JPH02209904A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To obtain the title polymer of high quality with effective inhibition of scale formation by feeding an aqueous emulsion of the polymerization initiator through the feeding path into the polymerization tank, then cleaning the feeding path with a solution containing a polymerization inhibitor. CONSTITUTION:Deionized water, partially saponified polyvinyl alcohol and a water-soluble methyl cellulose are charged into a stainless steel polymerization tank, and vinyl chloride or vinyl monomers including vinyl chloride are charged therein. Then, a polymerization initiator in an aqueous emulsion is fed through a feeding path into the polymerization tank and the feeding path 15 cleaned with a solution containing a polymerization inhibition, and vinyl chloride or a vinyl monomer mixture including vinyl chloride is polymerized to give the object polymer of high quality with effective prevention of polymer scale formation.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a vinyl chloride polymer, and in particular a method for producing a vinyl chloride polymer that can produce a high quality vinyl chloride polymer with high productivity. The present invention relates to a method for producing a polymer.

[Conventional technology]

During the production of vinyl chloride polymers, when a polymerization initiator is supplied into the polymerization vessel through a charging path consisting of charging piping, a charging port, etc., polymerization occurs within the charging path, especially at the charging port at the tip of the path. Initiators may adhere and remain and react with monomers during polymerization to form polymer scale. When this polymer scale grows, it clogs the feed channels, especially the feed ports. Therefore, the grown polymer scale must be removed.

Therefore, as a method to remove the polymerization initiator attached and remaining in the charging channel and to prevent the formation of polymer scale, there is a method of cleaning the charging channel with an organic solvent, and a method of closing the cleaning solution charging port to remove the monomer. Methods to prevent intrusion have been proposed.

[Problem to be solved by the invention]

However, in the former method of cleaning with an organic solvent, a large amount of organic solvent is required to completely remove the polymerization initiator that adheres to and remains in the charging path. It remains and causes quality deterioration and bad odor during molding. Therefore, there are restrictions on the amount of organic solvent to be used, and there is a problem in that sufficient washing cannot be performed and some amount of the polymerization initiator remains, and if polymerization is carried out for a long time, polymer scale will still be formed. Furthermore, in the latter method of closing the charging port, there is a problem in that monomers enter the charging path through the gap in the closed charging port, resulting in the formation of polymer scale.

Furthermore, it has been proposed to reduce the amount of organic solvent used for cleaning by incorporating an oil-soluble polymerization initiator in the form of an aqueous emulsion. This method avoids organic solvents remaining in the polymer product, but in the preparation route,
In particular, it has been difficult to prevent the polymerization initiator from adhering or remaining and forming polymer scale at the charging port.

An object of the present invention is to effectively remove the polymerization initiator that adheres to and remains in the charging path including the charging port, and to use a small amount of solvent, thereby effectively preventing the formation of polymer scale. It is an object of the present invention to provide a method that not only enables the present invention but also reduces the amount of residual organic solvent in the obtained polymer and obtains a high-quality product polymer.

[Means to solve the problem]

As a method for solving the above problems, the present invention provides a step of charging a polymerization initiator into a polymerization vessel through a charging path leading into the polymerization vessel, and a step of charging vinyl chloride or a vinyl monomer mixture containing vinyl chloride in an aqueous medium. A method for producing a vinyl chloride polymer that includes a step of polymerizing the vinyl chloride, characterized in that after the polymerization initiator is charged in the form of an aqueous emulsion, the charging path is washed with a cleaning solution containing a polymerization inhibitor. The present invention provides a method for producing a polymer.

The charging route that is cleaned in the method of the present invention is the charging route that was used for charging the polymerization initiator. This charging route does not need to be dedicated to charging the polymerization initiator. For example, if a path for charging a polymerization medium such as water is used for charging a polymerization initiator, it is necessary to clean the path.

The form of the charging path to be cleaned in the method of the present invention is not particularly limited, but it usually consists of piping connected to the polymerization vessel, and the tip of the path opens into the polymerization vessel to form a charging port. . The form of the inlet is not limited at all, and may be opened and closed with a valve, for example.

