JPH07149805A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To sufficiently wash a reactor, improve the operation rate of the reactor, and produce a polymer having a stable property in high productivity by surely performing the washing of a polymerizer for the polymerization of the vinyl chloride polymer and the coating of a polymer adhesion-preventing agent to the polymerizer by the rotation of a baffle. CONSTITUTION:When a vinyl chloride polymer is produced by polymerizing vinyl chloride or its mixture with a monomer capable of being polymerized with the vinyl chloride in the presence of a polymerization initiator in an aqueous medium, following operations are performed: performing the polymerization operation in the polymerizer having a baffle capable of being rotated from the outside of the polymerizer; discharging the polymerization product after the polymerization reaction is finished; washing the inner wall of the polymerizer and the surfaces of polymerizer attachments including the baffle with a cleanser to remove adherends adhered to the surfaces, while rotating the baffle; and subsequently performing a polymerization operation for the next batch. The washing of the polymerizer is performed in a closed state. After the washing is finished, the baffle is rotated and simultaneously a polymer adhesion-preventing agent is coated on the inner wall of the polymerizer and the surfaces of its attachments. The rotation shaft bearing of a baffle-support member is sealed with a water-sealing type seal using pressed vater. The baffle has a bar-like shape whose cross section is circular or elliptic.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the initiation of polymerization of vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable therewith (hereinafter collectively referred to as "vinyl chloride-based monomer") in an aqueous medium. In the method for producing a vinyl chloride polymer by polymerizing in the presence of an agent, a method for producing a vinyl chloride polymer by a method which stabilizes the quality of a product polymer, has high productivity, and is economically advantageous Regarding

[0002]

Polymerization of vinyl chloride type monomers is usually carried out in the presence of a polymerization initiator in an aqueous medium containing an emulsifier or a dispersant. In this polymerization process, vinyl chloride such as the inner wall of the polymerization vessel, the stirring blade that is an accessory device of the polymerization vessel, the baffle plate (hereinafter referred to as “baffle”), the wall surface of the reflux condenser, and the wall surfaces of various pipes installed in the polymerization vessel. The polymer scale adheres to the portions where the system monomers come into contact (hereinafter, these are collectively referred to as "inner wall surface of the polymerization vessel"), which reduces the yield of the polymer and the cooling ability of the polymerization vessel. In addition, the scale may be lowered, and the peeled scale may be mixed into the product to deteriorate the characteristics of the product (for example, fish eye). Therefore, when polymerizing the vinyl chloride-based monomer in the polymerization vessel, an anti-adhesion agent was applied to the inner wall surface of the polymerization vessel or the contents were extracted from the polymerization vessel and then adhered to the inner wall surface of the polymerization vessel. For example, the scale has been removed by washing with high-pressure water. In order to improve the efficiency of this cleaning, a stirring reactor equipped with a baffle attitude control device has been proposed. (JP-A-3-229629)

[0003]

In order to avoid the problems associated with scale deposition as described above, it is necessary to thoroughly wash the polymerization vessel after the reaction and evenly apply the anti-adhesion agent before the start of the reaction. Become. However, if the time required for this cleaning or the application of the anti-adhesion agent becomes long, there is a problem that the operating rate of the polymerization vessel is lowered and therefore the productivity is lowered.

Further, for example, in a cleaning operation in which high-pressure water is sprayed by using a cleaning nozzle to remove deposits, only the reachable area of the high-pressure water can be cleaned, and the inner wall surface of the polymerization vessel behind the baffle, or The back surface of the baffle, which does not face the cleaning nozzle, became a blind spot for spraying cleaning water, and cleaning was insufficient. Further, also in the case of applying the anti-adhesion agent with a sprayer or the like, similarly, there is a problem in that the above-mentioned portion is likely to be incompletely applied, and thus scale adhesion is likely to occur.

[0005]

In view of the above-mentioned conventional problems, the present inventors have proposed a method for economically producing a vinyl chloride polymer with a stable quality and a high productivity. As a result of repeated studies on the inside of the polymerization vessel after the reaction, it was difficult to clean the scale inside the polymerization vessel by rotating the baffle while rotating and rotating the baffle. The inventors have found that the back surface of the baffle that does not face the wall surface or the cleaning nozzle can be sufficiently cleaned, and have completed the present invention.

