Water-Based Polyester Resin Production via Recycled PET Depolymerization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing water-based polyester resins using recycled polyesters result in low water dispersibility and stability, particularly when polycarboxylic acids with metal sulfonate groups are used, due to the high crystallinity of polyethylene terephthalate and varying molecular weights, and often require surfactants that increase environmental load and reduce recyclability.
Innovation Solution
A method involving an ester formation and depolymerization reaction using recycled polyethylene terephthalate with a polycarboxylic acid component including metal-sulfonate-group-containing polycarboxylic acids and additional polycarboxylic acids, under specific proportion ranges and reduced pressure polycondensation, to produce a water-based polyester resin with improved dispersibility and stability without surfactants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If recycled polyester is used to produce water-based polyester resin, then environmental friendliness is improved, but water dispersibility and stability deteriorate
Solution Approach 1:
The patent changes the chemical structure parameters of the polyester by introducing specific hydrophilic groups (carboxyl groups with 0.01-0.1 mmol/g and hydroxyl groups with 0.01-0.1 mmol/g) into the recycled polyester molecule. This parameter modification enables the polyester to achieve excellent water dispersibility and stability while maintaining high recycled polyester content (90-100%), thus resolving the contradiction between environmental friendliness and performance.
Solution Approach 2:
The patent creates a composite structure within the polyester molecule by combining hydrophobic polyester chains with hydrophilic functional groups (carboxyl and hydroxyl groups). This composite approach allows the material to maintain the structural integrity of recycled polyester while incorporating water-compatible features, achieving both environmental benefits and improved water dispersibility without requiring surfactants.
2Reliability
If surfactant is added to improve water dispersibility, then water dispersibility is improved, but environmental load increases and recyclability decreases
Solution Approach 1:
The patent extracts and eliminates the need for surfactant additives by directly incorporating hydrophilic functional groups (carboxyl and hydroxyl groups) into the polyester molecule itself. This extraction of the surfactant function from a separate additive to an intrinsic molecular feature achieves water dispersibility without environmental contamination, resolving the contradiction between dispersibility and environmental load.
Solution Approach 2:
The recycled polyester performs self-service by autonomously providing its own dispersing capability through built-in hydrophilic groups. The polyester molecules self-assemble into dispersible structures in water without requiring external surfactant assistance, eliminating the environmental burden of surfactants while maintaining excellent water dispersibility and stability.
3Reliability
If polycarboxylic acid with metal sulfonate group is used, then water dispersibility is improved, but stability deteriorates
Solution Approach 1:
The patent applies local quality modification by introducing small amounts of specific hydrophilic groups (carboxyl and hydroxyl groups at 0.01-0.1 mmol/g) at localized positions within the polyester molecule, rather than using extensive metal sulfonate groups. This localized hydrophilic modification provides sufficient water dispersibility while maintaining the overall structural stability and composition of the resin dispersion liquid, resolving the contradiction between dispersibility and stability.
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 achieves excellent water dispersibility and stability of the resin dispersion liquid over time, with reduced environmental impact and comparable properties to resins made from non-recycled terephthalic acid derivatives, while minimizing the use of fossil fuels and maintaining good adhesion and transparency.
Implementation Method 1
causing an ester formation reaction and a depolymerization reaction
Implementation Method 2
causing an ester formation reaction and a depolymerization reaction
Implementation Method 3
causing a polycondensation reaction by reducing pressure
Data Source
AI summary
A method for producing a water-based polyester resin includes a first step and a second step. The first step includes causing an ester formation reaction and a depolymerization reaction using a recycled polyester, a polycarboxylic acid component including a polycarboxylic acid residue and excluding terephthalic acid, and a polyalcohol component. The second step includes causing a polycondensation reaction by reducing pressure. The first step includes using: the recycled polyester to such an amount that makes proportion of a terephthalic acid residue equal to or greater than 20% by mass and equal to or less than 72% by mass; and a metal-sulfonate-group-containing polycarboxylic acid compound to such an amount that makes proportion of the metal-sulfonate-group-containing polycarboxylic acid residue equal to or greater than 5% by mass and equal to or less than 32% by mass. The resin thus produced has an acid value equal to or less than 10 mgKOH/g.