EP4379130A1 - Caisse de tête et procédé d'application de compositions de revêtement sur un substrat de pâte humide mobile à l'aide de ladite caisse de tête - Google Patents

Caisse de tête et procédé d'application de compositions de revêtement sur un substrat de pâte humide mobile à l'aide de ladite caisse de tête Download PDF

Info

Publication number
EP4379130A1
EP4379130A1 EP22210936.5A EP22210936A EP4379130A1 EP 4379130 A1 EP4379130 A1 EP 4379130A1 EP 22210936 A EP22210936 A EP 22210936A EP 4379130 A1 EP4379130 A1 EP 4379130A1
Authority
EP
European Patent Office
Prior art keywords
coating composition
headbox
chamber
valve body
stream
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22210936.5A
Other languages
German (de)
English (en)
Inventor
Tjerk BOERSMA
Willy JASPERS
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sappi Netherlands BV
Original Assignee
Sappi Netherlands BV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sappi Netherlands BV filed Critical Sappi Netherlands BV
Priority to EP22210936.5A priority Critical patent/EP4379130A1/fr
Priority to PCT/EP2023/083624 priority patent/WO2024115610A1/fr
Publication of EP4379130A1 publication Critical patent/EP4379130A1/fr
Pending legal-status Critical Current

Links

Images

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/02—Head boxes of Fourdrinier machines
    • D21F1/026—Details of the turbulence section
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/02—Head boxes of Fourdrinier machines
    • D21F1/028—Details of the nozzle section
    • 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
    • D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp
    • D21H23/06—Controlling the addition
    • D21H23/14—Controlling the addition by selecting point of addition or time of contact between components
    • 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
    • D21H23/24—Addition to the formed paper during paper manufacture
    • D21H23/26—Addition to the formed paper during paper manufacture by selecting point of addition or moisture content of the paper

