US2218996A - Tanning material - Google Patents

Description

Patented o r. 22, 1940 PATENT OFFICE TANNING MATERIAL Arthur Voss and Walter Pense, Frankfort-on-the Main-Hochst,. Germany, assignors, by mesne assignments, to General Aniline 8; Film Corporation, New York, Delaware N. Y., a corporation of No Drawing. Application November 26, 1937, Se-

rial No. 176,714. In Germany December 2,

"4 Claims,

The present invention relates to tanning materials.

Numerous synthetic tanning materials are known which are made by producing in a watersoluble form bodies of of the aromatic series.

a high molecular weight By bodies of a high molecular weight there are to be understood in most cases bodies which are at least binuclear;

for instance naphthalenesulfonic acid has hardly any tanning action, whereas trinuclear bodies have already a highdegree of tanning action. Sulfonic acids with distinctly good tanning properties are known; they are in particular obtained by condensing the sulfonated aromatic nuclei with formaldehyde and thus connecting them by one or more methylene bridges. These tanning materials have the special property of producing a plumping action on the leather, but this action is not sufiicient when the products are usedas the sole tanning material, that-is without the addition of vegetable tanning materials have a plumping efi'ect.

In order to imitate vegetable tanning materials as much as possible, the attempt has been made to combine tanning substances which have no plumping effect and yield flat leather, with phlobaphene-like bodies, namely bodies which are themselves insoluble in water. As bodies of this kind there are preferably used condensation products of phenols and aldehydes, because they can readily be brought into a water-soluble form with the aid .of the non-plumping sulfonic acids by a process of peptization or condensation. Al-

ready in this water-soluble form they yield relatively well plumped leather.

Now we have found that the plumping effect of tanning materials of this kind may considerably be increased by the process described below:

Instead of combining the non-plumping tanning materials with phenol-aldehyde-condensation products insoluble in water, they are combined with phenol-aldehyde condensation products which have already a certain solubility in water, but so small a solubility that they are not suitable of themselves to transform pelt by the usual tanning process into a useful leather. More exactly defined, there are used phenol-aldehyde condensation products which are not soluble in water to a clear solution in a concentration suitable for'the tanningliquors of the usual concentration. There are used products which are soluble in water only in too large a dilution or which are'soluble only in hot water but separate again at ordinary temperature. They are soluble to a clear solution only in an alkaline agent. When combined with vegetable extracts they tend to precipitate so that in this combination they are likewise unsuitable as tanning materials,

Bodies of this kind may be obtained, for instance, from products of the condensation (which may be carried out in an acid or an alkaline medium) of phenol, ortho-, meta or paracresol or of 'a commercial cresol mixture, of xylenols or of naphthols with formaldehyde or acetaldehyde. Suitable parent condensation products are also dihydroxy-diphenylmethane or dihydroxy-diphenylethane. For converting these condensation products into bodies useful for the purpose of the invention, the condensation products are sulfonated in'such a manner that only so many sulfo-groups are introduced as are necessary fortheproperties above referred to. The proportion of the sulfo-groups is kept so low that 4 aromatic nuclei correspond with at most one sulfa-group. Such partly sulfonated condensation products are obtained by treating for instance a condensation product of phenol and aldehyde only for so long a time or only with such a quantity of concentrated sulfuric acid, or an equivalent sulfonating agent, that not more than about 6 per cent. of sulfur is contained in the purified and isolated tanning material. The sulfonation is preferably performed in the presence of a diluent. Or the. sulfonation is carried out with the aid of sulfite by condensing for instance phenol with formaldehyde and sodium sulflte in a proportion that for one mol of phenol at most. mol of sodium sulfite is used. Suitably the content of sulfur in the products should not be below 5 per cent, for the products then become too sparingly soluble in water. V

As peptizing components there are used they known aromatic sulfonated hydrocarbons or phenols of high molecular weight. Such sulfonic acids having more or less tanning action are obtained by the sulfonation ofphenol, cresol, naphthalene, alkvlated or aralkylated naphthalene, if necessary'with a subsequent condensation with for instance formaldehyde. There may also be used sulfo-compounds into which a non-sulfonated phenol-condensation product has already been condensed or peptized. The process is'for instance carried out as follows: naphthalene su1- fonic acid'is condensed or peptized at about o C. with a certain quantity of a resinous body obtained from phenol andformaldehyde, this body being substantially insoluble in water, until a product is formed which is soluble inwater to a clear solution. This product is mixed with a 55 product obtained by heating together for several hours cresol, formaldehyde and sodium sulflte in uch proportion that for 1 mol of cresol about t e equivalent quantity of formaldehyde and only half the equivalent quantity of sodium sulflte are used. As peptizing component there may also be used waste sulfite liquor.

The quantitative proportions of the peptizing component and of the component sulfonated so as to contain only at most 6 per cent. of sulfur may vary within wide limits according to the character of the tanning material and the plumping effect to be attained. When using a weakly sulfonated component sparingly soluble in water it is advantageous to use a large quantity of the .peptizing component.

The technical improvement which is the result of the process consists in the following: with the aid of the process it is possible to obtain tanning materials having a much larger proportion of substances of a plumping action (phlobaphenes) than has hitherto been usual; that it,,it is possible to prepare tanning materials having properties which are equal to those of the vegetable tanning materials not only with regard to the plumping action but also in view of the firmness and solidity of the leather. Moreover, this effect is attained in a particularlysimple manner. As compared with the introduction of a waterinsoluble phenol condensation product by peptization or condensation, the present invention has the advantage, apart from the improved properties, that it is not necessary to attain the formation of a uniform product, such as is necessary for a useful tanning process, by a complicated condensation or peptization; on the contrary the components are simply mixed at ordinary temperature and a tanning material 'having the properties described is thereby obtained.

The new tanning materials may also be combined with known vegetable tanning materials such as for instance quebracho or sumach.

The following examples serve to illustrate the invention, but they are not intended to limit it' u thereto; the parts are by weight:.

1. 110 parts of a condensation product "of the novolak type from cresol and formaldehyde are dissolved in 180 parts of anhydrous pyridine and parts of chlorosulfonic acid are caused to run into the solution'in the course of about 20 minutes at alow temperature (0 C. to 5 0.). The mass is then stirred for some time'at ordinary temperature (about 20 C.) The solid product contains between about 5 per cent and about 6 per cent of sulfur. As soon as a test portion dissolves in water to a clear solution, the fusedmaterial is mixed with 300 parts of water and such a quantity of caustic soda solution that the reaction of the solution obtained is just distinctly alkaline to phenolphthalein. The pyridine is then eliminated by blowing steam directly into the solution. On acidifying the solution of the weakly sulfonated phenol resin a resinous'precipitate is formed which, after removal of the -may directly be used for tanning. A full bodied leather is obtained.

2. 100 parts of cresol (commercial), '70 parts of formaldehyde and 55 parts of sodium sulilte (crystallized) are mixed and the mixture is kept gently boiling for about 8 to 10 hours, while continuously stirring. When a test portion of the syrupy mass is soluble in water to a clear solution, acidification of the aqueous solution precipitates a resin which can be redissolved in hot water free from the electrolyte; according to the concentration of the solution the resin separates again more or less completely in the cold. The solid product contains between about 5 per cent and about 6 per cent of sulfur.

The condensation product thus obtained is mixed with a sulfonation product which has been obtained as follows:

A mixture of '75 parts of phenol and parts of concentrated sulfuric acid is kept for 2 hours at 100 C. to 105 C.; after the mass has been allowed to cool to 30 C. to 40 C. 30 parts of formaldehyde (of 30 per cent. strength) are caused to run in within half an hour at this temperature, while well stirring; during this operation the viscosity of the mass considerably increases; the mass is then kept for a further half hour at 50 C.

The mixture of the two sulfonation products has an acid reaction; it is soluble in water-to a clear solution. By the addition of the quantity tity of alkali as is required for attaining the acidity suitable for tanning purposes, a tanning solution is obtained, with the aid of which leather -of water required for tanning and such a quanmay be produced which is of full body and of good firmness and solidity. An addition of vegetable extract is not necessary even when making sole leather.

3. parts ,of the dihydroxy-diphenyl-dimethyl-methane obtained by the'condensation of phenol and acetone are introduced at 65 C. to 70 C., while stirring well, into 150 parts of a crude mass of tetrahydronaphthalene-sulfonic acid obtained by the sulfonation of 130 parts of tetrahydronaphthalene by means of 110 parts of anhydride; 35 partsof concentrated sulfuric acid are then introduced into the viscous solution at ordinary temperature, while well stirring.

After the whole has been introduced, the temperature is kept at C. for one hour or until at test portion of the mass is soluble in hot water to'a clear solution and separates again in the cold. The solid product contains between about 5 per cent and about 6 per cent of sulfur. The weakly sulfonated phenol resin thus obtainedis mixed with the sulfonation component first named. The mixture is a homogeneous and viscous mass which is soluble in water to' a clear solution. The leather tanned therewith is of full body. The sole leather made with this product is not, inferior to that obtained with the aid of the vegetable tanning agents.

4. parts of cresol (commercial) are sulfonated with parts of concentrated sulphuric acid and into the sulfonation mixture thus obtained there are introduced at 60 C. to 70 C.

80 parts of a condensation product of 20 parts of e-naphthol, 40 parts of cresol and 35 parts of formaldehyde of 30 per cent. strength; in order to obtain the said condensation product the constituents named are mixed with 4 parts of sodium parts of cresol, 80 parts of formaldehyde and 60 parts of sodium sulfite. The mixture is a highly viscous syrupy substance, which dissolves in water to a clear solution and, like the tanning matters described above, is very well suitable for tanning sole leather without an addition of vegetable tanning material.

We claim:

1'. As new tanning agents mixtures containing a sulfonated condensation product of a-phenol with an aldehyde, said condensation product being obtained by sulfonation by means of asulfite and containing at most about 6 per cent. of sulfur, and a known synthetic tanning agent of the group consisting of sulfonated aromatic hydrocarbons and phenols of-high' molecular weight.

2. As new tanning agents mixtures containing I said condensation product being obtained by sulfonation by means of a sulfite and containing at most about 6 per cent. of sulfur, and a known synthetic tanning agent of the group consisting of sulfonated aromatic hydrocarbons and phenols of high molecular weight.

3. As new tanning agents mixtures containing a sulfonated condensation product of a phenol with an aldehyde, said condensation product being obtained by sulfonation by means of a sulfite and containing at least about 5 per cent. and at most about 6 per cent. of sulfur, and a known synthetic tanning agent of the group consisting of sulfonated aromatic hydrocarbons and phenols of high molecular weight.

4. As a new tanning. agent a mixture of a sulfonated watersoluble acid condensation. product of phenol. and formaldehyde with a sulfonated 'cresol-formaldehyd-e condensation product containing between about 5 per cent. and about 6 per cent. of sulfur and obtained by gently boiling a mixture of cresol, formaldehyde and crystalline sodium sulfite for about 8 to 10 hours.

ARTHUR VOSS. WALTER PENSE.