GB2314342A

GB2314342A - Aqueous composition for pre-tanning pelts or re-tanning leather

Info

Publication number: GB2314342A
Application number: GB9712313A
Authority: GB
Inventors: Alain Lauton
Original assignee: Ciba Geigy AG; Ciba Spezialitaetenchemie Holding AG
Current assignee: Novartis AG; BASF Schweiz AG
Priority date: 1996-06-17
Filing date: 1997-06-12
Publication date: 1997-12-24
Anticipated expiration: 2017-06-12
Also published as: GB9712313D0; ZA975260B; NZ328079A; CH691062A5; DE19724468A1; GB2314342B; ATA103997A; DE19724468B4; AU2491797A; AT409384B

Description

2314342 Anueous composition for pretanning Pelts or retannincl leather The

present invention relates to an aqueous composition for pretanning pelts or retanning leather, a process for pretanning pelts or retanning leather, and also the leather treated by the present process.

Mineral and especially chrome pretanning and tanning have great importance for the production of leather and furs. However, the chromium salt treatment baths involved present great problems, since the wastewaters have to be cleaned or disposed of at great cost. These ecological difficulties have driven the search for alternative processes which, on the one hand, are ecologically safer and, on the other, match the mineral tannages in the leather qualities achieved.

It is well known that leather can be tanned with glutardialdehyde without use of chromium salts, but the appreciably higher price mitigates against the general application of this method in many cases. In addition, the yellowing of glutardialdehyde-tanned leather is sometimes a disadvantage, for example in those cases where the leather is subsequently to be dyed only in light shades, if at all.

It is also known to tan leather with anionic aromatic syntans, in which case, however, the attainable shrinkage temperature does not meet all the requirements.

It has further been reported that leather has been treated with hydroxyalkylphosphine compounds, optionally together with a phenol and a mineral, vegetable or aldehydic tanning agent.

None of these processes makes it possible to produce leather which will comply with consumer requirements in all aspects.

It has now been found that aqueous compositions comprising a mixture of a hydroxyalkylphosphine compound and an anionic aromatic syntan are highly useful for pretanning pelts or retanning leather, the use of mineral salts being completely unnecessary.

Surprisingly, the shrinkage temperature is adequate and the leathers treated with such a mixture have firmer structure than leathers treated only with a hydroxyalkylphosphine compound, with advantageous consequences for further processing, for example for shaving to the desired thickness or for splitting.

The present invention accordingly provides an aqueous composition for pretanning pelts or retanning leather, comprising (A) a hydroxyalkylphosphine compound, (B) an anionic aromatic syntan, (C) water and optionally (D) an acid.

The aqueous composition of the invention provides very good results in pretanning, and the leather has a high shrinkage temperature. The pretanning may be followed by a nonmineral tannage, especially a tannage without the use of chromium salt, to produce wet white leather material, in which case an aqueous composition of the invention is again used with advantage for that purpose. However, it is also possible to use other, customary retanning compositions.

Suitable hydroxyalkylphosphine compounds (A) are generally compounds of the formula e [HO-R-P-R,1,XY (1) where R is alkyl or alkenyl having 1 to 24 carbon atoms, each R' is independently of the other(s) alkyl or alkenyl having 1 to 24 carbon atoms or R-OR X'8 is an anion, x is the valence of X, n is 2 or 3, and y is 0 or 1, subject to the proviso that the sum of n+y is 2 or 4. Preferred hydroxyalkylphosphine compounds (A) are those of the formula R 2 9M 1 e HO-R-P-P, X (2) 1 R3 where R is alkyl or alkenyl having 1 to 24 carbon atoms, IR,, R2 and R3 are each independently of the others alkyl or alkenyl having 1 to 24 carbon atoms or R-OH and X e is an anion.

R, IR,, R2 and R3 preferably each have 1 to 24 carbon atoms, and particularly suitable compounds among these are those in which IR,, R2 and R3 are each hydroxyalkyl having 1 to 4 carbon atoms.

