JPH05132503A - Spray polymerization method and nozzle for spray polymerization - Google Patents

Abstract

PURPOSE:To enable prolonged continuous operation in the redox polymerization of a sprayed monomer solution containing an organic unsaturated carboxylic acid or a salt thereof as a major component by preventing the polymerization from occurring within the sprayer. CONSTITUTION:A monomer solution containing an organic unsaturated carboxylic acid or a salt thereof as a major component is polymerized in a gaseous using a redox polymerization initiator by spray polymerization. A first liquid obtained by adding either of the oxidizing agent and the reducing agent which constitute the initiator to the monomer solution is fed to a nozzle for the first liquid, while a second liquid which is either the remainder of the initiator alone or a mixture thereof with the same monomer solution is fed to a nozzle for the second liquid. The two liquids are sprayed from the respective nozzles so as to be mixed nearby the orifices to thereby conduct polymerization in a gaseous phase.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is suitable for a method of spray-polymerizing a monomer solution containing an organic unsaturated carboxylic acid or a salt thereof as a main component by using a redox type polymerization initiator, and particularly suitable for producing a super absorbent polymer. The present invention also relates to a spray polymerization method and a spray polymerization nozzle.

[0002]

2. Description of the Related Art As a method for producing a super absorbent polymer from a monomer containing an organic unsaturated carboxylic acid or its salt as a main component, a reverse phase suspension method is the mainstream, and a solution polymerization method is also partially used. There is. These methods require subsequent steps such as drying and pulverization, and the inverse phase suspension method also produces fine particles having a particle size of 100 μm or less, which causes problems in homogenization and handling of products.

Japanese Patent Publication No. 32-10196 discloses an aqueous solution of a monomer consisting of a water-soluble salt such as acrylic acid, methacrylic acid or itaconic acid in the presence of an alkali metal persulfate or ammonium persulfate catalyst at 300 to 900 F (149 to 4).
A polymerization process is described in which the gas medium heated to 82 ° C. is atomized. Examples of the spraying method include a spray gun and a rotating disk, and a method of previously mixing an aqueous solution of a monomer and a catalyst and then supplying the same to a rotating disk, or a method of immediately mixing an aqueous monomer solution and an initiator solution and supplying the same to a rotating disk. Is also mentioned.

In JP-A-49-105889, an organic unsaturated carboxylic acid or a salt thereof is used to form an insoluble component in water by using a redox polymerization initiator composed of an organic hydroperoxide and a reducing agent. A spray polymerization method that does not accompany is described, and there are a rotating disk type, a pressure nozzle type, a two-fluid nozzle type, etc. as the atomizer, but from the viewpoint of long-term operation, the monomer and the polymerization initiator solution are separate conduits. It is described that the liquid supplied from a plurality of conduits is preferably mixed in the disk in a short time, such as a rotating disk type.

Japanese Patent Laid-Open No. 64-64106 discloses a gas phase prepared by mixing a solution containing a water-soluble ethylenically unsaturated monomer as a main component with water vapor or water vapor and at least one gas which is substantially inert to polymerization. And a method of producing a water-absorbent resin in which the polymerization is carried out in the gas phase. In JP-A-2-138306, a solution having a monomer concentration of at least 20% by weight is supplied to the gas phase, and Relative humidity 30
%, A method for producing a water-absorbent resin to be polymerized under the conditions is disclosed, and a monomer preliminarily mixed with a radical polymerization initiator,
By spraying in a gas phase at 40 to 180 ° C. using an atomizer and a spray nozzle (pressure nozzle), a particulate super absorbent resin having an average particle size of about 100 to 400 μm is obtained.

In the case where the polymerizable monomer and the polymerization initiator are mixed before spraying, there is a risk that the polymerization is initiated inside the nozzle in principle. In particular, when operating for a long time, there is always a residence time distribution, and there is a high risk of the polymerization reaction proceeding in the nozzle, which is a problem. Further, since the polymerization reaction is an exothermic reaction, if the reaction starts to occur even a little, it progresses in a runaway manner and causes clogging of the nozzle. In addition, Japanese Patent Laid-Open No. 4
In the method disclosed in 9-105889 in which a monomer and a polymerization initiator solution are supplied to a rotating disk through separate conduits, the monomer and the polymerization initiator are mixed on the disk, so that a residence time distribution occurs and the polymerization reaction There is a risk of starting on a disc, and it is difficult to drive for a long time.

