DE4421292A1 - Retanning of chrome-tanned leather - Google Patents

Abstract

Retanning chrome-tanned leather comprises applying a reaction prod. of (a) glycerol monoester of a satd. 12-18C monocarboxylic acid, (b) TDI, hexamethylene diisocyanate (HMDI) or isophorone diisocyanate (IPDI) and (c) dimethylolpropionic acid. The molar ratio NCO gps. of (b):OH gps. of (a)+(c) = 0.5-1.05, pref. 0.8-1.0. Molar ratio (c):(a) = 0.7-1.5, pref. 0.8-1.2; and the carboxyl gps. originating from (c) are at least partially neutralised.

Description

The invention relates to the use of certain ester urethanes for retanning of chrome-tanned leather. "Retanning" means post-treatment of pre-tanned (generally chrome-tanned) leather to add color, levelness, Softness, fullness and behavior against water (hydrophobicity), to optimize and Fix tannins.

The most important retanning agents today are alongside the group of so-called Syntane carboxyl group-containing polymers in salt form (EP-A-118 023 and 372 746, DE-OS 39 31 039). But also polyurethanes, if necessary Contain polyethylene oxide groups, ionic groups or methylol groups have already been used for retanning (DE-OS 25 04 081).

The retanning agents known to date do not meet all the expectations placed on them tations because they are either insufficiently hydrophobic or the handle, the color Availability, the loose grain or the subsequent finishing of the leather be disadvantageous influence. The multitude of desirable properties compel miss Retanning agents that give the leather optimum hydrophobicity are desirable lend (i.e. the leather as possible while maintaining the water vapor permeability make it impermeable to water), but grip, dyeability, loose grain and the appli do not adversely affect the decorability of the subsequent dressing.

Surprisingly, it has now been found that the use of polyether group pen-free ester urethanes of certain composition give the leather a happy Combination gives desirable properties.

The invention therefore relates to the use of reaction products

• a) at least one glycerol monoester of a saturated C ₁₂ -C ₁₈ monocarboxylic acid,
• b) at least one diisocyanate from the series tolylene diisocyanate, hexa methylene diisocyanate and IPDI (isophorone diisocyanate) and
• c) dimethylolpropionic acid (= 2,2-bis (hydroxymethyl) propionic acid),

wherein the amounts of components a) to c) are chosen so that the Molar ratio of the isocyanate groups of b) to the sum of the hydroxyl groups of a) and c) 0.5 to 1.05, preferably 0.8 to 1.0 and the molar ratio c / a 0.7 to 1.5, preferably 0.8 to 1.2 and the carboxyl groups originating from c) are at least partially neutralized, for retanning chrome-tanned leather.

The ester urethanes to be used according to the invention can, for example, be so be prepared that the glycerol ester a) with the diisocyanate b) and the resulting addition compound is reacted with the diol c). The neutralization of the Carboxyl groups of c) can take place before or after the reaction of c).

Suitable neutralizing agents include, for example, alkali and alkaline earths hydroxides, carbonates and bicarbonates, such as sodium hydroxide, potassium hydroxide, sodium carbonate and hydrogen carbonate, potassium carbonate, magnesium, Calcium and barium hydroxide, as well as ammonia, primary and secondary amines with 1 up to 30, preferably 3 to 18 carbon atoms, such as methylamine, ethylamine, n-propylamine, Isopropylamine, n-butylamine, isobutylamine, hexylamine, cyclohexylamine, Methylcyclohexylamine, 2-ethylhexylamine, n-octylamine, isotridecylamine, tallow fatty amine, Stearylamine, oleylamine, dimethylamine, diethylamine, di-n-propylamine, diisopropyl amine, di-n-butylamine, diisobutylamine, dihexylamine, dicyclohexylamine, dimethyl  cyclohexylamine, di-2-ethylhexylamine, di-n-octylamine, diisotridecylamine, ditallow fat amine, distearylamine, dioleylamine, ethanolamine, diethanolamine, n-propanolamine, Di-n-propanolamine and morpholine.

Preferably at least 50%, in particular at least 80%, of those from c) neutralized carboxyl groups.

The reactions can be carried out in the absence or presence of organic solvents occur. Preferred organic solvents are for the starting used compounds inert and include, for example, acetone, methyl ethyl ketone, tetra hydrofuran, dichloromethane, chloroform, perchlorethylene, ethyl acetate, dimethyl form amide and dimethyl sulfoxide.

