FI127948B

FI127948B - Method and device for starch application

Info

Publication number: FI127948B
Application number: FI20170013A
Authority: FI
Inventors: Christoph Henninger; BENJAMIN MéNDEZ-GALLON; Michael Doermann
Original assignee: Voith Patent Gmbh
Priority date: 2017-02-01
Filing date: 2017-02-01
Publication date: 2019-05-31
Also published as: AT519598A3; AT519598A2; FI20170013L; AT519598B1; DE102018100924A1

Abstract

Method and device for the application of starch on a moving fiber web, especially on a testliner or a corugated medium web, where first starch is applied to either one side or both sides of the fiber web and then the fær web is passed through a treatment nip formed by a first roll and a second roll, characterized in that at least one of the first or the second roll, preferably both rolls heve a hardness of 15 P&J (Pusey & Jones) or lower.

Description

Method and device for starch application

20170013 prh 20 -03- 2019

The invention relates to a method and a device for treating a fiber web. Especially, the invention relates to a method for the application of starch according to the preamble 5 of claim 1 and a device for the application of starch according to the preamble of claim 6.

For the production of paper, board and packaging web the use waste paper is increasing do to its economic and environmental benefits. Especially for grades like io testliner (TL) or corrugated medium (CM) waste paper is usually the only fiber source that is used. But the quality of the waste paper that is used for these grades has been seen deteriorated over the last years since the number of recycling cycles is increasing. The accumulation of fillers and a reduction of fiber quality due to mechanical and chemical damaging of the fibers lead to a reduction in several 15 strength properties of the produced board and packaging papers.

The addition of fillers like mineral pigments (e.g. CaC03, T1O2, sand...) reduces the wet web strength of the paper. This causes an increased number of sheet breaks during production.

The deteriorated fiber quality, e.g. the reduced fiber length, can be partially compensated by the treatment of the fiber web with synthetic binders like polymeriatex. Alternatively, the fiber web can be treated with natural binders like starch. Since the use of polymer-latex is usually expensive, the use of starch is often preferred.

The applicaction of starch is a standard for a long time. Starch may be applied directly in the pulp stock or may be sprayed on a wet web in the forming section of a paper machine. But starch is also applied in a more efficient way after the press section and a pre-drying section. Here, the starch can also be sprayed on the fiber web, but is 30 usually applied with a film press or a sizepress. As an example DE 10 2011 076718 describes the use of a size press in the production of testliner, in the case of recycled fibers with low quality.

Due to the mentioned decreasing quality of the fiber material, and also due to the increased production speed for most paper grades including TL and CM, there is a

-220170013 prh 20 -03- 2019 need in the industry for an efficient way to further increase the strength properties of the web.

The application WO 2012 072873 A3 shows a spray applicator device for starch.

The object of the invention is therefore to provide a technologically and economically efficient way to increase the strength of the fiber web.

A further object of the invention is to provide an efficient way to apply starch to a moving fiber web.

io Another object of the invention is to provide a method for the stable production of testliner (TL) and corrugated medium (CM) even with a low quality of the raw material.

The above objects and those which will become apparent later have been fully reached by a method according to the features of claim 1 and a device according to 15 the features of claim 6.

Concerning the method, the object is reached by method for the application of starch on a moving fiber web, especially on a testliner or a corrugated medium web, where first starch is applied to either one side or both sides of the fiber web and then the 20 fiber web is passed through a treatment nip formed by a first roll and a second roll, characterized in that at least one of the first or the second roll, preferably both rolls have a hardness of 15 P&J (Pusey & Jones) or lower.

The hardness according to P&J is a common measure for rolls. It can be determined 25 by commercially available devices like the Zwick 3108 P&J hardness tester, meeting the requirements of ASTM D531-89 standard.

If not stated otherwise, the term hardness of a roll is understood as the hardness of the outer layer or cover of the respective roll, even if the inner layers, i.e. those not 30 contacting the fiber web, may have a different hardness.

-320170013 prh 20-03-2019

The inventors surprisingly discovered that by using one or even two rolls with a relatively high hardness in a treatment nip, the starch can be transferred to the fiber web much more efficiently. Today, the rolls in standard sizepresses or film-presses have a hardness of 20 P&J or higher, that means, the rolls today are significantly 5 softer than in the present invention. This harder roll has been found to improve the starch transfer to the fiber web.

