The styrene block polymers identified in paragraph (a) of this section may be safely used as articles or as components of articles intended for use in contact with food, subject to provisions of this section.
(a) For the purpose of this section, styrene block polymers are basic polymers manufactured as described in this paragraph, so that the finished polymers meet the specifications prescribed in paragraph (b) of this section, when tested by the methods described in paragraph (c) of this section.
(1) Styrene block polymers with 1,3-butadiene are those produced by the catalytic solution polymerization of styrene and 1,3-butadiene.
(2) Styrene block polymers with 2-methyl-1,3-butadiene are those produced by the catalytic solution polymerization of styrene and 2-methyl-1,3-butadiene.
(3) Styrene block polymers with 1,3-butadiene, hydrogenated are those produced by the catalytic solution polymerization of styrene and 1,3-butadiene, and subsequently hydrogenated.
(b) Specifications: ----------------------------------------------------------------------------------------------------------------
Maximum Maximum
extractable extractable
fraction in fraction in 50
Molecular Glass distilled water percent ethanol
Styrene block polymers weight Solubility transition at specified at specified
(minimum) points temperatures, temperatures,
times, and times, and
(i) Styrene block polymers 29,000 Completely -98 C (-144 0.0039 mg/cm\2\ 0.002 mg/cm\2\
with 1,3-butadiene; for use as soluble in F) to -71 C (0.025 mg/in\2\) (0.01 mg/in\2\)
articles or as components of toluene. (-96 F) and of surface at of surface at 66
articles that contact food of 86 C (187 F) reflux C (150 F) for 2
Types I, II, IV-B, VI, VII-B, to 122 C temperature for hr on a 0.19 cm
and VIII identified in table 1 (252 F). 30 min on a 0.19 (0.075 in) thick
in Sec. 176.170(c) of this cm (0.075 in) sample.
chapter under conditions of thick sample.
use D, E, F, and G described
in table 2 in Sec. 176.170(c)
of this chapter.
(ii) Styrene block polymers 29,000 ......do...... ......do..... ......do......... Do.
with 1,3-butadiene; for use as
components of pressure-
sensitive adhesives that
contact food of Types I, II,
IV-B, VI, VII-B, and VIII
identified in table 1 in Sec.
176.170(c) of this chapter
under conditions of use C, D,
E, F and G described in table
2 in Sec. 176.170(c) of this
chapter, provided the pressure-
sensitive adhesives be applied
only to closure tapes for
sealing containers having a
capacity of not less than 160
cc (5.5 fluid ounces) and that
the area of the adhesive
exposed to food shall not
exceed 4.03 cm\2\ (0.625
in\2\). The pressure-sensitive
adhesive may contain terpene
resins as identified in Sec.
175.125(b)(2) of this chapter.2. Styrene block polymers with 29,000 ......do...... -65 C (-85 F) 0.002 mg/cm\2\ 0.002 mg/cm\2\
2-methyl-1,3-butadiene; for to -47 C (- (0.01 mg/in\2\) (0.01 mg/in\2\)
use as articles or as 53 F) and 86 of surface at of surface at 66
components of articles that C (187 F) to reflux C (150 F) for 2
contact food of Types I, II, 122 C (252 temperature for hr on a 0.071 cm
IV-B, VI, VII-B, and VIII F). 2 hr on a 0.071 (0.028 in) thick
identified in table 1 in Sec. cm (0.028 in) sample.
176.170(c) of this chapter. thick sample. (Optionally,
(Optionally, maximum net
maximum net residue soluble
residue soluble in chloroform
in chloroform shall not exceed
shall not exceed 0.00040 mg/cm\2\
0.00020 mg/cm\2\ (0.0025 mg/
(0.0013 mg/ in\2\) of
in\2\) of surface.)
(i) Styrene block polymers 16,000 ......do...... -50 C (-58 F) 0.002 mg/cm\2\ 0.002 mg/cm\2\
with 1,3-butadiene, to -30 C (- (0.01 mg/in\2\) (0.01 mg/in\2\)
hydrogenated (CAS Reg. No. 22 F) and 92 of surface at of surface at 66
66070-58-4): for use as C (198 F) to reflux C (150 F) for 2
articles or as components of 98 C (208 F). temperature for hr on a 0.071 cm
articles that contact food of 2 hr on a 0.071 (0.028 in) thick
Types I, II, IV-B, VI, VII-B, cm (0.028 in) sample.
and VIII identified in table 1 thick sample.
in Sec. 176.170(c) of this
chapter.(ii) Styrene block polymers 16,000 ......do...... ......do..... ......do......... Do.
with 1,3-butadiene,
hydrogenated (CAS Reg. No.
66070-58-4): for use at levels
not to exceed 42.4 percent by
weight as a component of
closures with sealing gaskets
that would contact food of
Types III, IV-A, V, VII-A,
VIII, and IX identified in
table 1 in Sec. 176.170(c) of
this chapter, and in condition
of use D as described under
table 2 in Sec. 176.170(c) of
this chapter.----------------------------------------------------------------------------------------------------------------
(c) The analytical methods for determining whether styrene block polymers conform to the specifications prescribed in this section are as follows and are applicable to the finished polymer.
(1) Molecular weight. Molecular weight shall be determined by intrinsic viscosity (or other suitable method).
(2) Glass transition points. The glass transition points shall be determined by either of the following methods:
(i) ASTM method D2236-70 (``Standard Method of Test for Dynamic Mechanical Properties of Plastics by Means of Torsional Pendulum,'' which is incorporated by reference; copies are available from American Society for Testing and Materials (ASTM), 100 Barr Harbor Dr., West Conshohocken, Philadelphia, PA 19428-2959, 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.) modified by using a forced resonant vibration instead of a fixed vibration and by using frequencies of 25 to 40 cycles per second instead of 0.1 to 10 cycles per second.
(ii) Direct reading viscoelastometric method titled ``Direct Reading Viscoelastrometric Method for Determining Glass Transition Points of Styrene Block Polymers'' (which is incorporated by reference; copies are available from the Center for Food Safety and Applied Nutrition (HFS-200), Food and Drug Administration, 5100 Paint Branch Pkwy., College Park, MD 20740, 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.), by which the glass transition points are determined in the tensile mode of deformation at a frequency of 35 hertz using a Rheovibron Model DDV-II (or equivalent) Direct Reading Viscoelastometer. Take maxima in the out-of-phase component of the complex modulus as the glass transition points. For block polymers of low styrene content or for simple block polymers, the polymer may be treated with 0.3 part per hundred dicumyl peroxide and cured for 30 minutes at 153 C to accentuate the upper transition point.
(3) Maximum extractable fractions in distilled water and 50 percent ethanol and the maximum net residue solubles in chloroform. The maximum extractable fractions in distilled water and 50 percent ethanol, and the maximum net residue solubles in chloroform, shall be determined in accordance with Sec. 176.170(d)(3) of this chapter using a sandwich form of the finished copolymer of the specified thickness and for the time and temperature specified in paragraph (b) of this section.
(d) The provisions of this section are not applicable to butadiene-styrene copolymers listed in other sections of this subpart.
(e) The provisions of this section are not applicable to styrene block polymers with 1,3-butadiene listed in Sec. 175.105 of this chapter. [42 FR 14572, Mar. 15, 1977, as amended at 42 FR 43621, Aug. 30, 1977; 47 FR 11844, Mar. 19, 1982; 51 FR 16828, May 7, 1986; 54 FR 24898, June 12, 1989; 58 FR 65546, Dec. 15, 1993]