FR2525650A1 - METHOD AND DEVICE FOR MAKING PAPER OR CARDBOARD - Google Patents

Abstract

1. A method of making paper or cardboard suitable for offset printing, for example rotary offset printing, in which the paper or cardboard in the form of a ribbon is subjected to at least one coating operation on at least one of its surfaces and then dried and optionally calandered before being wound, characterised in that drying after coating is carried out in two stages, the first stage before calandering, cutting, rewinding or similar treatment being limited so that the paper is left with a high water content, and the second stage after this treatment reducting the water content to a desired value.

Description

PAPERS OR CA R R ONS FOR OFFSET PRINTING.

  The present invention relates to paper or paperboard based on cellulosic fibers and more particularly to a novel process for the manufacture of paper or board having a good ability to

  offset printing and in particular to the rotary offset printing

still generated by coil offset.

  The invention also relates to a device for the implementation of the method as well as paper or paperboard (to simplify only the term of paper will be used thereafter) obtained by the implementation

of said method.

  Offset printing, especially rotary offset printing, is one of the most up-to-date and one of the most

  who knows the highest percentage increase

  the aim is to produce papers suitable for rotary offset printing, of more and more varied types, with very different grammages, and with dull or glossy aspects, and in the latter

  case of higher and higher brilliants.

  The papers suitable for offset printing are layer papers, ie papers coated on one or both sides, using a composition containing pigments and binders. After coating, the papers are dried at a given water content, for example of the order of 6% by weight, based on the weight of the paper, for low-grade grass papers, that is to say less than

  100 g / m This drying takes place before any calendering.

  This water content is determined in particular by the destination

  of paper, namely rotary offset printing or

offset format.

  Indeed, during the rotary offset printing and after passage in the presses, the printed paper is dried quickly, so

  to evaporate the volatile matter contained in the inks and to

  In these rapid drying, carried out by passing through a door oven at a temperature generally greater than 200 ° C, the paper is heated to a temperature above 100 ° C and the water contained therein

  has a tendency to evaporate Evaporation is more or less

  quee by the coating layers and especially by the inks used for this type of printing because the water vapor is trapped by these layers; blisters are formed and the paper can even burst The printed paper is then unusable These incidents occur mainly when the water content of the paper is quite high and especially when it comes to papers coated with several layers For example, it has been noted that they appear for a quantity of water greater than about 5 grams of water per m 2 of paper for a porosity of about 120 seconds. This porosity is measured by the BEKK device that measures the c 3 of i 2 rvr

  duration of the passage of 10 cm of air through 1 cm of paper under a

  pressure of 0.5 atmosphere Of course for a more porous paper, that is to say a porosity of less than 120 seconds, these incidents may occur for water contents greater than 5 grams per m of paper At the opposite for a paper less porous, a

  lower water content may be the cause of the cited incidents.

  In the case of offset printing format, drying after

  printing is usually longer and takes place without significant

  so many calories and blistering or bursting of the paper does not occur

do not believe.

  It was therefore brought, to avoid any risk of blistering, to sufficiently dry the paper after coating and before calendering

  possible, ie to dry to a low water content,

  capable of rotary offset printing.

  This important drying shows several disadvantages.

  It applies to the set of a paper ribbon that can

  have several destinations for which the degree of drying requires

  In fact, it is common to train at the slitting station, from a reel of paper of great width or width,

  several coils of lower widths can thus for example form-

  sea from a spool of 3.70 m width, three spools of 1 m width for rotary offset printing and a spool of 65 cm

  of width for offset printing format.

  In this case, the paper intended for the offset printing format has the same water content as that of the paper intended for rotary offset printing, that is to say a limited water content, not essential for the printing offset format This is wasted

  a significant amount of energy.

  In addition, the low water content of the papers before

  is disadvantageous for obtaining a paper with a very shiny appearance.

  This glow is due to several factors. A first factor is the coating composition used which comprises inorganic pigments such as kaolin, satin white, calcium carbonate, having granulometries and adapted shapes. A second factor to influence the gloss paper is the calendering which by the action of the pressure and the temperature provides a good smoothness to the papers, smooth which is accompanied by a gloss Nevertheless, a superior gloss can be obtained only taking into account a third factor Who is here

  water content of the paper before calendering Water contents inf 4-

  6 X before calendering can only obtain a low gloss, that is to say of the order of 50, measured value with GARDNER's apparatus, which measures as a percentage the luminous flux reflected after projection. on the paper an incident luminous flux of value 100,

  at an angle of incidence of 75 degrees.

  For example, to obtain a high-gloss paper with a value of 70, it is necessary for the paper before calendering to have a water content of greater than about 6%, expressed by weight relative to

  weight of paper Gold it was previously noted that paper with a high

  neur in water was incompatible with rotary offset printing.

