WO2012085476A1

WO2012085476A1 - Process for delignification and bleaching of paper pulp using activated hydrogen peroxide

Info

Publication number: WO2012085476A1
Application number: PCT/FR2011/053150
Authority: WO
Inventors: Jérôme BLANC; Christophe Calais; Jean-Luc Dubois
Original assignee: Arkema France
Priority date: 2010-12-23
Filing date: 2011-12-22
Publication date: 2012-06-28
Also published as: RU2529974C1; FR2969668B1; FR2969668A1; CN103261514A; BR112013012374A2; CN103261514B; CL2013001800A1

Abstract

The invention relates to a process for the delignification and bleaching of paper pulp, comprising at least one step of bringing the paper pulp into contact with hydrogen peroxide and a molybdenum-based complex of formula (I): in which R represents an unsaturated C5-C6 cycloalkyl group or an unsaturated C5-C6 heterocycloalkyl group, being substituted or unsubstituted, and Ar represents an aryl group, optionally having one or more substitution(s) on the aromatic ring(s) by one or more of the following groups: - linear or branched C1-C4 alkyl, - halogen, -NO₂, -OH, -COOH.

Description

METHOD FOR DELIGNIFYING AND WHITENING PAPER PULP USING ACTIVE HYDROGEN PEROXIDE

FIELD OF THE INVENTION

The present invention relates to a process for delignification and bleaching of paper pulp by means of activated hydrogen peroxide. TECHNICAL BACKGROUND

Pulp manufacturing uses wood as the starting material. The wood contains cellulose fibers, white in color, and colored lignin.

As a result, papermaking generally involves delignification (lignin removal) and / or pulp bleaching. In order to maintain the mechanical properties necessary for the manufacture and use of paper, it is desirable that the cellulose be as little degraded as possible during this process.

For example, it is known to use chlorinated compounds (chlorine, chlorine dioxide, hypochlorite) for the delignification and bleaching of the dough. Because of the cost of these compounds and the generation of chlorinated derivatives in the effluents, it is sought to reduce their implementation.

It is also known to use oxygen, ozone or hydrogen peroxide as delignification and bleaching agents. However, the use of these agents is not really satisfactory. These agents have a bleaching power and / or specificity lower than those of chlorinated products. In particular, these agents can cause cellulose degradation and higher lignin content. High lignin content limits the whiteness of the dough and leads to yellowing and premature aging of the paper. In addition, the depolymerization of the cellulose weakens the fibers and subsequently the strength of the resulting paper. Activation of hydrogen peroxide at a high temperature also leads to significant degradation of the cellulose. Also, catalytic activation techniques of hydrogen peroxide have been suggested.

In particular, it is known to use various transition metals and / or transition metal complexes for the activation of hydrogen peroxide.

For example, the document WO 03/080925 describes a process for bleaching and delignification of paper pulp based on the use of hydrogen peroxide activated by a copper-phenanthroline complex.

CA 1 129,161 discloses a process for bleaching and delignification of paper pulp using, in an acid medium, metal ion-activated hydrogen peroxide chosen from the group formed by tungsten, molybdenum and chromium. , osmium and selenium.

The article Catalysis and activation of oxygen and peroxide delignification of chemical pulps: a review, M. Suchy and D.S. Argyropoulos, April 2002 vol.

1 no. 2 Tappi Journal, reviews various studies to improve the delignification of pulp by oxygen or hydrogen peroxide.

This document notably mentions the use of complexes diperoxomolybdate in acid medium.

The article Activation of alkaline peroxide delignification using a vanadium peroxide complex, M. Suchy and D. S. Argyropoulos, June 2000, vol.

83 no. 6 Tappi Journal, is interested in the use of a peroxon vanadium complex in a basic medium.

However, it remains difficult to find a satisfactory compromise between the lowering of the lignin content and the preservation of the cellulose in the pulp.

In addition, the bleaching of the paper pulp with hydrogen peroxide is usually carried out at basic pH and therefore requires an activator of active hydrogen peroxide in a basic medium. However, as mentioned above, most of the methods of the state of the art implement an activator of hydrogen peroxide in acidic medium. There is therefore still a need to develop an improved delignification and pulp bleaching process over prior art processes, to achieve more efficient delignification and / or to reduce the degradation of cellulose. and / or reduce the consumption of chemical compounds (especially chlorinated). There is also a need for a delignification and pulp bleaching process that remains effective at basic pH.

