EP0651827B1 - Use of non-ionic organic dialkyl compounds to prevent the formation of fatty spew on leather - Google Patents

Abstract

PCT No. PCT/EP93/01807 Sec. 371 Date Feb. 17, 1995 Sec. 102(e) Date Feb. 17, 1995 PCT Filed Jul. 10, 1993 PCT Pub. No. WO94/02649 PCT Pub. Date Feb. 3, 1994.The present invention relates to a fatty spew inhibiting composition for leather comprising an oiling component in combination with a dialkyl ether additive corresponding to general formula II: R3-O-R4 (II) wherein R3 and R4, independently of one another represent an alkyl group containing 1 to 32 carbon atoms, the alkyl group being saturated or unsaturated, linear or branched, and the dialkyl ether additive having a total number of carbon atoms per ether molecule in the range from 14 to 36.

Description

Field of the Invention

The invention relates to the use of special dialkyl ethers to prevent fat rash on leather.

State of the art

In addition to the tannins, greasing agents are the most important tools to shape the character of leather. The effect of the fatliquor comes from a fiber-insulating lubrication and a hydrophobization. By covering the leather fibers with a grease film, the mutual friction is reduced and consequently the suppleness and stretchability of the fabric are improved. This has positive effects on the tensile strength of the leather, because in a stretchable material, many fibers align in the direction of tension when subjected to tensile stress and then offer greater resistance to tearing than the same fibers within a brittle material.

Vegetable and animal oils, fats and waxes are generally used as leather greasing agents, furthermore the hydrolysis, sulfation, oxidation and hardening products obtained from these substances by chemical conversion and finally mineral greasing agents; in detail:

The saponifiable fats and oils as well as the natural waxes and resins are among the esters. Among the oils and fats are the leather specialist Designated esters of glycerin and fatty acids that are solid or liquid at room temperature. For leather greasing, from the group of animal fats in particular trane, fish oil, beef tallow and beef claw oil, from the group of vegetable fats castor oil, rape oil and linseed oil are used. In waxes and resins, the fatty acids are esterified with higher molecular weight alcohols instead of glycerin. Examples of waxes are beeswax, Chinese wax, carnauba wax, montan wax and wool fat; The most important resins include rosin, yeast oil and shellac.

The chemical conversion of vegetable and animal fats gives products that are water-soluble and, in addition, have different emulsifying effects on water-insoluble fats. For example, the sulfated water-soluble oils of various types are known, the tears modified by oxidation, which are known as dégras or moellon, the soaps that are formed during the hydrolytic splitting of natural fats, hardened fats and finally free fatty acids such as stearic acid as stoving fats. Most animal and vegetable fats have a certain affinity for the leather substance, which is considerably increased by the introduction or exposure of hydrophilic groups.

Mineral greasing agents are also important for leather production. These hydrocarbons are similar to natural fats and oils in some properties, but cannot be saponified. These are fractions from petroleum distillation, which are called mineral oil in liquid form, petroleum jelly in pasty form and paraffin in solid form.

In many cases, however, undesirable stains form on the surface of the tanned and greased leather over time. In this case, the person skilled in the art speaks of "fatty spew". Grease rashes occur primarily on chrome-tanned leather after shorter or longer storage as a white, often veil-like covering that only covers individual areas or the entire leather surface. The rash is due to the emergence of solid fatty substances from the leather. It can be due to the natural fat or in the leather itself be caused by fatty substances that were only incorporated into the leather during the course of leather greasing.

Fat mixtures used to grease leather tend to develop a rash if they contain a lot of free fatty acids. Free fatty acids generally have a higher melting point than their glycerides. The hydrolytic cleavage of fatty substances during the storage of the leather increases the risk of fat rashes (cf. B. Kohnstein, Collegium 1913 , 68; W. Fahrion, Chem. Umschau 1917 , 29), but such fat rashes by no means only need to be free To consist of fatty acids. Oxy fatty acids can also give rise to fat rashes (C. Rieß, Collegium 1926 , 419).

