JPH0323082B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for polymerizing vinyl chloride monomers. More specifically, vinyl chloride monomers or mixtures of vinyl chloride monomers with copolymerizable monomers (hereinafter collectively referred to as "vinyl chloride monomers"),
The polymer obtained by polymerizing this monomer is called a "vinyl chloride polymer." ), in polymerizing
The present invention relates to a method for preventing polymer scale from forming on the inner wall surface of a polymerization vessel and/or on the surface of equipment attached to a polymerization vessel. Polymerization of vinyl chloride monomers is usually carried out by emulsifying or suspending the vinyl chloride monomers in an aqueous medium containing an emulsifier or dispersant in the presence of a polymerization initiator. In this polymerization process, the inner wall of the polymerization vessel,
Parts that come into contact with the vinyl chloride monomer, such as the stirring blades, bubbles, walls of the reflux condenser, and walls of various piping installed in the polymerization reactor (hereinafter collectively referred to as "inner walls of the polymerization reactor") etc.)
Polymer scale adheres to the polymer, which reduces the polymer yield and the cooling capacity of the polymerization vessel.
When exfoliated scale is mixed into the product, the physical properties of the product (for example, firmness) deteriorate, and excessive labor and time are required to remove the attached scale, resulting in a decrease in the operating rate of the polymerization vessel. Furthermore, if one attempts to remove attached scale by entering the polymerization vessel, one will be exposed to vinyl chloride monomer, which is not favorable from an occupational hygiene standpoint. Therefore, solving these problems has been a long-standing concern for manufacturers of vinyl chloride polymers. Conventionally, as a method to prevent polymer scale from adhering to the inner walls of polymerization vessels, polar compounds such as amine compounds, quinone compounds, and aldehyde compounds (Japanese Patent Publication No. 45-30343), dyes (Japanese Patent Publication No. 45-30835) and a free radical inhibitor (Japanese Unexamined Patent Publication No. 48-44375) are known. However, these methods have the disadvantage that they do not have a sufficient effect of preventing scale adhesion, and that the sustainability of the preventive effect is low. In addition, in the method of applying a mixture of a film-forming resin and a polymerization inhibitor (Japanese Patent Application Laid-Open No. 52-98081), the film-forming resin is insoluble in water, so it is necessary to dissolve it in an organic solvent before use. There are problems with toxicity and safety due to organic solvents. As a result of intensive studies to solve the problems of conventional methods, the present inventors have discovered that hydrophilic anionic dyes and hydrophilic cationic dyes can be reacted with methylolmelamine and methylolmelamine to form a crosslinked polymer substance. The present invention has been completed based on the discovery that by applying a polymer substance as a fixing agent, a very remarkable effect can be exerted on preventing scale adhesion, and the preventing effect can be sustained for a long time. That is, the purpose of the present invention is to industrially advantageously carry out the polymerization reaction of vinyl chloride monomers, and the purpose is to carry out the polymerization reaction of vinyl chloride monomers in an industrially advantageous manner. Before polymerizing the mixture with the monomer in an aqueous medium, the inner wall of the polymerization vessel and/or the surface of the equipment attached to the polymerization vessel is coated with
A solvent solution of a hydrophilic anionic dye, a hydrophilic cationic dye, a methylolmelamine, and a hydrophilic polymeric material capable of reacting with the methylolmelamine to form a crosslinked polymeric material, either individually or in combination. This can be easily achieved by applying the coating. The present invention will be explained in more detail below. The present invention is a method of applying a hydrophilic anionic dye, a hydrophilic cationic dye, methylol melamine, and a hydrophilic polymer substance capable of reacting with methylol melamine to form a crosslinked polymer substance to the inner wall of a polymerization vessel as an essential component. . In this method, only two components, methylolmelamine and a hydrophilic polymer substance capable of reacting with methylolmelamine to form a crosslinked polymer substance, used as a fixing agent for hydrophilic anionic dyes and hydrophilic cationic dyes, are applied to the inner wall of a polymerization vessel, etc. When the polymerization reaction of the vinyl chloride monomer is carried out by coating, a sufficient scale adhesion prevention effect cannot be obtained. In addition, when a hydrophilic anionic dye or a hydrophilic cationic dye is applied to the inner wall of a polymerization vessel to perform a polymerization reaction of vinyl chloride monomers, a relatively good effect of preventing scale adhesion can be obtained, but The scale adhesion prevention effect disappears. However, as described above, by using hydrophilic anionic dyes and hydrophilic cationic dyes, which have low long-lasting scale prevention effects, in combination with methylolmelamine and hydrophilic polymer substances according to the method of the present invention, excellent scale can be achieved. The unexpected effect is that an anti-adhesion effect can be obtained and the anti-adhesion effect can be maintained for a long time. The hydrophilic anionic dye used in the method of the present invention may be one that is soluble in water (having sufficient water solubility to be used as a coating solution), and is usually 0.05% by weight relative to water. % or more, preferably 0.1% by weight or more is used. Examples of these hydrophilic anionic dyes include CI Acid Orange 7, CI Acid Black 1, and C.I.
