CA2359162A1 - Transition metal complexes with polydentate ligands for enhancing the bleaching and delignifying effect of peroxo compounds - Google Patents

Abstract

This invention relates to transition metal complex compounds of polydentate ligands with improved delignifying and bleaching performance. These polydentate ligands are organic ligands which, in aqueous solution and in the presence of atmospheric oxygen, or hydrogen peroxide, form a complex with a transition metal, in particular cobalt, characterised in that the complexes are mono- or polynuclear and they have, when peroxo compounds are used, better delignifying and bleaching performances than conventional transition metal complex compounds.

A delignifying and bleaching method, in which these transition metal complex compounds with polydentate ligands having improved delignifying and bleaching performance are used as catalysts, is also described.

Description

,, 000325 BL / AL

Transition metal complexes with polydentate ligands for enhancing the bleaching and delignifying effect of peroxo compounds This invention relates to transition. metal complexes with polydentate ligands for enhancing the bleaching and delignifying effect of peroxo compounds, to their use and to a method for the delignification of fibrous materials.
The term "fibrous materials" will be used below to denote all lignin-containing fibres, which have either been 14 mechanically and/or chemically pretreated by the process of lignin production or pulp production or are subjected to this method as chemically or mechanically untreated natural fibres. These fibres may also have undergone several stages of chemical and/or mechanical processing, for example chemical pulping and a first delignifying treatment after pulping.
Lignin-containing fibres from wood or from annual plants should, as far as possible, be freed from lignin for most applications. The fibres should furthermore have high brightnesses, advantageously 90o ISO. These high brightnesses will be achieved only if lignin is substantially removed from the fibre or from the fibre surface. Using elemental chlorine and other chlorine-containing bleaching chemicals, it ha.s possible to delignify lignin-containing fibres efficiently and highly selectively in the past.
Since, when chlorine and/or chlorine-containing chemicals such as e.g. chlorine dioxide are used, it is not possible to avoid the formation of AOX ("adsor:bable organically bound halogen") in the waste water and OX ("organically bound halogen"} in the pulp, pulp manufacturers are making increased use of chlorine-free bleaching agents, such as for example oxygen and oxygen-contain:ing chemicals, which are intended to brighten the fibres to the highest possible brightness (elemental chlorine-free bleaches (ECF

