JPH0873508A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE: To provide a process for producing a vinyl chloride polymer whereby an esp. high-quality vinyl chloride polymer can be produced at a high productivity by using a reaction vessel with an improved internal jacket. CONSTITUTION: Vinyl chloride or a copolymerizable monomer mixture mainly comprising vinyl chloride is polymerized in an aq. medium in a rection vessel which has such a structure that partition plates 7 are installed in parallel with each other at a distance and vertically to the back side of an inner plate 6; an outer strip 8 is installed over the tops of the partition plates 7 to form a channel wall 5A having heat medium channels 9 divided by the partition plates 7 and formed between the inner plate 6 and the strip 8; and the wall 5A is fixed to the inside surface of the vessel with the strip 8. The wall 5A is fixed to the inside surface of the vessel 1, i.e., to the inside surface of the body 2 of the vessel 1 coming into contact with a material being subjected to heat-exchange and, if necessary, to the inside surface of the bottom end plate. The channel may be installed spirally in the vertical direction or spirally on the bottom end plate and circumferentially in zigzag at the vessel body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride polymer, and in particular to a high quality vinyl chloride polymer,
The present invention relates to a method for producing a vinyl chloride polymer that can be produced with high productivity.

[0002]

2. Description of the Related Art Generally, a tank container used for a polymerization reaction of vinyl chloride or a mixture of vinyl chloride-based copolymerizable monomers (hereinafter, collectively referred to as "vinyl chloride-based monomer") is The container body 1 is formed of a pressure-resistant closed container in which dish-shaped end plates are welded to both ends of a cylindrical body, and a jacket 13 for removing heat generation or heating contents is provided.
An external jacket type tank container (FIG. 4) attached to the outside of the container body 1 is used.

[0003] In this type of tank container, since the container body maintains pressure resistance, the plate thickness of the container is generally large, the thermal conductivity through the wall of the container body is low, and a vinyl chloride-based simple substance that is an exothermic reaction is generally used. It was difficult to obtain high productivity in the polymerization of monomers. Further, in the case of enlarging the tank container, from the viewpoint of strength, it is necessary to make the wall thickness of the container main body thicker than that of the small tank container, and there is a disadvantage that the thermal conductivity is further lowered.

Therefore, in order to solve this disadvantage of heat conduction, partition plates 14 are arranged side by side at a right angle to the inner surface of the container body 1 ', as shown in FIG. An inner jacket method in which a spiral flow path 16 partitioned by a partition plate 14 is formed between the inner strip 15 and the inner surface of the container body 1'by straddling the inner strip 15 (JP-A-57-57). No. 147502) is proposed.

While the inner jacket type tank container has excellent thermal conductivity, a large number of inner strips 1 are present on the inner surface of the tank container to which the contents come into contact during the polymerization reaction of the vinyl chloride monomer.
There is an inconvenience due to the exposed portion of the weld between the five. In other words, the welded portion has a rough surface roughness due to its construction, and a welding defect portion exists, but in the polymerization reaction of the vinyl chloride-based monomer, the surface of the portion where the reaction mixture contacts (hereinafter referred to as the liquid contact portion). If the roughness is rough, polymer scale tends to adhere, and if the generated scale peels and mixes into the product, the quality deteriorates (especially unprocessed material remains in the film when processed into a film, so-called fish. Causes eye (FE). In addition, when trying to prevent the adhesion of polymer scale that causes quality deterioration, it is necessary to extremely smooth the existing welding lines and to introduce special adhesion prevention / removal technology. There is an inconvenience that the cost increases.

The polymerization reaction of vinyl chloride type monomer is
Due to the corrosive nature of hydrogen chloride generated as the reaction progresses, stainless steel is usually used as the material for the inner surface of the tank container. Generally, residual stress due to welding is concentrated in the welded part of stainless steel material, and the polymerization reaction of vinyl chloride monomer is carried out using an inner jacket type tank container in which many weld lines are adjacent to the inner surface of the container. In this case, there is a concern of stress corrosion cracking due to hydrogen chloride (chlorine ion) generated as the reaction progresses. Therefore, it is necessary to carefully and continuously inspect the degree of deterioration of the welding line, which causes inconvenience that maintenance is complicated and inspection cost increases.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a vinyl chloride polymer with high quality and high productivity by using a tank container which has the advantages of the inner jacket method and solves the disadvantages thereof. The object is to provide a method which can be manufactured, and such an object can be achieved by using a specific tank container.

