EP2668333B1 - Method for producing a paper product - Google Patents

Description

The present invention relates to a process for producing paper products, such as paper, board and board, comprising the addition of methanesulfonic acid (MSA) to an aqueous composition containing at least one pulp for adjusting the pH.

Furthermore, the present invention relates to the use of methanesulfonic acid in the production of a paper product, in particular for adjusting the pH of an aqueous composition containing at least one fibrous material in the so-called constant part of the paper or board machine.

Paper or paper product in the context of the present invention designate flat products made of fibers, in particular from chemically or mechanically exposed plant fibers, which are formed by dehydration of a pulp suspension using at least one screen usually with the addition of fillers and other additives.

Generally, the manufacture of paper products on modern paper or board machines involves the dewatering of a pulp suspension, for example a pulp, pulp and / or waste paper suspension, on at least one moving screen to form a paper web. The term paper or board machine usually the following aggregates are summarized: Constant part, headbox, wire section, press section, dryer section, size press (surface sizing), film press, Yankee, calender, online calender, on-line coating unit and reeling. Often, the manufacture of paper products involves downstream steps of surface treatment (e.g., calendering, brushing) and equipment (e.g., slitting, size cutting, packaging). A general description of the process steps and plant components in the production of paper products is described, for example, in "Papermaker Paperback, 8th Edition, Dr. Curt Haefner-Verlag GmbH, Heidelberg".

In the so-called constant part (constant part), the pulp suspension is made ready for subsequent sheet formation in the wire section. Here, for example, the final or Ausgleichsmahlung the pulp is performed, which regulates substance quantities and material densities, as well as the control of the flow rates performed. Within the constant part, the addition of fillers, Process chemicals and / or functional chemicals done. As a constant part is usually referred to all plant parts and piping between the mixing and machine chest and the headbox of the paper or board machine. In the constant part of the paper or board machine is usually also the adjustment of the pH of the pulp suspension.

In the headbox, the fiber suspension with a consistency of less than 1.4% is usually applied to at least one moving endless screen (machine screen). In the subsequent so-called wire section, the pulp suspension dewaters to a pulp density of 12 to 24% (assisted for example by the application of vacuum or pressure) and the fibers entangled to a still wet fiber fleece (sheet formation). This non-woven fabric is then removed from the wire using, for example, a pick-up felt (felt belt) and passed into the subsequent wet pressing where the stock density is further increased to about 50%.

Thereafter, as a rule, the nonwoven fabric is dried in the so-called drying section by means of drying cylinders. For certain uses, the paper may be subjected to further processing steps (e.g., smoothing, brushing, calendering).

The pulp suspensions used for the production of paper or cardboard mostly contain fibers as well as fillers, in particular inorganic fillers such as calcium carbonate, kaolin, titanium dioxide, barium sulfate and several process and / or functional chemicals, such as sizing agent for increasing the hydrophilicity and the printability of the paper, as well as eg Retention aids, drainage aids, dyes, optical brighteners, wet strength agents, dry strength agents, defoamers, biocide.

As fibrous materials for the production of paper products are generally primary fibers and secondary fibers in question. Wood pulps, in particular pulps such as sulphate pulp (SA) (also called kraft pulp), sulphate pulp, sulphite pulp (SI) of deciduous and / or softwoods are used in particular as primary pulps. But it can also woody fibers, especially wood pulp such as groundwood (HS) (also called stone groundwood SGW), pressure ground (pressurized groundwood PGW), refiner pulp (refiner mechanical pulp RMP), thermomechanical pulp (thermo mechanical pulp TMP), thermomechanical pulp with chemical pretreatment (chemical thermal mechanical pulp CTMP) and thermomechanical pulp with sodium hydroxide peroxide pretreatment (BCTMP) in question. Secondary pulps include various waste paper grades that are recycled in the recycling of paper / board and board production, as well as deinked Waste paper (Deinked pulp DIP). DIP is made by a wastepaper recycling process, with a large portion of the inks removed from the pulp suspension. In the deinking process, the slurried, shredded waste paper is conventionally mixed with sodium hydroxide solution, water glass, complexing agent, surfactant and hydrogen peroxide. The printing inks detach from the fiber surface and are discharged by flotation from the pulp suspension.

