WO2012101137A1

WO2012101137A1 - Method for producing a paper product

Info

Publication number: WO2012101137A1
Application number: PCT/EP2012/051071
Authority: WO
Inventors: Stefan Fassbender; Christoph LESSIG
Original assignee: Basf Se
Priority date: 2011-01-25
Filing date: 2012-01-25
Publication date: 2012-08-02
Also published as: EP2668333A1; EP2668333B1; CA2825337A1; CN103384742A; BR112013019045A2

Abstract

The invention relates to a method for producing paper products, such as paper, paperboard and cardboard, comprising the step of adjusting the pH of an aqueous composition containing at least one fiber material by adding methanesulfonic acid (MSA).

Description

Process for producing a paper product 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 production of paper products on modern paper or board machines involves the dewatering of a pulp suspension, for example a pulp, wood pulp and / or recovered paper suspension, on at least one moving screen to form a paper web. Under the term Papierbzw. The following aggregates are usually grouped together: Constant part, headbox, wire section, press section, dryer section, size press (surface sizing), film press, Yankee cylinder, calender, on-line calender, on-line coater and reel. 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 "Papermill Paperback, 8th edition, Dr. med. 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 equalizing grinding of the pulp is carried out, which regulates substance quantities and material densities, and the regulation of the flow velocities is carried out. Within the constant part, the addition of filling Substances, process chemicals and / or functional chemicals. As a constant part is usually called 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 usually less than 1.4% is 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.

Fibers used in the manufacture of paper products generally include primary fibers and secondary fibers. 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 fibrous materials include various recovered paper grades, which are recycled in the recycling of paper / cardboard and paperboard production, and deinked ones 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, defibrated waste paper is usually mixed with caustic soda, 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 as it is the use of calcium carbonate (CaC0 ₃ ) as a filler possible, for example in the form of ground calcium carbonate (grated calumum carbonate GCC) or precipitated calcium carbonate (precipitated calcium carbonate PCC).

The pH of the pulp suspension is of crucial importance for paper production 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.

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. Document US 2010/0175839 describes a multi-step process for adjusting the pH of a pulp suspension, wherein the pulp is carbonated at least twice and at least once with a strong acid, e.g. Sulfuric acid, sulfurous acid or bisulfite, is treated and wherein a step for removing carbonate is included.

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, especially sulfuric acid, sulphurous acid, hydrochloric acid and bisulphite, followed by a weak base (e.g., 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 board, 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 the pH regulation of pulp suspensions is, in particular, the outgassing of carbon dioxide in the white water circuit. run and the associated fluctuations in the pH value. 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. The present application is directed to a process for making a paper product, such as paper, board and board, comprising the steps of: a) providing an aqueous composition containing at least one pulp; b) adding methanesulfonic acid to the aqueous composition containing at least one pulp to adjust the pH; c) dewatering the aqueous composition containing at least one pulp.

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 less deposits, e.g. 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 (e.g., 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.

The use of methanesulfonic acid thus makes it possible to significantly improve the quality of the production of paper products.

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 a For the purposes of the invention, fish papers are 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 to be understood as writing, printing and copying papers, for example 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 boards for special technical purposes, such as decor 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.

The pulp may in particular be selected from:

• pulp (ZS), such as sulphate pulp (SA) (also called kraft pulp), sulphate half-pulp, sulphite pulp (S1);

• mechanical pulp, such as groundwood (SG), 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 (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 fibrous material selected from the group consisting of sulphate pulp (SA), sulphate half-cell pulp, sulphite pulp (SI), groundwood (HS), pressure groundwood (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 fiber, in particular waste paper and / or deinked waste paper (DIP), is used as the pulp.

Most preferably, the aqueous composition contains at least one pulp which has been bleached by alkaline oxidative. The aqueous composition containing at least one pulp preferably has a pulp density of 0.01 to 5%, preferably 0, 1 to 5%, particularly preferably 0.2 to 1.4%.

The consistency of an aqueous composition containing at least one fiber (pulp suspension) is understood as meaning the percentage of the dry mass 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 41 19).

