Fluorometric method for monitoring surface additives in a papermaking process

Abstract

A method of monitoring and optionally controlling the addition of one or more surface additives to a papermaking process is disclosed. The method comprises the following steps: (a) adding a known amount of one or more surface additives to a papermaking process either alone or in known proportion with a known amount of one or more inert fluorescent tracers, wherein the surface additives can only be added alone when the surface additives are capable of fluorescing; (b) measuring the fluorescence of the surface additives and/or one or more inert fluorescent tracers at a point subsequent to adding the surface additives and after a sheet has been formed, wherein the surface additives can only be measured when they are capable of fluorescing and wherein fluorescence is measured with a reflectance based fluorometer; (c) correlating the amount of fluorescence of the surface additives when they are capable of fluorescing and/or inert fluorescent tracers on a sheet with the concentration of the surface additives in a coating on a sheet and/or thickness of a coating on a sheet; and (d) optionally controlling the addition of one or more surface additives to a papermaking process by adjusting the amount of the surface additives added to the papermaking process in response to the coating thickness on a sheet and/or concentration of the surface additives in a coating on a sheet.

1 . A method of monitoring and optionally controlling the addition of one or more surface additives to a papermaking process comprising the following steps:
 a. adding a known amount of one or more surface additives to a papermaking process either alone or in known proportion with a known amount of one or more inert fluorescent tracers, wherein the surface additives can only be added alone when the surface additives are capable of fluorescing;   b. measuring the fluorescence of the surface additives and/or one or more inert fluorescent tracers at a point subsequent to adding the surface additives and after a sheet has been formed, wherein the surface additives can only be measured when they are capable of fluorescing and wherein fluorescence is measured with a reflectance based fluorometer;   c. correlating the amount of fluorescence of the surface additives when they are capable of fluorescing and/or inert fluorescent tracers on a sheet with the concentration of the surface additives in a coating on a sheet and/or thickness of a coating on a sheet; and   d. optionally controlling the addition of one or more surface additives to a papermaking process by adjusting the amount of the surface additives added to the papermaking process in response to the coating thickness on a sheet and/or concentration of the surface additives in a coating on a sheet.   
     
     
         2 . The method of  claim 1 , wherein the sheet is a paper sheet or a board sheet. 
     
     
         3 . The method of  claim 1 , wherein the surface additives are selected from the group consisting of at least one of the following: starch, pigments, binders, plasticizers, and other additives to improve the physical properties of a paperboard sheet, including surface strength, brightness, printability, water resistance, adhesion of subsequent coatings. 
     
     
         4 . The method of  claim 1 , wherein one or more of the surface additives contain a covalently bonded fluorescent moiety. 
     
     
         5 . The method of  claim 3 , wherein the starch contains a covalently bonded fluorescent moiety. 
     
     
         6 . The method of  claim 1 , wherein the inert fluorescent tracers are selected from the group consisting of at least one of the following: fluorescein or fluorescein derivatives, rhodamine or rhodamine derivatives, a sulfonate salt of naphthalene, a sulfonate salt of pyrene, a sulfonate salt of stilbene, a sulfonate salt of biphenyl, phenylalanine, tryptophan, tyrosine, vitamin A (retinol), vitamin B2 (riboflavin), vitamin B6 (pyridoxin), vitamin E (α-tocopherols), NADH, ATP, ethoxyquin, caffeine, vanillin, naphthalene sulfonate formaldehyde condensate, a phenyl sulfonate formaldehyde condensate, sulfonated lignin, a polymer containing at least one of the following moieties naphthalene sulfonates, pyrene sulfonates, biphenyl sulfonates, or stilbene sulfonates. 
     
     
         7 . The method of  claim 1 , wherein the surface additives are added between or at a forming section of a papermaking process and a press section of a papermaking process. 
     
     
         8 . The method of  claim 1 , wherein the surface additives are added at the wet-end of a papermaking process. 
     
     
         9 . The method of  claim 1 , wherein the surface additives are added to a papermaking process between or at a water box and a sheet. 
     
     
         10 . The method of  claim 1 , wherein the fluorescence is measured at some point after the press section. 
     
     
         11 . The method of  claim 1 , wherein the fluorescence is measured after a dryer section of a papermaking process. 
     
     
         12 . The method of  claim 1 , wherein the fluorescence is measured after a dry line in a forming section. 
     
     
         13 . The method of  claim 1 , wherein the fluorescence is measured proximate to the press section. 
     
     
         14 . The method of  claim 5 , wherein the fluorescence of the starch and/or inert fluorescent tracers added in known proportion with said starch is measured after a dryer section and before a coating section of a papermaking process. 
     
     
         15 . The method of  claim 1 , wherein the surface additives and/or inert fluorescent tracers added in known proportion with said surface additives, excluding starch, is measured after a coating section of a papermaking process. 
     
     
         16 . The method of  claim 1 , wherein fluorescence is measured at one point or at a plurality of points. 
     
     
         17 . The method of  claim 16 , wherein the measurement of a plurality of points occurs by scanning a fluorometer in a cross-directional manner relative to the direction of said sheet in said papermaking process. 
     
     
         18 . The method of  claim 1 , wherein one or more controllers are in communication with the fluorometer and are programmed with an algorithm to collect said fluorescence measurements, correlate the amount of fluorescence of the surface additives and/or inert fluorescent tracers on a sheet with the concentration of the surface additives in a coating on a sheet and/or thickness of a coating on a sheet; and optionally adjust the amount of the surface additives added to the papermaking process, adjust paper machine operating parameters, adjust settings of a puddle-type or metering size press, or a combination thereof in response to the coating thickness on a sheet and/or concentration of the surface additives in a coating on a sheet in accord with a pre-determined protocol.