JPS6099109A - Removal of scale attached to polymerizer - Google Patents

Abstract

PURPOSE:To remove scake attached to a polymerizer efficiently, by bringing an organic liquid to dissolve or to swell vinyl chloride polymer, containing a specific organic compound, into contact with the inner face of a polymerizer wherein vinyl chloride is polymerized in an aqueous medium and the polymer is discharged. CONSTITUTION:In polymerizing vinyl chloride in an aqueous medium, discharging formed vinyl chloride polymer and the aqueous medium from a polymerizer, bringing an organic liquid into contact with the inner face of the polymerizer to remove scale attached to the inner face, 0.1-20wt% organic solution of a specific organic compound (e.g., ethyl carbamate, etc.) containing -OH, -CO, -O-, or -N= group and -CO-N= group in the molecule soluble in water and an organic solvent (e.g., methylene chloide, etc.) in the organic solvent is used to remove scale attached to the inner face of the polymerizer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing scale attached to a polymerization vessel.

Vinyl chloride polymers are often produced by mixing vinyl chloride monomers alone or with other monomers and polymerizing them in an aqueous medium. In this case, first put an aqueous medium in a polymerization container, add a large amount of vinyl chloride monomer to the aqueous medium and add a polymerization catalyst, and leave the vinyl chloride monomer alone or mixed with other monomers. It is dispersed in an aqueous medium and polymerized to obtain a vinyl chloride polymer.

When polymerizing vinyl chloride monomers in this manner, the produced vinyl chloride polymer is discharged from the polymerization vessel together with the aqueous medium. At this time, a polymer-like substance called scale often adheres to the inner surface of the container. If scale adheres, not only will the polymerization yield drop, but the scale will also impede the conduction of heat from the container, making it difficult to control the temperature inside the polymerization container, making it difficult for the polymerization reaction to proceed as desired. become unable. Additionally, scale sometimes detaches from the inner surface of the container and mixes into the product polymer. If schools are mixed into products, fish eyes will occur and the quality of processed products will deteriorate. Because school attachment brings such disadvantages,
During the polymerization, it was necessary to prevent the adhesion of scale as much as possible, and the adhering scale was removed as much as possible before boiling.

It has been proposed to coat the inner surface of the polymerization vessel with certain compounds to prevent school from adhering.

Applying a specific compound will certainly reduce the amount of scale deposited. However, it was not possible to reduce scale adhesion as much as desired. Moreover, if even a small amount of scale adheres to the inner surface of the container, it tends to accumulate in a particularly bulky manner on the inner surface of the container. In addition, when there is a scratch on the inner surface of the container, scale tends to form in the scratched area. Therefore, polymerization was carried out! :I″i, it was necessary to completely remove the scale so as not to damage the polymerization container.

Several methods have been proposed at this moment to prevent this. One method is to manually scrape off the scale by entering the polymerization container and using a tool such as a scraper. Another method is to spray high aregia water toward the inner surface of the container and remove the schools with a stream of water. Yet another method is to dissolve the cyscale using an organic solvent.

However, all of these methods have advantages and disadvantages and are not satisfactory. In other words, the manual method tends to damage the inner surface of the container, which actually encourages the formation of scale.

Depending on the method using high-pressure water, scale tends to remain in various places and it is difficult to completely remove the scale, so it ends up causing scale to accumulate. Depending on the method using a solvent, a thin film of polymer tends to form on the inner surface of the container, which leads to the formation of one-dimensional scale.

Among the methods using organic solvents, there is a method in which the organic solvent is mixed with water and a surfactant.

This is described in Japanese Patent Publication No. Shogu 2-/RIZ5P. This method requires filling a polymerization vessel with an organic solvent containing water and a surfactant, and then pressing and stirring. Therefore, a large amount of organic solvent is required, which is not economical, and the dissolving power of the organic solvent is reduced by water, so there is a drawback that it takes time to remove the school.

The inventor attempted to remove scale using various solvents. As a result, by cleaning the inside surface of the polymerization vessel with scale attached using an organic liquid in which a specific organic compound is dissolved, scale can be easily removed, and the vessel can then be tilted to prevent scale from adhering. It's possible to make headlines. It was confirmed that the organic liquid used in this case must have the ability to dissolve or swell the vinyl chloride polymer produced. In addition, specific organic compounds include those that have an 10H group and a -HN= group in their molecules, such as fatty acid amide of ethanolamine, and that are soluble in the above-mentioned organic liquids as well as in water. It was confirmed that this is necessary. Furthermore, certain organic compounds may be substituted with -II! for the -OH group mentioned above! , -0- group, -0- group, or -N= group. This invention was made based on such confirmation.

