Blocked Isocyanate Composition for Low-Temperature Curing
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Solution Overview
Problem
Conventional blocked isocyanates face challenges in achieving significant temperature reduction for removing the blocking agent, leading to limited applications and poor water resistance, especially in water-based coatings.
Innovation Solution
A blocked isocyanate is developed using a silicon-substituted alcohol as a blocking agent, which forms a β-silyl cation, allowing for removal at a lower temperature and ensuring excellent water resistance, with the blocking agent decomposing into a volatile aprotic compound, thus avoiding residue issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aliphatic alcohol is used as a blocking agent, then water resistance is improved, but removal temperature increases to near 200°C
Solution Approach 1:
The invention changes the chemical structure of the blocking agent by introducing a silicon atom with specific substituents (formula 1), which fundamentally alters the removal mechanism. The silicon-substituted alcohol can be removed at 120-180°C through formation of a volatile aprotic compound, compared to near 200°C for conventional aliphatic alcohols, while maintaining excellent water resistance.
Solution Approach 2:
The blocking agent combines silicon atom, organic groups, and hydroxyl group in a specific composite structure (formula 1). This composite structure provides both the water resistance of aliphatic alcohols and the low-temperature removal capability through the unique silicon-based chemistry that forms volatile decomposition products.
2Stability of the object's composition
If conventional blocking agents are used, then blocking stability is improved, but application versatility deteriorates due to high removal temperature requirements
Solution Approach 1:
The invention changes the chemical parameters of the blocking agent to achieve optimal balance. The silicon-substituted alcohol structure (formula 1) provides sufficient blocking stability while enabling removal at 120-180°C, expanding applications to include water-based coatings and systems requiring lower processing temperatures.
Solution Approach 2:
The blocking agent introduces local silicon-based functionality with specific organic substituents that provide the right balance of stability and removability. The silicon atom with its specific substituents creates a localized chemical environment that maintains blocking effectiveness while enabling low-temperature removal through volatile compound formation.
3Temperature
If oxime is used as a blocking agent, then removal temperature is reduced, but water resistance deteriorates due to hydrolysis
Solution Approach 1:
The invention changes the chemical composition from oxime to silicon-substituted alcohol structure (formula 1). This fundamental parameter change eliminates the hydrolysis susceptibility of oximes while maintaining low removal temperature (120-180°C) through the silicon-based volatile compound formation mechanism, achieving both low temperature removal and excellent water resistance.
Solution Approach 2:
The blocking agent is designed as a temporary component that is easily removed after serving its protective function. The silicon-substituted alcohol structure decomposes into volatile aprotic compounds at 120-180°C, leaving no harmful residues, similar to how oximes are easily removed but without their water resistance drawbacks.
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 silicon-substituted alcohol-based blocked isocyanate provides water resistance comparable to aliphatic alcohol-blocked isocyanates while being removable at a significantly lower temperature, enabling use in water-based coatings and curing at a relatively low temperature.
Implementation Method 1
the blocking agent is an organic silicon alcohol having an organic group bonded to a silicon atom, and said organic group is capable of forming a β-silyl cation together with the silicon atom
Implementation Method 2
the blocking agent decomposes into a volatile aprotic compound, thus avoiding residue issues
Data Source
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AI summary
One of the purposes of the present invention is to provide a blocking agent for blocking an isocyanate group to, thereby, prepare an isocyanate compound which has excellent water resistance and is reacted with another polymerizable compound to be cured at a relatively low temperature; another purpose is to provide a blocked isocyanate having an isocyanate group blocked with the blocking agent. The present invention provides a blocking agent for blocking an isocyanate group, wherein the blocking agent is an organic silicon alcohol having an organic group bonded to a silicon atom, and said organic group is capable of forming a β-silyl cation together with the silicon atom. In a preferred embodiment, the present invention provides a blocking agent which is an organic silicon alcohol represented by the general formula (1). In the formula (1), R1 is an alkylene group having 3 to 5 carbon atoms and may have a substituent, provided that the number of carbon atoms of the substituent is not included in the number of the carbon atoms of the alkylene group; R2 is an alkyl group having 1 to 10 carbon atoms; Z is an organic group capable of forming a β-silyl cation together with the silicon atom to which Z bonds; and n is an integer of 1 to 3. The present invention further provides a blocked isocyanate having a structure in which the isocyanate group is blocked with the aforesaid blocking agent, and a thermosetting composition comprising the blocked isocyanate.