SEPARATED TREATMENT OF PAPER SUBSTRATE WITH MULTIVALENT METAL SALTS AND OBAs

Abstract

A process for providing printable substrates by separately treating one or both surfaces of a paper substrate with an optical brightening agent (OBA) and a multivalent metal salt drying agent, where one or both surfaces of the paper substrate is treated with one of these two agents at the size press, and where the surface(s) is treated with the other of these two agents before or after the size press.

What is claimed is: 
     
         1 . A process comprising the following steps:
 (a) for a paper substrate about 10% or less by weight mechanical pulp fibers and having a first surface and a second surface, treating at least one of the first and second surfaces at a size press with one of the following two agents: (1) an optical brightening agent or; (2) a multivalent metal salt drying agent, to provide a treated paper substrate having one of the two agents; and   (b) before or after the size press, treating the at least one surface of the paper substrate of step (a) with the other of the two agents to provide a printable substrate;   (c) wherein the least one surface after steps (a) and (b) comprises the multivalent metal salt drying agent in an amount such that the at least one surface has a percent ink transferred (“IT %”) value equal to or less than about 65% and a black print density value of at least about 1.15;   (d) wherein the optical brightening agent is present after steps (a) and (b) in an amount sufficient to impart to the at least one surface an ISO brightness value of at least about 75.   
     
     
         2 . The process of  claim 1 , wherein steps (a) and (b) are carried out on both the first and second surfaces. 
     
     
         3 . The process of  claim 2 , wherein the first and second surfaces are treated with the multivalent metal salt drying agent at a pickup of from about 0.15 to about 3% by weight of the multivalent metal salt drying agent per ton of paper substrate. 
     
     
         4 . The process of  claim 3 , wherein the first and second surfaces are treated with the multivalent metal salt drying agent at a pickup of from about 0.35 to about 1.3% by weight of the multivalent metal salt drying agent per ton of paper substrate. 
     
     
         5 . The process of  claim 2 , wherein the first and second surfaces are treated with the optical brightening agent at a pickup 0.25 to about 3% by weight of the optical brightening agent per ton of paper substrate. 
     
     
         6 . The process of  claim 5 , wherein the first and second surfaces are treated with the optical brightening agent at a pickup of from about 1 to about 2% by weight of the optical brightening agent per ton of paper substrate. 
     
     
         7 . The process of  claim 1 , wherein the multivalent metal salt drying agent comprises one or more of: a calcium salt or a magnesium salt. 
     
     
         8 . The process of  claim 7 , wherein the multivalent metal salt drying agent comprises a calcium salt. 
     
     
         9 . The process of  claim 8 , wherein the calcium salt comprises calcium chloride. 
     
     
         10 . The process of  claim 1 , wherein the multivalent metal salt drying agent is present on the at least one of the first and second surfaces in an amount sufficient to provide an IT % value equal to or less than about 50%. 
     
     
         11 . The process of  claim 10 , wherein the multivalent metal salt drying agent is present on the at least one of the first and second surfaces in an amount sufficient to provide a IT % value equal to or less than about 40%. 
     
     
         12 . The process of  claim 1 , wherein the multivalent metal salt drying agent is present on the at least one of the first and second surfaces to provide a black print density value of at least about 1.25. 
     
     
         13 . The process of  claim 12 , wherein the multivalent metal salt drying agent is present on the at least one of the first and second surfaces to provide a black print density value of at least about 1.45. 
     
     
         14 . The article of  claim 1 , wherein the multivalent metal salt drying agent present on the at least one of the first and second surfaces to provide an edge acuity (EA) value of less than about 15. 
     
     
         15 . The process of  claim 14 , wherein the multivalent metal salt drying agent is present on the at least one of the first and second surfaces to provide an edge acuity (EA) value of less than about 10. 
     
     
         16 . The process of  claim 1 , wherein the optical brightening agent is present in an amount sufficient to impart an ISO Brightness value of at least about 85. 
     
     
         17 . The process of  claim 16 , wherein the optical brightening agent is present in an amount sufficient to impart an ISO Brightness value of at least about 90. 
     
     
         18 . The process of  claim 1 , wherein the optical brightening agents comprises one or more of: 4,4′-bis-(triazinylamino)-stilbene-2,2′-disulfonic acids, 4,4′-bis-(triazol-2-yl)stilbene-2,2′-disulfonic acids, 4,4′-dibenzofuranyl-biphenyls, 4,4′-(diphenyl)-stilbenes, 4,4′-distyryl-biphenyls, 4-phenyl-4′-benzoxazolyl-stilbenes, stilbenzyl-naphthotriazoles, 4-styryl-stilbenes, bis-(benzoxazol-2-yl) derivatives, bis-(benzimidazol-2-yl) derivatives, coumarins, pyrazolines, naphthalimides, triazinyl-pyrenes, 2-styryl-benzoxazole or -naphthoxazoles, or benzimidazole-benzofurans or oxanilides. 
     
