JP4685425B2 - Manufacturing apparatus and manufacturing method for water absorbent resin - Google Patents

Description

  The present invention relates to a production apparatus and production method for a water-absorbent resin that becomes a gel during polymerization, and more particularly to a production apparatus suitable for continuous production.

  In recent years, a water-absorbing resin with a high absorption capacity that absorbs several tens to several hundred times the weight of its own weight has been developed. In addition to sanitary materials such as sanitary products and disposable diapers, food for agricultural and horticultural use and for maintaining freshness Used in applications that require water absorption or water retention, such as in the field, industrial fields such as condensation prevention and cold insulation materials.

  Examples of such a water-absorbing resin include a hydrolyzate of starch-acrylonitrile graft polymer (Patent Document 1), a neutralized product of starch-acrylic acid graft polymer (Patent Document 2), and vinyl acetate-acrylic acid ester. Copolymer saponified product (Patent Document 3), acrylonitrile copolymer or acrylamide copolymer hydrolyzate (Patent Document 4), or a cross-linked product thereof, a self-cross-linked polymer obtained by reverse phase suspension polymerization Sodium acrylate (Patent Document 5), a polyacrylic acid partial neutralized cross-linked product (Patent Document 6), and the like are known.

  Conventionally, as a method for producing a water-absorbent resin, a technique such as a water-soluble polymerization method is known. For example, a method of adiabatic polymerization of a hydrophilic vinyl monomer aqueous solution in a specific container (Patent Document 7) or Examples thereof include a method in which a polymer gel is broken while stirring in a double-arm kneader (Patent Document 8), and a belt type continuous production apparatus (Patent Documents 9 and 10) in which the polymer gel is allowed to stand on the belt.

  However, in the conventional continuous production apparatus, since all the raw materials are mixed and then supplied to the polymerization machine, there is a problem that the liquid raw material is polymerized in the supply pipe and the supply pipe is blocked. As a countermeasure, a water-absorbent resin having a structure in which an aqueous monomer solution of a liquid raw material and at least one component of a polymerization initiator are passed through different supply pipes, and both supply pipes are adjacent to each other in the vicinity of at least one outlet. The manufacturing apparatus (Patent Document 11) is proposed, but also in this apparatus, when the apparatus is urgently stopped during operation, the monomer mixture is mixed at the portion where the monomer mixture and the polymerization initiator are mixed. There exists a problem of superposing | polymerizing and obstruct | occluding the nozzle front-end | tip part. Further, an additive aqueous solution that has been sufficiently deoxygenated before being supplied to the polymerization machine, for example, an internal cross-linking agent, a chain transfer agent, or a monomer mixture of a liquid raw material is left to stand at a temperature of 35 ° C. or more for a long time, and an oligomer is formed. There's a problem.

Japanese Patent Publication No.49-43395 Japanese Patent Laid-Open No. 51-125468 JP-A-52-14689 Japanese Patent Publication No.53-15959 Japanese Unexamined Patent Publication No. 53-46389 JP 55-84304 A JP-A-55-108407 JP-A-57-34101 Japanese Unexamined Patent Publication No. 62-156102 JP 2000-17004 A JP-A-11-240903

  The object of the present invention is to prevent clogging of the raw material supply pipe in the water absorbent resin production apparatus, and immediately in the event of an emergency stop of the apparatus, even if the raw material starts to polymerize in the supply pipe. An object of the present invention is to provide an apparatus and a method for manufacturing a water-absorbent resin capable of cleaning a supply pipe.

The present invention is an apparatus for producing a water-absorbent resin comprising a polymerization machine for polymerizing a raw material mixture in which a plurality of raw materials are mixed, and a raw material supply pipe for supplying the raw material as a raw material mixture from a storage tank for each raw material to the polymerization machine. All of the raw material supply pipes are once pulled up from each raw material storage tank to a position higher than the polymerization machine, and then communicated with the polymerization machine by a downward pipe of 1/10000 or more in the vertical direction. This is an apparatus for producing a water-absorbent resin.

