JP2007313425A - Production method for liquid composition with microbubbles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method for a liquid composition with microbubbles, which are highly condensed and very fine, and also have a long life. <P>SOLUTION: The production method for the liquid composition has the step of mixing a gas in a liquid which consists of a (A) component, which is a detergent with the Kraft point of 40-90°C, and a (B) component, which is a detergent with the critical micelle concentration of 5-200 mmol/L, wherein the weight ratio of the (A) component to the (B) component, (A)/(B) is 1/10-1/2,000. Therefore, the production method for the liquid composition with microbubbles, which are highly condensed and very fine, and also have the long life, is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a microbubble-containing liquid composition.

  Various researches (for example, Non-Patent Document 1) have been conducted on the technology for miniaturizing bubbles, and 60 to 10 μm bubbles are used for fishery techniques such as aquaculture, and 10 to 3 μm bubbles are used for medical techniques such as ultrasound contrast agents. It has been put into practical use. If the bubbles are further refined, it is considered that the gas / liquid surface area per unit volume increases, the residence time in the liquid phase increases, the gas pressurizing effect in the bubbles, and the high gas dissolving power. Utilizing these properties, applications such as water purification, microbial culture, and chemical reaction between gas and liquid are expected.

  By further increasing the gas / liquid interface area by increasing the concentration of such fine bubbles, and by sufficiently diffusing the fine bubbles by prolonging the lifetime of the fine bubbles, an improvement in the effect in the above application can be expected.

  Examples of the technology for further miniaturizing the bubbles include a method of applying ultrasonic waves to the electrolyzed water (for example, Patent Document 3) and a method of crushing the fine bubbles in the electrolyte-containing water (for example, Patent Document 4). Patent Document 2 also describes an example in which a porous material is dissolved to generate a gas in sodium dodecyl sulfate-added water. However, in the methods of Patent Documents 3 and 4, only a very low concentration of bubbles is obtained, and in the method of Patent Document 2, there is a problem that the lifetime of the fine bubbles is short.

  As a technique related to fine bubbles having a high concentration and a long lifetime, an ultrasonic contrast agent technique can be exemplified. For example, Patent Documents 1 and 5 disclose ultrasonic contrast agents that are long-lived and high-density fine bubbles by using a specific surfactant. However, even after passing through the separation step, these average bubble diameters are 3 μm or more and are sufficiently fine bubble diameters as an ultrasonic contrast agent, but are insufficient as industrially desired bubble diameters. . Non-Patent Document 2 describes a nanoscale ultrasonic contrast agent, but octafluoropropane having extremely low solubility in water is used as a gas for increasing the concentration, miniaturization, and extending the life. In ultrasonic contrast agents, gas is not particularly limited as long as interaction with ultrasound is obtained, so it is the mainstream to use perfluoroalkane or sulfur hexafluoride as a gas. From the viewpoint of use, these gases are disadvantageous because they cannot be highly dissolved.

As described above, industrially effective fine bubbles having both further miniaturization, higher concentration and longer life have not been realized. When considering industrial use such as industry and agriculture, a fine bubble-containing liquid that combines finer bubbles, higher concentration of bubbles and longer life in the liquid phase of bubbles, which cannot be achieved with the technology described above. Is required.
JP-A-8-176017 JP 2005-169359 A JP 2003-334548 A JP 2005-245817 A Japanese National Patent Publication No. 8-502979 "Chapter 6 of Foam Engineering", Editor-in-Chief: Ikuo Ishii, 2005 Brian E. Oeffinger, Margaret A. Wheatley Ultrasonics 42 (2004) 343-347

  An object of the present invention is to provide a method for producing a liquid composition containing fine bubbles, which is highly fine bubbles having a high concentration and which has an excellent long life.

This invention is a manufacturing method of the fine bubble containing liquid composition including the process of mixing gas in a liquid, Comprising: This liquid contains the following (A) component and (B) component, (A) component and ( B) A method for producing a fine bubble-containing liquid composition in which the weight ratio to the component is (A) / (B) = 1/10 to 1/2000.
(A) Surfactant having a Kraft point of 40 to 90 ° C. (B) It relates to a surfactant having a critical micelle concentration of 5 to 200 mmol / L.

  According to the production method of the present invention, it is possible to collect a fine bubble-containing liquid composition that has very fine bubbles at a high concentration and is excellent in the long life of the fine bubbles.

