JP3041485B2 - Method for producing vinyl chloride polymer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a vinyl chloride polymer, and more particularly, to a method for producing a high quality vinyl chloride polymer with high efficiency. The present invention relates to a method for producing a polymer.

(Prior art) Conventionally, when a vinyl chloride polymer is produced by a batch polymerization method, water, a surfactant such as a suspending agent / emulsifier, a polymerization initiator, a monomer and other additives are added to a polymerization vessel. The agent is charged, and the contents are heated to a predetermined polymerization temperature by means such as circulating warm water through the jacket to carry out polymerization. However, especially in a large-sized polymerization vessel, the charging time is long due to a large amount of charging, and a long time is required to raise the temperature because the heat transfer area of the jacket is relatively small with respect to the capacity of the polymerization vessel. This was one of the factors that hindered the operation rate of the polymerization reactor.

As a method for solving such a problem, a pre-warmed aqueous medium (a mixture in which a suspending agent is dissolved in water)
And a method of simultaneously charging a homogeneous mixture of a monomer and a polymerization initiator (Japanese Patent Publication No. 62-39601), using both water in which the entire amount of the suspending agent is dissolved and the monomer in which the entire amount of the polymerization initiator is dissolved. (See JP-B-60-26488). At the end of the charging of the whole amount, the monomer and the polymerization initiator are charged and uniformly mixed, and then heated to 50 to 80 ° C in advance. A method of charging degassed water (JP-A-58-21408) is known.

However, the polymerization initiator is dissolved in the monomer in advance,
A method of charging the mixture (Japanese Patent Publication Nos. 62-39601 and 60-2)
No. 6488) requires equipment such as a tank and a mixer for preparing the mixture, which not only complicates the operation for preparation, but also prevents the polymerization from starting during the preparation. There are restrictions such as keeping the temperature at a low temperature, reducing the charge ratio of the polymerization initiator to the monomer, or using only a polymerization initiator having a high decomposition temperature.
Further, it is considered that during the charging, the polymerization is rapidly started at the same time as the mixture comes into contact with the warm water before the mixture is uniformly suspended in the aqueous medium as oil droplets in the polymerization vessel and stabilized.
The obtained polymer particles have a large amount of coarse particles, and there is a disadvantage that fish eyes increase.In addition, a part of the mixture adheres to the inner wall surface of the polymerization vessel to increase the scale and remove heat of polymerization reaction. However, there is a drawback that the heat removal ability of the steel is reduced. As in the method according to JP-A-58-21408, a method in which a monomer and a polymerization initiator are charged into a polymerization vessel, and uniformly mixed and then heated water is charged, the monomer mixture is polymerized during the charging. There is a drawback that the scale is remarkably increased due to the direct contact with the inner wall surface of the vessel and the polymerization is started there, and that only low-quality polymer particles having inferior particle size and fish eye are obtained.

These drawbacks are that the higher the concentration of the polymerization initiator dissolved in the monomer, that is, the shorter the polymerization time, and the higher the temperature of the pre-heated water, that is, the time required for raising the temperature to a predetermined polymerization temperature Is shorter as the value is shorter.

On the other hand, in the method of heating water (water solution of a suspending agent) in which a suspending agent is dissolved as in Japanese Patent Publication No. 60-26488, it is considered that the surface activity of the suspending agent is decreased by heating. A large amount of scale adheres to the inner wall of the vessel, which not only increases fish eyes, but also results in coarser polymer particles, and in severe cases, consolidates in bulk, making it difficult to discharge from the reactor. There was a disadvantage. On the other hand, Tokuno Akira 58
No. -50603, as a method for preventing the formation of coarse particles and the increase of fish eyes of polymer particles, a suspending agent and a part of water to be present in the polymerization system are charged in a state of cold water, and then the monomer A method has been proposed in which the heated water is finally charged. However, according to this method, although there is an effect that generation of coarse particles and an increase in fish eyes can be prevented, the charging time cannot be shortened because water and monomer are charged sequentially. In addition, there is a drawback that the charging operation is complicated since cold water or hot water is used for the charging water.

Any of these known methods has the advantage that the charging time and / or the temperature raising time can be shortened, but the scale is attached to the wall of the polymerization vessel and the ability to remove the heat of the polymerization reaction is reduced. It was difficult to shorten the length, and the effect of increasing the operation rate of the polymerization reactor was insufficient. Further, the obtained polymer particles have a disadvantage that the quality is lowered, for example, the amount of coarse particles is large and fish eyes are increased.

(Problems to be Solved by the Invention) An object of the present invention is to prevent the scale from adhering to the inner wall surface of the polymerization vessel and to initiate polymerization without causing coarsening of polymer particles and increase of fish eyes. It is an object of the present invention to provide a method for producing a vinyl chloride-based polymer in which the operation time of a polymerization vessel is greatly improved by shortening the charging time and the temperature raising time.

