§177.1980 氯乙烯/丙烯共聚物(Vinyl chloride-propylene copolymers)

    　　§177.1980 Vinyl chloride-propylene copolymers.


　　     The vinyl chloride-propylene copolymers identified in paragraph （a） of this section may be safely used as components of articles intended for contact with food, subject to the provisions of this section.

　　（a） For the purpose of this section, vinyl chloride-propylene copolymers consist of basic copolymers produced by the copolymezation of vinyl chloride and propylene such that the finished basic copolymers meet the specifications and extractives limitations prescribed in paragraph （c） of this section, when tested by the methods described in paragraph （d） of this section.

　　（b） The basic vinyl chloride-propylene copolymers identified in paragraph （a） of this section may contain optional adjuvant substances required in the production of such basic copolymers. The optional adjuvant substances required in the production of the basic vinyl chloride-propylene copolymers may include substances permitted for such use by regulations in parts 170 through 189 of this chapter, substances generally recognized as safe in food, and substances used in accordance with a prior sanction or approval.

　　（c） The vinyl chloride-propylene basic copolymers meet the following specifications and extractives limitations:

　　（1） Specifications. （i） Total chlorine content is in the range of 53 to 56 percent as determined by any suitable analytical procedure of generally accepted applicability.

　　（ii） Intrinsic viscosity in cyclo-hexanone at 30 °C is not less than 0.50 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. 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 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.

　　（2） Extractives limitations. The following extractives limitations are determined by the methods described in paragraph （d） of this section:

　　（i） Total extractives do not exceed 0.10 weight-percent when extracted with n- heptane at 150 °F for 2 hours.

　　（ii） Total extractives do not exceed 0.03 weight-percent when extracted with water at 150 °F for 2 hours.

　　（iii） Total extractives obtained by extracting with water at 150 °F for 2 hours contain no more than 0.17 milligram of vinyl chloride-propylene copolymer per 100 grams of sample tested as determined from the organic chlorine content. For the purpose of this section, the organic chlorine content is the difference between the total chlorine and ionic chlorine contents determined as described in paragraph （d） of this section.

　　（d） Analytical methods: The analytical methods for determining whether vinyl chloride-propylene basic copolymers conform to the extractives limitations prescribed in paragraph （c） of this section are as follows and are applicable to the basic copolymers in powder form having a particle size such that 100 percent will pass through a U.S. Standard Sieve No. 40 and 80 percent will pass through a U.S. Standard Sieve No. 80:

　　（1） Reagents— （i） Water. All water used in these procedures shall be demineralized （deionized）, freshly distilled water.

　　（ii） n-Heptane. Reagent grade, freshly distilled n- heptane shall be used.

　　（2） Determination of total amount of extractives. All determinations shall be done in duplicate using duplicate blanks. Approximately 400 grams of sample （accurately weighed） shall be placed in a 2-liter Erlenmeyer flask. Add 1,200 milliliters of solvent and cover the flask with aluminum foil. The covered flask and contents are suspended in a thermostated bath and are kept, with continual shaking, at 150 °F for 2 hours. The solution is then filtered through a No. 42 Whatman filter paper, and the filtrate is collected in a graduated cylinder. The total amount of filtrate （without washing） is measured and called A milliliters. The filtrate is transferred to a Pyrex （or equivalent） beaker and evaporated on a steam bath under a stream of nitrogen to a small volume （approximately 50-60 milliliters）. The concentrated filtrate is then quantitatively transferred to a tared 100-milliliter Pyrex beaker using small, fresh portions of solvent and a rubber policeman to effect the transfer. The concentrated filtrate is evaporated almost to dryness on a hotplate under nitrogen, and is then transferred to a drying oven at 230 °F in the case of the aqueous extract or to a vacuum oven at 150 °F in the case of the heptane extract. In the case of the aqueous extract the evaporation to constant weight is completed in 15 minutes at 230 °F; and in the case of heptane extract, it is overnight under vacuum at 150 °F. The residue is weighed and corrected for the solvent blank. Calculation:

　　　　[Please see PDF for image: ER01JA93.403 ]

　　（3） Vinyl chloride-propylene copolymer content of aqueous extract— （i） Principle. The vinyl chloride-propylene copolymer content of the aqueous extract can be determined by determining the organic chlorine content and calculating the amount of copolymer equivalent to the organic chlorine content. The organic chlorine content is the difference between the total chlorine content and the ionic chlorine content.

