Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-08-26
2001-11-13
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S156000, C524S284000, C524S296000
Reexamination Certificate
active
06316533
ABSTRACT:
The present invention relates to a composition containing (A) one or more aromatic sulfonates, (B) one or more aldehyde resins and (C) a buffer, the preparation of this composition and the use for treating, in particular for neutralizing, leather tanned with mineral or mineral-free compounds.
For the production of leather and pelts, animal skins are tanned with tanning agents, with the result that the skins are converted into resistant leathers of pelts. The tanning agents, which essentially result in crosslinking of the collagen fibers of the skin, can be divided into inorganic or mineral and organic tanning agents. The organic tanning agents may furthermore be of synthetic or vegetable origin.
Mineral tanning, in particular chrome tanning, is of considerable importance for the production of leathers and pelts. For example, 90% of all leathers are chrome tanned. In chrome tanning, the skin absorbs chrome(III) salts which cross link the collagen fibers owing to complex formation with the carboxyl groups of the collagen. The resulting intermediates of the chrome tanning are commercially available as semifinished products, i.e. wetblues, and are ideal for further processing to give a very wide range of leather articles. Retanning, in which the actual leather character is established, is generally necessary for this purpose.
The retanning is carried out as a rule with anionic substances which may originate from the class consisting of the synthetic or vegetable tanning agents, for example including resin tanning agents, lignin sulfonates, polymeric tanning agents, aldehydes, paraffin sulfonyl chlorides, polyphosphates or inert fillers. Furthermore, anionic fatliquoring agents are used in the retanning for the production of supple and water repellent leather, and anionic dyes are used for the production of dyed leather.
A fundamental problem in the retanning of, for example, chrome leather with anionic substances is, however, that the cationic character of the tanned leather may rapidly cause the anionic substances to react, with the result that the substances cannot penetrate into the leather or cannot penetrate deeply enough.
This generally leads to superficial and nonuniform deposition of the substances on the leather and overloading of the grain. The consequences may be an unattractive appearance of the grain, loose grain, poor leather properties and cracking of the grain. Even precipitation of the substances on the leather surface is possible.
As a rule, the retanning of tanned leather is therefore preceded by neutralization, which is intended to weaken or reduce the cationic character of the leather but may also intervene in the chemistry of the tanning. The neutralization should therefore be neither insufficient nor excessive in its intensity. Insufficient neutralization does not adequately solve the abovementioned problems and can, for example, also be a cause of a poor shelf-life of the leathers. Over-neutralization on the other hand is often the cause of loose grain in the leather.
Oveneutralization is easily achieved with strong neutralizing agents, such as sodium carbonate, sodium bicarbonate or borax, which are therefore nowadays often used in combination with milder agents. With mild neutralizing agents, e.g. sodium formate, calcium format, sodium acetate, sodium sulfite, sodium thiosulfate or sodium polyphosphate, over neutralization is generally ruled out. However, the disadvantage of these agents is that the pH desired in the case of specific leather types cannot be achieved.
Also advantageous in the neutralizaton is the use of salts of organic and inorganic acids having a buffer effect, e.g. formates, acetates, oxalates, adipates, glutarates, citrates, lactates, carbonates, bicarbonates, polycarbonates, basic carbonates, silicates, borates or phosphates, so that the pH range desired for specific leather types can be more exactly controlled.
In addition to the salts having a buffer effect, tanning sulfonic acids, in particular based on naphthalene sulfonic acid/formaldehyde condensates, in combination with salts of acids having a buffer effect are also frequently used. Here, there is an interaction between the tanning sulfonic acids and, for example, the chromium complexes, with the displacement of sulfato groups and liberation of sulfuric acid. The liberated sulfuric acid is neutralized by the buffer. However, the disadvantage of such agents is that the leathers are strongly bleached and additional dye must therefore be used to obtain a desired dyeing of the leathers. In addition, the dyeings are less brilliant. Furthermore, the leathers are generally softer and less tight-grained, which is disadvantageous in particular for the upper leather sector.
It an object of the present invention to provide a composition and/or a process in which the disadvantages described above can be avoided or at least reduced. We have found that this object is achieved by a composition containing (A) one or more aromatic sulfonates, (B) one or more aldehyde resins and (C) one or more buffers.
It should be mentioned here that it is precisely the combination of the individual components (A), (B) and (C) and in particular the use of aldehyde resins as component (B), especially the use of aldehyde resins after their reaction with salts of sulfurous acid, which give rise to the surprising advantages of the novel composition. A further advantageous improvement in the novel composition can be achieved by a higher degree of sulfonation of the aromatic sulfonates as component (A).
The aromatic sulfonate according to (A) is generally selected from a sulfonated benzene and its derivatives, in particular toluene, phenol, cresol or resorcinol; sulfonated polycyclic aromatic compounds and their derivatives, in particular naphthalene, naphthol, (hydroxy)diaryl sulfones or (hydroxy)diaryl ethers, where aryl is preferably phenyl; sulfonated oligophenyls or their derivatives, preferably biphenyl or terphenyl; or mixtures thereof. In particular, naphthalene, toluene and xylene are suitable as starting materials.
In a further embodiment, the aromatic sulfonate according to (A) is a condensate of one or more aromatic sulfonates and an aliphatic aldehyde, preferably formaldehyde and/or acetaldehyde, in particular formaldehyde, or a condensate of one or more aromatic sulfonates and a condensate of one or more amides of carbonic acid and an aliphatic aldehyde, preferably formaldehyde and/or acetaldehyde, in particular formaldehyde. Suitable amides of carbonic acid are in particular urea and/or derivatives or urea, e.g. semicarbazide, guanidine, dicyandiamide and/or dicyandiamide derivatives, such as melamine. A urea/formaldehyde condensate, a melamine/formaldehyde condensate and/or melamine/urea/formaldehyde condensate are particularly preferred, especially a urea/formaldehyde condensate.
Advantageously, the sulfonated aromatic compound, which may be monosulfonated or polysulfonated, is prepared from a molar equivalent of an aromatic compound and 1-5, preferably 2-4, in particular about 3-4, molar equivalents of SO
3
. Preferably, the aromatic sulfonate is a mixture of monosulfonated and polysulfonated compounds, in particular a mixture of compounds having different degrees of polysulfonation, especially disulfonated or trisulfonated compounds. Concentrated sulfuric acid, for example 95-98% strength sulfuric acid, or fuming sulfuric acid, for example 24% oleum (2 mol of SO
3
), preferably serves as the SO
3
source. The reaction with concentrated or fuming sulfuric acid is preferably effected at about 100-160° C., in particular about 130-150° C., for about 1-4, preferably about 2, hours. The sulfonation products in this preferred process are in general polysulfonated, and, depending on the molecular ratio of aromatic compound to SO
3
, Up to 50% by weight of free sulfate may additionally be present in the end product. The product is then generally brought to a pH of about 6-10, preferably with sodium hydroxide solution.
The preparation of condensates of sulfonated aromatic compound and formaldehyde or forma
Grosser Thomas
Guenther Erhard
Igl Georg
Stübinger Adolf
Werner Jurgen
BASF - Aktiengesellschaft
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Rajguru U. K.
Seidleck James J.
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