EP2379806A1

EP2379806A1 - Method for producing a fibrous material web

Info

Publication number: EP2379806A1
Application number: EP09783963A
Authority: EP
Inventors: John Bergman; Holger Humberg
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2008-12-18
Filing date: 2009-10-13
Publication date: 2011-10-26
Also published as: DE102008054868A1; WO2010069627A1; CN102325942A

Abstract

In a method for producing a fibrous material web for single coated papers in particular, the fibrous material mixture used to form the web has, based on the total fresh fiber input, a hardwood semichemical pulp content of > 50 wt %, where the degree of beating of the hardwood semichemical pulp is selected to be > 55°SR.

Description

METHOD FOR PRODUCING A FIBROUS WEB

The invention relates to a method for producing a fibrous web for in particular simply coated papers.

Coated wood-containing papers, in particular coated wood-containing papers in the lower basis weight range <70 g / m ² (> 70% whiteness, <2.0 PPS roughness according to Parker Print Surf,> 45% gloss) and, in particular, those with single-coat are usually used with a mixture of long fiber pulp, deinked pulp (DIP, deinked pulp) and mechanically developed long fiber pulps (TMP or PGW / GW / SGW ...; TMP = thermomechanical pulp, PGW = Ground Wood). The mixture is driven so that the properties of the base paper meet the requirements of the coating process.

Long fiber pulp or NBKP (bleached softwood kraft pulp) contributes mainly to the strength properties. On the other hand, due to the high fines content, wood pulp influences the corresponding surface properties and the impermeability of the base paper.

Deinked pulp (DIP) is due to the mixed composition of Altpapiereintrags a mixture of the aforementioned fibers and can be used with appropriate treatment up to 100%.

In papermaking, the aim is always to minimize the costs of the substance input in the respective production process. It is depending on the regional high availability and the low price the use of hardwood is an interesting alternative.

Hardwood or short fibers have even lower strengths than natural or long fibers, which is due to their different fiber morphology. A replacement of bleached softwood kraft pulp (NBKP = Needle Bleached Kraft Pulp) with bleached hardwood pulp. Hardwood pulp (LBKP = leaf bleached kraft pulp) therefore makes little sense, since the main task of bleached softwood kraft pulp (NBKP) is to increase the strength of the paper. This requirement can not be met by the purely chemically digested bleached hardwood kraft pulp (LBKP).

A purely mechanical pulping of hardwood according to the TMP or PGW (TMP = thermomechanical pulp) method results in an unusable pulp with extremely low strength.

Another type of pulping process for hardwood is, in principle, a combination of mechanical and chemical pulping. Such processes are known as BCTMP or, for example, also as APMP processes (BCTMP = bleached chemothermomechanical pulp, bleached chemothermomechanical pulp; APMP = alkaline peroxide mechanical pulp). The material produced is also commonly referred to as semichemical or semichemical pulp.

Accordingly, a half-pulp is to be arranged in terms of a variety of properties between the purely chemically digested pulp and the purely mechanically digested pulp. Due to the driving style which can be influenced in particular by the chemical and energy input In the manufacturing process, the half-pulp can be made more strength-oriented or more volume-oriented. It is already known from DE 10 2006 051 024 Al to add to the pulp mixture at least a portion of bleached and chemically pulped wood pulp (BCTMP) to increase the volume of the web to be produced.

However, it has now been shown that other properties of such a hemi-pulp, in particular the suction behavior of the base paper, characterized by the porosity and the Cobb-Unger oil absorption or Cobb-Unger water absorption, are insufficient. The base paper is much more porous and absorbent, so that the coating color strikes stronger in the paper and the required surface properties of the finished paper, in particular smoothness and gloss are no longer achieved. In addition, the z-strength of the paper (Scott-Bond) is critical.

The use of bleached chemothermic-mechanical pulp (BCTMP, e.g., birch) may thus increase the porosity of the paper, resulting in undesirable sagging of the coating color into the middle of the sheet. As a result, the gloss and smoothness values of the paper may deteriorate or fall.

In the field of wood-free coated papers, which are usually also produced in a higher basis weight range> 65 g / m ² , a surface sizing of the paper is carried out in view of similar problems for controlling the Wegschlagverhaltens of the coating color. In this case, a hydrophobization of the surface is achieved by a starch or glue application, for which purpose a corresponding application unit with subsequent drying must be used. However, such a solution is not possible for the more lightweight wood-containing mass papers for cost reasons. In exceptional cases, a sizing in the mass is carried out.