(Means for Solving the Problems) An object of the present invention is to polymerize a mixture of a vinyl chloride monomer, that is, a vinyl chloride monomer or a monomer copolymerizable with vinyl chloride and a vinyl chloride monomer. When polymerizing in an aqueous medium in the presence of an initiator and a surfactant, at least 60% by weight of the total charged amount of each of water and a monomer having a temperature of less than 50 ° C. previously heated to a temperature of 50 to 95 ° C. Continuously and simultaneously charged into the polymerization reactor while exchanging heat, the internal temperature (t) of the polymerization reactor at the end of the charging of the total amount of water and monomer is increased to a predetermined polymerization temperature (T).
T-10 ≦ t ≦ T + 5 (° C.), followed by polymerization.

 Hereinafter, the present invention will be described in detail.

In carrying out the present invention, first, a degassed polymerization vessel is heated at a temperature of 50 to 95 ° C, preferably 50 to 80 ° C,
60% by weight of the total charged amount of each of the monomer and the monomer below ℃
More preferably, 90% by weight or more is continuously and simultaneously charged into a polymerization vessel while exchanging heat. If the temperature of the water is lower than 50 ° C., the time required for raising the temperature of the polymerization vessel after the charging becomes long, and the object of the present invention cannot be achieved. Further, when the temperature of water exceeds 95 ° C, and when the temperature of the monomer is 50 ° C or more,
It is dangerous because the pressure rises rapidly during heating or heat exchange. Since water has a higher heat than a monomer and is excellent in handling safety when heated, the temperature of water and the monomer used in the present invention is in the above-mentioned range, and the temperature of water is set to the temperature of the monomer. Higher than the temperature. It is desirable that water be degassed before heating.

In order to charge water and the monomer into the polymerization vessel, 60% by weight or more, preferably 90% by weight or more of the total charged amount of each of them is continuously and simultaneously charged while exchanging heat. If the above value is less than 60% by weight, it is considered that the temperature distribution of the contents of the polymerization vessel after charging becomes wide, but the obtained polymer particles are non-uniform and coarse, and fish eyes increase. For example, the pressure in the polymerization vessel fluctuates rapidly during the charging, which is not only dangerous but also does not lead to a reduction in the charging time. Furthermore, in this case, similar to the conventional method without heat exchange, there are problems such as the scale adhering to the inner wall surface of the polymerization vessel and the heat removal capability being reduced, and the scale being mixed into the product and increasing fish eyes. Occurs.

Also, by adopting a method in which water and monomer after heat exchange are mixed in a static mixer (also known as a line mixer, a static mixing stirrer or a mixer in a pipe) continuously and simultaneously charged into a polymerization reactor. According to the present invention, a higher quality vinyl chloride polymer can be obtained. Static mixers are described, for example, in "High Pressure Gas;
, Pp. 615-621, 1980 ".

The water and the monomer used in the present invention are such that the internal temperature (t) of the polymerization vessel at the end of the charging of the total amount of both is T-10 ≦ t ≦ T + 5 (° C.) with respect to a predetermined polymerization temperature (T). It is necessary to adjust the temperature to the above-mentioned range outside the polymerization vessel in advance. If the internal temperature is lower than (T-10) ° C., the effect of shortening the heating time is insufficient, and if the internal temperature exceeds (T + 5) ° C., the pressure in the polymerization vessel rises rapidly or the polymerization reaction runs away. It is a danger. Polymerization reaction (T)
Is usually carried out in the range of 40 to 70 ° C.

In the present invention, as a method of exchanging heat between water and a monomer, tube heat exchangers such as a multi-tube heat exchanger, a double tube heat exchanger, a coiled tube heat exchanger, and a spiral plate type heat exchanger are used. A simple method using a conventional heat exchange device such as a heat exchanger or a plate heat exchanger such as a flat plate heat exchanger is simple, but not limited thereto.
The smaller the temperature difference between water and monomer after heat exchange, the better,
The heat exchange is performed so as to be 10 ° C. or less, preferably 5 ° C. or less.

In carrying out the present invention, as a method of charging a polymerization initiator and a surfactant such as a suspending agent and an emulsifier into a polymerization vessel, water and monomers are charged or divided after charging is completed, or divided during polymerization, and are exclusively used. , And a method of continuously charging while mixing with water or monomer after heat exchange, and the like, but is not limited thereto. However, the most effective method for achieving the object of the present invention is to use for the polymerization of water and each component of a surfactant such as a polymerization initiator, a suspending agent and an emulsifier after heat exchange. This is a method in which all the components to be mixed are batch-mixed using a static mixer and continuously and simultaneously charged into a polymerization vessel. According to this method, the charging time can be shortened, and the polymerization initiator and the surfactant can be uniformly distributed to the dispersed oil droplets of the monomer using water as a medium. A polymer can be obtained.

