JPS6055002A - Novel continuous polymerization - Google Patents

Abstract

PURPOSE:To improve the production rate and workability in the production of a crosslinked polymer, by effecting a radical aqueous solution polymerization which finely dividing, with a shearing force, a hydrated gel-like crosslinked polymer formed with the progress in polymerization and continuously discharging the formed polymer. CONSTITUTION:A polymerization initiator and an aqueous solution of a monomer which, when polymerized in an aqueous solution, forms a hydrated gel-like polymer by the formation of a crosslinking structure are continuously fed to a vessel having a plurality of rotary agitator shafts. The radical aqueous solution polymerization is effected while the hydrated gel-like polymer formed with the progress in polymerization is being finely divided with a shearing force by the rotation of the agitator shafts. The formed divided hydrated gel-like polymer is continuously discharged from the vessel. It is preferable that the aqueous monomer solution fed to the polymerization vessel has a concentration of 10-80wt%. It is necessary that the vessel has a plurality of rotary agitator shafts, and examples of these vessels include double-arm kneader and three-screw kneader.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel continuous polymerization method for crosslinked polymers.

Conventionally, crosslinked polymers mainly composed of acrylamide, acrylic acid, or their salts have been known to have the ability to absorb and retain large amounts of water, as well as have ion exchange and chelating abilities, and have been used for sanitary products and agricultural and horticultural purposes. It is used in a wide variety of applications, including soil conditioners, dehydrators, ion exchange resins, and adsorbents. Known methods for producing these crosslinked polymers include a method in which an aqueous monomer solution is polymerized by reverse phase emulsification or suspension in a hydrophobic solvent, and a method in which an aqueous monomer solution is subjected to cast polymerization. However, in the reverse-phase emulsion polymerization method and the reverse-phase suspension polymerization method, large amounts of organic solvents are handled, which is dangerous in terms of disaster prevention, and also poses problems for workers. On the other hand, the method of cast polymerization of an aqueous monomer solution is superior to the former in that it does not use an organic solvent, but the polymerization equipment becomes complicated and expensive due to the removal of reaction heat during polymerization. In addition, in order to remove water from the produced hydrogel polymer and obtain a dried crosslinked polymer, it is necessary to mechanically subdivide the hydrogel polymer to increase its surface area and dry it. . At this time, a method of mechanically dividing the hydrogel-like polymer (cutting,
There are methods such as extrusion, but in either case there are problems such as the need for a large amount of energy because the hydrogel polymer has strong rubber-like elasticity.

In order to solve the above-mentioned problems, the inventors of the present invention have made the following points in Japanese Patent Publication No. 57-34101, Specification 1. proposed a batch-type radical aqueous solution polymerization method using a container with multiple rotating stirring shafts.

With this method, we were able to significantly improve productivity and workability compared to conventional techniques, but the inventors of the present invention have conducted extensive research to further improve productivity and workability. This has led to the present invention.

That is, the present invention continuously supplies an aqueous solution of monomers and a polymerization initiator that form a crosslinked structure to a hydrogel polymer by aqueous solution polymerization into a container having a plurality of rotating stirring shafts,
11. Radical aqueous polymerization is carried out while fragmenting the hydrous gel-like polymer produced as the 11th reaction progresses using the shearing force generated by the rotation of the stirring shaft, and the resulting fragmented hydrogel-like polymer is continuously discharged from the container. The present invention relates to a novel continuous polymerization method characterized by discharge.

The monomer used in the present invention forms a crosslinked structure through aqueous polymerization and forms a crosslinked structure with the hydrogel polymer. The crosslinked structure consists of a water-soluble monomer and two polymerizable double bonds within the molecule.
A cross-linked structure formed by copolymerization with a cross-linkable monomer having at least 100% cross-linkable monomers may also be used, such as starch, cellulose, polyvinyl alcohol, etc. A crosslinked structure may be obtained by aqueous solution polymerization of a water bath monomer in the presence of an aqueous polymer to form a graft bond or a complex at the same time as the polymerization.

Examples of water-soluble monomers include acrylic acid and methacrylic acid and their alkali metal salts or ammonium salts, acrylamide, methacrylamide, acrylonitrile, 2-hydroxyethyl (meth)acryl/
methyl acrylate, maleic acid, etc., and one or more of these can be used.

