JP4916827B2 - Method for drying water-soluble polymer-containing gel and water-soluble polymer - Google Patents

Description

  The present invention relates to a method for drying a water-soluble polymer-containing gel, and a water-soluble polymer obtained by drying by the drying method.

  It is known that a water-soluble polymer such as a (meth) acrylic acid (salt) polymer exhibits properties such as cohesiveness and thickening. For this reason, for example, in the pharmaceutical field, it is used as an additive or hydrophilic ointment base for the purpose of improving the adhesiveness and water retention of poultices and poultices, and in the paint field, it is a thickener for carpet compounds. It is used as a paint thickener, adhesive, and tackifier. In the field of production processes, it is frequently used as a red mud settling agent during alumina production and a flocculant for salt water purification in the soda industry. Furthermore, in the civil engineering and construction fields, it is used as a drilling soil treatment agent, dredged soil treatment agent, and a mudizing agent. In other general industrial fields, it is also used as a moisture absorbent, desiccant, surface modifier, and various thickeners. Has been. As described above, the water-soluble polymer is widely used in various fields.

  The water-soluble polymer is usually obtained by drying a hydrogel polymer prepared by aqueous solution polymerization.

As a method for drying the water-soluble polymer hydrated gel, in order to uniformly and efficiently dry the polymer hydrated gel, (i) after the polymer hydrated gel is left to dry to a predetermined moisture content, pulverization is performed, A method of performing stirring drying or fluidized drying (for example, see Patent Document 1), (ii) a method of drying a polymer-containing hydrogel while applying vibration (for example, see Patent Document 2), and the like are known. There is also known a vibration dryer that uniformly mixes, disperses, and stirs an object to be dried, uniformly heats and dries, and performs a drying process to a uniform quality (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 11-240914 (published on September 7, 1999) JP 2001-18222 A (published January 23, 2001) JP 2002-31481 A (published January 31, 2002)

  However, the conventional configuration has a problem that the drying efficiency is not sufficient, and drying takes a long time.

  Specifically, the method described in Patent Document 1 is a method in which a polymer water-containing gel is allowed to stand and dry to a predetermined water content, then crushed, and then dried in a stirred state and / or a fluidized state. is there. At this time, when the polymer hydrogel is allowed to stand and dry to a predetermined moisture content, the gel caking (aggregates), and the drying efficiency is lowered.

  In addition, in the method described in Patent Document 2, in order to prevent the polymer hydrogel from becoming a large lump, it is not dried by heating while applying vibration from the beginning, but the vibration is stopped or the vibration is weak. Remove moisture in advance and heat dry with vibration. However, even if this method is used, it has been difficult to prevent the polymer hydrogel from becoming a large lump. For this reason, like the method of Patent Document 1, the drying efficiency is not sufficient, and drying takes a long time. Furthermore, since the drying efficiency is low, the drying needs to be performed under reduced pressure, and the equipment becomes expensive. Further, when drying is performed under reduced pressure, it is difficult to perform continuous operation, and there is a problem that production efficiency is remarkably lowered.

  Moreover, even if the water-soluble polymer hydrogel was dried using the vibration drier described in Patent Document 3, it was difficult to suppress caking (aggregation) and perform drying in a short time.

  The present invention has been made in view of the above-mentioned problems, and its object is to contain water-soluble polymer that has high drying efficiency and can be dried in a short time by suppressing caking (aggregation). The object is to realize a gel drying method and a water-soluble polymer obtained by drying by the drying method.

  The present inventor has intensively studied to solve the above problems. As a result, the present inventor uses a continuous vibration drier to perform a specific vibration stroke even in the case of a water-soluble polymer water-containing gel having a high water content, which is highly tacky and easily causes caking (coagulation) during drying. The water-soluble polymer hydrated gel can be dried while suppressing the occurrence of caking (aggregation) by allowing hot water to pass through the lower part of the drying deck while being vibrated as described above. The present inventors have found that this can be done and have completed the present invention.

  That is, the water-soluble polymer hydrated gel drying method according to the present invention is a method for drying a water-soluble polymer hydrated gel by two-stage drying in order to solve the above-mentioned problem, and uses a continuous vibration dryer to finely The water-soluble polymer hydrated gel is loaded on the drying deck, the water-soluble polymer hydrated gel is vibrated with a vibration stroke of 4 mm or more, and hot air is passed through the water-soluble polymer hydrated gel from the bottom of the drying deck. Thus, after performing primary drying, secondary drying is performed using an aeration dryer.

  According to the above method, the water-soluble polymer hydrated gel is dried by performing primary drying under the above conditions until a predetermined water content at which the water-soluble polymer hydrated gel hardly causes caking (aggregation). The water-soluble polymer hydrogel can be dried while suppressing the occurrence of aggregation. As a result, since the contact efficiency between the water-soluble polymer hydrated gel and hot air can be maintained, caking (aggregation) is suppressed, the drying efficiency is high, and drying can be performed in a short time. . In addition, since the drying efficiency is high and drying can be performed in a short time, the cost for the drying process can be reduced.

  In addition, since caking (aggregation) is unlikely to occur, there is a low possibility that the dried product will contain undried material. For example, when pulverizing thereafter, the undried product has rubber elasticity, which causes pulverization troubles. Can be avoided.

  On the other hand, as one of the drying methods conventionally performed, there is a method in which a crusher is incorporated in a vibration drier, and drying is performed while crushing cakes (aggregates). However, this method has a problem that the water-soluble polymer water-containing gel is easily kneaded by a crusher, and the kneaded water-soluble polymer water-containing gel clogs the air holes of the drying plate. If the ventilation hole of the drying plate is closed, the drying efficiency is significantly reduced. The drying method according to the present invention is a brilliant solution of the above-mentioned problems of these conventional drying methods.

  In addition, since the drying time is short and the heat history of the water-soluble polymer hydrogel is small, a side reaction such as a cross-linking reaction hardly occurs, and a dry product with few insoluble components and little coloring can be obtained.

  In the method for drying a water-soluble polymer hydrated gel according to the present invention, primary drying can be performed by loading the refined water-soluble polymer hydrated gel so that the layer height is within a range of 5 mm to 50 mm. preferable.

  According to the above method, since the water-soluble polymer hydrated gel can be dried while further suppressing the occurrence of caking (aggregation), the drying efficiency is higher and the drying can be performed in a shorter time. There is an effect.

  In the method for drying a water-soluble polymer hydrated gel according to the present invention, primary drying can be performed by loading the refined water-soluble polymer hydrated gel so that the layer height is within a range of 10 mm to 40 mm. preferable.

  According to the above method, since the water-soluble polymer hydrated gel can be dried while further suppressing the occurrence of caking (aggregation), the drying efficiency is higher and the drying can be performed in a shorter time. There is an effect.

  In the method for drying a water-soluble polymer-containing gel according to the present invention, the vibration stroke is preferably in the range of 5 mm to 10 mm.

  According to the above method, since the water-soluble polymer hydrated gel can be dried while further suppressing the occurrence of caking (aggregation), the drying efficiency is higher and the drying can be performed in a shorter time. There is an effect.

  In the method for drying a water-soluble polymer hydrogel according to the present invention, the water-soluble polymer hydrogel refined is an extruded gel discharged from an extruder having a die diameter in the range of 2 mm to 20 mm. Is preferred.

  According to the above method, since the water-soluble polymer hydrated gel can be dried while further suppressing the occurrence of caking (aggregation), the drying efficiency is higher and the drying can be performed in a shorter time. There is an effect.

  In the method for drying a water-soluble polymer-containing gel according to the present invention, it is preferable that the aeration dryer used for secondary drying is a continuous aeration dryer.

  According to the said method, since all the drying processes can be performed continuously, there exists a further effect that drying efficiency is higher and it can dry in a shorter time.

  In the method for drying a water-soluble polymer-containing gel according to the present invention, it is preferable that the linear velocity of hot air in primary drying is in the range of 0.5 m / s to 2 m / s.

  According to the said method, there exists a further effect that drying efficiency is higher and it can dry in a shorter time. Specifically, when the passing linear velocity is less than 0.5 m / s, drying tends to take a long time, or undried material tends to be generated. Moreover, when a passing linear velocity exceeds 2 m / s, there exists a tendency for the raise of the drying efficiency with respect to the raise of a linear velocity to become small.

  In the method for drying a water-soluble polymer hydrogel according to the present invention, it is preferable that the mass average molecular weight of the water-soluble polymer in the water-soluble polymer hydrogel is in the range of 1 million to 20 million.

  If the mass average molecular weight of the water-soluble polymer in the water-soluble polymer-containing gel is within the above range, the drying method according to the present invention can be suitably applied. Specifically, in the case of a water-soluble polymer-containing gel having a mass average molecular weight of less than 1,000,000, it tends to caking (aggregate) during primary drying. Further, in the case of a water-soluble polymer hydrogel having a mass average molecular weight exceeding 20 million, it can be efficiently dried by a normal drying method without using the drying method according to the present invention.

  In the method for drying a water-soluble polymer hydrogel according to the present invention, the water-soluble polymer in the water-soluble polymer hydrogel is obtained by polymerizing a monomer composition containing 60 mol% or more of acrylic acid or a salt thereof. It is preferable that it is a polymer.

  A polymer obtained by polymerizing a monomer composition containing 60 mol% or more of acrylic acid or a salt thereof is more susceptible to caking (aggregation) during drying than other water-soluble polymers. A drying method can be suitably applied. The use of the drying method according to the present invention is preferable in that a quality polymer with little drying is small and a high-quality polymer is obtained.

  In the method for drying a water-soluble polymer hydrated gel according to the present invention, the water content of the water-soluble polymer hydrated gel at the dryer outlet in primary drying is preferably in the range of 5% by mass to 40% by mass. .

  According to the above method, since the water-soluble polymer hydrated gel can be dried while further suppressing the occurrence of caking (aggregation), the drying efficiency is higher and the drying can be performed in a shorter time. There is an effect.

