Nitrile rubbers which optionally contain alkylthio terminal groups and which are optionally hydrogenated
AssigneeLANXESS Deutschland GmbH
InventorsWerner OBRECHT, Rolf JOSTEN, Michael KLIMPEL
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Abstract
An improved polymerization and process method allows the production of special nitrile rubbers which are characterized by a specific anion content and an excellent storage stability and allow a particularly good vulcanization rate and moreover result in vulcanized materials that have advantageous properties, especially with regard to the contact with metal components of molded parts based on said vulcanized materials.
Claims19
A process for producing nitrile rubbers by emulsion polymerization of at least one α,β-unsaturated nitrile, at least one conjugated diene and optionally one or more further copolymerizable monomers in the presence of a molecular weight regulator, with the latex which is obtained in the polymerization and contains the nitrile rubber being subjected to coagulation and the coagulated nitrile rubber subsequently being washed, characterized in that
- (i) the latex obtained in the emulsion polymerization has a pH of at least 6 before the coagulation,
- (ii) the coagulation of the latex is carried out using at least one salt of a mono-, di- or trivalent metal, which is optionally a chloride, as precipitant,
- (iii) the coagulation of the latex is carried out in the presence of polyvinyl acetate, which is optionally partially or fully hydrolysed, as coprecipitant, and
- (iv) the coagulation of the latex and/or the work-up of the coagulated latex is carried out using water containing chloride ions if the salt of the mono-, di- or trivalent metal (ii) is not a chloride.
Dependencies are inferred from the claim text.