The application of the starch according to the invention may be realized in all application means known in the field, including but not limited to the following:

io It can be applied to only one side of the fiber web or to both sides simultaneously.

The starch may be directly applied to the fiber web for example by means of spray technology or by means based on pond technology.

The starch may alternatively be applied indirectly. Here, starch may be applied to one or both rolls -e.g. by metering or spraying- and then transferred to the fiber web at the 15 nip between the rolls.

Advantageous features of the inventive method are described in the dependent claims.

It may be advantageous to use even harder rolls. In some applications, at least one of the first or the second roll, preferably both rolls have a hardness of 5 P&J or lower, preferably 1 P&J or lower.

In an advantageous variant, the treatment nip may be formed by two hard rolls, 25 having a hardness of 15 P&J and less. This combination can further improve the starch transfer to the fiber web.

In another advantageous variant, the treatment nip may be formed by a hard roll, having a hardness of 15 P&J and less with a softer roll. The softer roll may have a 30 hardness of more than 15 P&J, especially more than 20 P&J

The fiber web according to the present invention may be a single layer or a multi-layer web. The layers of the multi-layer web can be produced in two, three or more forming

-420170013 prh 20 -03- 2019 sections and joined together, usually before the inventive starch application. Such multi-layer webs are common for TL and CM applications.

As described earlier, the fiber web can be produced, using fibers generated from waste- paper. Here, the strength generating effect of the invention is especially 5 beneficial.

In order to further improve the starch transfer, the lineload of the treatment nip may be chosen between 30 kN/m and 140 kN/m, preferably between 60 kN/m and 100 kN/m.

io The production speed for TL and CM on modern machines is very high, at least more than 800 m/min. The standard is more than 1000 m/min, going up to 1500 m/min or even 1900 m/min. At such high speeds, the efficient starch transfer is especially important, since they are usually operating at the upper strength limit of the web, and an increase in speed is probably limited by a lack of strength in the fiber web.

In some applications, it may be beneficial to adapt the properties of the starch used. There, a solid content of the starch between 6% and 25%, preferably between 8% and 18% can be chosen.

A viscosity between 5 mPas and 60 mPas, preferably between 10 mPAs and 40 20 mPas of the starch may be chosen.

The combination of the above mentioned solid contents and the viscosity has been found to be especially beneficial.

If not otherwise stated, viscosity values in this application are always understood as 25 Brookfield viscosities measured at 50°C with 100 rpm.

The starch may be applied at a temperature between 50°C and 80°C.

Usually, after the starch application and some further drying, the fiber web is reeled at 30 a reeler. In some preferred applications, e.g. for TL and CM, the basis weight of the fiber web at the reeler can be between 60 g/m² and 250 g/m², more often between 90 g/m² and 170 g/m².

-520170013 prh 20 -03- 2019 ln a preferred realization of the method, the application of starch in the inventive step is adjusted such that the starch content of the fiber web at the reeler lies between 2,5% and 6% of the basis weight. This amount of starch is usually sufficient to achieve the desired increase in strength properties.

In another preferred realization of the method, the crowning of the rolls may be adapted to obtain a length to the treatment nip that is homogeneous over the cross directional width of the rolls.

Concerning the device, the object is reached by a device for the application of starch io on a moving fiber web comprising a first roll and a second roll positioned to form a treatment nip for the fiber web as well as means for the direct or indirect application of starch on the fiber web characterized in that at least one of the first or the second roll, preferably both rolls have a hardness of 15 P&J (Pusey & Jones) or lower.

Again, advantageous features are described in the dependent claims.

It may be advantageous to use even harder rolls. In some applications, at least one of the first or the second roll, preferably both rolls have a hardness of 5 P&J or lower preferably 1 P&J or lower.

²⁰

In an advantageous embodiment, the treatment nip may be formed by a hard roll, having a hardness of 15 P&J and less with a softer roll. The softer roll may have a hardness of more than 15 P&J, especially more than 20 P&J. This combination can further improve the starch transfer to the fiber web.

In preferred embodiments of the application device, the diameters of the first roll and the second roll are the same or differ by less than 10%.

Depending on the fiber web and also on the production speeds, using such a relatively hard nip for size application may generate unwanted vibrations. If the two 30 rolls have the same size, or approximately the same size, this tendency to create vibrations can be reduced, therefore increasing the stable runability of the machine.

