DE2053016A1 - Process for liming animal hides or skins - Google Patents

Description

Rohm & Haas

Pat.Dr.Hh / Emm / 9

Process for liming animal hides or Skins

The ashing of pelts and hides or the after-ashes Enzymatically depilated pelts for the production of tannable pelts is still a tedious process Occurrence. Attempts have been made for decades to reduce the duration of liming. Are there Numerous substances have been found that accelerate hair loosening and skin breakdown. at Use of such additives, such as primary amines, reducing sulfur compounds especially sulphites and hydrosulphites, the liming times for most raw materials could be based on 24 to 48 hours can be reduced.

The substances that accelerate the liming process include, according to the German Patent specification 4j52 686 urea and according to a work by P. Pawlowitsch ("Der Gerber", 56th year, P. 97, 1950) hydrazine. As the sole addition to the However, both substances offer no more advantages than other, cheaper additives. So you have has little or no practical importance.

A process for liming pelts and hides and for post-ashing has now been enzymatically developed.

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hairy bare bones found that a fraction of the previously required for liming. According to the invention one leaves on the skins, Peel or pelt an aqueous solution of urea and hydrazine to act. It was unpredictable that urea and hydrazine, both of which have a moderately accelerating effect, contribute common application would allow such a shortening of the liming process.

The skins and pelts are made according to a usual soft, preferably an enzymatic soak, subjected to the process of the invention. In connection to the soft can be depilated enzymatically if the hair or wool is to be obtained. Since a scar contraction in the method according to the invention is not to be feared, on a special vows before the liming are waived.

Although it is possible to use urea and hydrazine alone for liming, the procedure will generally used in the form of a sulphide cremator. The nakedness does not become plump, like that that the otherwise usual addition of lime can be dispensed with. This also reduces sewage problems. In addition to or instead of sulfides, other reducing sulfur compounds can be used such as alkali sulfite, bisulfite, hydrosulfite or mercaptans or mercaptides. Of these, thioglycolic acid or its salts are particularly preferred.

As further possible additives that accelerate liming or reduce plumpness

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act, are salt additives, such as Kaliumrhodanld, potassium oxalate, potassium bitartrate, and amines, such as Dimethylamine, glycols, dioxane, acrylamide and methacrylamide are mentioned.

If a sulphide-free liming is used, lime and sulphurous ones are added Reducing agents such as sulphites or hyposulphites are recommended. This digestion process is particularly suitable for the production of glove and clothing leather.

In the process of the invention, urea is used in amounts of 0.2 to 2 %, preferably in the range from 0.5 to 1.0 %, and hydrazine, calculated as a commercially available 24 # aqueous solution, also in amounts of 0.2 to 2% %, preferably 0.5 to 1 %, based in each case on the salt or soft weight, are used. If a sulphide ash is carried out, the amount of sulphide is generally 60 to 80 % less than the amount used in conventional liming; If lime, caustic soda and reducing agents are used, 0.5 to 1.0 % sodium sulfide (calculated as 60 to 62% goods, based on the weight of the salt) is sufficient. The other additives, in particular reducing agents and salts, which have long been known as liming aids, are used in the usual amounts. In general, heavy goods require somewhat higher amounts of chemicals and longer exposure times than light pelts and pelts.

In the method of the invention for the production of grinding box (corrected grain), the liming times are or full-grain beef box, depending on the weight class, 4 to 6 hours, while hides up to 30 kg

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with 20 to 22 hours, over JO kg with 24 to 36 hours of liming time.

Softy and nappa leather require this process Liming times of 12 to 18 hours compared to the earlier 24 to 48 hours. A lime reminder to improve the softness and the handle is not necessary. The new procedure delivers under under these conditions a leather that, despite its good softness, has a uniform tight grain throughout Area, as © also in the derogatory parts. In addition to extremely fine pores, there is something special about it The behavior of these leathers during milling (drum drying) should also be mentioned, which allows it, too To process dry skins into these types of leather. The process leads to one which, however, is draft-free Leather that is characterized by its particular dimensional stability in use.

Sheepskins only need a liming time of 4 hours compared to 24 hours for conventional ones Way of working. The loss of the range is caused by the particular tightness of the grain in sensitive goods, like New Zealand pelts, vastly improved.

