Tanning composition and method based on an acetal of an aldehydic tanning agent

Abstract

A composition including an acetal of an aldehydic tanning agent for tanning hides and/or pelts, as well as a method for tanning hides and/or pelts in order to produce leather, wherein an acetal of an aldehydic tanning agent is used. By reducing the pH, the aldehydic tanning agent can be released, whereby a tanning step is initiated. The composition according to the invention and the method according to the invention are characterized by lower toxicity compared to conventional compositions and tanning methods based on aldehydic tanning agents. Furthermore, improved penetration of the tanning agents into deeper layers of the hide and/or the pelt is possible, so that particularly homogeneous tanning is achieved.

Claims

1. A composition for tanning at least one of hides or pelts, comprising: 5 wt % to 95 wt % of an acetal of an aldehydic tanning agent, 0 wt % to 90 wt % of a solvent, and 0.01 wt % to 5 wt % of a pH-regulating buffer component.

2. A composition for tanning hides and/or pelts, comprising: 5 wt % to 95 wt % of an acetal of an aldehydic tanning agent, 0 wt % to 5 wt % of a pH-regulating buffer component, and 4 wt % to 90 wt % of a solvent.

3. A composition for tanning hides and/or pelts, comprising: 5 wt % to 95 wt % of an acetal of an aldehydic tanning agent, 0.01 wt % to 5 wt % of a pH-regulating buffer component, and 4 wt % to 90 wt % of a solvent.

4. The composition as claimed in claim 1, wherein the acetal of an aldehydic tanning agent is an acetal of at least one of formaldehyde, propionaldehyde, glutaraldehyde or glyoxal.

5. The composition as claimed in claim 1, wherein the acetal of an aldehydic tanning agent comprises an alcohol component selected from at least one of methanol, ethanol, diethylene glycol or triethylene glycol.

6. The composition as claimed in claim 1, further comprising a content of polyoxyalkylene glycol selected from the group of polyoxyethylene diol, polyoxy-1,2-propylene diol or a mixture of polyoxyethylene diol and polyoxy-1,2-propylene diol.

7. The composition as claimed in claim 1, wherein that the acetal of an aldehydic tanning agent is the acetal as shown in at least one of formula A or formula B, wherein: Formula A is: ##STR00005## and Formula B is: ##STR00006## wherein x=0 to 8, y=2 to 6, R.sup.1=H, CH.sub.2, CHO, ##STR00007## and wherein z=2 to 6 and R.sup.2, R.sup.3, R.sup.4 and R.sup.5, each independently of one another, is/are selected from ##STR00008## and wherein m=0 to 8, n=0 to 8, and o=0 to 8.

8. The composition as claimed in claim 1, wherein the solvent is selected from the group of water, water-soluble organic solvents or a mixture of water and water-soluble organic solvents, and the water-soluble organic solvent is at least one of glycerol or a monoetherified polyoxyalkylene glycol.

9. The composition as claimed in claim 1, wherein the pH-regulating buffer component is one or a plurality selected from the group of carbonate buffer, borate buffer, or phosphate buffer.

10. A method for pretanning or retanning at least one of hides or pelts, comprising the following steps: providing the at least one of the hide or a pelt in a liquor with a pH of between 1 and 3.5, adding the composition as claimed in claim 1 on the at least one of the hide or pelt in the liquor, the composition added in the liquor acting on the at least one of the hide or the pelt in a tanning step, and adjusting of the pH of the liquor to between 3.8 and 5 in order to fix an aldehydic tanning agent in a fixing step.

11. A method for pretanning or retanning of at least one of hides or pelts in a liquor, comprising the following steps: providing the at least one of the hide or a pelt in a liquor with a pH of between 1 and 10, adding at least one of an acetal of an aldehydic tanning agent or the composition as claimed in claim 1 on the at least one of the hide or the pelt in the liquor, the at least one of the acetal added in the liquor or the composition added to the liquor acting on the at least one of the hide or the pelt in a penetration step, adjusting the pH of the liquor to between 1 and 3.6 in an activation step, wherein the aldehydic tanning agent is released, the aldehydic tanning agent released in the liquor acting on the at least one of the hide or the pelt in a tanning step, and adjusting of the pH of the liquor to between 3.8 and 5 in order to fix the aldehydic tanning agent in a fixing step.

12. The method as claimed in claim 11, wherein the acetal of an aldehydic tanning agent is at least one of an acetal of formaldehyde, propionaldehyde, glutaraldehyde, glyoxal or an acetal having a structure as shown in at least one of formula A or formula B, wherein: Formula A is: ##STR00009## and Formula B is: ##STR00010## wherein x=0 to 8, y=2 to 6, R.sup.1=H, CH.sub.2, CHO, ##STR00011## and wherein z=2 to 6 and R.sup.2, R.sup.3, R.sup.4 and R.sup.5, each independently of one another, is/are selected from ##STR00012## and wherein m=0 to 8, n=0 to 8, and o=0 to 8.

