JP7850629B2 - Method for preparing a thickening agent - Google Patents

Description

This invention relates to a method for producing a thickening agent used in the preparation of a coating solution for forming an anti-glare coating film.

Image display devices such as liquid crystal displays are equipped with anti-glare films to prevent a decrease in contrast caused by reflections of light, such as fluorescent lights, on the screen.

The anti-glare film comprises a substrate and an anti-glare coating laminated on the substrate. The anti-glare coating contains fine particles such as silica, which form an uneven surface. On a screen equipped with the anti-glare film, light incident on the anti-glare coating is scattered by the fine particles, suppressing light reflection.

Here, Patent Document 1 describes a method for forming an anti-glare coating film. In this method, a coating solution is prepared by mixing fine particles, a binder resin, and a thickener, and then diluting it with a solvent. Next, this coating solution is applied to a substrate, and the binder resin is cured to form an anti-glare coating film.

Japanese Patent Publication No. 2020-074016

Incidentally, in order to impart anti-glare properties to a coating film, it is necessary to create a coating solution with excellent dispersibility of fine particles. The method described in Patent Document 1 uses a thickening agent to impart such dispersibility to the coating solution. However, in the method described in Patent Document 1, the thickening agent may not be able to exhibit the desired function due to the influence of other components such as fine particles and binder resins; in other words, the desired viscosity may not be imparted to the coating solution.

In view of the above circumstances, the object of the present invention is to provide a method for producing a thickening solution that can be used in the preparation of a coating solution for forming an anti-glare coating film, and that can relatively easily produce a thickening solution that can impart suitable viscosity to the coating solution.

The method for producing a thickening agent according to the present invention is:
The aforementioned thickening liquid is used to prepare a coating solution for forming an anti-glare coating film.
The process includes a mixing step of mixing a thickening agent and a solvent to produce the thickened liquid,
In the mixing step, a stirring device is used that includes a container for filling with the thickener and the solvent, and a homomixer for mixing the thickener and the solvent in the container.
The mixing step comprises a preparation step of filling the container with the thickener and the solvent while stirring with the homomixer, and a main stirring step of continuing to stir the mixture composed of the thickener and the solvent to obtain the thickened liquid.
In the preparation step, the homomixer is rotated in the reverse direction so that the mixture is drawn in from above and discharged from below, and in the stirring step, the homomixer is rotated in the forward direction so that the mixture is drawn in from below and discharged from above.

With this configuration, by reversing the homomixer during the preparation process and reversing it during the stirring process, a thickening solution capable of providing the appropriate viscosity for the coating solution can be produced relatively easily.

Furthermore, in the method for producing the thickening liquid according to the present invention, preferably, in the preparation step, the ratio of the preliminary stirring time (minutes) in reverse rotation to the mass (kg) of the thickening agent is 1.0 or more, and more preferably, in the main stirring step, the ratio of the main stirring time (minutes) in forward rotation to the volume (L) of the mixed liquid is 0.5 to 2.0.

This configuration makes it easier to increase the viscosity and thixotropy value of the thickening agent.

Furthermore, preferably,
The homomixer used in the method for producing a thickening liquid according to the present invention comprises a stirring section configured to suck up the mixed liquid and discharge the mixed liquid upward, and a splash suppression section that suppresses the splashing of the mixed liquid discharged from the stirring section,
The scattering suppression unit has a lower plate positioned above the stirring unit and an upper plate positioned above the lower plate.

More preferably,
The homomixer has a stirring section comprising a turbine that moves the mixture upward or downward, and a stator that is formed in a cylindrical shape extending vertically and housing the turbine inside.
The diameters of the lower plate and the upper plate are formed to be larger than the diameter of the stator.
In the mixing step, the lower plate is placed at the gas-liquid interface in the container, and the upper plate is placed 50 to 150 mm above the gas-liquid interface.

With this configuration, the mixing efficiency is improved by the collision of the mixed liquid with the lower and upper plates of the splash suppression section, making it easier to impart suitable viscosity to the coating liquid using a thickening agent.

Furthermore, the method for producing a thickening liquid according to the present invention is preferably,
The stirring device is configured such that, when the height of the stator is X [mm], the distance between the upper surface of the stator and the lower plate is Y, and the distance between the bottom surface of the container and the lower end of the stator is Z,
Y > 1.5X
Z > 1.5X
Z-Y < 30
It satisfies the condition.

