KR20100080840A - Method for producing leather - Google Patents

Abstract

A method for producing leather, characterized in that animal skins or semifinished products are treated with a formaldehyde-free formulation of melamine in a solvent or solvent mixture, comprising at least one multivalent alcohol.

Description

Leather manufacturing method {METHOD FOR PRODUCING LEATHER}

FIELD OF THE INVENTION The present invention relates to a method of making leather, wherein the animal skin or semifinished product is treated with a solvent mixture comprising one or more polyhydric alcohols or with melamine preparations that do not contain formaldehyde in the solvent.

The invention also relates to a solvent mixture comprising one or more polyhydric alcohols or to melamine preparations which do not contain formaldehyde in the solvent.

In many cases, there has been a need, in particular for soft leathers for the manufacture of upper leathers, clothing and furniture, ie rich handles and soft leathers despite having sufficient strength. In order to produce a leather that is sufficiently soft and at the same time strong, not only must the processing be properly selected, but the softness and strength are influenced by tanning or in particular by retanning by the selection of a suitable tanning or retanning agent. I can receive it.

For the production of such soft and strong leather, resin tanning agents with melamine resin as active ingredient are used in many cases. In most cases, such melamine resins include melamine which reacts with at least one equivalent of formaldehyde, suitably aminated with at least one equivalent of monohydric or polyhydric alcohol. Dimer reactions, trimerizations and reactions and further oligomerization reactions occur, which are generally condensation, acet exchange or transamination reactions. The resin tanning agents described are therefore often polymeric mixtures having an unspecified structure. Such resin tanning agents can reduce formaldehyde, which is unintentional under certain conditions. On the other hand, reduced hemiamines with formaldehyde or melamine thereof are often responsible for the tanning or retanning effect and the desired softness of the leather. In many cases, high molecular weight is also referred to as contributing to the fullness of the leather.

In addition, so-called surface selectivity is also intended to be improved herein in comparison with the prior art (abundance ratio of core area to side).

It is an object of the present invention to provide a process by means of means which can produce full leather with good surface selectivity and good strength without particularly relying on tanning agents containing formaldehyde. Furthermore, it is an object of the present invention to provide a tanning agent formulation which is particularly suitable for the production of soft, rich leathers with good surface selectivity and good strength without releasing formaldehyde. It is also an object of the present invention to provide particularly soft and rich leathers and their potential uses, having good strength and good surface selectivity.

Thus, the method defined above, and also briefly as a method according to the invention, can also be found in the method described below.

In order to carry out the process according to the invention, animal hides or semi-processed products are used as starting materials. Animal skin is the skin of any given dead animal, such as a cow, camel, pig, goose, sheep, kangaroo, fish, ostrich or hunting animal. In the context of the present invention, animal skins are typically hairless—if epilation in the presence of lime—is preferably delimed. The semi-finished product is pickled animal skin or pretanned or suitably animal skin, preferably tanned by any desired process, in the presence of a polymeric tanning agent or by the action of a chromium salt. It is a manufactured semi-processed product.

In the present invention, it is not important whether the animal of the animal skin to be treated is slaughtered or killed by natural causes or by hunting.

Animal skin or semi-finished products are treated with melamine preparations which do not contain formaldehyde according to the invention. 'Free of formaldehyde' is understood herein to mean that the formaldehyde content is less than 0.01 mole per mole of melamine.

In one variant of the invention, the formaldehyde content of the formaldehyde used according to the invention is, for example, less than 20 ppm, preferably 15, as measured according to DIN ISO / TN 17226, or DIN 53315 (old version). less than ppm.

In a preferred embodiment of the invention, formaldehyde in the preparations which do not contain formaldehyde used according to the invention is not detectable.

Thus, melamine is pure melamine that does not react with formaldehyde or other aldehydes such as acetaldehyde or benzaldehyde.

According to the invention, melamine is used in a solvent mixture or solvent comprising at least one polyhydric alcohol. In the context of the present invention, polyhydric alcohols are understood to mean those compounds which are liquid at room temperature and carry at least two alcoholic hydroxy groups per mole. Such hydroxy groups may be secondary or primary hydroxy groups.

Preferred polyhydric alcohols are ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, glycerol and diglycerol.

In one embodiment of the invention, the formulations used according to the invention comprise two or more polyhydric alcohols. Preferably, the formulations used according to the invention comprise at least one dihydric alcohol and at least one trihydric alcohol.

