§177.1950 氯乙烯/乙烯共聚物(Vinyl chloride-ethylene copolymers)

    §177.1950 Vinyl chloride-ethylene copolymers



　　    The vinyl chloride-ethylene copolymers identified in paragraph （a） of this section may be safely used as components of articles intended for contact with food, under conditions of use D, E, F, or G described in table 2 of § 176.170 （c） of this chapter, subject to the provisions of this section.

　　（a） For the purpose of this section, vinyl chloride-ethylene copolymers consist of basic copolymers produced by the copolymerization of vinyl chloride and ethylene 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-ethylene 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-ethylene 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-ethylene 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 cyclohexanone 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 0.5 milligram of vinyl chloride-ethylene copol-ymer per 100 grams of sample tested as determined from the organic chlorine content. The organic chlorine content is determined as described in paragraph （d）（3） of this section.

　　（d） Analytical methods: The analytical methods for determining whether vinyl chloride-ethylene 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:

　　Code of Federal Regulations

　　[Please see PDF for image: ER01JA93.401 ]

　　（3） Vinyl chloride-ethylene copolymer content of aqueous extract— （i） Principle. The vinyl chloride-ethylene 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.

　　（ii） Total organic chlorine content. A weighed sample of approximately 400 grams is extracted with 1,200 milliliters of 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.

　　（a） A slurry of Amberlite IRA-400, or equivalent, is made with distilled water in a 150-milliliter beaker. The slurry is added to a chromatographic column until it is filled to about half its length. This should give a volume of resin of 15-25 milliliters. The liquid must not be allowed to drain below the top of the packed column.

　　（b） The column is regenerated to the basic （OH） form by slowly passing through it （10-15 milliliters per minute） 10 grams of sodium hydroxide dissolved in 200 milliliters of water. The column is washed with distilled water until the effluent is neutral to phenolphthalein. One drop of methyl red indicator is added to the A milliliters of filtered aqueous extract and, if on the basic side （yellow）, nitric acid is added drop by drop until the solution turns pink.

　　（c） The extract is deionized by passing it through the exchange column at a rate of 10-15 milliliters per minute. The column is washed with 200 milliliters of distilled water. The deionized extract and washings are collected in a 1,500-milliliter beaker. The solution is evaporated carefully on a steam plate to a volume of approximately 50 milliliters and then transferred quantitatively, a little at a time, to a clean 22-milliliter Parr cup, also on the steam plate. The solution is evaporated to dryness. Next 0.25 gram of sucrose and 0.5 gram of benzoic acid are added to the cup. One scoop （approximately 15 grams） of sodium peroxide is then added to the cup. The bomb is assembled and ignition is conducted in the usual fashion.

　　（d） After the bomb has cooled, it is rinsed thoroughly with distilled water and disassembled. The top of the bomb is rinsed into a 250-milliliter beaker with distilled water. The beaker is placed on the steam plate. The bomb cup is placed in the beaker and carefully tipped over to allow the water to leach out the combustion mixture. After the bubbling has stopped, the cup is removed from the beaker and rinsed thoroughly. The solution is cooled to room temperature and cautiously neutralized with concentrated nitric acid by slowly pouring the acid down a stirring rod until the bubbling ceases. The solution is cooled and an equal volume of acetone is added.

　　（e） The solution is titrated with 0.005 N silver nitrate using standard potentiometric titration techniques with a silver electrode as indicator and a potassium nitrate modified calomel electrode as a reference electrode. An expanded scale recording titrimeter. Metrohm Potentiograph 2336 or equivalent, should be used; a complete blank must be run in duplicate.

　　（iii） Calculations.

　　Code of Federal Regulations

　　[Please see PDF for image: ER01JA93.402 ]

　　where:

　　T=Milliliters of silver nitrate （sample minus blank）×normality of silver nitrate.

　　F=1,200/A （as defined above）

　　（e） The vinyl chloride-ethylene 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-ethylene copolymers used as provided in §§ 175.105 and 176.180 of this chapter.

　　　[42 FR 14572, Mar. 15, 1977, as amended at 49 FR 10110, Mar. 19, 1984]