JPH04108804A - Agent for preventing deposition of polymer scale and method for preventing deposition thereof - Google Patents

Abstract

PURPOSE:To provide the subject preventing agent containing a natural naphthoquinone pigment, a highly saponified PVA and a PVA having a specific saponification degree, capable of effectively preventing the deposition of polymer scale in the polymerization of a vinyl chloride monomer, causing little discoloration of produced polymer and giving a molded article having little fish-eye. CONSTITUTION:The objective preventing agent contains (A) a natural naphthoquinone pigment (preferably shikonin or naphthazarin), (B) a PVA having a saponification degree of >=95mol%, preferably >=98mol% and (C) a PVA having a saponification degree of 50-95mol%, preferably 70-93mol%. The agent is applied to the inner wall surface of a polymerizer.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a polymer scale adhesion inhibitor for the polymerization of vinyl chloride monomer or a monomer mixture mainly composed of vinyl chloride, and a polymer scale adhesion prevention agent. Regarding prevention methods.

[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.

When polymer scale adheres to the inner wall surface of the polymerization vessel, the yield of the polymer decreases, the cooling capacity of the polymerization vessel decreases, and the quality of the product polymer decreases due to the adhered polymer scale peeling off and contaminating the product. In addition, there are disadvantages such as a great deal of effort and time required to remove the polymer scale. Moreover, the polymer scale contains unreacted monomers, which can expose workers and cause physical injury.

Conventionally, in the polymerization of monomers having ethylenic double bonds, the method of preventing polymer scale from adhering to the inner wall surface of the polymerization vessel, etc. is to use a suitable substance as a polymer scale adhesion inhibitor. There is a known method of applying it to

Substances suitable as polymer scale adhesion inhibitors include:
For example, there are dyes and pigments described in Japanese Patent Publication No. 45-30835.

[Problem to be solved by the invention]

By the way, recently, molded products of vinyl chloride polymers, especially transparent sheets, bottles, etc., have been improved in terms of appearance and mechanical properties, such as degree of coloration, fish eyes, bulk specific gravity, gelation rate, initial coloration, and thermal stability. Demand from users for quality improvements in various physical properties such as properties is increasing. Therefore, it is desired to develop a polymer scale adhesion inhibitor that does not adversely affect the physical properties of the resulting polymer.

However, when the above dyes and pigments are used as polymer scale adhesion inhibitors, the following (i) and (ii)
), it has an adverse effect on the physical properties of the product polymer.

(i) Since the coating film made of the polymer scale adhesion inhibitor is easily melted, the obtained product polymer may be colored or its bulk specific gravity may be reduced.

(ii) Due to the weak adhesion of the coating film to the inner wall surface of the polymerization vessel,
During polymerization, the coating film peels off and partially disappears, and scale adheres there, which causes an increase in fins' eyes when the obtained polymer is processed into molded products such as sheets.

[Failure to solve the problem]

The object of the present invention is to be able to always effectively prevent the adhesion of polymer scale in the polymerization or copolymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride, and to have a significantly low degree of coloration. It is also an object of the present invention to provide a polymer scale adhesion inhibitor and a polymer scale adhesion prevention method that can obtain a high quality product polymer with very few fish eyes in a molded article.

That is, the present invention achieves the above object by using (A) a naphthoquinone natural dye, (B) polyvinyl alcohol with a saponification degree of 95 mol% or more, and (C) polyvinyl with a saponification degree of 50 mol% or more and less than 95 mol%. A polymer scale anti-adhesion agent for the polymerization of a vinyl chloride monomer or a vinyl chloride-based monomer mixture containing alcohol is provided.

The present invention also provides a method for preventing the adhesion of polymer scale during polymerization of a vinyl chloride monomer or a monomer mixture mainly composed of vinyl chloride in a polymerization vessel, the method comprising: The above (A), (B) and (C
A method for preventing the adhesion of polymer scale is provided, which comprises the step of carrying out the polymerization in a polymerization vessel in which a coating film containing a component (1) is formed.

