DE112007001033T5 - Method and device for the surface treatment of paper / cardboard - Google Patents

Abstract

method for surface treatment of paper / cardboard, characterized the method comprises treating a fibrous web with a drying shrinkage achieving chemical such that the chemical is substantially penetrates entirely through the fiber web thickness, and then the Fibrous web is made to become a treatment zone (N) between two heated metal surfaces (12, 15) with the result that the moisture within the fibrous web migrates to a central portion, whereby the middle section as a result of increasing humidity swells and the surface portion of a high drying tension is suspended because the surface portion is prevented from shrinking, and when the fibrous web emerges from the treatment zone, the Vaporized water quickly through the surface pores without escapes substantial condensation in the surface layers, resulting in an increased modulus of elasticity for the surfaces and at the same time to a low density for the middle section leads.

Description

The The present invention relates to a method and an apparatus for the surface treatment of paper / cardboard.

at For printing paper and cardboard, a high flexural strength is desired for an adequate running behavior and a reasonable Printability. The bending strength can be increased for example, by a surface sizing and also by different gradient structures (multiple structures and a gradient calendering). A high specific volume is desired to achieve a constant thickness with a smaller amount of pulp.

One of the aims of surface sizing is to improve the strength properties of paper or board, such as the internal bond strength (interlaminar strength) or the surface strength (plucking or picking). Chemicals for use in surface sizing are, due to their attractive price, water-soluble polymers that are primarily starch. The raw material for starch includes plants such as corn, wheat, barley, potato, cassava, etc., whose tubers, seeds, etc. are sources of source of starch. Starch (C ₆ H ₁₀ O ₅ ) consists of straight-chain amylose and branched amylopectin. Other chemicals for use in surface sizing include, for example, various cellulose derivatives (CMC) and polyvinyl alcohol (PVA).

wobei
S₁ und S₂ die Biegefestigkeiten des kalandrierten bzw. nicht kalandrierten Papiers repräsentieren und
h₁ und h₂ die Dicken des kalandrierten bzw. nicht kalandrierten Papapiers repräsentieren und
E₁ und E₂ das Elastizitätsmodul des kalandrierten bzw. nicht kalandrierten Papiers repräsentieren.The flexural strength is reduced in calendering as the web is compressed, resulting in lower caliper and reduced specific volume. The calculated flexural strength increases in proportion to the cube of the thickness according to the following formula:

in which
S ₁ and S _{2 represent} the bending strengths of the calendered or non-calendered paper, and
h ₁ and h ₂ represent the calendered or non-calendered papapier thicknesses, and
E ₁ and E _{2 represent} the elastic modulus of the calendered or non-calendered paper, respectively.

The The following general description deals with paper and board grades and various calendering and coating processes for a use in its production.

Paper and board types

There exists a wide range of different sorts of paper and cardboard and can on the basis of the basis weight (grammage) can be divided into two categories: papers with a single ply and a basis weight of 25-300 g / m ² and boards may in multi-layer technology, with a basis weight of 150-600 g / m ² . As is well known, the dividing line varies between paper and board, with cartons with the lowest basis weight being lighter than the heaviest papers. Usually paper is used for printing and cardboard for packaging.

The description given below is concerned with examples of currently used fiber web sizes, and significant deviations from the given values may occur. The main publication source for the descriptions is Papermaking Science and Technology, Papermaking Part 3, Finishing, edited by Jokio, M., published by Fapet Oy, Jyväskylä 1999, 361 pages , and Papermaking Science and Technology, Paper and Board Grades, edited by Paulapuro, H., published by Fapet Oy, Jyvaskyla 2000, 134 pages ,

Printing papers, which are made of mechanical pulp, that is those with a wood content include newsprint, uncoated Magazine paper and coated magazine paper.

