RU2487339C2 - Fluorescent method of tracking of surface additives in papermaking process - Google Patents

Abstract

FIELD: textiles, paper.

SUBSTANCE: method comprises the following steps: a) adding a known amount of one or more surface additives to a papermaking process in a known proportion with a known amount of one or more inert fluorescent markers, and the inert fluorescent markers are selected from the group consisting of fluorescein or derivatives of fluorescein and rhodamine, or derivatives of rhodamine, b) measuring the fluorescence of one or more inert fluorescent markers in the point after adding the surface additives and after the web formation, at that fluorescence is measured with a fluorometer of reflective type, c) establishing the correlation between the fluorescence value of the inert fluorescent markers on the web and the concentration of surface additives in the coating on the web and/or coating thickness on the web.

EFFECT: use of the proposed method enables paper machine to control the rate of adding at very low levels, with ability to assess quickly and regulate statically rate of adding beyond the technical specifications.

17 cl, 1 ex, 2 dwg

Description

Field of Invention

The invention relates to monitoring and possibly regulating the addition of one or more surface additives in a papermaking process.

BACKGROUND OF THE INVENTION

Existing practice of measuring the amount of surface additives usually consists of a manual destruction of the web and / or mass balance calculations, which are relative in nature.

In the case of starch transfer in the size press, a papermaking machine (e.g., a cartoning machine) will in many cases apply a much larger amount of starch to be added to the papermaking process to ensure that enough starch is retained on the surface of the web for the intended function. Past tests included the use of a metering size press, which reduced starch due to scraper application technology. While this made it possible to significantly reduce starch in the range from 50 to 70%, the risk associated with malfunctions due to unexpected and uncontrolled fluctuations in starch transport was too great. As a result, many paper machines have been converted to pudding type size presses in order to provide a sufficient amount of starch added to the web.

Therefore, a more accurate and timely measurement of the amount of surface additives on the canvas was required. This will potentially allow the papermaking machine to control the rate of addition at very low levels, with the ability to quickly evaluate and statistically control the rate of addition outside of specifications.

SUMMARY OF THE INVENTION

The present invention provides a method for tracking and possibly regulating 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 additives to the papermaking process, either individually or in a known proportion, with a known amount of one or more inert fluorescent indicators, while surface additives can be added separately only when surface additives are capable of fluorescence tion; (b) measuring the fluorescence of surface substances and / or one or more inert fluorescent markers at the point following the addition of surface additives and after the formation of the web, while surface additives can only be measured when they are capable of fluorescence, and fluorescence measured using a fluorometer reflective type; (c) establishing a correlation between the fluorescence value of surface additives, when they are capable of fluorescence, and / or inert fluorescence markers on the canvas and the concentration of surface additives in the coating on the fabric and / or coating thickness on the fabric; and (d) it is possible to control the addition of one or more surface additives to the papermaking process by adjusting the amount of surface additives added to the papermaking process in accordance with the thickness of the coating on the web and / or the concentration of surface additives in the coating on the web.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the operation diagram of a reflector-type fluorometer according to one embodiment of the invention.

Figure 2 is a graph of individual fluorescence versus individual dry starch transfer shown in combination of starch and an inert fluorescent marker.

DETAILED DESCRIPTION OF THE INVENTION

Terminology:

“Paper-making process” / “paper-making processes” are processes for the manufacture of any kind of paper products (for example, paper, napkins, cardboard, etc.) from pulp, including the formation of aqueous pulp for making paper, draining the pulp to form a web and drying the web . The stages of formation of paper pulp, drainage and drying can be carried out by any conventional method known to specialists in this field of technology. The papermaking process / processes may also include a pulp preparation step, i.e. the manufacture of pulp from raw wood material, and the stage of bleaching, i.e. chemical treatment of pulp to improve whiteness.

A “canvas” / “web” is a sheet (s) obtained as a result of or during a papermaking process / papermaking processes.

