JPH04261403A - Prevention of adhesion of polymer scale - Google Patents

Abstract

PURPOSE:To polymerize a vinyl-based polymer while preventing adhesion of polymer scale in a polymerizer by coating the inner wall and the surface of other parts of a polymerizer, with which a monomer is brought into contact during polymerization, with a liquid of phosphoric acid (salt), then heating the coated surface and polymerizing. CONSTITUTION:In polymerizing a vinyl-based monomer (e.g. styrene), the inner wall and the surface of other parts of a polymerizer, with which a monomer is brought into contact during polymerization, are coated with a solution of phosphoric acid and/or a phosphate in a mixture of water and an alcohol containing >=20wt.% alcohol with gauze, the coated face is heat-treated in a hot air atmosphere at 200 deg.C for 30 minutes, the polymerizer is charged with an aqueous solution containing calcium tertiary phosphate and sodium alpha-olefin sulfonate, heated to 90 deg.C while stirring, supplied with a vinyl-based monomer, a polymerization initiator such as benzoyl peroxide and a dispersant such as hydroxyethyl cellulose and the monomer is polymerized to give a high-quality polymer without adhesion of polymer scale.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for preventing the adhesion of polymer scale, particularly in the polymerization of vinyl monomers.
The present invention relates to a method for effectively preventing the deposition of polymer scale within a polymerization vessel.

0002

2. Description of the Related Art In a method of producing a polymer by polymerizing monomers in a polymerization vessel, there is a problem in 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, it not only requires a great deal of effort and time to remove it, but also reduces the yield of the polymer, increases the temperature of the polymerization vessel, and reduces the cooling capacity. Various inconveniences occur, such as a decrease in the quality of the product polymer due to the adhering polymer scale being mixed into the product.

Conventionally, as a method for preventing polymer scale from adhering to the inner wall surface of a polymerization vessel, for example, a method of applying polar compounds, dyes, pigments, etc. to the inner wall surface (Japanese Patent Publication No. 45
-30343, No. 45-30835), method of applying an aromatic amine compound (Japanese Patent Application Laid-open No. 51-50887)
, a method of applying a reaction product of a phenol compound and an aromatic aldehyde (JP-A-55-54317), a method of pre-treating the inner wall surface with a treatment liquid containing a titanium compound, a zinc compound, etc. (JP-A-2-47105). No.) etc. are known.

[0004] Although these methods have a scale prevention effect to some extent when polymerizing by a general suspension polymerization method in which vinyl monomers are added to an aqueous dispersant and polymerized by stirring, the effect is not completely achieved. Alternatively, fluidized bed polymerization, in which polymer particles with a uniform particle size are suspended in advance while a suspension is suspended by the flow of a dispersant, is polymerized while the monomer is dropped into the suspension and impregnated. In special polymerization methods such as suspended seed polymerization, prevention of scale deposition is difficult to achieve.

[0005]

[Problem to be solved by the invention] Therefore, the present inventors
The present invention was achieved as a result of intensive research and efforts to find a method that can effectively prevent the adhesion of polymer scale not only in general polymerization methods but also in special polymerization methods such as fluidized bed polymerization and suspended seed polymerization. reached.

[0006]

[Means for Solving the Problems] That is, in the polymerization of vinyl monomers, the present invention provides phosphoric acid and/or phosphate on the inner wall of the polymerization vessel and the surface of other parts with which the monomer comes into contact during polymerization. The subject matter is a method for preventing the adhesion of polymer scale to a surface, which is characterized by applying a liquid to the surface, heating the surface, and then polymerizing the surface.

Phosphoric acid and phosphate salts used in the present invention include phosphoric acids such as orthophosphoric acid, metaphosphoric acid, and pyrophosphoric acid, and combinations of these acids with sodium, potassium, magnesium,
Examples include phosphates with various metals such as calcium, zinc, and manganese. These phosphoric acids and phosphates may be used alone or in combination of two or more.

[0008] These compounds can be applied by dissolving them in water, alcohol such as methanol or ethanol, or a mixed solution of water and alcohol, and spraying this solution, or by using an applicator such as a cloth. There are two methods: one method is to apply the solution in a polymerization vessel, the other method is to fill the polymerization vessel with the solution and then draw it out. In this case, in order to improve the adhesion of the coating liquid to the walls of the polymerization vessel, it is preferable to use a solution containing 20% by weight or more of alcohol. The solution concentration of phosphoric acid and/or phosphate salt is preferably 0.1 to 3% by weight, and 0.1% by weight.
If it is lower than 3% by weight, the coating amount will be reduced and the scale prevention effect will be lowered, and if it is higher than 3% by weight, the effect will not change. Moreover, when hydrogen chloride is added to this solution, the scale prevention effect is further increased. The amount of hydrogen chloride added is preferably 0.2% by weight or more.