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bleaches) and totally chlorine-free bleaches (TCF
bleaches). In order to obtain approximately the same effect as with chlorine-containing bleaching agents, it is necessary to select more drastic conditions, such as for example higher reaction temperatures and longer reaction times. A disadvantage with oxygen-containing bleaching agents is that the reaction mechanisms of these chemicals are far less selective than is the-case with chlorine or chlorine-containing chemicals, so that the delignification or bleaching entails greater damage to the cellulose.
There is therefore a great need for methods, and also therefore for chemicals, which selectively and mildly break down by oxidation the residual lignin still present after pulping.
The chlorine-free bleaching agents, which are used for this purpose in the pulp industry, also include hydrogen peroxide. Hydrogen peroxide is used, above all, for environmental protection reasons. It is more expensive than chlorine-containing bleaching agents, and significantly less selective. For these reasons, hydrogen peroxide has to date been used under the mildest possible conditions wherever fibrous materials are to be brightened but not delignified. Under more intense reaction conditions, for example higher temperature, greater use of chemicals and/or longer reaction tim~a, although the residual lignin still present does become broken down to some extent, this is accompanied by :increased damage to the fibre and yield losses. A particularly undesirable feature is that the unselective reaction of hydrogen peroxide attacks the cellulose, so that the strength of the fibre is significantly reduced.
In order to make best use of the brightening effect of hydrogen peroxide, attempts have for some time been made to find catalysts which suppress the many unselective side reactions and thereby make more hydrogen peroxide available for the removal of chromophoric groups and/or activate hydrogen peroxide for the delignification. To that end, substances which, for example, have been described for bleaching or brightens:ng use in detergents are used time and time again. The results from the field of detergents, however, are scarcely applicable to the pulp and paper industry, since textile fibres are not comparable with lignin-containing fibres. The reason for this is that the chemical structure of stubborn stains in fabrics is very different from the structure of the wood lignin to be oxidised. Furthermore, the dirt is located on . the textile fibre, whereas the majority of the lignin to be removed is embedded in the cellulose fibre (middle lamella).
The previously known methods, for instance that described in DE 19 620 241, W0 97/44520 and WO 99/64156, use manganese or iron complexes as catalysts to activate peroxo compounds. These compounds have the disadvantage that they are difficult to synthesise. Furthermore, they significantly show an H2O2 degradation effect (catalase activity), the result of which is that only certain amounts of the transition metal complex compounds can be used.
An increase in the amount of catalyst. hence does not lead to an increase in the bleaching effect (see DE 19 620 241, Example 3), but rather to degradation of the hydrogen peroxide, which is thereby made unavailable for the bleaching. The consequences are inferior brightness, or increased kappa numbers, and significant damage to the fibrous mass. These compounds also have the disadvantage that they are degraded under bleaching conditions (at least pH 10, 80°C). This instability of the complexes during bleaching makes it appropriate to add the catalyst portionwise, as described explicitly in APPITA Annual Conference 1999, pp. 455 to 461. Although this procedure is possible at the laboratory scale, :it cannot be used industrially since additional mixing machines cannot be integrated into the bleaching tower:.
In view of the prior art described and discussed above, it is an object of the invention to develop a method for the improved and selective delignificat.i_on and/or bleaching of lignin-containing fibrous materials by using peroxo-containing and therefore environmentally friendly chemicals.
It has now been surprisingly found that certain transition 10, metal complex compounds with polyden.tate ligands considerably surpass the delignifying and bleaching performance of hitherto known catalytic systems. In this case, increasing the amount of catalyst leads to an increase in the bleaching effect and not, as in the case of conventional catalytic systems, to uncontrolled degradation of the hydrogen peroxide. The consequences are better brightnesses, or decreased kappa numbers, and gentle treatment of the fibrous mass.
This invention therefore provides a nnethod for the delignification and/or bleaching of fibrous materials with a) an aqueous suspension of fibres, which have a consistency of from 3~ to 40~;
b) a peroxo compound, which is used at from 0.1~ to 10~, based on the bone-dry fibrous mass; and with c) a mononuclear transition metal complex of the general formula (1), (~p~ ZYq Formula (1) wherein L is a polydentate ligand of t:he general formula (a) . (b) . (c) or (d) , ' 000325 BL / AL

N

Formula (a) Formula (b) R4~N~N~R4 N

Formula (c) ~N\ N- ~R4 R4 \

Formula (d) 5 in which R1, R2, and R3 independently of one another stand for hydrogen, a linear of branched alkyl or alkenyl residue, or an optionally substituted aryl or arylalkyl residue';
R4 independently of one another stands for an optionally N-substituted linear, branched or cyclic aminoalkyl residue', or an optionally substituted heteroaryl residue such as pyridyl, pyrazinyl, pyrazolyl, pyrrolyl, imidazolyl, pyrimidyl, triazolyl or quinolyl;

M is a transition metal ion,, advantageously iron in oxidation states (II) to (V); manganese in oxidation states (II) to (VII); or cobalt in oxidation states (II) to (IV); cobalt preferably being in oxidation states (II) or ' (III);

X is a coordinate species (neutral or anionic), such as for example CH3CaV, CH3C00 , C1-, Br-, H20, OH , HOO-, OCN-, SCN-, PO43-, NH3, N03 , N02 , NO, p2-~ pz2-;

Y is,a counter-ion or counter-molecule, such as for example C104-, Br-, Cl-, PF6-, N03-, BPh4-, SO42-, CH3C00 or mixtures. thereof ;

p is an integer from 0 to 4;

z is a complex charge (+/0/-);

q is z/[charge of Y];

or with d) instead of (c), a mononuclear transition metal complex of the general formula (2), [LmConXp] Zyq; Formula (2 ) wherein L is a ligand of the general formula (a), (b), (c) or (d) ;
Co stands for cobalt in oxidation states (II) to (IV) or mixtures of these oxidation states, the oxidation states (II) and (III) being particularly preferred;
X, Y, z and q are as described for formula (1);
m and n are integers from 2 to 4; and p is an integer from 0 to 12;
the transition metal complex (c) or (d) being used in an amount of from 10 ppm to 5000 ppm, bared on the amount of bone-dry (b. d.) fibres used.

