FI120463B - Method of making paper and paper - Google Patents

Description

Method of making paper and paper

The present invention relates to a process for making paper according to the independent claim below. Kek-5 is also targeted at paper.

In papermaking, a mineral-based filler such as natural finely ground calcium carbonate, precipitated calcium carbonate (PCC), kaolin, and talc is used to improve many of the paper's properties, such as optical and printing properties. The addition of a filler also allows the use of a lower amount of fiber in papermaking. The resulting cost savings are generally significantly higher than the cost of the filler additive.

15

It is therefore a general intention to add as much filler as possible to the fiber suspension used in paper making. However, due to the strength of the paper, no filler such as calcium carbonate can generally be added to the paper by more than about 20-25%.

20

In order to increase the amount of calcium carbonate, it has been proposed to add a calcium-based filler to the fiber suspension in the form of calcium hydroxide and to convert the calcium contained therein into carbon dioxide precipitated by carbon dioxide addition. This causes the calcium carbonate sodium to be precipitated and adhered directly to the fiber surfaces and also to the inside of the fibers and thereby a greater amount of carbonate is added to the paper.

However, one of the weaknesses of these known solutions is that the precipitation reactions require a relatively long time; the precipitation reactions are partially incomplete, the processes used are not continuous, or the equipment used is not easily integrated into the papermaking process.

2

U.S. Patent No. 6,471,825 proposes the precipitation of calcium hydroxide added in a fiber suspension directly to the fibers in the form of calcium carbonate. It is then proposed that the suspension containing the fibers and the calcium hydroxide be first treated in a disk refiner type 5 to disintegrate any fiber bundles prior to the introduction of the carbon dioxide gas into the suspension.

In wafer-type devices, the fiber suspension is subjected to a heavy treatment which has a degrading effect on the fiber material. After feeding carbon dioxide 10, the fiber suspension is stirred in a screw mixer. However, in precipitation reactors equipped with conventional blade or screw stirrers, it is difficult to ensure a rapid and efficient mixing of carbon dioxide and calcium hydroxide, and thus a complete reaction. In addition, it is difficult to obtain the adherence of the 15 precipitated calcium carbonates to the fibers.

United States Patent 5,679,220, in turn, proposes the precipitation of calcium hydroxide added to a fiber suspension in the form of calcium carbonate into the fibers with carbon dioxide gas, the fiber suspension 20 flowing from a long bipartite through a smooth tubular reactor. The calcium hydroxide-containing suspension is fed to the fiber suspension in the first section of the tubular reactor at mid-stages thereof. The carbon dioxide gas is supplied to the fiber suspension both before and after the calcium hydroxide-containing suspension is introduced therein. The carbon dioxide gas 25 is introduced into the reactor through an inlet formed on its wall, in order to cause the gas to be absorbed into a hating suspension inside the tube. The residence time of the fiber suspension in a relatively long mixing reactor over 2 meters is more than 1 minute.

Further, methods for making paper from filler-loaded fibrous material are known, as disclosed in EP-A-969141. It is characterized in that the paper is calendered after forming the web. The pre-treatment of a fiber material, wherein the fibers are provided with calcium carbonate, is not described in detail in the publication.

35 3

It is therefore an object of the present invention to provide an improved process for making paper. Another object of the invention is to provide better paper.

It is an object to provide a method in which the above-mentioned prior art problems are minimized.

The object here is to provide a process in which, firstly, a very good mixing of fibers, a mineral material such as calcium hydroxide 10 or calcium oxide, and a precipitating chemical such as carbon dioxide gas can be assured and the paper is thus prepared from the fibrous material.

It is also an object of this invention to provide a method which enables the deposition of calcium carbonate on or in the fibers to begin and to occur in a very short time and as completely as possible.

It is still the object of the present invention to provide a method for obtaining an increased filler content of paper compared to conventional practice.

It is a further object to provide a method which can, in a desired manner, influence the properties, typically optical and strength properties, of paper, cardboard or the like.

It is also an object to provide a process suitable for use in the precipitation of a mineral material for a wide variety of fiber suspensions and for any other solids present in the fiber suspension.

A further object is the continuous process of manufacturing a product in the form of paper, cardboard or the like web.

To achieve the above purposes, the method and paper of the invention are known from those set forth in the characterizing parts of the independent claims below.

4

The present invention relates to a process for making paper, which generally comprises the steps of: (a) combining a fibrous fibrous material and a reactive mineral such as calcium hydroxide (Ca (OH) 2) as a raw material for the pulp before feeding these materials to a precipitation reactor; (B) contacting the fiber suspension in the precipitating reactor with the reactive mineral dopant material to at least partially precipitate the reactive mineral material in the fiber suspension, wherein at least a portion of the precipitated mineral material so formed is and (b2) feeding the fiber suspension, its liquid and solid phases, into very small particles, droplets and / or droplets in said gas space of the precipitation reactor; (c) withdrawing the fiber suspension so treated from the precipitation reactor; 25, whereupon the pulp of paper formed by the fiber suspension is led to the forming part of the papermaking machine and made into paper by allowing it to drain through a permeable forming pad.

Typically, the precipitating reactor is supplied with a precipitant containing gas as a continuous gas stream to maintain the desired precipitating gas in the reactor. The amount of precipitant in the gas can be varied widely, depending for example on the source, quality of the precipitating gas and / or the desired paper properties. The gas fed to the precipitation reactor 35 generally contains> 5%, typically> 10%, if desired, up to 100% of a precipitating agent such as carbon dioxide. Thus, the gas containing the precipitating agent may be, for example, pure or almost pure carbon dioxide, flue gas or any other suitable carbon dioxide gas or gas mixture. Of course, if desired, any other precipitant suitable for the precipitation of the reactive mineral material used, other than carbon-5 oxide, may be used. The gas is typically introduced into the precipitation reactor such that overpressure will prevail in the precipitation reactor.