-620170013 prh 20 -03- 2019

Usually it will be advantageous if the diameters of the first roll and/or the second roll are between 0.25m and 2m, especially between 0.7m and 1.8m.

In another preferred embodiment of the device the first roll has a cover comprising a 5 metal or a ceramic with a layer thickness between 50pm and 150 pm and/or the second roll has a cover comprising one of a rubber, a polyurethane or a composite material with a layer thickness between 10mm and 20mm.

When choosing the layers, several aspects should be considered. At first, the desired hardness of the invention has to be reached. Additionally, a higher thickness of a io layer can increase the possible running time of the roll. On the other hand are rolls with e.g a thicker top layer more likely to generate unwanted vibrations. The values given above represent an optimal compromise for many applications.

It should be noted, that the rolls in the device may be in principal of any type used in 15 the field. In some embodiments it may for example be beneficial if at least one of the rolls is a shoe-roll or a controlled deflection roll.

The positioning of the rolls may be chosen freely. The first and the second roll may be places side by side with the fiber web moving vertically through the nip.

Alternatively they may be placed on top of each other with the web passing horizontally. But any oblique positioning is also possible.

If the fist and the second roll have different hardness, while they may be in general be positioned in any way, it may be preferable to choose the higher position for the soft roll.

In another preferred embodiment, at least one of the first or the second roll comprises sensor means to measure the nip load. In an even more preferred embodiment, these sensor means are means to measure a cross directional profile of the nip load. Such means can comprise among others fiber optical sensors, one or more sensors bases 30 on Piezzo elements, or film sensors.

-720170013 prh 20 -03- 2019 lf the first and the second roll have a different hardness, it may be beneficial to position sensor means at or in the softer roll. In an even more preferred embodiment, these sensor means are also capable of determining the length of the treatment nip (e.g. the machine directional length), especially over the whole cross-directional width 5 of the treatment nip.

Based on the measurements of such sensor means, it is possible to adjust for example the crowning of a roll and/or the nip load to adjust the conditions in the treatment nip and optimize the starch transfer to the web depending on the io characteristics of the produced product like for example the thickness of the web, the base weight or the quality of the used fiber material.

In the following, the invention is described in more details with reference to the accompanying drawings:

Figure 1 shows a schematic view of a device according to one aspect of the invention.

Figure 2 shows a schematic view a device according to another aspect of the invention.

Figure 3 shows a schematic view a device according to another aspect of the 20 invention.

Figures 4a and 4b show different embodiments of a roll with sensing means according to another aspect of the invention

In Figure 1 the device according to one aspect of the invention comprises a first roll 1 25 and a second roll 2, forming a treatment nip 6. The fiber web 5, which may for example be a testliner (TL) or corrugated medium (CM) web 5, passes through the nip 5. Since the rolls are placed in an oblique position, the web 5 is also moving in an oblique direction, preferably at an angle of about 45° w.r.t. the horizontal line.

Here, the starch is applied by two metering devices 3 to the surface of the rolls 1,2, 30 and from here transferred to the web 5 in the nip. In order to achieve an improved transfer of the starch to the web, one roll 1,2 or even both rolls 1,2, have a hardness

-820170013 prh 20 -03- 2019 of 15 P&J (Pusey & Jones) or lower. Especially at least one roll may have a hardness of less than 5 P&J or even less than 1 P&J.

The diameter of the rolls 1,2 is in the example of figure 1 chosen to be equal, in the range between 0.7m to 1.8m, but can be larger or smaller, depending on the 5 application.

The starch used between can have a solid content between 6% and 25%, preferably between 8% and 18%.

In addition, a viscosity between 5 mPas and 60 mPas, preferably between 10 mPAs and 40 mPas of the starch may be chosen.

io The nipload of the nip 5 can be set in the range between 30 kN/m and 140 kN/m, preferably between 60 kN/m and 100 kN/m. One roll 1, 2 can for example be chosen to comprise a layer of ceramic or metal, while the other roll may comprise layer of rubber, polyurethane or a composite material.

The typical starch amount that is transferred with a device according to the invention is usually between 2.5% and 6% of the basis weight.

Figure 2 shows an embodiment of another aspect of the invention.