Complex compounds of the formula (2;1 , in which X = Oz2- and m, n = 2 and p = 2, are particularly preferred.
Examples of ligands of the formula (a) which can be used according to the invention are:
N,N-bis(2-aminoethyl)propane-1,2,3-t:riamine;
N,N-bis(2-aminoethyl)-2-methylpropane-1,2,3-triamine;
N,N-bis{2-aminoethyl)-bis(pyridin-2-yl)methylamine;
N,N-bis(2-aminoethyl)-1,1-bis(pyridin-2-yl)-1-aminoethane;
N,N-bis[2-(N,N-dialkyl)aminoethyl]]-bis(pyridin-2-yl)methylamine;
N,N-bis[2-(N,N-dialkyl)aminoethyl]]-1,1-bis(pyridin-2-yl)-1-aminoethane;
N,N-bis(pyridin-2-ylmethyl)-bis{pyri~din-2-yl)methylamine (N4Py);
N,N-bis(pyridin-2-ylmethyl)-2,1-bis(pyridin-2-yl)-1-aminoethane (MeN4Py); and N,N-bis(pyridin-2-ylmethyl)-1,1-bis{pyridin-2-yl)-2-phenyl-1-aminoethane.
Examples of ligands of the formula (b) which can be used according to the invention are:
N-[2-amino-1-(aminomethyl)ethyl]propane-1,2,3-triamine;
bis[di(pyridin-2-yl)methyl]amine;
bis[1,1-di(pyridin-2-yl)ethyl]amine;
N-methyl-bis[di(pyridin-2-yl)methyl]amine; and N-methyl-bis[1,1-di(pridin-2-yI)ethyl]amine.
Examples of ligands of the formula (c) which can be used according to the invention are:
1,4-bis(2-aminoethyl)-1,4,7-triazacyc:lononane;
1,4-bis[2-(N,N-dialkyl)aminoethyl]-1,4,7-triazacyclononane;
2,4-bis(2-aminoethyl)-7-methyl-1,4,7-t:riazacyclononane;
1,4-bis[2-(N,N-dialkyl)aminoethyl]-7-methyl-1,4,7-triazacyclononane;
1,4-bis(pyridin-2-ylmethyl)-1,4,7-triazacyclononane; and 1-methyl-4,7-bis(pyridin-2-ylmethyl)-1,4,7_ triazacyclononane.

Examples of ligands of the formula (d) which can be used according to the invention are:
N,N,N'-tris(2-aminoethyl)ethylene-1,2-diamine;
N,N-bis(2-aminoethyl)-N'-(pyridin-2-ylmethyl)ethylene-1,2-diamine;
N,N,N'-tris(2-aminoethyl)-N'-methylE=_thylene-1,2-diamine;
N,N-bis(2-aminoethyl)-N'-methyl-N'-(pyridin-2-ylmethyl)ethylene-1,2-diamine;
N,N,N'-tris(pyridin-2-ylmethyl)ethylene-1,2-diamine;
N,N,N'-tris,(3-methylpyridin-2-ylmethyl)ethylene-1,2-diamine;
N-methyl-N,N',N'-tris(pyridin-2-ylmethyl)ethylene-1,2-diamine; and N-methyl-N,N',N'-tris(3-methylpyridi.n-2-ylmethyl)ethylene-1,2-diamine.
In a first aspect of the invention, transition metal complex compounds of polydentate lig~ands with improved delignifying and bleaching performance will be described.
These polydentate ligands are organic ligands which, in aqueous solution and in the presence of atmospheric oxygen and/or hydrogen peroxide, form a complex with a transition metal, in particular cobalt, characterised in that the complexes are mono- or polynuclear a:nd they have, when peroxo compounds are used, better deligni.fying and bleaching performances than conventional transition metal complex compounds.
The transition metal complex compounds with polydentate ligands, which are described here, w_L11 also be referred to as bleaching catalysts. In this context, the term "polydentate ligands" means ligands which have at least 4 or more heteroatoms (so-called donor atoms), preferably nitrogen, which can coordinate with t;he transition metal ion. Pentadentate ligands are preferred. Pentadentate N-donor ligands are particularly preferably used in the present invention.

