JPH0768288B2 - Polymerization reactor for the production of vinyl chloride polymers - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polymerization reactor for producing a vinyl chloride polymer, and more particularly to a new polymerization reactor capable of enhancing the quality of polyvinyl chloride produced.

<< Prior art and its problems >> In known polymerization reactions such as suspension polymerization, emulsion polymerization, fine particle suspension polymerization and solution polymerization for the production of vinyl chloride polymer or copolymer, in the prior art, Reactors with one stirring shaft located at the top or bottom of the reactor are used. The stirring shaft has one or more stirring blades and can generate a uniform mixture. Suitable stirring rotors used for polymerization of vinyl chloride monomer include paddle type (vertical blades, inclined blades), turbine type (vertical blades, inclined blades, bent blades), powdera type, bull margin type, etc. . These conventional reactors are equipped with baffles to enhance convection and circulation functions. However, because of friction and energy loss between the reactor wall and the flow of the mixture,
Increase energy consumption. Furthermore, conventional stirring mechanisms adversely affect turbulence and mixing effects within the reactor.
That is, turbulence occurs only in certain areas of the reactor. Therefore, the reactants do not mix uniformly and cannot produce high quality PVC.

The obstacles that occur with polyvinyl chloride processing are many spots (fish eyes) and porosity that degrades quality. Due to these imperfections, the final product produced has drawbacks such as spots and brittleness. Recovery of unreacted vinyl chloride monomer is extremely difficult during the manufacturing process.

In order to overcome the above-mentioned drawbacks, special dispersants have been added to the reactor or appropriate stirring mechanisms and effective VCM stripping techniques have been used with the polymerization reactor. However, the conventional stirring mechanism structure sprays PVC onto the top of the polymerization reactor, and the contact between the dispersant, vinyl chloride monomer, water and polyvinyl chloride is direct.
Therefore, the effect of the conventional stirring mechanism is poor, and the generated PVC
Has spots and is inferior in appearance.

In the polymerization method for producing a vinyl chloride polymer, the reaction yield can be actually improved by shortening the reaction temperature reaching time, the reaction material addition time and the reaction completion time. Japanese Kokai 54-47785 discloses adding a dispersant and water to a reactor at 30 ° C. with stirring, followed by hot deionized water. The particle size distribution is irregular due to the non-uniform contact between the hot deionized water, the dispersant, the catalyst and the vinyl chloride monomer. To avoid the non-uniform phenomenon,
The addition time of hot deionized water should be long. However, this takes time to raise the temperature, increases the amount of scale produced and reduces the effectiveness of this method.

<Outline of the Invention> A main object of the present invention is to provide a polymerization reactor for producing a vinyl chloride polymer. The polymerization reactor of the present invention is
It is suitable for use in conventional polymerization reactions such as suspension polymerization, emulsion polymerization and solution polymerization. The reactor of the present invention overcomes the drawbacks of the prior art.

Another object of the invention is to eliminate the use of baffles in the polymerization reactor. Since the baffles located in the polymerization reactor are unnecessary, the reactor increases convection between up and down flow, eliminates blind spots and reduces impingement forces between the reactants and the polymerization reactor. Therefore, the scale produced is significantly reduced.

Another object of the present invention is to provide a new polymerization reactor for the production of vinyl chloride polymers, which actually reduces the temperature rise time of the polymerization reactor.

Other objects and advantages of the present invention will be apparent from the following description and the accompanying drawings.

<< Example >> FIG. 1 is a schematic front view of a cross section of a polymerization reactor showing a preferred embodiment of the present invention.

