JPS6020402B2 - Method for separating trace amounts of vinyl chloride monomer from vinyl chloride resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating a small amount of vinyl chloride monomer from a vinyl chloride resin. This invention relates to a method for separating vinyl monomers by wet heating OK steam evaporation.

Most commercially available vinyl chloride resin powders are produced by suspension polymerization of vinyl chloride monomers in an aqueous medium.

In this case, among the unreacted monomers, the portion recovered in gaseous form from the vinyl chloride polymerization vessel and the portion dissolved in the aqueous medium can be easily separated from the vinyl chloride resin powder and recovered. . In addition, dried vinyl chloride resin (a slurry of an aqueous medium containing vinyl chloride resin powder is filtered or centrifuged to remove most of the medium, and approximately 60 to 40% of the aqueous medium is added to the dry resin). contains)
by known reduced pressure or heat treatment (including flash drying or fluidized drying methods in known industrial manufacturing methods),
Most of the small amount of vinyl chloride monomer normally adsorbed on the undried vinyl chloride resin (for example, 50% to 90%) can be removed; however, depending on the drying method, a large amount of the vinyl chloride monomer Waste gas with a concentration of A small amount of vinyl chloride monomer may remain. As a result of our earnest efforts to solve the technical problems in (1) and (2) above, the inventors of the present invention have found that as a separation medium in (2) above,
The undried vinyl chloride resin is dehydrated using water vapor instead of air or an inert gas by continuously treating the resin in an aqueous medium at a relatively high temperature for a very short period of time before drying. The monomers in the vinyl resin are sufficiently removed before the drying process, and the vinyl chloride monomers removed together with the aqueous medium are easily condensed and separated from the aqueous medium and released into the atmosphere as a pollutant gas. The present invention was completed by arriving at a method that causes almost no release.

As is clear from the foregoing, the first object of the present invention is to produce, for example, a suspension polymerization method, and recover coexisting unreacted vinyl chloride monomer to normal pressure or reduced pressure of 100 to 5 Q. The concentration of vinyl chloride monomer in the undried vinyl chloride resin, which has a vinyl chloride monomer content absorbed in a wet state of about 0.05 to 2%, is reduced to a non-polluting level, and the above-mentioned The second object of the present invention is to recover the adsorbed vinyl chloride monomer, and the second object of the present invention is to provide a simple and efficient method for separating vinyl chloride monomer, which is necessary for achieving the first object. There is something to do.

Other objects will become apparent from the following description of the invention.

When the present inventors conducted research for the above purpose, the separation and desorption of small or trace amounts of vinyl chloride monomer (hereinafter referred to as "contained monomer") contained in vinyl chloride polymers required Although increasing the temperature of the aqueous medium mixture (hereinafter referred to as PVC slurry) containing undried vinyl chloride resin is the most effective, it has been shown that if the temperature increase is extremely short, it does not impair the physical properties of the product vinyl chloride resin, contrary to expectations. confirmed.

As a specific means for the above-mentioned desorption, PVC slurry at room temperature to about 60 q0 is supplied to a steam evaporator, and the rapidly heated PVC slurry is heated in the steam evaporator at low pressure and normal pressure, as detailed below. , or by causing water vapor evaporation (evaporation of the aqueous medium) under a low degree of reduced pressure, and removing the vinyl chloride monomer mainly adsorbed on the vinyl chloride resin in the PVC slurry together with the evaporated water vapor (vapor of the aqueous medium). It has been confirmed that the method of separating by evaporation and continuously discharging the vinyl chloride resin in the PVC treated PVC from the steam evaporator in an extremely short total distillation time is extremely effective in maintaining the quality of vinyl chloride resin products. did. The present invention according to the above description has the following configuration.

That is, the present invention uses a vinyl chloride resin powder containing a certain amount of vinyl chloride monomer moistened and suspended in an aqueous medium of approximately the same amount to several times the amount of the powder, and an evaporative separator. The contents of the slurry consisting of vinyl chloride resin and an aqueous medium are continuously fed into a vessel whose temperature is 80 to 11 and 0, and the filling time of the feed to the evaporative separator is longer than 100 ml. Steam evaporation treatment is carried out within 120 seconds, and the amount of aqueous medium evaporated from the evaporative separator is 5% or more and 100% or less of the amount of pinyl chloride resin (per dry weight) in the feed. This is a method for separating a certain amount of vinyl chloride monomer from a pinyl chloride resin.

