Patent GB-998156-A (GB)
Title: Nacreous material containing titanium dioxide
Inventor: MILLER HAROLD ABE
IPC: C09C1/00
Filed: 1962-09-13
Abstract: Nacre-producing titanium dioxide platelets having a thickness not greater than 750 millimicrons, a ratio of length to thickness of at least four to one and an index of refraction at least 0.2 greater than that of any light transmitting medium in which they are subsequently suspended are prepared by depositing on a surface a substrate film which is soluble in a solvent which does not dissolve said platelets, depositing on said film another film of a solution of a titanium ester having alkyl groups containing up to 12 carbon atoms, removing the solvent from said solution, hydrolysing the titanium ester film in an atmosphere having a relative humidity of between 20-60%, thereby forming a film having a thickness not greater than 0.75 micron, removing the substrate film and hydrolysed film from said surface, separating one film from the other, and fracturing said hydrolysed film, thereby forming the titanium dioxide platelets. The preferred particle size of a platelet is a thickness of less than 100 millimicrons and a length of between 2 and 100 microns.  The refractive index of the platelets is at least 1.9 and it may be increased to the range 2.4-2.9 by heating the platelets to a temperature in the range of 300-800 DEG  C.  In a typical example, a cellulose nitrate film was formed on a glass plate and a coating of a 10% solution of tetrabutyl titanate in mineral spirits was deposited thereon.  The films were separated from each other by immersion of the plate in water, stripping the two films from the plate and dissolving the nitrocellulose substrate film using butyl acetate and the titanium dioxide film was fractured to obtain platelets.ALSO:A nacreous composition comprises titanium dioxide platelets suspended in a light transmitting medium, e.g. casein plastics, cellulose nitrate, methyl methacrylate, each of said titanium dioxide platelets having a thickness not greater than 750 millimicrons, a ratio of length of thickness of at least four to one and an index of refraction at least 0.2 greater than of said suspending medium.  A cellulose nitrate lacquer comprises 8% cellulose nitrate in butyl acetate and a platelet concentration therein of from 0.25 --> 5.0%. A methyl methacrylate casting syrup comprises methyl methacrylate containing 0.5% of the platelets.  The latter may be cast into sheet form using acetyl peroxide as catalyst, and buttons may be cut from said sheet.ALSO:A nacreous composition comprises titanium dioxide platelets suspended in a light transmitting medium, each of said titanium dioxide platelets having a thickness not greater than 750 millimicrons, a ratio of length to thickness of at least four to one and an index of refraction at least 0.2 greater than that of said suspending medium. The titanium dioxide platelets may be prepared by depositing a smooth substrate film, which is soluble in a solvent which does not dissolve said titanium dioxide platelets, on a clean surface, and over said substrate film, depositing a film of a solution of a titanium ester having alkyl groups containing up to 12 carbon atoms, removing the solvent from said solution, and hydrolysing said film in an atmosphere having a relative humidity of between 20-60%, thereby forming a film having a thickness not greater than 0.75 micron, removing the substrate and hydrolysed film from said surface, separating the substrate from the hydrolysed film, and then fracturing said hydrolysed film to form platelets.  The refractive index of the platelets may be improved to between 2.4 and 2.9 by heating to a temperature in the range of from 300 DEG C. to 800 DEG C. The platelets may be incorporated into a cellulose nitrate lacquer which is used to coat glass beads to produce simulated pearls or they may be suspended in a methyl methacrylate casting syrup from which pearl-like buttons may be produced.ALSO:Glass beads are coated by dipping with a lacquer comprising cellulose nitrate having titanium dioxide platelets suspended therein, each platelet having a thickness not greater than 750 millimicrons, a ratio of length to thickness of at least four to one and a refractive index at least 0,2 greater than the suspending medium to produce simulated pearls.