The present invention provides a liquid containing the component (A) and the component (B), wherein the weight ratio of the component (A) to the component (B) is (A) / (B) = 1/10 to 1/2000. The present invention relates to a fine bubble-containing liquid composition having a step of mixing gas.
(A) Surfactant having a Kraft point of 40 to 90 ° C. (B) Surfactant having a critical micelle concentration of 5 to 200 mmol / L The fine bubbles of the present invention are bubbles having an average bubble diameter of less than 3 μm. From the viewpoint of further expressing the effects of the present invention, it is preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.9 μm or less. The lower limit of the average cell diameter is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.05 μm or more from the viewpoint of ease of handling.

  According to the present invention, it is possible to collect a fine bubble-containing liquid composition in which bubbles are highly fine at a high concentration and the bubbles exist for a long time. In general, bubbles are thermodynamically unstable, causing coalescence of bubbles to coalesce, and contraction in which gas dissolves from the bubble into the surrounding liquid, and conversely, growth in which surrounding dissolved gas is taken into the bubble. It is known to cause. Especially for fine bubbles, the Laplace pressure due to the interfacial tension causes the internal pressure of bubbles with a diameter of around 1 μm to rise from several atmospheres to several tens of atmospheres. Has only a lifetime.

  The reason why the effect of the present invention is manifest is not clear, but it is considered that the inherently unstable fine bubbles are stabilized by the component (A) and this stabilization is efficiently performed by the component (B). It is done.

  That is, the component (A) of the present invention has a high Kraft point and is thermodynamically concentrated at the bubble interface, so a rigid membrane (for example, “Colloid Science II—Associated Colloids and Thin Films”), Chemical Society of Japan, 1995, published in Chapter 9, p295.), And therefore, the rigid membrane formed at the same time suppresses coalescence of microbubbles and suppresses gas permeability. It is considered that the gas was dissolved from the inside into the liquid and the life was extended. However, since the component (A) has low solubility in the liquid and the adsorption rate to the bubble interface is slow, coalescence and contraction occur before the component (A) becomes a rigid film. Therefore, it is considered that component (B) can be adsorbed early to suppress coalescence and shrinkage of microbubbles, and can exist as microbubbles until component (A) becomes a rigid film. In addition, the component (A) dissolved in the liquid decreases by adsorbing to the bubble interface film, but the component (B) becomes (A) due to the presence of the component (A) and the component (B) at a specific ratio. It is considered that the effects of the present invention are manifested by solubilizing the component or forming mixed micelles and efficiently dissolving the component (A) to promote the adsorption of the component (A).

<(A) component>
The component (A) of the present invention is a surfactant having a Kraft point of 40 to 90 ° C. A surfactant having a Kraft point of 40 to 90 ° C. is considered to function sufficiently as a bubble film, and is considered to contribute to the effects of the present invention such as long life of bubbles. The Kraft point is preferably 45 to 85 ° C, more preferably 50 to 80 ° C, from the viewpoint of efficiently forming a rigid film.

  The Kraft point is the chemistry and application of surfactants, as described in Chapter 3 (published on January 30, 1995, published by Dai Nippon Book Co., Ltd.). Is the temperature at which the solubility suddenly increases from a certain temperature.

  The Kraft point of the present invention can be measured according to the method described in Kaoru Tujii, Naoyuki Sato, and Takashi Takeuchi, Journal of Physical Chemistry, 84, 2287 (1980). That is, 1 g of a surfactant was added to 100 ml of distilled water, and the mixture was cooled in an ice bath to become cloudy, and then slowly heated at a rate of 1 ° C./minute to measure the temperature at which it became transparent You can ask for it.

  For the component (A) of the present invention, any of anionic, cationic, amphoteric and nonionic surfactants can be used. In addition, substances having a naturally occurring surface activity such as phospholipids, glycolipids, proteins, and saponins can also be used. From the viewpoint of bubble stability, the component (A) is preferably a surfactant having an alkyl group, and part or all of the hydrogen in the alkyl group may be substituted with fluorine. It is more preferable to have an alkyl group having 16 to 24 carbon atoms, and it is even more preferable to have an alkyl group having 17 to 18 carbon atoms. The alkyl group is preferably linear, and the hydrophobic group is more preferably composed of a linear alkyl group alone. Similarly, the component (A) is preferably a surfactant having no polyalkylene oxide group.