8. Naphthoquinone natural dye, which is the component (A) of the polymer scale adhesion inhibitor of the present invention, is 6-methyl-1,4
~ Naphthoquinone, 2-methyl-1,4-naphthoquinone,
Lawson, Nigeron, Plumbagin, Alcannin, Equituchrome A1 Subinochrome A, Vitamin Kl, Vitamin 2, Naphthazarin, 23-dihydroxynaphthazarin, 2-methylnaphthazarin, 2-hydroxynaphthazarin, 2-hydroxy 3-methyl Naphthazarin, 2
-Hydroxy-3-ethylnaphthazarin, 2-hydroxy-3-acetylnaphthazarin, 2,7-dimethylnaphthazarin, alkanna, shikonin, acetylshikonin,
Examples include isobutylshikonin, β, β'-dimethylacrylshikonin, β-hydroxyisowallershikonin, teracrylshikonin, and derivatives thereof. These can be used alone or in combination of two or more, and the combination is selected as appropriate.

Among these naphthoquinone-based natural pigments, particularly preferred are shikonins such as shikonin, acetylshikonin, isobutylshikonin, β, β'-dimethylacrylshikonin, β-hydroxyisowallershikonin, and teracrylshikonin, and naphthazarin, 2 , 3-dihydroxynaphthazarin, 2-methylnaphthazarin, 2-hydroxynaphthazarin, 2-hydroxy-3-methylnaphthazarin, 2-hydroxy-3-ethylnaphthazarin, 2-
Naphthazarins such as hydroxy-3acetylnaphthazarin and 2,7-dimethylnaphthazarin. These shikonins and naphthazarins can be obtained by extracting the roots of purple roots (purple roots) with an organic solvent.

(B) 1 Vinyl alcohol 95≦ The polyvinyl alcohol that is the component (B) of the polymer scale adhesion inhibitor of the present invention needs to have a saponification degree of 95 mol% or more, and in particular, a saponification degree of 98 mol%. It is preferable that the above is the same.Also, the residual property on the surface where the coating film is formed,
In order to improve monomer resistance and the like, it is preferable that the degree of polymerization of the polyvinyl alcohol as component (B) is high.

(C) Polyvinyl alcohol 50≦Ken<95 The polyvinyl alcohol which is the component (C) of the polymer scale adhesion inhibitor of the present invention has a saponification degree of 50 mol% or more and 95 mol%
It is particularly preferable that the degree of saponification is 70 mol% or more and less than 93 mol%. Also,
The degree of polymerization of the polyvinyl alcohol as component (C) is also determined in order to increase the persistence on the coating surface, monomer resistance, etc.
Higher is preferable.

The polymer scale adhesion inhibitor of the present invention includes the above (A)
, (B) and (C), a solvent may be included as necessary. In addition, this polymer scale adhesion inhibitor also has
In order to enhance the scale prevention effect, various anionic, cationic and amphoteric hydrophilic polymer compounds, surfactants, amine compounds, phenol group-containing compounds, quinone compounds, etc. can also be added.

The polymer scale adhesion prevention agent of the present invention prevents scale adhesion to the inner wall surface of the polymerization vessel by being formed as a coating film on the inner wall surface of the polymerization vessel.

Usually, when forming the coating film on the inner wall surface of a polymerization vessel, it is used in the form of a solution, that is, as a coating liquid.

Coating liquid as described above is prepared by adding the above-mentioned components (A), (B) and (C) to a suitable solvent.

