JPS638499A - Tanning method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a tanning method, and more particularly to a tanning method having two steps: pre-tanning and full tanning steps.

<Prior art> As is currently well known, various tanning agents have been proposed.
Although it is also used conveniently, mainly chrome tanning agents and tannin tanning agents are commonly used. Chrome tanning agents have been used since ancient times for their outstanding tanning effects, and various basic chromium sulfates are known based on differences in basicity and chromium content, and have contributed to the development of the leather industry. has contributed greatly to.

However, some drawbacks have been pointed out even in such effective roman tanning agents as the times have changed. The biggest problem is the environmental pollution problem of chromium compounds.
Measures to deal with chromium in tanning wastewater and chromium in leather sludge are required, and various studies have been conducted, and practical measures are also being promoted.

One measure for this is to pretann the pickled rawhide with at least one chromium (]I[) salt and then tannify it with formic acid and/or the reaction product of formic acid with chromium (I[[)]. Chromium (I[[
) Chrome tanning method in which pre-tanning is carried out using a tanning agent in the presence of at least one acid binder (Japanese Patent Publication No. 61-2
120 Publication) etc. have been reported.

On the other hand, the inventor has determined that the weight ratio 0.7≦Cr2°3/A12
A method for producing a chromium-aluminum tanning agent in which fFyi is to neutralize an acidic mixed aqueous solution consisting of a chromium sulfate-containing substance, an aluminum salt, and a carboxylic acid compound within the range of o3≦3 to make it highly basic. (Special Publication No. 60-40478%).

<Problems to be solved by the invention> However, the invention of Japanese Patent Publication No. 61-2120,
There were problems such as the flexibility of the tanned leather and the need to reduce chromium (Cr) 1 in the wastewater to prevent environmental pollution.

On the other hand, the invention disclosed in Japanese Patent Publication No. 60-40478 uses chromium to improve the heat resistance of leather tanned with an aluminum tanning agent alone, and also significantly reduces chromium in wastewater using the conventional chromium tanning method, reducing the chromium pollution load. However, it was found that there are some points that need to be improved as follows.

When tanning animal hides, acids are released into the solution as chromium and aluminum are applied to the hides, which tends to push the pH of the solution out of the preferred range required for a proper tanning operation, thus reducing the pH of the solution during the tanning process. It is necessary to keep the pH of the tanning solution around a certain appropriate value by applying some kind of acid binder to the tanning solution.Adjusting the pH of the tanning solution is extremely important during the tanning process, and the pH value If the pH is too low, the bonding of chromium and aluminum to the leather will be insufficient, resulting in poor tanning efficiency;
If the temperature is too high, there is a danger that chromium hydroxide and aluminum hydroxide will precipitate, making it impossible to obtain high-quality tanned leather.

Therefore, in the past, alkaline agents such as soda carbonate or bicarbonate were added to the tanning solution in several stages during the tanning process in order to adjust the pH. If the process control, such as the amount, method, and rate of addition of the alkaline agent measured at each stage, is not carefully controlled, troubles such as deterioration in the appearance and quality of the final tanned leather may occur. There were drawbacks.

The present inventor obtained the present invention as a result of research to solve the above problems.

Means for Solving the Problems> That is, the present invention provides vF characteristics in which pickled rawhide is pre-tanned with chromium (I [ This is a tanning method.

Effect> The present invention is a tanning method having two tanning steps: pre-tanning followed by full tanning.

The chromium (III) salt tanning agent used in pre-tanning is chromium sulfate, basic chromium sulfate, or their mirabilite-containing agents, but industrially, sodium dichromate aqueous solution is used in the presence or absence of carboxylic acid. Basic chromium sulfate produced by a reduction reaction in the presence of a free reducing agent is preferred.

Pre-tanning involves immersing rawhide that has been subjected to the usual liming, hair removal, deashing, etc. in an aqueous solution with a pH of 2 to 4 containing an acid such as sulfuric acid and an anti-swelling agent such as salt. Add chromium (,I[I) salt to the solution.

The amount of chromium (II) added at this time must be at most 1% as Cr2O3 based on the weight of the rawhide. This is because if the input amount is 1% or more, more than the chromium suspended in the bonding reaction between skin collagen and chromium will be transferred to the wastewater, increasing the amount of chromium (Cr) in the wastewater. For a chromium tanning agent containing 25% chromium (Cr2o3), 2%) is desirable.

After adding chromium (In> salt), drumming is carried out for about 1 to 4 hours to ensure sufficient tanning.

After the above pre-tanning yield, a full tanning is then carried out using a chromium-aluminum tanning agent.

In the present invention, the chromium-aluminum tanning agent used for full tanning is Cr2032~25L%, Al2
032-25 no.1. ++/shibonic acid compound 1-15
CrO/at lff1 ratio.
Chromium-aluminum tanning agent having Al2O3 of 0.7-3 and basicity of 20-55%, or 100 parts by weight of the chromium-aluminum tanning agent, 0.2-50 parts by weight of acid binder. It is a chromium-aluminum tanning agent that can be mixed to automatically adjust the basicity; the latter is usually preferred.