  Specifically, if the water content of the water-soluble polymer hydrated gel at the outlet of the dryer in primary drying is less than 5% by mass, there may be a problem in productivity. Further, when the water content of the water-soluble polymer hydrated gel at the dryer outlet in the primary drying is higher than 40% by mass, caking (aggregation) may occur in the secondary drying which is the next step of the primary drying.

  In the method for drying a water-soluble polymer-containing gel according to the present invention, it is preferable to increase the load per unit area in terms of dry matter more in the secondary drying than in the primary drying.

  According to the said method, since more water-soluble polymer water-containing gel can be dried, there exists the further effect that drying can be performed more efficiently.

  In the method for drying a water-soluble polymer hydrated gel according to the present invention, it is preferable that the water-soluble polymer hydrated gel after primary drying is crushed and then secondarily dried.

  According to the said method, since the drying efficiency in secondary drying can be raised more, there exists the further effect that drying can be performed more efficiently.

  In order to solve the above problems, the water-soluble polymer according to the present invention is obtained by drying a water-soluble polymer hydrogel by the drying method of the present invention.

  According to the above configuration, since the drying time is short and the heat history of the water-soluble polymer hydrogel is small, a side reaction such as a cross-linking reaction is unlikely to occur, and a water-soluble polymer with less insoluble components and less coloring is provided. There is an effect that can be.

  In the water-soluble polymer according to the present invention, the insoluble content is preferably 1% by mass or less.

  The method for drying a water-soluble polymer hydrogel according to the present invention, as described above, is a method for drying a water-soluble polymer water-containing gel by two-stage drying, and has been refined using a continuous vibration dryer. By loading the polymer hydrogel on the drying deck, vibrating the water-soluble polymer hydrogel with a vibration stroke of 4 mm or more, and passing hot air through the loaded water-soluble polymer hydrogel from the bottom of the drying deck. After the primary drying, secondary drying is performed using an aeration dryer.

  Thereby, there is an effect that caking (aggregation) is suppressed, drying efficiency is high, and drying can be performed in a short time.

  As described above, the water-soluble polymer according to the present invention is obtained by drying the water-soluble polymer-containing gel by the drying method of the present invention.

  As a result, it is possible to provide a water-soluble polymer that hardly causes a side reaction such as a cross-linking reaction and has few insoluble components and little coloration.

  The present invention will be described in detail below. In the present specification, “(meth) acrylic acid” means acrylic acid or methacrylic acid, and “acrylic acid (salt)” means acrylic acid or acrylate. Further, “weight” is treated as a synonym for “mass”, “weight%” is treated as a synonym for “mass%”, and “weight average molecular weight” is treated as a synonym for “mass average molecular weight”. In addition, “A to B” indicating a range indicates that the range is A or more and B or less.

  The method for drying a water-soluble polymer hydrated gel according to the present invention (hereinafter sometimes simply referred to as “hydrated gel”) is a method for drying a water-soluble polymer hydrated gel by two-stage drying, which comprises continuous vibration. Using a dryer, the water-soluble polymer hydrated gel was vibrated with a vibration stroke of 4 mm or more, and primary air was dried by passing hot air from the bottom of the drying deck through the loaded water-soluble polymer hydrated gel. Later, secondary drying is performed using a ventilation dryer.

  FIG. 1 is a plan view showing an example of equipment used in the drying method according to the present embodiment.

  As shown in FIG. 1, the present embodiment includes two dryers, a first-stage dryer (continuous vibration dryer) 51 and a second-stage dryer (aeration dryer) 52. The outlet of 51 and the inlet of the post-stage dryer 52 are directly connected. Accordingly, the dry raw material (water-soluble polymer-containing gel) charged into the pre-stage dryer 51 is firstly dried by the pre-stage dryer 51 and then directly guided to the post-stage dryer 52, where Next dried. In the representative drawing (FIG. 1), a vibration dryer is shown as the latter-stage dryer 52. In the secondary drying process, as shown in the following text, any ventilation type dryer may be used, and a wide variety of ventilation type dryers can be used. However, in consideration of drying efficiency, drying throughput, drying time, gel adhesion to the apparatus, etc., it is more preferable to use a vibration dryer among the aerated dryers in the secondary drying step.

  Hot air used for the pre-stage dryer 51 and the post-stage dryer 52 is obtained by the circulation blower 54 and the circulation air heater 53, and after passing through the pre-stage dryer 51 and the post-stage dryer 52, respectively, the dry dust collector 55, the dry exhaust fan. After 56, it is led again to the exhaust or circulation blower. Further, in the vicinity of the outlet of the latter-stage dryer 52, the dried polymer is cooled. The cool air used for the cooling is obtained by sucking the indoor air with the dry blower 58 and being cooled with the dry air heater. After passing through the vicinity of the outlet of the subsequent dryer 52, the cool dust collector 59 and the cooling exhaust fan 60 are used. Exhausted.

  The pre-stage dryer 51 is configured to vibrate the refined water-soluble polymer hydrated gel with a vibration stroke of 4 mm or more and allow hot air to pass through the loaded water-soluble polymer hydrated gel from the bottom of the drying deck. If it does not specifically limit, For example, Q unit (continuous drying and cooling machine) (made by Mitsubishi Materials Techno Corporation) etc. are mentioned.

  If the said vibration stroke is 4 mm or more, it can dry by suppressing caking, More preferably, it exists in the range of 4 mm or more and 25 mm or less, More preferably, it exists in the range of 5 mm or more and 10 mm or less.

  In the primary drying, the layer height of the refined water-soluble polymer hydrated gel is preferably stacked so as to be in the range of 5 mm to 50 mm, and is preferably in the range of 10 mm to 40 mm. It is more preferable to be loaded on. When the layer height is less than 5 mm, the amount of treatment decreases, so that the drying efficiency is low. When the layer height exceeds 50 mm, the water-soluble polymer hydrogel tends to aggregate.

  The frequency of vibration (frequency) may be appropriately set according to the type of water-soluble polymer hydrated gel, the moisture content, etc., but is preferably in the range of 0.046 to 0.1 Hz (600 to 1300 cpm), More preferably, it is in the range of 0.05 to 0.08 Hz (750 to 1200 cpm). Further, the excitation angle may be appropriately set depending on the type and water content of the water-soluble polymer hydrated gel, but is preferably in the range of 10 to 88 °, more preferably in the range of 30 to 85 °. is there.

  Although the linear velocity of the hot air in primary drying is not particularly limited, it is more preferably in the range of 0.5 m / s to 2 m / s. In addition, the said linear velocity is an average value of the whole airflow in a dryer, for example, can be measured by inserting the sensor part of an anemometer from the side wall of a dryer. It can also be calculated from the blower exhaust capacity. The anemometer is not particularly limited, and examples thereof include an anemo master anemometer (model 6162) manufactured by KANOMAX. The temperature of the hot air is not particularly limited, but is preferably in the range of 80 to 250 ° C, more preferably in the range of 120 to 230 ° C, and particularly preferably in the range of 160 to 210 ° C. The dew point of the hot air is not particularly limited, but is preferably 70 ° C. or lower, more preferably 60 ° C. or lower, and particularly preferably 50 ° C. or lower.

  The water content of the water-soluble polymer hydrated gel at the outlet of the dryer in primary drying may be set as appropriate according to the type of water-soluble polymer hydrated gel, etc. Although not particularly limited, it can be preferably set within a range of 5 mass% or more and 40 mass% or less. If the water content is within the above range, the water-soluble polymer water-containing gel after primary drying is unlikely to cause aggregation, so that secondary drying described later can be performed efficiently.

  Examples of the water-soluble polymer hydrogel that has been refined include granular and string-like extruded gels, finely pulverized gels, and finely cut gels. In addition, an extrusion gel means the gel extruded so that it might dry easily by extruding the gel-like thing of the polymer obtained by superposition | polymerization using an extruder. The finely pulverized gel means a fine gel obtained by pulverizing a polymer gel obtained by polymerization with a crusher or the like. The finely cut gel means a fine gel obtained by cutting a polymer gel obtained by polymerization with a cutting machine or the like.

  The water-soluble polymer hydrogel that has been refined is more preferably an extruded gel because the water-soluble polymer hydrogel is sufficiently dried to the inside of the hydrogel. The extruded gel is more preferably discharged from an extruder having a die diameter in the range of 2 mm to 20 mm.

  When the extruded gel is granular, the longest diameter is preferably in the range of 0.5 to 20 mm. The upper limit of the longest diameter is more preferably 15 mm, and still more preferably 8 mm. Moreover, when the said extrusion gel is string shape, it is preferable that a diameter is 15 mm or less and length is 50 cm or less. More preferably, the diameter is 10 mm or less and the length is 40 cm or less, and particularly preferably the diameter is 8 mm or less and the length is 30 cm or less. The size and shape of the extruded gel can be appropriately set according to conditions such as the die diameter and the extrusion speed.

In the primary drying of the drying method according to the present invention, the loading amount per unit area in terms of dry matter is not particularly limited, preferably be in a range of 0.5~30kg / m ^2, more preferably It is in the range of 1 to ²⁰ kg / m ² , particularly preferably in the range of ^{2 to} 15 kg / m ² .

  The aeration dryer used in the secondary drying in the drying method according to the present invention is not particularly limited as long as it is a dryer that performs drying while ventilating. For example, an aeration band dryer, a stirring dryer, a fluidized bed dryer, A vibration dryer etc. are mentioned. Moreover, these use conditions etc. are not specifically limited, Conventionally well-known conditions can be used. More preferably, the water-containing gel can be dried more efficiently by using a vibration dryer in secondary drying.

  In the drying method according to the present invention, the water-soluble polymer hydrated gel having a high water content, which is highly tacky and easily causes caking (aggregation) during the drying, is less likely to cause caking (aggregation) due to the primary drying described above. Therefore, the secondary drying can be performed without considering caking (aggregation) or the like. Therefore, the secondary drying is not limited to the primary drying, and the drying can be performed under the condition that the drying efficiency is high.

