EP0483183B1 - Procede et appareil de fabrication de papiers lisses et satines - Google Patents

Procede et appareil de fabrication de papiers lisses et satines Download PDF

Info

Publication number
EP0483183B1
EP0483183B1 EP19900910498 EP90910498A EP0483183B1 EP 0483183 B1 EP0483183 B1 EP 0483183B1 EP 19900910498 EP19900910498 EP 19900910498 EP 90910498 A EP90910498 A EP 90910498A EP 0483183 B1 EP0483183 B1 EP 0483183B1
Authority
EP
European Patent Office
Prior art keywords
web
cylinder
paper
smooth
dryer
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.)
Expired - Lifetime
Application number
EP19900910498
Other languages
German (de)
English (en)
Other versions
EP0483183A1 (fr
Inventor
Ivan I. Pikulik
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.)
Pulp and Paper Research Institute of Canada
Original Assignee
Pulp and Paper Research Institute of Canada
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 Pulp and Paper Research Institute of Canada filed Critical Pulp and Paper Research Institute of Canada
Publication of EP0483183A1 publication Critical patent/EP0483183A1/fr
Application granted granted Critical
Publication of EP0483183B1 publication Critical patent/EP0483183B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • D21F3/00—Press section of machines for making continuous webs of paper
    • D21F3/02—Wet presses
    • D21F3/0281—Wet presses in combination with a dryer roll
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00—Dryer section of machines for making continuous webs of paper
    • D21F5/02—Drying on cylinders
    • D21F5/04—Drying on cylinders on two or more drying cylinders

