JPS6156279B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved tanning process and compositions used in the process. The present inventors previously (Japanese Patent Publication No. 57-35240)
Therefore, he invented and filed an application for a new tanning method in which urotropin (hexamethylenetetramine) is added during the acid soaking process, and then chrome tanning is performed in the same bath. After that, various improvements to the method were investigated, and the present invention was achieved by discovering that by adding a small amount of chromium salt or aluminum salt along with urotropin in the pickling process, it is possible to produce excellent tanning. The tanning method, filed in Japanese Patent Publication No. 57-35240, involves adding urotropin to rawhide in the pickling process.
0.2 to 10 per 100 parts by weight (hereinafter simply referred to as parts)
When tanning is carried out using a smaller amount of chromium tanning agent than the conventional method, basicity regulators such as sodium carbonate, ammonium carbonate, acidic sodium carbonate, and acidic ammonium carbonate may be added or not added. , is a tanning method that yields high-quality tanned leather that is comparable to conventional leather, and at the same time significantly reduces chromium in the tanning wastewater. One of the conventionally known and widely used tanning methods is a tanning method using a chromium compound. As is well known, this chrome tanning method involves adding acids and neutral salts to rawhide that has undergone pre-treatments such as depilation, decalcification, fermentation, washing, etc., and then acidifying the rawhide with a chrome tanning agent. This is a method of tanning by adding basicity regulators, etc. The main component of the tanning agent most commonly used in this process is basic chromium sulfate, commonly designated as Cr(OH) _SO4 . Rawhide that has undergone hair removal, deashing, fermentation, and washing is slightly alkaline, so when it is immersed in the chromium tanning solution, chromium is deposited within the skin tissue and its reaction with collagen, a protein in the skin, is suppressed. The rawhide must be made acidic beforehand, so the rawhide must be soaked in acid as a pre-treatment. Sulfuric acid or a mixture of sulfuric acid and formic acid is usually used for acid soaking. Furthermore, since rawhide swells even in acidic conditions, a neutral salt such as common salt is usually added during the acid pickling process to prevent swelling. Generally, 30 to 100 parts of water is added to 100 parts by weight of rawhide, salt is added so that the Baume degree of the pickling solution becomes 6 to 7 Baume, and the drum is rotated. about 10
After a few minutes, sulfuric acid or an aqueous solution of sulfuric acid and formic acid is added, and acidification is carried out for 3 to 24 hours so that the pH of the acidification solution becomes about 3. Since the submerged heat shrinkage temperature (hereinafter abbreviated as Ts) of the leather is 35 to 40°C, the acid soaking treatment is usually carried out at 10 to 20°C. If the acid soaking temperature is too high, the temperature approaches Ts, causing the leather to rub inside the drum, causing scratches on the surface of the tanned leather and degrading its quality. After the acid pickling process has been completed, the leather is left in the same bath or in a new bath by adding 5 to 10 parts of chromium tanning agent ( _1.25 to 2.5 parts as _Cr2O3 ).
As tanning progresses and the Ts of the hide increases, the temperature of the bath may be increased to about 40°C. During the tanning process, an alkaline agent such as bicarbonate of soda is usually added to increase the basicity of chromium and increase its reactivity with the leather, but at this time, to prevent chromium precipitation, bicarbonate of soda is added in portions as an aqueous solution for about 8 hours. Perform tanning. The final pH of tanning is 3.5-4.0 and Ts is 77-120.
When the temperature reaches ℃, the leather is taken out, or it is immersed in a bath overnight, and then the leather is taken out and heated at room temperature for 1 to 3 days, and the finishing process is started until it becomes a product leather after squeezing with water. In conventional tanning as described above, the amount of chromium that binds to the leather is usually 50 to 70% of the amount added.
Unreacted chromium remains in the bath and becomes the tanning waste. Chromium is a heavy metal, and discharging it as is is a pollution problem, so it is necessary to remove chromium from the wastewater. For this reason, methods such as chemical treatment of the waste liquid after chrome tanning are used to remove and recover the chromium. The characteristic of chrome tanned leather is that its Ts is 77 to 120℃.
