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
  • D21H23/52—Addition to the formed paper by contacting paper with a device carrying the material
• • 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
  • B05C1/00—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating
  • B05C1/04—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length
  • B05C1/14—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a travelling band
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/28—Processes for applying liquids or other fluent materials performed by transfer from the surfaces of elements carrying the liquid or other fluent material, e.g. brushes, pads, rollers

Definitions

• the invention relates to a device and a method for transferring a substance to a web, such as a paper or cardboard web.
• a web such as a paper or cardboard web.
• the invention can be used in processes for manufacturing paper and cardboard, for instance.
• Stuff and surface sizing mainly serve for enhancing the strength and porosity characteristics of the web. In current techniques, this is usually done by bringing a size mixture (e.g. a starch mixture) to the web surface in the nip. The size mixture penetrates the web structure in the nip under capillary and pressure forces. Press devices that can be used for this purpose comprise i.a. a pond size press and a film size press.
• a size mixture e.g. a starch mixture
• Press devices that can be used for this purpose comprise i.a. a pond size press and a film size press.
• a coating agent such as a coating paste
• the coating agent contains a considerable amount of pigment, but the surface glue does not.
• Current techniques know the following coating methods, among others: blade coating, rod coating, film transfer coating, nozzle coating, air brush coating, curtain coating and dry coating.
• Web humidification is necessary for equalising the web moisture profile or tension differences during drying or finishing. Humidification is used in calendering especially in order to control web mouldability. In moisture gradient calendering, water is applied to the dry web just before the calendering treatment.
• the web is humidified by spraying water or water vapour on the web.
• Water can be sprayed directly by pressure or using compressed air in the form of water-air dust.
• FI patent specification 931021 describes a method and a device, in which a paper web is humidified in order to decrease the glass transition temperature of the paper immediately before the calendar nip.
• vapour is fed to the paper web surface facing the roll to be heated.
• the web is additionally brought into contact with the roll to be heated even before it reaches the calender nip.
• This method is operative as such, yet it entails intricate technical implementation. It is also difficult to adjust technically.
• the substance to be transferred is applied to a porous web made of a porous material, and subsequently the web and the porous web are conducted into contact in a transfer zone, where the substance is transferred from the porous web to the web.
• the substance is transferred to the web especially by pressing the porous web.
• the porous web may then be made of a suitably compressible material. Compressibility can be achieved by using an appropriate structural material or by providing a compressible structure from a substantially uncompressible structural material.
• the web may be of e.g. paper (boards included), wood fibre board or a raw material used in the manufacture of these.
• the invention yields the advantage of allowing the substance to be evenly dosed in the porous web, or with the exactly desired distribution, also in the cross direction, thus providing high profiling precision. Dosing in the porous web is easier, while being ideal, providing more even material compared to a web.
• the efficiency (high transfer capacity) and versatile control facilities of the process can also be considered advantages.
• Figure 1 is a schematic view of the transfer of a substance in the web nip with one porous web.
• Figure 2 shows transfer of a substance to the web in the nip between two porous webs
• Figure 3 shows the transfer of a substance to the web in a nip formed of two rolls with elastic surface s between two porous webs.
• Figure 4 shows transfer of a substance from a porous web using the centrifugal force as a means.
• Figure 5 shows the transfer of a substance from a porous web between two belts.
• a web denotes a web formed of especially paper, cardboard or pulps of these.
• the substance to be transferred denotes especially a substance to be applied to the web during the manufacturing process (finishing included).
• the state of the substance can be e.g. liquid, such as a solution, or a mixture of a liquid and a solid substance, such as a suspension, a dispersion or solid substance alone.
• the purpose of use of the substance may be e.g.
• humidifying agent such as water, or size, such as surface or stuff size
• a coating agent such as a coating paste or a dry-coating agent
• an agent acting on the web properties such as a substance altering, especially reinforcing the fibre structure, or a substance altering the optic properties of the web.
• a porous web such as a machine felt or a wire, is disposed to run in contact with the paper web through the transfer zone.
• the substance to be transferred is applied to the porous web before the porous web is conducted to the transfer zone.