In the solution according to the invention, it is desired that the fiber suspension, its liquid and solid phases 10, be fed with their gases into very small particles, droplets and / or particles. The fiber suspension is then disintegrated, by any known or new method per se, into pure liquid droplets; liquid drops containing a solid such as fibers and mineral; solid particles and / or liquid-coated solid particles. The fibrous material of the fiber suspension is then at least partially decomposed into discrete fibers. The liquid phase of the fiber suspension, in turn, is mainly decomposed into liquid droplets of <10 mm, typically <1 mm. Small droplets of liquid, fibers, and other solid particles are dispersed in their gases in an almost foggy manner into a gaseous 20 suspension having a volume flow rate substantially greater than that of the fiber suspension fed to the reactor. This creates a large contact area between the droplets and / or particles of the fiber suspension and the gas surrounding them, allowing extremely rapid and complete precipitation reactions between the dopant reactive mineral and the precipitant in the gas.

In applying the solution of the invention, it can further be assumed that substantially each individual fiber is surrounded by a gas mantle that causes the mineral material to precipitate from the surrounding fluid 30 and into the fiber quickly and efficiently. In the past, on the contrary, attempts have been made to introduce gas as fine bubbles into a more or less viscous fiber suspension, whereby precipitation has not been as rapid and complete.

When applying the solution of the invention, the fibers also form highly active regions of the precipitated material through which the fibers can be assumed to form mutual bonds with each other as the precipitation reactions continue at these points. These bindings improve the strength properties of the paper being manufactured.

According to a preferred embodiment of the invention, there is an activation zone formed in front of the precipitation reactor or preferably at the beginning of the precipitation reactor relative to the flow of the fibrous material. In the activation zone, the fiber suspension is subjected to forces which, for example, tribomechanically or tribochemically activate the fibers to increase the ability of the fibers to bind to one another or to bind the precipitated and / or precipitated mineral. Activation of the fibers has a beneficial effect on the strength properties of the paper being manufactured.

Preferably, the fiber suspension in the activation zone can both be disintegrated into small droplets and / or particles and activated. Preferably, this activation is effected under temporal conditions with fibers swollen, for example due to Ca (OH) 2 addition.

For example, the fiber suspension in the activation zone may be subjected to repetitive successive shocks, counter-shocks, shear forces, turbulent lenses, overpressure and vacuum pulses, or other similar forces which mechanically activate the fibers, particularly their surfaces, for example by fibrilizing or milling the fibers. mineral. On the other hand, fibers, particularly fiber surfaces, can thus also be chemically activated such that active OH groups are formed on the fiber surfaces.

According to a preferred embodiment of the invention, activation can be effected, for example, in a precipitation reactor having a so-called activation zone. a multi-ring impact flow-through mixer 30 having a plurality, typically 3 to 8, most typically 4 to 6, of concentric blades or the like, at least one of which being a rotor and adjacent peripheries of these rings in a static direction or at different speeds running rotors. Rootto thigh speeds can range from 5 to 250 m / s. The speed-35 difference between adjacent frames is 10-500 m / s, typically 50-200 m / s. Mills or mixers operating on this principle have previously been disclosed e.g. in Finnish patents 105669B, 105112B and WO 96/18454.

7

In a percussion flow-through mixer, the fiber suspension is typically passed through the mixer radially outward from the center of its periphery, whereby the wings or the like on the periphery can exert both shocks and counter strokes on the outwardly filamentous fiber activating effect. The impact mill reactor is capable of efficiently treating fiber suspensions of both high solids and very low solids contents for the precipitation process. Thus, the precipitation reactor according to the invention is capable of precipitating a mineral at a variety of solids contents, such as 0.1 to 40%, typically 1 to 15%, most typically 3 to 7%, to dry solids. The limit is mainly determined by the pumpability of the fiber suspension in the 15 inlet and outlet pipes.

The adjacent circuits, rotors, blades or the like of the flow mixer typically run in opposite directions, thereby providing an effective band of successive shocks, i.e., shocks and back shocks, applied to the filament suspension through the reactor. On the other hand, if solid rings, i.e. stators, are arranged between the co-operating circuits, i.e. the rotors, the rotor blade shocks and the counter stator counter-shocks are applied to the filamentous fiber suspension through the reactor. Rotors traveling in the same direction with a large speed difference give similar results.

At the same time, the blades of the flow mixer rotors and stators or the like can direct the fiber suspension to travel radially outward from the center of the rings. The expansion of the rotor and stator circuits as they extend outward from the center of the periphery creates a differential pressure between the inlet or center of the flow mixer and the outlet, or outermost circumference. The pressure drops as it exits the center. The resulting pressure difference facilitates the passage of the fiber suspension through the passage to -35.

8

Mechanical activation according to a preferred embodiment of the invention relates, for example, to the treatment of fiber surfaces to reveal free and reactive surfaces of the fiber to which the precipitating mineral materials are easy to adhere, or to exhibit fibrils to adhere to the fiber surfaces. The formation of fibrils increases the specific surface area of the fibers, whereby the fiber is able to bind more of the precipitating mineral material. Some of the fibrils formed may become detached from the fiber and thus increase the amount of fines of the fiber suspension, which in some cases is desirable.

Mechanical activation according to a preferred embodiment of the invention is also concerned when the pulses are subjected to vacuum and overpressure pulses to open, tear or to form openings which allow a greater amount of reactive mineral material contained in the fiber suspension to penetrate and penetrate the fiber more easily.