In the secondary drying of the drying method according to the present invention, the water-soluble polymer hydrated gel after the primary drying is less likely to agglomerate, so the load per unit area in terms of dry matter is not particularly limited, but is preferably 0.00. It can be in the range of 6 to 300 kg / m ² , more preferably in the range of 1.4 to 160 kg / m ² , and particularly preferably in the range of 3.2 to 80 kg / m ² . In addition, from the viewpoint of increasing the drying efficiency, it is more preferable to increase the secondary drying than the primary drying. Specifically, the load per unit area in terms of dry matter in the primary drying is set to 1. In this case, the load per unit area in terms of dry matter in the secondary drying is preferably in the range of 1.2 to 10, more preferably in the range of 1.4 to 8, particularly in the range of 1.6 to 6. preferable.

  In the drying method according to the present invention, the water-soluble polymer hydrogel after primary drying may be crushed and then secondary dried. When the drying method according to the present invention is used, caking (aggregation) hardly occurs in the water-soluble polymer water-containing gel after primary drying, but by slightly crushing the water-soluble polymer water-containing gel after primary drying, Since the agglomerate which exists can be solved, the drying efficiency in secondary drying can be improved more.

  Specifically, the crushing can be performed by providing a crusher between the outlet of the former dryer 51 and the inlet of the latter dryer 52. The crusher is not particularly limited, and a conventionally known crusher can be used.

  The water-soluble polymer water-containing gel is a gel-like product containing water, which is formed from a polymer obtained by polymerizing monomer components. The polymer is not particularly limited as long as it can constitute a water-soluble polymer hydrated gel, and examples thereof include an anionic polymer, a nonionic polymer, and a cationic polymer.

  Examples of the anionic polymer include (meth) acrylic acid (salt) -based polymers obtained by polymerizing a monomer component containing a (meth) acrylic acid (salt) monomer. The (meth) acrylic acid (salt) monomer is more preferably 60 mol% or more with respect to 100 mol% of the monomer component. That is, as the anionic polymer, a (meth) acrylic acid (salt) -based polymer obtained by polymerizing a monomer component containing 60 mol% or more of a (meth) acrylic acid (salt) monomer is more preferable. preferable. The higher the ratio of the (meth) acrylic acid (salt) monomer, the more remarkable the effect of the present invention. Therefore, the monomer component contains 70 mol% of the (meth) acrylic acid (salt) monomer. It is more preferable to include the above.

  The anionic polymer may be an acid type polymer having an acid group or a salt type polymer having no acid group. When producing a salt type polymer, the acid part is neutralized from the beginning. A salt-type monomer may be used.

  The water-soluble polymer hydrogel comprising the anionic polymer preferably has a solid content in the range of 20 to 60% by mass. By making solid content into such a range, when applying the drying method concerning this invention, a water-soluble polymer hydrated gel can be made into a preferable form. Even if the solid content is less than 20% by mass or exceeds 60% by mass, there is a risk that quality degradation such as a decrease in molecular weight or an increase in insoluble content may occur. A more preferable lower limit of the solid content is 25% by mass, and further preferably 30% by mass. Moreover, the upper limit of the said more preferable said solid content is 55 mass%, More preferably, it is 50 mass%.

  As described above, the (meth) acrylic acid (salt) -based polymer requires a (meth) acrylic acid (salt) monomer composed of (meth) acrylic acid and / or (meth) acrylate. It is obtained by polymerizing the monomer component. The (meth) acrylic acid (salt) -based water-soluble polymer-containing gel is a gel-like product containing water as a polymerization solvent and formed from the polymer thus obtained. As the above (meth) acrylate, neutralized product obtained by neutralizing (meth) acrylic acid with monovalent metal, divalent metal, ammonia, organic amine, etc., specifically, sodium (meth) acrylate , Potassium (meth) acrylate, magnesium (meth) acrylate, calcium (meth) acrylate, ammonium (meth) acrylate, and the like. These may be used alone or in combination of two or more. Among these, sodium (meth) acrylate is more preferable, and sodium acrylate is still more preferable.

  The monomer component may contain an acid monomer other than the (meth) acrylic acid (salt) monomer and other monomers.

  Examples of acid monomers other than the (meth) acrylic acid (salt) monomer include unsaturated monocarboxylic acid monomers such as α-hydroxyacrylic acid and crotonic acid; maleic acid, fumaric acid, itaconic acid , Unsaturated dicarboxylic acid monomers such as citraconic acid; vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfone Unsaturated sulfonic acid monomers such as acid, sulfoethyl (meth) acrylate, sulfopropyl (meth) acrylate, 2-hydroxysulfopropyl (meth) acrylate, sulfoethylmaleimide; (meth) acrylamide methanephosphonic acid, 2- ( Unsaturated phospho such as (meth) acrylamido-2-methylpropanephosphonic acid Acid monomer and monovalent metals these acid type monomer, a divalent metal, ammonium, neutralization, etc. formed by neutralization with an organic amine and the like. These may be used alone or in combination of two or more.

  Examples of the other monomers include acrylamide monomers such as (meth) acrylamide and t-butyl (meth) acrylamide; hydrophobic monomers such as (meth) acrylic acid ester, styrene, 2-methylstyrene, and vinyl acetate. 3-mer-2-buten-1-ol (prenol), 3-methyl-3-buten-1-ol (isoprenol), 2-methyl-3-buten-2-ol (isoprene alcohol), 2 -Hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol monoisoprenol ether, polypropylene glycol monoisoprenol ether, polyethylene glycol monoallyl ether, polypropylene glycol Unsaturated monomers having hydroxyl groups such as dimethyl monoethyl ether, glycerol monoallyl ether, N-methylol (meth) acrylamide, glycerol mono (meth) acrylate, vinyl alcohol; dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) ) Cationic monomers such as acrylates; Nitrile monomers such as (meth) acrylonitrile are suitable. These may be used alone or in combination of two or more.

  A solution polymerization method is preferred as the method for producing the (meth) acrylic acid (salt) -based water-soluble polymer-containing gel. More preferably, it is a method of polymerizing by a stationary polymerization method in an aqueous solution, and such a method is preferable because an insoluble content is small and a high molecular weight water-soluble polymer can be easily produced. . Moreover, as a polymerization form, a cast polymerization method or a belt polymerization method can be employed. The monomer concentration during the polymerization is preferably in the range of 20 to 60% by mass, more preferably in the range of 25 to 55% by mass, and still more preferably in the range of 30 to 50% by mass. is there.

  The polymerization method may be thermal polymerization or photopolymerization. In thermal polymerization and photopolymerization, etc., the polymerization temperature, the polymerization time, and in the case of photopolymerization, the polymerization conditions such as light intensity and wavelength, etc. are a single quantity in which (meth) acrylic acid (salt) monomer is essential. What is necessary is just to set suitably on the conditions normally performed when polymerizing a body component and preparing a (meth) acrylic acid (salt) type water-soluble polymer. That is, using the raw materials disclosed in this specification and other raw materials that can be used, the monomer component that essentially contains an acrylic acid (salt) monomer is polymerized to obtain the desired molecular weight and polymerization rate. The polymerization conditions may be appropriately set so that the (meth) acrylic acid (salt) -based water-soluble polymer is prepared.

  The thermal polymerization is preferably a static polymerization method in which a monomer is polymerized in the presence of a thermal polymerization initiator. When performing a static polymerization method, when preparing a (meth) acrylic acid polymer, it is preferable to perform in the presence of amines, and when preparing a (meth) acrylate polymer, polyvalent It is preferably carried out in the presence of alcohol and amicides.

  Specific examples of the polyhydric alcohol include, for example, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, propanediol, butanediol, butanetriol, glycerin, neopentyl glycol, hexylene glycol, and pentane. Although erythritol, a trimethylol ethane, a trimethylol propane, sorbitol etc. are mentioned, it is not specifically limited. Only one kind of these polyvalent alcohols may be used, or two or more kinds may be used in combination. Of the above exemplified compounds, glycerin is more preferred.

  The amount of the polyhydric alcohol added to the monomer component is not particularly limited, but is preferably in the range of 0.01 to 20% by mass, and more preferably in the range of 0.1 to 10% by mass. . Thereby, the polymerization degree of the (meth) acrylate water-soluble polymer can be further increased. When the addition amount of polyhydric alcohol is less than 0.01% by mass, or when the addition amount of polyhydric alcohol exceeds 20% by mass, (meth) acrylic acid having ultra high molecular weight and excellent water solubility It may be difficult to efficiently produce a salt-based water-soluble polymer.

  Examples of the amines include monoethanolamine, diethanolamine, triethanolamine, ethylamine, diethylamine, propylamine, butylamine, ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, methylethanolamine, dimethylethanolamine, diethyl Examples include ethanolamine, methyldiethanolamine, 3-amino-1-propanol, ethylhexylamine, ethoxypropylamine, dimethyllaurylamine, polyethyleneimine, pyridine, aminobenzoic acid, aminophenol, aniline, dimethylaniline, and the like. It is not something. Only one kind of these amines may be used, or two or more kinds may be used in combination. Of the compounds exemplified above, triethanolamine is more preferred.

Although the addition amount with respect to 1 mol of monomer components of the said amines is not specifically limited, The inside of the range of 1 * 10 ^{< -5} > ^-1 * 10 ^<-2> mol is preferable, and 1 * 10 < ^-4 > ^-3 * More preferably in the range of 10 ⁻³ mol. Thereby, the polymerization degree of the (meth) acrylic acid (salt) -based water-soluble polymer can be further increased. When the addition amount of amines is less than 1 × 10 ⁻⁵ mol, the progress of the polymerization is slow. When the addition amount of amines exceeds 1 × 10 ⁻² mol, it is difficult to efficiently produce a (meth) acrylic acid (salt) water-soluble polymer having an ultrahigh molecular weight and excellent water solubility. There is a risk of becoming.