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 (e.g., slimicides)

ventilator

defoamers

dispersants

Adsorbents (e.g., talc)

Fixatives (e.g., short chain cationic polymers)

Retention aids (e.g., long chain anionic and cationic polymers, partially cross-linked)

• Drainage accelerators and functional chemicals, such as

dye

Optical brightener

Engine sizing agent (rosin size, AKD, ASA, polymer size) surface sizing agent

Wet strength agent

Dry strength

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, drainage 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 pH of the aqueous composition containing at least one fibrous material can be adjusted by adding 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 pulp to a value in the range of 4 to 1 1, in particular in the range of 4.5 to 6 8, in particular in the range of 6.8 to 10.8. 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 process according to the invention relates to a process for the production of a paper product using the so-called neutral procedure (usually with use of calcium carbonate as filler), the pH of the aqueous composition containing at least one fibrous material is preferably in the range of 6.8 to 10.8; especially adjusted from 7.0 to 7.5.

Furthermore, the process for producing a paper product described in the present application may comprise further conventional process steps of paper or board production, eg steps in stock preparation comprising dispersion, sorting, grinding of the pulp, steps following the drying, such as calendering, brushing, Cutting as well as steps concerning the equipment. 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 takes place 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 is done 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. In particular, the method according to the invention relates to the production of a paper product selected from graphic paper, office communication paper, packaging paper, cardboard, cardboard, tissue paper and special 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. Furthermore, the present application is directed to the use of methanesulfonic acid in the manufacture of a paper product. In particular, the use according to the invention of methanesulfonic acid in the production of a paper product comprises adjusting the pH of an aqueous composition comprising at least one fibrous material.

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 paper and special paper, in particular a packaging material for the food industry.

Claims

claims

1. A process for producing a paper product comprising the following steps:

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

A method according to claim 1, characterized in that when dehydrating the aqueous composition (step c) a nonwoven fabric is formed, which in one or more further process step (s) is pressed and / or dried.

Method according to one of claims 1 or 2, characterized in that at least one pulp is selected from the group consisting of sulphate pulp (SA), sulphate pulp, sulphite pulp (Sl), groundwood (HS), pressure groundwood (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).

A method according to any one of claims 1 to 3, characterized in that the aqueous composition contains at least one pulp which has been bleached by alkaline oxidative.

Method according to one of claims 1 to 4, characterized in that at least one secondary pulp is used as the pulp.

Method according to one of claims 1 to 5, characterized in that the aqueous composition comprising at least one pulp has a consistency of 0.01 to 5%.

7. The method according to any one of claims 1 to 6, characterized in that the aqueous composition additionally contains at least one further additive selected from the group consisting of aluminum sulfate, Aluminiumnit- rat, polyaluminium chloride (PAC), aluminum hydroxide chloride, organic precipitant, biocide, deaerator, defoamer, dispersant, adsorbent, fixer, retention aid, dehydration accelerator, dye, optical brightener, engine sizer, wet strength agent, dry strength and internal wet web strength polymer (IWWS).

A method according to any one of claims 1 to 7, characterized in that the aqueous composition additionally contains 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 method according to any one of claims 1 to 8, characterized in that the pH of the aqueous composition containing at least one pulp is adjusted to a value in the range of 4 to 11.

10. The method according to any one of claims 1 to 9, characterized in that the addition of methanesulfonic acid to the aqueous composition containing at least one pulp takes place in the constant part of a paper machine.

1 1. A method according to any one of claims 1 to 10, characterized in that the paper product is selected from graphic paper, office communication paper, packaging paper, cardboard, cardboard, tissue paper and special paper pier.

12. The method according to any one of claims 1 to 1 1, characterized in that the paper product is a packaging material for the food industry.

13. Use of methanesulfonic acid in the manufacture of a paper product.

14. Use according to claim 13, characterized in that the use of methanesulfonic acid comprises adjusting the pH of an aqueous composition comprising at least one pulp.

Use according to any one of claims 13 or 14, characterized in that the use of methanesulphonic acid comprises adjusting the pH of an aqueous composition containing at least one pulp in the constant part of a paper and / or board machine.