CS198247B2 - Method of separating monomer vinyl chloride from water mixture containing polyvinyl chloride resin - Google Patents

Abstract

1532399 Removing residual monomer from P.V.C. STAUFFER CHEMICAL CO 28 June 1977 [14 July 1976] 26964/77 Heading C3L [Also in Division B1] The procedure for removing monomer from aqueous vinyl chloride polymer mixtures by reduction of pressure and increase of temperature is improved by passing the mixture over a vibrating surface during the treatment. The surface is preferably undulating and/or inclined. Low monomer contents are preferably achieved by repeatedly recycling the mixture for further treatment.

Description

The invention relates to an improved process for removing residual vinyl chloride monomer from aqueous polyvinyl chloride resin containing compositions.

Polyvinyl chloride is preferably produced by polymerizing vinyl chloride in an aqueous emulsion or suspension. The resin-containing aqueous mixture obtained from the polymerization reactor usually contains about 10 to 60 wt. % polyvinyl chloride and about 0.5 to about 10 wt. % Residual vinyl chloride monomer. The monomeric vinyl chloride tends to remain in the polymer until it is processed and is released upon drying or heating the resin during processing.

The major part of the vinyl chloride monomer can be removed from the polyvinyl chloride during drying. In doing so, however, the monomeric vinyl chloride is lost along with the gases leaving the dryer, which increases the production cost of polyvinyl chloride. In addition, the monomer vinyl chloride contained in the drier gases may pollute the environment in the vicinity of the drier.

In order to improve the recovery efficiency of vinyl chloride in production. and in order to reduce the amount of vinyl chloride leaving the environment, attempts have been made to reduce the concentration of monomeric vinyl chloride in the aqueous resin mixture prior to processing.

It has already been proposed to separate monomer from polyvinyl chloride by relieving pressure in the aqueous-containing reactor. the resin mixture and the vinyl chloride are distilled off or by steam distilling off the vinyl chloride. These methods are not industrially applicable when they form an aqueous resin mixture of latex because latices are foaming and difficult to achieve a low vinyl chloride monomer concentration. Even with suspension type resin compositions, it is difficult to achieve a low concentration of vinyl chloride monomer in the aqueous resin composition.

U.S. Patent 3,052,663 discloses a process for separating unreacted monomeric vinyl chloride from a polyvinyl chloride latex by contacting the latex with an aliphatic hydrocarbon. The process requires many difficult contact and filtration steps to separate polyvinyl chloride from the hydrocarbon phase. This process would not be suitable for resins to be spray dried to a white powder product consisting of small particles.

Polish Patent No. 56,169 discloses that the monomer may be removed from the latex and the foaming may be suppressed by passing the polyvinyl chloride on a sloping surface with varying slope. The patent does not disclose the amount of vinyl chloride monomer that remains in the latex.

The invention relates to an efficient process for removing vinyl chloride monomer from aqueous polyvinyl chloride-containing resin mixtures. ·. In the process of the present invention, the removal of monomer vinyl chloride and polyvinyl chloride latexes reduces foaming and minimizes flocculation due to foam drying. By the process of the invention, a latex containing less than 400 ppm of vinyl chloride monomer can be produced.

SUMMARY OF THE INVENTION The present invention provides a process for separating vinyl chloride monomer from an aqueous mixture comprising a polyvinyl chloride resin, wherein the aqueous resin mixture is conducted at a temperature above ambient and below the temperature at which the aqueous resin containing mixture is at elevated temperature adversely affected, and at a pressure of 338 Pa to 81.2 kPa over a surface vibrating at a frequency below 6000 cycles / min.

It is not necessary to use the lowest pressures, but the reduced pressure ensures faster removal of vinyl chloride monomer.

Heating the latex aids in the rapid removal of vinyl chloride monomer from the aqueous polyvinyl chloride resin mixture. A temperature in the range of about 43 ° C to about 82 ° C is suitable. The appropriate temperature level depends on the emulsifying agent, the concentration and composition of the latex, or the suspending agent, the concentration and particle size of the resin. Generally, monomer vinyl chloride is removed more rapidly at higher temperatures. Temperatures up to a value at which the properties of the aqueous resin composition deteriorate to such an extent that they are unsuitable for the intended use are useful.

