JPH0613577B2 - Method for producing vinyl chloride polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a vinyl chloride polymer, and more particularly to a vinyl chloride polymer capable of producing a high-quality vinyl chloride polymer with high productivity. The present invention relates to a method for producing a polymer.

[Prior Art] When a vinyl chloride polymer is produced, when a polymerization initiator is fed into a polymerization vessel through a charging passage including a charging pipe, a charging port, etc., the polymerization initiator is present in the charging passage, particularly at the tip of the passage. A polymerization initiator may adhere to and remain at the charging port, and may react with the monomer pair during polymerization to form a polymer scale. As this polymer scale grows, the charging path,
Especially clog the charging port. Therefore, removal of the grown polymer scale must be done.

Therefore, as a method of removing the polymerization initiator attached to the charging route and removing the residual polymerization initiator, a method of washing the charging route with an organic solvent, and further closing the cleaning liquid charging port to remove the monomer Methods to prevent intrusion have been proposed.

[Problems to be Solved by the Invention]

However, in the former method of washing with an organic solvent, a large amount of organic solvent is required to completely remove the polymerization initiator attached and remaining in the charging route, so that the organic solvent may be present in the product polymer. Remaining causes deterioration of quality and generation of offensive odor during molding. Therefore, there is a problem that the amount of the organic solvent used is limited, sufficient cleaning cannot be performed, the polymerization initiator remains to some extent, and a polymer scale is also formed when the polymerization is carried out for a long time. Further, in the latter method of closing the charging port, there is a problem that the monomer enters the charging route through the gap between the charging ports closed and polymer scale is generated.

It has also been proposed to reduce the amount of organic solvent used for washing by charging an oil-soluble polymerization initiator as an aqueous emulsion. By this method, it is possible to avoid the organic solvent from remaining in the product polymer, but in the charging route,
In particular, it has been difficult to prevent the polymerization initiator from adhering and remaining at the charging port, and preventing the formation of polymer scale.

The object of the present invention is to effectively remove the polymerization initiator that is attached to and remains in the charging route including the charging port with a small amount of solvent, and therefore effectively prevents the formation of polymer scale. In addition to the above, it is an object of the present invention to provide a method capable of obtaining a high quality product polymer by reducing the residual amount of the organic solvent in the obtained polymer.

[Means for Solving the Problems]

The present invention, as a method for solving the above problems, a step of charging a polymerization initiator into a polymerization vessel through a charging path leading to the inside of the polymerization vessel, and vinyl chloride or a vinyl-based monomer mixture containing vinyl chloride in an aqueous medium. In the method for producing a vinyl chloride polymer having a step of polymerizing, after charging the polymerization initiator in an aqueous emulsion state, the charging route is washed with a cleaning liquid containing a polymerization inhibitor. The present invention provides a method for producing a polymer.

The charging route washed in the method of the present invention is the charging route used for charging the polymerization initiator. This charging route does not have to be dedicated to charging the polymerization initiator. For example, when a route for charging the polymerization medium such as water is used for charging the polymerization initiator, the route needs to be washed.

The form of the charging route to be washed in the method of the present invention is not particularly limited, but usually comprises a pipe connected to the polymerization vessel, and the tip of the route is opened inside the polymerization vessel to form a charging port. . The form of the charging port is not limited at all, and may be opened and closed by a valve, for example.

In the method of the present invention, the polymerization initiator is charged in the form of an aqueous emulsion. This prevents unnecessary organic solvent from being introduced into the polymerization system due to the introduction of the polymerization initiator. The type of polymerization initiator used is not particularly limited, and those used in the production of conventional vinyl chloride-based polymers, such as diisopropyl peroxydicarbonate and di-2
-Percarbonate compounds such as ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate; t-butyl peroxyneodecanate, t
-Butyl peroxypivalate, t-hexyl peroxypivalate, α-cumyl peroxyneodecanate and other perester compounds; acetylcyclohexyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, Peroxides such as 3,5,5-trimethylhexanoyl peroxide; azobis-2,4-dimethylvaleronitrile, azobis (4-methoxy-2,4
Azo compounds such as dimethyl valeronitrile); hydrogen peroxide, calcium persulfate, ammonium persulfate and the like. These may be used alone or in combination of two or more.

