CN116867941A - Packing material - Google Patents

Abstract

The present invention relates to a method for producing filler for paper, comprising the following steps: providing a floating slurry from a paper regeneration treatment, wherein the floating slurry contains titanium dioxide; subjecting the floating slurry to mechanical and/or chemical treatment; subjecting the floating slurry to The mechanically and/or chemically treated laitance is mixed with titanium dioxide; as well as the filler obtainable according to said method, the paper containing the filler and the use of such paper as decorative paper.

Description

filler

The invention relates to a method for producing fillers for paper, the fillers obtainable according to the method, paper containing the fillers and the use of such paper as decorative paper.

The main component of paper is fiber material, and its main source is wood. A distinction is made between mechanical pulp (Holzstoff), in which the wood is mechanically processed, and chemical pulp (Zellstoff), in which the wood is chemically processed, respectively, based on the method of obtaining the fibrous material. The fiber material can also be obtained from the recycling of used paper (ie waste paper).

Non-fibrous additives used in papermaking are, for example, fillers such as pigments. It is possible to use, for example, kaolin, calcium carbonate, magnesite and/or titanium dioxide as fillers. These fillers are used inter alia to improve smoothness, printability and to influence the whiteness and opacity of the paper. Titanium dioxide is used especially as filler.

DE 196 27 523 C1 discloses a method for recovering fillers and paint pigments from the production of paper, cardboard and cardboard from paint wastewater, residual water sludge from deinking plants, internally operated sewage treatment plants or separation plants.

Fiber-containing residual water sludge containing fillers and paint pigments or residual water sludge in which the fibers have been mechanically and/or chemically separated (for example by flotation to obtain a laitance) is fed here

-Mix and

-Subsequently ground into

Pigment paste with fresh pigments as powder or fresh fillers,

Slurries containing fresh pigments and/or

Slurry containing fresh fillers.

Ordinary paper machines can be fed with titanium dioxide from various sources. A mixture of "fresh" titanium dioxide and titanium dioxide-containing laitance from paper recycling is therefore often used.

The problem here is that the laitance from the paper recycling process usually contains titanium dioxide in the form of flocculated titanium dioxide with an average particle size of greater than 2 μm. Therefore, such a laitance only introduces ash into the paper but has no effect on the opacity of the paper, since only titanium dioxide with an average particle size between 300 nm and 400 nm contributes to the opacity of the paper.

Here ash usually refers to the inorganic, non-combustible part of paper. Ash may include, for example, fillers, impurities and pigments.

The ash content, i.e. the type, content and composition of the filler, is decisive especially for the performance, quality and production costs of the paper. In particular, the resulting opacity is important.

The composition of ash can be high quality and cost intensive (e.g. high proportion of titanium dioxide) or low quality and low cost. On the one hand, with the exception of titanium dioxide, "ash" is generally cheaper than organic fibers; on the other hand, the addition and composition of ash can also produce and improve new paper properties, as well as optimize the production process technically and energy-wise.

High ash content can also impair paper machine performance, as the paper's reduced breaking load may make it more susceptible to tearing, and operating speeds must be reduced accordingly.

The object of the present invention is therefore to eliminate the above-mentioned disadvantages and to provide a method for the production of fillers and fillers obtainable by this method, which fillers can introduce high opacity into the paper and in which at the same time as much titanium dioxide as possible can be saved . Therefore, high ash retention is required to avoid loss of raw materials. Furthermore, this filler in the paper should give the paper high opacity and breaking load.

This object is achieved by a method according to claim 1, in particular by a method for producing filler for paper, which method comprises the following steps:

- providing laitance from a paper recycling process, wherein said laitance contains titanium dioxide,

- mechanical and/or chemical treatment of this laitance, and

- Mixing mechanically and/or chemically treated laitance with titanium dioxide.

The invention also relates to fillers obtainable by this method.

This method allows to provide a filler that can introduce high opacity into the paper while requiring as little "fresh" titanium dioxide as possible. Therefore, titanium dioxide can be saved due to high ash retention.

Furthermore, this filler is characterized in that its use causes almost no damage to the performance of the paper machine and can therefore be operated economically.

Papers containing such fillers are characterized in particular by a high opacity and a favorable breaking load.

In this specification, the term "comprising" may also mean "consisting of".