Pulp, such as groundwood, pressure ground, TMP, RMP, but also pulp are usually bleached during manufacture and / or before use. As a rule, a distinction is made between oxidative and reductive bleaching stages, these bleaching stages often being combined into bleaching sequences. Frequently, bleaching involves treatment with hydrogen peroxide under alkaline conditions. If the bleaching process concludes with an alkaline step, it is usually necessary to acidify the pulp suspension. In order to adjust the pH necessary for papermaking it is therefore usually necessary to add an acid to regulate the pH.

In general, depending on the pH, the pulp suspension used for the formation of paper generally comprises the addition of acidic aluminum salts and the neutral procedure in the pH between the conventional acidic procedure (pH in the range from 4.5 to 6.8) Range from 6.8 to 10.8. In the ideal case of a neutral driving style, the pH is adjusted to a value between 7.0 to 7.5. In recent decades, the neutral driving has become more and more prevalent, especially since it is possible to use calcium carbonate (CaCO ₃ ) as a filler, for example in the form of ground calcium carbonate (GCC) or precipitated calcium carbonate (precipitated calcium carbonate PCC).

The pH of the pulp suspension is of crucial importance for papermaking and directly influences the running behavior of the paper or board machine. A high pH leads to increased swelling of the fibers and complicates the dewatering of the pulp suspension. The accurate and reliable adjustment of the pH also helps to maintain the whiteness of the paper products and to prevent yellowing by alkalis. The choice of suitable pH-adjusting acids in the manufacture of paper products is very limited. Due to the requirements of availability, price and stability, the expert selects from a very limited number of acids which are suitable for papermaking. In the prior art, the use of phosphoric acid or a combination of phosphoric acid and phosphonates or the use of carbon dioxide for pH adjustment is described. Furthermore, the use of sulfuric acid and / or bisulfite to adjust the pH value in papermaking known. In addition, it is described that the pH of a pulp suspension can be adjusted by adding an electrolyte such as aluminum sulfate, aluminum nitrate, polyaluminum chloride (PAC) and aluminum hydroxide chloride.

The document WO 98/56988 describes a process for stabilizing the pH of a pulp suspension for papermaking using a combination of an alkali metal hydroxide and carbon dioxide.

The document US 2010/0175839 describes a multi-step process for adjusting the pH of a pulp slurry wherein the pulp is treated at least twice with carbon dioxide and at least once with a strong acid, eg, sulfuric acid, sulfurous acid or bisulfite, and wherein a carbonate removal step is included.

The document WO 2009/003770 discloses a papermaking process wherein a pulp suspension containing a mechanical pulp is subjected to an acid-base treatment to avoid lowering the whiteness. The pulp suspension is first treated with a strong acid, in particular sulfuric acid, sulfurous acid, hydrochloric acid and bisulfite, and then with a weak base (eg an alkali metal bicarbonate or alkali metal carbonate).

The use of phosphoric acid and phosphonates, as described in the prior art, leads increasingly to the formation and deposition of calcium phosphates in various parts of the paper machine. As a result of cleaning times, it comes increasingly to a standstill of the paper or board machine.

To increase the output of paper or paperboard, many modern paper machines operate at very high speeds of up to 1,800 meters per minute and production volumes of up to 1,000 t of paper per 24 h. A stoppage of the paper or board machine and the increased production of rejects are therefore the decisive factors for the efficiency and economy of the manufacturing process.

Furthermore, phosphorus compounds pollute the wastewater treatment plants of the paper mills, which generally have no phosphorus removal, in contrast to municipal sewage treatment plants.

