JPH0655792B2 - Method for producing acrylonitrile-based polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method for producing an acrylonitrile polymer.

More specifically, by polymerizing acrylonitrile alone or acrylonitrile as a main component, a mixture with another ethylenically unsaturated monomer copolymerizable with acrylonitrile is polymerized in an aqueous medium in the presence of a specific suspension stabilizer. The present invention relates to a method for producing an acrylonitrile-based polymer having a large particle size and being suitable for a base resin such as an ion exchange resin and a chelate resin, which substantially prevents the formation of lees.

<Prior art> The most important thing in suspension polymerization is to prevent agglomeration due to the aggregation of oil droplets during polymerization and to complete the polymerization while maintaining a stable dispersion state. For example, it is possible to prevent the generation of scale, further prevent the generation of fine powder particles, and make the particle diameter of the beads uniform.

The selection of the suspension stabilizer is important for solving the above-mentioned inconvenience, but its effect depends on the kind of the monomer used, the polymerization conditions and the like.

Various methods for this have been proposed.

In the suspension polymerization of acrylonitrile, for example, a method in which partially saponified polyvinyl alcohol and hydroxyalkyl cellulose and / or hydroxyalkyl / alkyl cellulose are used in combination (JP-A-50-123185), water-insoluble phosphate and alkyl cellulose or Method using hydroxyalkyl cellulose and anionic surfactant (JP-A-52-145489), method using alkyl cellulose and polyoxyethylene polyoxypropylene block polymer and / or gelatin (JP-A-61-5)
No. 3301) and the like.

On the other hand, in order to increase the particle size of the beads, the amount of the suspension stabilizer added may be reduced or the stirring speed may be decreased.

<Problems to be Solved by the Invention> However, when the known suspension stabilizer is used, non-sphericalized particles are present, the particle size distribution is wide, and it is possible to substantially prevent the formation of polymer lees. Have difficulty.

Further, in the method of using an alkyl cellulose and a polyoxyethylene polyoxypropylene block polymer, for example, when it is attempted to obtain a large particle size polymer having a central particle size of about 0.6 mm, suspension stability deteriorates, The obtained polymer has irregularities such that a spherical product cannot be obtained and fine powder particles are generated.

<Means for Solving Problems> The present inventors have selected (A) alkyl cellulose and (B) polyoxyethylene polyoxypropylene block polymer and gelatin in producing the acrylonitrile-based polymer. A method for producing an acrylonitrile polymer using a suspension stabilizer composed of at least one compound has been proposed.

After that, as a result of diligent study on means for increasing the particle size of the acrylonitrile-based polymer, when the suspension stabilizer is used, the pH of the aqueous medium is usually in the range of 6.7 to 8, but the acid etc. It was found that the particle size of the polymer is increased by adding the above to reduce the pH of the aqueous medium, and the present invention has been completed.

That is, the present invention, in order to produce an acrylonitrile-based polymer by suspension polymerization of acrylonitrile alone or a mixture of other acrylonitrile-based ethylenically unsaturated monomers copolymerizable with acrylonitrile in an aqueous medium, (A)
Polymerization was carried out by controlling the pH of the aqueous medium to 2 to 6.5 using a suspension stabilizer composed of alkyl cellulose and (B) polyoxyethylene polyoxypropylene block polymer and at least one compound selected from gelatin. A method for producing an acrylonitrile-based polymer having spherical particles and a sharp particle size distribution, which is characterized in that it is carried out.

The raw material monomer used in the method of the present invention is acrylonitrile monomer alone or a mixture of acrylonitrile and other ethylenically unsaturated monomer which is mainly composed of acrylonitrile and is copolymerizable therewith.

