Optical brightening compositions

Abstract

The instant invention relates to mixed salts of optical brighteners of formula (1), ##STR00001##
wherein M represents a mixture of Mg.sup.2+ with another cation, which provide for superior optical brightening effects when applied to the surface of paper.

Claims

1. A compound of formula (1), ##STR00009## wherein R.sub.1 is hydrogen or SO.sub.3.sup., R.sub.2 is hydrogen or SO.sub.3.sup., R.sub.3 is hydrogen, C.sub.1-4 alkyl, C.sub.2-3 hydroxyalkyl, CH.sub.2CO.sub.2.sup., CH.sub.2CH.sub.2CONH.sub.2 or CH.sub.2CH.sub.2CN, R.sub.4 is C.sub.1-4 alkyl, C.sub.2-3 hydroxyalkyl, CH.sub.2CO.sub.2.sup., CH(CO.sub.2.sup.)CH.sub.2CO.sub.2.sup. or CH(CO.sub.2.sup.)CH.sub.2CH.sub.2CO.sub.2.sup., benzyl, or R.sub.3 and R.sub.4 together with the neighboring nitrogen atom signify a morpholine ring, .[.and.]. wherein M is the required stoichiometric cationic equivalent for balancing the anionic charge in formula (1) and is a combination of Mg.sup.2+ together with at least 1 further cation selected from the group consisting of H.sup.+, alkali metal cation, alkaline earth metal cation other than Mg.sup.2+, ammonium, mono-C.sub.1-C.sub.4-alkyl-di-C.sub.2-C.sub.3-hydroxyalkyl ammonium, di-C.sub.1-C.sub.4-alkyl-mono-C.sub.2-C.sub.3-hydroxyalkyl ammonium, ammonium which is mono-, di- or trisubstituted by a C.sub.2-C.sub.3 hydroxyalkyl radical and mixtures thereof.Iadd., and wherein the molar ratio of the Mg.sup.2+ to the further cation in M is between 50:50 and 99.99:0.01.Iaddend..

2. The compound of formula (1) as claimed in claim 1, wherein R.sub.3 is hydrogen, methyl, ethyl, n-propyl, iso-propyl, -hydroxyethyl, -hydroxypropyl, CH.sub.2CO.sub.2.sup., CH.sub.2CH.sub.2CONH.sub.2 or CH.sub.2CH.sub.2CN; R.sub.4 is methyl, ethyl, n-propyl, isopropyl, 2-butyl, -hydroxyethyl, -hydroxypropyl, CH.sub.2CO.sub.2.sup., CH(CO.sub.2.sup.)CH.sub.2CO.sub.2.sup., CH(CO.sub.2.sup.)CH.sub.2CH.sub.2CO.sub.2.sup., or benzyl.

3. The compound as claimed in claim 1, wherein M is the required stoichiometric cationic equivalent for balancing the anionic charge in formula (1) and is a combination of Mg.sup.2+ together with 1, 2, 3, 4, 5 or 6 further cations.

4. A compound as claimed in claim 1, wherein M is the required stoichiometric cationic equivalent for balancing the anionic charge in formula (1) and is a combination of Mg.sup.2+ together with 1, 2 or 3 further cations.

5. A compound as claimed in claim 1, wherein M is the required stoichiometric cationic equivalent for balancing the anionic charge in formula (1) and is a combination of Mg.sup.2+ together with 1 or 2 further cations.

