JPH03131602A - Method for preventing deposition of polymer scale - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for preventing polymer scale from adhering to the inner wall surface of a polymerization vessel during the polymerization of a vinyl halide monomer such as vinyl chloride.

[Conventional technology]

BACKGROUND ART In a method of producing a polymer by polymerizing monomers in a polymerization vessel, there is a known problem that the polymer adheres as scale to the inner wall surface of the polymerization vessel. If polymer scale adheres to the inner wall surface of the polymerization vessel, it may cause a decrease in the yield of the polymer, a decrease in the cooling capacity of the polymerization vessel, and a decrease in the quality of the product polymer due to the adhered polymer scale peeling off and contaminating the product. Furthermore, there are disadvantages such as a great deal of effort and time being required to remove the polymer scale.

Conventionally, as a method for preventing polymer scale from adhering to the inner wall surface of a polymerization vessel, for example, a method of applying polar organic compounds, dyes, pigments, etc. to the inner wall surface (Japanese Patent Publication No. 45-3034
3, No. 45-30835), a method of coating an aromatic amine compound (Japanese Patent Laid-Open No. 51-50887), a method of coating a reaction product of a phenolic compound and an aromatic aldehyde (Japanese Patent Laid-Open No. 55-1988) No. 54317) have been proposed.

[Problem to be solved by the invention]

However, when the above conventional method is applied to the polymerization of vinyl halide monomers such as vinyl chloride or monomer mixtures mainly composed of such monomers, the effect of preventing polymer scale adhesion is always sufficient. It is difficult to say that this has been achieved to a satisfactory degree.

That is, in polymerization using halogenated vinyl monomers, the scale prevention effect varies depending on various conditions such as the mixing ratio of each component used, the type of polymerization catalyst, the polymerization type, and the material of the inner wall of the polymerization vessel. In suspension polymerization using a solid dispersant, it has been extremely difficult to effectively prevent polymer scale from adhering to the inner walls of the polymerization vessel.

Therefore, the present invention provides a method that can effectively prevent polymer scale from adhering to the inner wall surface of a polymerization vessel, regardless of the polymerization conditions, polymerization type, etc., particularly in the polymerization of vinyl halide monomers. The purpose is to provide.

[Means for Solving the Problems] The method for preventing the adhesion of polymer scale of the present invention is to first apply (a) a scale inhibitor to the inner wall surface of a polymerization vessel when polymerizing a vinyl halide monomer. Then, on the obtained coating film, (b) a coating solution containing an alkaline earth metal compound and an anionic dye is further applied to form a coating film, and the polymerization process is carried out in the polymerization vessel. This is what we do.

In the present invention, as shown in (a) and (b) above, two-stage coating is performed on the inner wall surface of the polymerization vessel, that is, a specific coating film is further formed on top of the coating film that has a scale prevention effect. This is a remarkable feature, and this means effectively and reliably prevents the adhesion of polymer scale.

In the present invention, the scale preventive agent described in (a) above is first applied to the inner wall surface of the polymerization vessel.

Examples of the scale preventive agent (a) used in the present invention include those described in U.S. Pat.
Dyes, pigments, polar organic compounds described in U.S. Pat. No. 48-29871); Metal complexes of polar organic compounds, organic Dye metal complex; U.S. Patent No. 4,105,839
The electron-donating organic compound, the electron-accepting organic compound, or at least one of these two organic compounds described in No. 4. Specification No. 173,696 (Special Publication No. 1973-
p
a coating liquid in which H is adjusted to 7 or less; (b) at least one kind selected from the group consisting of water-soluble cationic dyes having at least one pair of conjugated double bonds and at least one nitrogen atom in one molecule; (C) a coating liquid containing at least one compound selected from silicic acid, silicate compounds, and water-soluble salts of metals other than alkali metals, and having a pH adjusted to 7 or less; (d) These coating solutions further contain a monohydric alcohol having 3 to 5 carbon atoms, phytic acid, etc.; U.S. Pat.
202201), a polymer scale adhesion prevention product whose main ingredients are an organic compound having 5 or more conjugated π bonds in one molecule, a chelating reagent, and a metal compound that generates metal ions with a coordination number of 2 or more. silicic acid compounds, and those to which silicic acid compounds are added. These can be used alone or in combination of two or more.

