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

Abstract

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. 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.

We claim:  
     
         1 . A method for the delignification and/or bleaching of fibrous materials compromising contacting 
 a) an aqueous suspension of fibers, which have a consistency of from 3% to 40%; with    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 formula (1),    (LMX p ) z Y q   Formula (1)    wherein 
 L is a polydentate ligand of the formula (a), (b), (c) or (d),  
                     
   in which 
 R1, R2, and R3 independently of one another represent hydrogen, linear of branched alkyl or alkenyl, or an optionally substituted aryl or arylalkyl;  
 R4 independently of one another represents an optionally N-substituted linear, branched or cyclic aminoalkyl, or an optionally substituted heteroaryl;  
 M is a transition metal ion, selected from the group consisting of iron in oxidation states (II) to (V); manganese in oxidation states (II) to (VII); and cobalt in oxidation states (II) to (IV);  
 X is a coordinate species which can be neutral or anionic;  
 Y is a counter-ion or counter-molecule.  
 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 present in an amount of from 10 ppm to 5000 ppm, based on the amount of bone-dry fibers.  
   
     
     
         2 . The method according to  claim 1  wherein R4 is: 
 pyridyl, pyrazinyl, pyrazolyl, pyrrolyl, imidazolyl, pyrimidyl, triazolyl or quinolyl.  
 
     
     
         3 . The method according to  claim 1  wherein X is: 
 CH 3 CN, CH 3 COO − , Cl − , Br − , H 2 O, OH − , HOO − , OCN − , SCN − , PO 4   3− , NH 3 , NO 3   − , NO 2   − , NO, O 2− , O 2   2− .  
 
     
     
         4 . The method according  claim 1  wherein Y is: 
 ClO4-, Br-, Cl-, PF 6   − , NO 3   − , BPh 4   − , SO 4   2− , CH 3 COO − .  
 
     
     
         5 . The method according to  claim 1 , wherein the transition metal complex is present in an amount of from 50 ppm to 3000 ppm, based on the amount of bone-dry (b.d.) fibers used.  
     
     
         6 . The method according to  claim 5 , wherein the amount is from 200 ppm to 2000 ppm.  
     
     
         7 . The method according to  claim 5  wherein the amount is from 200 ppm to 1500 ppm.  
     
     
         8 . The method according to  claim 1 , wherein the transition metal complex is formula (1a).  
     
     
         9 . The method according to  claim 5 , wherein the transition metal complex is formula (1a).  
     
     
         10 . The method according to  claim 8 , where M in the transition metal complex of the formula (a), is cobalt(II) or (III).  
     
     
         11 . The method according to  claim 9 , where M in the transition metal complex of the formula (a), is cobalt(II) or (III).  
     
     
         12 . The method according to  claim 1 , wherein the transition metal complex is formula (1b).  
     
     
         13 . The method according to  claim 5 , wherein the transition metal complex is formula (1b).  
     
     
         14 . The method according to  claim 12 , where M in the transition metal complex of the formula (1b) is cobalt(II) or (III).  
     
     
         15 . The method according to  claim 13 , where M in the transition metal complex of the formula (1b) is cobalt(II) or (III).  
     
     
         16 . The method according to  claim 1 , wherein the transition metal complex is formula (1d).  
     
     
         17 . The method according to  claim 5 , wherein the transition metal complex is formula (1d).  
     
     
         18 . The method according to  claim 1 , further comprising preparing the transition metal complex “in situ”.  
     
     
         19 . The method according to  claim 5 , further comprising preparing the transition metal complex “in situ”.  
     
     
         20 . The method according to  claim 1 , further comprising the peroxo compound being present in an amount from 0.3 to 6%, based on the bone-dry fibrous mass.  
     
     
         21 . The method according to  claim 1 , further comprising contacting at a reaction temperature of 20° C. to 130° C.  
     
     
         22 . The method according to  claim 21 , where the temperature of 40° C. and 100° C.  
     
     
         23 . The method according to  claim 21 , where the temperature of 50° C. and 98° C.  
     