Definitions

  • the present invention relates to the field of paper machines, in general, and in particular to a headbox, such as a secondary headbox, for applying a coating composition onto a moving wet pulp substrate in a paper machine, as well as a method of applying a coating composition onto a moving wet pulp substrate in a paper machine equipped with such a headbox, a paper machine comprising such a headbox as well as the use of such a headbox in a method of applying a horizontal stream of a coating composition onto a horizontally moving wet pulp substrate in a paper machine.
  • a headbox such as a secondary headbox
  • Paper machines use a moving woven mesh, also known as wire, to create a continuous paper web by filtering out the fibres held in a wet paper stock and producing a continuously moving wet mat of fibre.
  • the wet paper stock is dispensed onto the wire mesh from a so-called headbox.
  • the headbox essentially holds the wet paper stock and must, on one hand, keep the fibers from clumping together by generating turbulence in its interior, and on the other hand, uniformly distribute the wet paper stock across the width of the wire. Fulfilling both requirements ensures the formation of a homogenous mat of wet pulp on the wire.
  • Such a homogenous layer will in any case depend on multiple factors, such as matching of the speed at which the coating composition contacts the moving wet pulp layer from the primary headbox to the speed of the moving wet pulp layer, as well adjusting the angle at which the coating composition contacts the moving wet pulp layer from the primary headbox, all the while warranting that the flow rate, width, thickness, rheology and consistency of the coating composition exiting the secondary head box is on-target.
  • the present invention provides for a headbox design that is capable of providing a stream, such as for example a curtain, of a coating composition onto a moving wet pulp substrate in a paper machine that results in the formation of a coating layer on the wet pulp substrate that is homogenous in thickness and width.
  • the headbox design of the present invention is particularly suited for coating compositions having a particular rheology profile, such as for example coating compositions comprising microfibrillated cellulose. It has further been found that the design of the headbox provides excellent rigidity, or less bending propensity, which leads to a more homogenous coating on the moving wet pulp substrate.
  • It is a second object of the present invention to provide a paper machine comprising a primary headbox for forming a wet pulp substrate and secondary headbox according to first object of the present invention for applying a stream, or jet, of a coating composition onto a moving wet pulp substrate.
  • a headbox (1) for a paper machine in particular a secondary headbox for applying a stream of, preferably a jet of, a coating composition onto a moving wet pulp substrate in a paper machine, comprising
  • the ratio (d 1 /d 2 ) between distance d 1 and distance d 2 is more than 1, preferably is between 1 and 3 and/or the distance d 2 is between 0.4 and 20 mm, preferably between 0.4 and 10 mm, more preferably between 0.8 and 3 mm. 1.
  • (di/d2) between distance d 1 and distance d 2 is constant, and is preferably about 2.
  • the headbox (1) according to the present invention is preferably a secondary headbox for applying a stream of a coating composition onto a moving wet pulp substrate in a paper machine, which wet pulp substrate is formed by dispensing a stock made of water, paper pulp and suitable additives from a primary headbox onto the moving wire mesh of the paper machine in the wet end of the paper machine.
  • the headbox (1) is preferably equipped with one or more pressure sensors, which one or more pressure sensors may be disposed in the stock chamber (2), stilling chamber (3) or slice chamber (4), or in each one, or in at least two of them.
  • one or more pressure sensors may be disposed in the stock chamber (2), stilling chamber (3) or slice chamber (4), or in each one, or in at least two of them.
  • the one or more pressure sensors are connected to a jet speed control unit, which control unit is capable receiving a pressure sensor signal and of adjusting the pressure in the headbox (1), depending on the pressure signal received, via a pressure control unit fluidly connected to the headbox (1), to ensure the speed V1 of the jet of coating composition is controlled such as to not deviate from a set value and/or such as to achieve the ratio of the speeds of said jet of a coating composition V 1 and moving wet pulp substrate V 2 is between 0.9 and 1.1.
  • the stock from which the wet pulp substrate is formed may comprise one or more pulps, preferably wood pulps, which may further be chemical wood pulps such as for example sulphite pulp or kraft pulp.
  • the chemical wood pulps may further be bleached chemical wood pulps.
  • a mixture of pulps in particular a mixture of chemical softwood pulp and chemical hardwood pulp, is used in the stock from which the wet pulp substrate is formed.
  • the wet pulp substrate formed from said stock comprises the one or more pulps given above.
  • turbulence is generated its interior with a mixing device, usually a submerged fan or perforated rollers spinning within the stock.
  • the headbox (1) according to the present invention which is preferably a secondary headbox, does not comprise a mixing device in one embodiment, in particular in the stock chamber (2) and the stilling chamber (3).
  • the needed shear for stable operation of the headbox is provided by inner surfaces of the headbox (1), which deviate the stock in the headbox (1) as it passes through the headbox (1), in particular in the stilling chamber (3).
