Patent GB-957535-A (GB)
Title: Pigment particles and nacreous compositions containing them
IPC: C09B67/00
Filed: 1962-01-30
Abstract: Nacreous pigments (producing pearl like effects when incorporated in transparent substances) are produced by enclosing a vaporizable nacreous pigment particle producing material in an evacuated space, simultaneously heating said material and a vaporizable inorganic metal salt substrate therefor to temperature at which said material and said substrate evaporates, depositing a thin film of said material and said substrate alternately on a moving surface sufficiently cool to condense alternate thin films of both said material and said substrates, dissolving said substrates in a liquid which is a solvent for said substrate and a non-solvent for said material, and then removing said material from said surface and fragmenting same to form nacreous pigment particles.  Pigments specified are zinc oxide, zinc sulphide, cryolite, titanium dioxide, zirconium dioxide, lead chloride, magnesium fluoride and calcium fluoride.  Substrate specified are alkali halides, alkali metal borates, boric acid and alkaline earth halides.ALSO:The invention comprises xanthine and guanine produced in plate form having a length:thickness ratio of at least 4:1. The xanthine or guanine is enclosed in an evacuated space and is simultaneously heated with an inorganic metal salt substrate therefor to a temperature at which xanthine or guanine and said substrate evaporate, depositing a thin film of xanthine (or guanine) and substrate alternately on a moving surface sufficiently cool to condense alternate thin films of both xanthine (or guanine) and substrate, the substrate then being dissolved in a solvent, and the layers of xanthine or guanine are then broken up into plate form.ALSO:Nacreous pigment compositions are prepared by incorporating single pigments into a light-transmitting supporting medium having an index of refraction which differs from that of the pigments by at least 0.2.  The pigment particles have a length: thickness ratio of at least 4 : 1.  Pigments employed are zinc oxide, zinc sulphide, synthetic guanine and xanthine, titanium dioxide, zirconium oxide, lead chloride, magnesium fluoride, calcium fluoride and cryolite.  Light-transmitting supporting media include cellulose nitrate, cellulose acetate, polyvinyl chloride and acetate and their copolymers, polyester resins, polyacrylic resins, epoxy resins, polyethylene, polypropylene, polystyrene, phenol formaldehyde resins and amine formaldehyde resins.ALSO:In the production of pigment particles a pigment particle producing substance is sublimed at the same time as a substrate for said pigment.  The vapours of the pigment forming substance and of the substrate are successively deposited on the same cooled surface from which the substrate is later removed by a solvent. In example (1) a rotating steel disc is mounted in a horizontal position in a vacuum chamber; substrate material is placed in a sector shaped ceramic boat supported in position under the disc, the vertex of the boat pointing to the axis of the rotating disc. Pigment material is placed in a simlar boat below the disc in a position symmetrical with the first but diametrically opposed to it.  The boats are heated by electric furnace, and the disc is protected by shields manipulated from outside the vacuum chamber. A permanent shield is in a vertical position close to the axis of rotation to prevent intermixing of the vapours.  (2) An endless belt of polyester film moves on two parallel horizontal rollers which are two feet apart axis to axis in a vacuum chamber. Substrate is placed in a narrow ceramic boat one quarter of the distance between the rollers, and pigment forming substance is placed in a similar boat parallel to the previous boat but closer to the other roller.  The boats are protected by a shield which can be manipulated from outside the vacuum chamber.  A second shield is in a vertical position midway between the two sources in order to prevent mixing.  The polyester belt moves at 500 inches per minute.  In the above processes the pigment producing substance may be zinc oxide, zinc sulphide, guanine, xanthine, titanium dioxide, zirconium oxide, lead chloride, magnesium fluoride, calcium fluoride, and cryolite. The substrate may be alkali metal halides, alkali metal borates, boric acid and alkaline earth metal halides.ALSO:In the production of pigment particles a pigment particle producing substance is sublimed at the same time as a substrate for said pigment.  The vapours of the pigment forming substance and of the substrate are alternately and successively deposited on the same cooled surface from which the substrate is later removed by a solvent which generally causes the pigment films to break up into small flakes which subsequently are milled.  In examples (1) a rotating steel disc is mounted in a horizontal position in a vacuum chamber.  Substrate material is placed in a sector shaped ceramic boat supported in position under the disc, the vortex of the boat pointing to the axis of the rotating disc.  Pigment material is placed in a similar boat below the disc in a position symmetrical with the first but diametrically opposed to it.  The boats are heated electrically, and the disc is protected by shields manipulated from outside the vacuum chamber.  A permanent shield is in a vertical position close to the axis of rotation to prevent intermixing of the vapours; (2) an endless belt of polyester film moves in two parallel horizontal rollers which are 2 feet apart axis to axis in a vacuum chamber.  Substrate is placed in a narrow ceramic boat one quarter of the distance between the rollers, and pigment forming substance is placed in a similar boat parallel to the previous boat but closer to the other roller.  The boats are protected by a shield which can be manipulated from outside the vacuum chamber.  A second shield is in a vertical position midway between the two sources in order to prevent mixing.  The polyester belt moves at about 500 inches per minute; (3) alabaster glass beads are coated with cellulose nitrate lasquer containing zinc sulphide pigment giving a simulated pearl.