JPH04154804A - Agent for preventing deposition of scale in production of vinyl chloride polymer and prevention process - Google Patents

Abstract

PURPOSE:To provide the subject preventing agent containing a xanthone-type natural pigment and a PVA having a specific saponification degree and giving a colorless polymer having high whiteness only a little forming fish-eye. CONSTITUTION:The objective preventing agent contains (A) a xanthone-type natural pigment (e.g. gentisin, swertiamarin, euxanthone, jacareubin, mangostin and mangiferin) and (B) a PVA having a saponification degree of >=70mol% (preferably >=98mol%) at a weight ratio (A:B) of preferably 100:(1-1,000). Deposition of scale can be prevented by applying the coating film containing the preventing agent to at least a part of the monomer-contacting part of a polymerizer in the polymerization of a vinyl chloride monomer.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an inhibitor that prevents polymer scale from adhering to a polymerization vessel during polymerization of vinyl monomers such as vinyl chloride, and a method for preventing scale adhesion using the same.

[Conventional technology]

Vinyl chloride polymers are produced by charging vinyl chloride monomers or a mixture of vinyl monomers containing vinyl chloride monomers as the main component into a polymerization vessel, and then placing them in an aqueous medium containing a suspending agent, a polymerization initiator, etc. Manufactured by polymerization. At that time, a problem arises in that the polymer adheres as scale to the inner wall surface of the polymerization vessel. When scale adheres, the cooling capacity of the polymerization vessel decreases and the yield of the polymer decreases. Furthermore, if the scale is exfoliated and mixed into the product, the polymer will become non-uniform and quality will deteriorate. Therefore, it is necessary to remove the scale for each batch, which requires a great deal of labor and time. Additionally, scale contains unreacted monomers that are toxic.
Sufficient care is required during work. As a method of preventing scale from adhering to the inner wall surface of a polymerization vessel, Japanese Patent Publication No. 45-30835 discloses a method of applying a dye or pigment as a scale inhibitor. However, when this method is used, disadvantages such as a decrease in the polymerization rate, dissolution of the coating film of the scale inhibitor and coloring of the polymer, and a decrease in bulk specific gravity may occur. In addition, this inhibitor has low adhesive strength and may peel off from the wall of the polymerization vessel, and if the scale generated at the peeled part is mixed into the polymer, the quality of the product polymer will deteriorate, and when the obtained polymer is molded. A fish eye occurs. Molded products with fish eyes not only have poor appearance but also low strength. PVC polymers are required to further improve their properties such as bulk specific gravity, gelation rate, initial coloration, and thermal stability. In terms of strength and strength, it is necessary that the coloring be small, homogeneous, and without fish eyes, so the development of scale adhesion prevention agents and methods to obtain high quality vinyl chloride polymers is desired. There is.

[Problem to be solved by the invention]

The present invention has been made to solve the above-mentioned problems, and it is possible to prevent polymer scale from adhering to the inside of the polymerization vessel when polymerizing vinyl monomers, and to achieve high quality with less coloring and fish eyes. It is an object of the present invention to provide a scale adhesion prevention agent and a scale adhesion prevention method during the production of a vinyl chloride polymer, which yields a vinyl chloride polymer.

[Means to solve the problem]