Components of the filler include titanium dioxide-containing laitance from paper recycling, wherein the laitance is mechanically and/or chemically treated.

In paper recycling, usually waste paper is pulped with water in a pulper. The recovered fibers are then typically freed of coarser impurities and subsequently finely sorted. In the so-called deinking process, in particular printing inks and fillers are further removed from the fiber mixture by flotation or washing processes.

In the flotation process, other particles present in the material suspension after the fiber separation stage that have been separated from the fibers, such as colored particles or fillers, are attached to the bubbles by collector chemicals during the flotation process and are removed by the flotation process. These bubbles are transported to the surface of the flotation cell. The result is a dirt-laden foam that may contain fibers and fillers in addition to separated colored particles. In addition, a small part remains in the flotation tank, which can also be called residual water sludge. The foam produced, preferably representing laitance, is skimmed off, cleaned and can be used as ash in papermaking. The residual water sludge can be treated or discarded by other methods, such as those described in DE 196 27 523 C1.

Therefore, the floating slurry must be distinguished from the remainder of the flotation cell (residual water sludge).

In the present case, the inventors have found that such laitances can be used advantageously if they are also mechanically and/or chemically treated and mixed with titanium dioxide.

The titanium dioxide added here relates to "fresh" titanium dioxide, ie titanium dioxide not obtained from paper recycling.

Suitable titanium dioxides include rutile, preferably obtained by chloride and/or sulfate production processes, especially anatase.

Suitable titanium dioxides are known, for example, under the trade names Titanium dioxide chloride Tiona RCL-722, Titanium dioxide chloride KRONOS 2800, Titanium dioxide sulfate LOMON LR-952, Titanium dioxide Cinkarna RC-87, Titanium dioxide sulfate HOMBITAN R 610L or Titanium dioxide sulfate NR 950.

A preferred feature of the method according to the invention is that the laitance is obtained by flotation by supplying and adding a flocculant, in particular an anionic flocculant (for example S-FLOCS-A21 from Servophil AG) by means of compressed air, preferably in the recovery in a device (preferably from the company Krofta) in order to remove titanium dioxide from screened water (Siebwasser) and supply it to papermaking.

In addition to titanium dioxide, such laitance may contain, inter alia, fine powders (chemical pulp), pigments such as iron oxides, kaolins and/or silicates.

In one embodiment of the method according to the invention, only the laitance is treated mechanically.

In another embodiment of the method according to the invention, only the laitance is chemically treated.

In another preferred embodiment of the method according to the invention, the laitance is treated mechanically and chemically.

The mechanical treatment and chemical treatment can be carried out one after another.

The mechanical treatment and chemical treatment can also be carried out simultaneously.

Preferably, a chemical treatment is performed first, followed by a mechanical treatment and then another chemical treatment.

In one embodiment, a chemical treatment is first carried out to destabilize the aggregates in the laitance, then a mechanical treatment is carried out to break up the aggregates in the laitance, and then a further chemical treatment is carried out to stabilize the aggregates of the powder in the laitance.

Preferably, the chemical treatment of the laitance prior to the mechanical treatment includes a chemical destabilization step. In this process, large anionic flocculated aggregates (after the _TiO recovery unit (Krofta)) are recovered by adding cationic polymers, such as cationically charged polyacrylamide (e.g. from Servophil AG) in aqueous or latex-containing solutions. S-FLOCS-K89), preferably used as a deflocculant, strongly converts electrical loads and therefore destabilizes them. Preferably, the attractive forces in the aggregates are thereby reduced so that subsequent mechanical treatment, in particular mechanical comminution, can be carried out more efficiently.

The cationic polymer is preferably used in an amount of 0.5 to 5 ppm, wt% absolutely dry (atro), relative to the total amount of laitance flowing through.

As an alternative, the opposite system can also be applied. In this case, cationic flocculated aggregates are first generated to recover TiO ₂ from the screened water, and then the TiO 2 is recovered from the screened water by adding a strong anionic antiflocculant such as an aqueous solution of a strong anionic polyacrylamide or a latex-containing solution such as Servophil AG's S- FLOCS-A82 polyacrylamide) performs electrical load conversion on this system.

The preferred amount of anionic anti-flocculating agent is 0.5 to 5 ppm relative to the total amount of floating slurry flowing through.

