JPS6025044B2 - Method for producing vinyl chloride polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to vinyl chloride alone or a monomer composite of vinyl chloride and a monomer copolymerizable with vinyl chloride (hereinafter collectively referred to as vinyl chloride monomer). .

) (hereinafter collectively referred to as vinyl chloride polymers) by suspension polymerization. The purpose is to industrially advantageously produce a finely powdered vinyl chloride polymer with a narrow particle size distribution and a high specific gravity by a suspension polymerization method.

Conventionally, when vinyl chloride polymers are manufactured by suspension polymerization, powdered vinyl chloride polymers suitable for extrusion, injection, or calendar molding, regardless of whether the polymer is a hard type or a soft type, are used. The particle size of the polymer is generally widely distributed between 80 and 250A.

In accordance with this, a wide range of high specific gravity values are also adopted. When a powdered polymer having such a particle size range is used for the above-mentioned appropriate purpose, it can be made into pellets and subjected to molding, so there are no major problems with particle size distribution or bulk specific gravity. However, powdered vinyl chloride polymers obtained by suspension polymerization with an average particle size of less than 100 μm can be used in powder coatings, hot melt adhesives, paste vinyl chloride resins or their extenders, and pigments. When used as a dispersion aid, etc., it is required that the particle size distribution is not too wide and that the specific gravity is a powder particle for the following reasons. In other words, from a production standpoint, the suspension polymerization method is essentially more advantageous than the emulsion polymerization method, and has industrial advantages in dehydration treatment by centrifugation, cyclone treatment in the drying process, and conservation treatment. This is because it allows a process to be adopted, and on the other hand, from an application standpoint, it gives good results in terms of ease of management of processing steps, recovery rate of powder, stability of product quality, etc. The present inventors have conducted intensive studies to obtain a polymer that satisfies these requirements, that is, a vinyl chloride polymer having a narrow particle size distribution and a fine particle size with a high specific gravity by suspension polymerization. The present invention was completed by discovering that a vinyl chloride polymer that achieves the object of the present invention can be obtained by a polymerization method that is a leap forward from the conventional suspension polymerization method.

That is, in the present invention, when carrying out suspension polymerization of vinyl chloride alone or a monomer polymer of vinyl chloride and a monomer copolymerizable with vinyl chloride, the liquid phase is formed in the interior space of the polymerization vessel. Polymerization is performed by supplying raw materials in an amount accounting for ~95 vol%, and the polymerization conversion rate is reached to 10% within a time of 90 to 240 minutes after the start of the polymerization, and the polymerization after reaching that point is This is a method for producing a vinyl chloride polymer, characterized in that the liquid phase in the vessel is maintained at 97 vol% or more of the internal space of the polymerization vessel.

In the present invention, during suspension polymerization, the first condition is that the liquid phase in the polymerization vessel after the polymerization conversion rate reaches 10% is
It is necessary to maintain it at 97 vol% or more of the internal space of the polymerization vessel.

In particular, a so-called full-liquid state in which there is substantially no gas phase within the polymerization vessel is most preferred. If the proportion of the gas phase is large, the particle morphology of the obtained polymer will not be uniform, resulting in particles that do not exhibit a spherical shape, a powder with a high specific gravity and a low specific gravity, and particles with a wide particle size distribution. Unable to achieve purpose. If the amount of raw materials supplied to the polymerization reactor is at or close to full from the beginning, it may be difficult to operate due to volume expansion when the temperature rises, whereas if it is too small, a large proportion of water will need to be added later. Since this reduces productivity and makes it difficult to obtain the desired polymer of the present invention, the initial amount of raw materials charged is set to 85 to 95 vol% of the internal space of the polymerization vessel.