6. A compound as claimed in claim 1, wherein the ratio of M to the rest of formula (1) is between 6.25:12.5 and 50:2.

7. A compound as claimed in claim 1, wherein the ratio of M to the rest of formula (1) is between 8:12.5 and 8:2.5.

8. The compound of formula (1) as claimed in claim 1, wherein R.sub.1 is hydrogen or SO.sub.3.sup., R.sub.2 is hydrogen or SO.sub.3.sup., R.sub.3 is hydrogen, CH.sub.2CO.sub.2.sup., CH.sub.2CH.sub.2CONH.sub.2 or CH.sub.2CH.sub.2CN, R.sub.4 is C.sub.2-3 hydroxyalkyl, CH.sub.2CO.sub.2.sup., CH(CO.sub.2)CH.sub.2CO.sub.2.sup. or CH(CO.sub.2.sup.)CH.sub.2CH.sub.2CO.sub.2.sup., excepting that R.sub.4 cannot be C.sub.2-3 hydroxyalkyl if R.sub.3 is hydrogen, or R.sub.3 and R.sub.4 together with the neighboring nitrogen atom signify a morpholine ring, and wherein M is the required stoichiometric cationic equivalent for balancing the anionic charge in formula (1) and is a combination of Mg.sup.2+ together with at least 1 further cation selected from the group consisting of H.sup.+, alkali metal cation, alkaline earth metal cation other than Mg.sup.2+, ammonium, mono-C.sub.1-C.sub.4-alkyl-di-C.sub.2-C.sub.3-hydroxyalkyl ammonium, di-C.sub.1-C.sub.4-alkyl-mono-C.sub.2-C.sub.3-hydroxyalkyl ammonium, ammonium which is mono-, di- or trisubstituted by a C.sub.2-C.sub.3 hydroxyalkyl radical and mixtures thereof.

9. The compound of formula (1) as claimed in claim 1, wherein R.sub.3 is hydrogen, CH.sub.2CO.sub.2.sup., CH.sub.2CH.sub.2CONH.sub.2 or CH.sub.2CH.sub.2CN; R.sub.4 is -hydroxyethyl, -hydroxypropyl, CH.sub.2CO.sub.2.sup., CH(CO.sub.2.sup.)CH.sub.2CO.sub.2.sup., or CH(CO.sub.2.sup.)CH.sub.2CH.sub.2CO.sub.2.sup., excepting that R.sub.4 cannot be C.sub.2-3 hydroxyalkyl if R.sub.3 is hydrogen.

.[.10. The compound of formula (I) as claimed in claim 1, wherein the molar ratio of Mg.sup.2+ to the at least one further cation in M is between 20:80 and 99.99:0.01..].

11. The compound of formula (I) as claimed in claim 1, wherein the at least one further cation in M is selected from the group consisting of H.sup.+, Li.sup.+, Na.sup.+, K.sup.+, Ca.sup.2+, N-methyl-N,N-diethanolammonium, N,N-dimethyl-N-ethanolammonium, triethanolammonium, tri-isopropanolammonium, and mixtures thereof.

12. The compound of formula (I) as claimed in claim 1, wherein the at least one further cation comprises Na.sup.+.

13. A sizing composition comprising a compound as claimed in claim 1.

14. Brightened paper brightened by a sizing composition, wherein the sizing composition comprises the compound of formula (1) as defined in claim 1.

15. A process for optical brightening of paper comprising the steps of a) applying a sizing composition comprising the compound of formula (1) as defined in claim 1 to the paper to form treated paper, b) drying the treated paper.