Newsprint consists either entirely of mechanical pulp or may contain some bleached softwood pulp (0-15%), and / or some mechanical pulp may be replaced with recycled pulp. As general values for newsprint, the following values can probably be considered: basis weight 40-48.8 g / m ² , ash content (SCAN-P 5:63) 0-20%, PPS-s10 roughness (SCAN-P 76-95) 3.0-4.5 μm, Bendtsen roughness (SCAN-P 21:67) 100-200 ml / min, density 600-750 kg / m ³ , brightness ( ISO 2470: 1999 ) 57-63% and opacity ( ISO 2470: 1998 ) 90-96%.

Uncoated magazine paper (SC = supercalendered) generally has 50-70% mechanical pulp, 10-25% bleached softwood pulp and 15-30% fillers. Typical values for calendered SC paper (including, for example, SC-C, SC-B, and SC-A / A +) are a basis weight of 40-60 g / m ² , an ash content (SCAN-P 5:63) of 0-35 %, Shine after Hunter ( ISO / DIS 8254/1 ) <20-50%, PPS-s10 roughness (SCAN-P 76:95) 1.0-2.5 μm, Density 700-1250 kg / m ³ , Brightness ( ISO 2470: 1999 ) 62-70% and opacity ( ISO 2470: 1998 ) 90-95%.

Table 1 shows typical values for coated papers containing mechanical pulp (MFC = machine smoothed, FCO = offset film, LWC = light coated, MWC = medium heavy, HWC = heavy). Table 1 MFC FCC LWC MWC HWC Basis weight (g / m ² ) 50-70 40-70 40-70 70-90 100-135 Shine after Hunter ( ISO / DIS 8254/1 ), (%) 25-40 45-55 50-65 65-70 PPS-s10 roughness (μm) (SCAN-P 76/95) 2.2-2.8 1.5-2.0 0.8-1.5 (offset) 0.6-1.0 (roto) 0.6-1.0 Density (kg / m ³ ) 900-950 1000-1050 1100-1250 1150-1250 Brightness ( ISO 2470: 1999 ), (%) 70-75 70-75 70-75 70-75 Opacity ( ISO 2470: 1998 ), (%) 91-95 91-95 89-94 89-94

coated Magazine paper (LWC = light weight coated) contains 40-60% mechanical pulp, 25-40% bleached softwood pulp and 20-35% fillers and coatings (paints). HWC (heavyweight) can even be painted more than twice (coated).

wood-free Printing papers made from chemical pulp, that is Fine paper grades include uncoated and coated printing papers based on chemical pulp, the proportion of mechanical Pulp is less than 10%.

Uncoated chemical pulp (WFU) based papers have 55-80% bleached birch pulp, 0-30% bleached softwood pulp and 10-30% fillers. In WFU, the values vary widely: basis weight 50-90 g / m ² (up to 240 g / m ² ), Bendtsen roughness 250-400 ml / min, brightness 86-92% and opacity 83-98%.

In chemical pulp (WFC) coated printing papers, the amount of coating varies greatly according to the requirements and the intended application. The following are typical values for single and double coated chemical pulp based printing papers: single coated: basis weight 90 g / m ² , Hunter gloss 65-80%, PPS s10 roughness 0.75-2.2 μm, brightness 80-88% and opacity 91-94%, and double-coated: basis weight 130 g / m ² , Hunter 70-80% gloss, PPS-s10 roughness 0.65-0.95 μm, brightness 83-90% and Opacity 95-97%.

Release papers have a basis weight which varies within the range of 25-150 g / m ^2.

Paperboard manufacturing involves the use of chemical pulp, mechanical pulp and / or recyc elter pulp with him. For example, cartons may be grouped into the following major categories according to the intended application.

Corrugated cardboard, which is provided with a liner and a fluting.

box cartons for making containers, boxes. box cartons include, for example, liquid packaging cartons (FBB = Carton, LPB = Liquid Packaging Carton, WLC = white-lined chipboard, SBS = solid bleached sulfite, SUS = solid unbleached sulfites).

graphic Cartons for producing, for example, cards, folders, folders, Containers, covers etc.