Examples of crosslinking monomers include ethylene glycol,
Diethylene glycol, triethylene glycol, propylene glycol, 1.4-phthanediol, 1.5-
Bentanediol, 1,6-hexanediol, neopentyl glycol, diacrylate or dimethacrylate of trimethylolpropane and pentaerythritol, triacrylate or trimethacrylate of trimethylolpropane and pentaerythritol, tetraacrylate or tetramethacrylate of pentaerythritol Examples include acrylate, N,N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide, triallyl isocyanurate, etc., and one or more of these can be used.

= 5- Among such 12 compounds, in the present invention, one or more selected from the group consisting of acrylic acid and methacrylic acid, their alkali metal salts or ammonium salts, acrylamide, and methacrylamide. A monomer mixture consisting of a monomer and a crosslinkable monomer (B) having two or more polymerizable double bonds in the molecule, with a molar ratio of crosslinkable monomer 03) of 50 or less is particularly preferred. As the crosslinkable monomer (B), one type or two types of Fi from among the above crosslinkable monomers can be used. In this case, if the amount of crosslinkable monomer (1) used exceeds 50 molar ratio to monomer (5), the water absorbency and ion exchange ability of the resulting crosslinked polymer will be low.

Even when no cross-linking monomers are used, if a cross-linked structure is formed due to the use of a large amount of ammonium persulfate, etc., the continuous polymerization of the present invention can be carried out.

The aqueous monomer solution used in the present invention is continuously fed into the polymerization vessel, and preferably has a concentration of 10 to 80% by weight. If the concentration is within this range, the hydrogel-like polymer produced as the polymerization progresses will be easily fragmented by the shearing force caused by the rotation of the stirring shaft.

The container having a plurality of rotating stirring shafts used in the present invention is
It is necessary that the shearing force can be applied to the hydrogel-like polymer produced as the polymerization progresses when monomers are polymerized in aqueous solution by the rotation of the rotating stirring shaft. It is necessary to have a plurality of rotating stirring shafts, and such vessels include, for example, a double-arm kneader (hereinafter referred to as a simple kneader) and a three-shaft kneader.
Examples include devices such as: When using a kneader, two rotating stirring shafts are rotated in opposite directions at a constant or non-uniform speed. In the case of constant velocity, the rotation radius of the two rotating stirring shafts is 1! It is used in a state in which the stirring shafts have portions equal to r, and in the case of non-uniform speeds, the rotation radii of the two rotating stirring shafts do not overlap with each other. As the rotating stirring shaft, any of the Sigma type, S type, Banbury type, or emergency type can be used.

Further, when using a kneader, it is preferable to use one whose inner surface is coated with a fluororesin in order to prevent the produced gel from adhering. Examples of fluororesins include tetrafluoroethylene resin, tetrafluoroethylene-perfluoropropyl vinyl ether copolymer, tetrafluoroethylene-67fluoropropylene copolymer, trifluoroethylene chloride resin, and ethylene-4fluoroethylene resin. Polymerized ethylene copolymer or the like can be used.

The polymerization container used in the present invention preferably has a lid on top to maintain an inert atmosphere against radical polymerization reactions during polymerization, and the inside of the polymerization container is preferably purged with an inert gas. During polymerization, a reflux condenser may be provided at the top of the polymerization vessel to condense moisture that evaporates due to the heat of the polymerization reaction, or an inert gas may be introduced into the polymerization vessel to release moisture from the system. Good too. Further, it is preferable to provide a jacket in the polymerization container for the purpose of heating the monomer aqueous solution and removing part of the heat of polymerization reaction during polymerization.

In the present invention, as a mechanism for continuously and automatically discharging the fragmented hydrogel polymer out of the container, for example, as shown in FIG. 1 (5), a plurality of Those with rotary blades with one or more paddle-shaped blades attached to a horizontal shaft installed above the rotating stirring shaft: 2nd (A)
As shown in the figure, a reactor with a discharge screw at the bottom of the reactor, such as a three-screw kneader: As shown in Figure 3,
Overflow is caused simply by lowering a portion of the wall of the container; alternatively, a portion of the wall of the container is formed into a weir whose height is adjustable and overflow is caused intermittently by varying the height of the weir. etc.

