JPH09124711A - Continuous suspension polymerization process for vinyl chloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the scale build-up on an inlet port of a polymn. initiator by supplying the polymn. initiator directly to the liq. phase in a polymerizer separetely from a vinyl chloride monomer. SOLUTION: After an aq. medium contg. 0.001-2wt.% (based on the monomer component described below) dispersant is charged into a polymerizer, a monomer component comprising vinyl chloride or its mixture with a monomer copolymerizable therewith is continuously fed into the polymerizer and the suspension polymn. is started. Then. an oil-sol. polymn. initiator having a viscosity adjusted to 1 Pa.s or lower is added to the liq. phase in the polymerizer through an inlet port having a diameter of 5-50mm at an average flow rate of 0.05-50m/sec to complete the polymn.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a continuous suspension polymerization method for vinyl chloride.

[0002]

2. Description of the Related Art Conventionally, in the polymerization of vinyl chloride-based monomers, a vinyl chloride monomer, an aqueous medium, a dispersant, a polymerization initiator and the like are usually charged in a stainless steel polymerization vessel to control the reaction temperature at a constant level. Then, a batch-type water suspension polymerization method is carried out in which polymerization is carried out while removing heat. By the way, a continuous suspension polymerization method has been proposed in order to significantly increase the productivity, but in the case of vinyl chloride, there is a problem of adhesion of scale to the polymerization vessel and what is called a glass ball that does not have voids in the polymer particles. There is a problem such as generation and deterioration of quality, and it has not been put to practical use.

Further, in the conventional continuous suspension polymerization method of vinyl chloride resin, it is known that the scale adheres to the vessel wall, the transfer pipe and the like when the equipment is continuously operated for a long period of time. If the scale adheres to the vessel wall, the heat removal ability of the polymerization vessel is reduced, so that the productivity is deteriorated. Further, if the scale is peeled and mixed with the product, the quality of the product is deteriorated.

Further, if the transfer pipe is clogged with scale, the plant must be stopped to remove the scale in order to remove it, which requires a great deal of labor and causes a significant decrease in productivity. There was a problem.
Therefore, in the case of continuous polymerization, for long-term safe operation,
Preventing scale from adhering is an essential condition.

In continuous suspension polymerization, the problem of adhesion of scale is the inlet of the polymerization initiator. At this charging port, the polymerization initiator continuously charged and the gaseous vinyl chloride-based monomer contact and polymerize, so that a strong lumpy scale is easily attached and grows with time. Due to the grown scale, the inlet of the polymerization initiator is blocked, which makes it impossible to add the polymerization initiator thereafter.

[0006] The inlet of the polymerization initiator is usually provided in the upper part of the polymerization vessel. However, when this is provided in the liquid phase portion, the nozzle of the inlet causes retention, so that the polymer particles produced here are retained. There are problems such as clogging and difficulty in removing the polymer retained during washing. Therefore, a method may be considered in which a polymerization initiator is mixed with a vinyl chloride monomer, a dispersant, an aqueous medium, etc. in a tank in advance to form a suspension, and the suspension is continuously charged into a polymerization vessel. If it is insufficient, polymerization is started before it is supplied to the polymerization vessel, and problems such as clogging of pipes and pumps are pointed out.

In batch-type suspension polymerization, many methods have been proposed to prevent polymerization at a charging port of a polymerization initiator and prevent adhesion of scale and clogging of piping. For example, in Japanese Patent Application Laid-Open No. 2-170807, a method of washing the charging route of the polymerization initiator with an organic solvent in which the polymerization initiator is easily soluble;
JP-A-2-209904 discloses a method in which a polymerization initiator is charged as an aqueous emulsion and then the charging route is washed with a cleaning liquid containing a polymerization inhibitor; JP-B-6-13573.
In JP-A No. 6-74293, a method of heating a polymerization initiator charging pipe and a charging port from the outside; in JP-B-6-74293, a polymerization initiator is charged into an aqueous emulsion, and then the charging pipe and the charging port are washed with steam. Methods for doing so are disclosed respectively.

In the batch type polymerization, in the method in which the polymerization initiator is charged independently before the start of the polymerization, the scale adhesion at the polymerization initiator charging port can be prevented by adopting the above-mentioned method. When the polymerization initiator is continuously added, the above method is not effective. Further, there is no disclosure of a method for preventing scale adhesion at the polymerization initiator charging port for continuous polymerization.