The problem with the use of carbon dioxide for pH regulation of pulp suspensions is in particular the outgassing of carbon dioxide in the white water circuit and the associated fluctuations in the pH. In addition, the dosage of the gaseous additive carbon dioxide requires more complex metering devices.

The object of the present invention is therefore to provide a pH-regulating additive, in particular an acid, for pulp suspensions in papermaking or an improved papermaking process. On the one hand, the process should fulfill all wastewater-relevant and environmental requirements and enable efficient, simple and cost-effective process management. For example, a simple metering, a low introduction of additional salt load into the screen or wastewater of the paper machine and a good dewatering behavior of the pulp suspension should be ensured.

It has surprisingly been found that the pH value of pulp suspensions in papermaking can be adjusted particularly effectively by adding methanesulfonic acid (MSA).

Methanesulfonic acid has a pK _s value of about -0.6 and thus represents a strong to very strong acid. Methanesulfonic acid is generally non-oxidizing and is characterized in particular by heat and hydrolysis resistance. Methanesulfonates are used, for example, in detergents and cleaners. Methanesulfonic acid is still used in acid plating solutions for metal coatings.

1. a) Bereitstellen einer wässrigen Zusammensetzung enthaltend mindestens einen Faserstoff;
2. b) Zugabe von Methansulfonsäure zu der wässrigen Zusammensetzung enthaltend mindestens einen Faserstoff zur Einstellen des pH-Wertes;
3. c) Entwässerung der wässrigen Zusammensetzung enthaltend mindestens einen Faserstoff.

The present application is directed to a method of making a paper product, such as paper, board and board, comprising the following steps:

1. a) providing an aqueous composition containing at least one pulp;
2. b) adding methanesulfonic acid to the aqueous composition containing at least one pulp to adjust the pH;
3. c) dewatering the aqueous composition containing at least one pulp.

• Methansulfonsäure ist biologisch leicht abbaubar und halogenfrei und entlastet somit die Abwasserbehandlung des Herstellungsverfahrens. Zudem entsteht keine bzw. eine deutlich geringere Phosphor- bzw. Phosphatbelastung im Abwasser der Papier- bzw. Kartonmaschine.
• Es bilden sich keine bzw. weniger Ablagerungen, wie z.B. Calciumphosphat, in den Anlagenteilen der Papier- bzw. Kartonmaschine.
• Aufgrund der hohen Säurekonstante von Methansulfonsäure sind vergleichsweise niedrige Zugabemengen notwendig. Die Salzfracht von Prozesswässern bei der Papierherstellung kann somit vermindert werden.
• Wirtschaftlichkeit/Effizienz des Herstellungsverfahrens wird verbessert.
• Methansulfonsäure ist farb- und geruchlos und zudem in hochreiner Qualität verfügbar, daher erfolgt keine Belastung des Herstellungssystems (Prozesswasser, Abwasser, Kreislaufwasser, Papiererzeugnisse) mit Fremdstoffen. Daher ist Methansulfonsäure insbesondere zum Einsatz bei der Herstellung von Papiererzeugnissen (z.B. Verpackungsmaterialien) geeignet, die im Lebensmittelbereich verwendet werden.
• Methansulfonsäure weist eine hohe thermische Stabilität auf, hat einen geringen Dampfdruck, ist hydrolysebeständig und unbegrenzt mit Wasser mischbar, daher sind Handhabung und Dosierung einfach.
• Methansulfonsäure ist halogenfrei und weist etwa im Vergleich zu Schwefelsäure eine geringe Korrosivität auf.

