JPS61209201A - Dispersing agent for reverse-phase suspension polymerization - Google Patents

Abstract

PURPOSE:To provide the titled dispersing agent containing a specific amount of monoalkylphosphoric acid having straight-chain alkyl group, capable of keeping the polymerizing system in stable state and enabling the production of fine granular polymer free from powdery polymer in high efficiency. CONSTITUTION:A dispersing agent containing >=80mol% monoalkylphosphoric acid having 12-24C straight-chain alkyl group is used as a dispersing agent for the reverse-phase suspension polymerization performed by adding an aqueous solution of a water-soluble ethylenic unsaturated monomer to a hydrophobic solvent inert to the polymerization reaction (e.g. n-hexane, benzene, toluene, etc.). The amount of the solvent is preferably 0.05-5.0wt% of the monomer. EFFECT:It is supposed that the dispersing agent is regularly arranged at the oil/water interface owing to the balance between the hydrogen bond of the phosphoric acid group and the hydrophobic straight-chain alkyl group to stabilize the interface and accordingly the reverse-phase suspension polymerization system can be maintained stably.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for performing reverse phase suspension polymerization by adding a water-soluble ethylenically unsaturated monomer aqueous solution to a polymerization inert and hydrophobic solvent. The present invention relates to a dispersant for use in reverse-phase suspension polymerization, and more specifically, to a dispersant for reverse-phase suspension polymerization that can stably maintain a polymerization system.

[・Conventional technology]

As a method for polymerizing water-soluble ethylenically unsaturated monomers, a so-called reverse-phase suspension polymerization method is well known, in which the monomers are suspended and dispersed in a hydrophobic solvent and polymerized. When carrying out this method, it is important to appropriately select a dispersant that can stabilize the dispersion of the monomer to be polymerized and prevent or reduce agglomeration of polymer particles. . In other words, by selecting a suitable dispersant, productivity can be significantly improved and a polymer with uniform physical properties can be obtained.

Examples of dispersants used in reverse-phase suspension polymerization of water-soluble ethylenically unsaturated monomers include non-containing agents such as sorbitan monostearate, nrubitan monooleate, ethoxylated fatty acid amides, and glycerin fatty acid esters. Ionic surfactants are known (Japanese Patent Publication No. 54-30710, etc.)0 In addition to the above, for example, allyl (A11y1
) group treated with maleic anhydride, polymers containing carboxyl groups that have affinity for organic solvents, and polymeric compounds such as lipophilic cellulose derivatives (% Kaisho 57-74509, etc.).

[Problems to be solved by the invention] However, when a dispersant of the former group (nonionic surfactants) is used, the resulting polymer becomes fine particles and dust is generated during the separation and drying process. This may cause problems such as smearing, making it difficult to handle. If the latter group of dispersants is used, the produced polymer will be in the form of small granules, which can improve the above-mentioned drawbacks, but during the polymerization operation, the polymer particles and the wall of the polymerization tank or the stirrer It is inevitable that sticking will occur between the polymers and the polymer, and a considerable portion of the reacted monomers will be lost as unusable deposits in the polymerization tank. Generally, it takes a great deal of effort to remove water-soluble ethylenically unsaturated monomers deposited in a polymerization tank, which hinders efficient production of particulate polymers.

[Means for solving problems]

As a result of intensive research in order to solve the above problems, the present inventors decided to use a dispersant containing monoalkyl phosphoric acid as an essential component, and found that a small granular polymer containing no fine granular polymer was used. The present invention was completed based on the discovery that it can be obtained stably.

That is, the present invention provides a dispersant for reverse phase suspension polymerization containing 80 mol % or more of a monoalkyl phosphoric acid having a linear alkyl group having 12 to 24 carbon atoms.

When using the dispersant for reverse-phase suspension polymerization of the present invention, as a solvent for reverse-phase suspension polymerization, in principle, all solvents that are inactive for polymerization and do not dissolve water can be used.

Considering the removal of polymerization heat and the drying process of the obtained polymer, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, or a mixed solution thereof having a boiling point of 30 to 200°C are preferred, and n-hexane is particularly preferred. , cyclohexane, benzene, toluene, or a mixed solvent thereof are preferably used.

