LT3608B - Process for preparing chromium extract - Google Patents

Abstract

The invention relates to methods for trivalent chrome complex compound extraction and can be used for leather and fur milling.The purpose of the invention is to prepare a chrome extract, featuring a better activity in leather tanning processes and reduce water sewage pollution.This aim is achieved by making chrome extract in the process of reducing the dichromate with protein originating materials, for example it can be hair in leather production.The extract, produced during chrome reduction with protein material, for example hair, features a higher activity in skin tanning processes, as chrome complexes, masked with organic acid remnants, and enables faster and better coherence of the leather with the collage, the chrome compound concentration in the solution is lower after tanning so the sewage water is less polluted. The leather is also tanned without alkalising tannin liquid up to pH 3.64 and this is noted when tanning the concentrated liquids through a spraying method; in this case the sewage water is not polluted in any way.

Description

The present invention relates to processes for the preparation of trivalent chromium complex compounds and can be used for the treatment of hides and skins.

Known techniques for the preparation of chromium extracts by reduction of dichromate in sulfuric acid with organic compounds: carbohydrates, glycerol, sulphite cellulose extract, chromed leather shavings, wood sawdust, cotton comb [Χημηη h TexHOJiorHH κόχη h Mex. Πολ pej. H. Π. CrpaxoBa. M., JIernpoM6EiTH3jIaT, 1985.], sulphitic fissures [Courtesy of Ex. SU No. 141249, 1961], formalin [Courtesy of Ex. SU No. 889621, 1981].

The drawback of the chromium extracts prepared by all known methods is that it is necessary to precisely regulate the basicity of the compounds by using alkalizing agents in the tanning process of leathers and hides. Chromium extracts with better tanning properties are prepared using carbohydrate reducing agents - glucose, molasses, syrup, which are nutrients. Chromium extracts reduced with other substances are less active in tanning, and leather and fur products have worse properties.

According to its technical nature and the desired effect, the method of preparation of the chromium extract by glucose reduction of dichromate in sulfuric acid solution is the closest to the proposed process [Takenouchi K. JALCA, 1980, vol. 75, N 5, p.150 166 (prototype)].

The main disadvantage of this method is that only a part of the chromium compounds is absorbed by the skin in the tanning process using such a chromium extract, while the remainder of the solution loses, contaminating the effluent with biologically harmful compounds. And when the spent chromium tanning solutions are recycled, they are even less active after coLT 3608 B visualization due to the change in chromium composition and particle size that occurs during alkalization.

The object of the invention is to prepare a chromium extract having a higher activity in the skin tanning process and reducing the contamination of waste water.

This object is achieved when the chromium extract is prepared by reduction of sodium or potassium dichromate with proteinaceous substances, e.g. waste from the manufacture of leather - bristles.

The essence of the invention is that the protein substance - bristles - is used instead of glucose for dichromate reduction. Since the protein material is not completely oxidized during the chromium reduction process, organic acid residues penetrate the inner sphere of the chromium complex and improve activity in the tanning process.

Method of preparation of chromium extract:

Dissolve 100 g of sodium or potassium dichromate in hot water at 70 to 90 ° C and make up 200% by weight of the dichromate. Subsequently, 100 g of concentrated sulfuric acid (100%) are added under stirring, the volume being equivalent to a basicity of 33%. The crushed bristles are gradually added to the acidified dichromate solution without interruption. Total reducing agent up to 23% by weight of the dichromate. Continue the boiling of the extract until the solution turns a bluish-green color for 60 minutes. The prepared chromium extract does not differ in appearance from the extract prepared in a known manner and is completely transparent.

The analytical results of chromium extracts are given in Table 1.

table

Indicators of Chromium Extracts

Indicator Prototype Offered way Concentration of chromium oxide, g / l 304.9 316.6 Baseline,% 33.2 31.0 Density, g / cm ³ 1.589 1,532 PH of a 1.0 g / l (Cr ₂ O ₃ ) solution 3.03 3.08 Dilution pH of a 1.0 g / l (Cr ₂ 0 ₃ ) solution (alkaline to 0.1 Na ₂ CO ₃ ) 6:00 6.25 Concentration of organic acids,% 6.4 8.1

From the data in Table 1, we can see that the reducing agent, using proteinaceous material, produces a lower base (31.0%) extract and contains more organic acids (8.1%), which penetrate and mask the inner sphere of the trivalent chromium complex. Masking is observed by alkalizing dilute solutions with sodium carbonate solution. This chromium extract solution becomes cloudy at pH 6.25, while in the case of reduced glucose it is pH 6.00.

The chromium extract prepared in the proposed manner is used for tanning collagen.

example. The activity of the chromium extracts in the tanning process is determined by their interaction with the gelatin and the change in its melting point. To this end, we prepared gelatin and chromium compound solutions, mixed them and adjusted the pH to 2.8 or 3.8. The concentration of gelatin in the prepared solutions was 8% and that of the chromium salt, expressed as Cr ₂ 0 ₃ , was 2% of the weight of the gelatin. The prepared gelatin tanning solutions were stored at 35 ° C. Gelatin tanning data are shown in Table 2.

table

Gelatin tanning data

Preparation of Chromate Extract Gelatin Gelatin Melting Point, ° C Preparation of Tanning pH after 1 hour at 20 hours.

