JP2001281241A - On-line colorimetry method of pulp slurry - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems that personal difference is large and it took much labor although the color matching of colored paper was made by comparing a standard color sample with the color of pulp slurry that is the raw material of paper for adjustment by expert's viewing, and that it is difficult to put a method using a chromatometer instead of a manual method into practical applications since the pulp slurry is not correlated with the measurement value of the paper of the color sample. SOLUTION: When pulp slurry with a pulp concentration of 3-5% is passed through a glass pipe at a flow rate of 0.8-4 m/sec and is measured by a chromatometer, the stagnation of the slurry and the generation of taminar flow causing a measurement error to occur can be prevented, and the colorimetry data of the pulp slurry becomes fully correlated with the measurement data of the sample color, thus performing the colorimetry of the pulp slurry on-line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the color of a pulp slurry used as a raw material for producing colored paper in a paper manufacturing plant.

[0002]

2. Description of the Related Art Colored paper is made by mixing a dye into white pulp.
It is produced by making a raw pulp colored in a desired color with a paper machine. In order to match the color of the colored paper made to the desired color, the pulp, dye, and other fillers must be blended so that the color of the raw pulp correlates with the standard sample color of the colored paper product. No. In the case of making colored paper, the blending ratio is determined for each standard sample color, and the raw pulp is blended based on the blending ratio.
Due to fluctuations in the pulp concentration, uneven coloring effect depending on the lot of the coloring agent, etc., even if the compounding is performed at a predetermined mixing ratio, a difference in color tone from a standard sample often occurs. When used paper pulp is used as a raw material pulp, it is easily changed depending on the color and fiber structure of the used paper.

[0003] Therefore, in a paper mill, before the colored paper is made, the color of the raw pulp is checked while constantly comparing the colored paper made by hand with the standard sample color based on the pulp slurry used for the production of the colored paper. Currently, we are making adjustments,
These color adjustment work is based on the experience of a skilled worker,
The color tone difference is visually determined and adjusted. However,
Even skilled workers have the problem that not only there is a difference in the judgment of the color tone, but also the work efficiency is not good.

[0004]

From the standpoint of improving work efficiency, handmade paper is omitted, and the color of the pulp slurry containing the colorant is matched to the standard sample color of the colored paper to be produced from the pulp slurry. Attempts have been made. However, since the paper is dry and the pulp slurry contains water, the color tone of the pulp slurry does not always match the color tone of the paper made using the pulp slurry. This is a difficult task.

[0005] Instead of the above-described judgment based on the experience of a skilled person, a method of objectively judging the color tone by using a colorimeter and a mechanical device has been adopted. In this case, a pulp slurry sample is frequently used. Since it is necessary to collect and measure the color and compare it with the color of the paper, it still requires human labor, and the colorimetric value is easily affected by the smoothness of paper, gloss, transparency of pulp, etc. The colorimetric error was large, and there was a problem in practical use.

[0006]

According to the present invention, there is provided a method for performing a colorimetric operation conventionally relying on the eyes of a skilled person with a machine and further performing the colorimetric operation online with the following means. Improves the accuracy of colorimetry,
It aims to streamline work. An outline of the present invention will be described with reference to the drawings. FIG. 1 is an arrangement diagram of a colorimetric device when performing online, and FIG. 2 is an explanatory diagram of a colorimetric method of the present invention. The raw material pulp is added with chemicals such as a dye and a sizing agent in a mixing box, subsequently stirred by a mixing chest, uniformly mixed, and transferred to a machine chest by a pump. Then, the paper is sent from the machine chest to the screen process of the paper machine and to the paper machine, where it is made into paper.
The pulp slurry blended in the mixing chest is diluted, if necessary, to a pulp concentration suitable for papermaking before papermaking.

In the present invention, a sample of a blended pulp slurry (hereinafter referred to as a pulp slurry in order to distinguish the blended pulp flowing after the mixing chest from the raw pulp before blending) is collected from a process before the paper machine. Measure the color. That is, in the case of FIG. 1, the slurry circulation pipe is branched from the pulp slurry pipe sent from the mixing chest to the machine chest, and further, as shown in FIG. The purpose is to continuously measure the color of the pulp slurry flowing in the branch pipe 2. When performing color measurement offline instead of online, the collected sample is placed in a container such as a sample bucket and circulated using a branching pipe for measurement to stabilize the flow of the sample before color measurement.

In FIG. 2, A is a colorimeter, G in a circle is a colorimeter, and the pulp slurry flows in the tube from bottom to top. The colorimetric portion G is a portion made of a transparent material such as glass so that the color of the pulp slurry can be measured. Colorimeter A
Includes a lighting device such as a xenon lamp that illuminates the colorimetric section G, irradiates the pulp slurry with illumination light, transmits a transparent material such as glass, receives the reflected light, and measures the color of the pulp slurry. The reason for flowing the pulp slurry upward from the bottom is to prevent talc, kaolin, and other inorganic pigments mixed in the pulp slurry from becoming stagnant in order to increase the opacity of the paper.