The use of methanesulfonic acid is associated in particular with the following advantages:

• Methanesulfonic acid is easily biodegradable and halogen-free and thus relieves the wastewater treatment of the manufacturing process. In addition, no or a significantly lower phosphorus or phosphate pollution in the wastewater of the paper or board machine.
• There are no or fewer deposits, such as calcium phosphate, in the plant parts of the paper or board machine.
• Due to the high acid constant of methanesulfonic acid comparatively low addition levels are necessary. The salt load of process waters in papermaking can thus be reduced.
• Efficiency / efficiency of the manufacturing process is improved.
• Methanesulfonic acid is colorless and odorless and also available in high-purity quality, so there is no burden on the production system (process water, wastewater, circulating water, paper products) with foreign substances. Therefore, methanesulfonic acid is particularly suitable for use in the manufacture of paper products (eg packaging materials) used in the food industry.
• Methanesulfonic acid has high thermal stability, has low vapor pressure, is resistant to hydrolysis, and is immiscible with water indefinitely, so handling and dosing are easy.
• Methanesulfonic acid is halogen-free and has a low corrosivity compared to sulfuric acid.

Through the use of methanesulfonic acid, thus, the profitability of the production of paper products can be significantly improved.

Paper or paper product in the context of the present invention designate flat products made of fibers, in particular from chemically or mechanically exposed plant fibers, which are formed by dehydration of a pulp suspension using at least one screen usually with the addition of fillers and other additives. As additives, a distinction is usually made between process chemicals (eg biocides, deaerators, retention aids) and functional chemicals (eg dyes, optical brighteners, wet strength agents). For the purposes of the present invention, paper or paper products are to be understood in particular as meaning graphic papers, office communication papers, packaging papers, hygiene papers and special papers. As graphic Papers in the context of the invention are to be understood as all papers which are used for printing, for example, in flexographic printing, high-pressure, offset printing or intaglio printing, for example newsprint papers. Office communication papers are written, printed and copied papers, eg photo printing and digital printing papers. Packaging papers are papers, cardboard and cardboard for packaging purposes, eg corrugated board. For the purposes of the invention, tissue papers are papers with a high specific volume and high suction force, which are typically used in the sanitary and kitchen sector or in the industrial sector. The term special papers refers to papers and cardboards for special technical purposes, such as decorative papers and filter papers.

Depending on their grammage, paper products can be classified into paper, cardboard and possibly cardboard. In accordance with DIN 6730, a basis weight of less than or equal to 225 g / m ² of paper and greater than 225 g / m ² of cardboard is used. Often, paper products with a basis weight in the range of 7 to 150 g / m ^{2 are} referred to as paper, in the range of 150 to 600 g / m ² as cardboard and from 600 g / m ² as cardboard. Cardboard and paperboard are predominantly made up of several layers.

In particular, the present invention relates to a method as described above, characterized in that when dewatering the aqueous composition (step c) a nonwoven fabric is formed, which is pressed and / or dried in one or more further process step (s).

In particular, the aqueous composition is a suspension (slurry) of a pulp in water. The aqueous composition may contain further dissolved, colloidally dissolved or solid constituents. In particular, it is known to those skilled ingredients that are used in the production of paper products or incurred.

• Zellstoff (ZS), wie Sulfatzellstoff (SA) (auch Kraftzellstoffstoff genannt), Sulfathalbzellstoff, Sulfitzellstoff (SI);
• Holzstoff, wie Holzschliff (HS) (auch Steinschliff oder stone groundwood SGW genannt), Druckschliff (pressurized groundwood PGW), Refiner Holzstoff (refiner mechanical pulp RMP), thermomechanischem Holzstoff (thermo mechanical pulp TMP), thermomechanischem Holzstoff mit chemischer Vorbehandlung (chemical thermal mechanical pulp CTMP), thermomechanischem Holzstoff mit Natronlauge/Peroxid-Vorbehandlung (BCTMP);
• Sekundärfaserstoff, wie Altpapier (AP) und deinktes Altpapier (deinked pulp DIP).

The pulp may in particular be selected from:

• Pulp (ZS), such as sulphate pulp (SA) (also called kraft pulp), sulphate half pulp, sulphite pulp (SI);
• Wood pulp, such as groundwood (HS) (groundwood or SGW), pressurized groundwood (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), thermomechanical pulp with chemical pretreatment (chemical thermal mechanical pulp CTMP), thermomechanical pulp with caustic soda / peroxide pretreatment (BCTMP);
• Secondary pulp, such as waste paper (AP) and deinked pulp (deinked pulp DIP).

