FR2551445A1 - PROCESS FOR THE CONTINUOUS PRODUCTION OF A RETICLE POLYMER - Google Patents

Abstract

PROCESS FOR THE CONTINUOUS PRODUCTION OF A CROSS-LINKED POLYMER INCLUDING THE STEPS OF CONTINUOUS INTRODUCTION OF AN AQUEOUS SOLUTION OF A POLYMER CAPABLE OF BEING CONVERTED BY POLYMERIZATION INTO AQUEOUS SOLUTION INTO A GEL OF CROSS-LINKED POLYMER CONTAINING WATER AND '' A POLYMERIZATION INITIATOR IN AN ENCLOSURE EQUIPPED WITH A PLURALITY OF ROTARY SHAFTS PARALLEL TO ONE THE OTHERS AND EACH EQUIPPED WITH AGITATION BLADES, THE POLYMER GEL CONTAINING WATER REMOVED FROM THE POLYMERIZATION IN PROGRESS BEING FINALLY DIVIDED BY SHEARING FORCES GENERATED BY THE AGITATION BLADES DRIVEN BY THE AGITATION SHAFTS, THE AQUEOUS RADICAL POLYMERIZATION SOLUTION BEING THUS CAUSED TO CONTINUE WITHOUT INTERRUPTION, THE RESULTING POLYMER GEL RESULTANTLY DIVIDED AND CONTAINED. WATER BEING CONTINUOUSLY REMOVED FROM THE REACTION ENCLOSURE.

Description

Process for the continuous production of a cross-linked polymer The invention

  The invention relates to a process for the continuous production of a crosslinked polymer. More particularly, the invention relates to a process for the continuous production of a crosslinked polymer gel containing

  water by polymerization in aqueous solution.

  Crosslinked polymers are already known in which acrylamide, acrylic acid or their salts are used as main constituents; these polymers are known for their ability to absorb and retain large volumes of water, ion exchange, and induce chelation, and have been found useful in a variety of applications such as sanitary articles, chemical agents and the like. For the preparation of these crosslinked polyamines, it is the process which comprises the polymerization of an aqueous monomer solution as well as the processes using the same. a water-in-oil emulsion or a suspension in a hydrophobic solvent as well as the method which comprises the polymerization by casting of an aqueous solution of monomer which have imposed the method of polymerization of a water-in-oil emulsion and the method of polymerizing a water-in-oil suspension leads to the use of large volumes of organic solvent and, therefore, have proved to be highly dangerous from the point of view of accident prevention and pose a serious problem of possible exposure of workers to the toxic effects of the organic solvent. The process which is based on the casting polymerization of an aqueous monomer solution. is excellent compared to the two processes which have just been described

  in the sense that it does not use any organic solvents

  However, this process requires the continuous removal of the heat of reaction during the polymerization time and inevitably leads to the use of a complicated and expensive polymerization device. Further, a dry, cross-linked polymer is obtained. From the polymer gel containing the water by the removal of the water necessarily entails a step of finely dividing the water-containing polymer gel mechanically to sufficiently increase the surface of the polymer for drying. in this case, the fine mechanical division of the water-containing polymer gel can be obtained by chopping or by extrusion, for example In each case, the work caused by the fine division of the polymer leads to the consumption of large amounts of water. energy because of the fact that the polymer gel containing

  the water has a high elasticity of the rubber type.

  As a solution to the various problems which have just been described, the inventors have proposed, in the published Japanese patent application SHO 57 (1982) -34101, a process for the discontinuous radical polymerization of an aqueous solution using a pressure vessel. Although this process has been successful in improving the productivity and feasibility to a certain extent compared with conventional methods, it still leaves much to be desired. The object of the invention is therefore to provide

  a new process for the continuous production of a crosslinked polymer.

  The invention also aims to provide a process for the continuous production of a crosslinked polymer gel containing water by aqueous solution polymerization. To this end, a process is used for the continuous production of a crosslinked polymer comprising the steps of continuously introducing the aqueous solution of a monomer suitable for being converted by polymerization into an aqueous solution into a polymer gel. crosslinked composition containing water and a polymerization initiator within a reaction chamber having a plurality of mutually parallel rotatable shaking shafts of fine division of a polymer gel containing water obtained by the current polymerization using the shearing forces of the agitator blades generated by the rotation of the aforementioned agitator shafts and

  continuous recovery of finely divided polymer gel containing water outside the reaction chamber.

