Field of the invention

The invention relates to a method and a system for manufacturing organic pigment. The invention also relates to organic pigment.

Background of the invention

The manufacture of various pigments, including mineral pigments as well as organic pigments, is previously known. This invention relates to the manufacture of organic pigments. In prior art, organic pigments have gradually become favoured over mineral pigments in many uses, because it is thus possible, among other things, to reduce the environmental load. For example in papermaking, the replacement of mineral pigments with organic pigments is reflected in more effective recycling of paper, and it may further enable the utilization of recycled paper in the production process of biofuels. Furthermore, the strength properties of paper, as well as smoothness of the paper surface obtained by calendering are typically improved when mineral pigments are replaced with organic pigments.

In prior art, organic pigments have been primarily made from oil-based materials, starch-based materials as well as pure cellulose by chemical production methods. Organic pigment made in this way is most typically used in a mixture with another material. However, oil-based organic materials are typically relatively expensive, and furthermore, they may involve problems in waste treatment. On the other hand, organic pigments based on starch as well as those made chemically of pure cellulose require a complex and expensive manufacturing process.

For the above-mentioned problems, recent approaches have been to develop a more advantageous raw material and method for manufacturing organic pigment. One such approach is disclosed in WO 2009/080894, presenting a method for mechanical grinding of raw materials of plant origin. Brief summary of the invention

It is an aim of this invention to present a solution to the above-mentioned problem in such a way that it is possible to measure the quality of the organic pigment as well as to control at least one functional parameter of at least one process device, taking into account the measurement result, during the process of manufacturing the organic pigment. For this purpose, a new system and method for manufacturing organic pigment is provided. Furthermore, organic pigment made by the new method is presented.

Feedstock, as well as pulps downstream of various devices, are not necessarily homogeneous. For the manufacture of organic pigment to be economically sufficiently profitable, its quality should be both measurable and controllable already during the manufacture. Therefore, in industry, there is need for measurements of particles in the size class of microns, from which measurements it can be concluded when the parameters of the devices processing the pulp have to be changed.

However, the methods of prior art do not present ways for directing and con- trolling the manufacture of organic pigment of plant origin, and for controlling its quality, in a continuous process. For example, the above-mentioned publication WO 2009/080894 does not mention how the quality control of the process, particularly the adjustment during the manufacture, should be implemented. Instead, following the teachings of WO 2009/080894, a person skilled in the art has to use slow and laborious methods of prior art to control the quality of the organic pigment to be manufactured. For example, scanning electron microscopy (SEM) of a single sample, followed by an analysis of the images with an image processing program in a reliable way to achieve a resolution suitable for the process control, will typically take about one man-day. This speed is naturally not sufficient for adjusting the process on the basis of these measurements. The measuring devices of prior art require manual pre-treatment of the sample before the measurement, and are thus not suitable for continuous measuring (i.e. on-line measurements). Moreover, the measuring devices of prior art are not capable of dividing the particles into different fractions, i.e. size classes. It is also possible to measure small particles by a measuring device based on laser diffraction (for example Coulter) or based on sedimentation (for example SediGraph). However, even these measuring devices are not capable of dividing particles into different fractions. The method of the present invention for manufacturing organic pigment is primarily characterized in that, in the method, raw material is refined into a suitable particle size to form organic pigment. Furthermore, in the method, a measuring device is used for measuring the size and/or particle size distribution and/or shape factor or other corresponding characteristic values of parti- cles smaller than 200 μιη, and at least one functional parameter of at least one process device is adjusted by utilizing said measurement.

According to an advantageous example, said measurement taken by the measuring device is continuous.

According to an advantageous example, the measuring results of the particles measured are presented in such a way that the measured particles are divided into at least three different size classes or fractions, more advantageously into at least four different size classes or fractions.

In an advantageous example, the method also comprises measuring, from the pulp downstream of refining, the size and/or particle size distribution of the particles smaller than 150 μιτι, preferably smaller than 100 μιτι. In an advantageous example, the method comprises measuring, from the fraction accepted in separation, the size and/or particle size distribution of the particles smaller than 100 μιη, preferably smaller than 80 μητι.