For example, the Akti-20 chemical waxing according to a preferred embodiment of the invention is when the fiber surfaces are activated such that active chemical groups are formed on the fiber surfaces, which are capable of binding to the precipitated or precipitated mineral. For example, active OH groups can be provided on the fiber surfaces, which are capable of bonding with the mineral material and attaching the mineral material to the fibers.

In a typical process of the invention, the fibrous material and the reactive mineral material, such as lime milk, Ca (OH) 2, are preferably combined into a fiber suspension before being fed to the precipitation reactor. A fiber suspension containing a fibrous material and a reactive mineral is typically formed by adding the reactive mineral to be precipitated as a slurry or suspension in the fibrous material suspension. The slurry or suspension can be rapidly and uniformly mixed with the fiber suspension. On the other hand, the precipitated reactive mi-35 mineral material can also be added to the fibrous material suspension in solid form, for example as a powder. When the reactive mineral material is added to the fiber material suspension prior to feeding the suspension to the precipitation reactor, the fibers will be able to absorb the reactive mineral material for several minutes if desired and, if alkaline, will further swell the fibers into a favorable form for activation and / or carbonation. In this case, the mineral material is more easily precipitated on the fiber surfaces and also inside the fibers by the al-5 precipitation. Of course, if desired, the fiber material and the mineral material can be introduced separately into the precipitation reactor and allowed to mix only in the precipitation reactor.

When applying the solution of the invention to the precipitation of mineral material, conditions such as raw materials, feedstock ratios, pH, pressure and temperature can be selected to suit the particular process. The solutions of the invention do not place any limitations on these.

For purposes of this specification, unless otherwise specifically stated, a fibrous suspension of a liquid suspension containing at least a fibrous material, a suspension of a fibrous suspension comprising at least a fibrous material and The mine-25 raw material is finely divided and the treated fiber suspension is a liquid-based suspension containing at least fibrous material and precipitated mineral particles.

The above suspensions may, of course, additionally contain other substances, such as already precipitated mineral particles or non-precipitated mineral matter.

As the reactive mineral material, calcium hydroxide (Ca (OH) 2), i.e. milk of lime, or other sources of Ca 2+ ions can be used in the process of the invention, so as to precipitate the fibers and / or in them. precipitated calcium carbonate (PCC). The invention also permits the use of other similar reactive minerals, such as calcium oxide or calcium sulfate, which can be precipitated and attached to fibers by precipitation of fibers.

The reactive mineral material to be used in the precipitation process is selected according to the property or properties of the fibers, the paper to be manufactured, or the manufacturing process. For example, the fiber suspension, especially the mineral precipitated into the fibers, can, for example, improve the whiteness, brightness, opacity, gloss, bulk, print, printability, drainage, drying, etc. of the paper.

10

The precipitating chemical is preferably a precipitating gas. Thus, for example, carbon dioxide can be used as the precipitating gas for calcium hydroxide. Thus, a carbonaceous gas such as pure or near-pure carbon dioxide (CO 2), flue gas or other suitable gas may be fed to the precipitation reactor. A suitable precipitant other than carbon dioxide may be considered.

The invention enables the precipitation of reactable substances in a fiber suspension not only on the fibers but also on the surfaces of other inorganic or organic particles in the suspension 20. Such particles may be, for example, other mineral particles, such as titanium oxide particles, or impurity particles or fiber-based fines particles. The solution of the invention can then also be used to cover the residual ink remaining on the precipitated calcium carbonate or other similarly incompletely cleaned fibers. The reactive material precipitated on the inorganic particles also has the ability to attach the particles to the fibers, thereby retarding them with the paper. The fiber precipitated mineral material, in turn, also has the ability to bind the fibers to each other, which increases the strength of the paper to be manufactured.

The fiber suspension fed to the precipitation reactor may contain, in addition to the fiber material and the reactive mineral material to be precipitated, other solids used in papermaking or the like, such as 35 - other minerals such as calcium oxide, calcium sulfate, impurities, various process refects and / or retention enhancers, starch, biocide 5 and.

Many of the substances described above can be introduced into the PCC-containing paper pulp after the reactor before the pulp is fed from the headbox to the forming unit, to one mobile forming tray (vii-10) or between two mobile forming plates (wire).

The invention is suitable for use in the manufacture of paper, board or other similar web or pulp products made of fibrous material. The invention is thus suitable for use in the manufacture of a wide variety of web products, such as newsprint, fine paper, magazine paper, kraft paper, tissue paper, specialty paper or board; in the manufacture of a product of a wide variety of pulps, such as a chemical, mechanical, chemi-mechanical, thermomechanical or semi-mechanical pulp, a recycled product or a mixture thereof; in the manufacture of paper from a wide variety of fibers, such as virgin, chemical or mechanical, bleached or unbleached, powdered or unrefined, desiccated or unbleached recycled paper or from mechanical pulp, production.

In the manufacture of paper, the filler-containing (e.g., PCC-containing) pulp obtained as described above is led from the headbox at a suitable fiber suspension consistency to a papermaking forming unit 35, which may be single or double wire (one or two movable forming pads). With this forming part, a continuous web of cohesive paper is formed from the 12 paper pulp ingredients as water and possibly dissolved substances and suspended fines drain through one or two of the forming substrates. The manufacturing process is preferably a neutral-alkaline papermaking process, which means that the pH of the fiber suspension is generally in the range of 6.5 to 9. The PCC-containing fiber suspension obtained in the pretreatment can first be led from the reactor to the pulp tank, from where it is passed through dilution with circulating water (e.g., a wire pit) to pulp processing equipment (deaerating, screening, etc.) located before the paper box 10 headbox. The PCC-treated treated fiber suspension may be mixed with other materials prior to the headbox, for example, paper structure agents such as wet-end adhesive compatible with the neutral-alkaline papermaking process (e.g. ASA, AKD) and / or process auxiliaries, e.g. 15 retention aids.

