CS242713B1 - Production method of leathers with encrease heat resistance - Google Patents

Abstract

Method of producing leather with increased resistance to heat, while adjusting the pH tanned leather to a value of 6.5 to 9 per leather 2.0 to 15 wt. alkaline soaps aliphatic carboxylic acids with carbon numbers of 8 to 21, excess soaps become removed by washing in running water and / or converted to insoluble chremite complexes by the action of basic chromium pigs in an amount % corresponding to 0.2 to 1 wt. oxide chromium, said values being applicable weight of leather.

Description

The present invention relates to a process for producing leather with increased heat resistance.

Leather products such as footwear, gloves and others are in some cases exposed to high temperature conditions. Most of the commonly produced leather darkens when heated, loses softness and strength, which is particularly undesirable, shrinks in the area, so that irreversible deformation of the product occurs.

Abroad, some factories produce leather with increased heat resistance, designed for welding gloves and parts of work shoes and workers' clothing in steel mills and smelters. Well known is the product of the French company Teehnique et Securita.

Several patents are known to increase the heat resistance of leather by mineral filling with water glass, talc, phosphorus compounds, or fluorinated elaomers. For example, Herfeld and Endisch (Leder und Huteaarket 27, 106, 1975) review such procedures.

A disadvantage of the filler materials is usually an increase in the stiffness of the leather, which is particularly unfavorable where high softness is desired, such as glove leather. Further, as detailed tests have shown, filler materials only increase the heat resistance in some cases and their effect is generally low (see also the above-mentioned work).

The above-mentioned disadvantages are substantially eliminated by the method of producing leather with increased heat resistance, which is characterized in that after adjusting the pH of the tanned leather to 6.5 to 9, the leather is treated with 2.0 to 15% by weight. Alkaline soaps of aliphatic carboxylic acids having a carbon number of 8 to 21, excess soaps are removed by washing in running water and / or converted to insoluble chromium complexes by treatment with basic chromium salts in an amount corresponding to 0.2 to 1 wt. chromium trioxide, the values refer to the weight of the leather.

Before converting the excess soaps into chromium complexes, the leather is acidified with formic, acetic or phthalic acid and / or a mixture of mineral acids and neutral salts, preferably sodium chloride or sodium sulfate in an amount of 1 to 10% by weight. to the weight of the leather which adjusts the pH of the leather surface layers to 2.8 to 4.8.

By the term excess soap is meant that part of the product that is diffused into the capillary structure of the skin by anezreagovalas by chromium groups to form fatty complexes; this fraction can be removed by washing or complexed with chromite! salts by overcompensation.

Leather treated according to the process of the invention is resistant to 300 ° C and does not increase its stiffness for 1 minute. The effect of a heat beam whose temperature is in the focus of 500 ° C, the surface charring up to 20 seconds. Repeated exposure is not appreciable at 280 ° C.

The advantage of the process according to the invention is to achieve the desired effect in an economical manner, since heat resistance is achieved by eliminating the critical, harmful factors that reduce the heat resistance of the collagen, instead of compensating for these factors by the addition of other enhancers.

Another advantage is to obtain heat resistance without impairing the softness of the leather. The leather made according to the new process is suitable for welding gloves and other products used in elevated temperature environments, or for the manufacture of footwear with direct vulcanization of the sole and elsewhere where the leather is exposed to temperatures up to 140 ° C or even higher in the short term.

Example 1

The leaches after leaching, mechanical treatment, descaling, pickling and pickling by conventional methods are made with chromium (III) basic salts having a basicity of 45 ° Sch in an amount corresponding to 1.7% of chromium trioxide per holy weight using 0.6% magnesium hydroxide for exfoliation. for 5 to 18 hours.

Then the leather is thrown away, left to rest for at least 12 hours and squeezed. After tearing to the desired thickness, they are weighed and cast into a tanner drum or other rotating vessel.

Here, they are first washed with water and then the remaining acids are neutralized with ammonia or other mild alkali so that the pH of the cut of the leather is 6.5 to 9.5.

The lower value usually applies to the middle part of the leather. Thereafter, 8% of unsaturated fatty acid alkaline soaps, e.g. obtained by saponification of animal fats, are added to the leather.

The amount is calculated on the post-crushed weight and based on the content of pure substances in the soap. The leather is allowed to move for 90 minutes and then dyed with aniline dyes to the desired shade.

After dyeing, the leather is washed with running water at 25 ° C for 20 minutes. Washing is followed by fixation of the free soaps in the skin with chromium sulphate added in powder form, for example Chromzaz, in an amount corresponding to 1.5% chromium trioxide per tensile weight and a basicity of 35 ° Sch.

Leave the leather to move for 45 minutes and then wash thoroughly with running water. Other operations such as drying, softening, etc. are carried out according to the usual procedure. '

Example 2

After cleavage, descaling and pickling by conventional methods, the ground is plated in 100% water,% sodium chloride and 1.1% sulfuric acid for 60 minutes. Thereafter, a chromium tanning compound having a basicity of 45 ° Sch in an amount corresponding to 1.6% of chromium trioxide and after 1 hour of movement 0.55% of caustic magnesite, e.g. Lovinite, n.p. Slovak Magnesite Works Košice.

Leave the leather to move for at least 5 hours and then rest until morning. After a short spin, the dome is thrown out and after 25 hours it is squeezed and squeezed. The lined leather is then neutralized in a barrel with a 1: 1 mixture of ammonia and sodium bicarbonate until the pH of the cut of the leather is greater than 7.5 over the entire cross-section.

Then 30% alkaline soap containing 25% fatty acids and leather are added and allowed to move for 60 minutes. This is followed by a 25 ° C warm water wash for 25 minutes.

0.6% formic acid is added to the washed leather and the leather is allowed to move until the pH of the leather surface layers is between 3 and 4.

Then a chromium tanning compound having a basicity of 45 ° Sch is added in an amount corresponding to 1.2% of chromium trioxide and the movement is continued for 60 minutes. The leather is then washed thoroughly with running water for 30 minutes, ejected and other finishing operations carried out according to the usual procedures.

Claims (2)

I HAVE MY INVENTION A process for the manufacture of leather with increased resistance to heat by tanning leather with basic chromium salts, characterized in that after the pH of the tanned leather has been adjusted to a value of 6.5 to 9, the leather is treated with 2.0 to. Alkaline soaps of aliphatic carboxylic acids having a carbon number of 8 to 21, the excess soaps are removed by washing in running water and / or converted to insoluble chromium complexes by treatment with basic chromium salts in an amount corresponding to 0.2 to 1% by weight. chromium trioxide, the values refer to leather weight. 2. The process according to claim 1, characterized in that, before converting the excess soaps into chromium complexes, the leather is acidified with formic, acetic or phthalic acid and / or amsai of mineral acids and neutral salts, preferably sodium chloride or sodium sulphate in an amount of 1-10%. wt. to the weight of usn, which adjusts the pH of the skin layers to 2.8 to 4.8.