That is, the gist of the present invention is to provide vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable therewith (“vinyl chloride-based monomer”) in the presence of a polymerization initiator in an aqueous medium. In the method for producing a vinyl chloride polymer by polymerizing into a polymer, the polymerization reaction is performed using a polymerization vessel having a baffle (“baffle”) whose rotation can be controlled from the outside of the polymerization vessel, and after the polymerization reaction is completed. After removing the reaction product from the polymerization vessel, and then rotating the baffle, the inner wall of the polymerization vessel and the surface of the equipment attached to the polymerization vessel including the baffle are washed with a cleaning agent to remove deposits adhering to the surface. The method for producing a vinyl chloride polymer is characterized in that the following batch polymerization operation is performed.

The present invention will be described in more detail below. The vinyl chloride monomer used in the method of the present invention is a vinyl chloride monomer alone or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith. When is a mixture, the proportion of the vinyl chloride monomer in the mixture is preferably 80% by weight or more. Examples of the monomer copolymerizable with the above vinyl chloride monomer include olefins such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl stearate, vinyl ethers such as ethyl vinyl ether and cetyl vinyl ether, and (meth Examples thereof include unsaturated carboxylic acid esters such as acrylic acid esters, maleic acid or fumaric acid esters, and unsaturated nitriles such as acrylonitrile.

For the polymerization of the vinyl chloride-based monomer, a generally known polymerization recipe of the vinyl chloride-based monomer in an aqueous medium can be adopted without particular limitation, and a dispersant or an emulsifier, The commonly used auxiliary agents such as a polymerization initiator can be used as they are. For example, as the dispersant, partially saponified polyvinyl acetate, cellulose derivative, gelatin,
Acrylic acid copolymer, one or a mixture of two or more protective colloid agents such as maleic acid copolymer can be used, as the emulsifier, an alkali metal salt of a higher alcohol sulfate ester, an alkylaryl sulfonic acid alkali metal salt, Anionic surfactants such as higher fatty acid alkali metal salts, esters of higher fatty acids and polyhydric alcohols, nonionic surfactants such as polyoxyethylene derivatives and the like can be used, and only one of these may be used. However, two or more kinds may be used in combination. The amount of these dispersants and emulsifiers to be used is not particularly limited, but is generally 0. 0 with respect to the total amount of vinyl chloride-based monomers.
It is used within the range of 01 to 2% by weight, preferably within the range of 0.03 to 1% by weight.

As the polymerization initiator, organic peroxides such as benzoyl peroxide, dilauroyl peroxide, t-butylperoxypivalate, bis (2-ethylhexyl) peroxydicarbonate and t-butylperoxyneodecanoate, Azo compounds such as azobisisobutyronitrile and azobis-2,4-dimethylvaleronitrile, and water-soluble peroxides such as hydrogen peroxide, potassium persulfate and ammonium persulfate can be used. The amount of these polymerization initiators used is generally in the range of 0.01 to 1% by weight based on the total amount of vinyl chloride-based monomers.

Further, in the polymerization reaction of vinyl chloride type monomers, generally known polymerization aids, for example, chain transfer agents such as trichloroethylene, dodecyl mercaptan and 2-mercaptoethanol, or antioxidants and other polymerization aids. Agents and the like can be used as necessary. The charging method of the vinyl chloride-based monomer is not particularly limited, and the vinyl chloride-based monomer may be charged all at once before the start of the polymerization, or a part thereof may be charged before the start of the polymerization and the rest after the start of the polymerization. It is also possible to prepare them all at once, continuously, or separately.

The polymerization temperature is determined by the target degree of polymerization of the product, the type of polymerization initiator used, etc.
The range of 90 ° C, mainly 35-70 ° C is used.
An aqueous dispersion of a vinyl chloride polymer produced by the above-mentioned polymerization reaction is used in a blowdown tank or a blend tank after collecting and removing unreacted vinyl chloride monomer under reduced pressure and / or heating. Transferred to a storage tank and stored temporarily.

After removing the aqueous dispersion of the produced vinyl chloride polymer, the polymerization vessel is washed prior to the next batch of polymerization reaction operation and, if necessary, coated with an anti-adhesion agent. The method of the present invention is applied when cleaning the above-mentioned polymerization vessel or applying the anti-adhesion agent. Water is usually used as the cleaning agent for cleaning, but is not particularly limited. The cleaning nozzle can be used without particular limitation as long as it is a nozzle that ejects a liquid, such as a fixed-type spray nozzle or a nozzle that ejects a liquid while rotating.

