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
  • D21H23/70—Multistep processes; Apparatus for adding one or several substances in portions or in various ways to the paper, not covered by another single group of this main group
• • 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
  • B05C5/005—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
  • B05C5/007—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
• • 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
  • B05C9/00—Apparatus or plant for applying liquid or other fluent material to surfaces by means not covered by any preceding group, or in which the means of applying the liquid or other fluent material is not important
  • B05C9/06—Apparatus or plant for applying liquid or other fluent material to surfaces by means not covered by any preceding group, or in which the means of applying the liquid or other fluent material is not important for applying two different liquids or other fluent materials, or the same liquid or other fluent material twice, to the same side of the work

Definitions

• the invention relates to a method for the direct application of a multi-layer to a running paper, cardboard or other fibrous web during its manufacture or / and finishing, the individual layers of the multi-layer being formed from several liquid to pasty application media, in particular aqueous pigment suspensions.
• paper, cardboard or other fibrous webs are mainly manufactured and refined in large widths of up to 10 m and more as well as at high machine speeds.
• these webs are to be treated by offline or online coating processes.
• a modern coating process in the form of contactless application is often used for this purpose, the applied medium being deposited as a contour layer on the fibrous web.
• the application medium consists of mixtures of mineral pigments, natural or synthetic binders and chemical auxiliaries.
• the smoothness or roughness of the coated substrate depends on the basic roughness or smoothness of the substrate, ie the fibrous web.
• the aim is to carry out this application in the so-called 1: 1 process. This means that only as much medium should be applied as is to remain on the fibrous web to be coated.
• the excess application method is known, in which approximately 8 to 10 times the amount of application medium is to be applied, which then has to be scraped back to the desired coat weight, for example 6-12 g / m 2 , using various doctor elements. It follows that the amount to be applied is very small for a 1: 1 order. In any case, an even application layer should be achieved, which extends across the entire web width or working width.
• Known 1: 1 applicators or units are curtain and spray applicators.
• certain forces for example electrostatic forces, which are given to the application medium or fall under the influence of gravity on the running surface or the fibrous web
• the spray jets of the spray applicator each form a contour line on the fibrous web and immobilize there after a certain time as a film.
• the fibrous web In order to be able to achieve a high degree of coverage of the fibrous web and thus better printing properties, the fibrous web must often be painted several times.
• the object of the invention is achieved in accordance with claim 1 in that the individual application media are delivered to the fibrous web without contact, in each case without prior drying, that is to say wet on wet and without excess quantities, that is to say 1: 1.
• the application medium which has a lower specific weight and / or a lower viscosity and or a lower surface tension than the next application medium or the next layer, is applied to an application medium or a layer with a higher specific weight and / or higher viscosity and / or a higher surface tension is applied.
• the fibrous web comes into contact with the application medium which has the highest of the values mentioned above.
• the first layer on the fibrous web is the layer with the highest of the values mentioned and the top layer is the application medium or the layer with the lowest values.
• lighter application media (with lower specific weight) remains on the heavier layer due to its physical buoyancy effect.
• the multiple layer formed can thus be built up in a very targeted manner. Above all, however, such a multilayer guarantees excellent coverage of the raw fibrous web. The fact that this can be accomplished with a single and compact application work saves huge investments, which represents a further advantage of the invention.
• the individual application media for forming the multi-layer are delivered separately from one another and, during their delivery in the direction of the fibrous web, are combined or bundled into a sandwich-like multiple jet or multiple curtain and in a bundled form on the fibrous web as an already established multi-layer be applied.
• the bundling can take place immediately after delivery from the machine-wide nozzle or only after individual jets or individual curtains have formed. After bundling, depending on the type of application (free jet nozzle application or curtain application), a sandwich-like jet or a sandwich-like curtain is created. In both cases, to a certain extent stabilized "prefabricated" layers lay on the fibrous web.
