JPH04149204A - Production of vinyl chloride-based polymer - Google Patents

Abstract

PURPOSE:To markedly improve the operating efficiency of a polymerizer by charging said polymerizer with both vinyl chloride monomer and water by a specified means in polymerizing said monomer in an aqueous medium to prevent scale sticking to the inner wall of said polymerizer and shorten the charging time. CONSTITUTION:When polymerization is to be made in the presence of an polymerization initiator and surfactant in an aqueous medium using, as feedstock, vinyl chloride monomer or its mixture with another copolymerizable monomer, respective >=60wt.% portions of the whole feedstock at <5O deg.C and water heated to 50-95 deg.C are simultaneously, continuously charged to a polymerizer while carrying out heat exchange. Then, polymerization is made normally at 40-70 deg.C. For charging said initiator and surfactant, it is preferable that the whole amounts thereof be charged simultaneously, continuously into the polymerizer together with the total amounts of the monomer stock and the water after heat exchange, while mixing by a static mixer.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing a vinyl chloride polymer, and more specifically, to a method for producing a vinyl chloride polymer with high efficiency. This invention relates to a method for producing a polymer.

(Prior art) Conventionally, when producing vinyl chloride polymers by the bunch polymerization method, water, surfactants such as suspending agents and emulsifying agents, polymerization initiators, monomers, and other substances are placed in a polymerization vessel. Additives are added and the contents are heated to a predetermined polymerization temperature by means such as circulating hot water through the jacket to carry out polymerization. However, especially in large polymerization vessels, the amount of material to be charged is large, which increases the preparation time, and the heat transfer area of the Jaquent is relatively small compared to the capacity of the polymerization vessel, so it takes a long time to raise the temperature. This was one of the factors that hindered the operating rate of the polymerization reactor.

As a method to solve these problems, a pre-warmed aqueous medium (a mixture of a suspending agent dissolved in water) and
Method of simultaneously charging a homogeneous mixture of monomer and polymerization initiator (Japanese Patent Publication No. 62-39601), total amount of both water in which the entire amount of suspending agent is dissolved and monomer in which the entire amount of polymerization initiator is dissolved. (Japanese Patent Publication No. 60-26488), the monomer and polymerization initiator are charged and mixed uniformly, then the polymerization temperature is adjusted to a predetermined polymerization temperature at the end of the preparation.
Method of charging water that has been heated and deaerated to 0°C (Japanese Patent Application Laid-Open No. 58-2
No. 1408) is known.

However, the method of dissolving a polymerization initiator in monomers in advance and preparing the mixture (Japanese Patent Publications No. 62-39601 and No. 60-26488) requires equipment such as tanks and mixers to prepare the mixture. This not only complicates the preparation operation, but also requires keeping the mixture at a low temperature to prevent polymerization from starting during preparation, or reducing the ratio of polymerization initiator to monomer. , or the use of only polymerization initiators with high decomposition temperatures. Furthermore, during the preparation process, the mixture is uniformly suspended in the aqueous medium as oil droplets in the polymerization vessel, and before it is stabilized, it comes into contact with hot water and polymerization starts suddenly. There is a disadvantage that there is a large amount of coarse particles (finshuai), and a part of the mixture adheres to the inner wall surface of the polymerization vessel, increasing scale, which reduces the heat removal ability to remove the heat of the polymerization reaction. There was a drawback that the amount of polymerization decreased.As with the method disclosed in JP-A No. 58-21408, a method in which monomers and a polymerization initiator are charged into a polymerization vessel, mixed uniformly, and then heated water is charged; The disadvantage is that the monomer mixture comes into direct contact with the inner wall surface of the polymerization vessel during charging, and polymerization starts there, resulting in a significant increase in scale, and that only low-quality polymer particles with poor particle size and fish eyes are obtained. there were.

