CS248390B1 - A method for coagulating synthetic latexes - Google Patents

Abstract

The present invention relates to a process for the coagulation of synthetic latexes with sulfuric acid. a mixture thereof with a salt in the presence of a coagulant co-agent, which is glutin and its low molecular weight hydrolysates.

Description

The invention relates to a process for the coagulation of synthetic latexes with reduced salt consumption, respectively.

in her absence.

The closest approach is to the methods of coagulation of synthetic latexes according to AO ČSSR 102 343, US patent 3,024,223 and AO USSR 1,065,424. However, none of them reliably solves the problem of coagulation of synthetic latexes at elevated temperatures.

The coagulation of synthetic latexes is currently carried out most commonly by a salt-acid system for the coagulation of the cascade, ie in a series of series-connected coagulation cylindrical vessels equipped with a stirrer.

In the first phase, so-called latex creaming is accompanied by agglomeration of latex particles due to the added brine. In the next phase, the latex is precipitated by acid. A prerequisite for coagulation to proceed without apparent technological difficulties is the perfect clarification of the waste coagulation serum and the achievement of a suitable coagulation size of the pulp.

Too coarse grit disrupts its continuous passage to the next stage of coagulation of the cascade. Conversely, if the pulp is too fine, there is an excessive drop in the next stage of the process. It is generally known that the size of the pulp can be influenced by varying the electrolyte concentration in the latex, or the pulp. in coagulation serum.

To achieve a sufficiently fine coagulation of the pulp and perfect clarification of the coagulation serum, a large amount of salt must be dosed during the creaming process. Since the current high salt consumption of synthetic rubber coagulation has a negative impact on the environment, there is currently a desire to coagulate at a reduced salt consumption. in her absence.

Reduction of the coagulation pulp size and hence the reduction of salt consumption can be achieved by carrying out the coagulation process in the presence of coagulation aids such as bone or skin glue according to AO ČSSR 102 343.

However, the use of glue to control the size of the pulp is difficult and sometimes even eliminated at higher temperatures of the latex, especially above 50 ° C, since the waste coagulation serum is poorly clarified, sometimes cloudy.

Rubber Age 1965, 97, 5, 73 discloses that in these coagulation systems salt or glue consumption can be reduced by the addition of suitable polyamines, the application of which contributes to improved clarification of the waste coagulation serum.

However, due to the high cost, the polyamines for technical practice are largely considered only as by-products from the production of hexamethylenediamine, known as Amine 248.

Therefore, in countries where the production of hexamethylenediamine is not established, the beneficial properties of polyamines cannot generally be exploited economically.

If the coagulation of butadiene-styrene latexes is carried out with sulfuric acid only, ie without prior NaCl creaming or without the addition of glue, the consumption of sulfuric acid during coagulation is excessively high, since in this case the acid serves not only to decompose the salts of resin and fatty acids, but also as an electrolyte. In this case, however, perfect clarification of the waste coagulation serum is not achieved even with a high acid dosage.

The use of collagen hydrolyzates having a molecular weight of about 20,000 is known in reducing salt consumption. In Soviet AO 1 065 424, dosing of collagen hydrolyzates with an average carboxyl end group content of 0.7 to 20% is recommended. however, it appears that the low molecular weight collagen hydrolysates themselves are unsuitable for coagulation, since at very low molecular weights they do not contribute to refining the coagulation pulp size. Also, the efficacy of collagen hydrolyzate in terms of sulfuric acid consumption in coagulation decreases in reducing their molecular weights.

Said shortcomings in the coagulation of synthetic latexes with sulfuric acid, respectively. salts and sulfuric acid can be removed by making the coagulation according to the invention, consisting in the fact that according to the subject, the co-coagulation agent for the coagulation of synthetic latices at pulse ^1>? tare above 50 ° C a mixture of glutin and its hydrolysates ratio 1:20 to 6: 1, preferably 1:10 to 1: 5 for a total amount of coagulation auxiliary agent in the range of 0.01 to 10 kg of the composition, based on 1 tonne of synthetic rubber.

Glutin means water-soluble collagen contained in a bone or skin glue.

Hydrolysates of less than 10,000 molecular weight, which mainly contain oligopeptides and alpha-amino acids, are referred to herein as low molecular weight hydrolysates.

The properties of the coagulation system can be advantageously varied as desired by the ratio of the two components in the coagulation aid. Increasing the glutin / glutin hydrolyzate ratio can be used to refine coagulation pulp.

