JPH03296502A - Apparatus and method for continuous reversed-phase suspension polymerization - Google Patents

Abstract

PURPOSE:To continuously produce polymer particles having a uniform particle diameter by causing a dispersion medium to flow as an upward current through a polymn. tower and by using the tower in which the sectional area decreases with coming down from the upper to the lower part of the tower. CONSTITUTION:The title apparatus comprises a polymerizable liq. drop- generating apparatus 1; a polymn. tower 2 which communicates with the apparatus 1; a dispersion medium line 3 which causes a dispersion medium to recirculate and to flow through the polymn. tower 2 as an upward current and comprises a dispersion medium-feeding line 8, a dispersion medium storage vessel 3, and a recirculation pump 4; and a recovery line 7 for recovering produced polymer particles. In the polymn. tower 2, the sectional area decreases step by step or continuously with coming down from the upper to the lower part of the tower.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to improvements in reverse-phase suspension polymerization.

[Prior Art] In conventional suspension polymerization, monomer droplets and polymer particles are dispersed in a dispersion medium, usually in the presence of a suspension stabilizing upper side.
This is done by powerful mechanical stirring.

However, in the dispersion method using stirring, the monomer droplets are destroyed or coalesced by the shear force of stirring, so it is difficult to make the particle size of the monomer droplets uniform. Therefore, there is a problem that the particle size distribution of the produced polymer particles is wide.

As a method for solving the above problem, a method using a polymerization reaction tower having a constant diameter is proposed in JP-A-51-150592. This is a method in which a dispersion medium is passed through a column as a downward flow or an upward flow, and a monomer liquid is polymerized in a fluidized bed state within the column.

However, in the above method, the polymer is produced in a batch manner, which is inefficient for actual industrial scale production. Moreover, the particle size distribution of the resulting polymer particles is also not sufficiently narrow.

As another method, two polymerization reaction towers are used, and the dispersion medium is passed as a downward flow in the first reaction tower and as an upward flow in the second reaction tower, and polymer production is continuously performed in JP-A-57-2.
There is one disclosed in Japanese Patent Publication No. 05402, and one disclosed in Japanese Patent Application Laid-open No. 58-91701, which is an improved method thereof.

However, both of the above methods are limited to normal-phase suspension polymerization, where the monomer liquid has a lower specific gravity than the dispersion medium, and cannot be applied to reverse-phase suspension polymerization, where the monomer liquid has a higher specific gravity than the dispersion medium. do not have. Furthermore, since it consists of a plurality of reaction sections, the apparatus is complicated.

[Problems to be Solved by the Invention] An object of the present invention is to provide a reverse-phase suspension polymerization method that can continuously obtain polymer particles having a uniform particle size.

[Means for solving the problem] In order to achieve the above object, the dispersion medium is circulated in the tower as an upward flow, and the rising speed of the dispersion medium in the upper, middle, and lower parts of the tower is different. The inventors have discovered that excellent results can be achieved by using a polymerization reaction tower having such a structure, and have accomplished the present invention.

That is, the present invention provides a polymerizable droplet generating device, a polymerization reaction tower connected to the polymerizable droplet generating device, a dispersion medium solution circulation line that circulates the dispersion medium solution as an upward flow through the reaction tower, and Provided is a reversed-phase suspension continuous polymerization apparatus comprising a recovery line for produced polymer particles, and characterized in that the polymerization reaction column has a column cross-sectional area that decreases from the top of the column to the bottom of the column.

In the present invention, the polymerizable solution containing the above monomer is
It is sufficient if the specific gravity is larger than the above-mentioned dispersion medium solution containing the suspension stabilizer. The present invention will be described below by taking up a case where the polymerizable solution is an aqueous solution and the dispersion medium solution is an oily solution as one embodiment of the present invention.

The polymerizable solution to be dispersed in the dispersion medium solution is an aqueous solution that has a higher specific gravity than the dispersion medium solution and has little or no compatibility with the dispersion medium solution, and contains monomers, polymerization initiators, crosslinking agents, aqueous medium, etc. including.