The reaction of the compounds a) and b) can by cobalt naphthenate, Zinc octoate, preferably dibutyltin dilaurate or dibutyltin diacetate, and by tertiary amines such as triethylamine or 1,4-diaza [2.2.2] bicyclooctane are catalyzed the.

The ester urethanes to be used according to the invention can be dispersed in water be, for example, by using the neutralizing agent as an aqueous solution is added and the organic solvent which may be present is removed. The Ester urethanes are advantageously used as aqueous preparations with a Ester urethane content of 1 to 40% by weight in an amount of 0.2 to 10% by weight, based on fold weight and ester urethane.

The ester urethanes to be used according to the invention emerge from the liquor protruding on the leather and make the leather hydrophobic and soft as well as scars solid without adversely affecting the dyeability.

The percentages in the following examples relate to the folding Weight, the dilution ratios are based on weight. All Commercial products (unless specifically marked) are commercial products from Bayer AG, Leverkusen.  

Examples Preparation of an ester urethane to be used according to the invention

A heatable, 500 ml three-necked round bottom flask serves as apparatus Stirrer, reflux condenser with drying tube and dropping funnel is provided.

17.9 g glycerol monostearate (0.05 mol) are placed in the flask. Successively 45 mg of dibutyltin diacetate, 50 ml of anhydrous acetone and 14.72 ml (17.9 g) are added Toluene diisocyanate-2.4 / -2.6 (ratio 80/20) (0.1028 mol). Well now Heated to boil for 30 minutes. Then allowed to 11.75 g of Triethylamine salt of 2,2-bis (hydroxymethyl) propionic acid (0.05 mol), dissolved in 50 ml of anhydrous acetone, added dropwise within 10 minutes. After one hour Reaction time under reflux, the formation of the ester urethane is complete. The solution is clear, moderately viscous and slightly yellow in color. For dispersing are now under Maintaining a weak reflux of the acetone 250 ml deionized water dripped. After removal of the acetone by vacuum distillation, an approx. 17% clear solution of the ester urethane.

example 1 Automotive upholstery leather from wet blues a) Comparison

2.4 kg of a folded, chrome-tanned leather (fold thickness 1.1 mm) are included 250% (based on fold weight) water of 40 ° C, 0.5% (an 8.5% aqueous formic acid), 0.1% of a neutral emulsifier (®Baymol AN liquid, which had been diluted 1: 5 with water) and 2% of a lightfast Treated tannin (®Tanigan 3 LN) for 30 minutes. After draining the Broth is rinsed with 300% water at 40 ° C for 10 minutes and the liquor drained again. The actual retanning begins with 150% water from 40 ° C, 1% of a 33% basic chrome tanning agent (®Chromosal B) and 3% a neutralizing chromium syntan mixed tanning agent (®Blancorol RC). To 45% are given 7% ®Chroinopol AFS (Stockhausen) (previously 1: 4 with  Water), runs for 30 minutes and adds another 1.5% a neutralizing synthetic tanning agent (Tanigan PAK-N), 4% one lightfast replacement tanning agent (Tanigan LD-N) and 3% of one Resin tannin (®Retingan R7) and treated for another 15 minutes. In this comparative example is now with 2% of an acrylate tanning agent (®Baytigan AR, previously diluted 1: 3 with water) 45 minutes treated long. The liquor pH is 5.3. Then add 1.5% Add sodium formate and 0.5% sodium carbonate, another 40 minutes run (liquor pH now 6.1). The cut of the leather with chrome cresol green is now blue. It is left for 40 minutes, washed with 300% warm 44 ° C. Water for 10 minutes, drains again and now begins to color:

30% water of 25 ° C and 0.8% ammonia (25% aqueous solution, the 1: 5 previously diluted with water) 5 minutes, gives one Mixture of 2% of a lightfast dispersing auxiliary tanning agent (®Baykanol SL), 3% of a lightfast yellow metal complex dye (®Baygenal beige L-NGR) and 0.3% of a lightfast metal complex color fabric (Baygenal gray L-NG) and let it run for 30 minutes. Then you give 10% Chromopol AFS (which had previously been diluted 1: 4 with water), after 30 minutes, add 150% water at 70 ° C, after another 5 minutes again 2% Baytigan AR (previously diluted 1: 3 with water ) after 30 minutes 2.5% formic acid (85% aqueous solution, which had been diluted 1:10 and 1.25% in two installments) was for 20 minutes (liquor pH now 4.12) and drains the liquor. After that washed again (with 300% water at 40 ° C) and after 10 minutes open lid rinsed with water at 25 ° C for 10 minutes. The leather are now removed, stretched wet and dried, air-conditioned, tunneled, grilled and excited and then judged.