  FIG. 1 is a schematic sectional view illustrating a typical reaction device that can be used for carrying out the process according to the invention; FIG. 2 is an elevational view of the stirrer blades to be used in the device; FIG. 3 is a side view illustrating a typical group of discharge blades; FIG. 4 is a schematic sectional view illustrating another typical reaction device that can be used to carry out the process according to FIG. FIG. 5 is a diagrammatic sectional view illustrating a typical combination of the reaction chamber according to FIG. 4 and a heating device and a drying device, FIG. perspective of the stirring blades to be used in the reaction device according to FIGS. 4 and 5 and

  Figure 7 is a schematic sectional view still shining another typical reaction device.

  The monomer for use in the present invention is capable of being converted by aqueous solution polymerization into a crosslinked polymer gel containing water. The crosslinked structure may be that which is obtained by the copolymerization of a polymer. water-soluble monomer and a crosslinking monomer having at least two polymerizable double bonds in its molecular unit or that obtained by subjecting a water-soluble monomer to aqueous solution polymerization in the presence of a hydrophilic sub-stance of high molecular weight such as

  starch, cellulose or polyvinyl alcohol and a water-soluble polyepoxide compound, whereby the polymerization is carried out in combination with grafting, complex bond formation or ester type.

  The aqueous monomer solution to be used according to the invention is introduced continuously into a polymerization chamber and must therefore contain the monomer at a concentration of 10 to 80% by weight, preferably 20 to 60% by weight. by weight

  As the concentration falls within this range, the polymer gel containing the water formed during the polymerization can be easily finely divided by the shearing force caused by the rotation of the stirring balls.

  Examples of water-soluble monomers useful for use in the polymerization include ethylenically unsaturated monomers such as acrylic and methacrylic acids and their alkali metal and ammonium salts, acrylamide, methacrylamide, acrylonitrile, and the like. , 2-hydroxyethyl (meth) acrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, methyl methacrylate, ethyl methacrylate and maleic acid. One of the constituents of a mixture of two or more members selected from

  group of monomers listed above can be used.

  Examples of crosslinking monomers usable for use in the present process include ethylene glycol diacrylates or dimethacrylates, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, trimethylolpropane and pentaerythritol; triacrylates or trimethacrylates of trimethylolpropane and pentaerythritol; pentaerythritol tetracrylates or tetramethacrylates: N, N'-methylene-bisacrylamide, N, N'-methylene-bismethacrylamide and triallyl isocyanurate One of the representatives of the aforesaid group or a mixture of two or more of These representatives may be used. The above-mentioned crosslinking monomer is, in general, used in an amount not exceeding 10 moles-Z, more preferably from 0.0005 to 5 moles-Z and, more preferably still, from 0.001 to 1 mole- Z with respect to the monomer

above mentioned soluble in water.

  Of the many monomers listed above, a monomer mixture of (A) one of the components or a combination of two or more components selected from the group consisting of acrylic and methacrylic acids and their alkali metal and ammonium salts , acrylamide and methacrylamide and (B) a monomer containing at least two polymerizable double bonds in its molecular unit, the crosslinking monomer according to (B) acting for no more than 10 mole-Z, is used in a particularly desirable manner. The crosslinking monomer (B) is one of the components or a mixture of two or more components selected from the group of crosslinking monomers listed above. If the amount of crosslinking monomer (B) to be used exceeds 10 mole-Z, more particularly 50 mole-Z relative to the monomer (A), the crosslinked polymer obtained is deficient in its ability to absorb water or in faculty

  ion exchange. As a result, the report

  The carrier of the crosslinking monomer (B) is in the range of 0.0005 to 5 mole-X, preferably 0.001 to 1 mole-Z.

  In addition, the concentration of this aqueous monomer solution is 10 to 80% by weight, preferably 20 to 60% by weight. Even when the crosslinking monomer (B) is not used at all, the continuous polymerization contemplated by the present invention can be carried out as long as the formation of the crosslinking structure is effected by the use of ammonium persulfate in large amounts. ,

for example.

  The aqueous monomer solution to be used in the context of the present invention is fed continuously into a polymerization chamber and, therefore, must contain the monomer in a concentration.

  from 10 to 80% by weight, preferably from 20 to 60% by weight As long as the concentration falls within this range, the polymer gel containing the water formed as the polymerization proceeds can be easily finely divided by the shear force generated by the rotation of the stirring shafts.

