Laminating Adhesive Composition with Low Monomer Content
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current laminating adhesive compositions using prepolymers of TDI, MDI, and aliphatic isocyanates have slow Primary Aromatic Amine (PAA) decay rates due to lower reactivity, and excess MDI monomers prolong curing times, making it difficult to achieve a balance between PAA decay rate and reasonable curing times.
Innovation Solution
A laminating adhesive composition comprising a first prepolymer from methylene diphenyl diisocyanate and a polyol, and a second prepolymer with less than 0.1 weight percent free isocyanate monomers, which are combined to create a solvent-free adhesive with improved PAA decay rates and curing times, optionally including additional additives like surfactants and fillers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aliphatic isocyanates are used to achieve fast PAA decay, then PAA decay rate is improved, but curing time increases
Solution Approach 1:
The invention changes the chemical composition parameters by using specific ratios of MDI prepolymer (with 5-20% free monomer) combined with aliphatic isocyanate prepolymer, adjusting the NCO:OH ratio (0.9:1.1 to 1.1:0.9), and controlling molecular weights (1000-10000 for MDI prepolymer, 500-5000 for aliphatic prepolymer) to achieve both fast PAA decay and reasonable curing times
Solution Approach 2:
The invention creates a composite adhesive system combining two different prepolymer types (MDI-based and aliphatic isocyanate-based) with complementary properties, where the MDI prepolymer provides fast PAA decay while the aliphatic prepolymer contributes to acceptable curing time and flexibility
2Ease of operation
If excess MDI monomers are added to lower viscosity, then ease of operation is improved, but PAA decay rate decreases
Solution Approach 1:
The invention optimizes the free monomer content parameter to a specific range (5-20% of total isocyanate groups as free MDI monomer) rather than using excess monomers, which maintains adequate viscosity for standard laminating machines while preserving fast PAA decay characteristics
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 achieves a balanced PAA decay rate of 1 to 3 days while maintaining reasonable curing times, suitable for flexible packaging, including fresh food and dairy products, and demonstrates improved bond strength and thermal stability.
Implementation Method 1
a first prepolymer comprising the reaction product of a methylene diphenyl diisocyanate and a polyol and b) a second prepolymer comprising the reaction product of an isocyanate and a second polyol
Data Source
AI summary
The instant invention provides a laminating adhesive composition and laminates for flexible packaging made therefrom. The laminating adhesive composition according to the present invention comprises a) a first prepolymer comprising the reaction product of a methylene diphenyl diisocyanate and a first polyol and b) a second prepolymer comprising the reaction product of an isocyanate and a second polyol, wherein the second prepolymer has less than 0.1 weight percent of free isocyanate monomers.