Particular preference is given to using tetrakis(hydroxymethyi)phosphonium salts.

The anion X e may be any inorganic or organic anion, for example'a nitrate, fluoride, phosphonate, carbonate, formate, acetate or propionate, but it is preferably chloride, bromide, phosphate or especially sulfate.

The particularly preferred hydroxyalkylphosphine compound (A) is tetrakis(hydroxymethyi)phosphonium sulfate.

The hyd roxyalkylphos phi ne compounds are known, for example from WO-A93/06249, or are preparable by methods known per se.

Suitable anionic aromatic syntans (B) includ for example those which are obtainable by condensation of sulfonated aromatic compounds alone or together with further, usually unsulfonated, aromatic compounds with formaldehyde andlor urea.

Examples of suitable aromatic compounds are naphthalene, biphenyl, terphenyl, phenols, cresols, 4,4'-d ihyd roxydi phenyl sulfone, 0naphthol, dihydroxybenzenes, resorcinol, ZZbis(hydroxyphenyl)propane and diaryl ethers, such as diphenyl ether and ditoly] ether, which were optionally sulfonated in a manner known per se.

Particularly suitable anionic aromatic syntans are the following compounds:

(1) condensation products of sulfonated phenol or cresoi and formaldehyde, (11) condensation products of naphthalenesulfonic acid and formaldehyde, (111) formaldehyde condensation products of 4,4'-dihydroxydi phenyl sulfones with (hydroxy)aryisuifonic acids, (N) formaldehyde condensation products of sulfo-containing aromatic hydroxy compounds with aralkyl halides, (V) urea-formaldehyde condensation products of phenols and phenolsulfonic acids, (V1) reaction products of phenol and a sulfonating agent in a molar ratio of (phenol):(503) within the range from 1:11.1 to 12.2, (V] 1) condensation products of sulfonated diaryl ethers and formaldehyde, (V] 11) condensation products of suffonated bi- or terphenyls and formaldehyde, (IX) condensation products of 4,4'-d ihyd roxydi phenyl sulfone and sulfonated 4,4'dihyd roxydi phenyl sulfone with formaldehyde, (X) formaldehyde condensation products of diaryl ether sulfonic acids and 4,4'- dihydroxydiphenyl sulfone, and (Xl) formaldehyde condensation products of phenol with ary(sulfonic acids or hydroxyaryisuifonic acids.

These condensation products are present in the form of the free acids, preferably in the form of the sulfonic acids, or in the form of salts, especially in the form of the lithium, potassium or especially sodium salts.

These condensation products are known, for example from Ulimann's Enzykiopadie der technischen Chemie Vol. 16, (4), 138 to 140 (1979), or are preparable by the processes described in the references cited therein.

Suitable acids (D) include not only inorganic but also organic acids, for example hydrochloric acid, sulfuric acid, formic acid, acetic acid, citric acid, lactic acid, oxalic acid, benzoic acid, phthalic acid, phenolsulfonic acid, phenolpolysulfonic acid or naphthalenesulfonic acid. Preference is given to using an organic acid, especially acetic acid or formic acid. If the solutions of the anionic aromatic syntans already have the desired pH as a consequence of the acid groups present therein, component (D) can be dispensed with, if desired.

Preferred aqueous compositions of the invention comprise, based on the total mixture, 1 to 30, preferably 2 to 20, % by weight of component (A), to 75, preferably 20 to 55, % by weight of component (B), sufficient acid to set a pH between 0.5 and 6.8, and water to make up to 100 %.

Of these compositions, those are particularly preferred which comprise, based on the entire mixture, 2 to 20 % by weight of component (A), 20 to 55 % by weight of component (B), sufficient acid to set a pH between 1 and 6.5, and water to make up to 100 %.

Based on the mixture of tanning agents (A) and (B), the proportion of component (A) is preferably between 5 and 95 % by weight and the proportion of component (B) is preferably between 5 and 95 % by weight.