Definitions

  • the present invention relates to a method and apparatus for drying wet fibrous webs, and more particularly, it applies to the continuous drying of wet printing papers such as newsprint.
  • a new drying method is disclosed which, compared with the conventional method, employs a smaller number of dryers, leads to better machine runnability, and yields products with greater tensile strength, better surface properties and printing characteristics.
  • This method is particularly suitable for drying wet cellulosic webs intended for printing products such as newsprint and bond paper.
  • a suspension of cellulosic fibres is ejected on an advancing forming fabric which retains a large portion of fibres and fine cellulosic material, and transmits a large portion of water. Additional water is removed from the wet cellulosic web by mechanical compression between two rotating press rolls. Water remaining in the pressed web is removed by evaporation in a dryer section of the paper machine.
  • the web is passed around a series of internally-heated rotating cylinders known as "dryers", which are usually arranged in an upper and a lower row.
  • the advancing web is heated by direct contact with a portion of the cylinder surface.
  • This drying method is well known, and is described for example in US 2299460.
  • the wet web is often sandwiched to the dryer surface by dryer fabrics.
  • One such fabric might wrap a part of the surface of the upper row of dryers, while another dryer fabric might wrap the bottom part of the lower row of dryers.
  • the wet paper proceeds around the initial drying cylinders adjacent to a single drying fabric.
  • the paper is supported by the fabric as it advances between the dryers, which reduces the tendency of the web to flutter, and the frequency of the breaks.
  • the single felted arrangement is used primarily, but not exclusively, on the initial section of cylinders where the sheet is very moist and weak, while the open draw is utilized between the remaining drying cylinders.
  • Application of a single drying fabric in a serpentine configuration is described for example in US 4172007.
  • a disadvantage of the single felted run is that only one half of dryers (usually those in the upper row) come into direct contact with the paper, while the other half of dryers are separated from the paper by the dryer fabric which reduces the amount of heat transferred from these dryers to wet web. Consequently, more dryers, or higher dryer temperatures are required with the serpentine arrangement of dryer felt.
  • Another method sometimes used for drying paper employs the "Minton Dryer” (US 1147809) in which the drying cylinder is located within a large evacuated chamber. At the decreased air pressure, the boiling point of water is reduced, which could potentially increase the rate of heat transfer.
  • the disadvantage of Minton dryers is that, in the absence of drying fabrics, the intimate contact between the dryer and the web is not established, and the rate of heat transfer is low.
  • Another problem associated with the Minton Dryer is the necessity to disrupt the vacuum whenever a sheet break occurs. In the absence of any support for the wet web during the transfer between dryers, this method cannot be used on fast machines.
  • the wet web is supported by jets of heated gas which provide the heat required for the evaporation of water, and carry away water vapours.
  • This operation is described for example in US 3739491.
  • the heat transfer rates achieved with this method are high, and the mechanical stress on the wet web is low.
  • the cellulosic web dried without contact with a supporting medium shrinks unevenly and subsequently develops undesirable deviation from polarity called cockle, which lowers the product quality and might lead to wrinkles or cuts during calendering. Difficulties with threading the dryer after a web break are another disadvantage of this drying method, presently used mainly for heavy basis weight grades or for initial drying of light basis weight products.
  • the web is dried entirely on a single, large-diameter, rotating, steam-heated cylinder known as a "Yankee dryer".
  • a notable feature of web drying on a single cylinder is that the initial contact between the dryer surface and the web is established in a press nip.
  • a metal, rubber covered press roll wrapped by a press felt or a fabric presses the web onto the dryer surface by a force of about 30 to 80 kN/m.
  • the soft wet-web fibres establish an intimate contact with the surface of the dryer which leads to a high heat transfer and drying rates.
  • the drying rate is further enhanced by impingement of hot air on the paper adhering to the dryer surface.
  • the jets of preheated air come from the so called "high velocity" hood, which surrounds a large portion of the Yankee dryer.
  • about half of the drying energy is derived from the steam inside the Yankee dryer, while the other half is supplied by the hot air.
  • creped tissue paper When paper is completely dried on a single, large diameter dryer, it adheres strongly to the dryer surface and cannot be safely peeled off without breaking the sheet, especially if the basis weight of the paper is low.
  • the web In production of creped tissue paper, the web is dried entirely on a single Yankee dryer, and the dry product is separated from the dryer surface by a creping blade.
  • the separated paper is densely wrinkled by the action of the blade, and usually has from 25 to 120 crepe ridges per inch. Paper creped in this manner has low tensile strength, high bulk, softness and water absorbency, and a rough surface. These properties make creped paper a good material for hygienic products, but unsuitable for application as a printing paper.
  • MG cylinders Heavier basis weight, often partially dried, cellulosic webs are sometimes also pressed to large diameter driers, called MG cylinders. These stronger and less adhesive webs might be peeled from the dryer surface, giving a product which has one side smooth and glossy, or "machine glazed" (hence MG cylinder).
  • machine glazed two sides of a product treated in this way are very different, namely the web side which was in contact with the dryer surface becomes smoother and glossier than the reverse side.
  • Such a product is suitable for products such as folding boxes in which only one side is visible, while lower demands are placed on the board side inside the box.
  • Yankee drying is presently used especially for light basis weight hygienic or wrapping papers which are removed from the dryer by a creping blade, and MG cylinders are used for some paperboard products in which the difference in the two paper sides is desirable.
  • the essential requirements of printing paper include good surface smoothness, identical properties of two paper sides, and resistance of the superficial fibres and fines to their removal by tacky ink during the printing process (low linting propensity). Regardless of the printing technique applied, the printing quality of paper improves with improving surface smoothness. Therefore, the smoothness of all printing papers is enhanced by calendering the dry paper in one or several nips formed by polished calender rolls.