This invention involves polymerizing vinyl chloride in an aqueous medium,
In this method, after the produced vinyl chloride polymer is discharged from the polymerization container along with the aqueous medium, an organic liquid is brought into contact with the inner surface of the container to remove scale attached to the inner surface. / or an organic solution containing 20% by weight of the vinyl chloride polymer, and in this case, an organic liquid having the ability to dissolve or swell the above-mentioned vinyl chloride polymer is used, and as a specific organic compound, the molecules and the above-mentioned organic The present invention relates to a method for removing scale attached to a polymerization container, characterized by selecting and using a scale that is soluble in a liquid.

In the method of this invention, an organic liquid is used as the liquid brought into contact with the polymerization container, and the organic liquid contains a specific organic compound at 0.00%. It is an organic solution in which the organic compound is dissolved at a ratio of / to 20% by weight. That is, the organic liquid used in the method of this invention is not just an organic liquid, but a solution prepared by dissolving a specific organic compound in an organic liquid.

The organic liquid constituting the organic solution must have the ability to dissolve or swell the vinyl chloride polymer produced by polymerization. When a straight vinyl chloride polymer with a degree of polymerization of 100θ is immersed in a large amount of organic liquid at 20°C for 7 hours, the vinyl chloride polymer dissolves or swells. When the polymer swells, it means that the polymer swells to a size that is at least Jh or more than the original particle size.

Methylene chloride is most suitable as such an organic liquid. In addition, examples of organic liquids include tetrahydrofuran, methyl ethyl ketone, acetone, N, N
-dimethylformamide, methylinbutylketone, benzene, toluene, N-methylpyrrolidone, dimethylsulfoxide, trichlorethylene, methylene chloride, dichloroethane, carbon tetrachloride, dichloropropane,
Trichloropropane, /, /, /-trichloroethane can be used.

Suitable organic liquids are those that are incompatible with water.
In addition, compared to those that dissolve vinyl chloride polymers well,
Those that cause good swelling are preferred.

In addition, organic liquids are less toxic and pose less of a fire hazard.
Moreover, an inexpensive one is preferable. In this respect, methylene chloride, dichloroethane, and trichloromethane are preferred.

Instead of using only seven types of organic liquids, it is possible to use a mixture of two or more types. When used as a mixture, it is preferable to include methylene chloride therein.

Further, in that case, as the other organic liquid used together with methylene chloride, it is preferable to use one having a boiling point of toC or higher. This is because such substances have low volatility and high solubility.

As the specific organic compound to be dissolved in the organic liquid, it is possible to use a compound containing two types of groups in the molecule: -0-1 or -
It is an N-group. Such a compound can be synthesized, for example, from a carboxylic acid, an ammonia or amine compound, and an epoxide. Specifically, concentrated aqueous ammonia is reacted with ethylene oxide to obtain β-aminoethyl alcohol, and this is reacted with roughlin acid perloride to obtain roughlin acid monoethanolamide. This compound can be used as a specific compound.

When used in this invention, seven specific compounds are exemplified from among commercially available compounds: Stahome (fatty acid jetanolamide) manufactured by Hokkaido Yushi Co., Ltd., Guyanol 3θ00 (fatty acid jetanolamide manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) TY-j/jlL (polyoxyethylene laflic acid monoethanolamide) manufactured by Matsumoto Yushi Co., Ltd., Marbon LK (loughric acid jetanolamide), Amizol CD (coconut oil manufactured by Yoken Fine Chemicals) fatty acid jetanolamide), Amizole 5DK (stearic acid jetanolamide), Amizole. DI (oleic acid jetanolamide), Amizole OME (coconut oil fatty acid monoethanolamide), Amizet/θC (coconut oil fatty acid monoethanolamide 10E, O,), Aminex HO (bovine fatty acid monoethanolamide ethoxylate), ti [g' Vertol M-//-P manufactured by Kasei Co., Ltd.
Vertol fatty acid dimethylamide ethylene oxide,
ethyl carbadate (propylene oxide adduct), etc.

Specific compounds generally have the property of being soluble in organic liquids and also in water. The specific compound is
Generally, as the number of carbon atoms in the molecule increases, the lipophilicity increases, and as the number of -OH, -0- and -N- groups increases,
It has a tendency to become more hydrophilic. Therefore, by appropriately increasing or decreasing the introduction of these groups, the lipophilicity and hydrophilicity of a particular compound can be adjusted to a certain extent.

In this invention, a specific compound is dissolved in the above organic liquid, and 0
．． It is used as a 7 to 20% by weight solution.