In particular, bleached and / or unbleached pulps and / or fibers of deciduous or softwoods described above may be used as fibrous materials. Preference is given to using beech sulphite pulp and / or long fiber sulphate pulp.

In particular, the aqueous composition comprises at least one pulp selected from the group consisting of sulphate pulp (SA), sulphate pulp, sulphite pulp (SI), groundwood (HS), pressure cut (PGW), refiner pulp (RMP), thermomechanical pulp (TMP), thermomechanical pulp with chemical pretreatment (CTMP), thermomechanical pulp with caustic soda / peroxide pretreatment (BCTMP), waste paper (AP) and deinked waste paper (DIP).

In a preferred embodiment, at least one secondary pulp, in particular waste paper and / or deinked waste paper (DIP), is used as pulp.

Most preferably, the aqueous composition contains at least one pulp which has been bleached by alkaline oxidative.

The aqueous composition comprising at least one fibrous material preferably has a consistency of from 0.01 to 5%, preferably from 0.1 to 5%, particularly preferably from 0.2 to 1.4%.

The consistency of an aqueous composition containing at least one pulp (pulp suspension) is understood as meaning the percentage of dry matter of the solids which can be filtered off in the composition in relation to the mass of the entire composition. The dry matter is usually stated as absolute dry matter (atro) or as dry matter during drying under standard conditions (oven-dry, otro). The determination of the consistency of pulp suspensions is described for example in DIN 54359 (EN ISO 4119).

• Prozesschemikalien, wie
  • Elektrolyt, beispielsweise Aluminiumsulfat, Aluminiumnitrat, Polyaluminiumchlorid (PAC), Aluminiumhydroxidchlorid, anorganische Fällungsmittel
  • Organischem Fällungsmittel
  • Biozid (z.B. Schleimbekämpfungsmittel)
  • Entlüfter
  • Entschäumer
  • Dispergiermittel
  • Adsorbiermittel (z.B. Talkum)
  • Fixiermittel (z.B. kurzkettige kationische Polymere)
  • Retentionshilfsmittel (z.B. langkettige anionische und kationische Polymere, teilweise auch vernetzt)
  • Entwässerungsbeschleuniger
  und Funktionschemikalien, wie
  • • Farbstoff
  • • Optischem Aufheller
  • • Masseleimungsmittel (Harzleim, AKD, ASA, Polymerleimungsmittel)
  • • Oberflächenleimungsmittel
  • • Nassfestmittel
  • • Trockenverfestiger
  • • internal wet web strength polymer (IWWS)

As further constituents, the aqueous composition may comprise at least one customary additive known to the person skilled in the art (process and functional chemicals). The additive can be selected from

• Process chemicals, like
  • Electrolyte, for example, aluminum sulfate, aluminum nitrate, polyaluminum chloride (PAC), aluminum hydroxide chloride, inorganic precipitants
  • Organic precipitant
  • Biocide (eg slimicide)
  • ventilator
  • defoamers
  • dispersants
  • Adsorbents (eg talcum)
  • Fixing agents (eg short-chain cationic polymers)
  • Retention aids (eg long-chain anionic and cationic polymers, sometimes also crosslinked)
  • drainage aids
  and functional chemicals, such as
  • • Dye
  • • Optical brightener
  • • engine glue (resin glue, AKD, ASA, polymer glue)
  • • surface sizing agent
  • • wet strength agent
  • • dry strength agent
  • Internal wet web strength polymer (IWWS)

In particular, the aqueous composition additionally contains at least one further additive selected from the group consisting of aluminum sulfate, aluminum nitrate, polyaluminum chloride (PAC), aluminum hydroxide chloride, organic precipitant, biocide, deaerator, defoamer, dispersant, adsorbent, fixer, retention aid, encrypion accelerator, dye, optical brightener , Engine sizing agent, wet strength agent, dry strength agent and internal wet web strength polymer (IWWS).

