JP2905318B2 - Dispersant for reversed phase suspension polymerization - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As one method of 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 for polymerization. Is well known. When carrying out this method, an aqueous solution of the monomer to be polymerized is stably dispersed in a hydrophobic solvent, and then a dispersant that can prevent or reduce agglomeration of the resulting polymer particles 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.

[0003] Examples of dispersants conventionally used in the reverse phase suspension polymerization of such water-soluble ethylenically unsaturated monomers include sorbitan monostearate, sorbitan monooleate and ethoxylated aliphatic. Nonionic surfactants such as amides and glycerin fatty acid esters are known (JP-B-54-30710). Further, in addition to the above, for example, when the carbon number of the alkyl group is 8
Copolymers comprising the above-mentioned alkyl (meth) acrylate, hydroxyalkyl (meth) acrylate, and unsaturated monomers copolymerizable with the above two monomers are known. (JP-A-63-56512). In this specification, (meth) acrylic acid means acrylic acid or methacrylic acid.

[0004]

However, when nonionic surfactants, which are the former group, are used as a dispersant, the resulting polymer becomes fine particles, and dust is generated in the separation and drying steps. Problems may occur, which may make handling difficult. When the latter group of polymer compounds is used as a dispersant, the resulting polymer becomes small granules, which can improve the above-mentioned disadvantages. Adhesion occurs between the tank walls and the stirrer, and a significant portion of the reacted monomer is lost as unusable polymerization tank deposits. Generally, it takes a great deal of effort to remove deposits on a polymerization tank of a water-soluble ethylenically unsaturated monomer, which hinders efficient production of a granular polymer.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, styrene and / or
Or propyl (meth) acrylate and glyceryl acrylate
By using an oil-soluble nonionic copolymer obtained by copolymerizing a roll and / or glycerol methacrylate as a dispersant in reverse-phase suspension polymerization, a small granular polymer containing no finely divided polymer can be obtained. The present inventors have found that coalescence can be stably obtained, and have completed the present invention. That is, the present invention relates to a lipophilic monomer comprising styrene and / or propyl (meth) acrylate, and glycerol acrylate and
And / or a dispersant for reverse phase suspension polymerization comprising an oil-soluble nonionic copolymer obtained by copolymerizing with a hydrophilic monomer comprising glycerol methacrylate .

Examples of the lipophilic monomer 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, and isopropyl methacrylate. These can be used alone or as a mixture. Further, as the hydrophilic monomer that can be used to obtain the dispersant for reversed phase suspension polymerization of the present invention ,
A acrylic glycerol and methacrylic acid Glycerol <br/> be exemplified. These hydrophilic monomers can be used alone or as a mixture of two kinds .

In the dispersant of the present invention, the balance between hydrophilicity and lipophilicity is an important factor, and styrene and / or propyl (meth) acrylate, glycerol acrylate and
And / or glycerol methacrylate can be controlled depending on the type and content thereof, and those suitable for the water-soluble ethylenically unsaturated monomer used for suspension polymerization and the dispersion medium during polymerization are selected. The ratio of the lipophilic monomer unit to the hydrophilic monomer unit in the nonionic copolymer of the present invention is 70 to 99.5 mol% for the former and 30 to 0.5 mol% for the latter.
More preferably, the former is 85 to 99 mol%, and the latter 15
１1 mol%. When the amount of the hydrophilic monomer unit exceeds 30 mol%, the solubility in an oily solvent as a dispersion medium is deteriorated, and the hydrophilic side becomes too strong, resulting in poor dispersion stability. The molecular weight of the nonionic copolymer of the present invention is preferably a number average molecular weight of 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 the 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-based initiator in the presence of a solvent capable of uniformly dissolving each monomer and the resulting copolymer.