The above monomer is not particularly limited as long as it is a water-soluble monomer. Specifically, (meth)acrylamide, fumaramide, aminoalkyl esters of unsaturated carboxylic acids (for example, dimethylamine ethyl methacrylate, etc.),
Examples include (meth)acrylic acid and in situ.

The above polymerization initiator is also preferably water-soluble. Specifically, persulfates (e.g., sodium salts, potassium salts, ammonium salts, etc.), ab-based initiators (e.g., 2,2-
azobis-(2-amidinopropane) dihydrochloride, etc.).

The crosslinking agent is preferably one that is easily soluble in the monomer. Specifically, ethylene glycol dicrycidyl ether,
Polyglycidyl ethers such as polyethylene glycol diglycidyl ether, haloepoxy compounds such as epichlorohydrin and α-methylchlorohydrin, polyaldehydes such as geltaraldehyde and glyoxal, noboliols such as glycerin, pentaerythritol, and ethylene glycol, and polyamines such as ethylene diamine. Examples include:

Examples of the aqueous medium include deionized water and the like.

In addition, a diluent, a blowing agent, a plasticizer, etc. may be added to the polymerizable aqueous solution as additives.

In the composition of the above polymerizable aqueous solution, the monomer preferably has a concentration of 10% by weight to saturated concentration, particularly 20% by weight to saturated concentration.

The type and amount of the polymerization initiator are appropriately selected depending on the type of monomer and the intended use of the polymer particles. Further, although a crosslinking agent does not have to be used, it can be used as appropriate depending on the use of the polymer particles.

The dispersion medium solution is an oily solution having a smaller specific gravity than the polymerizable aqueous solution (and has little or no compatibility with the polymerizable aqueous solution), and contains a suspension stabilizer, a dispersion medium, and the like.

As the suspension stabilizer, commonly used ones such as sorbitan fatty acid esters and polymeric dispersants may be used. Specifically, sorbitan monostearate, sorbitan monolaurate, ethyl cellulose, benzyl cellulose,
Examples include ethyl hydroxyethyl cellulose and maleated polyethylene.

The dispersion medium is not particularly limited as long as it has a specific gravity lower than the aqueous medium and is completely or hardly soluble in the aqueous medium, and examples thereof include aromatic hydrocarbons, aliphatic hydrocarbons, and )\logenated hydrocarbons. It will be done.

Specific examples include heptane, benzene, xylene, chloride, toluene, mineral oils, methylene chloride, and the like.

In the composition of the dispersion medium solution, the suspension stabilizer is 0.0
5 to 5% by weight of IO is preferred, especially 0.5 to 5% by weight.

The above-mentioned polymerizable aqueous solution and dispersion medium solution may be prepared by a conventional method, which is carried out by mixing the respective ingredients using a stirrer or the like.

Although the weight ratio of the polymerizable solution and the dispersion medium solution is not particularly limited, for example, the ratio of the polymerizable solution to 100 parts by weight of the dispersion medium solution is preferably 1 to 100 parts by weight, particularly 10 to 50 parts by weight.

In the reversed-phase suspension continuous polymerization apparatus used in the polymerization method of the present invention, the polymerization reaction tower is characterized in that the cross-sectional area of the tower gradually decreases from the upper part of the tower to the lower part of the tower. Therefore, the polymerization reaction tower of the present invention may have any shape as long as the cross-sectional area of the tower is reduced in this way. Specifically, such shapes include, for example, a step-shaped column in which the cross-sectional area of the column decreases in stages as shown in Figure 3, a column in which the cross-sectional area decreases in a stepless manner as shown in Figure 4, and As shown in FIG. 5, examples include a mixed type in which one part decreases stepwise and the other part decreases steplessly. In addition, when the polymerization reaction tower has at least a stage structure, the number of stages is not particularly limited and may be selected as appropriate. Furthermore, the connecting surfaces between the steps may be horizontal surfaces as shown in FIG. 6, but in order to avoid the accumulation of polymerizable droplets and/or generated polymer particles on the connecting surfaces, as shown in FIG. It is desirable that the surface be sloped as shown in the figure.