Preferably, the aqueous composition additionally comprises at least one inorganic filler selected from the group consisting of grinded calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, titanium dioxide and barium sulfate, preferably selected from the group consisting of ground calcium carbonate ( GCC) and precipitated calcium carbonate (PCC).

The pH of an aqueous composition comprising at least one fibrous material is adjusted in particular by adding methanesulfonic acid until the desired pH or the desired pH range has been reached. The person skilled in common methods for controlling the pH are known. The amount of methanesulfonic acid added depends on the type of aqueous composition containing at least one pulp and its initial value of the pH and the desired pH target value.

The adjustment of the pH of the aqueous composition containing at least one pulp may be effected by addition of a mixture of acids containing methanesulfonic acid. It is also conceivable to use a mixture of methanesulfonic acid and carbon dioxide or a mixture of acids containing methanesulfonic acid and carbon dioxide. In particular, methanesulfonic acid is added as the sole acid to adjust and / or stabilize the pH. In addition, it is conceivable to additionally carry out the adjustment or regulation of the pH of the aqueous composition by adding a base known to the person skilled in the art.

In particular, the present invention relates to a process for producing a paper product as described above, characterized in that the pH of the aqueous composition containing at least one fibrous material has a value in the range of 4 to 11, in particular in the range of 4.5 to 6, 8, in particular in the range of 6.8 to 10.8, is set.

If the method according to the invention relates to a method for producing a paper product using the acidic method of driving, in particular a pH in the range from 4.5 to 6.8 is set by addition of methanesulfonic acid. If the method according to the invention relates to a method for producing a paper product using the so-called neutral procedure (usually using calcium carbonate as filler), the pH of the aqueous composition containing at least one fibrous material is preferably in a range from 6.8 to 10 ,8th; especially adjusted from 7.0 to 7.5.

Furthermore, the method described in the present application for the production of a paper products may contain other common process steps of paper or board production, for. B. Steps in stock preparation including dispersing, sorting, grinding the pulp, post-drying steps such as calendering, brushing, cutting, and finishing steps.

The addition of methanesulfonic acid to the aqueous composition containing at least one pulp may occur at one or more different stages of the process of making the paper product. In particular, the addition of methanesulfonic acid to the aqueous composition containing at least one pulp in the constant part of a paper machine.

As a constant part for the purposes of the present invention is generally referred to all parts of the plant and pipeline between the mixing and machine chest and the headbox of the paper or board machine. In the so-called constant part (constant part), the pulp suspension is made ready for subsequent sheet formation in the wire section. Here, for example, the final or Ausgleichsmahlung the pulp is performed, which regulates substance quantities and material densities, as well as the control of the flow rates performed. In the constant part of the paper or board machine is in particular a uniform dilution of the aqueous composition containing at least one pulp (pulp suspension) of about 3 to 5% consistency (thick stock) to about 0.2 to 1.4% consistency. In addition, the pulp suspension of fiber bundles, sand, plastics, etc. cleaned. This takes place in particular in the so-called fabric fine sorting, for example via centrifugal, pressure and / or vibration sorters. Within the constant part, it is also possible to meter in fillers, process chemicals and / or functional chemicals. In the constant part of the paper or board machine is usually also the adjustment of the pH of the pulp suspension.

Particularly preferably, the addition of methanesulfonic acid to adjust the pH before, after and / or during the textile fine sorting of the aqueous composition containing at least one pulp. The fabric fine sorting takes place in particular by means of conventional sorting units, e.g. Centrifugal, pressure and / or vibration sorters. The addition of methanesulfonic acid preferably takes place before the last sorting unit in front of the headbox.

