JP2001131205A - Method of charging ethylenically unsaturated monomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of charging an ethylenically unsaturated monomer which can reduce undesired adhesion and residues of the water-soluble ethylenically unsaturated monomer and can prevent undesired adhesion and growth of a polymer of the ethylenically unsaturated monomer. SOLUTION: An aqueous solution comprising an ethylenically unsaturated monomer is charged via an inlet 15c into a mixing tower 15. A spray 30a starts to spray water 30b continuously to the inner surface of the mixing tower 15 before or when the monomer aqueous solution is charged. The mixing tower 15 comprises the first mixing part also used as a cyclone chamber and the second mixing part also used as a charging tube which follows the first mixing part, and an intermittent flow of water starts to be supplied from above to the outer surface of the second mixing part before the monomer aqueous solution is charged through a nozzle 15a into a polymerization chamber 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing a water-absorbing polymer (synonymous with a water-absorbing resin or a hydrophilic polymer) by, for example, polymerizing a water-soluble ethylenically unsaturated monomer. . More specifically, the solution containing the ethylenically unsaturated monomer is supplied to an inert gas defoamer (gas remover), a mixer for mixing a polymerization reaction initiator, a polymerization section, and the like. It relates to the method of charging.

[0002]

2. Description of the Related Art Water-absorbing polymers have been applied to a wide variety of applications such as absorbents for sanitary articles such as sanitary articles and disposable diapers; drip absorbents; These water-absorbing polymers are produced by polymerizing a hydrophilic monomer (for example, a water-soluble ethylenically unsaturated monomer) as a raw material in a batch system or a continuous system. The ethylenically unsaturated monomer (hereinafter, simply referred to as a monomer in some cases) is usually subjected to a polymerization reaction as a solution containing the monomer (hereinafter, referred to as a monomer solution).

For example, when the above monomers are polymerized in a continuous manner, 1) In a mixing tower (mixer), a charged monomer solution is mixed with a polymerization reaction initiator (hereinafter, referred to as a polymerization initiator). Then, 2) the monomer solution mixed with the polymerization initiator is introduced into the upper surface of the conveyor belt provided in the polymerization section via the introduction pipe forming the lower end of the mixing tower. Thereby, a monomer as a monomer solution is charged and polymerized in a continuous manner.

When the above monomers are polymerized in a batch system, a) a monomer solution is charged into a polymerization vessel such as a stainless steel vat or a kneader provided in a polymerization section via a charging pipe. In the polymerization vessel, the monomer solution and the polymerization initiator are mixed. Alternatively, b) after the monomer solution and the polymerization initiator are mixed in the mixing tower, this is charged into the polymerization vessel via a charging pipe forming the lower end of the mixing tower. Thereby, the monomer as a monomer solution is polymerized in a batch system.

[0005]

However, regardless of the above-mentioned batch type or continuous type, when the monomer solution is subjected to the polymerization reaction, there are places where the monomer solution tends to stay or scatter due to its structure. For example, the mixing tower or the charging pipe usually has an inner area from the top to the bottom (here, refers to an area of a region surrounded by an intersection formed by an inner surface of the mixing tower or the charging pipe and a plane perpendicular to a vertical line). ) Is reduced, and the monomer solution is likely to stay. Further, the monomer solution may be scattered and adhere to the outer surface of the charging tube. As described above, when the monomer solution stays and scatters, there is a possibility that a polymer of the monomer is formed there. This problem is particularly likely to occur when the monomer solution is highly concentrated and viscous.

[0006] As described in JP-A-61-126103, a monomer solution containing an ethylenically unsaturated monomer is inhibited from polymerizing by dissolved oxygen in the monomer solution. Therefore, the monomer solution is usually
After an inert gas is supplied to remove dissolved oxygen, it is subjected to a polymerization reaction. However, the monomer solution from which dissolved oxygen has been removed is liable to cause an undesired polymerization reaction due to conditions such as stirring, application of external stimulus such as light, mixing of impurities, and high concentration of monomer. Things are easily formed.

As a result, the above-mentioned conventional batch type, and
In a conventional method of charging a monomer solution employed in a continuous manner, for example, 1) a polymer of a monomer is placed in the vicinity of an opening (inner surface and outer surface) of a charging tube for supplying the monomer solution to the polymerization section. The problem of adhesion and growth occurs. Also, 2) in the mixing column where the monomer solution and the polymerization initiator are mixed,
There is a problem that the polymer adheres and grows.

The polymer adhered and grown is, for example,
1) Blocking the flow of the monomer solution. In addition, 2) it is mixed as a foreign substance into the monomer solution, and deteriorates the physical properties of the produced water-absorbing polymer. Further, 3) waste of monomers as a raw material of the water-absorbing polymer is also caused. These issues are
This is particularly important when performing continuous polymerization at an industrial level.

The present invention has been made to solve the above problems, and an object of the present invention is to reduce the undesired adhesion and residue of a water-soluble ethylenically unsaturated monomer, It is an object of the present invention to provide a method for charging an ethylenically unsaturated monomer, which can prevent undesirable adhesion and growth of a polymer of an unsaturated monomer.

[0010]

According to the present invention, there is provided a method for charging an ethylenically unsaturated monomer, comprising: a charging port for charging a solution; and a charging port positioned below the charging port. A step A of charging a solution containing a water-soluble ethylenically unsaturated monomer to a container formed with a discharge port for discharging the charged solution, and simultaneously with the step A, or Prior to the step A, a step B of supplying water to at least a part of a region on the inner surface of the container where the solution comprising a water-soluble ethylenically unsaturated monomer comes into contact. It is characterized by:

The method for charging an ethylenically unsaturated monomer according to the present invention further solves the above-mentioned problem by providing a method for forming a region surrounded by an intersection formed by an inner surface of the container and a plane perpendicular to a vertical line. The one having the smallest area is located on a plane including the outlet.