Compared to leather tanned by other methods, it has better heat resistance, is less likely to rot, and is resistant to chemicals, and the structure of the untanned leather and fibers has not changed significantly. It is particularly flexible and elastic compared to vegetable tanned leather. The present inventors have conducted extensive research on a method for reducing chromium in waste water without impairing the excellent characteristics of the above-mentioned chrome tanned leather, and have recently filed an application for Japanese Patent Publication No. 35240/1983. However, this method requires a long time from the pickling process to the end of tanning, and the productivity is inferior to the conventional method. In addition, in order to increase the effect of adding urotropin, the acid pickling temperature is preferably at least 25 to 30 degrees Celsius, preferably even higher.As it is higher than the conventional pickling temperature for chrome tanning (10 to 20 degrees Celsius), the tanned leather is It is easy to be damaged by the influence of mechanical friction such as rotation of the leather, and the effect is particularly great on raw hides that are less fresh. In order to improve these shortcomings, the inventors of the present invention continued to conduct intensive studies and found that after adding neutral salts and sulfuric acid at the beginning of the pickling process, a small amount of chromium was added at an appropriate time at the same time as urotropin or before or after. It was discovered that the method of adding salt or aluminum salt was superior and led to the present invention. The addition of these chromium salts and aluminum salts makes it possible to raise the temperature of the pickling treatment to over 30℃, around 50℃, and even higher, and also improves the resistance of the skin to friction caused by mechanical rotation. , it was possible to significantly shorten the acid soaking time. That is, for example, we succeeded in shortening the time required to finish tanning to 12 to 20 hours, which was about 30 hours or more in the case of acid soaking treatment of cowhide with the addition of urotropin and the chrome tanning method. That is, the gist of the present invention is a pickling treatment method characterized by pickling rawhide that has undergone preparatory work in the presence of urotropin and a chromium salt or/and an aluminum salt, and a method for pickling rawhide that has undergone preparatory work, and a method for pickling rawhide that is characterized by pickling rawhide that has undergone preparatory work in the presence of urotropin and a chromium salt or/and an aluminum salt; This is a tanning method characterized by comprising a composition containing / and an aluminum salt as a main component, and tanning treatment after the acid soaking treatment. According to the method of the present invention, for example, in cases where Ts is not required as a product quality, it may be possible to continue the tanning process without adding a tanning agent, and for example, the amount of chromium used can be further reduced. Not only is it possible to do so, but it also simplifies the work, shortens the process, and has other advantages, such as being able to easily obtain beautiful white leather. Of course, it is also possible to add this urotropin and chromium salt or aluminum salt and pickle it, then tan it using vegetable tannins, synthetic tanning agents, resin tanning agents, mineral tanning agents, or other tanning agents. There are different types of leather, each with their own unique characteristics. In the process of the invention, urotropin and chromium salts or/and aluminum salts are added together with acids such as sulfuric acid, hydrochloric acid, formic acid or mixtures thereof, neutral salts such as sodium chloride, sodium sulfate or mixtures thereof, and if necessary other additives. Water, rawhide, and these chemicals are mixed individually or in part in any order into an acid pickling device such as a drum, and then the mixture is charged and pickled. Do this.
At this time, as in the conventional method, the skin, water, neutral salt, and acid are added and rotated for an arbitrary period of time if necessary.