Among these various scale inhibitors, those containing anionic dyes are particularly preferred in the method of the present invention.

Examples of this anionic dye include C,1, Acid Yellow 38. C, 1, Acid Red 18.52.7
3°80, 87; C, I, acid violet 11.
78iC,I.

Acid Blue 1.40.59. 113. 116.
120°158, C, 1, Acid Orange 3,
7 ic, l aci nd black 1. 2. 124;
C, 1, Direct Orange 2.10.26.97;C
, 1, Direct Red 1, 3192, 186;
C,! , Direct Violet 1,22; C,1, Direct Blue 1. 6.71.86.106;C.

1. Direct black 2.19.32.38.77
;C,I.

Direct Green 1.26; Direct Yellow 1;
C, 1, Direct Brown 1.37. 10iiC,
I.

Food Yellow 3iC,! . Reactive Yellow 3;
C, 1, Reactive Blue 2. 4. ia;c,i
, Mordant Violet 5; C, 1, Mordant Black 5. C,I, Mordant Yellow 26; C,1
, Fluorescent Brightening Agent 30.3
2. C.I.

Examples include water-soluble anionic dyes such as Solbilized Butt Black 1; C8■ and Azoic Brown 2.

The above-mentioned scale inhibitor containing anionic dye as a main component may contain components other than anionic dye, for example,
U.S. Pat. Nos. 4.173.696 and 4.53, supra.
9.230 etc. can also be mentioned.

In the method of the present invention, the scale inhibitor (a) is
Usually, a first coating solution is prepared by dissolving or dispersing it in a suitable solvent, and this coating solution is applied to the inner wall surface of a polymerization vessel to form a coating film.

Examples of the solvent for dissolving or dispersing the scale inhibitor (a) include water and methanol.

Alcohol solvents such as ethanol and n-propyl alcohol; aliphatic hydrocarbon solvents such as n-hexane and n-hebutane; aromatic hydrocarbon solvents such as toluene, benzene, and xylene; methylene chloride.

1-chlorobutane, amyl chloride, dichloroethylene, 1
, 1.2-trichloroethane and other halogenated hydrocarbon solvents; acetone, methyl ethyl ketone and other ketone solvents; methyl formate and ethyl acetate.

Ester solvents such as methyl acetate and diethylene glycol acetate methyl ether; ethyl ether.

(2) Ether solvents such as 4-dioxane and ethylene glycol monomethyl ether; nonpronto solvents such as dimethylformamide, dimethyl sulfoxide, and acetonitrile; these may be used alone or as a mixture of two or more as appropriate. Ru.

Further, the pH of this first coating liquid is adjusted to an appropriate range as necessary. For example, U.S. Pat. No. 4,173.
The coating liquid prepared by dissolving the water-soluble anionic dye described in No. 696 is adjusted to have a pH of 7 or less as described above.

The first product containing the scale inhibitor of (a) prepared in this way
The coating liquid is usually used at a solid concentration of about 0.01 to 5% by weight.

This first coating liquid is applied to the inner wall surface of the polymerization vessel, and preferably to other parts that the monomer comes into contact with during polymerization, such as the stirring shaft,
It is applied to stirring blades, etc., and dried to form the coating film of the scale inhibitor (a). Drying can be carried out, for example, at room temperature to 100°C.
It can be carried out at °C.

In the coating film thus obtained, the dry coating amount of the scale inhibitor (a) is usually preferably about 0.001 to 5 g/a.

According to the first aspect of the present invention, the alkaline earth metal compound and anionic dye of (b) are then applied on the scale inhibitor coating film of (a) formed as described above. Apply the coating solution containing the liquid and dry.

