JPH0574605B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improved (co)polymerization method for vinyl chloride, and more specifically, to prevent polymer from adhering to the inner wall of a polymerization tank and parts of the equipment that come into contact with monomers during polymerization. This invention relates to a polymerization method that prevents. [Prior art] When vinyl chloride is polymerized alone or together with monomers that can be copolymerized with vinyl chloride, monomers are removed during polymerization from the inner walls of the polymerization tank, reflux condenser, stirring blades, baffle plates, and various attached piping connections. The cooling capacity of the polymerization tank may be reduced because the polymer adheres to parts of the equipment that come in contact with it during polymerization, or the polymer that peels off after it has adhered may turn into a vinyl chloride homopolymer or copolymer (hereinafter referred to as the product). This may cause problems such as contamination in the product (containing water) and deteriorating the quality of the product. Therefore, the inside of the polymerization tank is usually cleaned every time the polymerization is completed to remove the attached polymer (scale), and then the polymerization is performed again. This requires a great deal of labor and time, resulting in a decrease in the operating rate of the polymerization tank and an increase in product cost. [Problems to be solved by the invention] Many methods have been proposed in the past for preventing polymer adhesion to the inner wall of the polymerization tank.
Although these methods are effective in preventing polymer adhesion, they have various drawbacks such as slowing down the polymerization rate and deteriorating various physical properties of the product, and none of them are satisfactory as methods for industrial use. Improvement was needed. Methods that do not adversely affect the polymerization rate or physical properties of the product, such as applying epoxy resin to the inner wall (Japanese Patent Publication No. 50-6346) or applying epoxy resin mixed with other resins 1978-
8709), but such methods have the disadvantage that they are not very effective in preventing polymer adhesion. The purpose of the present invention is to: In the polymerization of vinyl chloride,
The object of the present invention is to provide a practical polymerization method that sufficiently prevents polymer adhesion without causing the above-mentioned adverse effects. [Means for Solving the Problems] As a result of repeated research to achieve the above object, the present inventors found that when polymerizing vinyl chloride, the monomers on the inner wall of the polymerization tank and other parts of the polymerization equipment and attached equipment during the polymerization operation were removed. The inventors have discovered that if a certain type of chemical solution is applied in advance to the areas that come into contact with the polymer, the adhesion of polymer can be greatly reduced, and even a small amount of adhering polymer can be easily removed by washing with water, etc., and the present invention has been achieved. . That is, in the present invention, when vinyl chloride is polymerized alone or together with monomers that can be copolymerized with vinyl chloride in an aqueous medium or in bulk, the inner wall of the polymerization tank and the parts of the equipment that come into contact with the monomer during polymerization are preliminarily treated. , is a vinyl chloride polymerization method characterized by applying a product obtained by a condensation reaction of polyhydric phenols and epichlorohydrin in the presence of a basic catalyst. In the present invention, a product obtained by a condensation reaction of polyhydric phenol and epichlorohydrin in the presence of a basic catalyst is used as a coating drug. In the present invention, the polyhydric phenols reacted with epichlorohydrin include catechol, hydroquinone, resorcinol, 4-t-butyl-1,2-
Divalent and divalent polyphenols including hydroquinones such as dihydroxybenzene, pyrogallol, hydroxyhydroquinone, phloroglycine, and diphenoquinone, 2,2-methylene-bis(4
-methyl-6-t-butylphenol), 2,2
-methylene-bis(4-ethyl-6-t-butylphenol), 4,4'-thio-bis(3-methyl-6-t-butylphenol) 4,4'-butylden-bis(3-methyl- 6-t-butylphenol), 1,1,3-tris(2'-methyl-4'-hydroxy-5'-t-butylphenyl)butane,
1,3,5-trimethyl-2,4,6-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)benzene, tetrakis[methylene-3-(3',
5'-t-butyl-4'-hydroxyphenyl)propionate] methane, bis[3,3-bis(4'-
Examples include polyhydric phenols which are so-called antioxidants such as hydroxy-3'-t-butylphenyl)butyric acid] glycol ester. The reaction between polyhydric phenols and epichlorohydrin is a condensation reaction using a basic catalyst. Generally, an aqueous solution of caustic soda is suitable as the basic catalyst used here. Epichlorohydrin is used in excess of the polyhydric phenols, and the molar ratio of epichlorohydrin is 1.1 to 1.1 to the polyhydric phenols.
20 is appropriate. Although the relationship between the scale adhesion prevention effect and the molar ratio of epichlorohydrin used is not clear, it is presumed that it is related to the number of epoxy groups in the resulting condensate or the molecular weight of the resulting condensate. The molecular weight of the resulting condensate is said to be determined by the molar ratio of epichlorohydrin used (for example, Shokodo's new epoxy resin). The temperature of this reaction is not particularly limited, but in the case of an aqueous solution, 80 to 120°C is appropriate in relation to the boiling point of water. The reaction product of polyhydric phenols and epichlorohydrin used in the present invention has a molecular weight of
It is preferably 4,000 or less (number average molecular weight, value measured by gel permeation chromatography and calculated in terms of polystyrene), preferably 200 to 2,000. In addition, those with a number average molecular weight of 4000 or more are 20
More preferably, it is less than % by weight. Although it is convenient to use the reaction product of polyhydric phenols and epichlorohydrin in the form of the aqueous solution obtained above for coating as is, it may be used together with a solvent that can dissolve the reaction product. Examples of solvents that can be used here include acetone, methanol, ethanol, tetrahydrofuran, dioxane, chloroform, and mixtures thereof. In carrying out the present invention, first, a solution of the above reaction product is applied to the inner wall of the polymerization tank. It is convenient for work operations to keep the solid content concentration in the range of 0.05 to 15% by weight. Here, the solid content refers to reaction products, and specifically, the sample was heated to 135°C.
