JP2003040904A - Polymerization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing a high quality polymer in large quantity by a droplet polymerization process even using a polymerizable monomer with high reaction rate. SOLUTION: This polymerization method is a process comprising mixing a first liquid and a second liquid in vapor phase and polymerizing in droplet state, where a polymerizable monomer and a polymerization initiator are each included at least in either the first liquid or the second liquid, characterized in that at least one of the first liquid and the second liquid is spouted in the vapor phase in droplet form so that the cross section of the spouting forms a closed loop-like liquid film.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for polymerizing by mixing two liquids in a gas phase.

[0002]

2. Description of the Related Art A droplet polymerization method is known in which a liquid containing a polymerizable monomer and a liquid containing a polymerization initiator are jetted into a gas phase and mixed to proceed a polymerization reaction. The droplet polymerization method is a particularly effective method when the polymerizable monomer is instantly polymerized by contact with a polymerization initiator. For example, a water-absorbent polymer is produced by radically polymerizing an aliphatic unsaturated carboxylic acid by contacting it with a polymerization initiator. At this time, the radical polymerization reaction becomes extremely fast depending on the selection of the polymerization initiator. Therefore, conventionally, it was general to produce a water-absorbing polymer by using a solution polymerization method or a reverse phase suspension polymerization method, but there is a limit to increase the polymerization rate because it is difficult to remove the heat of polymerization. . Therefore, in recent years, it has been proposed to produce a water-absorbent polymer using a droplet polymerization method in which the heat of polymerization is efficiently removed.

According to the droplet polymerization method, the pulverization step required in the solution polymerization method, the separation step between the water-absorbing polymer and the organic solvent required in the reverse phase suspension polymerization method, and the distillation recovery of the organic solvent. No process is required. Also, depending on the conditions, part of the heat of polymerization can be used for evaporation of the water contained in the water-absorbent polymer, so that the energy load in the subsequent drying step can be reduced and it is very advantageous in terms of energy. The advantage is that Further, the droplet polymerization method has an advantage that a water-absorbent composite can be produced in a short time without handling powder by directly dropping droplets mixed in a gas phase onto a fibrous base material. is there. At this time, the water-absorbing composite having a desired water-absorbing ability can be easily manufactured by adjusting the timing of dropping and adjusting the carry-in speed of the fibrous base material. Therefore, by utilizing the droplet polymerization method, the water absorption and the water absorption rate are high,
It is possible to provide a water-absorbent composite in which superabsorbent polymer particles are immobilized on a fibrous substrate with good stability (JP-A-9-67403, JP-A-10-113556).

[0004]

However, since the droplet polymerization method is a method of colliding and mixing the first liquid and the second liquid in the gas phase, it is different from the solution polymerization method and the reverse phase suspension method. In principle, it is considered difficult to efficiently produce a large amount of polymer. FIG. 1 shows a conventionally used droplet polymerization nozzle for producing a water-absorbing polymer. Here, the first liquid (3) is supplied to the five nozzles (1) via the introduction pipe, and the second liquid (4) is supplied to the five nozzles (2) via the introduction pipe. After the first liquid and the second liquid are ejected from the tip of the nozzle, they merge and fall to allow polymerization to proceed.

The inner diameter of the nozzle is usually set to 0.1 to 0.2 mm, but if the inner diameter is made thicker, the mixing will be uneven and the quality of the water-absorbent polymer produced will vary. Therefore, the inner diameter cannot be excessively increased for mass production. Therefore, in order to mass-produce the water-absorbent polymer, it is unavoidable to increase the number of nozzles to cope with it, but this is not realistic because the cost of the manufacturing equipment increases. Further, in order for the first liquid and the second liquid ejected from the tip of the nozzle to collide with each other without displacement, the tip of the nozzle needs to be fixed accurately, but there is a slight deviation due to long-term use. There is also a problem that manufacturing efficiency is reduced due to partial clogging of the nozzle and the nozzle.

In order to deal with such a problem, a method using a slit type nozzle as shown in FIG. 2 has been proposed (Japanese Patent Laid-Open No. 11-49805). Here, the first liquid (13) is ejected in the form of a liquid film through a slit (15) provided at the bottom of the first liquid nozzle (11), and the second liquid (14) is discharged into the second liquid nozzle (12). ) Is ejected in the form of a liquid film through a slit (16) opened at the bottom of (2), and the two liquid films join together in the gas phase and fall while advancing the polymerization. According to this method, it is certainly expected that the production efficiency of the water-absorbent polymer will be higher than that in the case of using the opposed nozzle of FIG.

However, when the slit type nozzle was actually used, the inventors of the present invention confirmed that the film thickness of the liquid film ejected from the tip of the slit (15, 16) was not uniform. . That is, since a large amount of liquid is ejected from the slit end portion compared to the slit center portion, the liquid film becomes thicker at the end portion and thinner at the center portion. Therefore, as a result of the first liquid and the second liquid having different thicknesses colliding at the collision point, the polymerization reaction also becomes uneven depending on the collision place. Further, the diameters of the liquid droplets generated from the mixed liquid after collision also vary, and it is not possible to manufacture a water-absorbing polymer having a uniform particle diameter.

As described above, in the conventional droplet polymerization method, it was not possible to efficiently produce a large amount of high quality polymer by using a polymerizable monomer having a fast reaction rate. Therefore, the present invention has an object to solve such a problem of the conventional technique. That is, an object of the present invention is to provide a method for efficiently producing a large amount of a high quality polymer by a droplet polymerization method using a polymerizable monomer having a fast reaction rate. In particular, it was an object to eliminate unevenness in the thickness of the liquid film, which is a problem of the slit type nozzle, and to manufacture a more homogeneous polymer.