As mentioned above, the shape of the polymerization reaction tower of the present invention can take various shapes as desired, but as an example, the case where the most standard and common polymerization reaction tower having the structure shown in FIG. 1 is used. The polymerization method of the present invention will be specifically explained below.

First, the dispersion medium solution is transferred from the supply line (8) to the storage tank (3).
to be introduced. Next, this dispersion medium solution is introduced from this storage tank (3) into the column lower part (11) through a circulation line (5) by a circulation pump (4). After the dispersion medium solution rises in the polymerization reaction tower (2) and fills the tower, the dispersion medium solution is returned to the storage tank (3) from the top of the tower (9) through the circulation line (5) and circulated. . A heating device installed in the storage tank (3) then heats the circulating dispersion medium solution stream to the desired polymerization temperature.

The polymerization temperature may be appropriately selected depending on the decomposition temperature of the polymerization initiator used, the boiling point of the dispersion medium, etc.

The polymerization reaction tower (2) has a lower part (11) having a relatively small cross-sectional area, a middle part (10) having a medium cross-sectional area, and an upper part (10) having a large cross-sectional area. 9
) It has a three-tiered tower structure.

Therefore, when the dispersion medium solution is circulated and passed as an upward flow in the polymerization reaction tower (2), the velocity of the fluid is generally inversely proportional to the passage cross-sectional area, so the flow rate of the upward flow is
), the middle part of the column (10), and the upper part of the column (9), the flow becomes smaller, and an ascending axial flow velocity distribution is formed in the column. Regarding this flow velocity distribution, polymerizable droplets settle in the upper part of the tower (9), and in the middle part of the tower (10
), the cross-sectional area of each column, the flow rate of the circulation pump, etc. are determined so that the polymerizable droplets stay in the column (11), and the produced polymer particles settle in the column lower part (11).

The sedimentation behavior of the polymerizable droplets and produced polymer particles in the tower depends not only on the flow rate of the dispersion solution but also on the droplets and/or the produced polymer particles.
Alternatively, the cross-sectional area of each column should be designed according to the composition of the polymerizable droplets used, the supply rate, the concentration of the droplets, and the polymerization rate of the monomer, etc., as it is affected by the concentration of the particles in the dispersion medium. At the same time, it is recommended to optimally set the flow rate of the circulation pump.

On the other hand, the polymerizable droplet generating device (1) is attached to the top of the polymerization reaction tower (2) from the supply line (6) to the polymerizable solution.
to be introduced. This device (1) generates a liquid column of a polymerizable solution using one or more orifices or nozzles, and gives regular vibrations to the generated liquid column by mechanical or electrical means to have a uniform droplet diameter. This generates a group of droplets.

Any known method can be used to apply the vibration. For example, a method of directly mechanically vibrating the nozzle (E
, E. K. Dabora, “The Review of Scientific Instruments.”
ificI instruments) J, Vo138
, No. 14.502 (1967), Method of applying pressure pulses to a fluid using a piezoelectric element (W, E, Ezo (W, E
, Yates) et al., “Proceedings of Ikhlas” 78
ICLAS' 78) J, 181 (1978)) and a method of applying an AC high voltage pulse to a fluid ejected from a nozzle (M, Sato, ``Journal of Electrostatics (Jourr+a)
l ofE Electrostatics) J, Vol.
15.237 (1984), etc.

The diameter of the generated droplets is determined by the liquid flow rate, liquid viscosity, orifice or nozzle diameter, vibration frequency, etc.

Further, the droplets may be generated either in the gas phase or in the liquid phase.

In the present invention, by using such a uniform droplet generating device, polymer particles having a uniform particle size can be obtained. In addition, the particle size can be arbitrarily adjusted by selecting the droplet generation conditions described above. Since the dispersion medium solution is not circulated, polymerizable droplets with a uniform particle size are collected from the above device (1) in the upper part of the column (9). ).

The introduced droplets settle slowly because the flow rate of the dispersion medium solution is low in the upper part of the column (9). For this reason, droplets generally do not flow out into the circulation line (5) attached to the upper part (9) of the tower.