In general, the process according to the invention can be used for the production of all paper products known to the person skilled in the art. More specifically, the method of the present invention relates to the production of a paper product selected from graphic paper, office communication paper, wrapping paper, cardboard, paperboard, tissue and specialty paper, preferably a method for producing a graphic paper or office communication paper. In a preferred embodiment, the invention relates to a method for producing a paper product, characterized in that the paper product is a packaging material for the food sector.

Further, the present application is directed to the use of methanesulfonic acid in the manufacture of a paper product, wherein the use of methanesulfonic acid in the manufacture of a paper product comprises adjusting the pH of an aqueous composition containing at least one pulp.

In particular, the use of methanesulfonic acid according to the invention relates to the production of paper products on industrially common paper and / or board machines. Preferably, the use of methanesulfonic acid comprises adjusting the pH of an aqueous composition containing at least one pulp in the constant part of a paper and board machine. Particularly preferably, the methanesulfonic acid can be used before the headbox.

In particular, the invention relates to the use of methanesulfonic acid in the manufacture of a paper product selected from graphic paper, office communication paper, packaging paper, cardboard, cardboard, tissue and specialty paper, in particular a packaging material for the food industry.

Claims (14)

1. A process for manufacturing a papery article comprising the steps of:

   a) providing an aqueous composition comprising at least one fiber stock;

   b) adding methanesulfonic acid to the aqueous composition comprising at least one fiber stock to adjust the pH;

   c) draining the aqueous composition comprising at least one fiber stock.
2. The process according to claim 1 wherein the step of draining the aqueous composition (step c) results in the formation of a fibrous web which is pressed and/or dried in one or more further process steps.
3. The process according to either of claims 1 and 2 wherein the fiber stock used is at least one fiber stock selected from the group consisting of sulfate pulp (SA), sulfate semi-pulp, sulfite pulp (SI), groundwood (HS), pressurized groundwood (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemical thermomechanical pulp (CTMP), thermomechanical pulp with caustic/peroxide pretreatment (BCTMP), waste paper (AP) and deinked waste pulp (DIP).
4. The process according to any one of claims 1 to 3 wherein the aqueous composition comprises at least one fiber stock which has been alkali-oxidatively bleached.
5. The process according to any one of claims 1 to 4 wherein at least one secondary fiber stock is used.
6. The process according to any one of claims 1 to 5 wherein the aqueous composition comprising at least one fiber stock has a stock density in the range from 0.01 to 5%.
7. The process according to any one of claims 1 to 6 wherein the aqueous composition additionally comprises at least one further additive selected from the group consisting of aluminum sulfate, aluminum nitrate, polyaluminum chloride (PAC), aluminum hydroxide chloride, organic precipitant, biocide, deaerator, defoamer, dispersant, adsorbent, fixative, retention aid, drainage accelerant, dye, optical brightener, internal sizing agent, wet strength agent, dry strength enhancer and internal wet web strength polymer (IWWS).
8. The process according to any one of claims 1 to 7 wherein the aqueous composition additionally comprises at least one inorganic filler selected from the group consisting of ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, titanium dioxide and barium sulfate.
9. The process according to any one of claims 1 to 8 wherein the pH of the aqueous composition comprising at least one fiber stock is adjusted to a value in the range from 4 to 11.
10. The process according to any one of claims 1 to 9 wherein the step of adding methanesulfonic acid to the aqueous composition comprising at least one fiber stock takes place in a paper machine approach flow.
11. The process according to any one of claims 1 to 10 wherein the papery article is selected from graphic paper, office communication paper, packaging paper, board, card, hygiene paper and specialty paper.
12. The process according to any one of claims 1 to 11 wherein the papery article is a packaging material for the food sector.
13. The use of methanesulfonic acid in the manufacture of a papery article wherein the use of methanesulfonic acid comprises adjusting the pH of an aqueous composition comprising at least one fiber stock.
14. The use according to claim 13 wherein the use of methanesulfonic acid comprises adjusting the pH of an aqueous composition comprising at least one fiber stock in a paper and/or board machine approach flow.