The aqueous composition of the invention is advantageously prepared by dissolving component (A) in water at a temperature of between 15 and 600C and then admixing the resulting clear solution with component (B) and optionally an acid (D).

The aqueous composition thus obtained is liquid and has good stability in storage.

The aqueous composition of the invention is of itself an excellent pretanning agent for all hides and skins and is very particularly useful as a-starting material for producing wet white leathers and furs. Pretanning may be followed by tanning, in which case an aqueous composition of the invention is advantageously again used for this purpose.

Pelts are preferably pretanned using 1 to 10 % by weight, especially 2 to 5 % by weight, of the aqueous composition of the invention, based on the weight of the pelt.

When the aqueous compositions of the invention are used for retanning leather, it is likewise preferable to use 1 to 10 % by weight, especially 2 to 5 % by weight, based on the weight of the leather.

The present invention accordingly further provides a process for pretanning pelts andlor for retanning leather, which comprises treating a pickled pelt or a pretanned leather in an aqueous liquor comprising (A) a hydroxyalkylphosphine compound, (B) an anionic aromatic syntan, (C) water and optionally (D) an acid.

The process of the invention is preferably carried out using an aqueous liquor comprising (A) tetrakis(hydroxymethyi)phosphonium sulfate, (B) an anionic aromatic syntan selected from the group consisting of (1) condensation products of sulfonated phenol or cresol and formaldehyde, (11) condensation products of naphthalenesulfonic acid and formaldehyde, (111) formaldehyde condensation products of 4,4'-di hyd roxydi phenyl sulfones with (hydroxy)aryisuifonic acids, (IV) formaldehyde condensation products of sulfo-containing aromatic hydroxy compounds with aralkyl halides, (V) urea-formaldehyde condensation products of phenois and phenoisuifonic acids, (V1) reaction products of phenol and a sulfonating agent in a molar ratio of (phenol):(S03) within the range from 1A.1 to 12.2, (V1 1) condensation products of sultonated diaryl ethers and formaldehyde, (V111) condensation products of sulfonated bi- or terphenyls and formaldehyde, (IX) condensation products of 4,4'-dihydroxydiphenyl suifone and sulfonated 4,4' dihydroxydiphenyl sulfone with formaldehyde, (X) formaldehyde condensation products of diaryl ether sulfonic acid and 4,4' dihydroxydiphanyl sulfone, and (Xl) formaldehyde condensation products of phenol with aryisulfonic acids or - hydroxyarylsuffonic acids, water and optionally (D) an acid.

There is no need for further additions to the treatment liquor.

The pretanning is carded out for example by treating the pickled pelt material with the aqueous composition of the invention at a temperature between 15 and 450C and a pH between 1 and 7.5 for 1 to 12 hours, for example in a rotating drum.

The resulting material can then be dewatered in a conventional manner and shaved or split to the desired thickness and thereafter be tanned in a conventional manner with a mineral tanning agent or preferably, to produce wet white material, with vegetable or synthetic tanning agents. This retanning can likewise be carded out with the aqueous composition of the invention, for example by treating the pretanned leather with the aqueous composition of the invention at a temperature between 15 and 450C and a pH between 1 and 7.5 for 1 to 12 hours, for example in a rotating drum.

Given appropriate process management, the present process can also be used to produce ready-tanned leathers.

With the present process, the use of mineral salts can be completely dispensed with.

In the methods and examples which follow, parts and percentages are by weight.

Example 1: 51 parts of naphthalenesulfonic acid are heated with 45 parts of dihydroxydiphenyl sulfone, 30 parts of water and 16 parts of formaldehyde (37 %) at 105 to 1 100C for about 2 hours until the condensate forms a clear solution in water. Then 50 parts of sodium hydroxide solution (30 %) are added to set a weakly acidic pH, followed by 193 parts of tetrakis(hydroxymethyi)phosphonium sulfate (25 %) and 5 parts of formic acid (85%).