Using the dispersant for reversed phase suspension polymerization of the present invention,
When a water-soluble ethylenically unsaturated monomer is subjected to reverse-phase suspension polymerization, an appropriate amount of the dispersant to be used is usually 0.1 to 10% by weight, preferably 0.5 to 5.0% by weight based on the monomer. It is. Further, when the dispersant for reversed phase suspension polymerization of the present invention is used, as a solvent for the reversed phase suspension polymerization, in principle, any solvent having polymerization inertness and water-insoluble property can be used. In consideration of the removal of the heat of polymerization and the drying step of the obtained polymer, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons or a mixed solvent thereof having a boiling point of 30 to 200 ° C. are preferable, and especially n- Hexane, cyclohexane, benzene, toluene or a mixed solvent thereof is preferably used.

The water-soluble ethylenically unsaturated monomer which can be polymerized by reverse phase suspension polymerization using the dispersant of the present invention includes various types. For example, alkali metal salts, ammonium salts, amine salts of acrylic acid or methacrylic acid, acrylamide or methacrylamide, water-soluble N-substituted acrylamide or methacrylamide, vinylpyrrolidone or sulfonated styrene, alkali metal salts of vinylsulfonic acid, etc. It is. In addition to these, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and the like can be mentioned. One or more of these monomers can be used in any combination. Further, other water-soluble monomers can be copolymerized as long as the hydrophilicity is not impaired. Further, if necessary, a water-soluble cross-linking agent having two or more polymerizable unsaturated groups, for example, methylene bisacrylamide or the like, or two or more capable of reacting with a functional group of an ethylenically unsaturated monomer. It is also possible to use a water-soluble crosslinking agent having a functional group, for example, ethylene glycol diglycidyl ether or the like, to cause a crosslinking reaction during or after (co) polymerization of the above monomer.

The concentration of the monomer in the aqueous monomer solution can be varied in a wide range, but is generally preferably from 15 to 80% by weight. The ratio of the amount of the monomer aqueous solution to the amount of the polymerization-inactive and hydrophobic solvent can be changed over a wide range, but usually, the ratio by volume is from 1: 1 to 1: 4. Is suitable. For the polymerization of the monomer, a known amount of a water-soluble radical polymerization initiator such as a peroxide, a hydroperoxide, or an azo compound is used. These polymerization initiators can be used as a mixture of two or more kinds, and further, chromium ions, sulfites, hydroxylamine, hydrazine, etc. can be added to be used as a redox polymerization initiator. It is. The oil-soluble nonionic copolymer of the present invention can be used alone as a good dispersant, but may be used in combination with another emulsifier or dispersant, if necessary.

[0011]

The dispersant for reversed phase suspension polymerization of the present invention has a hydroxyl group as a hydrophilic part and styrene and / or (meth) yl as a lipophilic part.
Because propyl acrylate is selected, the dispersant is regularly oriented at the oil / water interface when performing reversed-phase suspension polymerization, and the effect of stabilizing both interfaces is large. It is presumed that this is the cause that can be maintained stably.
Furthermore, when the dispersant of the present invention is used for reversed-phase suspension polymerization of anionic monomers such as sodium acrylate and sodium methacrylate, a greater stabilizing effect is exhibited by the hydrogen bonding interaction between the dispersant and the monomer. 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 1 103.2 g (1.0 mol) of styrene, 4.81 g (0.03 mol) of glycerol methacrylate, 100 g of acetonitrile, and 100 g of acetonitrile were placed in a 300 ml four-necked flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube. 2'-azobisisobutyronitrile (hereinafter A)
After adding and mixing 1.3 g, nitrogen gas replacement was sufficiently performed. After raising the temperature to 80 ° C., polymerization was carried out at 80 ° C. for 8 hours. After dilution 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
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
Using 1.3 g of N, polymerization and polymer isolation were carried out in the same manner as in Synthesis Example 1. 98.2 g of dispersant B was obtained, 400 MHz- ¹ HN
Glycerol methacrylate monomer unit from MR
The content was 5.2 mol%. The number average molecular weight determined by GPC was 35,000 (pst conversion).