  Examples of the polymerization initiator in the case of the thermal polymerization include hydrogen peroxide; persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; 2,2′-azobis- (2-amidinopropane) dihydrochloride. Water-soluble radical polymerization initiators such as azo compounds such as 2,2′-azobis- [2- (2-imidazolin) -2-yl] propane] dihydrochloride, and the like. Can be used. Among these thermal polymerization initiators, persulfate is particularly preferable.

  The amount of the thermal polymerization initiator used is preferably in the range of 0.0001 to 0.05 g with respect to 1 mol of the monomer component. The polymerization start temperature when thermal polymerization is performed is preferably in the range of 15 to 50 ° C. The polymerization is preferably controlled so that the maximum temperature of the reaction solution during polymerization is 150 ° C. or lower, more preferably 120 ° C. or lower, and even more preferably 110 ° C. or lower.

  As the polymerization initiator in the case of the photopolymerization, the following compounds can be used. 2,2'-azobis (2-amidinopropane), 2,2'-azobis (N, N'-dimethyleneisobutylamidine), 2,2'-azobis [2- (5-methyl-2-imidazoline-2 -Yl) propane], 1,1′-azobis (1 monoamidino-1-cyclopropylethane), 2,2′-azobis (2-amidino-4-methylpentane), 2,2′-azobis (2- N-phenylaminoamidinopropane), 2,2′-azobis (1-imino-1-ethylamino-2-methylpropane), 2,2′-azobis (1-allylamino-1-imino-2-methylbutane), 2,4′-azobis (2-N-cyclohexylamidinopropane), 2,2′-azobis (2-N-benzylamidinopropane) and its hydrochloric acid, sulfuric acid, acetate, etc. (4-cyanovaleric acid) and its alkali metal salts, ammonium salts, amine salts, 2- (carbamoylazo) isobutyronitrile, 2,2′-azobis (isobutyramide), 2,2′-azobis [2 -Methyl-N- (2-hydroxyethyl) propionamide], 2,2'-azobis [2-methyl-N- (1,1'-bis (hydroxymethyl) ethyl) propionamide], 2,2'- An azo photopolymerization initiator such as azobis [21-methyl-N-1,1′-bis (hydroxyethyl) propionamide].

2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-hydroxy-cyclohexyl A eutectic mixture of phenyl-ketone (Irgacure 184) and benzophenone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-methyl -1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2-benzyl-2- Dimethylamino-1- (4-morpholinophenyl) -butanone-1 (Irgacure 369) and 2,2-dimethoxy-1,2 3: 7 mixture with diphenylethane-1-one (Irgacure 651), bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4 -1: 3 mixture of trimethyl-pentylphosphine oxide (CGI403) and 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Darocur 1173), bis (2,6-dimethoxybenzoyl)- A 1: 3 mixture of 2,4,4-trimethyl-pentylphosphine oxide (CGI 403) and 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184), bis (2,6-dimethoxybenzoyl) -2,4 , 4-trimethyl-pentylphosphine oxide (CGI403) and 1: 1 mixture with -hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propane-1 -1: 1 liquid mixture with ONE (Darocur 1173), bis (η ⁵ -2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) ) -Phenyl) titanium, oligo [2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone], eutectic mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone Liquid mixture of 4-methylbenzophenone and benzophenone, 2,4,6-trimethylbenzoyldiphenyl O scan fins oxide and oligo [2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone] and the liquid mixture of methyl benzophenone derivatives.

  1- [4- (4-Benzoylphenylsulfanyl) phenyl] -2-methyl-2- (4-methylphenylsulfanyl) propan-1-one, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenyl- 1-propanone, α-hydroxycyclohexyl-phenyl ketone, ethyl-4-dimethylaminobenzoate, acrylated amine synergist, benzoin (iso- and n-) butyl ester, acrylic sulfonium (mono, di) hexafluorophosphate, 2-isopropylthioxanthone, 4-benzoyl-4′-methyldiphenyl sulfide, 2-butoxyethyl-4- (dimethylamino) benzoate, ethyl 4- (dimethylamino) benzoate, benzoin, benzoin alkyl ether, benzoin hydro Shi alkyl ethers, diacetyl and its derivatives, anthraquinone and its derivatives, diphenyl disulfide and its derivatives, benzophenone and its derivatives, benzyl and its derivatives.

  The amount of the photopolymerization initiator used is preferably 0.0001 g or more and more preferably 1 g or less with respect to 1 mol of the monomer component used for polymerization. Thereby, the mass average molecular weight and polymerization rate of the (meth) acrylic acid (salt) -based water-soluble polymer can be made sufficiently high. More preferably, it is 0.001 g or more and 0.5 g or less. The polymerization initiation temperature for photopolymerization is preferably in the range of 0 to 30 ° C. The polymerization is preferably controlled so that the maximum temperature of the reaction solution during polymerization is 150 ° C. or lower, more preferably 120 ° C. or lower, and even more preferably 110 ° C. or lower.

When carrying out the photopolymerization, it is preferable to irradiate the reaction solution or the like with near ultraviolet rays. For example, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, a fluorescent chemical lamp, or a fluorescent blue lamp is suitable as a device that irradiates near ultraviolet rays. Further, the wavelength region of near ultraviolet rays is preferably 300 nm or more, and preferably 500 nm or less. By irradiating the reaction liquid or the like with ultraviolet rays having a wavelength in this range, photopolymerization starts and the polymerization reaction proceeds at an appropriate rate. Moreover, when performing photopolymerization, it is preferable to superpose | polymerize by irradiating near ultraviolet rays with the intensity | strength of 0.1-100 W / m < ² >, and, thereby, an insoluble part can be decreased more.

  In the polymerization method, it is preferable to use a chain transfer agent together with the polymerization initiator. By using an appropriate amount of chain transfer agent, it is possible to produce a polymer having a higher weight average molecular weight and less insoluble content of the (meth) acrylic acid (salt) -based water-soluble polymer. As a result, the effects of the present invention can be more fully exhibited.

  Examples of the chain transfer agent include sulfur-containing compounds such as thioglycolic acid, thioacetic acid, and mercaptoethanol; phosphorous compounds such as phosphorous acid and sodium phosphite; hypophosphorous acid such as hypophosphorous acid and sodium hypophosphite Preferred compounds are alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-butyl alcohol. Among these, hypophosphorous acid compounds are preferable. More preferred is sodium hypophosphite.

  The amount of the chain transfer agent used may be appropriately set depending on the polymerization concentration, a combination with a photopolymerization initiator, and the like, but is preferably 0.0001 g or more with respect to 1 mol of the monomer component used for the polymerization. Moreover, 0.2 g or less is preferable. Further, it is more preferably 0.001 g or more and 0.15 g or less, particularly preferably 0.005 g or less and 0.10 g or less.

  Examples of the nonionic polymer include polyacrylamide obtained by polymerizing a monomer component containing the above-mentioned acrylamide monomer, and a monomer component containing the above-mentioned unsaturated monomer having a hydroxyl group. The polymer obtained by this is mentioned. The polyacrylamide can be produced, for example, by the method described in JP-A-60-192713, and specifically, can be produced by the method described in Synthesis Example 6 described later.

  More specifically, the method for producing polyacrylamide is a method of polymerizing an aqueous solution of acrylamide monomer, and the monomer concentration is preferably in the range of 10 to 35% by mass, more preferably 20 to 30% by weight. Within range. If the monomer concentration is too high, the temperature becomes high during the polymerization, and the quality of the resulting polymer tends to deteriorate. If the monomer concentration is too low, the polymer tends to take a long time to dry.

  In the method for producing polyacrylamide, it is preferable to use a known azo polymerization catalyst and an acidic sulfite or a sulfite and a specific metal salt in combination as a catalyst. When the azo polymerization catalyst is used alone, even if the monomer concentration is increased and the polymerization initiation temperature is lowered, the polymerization rate is slow and good polymerization cannot be performed.

  Examples of the azo polymerization catalyst include 2,2′-azobis (2-amidinopropane) hydrochloride, azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethyl-valero). Nitrile), 1,1′-azobis (cyclohexanecarbonitrile) and the like, more preferably 2,2′-azobis (2-amidinopropane) hydrochloride.

  The addition amount of the azo polymerization catalyst is in the range of 100 to 2000 ppm, preferably in the range of 400 to 1400 ppm with respect to the monomer. When the addition amount of the azo polymerization catalyst is too small, the polymerization is not performed satisfactorily, and when the addition amount is too large, the molecular weight of the resulting polymer tends to decrease.

  Examples of the acidic sulfite or sulfite include sodium salts and potassium salts. Moreover, the addition amount is in the range of 3 to 200 ppm, preferably in the range of 5 to 100 ppm with respect to the monomer. The amount of the acidic sulfite or sulfite added is the same as the amount of the azo polymerization catalyst added. If the amount is too small, the polymerization is not performed well, and if the amount is too large, the molecular weight of the resulting polymer tends to decrease. is there.

  The metal salt is a salt of at least one metal selected from cobalt, manganese, or iron. For example, a water-soluble second metal salt is used. Examples of these metal salts include sulfates, hydrochlorides, bromates, acetates, oxalates, nitrates, and the like. Of these, sulfate is preferable. The amount of the metal salt used is within a range of 0.1 to 20 ppm, preferably 0.2 to 2 ppm as a metal with respect to the monomer. When the addition amount of the metal salt is too small, the polymerization is not performed well, and even if the addition amount is too large, there is no difference in the effect.

  In general, the order of addition of the above additives into the polymerization system is preferably such that acid sulfite or sulfite is added last, for example, in the order of metal salt, azo polymerization catalyst, acidic sulfite or sulfite. be able to.