The result is a clear, light-coloured solution having a pH of 2.0 to 3.0. The solids content is 40 % by weight. The solution is stable in storage for at least 1 month even at 350C and is highly useful for pretanning and retanning leather.

The naphthalenesuffonic acid used is obtained by heating 520 parts of naphthalene and 560 parts of concentrated sulfuric acid at 140 to 1600C for several hours until the reaction product is completely soluble in water.

The dihyd roxyd i phenyl sulfone used is obtained by heating 540 parts of phenol _And 180 parts of 60 % oleum at 170 to 1800C for 3 hours and distilling off the excess phenol.

Example 2: 500 parts of molten phenol are slowly admixed with 440 parts of 66 % ofeum at 60-700C and then suffonated at 1 OWC for 1 hour. The phenoisuifonic acid formed is then slowly heated to 160 to 1650C in a vacuum of about 11 to 13 mm, so that only little phenol distils off, and held at that temperature until 1 g of the condensation product renders 3. 5 to 3.7 CM3 Of 1 N sodium hydroxide solution neutral to congo red. The condensation product formed in this way is admixed with 90 to 100 parts of phenol, and after the phenol has been thoroughly mixed in, the reaction mass is again slowly put under a vacuum and heated in a vacuum at 1650C until 1 g of the condensation product renders only 2.7 to 2.5 CM3 Of 1 N sodium hydroxide solution neutral to congo red.

parts of this condensation product are carefully melted with 54 parts of 30 % sodium hydroxide solution and admixed with 22 parts of 37 % formaldehyde solution and then condensed at 100 to 1050C for a sufficiently long time (about 6 hours) until a sample, diluted with a little water, remains clear on acidification with dilute sulfuric acid to pH 3.5.

The reaction mass is then diluted with 30 parts of water and admixed with 205 parts of tet rakis (hyd roxym ethyl) phosphon i um suifate (25 %), 3. 6 parts of formic acid (85 %) and 8 parts of phenoisuifonic acid (65 The product is a clear, light-coloured solution having a pH of 4.5 to 5.5. The solids content is 40 % by weight. The solution is stable in storage for at least 1 month even at 35% and is highly useful for pretanning and retanning leather.

Example 3: Example 2 is repeated with the 54 parts of 30 % sodium hydroxide solution replaced by an equivalent amount of lithium hydroxide, likewise affording a solution which is stable in storage and useful for pretanning and retanning leather.

Example 4: 478 parts of 20 % oleum are added with stirring to 500 parts of molten phenol while cooling to ensure that the temperature does not exceed 700C. This is followed by sultonation at 1050C for 1 hour. The phenoisuifonic acid formed is then slowly heated under a reduced pressure of 11 to 13 Torr to 150 to 1550C, and this temperature is maintained until 1 g of the condensation product renders 3.8 to 4.0 CM3 Of 1 N sodium hydroxide solution neutral to congo red.

parts of the resulting hydroxylphenyl sulfone (poiy) hydroxyphenyl sulfone monosuffonic acid are melted with 42 parts of water at 900C and admixed with 14.4 parts of urea. After cooling to 550C, 38.4 parts of formaldehyde (37 %) are added dropwise over 2 hours and stirred for about a further 4 hours until the condensate forms a clear solution in water.

The reaction product obtained is rendered weakly acidic with 37.2 parts of potassium hydroxide solution (50 %). Then 232 parts of tetrakis(hyd roxym ethyl) phosphoni um suifate (25 %) and 42 parts of acetic acid (75 %) are added.

-g- The product is a clear, light-coloured solution having a pH of 2.5 to 3.5. The solids content is 43 % by weight. The solution is stable in storage for at least 1 month even at 350C and is highly useful for pretanning and retanning leather.

Example 5: 55 parts of phenolsulfonic acid are mixed with 25 parts of dihyd roxydi phenyl sulfone, 35 parts of water and 56 parts of 30 % sodium hydroxide solution and then admixed with 61.5 parts of 37 % formaldehyde solution and condensed at 100 to 1050C for a sufficiently long time (about 6 hours) until a sample which has been diluted with a little water remains clear on acidification with dilute suffuric acid to pH 3.5.