Referring to FIG. 1, the polymerization reactor comprises a reaction vessel 1 and two stirring shafts 2, 3, one end of the first shaft 2 is fixed to the upper part of the reaction vessel 1, One end of the shaft 3 is fixed to the bottom of the reaction container 1. The axes 2 and 3 are parallel to the vertical axis of the reaction vessel 1. The ratio of the distance between the stirring shafts 2 and 3 to the inner diameter of the reaction vessel 1 is 0.1 to 0.8, and more preferably 0.25 to 0.50. Two stirring rotors 4,5
One of the four is fixed to the other end of the shaft 2 and the other one 5 is fixed to the other end of the shaft 3 so as to be rotatable together with the shaft, and they rotate in opposite directions so as to obtain the maximum flow velocity. Therefore, the blind spots and boundaries that occur in the reaction vessel 1 disappear while the stirring is being performed. The ratio of the diameter of the stirring rotary blade to the inner diameter of the reaction vessel 1 is 0.1 to 0.5, more preferably 0.2 to 0.4.
The reaction vessel 1 is further equipped with a heating jacket 6 if desired.

The polymerization reactor of the present invention is a conventional polymerization reaction for producing vinyl chloride polymer or copolymer, such as suspension polymerization, emulsion polymerization,
It can be commonly used for fine particle suspension polymerization and solution polymerization. In suspension polymerization, suitable antimixtures for use are vinyl chloride monomer, its copolymers and deionized water. Generally, the ratio of vinyl chloride monomer to deionized water is 25-100%. Monomer is vinyl chloride alone,
Alternatively, it may be a copolymer containing 50% of copolymerized monomer and vinyl chloride monomer. Examples of such copolymerized monomers include aliphatic vinyl acid (vinyl acetate); alkyl acrylate (methyl acrylate or ethyl ester); vinylidene halide (vinylidene chloride); acrylonitrile; alkyl isocrotonate (isocrotonic acid methyl ester). ); Ethylene; propylene; malonic acid and butadiene which may be used alone or in a mixed form. The amount of dispersant is about 0.01 to 10%, preferably about 0.04 to 2%, based on the weight of vinyl chloride monomer used. Examples of dispersants include methyl cellulose; hydroxyethyl cellulose; hydroxypropyl cellulose; hydroxypropyl methyl cellulose; gelatin; partially saponified polyvinyl acetate; clay and talc. The amount of the polymerization initiator used in the present polymerization reactor is 0.01 to 3%, preferably 0.03 to 1% based on the weight of the vinyl chloride monomer. Examples of oil-soluble initiators include azo compounds such as azo-bis-isobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile); lauryl peroxide, bis (3,5,5- Trimethylhexanoyl) -peroxide, t-butylperoxypivalate, dibenzoylperoxide, acetylcyclohexylsulfonyl peroxide, bis (2-ethylhexyl) peroxydicarbonate and bis (4-t-butylcyclohexyl)
Peroxides such as peroxydicarbonates may be mentioned. The above compounds are added to the reactor at a constant temperature or high temperature before the reaction is started, or after the reaction is started by a continuous metering pump. Suitably, the reaction temperature is 20-80 ° C and the effective reaction time is 2-20 hours. The emulsification method is also carried out using the present polymerization vessel. The reactants and reaction conditions used in the emulsification method are the same as in the suspension method, but an emulsifier is used in place of the dispersant, and a water-soluble, oil-soluble or redox polymerization initiator is used. Examples of suitable emulsifiers are carboxylic acid alkyl esters; sulfuric acid alkyl esters; phosphoric acid alkyl esters; sulfosuccinic acid dialkyl esters; benzenesulfonic acid alkyl esters; and polyoxyethylene alkyl ether sulfates. The amount of emulsifier is 0.1 to 10%, preferably 0.2 to 3%, based on the weight of vinyl chloride monomer used. Examples of water-soluble polymerization initiators are sodium persulfate; potassium persulfate: ammonium persulfate; ammonium persulfate and hydrogen peroxide. Examples of redox initiators are alkali metal persulfates; alkali metal sulfites; thiosulfates and bisulfites; eg S ₂ O ₈ ^-2 + Fe ⁺² and S ₂ O ₈ ^-2 + S ₂ O ₃ ^-2 or
^{_{HSO 3 -, SO 3 -2,}} S 2 O 3 -2, S 2 O 5 -2 and Cu ^+2, ClO ₃ ^- is and reaction products of H ₂ O _2. In addition to the above polymerizations, particulate suspension polymerizations and solution polymerizations can also be used in the present invention.