Urotropin and chromium salt or aluminum salt are added at the same time or before or after the addition, and acid soaking treatment is often performed by further rotating for an arbitrary period of time. Furthermore, after adding rawhide, water, and neutral salts such as sodium chloride, the mixture is rotated just enough to mix it uniformly, and then an acid such as sulfuric acid of an arbitrary concentration is added, and the mixture is further rotated. In many cases, urotropin and chromium salt or aluminum salt are added at the same time or before or after, and the rotation is continued. Furthermore, good results are often obtained by adding an acid such as sulfuric acid after adding urotropin or the like. In this case, the optimal time between adding acid such as sulfuric acid and adding urotropin etc. will vary depending on various conditions such as temperature and quality of mixing, but when using a regular drum etc., add an appropriate amount of chromium tanning agent after this treatment. When chrome tanning is carried out, a short time such as 2 hours or less is possible and is often preferred from the viewpoint of productivity. After this treatment, when tanning is performed without adding a tanning agent, the performance of the product leather is often improved if the tanning time is longer, such as one hour or more. The optimum timing for adding chromium salts and aluminum salts also varies depending on various conditions, but it is safe to add them at the same time as, immediately before, or immediately after adding urotropin, and this is often preferable from a work standpoint, but it may also be several hours before or after several hours. The optimal amount of urotropin, chromium salt, and aluminum salt used in the pickling process of the present invention varies depending on temperature, time, and other various conditions, but usually urotropin is 0.2 to 10 parts, preferably 1 to 5 parts per 100 parts of rawhide. part, chromium salt is _0.01-0.2 part as _Cr2O3 ,
Preferably 0.05 to 0.1 part, and aluminum salt is
As _{Al2O3 ,} 0.1 to 2 parts, preferably 0.5 to 1.5 parts are used. The addition of chromium salts and aluminum salts improves skin
Ts rises rapidly from about 35℃ to over 50℃, 25~
It enables acid soaking at 35°C or even higher temperatures, makes the leather stronger, increases its resistance to friction caused by drum rotation, etc., and significantly reduces damage to the leather. Therefore, the acidification treatment of the present invention is usually carried out at 20
℃ or higher, preferably 25℃ or higher, more preferably 25℃
Performed at ~50°C. In addition, the time for pickling treatment after adding urotropin varies greatly depending on temperature, rotation, stirring conditions, etc.
Although it may be a long time, such as 20 hours or more, it is usually around 10 hours or less, such as 1 to 15 hours. Various chromium salts can be used as the chromium salt used in the present invention, but ordinary chromium tanning agents such as chromium sulfate, chromium chloride, basic chromium sulfate, and chromium compounds having various organic substances as ligands are used. . Various aluminum salts can be used, but aluminum sulfate, aluminum chloride, etc. are usually used. Although the reaction mechanism is not clear, the addition of the chromium salt or aluminum salt can shorten the acid soaking time and, in turn, shorten the time required to finish tanning. By applying the acid pickling treatment of the present invention, for example, a chromium tanning agent such as basic chromium sulfate or a chromium compound having various organic substances as a ligand can be added to the chromium tanning agent when producing high Ts leather. is rawhide
Preferably 1.5 parts or less as Cr ₂ O ₃ per 100 parts
By adding only a small amount of 0.0025 to 1.5 parts, it is possible to obtain tanned leather of the same quality as conventional chrome tanning. To further elaborate on this example, rawhide
By adding 0.2 to 10 parts of urotropin and 0.1 to 2 parts of aluminum salt as Al ₂ O ₃ to 100 parts, the chromium tanning agent is 0 to 1.5 parts, preferably 0.0025 to 1.5 parts.
By adding 0.2 to 10 parts of urothrobin and 0.01 to 0.15 parts of chromium salt _{as Cr2O3} , the amount of chromium tanning agent used may be 0 to 1.5 parts, preferably 0.01 to 1.5 parts. . If too much chromium salt or aluminum salt is added during the pickling process, the effect of the pickling process will be weakened, and the elasticity of the tanned leather will decrease. In addition, if the amount of chromium salt or aluminum salt is too small, the acidification time will be longer and
This results in deterioration in quality such as damage to the tanned leather, and the effects of the present invention are not achieved. Furthermore, when the tanning process is performed without adding a tanning agent after the acid soaking treatment of the present invention, it often takes a slightly longer time than the usual time of around 10 hours. However, in this case, mixing and stirring operations such as rotation are rarely necessary for the entire long period of time, and the skin is soaked for most of the time by simply rotating for a short period of time, not more than a few hours, at the beginning and end or before and after. In many cases, it is sufficient to leave the material immersed in an acid solution, or in cases where a chrome tanning agent is added, it is often sufficient to rotate the product for up to 10 hours, then wash it with water and leave it to age for several days. When tanning is performed using another tanning agent instead of the chrome tanning agent after the acid soaking treatment of the present invention, examples of the tanning agent include various vegetable tanning agents such as various tannin extracts and their sulfite-modified products, and naphthalene-based tanning agents. Various synthetic tanning agents such as condensates of phenolic aromatic sulfonic acids and formaldehyde, condensates of formaldehyde with phenol, naphthol, urea, melamine, etc., condensates of dicyandiamide and formaldehyde, copolymers of maleic acid and styrene. These include resin tanning agents such as alkaline salts, basic aluminum salts and aluminum salts such as alum, oils such as cod oil and rapeseed oil, various zirconium salts, and aldehydes such as formaldehyde and glutaraldehyde. Even when these various tanning agents are used, the tanning process can be carried out by a method similar to the conventional method using each of these tanning agents. In the acid pickling process of the present invention, urotropin is often added at the same time as chromium salt or aluminum salt, but it is also possible and convenient to add chromium salt or aluminum salt in advance by mixing it with urotropin. Such compositions would be very useful. The composition in this case can be used in any proportion, but the most convenient is a mixture in the proportions of the prescribed usage, as Cr ₂ O ₃ per 100 parts of urotropin.
