FLUOROMETRIC METHOD FOR MONITORING SURFACE ADDITIVES IN A PAPERMAKING PROCESS

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 a composition containing 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 composition containing 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 prior to sheet formation;

c. optionally measuring the fluorescence of the composition containing 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;

d. correlating the amount of fluorescence of the surface additives when they are capable of fluorescing and/or inert fluorescent tracers with the concentration of the surface additives, and if step c) occurs, then 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

e. optionally controlling the addition of the composition containing 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 concentration of the surface additives, and if step c) occurs, then optionally controlling the addition of the composition containing 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 . 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 a composition containing 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 composition containing 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 in an apparatus that serves to hold or feed or apply an aqueous composition into said papermaking process;

c. optionally measuring the fluorescence of the composition containing 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;

d. correlating the amount of fluorescence of the surface additives when they are capable of fluorescing and/or inert fluorescent tracers with the concentration of the surface additives, and if step c) occurs, then 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;

e. optionally controlling the addition of a composition containing 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 concentration of the surface additives; and if step c) occurs, then optionally controlling the addition of a composition containing one or more surface additives to a papermaking process by adjusting the concentration of the surface additives in the apparatus in response to coating thickness on a sheet and/or concentration of the surface additives in a coating on a sheet.

3 . The method of claim 2 wherein said apparatus is a chemical feeder or receptacle that holds one or more chemicals.

4 . The method of claim 3 wherein said chemicals are surface additives.

5 . The method of claim 1 wherein the fluorescence is measured in a papermaking process after a paper is converted to a narrow web or a sheet before end use.

6 . The method of claim 2 wherein the fluorescence is measured in a papermaking process after a paper is converted to a narrow web or a sheet before end use.

7 . The method of claim 2 wherein the surface additives are added onto the sheet by one or more mechanisms: spray system, roller coater, blade coater, cast coater, rod coater, air knife coater, curtain coater, flexo coater, gravure coater, and screen coater.

8 . The method of claim 2 wherein the apparatus may also include one or more parts of a paper machine in a papermaking process where the surface additives come in contact with a sheet in the papermaking process.

9 . The method of claim 2 further comprising adjusting the concentration of the surface additives in the apparatus in response to the fluorescence measurements made of one or more samples from the apparatus by a handheld fluorometer, benchtop fluorometer, in-line fluorometer, or a combination thereof.