JPS5911303A - Polymerization of vinyl monomer - Google Patents

Abstract

PURPOSE:To prevent deposition of scale formed at a gas/liquid interface, by spraying a scale deposition-preventing agent over the inner wall or like area of a polymerization vessel and drying the sprayed agent to form a coated area of polka dots of a specified size. CONSTITUTION:A surface in contact with monomers, such as an inner wall or an agitator surface of a polymerization vessel, is dried and heated to 40-100 deg.C. Then, an aqueous solution containing 0.01-3wt% scale deposition-preventing agent is sprayed at a pressure of 2-20kg/cm<2> over the above surface and dried so that a coated area having polka dots of a diameter of 1-3,000mu may occupy at least 50% of the total coated area. Then, an aqueous medium, a vinyl or diene monomer, a polymerization initiator, etc., are fed into the polymerization vessel and polymerized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for polymerizing vinyl monomers that prevents scale adhesion. In particular, the present invention relates to a method for polymerizing vinyl monomers in which scale adhesion is prevented, and in particular, the polymerization process is carried out by coating a scale adhesion preventive agent in a polka dot pattern on the inner wall of a polymerization vessel, etc. The purpose is to prevent scale adhesion that occurs on the gas-liquid interface, such as on the inner wall of the vessel.

Conventionally, known methods for polymerizing monomers such as small vinyl or diene monomers include suspension polymerization, emulsion polymerization, solution polymerization, gas phase polymerization, and bulk polymerization. However, in all of these polymerization methods, there is a problem of polymer scale adhesion on the inner walls of the polymerization vessel, the stirring device, and the like.

In other words, when vinyl monomers are suspension-polymerized using these methods, polymer scale is deposited on the inner walls of the polymerization vessel and parts of the polymerization vessel that come into contact with the monomers, such as the stirring device, which reduces the yield of the polymer and the polymerization vessel. In addition to reducing the cooling capacity, this scale flakes off and mixes into the product, reducing the quality of the product. On the other hand, removing this scale requires excessive labor and effort. Not only is it time-consuming, but since unreacted ntH bodies are adsorbed in this scale, there is a risk of human injury due to monomers (vinyl chloride, etc.), which has become a very serious problem in recent years. There is a disadvantage.

In order to solve this problem of scale adhesion, it has been known to apply a scale preventive agent to the inner wall of the polymerization vessel, the stirring device, etc. A method of applying organic compounds, dyes, pigments, etc., a method of applying polar organic compounds or dyes treated with gold R salt,
A method of applying a mixture of an electron-donating compound and an electron-accepting compound, or a method of applying an aqueous solution in which an alkali metal or ammonium salt of a sulfonic acid type or carboxylic acid type dye is adjusted to a pH of 7 or less, etc. It is considered publicly known.

These methods are effective in preventing scale adhesion to a certain extent as long as the number of polymerization batches is small after the coating operation, but as the number of polymerization batches increases,
Scale adhesion is observed at the gas-liquid interface in the polymerization vessel, which often causes fisheye problems in the produced polymer.

Recently, even when taking out the polymer after completion of polymerization, the polymerization vessel is kept in a state cut off from the outside air without being opened, and then the next polymerization raw material is charged and polymerized in this state, which is the so-called closed system polymerization. However, in this closed system polymerization, there is a problem in that the above-mentioned disadvantages have a particularly large influence.

On the other hand, the scale adhesion prevention agent is applied to the inner walls of the polymerization vessel by coating or spraying, and in the closed system polymerization method, it is natural to use an automatic coating device built into the polymerization vessel. Conventionally, in any case, the coating was applied uniformly to the entire surface of the target surface (solid coating).

For example, Japanese Patent Application Laid-open No. 57-61001 proposes applying an even coating (applying a scale adhesion preventive agent) to the wall surface of a polymerization vessel in a short time by automatic coating means. Since this method is based on the premise that the target surface, such as the wall surface of a straight stand, must be completely covered with the coating film, it has the disadvantage of considerably over-coating. Disadvantage of scale adhesion on the walls of the gas phase inside the polymerization vessel -5
No. 01116 and No. 56-501117,
A method has been disclosed in which the amount of scale adhesion preventive agent applied is reduced by using water vapor, chloride and nil monomers, and low boiling point hydrocarbon compounds as carrier gases when spraying the scale adhesion preventive agent. In these methods, the coating is applied by spraying while the surface is wet and the entire surface is coated, so if the number of polymerization batches increases, scale will adhere to the walls of the gas phase inside the polymerization vessel. There are drawbacks.