These disadvantages arise as the concentration of the polymerization initiator dissolved in the monomer increases, i.e., the polymerization time decreases, and as the temperature of pre-heated water increases, i.e., the time required to raise the temperature to a predetermined polymerization temperature. The shorter the value, the more noticeable it is.

On the other hand, in the method disclosed in Japanese Patent Publication No. 60-26488, in which water in which a suspending agent is dissolved (suspending agent aqueous solution) is heated, the surfactant ability of the suspending agent decreases due to heating, but polymerization occurs. Not only does a large amount of scale adhere to the inner wall surface of the vessel, increasing the number of fish eyes, but also the obtained polymer particles become coarse and, in severe cases, solidify into lumps, making it difficult to discharge from the polymerization vessel. There was a drawback. On the other hand, in Japanese Patent Publication No. 58-50603, as a method for preventing the formation of coarse particles and the increase of fish eyes in polymer particles, a suspending agent and a part of the water present in the polymerization system are mixed with cold water. A method has been proposed in which the liquid is charged in the same state, then the monomer is added, and finally heated water is added. However, although this method has the effect of preventing the formation of coarse particles and an increase in fish eyes, it is not possible to shorten the preparation time because water and monomer are sequentially added. Moreover, since the water for preparation is either cold or hot, there is a drawback that the preparation work becomes complicated.

All of these known methods have the advantage of shortening the charging time and/or the temperature raising time, but the adhesion of scale to the walls of the polymerization vessel reduces the ability to remove the heat of the polymerization reaction, so the polymerization time can be reduced. It became difficult to shorten the length, and the effect of increasing the operating rate of the polymerization reactor was insufficient. In addition, the obtained polymer particles have a large coarse particle content, which leads to an increase in fish eyes, which leads to a deterioration in quality.

(Intelligence Problem to be Solved by the Invention) An object of the present invention is to prevent scale from adhering to the inner wall surface of a polymerization vessel, and to prevent the initiation of polymerization without causing coarsening of polymer particles or increase in fish eyes. The purpose of the present invention is to provide a method for producing a vinyl chloride polymer that greatly improves the operating rate of a polymerization vessel by shortening the charging time and temperature raising time.

(Means for Solving the Problems) This object of the present invention is to produce a vinyl chloride monomer, that is, a vinyl chloride monomer or a mixture of a monomer copolymerizable with vinyl chloride and a vinyl chloride monomer. When polymerizing in an aqueous medium in the presence of a polymerization initiator and a surfactant, water preheated to a temperature of 50 to 95°C and a monomer of less than 50°C, respectively. This is achieved by simultaneously charging 60% by weight or more of the total amount of the polymer into a polymerization vessel while exchanging heat, and then polymerizing.

The present invention will be explained in detail below.

In carrying out the present invention, water preheated to a temperature of 50 to 95°C (preferably 50 to 80°C) and a horse mackerel sowing material are added to a degassed polymerization vessel. 60% by weight or more, preferably 90% by weight or more of the total amount of the polymers, is continuously and simultaneously charged into the polymerization vessel while exchanging heat. If the water temperature is less than 50° C., the time required to raise the temperature of the polymerization vessel after charging becomes longer, making it impossible to achieve the object of the present invention. Also, if the water temperature exceeds 95℃,
If the temperature of the monomer is 50° C. or higher, the pressure will rise rapidly during heating or heat exchange, which is dangerous. Water has a higher specific heat than monomers and is safer to handle during heating. higher than the temperature. It is preferable to deaerate the water before heating it.

In order to charge the water and the monomer into the polymerization vessel, 60% by weight or more, preferably 90% by weight or more of the total amount of each of the two are continuously and simultaneously charged while exchanging heat. The above value is 6
If it is less than 0% by weight, this is thought to be due to the temperature distribution of the contents of the polymerization vessel after charging becoming wider, but the resulting polymer particles may become uneven and coarse, or the quality may deteriorate, such as an increase in fish eyes. Moreover, the pressure in the polymerization vessel changes rapidly during charging, which is not only dangerous but also does not lead to shortening of the charging time. Furthermore, in this case, as with conventional methods that do not perform heat exchange, there are problems such as scale adhering to the inner wall of the polymerization vessel, reducing the heat removal ability, and scale contaminating the product, increasing fish eyes. Live.