• Whether the layers are applied individually or in a bundle depends on how compact the application must be, how the space for installing the application or the type of application media to be used or depends on the product type.
• the multiple layer is formed from at least two and at most ten, preferably three layers. In this order of magnitude, particularly good coverage of the raw fibrous web is possible with small amounts of individual layers.
• the individual application media are emitted as a single jet or individual curtain from a machine-wide slot die or a machine-wide slot of a common nozzle, the distance between the individual jets or screens being less than 1 m, in particular less than 50 cm, but preferably about 20 cm, and the time intervals for a successive delivery from the individual wide slots are set to between 4 and 100 milliseconds.
• machine-wide is to be understood as meaning at least the width of the fibrous web to be produced or refined.
• a further embodiment of the invention can consist in the bundled multiple jet or multiple curtain reaching a flow rate Q T (for total flow rate). This is made up of the sum of the individual liquid flows of the individual curtains.
• the total flow rate Q T can be between 0.5 to 301 / min / m, in particular between 3 and 201 / min / m, preferably between 1 and 121 / min / m.
• Application media with solids contents between 5 and 70% are particularly suitable for this multilayer.
• the total coat weight applied ⁇ m Gésa m t can be calculated as follows:
• hj is the wet film thickness or the area-related volume of the individual application med iu ms per m 2
• Ki is the solids content of the respective application medium
• Pi is the specific weight of the respective application medium.
• the viscosity (according to Brookfield 100 rpm) of the first layer below should be between 500 and 100mPas.
• the acting expansion forces on the individual adjacent application media have a maximum difference of 30%, in particular ⁇ 20%, preferably 0 ⁇ 5%
• the adjustment of the expansion force difference by adding chemical additives is set on the basis of acrylic ester or acrylic acid or methaacrylic acid or acrylamide or acrylonitrile etc. and the percentage of these chemical additives being 0.01 to 3 T, in particular 0.01 to 0.5 T, preferably 0.01 to 0.2 T is and T is the proportion per 100 parts of the dry amount of pigment in the selected coating color.
• the multilayer is formed in such a way that the fineness of the mineral pigments, such as calcium carbonate or kaolin or TiO2 or talc, increases upwards.
• Amounts of binder, based on the dry weight of the pigments contained, can be in the order of 4 to 20 parts.
• Suitable binders are natural binders such as starch (corn, potatoes, tapioca, wheat, barley etc.), cacein, etc. and synthetic binders such as latices (based on styrene-butadiene or acrylate-based, etc.).
• T means the percentage of the agent per 100 parts of the dry amount of pigment in the application medium.
• the application of the multi-layer can be carried out most advantageously with a curtain applicator, with which several different liquid to pasty application media in the form of several or in the form of a bundle and closed curtain essentially following gravity and / or directed under the influence of electrostatic forces running fibrous web are delivered.
• a curtain applicator with which several different liquid to pasty application media in the form of several or in the form of a bundle and closed curtain essentially following gravity and / or directed under the influence of electrostatic forces running fibrous web are delivered.
• a spray or free jet applicator with which several different liquid to pasty application media in the form of several jets or in the form of a single bundled jet directed under pressure on the fibrous web to the running fibrous web be delivered.
• Figure 1 a schematic representation of the principle of the invention using the example of a fibrous web coated with a multilayer by means of a curtain applicator
• FIG. 2 to 5 a schematic representation of curtain applicators according to the invention with which a multilayer according to the invention is applied
• Figure 6 a schematic representation of the principle of the invention with representation of speed profiles in a multiple curtain
• FIG. 1 shows a fibrous web 1 onto which a multiple layer 2 consisting of several different liquid flows Q1, Q2, Q3, Q4; Qn (five different media are shown in the example) is applied directly.
• the thickness of the multilayer 2 is relatively constant and depends on the topography
• Liquid flows in the selected example are given in the form of as many individual curtains V1 to Vn falling perpendicularly on the fibrous web 1.
• the contactless curtain application used for this is not shown here.
• the individual liquid streams Q1 to Qn consist of several coating colors, which can differ in their composition or rheology and each consist of a mixture of mineral pigments, natural or synthetic binders and chemical auxiliaries.