I. Acid Blue 158, CI Acid Green 12,
Hydrophilic azo dyes such as CI Direct Red 2, CI Direct Brown 1, CI Direct Yellow 12, hydrophilic azine dyes such as CI Acid Black 2, CI Acid Blue 59, hydrophilic anthraquinone dyes such as CI Acid Blue 40, CI Acid Red 87, Examples include hydrophilic xanthene dyes such as CI Acid Red 52, hydrophilic quinoline dyes such as CI Acid Yellow 3, hydrophilic naphthalimide dyes such as CI Acid Yellow 7, hydrophilic nitro dyes such as CI Acid Yellow 1, etc. . These may be used alone or in a mixture of two or more. In addition, the hydrophilic cationic dye used in combination with the hydrophilic anionic dye may be one that is soluble in water (having sufficient water solubility to be used as a coating solution); 0.05 against
A substance that dissolves at least 0.1% by weight, preferably at least 0.1% by weight, is used. These hydrophilic cationic dyes include, for example, CI Basic Cred 2, C.I.
I. Basic Black 2nd grade hydrophilic azine dye,
Hydrophilic triphenylmethane dyes such as CI Basic Blue 1, CI Basic Violet 3, CI Basic Blue 5, CI Basic Blue 7, hydrophilic thiazine dyes such as CI Basic Blue 9, CI Basic Yellow 1 Hydrophilic thiazole dyes such as CI Basic Yellow 11 and hydrophilic methine dyes such as CI Basic Yellow 11 can be mentioned. These may be used alone or in a mixture of two or more. Further, examples of methylolmelamine include monomethylolmelamine, dimethylolmelamine, trimethylolmelamine, tetramethylolmelamine, pentamethylolmelamine, hexamethylolmelamine, and the like, and these may be used alone or in a mixture of two or more. Further, a mixture of methylolmelamine may be contained in the methylolmelamine to the extent that it is soluble in water. Furthermore, alkylated methylolmelamine obtained by alkylating the methylolmelamine with alcohol or the like, such as methylated methylolmelamine, can also be used. In addition, as the hydrophilic polymer substance, a hydrophilic polymer substance that reacts with methylolmelamine to form a crosslinked polymer substance is used, and a functional group that can react with the methylol group, imino group, or alkoxy group of methylolmelamine, For example, those having a hydroxyl group, a carboxyl group, an amide group, etc. and are hydrophilic are used. Specific examples include polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyethyleneimine, partially saponified polyvinyl acetate, and the like, and these may be used alone or in a mixture of two or more. In order to apply a hydrophilic anionic dye and a hydrophilic cationic dye to the inner wall of a polymerization vessel using methylolmelamine and a hydrophilic polymer substance as a fixing agent according to the method of the present invention, a solution of these components (an aqueous solution when viewed from the working surface) is required. ) may be applied to surfaces such as the inner wall of the polymerization vessel, either singly or in combination, but in order to make the application process more efficient, hydrophilic anionic dyes and hydrophilic cationic dyes may be used. It is preferable to dissolve the hydrophilic polymer substance in water, add methylolmelamine immediately before application, and apply the mixture as a four-component aqueous solution. In addition, when applying the above coating liquid to surfaces such as the inner wall of the polymerization vessel,
It is preferable to use the coating liquid with acidic properties. Therefore, when using the coating liquid alone,
It is best to use an aqueous solution containing a hydrophilic anionic dye and a hydrophilic cationic dye with a PH value of 7 or less, preferably 6 or less using a PH regulator, and when using a mixture of the above four components, The aqueous solution containing the above four components is preferably used with a PH value of 7 or less, preferably 6 or less, using a PH adjuster. As the above-mentioned PH adjuster, inorganic acids such as sulfuric acid, nitric acid, and phosphoric acid, hydrophilic organic acids such as acetic acid, lactic acid, and glycolic acid, and acid salts thereof are used. Furthermore, 1 to 20% by weight of a monohydric alcohol having 4 to 6 carbon atoms is added to the coating solution prepared as described above.
