JPS6025043B2 - Method for producing vinyl chloride polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adding a polymerization initiator when vinyl chloride or a mixture of vinyl chloride and other monomers polymerizable therewith is polymerized in an aqueous medium.

When vinyl chloride or a mixture of vinyl chloride and other monomers copolymerizable with vinyl chloride is polymerized in an aqueous medium, the monomers are separated by strong abrasion in a polymerization vessel in the presence of a dispersion stabilizer. A commonly used method is to disperse the polymer, heat it, and polymerize it through the action of a polymerization initiator.

The resin particles obtained by this method are widely used as plastic materials to make pipes, plates, records, etc., and also used with plasticizers to make synthetic leather, transparent sheets, etc. However, there are several disadvantages both when producing resin particles and when processing and molding them.

One of the most notable problems is that in the former case, scale builds up on the inner wall of the polymerization vessel, requiring a great deal of effort to remove the scale, which reduces production efficiency, and also causes monomer gas to scatter. Examples include increasing the concentration in the working environment. Regarding the latter, in recent years, resin particles have not necessarily been able to keep up with the rise in required quality standards, especially the growing movement to eliminate gel particles (fish eyes) in molded products. can be mentioned. In response to these problems, numerous improvements have been made in the resin manufacturing industry.

One of the leading methods is to uniformly dissolve a polymerization initiator in a monomer and then polymerize it. According to this method, as the initiator is uniformly melted, scale adhesion to the inner wall of the polymerization vessel is reduced compared to non-uniform melting, and the structure of the produced polymer particles becomes uniform between particles, thereby eliminating fish eyes. A phenomenon of reduction can be seen. A method for uniformly melting the initiator in batch polymerization is to insert a charge tank into the monomer charging line, charge the necessary amount of initiator in advance, and then pour the monomer into the polymerization vessel. Or, after charging water and monomer into a polymerization vessel, the initiator in the charge tank installed in a line other than the monomer loading line is pushed into the polymerization vessel with a certain amount of water, and the monomer floats upright. One method is to dissolve the initiator into the layer. However, in the former method, since the initiator and monomer come into contact with each other, polymer scale easily forms and adheres inside the charge tank very quickly, requiring frequent removal work, and the recovery of the monomer gas inside the charge tank. There are disadvantages such as the need for operations. Also, in the latter method, after charging the initiator into the polymerization vessel, water remaining at high pressure in the charge tank, or inert gas for purging it, must be removed before starting the next batch. There is an inconvenience that medicine cannot be added. As a result of considering a method for charging the initiator that does not involve an opening operation, we found that the above problems could be resolved by sucking the initiator into the polymerization vessel using an ejector that uses a small amount of water as an operating source, and dissolving it into the monomer. I was able to overcome it.

That is, in the present invention, when vinyl chloride or a mixture of vinyl chloride and other monomers copolymerizable with vinyl chloride is polymerized in an aqueous medium, some or all of the monomers to be subjected to polymerization are polymerized in advance. The present invention provides a method for producing a vinyl chloride polymer, which comprises charging the vinyl chloride polymer into a container, and then injecting a polymerization initiator into the polymerization container using an ejector using a small amount of water as an operating source to start polymerization. be.

An example of the polymerization apparatus used in the present invention is shown in Fig. 1.
An example of the same ejector is shown in Fig. 2.

The method of charging a polymerization initiator in the present invention will be explained below with reference to the drawings.

A monomer, water, polymerization agent, etc. are charged in advance into a polymerization can 1 from a charging line.