As the cleaning device, for example, a refraction type,
Cleaning device with automatic sliding type, manual sliding type, fixed type lance, or instead of the lance,
A so-called hose reel type cleaning device using a flexible hose can be used. Examples of the drive system of the cleaning device include a type that uses the pressure of gas such as air and nitrogen, an electric type, a type that uses a hydraulic or hydraulic liquid, or a manual type.

When this cleaning device is installed in a stirring tank, it is not necessary to open and close a manhole or the like every cleaning, which is advantageous in operation. At this time, in order to prevent the scale from adhering to the main body of the cleaning device (nozzle or the like), it is preferable to use a ball valve or the like so that the inside of the polymerization vessel can be blocked during polymerization. The type of anti-adhesion agent applied to the inner wall of the polymerization vessel is not particularly limited, and dye-based, phenol-based, amine-based,
Any quinone type, thiocarbamic acid type, or the like having a scale adhesion preventing effect can be used without particular limitation.

The method of applying the anti-adhesion agent is not particularly limited, and for example, a method such as brush coating or spray coating is used, and it is also possible to coat with an automatic spray coating apparatus having a spray nozzle incorporated in a polymerization vessel. . As a means for atomizing upon application by spraying, a one-fluid nozzle, a two-fluid nozzle and the like can be mentioned.

The outline of a polymerization vessel having a baffle whose rotation can be controlled from the outside of the polymerization vessel used in the method of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing an outline of an example of a polymerization vessel used in the method of the present invention, and FIG. 2 is an enlarged view of an attachment portion (rotation control portion) of a rotatable baffle in the polymerization vessel shown in FIG.

The polymerization vessel is roughly divided into a stirring tank 1 and a stirrer 2.
It is composed of. The stirrer 2 includes a stirring blade 3, a stirring shaft 4,
The stirring shaft includes a shaft sealing portion 5, a stirring shaft supporting portion 6, a speed reducer 7, a stirring motor 8, and the like. The stirring tank 1 includes a nozzle group 9 (not shown) for receiving raw materials and auxiliary agents, a discharge nozzle 10 for discharging the produced polymer, and a manhole 1.
1, a baffle 12 is provided. Further, the stirring tank 1 is provided with a jacket 13, and while the heat medium is received from the nozzle 14 attached to the stirring tank 1 and discharged from the nozzle 15, heat is exchanged with the contents of the polymerization vessel.

The baffle 12 has a plate shape, an E shape, or a D shape.
The shape is not particularly limited, such as a die or a rod, and the cross section thereof may be a quadrangle, a triangle, a circle, or the like, but the cross section is easy to clean and the application of the anti-adhesion agent is uniform. A rod-shaped baffle having a circular or elliptical shape is preferable. One end of the baffle 12 penetrates outside the tank via a nozzle 19 provided on the upper end plate 17 of the stirring tank 1. Also, the nozzle 1
As shown in FIG. 2, a baffle support portion 20 is fixed to 9 and a portion that penetrates outside the tank is kept airtight by a shaft sealing portion 21.

Although only one baffle is shown in this figure, a plurality of baffles may be provided so that the baffles can be rotated simultaneously or individually. Further, in the figure, one end of the baffle has a structure penetrating the upper end plate, but it may have a structure penetrating the lower end plate. The shaft sealing portion 21 is a shaft sealing mechanism that is supported by the rotating support rod 16 and the fixed support portion 20, respectively.

The gap between the inner surface of the nozzle 19 and the support rod 16 is made small so that the contents of the polymerization vessel do not enter the shaft seal portion to form scale deposits, and the reaction operation from the injection hole 25 is not affected. A fluid (for example, water, nitrogen gas, etc.) can be continuously injected. As the shaft sealing mechanism, a gland packing, a mechanical seal or the like is usually used, but from the viewpoint of durability and sealing property, a water sealing type that seals while pressurizing water is preferable as described above. .

A polymerization reaction is carried out using the above-mentioned polymerization vessel, and after the reaction is completed, the reaction mixture (aqueous dispersion of vinyl chloride polymer) and the like in the polymerization vessel is withdrawn, and subsequently the inner wall of the polymerization vessel When the above is washed by jetting high-pressure water with a washing nozzle, the baffle is rotated in accordance with the operation of this washing device, and the entire baffle is washed. This rotation angle is adjusted depending on the arrangement of the cleaning nozzle and the like, but is usually in the range of 30 to 360 °.