When used in combination, the workability of coating the coating liquid onto the inner wall of the polymerization vessel is improved, and the effect of preventing scale adhesion is further improved, which is preferable. The monohydric alcohols mentioned above include n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, n-amyl alcohol, iso-amyl alcohol, sec-amyl alcohol, t-amyl alcohol, and n-hexyl. Examples include alcohol, sec-hexyl alcohol, and the like. These may be used alone or in a mixture of two or more. The mixing ratio of the above four components is not particularly limited, but in order to obtain good coating performance, the ratio of hydrophilic anionic dye and hydrophilic cationic dye/methylolmelamine/hydrophilic polymer substance should be 100/100/
It is preferably within the range of 10-1000/10-1000. Further, the ratio of the hydrophilic anionic dye to the hydrophilic cationic dye is preferably within the range of 100/10 to 100 by weight. Further, from the viewpoint of coating workability due to viscosity, etc., it is preferable to use an aqueous solution containing 0.1 to 30% by weight of the above four components. This aqueous solution may be applied to the inner wall of the polymerization vessel by a commonly used application means such as spraying. In the coating film, methylolmelamine and the hydrophilic polymer substance undergo a crosslinking reaction to become water-insoluble, and the hydrophilic anionic dye and hydrophilic cationic dye are firmly adhered to surfaces such as the inner wall of the polymerization vessel. This crosslinking reaction can also be carried out by leaving it at room temperature for a long time, but preferably
It is preferable to accelerate the reaction by heating to ℃. The amount of the four components to be applied is usually 0.01% of the surface to which the total amount is applied, that is, the inner wall of the polymerization vessel, etc.
g/m ² or more, preferably in the range of 0.01 to 10 g/m ² . If the coating amount is less than 0.01 g/m ² , scale generation cannot be sufficiently suppressed. Also 10g/
If it exceeds m ² , no increase in the prevention effect can be expected, and on the contrary, the adhesion of the coated material to the wall surface tends to weaken. All commonly known polymerization recipes are employed for the polymerization of vinyl monomers in the method of the present invention,
The dispersant, emulsifier, polymerization initiator, etc. used do not need to be special, and commonly used dispersants, emulsifiers, polymerization initiators can be used.
For example, dispersants and emulsifiers include partially saponified polyvinyl acetate, acrylic acid copolymers, maleic anhydride copolymers, cellulose derivatives, gelatin,
Protective colloidal agents such as starch, natural polymer compounds, esters of higher fatty acids and polyhydric alcohols, nonionic surfactants such as polyoxyethylene derivatives, metal salts of higher fatty acids, higher alcohol sulfuric esters Anionic surfactants such as alkali salts of Examples of polymerization initiators include organic peroxides such as benzoyl peroxide, lauroyl peroxide, dioctyl peroxycarbonate, and acetylcyclohexylsulfonyl peroxide, azo compounds such as azobisisobutyronitrile and dimethylvaleronitrile, potassium persulfate, ammonium persulfate, etc. persulfates, etc. are used. The vinyl chloride monomer used in the method of the present invention includes not only the vinyl chloride monomer itself, but also vinyl chloride monomers and monomers copolymerizable therewith, mainly consisting of vinyl chloride monomer. It may be a mixture of Monomers that can be copolymerized include olefins such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl stearate, vinyl ethers such as ethyl vinyl ether and cetyl vinyl ether, acrylic esters, maleic acid, and fumaric acid. Any monomer that can be copolymerized with conventionally known vinyl chloride, such as unsaturated carboxylic acid derivatives such as esters and anhydrides, aromatic vinyl compounds such as styrene, and unsaturated nitrile compounds such as acrylonitrile, can be used. can. According to the method of the present invention, during the polymerization reaction, there is no or an insignificant amount of scale attached to the inner walls of the polymerization vessel, so the occurrence of scales in the final processed product is drastically reduced and the quality of the product is improved. Furthermore, since the number of times the inner walls of the polymerization vessel must be cleaned is significantly reduced, operation can be continued for a long time without cleaning, productivity is improved, and very advantageous results can be obtained from a cost perspective. In addition, not only does operational management such as cooling become easier, but it also becomes possible to use a reflux condenser as a new cooling means. Other coating materials used in the method of the present invention are water-soluble and are used after being dissolved in water.
There is no problem such as recovery of the solvent when using an organic solvent or deterioration of the working environment during drying of the coated film.Furthermore, the method of the present invention does not require the use of low-boiling point polymerization initiators, such as t - Even when butyl peroxypivalate or diisopropyl peroxydicarbonate is used, or when special auxiliary agents such as sorbitan ester are added for quality improvement, a stable scale adhesion prevention effect is exhibited. . The present invention will be explained in more detail by examples below, but the present invention will not exceed the gist thereof.