  In the above polyacrylamide production method, the polymerization temperature is usually in the range of −10 to 100 ° C., and the temperature at the start of polymerization is set to, for example, 20 ° C. or less, preferably 10 ° C. or less. The polymerization time is usually in the range of 0.5 to 10 hours.

  In the method for producing polyacrylamide, for example, an aqueous monomer solution is charged into a closed polymerization tank, nitrogen gas is blown into the aqueous monomer solution to remove dissolved oxygen, and then the above catalyst is added as an aqueous solution for polymerization.

  Examples of the cationic polymer include a polymer obtained by polymerizing a monomer component containing the above-described cationic monomer, and polymerization or copolymerization after quaternizing the dialkylaminoethyl (meth) acrylate. Polymer (hereinafter referred to as (meth) acrylic acid dialkylaminoethyl polymer) and the like. The polymer can be produced, for example, by the method described in JP-A-63-230714. Specifically, for example, it can be produced by the method described in Synthesis Example 5 described later.

  More specifically, examples of the dialkylaminoethyl (meth) acrylate include dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate. These dialkylaminoethyl (meth) acrylates can be synthesized by an ester exchange reaction between methyl (meth) acrylate and dialkylaminoethanol or an esterification reaction of (meth) acrylic acid with dialkylaminoethanol.

  In the production of the above (meth) acrylic acid dialkylaminoethyl polymer, it is preferable to polymerize or copolymerize (meth) acrylic acid dialkylaminoethyl which is substantially free of (meth) acrylic acid and then quaternized. Removal of vinyl (meth) acrylate from dialkylaminoethyl (meth) acrylate can be carried out by distillation operation using a distillation column with a high number of stages and a sufficient reflux ratio, but by treating with zeolite. It can also be done. Specifically, it is preferable to produce dialkylaminoethyl (meth) acrylate not containing vinyl (meth) acrylate as an impurity by the following method.

  A low-boiling component is first removed from a dialkylaminoethyl (meth) acrylate-containing solution synthesized by transesterification or esterification, and then purified by distillation under reduced pressure. Distillation can be performed by an ordinary method, for example, by continuous distillation or batch distillation at a reflux ratio of about 0.1 to 4 using a distillation column having 4 to 20 theoretical plates.

  The purity of dialkylaminoethyl (meth) acrylate obtained by distillation under reduced pressure is generally in the range of 97.0 to 99.9%, and vinyl (meth) acrylate is included in the range of 30 to 500 ppm.

  Next, the dialkylaminoethyl (meth) acrylate containing impurities is treated with zeolite. Zeolite treatment methods include a continuous method in which the treatment liquid is passed through a tower packed with zeolite, or a batch method in which zeolite is added to the treatment liquid for treatment, and then the zeolite is separated by filtration, centrifugation, or the like. It may be used.

  Various commercially available zeolites can be used. Among these, synthetic zeolites having uniform pores and showing molecular sieving action are called molecular sieves and can be preferably used. . The molecular sieve is particularly preferably one having a pore size of 5 mm or more.

  The amount of the zeolite used is preferably in the range of 0.1 to 5% by weight of the treatment liquid. The treatment temperature may be in the range from the freezing point to the boiling point of the dialkylaminoethyl (meth) acrylate, but is preferably in the range of 0 to 50 ° C. in consideration of the stability of the ester.

  The purification conditions for dialkylaminoethyl (meth) acrylate are preferably controlled so that the content of vinyl (meth) acrylate in the resulting dialkylaminoethyl (meth) acrylate is 20 ppm or less. More preferably, it is 10 ppm or less, More preferably, it is 3 ppm or less.

  A quaternary salt is obtained by neutralizing the dialkylaminoethyl (meth) acrylate obtained as described above with a mineral acid such as hydrochloric acid or sulfuric acid, or by reacting with an alkylating agent such as methyl chloride or dimethyl sulfuric acid. be able to.

  The polymerization of the quaternary salt may be a homopolymerization of only a dialkylaminoethyl quaternary (meth) acrylate, or a copolymerization with other vinyl monomers such as acrylamide.

  Examples of the polymerization initiator used in the above polymerization include azo compounds such as azobisdimethylvaleronitrile, azobiscyanovaleric acid sodium salt, azobisisobutyronitrile, azobisaminopropane hydrochloride, benzoyl peroxide, lauroyl Examples thereof include organic peroxides such as peroxides and inorganic oxides such as potassium persulfate, sodium persulfate, ammonium persulfate, and hydrogen peroxide. In addition, inorganic compounds such as ferrous sulfate, ferrous chloride and sodium bisulfite, and organic compounds such as dimethylaniline and 3-dimethylaminopropionitrile may be added.

  The mass average molecular weight of the water-soluble polymer in the water-soluble polymer-containing gel is not particularly limited as long as it forms a water-containing gel, but is preferably in the range of 1 million to 20 million. The “mass average molecular weight” in the present specification is a value measured by a light scattering method. The mass average molecular weight can be measured using a dynamic light scattering photometer under the following conditions.

Apparatus: Dynamic light scattering photometer (trade name: DSL-700, manufactured by Otsuka Electronics Co., Ltd.)
Solvent: 0.16M NaCl aqueous solution Sample concentration: 0.05-2 mg / ml
Sample pH: 10 (at 25 ° C)
Measurement temperature: 25 ° C
The water-soluble polymer according to the present invention is obtained by drying the water-soluble polymer-containing gel by the drying method according to the present invention described above. For this reason, since drying time is short and there is little heat history, side reactions, such as a crosslinking reaction, do not occur easily, there are few insoluble components, and there is little coloring. Specifically, the insoluble content of the water-soluble polymer is preferably 1% by mass or less. Moreover, the hunter whiteness (hunter whiteness) of the water-soluble polymer is preferably 87% or more.

  In the above description, the case where the outlet of the front dryer 51 and the inlet of the rear dryer 52 are directly connected has been described. However, the present invention is not limited to this. The outlet of the pre-stage dryer 51 and the entrance of the post-stage dryer 52 are not directly connected, and the water-soluble polymer-containing gel after primary drying is once filled with a container or the like from the outlet of the pre-stage dryer 51, and the post-stage dryer 52 It may be sequentially introduced into the entrance.

  However, when the outlet of the former dryer 51 and the inlet of the latter dryer 52 are directly connected as in this embodiment, a step of filling the water-soluble polymer hydrogel after primary drying is not necessary. Since the production cost is further reduced, the effect is particularly great.

  In the above description, the latter-stage dryer 52 is described as being configured to cool the dried polymer near the outlet, but is not limited thereto. The cooling structure may not be provided and may be separately cooled after the secondary drying.

  In other words, in the drying method according to the present invention, the water-soluble polymer hydrated gel that has been refined is loaded on the drying deck, and the water-soluble polymer hydrated gel is vibrated with a vibration stroke of 4 mm or more. This is a drying method in which hot water is passed through the united hydrogel from the bottom of the drying deck, but the water-soluble polymer hydrogel is efficiently dried by performing two-stage drying as in the above-described embodiment. can do.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  Hereinafter, although an example and a comparative example explain the present invention still in detail, the present invention is not limited to these examples. In the following description, for convenience, “parts by mass” may be simply referred to as “parts”.

  Prior to the examples, the following Reference Examples 1 to 28 were performed using a batch-type vibration dryer, and the effect of primary drying in the drying method according to the present invention was confirmed.

[Synthesis Example 1] (Anionic polymer, neutralization degree 100%, thermal polymerization)
In a beaker with a capacity of 5 L, 4865 parts of a 37% by weight aqueous solution of sodium acrylate, 36 parts of glycerin and 0.111 part of sodium persulfate as a polymerization initiator were stirred and mixed to dissolve them uniformly. By adding a small amount of sodium hydroxide to this aqueous solution, the pH of the aqueous solution was adjusted to 12.0. Thereafter, 5000 parts of a reaction solution was prepared by adding ion exchange water to the aqueous solution. Further, dissolved oxygen contained in the reaction solution was removed by bubbling nitrogen gas. The concentration of sodium acrylate in the reaction solution was 36% by mass. And the addition amount of glycerol with respect to sodium acrylate was 2.0 mass%, and the addition amount of sodium persulfate with respect to 1 mol of sodium acrylate was 0.0058g (2.5 * 10 < ^-5 > mol).

  After charging 5000 parts of the reaction solution into the polymerization vessel shown in FIGS. 2 and 3, the glass cock of the reaction solution inlet 2 and the reaction solution purge port 3 was closed and the thermometer 5 was inserted to seal the inside of the polymerization vessel. . As shown in FIGS. 2 and 3, the polymerization vessel includes a mold 1 including a reaction liquid injection port 2, a reaction liquid purge port 3, a thermometer 5, a polymerization unit 6, and a packing 4. It is.

  The said polymerization container was immersed in the constant temperature water tank (heating apparatus) previously prepared at 35 degreeC, and superposition | polymerization (stationary polymerization) was started. Therefore, the water bath temperature (heating temperature) at the start of polymerization is 35 ° C.

  After the polymerization vessel was immersed in a constant temperature water bath, the polymerization gradually proceeded, and the polymerization temperature reached a peak at 3.6 ° C. (peak temperature) after 3.6 hours from the time of immersion. During this time, the water bath temperature was maintained at 35 ° C. And after superposition | polymerization start temperature reached the peak, the water bath temperature was hold | maintained at 35 degreeC for further 0.5 hour. Next, the water bath temperature was continuously raised from 35 ° C. to 75 ° C. over 0.5 hours. Then, the temperature (heating temperature) was maintained for 2.0 hours to complete the polymerization. After completion of the polymerization, the polymerization vessel was cooled, the bolts and nuts were loosened, the mold was opened, and the contents were taken out. The content obtained was a transparent plate-like gel. The solid content was 37% by mass.

