JPH04154803A - 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 tannic natural pigment and a PVA having a specific saponification degree, effective for preventing the deposition of polymer scale and giving a colorless polymer having high whiteness and only a little forming fish-eye. CONSTITUTION:The objective preventing agent contains (A) a tannic natural pigment (e.g. chlorogenic acid, theogallin, catechin, gallocatechin or furobufen) 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 was 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 reduce coloring and fish eyes (high It is an object of the present invention to provide a scale adhesion inhibitor and a method for preventing scale adhesion during the production of a vinyl chloride polymer, by which a high quality vinyl chloride polymer can be obtained.

[Means for Solving the Problems] The scale adhesion preventive agent for producing vinyl chloride polymers of the present invention, which has been made to achieve the above-mentioned object, contains tannin-based natural pigments and polyvinyl alcohol with a saponification degree of 70 mol% or more. Contains. 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. A coating film containing tannin-based natural pigments and polyvinyl alcohol with a saponification degree of 70 mol% or more is formed on the surface. Tannin-based natural pigments include, for example, chlorogenic acid, isochlorogenic acid, theogarin, and other chlorogenic acids and their derivatives; catechin, gallocatechin, and other catechins and their derivatives; and leucoanthocyanins and these derivatives, such as flobuffene. can be mentioned. 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 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 tannin-based natural pigment and polyvinyl alcohol is IO [1:0.1 to 5000]. Preferably 1
00:1 to 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, furans, aprotic detergents such as dimethylformamide, dimethyl sulfoxide, and acetonitrile can be used. . These may be used alone or in combination. The total concentration of tannin-based natural pigments and polyvinyl alcohol in the coating solution 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 brushing, spray coating, 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 the upper part of the polymerization vessel and automatically performs spray coating, 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. For the carrier gas, vinyl chloride monomer (Japanese Patent Publication No. 56-5011.16)
Even if low boiling point hydrocarbon gas
117) may be used. The coating solution is dried at a temperature ranging from room temperature to 100'C. Drying can be done by applying warm air after coating, or by heating the coated surface, such as the inner wall of the polymerization vessel, to 30 to 80 degrees Celsius in advance.
The coating liquid may be applied directly to the heated surface. After drying,
Rinse the coated surface with water if necessary. The coating film is 0.001g
/m" or more, especially 0.05 to 2 g/m2.Also, the above coating operation may be carried out for each batch of polymerization, but the coating film formed is quite durable. The scale adhesion prevention agent and scale adhesion prevention method of the present invention can be applied regardless of the type of polymerization. Although it is applicable, it is effective in suspension polymerization, especially in suspension polymerization of dispersion systems containing Poval as a dispersant.As mentioned above, it forms a coating film on the areas where monomers come into contact, such as the inner wall of the polymerization vessel. After that, vinyl chloride monomer or a monomer copolymerizable with vinyl chloride is charged, and polymerization is carried out according to a conventional method.In addition, polymerization media used as necessary and monomers for dispersing the monomers are added. A dispersion aid, etc. may be added. To explain specifically 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. The pressure is reduced to about 0.1 to 760 mmHg, the monomers are charged, and water, a dispersion aid, a polymerization initiator, etc. are added as necessary during polymerization.The dispersion aid and polymerization initiator are Those conventionally used in the polymerization of vinyl chloride polymers can be used, and for 100 parts by weight of monomer, water is about 100 to 500 parts by weight, and dispersion aid is about 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.
m” or when the heat generation due to polymerization reaction disappears,
There is no temperature difference between the water entering and exiting the cooling jacket of the polymerization reactor (
It is considered complete when the 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. Examples of the polymerization initiator include butyl peroxyneodecanate, bis(2-ethylhexyl)peroxydicarbonate, 3,5.5-1-limethylhexanoyl peroxide, α-cumylperoxyneodecanate, Cumene hydroperoxide, cyclohexanone peroxide, t-butyl peroxybivalate, bis(2-
ethoxyethyl) peroxydicarbonate, benzoyl peroxide, lauroyl peroxide, 2.4
-dichlorobenzoyl peroxide, diisobrobyl peroxydicarbonate, a, a"-azobisisobutyronitrile, a, a'-azobis-2,4-dimethylvaleronitrile, potassium beroxonisulfate, ammonium belloxonisulfate, p - Menthane hydroperoxide can be used.Dispersants include, for example, partial oxides of polyvinyl acetate, polyacrylic acid, copolymers of vinyl acetate and maleic anhydride, cellulose derivatives such as hydroxypropyl methyl cellulose, natural or Synthetic polymer compounds can be used. Examples of solid dispersants include calcium phosphate and hydroxyapatite. Examples of emulsifiers include nonionic emulsifiers such as sorbitan monolaurate, sorbitan triolate, and polyoxyethylene alkyl ether, and 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 methylcaptide. 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. [Function] When producing a vinyl chloride polymer using a polymerization vessel, if a coating film of the scale adhesion preventive agent of the present invention is formed on the parts that come into contact with the monomer, such as the inner wall of the polymerization vessel, Adhesion of polymer scale 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, tannin-based natural pigments and polyvinyl alcohol are dissolved in a solvent, a pH adjuster is added, and a coating liquid of a scale adhesion inhibitor is prepared. Table 1 shows the types of tannin-based natural pigments (component A) and polyvinyl alcohol (component B) used in each example and comparative example, their weight ratio, solvent (solvent composition ratio), total concentration, and pH adjustment. The pH of the agent and coating solution is shown. 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 100 (1!) equipped with a stirrer, the stirring shaft, stirring blades, and other parts that come into contact with the vehicle body, and the jacket was 5
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 methyl cellulose, and 75 g of diisopropyl peroxydicarbonate were charged, and the mixture was heated without stirring for 57 g.
Polymerization was carried out at °C 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-100J), and 50 parts by weight of dioctyl phthalate as a plasticizer were kneaded at 160°C for 5 minutes using a two-roll mill. , form a sheet with a thickness of imm. Next, the formed sheet is 4 x 4 x 1.5 cm.
A sample for measurement is prepared by placing it in a mold and heating and pressurizing it at 160°C and 65 to 70 kgf/cm. The larger the L value, the higher the whiteness.The L value is determined as follows.According to the description of JIS Z 8722, a standard light C1 photoelectric colorimeter (manufactured by Nippon Denshoku Industries Co., Ltd., 2-1 (IDIDP
xYZ using a direct reading method of stimulus values.
Calculate the stimulus value Y of the color system. Geometric conditions for illumination and light reception are JIS Z 8722 (7) 4.3.1.
Condition d described in Section 1 was adopted. Stimulus value Y, JIS Z
8730 (described in 19801, formula, L = IOY
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 dilaurenite, 1 part by weight of Cetylua J Récole, 0.25 parts by weight of titanium oxide and 0.05 parts by weight of carbon black was added to 150 parts by weight. After kneading with two rolls at ℃ 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 scale adhesion amount, lightness index, and fish eye, and Table 3 shows the bulk specific gravity measurement results. 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 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 used as a single polymer regardless of the types of monomers and additives used in polymerization, and 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 tannin natural pigment and polyvinyl alcohol having a saponification degree of 70 mol% or more. 2. When polymerizing vinyl monomers containing vinyl chloride monomers, at least part of the part of the polymerization vessel in contact with the monomers is coated with tannin-based natural pigments and polyvinyl alcohol with a saponification degree of 70 mol% or more. 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.