Here, 'continuous' does not necessarily have to be strictly steady, and may be a state where the amount of discharge is pulsating or a state where the discharge is intermittently. That is, it is sufficient that the amount of the hydrogel polymer in the reaction vessel is kept approximately constant.

In the present invention, known water-soluble radical polymerization initiators can be used for radical aqueous solution polymerization of monomers.

For example, permic acid salts, hydrogen peroxide, water-soluble azo compounds, etc. can be mentioned, and these may be used alone, or they can be used together with sulfites, 9-hydrogensulfites, thiosulfates, L - Ascorbic acid, 1st
It may also be used as a redox initiator in combination with an iron salt or the like.

An example of the polymerization procedure according to the method of the present invention is to charge an aqueous monomer solution into a kneader having a lid and a discharge mechanism, purge the system with an inert gas such as nitrogen, and add a radical polymerization initiator. The hydrogel polymer produced as the polymerization progresses is fragmented by the shear force generated by the rotation of the kneader blades, and the monomer aqueous solution containing the polymerization initiator is continuously added. At the same time, in order to keep the amount of gel in the system almost constant, particles of the hydrogel polymer are discharged from the system by a discharge mechanism, and if necessary, the discharged hydrogel polymer particles are One example is a method of completing polymerization by heating the polymer.

Of course, the scope of the present invention is not limited by this example.

In this way, if polymerization is carried out based on the continuous polymerization method of the present invention, it is easy to continuously obtain particles of hydrogel-like polymer 10- which are finely divided and have a crosslinked structure in each particle. be able to.

Although the particle size varies depending on the reaction conditions, particles of 3 on or less can usually be obtained.

In the method of the present invention, the monomer is continuously supplied to the container and the produced hydrogel polymer is continuously discharged, resulting in extremely good workability. That is, 11
Compared to the monomer injection, polymerization, and discharge, which each require manual labor, the continuous system of the present invention has the advantage of not requiring manual labor after the reaction reaches a steady state.

In addition, in the method of the present invention, the finely divided hydrogel-like polymer present in the reaction vessel and the supplied aqueous monomer solution are uniformly mixed and polymerization occurs on the gel surface. Heat is generated uniformly over time, making it easy to remove the polymerization reaction heat and keep the temperature within the polymerization system constant. Therefore, it is possible to increase productivity by increasing the polymerization rate, and it is also easy to maintain constant product quality. Furthermore, it was an unexpected result that we were able to obtain a product with higher absorption capacity than the batch method. Furthermore, the particle size of the hydrogel-like polymer discharged is almost uniform, and there is also the effect that drying is easy. On the other hand, in the case of batch polymerization,
Since the heat of the polymerization reaction is released all at once, it is relatively difficult to remove the heat, which makes it difficult to increase the polymerization rate and increase productivity.Also, the quality of the product varies, and the absorption capacity is also relatively small.

Furthermore, the particle size of the finely divided hydrogel-like polymer is uneven, and some particles may be difficult to dry.

The method of the present invention is completely different from the method in which the material moves like a piston flow from the inlet to the outlet, as shown in, for example, JP-A-56-32514. It is uniformly mixed with the finely divided hydrogel polymer, and a part of it is discharged while polymerizing. Therefore, since the amount of the hydrogel polymer in the reactor is large compared to the calorific value, heat removal is easy.

On the other hand, in the above method where the material moves like a piston flow,
It is difficult to remove heat, so if you try to increase productivity, the temperature of the material will rise, which may lead to a decrease in performance.

The particles of the hydrogel polymer obtained by the polymerization method of the present invention can be used as absorbents, water retention agents, ion exchange resins, etc.
Although it is possible to use 11 in 17 with an adsorbent, it is preferable for handling to remove moisture by drying. The particles of the hydrogel polymer obtained by the polymerization method of the present invention have the advantage that they can be dried very easily. That is, the particles of the hydrogel polymer obtained by the present invention have a large surface area and can be easily dried in a short time by hot air drying.

