JPH06102687B2 - Suspension polymerization method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel suspension polymerization method capable of easily controlling the particle size analysis of product particles, and particularly obtained by a conventional suspension polymerization method. The present invention relates to a suspension polymerization method suitable for producing particles having a particle size of 5 to 50 μm, which was difficult to achieve.

(Prior Art) In recent years, the importance of the particle industry utilizing the function of the particles themselves has been increasing, and examples thereof include a gap retaining agent, a slipperiness imparting agent, a functional carrier, surface-active monodisperse particles, standard particles, and toner. It is applied in the field of functional fillers that control the fluidity and gloss properties of paints. Various methods are known for obtaining these particles by a polymerization method, but at present, the method mainly relies on an emulsion polymerization method. Furthermore, when it is used for a special purpose, soap-free polymerization, dispersion polymerization, seed polymerization, swelling polymerization and the like are also used. However, these polymerization methods have some drawbacks. For example,
The emulsion polymerization method has an advantage that particles having a narrow particle size distribution can be obtained, but it is very difficult to remove impurities such as an emulsifier, and the particle size of the obtained particles is limited to about 1 μm at most. Yes, it is extremely difficult to obtain larger particles. As an attempt to obtain larger particles, dispersion polymerization, seed polymerization, swelling polymerization, etc. have been studied, but they are complicated, require a long time, and cause a great disadvantage in terms of cost. Production is not possible,
Therefore, there is a problem that the application development research is not activated and can be applied only to a special application.

On the other hand, the suspension polymerization method has relatively few problems in the above-mentioned polymerization method and has a feature that the obtained product is in the form of particles. Therefore, it is used in, for example, electrophotography. It has been proposed to be applied to the production of a toner.

However, the suspension polymerization method has a problem that it is generally difficult to control the particle size and particle size distribution. That is, in suspension polymerization, the droplets dispersed by stirring have various diameters, and the droplets repeatedly disintegrate and coalesce during dispersion, so the particle size distribution of the obtained particles becomes extremely wide. It is difficult to obtain monodisperse particles having a narrow size.

In the products used in the various application fields described above, the non-uniformity of the particle size distribution is caused by the mechanical strength of the polymer, the chemical resistance,
It has important relationships with performance such as hue, transparency and moldability,
Control of particle size and particle size distribution is an important issue.

Therefore, establishment of a suspension polymerization technique capable of easily obtaining homogeneous polymer particles having a desired particle size has been an important issue in this field.

(Problems to be Solved by the Invention) The reason why particles are obtained in suspension polymerization is as follows. The disperse phase and the continuous phase, which should be separated in the stationary state originally,
The dispersed phase is split by the energy of stirring or the like and becomes a so-called droplet state, which exists in the continuous phase. This droplet is
In this state as it is, it is generally unstable which repeats fragmentation and coalescence, but the droplets are polymerized by the supply of energy such as heat and become rigid particles which can no longer be fragmented or coalesced. Therefore, in order to control the size of the particles by the suspension polymerization method, some control may be applied to the size of the droplets and the division and coalescence. However, considering the factors related to the droplet size,
Characteristics, structure, shape, size of disperser (stirrer) or size, shape of reaction container, charge amount of reaction liquid, or phase ratio of reaction liquid, viscosity, kind and amount of dispersant, etc.,
It cannot be controlled substantially in a unified manner. Therefore,
In reality, fixing some of these many elements,
At present, there is no choice but to determine the conditions for obtaining the desired particles. However, this method is too trial-and-error and it is difficult to deal with condition changes such as scale-up. This point is a serious obstacle to manufacturing, and so-called manufacturing flexibility is lacking, especially for the purpose of using the product in powder form.