  The enclosure used in the context of the present invention must comprise a plurality of rotary shaking shafts and must be able to exert shearing forces generated by the rotation of the shaking shafts equipped with stirring blades to exert a action on the polymer gel containing the water formed by the aqueous solution polymerization of the monomer The enclosure must comprise a plurality of rotary stirring shafts 30 arranged parallel to each other Examples of enclosures satisfying this The requirement includes two-arm kneading devices (hereinafter simply referred to as "kneader") and a three-shaft kneader. When the kneader is adopted, the two rotating shakers are rotated. in mutually opposite direction at equal or different speeds When the two trees are trained at an equal speed, they can be used at locations such that the rotational radii of the two trees overlap partially When the two trees are rerained at different speeds,

  they are used in such a way that their radius of rotation does not intersect. The rotary shafts to be used in the context of the present invention may be of any shape such as sigma type, S type, banbury "and of the fishtail type.

  The filler to be used in the present invention must have an inner surface covered with a fluorine-containing resin because the coating serves to prevent the formed gel from adhering to the inner surface. Fluorine-containing resins include tetrafluoroethylene-type resins, tetrafluoroethylene-perfluoropropylvinylether copolymers, tetra-fluoroethylene-hexafluoropropylene copolymer type, trifluoromonochlorethylene type resins, and ethylenetetrafluoroethylene type copolymers. The polymerization chamber to be used in the context of the present invention must comprise, in its upper part, a lid arranged so as to make it possible to replace the gas contained inside the polymerization chamber by a gasinerte and Therefore, it is possible to maintain the polymerization system under an inert atmosphere with respect to the radical polymerization reaction. Optionally, the polymerization chamber may comprise, in its upper part, a reflux condenser for condensing during In addition, the polymerization vessel may be arranged in such a way that the water formed, as indicated above, is brought out of the interior of the polymerization vessel. pregnant under the influence of a stream of inert gas introduced into the enclosure For the heating of the aqueous monomer solution or for partial removal Since the heat of the polymerization reaction during the polymerization is desirable, it is desirable for the polymerization chamber to be provided with a double jacket. Examples of inert gases which can advantageously be used in this reaction include nitrogen, carbon dioxide and argon. . The reaction chamber to be used for the process according to the invention will be described hereinafter with reference to the accompanying drawings. FIG. 1 represents a typical reaction chamber that can be used for the implementation of the invention. a two-arm type kneader comprising an enclosure 5 equipped with a thermometer 1, a feed tube 2 of raw material, an opening 3 for the inert gas and a cover 4 near the bottom part the kneader is equipped with a plurality of rotary stirring shafts 6 each equipped with sigma type stirring blades, as illustrated in FIG. 2. The chamber is kept under an inert atmosphere. Optionally, the chamber may comprise near its lower part, a double envelope which can be filled with a heat transfer medium for the control of the reaction temperature. The enclosure 5 is also equipped at its upper part with c a product outlet 8 and, moreover, in the vicinity of the product outlet 8, a mechanism for discharging the finely divided polymer gel containing the water. The discharge mechanism which may, for example, comprise a shaft horizontally disposed above a plurality of rotating shaker shafts provided by the reaction chamber and one or more paddle vanes attached to the horizontal shaft, as shown in Figures 1 and 3. The above-mentioned product outlet 8 and a tank 10 are

  connected to one another by a pipe 11 made of synthetic resin

  such as polyethylene, polypropylene or polyvinyl chloride. The vessel 10 is maintained in a

heating bath.

  The polymerization in the device constructed as just described is carried out by feeding the aqueous monomer solution enclosure containing the water soluble polymerization initiator through the feedstock introduction tube 2. and at the same time introducing an inert gas such as azo through an opening for inert gas 3 leading to the interior of the enclosure, the air contained in the system being thus replaced, and the temperature of the system being maintained at a prescribed level to induce polymerization As the polymerization progresses to provide a water-containing polymer gel, the produced polymer is finely divided by the shear forces generated by the rotation of the blades of the dyes. With the aid of rotary stirring 6 without interrupting the polymerization in progress, the aforementioned aqueous monomer solution feed containing the polymerization initiator is continued to allow the continuation of the polymerization and, in order to maintain the amount of gel contained in the system substantially at a fixed level, the polymer gel particles containing the water are discharged from the system by the unloading mechanism. , the polymer gel containing the water which is discharged from the chamber is heated inside the tank 10 to complete the polymerization which

  continues in the discharged polymer.