[0009]

Means for Solving the Problems As a result of intensive investigations by the present inventors, at least one of the first liquid and the second liquid was
It has been found that the problems of the prior art can be solved by jetting into the gas phase so that the jetted cross-section becomes a closed curved liquid film, and the present invention has been provided.

That is, the present invention is a polymerization method in which a first liquid and a second liquid are mixed in a gas phase and polymerized in a droplet form, wherein the polymerizable monomer and the polymerization initiator are each the first
Liquid or at least one of the second liquid,
Further, there is provided a polymerization method characterized in that at least one of the first liquid and the second liquid is jetted into a gas phase so that a jetted cross section becomes a liquid film having a closed curve shape.

In the polymerization method of the present invention, it is preferable that at least one of the first liquid and the second liquid is jetted so that the jet cross section includes a curved portion, particularly a curved portion having a constant radius of curvature. In addition, both the first liquid and the second liquid,
The jetting is preferably performed so that the jetted cross section becomes a liquid film having a closed curve shape, and at this time, it is preferable that the jetting is performed so that the closed curve of the first liquid is formed inside the closed curve of the second liquid. Further, the closed curve of the first liquid is preferably similar to the closed curve of the second liquid, and the center of gravity of the closed curve of the first liquid and the center of gravity of the closed curve of the second liquid are on the same axis. Preferably there is. The polymerization initiator used in the polymerization method of the present invention is composed of an oxidizing agent and a reducing agent, which are redox-based polymerization initiators, and a polymerizable monomer, an oxidizing agent, and a reducing agent,
It is preferably contained in at least one of the first liquid and the second liquid.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The polymerization method of the present invention will be described in detail below. In addition, in this specification, "-" means the range which includes the numerical value described before and behind that as a minimum value and a maximum value, respectively.

In the polymerization method of the present invention, the first liquid and the second liquid
When the liquids are mixed in the gas phase and polymerized in the form of liquid droplets, at least one of the first liquid and the second liquid is jetted so that the jetted cross section becomes a liquid film having a closed curve shape.

In the present specification, "spouting so as to form a liquid film having a closed curved cross section" means spouting so as to form a hollow liquid film when spouting. The specific shape is not particularly limited as long as the ejection cross section has a closed curve shape. For example, it may have a rectangular shape, an elliptical shape, a perfect circular shape, or a curve in which the curvature changes stepwise or continuously and is connected in a closed curve shape. May be. Further, these shapes may be partially mixed and connected as a closed curve as a whole. The case where the closed curve is formed only by the curves is preferable. Most preferable is a closed curve having a perfect circular shape.

According to the present invention, by jetting so that the jetted cross section becomes a liquid film having a closed curved shape, it is possible to greatly reduce the unevenness of the thickness of the jetted liquid film. For example, according to the present invention, the problem of liquid deviation at the slit end, which is found in a liquid film ejected using a conventional slit type nozzle, can be completely eliminated. For this reason, when the polymerization is performed according to the present invention, it is possible to suppress variations in the polymer particle size and variations in the degree of polymerization due to the variations in the thickness of the jetted liquid film.

In the present invention, the jetting direction is not particularly limited as long as the jetting is performed so that the jetted cross section becomes a closed curved liquid film. Therefore, it may be jetted with a velocity component directed to the inside of the closed curve, or may be jetted with a velocity component directed to the outside of the closed curve,
It may be jetted with a velocity component in the tangential direction of the closed curve, or may be jetted vertically downward. Also, these directions may be combined and ejected. It is preferable that the jetting is carried out by giving a velocity component toward the outside of the closed curve. When jetting with a velocity component in the tangential direction of the closed curve, it is preferable to select a tangential direction that does not intersect the closed curve.

The locus shape when the liquid falls is not particularly limited, but it is preferable that the liquid falls while following a so-called tulip type or onion type locus. Figure 3
Shows a state in which the liquid is ejected from the perfect circular opening formed on the bottom surface of the nozzle. At the time of ejection from the nozzle opening, the liquid pressure becomes high and a tangential velocity component is generated. In FIG. 3, the amount of ejected liquid increases from the left side to the right side. When the amount of ejected liquid is small, it drops in the form of large liquid droplets from the beginning (FIG. 3A), but when the amount of ejected liquid increases a little, what initially ejected in the form of a liquid column becomes droplets. Fall (Fig. 3
(B)). When the amount of jetted liquid is further increased, a hollow liquid film is formed. In the state shown in FIG. 3C, the cross-sectional diameter of the hollow liquid film reaches its maximum on the way and shrinks due to the effect of surface tension, and finally splits into droplets and falls. This state is called onion type. When the jet pressure is further increased, the hollow liquid film is divided into droplets and drops before contracting (FIG. 3 (d)).
This state is called tulip type. When the amount of ejected liquid becomes larger than this, it immediately becomes a fine liquid droplet (mist) immediately after ejection, and then spreads and falls (FIG. 3 (e)). For the drop behavior after these jets, see AHLefebvere, "
Atomization and sprays ", Taylor & Francis.

Such a trajectory of the liquid can be controlled by adjusting the velocity component on the same plane as the ejection surface and ejecting the liquid. By increasing the velocity component on the same plane as the ejection surface and toward the outside of the closed curve, it is possible to overcome the contraction, so that it is possible to control, for example, an onion type trajectory to a tulip type trajectory. The velocity component on the same plane as the ejection surface may be a velocity component outward in the radial direction of the closed curve, a tangential velocity component, or a combination thereof.