The amount of monomer charged at this time is a part of the total monomers used, that is, usually at least 2% by weight, preferably 70% by weight or more.
At least % by weight or the entire amount. The polymerization initiator solution is placed in a hopper.
2, the nozzle 13 of the ejector 4 generates a jet stream of water to draw the initiator solution through the introduction row 2, and inject it into the polymerization vessel 1 through the diffuser 14 and valve 3. At this time, the amount of water used for injecting the initiator is
3% by weight or less of the amount of water charged into the polymerization can at the initial stage of polymerization,
Preferably it is 1% by weight or less. Note that the water used here can contain a dispersion stabilizer, a scale adhesion inhibitor, or other polymerization agent as desired. In addition, the specifications of each part of the ejector 4 include the time required to inject the initiator into the polymerization can, the amount of water used at this time, and the difference between the original pressure of water and the pressure inside the polymerization can (this means that the timing of initiator injection depends on the content of the polymerization can). (Determined by whether it is before, during, or after heating the substance to the polymerization reaction temperature)
etc., can be determined as appropriate. In addition, in order to avoid scale adhesion to the ejector 4, the valve 3, and the piping below it, a normal scale adhesion prevention agent may be applied to the core part in advance to the extent that it does not adversely affect the quality of the polymer, or a small amount of dust may be applied to the core part. It is also possible to inject the polymerization inhibitor after charging the initiator.

Further, an aqueous dispersion stabilizer solution can also be used for cleaning.
The present invention can be applied to ordinary polymerization of vinyl chloride in an aqueous medium, that is, suspension polymerization, emulsion polymerization, and fine suspension polymerization.

Examples of other monomers that can be polymerized with vinyl chloride in the present invention include pinylester, vinylene, vinylidene halides, Q-monoolefins, alkyl acrylates, maleic acid, fumaric acid, and their esters. It is. Depending on the polymerization mode, a polymerization initiator that is soluble in the monomer or water-soluble is used.

These can be used in the form of solutions of aliphatic hydrocarbons, alicyclic or aromatic hydrocarbons in organic solvents, dispersed or emulsified in water, or used as they are if they are liquid themselves. The monomer-soluble initiator itself includes organic peroxides such as lauroyl peroxide and dioctyl peroxydicarbonate, azo compounds such as Q.Q'-azobisisobutyronitrile, and cumene hydroperoxide. Hydroperoxide, etc., are used. As the main body of the water-soluble initiator, water-soluble peracids such as potassium persulfate and hydroportable azo compounds such as 2,2-azobis-2-aminopropane are used. Dispersion stabilizers include partially saponified vinyl acetate polymers, cellulose derivatives, acrylic acid copolymers, polyvinylpyrrolidone, gelatin, higher fatty acid alkyl ester salts, alkylaryl sulfonates, polyoxyethylene derivatives, and sorbitan. Derivatives etc. are used.

Further, if necessary, conventional polymerization agents such as molecular weight regulators may also be used.

Furthermore, in order to further reduce scale adhesion, it is of course possible to add a normal scale adhesion inhibitor to the polymerization system or apply it to the inner wall of the polymerization vessel. According to the method of the present invention, it is only necessary to put the initiator into a container such as a funnel equipped with a valve at the suction port of the ejector at the time of preparation, and the maintenance of the initiator preparation equipment can be greatly improved. It can be effectively dissolved in the monomer layer to achieve scale reduction in the polymerization vessel as well as reduction of molded article fish eyes.

Next, examples of the present invention will be shown, but the present invention is not limited thereto.

In addition, the number of fish is 100 parts of polymer resin, 4 parts of dioctyl phthalate dispersion of 0.54 parts of edge color toner.
5 days, a combination of 2 times cadmium stearate and 1 day barium stearate at 14500 ml. p. m. and 28. p. m. After kneading for 6 minutes with a pair of 15-speed rolls rotated at
It is expressed as the number of non-colored particles present in this sheet. Example 1 A stainless steel polymerization can 1 equipped with an initiator charging device similar to that shown in FIG.
400% deionized water, 8% partially saponified vinyl acetate polymer
After filling the tank with water, the space was replaced with nitrogen, evacuated, and vinyl chloride single star 210k9 was added.