Giant. Fig. 2 shows a corrugated surface used in Examples 1 to 8; and Fig. 3 shows a manufacturing process diagram of the apparatus used in Examples 1 to 8. .

The term polyvinyl chloride refers to polymers and copolymers of vinyl chloride in which at least 70% of the units are vinyl chloride units. Accordingly, the invention includes polyvinylchlorides in which up to about. 30 ·. % Of vinyl chloride replaced by other monomers.

The term "aqueous resin mixture" or "aqueous mixture containing polyvinyl chloride resin" means an aqueous suspension or emulsion of polyvinyl chloride.

The latex obtained by emulsion polymerization of vinyl chloride typically contains an emulsifier, a catalyst catalyst, water and polyvinyl chloride in an amount of about. . from about 10 to about 60 wt. ·%. Lacsx typically contains about 0.5 to about 10 wt. % of unpolymerized vinyl chloride. Processes for the manufacture of polyvinyl chloride latexes. which optionally contain both polymerized and ethylenically unsaturated compounds which are copolymerizable with vinyl chloride are well known. All wool poles of chloride latex containing unreacted monomeric vinyl chloride can be processed by the process according to the invention.

Suspended polyvinyl chloride is usually made from an aqueous vinyl chloride suspension using a monomer-soluble catalyst and suspending agents that tend to keep the resin particles of the suspension in the aqueous phase. The aqueous suspension may contain about 10 to about 50 wt. % solids and usually contains 25 to 35 wt. % solids. Methods for making suspension polyvinyl chloride are well known.

The vibrating surface over which the aqueous resin composition is guided may be substantially horizontal or have a certain inclination. Preferably, the vibrating surface is inclined and the inclination angle may vary over the length of the surface. The inclined surface is preferred because the slope aids the flow of the aqueous resin mixture over the vibrating surface.

The surface may be smooth or may be modified by scoring, corrugation, bulges, dimples, protrusions, etc. The surface modification will increase the interaction between the vibrating surface and the aqueous resin composition and remove the vinyl chloride monomer from the composition. more efficient.

The vibrating surface may have the shape of a cone, flat plate or trough, over which the aqueous resin mixture flows. As already mentioned, the vibrating surface may be substantially horizontal or inclined to assist flow of the aqueous resin composition over the surface. Preferably, the vibrating surface is in the form of a vibrating trough. The chute may be arranged to be adapted to the space in which the pressure is kept below atmospheric pressure. For example, a spiral-shaped trough arranged in a cylindrical container makes it possible to achieve a large surface in a relatively small container.

The vibrating surface can oscillate or vibrate over a wide range of frequencies. Lower frequencies of the order of about 6,000 cycles per minute are preferred. Lower vibration frequencies are preferred because they can achieve greater vibration amplitude without exposing the device to excessive voltage. To suppress foaming, it is preferable to work at higher vibration frequencies. Optimum efficiency is achieved by balancing the amplitude of the oscillating or vibration motion with the vibration frequency.

The amplitude of vibration is not a decisive variable. The high amplitude of the vibration and movement of the vibrating surface increases the efficiency of removing the monomeric vinyl chloride from the aqueous mixture containing the polyvinyl chloride resin. However, it is known that high shear forces can adversely affect polyvinyl chloride latices. The vibration amplitude may increase to the point where the stability of the latex deteriorates due to high shear forces due to the large vibration amplitude of the vibrating surface. Generally, large vibration amplitudes increase the efficiency of the method. However, the amplitude of the vibration should not be so great as to adversely affect the operability of the apparatus in which the process is performed. Large ¹ vibration amplitudes can be used at lower frequencies.

The reasons why the method of removing vinyl chloride monomer from the aqueous resin mixture is effective is not fully understood. However, efficacy is believed to be due to a substantial reduction in the foaming of the aqueous mixture and to the rapid and thorough mixing of the aqueous mixture. the resin mixture as it flows down the vibrating surface. With rapid mixing of the aqueous resin mixture, the resin particles reach the surface of the aqueous mixture where the vinyl chloride can escape from the resin.

