Fluorometric method for monitoring surface additives in a papermaking process

1. A method of fluorometrically monitoring and optionally controlling the addition of at least one surface additive to a papermaking process, the papermaking process comprising forming a sheet, the sheet having a temperature and a flutter amplitude, the method comprising the following steps:

first measuring the fluorescence of a composition prior to the composition being added to the papermaking process, the composition comprising a concentration of the at least one surface additive;

adding a known amount of the composition to the papermaking process after the forming of the sheet;

second measuring the fluorescence of the sheet, the second measuring performed with a fluorometer apparatus, the fluorometer apparatus comprising a fluorometer, a non-contact temperature sensor, and optionally a displacement sensor, the fluorometer comprising a dichroic mirror and at least two fluorescence detectors;

third measuring the temperature of the sheet using the non-contact temperature sensor;

optionally fourth measuring the flutter amplitude using the displacement sensor;

correcting the second measuring using the measured sheet temperature;

first correlating the measured fluorescence of the composition with the concentration of the at least one surface additive in the composition;

second correlating the corrected measured fluorescence of the sheet with the concentration of the at least one surface additive in the composition;

optionally controlling at least a portion of the papermaking process and/or the addition of the at least one surface additive based on any of the measurements; wherein

if the at least one surface additive is incapable of fluorescing, then the composition further comprises an inert fluorescent tracer, the inert fluorescent tracer present in the composition in known proportion with a known amount of the at least one surface additive.

2. A method of fluorometrically monitoring and optionally controlling the addition of at least one surface additive to a papermaking process, the papermaking process comprising forming a sheet, the sheet having a temperature and a flutter amplitude, the method comprising the following steps:

first measuring the fluorescence of a composition prior to the composition being added to the papermaking process, the composition comprising a concentration of the at least one surface additive, the fluorescence corresponding with the concentration of the at least one surface additive in the composition;

adding a known amount of the composition to the papermaking process after the forming of the sheet;

second measuring the fluorescence of the sheet, the second measuring performed with a fluorometer apparatus, the fluorometer apparatus comprising a fluorometer, a non-contact temperature sensor, and a displacement sensor, the fluorometer comprising a dichroic mirror and at least two fluorescence detectors;

third measuring the temperature of the sheet using the non-contact temperature sensor;

fourth measuring the flutter amplitude using the displacement sensor;

correcting the second measuring for variations in the third measuring and/or the fourth measuring;

first correlating the measured fluorescence of the composition with the concentration of the at least one surface additive in the composition;

second correlating the corrected measured fluorescence of the sheet with the concentration of the at least one surface additive in the composition;

determining a coating thickness of the composition on the sheet using the values obtained from the first correlating and the second correlating; and

optionally controlling at least a portion of the papermaking process and/or the addition of the at least one surface additive based on any of the measurements; wherein

if the at least one surface additive is incapable of fluorescing, then the composition further comprises an inert fluorescent tracer, the inert fluorescent tracer present in the composition in known proportion with a known amount of the at least one surface additive.

3. An apparatus for monitoring and optionally controlling the addition of at least one surface additive to a papermaking process, the papermaking process comprising a sheet, the sheet having a temperature and a flutter amplitude, the apparatus comprising:

a fluorometer;

a temperature sensor; and

a displacement sensor; wherein

the fluorometer comprising an ultraviolet light source, a fluorescence detector, a reference detector, a reference reflector, a dichroic mirror, and optionally an electronic control unit, wherein the ultraviolet light source is operably positioned to shine ultraviolet light onto the dichroic mirror and the reference reflector,

a portion of the ultraviolet light reflected by the reference reflector to the reference detector, and another portion reflected by the dichroic mirror onto the sheet,

the fluorescence detector measuring light fluoresced from the sheet, the fluoresced light passing through the dichroic mirror and into the fluorescence detector;

the temperature sensor is a non-contact temperature sensor and is operatively positioned to measure the temperature of the sheet; and

the displacement sensor operatively positioned to measures the flutter amplitude of the sheet.

4. The apparatus of claim 3 , wherein the temperature sensor is an infrared temperature sensor.

5. The apparatus of claim 3 , wherein the apparatus provides input into the papermaking process, the input controlling at least a portion of the papermaking process, the input correlated with at least one of the following values: detected fluorescence, measured temperature of the sheet, and measured flutter amplitude of the sheet.

6. The apparatus of claim 3 , wherein the apparatus includes a second fluorometer, the second fluorometer comprising a fiber optic apparatus.

7. The method of claim 1 , wherein the composition is added onto the sheet by at least one of the following 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 composition is added onto the sheet by at least one of the following mechanisms: spray system, roller coater, blade coater, cast coater, rod coater, air knife coater, curtain coater, flexo coater, gravure coater, and screen coater.

9. The method of claim 1 , wherein the method further comprises the step of determining a coating thickness of the composition on the sheet based on the second correlating.

10. The method of claim 1 , wherein the method further comprises the steps of fifth measuring the temperature of the composition.

11. The method of claim 2 , wherein the method further comprises the steps of fifth measuring the temperature of the composition.

12. The method of claim 1 , wherein the first measuring is performed using a fluorometer comprising a fiber optic apparatus.

13. The method of claim 2 , wherein the first measuring is performed using a fluorometer comprising a fiber optic apparatus.

14. The method of claim 12 , wherein the first measuring is performed additionally using a refractometer.

15. The method of claim 13 , wherein the first measuring is performed additionally using a refractometer.