As the colorimeter A, for example, a tristimulus value direct-reading type colorimeter can be used. The tristimulus value direct reading type colorimeter has three primary colors X, Y, Z (red,
(Green, blue) The three sensors with the sensation corresponding to the light are used to measure the reflected light of the light illuminating the object to be measured, and the value is calculated by a microcomputer to calculate the color of the Munsell color system. It is a colorimeter that displays in system colors. In addition to the tristimulus value direct reading type colorimeter, a colorimeter such as a widely used spectral colorimeter can be used in the present invention. Reference numeral 3 denotes a flow control valve for controlling the flow rate of the pulp slurry flowing in the colorimetric branch pipe 2 to a predetermined speed while observing the flow meter. The anemometer and the flow control valve 3 are both provided upstream of the colorimeter to prevent damage to the transparent part of the colorimeter due to excessive pressure.

As a result of conducting various experiments using the above-described apparatus, it was found that the colorimetric value between the paper and the pulp slurry was
To correlate with a correlation coefficient of 95% or more, pulp concentration,
The flow rate has proven to be very important. The pulp concentration (the weight ratio of the pulp slurry weight to the dry pulp in the pulp slurry) is usually 0.1% when paper is made with a paper machine.
It is 5 to 1.2%, but in color measurement, 3 to 5%, which is higher than when paper is made, is suitable. A colorimeter irradiates a colorimetric object with light and measures the color by analyzing the reflected light. Therefore, when the pulp concentration is 3% or less, the reflectance of the illuminated light is low, and the color of the paper is different. Correlation decreases.

On the other hand, if it is 5% or more, the flow of the pulp slurry is not good, and when the pulp slurry is sent from the mixing chest to the machine chest, an obstacle such as clogging in a pipe occurs. Immediately before the paper machine, when diluting to a pulp concentration of 0.5 to 1.2% suitable for papermaking, the pulp slurry having a too high pulp concentration takes time and effort to dilute. Therefore, the colorimetric pulp concentration is suitably in the range of 3 to 5%, and a pulp concentration of 3 to 4% is particularly suitable in terms of colorimetry, pumping, and dilution. Therefore, in FIG. 1, in the mixing chest, it is desirable to adjust the pulp concentration to 3 to 4%, and to add water before the machine chest to thin the pulp slurry.

When measuring the color of a pulp slurry, the flow rate of the pulp slurry is also important. In the present invention, a pulp slurry having a pulp concentration of 3 to 5% is used, the pulp slurry is measured at various flow rates, and the correlation with the color of the standard sample paper is confirmed. It has been found that the correlation is best when the flow rate of the slurry is 0.8 m / sec to 4 m / sec. When the flow velocity is lower than 0.8 m / sec, it is also found that the flow of the pulp slurry in the colorimetric section becomes stagnant, the colorimetric value varies widely, and the correlation with the paper color becomes unstable. did. It has also been found that if stagnation occurs, the transparent portion of the colorimetric portion G is contaminated and a disadvantage arises that the transparent portion must be frequently cleaned.

When the flow rate of the pulp slurry is 4 m / sec or more, the stagnation disappears, but a laminar flow is generated, and the flow rate is partially different, as in the case of the flow rate of 0.8 m / sec or less. Variations increase and the correlation with paper color decreases. Fluctuations in flow velocity also cause variations in colorimetric values,
The colorimetric value fluctuates greatly even with a flow velocity fluctuation of 0.1 m / sec.
It was also found that in order to obtain a correlation of 95% or more under the above flow rate conditions, it is necessary to always control the flow rate within a fluctuation range of ± 0.1 m / sec during color measurement.

Therefore, according to the present invention, as shown in FIG. 2, a flow meter and a flow control valve 3 are provided upstream of the colorimeter, and the flow rate of the pulp slurry in the colorimeter is monitored by the flowmeter.
The flow rate was controlled so that a predetermined flow rate could be controlled. Of course, the flow meter and the flow control valve 3 are electrically linked, and when the flow rate detected by the flow meter slightly increases or decreases below a predetermined flow rate, the flow control valve 3 is automatically opened or throttled to return to the appropriate flow rate. An automatic flow control device may be provided. Fluctuations in the flow velocity directly affect the magnitude of the correlation coefficient. When the colorimetric accuracy of the prior art visually observed by an expert is replaced with the correlation coefficient obtained by the measuring method of the present invention, 0.9 is obtained.
Because of the above correlation coefficient, when it is desired to obtain colorimetric data with higher accuracy than in the prior art, it is necessary to control the flow velocity within a flow velocity fluctuation range within ± 0.1 m / sec.