The reaction mass is then admixed with 232.5 parts of tetrakis (hyd roxym ethyl) phosphon W m sulfate (25 %), 3.6 parts of formic acid (85 %) and 5 parts of sulfuric acid (40 %).

The product is a clear, light-coloured solution having a pH of 4.0 to 5.0. The solids content is 34 % by weight. The solution is stable in storage for at least 1 month even at 350C and is highly useful for pretanning and retanning leather.

Example 6: 100 parts of a pickled calf pelt are treated with 3 % of the composition prepared in Example 1 in a rotating drum at 250C for 3 to 6 hours, while pulverized sodium bicarbonate or sodium formate is used to set the pH to 6.0.

The resulting wet white leather is dewatered and shaved to the desired thickness. This leather is highly suitable for retanning with mineral, vegetable or synthetic tanning agents.

The leather can also be retanned with the same composition prepared in Example 2 to obtain a leather which has been tanned without heavy metal.

Claims

WHAT IS CLAIMED IS:

1. An aqueous composition for pretanning pelts or retanning leather, comprising (A) a hydroxyalkylphosphine compound, (B) an anionic aromatic syntan, (C) water and optionally (D) an acid.

2. An aqueous composition according to claim 1, including as component (A) a compound of the formula e [HO-R-P-R',,],,Xy where R is alkyll or alkenyl having 1 to 24 carbon atoms, each R' is independently of the other(s) alkyl or alkenyl having 1 to 24 carbon atoms or R-OH, X'9 is an anion, x is the valence of X, n is2or3, and y is 0 or 1, subject to the proviso that the sum of n+y is 2 or 4.

3. An aqueous composition according to claim 1, including as component (A) a compound of the formula R. 2 HO-R-F---FilX e (2) 1 K3 where R is alkyl or alkenyl having 1 to 24 carbon atoms, IR,, R2 and R3 are each independently of the others alkyl or alkenyl having 1 to 24 carbon atoms or R-OH and e X is an anion.

4. An aqueous composition according to claim 3, including as component (A) a compound of the formula (2) where R, R,, R2and R3 each have 1 to 4 carbon atoms.

5. An aqueous composition according to claim 4, including as component (A) a compound of the formula (2) where R,, R2and R3are each hydroxyalkyl having 1 to 4 carbon atoms.

6. An aqueous composition according to claim 5, including as component (A) a tetrakis(hydroxymethyl)phosphonium salt.

7. An aqueous composition according to claim 6, including tetrakis(hydroxymethyi)phosphonium sulfate as component (A).

8. An aqueous composition according to any one of claims 1 to 7, including as component (B) a compound selected from the group consisting of (1) condensation products of sulfonated phenol or cresol and formaldehyde, (11) condensation products of naphthalenesuifonic acid and formaldehyde, (111) formaldehyde condensation products of 4,4'-dihyd roxydi phenyl sulfones with (hydroxy)aryisuifonic acids, (IV) formaldehyde condensation products of suffo-containing aromatic hydroxy compounds with aralkyl hakes, (V) urea-formaldehyde condensation products of phenols and phenolsulfonic acids, (V1) reaction products of phenol and a suifonating agent in a molar ratio of (phenol):(S03)within the range from 1A.1 to 12.2, (V] 1) condensation products of sulfonated diaryl ethers and formaldehyde, (V] 11) condensation products of suifonated bi- or terphenyls and formaldehyde, (IX) condensation products of 4,4'-dihydroxydiphenyl sulfone and sulfonated 4,4' dihyd roxydi phenyl sulfone with formaldehyde, (X) formaldehyde condensation products of diaryl ether sulfonic acids and 4,4'- dihydroxydiphenyl sulfone, and (Xl) formaldehyde condensation products of phenol with aryisuffonic acids or hydroxyaryisuifonic acids.

9. An aqueous composition according to any one of claims 1 to 8, including component (B) in the form of the lithium, potassium or especially sodium salt.