The scale adhesion inhibitor of the present invention, which has been developed to achieve the above object, contains a xanthone natural pigment and polyvinyl alcohol having a saponification degree of 70 mol% or more. In addition, the method for preventing scale adhesion during the production of vinyl chloride polymers of the present invention can be applied to at least part of the portion of the polymerization vessel in contact with the monomers when polymerizing vinyl monomers containing vinyl chloride monomers. , xanthone natural pigment and saponification degree 70
A coating film containing polyvinyl alcohol in a mole % or more is formed. Examples of xanthone natural pigments include gentisin,
Examples include isogentisin, swertiamarin, euxanthone, jacaroibine, mangosteen, mangiferin, liquexanthone, asperxanthone, labenerin and derivatives thereof. As the polyvinyl alcohol, one having a high degree of saponification and an average degree of polymerization P is used in order to improve the residual property on the wall surface, monomer film formation resistance, etc. The saponification degree needs to be 70 mol% or more, and 8
It is preferably 0 mol% or more, more preferably 90 mol% or more. Particularly preferred is 98 mol% or more. Note that if the degree of saponification is less than 70 mol%, the residual property on the wall surface and the monomer film formation resistance will be insufficient. The average degree of polymerization F is preferably 1000 or more, more preferably 1500 or more. Particularly preferred is one with a value of 2000 or more. One kind of polyvinyl alcohol may be used alone, or a plurality of polyvinyl alcohols having different saponification degrees and average degrees of polymerization may be used in combination. The weight ratio of xanthone natural pigment and polyvinyl alcohol is 100:0.1 to 5000. Preferably
100: l-1000. The polymer scale inhibitor of the present invention is used by dissolving it in a suitable solvent to prepare a coating solution, applying it to the inner wall surface of a polymerization vessel, etc., and drying it. Solvents include water, and examples include methanol, ethanol, propatool, butanol, 2-butanol, 2-methyl-1-propatool, 2-methyl-2-propatool, 3-methyl-1-butanol, 2- Alcohol solvents such as methyl-2-butanol and 2-pentanol, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, methyl formate, ethyl formate,
Ester solvents such as methyl acetate and methyl acetoacetate, ether solvents such as 4-methyldioxolane and ethylene glycol diethyl ether, and aprotic solvents such as furans, dimethylformamide, dimethyl sulfoxide, and acetonitrile can be used. These may be used alone or in combination. The total concentration of the xanthone natural dye and polyvinyl alcohol in the coating liquid is set to about 0.001 to 20% by weight. In order to enhance the scale adhesion prevention effect, for example, hydrophilic polymers (anionic, cationic, amphoteric), surfactants, amine compounds, phenol group-containing compounds, and quinone compounds are added to the scale adhesion prevention agent coating solution. May be added. There are no particular restrictions on the pH of the scale adhesion inhibitor, but a pH adjuster may be added as necessary. Examples of pH adjusters include sulfuric acid, phosphoric acid, acetic acid, oxalic acid,
Examples include lactic acid, p-toluenesulfonic acid, phytic acid, thiogelcholic acid, gelcholic acid, sodium hydroxide, potassium hydroxide, aqueous ammonia, and ethylenediamine. The coating liquid prepared in this way can be applied to, for example, the inner wall of the polymerization vessel, stirring blades, stirring shafts, condensers, headers, etc.
It is applied to areas that come into contact with the monomer during the polymerization reaction, such as search coils, bolts, and nuts, and is dried to form a coating film. In addition to this, it is also desirable to apply the coating liquid to parts of the unreacted monomer recovery system, such as monomer distillation columns, condensers, monomer storage tanks, valve inner surfaces, etc., where scale may adhere. The material of the coated surface is not particularly limited, and may include, for example, stainless steel, other steel, and a glass-lined surface. The method for applying the coating liquid may be arbitrary, such as applying it to the surface, spray coating, or filling the polymerization vessel with the coating liquid and then drawing it out. For the coating, a method such as that disclosed in Japanese Unexamined Patent Publication No. 57-61001, in which a nozzle is provided in the upper part of the polymerization vessel and automatic spray coating can be used, can be used. Japanese Unexamined Patent Publication 1987-
As disclosed in Japanese Patent No. 11303, the scale preventive agent may be applied in a polka dot pattern. In addition, JP-A-55
An automatic coating method such as that disclosed in Japanese Patent No. 36288, in which the scale inhibitor is sprayed using water vapor as a carrier gas, may be used. Even if vinyl chloride monomer (Japanese Patent Publication No. 56-501116) is used as the carrier gas, low-boiling hydrocarbon gas (Japanese Patent Publication No. 56-5011) may be used as the carrier gas.