The reason for limiting this concentration is that if it is less than 0.7% by weight, a thin film of vinyl chloride polymer is likely to be formed on the inner surface of the container after being treated with this, and therefore scale is likely to adhere. . On the other hand, if the content is 1.20% by weight or more, even if the content is increased further, it will not have the same effect. Among these, preferred is θ, / to 75
Within the range of % by weight.

In this invention, vinyl chloride is polymerized in an aqueous medium, and the produced vinyl chloride polymer is discharged from a polymerization container together with the aqueous medium, and then an organic liquid solution of the above-mentioned specific compound is brought into contact with the inner surface of the container. There are no particular limitations on the temperature at which the solution is brought into contact with the inner surface of the container. The appropriate temperature is preferably determined based on the boiling point of the organic liquid used.

In general, a higher temperature is desirable because the higher the temperature, the easier it is to remove scale, but if the temperature is too high above the boiling point, high pressure is required to keep it in a liquid state. high temperatures are undesirable.

In order to understand the inner feelings of A Gongxing, a girl with a 9-year term,
The solution may be pooled in a container and stirred, but this requires a large amount of solution and is therefore not advantageous. A preferred contact method is to insert a nozzle into the container, spray the solution in liquid form from the nozzle, and the sprayed solution becomes a thin film that flows down along the inside of the container, washing away the inner surface. This is the way to do it.

In order to spray the solution, it is preferable to attach a nozzle for spraying at the top of the polymerization container in advance, so that the solution can be sprayed from this nozzle toward the inner surface of the container and the stirrer inside the container. .

The time for which the solution of the specific compound is brought into contact with the inner surface of the container varies depending on the amount of scale attached, the properties of the inner surface of the polymerization container, the materials constituting the polymer, etc., but is usually 30 to 7/θ.
It is enough within minutes.

When cleaning the inner surface of the polymerization container with a solution of a specific compound, prepare seven other solvent containers in addition to the polymerization container, and prepare a solution by dissolving the specific compound in an organic liquid in advance in the solvent containers. Preferably, it flows into the polymerization vessel. Two of these solvent containers are prepared, and when collecting the washed containers from the polymerization container, the collected solution containing a large amount of scale is put into the seven solvent containers, and the collected solution containing a small amount of scale is poured into the seven solvent containers. It is preferable that the solvent be placed in a different container, and the container used to store it may be changed depending on the scale content. This is because, in this way, the solution can be reused and the organic liquid can be easily recovered.

According to the method of this invention, an organic liquid solution of a specific compound is brought into contact with the inner surface of the polymerization container, and the organic liquid has the ability to dissolve or swell the produced vinyl chloride polymer. , the scale is dissolved or swollen by the organic liquid, and is therefore more easily removed. Therefore, the scale can be easily and reliably removed from the inner surface of the container by simply flowing water, and therefore, the scale can be easily removed. Still, certain organic compounds are dissolved in the solution, which makes it difficult to form a thin film of polymer on the inside surface of the polymerization vessel. Furthermore, since certain organic compounds are soluble in water, they can be easily removed by washing with water. Therefore, the polymerization container cleaned by the method of the present invention has less scale generation and adhesion during the next polymerization. Thus, according to the method of the present invention, scale can be easily removed and scale generation can be suppressed. The inventive method provides these advantages.

Next, examples and comparative examples will be given to explain the details of the method of the present invention and to clarify the reasons why the method of the present invention is superior.

Example/ In this example, school was removed using Sufform (trade name) manufactured by 11Koku Yushi Co., Ltd. as a specific organic compound. Sufform is said to be a compound represented by the following general formula.

The polymerization reaction was carried out as follows. That is, the internal volume 22
．． l? Into a stainless steel polymerization container of 1 liter, put 2 g of partially saponified polyvinyl acetate, 1 g of partially saponified polyvinyl acetate, 3.5 g of di(,2-ethylhexyl) baroxydicarbonate into 70 g of pure water, reduce the pressure inside the container, and heat at 3θ°C. After the mixture was made into OmmH'i, 8 pieces of single vinyl chloride (7 to 7) were placed in a container. Thereafter, polymerization was carried out at 52° C. for 2 hours. After the vinyl chloride polymer produced by polymerization was discharged together with water, the inside of the polymerization container was washed with water. At this time, a large amount of scale was attached to the inner surface of the polymerization container.

Prepare a solvent container separately from the polymerization container, put 7.50 g of the above specific compound into the solvent container, and add methyl isobutylgtone/jOg and ethylene chloride uK to the solvent container.
3. of the specific compound. % solution was made.

