanate component with an average NCO functionality of at least 2.8 and a polyol component with specific OH functionality and acid value, including a polyol with hydrogen-bridging groups, is used, with a weight ratio of polyol to polyisocyanate ranging from 100:15 to 100:40, enhancing the adhesive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional two-component polyurethane-based laminating adhesives are used, then the adhesive provides initial bond and final bond strength, but the bond strength and heat seal strength after heat treatment are not as good as expected
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive system by introducing a polyol component with hydrogen-bridging groups (such as carboxylic acid groups) and specific molecular weight ranges. This parameter change enables the adhesive to form strong hydrogen bonds with polyester and polyethylene terephthalate substrates, significantly improving heat seal strength and bond strength after heat treatment while maintaining initial adhesion.
2Ease of operation
If solvents are added to reduce viscosity for application purposes, then the adhesive offers high initial bonds, but the bond strength and heat seal strength after heat treatment deteriorate
Solution Approach 1:
The patent achieves the desired viscosity for application by controlling the molecular weight and functionality parameters of the polyol components rather than relying on solvent addition. The specific polyol composition (with OH functionality of 1.8-3.0 and acid value of 20-200 mg KOH/g) provides optimal flow characteristics for application while maintaining the ability to form strong hydrogen bonds after heat treatment, thus improving both heat seal strength and bond strength without the negative effects of solvents.
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 described adhesive composition demonstrates improved bond strength and heat seal strength, particularly after heat treatment, as evidenced by increased performance in laminate testing, including boil-in-bag resistance, indicating enhanced durability and reliability in laminating applications.
Implementation Method 1
a polyol component comprising at least one polyester polyol and a polyol having two or more OH groups and a hydrogen-bridging group
Data Source
AI summary
The present disclosure provides a two-component polyurethane adhesive composition comprising an aromatic polyisocyanate component and a polyol component comprising at least one polyester polyol and a polyol having two or more OH groups and a hydrogen-bridging group.