DE3515402A1 - Process for the stabilisation of concentrated liquid resinous tanning agent solutions - Google Patents

Abstract

Solutions of resinous tanning agents, which have been obtained by condensation of nitrogen-containing organic compounds, aromatic sulphonic acids and aldehydes, can be stabilised by adding certain amide compounds after condensation is complete.

Description

"Process for stabilizing concentrated liquid resin tanning

fabric solutions Among the synthetic tanning agents are resin tanning agents, the condensation of nitrogenous organic compounds with lower ones Aldehydes are produced, one of the most important and economically important Groups represent. They are mainly used as combination tanning agents and retanning agents used in conjunction with mineral tanning agents.

Such resin tanning agents have gained particular importance by Mixed condensation of nitrogen-containing compounds, especially dicyandiamide and melamine with lower aldehydes such as formaldehyde, with the addition of salts more aromatic Sulfonic acids are obtained.

Such products are described in German patents 1 183 683, 1,495,092, 1,720,269 and 1,720,270. They are characterized by the fact that they give the leather softness, body and strength.

For the production of condensation products of the type mentioned goes is preferably made from mixtures of dicyandiamide and melamine, one of these Components also completely or partially through urea or urea derivatives, such as ethylene urea or cyanamide can be replaced. The aldehyde is used in particular Formaldehyde, but other aldehydes such as acetaldehyde or formaldehyde also come emitting substances into consideration. Instead of melamine, its substitution products, such as B. alkylmelamines, alkylolmelamines, melam, melem, melon or similar acting Triazine derivatives such as ammelide, ammeline and the like can be used.

The aromatic sulfonic acids are preferred as neutral alkali salts, z. B. sodium salts are used. Examples are the alkali salts of benzenesulfonic acids, Phenolsulfonic acids, naphthalenesulfonic acids, sulfonated phenol-formaldehyde condensates, sulfonated dioxydiphenylmethane, sulfonated dioxydiphenylpropane, sulfonated Dioxydiphenolsulfonen, Dinaphthylmethanedisulfonsäure, Dihydroxydinaphthylmethanedisulfonsäure. All or some of the sulfonic acids mentioned can be replaced by lignosulfonic acids will.

The condensation takes place in a concentrated, preferably 40-65 percent aqueous solution, at 70 - looOC, where, for example, o, 35 -o, 6 mol of dicyandiamide, 0.4-0.65 moles of melamine, 2.5-4.5 moles of formaldehyde and 0.2-0.4 moles of neutral alkali salts aromatic sulfonic acids or 23.5 - 32.5 percent by weight, based on anhydrous Mixture of lignosulfonic acid salts are used.

The condensation products are not storage-stable in aqueous solution, which is why the resulting resin solutions by conventional methods, for. B.

by evaporation in a vacuum, by evaporation on the drying roller, or must be converted into dry, storable powder by spraying. These powders must be redissolved before they can be used.

It has now been found that the drying process and the later Redissolution of the products can be avoided if one uses the aqueous resin solutions by adding certain nitrogen-containing compounds immediately after Stabilized condensation and cooling. This gives you a highly concentrated one Product in dissolved form, compared to the powder product in terms of application technology Has advantages with otherwise unchanged good tanning properties.

The invention thus provides a process for stabilizing aqueous resin tanning solutions based on mixed condensates of nitrogen-containing organic compounds, neutral salts of aromatic sulfonic acids and lower aldehydes, characterized in that, after the condensation has ended and cooling to a temperature below 40 ° C, 50 - 300 g / l, based on the aqueous condensate solution, of a compound of the general formula or R1 = aryl, C1-C4-alkyl, NHR3 R2 = H, C1-C4-alkyl, CN R3 = H, C1-C4-alkyl, CN X = 0, NH, S added.

Suitable stabilizers are preferably urea, thiourea, Ethylene urea, benzamide, acetamide and their mixtures.

While non-stabilized resin solutions already after a few hours gel for days, the products stabilized in the specified manner also retain them their liquid consistency if stored for a longer period of time, although only a gradual one Increase in viscosity is observed.

The resin solutions are tanned in the usual way, preferably in combination used with mineral tanning agents, especially chrome tanning agents. The resins are in a narrow pH range between 4.2 and 5.2 can be precipitated by acid, whereby storage in the leather, especially during retanning after chrome tanning, Well controls. The resin tanning agents are used for all types of tanning of hides such as cattle hides, calf, sheep and goat skins, as well as wild hides and furs, usable.

Examples 1. Preparation of an unstabilized resin solution 64.3 Parts by weight of formal in (30%), 18.2 parts by weight of dinaphthylmethanedisulfonic acid Na salt, 10.4 parts by weight of melamine and 7.1 parts by weight of dicyandiamide are at pH of 7.6 (adjusted with 2N NaOH) and a temperature of 9o - 950C condensed. The condensation is terminated when 5 ml of codensate solution dissolved in 50 ml of distilled Water, titrated with 6.5 ml n / lo HCl, result in a turbidity. The condensation will stopped by cooling to approx. 40 ° C and the pH was adjusted to 8.5 - 9.0.

2. Preparation of the stabilized resin solution In the one described under 1) Condensate solution becomes a stabilizer according to the invention in an amount of 10 or 20% by weight immediately after the end of the condensation process stirred in. The stabilizing effect of the additives is shown in Table 1.

TABLE 1 Vers.-No- Stabilizer additive viscosity at 25 ° C after - days% by weight 4 13 34 41 80 110 1 without gelled 2 urea 10 25 27 - 49 143 320 3 urea 20 18 18 - 22 34 67 4 thiourea 10 23 28 - 83 gelled 5 thiourea 20 18 19 - 31 gelled 6 ethylene urea 10 26 - 41 - 95 259 7 Ethylene urea 20 19 - 19 - 21 27 8 Benzamide 10 - 140 - 140 600 - 9 acetamide 10 20 24 33 - 110 - 10 acetamide 5) # 18 19 21 - 70 - Urea 5) 11 benzamide 5) # - 210 220 - - gelled Urea 5) (Viscosity measured in seconds in a 4 mm Ford cup) Example 3 Neutralized and washed wet-blue cowhide leather with a fold thickness of 1.6-1.7 mm was obtained in a barrel for 45 minutes at So0C with a retanning liquor of 100% by weight water ( based on leather weight) and 4% by weight of the respective resin tanning solution (calculated as dry substance). After adding 0.5% by weight of formic acid to this liquor, retanning was carried out for a further 15 minutes. This was followed by greasing with a new liquor of 100% by weight of water and 7% by weight of a commercially available upper leather oiling agent for 45 minutes at 50.degree. The leather quality was assessed after the usual drying by a group of examiners who had to assign grades between 0 = unsatisfactory and lo = very good.

The results shown in Table 2 in rounded form are, show that the tanning properties of the resin tanning agents by the Stabilization cannot be adversely affected.

TABLE 2 (for example 3) Leather properties 1 2 3 6 7 Hand / softness 8 7 8 9 7 fullness 8 7 8 8 7 tightness of grain 8 8 8 8 8 shade (own color) 8 8 8 8 8 Example 4 Neutralized and washed wet-blue cow leather upper with a Seam thickness of 1.5 mm was retanned, colored and in several steps in the barrel greased. Retanning and dyeing were carried out one after the other in a liquor at So 0C (data in percent by weight, based on leather weight): fleet and additives Duration 100% by weight water 1% by weight naphthalenesulfonic acid-Na 15 minutes 1% by weight of dye 15 minutes 4% by weight of resin tanning agent 45 minutes (calculated as solids) 3 wt .-% phenol condensate 40 minutes (additional tanning agent) The fat was then with a new liquor of 100% by weight of water and 7% by weight of a conventional upper leather oiling agent carried out at So0C within 60 minutes, with 0.5% by weight after 45 minutes Formic acid was added.

The drying and the assessment of the leather quality were carried out as in example 3; Table 3 shows the rounded results. Here, too, it becomes clear that by stabilizing the liquid concentrated resin tanning solution the Leather quality is practically not degraded.

TABLE 3 (for example 4) Designation Properties 1 8 11 Hand / softness 8 8 8 fullness 8 8 8 tightness of grain 8 7 7 shade 8 8 8 rating: lo = very good - 0 = insufficient

Claims (3)

Claims 1. A process for stabilizing aqueous resin tanning solutions based on mixed condensates of nitrogen-containing organic compounds, neutral salts of aromatic sulfonic acids and lower aldehydes, characterized in that, after the condensation has ended and cooling to a temperature below 40 ° C, 50-300 g / l , based on aqueous condensate solution, of a compound of the general formula or R1 = aryl, C1-C4-alkyl, NHR3 R2 = H, C1-C4-alkyl, CN R3 = H, C1-C4-alkyl, CN X = 0, NH, S added. 2. The method according to claim 1, characterized in that as Stabilizer urea, thiourea, ethylene urea, benzamide, acetamide or whose mixtures are used. 3. Stabilized resin tanning solution based on mixed condensates from nitrogen-containing organic compounds, neutral salts of aromatic sulfonic acids and lower aldehydes, characterized by a content of a compound (I) or (II) of claim 1 in an amount of 50-300 g / l, based on the aqueous condensate solution.