Cycloaliphatic Polyester Polyols from Recycled PET via Glycolysis and Hydrogenation
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Solution Overview
Problem
The polyurethane industry faces challenges in producing cycloaliphatic polyester polyols with high recycle content that meet demanding specifications for color, clarity, viscosity, and hydroxyl number using recycled polymers like recycled polyethylene terephthalate, as existing methods often result in products with high viscosities or high levels of free glycols, making them less than ideal for use as polyol intermediates.
Innovation Solution
A process involving the heating of thermoplastic polyesters with glycols to create a digested intermediate, followed by hydrogenation of aromatic rings, optionally with the inclusion of hydrophobes, to produce cycloaliphatic polyester polyols with controlled hydroxyl numbers and viscosities, utilizing recycled materials such as recycled polyethylene terephthalate and propylene glycol in the presence of catalysts like titanium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If glycolysis is performed to convert recycled PET to polyols, then the viscosity is reduced, but the hydroxyl number becomes too high and free glycol levels increase
Solution Approach 1:
The patent changes the glycol to polyester molar ratio parameter from conventional values to at least 2.0, which fundamentally alters the glycolysis reaction outcome. This parameter change produces a product distribution with lower hydroxyl numbers and reduced free glycol levels while maintaining acceptable viscosity, resolving the contradiction between these two parameters.
2Ease of manufacture
If ethylene glycol is used as the glycol reactant for glycolysis, then the reaction is simplified, but the product becomes a crystalline or waxy solid that is less than ideal for polyol intermediates
Solution Approach 1:
The patent changes the glycol reactant from ethylene glycol to propylene glycol or other glycols with different molecular structures. This parameter change in the reactant identity produces liquid polyol products at room temperature rather than crystalline or waxy solids, while maintaining reaction simplicity through established glycolysis methodology.
3Ease of manufacture
If traditional glycolysis methods are used to produce polyols from recycled PET, then the process is well-established, but the resulting polyols have high viscosities or high levels of free glycols making them less than ideal for urethane manufacture
Solution Approach 1:
The patent applies parameter changes to the glycolysis process by setting the molar ratio of glycol to polyester at least at 2.0, which is higher than conventional ratios. This parameter modification fundamentally changes the product distribution to achieve lower hydroxyl numbers and reduced free glycol levels while maintaining process simplicity, thereby meeting stringent polyol specifications for urethane manufacture.
Solution Approach 2:
The patent recovers and reuses glycols from various sources including spent vehicle coolants and aircraft deicing operations. By recovering these glycols and using them as reactants in the modified glycolysis process, the patent simultaneously achieves process establishment through familiar chemistry and improved product quality through controlled reaction conditions.
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 method enables the production of high-recycle-content cycloaliphatic polyester polyols with desirable hydroxyl numbers, viscosities, and appearance, suitable for formulating polyurethane and polyisocyanurate products, providing a sustainable alternative to petrochemical-based polyols while maintaining performance and reducing environmental impact.
Implementation Method 1
digestion of rPET with glycols (also called 'glycolysis'), usually in the presence of a catalyst such as zinc or titanium. Digestion converts the polymer to a mixture of glycols and low-molecular-weight PET oligomers
Implementation Method 2
hydrogenating aromatic rings of corresponding aromatic polyester polyols
Data Source
AI summary
Cycloaliphatic polyester polyols and processes for making them from thermoplastic polyesters are disclosed. One process comprises heating a thermoplastic polyester with a glycol to give a digested intermediate and hydrogenating aromatic rings in the digested intermediate to produce the cycloaliphatic polyester polyol. Optionally, the digested intermediate is reacted with a hydrophobe to give a modified polyol prior to hydrogenation, and the modified polyol is hydrogenated to give the cycloaliphatic polyester polyol. The high-recycle-content cycloaliphatic polyester polyols have desirable attributes for formulating polyurethane dispersions, two-component polyurethane coatings, mono- or poly(meth)acrylates, polyisocyanurates, flexible and rigid foams, coatings, adhesives, sealants, and elastomers, and they provide a sustainable alternative to petrochemical-based polyols.