JPH0693006A - Production of vinyl chloride-based polymer - Google Patents

Abstract

PURPOSE:To produce a polymer reduced in fish eye of moldings in improved productivity while shortening a time requiring for raising the temperature by raising the temperature of a reactional mixture containing vinyl chloride by blowing steam into the reactional mixture in subjecting the reactional mixture to suspension polymerization. CONSTITUTION:An aqueous medium, a separating agent, a polymerization initiator and other auxiliaries are charged into a polymerizer and the interior in the polymerizer is degassed and vinyl chloride or a monomer mixture containing the vinyl chloride as a main ingredient is charged thereinto. Then, steam is directly blown from a position in the polymerizer, preferably a position communicating to a liquid phase part, especially a nozzle (preferably steam silencer, mixing nozzle, etc.) for blowing steam attached to the bottom into the polymerizer at a rate of <=1kg/min based on 100kg total amount of the reactional mixture to raise the temperature of the ractional mixture and when the temperature of the reactional mixture reaches prescribed temperature, steaming is stopped and polymerization is carried out while removing polymerization reaction heat by passing cooling water through a jacket to produce the objective vinyl chloride-based polymer. By the producing method, time required for raising temperature can be shortened and adhesion of polymer scales can also be prevented.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a vinyl chloride polymer by suspension polymerization of vinyl chloride or a monomer mixture containing vinyl chloride.

[0002]

2. Description of the Related Art Generally, in suspension polymerization of vinyl chloride or a monomer mixture containing vinyl chloride (hereinafter referred to as vinyl chloride), an aqueous medium and a dispersant are charged in a polymerization vessel equipped with a jacket and a reflux condenser. Then, after charging the polymerization initiator, then exhausting the inside of the polymerization vessel, charging the monomer, further adding other additives as necessary, and then passing warm water through the jacket It is carried out by a method in which the temperature of the reaction mixture is raised and the polymerization reaction is carried out while maintaining a predetermined temperature.

In recent years, as one of the methods for improving productivity, the time required for raising the temperature of the reaction mixture has been shortened.
As a method of shortening the temperature rising time, for example, a method of heating and charging at least one kind of an aqueous medium and a monomer such as vinyl chloride in advance (so-called hot charging method) has been proposed (Japanese Patent Publication No. Sho 62-39601). issue). This hot charge method is also excellent in that it compensates for the insufficient heating capacity of the polymerization vessel due to the enlargement of the polymerization vessel and the use of the reflux condenser.

[0004]

However, according to this hot charge method, since the polymerization initiator is rapidly decomposed at the same time as the charging of the polymerization initiator, the fish obtained when the obtained polymer is molded into a sheet or the like. There is a problem that the number of eyes is significantly increased and coarse particles are generated. Further, there is a problem that the adhesion of the polymer scale to the inner wall of the polymerization vessel is increased.

Therefore, the object of the present invention is to shorten the time required for temperature rise, to prevent the generation of coarse particles, and to reduce the number of fish eyes when the obtained polymer is molded. Another object of the present invention is to provide a method for producing a vinyl chloride-based polymer, which can effectively prevent polymer scale adhesion in a polymerization vessel.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have solved the above problems. The present invention, in the suspension polymerization of a vinyl chloride or a monomer mixture containing vinyl chloride, in a method for producing a vinyl chloride polymer having a step of performing a polymerization reaction by heating the reaction mixture in a polymerization vessel,
It is intended to provide a method for producing a polymer, characterized in that steam is blown into the polymerization vessel when the temperature is raised.

The polymer is produced by the method for producing a polymer of the present invention, for example, by the following method. First, an aqueous medium, a dispersant, a polymerization initiator, and other auxiliaries are charged into a polymerization vessel, the inside of the polymerization vessel is deaerated, then monomers are charged, and the mixture is stirred to uniformly mix the reaction mixture in the polymerization vessel. The temperature of the aqueous medium is preferably 40 ° C. or lower. It is also possible to charge the aqueous medium and the monomer at the same time in order to shorten the charging time. Next, the temperature of the reaction mixture is raised by blowing steam directly into the polymerization vessel. When the predetermined reaction temperature is reached, the blowing of steam is stopped, and cooling water is passed through the jacket to carry out the polymerization while removing the heat of the polymerization reaction. In addition, after the steam blowing is stopped during the polymerization, it is preferable to inject water through the nozzle for flushing in order to prevent adhesion of the polymer scale to the steam blowing nozzle and clogging of the polymer.

The steam may be blown so as to be uniformly dispersed in the polymerization vessel. For example, the steam may be blown so as to be uniformly dispersed in the polymerization vessel from a steam blowing nozzle attached to the polymerization vessel. The nozzle for steam blowing is
It is preferably attached at a position leading to the liquid phase portion in the polymerization vessel, and further preferably attached at the bottom of the polymerization vessel. It is preferable to use a steam silencer, a mixing nozzle, a tank mixing eductor or the like as the nozzle. Although commonly used spray nozzles and the like can also be used, they are not so preferable because they generate a lot of noise during use.

