JPH0528760B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to an improved chromium-aluminum tanning agent. <Prior Art> As is currently well known, various tanning agents have been proposed and used, but chrome tanning agents and tannin tanning agents are mainly used.
Chrome tanning agents have been used since ancient times due to their outstanding tanning effect.
Various basic chromium sulfates based on different basicities and differences in chromium content are known and have contributed significantly to the development of the leather industry. However, even with such effective chromium tanning agents, some drawbacks have been pointed out in line with the demands of the times. The biggest problem is the environmental pollution problem caused by chromium compounds, and measures to treat chromium in tanning wastewater and leather sludge are required, and various studies are being conducted and practical applications are being promoted. Countermeasures against this problem include (1) a so-called recycling method in which chromium-containing wastewater is returned to the chrome tanning process, (2) a so-called high-adsorption tanning agent method in which a tanning agent that improves chromium adsorption is used (3) ) The so-called chromium-saving tanning method, which uses the minimum necessary amount of chromium in conjunction with other tanning agents, has been proposed and partially implemented. The present inventor has previously discovered that, in the method according to (3) above, an acidic compound consisting of a chromium sulfate-containing material, an aluminum salt, and a carboxylic acid compound having a weight ratio of 0.7≦ _{Cr 2} O ₃ /Al 2 O ₃ ≦3 We have developed a method for producing a chromium-aluminum tanning agent characterized by neutralizing a mixed aqueous solution with an alkaline agent to make it highly basic (Japanese Patent Publication No. 40478/1983). <Problems to be solved by the invention> The invention disclosed in Japanese Patent Publication No. 60-40478 uses chromium to improve the heat resistance of leather tanned using an aluminum tanning agent alone, and also significantly reduces the amount of chromium in waste water using the conventional chromium tanning method. Although this contributes to reducing the chromium pollution load, 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 adsorbed onto the hide, which tends to push the pH of the solution out of the preferred range required for a proper tanning operation, thus reducing the PH value 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 tanning work, and the PH value If it is too low, the binding of chromium and aluminum to the leather will be insufficient, resulting in insufficient tanning effect.
On the other hand, if the pH value is too high, there is a danger that chromium hydroxide and aluminum hydroxide precipitate will be formed, making it impossible to obtain good tanned leather. Therefore, in the past, an alkaline agent such as soda carbonate or bicarbonate was 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 and thoroughly controlled, the appearance and quality of the final tanned leather may be impaired, which can easily occur. It was hot. The present inventors conducted research to improve the drawbacks of the invention disclosed in Japanese Patent Publication No. 60-40478 as described above, and as a result, the present invention was obtained. <Means for solving the problems> That is, the present invention provides (a) 2 to 25% by weight of Cr ₂ O ₃ ;
Contains at least 2-25% by weight of Al ₂ O ₃ and 1-15% by weight of a carboxylic acid compound, weight ratio Cr ₂ O ₃ /Al ₂ O ₃
Chromium with a basicity of 0.7 to 3 and a basicity of 20 to 55%.
This is a chromium-aluminum tanning agent characterized in that 0.2 to 50 parts by weight of a (ro)acid binder is mixed with 100 parts by weight of an aluminum tanning agent. <Function> The chromium-aluminum tanning agent of the above (a) in the present invention is obtained by spraying an acidic mixed aqueous solution consisting of a chromium sulfate-containing substance, an aluminum salt, and a carboxylic acid compound, neutralized with an alkaline agent to make it highly basic. It is dried and granulated. Here, the chromium sulfate-containing substance refers to chromium sulfate, basic chromium sulfate, or their mirabilite-containing substances, but industrially, sodium dichromate aqueous solution is mixed with organic Alternatively, basic chromium sulfate produced by a reduction reaction with an inorganic reducing agent is suitable. Next, the aluminum salt is mainly aluminum sulfate, but other basic aluminum sulfate, aluminum chloride, basic aluminum chloride, etc. may also be used as necessary. In addition, carboxylic acid compounds are used as masking agents for OH groups when forming a high base, for example, formic acid, acetic acid, oxalic acid,
Succinic acid, glutaric acid, adipic acid, phthalic acid,
