Bisphenol A (BPA) free epoxy resins
Inventors
Assignees
University of Massachusetts Lowell
Publication Number
US-9139690-B2
Publication Date
2015-09-22
Expiration Date
2032-04-27
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Abstract
An epoxy resin is provided that includes a diglycidyl ether of a substituted cycloaliphatic diol or bis-thiol, and a thermoset epoxy polymer is provided employing the same. The epoxy resin is bisphenol A free, and capable of forming thermoset epoxy polymers with fewer associated health and environmental concerns than conventional epoxies based on phenolic compounds.
Core Innovation
The invention provides a bisphenol A (BPA) free epoxy resin comprising a diglycidyl ether of a substituted cycloaliphatic diol or bis-thiol. This resin is used to form thermoset epoxy polymers which avoid the health and environmental issues traditionally associated with BPA- and phenolic-based epoxies. The core composition is represented by specific chemical formulas where substituents are clearly outlined, and examples include diglycidyl ethers of diols such as 2,2,4,4-tetramethyl-1,3-cyclobutanediol.
The invention addresses the need for new epoxy resins that are capable of forming BPA-free thermoset polymers, while maintaining performance characteristics similar to conventional BPA-based epoxies. BPA presence in epoxies used for food packaging is a significant health and environmental concern due to its structural similarity to estrogen and its link to endocrine disruption. The disclosed resin aims to eliminate these risks by avoiding the use of phenolic compounds.
The resin's synthesis includes a process that can utilize a single phase transfer catalyst for both the creation of the diglycidyl ether monomer and its subsequent chain extension, minimizing purification steps and process complexity. The resultant thermoset exhibits flexibility, adhesion, and heat resistance suitable for food and beverage container coatings, adhesives, and other applications, achieving these properties without the release of BPA or related compounds.
Claims Coverage
The patent contains multiple independent inventive features relating to BPA-free epoxy resins, their compositions, methods of synthesis, curing, and their use in containers and coatings.
BPA-free epoxy resin based on substituted cycloaliphatic diol diglycidyl ether
An epoxy resin represented by a specific chemical structure comprising a diglycidyl ether of a substituted cycloaliphatic diol or bis-thiol, where the substituents and structure are defined to exclude BPA and related phenolic structures.
Cured epoxy resin with reduced potential to release endocrine disrupting compounds
A cured epoxy resin composition formed from the reaction product of the above epoxy resin and a curative compound, specifically designed to minimize the potential to release endocrine disrupting compounds compared to BPA/phenolic-based counterparts.
Chain-extended epoxy resin synthesis using sequential monomer reactions
A method of preparing a chain extended epoxy resin by reacting a first substituted 1,3-cyclobutanediol molecule with epichlorohydrin in the presence of a catalyst to form a diglycidyl ether, then further reacting this ether with a second substituted 1,3-cyclobutanediol molecule (or aliphatic/cycloaliphatic analogue) with the same or a different catalyst to yield a chain-extended resin.
Container having a food-contact surface coated with BPA-free epoxy resin
A container—such as a food or beverage can—comprising a food-contact surface that is at least partially coated with a composition containing the disclosed epoxy resin and a curative compound. The container is specified as being of metal construction.
Method for producing a coated food-contact container
A method which comprises providing a coating composition with the described BPA-free epoxy resin, applying this composition to a substrate's food-contact surface, and forming a container from that substrate, with flexibility as to the stage at which coating is applied.
Method of preparing chain extended epoxy resin using cycloaliphatic molecules
A method of preparing a chain extended epoxy resin by reacting a first cycloaliphatic molecule with epichlorohydrin in the presence of a catalyst to form a diglycidyl ether, followed by reaction with a second cycloaliphatic molecule using a catalyst chosen from quaternary ammonium or phosphonium salts.
These inventive features cover BPA-free epoxy resin compositions, their synthesis and crosslinking, as well as their use and application in the manufacture of food- and beverage-contact containers and coatings.
Stated Advantages
Eliminates the potential to release BPA and related endocrine-disrupting compounds, thereby reducing associated health and environmental concerns.
Provides thermoset polymers with mechanical, thermal, and performance characteristics similar to or better than conventional BPA-based epoxies.
Exhibits limited UV absorbance due to the absence of phenolic groups, enabling easier crosslinking via photoinitiation and improved UV resistance.
Demonstrates lower viscosity compared to phenolic-based epoxies, allowing for better coating coverage and penetration.
Enables simplified synthesis using a single phase transfer catalyst for both steps, reducing purification requirements.
Has a range of glass transition temperatures, flexibility, and adhesion values suitable for demanding applications such as food and beverage can coatings and adhesives.
Documented Applications
Coating food and beverage cans, including as an inner lining for direct food contact.
Use in adhesives for metal substrates, with epoxy resins cured by polyamine hardeners.
Coating metal substrates via spray, coil, wash, sheet, and side seam application methods for can manufacturing.
Application in injection molding for drinking bottles, glasses, and sheets/films.
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