The method according to the invention may comprise, for example, at least one pre-treatment step or at least two pre-treatment steps. Furthermore, according to an advantageous example, the method of the invention comprises not more than five pre-treatment steps, not more than four pre-treatment steps, or not more than three pre-treatment steps. In an advantageous example, the method also comprises measuring the size and/or particle size distribution of particles smaller than 200 μιη from the feedstock of at least one pre-treatment device, and/or from the output of at least one pre-treatment device, and adjusting the operation of said pre-treatment device by utilizing said measurement. According to one example, the method comprises measuring the size and/or particle size distribution of particles smaller than 30 pm downstream of at least one separator and/or refiner.

The system according to the present invention for manufacturing organic pigment from raw material of plant origin is characterized in that the system comprises at least one process device for reducing the raw material into a suitable particle size, for forming organic pigment. Furthermore, the system comprises a measuring device arranged to measure the size and/or particle size distribution of particles smaller than 200 μητι, as well as adjusting means for adjusting at least one functional parameter of at least one device by utilizing the measurement performed by said measuring device.

According to an example, said measuring device is batch operated. Thus, a sample is typically taken to a laboratory for measuring. Even in this case, the measurements can be taken relatively quickly, because with the new measuring device, the measurement itself typically takes only a few minutes.

Preferably, said measuring device is a continuous measuring device. According to an advantageous example, the system comprises means for presenting the measured particles in such a way that the particles are divided into at least three different size classes or fractions, more advantageously into at least four different size classes or fractions. According to an advantageous example, said measuring device is arranged to measure at least either the size and/or particle size distribution of particles smaller than 150 pm, preferably smaller than 100 pm, from the pulp downstream of refining, or the size and/or particle size distribution of particles smaller than 100 pm, preferably smaller than 80 pm, from the accepted fraction of separation. The organic pigment according to the invention comprises organic pigment manufactured by the method according to the invention or by the system according to the invention. By the solution of the invention, it is possible to manufacture organic pigment that is substantially homogeneous in an advantageous way.

Description of the drawings

In the following, the invention will be described in more detail with reference to the appended drawings, in which shows the system for manufacturing organic pigment according to an advantageous embodiment of the invention in a reduced schematic chart,

Fig. 2 shows the system for manufacturing organic pigment according to another advantageous embodiment of the invention in a reduced schematic chart,

Fig. 3 shows the system for manufacturing organic pigment according to a third advantageous embodiment of the invention in a reduced schematic chart, Figs. 4a to 4d show some images on test runs for manufacturing organic pigment, in which the particles shown are divided into four different size classes, and

Fig. 5 shows a measured particle size distribution.

Detailed description of the invention

In the figures presented in this application, the following reference numerals are used:

1 organic pigment, 2 raw material(s) for organic pigment,

3 pre-treatment device,

3a first pre-treatment device,

3b second pre-treatment device,

4 refiner,

4a first refiner,

4b second refiner,

5 separator,

5a first separator,

5b second separator,

M measuring device,

M1 the first measuring point of the measuring device M,

M2 the second measuring point of the measuring device M

M3 the third measuring point of the measuring device M,

M4 the fourth measuring point of the measuring device M,

M5 the fifth measuring point of the measuring device M,

M6 the sixth measuring point of the measuring device M,

R rejected fraction,

R1 ,R2 rejected fractions from different separators,

A accepted fraction, and

A1 , A2 accepted fractions from different separators.

In this application, the term "organic pigment" is used. In this application, organic pigment 1 refers to pigments of plant origin, that is, pigments made from a material of plant origin. The organic pigment may comprise one or more different raw materials of plant origin. The organic pigment consists of a material or substance that has an effect on the optical properties of surfaces, and it may be translucent or opaque. The organic pigment may also be called biopigment.

In an advantageous embodiment, the raw material of plant origin is a fibre- based material. Such a fibre-based material is advantageously selected from meadowgrasses, grasses, cereal crops, vegetable matter, various water or sewage sludges, sludge pulps, industrial fibre-based waste flows, and starch- based materials. In an advantageous embodiment, the raw material of plant origin is a wood- based material. Such a wood-based material is advantageously selected from wood pieces, wood dust, sawdust, wood chips, moist wood, waste wood, fibre pulp, wood pulp, chemical pulp, mechanical pulp, or the like. The wood-based material may be softwood and/or hardwood, and it may contain mixtures of different wood species. If the raw materials of organic pigment comprise primarily wood-based material, the organic pigment can also be called wood pigment. In the process of manufacturing organic pigment 1 according to the invention, at least one refiner 4 is used for refining organic raw material of plant origin. In this application, the term "refining" refers to reducing material, for example mechanically, and it may be, for example, grinding, refining, pulverizing, comminuting, crushing, or corresponding action in which the particle size of the material is reduced. The operation of the refining devices, such as mills, is typically based on the application of pressure, cutting, abrasion, compression, and/or an effect of collision produced by blowing, or a corresponding principle of operation. It is also possible to apply special techniques, which include cleaving of particles by acoustic waves, and methods based on pres- sure or explosion to reduce particles. Most of the refining devices operate by a combination of several operating principles. The refining can be performed by utilizing, for example, a high pressure, a raised temperature, or a cooled temperature (lower than 0°C). The refining can be performed at a high consistency or at a low consistency, or at any consistency in between.