Wallpaper base.

calendering

The Surface properties and thickness profiles of different Papers and cartons are treated by calendering to the requirements of a printing process and further treatment to fulfill. Coated varieties are typically present precalendered and become a coating process (coating process) subjected to a final calendering after the coating process.

The Calenders are made in machine calender, soft calender and multi-roll calender assigned. A machine calender typically has 1-2 Column and both gap forming rollers are hard rollers. A soft calender generally has 1-4 columns and at least one of the gap forming rollers is coated by a soft coating. A multi-roll calender generally has 5-11 column. The roll assembly of a Multiroll calender includes both heated rolls and also soft coated rolls.

Specific Calenders include, for example, a wet stack calender, a damp calender and a long-gap calender.

Of the Wet stack calender is more or less a multi-roll calender identical, but with regard to the calendering process entirely different. The wet stack calender effectively uses a moisture gradient the web arriving at the calender being merely a moisture from about 1-2%. The wet stack calender is provided with water boxes for forming a water film on the web surface upstream of a gap, wherein the film is pressed onto the web surface in the gap. Thus, the web is wet (wet) only at the surface, which makes the surface more calendering as the overdriven interior receives. The wet stack calender is used as a pre-calender for some types of cardboard.

The Moisture smoothing unit is a machine calender, which is located in the drying section of a paper machine is located.

long-nip include a shoe calender that has a soft belt around a shoe roll and wherein the gap length is typically 50-400 mm, and also belt calender. The conventional one Belt calender consists of a thermo roll of soft calender, a belt loop and a counter roll inside the belt loop, the latter being either a hard roll or a soft roll. The belt passes over a counter roll and guide rollers / tension rollers. A special embodiment of the belt calender is a metal belt calender, wherein the calender belt has a metal belt, which runs around guide rollers and together with a Counter element, typically a roller, a long-nip zone with built a length of even more than 5000 mm. Internally the belt loop may further provide a pressing member be, for example, a deflection compensating roll that uses can be used to build a split point with higher Compression load in the middle of the way across the extended nip zone.

String techniques

As coated paper grades and brushing become more and more popular as a process, the coating processes and coating equipment are challenged by increasing demands. In the coating process, and more precisely in the pigment coating process, the paper surface is formed with a layer of coating color (coating color) on a coating head, whereupon the drainage of the water (Dewatering), which is brought in by the coating color composition. The formation of a coating color layer may be classified into the application of a coating color to the paper surface, that is, the application, and the setting of the final coating amount. The most important pigment coating method is a so-called blade coating, in which the amount of coating is adjusted by means of a so-called doctor blade. The most common types of blade coaters include a blade coater provided with an applicator roll and a blade coater provided with a jet applicator. The coating process also involves the use of a so-called film transfer coater, the use of which has become increasingly common in recent times. Another new technique that has been introduced for high-speed printing machines involves the use of curtain coaters (so-called curtain coating).

from From the point of view of practice, the most significant difference relates between the different coating devices on the order process and in particular to the occurring penetration, that is on the penetration of a coating color in the paper.

at the production of high quality coated printing papers not more and more attention in recent times only high quality but also productivity been laid. The quality is equal to one increasingly important aspect in lightly coated papers one Become mass product type. Almost all Coating equipment is under pressure of increasing quality, Productivity and running speed.

In the applicator roll application involved in blade coating, application is effected by the application of a roller which rotates in a brush pan to receive a coating color to the bottom surface of a paper which passes through a backing roll. The amount applied is normally 200-250 g / m ² . In the applicator roll application, the coating color effectively penetrates the base paper. In addition, the fibers of the base paper have sufficient time to swell (swell) before blade application, thus increasing the roughness volume of the paper.