[0012] In order to solve the above-mentioned problems, the method for charging an ethylenically unsaturated monomer according to the present invention further comprises a region surrounded by an intersection formed by an inner surface of the container and a plane perpendicular to a vertical line. The one having the smallest area is located below the plane including the inlet and above the plane including the outlet.

[0013] In the method of charging an ethylenically unsaturated monomer according to the present invention, in order to solve the above-mentioned problems, the container may be provided with the solution containing a water-soluble ethylenically unsaturated monomer. It is characterized in that it comprises a mixer for mixing with a polymerization reaction initiator.

[0014] In the method for charging an ethylenically unsaturated monomer according to the present invention, in order to solve the above-mentioned problems, the container may be added to the solution containing a water-soluble ethylenically unsaturated monomer. It is characterized by comprising a gas remover for removing the supplied inert gas.

According to the method for charging an ethylenically unsaturated monomer according to the present invention, a solution containing a water-soluble ethylenically unsaturated monomer is polymerized from a charging tube. Water is added to at least a part of an area of the inner surface of the inlet tube and / or the outer surface where the solution comes into contact at the same time as or before the step C of charging into the part and the step C or prior to the step C. And supplying step D.

In order to solve the above-mentioned problems, the method for charging an ethylenically unsaturated monomer according to the present invention further comprises the step of: And a transporting means for transporting the solution in a continuous manner is provided, and the introduction of the solution onto the upper surface of the transporting means is performed within a loading height of 0.5 cm to 50 cm. .

The method for charging an ethylenically unsaturated monomer according to the present invention further comprises a step of charging a solution containing a water-soluble ethylenically unsaturated monomer, in order to solve the above-mentioned problems. Washing the solution.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Note that the present invention is not limited by this.

[Method of charging ethylenically unsaturated monomer] The method of charging the ethylenically unsaturated monomer according to the present invention comprises the steps of: preparing a solution containing a water-soluble ethylenically unsaturated monomer; A method for introducing the solution into the container or the polymerization section or the like, which is performed simultaneously with or prior to the step of introducing the solution into the container or the polymerization section. This is a method including a step of supplying water to at least a part of a region where the solution comes into contact with a charging pipe or the like charged into the polymerization section. In other words, when the solution containing the water-soluble ethylenically unsaturated monomer is charged, at least a part of the region where the solution comes into contact, before the solution comes into contact, or when the solution is The method comprises the step of supplying water simultaneously with contact. By supplying water in this manner, the area where the solution comes into contact is wetted,
It is possible to prevent the solution from adhering and remaining on the area.

In the present invention, the "ethylenically unsaturated monomer" is not particularly limited as long as it is a water-soluble ethylenically unsaturated monomer that can be used as a raw material of a water-absorbing polymer. Specifically, for example, acrylic acid, and
Methacrylic acid and salts thereof; acrylamide; methacrylamide; acrylonitrile; 2-hydroxyethyl (meth) acrylate; methyl acrylate;
Ethyl acrylate; methyl methacrylate; ethyl methacrylate; maleic acid; Among the ethylenically unsaturated monomers exemplified above, acrylic acid and its salts (more specifically, alkali metal salts such as Li, Na and K, ammonium salts and the like) are preferably used as main raw materials. You. These ethylenically unsaturated monomers may be used alone in the polymerization reaction, or two or more of them may be used as a mixture. Hereinafter, the ethylenically unsaturated monomer is simply referred to as a monomer in some cases. In the present invention, the water-absorbing polymer is a hydrogel produced by polymerizing the above-mentioned "ethylenically unsaturated monomer" unless otherwise specified, and the hydrogel is pulverized and / or dried. Is a generic name for granular gels, water-absorbing fine particles, etc. obtained by applying

The above monomer is charged as a solution containing the monomer (hereinafter, referred to as a monomer solution) into a container or a polymerization section described below. As the monomer solution,
An aqueous monomer solution is more preferred. The concentration of the monomer aqueous solution is not particularly limited, but is preferably 20% by weight (mass percentage) to 50% by weight, more preferably 30% to 45% by weight. When the concentration is 20% by weight or more, the strength of the obtained water-absorbing polymer can be reliably set to a practical value. Also, 5
When the content is 0% by weight or less, heat of reaction generated by the polymerization reaction can be easily removed, and the polymerization reaction can be reliably controlled.

It is more preferable that an inert gas is supplied to the monomer solution before it is subjected to a polymerization reaction to remove dissolved oxygen contained in the monomer solution. The inert gas supplied to the monomer solution is not particularly limited as long as it is not reactive with the monomer described above.Specifically, for example, nitrogen, argon, helium,
In some cases, carbon dioxide or the like is suitably used. Further, the method for supplying the inert gas to the monomer solution is not particularly limited, and specifically, for example,
1) A method in which an inert gas (or a monomer solution) is injected from a nozzle by an ejector or an aspirator, and the inert gas is continuously blown (continuously supplied) into a flow of the monomer solution (or an inert gas). A) a method of introducing an inert gas introduction tube into the monomer solution stored in the monomer tank and introducing the inert gas. The above exemplified methods may be used alone or in combination. Although the degree of removal of dissolved oxygen from the monomer solution is not particularly limited, the amount of dissolved oxygen in the monomer solution is more preferably 2 mg / l or less, further preferably 1 mg / l.