After charging each component in the polymerization vessel and starting polymerization in this way, the polymerization is completed by maintaining the internal temperature of the polymerization vessel at a predetermined polymerization temperature while removing the reaction heat.Of course, the reflux condenser is used. Heat removal can be employed conventionally, and other additives can be used as desired.

The process according to the invention is applicable to polymerization in aqueous media, ie suspension polymerization, emulsion polymerization, fine suspension polymerization.

In the present invention, examples of the monomer that can be copolymerized with the vinyl chloride monomer include alkyl vinyl esters such as vinyl acetate and vinyl propionate, alkyl vinyl ethers such as lauryl vinyl ether and cetyl vinyl ether, and α-monomers such as ethylene and propylene. Examples include, but are not limited to, olefins, alkyl acrylates such as methyl acrylate and methyl methacrylate.

The surfactants and polymerization initiators such as suspending agents and emulsifiers used in the present invention are those used in ordinary suspension polymerization or emulsion polymerization of building chloride. Examples of the suspending agent include polyvinyl alcohol, partially saponified polyvinyl acetate, cellulose derivatives such as methylcellulose and hydroxypropylmethylcellulose, and synthetic high molecular substances such as maleic anhydride-vinyl acetate copolymer. Examples of the emulsifier include nonionic surfactants such as sorbitan esters or glycerin esters of higher fatty acids and polyoxyethylene adducts thereof, and anionic surfactants such as sodium lauryl sulfate and sodium dodecylbenzenesulfonate. You. Examples of the oil-soluble polymerization initiator include di-2-ethylhexylperoxydicarbonate, diethoxyethylperoxydicarbonate, α-cumylperoxyneodecanoate, t-butylperoxyneodecanoate, and t-butylperoxide. Organic peroxides such as oxypivalate, 3,5,5-trimethylhexanoyl peroxide and acetylcyclohexylsulfonyl peroxide, α, α′-azobisisobutyronitrile and α, α′-azobis-2 Azo compounds such as 4-dimethylvaleronitrile, oil-soluble polymerization initiators such as hydroperoxides such as cumene hydroperoxide, and potassium persulfate, and water-soluble polymerization initiators such as hydrogen peroxide. Or a mixture of two or more.

A chain transfer agent such as a mercaptoalkanol or an alkyl thioglycolate, an oil-soluble suspending aid such as polyvinyl alcohol having a saponification degree of 20 to 55 mol%, a pH adjuster, a redox polymerization initiator, if desired; It is also possible to use a reducing agent or a polymerization inhibitor as a system.
The polymerization is usually carried out under stirring at a temperature of 40 to 70 ° C., and the amounts and the number of parts to be charged of each component may be the same as those conventionally used in conventional vinyl chloride polymerization, and are particularly limited. Not something.

(Effects of the Invention) Thus, according to the present invention, as compared with the prior art, adhesion of scale to the inner wall surface of the polymerization vessel is prevented, and adverse effects such as coarsening of polymer particles and increase of fish eyes are caused. In addition, since the charging time and the temperature raising time for the polymerization reaction can be shortened, the operation rate of the polymerization vessel can be greatly improved.

(Example) Hereinafter, the present invention will be described more specifically with reference to examples. The percentages in Examples and Comparative Examples are based on weight unless otherwise specified. The physical property values of the vinyl chloride polymer shown in each example were measured by the following methods.

(1) Fisheye 45 g of dioctyl phthalate in 100 g of vinyl chloride polymer
g, cadmium stearate 2 g, barium stearate 1
g, and 1 g of green toner, and mixed.
The mixture was kneaded with a 6-inch roll for 6 minutes, pulled out to a sheet having a thickness of 0.4 mm, and the number of transparent particles observed in 100 cm ² of the sheet was indicated.

(2) Average particle size It was shown as a 50% passage diameter by sieve analysis of the particle size distribution using a metal mesh based on Tyler mesh.

(3) Coarse-grain fraction The particle size was determined by sieve analysis using a metal mesh based on a Tyler mesh and expressed as a ratio remaining in a 60-mesh metal mesh.

(3) Porosity Mercury intrusion porosimeter (5-
1721B) and the volume of mercury injected per gram of the granular vinyl chloride polymer during pressurization from normal pressure to 14000 pis.