While the device according to figure 2 may comprise similar rolls 1, 2 as the device in figure 1, they are positioned side by side and the fiber web 5 is moving vertically 20 through the nip. In this embodiment, the starch is applied to the rolls 1, 2, by spraying via spray applicators 3a.

It should be noted, that in a similar embodiment, the starch could be sprayed by the spray applicators 3a instead of the rolls 1, 2 directly to the moving web before it enters the nip.

All the features concerning roll size, hardness or composition, nip load and starch properties mentioned for the embodiment of figure 1 are also valid for the embodiment of figure 2.

The embodiment of figure 3 is very similar to the embodiment of figure 2. It only 30 differs in the way the starch is applied to the fiber web 5. The embodiments of figures and 2 show an indirect application, where starch is first applied to the first and second roll 1, 2 and transferred to the web 5 in the treatment nip 6. In contrast, figure shows an embodiment with a direct application. Here, starch is simultaneously sprayed by spray applicators 3a to the web 5 before it passes the treatment nip 6.

Devices like the embodiments shown in the figures are capable of being used to 5 perform methods according to the present invention.

Figures 4a apd 4b show a first or a second roll 1,2, comprising a set of sensor means to measure the nip load. The sensor means 4 in these examples are connected by a signal carrier 10. This signal carrier may carry electrical or optical signals, io depending on the nature of the sensing means.

In Figure 4a, the sensing means are all positioned along a line in crossmachine direction. In the embodiment in figure 4b, the sensor means are positioned helically around the circumference of the roll 1,2.

The sensor means 4 may for example be included in the top layer 20 or cover of the 15 roll 1,2, or be positioned between the top layer and the next following layer.

20170013 prh 20 -03- 2019

Claims

20170013 prh 20 -03-20199

A method for spreading starch on a moving fibrous web (5), in particular on a testliner web (5) or on a corrugated board web (5), wherein the first starch is applied to one of the fibrous web (5) or

5 on each side and then the fibrous web (5) is passed through a treatment pin (6) of the first roll (1) and the second roll (1), and the hardness of the first roll (1) and the second roll (2) is 15 P&J (Pusey & Jones) or smaller, preferably 5 P&J or less, most preferably 1 P&J or less, characterized in that the diameter of the first roll (1) and / or the second roll (2) is 0.7-2 m, in particular 0.710 1.8 m, the diameters of the first roll (1) and the second roll (2) being equal or less than 10%.

Method according to one of the preceding claims, characterized in that the line load in the treatment nipple (6) is 30-140 kN / m, preferably 60-100 kN / m.

15

Method according to one of the preceding claims, characterized in that the fibrous web (5) passes through the nip at a speed of more than 800 m / min, preferably 1000-1900 m / min.

Method according to one of the preceding claims, characterized in that the starch is applied in a form having a solids content of 6-25%,

20 preferably 8 to 18% and / or a viscosity of 5 to 60 mPas, preferably 10 to 40 mPas.

Method according to one of the preceding claims, characterized in that the starch content of the fibrous web (5) in the coil is 2.5-6% by weight.

Apparatus for spreading starch on a moving fibrous web (5), comprising: a first roll (1) and a second roll (2) positioned so that

25 form a treatment nip (6) for the fibrous web (5), and means (3, 3a) for directly or indirectly applying starch on the fibrous web (5), the first roll (1) and the second roll (2) having a hardness of 15 P & Jones) or smaller, preferably 5 P&J or less, most preferably 1 P&J or less, characterized in that the diameter of the first roll (1) and / or the second roll (2) is

-20.7-2 m, in particular 0.7-1.8 m, wherein the diameters of the first roll (1) and the second roll (2) are equal or differ by less than 10%.

Device according to Claim 6, characterized in that the first roll (1) has a cover (6) which contains metal or ceramic material,

5 with a layer thickness of 50-150 µm, and / or the second roll has a cover (6) comprising one of rubber, polyurethane or composite material, the layer thickness being 10-20 mm.

Device according to one of Claims 6 to 7, characterized in that at least one of the first roll (1) and the second roll (2) comprises sensor means (11) for measuring nip load.

Device according to one of Claims 6 to 8, characterized in that the hardness of the first roll (1) and the second roll (2) is 5 P&J or less, in particular 1 P&J or less.

Device according to one of Claims 6 to 9, characterized in that the means (3, 3a) for applying the starch directly or indirectly to the fibrous web (5) comprises at least one spray applicator (3a).