[0007]

The present invention relates to a method of spray-polymerizing a monomer solution containing an organic unsaturated carboxylic acid or a salt thereof as a main component by using a redox type polymerization initiator. It is an object of the present invention to provide a spray polymerization method and a spray polymerization nozzle that prevent the above and enable continuous operation for a long time.

[0008]

The spray polymerization method according to the present invention is a redox-based method for spray-polymerizing a monomer solution containing an organic unsaturated carboxylic acid or a salt thereof as a main component by using a redox-based polymerization initiator. A first liquid obtained by adding one of an oxidizing agent and a reducing agent constituting a polymerization initiator to a monomer solution is supplied to the first liquid nozzle, and the other of the oxidizing agent and the reducing agent is added with a monomer solution or It is supplied as a second liquid to the second liquid nozzle without being added, and is jetted so that the first liquid and the second liquid are mixed at the outlets of the first and second liquid nozzles to carry out the polymerization reaction in the gas phase. It is characterized by performing.

As a monomer solution for producing the super absorbent polymer, acrylic acid, methacrylic acid, maleic acid,
An aqueous solution or a mixed aqueous solution of an organic unsaturated carboxylic acid or a salt thereof such as itaconic acid or a salt thereof is used. Particularly preferred is acrylic acid or its salt. Examples of the salts of organic unsaturated carboxylic acids include ammonium salts, alkali metal salts and alkaline earth metal salts, particularly sodium, potassium and ammonium acrylates or methacrylates. Further, a copolymerizable monomer such as acrylamide, methacrylamide, or acrylic acid ester may coexist. The total concentration of organic unsaturated carboxylic acids or salts thereof in the aqueous solution is 20% by weight or more, preferably 25% by weight or more. In order to improve the water absorption performance, a cross-linking agent may be added in an amount of 0.5% by weight or less based on the weight of the monomer.

As the polymerization initiator, a redox system is used because the polymerization reaction time is short. As the combination of the oxidizing agent and the reducing agent which constitute the redox type polymerization initiator, those well known in general can be used. For example, a combination of H ₂ O ₂ and 1-ascorbic acid or amines can be mentioned.

The gas phase gas which polymerizes while the sprayed droplets fall is preferably nitrogen, helium, carbon dioxide gas or the like which is inert to the polymerization, but may be air. Moreover, there is no particular limitation on the humidity in the gas, including the case of using only steam.
The temperature condition of the gas is room temperature or higher and 200 ° C. or lower, preferably 150 ° C. or lower. The gas flow direction may be either countercurrent or parallel flow, but countercurrent (anti-gravitational direction) is better when the residence time needs to be lengthened.

As a method of controlling the particle size of the sprayed droplets, and hence the particle size of the polymerized resin, the method of changing the inner diameter or the outer diameter of the nozzle and the flow rate of the first liquid and the second liquid or both liquids are used. There is a method of changing the flow rate of the gas injected to the mixing place. In the former case, when the linear velocity of the liquid at the nozzle is high, the smaller the inner diameter, the narrower the liquid column that exits from the nozzle, and the smaller the droplet size. Further, when the linear velocity of the liquid is small, the smaller the outer diameter is, the smaller the surface tension acting on the liquid droplets is, so that liquid droplets having a small particle diameter are generated. In the latter case, the average particle size is 100 μm
A resin of the order is obtained, and a resin having a smaller average particle diameter is produced when the amount of injected gas is larger.

An example of the nozzle used in the present invention is, as shown in FIG. 1, a bundling type nozzle in which two liquid nozzles 1 and 2 are installed side by side, and the tip positions of both nozzles are aligned. Is. FIG. 2 is a cross-sectional view of the nozzle tip portion XX, showing a state in which the liquid nozzle 1 and the liquid nozzle 2 are lined up. From one of the liquid nozzles, the first liquid in which one of the oxidizing agent and the reducing agent constituting the redox polymerization initiator is added to the monomer solution is supplied, and the other of the oxidizing agent and the reducing agent is added to the monomer solution. Alternatively, if the second liquid is supplied to the other liquid nozzle without being added, the droplets ejected from both nozzles are mixed at the outlet of the nozzle, and the polymerization reaction is performed while dropping in the gas phase.