  • the headbox (1) according to the present invention is preferably a secondary headbox for applying a stream of a coating composition onto a moving wet pulp substrate in a paper machine, which stream of a coating composition is preferably in the form of a curtain of a coating composition.
  • the curtain form is mainly due to the outline of the second clearance that is formed when the second sealing element (8) on the rotatable valve body (5) moves away from the second sealing surface (10) on the valve case body (6), once the rotatable valve body (5) is rotated into an open position.
  • the thickness of the stream, or curtain can be controlled via the height of the second clearance achieved by the opened rotatable valve body (5).
  • the width of the stream, or curtain can be controlled via the width of the second clearance achieved by the opened rotatable valve body (5).
  • the headbox (1) according to the present invention is preferably a secondary headbox for applying a stream of a coating composition onto a moving wet pulp substrate in a paper machine, which moving wet pulp substrate moves at a speed V2.
  • the headbox (1) according to the present invention is preferably a secondary headbox for applying a stream of a coating composition onto a moving wet pulp substrate in a paper machine, which headbox (1) comprises a stock chamber (2) for providing a coating composition to the downstream stilling chamber (3). During operation of the headbox (1), the stock chamber (2) thus holds a coating composition.
  • the headbox (1), and in particular the stock chamber (2) is preferably pressurized, and more preferably is configured to be controllable with respect to the pressure within the stock chamber (2).
  • the stock chamber (2) is equipped with a plurality of inlets, which inlets are each fluidly connected to a plurality of conveyor pipes, that are suitable for conveying a preferably pressurized coating composition into the stock chamber (2).
  • the coating composition can be held in a preferably pressurized, holding tank from which the plurality of conveyor pipe lead to the plurality of inlets of the stock chamber (2).
  • the stock chamber (2) is equipped with a plurality of inlets, which are distributed along the width of the headbox, i.e. in a direction parallel to the rotation axis of rotatable valve body (5).
  • a lower part of the stock chamber (2) is tapered towards the first seal in the headbox (1), which seals the stock chamber (2) from the downstream stilling chamber (3), in the closed state.
  • the lower part of the stock chamber (2) is tapered towards the first seal in the headbox (1), which seals the stock chamber (2) from the downstream stilling chamber (3), in the closed state, wherein one surface of the stock chamber (2), in the lower part, is a substantially planar surface formed by the rotatable valve body (5) and the opposed surface to that surface is a convex surface of the valve case body (6).
  • the tapered form of the stock chamber (2) ensures that a coating composition passing through, from stock chamber (2) to stilling chamber (3), is accelerated and thus experiences more shear.
  • the headbox (1) is preferably a secondary headbox for applying a stream of a coating composition onto a moving wet pulp substrate in a paper machine, which headbox (1) comprises a stilling chamber (3) for providing a coating composition to the downstream slice chamber (4). During operation of the headbox (1), the stilling chamber (3) thus holds a coating composition.
  • the headbox (1) is preferably pressurized, and more preferably is configured to be controllable with respect to the pressure within the stilling chamber (3).
  • the stilling chamber (3) is fluidly connected to the stock chamber (2), in an open state, and thus the pressure of the stock chamber (2) is established in the stilling chamber (3) once the rotatable valve body (5) is rotated into an open state.
  • the stilling chamber (3) may comprise one or more surfaces that are configured to either induce or avoid turbulence when a coating composition flows through the stilling chamber (3), i.e. between the first sealing surface (9) and the second sealing surface (10).
  • the stilling chamber (3) comprises a concave surface positioned in between the first sealing surface (9) and the second sealing surface (10).
  • the coating composition is sheared, such as to achieve a thinning of the coating composition to allow a homogenous flow of coating composition across the headbox (1).
  • the first and second sealing elements (7, 8) are simultaneously moved along the same circular path C.
  • the headbox (1) is preferably a secondary headbox for applying a stream of a coating composition onto a moving wet pulp substrate in a paper machine, which headbox (1) comprises a slice chamber (4) for providing a stream of a coating composition ejected via the clearance formed by the second sealing element (8) and the second sealing surface (10), in a opened state of the rotatable valve body (5).
  • the thickness of the stream can be controlled via the height of the second clearance achieved by the opened rotatable valve body (5).
  • the width of the stream can be controlled via the width of the second clearance achieved by the opened rotatable valve body (5).
  • the headbox (1) is preferably a secondary headbox for applying a stream of a coating composition onto a moving wet pulp substrate in a paper machine, which headbox (1) comprises a valve assembly, which comprises a rotatable valve body (5) and a valve case body (6), where the rotatable valve body (5) is located within the valve case body (6) in a rotatable manner.
