Method of whitening lignin-containing paper pulps

• US 5,902,454 A
• Filed: 12/13/1996
• Issued: 05/11/1999
• Est. Priority Date: 12/13/1996
• Status: Expired due to Term

• Current Assignee: CIBA Vision Corporation (Bayer AG)
• Original Assignee: CIBA Specialty Chemicals
• Inventors: Nelson, Randall B.
• Primary Examiner(s): Silverman, Stanley S.
• Assistant Examiner(s): Fortuna, Jose A.
• Application Number:
  US08/766,909
• Time in Patent Office: 879 Days
• Field of Search: 162/72, 162/73, 162/74, 162/75, 162/76, 162/160, 162/158, 162/162, 162/183, 8/648, 8/919, 252/301.21
• US Class Current: 162/158
• CPC Class Codes: D21H 17/14 Carboxylic acids; Derivatives thereof
• CPC Class Codes: D21H 21/30 Luminescent or fluorescent substances, e.g. for optical bleaching D21H21/40 takes precedence
• CPC Class Codes: D21H 21/32 Bleaching agents bleaching cellulose pulp D21C9/10
• CPC Class Codes: Y10S 8/919 Paper

Abstract

A process to increase the whiteness of paper made from a lignin-containing pulp is disclosed which comprises adding to an aqueous slurry comprising a lignin-containing pulp, in the paper making step, an effective amount of a chelating agent to decrease the content of salts of iron and other heavy metals to 100 ppm or less by weight, based on the dry weight of the pulp, or adding to said aqueous slurry an effective amount of a fluorescent whitening agent, or both a) and b).

Claims

1. A process to increase the whiteness of paper made from a pulp which contains 5% or more of lignin on a dry basis which comprises:

a) adding to an aqueous slurry comprising said lignin-containing pulp, in a paper making step, an effective amount of a chelating agent to decrease the content of salts of iron and other heavy metals to 100 ppm or less by weight, based on the dry weight of the pulp, or

b) adding to said aqueous slurry an effective whitening amount of a fluorescent whitening agent, or both a) and b).

2. A process according to claim 1, wherein both a chelating agent and a fluorescent whitening agent are added to the pulp.

3. A process according to claim 1, wherein the pulp contains 10% or more of lignin on a dry basis.

4. A process according to claim 1, wherein a chelating agent is present which is selected from those that effect thermodynamic control of metal ions.

5. A process according to claim 4, wherein the chelating agent is selected from the group consisting of ethylenediaminetetraacetic acid, diethylene triaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid and nitrilotriacetic acid.

6. A process according to claim 4, wherein the chelating agent comprises a mixture of thermodynamic and kinetic controlling chelating agents.

7. A process according to claim 1, wherein, in the paper making step, the aqueous slurry comprising a lignin-containing pulp contains 25 to 500 ppm by weight, based on the dry weight of the pulp, of salts of iron and other heavy metals.

8. A process according to claim 7, wherein the aqueous slurry contains 100 to 400 ppm by weight, based on the dry weight of the pulp, of salts of iron and other heavy metals.

9. A process according to claim 1, which comprises adding to the aqueous slurry comprising a lignin-containing pulp, in the paper making step, from 0.01 up to about 1% by weight, based on the dry weight of the pulp, of a chelating agent.

10. A process according to claim 1, wherein the fluorescent whitening agent contains 2 to 6 sulfonic acid groups.

11. A process according to claim 10, wherein the fluorescent whitening agent contains 2 sulfonic acid groups.

12. A process according to claim 1, wherein the fluorescent whitening agent comprises a mixture of a fluorescent whitening agent which contains 2 sulfonic acid groups and a fluorescent whitening agent which contains 4 or 6 sulfonic acid groups.

13. A process according to claim 12, wherein the fluorescent whitening agent comprises a mixture of the compounds of the formulae ##STR30##

14. A process according to claim 1, wherein from 0.01 up to about 2% by weight, based on the dry weight of the pulp, of fluorescent whitening agent is employed.

