JPH11322837A - Method for producing vinyl chloride resin - Google Patents

Abstract

(57) [Summary] [Problem] Without deteriorating quality and productivity,
An unreacted vinyl chloride-based monomer is efficiently recovered, and a high-quality vinyl chloride-based resin with few foreign substances is obtained. SOLUTION: A cationic surfactant is added to a vinyl chloride resin slurry obtained by performing suspension polymerization using a polymer dispersant and an anionic surfactant in an aqueous medium, and stripping is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a vinyl chloride resin. More specifically, in a method of continuously recovering unreacted vinyl chloride monomer from a vinyl chloride resin slurry after polymerization, unreacted vinyl chloride can be efficiently produced without causing deterioration in quality and productivity. The present invention relates to a method for producing a high-quality vinyl chloride resin capable of recovering a system monomer and having few foreign substances.

[0002]

2. Description of the Related Art Conventionally, as a method for continuously recovering unreacted vinyl chloride monomer from a vinyl chloride resin slurry, it is known to use a multistage stripping tower having a perforated plate. . That is, the resin slurry to be treated is supplied to the uppermost perforated plate of the stripping tower under reduced pressure, vapor is passed through the perforated plate from the lowest stage, and the unreacted vinyl chloride monomer is recovered under reduced pressure by gas-liquid contact by bubbling. Is the way.

[0003] In this treatment method, the resin slurry on the perforated plate generates vigorous bubbling due to bubbling of steam from below. As a result, the generated bubbles may cause equipment troubles such as blockage of the recovery line, and the quality deterioration may be caused by the vinyl chloride resin adhering to the wall surface accompanying the bubbles becoming scale due to thermal deterioration. The operation has to be performed with the supply amount of the slurry reduced, and as a result, the throughput per unit time has decreased, leading to a decrease in productivity.

[0004] The foaming of the vinyl chloride resin slurry obtained by the combined use of the polymer dispersant and the anionic surfactant is higher than that of the vinyl chloride resin slurry obtained by the polymerization using the polymer dispersant alone. The system resin slurry was more pronounced, and its defoaming was more difficult.

[0005] For this reason, as a method for suppressing foaming, Japanese Patent Application Laid-Open No. 6-107723 discloses a method in which steam is jetted from another jet nozzle installed above the surface of the slurry to the surface of the slurry. The use of a polyether-based antifoaming agent as means for suppressing foaming of a vinyl chloride-based resin is proposed in the gazette, but none of these methods is sufficient.
In particular, no favorable defoaming measures have been proposed for vinyl chloride resins obtained by polymerization using a polymer dispersant and an anionic surfactant in combination.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present invention provides a method for continuously recovering unreacted vinyl chloride monomers from a vinyl chloride slurry after polymerization. It is an object of the present invention to provide a method for producing a high-quality vinyl chloride-based resin that can efficiently recover unreacted vinyl chloride-based monomer without causing a decrease in the resin content and that has little foreign matter.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, it has been found that the intended object can be achieved by adding a specific cationic surfactant to a vinyl chloride resin slurry. And completed the present invention.

That is, in the present invention, a cationic surfactant is added to a vinyl chloride resin slurry obtained by carrying out suspension polymerization using a polymer dispersant and an anionic surfactant in an aqueous medium, and stripping is performed. And a method for producing a vinyl chloride resin.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
Examples of the cationic surfactant used in the present invention include a primary amine salt, a secondary amine salt, a tertiary amine salt, a quaternary ammonium salt, a pyridinium salt and the like, which serve as an antifoaming agent.

Among the cationic surfactants used in the present invention, quaternary ammonium salts, particularly alkylmethylammonium salts represented by the following general formula (1), are preferred. ^{[RmN + (CH3) n]} X - (1) ( wherein R is an alkyl group, X represents a halogen atom .m +
n = 4, 1 ≦ m ≦ 3, 1 ≦ n ≦ 3) Further, among the alkylmethylammonium salts, those having 8 to 18 carbon atoms in the alkyl group are preferred because of high defoaming effect. Specifically, octyldimethylbenzylammonium chloride having 8 carbon atoms, octyltrimethylammonium chloride, decyldimethylbenzylammonium chloride having 10 carbon atoms, didecyldimethylammonium chloride, dodecyldimethylbenzylammonium chloride having 12 carbon atoms, dodecyltrimethylammonium chloride C14 tetradecyldimethylbenzylammonium chloride, tetradecyltrimethylammonium chloride, C16 hexadecyldimethylbenzylammonium chloride, hexadecyltrimethylammonium chloride, C18 octadecyldimethylbenzylammonium chloride, octadecyltrimethylammonium chloride Yes, these alone or It can be used in combination or more. When the number of carbon atoms is 8 or less and 18 or more, it is not preferable from the viewpoint of economy because it is expensive.