Further, Japanese Patent Laid-Open No. 6-32806 proposes a method for preventing scale from adhering to a polymerization vessel in continuous suspension polymerization, but does not describe how to add a polymerization initiator.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object thereof is to directly add a polymerization initiator to a polymerization vessel through a separate pipe in continuous suspension polymerization of vinyl chloride. At the same time, it is an object of the present invention to provide a continuous suspension polymerization method of vinyl chloride capable of preventing scale from adhering to the polymerization initiator at the inlet.

[0011]

The method for continuous suspension polymerization of vinyl chloride of the present invention is a method of continuously polymerizing vinyl chloride monomer alone or a mixture of vinyl chloride monomer and a monomer copolymerizable therewith. When supplied to a polymerization vessel and performing suspension polymerization in an aqueous medium containing a dispersant, a polymerization initiator is directly supplied to the liquid phase part in the polymerization vessel in addition to the above monomer. Is.

The continuous polymerization method referred to in the present invention is a method in which a raw material and auxiliary raw materials such as a polymerization initiator are continuously supplied to a single polymerization vessel or a polymerization vessel in which a plurality of polymerization vessels are combined to perform polymerization, and at the same time, the product is discharged. Say.

In the present invention, a vinyl chloride monomer alone or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith is called a vinyl chloride monomer. As the monomer copolymerizable with the vinyl chloride monomer, for example, vinyl acetate,
Vinyl esters such as vinyl propionate; (meth) methyl (meth) acrylate, ethyl (meth) acrylate, etc.
Acrylic acid ester: In addition to olefins such as ethylene and propylene, maleic anhydride, acrylonitrile, styrene, vinylidene chloride and the like can be mentioned, but not limited thereto.

As the dispersant used in the polymerization method of the present invention, those usually used for suspension polymerization of vinyl chloride are suitable, and examples thereof include methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxypropyl methyl cellulose. And the like; water-soluble polymers such as partially saponified polyvinyl alcohol, polyethylene oxide, acrylic acid and gelatin; and water-soluble emulsifiers such as sorbitan monolaurate and polyoxyethylene sorbitan monolaurate. These may be used alone or in combination of two or more.

The amount of the dispersant used is preferably 0.001 to 2% by weight based on the monomers used.

As the polymerization initiator used in the polymerization method of the present invention, an oil-soluble initiator usually used in suspension polymerization of vinyl chloride is suitable, and examples thereof include di-2-ethylhexyl peroxydicarbonate and di-ethyl ether. Ethoxyethyl peroxydicarbonate, α-cumyl peroxyneodecanate, t-butyl peroxyneodecanate, t-butyl peroxypivalate, t-butyl peroxy-3,
Examples include 5,5-trimethylhexanoate, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, lauroyl peroxide and the like. These may be used alone or in combination of two or more.

The amount of the above-mentioned polymerization initiator used is preferably 0.01 to 2% by weight based on the monomers used.

As the polymerization vessel for carrying out the continuous suspension polymerization in the present invention, either a single polymerization vessel or a plurality of polymerization vessels connected in series can be used.

In the polymerization method of the present invention, the above-mentioned polymerization initiator is not particularly limited as long as it is supplied to the liquid phase portion in the polymerization vessel, and the location for introducing the polymerization initiator is, for example, the main body of the polymerization vessel. The bottom portion or the side trunk portion is preferable.

The average flow velocity when the solution containing the above-mentioned polymerization initiator is charged is not particularly limited, but is 0.05 to 50 m /
Seconds (linear velocity) are preferred. If the average flow rate is less than 0.05 m / sec, the polymerized slurry will flow back and clogging (scale) of the polymer will easily occur at the charging port. Also, the average flow velocity is 5
When it exceeds 0 m / sec, it is not preferable from the viewpoint of safety and economy. When the polymerization initiator has a plurality of inlets, the average flow rate is applied to all of them.