The following examples are not intended to be limiting. Example 1 Methylolmelamine (manufactured by Sumitomo Chemical Co., Ltd., trade name Sumimaru M-50W), CI Acid Black 2, CI Basic Blue 9, water, and phosphoric acid were added in specific amounts to a 2% by weight aqueous solution of polyethylene imine, and mixed. An aqueous coating solution having a pH of 2.5 containing 1% by weight of imine, 5% by weight of methylolmelamine, 0.15% by weight of CI Acid Black 2, and 0.05% by weight of CI Basic Blue 9 was prepared. Apply this coating liquid to the inner wall of a stainless steel polymerization vessel with an internal volume of 400 mL and the surface of the stirring blade using an iron spray to apply the amount of liquid per 1 m ² of coating area.
It was sprayed in an amount of 100 g and dried by heating at 80° C. for 30 minutes to form a film on the inner wall surface. Using this polymerization vessel, 150 kg of deionized water, 60 g of partially saponified polyvinyl acetate, 100 kg of vinyl chloride monomer, and 25 g of t-butyl peroxypivalate were charged.
Polymerization was carried out at about 58°C until a predetermined polymerization rate was reached. After extracting the produced vinyl chloride polymer slurry, the inside of the vessel was washed with water, and after drying, the amount of scale attached was measured. The results are shown in Table 1. Furthermore, Table 1 shows the measurement results of the amount of scale deposited when the same polymerization as above was carried out in 30 consecutive batches. Example 2 The same procedure as Example 1 was carried out except that polyvinyl alcohol was used instead of polyethyleneimine. The results are shown in Table 1. Example 3 The same procedure as in Example 1 was carried out except that partially saponified polyvinyl acetate was used instead of polyethyleneimine. The results are shown in Table 1. Example 4 The same procedure as Example 1 was carried out except that polyacrylamide was used instead of polyethyleneimine. The results are shown in Table 1. Example 5 1% by weight of polyethyleneimine as coating liquid,
5% by weight of methylolmelamine, 0.05% by weight of CI Acid Blue 59, CI Basic Yellow 11
The same procedure as in Example 1 was conducted except that an aqueous solution having a pH of 2.5 containing 0.05% by weight of n-butyl alcohol and 5% by weight of n-butyl alcohol was used. The results are shown in Table 1. Example 6 The same procedure as Example 5 was carried out except that polyacrylic acid was used instead of polyethyleneimine. The results are shown in Table 1. Example 7 The coating liquid contained 1% by weight of partially saponified polyvinyl acetate, 5% by weight of methylolmelamine, 0.08% by weight of CI Acid Blue 59, 0.02% by weight of CI Basic Blue 9, and 5% by weight of n-butyl alcohol. The same procedure as in Example 1 was carried out except that an aqueous solution with a pH of 2.5 was used. The results are shown in Table 1. Example 8 The same procedure as Example 7 was carried out except that polyvinyl alcohol was used instead of partially saponified polyvinyl acetate. The results are shown in Table 1. Example 9 0.2% by weight of polyacrylamide as coating liquid,
1% by weight of methylolmelamine, 0.03% by weight of CI Direct Green 26, 0.02% by weight of CI Basic Blue 9 and 5% by weight of n-butyl alcohol.
The same procedure as in Example 1 was carried out except that an aqueous solution having a pH of 2.5 was used. The results are shown in Table 1. Example 10 The same procedure as Example 9 was carried out except that polyethyleneimine was used instead of polyacrylamide. The results are shown in Table 1. Example 11 Implemented except that an aqueous solution with a pH of 2.5 containing 0.5% by weight of polyvinyl alcohol, 5% by weight of methylolmelamine, 0.1% by weight of CI Direct Brown, and 0.1% by weight of CI Basic Cred 2 was used as the coating liquid. The procedure was as in Example 1. The results are shown in Table 1. Example 12 The same procedure as Example 11 was carried out except that partially saponified polyvinyl acetate was used instead of polyvinyl alcohol. The results are shown in Table 1. Example 13 Except that an aqueous solution with a pH of 2.5 containing 0.5% by weight of polyvinyl alcohol, 2% by weight of methylolmelamine, 0.08% by weight of CI Acid Black 2, and 0.02% by weight of CI Basic Yellow 11 was used as the coating liquid. was carried out in the same manner as in Example 1.