As a result of intensive studies on the above problems, the present inventors have previously proposed a novel suspension polymerization method that can easily solve these problems. That is, a method has been proposed in which the disperse phase component and the continuous phase component are simultaneously and continuously supplied to a disperser through independent paths, and the resulting dispersion is introduced into a polymerization tank and polymerized. As a result of further studying this method, the present inventors have found that the control of the shear region of the disperser is particularly important.

Generally, a disperser is composed of a fixed part (stator) and a rotating part, but a shear field required for dispersion is considered to occur in a gap between the stator and the rotating part. In a general disperser, a rotating blade having a turbine structure is used as a rotating part. In this type of disperser, the shear field is the gap between the outer periphery of the turbine blade and the stator. Therefore, the area generated in the shear field is regulated by the cross-sectional area of the turbine blade, and it is difficult to adjust the area and increase the area. Further, the stator is usually provided with a space for liquid passage in order to facilitate liquid passage, and since an effective shearing field does not occur in this space, this point also hinders effective granulation. . Therefore, the conventional disperser
When applied to the above suspension polymerization method, the shearing energy applied to the liquid to be dispersed tends to be insufficient.

The present invention has been made in view of the above situation.

Therefore, an object of the present invention is to provide a suspension polymerization method capable of easily controlling the particle size and particle size distribution of polymer particles produced.

(Means for Solving the Problems) As a result of further studies on the suspension polymerization method, the present inventors have used a disperser having a cylindrical rotating body, and in order to improve shearing efficiency. When it is arranged on a fixed part that has an internal shape that is almost the same as that of a cylindrical rotating body whose surface is smooth, an effective shear field is formed, and it is possible to extremely effectively manufacture fine particles with a narrow particle size distribution. Headline,
The present invention has been completed.

In the suspension polymerization method of the present invention, in producing a polymer or a polymer composition by suspension polymerization of a monomer composition, a disperse phase component comprising the monomer composition and a continuous phase component comprising an aqueous medium. Are held in independent tanks, and the dispersed phase component and continuous phase component are fed simultaneously from these tanks to the disperser through independent paths at the same time, and a desired magnitude is obtained by applying shearing force. Forming a dispersion having droplets of a desired size, and then introducing the obtained dispersion into a polymerization tank to complete the polymerization, thereby obtaining a polymer or a polymer composition, and As the above-mentioned disperser, a disperser in which a cylindrical rotating body having a smooth outer surface is rotatably disposed on a fixed portion having a smooth inner surface is used.

The term "cylindrical rotating body having a smooth outer surface" as used in the present invention means a cylindrical rotating body having a flat surface with no irregularities, and the same applies to the fixed portion.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is an example of an apparatus used to carry out the present invention. In the figure, 21 is a continuous phase tank, 22 is a disperse phase tank equipped with a condenser 26, and is connected to a disperser 25 equipped with a stirrer that is a device for applying a shearing force by respective flow paths 28 and 29. . Reference numeral 23 is a reaction tank provided with a condenser 26 and a heating jacket 27, and is connected to the disperser 25 by a flow path 30. 24 is a metering pump.

In the present invention, as a disperser in the above device,
A stationary part having a smooth inner surface and a cylindrical rotating body having a smooth outer surface, and a cylindrical rotating body rotatably arranged on the stationary part is used. FIG. 1 is a schematic vertical sectional view of an example of a disperser used in the present invention, in which 11 is a turbine rotary shaft, and a cylindrical rotary body 15 having a smooth surface is provided at the tip thereof. And is fluid-tightly supported by agitation seal 12. The disperser main body has a stator having an inner surface forming an internal space.
14 is fixedly attached. A tubular rotating body 15 is rotatably arranged in the internal space of the stator. In addition, 13 is a dispersion liquid discharge port, 16 is a continuous phase inflow port, 17 is a dispersion phase inflow port, and 18 is a gap in which the dispersion liquid is formed.