Also, when the anti-adhesion agent is applied to the inner wall of the polymerization vessel or the like before the next batch of raw materials are charged, the anti-adhesion agent can be applied to the entire surface of the baffle by rotating the baffle as described above. It becomes possible and scale adhesion can be prevented more effectively. By carrying out the washing operation and the application operation of the anti-adhesion agent according to the method of the present invention, the production / growth of scale adhesion is effectively suppressed, the quality of the obtained product is deteriorated, and the heat transfer efficiency of the polymerization vessel is reduced. It is possible to increase the number of batches that can be carried out before the number decreases. In particular, when the cleaning device and the anti-adhesive agent coating device are installed in the polymerization vessel as described above and the polymerization batches are stacked without opening the can, the frequency of the adhesion removal due to the operation stop and the can opening can be reduced. It is very useful for continuous can operation.

The baffle may be rotated during the polymerization reaction.

[0024]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto as long as the gist thereof is not exceeded. When the baffle was not rotated under the following conditions and when the baffle was not rotated, each batch was polymerized and the scale amount was evaluated.

[0025]

[Table 1] Polymerizer: Capacity 60 m ³ (equipped with two cylindrical rotary baffles) Polymerization recipe: Known suspension polymerization method Operation: Cleaning of container (complete removal of scale) → Application of anti-adhesion agent → Polymerization reaction → Extraction of reaction product → Washing of polymerization vessel →
Cleaning of cans (measure the amount of recovered scale) Washing conditions: High-pressure water (pressure 200 kgf / cm ² · G, flow rate 500 liters / min), 20 minutes Adhesion preventive agent: Dye system, spray using a two-fluid nozzle Application Baffle rotation angle: 90 ° (during cleaning and application of anti-adhesion agent) Scale amount: 40% or less of the case where the baffle was rotated, without rotation.

[0026]

According to the method of the present invention, cleaning of the baffle and application of the anti-adhesion agent can be surely performed, and it becomes possible to remarkably reduce scale adhesion in the polymerization vessel. This stabilizes the quality of the obtained vinyl chloride-based polymer, reduces the time required for cleaning the polymerization vessel, coating the anti-adhesion agent, and the frequency of operations such as scraping off the adhered scale, thus improving productivity. It is improved and economically advantageous.

Further, the method of the present invention is very useful for continuously producing a vinyl chloride polymer in a non-opening can, and its industrial utility value is extremely large.

[Brief description of drawings]

FIG. 1 is an overall view showing an example of a polymerization vessel for carrying out the method of the present invention.

FIG. 2 is an enlarged view of a baffle mounting portion (rotation control portion) in the polymerization vessel shown in FIG.

[Explanation of symbols]

 1 Stirring tank 2 Stirrer 5 Shaft sealing part of stirring shaft 6 Support part of stirring shaft 10 Discharge nozzle 11 Manhole 12 Baffle 20 Baffle support part 21 Baffle shaft sealing part 25 Seal injection hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Nishinaka 3-10 Shiodori, Kurashiki-shi, Okayama Mitsubishi Kasei Engineering Co., Ltd.

Claims (5)

[Claims] 1. Vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable therewith (hereinafter collectively referred to as “vinyl chloride monomer”) in an aqueous medium in the presence of a polymerization initiator. In the method for producing a vinyl chloride polymer by polymerization, the polymerization reaction is carried out using a polymerization vessel having a baffle (hereinafter referred to as "baffle") whose rotation can be controlled from the outside of the polymerization vessel After the completion, the reaction product is extracted from the polymerization reactor, and then the inner wall of the polymerization reactor and the surface of the equipment attached to the polymerization reactor including the baffle are washed with a cleaning agent while rotating the baffle to remove the deposits adhering to the surface. After that, the method for producing a vinyl chloride polymer is characterized in that the following batch polymerization operation is performed. 2. The method for producing a vinyl chloride polymer according to claim 1, wherein the washing is carried out with the polymerization vessel being closed. 3. After completion of washing, prior to the next batch of polymerization reaction operation, while rotating the baffle, the inner wall of the polymerization vessel and / or
Alternatively, the method for producing a vinyl chloride polymer according to claim 1 or 2, wherein an anti-adhesion agent is applied to the surface of a device attached to the polymerization vessel. 4. The vinyl chloride polymer according to claim 1, wherein the rotary bearing of the support portion of the baffle whose rotation can be controlled from the outside of the polymerization vessel is a water-sealed seal with pressurized water. Manufacturing method. 5. The method for producing a vinyl chloride polymer according to claim 1, wherein the baffle is a rod-type baffle, and its cross-sectional shape is circular or elliptical.