A “surface additive” / “surface additives” is an additive (s) for making paper that imparts one or more chemical and / or physical (eg mechanical) properties to the surface of the web. For example, the web may be a paper web, a tissue web, a cardboard web, or any other type of web resulting from a paper making process. For example, imparting chemical properties may allow the binding of “ink” to paper in a more efficient manner.

NADH is a nicotinamide adenine dinucleotide reduced (in the H-form) and / or its derivatives.

ATP (ATP) means adenosine triphosphate.

Preferred Embodiments

As described above, one or more additives added to the papermaking process is monitored by a fluorometric protocol. It requires that the medium subjected to fluorescence is suitable for fluorometric measurements, for example, the coating film is excited to its entire depth and its emission is recorded. One skilled in the art can determine this without undue experimentation.

The fluorometric protocol includes the following conditions: (1) one or more surface additives have fluorescence ability, proprietary and / or modified to achieve fluorescence, for example, using a fluorescent fragment or by reacting with a molecule in the system or by means other than its own characteristics ; (2) one or more inert fluorescent markers are added in a known proportion with surface additives; or (3) a combination thereof.

When the surface additive is capable of fluorescence, a correlation can be directly established between the fluorescence and the concentration of the surface additive in the coating / thickness of the coating containing the surface additive, for example, by calibrating the fluorescence intensity according to the concentration of the surface additive and / or the thickness of the coating containing the surface additive. A person skilled in the art can carry out such a procedure without undue experimentation.

In one embodiment, the surface additives have intrinsic fluorescence.

In another embodiment, a fluorescent moiety may be covalently attached to non-fluorescent surface additives. At the same time, functionalized surface additives acquire fluorescent properties.

When using an inert fluorescent marker, it is added to the surface additive in a known proportion. The amount of surface additive or the thickness of the coating containing the surface additive can be estimated by fluorescence of an inert fluorescent marker, for example, by calibrating the fluorescence intensity by the concentration of the additive in the coating on the fabric and / or the thickness of the coating containing the additive on the fabric. A person skilled in the art can carry out this procedure without undue experimentation.

In one embodiment, inert fluorescent markers can be added to the coating formulation with a specific known concentration, so that when measuring the concentration of inert fluorescent markers, you can get an idea of the amount of coating on the fabric or surface additives in the coating on the fabric.

You can also track both surface additives with fluorescence and inert fluorescence markers. The amount of coating on the fabric or surface additives in the coating on the fabric can be determined by fluorescence of an inert fluorescent marker and fluorescence of the surface additive by calibrating the fluorescence intensity by the concentration of the additive in the coating on the fabric and / or, by the thickness of the coating containing the additive on the fabric. A person skilled in the art can perform this procedure without undue experimentation.

Any type of one or more inert fluorescent markers can be used in the present invention.

Any person skilled in the art knows what an inert fluorescent marker is.

In one embodiment, the inert fluorescent marker is a substance that is chemically inactive with respect to any of the components in the papermaking process and does not degrade over time. It is completely soluble in the system at any acceptable concentration levels. The intensity of its fluorescence is always / essentially proportional to its concentration and does not decrease or otherwise decreases by the system.

In another embodiment, the inert fluorescent marker is an inert fluorescent marker that is not significantly or substantially affected by any chemical process in the papermaking process. To quantify what it means “noticeably or substantially does not affect”, this statement means that an inert fluorescent substance has no more than 10% change in its fluorescent signal under conditions that are usually found in the paper-making process. The conditions that are commonly observed in the papermaking process are known to those skilled in the papermaking industry.

In another embodiment, desirable characteristics of an inert fluorescent marker preferably include: high solubility in water, excellent chemical resistance, good fluorescent properties at measured wavelengths (for example, not suppressed by other additives in the components of the web / paper web / cardboard web), and they can monitor in the presence of typical optical brighteners, for example, outside the wavelengths of optical brighteners to prevent interference between optical brighteners and inert fluorescent markers.