In the case of beam application (jet application), the coating color is again delivered directly to the web surface by means of a nozzle. An advantage over the applicator roll application is the lack of a rotating roll and thus improved suitability for high running speeds. Another advantage is a less powerful impulse of application pressure, resulting in improved runnability. In jet application, the web dampening process is between a form roller and a so-called short dwell device. In the jet application, the amount applied is typically 130-220 g / m ² .

at the so-called. Short Dwell application, the coating color becomes an application chamber delivered, which is located immediately behind the doctor blade, wherein a side wall of the chamber is defined by a moving paper web formed, which is supported by the counter-roller. The moving paper web develops vortices in the application chamber, and the coating color has a flow rate the surface of the web, which is equal to the speed the paper web is. The short dwell application is moistening slightly if the application zone is low Pressure is exposed and the effective area is short. The swelling The paper fibers are sometimes only downstream the doctor blade, what the smoothed by the blade Roughen surface. Thus, the strike smoothness, which is achievable by a short dwell coater, opposite inferior to those produced by a job roll coater and a jet coater is achieved.

The the amount of coating remaining on the surface of the paper is influenced by a wide range of variables. If such Properties of base paper such as roughness, porosity and the water absorption increase, the amount of coating also decreases to. Similarly, when the dry content and the viscosity of a coating color increase, the amount of coating to. On the other hand, an increase in the water holding capacity decreases a coating the amount of paint. When the voltage, the working angle and the blade thickness of a scraper blade increases, the amount of coating becomes again reduced. As for the other factors, so lead an increase in running speed and an increase in application pressure an increase in the amount of paint.

In addition to the blade coaters described above, the coating treatment and surface treatment may also be performed by other means. Below are some very commonly used options. The size press unit consists of two rotating rollers. In this alternative, the coating to be applied to the surface of a web is applied to the web applied in a basin existing between the web and the rollers. In addition to surface sizing, the size press can also be used for pigment coating. The amount of coating is about 1.0-2.0 g / m ² / side. A problem with the standard size press is the instability of the application pool at high running speeds.

Attempts have been made to overcome the problem by designing film size presses in which a layer of a coating or sizing agent desired on the surface of a paper web is first applied to the surface of press rolls, the layers from there to the web Pass paper in a gap between the rollers. The applied applicators have units similar to the short dwell coaters. The advantages achieved by this device include controlled application even at high speeds and a possibility of pigment coating (2-6 g / m ² / side). In addition, the dry content of the coating color can be increased relative to a standard size press. The coating of film-coating colors can be carried out either in a one-sided or in a two-sided manner. The running behavior of a film transfer coating process is usually good relative to the blade strike. Compared to blade wiping, the wiping achieved by film transfer coating is usually better conform to contour and has greater coverage in this sense. However, it is not possible to achieve high coating rates (above 10 ... 12 g / m ² ) by film transfer coating.

At the Air brushing becomes the application of a coating color either by a single or multi-roll blade applicator or by means of a nozzle. The attitude the amount of brushing and the smoothing of the surface are again carried out by means of an air jet. The Airbrushing becomes almost exclusive applied to a board coating due to a thereby provided excellent covering. The disadvantages include a limited one Running speed of the process and very low dry contents the coating color. The coating applied by an airbrush is formed, has a consistent thickness, the surface contours compliant with the paper.

Accordingly, become fundamental solutions today with regard to painting a paper web with short dwell coater and applicator roll coaters, a plant on the base a jet coating and film size presses provided. A general Allzweckstreicheinrichtung it still has to be designed.

The Blades painting in its various forms is the furthest widespread pranking and it seems to remain so in the future. As the running speeds increase and the areas for one When applied, the application roller is likely to expand almost entirely through solutions be replaced the basis of a jet coating.

