EP0847453B1

EP0847453B1 - Process for the treatment of hides

Info

Publication number: EP0847453B1
Application number: EP96929284A
Authority: EP
Inventors: Giovanni Tempesti
Original assignee: Tempesti SpA
Current assignee: Tempesti SpA
Priority date: 1995-08-30
Filing date: 1996-08-20
Publication date: 2001-07-11
Anticipated expiration: 2016-08-20
Also published as: IT1260161B; ITMI951830A1; DE69613844D1; ITMI951830A0; AU6874996A; EP0847453A1; WO1997008346A1; ATE203059T1

Abstract

A process is described for the treatment of hides by vegetable tanning comprising stages of subjecting dressed and dyed hides to compression at a pressure equal to or greater than 380 atmospheres for about 4-5 hours and then of stuffing by treatment in a drum at room temperature with 15-20 % by weight of a mixture of fatty substances based on animal fats and oils and comprising 1.2-2.5 % by weight of sulphonated fish oil, continuing the said treatment until the temperature of the hides reaches a value of 34-36 DEG C. A composition for the stuffing of dressed and dyed hides is also described. The hides obtained by the process and the composition according to the invention are characterized by great softness to the touch accompanied by excellent resistance to mechanical stresses and deformation.

Description

In its most general form the present invention relates to the treatment of hides for the production of shoes, handbags, belts and the like.
In particular, the invention relates to a process for the treatment of hides comprising their vegetable tanning, and more precisely for the so-called stuffing stage; the invention also relates to compositions of fatty substances that can be used for the said stuffing stage.
The treatment of hides by vegetable tanning or dressing with tannin is a well-known process, the stages of which are outlined below:

soaking of the preserved hides, by immersing the hides in water, for the purpose of allowing the hides to reabsorb the water lost during preservation and make them more receptive to the subsequent treatments;
dehairing and liming, by treating the hides in drums with calcium hydroxide and sodium sulphide;
fleshing, or removal of flesh and fat from the flesh side;
deliming, or treatment of the hides in drums with solutions of weak acids or acid salts to remove the residual lime;
bating, or destruction of those residual parts that are unsuitable for the tanning stage proper (for example hairs or roots of residual hairs);
pickling, i.e. treatment of the hides in drums with salts, generally sodium chloride, and acids, such as formic, hydrochloric or sulphuric acid, so as to lower the pH to about 3;
tanning proper, effected by treating the hides in drums with concentrated extracts of various vegetable materials rich in tannins, for example the bark of oak, chestnut, holm oak, birch, wood of quebracho, cherry plums, fruit of the algoravilla, etc., also using, if necessary, synthetic tannins such as tanning auxiliaries;
treatment with acids, such as oxalic acid, to fix the tannins on the hide and to remove any excess tannins;
shaving, i.e. levelling of the hide on the flesh side using a shaving machine, so as to obtain a uniform thickness of the hide;
dyeing, carried out in drums using aniline dyes and fixing by treatment with formic acid in aqueous solution;
stuffing, usually carried out by treating the hides in drums with emulsions of fats and oils in water preheated to about 60°C, for about one hour;
wringing, i.e. pressing with a rotary press to eliminate the excess water or other liquids with which the hides are soaked,
smoothing and drying by hanging in ventilated rooms.

Of all the stages summarized above, the most important, as far as the softness of the final tanned hide is concerned, is the stuffing stage.
During this stage, fat molecules penetrate between the fibres of the hide; the deeper and more uniform this penetration, the greater the effect on softness to the touch (called "handle" by persons skilled in the art) of the hide and of the leather goods or footwear manufactured from it.
In the prior art the stuffing stage is carried out by treating the hides with an emulsion of fats and oils in water.
For example, Database WPI AN 90130979 & SU-A-1 493 679 disclose fat-liquoring compositions comprising marine animal oil and sulphonated fish oil and their corresponding use in the treatment of the leather used in the production of shoe uppers and in the haberdashery industry.
The above compositions are, at first, dispersed in a rotary pulsating unit in form of a oil/water emulsion until the size of oil particles is not greater than one micron and then the emulsion is poured in the rotating drum used for the treatment of leather.
GB-A-0773825 discloses fat-liquoring compositions for leather, comprising a mineral or fatty oil, an anionic surface active agent (such as sulphonated fatty oil), a non ionic surface active agent mixed with an ester of a polyethylene glycol, a cationic surface active agent and water.
The above compositions form a relatively stable aqueous emulsions which are used for stuffing the hides.
The problem at the root of the present invention is that of making available a process for the treatment of hides comprising vegetable tanning thereof, which process makes it possible to obtain a hide that has characteristics of softness to the touch superior to those obtained hitherto with known processes.
This problem is solved, according to the invention, by a process for the treatment of hides by vegetable tanning thereof, comprising the preparation of dyed hides according to conventional stages of processing and characterized in that it comprises the successive stages of:

subjecting the said dyed hides to compression at a pressure equal to or greater than 380 atmospheres for about 4-5 hours, until the water content of the said hides has a value of 25-30% by weight relative to the total weight of the hides;
subjecting the said hides to stuffing by treatment thereof in a drum rotated at room temperature (15-25°C) with 15-20% by weight, relative to the weight of the hides, of a mixture of fatty substances based on animal fats and oils and comprising, as a percentage by weight relative to the total weight of the mixture, 55-65% of tallow, 12-17% of marine animal oil, 22-27% of oxidized marine animal oil and 1.2-2.5% of sulphonated fish oil;
continuing the said treatment in the drum until the temperature of the hides reaches a value of 34-36°C.