By reducing this ratio, a better clarification of the coagulation serum is achieved, especially in the case of low molecular weight hydrolysates. In this way, the effect of non-reproducible molecular weights in collagen hydrolysis can be easily eliminated, and the coagulation process can be reliably controlled by varying the ratio of the two components in the mixture.

Example 1

To 65 liters of SBR 1500 butadiene-styrene latex with a dry matter content of 20% was added 30 ml of an aqueous solution of bone glue / product of the Feeding and Glue Company, Liptovský Mikuláš / at a concentration of 10% and 231 ml of dry matter brine. 26%. After 15 minutes, the latex thus cross-linked was gradually dispensed in 164 ml quantities into the coagulation serum of the following composition with stirring:

distilled water 26% brine 10% bone glue 10% sulfuric acid

265 ml

128 ml 16.4 ml 66.2 ml

5.4 ml of 10% sulfuric acid was added to the coagulation serum between the individual doses of the cream latex.

When the latex was poured into the serum, a very fine pore size of about 1 mm immediately formed, but the coagulation serum cleared very slowly, but complete clarification was not achieved within 20 minutes of stirring.

This example illustrates the fact that the actual application of the adhesive as a coagulation aid at higher latex temperatures is not suitable.

Example 2

The coagulation of SBR type 1500 latex was performed in a manner similar to that described in Example 1, except that the same amount of liquid glutin hydrolyzate (manufactured by Svit o. P. Otrokovice) was used instead of bone glue. The original sample was stripped of calcium by sedimentation for 24 hours after addition of excess soda solution. The molecular weight of the hydrolyzate sample used, determined by the formol titration method, was 530.

As the latex was added to the clotting serum, its immediate clarification was observed. Instead of coagulation pulp, however, pieces of coagulate of about 10 cm were formed, which are not suitable in terms of coagulation flooding on the coagulation cascade. Tanuto is best suited for grit size of about 3 cm.

Example 3

To illustrate the application of a small amount of glue in a large excess of glutin hydrolyzates, coagulation was performed in a similar manner to that described in Example 1, but instead of the glue itself, a mixture with glutin hydrolyzate prepared from the used quality / molecular weight glue was used by formol filtration. 11500) by heating in the presence of 0.5% NaOH at 120 ° C for 3 hours. The molecular weight of the hydrolyzates thus prepared, as determined by formol titration, was 350.

The laboratory prepared hydrolyzate was used in coagulation at a ratio of 15: 1 with glue at a total amount corresponding to the consumption of coagulation auxiliaries of 5 kg / t of synthetic rubber.

After the addition of all the amount of latex and sulfuric acid into the coagulation serum, a coagulation coarse of about 4 to 5 cm was formed. The coagulation serum was immediately clarified immediately after the latex was added to the serum.

Example 4

Type 1500 SBR latex was coagulated in a similar manner to that described in Example 1, except that the glutin hydrolyzate prepared on the basis of formaldehyde skins was used in a mixture with bone glue. The total amount of coagulating agent corresponded to the consumption of 5 kg / t of synthetic rubber. The hydrolysis conditions were the same as in Example 3. The ratio of the mixture of glutin hydrolyzates and glue was 1: 2.

The coagulation serum was immediately clarified and the resulting crumb of about 0.5 cm was easily transported.

The example illustrates the use of glutin in admixture with its hydrolyzate near the upper limit of the range.

Example 5

In this example, coagulation conditions close to optimal conditions of the defined range are illustrated.

Coagulation of SBR type 1500 latex was performed in a similar manner to that described in Example 1 except that the ratio of glutin to its hydrolyzates was used in a ratio of 9: 1 with a total amount of coagulating agent of 5 kg / t synthetic rubber. Liquid glutin hydrolyzate with a molecular weight of 500 was used in the experiment. The molecular weight of the glue was 11,500.

Upon addition of all of the latex and sulfuric acid, coagulation serum immediately became clear. The resulting pulp had a size of 3 cm and suited in terms of flooding.

Claims (1)

Process for the coagulation of synthetic latexes at elevated temperatures by the addition of sulfuric acid or a mixture thereof with a salt, characterized in that the coagulation is carried out in the presence of a coagulation aid which is a mixture of glutin and its hydrolysates in a ratio of 1:20 to 6: 1. 1:10 to 1: 5, with a total amount of coagulation aid in the range of 0.01 to 10 kg of the composition, based on 1 ton of synthetic rubber.