[Synthesis Example 2] (Anionic polymer, neutralization degree 100%, thermal polymerization)
In a 5 L beaker, 1929 parts of a 37% by weight aqueous solution of sodium acrylate, 846.2 parts of 2-acrylamido-2-methylpropanesulfonic acid, 1820 parts of ion-exchanged water and 41.3 parts of glycerin were dissolved. The pH of the solution was adjusted to 12.8 by adding about 340 parts of a 48% by weight aqueous solution of sodium hydroxide to the solution. Furthermore, after adding 0.117 parts of sodium persulfate as a polymerization initiator and stirring and dissolving, a small amount of ion-exchanged water was added to prepare 5000 parts of a reaction solution. Dissolved oxygen contained in the reaction solution was removed by bubbling nitrogen gas. The concentration of the monomer consisting of sodium acrylate and sodium 2-acrylamido-2-methylpropanesulfonate in the reaction solution was 33% by mass. And the addition amount of glycerol with respect to a monomer was 2.5 mass%, and the addition amount of sodium persulfate with respect to 1 mol of monomers was 0.010g.

  After 5000 parts of the reaction solution was charged into the polymerization vessel used in Synthesis Example 1, the glass cock was closed and a thermometer was inserted to seal the inside of the polymerization vessel.

  The said polymerization container was immersed in the constant temperature water tank (heating apparatus) previously prepared at 38 degreeC, and superposition | polymerization (stationary polymerization) was started. Therefore, the water bath temperature (heating temperature) at the start of polymerization is 38 ° C.

  After the polymerization vessel was immersed in a constant temperature water bath, the polymerization proceeded gradually, and the polymerization temperature reached a peak at 3.3 hours after reaching the time of immersion, reaching 62 ° C. (peak temperature). During this time, the water bath temperature was maintained at 38 ° C. And after superposition | polymerization start temperature reached the peak, the water tank temperature was hold | maintained at 38 degreeC for further 0.5 hour. Subsequently, the water bath temperature was continuously raised from 38 ° C. to 75 ° C. over 0.5 hours. Then, the temperature (heating temperature) was maintained for 2.0 hours to complete the polymerization. After completion of the polymerization, the polymerization vessel was cooled, the bolts and nuts were loosened, the mold was opened, and the contents were taken out. The obtained content is a transparent plate gel made of a polymer having a constitutional unit ratio derived from a monomer of sodium acrylate / 2-acrylamido-2-methylpropanesulfonate = 65/35 (molar ratio) Met. The solid content was 34% by mass.

[Synthesis Example 3] (Anionic polymer, neutralization degree 100%, thermal polymerization)
A beaker having a capacity of 5 L was charged with 1490 parts of a 37% by weight aqueous solution of sodium acrylate, 993.2 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2070 parts of ion-exchanged water, and 41.3 parts of glycerin. The pH of the solution was adjusted to 12.8 by adding about 400 parts of a 48% by weight aqueous solution of sodium hydroxide to the solution. Furthermore, after adding 0.106 parts of sodium persulfate as a polymerization initiator and stirring and dissolving, a small amount of ion-exchanged water was added to prepare 5000 parts of a reaction solution. Dissolved oxygen contained in the reaction solution was removed by bubbling nitrogen gas. The concentration of the monomer consisting of sodium acrylate and sodium 2-acrylamido-2-methylpropanesulfonate in the reaction solution was 33% by mass. And the addition amount of glycerol with respect to a monomer was 2.5 mass%, and the addition amount of sodium persulfate with respect to 1 mol of monomers was 0.010g.

  After 5000 parts of the reaction solution was charged into the polymerization vessel used in Synthesis Example 1, the glass cock was closed and a thermometer was inserted to seal the inside of the polymerization vessel.

  The said polymerization container was immersed in the constant temperature water tank (heating apparatus) previously prepared at 38 degreeC, and superposition | polymerization (stationary polymerization) was started. Therefore, the water bath temperature (heating temperature) at the start of polymerization is 38 ° C.

  After the polymerization vessel was immersed in a constant temperature water bath, the polymerization proceeded gradually, and the polymerization temperature reached a peak at 3.6 ° C. (peak temperature) 3.6 hours after the immersion. During this time, the water bath temperature was maintained at 38 ° C. And after superposition | polymerization start temperature reached the peak, the water tank temperature was hold | maintained at 38 degreeC for further 0.5 hour. Subsequently, the water bath temperature was continuously raised from 38 ° C. to 75 ° C. over 0.5 hours. Then, the temperature (heating temperature) was maintained for 2.0 hours to complete the polymerization. After completion of the polymerization, the polymerization vessel was cooled, the bolts and nuts were loosened, the mold was opened, and the contents were taken out. The obtained content is a transparent plate gel made of a polymer having a constitutional unit ratio derived from a monomer of sodium acrylate / 2-acrylamido-2-methylpropanesulfonate = 55/45 (molar ratio). Met. The solid content was 34% by mass.

[Synthesis Example 4] (Anionic polymer, neutralization degree 60%, photopolymerization)
In a beaker with a capacity of 500 ml, acrylic acid 76.1 g, sodium acrylate 37 mass% aqueous solution 402.6 g, ion-exchanged water 16.58 g, 2,2′-azobis (2-amidinopropane) dihydrochloride as a photopolymerization initiator 2.13 g of 5% aqueous solution and 2.64 g of 1% aqueous sodium diphosphite were added.

  The concentration of the monomer composed of acrylic acid and sodium acrylate in the reaction solution was 50 mass%, and the degree of neutralization was 60 mol%. The amount of 2,2'-azobis (2-amidinopropane) dihydrochloride used was 0.04 g per mole of monomer. Moreover, the usage-amount of sodium hypophosphite was the ratio of 0.01g with respect to 1 mol of monomers.

  After stirring and mixing the reaction solution, the reaction solution was introduced into a polymerization vessel shown in FIG. The polymerization container is made of SUS304, and a Teflon (registered trademark) film having a thickness of 0.08 mm (adhesive is a silicone system having a thickness of 0.05 mm) is attached to the bottom and the temperature is set to 35 ° C. at the bottom. The adjusted water is circulating. The polymerization vessel is provided with a thermometer 10, a heat conductive substrate 8 is provided on the bottom surface, and the heat conductive substrate 8 is covered with a release material 7. A water inlet 12 and a water outlet 13 are provided at the bottom of the polymerization vessel so that the cooling water 11 can be circulated.

  The polymerization vessel was covered with Saran Wrap 9 (registered trademark), and then dissolved oxygen in the reaction solution was removed by bubbling nitrogen.

Next, as shown in FIG. 5, from a top of 35 cm in height, a black light mercury lamp 14 (manufactured by Toshiba Lighting & Technology Corp., H100BL-L) installed sideways by a lamp holder 15 (manufactured by Toshiba Lighting & Technology Corp.) The reaction solution was used and irradiated with light. The light intensity is 3.7 W / m ² at the upper surface position of the reaction solution. The light intensity was a light meter (a UV meter (model UVA-365) manufactured by Custom).

As soon as the light irradiation was started, the polymerization started and reached the primary peak temperature of 73 ° C. after 16 minutes. Thereafter, after standing for 3 minutes, as shown in FIG. 6, the reflector shade 17 (SN-4057T, Toshiba Lighting & Technology Corporation) installed vertically from the top of the 15.5cm height by the lamp holder 15 (manufactured by Toshiba Lighting & Technology Corporation). The polymerization was completed by irradiation with a black light mercury lamp 16 (manufactured by TOSHIBA) (Toshiba Lighting & Technology Co., Ltd., H400BL-L) for 7 minutes. The light intensity is 17 W / m ² at the upper surface position of the reaction solution.

  When the gel polymer thus obtained was taken out from the polymerization vessel, it was easily released without any polymer remaining attached to the vessel. The solid content of the polymer composed of the partially neutralized polyacrylic acid was 52% by mass.

[Synthesis Example 5] (cationic polymer)
A 200 L glass pressure-resistant four-necked flask was charged with 2200 parts of dimethylaminoethyl methacrylate and 730 parts of water, and reacted at 30 ° C. under a pressure of 0.1 MPa for 5 hours while blowing methyl chloride. After completion of the reaction, excessively blown methyl chloride was removed to obtain an aqueous quaternary ammonium salt solution.

  The flask was charged with 1500 parts of the quaternary ammonium salt aqueous solution, 1860 parts of acrylamide, and 1640 parts of water in a 5 L beaker, and the dissolved oxygen contained in the solution was removed by bubbling nitrogen gas. Next, 0.65 part of sodium 4,4'-azobis-4-cyanovalerate, 0.070 part of ammonium persulfate and 0.040 part of sodium bisulfite were added and mixed. The reaction solution was placed in the polymerization vessel used in Synthesis Example 1, and polymerization was started in a constant temperature water bath whose temperature was adjusted to 30 ° C. in advance. After the polymerization reached the peak temperature, the polymerization was completed by maintaining the same temperature for 1 hour. In this way, a cationic hydrogel polymer was obtained. The obtained content was a transparent plate-like gel, and the solid content was 60% by mass.

[Synthesis Example 6] (Nonionic polymer, thermal polymerization)
A beaker having a capacity of 5 L was charged with 5000 parts of a 25% by mass aqueous solution of acrylamide, and nitrogen gas was bubbled to remove dissolved oxygen contained in the solution. Subsequently, 500 ppm of 2,2′-azobis-2- (amidinopropane) dihydrochloride, 20 ppm of sodium bisulfite and 0.5 ppm of ferric ammonium sulfate were added and mixed, and then the reaction solution was synthesized in Synthesis Example 1. The polymerization was completed by placing it in the polymerization vessel used in the above and immersing it in a constant temperature water bath previously prepared at 18 ° C. for 5 hours. The obtained content was a transparent plate-like gel, and the solid content was 25.5% by mass.

[Synthesis Example 7]
The polymerization of Synthesis Example 1 was performed at an increased scale. That is, the size of the polymerization vessel was increased to 1.2 m in length, 1.0 m in width, and 5 cm in width. Furthermore, 50 tons of this polymerization frame were arranged in a row to obtain 3 tons of hydrous gel per batch. The obtained hydrogel had a solid content of 37% by mass.

