§177.1655 Polysulfone resins
Polysulfone resins identified in paragraph （a） of this section may be safely used as articles or components of articles intended for use in contact with food, in accordance with the following prescribed conditions:
（a） For the purpose of this section, polysulfone resins are:
（1） Poly（oxy-p -phenylenesulfonyl-p -phenyleneoxy-p -phenyleneisopropylidene-p -phenylene） resins （CAS Reg. No. 25154-01-2） consisting of basic resins produced when the disodium salt of 4,4′-isopropylidenediphenol is made to react with 4,4′-dichlorodiphenyl sulfone in such a way that the finished resins have a minimum number average molecular weight of 15,000, as determined by osmotic pressure in monochlorobenzene; or
（2） 1,1′-Sulfonylbis[4-chlorobenzene] polymer with 4,4′-（1-methylethylidene）bis[phenol] （minimum 92 percent） and 4,4′-sulfonylbis[phenol] （maximum 8 percent） （CAS Reg. No. 88285-91-0） produced when a mixture of 4,4′-isopropylidenediphenol （minimum 92 percent） and 4,4′-sulfonylbis[phenol] （maximum 8 percent） is made to react with 4,4′-dichlorodiphenyl sulfone in such a way that the finished resin has a minimum number average molecular weight of 26,000, as determined by osmotic pressure in dimethylformamide.
（b） The basic polysulfone 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 polysulfone resins may include substances described in § 174.5（d） of this chapter and the following:
| List of substances | Limitations |
| Dimethyl sulfoxide | Not to exceed 50 parts per million as residual solvent in finished basic resin in paragraph (a)(1) of this section. |
| Monochlorobenzene | Not to exceed 500 parts per million as residual solvent in finished basic resin in paragraph (a)(1) of this section. |
| N-methyl-2-pyrrolidone | Not to exceed 0.01 percent (100 parts per million) as residual solvent in finished basic resin in paragraph (a)(2) of this section. |
（c） Polysulfone resins, when extracted at reflux temperatures for 6 hours with the solvents—distilled water, 50 percent （by volume） ethyl alcohol in distilled water, 3 percent acetic acid in distilled water, and n- heptane, yield total extractives in each extracting solvent not to exceed 0.0078 milligram per square centimeter （0.05 milligram per square inch） of resin surface. Note: In testing the finished polysulfone resins, use a separate resin test sample for each required extracting solvent.
（d） Polysulfone resins intended for repeated use in contact with food may be used under conditions of use A through H in table 2 of § 176.170（c） of this chapter. The resins intended for single-service food-contact use may be used only under condition of use H described in table 2 of § 176.170（c） of this chapter.
[51 FR 882, Jan. 9, 1986; 51 FR 4165, Feb. 3, 1986; 61 FR 29475, June 11, 1996]
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