Elevated temperature refers to a temperature higher than ambient temperature and lower than the temperature that adversely affects the aqueous resin composition. Latexes are very easily damaged by elevated temperature. The temperature at which the latex coagulates is dependent on the emulsifiers used in the latex preparation and the history of the material. The temperature is to a large extent dependent on the pressure at which the latex is maintained during the process over the vibrating surface. Typically, a suitable temperature is in the range of about 43 to about 82 ° C. Temperatures in the range of about 54 ° C to about 79 ° C are most preferred.

The temperature of the aqueous resin composition can be maintained at the desired level by heating the aqueous resin composition prior to contact with the vibrating surface, heating the vibrating surface, bringing steam directly into the stripping zone in which the aqueous resin mixture flows over the vibrating surface. do not have an adverse effect on the aqueous resin mixture.

In the process according to the invention, the aqueous resin mixture is passed through a vibrating surface at a pressure below atmospheric pressure. The efficiency of the apparatus increases with pressure reduction, but can be operated at any pressure below atmospheric pressure. Typically, an absolute pressure in the range of about 20 psig to about 100 psig is preferred. Most preferably, the working absolute pressure is in the range of about 10 to about 50 psi, as these pressures can be readily achieved using commercially available reliable equipment and aqueous resin compositions with reduced monomer vinyl chloride concentration can be allowed.

The aqueous resin mixture may be maintained at a pressure below atmospheric pressure by being mounted in a vessel in which the pressure is below atmospheric pressure. Since the monomer vinyl chloride is released from the aqueous resin mixture, the pressure must be maintained to the desired extent by means of an evacuation device. The vibration surface may be made to be part of the container.

For example, a container formed by a covered trough, over which the aqueous resin mixture flows, would be suitable. The tray and tray cover can vibrate simultaneously. The vessel and the surface may vibrate as a single unit, or · the surface may be mounted in the vessel in such a way that it can vibrate independently of the vessel in which it is installed.

The manner of mounting and the way in which vibrations are realized is known to those skilled in the art.

The process according to the invention is most effective in reducing the content of monomeric vinyl chloride in polyvinyl chloride resin emulsions. The invention is useful because the removal of monomeric vinyl chloride from polyvinyl chloride resin emulsions in an industrial manner is extremely difficult.

Giant. 1 illustrates the apparatus used in Examples 1 to 8. The vessel 10 is formed by a tube having a diameter of 254 mm, about 305 cm long, supported. on supports 2. Supports 2 are na30. 3, 1983, by means of spacers at the bottom to provide the slope required for each particular experiment. The container 10 is provided with blind flanges 3, in which transparent plastic windows 4 are incorporated in order to monitor the behavior of the aqueous resin mixture during the process.

The vibrating surface 5 is a metal surface firmly. mounted in the vessel 10. A smooth vibrating surface could be mounted in the vessel 10. On the one hand, a surface with 6 mm waves directed transversely in the direction of the short dimension could be mounted.

The vibrating device 8 is mounted on the container 10 as shown or on the supports 2. The surface 5 is subjected to vibration by allowing the container 10 in which it is installed to vibrate. Aqueous resin mixtures enter the vessel and are placed on a vibrating surface by a line 7.

The aqueous resin mixture flows along the vibrating surface 5, falls from the vibrating surface to the bottom of the container 10 and flows into the tank (not shown) via line 15.

A sample of the aqueous resin mixture after passing through the vibrating surface can be obtained by removing the latex from line 15.

The pressure below atmospheric is maintained in the vessel 10 by means of a steam ejector (not shown) to remove steam from the vessel 10 through line 12. The temperature of the aqueous resin mixture at the end of the vibrating surface is measured by a thermocouple 14.

The pressure in the vessel 10 is measured with a pressure gauge 17. The temperature of the aqueous resin mixture is maintained by introducing steam directly into the vessel 10 through line 21.

During the experiments, samples of the aqueous resin mixture entering and leaving vessel 10 are sampled to determine the amount of vinyl chloride monomer.