The above-mentioned container is a hollow member having a charging port for charging a monomer solution and a discharging port located below the charging port and discharging the charged monomer solution. The shape and the like are not particularly limited. Therefore, a hollow member having the same cross-sectional shape and area of the above-mentioned inlet port, outlet port, and container is also included in the category of the container. In addition, the above-mentioned container has a minimum area, which is a region surrounded by a line of intersection between an inner surface thereof and a plane perpendicular to a vertical line, and is located on a plane including the discharge port. And 2) a plane surrounded by an intersection formed by an inner surface thereof and a plane perpendicular to the vertical line and having a minimum area, is lower than a plane including the input port and includes a plane including the discharge port. Those located above are also included. As the container of the above 1) or 2), specifically,
For example, a mixer for mixing a monomer solution and a polymerization reaction initiator (hereinafter, referred to as a polymerization initiator); a gas remover such as a cyclone chamber for removing an inert gas supplied to the monomer solution; Can be.

The above-mentioned polymerization initiator is not particularly restricted but includes, for example, a redox initiator obtained by combining an oxidizing initiator and a reducing agent; a thermal decomposition initiator; a photopolymerization initiator; And the like. The polymerization initiators may be used alone or in combination of two or more. Further, the polymerization initiator may be used in the form of a solution such as an aqueous solution.

The above polymerization section is provided with means capable of polymerizing the above monomer in a continuous or batch system.
In the case of a continuous type, the means is a transfer means such as a transfer belt (preferably an endless type) or a drum dryer, and while continuously supplying (feeding) the monomer solution to the upper surface of the transfer means. Continuous static polymerization is performed.
In the case of a batch type, it is a polymerization vessel such as a stainless steel vat. Both charging of the monomer solution to the polymerization section,
This is done through the input pipe.

In the charging method of the present invention, as described above, at least a part of a region where the monomer solution comes into contact with, for example, 1) a container or 2) a charging tube for charging the monomer solution into the polymerization section. And supplying water.

The region of the above-mentioned container where the monomer solution comes into contact refers to the inner surface of the container. The region of the above-mentioned charging tube where the monomer solution comes into contact refers to the inner and outer surfaces of the charging tube. Point. The term "contact of the monomer solution" includes the case where the monomer solution scatters and comes into contact.

The timing at which the step of supplying water is performed is 1) before the solution comes into contact with the region, and 2) at the same time as the solution comes into contact with the region. This step may be performed at any one of the timings 1) and 2) or at both timings. 1)
In this case, a water film can be formed before the monomer solution comes into contact with the region, and it is possible to prevent the monomer solution from adhering and remaining on the region. Further, by performing at the timing of the above 2), the monomer solution that has come into contact with the above-mentioned region can flow off from the above-mentioned region together with water. In other words, when the above-mentioned region is the inner surface of the container, the monomer solution is discharged from the discharge port together with the water without adhering and remaining in the region. When the above-mentioned region is the inner surface of the charging tube, the monomer solution adheres to the region.
Without remaining, it is discharged out of the charging pipe together with water from the opening of the charging pipe (indicating a nozzle port or the like). Further, when the above-mentioned area is the outer surface of the charging pipe, the monomer solution is flowed down with the water together with the water without adhering and remaining in the area.

The method of supplying water is not particularly limited. Specifically, for example, 1) a method of spraying water on the above-mentioned area by using a spray or the like, and 2) a method of supplying water to the above-mentioned area. 3) A method of supplying water as a stream to the above-mentioned area, 4) A method of supplying water by cooling the inner surface of the above-described container or charging pipe and causing dew condensation on the inner surface. And the like. These methods may use only one kind, or may use two or more kinds in combination. Further, it is more preferable that these methods 1) to 4) are properly used depending on the area to which water is to be supplied. Specifically, for example, when water is supplied to the inner surface of the container or the outer surface of the charging pipe, the above 1) or 2) is used.
The method is more preferable, and when the water is supplied to the inner surface of the charging pipe, the method of 3) is more preferable. Even if the water is supplied intermittently to the area,
It may be supplied continuously.

In the above water, if necessary, additives such as a surfactant, a water-soluble salt, and the like, and a polymerization initiator; a deodorant; an antibacterial agent; a thickener; a chelating agent; Functional material can be included. In the water, if necessary, for example, a hydrophilic organic solvent such as various alcohols,
A water-soluble compound, an ethylenically unsaturated monomer, and the like can be included. The amount and type of the substance contained in the water are not particularly limited as long as adhesion and residue of the monomer solution can be prevented. The temperature of the water is not particularly limited as long as the polymerization of the ethylenically unsaturated monomer contained in the monomer solution is not induced, but is preferably in the range of 0 ° C to 50 ° C. Preferably, it is more preferably in the range of 5 ° C to 30 ° C.

When acrylic acid and its alkali metal salt (or ammonium salt) are used as the above-mentioned ethylenically unsaturated monomer, the neutralization ratio in the finally produced water-absorbing polymer (ie, The number of moles of the alkali metal salt (or ammonium salt) of acrylic acid / the number of moles of all monomers × 100 (%) is not particularly limited, but may be in the range of 0% to 90%. Preferably, 0%
More preferably, it is within the range of 80%. The neutralization ratio in the above water-absorbing polymer is adjusted by the mixing ratio of acrylic acid and its alkali metal salt (or ammonium salt) as a monomer to be subjected to the polymerization reaction, and may be adjusted after the polymerization reaction. It is possible. Specifically, for example, when a monomer having a neutralization ratio of 0% to 50% is used, the water-absorbing polymer (hydrogel) obtained by the polymerization reaction is treated with an alkali metal (or ammonium) carbonate or water. By treating with an oxide, the neutralization ratio in the water-absorbing polymer can be, for example, 55% to 80%.