To carry out the present invention, the continuous phase component consisting of the aqueous medium is held in the continuous phase tank 21, and the dispersed phase component consisting of the monomer composition is held in the dispersed phase tank 22. Each of these components is simultaneously and continuously supplied to the vicinity of the shearing region of the disperser 25 by driving the metering pumps 24 and 24 provided in the independent channels 28 and 29, respectively.

That is, the continuous phase inlet 16 and the dispersed phase inlet 17 of the disperser.
The continuous phase component and the dispersed phase component introduced from (1) are subjected to shearing force when passing through the gap 18 between the cylindrical rotating body 15 and the stator 14, and a dispersion liquid composed of the dispersed phase and the continuous phase is formed. It The dispersion liquid thus formed is discharged from the dispersion liquid discharge port 13, sent to the reaction tank 23 through the flow path 30, and suspension polymerization is carried out by a usual method.

In the present invention, the cylindrical rotating body in the disperser shown in FIG. 1 has a tapered shape, but other shapes may be used.

Also, the length of the tubular rotating body is at least 10 mm or more,
The gap between the outer surface and the inner surface of the fixed part is 0.01 to 5.0 mm.
It is preferable to set to, and the range of 0.05 to 2.0 mm is particularly preferable. Also, the rotation speed of the cylindrical rotating body is 3000 to 50000 rpm.
Is preferable, and a range of 10,000 to 30,000 rpm is particularly preferable.

In the present invention, the dispersed phase component and the continuous phase component are simultaneously and continuously supplied to the disperser at a predetermined flow rate, and in the disperser, a shearing force is applied in a narrow gap between the cylindrical rotating body and the fixed portion. Therefore, the shearing efficiency is improved, and the dispersion conditions such as the amount, size, or phase ratio of the droplets passing through the shearing area are completely controlled, and the dispersed phase and the continuous phase are always constant. Under the conditions, a shearing force is applied, so that a dispersion liquid having a narrow particle size distribution is obtained.

In the above method, when the desired particle size cannot be obtained by passing through the shearing region once, another dispersing machine is further provided, and the dispersion liquid passing through the dispersing machine at the first stage is passed through the second stage. It can be passed through an eye disperser. If necessary, this method can be stacked in multiple stages.

In the present invention, the continuous phase is formed by the continuous phase component consisting of an aqueous medium. A suspension stabilizer is preferably included in the continuous phase.

Examples of suspension stabilizers generally used in suspension polymerization include surface-active substances having a hydrophilic group and a hydrophobic group in the molecule. These surface-active substances have polar groups such as hydroxyl groups, carboxyl groups and salts thereof, sulfone groups and salts thereof as hydrophilic groups, and are composed of non-polar groups such as aliphatic and aromatic groups as hydrophobic groups. It is a compound that has the ability to prevent coalescence of droplets formed by the dispersion process and stabilize it.

Such suspension stabilizers include, for example, polyvinyl alcohol, casein, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, cellulose derivatives such as ethyl cellulose, starch and its derivatives, poly (meth) acrylic acid and salts thereof, and the like, and Inorganic powders such as calcium phosphate and finely powdered silica are mentioned. The suspension stabilizers such as these serve to coat the surface of the droplets during polymerization and prevent coalescence and agglomeration of droplets. .

Further, it is also possible to add neutral salts such as sodium chloride and sodium sulfate, and surfactants such as vinyl benzoate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, etc. as an auxiliary agent of the suspension stabilizer. .

On the other hand, the dispersed phase is formed by the dispersed phase component composed of the monomer composition. The polymerizable monomer used as the main component of the monomer is not particularly limited as long as it can be used for suspension polymerization, and examples thereof include styrene and o-
Methyl styrene, m-methyl styrene, p-methyl styrene, p-methoxy styrene, p-phenyl styrene,
p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn- Styrene and its derivatives such as octyl styrene, pn-nonyl styrene, pn-decyl styrene; vinyl acetate, vinyl propionate, vinyl benzoate and other organic acid vinyl esters; methacrylic acid, methyl methacrylate, methacrylic acid Ethyl, propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate,
Methacrylic acid and its derivatives such as diethylaminoethyl methacrylate; acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate,
Dodecyl acrylate, 2-ethylhexyl acrylate,
Stearyl acrylate, 2-chloroethyl acrylate,
Acrylic acid and its derivatives such as phenyl acrylate; Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole,
N-vinyl compounds such as N-vinylpyrrolidone; vinylnaphthalenes; acrylonitrile, methacrylonitrile,
A polymerizable monomer such as acrylamide can be used.