Examples include tartaric acid, citric acid, and lactic acid, and they may also be alkali metal salts, alkaline earth metal salts, or ammonium salts, and at least one or two or more of these may be used as appropriate. 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 preferable because an alkaline agent that is as mild as possible is preferable for operational reasons. The above-mentioned chromium sulfate-containing material, aluminum salt, and carboxylic acid compound are prepared as 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 perform high-temperature radicalization. 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. The particle size of the product is preferably about 40 mesh which can be dissolved in cold water, but 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). Cr ₂ O ₃ 2-25% by weight (preferably 8-20% by weight) Al ₂ O ₃ 2-25% by weight (preferably 5-16% by weight) Carboxylic acid compound 1-15% by weight (preferably 6-15% by weight) Weight%) Cr203/Al203 (weight ratio ₎ 0.7-3 (preferably 0.8-2) Basicity 20-55% (preferably _28-50 %) _Cr2O3 / _Al2O3 (weight ratio) less than 0.7 To become and,
When the amount of aluminum in the liquid increases and it becomes basic, even if we rely on the masking effect of carboxylic acid compounds, aluminum hydroxide is likely to be generated during operation, making it impossible to obtain a high basicity, and at the same time, it becomes difficult to perform the manufacturing process. However, this is because 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 it is also influenced by its type and the quantitative relationship between aluminum and chromium; less than 1% No effect of masking agent was observed, on the other hand, 15%
This is because even if the masking effect is exceeded, not only will no significant masking effect be observed, but it will also be disadvantageous in terms of cost. In addition, the content of Cr ₂ O ₃ and Al ₂ O ₃ is Cr ₂ O ₃ /
Depends on Al ₂ O ₃ (weight ratio). Further, as the acid binder (b) of the present invention, calcined magnesium oxide is suitable, and calcined magnesium oxide ore, calcined products of magnesium hydroxide or magnesium carbonate separated and collected from seawater or dolomite, and calcined magnesite are suitable. Examples include those whose main component is calcined magnesium oxide, such as magnesium oxide and magnesia clinker. Incidentally, calcined magnesium oxide includes, for example, dolomite, alkali metal carbonate, alkali bicarbonate,
It can also be used with sodium sulfite. These acid binders are usually used in powder form;
Reactions with free acids in tanning liquors are particularly influenced by particle size, with 100 mesh products often being preferred.
The reason for this is that particles with a particle size larger than 100 mesh remain as insoluble matter during the tanning operation, and this may deposit on the surface of the tanned hide, causing spots. The mixing ratio of the chromium-aluminum tanning agent (a) and the acid binder (b) depends on the basicity of the chromium-aluminum tanning agent, the type of acid binder, and the chromium-aluminum tanning agent after mixing the acid binder. Although it depends on the set basicity of the agent, in most cases (a) chromium-
For 100 parts by weight of aluminum tanning agent, (b)
The acid binder is preferably 0.2 to 50 parts by weight. The reason for this is that if it is less than 0.2 parts by weight, the alkaline content will be insufficient and the appropriate PH value of the tanning solution will not be obtained.On the other hand, if it exceeds 50 parts by weight, the PH value of the tanning solution will be out of the appropriate range, and during the tanning process. This is because a gel of chromium hydroxide and aluminum hydroxide is formed in the tanning process, making tanning work impossible. The tanning method using the chromium-aluminum tanning agent according to the present invention is basically no different from the usual chrome tanning method, and the tanning operation is not complicated at all. The present invention will be specifically described below with reference to Examples. <Example> Example 1 In a glass-lined reactor equipped with a thermometer and a stirrer, water 161.9Kg Basic chromium sulfate (Neochrome, Nihon Kagaku Kogyo Co., Ltd.) 100.0Kg Aluminum sulfate (Al ₂ (SO ₄ ) ₃ 57 %) 49.7Kg of sodium formate (HCOONa95%) 17.9Kg were taken, heated to 60°C, and stirred and mixed for 60 minutes. To this mixture, 13.9 kg of bicarbonate of soda was gradually added over 90 minutes. At this time, the base could be made highly basic without the formation of gel. After addition, the mixture was filtered according to a conventional method and then spray-dried to obtain 145.0 kg of dried granules. The composition of this granular dry product was Cr ₂ O ₃ 17.5% by weight Al ₂ O ₃ 5.8% by weight HCOONa 11.7% by weight Cr203/Al203 (weight ratio) 3.0 Basicity 33.3%, and the water solubility was very good. . Add 8.7 kg of calcined magnesium oxide (MgO95.0%) to 145.0 kg of this granular dry material and mix until uniform.
