Methods for tanning animal skins

Abstract

A method for tanning animal skin may include: putting the animal skin in contact with a first tanning bath comprising (weight percentages referring to a pelt weight of the animal skin): water, at least one C.sub.2-C.sub.8 aliphatic dialdehyde in a quantity within a range of 2%-30%, and/or at least one non-ionic surfactant in a quantity within a range of 0.1%-20%, wherein the first tanning bath has a pH within a range of 1-5 and a density within a range of 3°Bé-10°Bé; bringing the pH of the first tanning bath to a pH greater than 5 and less than or equal to 8; and/or washing the animal skin to obtain a tanned animal skin.

Claims

1. A method for tanning animal skin, the method comprising: putting the animal skin in contact with a first tanning bath consisting of (weight percentages referring to a pelt weight of the animal skin): water, at least one C.sub.2-C.sub.8 aliphatic dialdehyde in a quantity within a range of 2%-30%, at least one non-aldehyde tanning agent, that is not a chrome tanning agent, a quantity 4th a range of 0%-30%, and at least one non-ionic surfactant in a quantity within a range of 0.1%-20%, wherein the first tanning bath has a pH within a range of 1-5 and a density within a range of 3 degrees Baum é(°Bé)-10°Bé; bringing the pH of the first tanning bath to a pH greater than 5 and less than or equal to 8; washing the animal skin to obtain a tanned animal skin; and putting the tanned animal skin in contact with at least one second tanning bath comprising (weight percentages referring to the pelt weight of the animal skin): water, and at least one C.sub.2-C.sub.8 aliphatic dialdehyde in a quantity within a range of 2%-30%, wherein the at least one second tanning bath has a pH within a range of 1-5 and a density within a range of 3°Bé to 10°Bé, and is substantially free of the at least one non-ionic surfactant.

2. The method of claim 1, wherein a ratio between a concentration of the at least one C.sub.2-C.sub.8 aliphatic dialdehyde in the at least one second tanning bath and the concentration of the at least one C.sub.2-C.sub.8 aliphatic dialdehyde in the first tanning bath is less than or equal to 1:1.5.

3. The method of claim 1, wherein the at least one C.sub.2-C.sub.8 aliphatic dialdehyde is selected from: one or more of glyoxal, malonic dialdehyde, succinic dialdehyde, glutardialdehyde, adipinic dialdehyde, pimelic dialdehyde, or mixtures thereof.

4. The method of claim 1, wherein the at least one C.sub.2-C.sub.8 aliphatic dialdehyde is glutardialdehyde.

5. The method of claim 1, wherein the at east one non-ionic surfactant is a primary alcohol having from 8 to 22 carbon atoms, and wherein the primary alcohol is ethoxylated (EO) or ethoxylated/propoxylated (EO/PO).

6. The method of claim 1, wherein the putting of the animal skin in contact with the first tanning bath has a duration within a range of 1 hour-7 hours.

7. The method of claim 1, wherein a weight percentage ratio between the first tanning bath and the animal skin is within a range of 20%-1000%.

8. The method of claim 1, wherein the animal skin is a pickled skin.

9. The method of claim 1, wherein the animal skin is selected from: sheepskin, goatskin, cowhide, horse-skin, pigskin, deerskin, kangaroo-skin, reptile-skin, or ostrich-skin.

10. The method of claim 1, wherein a temperature of the first tanning bath is within a range of 10° C.-50° C.

11. The method of claim 1, wherein a temperature of the first tanning bath is within a range of 15° C.-40° C.

12. The method of claim 1, wherein the pH of the first tanning bath is brought to a pH higher greater than or equal to 5.5 and less than or equal to 7.

13. The method of claim 1, wherein a ratio between a concentration of the at least one C.sub.2-C.sub.8 aliphatic dialdehyde in the at least one second tanning bath and the concentration of the at least one C.sub.2-C.sub.8 aliphatic dialdehyde in the first tanning bath is less than or equal to 1:2.

14. The method of claim 1, wherein the at least one C.sub.2-C.sub.8 aliphatic dialdehyde comprises glutardialdehyde.

15. The method of claim 1, wherein the putting of the animal skin in contact with the first tanning bath has a duration within a range of 1.5 hour-4 hours.

16. The method of claim 1, wherein a weight percentage ratio between the first tanning bath and the animal skin is within a range of 30%-300%.

17. The method of claim 1, wherein the animal skin is selected from: sheepskin, goatskin, or cowhide.

18. The method of claim 1, wherein after putting the tanned animal skin in contact with at least one second tanning bath, the shrinkage temperature of the tanned animal skin is about 90° C.

19. A method for tanning animal skin, the method comprising: putting the animal skin in contact with a first tanning bath comprising (weight percentages referring to a pelt weight of the animal skin): water, at least one C.sub.2-C.sub.8 aliphatic dialdehyde in a quantity within a range of 2%-30%, and at least one non-ionic surfactant in a quantity within a range of 0.1%-20%, wherein the first tanning bath has a pH within a range of 1-5 and a density within a range of 3 degrees Baum é(°Bé)-10°Bé; bringing the pH of the first tanning bath to a pH greater than 5 and less than or equal to 8; washing the animal skin to obtain a tanned animal skin; and putting the tanned animal skin in contact with at least one second tanning bath consisting of (weight percentages referring to the pelt weight of the animal skin): water, at least one C.sub.2-C.sub.8 aliphatic dialdehyde in a quantity within a range of 2%-30%, and at least one non-aldehyde tanning agent, that is not a chrome tanning agent, in a quantity within a range of 0%-30%, wherein the at least one second tanning bath has a pH within a range of 1-5 and within a range of 3 degrees Baum é(°Bé)-10°Bé; bringing the pH of the first tanning bath to a pH greater than 5 and less than or equal to 8; washing the animal skin to obtain a tanned animal skin; and putting the tanned animal skin in contact with at least one second tanning bath consisting of (weight percentages referring to the pelt weight of the animal skin); water, at least C.sub.2-C.sub.8 aliphatic dialdehyde in a quantity within a range of 2%-30% and at least one non-aldehyde tanning agent, that is not a chrome tanning agent, in a quantity within a range of 0%-30%, wherein the at least one second tanning bath has a pH within a range of 1-5 and a density within a range of 3°Bé to 10°Bé, and is substantially free of the at least one non-ionic surfactant.