The method according to the invention is also preferably characterized in that the mechanical treatment of the laitance involves the use of shear forces. These shear forces are preferably generated by the complete assembly including the rotor and stator.

In particular, the unit including the corresponding complete set of components can be installed directly in the pipe conveying laitance to achieve high shear rates.

The degree of mechanical treatment can be determined by the speed of the motor or its frequency and the correspondingly generated shear forces, which are determined individually for each complete assembly.

A suitable unit known here is the "ShearMaster" from Bauer Verfahrenstechnik GmbH.

The principle here is that the laitance flows through the rotating part and the fixed part of the complete assembly of the unit, which assembly is preferably the same as the refiner (Refiner) or the high-frequency deconsolidator (Entstipper).

Multiple units including the complete assembly of rotor and stator may be connected in series or in parallel.

In one embodiment, a plurality of units (for example two) including a complete assembly of rotor and stator are connected in series.

The advantages of this arrangement are that the total residence time of the laitance in the complete assembly is longer (eg twice as long when using two machines) and that the energy input into the laitance is greater.

In another embodiment, a plurality of units (for example two) including a complete assembly of rotor and stator are connected in parallel.

The advantage of this arrangement is that large quantities of laitance can be processed in a shorter time, and the parallel complete set can be used as a backup for a failed complete set without requiring major technical efforts.

Combinations of complete assemblies including series and parallel connections of rotors and stators are also possible.

Furthermore, the method according to the invention preferably includes a step of chemical stabilization by adding a dispersant, preferably an anionic dispersant. This step is preferred for the time necessary to ensure and maintain the comminution effect.

The method according to the invention is also preferably characterized in that the chemical treatment of the laitance consists of incubating the laitance with a dispersant, preferably an anionic dispersant.

Suitable anionic dispersants include, for example, acrylic polymers or acrylate polymers.

Suitable anionic dispersants are known, for example under the trade names Topsperse GX N from COATEX, Dispex AA 4140 from BASF or S-DISP PA4 from Servophil AG.

The amount of dispersant, preferably anionic dispersant, is preferably 0.1 to 2.0% by weight absolute dry relative to the absolute dry amount of titanium dioxide in the laitance.

Chemical treatment of the laitance is advantageous since the individual particles of titanium dioxide, in particular those produced during the shearing process, are thereby temporarily stabilized in terms of electrical charge.

The advantage of mechanically and/or chemically treated laitance in this way is that the flocculated titanium dioxide (particle size greater than 2 μm) initially contained in the laitance is treated so that the particle size is reduced to about 300 nm to 400 nm, and thus can increase the non-toxicity of the paper. Transparency, preferably when the ash content is the same.

In a preferred embodiment, the chemical and mechanical treatment of the laitance comprises a first step of chemical stabilization as described above, a second step of mechanical treatment as described above and a third step of chemical stabilization as described above.

In a preferred embodiment, the chemical and mechanical treatment of the laitance consists of a first step of chemical stabilization, in which large anionic flocculated aggregates (after passing to the TiO ₂ recovery unit (Krofta)) are stabilized by adding a cationic polymer, preferably used as an anti-flocculating agent, while being strongly transformed into an electrical load, a second step of mechanical treatment using shear forces, and a third step of chemical stabilization by the addition of dispersants, preferably anionic dispersants.

The method according to the invention is also preferably characterized in that the laitance from the paper recycling process contains from 0.5% to 5% by weight of titanium dioxide. This is related to the titanium dioxide content prior to mechanical and/or chemical treatment.

The method according to the invention is also preferably characterized in that the laitance from the paper recycling process contains titanium dioxide with an average particle size greater than 2 μm.

The method according to the invention is also preferably characterized in that the mechanically and/or chemically treated laitance contains titanium dioxide with an average particle size of 300 nm to 400 nm, preferably 320 nm to 400 nm.

Particle sizes of 320 nm to 400 nm are particularly preferred since titanium dioxide particles of this size are particularly advantageous for achieving high opacity of the paper.

The average particle size can be determined by laser diffraction. The median D50 value was determined as the main measurement parameter.

The method according to the invention is also preferably characterized in that the mixing ratio of mechanically and/or chemically treated laitance to titanium dioxide is from 40% by weight: 60% by weight to 60% by weight: 40% by weight.