According to the above-described method for charging an ethylenically unsaturated monomer, when a solution containing a water-soluble ethylenically unsaturated monomer is charged, at least one of the regions where the solution comes into contact with the solution. Before the solution contacts the part, or
Water is supplied as soon as the solution comes into contact. Therefore, it is possible to prevent undesired adhesion and residue of the monomer solution and adhesion and growth of the polymer of the monomer. As a result, for example, 1) the flow of the monomer solution can be smoothed, 2) the adhered and grown polymer is mixed as a foreign substance into the monomer solution, and the physical properties of the produced water-absorbing polymer are reduced. It is possible to eliminate the possibility of lowering, and 3) it is possible to efficiently use a monomer solution as a raw material of a water-absorbing polymer.

In addition, the above-mentioned charging method is particularly characterized in that: 1) a region surrounded by an intersection formed by an inner surface thereof and a plane perpendicular to the vertical line and having a minimum area is formed on a plane including the discharge port. And 2) a region having a minimum area surrounded by an intersection formed by the inner surface of the container and a plane perpendicular to the vertical line and having a minimum area is located below the plane including the input port, and This is effective when applied to a container located above a plane including the outlet. The reason is that, in such a container, the flow of the monomer solution is limited by the portion having the minimum area, and the monomer solution tends to stay in the container for a long time. Further, the charging method is particularly effective when performing continuous polymerization at an industrial level. Hereinafter, a more detailed description of the charging method of the present invention will be given in the description of the apparatus for producing a water-absorbing polymer to which the method is applied.

[Apparatus for Producing a Water Absorbent Polymer] Hereinafter, an apparatus for producing a water absorbent polymer to which the charging method according to the present invention is applied will be described with reference to the drawings.

As shown in FIG. 1, for example, the above-mentioned manufacturing apparatus includes a monomer tank 11 for storing a monomer as a raw material of a water-absorbing polymer as a solution thereof; an ejector 12 for supplying an inert gas; And an initiator tank 1 for storing an oxidizing initiator constituting a redox-based initiator, respectively.
3. Reducing agent tank 14 for storing a reducing agent forming a redox initiator; mixing the above-mentioned monomer and a polymerization initiator (including a redox initiator composed of an oxidizing initiator and a reducing agent) Mixing tower (mixer) 15; a transport belt (transporting means) for continuously transporting the monomer charged (supplied) into the polymerization machine 18 from a nozzle port (discharge port) 15a provided in the mixing tower 15 in the transport direction. ) 16. Mixing tower 1
A spray 30a is provided in the upper part of the inside 5 as a means for supplying water 30b connected to the water storage tank 30.
Incidentally, in the manufacturing apparatus shown in FIG.
Indicates 8.

In the monomer tank 11, the above monomer is
For example, as an aqueous solution (hereinafter referred to as an aqueous monomer solution)
The monomer aqueous solution is stored, and after the dissolved oxygen is removed by an inert gas (nitrogen gas) supplied from the ejector 12, the monomer aqueous solution is supplied to the mixing tower 15 via the monomer supply path 17 and the charging port 15c. (Step A). At the same time as or before the monomer aqueous solution is charged, the spray 30a starts continuous spraying of the water 30b onto the inner surface of the mixing tower 15 (step B).

As shown in FIG. 2, the mixing tower 15 includes: 1) a first mixing section (also serving as a cyclone chamber as a gas remover) in which a monomer aqueous solution flows along a spirally-shaped line 15b; 2) It is configured to include a second mixing section following the first mixing section. The first mixing section,
For example, the inner surface formed in a columnar shape and the inner surface formed in a truncated cone shape are combined, and the area of a region surrounded by an intersection formed by the inner surface and a plane perpendicular to the vertical line decreases as going downward. It is configured to be. The second mixing section is, for example, in the form of a thin tube having a constant cross section, and its lower portion is slightly bent with respect to the vertical line (more specifically, in the same direction as the transport direction of the transport belt 16). (Bent). That is, the mixing tower 15 is a region surrounded by an intersection formed by an inner surface thereof and a plane perpendicular to the vertical line and having a minimum area (a position above the bending position of the second mixing unit). The area surrounded by the intersection between the inner surface and the plane perpendicular to the vertical line) corresponds to a container located below the plane including the inlet and above the plane including the outlet.
In addition, as described below, the second mixing section also serves as a charging pipe for charging the monomer aqueous solution into the polymerization section.

In the first mixing section, the aqueous monomer solution supplied from the monomer supply path 17 through the inlet 15c flows along the line 15b, and a swirling flow of the aqueous monomer solution is formed. Thereby, the bubbles of the inert gas can be removed (defoamed) from the aqueous monomer solution. In parallel with the removal of the inert gas, an oxidizing initiator such as sodium persulfate (NaPs); and a polymerization initiator such as an azo initiator, if necessary, are added to the monomer aqueous solution. It is supplied and mixed via supply paths 13a.

Meanwhile, in the mixing tower 15, at the same time as or before the monomer aqueous solution is charged as described above, the spray 30a starts spraying the water 30b on the inner surface thereof. Therefore, it is possible to prevent adhesion and residual of the aqueous monomer solution and adhesion and growth of the monomer polymer in the first mixing section also serving as the cyclone chamber.