The polymerization reactor of the present invention is illustrated by the following example.
The examples do not limit the scope of the invention in any way,
It should not be so interpreted.

Examples 1 to 8 In all cases, the polymerization reactor shown in FIG. 1 was used. The polymerization reactor used in this example has a capacity of 30 liters, and its dimensional relationship is shown in Table 1. When carrying out the polymerization, 16.6 kg of deionized water containing a suspending agent and a polymerization initiator (the components of which are shown in Table 2) were placed in the polymerization reactor. The internal pressure of the reactor was lowered to 100 mm Hgabs, and 8.3 kg of vinyl chloride monomer was further added to the polymerization reactor using nitrogen gas. The mixture in the polymerization reactor was stirred for 10 minutes, and hot water was passed through the heating jacket of the reactor to heat the reactor to a reaction temperature of 58 ° C. The reaction heat generated by the reaction was absorbed by the cold water passed through the heating jacket, and the reaction temperature of 58 ° C was maintained until the reaction pressure dropped to 7 kg / cm ² G. After the completion of the polymerization reaction, the pressure of the residual unreacted vinyl chloride monomer was 150 mm.
Returned to Hgabs. The resulting PVC slurry was filtered and dried, and the physical properties of the final PVC product are shown in Table 4. The reactor was washed with water and the scale was collected and weighed.

Comparative Examples 1-4 The polymerization methods and compositions of this Comparative Example were similar to those used in Examples 1-7. However, the stirring mechanism used in this comparative example is shown in Table 3. The results of these comparative examples are shown in Table 4.

Example 9 The polymerization reactor and method of this example was similar to that used in Example 1 except that the temperature of the deionized water used was 65 ° C. Among the obtained PVC powders, those having a size of more than 60 mesh accounted for 0.3% by weight of the total PVC produced. The number of spots on the final product is 15 per 100 cm ² ,
The gelation time was 30 seconds, and the amount of scale produced was 10 g / each batch.

Example 10 The polymerization method of this example is similar to that used in Example 1, but the polymerization reactor used was equipped with a reflux condenser. The heat transfer portion of this reflux condenser was similar to that of the reactor. Among the obtained PVC powders, those having a size of more than 60 mesh accounted for 0.4% by weight of the total PVC produced.
The number of specks on the final product was 30 per 100 cm ² , and the gel specific time was 24 seconds.

Comparative Example 5 The polymerization method of this Example was the same as that used in Example 9, and the stirring rotor used was the same as that of Comparative Example 1. Among the obtained PVC powders, those having a size of more than 60 mesh accounted for 0.8% by weight of the total PVC produced. The final product has a speckled number of 50 per 100 cm ² and a gel time of 46.
Seconds, the amount of scale produced was 50 g / each batch.

Comparative Example 6 The polymerization method of this Comparative Example was the same as that used in Example 10, and the stirring rotor used was the same as that of Comparative Example 1. Among the obtained PVC powders, those having a size of more than 60 mesh accounted for 1.8% by weight of the total PVC produced. The number of spots in the final product is 150 per 100 cm ² , and the gel time is 50.
It was seconds.

Example 11 The polymerization reactor and stirring mechanism used in this example were the same as those used in Example 1. Emulsion polymerization was used in this example. 4.0 kg of deionized water containing 2.5 g of sodium dodecyl sulfate, 6.0 g of sodium hydrogensulfate, and 1 kg of seed latex (0.3μ, solid content 30%) in the operation of the main polymerization
Was added to the reactor. Then, the pressure of the reactor is 150 mm Hg.
abs, add 4.3 kg of vinyl chloride monomer to the reactor,
Stir for minutes. After the temperature of the reactor reached the reaction temperature, ie 48 ° C., by passing hot water through the heating jacket, 1.0 g of ammonium persulfate was continuously added to the reactor within 4 hours. After reaction for 1 hour, the pressure in the reactor is 1kg / cm
75 g of lauric acid dissolved in 1.5 kg of water was added until it dropped to ² . After the polymerization reaction, a non-added emulsifier was further added to obtain a stable product. Table 5 shows the physical properties of the final product.