In an example, for refining raw material of plant origin, a refiner is preferably used, which is selected from an impact mill, an air jet mill, a sand grinder, a bead mill, a ball mill, a vibrating mill, a screw mill, and combinations of these. The refining can be performed in one or more refining steps by one or more refining methods.

The raw material 2 can be treated by one or more of the following methods of pre-treatment: cooling, freezing, drying, chemical treatment, heating, bio- technical treatment (for example, enzymatic treatment), or ultrasonic treat- ment, or any other known method of pre-treatment. The pre-treatment can be made, among other things, before the mechanical refining and/or between the refining steps and/or after the mechanical refining. The pre-treatment step may also be, for example, a pre-refining step or another mechanical and/or chemical pre-treatment that is performed by the pre-treatment device 3. According to an advantageous example, the moisture level of raw material 2 is adjusted in a pre-treatment step to affect the particle size of the organic pigment 1 to be formed.

According to an advantageous example, the raw material 2 of organic pigment is refined in at least one, at least two or at least three steps. Thus, pref- erably in each refining step, said raw material 2 is refined to a predetermined particle size. The refining result can be monitored and the refiner 4 can be adjusted by measurements downstream of each refiner 4. Advantageously, measurements by a measuring device M upstream of the refiner 4 to be adjusted are also utilized. By means of measurements upstream and down- stream of the refiner, it is also possible to secure that the refiner 4 is in good working order and to predict a possible need for maintenance.

In the refining, it is possible to make use of a grinding aid that is harder than the starting material, for example a mineral compound, grinding balls, or a corresponding material. The grinding aid can be used for refining with one or more refiners 4. The quantity and/or grindability of the grinding aid used, and/or the need for changing the grinding aid can be determined by measurements taken by the measuring device M. In an advantageous embodiment, the raw materials 2 of organic pigment are separated by at least one separator 5 downstream of at least one refiner 4. In an advantageous example, the system comprises at least two separators 5. Thus, one or more separators 5 can be placed, for example, downstream of one or more refiners 4 or one or more pre-treatment devices 3.

The invention is based on an idea, in which a new particle measuring device M is used for measuring particles in different process steps and for adjusting at least one functional parameter of at least one process device 3, 4, 5 by utilizing the measurement results. The adjustment can be made by adjusting means of prior art which are known for a person skilled in the art. In an advantageous example, the average particle size of the raw material 2 as well as the median particle size are adjusted for pulp treated with at least one process device to a predetermined range according to said process device by means of measurements taken by the measuring device M. For this purpose, it is possible to use, for example, particle size distributions (i.e. fraction distributions), that is, the way in which the material is shared out in each particle size class, or, for example, measured particle sizes.

Control measures can be taken, for example, if the particle size distribution does not meet the desired distribution, that is, the sample contains too much or too little of too large particles or too small particles, or if the sample contains too large or too wide particles. As the new measuring device can present the particle results directly as a ratio between different size class distributions, it is easier than before to define and implement the control meas- ures.

Document Laitinen, O., Loytynoja, L, Niinimaki, J., Tube flow fractionator - A simple method for laboratory fractionation, Paperi ja Puu - Paper and Timber, Vol. 88 / No. 6 / 2006 discloses a measuring device for measuring, among other things, the particle size and the particle size distribution in such a way that the measured particles can be divided into different fractions or size classes. However, the device of the document is not suitable, as such, for the needs of manufacturing organic pigment. However, the measuring device disclosed in said document Laitinen, O., Loytynoja, L., Niinimaki, J., Tube flow fractionator - A simple method for laboratory fractionation, Paperi ja Puu - Paper and Timber, Vol. 88 / No. 6 / 2006 can be modified according to the present invention in such a way that it can be used for measuring particularly small particles, wherein it can be utilized in the process of manufacturing organic pigment. Advantageously, the new measuring device com- prises a camera that is sufficiently accurate with respect to the size of the particles to be measured, so that the measuring device can also measure particularly small particles in the size class of microns.