In the method of the present invention, the polymerization initiator is introduced in the form of an aqueous emulsion. This prevents unnecessary organic solvents 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 may include those used in the production of conventional vinyl chloride polymers, such as diisopropyl peroxydicarbonate and di-2-
Bar carbonate compounds such as ethylhexyl peroxydicarbonate, jetoxyethyl peroxydicarbonate; L-butyl peroxyneodecanate, L-
Perester compounds such as butyl peroxy pivalate, 1-hexyl peroxy pivalate, α-cumyl peroxy neodecanate; acetyl cyclohexyl peroxide, 2.4.4-trimethylpentyl-2-peroxyphenoxy acetate , 3,5.5-trimethylhexanoyl peroxide; azobis-
Examples include azo compounds such as 2,4-dimethylvaleronitrile and azobis(4-methoxy2.4dimethylvaleronitrile); hydrogen peroxide, potassium persulfate, ammonium persulfate, and the like. These can be used alone or in combination of two or more.

When a polymerization initiator is made into an aqueous emulsion, the polymerization initiator is used as it is or after being dissolved in a solvent, it is made into an aqueous emulsion using a dispersant.

The dispersant used is not particularly limited, and may be one used in conventional suspension polymerization and emulsion polymerization of vinyl chloride polymers, such as the dispersants exemplified below regarding polymerization. Further, the aqueous emulsion of the polymerization initiator is preferably used in a state in which the viscosity is adjusted so that it can be easily prepared.

Further, in the method of the present invention, after charging the polymerization initiator, the charging path is cleaned with a cleaning liquid containing a polymerization inhibitor. Thereby, even if the polymerization initiator remains in the charging path, it can be efficiently removed or inactivated by this cleaning solution. Since this cleaning solution contains a polymerization inhibitor, it requires a significantly smaller amount to achieve its effect than a cleaning solution consisting only of an organic solvent.

The solvent used in the above-mentioned cleaning liquid is not particularly limited, and may be water or an organic solvent. Examples of organic solvents include n-hexane and n-hebutane.

Aliphatic hydrocarbons such as isooctane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; alcohols such as methanol, ethanol, and 2-propanol; halogenated hydrocarbons such as methyl chloride, methylene chloride, and chloroform; ethyl Examples include ethers such as 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 can be used alone or in combination of two or more.

Further, it is advantageous if the solvent is a solvent in which the polymerization initiator introduced into the polymerization vessel is easily soluble, since the polymerization initiator adhering to and remaining in the charging path can be more effectively washed away.

The solvent in which the polymerization initiator is easily soluble depends on the type of polymerization initiator used, but generally examples include isoparaffins having 5 to 30 carbon atoms and toluene. This isoparaffin is available under the trade name of, for example, Shell Sol 71 (manufactured by Shell Chemical Co., Ltd.). these are,
Usually, it is also used as a charging solvent for polymerization initiators. The solvent in which the polymerization initiator is easily soluble may be used alone or in combination with other solvents exemplified above.

Among these, alcohols such as ethanol and 2-propanol are preferred as the solvent used in combination, since they have a small residual amount in the product polymer and are efficient in wastewater treatment. When a mixed solvent with another solvent is used as the solvent, it is preferable that the polymerization initiator contains an easily soluble organic solvent in an amount of 50 weight or more, particularly 80 weight or more.