The monomer aqueous solution from which the inert gas has been removed and the oxidizing initiator and the like have been mixed are subsequently introduced into the second mixing section. In the second mixing section, for example, L-ascorbic acid (L-
A) The reducing agent such as A) is supplied via the reducing agent supply passage 14a.
Line mixed. Thereby, the monomer, the oxidizing initiator, and the reducing agent are mixed, and the polymerization reaction is started.
When a redox-based initiator containing an oxidizing initiator and a reducing agent is used as a polymerization initiator as described above, the supply and mixing of the reducing agent are performed in the first mixing section, and the oxidizing start is performed. The supply and line mixing of the agent may be performed in the second mixing section. Since the redox initiator functions only when the oxidizing initiator and the reducing agent are mixed, one of them is mixed from the cyclone chamber (first mixing unit), and the other is mixed with the cyclone chamber and the polymerization machine 18. (The second mixing section), the timing of the initiation of the polymerization reaction can be arbitrarily controlled.

Further, in the production apparatus shown in FIG. 1, for example, a redox-based initiator composed of a combination of persulfate, hydrogen peroxide, and L-ascorbic acid, and an azo-based initiator as a thermal decomposition type initiator (for example, , V-50; trade names manufactured by Wako Pure Chemical Industries, Ltd.) as the polymerization initiator, an oxidizing initiator (persulfate and hydrogen peroxide) and a thermal decomposition type initiator (azo And a reducing agent (L-ascorbic acid) in the second mixing section following the first mixing section. More preferred. When the above four components are mixed with the aqueous monomer solution as described above, it is possible to eliminate the possibility that the polymerization reaction starts in the first mixing section also serving as the cyclone chamber.

In other words, when the redox-based initiator and the thermal decomposition type initiator are continuously mixed into the aqueous monomer solution, the oxidizing initiator and the thermal decomposition type initiator are mixed from the first mixing section, and subsequently, It is more preferable that the reducing agent is line-mixed between the first mixing section and the polymerization machine 18 (second mixing section). Incidentally, the oxidizing initiator, the reducing agent, and the thermal decomposition initiator may be line-mixed with each other. Also in this case, it is preferable to mix the reducing agent last (more preferably, at a timing immediately before reaching the polymerization machine 18). In particular, as an initiator of the polymerization reaction, persulfate, hydrogen peroxide (both oxidizing initiator), as a reducing agent L- ascorbic acid (salt), 2,2 ^'- azobis (2-amidinopropane) Double When a hydrochloride (azo-based initiator) is used, the use of the above mixing method facilitates continuous production of a water-absorbing polymer at an industrial level.

Subsequently, the aqueous monomer solution introduced into the mixing tower 15 passes through a conveyor belt 16 provided in the polymerization machine 18 via a nozzle port 15a formed in the second mixing section also serving as a charging pipe. It is thrown into the upper surface of. At this time, at the same time as or before the monomer aqueous solution is charged into the polymerization machine 18 from the charging pipe (step C), 1) water 30b sprayed by the spray 30a is supplied to the inner surface of the charging pipe. 2) Water is intermittently supplied as a flow to the outer surface of the charging pipe by a water supply means (not shown) (step D). Therefore, adhesion and residual of the monomer aqueous solution and adhesion and
Growth is prevented.

The height at which the monomer aqueous solution is charged, that is, the shortest distance between the nozzle port 15a and the upper surface of the conveyor belt 16 is not particularly limited, but is preferably in the range of 0.5 cm to 50 cm. The input height is 0.5
cm or more, it is possible to eliminate the possibility that the aqueous solution of the monomer is scattered from the upper surface of the conveyor belt 16 and adheres to the leading end of the charging pipe. In addition, if it is 50 cm or less, for example, it is possible to eliminate the possibility that the droplets of the aqueous monomer solution scatter and adhere to the side wall of the polymerization machine 18 or the like.

The above-mentioned charging tube is bent in the same direction as the direction of transport of the aqueous monomer solution by the transport belt 16. This bent structure is: 1) In order to smoothly supply (supply) the monomer aqueous solution to the upper surface of the transport belt 16,
2) This is a structure for making the supply amount of the aqueous monomer solution to the upper surface of the conveyor belt 16 constant, but is not particularly limited to this structure. The supply amount of the monomer aqueous solution to the upper surface of the conveyor belt 16 (feed amount: equivalent to the liquid thickness when the width of the nozzle port 15a is fixed) is not particularly limited, but the liquid thickness is 1 mm to 50 mm. , More preferably within a range of 10 mm to 40 mm, and even more preferably within a range of 20 mm to 30 mm. When the liquid thickness is 1 mm or more, the production of the water-absorbing polymer can be performed at an industrial level. Further, when the liquid thickness is 50 mm or less, it is easy to remove reaction heat generated by the polymerization reaction, bumping during the polymerization reaction, increase in the soluble component contained in the obtained water-absorbing polymer, and water absorption. A decrease in the strength of the polymer can be prevented.

More specifically, the transport belt 16 is supported and supported by drive shafts 20 rotating at a constant speed in the same direction.
It is a driven endless type belt conveyor,
While being covered by the hood 41 provided above it,
It has been replaced with nitrogen. The upper surface of the transport belt 16 is
A certain area (cooling zone 1) located on the front side in the transport direction
8a) is cooled, and a certain area (heating zone 18b) located on the rear side in the transport direction is heated. The terms "heating" and "cooling" used herein are based on the temperature of the reaction system.

