JPH04154805A - 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 flavonoid-type natural pigment and a PVA having a specific saponification degree and giving a colorless polymer having high whiteness and only a little forming fish-eye. CONSTITUTION:The objective preventing agent contains (A) a flavonoid-type natural pigment (e.g. apigenin, primetin, baicalein, oogonine, scutellarein, luteolin, galangin and callistephin) 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. Vinyl chloride polymers are required to further improve their quality in terms of bulk specific gravity, gelation rate, initial coloration, thermal stability, etc. Especially for molded products such as transparent sheets and bottles, appearance and From the viewpoint of strength, it is necessary that the coloring be small, homogeneous, and without fish eyes, so it is desired to develop scale adhesion prevention agents and scale adhesion prevention methods to obtain high quality vinyl chloride polymers. .

[Means to solve the problem]

The scale adhesion inhibitor of the present invention, which has been developed to achieve the above object, contains a flavonoid natural pigment and polyvinyl alcohol having a saponification degree of 70 mol% or more. Furthermore, the method for preventing scale adhesion during the production of vinyl chloride polymers of the present invention provides a method for preventing scale adhesion during the production of vinyl chloride polymers when at least one of the parts of the polymerization vessel in contact with the monomers is Part contains flavonoid natural pigments and saponification degree 7
A coating film containing 0 mol% or more of polyvinyl alcohol is formed. Examples of flavonoid natural pigments include flavones and derivatives thereof such as abigenin, brimethin, pyriterein, ogonin, sphterrarein, luteolin, diosmetin, and tricin, galangin, gutiscetin, kaempferol, fisetin, morin, quercetin, and robinetin. , flavonols and their derivatives such as caricobuterin, gossibetin, myricetin, callistefin, bellargonin, fragalin, raffarin, salvianin, chrysanthymine, cyanine, keracyanin, shisonin, idenine, mecocyanin, rubrobracin, cyanidin-3-arabinocyto, oxyccoccyanin, Anthocyanins and their derivatives such as peonin, delphinin, delphin, nasunin, violanin, hyacin, aobanin, myrtilin, betunin, betunin, betunin, xyloside, enine, malvin, enzathin, uriginosine, and flavonoid C-glycosides such as orientin. and their derivatives, biarabonyls and their derivatives such as ginkgetin, chalcones and their derivatives such as calcumin, isocalcumin, pedisinin, and butyin, aurones and their derivatives such as allucidin, lebutosidin, and practeatin. can be mentioned. - Among the flavonoid natural pigments mentioned in 1, flavones such as abigenin, brimetin, pyriterein, and ogonin, galangin, datiscetin, kaempferol, fisetin, morin, quercetin, robinedine,
Particularly preferred are flavonols such as myricetin, flavonoid C-glycosides such as orientin, chalcones such as calcumin, incalcumin, pedisinin, butyin. Polyvinyl alcohol with a saponification degree 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 is preferably 1,000 or more, more preferably 1,500 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 flavonoid natural pigment and polyvinyl alcohol is 100:0.1 to 5000. Preferably it is 10 mouths: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 flavonoid natural pigment 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 coating liquid may be applied by any method such as brush coating, 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 Patent Application Laid-open No. 57-61001, in which a nozzle is provided in a part of the polymerization vessel and automatically performs spray coating, can be used. Unexamined Japanese Patent Publication 1983
As disclosed in Japanese Patent No. 11303, the scale preventive agent may be applied in a polka dot pattern. Also, JP-A-5
An automatic coating method such as that disclosed in Japanese Patent No. 5-36288, in which the scale inhibitor is sprayed using water vapor as a carrier gas, may be used. For carrier gas,
Vinyl chloride monomer (Special Publication No. 56-501116)
Even if low boiling point hydrocarbon gas
i17 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/
m2 or more, particularly preferably 0.05 to 2 g/m2. 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 Poval 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, and evacuating the inside of the polymerization vessel to reduce 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/Cl112. The polymerization reaction is completed when the internal pressure of the polymerization vessel is approximately 0 to 7 kg.
It is judged that the polymerization process is complete when the temperature decreases to /cm2, when the heat generated by the polymerization reaction disappears, and 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, the polymerization system may contain various substances conventionally used in the production of vinyl chloride polymers, such as polymerization initiators, dispersants, solid dispersants, emulsifiers, fillers, stabilizers, lubricants, and chain transfer agents. Even if additives are included, the anti-scaling agent works effectively. Specific substance names are listed below. Polymerization initiators include, for example, t-butyl peroxyneodecanate, bis(2-ethylhexyl)peroxydicarbonate, 3.5.5-trimethylhexanoyl peroxide, a-cumylperoxyneodecanate, cumene hydroper. oxide, cyclohexanone peroxide, t-butyl peroxypivalate, bis(2-