SUMMARY OF THE INVENTION

The invention firstly relates to a process for delignification and bleaching of pulp, comprising at least one step of contacting the paper pulp with hydrogen peroxide and a molybdenum-based complex of formula (I ):

in which

R represents a C5-C6 unsaturated cycloalkyl group or a substituted or unsubstituted C5-C6 heterocycloalkyl group; and

Ar represents an aryl group, optionally having one or more substitutions on the aromatic ring (s) with one or more linear or branched-halogen-C 1 -C 4 -alkyl groups; NO2, -OH, -COOH.

Preferably, R represents a C5 cycloalkyldienyl group or a C6 aromatic group, more preferably a cyclopentadienyl group.

Preferably, Ar represents a phenyl group.

For the purposes of the present invention, the term "unsaturated C5-C6 cycloalkyl" means an unsaturated cyclic carbon radical, substituted or unsubstituted, which may comprise 5 or 6 carbon atoms. For example, cyclopentadienyl may be mentioned.

By "substituted" group is meant that an atom or a group of atoms of the group, in particular hydrogen, is replaced by a C1-C6 alkyl group, hydroxyl or halogen in particular.

For the purposes of the present invention, the term "unsaturated heterocycloalkyl" means an unsaturated cycloalkyl radical as defined above, said cycloalkyl system comprising at least one heteroatom, chosen in particular from the group comprising sulfur, oxygen, nitrogen, phosphorus, and preferably being nitrogen. As unsaturated heterocycloalkyl there may be mentioned, for example, pyridine, which may or may not be substituted by one of the above groups.

For the purposes of the present invention, the term "aryl" means an aromatic system comprising at least one ring satisfying the Hukel rule of aromaticity, that is to say comprising 4n + 2 electrons Pi (Π) delocalizable on the the whole cycle (n being a natural number). Said aryl may comprise a (poly) ring of 6 to 24 carbon atoms, for example 6 to 12 carbon atoms, especially 6 to 10 carbon atoms, more particularly a 6 carbon atoms ring. Said aryl may comprise one heteroatom per ring. Said aryl is optionally substituted, for example by one of the groups mentioned above. For example, an aryl group may be phenyl, chlorobenzyl, nitrobenzyl, tolyl.

Unexpectedly, the molybdenum-based complex used in the process according to the invention is particularly effective compared to the activators of hydrogen peroxide of the prior art and this even in basic medium. Without being bound by this theory, the inventors attribute this particular efficiency to the presence of the molybdenum transition metal combined with the acetylenoaromatic bond which ensures the stabilization of the catalyst in its various oxidation states, Mo (V) and Mo (VI ).

Unless otherwise stated, all percentages will be given in mass values in the following. According to one embodiment, the molybdenum-based complex is oxo-peroxo-cyclopentadienyl-ethynylbenzene-molybdenum (VI) of formula

According to one embodiment, the pH of the pulp is adjusted to a value of 7 to 12, preferably 7 to 1 1, during the step of bringing the pulp into contact with the peroxide of hydrogen and the molybdenum-based complex, preferably by addition of sodium hydroxide. The maintenance of a basic pH makes it possible to place oneself in the optimal conditions for the action of hydrogen peroxide. The molybdenum-based complex according to the invention is thus particularly advantageous because it remains effective even when it is used in a basic medium.

According to one embodiment, the step of bringing the pulp into contact with the hydrogen peroxide and the molybdenum-based complex is carried out at a temperature of 10 ° C. to 120 ° C., preferably 20 ° C to 100 ° C, more preferably 30 ° C to 80 ° C.

According to one embodiment, the step of contacting the paper pulp with the hydrogen peroxide and the molybdenum-based complex has a duration of 1 minute to 4 hours, preferably 30 minutes to 3 hours.

According to one embodiment, during the step of bringing the pulp into contact with the hydrogen peroxide and the molybdenum-based complex, the consistency of the pulp is from 1% to 40% by weight of dry pulp, preferably from 5% to 30% by weight of dry pulp, based on the total weight of the dry paper pulp.

"Consistency" means the pulp concentration as defined in ISO Standard 41 19 of June 1996: this is the ratio of the anhydrous mass of filterable material of a suspended pulp sample to the mass. of the unfiltered sample, the test being carried out in accordance with the said International Standard. The paste concentration is expressed as a percentage by mass.