20. A method for tanning animal skin, the method comprising: putting the animal skin in contact with a first tanning bath consisting of (weight percentages referring to a pelt weight of the animal skin): water, at least one C.sub.2-C.sub.8 aliphatic dialdehyde in a quantity within a range of 2%-30%, at least one non-aldehyde tanning agent, that is not a chrome tanning agent; in a quantity within a range of 0%-30%, and at least one non-ionic surfactant in a quantity within a range of 0.1%-20%, wherein the first tanning bath has a pH within a range of 1-5 and a density within a range of 3 degrees Baum é(°Bé)-10°Bé; bringing the pH of the first tanning bath to a pH greater than 5 and less than or equal to 8; washing the animal skin to obtain a tanned animal skin; and putting the tanned animal skin in contact with at least one second tanning bath consisting of (weight percentages referring to the pelt weight of the animal skin): water, at least one C.sub.2-C.sub.8 aliphatic dialdehyde in a quantity within a range of 2%-30%, and at least one non-aldehyde tanning agent, that is not a chrome tanning agent, in a quantity within a range of 0%-30%, wherein the at least one second tanning bath has a pH within a range of 1-5 and a density within a range of 3°Bé to 10°Bé, and is substantially free of the at least one non-ionic surfactant.

Description

EXAMPLE 1

(1) A pickled sheepskin was subjected to tanning treatment according to the method of the present invention.

(2) The tanning bath had the following composition (weight percentages referring to the pelt weight of the skin treated): water, 60% of sodium chloride; 6% of glutaraldehyde, 12% of non-ionic surfactant (ethoxylated fatty alcohol—Foryl VLC3, Pulcra Chemicals); pH=3.2.

(3) The skin was treated in the tanning bath for 4 hours at 35° C. inside a drum. The percentage ratio between the weight of the tanning bath and the pelt weight of the skin was equal to 1,500%.

(4) At the end of the treatment, sodium carbonate was added to the bath until the pH of the bath had been adjusted to a value within the range of 5.5-8.

(5) The skin was then kept in the bath for 1.5 hours and subsequently washed with water and finally greased.

(6) The greased skin was then dried and subjected to conventional softening and staking treatments.

(7) At the end of these treatments, the shrinkage temperature Tc measured proved to be slightly lower than 90° C.

(8) The mechanical resistance values measured according to the test ISO 3377-2 on two samples of skin (1A and 1B) are indicated in Table 1.

EXAMPLE 2

(9) A portion of the skin obtained in Example 1, after the washing step (without being subjected to greasing), was treated in a second tanning bath.

(10) The tanning bath had the following composition (weight percentages referring to the pelt weight of the skin treated): water, 60% of sodium chloride; 3% of glutaraldehyde, pH=3.2.

(11) The skin was treated in the tanning bath for 4 hours at 35° C. inside a drum. The percentage ratio between the weight of the tanning bath and the pelt weight of the skin was equal to 1,500%.

(12) At the end of the treatment, sodium carbonate was added to the bath until the pH of the bath had been adjusted to a value within the range of 5.5-8.

(13) The skin was then kept in the bath for 1.5 hours and subsequently washed with water and finally greased.

(14) The greased skin was then dried and subjected to conventional softening and staking treatments.

(15) At the end of these treatments, the shrinkage temperature Tc measured proved to be slightly lower than 90° C.

(16) The mechanical resistance values measured according to the test ISO 3377-2 on two samples of skin (2A and 2B) are indicated in Table 1.

(17) TABLE-US-00001 TABLE 1 SAMPLE PARAMETER 1A 1B 2A 2B Average 1.16 mm 1.25 mm 1.20 mm 1.33 mm thickness (parallel) Average 1.16 mm 1.27 mm 1.18 mm 1.27 mm thickness (perpendicular) Average 1.16 mm 1.26 mm 1.19 mm 1.30 mm thickness (arithmetic average of parallel and perpendicular) Average tear 22 N 21 N 32 N 30 N load (parallel) Average tear 26 N 28 N 37 N 41 N load (perpendicular) Average tear 24 N 25 N 35 N 37 N load (arithmetic average of parallel and perpendicular)

(18) The treatment step effected in a single step in a tanning bath with glutaraldehyde and non-ionic surfactant (Example 1) allows tanned skins to be obtained having adequate mechanical resistance values, i.e. higher than 20 N.

(19) The additional treatment step effected with sole glutaraldehyde (Example 2) allows tanned skins to be obtained having mechanical resistance values about 50% higher with respect to the values observed on the skins obtained with the treatment in a single tanning bath with glutaraldehyde and non-ionic surfactant (Example 1).