ethoxyethyl) peroxydicarbonate, benzoyl peroxide, lauroyl peroxide, 2,4
-dichlorobenzoyl peroxide, diisopropyl peroxydicarbonate, a,a'-azobisisobutyronitrile, a,a'-azobis-2,4-dimethylvaleronitrile, potassium beloxonisulfate, ammonium belloxonisulfate, p- Menthane hydroperoxide 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 1, nonionic emulsifiers such as sorbitan monolaurate, sorbitan triolate, and polyoxyethylene alkyl ether; sodium alkylbenzenesulfonates such as sodium lauryl sulfate and sodium dodecylbenzenesulfonate; and anions such as sodium dioctylsulfosuccinate. and emulsifiers. 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 inhibitor According to the composition ratio shown in Table 1 below, flavonoid natural pigment and polyvinyl alcohol are dissolved in a solvent, and the pH is adjusted to
Add a conditioning agent to adjust the coating solution for the scale adhesion prevention agent. Table 1 shows the types of flavonoid natural pigments (component A) and polyvinyl alcohol (component B) used in each example and comparative example, their weight ratio, and the solvent (composition ratio of the solvent).
, total concentration, pFI adjuster and pH of the coating solution. As polyvinyl alcohol, commercially available products shown in Table 2 were used.・Polymerization test The obtained coating liquid has an internal volume of 100u! Use a sprayer to apply the coating to the inner wall of a stainless steel polymerization vessel with a stirrer, the stirring shaft, stirring blades, and other parts that come into contact with the vehicle mass, and apply the jacket to the
After heating and drying at a temperature of 10° C., the film is washed with water to form a coating film.・Into the polymerization vessel which has been subjected to scale prevention treatment in this way, 400 kg of water, 200 kg of vinyl chloride monomer, 250 g of partially saponified polyvinyl alcohol, 25 g of hydroxypropyl methyl cellulose, and 75 g of diisopropyl peroxydicarbonate were charged, and 57 g of diisopropyl peroxydicarbonate was added while stirring.
Polymerization was carried out at ℃ according to a conventional method.・Measurement of scale adhesion amount After completion of polymerization, scrape off the polymer scale adhering to the inner wall surface of the polymerization vessel from the wall surface and measure the weight per rn” of wall surface. ・Measurement of lightness index (L value) Next, each implementation The lightness index of the polymers obtained in Examples and Comparative Examples is measured to determine the presence or absence of coloration.The lightness index was measured by the following method: 100 parts by weight of vinyl chloride polymer, stabilizer (manufactured by Akishima Chemical Co., Ltd.) , TS-101), 0.5 parts by weight of a stabilizer (manufactured by Katsuta Kako Co., Ltd., C-1 (IOJ)), and 50 parts by weight of dioctyl phthalate as a plasticizer were kneaded at 160°C for 5 minutes using a two-roll mill. After that, form a sheet with a thickness of 1 mm. Next, the formed sheet is 4 x 4 x 1.5 cm.
Place in a mold of 160℃, 65-70kgf/cm2
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 8730 (1980), and it was evaluated that the larger the L value, the higher the whiteness. The L value is determined as follows. In accordance with the description of JIS Z 8722, 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. . Condition d described in JIS Z 8722 (7) Section 4.3.1 was adopted as the geometric conditions for illumination and light reception. Stimulus value Y, JIS Z
8730 (1980), the formula, L = JOY
By substituting for "", the L value is calculated. Table 1 shows the results.・Measurement of Fish Eye A mixture of 100 parts by weight of polymer, 50 parts by weight of dioctyl phthalate, 1 part by weight of dibutyltin dilaurate, 1 part by weight of cetyl alcohol, 0.25 parts by weight of titanium oxide and 0.05 parts by weight of carbon black was heated at 150°C. After kneading with two rolls for 7 minutes, a sheet with a thickness of 0.2 mm was prepared, and the number of fish eyes per 100 cm of sheet was measured by a light transmission method. - Measurement of bulk specific gravity of the obtained polymer. The bulk specific gravity was measured according to the method specified in JIS K-6721. Table 1 shows the amount of scale adhesion, lightness index, and fish eye, and Table 3 does not show the measurement results of bulk specific gravity. Note that Example 1
Comparative Examples 1 to 18 are examples 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 margin) 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. Furthermore, 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, and a high-quality vinyl chloride polymer that is less likely to cause fish eyes is produced. can be manufactured. Furthermore, there is no need to perform scale removal work for each batch of polymerization, resulting in high productivity.

Claims (1)

[Claims] 1. Flavonoid natural pigment and saponification degree of 70 mol%
A scale adhesion preventive agent for producing a vinyl chloride polymer, characterized by containing the above polyvinyl alcohol. 2. When polymerizing vinyl monomers containing vinyl chloride monomers, flavonoid natural pigments 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.