FR2799207A1 - Permeable container for use in leather tanning, is made of nonwoven polypropylene or polyester cloth and ensures gradual release of powdered tanning material into tanning bath - Google Patents

Abstract

Permeable container is made of nonwoven polypropylene or polyester cloth and ensures gradual release of powdered tanning material into tanning bath. The patent refers to process of leather tanning by static method or in drums, using tanning agent in form of powder which gradually and automatically dissolves in tanning bath during whole tanning process. The agent is supplied in container made of material permeable to liquids of tanning bath. The container is placed in tanning bath and tanning agent is automatically released into bath by way of gradual dissolution. An Independent claim is also included for permeable container capable of gradual release of powdered tanning matter into tanning bath owing to its permeability.

Description

The present invention relates to improvements in a leather tanning process which utilizes a novel method of gradual feeding of tanning materials into the tanning bath by means of a liquid permeable bath vessel and which is totally introduced into this bath.

Traditional processes of leather tanning in vats have not undergone significant technological changes in recent years. Basically, previously conditioned leathers are subjected to contact with tanning solutions for a suitable period of time, this time period varying according to the object being treated. The concentration of tanning liquor baths determines the final characteristics of the leather.

Better results are obtained when the tanning liquors have their concentration which gradually increases in the system, in other words when these liquors provide the leather with an adequate quantity of tanning material throughout the process. This ideal amount of tanning material can not be very low, or this causes a delay in the process, nor can it be very high as this will fatally impair its penetration into the substrate. .

Currently, vegetable tanning materials are added to the system in three main forms that are <B> - </ B> liquid form, <B> - </ B> solid form (in block form) <B> - </ B> powder form.

In all three cases above, it is necessary to guarantee a diet of tanning in a gradual form, by increasing its quantity in the bath according to a characteristic curve for each type of leather. B> to </ B> tanner. therefore, the control of the tanning material supply in the vegetable tanning processes determines the final characteristics of the object as well as its rationalization.

The addition of traditional type of plant material tanning in static tanning systems (in vats) is carried out by increasing the percentages of the tanning plant material (2%, etc.), so <B> to </ B > avoid "over-supply" of tanning material. For this, different weighings of the tanning material are necessary, as well as the control of its addition in the bath through counters, so as to prevent the repetition of a previous addition or an omission of one of these. The occurrence of so-called "dead" tanning, caused by the "over-supply" of tanning material, is still common.

One object of the present invention is a tanning process which ensures controlled dissolution of plant powder extracts directly inside the tanning vats without the need to open the container containing the tanning material. tanning. This is achieved by the use of a container according to the invention for packaging the tanning plant extract and which is made with a material permeable to liquids of the bath, which allows dissolution of its contents in the tank.

The permeable nature of the container ensures a controlled gradual dissolution of powdered tanning material directly into the tanning tanks. This method allows the concentration of bath tanning material to be increased according to a predetermined value for each type of object being processed, without the occurrence of It may then compromise the penetration of the tanning material into the leather.With such a gradual and controlled addition, the addition of tanning material (total solids) may also be constant, because the balance between the absorption of the tanning material by the leathers and the supply of tanning material, can be carried out perfectly by the determination of the quantity of containers <B> to </ B> add to the tanks of tanning.

The advantages of the leather tanning process which utilizes the permeable container according to the present invention over traditional tanning material feed methods are as follows: </ B> <B> - </ B> simplicity and safety in the effective control of the intake, presenting no risk of "over-supply" of tanning material <B> - </ B> the addition tanning material is carried out directly <B> By using the container, this guarantees the gradual dissolution of the tanning material and eliminates the need for sequential additions. <B> </ B> <B> - </ B> the frequent agitation of the material is avoided. system because the dissolution of tanning material is constant until the container is completely emptied -, <B> - </ B> is presented no variation in weight of the material tanning, as on the contrary the case of the tanning material in block form and that can reach up to <1% </ B> of -1 variation <-> </ b> - rationalization of tanning process, avoiding constant weighing, as happens with the use of tanning materials in the form of powders or liquids <B> - </ B> these weighings are indeed the biggest source of error in the tanning processes of this type makes their imprecision and the risk of non-operation <B> - </ B> by the use method according to the invention, the number of containers added to the system (without the need for weighing) ensures the ideal intake of tanning material <B>, </ B> <B> - </ B> elimination of the risks of "over-supply" of tanning material due to the permeability of the material used for the container, which guarantees an adequate dissolution curve of the tanning material -, <B> - </ B> significant reduction in the risk of tanning "death" caused by an "over-supply" of tanning material, which is solved by the Gradual dissolution brought by the container <B>, </ B> <B> - </ B> allows the use of materials of also tanning in drums, which is not possible for vegetable tanning materials in the form of solid products because, in this case, the permeable container can be made to open allowing the removal of the product as for a container of the usual type.