(5) Absorbency of plasticizer Labo Plast Mill (P-600 type) manufactured by Toyo Seiki Seisakusho
Use a vinyl chloride polymer 40 in a container maintained at 86 ° C.
0 g and 240 g of a polyester polymer plasticizer PN-250 (manufactured by Adeka Argus Chemical Co., Ltd.) were introduced, and the torque was recorded while stirring at 60 rotations, and the time until the mixing torque was reduced and stabilized was shown.

The scale adhesion state on the wall surface of the polymerization vessel shown in each example was shown based on the following criteria.

：: Almost no scale adhered. ス ケ ー ル: Scale adhered locally. ×: Adhered matter was generated on the entire inner wall. Example 1 After degassing a stainless steel polymerization vessel having an inner volume of 65 m ^3, a temperature of 70 was previously set. The total amount of both 27,000 kg of degassed water heated to ℃ and 23500 kg of vinyl chloride monomer at room temperature at 25 ° C is continuously and simultaneously transferred to the polymerization reactor in 20 minutes while exchanging heat using a multi-tube heat exchanger. During the charging, 580 kg of a 2% strength aqueous solution of partially saponified polyvinyl acetate and 15 kg of a 70% strength solvent solution of di-2-ethylhexylperoxydicarbonate were charged directly into the polymerization reactor via a dedicated charging pipe. . Polymerization was carried out with stirring while maintaining the internal temperature of the polymerization vessel at 58 ° C. at the end of the charging of all of these components at 57 ° C.,
When the pressure in the polymerization reactor dropped to 6 kg / cm ² , unreacted monomers were recovered from the polymerization reactor, and the polymerization was terminated. Subsequently, the content of the polymerization vessel was dehydrated and dried to obtain a vinyl chloride polymer.

Example 2 Polymerization was carried out in the same manner as in Example 1 except that all of the heat-exchanged degassed water and the monomer were continuously and simultaneously charged in a polymerization reactor for 20 minutes while mixing with a static mixer. Was.

Example 3 The heat-exchanged degassed water and the monomer were simultaneously and continuously mixed for 20 minutes while mixing with a line mixer with all the components of the partially saponified polyvinyl acetate and di-2-ethylhexyl peroxydicarbonate. Except for charging in the polymerization vessel,
Polymerization was carried out in the same manner as in Example 1.

COMPARATIVE EXAMPLE 1 Using degassed water preheated to a temperature of 40 ° C., the internal temperature of the polymerization vessel was 35 ° C. at the end of the charging of all the components in 40 minutes.
Polymerization was carried out in the same manner as in Example 1, except that the temperature was raised to 57 ° C. to carry out the polymerization.

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that degassed water and a vinyl chloride monomer were simultaneously charged into a polymerization vessel using another charging pipe without heat exchange.

Comparative Example 3 Degassed water was charged in 20 minutes, and then vinyl chloride monomer was added.
Polymerization was carried out in the same manner as in Example 1 except that charging was performed in 20 minutes, and partially saponified polyvinyl acetate and di-2-ethylhexyl peroxydicarbonate were directly charged into the polymerization reactor during charging of the monomer. .

Comparative Example 4 580k of a 2% aqueous solution of previously partially saponified polyvinyl acetate
27000 kg of deaerated water at a temperature of 70 ° C.
70% concentration of ethylhexyl peroxydicarbonate
Vinyl chloride monomer 23 at a temperature of 25 ° C in which 15 kg of a solvent solution is dissolved
Polymerization was carried out in the same manner as in Example 1 except that 500 kg was continuously and simultaneously charged into the polymerization vessel for 20 minutes.

The physical properties of the vinyl chloride polymer thus obtained are shown in Table 1. From Table 1, it is clear that the method of the present invention can significantly reduce the time required for raising the temperature and the time for charging, and can obtain a high-quality vinyl chloride polymer.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Akira Wada, Inventor 2777-1 Niihama, Shimaji, Kojima, Kurashiki-shi, Okayama Pref. (56) References JP-A-1-172407 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 2/00-2/30

Claims (2)

(57) [Claims] When a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer capable of copolymerizing with vinyl chloride is polymerized in an aqueous medium in the presence of a polymerization initiator and a surfactant, a temperature is previously determined. More than 60% by weight of the total charge of each of water heated to 50-95 ° C and monomer below 50 ° C is continuously and simultaneously charged into a polymerization vessel while exchanging heat, and the total amount of water and monomer The internal temperature (t) of the polymerization vessel at the end of the charging is adjusted so that T-10 ≦ t ≦ T + 5 (° C.) with respect to a predetermined polymerization temperature (T), and then polymerization is performed. A method for producing a vinyl polymer. 2. The method according to claim 1, wherein the water and the monomer after the heat exchange and the polymerization initiator and / or the surfactant are continuously and simultaneously charged into the polymerization vessel while mixing using a static mixer. The method for producing a vinyl chloride polymer according to claim 1.