UV-Curable Aqueous Emulsion for Plastic Coatings
Solution Overview
Problem
Existing UV-curable aqueous coating compositions for plastics suffer from poor water resistance, hardness, and gloss due to the presence of alkali metal ions, moisture, and lower crosslinking densities, failing to meet the requirements of plastic coating films.
Innovation Solution
A UV-curable aqueous emulsion comprising a urethane reaction product of polycarbonate or polyester polyol, isocyanate, reactive carboxylic acid, UV-curable acrylic oligomer, and acrylic monomer, with a specific ratio of functional groups and additives, is developed, which is then neutralized and mixed with water to create a solventless coating composition with improved properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a water-dispersible urethane acrylate containing alkali metal ions is used to create a UV-curable aqueous coating, then the coating can be applied as an environmentally friendly water-based system, but the film exhibits poor water resistance due to alkali metal ions on the film surface
Solution Approach 1:
The patent removes alkali metal ions from the coating system by using a cation exchange process where ammonium ions replace alkali metal ions during the emulsion preparation stage, preventing their presence in the final film and eliminating the source of poor water resistance
Solution Approach 2:
The patent introduces ammonium ions as an intermediary substance that temporarily occupies the place of alkali metal ions during emulsion formation, allowing the coating to be processed without harmful alkali metals while maintaining water-based formulation benefits
2Object-affected harmful factors
If a dispersant is used to disperse polyester urethane acrylate in water, then the coating can be formulated as an aqueous system, but the film shows poor water resistance, hardness, and gloss due to moisture on the film
Solution Approach 1:
The patent eliminates the need for traditional dispersants by directly incorporating hydrophilic groups into the polyurethane acrylate polymer structure itself, removing the source of moisture retention that plagues dispersant-based systems
Solution Approach 2:
The patent changes the chemical structure of the polymer by incorporating hydrophilic groups directly into the backbone, altering how water interacts with the coating from a moisture-trapping mechanism to a controlled hydrophilic pathway that prevents water accumulation
3Stability of the object's composition
If oligomers with larger molecular weights are used to ensure dispersion stability in water, then the aqueous coating dispersion becomes more stable, but the films have lower crosslinking densities that do not fulfill plastic coating requirements
Solution Approach 1:
The patent uses a mixture of oligomers with different molecular weights and functional group counts (combining smaller oligomers with higher functionality and larger oligomers for stability) to achieve both dispersion stability and sufficient crosslinking density in the final coating film
Solution Approach 2:
The patent creates a composite oligomer system combining multiple oligomer types with complementary properties - smaller oligomers provide high functionality for crosslinking while larger oligomers provide steric stabilization for dispersion stability, achieving both goals simultaneously
4Object-affected harmful factors
If a UV-curable aqueous coating composition is developed to be environmentally friendly, then organic solvent content is reduced, but the coating fails to achieve satisfactory film properties comparable to oil-based UV-curable coatings
Solution Approach 1:
The patent changes the chemical parameters of the polyurethane acrylate by controlling molecular weight, functional group density, and hydrophilic group incorporation to achieve optimal balance between water-based formulation requirements and film performance properties
Solution Approach 2:
The patent employs a composite formulation combining specifically designed polyurethane acrylate oligomers with hydrophilic groups and reactive carboxylic acid groups, creating a material that simultaneously achieves environmental acceptability through water-based formulation and reliable film properties through controlled molecular architecture
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 resulting coating film exhibits enhanced adhesion, pencil hardness, gloss, and resistance to moisture, chemicals, abrasion, and acids, comparable to oil-based UV-curable coatings, while being environmentally friendly and stable.
Implementation Method 1
UV-curable acrylic oligomer, 5 to 20% by weight of a UV-curable acrylic monomer... 0.01 to 1% by weight of a radical polymerization inhibitor... (b) 0.1 to 20% by weight of a urethane-reactive acrylate
Data Source
AI summary
The inventive UV-curable aqueous coating composition is characterized by using a UV-curable aqueous emulsion obtained by urethane reaction with a mixture comprising a poly-carbonate polyol or polyester polyol; an isocyanate compound; a urethane-reactive carboxylic acid; a UV-curable acrylic oligomer having 2 to 9 functional acrylate groups; a UV- curable acrylic monomer; and a urethane-reactive acrylate without an organic solvent. The inventive aqueous composition provides good environmental acceptability and satisfactory film properties comparable to those of the prior oily UV-curable coating composition and thereofore, it is useful for coating various plastics.