In the present invention, a cationic surfactant having an antifoaming effect is diluted with water and used to effectively disperse it in a vinyl chloride slurry. Due to the dispersibility of the defoamer and the ease of handling due to the high viscosity of the diluent, the weight dilution ratio of the defoamer / water is preferably 50 to 1 part by weight of the cationic surfactant per 100 parts by weight of water. The cationic surfactant may be used in an amount of 0.005 to 0.5 part by weight per 100 parts by weight of the vinyl chloride resin slurry, but 0.01 to 0.1 part by weight is preferable in terms of quality. no problem,
It is preferable because a good defoaming effect can be obtained.

The addition time of the cationic surfactant is as follows:
After the polymerization is completed, the mixture is charged into the polymerization vessel and uniformly dispersed, but is not particularly limited as long as it is supplied to the stripping tower after the polymerization. For example, tanks such as a blow-down tank and a cushion tank that are discharged after the polymerization is completed. And a method in which the mixture is introduced into a line supplied to the stripping tower, and a method in which spraying is performed from the top of the stripping tower. The operating condition of the stripping tower in the present invention is a condition within a range in which there is no problem with the quality of the vinyl chloride resin obtained under sufficient conditions to recover the residual vinyl chloride monomer from the treated vinyl chloride resin slurry. Usually, the temperature in the apparatus is 7
0 to 130 ° C., residence time in the apparatus 5 to 25 minutes, pressure in the apparatus 1 kg / cm ² G to −0.3 kg / cm ² G, the amount of steam used is 80 kg per 1000 kg / h of the vinyl chloride resin to be treated.
Conditions of ~ 250 Kg / h are used. In the present invention, the polymer dispersant and anionic surfactant used for suspension polymerization are conventionally known, and examples of the polymer dispersant include partially saponified polyvinyl alcohol, methylcellulose, pidroxyethylcellose, and hydroxypropyl. Cellulose, pidroxypropylmethylcellulose, gelatin and the like can be mentioned. Examples of anionic surfactants include sodium caprate, sodium laurate, sodium myristate, sodium palmitate, sodium caprylsulfate, sodium lauryl sulfate, sodium myristyl sulfate, sodium oleyl sulfate, monofatty acid glycerin sulfate, sodium ethyl sulfonate, Sodium stearylsulfonate, sodium oleylsulfonate, sodium dodecylbenzenesulfonate and the like can be mentioned.

[0013]

EXAMPLES The production method of the present invention will be described below based on Examples and Comparative Examples, but these do not limit the present invention at all. The measurement and evaluation in Examples and Comparative Examples were performed by the following methods.

The maximum supply amount of the slurry was determined by observing an observation window provided in the stripping tower and observing the state of foam scattering on the recovery line. That is, the tower diameter is 1200m
m, tower length 10000 mm, number of perforated plates 7 stages, 3 kg / cm ² G saturated steam from the lowermost stage of a stainless steel stripping tower with a viewing window having a perforated plate diameter of 1.5 mm 1000 kg / vinyl chloride resin in slurry 100 for h
While blowing at a rate of Kg / h, a vinyl chloride resin slurry is supplied onto the uppermost perforated plate, and the foaming liquid surface rises to the viewing window located 700 mm above the uppermost perforated plate surface. The state in which it was closed was defined as the maximum supply amount.

The quality of the vinyl chloride resin was evaluated by dehydrating and drying the slurry after the completion of the stripping to evaluate foreign substances in the dried product. That is, by weighing 100 g of the dried product and visually checking each particle one by one, the dry resin 10
The number of burnt resin and foreign substances contained in 0 g was measured.

The residual monomer concentration in the vinyl chloride resin was measured by a known method using a gas chromatograph. That is, 2 g of a vinyl chloride resin was weighed on a dry weight basis, dissolved by stirring with 40 cc of tetrahydrofuran, and 0.5 cc of the obtained solution was administered to a gas chromatograph (GC-14A, manufactured by Shimadzu Corporation) to detect hydrogen ion. The residual monomer concentration was measured according to

(Example 1) In a stainless steel polymerization machine equipped with a stirrer having a capacity of 30 m ³ and a jacket, 16100 kg of deionized water, 35.6 kg of a partially saponified polyvinyl alcohol having a saponification degree of 88 mol%, dodecylbenzenesulfonic acid 8.9 kg of sodium and 4.45 kg of di-2-ethylhexyl peroxydicarbonate were charged, and air in the polymerization machine was removed by a vacuum pump. Then, 8900 kg of a vinyl chloride monomer was charged, and the mixture was stirred at 58 ° C.
The reaction was stopped when about 7 hours had passed since the start of the reaction at the above temperature to obtain a vinyl chloride resin slurry having a slurry concentration of 30% by weight and an average particle diameter of 40 μm. Also, didecyldimethylammonium chloride which is a quaternary ammonium salt having 10 carbon atoms is used as a cationic surfactant, and water 100
10 parts by weight of didecyldimethylammonium chloride is uniformly diluted with respect to 100 parts by weight of a vinyl chloride-based resin slurry in a polymerization vessel at a ratio of 0.03 part by weight of didecyldimethylammonium chloride, and stirred and mixed. Was. At this time, the residual monomer concentration in the vinyl chloride resin was 15,000 ppm with respect to the weight of the resin solid. Next, this slurry was supplied to a stripping tower. The results are shown in Table 1. Foaming in the stripping tower was suppressed, the maximum slurry supply was 11.3 m ³ / hr, and the residual monomer of the obtained vinyl chloride resin was 0.1
ppm or less, the number of foreign matters was as good as 0.