The blowing of steam is started after charging the aqueous medium, the dispersant, the polymerization initiator, the monomers and other additives into the polymerization vessel as described above. Further, in parallel with the steam blowing, if hot water is passed through the jacket provided in the polymerization vessel to raise the temperature, the temperature raising time can be further shortened. In addition, the blowing of steam may be finished at any time until the temperature in the polymerization reactor reaches a predetermined reaction temperature, and preferably, it is finished between 5 ° C. before the predetermined reaction temperature and the predetermined reaction temperature. . The steam blowing speed varies depending on the polymerization conditions, but as a guide, it is a speed of 1 kg / min or less per 100 kg of the total amount of the reaction mixture charged, and may be increased or decreased within the range during heating. It suffices that the steam pressure is higher than the maximum pressure in the polymerization vessel, and for safety, it is preferably 1 kgf / cm ² or more higher than the maximum pressure in the polymerization vessel.

Further, even after the temperature inside the polymerization vessel reaches a predetermined reaction temperature, steam may be blown in as necessary such as adjusting the temperature inside the polymerization vessel. Furthermore, after the completion of the polymerization, the recovery efficiency of the unreacted monomer can be improved by blowing steam when recovering the unreacted monomer.

The monomers to be polymerized by applying the production method of the present invention include vinyl chloride alone and a monomer mixture containing vinyl chloride as a main component (generally, 50% by weight or more of vinyl chloride). As the comonomer to be copolymerized with vinyl chloride, vinyl acetate, vinyl propionate and other vinyl esters, methyl acrylate, ethyl acrylate and other acrylate or methacrylic acid esters, ethylene, propylene and other olefins, maleic anhydride Examples thereof include acids, acrylonitrile, styrene, vinylidene chloride, and other monomers copolymerizable with vinyl chloride.

When suspension polymerization is carried out in an aqueous medium using the above monomers, a dispersant is generally used. The type of this dispersant is not particularly limited, and those conventionally used can be used. For example, water-soluble cellulose esters such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose; water-soluble and oil-soluble partial kens. Polyvinyl alcohol; acrylic acid polymer; water-soluble polymers such as gelatin; sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, oil-soluble emulsifiers such as ethylene oxide / propylene oxide block copolymers; polyoxyethylene sorbitan monolaurate, Examples thereof include water-soluble emulsifiers such as polyoxyethylene glycerin oleate and sodium laurate, which are used alone or in combination of two or more kinds.

The polymerization initiator may also be those conventionally used for the polymerization of vinyl chloride and the like, and examples thereof include diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate. Peroxycarbonate compound, t-
Peroxy ester compounds such as hexyl peroxypivalate, t-butyl peroxy neodecaneate, α-cumyl peroxy neodecaneate, t-butyl peroxy neodecaneate, t-hexyl peroxy neodecaneate, acetylcyclohexyl Sulfonyl peroxide, peroxides such as 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, azobis-2,4-dimethylvaleronitrile, azobis (4-methoxy-2,4-
Azo compounds such as dimethyl valeronitrile), potassium persulfate, ammonium persulfate, hydrogen peroxide and the like,
These are used alone or in a combination of the top two.
The polymerization initiator may be added during the charging of water or the monomer, or after the charging is completed, and may be mixed in advance with the monomer and charged together with the monomer. Further, it may be charged as an aqueous emulsion together with an aqueous medium. Further, it is optional to add a polymerization regulator, a chain transfer agent, a pH regulator, a gelation improving agent, an antistatic agent, a polymer scale anti-adhesion agent, etc., which are appropriately used for the polymerization of vinyl chloride and the like.

The general suspension polymerization of vinyl chloride and the like according to the production method of the present invention will be specifically described below. First, an aqueous medium and a dispersant are charged. Next, the inside of the polymerization vessel is evacuated to reduce the pressure, and then a monomer is charged and a polymerization initiator is charged while stirring. Then, the temperature is raised until a predetermined reaction temperature (usually 30 to 80 ° C.) is reached while blowing steam into the polymerization vessel, and polymerization is carried out while maintaining the reaction temperature. During the polymerization, one or more kinds of water, a dispersant and a polymerization initiator are added, if necessary. When the internal pressure of the polymerization vessel drops to 0 to 7 kgf / cm ² · G, or when the difference between the inlet temperature and the outlet temperature of the cooling water that flows into and out of the jacket installed on the outer periphery of the polymerization vessel becomes almost equal. It is judged to be completed (that is, when the heat generated by the polymerization reaction has disappeared). An aqueous medium, a dispersant and a polymerization initiator charged at the time of polymerization are usually 20 to 500 parts by weight of an aqueous medium, 0.01 to 3 parts by weight of a dispersant, and 0.01 to 5 parts by weight.