This solution was heated to 0°C, and was circulated for 7017 minutes under a discharge pressure of 3 kg/ctdo through a wide-angle injection nozzle attached to the top of the polymerization vessel or toward the inner surface of the polymerization vessel. The amount was sprayed for 70 minutes. This solution was then collected from the polymerization vessel into a solvent vessel.

As a result, most of the scale was removed, and a thin film of the polymer remained on the inner surface of the polymerization container. Subsequently, the inner surface of the polymerization vessel was washed with pressurized water at i.5 Ky/dG. Then, there was no scale on the inner surface of the polymerization container.
It was in a clean state with no thin film of polymer. At this time, the amount of scale removed was 0 g.

Furthermore, using the polymerization vessel from which the scale had been removed, vinyl chloride was polymerized by the same procedure as described at the beginning, and then the scale was removed in the same manner. As a result, the amount of scale removed was St, 1 g.

The inner surface of the polymerization container from which the school had been removed was in a clean state with no school or thin film.

Comparative Example/ In this comparative example, the same decanting treatment as in Example/ was carried out, except that a common surfactant, "polyoxychetylene alkyl ether phosphate" was used instead of sulfoform, and the polymerization of vinyl chloride and The scale was removed.

After the first polymerization, polyoxyethylene alkyl ether phos 7ate and methyl imptyl ketone,
As a result of removing the scale using methylene chloride, the inner surface of the polymerized tea utensil became clean with no scale or thin film of polymer.

The school that was removed at this time, /l? It was Jg.

When the second polymerization was then carried out, a large amount of scale was found to have adhered to the inner surface of the polymerization container.

Therefore, the scale was removed in the same manner as after the first polymerization, and as a result, the inner surface of the polymerization container was clean and free of scale and #film. At this time, the amount of scale removed is /2. It was observed that a large amount of scale had formed during the rig.

Comparative Example This comparative example was carried out in the same manner as in Example 1, with the only difference being that sufform was not used. After the first polymerization of vinyl chloride, most of the scale had been removed, but only a thin film of polymer was observed to be attached. At this time, the amount of scale removed is /,! ? , jg.

Next, when a second polymerization of vinyl chloride was carried out, it was found that a large scale of %i'' was attached to the inner surface of the polymerization vessel. As a result of removing scale, 1.20.7 g of school was removed, but a thin film of polymer was found to be attached to the inner surface of the polymerization container.

Example 2 In this example, reagent grade ethyl carbamate H2NC! is used as a specific organic compound. 0002H5f was used to remove scale.

That is, in this example, an experiment was conducted in exactly the same manner as in Example 1, except that 70 g of ethyl carbamate was used instead of sufform in Example 2. As a result, the scale removal operation after the first polymerization left the inner surface of the polymerization container clean with no scale or thin film.

The amount of scale removed at this time is /F, 6 JgT.

Next @J Iil! The scale removal operation after the first polymerization also left the inner surface of the polymerization container clean with no school or thin film. At this time, the amount of scale removed was f, jg.

Comparison of the above examples and comparative examples shows that the known methods of cleaning with only an organic liquid or with a solution of a common surfactant dissolved in an organic liquid are effective to a certain extent in terms of removing scale. However, it has become clear that there is a drawback that scale tends to adhere during the subsequent polymerization.

However, by using a solution in which a specific organic compound is dissolved in an organic liquid according to the method of this invention, not only is it easy to remove scale, but also, during subsequent polymerization,
Scale adhesion can be significantly suppressed. In this respect, the method of this invention is superior.

Patent applicant: Tokuyama Sekisui Kogyo Co., Ltd.

Claims (1)

[Claims] / After polymerizing vinyl chloride in an aqueous medium and discharging the produced vinyl chloride polymer from a polymerization container together with the aqueous medium, an organic liquid is brought into contact with the inner surface of the container and adhered to the inner surface. In a method for removing scale, an organic solution in which 0.7 to 20% by weight of a specific organic compound is dissolved is used as an organic liquid, and in this case, the organic liquid has the ability to dissolve or swell the vinyl chloride polymer. As a specific organic compound, 10H,
-0-0--0- or -N= group and -6-N
A method for removing school adhering to a polymerization container, characterized in that a material containing a = group and soluble in water and the above-mentioned organic liquid is selected and used. 2. The method according to claim 1, wherein the organic liquid is methylene chloride. 3. The method according to claim 1, wherein the organic liquid is a mixture of methylene chloride and another organic liquid having a boiling point of 0° C. or higher. The method according to claim 1, wherein the organic liquid solution is injected toward the inner surface of the container and allowed to flow down along the inner surface. j. The method according to claim 1 or 2, wherein the organic liquid solution is filled into a container and then contacted by stirring.