A emerging new technology is also a so-called Curtain coating. Curtain coaters can divided into slow feed coater and slide feed coater become. In a sliding feed curtain coater a coating is added to it along a sloping Level flows, and a curtain develops when the Coating slip over the edge of the level. In tray feed bars becomes a coating through a distribution chamber to a narrow pumped vertical shaft, with a curtain (hence Curtain) developed along its lip and runs down to the web. A coating can be applied in one or more layers become.

in the Compare to the Blade painting brings the curtain painting or Curtain paint much less force on the track and leads thus, less interruptions caused by a web break be effected in the paper web, which improves the running behavior becomes. Curtain painting is not capable of smoothness to be provided equal to that by the blade swipe but the coverage achieved is better than the one achieved by the swabbing. The basic idea It was, after all, that curtain-painting machines finally became the Replace air brush.

The Finnish patent FI 115 732 discloses a method and apparatus by which the penetration of a surface sizing agent into a fibrous web can be improved by means of a vacuum device.

It is an object of the present invention to provide a solution capable of further improving the flexural strength and the specific volume of surface sized paper / board in terms of those achieved by standard surface sizing and subsequent calendering , To achieve this object, a method of the present invention is characterized characterizes that the method comprises treating a fibrous web with a drying shrinkage-imparting chemical such that the chemical substantially penetrates entirely through the fibrous web thickness, and then causing the fibrous web to advance to a treatment zone between two heated metal surfaces, with the result in that the moisture within the fibrous web migrates to a central portion whereby the middle portion swells as a result of increasing moisture and the surface portion is subjected to a high drying tension, because the surface portion is prevented from shrinking and when the fibrous web emerges from the treatment zone that escapes evaporated water quickly through the surface pores without substantial condensation in the surface layers, resulting in increased elastic modulus for the surfaces and at the same time low density for the middle section rt.

on the other hand a device of the present invention is characterized in that the device has an application unit, through which a Dry chemical shrinkage on a fibrous web can be applied so that the chemical is substantially entirely penetrates through the fiber web thickness, and the fiber web adapted thereto is that they are heated by a treatment zone between two Metal surfaces progressing with the result that the Moisture within the fibrous web to a middle section migrates, causing the middle section as a result of increasing Moisture swells and the surface portion of a high drying voltage is suspended because it prevents the surface section shrinks, whereby when the fibrous web is off the treatment zone, the evaporated water quickly through the surface pores without substantial condensation in the surface layers escapes, resulting in an increased modulus of elasticity for the surfaces and at the same time to one low density leads to the middle section.

The The present invention is described in greater detail below with reference described on the accompanying drawings.

1 FIG. 12 shows a schematic view of a principle of an exemplary device structure of the present invention. FIG.

2 shows a device structure for improved surface treatment.

With reference to 1 For example, the exemplary apparatus has a vacuum (vacuum) surface-sizing unit, such as described in the Finnish Patent FI 115 732 and a metal belt calender 10 on. The surface sizing unit has a first application device 1a for applying a starch solution to a first web side W1 and a first vacuum device 3a wherein the negative pressure present therein is used to create a pressure differential across the thickness of a web W and to cause the starch solution to migrate and penetrate the interior of the web W to a desired depth. The exemplary device further has a second applicator 1b , which is arranged to face a second web side W2, and a second vacuum device 3b , which is arranged so that it faces the first web page W1. This construction allows a two-sided surface treatment for the web W, with the web W downstream of the first vacuum device 3a by means of guide rollers 8th to the second applicator 1b is transported. After a surface treatment of the first web side W1, it may be advisable that the web W is dried, at least to some extent, before the surface treatment of its second side W2. This is shown by a non-contact dryer, denoted by the reference numeral 9 is designated and is, for example, an infrared dryer. Also shows 1 Deflection rollers and guide rollers, with the reference numerals 4a respectively. 5a are shown and serve to redirect the direction of the web W as desired.