  It has been proposed to modify the drying operation after offset printing by substituting for the sudden drying, a drying more

  soft, in order to obtain a slow and gradual evaporation of water con-

  held in the paper In this case, the print speed is high-

  slowed down and / or the drying oven must be extended and occupy a considerable area; in addition the energy consumed by this

  type of heating is more important.

  The invention obviates the disadvantages mentioned and proposes a new

  a process for producing paper (or paperboard) which makes them suitable for offset printing both in offset offset printing and in offset printing format, a process which saves energy and which is applicable to paper as well. only glossy and very glossy papers. According to the invention, a paper suitable for offset printing is prepared by the following succession of steps: a paper comprising a support layer based on cellulosic fibers is prepared in a manner known per se, at least one of the two faces is coated. with the aid of at least one coating composition comprising pigments and binders, the paper is dried in a limited manner after coating to leave a high water content, the coated paper is optionally calendered, it is dried a second time, after possible calendering, for

  reduce the water content to the desired value.

  The first drying before calendering is a limited drying which leaves the paper at a water content greater than about 6% by weight and of the order of 7%, which content makes it possible to obtain, if necessary, a very glossy paper. this limited drying is usually

  sufficient for a paper intended for offset printing format.

  The second drying according to the invention after the calendering, that is to say after passing the paper on the last pressure roller, is intended to reduce the water content of the paper to the desired value, that is, the value determined from which there is no risk of paper blistering or bursting during the rotary offset printing process. In the case of coated paper

  on both sides having a porosity of 120 seconds, said

  their determination of the water content is about 5 g / m This value may be higher for a paper that is more porous and lower for

a paper less porous.

  Advantageously, the second drying is applied only to

  part of the ribbon, for example the part intended for printing off-

rotating set.

  Preferably, the second drying is performed after slitting and advantageously at the same slitting station, just after the cutting of the paper tape in several widths to constitute coils which may have different destinations, namely coils for the rotary offset printing and reels for offset printing In these cases, this second drying is performed only on specified widths, especially those intended for rotary offset printing. In the context of this second drying, it is still possible to dry differently and / or to different degrees, each of the widths or

  groups of widths, that according to their subsequent use.

  the first drying after coating and before calendering can be carried out conventionally by passing for example ribbon

  lying on heated cylinders.

  The second drying according to the invention, after a calendering

  possible, for example by radiation such as

  infra-red, or by means of a microwave device or by conduction, for example by passing the portion of the strip of paper to be dried on at least one heated cylinder, or by convection per passage

  in a hot air oven or by other known heating means.

  The invention applies to all coated papers that are susceptible to

  blistering at the time of rotary offset printing, whether matte or shiny It is particularly applicable to

  shiny coatings that generally have multiple layers of

  The invention is particularly applicable to gloss coated papers intended for rotary offset printing in which the papers are covered by inks on their two faces and / or by several layers. of these inks, that is to say papers that after

  impression are very little permeable to water vapor.

  The invention also relates to a device for implementing the method. This device also comprises drying means.

  after sleeping, arranged before the calender, means of se-

  additional chase arranged after this calender, that is to say after the last pressure roller, and preferably mounted at the level of the

  slitter, just after cutting the coated paper tape and possibly

  calendered, which has been transformed into several widths to

  sea coils for rotary offset printing and possibly other widths to form coils for offset printing format. These heating means can be arranged only above and / or below the tapes forming the coils intended for

rotary offset printing.

  They can be formed of at least one infra-red ramp

  placed near the passage of the strip of paper to be dried.

  In a variant, these heating means consist essentially of at least one heated metal cylinder on which the strip of paper to be dried is applied at the moment of its passage. In another variant, these means are made of an oven or hot-air oven

  through which passes the paper to dry.

  The following examples illustrate the invention.

  are witnesses while the following are in accordance with

The invention.

EXAMPLE 1

  A paper paper with a basis weight of 110 g / m 2

  conventionally, by casting an aqueous composition containing

  cellulosic fibers, then after drying and coating both sides of the

  cellulosic layer formae with a coating composition con-

  nude for offset printing, likely to provide a very

  shine, the paper is dried after coating by

  The paper is then subjected to calendering

  while it still contains about 7% of its weight in water.

  The coating is carried out at a temperature of about 50 ° C. and a linear pressure of about 150 kg per centimeter. After calendering, the water content is slightly greater than 6% by weight and the paper ribbon has a gloss of 70 μm. using GARDNER's apparatus The paper ribbon, which is 3.70 m wide, is then split to form 3 ribbons of 1 meter width that are reeled for rotary offset printing and 0.65 cm wide ribbon that is reeled for offset printing The first three reels are used for rotary offset printing After printing, the paper presents

  many blisters in different places, including those corresponding to

  laying on the impression of several layers of ink and this on each

both sides of the paper.

EXAMPLE 2

  Offset printing paper of the same basis weight as in Example 1 is produced in the same way, except that calendering is carried out on paper with a low water content of about 4.5% by weight. At the exit of the calender, the paper has a water content of about 4% and a gloss which, measured as above, reaches only about 50%. The paper is used after slitting for rotary offset printing. printing, which is performed in the same conditions, including speed, that in Example 1, the printed paper does not present blistering.