  FIGS. 4 and 5 illustrate another typical reaction device that can be used in the practice of the present invention. It is a three-shaft type kneader comprising an enclosure equipped with a thermometer 21, a tube of 22, an opening for the inert gas 23 and a cover 24 The enclosure is equipped near its lower part with a plurality of mutually parallel rotary shaking shafts 26 comprising The "Banbury" type stirring blades, as shown in FIG. 5, and a discharge screw 29. The chamber is maintained under an inert gas. Optionally, the chamber is equipped near the bottom of a chamber. double jacket filled with a heat transfer medium for controlling the reaction temperature In the vicinity of the lower part of this chamber 25 is, moreover, disposed an outlet hole 28 for unloading. A feed device 30 The double blade is connected to this discharge hole 28, said supply device being optionally equipped with a double jacket 31 below the discharge hole 32, at one end of the double blade feeding device 15. 30, is arranged a device

  Conveying device 34, such as, for example, a conveyor belt This conveying device 34 is, if necessary, equipped with a drying device 35 The stirring vanes may be in various forms as illustrated in FIG. (A) (D).

  Polymerization is carried out in the apparatus constructed as described above, by introducing the aqueous monomer solution containing the water-soluble radical polymerization initiator through the raw material feed tube 22 to the interior of the enclosure. and at the same time introducing an inert gas such as nitrogen through the inert gas opening 23 to the interior of the enclosure to displace air remaining in the system and to maintain the interior temperature of the chamber. Pregnant at a Prescribed Level to Induce Polymerization As the polymerization progresses and provides a water-containing polymer gel 33, the polymer 33 is finely divided by the shear forces generated by rotation of the blades of the rotating shaker shafts. Without interrupting the polymerization in progress In addition, the supply of the aforesaid aqueous solution of monomer containing the polymerization initiator is continued for p to allow the continuation of the polymerization and at the same time to maintain substantially at a fixed level the amount of gel contained in the system, the gel being driven by the discharge screw 29 and led through the discharge opening 28 to the In the interior of the double-vane feeder 30, the polymer gel containing the water thus discharged is, if necessary, heated inside the feeder 30 to complete the polymerization which is still continuing within

  The polymer gel containing the water and located inside the feeder 30 is then discharged through the discharge opening 32 to the conveyor 34 and dried by the dryer 35.

  FIG. 7 illustrates yet another typical reaction device that can be used for practicing the invention. This device is generally similar to the device of FIG. 1 except for the fact that the wall on the side of the opening discharge 48 of the enclosure 45 has a sufficiently low height to allow the polymer gel containing the water thus produced, out of the interior of the chamber by overflow Optionally, this wall of the enclosure 45 may 25 arranged in the form of a height-adjustable dam that can be intermittently lowered to allow the overflow of the polymer gel to leave. The numerical symbols of FIG. 7 which are the sum of the numerical symbols in FIG. 1 plus the number 40, designate the same constituents as those of the

  FIG. 1 The polymerization is carried out in this device in the same way as that described with reference to the device of FIG. 1.

  The term "continuous", as used above, should not be construed as constant in the exact sense

  word but can be interpreted as describing the

  charging the polymer produced in a pulsed or intermittent manner The discharge of the produced polymer gel must only be "continuous" in the sense that the amount of polymer gel containing the water is substantially retained at a level set within the reaction chamber. As a water-soluble radical polymerization initiator which can be used to carry out the radical polymerization in aqueous solution of the monomer according to the invention, any known water-soluble radical polymerization initiator can be used. Examples of polymerization initiators include persulfates, hydrogen peroxide and water-soluble azo compounds. Such a polymerization initiator can be used alone or as an initiator of the polymerization initiator. redox type in combination with sulfite, hydrogen sulfite, thiosulfate, L-ascorbic acid or ferrous salt The amount of radical polymerization initiator to be used is in the range of 0.001 to 1%. weight, preferably from 0.005 to 0.5% by weight, relative to

  total amount of reactants.

  The reaction temperature varies with the kind of monomer to be used. When using, for example, a monomer mixture of (A) a representative or a combination of two or more representatives selected from the group consisting of acrylic acids or methacrylic acid and the alkali metal or ammonium salts of these acids, acrylamide and methacrylamide and (B) a crosslinking monomer having at least two double bonds polymerizable in the molecular unit, the reaction temperature generally falls within the range of from 60 to 110 ° C, preferably in the range from 70 to 100 ° C. If necessary, the polymerization product is aged at a temperature of 50 to 120 ° C, preferably 60 to 100 ° C. When the polymerization is carried out according to the present invention, it is possible to continuously and easily produce particles of finely divided polymer gel and containing water, each having a

crosslinked structure.