The method for cooling and heating the upper surface of the conveyor belt 16 is not particularly limited.
A method of cooling and heating the upper surface from the back side using a heater,
A method of cooling and heating the upper surface from the back side using a cold water shower or a hot water shower, and the like. When the upper surface is cooled from the back side using a cold water shower, the temperature of the cold water is not particularly limited, but is preferably in the range of 0 ° C to 30 ° C. When the upper surface is heated from the back side using a hot water shower or a heater,
The temperature of the upper surface after heating is not particularly limited, but is preferably 50 ° C or higher, more preferably 60 ° C or higher.

The transport belt 16 is passed through the nozzle port 15a.
The monomer charged on the upper surface is subjected to continuous static polymerization on the upper surface. The polymerization reaction on the upper surface of the conveyor belt 16 is performed in the cooling zone 18a under cooling conditions for a certain period of time, and subsequently, is performed in the heating zone 18b under heating conditions for a certain period of time. Thereby, the monomer aqueous solution subjected to the polymerization reaction is transported by the conveyor belt 16 to the polymerization machine 1.
The polymerization reaction is carried out while suppressing an excessive rise in the reaction temperature. Subsequently, a polymerization reaction and aging are performed while suppressing an excessive decrease in the reaction temperature, and a hydrogel (an embodiment of a water-absorbing polymer) 19 is produced.

Further, as shown in FIG. 1, near both ends in the width direction of the hydrogel 19 near the outlet of the polymerization machine 18,
Water 43 is dropped and supplied from the water dropping devices 42. This makes it possible to easily peel off the hydrogel 19 from the conveyor belt 16 without generating scratches or cuts (cracks) at both ends of the hydrogel 19. The hydrogel 19 peeled off from the conveyor belt 16 is supplied to a plurality of rotating rolls 40 provided between the polymerization machine 18 and the gel crusher 21.
Delivered to the roller conveyor composed of ... Below the rotating rolls 40, there is provided a water spraying device 44 for spraying water 45 upward, whereby the roll surfaces of the rotating rolls 40 and the hydrogel 19 supported by the roll surfaces are provided. Water is continuously supplied to the lower surface of the. As a result, it is possible to reduce the possibility that the hydrogel 19 sticks to the roll surface.

The hydrogel 19 carried into the gel crusher 21
Is crushed to a size of, for example, about 10 cm square. Subsequently, the crushed hydrogel 19 is granulated by a gel granulator 22 and has, for example, an average particle size of 0.5 mm to 3.0 mm.
mm granular gel (one form of a water-absorbing polymer). If necessary, the granular gel is further dried by a drier (not shown) and then finely pulverized by a mill-type pulverizer. For example, water-absorbing fine particles having an average particle diameter of 250 μm to 500 μm (one form of a water-absorbing polymer) It is said.

In the above polymerization reaction, a crosslinking agent may be used as required. The crosslinking agent is not particularly limited as long as it has two or more functional groups in the molecule and contributes to the formation of a crosslinked structure. By performing a polymerization reaction in the presence of a crosslinking agent, a water-absorbing polymer having excellent durability can be obtained. In some cases, a hydrogel (an embodiment of a water-absorbing polymer) obtained by a polymerization reaction may be used.
To form a crosslinked structure. In this case, an epoxy group having a reactivity with a functional group such as a carboxyl group of the hydrogel, an amino group, a hydroxyl group,
A crosslinking agent having two or more of these in a molecule is preferably used.

The method of the present invention is not limited to the application to the manufacturing apparatus shown in FIG. Specifically, for example, a mixer for mixing a monomer solution and a polymerization initiator, and a manufacturing apparatus in which a gas remover such as a cyclone chamber is separately provided, or one of the mixer and the gas remover The present invention can also be applied to a provided manufacturing apparatus or the like. Further, the present invention can be applied to a batch type manufacturing apparatus.

The method for charging an ethylenically unsaturated monomer of the present invention also includes a step of charging a solution containing a water-soluble ethylenically unsaturated monomer, and a step of washing the solution. The method may be. According to this method, various pipes (corresponding to the monomer supply path 17 in FIG. 1); an ejector, an aspirator; a mixer for mixing a monomer solution and a polymerization initiator; a charging pipe (monomer charging nozzle); In addition, in a region where the monomer solution comes into contact, it is possible to prevent the formation and deposition of a polymer and to produce a water-absorbing polymer at a stable and industrial level.

According to the method for charging an ethylenically unsaturated monomer of the present invention, a charging port for charging a solution and a discharging port located below the charging port and discharging the charged solution are further formed. Step A, in which a solution containing a water-soluble ethylenically unsaturated monomer is charged into the hollow member, and simultaneously with or before the step A, a water-soluble solution on the inner surface of the hollow member. A step B of supplying water to at least a part of the region where the solution containing the ethylenically unsaturated monomer of the above comes into contact.

The method for charging an ethylenically unsaturated monomer according to the present invention further comprises a region surrounded by an intersection formed by the inner surface of the hollow member and a plane perpendicular to the vertical line and having a minimum area. May be used when the ethylenically unsaturated monomer is charged into a hollow member located on a plane including the outlet.

The method for introducing an ethylenically unsaturated monomer according to the present invention further comprises a region surrounded by an intersection formed by the inner surface of the hollow member and a plane perpendicular to the vertical line and having a minimum area. But below the plane containing the input port,
Further, it may be used when the ethylenically unsaturated monomer is charged into a hollow member located above a plane including the outlet.