In a second aspect, a delignifying <~nd bleaching method will be described, in which these transition metal complex compounds with polydentate ligands having improved delignifying and bleaching performance are used as catalysts. In this context, it has been demonstrated that mononuclear transition metal complex compounds of the general formula (1), in particular t:he mononuclear complexes of the formula (1a) with the pentadentate ligand N4Py and derivatives thereof, which are described for the low-temperature bleaching of textile' fabrics in EP 0 909 809 and WO 00/12667, are useful as a: bleaching catalyst in the bleaching of fibrous material and can be employed therein.
It has furthermore been found that polynuclear, in particular binuclear cobalt complexes with polydentate ligands of the general formula (2) also activate peroxo compounds for the delignification or oxidative bleaching of fibrous materials.
It has been found that, when using t:he known iron or manganese complexes of the formula (1a), in particular 'with the ligand N4Py and derivatives thereof, in pulp bleaching or delignification with hydrogen peroxide, it is possible to achieve an improved effect compared with the reference test without the addition of catalyst.
It has furthermore been found that a cobalt complex of the formula (1a) can be obtained when the ligand N4Py known from the literature [M. Lubben, A. Meetsma et al., Angew.
Chem. 1995, 107, 1610, EP 0 909809, WO 95/34628], as described in WO 00/12667, is reacted with a corresponding cobalt(II) salt instead of the iron(I:I) salt. This cobalt-containing complex shows a significantly better effect in the bleaching test than the said iron. or manganese compound.
The introduction of cobalt as a transition metal ion in the way described above does not, however, appear expedient to the person skilled in t:he art. When following literature methods for the reaction of cobalt(II) salts with polydentate Iigands [G. A. Law~:ance, T. M. Manning et al., J. Chem. Soc., Dalton Trans., 1992, 1635; G. A.
5 Lawrance, M. A. O'Leary et al. Aust. J. Chem. 1988, 41, 1533, D. A. Buckingham, P. J. Cresswell et al., Inorg.
Chem. 1975, 14, 1485], with the lig~nd N4Py or derivatives thereof, a binuclear cobalt complex is obtained with a ~.t,-peroxo (~1,-02) bridge similar to formula (2a) , wherein X =
1O O22-. This compound class, which has not to date been described, provides better results in pulp bleaching or delignification compared with the mononuclear compounds of the formula (1a) prepared according to WO 00/12667, in particular the said cobalt complex of the formula (1a) (see Table 1).
Peroxo compounds with a structure according to formula (2), in which X = 022-, can generally be prepared by reacting the polydentate ligand or its salt (in the "one-pot method", see Example 2), dissolved in corresponding solvents such as methanol, water or mixtures thereof, with cobalt(II) salts and subsequent air oxidation. The results achieved with these compounds in pulp bleaching or delignification surpass the prior art discussed in the introduction.
The use, according to the invention, of the transition metal complex compounds substantially consists in creating conditions under which the peroxo connpound and the bleaching catalyst can react with one another, for the purpose of obtaining consecutive products which have a more strongly oxidising effect. Such conditions exist, in particular, when the two reaction partners encounter one another in aqueous solution. The aqueous fibrous mass already contains the bleaching catalyst according to the invention.,The peroxo compound may preferably be added separately to the aqueous fibrous mass, and in substance or as an advantageously aqueous solution. The bleaching a , 000325 BL / AL

catalyst may advantageously be kneaded into the aqueous fibrous mass, optionally with other bleaching additives, such as for example sodium hydroxide.
The bleaching catalyst may alternatively be prepared "in situ" by separate addition of the metal salt and the ligand, or its salt, to the aqueous solution of the bleaching additives, which is subseg~ently mixed into the fibrous mass. In the case of such an. "in situ'° method, the bleaching catalyst need not be isolated.
With these transition metal complexes according to the invention, which are used in concentrations of from 10 ppm to 5000 ppm, preferably from 50 ppm to 3000 ppm, advantageously from 200 ppm to 2000 ;fpm, and particularly preferably from 200 ppm to 1500 ppm, based on the amount of bone-dry (b.d.) fibres used, the delignification of fibres with the method according to ithe invention can, quite surprisingly, be increased significantly compared with the known, merely brightening pE~roxide stage, with the cellulose being broken down only slightly. What is particularly astounding is that thesEa increase factors are achieved with rather low residual lignin contents, where, according to the invention, there are lignin structures which are particularly difficult to x>reak down, strongly condensed and therefore relatively unreactive.
This enormous delignification and/or bleaching is achieved by employing the transition metal complexes and process conditions according to the invention.
The method according to the invention can be used for a wide variety of fibre types, for instance mechanically and/or chemically pretreated fibres, :including waste-paper fibres, but also untreated natural fibres.
As the peroxo compound, it is possible to use hydrogen peroxide or compounds which release hydrogen peroxide, but also organic or inorganic per-acids or salts thereof, for r 000325 BL / AI.