In another embodiment, the inert fluorescent marker is a marker approved by the FDA (United States Food and Drug Administration), which is required, for example, in food packaging.

In another embodiment, one or more inert fluorescent markers are selected from the group consisting of at least one of the following: fluorescein or fluorescein derivatives, rhodamine or rhodamine derivatives, naphthalene sulfonate salt, pyrene sulfonate salt, stilbene sulfonate salt, biphenyl sulfonate salt, phenyl sulfonate, tryptophan, tyrosine, vitamin A (retinol), vitamin B2 (riboflavin), vitamin B6 (pyridoxine), vitamin E (α-tocopherols), NADH, ATP, ethoxychine, caffeine, vanillin, naphthalene sulfonate-formaldehyde condensate, condensate enilsulfonat-formaldehyde, sulfonated lignin, a polymer containing at least one of the following groups: naphthalenesulfonates, pirensulfonaty, bifenilsulfonaty or stilbensulfonaty.

Depending on the papermaking process, the optimal concentration of inert fluorescent markers will vary. One of skill in the art can determine the amount of inert fluorescent markers without undue experimentation. It is preferred, for example, in the case of starch, that higher concentrations of inert fluorescent markers work better than lower concentrations of inert fluorescent markers.

The fluorometer used should be a reflector type fluorometer, since it is desirable that it determines the thickness of the applied thin coating on the surface of the matte web. One or more fluorometers may be used.

A reflective fluorometer is available from Nalco Company or Ocean Optics, Dunedin, FL.

A flow chart of a reflective type fluorometer is shown in FIG. 1. A reflective fluorometer uses optical fiber to excite a marker on the web and track its reflected fluorescence. The excitation light provides a suitable light source such as an LED, a xenon flash, or a discharge lamp. The light emitted from the source is filtered with a suitable excitation filter (e.g., from Semrock, Inc./Andover, Inc.) to eliminate unwanted wavelengths in the fluorescence region. The light is reflected at an angle of 90 degrees, and it is additionally filtered by a dichroic filter to obtain a new beam in the other direction. The beam is focused on the core of the fiber optic cable using a suitable lens. The other end of the optical fiber is placed close to or in contact with the surface of the paper web in order to illuminate a portion of its surface, causing fluorescent radiation. The radiation is captured by the same fiber that carries the reflected light back to the lenses on which it is collimated and sent back to the dichroic filter. The reflected excitation light is reflected back to the source, while fluorescence passes directly to the radiation filter. Filtered light is detected by a suitable optical detector, such as a photodiode or photomultiplier tube. An additional reference detector can be used to adjust the changing light source intensity.

Other designs of reflective fluorometers are apparent to those skilled in the art.

Various types of surface additives can be used in the present invention.

In one embodiment of the invention, surface additives are selected from the group consisting of at least one of the following substances: starch, pigments, binders, plasticizers and other additives to improve the physical properties of the paper / cardboard web, including surface strength, whiteness, printing properties, moisture resistance or adhesion to subsequent coatings.

In another embodiment, the surface additives comprise a covalently coupled fluorescent moiety.

In another embodiment, the starch comprises a covalently linked fluorescence moiety.

Surface additives can be added at various stages of the papermaking process.

In one embodiment, surface additives are added between the forming section of the papermaking process and the press section of the papermaking process.

In another embodiment, surface additives are added to the wet portion of the paper process.

In yet another embodiment, surface additives are added to the papermaking process between the water chamber and the web or at these sites.

The fluorescence of the web can be measured at various points in the papermaking process.

In one embodiment, fluorescence is measured at some point after the press portion.

In another embodiment, fluorescence is measured after the drying section of the papermaking process.

In another embodiment, fluorescence is measured after the drying line in the forming section.

In another embodiment, fluorescence is measured near the press portion.

In another embodiment, the fluorescence of starch containing a covalently linked fluorescence moiety and / or the fluorescence of inert fluorescent markers added in known proportions with starch is measured after the drying section and before the coating section in a paper-making process.