  • the results of calendering of paper include decreased roughness and increased gloss, which are desirable, and reduced paper thickness which is desirable only for some grades.
  • the undesirable results include a decrease in the tensile, tear and burst strength of paper, and a reduction of the cohesion of the superficial fibres and fines with the rest of the web.
  • Desirable properties of printing papers include low roughness, high gloss, large tensile and tear strength, low linting propensity and no difference in the characteristics of the two sides of paper. While smoothness and gloss of paper can be improved by calendering, this treatment has a negative effect on the strength and linting propensity of paper. Therefore, other and more expensive methods, such as the application of more expensive pulps to furnish, are sometimes used to reduce the amount of calendering required to optimize the properties of printing papers made of mechanical pulps. Clearly it is desirable to develop a process which would produce a smoother and glossier paper, especially newsprint, without negatively affecting the strength and linting properties of paper.
  • drying apparatus comprising a row of drying cylinders against which a web is held by a dryer felt and pressed by a series of press rolls to achieve a desired moisture content.
  • An object of the present invention is to provide a method and apparatus for drying an endless water-containing cellulosic web having opposed smooth sides, and/or improvements in relation to one or more of the matters discussed above.
  • a method for the continuous drying of endless cellulosic webs at a drying rate greater than that normally achieved on cylinder dryers is stronger, smoother, glossier, and has a greater surface strength than paper dried by conventional methods.
  • the method is particularly suitable for drying wet cellulosic webs intended for printing products such as newsprint and bond paper.
  • the method comprises drying a water containing cellulosic web for paper on at least two heated cylinders in such a manner that one paper side is adjacent to the surface of the first cylinder and the other side is adjacent to the surface of the second cylinder.
  • the water-containing cellulosic web is fed onto a first heated cylinder and a first side of the web is pressed against a smooth surface of the first heated cylinder with the first side contacting the smooth surface.
  • the resulting partially dried web is removed from the first cylinder and fed onto a second heated cylinder and is pressed against a smooth surface of the second heated cylinder with a second side of the web contacting the smooth surface of the second cylinder; the second side being opposed to the first side, whereafter the resulting dried cellulosic web is removed from said second cylinder.
  • the pressing of the partially dried web against the smooth surface of the second cylinder is carried out by pressing with a smooth, impermeable press roll applied against the web in contact with the first side.
  • an apparatus for carrying out the method includes first and second rotatable cylinders, each having a smooth cylindrical surface.
  • a heating means is provided to heat the cylindrical surfaces.
  • a roller is disposed to press a first side of the endless water-containing cellulosic web into contact with the smooth cylindrical surface of the first cylinder.
  • a smooth, impermeable press roll is disposed to contact the first side of the web downstream of the first cylinder and presses the web with its second side in contact with the cylindrical surface of the second cylinder.
  • Drive means is provided to drive the cylinders.
  • the first and second cylinders are large diameter cylinders, having a diameter of 3 to 8, usually about 6 metres, and the cylinders have a surface temperature of about 105 to 130°C preferably about 118°C.
  • the nip load at the pressing of the web against the first and second cylinders is suitably 65 to 150 kN/m, preferably about 100 kN/m.
  • the web suitably travels in contact with the cylinders at the regular velocity of the paper machine for example 600 to 1500 m/min. , and the method is particularly suitable for machines operating at speeds -above 1000 m/min.
  • the drying rate achieved is between 70 and 100, typically about 85 kg/m2h on the first cylinder and 15 to 30, typically about 25 kg2h on the second cylinder.
  • the web is pressed against the first cylinder by pressing a porous, compressible substrate, for example, a felt, in contacting engagement with the second side of the web.
  • a porous, compressible substrate for example, a felt
  • the web previously dewatered in a conventional press section, is pressed onto the first large diameter dryer by means of a felt, backed by a press roll equipped with some superficial cavities to accept water escaping from the press nip.
  • the partially dried web is pressed to the second large diameter cylinder by an unfelted smooth press roll.
  • the large diameter dryers operate without dryer fabrics and in the preferred embodiment, they are equipped with high velocity hoods, infrared heaters or other external means of drying. Drying of webs pressed on the surface of a smooth dryer leads to paper with higher strength, gloss, and smoothness than that of the conventionally dried paper.
  • the smooth unfelted press roll on the second large diameter dryer preserves the paper smoothness developed on the first dryer. The drying rates obtained by this method are 6 to 10 times greater than those achieved on conventional dryer sections.
  • the drying apparatus consists of two large diameter cylinders 1, 2 and two press rolls 3, 4 equipped with web transfer devices ( Figure 1). Web 5, is carried by the press felt 6 to the nip formed by the press roll 3 and dryer 1.
  • the transfer device consists of an air doctor 7, and a vacuum roll 8. The combined effect of the air doctor 7 and the vacuum roll 8 transfers the web from dryer 1 to the conveyor fabric 9. The web is picked up by the solid smooth press roll 4 and pressed onto the second dryer 2. The partially or completely dried web is removed from the dryer 2 by the air doctor 10 and, with the assistance of the vacuum roll 11 is transferred on the conveyor fabric 20 which carried it to the subsequent machine part such as an after-dryer or a calender.
  • the web 5 arrives to dryer 1 from a conventional press with a solids content between about 30% and 50% as it enters the nip formed by the press roll 3 and the dryer 1 .
  • the web is compressed by the press felt 6 to the dryer surface and an intimate contact is established between the web fibres and the surface of the dryers.
  • the nip loads required to establish such a contact resemble those commonly used in the press sections of paper machines (I.I. Pikulik and I.T. Pye, Survey of Press Sections of Canadian Pulp, Paper and Board machines, TS CPPA, Montreal, 1986).