In the polymerization method of the present invention, the first liquid and the second liquid
At least one of the liquids is ejected so that the ejection cross section forms a liquid film having a closed curved shape. Therefore, if one is jetted so that the jetted cross section becomes a liquid film having a closed curved shape, the jetting method of the other is not particularly limited. Further, both the first liquid and the second liquid may be jetted so that the jetted cross section forms a liquid film having a closed curve shape.

In a preferred embodiment of the present invention, it is preferable that both the first liquid and the second liquid are jetted so that the jet cross section forms a liquid film having a closed curve shape. At this time, it is preferable that the closed curve which is the ejection cross section of the first liquid is ejected so as to be inside the closed curve which is the ejection cross section of the second liquid. The two closed curves preferably have similar shapes. The centers of gravity of the two closed curves are preferably on the same axis. At this time, the first liquid and the second liquid may be jetted so as to collide with each other. For example, if the first liquid is jetted so that the closed curve spreads, the second liquid may be jetted so that the closed curve narrows or may spread so long as it collides with the first liquid. , May be ejected so as not to change.

Further, the first liquid and the second liquid are mixed with each other so as to follow a tulip type or onion type trajectory after mixing.
It is preferable to select the ejection speed and ejection direction of the liquid and the second liquid in combination. For example, an example can be given in which the first liquid is ejected by itself so as to follow a tulip-shaped or onion-shaped locus, and the second liquid is caused to collide at a speed that does not significantly change the locus of the first liquid. Also, the first
The liquid mixture may be set to follow a tulip-shaped or onion-shaped trajectory by applying air pressure from the inside after the collision of the liquid and the second liquid.

The size of the droplets formed after mixing the first liquid and the second liquid is 5 to 3000 μm, especially 50 to 1000 μm.
m is preferred. Polymerization is started immediately after the two liquids are mixed, and the liquid drops in the polymerization chamber while the polymerization proceeds even in the droplets.
The atmosphere in the polymerization chamber can be arbitrarily set as long as it does not hinder the polymerization reaction. Normally, nitrogen is used as the atmosphere gas,
Helium, carbon dioxide, or the like is used, but air or water vapor can also be used. When water vapor is fed into the atmosphere, based on the concentration of the polymerizable monomer-containing liquid to be subjected to the reaction, the water content required for the polymer particles to be produced, etc., how much water is evaporated from the polymerizable monomer-containing liquid It may be set from the viewpoint of whether to do it. The temperature of the atmosphere is usually room temperature to 150 ° C, preferably room temperature to 100 ° C.

The nozzle for carrying out the polymerization method of the present invention will be described below. Here, as long as the nozzle can carry out the polymerization method of the present invention, conventionally known nozzle mechanisms can be appropriately selected or combined and used. For example, it is possible to use a nozzle having at the bottom an opening having the same closed curve shape as the ejection cross section. At this time, the direction in which the liquid is ejected from the opening can be adjusted by appropriately selecting the shape of the ejection guide portion that guides the liquid to the opening at the bottom of the nozzle. For example, if the ejection guide portion is provided with a tubular guide passage having a cross section of the same closed curve as the opening perpendicularly to the ejection surface, the liquid is ejected straight from the opening. Further, the ejection guide portion is provided with a cylindrical guide passage having a closed curved cross section similar to the opening, and the closed curve cross section is formed so as to increase from the upper portion of the ejection guide portion toward the lower portion (opening portion). If the nozzle is used, it is possible to eject with a velocity component outward of the closed curve. further,
The ejection guide part is provided with a tubular guide passage having a closed curved cross section similar to the opening, and the closed curved cross section is formed so as to become smaller from the upper part of the ejection guide part toward the lower part (opening). If a nozzle is used, jetting with an inward velocity component of a closed curve is possible.

Further, it is possible to use a nozzle having a nozzle opening portion or a flow path adjusting portion immediately before the opening portion. For example, the liquid sent through the cylindrical guide path to just above the nozzle opening is collided with the conical deflection part to change the flow path so that the circular opening spreads inside or outside the closed curve. It is possible to use a nozzle capable of ejecting the liquid onto the nozzle. The ejection speed and direction from the opening can be adjusted by appropriately selecting the shape of the deflecting portion. Further, the thickness of the liquid film can also be controlled by changing the nozzle shape or size or adjusting the flow velocity at the time of jetting.

Further, in the present invention, it is possible to utilize a nozzle for adjusting the jetting direction and speed of the liquid by air pressure. For example, by applying air pressure to the opening in a desired direction, the liquid supplied to the opening can be ejected in that direction. Further, the air pressure may be applied to the liquid inside the opening, or may be applied to change the locus after the collision of the first liquid and the second liquid.

When the jetting cross section includes a curved portion or is a hollow circle, in order to jet the liquid with a velocity component in the tangential direction of the curved line or circle, in order to jet the liquid, the liquid is rotated in the nozzle and opened. It is preferable to use a nozzle having a mechanism for ejecting the liquid from the part. For example, it is possible to have a velocity component in the tangential direction at the opening by sending the liquid while applying pressure to the jetting guide having a spiral guide groove.
Alternatively, instead of using the spiral guide groove, centrifugal force may be utilized to cause the cylindrical inner wall to spirally descend while rotating.