[0008]

The summary of the present invention is as follows.
The partition plates are arranged side by side at a right angle to the back surface of the inner plate, and the outer strip is laid across the tip of the partition plate, so that the heat separated by the partition plate between the inner plate and the outer strip. Polymerization of vinyl chloride monomer in an aqueous medium is performed in a tank container having a structure in which a channel wall having a medium channel is formed and the channel wall is fixed to the inner surface of the container body with an outer strip. Exist in.

<Bath container> Bath container body As a bath container that can be used in the method of the present invention, for example, those described in JP-A-4-141223 can be used. That is, as shown in FIGS. 1 to 3, the inner plate 6
By arranging the partition plates 7 at a right angle to the back surface of the partition plate and arranging the outer strip 8 between the tips of the partition plates 7,
Flow path wall (hereinafter referred to as "temperature control element") 5A (5B) having a heat medium flow path 9 (9 ₁ , 9 ₂ ) partitioned by a partition plate 7 between the inner plate 6 and the outer strip 8 And the flow path wall 5A (5B) is contacted with the inner surface of the container body 1 by the outer strip 8, that is, the heat exchange target material.
The one fixed to the inner surface of the body portion 2 and the bottom mirror surface plate 3 (if necessary) can be used. (Hereinafter, a tank container of such a system is referred to as a "temperature control element system tank container".)

The temperature control element 5A (5B) is fixed by, for example, fixing a lug provided on the temperature control element or by direct welding (continuous or intermittent) to the upper end of the temperature control element as shown in FIG. It is connected to the cylindrical body portion 2 as shown, and the lower end thereof is connected to the bottom mirror plate 3 around the tank container nozzle 12 as shown in FIG. 2B or the tank container nozzle 12 as shown in FIG. Just go.

When stirring is performed from the lower part of the tank container, a stirring shaft is often installed at a position corresponding to the tank container nozzle 12 in FIG. 1 and the like, but in this case also, the bottom mirror plate 3 around the stirring shaft is provided. The lower end of the temperature control element may be connected and fixed.
The shape of the flow path of the heat medium in the temperature control element 5A (5B) is not particularly limited, and may be a spiral shape in the vertical direction as shown in FIG. 1 or as shown in FIG. May have a spiral shape, and the body portion of the container body may meander in the circumferential direction. As the heat medium flowing in the flow path, steam, hot water or the like is used for heating, normal temperature water such as industrial water for cooling, water cooled by a separate refrigerator, refrigerant such as ethylene glycol, CFC, etc. The low-temperature boiling point refrigerant and the like can be used, but are not particularly limited.

The thickness of the inner plate 6 depends on the distance between the partition plates 7 from the viewpoint of strength, but the partition plate 7 is larger than the body length of the container body 1.
Since the distance between the two is small, the plate thickness of the inner plate 6 can be made small. As described above, the material of the inner plate 6 is made of stainless steel (solid stainless steel, stainless steel / carbon steel clad material, etc., especially SUS316L in consideration of the corrosion resistance of the liquid contact portion with the reaction mixture of vinyl chloride-based monomer. However, the material is not particularly limited as long as it is a material having resistance to stress corrosion cracking due to chlorine ions.

The surface of the inner plate 6 is preferably smooth, and in order to smooth the surface, methods such as buffing and electropolishing which are usually carried out industrially can be used without particular limitation. it can. The surface roughness is Rmax.
It is usually 10 μm or less, preferably 3 μm or less, more preferably 1 μm or less. Rmax is measured by JISB
The method specified in 0601 may be used.