As described above, merely applying phosphoric acid and/or phosphate solution to the wall surface of the polymerization vessel and other parts that come into contact with monomers does not provide a good scale adhesion prevention effect;
Furthermore, it is necessary to heat-treat the coated surface. The heat treatment conditions include heating at a temperature of 110° C. or higher for a predetermined period of time. Heating time varies depending on temperature. For example, at 200℃, 30
A heating time of 15 minutes is sufficient, but at 150℃, it is more than 3 hours, or 13 minutes.
At 0°C, heating for 6 hours or more is required, and at less than 110°C, even if heated for a long time, a sufficient scale prevention effect cannot be obtained. Examples of the heating method include a method of sending hot air or steam into the polymerization vessel, a method of heating the jacket of the polymerization vessel with hot water, etc., and these methods may be used alone or in combination.

Vinyl monomers to which the method of the present invention is applied include styrene monomers such as styrene, chlorostyrene, t-butylstyrene, and α-methylstyrene, as well as halogenated monomers such as vinyl chloride. Examples include vinyl, vinyl esters such as vinyl acetate and vinyl propionate, acrylic acid, methacrylic acid and their esters or salts, maleic acid, fumaric acid and their esters or anhydrides, acrylonitrile, vinyl ethers, etc. They may be used alone or in combination of two or more.

In the present invention, any commonly used substances can be used without any restriction as to the substances added to the polymerization system. For example, poorly water-soluble inorganic dispersants such as calcium phosphate, sodium pyrophosphate, and hydroxyapatite, partially saponified polyvinyl alcohol, methylcellulose, water-soluble polymer suspending agents such as polyacrylate, sodium laurate, sodium dodecylbenzenesulfonate, α
- Anionic surfactants such as sodium olefin sulfonate, nonionic surfactants such as sorbitan monolaurate, polyoxyethylene octylphenol ether, polyoxyethylene alkyl ether, DOP, D
Plasticizers such as BP and BBP, edible oils and fats such as coconut oil, palm oil, and palm kernel oil, chain transfer agents such as trichlorethylene and mercaptans, and benzoyl peroxide, 1
, 1-di-t-butylperoxy 3,3,5-trimethylcyclohexane, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, cumene hydroperoxide, lauroyl peroxide, etc. Polymerization initiators and the like are used. Even in polymerization systems in which these substances are present, the method of the present invention can effectively prevent the deposition of polymer scale.

0012

[Examples] The present invention will be explained in detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples. In addition, in the following description, "%" means "% by weight"
” means. Example 1 H3 PO was applied to the inner wall of a 5-liter stainless steel polymerization vessel.
4 1% water/methanol solution (methanol content 20%)
After applying with gauze, heat treatment was performed for 30 minutes in a hot air atmosphere at 200°C. In this polymerization vessel, 7.2 g of tricalcium phosphate and 1% of sodium α-olefin sulfonate were added.
20 cc of an aqueous solution and 360 g of polystyrene particles having a particle size of 500 to 600 μm were added, and the temperature was raised to 90° C. with stirring. Next, while maintaining the internal temperature of the polymerization vessel at 90°C,
A mixed solution in which 12.6 g of coconut oil was dissolved in styrene monomer, and 5 g of benzoyl peroxide and 3.6 g of 1,1,-di-t-butylperoxy-3,3,5-trimethylcyclohexane were dissolved in styrene monomer. Te, 0
．． An emulsion prepared by emulsifying 50 g of a 2% hydroxycellulose aqueous solution was added dropwise at the same time from separate ports over a period of 5 hours. After the addition was completed and held at 90°C for 1 hour,
Polymerization was completed. After the polymerization was completed, the amount of scale attached to the inner wall surface of the polymerization vessel was measured. The results are shown in Table 1.

Examples 2 to 8 Polymerization was carried out in the same manner as in Example 1, except that the concentration of the H3PO4 solution and the type of compound were changed as shown in Table 1, and the amount of scale was measured. The results are shown in Table 1.