Hereinafter, the configuration of the present invention will be explained in detail. First, the vinyl chloride resin powder containing a certain amount of vinyl chloride monomer (hereinafter referred to as monomer-containing resin powder) used in the present invention is mainly produced by a suspension polymerization method of vinyl chloride monomer. It refers to a product that contains a large amount of water and a quantity of pinyl chloride monomer (approximately 2% or less or 0.02% based on the vinyl chloride resin content) while the unpolymerized monomer remains separated. However, if the wet vinyl chloride resin powder obtained by the suspension polymerization method is dried by a known method, the residual content (for example, 0.02% or more.
(approximately 2%) of vinyl chloride monomer, or vinyl chloride resin powder produced by emulsion polymerization, bulk polymerization, etc. of vinyl chloride monomer and dried by a known method to become a powder. Other copolymer resin powders, in which one of the main components of the resin is vinyl chloride, and the powder contains a certain amount of vinyl chloride monomer. say something In addition, the aqueous medium used to wet and suspend the monomer-containing resin powder used in the present invention is water or water and a small amount or a certain amount of a surfactant, a suspending agent, a low boiling point organic Small amounts or amounts of additives used to adhere to or penetrate into solvents and other vinyl chloride resin products (or intermediately processed products).
Hereinafter, the above-mentioned surfactant, suspending agent, low boiling point organic solvent, and other additives will be partially or completely removed in the steam evaporation treatment of the present invention, which will be described later.
It may be distilled and separated with water evaporation, or conversely, it may be moved out of the steam evaporator together with a slurry containing wet vinyl chloride resin powder.

In the method of the present invention, the purpose of using or making these various agents exist is to facilitate uniform and rapid wetting of the monomer-containing resin powder with the aqueous medium, or to prevent the symptoms of water vapor evaporation described below. The purpose is to sufficiently and easily separate a quantity of vinyl chloride monomer, or to maintain the thermal stability and other (processing) physical properties of the vinyl chloride resin (powder product) to be treated against the thermal history in the steam evaporation process. It does not preclude the presence of a suitable amount as long as the purpose of the present invention is not impaired. Next, the monomer-containing resin powder used in the present invention is wetted by mixing the powder and the aqueous medium in a desired ratio, moistening the powder, and performing a mulch etc. using a known method to wet and suspend the powder. If the powder is produced by suspension polymerization of vinyl chloride monomers and is in the form of a wet slurry from which only the reacting monomers have been separated, no treatment other than the preliminary heating described below may be carried out. If the powder is a wet powder obtained by removing water (dispersion medium) from the wet slurry, it is sufficient to add and mix the necessary aqueous medium to form a slurry. Although it varies depending on the physical properties of the monomer-containing resin powder, the shape of the powder, the particle size, etc., the amount of the aqueous medium contained in the monomer-containing resin powder moistened by the wetting is the same as that of the wet powder. , 20% to 60%, mostly 3
0% to 50%, and the ratio of the wet powder to the aqueous medium used for slurry formation is 1:0.8 to 5, preferably 1:1 to 2, by weight. When the usage ratio of the aqueous medium for slurry formation is less than 0.8, it is difficult to uniformly disperse the slurry in the steam evaporator and to smoothly discharge the slurry, which is the purpose of the present invention. sufficient separation of vinyl chloride monomer becomes difficult.

On the other hand, if the amount of the aqueous medium used is too large, an extra amount of heat is required to raise the temperature of the slurry, making it difficult to cool down the slurry quickly after the steam evaporation treatment. Hereinafter, the steps of the present invention will be explained with reference to the drawings.

In the figure, 1 is a slurry tank, 2 is a monomer-containing resin powder (or slurry) receiving pipe, and 3 is a
Water or aqueous medium receiving piping. A predetermined proportion of monomer-containing resin powder and water (or an aqueous medium) are placed in a slurry tank and allowed to concentrate for a predetermined period of time to form a slurry consisting of wet resin powder and water. As can be easily inferred from the above, the slurry tank can also serve as a suspension polymerization vessel. The temperature of the slurry may normally be at room temperature, but may be raised to, for example, 50 pm in order to speed up the temperature rise in a water evaporator, which will be described later. The slurry is supplied from the extraction pipe 4 of the slurry tank 1 to the steam evaporator 7 via the pump 5 and the slurry receiving piping 6 of the steam evaporator. In the evaporator 7, a certain amount of the slurry is received and accumulated, and steam is blown into the accumulated substance from, for example, a steam blowing pipe 8 to maintain the accumulated substance in a boiling state. As for the heating method, instead of the steam blowing, an appropriate external heating method such as a steam coil equipment may be used.The appropriate slurry temperature in the vessel is 800 to 11 psi, and the appropriate pressure is 20 psi. Hikaru Hiyūnaishi lk9/KyōG
Preferably it is 50 days/day or 0.5k9/me G. In the case of implementation under reduced pressure, a vacuum pump 11, which will be described later, is used. The wet slurry supplied into the steam evaporator 7 is heated in the vessel by the heating method from room temperature to 50 qo to 80 to 110 oo, and the inside or surface of the wet vinyl chloride resin powder in the slurry ( The vinyl chloride monomer adsorbed (particularly on the surface) is desorbed by the heating and boiling process and is immediately separated along with water vapor.