Next, an example of a method of measuring the color of the pulp slurry using the above colorimeter and performing color matching with the color of the standard sample paper will be described. First, the pulp slurry used for the production of the paper having the standard color sample color is passed through the colorimetric section of the colorimetric branch pipe of the actual machine shown in FIG. 2 at a flow rate of 0.8 to 4 m / sec, and the color is measured. At the same time, the color of the standard sample paper made with the pulp slurry is measured, and the colorimetric data of both are obtained. In addition to the colorimetric data, the details of the pulp slurry, such as the mixing ratio of pulp, dye, and other chemicals, are registered in the brand-specific mixing instructions. A colorimeter different from the colorimeter used for colorimetry of the pulp slurry may be used for colorimetry of the standard sample color paper, but it is desirable to use the same colorimeter as much as possible.

When producing the above registered standard sample color paper, the raw material pulp, the dye and other chemicals are blended based on the brand-specific blending instructions, and the colorimetry of the colorimetric branch pipe 2 of the actual machine is performed. The pulp slurry is passed through the section G, and the color of the pulp slurry is measured. Then, the pulp slurry is passed through the slurry circulation pipe until the difference between the colorimetric data of the pulp slurry and the colorimetric data of the standard sample pulp slurry is within an allowable limit, for example, a correlation coefficient of 0.95 or more. While circulating, an additional dye or pulp is added to the mixing chest to adjust the color. When the difference falls within a predetermined limit. The pulp slurry is sent to a machine chest for papermaking. Sampling a piece of paper from the paper made and measuring the color, comparing it with the color measurement data of the standard sample, and if there is a difference, change the mixing ratio of the dye etc. in the next mixing lot to eliminate the difference I do.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Since the pulp slurry and the standard sample paper have different forms, it is difficult to set light reflectance and the like to the same irradiation conditions, and therefore, the colorimetric data usually do not match. However, if there is a correlation between the two, the color of the colored paper can be managed by managing the colorimetric values of the pulp slurry. In the case of the present invention, as described above,
If the pulp concentration is 3 to 5%, the flow rate of the pulp slurry in the colorimetry section is 0.8 to 4 m / sec, and the allowable fluctuation range is 0.1 m / sec, stagnation of the pulp slurry and laminar flow which may cause measurement errors will occur. The occurrence can be prevented, and the two colorimetric data are well correlated. Therefore, comparing the colorimetric data of the pulp slurry with the colorimetric data of the standard sample color, a paper having a color tone corresponding to the predetermined sample color can be obtained depending on whether the correlation coefficient of the colorimetric values is larger or smaller than a predetermined value. You can judge whether it can be manufactured. In addition,
As shown in FIG. 2, if the cross-sectional area of the branch pipe of the colorimetric part is smaller than that of the front and rear parts, the flow velocity in that part becomes faster,
Since stagnation is unlikely to occur, it is desirable to reduce the cross-sectional area of the colorimetric section as shown in FIG.

Even for the same sample, if the colorimetric conditions are different, the colorimetric value may be different, so it is necessary to frequently calibrate the colorimeter. For calibration, a white surface to which a stable mineral such as barium sulfate is pressed is usually used as a standard white surface, but frequent calibration work is troublesome, so as shown in FIG.
An automatic calibration device that performs automatic calibration can also be used.
However, when the transparent portion of the colorimetric section is contaminated due to long-term use, it cannot be calibrated by the automatic calibrating device. Therefore, it is necessary to periodically flow a cleaning liquid in the glass tube and perform cleaning.

As the material of the colorimeter, besides glass, transparent plastic can be used. However, plastic is easily contaminated and may be damaged depending on the chemical used for cleaning. It is necessary to check in advance whether such a cleaning chemical should be used.

[0020]

Conventionally, the color matching operation of colored paper relies on visual observation by a skilled worker, which is troublesome and has a large difference depending on the skill of the worker. The present invention provides a pulp slurry by branching a colorimetry pipe from a pulp slurry transfer pipe, providing a transparent colorimetry section in the branch pipe, and flowing the pulp slurry at a flow rate within a certain range to measure the color. And the colorimetric values of the standard sample color paper could be correlated.
As a result, online, it is possible to match the color of the colored paper product with the pulp slurry that is the raw material without human intervention.
Moreover, it can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a layout diagram of a colorimeter.

FIG. 2 is an explanatory diagram of a color measurement method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slurry circulation pipe 2 Branch pipe for color measurement 3 Flow control valve A Colorimeter G Colorimeter

Claims (2)

[Claims] 1. A method for measuring the color of a pulp slurry of colored paper, wherein a pulp slurry having a pulp concentration of 3 to 5% is placed in a colorimetric portion in a tube having a colorimetric portion made of a transparent material such as glass.
A pulp slurry color measurement method comprising flowing the transparent material at a flow rate of 0.8 to 4.0 m / sec and passing the transparent material through a colorimeter to measure the color of the pulp slurry. 2. The pulp slurry color measurement method according to claim 1, wherein the pulp slurry is caused to flow at a flow rate within a fluctuation range of ± 0.1 m / sec.