10. An aqueous composition according to any one of claims 1 to 9, including as component (C) an organic acid, especially acetic acid or formic acid.

11. An aqueous composition according to any one of claims 1 to 10, comprising, based on the total mixture, 1 to 30 % by weight of component (A), 10 to 75 % by weight of component (B), sufficient acid to set a pH between 0.5 and 6.8, and water to make up to 100

12. An aqueous composition according to any one of claims 1 to 11, comprising, based on the total mixture, 2 to 20 % by weight of component (A), 20 to 55 % by weight of component (B), sufficient acid to set a pH between 1 and 6.5, and water to make up to 100 %.

13. An aqueous composition according to any one of claims 1 to 12, comprising, based on the mixture of tanning agents (A) and (B), 5 to 95 % by weight of component (A) and 5 to 95 % by weight of component (B).

1 - 4. A process for pretanning pelts or for retanning leather, which comprises treating a pickled pelt or a pretanned leather in an aqueous liquor comprising (A) a hydroxyalkylphosphine compound, (B) an anionic aromatic syntan, (C) water and optionally (D) an acid.

15. A process for pretanning pelts or for retanning leather, which comprises treating a pickled pelt or a pretanned leather in an aqueous liquor comprising (A) tetrakis(hydroxymethyl)phosphonium sulfate, (B) an anionic aromatic syntan selected from the group consisting of (1) condensation products of suffonated phenol or cresol and formaldehyde, (11) condensation products of naphthalenesuffonic acid and formaldehyde, (111) formaldehyde condensation products of 4,4'-dihydroxydiphenyl sulfones with (hydroxy)aryIsulfonic acids, (R) formaldehyde condensation products of sulfo-containing aromatic hydroxy compounds with aralkyl halides, (V) urea-formaldehyde condensation products of phenols and phenoisuifonic acids, (M) reaction products of phenol and a sulfonating agent in a molar ratio of (phenol):(S03) within the range from 1A.1 to 122, (V1 1) condensation products of sulfonated diaryl ethers and formaldehyde, (V111) condensation products of sulfonated bi- or terphenyls and formaldehyde, (IX) condensation products of 4,4'-dihydroxydiphenyl sulfone and suifonated 4,4'dihyd roxydi phenyl sulfone with formaldehyde, (X) formaldehyde condensation products of diaryl ether sulfonic acid and 4,4'- dihyd roxydi phenyl sulfone, and (Xl) formaldehyde condensation products of phenol with aryisuifonic acids or hydroxyaryisuifonic acids, (C) water and optionally (D) an acid.

16. A process for pretanning pelts or for retanning leather, which comprises treating the pickled pelt material or the pretanned leather with an aqueous composition according to any one of claims 1 to 13 at a temperature between 15 and 45T and a pH between 0.5 and 6.8 for 1 to 12 hours.

1'T A process according to any one of claims 14 to 16, wherein the pickled pelt material or the pretanned leather is treated with 1 to 10 % by weight, based on the weight of the leather or pelt, of an aqueous composition comprising, based on the total mixture, 1 to 30 % by weight of hydroxyalkylphosphine compound, 10 to 75 % by weight of an anionic aromatic syntan, sufficient acid to set a pH between 1 and 6.5 and water to make up to 100 %.

18. A process according to claim 17, wherein the pickled pelt material or the pretanned leather is treated with 4 to 8 % by weight, based on the weight of the leather or pelt, of an aqueous composition comprising, based on the total mixture, 2 to 20 % by weight of hydroxyalkylphosphine compound, to 55 % by weight of an anionic aromatic syntan, sufficient acid to set a pH between 1 and 6.5, and water to make up to 100

19. The leather material tanned according to any one of claims 14 to 18.

20. An aqueous composition according to claim 1 substantially as hereinbefore described with reference to any one of foregoing Examples 1 to 5.

21. A process according to claim 14 substantially as hereinbefore described with reference to foregoing Example 6.