According to the invention, the leather tanning method applicable in static tanning (in tanks) or in drums uses powdered tanning material and is characterized by that it comprises the gradual and automatic dissolution of the powder tanning material <B> to </ B> inside the bath during the entire tanning process, which is determined by the permeable nature of the material with which the container is made, which maintains the powdered tanning material which is incorporated in the tanning bath together with its contents.

According to <B> to </ B> other features of the invention <B> - </ B> the permeable material with which the container is made is a nonwoven material <B>; </ B> <B> The nonwoven material is made of polypropylene filaments. The nonwoven material is formed of polyester filaments.

The invention also extends to a permeable container for gradual feeding of tanning material in static tanning processes (in tanks) or in drums and uses powdered tanning material. , characterized in that the container is made of a material permeable to the liquids of the tanning bath and at the same time incorporated the powdered tanning material into the tanning bath for the purpose of gradual dissolution of this material.

According to other characteristics of the invention, the permeable material from which the container is made is nonwoven material. The nonwoven material is formed of polypropylene filaments. B>, </ b> <B> - </ B> The nonwoven material is formed of polyester filaments.

Thus, the permeable material which constitutes the container is preferably a woven material. In particular, the nonwoven materials used for producing the container are constituted by continuous heat-sealed filaments which provide good resistance to tearing at tensile stresses. Non-woven materials made from polypropylene yarns are especially suitable for the manufacture of the container according to the invention. Polyester filaments can also be used to form the container of the invention.

The invention will be better understood, and other objects, features, details and advantages thereof will appear more clearly the following explanatory description made with reference to the attached schematic drawing given only <B> to </ B> title d illustrating an embodiment of the invention and wherein the single figure is a graph for understanding the invention.

Referring now <B> to </ B> the figure, this is graphical which compares the dissolution curves for <B>: </ B> a tanning material in solid form (curve <B> 1), </ B> a tanning material in the form of extracts of powdered tanning plant material (curve 2) freely added to the system, and a tanning material in the form of extracts of plant material of powdered tanning added to system at the same time as the container which contains them (curve <B> 3), </ B> as recommended by the present invention.

According to the invention, the dissolution of the tanning material lying within the vessel is determined by the permeable nature of the material used in its manufacture. Preferably, this material is a nonwoven material made of heat-sealed continuous filaments which provides better resistance to tearing and tensile stresses. In particular, the nonwoven materials used can be made from polypropylene filaments. Polyester filaments can also be used for the container of the invention.

various curves of the figure show the rate of dissolution of the tanning material, the concentration of all the tanning solids TS) which are present in the bath being given in ordinate as a function of time figured on the abscissa. In order for the result of the experiment to be consistent, leather was not added to the system because it would absorb the solid matter, thus changing the rate of dissolution of the tanning materials would compromise their comparison.

<B> It </ B> should be emphasized that the <B> 3 </ B> curve of the graph shown <B> to </ B> the figure, which represents the dissolution of the tanning material in the arrangement according to the The invention is also a function of the characteristics of the permeable material with which the container is made. Therefore, the dissolution of the tanning material packaged in the container can be affected by the characteristics of the permeable material, such as <B>, </ B> among others, the thickness, the porosity, the density as well as the material filaments of this material.

The balance of the tanning material supply determined by the percentage of all the solids present in the bath. After the incorporation of the leathers, previously conditioned in tanning, then begins the absorption of the tanning material, which decreases the concentration of the bath solids. The maintenance of the percentage of solids present is then effected through the gradual dissolution of the product remaining in the container. The quantity of containers used varies according to the load (in kilograms) of the leathers present in the system.

The example given below allows a better appreciation and a better understanding of the object of the invention, highlighting its characteristics and the advantages it presents.

EXAMPLE 4 samples of leather treated for tanning 4.2) from the same animal was subjected to a static tanning process (in vats). such samples were cut into pieces of equal surfaces and the same thickness (4.5 mm).

Sample <B> A </ B> was tanned with powdered acacia tanning extract.

Sample B was tanned with acacia tanning extract in liquid form (with approximate concentration <50%). <B> C </ B> sample was submitted tanning with acacia tanning extract in solid form.

The <B> D </ B> sample was tanned with an acacia tanning plant extract packaged in the permeable container according to the present invention.