A particularly preferred nozzle in the present invention is a double concentric spiral jet nozzle in which two combinations of the guide portion and the circular opening for making such a rotational movement are formed concentrically. In the present specification, the double concentric swirl jet nozzle has a first circular opening for jetting a first liquid and a second circular opening for jetting a second liquid, and is used for the above polymerization method. A first guide part having a circular cross section is connected to the first circular opening, and further, the first liquid follows the spiral trajectory of the first liquid on the inner wall of the first guide part. 1st liquid supply means for supplying the 1st liquid so as to descend to the 1 circular opening is installed; a 2nd guiding part having a circular cross section is connected to said 2nd circular opening,
Further, a second liquid supply means is provided for supplying the second liquid so that the second liquid descends to the second circular opening while following the spiral trajectory of the inner wall of the second guiding portion; 1
It means a nozzle in which a circular opening, the second circular opening, the first guiding portion, and the second guiding portion are concentrically arranged.

If the double concentric spiral jet nozzle is used, the first liquid is ejected in a conical shape from the inner first liquid opening and the second liquid is ejected in a conical shape from the outer second liquid opening. Can be made. The ejection angle and ejection speed of the first liquid and the second liquid are adjusted so that they collide with each other after ejection. For example, the first
The ejection speed of the liquid may be adjusted to be higher than the ejection speed of the second liquid so that the two liquids collide with each other, or air pressure is applied to either the first liquid or the second liquid to make the ejection trajectory. The two liquids may be made to collide efficiently by adjusting.

A concrete example of the double concentric spiral jet nozzle is shown in FIG. FIG. 4A is a horizontal sectional view of the upper part of the guiding portion of the double concentric spiral jet nozzle, and FIG. 4B is a vertical sectional view of the double concentric spiral jet nozzle. As shown in FIG.
Two introducing pipes (23a, 23b) for introducing the first liquid are installed in the first guiding part (21). The first liquid is sent in the direction of the arrow through the introduction pipes (23a, 23b) and is vigorously introduced into the first guide portion (21). The first liquid follows a spiral locus along the inner wall of the first guiding portion (21) by centrifugal force and gravity, and then the first circular opening (2
4) is reached (FIG. 4 (b)). Similarly, two introducing pipes are also installed in the second guiding part (not shown), and the second liquid is vigorously introduced into the second guiding part (22) through this introducing pipe, and a spiral locus is formed. The second circular opening (25) is reached while following the path. The first liquid and the second liquid that have reached the circular opening are ejected with a velocity component in the tangential direction at the opening as shown in FIG. 4C, and merge in the gas phase. The shape of the double concentric spiral jet nozzle shown in FIG. 4 can be appropriately changed depending on the types of the first liquid and the second liquid, the purpose of polymerization, and the like. For example, the number of introducing pipes can be increased or decreased, and the diameter or length of the guiding portion or the inner wall angle can be adjusted.

In the polymerization method of the present invention, the polymerizable monomer and the polymerization initiator are contained in at least one of the first liquid and the second liquid, respectively. It is necessary to prevent the polymerization of the liquid containing the polymerizable monomer from proceeding before the two liquids are mixed. For example, when a redox type polymerization initiator composed of an oxidizing agent and a reducing agent is used as the polymerization initiator, the first liquid may contain the oxidizing agent and the second liquid may contain the reducing agent. At this time, the polymerizable monomer can be contained in either one or both of the first liquid and the second liquid. Alternatively, the first liquid may contain a polymerizable monomer, and the second liquid may be prepared by mixing an oxidizing agent and a reducing agent immediately before use.

The type of polymerizable monomer used in the polymerization method of the present invention is not particularly limited. For example, vinyl compounds,
A vinylidene compound, a vinylene compound, a cyclic olefin compound or the like can be appropriately selected and used according to the application. These polymerized monomers are roughly classified into water-soluble polymerized monomers and oil-soluble polymerized monomers depending on the type of substituent.
Examples of the water-soluble polymerizable monomer include olefinic unsaturated carboxylic acid or a salt thereof, olefinic unsaturated sulfonic acid or a salt thereof, olefinic unsaturated amine, olefinic unsaturated amide, and the like. Examples of the oil-soluble polymerizable monomer include styrene, isobutene, vinyl chloride, vinyl acetate, acrylic acid esters, methacrylic acid esters and the like. For specific examples and reaction examples of the polymerizable monomer that can be used in the present invention, see Takayuki Otsu, “Chemistry of Polymer Synthesis” (Chemical Dojin) 34.
Pp. 43, etc. can be referred to. These monomers may be used alone or in combination of two or more.

The polymerizable monomer preferably used when producing the water-absorbent polymer by the polymerization method of the present invention will be specifically described below. In the case of producing a water-absorbing polymer, an aliphatic unsaturated carboxylic acid or its salt is preferably selected as the polymerizable monomer. Specifically, unsaturated monocarboxylic acids or salts thereof such as vinyl compound acrylic acid or a salt thereof, vinylidene compound methacrylic acid or a salt thereof, maleic acid or a salt thereof, fumaric acid or a salt thereof, itaconic acid. Alternatively, unsaturated dicarboxylic acids such as salts thereof or salts thereof can be exemplified. You may use these individually or in mixture of 2 or more types. Among these, acrylic acid or a salt thereof and methacrylic acid or a salt thereof are preferable, and acrylic acid or a salt thereof is particularly preferable. When producing a water-soluble or water-absorbing polymer, it is preferable to use these aliphatic unsaturated carboxylic acids or salts thereof in an amount of 50 mol% or more based on the total amount of the polymerizable monomer, and 80 mol%
It is more preferable to use the above.