EXAMPLE 3

  Offset printing paper of the same grammage as in Example 1 is produced in the same way, but at the rebar station while the main ribbon has been cut in 4 widths as before, the papers of the three widths of 1 m

  wide, fast drying by passage between infra-red ramps.

  This drying has the effect of reducing the water content to a value of approximately 4.5% by weight, which corresponds to approximately 4.95 g of water per

m 2 of paper.

  The paper obtained is coiled. Used for rotary offset printing, it does not have, after having been printed, the defects of the printed paper of Example 1. The highly glossy printed paper is free from blisters or splinters, even at the corresponding locations. several layers of ink, on the same side of the paper or even on

two faces.

EXAMPLE 4

  Offset printing paper is manufactured as in Example 3, except that the second drying of the only webs intended for rotary offset printing is carried out by passing at a speed of the order of 600 m / min in a furnace. a length of about 8 meters, with hot air brings about 210 C and circulating at a speed of the order of 40 m / s This drying has the effect of reducing the water content to a value of about 4.4% by weight, which corresponds to approximately 4.85 g

of water per m 2 of paper.

  Uses in rotary offset printing under the same conditions

  than previously, the printed paper does not show any defects

such as blistering or bursting.

EXAMPLE 5

  An offset printing paper having a basis weight of 135 is manufactured in the same manner as in Example 1 Prior to calendering, the paper has a water content of about 6.5%, which decreases to 6% after The resulting paper, very glossy, is slit as before and undergoes rapid contact drying on a metal cylinder heated to about 250 ° C until its

  water content is approximately 3.5% by weight of paper, which corresponds to

  The dried paper is coiled. It is then used for rotary offset printing under the same conditions as above. As in Example 3, the

  Printed paper is free of blemishes such as blisters or splinters.

EXAMPLE 6

  A matte coated paper is produced for offset printing of

  basis weight of an aqueous composition containing

  after drying, coating of both sides of the cellulosic layer formed with a coating layer known for offset printing and likely to provide a matt paper After oz 1 1 no ebbo TD anb slai sinujgp 01 ap qdwexa Ise jalded el luolssaadml seidy -luan mapaupid anb suoli Tpuoa jumps that salt over to AT: IL,: 4 oi: Iasgjo uo-îssaadwll inod 9 sl Tl: ln a: llnsua: Ise Ilqui jalded np splod ua g ç uoij Auap anal -VA a Enb Snr enuluilp nue ua ineuoq anal the D OOZ uoi T Aua egjneqv inoj a siz) AL> j: l: lu; DSS Ud a AI: ILIIOI: Iasj; o uojss ;, idm-j TQ se 9 U 1 1 _, ap 9 Saz-rel SOI Sa Tnas has OvpuîDjai saidy -sozle T sani D Isnid ua (wharf Liéq Dizj 1 p npuaiaji: Ise u-eqnj ial ualq no) inpuajai zulqoq vi gu la Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl Gl q q q q q q q q q q q q q q q 2 S uo

Claims (11)

  1 Process for producing paper or paperboard, suitable for   offset printing, especially to rotary offset printing, in the   wherein the paper or cardboard in the form of a ribbon undergo at least one coating operation on at least one of their faces and then are dried and possibly calendered before being wound, characterized in that the drying is carried out after coating in two stages, a first limited drying, before a possible calendering, which leaves the paper a high water content, and a second drying after calendering,   which reduces the water content to the desired value.   Process according to Claim 1, characterized in that the second drying is carried out on the single part of the ribbon intended for rotary offset printing.   Method according to one of claims 1 or 2, characterized   in that the second drying is carried out only on one or more   the defined widths of the ribbon cut after slitting.   4 Process according to claim 3, characterized in that the   The second drying is carried out at the slitting station immediately after the eg ribbon.   Process according to claim 4, characterized in that the second drying is different from one width to another or from a group of widen to another group.   Process according to one of Claims 1 to 5, characterized in   the first drying before calendering is limited to leave the paper has a water content greater than 6 X and of the order of 7 X.   Method according to one of claims 1 to 6, characterized   that the second drying reduces the water content of the paper to a value of less than 5 g / m 2 for a paper having a porosity of about 120 seconds.   Process according to one of Claims 1 to 7, characterized in   what it applies to a very glossy paper.   9 Device for the implementation of the method-according to one of the   claims 1 to 8, characterized in that it comprises means for   drying after the calender, that is after the last wheel water pressure.   Device according to claim 9, characterized in that   the drying means arranged after the calender are at the control station.   splitting. 11 Paper or paperboard suitable for offset printing, in particular   rotary offset printing, achieved by the implementation of the   assigned according to one of claims 1 to 8.   12 Printed paper or paperboard obtained from paper or paperboard according to claim 11.