By "dry" paper pulp is thus meant the anhydrous mass of material of a sample of slurry in suspension as defined in the above-mentioned ISO standard 41 19, being measured after filtering and drying in accordance with said standard.

According to one embodiment, the initial content of hydrogen peroxide during the step of bringing the pulp into contact with the hydrogen peroxide and the molybdenum-based complex is less than or equal to 10% by weight dry pulp, preferably less than or equal to 4% by weight of the dry pulp, and more particularly is from 0.1% to 2% by weight of the dry pulp.

According to one embodiment, the molybdenum-based complex content in the step of bringing the pulp into contact with the hydrogen peroxide is from 0.001% to 1% by weight of the dry pulp, preferably from 0.01% to 0.2% by weight of the dry pulp, preferably from 0.01% to 0.1% by weight of the dry pulp.

According to one embodiment, the method comprises:

the preparation of an aqueous solution of molybdenum-based complex by reacting a precursor of the molybdenum-based complex with aqueous hydrogen peroxide, and then adding the molybdenum-based aqueous molybdenum complex solution to the pulp paper ; or

the addition to the pulp of a precursor of the molybdenum-based complex in solid form or in aqueous solution.

Said precursor of the molybdenum-based complex is preferably a complex of formula CpMo (CO) 3 (C≡CPh) in which Cp is a cyclopentadienyl group and Ph is a phenyl group. It is preferably tricarbonyl-cyclopentadienyl-ethynylbenzene-molybdenum (VI).

The second variant of this embodiment is advantageous in that the molybdenum-based complex is formed in situ in the pulp, by reaction with the hydrogen peroxide already present. It is thus not necessary to add hydrogen peroxide. The invention also relates to a process for the manufacture and treatment of pulp comprising:

a first step of cooking wood, preferably in the presence of sodium hydroxide and sodium sulphide, so as to obtain a pulp;

optionally, a preliminary step of delignification and bleaching of the oxygen paper pulp;

delignification and bleaching of the paper pulp according to the process according to the invention described above;

optionally, a complementary step of delignification and bleaching of the paper pulp by alkaline extraction and / or by treatment with ozone and / or by treatment with peracetic acid and / or by contact with peroxide; hydrogen and / or a chlorinated compound, such as chlorine dioxide.

This complementary step of delignification and bleaching may be indifferently before or after the step or steps of delignification and bleaching said preliminary and according to the process according to the invention.

The choice of this complementary step is made according to the desired application.

The invention also relates to a papermaking process comprising the manufacture and treatment of paper pulp according to the preceding method, followed by sheet forming and drying.

It is understood that a paper pulp manufactured according to the process of the invention may have no trace of the above-mentioned molybdenum-based complex and / or its precursor, especially because of washing, dilution and other operations. processes aimed in particular at removing impurities.

The present invention overcomes the disadvantages of the state of the art. In particular, it provides a delignification and pulp bleaching process to achieve more efficient delignification and / or to reduce the degradation of the cellulose and / or to reduce the consumption of chemical compounds. It also provides a process for delignification and pulp bleaching remaining effective at basic pH, compared to the methods of the state of the art.

This is accomplished through the use of hydrogen peroxide activated by a molybdenum-based complex of formula (I) or more particularly of formula (II).

According to some particular embodiments, the invention also has one or preferably more of the advantageous features listed below.

With respect to the use of hydrogen peroxide alone, the invention makes it possible to obtain greater delignification and results in equivalent or less degradation of the cellulose fibers.

With respect to the use of catalytically activated hydrogen peroxide according to the state of the art (for example with phenanthroline complexed with copper or with ammonium molybdate), the invention makes it possible to degrade the fibers to a lesser extent. of cellulose and to obtain a more efficient delignification (or alternatively to consume less hydrogen peroxide).

With respect to the activators of hydrogen peroxide of the prior art which are only active in an acidic medium, the molybdenum-based complex of formula (I) or (II) remains effective in a basic medium and thus proves particularly suitable for delignification and bleaching of pulp.

- The molybdenum-based complex of formula (II) allows a particularly effective delignification.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention is now described in more detail and without limitation in the description which follows.