Synthesis Example 3 Polymerization and isolation were 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. Was. 125.3 g of dispersant C were obtained, 40
From 0 MHz- ¹ H-NMR, it contained 2.2 mol% of a glycerol methacrylate monomer unit. The number average molecular weight determined 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
Using 100 g and 1.3 g of AIBN, polymerization and isolation were carried out in the same manner as in Synthesis Example 1. 127.8 g of dispersant D were obtained, 400M
Hz- ¹ H-NMR methacrylic acid glycerol monomer unit contained 5.1 mol% than. The number average molecular weight determined by GPC was 37,000 (pst conversion).

EXAMPLE 1 127.5% aqueous 80% acrylic acid solution was placed in a 500 ml four-necked flask.
g of the solution, and while stirring under cooling, 140 g of a 30% aqueous sodium hydroxide solution was added dropwise to neutralize the solution. Next, a solution in which 0.23 g of potassium persulfate was dissolved 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,
400 ml of cyclohexane and 1.25 g of the dispersant A of Synthesis Example 1 were charged into a 1-liter four-necked flask equipped with a dropping funnel and a nitrogen gas inlet tube, and the temperature was raised to 75 ° C. while blowing out nitrogen gas to expel dissolved oxygen. did. Next, the monomer / initiator aqueous solution was added dropwise over 30 minutes while stirring at 350 rpm under a refluxing condition of cyclohexane, and then polymerization was performed for 3 hours under the refluxing condition. 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 deposits were found in the tank.

Examples 2 to 4 Polymerization was carried out in the same manner as in Example 1 except that the dispersant A of Example 1 was replaced by the dispersants B, C and D of Synthesis Examples 2 to 4. . The yield of the obtained sodium polyacrylate,
Table 1 shows the average particle size of the particles. In any case, deposits in the tank were hardly observed.

[0019]

[Table 1]

Comparative Example 1 In place of 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 units and having a number average molecular weight of 27,000) was used. Example 1 except that
When the same operation as described above was carried out, the generated sodium polyacrylate became clumped during the dropping of the monomer initiator solution, and the stirring became impossible.

Comparative Example 2 The same operation as in Example 1 was carried out except that 1.25 g of sorbitan monostearate was used instead of dispersant A of Example 1, to find that 86.5 g of sodium polyacrylate fine particles were obtained. The average particle size was 50 μm. Further, considerable deposits were observed in the reaction tank.

Comparative Example 3 In place of Dispersant A of Example 1, a copolymer of lauryl methacrylate (90% by weight) and hydroxyethyl methacrylate (10% by weight) synthesized in the same manner as in Synthesis Example 1 1.25
Except for using g, the same operation as in Example 1 was carried out, but no bead-like polymer was obtained, and the whole of the container was solidified.

[0023]

As specifically described in Examples, when a polymer is produced using the dispersant for reversed phase suspension polymerization of the present invention, almost no polymer aggregates are observed, Further, the produced polymer has an average particle size of several hundred μm, and it is possible to remarkably improve the workability and productivity in all the steps of producing the polymer. For example, when the dispersant of the present invention is used, since there is almost no polymer agglomerate in the reaction tank, there is an effect that long-term production can be performed without removing deposits in the tank. .

Claims (2)

(57) [Claims] 1. A lipophilic monomer comprising styrene and / or propyl (meth) acrylate, and glyceryl acrylate.
Dispersant for reverse phase suspension polymerization comprising an oil-soluble nonionic copolymer obtained by copolymerizing a hydrophilic monomer comprising a roll and / or glycerol methacrylate . 2. The oil-soluble nonionic copolymer comprises 70 to 99.5 mol% of a lipophilic monomer unit and 30 to 9% of a hydrophilic monomer unit.
The dispersant for reverse phase suspension polymerization according to claim 1, which contains 0.5 mol%.