PET to PBT Conversion via 1,4-Butanediol Depolymerization
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Solution Overview
Problem
Current methods fail to effectively utilize polyethylene terephthalate (PET) scrap, leading to significant waste and resource inefficiency, as they cannot convert PET into polybutylene terephthalate (PBT) with desirable properties or high ethylene glycol content without generating undesirable byproducts like diethylene glycol.
Innovation Solution
A process involving the depolymerization of PET with 1,4-butane diol at elevated temperatures and pressures, under inert conditions, to produce a modified random polybutylene terephthalate copolymer with residues from PET, including ethylene glycol and isophthalic acid, which exhibits performance properties similar to virgin PBT without the need for complete removal of diethylene glycol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If PET is converted to PBT by reaction with 1,4-butane diol to replace ethylene glycol, then the product purity is improved, but diethylene glycol byproduct is formed which contaminates the final product
Solution Approach 1:
The patent converts the harmful diethylene glycol byproduct into a beneficial component by incorporating it back into the polymer structure during the polycondensation step, creating copolymer units that improve processability and reduce the need for stringent purification
Solution Approach 2:
The patent changes the reaction parameters by conducting the conversion at elevated temperatures (180-230°C) and using specific catalysts to control the formation and incorporation of diethylene glycol units, transforming them from contaminants to functional components of the copolymer
2Manufacturing precision
If complete removal of diethylene glycol is implemented to produce high purity PBT, then the product quality is improved, but the process complexity and cost increase
Solution Approach 1:
The patent employs a self-service approach where the diethylene glycol byproduct is automatically incorporated into the polymer structure during the polycondensation reaction, eliminating the need for separate purification steps to remove it
Solution Approach 2:
The patent extracts the problematic diethylene glycol from the reaction mixture through distillation under reduced pressure, separating it from the polymer product and allowing for simpler downstream processing
3Productivity
If PET scrap is converted to PBT to utilize waste materials, then resource efficiency is improved, but the presence of residues from PET reduces the performance properties of the final product
Solution Approach 1:
The patent creates a composite copolymer structure that combines units derived from PET scrap with units from 1,4-butane diol, where the heterogeneous composition provides both waste utilization and acceptable performance properties through the synergistic effect of different copolymer units
Solution Approach 2:
The patent applies local quality by allowing different regions of the copolymer chain to have different compositions, with some segments containing PET-derived units and others containing pure PBT units, thereby maintaining overall performance while utilizing waste material
4Reliability
If conventional PBT production from monomers is used, then the product quality is maintained, but non-renewable resource consumption increases
Solution Approach 1:
The patent recovers and reuses ethylene glycol that would otherwise be discarded from PET recycling streams, converting it into valuable copolymer units in the PBT synthesis process, thereby reducing waste and non-renewable resource consumption
Solution Approach 2:
The patent makes the synthesis process universal by accepting various PET scrap sources and converting them into useful PBT copolymer, eliminating the need for virgin monomers and enabling the same process to handle different feedstock types
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 process allows for the efficient conversion of PET scrap into PBT with improved performance properties, reducing waste and non-renewable resource consumption, while also reducing CO2 emissions by using biomass-derived 1,4-butane diol, thus providing a sustainable alternative to traditional PBT production.
Implementation Method 1
depolymerizing a polyethylene terephthalate component with a 1,4-butane diol component at a temperature ranging from 180° C. to 230° C.
Implementation Method 2
converting waste poly(ethylene terephthalate) to either poly(ethylene-co-butylene terephthalate) or poly(butylene terephthalate) (PBT) by reaction with 1,4-butane diol
Implementation Method 3
increasing the temperature of the molten mixture to an elevated temperature under conditions sufficient to form a modified random polybutylene terephthalate copolymer
Implementation Method 4
at a pressure that is at least atmospheric pressure
Implementation Method 5
agitating the molten mixture at subatmospheric pressure
Data Source
AI summary
In one embodiment, the invention relates to a two step process in which a 1,4-butane diol component reacts with a polyethylene terephthalate component under conditions that depolymerize the polyethylene terephthalate component into a molten mixture and the molten mixture is placed under subatmospheric conditions that produce the modified polybutylene terephthalate random copolymers. In another embodiment, the invention relates to a three step process in which a diol component selected from the group consisting of ethylene glycol, propylene glycol, and combinations thereof reacts with a polyethylene terephthalate component under conditions sufficient to depolymerize the polyethylene terephthalate component into a first molten mixture; and where the first molten mixture is combined with 1,4-butane diol under conditions that create a second molten mixture that is subsequently placed under subatmospheric conditions that produce the modified polybutylene terephthalate random copolymers. The invention also relates to compositions made from processes of the invention.