The manufacture of paper pulp according to the invention comprises a step of cooking wood, preferably in the presence of sodium hydroxide and sodium sulfide so as to obtain a pulp (chemical pulp). The firing step can be carried out for a period of 8 to 12 hours, at a temperature ranging from 80 ° C to 200 ° C, being for example 170 ° C.

The pulp thus obtained is delignified and bleached, either only by using the molybdenum complex-activated hydrogen peroxide according to the invention, or by using also one or more additional treatments, before or after the treatment involving the complex based on molybdenum.

The additional treatments may be a hydrogen peroxide treatment (activated or not by said molybdenum-based complex), an oxygen treatment, an ozone treatment, a treatment with chlorinated compounds and in particular carbon dioxide. chlorine or treatment with any other bleaching agent (peracetic acid ...). These treatments may also be any conventional step of known bleaching processes (extraction, washing, chelation, etc.).

The use of the treatment with molybdenum complex activated hydrogen peroxide makes it possible in any case to reduce the duration or the consumption of reagents of these additional treatments (for example chlorine dioxide and / or diacid peracetic), for an equivalent or improved result in terms of delignification and bleaching, compared to the treatments of the state of the art.

It should be noted that the molybdenum-based complex activated hydrogen peroxide treatment step can be carried out once or repeatedly (for example twice).

Between two successive stages of treatment involving the molybdenum-based and / or additional complex, the pulp can be pressed and washed. It is dried on a dough press when all the processing steps are completed or it is sent to a paper machine.

The molybdenum-based complex used according to the invention has the formula (I). The preferred molybdenum-based complex in the invention is that of formula (II). It is the oxo-peroxo-cyclopentadienyl-ethynylbenzene-molybdenum (VI) complex. The oxo-peroxo-cyclopentadienyl-ethynylbenzene-molybdenum (VI) complex has been described in the document "Selective oxidation of aromatic primary alcohols to aldehydes using molybdenum acetylide oxperoxo complex as catalyst" Ankush V. Biradar, Mohan K. Dongare, Shubhangi B. Umbarkar, Tetrahedron Letters 50 (2009) 2885-2888. However, the application of such a complex to delignification and bleaching of paper pulp is neither taught nor suggested.

The treatment step with the molybdenum-based complex activated hydrogen peroxide supposes the addition of hydrogen peroxide and the molybdenum-based complex or its precursor to the pulp. This contacting step can be implemented according to different variants.

In particular, it is possible in advance to prepare an aqueous solution of the molybdenum-based complex by incorporating a precursor of said complex into an aqueous solution of hydrogen peroxide, and then adding this solution to the pulp.

The molybdenum complex on the one hand and hydrogen peroxide on the other can also be added separately to the pulp. The molybdenum-based complex can in particular be incorporated in the form of an aqueous solution.

It is also possible to add separately to the pulp the precursor of the molybdenum-based complex on the one hand and hydrogen peroxide on the other hand, so that the molybdenum-based complex is formed in situ in pulp. The precursor of the molybdenum-based complex can in particular be incorporated in solid form or in the form of an aqueous solution.

Said precursor is, for example, a complex CpMo (CO) 3 (C≡CPh) where Cp denotes a cyclopentadienyl group and Ph denotes a phenyl group. It is preferably tricarbonyl-cyclopentadienyl-ethynylbenzene-molybdenum (VI). Other precursors can be envisaged, provided that they allow the formation of said molybdenum complex in the pulp. The operating conditions (consistency of the paste, time, temperature, etc.) of the treatment step with the hydrogen peroxide and the molybdenum-based complex or its precursor are those specified above.

The amount of lignin in the paper pulp can be measured by the kappa index, according to the ISO 302 standard of July 1987.

The more or less good preservation of cellulose in the pulp can be characterized by the degree of polymerization. This is calculated from a measurement of the viscosity of the pulp by the capillary viscometer method (TAPPI test method T 230 om-08).

The consistency of the dough corresponds, as explained above, to the pulp concentration as defined in ISO Standard 41 19 of June 1996. It is measured in accordance with this Standard.

The proportion of hydrogen peroxide remaining at the end of the treatment can be determined by iodometric determination. This method can be implemented as follows:

at the end of the treatment, the paper pulp is filtered in accordance with ISO Standard 41 19. A solution of sulfuric acid (at 300 g / l) and a solution of potassium iodide (at 10Og / l) are added to the filtrate. ). Potassium iodide, oxidized by hydrogen peroxide, releases diode into the filtrate. The diode thus liberated is then titrated by successive additions of a solution of sodium thiosulphate (at 24.8 g of Na ₂ S ₂ O ₃ .5H ₂ O / l) in the filtrate.