Mixed chromium-aluminum tanning agent 153.7Kg
I got it. The composition of this chromium-aluminum tanning agent was as follows. Cr ₂ O ₃ 16.5% by weight Al ₂ O ₃ 5.5% by weight HCOONa 11.0% by weight MgO 5.4% by weight Basicity 60.7% Example 2 In the same reactor as Example 1, add 465.3 kg of water and basic chromium sulfate (Nihon Kagaku Kogyo Co., Ltd. ) Neochrome) 100.0Kg aluminum sulfate (Al ₂ (SO ₄ ) ₃ 57%) 213.8Kg sodium acetate (CH ₃ COONa98.5%) 43.7Kg were taken, heated to 60°C, and stirred and mixed for 60 minutes. 59.9 kg of bicarbonate of soda was gradually added to this mixture over 120 minutes. At this time, the base could be made highly basic without the formation of gel. After addition, the mixture was filtered according to a conventional method and then spray-dried to obtain 317.2 kg of dried granules. The composition of this granular dry material is Cr ₂ O ₃ 8.0% by weight Al ₂ O ₃ 11.4% by weight CH ₃ OONa 13.5% by weight Cr203/Al203 (weight ratio) 0.7 Basicity 33.3%, and the water solubility is very good. It was hot. Add 19.0 kg of calcined magnesium oxide (MgO95.0%) to 317.2 kg of this granular dry material and mix until uniform.Chromium-aluminum tanning agent
Obtained 336.2Kg. The composition of this chromium-aluminum tanning agent was as follows. Cr ₂ O ₃ 7.5% by weight Al ₂ O ₃ 10.8% by weight CH ₃ COONa 12.7% by weight MgO 5.4% by weight Basicity 61.7% Example 3 In the same reactor as Example 1, add water 209.9Kg Basic chromium sulfate (Nihon Kagaku Kogyo) Neochrome Co., Ltd.) 100.0Kg aluminum sulfate (Al ₂ (SO ₄ ) ₃ 57%) 75.6Kg sodium formate (HCOONa 95.0%) 21.1Kg were taken, heated to 60°C, and stirred and mixed for 60 minutes. To this mixture, 31.1 kg of bicarbonate of soda was gradually added over 120 minutes. At this time, the base could be made highly basic without the formation of gel. After addition, the mixture was filtered according to a conventional method and then spray-dried to obtain 187.9 kg of dried granules. The composition of this granular dry product was Cr ₂ O ₃ 13.5% by weight Al ₂ O ₃ 6.8% by weight HCOONa 10.6% by weight Cr203/Al203 (weight ratio) 2.0 Basicity 40.0%, and the water solubility was very good. . 11.3 kg of calcium carbonate (CaCO ₃ 99.0%) and 4.7 kg of calcined magnesium oxide (MgO 95.0%) were added to 187.9 kg of this granular dry material and mixed until homogeneous to obtain 203.9 kg of chromium-aluminum tanning agent. . The composition of this chromium-aluminum tanning agent was as follows. Cr ₂ O ₃ 12.4% by weight Al ₂ O ₃ 6.3% by weight HCOONa 9.8% by weight MgO 2.2% by weight CaO 3.1% by weight Basicity 65.4% Test Example 1 Example 1 to 100 parts by weight of acid-soaked skin (light steer) Using 7 parts each of the chromium-aluminum tanning agent produced in Step 3 and Comparative Example 1,
Tanning was carried out in a conventional manner on a drum at 20 rpm. At this time, the tanning time was 7 hours after adding the chromium-aluminum tanning agent, and the temperature of the tanning solution was 40℃.
The temperature was adjusted to ℃. The Cr ₂ O ₃ and Al ₂ O ₃ contents of the resulting tanned leather, the heat shrinkage temperature, and the Cr and Al contents in the wastewater,
The pH was as shown in Table 1. Furthermore, the leathers tanned using the chromium-aluminum tanning agents of Examples 1 to 3 had better flexibility and grain surfaces than those of the comparative examples. Test example 2 For 100 parts by weight of pickled skin (light steer),
Tanning was carried out using 7 parts by weight of Comparative Example 2 using a drum at 20 rpm. Two hours after the addition of the dried granules, a total of 1.66 parts by weight of sodium bicarbonate was added in three portions every 30 minutes to raise the pH of the tanning solution. The tanning time at this time was adjusted to 7 hours after the addition of the dried granules, and the temperature of the tanning solution was adjusted to 40°C. The Cr ₂ O ₃ and Al ₂ O ₃ contents of the resulting tanned leather, the heat shrinkage temperature, and the Cr and Al contents in the wastewater,
The pH was as shown in Table 1. Comparing with the example, the pH due to the addition of bicarbonate of soda
The ascent work was complicated, and the Cr concentration in the wastewater was more than double.

[Table] <Effects of the invention> The chromium-aluminum tanning agent of the present invention has the following properties:
The ability to automatically adjust the basicity of the tanning bath eliminates the complicated PH adjustment of the tanning agent by adding an alkaline agent in the past, and the tanning bath can be easily controlled.Moreover, it penetrates deep into the leather to remove chromium and aluminum. The distribution of the grains becomes uniform, and a well-finished leather with a flexible grain surface and good tightness is obtained. In particular, the amount of chromium used can be reduced, reducing the amount of chromium in wastewater to at least 1/5 of the conventional method.
Since it has the effect of significantly reducing the amount of chromium pollution load, environmental measures for wastewater can be easily taken.

Claims (1)

[Claims] 1 (a) _{Cr2O3 2-25 %} by weight, _Al2O3 2-25% by weight,
It contains at least 1 to 15% by weight of a carboxylic acid compound, the weight ratio Cr ₂ O ₃ /Al ₂ O ₃ is 0.7 to 3, and the basicity is
Chromium-aluminum tanning agent that is 20-55%
A chromium-aluminum tanning agent characterized by mixing 0.2 to 50 parts by weight of a (ro)acid binder to 100 parts by weight.