Composition for inhibiting calcium salt scale formation

A method for inhibiting calcium salt scale formation in a chemical pulping process comprising adding an effective scale inhibiting amount of a composition to the alkaline aqueous mixture in the digester of said chemical pulping process and/or to the black liquor of a chemical pulping process, said composition consisting of at least one phosphonate component (I) selected from at least one of the compounds (i), (ii), (iii) and (iv), and at least one component (II) consisting of at least one carboxylated fructan compound, wherein compound (i) is at least one aminoalkylene phosphonic acid, or its corresponding aminoalkylene phosphonate salt, selected from compounds having the general formula (X)a[N(W)(Y)2-a]z

• wherein X is selected from C1-C200,000, linear, branched, cyclic or aromatic hydrocarbon radicals which radicals are optionally substituted by one or more or more C1-C12 linear, branched, cyclic or aromatic groups (which radicals and/or groups are) optionally substituted by OH, COOH, COOG, F, Br, Cl, I, OG, SO3H, SO3G and SG moieties;
• ZPO3M2;
• [V—N(K)]n—K;
• [V—N(Y)]n—V or [V—O]x—V;
• wherein V is a C2-50 linear, branched, cyclic or aromatic hydrocarbon radical, optionally substituted by one or more C1-12 linear, branched, cyclic or aromatic groups (which radicals and/or groups are) optionally substituted by OH, COOH, COOR′, F, Br, Cl, I, OR′, SO3H, SO3R′ or SR′ moieties, wherein R′ is a C1-12 linear, branched, cyclic or aromatic hydrocarbon radical, wherein G is selected from C1-C200,000, linear, branched, cyclic or aromatic hydrocarbon radicals, optionally substituted by one or more C1-C12 linear, branched, cyclic or aromatic groups (which radicals and/or which groups are) optionally substituted by OH, COOH, COOR′, F, Br, Cl, I, OR′, SO3H, SO3R′ and SR′ moieties;
• ZPO3M2;
• [V—N(K)]n—K;
• [V—N(Y)]n˜V or [V—O]x—V;
• wherein Y is ZPO3M2, [V—N(K)]n—K or [V—N(K)]n—V;
• and x is an integer from 1-50,000;
• z is from 0-200,000, whereby z is equal to or smaller than the number of carbon atoms in X, and a is 0 or 1;
• n is an integer from 0 to 50,000;
• z=1 when a=0;
• and X is [V—N(K)]n—K or [V—N(Y)]n—V when z=0 and a=1;
• Z is a C1-6 alkylene chain;
• M is selected from H and from alkali, earth alkali, ammonium, and protonated amine ions;
• W is selected from H, X and ZPO3M2;
• K is ZPO3M2 or H whereby K is ZPO3M2 when z=0 and a=1 or when W is H or X;
• with the proviso that the aminoalkylene phosphonic acid (and its corresponding aminoalkylene phosphonate), contains, at least, two phosphonic acid (or corresponding phosphonate) groups;
• wherein compound (II) is at least one alkylene phosphonic acid, or its corresponding alkylene phosphonate, having the formula:
• D-[C(OH)(PO3M2)2]y
• wherein D is selected from C1-100 linear, branched, cyclic or aromatic hydrocarbon chain, optionally substituted by a C1-12 linear, branched, cyclic or aromatic group (which chain and/or which group can be) optionally substituted by SO3H, SO3J, COOJ, OJ and SJ moieties;
• or [V—O]x—V wherein V is a C2-C50 linear, branched, cyclic or aromatic hydrocarbon radical, optionally substituted by one or more C1-C12 linear, branched, cyclic or aromatic groups (which radicals and/or groups are) optionally substituted by SO3H, SO3R′, COOR′, OR′ or SR′ moieties wherein J is selected from C1-C100 linear, branched, cyclic or aromatic hydrocarbon radicals, optionally substituted by one or more C1-C12 linear, branched, cyclic or aromatic groups (which radicals and/or groups can be) optionally substituted by SO3H, SO3R′, COOR′, OR′ or SR′ wherein R′ is a C1-12 linear, branched, cyclic or aromatic hydrocarbon chain and x is an integer from 1-50,000;
