JPH0559108A - Dispersant for reverse phase suspension polymerization - Google Patents

Abstract

(57) [Summary] [Structure] An oil-soluble nonion obtained by copolymerizing a lipophilic monomer composed of styrene and / or propyl (meth) acrylate with a hydrophilic monomer composed of a hydroxyalkyl ester of (meth) acrylic acid. Dispersing agent for reverse phase suspension polymerization comprising a hydrophilic copolymer. [Effect] When a polymer is produced using the dispersant for reverse phase suspension polymerization of the present invention, almost no aggregates of the polymer are observed, and the produced polymer has a particle size of several hundred μm. Since it has an average particle size, it is possible to significantly improve workability and productivity in all steps of polymer production.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dispersant used in reverse phase suspension polymerization by adding a water-soluble ethylenically unsaturated monomer aqueous solution to a polymerization-inert and hydrophobic solvent. More specifically, the present invention relates to a dispersant for reversed-phase suspension polymerization capable of stably maintaining the polymerization system.

[0002]

2. Description of the Related Art As one of the methods for polymerizing a water-soluble ethylenically unsaturated monomer, a so-called reverse phase suspension polymerization method in which an aqueous monomer solution is suspended and dispersed in a hydrophobic solvent to perform polymerization. Is well known. When carrying out this method, an aqueous solution of a monomer to be polymerized is stably dispersed in a hydrophobic solvent, and then a dispersant capable of preventing or reducing agglomeration of polymer particles to be produced is appropriately selected. Is an important point. In other words, by selecting a suitable dispersant, productivity can be significantly improved, and a polymer having uniform physical properties can be obtained.

Examples of dispersants conventionally used in such reverse phase suspension polymerization of water-soluble ethylenically unsaturated monomers include, for example, sorbitan monostearate, sorbitan monooleate and ethoxylated aliphatic compounds. Nonionic surfactants such as amides and glycerin fatty acid esters are known (Japanese Patent Publication No. 54-30710, etc.). In addition to the above, for example, the number of carbon atoms in the alkyl group is 8.
The above-mentioned alkyl (meth) acrylate monomers, hydroxyalkyl (meth) acrylate monomers, and copolymers containing unsaturated monomers copolymerizable with the above two monomers as constituent components are known. (Japanese Patent Laid-Open No. 63-56512). In addition, in this specification, (meth) acrylic acid means acrylic acid or methacrylic acid.

[0004]

However, when the former group of nonionic surfactants is used as a dispersant, the produced polymer becomes fine particles and dust is generated in the separation and drying process. It may cause problems such as rusting, and it may be difficult to handle it. When the polymer compounds of the latter group are used as the dispersant, the produced polymer becomes small granules, which can improve the above-mentioned drawbacks, but during the polymerization operation, the polymer particles and the polymerization tank Adhesion occurs between the tank wall and the stirrer, and a considerable part of the reacted monomers is lost as unusable polymerization tank deposits. Generally, it takes a lot of labor to remove the deposits of the water-soluble ethylenically unsaturated monomer in the polymerization tank, which hinders the efficient production of the granular polymer.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that styrene and / or
Alternatively, by using an oil-soluble nonionic copolymer obtained by copolymerizing propyl (meth) acrylate and hydroxyalkyl (meth) acrylate as a dispersant in reverse phase suspension polymerization, fine particles can be obtained. The present inventors have completed the present invention by finding that it is possible to stably obtain a small granular polymer that does not contain a granular polymer. That is, the present invention is an oil-soluble nonionic copolymer obtained by copolymerizing a lipophilic monomer composed of styrene and / or propyl (meth) acrylate and a hydrophilic monomer composed of hydroxyalkyl ester of (meth) acrylic acid. The present invention relates to a dispersant for reversed phase suspension polymerization.

Examples of lipophilic monomers that can be used to obtain the dispersant for reverse phase suspension polymerization of the present invention include styrene, normal propyl acrylate, normal propyl methacrylate, isopropyl acrylate, isopropyl methacrylate and the like. These can be used alone or in combination. Further, as the hydrophilic monomer that can be used to obtain the dispersant for reverse phase suspension polymerization of the present invention,
2-hydroxyethyl acrylate, methacrylic acid 2
-Hydroxyethyl, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, glycerol acrylate, glycerol methacrylate and the like can be exemplified. These hydrophilic monomers can be used alone or in a mixture of two or more kinds.

In the dispersant of the present invention, the balance between hydrophilicity and lipophilicity is an important factor, and it depends on the type and content of styrene and / or propyl (meth) acrylate and hydroxyalkyl (meth) acrylate. It is controllable, and a suitable one is selected depending on the water-soluble ethylenically unsaturated monomer used for suspension polymerization, the dispersion medium at the time of polymerization, and the like. The ratio of the lipophilic monomer unit and the hydrophilic monomer unit in the nonionic copolymer of the present invention is
The former 70 to 99.5 mol% and the latter 30 to 0.5 mol% are preferable,
More preferably, the former is 85 to 99 mol% and the latter is 15 to 1 mol%. When the content of the hydrophilic monomer unit exceeds 30 mol%, the solubility in an oil solvent as a dispersion medium is deteriorated and the hydrophilic side becomes too hard, resulting in poor dispersion stability. The number average molecular weight of the nonionic copolymer of the present invention is preferably 500 to 500,000. When the number average molecular weight is less than 500 or more than 500,000, a sufficient dispersion stabilizing effect is not exhibited even if hydrophilicity and lipophilicity are balanced.
The oil-soluble nonionic copolymer of the present invention can be produced by radical polymerization with an azo or peroxide initiator in the presence of a solvent capable of uniformly dissolving each monomer and the produced copolymer.