The solid content concentration is determined by placing the sample in an air bath and measuring the amount of non-volatile components after drying for 1 hour. In the present invention, "coating" does not refer to a mode of operation, but means that a reaction product is present on the vessel wall as a result, and the method of coating is not particularly limited. Usually, it can be applied by brushing or spraying. Further, the amount of coating is not particularly limited, but it is usually preferably 0.005 to 10 g/m ² in terms of solid content. In the present invention, after the above coating, it is preferable to wash the coated surface with water. This operation washes out any excess coating solution applied and, moreover, advantageously slows down the vinyl chloride polymerization reaction by removing excess reaction products and water-soluble salts and other impurities. In this way, adverse effects such as deterioration of the physical properties of the obtained product are avoided. Note that instead of water, the coated surface may be washed with acidic water adjusted to a pH of 6 or less with an inorganic acid such as hydrochloric acid, nitric acid, phosphoric acid, or carbonic acid, or an organic acid such as formic acid, acetic acid, or phytic acid. Coating may be carried out before the start of each polymerization, or polymerization may be continued for several batches or more by simply washing with water after coating. Polymerization to which the present invention can be applied includes not only homopolymerization of vinyl chloride, but also monomers copolymerizable with vinyl chloride, such as olefins such as ethylene and propylene, vinyl monomers such as vinyl acetate and styrene, acrylonitrile, and acrylic acid esters. It can be effectively applied to copolymerization with acrylic monomers such as maleic acid, maleic esters, fumaric acid, dicarboxylic acid monomers such as fumaric esters, etc. The amount of these copolymerizable monomers used is preferably 20% by weight or less based on vinyl chloride. Furthermore, the polymerization format to which the present invention can be applied is as follows:
These include aqueous suspension polymerization, aqueous emulsion polymerization, and so-called bulk polymerization in which the monomer itself is used as a polymerization medium, and the polymerization can be effectively carried out under each of the usual polymerization conditions. [Example] The present invention will be explained below with reference to Examples. Production Example 1 Preparation of Coating Solution 1 In a three-neck flask equipped with a reflux condenser, thermometer, and stirrer, dissolve 55.0 g (0.5 mol) of resorcin and 27.2 g of caustic soda in 245 g of water, and stir vigorously. while heating at 50°C for 10 minutes. 56.4 g (0.61 mol) of epichlorohydrin was added thereto, the temperature was gradually raised to 95°C over 20 minutes, and this temperature was maintained for 40 minutes. After cooling, stirring was stopped. When the molecular weight distribution of the obtained reaction product was measured using gel permeation chromatography, it was found that
It was between 300 and 1500. The concentration of the resulting reaction product solution was 32% by weight. This solution was diluted with water to give a coating solution of 2% by weight. Production Example 2 Preparation of Coating Solution 2 The azeotropic mixture of epichlorohydrin and water is condensed and separated, and the lower layer epichlorohydrin is returned to the reactor.
278 g of epichlorohydrin was placed in a three-necked flask equipped with a reflux condenser, a thermometer, and a stirrer equipped with a water separator to separate and remove water.
(0.6 mol), 25.2 g (0.2 mol) of pyrogallol, and 34.2 g (0.1 mol) of bisphenol A were added. This solution was heated to reflux at 119° C. with stirring, and 60 g (0.6 mol) of a 40% by weight aqueous solution of caustic soda was added dropwise thereto over 3.5 hours. During the reaction, epichlorohydrin condensed in a reflux condenser was separated from water and then returned to the reactor. Four hours after the start of the reaction, unreacted epichlorohydrin and water were completely distilled off. This reaction product was dissolved in ethanol, filtered to remove sodium chloride, and then diluted with ethanol to reduce the solid content to 2.
A coating solution of % by weight was obtained. In addition, the molecular weight distribution of the reaction product was 300-700. Example 1 The coating liquid prepared in Production Example 1 above was mixed into an internal volume of 7
was sprayed onto the inner wall of a stainless steel polymerization tank using a sprayer, and then the wall surface was washed with water adjusted to pH 4 with hydrochloric acid. After such treatment, deionized water 3000,
t-butyl peroxypivalate 0.6g, saponification level 80
2 g of partially saponified polyvinyl alcohol (mol%) was charged, and the air inside was removed using a vacuum pump. After that, 2000g of vinyl chloride was charged and the pressure was increased to 57℃ at 57℃.
The reaction was continued until Kg/cm ² was reached. After the reaction was completed, unreacted monomers were collected, and after the polymer slurry was discharged, the weight of the polymer adhering to the inner wall of the polymerization tank was determined. The polymer slurry was dehydrated and then dried to obtain a product, and its physical properties were measured as described below. The results are shown in Table 1. (1) Average degree of polymerization: According to JIS K-6721. (2) Apparent specific gravity: According to JIS K-6721. (3) Fixture: Vinyl chloride polymer 100g 2-ethylhexyl phthalate 50g Stabilizer manufactured by Toa Rika Co., Ltd. "Adbastab BC-1000J" 5g The above mixture was heated at 150℃ using two rolls with a roll gap of 0.3mm for 5 minutes. Knead to create a sheet.
Then, look through and count the number of fisheyes that exist in an area of 10cm x 10cm. (4) Porosity: By mercury intrusion method. Comparative Example 1 Polymerization was carried out in the same manner as in Example 1, except that no reaction product was applied. The results are shown in Table 1. The amount of polymer attached to the inner wall is extremely large. Example 2 Polymerization was carried out in the same manner as in Example 1, except that the coating solution obtained in Production Example 2 was used instead of the coating solution prepared in Production Example 1. The results are shown in Table 1. The obtained product had good physical properties and was almost free of scale.

