JPH06211904A - Spray polymerization and spray polymerization nozzle - Google Patents

Abstract

PURPOSE:To provide a spray polymn. method and a spray polymn. nozzle which can improve the extent of mixing of the feedstock solns. in spray polymn. of a monomer in the form of a soln. contg. an org. unsatd. carboxylic acid or a salt thereof as the main component in the presence of a redox polymn. initiator, and hence can provide a product improved in quality. CONSTITUTION:A method for spray polymn. of a monomer in the form of a soln. contg. an org. unsatd. carboxylic acid or a salt thereof as the main component in the presence of a redox polymn. initiator, which comprises feeding a first soln. prepd. by adding either one of an oxidizing agent and a reducing agent constituting the redox polymn. initiator to the monomer soln. to a nozzle for the first soln., feeding the other one of the oxidizing agent and the reducing agent as a second soln. with or without addn. thereto of the monomer soln. to a nozzle for the second soln., and ejecting the first and second solns. from the respective nozzles in such a way that they collide with each other in the form of respective soln. columns at an angle of at least 15 deg. between the direction of ejection of the first soln. and the direction of ejection of the second soln, to effect a polymn. reaction in a vapor 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 crushing. A gas phase polymerization method has been proposed as a method capable of omitting or simplifying the subsequent steps.

Japanese Examined 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 salt or an 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,
A highly water-absorbent resin is obtained by spraying in a gas phase at 40 to 180 ° C. using an atomizer and a spray nozzle (pressure nozzle).

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, JP-A-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.

As a method for solving such problems and preventing polymerization in a sprayer and enabling continuous operation for a long time, the present inventors have used an organic unsaturated carboxylic acid or its salt as a main component. When spray-polymerizing a monomer solution using a redox-type polymerization initiator, the first liquid, in which one of the oxidizing agent and the reducing agent constituting the redox-type polymerization initiator is added to the monomer solution, is the first liquid nozzle. The other of the oxidizing agent and the reducing agent is supplied to the second liquid nozzle as the second liquid with or without addition of the monomer solution, and the first and second liquid nozzles at the outlets of the first and second liquid nozzles. It was proposed that the liquid and the second liquid be jetted so as to be mixed to carry out the polymerization reaction in the gas phase. (Japanese Patent Application No. 3-324005).

[0008]

DISCLOSURE OF THE INVENTION The present invention is disclosed in Japanese Patent Application No. 3-324005, in which a monomer solution containing an organic unsaturated carboxylic acid or a salt thereof as a main component is spray-polymerized by using a redox polymerization initiator. The present invention relates to a further improvement of the described invention, and to provide a spray polymerization method and a spray polymerization nozzle in which the mixing degree of raw material liquids respectively flowing out from two nozzles is improved and a product with improved quality is obtained. With the goal.

[0009]

The spray polymerization method according to the present invention uses a redox system when a monomer solution containing an organic unsaturated carboxylic acid or a salt thereof as a main component is spray polymerized using a redox system polymerization initiator. The first liquid obtained by adding one of the oxidizing agent and the reducing agent constituting the polymerization initiator to the monomer solution is supplied to the first liquid nozzle, and the other of the oxidizing agent and the reducing agent is added with the monomer solution. The second liquid is supplied to the second liquid nozzle as a second liquid without being added, and the first liquid and the second liquid flowing out from the first and second liquid nozzles have respective outflow directions at an angle of 15 degrees or more. It is characterized in that it is ejected so as to collide in a liquid column state to cause a polymerization reaction in a gas phase. Further, the nozzle for spray polymerization of the polymerizable monomer is characterized by comprising two liquid nozzles installed such that the extension lines of the nozzle intersect at an angle of 15 degrees or more.

As a monomer solution for producing a 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 the organic unsaturated carboxylic acid or its salt 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 is polymerized 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 water vapor.
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.

