Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/22—Addition to the formed paper
  • D21H23/46—Pouring or allowing the fluid to flow in a continuous stream on to the surface, the entire stream being carried away by the paper
  • D21H23/48—Curtain coaters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C11/00—Component parts, details or accessories not specifically provided for in groups B05C1/00 - B05C9/00
  • B05C11/10—Storage, supply or control of liquid or other fluent material; Recovery of excess liquid or other fluent material
  • B05C11/1039—Recovery of excess liquid or other fluent material; Controlling means therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C5/00—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work
  • B05C5/007—Slide-hopper coaters, i.e. apparatus in which the liquid or other fluent material flows freely on an inclined surface before contacting the work
  • B05C5/008—Slide-hopper curtain coaters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C5/00—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work
  • B05C5/02—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work the liquid or other fluent material being discharged through an outlet orifice by pressure, e.g. from an outlet device in contact or almost in contact, with the work
  • B05C5/0254—Coating heads with slot-shaped outlet
  • B05C5/0266—Coating heads with slot-shaped outlet adjustable in length, e.g. for coating webs of different width
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/78—Controlling or regulating not limited to any particular process or apparatus

Definitions

• the invention relates to a method for determining the amount of coating 5 agent in coating agent layers applied on a fibrous web, in respect of individual coating agent layers in multilayer curtain coating, in which method the fibrous web is coated by curtain coating with two or more coating agent layers using a slide-fed curtain coater comprising a nozzle beam with at least two feed chambers and the nozzle slots relating to them for feeding at least 10 two coating agent layers on the runoff slide formed by the nozzle beam.
• the invention also relates to an apparatus for implementing the method.
• the thickness of the coating has been measured, among others, by carrying out web measurement, for example, by means of a measuring frame both before and after applying the coating.
• the amount of coating in the different layers cannot be determined by measuring the web with online meters after applica-
• the width of the coating curtain or the width of the nozzle beam of the curtain device differs from the coating itself.
• the band established by the coating applied on the fibrous web does not necessarily correspond to the width of the coating band on the runoff slide of the nozzle beam or to the width of the coating curtain falling later from the runoff slide or at least does not directly correlate with it.
• the nozzle beam is used to adjust the edges of the coating paste layers formed on the runoff slide and part of the coating material is recycled at the same time, resulting in that the width of the coating curtain is analogous to the width of the realized coating or at least directly correlates to its width - minor nominal crawling can occur though in the coating curtain prior to the application point.
• the edges of the coating material layers are not adjusted on the runoff slide of the nozzle beam, but in so called over-the-edge coating part of the coating curtain exceeds the edges of the web.
• the edges of the coating material layers are adjusted on the runoff slide of the nozzle beam and part of the coating material is recycled at this stage and in addition, part of the coating curtain is guided over the edges of the web.
• the final amount of the coating on the web itself depends among others on this selection of the coating method as well as on how large proportion of the total flow of the coating material flows specific to separate coating material layers that circulate in the coating apparatus ends up on the surface of the fibrous web and how large proportion is recycled or guided to pass the fibrous web.
• the object of the present invention is to solve the foregoing problems and to provide a simple and reliable method for measuring the amount of coating in individual coating agent layers, also regardless of the aforesaid coating methods .
• a further aim is to reduce the costs of the technology based on the cur- rent measuring methods.
• the method according to the invention is characterised by what is disclosed in the characterising part of the first claim.
• Preferred embodiments of the invention are disclosed in the dependent claims.
• the measurement of the flow of coating agent is first arranged to be carried out on each coating agent layer, on its feed line, before the coating agent is fed into the coating agent layer feed chamber in the nozzle unit and from there further to the runoff slide.
• the measurement of the amount of coating agent is, therefore, carried out in layers, preferably separately for each layer of coating agent.
• the amount of coating agent in an individual coating agent layer is calculated in accordance with the invention, on the basis of the measurement results, by taking into account at least the running speed of the machine and the width of the coating belt, that has finally been applied on the fibrous web or the width of the coating curtain applied on the web or even the width of the coating on the runoff slide of the nozzle beam.
• the observation of the width of the coating covers all the aforesaid manners freely selected.
• the width stands for the width in cross direction (CD) to the fibrous web.
