JPH0214921B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to an improved method for polymerizing vinyl monomers. Conventionally, known methods for polymerizing vinyl monomers include suspension polymerization, emulsion polymerization, solution polymerization, gas phase polymerization, and bulk polymerization.
In all of these polymerization methods, there was a problem of polymer scale adhesion on the inner walls of the polymerization vessel, the stirring device, and the like. In other words, when vinyl monomers are polymerized using these methods, polymer scale adheres to the inner walls of the polymerization vessel and parts that come into contact with the monomers, such as the stirring device, which reduces the yield of the polymer and the cooling of the polymerization vessel. In addition to reducing performance, this scale flakes off and mixes into the product, reducing the quality of the product.On the other hand, it takes excessive effort and time to remove the attached scale. Not only that, but unreacted monomers are adsorbed in this scale, so there is a risk of human injury due to monomers (vinyl chloride, etc.), which has become a very serious problem in recent years. There is a disadvantage. However, as a method for preventing polymer scale, it is already known to apply polar organic compounds such as amine compounds, quinone compounds, and aldehyde compounds to the inner walls of the polymerization vessel and the stirring device. When used dissolved in a solvent, suspension polymerization exhibits long-lasting properties, but emulsion polymerization or polymerization systems that use emulsifiers have the drawback that it is difficult to prevent scale adhesion, and organic There are problems with the toxicity and safety of the solvent itself. On the other hand, when water is used as a solvent, polymerization methods using aqueous media such as suspension polymerization and emulsion polymerization have poor durability of the coating film, and this also depends on the type of vinyl monomer and the polymerization system. Since it is easily influenced by the composition of the silica, etc., it has a disadvantage that the scale prevention effect is small and it is poor in practical use. On the other hand, these methods of coating polar organic compounds show long-term sustainability in suspension polymerization, but have the disadvantage that it is difficult to prevent scale adhesion in emulsion polymerization or polymerization systems that use emulsifiers. be. In addition, for example, stainless steel polymerization cans are used to polymerize vinyl chloride, but when styrene, styrene-acrylonitrile, etc. are polymerized in these polymerization cans, there is a lot of scale adhesion, so in this case, a glass-lined polymerization can is used. ing. However, glass-lined polymerization cans have a low heat transfer coefficient, are easily damaged, and are difficult to process, making it particularly difficult to manufacture large-sized polymerization cans. The present invention aims to provide a method by which various vinyl monomers can be polymerized without such difficulties, and this method is capable of polymerizing various vinyl monomers in an aqueous medium. In advance, apply (a) sulfomethylated polyacrylamide, sodium polyacrylate, sodium alginate, acrylamide to the inner wall of the container and other areas that will come into contact with the monomer.
Contains at least one water-soluble anionic polymer compound selected from sodium vinyl sulfonate copolymer, sodium polymethacrylate, and sodium polystyrene sulfonate, and (b) water-soluble inorganic salts of metals other than alkali metals. The present invention relates to a method for polymerizing vinyl monomers, which comprises applying and drying an aqueous solution containing (c) a monohydric alcohol having 3 to 6 carbon atoms in the aqueous solution. The present invention relates to a method for polymerizing vinyl monomers, which is characterized in that an aqueous solution is applied in advance to the inner wall of a polymerization vessel and other parts that come into contact with the monomer, and then dried. When the method of the present invention is used, it is possible to extremely reduce the adhesion of polymer scale on the inner wall of the polymerization vessel, the stirring blades, the stirring shaft, and other parts that come in contact with the monomers. In a polymerization method using an aqueous medium such as a polymerization method or an emulsion polymerization method, the present invention has the advantage that it can be performed without being affected by the type of vinyl monomer, the composition of the polymerization system, etc. Furthermore, the present invention has the effect that scale adhesion hardly occurs regardless of whether the polymerization vessel is a stainless steel polymerization vessel or a glass-lined polymerization vessel. It has the characteristics that it can be carried out in fields where it has not been possible to do so with a stainless steel polymerization can, and that water, which is non-toxic and harmless in terms of safety and hygiene, can be used as a coating solvent. The present invention provides that, when the solvent of the coating agent is water, a scale inhibitor consisting of a combination of the above-mentioned components (a) and (b) is effective in preventing scale adhesion, and further contains a monohydric alcohol. This product was developed based on the fact that it improves wettability to the polymerization vessel walls, etc., making the application work easier (uniform application is easier), and provides a remarkable scale prevention effect. The mechanism by which polymer scale adhesion is prevented by the method of the present invention is probably that
