CS264557B1 - 3air.obuzifj.kuj íoí mixture for tanning leather - Google Patents

Abstract

In the tanning of leather using chromium salts, a number of neutralizing agents are used to bind the acidity produced during the binding of chromium to leather. It is advantageous to use agents that react slowly, so that the neutralizing agent can be added simultaneously with the tanning chromium salts. According to the solution, the pellets used for this purpose, which are produced by burning sulphate leachates, which are waste products of pulp production using magnesium salts, have the advantage that they do not contain substances insoluble in acids and their reactivity in the mixture with chromium salts is optimally affected by the course of the binding of chromium to leather, so that with good quality leather, a substantial reduction in the amount of chromium salts in the waste baths is achieved. Pellets I'. -10 are added in an amount of 1 to 10% by weight, calculated on the weight of the resulting mixture, and contain 15 to 95% by weight of magnesium oxide and 2 to 12% by weight of calcium oxide.

Description

BACKGROUND OF THE INVENTION The present invention relates to a self tanning leather tanning composition comprising chromium salts and a sequential acid binding agent suitable for high chromium tanning processes.

The self-base leather tanning compositions used hitherto use either pure powdered magnesium oxide or technical magnesium oxide produced by heat treatment of minerals containing magnesium carbonate, calcium carbonate and silicates as an acidity binding agent. Magnesium oxide in pure form is economically disadvantageous, it dissolves relatively quickly, so that the acidity is unevenly blunted up to the formation of spots of precipitated chromium hydroxide. When mixtures containing silicates are used, these are deposited in tanned leather and have a negative effect on some processing operations of the properties of the resulting leather.

Some of the disadvantages of the prior art solutions are overcome by the self-base composition of the present invention which contains salts of trivalent chromium, such as chromium (III) sulfate, chromium-potassium alum, chromium (III) chloride or chromium (III) basic. The essence of the solution is that the mixture contains, as a phase-acidifying substance, pellets with a high MgO content, which arise from the combustion of sulphite leaches containing magnesium salts. The amount of pellets added is such that the amount of MgO contained in the pellets is 4 to 60%, calculated on the weight of C ^ O ^ ^ in the mixture contained. Further, the composition may contain complexing agents with chromium salts, such as sulfates, sulfites, organic monobasic acids, and a variety of other materials, e.g. Pellets containing up to 95% MgO and 2 to 12 wt. CaO, formed during the combustion of sulphite leaches containing magnesium salts, and due to heat treatment at temperatures up to 1700 ° C, the individual particles of magnesium oxide are sintered. Thus, while maintaining the high purity of the oxide of magnesium

2,264,557 slows down its action as an acid-binding agent, and the pH of the tanning bath prepared from the composition of the invention is more favorable for better utilization of chromium salts and improved quality of the leather produced.

This increased quality results mainly in a better level of coloring of the leather as well as a uniform quality of the use of the surface treatment in the subjective evaluation of the leather, which is an important component of assessing the utility properties of the product. Even with a lower chromium supply, leather is well tanned. A further effect is obtained by post-tanning. While maintaining all the benefits of progressive binding acidity does not occur when applications MgO pellets blunting the cutting tools at postuhování and trimming _of like it when applying products containing insoluble particles - eg. Burnt magnesite minerals. This increases labor productivity.

The description of the invention is complemented by the following examples of use, with only a few of the many possible variants. The invention can be used in all mineral agent plants and tanneries.

Example 1

Mix 500 kg of chromium-potassium alum and 50 kg of pellets with the following composition on a trough mixer:

MgO 93.2 wt.

% CaO 4, 4 wt.

^ βρΟβ 0,4% w / w

SO4 0.9 wt.

insoluble residue in HB1 1: 1 1.1 wt.

The mixture is used for tanning of tanned leather.

Example 2

2700 kg of basic chromium sulphate obtained by reduction of sodium dichromate in an acidic medium having a basicity of 45 ° Sch and a content of C ^O ^ of 27% and 300 kg of pellets of the same composition as in Example 1 are mixed in the mixing silo.

- 3,264,557

Example 3

In a drum mixer, mix 900 kg of basic chromium sulphate from Example 2 and 20 kg of pellets from Example 1.

Example 4

Commonly prepared and decalcified peat is plated in a tanning barrel in a bath of 80% water, 8%

NaCl and 1 wt. for 120 min. at max 25 ° C. 6% of the mixture prepared in Example 2 is then added to this bath and tanning is carried out for 120 min. Leave to rest until morning and then throw on the mats. The pH of the resulting bath was 4.0 to 4.2. The leather is heat-resistant, smooth, clean, the chromium content in the waste bath is max. 0.5 g / l. Leather is further adjusted according to the required assortment. All doses are given in% by weight. calculated on the weight of the ground delivered to the barrel. Compared to conventional sodium bicarbonate neutralization tanning processes, the variability is achieved even with reduced supply of chromium tanning salts and the chromium oxide content decreases from the original 8 * 10 g / l to 0.20.8 g / l with the above technology.

Claims (1)

A self-base composition for tanning leather based on chromium salts, optionally containing other impurities, characterized in that it comprises pellets from the combustion of sulphite leaches containing magnesium salts with a sweetening of 85 to 95% by weight as an acid-binding substance. % magnesium oxide and 2 to 12 wt. % calcium oxide in an amount of 1 to 10 wt. calculated on the weight of the resulting mixture.