In emulsifying the polymerization initiator into an aqueous emulsion, the polymerization initiator is used as it is or after being dissolved in a solvent, an aqueous emulsion is obtained using a dispersant. The dispersant used is not particularly limited and may be one used in the suspension polymerization or emulsion polymerization of a conventional vinyl chloride polymer, and examples thereof include the dispersants exemplified below for the polymerization. Further, the aqueous emulsion of the polymerization initiator is preferably used in such a state that the viscosity is adjusted to facilitate the preparation.

Further, in the method of the present invention, after charging the polymerization initiator, the charging route is washed with a cleaning liquid containing a polymerization inhibitor. As a result, even if the polymerization initiator remains in the charging route, it can be efficiently removed or inactivated by this cleaning liquid. Since this cleaning liquid contains a polymerization inhibitor,
The effect is achieved with a remarkably small amount as compared with a cleaning solution consisting only of an organic solvent.

The solvent used for the above cleaning liquid is not particularly limited, and may be water or generally an organic solvent. Examples of the organic solvent include aliphatic hydrocarbons such as n-hexane, n-heptane and isooctane; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; alcohols such as methanol, ethanol and 2-propanol; Methyl,
Halogenated hydrocarbons such as methylene chloride and chloroform;
Examples thereof include ethers such as ethyl ether and dichloroethyl ether; ketones such as acetone and methyl ethyl ketone; esters such as methyl formate, methyl acetate, n-butyl acetate and ethyl formate, and derivatives thereof.
These may be used alone or in combination of two or more.

Further, when the solvent is a solvent in which the polymerization initiator introduced into the polymerization vessel is easily soluble, it is advantageous that the polymerization initiator attached to and remaining in the charging route can be more effectively washed.

Although the solvent in which the polymerization initiator is easily soluble depends on the type of the polymerization initiator used, isoparaffins having 5 to 30 carbon atoms, toluene and the like are generally exemplified. The isoparaffins are available, for example, under the trade name of Shelsol 71 (manufactured by Shell Chemical Co.). They are,
Usually, it is also used as a solvent for charging a polymerization initiator. The solvent in which the polymerization initiator is easily soluble may be used alone, or may be used together with the other solvent exemplified above.
Among them, as the solvent to be mixed and used, alcohols such as ethanol and 2-propanol are preferable in that the residual amount in the product polymer is small and the efficiency of wastewater treatment is good. When a mixed solvent with another solvent is used as the solvent, it is preferable to contain 50% by weight or more, particularly 80% by weight or more, of an organic solvent showing a readily soluble polymerization initiator.

The polymerization inhibitor contained in the cleaning liquid of the present invention is not particularly limited, and may be one used in the usual production of vinyl chloride-based polymers. For example, 2,2-di (4'-hydroxyphenyl) propane, hydroquinone, p-methoxyphenol, t-butylhydroxyanisole, n-octadecyl-3- (4-hydroxy-3,5-di-t-butylphenyl) Propionate, 2,5-di-t-butylhydroquinone, 4,4'-butylidene bis (3-methyl-6-t
-Butylphenol), 3,5-di-t-butyl-4-hydroxytoluene, 2,2'-methylene-bis (4-ethyl-6-t-butylphenol), triethyleneglycol-bis [3- (3- t-butyl-5-methyl-4-
Hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4]
-Hydroxyphenyl) propionate], t-butylcatechol, 4,4'-thiobis (6-t-butyl-m-
Cresol), tocopherol, nordihydroquaiaretic acid, and other phenolic compounds; phenylnaphthylamine, N, N'-diphenyl-p-phenylenediamine,
4,4-bis (dimethylbenzyl) diphenylamine, semicarbazide, semicarbazide hydrofluoride, hydrochloride, nitrate, acidic sulfate, sulfate, chlorate, formate,
Acid oxalate, acid maleate and maleate,
1-acetyl semicarbazide, 1-chloroacetyl semicarbazide, 1-dichloroacetyl semicarbazide, 1
-Semicarbazide derivatives such as benzoyl semicarbazide and semicarbazone, carbohydrazide, thiosemicarbazide and thiosemicarbazone and derivatives thereof,
Amine compounds such as thiocarbazide, thiocarbazide and their derivatives; nitro compounds such as nitroanisole, N-nitrosodiphenylamine, nitroaniline, N-nitrosophenylhydroxylamine aluminum salt; triphenylphosphite, diphenylisodecylphosphite, Phenyldiisodecyl phosphite, 4,4'-butylidene-bis (3-methyl-6-t-
Phosphorus compounds such as butylphenyl-di-tridecyl) phosphite, cyclic neopentanetetraylbis (octadecylphosphite), tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite; styrene, 1,3 -Unsaturated hydrocarbon compounds such as hexagen and methylstyrene; such as dilauryl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, dodecyl mercaptan, and 1,3-diphenyl-2-thiourea Examples thereof include thio compounds. Among these, t-butylhydroxyanisole, in that the initial colorability of the product polymer and the effect of preventing polymer scale formation can be improved,
Di-t-butyl hydroquinone is preferred. These polymerization inhibitors may be used alone or in combination of two or more.