[0015]

Example: A deionized water was placed in a stainless steel polymerization vessel with an internal volume of 2.1 m ³ (with a stirrer and a jacket).
50 kg, 210 g of partially saponified polyvinyl alcohol and 140 g of cellulose ether were added as an aqueous solution and added. After degassing the inside of the polymerization vessel to 50 mmHg, vinyl chloride monomer 6
85 kg was charged and, while stirring, 380 g of di-2-ethylhexyl peroxydicarbonate was further injected with a pump. The temperature in the polymerization vessel is 32 when all the preparations are completed.
It was ℃. Then, steam was blown into the liquid phase portion in the polymerization vessel from the nozzle attached to the bottom of the polymerization vessel at a rate of 3.0 kg / min to start the temperature rise. When the temperature inside the polymerization vessel reached 54 ° C., the blowing of steam was gradually reduced, and the blowing of steam was terminated immediately before the temperature inside the polymerization vessel reached 57 ° C. Cold water was passed through the jacket to continue the polymerization while maintaining the inside of the polymerization vessel at 57 ° C. When the internal pressure of the polymerization reactor reached 6.0 kgf / cm ² · G, the polymerization was stopped to recover the unreacted monomer, and the obtained polymer was taken out of the polymerization reactor in a slurry form and dehydrated and dried.

With respect to the obtained vinyl chloride polymer, bulk specific gravity, particle size distribution, plasticizer absorption amount and fish eye were measured by the following methods. The results are shown in Table 1. (1) Bulk Specific Gravity: Measured according to JIS K 6721. (2) Particle size distribution: # 60, # 80, # 100 according to JIS Z 8801
Each of the sieves # 120, # 150, and # 200 was used for sieving, and the passing amount (% by weight) was measured. (3) Absorption of plasticizer: Glass fiber is packed in the bottom of an aluminum alloy container having an inner diameter of 25 mm and a depth of 85 mm, and 10 g of a sample vinyl chloride polymer is sampled and charged. To this, 15 cc of dioctyl phthalate (hereinafter referred to as DOP) is added and left for 30 minutes to allow the DOP to sufficiently penetrate the polymer. Then 15
Excess DOP was centrifuged under an acceleration of 00 G to obtain polymer 10
The amount of DOP absorbed in g was measured and converted per 100 g of polymer. (4) Fish eye: 100 parts by weight of vinyl chloride polymer, 1 part by weight of tribasic lead sulfate, and lead stearate.
A mixture prepared by mixing 1.5 parts by weight, 0.2 parts by weight of titanium oxide, 0.1 parts by weight of carbon black and 50 parts by weight of DOP with a roll was kneaded at 145 ° C. for 5 minutes, and then formed into a sheet having a thickness of 0.2 mm. After molding, the number of fish eyes contained in 100 cm ^{2 of} the sheet was counted. Table 1 shows the results of observing the time required to raise the temperature in the polymerization vessel and the state of scale adhesion in the polymerization vessel after completion of the polymerization.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that steam was not blown into the polymerization vessel during heating, but the temperature was raised by passing hot water through the jacket. Got united. With respect to the obtained polymer, bulk specific gravity, particle size distribution, plasticizer absorption amount and fish eye were measured in the same manner as in Example 1. The results are shown in Table 1. Table 1 shows the results of observing the time required to raise the temperature in the polymerization vessel and the state of scale adhesion in the polymerization vessel after completion of the polymerization.

Comparative Example 2 After degassing the inside of the polymerization vessel to 50 mmHg, deionized water heated to 70 ° C. 856 kg, partially saponified polyvinyl alcohol
An aqueous solution of 210 g, 140 g of cellulose ether, and 685 kg of vinyl chloride monomer were simultaneously charged (hot charge method). Stirring was started in the middle of the charging, and after the charging was completed, 380 g of di-2-ethylhexyl peroxydicarbonate was continuously pressed in with a pump. The temperature inside the polymerization vessel was 56 ° C. when all the charging was completed. While confirming that the temperature in the polymerization vessel increased, cold water was gradually introduced into the jacket, and the polymerization was continued while maintaining the temperature in the polymerization vessel at 57 ° C.
Then, the same operation as in Example 1 was performed to obtain a vinyl chloride polymer. When the internal pressure of the polymerization reactor reached 6.0 kgf / cm ² · G, the polymerization was stopped to recover the unreacted monomer, and the obtained polymer was taken out of the polymerization reactor in a slurry form and dehydrated and dried.
With respect to the obtained vinyl chloride polymer, the bulk specific gravity, particle size distribution, plasticizer absorption amount and fish eye were measured in the same manner as in Example 1. The results are shown in Table 1. In addition, Table 1 shows the results of observing the state of scale adhesion in the polymerization vessel after completion of the polymerization.

[0019]

[Table 1]

[0020]

According to the method for producing a vinyl chloride polymer of the present invention, the time required for raising the temperature can be shortened, so that the productivity is improved. In addition, the generation of coarse particles in the polymer is suppressed, the number of fish eyes when the obtained polymer is formed into a sheet or the like is small, and the adhesion of polymer scale in the polymerization vessel is prevented.

Claims (1)

[Claims] 1. A method for producing a vinyl chloride-based polymer, which comprises a step of performing a polymerization reaction by raising a temperature of a reaction mixture in a polymerization vessel during suspension polymerization of vinyl chloride or a monomer mixture containing vinyl chloride. A method for producing a polymer, wherein steam is blown into the polymerization vessel when the temperature is raised.