Using the dispersant for reverse phase suspension polymerization of the present invention,
When reverse-phase suspension polymerization of a water-soluble ethylenically unsaturated monomer is used, an appropriate amount of the dispersant used is usually 0.1 to 10% by weight, preferably 0.5 to 5.0% by weight, based on the monomer. Is. Further, when the dispersant for reverse phase suspension polymerization of the present invention is used, as a solvent at the time of reverse phase suspension polymerization, in principle, all solvents which are polymerization inactive and have a property of not dissolving water can be used. Considering the removal of the heat of polymerization and the drying step of the obtained polymer, an aliphatic hydrocarbon, an alicyclic hydrocarbon, an aromatic hydrocarbon or a mixed solvent thereof having a boiling point of 30 to 200 ° C. is preferable, and particularly n- Hexane, cyclohexane, benzene, toluene or a mixed solvent thereof is preferably used.

As the water-soluble ethylenically unsaturated monomer which can be polymerized by reverse phase suspension polymerization to which the dispersant of the present invention is applied, various kinds can be mentioned. For example, acrylic acid or methacrylic acid alkali metal salt, ammonium salt, amine salt, acrylamide or methacrylamide, water-soluble N-substituted acrylamide or methacrylamide, vinylpyrrolidone, sulfonated styrene, vinylsulfonic acid alkali metal salt, etc. Is. Besides these, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and the like can be mentioned. These monomers may be used alone or in any combination. Further, other water-soluble monomers may be copolymerized within the range that does not impair the hydrophilicity. Further, if necessary, a water-soluble crosslinking agent having two or more polymerizable unsaturated groups, such as methylenebisacrylamide, or two or more groups capable of reacting with the functional group of the ethylenically unsaturated monomer. It is also possible to use a water-soluble crosslinking agent having a functional group, for example, ethylene glycol diglycidyl ether, to carry out a crosslinking reaction during (co) polymerization of the above-mentioned monomer or after the polymerization.

Although the monomer concentration of the aqueous monomer solution can be varied within a wide range, it is generally preferably 15 to 80% by weight. The ratio of the amount of the monomer aqueous solution to the amount of the polymerization-inert and hydrophobic solvent can be changed over a wide range, but the volume ratio is usually 1: 1 to 1: 4. Is preferred. For the polymerization of the monomers, water-soluble radical polymerization initiators such as peroxides, hydroperoxides or azo compounds are used in known amounts. These polymerization initiators can be used as a mixture of two or more kinds, and further, chromium ion, sulfite, hydroxylamine, hydrazine and the like can be added and used as a redox polymerization initiator. Is. The oil-soluble nonionic copolymer of the present invention can be a good dispersant by itself, but it is also possible to use other emulsifiers and dispersants in combination, if necessary.

[0011]

The dispersant for reversed phase suspension polymerization of the present invention comprises a hydroxyl group as a hydrophilic part and styrene and / or (meth) as a lipophilic part.
Since propyl acrylate is selected, the dispersant is regularly oriented at the oil / water interface during reverse phase suspension polymerization, and the effect of stabilizing both interfaces is large. It is inferred that this may be the reason why it can be stably maintained.
Furthermore, when the dispersant of the present invention is used for reverse phase suspension polymerization of anionic monomers such as sodium acrylate and sodium methacrylic acid, a greater stabilizing effect is exhibited due to the hydrogen bonding interaction between the dispersant and the monomers. it can.

[0012]

EXAMPLES The present invention will be specifically described below with reference to synthesis examples, examples and comparative examples, but the present invention is not limited to these examples.

Synthesis Example 1 In a 300 ml four-necked flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 104.2 g (1.0 mol) of styrene, 4.81 g (0.03 mol) of glycerol methacrylate, 100 g of acetonitrile, 2, 2'-azobisisobutyronitrile (hereinafter A
After adding 1.3 g of IBN (abbreviated as IBN) and mixing, nitrogen gas replacement was sufficiently performed. After the temperature was raised to 80 ° C, polymerization was carried out at 80 ° C for 8 hours. After diluting with acetone, the polymer solution was precipitated from an n-hexane / water two-layer solvent system, filtered and dried to obtain 99.0 g of Dispersant A. 400 MHz- ¹ content of methacrylic acid glycerol monomer unit than H-NMR 3.2
It becomes mol%. The number average molecular weight by GPC is 36,000.
(pst conversion).