16. A process for the preparation of a compound of formula (1) ##STR00010## wherein R.sub.1 is hydrogen or SO.sub.3.sup., R.sub.2 is hydrogen or SO.sub.3.sup., R.sub.3 is hydrogen, C.sub.1-4 alkyl, C.sub.2-3 hydroxyalkyl, CH.sub.2CO.sub.2.sup., CH.sub.2CH.sub.2CONH.sub.2 or CH.sub.2CH.sub.2CN, R.sub.4 is C.sub.1-4 alkyl, C.sub.2-3 hydroxyalkyl, CH.sub.2CO.sub.2.sup., CH(CO.sub.2.sup.)CH.sub.2CO.sub.2.sup. or CH(CO.sub.2.sup.)CH.sub.2CH.sub.2, CO.sub.2.sup., benzyl, or R.sub.3 and R.sub.4 together with the neighboring nitrogen atom signify a morpholine ring, and wherein M is the required stoichiometric cationic equivalent for balancing the anionic charge in formula (1) and is a combination of Mg.sup.2+ together with at least 1 further cation selected from the group consisting of H.sup.+, alkali metal cation, alkaline earth metal cation other than Mg.sup.2+, ammonium, mono-C.sub.1-C.sub.4-alkyl-di-C.sub.2-C.sub.3-hydroxyalkyl ammonium, di-C.sub.1-C.sub.4-alkyl-mono-C.sub.2-C.sub.3-hydroxyalkyl ammonium, ammonium which is mono-, di- or trisubstituted by a C.sub.2-C.sub.3 hydroxyalkyl radical and mixtures thereof, comprising the steps of having a reaction A, followed by a reaction B, followed by a reaction C, wherein in reaction A a compound of formula (10) is reacted with a compound of formula (II) to form a compound of formula (12); ##STR00011## in reaction B a compound of formula (12) is reacted with a compound of formula (13) to form a compound of formula (14); ##STR00012## and in reaction C the compound of formula (14) is reacted with a compound of formula (15) to form the compound of formula (1); ##STR00013## with R.sub.1, R.sub.2, R.sub.3 and R.sub.4 being as defined above; M1 is identical or different in formula (13) and (14) and is the required stoichiometric cationic equivalent for balancing the anionic charge in these formulae and is at least 1 cation selected from the group consisting of H.sup.+, alkali metal cation, alkaline earth metal cation other than magnesium, ammonium, mono-C.sub.1-C.sub.4-alkyl-di-C.sub.2-C.sub.3-hydroxyalkyl ammonium, di-C.sub.1-C.sub.4-alkyl-mono-C.sub.2-C.sub.3-hydroxyalkyl ammonium, ammonium which is mono-, di- or trisubstituted by a C.sub.2-C.sub.3 hydroxyalkyl radical and mixtures thereof, M2 is independently from each other identical or different in formula (10) and (12) and is the required stoichiometric cationic equivalent for balancing the anionic charge in these formulae in the case that either R.sub.1 or R.sub.2 or both R.sub.1 and R.sub.2 are SO.sub.3.sup., and has the same definition as M1, with the proviso, that at least 1 of the reactions A, B or C is carried out in the presence of the cation CAT, with the cation CAT being Mg.sup.2+.

17. A process for the preparation of compound of formula (1) ##STR00014## wherein R.sub.1 is hydrogen or SO.sub.3.sup., R.sub.2 is hydrogen or SO.sub.3.sup., R.sub.3 is hydrogen, C.sub.1-4, alkyl, C.sub.2-3 hydroxyalkyl, CH.sub.2CO.sub.2.sup., CH.sub.2CH.sub.2CONH.sub.2 or CH.sub.2CH.sub.2CN, R.sub.4 is C.sub.1-4 alkyl, C.sub.2-3 hydroxyalkyl, CH.sub.2CO.sub.2.sup., CH(CO.sub.2.sup.)CH.sub.2CO.sub.2.sup. or CH(CO.sub.2.sup.)CH.sub.2CO.sub.2.sup., benzyl, or R.sub.3 and R.sub.4 together with the neighboring nitrogen atom signify a morpholine ring, and wherein M is the required stoichiometric cationic equivalent for balancing the anionic charge in formula (1) and is combination of Mg.sup.2+ together with at least 1 further cation selected from the group consisting of H.sup.+, alkali metal cation, alkaline earth metal cation other than Mg.sup.2+, ammonium, mono-C.sub.1-C.sub.4-alkyl-di-C.sub.2-C.sub.3-hydroxyalkyl ammonium, di-C.sub.1-C.sub.4-alkyl-mono-C.sub.2-C.sub.3-hydroxyalkyl ammonium, ammonium which is mono-, di- or trisubstituted by a C.sub.2-C.sub.3 hydroxyalkyl radical and mixtures thereof, comprising the step of mixing a compound of formula (20) with a component b), wherein component b) is a magnesium salt MS2, in aqueous medium; ##STR00015## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 have the definition above; and wherein T balances the anionic charge and is the required stoichiometric equivalent of a cation selected from the group consisting of H.sup.+, alkali metal cation, ammonium, mono-C.sub.1-C.sub.4-alkyl-di-C.sub.2-C.sub.3-hydroxyalkyl ammonium, di-C.sub.1-C.sub.4-alkyl-mono-C.sub.2-C.sub.3-hydroxyalkyl ammonium, ammonium which is mono-, di- or trisubstituted by a C.sub.2-C.sub.3 hydroxyalkyl radical and mixtures thereof.

