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Initiating a Regulatory 'Cure' for UV/EB Processed Food-Contact Coatings

November 1, 2002

By Keller and Heckman LLP’s Packaging Practice Group

The use of ultraviolet (UV) and electron beam (EB) radiation is becoming an increasingly popular technology for use in the curing of food-contact coatings. As use of the technology expands to encompass more applications, manufacturers will continue to grapple with establishing a suitable regulatory status with the U.S. Food and Drug Administration (FDA).

The technology represents a unique way in which coatings are cured or dried using UV light or EB radiation instead of conventional heat. In essence, UV light and focused electron beams interact with specially formulated resins to cure food-contact coatings (the technology also is used to cure ink and adhesive formulations used in food packaging).

Proponents of UV/EB technology claim that it is quicker and cheaper than the curing of coatings by conventional methods. In addition, UV/EB curing is considered to be advantageous from an environmental perspective because solvents normally used in conventional curing are not used in UV/EB curing. Among other uses, UV/EB technology is currently being employed to cure coatings on beverage cans, one of the world's largest food-packaging markets.

As the use of the UV/EB technology to cure coatings becomes even more popular, and additional coatings applications are found, manufacturers of coatings face a significant regulatory question: how does one establish a suitable FDA status for an otherwise cleared food-contact coating that is cured using UV/EB technology? The purpose of this article is to provide information on how a coatings manufacturer can address this emerging compliance issue.

UV/EB Curing Process

To understand how to establish a suitable FDA status of a food-contact coating that is cured using UV/EB technology, it is first helpful to understand how the technology works.1

UV/EB curing describes the use of UV or visible light and EB radiation to polymerize a resin to form a coating on a substrate. The process also is known as "radiation curing," because UV and EB are radiant energy sources. The energy sources for UV or visible light are typically medium-pressure mercury lamps, pulsed xenon lamps, or lasers. Electron beam accelerators are used to generate the electron stream capable of curing thicker, pigmented coatings. Unlike photons of light (i.e., UV light), which generally are absorbed at the surface of a coating, electrons penetrate through denser matter.

In the case of EB radiation curing, high-energy electrons interact directly with a coating formulation to generate a highly reactive resin. If UV or visible light is utilized as the energy source, a photoinitiator is added to the resin formulation. The photoinitiator, when exposed to UV or visible light, generates free radicals, or actions, which initiate crosslinking between the resin components.

A typical coating formulation contains:

  1. polymeric or resinous materials to form the backbone of the coating (e.g., acrylic, epoxy, or vinyl resins, polypropylene, polyethylene, or styrene polymers, elastomeric rubber material);
  2. additives used in the manufacture of the coating (e.g., stabilizers, colorants, defoamers, antioxidants, release agents, catalysts, crosslinking agents, surfactants); and
  3. in the case of UV-cured coatings, photoinitiators, which typically absorb light to produce free radicals to induce the crosslinking of the polymeric and resinous material in the coating.

FDA's Regulation of UV/EB Cured Coatings

A separate article in this month's focus titled, "What's Under the Coat of Section 175.300?" (see link at end of article), provides some background information regarding the manner in which coatings for food-contact articles are regulated in the United States. This information is necessary to understand how to establish a suitable FDA status for a UV/EB cured coating in contact with food.

As indicated in that article, a particularly unique feature of the "can coatings regulation" (found at 21 C.F.R. §175.300), is that it anticipates the reaction of substances cleared in the regulation pursuant to a permitted curing process for the finished coating. Specifically, Section 175.300(a)(1)-(3) permits the use of coatings characterized by one or more of the following:

  1. cured by oxidation;
  2. cured by polymerization, condensation, and/or cross linking without oxidation; and
  3. prepared from the pre-polymerized substances.

Based on this language, we have long taken the position that reaction products of substances listed in the coating regulation are covered by the regulation for use in coatings, provided the reaction products can properly be attributed to one of the permitted curing processes for the finished coating.

It is noteworthy that each of these subsections (§§175.300(a) (1) - (3)) describes a chemical process by which can coatings are cleared. The regulation does not, though, describe the particular triggering occurrence-such as heat, visible light, UV light, or EB radiation-that leads to the chemical reaction. Any one of these triggering mechanisms may be considered permitted by Section 175.300, provided the coating otherwise complies with Section 175.300, and provided that adequate curing takes place so that the coating meets FDA's suitable purity standards.

Accordingly, it is perfectly acceptable under the Federal Food, Drug, and Cosmetic Act ("the Act") and its implementing regulations to utilize UV/EB curing methods to manufacture can coatings under Section 175.300. While the regulation does identify permitted "curing" processes-oxidation; polymerization, condensation, and/or cross- linking without oxidation; as well as "prepared from pre-polymerized substances"-the regulation does not indicate how these chemical curing mechanisms are accomplished.

Of course, each material used in the coating must be suitably cleared. If, for example, a photoinitiator being thus used were not cleared, the manufacturer would need to assess whether it becomes a food additive, thus triggering the need for clearance. Provided that whatever curing "trigger" that is used results in a suitably pure package, and further provided that the can coating otherwise complies with the requirements of Section 175.300, the can coating may be marketed in compliance with the Act, whether cured with UV/EB treatment or some other mechanism.

As mentioned above, articles intended for use in contact with food must also be of a purity suitable for their intended use. This means that impurities or byproducts that might be present in a can coating must be evaluated to assure that the residual level of a given impurity or byproduct is safe. Therefore, a manufacturer should assess whether any problematic substances are generated due to the curing process (e.g., photoinitiator byproducts) and, if so, whether these are present at suitably low levels not presenting a potential health or safety concern.

If specific FDA clearance is necessary for a coating not otherwise cleared under Section 175.300, a Food Contact Notification (FCN) to cover the use of the UV/EB cured coating must be submitted to FDA.2 In addition to the administrative, chemistry, and toxicology information typically required in an FCN submission, the notification also should demonstrate that the UV/EB curing process does not result in additional migrants or otherwise create degradation products that raise a safety concern. In the case of a UV cured coating, any free radicals generated from the degradation of the photoinitiator should be accounted for in an FCN, and sufficient data should be submitted to support the safety of those substances at their detected levels in the cured coating.

Conclusion

In sum, as potential new food packaging markets emerge for UV/EB cured coatings, manufacturers need to be diligent to ensure that the coating, per se, not only complies with the Federal Food, Drug, and Cosmetic Act and all applicable food additive regulations, including Section 175.300, but that the UV/EB curing process does not result in the addition of any uncleared food additives that require additional FDA premarket clearance or any impurities or degradation products that raise a safety concern.

FOOTNOTES

1Some of the technical information in this article was obtained from RadTech International North America, the association for the advancement of UV and EB technology. RadTech serves as an industry forum, addressing the educational needs of the users and suppliers of UV and EB equipment and materials. More information is available at www.radtech.org.

2Section 409(h) of the Act (21 U.S.C. §348(h)). Under the FCN program, a manufacturer or supplier of a food-contact material may submit a notification to FDA regarding the identity and use of the new food-contact substance, along with information supporting the conclusion that the substance is safe for the intended use. If FDA does not object in writing to the notification within 120 days of its receipt, the submitter may market the product. Unlike food additive regulations, the notifications may be relied upon only by the submitter and its customers.