• the measurement of the amount of coating agent can obviously be carried out for one or more or each coating agent layer.
• the coating agent feed may be increased or reduced as desired for each coating agent layer.
• the method according to the invention is simple and reliable. By means of the method, it is possible to completely avoid online measurement following application. Significant savings are at the same time made in respect of the investment and operating costs of the latter measuring frame.
• the method according to the invention is particularly well suited for the multilayer curtain coating of printing papers and special papers, where the amounts of coating agent in individual coating agent layers may be small. In such a case, determining the amount of coating agents and the grammages of different layers by other methods is particularly difficult. Especially in connection with special papers, the amounts of coating agent may be particularly small due to, for example, the high price of the coating agents.
• Figure 1 shows highly diagrammatically an arrangement implementing the method for determining the amount of coating agent specific to a layer of coating agent
• Figure 2 shows a diagrammatic cross-sectional view of the area of one edge of the nozzle beam in connection with an embodiment of the invention.
• Figure 1 shows highly diagrammatically the arrangement according to the invention for coating a fibrous web W by means of a slide-fed applicator beam 1 as multilayer curtain coating.
• the web W is coated with coating 14 consisting of three separate coating material layers.
• the measurement of the coating agent flow itself may be carried out on the feed line 22 of each coating agent layer 44, respectively, before feeding the coating agent into the coating agent layer specific feed chamber 12 in the nozzle unit 10. Measurement is most preferably carried out after the coating agent feeder pump 54 by means of the measuring devices 28 arranged in each feed line 22, respectively.
• the measurement result can be entered into an adjustment device 10, by means of which the layer-specific feed of coating agent may be adjusted as desired.
• the measurement data obtained from the measuring frame preceding the coating device can be entered into the adjustment device 10.
• the adjustment of the amount of feed of coating agent may take place, for example, by means of the coating agent feeder pumps 54 or in another known manner of adjustment affecting the amount of flow.
• both the web speed that is, the running speed of the machine, and the width of the coating curtain 4 are taken into account.
• the width of the coating differs from the one of the coating curtain, especially the width of the coating is taken into account.
• the method may, thus, be applied to multilayer curtain coating both as dry edge coating and as over-the-edge coating.
• the over-the-edge coating where the coating curtain is dimensioned to extend beyond the edges of the web, is in addition taken into account the part of the total flow of coating agents not remaining on the web. In principle this is obtained from the difference in width between the coating curtain and the web.
• dry edge coating can be taken into account the width of the dry edge, that is, of the unapplied web strip or, correspondingly, the width of the coating applied and, if necessary, of the coating applied on the web, the part on its edge area which is to be removed, for example by suction.
• over-the-edge application and also in dry edge coating when a part of the coating agent on the edge of the coating is recovered from its edge or edge bank is also taken into account the possible return cycle of the coating agent to the ma- chine cycle and the applicator device.
• multilayer curtain coating is normally used coating agent by-passing 47 from the feed chamber 12, which prevents the coating agent from clodding or accumulating on the walls.
• the proportion of the by-pass of the total flow of the coating agent, that is, paste, is typically only 5%, but this proportion of the by-pass may be increased up to 30%. This can be done, for example, if it is desirable to influence the cross direction profile of the coating in a specific way. The wider the machine used, the lower the by-pass proportion can, in any case, be set.
• the proportion of the by-pass-loop for separate coating material layers can vary even a lot in multilayer curtain coating when using the adjustment of the width of separate coating material layers and, thus, trimming already on the runoff slide.
• the proportion of the by-pass loop should be taken into account for each separate coating material layer separately, in order to determine the amount of coating agent on the fibrous web.
• the effect of the by-passing on the measurement itself can be avoided altogether, if necessary. If the measurement of the coating agent is carried out outside the by-passing loop, variations in the by-pass part have no effect on the measurement result. In this case, the return of the by-pass to the feed line 22 does not take place until after the measurement 28, as arranged in the embodiment of Figure 1.
• the measurement of the by-pass can, however, be arranged either separately in the by-pass line 26 itself, or the return of the by-pass is arranged before the measurement 28 of the amount of coating agent 28 and its proportion is deducted from the measurement result, that is, from the total flow of coating agent.
• the relative proportion of the by-pass in the total flow with different amounts of coating is known rather accurately without separate measurement and the proportion delivered to the web can thus be accurately calculated from the difference between the total flow and the by-pass.