As the salt of the aliphatic unsaturated carboxylic acid, a water-soluble salt such as an alkali metal salt, an alkaline earth metal salt or an ammonium salt is usually used. The degree of neutralization is appropriately determined depending on the purpose, but in the case of acrylic acid, 20 to 90 mol% of the carboxyl groups are preferably neutralized with an alkali metal salt or ammonium salt. When the degree of partial neutralization of the acrylic acid monomer is less than 20 mol%, the water absorbing ability of the water absorbent polymer produced tends to be significantly reduced.

To neutralize the acrylic acid monomer, alkali metal hydroxides, bicarbonates, ammonium hydroxides, etc. can be used, but alkali metal hydroxides are preferred, and specific examples thereof are shown. Include sodium hydroxide and potassium hydroxide.

When the water absorbing polymer is produced by the polymerization method of the present invention, in addition to the above-mentioned aliphatic unsaturated carboxylic acid, a polymerizable monomer copolymerizable therewith, such as (meth) acrylamide, (poly ) Ethylene glycol (meth) acrylate and 2-hydroxyethyl (meth) acrylate can be copolymerized. Also,
Although it is a low water-soluble monomer, it can be copolymerized in an amount within a range that does not deteriorate the performance of the water-absorbing polymer that also produces alkyl acrylates such as methyl acrylate and ethyl acrylate. In addition, in this specification, the term “(meth) acrylic” means both “acrylic” and “methacrylic”.

The concentration of the polymerizable monomer contained in the polymerizable monomer-containing liquid used in the present invention can be appropriately determined depending on the purpose. For example, in the case of a polymerizable monomer-containing liquid containing an aliphatic unsaturated carboxylic acid or its salt as a main component, the concentration of the polymerizable monomer is preferably 20% by weight or more, more preferably 25% by weight or more. preferable. When the concentration is less than 20% by weight, it is difficult to generate droplets having an appropriate viscosity, and it tends that the water absorbing ability of the water absorbing polymer after polymerization cannot be sufficiently obtained. From the viewpoint of handling the polymerization reaction liquid, the upper limit is preferably about 80% by weight.

The polymerizable monomer-containing liquid used in the present invention may contain a crosslinking agent. For example, an aliphatic unsaturated carboxylic acid or a salt thereof, especially acrylic acid or a salt thereof may form a self-crosslinking polymer by itself, but when a crosslinking agent is used together, a crosslinked structure can be positively formed. it can. In addition, when a crosslinking agent is used in combination, the water absorption performance of the water absorbent polymer that is generally formed is improved. As the cross-linking agent, a divinyl compound copolymerizable with the above-mentioned polymerizable monomer, for example, N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol (meth) acrylate, etc., and a carboxylic acid capable of reacting 2 Water-soluble compounds having at least one functional group, for example, polyglycidyl ethers such as ethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether are preferably used. Of these, particularly preferred is
It is N, N'-methylenebis (meth) acrylamide. The amount of the cross-linking agent used is 0.001 to 1% by weight, preferably 0.01 to 0.5, with respect to the charged amount of the monomer.
% By weight. In addition, these cross-linking agents may be contained in the initiator mixed liquid. In addition to the above, in the polymerization method of the present invention, JP-A-9-255704 [0012] to [001] is also used.
It is also possible to use the materials described in [5].

The type of the polymerization initiator used in the polymerization method of the present invention is not particularly limited as long as it can initiate the polymerization of the polymerizable monomer. For example,
A thermal decomposition type polymerization initiator such as a peroxide such as benzoyl peroxide, acetyl peroxide, lauroyl peroxide, or an azo compound such as azobisisobutyronitrile can be used. In addition, the redox polymerization initiator as described above can be preferably used. As the redox-based polymerization initiator, it is generally preferable to use a combination of a radical generator exhibiting an oxidizing property and a reducing agent.

Examples of the oxidizing agent for the aqueous redox type polymerization initiator include persulfate and hydrogen peroxide.
Further, as a reducing agent for the water-based redox-based polymerization initiator,
Examples thereof include inorganic reducing agents such as ferrous salts and sodium sulfite, and organic reducing agents such as alcohols, amines and ascorbic acid. Examples of the oxidizing agent for the non-aqueous redox polymerization initiator include hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide, dialkyl peroxides, diacyl peroxides and the like. Further, as a reducing agent for the non-aqueous redox polymerization initiator, tertiary amines, naphthenates,
Examples thereof include mercaptans.

The oxidizing agent of the redox type polymerization initiator is 0.01 to 10% by weight, especially 0.1% by weight based on the polymerizable monomer.
It is preferable to use it in an amount of 2% by weight. Further, the reducing agent of the redox polymerization initiator is preferably used in an amount of 0.01 to 10% by weight, particularly 0.1 to 2% by weight, based on the polymerizable monomer. Regarding the polymerization initiator, in addition to the above, Takayuki Otsu “Revised Polymer Synthesis Chemistry”
(Chemical coterie) The materials and techniques described on pages 59 to 69 can also be used.