Comparative Example 1 Example 1 except that the H3 PO4 liquid was not treated.
Polymerization was carried out in the same manner as above, and the amount of scale was measured. The results are shown in Table 1.

[0015]

[Table 1]

Examples 9 to 17 Polymerization was carried out in the same manner as in Example 1, except that the heat treatment conditions after application of the H3PO4 liquid were changed as shown in Table 2, and the amount of scale attached was evaluated. The results are shown in Table 2.

[0017]

[Table 2]

Examples 18-20 Example 1 except that hydrochloric acid was added to the water/methanol solution of the H3 PO4 coating solution to obtain the hydrogen chloride concentration shown in Table 3.
Polymerization was carried out in the same manner as above, and the amount of scale adhesion was evaluated. The results are shown in Table 3.

[0019]

[Table 3]

Example 21 A 1% water/methanol solution of H3PO4 (
After applying methanol (20%) with gauze, heat at 200°C.
A heat treatment was performed for 30 minutes in a hot air atmosphere. A circulation line was provided in which the aqueous dispersion medium was taken out by a centrifugal pump from an aqueous dispersion medium outlet provided at the bottom of the reactor and introduced into the reactor from an inlet at the top of the reactor. In this reactor, 3000 ppm of tricalcium phosphate fine powder, 50 ppm of polyvinyl alcohol, and 50 ppm of anionic surfactant were added.
Add 3 liters of aqueous dispersion medium prepared so that
The descending flow rate in the reactor is 2 cm/sec. I kept it circulating so that Next, the benzoyl peroxide concentration is 0.
25% styrene monomer is discharged through a small orifice into a droplet generation column filled with an aqueous dispersion medium having the above composition, and mechanical vibration is applied using a vibrator to generate droplets of the monomer. was produced in an aqueous dispersion medium and continuously introduced into the reactor from the upper part of the reactor via an inlet pipe. The droplets in the reactor become suspended due to the balance between the buoyancy of the droplets and the downward flow of the dispersion medium, but as the polymerization progresses, the droplets, whose specific gravity becomes heavier, rise 5 cm from the bottom of the reactor. It was introduced into the next reaction completion tank from the outlet installed at the position. In this manner, the amount of scale on the inner wall surface of the reactor was measured after continuous polymerization for 20 hours. The results are shown in Table 4.

Examples 22 and 23 Polymerization was carried out in the same manner as in Example 21, except that the polymerization time was changed as shown in Table 4, and the amount of scale attached was measured. The results are shown in Table 4.

Comparative Examples 2 to 4 Polymerization was carried out in the same manner as in Examples 21 to 23, except that the H3PO4 solution was not treated, and the amount of scale attached was measured. The results are shown in Table 4.

[0023]

[Table 4]

[0024]

[Effects of the Invention] As mentioned above, the present invention exhibits a good scale prevention effect and has extremely high utility value. In particular, even when polymerization is carried out using special polymerization methods such as fluidized bed polymerization or suspension seed polymerization using styrene monomers,
Demonstrates excellent scale prevention effect. In the present invention,
The reason why a good scale prevention effect is obtained is not clear, but it is thought to be because phosphoric acid and/or phosphates form a strong polyphosphoric acid film on the surface of the polymerization vessel etc. by heat treatment.

Claims (8)

[Claims] Claim 1: In the polymerization of vinyl monomers, a liquid of phosphoric acid and/or phosphate salt is applied to the inner wall of the polymerization vessel and the surface of other parts that the monomer comes into contact with during polymerization, and then the coated surface is A method for preventing polymer scale from adhering to the surface, the method comprising performing polymerization after heating. 2. The method according to claim 1, wherein the phosphoric acid and/or phosphate solution contains 0.2% by weight or more of hydrogen chloride. 3. The method according to claim 1, wherein the solvent for the phosphoric acid and/or phosphate solution is a mixed solution of water and alcohol containing 20% by weight or more of alcohol. 4. The method according to claim 1, wherein the temperature at which the coated surface is heated is 110° C. or higher. 5. The method according to claim 1, wherein the vinyl monomer is a styrene monomer. [Claim 6]Claim 1 wherein the polymerization method is a suspension polymerization method.
5. The method described in 5. 7. The method according to claim 6, wherein the suspension polymerization method is a suspension fluidized bed polymerization method. 8. The method according to claim 6, wherein the suspension polymerization method is a suspension seed polymerization method.