The aforementioned compression is preferably carried out at a pressure of 380-420 atmospheres, using a plate press.
It is preferable for the drum used in the treatment described above to be rotated at a speed of 16-18 rev/min.
Drum treatment of the hides with the mixture of fatty substances generally takes from 1.5 to 4 hours.
It is expedient for the aforementioned mixture of fatty substances to contain from 0.3 to 1.0% of a fungicide.
It is possible to use commercially-available prepared mixtures of marine animal oil and of oxidized marine oil, provided that the ratio of the two components of which they are constituted is within the range of values stated above.
The hide obtained by the process according to the invention can then be sent to the usual stages of smoothing and drying and to optional stages of finishing, polishing, stamping, etc., before being used for the manufacture of leather goods, shoe uppers, etc.
The hide produced using the process of the invention is characterized, relative to all hides produced hitherto using known processes of the art, in that it has a very special "handle" that is immediately recognizable by any person skilled in the art. That is, the hide is extremely and pleasantly soft to the touch, though without displaying excessive yielding, and on the contrary exhibiting excellent properties of resistance to mechanical deformation.
According to a theory, which is not binding, it can be said that the special handle of the hide obtained with the process according to the invention is due both to the particular way in which the hide is prepared during the stuffing stage and to the specific composition of fatty substances used for that stage.
The stage of compression to which the hide is subjected has the purpose of adjusting its moisture content to an ideal value for penetration of the fatty substances during the subsequent stage of stuffing. An excessively high moisture content would not permit sufficient and uniform penetration of the fatty substances, producing a hide with a handle that is too "greasy" and therefore too yielding.
In addition, the composition of the mixture of fatty substances used for the stuffing stage is critical for achieving an optimum result in terms of handle of the final hide. An excessive deviation from the ranges stated for the various components can result in hides that are too dry or conversely too soft and characterized by a greasy handle.
The characteristics and advantages of the process according to the present invention will be further illustrated by means of a number of examples of application of the aforementioned process, these nonlimiting examples being given below by way of illustration.

EXAMPLE 1

750 "shoulders" (i.e. those portions of hide corresponding to the neck) of hides of adult cow each weighing approx. 5.5-5.8 kg were subjected to the usual stages of the conventional process of vegetable tanning described above.
The hides obtained from the aforementioned stages of processing, after a first squeezing and then levelling stage, had a thickness of 2.3 mm, a pH of around 3.5 and an average weight of 3.75 kg.
These hides were sent to the dyeing stage and then put on top of one another to form three stacks of 250 hides each; each stack was placed on a plate press and compressed at a pressure of 400 atmospheres for 4.5 hours.
After the aforementioned period of time, the stacks of hides were removed from the press and the individual hides were carefully separated manually from each other.
At this point the average weight of each hide was found to be approx. 3.5 kg and the moisture content was 27%.
The hides were then again divided into three lots of 250 hides each and each lot was placed in a drum with a diameter of 3 metres and a volume of approx. 11 m³.
To each lot of hides contained in the drum (total weight approx. 875 kg) was added, at room temperature of 20°C, 160 kg of a mixture of fatty substances with the following composition (as percentage by weight relative to the total weight):

rendered beef tallow 56%
marine animal oil
(Kurtalin BR® from Industria Chimica Lombarda S.r.l.) 15%
oxidized marine animal oil
(Kurtalin KBS® from Industria Chimica Lombarda S.r.l.) 27%
sulphonated fish oil (Sulfonutrex 54/S® from Houghton) 1.5%
fungicide based on phenolic products
(Cuoiocid® from Cuoiochimica S.r.l.) 0.5%

The composition shown above was prepared by adding the tallow, made fluid by heating at 60°C, to the mixture of the other components and allowing the whole to cool to room temperature. The final mixture, at a temperature of 20°C, had a semi-solid, creamy-waxy consistency.
The hides were kept in contact with the aforementioned mixture for about 3.5 hours in the drum, rotating at a speed of 16 rev/min, until the temperature of the hides reached a value of 34°C.
At this point the hides were taken out of the drum and sent to the subsequent stages of smoothing and drying. The final product obtained from the drying stage had a fatty substance content equal to 21% by weight.