For lambskins and kidskins for glove and clothing leather When using this system, the liming times are reduced from 8 to 10 days to 1 to 2 Days shortened.

Calfskins also become draft-free, flat and softly swollen Obtain nakedness. There is no need for the so-called swear to be connected upstream. - A swear In the conventional method, in addition to hair lightening, the task of a

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To bring about durohalcalization and thereby the dreaded scar contraction during the following liming to prevent.

The alkaline skin digestion of enzymatically depilated pelts can be compared with a 24 to 48 hour post-incinerator with a 1 to 2 ° Be
Shorten the strong sodium sulphide solution to 4 hours. Particularly noteworthy is the improvement in the quality of the pelts post-treated in this way on calfskins and cowhides.

Finally, it is also possible to carry out a barrel sweat with the liming system according to the invention, the addition of reducing agents is recommended. Carrying out an enzymatic Pickle following the invention. Moderate liming is advantageous for achieving high leather quality.

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Examples example 1

100 kg of salted cowhides of the weight class 25-29 1/2 kg are soaked in the usual way. Then takes place the liming in the passport with the following composition: (the ^ -indications refer to the salt weight):

200 % water, 26 ° C

0.6 % urea

0.4 Jf hydrazine hydrate solution 24 #ig 1.0 % Sohwefelnodium conc. 66 # (shed)

Move JO minutes and leave JO minutes. Danaoh 2.5 % caustic soda 99 #ig (leaflets), which are previously dissolved 1 ι 5, added and agitated for 30 minutes. In the course of the night you can turn 3 times for 5 minutes each time. The entire liming time is 15-16 hours. It is then washed and fleshed in the usual way.

Example 2

100 kg of dried goat skins are first soaked. The liming takes place in the reel with the method specified below Composition, where the ^ data relate to the soft weight.

300 % water, 30 ° C

5 % hydrated lime
0.3 % urea

0.2 % hydrazine hydrate solution 24 #Lg 0.7 % diethylamine solution 40

0.8 % caustic soda 99 #lg (leaves),

which previously 1 ι 5 is solved.

Now move for 30 minutes. In addition to it one sets

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0.25 % sodium dithionite and 0.8 % sodium sulfite calz. and moves again JO minutes. The entire time of liming is 24 to 6 hours, depending on the desired quality of the leather, with 10 minutes of reeling in the morning, noon and evening. Then the skin is depilated and fleshed.

Example 3

For liming 100 kg sheepskins, the following solution is first made up (the ^ values refer to the soft weight of the skin):

30 % Water, 30 ^° C

2.0 % Hydrated lime

0.7 % Dimethylamine solution 40

0.2 % Hydrazine hydrate solution 24

0.3 % urea

0.8 % Sulfur sodium conc. 66 # (shed)

0.8 % caustic soda 9.0 #ig (leaf clay), previously dissolved 1: 5 in water.

After thorough mixing, the peel is added and

Rotated for 60 minutes at 3-5 rpm. Then left for 1 hour lie.

Then it is made up with 150 % water of 25 ⁰ G.

After a liming time of 5 hours, it becomes 15-20 minutes rotated and then rinsed in the usual way.

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Claims (7)

e. m. b. η. Darmstadt patent claims 1. j Procedure for the ironing of pelts and skins or ^ -for the Naohesohern enzymatically depilated pelts, characterized, that an aqueous solution of urea and hydrazine is allowed to act on the pelts, hides or pelts. 2. The method naoh claim 1, characterized in that one or more reducing agents Adds sulfur compounds. 3. The method naoh claim 2, characterized in that sodium, aanoniun or calcium sulphide is used as the reducing compound. 4. The method naoh claims 2 and 3, characterized in that one is used as the reducing sulfur compound a mercaptan begins. 5. The method naoh claim 4, characterized in that the mercaptan is thioglycolic acid or salts thereof Acid used. 6. The method naoh the claims 1 to 5 * characterized in that nan also dn organic AaIn used. 7. The method naoh claim 6, characterized in that there is used as the organic amine dimethylamine. 209823/0863