• the individual liquid streams Q1 to Qn are passed on to the fibrous web without contact and without prior drying - i.e. wet in wet and without excess amounts - that is to say without contact.
• the application medium which has a lower specific weight p and / or a lower viscosity ⁇ and or a lower surface tension ⁇ than the next application medium or the next liquid flow or the next layer, on an application medium or Layer with a higher specific weight and / or higher viscosity and / or a higher surface tension is applied. It is thereby achieved that the fibrous web 1 comes into contact with that application medium which has the highest values (this is then Q1 with specific weight p1, viscosity ⁇ 1 and surface tension 51.
• the first layer, or lower layer U is the layer with the highest values on the fibrous web and, as the top layer D, that application medium Qn or that layer with the lowest values of p, ⁇ , or ⁇ .
• FIG. 2 shows the application of the invention using the example of a double-curtain applicator unit 3, shown in cross section and schematically, for applying the multiple layer 2, as described in principle in FIG.
• Two feed chambers 4 and 5 for two different application media or liquid flows Q1 and Q2 can be seen, which are applied in the form of two spatially separated curtains V1 and V2 to an inclined guide surface 6.
• the guide surface 6 is inclined in the direction of the first curtain V1.
• the two curtains V1 and V2 are combined or bundled to form a double layer 7 and in this bundled form, i.e. placed as a multiple curtain 8 (here double curtain) and thus delivered to the fibrous web 1 running underneath in the running direction L.
• the layer resulting from the second curtain V2 or a liquid flow Qn comes to lie on the fibrous web as the cover layer D.
• the cover layer D has the finer particles and the lower values than the lower layer U of the layer or of the liquid flow Q1 or the further layers also underneath in the case of several curtains.
• the length of the bundled vertically falling curtain is approximately 50 to 300 mm.
• a blade-like leveling element 9 is also shown in FIG. 2, which is to equalize and smooth the applied multilayer 2 - here double layer.
• FIG. 3 shows another principle of applying a multilayer 2.
• the curtains V1 and V2 are bundled into a multiple or double curtain 8 under the action of electrostatic forces.
• a corresponding electrode 10 pulls the curtains V1 and V2 shown here towards the center, so that here too the curtain V2 again forms the upper layer, that is to say the top layer D of the multiple coating 2 according to FIG. 1.
• the application medium Q1 and Q2 resulting from distribution chambers 4 and 5 becomes immediately after emerging from the slot nozzle 11 of the order work 3 bundled without a guide surface or other forces are involved.
• a partition 12 for example made of polytetrafluoroethylene, inside the application unit 3. It can be seen that the existing curtain V2 is again as top layer D according to the explanation occurs in Figure 1.
• FIG. 5 is intended to show that the multilayer can also be delivered onto the fibrous web 1 from two individually delivered curtains V1 and V2 without prior bundling.
• V2 is deposited again as the cover layer D.
• Leveling elements 9 are also shown again in FIGS. 4 and 5.
• applicator units 3 shown in FIGS. 2 and 3 contain several parallel slot nozzles 11, which are fed by separate feed systems 13 and 14, respectively.
• the outflow speed of the individual application media from the nozzle or at the point where they are bundled is selected so that in the cross section of the curtain 8 a speed profile is similar to the speed profiles shown in FIG. Case a)
• the outflow speed of all application media or liquid flows Q1 to Qn is the same, so that a speed profile without a relative speed is established between the phase boundaries of the individual liquid application media. No shear or stretch processes take place at the phase boundaries in the multiple curtain.
• Speed profiles with a zigzag-like course are unsuitable for the formation of multi-layer curtains because relative speeds initiate stretching and mixing processes that deform, arch or disrupt the multi-layer or multilayer curtain.
• the finer and whiter pigments such as those of calcium carbonate or kaolin or TiO 2 or talc, form the top layer D of the multilayer 2.
• the method according to the invention thus enables a high-quality application layer.
• the invention is therefore particularly suitable for paper and cardboard webs which are said to have high printing properties.

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

Applications Claiming Priority (2)

Publications (1)

Family

ID=35679957

Family Applications (1)

Country Status (5)

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• 2004
  • 2004-12-23 DE DE102004062119A patent/DE102004062119A1/de not_active Ceased
• 2005
  • 2005-11-18 JP JP2007547420A patent/JP2008525649A/ja active Pending
  • 2005-11-18 WO PCT/EP2005/056047 patent/WO2006069851A1/de active Application Filing
  • 2005-11-18 EP EP05808126A patent/EP1831464A1/de not_active Withdrawn
• 2007
  • 2007-06-22 US US11/767,026 patent/US20070248763A1/en not_active Abandoned

Non-Patent Citations (1)

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