The metal belt calender 10 has a calender strap 12 which is made of metal and which is around guide rollers 13 circulates. The calendering belt 12 walk around a roller 15 around, which is located outside of him, with a calendering zone between the belt 12 and the roller 15 is being built. A material web W to be calendered passes through a calendering zone N, being exposed to a desired pressure pulse and a desired thermal effect as a function of time. In 1 is a dash-dot line 19 shown to represent a type of pressure effect that always occurs when inside the calender belt 12 a nip 14 is arranged, which acts as a pressing element, whereby the belt against the roller 15 is forced to establish a higher pressure nip within the calendering zone. On the other hand, a dashed line 18 shown to represent a type of pressure effect, which always occurs when a contact pressure acting within the calendering zone only by means of a tension of the belt 12 is generated when the nip roll 14 from a pressure contact with the belt 12 disengaged (or if no gap roll at all 14 inside the belt 12 one is built).

According to the The present invention has been discovered that flexural strength and / or the specific volume of a surface sized Paper / cardboard can be improved by surface gluing effected with a vacuum operated applicator which is a treatment process for preventing or limiting one Drying shrinkage follows, resulting in increased drying stresses. This phenomenon is due to a drying shrinkage assist effect of strength, thereby preventing the Drying shrinkage after adding starch leads to increased drying stresses. By doing a metal belt calender in a treatment process downstream surface gluing, drying can be used a track in a supported state within a closed Slit realizing through a metal belt and a roller will be brought, with what a controlled development the drying voltages is enabled. The surfaces a fibrous web between the hot surfaces of a metal belt calender experience drying and moisture migrates to a middle section, causing the increased Moisture swelling of the middle sections of a fibrous web and thereby cause an increase in the specific volume, which the thickness increases. At the same time, the surfaces develop Drying stresses, whereby a modulus of elasticity of the Surface sections is increased. If the fiber web emerges from the treatment zone, escapes in the middle Section existing water evaporated through the surface layers without condensation (which is a relaxation of the just obtained Modulus of elasticity effect), whereby the in the metal belt calender achieved structure substantially unchanged remains, and the result is an improved flexural strength of the Fibrous web. This creates great savings in terms of on the raw materials and improvements in terms of quality.

2 shows another possibility for improving a surface treatment. A treatment solution 30 from 2 is accomplished by combining a film transfer coater and a metal belt calender. A surface treatment agent, such as a starch-based surface adhesive, becomes at the top of an applicator roll 31 by means of an applicator device 32 distributed. From the top of the applicator roll, the surface treatment agent is supplied to the surface of a fibrous web W in a film transfer nip. The film transfer nip is between the applicator roll 31 and a counter roll 34 built. Through the gap further extends a metal belt 33 for effecting painting and metal belt calendering of a fibrous web in a single nip. A metal belt gap allows the application of high temperatures. As it emerges from the nip, the fibrous web is skin-dry due to contact drying and, depending on running speed and temperatures, it is possible to achieve sufficiently high dry levels to eliminate the need for separate drying. This hybrid solution provides great savings in terms of investment and operating costs, while allowing an increase in the flexural strength of a fibrous web by preventing drying shrinkage in the metal belt nip.