If hydrogen peroxide remains after treatment, it means that it is possible to prolong the treatment to increase delignification and bleaching, or that the initial dose of peroxide can be reduced. 'hydrogen.

EXAMPLES

The following examples illustrate the invention without limiting it.

Comparison of the invention with bleaching processes of the state of the art As a raw material for the following tests, a softwood pulp from Northern Europe, supplied previously delignified with oxygen, is used. This paste initially has a kappa number of 1 1, 3 and a degree of polymerization of 1540.

Sufficient water is added to the pulp to achieve a consistency of 10% by weight of dry pulp relative to the weight of the dry pulp.

These three parameters are determined according to the above methods.

Test 1: Treatment with the molybdenum-based complex according to the invention A sample of this paper pulp comprising 20 g of dry paper pulp is introduced into a plastic bag.

Are added successively to this sample (in percentages by weight relative to the total weight of the dry pulp):

0.4 g (2% by weight) of NaOH,

0.01 g (0.05% by weight) of tricarbonyl-cyclopentadienyl-ethynylbenzene-molybdenum (VI),

0.4 g (2% by weight) of H ₂ O ₂ .

The oxo-peroxo-cyclopentadienyl-ethynylbenzene-molybdenum (VI) molybdenum complex is formed in situ in the pulp. It is present at 0.044% by weight relative to the total weight of the dry pulp, considering that the conversion of the precursor introduced into the sample is total.

The bag is sealed by heat sealing and kneaded manually to homogenize the mixture. It is immersed in a water bath at a temperature of 50 ° C for 3 hours. The sachet is recovered and the pulp obtained is filtered on a Biichner filter (according to ISO Standard 41 19 of June 1996), in order to isolate the filtrate from the fiber cake.

We measure:

the pH of the filtrate,

the proportion of hydrogen peroxide remaining in the filtrate by the aforementioned iodometric assay method, the kappa index of the fiber cake,

the degree of polymerization of the fiber cake.

Test 1a: preliminary preparation of a solution of molybdenum-based complex according to the invention

An aqueous solution comprising 0.4 g of H 2 O 2 in 50 ml of water is prepared. To this solution are added 0.01 g of tricarbonyl-cyclopentadienyl-ethynylbenzene-molybdenum (VI) precursor in solid form. This mixture is stirred until the precursor is dissolved for 1 to 2 minutes. A solution of molybdenum oxo-peroxocyclopentadienyl-ethynylbenzene-molybdenum (VI) complex is thus obtained.

The procedure is the same as for example 1 by treating an initial sample of paper pulp comprising 20 g of dry pulp with (in percentages by weight relative to the total weight of the dry pulp):

0.4 g (2% by weight) of NaOH, and

the solution of molybdenum-based complex thus prepared.

Test 2 (comparative test): treatment with hydrogen peroxide alone

0.4 g (2% by weight) of NaOH and

0.4 g (2% by weight) of H ₂ O ₂ .

Test 3 (Comparative Test): Treatment with the Cuiyre-Phenanthroline Complex The procedure is the same as for Example 1 by treating an initial sample of paper pulp comprising 20 g of dry paper pulp with (in percentages by weight relative to to the total weight of the dry pulp):

0.4 g (2% by weight) of NaOH,

0.4 g (2% by weight) of H ₂ O ₂ and 0.01 g (0.05% by weight) of copper-phenanthroline Cu (phen) ₂ complex of document WO 03/080925.

Test 4 (comparative test): ammonium molybdate treatment

0.4 g (2% by weight) of NaOH,

0.4 g (2% by weight) of H ₂ O ₂ and

0.01 g (0.05% by weight) of ammonium molybdate of formula

The results of the bleaching are shown in the table below.