When it is considered that the polymerization reaction is almost completed before the liquid drops are dropped into the gas phase until they drop, the dropping time 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, when a monomer solution containing an organic unsaturated carboxylic acid or a salt thereof as a main component is subjected to spray polymerization using a redox type polymerization initiator, it is reduced with an oxidizing agent constituting the redox type polymerization initiator. One of the agents added to the monomer solution is used as the first solution, and the other of the oxidizing agent and the reducing agent is the second solution without addition of the monomer solution or addition of the monomer solution. To use as. The first liquid and the second liquid are jetted from separate nozzles so that the respective outflow directions are at an angle of 15 degrees or more and collide in a liquid column state. In this way, by making the outflow directions of both solutions collide with each other at an angle, a part of the outflow energy from the nozzle is utilized for mixing. The first and second intersecting angles flowing out from the respective nozzles are appropriately selected according to the properties of the raw material monomer solution used, the flow rate ratio, and the like. For example, the angle can be reduced if the linear velocity of the liquid is high. To obtain a sufficient mixing effect, it is necessary to have an angle of 15 degrees or more, and a particularly preferable angle is 20 degrees or more. The upper limit is not particularly limited as long as the liquid column can be formed after the collision of the first liquid and the second liquid, but it is 120 degrees or less, particularly preferably 100 degrees or less as an industrial apparatus. Further, the first liquid and the second liquid discharged from the respective nozzles need to collide in a liquid column state so that the two liquids merge to form a liquid column. By colliding in a liquid column state as described above, the liquids can be mixed at a set flow rate ratio, and the polymerization reaction is favorably performed. When the first liquid and the second liquid are made into particles and then caused to collide with each other, the mixing ratio differs from the set flow ratio, and it is difficult to obtain a desirable result.

A study on the length (L) of the liquid column flowing out of the nozzle has been conducted, for example, by Takahashi et al. (Chemical Engineering, Vol. 36, p. 527, 1972), L: length of liquid column ( cm) D ₀ : inner diameter of nozzle (cm) a ₀ : inner radius of nozzle (cm) δ ₀ : initial amplitude of surface turbulence (cm) ρ: liquid density (g / cm ³ ) u ₀ : liquid flow velocity (cm / sec) ) Σ: liquid surface tension (dyne / cm) μ: liquid viscosity (g / cm · sec), when D ₀ <0.3 cm, L / D ₀ = ln (a ₀ / δ ₀ ) [(ρD ₀ u ₀ ² / σ) ^0.5
+3 μu ₀ / σ]. However, Z (Ohnesorge number) = μ / (ρD ₀ σ) ^0.5 > 0.
In the case of 015, ln (a ₀ / δ ₀ ) = 12 Z (Ohnesorge number) = μ / (ρD ₀ σ) ^0.5 ≦ 0.
When 015, ln (a ₀ / δ ₀ ) = 6.5Z ^−0.15 . In designing the nozzle for spray polymerization of the polymerizable monomer of the present invention, the distance from the outlets of the two nozzles to the position where the extension lines of the nozzles intersect is set to be the length L of the liquid column or less.

As shown in FIG. 1, an example of the spray polymerization nozzle of the polymerizable monomer of the present invention is provided with two liquid nozzles 1 and 2 separately, and the extension line thereof is 15 degrees or more. It is composed of two liquid nozzles installed so as to intersect at an angle of. As shown in FIG. 2, another example of the spray-polymerizing nozzle for the polymerizable monomer of the present invention has two liquid nozzles 1 and 2 in a nozzle block 3 whose extension lines are 15 It is installed so that it intersects at an angle of more than one degree. Further, the distance between the nozzle tips can be freely set within a range in which the fluid can collide in a liquid column state, and the nozzle tips may be in contact with each other.

The particle size of the sprayed droplets, and thus of the polymerized resin, is controlled, for example, by changing the inner diameter of the nozzle. When the linear velocity of the liquid in the nozzle is high, the smaller the inner diameter, the narrower the liquid column that emerges from the nozzle, and the smaller the diameter of the liquid droplets. The inner diameter of the nozzle may be appropriately selected depending on the properties of the raw material monomer solution used, the size of the intended polymerization product, and the like. Preferably 0.1-2.0 mm,
More preferably, it is in the range of 0.15 to 1.0 mm.

As described above, in the present invention, the first liquid and the second liquid that have flowed out from the respective separate nozzles are mixed by colliding at a specific crossing angle and in a liquid column state, and the resulting droplets are mixed. By carrying out the polymerization reaction in the gas phase, the degree of mixing of the raw material liquid can be improved, and a product with improved quality can be manufactured.