Examples of alkaline earth metal compounds that are components of the coating liquid (b)' used in this second coating step include silicates, carbonates, and phosphates of alkaline earth metals such as magnesium, calcium, and barium. Examples include salts, sulfates, nitrates, borates, acetates, hydroxides, oxides, halides, and the like. These may be used alone or in combination of two or more.

Among these, particularly preferred are magnesium carbonate, calcium carbonate, and magnesium phosphate. These include calcium phosphate, barium phosphate, calcium sulfate, calcium borate, magnesium hydroxide, calcium hydroxide, barium hydroxide, magnesium chloride, calcium chloride, and the like.

Further, as the anionic dye which is another component of the coating liquid (b), the anionic dyes exemplified with respect to the scale inhibitor in the above (a) can be used.
Combinations of more than one species can also be used.

The coating liquid (b) is prepared by dissolving or dispersing one or more alkaline earth metal compounds and anionic dyes in an appropriate solvent. In this case, the alkaline earth metal compound and the anionic dye are too:t~ on a weight basis.
100:10000, especially 100:10-1
It is preferable to use the ratio of 00:1000.

The concentration of the alkaline earth metal compound in the coating liquid (b) is not particularly limited as long as the dry coating amount described below can be obtained, but it is usually 0.005 to 10% by weight, preferably 0.01 to 5% by weight.
Heavy view% weight.

Examples of the solvent used in preparing the coating liquid (b) include water and organic solvents that are easily miscible with water, such as alcohol solvents, ester solvents, and ketone solvents. It can be used alone or as a mixed solvent of two or more.

Here, in order to sufficiently dissolve the alkaline earth metal compound and obtain a uniform and strong coating film when the coating liquid (b) is applied, the pH of the coating liquid (b) should be set to 6 or less, especially pH 5 or less. It is preferable to adjust it to

Examples of the pH adjuster used to adjust the pH of the coating solution (b) include sulfuric acid, hydrochloric acid, and phosphoric acid.

Nitric acid, carbonic acid, perchloric acid, molybdic acid, tungstic acid, phosphomolybdic acid, phosphotungstic acid.

Silicomolybdic acid, silicotungstic acid, formic acid.

Acetic acid, oxalic acid, lactic acid, maleic acid, glycolic acid, thioglycolic acid, para-toluenesulfonic acid.

Mention may be made of tannic acid and phytic acid and their acid salts. Among these, hydrochloric acid, phosphoric acid, perchloric acid, molybdic acid, and tungstic acid.

Phosphomolybdic acid, phosphotungstic acid, silicomolybdic acid, silicotungstic acid, para-toluenesulfonic acid,
Phytic acid and acidic salts thereof are preferred, and it is convenient to prepare an aqueous solution of these pH adjusters at an appropriate concentration in advance to adjust the pH of the coating solution (b).

Next, after applying this coating solution (B) to the coating surface of the scale inhibitor of (A) above,
It should be dried at a moderate temperature. It is necessary to form a coating film by sufficient drying. During coating, the temperature of the inner wall of the polymerization vessel, etc. is preferably kept at room temperature to about 100°C.

The dry coating amount of the alkaline earth metal compound in this coating liquid (b) is usually preferably 0.001 to 5 g/rd.

11 After the two-step coating process has been applied to the inner wall of the polymerization vessel, and preferably other areas that come into contact with monomers during polymerization, to form a coating film, the polymerization vessel is coated in a conventional manner. Accordingly, polymerization is carried out by adding a halogenated vinyl monomer 2 polymerization initiator, other necessary polymerization media, and additives 1, such as a monomer dispersion aid.

The vinyl halide monomer to which the method of the present invention is applied includes not only vinyl halides such as vinyl chloride and vinyl fluoride, but also vinylidene monomers such as vinylidene chloride and vinylidene fluoride. vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid, methacrylic acid and their Esters or salts; butadiene.

