EP0648846A2 - Retans with softening and hydrophobic action - Google Patents

Abstract

Copolymers containing incorporated radicals of long-chain alcohols and neutralised carboxyl groups are suitable for use as retans for leather. They produce an excellent combination of hydrophobicity, softness and firm grain.

Description

The invention relates to improved retanning agents for producing soft hydrophobic leather.

While the tanning leads to an increase in the shrinking temperature of the leather, the retanning has hardly any influence. "Retanning" means the aftertreatment of pre-tanned (generally chrome-tanned) leather in order to optimize color, levelness, softness, fullness and the behavior against water (hydrophobicity) and to fix tannins.

The most important retanning agents today are, in addition to the group of so-called syntans, carboxyl group-containing polymers in salt form (EP-A-118 023 and 372 746, DE-OS 39 31 039). But polyurethanes, which may 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 of the expectations placed on them because they either insufficiently hydrophobize or adversely affect the feel, the dyeability, the solid grain or the subsequent finishing of the leather. The multitude of desirable properties requires a compromise. Retanning agents are desired which give the leather an optimal hydrophobicity (i.e. make the leather as water-impermeable as possible while maintaining its water vapor permeability), but with a feel, dyeability, solid grain and do not adversely affect the applicability of the subsequent dressing.

It has now surprisingly been found that the use of certain copolymers which contain built-in residues of long-chain alcohols and neutralized (and optionally free) carboxyl groups gives a happy combination of hydrophobicity, softness and firmness.

• (A) Terpolymerisat mit als Zahlenmittel bestimmten Molekulargewichten $\overline{\text{M}}$
  
  _n von 5000 bis 60 000 aus
  • a) Maleinsäureanhydrid,
  • b) 80 bis 120 Mol-%, bezogen auf Komponente a), Diisobutylen und
  • c) 1 bis 12 Mol-%, bezogen auf Komponente a), mindestens eines Monomeren der Formel
    
     worin

  R¹

  Wasserstoff oder Methyl,

  R²

  Wasserstoff, Methyl, Ethyl, -OR³,

  

  

  gegebenenfalls durch C₁-C₄-Alkyl substituiertes Phenyl oder Hydroxymethyl und

  R³

  C₁-C₄-Alkyl bedeuten,

• (B) aliphatischem und/oder cycloaliphatischem einwertigem C₆-C₂₄-Alkohol und
• (C) Base,

wobei 20 bis 80, vorzugsweise 30 bis 75 % der den Anhydridgruppen des Terpolymerisats entsprechenden Carboxylgruppen mit Alkohol (B) verestert und mindestens 20 % der restlichen Carboxylgruppen mit Base (C) neutralisiert sind, als Nachgerbstoff für Leder.The invention therefore relates to the use of reaction products

• (A) Terpolymer with molecular weights determined as number average $\overline{\text{M}}$
  
  _n from 5000 to 60,000
  • a) maleic anhydride,
  • b) 80 to 120 mol%, based on component a), diisobutylene and
  • c) 1 to 12 mol%, based on component a), of at least one monomer of the formula
    
  wherein

  R¹

  Hydrogen or methyl,

  R²

  Hydrogen, methyl, ethyl, -OR³,

  

  

  phenyl or hydroxymethyl optionally substituted by C₁-C₄-alkyl and

  R³

  Are C₁-C₄ alkyl,

• (B) aliphatic and / or cycloaliphatic monohydric C₆-C₂₄ alcohol and
• (C) base,

wherein 20 to 80, preferably 30 to 75% of the carboxyl groups corresponding to the anhydride groups of the terpolymer are esterified with alcohol (B) and at least 20% of the remaining carboxyl groups are neutralized with base (C) as a retanning agent for leather.

Maleic anhydride (monomer a) and diisobutylene (monomer b) usually polymerize alternately. In the presence of a third comonomer c), alternating copolymers are also formed, the molar ratio of a: (b + c) in the copolymer being about 1: 1.

Preferred monomers c) include, for example, styrene, α-methylstyrene, p-methylstyrene, vinyl acetate, allyl acetate, isobutyl vinyl ether, allyl alcohol and methallyl alcohol.