A suitable mixing ratio of mechanically and/or chemically treated laitance to titanium dioxide is, for example, 50 to 50% by weight or 56 to 44% by weight.

Such mixing ratios are particularly advantageous since they reflect the actual conditions of the paper machine and ensure maximum efficiency or productivity coefficient of the paper machine relative to titanium dioxide consumption.

In one embodiment, the method according to the invention for producing filler for paper can be operated as an independent method. The resulting filler can be unloaded, stored or transported for use at another time and/or at another location.

Preferably, the method according to the invention is characterized in that the method according to the invention is integrated in a papermaking device.

In particular, the method according to the invention is integrated into a papermaking device as follows. The entire plant can be installed in the laitance line between the Krofta or titanium dioxide recovery unit and the paper machine main line, before the vertical classifier, as a new/retrofit component.

The invention also relates to fillers obtainable by the method described above.

All definitions and preferred embodiments listed for the above-described method apply analogously to the filler according to the invention.

The invention also relates to paper containing fillers obtainable by the above-mentioned method.

All definitions and preferred embodiments listed for the above-mentioned methods and for the above-mentioned fillers apply analogously to the paper according to the invention.

The paper according to the invention is preferably characterized in that it contains from 10% to 50% by weight of filler, relative to the total mass of the paper.

Preferably, the filler is a mixture of mechanically and/or chemically treated laitance and titanium dioxide, wherein the mixing ratio of the mechanically and/or chemically treated laitance and titanium dioxide is 40% by weight: 60% by weight to 60% by weight. Weight %: 40% by weight.

Suitable mixing ratios of mechanically and/or chemically treated laitance and titanium dioxide are also, for example, 50% by weight: 50% by weight or 56% by weight: 44% by weight.

The paper according to the invention is preferably characterized in that it has an ash content of 10% to 50% by weight relative to the total mass of the paper.

The paper according to the invention is preferably characterized in that it has an ash retention of at least 75% at an ash content of 39% to 42% and/or an ash retention of at least 85% at an ash content of 34% to 37.5% rate and/or have an ash retention rate of at least 85% or 87% at an ash content of 29% to 32%.

Ash retention (AR) is calculated as follows:

StWG stands for substance-water mixture.

(TiO ₂ ) powder refers to "fresh" titanium dioxide.

(TiO ₂ )page refers to the total amount of titanium dioxide in the paper.

(TiO ₂ )StWG refers to the total amount of titanium dioxide in the substance-water mixture.

C (TiO ₂ in laitance) refers to the proportion of titanium dioxide in laitance.

The paper according to the invention is preferably characterized in that it has an opacity of at least 80% or at least 90% or at least 91% or at least 92% or at least 93% and at most 99%.

Opacity is determined as follows.

First, the papers were impregnated with melamine resin, dried, and then each sheet was individually pressed onto plywood with white and black backgrounds.

Then, the paper on the plate was measured using a spectrophotometer "Datacolor Spectflash 800V".

In each case, the average of the three measurements was determined. Remove outliers before calculating the average.

CIELAB L, a, and b values are measured on white and black backgrounds (splints).

Opacity is determined by determined black and white y values.

Opacity=(Y black/Y white)*100%

These values are automatically calculated by the program on the colorimeter.

A preferred feature of the paper according to the invention is that the paper has a breaking load of at least 15 N/15 mm width, preferably at least 20 N/15 mm width.

The breaking load is measured according to the following method. First clamp the paper strip (15mm wide) and straighten it so that it does not touch the measurement surface.

The tensile test starts in automatic mode and waits for tearing. The determined value can be read on the instrument. A suitable measuring instrument is, for example, the "Horizontal Strength Tester K465" from Messmer&Büchel.

A preferred feature of the paper according to the invention is that the paper has a wet breaking load of at least 5 N/15 mm width, preferably at least 6 N/15 mm width.

The wet breaking load is measured according to the following method. Post-cure the paper in a drying oven at approximately 105°C for approximately 3 minutes. The paper strip (15 mm wide) is then placed in the water in the water container for approximately 10 seconds or according to the appropriate mass specification. Excess water is drained off.