  • the valve assembly controls the flow of coating composition from the stock chamber (2) into the stilling chamber (3) and for controlling the flow of coating composition from the stilling chamber (3) to the slice chamber (4).
  • the rotatable valve body (5) and the valve case body (6) may be formed of any suitable material, and are preferably formed of metal such as for example brass, bronze, copper or steel.
  • the rotatable valve body (5) and the valve case body (6) are formed of stainless steel and alloys thereof.
  • the rotatable valve body (5) is rotatable with respect to the valve case body (6), into a closed state, and into one or more opened states. In its opened state, a coating composition can flow through the headbox (1).
  • the rotatable valve body (5) can be adjusted by rotation to be in a more open state or a less open state, which in turn adjusts the size of the resulting clearance at the first and second seal, and ultimately regulating the pressure, speed and flow rate of the coating composition exiting the second clearance.
  • the rotatable valve body (5) When the rotatable valve body (5) is rotated from an closed state to the open state, the first and second sealing elements (7, 8) are simultaneously moved away along a circular path from a first and second sealing surface (9, 10), and since the rotatable valve body (5) has predefined geometry and/or cross-sectional shape, together with the valve case body (6), the size ratio between first and second clearance is determined by the degree of opening and the geometry and/or cross-sectional shape of the rotatable valve body (5) and valve case body (6).
  • the rotatable valve body (5) and the valve case body (6) have a geometry and/or cross-sectional shape such that in any open state, the first clearance is larger than the second clearance.
  • the rotatable valve body (5) and the valve case body (6) have a geometry and/or cross-sectional shape such that in any open state, the first clearance is larger than the second clearance and the size of the first clearance and size of the second clearance have a constant ratio, which ratio is preferably about 2, and which may be between 1 and 3. Because the first clearance is larger, the stilling chamber (3) can be provided with sufficient coating composition from the stock chamber (2) and warrant the pressure that is provided from the pressure in the stock chamber (2).
  • the first clearance is larger than the second clearance by a factor of more than 1, preferably by a factor of more than 1 and up to 3.
  • the coating composition upon being forced through the first larger clearance, is accelerated and exposed to a first amount of shear, and when forced through the second clearance, is further accelerated and exposed to a second amount of shear.
  • the consecutive acceleration and/or shearing leads to a decrease in viscosity which enables the coating composition to be coated homogenously onto the moving wet pulp substrate.
  • the clearances which on one side may be delimited in width, which is generally constant, by the sidewalls of the headbox (1) which may for example be formed by lateral walls of the valve case body (6) or by separate wall plates affixed to the valve case body (6), and which may be delimited in height by the respective sealing elements of the rotatable valve body (5) and sealing surfaces (9, 10) of the valve case body (6), in the open state, have a rectangular shape, where the larger sides correspond to the width and the smaller sides correspond to the height.
  • the rotatable valve body (5) in an open state, leads to a height of the second clearance of from 0.3 to 5 mm, preferably of from 0.8 mm to 3 mm, which translates into essentially the same height, or stated alternatively, thickness, of the stream of a coating composition exiting the slice chamber (4).
  • the rotatable valve body (5) comprises a first and second sealing element (7, 8) and said valve case body (6) comprises a first and second sealing surface (9, 10), wherein in a closed state, the first sealing element (7) is in sealing contact with a first sealing surface (9) on the valve case body (6), thereby forming a first seal which seals the stock chamber (2) from the stilling chamber (3), and the second sealing element (8) is in sealing contact with a second sealing surface (10) on the valve case body (6) forming a second seal, which seals the stilling chamber (3) from the slice chamber (4), wherein in an open state, the first sealing element (7) is spaced from the first sealing surface (9) on the valve case body (6), preferably by a first distance d 1 , thereby forming a first clearance having a first size s 1 , and thereby fluidly connecting the stock chamber (2) to the stilling chamber (3) and the second sealing element (8) is spaced from the second sealing surface (10) on the valve case body (6), preferably by a second distance
  • the headbox (1) is preferably a secondary headbox for applying a stream of a coating composition onto a moving wet pulp substrate in a paper machine, and is rotatable as a whole such as to modify the direction of the stream of the coating composition exiting the slice chamber (4) and/or wherein the headbox (1) is moveable as a whole in one or more directions, preferably at least in a direction perpendicular to the plane of the moving wet pulp substrate, such as to modify the direction of the stream of the coating composition contacting the moving wet pulp substrate in a paper machine, which moving wet pulp substrate is preferably moving in a horizontal direction.