example peracetic acid, peroxymonosralfuric acid or percarboxylic acid and salts thereof. Mixtures of different peroxo compounds can be uaed in a delignifying stage. Adaptation to special proces:~ requirements is therefore possible.
The method according to the invention can be employed in a wide consistency range (the consistency is equal to the ratio of the bone-dry (b. d) fibrous mass to the total weighty. The consistency may be betvueen 3~ and 40%, although it is advantageously a consistency of between 10~
and 15 0 .
In order to achieve an optimum delic~nifying or bleaching effect, between 0.1o and 10~, although advantageously between 0.3% and 60, of a peroxo compound should be used, in each case based on the bone-dry (b.d.) fibrous mass to be delignified.
The method according to the invention shows excellent delignifying or bleaching results when from 10 ppm to 5000 ppm, preferably from 50 ppm to 3000 ppm, advantageously from 200 ppm to 2000 ppm, and particularly preferably between 200 ppm and 1500 ppm, of the transition metal complex according to the invention are used, based on the bone-dry (b.d.) fibrous mass. The breakdown of the residual lignin takes place very efficiently vuhen the pH
at the start of the reaction is more than 10, preferably more than 11.
The reaction temperature can be selected in a wide range, according to the raw fibrous material in question. Between 20°C and 130°C, although advantageously between 40°C and 30. 110°C, most fibres can be delignified. The temperature range between 50°C and 98°C is particularly preferred, because in this case it is still pos:~ible to delignify very selectively under mild conditions, and with relatively short reaction times.

The reaction time, like the reaction temperature, can also be selected in a wide range, between 5 and 240 minutes (min). However, a reaction time of from 30 to 150 min is preferred. The delignification is particularly extensive when the reaction is employed over a time period of from 45 to 120 min. These reaction times are shorter than in the case of customary peroxide stages.
The transition metal complexes used according to the invention for delignifying and/or bleaching not only improve the effect of a simple peroxide stage, but they also increase the delignification or bleaching of an oxygen stage, which is carried out with the addition of peroxide. If bleaching is carried out with the addition of oxygen, particularly good results are achieved when an overpressure of between 0.15 MPa and 1.5 MPa is applied. A
reaction pressure of from 0.2 MPa to 0.9 MPa is preferably applied.
The complexing of transition metal ions has an advantageous effect. Diethylenetriamine pentaacetic acid (DTPA), diethylenetriamine penta(methylene phosphonic acid) (DTPMPA) or poly(oc-hydroxyacry7lic acid) , which are even stable at quite high pH values, are advantageously used. In addition, or as an alternative, water glass and/or magnesium sulfate can be used.
The method according to the invention. will be described below with some exemplary embodiments:
The studies of catalysed delignification stages with peroxide, and optionally also with oxygen-containing chemicals, were carried out using a k:raft pulp (softwood, spruce/pine, kappa number 24.0), which was previously subjected to an acid wash (1.7~ HzS04, 70°C, 3~
consistency, residence time 0.5 hours (h)) and was then characterised as follows:
kappa number: 23.5 brightness: 30.50 ISO
viscosity: 32.3 mPa*s Unless otherwise indicated, all the tests were carried out with a 10°s consistency, a reaction temperature of 80°C and a reaction time of 90 min. Data in "o" are based on the amount of bone-dry (b. d.) fibres. The analyses were carried out according to the following standards:
The kappa number was established according to Zellcheming instruction sheet IV/37/80. The viscosity of the pulp was determined according to TAPPI instruction T230 om-82. The brightness was measured with an Elre~pho 2000 (from Datacolor).
The invention will be explained by the following examples, without implying any, limitation.
Example 1 Synthesis of { [Co (N4Py) ] 202}C12 (C104) 2, referred to below as (Co-N4Py) 2 (~,~,-O2) A solution of 1.43 g (3.89 mmol) of t:he ligand N4Py in a small amount of methanol (approx. 5 ml) was added at room temperature to a solution of 925 milligrams (mg) (3.89 mmol) of CoCl2 x 6H20 and 1.09 grams I;g) (7.78 mmol) of sodium perchlorate monohydrate in 10 millilitres (ml) of water. Air in moderation was then introduced into the reaction solution over 2 h. A red-brown solid immediately precipitated. The product was filtered off and dried in air . 2 . 07 g ( 92~ ) of (Co-N4Py) 2 ( ji-O2 ) was obtained as a red-brown powder.
C46H42N10C14C02O10 ( 1154 . 6 g/moI ) Calculated C 47.85 H 3.67 N 12.13 Co 10.2 Found C 47.74 H 3.72 N 11.73 Co 9.9 Example 2 Synthesis of (Co-N4Py)2(~-Oz) by the "one-pot method"
2.5 M aqueous NaOH solution was added to a solution of 476 mg (2.00 mmol) of CoCl2 x 6H20 and 1.54 g (2.00 mmol) 5 of N4Py-4HC104 in 100 ml of methanol./water (1:1) until pH
> 7. Air in moderation was then passed through the reaction solution over 2 h. The solution was then vacuum-evaporated to half volume, the red-crystalline solid was filtered off and the latter was dried in air (820 mg, 10 72~).
Examples 3 - 16 The chemicals were added to 30 g of b.d. pulp so that an aqueous solution of the additives and the catalyst was first mixed in. The pH needed for the reaction was then 15 adjusted using NaOH. The corresponding amount of hydrogen peroxide was subsequently kneaded in and the pH was measured. The sample was then held at temperature in a polyethylene bag (PE bag) in a water bath. The results without (Comparative Example A) and with bleaching catalyst ( (Co-N4Py) 2 (~.-OZ) , (Co-MeN4Py) 2 (~,1,-O2) ; Co-N4Py(CH3CN) and Fe-MeN4Py(CH3CN)) can be found in Table 1.
Comparative Examples A - G
The chemicals were added to 30 g of x~.d. pulp so that an aqueous solution of the additives and. the catalyst was first mixed in. The pH needed for the reaction was then adjusted using NaOH. The corresponding amount of hydrogen peroxide was subsequently kneaded in and the pH was measured. The sample was then held at temperature in a PE
bag in a water bath. The results with the selected comparative catalysts (CC) can be found in Table 1.