Often 0.1 to 100 parts of chromium salt or/and ₁ to 1000 parts of aluminum salt as _Al2O3 are used. It goes without saying that neutral salts such as sodium chloride used in the pickling process and other additives can be added to this composition as necessary and as much as possible. The method of the present invention can be applied to the skins of various animals such as cows, sheep, goats, pigs, and horses, and is an excellent method that can yield leather of excellent quality. Particularly in the case of chrome tanning, it is also a feature of the present invention that the amount of chromium used, especially the amount of chromium in the waste liquid, can be significantly reduced. The present invention will be specifically explained below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In Examples and Comparative Examples, the amount of chemicals added is expressed in parts per 100 parts by weight of the skin after decalcification and fermentation, and the time for addition of chemicals is expressed in time from the time when sodium chloride was added. Example 1 After hair removal, deashing, and fermentation, five North American steer skins were washed with twice the amount of water, drained for 5 minutes, and weighed to be 7.5 kg. (100 copies)
The skin after draining was placed in a test drum having a diameter of 1 m and rotating 15 times/min, and 20 parts of water and 6 parts of sodium chloride were added, and the drum began to rotate. After 10 minutes, add an aqueous solution of twice the amount of sulfuric acid and 20 parts of water.
After 2 minutes, 2 parts of urotropin was added, and after 1 hour, 0.3 part of Barechrome-S [Nippon Denko Co., Ltd. powdered chromium tanning agent containing 25% Cr ₂ O ₃ ] (0.075 as Cr ₂ O ₃ ) was added.
Rotation was continued for 11 hours after addition of 100% of the mixture. The time required and bath temperature after adding sodium chloride at that time,
Liquid heat shrinkage temperature of tanned leather (hereinafter expressed as Ts)
Table 1 shows the relationship with the pH of the bath. Next, bare chrome-S3 part (0.75 as Cr ₂ O ₃
The temperature of the bath was 38° C. after adding 50% of the solution and rotating for 8 hours. The leather was taken out of the drum and left to age at room temperature for two days. As a result, the time required from pickling treatment to completion of tanning was 20 hours. The Ts, elasticity, degree of damage, pH of the bath, unreacted Cr ₂ O ₃ in the bath, time required from acid soaking to completion of tanning, etc. of the tanned leather thus obtained are shown in the table.
Shown in 2. Example 2 The procedure was the same as in Example 1 up to the point where an aqueous solution of 2 parts of sulfuric acid and 20 parts of water was added, and after 25 minutes, 2 parts of urotropin was added and at the same time 0.1 part of Barechrome-S (Cr ₂ O ₃
After adding 0.025 parts of chloride (as 0.025 parts), rotation was continued for 3 hours. At that time, the pH of the bath was 3.0 and the Ts was 65°C. After 3 hours and 25 minutes, 3.2 parts of Barechrome-S (0.8 parts as Cr ₂ O ₃ ) was added, and the drum was continued to rotate for 9 hours (bath temperature at this time: 38°C), and 2.6 parts of acidic ammonium carbonate and water were added. 15 parts of water bath solution was added in three 1/3 portions every 60 minutes, and rotation was continued for an additional 30 minutes. The leather was removed from the drum and left at room temperature for 2 days to undergo heat formation. As a result, the time from pickling treatment to completion of tanning was approximately 16 hours. The quality of the tanned leather thus obtained, the physical properties of the bath, the required tanning time, etc. are shown in Table 2. Example 3 The process was carried out in the same manner as in Example 1 up to the point where an aqueous solution of 2 parts of sulfuric acid and 20 parts of water was added, and after 25 minutes, a composition consisting of 2 parts of urothrobin and 0.3 parts of Barechrome-S was added, and the rotation was continued for 3 hours. Table 1 shows the relationship between the time required after adding sodium chloride, bath temperature, Ts of the tanned leather, and PH of the bath. Next, add 3.2 parts of bare chrome-S added during the chrome tanning process.