[Reference Example 1]
The plate-like gel obtained in Synthesis Example 1 was cut into strips and then supplied to a meat chopper (manufactured by Hiraga Kakujo Co., Ltd., No. 32E type, die diameter: 4.5 mmφ), and the shape of the icicles (granules) connected in a string shape Shaped extruded gel was obtained. After the gel particles connected in a string form are broken into fine particles by hand, 1.1 kg uniformly on the deck of a batch vibration dryer (QAD, manufactured by Mitsubishi Materials Techno Corporation) set and operated under the conditions shown in Table 1. Loaded. The gel layer height at this time was 20 mm, and the gel loading density (loading amount per unit area) was 11.7 kg / m ² (loading density in terms of dry matter was 4.3 kg / m ² ).

  Drying started as soon as the gel was loaded on the deck, and the data shown in Table 2 was obtained. During drying, the gel vibrated in an independent particle state without caking (aggregation).

  The moisture content was measured with a Kett infrared moisture meter (FD-230) by collecting a small sample every predetermined time during drying. Drying was completed in 23 minutes. After cooling, the mixture was pulverized with a desktop pulverizer and classified with a 20 mesh wire mesh to obtain a polymer (sodium polyacrylate) powder (A-1). As physical properties of the polymer powder (A-1), solution viscosity, insoluble matter, and Hunter whiteness were measured by the following methods. The results are shown in Table 2.

(Measurement method of solution viscosity)
(A) In the case of polymer powders obtained from the hydrogels of Synthesis Examples 1 to 4 and 7 After adding 20 ml of methanol to a beaker having a capacity of 500 ml, 1 g of polymer powder was added in terms of pure matter. While stirring this solution with a magnetic stirrer, 500 ml of ion-exchanged water was added to the beaker. Then, after using a jar tester and stirring at 100 rpm for 50 minutes, the temperature was adjusted to 30 ° C. and the viscosity was measured with a B-type viscometer (manufactured by TOKIMEC) (30 rpm).

(B) In the case of polymer powder obtained from hydrous gel of Synthesis Example 5 500 ml of ion-exchanged water was placed in a beaker having a capacity of 500 ml, and 5 g of polymer powder was added in terms of pure matter while stirring with a magnetic stirrer. After using a jar tester and stirring at 100 rpm for 1 hour, 5.5 g of sodium chloride was added and stirring was continued for 30 minutes. Next, the temperature was adjusted to 25 ° C., and the viscosity was measured with a B-type viscometer (manufactured by TOKIMEC) (30 rpm).

(C) In the case of polymer powder obtained from the hydrogel of Synthesis Example 6 Into a beaker having a capacity of 500 ml, 500 ml of a 4% by mass sodium chloride aqueous solution was added, and the polymer powder was converted to a pure equivalent of 2 while stirring with a magnetic stirrer. .5 g was added. After stirring for 1 hour at 100 rpm using a jar tester, the temperature was adjusted to 25 ° C., and the viscosity was measured with a B-type viscometer (manufactured by TOKIMEC) (30 rpm).

[Measurement method of insoluble matter]
After putting 20 ml of methanol into a 500 ml beaker, 1 g of polymer powder was added in terms of pure matter. While stirring with a magnetic stirrer, 500 ml of ion-exchanged water was added, and after stirring for 50 minutes at 100 rpm using a jar tester, the mixture was filtered using a 32 mesh filter to remove insoluble matter in water (insoluble The dissolved part) was taken out. Then, this insoluble matter (insoluble matter) is quickly weighed so as not to dry, and the following calculation formula: Insoluble matter (mass%) = [mass of insoluble matter (g) / 500 (g)] × 100
Was used to calculate the insoluble matter.

[Hunter whiteness measurement method]
Hunter whiteness was measured with Spectrophotometer SE2000 (manufactured by Nippon Denshoku).

[Reference Examples 2 and 3]
Drying was carried out in the same manner as in Reference Example 1 except that the gel layer height during loading was changed to the values shown in Table 2, and polymer powders (A-2) and (A-3) were obtained. The physical properties of the polymer powders (A-2) and (A-3) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Examples 4 and 5]
Drying was performed in the same manner as in Reference Example 1 except that the stroke (vibration stroke) of the vibration dryer was changed to the value shown in Table 2, and polymer powders (A-4) and (A-5) were obtained. The physical properties of the polymer powders (A-4) and (A-5) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Examples 6 to 8]
Except that the gel was extruded with the die diameter of the meat chopper shown in Table 2 and the particle size of the gel was changed, drying was performed in the same manner as in Reference Example 1 to obtain polymer powders (A-6) to (A-8). It was. The physical properties of the polymer powders (A-6) to (A-8) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Examples 9 and 10]
Drying was performed in the same manner as in Reference Example 1 except that the vibration angle of the vibration drier was changed to the values shown in Table 2, and polymer powders (A-9) and (A-10) were obtained. The physical properties of the polymer powders (A-9) and (A-10) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Examples 11 and 12]
Drying was performed in the same manner as in Reference Example 1 except that the hot air temperature during drying was changed to the values shown in Table 2, and polymer powders (A-11) and (A-12) were obtained. The physical properties of the polymer powders (A-11) and (A-12) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Examples 13 to 15]
Drying was performed in the same manner as in Reference Example 1 except that the linear velocity of hot air during drying was set to the values shown in Table 2, and polymer powders (A-13) to (A-15) were obtained. The physical properties of the polymer powders (A-13) to (A-15) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Example 16]
Instead of using the plate-like gel obtained in Synthesis Example 1, drying was performed in the same manner as in Reference Example 1 except that the acrylic acid polymer obtained in Synthesis Example 2 was used, and polymer powder (A -16) was obtained. The physical properties of the polymer powder (A-16) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Example 17]
Instead of using the plate-like gel obtained in Synthesis Example 1, drying was performed in the same manner as in Reference Example 1 except that the acrylic acid-based polymer obtained in Synthesis Example 3 was used, and polymer powder (A -17) was obtained. The physical properties of the polymer powder (A-17) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Example 18]
Instead of using the plate-like gel obtained in Synthesis Example 1, drying was performed in the same manner as in Reference Example 1 except that the acrylic acid-based polymer obtained in Synthesis Example 4 was used, and polymer powder (A -18) was obtained. The physical properties of the polymer powder (A-18) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Example 19]
Instead of using the plate-like gel obtained in Synthesis Example 1, drying was performed in the same manner as in Reference Example 1 except that the cationic polymer obtained in Synthesis Example 5 was used, and polymer powder (A-19 ) The physical properties of the polymer powder (A-19) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Example 20]
Instead of using the plate-like gel obtained in Synthesis Example 1, drying was performed in the same manner as in Reference Example 1 except that the nonionic polymer obtained in Synthesis Example 6 was used, and polymer powder (A-20 ) The physical properties of the polymer powder (A-20) were measured in the same manner as in Reference Example 1, and the results are shown in Table 2.

[Reference Example 21]
Drying was carried out in the same manner as in Reference Example 1 except that the gel layer height at the time of loading was changed to the values shown in Table 3 to obtain a polymer powder (A-21). The physical properties of the polymer powder (A-21) were measured in the same manner as in Reference Example 1, and the results are shown in Table 3.

[Reference Example 22]
Drying was performed in the same manner as in Reference Example 1 except that the stroke of the vibration drier was changed to the values shown in Table 3, and polymer powder (A-22) was obtained. The physical properties of the polymer powder (A-22) were measured in the same manner as in Reference Example 1, and the results are shown in Table 3.

[Reference Example 23]
Instead of using the plate-like gel obtained in Synthesis Example 1, drying was performed in the same manner as in Reference Example 22 except that the acrylic acid polymer obtained in Synthesis Example 2 was used, and polymer powder (A -23) was obtained. The physical properties of the polymer powder (A-23) were measured in the same manner as in Reference Example 1, and the results are shown in Table 3.

[Reference Example 24]
Instead of using the plate-like gel obtained in Synthesis Example 1, drying was performed in the same manner as in Reference Example 22 except that the acrylic acid polymer obtained in Synthesis Example 3 was used, and polymer powder (A -24) was obtained. The physical properties of the polymer powder (A-24) were measured in the same manner as in Reference Example 1, and the results are shown in Table 3.

[Reference Example 25]
Instead of using the plate-like gel obtained in Synthesis Example 1, drying was performed in the same manner as in Reference Example 22 except that the acrylic acid polymer obtained in Synthesis Example 4 was used, and polymer powder (A -25) was obtained. The physical properties of the polymer powder (A-25) were measured in the same manner as in Reference Example 1, and the results are shown in Table 3.

[Reference Example 26]
Instead of using the plate-like gel obtained in Synthesis Example 1, the cationic polymer obtained in Synthesis Example 5 was used, and the temperature of the hot air was set to the value shown in Table 3, and was the same as Reference Example 22. Was dried to obtain a polymer powder (A-26). The physical properties of the polymer powder (A-26) were measured in the same manner as in Reference Example 1, and the results are shown in Table 3.

[Reference Example 27]
Instead of using the plate-like gel obtained in Synthesis Example 5, drying was performed in the same manner as in Reference Example 26 except that the nonionic polymer obtained in Synthesis Example 6 was used, and polymer powder (A-27 ) The physical properties of the polymer powder (A-27) were measured in the same manner as in Reference Example 1, and the results are shown in Table 3.

[Reference Example 28]
A polymer powder (A-28) was obtained by drying in the same manner as in Reference Example 21 except that the stroke of the vibration dryer was changed to the values shown in Table 3. The physical properties of the polymer powder (A-28) were measured in the same manner as in Reference Example 1, and the results are shown in Table 3.