Auxiliary Equipment for Tank Container The shape of the stirring blades, baffles, etc., which are the auxiliary equipment of the tank container (polymerization tank) used in the method of the present invention, is not particularly limited, and the conventional suspension polymerization method and emulsion weight method are used. In the legal method or the fine suspension polymerization method, generally used facilities and equipment can be used.

<Polymerization Formulation> As a polymerization method of the vinyl chloride type monomer in an aqueous medium, there are generally a suspension polymerization method, an emulsion polymerization method and a fine suspension polymerization method. Suspension polymerization of vinyl chloride-based monomers is usually carried out by polymerizing vinyl chloride-based monomers in an aqueous medium containing a dispersant in the presence of an oil-soluble polymerization initiator. Emulsion polymerization of vinyl chloride-based monomer, vinyl chloride-based monomer in an aqueous medium in the presence of an emulsifier and a water-soluble polymerization initiator, fine suspension polymerization, vinyl chloride-based monomer It is carried out by homogenizing and polymerizing in the presence of an emulsifier and an oil-soluble polymerization initiator in an aqueous medium.

Monomers The vinyl chloride monomer used in the method of the present invention includes vinyl chloride monomers alone and a mixture of copolymerizable monomers mainly composed of vinyl chloride monomers. As the other monomer copolymerizable with the vinyl chloride monomer, those generally used in the related art can be used and are not particularly limited. Examples of the above-mentioned other monomers include vinyl acetates such as vinyl acetate, vinyl propionate and vinyl stearate, alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, octyl vinyl ether, lauryl vinyl ether and cetyl vinyl ether, ethylene and the like. Α-olefins, acrylic acid,
Mono-unsaturated acids such as methacrylic acid, alkyl esters such as methyl esters of these mono-unsaturated acids, di-unsaturated acids such as maleic acid, fumaric acid, itaconic acid, etc. of these di-unsaturated acids Examples thereof include alkyl esters, vinylidene compounds such as vinylidene chloride, unsaturated nitriles such as acrylonitrile, and mixtures of two or more thereof. These other monomers are usually vinyl chloride monomers,
It is used in a proportion of 30% by weight or less, preferably 20% by weight or less, but there is no particular limitation.

Dispersant The dispersant that can be used in the method of the present invention is not particularly limited, and may be one that has been generally used in the suspension polymerization method of vinyl chloride-based monomers. Examples of the dispersant include partially saponified polyvinyl acetate (so-called polyvinyl alcohol), cellulose derivatives such as hydroxypropylmethyl cellulose, and water-soluble polymers such as gelatin. In addition, anionic surfactants such as sodium lauryl sulfate and nonionic surfactants such as sorbitan fatty acid esters and glycerin fatty acid esters may be used as a dispersion aid. These dispersants or dispersion aids can be used alone or in combination of two or more. The amount of these dispersants used is not particularly limited, and its type, stirring strength, polymerization temperature,
Although it may be slightly different depending on the kind and composition of other monomers to be copolymerized with the vinyl chloride monomer, the particle size of the intended vinyl chloride polymer, etc., it is generally 0 with respect to the total amount of the vinyl chloride monomer. It is used in the range of 0.001 to 2% by weight, preferably 0.03 to 1% by weight.

Emulsifiers Examples of emulsifiers used in the emulsion polymerization method and the fine suspension polymerization method include higher alcohol sulfate ester salts (alkali metal salts and ammonium salts), alkylbenzene sulfonates (alkali metal salts and ammonium salts), and higher salts. Examples include fatty acid salts (alkali metal salts, ammonium salts) and other anionic surfactants, nonionic surfactants, and / or cationic surfactants. These surfactants may be used alone or in combination of two or more. The amount of the emulsifier used is usually 0.1 to 3% by weight (preferably 0.3 to 1% by weight) based on the vinyl chloride-based monomer, but is not particularly limited. Further, these emulsifiers may be added after the completion of the polymerization reaction, separately from the emulsifier for polymerization.