The new particle measuring device modified according to this new solution can be utilized in the adjustment of the process of manufacturing organic pigment. According to a particularly advantageous example, the new meas- uring device is used as a continuous measuring device. Said new measuring device is also well suited for continuous measuring, because its use typically does not require any other pre-treatment of the sample than dilution substantially to a given consistency, which sample consistency control can be auto- mated according to prior art.

Said new particle measuring device M can be preferably used for analyzing particles smaller than 200 pm. In an advantageous example, the measuring device M is used for measuring particles having a size of at least 1.8 pm. In an advantageous example, the measuring device is used for measuring particles of about one micrometer or an even smaller size. Particle size analyses can be made on the basis of image analysis and/or signals mentioned in said document. Preferably, at least image analysis is used for the particle size determinations. In an advantageous example, image analysis is used for analyzing at least 2000 particles per fraction, to obtain a sufficiently reliable result. By the measurements, it can be detected if the particles are refined to a greater or smaller extent that would be necessary.

Advantageously, the new measuring device M, which is surprisingly suitable for measuring even small particles, measures the particle size distribution of each sample as well as the quantity of particles of different sizes in each selected size class fraction. In an advantageous example, the measuring device divides the measured particles to at least three size class distributions or fractions, more advantageously to at least four size class distributions or fractions. Thus, according to an advantageous example, the particles included in each fraction can be analyzed separately.

The measurements taken by the measuring device M can be utilized in the adjustment of the devices 3, 4, 5. According to an advantageous example, such measurements by the measuring device M, in which the particles are divided into different size classes, are utilized in addition to or instead of the particle size measurements, for the adjustment of at least one process device 3, 4, 5. An advantage of the new measuring device M is the fact that the particle size distribution can be obtained, for example, according to the number of parti- cles or, for example, as a distribution of the surface area of the particles. These values reflect well the particle fraction of this size class. Furthermore, it has previously been very laborious to calculate characteristic values, such as the form factor, the length/width ratio, the specific perimeter, or the like, for particles smaller than 200 pm, for example for particles of smaller than 100 pm, with sufficient repeatability.

Figures 1 to 3 show some examples of the systems according to the invention in reduced schematic charts. The figures show various possible interme- diate steps for manufacturing organic pigment 1 according to the invention. The system according to the invention comprises at least one refiner 4, 4a, 4b, and at least one measuring device M. Preferably, the system also comprises at least one separator 5, 5a, 5b. Furthermore, the systems may comprise at least one pre-treatment device 3, 3a, 3b, or at least two pre-treat- ment devices 3, 3a, 3b. Naturally, the system may also comprise more pre- treatment devices, refiners and separators than those shown in the reduced schematic charts. The refiners 4a, 4b can be arranged both one after the other, without a separator 5a, 5b between the refiners 4a, 4b, and in such a way that a separator 5a, 5b is provided between at least some of the refiners 4a, 4b.

In an advantageous example, the system for manufacturing organic pigment according to the invention comprises at least one pre-treatment device 3. In an example, at least the particle size and/or the particle size distribution is measured by a measuring device M from the raw material 2 supplied to the pre-treatment device 3. On the basis of this measurement, it is possible to adjust, for example, the quality of the raw materials to be supplied to the pre- treatment, and/or at least one functional parameter of the pre-treatment device 3, 3a, 3b. These parameters are device-specific and known to per- sons skilled in the art. In an example, the particle size and/or the particle size distribution is measured by the measuring device M from the raw material 2 downstream of the pre-treatment device 3. This measurement by the measuring device M can be used alone or together with, for example, a measurement upstream of the pre-treatment device 3, to adjust at least one functional parameter of the pre-treatment device 3. Alternatively or in addition, said measurement can be used, for example, to determine the proportion of raw material 2 to be recirculated to the pre-treatment device 3 (not shown in Figs. 1 to 4). Control measures on the pre-treatment device are taken preferably when the particle size and/or the particle size distribution does not meet the requirement. It is also possible that the particles output from the pre-treat- ment device or the pre-refining device are so large that it is not worthwhile to measure them with said measuring device M modified for small particles.