Table 1 shows the results of the tanning process performed in the same manner as in Example 1 except that the amount was changed to 3.0 parts (0.75 parts as Cr ₂ O ₃ ).
Shown in 2. Example 4 Barechrome-S3.2 was added during the chrome tanning process by adding a composition consisting of 2 parts of urotropin and 0.5 parts of Barechrome-S ( _0.125 parts as _Cr2O3 ).
Table 2 shows the results of acid soaking and tanning performed in the same manner as in Example 3, except that the part was changed to 2.8 parts (0.7 parts as Cr ₂ O ₃ ). Example 5 2 parts of urotropin and aluminum sulfate [Al ₂
(SO ₄ ) ₃ 18H ₂ O] 3 parts (0.45 parts as Al ₂ O ₃ ) was added, and 3.2 parts of bare chrome-S (0.8 parts as Cr ₂ O ₃ ) added during the chrome tanning process was added.
When acid soaking and tanning were carried out in the same manner as in Example 3 except that the amount was changed to 3.0 parts, bare chrome-
The pH of the bath before adding S was 3.4, and the Ts was 63°C. The quality of the tanned leather thus obtained, the physical properties of the bath, the required tanning time, etc. are shown in Table 2. Example 6 The procedure of Example 1 was repeated up to the point where an aqueous solution of 2 parts of sulfuric acid and 20 parts of water was added, and after 15 minutes, 0.354 parts of chromium sulfate [Cr ₂ (SO ₄ ) 3.18H ₂ O] (Cr ₂ O ₃ as
After 25 minutes, 2 parts of urotropin was added and rotation was continued for 11 hours. Thereafter, chrome tanning was carried out in the same manner as in Example 1, and the same results as in Example 1 were obtained. Example 7 The same process as in Example 1 was carried out except that 0.156 parts of chromium chloride (0.075 parts as Cr ₂ O ₃ ) was used instead of 0.3 parts of bare chromium S as the chromium salt. Got the results. Example 8 Al ₂ (SO ₄ ) ₃ as aluminum salt, 1.178 parts of aluminum chloride (as Al ₂ O ₃ ) instead of 18H ₂ O 3 parts
The same results as in Example 5 were obtained by processing in the same manner as in Example 5, except that 0.45 parts) was used. Example 9 Bare chrome - Instead of 0.3 parts of S [Cr ₂ (SO ₄ ) ₃ ]
0.193 parts ( _0.075 parts as _Cr2O3 ) and [ _Al2
(SO ₄ ) ₃ ]0.771 part (0.23 part as Al ₂ O ₃ ) was used, but the same process as in Example 1 was carried out to obtain the same results as in Example 1. Comparative Example 1 1.2 parts of bare chrome-S (0.3 parts as Cr ₂ O ₃ ) was added at the same time as 2 parts of urotropin, and 2.6 parts of bare chromium-S added during the chrome tanning process.
Example 3 except that part (0.65 part as Cr ₂ O ₃ )
Table 2 shows the results of acid soaking and tanning in the same manner as above. Comparative Example 2 Example 1 until adding urotropin
The drum was rotated for 4 hours without adding chromium salt or aluminum salt, and then soaked overnight. Table 1 shows the relationship between the time required after adding sodium chloride, bath temperature, Ts of the tanned leather, and PH of the bath. Twenty-two hours after the addition of sodium chloride, 3.3 parts of Barechrome-S (0.83 parts as Cr ₂ O ₃ ) was added, and the temperature of the bath was 38° C. after rotation for 8 hours. After soaking overnight, the leather was removed from the drum and left to age at room temperature for 2 days. The results are shown in Table-2. Comparative Example 3 According to the conventional chrome tanning method, 80 parts of water and 8 parts of sodium chloride were added to 100 parts of demineralized leather, and the drum began to rotate.After 10 minutes, 0.8 parts of sulfuric acid and 0.4 parts of formic acid were added. After 3 hours, add 3.3 parts of Barechrome-S (0.83 parts as Cr ₂ O ₃ ), and after 5 hours, add 0.3 parts of acidic sodium carbonate and 3 parts of water in 4 portions every 30 minutes. liquid was added. The drum rotation was stopped 11 hours after the sodium chloride was added. The bath temperature at that time was 38°C. After soaking overnight, rotate the drum again for 1 hour.