  • the direction, or angle, at which the stream of a coating composition contacts the moving wet pulp substrate in the paper machine will depend on the position and angle of the headbox (1) relative to the plane the moving wet pulp substrate. For instance, when the headbox (1) is moved away in at least in a direction perpendicular to the plane of the moving wet pulp substrate, the stream will be deviated from its original direction towards the direction of gravity, the longer it is allowed to fall. On the other hand, the initial angle will make that deviation more or less pronounced if headbox (1) is rotated such that the direction of the stream of the coating composition exiting the slice chamber (4) is closer or further from the direction of gravity.
  • the headbox (1) according to the present invention is rotatable as a whole and/or moveable as a whole, via linear or rotary actuators coupled to the headbox (1) as a whole, where preferably linear actuators are configured such as to move the headbox (1) as a whole and/or rotary actuators are configured such as to rotate the headbox (1) as a whole.
  • the headbox (1) according to the present invention is rotatable as a whole by an angle of -15 to 15° with respect to the plane of the moving wet pulp substrate in the paper machine.
  • the headbox (1) according to the present invention is in general rotatable towards, or away from, the plane of the moving wet pulp substrate
  • the headbox (1) according to the present invention is moveable as a whole to a distance of from 10 to about 80 mm, at least in a direction perpendicular to the plane of the moving wet pulp substrate. It is noted that the headbox (1) according to the present invention may also moveable along the direction of movement of the moving wet pulp substrate in the paper machine. This allows the headbox (1) to be positioned above a section of the moving wet pulp substrate in the paper machine that is either upstream or downstream, or stated alternatively, closer of farther from a primary headbox (1), in the direction of movement of the moving wet pulp substrate in the paper machine.
  • the headbox (1) according to the present invention is positioned in the wet end section of the paper machine, and is in particular positioned in the wet end section where the moving wet pulp substrate has a solids content of less than 20% by weight, or of about 4 to 20%, preferably of about 4 to 8% by weight.
  • the headbox (1) according to the present invention the rotatable valve body (5) has an elongated shape, and may be formed as shaft, which rotatable valve body is rotatable around a longitudinal axis (A) of the rotatable valve body (5).
  • the distance in radial direction, from the longitudinal axis (A) of the rotatable valve body (5) to the first sealing element (7) is equal to the distance in radial direction, from the longitudinal axis (A) of the rotatable valve body (5), to the second sealing element (8).
  • the rotatable valve body (5) may have a length, along its longitudinal axis, of about from 1 m to about 8 m, preferably a width of about from about 2 m to about 7 m.
  • the rotatable valve body (5) being preferably a shaft, is rotatable along a longitudinal axis (A) of the shaft, wherein the first and second sealing elements (7, 8) are located at the same radial distance from the longitudinal axis (A) of the shaft.
  • the rotatable valve body (5) comprises an axle extending along a longitudinal axis (A) of the rotatable valve body (5), which axle is coupled to a controllable rotary driving means, such as to rotate the rotatable valve body (5) in one or the other direction.
  • the axle extending along a longitudinal axis (A) of the rotatable valve body (5) and the rotatable valve body (5) are made integrally from one piece of material, such as steel, for example by machining from one blank. Suitable technologies include milling, turning or combinations of both.
  • the rotatable valve body (5) is preferably made from one piece of a massive material, i.e. the rotatable valve body (5) is not hollow.
  • the rotatable valve body (5) comprises one or more rods connected via an articulation to a periphery of the rotatable valve body (5), which rod(s) may for example be coupled to a controllable linear driving means, such as to rotate the rotatable valve body (5) in one or the other direction.
  • the axle extending along a longitudinal axis (A) of the rotatable valve body (5) and the rotatable valve body (5) are made integrally from one piece of material, such as steel, for example by machining from one blank. Suitable technologies include milling, turning or combinations of both.
  • the first and/or second sealing elements (7, 8) are formed by sealing ribs, in particular sealing ribs extending, in a preferably rectilinear manner, in parallel to a longitudinal axis (A) of the rotatable valve body (5), said ribs preferably having a rounded, square or pointed tip.
  • the headbox (1) according to the present invention, the first and second sealing elements (7, 8) are formed by rectilinear edges extending in parallel to a longitudinal axis (A) of the rotatable valve body (5), preferably having a square tip.
  • the first and second sealing elements (7, 8) are formed by rectilinear edges extending in parallel to a longitudinal axis (A) of the rotatable valve body (5), preferably having a square tip, and are connected to each other via a planar surface spanning between the first and second sealing elements (7, 8).
  • the first and second sealing elements (7, 8) are formed by rectilinear edges extending in parallel to a longitudinal axis (A) of the rotatable valve body (5), preferably having a square tip, and are connected to each other via a non-planar surface, which may be concave or convex, spanning between the first and second sealing elements (7, 8).