In an advantageous example, the pre-treated raw material 2 is led from the pre-treatment to a separator 5 (not shown in Figs. 1 to 4) or a refiner 4 (shown in Figs. 1 to 3) following the pre-treatment device 3.

The raw material 2 is led to the first refiner 4, 4a either without or after the pre-treatment in the pre-treatment device 3. In an advantageous embodiment, the particle size and/or the particle size distribution is measured by the measuring device M downstream of the first refiner 4, 4a. This measurement taken by the measuring device M can be utilized either alone or together with, for example, a measurement upstream of the refiner 4, 4a, to adjust at least one functional parameter of said refiner 4, 4a in such a way that the refined pulp would be as homogeneous as possible. The functional parame- ters of the refiner may include, for example, the rotational speed of the refiner, the feeding speed, the refining time, the blade gap, the refining consistency, the pressure, etc. The functional parameters depend on the refiner type and are known to persons skilled in the art. For example, if the refiner is an air jet mill, possible control parameters include, among other things, the rotational speed of the separator of the air jet mill, the pressure of supply air, and the feeding speed. For example for a bead mill, possible control parameters include, among other things, the size of the refiner balls, the degree of filling of the refiner (the quantity of balls in the refiner), the consistency of the pulp, and the rotational speed of the refiner. For example for a TMP type refiner, possible control parameters include, among other things, the blade gap of the refiner, pulp throughput in a given time, and the dry matter content of the pulp.

By means of measurements taken from the feedstock of the refiner 4, 4a, 4b, it is possible to adjust, for example, at least one functional parameter of the refiner and/or at least one process step upstream of the refiner in such a way that the material to be fed into the refiner would be as homogeneous as possible. If there is more than one refiner, one or more other refiners can be adjusted accordingly, always upstream of said refiner, on the basis of measurements taken upstream and/or downstream of the refiner in question. Con- trol measures on the refiner 4 are taken preferably when the particle size and/or the particle size distribution does not meet the requirement. It is also possible that the particles entering the refiner 4, 4a are so large that it is not worthwhile to measure them with said measuring device M modified for small particles.

In an advantageous example, the refining step by one or more refiners 4, 4a, 4b is followed by separation of the raw material 2, preferably with at least one separator 5, 5a, 5b. The separation by the separator 5, 5a, 5b can be implemented after either all or only some of the refining steps by the refiners 4, 4a, 4b. In an advantageous example, the raw material is separated by at least one separator 5, 5a, 5b after the refining step in the last refiner 4, 4b.

In an advantageous embodiment, the particle size and/or the particle size distribution is measured by the measuring device M from the accepted frac- tion A, A1 , A2 of one or more separators 5, 5a, 5b. On the basis of this measurement from the accepted fraction A, A1 , A2 by the measuring device M, it is possible to adjust at least one functional parameter of the separator 5. The functional parameters of the separators are device-specific and known to persons skilled in the art. In the adjustment of said separator, it is possible to take into account the measurement taken by the measuring device M, and/or the measurement results taken by a measuring device upstream of said separator. In the adjustment of the separator 5, 5a, 5b, it is also possible to take into account, for example, measurements taken from the rejected fraction R, R1 , R2 of said separator. Control measures on the separator are taken preferably when the measured particle size and/or the particle size distribution does not meet the requirement.

Figure 1 shows a system, in which raw material 2 is fed through a pre-treat- ment device 3 to a refiner 4. Downstream of the refiner 4, the particles down- stream of said refiner are preferably measured at a first measuring point M1 , and at least one functional parameter of at least one process device (pre- treatment device, refiner, separator) is adjusted on the basis of this measurement. After the refining by the refiner 4, the refined raw material is led to a separator 5. Downstream of the separator, the accepted fraction of said separator is preferably measured at a second measuring point M2, and at least one functional parameter of the separator 5 is adjusted on the basis of said measurement. It is also possible to measure the rejected fraction of the separator at a measuring point M5, which measurement can be utilized, for example, in adjusting said separator or securing the condition of said separator.

Figure 2 shows a system, in which raw material 2 is fed through a pre-treat- ment device 3 to a first refiner 4a. After this, the particles downstream of the refiner are measured from the raw material refined in the first refiner 4a at a first measuring point M1 , and the operation of at least one process device 3, 4a, 5a is adjusted on the basis of said measurement.