With this configuration, the stirring efficiency of the mixed liquid can be further improved.

As described above, the present invention provides a method for producing a thickening solution that can be used in the preparation of a coating solution for forming an anti-glare coating film, and that can relatively easily produce a thickening solution suitable for the coating solution.

This is a schematic diagram of a stirring device used in a method for preparing a thickened liquid according to one embodiment. Figure 1 is an exploded view of the stirring section of the homomixer in the stirring device.

The following describes a method for producing a thickening agent according to one embodiment of the present invention, with reference to the drawings.

The method for producing the thickening liquid in this embodiment includes a mixing step of stirring a mixture containing a thickening agent and a solvent to obtain the thickening liquid.

Examples of the aforementioned thickening agents include organic clays such as smectite, talc, bentonite, montmorillonite, and kaolinite.

Examples of the aforementioned solvents include monohydric alcohol solvents such as methanol, ethanol, isopropyl alcohol, butanol, and 2-methoxyethanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclopentanone; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; ether solvents such as diisopropyl ether and propylene glycol monomethyl ether; polyol solvents such as ethylene glycol and propylene glycol; acyclic aliphatic hydrocarbon solvents such as hexane, heptane, and octane; cyclic aliphatic hydrocarbons such as cyclohexane and cycloheptane; and aromatic hydrocarbon solvents such as benzene, toluene, and xylene. These may be used individually or in combination.

In the mixing step of this embodiment, the relative permittivity of the solvent is set to 2 to 6. That is, in the mixing step, the solvent is selected such that its relative permittivity is between 2 and 6.

The mass ratio of the thickening agent to the total mass of the thickening liquid is preferably 4 to 10% by mass, and more preferably 5 to 8% by mass. Furthermore, the mass ratio of the solvent to the total mass of the thickening liquid is preferably 90% by mass or more, and more preferably 95% by mass or more.

For the stirring in the mixing step, the stirring device 1 shown in Figures 1 and 2 is used. The stirring device 1 comprises a container 10 for filling with the thickener and the solvent, and a homomixer 20 for stirring the mixed liquid M composed of the thickener and the solvent within the container 10.

The container 10 of this embodiment has a circular bottom portion 11 in plan view and side walls 12 rising from the outer edge of the bottom portion 11. The container 10 has a cylindrical storage space V for the mixed liquid M defined by the bottom portion 11 and the side walls 12.

The bottom portion 11 has a circular bottom surface 111 in contact with the mixed liquid M. The diameter R of the bottom surface 111 is preferably 370 to 650 mm, and more preferably 370 to 500 mm. The capacity of the containment space V is preferably 10 to 500 L, and more preferably 50 to 200 L. In this embodiment, the ratio of the volume of the thickening liquid to the capacity of the containment space V, i.e., the capacity of the container 10, is set to 0.4 to 0.9.

The homomixer 20 comprises a shaft portion 21 having a rotating shaft extending in the vertical direction, and a stirring portion 22 connected to the lower end of the shaft portion 21.

The shaft portion 21 is connected to a drive unit that rotates it around the aforementioned rotation axis. This drive unit comprises a motor and a housing that accommodates the motor.

As shown in Figure 2, the stirring section 22 has a turbine 22a connected to the lower end of the shaft 21 and a stator 22b that houses the turbine 22a.

The turbine 22a has a cylindrical connecting portion 23 connected to the lower end of the shaft portion 21, a cylindrical enlarged diameter portion 24 extending downward from the lower end of the connecting portion 23 and having a larger outer diameter than the connecting portion 23, and a plurality of stirring blades 25 extending radially outward from the side surface of the enlarged diameter portion 24.

The turbine 22a in this embodiment has four stirring blades 25. Each stirring blade 25 is arranged around the rotation axis at equal intervals. Each stirring blade 25 is inclined with respect to the rotation axis so as to have an upward-facing upper surface 251 and a downward-facing lower surface 252. Here, the rotation of the turbine 22a that generates an upward flow of the mixed liquid M between the upper surface 251 of the first stirring blade 25 and the lower surface 252 of the second stirring blade 25 adjacent to the first stirring blade 25 is called forward rotation (clockwise rotation when viewed from above in Figure 2), and the rotation of the turbine 22a that generates a downward flow of the mixed liquid M between them is called reverse rotation (counterclockwise rotation when viewed from above in Figure 2).

