| KN series rubber oils which was made by three times high pressurehydrogenation was attached to the users immediately. Especially, the users was keenon the yellowing resistance of KN series rubber oils. Comparing with the manner ofmiddle pressure hydrogenation, the KN series rubber oils produced by high pressurehydrogenation has several advantages, such as light colour (which Saybolt colour was+30), very low aromatic hydrocarbons content (C_A=0), low ultraviolet absorption(260nm ultraviolet absorption less 0.2) and high naphthenic hydrocarbon content etc.Particularly, the light and thermal stabilities of the KN series rubber oil wereimproved greatly. However, high pressure hydrogenation treatment had not solved theproblem that the rubber oil would become yellow under the sunshine. Some users ofrubber oil brought a common problem that the color stability of the hydrotreatedrubber oil was poor, which turned yellow easily under the condition of hightemperature(160℃) and sunlight. Because of intensity sunlight, the yellowingphenomenon of the hydrogenation rubber oil was more serious at the July andAugust every year. The oil-extended rubber also yellows under the sunlight. Theproduction of supper white rubber and its new products was affected. Therefore, thestudy on the reason of yellowing of hydrogenation rubber oil as soon as possible wasvery important. And establishment of the light and thermal stabilities test methodswas very urgent. It is of important actual value and theoretic meaning to improve thelight and thermal stabilities of hydrotreated rubber oil.In this paper, the light and thermal stabilities of hydrotreated rubber oil werestudied systematically. Firstly, the physical property and chemical compositionchanges of the hydrotreated rubber oil under the conditions of heating and irradiating were analyzed and the main reason for yellowing was found. Secondly, the ultravioletlight stability test method and the thermal stability test method for thehydrotreated rubber oil were established. The two methods could assess the light andthermal stabilities of rubber oil quickly and accurately. Thirdly, the best additiverecipe which could improve the light and thermal stabilities of hydrotreated rubber oilobviously was found. The obtained conclusions was as follows.(1) The change rules of kinematic viscosity, acidity, density, sulfur content,nitrogen content, ultraviolet absorption and hydrocarbon constitution of hydrotreatedrubber oil which was continuously irradiated and heated(160℃) were studied. Thetest results indicated that the physical properties which were colour, acidity, molecularweight, kinematic viscosity and density increased with prolonging of the time ofirradiating and heating. The properties of ultraviolet absorption, basic nitrogen hadlittle descended. And the index of refraction, sulfur content, nitrogen content werebasically unchanged.(2) The analysis results of thin-layer chromatographic and infrared spectrogramindicated that the saturated hydrocarbon content of rubber oil descended, and aromaticand resin contents increased, after the rubber oil was irradiated under the ultraviolet.(3) The factors which could influence the test method for light stability ofhydrotreated rubber oil such as irradiation intensity, test time, sample weight and thedistance between the sample and ultraviolet lamp, vessel etc were studied. Anultraviolet light stability test method for the hydrotreated rubber oil was established.(4) The factors which could influence the test method for thermal stability ofhydrotreated rubber oil such as test temperature, test time, sample weight, vessel andapparatus, etc. were studied. A thermal stability test method for the hydrotreatedrubber oil was established.(5) Several kinds of ultraviolet absorbents and oxidation inhibitors were tested.The best additive recipe which could improve the light and thermal stabilities ofhydrotreated rubber oil obviously was found. Consequently, an feasible project forindustrial production was provided. And this additive recipe has been applied inKaramay lubricant oil plant and has gained significant economic benefit. |
