Saturday, November 28, 2009

Polyone Corp. Reveals FDA Compliant Nanocomposite Plastics for Food Contact

Polyone Corporation David A. Jarus and Guoqiang Qian have developed nanocomposite plastics that can be used in contact with food and are compliant with U.S. Food and Drug regulations. United States Patent Application 20090292055 details nanocomposites that are made from melt-mixing of polyethylene with organoclay in the presence of a maleated polypropylene. Unexpectedly, the maleated polypropylene and polyethylene are sufficiently compatible to permit excellent dispersion of the organoclay in the nanocomposite. Because maleated polypropylene is compliant with U.S. Food and Drug Administration regulations, though maleated polyethylene is not, one can use resulting nanocomposites for articles to be in contact with human food.

PolyOne Corporation provides specialized polymer materials with operations in thermoplastic compounds, specialty polymer formulations, color and additive systems, thermoplastic resin distribution, and specialty polyvinyl chloride (PVC) resins

The mixture of organoclays and polyolefins, commonly called nano-olefins, is highly desired because the organoclays can contribute stiffness and toughness properties to polyolefins for extruded or molded articles. Polyolefins for molded or extruded articles have been useful since the mid-20th Century. Organoclays, smectite inorganic clays intercalated with organic ions, such as quaternary ammonium, have become useful in the last decade. Organoclays are expensive additives for polyolefins such as polypropylene (PP).

When used packaging, particularly food packaging such as films, each of the ingredients need to be listed in the USA Title 21 of the Code of Federal Regulations, which is regulated by the United States Food and Drug Administration (FDA).

Polyone’s polyethylene nanocomposite is FDA compliant. "FDA compliant" means that each of the ingredients of the polyolefin nanocomposites of the invention are listed in 21 CFR as generally regarded as safe ("GRAS") for food contact applications.

Polyone solved the dispersion problem by using a polypropylene-based compatibilizer with a mixture of organoclay and a polyethylene resin matrix. More particularly, the polypropylene-based compatibilizer is a maleated polypropylene. Unexpectedly, it was found that even though a maleated polypropylene ("PP-g-MAH") is considered to be immiscible with polyethylene ("PE"), the PP-g-MAH provides acceptable compatibility for dispersing the organoclay into the PE matrix. The unexpected compatibility (in spite of apparent immiscibility) of PP-g-MAH with PE means that a nanoconcentrate (highly concentrated organoclay in thermoplastic matrix) can be blended with adequate organoclay dispersion and with FDA compliant ingredients. Nanocomposites also offer flame-retardancy properties because such nanocomposite formulations burn at a noticeably reduced burning rate and a hard char forms on the surface. They also exhibit minimum. dripping and fire sparkling.

Organoclay is obtained from inorganic clay from the smectite family. Smectites have a unique morphology, featuring one dimension in the nanometer range. Montmorillonite clay is the most common member of the smectite clay family. The montmorillonite clay particle is often called a platelet, meaning a sheet-like structure where the dimensions in two directions far exceed the particle's thickness.

The nanocomposite can serve either as a concentrate or as a compound. If the former, then the nanocomposite is an intermediate product, an ingredient to be added with other ingredients to subsequent compounding steps in a batch or continuous mixing apparatus. The dilution or "let-down" of the concentrate into the compound can result in an organoclay concentration in the compound ranging from about 4 to less than 15 weight percent, and preferably from about 6 to about 12 weight percent, to maximize stiffness and toughness performance properties with minimal concentration of organoclay in the nanocomposite. Ultimately, the compound is formed into an article or film using a subsequent extrusion or molding techniques

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