When the polymerizable droplets settle to the tower center (10), the rising speed of the dispersion medium solution is greater than that at the top of the tower, so the droplets stay in the tower center while repeating vertical movements, and polymerization progresses. In this floating state, the polymerizable droplets are neither destroyed nor coalesced, so polymerization proceeds while maintaining a uniform droplet diameter. The resulting polymer particles are also of uniform size. As the polymerization progresses, the specific gravity of the polymerizable droplets increases, so they gradually begin to settle.

Then, only the polymer particles whose specific gravity has further increased after reaching the desired polymerization rate settle into the lower part of the column (11).

The polymer particles settle in the lower part of the column (11) and are continuously or intermittently extracted and recovered as a slurry from the polymer recovery line (7). At this time, an amount of the dispersion medium solution corresponding to the dispersion medium solution discharged as the polymer slurry +)- is supplied from the dispersion medium solution supply line (8),
The amount of dispersion medium solution in the circulation system is maintained at a constant amount.

In order to efficiently recover the polymer particles, it is preferable to further provide a separation section (13) for the produced polymer particles under the lower part (11) of the column, as shown in FIG. In this case, the circulating dispersion medium solution does not flow through the separation section (13) as shown in FIG. 8, so the fluid remains almost stationary within the separation section (13).

Therefore, the generated bomber particles efficiently settle and precipitate within the separation section (13). The produced polymer particles thus precipitated are continuously or intermittently taken out from the polymer recovery line (7) using a slurry transfer pump or the like.

The desired polymerization rate of the recovered polymer particles can be achieved by appropriately selecting the flow rate of the dispersion medium solution, but if you wish to further increase the polymerization rate, the polymer particles can be reacted in an ordinary polymerization vessel equipped with a stirrer, etc. You can also do it.

[Effects of the Invention] According to the present invention, in reverse-phase suspension polymerization, only particles that have sufficiently progressed in polymerization are discharged, so that the generated polymer particles are effectively separated, resulting in highly uniform polymer particles. can be obtained continuously.

That is, the obtained polymer particles have a high degree of uniformity in particle size without any particular classification operation, and uniform polymer particles can be obtained at a high yield.

Furthermore, the polymerization reaction apparatus of the present invention requires only one reaction column and has a simple configuration.

[Example] Hereinafter, the present invention will be explained in more detail with reference to an example using a polymerization apparatus shown in FIG.

(Example 1) 510 g of gQwt% acrylic acid was neutralized with 600 g of 30 wt% sodium hydroxide aqueous solution, 0.4 g of potassium persulfate was used as a polymerization initiator, and Bunacol EX was used as a crosslinking agent.
A polymerizable aqueous solution was prepared by adding 20.4 g of -810 (manufactured by Nagase Chemical Industries, Ltd.) together with 40 g of ion-exchanged water.

The polymerizable aqueous solution was continuously supplied to the uniformly weighted droplet generator (1) from the monomer supply line (6). The homogeneous polymerizable droplet generating device (1) has one orifice opening with a diameter of 0.1 mm, and applies mechanical vibration of 6000 Hz to the polymerizable aqueous solution to generate a group of uniformly polymerizable droplets of 1.5 g per minute. generated. The generated homogeneous polymerizable droplet group was continuously supplied to the upper part of the polymerization reaction tower (2) through which the dispersion medium solution was flowing.

The polymerization reaction tower (2) consists of three reaction sections, the upper part of the tower (9
) has an inner diameter of 125 mm, a height of 140 II 1 m, and a tower center (1
0) has an inner diameter of 50 mm, a height of 400 mm, and a tower lower part (11
) has an inner diameter of 45 mm and a height of 1100 a, and the dispersion medium solution flowing in the column is circulated at a rate of 1°51 per minute by the circulation pump (4).
It was adjusted to 2. As the dispersion medium solution, a cyclohexane solution in which 0.2 wt% ethyl cellulose was dissolved was used.

