Injection molding packaging material

For nucleation of nylon and PP, sodium benzoate [532-32-1] is the traditional material of choice. Use levels are of the order of 0.1% with injection-molded packaging closures being a major application. Sodium benzoate does not impart any improvement in optical properties. Low molecular weight polyolefins, ionomers,... 

Large quantities of secondary cellulose acetate are used worldwide in the manufacture of filter material for cigarettes. Because of its excellent clarity and ease of processing, cellulose acetate film is widely used in display packaging and extmded plastic film for decorative signs (see Packaging materials). Injection-molded plastics of cellulose acetate are used in toothbmsh handles, computer bmshes, and a large variety of other appHcations (7). 

The primary crystalline polymer based on CHDM is the terephthalate, poly(1,4-cyclohexylenedimethylene terephthalate) (PCT). This polyester was originally developed for fiber applications but has since found wider utility as a reinforced polymer for injection molding and (when copolymerized with a small amount of isophthalic acid) as a material for crystallized food packaging trays. The key property of PCT which sets it apart from other thermoplastic polyesters in these latter applications is its melting point. 

Figure 3 shows the end uses, arranged in categories, of the PVC produced in the United States (5). About 35% of the PVC resin is extruded into pipe, complex forms, or flat sheets. Another 32% is calendered into film and flooring materials. About 12% is injection-molded or blow-molded into packages, records, and other forms a lesser amount is coated onto paper or fabric. Approximately 4% is exported. It is easy to see how the demand for this extraordinarily versatile material would stimulate great interest in its production. 

Poly(dihydroxymethylcyclohexyl terephthalate) was introduced by Eastman Kodak as Kodel in 1958. Here, the insertion of the cyclohexyl moiety gives a more hydrophobic material (in comparison to PET and PBT) as well as a more moldable product that can very readily be injected-molded. (See Figure 7.) The polymer s sole raw material is dimethyl terephthalate. Reduction of dimethyl terephthalate yields the dialcohol, cyclohexa-nedimethanol. Kodel, along with its blends and mixtures, is often extruded into film and sheeting for packaging. Kodel-type materials are used to pack-... 

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