It is also possible that the PCC-containing fiber suspension forms part of the final paper stock composition determining pulp obtained by mixing said treated fiber suspension into one or more other pulp fractions containing other fibers.

By pre-treating the fibrous material of the pulp, feeding the fibers and the reactive mineral material as a finely divided fiber suspension into the precipitate gas, i.e., contrary to what has been done previously, the reactive mineral substance, fibrous material and precipitating gas are mixed with considerable ease and efficiency.

Precipitation reactions can start immediately and reactions occur rapidly on the remarkably large contact surfaces between the small fiber suspension droplets and the gas. Precipitation occurs easily on the fiber surfaces and also within the fibers. By adjusting the fiber composition, the reactive mineral composition, and / or the co-35 composition of the precipitating gas, the achievable paper properties such as strength and optical properties can be adjusted by the method and apparatus of the invention.

13

It is expected that the reactions will be quicker and more efficient the finer the fiber suspension can be dispersed, i.e. dispersed.

A flow-mixer operating on a blow mill principle provides a fiber suspension to be dispersed in the precipitating gas into a mist-like gas suspension in which the gas, the fibers and the reactive mineral material to be precipitated are very effectively admixed. The solution of the invention enables the components involved in the precipitation process to be microhomogenized into a gas suspension in which reactions between the different components can take place immediately. This is particularly advantageous when, for example, the activated fiber is susceptible to return to the non-activated state, i.e., when the fibrils or openings formed in the fibers are easily closed. Mineral material 15 in the fiber suspension tends, at least in part, to inhibit fibril recovery. If necessary, the fiber suspension may be reactivated one or more times.

By activating the fiber material prior to the precipitation process and / or during the precipitation process so as to increase the ability of the fibers to bind to each other and bind the precipitated mineral material, both an enhanced precipitation process and improved paper properties are obtained. Even a single treatment in a precipitation reactor may be sufficient to achieve the desired precipitation process and the desired paper properties.

The invention will now be described with reference to the accompanying drawings, in which Figure 1 schematically and exemplifies a vertical section of one of the precipitates of the process according to the invention from an is reactor; Figure 2 is a schematic and exemplary horizontal section of a disruption and activation condition fitted to the precipitation reactor of Figure 1; Figure 3 is a schematic and exemplary vertical section of another precipitation reactor of the process of the invention; Figure 4 is a schematic and exemplary horizontal sectional view of the decomposition and activation device of the type 3 precipitation reactor; Figure 5 is a schematic and exemplary vertical section of the precipitation reactor array of the process of the invention; Fig. 6 is a schematic and exemplary vertical section of a second precipitation group of the process of the invention; Fig. 7 is a schematic and exemplary vertical section of a third precipitation group of a process of the invention; and Fig. 8 is a schematic diagram of a papermaking process.

Figure 1 shows a continuous settling reactor 10 according to the invention comprising a settling vessel 12, a digestion and activation device 14 fitted to the precipitation vessel, a fiber suspension feed pipe 16, a precipitating gas feed pipe 18 and a treated fiber suspension drain pipe 20. The apparatus further comprises a drive device 22 and a seal 24 between drive 22 and device 14.

25

The decomposition and activation device 14, the horizontal section of which is shown in Fig. 2, is a so-called. flow-through mixer with six concentric circles 26, 26 ', 26', 28, 28 ', 28 "with blades 26a, 26'a, 26" a, 28a, 28'a, 28 "a. The apparatus 14 disintegrates the fiber suspension into small particles, 30 droplets of liquid and / or solid particles. In the same device 14, the fibers of the fiber suspension are activated so that the ability of the fibers to bind to one another and the ability to receive the precipitated mineral material increases. The residence time in the dissolution and activation device is short <10 s, typically <2 s, most typically even less than 1 s.

As indicated by the arrows in Fig. 2, the first circumferences 26, 26 ', 26' of the disintegrator act as rotors which, in the case shown in the figure, run counterclockwise. Also, the second rings, adjacent to the first rings, 28, 28 ', 28', act as rotors, but in the case shown in the figure, run clockwise. The circles are provided with blades 26a, 26a ', 26a ", 28a, 28a', 28a" which encounter a fiber suspension radially outwardly passing through the device, subjecting it to repeated shocks and repulsions. At the same time, overpressure is created between the blades of adjacent rotors, as the blades approach each other, and, as the blades are spaced apart, underpressure. Differences in pressure produce extremely rapid overpressure and vacuum pulses in the fiber suspension. In addition, shear forces and turbulence are generated in the fiber suspension passing through the device 14.

A fiber suspension or fiber slurry containing fibrous material and reactive mineral material is fed by tube 16 to center 30 of the disintegration and activation device, from which the fiber suspension, due to rotor blades and pressure difference between center and outer periphery, If necessary, the fiber suspension may also be fed to the device 14 between the rings. The fiber material and the reactive mineral material 20 may, if desired, be fed to the decomposition and activation device 14 by separate tubes, whereby a fiber suspension containing the fiber and mineral material is formed only in this device.

Impacts and counter-attacks by rotor blades in opposite directions, shear forces, turbulence, and vacuum and overpressure pulses disintegrate the fiber suspension into fine particles, liquid droplets, and solid particles, while activating the fibers, for example, by fibrillating them. Activation is effective, for example. due to strong shocks affecting the fiber suspension and the resulting high shear forces. However, in the solution of the invention, the fiber suspension is able to pass through a relatively open path through the periphery and therefore not be subjected to the same grinding and fiber breaking forces as the fibers which are treated in plate or cone mill type solutions. In the solution of the invention, the fibers only momentarily encounter the surfaces of the rotor-35 blades, if at all.

