| 摘要 |
1,237,866. Nacreous pigments; artificial pearls. MAY & BAKER Ltd. 6 Sept., 1968 [8 Sept., 1967], No. 41182/67. Headings C4A and C4X. Nacreous pigments comprising a plurality of thin, clear, homogeneous layers of TiO 2 or ZrO 2 or alkaline earth metal titanate, each layer interleaved with a thin, clear, homogeneous layer of an oxide or hydroxide of Al, Mg/Al, Ca/Al, Sr/Al, or Mg, such that the refractive index of the former layers exceeds that of the latter by at least 0À05, are claimed per se. A move general process for preparing these and similar pigments comprises applying to a support firstly a release layer which is wetted by composition (I) below and which is insoluble in compositions (I) and (II) but soluble in a release solvent, and then, alternately, uniform layers of (I) a hydrolysable titanic or zirconic ester or alkaline earth metal titanic ester and (II) a compound capable of hydrolysis by water vapour to a clear layer of inorganic oxide or hydroxide or a mixture thereof, such that after hydrolysis of each hydrolysable layer and, if necessary, heating, the refractive index of layers (I) exceeds that of layers (II) by at least 0À05, hydrolysing each layer after application with water vapour, releasing the multi-layer product from the support by dissolution and, if required, heating the layers before or after pigment release to obtain the required refractive index disparity. Apart from the oxides and hydroxides listed above the process is also applicable to those of Si, Ba/Al, Ca, Sn/Na, and Li/Ti; this layer may also contain up to 10% by wt. of the hydrolysable Ti, Zr or alkaline earth metal titanate ester. The release layer may be polyethylene glycol, cellulose diacetate, or polyvinyl pyrrolidone. Each pigment layer may be 0À01-1Á thick, preferably 0À03-0À1Á for white and 0À05-0À3 for coloured pigments. The pigment may be dehydrated by heating to 450‹ C., and comminuted to 1-70 Á, although particles of 1-2 mm. have certain uses. |