However, as mentioned above, the temperature of the slurry is undesirably high in terms of maintaining the heat resistance stability of the vinyl chloride resin. By setting the reaction time to an extremely short time as described above, it is possible to achieve the purpose of separating a significant amount of vinyl chloride monomer without impairing the heat resistance stability. The vinyl chloride monomer adsorption characteristics (adsorption power) of vinyl chloride resin powder vary significantly depending on the manufacturing method of the resin powder, so it cannot be generalized; Therefore, the content of vinyl chloride monomer is 0.
．． A 2% slurry was treated with sand at a slurry temperature of 90 qo and a residence time of 3 to give 0.0% vinyl chloride monomer powder in the wet vinyl chloride resin powder after treatment in the steam evaporator 7.
It can be reduced to 1%.

The slurry (temperature: 800-110 am) made of the wet vinyl chloride resin powder and aqueous medium treated as described above is continuously extracted from the extraction pipe 13, and the cooler 14, the pump 15, and the open Open tank 1 via tank receiving pipe 16
7 accepted.

The slurry temperature is cooled to below 50° C., preferably below 30° C., at the outlet of the cooler 14. On the other hand, the vinyl chloride monomer vaporized and separated along with most of the water vapor in the water evaporator 7 is mostly separated together with the condensed water in the cooler 9, so it passes through the extraction pipe 10 to the fractional distillation recovery device (Fig. (not shown).

A small amount of exhaust gas is passed through the vacuum pump 11 (no need to operate if under normal pressure or pressurization) and undergoes necessary exhaust gas treatment (e.g. activated carbon treatment:
(not shown), etc., and discharged into the atmosphere from the pipe 12. On the other hand, the vinyl chloride resin slurry received in the open tank 17 and subjected to steam evaporation treatment may be
The vinyl chloride resin powder is extracted from the extraction tube 18 and dried by a known method to remove the amount of vinyl chloride monomer (the content of the vinyl chloride monomer in the dried product is preferably 0.005% or less). 0.003% or less).

The present invention will be explained below with reference to Examples.

Example 1, Comparative Examples 1 to 3 Using the apparatus shown in the drawings, vinyl chloride monomer was separated from undried vinyl chloride resin containing a certain amount of vinyl chloride monomer.

The resin is produced by suspension polymerization of vinyl chloride monomer in water (suspending agent is 0.05% partially saponified polyvinyl acetate) (initiator is lauroyl peroxide), and unreacted vinyl chloride monomer is The undried resin was collected and separated to normal pressure, and the dispersion (water) was separated by furnace.The moisture in the undried resin was 50%, and the residual vinyl chloride monomer was 0.5%.
%belongs to. 100 parts by weight (hereinafter all parts by weight) of this material are supplied to the slurry tank 1 per hour,
At the same time, 100 parts of water per hour was supplied to the tank, and the slurry was slurried at room temperature to form a uniform slurry (200 parts), which was then supplied to the steam evaporator 7 via piping 6. 1.5 to 2.5 parts of the slurry was accumulated in the vessel (settling time 27 to 49 seconds), water vapor was blown into the accumulated material from piping 8, the temperature was raised to 9°C, and vacuum was applied. The pump 11 was operated to maintain the internal pressure at 60 mcm, and the water vapor in the base was evaporated every hour, cooled and condensed in the cooler 9, and extracted from the pipe 10. On the other hand, the slurry subjected to steam evaporation treatment in the steam evaporator 7 is transferred to the pipe 13.
, lowered to 40:00 through the cooler 14 and pump 15,
It was accepted into open tank 17.

