CS218382B1 - Method of manufacturing synthetic tan - Google Patents

Abstract

The invention relates to a method for producing synthetic tannins based on phenols and modified sulphite liquors. The invention is used in the production of synthetic tannins from monovalent and divalent phenols, their sulphonates or mixtures of these raw materials and decalcified cooking liquors, which are waste products of the sulphite cellulose production process, treated by heating with sodium hydroxide at pH 8 to 9 to a temperature of 90 to 105 degrees Celsius. In this way, higher utility properties are achieved compared to products that use untreated sulphite liquor. The invention can be used in all synthetic tanning plants and in all tanneries for tanning leather.

Description

The invention relates to the production of synthetic tanning agents based on modified sulfide leaches and phenolic raw materials. Tanning agents are used to manufacture and treat leather.

Currently, thickened and descaled waste liquors are used for the preparation of tannins. They contain a small amount of free organic acids and active groups. Products prepared from phenol and conventional sulphite leaches have low buffering capacity and a higher content of free phenols.

Some of the disadvantages of the processes used hitherto are eliminated by the process according to the invention, which consists in the production of filler and bleached synthetic tanning agent based on monovalent and polyvalent phenols, their homologues, sulfonates or mixtures of these raw materials and decalcified boiling liquor of wood in a sulphite process. These cooking liquors are adjusted to 80-100 ° C prior to use, after alkalinization to a pH of 8.5-9.5, preferably with sodium hydroxide, and maintained at this temperature for 5-12 hours with simultaneous oxidation, preferably with air. . The repair can also be carried out at a lower temperature, the reaction time being then disproportionately extended. Under these conditions, sugars, predominantly pentosanes, will oxidize to organic acids and release of active, predominantly aldehyde and hydroxyl groups. The pH drops from the original 8.5 to 9.5 to 6 to 7.

Synthetic tannins, which have been used in the production of such treated sulphite liquor, have a lower content of free phenols, greater buffering effect in tanning baths.

Its use achieves a better quality of tanned leather, which is similar in nature to leather tanned by natural tanning agents.

The process according to the invention is exemplified by the following application examples, which are only one of many possible variants.

Example 1

2600 kg of concentrated decalcified boiling liquor from sulphite cooking cellulose (sulphite leaches) of dry matter 380 g / l are made alkaline by adding 30 kg of 40% sodium hydroxide solution to pH 9.0, heated to 90-95 ° C and maintained for 5 hours. Mix the sulphite liquor with air while oxidizing at the same time, the pH drops to 6.7 to 6.8 and during further standing to 6.5.

Example 2

Into the sulphonation boiler we add 590 kg of betanaphthol and 521 kg of sulfuric acid 96%. While stirring, heat to 105 to 110 ° C for 60 minutes.

Example 3

700 kg of water, 753 kg of phenol solution containing 10% water and 2600 kg of sulphite liquor prepared according to Example 1 are introduced into the reaction boiler. Next, bethanaphthol sulphonate prepared according to Example 2 is added and the temperature is adjusted to 65 ° C. We start with the addition of 712 kg of formaldehyde 40%. The temperature is maintained by cooling between 75 and 80 ° C. After addition of formaldehyde, stir at 75 ° C for 60 minutes and then neutralize with ammonia water. Usually the consumption to pH of a 0.5% solution of 3.5 to 3.7 is 270 kg. After neutralization, turn the product into drums or dry in a spray drier.

Example 4

We add 800 kg of water, 900 kg of technical mixture of monovalent and divalent phenols, modified sulphite liquor prepared according to example 1 and sulphonate prepared according to example 2 to the reaction boiler. Adjust the temperature to 60 ° C and start adding 700 kg of formaldehyde. We maintain the temperature between 60 and 65 ° C. After the addition of formaldehyde is complete, allow to stir for 60 minutes and neutralize with caustic soda 40%. To neutralize to a solution value of 0.5% 3.2 to 3.5, 190 kg of sodium hydroxide solution is usually required. The resulting product is used in the liquid state or spray dried.

Composition of technical mixture of divalent phenols:

vacuum pitch 3.45% neutral oil 3.03% cresols 3.80% xylenols 2.35% pyrocatechin 45.80% '

3-methylpyrocatechin 12.75%

4-methylpyrocatechin 28.75%

Example 5

We add 800 kg of water, 900 kg of technical mixture of divalent phenols, 700 kg of sodium sulfite - crystalline to the reaction boiler, adjust the temperature to 50 ° C and add 398 kg of formaldehyde 40%. Maintain the temperature at 50 to 60 ° C. When the addition of formaldehyde is complete, add decalcified sulphite liquor and heat to boiling for 3 hours. Cool to 70 ° C and gradually add 50 kg of 40% hydrogen peroxide and complete the condensation with 260 kg of 40% formaldehyde at 60 ° C. Gradual addition of 250 kg of sulfuric acid adjusts the pH of the 0.5% solution to 3.2 to 3.5. The finished product is used liquid or dried in a spray dryer.

Claims (1)

SUBJECT Process for the production of synthetic tannins based on monovalent and divalent phenols, their homologues, sulphonates, or a mixture of these raw materials and cooking liquors, which are discharged in the sulphite process for the production of wood pulp, by condensation under acidic conditions at 50 to 95 ° C for 1 to 3 hours in an environment with a pH of 1.0 to 2.5, SUMMARY OF THE INVENTION characterized in that the decalcified lye is heated to 90 to 105 ° C for 5 to 12 hours with simultaneous oxidation at an initial pH of 8.5 to 9.5, while the condensation is subsequent to the mole ratio of phenols to moles % of formaldehyde and the dry matter of sulphite leaches in the range of 1: 0,6: 50 to 1: 1: 100.