The polymerization inhibitor contained in the cleaning solution of the present invention is not particularly limited, and may be one used in the production of ordinary vinyl chloride polymers. For example, 2,2-di(4'-hydroxyphenyl)propane, hydroquinone, p-methoxyphenol, t-7'ylhydroxyanisole, n-octadecyl-3-(4-hydroxy-3,5-di-t- butylphenyl) propionate, 2.5-di-butylhydroquinone, 4.4'-butylidenebis(3-methyl-6-L-butylphenol), 3.5-di-t-butyl-4-hydroxytoluene, 2. 2'-methylene-
Bis(4-ethyl-6-t-butylcatechol), triethylene glycol-bis(3-(3-t-butyl-5
-Methyl-4-hydroxyphenyl)propionate]
, pentaerythrityl-tetrakis (3-(3,5-di-butyl-4-hydroxyphenyl)propionate), t-butylcatechol, 4,4'-thiobis(6
-t-butyl-m-cresol), tocopherol, nordihydroguaiaretic acid, and other phenolic compounds;
Phenylnaphthylamine, N,N'-diphenyl-p-
Phenylenediamine, 4,4-bis(dimethylbenzyl)diphenylamine, semicarbazide, hydrofluoride, hydrochloride, nitrate, acidic sulfate, sulfate, chlorate, formate, acidic oxalate, acidic maleic acid salt of semicarbazide acid salts and maleate salts, 1-acetyl semicarbazide,
1-chloroacetyl semicarbazide, ■-dichloroacetyl semicarbazide, ■-benzoyl semicarbazide,
Derivatives of semicarbazide such as semicarbazone, carbohydrazide, thiosemicarbazide, thiosemicarbazone, etc. and derivatives thereof, amine compounds such as thiocarbazide, thiocarbazide, etc. and derivatives thereof; nitroanisole, N-nitrosodiphenylamine, nitroaniline, N- Nitro compounds such as nitrosophenylhydroxylamine aluminum salt; triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di -tridecyl) phosphite, cyclic neopentanetetrylbis(octadecyl phosphite), tris(nonylphenyl) phosphite, tris(dinonylphenyl)
Phosphorus compounds such as phosphites: Unsaturated hydrocarbon compounds such as styrene, 1,3-hexadiene, and methylstyrene; dilaurylthiodipropionate, simiristylthiodipropionate, distearylthiodipropionate, dodecyl Mercaptan, 1,3-diphenyl-2-
Examples include thio-based compounds such as thiourea. Among these, L-butylhydroxyanisole and di-monobutylhydroquinone are preferred in that they can improve the initial coloration of the product polymer and the effect of preventing the formation of polymer scale. These polymerization inhibitors can be used alone or in combination of two or more.

The concentration of this polymerization inhibitor in the cleaning solution is not particularly limited, but may generally be in the range of 0.0001 to 90% by weight. If the concentration of the polymerization inhibitor in the cleaning solution is too low, the ability to suppress the action of the polymerization initiator remaining in the charging path and prevent the formation of polymer scale will be weak; if the concentration is too high, the ability to prevent the formation of polymer scale will be weak. This may delay the polymerization reaction.

In the method of the present invention, the amount of cleaning liquid used is:
The amount may be enough to clean the entire inner surface of the feeding route including the piping and the feeding port. The polymerization initiator can be removed with a much smaller amount of cleaning solution than when cleaning with only a solvent. Further, the amount of cleaning liquid used is preferably such that the amount of polymerization inhibitor contained in the total amount of cleaning liquid used is 1% by weight or less relative to the amount of monomer charged.

The temperature of the cleaning liquid containing a polymerization inhibitor used in the method of the present invention is preferably 150°C or below the boiling point of the solvent used in the cleaning liquid, and more preferably the half-life of the polymerization initiator used is 1 hour. The temperature is within

A preferred combination of a solvent and a polymerization inhibitor in the cleaning solution used in the method of the present invention is a combination in which the polymerization inhibitor exhibits 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 l solvent Examples include t-butylhydroxyanisole, isoparaffins/ethanol mixed solvent and t-7'-methylhydroxyanisole, toluene/benzene/ethanol mixed solvent and triphenyl phosphite. The use of a cleaning liquid consisting of a combination of these has good dispersibility and is therefore advantageous in terms of stability and storage stability of the cleaning liquid.

The method of the present invention can be applied to any conventionally known polymerization of vinyl chloride or vinyl monomer mixtures containing vinyl chloride. Examples of polymerization formats include suspension polymerization,
Examples include emulsion polymerization.

Examples of vinyl monomers other than vinyl chloride include EVA, ethylene, propylene, 1-butene, 1-bentene, and 1-bentene.
hexene, 1-heptene, 1-octene, 1-nonene,
α-olefins such as 1-decene, l-undecene, ■-dodecene, 1-1 lysocene, 1-tetradecene, acrylic acid and methyl acrylate, acrylic acid esters such as ethyl acrylate, methacrylic acid and methyl methacrylate, Methacrylic acid esters such as ethyl methacrylate,
Maleic acid and its esters, vinyl compounds such as vinyl acetate, vinyl propionate, and alkyl vinyl ether; maleic anhydride; acrylonitrile; styrene; vinylidene chloride; and other monomers copolymerizable with vinyl chloride and mixtures thereof. .