In addition, by adopting a method in which the water and monomer after heat exchange are mixed in a static mixer (also known as a line mixer, static mixing agitator, or in-line mixer), they are continuously and simultaneously charged into the polymerization vessel. According to the present invention, a vinyl chloride polymer of higher quality can be obtained. The static mixer is, for example, "High Pressure Gas; Vol. 17, Vol. 12.
No. 615-621, 1980, commercially available products may be used.

The water and monomer used in the present invention have an internal temperature (1) of the polymerization vessel at the end of charging the total amount of both at a predetermined polymerization temperature (T) such that T-10≦t≦T +5 (' C) It is necessary to adjust the temperature outside the polymerization vessel to the above-described temperature range in advance. Internal temperature is (T-10) ”C
If it is less than that, the effect of shortening the heating time will be insufficient,
Moreover, if the temperature exceeds (T+5)''C, the pressure in the polymerization vessel will suddenly increase and the polymerization reaction will run out of control, which is dangerous.The polymerization reaction (T) is usually carried out at a temperature in the range of 40 to 70°C.

In the present invention, methods for exchanging heat between water and monomers include tube heat exchangers such as multi-tube heat exchangers, double-tube heat exchangers, and spiral tube heat exchangers, and spiral plate heat exchangers. A convenient method is to use a conventional heat exchange device such as a plate heat exchanger such as a heat exchanger or a flat plate heat exchanger, but the method is not limited thereto. The smaller the temperature difference between the water and the monomer after heat exchange, the better.
Heat exchange is performed so that the temperature is below o'c, preferably below 5°C.

In carrying out the present invention, polymerization initiators, suspending agents,
Methods for charging surfactants such as emulsifiers into the polymerization vessel include methods of charging them directly into the polymerization vessel during or after charging water and monomers, or dividing them during polymerization via dedicated independent piping; Examples include, but are not limited to, a method of continuously charging while mixing with water and monomer after exchange. However, the most effective method for achieving the purpose of the present invention is to use water after heat exchange and polymerization of surfactant components such as monomers, polymerization initiators, suspending agents and emulsifiers. This is a method in which the entire amount of the polymers is combined and simultaneously charged into a polymerization vessel without mixing using a state mixer. According to this method, it is possible to shorten the preparation time (and also to uniformly distribute the polymerized fat opener and surfactant into the monomer-dispersed oil droplets using water as a medium), resulting in even higher yields. High quality vinyl chloride polymer can be obtained.

In this way, after charging each component into a polymerization vessel and initiating polymerization, the V temperature of the polymerization vessel is maintained at a predetermined polymerization temperature while removing the reaction heat to complete the polymerization. Heat removal by a reflux condenser can be employed as is conventional, and other additives can be used as desired.

The method according to the invention is applicable to polymerizations in aqueous media, ie suspension polymerization, emulsion polymerization, microsuspension polymerization.

In the present invention, monomers that can be copolymerized with vinyl chloride monomers include, for example, alkyl vinyl esters such as vinyl acetate and vinyl propionate, lauryl vinyl ether,
Alkyl vinyl ethers such as cetyl vinyl ether,
Examples include, but are not limited to, α-monoolefins such as ethylene and propylene, and acrylic acid alkyl esters such as methyl acrylate and methyl methacrylate.