Examples of the solvent used for preparing such a coating solution include water; methanol, ethanol, propatool, butanol, 2-butanol, 2-methyl-1-propatool, 2-methyl-2-propatool, 3 -Methyl-1-
Alcohol-based i-agents such as butanol, 2-methyl-2-butanol, and 2-pentanol; Ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; Ester-based agents such as methyl formate, ethyl formate, methyl acetate, and methyl acetoacetate. Solvents: Ether solvents such as 4-methyldioxolane and ethylene glycol diethyl ether; Furan; aprotic solvents such as dimethylformamide, dimethyl sulfoxide and acetonitrile; and the like. These solvents may be used alone or as a mixed solvent of two or more.

The total concentration of components (A), (B) and (C) in the coating liquid is not particularly limited as long as the coating amount per unit area described below is obtained, but it is usually 0.001 to 20% by weight, preferably 0.001 to 20% by weight. It is about 0.005 to 5% by weight. Further, the content ratio of each of component (B) and component (C) to component (A) in the coating liquid is usually 0.0% per 100 parts by weight of component (A).
The amount is 1 to 5000 parts by weight, preferably 1 to 1000 parts by weight. If the amount of component (B) or component (C) is too large or small compared to component (A), there is a possibility that the effect of improving the scale prevention effect by using the three components together may not be obtained. More preferably, (B) in the coating liquid
It is better to set the content ratio of the component and the component (C) to 1150 to 50/1.

Moreover, the pH of the coating liquid is not particularly limited. A PH adjuster can be added if necessary. The pH adjusters include sulfuric acid, phosphoric acid, acetic acid, oxalic acid,
Examples include lactic acid, p-)luenesulfonic acid, phytic acid, thioglycolic acid, glycolic acid, sodium hydroxide, potassium hydroxide, aqueous ammonia, and ethylenediamine, which are used as appropriate.

To form a coating film on the inner wall surface of the polymerization vessel using the coating liquid prepared as described above, first, apply the coating liquid to the inner wall surface of the polymerization vessel, and then, for example, After sufficiently drying at a temperature up to °C, further washing with water is performed as necessary. In this way, since a coating film is formed on the inner wall surface of the polymerization vessel, adhesion of polymer scale to the inner wall surface of the polymerization vessel is prevented.

Further, it is preferable that the coating liquid is applied not only to the inner wall surface of the polymerization vessel but also to other parts that come into contact with the monomer during polymerization, thereby forming a coating film.

For example, it is preferable to form a coating film on stirring blades, stirring shafts, baffles, condensers, headers, search coils, bolts, nuts, etc. by applying the coating liquid. In particular, stirring blades,
Usually, a coating film should be formed on the stirring shaft and the baffle by applying the coating solution. To form a coating film by applying a coating liquid to these parts, it is possible to perform the same process as in the case of forming a coating film on the inner wall of the polymerization vessel.

More preferably, the coating liquid is applied to areas where polymer scale may adhere even to areas other than those that come into contact with monomers during polymerization, such as equipment and piping of an unreacted monomer recovery system. It is preferable to apply the coating liquid to the inner surface to form a coating film.

More specifically, such sites include the inner surfaces of monomer distillation columns, condensers, monomer storage tanks, valves, and the like. The coating film may be formed at these locations in the same manner as in the case of forming the coating film on the inner wall of the polymerization vessel.

In this way, by forming a coating film on areas that come into contact with monomers during polymerization and other areas where polymer scale may adhere, it will prevent polymer scale from adhering to those areas. Ru.

The method of applying the coating liquid to the inner wall surface of the polymerization vessel is not particularly limited, and includes, for example, brush coating, spray coating, and a method of filling the polymerization vessel with the coating liquid and then drawing it out.
Others: JP-A-57-61001, JP-A No. 55-3628
No. 8, Special Publication No. 56-501116, No. 5650111
It is also possible to use the automatic coating method described in No. 7, JP-A-59-11303, and the like.

Further, the method of drying the surface that is wet due to the application of the coating liquid is not limited, and for example, the following method can be used.