Table 1 Example/ Catalyst Ha0= Na~H ResidualKappa ComparativeType IpPml h1 I~1 IisOs Number Example After acid wash - 23 . 5 A - 4.0 2.0 2.04 14.7 (Co-N4Py)2tw-o2~70 4.0 2.0 1.94 13. 6 4.. !Co-N4Py)zcu-o2>200 4.0 2.0 1.64 12.3 (Co-N4Py)i(EL-oz>600 4.0 2.0 1.04 10.3 (Co-N4Py?Ztw-o2~1000 4.0 2. 0.52 9.5 SCo-N4Py)z(/t-oZ>1000 4. 0 2.5 0. 07 8.4 (Co-N4Py)?c~-o2>1000 4.0 3. <0.01 8.4 (Co-N4Py)Zcu-oZ~1500 4.0 2.0 0.38 8.6 (Co-N4Py)2c~.-o2>2000 4.0 2 . 0.13 8.3 cc 1 33 4.0 2.0 1.32 14.7 C CC 2 10 0 4 . 0 2 . 0 . 31 14 . 2 cc 1 167 4.0 2.0 0 13.7 cc 2 70 4.0 2.0 0.33 10.9 cc 2 10 0 4 . 0 2 . 0 .14 9 . 9 cc 2 15 0 4 . 0 2 . 0 9 . 8 11 Co-N4Py(CHiCN)200 4.0 2.0 1.45 13.0 12 Co-N4Py(CH~CN)600 4.0 2.0 0.57 11.2 13 Fe-MeN4Py(CH3CI~)150 4.0 2.0 1.04 13.4 14 Fe-MeN4Py(CH3Ct3)300 4.0 2.0 0.44 12.5 (Co-MeN4Py)z(u-150 4.0 2.0 1.39 12.5 oz 16 ico-MeN4Py)z(u-1200 4.0 2.0 0.64 8.8 ,_ Table 1 (continued) ~~Ple~ Bright- Viscosity ,OKappa Deligaificatioa Comparative sass [mPa*s~ w.r.t. [%~
Example [% ISO] A

after acid wash 30.5 32.3 A 51.8 26.2 - 37.4 3 ~ ~ 1.1 42.1 4 ~ ~ 2.4 47.7 56.6 22 4.4 56.2 6 55.9 21.6 5.2 -59.6 7 57.4 19.5 6.3 64.3 8 56.9 19.2 6.3 64.3 55.9 20.g 6.1 63.4 54.3 19.8 6.4 64.7 B ~ ~ 0.0 37.4 C ~ 23.4 0.5 39.6 1.0 41.7 23.9 23.9 3.8 53.6 F 18.1 18.1 4.8 57.9 16.1 16.1 4.9 58.3 11 nm nm 1.7 44.7.