The dispersant for reversed-phase suspension polymerization of the present invention contains a monoalkyl phosphoric acid having a linear alkyl group having 12 to 24 carbon atoms as an essential component. In this case, the alkyl group may contain an unsaturated bond. When the number of carbon atoms is less than 12 or more than 24, the function as a dispersing agent is insufficient, leading to the generation of aggregated polymers. Similarly, even if a monoalkyl phosphoric acid or a dialkyl phosphoric acid having a branched alkyl group is used, only an aggregated polymer is obtained. Only by using a linear alkyl phosphoric acid can a stable small granular polymer containing no particulate polymer be obtained.

The dispersant for reverse-phase suspension polymerization of the present invention can be used in combination with other dispersants, but when used in combination with other dispersants, it is necessary to stably obtain small granular polymers. , linear alkyl phosphoric acid content is required to be 80 mol% or more, i5.80%
If it is less than that, the generation of aggregated polymers or gelation may occur, which is not the intention of the present invention. In the dispersant for reverse-phase suspension polymerization of the present invention, examples of the dispersant that can be used in combination with the monoalkyl phosphoric acid include conventionally known dispersants for reverse-phase suspension polymerization. These known dispersants can be used within a range that does not interfere with the dispersion effect of the monoalkyl phosphoric acid, that is, within a range of 20 mol % or less in the total dispersant.

The appropriate amount of the dispersant for reverse-phase suspension polymerization of the present invention is usually 0.01 to 10% by weight, preferably 0.01 to 10% by weight, based on the monomer.
The amount ranges from 0.05 to S, O weight percent. Added amount is 0.0
If it is less than 1% by weight, the desired dispersion effect cannot be obtained,
Also, if more than 10% by weight is added,
Water-soluble ethylenically unsaturated monomers that can be polymerized by reverse-phase suspension polymerization using the dispersant of the present invention include: Various types can be mentioned.

For example prucarium metal salts, ammonium salts, amine salts or acrylamide or methacrylamide or water-soluble N-substituted acrylamide or methacrylamide of acrylic acid or methacrylic acid or vinylimidazole, vinylpyridine, vinylpyrrolidone or sulfonated methylene, vinylsulfonic acid. Alkali metal salts, etc. These monomers can be used in any combination of one or more types. Further, other water-soluble monomers can be copolymerized within a range that does not impair hydrophilicity.

Furthermore, if necessary, a water-soluble crosslinking agent having two or more polymerizable unsaturated groups, such as methylene bisacrylamide, or two or more that can react with the functional group of the ethylenically unsaturated monomer. It is also possible to carry out a crosslinking reaction during or after the (co)polymerization of the monomers using a water-soluble crosslinking agent having a functional group such as ethylene glycol diglycidyl ether.

The monomer concentration of the monomer aqueous solution in the present invention can be varied within a wide range, but is generally preferably 15 to 80% by weight.

Further, the ratio of the above monomer aqueous solution to the amount of the polymerization-inactive and hydrophobic solvent can be changed over a wide range, but the volume ratio is usually in the range of 1=1 to 1:4. suitable.

For monomer polymerization, a water-soluble radical polymerization initiator,
For example, peroxides, no-hydroboroxides, or azo compounds are used in known amounts. These polymerization initiators can also be used in combination of two or more types,
Furthermore, it is also possible to add chromium ion, sulfite, hydroxylamine, hydrazine, etc. and use it as a redox polymerization initiator.

[Effect]

The mechanism of action by which the dispersant for reverse-phase suspension polymerization of the present invention provides excellent effects is not necessarily clear, but considering the fact that monoalkyl phosphoric acid having a linear alkyl group is effective, Due to the balance between the hydrogen bonds of the phosphoric acid groups and the hydrophobic linear alkyl groups at the oil/water interface, the dispersant is oriented in an orderly manner, which stabilizes both interfaces and therefore stabilizes reversed-phase suspension synthesis. It is presumed that it can be maintained.

〔Example〕

The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited only to these Examples.

Example 1 A 500 td four-day round bottom flask equipped with a stirrer, reflux condenser, dropping pouch and nitrogen gas inlet tube was charged with 250 d of cyclohexane and 1.22 d of monocetyl phosphoric acid, nitrogen gas was blown in to drive out dissolved oxygen, and the temperature was heated to 75°C. Separately, in a flask, add 98% caustic soda to ion-exchanged water at 40F while externally cooling the acrylic acid Sat to 13.4℃.
It was neutralized with a solution of F.

Next, after adding and dissolving 0.1 f of potassium persulfate, nitrogen gas was blown into the aqueous solution to remove oxygen present in the aqueous solution.