EXAMPLE 2

750 hides treated as in the preceding Example and each with an average weight of about 3.75 kg, a thickness of 2.3 mm and a pH of around 3.5 were put on top of one another to form three stacks of 250 hides each; each stack was placed on a plate press and compressed at a pressure of 420 atmospheres for 4 hours.
After the said period of time, the stacks of hides were removed from the press and the individual hides were carefully separated manually from one another.
At this point the average weight of each hide was found to be approx. 3.5 kg and the moisture content was 26%.
The hides were then again divided into three lots of 250 hides each and each lot was placed in a drum with a diameter of 3 metres and a volume of approx. 11 m³.
To each lot of hides contained in the drum (total weight approx. 875 kg) was added, at room temperature of 20°C, 140 kg of a mixture of fatty substances with the following composition (as percentage by weight relative to the total weight):

rendered beef tallow 63%
marine animal oil
(Kurtalin BR® from Industria Chimica Lombarda S.r.l.) 12%
oxidized marine animal oil
(Kurtalin KBS® from Industria Chimica Lombarda S.r.l.) 22.5%
sulphonated fish oil
(Sulfonutrex 54/S® from Houghton) 2.0%
fungicide based on phenolic products
(Cuoiocid® from Cuoiochimica S.r.l.) 0.5%

The composition stated above was prepared as in Example 1.
The hides were kept in contact with the aforementioned mixture for about 4 hours in the drum rotating at a speed of 18 rev/min, until the temperature of the hides reached a value of 35°C.
At this point the hides were taken out of the drum and sent to the subsequent stages of smoothing and drying. The final product obtained from the drying stage had a fatty substance content equal to 19% by weight.

EXAMPLE 3

750 hides treated as in Example 1 and having an average weight of approx. 3.75 kg each, a thickness of 2.3 mm and a pH of around 3.5 were put on top of one another to form three stacks of 250 hides each; each stack was placed on a plate press and compressed at a pressure of 380 atmospheres for 5 hours.
After the said period of time, the stacks of hides were removed from the press and the individual hides were carefully separated manually from one another.
At this point the average weight of each hide was found to be approx. 3.5 kg and the moisture content was 28%.
The hides were then again divided into three lots of 250 hides each and each lot was placed in a drum with a diameter of 3 metres and a volume of approx. 11 m'.
To each lot of hides contained in the drum (total weight approx. 875 kg) was added, at room temperature of 20°C, 175 kg of a mixture of fatty substances with the following composition (as percentage by weight relative to the total weight):

rendered beef tallow 60%
marine animal oil
(Kurtalin BR® from Industria Chimica Lombarda S.r.l.) 17%
oxidized marine animal oil (Kurtalin KBS® from Industria Chimica Lombarda S.r.l.) 21.3%
sulphonated fish oil
(Sulfonutrex 54/S® from Houghton) 1.2%
fungicide based on phenolic products
(Cuoiocid® from Cuoiochimica S.r.l.) 0.5%

The composition stated above was prepared as in Example 1.
The hides were kept in contact with the aforementioned mixture for about 3 hours in the drum rotating at a speed of 18 rev/min, until the temperature of the hides reached a value of 34°C.
At this point the hides were taken out of the drum and sent to the subsequent stages of smoothing and drying. The final product obtained from the drying stage had a fatty substance content equal to 22% by weight.
The hides prepared according to the above examples all possessed handle characterized by extreme softness yet accompanied by characteristics of excellent elasticity and resistance to mechanical deformation.
The composition of fatty substances used in the process according to the invention offers the advantage that it is absolutely stable and can be stored perfectly at room temperature for long periods of time. It is not therefore necessary for the composition to be prepared at the very moment of application of the process according to the invention, on the contrary it can be prepared in great quantities, to meet the needs of production for several weeks.
Finally it should be noted that the process according to the invention and the composition that this uses make it possible to obtain hides endowed not only with a particularly soft handle, but also with a particularly agreeable odour which contributes, together with the handle, to unequivocal characterization of the hides, making them immediately distinguishable from similar products.

Claims

Process for the treatment of hides by vegetable tanning thereof, comprising the preparation of dyed hides according to conventional stages of processing and characterized in that it comprises the successive stages of:

subjecting the said dyed hides to compression at a pressure equal to or greater than 380 atmospheres for about 4-5 hours, until the water content of the said hides has a value of 25-30% by weight relative to the total weight of the hides;

subjecting the said hides to stuffing by treatment thereof in a drum rotated at room temperature (15-25°C) with 15-20% by weight, relative to the weight of the hides, of a mixture of fatty substances based on animal fats and oils and comprising, as a percentage by weight relative to the total weight of the mixture, 55-65% of tallow, 12-17% of marine animal oil, 22-27% of oxidized marine animal oil and 1.2-2.5% of sulphonated fish oil;

continuing the said treatment in the drum until the temperature of the hides reaches a value of 34-36°C.
Process according to Claim 1, wherein said compression is carried out at a pressure of 380-420 atmospheres, using a plate press.
Process according to Claim 2, wherein said drum is rotated at a speed of 16-18 rev/min.
Composition for the stuffing of vegetable-tanned hides, comprising, as percentages by weight relative to the total weight of the composition, 55-65% of tallow, 12-17% of marine animal oil, 22-27% of oxidized marine animal oil and 1.2-2.5% of sulphonated fish oil.
Composition according to Claim 4 further containing from 0.3 to 1.0% by weight, relative to the total weight of the composition, of a fungicide.