Microcellular Polyurethane Elastomer Viscosity Control
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Solution Overview
Problem
Conventional methods for preparing polyurethane elastomers using naphthalene diisocyanate result in prepolymers with short shelf life and high viscosity, requiring high-temperature operation, and the addition of other diisocyanates like p-MDI or TDI compromises the properties of the elastomers.
Innovation Solution
A method involving the reaction of naphthalene diisocyanate with a polyol, followed by the introduction of a plasticizer and additional naphthalene diisocyanate to create a prepolymer with an allophanate structure, and the use of an emulsifier to prevent phase separation when mixing with water, optimizing viscosity and shelf life, and enhancing processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NDI is reacted with a polyol to prepare a prepolymer, then the prepolymer has short shelf life and high viscosity, but adding other diisocyanates like p-MDI or TDI deteriorates the properties of the polyurethane elastomer
Solution Approach 1:
The patent introduces an emulsifier comprising a specific compound (a) selected from various diisocyanates and a C2-10 hydrocarbon (b) with two to four hydroxyl groups, where the weight ratio of (a) to (b) is controlled at 1:5 to 1:20. This compositional parameter change optimizes both shelf life and viscosity without compromising elastomer properties, as the specific ratio prevents harmful phase separation while achieving desired rheological properties.
Solution Approach 2:
The patent creates a composite emulsifier system combining compound (a) and compound (b) in a specific weight ratio. This composite approach allows the synergistic effect of both components: compound (a) provides the necessary reactivity and stability, while compound (b) contributes to viscosity reduction and phase compatibility, achieving both improved shelf life and manufacturability without using p-MDI or TDI alone.
2Ease of manufacture
If the prepolymer has high viscosity, then operation requires high temperature of at least 100° C., but this makes it difficult to handle feeds
Solution Approach 1:
By incorporating the emulsifier with compounds (a) and (b) in the specified weight ratio of 1:5 to 1:20, the patent fundamentally changes the rheological parameters of the prepolymer system. This composition modification reduces viscosity to acceptable levels, enabling processing at lower temperatures and improving feed handling without requiring high-temperature operation.
3Stability of the object's composition
If an emulsifier is introduced to optimize viscosity and shelf life, then phase separation of hydrogen-containing composition containing excess water is suppressed, but the emulsifier composition must be precisely controlled
Solution Approach 1:
The patent establishes specific parameter ranges for the emulsifier composition, particularly the weight ratio of compound (a) to compound (b) at 1:5 to 1:20. By defining this precise parameter range, the patent achieves optimal phase stability and prevents water separation while maintaining manageable process complexity. The specified ratios ensure consistent performance without requiring overly complex formulation control.
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 method improves the viscosity and shelf life of the prepolymer, reduces the need for high-temperature processing, and enhances the mechanical and durability properties of the resulting microcellular polyurethane elastomers, making them suitable for applications in helper springs and suspension devices.
Implementation Method 1
reacting naphthalene diisocyanate (NDI) with a polyol to obtain a prepolymer containing an isocyanate (NCO) group
Implementation Method 2
mixing the prepolymer having a terminal free isocyanate (NCO) group obtained in step (ii) with water and an emulsifier and then foaming the prepolymer blend
Implementation Method 3
foaming the prepolymer blend to prepare a polyurethane elastomer
Data Source
AI summary
This invention relates to a method of preparing a microcellular polyurethane elastomer by reacting naphthalene diisocyanate with a polyol to prepare a prepolymer containing an isocyanate (NCO) group, followed by mixing the prepared polyurethane prepolymer with a plasticizer, water, an emulsifier and the like, and then foaming the prepolymer blend to prepare a polyurethane elastomer, wherein the emulsifier is a mixture of (a) a compound selected from the group consisting of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, 1,4′-cyclohexane diisocyanate and mixtures thereof, and (b) a C2-10 hydrocarbon having a molecular weight of 500 or less with two to four hydroxyl groups, or mixtures thereof. The method of the invention can optimize the viscosity and properties of the prepolymer resulting from the reaction of naphthalene diisocyanate with a polyol, thus improving processability.