Prototype 2.8 Gel did not form 55 3.8 100 100 Suggested method 2.8 Gel did not form 98 3, 8 101 102

From the data in Table 2 we can see that the proposed extract also fermentes gelatin at pH 2.8 - after 20 hours. melting gelatine melting point 98 ° C (pure gelatin melting point after 20 hours of thermostatization at 38 ° C). We see that at pH 3.8 after 1 hour. is after 20 or. tanning gelatin melts at 1 and 2 ° C higher in the case of tanning extracts prepared by chromium reduction with bristles.

example.

The activity of the chromium extracts in the tanning process was determined from their interaction with the litter powder, and the lg powder was picked in 10 ml volume buffer (NaClIC - HClO ₄ ). .Po 2 or. the pH of the maintenance solutions was 2.5, 3.0, 3.5, or 4.0. To these solutions was added 20 ml of chromium extract in a solution containing 16.0 g / l of chromium oxide. We tanned the balding powder for 26 hours. At 30 ° C.

The tanning data for balding powder are presented in Table 3.

table

Data on tanning of powdered hair

Chromium extract method of preparation Tanning pH of the solution Cr ₂ O ₃ absorption,% after 3 or. after 5 or. after 26 or. Prototype 2.5 39, 4 46, 0 47.9 3.0 43.3 46, 9 52.1 3.5 44.2 47.6 54.8 4.0 47.0 48.4 55.2 Suggested method 2.5 45, 8 48.0 49.1 3.0 47.0 49, 9 53, 9 3.5 48.4 50, 5 55, 7 4.0 48.7 52, 6 56, 7

From the data in Table 3 we can see that the bald powder with 10 drinks more chromium compounds from the chromium extract prepared according to the proposed method.

example. Sheepskin samples were picked after picking using extracts prepared by known and proposed methods.

We tanned according to the method for sheepskin dressing: sk. k. 7, t ° -42 ± 2 ° C, solution composition:

sodium chloride - 40 g / l chromium compound, calculated as i, Cr ₂ O ₃ - 1.0 g / l fat emulsion: industrial oil I-12A Prevocel W-OF-100

- 10 g / l

1.0 g / l

turpentine -0.5 ml / L urotropin - 0.5 g / L 5 Sheepskin specimens in the table. for tanning data see 4 Table 4

Tanning data for sheepskin samples

Chromium extract method of preparation Tanning data duration or. skin T ° C Cr ₂ O ₃ concentration in solution in g / l after tanning Cr ₂ O ₃ content in skin,% Prototype 3 65.0 0.85 0.5 5 71.9 0.80 0.7 6th 73.8 0.75 0.8 Suggested method 3 70.4 0.81 0.8 5 73, 9 0.74 1.1 6th 75.9 0.71 1.2

From the data presented in Table 4 we can see that the extract, prepared according to the proposed method, has better tanning properties: masked chromium complexes penetrate the skin tissue faster and bind to collagen - skin tissue welding temperature (T _s ) after 5 hours. tanning 73.9 ° C, ie reaches the required7 3 ° C. At the same time, chromium compounds are better removed from solution, which correlates with the amount of chromium oxide in the skin.

example. Sheepskin samples were tanned using concentrated solutions of 50 g / l chromium oxide. They were sprayed onto pickled sheepskin specimens using ml per dm ^{2 of} skin and stored at 20 ° C. Po or. we sprayed 1 M sodium carbo2 nat solution with 1 ml per dm of skin. After 5 or. tanning determined skin pH (0.1 N KCl extract), weld temperature (T _s ) and chromium oxide concentration in the extract. The data are shown in Table 5.

table

Concentrated solution tanning data for sheepskin specimens

Method of preparing the chromium extract Initial Feed- Skin Skin pH (0, IN KCI excerpt) Concentration of Cr ₂ O ₃ in the extract, g / i solution PH mini mas Ts, ° C Prototype 2.25 no 58, 8th 3, 0 0, 40 2.25 yes 80, 3 4.1 0.10 Suggested method 2.45 no 78, 4 3, 6 0.13 2.45 yes 85, 0 4.3 0.03

The data in the table show that, when tanned with the chromium extract prepared by the proposed method (bristle reducer), the masked chromium compounds bind more strongly to collagen than the known tanning chromium extract prepared by chromium reduction with glucose. In addition, the chromium extract prepared in the proposed manner tanned the skin and without alkalizing, its welding temperature rises to 78 ° C, while the chromium compounds, which are known to be reduced in the known manner, do not ferment the skin.

The proposed method of preparing chromium extract has the following advantages over the known one:

bristles for the manufacture of chromium from the skin and not the nutrient glucose;

The chromium extract prepared according to the proposed method is more active in the skin tanning process because the chromium complexes masked by organic acid residues diffuse into the skin and bind more strongly to collagen: 1-2 ° C higher melting point of gelatin, 2-5 ° C higher skin welding temperature, 0,3- 0.4% higher chromium compounds (based on Cr ₂ O ₃ ) in the skin, lower concentration of chromium compounds in the solution after tanning, while reducing pollution of waste water;

- the chromium extract prepared according to the proposed method tans gelatin and skin 15 without being alkalized in tanning solution to pH

3.6-4.0, especially when sprayed with concentrated solutions (50 g / l Cr ₂ O ₃ ); in this case, the waste water is not polluted at all.

Claims (1)

A method of preparing a chromium extract by dissolving sodium or potassium dichromate in water, adding 5 sulfuric acid and gradually adding chromium reducing agent to the resulting solution, characterized in that a chromium reducing agent is used as a chromium reducing agent to improve the activity of the chromium extract such as bristles.