• y is an integer from 1-50 whereby y is equal or smaller then the number of carbon atoms in D;
• and M is selected from H and from alkali, earth alkali, ammonium ions, and protonated amine ions,
• wherein compound (iii) is selected from at least one phosphono-alkane-polycarboxylic acids and its corresponding salts based on alkali, earth alkali, ammonium, and protonated amine ions, wherein the alkane moiety is a C3-20 linear, branched, cyclic or aromatic hydrocarbon chain and wherein the molar ratio of phosphonic acid radical to carboxylic acid radical is in the range of from 2:3 to 1:7,
• wherein compound (iv) is selected from at least one linear or branched hydrocarbon chains having from 6 to 2,000,000 carbon atoms containing amino groups substituted by ZPO3M2, and/or -E-N(W)(Y), with respect to the hydrocarbon chain, in either terminal or branched positions whereby the molar ratio of the aminoalkylene phosphonic acid substituents to the number of carbon atoms in the hydrocarbon chain is in the range of from 2:1 to 1:40 whereby at least 30% of the available NH/NH2 functionalities have been converted into the corresponding aminoalkylene phosphonic acid and/or into -E-N(W)(Y) substituted groups and wherein the alkylene moiety is selected from C1-6;
• wherein E is selected from C1-C2,000 linear, branched, cyclic or aromatic hydrocarbon radicals, optionally substituted by one or more C1-C12 linear, branched, cyclic or aromatic groups (which radicals and/or which groups can be) optionally substituted by OH, COOH, COOL, F, Br, Cl, I, OL, SO3H, SO3L and SL moieties;
• [V—N(Y)]n—V or [V—O]x—V wherein V is a C2-50 linear, branched, cyclic or aromatic hydrocarbon radical, optionally substituted by one or more C1-12 linear, branched, cyclic or aromatic groups (which radicals and/or groups are) optionally substituted by OH, COOH, COOR′, F, Br, Cl, I, OR′, SO3H, SO3R′ or SR′ moieties wherein R′ is a C1-12 linear, branched, cyclic or aromatic hydrocarbon radical;
• wherein L is selected from C1-C2,000 linear, branched, cyclic or aromatic hydrocarbon radicals, optionally substituted by one or more C1-C12 linear, branched, cyclic or aromatic groups (which radicals and/or which groups can be) optionally substituted by OH, COOH, COOR′, F, Br, Cl, I, OR′, SO3H, SO3R′ and SR′ moieties;
• ZPO3M2;
• [V—N(K)]n—K;
• [V—N(Y)]n—V or [V—O]x—V;
• wherein Y is ZPO3M2, [V—N(K)]n—K or [V—N(K)]n—V;
• and x is an integer from 1-50,000;
• n is an integer from 0 to 50,000;
• M is selected from H and from alkali, earth alkali, ammonium and protonated amine ions;
• W is selected from H, E and ZPO3M2;
• K is ZPO3M2 or H whereby K is ZPO3M2 when W is H or E;
• with the proviso that the aminoalkylene phosphonic acid (and its corresponding aminoalkylene phosphonate) contains, at least, two phosphonic acid aminoalkylene phosphonic groups (or corresponding aminoalkylene phosphonate groups),
• wherein the further component (II) consists of a carboxylated fructan component and is selected from the group of (a) carboxyalkylfructan having from 1 to 4 carbon atoms in the alkyl moiety, (b) dicarboxyfructan having a degree of oxidation (DO) of from 10 to 100% expressed as a molar percentage of monosaccharide units converted into the corresponding dicarboxy analogues, (c) 6-carboxyfructan, and/or (d) fructan polycarboxylic acid, having a degree of carboxyalkylation or carboxyacylation of from 0.2 to 3.0, or (e) mixtures thereof,
• wherein the weight ratio of the first component(s) (I) to the second component(s) (II) in the composition to be added to the alkaline aqueous mixture in the digester of said chemical pulping process or to the black liquor of a chemical pulping process is in the range of from 20:1 to 1:6.