Comparative Example 7 The polymerization method and composition used was similar to that used in Example 11. The stirring mechanism used was the same as in Comparative Example 1.

Example 12 A transparent acrylic resin 20 liter reactor was equipped with various types of stirrers as shown below. The time required for mixing to be completed was measured and is shown below: Mixing mechanism Mixing time (sec) Paddle type 30.1 Powder type 18.5 Turbine type 24.6 Bull margin type 22.8 Inventive type 8.2 Example 13 Reaction used for polymerization reaction The container is shown in FIG. 1, and the dimensions of each part are shown in Table 6. The reactor volume was 30 liters. 8.31 g PVA and 3.9 g 2,2'-azobis (2,4-dimethylvaleronitrile) were charged to the reactor. The reactor pressure was evacuated and then 8.3 kg vinyl chloride monomer and 16.6 kg deionized water were added at 70 ° C. After the stirrer was started and the addition of deionized water was completed, the reactor temperature was about 57.8.
C and the reaction temperature was maintained. Reactor pressure is 60
Unreacted vinyl chloride monomer was recovered until it dropped to kg / cm ² G. Water was removed from the polyvinyl chloride slurry and dried.

Example 14 The reactor used in Example 13 was used in this example. To this reactor, 8.31 g of PVA, 3.9 g of azobisisobutyronitrile and 15.9 kg of deionized water were added at room temperature. Then the reactor was evacuated. The stirrer was started and 8.3 kg of vinyl chloride monomer was added to the reactor. At the same time, 180 ° C. steam was blown into the reactor for 3 minutes. When the temperature of the reactor reached 58.1 ° C, the polymerization reaction started. Unreacted vinyl chloride monomer was recovered until the reactor pressure dropped to 6.0 kg / cm ² G.
Water was removed from the polyvinyl chloride slurry and dried.

Comparative Example 8 The polymerization method used in this example was the same as that of Example 13, but a different stirring mechanism was used. Table 7 shows the dimensions and sizes of the stirring mechanism.

The results of the polymerization reaction are shown in Table 8.

Comparative Example 9 The polymerization method used in this example was the same as that used in Example 14, but a different stirring mechanism was used. Table 7 shows the contents and size of the stirring mechanism.

The results of the polymerization reaction are shown in Table 8.

Comparative Example 10 In this case, the reactor used in Example 13 was used. PVA8.3
1g, 2,2'-azobis (2,4-dimethylvaleronitrile)
3.9 g and 16.6 kg deionized water were added to the reactor at room temperature.
After evacuating the reactor, 8.3 g of vinyl chloride monomer was added. The stirrer was started and hot water was passed through the heating jacket of the reactor to raise the temperature until the temperature of the reactor reached 58 ° C. and maintained at this reaction temperature. Unreacted vinyl chloride monomer was recovered until the pressure dropped to 6 kg / cm ² G. Water was removed from the polyvinyl chloride slurry and dried.

Example 15 The reactor used in this case had a capacity of 200 liters. The dimensions of the reactor are shown in Table 6. PVA60 in reactor
g, 2,2'-azobis (2,4-dimethylvaleronitrile) 2
0 g and bis (2-ethylhexyl) peroxydicarbonate 8 g were added. The reactor pressure was evacuated and 62 kg of vinyl chloride monomer was added. At the same time, 90 kg of deionized water was added at 67 ° C and the stirrer was started. After the addition of deionized water was completed, the temperature of the reactor was brought to 59 ° C. and this reaction temperature was maintained until the polymerization reaction was completed and the pressure in the reactor dropped to 7 kg / cm ² G. Unreacted vinyl chloride monomer was recovered, water was removed from the polyvinyl chloride slurry and dried.

Comparative Example 11 The polymerization method used in this case was the same as that used in Example 15. The reactor volume was 200 liters. However, in this case, a different stirring mechanism is used,
The dimensions are shown in Table 7.