Soaps and licker greases are split in chrome leather, especially in insufficiently deacidified chrome leather, with the release of fatty acids. Sulphated oils and fats show a different tendency to form fat rashes, the tendency to rash generally decreases with a longer lifespan (A.Pankhurst, RGMitton, RFInnes, N.Johnson, Journal of International Society of Leather Trades Chemists 1952 , 379).

Fat rashes are more likely to occur the more the leather contains fat substances that tend to form rashes. The amount, composition and location of the fat mixture of natural fat and lickerfat present in the leather are decisive for the extent and composition of the rash (see O.Grimm, Österr. Lederzeitung 1954 , 253). Loosely structured leather is less prone to rash than leather with a dense fiber structure. Grease rashes are observed more often at low temperatures than at warmer outside temperatures.

The crystalline fat rashes develop in the hair holes and gland canals, whereby small crystals are initially formed in the depth, which gradually fill the entire hair hole as larger fat crystals, swell beyond the leather surface and matted into a dense crystal film. All fats that contain stearin or palmitin derivatives can cause crystalline fat rashes, with increasing Concentration increases the risk of a rash (see O. Hagen, Switzerland. Ledertechn. Rundsch. 1949 , 1).

In particular, the so-called neutral fats, i.e. substances suitable for leather greasing which do not contain any ionic groups in the molecule, e.g. Fats, waxes and hydrocarbons to form fat rashes. Those neutral fats which represent stearin and / or palmitin derivatives, e.g. corresponding triglycerides. Neutral greases are of particular importance in the so-called licker process of chrome-tanned leather. A licker usually contains about 20 to 40% by weight of an emulsifier and 60 to 80% by weight of a neutral fat. It is a widespread practice in the leather processing industry to use neutral greases for greasing the tanned leather which can be sulfated in a simple manner. If, for example, a triglyceride is reacted with a minor amount of concentrated sulfuric acid or oleum, the reaction mixture obtained can be used directly as a licker since it contains an emulsifier in the form of the sulfated triglyceride and the neutral fat in the form of the unreacted triglyceride. In this connection, reference is expressly made to the example part of this application.

In addition to the use of greasing agents from the group of neutral fats, the natural fats already present in the leather play a major role in the occurrence of fat rashes.

Skin fat consists of a mixture of differently structured lipids, the type and proportions of which are summarized in Table 1 for some important animal species (cf. Martin Hollstein, "Leather library; Volume 4: degreasing, greasing and waterproofing in leather production"; p. 116- 136). Table 1 shows that the triglycerides represent the most important group of skin lipids in terms of quantity. In connection with the formation of fat rash, it is particularly critical from the point of view of the leather technician that these triglycerides are predominantly based on saturated fatty acids: lauric, myristic, palmitic and stearic acid are typical components of this group. The wax esters also contain as Components include these fatty acids, which are particularly critical with regard to their tendency to fat rash. Table 1: Composition of the total lipids of the skin of various animal species (in% based on the total lipid of fresh skin) Lipid Animal species Beef goat sheep Triglycerides 53 68 56 Wax ester 11 12th 23 Phospholipids 1 8th 6 cholesterol 4th 8th 5 free fatty acids 0 4th 5 Hydrocarbons 1 - -

It is therefore clear that the natural fat already present in the leather represents a constant latent potential for the formation of fat rash. It is also known that the natural fat content of the raw material has remained consistently high over the past 10 years. The reason, according to Ernst Pfleiderer, can be seen in the changed rearing and feeding methods in livestock farming; The leather processing industry has been complaining about the increased fat content of large skin provinces, veal skins and pigskins for years (cf. Das Leder, 1983 [34] 181-185).

The statements made by Pfleiderer could be confirmed in our own probing investigations on ashes and split beef scars. Natural fat portions of up to 8% and more were found in the abdominal parts.

Leather with a high natural fat content therefore requires special measures to suppress the tendency to form fat rashes. For example, it is possible and quite common in practice, the leather accordingly to degrease, which however requires a special operation. Other options are almost meaningless in practice.