The concentration of the polymerization inhibitor in the cleaning liquid is not particularly limited, but is usually 0.0001 to 90% by weight. If the concentration of the polymerization inhibitor in the cleaning liquid is too low, the ability to suppress the action of the polymerization initiator remaining in the charging route to prevent the formation of polymer scale is weak, and if the concentration is too high, vinyl chloride-based It may delay the polymerization reaction of the coalescence.

In the method of the present invention, the amount of the cleaning liquid used is
The amount may be such that the entire inner surface of the charging path including the piping and charging port can be cleaned. The required amount of the cleaning liquid can remove the polymerization initiator in an extremely small amount as compared with the case of cleaning with only the solvent. The amount of the cleaning liquid used is preferably such that the polymerization inhibitor contained in the total amount of the cleaning liquid used with respect to the charged amount of the monomer is 1% by weight or less.

The concentration of the cleaning solution containing the polymerization inhibitor used in the method of the present invention is preferably -50 ° C to a concentration not higher than the boiling point of the solvent used in the cleaning solution, more preferably the half-life of the polymerization initiator used is within 1 hour. Is the temperature at which

A preferred combination of the solvent and the polymerization inhibitor in the cleaning liquid used in the method of the present invention is a combination in which the polymerization inhibitor has good solubility in the solvent, and typical examples include isoparaffins and t-butylhydroxyanisole. , Isoparaffins and di-t-butylhydroquinone, toluene and hydroquinone, water and 4,4-bis (dimethylbenzyl) diphenylamine, n-hexane and 3-t-butyl-4-hydroxyanisole, isoparaffins / toluene mixed solvent Examples thereof include t-butylhydroxyanisole, isoparaffins / ethanol mixed solvent and t-butylhydroxyanisole, toluene / benzene / ethanol mixed solvent and triphenylphosphite. The use of a cleaning liquid composed of these combinations has good dispersibility, and is advantageous in terms of stability and storability of the cleaning liquid.

The method of the present invention can be applied to any conventionally known polymerization of vinyl chloride or a vinyl-based monomer mixture containing vinyl chloride. Examples of the polymerization method include suspension polymerization,
Emulsion polymerization may be mentioned.

Examples of vinyl-based monomers other than vinyl chloride include ethylene, propylene, 1-butene, 1-pentene, 1-
Hexene, 1-heptene, 1-octene, 1-nonene,
Α-olefins such as 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, acrylic acid and methyl acrylate, acrylic acid esters such as ethyl acrylate, methacrylic acid and methyl methacrylate, methacryl Methacrylic acid esters such as ethyl acidate,
Maleic acid and its esters, vinyl compounds such as vinyl acetate, vinyl propionate, and alkyl vinyl ether; maleic anhydride; acrylonitrile; styrene; vinylidene chloride; other monomers copolymerizable with vinyl chloride and mixtures thereof. .

When a dispersant is used in the polymerization of the present invention, the dispersant to be used is not particularly limited and may be a conventionally used dispersant. For example, water-soluble cellulose ethers such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxypropyl methyl cellulose; water-soluble starch ethers; partially saponified polyvinyl alcohol; acrylic acid polymers such as polyacrylic acid; water-soluble polymers such as gelatin; Oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, ethylene oxide-propylene oxide block copolymer; water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate and sodium laurate Can be mentioned. These may be used alone or in combination of two or more.

