Device for applying a treatment substance

Abstract

Device for applying a treatment substance (2.1, 2.2), in particular starch, on at least one side of a running product web (13), in particular a paper or board web, by means of a least one curtain coater (1.1, 1.2) having a discharge nozzle (14.1, 14.2) and at least one press nip (N) following the curtain coater (1.1, 1.2) for forming a hydraulic pressure when the product web (13) passes through a press nip (N) which is formed by one of two rotating press rolls and which causes the treatment substance (2.1, 2.2) to penetrate into the product web (13), wherein the at least one press nip (N) is equipped with at least one heated applicator roll (7, 8) as a press roll to increase the penetration of the treatment substance (2.1, 2.2) into the product web (13), and at least one of the two press rolls (8) is designed with a fixed or adjustable crown (16) for the adjustment of a line load in a range of 20 to 200 kN/m.

Claims

1. Device for applying indirectly a treatment substance, the treatment substance including: starch, on at least one side of a running product web, the running product web including at least one of a paper or board web, by means of at least one curtain coater having a discharge nozzle; at least one press nip for forming a hydraulic pressure when the product web passes through a press nip which is formed by one of two rotating press rolls and which causes the treatment substance to penetrate into the product web, wherein the at least one curtain coater has a discharge nozzle having an outlet slot with a manufacturing tolerance in a range of ±2.5 μm to ±10 μm in slot length with a slot width of 0.2 to 2.0 mm and the at least one press nip is equipped with at least one heated applicator roll as a press roll to increase the penetration of the treatment substance into the product web, and at least one of the two press rolls includes a crown for adjusting of a line load in a range of 20 to 200 kN/m to increase the range of manufacturing tolerances of the discharge nozzle; and a sump being formed at, or immediately in front of, the press nip when the line load is in the range of 20 to 200 kN/m, wherein the sump is formed at a feed area of the press nip where a parallelism of roll contact surfaces is achieved by compensating for a deflection of the rolls due to the line load.

2. Device according to claim 1, wherein the press nip is a hard nip.

3. Device according to claim 1, wherein a distance of the respective curtain coater with respect to the press nip is adjustable for an arrangement for an indirect application of the treatment substance with a selectable dwell time for a transfer of heat from the least one heated applicator roll to the treatment substance.

4. Device according to claim 1, wherein the curtain coater is configured to apply a multi-layer curtain.

5. Device according to claim 1, wherein the press roll with adjustable crown is a controlled deflection roll.

6. Device according to claim 1, wherein both press rolls of the press nip are heated applicator rolls.

7. Device according to claim 1, wherein the applicator rolls of the press nip have coatings with less than a hardness of 30 P&J.

8. Device according to claim 1, wherein the press rolls of the press nip are applicator rolls for a roll surface temperature of 50° C. to 150° C.

9. Device according to claim 1, wherein the press nip is configured to accommodate line loads in the range of 20 kN/m to 200 kN/m.

10. Device according to claim 1, wherein an angle α for a contact point of the curtain of the treatment substance on an applicator roll of the press nip is between −90° and +45°.

11. Device according to claim 1, wherein the at least one curtain coater is configured to control a solids content of the treatment substance in at least one layer of 25% to 55%.

12. Device according to claim 1, wherein the crown is fixed or adjustable.

Description

(1) The invention is explained in more detail below using the exemplary embodiments shown in the appended figures.

(2) FIG. 1 schematically shows a device including liquid film coating devices and discharge nozzles according to a first exemplary embodiment,

(3) FIG. 2 schematically shows a device including liquid film coating devices and discharge nozzles according to a second exemplary embodiment.

(4) As FIG. 1 shows, the invention relates to a device for the indirect application of a treatment substance 2.1, 2.2, in particular starch, on at least one side of a running product web 13, in particular a paper or board web, by means of at least one curtain coater 1.1, 1.2 having a discharge nozzle 14.1, 14.2. The at least one curtain coater 1.1, 1.2 is followed by a press nip N for forming a hydraulic pressure when the product web 13 passes through the press nip N, which causes the treatment substance 2.1, 2.2 to penetrate into the product web 13. The press nip N is preferably a hard nip, which is formed by two hard rolls, the applicator rolls 7, 8.

(5) The at least one curtain coater 1.1, 1.2 is designed to discharge a treatment substance 2.1, 2.2 having a solids content in at least one layer of between 10% and 40%. To increase the penetration of the treatment substance 2.1, 2.2 into the product web 13, the at least one press nip N is equipped with at least one heated applicator roll 7, and the heated applicator roll 7 and/or a counter element is designed as an applicator roll 8 having a fixed or an adjustable crown 16.

(6) The curtain coater 1.1, 1.2 has a discharge nozzle 14.1, 14.2 having an outlet slot 15 which has an accuracy in the range of ±2.5 μm to ±10 μm in the slot length with a slot width of preferably 0.2 to 1.5 mm.

