White Pigment Reflecting Ir Radiation, Production and Use Thereof

Abstract

The invention relates to a pigment which reflects IR radiation, comprising an IR-reflecting core, the IR-reflecting core being provided with a substantially enveloping coating which is transparent to IR radiation, and in that the IR-reflecting pigment is substantially white. The invention further relates to a process for producing these pigments and also to their use.

1 . A pigment which reflects IR radiation, comprising an IR-reflecting core, wherein the IR-reflecting core is provided with a substantially enveloping coating which is substantially transparent to IR radiation and in that the IR-reflecting pigment is substantially white. 
   
   
       2 . The IR-reflecting pigment of  claim 1 , wherein the IR-reflecting core is platelet-shaped or spherical. 
   
   
       3 . The IR-reflecting pigment of  claim 1 , wherein in, on and/or under the coating that is substantially transparent to IR radiation there are white pigments which preferably have an average primary particle size of 180 to 400 nm. 
   
   
       4 . The IR-reflecting pigment of  claim 3 , wherein the white pigments have an average primary particle size of 250 to 370 nm. 
   
   
       5 . The IR-reflecting pigment of  claim 3 , wherein the white pigments are selected from the group consisting of titanium dioxide, zinc oxide, magnesium oxide, zinc sulfide, calcium fluoride, lithium fluoride, sodium fluoride, potassium fluoride, calcium carbonate, lithopones, magnesium carbonate, barium sulfate, barium titanate, barium ferrite, and mixtures thereof. 
   
   
       6 . The IR-reflecting pigment of  claim 3 , wherein the white pigments are TiO 2 , ZnS and/or ZnO. 
   
   
       7 . The IR-reflecting pigment of  claim 1 , wherein the white pigments are present in an amount of 20% to 80% by weight, preferably 35% to 70% by weight, based on the weight of the total IR-reflecting pigment. 
   
   
       8 . The IR-reflecting pigment of  claim 1 , wherein the white pigments are arranged substantially uniformly around the IR-reflecting core and are present preferably in an amount of 0.3 to 10 g, preferably of 0.5 to 7 g, per 1 m 2  of surface area of the IR-reflecting core in the IR-reflecting pigment. 
   
   
       9 . The IR-reflecting pigment of  claim 1 , wherein the substantially IR-transparent coating comprises or consists of metal oxide. 
   
   
       10 . The IR-reflecting pigment of  claim 9 , wherein the metal oxide is selected from the group consisting of silicon dioxide, aluminum oxide, aluminum hydroxide, boron oxide, boron hydroxide, and mixtures thereof. 
   
   
       11 . The IR-reflecting pigment of  claim 1 , wherein the substantially IR-transparent coating is present in a fraction of 4% to 30% by weight, based on the weight of the total IR-reflecting pigment. 
   
   
       12 . The IR-reflecting pigment of  claim 1 , wherein the IR-reflecting core is a platelet-shaped metal pigment or a spherical metal particle, the metal being selected preferably from the group consisting of aluminum, copper, zinc, iron, silver, and alloys thereof. 
   
   
       13 . The IR-reflecting pigment of  claim 12 , wherein the IR-reflecting core is a platelet-shaped metal pigment having a size of 5 to 150 μm. 
   
   
       14 . The IR-reflecting pigment of  claim 12 , wherein the IR-reflecting core is a platelet-shaped metal pigment having a size of 5 to 12 μm. 
   
   
       15 . The IR-reflecting pigment of  claim 12 , wherein the IR-reflecting core is a platelet-shaped aluminum pigment. 
   
   
       16 . The IR-reflecting pigment of  claim 12 , wherein the IR-reflecting core is platelet-shaped aluminum pigment, the IR-transparent coating is SiO 2 , and the white pigment is preferably TiO 2 , ZnS and/or ZnO having an average primary particle size of preferably 250 to 320 nm. 
   
   
       17 . The IR-reflecting pigment of  claim 1 , wherein the IR-transparent coating is or comprises organic polymer. 
   
   
       18 . The IR-reflecting pigment of  claim 17 , wherein the IR-transparent coating is present in a fraction of 4% to 30% by weight, based on the weight of the total IR-reflecting pigment. 
   
   
       19 . The IR-reflecting pigment of  claim 17 , wherein the IR-reflecting core is a platelet-shaped metal pigment or a spherical metal particle, the metal being selected preferably from the group consisting of aluminum, copper, zinc, iron, silver, and alloys thereof. 
   
   
       20 . The IR-reflecting pigment of  claim 19 , wherein the IR-reflecting core is a platelet-shaped metal pigment having a size of 5 to 150 μm. 
   
   
       21 . The IR-reflecting pigment of  claim 19 , wherein the IR-reflecting core is a platelet-shaped metal pigment having a size of 5 to 12 μm. 
   
   
       22 . The IR-reflecting pigment of  claim 19 , wherein the IR-reflecting core is a platelet-shaped aluminum pigment. 
   
   
       23 . The IR-reflecting pigment of  claim 1 , wherein the IR-reflecting core is a pearlescent pigment which, preferably largely, reflects IR radiation from 6 to 14 μm. 
   
   
       24 . A process for producing an IR-reflecting pigment of  claim 1 , wherein a coating which is substantially transparent to IR radiation is applied, together with white pigments and/or with particlelike coating outgrowths that scatter visible light, to an IR-reflecting core. 
   
   
       25 . The process for producing an IR-reflecting pigment of  claim 24 , wherein white pigments are applied, together with metal oxide, to the IR-reflecting core by a wet-chemical sol-gel process. 
   
   
       26 . The process for producing an IR-reflecting pigment of  claim 25 , wherein SiO 2  as metal oxide is applied to the IR-reflecting core by a wet-chemical sol-gel process. 
   
   
       27 . The process for producing an IR-reflecting pigment of  claim 24 , wherein a dispersion comprising highly volatile organic solvent, IR-reflecting cores, white pigments, preferably with an average size of 180 to 400 nm, and organic film-forming agent is spray-dried. 
   
   
       28 . The use of an IR-reflecting pigment of  claim 1  in inks, paints, varnishes, printing inks, security-printing inks, and cosmetics. 
   
   
       29 . The use of an IR-reflecting pigment of  claim 1  in emulsion paints for the interior or exterior sector. 
   
   
       30 . A coating composition wherein the coating composition comprises an IR-reflecting pigment of  claim 1 . 
   
   
       31 . The coating composition of  claim 30 , wherein the coating composition is a cosmetic, varnish, paint or ink, more particularly printing ink, security-printing ink or emulsion paint. 
   
   
       32 . An article wherein the article is coated with an IR-reflecting pigment of or with a coating composition of  claim 30 .