The continuous polymerization method of the present invention has the advantage that a continuous heating device can be effectively used in place of the dryer and 17. That is, in the case of batch polymerization, a hopper or the like is required to connect to the continuous heating machine, but in the present invention, this is unnecessary.

In carrying out the present invention, the water-containing gel polymer discharged from the polymerization container may be heated prior to drying, thereby increasing the M (unit ratio). It is possible to connect the dryer with a continuous type 13- dryer.

Hereinafter, the method of the present invention will be explained in more detail with reference to Examples.

Example l Internal volume 21 shown in FIG. 1(A). Aperture 160+nmX
150mm, depth 135+n+n, two sigma-type stirring blades with a rotational diameter of 70mm, the wetted part is made of tetrafluoroethylene-perfluoropropyl vinyl ether copolymer lever.
A jacketed stainless steel double-arm lacquering machine (Nigu) was equipped with a discharge device and a lid, and in this Nigu, 75 moles of partially neutralized acrylic acid 399 y, N, which had been neutralized with caustic soda, was added. An aqueous monomer solution consisting of 0.036 r of N'-methylenebisacrylamide and 600 ml of water was introduced, and nitrogen gas was blown into the reaction system to purify the reaction system. Next, two sigma-type stirring blades were rotated at speeds of 67 and 56 rpm, respectively, and while heating 45°C hot water was passed through the jacket, V-so (manufactured by Wako Tsumugi Pharmaceutical Co., Ltd., 2.2'- Azobis (
2-amidinopropane) hydrochloride) 0.23
A solution of y in water]Or was added. Polymerization started 15 minutes after adding the polymerization initiator. The aqueous monomer solution produced a soft hydrogel as the polymerization progressed]7, and was gradually divided into smaller pieces by rotation of the stirring shaft. 35 minutes after the addition of the polymerization initiator, the temperature inside the reaction system reached 80°C. Here, the hot water passed through the jacket was heated to 94°C. Then 75
A monomer aqueous solution consisting of 14.36 kg of partially neutralized acrylic acid whose mol% had been neutralized with caustic soda, 1.3 F of N,N'-methylenebisacrylamide, and 21.6 kg of water was blown with 9 elemental gas. The solution from which dissolved oxygen had been removed and the solution containing V-508,29 dissolved in 360 cc of water were each sent to a mixing tank by a metering pump, and the uniformly mixed solution was fed into a kneader over 24 hours.

The monomer aqueous solution continuously supplied to the kneader became a finely divided hydrogel-like polymer and was continuously discharged by a discharge blade, and the temperature in the system was kept constant at approximately 90'C. The discharged hydrogel polymer was kept at 90° C. under a nitrogen atmosphere for another 20 minutes to complete the polymerization.

The discharged hydrogel polymer was finely divided into particles with a diameter of about 2 to 7 mm, and was smooth and easy to handle, and could be easily dried.

The discharged hydrogel polymer was placed on a 50-mesh wire gauze, dried in a hot air dryer at 150° C., and then pulverized in a vibrating pulverizer.

The obtained pulverized material (hereinafter referred to as absorbent (1)) has a 0.
22 is a non-woven tea bag type bag (40mm x 150
+el), immersed in 0.9% saline solution,
The weight after minutes was measured. The weight of only the tea pack type bag immersed was used as a blank, and the absorption capacity was calculated according to the following formula.

The results are shown in Table 1. The absorption capacity was determined for each pulverized product obtained from the hydrogel polymer sampled every 3 hours after the continuous supply of the monomer aqueous solution was started.

Table 1 ■ From these results, it can be seen that the crosslinked polymer obtained by the method of the present invention can be effectively used as an absorbent.

Example 2 Internal volume 10t1 opening 240x220 sections, depth 260
Rotational diameter of the fin and the tail is 11 (in a jacket-handed stainless steel triaxial kneader with two 1W+N Banbury-type stirring blades and one discharge screw with a diameter of 35 mm - Darruder)
The inner surface of the tube was coated with trifluoromonochloroethylene resin. This kneader was equipped with a %M amateur monomer introduction tube and a thermometer.