16

1 and 2, the solution pretreatment step of the method of the invention illustrates in Figures 1 and 2 a condensing gas through a conduit 18 to the center 30 of the disassembly and activating device peripherals, from which gas is deposited in the The precipitating gas may also be supplied, if desired, to and / or between the rings of the disintegrator and activator. Precipitation reactions may already occur in the gas state of the decomposition and activation device.

10

During the treatment of the disintegration and activation device 14, the fiber suspension forms fine droplets and particles which disperse from the device 14 into the surrounding gas space portion 34 '. Fine droplets and particles are ejected from the disintegrator and activator mainly through its entire 15 outermost peripheral region as a misty stream 36. Outside the disintegrator and activator, the precipitation reactions can continue for a relatively long time as the fine droplets and particles spread over a wide area into the precipitation vessel. The treated fiber suspension descends to the bottom of the settling vessel in a pond and removes the put-20 beam 20 from the vessel.

The size, shape, width, and height of the precipitation vessel 12 may be selected such that droplets and particles ejected from the disintegration and activation device have a residence time of as much as possible in the gas space 34 'of the precipitation vessel. For example, by increasing the height of the precipitation vessel 12 to a tower, the residence time of the fiber suspension can be extended.

The processes in the precipitation reactor 10 can also be controlled by adjusting, for example, the number of rings, the distance between the rings, the distance between the blades of each ring, the dimensions of the blades and the position of the blades in the decomposition and activation device.

The fiber suspension leaving the bottom of the precipitation vessel 12 can be recycled to the same precipitation reactor or fed to another reactor to complete the treatment.

17

Figures 3 and 4, which show another precipitation reactor for the process pretreatment step of the process according to the invention with a decomposition and activation device, have the same reference numerals as in Figures 1 and 2. Figure 3 shows another precipitation reactor 5 10 according to the invention , that the reactor comprises a decomposition and activation device 14 with a closed periphery 32 and that the precipitation reactor does not comprise a separate precipitation space extending beyond the decomposition and activation device. The solution of Figures 3 and 4 is suitable for use, for example, when the precipitation reactions can be expected to take place as desired already in the decomposition and activation state of the reactor gas.

3 and 4, the outer periphery 28 'is surrounded by a housing 40 which closes the periphery. An outlet 42 is formed in the housing for discharging the treated fiber suspension from the device 14. The treated fiber suspension can be led from the outlet 42 to the tube for further processing or further processing.

The reactor of Figure 3 is also suitable for use in activating a fiber suspension when no precipitation occurs in this device. Both the precipitation reactors of Figures 1 and 3 can be arranged in series or in series. Figure 5 shows a group of three precipitation reactors according to Figure 1. Where applicable, the same reference numeral as in the preceding figures is used.

25

Figure 5 shows three precipitation reactors 10, 10 'and 10' in which a fiber suspension containing Ca (OH) 2 is treated with CO2 to carbonate the Ca2 + ions, i.e. to precipitate CaCO3. The reactors are connected sequentially so that from the first reactor 10 a partially treated fiber suspension containing fiber, precipitated carbonate and non-precipitated calcium hydroxide is discharged from the outlet pipe 20 into the feed pipe 16 'of the second reactor. Correspondingly, the treated fiber suspension from the second reactor 10 'is led from the outlet pipe 20 to the "feed pipe 16" of the third reactor 10'.

Carbon dioxide-containing gas is introduced into each reactor through tubes 18, 18 ', 18'. The feed tube 18 feeds to the first reactor 10 a carbon dioxide gas, which initiates deposition (carbonation) and formation of active carbonate on the fibers already in the decomposition and activation device 14. The precipitated calcium carbonate is precipitated on the fibers as well as on the other fibers. The carbonate 5 also precipitates as discrete particles in the fiber suspension. The second and third precipitation reactors 10 ', 10 "may be led by tubes 18', 18" to the same or other carbon dioxide-containing gas to complete the precipitation reactions (carbonation). The gas is discharged from the reactors by the discharge pipes 21, 21 ', 21'.

10

The fiber suspension fed to the precipitation reactor 10 can be activated prior to being fed to the reactor in a separate activator connected to the precipitation reactor 10. The activator is preferably a blow mill type flow-through mixer.

15

Figure 6 shows another precipitation reactor array having two sequentially arranged precipitation reactors 10, 10 'according to Figure 1. An activating device 44 having a structure essentially similar to the flow-through mixer 20 of Figure 3 is coupled in front of the first precipitation reactor 10. The activating device activates the fiber material fed to the precipitation reactor. However, no precipitating gas is fed to the activator.

The fibrous material is introduced through tube 46 through upper activator 25 44. Activated fibrous material is introduced via intermediate vessel 48 to first precipitation reactor 10. The fibrous material may be loaded with precipitating mineral material, calcium hydroxide, by tube 50 before activator 44 or tube 52 after activator. In the intermediate container 48, the fibrous material may swell under desired conditions for a desired period of time. From the interlayer 30, the fiber suspension containing the fibrous material and the mineral to be precipitated is passed through a tube 16 downstream to the decomposition and activator device 14 of the precipitation reactor. and carbon dioxide. The gas is fed to a gas scrubber and cooling unit 54 for treatment. The carbon dioxide-treated gas treated in the unit 54 is recycled via a tube 18 to a precipitation reactor 10.

