JPS6038407B2 - Suspension polymerization method of vinyl chloride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When carrying out suspension polymerization of vinyl chloride monomers or vinyl monomer polymers mainly composed of vinyl chloride monomers, the present invention provides a method in which polymer scale (hereinafter referred to as scale) is present in the polymerization vessel. This invention relates to a suspension polymerization method that does not cause adhesion.

When carrying out suspension polymerization of vinyl chloride monomer or a vinyl monomer mixture mainly composed of vinyl chloride monomer in an aqueous medium in the presence of an oil-soluble polymerization initiator, it is necessary to trend,
The polymer yield and cooling capacity of the polymerization vessel are reduced due to scale adhesion to the jama plates, etc., and the physical properties of the product (e.g. fish eyes) are reduced due to the contamination of exfoliated scale into the product. There have been various drawbacks in that the removal requires excessive labor and time, resulting in a decrease in the operating rate of the polymerization reactor. In addition, if the product is placed in cans to remove attached scale, there is a risk of exposure to the monomer, causing occupational health problems, so scaling prevention has been a long-standing issue. As a conventional scale prevention method, Hakama Kosho 45-3
0 Milk 3 Special Publication Showa 45-30835 or Special Publication No. 48-75
As disclosed in Section 7, a method is known in which organic resin compounds, dyes, pigments, resins, etc. are applied to the wall surface of a polymerization vessel.

However, these coating methods require complicated coating operations, require labor and time, and reduce the operating rate of the polymerization vessel.
Even if these substances are applied, the scale prevention effect is not sufficient, and there is a concern that the cooling capacity of the polymerization vessel will be reduced due to the application, and the obtained product will be colored, resulting in a reduction in product value. . On the other hand, special Kanryo 49-427
8 Fufu Sekisho 49-73484, or Hakama Kosho 46-12 female 2
The method of adding nitrite, a reducing agent, or an inorganic oxidizing agent as in 1 has the advantage of omitting complicated operations such as coating and eliminating concerns about deterioration of the cooling capacity of the polymerization reactor, but it does not have the effect of preventing scale. It is still difficult to say that these methods are sufficient, and it is necessary to limit the polymerization catalysts used.Furthermore, their addition impairs the thermal stability of the product, which reduces its industrial utility value. The present invention overcomes these conventional drawbacks and provides a suspension polymerization method that can almost completely prevent scale and produce products of good quality.

The method of the present invention involves suspension polymerization of vinyl chloride monomer or a vinyl monomer mixture mainly composed of vinyl chloride monomer in an aqueous medium containing a dispersant and an oil-soluble polymerization initiator. dithiocarboxylate of 0.05 to monomer
Adding ~10 pm of a water port polyvalent metal salt of trivalent or higher to the above to the aqueous medium.
00 imitation pm and/or nitrite to a single islet.
．． This is a method of preventing scale by adding 0.005 to 1 ppm.

To explain in more detail, in the present invention 1, the water-dropping dithiocarboxylic acid salt is added to the monomer in an amount of 0.05 to 10 pm, and if the amount is less than 0.05 ppm, the scale prevention effect is not sufficient, Addition of more than 5 pm is not preferable as it will have a negative effect on the product.

In addition, adding the water-soluble dithiocarboxylic acid salt of the present invention to the inner wall of the polymerization vessel has a greater scale prevention effect than coating it on the inner wall of the polymerization vessel, and in terms of product quality, it can be used up to a high concentration compared to conventional additives. The feature is that addition is allowed. The scale-preventing action mechanism of water-soluble dithiocarboxylic acid salts is estimated as follows, since water-insoluble dithiocarboxylic acid salts or dithiocarboxylic acid converters do not have a scale-preventing effect.

In other words, the water-soluble dithiocarboxylic acid salt is selectively coordinated and adsorbed to the scale generation site on the wall of the polymerization vessel, preventing direct contact of the monomer with the wall of the polymerization vessel, or preventing polymerization in the aqueous phase. It is thought that scaling may be prevented by inhibiting the production of substances or by both of these mechanisms, but it is not clear at present. The water-soluble dithiocarboxylic acid salts used in the present invention include metal salts such as sodium, lithium, and potassium salts, ammonium salts, and hydrochlorides such as dimethyldithiocarbamic acid, diethyldithiocarbamic acid, ethylxanthate, and methylxanthate. There are no particular limitations, and they can be used alone or in a mixture of two or more.