Downstream of the first refiner 4a, the refined raw material is led to a first separator 5a. Downstream of the first separator 5a, the accepted fraction of the first separator 5a is preferably measured at a second measuring point M2, and at least one functional parameter of at least one process device 5a, 4b is adjusted on the basis of this measurement. Downstream of the first separator 5a, the accepted fraction A1 is led to a second refiner 4b. The rejected fraction R1 of the first separator can be led, for example, back to the first refiner 4a.

From the raw material refined in the second refiner 4a, the particles downstream of the second refiner 4b are measured preferably at a third measuring point M3, and the operation of at least one process device 4b, 5b is adjusted on the basis of said measurement. Downstream of the second refiner 4b, the refined raw material is led to a second separator 5b.

Downstream of the second separator 5b, the accepted fraction of the second separator is preferably measured at a fourth measuring point M4, and at least one functional parameter of at least one process device 5b is adjusted on the basis of said measurement. It is also possible to measure the rejected fraction R1 , R2 from the first separator 5a or the second separator 5b at a measuring point M5, M6 in the reject line, which measurement can be utilized, for example, for adjusting said separator or for securing the working order of said separator.

Figure 3 shows a system, in which raw material 2 is fed through a first pre- treatment device 3a to a first refiner 4a. After this, the particles downstream of the first refiner 4a are measured from the raw material refined in the first refiner 4a at a first measuring point M1 , and the operation of at least one process device 3a, 4a, 5a is adjusted on the basis of said measurement. Downstream of the refiner 4a, the refined raw material is led to a first separator 5a.

Downstream of the first separator 5a, the accepted fraction of the first sepa- rator 5a is preferably measured at a second measuring point M2, and at least one functional parameter of at least one process device 5a, 3b is adjusted on the basis of this measurement. The accepted fraction A1 of the first separator 5a is led to a second pre-treatment device 3b. The rejected fraction R1 of the first separator can be led, for example, back to the first refiner 4a. After the pre-treatment in the second pre-treatment device 3b, the pulp is led to a second refiner 4b.

From the raw material refined in the second refiner 4b, the particles downstream of the second refiner 4b are preferably measured at a third measuring point M3, and the operation of at least one process device 3b, 4b, 5b is adjusted on the basis of said measurement. Downstream of the second refiner 4b, the refined raw material is led to a second separator 5b.

Downstream of the second separator 5b, the accepted fraction of the second separator 5b is preferably measured at a fourth measuring point M4, and at least one functional parameter of at least one process device 5b is adjusted on the basis of this measurement.

It is also possible to measure the rejected fraction R1 , R2 from the first sepa- rator 5a or the second separator 5b at the measuring point M5, M6, which measurement can be utilized, for example, for adjusting said separator or securing the working order of said separator.

In an example, the method according to the invention comprises one or more of the following steps and/or partial steps:

1. Control actions relating to the pre-treatment:

- Feeding raw material 1 for organic pigment 1 to the pre-treatment device 3, 3a, 3b.

- Using the measuring device M to measure the particle size and/or the particle size distribution of the fed raw materials 2 upstream of the pre- treatment device 3, 3a, 3b.

- Pre-treating the raw material 2 chemically and/or mechanically in at least one pre-treatment device 3, 3a, 3b.

- Using the measuring device M to measure the particle size and/or the particle size distribution of the raw material 2 treated in at least one pre-treatment device 3, 3a, 3b.

- Adjusting at least one functional parameter of the pre-treatment device 3, 3a, 3b by utilizing the measurement taken from the fed raw material 2 and/or by utilizing the measurement taken after the treatment in the pre-treatment device.

- Securing the working order of the pre-treatment device 3, 3a, 3b on the basis of both of said measurements.

- Adjusting the quantity of material to be recirculated to the pre-treat- ment device 3, 3a, 3b by utilizing the measurement taken by said measuring device.

2. Control actions relating to the refining:

- Leading raw material 2 to be refined in the refiner 4, 4a, 4b. Prefera- bly, the average size of particles entering the refining is not greater than 200 pm, more advantageously not greater than 150 pm, for example 80 to 150 pm.

- Measuring the particle size and/or particle size distribution of the raw material fed to refining.

- Refining the raw material 2 into smaller particles in the refiner 4, 4a, 4b. - Using the measuring device M downstream of the refiner 4, 4a, 4b to measure the particle size and/or the particle size distribution of the raw material after the refining.