15. A process according to claim 1, wherein a fluorescent whitening agent and a fluorescent whitening agent enhancer are added.

16. A process according to claim 15, wherein the additive is cationic starch, polyvinyl alcohol or an enzyme.

17. A process according to claim 1, wherein the fluorescent whitening agent is selected from the group consisting of 4,4'"'"'-bis-(triazinylamino)-stilbene-2,2'"'"'-disulfonic acids, 4,4'"'"'-bis-(triazol-2-yl)stilbene-2,2'"'"'-disulfonic acids, 4,4'"'"'-dibenzofuranyl-biphenyls, 4,4'"'"'-(diphenyl)-stilbenes, 4,4'"'"'-distyryl-biphenyls, 4-phenyl-4'"'"'-benzoxazolyl-stilbenes, stilbenyl-naphtho triazoles, 4-styryl-stilbenes, bis-(benzoxazol-2-yl) derivatives, bis-(benzimidazol-2-yl) derivatives, coumarins, pyrazolines, naphthalimides, triazinyl-pyrenes, 2-styryl-benzoxazole or -naphthoxazoles, benzimidazole-benzofurans and oxanilides.

18. A process according to claim 17, wherein the 4,4'"'"'-bis-(triazinylamino)-stilbene-2,2'"'"'-disulfonic acid fluorescent whitening agent is of the formula:

in which R₁ and R₂, independently, are phenyl, mono- or disulfonated phenyl, phenylamino, mono- or disulfonated phenylamino, morpholino, --N(CH₂ CH₂ OH)₂, --N(CH₃)(CH₂ CH₂ OH), --NH₂, --N(C₁ -C₄ alkyl)₂, --OCH₃, --Cl, --NH--CH₂ CH₂ SO₃ H, CH₂ CH₂ OH or ethanolaminopropionic acid amide; and

M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetra-substituted by C₁ -C₄ alkyl, C₁ -C₄ hydroxyalkyl or a mixture thereof.

19. A process according to claim 18, wherein the fluorescent whitening agent is of the formula (1) in which each R₁ is 2,5-disulfophenyl and each R₂ is morpholino, --N(C₂ H₅)₂, --N(CH₂ CH₂ OH)₂ or ethanolaminopropionic acid amide;

or each R₁ is 3-sulfophenyl and each R₂ is NH(CH₂ CH₂ OH) or N(CH₂ CH₂ OH)₂ ;

or each R₁ is 4-sulfophenyl and each R₂ is N(CH₂ CH₂ OH)₂, N(CH₂ CHOHCH₃)₂, morpholino, or ethanolaminopropionic acid amide;

or each R₁ is phenylamino and each R₂ is morpholino, NH(CH₂ CH₂ OH), N(CH₂ CH₂ OH)CH₃, N(CH₂ CH₂ OH)₂ or ethanolaminopropionic acid amide, and, in each case, the sulfo group is SO₃ M in which M is sodium.

20. A process according to claim 19, wherein the fluorescent whitening agent is of the formula ##STR31##

21. A process according to claim 17, wherein the 4,4'"'"'-bis-(triazol-2-yl)stilbene-2,2'"'"'-disulfonic acid fluorescent whitening agent is of the formula:

in which R₃ and R₄, independently, are H, C₁ -C₄ alkyl, phenyl or monosulfonated phenyl; and

M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetra-substituted by C₁ -C₄ alkyl, C₁ -C₄ -hydroxyalkyl or a mixture thereof.

22. A process according to claim 21, wherein the fluorescent whitening agent is of the formula (2) in which R₃ is phenyl, R₄ is H and M is sodium.

23. A process according to claim 17, wherein the 4,4'"'"'-dibenzofuranyl-biphenyl fluorescent whitening agent is of the formula:

##STR32## in which R_a and R_b, independently, are H or C₁ -C₄ alkyl, and M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetra-substituted by C₁ -C₄ alkyl, C₁ -C₄ -hydroxyalkyl or a mixture thereof.