Synthesis Example 2 104.2 g (1.0 mol) of styrene, 8.02 g (0.05 mol) of glycerol methacrylate, 100 g of acetonitrile, AIB
Polymerization and polymer isolation were performed in the same manner as in Synthesis Example 1 using 1.3 g of N. 98.2 g of dispersant B was obtained, 400MHz- ¹ HN
Glycerol Methacrylate Monomer Unit from MR
The content was 5.2 mol%. The number average molecular weight by GPC was 35,000 (pst conversion).

Synthesis Example 3 Polymerization / isolation was carried out in the same manner as in Synthesis Example 1 using 128.2 g (1.0 mol) of n-propyl methacrylate, 3.2 g (0.02 mol) of glycerol methacrylate, 100 g of acetonitrile and 1.3 g of AIBN. It was 125.3 g of dispersant C are obtained, 40
According to 0 MHz- ¹ H-NMR, it contained 2.2 mol% of a glycerol methacrylate monomer unit. The number average molecular weight by GPC was 33,000 (pst conversion).

Synthesis Example 4 128.2 g (1.0 mol) of isopropyl methacrylate, 8.02 g (0.05 mol) of glycerol methacrylate, acetonitrile
Polymerization and isolation were performed in the same manner as in Synthesis Example 1 using 100 g and AIBN 1.3 g. 127.8 g of dispersant D is obtained, 400M
From Hz- ¹ H-NMR, it contained 5.1 mol% of a glycerol methacrylate monomer unit. The number average molecular weight by GPC was 37,000 (pst conversion).

Example 1 80% acrylic acid aqueous solution 127.5 was added to a 500 ml four-necked flask.
g was taken, and 140 g of a 30% caustic soda aqueous solution was added dropwise while stirring under cooling to neutralize. Next, a solution prepared by dissolving 0.23 g of potassium persulfate in 7.5 g of ion-exchanged water was added and mixed, and dissolved oxygen was removed by blowing nitrogen gas to prepare a monomer / initiator aqueous solution. Stirrer, reflux condenser,
A 1-liter four-necked flask equipped with a dropping funnel and a nitrogen gas introduction tube was charged with 400 ml of cyclohexane and 1.25 g of the dispersant A of Synthesis Example 1, and blown with nitrogen gas to raise the temperature to 75 ° C. while expelling dissolved oxygen. did. Then, the monomer / initiator aqueous solution was added dropwise under reflux conditions of cyclohexane for 30 minutes while stirring at 350 rpm, and then polymerization was performed for 3 hours under reflux conditions. After the polymerization, the produced polymer was separated by filtration and dried under reduced pressure at 80 ° C to 100 ° C to obtain 86.2 g of granular sodium polyacrylate. The average particle size of the obtained polymer was 290 μm, and almost no deposit was observed in the tank.

Examples 2 to 4 Polymerization was carried out in the same manner as in Example 1 using the dispersant B, the dispersant C and the dispersant D of Synthesis Examples 2 to 4 instead of the dispersant A of Example 1. .. Yield of sodium polyacrylate obtained,
The average particle size of the particles is shown in Table 1. In all cases, almost no deposits were observed in the tank.

[0019]

[Table 1]

Comparative Example 1 Instead of the dispersant A of Example 1, 1.25 g of a copolymer of stearyl methacrylate and glycerol methacrylate (containing 4.5 mol% of glycerol methacrylate monomer unit, number average molecular weight of 270000) was used. Example 1 except that
When the same operation as above was performed, the generated sodium polyacrylate became lumpy during the dropping of the monomer initiator solution, and stirring was impossible.

Comparative Example 2 The same operation as in Example 1 was conducted except that 1.25 g of sorbitan monostearate was used in place of the dispersant A of Example 1, and 86.5 g of sodium polyacrylate fine particles were obtained. Obtained, the average particle size was 50 μm. Further, a considerable amount of deposit was found in the reaction tank.

Comparative Example 3 Instead of the dispersant A of Example 1, a copolymer of lauryl methacrylate (90% by weight) and hydroxyethyl methacrylate (10% by weight) synthesized by the same formulation as in Synthesis Example 1 was used. 1.25
When the same operation as in Example 1 was carried out except that g was used, a beaded polymer was not obtained, and the whole inside the container was solidified.

[0023]

As described in detail in the examples, when a polymer is produced using the dispersant for reverse phase suspension polymerization of the present invention, almost no aggregate of the polymer is observed, Further, the produced polymer has an average particle diameter of several hundred μm, and it is possible to remarkably improve workability and productivity in all steps of producing the polymer. For example, when the dispersant of the present invention is used, there is almost no polymer agglomerate in the reaction tank, so that it has the effect of enabling long-term production without removing the deposits in the tank. ..

Claims (2)

[Claims] 1. An oil-soluble nonionic copolymer obtained by copolymerizing a lipophilic monomer composed of styrene and / or propyl (meth) acrylate and a hydrophilic monomer composed of a hydroxyalkyl ester of (meth) acrylic acid. A dispersant for reversed phase suspension polymerization. 2. The oil-soluble nonionic copolymer comprises a lipophilic monomer unit of 70 to 99.5 mol% and a hydrophilic monomer unit of 30 to 99.5 mol%.
The dispersant for reverse phase suspension polymerization according to claim 1, which contains 0.5 mol%.