When a water-absorbent composite in which a water-absorbent polymer is fixed to a fibrous base material is produced using the polymerization method of the present invention, a sheet-shaped fibrous base material is fed into the polymerization chamber. It is preferable that the polymer particles falling in the course of polymerization are attached while moving this in parallel with the floor of the polymerization chamber. As the fibrous base material, any material may be used as long as it is formed in a certain shape and polymer particles in the process of polymerization are easily attached, and cloth, paper, pulp, non-woven fabric and the like can be used. Above all, it is preferable to use a fluff pulp or a non-woven fabric, in which the fibrous base material is roughly accumulated, the polymer particles can easily enter the inside, and the polymer particles can strongly adhere to the fibrous base material. Particularly preferred is a non-woven fabric made of (semi) synthetic fibers such as polyester, polyolefin, polyamide, acetate, etc., which has high strength even in a wet state. The fiber thickness of the fibrous base material forming the nonwoven fabric is preferably 10 to 50 μm, and the basis weight of the nonwoven fabric is preferably 10 to 100 g / m ² , and particularly preferably 20 to 50 g / m ² .

The polymerization rate at the time when droplets during polymerization are contacted in the gas phase or on the fibrous base material to form agglomerated particles is
Various conditions are set so as to be 3 to 97%, preferably 20 to 97%, and more preferably 50 to 95%. If the polymerization rate is too low, even if the liquid droplets collide with each other, they do not become aggregated particles and are integrated into large particles, or when the liquid droplets drop onto the fibrous base material, the liquid becomes a base material. It spreads over or is absorbed or impregnated to make it difficult to adhere to the fibrous base material in the form of agglomerated particles. If it is too high, the adhesive force with the substrate will not be developed, and the fixability between the fibrous substrate and the water-absorbent polymer will be poor.

The polymer particles are preferably attached to the fibrous base material so that the content of the polymer particles in the finally obtained water-absorbent composite is 50 to 400 g / m ² . Although it depends on the use, it is generally more preferable that the adhesion is 80 to 300 g / m ² . When the content of polymer particles in the water-absorbent composite is low, the water-absorbing ability is naturally low.
Further, if the content is too large, it is generally uneconomical, and the ratio of the portion bonded to the fibrous base material is reduced, so that the binding force to the fibrous base material is weakened.

At least some of the polymer particles constituting the water-absorbent composite produced by the production method of the present invention are bound to each other by the polymer particles (primary particles) in the process of polymerization to form agglomerated particles. It is preferable that a part of the polymer particles (primary particles) constituting the aggregated granules are not directly bonded to the fibrous base material. Since such agglomerated particles have a large specific surface area, they have a high water absorption rate,
Moreover, since only a part of the primary particles constituting the agglomerated granules are bonded to the fibrous base material, the constraint imposed by the fibrous base material when absorbing water and swelling is small, and the water absorbing ability is excellent. Further, since the bonding surfaces of the primary particles constituting the agglomerated particles are integrated, the agglomerated particles may collapse into primary particles and fall off from the fibrous base material not only before water absorption but also after water absorption. Few. It is preferable that 30% by weight or more of the polymer particles are agglomerated particles, and 50% by weight or more, particularly 80% by weight or more are agglomerated particles.
Generally, the larger the ratio of the agglomerated particles, the better the performance as a water absorbing material. The particle size of the agglomerated particles is substantially 100
It is preferably in the range of ˜3000 μm. Particle size is 10
If it is smaller than 0 μm, the water absorption performance tends not to be sufficiently exhibited. When the particle size is more than 3000 μm, the adhesive force to the sheet-shaped fibrous base material tends to be weak. The ratio and particle size of the agglomerated particles can be controlled mainly by appropriately adjusting the density, distribution state, flow state and the like of particles in the gas phase during polymerization. For example, in order to increase the ratio of agglomerated particles, the amount of falling polymer per unit cross-sectional area of the polymerization chamber should be increased or the polymerization chamber should be increased so that the chances of particles in the polymerization contacting each other during the fall increase. An ascending flow may be generated to slow down the falling speed of the polymer particles. Another method is to generate a drift in the polymerization chamber so that the distribution of the falling polymer particles is biased.

After applying the water-absorbent polymer to the fibrous base material, a water-absorbent composite can be obtained by appropriately performing a water content adjusting step, a surface cross-linking step, a residual monomer treatment step and the like.
The water-absorbent composite thus produced can be used in various applications where water-absorbent polymers have been used so far. "Water-absorbing polymers" 81-111 (Fusayoshi Masuda, Kyoritsu Shuppan, 1987), "Development trends of superabsorbent polymers and their applications" (Eizo Omori, Techno Forum, 19
87), Kenji Tanaka, "Industrial Materials" Vol. 42, No. 4, 18-25
Pp. 1994, Nobuyuki Harada, Tadao Shimomura, pp. 26-30, various uses of the water-absorbent polymer are introduced and can be used appropriately. Examples include paper diapers, sanitary products, freshness-retaining materials, moisturizers, cold-preserving agents, anti-condensation agents, and soil conditioners.

Furthermore, JP-A-63-267370, JP-A-63-10667 and JP-A-63-29.
5251, JP-A-270801, JP-A-6
3-294716, JP-A-64-64602, JP-A-1-231940, JP-A-1-243.
No. 927, Japanese Patent Laid-Open No. 2-30522, Japanese Patent Laid-Open No. 2-2522
No. 153,731, Japanese Patent Laid-Open No. 3-21385,
JP-A-4-133728, JP-A-11-1561
It can also be used for the application of the sheet-shaped water-absorbent composite proposed in Japanese Patent No. 18, etc.

[0047]

EXAMPLES The features of the present invention will be described more specifically below with reference to examples and comparative examples. Materials shown in the following examples,
The usage amount, ratio, processing content, processing procedure, etc. can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the following specific examples.