19

From the bottom of the precipitation reactor, the treated fiber suspension accumulating therein is discharged into the discharge pipe 20.

The second precipitation reactor 10 'of Figure 6 functions essentially as the first precipitation reactor 10 of en-5. The fiber suspension removed from the first reactor 10 into the tube 20, which typically contains calcium carbonate precipitated in addition to the fiber material and calcium hydroxide. 14 '. Carbon dioxide-containing gas 10 is introduced from the washing and cooling device 54 to the second reactor 10 '. At the bottom of the second reactor 10 ', a predominantly pre-treated fiber suspension is removed by tube 20', where the desired amount of calcium carbonate is typically deposited on the fibers. The upper part of the second reactor 10 'is degassed, which is taken to the gas washing and cooling unit 54 for further recycling.

Figure 7 shows a third precipitation reactor array comprising three series-mounted precipitation reactors 10, 10 '10 ". The reactors are superimposed and the fiber suspension is fed to the decomposition and activation devices 20 from above, the first reactor 10 being at the top and the third reactor 10 'at the bottom, whereby the fiber suspension will flow substantially downward when flowing through the reactors. A separate fibrous material pre-activation device 44 and an intermediate tank 25 48 are provided in front of the third precipitation reactor array.

Advantages of the invention include: the fact that it is possible to simultaneously activate the fiber material and decompose it for precipitation, 30 - very rapid, efficient and complete precipitation reactions are obtained, even one run of the precipitation reactor gives good results; the activation provides a powerful and efficient treatment of the fibers without, in particular, interrupting or otherwise damaging the fibers; activation can be adjusted; 20 provides a highly efficient blend of fiber suspension, mineral material, and gas, resulting in treatment of each small volume unit in the fiber suspension and precipitation of each volume unit; 5 - can also affect the deposition of fibers within the fiber; precipitation reactions are capable of binding the fibers to one another, whereby the strength of the paper can be assumed to increase; precipitation reactions are capable of covering ink residues remaining in the fiber after decontamination; precipitation reactions are capable of binding inorganic and organic particles to the fibers and thereby retaining them in the paper, and that the precipitation can better optimize the properties of the paper being produced, such as brightness, strength, opacity; the pretreatment can be integrated into a continuous papermaking process in which a continuous paper pulp stream is formed from the PCC-containing fiber suspension obtained from the pretreatment, which is fed from the headbox to the forming part.

Figure 8 schematically illustrates a method for making paper. From the pulp container M into which the fiber suspension is derived from the pre-treatment process described above, the fiber material is passed through a dilution 25 (e.g. wire well P) to the pulp processing apparatus, from where the pulp is fed to the headbox H and forming part F.

The purpose of the experiments set forth in the following example is to compare the carbonation of the fiber / PCC product of the present invention with the fiber / PCC product produced by the other methods described. The invention is intended only to illustrate the invention and is not intended to limit it in any way.

In all experiments, machine powdered pine fiber, having a consistency of about 3.5%, Ca (OH) 2 slurry, having a dry matter content of about 17%, and a similar composition of CO 2 gas were used for fine paper production.

(K1) By the process of the invention, the fiber / PCC fiber-5 product was prepared by mixing the required amount of Ca (OH) 2 slurry with the pine fiber containing fiber stock to obtain a fiber / PCC ratio of 70/30 after precipitation, and then pumping the fiber / Ca (OH) 2 slurry twice through the precipitation reactor shown in Figure 1. The fiber / Ca (OH) 2 suspension was then pumped into a CO 2 containing gas as a fine suspension in accordance with the invention. An excess of CO2-containing gas was injected into the apparatus. After this treatment, the fiber / PCC product had a pH of 7.

(V1) For comparison, a fiber / PCC product was prepared by pumping a Fiber / Ca (OH) 2 slurry six times through a chemical mixer using a fluidizing chemical mixer. In addition, an excess of CO2-containing gas was fed to the chemical mixer. Immediately after treatment, the fiber / PCC product had a pH of 7.

(V2) For the second comparison, a precipitation similar to Experiment (V1) was made except that the chemical mixer was not allowed to fluidize but only supplied with excess CO2-containing gas. The fiber / Ca (OH) 2 suspension was pumped eight times through a chemical mixer. Immediately after treatment, the fiber / PCC product had a pH of 7.

(K1) The pH of the product prepared by the process of the invention was 7 for a further 24 hours after preparation, indicating that the carbonation was complete.

(V1) The pH of the product prepared by the procedure of this example was 30 to 10 hours further 24 hours after preparation, indicating that the carbonation was not complete and that carbonation of the product had to be continued for several minutes to complete the carbonation reactions. Incomplete carbonation adversely affects the wet end chemistry of the papermaking machine.

(V2) The pH of the product prepared by the method of this example was still 11 hours 24 hours after preparation, indicating that the carbonation was not complete but that the carbonation of the product had to be continued for several minutes to complete the carbonation reactions.

In all cases, the time used for the actual carbonation was very short, but only in the process of the invention the carbonation was complete in a very short time and no further carbonation was required.

The invention is not intended to be limited to the exemplary descriptions and examples set forth above, but is intended to be extensively applied within the scope of the following claims. Thus, the solution according to the invention can be used in a further process for preparing paper, cardboard or the like as a raw material for paper, cardboard or the like, to activate the fibers and their surfaces, for example by increasing their mechanical or chemical bonding ability, mechanically or chemically proliferate, forming active OH groups on their surfaces and / or opening their inner lumen allowing e.g. mineral-20 also precipitates into the inner parts of the fiber. Hereby, the fiber material is pretreated in a blow mill flow-through mixer having a plurality of, typically 3-8, most typically 4-6, concentric vane rings, at least one of the two rings acting as rotors and the adjacent circles being rotor or rotor 10, -500 m / s, typically 50-200 m / s, feeders for feeding the fibrous material mainly to the center of said rings, and 30 - an open outer ring that allows the fiber suspension to flow radially outwardly through the rings in different directions, or an outer ring provided with a plurality of outlet openings for radially outwardly extending fiber suspension through the rings.