Polymerization Initiator The polymerization initiator used in the method of the present invention is not particularly limited and may be one that has been conventionally used generally in each polymerization method of vinyl chloride monomers. Examples of the polymerization initiator used in the suspension polymerization method include t-butylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-hexylperoxyneodecanoate and α-quan. Perester compounds such as milperoxy neodecanoate, diacyl or dialkyl peroxide compounds such as dilauroyl peroxide, diisopropyl peroxydicarbonate, di-2
Examples include percarbonate compounds such as ethylhexyl peroxydicarbonate, azo compounds such as azobis (2,4-dimethylvaleronitrile) and azobisisobutyronitrile. These polymerization initiators can be used alone or in combination of two or more. Although the amount of the polymerization initiator used varies depending on the type of the initiator, the polymerization temperature, the desired reaction time, etc., it is generally in the range of 0.01 to 1% by weight based on the total amount of the vinyl chloride monomer.

The polymerization initiator used in the emulsion polymerization method is a water-soluble peroxide such as persulfate (sodium salt, potassium salt, ammonium salt), hydrogen peroxide, or the like. Examples of the water-soluble redox-based initiators include a combination of a water-soluble reducing agent (eg, sodium sulfite, sodium pyrosulfite, sodium bisulfite, ascorbic acid, sodium formaldehyde sulfoxylate, etc.).

The polymerization initiator used in the fine suspension polymerization method is azobisisobutyronitrile or azobis (2,4-
Dimethyl valeronitrile), lauroyl peroxide,
Examples thereof include a monomer-soluble (oil-soluble) initiator such as t-butylperoxypivalate, or a redox-based initiator composed of a combination of these oil-soluble initiators and the above water-soluble reducing agent.

Other auxiliaries Further, in the method of the present invention, if necessary, a polymerization degree adjusting agent (chain transfer agent, crosslinking agent) used for the polymerization of vinyl chloride-based monomers, an antioxidant, a pH Various polymerization aids such as regulators and activators of redox type initiators can be appropriately added, and the charging amount of each of these components is generally the same as that conventionally used for polymerization of vinyl chloride monomers. It does not matter under normal conditions.

As the degree-of-polymerization regulator used for the polymerization of vinyl chloride-based monomers, trichlorethylene, carbon tetrachloride, chain transfer agents such as 2-mercaptoethanol and octylmercaptan, diallyl phthalate and triallyl isocyanurate. Examples thereof include cross-linking agents such as ethylene glycol diacrylate and trimethylolpropane trimethacrylate.

<Polymerization Method> Charge Method When carrying out the method of the present invention, an aqueous medium, a vinyl chloride monomer, a polymerization initiator, a dispersant in a suspension polymerization method, an emulsion polymerization method, or the like is added to a polymerization vessel (tank vessel). The charging ratio of the emulsifier and other various polymerization aids in the fine suspension polymerization method, and the charging method are not particularly limited.

Polymerization temperature : The polymerization temperature employed in the method of the present invention includes the type of polymerization initiator used, the polymerization method, the presence or absence of a polymerization degree modifier,
Generally, it varies from 0 to, although it varies depending on the target degree of polymerization and the like.
90 ° C., especially 40 to 70 ° C. is often used.
Further, in the reaction, even if the polymerization is carried out at a constant temperature,
Alternatively, the polymerization temperature may be changed during the polymerization. Polymerization Termination Method In the method of the present invention, examples of a method of terminating the polymerization reaction include a method of adding a so-called polymerization inhibitor or a polymerization terminator, a method of recovering unreacted monomers from a polymerization tank, and the like.

<Post-Treatment Method> The operations of dehydrating and drying the slurry of the vinyl chloride polymer produced by the suspension polymerization method are generally performed such as centrifugal dehydration and fluidized drying.
Drying means may be used without any particular limitation. Operations such as drying of the latex of the vinyl chloride polymer produced by the emulsion polymerization method and the fine suspension polymerization method can be performed by spray drying using a conventionally used rotating disk or a spray nozzle such as a two-fluid nozzle. Means may be used without any particular limitation. Before the drying treatment, part of the water content in the latex may be removed in advance to increase the concentration of the vinyl chloride polymer in the latex, or the concentration operation may be performed. You can go.