(Preparation of raw materials) 125 parts by weight of 80% by weight acrylic acid aqueous solution, 57.3 parts by weight of 48.5% by weight aqueous sodium hydroxide solution, 6.4 parts by weight of water, and N, N- as a crosslinking agent. Solution A was prepared by adding 0.15 part by weight of methylenebisacrylamide and 5.0 parts by weight of a 30% by weight aqueous hydrogen peroxide solution as an oxidizing agent. Solution A had a monomer concentration of 60% by weight and a degree of neutralization of 50 mol%.
Separately from this, 125 parts by weight of an 80% by weight aqueous acrylic acid solution was added to a 48.5% by weight aqueous sodium hydroxide solution 57.
Solution B was prepared by adding 3 parts by weight, 9.9 parts by weight of water, 0.15 parts by weight of N, N-methylenebisacrylamide as a crosslinking agent and 1.5 parts by weight of L-ascorbic acid as a reducing agent.
Was prepared. The monomer concentration and the degree of neutralization of solution B were the same as those of solution A.

(Examples 1 to 4) A double concentric spiral jet nozzle (Fig. 4) having the discharge port diameter shown in Table 1 was used, and the inner discharge port and the outer discharge port were each of the types of solutions shown in Table 1. Was supplied. The liquid temperature of each solution was 40 ° C., and jetting was performed using a pump at the flow rates and discharge pressures shown in Table 1. The solution A and the solution B collided and atomized near the outlet of the nozzle to form droplets, which dropped in the gas phase (in air, temperature 50 ° C.) while proceeding with polymerization. Part of the droplets collide in the gas phase to form agglomerated particles, and drop onto a polyester non-woven fabric base material (weight per unit area: 30 g / m ² ) installed 3 m below the tip of the discharge port of the nozzle, Polymerization was completed on the substrate. At the same time, a part of the droplets dropped onto the base material, and after forming agglomerated particles on the base material, the polymerization was completed on the base material. Through such a complexing step, the water-absorbing polymer was supported on the base material. The water content of the water-absorbent polymer carried on the substrate was 20 to 30% by weight. Further, an ethanol solution of 0.5% by weight of ethylene glycol diglycidyl ether (EGDGE) was sprayed on the composite so as to be 3000 ppm by weight with respect to the EGDGE-supported polymer (dry polymer base). The EGDGE ethanol solution-treated composite was further dried by a 110 ° C. hot air dryer until the water content of the polymer was 5% to obtain an absorbent composite having a polymer loading of 200 g / m ^2. It was

Comparative Example 1 Instead of the double concentric spiral jet nozzles of Examples 1 to 4, the opposed nozzle shown in FIG. 1 was used. Five pairs of nozzles through which the solution A flows out are arranged at 1 cm intervals, and five pairs of nozzles through which the solution B flows out are also arranged at 1 cm intervals. The nozzles from which the solution A flows out and the nozzles from which the solution B flow out face each other to form a total of five facing nozzle pairs. The inner diameter of each nozzle is 0.13m
The crossing angle between the solution A and the solution B flowing out from the facing nozzle was adjusted to 30 °, and the distance between the facing nozzle tips was adjusted to 4 mm. Solution A with a liquid temperature of 40 ° C.
And solution B were pumped so that the flow rate was 20 ml / min.

The solution A and the solution B merge at the point where they are jetted in a liquid column shape from the nozzles of the respective nozzle pairs, form a liquid column of about 10 mm each, and then become droplets in the vapor phase while proceeding with polymerization. (In air, temperature 50 ° C.), some of the droplets collide in the gas phase to form agglomerated particles,
It dropped onto a polyester non-woven fabric base material (Basis weight: 30 g / m ² ) installed 3 m below the tip of the nozzle outlet, and the polymerization was completed on the base material. At the same time, some of the droplets drop onto the base material to form agglomerated particles on the base material,
Polymerization was completed on the substrate. Through such a complexing step, the water-absorbing polymer was supported on the base material. The water content of the water-absorbent polymer carried on the substrate was 20% by weight. Then, the same treatments as in Examples 1 to 4 were carried out to obtain an absorbent composite having a water content of the polymer of 5% and a supported amount of the polymer of 200 g / m ² .

(Comparative Example 2) A slit type nozzle shown in FIG. 1 of JP-A-11-49805 was used instead of the double concentric spiral jet nozzles of Examples 1 to 4. Solution A
The width of each slit through which the solution B and solution B flow out is 0.05
The length was 10 mm, the length was 10 mm, the crossing angle of the solution A and the solution B flowing out from each of the facing slits was 30 degrees, and the distance between the tips of the facing slits was 10 mm. Using this opposing nozzle, the solution A and solution B having a liquid temperature of 40 ° C. have a flow rate of 150 m
It was supplied by a pump so that the flow rate was 1 / min. The solution A and the solution B were discharged from each slit in a liquid film form, but the liquid film width became shorter as the distance from the discharge port increased. At a position 2 cm from the discharge port, both liquid films collide with each other, atomize into droplets, and progress into polymerization while in the gas phase (in air, at a temperature of 50
(° C), some of the droplets collide in the gas phase to form agglomerated granules, and the polyester non-woven fabric base material is placed 3 m below the tip of the discharge port of the nozzle (Basis weight: 30 g / m ² )
It dropped to complete the polymerization on the substrate. At the same time, a part of the droplets dropped onto the base material, and after forming agglomerated particles on the base material, the polymerization was completed on the base material. Through such a complexing step, the water-absorbing polymer was supported on the base material. The water content of the water-absorbent polymer carried on the substrate was 30% by weight. Then, the same treatment as in Examples 1 to 4 was performed to obtain a polymer having a water content of 5% and a polymer loading of 200.
An absorptive composite of g / m ² was obtained.