The present inventors have completed the present invention as a result of intensive research in order to solve such disadvantages of the conventional technology.This invention is based on the method that is applied to the inner wall of the polymerization vessel, the surface of the stirrer, etc. before polymerizing the vinyl monomer. Dry the surface that the vehicle body comes into contact with,
By spraying the scale adhesion prevention agent liquid onto this dry surface and drying it, a polka dot pattern coating area with a diameter of 1 to 30,001 cm is formed on the dry surface, and the polka dot pattern coating area accounts for 50% of the entire coated surface.
As described above, the present invention relates to a method for polymerizing vinyl monomers, which is characterized by forming vinyl monomers.

According to the method of the present invention, by first forming a polka dot pattern coating on the wall surface of the polymerization vessel, the number of polymerization patches can be reduced to, for example, 2.
Even if the number of times is 0 to 30 or more, scale adhesion is prevented even near the gas-liquid interface in the polymerization vessel where scale tends to form. Therefore, the closed system polymerization operation can be carried out over a long period of time, giving the advantage that a polymer of good quality can be obtained. In addition, as can be seen from the above, the entire amount of the scale adhesion preventive agent sprayed toward the walls of the polymerization reactor is consumed in forming the polka dot pattern, so there is no waste during application. advantages are given.

When spraying the scale adhesion prevention agent liquid, the method of atomizing it is to use a fluid spray nozzle that atomizes it using hydraulic pressure, or to mix the scale adhesion prevention agent liquid internally with gas and atomize it. Examples include a method using a two-fluid spray nozzle. - In the case of a fluid spray nozzle, the fine particles are controlled by hydraulic pressure, and in general, 2 to 20 KP/craG is sufficient to form a polka dot pattern coated area with the above-mentioned diameter. In the case of a two-fluid spray nozzle, it is controlled by the gas pressure and the scale adhesion prevention agent liquid pressure, and in general, the gas pressure may be 2 to 20 Kl/CI G, and the scale adhesion prevention agent liquid pressure may be 1 to 10 KP/alG. .

In addition, examples of the gas in the case of two-fluid spraying include air, nitrogen, propane, butane, vinyl chloride, and fluorinated hydrocarbons.

By spraying the scale adhesion prevention agent liquid as described above and quickly drying it on the drying surface, a polka dot pattern coated area with a diameter of 1 to 3000 microns is formed. The reason why the diameter of this polka dot pattern is limited to the above range is that if it is less than 1 micron, the coating efficiency will be significantly reduced, while if it is more than 3000 microns, it will be difficult to dry quickly, and the coating will be formed in a polka dot pattern. This is because it becomes difficult. A more desirable size of the polka dots is 10 to 1000 microns in diameter.

In order to form a polka-dot-patterned coating surface, it is necessary to quickly dry the sprayed droplets on a drying surface such as the polymerization vessel wall, and for this purpose, this drying surface is heated to 40 to 100°C. This is desirable. By spraying onto such a heated drying surface, the fine droplets are instantly dried and a polka dot pattern coated area is formed. Note that when conducting closed system polymerization, it is difficult to dry the walls of the polymerization vessel by simply pouring hot water into the jacket, so the pressure inside the polymerization vessel must be reduced to -100 mmHg to -710 mmHg. The method used is to dry it.

Figure 2 of the attached drawings is a schematic representation of the polka-dot pattern coated area based on the results of microscopic photography. This is the part where the coating film is formed. On the other hand, FIG. 1 shows a conventional coating state, in which the coating film is formed uniformly on the coated surface.

The present inventors believe that the scale adhesion preventive agent does not necessarily have to be applied evenly over the entire surface of the polymerization reactor wall, but it is particularly desirable that the polka dot pattern coating area be 50% or more of the entire coated surface. It has been found that if the amount is 60% or more, an excellent scale adhesion prevention effect can be achieved even if the coating is not applied uniformly over the entire surface. This was completely unknown in the past, and it is noteworthy that confirmation of this surprising fact has led to savings in the amount of anti-scaling agent and reduction in coating time.

