Polyvinyl Acetal with Reduced Flowability for Rigid Films
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Solution Overview
Problem
Existing polyvinyl acetals have high flowability, which results in plasticized films with reduced mechanical stability and difficulty in coextrusion with mixtures of varying mechanical stability, necessitating the development of materials with reduced flowability for applications requiring more rigid behavior and improved mechanical stability.
Innovation Solution
Polyvinyl acetals with a degree of acetalization between 70-84 mol% and specific molar ratios of syndiotactic sequences of vinyl alcohol groups, produced through an acid-catalyzed reaction without emulsifiers, where the reaction conditions control the formation of vinyl alcohol domains and stereochemistry of hydroxyl groups to achieve reduced flowability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polyvinyl acetal is produced with conventional processes, then high flowability is achieved, but mechanical stability and rigidity of plasticized films deteriorate
Solution Approach 1:
The patent applies parameter changes by controlling the molar ratio of syndiotactic sequences of vinyl alcohol groups with 3 members to 0.05-0.20 and the degree of acetalisation to 70-84 mol%, which fundamentally alters the polymer chain conformation and intermolecular interactions, resulting in reduced flowability and enhanced mechanical stability of plasticized films
Solution Approach 2:
The patent creates a composite molecular structure within the polyvinyl acetal by controlling the sequence distribution of acetal units, acetate units, and vinyl alcohol units, where the specific syndiotactic sequence configuration acts as a structural composite that simultaneously influences flowability and mechanical properties
2Ease of manufacture
If polyvinyl acetal has high flowability, then processing is easier, but coextrusion with mixtures of varying mechanical stability becomes difficult
Solution Approach 1:
By precisely controlling the molar ratio of syndiotactic sequences to 0.05-0.20 and degree of acetalisation to 70-84 mol%, the patent modifies the rheological parameters of polyvinyl acetal to achieve an optimal balance between processability and coextrusion compatibility, allowing stable processing while enabling combination with materials of varying mechanical properties
3Stability of the object's composition
If the sequence of repeating units is in thermodynamic equilibrium, then stability is improved, but flowability increases excessively
Solution Approach 1:
The patent deviates from thermodynamic equilibrium by controlling the molar ratio of syndiotactic sequences to 0.05-0.20, creating a non-equilibrium sequence distribution that stabilizes the polymer chain conformation and reduces molecular mobility, thereby decreasing flowability while maintaining compositional stability
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 polyvinyl acetals exhibit reduced flowability, as indicated by solution viscosity and melt flow rates, leading to more rigid and mechanically stable plasticized films suitable for applications in laminated safety glasses and photovoltaic modules.
Implementation Method 1
reacting the polyvinyl alcohol with the aldehyde at a temperature of 0 to 30 °C by addition of an acid catalyst
Implementation Method 2
completing the reaction by heating the reaction mixture of a) after complete dosage of the acid catalyst to 69 to 80 °C
Implementation Method 3
cooling the reaction mixture of b) to 15 to 45°C and separating the polyvinyl acetal
Data Source
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AI summary
The invention is directed to a polyvinyl acetal with a degree of acetalization of 70 - 84 mol %, characterised by an molar ratio of the amount of continuous syndiotactic sequences of vinyl alcohol groups with 3 members of at least 0.152, based on the total amount of vinyl alcohol groups in the polyvinyl acetal.