  From the results using the batch type vibration dryer shown in Tables 2 and 3, it was confirmed that if the stroke was 4 mm or more, the caking was suppressed and the drying could be performed. In addition, the polymer powder obtained by drying under the condition where the stroke is 4 mm or more has a higher solution viscosity than the polymer powder obtained by drying under the condition where the stroke is less than 4 mm. It was confirmed that the hunter whiteness tends to be low and low. This is because the polymer powder obtained by drying under the condition where the stroke is 4 mm or more has a shorter drying time and less heat history than the polymer powder obtained by drying under the condition where the stroke is less than 4 mm. Because.

  Based on these results, in order to further shorten the drying time, two-stage drying using two continuous dryers shown in the following examples was performed.

[Example 1]
After the plate-like gel obtained in Synthesis Example 7 is cut into strips, it is supplied to a meat chopper (No. 72 type, die diameter 4.5 mmφ, manufactured by Hiraga) at a rate of 9.0 kg / min. An extrudate (granular) extruded gel connected in a continuous manner was obtained.

  While the gel particles connected to the string are broken into fine particles by a gel crusher (dispersing machine), the continuous drier shown in FIG. 1 (drying composed of a front dryer and a rear dryer) is used. System). Table 4 shows the specifications and operating conditions of the former dryer 51 and the latter dryer 52.

  The post-stage dryer 52 uses a vibration dryer which is a preferred form as a secondary dryer. By using a vibration drier for both primary drying and secondary drying, it becomes a very efficient drying method with less gel adhesion to the walls of the apparatus.

The gel loading density (loading amount per unit area) in primary drying is 20.6 kg / m ² (loading density in terms of dry matter is 7.6 kg / m ² ), and loading in terms of dry matter in secondary drying. The density was set to 16.7 kg / m ² . That is, the load per unit area in terms of dry matter in secondary drying when the load per unit area in terms of dry matter in primary drying was set to 2.2.

  The gel layer height in the vicinity of the inlet of the pre-stage dryer 51 was 35 mm, and the residence time was about 8 minutes. The moisture content of the product in the middle of drying discharged from the outlet of the pre-stage dryer 51 was 32% by mass, and it was granular with fluidity. Then, the entire amount of the product in the middle of drying was supplied to the subsequent dryer 52.

  The residence time in the latter-stage dryer 52 was about 35 minutes (the total of the residence time in the drying zone of about 33 minutes and the residence time in the cooling zone of about 2 minutes). The temperature of the dry matter discharged from the latter-stage dryer was 60 ° C. The water content of the obtained dry matter was 1.3% by mass. The dry matter was pulverized with a table pulverizer and classified to a 20 mesh pass to obtain a polymer powder (B-1) composed of sodium polyacrylate. As a result of measuring the physical properties of the polymer powder (B-1) in the same manner as in Reference Example 1, the solution viscosity was 670 mPa · s, the insoluble content was 0.15% by mass, and the Hunter whiteness was 91.6%. Met.

[Comparative Example 1]
Drying was performed in the same manner as in Example 1 except that the strokes of the former dryer 51 and the latter dryer 52 were set to 3 mm, to obtain a polymer powder (C-1).

As in Example 1, the gel loading density (loading amount per unit area) in primary drying is 20.6 kg / m ² (loading density in terms of dry matter is 7.6 kg / m ² ) The loading density in terms of dry matter in drying was set to 16.7 kg / m ² . That is, the load per unit area in terms of dry matter in secondary drying when the load per unit area in terms of dry matter in primary drying was set to 2.2.

  The moisture content of the product in the middle of drying discharged from the outlet of the pre-stage dryer 51 was 42% by mass, and it was agglomerated in the form of a cake.

  The water content of the polymer powder (C-1) was 3.4% by mass. The physical properties of the polymer powder (C-1) were measured in the same manner as in Reference Example 1. As a result, the solution viscosity was 590 mPa · s, the insoluble matter was 3.2% by mass, and the Hunter whiteness was 89. 3%.

[Example 2]
Polymer powder (D-1) was dried in the same manner as in Example 1 except that the supply to the meat chopper was performed at a speed of 14.1 kg / min and the gel layer height in the vicinity of the inlet of the pre-stage dryer 51 was 55 mm. )

The gel loading density (loading amount per unit area) in primary drying is 32.2 kg / m ² (loading density in terms of dry matter is 11.9 kg / m ² ), and loading in terms of dry matter in secondary drying. The density was set at 26.2 kg / m ² . That is, the load per unit area in terms of dry matter in secondary drying when the load per unit area in terms of dry matter in primary drying was set to 2.2.

  The water content of the product in the middle of drying discharged from the outlet of the pre-stage dryer 51 was 36% by mass, and although some agglomerates were partially observed, the majority were smooth and smooth granules.

  The temperature of the dry matter discharged from the latter-stage dryer 52 was 63 ° C. The water content of the obtained dry matter was 1.8% by mass.

  The physical properties of the polymer powder (D-1) were measured in the same manner as in Reference Example 1. As a result, the solution viscosity was 630 mPa · s, the insoluble content was 0.42% by mass, and the Hunter whiteness was 90.7%. Met.

Example 3
Drying was carried out in the same manner as in Example 1 except that the residence time in the rear dryer 52 was changed to 20 minutes by changing the excitation angle in the rear dryer 52 to obtain a polymer powder (E-1).

The gel loading density (loading amount per unit area) in primary drying is 20.6 kg / m ² (loading density in terms of dry matter is 7.6 kg / m ² ), and loading in terms of dry matter in secondary drying. The density was set at 28.9 kg / m ² . That is, when the load per unit area in terms of dry matter in primary drying is 1, the load per unit area in terms of dry matter in secondary drying is set to 3.8.

  The moisture content of the product in the middle of drying discharged from the outlet of the pre-stage dryer 51 was 32% by mass, and it was a granule that was smooth and fluid.

  The temperature of the dry matter discharged from the latter-stage dryer 52 was 61 ° C. The water content of the obtained dry matter was 2.1% by mass.

  The physical properties of the polymer powder (E-1) were measured in the same manner as in Reference Example 1. As a result, the solution viscosity was 640 mPa · s, the insoluble content was 0.36% by mass, and the Hunter whiteness was 90.3%. Met.

  The method for drying a water-soluble polymer-containing gel of the present invention suppresses caking (aggregation), has high drying efficiency, and can be dried in a short time. Therefore, the obtained water-soluble polymer hardly undergoes side reactions such as a crosslinking reaction, has few insoluble components, and has little coloring. For this reason, it can be suitably applied to the drying of the water-soluble polymer hydrogel.

It is a top view which shows schematic structure of an example of the equipment used with the drying method which concerns on this Embodiment. 1 is a plan view showing a schematic configuration of a reaction apparatus for producing a (meth) acrylic acid (salt) -based water-soluble polymer used in Synthesis Example 1. FIG. It is sectional drawing which shows schematic structure of the reaction apparatus of FIG. It is a side view which shows schematic structure of the reaction container for manufacturing the (meth) acrylic acid (salt) type water-soluble polymer used in the synthesis example 4. It is a side view which shows schematic structure of the reaction apparatus in the primary reaction for manufacturing the (meth) acrylic acid (salt) type water-soluble polymer used in the synthesis example 4. It is a side view which shows schematic structure of the reaction apparatus in the secondary reaction for manufacturing the (meth) acrylic acid (salt) type water-soluble polymer used in the synthesis example 4.

Explanation of symbols

51 Pre-stage dryer (continuous vibration dryer)
52 Subsequent dryer (aeration dryer)

Claims (11)

A method of drying a water-soluble polymer-containing gel by two-stage drying,
Using a continuous vibration drier, the fine water-soluble polymer hydrogel was loaded on the drying deck so that the layer height was in the range of 5 mm to 50 mm , and the water-soluble polymer hydrogel was 4 mm or more. The water-soluble polymer is characterized in that it is vibrated by a vibration stroke and subjected to primary drying by passing hot air through the water-soluble polymer hydrated gel from the bottom of the drying deck, followed by secondary drying using a ventilation dryer. A method for drying a polymer hydrous gel.   The water-soluble polymer hydrated gel according to claim 1, wherein the water-soluble polymer hydrated gel is subjected to primary drying by loading the refined water-soluble polymer hydrated gel so that the layer height is within a range of 10 mm to 40 mm. Drying method. The method for drying a water-soluble polymer hydrogel according to claim 1 or 2 , wherein the vibration stroke is in a range of 5 mm to 10 mm. The water-soluble polymer hydrogel was miniaturized, to any one of claims 1-3, characterized in that the die size of extruded gel discharged from the extruder is in the range of 2mm or more 20mm or less A method for drying the water-soluble polymer-containing gel as described. The method of drying a water-soluble polymer-containing gel according to any one of claims 1 to 4, wherein the ventilation dryer used for secondary drying is a continuous ventilation dryer. The water-soluble polymer hydrogel according to any one of claims 1 to 5, wherein the linear velocity of hot air in primary drying is in the range of 0.5 m / s to 2 m / s. Method. The water-soluble polymer according to any one of claims 1 to 6, wherein a mass average molecular weight of the water-soluble polymer in the water-soluble polymer-containing gel is in the range of 1 million to 20 million. A method for drying a hydrogel. Water-soluble polymer in the water-soluble polymer water-containing gel, claim, characterized in that a polymer obtained by polymerizing acrylic acid or monomer composition containing a salt thereof 60 mol% or more 1-7 The method for drying a water-soluble polymer-containing gel according to any one of the above. The water content of the water-soluble polymer hydrated gel at the outlet of the dryer in primary drying is within a range of 5% by mass or more and 40% by mass or less, according to any one of claims 1 to 8 . A method for drying a water-soluble polymer-containing gel. The drying amount of the water-soluble polymer hydrogel according to any one of claims 1 to 9 , wherein the load per unit area in terms of dry matter is increased in the secondary drying than in the primary drying. Method. The method for drying a water-soluble polymer hydrated gel according to any one of claims 1 to 10, wherein the water-soluble polymer hydrated gel after primary drying is crushed and then secondarily dried.

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