That is, after applying the coating liquid, a method in which appropriately heated hot air is applied to the coating surface, or a method in which the inner wall surface of the polymerization vessel and other surfaces to which the coating liquid is to be applied are heated to, for example, 30 to 80°C in advance. , a method of directly applying a coating liquid to the heated surface, etc. can be used. After the coated surface is dried, the coated surface is washed with water if necessary.

The coating film thus obtained has a coating amount per unit area of usually 0.001 g/bo or more, particularly 0.05 to 0.
2 g/n (preferably.

The above coating operation may be performed every time one to ten batches of polymerization are carried out. Since the formed coating film has high durability and the effect of preventing the adhesion of polymer scale continues, it is not necessary to carry out the process every time one batch of polymerization is carried out. Therefore, the productivity of the product polymer is improved.

Ri□Kin After forming a coating film on the inner wall of the polymerization vessel and preferably on other areas that will come into contact with the monomer during polymerization as described above, polymerization is carried out in the polymerization vessel by a conventional method. I do. That is, in addition to the monomer and polymerization initiator (catalyst), if necessary, a polymerization medium such as water, and a suspending agent,
A dispersant such as a solid dispersant, a nonionic emulsifier, an anionic emulsifier, etc. is charged, and then polymerization is carried out by a conventional method.

The monomer to be polymerized by applying the method of the present invention is a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable with vinyl chloride. Examples of monomers copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid, methacrylic acid, and esters or salts thereof; maleic acid, fumaric acid, and esters or salts thereof; Anhydrides; examples include styrene, acrylonitrile, vinylidene halides, and vinyl ethers.

Furthermore, although the type of polymerization to which the method of the present invention is applied is not particularly limited, suspension polymerization, particularly suspension polymerization of a polymerization system containing partially saponified polyvinyl alcohol and/or fully saponified polyvinyl alcohol as a dispersant, is particularly preferred. Shows effective scale prevention effect.

Hereinafter, the boat-based polymerization method will be specifically explained using suspension polymerization as an example.

First, water and a dispersant are charged into a polymerization vessel, and then a polymerization initiator is charged. Next, the inside of the polymerization vessel was evacuated and 0.1 to 7
After reducing the pressure to 60 mmHg, charge the monomer (at this time, the internal pressure of the polymerization vessel is usually 0.5 to 30 kgf/cml・
G), then polymerized at 30-80°C. During polymerization, one or more of water, a dispersant, and a polymerization initiator are added as necessary. Polymerization is carried out at an internal pressure of 0 to 7 kgf/a11. G, or when the difference between the inlet and outlet temperatures of the cooling water flowing into and out of the jacket installed around the outer periphery of the polymerization vessel has almost disappeared (that is, when the heat generated by the polymerization reaction has disappeared), It is considered complete. The water, dispersant, and polymerization initiator charged during polymerization are usually 20 to 500 parts by weight of water and 0.01 to 30 parts by weight of dispersant per 100 parts by weight of monomer.
parts by weight, and 0.01 to 5 parts by weight of the polymerization initiator.

When polymerization is performed by applying the polymer scale adhesion prevention method of the present invention, polymer scale adhesion can be prevented regardless of the material of the inner wall surface of the polymerization vessel, for example,
Even when polymerization is carried out in a polymerization vessel made of stainless steel or other steel, a glass-lined polymerization vessel, etc., the adhesion of polymer scale can be effectively prevented.