Further, the surfactants such as suspending agents and emulsifiers and polymerization initiators used in the present invention are those used in ordinary suspension polymerization or emulsion polymerization of vinyl chloride. Examples of the suspending agent include polyvinyl alcohol, partially saponified polyvinyl acetate, cellulose derivatives such as methylcellulose and hydroxypropylmethylcellulose, and synthetic polymer substances such as maleic anhydride-vinyl acetate copolymer. In addition, as emulsifiers, nonionic surfactants such as sorbitan esters or glycerin esters of higher fatty acids and polyoxyethylene adducts thereof;
Examples include anionic surfactants such as sodium lauryl sulfate and sodium/lium dodecylbenzenesulfonate. Examples of the oil-soluble polymerization initiator include di-2-ethylhexylperoxydicarbonate, jetoxyethylperoxydicarbonate, α-cumylperoxyneodecanoate, t-butylbaroxylinodecanoate, L-butylbaroxypiha Rate, 3.5.5-1
- organic peroxides such as lymethylhexanoyl peroxide and acetylcyclohexylsulfonyl peroxide, azo compounds such as α,α-azobisisobutyronitrile and α,αazobis-2,4-dimethylvaleronitrile, cumene; Examples include oil-soluble polymerization initiators such as hydroperoxide, and water-soluble polymerization initiators such as potassium persulfate and hydrogen peroxide, and one or a mixture of two or more of these may be used.

In addition, if desired, chain transfer agents such as mercaptoalkanol and thioglycolic acid alkyl ester, oil-soluble suspension aids such as polyvinyl alcohols with a degree of saponification of 20 to 55 mol%, pHm adjuster 1 redox polymerization initiator system It is also possible to use a reducing agent or a polymerization inhibitor. Polymerization is usually carried out at a temperature of 40 to 70°C with stirring, and the amount and number of parts of each component to be charged may be the conventional conditions conventionally carried out in vinyl chloride polymerization, and are not particularly limited. It's not a thing.

(Effects of the Invention) Thus, the present invention prevents scale from adhering to the inner wall surface of the polymerization vessel, compared to the prior art, and prevents adverse effects such as coarsening of polymer particles and increase in fish eyes. Therefore, the time for charging the polymerization reaction pot and the time for raising the temperature can be shortened, and the operating rate of the polymerization vessel can be greatly improved.

(Example) The present invention will be described in more detail with reference to Examples below. Note that the percentages in Examples and Comparative Examples are based on weight unless otherwise specified. In addition, the physical property values of the vinyl chloride polymer shown in each example were measured by the following method.

(1) 4 D g of dioctyl phthalate, 2 g of cadmium stearate, 1 g of barium stearate, and 1 g of green toner were added to 100 g of fisheye vinyl chloride polymer, mixed, and then mixed with a 6-inch roll at 145°C. Knead for 6 minutes and draw out into a sheet with a thickness of 0.4 m.
It is indicated by the number of transparent particles observed in CTA.

(2) Average particle size The particle size distribution was analyzed using a wire gauze based on Tyler mesh, and the particle size was expressed as a 50% passing diameter.

(3) Coarse particle content The particle size was analyzed using a wire mesh based on Tyler Messier standards, and the percentage remaining on a wire mesh of 60 mesh was shown.

(4) Porous Mercury intrusion porosimeter manufactured by Aminco (5-7)
The amount of mercury injected per gram of the granular vinyl chloride polymer during pressurization from normal pressure to 14,000 psi is shown.

(5) Plasticizer absorbing lab blast mill manufactured by Toyo Seiki (P-600 type)
400g of vinyl chloride polymer and polyester polymer plasticizer PN-250 were placed in a container kept at 86"C.
(manufactured by Adeka Argus Chemical Co., Ltd.) 240 g was added and the torque was recorded while stirring at 60 revolutions, and the time required for the mixing torque to decrease and become stable was expressed.

