Modified Vinyl Alcohol Polymer Coating Agent Methanol Reduction
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Solution Overview
Problem
Existing coating agents containing modified vinyl alcohol polymers face challenges with high residual methanol content and the formation of water-insoluble components, which affect coating performance, adhesiveness, and water resistance of coated products.
Innovation Solution
A modified vinyl alcohol polymer with a residual methanol content of less than 3.0 mass % and a controlled amount of insoluble components is developed, optimizing particle diameter and pre-drying washing conditions to enhance coating agent performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a PVA containing structural units from ethylenically unsaturated dicarboxylic acid derivatives is dried using conventional methods, then methanol is removed from the polymer, but water-insoluble components form due to crosslinking reactions at high temperature
Solution Approach 1:
The patent changes the drying parameters by limiting the drying temperature to 60°C or lower and extending the drying time, preventing crosslinking reactions while effectively removing methanol. This parameter optimization resolves the contradiction between methanol removal and preventing water-insoluble component formation
Solution Approach 2:
The patent performs preliminary washing with a water-insoluble solvent (such as acetone or ethyl acetate) before drying to remove residual methanol from the polymer particles. This preliminary action reduces methanol content before the drying step, allowing gentle drying without crosslinking while still achieving low methanol emissions
2Loss of substance
If high temperature drying is used to remove methanol efficiently, then methanol content is reduced, but energy consumption increases and production efficiency decreases
Solution Approach 1:
The patent changes the drying temperature parameter to 60°C or lower, which reduces energy consumption compared to conventional high-temperature drying. By extending the drying time and using lower temperature, the same methanol removal efficiency is achieved with significantly reduced energy input
Solution Approach 2:
The preliminary washing step with water-insoluble solvent removes a significant portion of methanol before drying, reducing the methanol load that needs to be removed during drying. This allows efficient methanol removal at lower temperatures, reducing energy consumption while maintaining production efficiency
3Loss of substance
If conventional drying methods are used on modified PVA, then methanol is removed, but the PVA particles dissolve and fuse together due to high water solubility
Solution Approach 1:
The patent performs preliminary washing with a water-insoluble solvent (acetone, ethyl acetate, or toluene) before drying. This preliminary action removes residual methanol and reduces the water solubility of the PVA particles, preventing them from dissolving and fusing during the subsequent low-temperature drying process
Solution Approach 2:
The patent changes the drying temperature to 60°C or lower, which is below the temperature at which the modified PVA particles would dissolve and fuse. This temperature parameter control, combined with extended drying time, allows methanol removal while maintaining particle integrity and processability
4Loss of substance
If prolonged heating at high temperature is used to remove methanol, then methanol content is reduced, but water-insoluble components form and coating performance deteriorates
Solution Approach 1:
The patent changes the drying temperature to 60°C or lower and extends the drying time, which removes methanol without causing crosslinking reactions that would form water-insoluble components. This parameter control maintains the polymer's solubility and coating performance while achieving low methanol content
Solution Approach 2:
The preliminary washing with water-insoluble solvent removes residual methanol before drying, reducing the need for prolonged high-temperature heating. This allows gentle drying that preserves coating performance while still achieving efficient methanol removal
Data Source
AI summary
The present invention provides a coating agent having a reduced methanol content, an adhesive including the coating agent and excellent in coating performance and adhesiveness, and a coated product including the coating agent and excellent in water resistance and alcohol resistance. The present invention relates to a coating agent comprising a modified vinyl alcohol polymer (A), the modified vinyl alcohol polymer (A) comprising a structural unit derived from a derivative (a) of an ethylenically unsaturated dicarboxylic acid in a content (X) of 0.05 mol % or more and 10 mol % or less, having a degree of saponification of 80.0 mol % or more and 99.9 mol % or less, having a methanol content of less than 3.0 mass % as measured by headspace gas chromatography, and having an amount of 0.1 ppm or more and less than 2,000 ppm of a component insoluble in a 90° C., 5 mass % aqueous solution.