Giant. 2 shows a cross-section of a vibrating surface

It shows the structure of the corrugated surface used in Examples 1 to 8. The waves have an amplitude of 6 mm and a period of 13 mm. cích 7yccemc

Giant. 3 shows a schematic diagram of the manufacturing process of the apparatus used in Examples 1 to 8. The same reference numerals in FIGS. 3 and 1 designate the same parts of the apparatus.

The vessel 37 comprises an aqueous resin mixture in a vinyl chloride polymerization reactor. The aqueous resin mixture is preconditioned. monomer by releasing the pressure in the polymerization reactor. Then, the aqueous resin mixture is passed through line 35, valve 36, and line 34 to pump 38. Pump 36 is a Moyno ™ pump and pumps the aqueous resin mixture through line 7 through valve 6 to a vessel 10 that includes a vibrating surface over which the aqueous resin mixture flows.

After passing over the vibrating surface, the aqueous resin mixture proceeds from vessel 10 to vessel 31. Ventilation duct 45 provides equal pressure in vessel 31 and vessel 10 so that the aqueous resin mixture can flow from vessel 10 to vessel 31 without obstruction.

Samples of the aqueous resin mixture from line 7 can be taken through line 39 and valve 40. Samples of the aqueous resin mixture after passing over the vibrating surface are obtained using valve 16, line 26 and valve 25.

The pressure in the vessel 10 is measured by a pressure gauge 17. The pressure below atmospheric is maintained in the vessel 10 by a pressure control device (not shown) which removes gases from the vessel 10, via a line 12 and a valve 13.

The aqueous resin composition from the vinyl chloride polymerization reactor is pumped through the vibrating surface and the effect of one pass through the vibrating surface on the monomer vinyl chloride content of the aqueous resin composition can be determined. The aqueous resin mixture trapped in the vessel 31 can be circulated through the vibrating surface and then the effect of multiple passes through the vibrating surface on the monomer vinyl chloride content of the aqueous resin mixture can be determined.

A practical experiment is conducted in which the aqueous resin mixture is passed over a vibrating surface. The concentration of vinyl chloride monomer in the aqueous resin mixture in line 15 after one pass is determined. When all of the aqueous resin mixture from vessel 37 is transferred to vessel 31, the continuous circulation of the aqueous resin mixture from vessel 31 over the vibrating surface, line 32, valve 33, line 34, and pump 38 begins. At predetermined time intervals with valve 43, line 44 and valve 46 take samples of the aqueous resin mixture from vessel 31. A two-valve arrangement must be used to be able to take samples from vessel 31, which is maintained at a pressure below atmospheric pressure. Using the apparatus shown in FIG. 3, the effect of vibration frequency and amplitude, surface inclination, surface texture, circulation rate, temperature and reduced pressure can be easily determined.

Samples of the aqueous resin mixture were dissolved in tetrahydrofuran and the vinyl chloride monomer was analyzed by gas chromatography.

Unless otherwise indicated, all concentration data are by weight.

He did

Effects of vibration

Samples of the latex containing about 34.7% vinyl chloride polymer were circulated over the surface of the device shown in Figure 1. The trough surface is corrugated. Its length is 3050 millimeters, the waves have an amplitude of 6 mm and a period of 12 mm and run transversely in the direction of a short surface dimension (100 mm).

The apparatus is maintained in a substantially horizontal position (inclination of about 4 mm / m). A sample of about 70 kg of latex is circulated through the vibrating surface at a rate of 7.1 kg / min. The latex temperature is maintained at 73 ° C by dispensing steam directly into the vessel in which the surface is mounted. The pressure applied to the latex is maintained at about 67.72 kPa, i.e. below atmospheric pressure.

The surface vibrates at 3600 cycles per minute with an amplitude of 0.2 mm in the vertical direction. Vibration frequency and amplitude are measured using an I. R. D. Incubator Analyzer Model 350 (I. R. D. Incorporated). The test results are shown in Table 1.