In one embodiment of the invention, the selected solvent mixture is a combination comprising glycerol as trihydric alcohol and ethylene glycol, diethylene glycol or triethylene glycol as dihydric alcohol; Particular preference is given to a combination of glycerol and triethylene glycol.

In a variant of the invention, the preparations used according to the invention in each case comprise in the range of 70 to 50% by weight of dihydric alcohol, and in the range of 50 to 90% by weight of trihydric alcohol, relative to the total solvent mixture.

The formulations used according to the invention preferably do not comprise halogenated solvents such as, for example, chlorobenzene, chloroform or carbon tetrachloride. As used herein, "comprising no halogenated solvent" is meant to mean less than 100 ppm of halogenated solvent, preferably free of halogenated solvents, which can be detected by measurement methods known per se, for example, elemental analysis. I understand.

In one embodiment of the invention, the formulations used according to the invention comprise only one or more polyhydric alcohols as organic solvents or solvents.

The formulations used according to the invention may further comprise water.

In one embodiment of the invention, the formulations used according to the invention comprise 0.1 to 20% by weight of melamine, with 1 to 10% by weight being preferred.

In one embodiment of the invention, the process according to the invention for the production of leather is carried out as a tanning process, also referred to below as the tanning process according to the invention, preferably the retanning process ), As a retanning method, hereinafter referred to as a retanning method according to the present invention.

The tanning process according to the invention is generally carried out by a process of applying one or more preparations according to the invention several times, either before or after the tanning step, one part or part of the tanning step. The tanning method according to the invention is preferably carried out at a pH of 2.5 to 11, preferably at a pH of 4 or less, and during the tanning process according to the invention, a pH increase of about 0.3 to 3 units is achieved. Frequently observed.

The tanning process according to the invention is generally carried out at a temperature of 10 to 45 ° C., preferably of 20 to 30 ° C. A period of 10 minutes to 12 hours has proved useful, with 1 to 3 hours being preferred. The tanning method according to the invention can be carried out by drumming in any desired vessel, for example a rotating drum or barrel, which is customary in tanning.

In one embodiment of the invention, on the one hand it does not contain 0.01 to 10% by weight of formaldehyde, both with respect to the melamine content in the formulations used according to the invention and on the other hand with respect to the shaved weight. Melamine preparations are used, with 0.5 to 3% by weight being preferred.

In a variant of the tanning method according to the invention, melamine preparations which do not contain formaldehyde are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, Volume A15, pages 259-282, and in particular page 268, 5th Edition (1990) Verlag Chemie Weinheim, one or more conventional tanning agents, in particular tanning or retanning agents that do not contain one or more formaldehydes, for example chromium tanning agents, mineral tanning agents, phyllosilicates, polymers Used with tanning or vegetable tanning agents. The weight ratio of melamine: conventional tanning agent or conventional tanning agent is 0.01: 1 to 100: 1 for convenience (in terms of solids content in each case). In an advantageous variant of the tanning process according to the invention, only a few ppm of conventional tanning agents are added to the preparations according to the invention.

In one variant of the tanning method according to the invention, melamine preparations which do not contain formaldehyde are used together with one or more fatliquoring agents or oleophilic components.

In one variant of the tanning method according to the invention, the melamine preparations that do not contain formaldehyde are added in one or several portions before or during pretanning. Addition in pickle state may also be allowed.

To carry out the retanning process according to the invention, the starting materials used are typically tanned semi-finished products, ie chrome tanning agents, phyllosilicates, mineral tanning agents, polymer tanning agents, aldehydes or vegetable tannings. Zero typically tanned semi finished products or semi finished products made according to the invention as described above. In order to carry out the retanning method according to the invention, melamine preparations which do not contain at least one formaldehyde are operable on semi-finished products, ie are treated with melamine preparations which do not contain at least one formaldehyde.

The retanning method according to the invention can be carried out under other conventional conditions. For convenience, one or more, i.e. 2 to 6, treatment steps are selected, and washing with water may be done in the treatment step. The temperature in the industrial treatment step is in each case 5 to 60 ° C, preferably 20 to 45 ° C. For convenience one or more additional compositions are used during retanning, for example eggplants, polymer tanning agents and eggplants based on acrylates and / or methacrylates, tanning agents based on vegetable tanning agents, fillers, Leather dyes or lubricants are used.