18. The process as defined in claim 17 for the preparation of compound of formula (1), wherein the magnesium salt MS2 is selected from the group consisting of magnesium acetate, magnesium bromide, magnesium chloride, magnesium formate, magnesium iodide, magnesium nitrate, magnesium sulphate and magnesium thiosulphate.

19. The process as defined in claim 17 for the preparation of compound of formula (1), wherein the mixing is done in aqueous solution.

Description

EXAMPLES

(1) The cation content was determined by capillary electrophoresis.

(2) The following examples shall explain the instant invention in more details without limiting the claimed scope. If not indicated otherwise, % and parts are meant by weight.

Example 1

(3) Sizing compositions are prepared by adding an optical brightener of formula (21) in such an amount, that a range of final concentrations of from 2.5 to 12.5 g/l of optical brightener is achieved, to a stirred, aqueous solution of magnesium chloride (final concentration is 8 g/l) and an anionic oxidized potato starch (Perfectamyl A4692 from AVEBE B.A.) (final concentration is 50 g/l) at 60 C.

(4) The sizing solution is allowed to cool, then poured between the moving rollers of a laboratory size-press and applied to a commercial 75 g/m.sup.2 AKD (alkyl ketene dimer) sized, bleached paper base sheet. The treated paper is dried for 5 minutes at 70 C. in a flat bed drier. The dried paper is allowed to condition, then measured for CIE whiteness on a calibrated Elrepho spectrophotometer.

(5) The Example is repeated both in the absence of magnesium chloride, i.e. only the sodium salt of the optical brightener is present, and with the magnesium chloride replaced by an equivalent amount of calcium chloride.

(6) The results are summarized in Table 1, and clearly demonstrate the advantage of using magnesium chloride over the use of calcium chloride and over the use only of the sodium salt of the optical brightener in order to reach higher whiteness levels. The surprising nature of the invention is further illustrated by the observation that chloride salts of other divalent Group II metal ions, such as calcium chloride, even have a negative impact on the whitening effect of the optical brightener.

(7) TABLE-US-00001 TABLE 1 Compound of formula Magnesium Calcium (21) (g/l) Chloride (g/l) Chloride (g/l) CIE Whiteness 0 0 0 104.6 0 8 0 104.7 0 0 8 104.8 2.5 0 0 122.3 2.5 8 0 126.7 2.5 0 8 123.4 5.0 0 0 128.3 5.0 8 0 133.1 5.0 0 8 128.0 7.5 0 0 129.8 7.5 8 0 133.7 7.5 0 8 128.6 10.0 0 0 131.1 10.0 8 0 134.5 10.0 0 8 128.2 12.5 0 0 130.6 12.5 8 0 134.2 12.5 0 8 127.3

Example 2

(8) Sizing solutions are prepared by adding an optical brightener of formula (22) in such an amount, that a range of final concentrations of from 2.0 to 10.0 g/l of optical brightener is achieved, to a stirred, aqueous solution of magnesium chloride (final concentration is 8 g/l) and an anionic oxidized potato starch (Perfectamyl A4692 from AVEBE B.A.) (final concentration 50 g/l) at 60 C.

(9) The sizing solution is allowed to cool, then poured between the moving rollers of a laboratory size-press and applied to a commercial 75 g/m.sup.2 AKD (alkyl ketene dimer) sized, bleached paper base sheet. The treated paper is dried for 5 minutes at 70 C. in a flat bed drier. The dried paper is allowed to condition, then measured for CIE whiteness on a calibrated Elrepho spectrophotometer.

(10) The Example is repeated both in the absence of magnesium chloride, and with the magnesium chloride replaced by an equivalent amount of calcium chloride.

(11) The results are summarized in Table 2, and clearly demonstrate the advantage of using magnesium chloride to reach higher whiteness levels in comparison to where the optical brightener is present only as the sodium salt.