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

○ Almost no scale adhesion △: Local scale adhesion was observed ×: Adhesive substances were generated on the entire inner wall Example 1 After degassing a stainless steel polymerization vessel with an internal volume of 65 rrr,
27,000 kg of degassed water preheated to 70°C and 23,500 kg of vinyl chloride monomer at room temperature of 25°C were heated while exchanging heat using a shell-and-tube heat exchanger.
During this charging, a 2% aqueous solution of partially saponified polyvinyl acetate 580k
g, and 15 kg of a 70% concentration solvent solution of di-2-ethylhequinruboxydicarbonate were directly charged into the polymerization vessel via a dedicated charging pipe. The internal temperature of the polymerization vessel, which was 2258°C at the end of charging the entire amount of each component, was thereafter maintained at 57°C while polymerization was carried out with stirring, and when the pressure of the polymerization vessel dropped to 6 kg/cut. The unreacted monomer was recovered from the polymerization vessel, and the polymerization was terminated. Subsequently, the contents of the polymerization vessel were dehydrated and dried to obtain a vinyl chloride polymer.

Example 2 Degassed water preheated to a temperature of 64°C and a preheated temperature of 40″C
Example 1 except that vinyl chloride monomer heated to
Polymerization was carried out in the same manner as described above.

Example 3 Polymerization was carried out in the same manner as in Example 1, except that both the heat-exchanged degassed water and the monomer were mixed in a static mixer and simultaneously charged into the polymerization vessel continuously for 20 minutes. Ta.

Example 4 The heat-exchanged degassed water and monomer were continuously mixed for 20 minutes with the total amount of each component of partially saponified polyvinyl acetate and di-2-ethylhexyl peroxydicarbonate using a line mixer. Except for charging it into the polymerization vessel at the same time,
Polymerization was carried out in the same manner as in Example 1.

Comparative Example 1 Polymerization was carried out by using degassed water preheated to 40°C and raising the internal temperature of the polymerization vessel, which was 35°C at the end of charging the entire amount of each component, to 57°C in 40 minutes. Other than that, Example 1
Polymerization was carried out in the same manner as described above.

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

Comparative Example 3 Degassed water was charged for 20 minutes, then vinyl chloride monomer was charged for 20 minutes, and while the monomers were being charged, partially saponified polyvinyl acetate and di-2-ethylhexyl peroxydicarbonate were directly polymerized in a polymerization vessel. Example 1 except that it was prepared in
Polymerization was carried out in the same manner as described above.

Comparative Example 4 2% aqueous solution of partially saponified polyvinyl acetate 580
27,000 kg of degassed water at a temperature of 70°C in which 23,500 kg of vinyl chloride monomer was dissolved at a temperature of 25°C in which 15 kg of a 70% concentration solvent solution of di-2-ethylhexyl peroxydicarbonate was dissolved were continuously dissolved in 20 minutes. Polymerization was carried out in the same manner as in Example 1, except that the polymerization vessel was charged at the same time.

Table 1 shows the physical properties of the vinyl chloride polymer thus obtained. From Table 1, it is clear that according to the method of the present invention, the heating time and preparation time can be significantly shortened, and high quality vinyl chloride polymers can be obtained.

Ichikura Shamizushima branch 2767-1 Niihama, Kojima Shioio, Ishiki City °In-house Zeon Japan Co., Ltd.

Claims (3)

[Claims] (1) When polymerizing vinyl chloride monomer or a mixture of vinyl chloride monomer and a monomer copolymerizable with vinyl chloride in an aqueous medium in the presence of a polymerization initiator and a surfactant, At least 60% by weight of water heated to a temperature of 50 to 95°C and a monomer at a temperature of less than 50°C are simultaneously charged into a polymerization vessel continuously while exchanging heat, and then polymerization is carried out. Characteristic method for producing vinyl chloride polymers. (2) Add water so that the internal temperature (t) of the polymerization vessel at the end of charging the total amount of water and monomer satisfies T-10≦t≦T+5 (°C) for the predetermined polymerization temperature (T). 2. The method for producing a vinyl chloride polymer according to claim 1, which comprises heating water and the monomer in advance. (3) A patent claim characterized in that water and monomers after heat exchange, and a polymerization initiator and/or surfactant are continuously and simultaneously charged into a polymerization vessel while being mixed using a static mixer. A method for producing a vinyl chloride polymer according to item 1 or 2.