A period of 10 minutes to 12 hours has proven useful for the retanning method according to the invention, with 1 to 3 hours being preferred. The retanning method according to the invention can be carried out by drumming in any desired container, for example a barrel or a rotating drum, which is commonly used for tanning.

In one embodiment of the litaning according to the invention, on the one hand with respect to the content of melamine and on the other hand with respect to the shaved weight, all of the melamine preparations which do not contain formaldehyde according to the invention are used from 0.01 to 10% by weight. 0.5 to 5% by weight is preferred.

The invention also relates to leather produced by the process according to the invention. The leather according to the invention has good fullness, softness and dyeing strength and the flatness of the grain brake and the tight-grained character of the silver after milling, for example for leather for furniture and clothing ), And better performance characteristics such as embossability. The leather according to the invention is suitable, for example, for upper leather, garments, for example garment items such as jackets, coats or pants, and furthermore articles of furniture.

The invention also relates to melamine preparations which do not contain formaldehyde, which comprise at least one polyhydric alcohol. Polyhydric alcohols and melamine, which do not contain the term formaldehyde, are defined above.

Preferred polyhydric alcohols are ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols having a mean molecular weight M _w in the range from 250 to 5000 g / mol, glycerol and diglycerol.

In one embodiment of the invention, the preparations according to the invention comprise two or more polyhydric alcohols. Preferably the preparations according to the invention comprise at least one dihydric alcohol and at least one trihydric alcohol.

In one embodiment of the present invention, the selected solvent mixture comprises glycerol as the trihydric alcohol, and ethylene glycol, diethylene glycol or triethylene glycol as the dihydric alcohol; Particular preference is given to a combination of glycerol and triethylene glycol.

In one variation of the invention, the preparations according to the invention in each case comprise in the range of 50 to 90% by weight of dihydric alcohol, and in the range of 10 to 50% by weight of trihydric alcohol, relative to the total solvent mixture.

The preparations according to the invention preferably do not comprise halogenated solvents such as, for example, chlorobenzene, chloroform or carbon tetrachloride. As used herein, “without halogenation solvent” is understood to mean that less than 100 ppm of halogenated solvent, preferably halogenated solvent, can be detected by conventional methods.

The preparations according to the invention preferably do not comprise acids such as sulfuric acid, hydrochloric acid, or phosphoric acid.

In one embodiment according to the invention, the preparations according to the invention comprise at least one base, in particular at least one alkali metal hydroxide or alkali metal carbonate. Potassium hydroxide and especially sodium hydroxide are preferred. For example, a suitable amount of alkali metal hydroxide is 0.1 to 10% by weight relative to melamine.

In one embodiment, the preparations according to the invention have a narrow pH in the range of 7-12, preferably 8-11.

In one embodiment of the invention, the preparations according to the invention comprise at least one polyhydric alcohol as the only organic solvent or solvent.

The formulations according to the invention may additionally comprise water.

In one embodiment according to the invention, the preparations according to the invention comprise 0.1 to 20% by weight of melamine, with 1 to 10% by weight being preferred.

In many cases, the preparations according to the invention have the appearance of a solution. In general, the preparations according to the invention appear completely transparent at the temperature of use in the process according to the invention. That is, when observed with the naked eye, it does not have any turbidity.

The preparations according to the invention may be reaction mixtures comprising the reaction product of melamine or reaction mixtures possibly comprising a solution of melamine. In certain embodiments of the invention, the formulation of the invention is a melamine solution.

In one embodiment of the invention, the preparations according to the invention are colorless. In another embodiment of the invention, the preparations according to the invention may be yellow, amber or brown. Without wishing to be bound by any particular theory, any coloration is not in all cases due to the reaction product of the polyhydric alcohol and melamine, but is expected to be due to the interaction between two or more melamine molecules.

The invention also relates to a process for the preparation of the preparations according to the invention. For the preparation of the preparations according to the invention, it can be used for the preparation of melamine which is mixed with a polyhydric alcohol or a solvent mixture comprising at least one polyhydric alcohol.

Production methods known per se can be used for mixing. Stirring is preferred to effect mixing. For example, mixing can be carried out at room temperature or without heating, for example in the temperature range from 40 to 190 ° C., in particular from 120 to 170 ° C.

Mixing may preferably be carried out at atmospheric pressure, but may also be permitted under pressures such as, for example, 1.5 to 15 bar.

The preparations according to the invention are very suitable, for example, for the production of leather by the process described above. The invention therefore also relates to the use of the preparations according to the invention for the manufacture of leather.

