§178.3790 半刚性和刚性乙烯塑料中的聚合物改性剂(Polymer modifiers in semirigid and rigid vinyl chloride plastics)

　　§178.3790 Polymer modifiers in semirigid and rigid vinyl chloride plastics.

　　    The polymers identified in paragraph （a） of this section may be safely admixed, alone or in mixture with other permitted polymers, as modifiers in semirigid and rigid vinyl chloride plastic food-contact articles prepared from vinyl chloride homopolymers and/or from vinyl chloride copolymers complying with § 177.1950, § 177.1970, and/or § 177.1980 of this chapter, in accordance with the following prescribed conditions:

　　（a） For the purpose of this section, the polymer modifiers are identified as follows:

　　（1） Acrylic polymers identified in this subparagraph provided that such polymers contain at least 50 weight-percent of polymer units derived from one or more of the monomers listed in paragraph （a）（1）（i） of this section.

　　（i） Homopolymers and copolymers of the following monomers:

　　n-Butyl acrylate.

　　n-Butyl methacrylate.

　　Ethyl acrylate.

　　Methyl methacrylate.

　　（ii） Copolymers produced by copolymerizing one or more of the monomers listed in paragraph （a）（1）（i） of this section with one or more of the following monomers:

　　Acrylonitrile.

　　Butadiene.

　　a-Methylstyrene.

　　Styrene.

　　Vinylidene chloride.

　　（iii） Polymers identified in paragraphs （a）（1） （i） and （ii） of this section containing no more than 5 weight-percent of total polymer units derived by copolymerization with one or more of the following monomers:

　　Acrylic acid.

　　1,3-Butylene glycol dimethacrylate.

　　Divinylbenzene.

　　Methacrylic acid.

　　（iv） Mixtures of polymers identified in paragraph （a）（1） （i）, （ii）, and （iii） of this section; provided that no chemical reactions, other than addition reactions, occur when they are mixed.

　　（2） Polymers identified in paragraph （a）（1） of this section combined during their polymerization with butadiene-styrene copolymers; provided that no chemical reactions, other than addition reactions, occur when they are combined. Such combined polymers may contain 50 weight-percent or more of total polymer units derived from the butadiene-styrene copolymers.

　　（b） The polymer content of the finished plastic food-contact article consists of:

　　（1） Not less than 80 weight-percent of polymer units derived from the vinyl chloride polymers identified in the introduction to this section and not more than 5 weight-percent of polymer units derived from polymers identified in paragraph （a）（1） of this section and may optionally contain up to 15 weight-percent of polymer units derived from butadiene-styrene copolymers; or

　　（2） Not less than 50 weight-percent of polymer units derived from the vinyl chloride polymers identified in the introduction to this section, not more than 50 weight-percent of polymer units derived from homopolymers and/or copolymers of ethyl acrylate and methyl methacrylate, and not more than 30 weight-percent of polymer units derived from copolymers of methyl methacrylate, a -methylstyrene and acrylonitrile and may optionally contain up to 15 weight-percent of polymer units derived from butadiene-styrene copolymers.

　　（c） No chemical reactions, other than addition reactions, occur among the vinyl chloride polymers and the modifying polymers present in the polymer mixture used in the manufacture of the finished plastic food-contact article.

　　（d） The finished plastic food-contact article, when extracted with the solvent or solvents characterizing the type of food and under the conditions of time and temperature characterizing the conditions of its intended use as determined from tables 1 and 2 of § 176.170（c） of this chapter, yields extractives not to exceed the limits prescribed in § 177.1010 （b） （1）, （2）, （3）, and （4） of this chapter when tested by the methods prescribed in § 177.1010 （c） of this chapter.

　　（e） Acrylonitrile copolymers identified in this section shall comply with the provisions of § 180.22 of this chapter.