- Adjusting at least one functional parameter of the refiner 4, 4a, 4b by utilizing a measurement taken upstream of the refiner 4, 4a, 4b and/or by utilizing a measurement taken downstream of the refiner 4, 4a, 4b.

- Adjusting the quantity of material to be recirculated to the refining 4, 4a, 4b by utilizing a measurement taken by a measuring device M after the refining.

- Securing the working order of the refiner 4, 4a, 4b on the basis of measurements upstream and downstream of the refiner.

3. Control actions relating to the separation:

- Leading raw material 2 to the separator 5, 5a, 5b for separation.

- Measuring the raw material to be fed to the separator 5, 5a, 5b, that is, the particle size and/or the particle size distribution of the raw material.

- Separating the raw materials fed to the separator in such a way that at least part of the fraction belongs to the accepted fraction A, A1 , A2.

- Measuring said accepted fraction of the separator 5, 5a, 5b.

- Measuring the rejected fraction R, R1 , R2 of the separator 5.

- Adjusting at least one functional parameter of the separator 5, 5a, 5b by utilizing a measurement taken by a measuring device upstream of said separator, and/or by utilizing a measurement taken by a measuring device downstream of said separator, preferably by utilizing a measurement taken from the accepted fraction by a measuring device.

If the system comprises several similar process devices, for example several separators 5, 5a, 5b and/or refiners 4, 4a, 4b and/or pre-treatment devices 3, 3a, 3b, corresponding control actions can be taken for one or more other process devices.

The aim is typically to provide a suitable particle size distribution, which does not include any too large particle. In an advantageous example for manufacturing organic pigment 1 , the average particle size and the median of the raw material in the finished organic pigment 1 are not greater than 40 μιτι, more advantageously not greater than 30 pm. In an advantageous example, the target size (average and median of particles) in the organic pigment 1 downstream of the last separator and/or in the finished organic pigment is not greater than 20 μηη, or even not greater than 10 μΜ, but preferably at least 5 μιτι, for example 7 to 10 pm.

In an example, at least one measuring device M5, M6 is used for measuring the rejected fraction R, R1 , R2 of the separator 5, 5a, 5b. It is thus possible to make sure that an unnecessarily great part of the material is not led into the rejected fraction.

The method according to the invention comprises a particle size measurement and/or a particle size distribution measurement downstream of at least one refiner 4 and/or downstream of at least one separator 5. Preferably, particle measurements are taken upstream and/or downstream of a refiner as well as upstream and/or downstream of a separator. Furthermore, the particle size is advantageously measured in connection with at least one pre- treatment device, upstream and/or downstream of said pre-treatment device.

The measuring device M is arranged to measure the size and/or size distri- bution of particles smaller than 200 pm, preferably smaller than 150 μητι. In an advantageous embodiment, at least one measuring device M is arranged to measure the size and/or size distribution of particles smaller than 100 pm, preferably smaller than 80 pm. In an advantageous embodiment, at least one measuring device M is arranged to measure the size and/or size distribution of particles smaller than 50 pm, preferably smaller than 30 pm. In an advantageous embodiment, at least one measuring device M is arranged to measure the size and/or size distribution of particles smaller than 25 pm, preferably smaller than 20 pm or smaller than 15 pm. The particle size measurements and particularly the particle size distribution measurements can be taken efficiently by means of the new measuring device M also in a batch-operated way, for example in a laboratory. In a significantly more efficient way, the adjustment can be implemented by applying a so-called on-line measuring device, that is, a continuous measuring device according to the invention for process control and/or for quick quality assurance. The organic pigment can be subjected to further treatment after the refining and separation, for example by bleaching and/or treating the surfaces of the organic pigment, for example, by coating or dispersion.

The organic pigment made by the method according to the invention can be used as such or in a mixture with other substances for various products. The organic pigment according to the invention may be suitable for use, for example, in cosmetics industry, toothpastes, paint industry, hygienic prod- ucts, plastics industry, coatings industry, composites industry, plates industry, papermaking, or corresponding applications. In papermaking, the organic pigment can be used, for example, as a pigment for the surface treatment or coating of the paper, and/or as filler in paper. In this context, paper refers to any fibre-based products, such as paper, paperboard, cardboard, or fibre composite.

