JPS61231003A - Dispersant for reversed phase suspension polymerization - Google Patents

Abstract

PURPOSE:The titled dispersant which can stabilize a polymerization system in reverse phase suspension polymerization and consistently give small polymer granules free of fine polymer particles, obtained by copolymerizing an ethylenically unsaturated monomer with a specified monomer. CONSTITUTION:At least one ethylenically unsaturated monomer (A) having a 6C or higher alkyl group and/or an aromatic ring [e.g., 6-36C alkyl (meth) acrylate] is copolymerized with 3-40wt% at least one monomer (B) having at least one amide group in the molecule (e.g., N-vinyl-2-pyrrolidone) to obtain the titled oil-soluble copolymer of a MW of 3,000-500,000. A 15-80wt% aqueous solution containing a water-soluble ethylenically unsaturated monomer and optionally other water-soluble monomers is (co)polymerized in the presence of 0.1-10wt% above-produced dispersant and a polymerization initiator in at least one solvent selected from among aliphatic hydrocarbons, alicyclic hydrocarbons and aromatic hydrocarbons all of which have a b.p. of 30-200 deg.C.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for performing reverse phase suspension polymerization by adding an aqueous solution of a water-soluble ethylenically unsaturated monomer to a polymerization inert and hydrophobic solvent. The present invention relates to a dispersing agent used for inverse phase suspension polymerization, and more specifically, to a dispersing agent for use in 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. In implementing this method, it is important to accurately 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 sorbitan monostearate, sorbitan monooleate, ethoxylated aliphatic amides, and glycerin fatty acid esters. Nonionic surfactants are known (Japanese Patent Publication No. 54-30710
Publications, etc.).

In addition to the above, for example, resins containing allyl groups treated with maleic anhydride, polymers containing carboxyl groups that have affinity for organic solvents, lipophilic cellulose derivatives, etc. Molecular compounds and the like are known (JP-A-57-74309, etc.).

[Problem that the invention seeks to solve]

However, when a dispersant of the former group (nonionic surfactants) is used, the resulting polymer becomes fine particles, which causes problems such as generation of dust during the separation and drying process, making it difficult to handle. It can be difficult. If the latter group of dispersants is used, the produced polymer will be in the form of small granules, and although the above-mentioned drawbacks can be improved, during the polymerization operation, the polymer particles may come into contact with the wall of the polymerization tank or the stirrer. It is inevitable that sticking will occur between the two, and a considerable portion of the reacted monomer will be lost as unusable fouling 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]

The present inventors have solved the above problems (as a result of intensive research, they found that ethylenically unsaturated monomers and at least one
By using an oil-soluble copolymer obtained by copolymerizing with a monomer having amide groups as a dispersant during reverse phase suspension polymerization, a small granular polymer that does not contain a fine granular polymer can be produced. The present invention was completed based on the discovery that it is possible to stably obtain the following.

That is, the present invention provides a dispersion for reverse phase suspension polymerization comprising an oil-soluble copolymer obtained by copolymerizing an ethylenically unsaturated monomer and a monomer having at least one amide group in the molecule. The purpose is to provide an agent for

Ethylenically unsaturated monomers that can be used to obtain the dispersant for reversed-phase suspension polymerization of the present invention include carbon atoms of 6
Those having the above alkyl group are preferable, such as alkyl methacrylate or alkyl acrylate (hereinafter referred to as alkyl) having an alkyl group having 6 to 36 carbon atoms.
Meta) acrylate. ), unsaturated dicarboxylic diesters such as dialkyl maleates, dialkyl fumarates, and dialkyl itaconates, alkyl vinyl esters and alkyl vinyl ethers having an alkyl group having 6 or more carbon atoms, and the like. . Furthermore, monomers having an aromatic ring such as styrene and alkylstyrene having an alkyl group having one or more carbon atoms can also be preferably used. Among these, alkyl (meth)acrylates, alkyl vinyl esters, and styrene are particularly preferred.

The above-mentioned alkyl (meth)acrylates include (meth)acrylates having a linear alkyl group such as octyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl ( Examples include (meth)acrylates having a branched alkyl group such as meth)acrylate and isostearyl (meth)acrylate, or mixtures thereof.