FIG. 3 shows another type of nozzle used in the present invention, in which one liquid nozzle 1 is inserted into the other liquid nozzle 2 and the tip positions of both nozzles are aligned. It is a double type nozzle. Figure 4 shows this nozzle tip Y
It is a cross-sectional view taken along line -Y.

FIG. 5 shows another example of the double type nozzle. One liquid nozzle 1 is inserted into the other liquid nozzle 2 and the tip position of the inserted nozzle 1 is shown. Reference numeral 11 is a double nozzle that projects from the tip (tip hole) 22 of the outer nozzle 2. FIG. 6 is a sectional view of the nozzle tip portion ZZ.

FIG. 7 shows an example of a nozzle (opposite type nozzle) of a type for injecting a high-speed air flow to a place where the first liquid and the second liquid are mixed, and the two liquid nozzles 1 and 2 are respectively. The extension lines of the tip ends of the gas nozzles are separately installed at the intersecting angles, and the gas nozzles 4 are provided so as to eject the airflow at the positions where the liquids ejected from the two liquid nozzles intersect.

FIG. 8 shows another example of a nozzle (concentric circle type nozzle) of a type for injecting a high-speed air stream to a place where the first liquid and the second liquid are mixed, which is used as a gas nozzle. A second circular pipe 6 having an inner diameter larger than the outer diameter of the first circular pipe 5 and a third circular pipe 7 having an inner diameter larger than the outer diameter of the second circular pipe 6 are concentrically arranged around the circular pipe 5. In the overlapped triple pipe structure, the gap between the first circular pipe and the second circular pipe is the first liquid nozzle 1, and the gap between the second circular pipe and the third circular pipe is the second liquid pipe. The inside of the gas nozzle 2 and the first circular pipe 5 constitutes a gas nozzle 4. It is preferable that the inside of the first circular pipe 5 constitutes a gas nozzle, but an outer nozzle (a gap between the second circular pipe and the third circular pipe) may be used as a gas nozzle.

When it is considered that the polymerization reaction is almost completed before the liquid drops are dropped into the gas phase until they fall, the drop time at a drop distance of about 10 m is several seconds to ten and several seconds. Therefore, in order to make the spray polymerization method successful, the total of the induction period and the reaction time of the polymerization reaction must be 10 seconds or less. Therefore, the type and amount of the polymerization initiator, the temperature of the gas phase in which the liquid drops fall, and the like may be determined so as to satisfy such conditions.

In the present invention, it is a requirement that one of the oxidizing agent and the reducing agent constituting the redox type polymerization initiator is added to the monomer solution as the first liquid, and the other is the monomer. It may be used as the second liquid without adding the solution, or may be used as the second liquid by adding the monomer solution, and the both solutions are jetted from separate nozzles and mixed at the outlet of the nozzle, Allow the polymerization reaction to take place in phase.

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples.

[0021]

[Example of preparation of monomer solution] 125 parts by weight of 80% by weight acrylic acid aqueous solution, 65.1 parts by weight of 42.6% by weight sodium hydroxide aqueous solution and 0.14 parts by weight of a cross-linking agent (N, N'-methylenebisacrylamide). Then, 2.8 parts by weight of a 30% by weight aqueous hydrogen peroxide solution was further added as an oxidizing agent to prepare a solution A. The monomer concentration of solution A is 60% by weight,
The degree of neutralization was 50 mol%. Separately 80% by weight
125 parts by weight of the acrylic acid aqueous solution of 61.4 parts by weight of a 41.4% by weight aqueous sodium hydroxide solution and a crosslinking agent (N,
(N'-methylenebisacrylamide) 0.14 parts by weight was added, and 1-ascorbic acid 0.34 was further added as a reducing agent.
Solution B was prepared by adding parts by weight. The monomer concentration and the degree of neutralization of solution B were the same as those of solution A.

In Examples and Comparative Examples, these monomer aqueous solutions were heated to 45 ° C. and supplied. On the other hand, in the solution polymerization experiment, the induction period and the reaction time when the monomer aqueous solutions A and B were mixed in equal amounts at 45 ° C. were each about 0.5.
Seconds, about 2 seconds.

