Chlorinated rubber
Chlorinated rubber is not a very precise name because this type of polymer is a thermoplastic material and not, as the name suggests, an elastomer .
The English expression Chlorinated Rubber (CAS number: 9006-03-5) is more precise , which - albeit ambiguous - "includes" the manufacturing process in the name: in chlorinated hydrocarbons as solvents , mainly CC double-bond-containing polymers such as natural or synthetic are used rubbers , e.g. B. polybutadiene , polyisoprene reacted with chlorine . Both chlorine atoms are added to the double bonds and hydrogen atoms with hydrogen chloride substituted elimination.
After the reaction, the chlorine content can make up approx. 65% by weight of the polymer. The mean molar mass is in the range between 50,000 and 350,000 g / mol. By the chlorination the rubbers lose their elastomeric character and become thermoplastic plastics . Serious changes take place at the molecular level. During the chlorination of polyisoprene, chain breakage and recombination result in 6-ring structures along the polymer chain at intervals of about 2 monomer units. The majority of the secondary and tertiary carbon atoms are connected to one chlorine atom each. The solvent from the manufacturing process is then separated from the chlorinated rubber and recovered.
The commercial form is a finely divided, white to yellowish powder. The density is in the range of 1.5 g / cm 3 . The removal of the chlorinated solvents used must be done very carefully, since significant residual amounts of z. B. Tetrachloromethane prohibit marketing due to toxicity.
Manufacturer
While a few well-known products from different manufacturers could still be found in the 1980s, the number of manufacturers has decreased rapidly in the last two decades due to the high single-digit percentage of carbon tetrachloride. Modern products according to the prior art therefore have a very low content of carbon tetrachloride of equal to or less than 0.005%. Chlorinated rubbers are known especially in Europe under the name Pergut ® .
Applications
Chlorinated rubber is soluble in aromatic solvents, chlorinated hydrocarbons, various esters and some plasticizers . Chlorinated rubber is not unlike PVC as a plastic . Because of the low water vapor permeability, good resistance to low and high temperatures, moisture, acids , salts and alkalis chlorinated rubber is used as a binder for lacquers and paints in heavy corrosion protection , for traffic paints, on concrete (including swimming pools) and for printing inks and adhesives , especially used in combination with polychloroprene . Chlorinated rubber and plasticizers are usually used in coatings in a ratio of 2: 1. I.a. Chlorinated rubber is used as an adhesion promoter for rubber-metal compounds during vulcanization .
Individual evidence
- ↑ Entry on chlorinated rubbers. In: Römpp Online . Georg Thieme Verlag, accessed on June 16, 2014.
- ↑ Paints and Coatings, Chapter 2.3 . In: James E. Bailey et al. a. (Ed.): Ullmann's Encyclopedia of Industrial Chemistry . Wiley-VCH Verlag, Weinheim 2001, ISBN 3-527-20160-2 (online version 2006).
- ↑ Trade names of various manufacturers .
- ↑ Technical product information on Pergut ® , Bayer MaterialScience AG Download: ( Memento of the original from December 29, 2013 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. .
- ↑ Raymond Kirk, Donald F. Othmer: Encyclopedia of Chemical Technology . 5th Ed. John Wiley Publisher, New York 2001, ISBN 0-471-48494-6 .