24. A process according to claim 23, wherein the fluorescent whitening agent is the compound of the formula ##STR33##

25. A process according to claim 17, wherein the 4,4'"'"'-distyryl-biphenyl fluorescent whitening agent is of the formula:

in which R₅ and R₆, independently, are H, SO₃ M, SO₂ N(C₁ -C₄ alkyl)₂, O--(C₁ -C₄ alkyl), CN, Cl, COO(C₁ -C₄ alkyl), CON(C₁ -C₄ alkyl)₂ or O(CH₂)₃ N.sup.⊕

(CH₃)₂ An^-, in which M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetra-substituted by C₁ -C₄ alkyl, C₁ -C₄ -hydroxyalkyl or a mixture thereof, An^- is an anion of an organic or inorganic acid or a mixture thereof, and n is 1.

26. A process according to claim 25, wherein the fluorescent whitening agent is of the formula (4) in which each R₆ is H and each R₅ is a 2-SO₃ M group in which M is sodium or each R₅ is O(CH₂)₃ N.sup.⊕

(CH₃)₂ An^-, in which An^- is acetate.

27. A process according to claim 17, wherein the fluorescent whitening agent is a 4-phenyl-4'"'"'-benzoxazolyl-stilbene of the formula:

##STR34## in which R₇ and R₈, independently, are H, Cl, C₁ -C₄ alkyl or SO₂ --C₁ -C₄ alkyl or is a stilbenyl-naphthotriazole of the formula;

##STR35## in which R₉ is H or Cl;

R₁₀ is SO₃ M, SO₂ N(C₁ -C₄ alkyl)₂, SO₂ O-phenyl or CN;

R₁₁ is H or SO₃ M; and

M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetra-substituted by C₁ -C₄ alkyl, C₁ -C₄ hydroxyalkyl or a mixture thereof.

28. A process according to claim 17, wherein the fluorescent whitening agent is a 4-styryl-stilbene of the formula:

##STR36## in which R₁₂ and R₁₃, independently, are H, SO₃ M, SO₂ N(C₁ -C₄ alkyl)₂, O--(C₁ -C₄ alkyl), CN, Cl, COO(C₁ -C₄ alkyl), CON(C₁ -C₄ alkyl)₂ or O(CH₂)₃ N.sup.⊕

(CH₃)₂ An^- in which An^- is an anion of an organic or inorganic acid or a mixture thereof and M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetra-substituted by C₁ -C₄ alkyl, C₁ -C₄ hydroxyalkyl or a mixture thereof.

29. A process according to claim 28, wherein the fluorescent whitening agent is of the formula (7) in which each of R₁₂ and R₁₃ is 2-cyano or 2-SO₃ M in which M is sodium or O(CH₂)₃ N.sup.⊕

(CH₃)₂ An^- in which An^- is acetate.

30. A process according to claim 17, wherein the fluorescent whitening agent is a bis-(benzoxazol-2-yl) derivative of the formula:

##STR37## in which R₁₄, independently, is H, C(CH₃)₃, C(CH₃)₂ -phenyl, C₁ -C₄ alkyl or COO--C₁ -C₄ alkyl, and X is --CH═

CH-- or a group of the formula;

##STR38##

31. A process according to claim 17, wherein the fluorescent whitening agent is a bis-(benzimidazol-2-yl) derivative of the formula:

in which R₁₅ and R₁₆, independently, are H, C₁ -C₄ alkyl or CH₂ CH₂ OH;

R₁₇ is H or SO₃ M;

X₁ is --CH═

CH-- or a group of the formula;

##STR39## and M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetra-substituted by C₁ -C₄ alkyl, C₁ -C₄ -hydroxyalkyl or a mixture thereof.

32. A process according to claim 17, wherein the fluorescent whitening agent is a coumarin of the formula:

##STR40## in which R₁₈ is H, Cl or CH₂ COOH, R₁₉ is H, phenyl, COO--C₁ -C₄ alkyl or a group of the formula;

##STR41## and R₂₀ is O--C₁ -C₄ alkyl, N(C₁ -C₄ alkyl)₂, NH--CO--C₁ -C₄ alkyl or a group of the formula;

##STR42## in which R₁ and R₂, independently, are phenyl, mono- or disulfonated phenyl, phenylamino, mono- or disulfonated phenylamino, morpholino, --N(CH₂ CH₂ OH)₂, --N(CH₃)(CH₂ CH₂ OH), --NH₂, --N(C₁ -C₄ alkyl)₂, --OCH₃, --Cl, --NH--CH₂ CH₂ SO₃ H or --NH--CH₂ CH₂ OH, R₃ and R₄, independently, are H, C₁ -C₄ alkyl, phenyl or monosulfonated phenyl and R₂₁ is H, C₁ -C₄ alkyl or phenyl.

33. A process according to claim 17, wherein the fluorescent whitening agent is a pyrazoline of the formula:

##STR43## in which R₂₂ is H, Cl or N(C₁ -C₄ alkyl)₂, R₂₃ is H, Cl, SO₃ M, SO₂ NH₂, SO₂ NH--(C₁ -C₄ alkyl), COO--C₁ -C₄ alkyl, SO₂ --C₁ -C₄ alkyl, SO₂ NHCH₂ CH₂ CH₂ N.sup.⊕

(CH₃)₃ or SO₂ CH₂ CH₂ N.sup.⊕

H(C₁ -C₄ alkyl)₂ An^-, R₂₄ and R₂₅ are the same or different and each is H, C₁ -C₄ alkyl or phenyl, R₂₆ is H or Cl, An^- is an anion of an organic or inorganic acid, and M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetra-substituted by C₁ -C₄ alkyl, C₁ -C₄ hydroxyalkyl or a mixture thereof.

34. A process according to claim 17, wherein the fluorescent whitening agent is a naphthalimide of the formula:

##STR44## in which R₂₇ is C₁ -C₄ alkyl or CH₂ CH₂ CH₂ N.sup.⊕

(CH₃)₃ An^- in which An^- is an anion of an organic or inorganic acid, R₂₈ and R₂₉, independently, are O--C₁ -C₄ -alkyl, SO₃ M or NH--CO--C₁ -C₄ alkyl; and

M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetra-substituted by C₁ -C₄ alkyl, C₁ -C₄ hydroxyalkyl or a mixture thereof.

35. A process according to claim 17, wherein the fluorescent whitening agent is a 2-styryl-benzoxazole- or -naphthoxazole derivative having the formula:

##STR45## in which R₃₁ is CN, Cl, COO--C₁ -C₄ alkyl or phenyl;

R₃₂ and R₃₃ are the atoms required to form a fused benzene ring or R₃₃ and R₃₅, independently, are H or C₁ -C₄ alkyl; and

R₃₄ is H, C₁ -C₄ alkyl or phenyl.

36. A process according to claim 17, wherein the fluorescent whitening agent is a benzimidazole-benzofuran derivative having the formula:

##STR46## in which R₃₆ is C₁ -C₄ alkoxy;

R₃₇ and R₃₈, independently, are C₁ -C₄ alkyl; and

An^- is an anion of an organic or inorganic acid.

37. A process according to claim 10, wherein the fluorescent whitening agent is an oxanilide derivative having the formula:

##STR47## in which R₃₉ is C₁ -C₄ alkoxy, R₄₁ is C₁ -C₄ alkyl, C₁ -C₄ alkyl-SO₃ M or C₁ -C₄ alkoxy-SO₃ M in which M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetra-substituted by C₁ -C₄ alkyl, C₁ -C₄ hydroxyalkyl or a mixture thereof, preferably Na, Li or K, and R₄₀ and R₄₂ are