^* The proportions of hydrogen peroxide remaining are given in percentages by weight relative to the total weight of hydrogen peroxide initially introduced into the paper pulp sample. These results show that:

- the use of ammonium molybdate (test 4), although it represents a gain in terms of industrial costs, does not provide any improvement over the use of copper-phenanthroline (test 3): delignifies less well while degrading cellulose as much. This test demonstrates that the mere presence of the molybdenum transition metal in the activator is not sufficient to improve the bleaching performance;

The molybdenum-based complex according to the invention (test 1):

· Allows the activation of delignification hydrogen peroxide (kappa number lower than that of test 2),

• preserves the cellulose (degree of polymerization close to the initial value and much higher than that of tests 3 and 4),

• limits the decomposition of hydrogen peroxide (proportion of hydrogen peroxide remaining significantly higher than that of tests 3 and 4).

The pulp treated according to the process of the invention obtained at the end of test 1 is then:

- sent to a paper machine to be directly dried and shaped into sheets; or

- sent to a dough press machine to be dried and preformed into sheets, baled for transfer to a paper mill for further processing.

Claims

A process for delignification and bleaching of pulp, comprising at least one step of contacting the pulp with hydrogen peroxide and a molybdenum-based complex of the formula

(I):

in which

R represents a C5-C6 unsaturated cycloalkyl group or a substituted or unsubstituted C5-C6 heterocycloalkyl group, and

2. Process according to claim 1, wherein R represents a C5 cycloalkyldienyl group or a C6 aromatic group, preferably a cyclopentadienyl group.

3. Method according to one of claims 1 or 2, wherein Ar represents a phenyl group.

4. Method according to one of claims 1 to 3, wherein the molybdenum-based complex is oxo-peroxo-cyclopentadienyl-ethynylbenzene-molybdenum (VI) of formula (II):

5. Method according to one of claims 1 to 4, wherein the pH of the paper pulp is adjusted to a value of 7 to 12, preferably 7 to 1 1, during the step of bringing into contact the the pulp with hydrogen peroxide and the molybdenum-based complex, preferably by addition of sodium hydroxide.

6. Method according to one of claims 1 to 5, wherein the step of contacting the pulp with the hydrogen peroxide and the molybdenum-based complex is carried out at a temperature of 10 ° C at 120 ° C, preferably 20 ° C to 100 ° C, more preferably 30 ° C to 80 ° C.

7. Method according to one of claims 1 to 6, wherein the step of contacting the pulp with the hydrogen peroxide and the molybdenum-based complex has a duration of 1 minute to 4 hours, preferably from 30 minutes to 3 hours.

The method according to one of claims 1 to 7, wherein the consistency of the pulp during the step of contacting the pulp with the hydrogen peroxide and the molybdenum-based complex is from 1% to 40% by weight of dry pulp, preferably from 5% to 30% by weight of dry pulp, based on the total weight of the dry pulp.

9. Process according to one of claims 1 to 8, wherein the initial content of hydrogen peroxide in the step of contacting the pulp with the hydrogen peroxide and the molybdenum-based complex is less than or equal to 10% by weight of the dry pulp, preferably less than or equal to 4% by weight of the dry pulp, and more particularly is 0.1% to 2% by weight of the pulp dry paper.

10. Process according to one of claims 1 to 9, wherein the molybdenum-based complex content during the step of contacting the pulp with the hydrogen peroxide and the molybdenum-based complex. is from 0.001% to 1% by weight of the dry pulp, preferably from 0.01% to 0.2% by weight of the dry pulp.

11. Method according to one of claims 1 to 10, comprising:

the preparation of an aqueous solution of molybdenum-based complex by reaction of a precursor of the molybdenum-based complex with aqueous hydrogen peroxide and then the addition of the molybdenum-based aqueous molybdenum complex solution to the pulp paper; or

the addition to the pulp of a precursor of the molybdenum-based complex.

12. Method according to one of claims 1 to 1 1, comprising the addition to the pulp of a precursor of the molybdenum-based complex, having the formula CpMo (CO) 3 (C≡CPh) where Cp designates a cyclopentadienyl group and Ph a phenyl group, preferably being tricarbonyl-cyclopentadienyl-ethynylbenzene-molybdenum (VI).

13. A method of manufacturing and processing pulp comprising:

delignification and bleaching of the paper pulp according to the method of one of claims 1 to 12; optionally, a complementary step of delignification and bleaching of the paper pulp by alkaline extraction and / or by treatment with ozone and / or by treatment with peracetic acid and / or by contact with peroxide; hydrogen and / or a chlorinated compound, such as chlorine dioxide.

A papermaking process comprising the manufacture and processing of paper pulp according to the method of claim 13, followed by sheet forming and drying.