§177.2440 Polyethersulfone resins
Polyethersulfone resins identified in paragraph （a） of this section may be safely used as articles or components of articles intended for repeated use in contact with food in accordance with the following prescribed conditions:
?。╝） For the purpose of this section, polyethersulfone resins are:
?。?） Poly（oxy-p -phenylenesulfonyl-p -phenylene） resins （CAS Reg. No. 25667-42-9）, which have a minimum number average molecular weight of 16,000.
（2） 1,1′-sulfonylbis[4-chlorobenzene] polymer with 4,4′-（1-methyl-ethyl-idene）bis[phenol] （maximum 8 percent） and 4,4′-sulfonylbis[phenol] （minimum 92 percent） （CAS Reg. No. 88285-91-0）, which have a minimum number average molecular weight of 26,000.
?。?） In paragraphs （a）（1） and （a）（2） of this section, the minimum number average molecular weight is determined by reduced viscosity in dimethyl formamide in accordance with ASTM method D2857-70 （Reapproved 1977）, “Standard Test Method for Dilute Solution Viscosity of Polymers,” which is incorporated by reference. Copies 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 Division of Petition Control （HFS-215）, Center for Food Safety and Applied Nutrition, 1110 Vermont Ave. NW., suite 1200, Washington, DC, or 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 basic resins identified in paragraphs （a）（1） and （a）（2） of this section may contain optional adjuvant substances described in § 174.5（d） of this chapter and the following:
| List of substances | Limitations |
| Diphenylsulfone | .Not to exceed 0.2 percent as residual solvent in the finished basic resin described in paragraph (a)(1) of this section |
| Dimethyl sulfoxide | Not to exceed 0.01 percent as residual solvent in the finished basic resin described in paragraph (a)(1) of this section. |
| N-methyl-2-pyrrolidone | Not to exceed 0.01 percent as residual solvent in the finished basic resin described in paragraph (a)(2) of this section. |
?。╟） The finished food-contact article, when extracted at reflux temperatures for 2 hours with the following four solvents, yields net chloroform-soluble extractives in each extracting solvent not to exceed 0.02 milligram per square inch of food-contact surface: distilled water, 50 percent （by volume） ethyl alcohol in distilled water, 3 percent acetic acid in distilled water, and n -heptane. （Note: In testing the finished food-contact article, use a separate test sample for each required extracting solvent.）
（d） In accordance withgood manufacturing practice, finished food-contact articles containing the polyethersulfone resins shall be thoroughly cleansed before their first use in contact with food.
[44 FR 34493, June 15, 1979, as amended at 47 FR 38885, Sept. 3, 1982; 49 FR 10111, Mar. 19, 1984; 50 FR 47211, Nov. 15, 1985; 60 FR 48648, Sept. 20, 1995]
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