The paper strip (15 mm wide) is then clamped and straightened so that it does not touch the measuring surface. The tensile test starts in automatic mode and waits for tearing. The determined value can be read on the instrument. A suitable measuring instrument is, for example, the "Horizontal Strength Tester K465" from the company Messmer&Büchel.

The invention also relates to the use of the paper defined above as decorative paper.

All definitions and preferred embodiments listed for the method described above and for the fillers mentioned above and for the paper mentioned above apply analogously to the use of the paper according to the invention.

Decorative paper is usually a special paper used for surface beautification (such as artificial boards). Known decorative papers are mainly produced from hardwood chemical pulp. This kind of decorative paper can be used directly in plain color or printed with various patterns. For example, they are used on furniture surfaces, floors and panels.

The invention will be explained in more detail below with reference to some non-limiting examples.

Specific implementation form

Example 1

Different papers were produced using untreated and treated laitance and analyzed. The results are summarized in Tables 1 to 3 below.

Laitance comes from conventional paper machines and is processed as follows.

The _TiO2 content in the laitance is 2.7% by weight. The laitance was shear-mixed and stabilized simultaneously with an anionic dispersant (Topsperse GX N from COATEX) in a ratio of 0.8% by weight relative to the _TiO content (absolute dry/absolute dry). The shear is produced by the "Ultra Turrax CAT X1740" in 30 seconds at 250Hz. The mass of the treated floating slurry part is 300g.

The paper studied has the following key data:

FLG[gsm]:80

Mass (page), g: 2.51

Amount of water per can, grams: 2000

Chemical pulp per can, g: 50

Opacity, %: 90-93

Ash content (at 900 degrees), %: 29-42

Ash retention rate, %: 74-91

Table 1:

Table 2:

table 3:

StWG: substance-water mixture

ΔL: brightness difference

EKA: Trade name of retention aid EKA NP

Opacity: degree of opacity

Formation: the spatial distribution of fibers and fillers in the paper web

The ash retention rate is calculated according to the following formula:

In addition, the saving potential of "fresh titanium dioxide" is analyzed.

The results are shown in Table 4 below:

Table 4:

STD: existing technology

Wet Opacity: The opacity of impregnated and pressed paper, measured as defined in the specification above.

The papers defined in Tables 1 to 3 were analyzed and actual and target (potential) consumption were deduced. Table 4 summarizes the corresponding values.

Example 2:

Produce three sheets of paper according to Table 5 below and check the efficiency for possible color shift.

table 5:

ΔE: Color difference (according to CIELab color space). Color difference can be calculated by the following formula (in automatic mode)

Color measurements were performed on paper N1 and N2 minus 20%, and the resulting color difference remained within the tolerance.

The results are shown in Figure 1.

Example 3:

Different papers were tested for breaking load and wet breaking load. The results are summarized in Table 6. The paper according to the invention has a higher breaking load and a higher wet breaking load.

Table 6:

mA, gsm: face weight

Wet breaking load, N/15mm strip: Static strength in wet conditions

Breaking Load, N/15mm Strip: Static Strength

Breaking load and wet breaking load are determined as defined in the instructions.

Example 4:

Some papers were examined with a scanning electron microscope. The results are shown in Figures 3 to 6. Shown in each case are screenshots at different magnifications.

Figure 2: Prior art 50 wt% _TiO2 , 50 wt% untreated laitance, 40 wt% ash, 80gsm

Figure 3: V1 50 wt% _TiO2 , 50 wt% treated laitance, 0.1 wt% absolutely dry dispersant, versus absolutely dry titanium dioxide in laitance (30 sec-250Hz-batch), 40 Weight % ash, 80gsm

Figure 4: V2 50 wt% _TiO2 , 50 wt% treated laitance, 0.4 wt% absolutely dry dispersant, versus absolutely dry titanium dioxide in laitance (30 sec-250Hz-batch), 40 Weight % ash, 80gsm

Figure 5: V3 50 wt% _TiO2 , 50 wt% treated laitance, 0.8 wt% absolutely dry dispersant, versus absolutely dry TiO2 in laitance (30 sec-250Hz-batch), 40 Weight % ash, 80gsm

In Figure 2, a closed surface and many titanium dioxide aggregates can be seen. The individual particles of pigment, which have a major influence on good opacity, are barely visible. In this case, no treatment is performed on the laitance, or the laitance is used in its natural state.