  Specifically, as the component (A), as the anionic surfactant, a linear saturated fatty acid salt having an alkyl group having 16 to 24 carbon atoms, a branched fatty acid salt having an alkyl group having 18 to 24 carbon atoms, or 20 carbon atoms. Unsaturated fatty acid salt having -24 alkenyl groups, linear or branched alkyl sulfate ester having 16 to 24 carbon atoms, linear alkyl benzene sulfonate having 16 to 24 carbon atoms, branched alkyl benzene sulfonic acid having 16 to 24 carbon atoms Examples thereof include a salt, a linear or branched alkyl sulfonate having 16 to 24 carbon atoms, an alkenyl sulfonate having 18 to 24 carbon atoms, and a monoalkyl phosphate having 16 to 24 carbon atoms.

  Examples of the cationic surfactant include alkylamine salts having 18 to 24 carbon atoms, alkylethylenediamine salts having 18 to 24 carbon atoms, and alkyltrimethylammonium salts having 20 to 24 carbon atoms.

  Examples of the amphoteric surfactants include alkyl carboxybetaines having 18 to 24 carbon atoms and alkylsulfobetaines having 18 to 24 carbon atoms.

  Examples of the nonionic surfactant include a fatty acid glycerin ester having 16 to 24 carbon atoms, a fatty acid polyglycerin ester having 18 to 24 carbon atoms, and a mono fatty acid ester having 18 to 24 carbon atoms of a sorbitan alkylene oxide adduct.

  Among these, anionic surfactants are preferable. Specifically, sodium stearate, sodium behenate, potassium stearate, potassium behenate, sodium octadecyl sulfate, sodium hexadecyl sulfate, monopotassium monostearyl phosphate, Monopotassium stearyl phosphate, ammonium perfluoroundecylcarboxylate, and stearylamine acetate are more preferable, and potassium stearate and sodium octadecyl sulfate are still more preferable.

  In addition, (A) component may be used independently according to a use, or (A) component may be mixed and used.

<(B) component>
The component (B) of the present invention is a surfactant having a critical micelle concentration (hereinafter also referred to as cmc) of 5 to 200 mmol / L. If the surfactant has a critical micelle concentration of 5 to 200 mmol / L, it is considered that the surfactant is instantaneously adsorbed to the bubbles, and is considered to contribute to the effects of the present invention such as provisional coalescence suppression. The critical micelle concentration is preferably 5 to 150 mmol / L, more preferably 5 to 120 mmol / L, and still more preferably 5 to 100 mmol / L, from the viewpoint of provisional coalescence suppression.

  The critical micelle concentration is the lowest concentration at which the surfactant forms micelles. The critical micelle concentration of the present invention can be determined by a surface tension method under conditions of 25 ° C. and 1 atm by preparing a solution in which the concentration of a surfactant is changed in distilled water.

  In the component (B) of the present invention, any of anionic, cationic, amphoteric, and nonionic activators can be used. However, carbon has a high cmc and is used for provisional coalescence suppression. A surfactant having an alkyl group or an alkenyl group of several 6 to 15 is preferred.

  (B) Specifically, as the anionic surfactant, a linear or branched saturated fatty acid salt having an alkyl group having 6 to 14 carbon atoms, an unsaturated fatty acid having an alkenyl group having 6 to 14 carbon atoms Salt, linear or branched alkyl sulfate ester having 6 to 12 carbon atoms, linear alkyl benzene sulfonate having 6 to 8 carbon atoms, branched alkyl benzene sulfonate having 6 to 10 carbon atoms, linear chain having 6 to 12 carbon atoms Or branched alkyl sulfonate, C 6-12 alkenyl sulfonate, C 6-12 monoalkyl phosphate, C 6-12 monoalkenyl phosphate, C 6-8 par. Examples thereof include fluoroalkyl carboxylates, alkyl methyl taurates having 6 to 12 carbon atoms, and alkylene oxide adducts thereof.

  Examples of the cationic surfactant include linear or branched alkylamine salts having 6 to 12 carbon atoms, alkylethylenediamine salts having 6 to 12 carbon atoms, alkyltrimethylammonium salts having 6 to 12 carbon atoms, and 6 to 10 carbon atoms. Examples thereof include dialkyldimethylammonium salts.