     
         19 . The process of  claim 18 , wherein the optical brightening agent comprises one or more stilbene-based sulfonates. 
     
     
         20 . The process of  claim 19 , wherein these one or more stilbene-based sulfonates comprise derivatives of 4,4′-diaminostilbene-2,2′-disulphonic acid, 4,4-bis(triazine-2-ylamino)stilbene-2,2′-disulphonic acid, disodium salts of distyrlbiphenyl disulfonic acid, or disodium salts of 4,4′-di-triazinylamino-2,2′-di-sulfostilbene. 
     
     
         21 . The process of  claim 1 , wherein the optical brightening agent is present on the at least one of the first and second surfaces in an amount sufficient to impart a CIE Whiteness value of at least about 115. 
     
     
         22 . The process of  claim 21 , wherein the optical brightening agent is present on the at least one of the first and second surfaces in an amount sufficient to impart a CIE Whiteness value of at least about 125. 
     
     
         23 . The process of  claim 22 , wherein the optical brightening agent is present on the at least one of the first and second surfaces in an amount sufficient to impart a CIE Whiteness value of at least about 145. 
     
     
         24 . The process of  claim 1 , wherein step (b) is carried out before step (a). 
     
     
         25 . The process of  claim 1 , wherein step (b) is carried out after step (a). 
     
     
         26 . The process of  claim 1 , wherein step (b) is carried out by spraying the other of the two agents onto the at least one surface of the paper substrate of step (a). 
     
     
         27 . The process of  claim 1 , wherein step (a) is carried out by treating the at least one of the first and second surfaces of the paper substrate with the optical brightening agent, and wherein step (b) is carried out by treating the at least one surface of the paper substrate of step (a) with the multivalent metal salt drying agent. 
     
     
         28 . The process of  claim 1 , wherein step (a) is carried out by treating the at least one of the first and second surfaces of the paper substrate with the multivalent metal salt drying agent, and wherein step (b) is carried out by treating the at least one surface of the paper substrate of step (a) with the optical brightening agent. 
     
     
         29 . The process of  claim 1 , wherein the paper substrate comprises less than about 5% by weight mechanical pulp fibers. 
     
     
         30 . The process of  claim 29 , wherein the paper substrate comprises less than about 1% by weight mechanical pulp fibers. 
     
     
         31 . A process comprising the following steps:
 (a) for a paper substrate comprising greater than about 10% by weight mechanical pulp fibers and having a first surface and a second surface, treating at least one of the first and second surfaces at a size press with one of the following two agents: (1) an optical brightening agent or; (2) a multivalent metal salt drying agent, to provide a treated paper substrate having one of the two agents; and   (b) before or after the size press, treating the at least one surface of the paper substrate of step (a) with the other of the two agents to provide a printable substrate;   (c) wherein the least one surface after steps (a) and (b) comprises the multivalent metal salt drying agent in an amount such that the at least one surface has a percent ink transferred (“IT %”) value equal to or less than about 65% and a black print density value of at least about 1.15;   (d) wherein the optical brightening agent is present after steps (a) and (b) in an amount sufficient to impart to the at least one surface an ISO brightness value of at least about 75.   
     
     
         32 . The process of  claim 31 , wherein steps (a) and (b) are carried out on both the first and second surfaces. 
     
     
         33 . The process of  claim 32 , wherein the first and second surfaces are treated with the multivalent metal salt drying agent at a pickup of from about 0.15 to about 3% by weight of the multivalent metal salt drying agent per ton of paper substrate. 
     
     
         34 . The process of  claim 33 , wherein the first and second surfaces are treated with the multivalent metal salt drying agent at a pickup of from about 0.35 to about 1.3% by weight of the multivalent metal salt drying agent per ton of paper substrate. 
     
     
         35 . The process of  claim 32 , wherein the first and second surfaces are treated with the optical brightening agent at a pickup 0.25 to about 3% by weight of the optical brightening agent per ton of paper substrate. 
     
     
         36 . The process of  claim 35 , wherein the first and second surfaces are treated with the optical brightening agent at a pickup of from about 1 to about 2% by weight of the optical brightening agent per ton of paper substrate. 
     
     
         37 . The process of  claim 31 , wherein the multivalent metal salt drying agent comprises one or more of: a calcium salt or a magnesium salt. 
     
     
         38 . The process of  claim 37 , wherein the multivalent metal salt drying agent comprises a calcium salt. 
     
