Process for waterproofing chromium tanned bovine hides

Description

[0001] The present invention regards a process for waterproofing chromium tanned bovine hides, comprising a washing step, a step for freeing the hides from acid, a re-tanning step, a dyeing step, a fixing step and possible finishing steps, in which, during the step for freeing the hides from acid and the re-tanning step, compounds are used containing a certain amount of a product known with the trademarks DENSODRIN LD 6359 and DENSODRIN CD.

[0002] The use of a suitable proportion of these compounds permits to make the hides waterproof and water repellent, without, however, altering the hide surface, which then can undergo subsequent finishing treatments.

[0003] The leather dressed by means of the method of the invention is soft, scratch and wear resistant and, therefore, it can be advantageously used to provide clothing articles, in particular sports clothing articles.

[0004] One of the problems encountered by people working in the field of leather dressing is to make leather waterproof and water repellent, without preventing transpiration.

[0005] To this purpose several tecniques are known in the art which comprise leather dressing by means of silicone based compounds or fluoridated compounds, which are applied onto hides and fabrics by dipping, spraying or other known methods.

[0006] The effect of these treatments, however, lasts little, and further said treatments do not allow the hides to be subsequently finished, wherefore, after having made the leather waterproof, it is not possible to proceed to enamelling, dressing, etc. processes.

[0007] Substantially, once treated, the hides can no longer undergo surface treatments for improving their aesthetic characteristics and make the hide surface more resistant, wherefore the leather thus provided is delicate, it gets easily dirty and scratched and, therefore, it is not suitable for making clothing articles, such as, for example, motor-cycling garments, which are naturally subject to shocks, friction, etc.

[0008] Therefore, the need is felt in the field for means which permit to make the hides waterproof and water repellent, without, however, preventing the subsequent finishing treatments, which make it possible to alter the hide surface and to improve the hide characteristics.

[0009] The above mentioned problem is now solved by the present invention, which provides a process for making the hides waterproof and water repellent, said process comprising a plurality of steps including, in particular, a step for freeing the hides from acid and a re-tanning step, in both of which a certain amount of a compound known with the names DENSODRIN LD 6359 and DENSODRIN CD (BASF's registered trademarks) is used.

[0010] The process of the invention, which chemically affects the hide texture, permits to obtain hides which can subsequently undergo usual finishing operations, thus providing a product which combines the aesthetic and strength characteristics of this material with important waterproofing and water-repellency characteristics.

[0011] The method of the invention can be better understood from the following detailed description, given by way of non restrictive example.

[0012] The product amounts mentioned in the example refer to the struck weight of the hides to be treated.

[0013] The first step of the method consists in washing the hides in a drum to remove the chromium and the natural grease from the hide surface.

[0014] The washing solution comprises 200% water at a temperature of about 40°C and 0.2% formic acid diluted with cold water with a ratio of 1/10.

[0015] The washing step in the drum lasts about 20-30 minutes, after which the solution is drained.

[0016] The second step consists of an operation for freeing the hides from acid with a solution comprising 150% water at 35°C, from 0.8% to 1.2% powdered sodium formate and 1% powdered Neutrigan (a trademark registered by the Company BASF).

[0017] The hides are rotated for about 30 minutes, after which from 6% to 9% DENSODRIN LD 6359 (produced by BASF) and from 2% to 5% DENSODRIN CD diluted with hot water with a ratio of 1/3 are added to the solution.

[0018] The solution is rotated for further 90 minutes, after which it is drained.

[0019] The third step consists in re-tanning the hides in a solution comprising 100% water at 40° C, from 1 % to 2% powdered mimosa tannin, from 0.1% to 2% powdered Basyntan SL (produced by BASF); the drum is rotated for about 20 minutes, thereafter from 1.5% to 3% Lipoderm Licker SLW (produced by BASF) diluted in 1/3 hot water is added, the solution is rotated for further 15 minutes, then from 1% to 2% DENSODRIN LD 6359 and from 6% to 10% DENSODRIN CD diluted in 1/3 hot water are added and the solution is rotated for further 90 minutes.

[0020] Finally 0.2% formic acid diluted with cold water with a ratio of 1/10 is added, the solution is rotated for further 10 minutes, then it can be drained and cooled.

[0021] The fourth step is a dyeing step in which the hides are dipped into a solution comprising 50% cold water and a convenient amount of dye and the solution is rotated for 60 minutes.

[0022] After an hour rotation the hides are controlled cross-sectionally.

[0023] The hide is cut and checked to see if the dye has totally penetrated the texture; if so, the processing is carried on, otherwise the drum is rotated for further 30 minutes and the check is then repeated until the desired result is achieved.

[0024] In the end 100% water at 60° C and from 0.1% to 0.5% formic acid diluted with cold water with a ratio of 1/10 are added and the solution is rotated for further 10 minutes and then for further 30 minutes.

