CS200305B3 - Process for continuous multistage coagulation of latexs of diphasic multicomponent resins - Google Patents

Description

The invention relates to a process for the continuous coagulation of latexes of biphasic multi-component resins or mixtures thereof with other latex electrolyte solutions under constant agitation according to the author's certificate No. 173 244

A typical representative of a two-phase multi-component resin is the acrylonitrile-styrene-polybutadiene elastomer terpolymer. The coagulation of the two-phase latexes is carried out on a technical scale in batches or continuously. The lack of sophisticated procedures is mainly in the large volume of equipment and the difficulty of ensuring proper automatic management of the process.

When switching to continuous coagulation methods, there are deficiencies in coagulate quality and increased blindness. Defects in coagulum quality result in lower bulk density after drying, poor particle size distribution, which causes difficulties in transporting the coagulum with mother serum.

Further, a continuous coagulation method according to the author's certificate No. 173 244 is known in which the continuous coagulation of latexes of two-phase multi-component resins or mixtures thereof with other latexes is carried out with dilute electrolyte solutions while constantly coagulating the coagulation mixture by coagulating at the inlet temperature. of latex and electrolyte not more than 10 ° lower than the coagulation temperature threshold of the latex, and at a temperature in the reactor up to 5 ° C higher than the coagulation temperature of the latex, the mean residence time of the coagulation mixture is greater than 10 minutes. heated latex and electrolyte are fed to the reactor each

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200 3SS separately.

When carrying out continuous coagulation in this way, the main drawback is that to mix and mix the electrolyte and latex thoroughly with considerable agitation intensity, intensive stirring prevents the development of matured coagulate particles of suitable size for further processing operations.

In addition, in one reactor, the protective layer of the emulsifier must be disrupted, so-called rapid coagulation and particle maturation. These individual phases of the coagulation prooes require a different technological mode that cannot be provided in a single reactor. In coagulation carried out by the process of the present invention, it has been found that the quality of the coagulate is not significantly dependent on the inlet temperature of the latex and that it is possible to sufficiently dimension the influence of the inlet temperature by the maturing stage *

When working with latexes of heat-resistant polymers, where coagulaol has to be carried out at a temperature above the boiling point of the reaction mixture, the removal of the hot reaction mixture is a serious problem.

These drawbacks can be overcome by the process according to the invention, in which the latent coagulation process of the two-phase multicomponent resins or their mixtures with other latexes is carried out by electrolyte solutions with stirring at a reaction temperature of up to 5 ° C above the latex coagulation threshold. two to five degrees, preferably in three steps, such that the ss in the first stage mixes the latex and the electrolyte, wherein the temperature of the mixture is less than 90 ° C and the residence time is less than 20 minutes, then / or the further step of heating the reaction mixture to a VIoat polymer softening temperature level, wherein the temperature range may be up to 20 ° C lower or up to 15 ° C higher than the Vioat softening temperature, and in the final stage coagulate ripening at temperature up to 5 ° C higher than the coagulae temperature threshold and after the coagulation proo For example, the coagulation mixture is cooled below the Vicat softening temperature of the polymer and the total residence time of the coagulation mixture in coagulation stages 2 to 5 is at least 30 minutes.

In the first mixing step, the protective layer of the emulsifier on the latex particle is disrupted. The latex and electrolyte solution are fed separately to the first coagulation stage, or are mixed just prior to entry into the 1 coagulation stage. The temperature in the first stage is less than 90 ° C and the residence time is less than 20 minutes. The temperature in the other coagulation stages and the residence time are higher than in the first stage. In the last steps of the coagulation line, the temperature is preferably maintained at the softening temperature of the Vioat or Da polymer in question at a lower temperature level. The use of a temperature higher than the softening temperature of a given Vioat polymer is not excluded, but there is an increased demand for mixing intensity, regulation of the clot residence time at a given stage, since the risk of large-scale sludge formation is increased.

Determination of the Vioat softening temperature is carried out according to CSN 64-05-21 method A. In the first stage, apart from the breakage of the protective layer, only partio aggregation occurs, which stops after a certain time. In the second and possibly further stages of coagulation at elevated temperature after the end of the induction period, coagulation occurs and coagulate β is formed by suitable particle size distribution with a minimum content of the threshold fractions, which is advantageous for further

200 393 product processing.

In the last step, agglomeration of the coagulate particles is carried out with stirring at an elevated temperature of at least 90 to 100 ° C, with a residence time of more than 30 minutes. Stirring intensity τ3 «is lower than in stage 2, usually using a frame or paddle mixer and operating at peripheral speeds of 2 to 3 m / s. At this stage, mature, hard and non-adhesive is obtained! coagulate.

According to the invention, more than three stages can be used. The temperature regime then follows the second stage temperature and is in the range of 90 to 120 ° C, the total residence time in these further stages being at least 30 minutes. A reactor can be placed on the coagulation line, in which the coagulate dispersion is cooled to a temperature suitable for further processing.

Mixing intensity is also associated with controlling the coagulation progress, especially in the first and second coagulation stages. The mixing intensity is controlled according to the geometry of the reactors and agitators.

Individual stages can also consist of multiple reactors with the same technological conditions. Only one reactor is preferred for the second coagulation stage, in which coagulation is completed, since pipeline clogging may occur when the coagulated latex is transferred from one reactor to another.

The present invention can also be used in two-stage coagulation, where coagulation and maturation of the coagulate are completed in the second stage.