Of course, water-soluble dithiocarboxylic acid salts have a scale preventing effect, but since dithiocarboxylic acids are unstable, it is preferable to use them in the form of salts. The present invention 2 uses a water-soluble polyvalent metal salt of trivalent or higher valence to an aqueous medium at a concentration of 10 to 100 pm and or a nitrite to a monomer at a concentration of 0.005 to 1 ppm.
m, the method of adding it to Invention 1.

An aqueous solution of a trivalent or higher polyvalent metal salt alone does not have a scale-preventing effect, but if it is added to Invention 1 of the present invention, a remarkable synergistic scale-preventing effect can be obtained, although the mechanism of action is unknown. understood.

The amount of water-borne polyvalent metal salt of trivalent or higher valence to be used is 10 to 100 pm in the aqueous medium; if it is less than 1 pm, a synergistic effect of scale prevention cannot be expected, and if it is more than 100 pm, a synergistic effect of scale prevention cannot be expected. This is not desirable because it affects the product. How to obtain scale prevention effect with nitrite alone
85, the polymerization catalyst has 16 to 18 carbon atoms.
It is necessary to limit the use of unbranched dialkyl peroxydicarbonate having an alkyl group of (thermal stability) is impaired.

If the amount of nitrite added is reduced in order to avoid these problems, the scale prevention effect cannot be obtained. In other words, present invention 2
Although the scale prevention effect cannot be obtained by adding nitrite in the amount within the range claimed in the above, a remarkable synergistic scale prevention effect can be obtained if it is added in combination with the present invention 1. Although the synergistic effect is not clear, it is thought that some kind of interaction between dithiocarboxylate and nitrite exerts a remarkable scale prevention effect. The amount of nitrite used in the present invention 2 is 0.005 to 1 ppm based on the monomer.
If it is less than 0.005 ppm, a synergistic effect of preventing kale cannot be expected, and if it is more than 1 ppm, it will have a negative effect on the quality of the product, and even if it is added more than 1 ppm, the synergistic effect of preventing scale will not increase. It is not preferable to add it.

The water-soluble trivalent or higher valent metal salts used in the present invention include sulfates, nitrates, sulfites, halides, and the like, and these metal salts have a trivalent or higher valence.

Specifically, they include double salts containing trivalent or higher valent metals such as aluminum trichloride, aluminum sulfate, stannic chloride, ferric chloride, titanium trichloride, titanium tetrachloride, and alum, and are not particularly limited, and can be used alone or A mixture of two or more types is used. The nitrites used in the present invention include inorganic and organic nitrites, including inorganic salts such as sodium nitrite, potassium nitrite, barium nitrite, and calcium nitrite, and organic nitrites such as dicyclohexylamine carp nitrate. It is not limited and can be used alone or in combination of two or more.

Monomers copolymerizable with vinyl chloride used in the present invention include vinylidene chloride, ethylene, propylene,
Vinyl acetate, etc., and is not particularly limited.

Dispersants used in the present invention are synthetic and natural polymers such as partially saponified polyvinyl acetate, cellulose derivatives, starch, gelatin, tricalcium phosphate, inorganic dispersants, or known emulsifiers, and are not particularly limited. They can be used alone or in a mixture of two or more.

Polymerization initiators used in the present invention include benzoyl/gu oxide, lauroyl/gu oxide, diisopropyl peroxydicarbonate, diethylhexyl peroxydicarbonate, disec-butyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, Particularly limited if it is a known oil port radical polymerization initiator such as peroxide such as acetylcyclohexylsulfonyl peroxide, azo compound such as azobisisobutyronitrile, azobisdi*methoxydimethylvaleronitrile, azobisdimethylvaleronitrile, etc. They may be used alone or in a mixture of two or more, but azo compounds are advantageous.

Further, depending on the case, various molecular weight regulators, buffers, organic solvents, etc. may be used without any problem.

According to the method of the present invention, not only a remarkable scale prevention effect can be obtained, but also fish eyes in the molded article are reduced, and the molded article has good thermal stability, so that its industrial value is great.

EXAMPLES Next, the present invention will be explained with reference to Examples, but these are not intended to limit the scope of the present invention in any way.

Examples 1 to 6 In a stainless steel polymerization vessel with an internal volume of 1500, 800 k9 of ion exchange water in which 400 k of partially saponified polyvinyl acetate was dissolved and 999 k of azobisdimethylvaleronitrile were added.
Prepare 0 tsp. After degassing, prepare vinyl chloride 400k9. 5
Polymerization was carried out at 70°C for 9 hours. Table 1 shows the results of adding potassium dimethyldithiocarbamate or potassium dimethyldithiocarbamate and sodium nitrite at the time of preparing the container. Incidentally, samples with addition amounts other than those specified in the present invention are listed as comparative examples. Table 1 *1 Thermal stability was determined by kneading the formulation in Table 2 for 5 minutes with a 160qo roll to make a sheet, then stacking the sheets and pressing under a pressure of 170o0 and 15cm for 18 minutes. A plate with a thickness of 5 ribs was prepared, and the degree of coloration of the plate was observed with the naked eye.