  • nip loads for example those above 100 kN/m, might lead to a better water removal in the press nip and a slightly greater solids content of web leaving the nip.
  • high nip loads are not required for the achievement of high heat transfer rates, and therefore high drying rates.
  • high nip loads enhance the development of high gloss and the smoothness of paper, low roughness and higher paper gloss are obtained when press nip loads of 40 to 150 kN/m are used.
  • the surface of the dryers 1 and 2 is smoothly polished because characteristics of roll surface are duplicated on the paper surface and a low roughness is desirable for good printing properties of paper.
  • the backing press rolls 3 might be equipped with some cavities such as suction holes, blind drilled holes, or grooves, which can receive water expressed from the web and press felt.
  • the press roll 4 must be smooth without any large superficial features. Roll 4 is in contact with the smooth and glossy side of paper which was previously glazed by dryer 1 . In a conventional felted press nip, such as that formed between dryer 1 and roll 3 or between conventional press rolls, one paper side is compressed against the surface of the press felt.
  • the surface of the felt is rougher and stiffer than that of moist paper. Compression of the smooth bottom side of web 5 in a conventional manner, that is by a press felt 12 as shown in Figure 2 increases the roughness and decreases the gloss of this paper side, and largely eliminates improvements of the paper surface achieved on the first dryer. Therefore, a unique feature of this invention is the compression of the web by a smooth, impermeable roll 4 on the surface of heated cylinder 2 . Conventional press roll covers made of hard rubber or other material are suitable for this roll. Loads in the nip formed by press roll 4 and dryer 2 will depend on the desired properties of the product. Higher nip loads increase the drying rate on the second dryer and smoothness of the top side of paper.
  • the smoothness of the top paper side is also greater if the humidity of paper arriving at the second dryer is increased. Equal smoothness and gloss of the two paper sides can be achieved by adjusting dryer surface temperature, parameters of high velocity hoods, and nip loads of the two dryers.
  • Water removal capacity of a dryer is doubled when it is equipped with a so called high velocity hood as indicated in Figure 3.
  • the jets of preheated air which impinge from the high velocity hood 13 on web 5 as it proceeds around the dryer provide the heat required for evaporation of water and carry water vapour away from the vicinity of the paper.
  • the high velocity hood can be used when this invention is applied to high speed machines, heavy basis weight printing papers, or whenever an increase in the drying capacity is required.
  • the construction and operating parameters of the high velocity hood are not the subject of this invention.
  • a hood such as that described by T. Gardner [Tappi, 47 (4) 210 (1964)] or other efficient hoods could be employed.
  • other external heat sources for example infrared heat could be used to increase the drying rate.
  • Dryers 1 and 2 can be heated by various means, such as internally by compressed steam or direct flame, electrical induction, infrared radiation or externally e.g. by electrical induction or other means.
  • the majority of Yankee dryers and MG cylinders currently used, are heated internally by medium pressure steam, and similar techniques are also applicable to the present invention.
  • the optimum temperature of the dryer surface will depend on the properties of the web. If the dryer temperature is too high and the web has a low permeability to water vapours, a layer of pressurized steam could develop between the dryer surface and the paper in a manner similar to that used in impulse drying. At high machine speeds and short nip residence time this steam would not displace liquid water as it occurs during impulse drying, but it could partially separate the web from the dryer wall, reduce the area of intimate contact between the dryer and the fibres. This would result in a lower heat transfer rate and a slower rate of drying. Too low a temperature at the drier surface would result in a low temperature difference between paper and dryer, and therefore a low heat transfer rate, and a low rate of drying.
  • the dryer surface temperature might range from about 100°C to about 170°C, and temperatures in the range of 108°C to 140°C were found to be especially convenient for the drying of newsprint.
  • the amount of water removal on the dryers described in this invention depends on the web-dryer contact time which, in turn, depends on the diameter of the dryers and on machine speed.
  • the diameter of the dryers is determined by the basis weight of products, moisture content in the pressed web, and machine speed. Two or more dryers with large diameters can provide the residence time required for complete drying of low basis weight printing grades. However, various practical reasons restrict the size of dryers. For example, modern machines producing creped papers usually employ a single dryer with a diameter of about 6 to 7 m.
  • the web is pressed on the first dryer cylinder with the solids content similar to that obtained at the end of a conventional press section, namely 35% to 50%.
  • the web is removed from the first cylinder at a solids content of 55% to 75% and pressed to the second dryer.
  • the cellulosic fibres are less swollen, more rigid and a less perfect contact with the surface of the second dryer will be established upon pressing. For this and other reasons, the rate of drying is lower on the second dryer than on the first dryer.
  • paper is dried to its final solids content, namely about 90%, on just two large diameter dryers, as this method of drying provides a high drying rate, good paper surface smoothness and gloss and improved paper strength. A smaller, but still substantial improvement in the paper smoothness and gloss can be obtained when paper is pressed to a dryer with a smaller diameter. Paper partially dried in this manner can then be dried further by other methods.
  • the two dryers equipped with presser rolls could be installed within conventional cylinder dryer section to improve the surface properties of the product.
  • a scheme of a conventional dryer section is shown in Figure 4.
  • a conventional dryer section modified by installation of two press roll equipped dryers is shown in Figure 5.
  • the dryer section modified as shown in Figure 5 provides an increased rate of drying only on two dryers, 14 and 15 , to which paper is pressed by press rolls 16 .
  • Additional dryer cylinders can be equipped with press rolls if further increase in the drying capacity and improvement in the paper surface properties is desirable.