The invention can be applied, among other things, according to the following examples. Example 1

Organic pigment is formed from debarked spruce material which is pre- treated into spruce sawdust. The pre-treated sawdust is separated in such a way that the particle size of the supplied material is initially not greater than 4 mm. The particles having a size smaller than 4 mm are pre-refined at a consistency of 1 to 3% in a bead mill into a particle size, in which the median particle size (vol.-%) is about 300 pm. After this, the material is led to the actual refining. For the refining, it is possible to apply, for example, two bead mills one after the other. Downstream of the first refiner, measurements on the particle size and the particle distribution are taken to conclude, how large a share of the material is to be recirculated to the first refiner. The rest of the material is led further to the second refiner. On the basis of the measurements downstream of the first refiner, it is also possible to make sure that the material to be supplied remains substantially homogeneous. Downstream of the second refiner, measurements are taken on the particle size and the particle size distribution of the material. With these measurements it is secured that the material downstream of the second refiner is in the target size. The final particle size of the product after both refining steps may be, for example, about 15 pm (median).

Example 2 Organic pigment is formed of debarked birch material which has been pre- treated to form so-called birch splinters. The birch splinters are subjected to further treatment in, for example, an impact mill into a particle size of about 1 to 4 mm. After this, the material is dried. The pre-treated material is refined in, for example, a Hosokawa-Alpinen air jet mill into a particle size of about 7 μιη (average). Thus, no reject at all is typically formed in the manufacture of the material. After the refining, the particle size of the material is measured to secure the quality of the material formed and to determine the changes needed in the parameters of the refiner.

Example 3

As shown in Fig. 1 , organic pigment is made of debarked spruce material which has been pre-treated into spruce sawdust.

The sawdust is refined in two separate mills, the first refining being a pre- treatment step and the second refining the actual refining step. The pre- refining can be performed, for example, with an impact mill and the actual refining with an air jet mill.

Both the impact mill and the air jet mill comprise an internal separator, so that typically no reject is formed. The particle size is adjusted by changing the refining parameters, such as the feeding rate of the feedstock, the rotational speed of the impact mill, the rotational speed of the separator inside the impact mill, the pressure of supply air in the air jet mill, and/or the rotational speed of the separator inside the air jet mill. The average particle size after the pre-refining is suitably about 700 pm and after the actual refining 10 to 20 pm. In a test run, the particle size after the second refining was 15.2 pm. Figures 4a to 4d show some examples of organic pigment made according to Example 3. In Figs. 4a to 4d, the particles are divided into four different size classes so that one image of each particle size class is shown. Figure 4a shows an image of the size class containing the largest particles, and Fig. 4d shows an image of the size class containing the smallest particles. In a cor- responding manner, Fig. 4b and Fig. 4c show the size classes containing the second largest particles and the second smallest particles, respectively. From Figs. 4a to 4d, it is also possible to perceive the share of each particle size class in relation to the whole sample. The signals of the measuring device M can be used for determining the particle size distribution. Figure 5 shows the particle size distribution of a product made by the method according to Example 3.

On the basis of the pictures taken of the different fractions, example images of different fractions being shown in Figs. 4a to 4d, an image processing program can be used to calculate known characteristic values for the analyzed samples. Examples of these are given in tables 1 to 3. A sufficient number of images must be taken for each fraction, to be able to calculate the particle size distribution with a sufficient accuracy.

The process can be controlled, taking into account e.g. at least one or at least two, more advantageously at least three or at least four characteristic values shown in Tables 1 to 3. Instead of or in addition to these, the particle size distribution defined by means of the signals can be used for controlling the process. Table 1. Mass ratio of different frac tions

Table 2. Fibre length

Table 3. Properties of particles

(minimum particle size 4 μιτι)

Surface area (mm ² ) 0.000257

Length (mm) 0.020

Width (mm) 0.012

Sphericity 0.77

Particle size (Mm) 15.20

Sphericity refers to the ratio between the surface area and the maximum diameter of the particle. The sphericity value varies from 0 to 1 , wherein a low value indicates a long particle and a high value indicates a round particle.

The particle size refers to the particle diameter which has been calculated from the projection area so that the particle has been assumed to be spheri- cal in shape.

The organic pigment presented can be formed not only in the ways presented in the examples but also in other suitable ways including the idea of the invention. Thus, the invention is not limited solely to the examples pre- sented in the figures and in the above description.