*2 Fish eye (co/10 x 10) Fish eye is the composition of Table 3. After kneading for 8 minutes with a 140 oo roll, take out the sheet and let light pass through the fish eye in the 10 x 10 c fin. I taught it.

Table 2 *3 Manufactured by Nitto Kasei (N-200) *4 Manufactured by Kawaken Fine Chemicals Table 3 From Table 1, potassium dimethyldithiocarbamate is added to the monomer at a concentration of 10 ppm or more or sodium nitrite is added to lpp.
If more than m is added, the thermal stability of the product deteriorates, so the preferred range of use of these is 0 for the monomer.
．． 05 to 10 pm, and the latter is found to be less than 1 ppm.

Examples 7 to 16 In a stainless steel polymerization vessel with an internal volume of 1500, 800 k9 of water in which 400 g of methyl cellulose was dissolved, and 10 g of vinyl acetate.
1k9 trichlorethylene, 120% diethylhexyl peroxydicarbonate, 2 mineral spirits
After 50 minutes, 200 tons of stearic acid was charged, and after degassing, vinyl chloride 390k9 was charged, and polymerization was carried out at 60° C. for 9 hours.

At this time, sodium ethylxanthate, aluminum chloride, and potassium nitrite were added. Table 4 shows the results of continuous feeding using this recipe and examining the scale prevention effect. Comparative examples include those in which potassium nitrite or aluminum chloride was added alone, and those without the addition of potassium nitrite or aluminum chloride. Table 4 From Table 4, the synergistic effect of preventing scale by aluminum chloride and potassium nitrite on sodium ethylxanthate is 1 pm or more for aluminum chloride relative to the aqueous medium, and 0.005 pm for potassium nitrite relative to the monomer.
It can be seen that it can be obtained when the amount is more than ppm.

It can be seen from Examples 1 and 2 that the preferred amount of nitrite used is 0.005 to 1 ppm based on monomer. Examples 17 to 25 800 k9 of ion-exchanged water in which 400 g of partially saponified polyvinyl acetic acid was dissolved in a stainless steel polymerization vessel with an internal volume of 1500
, azobisdimethoxydimethylvaleronitrile 30 minutes,
90 tons of azobisdimethylvaleronitrile, 150 tons of mineral spirit and 400 tons of cetyl alcohol were charged, and after degassing, vinyl chloride 400k9 was charged and polymerization was carried out at 50° C. for 9 hours.

At this time, 5 ppm of sodium jettyldithiocarbamate was added to the monomer and 1 part of various water-soluble metal salts were added to the aqueous medium.
0 Cape pm was added and continuous feeding was carried out until scale formation was observed. The results are shown in Table-5. Note that additive-free products were listed as comparative examples. Table 5 From Table 5, it can be seen that a water-soluble monovalent polyvalent metal salt of trivalent or higher valence shows a clear synergistic effect in preventing scale when used in combination with sodium jettyldithiocarbamate.

Comparative Example 10 In a stainless steel polymerization vessel with an internal volume of 300 mm, 150 mm of ion exchange water in which 75 mm of partially saponified polyvinyl acetate was dissolved, 2
- Charge 22.5 kg of ethylhexyl peroxydicarbonate, and after degassing, charge 75 kg of vinyl chloride.
Prepolymerization was carried out in O for 5 hours.

Next, add 30 k9 of ion-exchanged water containing partially saponified polyvinyl acetate at 60 pm to the aqueous medium and 30 k9 to the monomer per hour.
15 kg of vinyl chloride containing 0 PM of di-2-ethylhexyl peroxydihydroponate is continuously charged, and at the same time, 45 k9 of the reaction solution is taken out per hour. The amount of scale in the polymerization vessel after the start of continuous charging was 2,000 yen.
Example 26 Sodium dimethyldithiocarbamate 5 ppm to monomer and aluminum sulfate 10 pm to water medium were added to the aqueous medium of Comparative Example 16 in the preliminary and continuous additions, and other conditions were the same as Comparative Example 16. The amount of scale in this case was 10 days.

This shows that the present invention has a clear scale prevention effect even in continuous polymerization.