Figure 3 shows a scanning electron microscope image of paper produced with treated laitance. The treatment was carried out using UltraTurrax with a rotor frequency of 250 Hz, a treatment time of 30 seconds and by adding 0.1% by weight of absolutely dry anionic dispersant (Topsperse GX N from COATEX). It can be seen that although the number of titanium dioxide aggregates is reduced and individual particles can be detected, the surface remains relatively closed.

Figure 4 shows a scanning electron microscope image of paper produced with treated laitance. The treatment was carried out using UltraTurrax with a rotor frequency of 250 Hz, a treatment time of 30 seconds and by adding 0.4% by weight of absolutely dry anionic dispersant (Topsperse GX N from COATEX). Here the surface becomes more porous, which is very advantageous for decorative papers. Chemical pulp fibers are better and more completely covered by individual titanium dioxide particles, and individual particles can be recorded clearly and distinctly.

Figure 5 shows a scanning electron microscope image of paper produced with treated laitance. The treatment was carried out using UltraTurrax with a rotor frequency of 250 Hz, a treatment time of 30 seconds and by adding 0.8% by weight of absolutely dry anionic dispersant (Topsperse GX N from COATEX). The surface is porous, which is very advantageous for decorative paper. The pulp fibers are almost completely covered by individual titanium dioxide particles, and the individual particles can be recorded clearly and distinctly. Aggregations of titanium dioxide are barely visible.

Example 5:

Systems or prototypes for mechanical and chemical treatment of laitance are installed on paper machines within the Hydromix line of TiO ₂ recovery units. The schematic diagram of the production device is shown in Figure 6.

The two units (1) are installed in parallel in the line (2) in order to be able to process the entire volume flow. A container called a dosing station (4) ensures dosing of the dispersant with a dosing pump (5). The control of aggregation or the generation of shear forces is controlled by the frequency controller (3). The volumetric flow rate of the laitance is continuously monitored and the dispersant dosage is adjusted accordingly. The total volume flow of the laitance can be distributed and directed via the control valve (6).

(1)- ShearMaster or unit used to generate shear force

(2)-Laitance pipeline

(3)-Motor control

(4)-Dispersant batching station

(5)-Dispersant dosing pump

(6)-Control valve / division of laitance flow (if required).

Claims (15)

1. A method for producing filler for paper, which includes the following steps: - providing laitance from a paper recycling process, wherein said laitance contains titanium dioxide, - mechanical and/or chemical treatment of these laitances, and - Mixing mechanically and/or chemically treated laitance with titanium dioxide. 2. The method according to claim 1, characterized in that the floating slurry is obtained by supplying compressed air and adding a flocculant. 3. Method according to any one of the preceding claims, characterized in that the mechanical treatment of the laitance comprises the use of shearing forces. 4. Method according to any one of the preceding claims, characterized in that the chemical treatment of the laitance comprises incubating the laitance with a dispersant, preferably an anionic dispersant. 5. Method according to any one of the preceding claims, characterized in that the laitance from the paper regeneration treatment contains from 0.5% to 5% by weight of titanium dioxide. 6. Method according to any one of the preceding claims, characterized in that the laitance from the paper recycling process contains titanium dioxide with an average particle size greater than 2 μm. 7. Method according to any one of the preceding claims, characterized in that the mechanically and/or chemically treated laitance contains titanium dioxide with an average particle size (D50) of 300 to 400 nm. 8. The method according to any one of the preceding claims, characterized in that the mixing ratio of the mechanically and/or chemically treated laitance and titanium dioxide is 40% by weight: 60% by weight to 60% by weight: 40% by weight. . 9. Method according to any one of the preceding claims, characterized in that it is integrated in a papermaking device. 10. A filler for paper obtainable by the method of any one of claims 1 to 9. 11. Paper comprising the filler of claim 10. 12. Paper according to claim 11, characterized in that the paper contains 10 to 50% by weight of filler relative to the total mass of the paper. 13. Paper according to claim 11 or claim 12, characterized in that the paper contains an ash content of 10% to 50% by weight relative to the total mass of the paper. 14. Paper according to any one of claims 11 to 13, characterized in that it has an opacity of at least 80%. 15. Use of the paper according to any one of claims 11 to 14 as decorative paper.