In the present invention, the diameter of the polka dots and the coating area for the polka dot pattern coating are determined by attaching test pieces to several locations on the coating surface, and using any conventionally known microscope for these test pieces. Any compound, inorganic compound, or polymer compound that has been proposed as having a scale adhesion prevention effect is included.
For example, azo group, nitro group, nitroso group, azomethine group,
Those using a nitrogen compound having an azine group, an amino group, etc., or an organic compound containing a sulfur compound or an oxygen compound as a coating agent (Japanese Patent Publication No. 30343/1973), and those using a dye or pigment as a coating agent (Japanese Patent Publication No. 45-1973). -30835), a coating agent using an aqueous solution of an organic compound or dye having a sulfonic acid group or a carboxylic acid group with a p)T of less than 7.0121 (Japanese Patent Publication No. 56-5443), a sulfonic acid group Alternatively, those using a mixed aqueous solution of a dye having a carboxylic acid group and a silicate compound as a coating agent (Japanese Patent Publication No. 56-5444), those using a nitrite as a coating agent (Japanese Patent Publication No. 50-44277), and those using a ferrocyan group as a coating agent. , those using an inorganic salt or inorganic complex having a ferricyan group or thiocyan group as a coating agent (Japanese Patent Publication No. 52-24070), those using a free radical inhibitor as a coating agent (Japanese Patent Publication No. 54-33273), polyethyleneimine (Japanese Unexamined Patent Publication No. 50-51185) and a coating agent made by crosslinking a hydroxyl group-containing polymer material with an organic titanate (Japanese Patent Publication No. 51-29917). One or more of these are dissolved or dispersed in an appropriate medium before use. As the medium (solvent), one or a mixed solvent of two or more of water, alcohol solvents, ester solvents, ketone solvents, hydrocarbon solvents, chlorinated hydrocarbon solvents, etc. is used. The dissolved concentration of the scale adhesion prevention agent in these media is 0,
It is desirable to set the content to about 1 to 3% by weight, especially 01% by weight.
~1% by weight.

As can be understood from the above, the amount of coating solution to be applied is such that the amount of the coating solution is such that the polka dot pattern coating area formed by drying of the spray droplets is 50% or more of the entire target coating surface. However, there is no need to spray a large amount of water to evenly coat the target surface as in the conventional method.

After the coating of the scale adhesion preventive agent on the inner walls of the polymerization vessel and other parts that come into contact with the vehicle body is completed, apply water medium, vinyl or diene monomer, polymerization initiator, etc. to the polymerization vessel in the usual manner. Necessary additives such as monomer dispersion aids are added and polymerized.

Specific examples of the above monomer include vinyl chloride, vinyl acetate, vinyl propionate, acrylic acid, methacrylic acid, or esters or salts thereof.

Examples include maleic acid or fumaric acid, and their esters or anhydrides, butadiene, chlorobrene, isoprene, styrene, acrylonitrile, C7'7' vinylidene, vinyl ether, and the like.

Furthermore, conventionally known dispersion aids, polymerization initiators, etc. are used to be added to the polymerization system.

Next, examples of the present invention will be shown.

Example 1 A 1.0% by weight aqueous solution of an equal weight mixture of Direct Bluff 1 and sodium silicate was prepared, and this was adjusted to pH 5 with phosphoric acid.
, 0 to prepare a scale adhesion inhibitor coating solution.

The following polymerization experiment was conducted using a stainless steel polymerization vessel with an internal volume of 2 ni''.

First, the jacket of the polymerization vessel was held at 90° C. for 10 minutes to dry the inner wall of the polymerization vessel. While maintaining the jacket temperature at the same temperature, the scale adhesion inhibitor coating solution was applied to the inner wall of the polymerization vessel using a two-fluid spray nozzle under the conditions shown in Table 1 (air was used as the carrier gas). experiment/i
In the case of Nos. 61 to 6, the coating droplets sprayed onto the wall surface of the polymerization vessel were instantly dried, and a polka dot pattern coating surface was formed. The diameter of the polka-dot pattern (average diameter μ) and the area ratio (%) of the polka-dot pattern to the entire coated surface were as shown in the same table for each experimental sheet (these coating conditions were different from the test piece). (Based on the results of the survey) however,
Experiments /161-2 and /167-8 described below are comparative examples.

After coating in this way, without washing with water, prepare the following weight ratio (total amount of preparation: 1.7 i
), polymerization was carried out at 70°C for 7 hours and further at 80°C for 2 hours.

Styrene monomer 70 parts by weight Acrylonitrile 30 Water
120 〃Hydroxyapatite
0.5 Sodium lauroyl sulfate
001 Lauroyl peroxide 0.3
5. / After the polymerization reaction was completed, the polymerized contents Y were taken out, the interior of the polymerization vessel was washed with water, and the scale adhesion was examined, and the results were @
It was as shown in Table 1.

For comparison, the scale adhesion inhibitor coating solution was applied without drying the polymerization vessel wall etc. before application, and then the jacket temperature was raised to 90°C and dried for 5 minutes. The results obtained when polymerization was carried out using similar materials (experiments/I67 and A2B) are also listed in the same table.

As shown in the table, the coating film forming area is not necessarily 10
It was confirmed that an excellent scale adhesion prevention effect is exhibited even when the content is not 0%.

16- Example 2 Acid Black 14 was made into an aqueous solution of 0.1% by weight, and this was adjusted to pH 2.5 with fluoric acid to prepare a scale adhesion inhibitor coating solution.

The following polymerization experiment was conducted using a stainless steel polymerization vessel with an internal volume of 130 mm.

