§177.2460 Poly（2,6-dimethyl-1,4-phenylene） oxide resins.
The poly（2,6-dimethyl-1,4-phenylene） oxide resins identified in paragraph （a） of this section may be used as an article or as a component of an article intended for use in contact with food subject to the provisions of this section.
（a） Identity. For the purposes of this section, poly（2,6-dimethyl-1,4-phenylene） oxide resins consist of basic resins produced by the oxidative coupling of 2,6-xylenol such that the finished basic resins meet the specifications and extractives limitations prescribed in paragraph （c） of this section.
（b） Optional adjuvant substances. The basic poly（2,6-dimethyl-1,4-phenylene） oxide resins identified in paragraph （a） of this section may contain optional adjuvant substances required in the production of such basic resins. The optional adjuvant substances required in the production of the basic poly（2,6-dimethyl-1,4-phenylene） oxide resins may include substances permitted for such use by regulations in parts 170 through 189 of this chapter, substances generally recognized as safe in food, substances used in accordance with a prior sanction or approval, and the following:
| List of substances | Limitations (expressed as percent by weight of finished basic resin) |
| Diethylamin | Not to exceed 0.16 percent as residual catalyst. |
| Methyl alcohol | Not to exceed 0.02 percent as residual solvent. |
| Toluene | Not to exceed 0.2 percent as residual solvent. |
（c） Specifications and extractives limitations. The poly（2,6-dimethyl-1,4-phenylene） oxide basic resins meet the following:
（1） Specifications. Intrinsic viscosity is not less than 0.30 deciliter per gram as determined by ASTM method D1243-79, “Standard Test Method for Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference, modified as follows. Copies of the incorporation by reference may be obtained from the American Society for Testing Materials, 100 Barr Harbor Dr., West Conshohocken, Philadelphia, PA 19428-2959, or may be examined 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.
（i） Solvent: Chloroform, reagent grade containing 0.01 percent tert- butylcatechol.
（ii） Resin sample: Powdered resin obtained from production prior to molding or extrusion.
（iii） Viscometer: Cannno-Ubbelohde series 25 dilution viscometer （or equivalent）。
（iv） Calculation: The calculation method used is that described in appendix X.1.3 （ASTM method D1243-79, cited and incorporated by reference in paragraph （c）（1） of this section） with the reduced viscosity determined for three concentration levels （0.4, 0.2, and 0.1 gram per deciliter） and extrapolated to zero concentration for intrinisic viscosity. The following formula is used for determining reduced viscosity:
Code of Federal Regulations
[Please see PDF for image: ER01JA93.406 ]
where:
t=Solution efflux time.
to=Solvent efflux time.
c=Concentration of solution in terms of grams per deciliter.
（2） Extractives limitations. Total resin extracted not to exceed 0.02 weight-percent when extracted with n- heptane at 160 °F for 2 hours as determined using 200 milliliters of reagent grade n- heptane which has been freshly distilled before use and 25 grams of poly （2,-6-dimethyl-1,4-phenylene） oxide resin. The resin as tested is in pellet form having a particle size such that 100 percent of the pellets will pass through a U.S. Standard Sieve No. 6 and 100 percent of the pellets will be held on a U.S. Standard Sieve No. 10.
（d） Other limitations. The poly（2,6-dimethyl-1,4-phenylene） oxide resins identified in and complying with this section, when used as components of the food-contact surface of any article that is the subject of a regulation in parts 174, 175, 176, 177, 178 and § 179.45 of this chapter, shall comply with any specifications and limitations prescribed by such regulation for the article in the finished form in which it is to contact food.
（e） Uses. The poly（2,6-dimethyl-1,4-phenylene） oxide resins identified in and complying with the limitations in this section may be used as articles or components of articles intended for repeated food-contact use or as articles or components of articles intended for single-service food-contact use only under the conditions described in § 176.170（c） of this chapter, table 2, conditions of use H.
[42 FR 14572, Mar. 15, 1977, as amended at 49 FR 10111, Mar. 19, 1984; 63 FR 8852, Feb. 23, 1998]