No. 17 Publication) may be used. The coating liquid is dried at a temperature ranging from room temperature to 100°C. For drying, hot air may be applied after coating, or the coated surface such as the inner wall of the polymerization vessel may be heated to 30 to 80° C. in advance, and the coating liquid may be directly coated on the heated surface. After drying, wash the coated surface with water if necessary. The coating film is 0.001g/
m" or more, particularly 0.05 to 2 gem". Furthermore, the above coating operation may be carried out every time a batch is polymerized, but since the coating film formed once has considerable durability and the scale adhesion prevention effect lasts, the coating operation is usually carried out once. ~ You can do this every ten or so batches. The scale adhesion inhibitor and method for preventing scale adhesion of the present invention are applicable regardless of the type of polymerization, but are effective in suspension polymerization, particularly in suspension polymerization of a dispersion system containing Popal as a dispersant. After forming a coating film on the parts that come in contact with the monomers, such as the inner wall of the polymerization vessel as described above, vinyl chloride monomer or a monomer that can be copolymerized with vinyl chloride is charged, and polymerization is carried out according to a conventional method. . In addition, a polymerization medium, a dispersion aid for dispersing the monomer, and the like may be added as necessary. To specifically explain an example of suspension polymerization, polymerization is generally carried out by charging water and a dispersion aid into a polymerization vessel, then adding a polymerization initiator, evacuating the inside of the polymerization vessel, and reducing the pressure to approximately 0.1 to 760 mmHg. , monomers are charged, and water, a dispersion aid, a polymerization initiator, etc. are added as necessary during polymerization. As the dispersion aid and polymerization initiator, those conventionally used in the polymerization of vinyl chloride polymers can be used.For 100 parts by weight of the monomer, approximately 100 to 500 parts by weight of water and the dispersion aid are used. Approximately 0.
The polymerization initiator is used in an amount of about 0.01 to 30 parts by weight, and the polymerization initiator is used in an amount of about 0.01 to 5 parts by weight. The polymerization temperature is usually 30 to 80°C,
The internal pressure of the polymerization vessel is approximately 0.5 to 30 kg/cm2. The polymerization reaction is completed when the internal pressure of the polymerization vessel is approximately 0 to 7 kg/c.
When the temperature drops to m2, there is no heat generated by the polymerization reaction,
The process is judged to be complete when the temperature difference between the water flowing in and out of the cooling jacket of the polymerization vessel disappears. The scale adhesion prevention agent and scale adhesion prevention method of the present invention utilize vinyl monomers containing vinyl chloride monomers, that is,
It is effective for polymerizing vinyl chloride monomer alone or vinyl chloride monomer and other monomers that can be copolymerized with vinyl chloride monomer. Monomers copolymerizable with vinyl chloride include, for example, vinyl esters such as vinyl acetate and vinyl propionate, salts of acrylic acid, methacrylic acid and their esters, maleic acid or fumaric acid and their esters, Examples include anhydrides, styrene, acrylonitrile, vinylidene halides, and vinyl ethers. In addition, various additives conventionally used in the production of vinyl chloride polymers, such as polymerization initiators, dispersants, solid dispersants, emulsifiers, fillers, stabilizers, lubricants, and chain transfer agents, are added to the polymerization system. The scale adhesion inhibitor works effectively even if it contains. Specific substance names are listed below (polymerization initiators include, for example, t-butylperoxyneodecanate, bis(2-ethylhexyl)peroxydicarbonate, and 3.5.5-trimethylhexanoylperoxycarbonate. oxide, α-cumyl peroxyneodecanate, cumene hydroperoxide, cyclohexanone peroxide, t-butylperoxybiparate, bis(2-ethoxyethyl) peroxydicarbonate, benzoyl peroxide, lauroyl peroxide, 2,4-
Dichlorobenzoyl peroxide, diisopropyl peroxydicarbonate, Ja'-azobisisobutyronitrile, a,a'-azobis-2,4-dimethylvaleronitrile, potassium belloxonisulfate, ammonium belloxonisulfate, p-menthane hydroper Oxide can be used. As the dispersant, for example, a partial oxide of polyvinyl acetate, polyacrylic acid, a copolymer of vinyl acetate and maleic anhydride, a cellulose derivative such as hydroxypropylmethylcellulose, a natural or synthetic polymer compound such as gelatin, etc. can be used. Examples of solid dispersants include calcium phosphate and hydroxyapatite. Emulsifiers include, for example, sorbitan monolaurate, sorbitan triolate, nonionic emulsifiers such as polyoxyethylene alkyl ether, sodium lauryl sulfate,
Examples include sodium alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, and anionic emulsifiers such as sodium dioctylsulfosuccinate. Examples of fillers include calcium carbonate and titanium oxide. Stabilizers that can be used include, for example, tribasic lead sulfate, calcium stearate, dibutyltin dilaurate, and dioctyltin methyl butide. Examples of the lubricant include rice wax, stearic acid, and cetyl alcohol. Examples of the plasticizer include dioctyl phthalate and dibutyl phthalate. Examples of chain transfer agents include trichlorethylene and mercaptans.