When a dispersant is used in the polymerization of the present invention, the dispersant used is not particularly limited, and any conventionally commonly used dispersant may be used. For example, water-soluble cellulose ethers such as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose; 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 triolate, glycerol tristearate, and ethylene oxide propylene oxide block copolymers; water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerol oleate, and sodium laurate. It will be done. These can be used alone or in combination of two or more.

Other conditions for polymerization in the method of the present invention, such as the method of charging an aqueous medium, vinyl chloride and other vinyl monomers, and a dispersant to the polymerization vessel, may be carried out in the same manner as conventional methods and are not particularly limited. .

Further, the polymerization conditions such as the charging ratio are also the same.

Furthermore, if necessary, polymerization regulators, chain transfer agents, pi regulators, gelling improvers, antistatic agents, scale inhibitors, etc. that are commonly used in the production of vinyl chloride polymers may optionally be added. It 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 aqueous emulsified polymerization initiator may be added before or during polymerization.

Also, it may be prepared continuously or intermittently.
In either case, it is necessary to wash with a washing liquid after preparation.

Moreover, the polymerization temperature is adjusted in the range of about 10 to 95°C depending on the desired degree of polymerization of the polymer to be produced.

〔Example〕

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

Examples 1 to 7, Comparative Examples 1 to 8 In each case, the internal volume was 20,004! 980 kg of deionized water, 382 g of partially saponified polyvinyl alcohol, and 143 g of water-soluble methylcellulose were placed in a stainless steel polymerization vessel.
After charging and deaerating the inside of the polymerization vessel, vinyl chloride 700k
I prepared g.

Next, 580% of a 50% aqueous emulsion of di-2-ethylhexyl peroxydicarbonate as a polymerization initiator was prepared.
After introducing g into the polymerization vessel using a metering pump, the pipe (inner diameter 1 cm, length 3 m) through which the polymerization initiator passed and the feed port connected to it were washed (however, in Comparative Example 8, this was not done). Table 1 shows the solvent, polymerization inhibitor and their concentration in the cleaning solution used, as well as the amount of cleaning solution used.

While stirring the inside of the polymerization vessel, the temperature was raised to 57°C to start polymerization, and when the internal pressure of the polymerization vessel decreased to 6.0 kg/cii, the polymerization was stopped. Unreacted monomers were collected, dehydrated,
A vinyl chloride polymer was obtained by drying.

After polymerization, disassemble the polymerization initiator charging piping and charging port, observe the state of polymer scale adhesion at these locations, evaluate using the following criteria, and evaluate the amount of residual organic solvent in the polymer as shown below. It was measured using the method.

(Method for evaluating scale adhesion) A: No scale adhesion.

B: Some scale was attached.

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

(Method for measuring the amount of residual organic solvent) 5 g of the obtained polymer was placed in a vial, heat treated at 130"C for 30 minutes, and the gas phase of the vial was analyzed by gas chromatography to determine the amount of residual organic solvent measured. The amounts are shown in ppm. The results are shown in Table 1.

Examples 8 to 13 Di-t-butylhydroquinone was used as a cleaning liquid, o, ooos wt%, 0.01 wt%, 0.1 wt%, respectively.
Polymerization was carried out in the same manner as in Example 1, except that methyl ethyl ketone solution 500111 containing 1% by weight, 10% by weight, or 17% by weight was used, and the state of adhesion of polymer scale was evaluated in the same manner. . The results are shown in Table 2.

Table 2 [Effects of the Invention] In the method for producing vinyl chloride polymers of the present invention, the polymerization initiator that adheres to and remains in the charging path can be removed more effectively than in conventional methods, and with a small amount of organic solvent. Can be removed. Therefore, the formation of polymer scale can be effectively prevented, there is no need to remove the polymer scale, and the vinyl chloride polymer can be produced with high productivity. Furthermore, the amount of organic solvent remaining in the product polymer is small, and a high-quality vinyl chloride polymer can be obtained.

Agent Patent Attorney Shushi Iwamiya

Claims (1)

[Claims] A chlorination process comprising the steps of charging a polymerization initiator into a polymerization vessel through a charging path leading into the polymerization vessel, and polymerizing vinyl chloride or a vinyl monomer mixture containing vinyl chloride in an aqueous medium. A method for producing a vinyl chloride polymer, which comprises charging the polymerization initiator in the form of an aqueous emulsion, and then cleaning the charging route with a cleaning solution containing a polymerization inhibitor. .