The surface-treating agent used in the above-mentioned solutions is preferably a CHO polymer. The CHO polymers are polymers containing only carbon (C), hydrogen (H) or oxygen (O). Upstream of the metal belt calendering, a CHO polymer or a CHO polymer containing a mixture may be applied to the surface of a paper or board. The most common CHO polymers are the following:
Poly (methylene glycol)
Poly (ethylene glycol)
Poly (propylene glycol)
Poly (tetramethylene glycol)
Poly (vinyl methyl ether)
Poly (vinyl ethyl ether)
Poly (vinyl isobutyl ether)
Poly (vinyl alcohol)
Poly (vinyl methyl ketone)
Poly (vinyl ethyl ketone)
Poly (methyl isopropenyl ketone)
Poly (vinyl acetate)
Poly (vinyl propionate)
Poly (vinyl laurate)
Poly (acrylic acid)
Poly (methacrylic acid)
Poly (methyl acrylate)
Poly (ethyl acrylate)
Poly (methyl methacrylate)
Poly (ethyl methacrylate)
Poly (n-butylmethacrylate)
Poly (tert-butylmethacrylate)
Poly (lauryl methacrylate)
Poly (hydroxyethyl methacrylate)
Poly (glycidyl methacrylate)
Poly (acetylacetoxy)
Poly (glycolide)
Poly (D, L-lactide)
Poly (3-hydroxybutyrate)
Poly (ethylene adipate)
Poly (caprolactone)
Poly (pivalolactone)
Poly (ethylene-co-maleinsureanhydrid)
Poly (styrene-co-maleic anhydride)
Poly (sebacic anhydride)
Poly (alkyl carbonate)
Poly (orthoester) based on hexamethylenediol
Poly (orthoester) based on transcyclohexanedimethanol
cellulose
ethylcellulose
hydroxypropyl
cellulose triacetate
Poly (4-hydroxystyrene)
Poly (4-methoxystyrene)
Poly (2,6-dimethyl-1,4-phenylene oxide)
Poly (ether ether ketone)
Poly (ethylene terephthalate)
Poly (diallyl phthalate)
Poly (diallyl isophthalate)
Poly (bisphenol A carbonate)
Carboxymethylcellulose (CMC)

The Application of the polymer may, for example, by nozzles However, other applicators are also involved possible. In a metal belt calender drying the paper web or cardboard web effectively, so not necessarily a separate dryer is required. Depending on the case, the paper web or board web also be dried before the metal belt calendering. This method especially for a finishing process of not coated varieties are particularly preferred. The not painted Varieties can calendar separately before calendering get abandoned. For coated varieties is the process preferably for use as a pretreatment suitable for painting. A polymer treatment and a metal belt calendering can also after painting or between coating units be effected. A metal belt calender can also be used in the dryer section be positioned.

The surface of the printing paper can be treated by means of tailor made chemicals so that an improvement of the printing surface is achieved by using a very small amount (less 0.5 g / m ² ) of a chemical. Such a chemical is, for example, a polymer whose hydrophobic properties are highly dependent on how the polymer molecule sits on the surface. By opening the polymer molecular micelles (or molecular clusters) on the surface of the paper fibers, the hydrophobic groups on molecules are directed away from the surface. Thus, the opening of the molecular micelles can be used to maximize the hydrophobic effect (or the effect on the resulting print quality). The opening of the micelles to the surface of the fibers may be assisted by a heat treatment subsequent to chemical application, for example by treatment in a long-term calendering belt zone (tens of milliseconds or longer). In particular, the process can be carried out with a metal belt calender. Alternatively, the treatment may include various thermal treatments used in drying, such as hot air blowing.

however see a calendering and a heat treatment at the same time take advantage, since the printing paper anyway after the chemical Treatment must be calendered, and consequently, the micellar treatment can integrated with calendering.

The Chemical can be experienced by any previously known application applied, such as a spray film transfer, a swabbing or curtain painting. In the case of one Multiple curtain coating preferably includes the topcoat layer this polymer.

• – Die Anforderung an eine chemische Behandlung kann minimal gestaltet werden und es können noch bedeutsame Vorteile erzielt werden, wobei der Effekt der Chemikalie maximal gestaltet wird, da der hydrophobische Effekt der Polymere durch die thermische Behandlung verstärkt wird.
• – Das Streichen, die chemische Behandlung und die Kalandrierprozesse können weiter integriert werden.

Thus, it can be anticipated that the final sequence of the chemical formulation will occur at the paper surface if the structure of the polymer molecules is conditioned for a desired end result by a thermal treatment effected on the surface of the paper. This solution provides significant benefits:

• - The requirement for a chemical treatment can be minimized and still significant advantages can be achieved, whereby the effect of the chemical is maximized, since the hydrophobic effect of the polymers is enhanced by the thermal treatment.
• - The brushing, the chemical treatment and the calendering processes can be further integrated.

