EVOH

Ethylene-vinyl alcohol copolymer, usually abbreviated EVOH is a copolymer composed of the monomers ethene, formal, and vinyl alcohol ( ethenol ).

Production and Properties

Since ethanol is a tautomer of acetaldehyde, a copolymer of ethylene and vinyl acetate is prepared by polymerizing first. For this copolymer, the acetyl group is abhydrolysiert and there is ethylene-vinyl alcohol copolymer, and acetic acid. This copolymer is used as the plastic in the rule for the packaging of food products and, more recently, for the manufacture of the tank container in the automobile industry. The primary purpose of which is the production of a barrier to keep oxygen in foods and carbon dioxide in tank containers. Ethylene -vinyl alcohol copolymer is either extruded or laminated as a thin layer on cardboard, foil or other material. The properties of the copolymer depend on ethene in the copolymer content. Low ethene shares lead to a copolymer with improved separation properties, higher ethene shares lower the processing temperature ( softening ) of the copolymer.

Structure

The exact sequence of ethylene and vinyl alcohol structural units in the ethylene - vinyl alcohol copolymer is random, one example is:

Industrial Production

EVAL Europe has taken in 2004 in Zwijndrecht (Belgium ), the largest production facility in the world with a capacity of 24,000 t / year in operation.

Use in medicine

In interventional radiology, ethylene -vinyl alcohol copolymer can be used as Flüssigembolisat. Under the trade name Onyx is in the U.S. a preparation in different EVOH concentrations in the market, which have different viscosities and are used according to the current rules of the target vessels. Besides the solvent, dimethyl sulfoxide ( DMSO) Onyx tantalum powder contains, as contrast agents. About a microcatheter blood vessels are filled with endovascular this liquid mixture that hardens within 5 minutes. As 20% EVOH solution Onyx was launched in April 2007 as a " Humanitarian Use Device" (HUD ) approved for the treatment of intracranial aneurysms that are not surgically removed. Furthermore, there is a 6% (Onyx 18) and an 8% EVOH solution (Onyx 34), which in addition to intracranial vascular malformations such as aneurysms ( the original application ) and peripheral vascular malformations, such as arteriovenous malformations, are supplied.