12 54.8 nm :3.5 -52.3 13 nm nm :L . 4 3 . 0 14 nm .~.2 46.8 nm nm .? .
2 46.8 16 nm nm _'i . 6 2 . 6 CC 1 = CoCl2 * 6H20 CC 2 = Catalyst K2 from w0 97/44520 (:Mn-TMTACN(u-Oj3j 5 nm = not measured Table 1 clearly shows that increase factors in the delignification of up to 65~ can be achieved by using the catalysts (Co-N4Py) 2 (jt.-02) and (Co-MeN4Py) z (~.-p2) , which considerably surpasses the delignif~~ing and bleaching performance of the comparative catalyst Mn-TMTACN(j,.i,-O)3 (CC 2). With the mononuclear comple~:es Co-N4Py(CH3CN) and Fe-MeN4Py(CH3CN) described in EP 0 909 809 and WO 00/12667 for the low-temperature bleaching of textile fabrics, it was likewise possible-to increase the delignifying performance by up to 52~ compared with the reference test.
In the catalytic systems according to the invention, unlike the CC Mn-TMTACN (~.t,-O) 3, increasing the amount of catalyst led to an increase in the bleaching effect and not to uncontrolled degradation of the hydrogen peroxide.
Examples l7 - 18 The ligand or its salt and the corresponding transition metal salt were dissolved in water and added to an aqueous solution of MgS04, DTPA and NaOH. This solution was kneaded into 30 g of b.d. pulp. The corresponding amount of hydrogen peroxide was subsequently mixed in and the pH
was measured. The pulp prepared in this way was then held at temperature in a PE bag in a water bath. The results without ligand addition (Comparative Example A) and with the ligand N4Py, or its salt, are li:~ted in Table 2.
Comparative Example H
A further test was conducted similarly, but the ligand, or its salt, was used alone, i.e. withou.t addition of transition metal salt. The results are also listed in Table 2.

000325 BL / per, , Table 2 ~.._ Example/ Catalyst HZOa NaOH Residual Kappa Comparative o W ~m~ [~~ t°o Example ~~ H2~2 number t%1 after acid wash -23.5 A 1147 - 4.0 2.0 2.04 14.7 17 (N4Py*4HC104)..
353 + 4.0 2.0 0.46 9.3 18 1995 (CoCl2*6H2o~
615 (N4Py*4HC104)4 2 . 0 .11 g , H 1147 + . 0 2.39 2 (CoCl2*6H20) 0 2.0 15.4 (N4Py*4HClo4)4.0 Table 2 (continued) ---Example/ Bright- Viscosity LII~;appa Delignification Comparative aess t% tmPa*s~ v~.z~.t. A
Example ISO
after acid wash 30.5 32.3 51.8 26 . 37.4 17 nm 21.5 5:4 60.4 18 nm 19.3 6 . 65.2 H ~ 27.6 -U.7 34 .

not measured

Claims (25)

1. Method for the delignification and/or bleaching of fibrous materials with a) an aqueous suspension of fibres, which have a consistency of from 3% to 40%;
b) a peroxo compound, which is used at from 0.1% to 10%, based on the bone-dry fibrous mass; and with c) a mononuclear transition metal complex of the general formula (1), [LMX p]2Y q ~~Formula (1) wherein L is a polydentate ligand of the general formula (a), (b). (c) or (d), in which R1, R2, and R3 independently of one another stand for hydrogen, a linear of branched alkyl or alkenyl residue, or an optionally substituted aryl or arylalkyl residue;
R4 independently of one another stands for an optionally N-substituted linear, branched or cyclic aminoalkyl residua, or an optionally substituted heteroaryl residue such as pyridyl, pyrazinyl, pyrazolyl, pyrrolyl, imidazolyl, pyrimidyl, triazolyl or quinolyl;
M is a transition metal ion, advantageously iron in oxidation states (II) to (V); manganese in oxidation states (II) to (VII); or cobalt in oxidation states (II) to (IV); cobalt preferably being in oxidation states (II) or (III) ;
X is a coordinate species (neutral or anionic), such as for example CH3CN, CH3COO-, Cl-, Br-, H2O, OH-, HOO-, OCN-, SCN-, PO4 3-, NH3-, NO3-, NO2-, NO, O2-, O2 2-;
Y is a counter-ion or counter-molecule, such as for example ClO4-, Br-, Cl-, PF6-, NO3-, BPh4-, SO4 2-, CH3COO or mixtures thereof;

p is an integer from 0 to 4;
z is a complex charge (+/0/-);
q is z/[charge of Y];

the transition metal complex being used in an amount of from 10 ppm to 5000 ppm, based on the amount of bone-dry (b. d.) fibres used.