The height of each stirring blade 25 is 40-60 mm, and its width is 15-30 mm. The width of the stirring blade 25 refers to the average value of the width at the top end, the width at the bottom end, and the width at the midpoint between the top and bottom ends.

The stator 22b is configured to house the turbine 22a and has a cylindrical flow straightening section 26 extending along the rotation axis of the turbine 22a, and a discharge section 27 positioned above the flow straightening section 26 and discharging the mixed liquid M flowing upward within the flow straightening section 26. The stator 22b is connected to the housing via a plurality of rod-shaped fixing members 28. In other words, the stator 22b is fixed to the housing by a plurality of fixing members 28 connecting it to the housing.

The flow straightening section 26 is formed to surround the turbine 22a. The lower end 261 of the flow straightening section 26 corresponds to the lower end 261 of the stator 22b. The flow straightening section 26 has a circular opening 262 at its lower end 261. The flow straightening section 26 has a length (mm) in the vertical direction. The length of the flow straightening section 26 corresponds to the height X of the stator 22b. Furthermore, the outer diameter of the flow straightening section 26 corresponds to the diameter r of the stator 22b.

In the mixing process of this embodiment, the container 10 and the homomixer 20 are selected such that the ratio of the diameter r of the stator 22b to the diameter R of the bottom surface 111 (r/R) is 0.2 to 0.3, preferably 0.14 to 0.30.

The discharge section 27 is formed in a disc shape extending from the upper end of the rectifier section 26 toward the rotation axis. That is, the discharge section 27 has an extended portion 271 that extends intersecting the rotation axis. The upper surface of the extended portion 271 forms the upper surface 272 of the stator 22b. The discharge section 27 has a circular insertion opening 273 through which the connection portion 23 of the turbine 22a is inserted, and a plurality of discharge ports 274 that are arranged radially outward from the insertion opening 273 and extend circumferentially. Each discharge port 274 is formed to be arranged around the rotation axis at equal intervals.

When the turbine 22a rotates in the forward direction, the mixed liquid M is drawn into the rectifier section 26 via the opening 262, moves from bottom to top within the rectifier section 26, and is discharged to the outside of the stator 22b via the discharge port 274. Conversely, when the turbine 22a rotates in the reverse direction, the mixed liquid M is drawn into the rectifier section 26 via the discharge port 274, moves from top to bottom within the rectifier section 26, and is discharged to the outside of the stator 22b via the opening 262.

The homomixer 20 of this embodiment further includes a splash suppression unit 29 positioned above the stirring unit 22 to suppress the splashing of the mixed liquid M. The splash suppression unit 29 has a disc-shaped lower plate 291 positioned above the stirring unit 22, and a disc-shaped upper plate 292 positioned even higher than the lower plate 291. The lower plate 291 and the upper plate 292 are positioned opposite the upper surface 272 of the discharge unit 27 (stator 22b). The lower plate 291 and the upper plate 292 have diameters larger than the diameter of the flow straightening unit 26. Preferably, the lower plate 291 and the upper plate 292 have diameters larger than twice the diameter of the flow straightening unit 26.

The stirring device 1 of this embodiment is configured to allow adjustment of the following: Y (mm) between the upper surface 272 of the stator 22b and the lower surface of the lower plate 291 of the splash suppression section 29; Z (mm) between the bottom surface 111 of the container 10 and the lower end 261 of the stator 22b (lower end 261 of the flow straightening section 26); and D between the lower plate 291 and the upper plate 292 of the splash suppression section 29. X + Y + Z equals the height H (mm) of the mixed liquid M.

The mixing process of this embodiment comprises a preparation step in which the thickening agent and the solvent are filled into the container 10 while being stirred with a homomixer 20, and a main stirring step in which the mixture M is continuously stirred to produce the thickened liquid.

In the mixing process of this embodiment, the container 10 is positioned so that its bottom surface 111 aligns with the horizontal plane. That is, the container 10 is positioned so that the gas-liquid interface I of the stationary mixed liquid M aligns with the horizontal plane. Furthermore, in the mixing process of this embodiment, the lower plate 291 of the splash suppression unit 29 is positioned along the gas-liquid interface I (so that the entire stirring unit 22 is immersed in the mixed liquid M), and the upper plate 292 is positioned 50 to 150 mm above the gas-liquid interface I.