【table】

〔Effect of the invention〕

It is not clear why the reaction product of polyhydric phenol and epichlorohydrin can be applied to the inner wall of a vinyl chloride polymerization tank to prevent polymer adhesion, but it is likely that the epoxy group in this reaction product is connected to the metal on the reactor wall. This is thought to be due to the good adhesion of the reaction product and the fact that polyhydric phenols, which are constituent elements in the reaction product, have a radical scavenging effect, which prevents the polymerization of vinyl chloride on the inner surface of the polymerization tank. Therefore, radicals are prevented from reaching the wall surface and growing during the polymerization reaction, which is thought to be effective in preventing polymer adhesion. Also, the reason why those with relatively low molecular weights show good effects is probably because the coating material is difficult to peel off due to the flexibility of the reaction product. According to the present invention, there is significantly less adhesion of polymer to the inner walls of the polymerization tank, and the adhering polymer can be easily washed away with simple water washing.

Claims (1)

[Claims] 1. When vinyl chloride is polymerized alone or together with a monomer that can be copolymerized with vinyl chloride in an aqueous medium or in bulk, polyhydric phenol is added to the inner wall of the polymerization tank and the parts of the equipment that come into contact with the monomer during polymerization. 1. A method for polymerizing vinyl chloride, which comprises applying a product obtained by a condensation reaction between a group of compounds and epichlorohydrin in the presence of a basic catalyst.