Those added to the polymerization system can be used without any restrictions. That is, for example, t-butylperoxyneodecanoate, bis(2-ethylhexyl)peroxydicarbonate, 3,5°5-trinotylhexanoyl peroxide, α-cumylperoxyneodecanoate, cumene hydroper oxide, cyclohexanone peroxide, t-butyl peroxypivalate, bis(2-ethoxyethyl) peroxydicarbonate,
Benzoyl peroxide, lauroyl peroxide, 2,4-dichlorohensyl peroxide, diisopropyl peroxydicarbonate, α, α'-azobisisobutyronitrile, α, α'-azobis-2,4-
dimethylvaleronitrile, potassium beroxonisulfate,
Polymerization initiators such as ammonium peroxodisulfate and p-menthane hydroperoxide; partially saponified polyvinyl alcohol, completely saponified polyvinyl alcohol, polyacrylic acid, copolymer of vinyl acetate and maleic anhydride,
Suspending agents such as cellulose derivatives such as hydroxypropyl methylcellulose, natural or synthetic polymer compounds such as gelatin; Solid dispersing agents such as calcium phosphate and hydroxyapatite; Nonions such as sorbitan monolaurate, sorbitan triolate, and polyoxyethylene alkyl ether Emulsifiers; anionic emulsifiers such as sodium alkylbenzenesulfonates such as sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium dioctylsulfosuccinate; fillers such as calcium carbonate and titanium oxide; tribasic lead sulfate, calcium stearate, dibutyl tin Stabilizers such as dilaurate and dioctyltin methylcaptide; lubricants such as rice wax, stearic acid, and cetyl alcohol; plasticizers such as DOP and DBP; mercaptans such as t-dodecyl mercaptan, chain transfer agents such as trichloroethylene, etc. Even in polymerization systems, the method of the present invention can effectively prevent the deposition of polymer scale.

〔Example〕

Hereinafter, the present invention will be explained in detail by giving Examples and Comparative Examples. In addition, experiment N marked with * in Table 1 below
o is a comparative example, and the other experiment numbers are examples of the present invention.

Polymerization was carried out in the following manner using a stainless steel polymerization vessel equipped with a stirrer and having an internal volume of 10,001 mm.

In each experiment, first, component (A) (naphthoquinone natural pigment), component (B) (fully saponified polyvinyl alcohol), and component (C) (partially saponified polyvinyl alcohol) were added together as shown in Table 1. □ Dissolve in a solvent to achieve the desired concentration, then measure the pH,
Each coating liquid was prepared by adding a pH adjuster as necessary. Next, this coating solution is applied to the inner wall of the polymerization vessel, stirring shaft, stirring blade, and other parts that come into contact with the monomer during polymerization, heated at 50°C for 10 minutes, dried to form a coating film, and then washed with water. did.

However, experiment No. 101 is a comparative example in which no coating liquid is applied, and experiment Nos. 102 to 104 are results in which component (A) and (B) are not applied.
This is a comparative example in which a coating liquid containing only one or two of the three components () and (C) was applied.

Experiment No. 118 and 119 are azine-based synthetic dyes C and I.

This is a comparative example using Acid Black 2 as the (8) component.

(A) component in the coating liquid used in each experiment, (B)
Types of components and (C) components, weight ratio of (A) components, (B) components, and (C) components in the coating liquid (8)/(B)/(C)
), type of solvent used, (A) + (B
) + (C) total concentration, type of added pH adjuster,
Table 1 also shows the pH of the coating solution.

Thereafter, 400 kg of water, 200 kg of vinyl chloride, 250 g of partially saponified polyvinyl alcohol, 25 g of hydroxypropyl methylcellulose, and 75 g of diisopropyl peroxydicarbonate were charged into the polymerization vessel in which the coating film was formed by the coating process, and the mixture was stirred. Nakara 5
Polymerization was carried out at 7°C for 6 hours.

After the polymerization was completed, the amount of polymer scale adhering to the inner wall of the polymerization vessel (polymer scale adhesion amount) was measured.

Moreover, the whiteness of the polymer obtained in each experiment No. was measured by the following method.

100 parts by weight of polymer, 1 part by weight of stabilizer TS-1o1 (manufactured by Akishima Kagaku Co., Ltd.) and 0.5 part by weight of C-1oo,r (manufactured by Katsuta Kako Co., Ltd.), and 50 parts by weight of plasticizer DOP,
After kneading for 5 minutes at 160°C using a two-roll mill, the mixture was formed into a sheet with a thickness of 1 mm. Then this sheet was put into a formwork of 4 an
A sample for measurement was prepared by heating and pressure molding using fl. Regarding this measurement sample, JIS Z8730 (1980
), and it was evaluated that the larger the L value, the higher the whiteness.