b) according to the invention

Instead of the Baytigan AR, the one to be used according to the invention is used Esterurethan and otherwise leaves all other process parameters constant. The Assessment of the two leathers revealed:  

The leather made according to the state of the art is not quite as soft as the invention; the scar throw of the invention is clear better than that of the prior art. If you look at the leather after State of the art drops a drop of water, then it immediately sinks into the Leather, while it takes some time for the brown leather according to the invention Time slowly penetrates underground.

Example 2 Split leather a) Comparison

8 wet-blue split halves with a thickness of 1.3 mm, which have been chrome-tanned were washed in water at 50 ° C (200%) for 10 minutes and the Fleet discarded. Then you give 100% (based on fold weight) of water of 40 ° C, adds 2% of a neutralizing, synthetic tanning agent (Tanigan PAK-N) and 0.5% sodium bicarbonate and leaves another 90 Minutes run. The pH at this point is 5.82%.

Pre-greasing begins with 2% of a synthetic fat (®Coripol DX 902 (Stockhausen), which had previously been diluted 1: 4 with water) and runs 15 minutes. Then you tan after:

2% of a partially neutralized polyacrylic acid (Baytigan AR, previously 1: 3 with Water had been diluted) are added, and 1.5% of an acid Polyetheresters (®Levotan C). After 45 minutes, 6% become one synthetic, lightfast exchange tanning agent (Tanigan LD-N) added and Let it run for 15 minutes. The pH at that point is 5.36. Then there 0.5% formic acid (85%, previously diluted 1:10 with water ) and run for 15 minutes and drain the fleet; pH 4.6. Man washes with 200% water at 60 ° C for 10 minutes and discards the liquor. Then it is greased: 100% water (60 ° C), 6% of a lightfast synthetic Grease it (Coripol DX 902) mixed with 1% of a synthetic Claw oil replacement product (Coripol ICA) are allowed to run for 45 minutes. Of the  pH is 4.62. Then 1.5% of an acrylate binder (®Euderm Reason 25A, which had previously been diluted 1: 4 with water) and acidified after 30 minutes with 0.5% formic acid (85%, 1:10 with water had been diluted). After 20 minutes, a pH of 4 is established.

It is rinsed with water at 20 ° C. for 5 minutes and the leather can then be removed to take. After vacuum drying for 3 minutes at 70 ° C Dried leather hanging. You air-conditioned, run, ventilate and run again after.

Part of the leather is then coated with a ®Levacast coating (2-component reactive coating with the reverse process of leather with With the help of an isocyanate prepolymer and a partially blocked, oligomeric hardener in methyl ethyl ketone solution).

b) according to the invention

The example is repeated. Here, instead of the partially neutralized poly acrylic acid (Baytigan AR) 3.5% of the ester to be used according to the invention taken urethans.

The split leather that has been manufactured according to the state of the art and according to 24 hours was tested, was significantly harder than that of the invention. The same leather then coated with Levacast showed after 24 hours in the invention a better scar throw than in the leather after the state of the art. The scar throw is the behavior when you fold the leather: a good scar throw is characterized by the fact that the Wrinkles of leather only small wrinkles occur.

The leather that was made according to the state of the art is more hydrophilic than the invention. With state-of-the-art leather a drop of water immediately sinks into the substrate; manufactured according to the invention Leather holds the drop of water for a long time. Surprisingly, this one Effect but no negative influence on the adhesion of the later coating.

Claims (2)

Use of implementation products

• a) at least one glycerol monoester of a saturated C₁₂-C₁₈ monocarboxylic acid,
• b) at least one diisocyanate from the series tolylene diisocyanate, hexamethylene diisocyanate and IPDI and
• c) dimethylolpropionic acid,

wherein the amounts of components a) to c) are chosen so that the Molar ratio of the isocyanate groups of b) to the sum of the hydroxyl groups of a) and c) 0.5 to 1.05 and the molar ratio c / a 0.7 to 1.5 and that from c) originating carboxyl groups are at least partially neutralized, for retanning chrome-tanned leather.