Other conditions upon polymerization in the method of the present invention, for example, a method for charging an aqueous medium, vinyl chloride and other vinyl-based monomers to the polymerization vessel, a dispersant, etc. may be carried out in the same manner as in the past, and are not particularly limited. . The same applies to the polymerization conditions such as the charging ratio.

Further, if necessary, it is also possible to add a polymerization regulator, a chain transfer aid, a pH regulator, a gelation improver, an antistatic agent, an anti-scale agent, etc., which are usually used in the production of vinyl chloride polymers. Is.

In the method of the present invention, an aqueous medium, vinyl chloride or a monomer mixture containing vinyl chloride, a polymerization initiator, and other necessary additives are charged into a polymerization vessel, but the order of charging is not particularly limited. The polymerization initiator in the form of an aqueous emulsion may be charged anywhere before the initiation of polymerization or during the polymerization.
Further, it may be charged continuously or intermittently.
In any case, it is necessary to wash with a washing liquid after the preparation.

Further, the polymerization temperature is adjusted within a range of approximately 10 to 95 ° C depending on the degree of polymerization of the polymer produced.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

Examples 1 to 7 and Comparative Examples 1 to 8 In each example, a stainless steel polymerization vessel having an internal volume of 2000 was charged with 980 kg of deionized water, 382 g of partially saponified polyvinyl alcohol and 143 g of water-soluble methyl cellulose, and the inside of the polymerization vessel was degassed. Then, 700 kg of vinyl chloride was charged.

Then, as a polymerization initiator, di-2-ethylhexyl peroxydicarbonate 50% aqueous emulsion liquid 580
After introducing g into the polymerization vessel using a metering pump, the piping (internal diameter 1 cm, length 3 m) through which the polymerization initiator circulated and the charging port associated therewith were washed (however, not washed in Comparative Example 8). Table 1 shows the solvent of the cleaning liquid used in each example, the polymerization inhibitor and its concentration, and the amount of the cleaning liquid used.

While stirring the inside of the polymerization vessel, the temperature was raised to 57 ° C. to start the polymerization, and the polymerization was stopped when the internal pressure of the polymerization vessel dropped to 6.0 kg / cm ² , the unreacted monomer was recovered, dehydrated, It was dried to obtain a vinyl chloride polymer. After the polymerization, the charging pipe and charging port of the polymerization initiator are decomposed, the adhered state of the polymer scale at these places is observed, and the amount of the residual organic solvent in the polymer is evaluated according to the following criteria. Was measured by the method.

(Evaluation method of scale adhesion state) A: No scale adhesion.

B: A little scale was attached.

C: A large amount of scale adhered and the charging port was blocked.

(Measurement method of the amount of residual organic solvent) 5 g of the obtained polymer was put in a vial bottle and heated at 130 ° C. for 30 minutes.
Heat treatment for minutes, analyze the gas phase of the vial by gas chromatography, and measure the amount of residual organic solvent.
Shown in ppm. The results are shown in Table 1.

Examples 8-13 Di-t-butylhydroquinone was used as a cleaning liquid in an amount of 0.0005% by weight, 0.01% by weight, 0.1% by weight, 1% by weight,
Polymerization was performed in the same manner as in Example 1 except that 500 ml of a methyl ethyl ketone solution containing 10% by weight or 17% by weight was used, and the adhesion state of the polymer scale was evaluated in the same manner. The results are shown in Table 2.

[Effect of the Invention] In the method for producing a vinyl chloride-based polymer of the present invention, the polymerization initiator attached and remaining in the charging route is effectively removed as compared with the conventional method, and is removed with a small amount of an organic solvent. be able to. Therefore, the production of polymer scale can be effectively prevented, the work of removing the polymer scale is unnecessary, and the vinyl chloride polymer can be produced with high productivity. Moreover, the amount of organic solvent remaining in the product polymer is small, and a high-quality vinyl chloride polymer can be obtained.

Claims (1)

[Claims] 1. Vinyl chloride having a step of charging a polymerization initiator into a polymerization vessel through a charging path leading to the inside of the polymerization vessel, and a step of polymerizing vinyl chloride or a vinyl-based monomer mixture containing vinyl chloride in an aqueous medium. A method for producing a vinyl chloride polymer, comprising: charging the polymerization initiator in an aqueous emulsion state, and then washing the charging route with a washing liquid containing a polymerization inhibitor.