The pretreatment is preferably carried out when the fibers are swollen, for example by the addition of Ca (OH) 2. The pretreatment of the fibers 35 23 according to the invention is particularly well suited for use in activating the fibrous material prior to contacting the fibrous material with the reactive mineral material which is to be precipitated onto the fibers. However, the pretreatment according to the invention is well suited for use in other processes in which it is desired to pretreat the fibrous material to achieve similar properties in the fibrous material.

In the paper produced by the process of the invention, the PCC serving as filler 10 is "hidden" in the fiber network and in the lumen of the fibers so that it does not affect bond formation or sheet formation. Paper has improved strength properties compared to paper in which the PCC is derived from a mineral added directly to the pulp fibers.

15

The 80 g / m 2 paper according to the invention was produced at a PCC / fiber ratio of 30/70 and the reference was paper to which PCC had been introduced in normal addition. The paper of the invention had a better tensile strength index (19.3 → 30.9) and a tear index (7.0 → 9.0). The refractive index increased from 20 to 31.

The paper also has a lower porosity (sheet condensation) and improved opacity and formatting compared to the reference. The brightness of the sheet also decreases compared to the same amount of normal filler paper, because some of the fillers are "hidden".

The PCC-equipped fiber pre-treated fiber in the paper preferably comprises at least 20 wt% PCC based on the total dry weight of the treated fiber, preferably 20-50 wt%. Preferably, the fiber comprises at least 25 wt.% PCC, e.g. 25 wt.% To 50 wt.%, As described above, produced on the fiber. Other fibers may also be present in the pulp, whereby the proportion of PCC obtained in the above-mentioned manner in the total weight of the paper is reduced accordingly. Preferred is a paper product wherein all of the fiber raw material is fiber pretreated as described above, wherein 35 PCCs are at least 20 wt%, preferably 20 wt% to 50 wt%, more preferably at least 25 wt%, e.g. 25 p -% - 50 p-%.

24

The paper-containing PCC obtained by the process of the invention obtained on the fibers as described above is a nanocouple precipitated calcium carbonate, typically having a particle size of less than 100 nm. The choice of precipitation conditions can influence the average particle size and size distribution.

It is also possible to supplement the nanoscale filler present in the pre-treated fibers with another filler additive. This additional filler may be a normal size filler, e.g., separately precipitated PCC or a chemically other filler.

After drying the paper web, the paper produced by the manufacturing process of the invention can be post-treated in a paper machine on-line or in a separate post-treatment process. For example, calendering can be performed to finish the surface with a paper web. The paper web produced by the method described above may, after any calendering, act as printing paper (e.g., SC paper), or the paper web, after any calendering, may be coated online or in a separate coating machine (e.g., LWC paper), wherein the coating 20 . If the fibrous material to which PCC undergoes pre-treatment is a chemical pulp, the printing paper product consisting predominantly or exclusively of this pulp may be uncoated fine paper, i.e. WFU, or coated fine paper, i.e. WFC or copy paper. However, the invention is not limited to printing papers, but can be applied to all paper products. Thus, for the purposes of the claims, the term "" paper "refers to all flexible fiber-based products initially made in the form of web, regardless of their basis weight, including cardboard.

Claims (21)