13. The method as claimed in claim 11, wherein the acetal comprises an alcohol component selected from at least one of methanol, ethanol, diethylene glycol or triethylene glycol.

14. The method as claimed in claim 11, wherein a content of added acetal based on a total weight of the at least one of the pelt or the hide is 0.25 wt % to 10 wt %.

15. The method as claimed in claim 11, wherein after addition of the acetal, the pH of the liquor is adjusted to 1 to 2.5.

16. The method as claimed in claim 11, wherein a temperature of the liquor during tanning is between 10 C. and 50 C.

17. A leather produced according to the method as claimed in claim 11.

18. A crust leather produced by treatment of the leather as claimed in claim 17, further comprising one or a plurality of further steps selected from the group including one or more of retanning, fat liquoring, filling, or dyeing.

19. A dressed leather produced from the leather as claimed in claim 17, the dressed leather being adapted for use in production of at least one of an automobile, furniture, clothing, glove, leather product, aircraft, lining or shoe upper article.

Description

EXAMPLES

(1) As described and claimed herein, acetals of aldehydic tanning agents can be used for pretanning and/or retanning of hides, in particular animal hides, and/or pelts, wherein these can be from an animal from the group of cattle, pigs, goats, roebucks, sheep, and/or deer.

(2) The above-mentioned acetals of aldehydic tanning agents and use thereof, as described and claimed herein, can also be applied in pretanning and/or retanning of hides, in particular animal hides, and/or pelts that are pretreated by means of known conventional methods. In this context, examples of suitable methods for pretreatment include liming, deliming, bating, pickling and/or mechanical treatment.

(3) The method according to the invention for the pretanning, (primary) tanning and/or retanning of hides, in particular animal hides and/or pelts, as described and claimed herein, can be carried out in an aqueous medium, in particular in an aqueous liquor. In this case, the pH can be adjusted to values of 1 to 10.

(4) A suitable temperature for carrying out the method according to the invention can be between 10 C. and 50 C. The temperature is preferably at a level between 15 C. and 35 C., in particular 25 C.

(5) A suitable duration of the actual tanning step, i.e. the incubation time of the hides and/or pelts with the released aldehyde (corresponds to the aldehydic tanning agent) can be from 10 min to up to 12 h.

(6) The method according to the invention, as described and claimed herein, is outstandingly suitable for being carried out in existing tanneries. More particularly, a hide to be tanned and/or a pelt to be tanned can be prepared in a conventional tanning receptacle. All further steps of the method according to the invention can then for example be carried out in this vessel and/or in a drum.

(7) Moreover, in the method according to the invention as described and claimed herein, further tanning agents for pretanning and/or retanning of hides, in particular animal hides and/or pelts, can also be used in combination in addition to the acetal of an aldehyde and/or the aldehydes. Examples of suitable further tanning agents can include mineral tanning agents such as chromium, aluminum, zirconium, titanium, and iron salts, synthetic tanning agents (synthanes), polymeric tanning agents and/or vegetable tanning agents (plant tanning agents).

(8) The indications in wt % in the following specific examples are based on the total weight of the hide to be tanned and/or the pelt to be tanned.

Example 1

(9) The hide to be tanned and/or the pelt to be tanned are prepared in 3000 mL of water (also referred to below as aqueous liquor) with a pH adjusted to 7.5 to 8.5 and a temperature of 25 C. in a suitable vessel.

(10) 4.5 wt % of an acetal of an aldehydic tanning agent, for example an acetal of glutaraldehyde, is then added to the aqueous liquor. In this case, the acetal was produced as described in U.S. Pat. No. 2,885,443 and/or U.S. Pat. No. 4,448,977.

(11) In a penetration step, the liquor with the acetal is allowed to act on the hide and/or the pelt, for example in a rotatable drum provided for this purpose. An exposure time can be freely selected, for example depending on the thickness of the hide and/or the pelt. The thicker a hide and/or pelt is, the longer the set exposure time should be in order to achieve sufficient penetration of the acetal into the deeper hide layers. For example, the exposure time can be between 2 h and 7 h. A preferred exposure time in this case is 5 h.

(12) After the penetration step is completed, 2 wt % of formic acid is added and the pH is adjusted to 1.8 to 2.5. The reduction in pH causes the aldehydic tanning agent, for example in the form of glutaraldehyde, to be released. The released aldehydic tanning agent can then react with the proteins of the hide and/or the pelt, in particular with collagen. In this manner, the actual tanning is initiated.

(13) After this, the released aldehyde is allowed to act on the hide and/or the pelt in a tanning step, for example in the rotatable drum. Here, a suitable exposure time can be between 1.5 h and 5 h, preferably 3 h.