• the porous web may be located especially above or underneath the web.
• the porous web or the web is preferably supported by the bearing surfaces at least over part of the travel, most preferably from both sides.
• the bearing surfaces may consist of rolls, such as soft or hard rolls, belt-like constructions, such as belt-like construction s in endless circulation, or static constructions.
• the porous web and the web are preferably pressed against each other in the transfer zone.
• the porous web gets into contact with the web so that the substance is transferred into the web under the effect of various mechanisms and driving forces.
• a major driving force consists of the hydrostatic pressure difference generated by the compression of the porous web in the transfer zone, this pressure difference driving the substance into the web.
• the contact pressure generated by compression forces enhances the contact between porous materials, which otherwise could be incomplete.
• the capillary forces of the web which increase as the web is compressed and the pores are diminished, favour transfer of the substance into the web pores.
• the web and the porous web are preferably separated as rapidly as possible to prevent substance from returning to the porous web.
• the operation of the transfer zone may be based on pressure difference, for instance, such as overall pressure difference or partial pressure difference, concentration difference, utilisation of capillary forces, acceleration forces of the mass of the substance to be transferred, such as the centrifugal force or gravitation, or electrostatic attractive forces.
• pressure difference for instance, such as overall pressure difference or partial pressure difference, concentration difference, utilisation of capillary forces, acceleration forces of the mass of the substance to be transferred, such as the centrifugal force or gravitation, or electrostatic attractive forces.
• a surplus of dosed substance can be removed from the porous web before the transfer zone in order to achieve better dosage precision in the actual web contact.
• Removal can be performed in one or more removal zones.
• the zones may be located in the direction of travel of the porous web before or after the application zone.
• Substance transfer in the removal zones may be based on the same phenomena as in the transfer zones.
• the substance to be transferred can be applied to the porous web by using e.g. film transfer or pond pressing techniques, by circulating the porous web in a basin filled with the substance to be transferred, by spraying, brushing, scattering, bleeding under the force of gravity or adhering by contact from another surface, e.g. another porous web, a dense belt or a roll surface.
• the use of electrostatic charges can enhance the transfer process in the application zone.
• the substance to be introduced can be especially water.
• the substance to be introduced can also be a stuff or surface size, e.g. a starch mixture, a coating agent, e.g. a coating paste, or a dry-coating agent, an agent reinforcing the fibre structure of the web, e.g. a cross-linking polymer, or any other substance yielding improved properties for the final use.
• the porous web may be in endless circulation. This yields the benefit of a simple construction, among other things. Material waste is also reduced, and the system is easier to automate and equip with necessary gauges and control devices.
• the substance is transferred from the porous web to the web in a transfer zone.
• the transfer zone may consist of a contact zone between the paper and the porous web, where either the web or the porous web, or both of them, are supported with bearing surfaces.
• the bearing surfaces also have the function to bring the web and the porous web into sufficient press contact for the transfer process to be successful.
• the bearing surfaces may consist of ordinary rotating or static constructions used in paper or cardboard manufacture. Rolls forming the nip may especially act as a bearing surface. Conceivable solutions include e.g. a hard nip (two hard rolls), a soft nip (a soft and a hard roll) and a long nip ("a belt or shoe nip").
• the bearing surface may also consist of e.g. a drying cylinder, a Yankee drying ccvylliinnddeerr oorr aa ⁇ prreessss rroollll..
• the bearing surface may also consist of a belt, especially a metal belt or a polymer belt, a wire or a drying wire.
• Belt-like bearing surfaces can be additionally supported by e.g. a roll, a second belt, a hydraulic shoe or a static support construction, such as a hydraulic support zone.
• the bearing surface may also consist of a non-rotary construction, such as a glide shoe or a rod or a similar beam.
• a hydraulically lubricated glide zone can be especially used in a similar manner as in a shoe calender, for instance.
• the porous web can consist of a porous belt specially designed for this purpose.
• the operation of the porous web can also be combined with the operation of wires and belts already existing in current production lines.
• a drying wire simultaneously used as a porous web can be mentioned as an example of this.
• the porous web can then be made of a suitably compressible material. Compressibility can be achieved by using a suitable structural material or by converting a substantially uncompressible structural material into a compressible structure.
• the porous web may nevertheless be made of a substantially uncompressible material.
• Metal wires and certain plastic wires can be cited as examples of this.