The L value was determined as follows.

■ In accordance with the description of JIS Z 8722, a standard light C1 photoelectric colorimeter (Z-1001 manufactured by Nippon Denshoku Kogyo Co., Ltd.) was used.
X
The stimulus value Y of the 77 color system was determined. Geometric conditions for illumination and light reception are JIS Z 8722 (7) 4.3.
．． Condition d described in Section 1 was adopted.

(2) Next, L was determined by the formula described in JIS Z 8730 (1980): 1-=lQY1/2.

Furthermore, the fish eyes when the polymers obtained in each experiment No. were molded into sheets were measured by the following method.

A mixture prepared at a blending ratio of 100 parts by weight of polymer, 50 parts by weight of DOP, 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 rolled on a 6-inch roll. After kneading the mixture at 150° C. for 7 minutes, it was formed into a sheet with a thickness of 0.2 mm, and the number of Fin Shuai contained per 100 cIfl of the obtained sheet was determined by a light transmission method.

The results of each measurement are shown in Table 1.

In each experiment No., (B) commercially available products shown in Table A below were used as fully saponified polyvinyl alcohol,
(C) Commercially available products shown in Table B below were used as partially saponified polyvinyl alcohol.

Table A (fully saponified polyvinyl alcohol) Table B (partially saponified polyvinyl alcohol) Also, experiment No. 101.118.119.105.1
Regarding the polymer obtained in 06.107.112゜115, the bulk specific gravity was measured using a bulk specific gravity measuring device (manufactured by Kuramochi Scientific Instruments Manufacturing Co., Ltd.; Bulk Specific Gravity Meter) in accordance with the description in Section 3.3 of JIS K 6721. was measured. The results are shown in Table 2.

Table 2 [Effects of the Invention] According to the present invention, it is possible to always effectively prevent the deposition of polymer scale in the polymerization or copolymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride. The coating film formed using the polymer scale adhesion inhibitor of the present invention does not peel off or dissolve in the polymerization system. Therefore, when the present invention is applied, there is no fear that the product polymer will be colored, and as a result, a high degree of whiteness with an L value of 70 or more can be obtained, as well as significantly less fish eyes and a low bulk specific gravity. It is possible to produce a product polymer of high quality without deterioration.

Furthermore, according to the present invention, the adhesion of polymer scale can be effectively prevented regardless of the polymerization conditions such as the type of monomer and polymerization initiator used, the polymerization type, and the material of the inner wall of the polymerization vessel. can do. In particular, in suspension polymerization, no matter which polymerization vessel is used, such as a stainless steel polymerization vessel or a glass-lined polymerization vessel, or even when a polymerization initiator with strong oxidizing power is used, the polymer scale adhesion can be more effectively prevented.

Therefore, when polymerization is carried out by applying the present invention,
It is not necessary to remove polymer scale after each polymerization, which improves productivity and allows production of high-quality product polymers.

Claims (2)

[Claims] (1) A vinyl chloride monomer or Polymer scale anti-adhesion agent for polymerization of monomer mixtures mainly consisting of vinyl chloride. (2) A method for preventing the adhesion of polymer scale during polymerization of a vinyl chloride monomer or a monomer mixture mainly composed of vinyl chloride in a polymerization vessel, in which (A) In a polymerization vessel in which a coating film containing a naphthoquinone natural pigment, (B) polyvinyl alcohol with a saponification degree of 95 mol% or more, and (C) polyvinyl alcohol with a saponification degree of 50 mol% or more but less than 95 mol% is formed. , a method for preventing adhesion of polymer scale, comprising the step of performing the polymerization.