Further, the present invention is characterized in that using the production apparatus of the present invention, each raw material is supplied as raw material mixture from a plurality of raw material storage tanks through a raw material supply pipe to the polymerization machine and polymerized to obtain a polymer. This is a method for producing a water-absorbent resin.

  In the present invention, since the supply pipe of the raw material is once pulled up to a high place and then communicated to the polymerization machine by the lower pipe, even when the raw material starts polymerization in the supply pipe or an oligomer is generated, The raw material and the polymer in the supply pipe can be quickly discharged using the pressure in the supply pipe. In particular, by providing a facility for introducing an inert gas or a cleaning liquid to the supply pipe, the raw material or polymer in the supply pipe can be discharged and cleaned more easily.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing the overall configuration of a preferred embodiment of the production apparatus of the present invention, and FIGS. 2 and 3 are schematic diagrams showing the configuration of a raw material mixture drainage facility and a cleaning facility. In the figure, 1a to 1f are manual valves for flow rate adjustment, 2, 3 and 4 are automatic valves, 5a to 5f are automatic three-way valves, 6a to 6f and 7 are raw material supply pipes, 8 is a supply device, 11a, 11b and 17 Is a hydraulic or air cylinder for driving, 13 is a mixer, 14 is a flexible tube, 15 is a nozzle, 16 is a washing water receiver, 18 is a belt, 19 is a roller, 20 is a washing water drain pipe, 21 is a rotating shaft, 22 is a polymerization Machine cover, 23 automatic valve, 24 polymer gel, 25 gel crusher, 26a-26f supply pump, 31 polymerizer, 32 cooling unit, 33 heating unit, 34 nitrogen introduction pipe, 35 It is a vent.

  In addition, this embodiment is an example using a belt-type continuous polymerization machine as a polymerization machine, and is an apparatus that once mixes all raw materials in the supply device 8 and supplies the raw material mixture to the belt for polymerization. An example in which 6 types of raw materials A to F are mixed and polymerized will be shown. In the present invention, the polymerization machine is not limited to a continuous polymerization machine, but as described above, when continuously produced using a continuous polymerization machine, all the raw materials are mixed before being supplied to the polymerization machine. Therefore, the raw material mixture starts to be polymerized before being supplied to the polymerization machine, and the supply device and the piping are likely to be clogged. Therefore, the present invention is preferably applied to a continuous polymerization machine.

  The raw materials A to F are respectively prepared in a mixing tank and supplied to a raw material storage tank such as a storage tank or a flow rate check tank using a supply pump or pressure feed and a head difference, and the flow rate is further adjusted from the raw material storage tank by supply pumps 26a to 26f. Then, it is supplied to the polymerization machine 31 through the supply device 8 (the mixer 13, the flexible tube 14, the cylinders 11a and 11b, and the automatic valve 4 in FIG. 2 correspond thereto).

  In the present invention, at least one of the raw material supply pipes from the raw material storage tank to the polymerization machine 31 is pulled up to a point higher than the polymerization machine 31, and then a downward pipe of 1/10000 or more is used in the vertical direction. The supply pipe using such a down pipe is applied to a place where the raw material or the raw material mixture may be clogged due to initiation of polymerization or generation of oligomers. The point at which the raw material supply pipe is pulled up is preferably the highest point possible in the building where the manufacturing apparatus is installed or at least 0.25 m higher than the polymerization machine.

  FIG. 1 shows an example in which all the raw material supply pipes 6a to 6f and the supply pipe 7 for mixing the raw materials A to E are configured using descending pipes. As described above, since the supply pipes 6a to 6f and 7 are configured by descending pipes, even if polymerization is started in the supply pipe 7 or oligomers are generated, the raw material in the supply pipe 7 is caused by the pressure due to the difference in height. And the polymer can be easily discharged.