A monomer aqueous solution consisting of 1995% partially neutralized acrylic acid, 75% by mole of which had been neutralized with caustic soda, 3.3% trimethylolpropane triacrylate, and 3000f water was introduced into this kneader, and nitrogen gas was introduced into the kneader. was blown into the reaction system to purify it with nitrogen. Next, a Banbury-type stirring blade was rotated at a speed of 30 rpm, and 2.252 kg of ammonium persulfate and 2.259 kg of sodium bisulfite were added as polymerization initiators while heating the jacket by passing hot water at 40°C.

Polymerization started 15 minutes after adding the polymerization initiator.

As the polymerization progressed, the monomer aqueous solution produced a soft hydrogel, which was gradually divided into smaller pieces by rotation of the stirring shaft. 25 minutes after adding the polymerization initiator, the temperature inside the reaction system reached 90°C. Here, the hot water passed through the jacket was heated to 87°C. Next, nitrogen gas was blown into a monomer aqueous solution consisting of partially neutralized acrylic acid 359, in which 75 mol % had been neutralized with caustic soda, 9), trimethylolpropane triacrylate 594f, and water 540 K9. A solution from which oxygen had been removed, a solution of ammonium persulfate 4051F dissolved in 9 parts to 10 parts of water, and a solution of sodium hydrogen sulfite 4052 dissolved in 10 Kq of water were each fed into a Nigu over a period of 5 days. After starting the addition of the monomer, the rotation of the discharge screw was adjusted so that the needle of the hydrogel polymer staying in the kneader remained constant.

The drop mass aqueous solution continuously fed into the kneader was continuously discharged in the form of fragmented hydrogel-like aggregates, and the temperature in the system was constant at approximately 83°C.

The hydrogel-like polymer discharged by rotating the discharge screw is fed to a biaxial paddle feeder (■Nara Kikai Manufactured by K) heated through a jacket with 90°C hot water.
The heating was completed for 15 minutes with an average residence time. Then,
The hydrogel polymer discharged from the paddle feeder is
It was dried with hot air at 160°C in a continuous ventilation band dryer. The dried material was sampled once every half day from 1 to 1, and ground in the same manner as in Example], and the obtained pulverized product (hereinafter referred to as absorbent (2)).

The absorption capacity was measured. The results are shown in Table 2.

Table 2 Absorbent (2) was also excellent as an absorbent.

Example 3 In order to observe the behavior of a monomer aqueous solution that was continuously supplied, 0.2 y of a pink fluorescent pigment (trade name Kobocolor, manufactured by Nippon Shokubai Chemical Co., Ltd.) was degassed, and then an initiator was added. Example 1 Dispersed in the mixed monomer aqueous solution SCC
It was added during the continuous polymerization and its behavior was observed.

When the colored monomer aqueous solution was added, the entire system immediately turned pink. From this, the monomer aqueous solution is
It can be seen that it is uniformly mixed with the crushed hydrogel polymer and is thinly coated on the surface of the hydrogel polymer.

Subsequently, polymerization was continued while adding an uncolored monomer aqueous solution, and hydrogel-like polymer particles with a pink center and a transparent outside were obtained. From this, the hydrous gel-like polymer is crushed in the kneader, and the aqueous monomer solution is attached to its surface and polymerized7, thereby increasing the gel particle size, which is then crushed again. I understand.

Example 4 The upper side of the kneader used in Example 1 was 150 mm
It was cut over 50 mm to make it easier for the hydrogel polymer to overflow.

Put a lid on this kneader, add 250g of acrylamide,
An aqueous monomer solution (aqueous solution concentration: 35% by weight) consisting of 97W of potassium acrylate, 3v of N,N'-methylenebisacrylamide and 650t of water was introduced, and nitrogen gas was blown into the reaction system to replace the inside of the reaction system with nitrogen.

Next, two sigma type stirring blades of 44 and 24 r were installed.
pm, and while heating by passing 40°C hot water through the jacket, add 35cI) hydrogen peroxide aqueous solution 0.51 and L-ascorbic acid 0.0065' as a polymerization initiator.
was added. Polymerization started 1 minute after the addition of the polymerization initiator, and as the polymerization progressed, the monomer aqueous solution formed a soft hydrogel, which was gradually divided into smaller pieces by rotation of the stirring shaft. Fifteen minutes after adding the polymerization initiator, the temperature in the reaction system reached 64° C., and the hydrogel polymer had been subdivided into fine particles with a diameter of about 3 vP. Here, the hot water passed through the jacket was heated to 90°C.