Example 27 In a stainless steel polymerization vessel with an internal volume of 300 kg, 150 k9 of ion-exchanged water in which 25 kg of methyl cellulose and 509 kg of partially saponified polyvinyl acetate were dissolved, and 150 kg of Gsec. -Butyl peroxydicarbonate 20 times, mineral spirit 40 times,
Stearic acid 50% is prepared, vinyl chloride 75k is degassed.
9 was charged and polymerization was carried out at 520 for 10 hours.

At this time, 7.5p each of the substances shown in Table 6 was added to the single leather body.
Table 6 shows the scale prevention effect when pm was added. Table 6 From Table 6, it can be seen that reducing agents and oxidizing agents do not show any scale preventing effect, but the water-soluble dithiocarboxylic acid salt according to the present invention shows a remarkable scale preventing effect.

Examples 28 to 35 A stainless steel polymerization vessel with an internal volume of 300 was charged with 150 kg of ion-exchanged water in which 75% of partially saponified polyvinyl acetate was dissolved, 50% of mineral spirit, and potassium dimethyldithiocarbamate at a concentration of 5ppm based on the monomer, and degassed. Afterwards, vinyl chloride 75k9 was charged and polymerization was carried out for 9 hours.

At this time, a polymerization catalyst as shown in Table 7 was added, and the mixture was continuously charged until scale formation was observed. The results are shown in Table 7. Table 7 From Table 7, it can be seen that the scale prevention effect is more advantageously obtained when an azo catalyst is used as a polymerization catalyst than a peroxide catalyst.

Example 36 800 k9 of ion-exchanged water in which 400 g of partially saponified polyvinyl acetate was dissolved in a stainless steel polymerization vessel with an internal volume of 1500
, azobisdimethylvaleronitrile 80 μm was charged, and after degassing, polymerization was carried out for 9 hours at 900 μg of pinyl chloride 400 k×0.

Prior to this polymerization, the substances shown in Table 8 were applied to the inner wall of the polymerization vessel or added to the interior of the polymerization vessel, and polymerization was carried out. In this case, the scale prevention results are shown in Table 8 when the amount of added substances present in the polymerization vessel was the same. Table 8 From Table 8, it can be seen that no scale prevention effect can be obtained at all when a substance having a thiocarbonyl group, thioether group, or thioalcohol group is applied to the inner wall of the polymerization vessel or added to the inside of the polymerization vessel.

Furthermore, it can be seen that even when a dithiocarboxylic acid salt is applied, almost no scale prevention effect is obtained, and a significant scale prevention effect is obtained only when a water-soluble dithiocarboxylic acid salt is added. Since a remarkable scale prevention effect is obtained only when a water-soluble dithiocarboxylic acid salt is added, the substance of the present invention is thought to be the main cause of scale generation, although the cause is currently not clear. This is thought to be because it exhibits a specific effect on objects.

Examples 37-40 Ion-exchanged water 150k9 in which partially saponified polyvinyl acetate 75k9 was dissolved in a stainless steel polymerization vessel with an internal volume of 300,
50 ppm of mineral spirit, 15 min of azobisdimethylvaleronitrile, and various dithiocarboxylic acid salts shown in Table 9 were added to the monomer, and after degassing, vinyl chloride 75k9 was added and polymerization was carried out at 6000 for 9 hours. .

The results of repeating polymerization using this recipe and investigating the number of times it was repeatedly charged until scale formation was observed are also shown in the table below.
9. Table 19 Examples 41 to 49 In Example 37, 5 ppm of sodium dimethyldithiocarbamate was used as the dithiocarboxylate, and various water-droptable polyvalent metal salts of trivalent or higher as shown in Table 10 were added to the aqueous medium. Table 1 shows the results of polymerization carried out in the same manner except that 100 ppm was used (no addition was made in Example 51).
0.

Claims (1)

[Scope of Claims] 1. When carrying out suspension polymerization of vinyl chloride or a vinyl monomer mixture mainly composed of vinyl chloride in an aqueous medium containing a suspending agent and an oil-soluble polymerization initiator, 1.
At the same time, or continuously from the time of polymerization preparation to the final stage of polymerization, 0.05 to 0.05 to
A suspension polymerization method for vinyl chloride, characterized in that 100 ppm is added. 2. In the method according to claim 1, a water-soluble polyvalent metal salt of trivalent or higher valence is further added to the aqueous medium in an amount of 10 to 10
0 ppm and/or nitrite to monomer
Suspension polymerization method of vinyl chloride adding 0.05 to 1 ppm.