  Although the particle diameter of the produced polymer is variable depending on the reaction conditions actually employed, the polymer particles can be obtained in diameters generally not exceeding 3 cm, and preferably falling within the range of 0.05 to 1 cm. According to the process according to the invention and since the monomer is introduced continuously into the polymerization chamber and the polymer gel containing the water produced is continuously withdrawn from this same enclosure, the process has an operational efficiency. Because of the discontinuous polymerization process which involves a great deal of manual work in the steps of monomer introduction, polymerization initiation and removal of the product polymer, the continuous process according to the present invention has the advantage of not require virtually no manual work once the reaction has reached its constant state. Moreover, thanks to the process according to the invention, the heat generation of the polymerization reaction is uniform during the polymerization since the finely divided polymer gel containing water retained within the The reaction vessel and the freshly introduced aqueous monomer solution are uniformly mixed and the polymerization of the monomer proceeds.

  On the surface of the polymer gel, thus, the removal of heat from the polymerization reaction and the maintenance of a constant temperature of the polymerization system are easy. Therefore, it is easy to increase the temperature of the polymerization system. polymerization rate, the productivity of the polymerisation and the maintenance of a

$ 255144

  The unpredictable polymer obtained by carrying out the continuous process according to the invention exhibits a high degree of absorption when compared to the polymer obtained by the batch process. the process according to the invention has the consequence of making it possible to manufacture polymer gel particles containing water in the form of particles of substantially uniform diameter and in an easily dry form in the case of discontinuous polymerization, since the heat of polymerization is emitted concentrically, the removal of heat is relatively difficult and, therefore, it is difficult to increase the rate of polymerization and increase the productivity of the polymerization. a dispersion of

  The quality and a relatively low absorption capacity The polymer gel containing the finely divided water is in the form of widely dispersed particle size particles and some of these particles are not readily dryable.

  The process according to the present invention is entirely different in its operational principles of the process according to published Japanese Patent Application SHO 56 (1981) -32514 according to which the material is made to be placed in the manner of that which is obtained. The aqueous monomer solution introduced into the enclosure is uniformly mixed with the finely divided polymer gel particles containing the water and the assembly is subjected in this state to the As a result, the polymer gel retained within the reaction chamber is large for the amount of heat generated.

  the removal of heat is easy.

  Contrary to this, in the case of the process which involves the movement of the particles in the manner of a flow generated by a piston, the removal of the heat is difficult. An attempt to increase the polymerization productivity is likely to lead to the removal of heat. rise in the temperature of the materials and lead to the degradation of the quality of the product. The water-containing polymer gel particles obtained by the polymerization process according to the invention can be used in their unmodified form as adsorbents, water retention agents, ion exchange resins and absorbents. However, when they are dried, they can be handled more easily. The water-containing polymer gel particles obtained by the polymerization process according to the invention have the advantage that they can be dried very easily. the particles of

  The water-containing polymer gel obtained by the present invention has a large surface, so that they are easily and quickly dried by exposure to a stream of hot air.

  The process according to the invention for continuous polymerization has the advantage that a continuous dryer can be used effectively for drying the product. The device used for batch polymerization requires the use of a hopper, for example connect a continuous dryer to the device itself The device according to the invention does not require

  such additional equipment.

  In the actual practice of the present invention, the conversion of monomer to polymer can be improved by heating the polymer gel containing the water.

  which has just been removed from the polymerization chamber before drying the polymer For this particular feature of the invention, the combination of a continuous heating device and a continuous drying device 35 may be envisaged.

  Hereinafter, the method according to the invention will be decriplus specifically with reference to the examples of implementation.

following works.