In addition to the above-mentioned first condition, the present invention also requires the following second condition. That is, a vinyl chloride monomer, a polymerization catalyst,
It is an essential condition that the raw materials consisting of a suspending agent, other desired additive components, and water are added, and that the polymerization conversion rate is reached to 10% within 90 to 240 minutes after the start of mixing. If this condition is not satisfied and the reaction time is shorter than 9 minutes, coarse particle polymers tend to be produced, while if the reaction time exceeds 240 minutes, the polymerization yield decreases, and both are inappropriate. A more preferable time period for this polymerization conversion to reach 10% is 10%.
It is 0 to 200 minutes. The reason why the purpose of the present invention can be achieved by satisfying the above conditions is that the generation rate of primary particles, which serve as seeds for the formation of fine particles, is better to be low, and that This is understood to be because the agglomeration of primary particles that occurs in the process is avoided.

In the suspension polymerization according to the present invention, it is sufficient to follow normal suspension polymerization operations, except that the above-mentioned specific conditions are required to be met. As the suspending agent, conventionally known suspending agents such as partially saponified polyvinyl alcohol, methylcellulose, hydroxymethylcellulose, copolymer of vinyl acetate and maleic acid, gelatin, starch, etc. can be used.

The amount used may be the amount normally used, but especially 0.08 to 2.0 parts by weight per 100 parts by weight of the vinyl chloride monomer. It is desirable to use parts by weight of . The simultaneous use of an oil port emulsifier such as a higher alcohol, a higher fatty acid, or a partial ester compound of a higher fatty acid and a polyhydric alcohol such as glycerin or sorbitan together with a suspending agent may impart porosity to the polymer particles. desirable.

Examples of polymerization catalysts include benzoyl peroxide, lauroyl/gu-oxide, and diisopropylene.

Organic peroxides such as pill/guichi oxydicarbonate and di-2-ethylhexyl peroxydicarbonate, Q.Q.
Examples include azo compounds such as '-dimethylvaleronitrile, Q.Q'-azobisisoputilonitrile, and the like. In addition, monomers that can be copolymerized with vinyl chloride include:
Examples include vinyl ester, pinylether, acrylic ester, vinyl ketone, vinylidene halide, and monoolefin monomer.

The amount of this copolymerizable monomer used is less than 50 mol % based on the vinyl chloride monomer. In the present invention, as mentioned above, it is particularly necessary to reduce the gas phase portion during the polymerization reaction and to control the time required from the time when the raw materials are mixed and the time when the polymerization conversion rate reaches 10%. Regarding the former, it is preferable to replenish the amount of pure water equivalent to the volume reduction of the liquid phase due to the reaction during the polymerization reaction to constantly keep the inside of the polymerization reactor full of liquid. Regarding the latter, it may be adjusted as appropriate depending on the heating time until a predetermined polymerization temperature is reached, the type of catalyst used, or the amount used. Next, an embodiment of the present invention will be explained using FIG. Raw materials such as a vinyl chloride monomer, water, a suspending agent, and a polymerization initiator are supplied through a raw material common feed pipe 10 to a polymerization vessel 1 equipped with a jacket 8 for heating or cooling. The polymerization vessel has a chamber on the top thereof equipped with a cooling jacket 9, a nitrogen pressure control valve 4, a pressure gauge 7, and a liquid level bell gauge 6.
3, and a gas phase exists in the upper part of the chamber. A regulating valve 5 is provided at the connection between the polymerization vessel and the chamber to control the amount of water supplied.

Since the liquid phase inside the chamber is water and does not participate in the polymerization reaction itself, the space inside the chamber is not included in the volume of the interior space of the polymerization vessel as referred to in the present invention. After supplying the raw materials so that a gas phase remains inside the polymerization reactor, the raw materials are heated to a predetermined temperature (e.g., ℃) while being roped using the rope-strengthening machine 2, and then heated within a time period of 90 to 24 years after the start of the polymerization. At the same time, the polymerization conversion rate reached 10% and water was added to make it full. Thereafter, the polymerization reaction is continued until a predetermined polymerization conversion rate is reached while replenishing water that has decreased in volume due to the progress of polymerization.

When the polymerization is completed, the suspension is extracted from the suspension extraction tube 11. According to the present invention, a finely powdered vinyl chloride polymer having a narrow particle size distribution and a large bulk specific gravity can be produced industrially easily and advantageously.