Table 2 shows the results of removing the leather and aging it for 2 days.
Shown below. Comparative Example 4 Bare Chrome - Acid soaking and tanning were carried out in the same manner as Comparative Example 3, except that 3.3 parts of S (0.83 parts as Cr ₂ O ₃ ) was changed to 8 parts (2.00 parts as Cr ₂ O ₃ ). The results are shown in Table-2.

【table】

【table】

[Table] Example 10 After hair removal, deashing, and fermentation, three pieces of domestic pork skin were washed with twice the amount of water, drained for 10 minutes, and weighed, and the weight was 13.4 kg. (100 copies) Diameter 1
The skin after draining was placed in a test drum rotating 15 times/min, 20 parts of water and 6 parts of sodium chloride were added, and the drum was started to rotate. After 10 minutes, 0.5 part of degreaser F-400 (manufactured by Taiko Yushi Kagaku Kogyo Co., Ltd.) was added, and after 20 minutes, an aqueous solution of 2 parts of sulfuric acid and 20 parts of water was added. Subsequently, after 15 minutes, 2 parts of urotropin and Barechrome-S (manufactured by Nippon Denko Co., Ltd.) were added.
0.3 part (0.075 part as Cr ₂ O ₃ ) was added, and after 45 minutes, 0.5% fatliquor Ritzker SAF (manufactured by BASF) was added, and after rotating for 4 hours, it was soaked overnight. The PH of the bath after rotation was 3.5 and Ts of 70°C, and the PH of the bath after immersion was 4.0 and Ts of 83°C. Next, bare chrome-S3 part (0.75 as Cr ₂ O ₃
After 8 hours of rotation, an aqueous solution of 2.6 parts of ammonium acid hydrcarbonate and 15 parts of water was added in three 1/3 portions every 60 minutes, and rotation was continued for an additional 30 minutes. Ta. Remove the leather from the drum and leave it at room temperature for 2 days.
It was matured. The Ts of the leather thus obtained is 112
℃, the pH of the bath was 5.5, and the Cr ₂ O ₃ in the bath was 0.01 g/100 ml. Example 11 Five pieces of imported picklehide goat skin (weight 10 kg) from the Philippines were rotated 1 meter in diameter 15
100 parts of water and 5 parts of sodium chloride were added to the test drum, and the drum was started to rotate. After 10 minutes, 2 parts of urotropin and paired chromium-S0.3
After 60 minutes, 1.4 parts of sulfuric acid and 14 parts of water were added, and the rotation was continued for 6 hours. At that time, the pH of the bath was 3.5 and the Ts was 69°C. Next, 3 parts of BARE CHROME-S was added, and after rotating for 8 hours, a water bath solution of 2.6 parts of acidic ammonium carbonate and 15 parts of water was added in 3 portions of 1/3 every 60 minutes, and then for another 30 minutes. Rotated for a minute. Aging for 2 days, the Ts of the leather thus obtained was 110℃, the pH of the bath was 5.4, and the Cr ₂ O ₃ in the bath was 0.0005.
g/100ml. Example 12 The same rawhide as in Example 1 was placed in the drum used in Example 1, 20 parts of water and 5 parts of sodium chloride were added, and the drum was started to rotate. After 10 minutes, a solution of 1.7 parts of sulfuric acid dissolved in 20 parts of water was added, and after 15 minutes, 1.5 parts of urotropin and Barechrome-S (manufactured by Nippon Denko Corporation) were added.
0.2 part of the composition was added and rotation continued for 6 hours. At this time, the bath temperature was 45°C. Further, the soaking was continued overnight. The next morning, it was rotated again for 30 minutes and then washed with water to obtain white leather with a Ts of 85°C. Example 13 After performing the same procedure as in Example 12 until re-rotating for 30 minutes the next morning, acidic ammonium carbonate was added while rotating.