Example 2 Production was carried out in the same manner as in Example 1 except that dodecyltrimethylammonium chloride, a quaternary ammonium salt having 12 carbon atoms, was used as the cationic surfactant. The results are shown in Table 1. Foaming in the stripping tower is suppressed, the maximum slurry supply rate is 10.9 m ³ / hr, the residual monomer concentration of the obtained vinyl chloride resin is 0.1 ppm or less, and the number of foreign substances is 0.
And good. .

Example 3 Production was carried out in the same manner as in Example 1 except that octadecyldimethylbenzylammonium chloride, a quaternary ammonium salt having 18 carbon atoms, was used as the cationic surfactant. The results are shown in Table 1. Foaming in the stripping tower was suppressed, the maximum slurry supply amount was 11.0 m ³ / hr, the residual monomer concentration of the obtained vinyl chloride resin was 0.1 ppm or less, and the number of foreign matters was 0, which was good. Was.

Example 4 Production was carried out in the same manner as in Example 1 except that tetradecylamine acetate as a primary amine salt was used as a cationic surfactant. The results are shown in Table 1. Foaming in the stripping tower was rather violent, and the maximum slurry supply was 8.2 m ³ / hr. The residual monomer concentration of the obtained vinyl chloride resin is 0.1 ppm or less,
The number of foreign matter was 0, which was good.

Example 5 Production was carried out in the same manner as in Example 1 except that hexadecylpyridinium chloride of a pyridinium salt was used as the cationic surfactant. The results are shown in Table 1. The results are shown in Table 1. The foaming in the stripping tower is rather severe, and the maximum slurry supply is 8.
It was 5 m ³ / hr. The obtained vinyl chloride resin had a residual monomer concentration of 0.1 ppm or less, and the number of foreign matters was as good as 0. Comparative Example 1 Production was carried out in the same manner as in Example 1 except that no defoaming agent was added to the vinyl chloride resin slurry. The results are shown in Table 1. Here, foaming in the stripping tower was not suppressed, and the state of scattering of the vinyl chloride resin entrained by the foam into the recovery line was so severe that it was difficult to operate.

Comparative Example 2 A polyether-based antifoaming agent (Daiichi Kogyo Seiyaku, trade name: Antifloss F244) was added as a defoaming agent to a vinyl chloride resin slurry in an amount of 0.03 parts by weight based on 100 parts by weight of the vinyl chloride resin slurry. Production was carried out in the same manner as in Example 1 except that the components were charged in the ratio of parts. Table 1 shows the results
It was shown to. Foaming in the stripping tower was not suppressed, and the vinyl chloride resin entrained by the foam was scattered to the recovery line, making it difficult to operate.

Comparative Example 3 Silicone antifoaming agent (Shin-Etsu Chemical Co., trade name K) was used as an antifoaming agent in a vinyl chloride resin slurry.
M71) was produced in the same manner as in Example 1 except that 0.03 parts by weight of M71) was added to 100 parts by weight of the vinyl chloride resin slurry. The results are shown in Table 1. Foaming in the stripping tower was not suppressed, and the vinyl chloride resin entrained by the foam was scattered to the recovery line, making it difficult to operate.

[0024]

[Table 1]

As can be seen from Table 1, a specific cationic surfactant is added to the vinyl chloride resin slurry after polymerization as in the present invention, and stripping is performed.
It was confirmed that the unreacted vinyl chloride-based monomer was efficiently recovered without causing deterioration in quality and decrease in productivity.

[0026]

As described above, according to the method for producing a vinyl chloride resin of the present invention, unreacted vinyl chloride monomers can be recovered with high efficiency without deteriorating quality or lowering productivity. And a high-quality vinyl chloride resin with less foreign matter can be obtained.

Claims (4)

[Claims] 1. A method in which a cationic surfactant is added to a vinyl chloride resin slurry obtained by performing suspension polymerization using a polymer dispersant and an anionic surfactant in an aqueous medium, and stripping is performed. A method for producing a vinyl chloride resin. 2. The vinyl chloride resin according to claim 1, wherein the cationic surfactant is selected from primary amine salts, secondary amine salts, tertiary amine salts, quaternary ammonium salts and pyridinium salts. Production method. 3. A quaternary ammonium salt represented by the following general formula (1):
3. The method for producing a vinyl chloride resin according to claim 2, wherein the alkyl methyl ammonium salt is represented by the formula: ^{[RmN + (CH3) n]} X - (1) ( wherein R is an alkyl group, X represents a halogen atom .m +
n = 4, 1 ≦ m ≦ 3, 1 ≦ n ≦ 3) 4. The method for producing a vinyl chloride resin according to claim 3, wherein the alkyl group of the alkylmethylammonium salt has 8 to 18 carbon atoms.