[Code of Federal Regulations]
[Title 21, Volume 3]
[Revised as of January 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR173.21]
[Page 122]
TITLE 21--FOOD AND DRUGS
CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN
SERVICES (CONTINUED)
PART 173 SECONDARY DIRECT FOOD ADDITIVES PERMITTED IN FOOD FOR HUMAN
Subpart A Polymer Substances and Polymer Adjuvants for Food Treatment
Sec. 173.21 Perfluorinated ion exchange membranes.
Substances identified in paragraph (a) of this section may be safely
used as ion exchange membranes intended for use in the treatment of bulk
quantities of liquid food under the following prescribed conditions:
(a) Identity. The membrane is a copolymer of ethanesulfonyl
fluoride, 2-[1-[difluoro-[(tri fluoro ethenyl) oxy] methyl]-1,2,2,2-
tetra fluoro ethoxy]-1,1,2,2,-tetra fluoro-, with tetra fluoro ethylene
that has been subsequently treated to hydrolyze the sulfonyl fluoride
group to the sulfonic acid. The Chemical Abstracts Service name of this
polymer is ethane sulfonic acid, 2-[1-[difluoro-[(tri fluoro
ethenyl)oxy] methyl]-1,2,2,2-tetra fluoro ethoxy]-1,1,2,2,-tetra fluoro-
, polymer with tetra fluoro ethane (CAS Reg. No. 31175-20-9).
(b) Optional adjuvant substances. The basic polymer identified in
paragraph (a) of this section may contain optional adjuvant substances
required in the production of such basic polymer. These optional
adjuvant substances may include substances used in accordance with Sec.
174.5 of this chapter.
(c) Conditions of use. (1) Perfluorinated ion exchange membranes
described in paragraph (a) of this section may be used in contact with
all types of liquid foods at temperatures not exceeding 70[deg] (158
[deg]F).
(2) Maximum thickness of the copolymer membrane is 0.007 inch (0.017
centimeter).
(3) Perfluorinated ion exchange membranes shall be maintained in a
sanitary manner in accordance with current good manufacturing practice
so as to prevent microbial adulteration of food.
(4) To assure their safe use, perfluorinated ionomer membranes shall
be thoroughly cleaned prior to their first use in accordance with
current good manufacturing practice.
[59 FR 15623, Apr. 4, 1994]
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