Solid-State Polycondensation Pressure and Gas Flow Control
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Solution Overview
Problem
Existing solid-state polycondensation processes for polyesters require large amounts of inert gas or low pressures to remove by-products, leading to economic and technical inefficiencies, including gas loss and vacuum technology complexities.
Innovation Solution
A process using a combination of moderate reduced pressure (10 mbar to 200 mbar) and low inert gas flow (R value range of 0.005 to 0.05) to efficiently remove by-products during solid-state polycondensation of polyesters, reducing the need for extensive gas purification and vacuum systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large amounts of inert gas are used to remove by-products in solid-state polycondensation, then by-product removal efficiency is improved, but gas loss and economic cost increase
Solution Approach 1:
The patent changes the pressure parameter from high vacuum (0.01-1 mbar) to moderate reduced pressure (10-200 mbar), which fundamentally alters the by-product removal mechanism. This parameter change allows effective by-product removal without requiring large amounts of inert gas, thus resolving the contradiction between productivity and substance loss
Solution Approach 2:
The patent introduces a moderate reduced pressure environment as an intermediary mechanism between the reaction zone and the vacuum pump. This intermediary pressure level enables efficient by-products removal while protecting the vacuum pump from condensation and corrosion issues, reducing the need for extensive gas purification
2Productivity
If low pressure (vacuum) is applied to remove by-products, then by-product removal is improved, but vacuum technology complexity and cost increase
Solution Approach 1:
The patent changes the pressure parameter from deep vacuum (0.01-1 mbar) to moderate reduced pressure (10-200 mbar). This parameter change significantly simplifies the vacuum technology requirements, allowing the use of simpler, less expensive vacuum pumps and reducing system complexity while maintaining effective by-product removal
Solution Approach 2:
The patent employs a simpler, more economical vacuum system designed for moderate reduced pressure rather than high vacuum. This approach uses less expensive vacuum technology that is sufficient for the application, avoiding the need for complex and costly high-vacuum equipment
3Productivity
If high vacuum pressure is maintained, then by-product removal is improved, but condensation and corrosion problems in vacuum pump increase
Solution Approach 1:
The patent changes the pressure parameter from high vacuum (0.01-1 mbar) to moderate reduced pressure (10-200 mbar). This parameter change raises the condensation point of by-products, preventing them from condensing in the vacuum pump and thereby eliminating corrosion and blockage problems while maintaining effective by-product removal
Solution Approach 2:
The patent converts the potential harm of by-product condensation into a benefit by operating at a pressure level where condensation does not occur. The moderate reduced pressure environment naturally prevents condensation, turning what would be a harmful effect into a protective feature for the vacuum pump
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
This approach allows for cost-effective and efficient removal of by-products, minimizing gas loss and vacuum system requirements, while maintaining high molecular weight polyester production, thus overcoming the inefficiencies of previous methods.
Implementation Method 1
The removal of these by-products is effected by application of a reduced pressure or with the aid of an inert gas such as nitrogen flowing through the reaction vessel in order to carry the by-products out of the reaction vessel
Implementation Method 2
the by-products of the SSP reaction (water, monomers, such as ethylene glycol, by-products such as acetaldehyde or oligomers) have to be removed effectively from the reaction vessel
Implementation Method 3
The removal of these by-products is effected by application of a reduced pressure
Data Source
AI summary
A method and an apparatus for solid-state polycondensation of polyesters, preferably polyethylene terephthalate and/or copolymers thereof. The method and apparatus are both characterized by a solid-state polycondensation being performed with polyester prepolymer particles in a reaction chamber in which an absolute pressure is in the range from 10 mbar to 200 mbar, and a process gas flow in the range of an R-value of 0.005 to 0.05. The polycondensation is carried out over a time of from 2 to 30 hours and at a temperature of from 180° C. to 5° below a crystalline melting point of the polyester prepolymer particles in order to achieve an intrinsic viscosity of from 0.70 to 0.95 dl/g. The R value is defined as a ratio of an hourly amount of process gas (in kg) flowing through the reaction space to an hourly amount of polymer (in kg) flowing through the reaction space:R=m(gas)/hm(polymer)/h.