The gas flow rate inside the reaction tower was 20 cm / sec ascending flow and the gas temperature was 45 ° C., and all the following Comparative Examples and Examples were carried out under these conditions.

[0024]

[Comparative Example 1] Aqueous solutions of A and B were supplied to the rotating disk through separate supply pipes at a flow rate of 50 ml / min. This rotating disk has a diameter of 100 mm and lies horizontally.
It was spinning at 800 rpm. Polymerization started to form on the disk within a few minutes after the start of the operation, and the accumulation of the polymer rapidly occurred thereafter, which made the operation difficult, so the operation was stopped.

[0025]

[Comparative Example 2] Full-cone nozzle made of ikeuchi 1 / 4MJ050
Using s316W, a total of 50 ml of 25 ml each of A and B monomer aqueous solutions was supplied. These solutions were supplied to the nozzle after mixing with an online mixer having a residence time of about 0.2 seconds immediately before the nozzle. Immediately after the start of operation, a polymerization reaction occurred in the mixer and the pipe was blocked by the highly viscous substance, so the operation was stopped.

[0026]

[Comparative Example 3] In addition to an inlet for gas fluid for forming droplets, a nozzle of a type having two inlets for liquid and capable of mixing two liquids inside is used, and nitrogen gas is used for the inlet for gas fluid. 150
Nl / divided, two solutions of A and B 120ml /
The nozzle was fed in minutes. The two solutions were mixed inside the nozzle, then exited from the liquid fluid outlet, and were dispersed into droplets by the gas fluid. Although the calculated residence time inside the nozzle was 0.2 seconds or less, a highly viscous substance was generated inside the nozzle 1 to 2 minutes after the start of the operation, and the operation could not be continued.

[0027]

Example 1 A type in which the two nozzles shown in FIG. 1 are bundled, and a combination of two nozzles having an inner diameter of 0.7 mm and a combination of two nozzles having an inner diameter of 0.4 mm are used.
A spray polymerization test was performed by supplying the monomer solutions of A and B to the different nozzles at the liquid linear velocities (nozzle tip velocities) shown in Table 1. This nozzle was excellent in continuous operation performance and could be continuously operated for 1 hour or more. The results are shown in Table 1. As is clear from Table 1, the average particle diameter is not so much influenced by the linear velocity of the monomer solution, but has a correlation with the inner diameter of the nozzle tip portion, that is, the cross-sectional area.

[Table 1]

[0028]

[Embodiment 2] A double-type nozzle of the type shown in FIG. 3, in which the outer tube has an inner diameter of 0.9 mm and the outer tube has an inner diameter of 0.6.
A mm nozzle was used. The cross-sectional area of the opening (outer nozzle) between the outer wall of the inner tube and the inner wall of the outer tube was the same as the cross-sectional area of the opening of the inner tube (inner nozzle). A spray polymerization test was carried out by supplying the monomer aqueous solution A to the inner nozzle and the monomer aqueous solution B to the outer nozzle at the liquid linear velocity (nozzle tip velocity) shown in Table 2, respectively. This nozzle was excellent in continuous operation performance and could be continuously operated for 1 hour or more. The results are shown in Table 2.
Shown in. As is clear from Table 2, the average particle diameter is not so much influenced by the linear velocity of the monomer solution, but has a correlation with the inner diameter of the outer tube at the nozzle tip portion, that is, the cross-sectional area.

[Table 2]

[0029]

[Embodiment 3] A double type nozzle of the type shown in FIG. 5, in which the outer tube has an inner diameter (hole diameter) of 0.6 mm and the inner tube has an inner diameter of 0.3 m.
m, a nozzle having a length of 0.7 mm in which the inner tube is protruded from the hole of the outer tube is used, and a monomer aqueous solution of A or B or a monomer aqueous solution of B and a 15% hydrogen peroxide H ₂ O ₂ aqueous solution are used. The spray polymerization test was carried out by supplying the liquid linear velocity (nozzle tip velocity) to different nozzles. The results are shown in Table 3. This nozzle was excellent in continuous operation performance and could be continuously operated for 1 hour or more.