(7) As shown by the arrows X, the distance of each curtain coater 1.1, 1.2 to the press nip N is adjustable for an arrangement for indirect application of the treatment substance 2.1, 2.2 with a selectable dwell time of the heat transfer from the at least one heated applicator roll 7 to the treatment substance 2.1, 2.2 and/or the product web 13, as will be explained below.

(8) The applicator roll 8 with adjustable crown 16 is preferably a controlled deflection roll. Preferably, both applicator rolls 7, 8 of the press nip N are also designed as heated rolls. The applicator rolls 7, 8 of the press nip N preferably have coatings with less than 30 P&J. Furthermore, the applicator rolls 7, 8 of the press nip N are designed for a roll surface temperature of 50° C. to 150° C., preferably 100° to 120° C. The line load can be selected in the range of 20 kN/m to 200 kN/m

(9) An angle α for a contact point of the curtain of the treatment substance 2.1, 2.2 on an applicator roll 7, 8 of the press nip N is preferably between −90° and +45°. Furthermore, the respective curtain coater 1.1, 1.2 is designed to control the solids content of the treatment substance 2.1, 2.2 in at least one layer of 25% to 55%.

(10) The application weight of the treatment substance per side can be 0.5 to 6 g/m.sup.2 and the temperature of the treatment substance, in particular the starch, can be in the range of 55° to 99° C. before it is applied to an applicator roll 7, 8. Furthermore, the viscosity of the treatment substance can be significantly higher than that in film presses, namely 20 to 500 mPa s (Brookfield 100 rpm). The specific volume flow from the nozzle of the curtain coater 1.1, 1.2 is in the range of 4 l/(min×m) to 30 l/(min×m). A film of the treatment substance 2.1, 2.2, in particular starch, in the range of 5 ml/m.sup.2 to 100 ml/m.sup.2 is preferably applied to the respective applicator roll 7, 8.

(11) Finally, guide rolls 12 can also be provided which determine a treatment path of the running product web 13 between curtain coater 1.1, 1.2 and press nip N.

(12) According to FIG. 1, for a one-sided and, for example, single-layer application, the treatment substance 2.1, in particular starch, is firstly applied by a curtain coater 1.1 to a rotating applicator roll 7. For a two-sided application, a further, for example single-layer treatment substance (film) 2.2 is applied to a second rotating applicator roll 8 using a second curtain coater 1.2. The dwell time of the treatment substance 2.1, 2.2 on the respective applicator roll 7, 8 until it enters the press nip N can be selected individually for each side and can therefore also be selected differently. The position of the respective curtain coater 1.1, 1.2 with respect to the associated applicator rolls 7, 8 can be changed in the direction of the arrow X for this purpose by means, for example, of horizontal and possibly additional vertical displacement.

(13) A specific length of the outer roll circumference defines a dwell time, so that the time between the curtain contact and its entry into the press nip N can be set, thus increasing or decreasing the dwell time, as indicated by the angle α. If the applicator roll 7, 8 is heated, the dwell time can be used to influence an increase in temperature of the treatment substance 2.1, 2.2 before it enters the press nip N. The treatment substance 2.1, 2.2 can then be thermally pre-treated and pressed into the product web 1 on both sides in the press nip N between the applicator rolls 7, 8.

(14) In a known manner, a starter trough 4.1, 4.2 with quick-start equipment 5.1, 5.2. can be assigned to each curtain coater 1.1, 1.2. The same applies to the provision of collecting troughs 9.1, 9.2, doctors 10.1, 10.2 and spray-water nozzles or steam nozzles 11.1, 11.2 for cleaning of the applicator rolls 7, 8. The diameter of the applicator rolls 7, 8 can be, 400 to 1800 mm, for example. Instead of heated applicator rolls 7, 8, heated transfer belts can also be used.

(15) According to FIG. 2, a multilayer curtain coater 1.1, 1.2 is provided respectively. Two-layered liquid film coating is used for example. Both curtain coaters 1.1, 1.2 can also be designed differently as multi-layered. When a two-layered design is used, starch for penetrating into the product web can be applied as an inner layer, for example. The outer (second) layer can be, for example, a pigment coating. The solids content of the starch in the 1.sup.st layer can be, for example, 6% to 50%, preferably 15% to 35%. The solids content of the coating colour in the 2.sup.nd layer can be in the range of 20% and 68%. Alternatively, the respective, for example two-layered, curtain can consist of two starch layers. The 1.sup.st layer can have a lower concentration of starch, in order to achieve higher penetration for high delamination strength. A 2.sup.nd layer with a higher starch concentration increases the modulus of elasticity of the outer layers close to the surface and therefore achieves a higher bending stiffness.

(16) This results in great technological advantages, and a high economic efficiency of the system results from the considerably reduced energy consumption for the evaporation of excess water with a high starch concentration. With the same strength it is possible to save raw materials by reducing the quantity of fibre in the paper or board.

(17) In all other respects, the above explanations relating to FIG. 1 apply accordingly.

(18) The invention now being folly described, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the appended claims.