21 CFR §173.65

1. (a)The copolymer is prepared in appropriate physical form and is derived by the polymerization of a grade of divinylbenzene which comprises at least 79 weight-percent divinylbenzene, 15 to 20 weight-percent ethylvinylbenzene, and no more than 4 weight-percent nonpolymerizable impurities.
2. (b)In accordance with the manufacturer's directions, the copolymer described in paragraph (a) of this section is subjected to pre-use extraction with a water soluble alcohol until the level of divinylbenzene in the extract is less than 50 parts per billion as determined by a method titled, “The Determination of Divinylbenzene in Alcohol Extracts of Amberlite XAD-4,” which is incorporated by reference. Copies of this method are available from the Office of Food Additive Safety (HFS-200), Center for Food Safety and Applied Nutrition, Food and Drug Administration, 5001 Campus Dr., College Park, MD 20740, 240-402-1200, or available for inspection at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. The copolymer is then treated with water according to the manufacturer's recommendation to remove the extraction solvent to guarantee a food-grade purity of the resin at the time of use, in accordance with current good manufacturing practice.
3. (c)The temperature of the aqueous food stream contacting the polymer is maintained at 79.4 °C (175 °F) or less.
4. (d)The copolymer may be used in contact with food only of Types I, II, and VI-B (excluding carbonated beverages) described in table 1 of paragraph (c) of § 176.170 of this chapter.