Dihydroxy Compound Recovery from Waste Resin by Selective Crystallization
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Solution Overview
Problem
Existing methods for recycling synthetic resins fail to effectively separate and recover desired synthetic resins from waste resin compositions due to the presence of organic impurities, which have similar physical and chemical properties, making it difficult to distinguish and recycle the desired resins.
Innovation Solution
A method involving the use of an alkaline solution with specific solvents to depolymerize waste resin compositions, followed by crystallization based on solubility differences to separate and purify dihydroxy compounds, allowing for the production of high-purity dihydroxy compounds and recycled resins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If metal detection and optical sorting methods are used to remove foreign substances, then metal and colored foreign substances can be removed, but organic impurities with similar properties to the desired resin cannot be effectively separated
Solution Approach 1:
The invention changes the chemical parameter of the waste resin composition by adding specific organic solvents (toluene, xylene, or their mixtures) to dissolve the desired polycarbonate resin while leaving organic impurities undissolved. This parameter change enables selective dissolution and separation based on solubility differences, achieving effective separation of organic impurities that cannot be distinguished by metal detection or optical sorting methods.
Solution Approach 2:
The invention extracts the desired polycarbonate resin from the waste resin composition by selective dissolution in organic solvents. The soluble polycarbonate resin is separated from the insoluble organic impurities through filtration or decantation, effectively removing organic impurities that have similar physical and chemical properties to the desired resin.
2Ease of manufacture
If conventional recycling methods are used, then processing is simple, but the ability to recover high-purity desired resin from compositions containing organic impurities is insufficient
Solution Approach 1:
The invention introduces a parameter change by utilizing solubility differences between the desired polycarbonate resin and organic impurities. By controlling the addition of organic solvents and maintaining specific temperature conditions, the process achieves high-purity resin recovery through selective dissolution, followed by precipitation or filtration to separate impurities.
Solution Approach 2:
The invention employs phase transition by dissolving the polycarbonate resin in organic solvents at elevated temperatures and then precipitating it by cooling or adding non-solvents. This phase transition enables effective separation of the desired resin from organic impurities, achieving high purity recovery while maintaining relatively simple processing steps.
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 enables the effective separation and recycling of high-purity dihydroxy compounds and recycled resins from waste resin compositions, enhancing the quality and efficiency of resin recycling.
Implementation Method 1
an alkaline solution containing a first solvent, water, and a waste resin composition is treated to give a reaction solution containing a first solvent and a mixture of dihydroxy compounds
Implementation Method 2
a difference between the solubility of the first dihydroxy compound in the second solvent at 25°C and the solubility of the other dihydroxy compound in the second solvent at 25°C is greater than or equal to 0.1 g/(10 mL)
Implementation Method 3
the first dihydroxy compound is crystallized from a crystallization solution obtained by adding a second solvent to the reaction solution
Data Source
AI summary
Provided is a method of recycling a waste resin composition containing a synthetic resin and organic impurities. A method of manufacturing a dihydroxy compound from a waste resin composition, the method including, a step (a1) in which an alkaline solution containing a first solvent, water, and a waste resin composition containing a resin having at least two constitutional units selected from the group consisting of general formulae (1) to (4) set forth below: is treated to give a reaction solution containing a first solvent and a mixture of dihydroxy compounds containing a first dihydroxy compound selected from the group consisting of general formulae (1') to (4') set forth below: and at least one other dihydroxy compound selected from the group consisting of the general formulae (1') to (4'); and a step (b1) in which the first dihydroxy compound is crystallized from a crystallization solution obtained by adding a second solvent to the reaction solution, wherein a difference between the solubility of the first dihydroxy compound at 25°C in the second solvent and the solubility of the other dihydroxy compound at 25°C in the second solvent (solubility of the other dihydroxy compound minus solubility of the first dihydroxy compound) is greater than or equal to 0.1 g/(10 mL).