These effects of the present invention can be further enhanced by taking measures to prevent scale formation and adhesion due to polymerization reactions. Such means include known scale prevention techniques, such as applying a compound such as a polar compound or a polymerization inhibitor to the entire internal surface of the polymerization vessel and associated equipment;
Alternatively, a method of introducing these compounds into a polymerization system, or a method of using both together can be mentioned. The present invention will be explained in more detail below by giving Examples and Comparative Examples. still,
The percentages stated below mean percentages by weight. Further, the powder characteristics of the powdered vinyl chloride polymer obtained in each example were measured by the following method.

m Particle size distribution: The diameter of the particles was measured using a transmission electron microscope, and the distribution was observed.

(2) High specific gravity: The bulk specific gravity measurement method of JIS K6721 was followed.

{3' Plasticizer absorption: Add 10 parts of vinyl chloride polymer and 20 parts of dioctyl phthalate (DOP), and after leaving it for 1 hour, separate and remove unabsorbed DOP with a centrifuge to determine the amount of DOP absorbed by the polymer. is expressed as a percentage of the vinyl chloride polymer.

Example 1 Suspension polymerization was carried out by adding pure water to the polymerization system during the polymerization reaction using a polymerization vessel as shown in FIG.

The size of the polymerization vessel is 1200 mm in diameter and 240 mm in internal volume.
The volume of the chamber, which is connected to the polymerization vessel, has a gas phase part, and maintains a state in which the polymerization reaction does not substantially occur through cooling, is 150 mm. An 8% orthophosphoric acid aqueous solution was sprayed on the surface as a coating type scale inhibitor.

After about 30 minutes, the inside of the polymerization vessel was thoroughly washed with water.
Next, 5k9 made of vinyl chloride monomer, 1121k pure water
9. Partial saponification with a degree of saponification of 77% and an average degree of polymerization of 900, VA (polyvinyl alcohol) 1890 ml, and 2-ethylhexyl peroxydicarbonate 426 ml were added. occupied.
Thereafter, the temperature was increased linearly to 9°C under the heat of 16 pm. During this time, pure water was replenished so that the gas phase was filled with liquid to 10 ol % when the stripe raising was completed. After that, while replenishing pure water, the polymerization reaction continued in a full liquid state.
The operation was carried out at $°C for 8 hours, and the polymerization conversion rate was 84.3%. The obtained reaction suspension was dehydrated by centrifugation,
A finely powdered vinyl chloride polymer was obtained by fluidized drying. Table 1 shows the powder properties of this polymer. The polymerization conversion rate at each time point was determined from the volume reduction rate of the reaction suspension (ie, the amount of pure water supplied). The test results obtained are listed in Table 1. Examples 2 to 7 and Comparative Example 1 Polymerization was carried out under the same polymerization conditions as in Example 1, except that the type and amount of the catalyst used in Example 1 and the heating time after charging the raw materials were changed.

The results of these tests are shown in Table 1.

Comparative Example 2 In Example 1, water replenishment was stopped after the completion of temperature rise, and the other polymerization conditions were exactly the same as in Example 1.

The test results obtained are listed in Table 1.

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[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a polymerization apparatus used in the method for producing a vinyl chloride polymer of the present invention. 1...Polymerization vessel, 3...Chamber, 4
...Nitrogen pressure control valve, 5...Water replenishment amount adjustment valve, 7...Chamber pressure gauge, 8...
...Heating or cooling jacket for polymerization vessel, 10...
... Raw material supply pipe, 11... Reaction suspension extraction pipe.

Claims (1)

[Claims] 1. When carrying out suspension polymerization of vinyl chloride alone or a monomer mixture of vinyl chloride and a monomer copolymerizable with vinyl chloride, the liquid phase is located between 85 and 95 mm in the internal space of the polymerization vessel.
Polymerization is performed under stirring by supplying raw materials in an amount accounting for vol%, and the polymerization conversion rate reaches 10% within 90 to 240 minutes after the start of stirring, and after reaching the polymerization conversion rate, the liquid phase in the polymerization vessel A method for producing a vinyl chloride polymer, characterized in that the amount of vinyl chloride is maintained at 97 vol % or more in the internal space of a polymerization vessel.