The invention has for its object to provide an improved method of the type mentioned, in which the aforementioned problems are eliminated. The process should be suitable at the lowest possible cost, in particular for the production of lightweight single-coated papers.

According to the invention, this object is achieved by a method for producing a fibrous web for particularly simply coated papers, in which a fibrous mixture is used for web formation, based on the total fresh fiber input contains a proportion of hardwood hemi-pulp> 50 wt .-%, wherein the freeness of Hardwood - half-pulp> 55 ° SR is selected.

Because of this embodiment of the method, it is now possible, in particular, to produce lightweight, simply coated papers with hardwood semi-cellulose as the main component at minimal cost, with an optimum quality, in particular with regard to gloss and smoothness. In this case, the hardwood half-pulp which forms the main component of the total fresh-fiber input is processed in such a way that it is ground to a maximum and strength-oriented, which is ensured in particular with a freeness of> 55 ° SR. The invention thus makes use of the circumstance that the driving mode of the production process and in particular the chemical and / or energy input of the semichemical material can be made more strength-oriented or rather volume-oriented, with the strength-oriented driving style and the correspondingly higher grinding degree being particular, through the process for the production of lightweight, simply coated papers with hardwood semi-cellulose is advantageously applicable.

The fresh fiber entry can contain at least substantially only hardwood half-pulp or alternatively also a proportion of softwood half-pulp, the degree of grinding of the softwood half-pulp preferably being chosen to be> 60 ° SR. Instead of a pure Hardwood BCTMPs or -APMPs including a softwood long fiber BCTMP or APMP can proportionately be used, the highly grind out, ie having a freeness> 60 ⁰ SR, may further reduce the porosity. For example, it is possible to use 80% hardwood and 20% softwood BCTMP and / or APMP. By varying the proportion, the strength properties and quality properties, in particular porosity and / or color absorption, can be controlled.

It is particularly advantageous if the pulp mixture, based on the total fresh fiber input, contains a proportion of, in particular, purely chemically digested long-fiber pulp of at least 10% by weight. It is thus possible, in particular, for the residual substance input provided next to the hardwood semi-cellulose to consist of at least 10% long-fiber pulp. Furthermore, it is possible that the intended next to the hardwood half-pulp residual substance entry consists of at least 10% long-fiber wood pulp. In this case, preferably long-grain wood pulp is groundwood and / or in particular highly ground thermomechanical groundwood (TPM) is used. The freeness of the wood pulp is preferably selected to be> 60 ^° SR. This reduces the porosity of the fibrous web and thus improves the absorbency, ie reduces, since the fibrous web becomes denser. According to an advantageous practical embodiment of the method according to the invention, a mass sizing of the base paper takes place. For such a size sizing, preferably> 0.2% by weight of starch, in particular> 0.4% by weight of starch, and / or> 0.1% by weight of CMC (carboxymethylcelluloses), in particular> 0, 2 wt .-% CMC, in particular> 0.5 wt .-% CMC, in particular> x wt .-% CMC, with 0.2 ≤ x ≤ 0.5, and / or <0, 1 wt .-% AKD (Alkylated ketene dimers) and / or <0.1% by weight of ASA (alkenyl succinic acid) used.

It is particularly advantageous if the base paper is precalendered before the line, with the Vorkalandrierung a porosity densification of the base paper in particular> 10% and preferably> 20% is brought about, wherein the calendering preferably by means of a hardnip, a softnip, a double -Softnips and / or a lengthened in the running direction Schuhnips done.

The absolute porosity is strongly dependent on the current raw material composition and grinding. Typically, the porosity on the uncalendered paper is 800-1000 ml / min and after the precalender 600-800 ml / min or less. When using higher quantities

Pulp, however, can rapidly reduce porosity in uncalendered paper to lower levels.

To improve the compaction effect, the fibrous web can be subjected to pre-calendering or before the pre-calender by means of a steam blower box and / or by means of a water spray application.

For greater compression of the base paper, the fibrous web can be performed in the press section by at least one Schuhpressnip. The shoe press should advantageously be highly loaded in order to achieve the greatest possible drainage and compaction of the paper, which is then above a compression in conventional roller presses. Advantageously, the peak pressure in the shoe press nip is selected in particular in a range of about 6 to about 6 MPa, in particular in a range of about 8 to about 10 MPa and preferably> 10 MPa.

Although 10 MPa represent the currently technically feasible state of the art with respect to the maximum peak pressure. Moreover, in the context of the invention, higher pressures which go beyond this would certainly be advantageous.

