Polyurethane Elastomer Moldings via High-Pressure Countercurrent Process
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Solution Overview
Problem
Current methods for producing polyurethane elastomer moldings with Shore D hardness 60 or more face challenges such as poor mechanical properties, surface defects, and inefficiencies in filling complex molds, particularly due to high viscosity and the need for release agents and emulsifiers.
Innovation Solution
A process involving the mixing of polyesterdiol with a specific OH number, a chain extender, isocyanate prepolymers, and optional catalysts and additives, with a weight ratio of 70:30 to 40:60, is used to create a reaction mixture that is then hardened in a mold using a high-pressure process, eliminating the need for release agents and emulsifiers, and allowing for the production of compact, high-strength polyurethane elastomer moldings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the high-pressure process is used to fill complex molds rapidly, then productivity and mold filling efficiency are improved, but the mechanical properties and surface quality of moldings with hardness 60 Shore D or more deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the polyol component by specifying precise OH number ranges (20-100 mg KOH/g for polyesterdiol, 20-200 mg KOH/g for polyesterol) and functionality ranges (1.95-2.2). These parameter changes optimize the reaction mixture's viscosity and reactivity, enabling the high-pressure process to produce moldings with both excellent mechanical properties and surface quality at hardness 60 Shore D or more
Solution Approach 2:
The patent creates a composite chemical system by combining specific polyesterdiol (a), chain extender (b), and isocyanate prepolymers (c) in defined weight ratios. This composite material approach ensures proper phase compatibility and reaction kinetics, allowing the high-pressure process to achieve both rapid mold filling and high-quality mechanical properties without the defects associated with conventional formulations
2Strength
If polytetrahydrofuran is used as the polyol component, then the polyurethane elastomer achieves adequate mechanical properties, but the polyol demixes at room temperature requiring emulsifier, and the isocyanate component becomes unstable and susceptible to phase-separation
Solution Approach 1:
The patent extracts polytetrahydrofuran from the polyol component formulation and replaces it with polyesterdiol having specific OH numbers and functionalities. This extraction eliminates the phase separation and stability problems associated with polytetrahowrifuran while maintaining the desired mechanical properties through the carefully selected polyesterdiol and chain extender combination
Solution Approach 2:
The patent replaces expensive polytetrahydrofuran with more stable and cost-effective polyesterdiol components. The new formulation achieves better long-term stability and eliminates the need for emulsifiers and release agents, making the system more economically viable while improving compositional stability
3Ease of manufacture
If the low-pressure process is used with simple molds, then cost-effective production is achieved, but the conveying pressure and rate are insufficient to fill complex, large-volume closed molds
Solution Approach 1:
The patent optimizes the reaction mixture parameters by controlling the OH numbers and functionalities of the polyol components, which results in optimal viscosity and reactivity characteristics. These parameter changes enable the mixture to be successfully processed by the high-pressure countercurrent method, allowing filling of complex, large-volume molds while maintaining cost-effectiveness
4Shape
If catalyst is selected to retain low viscosity for long period to fill large moldings, then complex molds can be filled, but the hardening time increases resulting in uneconomic production
Solution Approach 1:
The patent changes the chemical parameters of the reaction mixture by selecting polyesterdiol and polyesterol with specific OH numbers and functionalities, and by using defined chain extenders. These parameter changes optimize the reaction kinetics and viscosity profile, enabling the system to fill complex molds rapidly with high-pressure conveying while maintaining short hardening times for economical production
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
This process results in polyurethane elastomer moldings with excellent surface properties, improved mechanical strength, and the ability to fill complex molds efficiently, while reducing production costs by omitting expensive raw materials and agents, and enhancing the heat distortion temperature and surface quality.
Implementation Method 1
mixing (a) polyesterdiol with OH number from 20 to 100 mg KOH/g and (b) chain extender composed of diol with molar mass below 300 g/mol, with (c) isocyanate prepolymers obtainable via reaction of diisocyanate with polyesterols
Implementation Method 2
production of compact elastomer moldings by the high-pressure countercurrent process
Data Source
AI summary
In a process for the production of pore-free polyurethane elastomer moldings with Shore D hardness of at least 60 in accordance with DIN 53505, (a) polyesterdiol with OH number from 20 to 100 mg KOH/g and (b) a chain extender composed of diol with molar mass below 300 g/mol, is mixed with (c) isocyanate prepolymers obtainable via reaction of diisocyanate with polyesterols with functionality from 1.95 to 2.2 and with OH number from 20 to 200 mg KOH/g to form a reaction mixture. The reaction mixture is charged to a mold and hardened to form the polyurethane elastomer. Polyurethane elastomer moldings are thus obtainable by this process, and these polyurethane moldings may be used as cladding component for commercial vehicles, bodywork component in vehicle construction, or a cladding component of a machine installation.