Furthermore, in the mixing step of this embodiment, Y is set to be greater than X, Z is greater than X, and Z is also greater than Y. Preferably, the relationship between X, Y, and Z is
Y > 1.5X
Z > 1.5X
Z-Y < 30
These intervals are set to satisfy the following conditions. This improves the dispersibility of the thickener in the mixed liquid M and makes aggregation less likely to occur over time.

In the preparation process, the solvent is filled into the container 10, and the turbine 22a is rotated in reverse. As a result, in the preparation process, the solvent is drawn into the rectifier section 26 via the discharge port 274, moves from top to bottom within the rectifier section 26, and is discharged to the outside of the stator 22b through the opening 262. The solvent discharged through the opening 262 moves towards the bottom surface 111. Upon reaching the bottom surface 111, the solvent further moves from the center towards the outer periphery, reaching the inner surface of the side wall 12, and then moves upward along this inner surface. In the preparation process, the solvent circulates within the container 10 through the movement described above, creating a first circulation state.

In the preparation step described above, the thickening agent is added to the container 10 (the solvent) in the first circulation state. Furthermore, in the preparation step described above, even after the mixing of all the thickening agent and the solvent is complete (after the preparation of the mixed liquid M is complete), stirring by reverse rotation of the turbine 22a is continued. Hereinafter, the time during which stirring by reverse rotation is continued after the mixing of all the thickening agents is complete will be referred to as the pre-stirring time (in minutes). The pre-stirring time is preferably between 1 minute and 15 minutes.

In the aforementioned preparation step, the ratio of the pre-stirring time (minutes) to the total mass (kg) of the thickening agent used is preferably 1.0 or greater, and more preferably 1.3 or greater.

In the aforementioned preparation process, the rotational speed of the turbine 22a is preferably 2500 rpm or higher, more preferably 3000 rpm or higher, and even more preferably 3500 rpm or higher.

In the aforementioned stirring process, the turbine 22a is rotated in the forward direction. As a result, the mixed liquid M is drawn into the rectifier section 26 through the opening 262, moves upward within the rectifier section 26, and is discharged to the outside of the stator 22b through the discharge port 274. The mixed liquid M discharged through the discharge port 274 moves towards the lower plate 291 of the splash suppression section 29. Upon reaching the lower surface of the lower plate 291, the mixed liquid M moves from the radial center of the lower plate 291 towards the outer periphery, reaching the inner surface of the side wall 12, and then moves downward along this inner surface. In this stirring process, the mixed liquid M moves as described above, creating a second circulation state within the container 10.

Here, the starting point of the stirring time (in minutes, hereinafter referred to as the stirring time) in the stirring step is defined as the point at which the forward rotation of the turbine 22a begins. In the stirring step, the ratio of the stirring time to the volume (L) of the mixed liquid M is preferably 0.1 to 2.5, more preferably 0.5 to 2.2, and even more preferably 1.0 to 1.9.

In the aforementioned stirring step, it is preferable to rotate the turbine 22a to such an extent that the mixed liquid M rises not only to the lower plate 291 of the splash suppression unit 29, but also to the upper plate 292. From this viewpoint, the rotation speed of the turbine 22a is preferably set to 1000 rpm or more and 5000 rpm or less, more preferably 2000 rpm or more and 4000 rpm or less, and even more preferably 2500 rpm or more and 3500 rpm or less. This ensures that the mixed liquid M is vigorously stirred, and circulation of the mixed liquid M occurs not only on the lower plate 291 but also due to the rebound from the upper plate 292, thereby improving stirring efficiency.

The thickening liquid produced by the method of this embodiment has viscosity suitable for use as a coating liquid for forming an anti-glare coating film. Specifically, when the viscosity is measured using an E-type viscometer at a temperature of 30°C, the thickening liquid of this embodiment exhibits a viscosity of 30 m·Pas or more at a low shear speed of 5 rpm. The viscosity at low shear is preferably 40 m·Pas or more, and more preferably 50 m·Pas or more. Furthermore, the thickening liquid of this embodiment exhibits a viscosity of 10 m·Pas or less at a high shear speed of 50 rpm. Moreover, the thixotropy value of the thickening liquid of this embodiment, calculated by dividing the viscosity at low shear by the viscosity at high shear, is between 3 and 7.

The coating solution prepared using the thickening agent of this embodiment includes, in addition to the thickening agent, particles for imparting anti-glare properties to the coating film and a binder resin.