It is also advantageous if the fibrous web in the press section, as viewed in the web running direction, is pre-dewatered in a further press nip in front of the press nip, wherein the press nip in the press section is preferably used as a second press nip. The peak pressure is advantageously selected again as indicated above. The arrangement of the Schuhnips as a second nip brings, inter alia, the advantage that the compression effect after a pre-dewatering in a roll press is higher.

In principle, it is also conceivable to use two shoe press nips in the press section. In particular, these shoe press nips can again fulfill the aforementioned conditions with regard to the peak pressure.

According to a further preferred embodiment of the method according to the invention is considered in the web running direction after the two in each case a Schuhnip comprehensive or formed by a Schuhnip sen used as a roll press third press used to smooth the fibrous web and / or to compact.

In addition, inorganic fillers or fillers can be added to the base paper. These fillers or fillers may preferably comprise fine-grained PCC (Precipitated Calcium Carbonate, precipitated calcium carbonate), GCC (Ground Calcium Carbonate, ground calcium carbonate), kaolin and / or the like. This leads to a compression and thus to an improvement of the suction behavior.

The dry content of the coating color used is expediently chosen to be> 62%, preferably> 64%.

The coating color can be applied in particular by the film coating method and / or the curtain coating method. The preferably used on-line film coating process places lower demands on the web strength as compared to the Bladestreich process, which results in the possibility of treating the fibers more towards quality and further milling. The curtain coating process or the curtain coater places even lower demands on the web strength and brings about even lower penetration of the coating color during contactless coating application.

Advantageously, a multinip calender, in particular after the coating application, can also be used in particular, such a multinip calender advantageously comprising at least four nips. Preferably, an online multinip calender is used. A multinip calender brings with it the advantage of a high compaction of the paper and a stronger calendering effect. As an alternative to a multinip calender, for example, one or two shoe calenders are also conceivable for smoothing and compacting the paper, whereby online shoe calenders are preferably used.

Alternatively or additionally, it is also conceivable to use a RoIl blade gap former and / or a hybrid former, which in comparison to a pure blade or blade roll gap former, which is likewise conceivable in principle, an increase in the Scott bond brings with it. However, the angle of wrap on the forming roller should expediently be <32 °, in order to still keep enough water in the strip part for improving the formation of the rapidly dewatering pulp.

Alternatively or additionally, an impingement or impingement flow drying is advantageously also conceivable, for example by means of a so-called "HiDryers", as is known, for example, from EP 1 91 1 877 A and DE 10 2004 039 785 A1. A corresponding impingement or impingement-flow dryer (ΗiDryer "concept / Voith) can be provided in particular according to a press of the above-described arrangement with closed web guide, which is advantageous in view of the reduction in draw and the low strength potential of the web or impingement flow drying to a dry content of at least 56% on the first cylinder, ie the first draft of a smooth surface.

The hardwood half-pulp may in particular be produced by the BCTMP and / or the APMP process (BCTMP = bleached chemothermomechanical pulp; APMP = alkaline peroxide mechanical pulp). Fig. 1 shows a purely exemplary machine layout for lightweight coated grades with simultaneous on-line filmline and on-line calender.

In this case, a film coater 18, an air dryer 20, an on-line calender 22 and a reel 24 are provided following the headbox and former 10, a press section 12 and a dryer section 14 comprising paper machine 16. In principle, however, a different machine layout is also conceivable.

For the production of a fibrous web, in particular for lightweight, single-coated papers, a fiber mixture is used to form the web, based on the total fresh fiber content contains a proportion of hardwood half-pulp> 50 wt .-%, the degree of grinding of hardwood semi-pulp> 55 ° SR is selected ,

In the present exemplary embodiment of a corresponding machine concept, for example, a DuoFormer TQv, ie a vertical roll-blade gap former, a tandem NipcoFlex press (TNFP), a hard-nip pre-smoothing, an online sprocket speed distributor and / or a Online Januskalander be provided with eg 1 10 rolls. For example, a mass sizing with AKD and / or ASA of, for example, about 0.1% by weight is conceivable. The furnish, ie total fresh fiber furnish may comprise, for example, 50% by weight of hardwood semi-pulp produced by the APMP process, 30% by weight of hardwood pulp produced by the NBKP process and 20% by weight of groundwood softwood. In this case, the degree of beating for the APMP Hardwood semi-chemical pulp, for example, ~ 55 ° SR, the NBPK-Hardwood semichemical pulp ~ 24 ° SR and for pulp ~ 70 ⁰ SR, respectively. The maximum operating speed, for example, at an end-face weight in the range of about 48 to about 65 g / m ² (about 34 to about 35 g / m ^{2 base} paper) may be about 1800 m / min. For example, the gloss values can range from about 42 to about 65%, preferably from about 52 to about 56%. Alternatively or additionally, the machine concept may in particular also comprise at least one of the aforementioned aggregates (eg pre-calender with hard nip, soft nip, double softnip and / or nip extended in the direction of web travel, steam blower box and / or water spray application before the pre-calender, at least one shoe tip in the Press section, in particular as a second nip, two shoe tips in the press section, two shoe tips followed by a third press, which is designed as a smoothing and / or compacting roller press, a film coater and / or a curtain coater, a multinip calender, preferably with at least four nips , preferably as online multinip calenders, one or two shoe calenders for smoothing and / or compacting, roll-blade gapformers, hybrid formers, hidryer or high-performance dryers).