The invention is illustrated by the examples.

Dynamic viscosity was always measured according to DIN ISO standard 3219 (formerly DIN standard 53018) at 23 ° C.

I. Preparation of the preparations according to the invention

I.1 Preparation of the Formulation (F.1) According to the Invention

36.8 μg (0.29 μmol) of melamine, 198.7 μg (1.32 μmol) of triethylene glycol, 912.9 μg of glycerol (9.92 μmol) and 0.4 μg of sodium hydroxide solution (50 wt%) were first taken into a 2000 ml flask and stirred while stirring. Heated to ° C. The formulation thus obtained was stirred at 140 ° C. for 4 hours. The formulation is then cooled to room temperature. A slightly yellow, transparent, homogeneous and stable formulation (F.1) was obtained. Dynamic viscosity was 390 mPa * s at 23 degreeC.

I.2 Preparation of Formulations (F.2) According to the Invention

36.8 μg (0.29 μmol) of melamine, 200.2 μg (1.33 μmol) of triethylene glycol, 920.0 μg of glycerol (10.0 μmol) and 0.4 μg of sodium hydroxide solution (50 wt%) were first taken into a 2000 ml flask, and stirred with 80 Heated to ° C. The formulation thus obtained was stirred at 80 ° C. for 5 hours. The formulation is then cooled to room temperature. A colorless, transparent, homogeneous and stable formulation (F.2) was obtained. Dynamic viscosity was 385 mPa * s at 23 degreeC.

I.3 Preparation of the formulation according to the invention (F.3)

36.8 μg (0.29 μmol) of melamine, 200.2 μg (1.33 μmol) of triethylene glycol, 920.0 μg of glycerol (10.0 μmol) and 0.4 μg of sodium hydroxide solution (50 wt%) were first taken into a 2000 ml flask, and stirred with 170 Heated to ° C. The formulation thus obtained was stirred at 170 ° C. for 3 hours. The formulation is then cooled to room temperature. A clear, homogeneous and stable amber formulation (F.3) was obtained. The kinematic viscosity was 418 mPa · s at 23 ° C.

I.4 Preparation of the Formulation (F.4) According to the Invention

36.8 μg (0.29 μmol) of melamine, 200.2 μg (1.33 μmol) of triethylene glycol, 245.6 μg of glycerol (2.67 μmol) and 0.4 g of sodium hydroxide solution (50 wt%) were first taken in a 1000 ml flask and stirred with 170 Heated to ° C. The formulation thus obtained was stirred at 170 ° C. for 3 hours. The formulation is then cooled to room temperature. A clear, homogeneous and stable light brown formulation (F.4) was obtained. Dynamic viscosity was 589 mPa * s at 23 degreeC.

I. 5 Preparation of Formulations (F.5) According to the Invention

36.8 μg (0.29 μmol) of melamine, 240.2 μg (1.60 μmol) of triethylene glycol, 245.6 μg of glycerol (2.67 μmol) and 0.4 μg of sodium hydroxide solution (50 wt%) were first taken into a 2000 ml flask and stirred while stirring. Heated to ° C. The formulation so obtained was stirred at 140 ° C. for 3 hours. The formulation is then cooled to room temperature. A clear, homogeneous and stable light brown formulation (F.5) was obtained. Dynamic viscosity was 426 mPa * s at 23 degreeC.

The results are summarized in Table 1.

Table 1: Properties of Formulations

II. Retanning experiments of the preparations according to the invention

Preparation of leather for uppers (general method)

The data in% are by weight and are values for always shaved weight. For formulations, the percent formulation refers to the solids content or the active substance content, unless stated otherwise.

Two commercially available cattle wet blues (Packer, USA) were shaved to a thickness of 1.7 to 1.9 mm. The semi-finished product, including the side sections, was further processed and cut into seven strips of about 800 g each for this purpose. Thereafter, 1.5% by weight of sodium formate and 0.5% of sodium bicarbonate and 1% of naphthalene sulfonic acid / formaldehyde condensate prepared according to US 5,186,846, Example "Dispersant 1", were placed in a drum (50 l) for 10 minutes. The pieces were applied at a liquor length of 200% (by weight shaved) at intervals. After 70 minutes, the liquor was removed. The pieces were then distributed to individual drums 1 to 7 for drumming.

