Isocyanate Composition Tuning for Low-Yellowing Polyurethane Elastomers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing polyurethane elastomers using NDI, PPDI, and CHDI isocyanates suffer from high reactivity leading to color increase and poor weather resistance, affecting appearance and product quality.
Innovation Solution
An isocyanate composition with a controlled effective factor ranging from 3.80 to 5.30, incorporating chlorine-containing substances, is designed to inhibit color change and enhance weather resistance and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high melting point isocyanates (NDI, PPDI, CHDI) are used to improve heat resistance and mechanical properties, then the polyurethane elastomer achieves high hardness, good resilience, and excellent dynamic performance, but the high reactivity of NCO groups causes color increase and poor weather resistance
Solution Approach 1:
The patent introduces a new parameter 'effective factor E' ranging from 3.80 to 5.30 to characterize and control the reactivity of isocyanate groups. By adjusting this parameter through blending different isocyanates (NDI, PPDI, CHDI, MDI, TDI) in specific ratios, the patent optimizes both mechanical properties and weather resistance, resolving the contradiction between high reactivity (needed for strength) and excessive reactivity (causing yellowing).
Solution Approach 2:
The patent creates a composite isocyanate system by combining multiple isocyanate types (aromatic NDI/PPDI/CHDI for mechanical strength and aliphatic MDI/TDI for weather resistance) in controlled proportions based on the effective factor E. This composite approach allows the final polyurethane elastomer to simultaneously achieve high tensile strength, elongation, and color stability that cannot be obtained with single isocyanate types.
2Strength
If aromatic isocyanates (NDI, PPDI) are used to achieve high hardness and good resilience, then the elastomer performs well in high dynamic load scenarios, but the aromatic structures cause significant steric hindrance and lead to obvious yellowing
Solution Approach 1:
The patent merges aromatic isocyanates (NDI, PPDI, CHDI) which provide high hardness and resilience with aliphatic isocyanates (MDI, TDI) which provide color stability. The specific blending ratios controlled by effective factor E ensure that the aromatic components contribute mechanical strength while the aliphatic components suppress yellowing, achieving a synergistic effect that resolves the contradiction between hardness and color stability.
3Productivity
If the NCO group reactivity is increased to improve polymerization efficiency, then the production process is accelerated, but the color increase and weather resistance deteriorate
Solution Approach 1:
The patent uses the effective factor E (3.80-5.30) as a controlled parameter to adjust NCO group reactivity to an optimal level. This parameter optimization ensures sufficiently fast polymerization efficiency for industrial production while preventing excessive reactivity that would cause color increase and poor weather resistance, thus resolving the contradiction between productivity and product quality.
Data Source
AI summary
Disclosed in the present invention are an isocyanate composition, a modified composition, and a polyurethane elastomer, the isocyanate composition having an effective factor of 3.80-5.30. By means of designing and controlling the effective factor, the isocyanate composition has excellent reaction activity and thus can be used for preparing high-performance polyurethane products. The isocyanate composition can improve stability of polyurethane products, and particularly, can remarkably improve resistance to color changes and weather resistance of polyurethane elastomers, suppress increases of color codes and yellowing under humid and hot conditions, and improve the tensile strength and tearing strength of polyurethane elastomers, such that the polyurethane elastomers have excellent comprehensive performance in the areas such as weather resistance, stability and mechanical properties.