JPS629123B2 - - 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, there are already known methods for applying polar organic compounds such as amine compounds, quinone compounds, and aldehyde compounds to the inner wall of the polymerization vessel and the stirring device of this polymer scale.
Since all of these application methods are dissolved in an organic solvent, they are effective in preventing skating, but there are issues with toxicity and safety due to the organic solvent, and if water is used as a solvent, the anti-scaling effect may be reduced. The disadvantage is that it is small and impractical. 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, a stainless steel polymerization can is used to polymerize vinyl chloride, but when styrene, styrene-butadiene, acrylonitrile-butadiene-styrene, etc. are polymerized in this polymerization can, there is a lot of scale adhesion. Lined polymer cans are used. However, glass-lined polymerization cans have the drawbacks of a low heat transfer coefficient and poor durability, and are difficult to process, particularly in the production of large-sized polymerization cans. The present invention aims to provide a method capable of polymerizing various vinyl monomers without such difficulties. An aqueous solution containing in advance (a) a water-soluble anionic polymer compound, (b) a water-soluble cationic dye, and (c) a monohydric alcohol having 3 to 6 carbon atoms in the part that the polymer contacts. The present invention relates to a method for polymerizing vinyl monomers, which comprises coating and drying the vinyl monomer. When using the method of the present invention, it is possible to extremely reduce the adhesion of polymer scale on the inner wall of the polymerization vessel or on the parts that come into contact with the monomers, such as the stirring blades and the stirring shaft. In various polymerization methods such as polymerization method and emulsion polymerization method, the advantage is brought about that it can be exhibited 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. The present invention is characterized in that it can be carried out in stainless steel polymerization cans even in areas where it has not been possible to carry out the process, and 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. Examples of water-soluble anionic polymer compounds as component (a) used in the method of the present invention include sulfomethylated polyacrylamide, sodium polyacrylate, sodium alginate, acrylamide-sodium vinylsulfonate copolymer, and polymethacrylic acid. Examples include anionic polymer electrolytes having an alkali metal salt or ammonium salt of a carboxyl group or a sulfonic acid group in the side chain, such as soda and sodium polystyrene sulfonate. On the other hand, water-soluble cationic dyes as component (b) used in combination with component (a) above include water-soluble azine dyes such as CI Basic Cred 2, CI Basic Blue 16, and CI Basic Black 2: CI
Water-soluble acridine dyes such as Basic Orange 14 and CI Basic Orange 15: CI Basic Blue 1, CI Basic Violet 3, CI Basic Blue-26, CI Basic Violet 14, CI Basic Blue 5,
Water-soluble triphenylmethane dyes such as CI Basic Blue 7: CI Basic Blue 9, C.
Water-soluble thiazine dyes such as I. Basic Yellow 1, CI Basic Blue 24, CI Basic Blue 25, CI Basic Green 5:
Water-soluble methine dyes such as CI Basic Red 12 and CI Basic Yellow 11; Water-soluble diphenylmethane dyes such as CI Basic Yellow 2; Water-soluble xanthene dyes such as CI Basic Violet 10 and CI Basic Red 1:
CI Basic Orange 2, CI Basic
Water-soluble azo dyes such as Brown 1: CI Basic Orange 2, CI Basic Water-soluble azo dyes such as Brown 1: CI Basic Blue
Examples include water-soluble oxazine dyes such as 12 and CI Basic Blue 6. Both components (a) and (b) exemplified above are required to be water-soluble compounds, but in the present invention, each of these components does not necessarily have to have a high solubility in water. If the solubility is approximately 0.1% or more, it can be suitably used. 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) = 100/5 to 100/100, especially 100/15 to 100. /50 (weight ratio) is preferable. 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,
A monohydric alcohol having 3 to 6 carbon atoms is added, including n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, n-amyl alcohol, t-amyl alcohol, iso-butyl alcohol, -Amyl alcohol, sec-
Examples include amyl alcohol and sec-hexyl alcohol, and these can be used to improve the wettability by adding one or more of them to a concentration of approximately 1 to 20% by weight in the final aqueous solution. The purpose of improving is achieved. In addition, ester solvents that can be easily mixed with water,
There is no problem in using ketone solvents etc. together with water.
When such an organic solvent is used in combination, drying after application to the inner wall of the polymerization vessel becomes easy. 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 in 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.
The scale prevention effect is fully exhibited by setting the amount to be at least g/m ² . 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 into contact with the monomer, apply the aqueous medium, Biruni monomer,
A polymerization initiator and other necessary additives such as monomer dispersion aids are charged and polymerization is carried out. During this polymerization, alkaline substances such as alkali metal or alkaline earth metal oxides, hydroxides, carbonates, phosphates, bicarbonates, silicates, acetates, and ammonium compounds are added directly to the polymerization system. It is also an effective means to further improve the effect of the present invention (scaling prevention effect), but this is done in an amount that does not impair the quality of the polymer, that is, in the total amount of the monomer or monomer mixture. On the other hand, it is usually 1
It is preferable that the amount is less than or equal to weight percent. The method of the present invention is effective for all polymerization systems. Therefore, it can be applied to both suspension polymerization and emulsion polymerization, which are effective for the polymerization of vinyl monomers, and can also be applied to various additives added to the polymerization system, such as partially saponified polyvinyl alcohol, methyl cellulose, etc. Suspending agents, anionic emulsifiers such as sodium lauryl sulfate, sodium dodecylbenzenesulfonate, and sodium dioctyl sulfosuccinate, nonionic emulsifiers such as sorbitan monolaurate and polyoxyethylene alkyl ether, 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, chain transfer agents such as trichlorethylene and mercaptans, and PH regulators. , diisopropyl peroxydicarbonate, α,α-azobis-
The purpose of preventing scale deposition is achieved in a polymerization system in which a polymerization catalyst such as 2,4-dimethylparellonitrile, lauroyl peroxide, potassium persulfate, cumene hydroperoxide, p-menthane hydroperoxide, etc. 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 by:
For example, this is the case in the production of (co)polymers of vinyl halides such as vinyl chloride or vinylidene halides, or by suspension or emulsion polymerization of monomer mixtures mainly composed of them. In addition, we manufacture beads and latex of polymers such as polystyrene, polymethyl methacrylate, and polyacrylonitrile in stainless steel polymerization cans, and manufacture synthetic rubbers such as SBR, NBR, CR, IR, and IIR (these synthetic rubbers are usually processed by emulsion polymerization). In the production of ABS resin, scale adhesion on the inner walls of the polymerization vessel is prevented. 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 liters and a 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 way, and the internal temperature was raised to 57°C while stirring.
Polymerization was carried out at ℃ 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, 120 g of hydroxyapatite, 0.62 g of sodium acid sulfite, 125 g of benzoyl peroxide, and t-butyl perbenzoate were placed in the polymerization vessel coated in this manner.
25g was charged and polymerization was carried out at an internal temperature of 90°C for 7 hours while stirring. After the polymerization was completed, the amount of scale was measured and found to be as shown in Table 2.

【table】

Claims (1)

[Claims] 1. When polymerizing vinyl monomers in an aqueous medium, the inner wall of the polymerization vessel and other parts that come into contact with the monomers are coated with (a) a water-soluble anionic polymer compound and (b) a water-soluble cationic dye in advance. , (c) Number of carbon atoms: 3
A method for polymerizing vinyl monomers, which comprises applying an aqueous solution containing ~6 monohydric alcohols and drying the solution.