• the porous web may be a detached porous belt circulating loosely around the surface of the bearing surface and adapting to the shape of this.
• the porous web may be a porous layer solidly adhering to the surface of the bearing surface. In this embodiment, it replaces any coating of the bearing surface.
• an ordinary circular roll or endless belt can be coated with a porous layer.
• either one single porous web can be used in contact with one side of the web alone, or two porous webs in contact with both the web sides. In the latter case, the same substance can be transferred from the two porous webs, or different substances from different paths.
• the web may be in contact with the porous web, for instance, either on one side alone or on both sides.
• the porous web can be disposed to run above the web or under the web, for instance. From a porous web rum ing above the web, substance is transferred to the web also under the effect of the force of gravity. Such a solution is applicable to a separate transfer nip, for instance.
• the transfer zone may be supported by bearing surfaces either on one side alone or on both sides.
• a nip contact is an example of a solution with support on both sides.
• a porous web used in the manner of a drying wire for pressing paper against the drying cylinder is an example of a solution involving support on one side alone. In this case, the tension of the porous web achieves the pressing action required in the transfer zone.
• the transfer zone may be supported by bearing surfaces over a portion of its length and unsupported over the remaining portion.
• porous web(s), the bearing surface(s) and the web may be in contact with the transfer zone in various mutual arrangements.
• the following examples are cited:
• the operation of the application zone may be based on the same mechanisms and driving forces as those of the transfer zone.
• the substance transfer in the transfer zone can be enhanced by disposing the porous web and the web in contact with this to run along a curved path, following the outer surface of a roll, for instance. With the porous web on the inside, the centrifugal force exerted on the substance phase drives the substance towards the web which is on the outer side.
• Transfer can also be enhanced by heating the porous web and the substance to be transferred contained in the path. Heating may be performed e.g. by means of the bearing surface in contact or by acting directly (using microwaves, for instance) on the porous web and the substance to be transferred. As a result of the heating, the evaporation process generated in the porous web and the transfer resemble an impulse press process. The gaseous phase formed during heating forces the substance to be transferred to proceed very efficiently in the direction of the web. If the substance to be transferred is water, the temperature should be high enough for evaporation, preferably in the range from 100 to 350 °C. Heating also reduces the viscosity of the substance to be transferred, resulting thus in higher viscosity and easier substance transfer.
• Transfer can also be enhanced by blowing a gas, e.g. air, through the bearing surface (e.g. a roll mantle or a belt) to the porous web, where it contributes to propelling the substance to be transferred towards the web by a pressure difference.
• a gas e.g. air
• the blown substance may especially be the same as the substance to be transferred to the web.
• the bearing surface itself, a roll, for instance should naturally be porous or perforated.
• the roll may resemble a suction roll, for instance, in which blowing is performed through perforations instead of suction.
• the amount of transferred substance vapour such as water vapour
• the amount of transferred substance vapour can be dimensioned so that the heating effect of the transferred substance and the pressure increase contribute to the plastication of the fibres. This is a manner of enhancing calendering, for instance.
• the vapour amounts to be applied may typically rise up to 10 g/m 2 .
• the substance transfer in the transfer zone can be enhanced also by cooling the porous web and/or bearing surface in contact with the web.
• Particularly efficient substance transfer is achieved by heating the substance transfer side of the porous web and by cooling the opposite pulp path side of the porous web or the bearing surface.
• Substance transfer to or from the porous web and enhancing it outside the transfer zone, especially in the application zone or the removal zone, may be based on the same principles as those applied to the transfer zone. Total or partial pressure difference, concentration difference, electrostatic forces, a capillary effect and inertial forces of the pulp can be especially utilised. These effects are achieved e.g. by using blowing, compression of the porous web, heating or cooling and reversal (acceleration).
• a transfer zone such as a transfer nip, may be at a suitable location between the press section and the reeler of a paper or cardboard manufacturing machine, for instance.
• a solution in which the substance to be transferred is dosed to the porous web and is pressed against the drying cylinder is especially usable.
• the transfer zone may also locate in an on-line or of-line finishing line.
• the transfer nip can be combined with the calender nip. Then the transfer process of the substance, mainly water in this case, and the calendering process can be combined in the same nip or in consecutive nips (multinip).