The above-mentioned chromium-aluminum tanning agent is made by neutralizing an acidic mixed aqueous solution consisting of a chromium sulfate-containing substance, an aluminum salt, and a carboxylic acid compound with an alkaline agent to make it highly basic, and then spray-drying and granulating it. .

Here, the W&acid chromium-containing substance has the same compositional components as chromium (]I[)[ used in pre-tanning as described above.

Next, aluminum salts are mainly aluminum sulfate, but other basic aluminum sulfates,
Aluminum chloride, FA basic salt heptaaluminum, etc. may also be used as necessary.

As is well known, carboxylic acid compounds are used as masking agents for OH groups when forming a high base, and include, for example, g4 acid, acetic acid, oxalic acid, succinic acid, glutaric acid, adipic acid, and phthalic acid. , tartaric acid, citric acid, lactic acid, etc., and they may also be alkali metal salts, alkaline earth metal salts, or ammonium salts, and at least one or two or more of them may be used as desired.

Further, the alkaline agent is not particularly limited as long as it neutralizes each of the above-mentioned chemicals to make them highly basic, but for example, caustic alkali, alkali carbonate, alkali bicarbonate, or sodium aluminate can be used. Among these, sodium bicarbonate is particularly preferred since alkali agents that are as mild as possible are preferable for operational purposes.

The above-mentioned chromium sulfate-containing material, aluminum salt, and carboxylic acid compound are made into a mixed aqueous solution, and then mixed and stirred with an alkaline agent at a temperature of room temperature to 80° C. to gradually neutralize and quench the high base.

Next, after the addition of the alkali agent is completed, the mixture is continued to be aged for a while, and if necessary, after filtering, it is spray-dried by a conventional method to form a granular product. It is preferable for the product to pass through a 4o mesh that can be dissolved in cold water, but the product is not limited thereto.

The composition of the chromium-aluminum tanning agent obtained by the above method is preferably in the following proportions (% by weight).

Cr2O3 2-251ffi% (preferably 8-20% by weight) A + □03 2-251ffi% (preferably 5-16% by weight) Carboxylic acid compound 1-15% by weight (preferably 6-15% by weight) Cr203 /41203 (Jutan ratio) 07~3(
Preferably 0.8-2) Basicity 20-55% (preferably 2
8~50%) Its principle Et3Lt, Cr2O3/to1203(1!!l
When the a ratio) is less than 0°7, the amount of aluminum in the liquid increases, and even if the basic system relies on the masking effect of carboxylic acid compounds, aluminum hydroxide is likely to be formed during operation, resulting in high levels of aluminum hydroxide. At the same time that basification cannot be obtained, the manufacturing process must be extremely careful, and the tanning performance of the resulting product inevitably tends to decrease more than compensate for the drawbacks of chromium. On the other hand, if it exceeds 3, the advantages based on the addition of aluminum will not be obtained much, and the tanning agent will not be substantially different from conventional chrome tanning agents.

In addition, the content of the carboxylic acid compound used as a masking agent depends on the desired set basicity, but is also influenced by its type and the quantitative relationship between aluminum and chromium, and is less than 1%. If the amount exceeds 15%, no significant masking effect will be observed, and it will also be disadvantageous in terms of cost.

Furthermore, the content of CrO and Al2O3 is Cr203
/A I203 (1M ratio) dependent.

Such chromium-aluminum tanning agents are included in the present invention.
3. It is desirable to have the ability to automatically adjust basicity.

This function means that the pH in the bath becomes acidic as the leather is tanned, and the system automatically adjusts to adjust to this pH change to maintain a predetermined pH.
This refers to the ability to maintain H, and this can be achieved by incorporating an acid binder.

As such an acid binder, calcined magnesium oxide is suitable, and natural magnesium oxide ore, calcined magnesium hydroxide or magnesium carbonate separated and collected from seawater or dolomite, calcined magnesite, magnesia clinker, etc. Examples include those whose main component is calcined magnesium oxide.

Incidentally, calcined magnesium oxide can also be used together with, for example, dolomite, alkali gold, carbonate, alkali bicarbonate, sodium sulfite, and the like.

These acid binders are usually used in powder form, but their reaction with free acids in tanning liquors is particularly influenced by particle size, and 100 mesh products are often preferred. The reason for this is 100
This is because grains larger than mesh remain as insoluble matter during the tanning process, and this may deposit on the surface of the tanned leather, causing spots.

It is preferable to mix 0.2 to 50 parts of the acid binder to 10011 parts of the chromium-aluminum tanning agent before mixing the acid binder.

The amount of the chromium-aluminum tanning agent to be used in the total tanning may be appropriately determined depending on the flexibility of the tanned leather and the chromium content in the waste water and the composition of the chromium-aluminum tanning agent.