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

[0020]

[Preparation of Monomer Solution] 80% by weight acrylic acid aqueous solution 1
In 25 parts by weight, 65.1 parts by weight of a 42.6% by weight sodium hydroxide aqueous solution, 0.1 part by weight of a cross-linking agent (N, N'-methylenebisacrylamide), and 30 parts by weight as an oxidizer.
Solution A was prepared by adding 5.6 parts by weight of a hydrogen peroxide aqueous solution of 10% by weight.
Was prepared. Solution A had a monomer concentration of 60% by weight and a degree of neutralization of 50 mol%. Separately, 125 parts by weight of 80% by weight acrylic acid aqueous solution, 67.1 parts by weight of 41.4% by weight sodium hydroxide aqueous solution and a cross-linking agent (N, N'-).
Solution B was prepared by adding 0.1 part by weight of methylenebisacrylamide and 1.34 parts by weight of 1-ascorbic acid as a reducing agent. The monomer concentration and the degree of neutralization of solution B were the same as those of solution A.

The monomer reaction rate was calculated from the ratio of the monomer and polymer in methanol by collecting the falling droplets in methanol in order to immediately stop the polymerization reaction in the droplets 5 m below the nozzle. . The water absorption of the polymer was calculated from the ratio between the weight of the swollen polymer and the weight of the polymer initially charged after directly collecting the droplets and vacuum-drying and then charging the polymer in deionized water.

[0022]

[Comparative Example 1] 2 having an inner diameter of 200 μm having the structure shown in FIG.
Two nozzles are installed side by side, and a binding type nozzle (the crossing angle of the effluent from each nozzle is 0 degree) in which the tip positions of both nozzles are aligned is used. Liquid B is discharged from the nozzle at a flow rate of 2 m /
It was supplied by a pump so that it would be seconds. The liquid A and the liquid B merged at the exit of the nozzle to form a liquid column for about 10 mm, and then dropped as a droplet in a rising stream of nitrogen (70 ° C.). The reaction rate and water absorption rate of the collected droplets were measured by the methods described above. The results are shown in Table 1 and FIG.

[0023]

Comparative Example 2 The same operation as in Comparative Example 1 except that two nozzles having the structure shown in FIG. 1 and an inner diameter of 200 μm were used, the angle between the nozzles was 10 degrees, and the distance between the tips of the nozzles was 1 mm. And obtained the data. The results are shown in Table 1 and FIG.

[0024]

[Examples 1 to 4] Data was obtained by performing the same operation as in Comparative Example 1 except that the same nozzles as in Comparative Example 2 were used and the internozzle angles were set to 20, 30, 40 and 50 degrees. It was The results are shown in Table 1 and FIG.

[Table 1]

From the results shown in Table 1 and FIG. 4, it can be seen that when the angle between the nozzles is 15 degrees or more, both the reaction rate and the water absorption rate rise sharply.

[0026]

EFFECTS OF THE INVENTION Since the first liquid and the second liquid are efficiently mixed at a set flow rate after flowing out from their respective nozzles, it is expected that the spray polymerization time will be shortened and the uniformity of products will be improved. It

[Brief description of drawings]

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

FIG. 2 is a diagram showing another example of a nozzle structure for carrying out the present invention.

FIG. 3 is a bundling type nozzle used in Comparative Example 1 in which two nozzles are installed side by side and the tip positions of both nozzles are aligned.

FIG. 4 is a diagram showing a reaction rate and a water absorption rate of super absorbent polymers obtained in Examples and Comparative Examples.

Claims (2)

[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 first liquid and the second liquid that are supplied as liquid to the second liquid nozzle and flow out from the first and second liquid nozzles collide with each other at an angle of 15 degrees or more and in a liquid column state. The spray polymerization method is characterized in that the polymerization reaction is carried out in the gas phase by jetting as described above. 2. A nozzle for spray polymerization of a polymerizable monomer, comprising two liquid nozzles installed so that extension lines of the nozzles intersect at an angle of 15 degrees or more.