The results are shown in Table 1. Example 14 The same procedure as Example 13 was carried out except that polyethyleneimine was used instead of polyvinyl alcohol. The results are shown in Table 1. Example 15 The same procedure as Example 13 was carried out except that partially saponified polyvinyl acetate was used instead of polyvinyl alcohol. The results are shown in Table 1. Example 16 The same procedure as Example 13 was carried out except that polyacrylamide was used instead of polyvinyl alcohol. The results are shown in Table 1. Comparative Example 1 The same procedure as in Example 1 was carried out except that the coating liquid was not applied at all to the inner wall of the polymerization vessel and the surface of the stirring blade. . The results are shown in Table 2. Comparative Example 2 The same procedure as in Example 1 was carried out except that an aqueous solution containing 5% by weight of methylolmelamine and 1% by weight of polyvinyl alcohol was used as the coating liquid.
The results are shown in Table 2. Comparative Example 3 The same procedure as in Example 1 was carried out except that an aqueous solution containing 5% by weight of methylolmelamine and 1% by weight of partially saponified polyvinyl acetate was used as the coating liquid. The results are shown in Table 2. Comparative Example 4 The same procedure as in Example 1 was carried out except that an aqueous solution containing 5% by weight of methylolmelamine and 1% by weight of polyacrylamide was used as the coating liquid. The results are shown in Table 2. Comparative Example 5 The same procedure as in Example 1 was carried out except that an aqueous solution containing 5% by weight of methylolmelamine and 1% by weight of polyethyleneimine was used as the coating liquid. The results are shown in Table 2. Comparative Example 6 The same procedure as in Example 1 was carried out, except that an aqueous solution with a pH of 2.0 containing 0.2% by weight of CI Acid Black 2 (sulfuric acid was used as the pH adjuster) was used as the coating liquid. The results are shown in Table 2. Comparative Example 7 1% by weight of polyethyleneimine as a coating liquid,
Example 1 was carried out in the same manner as in Example 1, except that an aqueous solution containing 5% by weight of methylolmelamine and 0.15% by weight of CI Acid Black 2 with a pH of 2.0 (sulfuric acid was used as the pH adjuster) was used. The results are shown in Table 2. Comparative Example 8 The same procedure as in Example 1 was carried out, except that an aqueous solution with a pH of 2.0 containing 0.2% by weight of CI Basic Blue 9 (sulfuric acid was used as the pH adjuster) was used as the coating solution. The results are shown in Table 2. Comparative Example 9 A coating liquid containing 1% by weight of polyvinyl alcohol, 5% by weight of methylolmelamine, and 0.15% by weight of CI Basic Blue 9, pH 2.0.
The same procedure as in Example 1 was carried out except that an aqueous solution of (sulfuric acid was used as the PH adjuster) was used. The results are shown in Table 2. Comparative Example 10 Example except that an aqueous solution with a pH of 2.0 containing 0.05% by weight of CI Acid Blue 59 and 0.05% by weight of CI Basic Yellow 11 was used as the coating liquid (sulfuric acid was used as the PH adjuster). It was done in the same way as 1. The results are shown in Table 2. Comparative Example 11 Except that an aqueous solution with a pH of 2.0 containing 0.15% by weight of CI Atsushid Black 2 and 0.05% by weight of CI Basic Blue 9 was used as the coating liquid (sulfuric acid was used as the PH adjuster). The same procedure as in Example 1 was carried out. The results are shown in Table 2.

【table】

【table】

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[Table] Reference Examples 1 to 6 In Example 3, Example 9, Example 13, Comparative Example 1, Comparative Example 7, and Comparative Example 11, the vinyl chloride polymers obtained in specific batches of polymerization reactions are shown below. The quality was evaluated using the following method. 100 parts of the obtained vinyl chloride polymer, 50 parts of dioctyl phthalate, and 3 parts of a lead-based stabilizer were thoroughly mixed, and the resulting mixture was kneaded for 5 minutes with a roll at 155°C. The number of fish eyes observed in 25 cm ² of the obtained rolled sheet was counted. The results are shown in Table 3.

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Claims (1)

[Claims] 1. When polymerizing a vinyl chloride monomer or a mixture of vinyl chloride monomer as a main component and a monomer copolymerizable with it in an aqueous medium, apply it to the inner wall of the polymerization vessel and/or the surface of the incidental equipment of the polymerization vessel in advance. , a hydrophilic anionic dye, a hydrophilic cationic dye, methylol melamine, and a hydrophilic polymer substance capable of crosslinking with methylol melamine, each of which is applied in a solvent solution or in a combined solvent solution. A method for polymerizing vinyl chloride monomers characterized by: