| 摘要 |
<p>A white barium zirconium borate pigment BaO.ZrO2.B2O3 is prepared by heating a mixture of either (1) zirconium dioxide and barium metaborate or compounds convertible to such upon heating, e.g. zirconium sulphate tetrahydrate and barium sulphide, carbonate or hydroxide with boron trioxide or boric acid, or (2) barium metazirconate and boron trioxide or a boron compound convertible to the trioxide upon heating. The heating is preferably carried out between 800 DEG -1300 DEG C. for 10 mins.-24 hours. The zirconium dioxide used may be either the mineral baddeleyite or it may be prepared by precipitation in the hydrous form from zirconium sulphate tetrahydrate or zirconium tetrachloride solutions. The zirconium sulphate tetrahydrate may be prepared by recrystallizing precipitated basic zirconium sulphate from sulphuric acid. The barium metaborate used may be precipitated by reacting solutions of barium sulphide or hydroxide with sodium tetraborate. Example 1 refers to the above stoichiometric quantities of barium carbonate, boric acid and zirconium dioxide being mixed in a mortar and pestle and fired at 1050 DEG C. for one hour after which the cooled product was reground and fired for a further hour at 1050 DEG C. X-ray analysis of the resulting crystalline product indicated that a compound had been formed. Example 2 refers to a ground mixture of barium carbonate, boric acid and recrystallized zirconium sulphate tetrahydrate being fired at 1100 DEG C., reground p and refired at 1100 DEG C. for a further half hour. Example 3 refers to hydrous zirconium dioxide being precipitated from zirconium sulphate tetrahydrate solution with sodium hydroxide. A slurry of the hydrous zirconium dioxide and boric acid was then gently refluxed and barium hydroxide added and the refluxing continued for two hours. The resulting wet cake was dried at 140 DEG C. and fired as in Example 1. Example 4 refers to the barium zirconium borate compound being prepared together with excess barium metaborate. Example 5 refers to the barium zirconium borate compound being prepared together with excess zirconium dioxide. Specifications 813,228 and 879,499 are referred to.</p> |