  • press rolls acting on the wet webs on the initial dryers where the web solids content is too low must be felted to provide a route for escape of water removed from paper in the press nip, and press rolls acting on dryer webs (for example with solids content of 57% or greater), should be unfelted and smooth to prevent marking of the sheet.
  • Paper could be pressed to any dryer cylinder, however, as the web solids content increases, beneficial effects of web pressing on dryers declines.
  • drying rates of 160 kg water per m2 per hour are achieved at dryers of tissue machines.
  • drying rates of about 90 kg water per m2 per hour were obtained when drying newsprint, even without the assistance of air impingement.
  • the average drying rate on conventional newsprint drying cylinders is only about 15 kg water per m2 per hour (TAPPI Technical Information Sheet 0404-15, revised in 1986).
  • the web is dried on two dryers with diameters of about 5-7 m.
  • Two large diameter dryers even if equipped with high velocity hoods, might not be able to entirely dry the web on very rapid machines, especially if they produce products with a higher basis weight.
  • additional dryers can be used to complete drying of the web after the second dryer.
  • the web pressed onto the dryer surface has a relatively low solids content, as required for the development of good paper surface properties.
  • Once high gloss and smoothness are achieved in the paper after drying on the two consecutive large dryers to a solids content of 70% or more, these desirable properties are retained in paper which was subsequently dried by other means.
  • This additional drying can be accomplished on conventional drying cylinders, or by other techniques.
  • the excessive moisture which remains in the web leaving the second dryer could be evaporated on a dryer which combines the air impingement with an air passage through the sheet (US 3248798), and which is known as Papridryer.
  • Example 1 Showing that paper pressed to just one dryer is stronger, and has one smooth and one glossy side.
  • Newsprint sheet with a basis weight of 50 g/m2 was prepared on a pilot paper machine equipped with a twin former and operating at 800 m/min, from a furnish composed of 18% softwood kraft pulp and 82% stone groundwood pulp.
  • the sheet was pressed on a paper machine in two press nips loaded to 45 and 90 kN/m respectively, and reeled at a solids content close to 40%. Further treatment of the sheet was carried out on the pilot drying machine shown in Figure 6.
  • the wet paper was unwound from the reel 18 and carried at a speed of 100 m/min by the press felt 6 into a nip formed by the press roll 3 and dryer roll 1 .
  • the dryer roll was heated externally by electrical induction.
  • the press nip load was 100 kN/m and the roll temperature was about 125°C.
  • the diameter of the press roll 3 was 0.76 m and that of the dryer 1 was 0.88 m.
  • the residence time of paper on the dryer roll was about 1.60 s which corresponds to a residence time on a dryer with a diameter of 6 m, operating at 700 m/min.
  • the solids content of the sheet at reel 18 was 39.2% and of that at reel 19 was 61.2%. This corresponds to a drying rate of 104 kg water per m2 of dryer per hour.
  • the tensile energy absorption (TEA), is a reflection of both the tensile strength and stretch of paper. Paper prepared according to the invention had TEA 38% greater than the control sample. While an increase of the tensile strength by conventional methods, such as by refining or by addition of strength chemicals, is often accompanied by a decline of the tear strength, this negative effect did not occur when the invention was applied.
  • Example 2 showing that smoothness developed on the first dryer is destroyed by pressing paper with a felt to the second dryer.
  • Wet newsprint web was prepared as described in Example 1, and treated on the pilot dryer machine shown in Figure 6. Paper was unwound from reel 18 , passed through the press nip and over the dryer 1 and collected on reel 19 . A sample of paper treated in this manner was removed, and reel 19 was relocated to position 18 . The sheet was then passed again through the nip and over the dryer in such a manner that the paper side that had faced the felt during the first pass faced the dryer on the second pass. Solids content of the initial paper was 43.8%, after the first pass 67.3%, and after the second pass 80.3%. Some parameters of operation and paper test results from this experiment are shown in Table II.
  • Example 3 showing improvements in smoothness, strength and printing quality of paper dried according to this invention.
  • the newsprint web was prepared as described in Example 1, and treated on the pilot dryer machine shown in Figure 6, equipped with a smooth, hard press roll 3 . Paper was unwound from reel 18 in the press nip, was compressed between the felt 6 and the dryer 1 , proceeded around the dryer 1 , and was collected on the reel 19 . The reel 19 with the partially dried paper was then relocated to the position 18 and the felt 6 was removed. The sheet was passed again through the nip formed by the smooth roll 3 and dryer 1 , proceeded over the dryer in such a manner that the paper side that contacted the felt during the first pass faced the dryer during the second pass, while the reverse side faced the hard and smooth press roll. This procedure simulated the apparatus shown in Figure 1.
  • the solids content of the original paper was 37.9%, after the first pass 66.3%, and after the second pass 74.8%. Samples were removed from the original paper and paper treated according to this invention, and both were dried sandwiched between blotters on a photographic dryer.
  • Paper characterized in Table III was pressed at 100 kN/m and dried on a cylinder heated to about 118°C.
  • the paper described in Table III develops the required bulk and smoothness with less calendering.
  • An important quality criterion of printing paper grades is the print density index, which is a measure of the surface darkness achieved by a certain quantity of ink.
  • Table IV indicates that, although the paper prepared according to this invention was only lightly calendered, it had a print density index similar to that of heavily calendered conventional paper.
  • Example 4 showing web solids contents which can be obtained on two large diameter dryers equipped with press rolls.
  • the amount of water removed from a web pressed onto a heated cylinder depends on the web residence time.
  • the average drying rates obtained in several experiments similar to those described in Examples 2 and 3 were 88 kg/m2h for the first pass and 23 kg/m2h for the second pass. If it is assumed that similar drying rates could be obtained on a large diameter industrial dryer, the solids content obtainable at various machine speeds could be calculated.
  • Table V contains solids contents calculated for a newsprint sheet with a basis weight of 50 g/m2 previously pressed to a solids content of 45% and dried on two 6 m diameter driers, the perimeter of each of which is wrapped by the web, for a distance of 17 m. Drying rates of 88 kg/m2h and 23kg/m2h are assumed for the two passes .

