High-Recycle Polyester Polyols via Glycolysis and Hydrophobe Modification
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Solution Overview
Problem
The polyurethane industry faces challenges in producing high-quality polyols from recycled materials, particularly recycled polyethylene terephthalate (rPET), which often result in products with high viscosities, particulates, or phase separation issues, failing to meet the demanding specifications for color, clarity, and hydroxyl number requirements.
Innovation Solution
The development of polyester polyols through a reaction between thermoplastic polyesters, glycols, and specific hydrophobes such as ricinoleic acid, ethoxylated castor oils, and sunflower oil, with a molar ratio of glycol to thermoplastic polyester at least 2.0 and hydrophobe content between 3 to 70 wt.%, resulting in polyols with desirable hydroxyl numbers, viscosities, and clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If glycolysis is performed on recycled PET to produce polyol intermediates, then the viscosity is reduced, but the hydroxyl number becomes too high and free glycol levels increase
Solution Approach 1:
The patent extracts and removes excess glycol and low-molecular-weight oligomers from the glycolysis product mixture through distillation and filtration processes, isolating the desired bis(hydroxyalkyl) terephthalate intermediate with controlled hydroxyl number while discarding the harmful excess components
Solution Approach 2:
The patent changes the molecular weight distribution parameters of the glycolysis products by controlling reaction conditions and using fractionation processes to obtain a specific product range with desired viscosity and hydroxyl number characteristics, rather than using the full distribution of glycolysis products
2Device complexity
If ethylene glycol is used as the glycol reactant for glycolysis, then the number of possible reaction products is minimized, but the glycolysis product becomes a crystalline or waxy solid at room temperature
Solution Approach 1:
The patent modifies the molecular structure of the polyol intermediate by incorporating aromatic rings from terephthalate units, which disrupts crystalline packing and prevents solidification at room temperature, while maintaining the benefits of using ethylene glycol as the reactant
Solution Approach 2:
The patent creates a composite molecular structure combining aliphatic glycol units with aromatic terephthalate units, resulting in a material that exhibits liquid behavior at room temperature due to the aromatic content, while retaining the reduced product variety advantage of using ethylene glycol
3Reliability
If recycled PET is used to manufacture polyols, then sustainability is improved, but the product quality fails to meet specifications for color, clarity, and hydroxyl number
Solution Approach 1:
The patent performs preliminary purification steps including filtration to remove particulates, distillation to separate fractions, and washing to remove contaminants before the main polyol synthesis, ensuring that recycled PET feedstock is adequately prepared to meet final product specifications
Solution Approach 2:
The patent uses bis(hydroxyalkyl) terephthalate as a purified intermediate product that serves as a bridge between recycled PET and final polyol, allowing quality control and specification compliance to be achieved at the intermediate stage before final product formation
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 enables the production of high-recycle-content polyols that are transparent, free-flowing, and stable, suitable for a wide range of polyurethane applications, including foams, coatings, and adhesives, while reducing reliance on bio- or petrochemical sources.
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
The hydrophobic materials provide polyols with reduced viscosity at a given hydroxyl number and improved hydrocarbon solubility compared with traditional polyester polyols
Data Source
AI summary
Polyester polyols made from thermoplastic polyesters are disclosed. The polyols are reaction products of a thermoplastic polyester, a glycol, and a hydrophobe selected from ricinoleic acid, ethoxylated castor oil, saturated or unsaturated C9-C18 dicarboxylic acids, tung oil, soybean oil, sunflower oil, cardanol-based products, recycled cooking oil, isostearyl alcohol, hydroxy-functional materials derived from epoxidized, ozonized, or hydroformylated fatty esters or fatty acids, and mixtures thereof. In one process, the polyols are made by reacting the thermoplastic polyester with a glycol to give a digested intermediate, which is then reacted with the hydrophobe. In another process, the thermoplastic polyester, glycol, and hydrophobe are combined and reacted in a single step. These hydrophobes facilitate the production from recycled thermoplastics of polyols that have good transparency and little or no particulate settling or phase separation. High-recycle-content polyols having desirable properties and attributes for formulating polyurethane products, including aqueous polyurethane dispersions, can be made. The polyols provide a sustainable alternative to bio- or petrochemical-based polyols.