Terpolymers from a), b) and c) are known; see. e.g. DE-OS 27 01 760. They can be prepared by free-radically initiated polymerization. The polymerization takes place in an organic solvent which is inert under polymerization conditions, in particular in an aromatic solvent such as toluene or xylene

Suitable radical formers include, for example, diacyl peroxides such as diacetyl peroxide, dibenzoyl peroxide, di-p-chlorobenzoyl peroxide, peroxy esters such as tert-butyl peroxyacetate, tert-butyl peroxybenzoate, dicyclohexyl peroxydicarbonate, alkyl peroxides such as bis- (tert-butyl) doxyperyl peroxybutyl peroxy butyl peroxide Hydroperoxides such as cumene hydroperoxide, tert-butyl hydroperoxide, ketone peroxides such as cyclohexanone hydroperoxide, methyl ethyl ketone hydroperoxide, acetylacetone peroxide or azoisobutyrodinitrile. The usual amounts are 0.01 to 5% by weight, preferably 0.1 to 3% by weight, based on the sum of the monomers a), b) and c) to be polymerized.

The reaction of the terpolymers A with the alcohols B can take place either directly in the solution of the terpolymers A or after isolation of the solid terpolymers A in bulk, solution or suspension. The reaction can be carried out at temperatures from 60 to 180, preferably 80 to 140 ° C.

Primary and secondary alcohols B are preferred. Suitable representatives include, for example, n-hexanol, cyclohexanol, n-octanol, 2-ethylhexanol, n-dodecanol, n-tetradecanol, n-hexadecanol, stearyl alcohol, eicosanol and behenyl alcohol or mixtures thereof.

The reaction can be carried out in the absence or presence of an acid catalyst. Suitable as such are, for example, mineral acids such as sulfuric acid or anhydrous hydrogen chloride, aliphatic and aromatic sulfonic acids such as methanesulfonic acids and p-toluenesulfonic acid, fluorinated aliphatic carboxylic acids such as perfluorobutanoic or -octanoic acid, and acidic ion exchangers. If esterification is carried out in the presence of an acidic catalyst, it is advantageous to remove the water of reaction in a water-immiscible organic solvent, such as e.g. Toluene or xylene to work and separate the water of reaction formed azeotropically. In the case of esterification in the absence of a catalyst, the anhydride groups mainly give the half ester, and in the case of acid-catalyzed esterification mixtures of half and diesters of the dicarboxylic acid residues.

Base C is added to convert the esterification products obtained into a water-soluble or - dispersible form - preferably as an aqueous solution. Suitable bases C include, for example, alkali metal hydroxides and alcoholates as well as ammonia and primary, secondary and tertiary aliphatic amines with up to 6 carbon atoms per molecule (which can carry up to 1 hydroxyl group per alkyl radical), in particular sodium and potassium hydroxides and ammonia, ethylamine, Propylamine, n-butylamine, diethanolamine, dimethylamine and triethylamine. Base C can be added to the polymer melt or solution or dispersion. The amount of base C is such that at least 20% of the carboxyl groups remaining after the esterification reaction are converted. It is possible to convert all remaining carboxyl groups; however, it can also be advantageous to neutralize only 20 to 80% of the remaining carboxyl groups (in this connection, anhydride groups which have not been converted in the esterification reaction should be formally counted as 2 carboxyl groups). When residual anhydride groups are reacted with alkali lye, the corresponding carboxylates are formed, while with ammonia, primary and secondary amines the half-amide / half-ammonium salts and with tertiary aliphatic amines usually the di-ammonium salts (each based on 1 original anhydride group) can be obtained. The reaction with base C produces aqueous solutions or dispersions which may still contain organic solvents. They can be used directly as such or after removal of the solvent for retanning leather. In particular, they are suitable for everyone from chrome leather (cow, goat, pig, etc.).

The aqueous solutions or dispersions obtained are preferably used on neutralized wet blue material, i.e. on chrome leather, which has been adjusted to a pH of 4 to 7, preferably 5.5 to 6.5, by means of conventional neutralizing agents (e.g. sodium bicarbonate, formate, etc.) or neutralizing tanning agents. In general, amounts of 0.5 to 8, preferably 1 to 4, in particular 1 to 2,% by weight, calculated as dry matter and based on the wet-blue fold weight, are used.

