Aqueous EVOH Dispersion Stabilization for Crack-Free Coatings
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Solution Overview
Problem
Aqueous ethylene/vinyl alcohol-based copolymer dispersions face challenges with long-term storage stability and film-forming properties, particularly when subjected to low-temperature or short-time drying, and thick coatings, which can result in cracked coatings and inferior gas barrier performance.
Innovation Solution
An aqueous ethylene/vinyl alcohol-based copolymer dispersion comprising ethylene/vinyl alcohol-based copolymers with specific ethylene content and degree of saponification, combined with base-neutralized ethylene/α,β-unsaturated carboxylic acid-based copolymers and polyvinyl alcohol, which improves storage stability and film-forming properties, and when applied with an inorganic filler, enhances gas barrier performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aqueous EVOH dispersion is used for coating, then working environment and economic advantages are improved, but long-term storage stability and film-forming properties deteriorate
Solution Approach 1:
The patent introduces a specific surfactant as an intermediary substance to mediate between the EVOH copolymer particles and water. The surfactant adsorbs at the interface, reducing surface tension and preventing particle aggregation during storage, thereby improving long-term storage stability while maintaining the aqueous dispersion system's environmental advantages
Solution Approach 2:
The patent optimizes multiple parameters including the HLB value of the surfactant (specifically using nonionic surfactants with HLB between 8-16), the solid content concentration (10-40%), and the particle size distribution (0.1-5 μm). These parameter adjustments collectively improve storage stability without compromising the aqueous system's environmental benefits
2Loss of time
If low-temperature or short-time drying is applied, then energy consumption and processing time are reduced, but coating quality deteriorates with cracks appearing
Solution Approach 1:
The patent performs preliminary actions during the dispersion preparation stage by carefully controlling particle size distribution (0.1-5 μm) and using surfactant treatment to pre-condition the EVOH particles. This preliminary preparation ensures that during rapid drying, the particles can reorganize and fuse properly without forming cracks, enabling quality coatings even with short drying times
Solution Approach 2:
The patent creates a dynamic particle suspension where the surfactant-coated EVOH particles remain mobile and can reorganize during the drying process. This dynamic behavior allows particles to adjust their positions and fuse continuously as water evaporates, preventing crack formation even when drying occurs rapidly at low temperatures
3Quantity of substance
If thick coatings are applied, then coverage and protection are improved, but film-forming properties deteriorate causing cracks
Solution Approach 1:
The patent segments the coating into numerous small particles (0.1-5 μm diameter) that are uniformly distributed in the aqueous dispersion. When applied as a thick coating, these fine segments can pack closely together and fuse individually during drying, maintaining film integrity even at high application thicknesses where conventional coatings would crack
Solution Approach 2:
The patent creates a composite structure where surfactant molecules form an interfacial layer around EVOH copolymer particles. This composite particle structure improves the overall film-forming capability, allowing thick coatings to maintain flexibility and cohesion during the drying process, preventing crack development
4Productivity
If EVOH solid content in solution is increased, then coating efficiency is improved, but viscosity increases making it difficult to use
Solution Approach 1:
The surfactant acts as a mediator between high-concentration EVOH particles and water, allowing much higher solid contents (10-40%) to be achieved without excessive viscosity increase. The surfactant reduces particle-particle interactions and maintains fluidity, enabling high-productivity coatings while remaining easy to apply
Solution Approach 2:
The patent changes the physical state and distribution parameters of EVOH from dissolved molecules to dispersed particles with specific size distribution (0.1-5 μm). This parameter change allows high solid content to be achieved with lower viscosity compared to molecular solutions, as the particulate form with surfactant coating prevents excessive intermolecular entanglement
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 dispersion achieves excellent long-term storage stability and high gas barrier performance even with low-temperature or short-time drying and thick coatings, preventing cracks and maintaining superior gas barrier properties.
Implementation Method 1
a base-neutralized ethylene/α,β-unsaturated carboxylic acid-based copolymer... as a dispersion stabilizer
Implementation Method 2
a polyvinyl alcohol... which improves storage stability and film-forming properties
Implementation Method 3
the technique of applying solutions or aqueous dispersions of EVOH, followed by drying
Data Source
AI summary
It is an object of the present invention to provide an aqueous ethylene-vinyl alcohol-based copolymer dispersion which is excellent in long-term storage stability and in film-forming properties even when subjected to low-temperature or short-time drying or applied to give thick coats and can give coatings showing high gas barrier performance. The prevent invention is an aqueous ethylene/vinyl alcohol-based copolymer dispersion, which comprises: (A) an ethylene/vinyl alcohol-based copolymer with an ethylene content of 15-65 mole percent and a degree of saponification of not lower than 80 mole percent, (B) a base-neutralized ethylene/α,β-unsaturated carboxylic acid-based copolymer and (C) a polyvinyl alcohol with a degree of saponification of 75-100 mole percent and a degree of polymerization of 100-3500, the content of the polyvinyl alcohol (C) being 0.5-100 parts by weight per 100 parts by weight of the ethylene/vinyl alcohol-based copolymer (A).