In addition, examples of the alkyl vinyl esters include vinyl laurate, vinyl stearate, and carbon atoms having 10 to 2 carbon atoms.
0 vinyl alkanoate can be exemplified.

Examples of monomers having at least one amide group in the molecule that can be used to obtain the dispersant for reversed-phase suspension polymerization of the present invention include N-vinyl-2-pyrrolidone, N-vinyl N-vinyl cyclic amides such as caprolactam, N,N-dimethylacrylamide, N,N-dialkyl(meth)acrylamides such as N,N-diethylmethacrylamide, N such as N,N-dimethylaminopropylacrylamide; Examples include N-dialkylaminoalkyl (meth)acrylamide and N-vinyl-N-methylacetamide. Among these, N-vinyl-2-pyrrolidone and N,N-dimethylacrylamide are particularly preferred.

The dispersant for reverse phase suspension polymerization of the present invention contains one or more ethylenically unsaturated monomers as described above and one or more monomers having at least one amide group in the molecule. Any copolymer may be used as long as it is an oil-soluble copolymer; The composition ratio is preferably 3 to 40% by weight, particularly preferably 5 to 30% by weight. Further, its molecular weight is preferably 3,000 to 500,000, particularly 500,000 to 500,000.
0 to 100,000 is preferable. As for the molecular weight distribution,
It is preferably 20 or less, particularly preferably 10 or less, but is not particularly limited thereto.

The dispersant for reversed-phase suspension polymerization of the present invention can be prepared by a commonly used method, for example, by mixing each monomer, using a polymerization initiator such as an ab-based catalyst or a peroxide-based catalyst, and adding a suitable solvent. It can be produced by a radical polymerization method or the like in the presence of or in a bulk state.

When monomers are subjected to reverse phase suspension polymerization using the dispersant for reverse phase suspension polymerization of the present invention, the appropriate amount of the dispersant to be used is usually 0.1 to 10% by weight based on the monomer. %, preferably 0
．． It is 5 to 5.0% by weight.

When using the dispersant for reversed-phase suspension polymerization of the present invention, as a solvent for reversed-phase suspension polymerization, in principle, any solvent that is inactive for polymerization and does 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 preferable. hexane,
Cyclohexane, benzene, toluene or a mixed solvent thereof is preferably used.

Various types of water-soluble ethylenically unsaturated monomers can be mentioned as the water-soluble ethylenically unsaturated monomers that can be polymerized by reverse-phase suspension polymerization using the dispersant of the present invention. For example, alkali 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 styrene, vinylsulfonic acid. Alkali metal salts, etc. Besides these things,
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate,
Diethylaminoethyl methacrylate and the like can be mentioned. 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 between the amount of the monomer aqueous solution and the amount of the polymerization-inactive and hydrophobic solvent can be changed over a wide range, but usually the volume ratio is 1=1 to 1:4. A range of is suitable.

For monomer polymerization, a water-soluble radical polymerization initiator,
For example, peroxides, hydroperoxides, or azo compounds are used in known amounts. These polymerization initiators can be used in combination of two or more types, and furthermore, chromium ions, sulfites, hydroxylamine,
It is also possible to add hydrazine or the like and use it as a redox polymerization initiator.

[For production]

The dispersant for reverse-phase suspension polymerization of the present invention has an amide moiety having scratching properties and a non-polar moiety, and when performing reverse-phase suspension polymerization, this dispersant is present at the oil/water interface. It is presumed that the reversed phase suspension polymerization system can be stably maintained because it is regularly oriented and stabilizes both interfaces.

〔Example〕

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

In addition, the dispersants used in the examples are listed below.

Dispersant A 5QOn equipped with a stirrer, reflux condenser, and nitrogen gas introduction tube
+1 4th round bottom flask, vinyl stearate 85
g1 15 g of vinylpyrrolidone and 100 g of toluene were added, and further 2.5 g of dilauroyl peroxide was added. After sufficient nitrogen gas replacement, the reaction was carried out at a temperature of 80°C for 4 hours and at 95°C for 1 hour. 100 g of the obtained toluene solution was collected and reprecipitated in 31 methanol, filtered and dried to obtain 45 g of white powder. The nitrogen content of this product is 2.1%, and the number average molecular weight by GPC is 8.
400 (PS converted).