In the further course of retanning, the neutralized wet blue material can possibly be treated with commercially available retanning agents (replacement, white, resin and polymeric tanning agents), vegetable tanning agents and fatliquoring agents. If you want to produce dyed leather, you dye with dyes. In addition, it is also possible to use the solutions or dispersions on purely vegetable-tanned leathers for retanning before dyeing and greasing.

The aqueous solutions or dispersions obtained can also be used in other stages of retanning, e.g. after treatment with replacement, white or vegetable tannins.

The leather retanned according to the invention is notable for a very soft and full grip, as well as good grain strength and grain smoothness, and has a clear pigmentation. Because of their high lightfastness and good thermal resistance to yellowing, they are ideal for producing light-colored leather. In addition, the leather retanned with the dispersions according to the invention show water-repellent properties.

The following examples show the preparation of the aqueous solutions or dispersions to be used according to the invention and their use in different formulations for retanning various types of leather.

Unless stated otherwise, the percentages in the examples below relate to the weight. Unless otherwise stated, mixing and dilution ratios also relate to the weight.

Examples A. Production of retanning agents 1. Retanning agents I

_n von 15.000 aufweist, und gibt dazu 378 g Toluol sowie 57,0 g eines Fettalkoholgemisches, bestehend aus aliphatischen Monoalkoholen mit linearen Alkylketten mit einer Kettenlänge zwischen 12 und 18 C-Atomen. Unter Rühren und Überleiten von N₂ wird das Reaktionsgemisch auf 80°C erhitzt und 24 Stunden bei dieser Temperatur gehalten. Zu der entstandenen klaren Lösung gibt man unter weiterem Rühren eine Lösung von 30 g NaOH in 1200 ml Wasser, wobei sich eine relativ viskose Emulsion bildet. Aus dieser Emulsion wird unter vermindertem Druck bei 50 bis 60°C das Lösungsmittel abdestilliert. Zurück bleibt eine feinteilige Emulsion mit einem Feststoffgehalt von 12,7 Gew.-%.In a 1 liter three-necked flask equipped with a stirrer and reflux condenser, 105 g of a terpolymer of maleic anhydride, 2,4,4-trimethylpentene-1 and styrene, which has a molecular weight, are placed $\overline{\text{M}}$

_n of 15,000, and adds 378 g of toluene and 57.0 g of a fatty alcohol mixture consisting of aliphatic monoalcohols with linear alkyl chains with a chain length between 12 and 18 carbon atoms. While stirring and passing N₂, the reaction mixture is heated to 80 ° C and held at this temperature for 24 hours. A solution of 30 g NaOH in 1200 ml water is added to the resulting clear solution with further stirring, a relatively viscous emulsion being formed. The solvent is distilled off from this emulsion under reduced pressure at 50 to 60 ° C. What remains is a finely divided emulsion with a solids content of 12.7% by weight.

2. Retanning agent II

_n = 15.000) eingesetzt werden. Zur Herstellung der wäßrigen Emulsion gibt man zur Lösung des veresterten Polymeren eine Lösung von 20 g NaOH in 2300 g Wasser. Nach Abdestillieren von Toluol unter Vakuum erhält man eine feinteilige Emulsion des Nachgerbmittels II mit einem Feststoffgehalt von 9,5 Gew.-%.The retanning agent II is prepared in a similar manner to that described in Example 1, with the difference that 127.4 g of a C₁₄-C₂₂-alkanol mixture (composition: 2% c₁₄, 51 ± 4% C₁₆, 28 ± 4%) C₁₈, 14 ± 4% C₂₀, 3% C₂₂) for the esterification of the terpolymer from maleic anhydride, 2,4,4-trimethylpentene (1) and styrene ( $\overline{\text{M}}$

_n = 15,000) can be used. To prepare the aqueous emulsion, a solution of 20 g of NaOH in 2300 g of water is added to the solution of the esterified polymer. After toluene has been distilled off under vacuum, a finely divided emulsion of retanning agent II with a solids content of 9.5% by weight is obtained.

3. Retanning agent III

_n = 20.000).The following reaction mixture is introduced into a 2 l three-necked flask with stirring and passing over N₂:
178 g toluene
170 g diisobutylene (technical mixture of 75-80% by weight 2,4,4-trimethylpentene-1 and 20-25% by weight 2,4,4-trimethylpentene-2)
102 g maleic anhydride
After heating to 75 ° C, the following solution is pumped into the reaction mixture via a metering pump within 4 hours:
4 g of azoisobutyronitrile
50 g toluene
While the initiator solution is being pumped in, the reaction temperature is increased continuously from 75 to 95.degree. 30 minutes before the end of metering, 6 g of styrene are added to the polymerization solution at once. The mixture is then stirred for a further 6 hours at 95 ° C ( $\overline{\text{M}}$

_n = 20,000).

After cooling to 80 ° C, 178 g of a C₁₂-C₁₈ fatty alcohol mixture and 400 g of toluene are added to this solution and esterified at 80 ° C for 24 hours. A solution of 51.9 g of NaOH in 1500 ml of water is then added to this polymer solution and the toluene is distilled off from the resulting emulsion at 50-60 ° C. under reduced pressure. The remaining aqueous emulsion of retanning agent III has a solids content of 15.7% by weight.

4. Retanning agents IV

The retanning agent IV is prepared in a similar manner to the retanning agent III, with the difference that the solution of the terpolymer is reacted with the following mixture:
237 g C₁₂-C₁₈ fatty alcohol mixture
650 g toluene.

After esterification at 80 ° C. for 24 hours, a solution of 41.6 g of NaOH in 2000 g of water is added to this solution with stirring, an emulsion being formed. After the toluene has been distilled off under reduced pressure at 50-60 ° C., a finely divided emulsion having a solids content of 20.7% by weight is obtained.

B. Application Example 1: Production of white furniture leather

To produce furniture leather, 50 kg are chrome-tanned and folded to 1.2 to 1.4 mm wet blues in the tanning drum in the usual manner, first in 250 to 350% water (based on the shaved weight, like all the following% data) of 40 ° C and addition of 0.3 to 0.5% formic acid (85%, 1:10 diluted with water) and 2.0% of a lightfast commercial white tanning agent for 30 minutes. The pH of the fleet is around 3.8. The liquor is drained and then washed in 300% water at 40 ° C for 10 minutes.

After draining the liquor, after-chroming in 150% water at 40 ° C with 1% of a commercially available chrome tanning agent and 3% of a commercially available, self-dulling chromium-syntan mixed tanning agent, greased with 7% of a commercially available synthetic greasing agent in 30 minutes and then 1.5% of a commercially available, light-fast neutral tanning agent, 4.0% of a commercially available white tanning agent and 3.0% of a commercially available resin tanning agent were added.

After a running time of 15 minutes, 1%, based on dry substance, of dispersion IV according to the invention is added as a 20.7% setting and the mixture is left to run for a further 45 minutes.

The liquor pH is around 5.2.

1.5% sodium formate and 0.5% sodium bicarbonate are added (liquor pH: approx. 6.1) and the liquor is drained after 40 minutes. The leathers are then washed with 300% water at 40 ° C. for 10 minutes, greased and finished in the usual manner (stretched, wet stretched and dried, air-conditioned, stollen, milled and stretched).

The resulting leathers are of good fullness and softness and are characterized by excellent grain smoothness. The light fastness is level 5 to 6 (xeno test) and the heat yellowing (24 hours, 120 ° C) is level 3 to 4 (gray scale).

Example 2: Production of colored car upholstery leather

For the production of car upholstery leather, 50 kg of chrome-tanned and blown to 1.1 to 1.3 mm wet blues in the tanning drum as described in Example 1 are washed, washed with formic acid, pretanned with a white tanning agent, washed again, retanned with chrome, greased and retanned with 1.5% (based on shaved weight, like all the following% data) of a commercially available neutralization tanning agent, 4.0% of a commercially available replacement tanning agent and 3% of a commercially available resin tanning agent.