[0027]

EXAMPLES Next, specific embodiments of the method of the present invention will be described with reference to Examples, but the present invention is not limited as long as the gist thereof is not exceeded.
The present invention is not limited to the examples below. Example 1 With an internal volume of 400 liters, the inner wall of the vessel (that is, the surface of the inner plate of the temperature control element) was electrolytically polished to Rmax1.
100 kg of vinyl chloride monomer, 150 kg of deionized water, 60 g of partially saponified polyvinyl acetate as a dispersant, and dioctyl peneoxydicarbonate as an initiator in a stainless steel temperature control element type tank container with a stirrer of about 2 μm. After charging 40 g, warm water was circulated through the temperature control element and heated to 57 ° C. to start polymerization. Polymerization was carried out while maintaining this temperature until a predetermined polymerization rate was reached.
Then, unreacted vinyl chloride monomer was recovered, the produced slurry was extracted, ventilated, and the tank container was opened to observe the scale adhesion state to the inner wall of the tank container. After observing the scale adhering condition, the inner wall of the tank container was washed with low-pressure ion-exchanged water, and the next batch test up to 5 batches was repeated under the same conditions. The results are shown in Table 1.

Comparative Example 1 A vinyl chloride monomer was polymerized under the same conditions as in Example 1 except that the tank container was of the internal jacket type, and the same evaluation was carried out. The results are shown in Table-1.

[0029]

[Table 1] Criteria: ◯: Adhered to the inner wall of less than 10% of the total surface area Δ: Adhered to the inner wall of 10% or more and less than 50% of the total surface area ×: Adhered to the inner wall of 50% or more of the total surface area

[0030]

EFFECTS OF THE INVENTION By polymerizing vinyl chloride-based monomers using a temperature control element type vessel, the thickness of the plate separating the heat medium from the contents during the polymerization can be reduced as in the internal jacket method. Since it can be made thin, the heat conductivity is excellent, the heat of polymerization can be efficiently removed, and the vinyl chloride polymer can be produced with high productivity. Further, in the method of the present invention, since the proportion of the welded portion occupying the inner surface of the tank container is small, adhesion and production of polymer scale is reduced, and the quality of the obtained product is good.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an example of a tank container used for carrying out the method of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a vertical cross-sectional view showing another example of a tank container used for carrying out the method of the present invention.

FIG. 4 is a vertical cross-sectional view showing an example of a conventional tank container.

FIG. 5 is an enlarged vertical sectional view of an essential part showing another example of a conventional tank container.

[Explanation of symbols]

 1 Container Main Body 2 Cylindrical Body 3 Bottom Mirror Surface Plate 4 Top Mirror Surface Plate 5A Channel Wall 5B Channel Wall 6 Inner Plate 7 Partition Plate 8 Outer Strip 9 Channel 10 Heat Medium Inlet 11 Heat Medium Outlet 12 Tank Container Nozzle

Claims (4)

[Claims] 1. When polymerizing vinyl chloride or a mixture of vinyl chloride-based copolymerizable monomers in an aqueous medium, the polymerization is performed with a partition plate spaced at right angles to the back surface of the inner plate. By arranging them side by side and straddling the outer strip between the tips of the partition plates, a flow channel wall having a heat medium flow channel partitioned by the partition plate is formed between the inner plate and the outer strip. A method for producing a vinyl chloride polymer, which is carried out in a tank container having a structure in which a channel wall is fixed to an inner surface of a container body by an outer strip. 2. The method for producing a vinyl chloride polymer according to claim 1, wherein the polymerization is carried out in a tank container in which the channel wall is adhered and fixed to the inner surface of the container body with an outer strip. 3. The production of a vinyl chloride polymer according to claim 1 or 2, wherein the flow path wall has a spiral shape and the polymerization is carried out in a tank container fixed to the inner surface of the body and the bottom mirror surface plate of the container body. Method. 4. A flow passage wall spirally provided on the inner surface of the bottom mirror surface plate portion of the container body, and spirally meandering on the inner surface of the body portion of the container body connected to the bottom mirror surface plate portion. The method for producing a vinyl chloride polymer according to claim 1 or 2, wherein the polymerization is carried out in a tank container in which is fixed.