The multistage continuous coagulation process of the invention has the following advantages over other processes:

a) In the first coagulation step, the latex is already perfectly homogenized with the electrolyte solution. At lower temperature, the protective emulsifier layer of the latex polymerization particles is broken.

b) The partially coagulated latex with the electrolyte solution is well flowable and can be easily transported to the second coagulation stage, where it finishes coagulation and reduces the proportion of unripe coagulate that passes to the next plant and reduces the fouling of the reactor and piping .

c) It is not necessary to heat large quantities of latex to a higher temperature for a long time, as is the case in processes where the latex is sprayed at a temperature close to the reaction temperature in the second stage. This reduces the thermal stress of the latex prior to the coagulation process.

d) The coagulate obtained according to the invention separates well from the mother serum and achieves a substantially higher hourly performance on a separation device (e.g. a centrifuge). The coagulate obtained has on average less moisture than a coagulate separated on the same apparatus, but prepared in a different way. .

Example 1

The process was performed according to the author's certificate No. 173 244. A stirred flow coagulation reactor with two levels of oblique blades with a circumferential xyleness of 3.7 m / s and centered the coagulation temperature in the 98 ° C reactor was fed separately with 1% aqueous solution above the surface.

200 3US CaOIg solution at 97 ° C and latex degassing ABS at 89 ° C. The coagulation temperature threshold (see page 2 of Authorization Certificate No. 167 671) for this resin was 94 ° C. The mean residence time in the coagulation reactor was 40 minutes. To leave the coagulation reactor, the reaction mixture was cooled to 50 ° C in a flow stirred tank reactor with a paddle stirrer of 1.8. The obtained coagulete ee poorly blasted The filtration centrifuge achieved a performance of 0.25 tons of polymer / h with an average humidity of 37%

Occasionally, the latex inlet throat and the overflow pipe were plugged into the downstream reactor. The bulk density of the dried coagulate was 0.25 g / m.

Example 2

As in Example 1, only the next reaction stage, the so-called ripening, was employed, with the following modes operating at a temperature of 98 ° C, a frame-shaped impeller with a peripheral speed

2.5 m / s. The residence time in this reactor was 120 minutes. * Pipeline clogging problems were the same as those of Example 1, but the coagulate quality after the second stage was improved. · The bulk density of the dried coagulate was 0.32 g / m 2. coagulate from the mature stage to a separation device. The performance of the filter centrifuge under the same conditions as in Example 1 increased to 0.34 t polymer / h.

Example 3

The degassed ABS latex of Example 1 at 80 ° C was mixed in a flow-through unheated reactor with 1.056 CaCl 3 solution at the same temperature. The latex feed was above the liquid level. The mean residence time in the reactor was 1 minute. The propeller mixer was in the reactor, having a circumferential fineness of 1.5 m / s.

The mixture from the first stage was fed to a stirred blade reactor with three wide blades with a circumferential fineness of 2.8 m / s. The incoming mixture was heated by the reactor jacket and direct reduced steam to 100 ° C. The mean residence time was 20 minutes ·

The mixture from the second stage was fed to a third flow-through reactor equipped with a paddle mixer having a circumferential purity of 3.0 m / s. The average residence time in the reactor was 100 minutes · The reactor temperature was maintained at 98 ° 0 · This arrangement eliminated pipeline and reactor seizure problems · A coagulet was obtained that was well blasted, the residual moisture after centrifugation averaged 31 56 · Bulk the weight of the dried ABS powder was 0.38 g / m < 2 >

The performance of the filter centrifuge under the same conditions as in Example 1 was increased to 0.55 t polymer / hr.

Example 4

It was treated with the apparatus of Example No. 3, but degassed ABS latex was coagulated with a Vioat softening point of 108 ° 0. The coagulation temperature threshold of this resin was 97 ° 0. The temperature in the second reactor was 110 ° C and operated at a slightly elevated pressure of 0.14 to 0.2 MPa. The temperature in the third reaction step was 98 ° 0.

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The coagulate which separated well was obtained, the residual moisture after centrifugation was 33%. The raw weight of the dried powder was 0.37 g / cnP.

Example 5

The latex ABS resin with a Vioat softening point of 106 ° C was fed at 75 ° C to a flow reactor stirred by a propeller stirrer with a peripheral speed of 5 m / e. At the same time, a 1% aqueous calcium chloride solution was fed to the same reactor. The mean residence time of the mixture was 2 minutes at an average reactor temperature of 75 ° C. From the first stage, the mixture was continuously fed into a second coagulation reactor, where coagulation was carried out at 100 ° C and under a pressure of 0.05 MPa. The reactor was stirred with a paddle mixer at peripheral speed

3.5 m / s. The mean residence time in the second stage was 60 minutes. A coagulate was obtained which separated well. The performance of the filter centrifuge operating under the same conditions as in Example 1 was 0.53 t polymer / h.

SUBJECT OF THE INVENTION

Claims (1)

SUBJECT OF THE INVENTION Process for the continuous coagulation of latexes of polyphase multicomponent resins or mixtures thereof with other latexes using electrolyte solutions under constant agitation according to the author's certificate No. 173 244, characterized in that the coagulation process is carried out stepwise in two to five steps, preferably in step steps, and by mixing latex and electrolyte in stage 1, the temperature of the mixture being less than 90 ° C and the residence time shorter than 20 minutes, after which the reaction mixture is heated to the softening temperature of the polymer according to the second and / or subsequent stages Vioata, wherein the temperature range can be up to 20 ° C less or up to 15 ° C higher than the Vioat softening temperature, and in the last step the coagulate is matured at a temperature up to 5 ° 0 higher than its coagulation temperature threshold, and upon completion of the coagulation process, the coagulation mixture is cooled below the softening point of the polymer of The vioata and total residence time of the coagulation mixture in coagulation stages 2 to 5 are at least 30 minutes.