Ethylene-Vinyl Alcohol Copolymer Aqueous Solution for Coating
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Solution Overview
Problem
Partially saponified polyvinyl alcohol (PVA) used in release papers is less water-resistant, leading to elution during adhesive processing and inability to use water-dispersible varnishes, and ethylene-vinyl alcohol copolymers require high temperatures and long dissolution times due to low water solubility and shear-induced fibrillar precipitate formation.
Innovation Solution
An aqueous solution containing an ethylene-vinyl alcohol copolymer with 1-20 mol% ethylene units, a specific crystallinity range as determined by pulse NMR, and a monohydric alcohol with 1-4 carbon atoms, which reduces fibrillar precipitate formation and enhances solubility, allowing for improved coating processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene-vinyl alcohol copolymer is used to improve water resistance, then water resistance is improved, but solubility in water deteriorates requiring high temperature and long dissolution time
Solution Approach 1:
The patent applies parameter changes by controlling the ethylene unit content within 1-20 mol% and saponification degree within 80-99.99 mol%, along with specific crystallinity ranges, to achieve optimal balance between water resistance and solubility. This resolves the contradiction by adjusting material parameters to prevent both excessive hydrophobicity and poor water resistance.
Solution Approach 2:
The patent uses composite material approach by creating an ethylene-vinyl alcohol copolymer that combines hydrophobic ethylene units with hydrophilic vinyl alcohol units in specific proportions. This composite structure at molecular level provides both water resistance from ethylene segments and solubility from vinyl alcohol segments, resolving the contradiction between these opposing properties.
2Loss of energy
If saponification degree is reduced to avoid cost increase for dissolution, then dissolution cost is reduced, but particles aggregate to form lumps increasing dissolution time
Solution Approach 1:
The patent applies parameter changes by optimizing the saponification degree within 80-99.99 mol% range, preventing both excessive hydrophobicity (which would require high dissolution costs) and poor solubility (which would cause lump formation and extended dissolution time). This parameter optimization resolves the contradiction between dissolution cost and dissolution time.
3Ease of operation
If shear stress is applied during preparation and coating, then coating process is enabled, but fibrillar precipitate forms reducing processability
Solution Approach 1:
The patent applies parameter changes by controlling the ethylene unit content (1-20 mol%) and crystallinity within specific ranges, which optimizes the polymer's response to shear stress. This prevents excessive fibrillar precipitate formation during coating while maintaining adequate processability, resolving the contradiction between ease of operation and reliability.
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 results in high solubility of the ethylene-vinyl alcohol copolymer, reduced fibrillar precipitate formation under shear stress, and excellent oxygen barrier properties in coated articles.
Implementation Method 1
an aqueous solution containing an ethylene-vinyl alcohol copolymer which is highly soluble in water
Implementation Method 2
a crystallinity in water Cw (30° C.) at 30° C. and a crystallinity in water Cw (70° C.) at 70° C. as determined by pulse NMR
Data Source
AI summary
The present invention provides an aqueous solution containing an ethylene-vinyl alcohol copolymer (A), an alcohol (B) having 1 to 4 carbon atoms and water (C), wherein an ethylene unit content of the ethylene-vinyl alcohol copolymer (A) is 1 mol % or more and less than 20 mol %; a crystallinity in water Cw (30° C.) at 30° C. and a crystallinity in water Cw (70° C.) at 70° C. as determined by pulse NMR satisfy Formula (I); the ethylene-vinyl alcohol copolymer (A) is contained in 0.1 to 100 parts by mass based on 100 parts by mass of water (C); and the alcohol (B) is contained in 0.01 to 30 parts by mass based on 100 parts by mass of water (C). Thus, there is provided an aqueous solution of an ethylene-vinyl alcohol copolymer, which forms a less number of lumps and generates a reduced amount of fibrillar precipitate even when a shear stress is applied.4≤100-Cw(30°C.)100×[Cw(30°C.)-Cw(70°C.)]≤22(I)