In another embodiment, the fluorescence of surface additives and / or inert fluorescent markers added in a known proportion to these surface additives, excluding starch, is measured after the coating section of the papermaking process.

Fluorescence can be measured at a fixed point (single point), for example, a measurement in the direction of the machine, or at many points, for example, by scanning many points in a direction transverse to the web in a transverse manner relative to the direction of movement of the paper web. To accomplish this task, a reflective fluorometer can be used in various ways. Any person skilled in the art can use various implementation methods.

In one method, fluorescence is measured at one point or at multiple points.

In another embodiment, the fluorometer can be configured to measure in the machine direction, that is, positioned at a fixed point.

In another embodiment, the measurement of multiple points occurs by scanning the fluorometer in the transverse direction relative to the direction of the specified fabric in the specified papermaking process, similar to how other devices for tracking the fabric, such as brightness or base weight sensors, work.

In yet another embodiment, the fluorometer is configured so that flow measurements can be made.

To implement the above protocol, you can use the controller.

One or more controllers are associated with a fluorometer and programmed with an algorithm to collect the indicated fluorescence measurements, establish a correlation between the fluorescence value of surface additives and / or inert fluorescent markers on the fabric and the concentration of surface additives in the coating on the fabric and / or coating thickness on the fabric; and possibly regulate the amount of surface additives added to the papermaking process, adjust the operating parameters of the papermaking machine, adjust the settings of the pudding or dosing type gluing machine or their combination in accordance with the thickness of the coating on the fabric and / or the concentration of surface additives in the coating on the fabric according to the pre specified protocol.

Regulation of the amount of surface additives added to the papermaking process in accordance with the thickness of the coating on the web and / or the concentration of surface additives in the coating on the web can be done in various ways.

As indicated above, this response may be provided by the controller, or it may be performed manually by paper process operators.

Adjustment can be performed in various ways.

In one embodiment, the adjustment can be performed using a sprayer boom, in which the feed rate of surface additives to the paper web can be adjusted.

In another embodiment, it is possible to independently adjust the feed rate of the additive in a plurality of zones across the web based on the fluorescence readings when scanning the fluorometer in the transverse direction relative to the direction of the web in the paper process.

In another embodiment, it is possible to adjust the parameters of the papermaking process, such as the speed of the web in the paper machine and / or the moisture content of the web.

In another embodiment, it is possible to adjust the settings of the metering size press in accordance with the thickness of the coating on the web and / or the concentration of surface additives in the coating on the web to maintain the desired thickness or to increase the tonnage of products or minimize the cost of additives or energy costs.

The following examples do not limit the invention.

EXAMPLES

Protocol

Testing of coating weight or thickness was performed using a standard test report. Several coating solutions containing various amounts of coating solids were applied to the surface of the test samples. Preferably, the ratio of solids to inert fluorescent marker is constant for all solutions. The coating weight on each sample may vary during coating using various application techniques. After drying, the dry coating mass or transfer was measured by the mass difference. Each individually sample web was weighed before and after coating, and the dry coating weight was calculated by the mass difference. The fluorescence intensity of the dry starch film was measured in several places of this sample of the fabric. A series of fluorescence intensities was then averaged to obtain one fluorescence intensity value for each web sample. Two different fluorometers were used to measure the fluorescence intensity of each web sample.

Example 1

The test was carried out according to the above protocol on three starch solutions containing an increasing amount of starch solids while maintaining a constant ratio of starch and inert fluorescent marker. The substrate for each test was an uncovered 21-point cardboard web. Each solution was applied to individual web samples of four different thicknesses using manual application. A fourth starch solution containing no inert fluorescent marker was also applied to a series of samples for comparison with marker solutions. The blank used in this test was an uncoated web sample.