  In this embodiment, as shown in FIGS. 2 and 3, automatic three-way valves 5 a to 5 f are provided in 6 a to 6 f immediately before the supply pipe 7, and when an emergency stop is caused due to a trouble or the like. The feed of the raw material to the polymerization machine 31 is stopped by the automatic three-way valves 5a to 5f. At the same time, the nozzle 15 for supplying the raw material mixture is lifted from the belt 18 of the polymerization machine 31 by the cylinders 11a and 11b driven by hydraulic pressure or air. It is done. After the nozzle 15 is lifted, the cleaning water receiver 16 is inserted into the lower portion of the nozzle 15 by a cylinder 17 driven by hydraulic pressure or air. Thereafter, the automatic valve 3 is opened, and the raw material in the supply pipe 7 is discharged by the inert gas (or air) through the washing water receiver 16 and the washing water drain pipe 20. Thereafter, the automatic valve 3 is closed, the automatic valve 2 is opened, and the supply pipe 7, the nozzle 15, the mixer 13, and the like can be cleaned with cleaning water. Even if a part of the raw material is polymerized in the supply pipe 7, the nozzle 15, the mixer 13, etc., it can be removed by washing with washing water before becoming a high molecular weight gel that cannot be washed with washing water. it can.

  In the present invention, the temperature of the raw material or the raw material mixture is supplied to the polymerization machine 31 at 5 ° C. to 35 ° C. or less, so that the raw material can be left for a long time under low dissolved oxygen due to the emergency stop of the device due to trouble. The raw material and the raw material mixture can be prevented from reacting in the supply pipes 6a to 6f and 7 due to the temperature rise, and at the same time, the supply temperature of the raw material and the raw material mixture to the polymerization machine 31 is set to 35 ° C. or less. The maximum temperature reached during the polymerization gelation reaction can be 105 ° C. or lower.

  In the present invention, the raw material is a generic term for a liquid raw material monomer, an internal crosslinking agent, a reducing agent, a polymerization initiator, a chain transfer agent, etc., and the raw material mixture means a mixture of two or more of them. .

  In the present invention, by providing check valves (check valves) in the supply pipes 6a to 6f and 7, the raw material supply pipes 6a to 6f and 7 are caused to flow back into the supply pipes 6a to 6f and 7 due to troubles or erroneous operations, and polymerization occurs to supply pipes 6a. Troubles that block .about.6f and 7 can be prevented.

  The monomer of the liquid raw material used in the present invention is not particularly limited as long as it can become a water-absorbing resin by polymerization. For example, acrylic acid, methacrylic acid, maleic acid, vinyl sulfonic acid, styrene sulfonic acid, 2 Anionic unsaturated monomers such as (meth) acrylamide-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid and salts thereof; acrylamide, methacrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl ( (Meth) acrylate, methoxypolyethylene Nonionic hydrophilic group-containing unsaturated monomers such as glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone, N-vinylacetamide, N-acryloylpiperidine, N-acryloylpyrrolidine; N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide and their four And cationic unsaturated monomers such as grade salts. These can use 1 type (s) or 2 or more types.

  Among these, acrylic acid or a salt thereof (for example, a salt of sodium, lithium, potassium, ammonium, amines, etc.) is preferably used as a main component, and the amount of other monomers other than acrylic acid or a salt thereof is used. Is usually preferably less than 50 mol%, more preferably 30 mol% or less in the total monomer. The monomer concentration of the hydrophilic monomer aqueous solution is generally variable over a wide range, but is preferably 10 to 60% by mass. More preferably, it is 25-45 mass%, More preferably, it is 30-45 mass%. When it is less than 10% by mass, the productivity is low.

  On the other hand, if it exceeds 60% by mass, the ratio of the self-crosslinked portion of the polymer chain increases, and the absorption capacity of the resulting water-absorbent resin may be reduced.

  As the acrylate, ammonium acrylate obtained by hydrolyzing acrylonitrile scientifically or using a microorganism is also used.

  Upon polymerization, starch / cellulose, starch / cellulose derivatives, polyvinyl alcohol, polyacrylic acid (salt), hydrophilic polymers such as cross-linked polyacrylic acid (salt), and chains such as hypophosphorous acid (salt) A transfer agent may be added.