Other ethylenically unsaturated monomers copolymerizable with acrylonitrile, for example, styrene, methylstyrene,
Styrene derivatives such as ethylstyrene, chlorostyrene, aminostyrene and cyanostyrene; nitriles such as methacrylonitrile, α-chloroacrylonitrile, vinylidene cyanide, crotonnitrile, 2-cyanoethyl acrylate and 2-cyanoethyl methacrylate;
Acrylic acid and methyl acrylate, ethyl acrylate,
Acrylic esters such as butyl acrylate; Methacrylic acid esters such as methacrylic acid and methyl methacrylate, glycidyl methacrylate; aliphatic vinyl derivatives such as vinyl acetate and vinyl butyrate; diethyl maleate
Vinyl ketones such as methyl vinyl ketone; acrylamide derivatives such as acrylamide and N-phenyl acrylamide; heterocyclic vinyl compounds such as N-vinyl phthalimide, vinyl imidazole and vinyl viridine; divinyl benzene, trivinyl benzene, divinyl toluene, divinyl ketone, Examples thereof include cross-linking polymerizable compounds having an unsaturated bond such as diallyl phthalate, diallyl maleate, N, N'-methylenebisacrylamide, ethylene glycol dimethacrylate and polyethylene glycol dimethacrylate.

These copolymerizable ethylenically unsaturated monomers can be used in an amount of usually 40% by weight or less based on the acrylonitrile monomer.

Polymerization is possible even when the amount of the copolymerizable monomer is 40% by weight or more, but when the amount of the copolymerizable monomer is 40% by weight or more, the reaction active site is used when used as an ion exchange resin or a chelate resin. The content of the nitrile group in (1) becomes small, which causes deterioration of performance, which is not preferable.

In the method of the present invention, it is essential to use a suspension stabilizer of at least one compound selected from (A) alkyl cellulose and (B) polyoxyethylene polyoxypropylene block polymer and gelatin as a suspension stabilizer. .

Examples of the (A) alkyl cellulose of the suspension stabilizer used in the method of the present invention include alkyl celluloses such as methyl cellulose and ethyl cellulose; hydroxyalkyl celluloses such as hydroxyethyl cellulose and hydroxypropyl cellulose; hydroxyethyl propyl cellulose and hydroxypropyl methyl cellulose. Hydroxyalkylalkylcelluloses are used.

The suspension stabilizer (B) polyoxyethylene polypropylene block polymer used in the method of the present invention is HO (C ₂ H _{4
O) a- (C 3 H 6} O) b- (C 2 H 4 O) indicates a compound having an cH made structure, molecular weight 1,000～16,0
00, the total molecule of which the ethylene oxide content is in the range of 10 to 80 mol%, and the gelatin is JIS 1
~ 5 types can be used.

In carrying out the method of the present invention, the ratio of (A) alkyl cellulose and (B) at least one compound selected from polyoxyethylene polyoxypropylene block polymer and gelatin is (A) / (B) = 1/100. ~ 1
It is used in the range of 00 (weight ratio). This usage rate (A
When / B) is 1/100 or less, the shape is deteriorated due to coalescence of particles, the particles are coarsened, and the amount of deposits on the polymerization tank is increased, which is not preferable. On the other hand, if the usage ratio (A / B) is 100 or more, the shape is deteriorated due to coalescence of particles and a sharp particle size distribution is not obtained, which is not preferable. In order to obtain a polymer having a large particle size and a uniform bead shape, the use ratio is (A) / (B)
= 1/50 to 50 (weight ratio) is preferably used.

The amount of the suspension stabilizer added has a great influence on the particle size of the polymer to be obtained, and therefore it is determined by conducting preliminary experiments depending on the ratio of the monomers and the suspension stabilizers (A) and (B) used. Generally, the total amount of suspension stabilizers is 0.00
It is used in the range of 05 to 5% by weight, preferably 0.002 to 2% by weight.