198247 9 10 Table · 1 Concentration of vinyl chloride monomer · (Ppm) Time without vibration · With vibration Minutes Start 13 139 ! 19 327 1st pass 2 728 ! 1 932 10 2 010 833 20 May 1023 i 546 30 733 i 444 40 580 254 50 574 . 188

The table clearly shows that vibration will increase the efficiency of separating vinyl chloride monomer from the latex. Two latex samples used in this. . In the example, latexes of the same type, but produced. at different times.

Example 2

Effect of ripple

The apparatus of Example 1 was used to separate the monomeric vinyl chloride from the latex at 74-76. ° C and a pressure of 64.33 to 67.72 kPa, i.e. at a pressure below atmospheric pressure. The surface vibrates at 870 cycles per minute with an amplitude of 1.35 mm in the vertical direction, the vibrating surface having a slope of 33.9 mm / m.

Replace the corrugated surface with a 133.3 mm wide flat plate and repeat the experiment using a second sample of polyvinyl chloride latex. ·

112.5 was used in the experiments. kg of latex containing about 37% solids on dry weight basis. The latex circulation rate is 23.08 kg / min. ί

The starting material is passed over the vibrating surface and is determined. the content of vinyl chloride monomer in the latex after one pass. The latex sample is then circulated through a vibrating surface. At certain intervals, the tank is removed. 31 take samples and measure the concentration of vinyl chloride monomer. · ’

The results of these experiments are shown in Table 2. ·

Table 2

Start 5 10 20 Ϊ 30 60 90

1st pass. , i

Vinyl chloride (ppm) i

Time (minutes) surface width

wavy 101.2 mm 25 081 829 740 561 412 - 310 151 82 areas 133,3 mm 18 373 1 600 843 486 345 - 269 204 105 areas modified 2 080 1106 632 449 : 350 265 136

results for 101.2 mm width

For comparative purposes, the results obtained using a 133.3 mm wide surface are converted to 101.2 mm wide, assuming the concentration of vinyl chloride monomer is proportional to the surface area. The adjusted values are obtained from the values for the width of 113 mm by multiplying them by 133.3

101,2 ·

The results of the experiment clearly show that the corrugation substantially improves the efficiency of the vibrating surface in removing monomer vinyl chloride from the polyvinyl chloride latex.

Example 3 Effect of the slope of a vibrating surface

To remove monomer vinyl chloride from the polyvinyl chloride latex, a device according to Example 1 is used.

The surface vibrates at 870 cycles / min with an amplitude of 2 · mm in the vertical direction.

During the main part of each experiment, the pressure is maintained at about 50 psi. At the beginning of the experiment, when the monomeric vinyl chloride is rapidly released from. latex, the pressure is higher.

The results are shown in Table 3.

'. ... ,,. : 12

Table 3 slope mm / m 4.2 16.9 33.8 101.5 circulation rate - kg / min 9.38 9.38 9.38 8.51 sample weight kg 67.50 67.50 67.50 75.15 ° C 74 74 74 68—70 Time Ending race vinyl chloride (ppm) Start 15 632 16 799 10 925 12 194 First pass 4 013 8 222 3 550 - 10 1041 597 81 1 271 20 May 706 217 20 May - 30 465 160 20 May 683 40 331 - - 50 219 119 - 509 60 122 : - 11 297 70  - 1—3 9

The data in Table 3 clearly shows that the effectiveness of the vibrating surface to remove monomer. The latex vinyl chloride can be increased by increasing the inclination of the vibrating surface.

Example 4

Effect. latex flow rates

It shall apply. the apparatus of Example 1 for determining the effect of the latex flow rate. to remove vinyl chloride monomer. The slope of the vibrating surface is set to 33.8. mm / / m. Latex samples weighing about 76.5 kg. containing about 40.7% polyvinyl chloride was circulated over a corrugated surface that vibrated at 870 cycles per minute. p. with an amplitude of 2.1 mm in the vertical direction. . The latex from the alkali-containing tank is passed through a vibrating surface and then circulated through the surface. Samples are taken from tank 31 at periodic intervals and the vinyl chloride content of the latex is determined.

The results are shown in the table. 4.