　　（ii） Total chlorine content. A weighed sample is extracted with water at 150 °F for 2 hours, filtered, and the volume of filtrate is measured （A milliliters） as described in paragraph （d）（2） of this section. Two drops of 50 percent by weight sodium hydroxide solution are added to prevent loss of chloride from ammonium chloride, if present, and the solution is evaporated to approximately 15 milliliters. The concentrated filtrate is quantitatively transferred to a 22-milliliter Parr bomb fusion cup and gently evaporated to dryness. To the contents of the cup are added 3.5 grams of granular sodium peroxide, 0.1 gram of powdered starch, and 0.02 gram potassium nitrate; and the contents are mixed thoroughly. The bomb is assembled, water is added to the recess at the top of the bomb and ignition is conducted in the usual fashion using a Meeker burner. The heating is continued for 1 minute after the water at the top has evaporated. The bomb is quenched in water, rinsed with distilled water, and placed in a 400-milliliter beaker. The bomb cover is rinsed with water, catching the washings in the same 400-milliliter beaker. The bomb is covered with distilled water and a watch glass and heated until the melt has dissolved. The bomb is removed, rinsed, catching the rinsings in the beaker, and the solution is acidified with concentrated nitric acid using methyl purple as an indicator. The beaker is covered with a watch glass, and the contents are boiled gently for 10-15 minutes. After cooling to room temperature the solution is made slightly alkaline with 50 percent by weight sodium hydroxide solution, then acidified with dilute （1:5） nitric acid. Then 1.5 milliliters of 2 N nitric acid per 100 milliliters of solution is added and the solution is titrated with 0.005 N silver nitrate to the equivalence potential end point using an expanded scale pH meter （Beckman Model 76, or equivalent）. A complete blank must be run in duplicate. Calculation:

　　　[Please see PDF for image: ER01JA93.404 ]

　　where:

　　A=volume of filtrate obtained in extraction.

　　B=milliliters of silver nitrate solution used in sample titration×normality of silver nitrate solution.

　　C=milliliters of silver nitrate solution used in blank titration×normality of silver nitrate solution.

　　（iii） Ionic chlorine content. A weighed sample is extracted with water at 150 °F for 2 hours, filtered, and the volume of filtrate is measured （A milliliters） as in paragraph （d）（2） of this section. Two drops of 50 percent by weight sodium hydroxide solution are added and the solution is evaporated to approximately 150 milliliters. The solution is quantitatively transferred to a 250-milliliter beaker, methyl purple indicator is added, and the solution is neutralized with 0.1 N nitric acid. For each 100 milliliters of solution is added 1.5 milliliters of 2 N nitric acid. The solution is titrated with 0.005 N silver nitrate to the equivalence potential end point, using the expanded scale pH meter described in paragraph （d）（3）（ii） of this section. A complete blank must be run in duplicate. Calculation:

　　　　[Please see PDF for image: ER01JA93.405 ]

　　where:

　　A=volume of filtrate obtained in extraction.

　　D=milliliters of silver nitrate solution used in sample titration×normality of silver nitrate solution.

　　E=milliliters of silver nitrate solution used in blank titration×normality of silver nitrate solution.

　　（iv） Organic chlorine content and vinyl chloride-propylene copolymer content of aqueous extract. The organic chlorine content and the vinyl chloride propylene copolymer content of the aqueous extract is calculated as follows:

　　（a） Organic chlorine content. Milliequivalents of organic chlorine in aqueous extract of 100 grams of sample equal milliequivalents of total chlorine in aqueous extract of 100 grams of sample （as calculated in paragraph （d）（3）（ii） of this section） minus milliequivalents of ionic chlorine in aqueous extract of 100 grams of sample （as calculated in paragraph （d）（3）（iii） of this section）.

　　（b） Vinyl chloride-propylene copolymer content. Milligrams of vinyl chloride-propylene copolymer in aqueous extract of 100 grams of sample equal milliequivalents of organic chlorine in aqueous extract of 100 grams of sample （as calculated in paragraph （d）（3）（iv） （a） of this section） multiplied by 84.5.

　　　　Note: The conversion factor, 84.5, is derived from the equivalent weight of chlorine divided by the chlorine content of the heptane extractable fraction.）

　　（e） The vinyl chloride-propylene copolymers 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.

　　（f） The provisions of this section are not applicable to vinyl chloride-propylene copolymers used in food-packaging adhesives complying with § 175.105 of this chapter.

　　　　[42 FR 14572, Mar. 15, 1977, as amended at 49 FR 10111, Mar. 19, 1984]