Recycled Polycarbonate Resin Purification by Solvent Precipitation
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Solution Overview
Problem
Existing methods for recycling polycarbonate resins often result in degraded mechanical properties, color tone, and weather resistance, limiting their practical usefulness, especially when combined with other resins and additives, which are difficult to separate.
Innovation Solution
A method involving the use of specific solvents and filter aids to produce a recycled polycarbonate resin with controlled molecular weight ratio (Mw/Mn ≤ 2.2) by dissolving spent resin in methylene chloride or phenol-based solvents and precipitating it with ketone-, alcohol-, or saturated hydrocarbon-based solvents, removing undissolved substances to achieve desired properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polycarbonate resin is dissolved in a solvent and precipitated to recycle it, then the recycling process is simpler than decomposition methods, but the reclaimed resin often has insufficient mechanical properties and color tone
Solution Approach 1:
The patent applies parameter changes by carefully controlling the molecular weight ratio (Mw/Mn ≤ 2.2) as a key parameter to distinguish high-quality recycled resin from conventional recycled resin. The process involves changing solvent parameters (using specific good solvents like methylene chloride or phenol-based solvents and poor solvents like ketone-based, alcohol-based, or saturated hydrocarbon-based solvents) and controlling precipitation conditions to achieve the desired molecular weight distribution and property quality
Solution Approach 2:
The patent uses filter aids (celite, activated white earth, activated carbon, or synthetic adsorbents) to remove undissolved substances and impurities from the resin solution before precipitation, effectively copying the purification function needed to restore the resin's original quality. This filtering step creates a clean solution that precipitates into high-quality recycled resin with restored mechanical properties and color tone
2Loss of substance
If spent polycarbonate resin compositions containing additives and inorganic substances are recycled, then material recovery is achieved, but the presence of difficult-to-separate contaminants limits recycling use
Solution Approach 1:
The patent introduces filter aids as intermediary substances that mediate between the contaminated spent resin and the final recycled product. These filter aids (celite, activated white earth, activated carbon, or synthetic adsorbents) act as intermediaries to adsorb and remove additives, inorganic substances, and other contaminants from the resin solution, enabling effective separation without requiring direct treatment of the complex spent resin composition
Solution Approach 2:
The patent extracts and removes undissolved substances and contaminants from the resin solution through filtration using filter aids before the precipitation step. This extraction process separates the desired polycarbonate resin from unwanted additives and inorganic substances, ensuring the recycled resin meets quality requirements for practical use
3Adaptability or versatility
If the molecular weight ratio Mw/Mn of spent polycarbonate resin is high (≥2.8), then the resin has undergone degradation, but direct recycling without purification maintains broad applicability
Solution Approach 1:
The patent applies parameter changes by transforming the molecular weight distribution parameter through selective dissolution and controlled precipitation. By using specific good solvents and poor solvents with controlled ratios and conditions, the process reduces the Mw/Mn ratio from ≥2.8 in spent resin to ≤2.2 in recycled resin, improving molecular weight uniformity while maintaining the ability to handle various spent resin compositions
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 method produces a recycled polycarbonate resin with improved color tone, weather resistance, and mechanical properties suitable for practical use, effectively handling mixed resin compositions.
Implementation Method 1
preparing a polycarbonate resin solution by dissolving the spent polycarbonate resin composition in a good solvent containing methylene chloride and/or a phenol-based solvent
Implementation Method 2
precipitating the recycled polycarbonate resin by mixing the polycarbonate resin solution and a poor solvent containing one or more selected from the group consisting of a ketone-based solvent, an alcohol-based solvent, a saturated hydrocarbon-based solvent and water
Implementation Method 3
contacting the polycarbonate resin solution and one or more filter aids selected from the group consisting of celite, activated white earth, activated carbon and a synthetic adsorbent, and removing undissolved substances
Data Source
AI summary
Provided is a method for producing a recycled polycarbonate resin whose color tone, weather resistance and mechanical physical properties are sufficient for practical use. The production method is a method for producing a recycled polycarbonate resin in which a recycled polycarbonate resin having an Mw/Mn of 2.2 or less is obtained from a spent polycarbonate resin composition containing a polycarbonate resin having an Mw/Mn of 2.8 or more, the method comprising step (S1) of preparing a polycarbonate resin solution by dissolving the spent polycarbonate resin composition in a good solvent containing a methylene chloride solvent and/or a phenol-based solvent, step (S2) of precipitating the recycled polycarbonate resin by mixing the polycarbonate resin solution and a poor solvent containing one or more selected from the group consisting of a ketone-based solvent, an alcohol, a saturated hydrocarbon-based solvent and water, and step (S3) of recovering the precipitated recycled polycarbonate resin.