Examples of the aforementioned particles include inorganic particles and organic particles. Examples of the inorganic particles include silicon dioxide particles, titanium dioxide particles, aluminum oxide particles, zinc oxide particles, tin oxide particles, calcium carbonate particles, barium sulfate particles, talc particles, kaolin particles, and calcium sulfate particles. Examples of the aforementioned organic particles include polymethyl methacrylate resin particles (PMMA particles), silicone resin particles, polystyrene resin particles, polycarbonate resin particles, acrylic styrene resin particles, benzoguanamine resin particles, melamine resin particles, polyolefin resin particles, polyester resin particles, polyamide resin particles, polyimide resin particles, and polyfluoroethylene resin particles. These may be used individually or in combination.

Examples of the binder resin include thermosetting resins and photocurable resins. Examples of the thermosetting resin include tricyclodecanedimethanol diacrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane triacrylate, pentaerythritol tetra(meth)acrylate, dimethylolpropane tetraacrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol(meth)acrylate, 1,9-nonanediol diacrylate, 1,10-decanediol(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, dipropylene glycol diacrylate, isocyanuric acid tri(meth)acrylate, and ethoxylated glyceryl Examples include polyfunctional acrylic monomers such as pentaria acrylate and ethoxylated pentaerythritol tetraacrylate, and monofunctional monomers such as ethoxylated o-phenylphenol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, 2-ethylhexyl acrylate, lauryl acrylate, isooctyl acrylate, isostearyl acrylate, cyclohexyl acrylate, isoflonyl acrylate, benzyl acrylate, 2-hydroxy-3-phenoxyacrylate, acryloylmorpholine, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and hydroxyethylacrylamide.

Furthermore, examples of the binder resin include urethane (meth)acrylate obtained by reacting a hydroxy (meth)acrylate obtained from (meth)acrylic acid or (meth)acrylic acid ester and a polyol with a diisocyanate. Examples of the polyols mentioned above include ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol hydroxypivalate ester, tricyclodecanedimethylol, 1,4-cyclohexanediol, spiroglycol, hydrogenated bisphenol A, ethylene oxide-added bisphenol A, propylene oxide-added bisphenol A, trimethylolethane, trimethylolpropane, glycerin, 3-methylpentane-1,3,5-triol, pentaerythritol, dipentaerythritol, tripentaerythritol, glucose compounds, and the like.

In preparing the coating solution, the thickening liquid, the particles, and the binder resin are mixed. It is preferable to use the same stirring device 1 used to prepare the thickening liquid when preparing the coating solution.

The coating solution prepared using the thickening agent of this embodiment exhibits suppressed dripping and excellent particle dispersibility, and consequently, is suitable for forming an anti-glare coating film.

Furthermore, the method for producing the thickening liquid according to the present invention is not limited to the embodiments described above. Also, the method for producing the thickening liquid according to the present invention is not limited by the effects described above. The method for producing the thickening liquid according to the present invention can be modified in various ways without departing from the spirit of the present invention.

The present invention will be further explained below with reference to examples.

As shown in Table 1, the mixing conditions were set, and a thickened solution was prepared using smectite as the thickening agent and 65 L of toluene (dielectric constant 2.4) as the solvent. A stirring device as shown in Figure 1 was used to prepare each thickened solution. The container used had a bottom diameter R of 440 mm and a capacity of 100 L. The homomixer used consisted of a stator with a height X of 100 mm and a diameter r of 105 mm, a lower plate with a diameter of 300 mm, and an upper plate with a diameter of 300 mm.

[Evaluation of the viscosity-enhancing properties of thickening agents]
An E-type viscometer was used to measure the viscosity at a rotor speed of 5 rpm and at a rotor speed of 50 rpm. The measurement temperature was 30°C. The thixotropy value (TI value) was calculated by dividing the viscosity measured at 5 rpm by the viscosity measured at 50 rpm. The results are shown in Table 1.