(14) After the exposure time of the tanning step has elapsed, 2 wt % of sodium hydrogen carbonate is added. After this, the aqueous liquor is allowed to act on the pretanned hide and/or the pretanned pelt in order to fix the aldehyde as completely as possible. The exposure time can for example be between 1.5 and 4.5 h, in particular 3 h. The pH is then adjusted to 4.0 to 4.2.

(15) After fixation of the pretanned hide and/or the pretanned pelt, the liquor is discarded, and the pretanned hide and/or the pretanned pelt is washed with water, in particular with approx. 3000 mL of water.

(16) After this, the pretanned hide and/or the pretanned pelt can be dried and for example adjusted to a thickness of 1.1 to 1.3 mm.

Example 2

(17) The hide to be tanned and/or the pelt to be tanned are prepared in 3000 mL of water (also referred to below as aqueous liquor) with a set pH of 3.0 to 3.2 and a temperature of 25 C. in a suitable vessel. In the method according to example 2, unlike the method according to example 1, no penetration step is provided in which the aldehydic tanning agent in the form of the acetal is first allowed to act on the hide and/or the pelt without reacting with proteins.

(18) 2.1 wt % of an acetal of an aldehydic tanning agent, for example an acetal of glutaraldehyde, is then added to the aqueous liquor. The low pH of the liquor causes the aldehyde, for example in the form of glutaraldehyde, to be directly released and allows it to react with the proteins of the hide and/or the pelt. This step therefore corresponds to the actual tanning step. After this, the released aldehyde is allowed to act on the hide and/or the pelt, for example in the rotatable drum. In this case, a suitable exposure time can be between 3 h and 7 h, preferably 5 h.

(19) After the exposure time of the tanning step has elapsed, 1 wt % of a mixture, in particular a 1:1 mixture, of sodium formate and sodium hydrogen carbonate is added. The pH is then adjusted to 4.0 to 4.2. The liquor is then allowed to act on the hide and/or the pelt for 1.5 h to 4.5 h, in particular for 3 h. After this, 2 wt % of sodium hydrogen carbonate is added, wherein the liquor is again allowed to act on the hide and/or pelt for 2 h to 6 h, in particular for 4 h. After this, the pH is again adjusted to 4.0 to 4.2. The aldehyde is fixed by means of these steps.

(20) After fixation of the pretanned hide and/or the pretanned pelt, the liquor is discarded, and the pretanned hide and/or the pretanned pelt is washed with water, in particular with approx. 3000 mL of water.

(21) After this, the pretanned hide and/or the pretanned pelt can be dried, and for example adjusted to a thickness of 1.1 to 1.3 mm.

(22) Comparative Tests

(23) Comparative tests were conducted in order to investigate the quality of the leather produced compared to leather produced by means of a conventional method using the tanning agent glutaraldehyde (GA).

(24) In this case, the methods were carried out analogously to examples 1 and 2, except that the acetal was replaced with 4.5 wt % of glutaraldehyde by adding an aqueous 20% GA solution. After this, color, shrinking temperature, and shavability were determined according to ISO.

(25) Results

(26) TABLE-US-00001 Shavability Shrinking temperature Color Example 1 2 78 2 Example 2 3 76 2 GA reference 3 75 2 sample (key: 1 = very good, 2 = good, 3 = satisfactory, 4 = sufficient)

(27) All three leather samples produced were treated in a rotatable drum together with a mixture of the following components (wt % based on the weight of the leather samples):

(28) 100 wt % of water, 28 wt % of the sulfone tanning agent SELLATAN MBS gran, and 12 wt % of the sulfone tanning agent SELLATAN HAT liq., 3 wt % of the resin tanning agent MAGNOPAL DP and 2 wt % each of the fatliquoring components CORIPOL ALF and CORIPOL ESA were added and incubated in the drum. After 3 h, the pH was adjusted to 4.6. 2 wt % of the dye SELLA FAST Orange 2GC was added and incubation was carried out for 8 h. After this, the pH was adjusted to 4.0 by adding formic acid. The liquid was then discarded, and the leather was washed once with 300 wt % of water.

(29) 100 wt % of water was heated to a temperature of 45 C., and 4 wt % of CORIPOL ALF and 8 wt % of CORIPOL ESA were added as fatliquoring components.

(30) After an exposure time of 60 min, the pH was set to 3.5 by adding formic acid. After this, the leather was washed twice with 100 wt % of water and stored wet overnight. The leather was then vacuum-dried. After the leather was then stretched, it was evaluated as shown below:

(31) TABLE-US-00002 GA reference sample Example 1 Example 2 Fullness 0 0 0 Fullness in the 0 0 0 abdominal area Softness 0 0.5 0.5 Grain 0 0 0 Color of crust 0 +0.5 +0.5 Homogeneity 0 0 0 Feel Silky Silky Dry (key: +2/2 = significant deviation, +1/1 = deviation, 0 = no deviation)