Landscapes

  • Paper (AREA)
  • Drying Of Solid Materials (AREA)

Abstract

L'invention concerne un procédé et une machine de séchage de bande fibreuse, adaptés notamment à des machines à vitesse rapide produisant des papiers d'impression. On obtient des vitesses de séchages élevées par compression ultérieure des deux surfaces de la bande humide (5) sur des cylindres sécheurs (1, 2) de grand diamètre chauffés entre 100 et 150 °C. Dans le premier pincement, la bande (5) est pressée sur un cylindre sécheur (1) par un rouleau de presse feutré (3) tandis qu'un rouleau lisse non feutré (4) presse ladite bande (5) sur le second sécheur (2). L'invention, lorsqu'on la met en ÷uvre, permet d'obtenir des vitesses de séchage sensiblement supérieures à celles de trains de séchage classiques. Le produit obtenu selon l'invention est 30 % plus résistant que le papier non calandré séché de manière classique, et sans calandrage présente un lissé et un satiné similaires à ceux de papiers classiques calandrés.

Claims (12)

  1. Procédé de séchage d'une feuille cellulosique sans fin (5) contenant de l'eau, pour la formation d'une feuille séchée, comprenant :
       l'avance d'une feuille cellulosique contenant de l'eau, ayant une teneur en matières solides comprise entre 35 et 50 % en poids et ayant une première et une seconde face opposées, sur un premier cylindre chauffé (1),
       le pressage de la feuille contre une surface lisse du premier cylindre chauffé, la première face étant au contact de la surface lisse,
       l'extraction de la feuille cellulosique partiellement séchée du premier cylindre (1) alors qu'elle a une première face lisse,
       l'avance de la feuille partiellement séchée sur un second cylindre chauffé (2),
       le pressage de la feuille partiellement séchée contre une surface lisse du second cylindre chauffé, et
       l'extraction de la feuille cellulosique résultante séchée du second cylindre (2),
       caractérisé en ce que :
       l'étape de pressage de la feuille contre une surface lisse du premier cylindre chauffé avec la première face au contact de la surface lisse est réalisée par pressage d'un substrat compressible poreux (6) au contact de la seconde face de la feuille et par échappement de l'eau de la feuille cellulosique à travers le substrat compressible poreux afin que la feuille cellulosique soit partiellement séchée et que la première surface soit lisse, et
       l'étape de pressage de la feuille partiellement séchée contre la surface lisse du second cylindre chauffé est réalisée avec la seconde face de la feuille au contact de la surface lisse du second cylindre afin que la feuille subisse un séchage supplémentaire,
       le pressage de la feuille partiellement séchée contre la surface lisse du second cylindre est réalisé à l'aide d'un rouleau imperméable et lisse de pressage (4) roulant contre la feuille au contact de la première face lisse, et
       la feuille cellulosique séchée est retirée du second cylindre avec une première et une seconde face lisse opposées formées sur la feuille.
  2. Procédé selon la revendication 1, caractérisé en ce que le substrat compressible poreux est un feutre (6), et le pressage comprend un pressage du feutre contre la seconde face avec un rouleau de pressage (3) ayant un dispositif capable d'accepter l'eau chassée de la feuille, à travers le feutre, à une emprise formée par le rouleau de pressage et le premier cylindre.
  3. Procédé selon la revendication 1, caractérisé en ce que la feuille partiellement séchée retirée du premier cylindre (1) a une teneur en matières solides comprise entre 55 et 75 % en poids.
  4. Procédé selon la revendication 1, caractérisé par la projection à la seconde face de la feuille d'air chaud sur le premier cylindre chauffé (1) afin qu'un séchage supplémentaire de la feuille soit réalisé, et la projection sur la première face de la feuille d'air chaud sur le second cylindre chauffé (2) afin que la feuille subisse un séchage supplémentaire.
  5. Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce que la première et la seconde face lisse de la feuille ont des caractéristiques de régularité pratiquement identiques, et la feuille cellulosique séchée est récupérée sous forme d'une feuille de papier non calandrée.
  6. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que, pendant la fabrication du papier, le premier cylindre chauffé (1) a une température de surface comprise entre 105 et 130 °C et la charge à l'emprise du premier cylindre chauffé est comprise entre 65 et 150 kN/m, et
       la teneur en matières solides de la feuille lorsqu'elle est retirée du premier cylindre chauffé est comprise entre 55 et 75 % en poids, et le second cylindre chauffé a une température de surface de 105 à 130 °C et une charge à l'emprise de 65 à 150 kN/m, et la feuille non calandrée récupérée à partir du second cylindre chauffé a pratiquement les mêmes caractéristiques sur sa première et sa seconde face opposées.
  7. Procédé selon la revendication 6, caractérisé en ce que le substrat compressible poreux est un feutre (6), et le pressage comprend un pressage du feutre contre la seconde face avec un rouleau de pressage (3) ayant un dispositif d'acceptation de l'eau chassée de la feuille, à travers le feutre, à une emprise formée entre le rouleau de pressage et le premier cylindre.
  8. Procédé selon la revendication 7, caractérisé par la projection sur la seconde face de la feuille (5) d'air chaud au niveau du premier cylindre chauffé (1) afin qu'un séchage supplémentaire de la feuille soit réalisé, et la projection sur la première face de la feuille d'air chaud au niveau du second cylindre chauffé (1) afin que la feuille subisse un séchage supplémentaire.
  9. Appareil de séchage d'une feuille cellulosique sans fin (5) contenant de l'eau pour la formation d'une feuille séchée ayant des faces lisses opposées, comprenant :
       un premier cylindre rotatif (1) ayant une surface cylindrique lisse,
       un dispositif (3) à rouleau de pressage destiné à repousser, avec une charge d'emprise, une première face d'une feuille cellulosique sans fin contenant de l'eau en contact avec la surface cylindrique lisse du premier cylindre,
       un second cylindre rotatif (2) destiné à être au contact de la feuille, en aval du premier cylindre (1), et
       un dispositif destiné à chauffer les surfaces cylindriques du premier et du second cylindre,
       caractérisé en ce que :
       le second cylindre rotatif (2) a une surface cylindrique lisse destinée à être au contact de la seconde face de la feuille,
       un rouleau imperméable et lisse (4) de pressage est destiné à être au contact de la première face de la feuille cellulosique et à repousser la feuille contre la surface cylindrique lisse du second cylindre, un dispositif étant destiné à transmettre un feutre compressible sur le rouleau de pressage entre la feuille et le rouleau de pressage,
       si bien que l'appareil forme une feuille séchée ayant des faces lisses opposées.
  10. Appareil selon la revendication 9, caractérisé par un dispositif d'entraînement destiné à faire tourner le premier et le second cylindre.
  11. Appareil selon la revendication 10, caractérisé en ce que le rouleau de pressage (4) comporte un dispositif destiné à accepter l'eau chassée de la feuille (5) à travers le feutre, à une emprise du rouleau de pressage et du premier cylindre.
  12. Appareil selon la revendication 11, caractérisé par un dispositif de projection d'air chaud destiné à diriger de l'air chaud sur la seconde face de la feuille au niveau du premier cylindre et sur la première face de la feuille au niveau du second cylindre.
EP19900910498 1989-07-20 1990-07-19 Procede et appareil de fabrication de papiers lisses et satines Expired - Lifetime EP0483183B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US38272589A 1989-07-20 1989-07-20
US382725 1989-07-20