With a polymerization initiator only, an average flow rate of 0.05 m
If / second cannot be obtained, it may be diluted with an appropriate solvent. Examples of the solvent include aliphatic hydrocarbons such as n-hexane and n-heptane; aromatic hydrocarbons such as benzene, toluene and xylene; alcohols such as methanol and ethanol; methyl chloride, methylene chloride and the like. Halogenated hydrocarbons; ethers such as ethyl ether and dichloroethyl ether; ketones such as acetone and methyl ethyl ketone can be used.

When the use of an organic solvent is not preferable, it is preferable that the polymerization initiator is emulsified and then diluted with water. The dispersant used at the time of emulsification is not particularly limited, but a dispersant used at the time of polymerization can be used, in particular, partially saponified polyvinyl alcohol, modified celluloses, polyacrylic acid, polyethylene oxide, etc. Is preferred.

In the case of a water-soluble polymerization initiator, it may be appropriately diluted with water.

It is preferable that the inlet of the above-mentioned polymerization initiator is small in order to obtain a predetermined linear velocity and prevent backflow of the polymerization slurry, but if it is too small, polymer particles may be clogged. In the case of a pipe having a circular inlet, a diameter of 5 to 50 mm is preferable.

The viscosity of the above-mentioned polymerization initiator is not particularly limited, but when the viscosity is higher than 1 Pa · s, it is preferably diluted by the above method.

In the polymerization method of the present invention, polymerization regulators, chain transfer agents, polymerization inhibitors, pH regulators, stabilizers, scale inhibitors and the like which are commonly used in the polymerization of vinyl chloride may be added.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

(Example 1) In a stainless steel polymerization vessel equipped with a jacket having an internal volume of 200 L and a stirring blade, 90 kg of ion-exchanged water at 40 ° C and a partially saponified polyvinyl alcohol having a saponification degree of 72 mol% (Nippon Gosei Kagaku Kabushiki Kaisha) "Gothenol KZ-06" (60 g) and hydroxypropyl methylcellulose (Shin-Etsu Chemical Co., Ltd. "Metrose 65SH5")
0 ") After charging 37.5 g, the inside of the polymerization vessel was set at 13,30
A vacuum was applied to 0 Pa, and 75 kg of vinyl chloride monomer was charged. Then, 75 g of a polymerization initiator α-cumylperoxyneodecanate (“PARKMILL ND” manufactured by NOF CORPORATION) was press-fitted with nitrogen, and then the temperature inside the polymerization vessel was raised to 57.5 ° C.

On the other hand, in a stainless steel raw material tank equipped with another jacket having an inner volume of 2 m ³ and a stirring blade, 900 kg of ion-exchanged water at 40 ° C., partially saponified polyvinyl alcohol (“Gosenol KZ-06” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) ) 6
After charging 00 g and hydroxypropyl methylcellulose (“Metrose 65SH50” manufactured by Shin-Etsu Chemical Co., Ltd.) 375 g, the inside of the raw material tank was evacuated to 13,300 Pa, and 750 kg of vinyl chloride monomer was charged to prepare a raw material suspension. The temperature at this time was 38 ° C.

At the same time when the internal temperature of the polymerization vessel reached 57.5 ° C. and the polymerization reaction started, the raw material suspension heated to 57 ° C.
Supply at the rate of 5 Kg / hr to the liquid phase part of the body of the polymerization vessel,
At the same time, a solution prepared by diluting the polymerization initiator α-cumylperoxyneodecanate (“PARKMILL ND” manufactured by NOF CORPORATION) 5 times with methanol was fed at a rate of 125 g / hr from a nozzle having a diameter of 5 mm to a body part on the side of the polymerization vessel. The injection was started in the liquid phase part of. The flow velocity at this time was 0.16 m / sec (linear velocity). Then, a distribution operation for extracting the product so that the inner volume of the polymerization vessel became constant was started to carry out a continuous polymerization reaction. 30
After performing the time circulation operation, it was cooled and exhausted to stop the continuous polymerization reaction. At this time, no deposits were observed in the vicinity of the polymerization initiator charging port and on the peripheral wall.