If the total amount of suspension stabilizers used is less than 0.0005% by weight, the formation of deposits on the polymerization tank, deterioration of the shape due to coalescence of particles, and broadening of the particle size distribution will cause coarsening of the particles. Further, if the proportion of the suspension stabilizer used is more than 5% by weight, the particle size becomes irregular, which causes deterioration of the particle shape, which is not preferable.

In the method of the present invention, the polymerization is carried out in an aqueous medium composed mainly of water.

The ratio of monomer / water for obtaining a good dispersion state is generally used in the range of monomer / water = 1/1 to 10 (volume ratio).

In order to further reduce the amount of the acrylonitrile-based monomer dissolved in water in the polymerization medium and to further suppress the formation of polymer meal,
A poorly water-soluble organic compound and a water-soluble inorganic compound can also be added.

Examples of such poorly water-soluble organic compounds include hexane, heptane, octane, decane, and other aliphatic hydrocarbons; benzene, toluene, xylene, ethylbenzene, and other aromatic hydrocarbons; cyclohexane, cyclohexene, and other aliphatic cyclic hydrocarbons. Kinds; carbon tetrachloride, dichloroethane,
Halogenated hydrocarbons such as trichloroethane, trichloropropane, chlorobenzene, dichlorobenzene, and brombenzene; and esters such as methyl benzoate ethyl benzoate and methyl propionate. The addition amount of these is generally in the range of 20 to 200% by weight with respect to the monomer.

Further, examples of the water-soluble inorganic compound include sodium chloride, magnesium chloride, calcium chloride, potassium sulfate, sodium sulfate and the like. These are added in an amount of 0.5 to 20% by weight based on water.

Further, as a suspension stabilizing aid, tricalcium phosphate,
Known water-insoluble inorganic compounds such as calcium carbonate, magnesium carbonate and bentonite can be added and polymerized.

According to the method of the present invention, the pH of the aqueous medium is from 2 to 6 during the polymerization reaction.
The pH is controlled in the range of 5, preferably in the range of pH 3 to 6.5.

When the pH of the aqueous medium is 2 or less, the suspension stability is deteriorated, the particle shape is deteriorated, and the amount of deposits on the polymerization tank is increased, which is not preferable. The pH of the aqueous medium is 6.5 or more and 10
Even in the range up to the range, a polymer having a sharp particle size distribution with spherical particles can be obtained, but in order to obtain a polymer having a large particle size, for example, the amount of the suspension stabilizer added is reduced or the stirring speed is slowed down. If so, the particle diameter tends to be irregular and the particle shape tends to deteriorate.

On the other hand, when the pH of the aqueous medium is 10 or higher, the shape is deteriorated due to coalescence of particles and the particle size distribution becomes broad, which causes coarsening of the particles.

Examples of methods for controlling the pH of the aqueous medium include a method of adding a buffer and a method of adding an acid.

Examples of the buffer include potassium hydrogen phthalate / sodium hydroxide, sodium citrate / sodium hydroxide,
Examples include combinations of sodium dihydrogen citrate / citric acid, sodium dihydrogen citrate / sodium hydroxide, acetic acid / sodium acetate, and the like.

The pH can also be controlled by adding a hydrochloride or sulfate of aluminum, zinc, chromium, iron or the like.

Examples of the acid include mineral acids such as sulfuric acid and hydrochloric acid, formic acid, acetic acid,
Organic acids such as lauric acid may be mentioned.

The amount of the buffer or acid used may be such that the pH of the aqueous medium is maintained at 2 to 6.5 during the polymerization reaction period, a method of adding it all at once before the polymerization reaction, or a method of supplementing it appropriately during the polymerization reaction. Any of the above methods can be applied.

In carrying out the method of the present invention, the polymerization catalyst can be used without particular limitation as long as it is an oil-soluble catalyst known as a polymerization catalyst for acrylonitrile.