LIST OF REFERENCE NUMBERS

10 headbox and shaper

12 press section

14 drying section

16 paper machine

18 movie coater

20 air drying

22 online calenders

10 24 rewinding

Claims

claims

1. A process for the production of a fibrous web for particularly simply coated papers, in which for web formation a fiber mixture is used, which based on the Gesamtfrischfa- sereintrag contains a proportion of hardwood hemi-pulp> 50 wt .-%, wherein the freeness of hardwood semi-pulp > 55 ° SR is selected.

2. The method according to claim 1, characterized gekennzei chnet that the fresh fiber entry contains at least substantially only deciduous wood half-pulp.

3. The method according to claim 1, characterized gekennzei chnet that the fresh fiber entry contains a proportion of softwood half-pulp, the degree of grinding of the softwood half-pulp is preferably selected> 60 ⁰ SR.

4. The method according to any one of the preceding claims, characterized in that the pulp mixture based on the Gesamtfrischfaserein- a proportion of especially pure chemically digested long fiber pulp of at least 10 wt .-% contains.

5. The method according to any one of the preceding claims, characterized gekennzei chnet that the pulp mixture based on the Gesamtfrischfaserein- contribution contains a proportion of mechanically digested in particular long-fiber pulp of at least 10 wt .-%.

6. The method according to any one of the preceding claims, characterized gekennzei chnet that a mass sizing of the base paper takes place, wherein for the sseleimung preferably> 0.2 wt .-% strength, in particular> 0.4 wt .-% strength, and / / or> 0.1% by weight of CMC, in particular> 0.2

Wt .-% CMC, in particular> 0.5 wt .-% CMC, and / or <0.1 wt .-% AKD and / or <0.1 wt .-% ASA is used.

7. The method according to any one of the preceding claims, characterized gekennzei chnet that the base paper is precalendered before the line, wherein the Vorkalandrierung a porosity densification of the base paper in particular> 10% and preferably> 20% is brought about, the Kaladrierung preferably by means of a Hard- nips, a softnip, a double softsnip and / or an in

Web running direction extended or Schuhnips made.

8. The method according to any one of the preceding claims, characterized gekennzei chnet that the fibrous web is applied to improve the compaction effect of pre-calendering by means of a steam blower box and / or by means of a Wassersprühauftrags.

9. The method according to any one of the preceding claims, characterized gekennzei chnet, in that the fibrous web in the press section is guided through at least one shoe press nip for greater compression of the base paper, wherein the peak pressure in the shoe press nip is in particular in a range of about 6 to about 10 MPa, in particular in a range of about 8 to about 10 MPa and preferably> 10 MPa is chosen.

10. The method according to claim 9, characterized geke nnze i chne t that the fibrous web in the press section in the web running direction is pre-dewatered before the Schuhpressnip in another press nip, wherein the Schuhpressnip is preferably used in the press section as a second press nip.

11. The method according to claim 9 or 10, characterized geke nnze i chne t that two shoe press nips are used in the press section.

12. The method according to claim 11, characterized geke nnze i chne t that considered in the web running direction after the two in each case a Schuhnip comprehensive or formed by a Schuhnip a pressed press is used as a roll press to smooth the fibrous web and / or compress ,

13. The method according to any one of the preceding claims, characterized geke nnze i chne t that inorganic base or fillers are added to the base paper, said fines or fillers preferably comprise fine-grained PCC, GCC, kaolin and / or the like.

14. Method according to one of the preceding claims, characterized in that the dry content of the coating color used is> 62%, preferably> 64%.

15. The method according to any one of the preceding claims, characterized gekennzei chnet that coating color is applied by the film coating process and / or the curtain coating process.