(Evaluation) The water-absorbing composites obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were subjected to the following measurements. 1) Measurement of particle size The particle size of the absorbent polymer supported on the water-absorbent composite was measured using an optical microscope.

2) Measurement of water retention capacity of physiological saline solution The water-absorbent composite was cut so that the weight W1 of the water-absorbent polymer supported on the water-absorbent composite was 1 g, and a 250 mesh nylon bag (20 cm × 10 cm) was cut. In room temperature physiological saline (concentration 0.9% by weight) 500 ml 30
Soaked for a minute. Then, the nylon bag was pulled out, suspended for 15 minutes to drain water, and then dehydrated for 90 seconds at 90 G using a centrifuge. After dehydration, the weight W2 of the nylon bag was measured. Further, the non-woven fabric not supporting the water-absorbent polymer was cut into the same size as the water-absorbent composite, and the same operation was performed to measure the weight W3 after dehydration. The water retention capacity of physiological saline was calculated according to the following formula. Here, the units of W1 to W3 are all g.

[0055]

[Equation 1]

3) Calculation of manufacturing speed The supply speed Ra of the solution A supplied to the discharge port and the supply speed Rb of the solution B supplied to the discharge port are measured, and the sum thereof is 0.6 (60%) which is the monomer concentration. And the number of discharge port pairs n
The production rate was calculated by dividing by. The calculation formula is as follows. In Examples 1 to 4 using the double concentric spiral jet nozzle, the calculated production speed is the production speed per nozzle having one inner discharge port and one outer discharge port, and the counter nozzle is In Comparative Example 1 used and Comparative Example 2 using the slit type nozzle, the manufacturing speeds are for a pair of nozzles facing each other.

[0057]

[Equation 2]

[0058]

[Table 1]

As is clear from Table 1, in the examples in which the solution was jetted using the double concentric swirl jet nozzle so as to satisfy the conditions of the present invention, the water absorbency having a desired particle size and high water retention capacity was obtained. The complex could be efficiently produced. On the other hand, in Comparative Example 1 using the counter nozzle, the manufacturing efficiency was low, and when the slit type nozzle was used, the particle size and the water retention capacity were poor.

[0060]

According to the present invention, a high-quality polymer can be efficiently produced in a large amount by the droplet polymerization method even when a polymerizable monomer having a fast reaction rate is used. According to the present invention, it is possible to eliminate unevenness in the thickness of the liquid film, which is a problem of the slit type nozzle, and to manufacture a more homogeneous polymer.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a counter nozzle that has been conventionally used.

FIG. 2 is a diagram showing an example of a slit-type nozzle that has been conventionally used.

FIG. 3 is a diagram showing a state where liquid is ejected from a perfect circular opening at different speeds.

FIG. 4 is a sectional view showing a specific example of a double concentric spiral jet nozzle.

[Explanation of symbols]

1,11 Nozzle for first liquid 2,12 Nozzle for second liquid 3,13 1st liquid 4,14 second liquid 15 and 16 slits 21 First induction part 22 Second guiding part 23a, 23b introduction pipe 24 First circular opening 25 Second circular opening

Continued front page    (72) Inventor Shunichi Hinomori             1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Corporation             Ceremony company Yokkaichi office (72) Inventor Kiichi Ito             1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Corporation             Ceremony company Yokkaichi office F term (reference) 4J011 AC06 BB01 BB02 BB13                 4J015 CA01

Claims (8)

[Claims] 1. A first liquid and a second liquid are mixed in a gas phase,
A polymerization method of polymerizing in a droplet form, wherein a polymerizable monomer and a polymerization initiator are contained in at least one of the first liquid and the second liquid, respectively, and the first liquid and the second liquid. A polymerization method characterized in that at least one of the liquids is jetted into a gas phase so that a jetted cross section forms a liquid film having a closed curve shape. 2. The polymerization method according to claim 1, wherein at least one of the first liquid and the second liquid is jetted so that the jet cross section includes a curved portion. 3. The polymerization method according to claim 2, wherein at least one of the first liquid and the second liquid is jetted so that the jet cross section includes a curved portion having a constant radius of curvature. 4. Both of the first liquid and the second liquid,
The polymerization method according to any one of claims 1 to 3, wherein the ejection is performed so that the ejection cross section forms a liquid film having a closed curve shape. 5. The first liquid and the second liquid are ejected so that a closed curve that is the ejection cross section of the first liquid is formed inside a closed curve that is the ejection cross section of the second liquid. The polymerization method according to claim 4, wherein 6. A closed curve which is a jetting cross section of the first liquid,
The polymerization method according to claim 4 or 5, wherein the injection liquid has a closed curve similar to the jetted cross section of the second liquid. 7. The polymerization method according to claim 6, wherein the center of gravity of the closed curve that is the ejection cross section of the first liquid and the center of gravity of the closed curve that is the ejection cross section of the second liquid are on the same axis. . 8. The polymerization initiator comprises an oxidizing agent and a reducing agent, which are redox polymerization initiators, and the polymerizable monomer, the oxidizing agent, and the reducing agent are contained in at least one of the first liquid and the second liquid, respectively. The polymerization method according to claim 1, wherein the polymerization method is included.