• a pressure increase for example a pump is arranged to a suitable location in the by-pass return line for boosting the by-pass flow.
• the measurement of the coating material flow can, as such be carried out by means of prior art equipment, especially by using non-contacting measurement.
• measuring methods applicable to the solution relating to the invention may be mentioned electromagnetic quantity measurement, if coating agents provided with electric properties are used, so-called Coriolis mass quantity measurement, vortex metering, flow measurement based on ultra- sound, thermal mass quantity measurement and flow measurement based on pressure difference.
• As measuring parameters can, therefore, according to need be selected flow rate, density of coating agent and water content of coating or, for example, the proportion of corresponding volatile components.
• the amounts of coating in respect of both mass and thickness can be determined for a finished product both per the entire coating or per individual layer, for example, on the basis of coating agent mass, dry matter content and density.
• the web was thus measured with two separate measuring frames, both before and after applying the coating, and the amount of coating was calculated on the basis of the difference.
• the humidities and amounts of the web and coating across the coating head have been calculated and e.g. grammages have been calculated on the basis of them.
• the measuring frame 20 preceding the coating device 1 is arranged, for example, the measurement of the humidity of the fibrous web and possibly also of grammage.
• the measurement can preferably be arranged as online measurement and the measurement data be transmitted to the said adjustment unit 10.
• the device comprises a laterally movable adjustment device 40 lo- cated on at least one of the edge areas of the runoff slide 28, the said device including, in the embodiment shown herein, a cover element 41, a blade part 42 and a base element 50.
• the blade part 42 limits the lateral dimension S of the coating paste 29 flowing down the flow plane. For instance a band the size of which is equal to B can be edged off from the coating sliding along the runoff slide 28.
• the coating agent can be guided back the machine cycle.
• the arrangement can, therefore, be adjusted both the width and the cross directional CD location of the coating curtain. It is at the same time possible to maintain the feed profile of the beam unchanged in the transverse direction, irrespective of application width.
• the flow of paste B outside the application width can, thus, be guided additionally via pipe elements 46 back to the machine cycle or, if necessary, out of the machine cycle.
• a chute member (not shown), which enables the paste outside this application width to flow into the pipe elements 46 in the base element 50.
• This solution allows the paste discharged from an individual nozzle slot to be treated in the desired manner, which means that, for example, some of the paste layers may, if desired, be recirculated to the machine cycle and fed again into the feed chamber, preferably together with the by-pass 47.
• a wider nozzle slot 30 in cross direction is applied for instance for a single coating material layer resulting in that this trimmed band B is formed wider than the other layers so that in comparison to other layers an equally wide coating material film is accomplished in the actual coating curtain.
• the trimmed bands of different sizes can be employed for instance if possible imperfection in edge areas caused by flow disturbances are to be eliminated for separate coating material layers by using a particularly large trimming band.
• the measuring method according to the invention can preferably be com- bined with this coating curtain width adjustment, where the part of the coating cut off from the coating agent in each coating agent layer can be recircu- lated back to the feed.
• the amount of coating agent per layer returned in connection with width adjustment is now easy to note by measuring by means of the measuring arrangement according to the invention and thus the layer-specific amounts of coating applied on the web can then be reliably determined regardless of whether the trimming of the width of the coating is applied for instance for a single or several coating material layers or moreover even trimming of different magnitude for separate coating material layers.
• the recirculated coating agent can also be arranged to be returned ei- ther into the by-passing flow line 26 or directly into the feed line and in each case either before or after the measuring point for measuring the amount of coating agent according to the invention. Thanks to this further development of the invention it is possible by an unfailing and reliable manner to continuously determine the amounts of coating agents independently from the aforesaid diverse running parameters.

Landscapes

• Coating Apparatus (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Paper (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=37232240

Family Applications (1)

Country Status (4)

Cited By (2)

Citations (5)

• 2006
  • 2006-10-03 FI FI20065633A patent/FI120206B/fi active IP Right Grant
• 2007
  • 2007-10-02 DE DE212007000068U patent/DE212007000068U1/de not_active Expired - Lifetime
  • 2007-10-02 AT AT0901007U patent/AT11309U1/de not_active IP Right Cessation
  • 2007-10-02 WO PCT/FI2007/050535 patent/WO2008040851A1/en active Application Filing

Patent Citations (5)

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