Fat swings, which can be clearly distinguished from mineral rashes by disappearing when heated with a burning match, can be removed, for example, by rubbing the leather with a cloth soaked in petrol; In order to prevent a rash from developing again, it has been recommended to oil the scars with a neutral mineral oil (cf. F. Stather, "Tanning chemistry and tanning technology", Berlin 1967 , p. 740). A.Gluszcak and KJBienkiewicz report on the use of a mixture of wood dust, water, hexane and carbon tetrachloride to remove fat rash (cf. Przegl. Skorzany 1985 , 40 (11-12), 232; cited from Chem. Abstracts 105 (6): 45160e).

The formation of a fat rash on commercially available clothing and glove leather observed within a period of two to four weeks could be prevented by using glutaraldehyde in the tanning process or by using a mineral oil-containing licker (see A.Gluszcak, KJBienkiewicz, Przegl. Skorzany 1985 , 40 (11-12), 232; cited from Chem. Abstracts 105 (6): 45160e). The Gluszcak and Bienkiewicz method, however, has the disadvantage of being limited to a specific tanning method; however, it does not affect chrome-tanned leather, which is still by far the largest share of all leather on the market.

However, since in the course of leather processing, after tanning, greasing is required as an almost obligatory step in order to achieve the desired product properties, it has become common practice to work with special synthetic greasing agents whose tendency to form a fat rash is low.

One class of fatliquor commonly used in this regard is halogenated compounds such as chlorinated hydrocarbons. However, the increasing ecological and toxicological requirements for agents that get into the environment or with which the consumer comes into contact make this class of substances increasingly unattractive. The use of chlorinated paraffins as additives to fat liquor emulsions to help reduce rashes J.Golonka (Przegl. Skorzany 42 (2), 35; cited from Chem. Abstracts 107 (18): 156865z) describes how to prevent chromium-tanned pig fields.

The methods known from the prior art for preventing fat rash are therefore unsatisfactory overall.

From the context described, it is clear that the leather industry has a constant need for additives or greasing agents that effectively prevent fat rashes and thereby supplement the range of commercially available products and be able to react flexibly to the changing demands of the market. In particular, there is a need for ecologically or toxicologically safe additives and fatliquoring agents which, when used, do not lead to an undesirable formation of fat rash.

Description of the invention

It has now been found that certain compounds of the general formula (II) meet the above requirements excellently in all respects and can advantageously be used as additives which prevent fat exchange in the greasing of leather.

The present invention therefore relates to the use of dialkyl ethers of the general formula (II)

R³-0-R⁴ (II)

in which the radicals R³ and R⁴ independently of one another are an alkyl group having 1 to 32 and in particular 7 to 22 C atoms, the alkyl groups being saturated or unsaturated, straight-chain or branched, with the proviso that the total number of C atoms per ether molecule is in the range from 14 to 36 and the dialkyl ethers have a pour point below 6 ° C. to prevent fat rash on leather.

Another object of the invention are compositions which prevent fat rash and which contain a fatliquor and an anti-fat rash Additive, the additive being a dialkyl ether of the general formula (II)

R³-0-R⁴ (II)

is in which the radicals R³ and R⁴ independently of one another are an alkyl group having 1 to 32 and in particular 7 to 22 carbon atoms, where the alkyl groups can be saturated or unsaturated, straight-chain or branched, with the proviso that the total number of carbon atoms per ether molecule is in the range from 14 to 36 and the pour point of the dialkyl ether is below 6 ° C.

Preferred compositions are those in which the fatliquor is a neutral fat. Neutral fat is understood in the sense of the nomenclature common in leather technology to mean any greasy and poorly water-soluble substance. Examples of neutral oils are triglycerides, alkanes and fatty acids.

The invention further relates to a process for greasing leather, in which tanned leather is treated with an additive which prevents fat and a fat rash, a dialkyl ether of the general formula (II) being used as the additive.

