Cellulose-Polyester Separation via Controlled Alkali Hydrolysis
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Solution Overview
Problem
Current methods for recycling complex materials like textiles, such as cotton-polyester mixtures, face challenges due to high energy consumption, costly chemicals, and environmental impact, particularly with existing hydrolysis processes that require large amounts of sodium hydroxide and result in significant cotton degradation.
Innovation Solution
A process involving a blend of a raw material composition with a hydrolyzing liquor containing an alkaline solution at controlled temperatures and alkali concentrations, allowing for the separation of cellulose from polyester while minimizing energy use and chemical consumption, and maintaining the cellulose in a solid phase throughout the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large amounts of sodium hydroxide are used for polyester hydrolysis, then the separation efficiency is improved, but the cost and energy consumption increase significantly
Solution Approach 1:
The invention changes the concentration parameter of the alkaline solution from traditional high concentration (5-15% NaOH) to optimized concentration (0.5-5% NaOH), and adjusts the temperature parameter to 90-110°C, achieving effective polyester hydrolysis with reduced chemical consumption and cost
Solution Approach 2:
The invention applies partial action by using only the necessary amount of alkali (0.5-5% NaOH) sufficient for polyester hydrolysis, avoiding excessive alkali usage while maintaining effective separation, thus reducing both chemical consumption and associated costs
2Productivity
If harsh acid treatment is applied to degrade cellulose, then polyester separation is achieved, but the cellulose quality deteriorates and cannot be used for further processing
Solution Approach 1:
Instead of using acid treatment to separate polyester (which degrades cellulose), the invention inverts the approach by using alkaline treatment that selectively hydrolyzes polyester while preserving cellulose integrity, enabling both separation and maintenance of cellulose quality for further processing
Solution Approach 2:
The invention converts the traditionally harmful effect of alkali on cellulose (which causes degradation) into a beneficial selective process by controlling conditions (0.5-5% NaOH, 90-110°C) to hydrolyze polyester while leaving cellulose intact, thus achieving separation without quality loss
3Productivity
If high temperature and long treatment time are used for polyester hydrolysis, then separation completeness is improved, but cotton degradation increases
Solution Approach 1:
The invention optimizes the temperature parameter to 90-110°C (avoiding excessive heat) and adjusts treatment time to 0.5-4 hours, achieving complete polyester hydrolysis while minimizing cotton degradation through precise parameter control
Solution Approach 2:
The invention applies sufficient but not excessive treatment (0.5-4 hours at 90-110°C) to achieve complete polyester separation, avoiding prolonged exposure that would cause cotton degradation while ensuring thorough hydrolysis
4Loss of time
If phase transfer catalyst is added to accelerate polyester hydrolysis, then treatment time is reduced, but the process complexity and cost increase
Solution Approach 1:
The invention extracts and eliminates the need for phase transfer catalysts from the hydrolysis process by optimizing the alkaline solution concentration (0.5-5% NaOH) and temperature (90-110°C) to achieve effective polyester hydrolysis through simplified chemistry, reducing both process complexity and cost
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 process efficiently separates cellulose from polyester with reduced sodium hydroxide usage, making it suitable for industrial implementation and enabling the production of high-quality cellulose for further processing into paper pulp or regenerated fibers.
Implementation Method 1
the process comprises providing a blend, wherein the blend comprises a raw material composition and a hydrolyzing liquor, wherein the raw material composition comprises a polyester composition... keeping the blend at a temperature of 100° C. or above
Data Source
AI summary
A process for separation of the cellulosic part from a raw material composition comprising polyester and cellulose is provided. A blend is prepared comprising a raw material composition comprising polyester and cellulose and a hydrolyzing liquor wherein the hydrolyzing liquor comprises a first mixture comprising an alkaline solution containing hydroxide ions. The hydrolyzing liquor is added to give the blend an effective alkali concentration in a range from 5 g/l to 150 g/l, wherein the effective alkali concentration is calculated as NaOH, and the hydrolyzing liquor:raw material composition ratio is from 1.5:1 up to 25:1 and keeping the blend at a temperature of 100° C. or above.