A solution prepared by dissolving 0.5 parts in 5 parts of water was added three times at 1 hour intervals, followed by washing with water to obtain leather equivalent to Example 12. Example 14 The same rawhide as in Example 1 was placed in a test drum,
After adding 50 parts of water and 6 parts of sodium chloride, rotate for 10 minutes.
Thereafter, a mixed solution of 1 part of sulfuric acid, 0.3 parts of formic acid, and 13 parts of water was added, and the mixture was rotated for 2 hours. The pH at this time is
2.7, the bath temperature was 20℃. Then urotropin 2
An aqueous solution containing 0.3 parts of Barechrome-S, 0.7 parts of sulfuric acid, and 7 parts of water was added, and the mixture was rotated for 3 hours. At this time, the pH was 3.8, the bath temperature was 38°C, and the temperature was 75°C. After soaking overnight, pH was 4.0 and Ts was 90℃. Example 15 After carrying out the same procedure as in Example 14 up to one-liquid immersion,
While rotating, add 1.5 parts of acidic ammonium carbonate to 5 parts of water.
After adding the solution dissolved in the bath three times at 1 hour intervals,
Leather equivalent to Example 14 was obtained by washing with water. Example 16 Five pieces of the same rawhide as in Example 1, 60 parts of water, and 6 parts of sodium chloride were placed in a test drum and heated at 10 revolutions per minute.
Rotated for a minute. Thereafter, an aqueous solution consisting of 1.5 parts of sulfuric acid and 15 parts of water, 2 parts of urothrobin, and 0.3 parts of Barechrome-S were added, and the mixture was rotated for 2 hours. The pH of the bath solution at this time was 3.5. After the bath was drained, 10 parts of anhydrous sodium sulfate was added and the mixture was rotated for 6 hours. (15 rotations/
minutes) then mimosa powder - vegetable tannin agent) 25
After adding 0.3 parts of anhydrous sodium bisulfite and rotating for 3 hours, 25 parts of water was added and the mixture was further rotated for 6 hours.
The pH of the bath at this time was 3.5, and the penetration of mimosa powder into the leather was perfect. Thereafter, the leather was washed under running water for 1 hour, taken out, and finished in a conventional manner.

Claims (1)

[Scope of Claims] 1. A method for pickling treatment, which comprises pickling rawhide that has undergone preparatory work in the presence of urotropin and a chromium salt or/and an aluminum salt. 2 The amount of urotropin per 100 parts by weight of rawhide,
The method according to claim 1, wherein the amount is 0.2 to 10 parts by weight. 3 The amount of chromium salt per 100 parts by weight of rawhide,
The method according to claim 1, wherein the amount of Cr ₂ O ₃ is 0.01 to 0.2 parts by weight. 4. The method according to claim 3, wherein the chromium salt is basic chromium sulfate, chromium sulfate, or chromium chloride. 5. The method according to claim 1, wherein the amount of aluminum salt is 0.1 to 2 parts by weight as Al ₂ O ₃ based on 100 parts by weight of rawhide. 6. The method according to claim 5, wherein the aluminum salt is aluminum sulfate or aluminum chloride. 7. A composition containing urotropin and chromium salt or/and aluminum salt as main components used in the pickling process. 8. The composition according to claim 7, wherein the amount of chromium salt is 0.1 to 100 parts by weight as Cr ₂ O ₃ based on 100 parts by weight of urotropin. 9. The composition according to claim 8, wherein the chromium salt is basic chromium sulfate, chromium sulfate or chromium chloride. 10. The composition according to claim 7, wherein the amount of the aluminum salt is 1 to 100 parts by weight as Al ₂ O ₃ based on 100 parts by weight of urotropin. 11 Claim 1, wherein the aluminum salt is aluminum sulfate or aluminum chloride.
The composition according to 0. 12. A tanning method characterized in that the rawhide that has undergone the preparatory work is pickled in the presence of urotropin and a chromium salt or/and an aluminum salt, and then subjected to a chrome tanning treatment. 13. The method according to claim 12, wherein the amount of chromium tanning agent used in the chrome tanning treatment is 1.5 parts by weight or less as Cr ₂ O ₃ based on 100 parts by weight of rawhide.