  • sealing elements may be formed integrally on the rotatable valve body (5), and may be obtained from machining a blank into a rotatable valve body (5) with sealing elements.
  • the sealing elements may be formed separately from the rotatable valve body (5) and fixed to the rotatable valve body (5).
  • the headbox (1) in a closed state, the rotatable valve body (5) in the headbox (1) is at a rotation angle ⁇ of 0°, i.e. when both seals are formed by contact between the sealing elements and the sealing surfaces (9, 10), and in an opened state, the rotatable valve body (5) in the headbox (1) is at a rotation angle ⁇ of up to 40°, e.g. between 1 and 40°.
  • the rotatable valve body (5) has a cross-sectional shape, in a direction perpendicular to its longitudinal axis, that is in partially circular, wherein the circular section of the cross-sectional shape of the rotatable valve body (5) is slidingly in sealing contact with valve case body (6).
  • the circular section of the cross-sectional shape of the rotatable valve body (5) is slidingly in sealing contact with a circular recess in the valve case body (6), or alternatively is slidingly in sealing contact with a circular recess in the valve case body (6) comprising additionally one or two gaskets.
  • the partially circular section of the rotatable valve body (5) ensures that the rotatable valve body (5) may be rotated into either open or closed state of the headbox (1) while keeping in sealing contact with gaskets that are located on the valve case body (6).
  • the one or two gaskets are held in one or more recesses, respectively, that are formed in the valve case body (6).
  • the first sealing surface (9) is a convex surface of the valve case body (6), said convex surface having preferably a circular shape.
  • the flow of a coating composition flowing through the clearance, from the stock chamber (2) to the stilling chamber (3) that is formed in an open state of the headbox (1) is directed by the convex surface of the valve case body (6).
  • the second sealing surface (10) is a planar surface of the valve case body (6).
  • the flow of a coating composition flowing through the clearance, from the stilling chamber (3) to the slice chamber (4) that is formed in an open state of the headbox (1) is directed by the planar surface of the valve case body (6), thereby providing a stable and unidirectional stream, or jet, of coating composition.
  • the planar surface of the valve case body (6) extends in opposing directions, with respect to the second seal, i.e. both in an upstream direction and an downstream direction with respect to the flow of a coating composition,
  • the stilling chamber (3) comprises a concave surface on the valve case body (6), in between the first sealing surface (9) and the second sealing surface (10).
  • the convex surface of the first sealing surface (9) on the valve case body (6) transitions into the concave surface on the valve case body (6) of the stilling chamber (3).
  • the concave surface on the valve case body (6) of the stilling chamber (3) is configured such that it directs the flow of a coating composition towards the second clearance and/or in a direction that lies in the plan of the planar surface of the valve case body (6). In that case, the concave surface on the valve case body (6) of the stilling chamber (3) transitions into the planar surface of the valve case body (6).
  • the slice chamber (4) in an open state, the slice chamber (4), at the second sealing element (8) and second sealing surface (10), forms a clearance in the form of a horizontal rectangular slit, for ejecting the stream, or curtain, of a coating composition from the stilling chamber (3) into the slice chamber (4), where the height of the clearance, and consequently, of the horizontal slit is of from 0.3 to 5 mm, preferably of from 0.8 mm to 3 mm.
  • the width of the horizontal rectangular slit is about from 1 m to about 8 m, preferably about from about 2 m to about 7 m.
  • the slice chamber (4) comprises, at its downstream end, a bottom lip (11) for guiding the stream of a coating composition exiting the slice chamber (4) through the second clearance.
  • the bottom lip (11) has a variable length, since when the rotatable valve body (5) is rotated into an open position, the second sealing element (8) moves away from the second sealing surface (10) along a circular path thereby also moves the second clearance, where the jet is formed, further downstream of the intended direction of flow of the coating composition.
  • the coating composition when the headbox (1) is in an open state, leaves the stilling chamber (3) through the second clearance into the slice chamber (4) in the form of a stream, or jet, of a coating composition and subsequently leaves the slice chamber (4) to fall onto the moving wet pulp substrate in a paper machine.
  • a bottom lip extending from the slice chamber (4) allows creating a stable stream or jet of a coating composition.
  • the length of the bottom lip, in a closed state of the headbox (1), is fix, and defined as the distance between the second seal and the downstream end of the bottom lip, and may be, for example 32 mm.
  • the length of the bottom lip, in an open state of the headbox (1) is variable instead of fix, and is inferior to the length of the bottom lip, in a closed state of the headbox (1), and is defined as the distance between the second clearance, in an open state of the headbox (1), and the downstream end of the bottom lip, and may be of from 4 mm to 32 mm, preferably of from 9 to 17 mm.