A process for making paper, wherein the filler-containing pulp is fed in a determined consistency to the forming portion of the papermaking machine, the water is removed from the pulp by letting it be filtered through a water-permeable molding substrate, such as a wire, and the paper in this manner. is processed to produce a finished paper product, characterized in that the pulp is manufactured as follows: (a) fibrous material which contains fiber and is used as a raw material for the pulp, and reactive mineral, such as calcium hydroxide (Ca (OH)) 2 ), is combined into a fiber suspension before these substances are measured into a precipitation reactor; (b) contacting the fiber suspension in the precipitation reactor with said reactive mineral substance precipitating agent, to precipitate the reactive mineral substance present in the fiber suspension at least partially, with at least a portion of the precipitated mineral substance precipitating on fibers being suspended in the fiber suspension. (b1) gas being measured into the precipitation reactor, which gas comprises said reactive mineral precipitate, such as carbon dioxide, to form a gas space comprising said precipitant in the precipitation reactor, and (b2) the fiber suspension, its liquid phases, and solid phases. measured into the said gas space of the precipitation reactor, broken down into very small parts, droplets and / or particles; (c) the manner treated fiber suspension is discharged from the precipitation reactor; then the manner treated fiber suspension is fed to the papermaking molding portion, and paper is made from it by allowing it to be filtered through a water permeable molding substrate. Process according to claim 1, characterized in that in step (b2) the liquid phase of the fiber suspension is decomposed as liquid droplets of substantially <10 mm, typically <1 mm, into the gas space. 35 3. A method according to claim 1, characterized in that the fiber suspension is directed in a pre-precipitation reactor or a relative flow of the fiber suspension in the precipitator reactor in the former part, activating zone forces which activate the fibers so that the fibers are capable of bonding to each other and to bind precipitated and / or precipitated mineral substance increases. 5 Method according to claim 3, characterized in that, in order to effect the activation, forces are directed towards the fiber suspension, such as up-beating, impact, cutting forces, turbulence, over and under-pressure pulses or other corresponding forces, which 10. mechanically the fibers, especially their surfaces, for example, by fibrillation or grinding of the fibers and by opening the inner parts (lumen) of the mineral substance, and / or mechanically activating the surfaces of the fibers, for example by forming active OH groups in the surfaces of the fibers. 15 5. A method according to claim 3, characterized in that successive powerful blows and counter strokes flowing through the activation zone are directed by blades or the like, preferably at a rate of 5-250 m / s in the fiber suspension flow. 20 Method according to claim 3, characterized in that in the precipitation reactor, in whose activation zone there is one on the so-called. the percussion principle operates a multitude of flow mixers, typically 3-8, most typically 4-6 concentric, leaf-shaped circles, of which at least every other circle acts as a rotor and the adjacent circles as stators or rotors, and in which the speed difference between the stators or the rotors of adjacent circles are 10-500 m / s, typically 50-200 m / s, the fiber suspension is passed through the flow mixer radially outwardly from the center of its circles, the blades present on the circles repeating the leaking liquid fiber suspension repeatedly , cutting forces, turbulence and / or overpressure and suppression pulses, which together have a fiber activating effect. 35 Process according to claim 6, characterized in that at least part of the gas which is measured into the precipitation reactor and contains the mineral substance precipitating substance is measured into the reactor through the activation zone, whereby the fibers activated in this activation zone will immediately upon activation or shortly thereafter in contact with the said precipitating substance. 5 Method according to claims 3-7, characterized in that the fiber suspension containing fibrous material and reactive mineral material has a short residence time of <10 seconds, typically <2 seconds, most typically <1 second, in the activation zone. 10 Method according to claim 1, characterized in that gas containing> 5%, typically> 10%, of precipitating substance, such as carbon dioxide, is measured in the precipitation reactor. 15 Process according to Claim 1, characterized in that the precipitating substance containing the gas is pure or almost pure carbon dioxide, flue gas, any other carbon dioxide containing gas or contains any other gas suitable for precipitation of the reactive mineral substance used, or is a mixture of these gases, and that the precipitating substance containing the gas is measured into the precipitation reactor so that in the precipitation reactor an overpressure is saved. Method according to claim 1, characterized in that the 25. the fiber suspension is passed through two or more successive precipitation reactors, in which precipitation reactors gas compositions in the gas spaces may be different, for example, that the precipitating substance containing the gas in the first the precipitation reactor is pure or almost pure carbon dioxide and in the flowing precipitation reactor or subsequent precipitation reactors is flue gas or a less carbon dioxide gas, or so that the precipitant containing the gas in the first precipitation reactor or first precipitation reactors is less carbon dioxide gas and the following the precipitation reactor or the following precipitation reactors are pure or nearly pure carbon dioxide. Process according to claim 1, characterized in that the reactive mineral substance contains calcium hydroxide, calcium sulfate, calcium oxide, some other suitable and precipitating reactive mineral substance and / or a mixture thereof, and The mineral substance is chosen so that the product to be made from fibers achieves the required properties, for example the requested optical properties. 13. A process according to claim 1, characterized in that the fiber material 10 contains pure fiber obtained from a chemical, mechanical, chemical-mechanical, thermomechanical, semi-chemical or other similar process; de-dyed or un-de-dyed recovered fibers obtained from newsprint, kraft paper, creped tissue paper, specialty paper or paperboard, fibers obtained from machine shot, or other such fibers, bleached or unbleached fibers, main or unalloyed fibers, dried or unmixed fibers, of these. 20 Process according to Claim 1, characterized in that the fibrous material contains, in addition to the fibers, fine material, such as fiber-carrying fine material, impurities and / or mineral matter. 25 Process according to claim 1, characterized in that the fiber material is measured into the precipitation reactor in a consistency of 0.1-40%, more typically 1-15%, most typically 3-7%. The method of claim 1, wherein the fibrous material used as a raw material for pulp is pretreated to activate the fibers and their surfaces, for example increasing their ability to bond to each other mechanically or chemically, their ability to bind mineral material mechanically or chemically increases, on their surfaces active OH groups are formed and / or their inner part (lumen) is opened to allow e.g. precipitation of mineral substance also in the inner parts of the fiber, characterized in that the process comprises pretreatment of the fibrous material in a so-called. the percussion principle operates flow mixers with several, more typically 3-8, most typically 4-6 concentric, leaf-shaped circles, of which at least every other circle acts as a rotor and the circles adjacent to them as stators or rotors, and in which the speed difference between the stators or rotors of adjacent circles are 10-500 m / s, typically 50-200 m / s, feeders for feeding fiber material mainly into the center of said circles, and an open outer circle allowing it to radially extend through the circles the fluted fiber suspension is removed from the circle in different directions, or an outer circle provided with one or more drains to remove the radially projected fiber suspension, after which mineral substance is deposited on the surface of the fibers by contacting the fiber suspension. with a reactive mineral substance precipitating substance, followed by fiber suspension The pulp containing the pulp is fed to the papermaking molding portion and paper is made from it by allowing it to be filtered through a water permeable molding substrate. 20 17. A process according to claim 16, characterized in that the activation is performed when the fibers are swollen, for example as a result of the addition of Ca (OH) 2. 18. Paper made by using at least partially fiber in the pulp which has been pretreated with a pretreatment process as mentioned in any of claims 1 to 17, comprising at least 20% by weight of nano-size filler particles, especially PCC, relative to the total weight of the pretreated fiber. The paper according to claim 18, characterized in that its fibrous raw material consists in its entirety of the aforementioned pretreated fiber. 35 The paper according to claim 18 or 19, characterized in that it is glued with adhesive of the hydrogen end. 36 Paper according to claim 18, 19 or 20, characterized in that it is calendered and / or coated paper.