摘要：

(C. 106-285) 8 Clains. 1. This invention relates to a synthetic drying oil Composed of an oily copolymer of butadiene and styrene combined with a small amount of maleic anhydride or its equivalent and an enamel containing this oil. Synthetic drying oils can be prepared by various methods from butadiene alone or from Inixtures containing butadiene together with ma terials copolymerizable therewith. Sodium poly merization, emulsion polymerization as well as bulk polymerization in the presence of a diluent and a peroxide type catalyst have been used for this purpose with varying degrees of success. However, among the difficulties encountered with various synthetic drying oils were poor drying rate, poor flexibility, poor adhesion of air-dried coatings, poor wetting properties and consequent difficulty of grinding in pigments, poor gloss and streakiness of brushed enamel films. And while SOne of these disadvantages have been over come in the past, this usually resulted in ag gravation of other undesirable characteristics. In general the Sodium catalyzed polymers have been found to be most economical to produce and to have a good drying rate, but at the same time this type of drying oil was found to have particu larly poor pigment wetting power and enamels prepared therefrom gave dull and very streaky films by brushing. It has now been discovered that these disadvantages of sodium polymerized Synthetic drying oils can be overcome by reacting the drying oil with an anhydride of an unsatu rated dicarboxylic acid such as maleic anhydride, chloro-inaleic anhydride or citraconic anhydride. The treatment with maleic anhydride has been found to be especially effective, For the purposes of this invention it is par ticularly desirable to use drying oils which have been obtained by copolymerizing 60 to 90 parts of butadiene-13 with 40 to 10 parts of styrene, preferably about 75 to 85 parts of the former and 25 to 15 parts of the latter, the polynerization being carried out at 20 to 100° C., preferably be low the melting point of the catalyst or between 65 and 85° C., in a reaction diluent. Tempera tures near the lower end of the range set forth are generally more Suitable for batch polymeriza tions and temperatures near the upper end of the range are particularly Suited for continuous operation. As a polymerization catalyst about 0.1 to 10 parts, preferably about 1 to 3 parts of a finely dispersed metallic sodium catalyst is used in the optional presence of various polymeriza tion modifiers which tend to promote the re IO

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