Aqueous Coating Composition Sagging Prevention
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Solution Overview
Problem
Conventional aqueous coating compositions for large and thick articles, such as railroad vehicles, face challenges in coating workability and finished appearance due to environmental conditions like temperature and humidity, leading to sagging and poor film quality.
Innovation Solution
An aqueous coating composition comprising an aqueous acrylic resin dispersion, aqueous polyolefin wax dispersion, and a water-dispersible polyisocyanate, with specific solubility and boiling point characteristics, along with an organic solvent, to form a two-component curing system that ensures good coating workability and appearance under varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a normal temperature film-forming type coating composition is used for large and thick articles, then thermal curing is avoided, but coating workability and finished appearance deteriorate under varying environmental conditions
Solution Approach 1:
The patent modifies the chemical composition parameters of the coating system by introducing a two-component curing mechanism involving polyisocyanate and hydroxyl-containing resin. This chemical parameter change enables the coating to cure at normal temperatures while maintaining film quality, resolving the contradiction between avoiding thermal curing and ensuring coating precision.
Solution Approach 2:
The patent creates a composite coating system combining multiple components: polyisocyanate curing agent, hydroxyl-containing resin, water-soluble organic solvent, and water. This composite material approach allows the coating to achieve both normal temperature curing and high film quality by leveraging the synergistic effects of different materials.
2Object-affected harmful factors
If water is used as the sole solvent in aqueous coating composition, then environmental friendliness is improved, but coating workability deteriorates under low temperature and high humidity conditions due to slow evaporation
Solution Approach 1:
The patent changes the solvent composition parameters by introducing water-soluble organic solvents with specific boiling points (150-230°C) and solubility characteristics. This parameter modification allows the coating to maintain environmental friendliness while improving evaporation characteristics and coating workability under various environmental conditions.
Solution Approach 2:
The patent uses water-soluble organic solvents as intermediary substances between water and the coating resins. These intermediaries improve the overall evaporation rate and coating flow characteristics without compromising the environmentally friendly nature of the aqueous-based system.
3Use of energy by moving object
If the coating composition cures at normal temperature, then energy consumption is reduced, but coating film formation becomes sensitive to environmental conditions like temperature and humidity
Solution Approach 1:
The patent develops a composite two-component system where polyisocyanate reacts with hydroxyl-containing resin to form crosslinked coating films. This composite chemical system provides reliable and stable coating performance at normal temperatures by creating a robust crosslinked network structure that is less sensitive to environmental variations.
Solution Approach 2:
The patent optimizes the chemical parameters of the curing system by selecting specific polyisocyanate and hydroxyl-containing resin combinations with controlled reactivity. This parameter optimization ensures consistent coating film formation across varying environmental conditions while maintaining normal temperature curing and low energy consumption.
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 composition effectively prevents sagging and maintains high coating film quality, achieving superior workability and appearance even under diverse environmental conditions, including high temperature and high humidity.
Implementation Method 1
a water-dispersible polyisocyanate (C)... The coating composition is to form a coating film by a curing reaction between isocyanate group and hydroxyl group or the like
Implementation Method 2
the changes in the environment such as ambient temperature or humidity. For example, under low temperature and/or high humidity conditions, sagging of the applied coating composition occurred because of the slow evaporation rate of water as a solvent
Data Source
AI summary
The challenge of the present invention is to provide an aqueous coating composition having good coating workability and good finished appearance. The aqueous coating composition of the present invention is an aqueous coating composition including an aqueous base component (I) and a water-dispersible curing agent (II), wherein the aqueous base component (I) includes an aqueous acrylic resin dispersion (A) and an aqueous polyolefin wax dispersion (B), wherein the water-dispersible curing agent (II) includes a water-dispersible polyisocyanate (C), wherein at least one of the aqueous base component (I) and the water-dispersible curing agent (II) includes an organic solvent (D) having a solubility in water at 20°C of 0.5 to 10 g/100gH2O, wherein the aqueous acrylic resin dispersion (A) has a hydroxyl value in the range of 5 to 200 mgKOH/g, wherein an acid value in the range of 5 to 100 mgKOH/g, and wherein a number-average molecular weight in the range of 1,000 to 100,000, and the aqueous polyolefin wax dispersion (B) has an average particle diameter in the range of 50 to 1,000 nm.