Such oil-soluble catalysts include azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile:
Examples thereof include organic peroxides such as diisopropyl peroxydicarbonate, lauroyl peroxide, benzoyl peroxide, t-butyl peroxybenzoate, and t-butyl peroxide, which may be used alone or as a mixture. You can

Although the amount of the catalyst used is not particularly limited, it is usually added in a proportion of 0.01 to 3% by weight based on the total charged monomers.

In the polymerization reaction, a monomer, a solvent, a polymerization stabilizer, and a polymerization catalyst are charged into a polymerization tank with stirring or without stirring, and then, as it is or after removing oxygen in the reaction system as necessary, at normal pressure or Polymerization is performed under pressure and at a predetermined temperature for a predetermined time while stirring.

The stirring speed is not particularly limited, but since it greatly affects the particle size of the obtained polymer, the type of the monomer and the suspension stabilizer,
It is advisable to conduct a preliminary experiment as appropriate according to the amount used and the type of polymerization tank.

The polymerization temperature may be selected at a temperature corresponding to the decomposition temperature of the polymerization catalyst, but a range of 50 ° C to 150 ° C is generally used.

After completion of the polymerization, when a water-soluble organic solvent is used as a reaction solvent, the solvent is removed by subjecting it to an operation such as distillation.

As described above, the polymer thus produced can be used as it is or after being washed and dried, as a raw material for a chelate resin, an ion exchange resin or the like.

<Effects of the Invention> According to the method of the present invention, the acrylonitrile-based polymer produced has a spherical particle shape without inducing the formation of polymerized lees, as compared with the conventionally known method, and has a particle shape. It has an advantage that a polymer having a sharp diameter distribution can be produced.

Further, since the acrylonitrile polymer obtained by the method of the present invention has a uniform particle size, the physical strength is large,
Since it can be used extremely effectively as a raw material for ion exchange resins and the like, its industrial value is extremely large.

<Example> The method of the present invention will be described in more detail with reference to Examples.
The method of the present invention is not limited by the following examples unless it exceeds the gist.

Comparative Example 1 In a cylindrical flask of 2, equipped with a reflux condenser, a nitrogen inlet tube, a stainless steel three-blade stirrer and a thermometer,
(A) As the alkyl cellulose, hydroxypropylmethyl cellulose manufactured by Shin-Etsu Chemical Co., Ltd. (hereinafter abbreviated as HPC)
Is METOLOSE 65SH-400 (methoxy group 28
%, Hydroxypropoxy group 6%, 2% aqueous solution viscosity 40
0 cps) and 0.04 part by weight of (B) Pluronic F which is a polyoxyethylene polyoxypropylene block polymer (hereinafter abbreviated as EO-PO) having a molecular weight of 8300 ethylene oxide content of 80 mol% manufactured by Asahi Denka Co., Ltd. as a suspending agent. 1.2 parts by weight of -68, 25 parts by weight of sodium sulfate and 975 parts by weight of water were charged and dissolved, and the pH was measured and found to be 7.8.

In the above aqueous medium, 212 parts by weight of acrylonitrile and 4 parts by weight of
Divinylbenzene 53 containing 4% by weight of ethylstyrene
Parts by weight, 159 parts by weight of toluene, and 1.86 parts by weight of lauroyl peroxide were charged.

Suspension stabilizer (A) / (B) = 1/30 (weight ratio) [suspension stabilizer weight / total monomer] × 100 = 0.468% Then, under a nitrogen atmosphere, 300 r.p.m. p. While stirring at a rotation speed of m, the temperature was raised to 60 ° C. in about 1 hour, and the polymerization reaction was carried out by maintaining 60 ° C. for 3 hours, 70 ° C. for 1 hour, and 80 ° C. for 1 hour.

After the polymerization reaction, the toluene was removed from the reaction system by steam distillation, and the product was washed with water. As a result, 442 parts by weight (undried) of an acrylonitrile polymer having the physical properties shown in Table 1 was obtained.

