Ethylene vinyl alcohol copolymer

General structure of ethylene vinyl alcohol copolymer

Ethylene-vinyl alcohol copolymer , abbreviation EVOH , occasionally EVAL is a copolymer , the formal from the monomer ethylene and vinyl alcohol is constructed.

Manufacture and properties

Brand new pipe made of cross-linked polyethylene with an oxygen diffusion barrier made of ethylene-vinyl alcohol copolymer

Since vinyl alcohol is an unstable tautomer of acetaldehyde , a copolymer of ethene and vinyl acetate is first made. Of the ethylene-vinyl acetate copolymer which are acetyl groups by hydrolysis separated to obtain an ethylene-vinyl alcohol copolymer, and acetic acid is produced.

Ethylene-vinyl alcohol copolymer is either extruded or laminated as a thin layer onto cardboard, foil or other plastics. The properties of the copolymer depend on the proportion of ethene in the copolymer. Low proportions of ethene lead to a copolymer with improved separation properties, while higher proportions of ethene lower the processing temperature (softening temperature) of the copolymer.

Ethylene-vinyl alcohol copolymer has a high barrier effect against oxygen , i.e. it reduces the diffusion of oxygen through the layer of ethylene-vinyl alcohol copolymer. A complete prevention of oxygen diffusion, such as with metals, is not possible with ethylene-vinyl alcohol copolymer.

Ethylene-vinyl alcohol copolymer is used in the packaging of food in order to reduce the entry of oxygen into the food.

Plastic pipes, primarily those made of cross-linked polyethylene (PE-X), which are used to transport hot water, are coated on the outside with a layer of ethylene-vinyl alcohol copolymer to reduce oxygen diffusion into the hot water and thus corrosion of metallic components in the hot water circuit to reduce. The connection between the outer wall of the plastic pipe and the layer of ethylene-vinyl alcohol copolymer is made via an adhesion promoter, which is often colored.

Ethylene-vinyl alcohol copolymer is also used in the manufacture of tank containers in the automotive industry. The primary purpose here is to reduce the emission of hydrocarbons from the tank containers.

structure

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

${\displaystyle \mathrm {{-}(CH_{2}{-}CH_{2})_{m}{-}(CH_{2}{-}CHOH)_{n}{-}(CH_{2}{-}CH_{2}){-}(CH_{2}{-}CHOH){-}(CH_{2}{-}CHOH){-}(CH_{2}{-}CH_{2}){-}\;\,} }$

industrial production

The Japanese Kuraray Group, which sells EVOH under the EVAL logo, is the world's largest manufacturer with locations in Okayama (Japan, 10,000 tons per year), Pasadena / Houston (USA, 58,000 tons per year) and Zwijndrecht (Belgium, 35,000 tons per year). The Nippon Gohsei Group, which is also Japanese, sells EVOH under the name SoarnoL, and produces at its locations in Japan (Mizushima, 10,000 tons per year), USA (La Porte / Houston, 38,000 tons per year) and England (Hull, 18,000 tons per year). The Taiwanese company Chang Chun Group sells EVOH made in Taiwan under the brand name EVASIN.

Use in medicine

In interventional radiology , ethylene vinyl alcohol copolymer can be used as a liquid embolizate . Under the trade name Onyx , a preparation in different EVOH concentrations is on the market in the USA , which have different viscosities and are used depending on the flow modalities of the target vessels. In addition to the solvent dimethyl sulfoxide (DMSO), Onyx contains tantalum powder as a contrast medium. Blood vessels are endovascularly filled with this liquid mixture via a microcatheter , which hardens within 5 minutes. As a 20% EVOH solution, Onyx has been approved as a "Humanitarian Use Device" (HUD) since April 2007 for the treatment of intracranial aneurysms that cannot be surgically removed. There is also a 6% ( Onyx 18 ) and an 8% EVOH solution ( Onyx 34 ), which are used to treat not only intracranial vascular malformations such as aneurysms (the original area of ​​application) but also peripheral vascular malformations, for example arteriovenous malformations .

Web links

• Entry barrier plastics . In: Lexicon of plastics testing and diagnostics , Version 2.0, 2012.

Individual evidence

1. ↑ Compendium of Polymer Terminology and Nomenclature , IUPAC Recommendations, RSC Publishing, Cambridge, 2008, pp. 403f.
2. ↑ Kuraray: EVAL ™ EVOH by Kuraray (accessed January 16, 2020)
3. ↑ Soarnol®: About Soarnol® business. Accessed January 16, 2020 (English). 
4. ↑ Nippon Gohsei Manufacturers of SoarnoL ™ (EVOH), Nichigo G-Polymer ™, Gohsenol ™, Specialty Film and Nichigo G-Tape ™. Retrieved January 16, 2020 (UK English). 
5. ↑ Chang Chun Group: ETHYLENE VINYL ALCOHOL COPOLYMER. Accessed January 16, 2020 (English). 
6. ^ ^{A b} V. Panagiotopoulosa, E. Gizewskia, S. Asgaria, J. Regela, M. Forstinga, I. Wankea: Embolization of Intracranial Arteriovenous Malformations with Ethylene-Vinyl Alcohol Copolymer (Onyx). In: AJNR January 2009 30: 99–106 doi: 10.3174 / ajnr.A1314
7. ↑ FDA: Onyx Liquid Embolic System
8. ↑ FDA: Approval Letter (PDF; 377 kB).
9. ↑ Furuzan Numan, Alp Ömeroğlu, Batuhan Kara, Murat Cantaşdemir, İbrahim Adaletli, Fatih Kantarcı: Embolization of Peripheral Vascular Malformations with Ethylene Vinyl Alcohol Copolymer (Onyx) In: Journal of Vascular and Interventional Radiology Volume 15, Issue 9, September 2004, pages 939-946 doi: 10.1097 / 01.RVI.0000130862.23109.52 .