Summary

The present invention relates to a method and apparatus for surface treating paper / board. The method comprises treating a fibrous web with a drying shrinkage-causing chemical such that the chemical penetrates substantially entirely through the thickness of the fibrous web and thereafter causing the fibrous web to move to a treatment zone (N) between two heated metal surfaces (FIG. 12 . 15 ) proceeds with the result that the moisture within the fibrous web migrates to a middle portion, whereby the middle portion swells as a result of the increasing humidity and the surface portion is subjected to a high drying tension because the surface portion is prevented from shrinking. As the fibrous web emerges from the treatment zone, the vaporized water rapidly escapes through the surface pores without substantial condensation in the surface layers, resulting in an increasing modulus of elasticity at the surfaces and at the same time a low density at the central portion.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - FI 115 732 [0041]
• - FI 115732 [0047]

Cited non-patent literature

• Papermaking Science and Technology, Papermaking Part 3, Finishing, edited by Jokio, M., published by Fapet Oy, Jyvaskyla 1999, 361 pages [0007]
• - Papermaking Science and Technology, Paper and Board Grades, edited by Paulapuro, H., published by Fapet Oy, Jyvaskyla 2000, 134 pages. [0007]
• - ISO 2470: 1999 [0009]
• - ISO 2470: 1998 [0009]
• - ISO / DIS 8254/1 [0010]
• - ISO 2470: 1999 [0010]
• - ISO 2470: 1998 [0010]
• - ISO / DIS 8254/1 [0011]
• - ISO 2470: 1999 [0011]
• - ISO 2470: 1998 [0011]

Claims (6)

A method of surface treating paper / paperboard, characterized in that the method comprises treating a fibrous web with a drying shrinkage chemical such that the chemical substantially penetrates entirely through the fibrous web thickness and thereafter causing the fibrous web to become one Treatment zone (N) between two heated metal surfaces ( 12 . 15 ), with the result that the moisture within the fibrous web migrates to a central portion, whereby the middle portion swells as a result of increasing humidity and the surface portion is subjected to a high drying tension, because the surface portion is prevented from shrinking, and when the surface portion shrinks Fiber web emerges from the treatment zone, the vaporized water quickly escapes through the surface pores without substantial condensation in the surface layers, resulting in an increased modulus of elasticity for the surfaces and at the same time to a low density for the middle section. Method according to claim 1, characterized in that the method comprises the use of a treatment unit equipped with a metal belt ( 10 ), the treatment zone between the heated metal surfaces ( 12 . 13 ) realized. A method according to claim 1 or 2, characterized in that the treatment chemical has starch. Device for the surface treatment of paper / cardboard, characterized in that the device has an application unit ( 1 ) by which a chemical capable of drying shrinkage can be applied to a fibrous web such that the chemical penetrates substantially entirely through the fiber web thickness, and the fibrous web is adapted to pass through a treatment zone (N) between two heated metal surfaces ( 12 . 15 ), with the result that the moisture within the fibrous web migrates to a central portion, whereby the middle portion swells as a result of increasing humidity and the surface portion is subjected to a high drying tension, because the surface portion is prevented from shrinking, whereby the fibrous web emerges from the treatment zone, the vaporized water escapes rapidly through the surface pores without substantial condensation in the surface layers, resulting in an increased modulus of elasticity for the surfaces and at the same time a low density for the central portion. Device according to claim 4, characterized in that the device comprises a treatment unit ( 10 ), the treatment zone (N) between the heated metal surfaces ( 12 . 15 ) Has. Device according to claim 4 or 5, characterized in that the application unit ( 1 ) An institution ( 1a . 1b ) for applying a chemical disposed on one side of a fibrous web to apply a chemical to a surface (W1, W2) of the treated fibrous web, and a negative pressure device (US Pat. 3a . 3b ) disposed on the other side of the fibrous web and used to establish a pressure differential across the thickness of a fibrous web (W), resulting in migration of the chemical from the side facing the applicator to the opposite one Page leads.