     
         24 . Transition metal complex having the formula (1b), namely  
       (LMX p ) z Y q   Formula (1)  
       wherein 
 L is a polydentate ligand of the formula,  
                     
 
     
     
         25 . A method for the delignification of fibrous materials comprising contacting 
 a) an aqueous suspension of fibers, which have a consistency of from 3% to 40%; with    b) a peroxo compound, which is used at from 0.1% to 10%, based on the bone-dry fibrous mass; and with    c) as a bleaching catalyst a mononuclear transition metal complex of the general formula (2),    (LMX p ) z Y q ;  Formula (1)    wherein 
 L is a polydentate ligand of the formula,  
                     
   in which 
 R1, R2, and R3 independently of one another represent hydrogen, a linear of branched alkyl or alkenyl, or an optionally substituted aryl or arylalkyl;  
 R4 independently of one another represents an optionally N-substituted linear, branched or cyclic aminoalkyl, or an optionally substituted heteroaryl;  
 M is a transition metal ion, selected from the group consisting of iron in oxidation states (II) to (V); manganese in oxidation states (II) to (VII); or cobalt in oxidation states (II) to (IV);  
 X is a coordinate species which can be (neutral or anionic),  
 Y is a counter-ion or counter-molecule;  
 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 fibers.  
   
     
     
         26 . A method for the delignification of fibrous materials with comprising treating 
 d) an aqueous suspension of fibers, which have a consistency of from 3% to 40%; with    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 formula (2),    (L m Co n X p ) z Y q ;  Formula (2)    wherein 
 L is a ligand of the 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 present used in an amount of from 10 ppm to 5000 ppm, based on the amount of bone-dry fibers used.  
   
     
     
         27 . The method according to  claim 26 , wherein the transition metal complex is present in an amount of from 50 ppm to 3000 ppm based on the amount of bone-dry (b.d.) fibers used.  
     
     
         28 . The method according to  claim 27  where the amount is 200 ppm to 2000 ppm.  
     
     
         29 . The method according to  claim 27  where the amount is 200 ppm to 1500 ppm.  
     
     
         30 . The method according to  claim 26 , wherein the transition metal is formula (2a)  
     
     
         31 . The method according to  claim 27 , wherein the transition metal is formula (2a).  
     
     
         32 . The method according to  claim 26 , wherein the transition metal complex is formula (2c).  
     
     
         33 . The method according to  claim 27 , wherein the transition metal complex is formula (2c).  
     
     
         34 . The method according to  claim 26 , further compromising preparing the transition metal complex “in situ”.  
     
     
         35 . The method according to  claim 27 , further compromising preparing the transition metal complex “in situ”.  
     
     
         36 . The method according to  claim 26 , wherein the peroxo compound is present from 0.3% to 6%, based on the bone-dry fibrous mass.  
     
     
         37 . The method according to  claim 26 , wherein the reaction temperature is between 20° C. to 130° C.  
     
     
         38 . Transition metal complex having the formula (2a), where X=O 2   2− .  
     
     
         39 . Transition metal complex having the formula (2b) or (2c), where X=O 2   2− .  
     
     
         40 . Transition metal complex according to  claim 38 , where m and n=2, and p=1.  
     
     
         41 . Transition metal complex according to  claim 39 , where m and n=2, and p=1.  
     
     
         42 . A method for the delignification of fibrous materials with comprising contacting 
 d) aqueous suspension of fibers, which have a consistency of from 3% to 40%; with    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 formula (2),    (L m Co n X p ) z Y q ;  Formula (2)    wherein 
 L is a ligand of the formula (a),  
 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;  
 Y, z and q are as described for formula (1);  
 m and n are integers from 2 to 4; and  
 X in O 2   2− , and  
 p is an integer from 0 to 12;  
 the transition metal complex being present used in an amount of from 10 ppm to 5000 ppm, based on the amount of bone-dry fibers used.  
   
     
     
         43 . A method for the delignification of fibrous materials with comprising contacting 
 d) aqueous suspension of fibers, which have a consistency of from 3% to 40%; with    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 formula (2),    (L m Co n X p ) z Y q ;  Formula (2)    wherein 
 L is a ligand of the formula (b) or (c);  
 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;  
 Y, z and q are as described for formula (1);  
 m and n are integers from 2 to 4; and  
 X in O 2   2− , and  
 p is an integer from 0 to 12;  
 the transition metal complex being present used in an amount of from 10 ppm to 5000 ppm, based on the amount of bone-dry fibers used.  
   
     
     
         44 . A method for the delignification of fibrous materials with comprising contacting 
 d) aqueous suspension of fibers, which have a consistency of from 3% to 40%; with    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 formula (2),    (L m Co n X p ) z Y q ;  Formula (2)    wherein 
 L is a ligand of the formula (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;  
 Y, z and q are as described for formula (1);  
 m and n are integers from 2 to 4; and  
 X in O 2   2− , and  
 p is an integer from 0 to 12;  
 the transition metal complex being present used in an amount of from 10 ppm to 5000 ppm, based on the amount of bone-dry fibers used.