Aqueous Polyurethane Coating Reducing MFFT Without Coalescent
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Solution Overview
Problem
The challenge is to reduce the amount of coalescent in aqueous coating compositions containing polyurethane and vinyl polymer while maintaining a specific Minimum Film Formation Temperature (MFFT) and ensuring sufficient stain resistance against substances like ammonia, water, ethanol, coffee, and red wine.
Innovation Solution
An aqueous coating composition comprising polyurethane A, obtained by reacting polyisocyanates with at least two cyclic groups and non-cyclic aliphatic diisocyanates, along with isocyanate-reactive components, which reduces the MFFT without increasing coalescent levels, while maintaining stain resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coalescent is added to reduce MFFT, then film formation temperature is improved, but VOC content and air quality impact worsen
Solution Approach 1:
The invention changes the chemical composition parameters of the polyurethane binder by incorporating specific cyclic diisocyanates (H12MDI, IPDI, TMDI) in controlled amounts (1-60 wt%) alongside aliphatic diisocyanates. This compositional parameter change inherently lowers the MFFT of the coating system without requiring additional coalescent additives, thereby reducing VOC content while maintaining film formation temperature control.
Solution Approach 2:
The invention creates a composite polyurethane binder system combining multiple isocyanate types (cyclic and aliphatic) with specific functional components. This composite material approach achieves synergistic effects where the cyclic diisocyanate segments contribute to lower MFFT while the aliphatic segments maintain stain resistance, eliminating the need for separate coalescent additives.
2Object-generated harmful factors
If coalescent amount is reduced, then VOC content is improved, but stain resistance worsens
Solution Approach 1:
The invention modifies the polyurethane binder's chemical structure by incorporating cyclic diisocyanate segments that inherently provide low MFFT properties. This parameter change in the binder composition allows the coating to achieve proper film formation and maintain stain resistance against ammonia, water, ethanol, coffee, and red wine without relying on coalescent additives.
Solution Approach 2:
The polyurethane binder serves multiple functions simultaneously: it provides structural integrity, controls MFFT through its cyclic diisocyanate content, and maintains stain resistance. The binder essentially serves itself by incorporating the necessary functional segments, eliminating the need for separate coalescent and stain-resistant additive systems.
3Temperature
If cyclic diisocyanate content is increased, then MFFT is reduced, but manufacturing complexity worsens
Solution Approach 1:
The invention establishes specific parameter ranges for cyclic diisocyanate content (1-60 wt% of total isocyanate) and defines clear compositional relationships between different isocyanate types. These standardized parameter specifications simplify the formulation process and make the manufacturing process controllable and reproducible, despite the multi-component nature of the system.
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 solution effectively lowers the MFFT to below 50°C, even below 5°C, with a reduced amount of coalescent, and maintains stain resistance, addressing VOC and air quality concerns by minimizing coalescent usage.
Implementation Method 1
reacting a polyisocyanate and isocyanate-reactive compound to form a polyurethane pre-polymer
Implementation Method 2
the MFFT of a coating composition can be reduced by the presence of coalescents
Data Source
AI summary
The present invention relates to an aqueous coating composition comprising polyurethane A and vinyl polymer, wherein the polyurethane A comprises as building blocks at least: (a) a polyisocyanate(s) containing at least two cyclic groups, (b) a non-cyclic aliphatic diisocyanate(s) whereby the non-cyclic aliphatic group connecting the two isocyanate groups has from 4 to 36 carbon atoms, and (c) a component(s) containing an isocyanate-reactive group(s), whereby the summed amount of (a) and (b) is 10 to 60 wt. %, relative to the total weight amount of components used to prepare the polyurethane A; and whereby the weight ratio between (a) and (b) is in the range from 50:50 to 99:1.