Examples 1 to 5, Comparative Examples 2 and 3 Polymerization was carried out in the same manner as in Comparative Example 1 except that sulfuric acid or caustic soda was added to the aqueous medium to adjust the pH, and the physical properties shown in Table 2 were obtained. An acrylonitrile polymer was obtained.

Examples 6 to 8 Various buffer solutions were prepared according to the formulations shown in Table 3. Polymerization was carried out in the same manner as in Comparative Example 1 except that 700 parts by weight of water and 275 parts by weight of various buffer solutions were added instead of 975 parts by weight of water. The pH in the aqueous medium was almost the same as that of the buffer solution. As a result, an acrylonitrile polymer having physical properties as shown in Table 4 was obtained.

Examples 9 and 10 Polymerization was carried out in the same manner as in Comparative Example 1 except that an aluminum or iron sulfate was added to the aqueous medium to obtain an acrylonitrile polymer having the physical properties shown in Table 5. It was

Examples 11 to 15 Using the same apparatus as used in Comparative Example 1, a suspension stabilizer as shown in Table 6, 29.3 parts by weight of sodium sulfate and 975 parts by weight of water were charged and dissolved, and After adjusting the pH of the aqueous medium to 5.0 by adding sulfuric acid, 212 parts by weight of acrylonitrile, 120 parts by weight of an ethylene-based monomer as shown in Table 6, toluene and lauroyl peroxide 1.
86 parts by weight were charged.

Then, under a nitrogen atmosphere, 280 r. p. While stirring at a rotation speed of m, the temperature was raised to 60 ° C. in about 1 hour, and the polymerization reaction was carried out by maintaining 60 ° C. for 3 hours, 70 ° C. for 1 hour, and 80 ° C. for 1 hour.

After the polymerization reaction, the toluene was removed from the reaction system by steam distillation, and the product was washed with water. As a result, an acrylonitrile polymer having the physical properties shown in Table 6 was obtained.

Comparative Example 4 A compound was prepared in the same manner as in Example 13 except that sulfuric acid was not added to the aqueous medium, and the pH of the aqueous medium was 6.7.
Met.

Upon polymerization, an acrylonitrile polymer having the physical properties shown in Table 7 was obtained.

Claims (6)

[Claims] 1. Acrylonitrile alone or a mixture of acrylonitrile as a main component and another ethylenically unsaturated monomer copolymerizable with acrylonitrile is subjected to suspension polymerization in an aqueous medium,
In producing the acrylonitrile polymer, a suspension stabilizer composed of (A) an alkyl cellulose and (B) a polyoxyethylene polyoxypropylene block polymer and at least one compound selected from gelatin is used to prepare an aqueous medium. A method for producing an acrylonitrile-based polymer, characterized in that the polymerization is carried out while controlling the pH to 2 to 6.5. 2. An ethylenically unsaturated monomer is a styrene derivative, nitriles, acrylic acid and acrylic acid esters, methacrylic acid and methacrylic acid esters, aliphatic vinyl derivatives, vinyl ketones, heterocyclic vinyl compounds, The method for producing an acrylonitrile-based polymer according to claim 1, which is a cross-linking polymerizable compound having an unsaturated bond. 3. The acrylonitrile polymer according to claim 1 or 2, wherein the suspension stabilizer (A) is an alkylcellulose, a hydroxyalkylcellulose, or a hydroxyalkylalkylcellulose. Manufacturing method. 4. The pH of the aqueous medium by adding a buffering agent
The method for producing an acrylonitrile-based polymer according to claim 1, 2, or 3, characterized in that: 5. An aqueous medium is prepared by adding a hydrochloride and / or sulfate of aluminum, zinc, chromium, iron or the like.
Claims 1 and 2 characterized by controlling pH
Alternatively, the method for producing an acrylonitrile-based polymer according to item 3. 6. The method for producing an acrylonitrile polymer according to claim 1, 2, or 3, wherein the pH of the aqueous medium is controlled by adding an acid.