These monomers can be used alone or in combination of two or more kinds in various compositions as required.

In the present invention, a polymerization initiator is used, but the polymerization initiator is preferably soluble in the polymerizable monomer. Examples of such a polymerization initiator include 2,2'-azobisisobutyronitrile), 2,2'-azobis- (2,4-dimethylvaleronitrile) and 2,2'-azobis-4-methoxy- 2,4-Dimethylvaleronitrile, other azo or diazo polymerization initiators; benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxycarbonate, other peroxide polymerization initiators and the like.

In the present invention, for the purpose of controlling the molecular weight and the molecular weight distribution, or for the purpose of controlling the reaction time, it is preferable to use two or more of the above polymerization initiators in combination in various compositions. Further, if necessary, a water-soluble initiator such as ammonium persulfate or potassium persulfate may be used in combination.

The amount of the polymerization initiator used is 100 parts of the polymerizable monomer,
It is usually 0.1 to 20 parts, preferably 1 to 5 parts.

If necessary, dyes, pigments and other components can be added to the dispersed phase, and if a pigment such as carbon black is added, it can be applied to the production of toner for electrophotography.

The above dispersed phase component and the above continuous phase component are respectively introduced into a disperser to produce a dispersion having a predetermined particle size and particle size distribution, and then the dispersion is subjected to suspension polymerization. The turbid polymerization reaction is usually carried out at a polymerization temperature of 50 ° C. or higher, and the temperature is set in consideration of the dispersion temperature of the polymerization initiator. If the set temperature is too high, the polymerization initiator will be rapidly decomposed and the molecular weight will be affected, which is not preferable.

(Operation) The operation of the present invention will be described in relation to the conventional art.

Needless to say, it is important to control the size of droplets before the polymerization reaction in order to control the size of the particles obtained in the suspension polymerization method. The droplets are split by the turbulent flow energy generated by stirring the reaction liquid or the shearing force generated by the stirring blade. On the other hand, the coalescence of the droplets is caused by the contact between the droplets. The final droplet size is determined by the balance of this fragmentation and coalescence.

Looking first at fragmentation, various methods of obtaining droplets with a particle size of 50 μm or less were investigated, and it was found that the shearing force by the stirring blades of the disperser was the main factor that governs fragmentation. At this time, the size of the liquid droplets generated by the division is determined by the state before the division, the magnitude of the shearing force, the number of times of repeating the shearing, and the like. In a conventional disperser, a large droplet and a small droplet are subjected to the same shearing force, and thus a large droplet is subjected to the shearing force and is divided into droplets of a certain size, but a small droplet is supplied. Even if it does, the droplets are further broken into smaller droplets and finally broken down to an emulsified state. The emulsified components cannot coalesce again into large particles, which is a loss. In addition, in a general disperser (stirrer), droplets carried on a circulating flow generated by stirring are subdivided when passing through a shearing region, and at the same time, turbulent flow fields existing throughout the device are disturbed. There is an opportunity to be subdivided by flowing energy.
However, since the movement of the droplets flowing in the apparatus is almost random, it is unavoidable that a distribution occurs in the subdivision conditions encountered by each droplet.

Therefore, it is a necessary condition for controlling the size of the droplets that all the droplets are exposed to the shear force as often as possible. Further, in order to control the particle size distribution, it is important to supply the liquid to be dispersed in a constant state to the shearing force-applying portion of the disperser.