Full tanning is carried out for about 4 to 8 hours, but is not particularly limited.

The present invention will be specifically described below with reference to Examples.

<Examples> Example 1 Bovine hide (100 parts by weight) that had been limed, depilated, and deashed in a conventional manner was acidified using common salt, liii acid, and 60 parts of water. I)H at this time was 2.6. Add this to chrome (
II[)W (Neochrome manufactured by Nihon Kagaku Kogyo Co., Ltd.) Cr
20325%, basicity 33°3%) was added and drummed for 2 hours. Next, 5 parts of the chromium-aluminum tanning agent shown below was added and drumming was carried out for 6 hours. Two hours after addition of the chromium-aluminum tanning agent, bicarbonate of soda was added four times every 30 minutes to bring the final pH to 4.1.
I made it. The temperature at this time was 38°C. The tanned leather is Cr2031.96%, AI2031. '2
4%, the heat shrinkage temperature was 112°C, and the chromium (Cr) in the tanning waste water was 10102 pl)'. Finishing in a conventional manner resulted in a flexible, soft-feeling leather.

Preparation of chromium-aluminum tanning agent〉Pour water into a glass-lined reactor equipped with a thermometer and a stirrer.
6 5 5 Ky basic chromium sulfate (Nihon Kagaku Kogyo)
(manufactured by) Neochrome > 1000
Kg aluminum sulfate (A12 (S04) 357%)
2138 kg of sodium formate (HCOONa 95%) 76 kg were taken, heated to 60°C, and stirred and mixed for 60 minutes. To this mixed solution, sodium bicarbonate 599 tuna was gradually added over 180 minutes to make it highly basic. After addition, the mixture was filtered according to a conventional method and then spray-dried to obtain 3172 kg of dried granules. The composition of this dried granular material was as follows.

0r203 8.0ffi1%Al2O3
11.4% HCOONa 11.211%Cr2O3
/^1203 (ll ratio) 0.7 basicity
33.3% Example 2 A cowhide (100-weight suspension) that had been limed, depilated, and demineralized in a conventional manner was soaked in salt, sulfuric acid, and 60 parts of water.The pH at this time was 2.6. This was followed by chromium<1) salt (
Nihon Kagaku Kogyo (manufactured by Neochrome) Cr20315%
, basicity 33.3%) was added and drummed for 2 hours. Next, 5 parts of the chromium-aluminum tanning agent shown below was added and drumming was carried out for 6 hours. Two hours after addition of the chromium-aluminum tanning agent, sodium bicarbonate was added in 4 portions every 3 portions to bring the final pH to 4.1. The temperature at this time was 38°C. The obtained tanned leather is C
r2031.42%, A12031.06%, heat shrinkage temperature is 108'C, chromium (C
r) was 93 ppm. Finishing in a conventional manner resulted in a flexible, soft-feeling leather.

Preparation of chromium-aluminum tanning agent> Add water to a glass-lined reactor equipped with a thermometer and a stirrer.
6 1 K! J basic chromium sulfate (manufactured by Nihon Kagaku Kogyo Co., Ltd.) Neochrome > 100 (19
Fluminium sulfur (AI (804) 357%)
952 Ky Sodium Formate (ICOONa 95%) 254 Kfi was taken, heated to 60°C, and stirred and mixed for 60 minutes. To this mixture, sodium bicarbonate 267 K9 was gradually added over 180 minutes to make it highly basic. After addition, the mixture was filtered according to a conventional method and then spray-dried to obtain 2014 kg of dried granules.

The composition of this dried granular material was as follows.

Cr2O3 12.6% by weight A +203 8.01%HCOONa
11.9ffiM%Cr2O3/Al2
O3 (weighted) 1.58 basicity
33.3% this granular dry product 2014 K'j to calcined magnesium oxide (Mg095.0%) 1217 to! j was added and mixed until uniform, yielding 2135 kg of chromium-aluminum tanning agent.

The composition of this chromium-aluminum tanning agent was as follows.

Cr2O3 11.9% by weight Al2O37.5% by weight HCOONa 11.218% MgO5,
4% by weight Basicity 61.8% <Effects of the Invention> According to the method of the present invention, the tanning agent penetrates well into the interior of the tanned leather, and the distribution of chromium and aluminum becomes uniform, resulting in a firm and flexible silver surface. You will get good quality and good finished leather.

Furthermore, the amount of chromium used can be reduced, the chromium in the wastewater can be reduced to at least 115 or less as in the conventional method, and the amount of chromium contamination can be significantly improved, making it easier to take environmental measures for wastewater.

Claims (2)

[Claims] (1) Pre-tanning the pickled rawhide with chromium (III) salt,
A tanning method characterized by subsequently performing full tanning with a chromium-aluminum tanning agent. (2) The tanning method according to claim 1, wherein the chromium-aluminum tanning agent has an automatic basicity adjustment ability.