EXAMPLE 1

  A double-arm, double-jacketed type stainless steel kneader (hereinafter called "kneader" to be brief) constructed as illustrated in FIG. 1 and having an internal volume of 2 liters, has an opening of 160 mm × 150 mm, a depth of 135 mm, is equipped with two sigma-type stirring blades having a rotational diameter of 70 mm and further has a tetrafluoroethylene-perfluoropropylvinylether copolymer coating formed on the surfaces which are exposed to contact with the A solution of the monomer containing 399 g of partially neutralized acrylic acid, 75 mole-2 of which is neutralized with caustic soda, 0.036 g of N, N'-methylene, is provided. Bis-acrylamide and 600 g of water are introduced into the kneader and nitrogen is blown into the kneader to expel oxygen from the dye system. Then, the two sigma stirring blades are rotated at respective speeds of 67 and 56 rpm and heated water is circulated at 45 ° C in the jacket; a solution of 0.23 g of 2,2'-azo-bis (2-amidinopropane) dihydrochloride (manufactured by Wako Junyaku Kabushiki Kaisha and marketed under the trademark V-50) in 10 g of water is introduced As initiator of the polymerization The polymerization begins to occur 15 minutes after the introduction of the polymerization initiator. As the polymerization progresses, the aqueous polymer solution gives rise to the formation of a soft gel The internal temperature of the reaction system reached 80 OC after 35 minutes after the addition of the polymerization initiator. At this time, the temperature of the reaction system was gradually reduced by rotation of the stirring shafts. Hot water circulating in the jacket was heated to 94 ° C. Then, an aqueous solution of monomer containing 14.36 kg of partially neutralized acrylic acid having a 75 mole% neutralized portion of the acid. caustic, as well as 1.3 g of N, N'-methylene-bis-acrylamide and 21.6 g of water is introduced after the dissolved oxygen is removed by bubbling nitrogen; this product and a solution of 8.2 g of V-50 in 360 cm of water are introduced by constant velocity volumetric pumps in a mixing chamber. The resulting homogeneous mixture was introduced into

  the kneader for a period of 24 hours.

  The aqueous monomer solution thus introduced continuously by the kneader was converted into a gel of

  finely divided polymer containing water and, in this form, continuously withdrawn through a discharge opening.

  During this time, the internal temperature of the system was substantially maintained at 90 ° C. The polymer gel containing the removed water was maintained under an atmosphere.

  nitrogen at 90 ° C for 20 minutes to complete the polymerization that continues to occur within the polymer.

  The polymer gel containing the water thus removed is in the form of finely divided particles having a diameter of 2 to 7 mm. These particles do not stick.

  together and are easy to handle and easy to dry.

  The polymer gel containing the water thus removed from the enclosure was distributed over a wire mesh of 50 mesh mesh, dried in a 150 C hot air dryer. then sprayed

in a vibrating mill.

  A 0.2 g portion of the sputtered product (hereinafter referred to as "absorbent (1)") was placed in a bag (40 mm × 150 mm) of nonwoven fabric in the form of a tea bag, immersed in water. in a saline solution to

  0.9% for 10 minutes then removed from the water and weighed.

  The absorbency of this specimen was calculated according to the formula below, using as a control the

empty bag of its contents.

  Absorbency Weight after absorption (g) control (q) Fc 15 dasrtoWeight after absorption (g) The results are shown in Table 1 The data shown in this table illustrate the absorbency recorded for the sprayed products of gel lots. polymer containing water collected at intervals of three hours since the beginning of the introduction

  continuous aqueous monomer solution.

TABLE 1

  Elapsed time 0 3 6 9 12 15 18 21 24 Absorbency 66 70 72 70 71 71 69 71 71

  From these figures, it follows that the crosslinked polymer obtained by the process according to the invention is effectively used as an absorbent.

EXAMPLE 2

  A stainless steel jacketed kneader with three shafts (hereinafter "kneader" for brevity) constructed as illustrated in Figures 4 and 5, having an interior volume of 10 liters, having an opening of 240 x 220 mm , having a depth of 260 mm and equipped with two Banbury type stirring blades with a rotational diameter of 110 mm and comprising

  a discharge screw with a diameter of 35 mm, comprises a coating of trifluoromonochlorethylene resin formed on its inner surface. This kneader is equipped with a nitrogen inlet tube, a mono-mother inlet tube and of a thermometer.

  An aqueous solution of monomer containing 95 g of partially neutralized acrylic acid, a portion of 75 mole-Z is neutralized with caustic soda, 3.3 g of trimethylol propane triacrylate and 3000 g of water, is introduced into the kneader and blowing nitrogen inside the kneader to drive oxygen out of the reaction system. Next, the Banbury-type stirring blades were rotated at the speed of 30 rpm and the hot water was heated. a temperature of 40 ° C was circulated in the jacket; 2.25 g of ammonium persulfate and 2.25 g of sodium acid sulfite were introduced as a polymerization initiator. Polymerization started.

  minutes after the addition of the polymerization initiators.