On the other hand, coalescence is considered to occur due to contact between droplets. Generally, the smaller the particle diameter, the larger the surface energy per unit volume and the particles can stably exist. A factor that further widens the particle size distribution is that large particles are mixed with small particles in the same system. When a small particle collides with a large particle, it is easily absorbed by the small particle. However, in order to make the particles small enough to have a sufficiently stable interfacial energy, it is necessary to supply that much energy, so it is effective to split the particles intensively in a narrow shear region, and It is important to bring about a condition that the particles are regularly split so that the shear force is evenly applied to the particles.

In the present invention, the disperse phase component and the continuous phase component are directly supplied to the vicinity of the shear region of the disperser at a desired flow rate through independent paths. And in that case, as described above, as the disperser, the one composed of the cylindrical rotating body having the smooth outer surface and the fixed portion having the smooth inner surface is used. The narrow gap forms a shear region, and the supplied components are intensively and efficiently given a shear force there. Therefore, according to the present invention, the dispersion conditions such as the amount, size, or phase ratio of droplets passing through the shear region are completely controlled, and the dispersed phase and the continuous phase are always under constant conditions. When subjected to shearing force, a dispersion liquid having a narrow particle size distribution can be obtained.

(Example) Hereinafter, the present invention will be specifically described based on Examples.

Example 1 An aqueous solution containing 1% of polyvinyl alcohol (manufactured by Tokyo Kasei Co., Ltd., polymerization degree of about 2000, saponification degree of about 80%) in water and sodium sulfate in an amount of 3% in water was prepared as continuous phase components. , Placed in the continuous phase vessel of the apparatus shown in FIG. Also,
400 g of styrene and butyl acrylate as dispersed phase components
Add 100 g of 2,2'-azobisisobutyronitrile 1
A solution having 5 g dissolved therein was prepared and placed in the dispersion phase tank of the apparatus shown in FIG.

The dispersed phase components were then fed to the disperser at 100 ml / min and the continuous phase components at 400 ml / min. As the disperser, the one having the structure shown in FIG. 1, the rotating body having a maximum diameter of 50 mm, and the distance between the cylindrical rotating body and the fixed portion set to 1.00 mm is used.
It was operated at 9000 rpm. The dispersion liquid that passed through the disperser was introduced into the reaction vessel and stirred with a turbine type stirring blade at 300 rpm.
The reaction was carried out at 85 ° C for 8 hours.

The polymer composition obtained as described above was cooled and filtered, then sufficiently washed with water, a slurry of polymer particles was obtained by centrifugation, and this was dried to obtain polymer particles.

The particle size of the obtained polymer particles was measured using a Coulter counter (aperture 100 μm) (number distribution)
Is shown in FIG. The polymer particles had a narrow particle size distribution as shown in FIG. 3, and the mode value was about 5.1 μm.

Comparative Example 1 Suspension polymerization was carried out under the same conditions as in Example 1, except that the dispersing machine having a structure having a four-blade turbine rotor was used.

The particle size of the obtained polymer particles was measured using a Coulter counter (aperture 100 μm) (number distribution)
Is shown in FIG. The polymer particles had a particle size distribution as shown in FIG. 4, and the mode value was about 7.0 to 8.0 μm. This particle size distribution was wider than that of Example 1.

Example 2 As a continuous phase, an aqueous solution containing 3% of calcium phosphate in water and 0.03% of sodium dodecyl sulfonate in water was prepared, and placed in a continuous phase tank of the apparatus shown in FIG. Also, as a dispersed phase, in a mixed solution of styrene 400 g and butyl acrylate 100 g, 2,2'-azoisobutyronitrile 15 g
A solution in which was dissolved was prepared and placed in the dispersion phase tank of the apparatus shown in FIG. After that, the same operation as in Example 1 was performed.