Example 2 In a stainless steel polymerization vessel equipped with a jacket having an internal volume of 200 L and a stirring blade, 90 kg of ion-exchanged water at 40 ° C. and a partially saponified polyvinyl alcohol having a saponification degree of 72 mol% (Nippon Gosei Kagaku Co., Ltd.) were used. "Gosenol KZ-06" manufactured by Sumitomo Chemical Co., Ltd., and polyethylene oxide having a weight average molecular weight of 4.3 million ("PEO-1" manufactured by Sumitomo Seika Co., Ltd.)
8 ”) After charging 11 g, the inside of the polymerization vessel is 13,300 P
It was evacuated to a and charged with 75 kg of vinyl chloride monomer. Then, 75 g of a polymerization initiator α-cumylperoxyneodecanate (“PARKMILL ND” manufactured by NOF CORPORATION) was press-fitted with nitrogen, and then the temperature inside the polymerization vessel was raised to 57.5 ° C.

On the other hand, in a stainless steel raw material tank equipped with another jacket having an inner volume of 2 m ³ and a stirring blade, 900 kg of ion-exchanged water at 40 ° C., partially saponified polyvinyl alcohol (“Gosenol KZ-06” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) ) 7
After charging 50 g and 110 g of polyethylene oxide having a weight average molecular weight of 4.3 million (“PEO-18” manufactured by Sumitomo Seika Chemical Industries, Ltd.), the inside of the raw material tank was evacuated to 13,300 Pa, and 750 kg of vinyl chloride monomer was charged, and the raw material was charged. A suspension was prepared. The temperature of the raw material suspension at this time was 36 ° C.

At the same time as the internal temperature of the polymerization vessel reached 57.5 ° C. and the polymerization reaction started, the raw material suspension heated to 55 ° C.
Supply at the rate of 5 Kg / hr to the liquid phase part of the body of the polymerization vessel,
At the same time, a polymerization initiator α-cumylperoxyneodecanate (“PARKMILL ND” manufactured by NOF CORPORATION) was emulsified (concentration: 50% by weight) and further diluted 5 times with water to obtain a solution having a rate of 375 g / hr. Then, the injection was started from a nozzle having a diameter of 5 mm to the liquid phase portion of the trunk portion on the polymerization vessel side. The flow velocity at this time was 0.53 m / sec (linear velocity). Then
A continuous flow operation for extracting the product so that the inner volume of the polymerization vessel was constant was started to carry out a continuous polymerization reaction. After carrying out a circulation operation for 30 hours, it was cooled and exhaust gas was discharged to stop the continuous polymerization reaction. At this time, no deposits were observed in the vicinity of the polymerization initiator charging port and on the peripheral wall.

Comparative Example 1 A continuous polymerization reaction was carried out in the same manner as in Example 1 except that a solution prepared by diluting a polymerization initiator with methanol was added to the gas phase section above the polymerization vessel. Eighteen hours after the initiation of continuous polymerization, the nozzle was clogged with deposits and the polymerization initiator could not be added.

Comparative Example 2 750 g of a polymerization initiator was added at the time of preparing a raw material suspension, and the obtained raw material suspension was cooled to 21 ° C. in a raw material tank and passed through a heat exchanger before charging. A continuous polymerization reaction was carried out in the same manner as in Example 2 except that the temperature was raised to 55 ° C. and continuously charged into the polymerization vessel at a rate of 55 Kg / hr. 26 hours after the initiation of continuous polymerization,
Since the transport pump for the raw material suspension was clogged and it became impossible to transport it, the raw material suspension was cooled and exhausted to stop the continuous polymerization reaction.
At this time, no adhesion of a lumpy scale or the like was observed at the inlet of the polymerization initiator. However, since a polymerization reaction occurred in the raw material tank, formation of a polymer was observed, which caused the pump to be clogged, and scale was attached to the pipe.

[0036]

EFFECT OF THE INVENTION The continuous suspension polymerization method of vinyl chloride of the present invention has the above-mentioned constitution, and by supplying the polymerization initiator to the liquid phase portion in the polymerization vessel, the scale is prevented from adhering to the inlet. Therefore, suspension polymerization can be stably performed continuously for a long time.

Claims (1)

[Claims] 1. A vinyl chloride monomer alone or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith is continuously fed to a polymerization vessel and suspended in an aqueous medium containing a dispersant. A method for continuous suspension polymerization of vinyl chloride, characterized in that, when carrying out the polymerization, a polymerization initiator is directly supplied to a liquid phase part in a polymerization vessel in addition to the above-mentioned monomer.