Dispersant B In a device similar to that used for Dispersant A, add 80 g of stearyl methacrylate, 2 N,N-dimethylacrylamide
0 g, ) 100 g of toluene was added, and further 2 g of 2.2'-azobis(2,4-dimethylvaleronitrile) was added. After sufficient nitrogen gas replacement, the temperature was 65℃ for 5 minutes.
After reacting at 95°C for 1 hour, the same treatment as for dispersant A was performed, and the nitrogen content was 2.8%, the number average molecular weight was 27,
43 g of a white powdery polymer of 000 was obtained.

Dispersant C: 88 g of stearyl methacrylate in the same device as Dispersant A.
1 vinyl pyro IJ l'n 12g, ) luene 100g
was added, and further 1.2 g of tert-butyl perbenzoate was added, and the reaction was carried out at a reaction temperature of 110°C for 8 hours, followed by the same treatment as for dispersant A to obtain a nitrogen content of 1.5% and a number average molecular weight. 43 g of a white powdery polymer of 46.000% was obtained.

The procedure was the same as for dispersant B except that 92 g of styrene and 8 g of N,N-dimethylacrylamide were used as dispersant monomers to obtain 35 g of a waxy polymer with a nitrogen content of 0.95% and a number average molecular weight of 8500. Ta.

Dispersant E A white powdery polymer having a nitrogen content of 1.7% and a number average molecular weight of 25,000 was obtained by operating in the same manner as Dispersant A except for replacing vinylpyrrolidone with N-vinylcaprolactam.

Example 1 In a 50 mm 14 round bottom flask equipped with a stirrer, reflux condenser, dropping funnel and nitrogen gas inlet tube, cyclohexane 2
50n+1 and 1.2 g of dispersant A were charged, nitrogen gas was blown in to drive out dissolved oxygen, and the temperature was raised to 75°C. Separately, in a flask, 30 g of acrylic acid was added to 40 g of ion-exchanged water while cooling from the outside with 98% caustic soda added 13.
It was neutralized with a solution of 4 g. Next, 0.1 g of potassium persulfate was added and dissolved, and then nitrogen gas was blown into the solution to remove oxygen present in the aqueous solution. Add this solution to step 4 above.
The mixture was added dropwise to a double flask over 30 minutes for polymerization. After the dropwise addition was completed, the reaction was continued for an additional hour while maintaining the temperature at 75°C. Thereafter, the solvent cyclohexane was distilled off under reduced pressure, and the remaining polymer portion was dried under reduced pressure at 80 to 100°C to obtain small granular sodium polyacrylate with a center particle size of 100 to 350 μm. The amount of deposits in the tank was 0.3 g.

Examples 2 to 5 In Example 1, instead of dispersant A, dispersant, agent B, and dispersant C were used.
1. Polymerization was carried out using Dispersant D and Dispersant E, respectively. Table 1 shows the center particle diameter and the amount of adhesion in the tank of the obtained sodium polyacrylate.

Table 1 Example 6 In Example 1, 25 g of sodium vinyl sulfonate was used instead of sodium acrylate as the ethylenically unsaturated monomer aqueous solution, and an aqueous monomer solution was used in which this was dissolved in 75 g of ion-exchanged water. However, small granular particles of sodium polyvinylsulfonate having a center particle diameter of 100 to 400 μm were obtained.

The amount of deposits in the tank was 0.8 g.

Comparative Example Polymerization was carried out according to Example 1. However, when 1.2 g of sorbitan monostearate was used instead of dispersant A, only fine particulate polymers with a center particle size of 30 to 70 μm were obtained. The amount of deposits in the reaction tank was 0.9 g.

〔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 size of 100 to 400 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. Reverse phase suspension polymerization consisting of an oil-soluble copolymer obtained by copolymerizing an ethylenically unsaturated monomer and a monomer having at least one amide group in the molecule. Dispersant for use. 2. The dispersant for reverse-phase suspension polymerization according to claim 1, wherein the ethylenically unsaturated monomer has an alkyl group having 6 or more carbon atoms. 3. The dispersant for reverse-phase suspension polymerization according to claim 1, wherein the composition ratio of the monomer having at least one amide group in the molecule is 3 to 40% by weight in the total monomers. . 4. The dispersant for reverse-phase suspension polymerization according to claim 1, wherein the ethylenically unsaturated monomer has an aromatic ring.