After a running time of 15 minutes, 1.5%, based on dry substance, of dispersion III according to the invention is added as a 15.7% setting and the mixture is left to run for a further 45 minutes.

The liquor pH is around 5.0. The pH is raised to approximately 6.0 by adding 1.5% sodium formate and 0.4% sodium bicarbonate and the liquor is drained after 40 minutes.

After washing for 10 minutes in 300% water at 40.degree. C. and draining the liquor, the dyeing is carried out in 30% in 30% water at 25.degree. C. with the addition of 1.0% of a commercial dyeing aid with 5.0% of a mixture of commercial leather dyes .

After adding 10% of a synthetic fatliquor, fat is applied for 30 minutes. Then 150% water at 70 ° C is added and after 5 Minutes the dye was fixed by adding 2.5% formic acid (85%, 1:10 diluted with water, addition in 2 installments). The liquor pH is around 4.0.

After draining the liquor, it is washed with 300% water at 40 ° C., rinsed at 25 ° C. for 10 minutes and then the leather is finished in the normal manner.

The resulting leathers are of good fullness and softness and are characterized by excellent smooth scars with fine mill grain.

Example 3: Production of upper leather

For the production of upper leather, 35 kg of chrome-tanned and folded to 1.6 to 1.7 mm wet blues in the tanning drum are initially in 200% water (based on fold weight, as follows all%), from 50 ° C and 0.4% formic acid (85%, TAPE 2, 1:10 diluted with water) for 15 minutes. After draining the liquor is neutralized in 100% water at 40 ° C with 2% of a commercial neutralization tanning agent and 0.8% sodium bicarbonate. After 45 minutes of neutralization, the liquor pH is approx. 5.2.

Then 1.5%, based on dry substance, of dispersion I according to the invention (see preparation example 1) is added as a 12.7% setting and the mixture is left to run for 30 minutes. The liquor pH is around 5.0.

3% of a commercially available replacement tanning agent, 4% quebracho and 1.5% dye are added and after a running time of 90 minutes with 0.5% formic acid (85%, 1:10 diluted with water) to a pH of approx. 4. 2 acidified.

After draining the liquor, grease in 100% water at 50 ° C, acidified again with formic acid to a pH of 3.9 and draining the liquor again. After rinsing in water at 25 ° C for 10 minutes, the leathers are stretched out in a customary manner, vacuum and hanging-dried, air-conditioned, rolled and vacuum-dried again (1/2 minute at 70 ° C). The resulting leathers are characterized by uniform dyeability with a full, soft feel and good firm grain.

Example 4: Production of split leather

To produce split leather, 25 kg of chrome gaps produced in the usual way (gap thickness approx. 1.3 mm) are washed in 200% water (based on gap weight like all the following information) at 50 ° C. for 10 minutes.

After the liquor has been drained, it is neutralized in 100% water at 40 ° C. with 2% of a commercially available neutralizing tanning agent and 1.5% sodium bicarbonate to a pH of approximately 5.8 over 90 minutes.

After pre-greasing with 2% of a synthetic fatliquoring agent for 15 minutes, 1.2%, based on dry matter, of the dispersion II according to the invention from preparation example 2 is added as a 9.5% setting and the split leather is drummed for 45 minutes.

Then 6.0% of a commercially available white tanning agent is added and after 45 minutes the pH of about 5.5 by adding 0.5% formic acid (85%, 1:10 diluted with water) to about 15 minutes 4.5 lowered.

After draining the liquor, the leathers are washed in 200% water for 10 minutes at 60 ° C and greased in 100% water at 60 ° C with 7.0% of a commercially available fat mixture.

The liquor pH is around 4.5.

It is now possible to add 0.5%, based on dry matter, of the above-mentioned dispersion to achieve greater fullness and softness in the fat.

Finally, the leathers are acidified to a pH of approx. 4.0 by adding 0.5% formic acid (85%, 1:10 diluted with water). The leathers are rinsed in the customary manner (water at 20 ° C., 5 minutes), stretched out, vacuum and hanging dried, air-conditioned, stollen, aired, rerolled and again vacuum dried (1/2 minute, 70 ° C.).