[Table 3]

[0030]

Example 4 Using the facing type nozzle shown in FIG. 7 or the concentric type nozzle shown in FIG. 8, monomer solutions of A and B were supplied to different nozzles under the conditions shown in Table 4 for gas. A spray polymerization test was performed by supplying nitrogen gas from the nozzle.
The two liquids A and B are mixed after they exit the supply line, and at the same time, they are dispersed into droplets by the jet stream. The results are shown in Table 4. These methods are suitable for producing particles with an average diameter of 400 μm or less. Both the opposed type nozzle and the concentric type nozzle were excellent in continuous operation performance and could be continuously operated for 1 hour or more.

[Table 4]

[0031]

EFFECTS OF THE INVENTION Since the polymerization of the monomer inside and on the nozzle can be eliminated to prevent the clogging of the nozzle and the accumulation of the polymer, long-term continuous operation becomes possible and the maintenance and cleaning of the nozzle become easy.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a nozzle for carrying out the present invention.

FIG. 2 is a cross-sectional view of the nozzle shown in FIG.

FIG. 3 is a view showing another example (double type nozzle) of a nozzle for carrying out the present invention.

4 is a cross-sectional view of the nozzle shown in FIG.

FIG. 5 is a view showing another example of a double type nozzle for carrying out the present invention.

6 is a cross-sectional view of the nozzle shown in FIG.

FIG. 7 is a cross-sectional view of an example of a nozzle (opposed nozzle) of a type that ejects a high-speed airflow to a place where the first liquid and the second liquid are mixed.

FIG. 8 is another example of a nozzle of a type that ejects a high-speed air stream to a place where the first liquid and the second liquid are mixed (concentric nozzle).
FIG.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Ohara 1-1-14, Minami Sanrokusho, Yokohama-shi, Kanagawa JGC Corporation Yokohama Office

Claims (7)

[Claims] 1. When a monomer solution containing an organic unsaturated carboxylic acid or a salt thereof as a main component is spray-polymerized by using a redox-based polymerization initiator, the redox-based polymerization initiator is mixed with an oxidizing agent and a reducing agent. The first liquid in which one of them is added to the monomer solution is supplied to the nozzle for the first liquid, and the other of the oxidizing agent and the reducing agent is added to the second nozzle without or with the addition of the monomer solution.
The liquid is supplied to the second liquid nozzle, and jetted so that the first liquid and the second liquid are mixed at the outlets of the first and second liquid nozzles to carry out the polymerization reaction in the gas phase. Characteristic spray polymerization method. 2. The spray polymerization method according to claim 1, wherein the first liquid nozzle and the second liquid nozzle are installed side by side, and a set of liquid nozzles in which both tip positions are aligned is used. 3. The spray polymerization method according to claim 1, wherein a double type nozzle in which the first liquid nozzle is inserted in the second liquid nozzle is used. 4. Use of two liquid nozzles installed separately at an angle at which the extension lines of the tips intersect, and jets an air flow at a position where the liquids jetted from these two liquid nozzles intersect. The spray polymerization method according to claim 1. 5. A second circular pipe having an inner diameter larger than the outer diameter of the first circular pipe and an inner diameter larger than the outer diameter of the second circular pipe centering on the first circular pipe used as a gas nozzle. A triple pipe structure in which third circular pipes are concentrically stacked, and a gap between the first circular pipe and the second circular pipe is provided with a first liquid nozzle, a second circular pipe and a third circular pipe. 2. The spray polymerization method according to claim 1, wherein the gap between and is used as a second liquid nozzle. 6. A polymerizable monomer comprising: two liquid nozzles, which are separately installed at an angle at which the extension lines of the tips intersect, and a gas nozzle for injecting an air stream at the intersection of the liquids. Spray polymerization nozzle. 7. A second circular pipe having an inner diameter larger than the outer diameter of the first circular pipe and an inner diameter larger than the outer diameter of the second circular pipe centering around the first circular pipe used as a gas nozzle. A triple pipe structure in which third circular pipes are concentrically overlapped, and a gap between the first circular pipe and the second circular pipe is a first liquid nozzle, a second circular pipe and a third circular pipe. A nozzle for spray polymerization of a polymerizable monomer, characterized in that a gap between and forms a second liquid nozzle.