(12) TABLE-US-00002 TABLE 2 Compound of formula Magnesium Calcium (22) (g/l) Chloride (g/l) Chloride (g/l) CIE Whiteness 0 0 0 104.6 0 8 0 104.7 0 0 8 104.8 2.0 0 0 119.2 2.0 8 0 122.5 2.0 0 8 121.5 4.0 0 0 127.2 4.0 8 0 131.1 4.0 0 8 127.9 6.0 0 0 131.1 6.0 8 0 135.4 6.0 0 8 131.6 8.0 0 0 133.7 8.0 8 0 138.1 8.0 0 8 133.5 10.0 0 0 136.0 10.0 8 0 139.7 10.0 0 8 134.7

Example 3

(13) Sizing compositions are prepared by adding an optical brightener of formula (22) in such an amount, that a range of final concentrations of from 0 to 12.5 g/l of optical brightener is achieved, to a stirred, aqueous solutions of magnesium chloride (final concentrations are 6.25 and 12.5 g/l) and an anionic oxidized corn starch (final concentration 50 g/l) (Penford Starch 260) at 60 C. Each sizing solution is allowed to cool, then poured between the moving rollers of a laboratory size-press and applied to a commercial 75 g/m.sup.2 AKD (alkyl ketene dimer) sized, bleached paper base sheet. The treated paper is dried for 5 minutes at 70 C. in a flat bed drier.

(14) The dried paper is allowed to condition, and then measured for CIE whiteness on a calibrated Auto Elrepho spectrophotometer. The results are shown in Table 3.

Example 4

(15) Sizing compositions are prepared by adding an optical brightener of formula (22) in such an amount, that a range of final concentrations of from 0 to 12.5 g/l of optical brightener is achieved, to a stirred, aqueous solutions of magnesium thiosulphate hexahydrate (final concentrations are 10 and 20 g/l) and an anionic oxidized corn starch (final concentration 50 g/l) (Penford Starch 260) at 60 C. The sizing solution is allowed to cool, then poured between the moving rollers of a laboratory size-press and applied to a commercial 75 g/m.sup.2 AKD (alkyl ketene dimer) sized, bleached paper base sheet. The treated paper is dried for 5 minutes at 70 C. in a flat bed drier.

(16) The dried paper is allowed to condition, and then measured for CIE whiteness on a calibrated Auto Elrepho spectrophotometer. The results are shown in Table 3.

(17) TABLE-US-00003 TABLE 3 CIE Whiteness Magnesium salt added Magnesium Magnesium thiosulphate Compound no Mg salt, chloride (g/l) hexahydrate (g/l) of formula i.e. Na salt (example 3) (example 4) (22) (g/l) only 6.25 12.5 10.0 20.0 0 102.8 102.9 103.5 102.2 102.7 2.5 119.6 122.4 125.5 125.1 123.6 5.0 128.9 131.1 132.5 132.9 132.7 7.5 135.1 136.3 137.9 137.7 137.9 10.0 139.2 140.9 141.4 141.1 141.0 12.5 141.1 142.3 142.8 142.4 142.4

(18) The results clearly demonstrate the advantage of using magnesium chloride or magnesium thiosulphate to reach higher whiteness levels in comparison to where optical brightener is present only as the sodium salt.

Example 5

(19) 115.6 parts of aniline-2,5-disulphonic acid monosodium salt are added to 74.5 parts of cyanuric chloride in 400 parts of ice and 300 parts of water. The pH of the reaction is maintained at approx. 4 to 5 by dropwise addition of an approx. 30% aqueous NaOH solution while keeping the temperature below 10 C. by using an external ice/water bath. After completion of the reaction, the temperature is gradually increased to 30 C. using an external heating system and 74.1 parts of 4,4-diaminostilbene-2,2-disulphonic acid are added. The resulting mixture is heated to 50 to 60 C. while maintaining the pH at approx. 5 to 7 by dropwise addition of an approx. 30% NaOH aqueous solution until completion of the reaction. 63.8 parts of aspartic acid are then added followed by 89.8 parts of magnesium hydroxide and the resulting slurry is heated to 90 to 95 C. until completion of the reaction. The temperature is gradually decreased to room temperature and insoluble materials are filtered off. The final concentration was adjusted to 0.125 mol of compound of formula (3) per kg of solution, for this purpose water was either added or removed by distillation. M in this case is composed of a mixture of sodium and magnesium cations.