  In the present invention, the water-absorbing resin preferably has a crosslinked structure, and is a self-crosslinking type that does not use a crosslinking agent, or an internal crosslinking agent having two or more polymerizable unsaturated groups or two or more reactive groups. Examples of the copolymerized or reacted type can be given. A water-absorbing resin having a crosslinked structure obtained by copolymerizing or reacting an internal crosslinking agent with a hydrophilic unsaturated monomer is preferable.

  Specific examples of the internal cross-linking agent of the present invention include, for example, N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, and trimethylolpropane. Tri (meth) acrylate, trimethylolpropane di (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (Meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly (meth) allyloxyalkane, (poly) ethyl Glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, 1,4-butanediol, pentaerythritol, ethylenediamine, polyethyleneimine, glycidyl (meth) acrylate, and the like. Two or more of these internal crosslinking agents may be used.

  Examples of the polymerization initiator of the present invention include, but are not limited to, a redox initiator comprising a combination of an oxidizing initiator and a reducing agent; a thermal decomposition initiator; a photopolymerization initiator; It is not something. These initiators (polymerization initiators) may be used alone or in combination of a plurality of types depending on the type of the monomer. For example, when an acrylic acid monomer is used as a raw material, for example, a persulfate (oxidizing initiator) such as sodium persulfate (NaPs) and L-ascorbic acid (salt) (reducing agent) Combination: persulfate, hydrogen peroxide (all oxidative initiator), L-ascorbic acid (salt) (reducing agent) combination; persulfate, hydrogen peroxide (all oxidative initiator), azo A combination of an initiator (thermal decomposition type initiator), L-ascorbic acid (salt) (reducing agent), and the like are preferably used. The crosslinking agent is not particularly limited as long as it has two or more functional groups in the molecule and contributes to the formation of a crosslinked structure. Further, in some cases, a crosslinking agent may be added after the polymerization reaction to form a crosslinked structure.

Examples of the reducing agent that is an additive used in the present invention include L-ascorbic acid (salt), bisulfite, amine, iron chloride, and molle salt. The azo polymerization initiator include 2,2'-azobis (2-Amiji Bruno propane) 2 water-soluble azo polymerization initiators such as hydrochloride.

  In the present invention, the feed pipe 6e and the mixer 13 for the raw material F to be mixed at the end are preferably installed vertically so that the raw material and the raw material mixture do not stay in the supply pipe 6e and the mixer 13 for a long time. By supplying the raw material and the raw material mixture vertically, it is possible to prevent clogging due to polymerization due to long-term residence.

  In the present invention, in order to prevent the supply pipe 7 and the mixer 13 from being blocked, the average residence time after the raw materials are mixed in the supply pipe 7 and the mixer 13 is 0.01 to 10 seconds, preferably 0.8. 1-2 seconds. If the residence time is shorter than 0.01 seconds, the mixing of raw materials, particularly the polymerization initiator, becomes uneven. If the residence time exceeds 10 seconds, the polymerization may start in the supply pipe 7 or the mixer 13 to cause clogging.

  In addition, in the production apparatus of the present invention, a material inactive to the raw material such as stainless steel, Teflon (registered trademark), glass, silicone, polyolefin, polyester, polyvinyl chloride, or the like is used for the portion that contacts the initiator. Is preferred.

  In the case of using a plurality of polymerization initiators, at least one of them may be supplied through a supply pipe different from the raw monomer aqueous solution, and the component starts polymerization as soon as it is put into the monomer aqueous solution. It is preferable to supply (final component) through a supply pipe (in the case of FIG. 1, supply pipe 6e) different from other raw materials. For example, when a redox polymerization initiator composed of a combination of an oxidizing polymerization initiator and a reducing agent is used, one of the oxidizing polymerization initiator and the reducing agent is fed into the monomer aqueous solution in the supply pipe 7. It is preferable to supply the other through the supply pipe 6e.