The particle size of the obtained polymer particles was measured using a Coulter counter (aperture 100 μm) (number distribution)
Is shown in FIG. The polymer particles had a narrow particle size distribution as shown in FIG. 5, and the mode value was about 4.8 μm.

Comparative Example 2 Suspension polymerization was carried out under the same conditions as in Example 2, except that the dispersing machine used had a structure in which the rotor had a turbine with four blades.

The particle size of the obtained polymer particles was measured using a Coulter counter (aperture 100 μm) (number distribution)
Is shown in FIG. The polymer particles had a particle size distribution as shown in FIG. 6, and the mode value was about 6.0 to 7.0 μm. This particle size distribution was wider than that of Example 2.

(Effect of the invention) Since the suspension polymerization method of the present invention has the above-mentioned constitution, the dispersed phase component and the continuous phase component can be directly supplied to the vicinity of the shear region of the disperser at a desired flow rate through an independent path. In the disperser, shearing force is intensively applied in the narrow gap formed between the cylindrical rotating body having a smooth outer surface and the fixed portion having a smooth inner surface, so that foaming does not occur. ,
The dispersion can be performed very efficiently. Therefore,
According to the present invention, since the particle size and the particle size distribution can be easily controlled, it is possible to produce a polymer or a polymer composition having a desired particle size and a narrow particle size distribution. Therefore, the present invention is useful for producing a material that requires a fine particle size and a narrow particle size distribution.

Furthermore, according to the present invention, the dispersed phase component and the continuous phase component are prepared in independent devices and supplied through separate paths, so that changing the phase ratio has no effect on other manufacturing factors. Few. Furthermore, unlike the conventional batch reactor, there is an advantage that it is not affected by the size of the reaction vessel. Therefore, the so-called flexibility in the production of the polymer or the polymer composition can be expanded, and the change of conditions such as scale-up can be easily dealt with.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a disperser used in the present invention, FIG. 2 is a schematic configuration diagram of an example of an apparatus used in the suspension polymerization method of the present invention, and FIGS. 3 is a graph showing a particle size distribution of polymer particles of Example 1, Comparative Example 1, Example 2 and Comparative Example 2, respectively. 11 …… Turbine rotating shaft, 12 …… Stirring seal, 13 Dispersion outlet, 14 …… Stator, 15 …… Cylindrical rotating body, 16 …… Continuous phase inlet, 17 …… Dispersed phase inlet, 18… … Dispersion forming gap, 21 …… Continuous phase tank, 22 …… Dispersion phase tank, 23 …… Reaction tank,
24 …… Metering pump, 25 …… Disperser, 26 …… Condenser, 27…
… Heating jackets, 28,29 and 30… flow paths.

Claims (4)

[Claims] 1. When producing a polymer or a polymer composition by suspension polymerization of a monomer composition, a dispersed phase component composed of the monomer composition and a continuous phase component composed of an aqueous medium are independently prepared. Liquid droplets of a desired size by holding them in a tank and continuously supplying the dispersed phase component and the continuous phase component from these tanks to the disperser at the same time through independent paths and applying a shearing force. A suspension polymerization method, which comprises forming a dispersion liquid having, and then introducing the dispersion liquid into a polymerization tank to complete the polymerization to obtain a polymer or a polymer composition,
The suspension polymerization method is characterized in that, as the disperser, a disperser in which a cylindrical rotating body having a smooth outer surface is rotatably disposed on a fixed portion having a smooth inner surface is used. 2. The suspension polymerization method according to claim 1, wherein the cylindrical rotating body has a length of at least 10 mm or more. 3. The rotational speed of the outer surface of the cylindrical rotary member is 3000 to 50.
The suspension polymerization method according to claim 1, which is 000 rpm. 4. The suspension polymerization method according to claim 1, wherein the gap between the outer surface of the cylindrical rotating body and the inner surface of the fixed portion is 0.05 to 5.0 mm.