Comparative Example 12 The reactor used in Example 15 was used in this case. PVA6
0g, 2,2'-azobis (2,4-dimethylvaleronitrile)
20 g, bis (2-ethylhexyl) peroxydicarbonate and 90 kg deionized water were charged to the reactor at room temperature. The reactor pressure was evacuated and 62 kg of vinyl chloride monomer was added. The stirrer was started until the vinyl chloride addition was complete. Pass hot water through the heating jacket of the reactor and keep the temperature at 58 ° C.
Raised to. Polymerization reaction is completed, reactor pressure is 7kg /
This temperature was maintained until it dropped to cm ² G. Unreacted vinyl chloride monomer was recovered, polyvinyl chloride slurry was taken out, water was removed and dried.

Example 16 The reactor and stirring mechanism used in this case were similar to those used in Example 15, but emulsion polymerization was carried out instead of suspension polymerization. The reactor was charged with 5 kg of deionized water containing 18.6 g of sodium lauryl sulfate, 44.7 g of sodium dodecyl sulfate and 7.5 g of seed latex (0.3μ, 30% solids). The reactor pressure is vacuum and the vinyl chloride monomer at 60 ° C
32 kg and 20 kg deionized water were added to the reactor at the same time. After the addition was complete, the reactor temperature was 48 ° C. 7.4 g ammonium persulfate was added by a continuous flow control pump.
The injection time was about 4 hours. Further, after reacting for 1 hour, 558 g of lauric acid was added. The reaction pressure was reduced to about 1 kg / cm ² G, and the reaction was completed.

Comparative Example 13 The polymerization method in this case was the same as that used in Example 16, but a different stirring mechanism was used. The dimensions of the stirrer are shown in Table 7.

Comparative Example 14 In this case, the reactor used in Example 16 was used, but the amount of deionized water at room temperature was 25 kg. In this example, 60 ° C
No deionized water was used. After the addition of vinyl chloride monomer was complete, hot water was passed through the heating jacket of the reactor. The rest of this step was performed as in Example 5.

[Brief description of drawings]

FIG. 1 is a schematic front view of a cross section of a polymerization reactor showing a preferred embodiment of the present invention. 1 …… Reaction container 2,3 …… Stirring shaft 4,5 …… Stirring rotor

Claims (7)

[Claims] 1. A reaction vessel having a predetermined diameter is provided,
A stirring mechanism is disposed in the reaction vessel, and the stirring mechanism has two stirring shafts, and the upper end of the first stirring shaft of the two stirring shafts is disposed above the reaction vessel. The second stirring shaft extends downward from the lower end of the second stirring shaft, and the lower end of the second stirring shaft is arranged at the bottom of the reaction vessel and extends upward from the lower end of the second stirring shaft in parallel with the first stirring shaft. A first stirring rotor is rotatably disposed on the upper end of the second stirring shaft, and both stirring rotors are rotated in opposite directions. The polymerization reactor for producing a vinyl chloride polymer, wherein the distance between each stirring rotary blade and the lowest point on the bottom surface of the reaction vessel is different. 2. The polymerization reactor according to claim 1, wherein the ratio of the diameter of the stirring rotor to the diameter of the reaction vessel is 0.10 to 0.50. 3. The polymerization reactor according to claim 1, wherein the ratio of the distance between the two stirring shafts to the diameter of the reaction vessel is 0.20 to 0.70. 4. The ratio of the lowest point of the bottom surface of the reaction vessel and the distance between the bottom of the reaction vessel and one of the stirring rotors to the height of the packing is 0.05 to.
The polymerization reactor according to claim 1, which is 0.50. 5. The polymerization reactor according to claim 4, wherein the ratio is 0.20 to 0.40. 6. The ratio of the lowest point of the bottom of the reaction vessel and the distance between the lowest point of the stirring vessel and the other one of the stirring rotors to the height of the packing is 0.
The polymerization reactor according to claim 1, which is 50 to 0.80. 7. The polymerization reactor according to claim 6, wherein the ratio is 0.50 to 0.60.