  The polymerization machine 31 of the production apparatus of the present invention may be of any polymerization type. For example, a polymerization method in which stationary polymerization is continuously performed can be given. Static polymerization refers to polymerization without substantial stirring from the start of polymerization until the polymerization system reaches the maximum temperature due to the heat of polymerization. The polymerization machine used for the stationary polymerization is not particularly limited as long as it has a space that can heat and / or cool the surface in contact with the polymerization system and evaporate the solvent from the polymerization system.

  The polymerizer 31 of the embodiment illustrated in FIGS. 1 to 3 includes a belt 18, a roller 21 via a motor and / or a speed reducer for driving the belt 18, and a polymer gel (or raw material mixture) 24 on the belt 18. A cooling unit 32 for cooling the water, a heating unit 33 for heating, a nitrogen introduction pipe 34 for introducing nitrogen into the atmosphere, and a polymerization apparatus cover 22 for covering the whole. The raw material mixture is supplied from the nozzle 15 to the belt 18 via the flexible tube 14 from the mixer 13 of the supply device 8, and polymerization is performed without stirring as it is.

  The thickness of the raw material mixture on the belt 18 is preferably in the range of 12 to 50 mm, and more preferably in the range of 15 to 30 mm. If the thickness is less than 10 mm, the productivity is low. On the other hand, if the thickness exceeds 50 mm, it becomes difficult to control the polymerization temperature, and the maximum temperature reaches 95 ° C. The amount of dissolved matter increases.

  Further, it is preferable to introduce nitrogen from the nitrogen introduction pipe 34 so that the oxygen concentration in the polymerization atmosphere is 5% by volume or less. More preferably, it is 1 volume% or less. If the oxygen concentration exceeds 5% by volume, the dissolved oxygen concentration may increase before the polymerization starts, and the induction period may become longer.

  When the polymer obtained by polymerization is in the form of a hydrogel, the hydrogel polymer is pulverized and classified to an appropriate size for drying, and the hydrogel polymer having an average particle size of about 1 to 10 mm. It can be. Although it does not restrict | limit especially in the grinding | pulverization of a hydrogel polymer, For example, a meat chopper and a cutting mill can be used. FIG. 1 shows an example in which a crusher 25 is provided and discharged from the apparatus as a crushing gel.

  A normal dryer or a heating furnace can be used for drying the hydrated gel polymer. For example, a thin agitation dryer, rotary dryer, disk dryer, fluidized bed dryer, airflow dryer, infrared dryer, and the like. The water-absorbent resin obtained by drying can be used as it is in the form of coarse particles or as a powder after being pulverized.

  The water-absorbing resin obtained in the present invention may be further subjected to a crosslinking treatment in the vicinity of the surface, whereby a water-absorbing resin having a large absorption capacity under load can be obtained. For the surface cross-linking treatment, a cross-linking agent capable of reacting with a functional group of the water-absorbent resin, for example, an acidic group, may be used, and a known cross-linking agent usually used for the application is exemplified.

  Examples of the surface crosslinking agent include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3- Pentadiol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbitol, etc. Alcohol compounds; polyhydric epoxy compounds such as ethylene glycol diglycidyl ether, polyethylene diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycidol Polyvalent amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and their inorganic or organic salts (eg, aditinium salts); 2,4-tolylene diisocyanate Polyisocyanate compounds such as hexamethylene diisocyanate; 1,2-ethylenebisoxa Polyvalent oxazoline compounds such as phosphorus; 1,3-dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one, 4,5-dimethyl-1,3-dioxolan-2-one, 4, 4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxane-2 Alkylene carbonate compounds such as -one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, 1,3-dioxopan-2-one; epichloro Haloepoxy compounds such as hydrin, epibromohydrin, α-methylepichlorohydrin, and their polyvalent amine adducts (for example, “Caimen (registered trademark)” manufactured by Hercules); zinc, potassium Siumu, magnesium, aluminum, iron, polyvalent metal compounds such as hydroxides and chlorides such as zirconium and the like. Among these, polyhydric alcohol compounds, polyhydric epoxy compounds, polyhydric amine compounds and salts thereof, and alkylene carbonate compounds are preferable. These surface crosslinking agents may be used alone or in combination of two or more.