First, the jacket of the polymerization vessel was held at 80° C. for 15 minutes to dry the inner wall of the polymerization vessel. While maintaining the jacket temperature at the same temperature, the scale adhesion inhibitor coating liquid was applied using a two-fluid spray nozzle at a liquid pressure of 3. OKf/crl G
, sprayed for 33 seconds at an air pressure of 8/cnrG,
Dried instantly. As a result, a polka dot pattern coated surface with an average diameter of 90 μm was formed, and the area ratio (%) of the polka dot pattern coated portion to the entire coated surface was 80%.

After coating in this way, without washing with water, prepare the following weight ratio (total amount of preparation: 110 m
'), polymerization was carried out at 57°C for 6 hours.

Seven parts vinyl chloride - 100 parts by weight Water 130 Partially saponified polyvinyl alcohol 0.04 #Hydroxypropylmethylcellulose 002 After the polymerization reaction was completed, the polymer contents were taken out and the inside of the polymerization vessel was washed with water.

The above steps of preparation, polymerization, content removal, and water washing were considered as one batch, and when the number of polymerization patches was increased, the amount of scale adhesion and the fish eyes of the polymer were investigated.
It was as shown in the table.

However, the fish eye was measured under the following conditions.

Measuring method for 741 fish): 100 parts by weight of polymer, 50 parts by weight of DOP, 1 part by weight of dibutyltin dilaurate, 1 part by weight of cetyl alcohol, 0.25 part by weight of titanium oxide, and 0.5 parts by weight of carbon black.
0.005 parts by weight of the mixture was kneaded for 7 minutes with two rolls at 150°C, formed into a sheet having a thickness of 0.2 cm, and formed into a sheet of 100 cm by a light transmission method. The number of fisheyes contained in each sheet was investigated.

For comparison, the scale adhesion prevention agent coating liquid was applied without drying the polymerization vessel wall surface etc. before application.The coating was 100%.
), and the results were also shown in the same table when polymerization was carried out using the same preparations as above, except that the jacket temperature was then raised to 90° C. and drying was carried out for 5 minutes.

19-20 Example 3 Solvent Black 7 was made into a 0.05% by weight methyl alcohol solution to prepare a scale adhesion inhibitor coating liquid.

The following polymerization experiment was conducted using a stainless steel polymerization vessel with an internal volume of 2 m''.

First, the polymerization vessel jacket was maintained at 50°C, and the internal pressure was -55°C.
The pressure inside the polymerization vessel was reduced to 50 mmHg.

The interior walls were kept dry. While maintaining the jacket temperature and vacuum, - use the fluid spray nozzle to increase the fluid pressure to 8.
0.4 under the condition of 5Q/m'! Spray applied and dried instantly. As a result, a polka dot pattern coated surface with an average diameter of 250 μm was formed, and the area ratio (%) of the polka dot pattern coated portion to the entire coated surface was 60%.

After coating in this way, without washing with water, prepare the following weight ratio (total amount of preparation: approximately 1.7 r).
&), polymerization was carried out at 52°C for 7 hours.

Chloride and nil monomer 100 parts by weight water
]50 Partially saponified polyvinyl alcohol 0.06 // After the polymerization reaction was completed, the polymerization contents were taken out and the inside of the polymerization vessel was washed with water.

The above steps of preparation, polymerization, content removal, and water washing were made into one batch, and when the number of polymerization batches was increased, the amount of scale adhesion and the fish eyes of the polymer were investigated.
It was as shown in the table.

For comparison, the scale adhesion prevention agent coating liquid was applied without drying the polymerization vessel etc. before coating (100% coating),
The same table also shows the results obtained when polymerization was carried out using the same preparations as above, except that the jacket temperature was then raised to 90° C. and dried for 5 minutes.

[Brief explanation of drawings]

Figure 1 shows the state in which the scale adhesion preventive agent is uniformly applied to the entire coating surface on the inner wall of the polymerization vessel, and Figure 2 schematically shows the state in which the scale adhesion preventive agent is applied in a polka dot pattern. It is something that Patent Applicant Shin-Etsu Chemical Co., Ltd. Agent Figure 1

Claims (1)

[Claims] 1. Before polymerizing the vinyl monomer,
By drying the inner wall of the polymerization vessel, the surface of the stirrer, and other surfaces that come into contact with the vehicle body, and spraying the scale adhesion prevention agent liquid onto the dry surfaces and drying them, the surface has a diameter of 1 to 3000.
A method 2 for polymerizing vinyl monomers, characterized in that a micron polka dot pattern coating area is formed such that the polka dot pattern coating area accounts for 50% or more of the entire coating surface, The method for polymerizing vinyl monomers according to claim 1, wherein the drying surface to be sprayed is heated to 40 to 100°C.