With 100% water, in each case 2% of an aqueous formulation of 40% strength polyacrylic acid (M _n 70 000 g / mol, pH 5.5) was added to drums 1-7 for druming at 25-35 ° C. It was. As shown in Table 1, after 20 minutes of drumming, in each case, 2% kaolin, average particle diameter (weight average) 1.3 μm (measured after vigorously stirring for 30 minutes in water at 50 ° C. according to ISO 13320-1) , cf. example B1.1 of WO 2004/22790 and page 3, line 12, etc.) and also 3% plant tanning agent mimosa and 5% of the preparations according to the invention were measured continuously. After 60 minutes, in each case 50% by weight (solid content) of 2% by weight of the aqueous dyeing formulation was measured and the dye has the following composition:

70 parts by weight of the dye of EP-B 0 970 148, Example 2.18,

San Brown 75 (iron composite), color index 1.7.16 30 parts by weight.

Drumming was only processed for an additional 30 minutes in the drum.

The acidification was then carried out in several 0.3-0.5% formic acid steps for a pH of 3.9-4.1. After 20 minutes, the liquor consumption was assessed and discarded. The leather was washed with 200% water.

Thereafter, after 60 minutes at 4 revolutions per branch according to WO 03/023069, Example A and 15 revolutions per minute, 1% of the aforementioned dye mixture was metered in with 100% water. After 20 minutes, acidified to pH 3.7 with 1% formic acid.

The leather thus obtained was washed, dyed, staked and evaluated according to the test criteria described in Table 2. According to the invention leathers L.1 to L.2 were obtained. Evaluation was made according to a scorecard of 1 (very good) to 5 (bad).

An aqueous formulation prepared as follows was used as comparative tanning agent C-F.6:

418 g of aqueous sodium sulfite solution (20 wt%) was first taken into a 2 l 4-neck flask and 325 g of 30 wt% aqueous formaldehyde solution was added dropwise over 20 minutes with stirring. The temperature was not allowed to exceed 60 ° C. After the addition was completed, the temperature was raised to 80 ° C. and an aqueous suspension of 188.4 g of naphthalene sulfonic acid (isomer mixture) and 45 g of melamine in 200 ml of water was added within 15 minutes.

Stir at 80 ° C. for 2 hours, then add 170.7 g of 50 wt% aqueous urea solution over 20 minutes. Stir at 80 ° C. for an additional hour, after which 6.9 g of aqueous sodium hydroxide solution (50 wt%) was added over 10 minutes and the temperature did not exceed 83 ° C. Stir at 80 ° C. for an additional 90 minutes, then cool the mixture to room temperature. The pH was set to about 8 with 2.7 g of 25% by weight aqueous sulfuric acid.

Table 2: Upper leather according to the present invention and its properties

The leather according to the invention has particularly pronounced abundance and softness with good silver cotton firmness. Experiments show no contribution or negligible contribution to the fact that the leather according to the invention does not contain formaldehyde completely compared to natural leather (about 2-5 ppm formaldehyde), while at the same time good silver solidity and The combination of significant richness effects and the need for softness is shown. It is also advantageous here that the so-called surface selectivity can be improved in comparison with the prior art (the richness ratio of the core region to the side).

Claims (10)

A method of making a leather, wherein the method of making a leather is treated with an animal skin or a semi-processed product with a solvent mixture comprising one or more polyhydric alcohols or a melamine preparation containing no formaldehyde in the solvent. The method of claim 1 wherein the polyhydric alcohol is selected from ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, glycerol and diglycerol. The method of claim 1, wherein the solvent mixture selected is a combination comprising glycerol and ethylene glycol, diethylene glycol or triethylene glycol. The method of claim 1, wherein the solvent or solvent mixture does not contain a halogenated solvent. 5. The method of claim 1, wherein at least one tanning or retanning agent that does not contain formaldehyde is additionally used. 6. Melamine formulations that do not contain formaldehyde in a solvent mixture or solvent comprising one or more polyhydric alcohols. The melamine preparation of claim 6, wherein the polyhydric alcohol is selected from ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, glycerol and diglycerol. 8. The melamine preparation of claim 6 or 7, wherein the solvent mixture selected is a combination comprising glycerol and ethylene glycol, diethylene glycol or triethylene glycol. Use of a melamine preparation that does not contain the formaldehyde of any one of claims 6 to 8 for carrying out the method according to any one of claims 1 to 5. Leather obtainable according to the method of any one of claims 1 to 5 or 9.