R³-0-R⁴ (II)

used in which the radicals R³ and R⁴ independently of one another are an alkyl group having 1 to 32 and in particular 7 to 22 carbon atoms, the alkyl groups being saturated or unsaturated, straight-chain or branched, with the proviso that the total number of carbon atoms per ether molecule is in the range from 14 to 36, the dialkyl ether having a pour point below 6 ° C.

In a preferred embodiment of the method according to the invention, a neutral fat is used as the fatliquor. The method according to the invention is particularly suitable for greasing chrome-tanned leather.

The greasing process is carried out in a conventional manner. In the course of the greasing process, the grease must be transported into the capillary spaces between the leather fibers and the fibrils, and fibers and fibrils must be coated with a grease film as evenly as possible. Apart from the stoving method, the greasing process is always carried out on moist leather, because the leather fibers are separated from one another by water in the moist state. The fat then penetrates slowly, but very evenly into the damp leather.

The amount of fatty substances deposited in the leather is not subject to any particular restrictions and essentially depends on the particular type of leather. For example, vegetable-tanned bottom leather and insole leather contain little fat (approx. 0.5-2%), vegetable-tanned pale leather 15-23%, drive belt leather 5-20%, harness leather and some technical special leather 25% and more. Chrome-garment upper leather usually contain only 2-6% fat, chrome-garment leather a little more (4-10%), waterproof leather about 15-21%.

The practical implementation of leather greasing can be done by simply oiling the wet leather before drying, also by lubricating the wet leather on the board ("cold greasing"), by greasing the wet leather in a drum ("warm greasing"), by baking the dry leather and by treating the wet leather with an aqueous fat emulsion, the so-called fat licker. The latter process plays a particularly important role in chrome-tanned leathers. It is therefore the preferred form of leather greasing in the context of the present invention.

The compounds (II) are prepared by known synthetic organic chemical methods. They are also commercially available in a wide variety.

The extent of the suppression of fat rash by the compounds (II) is original and novel compared to the prior art mentioned. The effectiveness of the compounds according to the invention is not based on individual parameters such as the pour point, but rather results only by combining all the features. In this context, please refer explicitly to Table 3 of the example section.

The usable proportions of the compounds (II) according to the invention or their mixtures in fatliquoring agents range from 5 to 70% by weight, preferably from 5 to 30% by weight, based on the mixture as a whole.

The following examples are intended to explain the subject matter of the invention and are not to be interpreted as restrictive.

Examples 1. Substances used

The examples and comparative examples described under No. 2 and No. 3 were carried out on the basis of commercially available products, which are listed in Table 1: Table 1: designation chemical constitution AS ¹⁾ (%) Commercial product of the company Chromosal B basic chromium sulfate 33 Bayer AG Pellutax AW aromatic sulfonic acid condensation product 98 BASF Coratyl G Na-Al-silicate 100 handle Sella real black FN Black dye 100 Ciba Geiby Drasil ANG Polymer tanning agent 40 handle Pellutax SWLF aromatic sulfonic acid condensation product 100 BASF 1) AS = active substance

2. Preparation of the leather

Chrome-tanned cowhide leather (wet-blue) with a thickness of 1.7 mm was used for all tests. The individual steps can be found in Table 2. The pH of the liquor was 3.8 at the beginning. All percentages in Table 2 refer to the fold weight. Table 2: Operation % Product / comments ° C running time To wash 200 water 40 10 min Drain the fleet Retanning 100 water 40 3rd Chromosal B 3rd Pellutax AW 1.5 Coratyl G 45 min Drain the fleet coloring 100 water 40 1 Sella real black FN 30 min + 3 Drasil ANG 15 minutes + 3 Pellutax SWLF 30 min Drain the fleet Bold ¹⁾ 100 water 50 15 Fatliquor 5 Additive 45 min + 0.7 Formic acid 30 min Leather overnight on trestle, stretch out, vacuum dry at 70 ° C (2 min), hang dry, light up, studs 1) Sulphated palm oil was always used as a fatliquor; This was obtained in the usual way by reacting 100 parts by weight of palm oil (iodine number range: 41-50; C chain distribution: C16 = 45-54%; C18 = 5-10%) with 18 parts by weight of conc. Sulfuric acid. The fatliquor was first mixed with the respective additive (see Table 3) and this mixture was emulsified in water.