[Effect]

When producing a vinyl chloride polymer using a polymerization vessel, if a coating film of the scale adhesion prevention agent of the present invention is formed on the parts that come into contact with monomers, such as the inner wall of the polymerization vessel, polymer scale can be prevented. adhesion is prevented.

【Example】

The present invention will be explained in detail below. - Preparation of scale adhesion preventive agent According to the composition ratio shown in Table 1 below, xanthone natural pigment and polyvinyl alcohol are dissolved in a solvent, a pH adjuster is added, and a coating liquid of a scale adhesion preventive agent is prepared. Table 1 shows the xanthone natural pigment (component A) and polyvinyl alcohol (component B) used in each example and comparative example.
), their weight ratios, solvents (compositional ratios of solvents), total concentrations, pH adjusters, and pH of coating solutions. As polyvinyl alcohol, commercially available products shown in Table 2 were used.・Polymerization test The obtained coating liquid was applied using a sprayer to the inner wall of a stainless steel polymerization vessel with an internal volume of 1000 g equipped with a stirrer, the stirring shaft, stirring blades, and other parts that come into contact with the vehicle body, and the jacket was
After heating and drying at 0°C for 10 minutes, the film is washed with water to form a coating film. Into a polymerization vessel subjected to scale prevention treatment in this manner, 400 kg of water, 200 kg of vinyl chloride monomer, 250 g of partially saponified polyvinyl alcohol, 25 g of hydroxypropyl methylcellulose, and 75 g of diisopropyl peroxydicarbonate were charged, and while stirring,
Polymerization was carried out according to a conventional method at ℃.=・Measurement of scale adhesion amount After completion of polymerization, scrape off the polymer scale adhering to the inner wall of the polymerization vessel from the wall and measure the weight per wall surface 1 IT1″.・Lightness index ( Next, the lightness index of the polymers obtained in each example and comparative example was measured to determine the presence or absence of coloration.The lightness index was measured by the following method: Vinyl chloride polymer 100 Parts by weight, 1 part by weight of stabilizer (manufactured by Akishima Kagaku Co., Ltd., TS-101), 0.5 parts by weight of stabilizer (manufactured by Katsuta Kako Co., Ltd., C-100J), and 50 parts by weight of dioctyl phthalate as a plasticizer were milled on a two-roll mill. After cross-wiring at 160°C for 5 minutes, a sheet with a thickness of 1 mm is formed.Then, the formed sheet is 4 x 4 x 1.5 cm.
Put it in the formwork of 160'C165~70kgf/cm"
A sample for measurement is created by heating and pressure molding. The brightness index of this sample was determined according to Hunter's color difference formula described in JIS Z 873G (19801), and it was evaluated that the larger the L value, the higher the whiteness.The L value was determined as follows: JIS Z 8722. According to the description, use a standard light C1 photoelectric colorimeter (manufactured by Nippon Denshoku Industries Co., Ltd., Z-1001DP type colorimeter) to determine the stimulus value Y of the xYZ color system by the stimulus value direct reading method.Illumination and light reception The geometric conditions of JIS Z 8722 (condition d described in section D4.3.1) were adopted.
73011980), the formula, L = IOY”
The L value is calculated by substituting it into ``.The results are shown in Table 1. ・100 parts by weight of the fisheye measurement polymer, 50 parts by weight of dioctyl phthalate, 1 part by weight of dibutyltin dilaurate, 1 part by weight of cetyl alcohol, After kneading a mixture of 0.25 parts by weight of titanium oxide and 0.05 parts by weight of carbon black with two rolls at 150°C for 7 minutes, a sheet with a thickness of 0.2 mm was prepared, and a sheet of 100 cm was mixed by a light transmission method. The number of fish eyes was measured. - Measurement of bulk specific gravity The bulk specific gravity of the obtained polymer was measured according to the method specified in JIS K-6721. Table 1 shows the measurement results of scale adhesion amount, lightness index, and fish eye, and Table 3 shows the measurement results of bulk specific gravity. Note that Example 1
-18 is an example to which the present invention is applied, and Comparative Examples 1 to 5 are examples to which the present invention is not applied. (The following is a blank space) Table 2 Table 3 According to these test results, it can be seen that the vinyl chloride polymers polymerized in each example had a high brightness index of 70 or more, a high degree of whiteness, and little discoloration. It also has high quality with fewer fish eyes.

【Effect of the invention】

As explained above in detail, the scale adhesion inhibitor of the present invention during the production of vinyl chloride polymers can be applied to the polymer regardless of the types of monomers and additives used in polymerization, or the material of the polymerization vessel. It is possible to prevent scale adhesion. Since this scale adhesion inhibitor does not dissolve in the polymerization system, a vinyl chloride polymer with no coloration and high whiteness can be obtained. In addition, according to the method for preventing scale adhesion of the present invention, since scale adhesion is prevented, scale is not mixed into the polymer product (i.e., a high-quality vinyl chloride polymer that is less likely to cause fish eyes). Furthermore, it is not necessary to perform scale removal work for each batch of polymerization, resulting in high productivity.

Claims (1)

[Scope of Claims] 1. A scale adhesion preventive agent for the production of vinyl chloride polymers, which comprises a xanthone natural pigment and polyvinyl alcohol with a degree of saponification of 70 mol% or more. 2. When polymerizing vinyl monomers containing vinyl chloride monomers, xanthone natural dyes and polyvinyl alcohol with a saponification degree of 70 mol% or more are added to at least part of the part of the polymerization vessel in contact with the monomers. 1. A method for preventing scale adhesion during production of a vinyl chloride polymer, the method comprising forming a coating film containing a vinyl chloride polymer.