Example 6

(20) 115.6 parts of aniline-2,5-disulphonic acid monosodium salt are added to 74.5 parts of cyanuric chloride in 400 parts of ice and 300 parts of water. 26.8 parts of magnesium hydroxide are added while keeping the temperature below 10 C. by using an external ice/water bath. After completion of the reaction, the temperature is gradually increased to 30 C. using an external heating system. 25.7 parts of magnesium hydroxide are added, followed by 74.1 parts of 4,4-diaminostilbene-2,2-disulphonic acid. The resulting mixture is heated to 50 to 60 C. until completion of the reaction. 63.8 parts of aspartic acid and 100 parts of water are then added followed by 89.8 parts of magnesium hydroxide and the resulting slurry is heated to 90 to 95 C. until completion of the reaction. The temperature is gradually decreased to room temperature and insoluble materials are filtered off. The final concentration was adjusted to 0.125 mol of compound of formula (3) per kg of solution using UV spectroscopy, for this purpose water was either added or removed by distillation. M in this case is composed of a mixture of sodium and magnesium cations.

Comparative Example 7

(21) Comparative optical brightening solution 7 is prepared by dissolving compound of formula (22) in water with a final concentration of 0.125 mol/kg.

Example 8

(22) Sizing compositions are prepared by adding an aqueous solution of an optical brightener, prepared according to example 5, in such an amount, that final concentrations of from 0 to 80 g/l of the aqueous solution of the optical brightener, prepared according to example 5, are achieved, to a stirred, aqueous solution of an anionic oxidized potato starch (Perfectamyl A4692 from AVEBE B.A.) (final concentration 50 g/l) at 60 C. Each sizing solution is allowed to cool, then poured between the moving rollers of a laboratory size-press and applied to a commercial 75 g/m.sup.2 AKD (alkyl ketene dimer) sized, bleached paper base sheet. The treated paper is dried for 5 minutes at 70 C. in a flat bed drier.

(23) The dried paper is allowed to condition, and then measured for CIE whiteness on a calibrated Auto Elrepho spectrophotometer. The results are shown in Table 4.

Example 9

(24) Sizing compositions are prepared by adding an aqueous solution of an optical brightener prepared according to example 6, in such an amount, that final concentrations of from 0 to 80 g/l of the aqueous solution of the optical brightener, prepared according to example 6, are achieved, to a stirred, aqueous solution of an anionic oxidized potato starch (Perfectamyl A4692 from AVEBE B.A.) (final concentration 50 g/l) at 60 C. Each sizing solution is allowed to cool, then poured between the moving rollers of a laboratory size-press and applied to a commercial 75 g/m.sup.2 AKD (alkyl ketene dimer) sized, bleached paper base sheet. The treated paper is dried for 5 minutes at 70 C. in a flat bed drier.

(25) The dried paper is allowed to condition, and then measured for CIE whiteness on a calibrated Auto Elrepho spectrophotometer. The results are shown in Table 4.

Comparative Example 10

(26) Sizing compositions are prepared by adding an aqueous solution of an optical brightener prepared according to example 7, in such an amount, that final concentrations of from 0 to 80 g/l of the aqueous solution of the optical brightener, prepared according to example 6, are achieved, to a stirred, aqueous solution of an anionic oxidized potato starch (Perfectamyl A4692 from AVEBE B.A.) (final concentration 50 g/l) at 60 C. Each sizing solution is allowed to cool, then poured between the moving rollers of a laboratory size-press and applied to a commercial 75 g/m.sup.2 AKD (alkyl ketene dimer) sized, bleached paper base sheet. The treated paper is dried for 5 minutes at 70 C. in a flat bed drier.

(27) The dried paper is allowed to condition, and then measured for CIE whiteness on a calibrated Auto Elrepho spectrophotometer. The results are shown in Table 4.

(28) TABLE-US-00004 TABLE 4 CIE Whiteness Concentration of Comparative the optical application brightening example solution (g/l) example 8 example 9 10 0 101.5 101.5 101.5 10 119.5 119.6 119.2 20 127.4 128.4 126.7 40 133.6 135.0 132.6 60 137.1 138.6 135.8 80 138.2 140.2 136.8

(29) The results clearly demonstrate the advantage of using a mixed salt of an optical brightener comprising magnesium cation.