[0025] A piece of hide is cut, dried and, once dry, it is checked to see if the dye corresponds to the sample and if the desired softness has been achieved.

[0026] If the controls are favourable, the hides are drained and cooled.

[0027] Thereafter there is a fixing step in a solution comprising 100% water at 35° C and from 2% to 4% powdered Chromitan MSN (produced by BASF).

[0028] The container is rotated for 90 minutes, after which the hides can be drained and cooled.

[0029] The hides, after having been placed into containers, are let to rest for 12 hours, after which they can be sent to the drying apparatus.

[0030] At the end of this cycle the hides, once dried, can undergo known processes, the purpose of which is to characterize the product and make it ready for cutting and sewing, said processes possibly comprising surface emery-polishing, puttying, trimming and spray finishing with a known method.

[0031] The washing step, the step for freeing the hides from acid, the re-tanning step, the dyeing step and the fixing step are also provided in the treatments of the known method.

[0032] The invention is characterized in that, during the step for freeing the hides from acid and the re-tanning step, it uses DENSODRIN LD 6359 and DENSODEIN CD, in the indicated ratios.

[0033] Also this product is already known, it is used in some processes for dressing footwear leather.

[0034] However, before now it had never been used for dressing leather to produce clothing articles, in order to make it waterproof and water repellent.

[0035] The described treatment chemically affects the hide texture to provide the desired result, making the hides permanently waterproof and water repellent.

[0036] Since it is not covered by a layer of a water repellent material, as it occurs with the known techniques, the so dressed leather can undergo the usual treatments for making the hides scratch and wear resistant, soft, etc., thus providing a product which can be used for manufacturing clothing articles, and which is particularly suitable, for example, for producing sports clothing articles, such as motor-cycling garments or the like, which are conspicuous for having acquired these characteristics of waterproofing and water repellency.

[0037] The products and ratios indicated in the example have been obtained during some tests and have provided the best results.

[0038] However, it is clear that those skilled in the art can easily determine possible different product ratios depending on the kind of leather to be dressed and on the operating conditions.

[0039] Likewise, some of the mentioned products may be replaced by other products having the same characteristics, without thereby departing from the scope of the invention.

Claims

1. A process for making hides waterproof and water repellent, comprising a washing step, a step for freeing the hides from acid, a re-tanning step, a dyeing step, a fixing step and possible finishing steps, characterized in that, during the step for freeing the hides from acid and the re-tanning step, it uses suitable amounts of DENSODRIN LD 6359 and DENSODRIN CD.

2. The process of claim 1, wherein during the step for freeing the hides from acid the percentage of DENSODRIN LD 6359 varies from 6% to 9% and the percentage of DENSODRIN CD varies from 2% to 5%, said percentages referring to the struck weight of the leather to be dressed.

3. The process of claim 2, wherein during the re-tanning step the percentage of DENSODRIN LD 6359 varies from 1% to 2% and the percentage of DENSODRIN CD varies from 6% to 10%, said percentages referring to the struck weight of the leather to be dressed.

4. A process for making hides waterproof and water repellent according to any of the preceding claims, characterized in that it comprises:

• a first washing step in a solution of water and formic acid;

• a step for freeing the hides from acid in a solution of water, sodium formate, neutrigan, DENSODRIN LD 6359 and DENSODRIN CD;

• a re-tanning and greasing step in a solution of water, powdered mimosa tannin, powedered Basyntan SL, Lipoderm Licker SLW, DENSODRIN LD 6359 and DENSODRIN CD and formic acid;

• a dyeing step in cold water and dye and, finally, a fixing step in water and Chromitan MSN.

5. A process for waterproofing chromium tanned bovine hides, characterized in that it comprises the following steps:

• washing the hides in a drum, in a solution comprising 200% water and 0.2% diluted formic acid with a ratio of 1/10;

• freeing the hides from acid in a solution comprising 150% water, from 0.8% to 1.2% powdered sodium formate and 1% Neutrigan, subsequently adding to the solution from 6% to 9% DENSODRIN LD 6359 and from 2% to 5% of DENSODRIN CD diluted with water with a ratio of 1/3;

• re-tanning and greasing in a solution comprising 100% water, from 1% to 2% powdered Mimosa, from 0.1% to 2% powdered Basyntan SL, subsequently adding from 1.5% to 3% Lipoderm Licker SLW and then from 1% to 2% DENSODRIN LD 6359, from 6% to 10% DENSODRIN CD diluted with 1/3 water and finally adding 0.2% formic acid diluted with cold water with a ratio of 1/10;

• dyeing in a solution comprising 50% cold water and a convenient amount of dye, and subsequently adding 100% water and from 0.1% to 0.5% formic acid diluted with water with a ratio of 1/10;

• fixing in a solution comprising 100% water at 35° C and from 2% to 4% Chromitan MSN.