[0057]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 A water absorbing polymer was produced using the production apparatus shown in FIG. In this embodiment, the transport belt 16 is a stainless steel endless belt having a length of 24 m (that is, a distance between the centers of the drive shafts 20). Further, rubber side dams each having a height of about 5 cm are provided on both sides in the width direction of the conveyor belt 16, and the distance between the side dams is 60 mm.
cm. Conveyor belt 16
Is 1 m / min, and the cooling zone 18a
Is 15 m, and the length of the heating zone 18 b is 9 m. The cooling zone is cooled to 15 ° C. by a cooler, and the heating zone is heated to 70 ° C. by a heater.

As a raw material of the water-absorbing polymer, 65% neutralized sodium acrylate (ethylenically unsaturated monomer) was used. First, a 35% by weight aqueous solution of the sodium acrylate was prepared, and a solution obtained by adding polyethylene glycol diacrylate as a cross-linking agent to the aqueous solution in an amount of 0.04 mol per 1 mol of sodium acrylate as an aqueous monomer solution. It was supplied to the monomer tank 11. continue,
Nitrogen gas (inert gas) was supplied at 1 L / min from the nozzle by the ejector 12, and the nitrogen gas was continuously blown into the flow (0.95 L / min) of the monomer aqueous solution supplied from the monomer tank 11. . Thus, dissolved oxygen contained in the monomer aqueous solution was continuously removed. As a result, the amount of dissolved oxygen in the monomer aqueous solution is
0.3 mg / L.

The aqueous monomer solution was subsequently charged into the mixing tower 15. The mixing tower 15 is provided with a Teflon coating inside, and as shown in FIG. 2, 1) a first mixing section (also serving as a cyclone chamber) in which a monomer aqueous solution flows along a spiral line 15b. And 2) a second mixing section (also serving as a charging pipe) subsequent to the first mixing section. Further, in the mixing tower 15, the water 30 b is continuously sprayed at a rate of 10 ml / min from the spray 30 a during a period from immediately before the introduction of the monomer aqueous solution to the mixing tower 15 to the completion of the introduction of the monomer aqueous solution. Was done.

In the first mixing section, 0.5 mol% of 0.02 g was added to 1 mol of the sodium acrylate.
Aqueous sodium persulfate solution, 0.001 g of 0.14% by weight aqueous hydrogen peroxide (both oxidizing initiators)
0.5 wt% of 02G 2, 2 ^'- azobis (2-amidinopropane) dihydrochloride aqueous solution (thermal decomposition type initiator) was dropwise supplied different initiators tank 13 ... at the same time from each. Then, defoaming of nitrogen gas from the monomer aqueous solution by forming a swirling flow and mixing of the oxidizing initiator and the thermal decomposition initiator into the monomer aqueous solution were simultaneously performed.

The aqueous monomer solution exiting the first mixing section (also serving as a cyclone chamber) was introduced into the second mixing section (also serving as a charging pipe). In the second mixing section, 0.002 g of 0.2 mol / mol of the sodium acrylate was added.
A weight% L-ascorbic acid (reducing agent) aqueous solution was supplied from the reducing agent tank 14 and line-mixed with the monomer aqueous solution.

The aqueous monomer solution from which the nitrogen gas has been removed (defoamed) is supplied to a nozzle port (opening) 1 formed in the above-mentioned charging tube.
The liquid was continuously supplied to the upper surface of the transport belt 16 via the liquid supply line 5a so that the liquid thickness became 25 mm. At this time, the charged height of the aqueous monomer solution was about 1 cm. The inner and outer surfaces of the charging pipe are coated with Teflon, and an aqueous monomer solution is charged into the polymerization machine 18 from the charging pipe to the outer surface of the charging pipe located in the polymerization machine 18. Prior to this, water was being supplied from above as an intermittent flow.

On the conveyor belt 16, the polymerization of sodium acrylate started about 30 seconds after the introduction of the aqueous monomer solution, and reached a polymerization peak 9 minutes later. The peak temperature at this time was 85 ° C. As a result of continuing the polymerization reaction for another 15 minutes after the polymerization peak, a hydrogel (one form of a water-absorbing polymer) 19 was produced.

The water-containing gel 19 was supplied with water 43 at a rate of 5 ml per minute from the water dropping devices 42. The hydrogel 19 peeled off from the support surface of the conveyor belt 16 was subsequently transferred to a roller conveyor composed of a plurality of rotating rolls 40. Water 45 was sprayed from the water spraying device 44 at a rate of 10 ml per minute onto the roll surfaces of the rotating rolls 40 and the lower surface of the hydrogel 19 supported by the roll surfaces.

The hydrogel 19 carried into the gel crusher 21
Was crushed to a size of about 10 cm square. The crushed hydrogel 19 was then charged into a screw-type extruder (corresponding to a gel granulator 22) provided with spiral projections inside the body. Then, the hydrogel 19 was extruded from a perforated plate having a hole diameter of 9.5 mm provided in the screw-type extruder to granulate the hydrogel 19.

The granulated hydrogel 19, that is, the granulated gel was subjected to hot-air drying at 170 ° C. for 43 minutes, and then subjected to a roll mill (mill-type pulverizer) (not shown) to obtain a particle size of 850 μm.
m or less (not shown). continue,
The water-absorbing fine particles were classified with a sieve having a sieve of 150 μm, and particles having a particle size of 150 μm or less were removed. The average particle size of the water-absorbing fine particles obtained by the classification is about 300 μm
Met.