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The data presented in Table 4 ' monomer vinyl chloride is removed more quickly from polyvinyl chloride, latex. Of the amount of monomer vinyl chloride contained in the latex after 5 minutes is. however, it is apparent that more monomer vinyl chloride is removed from the polyvinyl chloride each time it passes through the vibrating surface. when the flow rate is lower.

During operation, the harmful effects of pumping latex must be balanced with the rate at which monomer vinyl chloride is to be removed from the latex.

Example 5

The effect of the flow rate on the amount of vinyl chloride monomer removed from the polyvinyl chloride latex per pass through the vibrating is determined. The surface is set to a slope of 4.2 mm / m @ 2 and is vibrated over 3600 cycles per minute in a vertical direction with an amplitude of 2 mm. In all experiments, the batch was preheated to 71-74 ° C. The pressure in the experiment was maintained at about 10 psig. The results are shown in Tab. 5.

Table 5

Dosing rate. Content of polyvinyl-monomeric vinyl chloride kg / min chloride in (ppm) latex in% feed. after one pass

0.22 38.6 29 500 795.7 2.43 38.7 22 886 734 3.74 38.6 29 500 - 968.3 6.66 33.4 28 180 723.7 9,05 * 41.8 12 534 1197

*. Vacuum 57.5 kPa.

The data from Table 5 show that the vinyl chloride monomer content of the latex can be substantially reduced by one pass through the vibrating surface. ......

Example 6

The interaction of the parameters which influence the removal of the vinyl chloride monomer from the polyvinyl chloride latex is determined by operating the apparatus of Example 1 under different operating conditions.

The corrugated surface of Example 1 is allowed to vibrate when vibration is used. at 3600 cycles per minute at an amplitude of 0.2 mm in the vertical direction. The content of vinyl chloride monomer in the latex is measured after one pass through the surface. The surface slope is set to 4.2 mm / m.

The results of the experiments are shown in Table 8

Table 6 Polyvinyl chloride content of latex in% Dosing rate kg / min Handle temperature ° C Pressure kPa Vinyl chloride monomer content (ppm) Handle Product Vibration 32 0.35 63 54.1 25 231 1760 Yes 32 0.35 63 54.1 25 231 2247 No 38.6 0.38 58 57.5 20 707 4440 Yes 38.6 3.74 69 67.7 29 500 968 Yes '33,4 6.66 72 67.7 28 180 724 Yes 41.8 9.05 71—74 57.5 12 534 1197 Yes 39.3 8.6 60 60.9 16 037 3761 Yes 39.3 7.5 60 60.9 16 037 4467 No 36.7 7.5 64 67.7 16 368 1414 ' Yes 36.7 6.7 64 67.7 16 368 ‘2993 No 38.7 2.43 71—74 67.7 22 886 734 Yes 38.7 2.43 71—74 67.7 22 886 1371. No

The results shown in Table 6 clearly show the effect that the individual parameters have on the vibrating surface removal efficiency. of vinyl chloride monomer from polyvinyl chloride latex.

Example 7

The apparatus of Example 1 was used to determine the effect of latex temperature on the separation of vinyl chloride monomer. Inclination of vibrating surface. and the vibration is performed at 870 cycles per minute at an amplitude of 1.8 mm in the vertical direction. The 71.5 kg latex sample was circulated at 26.3. kg / min over the vibrating surface, the pressure was maintained at 77.7 in all experiments. to 84.5 kPa.

The latex is passed from the storage tank 37 through the vibrating surface to the tank 31. Then the latex is circulated through the vibrating 'surface' and samples are taken from the tank 31 in which the vinyl chloride content of the latex is measured.

The results of the experiments are shown in Table 7.

Table 7

Time [minutes] Temperature Noc: 2 ° C Content of monomer vinyl chloride (PPm) Temperature Noc: 2 ° C The content of vinyl chloride monomer (PPm) Start 44 855 43 533 5 65 2 801 63 2 411 10 64 1298 62 1512 20 May 63 498 60 887 30 . 61 250 59 506 60 60 91 70 59 142 90 62 20 May 60 56

The results shown in Table 7 show that higher temperatures are more effective in removing monomer vinyl chloride from the polyvinyl chloride latex.

