Paper laminates comprising tungsten treated titanium dioxide having improved photostability

Abstract

This disclosure relates to a resin-impregnated, opaque, cellulose pulp-based sheet comprising an inorganic particle, wherein the inorganic particle comprises at least about 0.002% of tungsten, based on the total weight of the inorganic particle, and has a photostability ratio (PSR) of at least about 2, as measured by the Ag + photoreduction rate, and color as depicted by an L* of at least about 97.0, and b* of less than about 4. The disclosure also relates to paper laminates prepared from these resin-impregnated, opaque, cellulose pulp-based sheets.

1 . A resin-impregnated, opaque, cellulose pulp-based sheet comprising an inorganic particle, wherein the inorganic particle comprises at least about 0.002% of tungsten, based on the total weight of the inorganic particle, and has a photostability ratio (PSR) of at least about 2, as measured by the Ag +  photoreduction rate, and color as depicted by an L* of at least about 97.0, and b* of less than about 4. 
     
     
         2 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 1  wherein the inorganic particle is an inorganic metal oxide or mixed metal oxide particle. 
     
     
         3 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 2  wherein the inorganic metal oxide particle is titanium dioxide. 
     
     
         4 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 3  further comprising a resin. 
     
     
         5 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 4  wherein the resin is a thermosetting resin. 
     
     
         6 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 5  wherein the thermosetting resin is a polymer of diallyl phthalate, epoxide, urea formaldehyde, urea-acrylic acid ester. copolyester, melamine formaldehyde, melamine phenol formaldehyde, dicyandiamide-formaldehyde, urethane, unsaturated polyester, curable acrylic and phenol formaldehyde or mixtures thereof. 
     
     
         7 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 3  wherein the amount of the titanium dioxide in the resin-impregnated, opaque, cellulose pulp-based sheet is up to and including about 60 wt. %, based on the total dry weight of the cellulose pulp-based sheet prior to resin impregnation. 
     
     
         8 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 7  wherein the amount of the titanium dioxide in the the resin-impregnated, opaque, cellulose pulp-based sheet ranges from about 20 to about 40 wt. %, based on the total dry weight of the cellulose pulp-based sheet prior to resin impregnation. 
     
     
         9 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 3  wherein tungsten is present in the amount of at least about 0.004%, based on the total weight of the inorganic particle. 
     
     
         10 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 3  wherein the photostability ratio (PSR) is at least about 4. 
     
     
         11 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 3  wherein L* is at least about 98. 
     
     
         12 . resin-impregnated, opaque, cellulose pulp-based sheet of  claim 3  wherein b* is less than about 3. 
     
     
         13 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 3  wherein tungsten is added to the titanium dioxide particle by cooxidation or post-oxidation. 
     
     
         14 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 3  wherein tungsten is added to the titanium dioxide particle from an alloy comprising tungsten. 
     
     
         15 . The resin-impregnated, opaque, cellulose pulp-based sheet of  claim 3  wherein the titanium dioxide particle further comprises alumina in the amount of about 0.06 to about 5% based on the total weight of the titanium dioxide particle. 
     
     
         16 . A paper laminate prepared from a resin-impregnated, opaque, cellulose pulp-based sheet comprising an inorganic particle, wherein the inorganic particle comprises at least about 0.002% of tungsten, based on the total weight of the inorganic particle, and has a photostability ratio (PSR) of at least about 2, as measured by the Ag +  photoreduction rate, and color as depicted by an L* of at least about 97.0, and b* of less than about 4. 
     
     
         17 . The paper laminate of  claim 16  further comprising a dried overlay. 
     
     
         18 . The paper laminate of  claim 16  wherein the inorganic particle in the coating composition is an inorganic metal oxide or mixed metal oxide particle. 
     
     
         19 . The paper laminate of  claim 18  wherein the inorganic metal oxide particle is titanium dioxide. 
     
     
         20 . The paper laminate of  claim 16  wherein tungsten is present in the amount of at least about 0.004%, based on the total weight of the inorganic particle. 
     
     
         21 . The paper laminate of  claim 19  wherein the titanium dioxide particle further comprises alumina in the amount of about 0.06 to about 5% based on the total weight of the titanium dioxide particle.