Next, with valves 3, 5, and 6 closed, 120 g of a 70% indodecane solution of dioctyl peroxydicarbonate was put into the initiator hopper 2, and valves 5 and 3 were opened in this order, so that the original pressure was 1.
8k9/ml of deionized water was introduced into polymerization vessel 1 via valve 5 and ejector 4. Next, the valve 6 was opened, and the initiator was sucked by the ejector 4 and injected into the polymerization vessel 1. Then add 0.5 mL of deionized water to the initiator hopper for cleaning purposes.
2 and let it suck, and when it runs out, turn on valve 3.
was closed, and then valves 5 and 6 were closed. During this period, the amount of deionized water that entered through valve 5 was 19.5 hours. Next, the hinahai was started, and the polymerization reactor 1 was heated to 5,000 ℃ to carry out a polymerization reaction. When the pressure inside the vessel dropped to 6k9/0, the reaction was terminated by cooling. The amount of scale adhering to the inner wall of the polymerization vessel and the net azusa blade was 21.3 days. The number of fish eyes in the obtained polymer was 23. Polymerization of the above recipe was repeated 10 times, but the initiator ejector and lower line were not clogged with scale.

Comparative Example 1 The amount of deionized water was 420 liters,
A polymerization reaction was carried out in the same manner as in Example 1, except that the initiator was added onto the water surface after the partially saponified vinyl acetate polymer without using an ejector.

The amount of scale adhesion was 395, and the number of fish eyes on the polymer was 160. Comparative Example 2 An experiment similar to Example 1 was conducted using the polymerization equipment shown in FIG. 3, except that the following charging method was used.

That is, the initiator solution is introduced from the hopper 22 into the 200 stainless steel charge tank 24 inserted into the monomer charging line via the valve 26, and then the vinyl chloride monomer is introduced into the container 24 via the valve 25. While doing so, the valve 23 was opened and both were charged into the polymerization can 21. Thereafter, the valves 25 and 26 were closed, and 10 liters of deionized water was flowed into the charge tank 24 through the valve 27, and after cleaning the inside, the water was introduced into the polymerization reactor 21, and then the casing was started to perform a polymerization reaction. After the completion of the polymerization reaction, the amount of scale adhering to the inner wall of the polymerization vessel and the coagulation blade was 25.6 mm, and the number of fish eyes on the polymer was 27. The polymerization of this formulation was
When the batch was operated, the lower part of the charge tank 24, the valve 23, and the line below it became clogged with scale.

Example 2 A polymerization vessel similar to that used in Example 1 had no deionized water spots.
210 parts of partially saponified vinyl acetate and 70 parts of methoxy cellulose were charged, and the space was replaced with nitrogen and then evacuated.
Vinyl acetate monomer 30k9, vinyl chloride monomer 180k
Added 9.

Next, finely powdered lauroyl peroxide 170 ml was dispersed in 5 ml of deionized water and poured into a polymerization reactor in the same manner as in Example 1 using a 35 ml ejector of deionized water at an original pressure of 18 k9/ml. Next, the polymerization reaction was started at 6,000 ℃, and when the pressure inside the reactor dropped to 20 k9', the reaction was terminated by cooling. The amount of scale deposited on the inner wall of the polymerization vessel and the damaged Azusa blade was 46.4 days. Comparative Example 3 A polymerization reaction was carried out using the same recipe as in Example 2, except that 420% of deionized water was charged and the initiator was added in the same manner as in Comparative Example 1 without using an ejector.

The amount of scale adhesion was 1140 mm.

[Brief explanation of the drawing]

Fig. 1 shows an example of a polymerization apparatus equipped with an ejector used in the present invention, Fig. 2 is a sectional view showing an example of the ejector, and Fig. 3 shows a polymerization apparatus equipped with a conventional initiator introduction device. This is an example. 1, 21... Polymerization can, 2, 22... Initiator hot/f-3, 5, 6, 23, 26, 26.../
Valve, 4... Ejector, 7... Check valve,
11... Water chamber, 12... Initiator inlet, 13... Nozzle, 14... Differential user, 24... Charge tank, 27... Cleaning liquid inflow valve. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. When polymerizing vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable with it in an aqueous medium, after charging some or all of the monomers to be subjected to polymerization in advance into a polymerization vessel, A method for producing a vinyl chloride polymer, which comprises injecting a polymerization initiator into a polymerization vessel using an ejector using a small amount of water as an operating source to initiate polymerization.