The polymerization temperature in the polymerization reaction tower (2) is the same as that in the dispersion medium solution storage tank (3).
The temperature of the circulating dispersion medium was maintained at 75°C by adjusting the temperature. The slurry containing the produced polymer is continuously extracted from the lower part of the polymerization reaction tower (2) at a rate of 12x (l/min) through the polymer recovery line (7), and supplementary dispersion medium is added to the dispersion medium through the dispersion medium supply line (8). The recovered polymer was dried and the particle size was measured (directly measured from a micrograph), and as a result, 120 μl of almost uniform polymer was obtained (see photo).

(Example 2) Polymerization was carried out using the same method and equipment as in Example 1.

However, the vibration frequency of the homogeneous polymerizable droplet generating device (1) was set to 2000 Hz, and the flow rate of the dispersion medium solution flowing through the polymerization reaction tower (2) was set to 3.0 Hz per minute. Changed to Or.

As a result of drying the recovered polymer and measuring the particle size, it was found that 170
μl of nearly homogeneous polymer was obtained.

(Example 3) Polymerization was carried out using the same method and equipment as in Example 1.2. However, the orifice diameter of the homogeneous polymerizable droplet generator (1) was 0.3 am, and the vibration frequency was 2000 Hz.

The flow rate of polymerizable liquid was increased to 7.5 g per minute, and the polymerization reaction tower (2)
The flow rate of the dispersion medium solution flowing therethrough was changed to 8.012 per minute. As a result of drying the recovered polymer and measuring the particle size, 2
A nearly uniform polymer with a 90μ shoulder was obtained.

(Comparative Example 1) (Usual batch type reversed-phase suspension polymerization method) 5g with a stirrer, reflux condenser, dropping funnel and nitrogen inlet tube
Cyclohexane 1600t+2 in a 4 neck round bottom flask
．． 5 g of ethyl cellulose was charged and the temperature was raised to 75°C. The same polymerizable aqueous solution as in Example 1 was added dropwise from the above four-bottle flask over 1.5 hours under a nitrogen atmosphere, polymerized at a rotation speed of 400 rpm, and then heated at a temperature of 70 to 75°C for 0.5 hours. The polymerization was completed by holding. As a result of drying the obtained polymer particles and measuring the particle size, polymer particles with a wide particle size distribution as shown in Table 1 were obtained. When attempting to obtain only polymer particles of a desired particle size by classification, the yield became extremely poor.

Table 1 12... Connection surface between steps, Separation of children.

generated polymer particles

Claims (5)

[Claims] (1) A polymerizable droplet generating device, a polymerization reaction tower connected to the polymerizable droplet generating device, a dispersion medium solution circulation line that circulates the dispersion medium solution as an upward flow in the reaction tower, and a generated polymer 1. A reversed-phase suspension continuous polymerization apparatus comprising a particle recovery line, the polymerization reaction column having a column cross-sectional area that decreases from the top of the column to the bottom of the column. (2) Claim (1) wherein the reduction in the cross-sectional area of the polymerization reaction tower from the upper part to the lower part is stepwise and/or stepless.
) Reverse-phase suspension continuous polymerization apparatus described. (3) The polymerization reaction tower consists of an upper part connected to the polymerizable droplet generator, a middle part having a cross-sectional area smaller than the cross-sectional area of the upper part and larger than a cross-sectional area of the lower part, and a lower part. The reversed-phase suspension continuous polymerization apparatus according to claim (1). (4) The reversed-phase suspension continuous polymerization apparatus according to any one of claims (1) to (3), wherein the polymerization reaction tower further has a separation section for separating produced polymer particles. (5) A reverse phase suspension in which polymerizable droplets are introduced into a polymerization reaction tower in which a dispersion medium solution flows from the bottom to the top of the reaction tower, polymerized in the polymerization reaction tower, and the produced polymer particles are recovered from the bottom of the tower. In the turbidity polymerization method, the rate of rise of the dispersion medium solution in the polymerization reaction tower decreases as the cross-sectional area of the tower increases as it rises from the bottom of the tower to the top, and polymerizable droplets settle at the top of the tower. , a reversed-phase suspension continuous polymerization method characterized in that the polymerizable droplets are retained in the middle part of the tower, and the produced polymer particles are settled in the lower part of the tower.