A surface cross-linking agent comprising 0.5 parts by weight of 1,4-butanediol, 0.5 parts by weight of propylene glycol, 1 part by weight of isopropyl alcohol, and 3 parts by weight of water with respect to 100 parts by weight of the above water-absorbing fine particles. Mix the solution
By performing a heat treatment at 195 ° C., water-absorbing fine particles subjected to a surface cross-linking treatment as one form of the water-absorbing polymer were obtained.

After the continuous operation of the above manufacturing apparatus for one week, the operation was terminated, and the manufacturing apparatus was observed.
As a result, in the cyclone chamber (first mixing section), neither sodium acrylate as a monomer (the solution thereof) nor adhesion of a polymer of the monomer was observed. The adhesion of the polymer was hardly observed on the outer surface and the inner surface of the charging tube.

Comparative Example 1 No water 30b was flowed from the spray 30a into the cyclone chamber (first mixing section), and no water was supplied to the outer surface of the charging pipe located in the polymerization machine 18. Except for the above, water-absorbing fine particles were produced in the same manner as in Example 1 above.

After the continuous operation of the above manufacturing apparatus for one week, the operation was terminated, and the manufacturing apparatus was observed.
As a result, adhesion of a white polymer of sodium acrylate was observed in the cyclone chamber and on the inner and outer surfaces of the charging tube.

[0072]

As described above, according to the method of charging an ethylenically unsaturated monomer according to the present invention, when a solution containing an ethylenically unsaturated monomer is charged, the solution is contacted with the solution. In the region where the polymerization occurs, it is possible to prevent the undesired adhesion and residue and the adhesion and growth of the polymer of the monomer. As a result, for example, 1) the flow of the monomer solution can be smoothed, 2) the adhered and grown polymer is mixed as a foreign substance into the monomer solution, and the physical properties of the produced water-absorbing polymer are reduced. It is possible to eliminate the possibility of lowering, and 3) it is possible to efficiently use a monomer solution as a raw material of a water-absorbing polymer.

More specifically, when the above-mentioned region is the inner surface of the container, the monomer solution is discharged to the outside of the container together with water without adhering to or remaining in the region.
When the above-mentioned area is the inner surface of the charging pipe, the monomer solution is discharged from the opening of the charging pipe together with water to the outside of the charging pipe without adhering and remaining in the area. Further, when the above area is the outer surface of the input tube, the monomer solution
Without being attached to or remaining in the area, the water is flowed down the inlet pipe together with the water.

[Brief description of the drawings]

FIG. 1 is a schematic constitutional view showing an example of an apparatus for producing a water-absorbing polymer to which the method of the present invention is applied.

FIG. 2 is an enlarged view showing a schematic configuration of a mixing tower (also serving as a cyclone chamber) provided in the manufacturing apparatus shown in FIG.

[Description of Signs] 15 Mixing tower (gas remover; mixer; input pipe; container; hollow member) 15a nozzle port (discharge port) 15c input port 16 transport belt (transport means) 18 polymerization machine (polymerization section) 30b water

Continuing from the front page (72) Inventor Koji Miyake 992, Nishioki, Okihama-shi, Abashiri-ku, Himeji-shi, Hyogo Nippon Shokuhin Co., Ltd. F-term in Nippon Shokubai (reference) 4J011 BB01 BB03 BB06 BB11 DA04 DB12 DB13 DB21 DB27

Claims (8)

[Claims] 1. A water-soluble ethylenically unsaturated monomer is provided in a container having an inlet for charging a solution and an outlet positioned below the inlet for discharging the charged solution. Step A, in which a solution containing water is added, and simultaneously with or before the step A, the solution containing a water-soluble ethylenically unsaturated monomer on the inner surface of the container is A step B of supplying water to at least a part of the contact area. 2. A region surrounded by an intersection formed by an inner surface of the container and a plane perpendicular to a vertical line and having a minimum area is located on a plane including the discharge port. The method for charging the ethylenically unsaturated monomer according to claim 1. 3. A region surrounded by an intersection formed by an inner surface of the container and a plane perpendicular to the vertical line and having a minimum area is lower than a plane including the input port and the discharge port. The method for charging an ethylenically unsaturated monomer according to claim 1, wherein the method is located above a plane containing: 4. The container according to claim 1, wherein said container comprises a mixer for mixing said solution containing a water-soluble ethylenically unsaturated monomer and a polymerization reaction initiator. 4. A method for charging the ethylenically unsaturated monomer according to any one of claims 3 to 3. 5. The container according to claim 1, wherein said container comprises a gas remover for removing an inert gas supplied to said solution containing a water-soluble ethylenically unsaturated monomer. The method for charging the ethylenically unsaturated monomer according to any one of claims 1 to 3. 6. A step C of charging a solution containing a water-soluble ethylenically unsaturated monomer into a polymerization section from a charging pipe, and simultaneously with the step C or prior to the step C, Supplying water to at least a part of a region on the inner surface and / or outer surface of the charging tube where the solution comes into contact, and a step D of supplying ethylenically unsaturated monomer. . 7. A transfer means for feeding the solution from the inlet pipe to the upper surface of the polymerization unit and continuously transferring the solution to the upper surface of the polymerization unit. 0.5cm of the above solution
The method for charging an ethylenically unsaturated monomer according to claim 6, wherein the charging is performed within a range of a charging height of about 50 cm. 8. A method for producing an ethylenically unsaturated monomer, comprising the steps of: introducing a solution containing a water-soluble ethylenically unsaturated monomer; and washing the solution. Input method.