When components (a) and (b) are dried on the wall of the polymerization vessel, they react with each other to form a film that is no longer soluble or slightly soluble in water, and is sufficiently adsorbed to the wall. This is presumed to be due to the effect of preventing specific adsorption of all dissociated molecules and undissociated molecules present in the polymerization system during various polymerizations. Next, the content of the present invention will be explained in more detail. The water-soluble anionic polymer compound as component (a) used in the method of the present invention includes sulfomethylated polyacrylamide, sodium polyacrylate, sodium alginate, acrylamide-sodium vinyl sulfonate copolymer, and sodium polymethacrylate. ,
or sodium polystyrene sulfonate,
These may be used alone or as a mixture of two or more. On the other hand, water-soluble inorganic salts of metals other than alkali metals as component (B) used in combination with component (A) above include alkaline earth metals such as magnesium, calcium, and barium, and zinc group metals such as zinc. , aluminum group metals such as aluminum, tin group metals such as titanium and tin, iron group metals such as iron and nickel, chromium group metals such as chromium and molybdenum, manganese group metals such as manganese, copper group metals such as copper and silver, Examples include silicates, carbonates, phosphates, sulfates, nitrates, borates, hydroxides, oxides, and halides of metals selected from platinum group metals such as platinum. In carrying out the method of the present invention, first, an aqueous solution containing the above-described components (a) and (b) is prepared by dissolving the components (a) and (b) in water at a concentration appropriate for the coating operation. However, the total concentration of these two components should be approximately 0.01% by weight or more; if the concentration is lower than this, water consisting of components (a) and (b) will form on the inner wall of the polymerization vessel. It becomes difficult to form a poorly soluble film with a desired thickness. On the other hand, there is no particular limit on the upper limit of this concentration, but if the concentration is higher than necessary, it will be economically disadvantageous, and in extreme cases, it will interfere with the coating work, so it is generally not recommended. should be up to about 5% by weight. The most effective ratio of component (a) to component (b) for scale prevention in an aqueous solution is component (a)/component (b) = 100/10 to 100/100, especially 100/20 to 100. /50
(weight ratio). When the aqueous solution prepared in this way is applied to the inner wall of a polymerization vessel made of stainless steel or the like, in order to improve the wettability of the wall surface,
Monohydric alcohols having 3 to 6 carbon atoms are often added, including n-propyl alcohol,
iso-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, n-amyl alcohol, t-amyl alcohol, iso-amyl alcohol, sec-amyl alcohol, sec-hexyl alcohol, etc. The purpose of improving wetting can be achieved by including one or more of these at a concentration of approximately 1 to 20% by weight in the final aqueous solution. . In the method of the present invention, the above-mentioned aqueous solution is applied in advance to the inner wall of the polymerization vessel and other parts that come into contact with the monomer, and then dried. As a means of drying this application, appropriately heated air is applied to the applied surface after application. Either method can be used, such as blowing air to dry it, or preheating the inner wall of the polymerization vessel and other parts that come into contact with the monomer (40 to 100°C), applying it directly to the heated surface, and drying it. After the coated surface is sufficiently dry, wash it with water if necessary. Since the film formed by drying is insoluble in water, it will not be eluted and removed by washing with water. The amount of aqueous solution applied to the inner wall of the polymerization vessel, etc. after drying is 0.001 to the inner wall of the polymerization vessel, stirrer, etc.
g/m ² or more, and thereby the scale prevention effect is fully exhibited. In addition, before applying the aqueous solution described above to the inner walls of the polymerization vessel, etc., there is no problem in undercoating the inner walls of the polymerization vessel in advance with a conventionally known organic solvent solution type scale prevention coating solution. According to this method, the formation of the scale prevention film on the inner wall of the polymerization vessel by the aqueous solution is more reliably and firmly performed. After completing the coating treatment on the inner walls of the polymerization vessel and other areas that come in contact with the monomer, the aqueous medium, vinyl monomer,
A polymerization initiator and other necessary additives such as monomer dispersion aids are charged and polymerization is carried out. In addition, alkaline substances such as oxides, hydroxides, carbonates, phosphates, bicarbonates, silicates, and acetates of alkali metals and alkaline earth metals, or ammonia or various ammonium salt compounds are polymerized. When added in a small amount, the effect of further promoting scale prevention effect is brought about. However, if they are added too much, they may impair the quality of the polymer, so it is usually preferable to add them in an amount of 1% or less based on the monomer or monomer mixture. The method of the present invention can be applied to both suspension polymerization and emulsion polymerization, which are effective for polymerizing vinyl monomers, and various additives added to the polymerization system.
