Bisphenol A (BPA) free epoxy resins
Inventors
Assignees
University of Massachusetts Lowell
Publication Number
US-9434867-B2
Publication Date
2016-09-06
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 an epoxy resin composition that is free from bisphenol A (BPA), instead utilizing diglycidyl ethers of substituted cycloaliphatic diols or bis-thiols as the core component. The epoxy resin is engineered to form thermoset epoxy polymers with mechanical, thermal, and chemical properties that are similar to or better than conventional BPA-based epoxies, but without the health and environmental concerns associated with BPA and related phenolic compounds.
The primary problem addressed by the invention is the need for a novel epoxy resin capable of creating BPA-free thermoset epoxies that can serve as practical alternatives to existing bisphenol A-based epoxies, especially for applications where BPA’s potential health effects, including its role as an endocrine disruptor, are a significant concern. The resin addresses this by eliminating phenolic compounds and minimizing the potential to release estrogenic or endocrine disrupting compounds.
The invention discloses specific embodiments of the epoxy resin composition, defining the general structure of the monomers involved and suitable synthesis methods, including a process where a single phase transfer catalyst is used in both steps to simplify production and reduce purification requirements. The resin can be crosslinked with standard curatives to produce adhesives or coatings for food and beverage containers, maintaining or surpassing the functional performance of phenolic-based resins.
Claims Coverage
The patent contains several inventive features primarily focused on BPA-free epoxy resin compositions, specific monomer structures, synthesis methods, and corresponding adhesive compositions.
Epoxy resin adhesive composition based on diglycidyl ethers of substituted cycloaliphatic diols
An adhesive composition comprising an epoxy resin represented by a core structure derived from diglycidyl ethers of substituted cycloaliphatic diols or bis-thiols, wherein the resin formulation is BPA-free. The R group within the molecule is derived from specified cycloaliphatic diol diglycidyl ethers, including but not limited to 2,2,4,4-tetramethyl-1,3-cyclobutanediol and related derivatives. The formulation allows for additional specification of the substituents such as O or S, and R5, R6, R11, R12 chosen from hydrogen, methyl, or ethyl groups.
Adhesive composition viscosity and structure control
Defines an epoxy resin adhesive composition whose viscosity is less than about 100 poise at 25°C when measured as a 40% weight solution in methyl ethyl ketone or equivalent solvent. Also specifies certain preferred chemical structures of the epoxy resin, including all methyl groups in specific positions and structures represented by defined schemes.
Cured adhesive composition with reduced endocrine disruption potential
A cured adhesive composition comprising the reaction product of the disclosed BPA-free epoxy resin and a curative compound, in which the resultant cured resin exhibits a reduced potential for release of endocrine disrupting compounds compared to BPA- or phenolic-based epoxy resins. The curative may be a formaldehyde hardener, polyamine hardener, or polythiol hardener.
Chain extension synthesis method using substituted cycloaliphatic diols
An adhesive composition in which the epoxy resin is a chain-extended product, prepared by: (a) reacting a first substituted 1,3-cyclobutanediol with epichlorohydrin in the presence of a first catalyst to form a diglycidyl ether, and (b) reacting the diglycidyl ether with a second substituted 1,3-cyclobutanediol in the presence of a second catalyst (optionally the same as the first) to form the chain-extended epoxy resin. A specific embodiment details the use of 2,2,4,4-tetramethyl-1,3-cyclobutanediol and tetrabutyl ammonium hydrogen bisulfate as the catalyst.
The claims cover BPA-free epoxy resin adhesive compositions derived from substituted cycloaliphatic diols, controlled viscosity features, curable adhesive products with minimized endocrine activity, and specific synthesis routes to create chain-extended resins using well-defined starting materials and catalysts.
Stated Advantages
The epoxy resin is BPA-free, reducing health and environmental concerns linked with BPA and phenolic compounds.
Capable of forming rigid thermoset epoxy polymers with functional properties similar to or better than those of bisphenol A-based epoxies.
Minimizes the potential to release estrogenic or endocrine disrupting compounds in final cured products.
Exhibits suitable flexibility, heat resistance, chemical resistance, and adhesion properties for food and beverage container coatings and adhesives.
Offers lower viscosity than phenolic-based epoxies, enabling improved coating coverage and penetration.
Naturally exhibits limited UV absorbance, allowing for effective photoinitiated crosslinking without extra chemical modification.
Can be synthesized in a two-step process using the same catalyst, reducing purification needs and simplifying production.
Documented Applications
Coating the food-contact surfaces of packaging articles, such as food and beverage cans, including interior coatings.
Adhesive compositions for bonding applications, using amine or polyamine hardeners for single-joint lap-shear tests on metals.
Application methods for coatings including spray coating, coil coating, wash coating, sheet coating, and side seam coatings on metal substrates.
Use in injection molding for articles such as drinking bottles, drinking glasses, or in sheet/film applications.
Coating of metal substrates for food and beverage containers before or after forming, suitable for two-piece or three-piece can manufacturing.
Commercial coating and curing methods including electrocoating, extrusion coating, laminating, powder coating, and other related industrial methods.
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