• the overall transfer process can be controlled e.g. by regulating the amount of applied substance either in the cross direction (CD) or in the machine direction (MD) of the path.
• Sub-processes of the transfer process can be acted on in the application zone, the removal zone or the transfer zone. If it is desirable to regulate the amount of substance to be transferred in the cross direction, for instance, the driving forces of the transfer process can be acted on in the different sub-processes in the application, removal or transfer zone.
• An example of this is profiling of the compression pressure in the transfer zone or profiling of the blowing operations.
• profiling can be performed by controlling the transfer process in the application or the removal zone.
• the purpose of this is principally to control the concentration of the substance to be transferred in the porous web before it reaches the transfer zone. This can be effected by acting on the prevailing driving forces.
• a paper web 1 is conducted into press contact with a porous belt 2 in a transfer zone (nip) A between rolls 3 and 4.
• the porous belt is made of a resilient material and has been infiltrated in the application zone B with a substance to be transferred 5.
• the hydrostatic substance concentration in the paper before the transfer zone is lower than in the belt, so that there is a tendency of mass transfer to the paper.
• the belt can be appreciably compressed, this being an additional reason for efficient mass transfer to the paper.
• Belt compression also increases the nip length, resulting in an increase in the available distance and time of mass transfer.
• the belt and the web are immediately separated in order to prevent the substance from returning from the web to the belt.
• the transfer zone as the compression releases, the belt resumes its specific thickness.
• the web may also be compressed in the nip. Any substance and impurities remaining in the belt can be removed in the removal zone C if necessary.
• the substance 5 is applied to the belt 2 by spraying with nozzles 6.
• the nozzles are aligned in a row transverse to the belt so as to produce the desired regular jet pattern on the belt. If necessary, a set of nozzles can be used for profiling especially by applying the substance in larger amounts at the edges of the belt. This allows control of an optimally even moisture distribution of the web in the cross direction.
• substance and impurities can be removed from the belt by blowing air with blowers 7, for instance.
• the rolls 3 and 4 support the paper web 1.
• the web is unsupported over a certain distance, and it can be conducted to another unit, for instance, where substance is transferred to the web from the opposite side of the web, for instance.
• the paper web 1 may also be compressed, provided that the pressure is high enough.
• the roll 4 on the paper web side may be especially a roll with a hard surface
• the roll 3 on the belt side may be especially a heated roll and the substance to be transferred may be water.
• the paper web 1 is conducted in the nip between the rolls 3 and 4.1 in the transfer zone A between two belts 2.1 and 2.2.
• the substance to be transferred has been applied to the belts.
• the substance is transferred to the web.
• different substances may be simultaneously transferred from different sides of the web. This arrangement allows for efficient substance transfer with minimal compression of the paper.
• the paper web 1 is also taken to the transfer zone A between two belts 2.1 and 2.2.
• the rolls 3 and 4 are coated with elastic but not porous coating 8. The coating is compressed in the nip, and thus the nip length and consequently the available distance of substance transfer are further increased.
• the paper web 1 is conducted to the roll application station B between the porous belt 2.3 and the hitch roll 9.
• Substance (e.g. coating agent) 5 transferred with a lift roll 10 is applied to the outer surface of the belt on the hitch roll.
• the substance layer applied is regulated with a levelling device 11. The substance tends to pass from the belt to the web.
• the web and the belt are conducted to the transfer roll 12 with the belt against the roll surface. Then the substance will be driven from the belt to the web under the centrifugal force. After the transfer roll, the web and the belt are separated.
• two support belts 13 and 14 circulate around the support rolls, the support belts running in facing alignment over a certain distance so as to form a transfer zone A between them.
• the support belts may consist of metal or polymer belts, for instance.
• a porous belt 2.4 has been disposed to run around the lower belt, and the substance to be transferred 5 is applied to the belt in the application zone B before the transfer zone.
• substance is absorbed into the web from the porous belt.
• the substance is removed from the belt in the removal zone C.

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ID=8563733

Family Applications (1)

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Cited By (2)

Citations (1)

• 2002
  • 2002-04-10 FI FI20020684A patent/FI115850B/sv not_active IP Right Cessation
• 2003
  • 2003-04-09 WO PCT/FI2003/000267 patent/WO2003084681A1/en not_active Application Discontinuation
  • 2003-04-09 AU AU2003226840A patent/AU2003226840A1/en not_active Abandoned

Patent Citations (1)

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