For example, partially saponified polyvinyl alcohol, suspending agents such as methylcellulose, various other emulsifying agents,
Fillers such as calcium carbonate and titanium oxide, stabilizers such as tribasic lead sulfate, calcium stearate, dibutyltin dilaurate, and dioctyltin mercaptide, lubricants such as rice wax and stearic acid, plasticizers such as DOP and DBP, trichloroethylene, and mercaptan. Chain transfer agents such as PH regulators, diisopropyl peroxydicarbonate, α,α′-azobis-2,4-dimethylvaleronitrile, lauroyl peroxide, potassium persulfate, cumene hydroperoxide,
The purpose of preventing scale deposition is achieved in a polymerization system in which a polymerization catalyst such as p-menthane hydroperoxide is present. The method of the present invention is applied to the polymerization of various vinyl monomers, and specific examples of these monomers include vinyl halides such as vinyl chloride, vinyl esters such as vinyl acetate and vinyl propionate,
Acrylic acid, methacrylic acid or their esters or salts, maleic acid or fumaric acid, and their esters or anhydrides, butadiene,
Examples include diene monomers such as chloroprene and isoprene, as well as styrene, acrylonitrile, vinylidene halides, and vinyl ether. The method of the present invention is particularly preferably carried out in the case of producing polymers by suspension polymerization of vinyl halides such as vinyl chloride or vinylidene halides, or monomer mixtures based on these. . Next, examples and comparative examples of the method of the present invention will be given. However, experiments marked with * in each table
No. represents a comparative example, and other experiment numbers represent the present invention. Example 1 Components (a) and (b) as shown in Table 1 were dissolved in water so that the total concentration of these two components was about 0.1% by weight, and then dissolved as shown in Table 1. A coating solution was obtained by adding (c) monohydric alcohol to the solution. This coating solution was applied to the inner wall of a stainless steel polymerization vessel with an internal volume of 100 equipped with a stirrer and the portion of the stirrer that would come in contact with the monomer, and was heated and dried at 50° C. for 10 minutes, followed by washing with water. Thereafter, 26 kg of vinyl chloride monomer, 52 kg of water, 26 g of partially saponified polyvinyl alcohol, and 8 g of α,α'-dimethylvaleronitrile were charged into the polymerization vessel coated in this manner, and the mixture was heated to an internal temperature while stirring.
Polymerization was carried out at 57°C for 10 hours. After the polymerization was completed, the scale adhesion amount (g/m ² ) was measured, and the results shown in Table 1 were obtained. However, the amount of monohydric alcohol (c) added in Table 1 is based on an aqueous solution prepared by dissolving components (a) and (b) in water.
It is shown in the amount added (parts by weight) per 100 parts by weight.

[Table] Example 2 Components (a) and (b) as shown in Table 2 are dissolved in water so that the total concentration of these two components is about 0.1% by weight, and the solution is further diluted with 100% by weight. A coating liquid was obtained by adding 5 parts by weight of isobutyl alcohol per part by weight. This coating solution was applied to the inner wall of a stainless steel polymerization vessel equipped with a stirrer and the portion of the stirrer that comes into contact with the monomer, heated and dried at 90°C for 10 minutes, and then thoroughly washed with water. Next, 50 kg of styrene monomer, 43.2 kg of water, 100 g of partially saponified polyvinyl alcohol, 125 g of benzoyl peroxide, and 25 g of t-butyl perbenzoate were charged into the polymerization vessel coated in this manner, and the mixture was heated to an internal temperature while stirring. Polymerization was carried out at 90°C for 7 hours. After the polymerization was completed, the amount of scale was measured and found to be as shown in Table 2.

[Table] Example 3 In Experiment No. 5 of Example 1, the same procedure as in the same experiment was carried out except that sodium hydroxide was added in an amount equivalent to 0.01% by weight based on the monomer charged in the aqueous medium. When polymerization was carried out, the amount of scale attached was 1
g/ ^m2 .

Claims (1)

[Claims] 1. When polymerizing vinyl monomers in an aqueous medium, (a) sulfomethylated polyacrylamide, sodium polyacrylate, alginic acid is added to the inner wall of the polymerization vessel and other parts that come into contact with the monomers. at least one water-soluble anionic polymer compound selected from soda, acrylamide-sodium vinyl sulfonate copolymer, polysodium methacrylate, and sodium polystyrene sulfonate; and (b) a water-soluble inorganic compound of a metal other than an alkali metal. A method for polymerizing vinyl monomers, which comprises applying and drying an aqueous solution containing salts. 2 In addition to components (a) and (b) as the aqueous solution,
The method for polymerizing vinyl monomers according to claim 1, further comprising (c) using an aqueous solution containing a monohydric alcohol having 3 to 6 carbon atoms.