Next, potassium acrylate 4 was added to acrylamide 12.
．． 66 Nitrogen gas was blown into a monomer aqueous solution consisting of 1447 Kr, N, N'-methylenebisacrylamide and 29.2 Kr/water to drive out dissolved oxygen, 3
5-width hydrogen peroxide solution 247 dissolved in water I K9,
A solution of 0.288 F of t-ascorbic acid dissolved in one part of water was sent to a mixing tank using a fixed pump, and the uniformly mixed solution was fed into a kneader over a period of 24 hours.

The monomer aqueous solution that had been continuously supplied to the kneader became a finely divided hydrogel-like polymer that overflowed from the kneader and was continuously discharged. The temperature in the system was approximately 85°C throughout.

The discharged hydrogel polymer was heated with air W for another 20 minutes.
Polymerization was completed by maintaining the temperature at 85° C. under ambient atmosphere. The discharged water-containing gel polymer is crushed into pieces L1 with a diameter of 1 to 15 mm, and is easy to handle as it has a rough texture of 1°.
The neck was something that could be easily dried. This hydrogel polymer was placed on a 50-mesh wire mesh and heated to 180°C.
It was dried with hot air for 1 hour. The obtained dried product (hereinafter referred to as water retention agent 1)
1)) is granular and has a moisture content ij, 571j 444
°%te was there.

Mix water retention agent fiI O, 59 and silica sand No. 7 1002 (
-7,100 mesh Place on a wire mesh, pour tap water until the mixture is saturated, 2QU, 65%RH
The samples were left under the following conditions and the changes were investigated over the course of 1-° water retention.

Table 3 shows the change in water retention of this mixture.

Table 3 It is clear that the crosslinked polymer obtained by the method of the present invention can also be effectively used as a water retention agent.

[Brief explanation of the drawing]

FIG. 1(A) is a front explanatory view of a reaction vessel and a heating device for the discharged hydrogel polymer in Example 1 of the present invention, and FIG. 1(B) is a side view of a discharge blade. FIG. 2(A) is an explanatory front view of a reaction container in Example 2 of the present invention. The second) figure is an explanatory side view of a reaction vessel, a heating device, and a belt dryer in Example 2 of the present invention. FIG. 3 is an explanatory front view of a reaction vessel and a heating device in Example 4 of the present invention. 1. Toki Fuchi 2. Mixed aqueous solution inlet tube of monomer and initiator 3, nitrogen gas inlet tube 4. Jacket 5, double-arm kneader 6, sigma stirring blade 7, butt 8. Canada
Heat bath 23-9, discharge blade 10. Canopy made of polyethylene film 11, triaxial kneader】2. Banbury type stirrer blade 13, discharge screw ]4. double paddle feeder 15,
Belt dryer 16. -Double-arm kneader with cut-off upper sides- Patent applicant Nippon Shokubai Chemical Co., Ltd. 25- 24- Figure 2 (A) De * 2 [! (B) 3 calendars = F L liver - 1, 1 Figure 3-7--1

Claims (1)

[Claims] 1. An aqueous solution of a single-sided polymer that forms a crosslinked structure to become a hydrogel polymer by aqueous solution polymerization and a polymerization initiator are continuously supplied by rc into a container having a plurality of rotating stirring shafts. , radical aqueous solution polymerization is carried out while fragmenting the hydrogel-like polymer produced as the polymerization progresses by the shear force generated by the rotation of the stirring shaft, and the fragmented hydrogel-like polymer produced (~) is continuously poured into a container. A novel continuous polymerization method characterized by: discharging to the outside. 2. A novel continuous polymerization method according to claim 1, wherein the monomer aqueous solution concentration is 10 to 80% by weight. 3. A plurality of A novel continuous polymerization method according to claim 1, wherein the container having the rotary agitation 1141 is a double-arm kneader. 4. A patent in which the double-arm kneader has an inner surface coated with a fluororesin. A novel continuous polymerization method according to claim 3.