2. Method according to claim 1, characterised in that the transition metal complex is used. in an amount of from 50 ppm to 3000 ppm, advantageously from 200 ppm to 2000 ppm, and particularly preferably from 200 ppm to 1500 ppm, based on the amount of bone-dry (b.d.) fibres used.

3. Method according to claim 1 or 2, characterised in that the transition metal complex of the formula (1a) is used.

4. Method according to claim 3, characterised in that the transition metal complex of the formula (1a), where M
is cobalt(II) or (III), is used.

5. Method according to claim 1 or 2, characterised in that the transition metal complex of the formula (1b) is used.

6. Method according to claim 5, characterised in that the transition metal complex of the formula (1b), where M
is cobalt(II) or (III), is used.

7. Method according to claim 1 or 2, characterised in that the transition metal complex of the formula (1d) is used.

8. Method according to claim 1 or 2, characterised in that the transition metal complex is prepared "in situ".

9. Method according to one or more of the preceding claims, characterised in that the peroxo compound is used at from 0.3 to 6%, based on the bone-dry fibrous mass.

10. Method according to one or more of the preceding claims, characterised in that the reaction temperature is between 20°C and 130°C, advantageously between 40°C and 100°C, particularly preferably between 50°C and 98°C.

11. Transition metal complex having the general formula (1b).

12. Use of the transition metal complex according to claim 11 as a bleaching catalyst in a bleaching and/or delignification method.

13. Use of a transition metal complex of the general formula (1a), (1c) and (1d) as a bleaching catalyst in a bleaching and/or delignification method.

14. Method for the delignification of fibrous materials with d) an aqueous suspension of fibres, which have a consistency of from 3% to 40%;
e) a peroxo compound, which is used at from 0.1% to 10%, based on the bone-dry fibrous mass; and with a) a mononuclear transition metal complex of the general formula (2), [L m Co n X p]z Y q; ~Formula (2) wherein L is a ligand of the general formula (a), (b), (c) or (d);
Co stands for cobalt in oxidation states (II) to (IV) or mixtures of these oxidation states, the oxidation states (II) and (III) being particularly preferred;
X, Y, z and q are as described for formula (1);
m and n are integers from 2 to 4; and p is an integer from 0 to 12;

the transition metal complex being used in an amount of from 10 ppm to 5000 ppm, based on the amount of bone-dry (b.d.) fibres used.

15. Method according to claim 14, characterised in that the transition metal complex is used in an amount of from 50 ppm to 3000 ppm, advantageously from 200 ppm to 2000 ppm, and particularly preferably from 200 ppm to 1500 ppm, based on the amount of bone-dry (b.d.) fibres used.

16. Method according to claim 14 or 15, characterised in that the transition metal complex of the formula (2a) is used.

17. Method according to claim 14 or 15, characterised in that the transition metal complex of the formula (2c) is used.

18. Method according to claim 14 or 15, characterised in that the transition metal complex is prepared "in situ".

19. Method according to one or more of the preceding claims, characterised in that the peroxo compound is used at from 0.3% to 6%, based on the bone-dry fibrous mass.

20. Method according to one or more of the preceding claims, characterised in that the reaction temperature is between 20°C and 130°C, advantageously between 40°C and 100°C, particularly preferably between 50°C and 98°C.

21. Transition metal complex having the general formula (2a), where X = O2 2-.

22. Transition metal complex having the general formula (2b) or (2c), where X = O2 2-.

23. Transition metal complex according to claims 21 or 22, characterised in that m and n = 2, and p = 1,

24. Use of the transition metal complex according to claims 21 or 22 as a bleaching catalyst in a bleaching and/or delignification method.

25. Use of a transition metal complex of the general formula (2d) as a bleaching catalyst: in a bleaching and/or delignification method.