§177.1680 Polyurethane resins
The polyurethane resins identified in paragraph （a） of this section may be safely used as the food-contact surface of articles intended for use in contact with bulk quantities of dry food of the type identified in § 176.170（c） of this chapter, table 1, under Type VIII, in accordance with the following prescribed conditions:
（a） For the purpose of this section, polyurethane resins are those produced when one or more of the isocyanates listed in paragraph （a）（1） of this section is made to react with one or more of the substances listed in paragraph （a）（2） of this section:
（1） Isocyanates:
Bis（isocyanatomethyl） benzene （CAS Reg. No. 25854-16-4）.
Bis（isocyanatomethyl） cyclohexane （CAS Reg. No. 38661-72-2）.
4,4′-Diisocyanato-3,3′-dimethylbiphenyl （bi-tolylene diisocyanate）.
Diphenylmethane diisocyanate.
Hexamethylene diisocyanate.
3-Isocyanatomethyl - 3,5,5 - tri-methyl-cyclo-hexyl isocyanate.
4,4-Methylenebis（cyclohexyl isocyanate）.
Toluene diisocyanate.
（2） List of substances:
Adipic acid.
1,4-Butanediol.
1,3-Butylene glycol.
1,4-Cyclohexane dimethanol （CAS Reg. No. 105-08-8）.
2,2-Dimethyl-1,3-propanediol.
Ethylene glycol.
1,6-Hexanediol （CAS Reg. No. 629-11-8）.α-Hydro-ω-hydroxypoly（oxy-1,4-butanediyl） （CAS Reg. No. 25190-06-1）.
α-Hydro-omega-hydroxypoly （oxy-tetra-methyl-ene）.
α，α′-（Isopropylidenedi-p-phenylene）bis[omega-hydroxypoly （oxy-pro-pylene）（3-4 moles）], average molecular weight 675.
Maleic anhydride.
Methyl oxirane polymer with oxirane （CAS Reg. No. 9003-11-6）.
Methyl oxirane polymer with oxirane, ether with 1,2,3-propanetriol （CAS Reg. No. 9082-00-2）.
α，α′α″，α″′-Neopentanetetrayltetrakis [omega-hydroxypoly （oxypropylene） （1-2 moles）], average molecular weight 400.
Pentaerythritol-linseed oil alcoholysis product.
Phthalic anhydride.
Polybutylene glycol.
Polyethyleneadipate modified with ethanolamine with the molar ratio of the amine to the adipic acid less than 0.1 to 1.
Poly（oxycarbonylpentamethylene）.
Polyoxypropylene ethers of 4.4′-isopropyl-idenediphenol （containing an average of 2-4 moles of propylene oxide）.
Polypropylene glycol.
α，α′，α″-1,2,3-Propanetriyltris [omega-hydroxypoly （oxypropylene） （15-18 moles）], average molecular weight 3,000.
Propylene glycol.
α，α′，α″-[Propylidynetris （methylene）] tris [omega-hydroxypoly （oxypropylene） （minimum 1.5 moles）], minimum molecular weight 400.
α-[ρ（1,1,3,3-Tetramethylbutyl） - phenyl]-omega-hydroxypoly（oxyethylene） （5 moles）, average molecular weight 425.
Trimethylol propane.
（b） Optional adjuvant substances employed in the production of the polyurethane resins or added thereto to impart desired technical or physical properties may include the following substances:
| List of substances | Limitations |
| 1-[(2-Aminoethyl)amino]2-propanol. | As a curing agent. |
| 1-(3-Chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride | As a preservative. |
| Colorants used in accordance with § 178.3297 of this chapter. | |
| Dibutyltin diacetate | As a catalyst. |
| Dibutyltin dichloride | Do. |
| Dibutyltin dilaurate | Do. |
| N,N-Dimethyldodecylamine | Do. |
| N-Dodecylmorpholine | Do. |
| a,a′-[Isopropylidenebis[p-phenyleneoxy(2-hydroxytrimethylene) ]]bis[omega-hydroxypoly-(oxyethylene) (136-170 moles)], average molecular weight 15,000 | As a stabilizer. |
| 4,4′-Methylenedianiline | As a curing agent. |
| 1,1′,1″-Nitrilotri-2-propanol | Do. |
| 2,2′-(p-Phenylenedioxy) diethanol | Do. |
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Code of Federal Regulations 321
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| Polyvinyl isobutyl ether | |
| Polyvinyl methyl ether | |
| Soyaalkyd resin | Conforming in composition with § 175.300 of this chapter and containing litharge not to exceed that residual from its use as the reaction catalyst and creosol not to exceed that required as an antioxidant. |
| Tetrakis [methylene-(2,5-di-tert-butyl-4-hydroxy-hydro-cinna-mate)]methane (CAS Reg. No. 6683-19-8) | Stabilizer. |
| N,N,N′N′-Tetrakis (2-hydroxypropyl)ethylenediamine | As a curing agent. |
| Triethanolamine | Do. |
| Trimethyleneglycol di (p-aminobenzoate) (CAS Reg. No. 57609-64-0) | As a curing agent. |
（c） An appropriate sample of the finished resin in the form in which it contacts food, when subjected to ASTM method D968-81, “Standard Test Methods for Abrasion Resistance of Organic Coatings by the Falling Abrasive Tester,” 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. ）, using No. 50 Emery abrasive in lieu of Ottawa sand, shall exhibit an abrasion coefficient of not less than 20 liters per mil of film thickness.
[42 FR 14572, Mar. 15, 1977, as amended at 46 FR 57033, Nov. 20, 1981; 49 FR 10110, Mar. 19, 1984; 50 FR 51847, Dec. 20, 1985; 56 FR 15278, Apr. 16, 1991; 56 FR 42933, Aug. 30, 1991]