[Performance evaluation of thickening agents]
Using each of the prepared thickening solutions, a coating solution for forming an anti-glare coating film was prepared. In addition to the thickening solution, the coating solution used Techpolymer SSX-103DXE (manufactured by Sekisui Chemical Co., Ltd.) as particles, NK Oligomer UA-53-80BK (manufactured by Shin Nakamura Chemical Co., Ltd.) as a binder resin, Viscoat #300 (manufactured by Osaka Organic Chemical Industry Co., Ltd.) and 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) as monomers, Omnirad 907 (manufactured by IGM Resin Co., Ltd.) as a photoinitiator, and GRANDIC PC4100 (manufactured by DIC Corporation) as a surface tension modifier. The ratio of the thickening agent to the total mass of the coating liquid was 1.5 parts by mass, 50 parts by mass of Techpolymer SSX-103DXE, 50 parts by mass of NK oligomer UA-53-80BK, 50 parts by mass of Viscoat #300, 20 parts by mass of 4-hydroxybutyl acrylate, 5 parts by mass of Omnirad 907, and 1 part by mass of GRANDIC PC4100. Each coating liquid was applied to a substrate, and a coating film was formed on the substrate by curing the coating liquid. The anti-glare properties of the coating film were evaluated by measuring the average length of the roughness curve elements (average spacing between irregularities Sm) as specified in JIS B 0601:2013. A coating film with an Sm of 0.1 or higher was evaluated as exhibiting sufficient anti-glare properties. A Sm of 0.15 or higher is preferred, and 0.19 or higher is more preferred. The results are shown in Table 1.

As shown in Table 1, thickening agents with a TI value of 3 to 7 are considered suitable for forming anti-glare coatings. Furthermore, it is clear that performing reverse rotation during the preparation process and forward rotation during the main stirring process is crucial for producing thickening agents with a TI value of 3 to 7.

1: Agitator, 10: Container, 11: Bottom, 111: Bottom surface, 12: Side wall, 20: Homomixer, 21: Shaft, 22: Agitation section, 22a: Turbine, 22b: Stator, 23: Connection section, 24: Enlarged diameter section, 25: Agitator blade, 251: Top surface, 252: Bottom surface, 26: Flow straightening section, 261: Lower end, 262: Opening, 27: Discharge section, 271: Extended section, 272: Top surface, 273: Insertion port, 274: Discharge port, 28: Fixing member, 29: Splash suppression section, 291: Lower plate, 292: Upper plate

Claims (6)

A method for preparing a thickening agent,
The aforementioned thickening liquid is used to prepare a coating solution for forming an anti-glare coating film.
The process includes a mixing step of mixing a thickening agent and a solvent to produce the thickened liquid,
In the mixing step, a stirring device is used that includes a container for filling with the thickener and the solvent, and a homomixer for mixing the thickener and the solvent in the container.
The mixing step comprises a preparation step of filling the container with the thickener and the solvent while stirring with the homomixer, and a main stirring step of continuing to stir the mixture composed of the thickener and the solvent to obtain the thickened liquid.
A method for producing a thickened liquid, comprising: in the preparation step, the homomixer is rotated in the reverse direction so that the mixed liquid is drawn in from above and discharged from below the homomixer; and in the main stirring step, the homomixer is rotated in the forward direction so that the mixed liquid is drawn in from below the homomixer and discharged from above the homomixer. The method for producing a thickened liquid according to claim 1, wherein the ratio of the pre-stirring time (minutes) in the reverse rotation to the mass (kg) of the thickening agent in the preparation step is 1.0 or more. The method for producing a thickened liquid according to claim 1 or 2, wherein the ratio of the stirring time (minutes) in the forward rotation to the volume (L) of the mixed liquid is 0.5 to 2.0 in the stirring step described above. The homomixer comprises a stirring section configured to suck in the mixed liquid and discharge the mixed liquid upward, and a splash suppression section that suppresses the splashing of the mixed liquid discharged from the stirring section.
The method for producing a thickened liquid according to claim 1 or 2, wherein the scattering suppression unit has a lower plate positioned above the stirring unit and an upper plate positioned above the lower plate. The homomixer has a stirring section comprising a turbine that moves the mixture upward or downward, and a stator that is formed in a cylindrical shape extending vertically and housing the turbine inside.
The diameters of the lower plate and the upper plate are formed to be larger than the diameter of the stator.
The method for producing a thickened liquid according to claim 4, wherein in the mixing step, the lower plate is placed at the gas-liquid interface in the container, and the upper plate is placed 50 to 150 mm above the gas-liquid interface. The stirring device is configured such that, when the height of the stator is X (mm), the distance between the upper surface of the stator and the lower plate is Y, and the distance between the bottom surface of the container and the lower end of the stator is Z,
Y > 1.5X
Z > 1.5X
Z-Y < 30
A method for producing a thickening liquid according to claim 5, which satisfies the following conditions.