This solution was added dropwise to the above-mentioned 4-hole flask over 50 minutes to polymerize. After the polymerization was completed, the reaction was continued for an additional hour while maintaining the temperature at 75°C.

Thereafter, the solvent cyclohexane is distilled off under reduced pressure, and the remaining polymer portion is dried under reduced pressure at 80 to 100°C to obtain a small granular polymer of polyacid and sodium acid with a center particle size of 100 to 350 μm. Ta. The amount of deposits in the tank is 0
It was ゜2f.

Example 2 Monostearyl phosphoric acid instead of monocetyl phosphoric acid 1.
Polymerization was carried out according to Example 1 except that 2f was used, and a small granular polymer with a center particle size of 100 to 350 μm was obtained. The amount of deposits in the tank was 0.3F.

Example 5 Monolauryl phosphoric acid 1.2 instead of monocetyl phosphoric acid
Polymerization was carried out according to Example 1 except that t was used, and a small granular polymer containing no aggregates and having a center particle size of 120 to 350 μm was obtained.

The amount of deposits in the tank was 0.5F.

Example 4 Monobehenyl phosphoric acid 1.2 instead of monocetyl phosphoric acid
Polymerization was carried out in the same manner as in Example 1 except that F was used, and a small granular polymer containing no aggregates and having a center particle size of 80 to 500 μm was obtained. The amount of deposits in the tank is 0.52
Met.

Example 5 The same procedure as in Example 2 was carried out. However, when sodium vinyl sulfonate 25F was used instead of sodium acrylate as the ethylenically unsaturated monomer aqueous solution and an aqueous monomer solution prepared by dissolving this in 751 ion exchange water was used, the median particle size was 150~
A small granular polymer of 300 μm of sodium polyvinylsulfonate was obtained. The amount of deposits in the tank was 0.62.

Example 6 Polymerization was carried out according to Example 1. However, as a monomer, dimethylaminoethyl methacrylate 20% by weight aqueous solution 8
2゜2'-azobis(2,4-
When polymerization was carried out using dimethylvaleronitrile (trade name V-65, manufactured by Wako Pure Chemical Industries, Ltd.) o, 1st,
A small granular polymer containing no aggregates and having a median particle size of 200 to 350 μm was obtained. The amount of deposits in the reaction tank was 0.51.

Example 7 Polymerization was carried out according to Example 1. However, instead of using 1.2f of monocetyl phosphoric acid as a dispersant, 1.2 f of monocetyl phosphoric acid was used as the dispersant. When polymerization was carried out using a mixture of Ot and dicetyl phosphoric acid 0.2f, small granular polymers containing no aggregates and having a central particle diameter of 100 to 550 .mu.m were obtained. The amount of deposits in the tank was 0.3 f.

Comparative Example 1 Polymerization was carried out according to Example 1. However, monooctyl phosphoric acid 1,2 is used as a dispersant instead of monocetyl phosphoric acid.
When t was used, the polymerization system gelled, and a stable particulate polymer could not be obtained.

Comparative Example 2 Polymerization was carried out according to Example 1. However, when 1.2 tons of sorbitan monostearate was used as a dispersant, only fine particulate polymers with a center particle size of 50 to 70 Am were obtained. The amount of deposits in the reaction tank was 0.9 t.

Comparative Example 3 Polymerization was carried out according to Example 1. However, instead of monocetyl phosphoric acid, sesquicetyl phosphoric acid (equimolar mixture of monocetyl phosphoric acid and dicetyl phosphoric acid) 1. When S t was used, the polymerization system gelled, and a stable particulate polymer could not be obtained.

〔Effect of the invention〕

As specifically shown in the examples, when producing a polymer using the dispersant for reversed-phase suspension polymerization of the present invention, the formation of polymer aggregates was hardly observed; Moreover, the produced polymer has a center particle diameter of 80 to 350 μm, and workability and productivity can be significantly improved throughout the entire process of polymer production. For example, if the dispersant for reverse phase suspension polymerization of the present invention is used, the amount of polymerized material adhering to the polymerization equipment or stirrer can be kept to an extremely small amount, so the polymerization equipment can be used continuously. .

Claims (1)

[Claims] 1. A dispersant for reverse phase suspension polymerization containing 80 mol % or more of monoalkyl phosphoric acid having a linear alkyl group having 12 to 24 carbon atoms.