  As the polymerization progressed, the aqueous polymer solution gave rise to the formation of a soft gel containing water. By rotating the stirring shafts, the soft gel containing the water was gradually finely divided. The internal temperature of the reaction system rose to 90 ° C within 25 minutes after the addition of the polymerization initiators at this time. The temperature of the hot water circulated in the jacket was raised to 87 ° C., and then an aqueous monomer solution containing 359 kg of partially neutralized acrylic acid, a portion of 75 mole-7 of which was neutralized with the caustic acid and 594 g of trimethylolpropane triacrylate and 540 kg of water are introduced and the dissolved oxygen is removed by nitrogen bubbling thereafter, a solution of 405 g of ammonium persulfate in 10 kg. of water and a solution of 405 g of sodium acid sulfite in 10 kg of water were introduced over a period of five days.

  the addition of the monomer, the rotation of the discharge screw was controlled in such a way that the amount of polymer gel containing the water retained inside the kneader is constant.

  The aqueous monomer solution introduced into

  The continuous temperature in the mixer was converted into a finely divided polymer gel containing the water and, in this form, continuously removed from the kneader. During this time, the internal temperature of the system was kept substantially constant at about 83 ° C.

  The polymer gel containing the water removed by the rotation of the discharge screw, was introduced into a double-vane feeder (manufactured by Kabushiki Kaisha Nara Kikai Seisakusho), heated by a double jacket filled with hot water at 90 ° C and heated for an average retention time of 15 minutes The polymer gel containing water and discharged from the paddle feeder was dried by a stream of hot air at 160 ° C on a dryer Continuous circulation tape samples of this polymer were taken at half-day intervals. Each test specimen was pulverized and the pulverized product (hereinafter referred to as "absorbent (2)") has been subjected to tests in order to qualify its capacities as absorbent

  The results are shown in Table 2.

TABLE 2

  Number of days elapsed 0 5 1 1 5 2 2 5 3 3 5 4 4 5 5 Absorbency 65 66 65 65 65 64 65 66 66 65 It follows from these data that the absorbent (2)

  is also an excellent absorbent.

EXAMPLE 3

  For the visual observation of the behavior of the monomer aqueous solution added continuously, an amount of 5 cm 3 of aqueous monomer solution was added to the polymerization system and during the continuous course of the polymerization according to Example 1. deaerated containing 0.2 g of pink fluorescent pigment (manufactured by Nippon Shokubai Kagaku Kogyo Co, Ltd. and marketed under the brand name "Epocolor"), the whole

being observed visually.

  At the moment when the aqueous solution of colored monomer was added, the whole system turned pink. This shows that the aqueous monomer solution was uniformly mixed with the crushed polymer gel containing water and was made to form. the surface of the polymer gel containing water has a thin coating.

  Upon addition of an aqueous solution of uncolored monomer to continue the polymerization, polymer gel particles containing water stained pink in the center and transparent in the outer portions were obtained. This fact demonstrates that the polymer gel containing water was sprayed inside the kneader and the aqueous monomer solution deposited on the surface of the ground polymer was polymerized in this state, the gel particles thus gaining in diameter and the particles of increased sizes being pulverized again and the procedure repeated.

EXAMPLE 4

  The kneader used in Example 1 was modified to provide the construction shown in FIG. 7 by giving it a section of 150 mm × 50 mm, the upper part of one of the walls having been cut to facilitate the

  overflow of the polymer gel containing water.

  On the kneader was then fitted a lid.

  An aqueous monomer solution (35% by weight concentration) containing 250 g of acrylamide, 97 g of potassium acrylate, 3 g of N, N'-methylene-bis-acrylamide and 650 g of water was introduced into the kneader and nitrogen was blown into the kneader to expel oxygen from the

reaction system.

  Then, two stirring blades of the sigma type were rotated at respective speeds of 44 and 24 rpm, hot water at 40 C was circulated in the jacket to heat the kneader and 0 5 g of a 35% aqueous solution of hydrogen peroxide and 0.006 g of L-ascorbic acid were added as polymerization initiators. The polymerization began to occur one minute after the addition. During the progress of the polymerization, the aqueous monomer solution gave rise to the formation of a soft gel containing water. This gel was gradually finely divided by rotation of the stirring shafts. 15 minutes after the addition of the polymerization initiators, the lower temperature of the reaction system reached 64 ° C and the water-containing polymer gel was finely divided into particles of about 3 mm in diameter. at this time, the temperature of the hot water circulating in the jacket was raised to 90 ° C. Then an aqueous monomer solution containing 12 kg of acrylamide, 4.66 kg of potassium acrylate, 144 g of N , N'-methylene bis-acrylamide and 29.2 kg of water, the whole being purged of dissolved oxygen by bubbling nitrogen, a solution of 24 g of a 35% aqueous solution of hydrogen peroxide in 1 kg of water, and a solution of 0.288 g of L-ascorbic acid in 1 kg of water were separately conveyed by constant speed pumps to a mixing chamber to be uniformly mixed. was delivered to the kneader during a

24 hours period.