  The amount of the surface cross-linking agent is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the water absorbent resin. A normal dryer or a heating furnace can be used for the heat treatment. For example, a thin agitation dryer, rotary dryer, disk dryer, fluidized bed dryer, airflow dryer, infrared dryer, and the like.

  In that case, heat processing temperature becomes like this. Preferably it is 40-250 degreeC, More preferably, it is 90-230 degreeC, More preferably, it is 120-220 degreeC. As heat processing time, 1-120 minutes are preferable normally and 10-60 minutes are more preferable. The water-absorbent resin obtained by the production method of the present invention is composed of inorganic fine particles such as titanium oxide, silicon oxide and activated carbon; organic fine particles such as polymethyl methacrylate; hydrophilic fibers such as pulp; and synthetic fibers such as polyethylene fibers and polypropylene fibers. Fibers; surfactants such as polyethylene glycol and polyoxyethylene sorbitan monostearate; deodorants; antibacterial agents and the like may be added during or after production.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited only to these Examples. In the examples, “parts” represents “parts by mass” unless otherwise specified. As for “%”, unless otherwise specified, the nitrogen concentration and the oxygen concentration represent “volume%”, and other than these represent “mass%”.

[Water absorption ratio]
About 0.2 g of the water-absorbing resin A (g) was uniformly placed in a non-woven teabag bag (50 × 70 mm) and immersed in a 0.9 mass% sodium chloride aqueous solution. After 60 minutes, the tea bag was pulled up, drained for a certain period of time, and then the mass W (g) of the tea bag was measured. The same operation was performed without using the water absorbent resin, and the mass B (g) of the bag at that time was measured. The absorption capacity of the water-absorbent resin was calculated from the measured values according to the following formula.

    Water absorption magnification (g / g) = (WB) / A

[Soluble content]
About 0.5 g of water-absorbing resin C (g) was dispersed in 1000 g of deionized water, stirred for 20 hours, and then filtered through filter paper. Next, 50 g of the obtained filtrate was put into a 100 ml beaker, and 2 ml of 0.05N sodium hydroxide aqueous solution, 5 ml of N / 100-methylglycol chitosan aqueous solution, and 3 drops of 0.2 mass% toluidine blue aqueous solution were added to the filtrate. . Next, the beaker solution was subjected to colloidal titration using an N / 400-polyvinyl potassium sulfate aqueous solution, and the titration point D (ml) was determined with the time point when the color of the solution changed from blue to reddish purple. Moreover, it replaced with 50 g of filtrates, performed the same operation using 50 g of deionized water, and calculated | required titer E (ml) as a blank. Then, from these titration amounts and the average molecular weight F of the monomer constituting the water-absorbent resin, the amount of soluble component (% by mass) was calculated according to the following formula.

    Soluble content (mass%) = (ED) × (0.005 / C) × F

[Residual monomer]
After adding 0.5 g of water-absorbing resin to 1000 g of deionized water and extracting with stirring for 2 hours, the swollen gelled water-absorbing resin was filtered off using filter paper, and the residual monomer in the filtrate was subjected to liquid chromatography. Analyzed with On the other hand, a calibration curve obtained by analyzing a monomer standard solution having a known concentration in the same manner was used as an external standard, and the amount of residual monomer in the water absorbent resin was determined in consideration of the dilution rate of the filtrate.

Example 1
A steel support belt with a circumference of 4.5 m running at a width of 30 cm and 15 cm / min and a side weir made of Teflon (registered trademark) resin with a height of 50 mm are attached to both sides, and a taper shape of 5/1000, A manufacturing apparatus having a cover with a height of 20 cm was used.

  An aqueous solution comprising 10.7 parts of acrylic acid and 70.07 parts of a 37% by weight aqueous sodium acrylate solution, 0.08 part of a polyethylene glycol diacrylate (average molecular weight 478) as a crosslinking agent, and 19.15 parts of water ( The raw material A) was adjusted, cooled to 30 ° C., degassed by introducing nitrogen gas, and the dissolved oxygen concentration was adjusted to 0.5 ppm or less. The dissolved oxygen concentration was measured using INPRO 6800 manufactured by METTLER TOLEDO.