The amount received was 200 parts per hour, and there was no weight loss due to steam injection (condensation) or evaporation in the steam evaporator 7. For comparison, the same method was used except that the temperature in the steam evaporator 7 was set to 60 days, the pressure was set to 50 days, and the residence time was set to 1 point (sample A). , Comparative Example 1),
Similarly, the temperature in the steam evaporator T is set to 120qo.
When the same procedure was carried out except that the pressure was changed to 1.5X9/Cucumber G (Sample B, Comparative Example 2), the amount of evaporated steam in the steam evaporator 7 (condensed in the cooler 9, When carried out in exactly the same manner except that the amount obtained after 10 days was 2 parts (Sample C, Comparative Example 3), each sample was attached to
Table 1 shows the results of measuring the vinyl chloride monomer concentration in the dry exhaust gas and dehydration furnace water by performing over-furnace dehydration and flash drying on a laboratory scale.

As is clear from the table, the concentration of pinyl chloride monomer contained in the wet vinyl chloride resin (further dehydrated product) after steam evaporation treatment by the method of the present invention is different from that of the wet vinyl chloride resin (furnace over-dehydrated product) by the method of each comparative example. Compared to the super-dehydrated product, the concentration of monomers contained is significantly lower or the thermal stability is better, demonstrating the novelty and difficult analogy of the method of the present invention. Table 1 Change in quality of resin 1 depending on water vapor evaporation conditions K-1 Note 1. The same suspension polymerization product (wet pinyl chloride polymer) as used in Example 1 was used as the resin.2. ND indicates non-detection.

3. Evaluation of thermal stability A to 0 indicates evaluation by the test method described below.

Example 2, Comparative Examples 4 to 6 Using the apparatus shown in the attached drawings, vinyl chloride monomers were separated from dry vinyl chloride resin containing a trace amount of vinyl chloride monomer.

The resin is produced by suspension polymerization of pinyl chloride monomer in water (suspending agent is 0.05% partially saponified polyvinyl acetate) (initiator azobis 2,4-dimethylpareronitrile), and is known hereafter. According to the method, the unreacted vinyl chloride monomer is recovered, the water of the dispersed soot is washed separately in a furnace, and the water produced by flash drying is 0.5% and the residual vinyl chloride monomer is 0.10%.
%belongs to. 50 parts of this material were supplied per hour to the slurry tank 1, and at the same time, 150 parts of water was supplied to the tank per hour, and the slurry was stirred at room temperature to sufficiently moisten the slurry. Also, Comparative Examples 4 to 6 are Comparative Example 1
Samples E~3 and 3 were treated in exactly the same manner to obtain samples E~3. The results are shown in Table 2. As is clear from the table, the effects of the method of the present invention are as follows: the steam evaporation method, which is outside the scope of the method of the present invention, and the untreated product (vinyl chloride resin dried by a known method, which was treated in Example 2). Compared with sample 1), the results were excellent, as were the results of comparison between Example 1 and Comparative Examples 1 to 3.As described above, according to the method of the present invention, only the undried resin after vinyl chloride suspension polymerization Even if the dried resin is dried by a known method and has a large residual vinyl monomer content, it can be sufficiently reduced to a non-polluting level and exhaust emissions during drying can be suppressed to a minimum.

Table 2 Change in quality of resin 2 due to water vapor evaporation “2 Note 1
, 2, and 3K, the quality test method is the same as the notes in Table 1 [-Dried resin color: Judging by the naked eye in indoor light (daylight color), the one with the highest whiteness as a vinyl chloride resin powder is pure white,
The next rank was those with a slightly yellowish tinge rather than pure white.

'o} Thermal stability of dry resin: Add 5 grams of dioctyl phthalate, 0.3 grams of barium stearate, and 0.5 grams of cadmium stearate to 100 grams of vinyl chloride polymer, mix, and then mix on a 150 CO roll for 20 minutes. The film was then rolled and taken out as a single sheet, and the transparency and degree of coloring of the obtained film were compared using the following criteria.

[Brief explanation of the drawing]

The figure shows the main parts (flow sheet) of an apparatus for removing vinyl chloride monomer from vinyl chloride resin used in the present invention.
1 is a slurry tank, 7 is a steam evaporator, 9 is a cooler, and 17 is an open tank.

Claims (1)

[Claims] 1. Vinyl chloride resin powder containing a trace amount of vinyl chloride monomer is wetted and suspended in an aqueous medium of approximately the same amount to several times the amount of the powder, and the chloride content is removed using an evaporative separator. A slurry consisting of a vinyl resin and an aqueous medium is continuously fed into a vessel whose temperature is 80° to 110°C, and the residence time of the feed to the evaporative separator is 10 seconds or more.
2 seconds or less, and the amount of the aqueous medium evaporated from the evaporative separator is 5% or more and 100% or less of the amount of vinyl chloride resin (per dry weight) in the feed. A method for separating trace amounts of vinyl chloride monomer from vinyl chloride resin.