     
         39 . The process of  claim 38 , wherein the calcium salt comprises calcium chloride. 
     
     
         40 . The process of  claim 31 , wherein the multivalent metal salt drying agent is present on the at least one of the first and second surfaces in an amount sufficient to provide an IT % value equal to or less than about 50%. 
     
     
         41 . The process of  claim 40 , wherein the multivalent metal salt drying agent is present on the at least one of the first and second surfaces in an amount sufficient to provide a IT % value equal to or less than about 40%. 
     
     
         42 . The process of  claim 31 , wherein the multivalent metal salt drying agent is present on the at least one of the first and second surfaces to provide a black print density value of at least about 1.25. 
     
     
         43 . The process of  claim 42 , wherein the multivalent metal salt drying agent is present on the at least one of the first and second surfaces to provide a black print density value of at least about 1.45. 
     
     
         44 . The article of  claim 41 , wherein the multivalent metal salt drying agent present on the at least one of the first and second surfaces to provide an edge acuity (EA) value of less than about 15. 
     
     
         45 . The process of  claim 44 , wherein the multivalent metal salt drying agent is present on the at least one of the first and second surfaces to provide an edge acuity (EA) value of less than about 10. 
     
     
         46 . The process of  claim 41 , wherein the optical brightening agent is present in an amount sufficient to impart an ISO Brightness value of at least about 85. 
     
     
         47 . The process of  claim 46 , wherein the optical brightening agent is present in an amount sufficient to impart an ISO Brightness value of at least about 90. 
     
     
         48 . The process of  claim 41 , wherein the optical brightening agents comprises one or more of: 4,4′-bis-(triazinylamino)-stilbene-2,2′-disulfonic acids, 4,4′-bis-(triazol-2-yl)stilbene-2,2′-disulfonic acids, 4,4′-dibenzofuranyl-biphenyls, 4,4′-(diphenyl)-stilbenes, 4,4′-distyryl-biphenyls, 4-phenyl-4′-benzoxazolyl-stilbenes, stilbenzyl-naphthotriazoles, 4-styryl-stilbenes, bis-(benzoxazol-2-yl) derivatives, bis-(benzimidazol-2-yl) derivatives, coumarins, pyrazolines, naphthalimides, triazinyl-pyrenes, 2-styryl-benzoxazole or -naphthoxazoles, or benzimidazole-benzofurans or oxanilides. 
     
     
         49 . The process of  claim 48 , wherein the optical brightening agent comprises one or more stilbene-based sulfonates. 
     
     
         50 . The process of  claim 49 , wherein these one or more stilbene-based sulfonates comprise derivatives of 4,4′-diaminostilbene-2,2′-disulphonic acid, 4,4-bis(triazine-2-ylamino)stilbene-2,2′-disulphonic acid, disodium salts of distyrlbiphenyl disulfonic acid, or disodium salts of 4,4′-di-triazinylamino-2,2′-di-sulfostilbene. 
     
     
         51 . The process of  claim 31 , wherein the optical brightening agent is present on the at least one of the first and second surfaces in an amount sufficient to impart a CIE Whiteness value of at least about 100. 
     
     
         52 . The process of  claim 50 , wherein the optical brightening agent is present on the at least one of the first and second surfaces in an amount sufficient to impart a CIE Whiteness value of at least about 105. 
     
     
         53 . The process of  claim 52 , wherein the optical brightening agent is present on the at least one of the first and second surfaces in an amount sufficient to impart a CIE Whiteness value of at least about 115. 
     
     
         54 . The process of  claim 31 , wherein step (b) is carried out before step (a). 
     
     
         55 . The process of  claim 31 , wherein step (b) is carried out after step (a). 
     
     
         56 . The process of  claim 51 , wherein step (b) is carried out by spraying the other of the two agents onto the at least one surface of the paper substrate of step (a). 
     
     
         57 . The process of  claim 51 , wherein step (a) is carried out by treating the at least one of the first and second surfaces of the paper substrate with the optical brightening agent, and wherein step (b) is carried out by treating the at least one surface of the paper substrate of step (a) with the multivalent metal salt drying agent. 
     
     
         58 . The process of  claim 51 , wherein step (a) is carried out by treating the at least one of the first and second surfaces of the paper substrate with the multivalent metal salt drying agent, and wherein step (b) is carried out by treating the at least one surface of the paper substrate of step (a) with the optical brightening agent. 
     
     
         59 . The process of  claim 31 , wherein the paper substrate comprises from about 15 to 100% by weight mechanical pulp fibers. 
     
     
         60 . The process of  claim 59 , wherein the paper substrate comprises from about 50 to 95% by weight mechanical pulp fibers.