It may contain diene monomers such as chloroprene and isoprene; comonomers that can be copolymerized with halogenated vinyl monomers such as styrene, acrylonitrile, α-methylstyrene, and vinyl ether.

Furthermore, the type of polymerization to which the method of the present invention is applied is not particularly limited, and includes suspension polymerization, emulsion polymerization, and solution polymerization.

It is effective in any polymerization format such as bulk polymerization.

Therefore, any commonly used additives added to the polymerization system can be used without any restrictions. That is, for example, suspending agents such as partially saponified polyvinyl alcohol, methylcellulose, and polyacrylate; solid dispersing agents such as calcium phosphate and hydroxyapatite; sodium lauryl sulfate and sodium dodecylbenzenesulfonate.

Anionic acid emulsifiers such as dioctyl sodium sulfosuccinate; nonionic emulsifiers such as sorbitan monolaurate and polyoxyethylene alkyl ether; fillers such as calcium carbonate and titanium oxide - tribasic lead sulfate, calcium stearate, dibutyltin dilaurate, dioctyl Stabilizers such as tin mercaptide; Lubricants such as rice wax and stearic acid; Plasticizers such as DOP and DBP; Chain transfer agents such as trichloroethylene and mercaptans; pH regulator; diisopropyl peroxydicarbonate, α,
α-azobis-2,4-dimethylvalero, nitrile,
Even in polymerization systems in which polymerization catalysts such as lauroyl peroxide, potassium persulfate, cumene hydroperoxide, p-menthane hydroperoxide, etc. are present, the method of the present invention can effectively prevent the deposition of polymer scale. can.

Polymerization in which the method of the present invention is particularly suitably carried out is suspension polymerization or emulsion polymerization using a halogenated vinyl monomer such as vinyl chloride or a monomer mixture containing the above-mentioned comonomer. .

In carrying out the method of the present invention, the application of the coating liquid may be carried out in every batch or once in several batches, as appropriate, and this will prevent polymer scale from adhering to the inner walls of the polymerization vessel, etc. The polymerization vessel can be used repeatedly.

〔Example〕

Hereinafter, the present invention will be explained in detail by giving Examples and Comparative Examples. In each table below, the experimental results marked with * are comparative examples, and the other experimental results are examples of the present invention.

Example 1 In each experiment, a stainless steel polymerization vessel with an internal volume of 2ON and equipped with a stirrer was used.

In Experiments 2 and 4 to 12, the anionic dye shown in Table 1 was dissolved or dispersed in water to a concentration of 0.5% by weight as a scale inhibitor, and the solution was adjusted to pH 3 with hydrochloric acid.
In a13 to 15, the solution of the scale inhibitor shown in Table 1 was used as the coating solution (a), and this was applied to the inner wall of the polymerization vessel and other parts that would come into contact with the monomer during polymerization, and heated at 50°C for 15 minutes. and dried to form a coating film.

Then, an alkaline earth metal compound and an anionic dye are dissolved or dispersed in water at a total concentration of 0.5% by weight,
The pH was adjusted to 2.5 using a pH adjuster to prepare a coating solution (b). This coating liquid (b) was applied onto the coating film formed as described above, dried and washed with water to form a coating film.

However, Experiment Nal~3 is a comparative example in which no coating liquid was applied or only one of coating liquid (a) or (b) was applied. The scale inhibitor of the coating solution (a), the alkaline earth metal compound of the coating solution (b), the anionic dye, the pH adjuster, and the pH of the coating solution (b) used in each experiment.
1 Furthermore, Table 1 shows the weight ratio of alkaline earth metal compound/anionic dye in the coating liquid (b), coating temperature, and drying time.