  71.2 kg / hr of the above aqueous solution (raw material A) and 0.982 mass% V-50 (azo polymerization initiator manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution (raw material B) 612 g / degassed by introducing nitrogen gas. hr, 0.982 mass% sodium persulfate aqueous solution (raw material C) 612 g / hr and 0.088 mass% L-ascorbic acid aqueous solution (raw material D) were mixed at 612 g / hr, and nitrogen gas was further introduced. A degassed 0.07 mass% aqueous hydrogen peroxide solution (raw material E) was line-mixed at 612 g / hr, and supplied at 30 ° C. to the above polymerization machine having an atmospheric temperature of 30 ° C. in a nitrogen stream atmosphere.

  The raw material supply piping of the production apparatus used in this example and the supply piping from the storage tanks of the raw materials A to E use a 1/1000 downward piping in the vertical direction after passing through a point 1 m higher than the cover of the polymerization machine. And fed to the polymerization machine. A cleaning device was attached to the supply pipes for the raw materials A to E.

  During the polymerization under the above conditions, a failure was found in the belt type polymerization machine, the supply of the raw material mixture to the polymerization machine was stopped, and within 2 minutes after the stop, the raw material mixture in the supply pipe from each raw material mixing mixer to the polymerization machine was removed. The liquid was drained, washed with water, and blown with nitrogen. One day later, the operation was resumed, but the supply piping was not blocked.

(Example 2)
The same polymerization machine as in Example 1 was used. The raw material supply piping of the manufacturing apparatus used in this example and the supply piping from the storage tank of each raw material used a downward piping of 1/100 in the vertical direction after passing through a point 1 m higher than the cover of the polymerization machine.

  An aqueous solution comprising 10.7 parts of acrylic acid and 70.07 parts of a 37% by weight aqueous sodium acrylate solution, 0.08 part of a polyethylene glycol diacrylate (average molecular weight 478) as a crosslinking agent, and 19.15 parts of water ( The raw material A) was adjusted, cooled to 10 ° C., introduced with nitrogen gas, degassed, and the dissolved oxygen concentration was reduced to 0.5 ppm or less. The dissolved oxygen concentration was measured using INPRO 6800 manufactured by METTLER TOLEDO.

  71.2 kg / hr of the above aqueous solution (raw material A) and 0.982 mass% V-50 (azo polymerization initiator manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution (raw material B) 612 g / degassed by introducing nitrogen gas. hr, 0.982 mass% sodium persulfate aqueous solution (raw material C) 612 g / hr and 0.088 mass% L-ascorbic acid aqueous solution (raw material D) were mixed at 612 g / hr, and nitrogen gas was further introduced. A degassed 0.07 mass% aqueous hydrogen peroxide solution (raw material E) was line-mixed at 612 g / hr and supplied at 10 ° C. to the above polymerizer having an atmospheric temperature of 30 ° C. in a nitrogen stream atmosphere.

  During polymerization, a malfunction of the belt type polymerizer was found and the supply of the raw material mixture to the polymerization machine was stopped. Within 2 minutes after the stop, the raw material mixture in the supply pipe from the mixing mixer for raw materials C and E to the polymerization machine was removed. The liquid was drained, washed with water, and blown with nitrogen. After 1 hr, the operation was resumed, but the supply piping was not blocked. Further, no solid precipitate was found in the raw material mixture extracted from the raw material supply pipe.

(Example 3)
Within 2 minutes after the end of the operation in Example 2, the raw material mixture in the supply pipe from the mixing mixer for raw materials C and E to the polymerization machine was drained, washed with water, and blown with nitrogen. The supply piping of the raw material and the raw material mixture was kept at 10 ° C., and the inside of the supply piping was drained the next day (after 24 hours).

  By opening the drain valve at the bottom and using the drainage equipment, the entire volume could be drained easily just by opening the vent valve at the highest point of the supply piping. Moreover, the white solid which seems to be an oligomer did not precipitate in the liquid extracted from the supply piping.

(Comparative Example 1)
During operation under the conditions of Example 2, trouble occurred and the polymerization machine was stopped. After stopping, the raw material mixture in the supply pipe from the mixing mixer for the raw materials C and E to the polymerization machine was not drained. After 10 minutes, an attempt was made to resume the operation, but the operation could not be resumed because the raw material supply pipe from the raw material mixing mixer to the polymerization machine had already been blocked.

(Comparative Example 2)
Using the apparatus of Example 2, within 2 minutes after the operation was completed, the raw material mixture in the supply piping from the mixing mixer for raw materials C and E to the polymerization machine was drained, washed with water, and blown with nitrogen. After that, because the refrigerant circulation device that had cooled the supply pipe failed, the temperature in the supply pipe of the raw material and the raw material mixture rose to 40 ° C. After 2 hours, a small amount of liquid in the supply pipe was drained, and a solid was deposited. Was. After repairing the refrigerant circulation device and operating in this state, immediately after the start of operation, part of the supply pipe from the raw material mixing mixer to the polymerization machine became blocked, and the supply of raw material became unstable, The amount of charge cannot be adjusted.

It is the schematic which shows the structure of one Embodiment of the manufacturing apparatus of this invention. It is the schematic which shows the structure of the drainage equipment and washing | cleaning equipment of the manufacturing apparatus of FIG. It is the schematic which shows the structure of the drainage equipment and washing | cleaning equipment of the manufacturing apparatus of FIG. 1 from a different direction from FIG.

Explanation of symbols

1a to 1f Flow rate adjusting manual valve 2, 3, 4 Automatic valve 5a to 5f Automatic three-way valve 6a to 6f, 7 Raw material supply pipe 8 Supply device 11a, 11b, 17 Drive hydraulic or air cylinder 13 Mixer 14 Flexible tube 15 Nozzle 16 Washing water receiver 18 Belt 19 Roller 20 Washing water drain pipe 21 Rotating shaft 22 Polymerizer cover 23 Automatic valve 24 Polymer gel 25 Gel crusher 26a-26f Supply pump 31 Polymerizer 32 Cooling unit 33 Heating unit 34 Nitrogen introduction pipe 35 Vent

Claims (7)

An apparatus for producing a water absorbent resin, comprising: a polymerization machine that polymerizes a raw material mixture in which a plurality of raw materials are mixed; and a raw material supply pipe that supplies the raw material as a raw material mixture from a storage tank of each raw material to the polymerization machine, All of the raw material supply pipes are once pulled up from each raw material storage tank to a position higher than the polymerization machine, and then communicated with the polymerization machine by a downward pipe of 1/10000 or more in the vertical direction. Water-absorbing resin production equipment.   The water absorption according to claim 1, wherein the manufacturing apparatus includes a raw material drainage facility that supplies an inert gas into the raw material supply pipe and extracts the raw material, and a cleaning facility that supplies cleaning water into the raw material supply pipe. Production equipment for functional resin.   The water-absorbent resin production apparatus according to claim 1 or 2, wherein the production apparatus is a continuous production apparatus provided with a supply device that supplies a raw material mixture obtained by mixing all raw materials to the polymerization machine. Using the water-absorbent resin production apparatus according to any one of claims 1 to 3 , each raw material is supplied from a plurality of raw material storage tanks as a raw material mixture to the polymerization machine via a raw material supply pipe, and polymerized. A method for producing a water-absorbent resin, comprising obtaining a polymer. The method for producing a water-absorbent resin according to claim 4 , wherein other raw materials excluding at least one polymerization initiator are mixed before reaching the polymerization machine, and the polymerization initiator is finally mixed with the other raw materials. The method for producing a water absorbent resin according to claim 4 or 5 , wherein the raw material mixture is supplied to the polymerization machine at 5 to 35 ° C. The method for producing a water-absorbing resin according to any one of claims 4 to 6 , wherein a raw material mixture obtained by mixing all raw materials is continuously supplied to a polymerization machine by a supply device to continuously produce a polymer.

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