Modified Isocyanate Mixture Stabilization via Composite Terminator
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Solution Overview
Problem
Existing methods for preparing liquid isocyanates containing carbodiimide (CDI) and/or uretonimine (UTI) groups face challenges with incomplete termination, poor storage stability, especially at low outdoor temperatures, and increased viscosity during high-temperature heating, leading to issues with color number and pressure in storage vessels.
Innovation Solution
A method involving the use of halosilane organic compounds and sulfonic anhydride substances as terminators, which effectively terminate the carbodiimidization reaction, maintaining low viscosity and color stability at both normal and high temperatures, by adding a compounded terminator to the reaction solution containing phospholene catalyst-activated isocyanate groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trimethylsilyl trifluoromethanesulfonate (TMST) is used to terminate the phospholene catalyst, then the catalyst termination effect is achieved, but the storage stability is poor and color number increases rapidly
Solution Approach 1:
The patent uses a composite terminator system comprising both silylated acid (trimethylsilyl trifluoromethanesulfonate) and non-silylated acid (trifluoromethanesulfonic acid or p-toluenesulfonic acid) in specific proportions (molar ratio 1:0.1 to 1:1). This composite approach combines the rapid termination capability of silylated acid with the stability-enhancing and color-control properties of non-silylated acid, resolving the contradiction between termination effectiveness and storage stability with color maintenance.
2Reliability
If silylated acid such as trimethylsilyl trifluoromethanesulfonate is used to terminate the catalyst, then the termination effect is achieved, but the viscosity increases significantly during high temperature heating
Solution Approach 1:
The patent combines silylated acid and non-silylated acid terminators where the non-silylated acid component (trifluoromethanesulfonic acid or p-toluenesulfonic acid) specifically addresses high-temperature stability. This composite system prevents the significant viscosity increase during high-temperature heating that occurs when using silylated acid alone, while maintaining effective catalyst termination.
3Reliability
If the molar equivalent ratio of terminator and catalyst is increased to achieve complete termination, then the stability is improved, but the color number of the product is not ideal
Solution Approach 1:
The patent assigns different functional roles to different terminator components: silylated acid (trimethylsilyl trifluoromethanesulfonate) provides rapid termination at lower ratios, while non-silylated acid (trifluoromethanesulfonic acid or p-toluenesulfonic acid) in controlled proportions (10-50% of total terminator) specifically controls color development. This differentiated functional assignment allows complete termination and stability improvement without excessive color increase.
4Reliability
If acid is used to terminate the catalysis, then the termination effect is achieved, but the termination is not effective enough
Solution Approach 1:
The patent merges two types of acid terminators: silylated acid (trimethylsilyl trifluoromethanesulfonate) which provides rapid and effective catalyst deactivation, and non-silylated acid (trifluoromethanesulfonic acid or p-toluenesulfonic acid) which enhances overall termination effectiveness and stability. The combination achieves complete and effective termination that neither component can achieve alone at equivalent concentrations.
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 modified isocyanate mixture exhibits excellent storage stability at normal temperatures, maintains low NCO content, and shows minimal viscosity change even at high temperatures, with a significantly reduced color number, typically ranging from 20-40 APHA, ensuring stability and performance.
Implementation Method 1
Under certain reaction conditions, the isocyanate is heated and partially converted into carbodiimide and/or uretonimine derivatives, and the preparation method can refer to the methods in US-A-6120699, US-A-2853473 and EP-A-515933. Phospholene catalyst, especially phospholene oxide catalyst, is expected to have high activity, in order to be able to activate the carbodiimidization under mild temperature conditions
Implementation Method 2
In order to terminate the reaction of forming NCO to continuously produce CDI groups and UTI groups, a limited amount of terminator can be added to the reaction solution, thereby deactivating the high-efficiency catalyst. Suitable terminators are mentioned in patent specifications EP-A-515933, CN-A-1721395, US-A-4120884, CN-A-1789241, and CN-A-102718683, including Lewis acids, acyl chlorides, chloroformic acids, aromatic sulfonic acids/esters, silylated acids, alkyl sulfates and halides of main group elements
Implementation Method 3
Isocyanates can form carbodiimide derivatives after releasing CO2 by polycondensation under certain conditions, the carbodiimide group can be adducted with the isocyanate to form the uretonimine group
Implementation Method 4
the carbodiimide group can be adducted with the isocyanate to form the uretonimine group
Data Source
AI summary
Disclosed is a light colored modified isocyanate mixture and a preparation method thereof. The method comprises the following steps: a) reacting isocyanate groups of a raw material isocyanate under the action of a phospholenecatalyst, and finally obtaining a modified isocyanate reaction solution containing carbodiimide and/or uretonimine derivatives; and b) adding a compounded terminator of a halosilane organic and a sulfonic anhydride to the reaction solution obtained in step a so as to terminate the reaction of carbodiimidization. The modified isocyanate prepared by the method has the characteristics of a liquid state at room temperature, being stable in storage at room temperature and high temperature, and low color number.