What are the Requirements for Ethylene Vinyl Alcohol Copolymers?
Are there legal or regulatory items that need to be considered concerning use of ethylene vinyl alcohol copolymer?
The food-contact use of ethylene vinyl alcohol copolymers is regulated by Title 21 of the Code of Federal Regulations (CFR) § 177.1360 ("Ethylene-vinyl acetate-vinyl alcohol copolymers"). Section 177.1360 permits the use of the copolymers made by "the partial or complete alcoholysis or hydrolysis of ethylene-vinyl acetate copolymers complying with Section 177.1350" in direct contact with food. Vinyl alcohol is unstable, so it cannot be used as a monomer. Instead, vinyl acetate is copolymerized with ethylene to form ethylene-vinyl acetate copolymers (EVA). The terminal acetate units on the polymer chain can then be hydrolyzed to -OH groups. The acetate groups may be partially or almost completely hydrolyzed, but there always are some acetate groups remaining along with the -OH groups. The Food and Drug Administration (FDA) regulates the copolymer as "ethylene-vinyl acetate-vinyl alcohol" (EVOH), although industry often merely refers to it as "ethylene vinyl alcohol."
The copolymers are rarely used directly with food. Because the copolymers are not good barriers to moisture, the material instead usually serves as a component of a multilayer structure where another layer, such as a polyolefin, is in direct contact with the food.
Section 177.1360, paragraphs (a)(2-4) limit ethylene and vinyl alcohol monomer content, depending on the types of food contacted, temperature conditions of use, and intended thickness of the film. Different extractive limitations apply also, depending on the monomer content of the copolymers. For example, Section 177.1360(a)(3) permits the food-contact use of EVOH copolymers containing 17-40 percent ethylene and 60-83 percent vinyl alcohol units by weight, as described in paragraph (d). Paragraph (d) prescribes that the finished food-contact article may be used in contact with all foods, except those containing more than 8 percent alcohol, under Conditions of Use B ("Boiling water sterilized") through H ("Frozen or refrigerated storage: Ready-prepared foods intended to be reheated in container at time of use"), provided that the finished article does not exceed 0.018 cm (0.007 in) and complies with extractive limitations. The extractive limitations in paragraph (d) are that the film, when extracted with distilled water at 100°C for 30 minutes, not yield EVOH oligomers exceeding 0.093 mg/cm2 of food-contact surface area using the methods described in the regulation.
Vinyl acetate monomer is a weak carcinogen in rodents, and it is recommended that EVOH be analyzed for residual vinyl acetate to ensure that the product is suitably pure for its intended use, as required by 21 CFR § 174.5.