  The aqueous monomer solution thus continuously introduced into the kneader was converted into a gel of

  A finely divided polymer containing water and, in this state, allowed to overflow through the cut wall and continuously out of the kneader. During this time, the internal temperature of the system was substantially kept constant at about 85 ° C.

  The removed polymer gel containing water was maintained in a nitrogen atmosphere at 85 ° C. for 20 minutes to complete the polymerization which was still proceeding in the polymer. The polymer gel containing the water removed from the system was in the form of finely divided particles of the order of 1 to 5 mm in diameter The particles showed no cohesiveness and allowed easy handling and could be easily dried The polymer gel containing water was spread over a web metal mesh with a mesh width of 0.33 mm (50 mesh) and then dried under a stream of hot air at 180 ° C. for one hour The dried product (hereinafter referred to as "water retention agent (1) ") global was in granular form and had a

water content of 5% by weight.

  A portion of 0.5 g of the water retention agent (1) was mixed with 100 g of silica sand. The mixture was distributed over a wire mesh with a mesh width of 0.149. mm (100 mesh), wetted with tap water until saturation, dropped to 20 C and 10 under a relative humidity of 65 /, and then tested for its water retention capacity over time. the amount of water retained by the mixture is

shown in Table 3.

TABLE 3

  Number of days of rest O 2 4 6 8 Mixture of water retention agent with sand 80 g 51 g 36 g 20 g 15 g Sand alone 30 g 9 g Ig 09 Og

  As shown in the table, it is noted that the crosslinked polymer obtained by the process according to the invention is effectively usable as a water retention agent.

  It goes without saying and as it already follows from the foregoing, the invention is in no way limited to those of its modes of application and of realization which have been more especially envisaged; she embraces it, at

otherwise, all variants.

Claims (6)

  A process for continuously producing a crosslinked polymer comprising the steps of continuously introducing an aqueous solution of a polymer capable of being converted by aqueous solution polymerization into a crosslinked polymer gel containing water and a polymerization initiator in an enclosure equipped with a plurality of rotating shafts parallel to each other and each equipped with stirring blades, the polymer gel containing water removed from the chamber. the polymerization in progress being finely divided by shear forces generated by the stirring blades driven by the stirring shafts, the aqueous solution of radical polymerization thus being brought to continue without interruption, the resultant polymer gel finely divided and containing water being removed continuously from the enclosure of reaction.   Process according to Claim 1, characterized   in that the concentration of the aqueous monomer solution is in the range of 10 to 80% by weight.   3 Process according to claim 1, characterized in that the chamber equipped with a plurality of rotary shaking shafts is of the two-arm kneading type. 4 Process according to claim 1, characterized   in that the chamber equipped with a plurality of rotary shaking shafts is equipped with a plurality of parallel rotary shaking shafts each other, each equipped with stirring blades, said enclosure also including an unloading auger.   Method according to claim 3, characterized   in that the polymer gel containing the water is removed continuously from said chamber by rotating the blade-shaped blades disposed near the unloading outlet of the enclosure.   6 Process according to claim 3, characterized in that the polymer gel containing the water thus formed is caused to overflow on a wall disposed near the unloading opening of the chamber and consequently leaves continuously from said pregnant. Method according to claim 1, characterized   in that the polymer gel containing the water which is continuously retained from the enclosure is subjected to a post-heating.   Process according to Claim 1, characterized in that the monomer comprises an ethylenically unsaturated monomer and not more than 10 mol% of crosslinking monomer. Process according to claim 1, characterized in that the monomer comprises (A) one of a combination of two or more components of the group consisting of acrylic and methacrylic acids and their alkali salts and ammonium of acrylamide and methacrylamide and (B) a crosslinking monomer having at least two polymerising double bonds in its molecular pattern.   Process according to Claim 9, characterized in that the concentration of the monomer in the aqueous solution is in the range of 20 to 60% by weight. Process according to Claim 9, characterized in that the ratio of the crosslinking monomer of (B) to the monomethylenically unsaturated monomer of (A) is in the range of 0.0005 to 5 moles-X.   Process according to Claim 9, characterized in that the reaction is carried out at a time   a temperature in the range of 60 to 110 ° C.