The resulting gaps have a very high degree of whiteness and are characterized by a soft full grip, with the velor side having a soft, uniform short cut.

Example 5: Production of clothing nappa

To produce clothing nappa, 20 kg of New Zealand sheep wet blue are washed in 200% water (based on shaved weight, like all the following information) at 40 ° C and 0.5% of a commercially available emulsifier for 20 minutes. After draining the liquor, after-chroming in 100% water at 40 ° C with a commercially available self-dulling chrome-syntan retanning agent for 15 minutes, adding 1% of a commercially available synthetic fatliquor and after 45 minutes running time with 3% of a commercially available neutralizing tanning agent and 0.3 % Sodium bicarbonate neutralized to pH 5.5 over 45 minutes.

After adding 300% water at 40 ° C, the liquor is drained off after 10 minutes.

Subsequently, in 100% water at 40 ° C., 1.5%, based on dry matter, of dispersion III according to the invention from preparation example 3 is added as a 15.7% setting and drummed for 45 minutes.

3% of a commercially available replacement tanning agent is added and 3% dye is added after a running time of 20 minutes. After 40 minutes, the mixture is acidified with 2% formic acid (85%, 1:10 diluted with water) to a pH of approximately 3.8 over 30 minutes.

After draining the liquor, overdyeing in 200% water at 50 ° C with 1.5% dye and a further 20 minutes with 1.5% formic acid (85%, 1:10 diluted with water) to a pH of 3 , 5 acidified.

The leathers are rinsed cold and finished in the usual way (dried, milled, stollen, etc.).

The leathers have a soft, full feel and are characterized by a fine, smooth grain and an even, brilliant color.

Example 6: Production of vegetable leather

To produce vegetable upper leather, vegetable-tanned leather is washed in 300% water (based on the shaved weight, like all the following information) at 30 ° C for 10 minutes in the usual way and after draining the liquor in 100% water at 30 ° C with 1 % of a commercial bleach tanning agent bleached for 20 minutes (pH of the liquor: approx. 3.3) and washed with 300% water at 40 ° C.

After the liquor has been drained, 100% water at 40 ° C. is treated with 1.5%, based on dry substance, of the dispersion IV according to the invention from preparation example 4 as a 20.7% setting over 20 minutes. The pH of the liquor is around 4.3.

It is then dyed with 1.3% of a commercially available dye mixture for 20 minutes and greased with about 9% of a commercially available fat mixture of synthetic and natural fats for 20 minutes (pH value: about 4.2).

Finally, 0.5% formic acid (85%, 1:10 diluted with water) is added for fixation (pH value: approx.3.4). The leathers are washed (300% water at 20 ° C) and finished in the usual way (ejected, vacuum and hanging dried, air-conditioned, rolled and vacuum dried at 60 ° C for 1/2 minute).

The resulting leathers are soft, of good fullness and have a pleasant slimy grip.

Claims (3)

Use of implementation products (A) Terpolymer with molecular weights determined as number average $\overline{\text{M}}$

_n from 5000 to 60,000 a) maleic anhydride, b) 80 to 120 mol%, based on component a), diisobutylene and c) 1 to 12 mol%, based on component a), of at least one monomer of the formula

wherein R¹ is hydrogen or methyl, R² is hydrogen, methyl, ethyl, -OR³,

phenyl or hydroxymethyl optionally substituted by C₁-C₄-alkyl and R³ is C₁-C₄-alkyl, (B) aliphatic and / or cycloaliphatic monohydric C₆-C₂₄ alcohol and (C) base, 20 to 80% of the carboxyl groups corresponding to the anhydride groups of the terpolymer are esterified with alcohol (B) and at least 20% of the remaining carboxyl groups are neutralized with base (C), as retanning agent for leather. Use according to claim 1, according to which the monomer c) is selected from the series styrene, α-methylstyrene, p-methylstyrene, vinyl acetate, allyl acetate, isobutyl vinyl ether, allyl alcohol, methallyl alcohol and mixtures thereof. Use according to claim 1, according to which 30 to 75% of the carboxyl groups corresponding to the anhydride groups of the terpolymer are esterified with alcohol B.