Figure 2 shows the dependence of the fluorescence intensity (in arbitrary units - relative units of fluorescence ("RFU") on the mass of dry starch coating (selection, in g / m ² ). Each point corresponds to a separate sample of the fabric. Figure 2 shows that the measured fluorescence intensities of the entire series of web images are lined up diagonally in the graph area Linear regression at all points very clearly shows a direct and reliable correlation between the transfer of dry starch and the amount of inert fluorescent marker a, which is present in the layer measured by fluorescence intensity. The trend line has a y-segment very close to zero and the coefficient R ^{2 is} greater than 0.96. In some cases, one point is significantly removed from the line. The same random points were observed on two separate fluorometers, meaning that they refer to a sample of the web and not to a device error. These points appear to be due to defects in the starch layer on the paper web. These data demonstrate that using the claimed method it is possible to detect defects in the coating.

Claims (17)

1. A method for tracking and possibly regulating the addition of one or more surface additives to a papermaking process, comprising the steps of:
a) adding a known amount of one or more surface additives to the papermaking process in a known proportion with a known amount of one or more inert fluorescent markers, wherein the inert fluorescent markers are selected from the group consisting of fluorescein or fluorescein derivatives and rhodamine or rhodamine derivatives;
b) measuring the fluorescence of one or more inert fluorescence markers at a point after the addition of surface additives and after the formation of the web, while fluorescence is measured using a reflector type fluorometer;
c) establishing a correlation between the fluorescence value of inert fluorescent markers on the canvas and the concentration of surface additives in the coating on the canvas and / or the thickness of the coating on the canvas and
d) it is possible to control the addition of one or more surface additives to the paper process by adjusting the amount of surface additives added to the paper process according to the thickness of the coating on the web and / or the concentration of surface additives in the coating on the web. 2. The method according to claim 1, wherein the web is a paper web or a cardboard web. 3. The method according to claim 1, in which the surface additives are selected from the group comprising at least one of the following substances: starch, pigments, binders, plasticizers and other additives to improve the physical properties of the paper / cardboard sheet, including surface strength, whiteness, printing properties, moisture resistance, adhesion to subsequent coatings. 4. The method according to claim 1, in which one or more surface additives contains a covalently linked fluorescent moiety. 5. The method according to claim 3, in which the starch contains a covalently linked fluorescent moiety. 6. The method according to claim 1, in which surface additives are added between the forming part of the paper process and the press part of the paper process or in these parts. 7. The method according to claim 1, in which surface additives are added in the wet part of the paper process. 8. The method according to claim 1, in which surface additives are added in the papermaking process between the water chamber and the web or in these areas. 9. The method according to claim 1, in which the fluorescence is measured at some point after the press part. 10. The method according to claim 1, in which the fluorescence is measured after the drying part of the papermaking process. 11. The method according to claim 1, in which the fluorescence is measured after the drying line in the forming part. 12. The method according to claim 1, in which the fluorescence is measured near the press part. 13. The method according to claim 5, in which the fluorescence of starch and / or inert fluorescent markers, added in a known proportion to the specified starch, is measured after the drying part and to the coating part in the paper making process. 14. The method according to claim 1, in which surface additives and / or inert fluorescent markers added in a known proportion to these surface additives, excluding starch, are measured after the coating part of the paper-making process. 15. The method according to claim 1, in which fluorescence is measured at one point or at multiple points. 16. The method according to clause 15, in which the measurement of many points occurs by scanning the fluorometer in the transverse direction relative to the direction of the specified fabric in the specified paper-making process. 17. The method according to claim 1, in which one or more controllers are associated with a fluorometer and programmed with an algorithm for collecting these fluorescence measurements, establishing a correlation between the fluorescence value of inert fluorescence markers on the canvas and the concentration of surface additives in the coating on the canvas and / or coating thickness on the canvas; and possibly regulating the amount of surface additives added to the papermaking process, adjusting the operating parameters of the papermaking machine, adjusting the settings of the pudding or dosing type gluing machine, or combining them in accordance with the thickness of the coating on the fabric and / or the concentration of surface additives in the coating on the fabric according to a predetermined protocol.

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