Example '8

The apparatus of Example 1 was used to reduce the vinyl chloride monomer content of the polyvinyl chloride latex to below 10 ppm. _

A sample of latex weighing 71.5 kg ' is passed through the apparatus of the example. The latex was circulated through a vibrating surface at a rate of 14 kg / min and samples were taken from the vessel 31 to determine the monomer vinyl chloride content.

The inclination of the vibrating surface is set to 33.8 mm / m and the vibrations are performed at 870 cycles per minute at an amplitude of 1.8 mm in the vertical direction. . The latex is maintained at a pressure of about 10 to about 10 psi when passing through the vibrating surface.

The results of the experiment are shown in Table 8.

Table 8

Minute time Latex Handle Temperature (° C) Latex temperature in vessel 10 (° C) Content of monomer vinyl chloride (PPm) 0 37 037 5 66 65 1517 10 68 73 1194 20 May 69 71 366 30 71 73 234 60 76 77 109 90 72 74 34.6 105 72 75 5.6

The garments in Table 8 show that the vinyl chloride monomer content of the polyvinyl chloride latex can be reduced to a relatively low value by the methods of the invention.

High temperature and vibration reduce the mechanical stability of the latex during the experiment.

The mechanical stability of the control is 16 minutes. After 105 minutes of circulation through the vibrating surface, mechanical stability is reduced to 4 minutes.

Mechanical stability is determined by placing a 100 ml sample in a Hamllton Beach TM milk shaker and measuring the number of minutes required to coagulate the latex.

Example 9

The aqueous mixtures containing the polyvinyl chloride resin are passed over a surface of 37.2 m long and 22.2 mm wide. The surface is grooved in a short dimension. The slope of the surface in the longitudinal direction is an average of 48 .mu.m / meter. The surface is vibrated at a frequency of 950 cycles / mln and an amplitude of 2.5 mm in the vertical direction. The resin mixture flows through the trough in the longitudinal direction.

15,200 L of an aqueous resin mixture is produced and the mixture is circulated over a vibrating surface. The aqueous resin mixture is pumped from the reactor through a vibrating surface and returned to the reactor. The resin mixture is periodically sampled from the pipeline to the pump to determine the amount of vinyl chloride monomer.

Table 9 summarizes the results.

Type of resin mixture Table 9 Emulsion Emulsion Emulsion Suspension Suspense

Circulation rate (1 / mln) 304 285 342 475 570 Pressure kPa 57.5 64.3 64.3 57.5 62.6 Temperature ° C 69 66 66 66 66 Solids content (%) 24.9 34.0 36.5 31.2 27.7 Time (h) Concentration monomeric vinyl chloride (ppm) 0 4786 7780 259 * 156 * 1 492 32 21 - 42 1.5 188 17 24 15 Dec 22.6 2,0 206 11 - 16 20 May 13.2

* The sample is pre-stripped with water vapor

Example 9 illustrates that the process according to the invention effectively removes vinyl chloride monomer from an aqueous scale polyvinyl chloride based resin mixture.

This example also shows that the monomer vinyl chloride monomer content of aqueous slurry type resins can be effectively reduced.

Claims (5)

A method for separating vinyl chloride monomer from an aqueous mixture comprising a polyvinyl chloride resin, characterized in that the aqueous resin mixture is conducted at a temperature above ambient temperature and below the temperature at which the aqueous resin containing mixture is adversely affected by the elevated temperature, and at a pressure of 338 Pa to 81.2 kPa over the surface vibrating at a frequency below 6000 cycles / mln. 2. Process according to claim 1, characterized in that it is operated at a temperature of from 43 to 82 ° C. 3. Process according to claim 2, characterized in that the process is carried out at an absolute pressure of 3.4 to 67.7 kPa. 4. Process according to claim 1, characterized in that it is operated at a temperature of from 54 to 80 [deg.] C. and an absolute pressure of from 33.9 to 67.7 kPa. 5. The method of claim 1, wherein the vibrating surface is modified.