  • a paper machine according to the present invention is capable of producing paper having a uniform coating, in thickness and composition, in an economical and simplified way, as the headbox (1) is especially rigid due to its design and can deliver a stable jet of coating composition.
  • the paper machine according to the present invention is capable of producing paper having a uniform coating of microfibrillated cellulose, which is exceptionally difficult to apply such that the coating is uniform.
  • the ratio of the speeds is in the aforementioned range, the coating, upon touching down on the moving substrate is neither overstretched nor compressed by the moving substrate, which avoids major shear in the bulk of the coating composition at the time of touching down.
  • the stilling chamber (3) is completely filled with a coating composition during operation of the headbox (1), so that no air cavity, or air cushion is formed.
  • the stream of a coating composition can be applied onto a moving wet pulp substrate in a paper machine according to the second object such that the stream of a coating composition contacting the moving wet pulp substrate contacts the moving wet pulp substrate at an angle of between 3 and 75°, preferably of 15 to 40°.
  • Controlling the angle at which a coating composition can be applied onto a moving wet pulp substrate can be useful when adjusting the degree of shear that is imparted on the coating composition immediately after contacting the moving wet pulp substrate. At smaller angles, the lateral shear is minimized, as the stream of a coating composition gets barely deflected whereas at larger angles, the stream of a coating composition gets deflected significantly in the direction of the moving wet pulp substrate.
  • the length of the falling stream of a coating composition is between 3 mm and 500 mm.
  • the length of the falling stream of a coating composition corresponds to the distance between the point where the stream leaves the bottom lip (11) extending from the slice chamber (4) to the point where the stream of a coating composition contacts the moving wet pulp substrate.
  • the flow rate of the stream of a coating composition is in the range of 50 till 4000 I/min per meter width of the second clearance.
  • the width of the stream of a coating composition is in the range of about from 1 m to about 8 m, preferably a width of about from about 1,5 m to about 5 m, or from about 2 m to about 7 m.
  • the speed of the stream of a coating composition is in the range of 50 to 700 m/min or may be in the range of 50 to 1200 m/min.
  • the coat weight of microfibrillated cellulose that can be applied to the wet pulp substrate is of from 3 to 20 gr/m 2 in dry weight (air dry, lutro ) .
  • the coating composition comprises microfibrillated cellulose.
  • the coating composition is an aqueous suspension of microfibrillated cellulose.
  • the microfibrillated cellulose may be comprised in an amount of less than 2.5 weight percent, based on the total weight of the coating composition, more preferably in an amount of from 0.5 to 2.0 weight percent, even more preferably in an amount of 0.8 to 1.0 weight percent.
  • the microfibrillated cellulose is preferably microfibrillated cellulose made from hardwood.
  • coating compositions comprising microfibrillated cellulose are a prominent example of coating compositions that can be applied with the headbox (1) according to the present invention, and in the method of applying a stream of a coating composition onto a moving wet pulp substrate in a paper machine according to the present invention
  • other coating compositions that may be applied are coating compositions that, in general, are shear-thinning and/or which have a viscosity of about 5 to 100 mPas when under shear rate of about 1000 to 8000 s -1 , when measured according to ISO 3219 on a Physica Anton Paar MCR 300 using spindle CC27 SN4989 and cup CC27 SS43953.
  • the moving wet pulp substrate has a solids content of less than 20% by weight, about 4 to 20%, preferably of 4 to 8% by weight, based on the total weight of the moving wet pulp substrate.
  • the remaining weight is formed by at least 80% by weight of aqueous liquids such as water. It is believed that since the water content in the moving wet pulp substrate is high, an entanglement between the loosened wet pulp substrate fibers and the microfibrillated fibers of the coating composition is thereby enhanced, and therefore results in better adhesion between these layers in the final paper product.
  • a coating composition comprising microfibrillated cellulose at about 8 g/l was prepared and provided to a headbox (1) according to the present invention via feeding lines placed along the longitudinal dimension of the headbox (1) (i.e. transverse paper machine direction), and fed to the stock chamber (2) of the headbox (1) at about a pressure of 51 kPa.
  • the headbox (1) was then opened by an angle of 14 °, such as to provide a jet having a thickness of 1.4 mm and of a width of 1000 mm, at a flow rate of 840 I/min per meter width of the second clearance of the headbox (1).
  • the angle of the headbox (1) with respect to the plane of the moving wet substrate was about 12° and the headbox (1) was positioned at about 5mm above the moving wet substrate.
  • the velocity of the moving wet substrate and the velocity of the jet exiting the headbox (1) was 10 m/s and 10,08 m/s, respectively.
  • the moving wet substrate was prepared by discharging a stock having a consistency of about 10 g/l of a chemical wood pulp having refining degree more than 90 °SR
  • the weight of the coating composition on the moving wet substrate was checked by online measuring of the freshly deposited coating composition and found to be homogenous across the entire width, and to be about 14 gr/m 2 .

Landscapes

  • Paper (AREA)
EP22210936.5A 2022-12-01 2022-12-01 Caisse de tête et procédé d'application de compositions de revêtement sur un substrat de pâte humide mobile à l'aide de ladite caisse de tête Pending EP4379130A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP22210936.5A EP4379130A1 (fr) 2022-12-01 2022-12-01 Caisse de tête et procédé d'application de compositions de revêtement sur un substrat de pâte humide mobile à l'aide de ladite caisse de tête
PCT/EP2023/083624 WO2024115610A1 (fr) 2022-12-01 2023-11-29 Caisse de tête et procédé d'application de compositions de revêtement sur un substrat de pâte à papier humide mobile à l'aide de ladite caisse de tête

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP22210936.5A EP4379130A1 (fr) 2022-12-01 2022-12-01 Caisse de tête et procédé d'application de compositions de revêtement sur un substrat de pâte humide mobile à l'aide de ladite caisse de tête

Publications (1)

Publication Number Publication Date
EP4379130A1 true EP4379130A1 (fr) 2024-06-05

Family

ID=84369784

Family Applications (1)

Application Number Title Priority Date Filing Date
EP22210936.5A Pending EP4379130A1 (fr) 2022-12-01 2022-12-01 Caisse de tête et procédé d'application de compositions de revêtement sur un substrat de pâte humide mobile à l'aide de ladite caisse de tête

Country Status (2)

Country Link
EP (1) EP4379130A1 (fr)
WO (1) WO2024115610A1 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5104011A (en) * 1990-08-03 1992-04-14 Ingersoll-Rand Company Self-cleaning feed apparatus
US5456804A (en) * 1994-08-22 1995-10-10 Ingersoll-Rand Company Inlet slice assembly, for a pulp slurry processing machine

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5104011A (en) * 1990-08-03 1992-04-14 Ingersoll-Rand Company Self-cleaning feed apparatus
US5456804A (en) * 1994-08-22 1995-10-10 Ingersoll-Rand Company Inlet slice assembly, for a pulp slurry processing machine

Also Published As

Publication number Publication date
WO2024115610A1 (fr) 2024-06-06

Similar Documents

Publication Publication Date Title
US5447753A (en) Method of manufacturing coated paper for printing
EP1123665B1 (fr) Papier de cigarettes
US5645689A (en) Multilayer headbox
EP1456467B1 (fr) Procede et dispositif d'application d'un materiau sur une bande
US20190309481A1 (en) Method with a horizontal jet applicator for a paper machine wet end
US20110083603A1 (en) Curtain coater
FI20180087A1 (en) Method and apparatus for applying starch
ZA201005687B (en) Curtain coater
EP2784213B1 (fr) Caisse de tête pour une machine de production d'une bande de matière fibreuse
JPH03161599A (ja) ロールコータ、ロールコータの使用方法、ロールコータ用デッケル
EP4379130A1 (fr) Caisse de tête et procédé d'application de compositions de revêtement sur un substrat de pâte humide mobile à l'aide de ladite caisse de tête
JP2011508833A (ja) 移動オリフィスを用いてスリット帯状包装紙を作る方法及び装置
EP2215305B1 (fr) Procédé pour délivrer une pâte à haute consistance à un support de formation et à une caisse de tête de pâte à haute consistance
EP0460771A1 (fr) Appareil et procédé pour empêcher la formation de stalagmite lors du couchage du papier
WO2023169741A1 (fr) Buse d'application, unité d'application et procédé
CA2248892C (fr) Applicateur de film a alimentation inversee
EP4245916A1 (fr) Procédé de traitement d'une bande de fibres et système de traitement pour le traitement d'une bande de fibres
CA2300280C (fr) Appareil et procede de production de turbulences de pate dans une section de mise en feuille a table plate
CN213408280U (zh) 在用于纤维幅材的表面胶的生产中的浆料容器
EP2894254B1 (fr) Dispositif de revêtement pour l'application de couleur de revêtement sur une bande de fibres et procédé associé
AT508526B1 (de) Vorrichtung und verfahren zum zuführen von faserpulpe zu einem bahnbildungsträger
DE102022105518B4 (de) Auftragsdüse, Auftragswerk und Verfahren
FI20185739A1 (en) Fiber web treatment method and treatment system for fiber web treatment
EP4297911A1 (fr) Dispositif de coulée, système et procédé de coulée d'un film mfc
EP3540117B1 (fr) Caisse de tête multicouche d'une machine de fabrication d'une bande de matière fibreuse et procédé de formation d'une bande de matière fibreuse dans une section de formation d'une machine de production d'une bande de matière fibreuse

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN PUBLISHED

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC ME MK MT NL NO PL PT RO RS SE SI SK SM TR