Publications (2)

Publication Number Publication Date
EP0483183A1 EP0483183A1 (fr) 1992-05-06
EP0483183B1 true EP0483183B1 (fr) 1994-03-16

Family

ID=23510147

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900910498 Expired - Lifetime EP0483183B1 (fr) 1989-07-20 1990-07-19 Procede et appareil de fabrication de papiers lisses et satines

Country Status (9)

Country Link
EP (1) EP0483183B1 (fr)
JP (1) JP2588637B2 (fr)
AU (1) AU629372B2 (fr)
BR (1) BR9007535A (fr)
CA (1) CA2062983C (fr)
DE (1) DE69007484T2 (fr)
FI (1) FI107172B (fr)
NO (1) NO303236B1 (fr)
WO (1) WO1991001407A1 (fr)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2082671B1 (es) * 1991-12-13 1996-10-16 Pastor Francisco Garcia Perfeccionamientos en el proceso mecanico de prensado en la fabricacion de papel.
DE4407405C2 (de) * 1994-03-05 2000-03-16 Voith Sulzer Papiermasch Gmbh Trockenpartie
FI108054B (fi) * 1994-05-31 2001-11-15 Metso Paper Inc Menetelmä paperirainan kulun stabiloimiseksi paperinjohtotelan yhteydessä erityisesti puristinosan ja kuivatusosan välillä ja laite menetelmän toteuttamiseksi
JP3006482B2 (ja) * 1995-05-12 2000-02-07 富士ゼロックス株式会社 情報検索装置および方法
FI122691B (fi) * 2007-06-05 2012-05-31 Upm Kymmene Corp Menetelmä paperin valmistamiseksi
US9670617B2 (en) * 2011-02-15 2017-06-06 Georgia-Pacific Consumer Products Lp System and methods involving fabricating sheet products