Next, 40k of water was added to the polymerization vessel in which the coating film was formed.
g, 17 kg of vinyl chloride, 4 kg of vinyl acetate, 12 g of partially saponified polyvinyl alcohol, 4 g of hydroxypropyl methylcellulose, 200 g of trichloroethylene, and 0.5 kg of α,α゛-dimethylvaleronitrile were charged, and polymerization was carried out at 58°C for 6 hours with stirring. went. After the polymerization was completed, the amount of polymerization scale attached to the inner wall surface of the polymerization vessel was measured. The results are shown in Table 1.

Table 1 Note *1 Coating liquid I: Benzene solution of benzalaniline used in Experiment No. 11 of Example 1 of Japanese Patent Publication No. 45-30343.

*2 Coating liquid ■: Japanese Patent Publication No. 56-5443, Experimental Test 4
0 used in C, 1, Acid Orange 3, C,! , a solution containing Paysic Orange 14 and phytic acid.

*3 Coating liquid m: Japanese Patent Publication No. 53-46235, Experiment N
A coating liquid obtained by treating with a methanol solution (1%) chloranil containing diphenylene oxide and Oil Red SA described in A42 in a 100:100 (mole ratio) at 90°C for 30 minutes.

Example 2 Coating liquid (a) and coating liquid (b) were applied to a stainless steel polymerization vessel with an internal volume of 20 f and equipped with a stirrer in the same manner as in Example 1 to form a coating film. However, in Experiments 16 to 18, no coating liquid was applied, or coating liquid (A) or (
This is a comparative example in which only one of (b) was applied.

The scale inhibitor of the coating liquid (a) used in each experiment,
Table 2 shows the alkaline earth metal compound, anionic dye, pH adjuster, and alkaline earth metal/anionic dye weight ratio in the coating solution (b).

Next, 10 g of water, 70 g of tribasic calcium phosphate, 1 g of sodium dodecylbenzenesulfonate, 30 g of benzoyl peroxide, and 5 kg of vinyl chloride were charged into the polymerization vessel in which the coating film was formed, and polymerization was carried out at 60°C for 9 hours. went.

After the polymerization was completed, the amount of polymer scale attached to the inner wall surface of the polymerization vessel was measured. The results are shown in Table 2.

Table 2 Injection Umbrella 4 Coating liquid ■: Benzene solution of rosebenzoquinone used in Jikkenma 17 of Example 1 of Japanese Patent Publication No. 45-3σ343.

Rate 5 Coating liquid V: A coating liquid obtained by treating the ethanol solution of diamino-naphthalene and nigrosine used in Experiment NCL31 in Japanese Patent Publication No. 53-46235 with thiophenol at 90°C for 30 minutes.

Book 6 Coating liquid ■: A complex of nibrosine base and AgNOx described in Experimental Level 19 of Example 1 of Japanese Patent Publication No. 51-37308 is dissolved in a mixture of methylene chloride and methanol (50:50 weight ratio). liquid prepared by

*7 Coating liquid ■: C, 1, Acid Black 2 described in Actual MNa19 of Example 1 in Japanese Patent Publication No. 56-5442
and an aqueous solution of iron(I) chloride (por, o).

(Effects of the Invention) According to the method of the present invention, when polymerizing a vinyl halide monomer, polymer scale can always be effectively adhered to the inner wall of the polymerization vessel, etc., regardless of the polymerization conditions. It became possible to prevent this.

For example, when carrying out suspension polymerization of vinyl chloride monomer using a solid dispersant, it has conventionally been difficult to prevent the adhesion of polymer scale, but with the method of the present invention, even in such polymerization, it has been difficult. Adhesion of polymer scale can be extremely effectively and reliably prevented.

Claims (1)

[Claims] A method for preventing polymer scale from adhering to the inner wall of a polymerization vessel when polymerizing a vinyl halide monomer in a polymerization vessel, the method comprising: First, (a) a scale inhibitor is applied to the inner wall surface, and then (b) a coating solution containing an alkaline earth metal compound and an anionic dye is applied on the resulting paint film to form a paint film. A method for preventing polymer scale adhesion, characterized by: