JPH06102685B2 - 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 distribution of product particles, and in particular, it is 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 1 to 50 μm, which has been 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-maintaining agent, a slipperiness-imparting agent, a functional simple substance, 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. When used for special purposes, soap-free polymerization, dispersion polymerization, seed polymerization, swelling polymerization, etc. are also used. However,
These polymerization methods have several drawbacks. For example, the emulsion polymerization method has the advantage that particles having a narrow particle size distribution can be obtained, but it is very difficult to remove non-negligible impurities such as emulsifiers, and the particle size of the obtained particles is at most 1 μm. It is very small, and it is extremely difficult to obtain particles having a size larger than that. Dispersion polymerization, seed polymerization,
By swelling polymerization or the like, it is possible to obtain particles having a large particle size, but the method is complicated and requires a long time, and also causes a great disadvantage in terms of cost, which is not suitable for mass production,
After all, there is a problem that it can only be applied to special purposes.

On the other hand, the suspension polymerization method has relatively few problems in the above-mentioned polymerization method, for example, it has a feature that the obtained product is in the form of particles, and the dispersed phase is preliminarily used. It has already been reported that the particle size distribution becomes narrower when the bulk polymerization is carried out (JP-A-57-25308).

(Problems to be Solved by the Invention) 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 the suspension polymerization method, the droplets dispersed by stirring have various diameters.
Since the droplets repeatedly disintegrate and coalesce during dispersion, the particle size distribution of the particles obtained becomes extremely wide, and it is difficult to obtain monodisperse particles in which the particle size distribution is particularly narrow. Further, according to the suspension polymerization method using the conventionally known preliminary bulk polymerization, it is only possible to control the breakup and coalescence of the droplets, and therefore, the polymer particles having a desired particle size and a narrow particle size distribution can be obtained. It is impossible to control the particle size so that

By the way, 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,
There is an important relationship with performance such as chemical resistance, hue, transparency and moldability, and control of particle size and particle size distribution is an important issue.

The present invention has been made in view of the above-mentioned actual state of the art.

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 product particles.

Another object of the present invention is to provide a suspension polymerization method capable of producing polymer particles having a particle size in the range of 1 to 50 μm, which has been conventionally said to be difficult to produce by the suspension polymerization method. is there.

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,
Divided by energy such as stirring, the dispersed phase splits into a so-called droplet state and exists in the continuous phase. In this state, the droplets are generally unstable, which repeats fragmentation and coalescence. However, the droplets are polymerized by the supply of energy such as heat and are no longer rigid or rigid. Particles. Therefore, in order to control the size of the particles by the suspension polymerization method, some control may be added to the size of the liquid droplets and the division and coalescence.
However, considering the factors related to the size of this droplet, the characteristics, structure, shape and size of the disperser (stirrer), or the size and shape of the reaction vessel, the charge amount of the reaction liquid, or In addition, the phase ratio of the reaction solution, the viscosity, the type and amount of the dispersant, and the like are not controllable substantially in a unified manner. Therefore, in reality, it is unavoidable to fix some of these various factors and determine certain conditions for the particles to be obtained. However, with this method,
It 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.

The present inventors have conducted extensive studies on the above problems, and as a result, first, a dispersed phase composed of a prepolymerized monomer component and a continuous phase composed of an aqueous medium were simultaneously supplied to a disperser to obtain a desired dispersion. A new suspension polymerization method has been proposed in which the polymerization is completed after the formation of the liquid (Japanese Patent Laid-Open No. 3-56501). It was found that the viscoelastic property behavior was difficult to predict, and sufficient results could not be obtained, especially when a chemically active pigment such as carbon black was contained. Therefore, as a result of further examination, it was found that when the disperse phase component containing carbon black is prepolymerized so as to be in a specific state, polymer composition particles having a particle size of 1 to 50 μm can be easily obtained. The present invention has been completed and the present invention has been completed.

(Means for Solving the Problem) The suspension polymerization method of the present invention comprises a monomer composition containing carbon black when a polymer composition is produced by suspension polymerization of a monomer composition. The disperse phase component and the continuous phase component consisting of the aqueous medium are held in independent tanks respectively, and the disperse phase component consisting of the monomer composition is preliminarily polymerized by heating in the range of a polymerization rate of 1 to 30%, Viscosity at 60 ℃ is 1
Forming a dispersed phase component of -30 centipoise, and supplying the prepolymerized dispersed phase component and continuous phase component simultaneously and continuously through independent paths to a device for applying shearing force, and applying shearing force. Is characterized in that a dispersion liquid having a desired size of droplets is formed, and then the dispersion liquid is introduced into a polymerization tank to complete the polymerization to obtain a polymer composition.

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

FIG. 1 is an example of a device used to practice the present invention. In the figure, 1 is a continuous phase tank, 2 is a dispersion phase tank, and they are connected to a dispersion machine 5 equipped with an agitator which is a device for applying a shearing force by means of channels 8 and 9, respectively. 3 is a reaction tank equipped with a condenser 6 and a heating jacket 7, and is connected to the disperser 5 by a flow path 10. 4 is a metering pump.

To carry out the present invention, a continuous phase component consisting of an aqueous medium is held in a continuous phase tank 1 and a dispersed phase component consisting of a monomer composition containing 0.5% by weight or more of carbon black is held in a dispersion phase tank 2. To do. The disperse phase component is preliminarily bulk polymerized so as to have a polymerization rate and a viscosity in the above-mentioned range by heating in advance in the disperse phase. Next, these components are simultaneously and continuously supplied to the vicinity of the shear region of the disperser 5 equipped with a stirrer by driving the metering pumps 4 and 4 provided in the independent flow paths 8 and 9, respectively. It
The respective components supplied in the vicinity of the shearing region of the disperser are dispersed by the shearing force of the stirrer to form a dispersion liquid composed of a dispersed phase and a continuous phase. The formed dispersion liquid is sent to the reaction tank 3 through the flow path 10 and suspension polymerization is carried out by a usual method.

In the present invention, the above-mentioned dispersed phase component and continuous phase component are simultaneously and continuously supplied to a disperser equipped with a stirrer at a predetermined flow rate, so that the amount, size, or size of droplets passing through the shearing region, or The dispersion conditions such as the phase ratio are completely controlled, and the dispersed phase and the continuous phase are always subjected to the shearing force under a constant condition, so that the dispersion liquid having a narrow particle size distribution is obtained.

In the above case, if the desired particle size cannot be obtained with one pass through the shearing region, another disperser is provided, and the dispersion liquid passed through the first-stage disperser is passed through the second-stage disperser. It may be passed through the disperser. If necessary, this method can be stacked in multiple layers. Since the obtained dispersion has a sufficiently large interfacial energy, coalescence hardly occurs even under normal stirring conditions.

In the present invention, the continuous phase is formed by the continuous phase component consisting of an aqueous medium. It is preferred to include a suspension stabilizer 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. The compound has the ability to prevent and stabilize the coalescence of the monomer composition particles formed by the dispersion step.

Such suspension stabilizers include, for example, polyvinyl alcohol, casein, gelatin, methylcellulose, methylhydroxypropylcellulose, cellulose derivatives such as ethylcellulose, starch and its derivatives, poly (meth) acrylic acid and salts thereof. During the polymerization, these suspension polymers coat the surface of the droplets and prevent the droplets from coalescing and agglomerating.

A neutral salt such as sodium chloride or sodium sulfate may be added to the continuous phase for the purpose of preventing emulsification. Also,
Further, a thickener such as glycerin or ethylene glycol may be added for the purpose of preventing coalescence of the monomer composition particles formed in the dispersion step.

On the other hand, the dispersed phase is formed by prepolymerizing a dispersed phase component composed of a monomer composition containing carbon black.

The polymerizable monomer used as the main component of the monomer composition is not particularly limited as long as it can be used for suspension polymerization, but when the production of the toner is described, it will be described below. Can be used.

For example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene,
p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene , Styrene such as pn-octylstyrene, pn-nonylstyrene and pn-decylstyrene, and derivatives thereof; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl chloride, vinylidene chloride. , Vinyl halides such as vinyl bromide and vinyl fluoride; organic acid vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylic acid n-butyl, n-octyl methacrylate, dodecyl methacrylate, methac 2-ethylhexyl phosphate,
Methacrylic acid and its derivatives such as stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate; acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate. , N-octyl acrylate, dodecyl acrylate,
Acrylic acid and its derivatives such as 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; vinyl methyl ketone, vinyl hexyl ketone , Vinyl isopropenyl ketone, and other vinyl ketones; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, and other N-vinyl compounds; vinyl naphthalene; acrylonitrile, methacrylonitrile, acrylamide, and other polymerizations Examples of the monomer include a polymerizable monomer.

These monomers may be used alone or in combination of two or more as needed in various compositions.

The carbon black to be contained in the above-mentioned monomer can be used without any limitation on the number average particle size, the amount of oil supply, the pH, etc., and the following are commercially available products. For example, US Cabot Corp. Regal 400, 660, 330, 300, S
RF-S, STERING SO, V, NS, R; Raven H20, MT made by Columbia Carbon Japan Co., Ltd.
-P, 410, 420, 430, 450, 500, 760, 780, 1000, 103
5, 1060, 1080; # 10B, # 5B, # 240O manufactured by Mitsubishi Kasei Corporation
Examples include B and MA-100. These carbon blacks can be used alone or in combination of two or more kinds.

The content of carbon black is preferably 0.5% by weight or more. When the content of carbon black is lower than 0.5% by weight, sufficient coloring power cannot be obtained when the resulting suspension polymer fine particles are used as a toner for electrophotography.

In the present invention, a polymerization initiator is used, but it is preferable that the polymerization initiator is soluble in the polymerizable monomer. As such a polymerization initiator, 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, other azo-based or Diazo polymerization initiator; benzoyl peroxide,
Examples thereof include methyl ethyl ketone peroxide, isopropyl peroxy carbonate, and other peroxide type polymerization initiators.

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.

The dispersed phase component is prepolymerized in the dispersed phase tank by a bulk polymerization method by heating. Prepolymerization has a polymerization rate of 1
~ 30%, preferably 5-15%,
Then, it is necessary to form a dispersed phase component having a viscosity at 60 ° C. of 1 to 30 centipoise, preferably 1 to 10 centipoise.

It should be noted that the degree of polymerization in the prepolymerization cannot actually be lower than 1%, but if it is higher than 30%, granulation becomes difficult and the particle size distribution becomes broad. Further, when the viscosity of the dispersed phase component formed by the prepolymerization is lower than 1 centipoise or higher than 30 centipoise, the particle size of a relatively large portion is increased and the entire particle size distribution is widened.

The dispersed phase component and continuous phase component preliminarily polymerized as described above 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. However, the suspension polymerization reaction is usually carried out at a polymerization temperature of 50 ° C. or higher, and the temperature is set in consideration of the decomposition 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 broken by the turbulent flow energy of the stirring of the reaction liquid or the shearing force of 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 the fragmentation, in order to obtain droplets with a particle size of 50 μm or less (10 μm or less in the case of toner), the shearing force of the stirring blade of the disperser is the main factor that controls the fragmentation. It turned out that At this time, the size of the liquid droplets produced 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, resulting in loss. In addition, in a general disperser (stirrer), droplets on a circulating flow generated by stirring are subdivided when passing through a shear region, and even in a turbulent flow field existing in the entire device. There is an opportunity to be subdivided by turbulent energy. However, since the movement of the droplets flowing in the apparatus is almost random, it is inevitable that the conditions of the subdivision that each droplet encounters will have a distribution.

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, but generally, the smaller the particle size of a particle, the larger the surface energy per unit volume and the stable existence as a particle. . Further, a factor that causes the particle size distribution to be broadened is that large droplets are mixed with small droplets in the same system. When a small droplet collides with a large droplet, there is a phenomenon that it is easily absorbed by it.
By the way, in order to make the droplet small enough to have a sufficiently stable interfacial energy, it is necessary to supply such a large amount of energy, so it is effective to break the droplet intensively in a narrow shear region, In addition, it is important to bring about a condition that the droplets are regularly divided so that the shearing force is evenly applied to all the droplets.

In the present invention, as described above, the disperse phase component and the continuous phase component are held in independent tanks, respectively, through independent paths, and continuously supplied to a device for applying a shearing force at a narrow shearing region. Since the shearing force is intensively applied with,
It will be possible to deliver each component in a constant state, and all droplets will be subjected to shear forces with equal frequency. Therefore, a dispersion liquid having a desired particle size and a narrow particle size distribution is formed. Further, since the obtained dispersion has a sufficiently large interfacial energy, coalescence hardly occurs even under normal stirring conditions. Therefore, if the dispersion liquid is subsequently subjected to suspension polymerization, a polymer or a polymer composition having a desired particle size and particle size distribution can be obtained.

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

In the following examples, “%” and “part” are based on weight unless otherwise specified.

Example 1 Tribasic calcium phosphate as a continuous phase component 3 in water
%, And an aqueous solution containing 3% of sodium chloride with respect to water was prepared and placed in the continuous phase tank 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 in which 5 g was dissolved was prepared, 20 g of carbon black (# 40 manufactured by Mitsubishi Kasei Co., Ltd.) was added to this mixed solution, and the mixture was dispersed for 20 minutes by an ultrasonic disperser. Then, this dispersion is first
It was placed in the dispersion phase tank of the apparatus shown in the figure.

Dry nitrogen was bubbled through the tank at a rate of 50 ml each time, and the atmosphere was replaced with nitrogen gas. Warm water at 70 ° C was circulated in a heating jacket provided in the dispersion phase tank, and the mixture was stirred for 3.5 hours while maintaining the inside at 60 ° C to carry out a prepolymerization reaction. A part of the reaction solution was sampled, weighed, added to a large amount of methyl alcohol, undissolved components were filtered off, dried and weighed. The polymerization rate was obtained from the weight difference at this time. The polymerization rate at this time is 10.5
%Met. Similarly, a part of the reaction solution was placed in a cell kept at 60 ° C., and a B type viscometer (manufactured by Tokyo Keiki Co., Ltd.
Its viscosity was 6 cp when measured by a mold).

Using the apparatus shown in FIG. 1, the disperse phase component was supplied at 50 ml / min and the continuous phase component was supplied at 250 ml / min to the disperser by a metering pump. As the disperser, a stator-rotor type disperser is used.
It was operated at 8500 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. 2, and the mode value was about 5 μm.

Example 2 In Example 1, the amount of carbon black was 50 g, the prepolymerization reaction time was 5.0 hours, and the supply rate of the dispersed phase component was 75 ml /
The operation was performed in the same manner as in Example 1 except that the continuous phase component supply rate was 225 ml / min and the disperser rotation speed was 9500 rpm. After the prepolymerization reaction, the polymerization rate was 7.8%.
The viscosity at 0 ° C was 5 cp.

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 4 μm.

Comparative Example 1 As a continuous phase component, tribasic calcium phosphate was added to water to 3
%, 2 l of an aqueous solution containing 3% of sodium chloride in water
Was prepared, and as a disperse phase component, a solution prepared by dissolving 15 g of 2,2'-azobisisobutyronitrile in a mixed solution of 400 g of styrene and 100 g of butyl acrylate was prepared. It was placed in the reaction tank. A disperser (manufactured by Tokushu Kika, Homomixer) was installed in the reaction tank and dispersed at 9000 rpm for 8 minutes. Then, the mixture was reacted at 85 ° C. for 8 hours while stirring at 300 rpm with a turbine-type stirring blade.

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 wide particle size distribution as shown in FIG.

Comparative Example 2 The procedure of Example 1 was repeated except that the prepolymerization reaction was carried out by circulating hot water at 90 ° C. for 7 hours while maintaining the internal temperature at 85 ° C. . The polymerization rate after the prepolymerization reaction was 75%, and the viscosity at 60 ° C was 350 cp.

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 obtained had a wide particle size distribution as shown in FIG.

(Effect of the Invention) The suspension polymerization method of the present invention has the above-mentioned constitution and can easily control the particle size and the particle size distribution. It is possible to produce a coalesced composition. Therefore, the present invention is useful for the production of materials, particularly electrophotographic toner, which require a fine particle size and a narrow particle size distribution.

Furthermore, according to the invention, the dispersion can be carried out in a narrow, enclosed area, so that less foaming occurs when obtaining the dispersion. Further, since the dispersed phase component and the continuous phase component are prepared by independent devices and supplied through separate paths, even if the phase ratio is changed, other manufacturing factors are less affected. 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 it is possible to easily deal with the change of conditions such as scale-up.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of an apparatus for use in the suspension polymerization method of the present invention, and FIGS. 2 to 5 are, respectively,
3 is a graph showing the particle size distribution of polymer particles of Example 1, Example 2, Comparative Example 1 and Comparative Example 2. 1 ... Continuous phase tank, 2 ... Dispersion phase tank, 3 ... Reaction tank, 4 ...
... metering pump, 5 ... disperser, 6 ... condenser, 7 ... heating jacket, 8, 9 and 10 ... flow path.

Claims (3)

[Claims] 1. When a suspension composition of a monomer composition is used to produce a polymer composition, a disperse phase component comprising a monomer composition containing carbon black and a continuous phase component comprising an aqueous medium. In a separate tank, preliminarily polymerizing the disperse phase component consisting of the monomer composition in the range of a polymerization rate of 1 to 30% by heating, and the viscosity at 60 ° C. of the disperse phase component of 1 to 30 centipoise. And the preliminarily polymerized dispersed phase component and continuous phase component are simultaneously and continuously fed to respective devices for applying a shearing force through independent paths, and a liquid having a desired size is applied by applying a shearing force. A suspension polymerization method, characterized in that a dispersion having droplets is formed, and then the dispersion is introduced into a polymerization tank to complete polymerization to obtain a polymer composition. 2. The suspension polymerization method according to claim 1, wherein the content of carbon black is 0.5% by weight or more. 3. The suspension polymerization method according to claim 1, wherein the shearing force is applied a plurality of times by a device that applies a plurality of shearing forces.