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1873949A (en) * 1930-01-29 1932-08-30 Harrison R Williams Paper drying means
US1951710A (en) * 1931-11-12 1934-03-20 Burgess Cellulose Company Process and apparatus for drying fibrous sheets
GB2052586B (en) * 1979-05-19 1984-03-14 St Annes Board Mill Co Ltd Drying paper
FI812060L (fi) * 1980-07-02 1982-01-03 Black Clawson Int Foerfarande och anordning foer framstaellning av papper och kartong
SE446408B (sv) * 1985-04-03 1986-09-08 Scandiafelt Ab Maskin for formering, pressning och torkning av tunna pappersbanor

Also Published As

Publication number Publication date
EP0483183A1 (fr) 1992-05-06
DE69007484T2 (de) 1994-06-23
NO920196D0 (no) 1992-01-15
FI920223A0 (fi) 1992-01-17
BR9007535A (pt) 1992-04-28
NO920196L (no) 1992-01-15
AU629372B2 (en) 1992-10-01
JP2588637B2 (ja) 1997-03-05
WO1991001407A1 (fr) 1991-02-07
AU5958390A (en) 1991-02-22
CA2062983A1 (fr) 1991-01-21
FI107172B (fi) 2001-06-15
JPH04506839A (ja) 1992-11-26
NO303236B1 (no) 1998-06-15
DE69007484D1 (de) 1994-04-21
CA2062983C (fr) 1995-06-20

Similar Documents

Publication Publication Date Title
US5127168A (en) Method for manufacture of smooth and glossy papers and apparatus
EP0733737B1 (fr) Dispositif pour le séchage d'une bande
US4359827A (en) High speed paper drying
US4596633A (en) Surface treatment of paper and paperboard
US7582187B2 (en) Process and apparatus for producing a tissue web
EP0726353B1 (fr) Procédé de fabrication de papier à surfaces travaillées et partie sèche d'un machine à papier
CA1178804A (fr) Secheur a vide pour procede de fabrication du papier a haute vitesse
US4139410A (en) Method of dewatering and drying in a Yankee machine
US8349138B2 (en) Device for treating a pulp web in an extended nip pressing unit
EP1285127B1 (fr) Procede de calandrage d'une bande de carton
JPS6356360B2 (fr)
EP0483183B1 (fr) Procede et appareil de fabrication de papiers lisses et satines
US5873180A (en) Papermaking dryer section with partitioned vacuum box for threading
GB2052586A (en) Drying paper
US3149025A (en) Manufacture of cellulosic product
EP1208266B1 (fr) Procede et dispositif destines au traitement de surface d'une bande de papier et/ou d'une bande de carton
US6860968B1 (en) Tissue impulse drying
US5593547A (en) Press section of a paper machine
Poirier et al. Papermaking
EP0514595A1 (fr) Procédé pour la fabrication du papier et du carton glacé en utilisant de séchage d'impulse
CA1182634A (fr) Sechage rapide du papier
Pikulik [$ Papridry^{TM} $], A New Technique for Drying of Paper and Board
Pikulik 1.1 Approach Flow System The forming process is preceded by an approach flow system that receives the aqueous fiber suspension, or stock, and prepares it for the forming process. Fibres are produced using kraft process or other pulping/bleaching processes (see Bleaching of wood pulps) and the proportions of fibers from different sources are blended here. Drained water from the forming process, known as whitewater, contains useful fibrous material and is continuously recycled back into the stock. Screens and centrifugal cleaners in the approach flow system remove oversize and heavy contaminants from the pulp. Additives such as minerals, pigments and dyes are introduced to make particular grades of paper and paper board. Air bubbles may be removed from the pulp suspension. The mass concentration, or consistency, of the suspension is kept low to prevent fibre flocculation prior to forming and is usually adjusted to a value in the range of 0.5 to 1.5%.

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

17P Request for examination filed

Effective date: 19920210

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE FR GB IT SE

17Q First examination report despatched

Effective date: 19920810

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR GB IT SE

REF Corresponds to:

Ref document number: 69007484

Country of ref document: DE

Date of ref document: 19940421

ET Fr: translation filed
ITF It: translation for a ep patent filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

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

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

EAL Se: european patent in force in sweden

Ref document number: 90910498.6

26N No opposition filed
REG Reference to a national code

Ref country code: GB

Ref legal event code: IF02

REG Reference to a national code

Ref country code: GB

Ref legal event code: 732E

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20090710

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 20090708

Year of fee payment: 20

Ref country code: DE

Payment date: 20090716

Year of fee payment: 20

Ref country code: GB

Payment date: 20090715

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: IT

Payment date: 20090718

Year of fee payment: 20

REG Reference to a national code

Ref country code: GB

Ref legal event code: PE20

Expiry date: 20100718

EUG Se: european patent has lapsed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 20100718

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 20100719