3. Assessment of fat rashes

The leather pretreated according to No. 2 was tested for its tendency to form fat rashes. The method used is a modification of HAOllert's method (see "Das Leder" 1989, p. 256). The good correlation of the test results with the results of long-term storage indicated by Ollert could be confirmed in our own investigations. In particular, it was found that the good effect of agents known from the prior art, such as chlorinated paraffins, was recorded and confirmed in the test.
In detail:

The leather to be tested (pretreated according to No. 2) was punched out in a circle - without conditioning - (diameter: 155 mm). The leather washers were then used to cover the opening of a 1 liter flat ground cup filled with 300 ml of tap water (outside diameter: 155 mm), the grain side being on the top (outside). The leather was fixed with a tension ring and then the water was heated to boiling and kept at the boiling temperature for 2 minutes. In this way, the pretreated leather was exposed to a defined thermal load, with water vapor escaping from the scars. The clamping ring was then removed, the leather disc covering the flat ground cup was removed and the water poured out. The drops of water stuck to the walls of the vessel when the water was poured out were left in the vessel, i.e. the glass was not additionally dried. The leather, which was still damp due to the steam treatment described, was now transferred directly to the ground cup and sealed with a glass pane. The leathers were then stored in the closed cup at a temperature of 25 ° C. for 5 days. After this time, the leather was visually checked for fat rash.

The experiments were repeated 10 times for each additive. The results are summarized in Table 3.

It was found that 80% of the leather fat rash was found when using the pure fatliquor (comparison V1).

In contrast, the examples based on the additives according to the invention (tests B4 and B5) were free of fat rashes. Table 3: attempt Additive Number of leathers with fat rash without fat rash V1 - 8th 2nd V5 Chlorinated paraffin ^b) 0 10th B4 Di-n-octyl ether 0 10th B5 Di-2-ethylhexyl ether 0 10th a) Leather resinified b) agent known from the prior art, but to be substituted because of its halogen content

Claims (6)

1. The use of dialkyl ethers for preventing fatty spew on leather, characterized in that dialkyl ethers with a pour point below 6°C which correspond to general formula (II):
   
           R³-O-R⁴     (II)
   
   in which R³ and R⁴ independently of one another represent an alkyl group containing 1 to 32 and, more particularly 7 to 22 carbon atoms, the alkyl groups optionally being saturated or unsaturated, linear or branched, with the proviso that the total number of carbon atoms per ether molecule is in the range from 14 to 36,
   are used in the oiling of leather.
2. A fatty spew inhibiting composition containing an oiling component and a fatty spew inhibiting additive, characterized in that the additive is a dialkyl ether with a pour point below 6°C which corresponds to general formula (II):
   
           R³-O-R⁴     (II)
   
   in which R³ and R⁴ independently of one another represent an alkyl group containing 1 to 32 and, more particularly 7 to 22 carbon atoms, the alkyl groups optionally being saturated or unsaturated, linear or branched, with the proviso that the total number of carbon atoms per ether molecule is in the range from 14 to 36.
3. A composition as claimed in claim 4, characterized in that the oiling component is a neutral fat.
4. A process for oiling leather in which tanned leather is treated with an oiling component and a fatty spew inhibiting additive, characterized in that the additive is a dialkyl ether with a pour point below 6°C which corresponds to general formula (II) :
   
           R³-O-R⁴     (II)
   
   in which R³ and R⁴ independently of one another represent an alkyl group containing 1 to 32 and, more particularly 7 to 22 carbon atoms, the alkyl groups optionally being saturated or unsaturated, linear or branched, with the proviso that the total number of carbon atoms per ether molecule is in the range from 14 to 36.
5. A process as claimed in claim 4, characterized in that a neutral fat is predominantly used as the oiling component.
6. A process as claimed in claim 4 or 5, characterized in that chrome-tanned leather is used.