For tanning, a bath volume <B> 600% </ B> of the weight of the samples was used. Such a volume of water was sufficient for the samples to be completely immersed.

The concentration used was <B> 6 '</ B> Be (Baumé), the concentration during the first 2 hours having been <B> 30 </ B> Be.

For comparative purposes, the amount of tanning extract used to obtain <B> 30 <B> Be in the first 2 hours was added at one time. The amount of tanning extract varied according to its total solid concentration.

The tanning results of the samples were <B> - </ B> SAMPLE <B> A </ B> (with addition of powdered tanning material) <B> - </ B> after addition, the concentration reached was immediately <B> 3 '</ B> Be -1 after 2 hours, there was a penetration of approximately <B> 10% </ B> of the two leather cakes (crust and flower) <B> </ B> <B> - </ B> SAMPLE B (with addition of tanning material in liquid form) <B> - </ B> the same results were obtained as for the sample below. top with approximately 10% penetration on crust and flower -, <B> - </ B> SAMPLE <B> C </ B> (tanning in block form) <B> - </ B> n did not show sufficient dilution to reach the <B> 30 </ B> Be in the first 2 hours, because the partial dilution of the tanning material in the leather was <6% <6%; </ <B> - </ B> SAMPLE <B> D </ B> (powdered tanning material in a permeable container c according to the invention) <B> - </ B>, a complete dilution was obtained and the penetration of the plant extract was slightly higher <B> than the previous samples, reaching approximately <B> 15%. </ B>

After the initial 2 hour period, the concentration was increased to <60> <B> and maintained <B> at that value until the samples had <B> transverse tanning. > 100%. </ B>

<B> CONCLUSIONS </ B> <B> 1. </ B> As regards the addition of tanning substances in the form of powders or liquids (samples <B> A </ B> and B) <B> - < / B> The number of additions has slightly greater <B> than </ B> than the samples <B> C </ B> (blocks) and <B> D </ B> (invention). To maintain the concentration of <B> 60 </ B> Be, the addition was carried out almost every hour, The tanning time was 4 days.

<B> II. </ B> As for the addition of block tanning materials (sample <B> C) - </ B>, a variation in the dissolution curve caused by the variation was obtained. the concentration of solids. penetration was total in <B> 3 </ B> days and a half.

<B> 111. </ B> For the <B> D - </ B> sample no significant variation in the dissolution curve was obtained. The concentration of the bath was in this case easily controlled. Total tanning was achieved in <B> 3 </ B> days with cross tanning of <B> 100%. </ B>

<B> It has thus been observed that the addition of powdered tanning material contained in the permeable container, in accordance with the present invention, resulted in more even tanning and a more uniform tanning. substantial reduction in the addition of tanning material. The percentage of tanning extract remaining in the tanks was lower because the absorption of tanning was higher. Subsequent analysis of the degree of tanning 4 samples showed an improvement of <B> 5% </ B> in the sample <B> D, </ B> which indicates a better fixation of the tanning material in the leather . Leather lining was not observed. Indeed, it is inherent <B> to </ B> theirs of the tanning extract used.

The invention is not limited to the exemplary embodiment illustrated and shown in detail. Various modifications can be made without departing from its scope as indicated in the appended claims. In particular, the tanning process according to the invention can also be used in drums.

Claims (1)

A leather tanning method applicable in static tanning (in tanks) or in drums, using powdered tanning material, characterized in that it comprises the automatic gradual dissolution of the powder tanning material <B> to </ B> the inside of the bath during the entire tanning process, which is determined by the permeable material of material with which is made the container which holds the powdered tanning material and which is incorporated in the tanning bath at the same time as the contents. <B>. </ B> A process for leather tanning according to claim 1, characterized in that the permeable material with which the container is made is nonwoven material. A process for leather tanning according to claim 2, characterized in that the nonwoven material is formed of polypropylene filaments. A method for leather tanning according to claim 2, characterized in that the nonwoven material is formed of polyester filaments. Permeable container for gradual feeding of tanning material in static tanning processes (in tanks) or in drums using powdered tanning material, characterized in that recipi is made of a material permeable to the liquids of the tanning bath and incorporated at the same time as the powdered tanning material in a tanning bath for a gradual dissolution of this material. <B>. </ B> A permeable container for gradual feeding of tanning material according to claim 5, characterized in that the permeable material of which the container is made is a nonwoven material. A permeable container for gradual feeding of tanning material according to claim 6, characterized in that the nonwoven material is formed of polypropylene filaments. <B> 8. </ B> A permeable container for gradual feeding of tanning material according to claim 6, characterized in that the nonwoven material is formed of polyester filaments.