  Examples of the amphoteric surfactant include alkyl carboxy betaines having 6 to 10 carbon atoms, alkyl sulfobetaines having 6 to 10 carbon atoms, and alkylamide amino acid salts having 6 to 10 carbon atoms.

  Examples of the nonionic surfactant include aliphatic alcohol alkylene oxide adducts having 6 to 8 carbon atoms, fatty acid esters having 6 to 10 carbon atoms of sorbitan alkylene oxide adducts, and the like.

  Among these, anionic surfactants are preferable from the viewpoint of having a high critical micelle concentration and performing provisional coalescence suppression, and specifically, sodium caprate, sodium laurate, sodium myristate, caprin Potassium acid, potassium laurate, potassium myristate, sodium dodecyl sulfate, sodium decyl sulfate, monopotassium monolauryl phosphate, ammonium perfluorooctylcarboxylate, laurylamine acetate, potassium caprate, potassium laurate, myristine Potassium acid and sodium lauryl sulfate are more preferable.

  In addition, (B) component may be used independently according to a use, or (B) component may be mixed and used.

<Liquid>
The liquid used in the present invention contains (A) a surfactant having a Kraft point of 40 to 90 ° C. and (B) a surfactant having a critical micelle concentration of 5 to 200 mmol / L. The weight ratio of the component (A) to the component (B) is (A) / (B) = 1/10 to 1/2000. From the viewpoint of collecting a finer bubble-containing liquid composition, A) / (B) = 1/20 to 1/1500, more preferably (A) / (B) = 1/50 to 1/1200.

  The amount of the component (A) in the liquid used in the present invention is preferably 0.001 to 1% by weight, more preferably 0.0005 to 0, from the viewpoint of finer and higher concentration of the bubbles of the present invention. 0.5 wt%, more preferably 0.0005 to 0.2 wt%, and particularly preferably 0.0005 to 0.1 wt%.

  The types of the component (A) and the component (B) can be arbitrarily combined, but the same kind of ionic surfactant or ionic compound is used from the viewpoint that the component (B) has an effect of efficiently adsorbing the component (A). It is preferable to combine a surfactant and a nonionic surfactant.

  Examples of the main component constituting the liquid of the present invention include water, fats and oils, organic solvents, and the like, and water is preferable from the viewpoint of miniaturization and long life of the present invention.

<Gas>
The gas of the present invention is appropriately selected, and examples thereof include air, nitrogen gas, oxygen gas, ozone gas, methane gas, hydrogen gas, and carbon dioxide gas. From the above viewpoint, air, nitrogen gas, oxygen gas, ozone gas, methane, and hydrogen gas are preferable, and oxygen gas and ozone gas are preferable from the viewpoint of sterilization and cleaning.

<Process for mixing gas into liquid>
Examples of the process of mixing gas into the liquid include, for example, the pore method described in Ikui Ishio “Foam Engineering”, Chapter 6, pages 424-425 (March 25, 2005, published by Techno System Co., Ltd.). From the viewpoint of obtaining a high-concentration fine-bubble-containing composition, a pressure control method, a pressure control control method, a gas-liquid two-phase fluid mixing / shearing method, an ultrasonic method, and the like can be used. . Hereinafter, the pore method and the pressure adjustment control method will be described.

<Pore method>
In the case of adopting the pore method, the step of mixing the gas into the liquid can be performed by mixing the gas into the liquid through the pores such as the porous membrane. Specifically, for example, the liquid is brought into contact with one of the porous membranes, and the other side of the porous membrane is brought into contact with the pressurized gas, so that the gas is porous through the pores of the porous membrane. It passes through the holes and is mixed into the liquid. When the porous membrane is tubular, the liquid can be continuously flowed in one direction in the tube of the tubular porous membrane, and gas can be injected from outside the tube through the pores of the porous membrane. .

  Examples of the gas pressurization method include a method of forcibly filling a gas in the sealed space, and a method of compressing the air with a piston after filling the gas in the sealed space. Although pressurization is set appropriately, 1 to 10 MPa is preferable, and 2 to 5 MPa is more preferable.

  Regarding the pore diameter of the porous membrane, it is preferable that the pore diameter is uniform from the viewpoint of collecting a uniform bubble diameter, and from the viewpoint of collecting a finer bubble-containing liquid composition, the smaller pore diameter is preferable. . Therefore, the average pore diameter of the porous membrane is preferably 0.01 to 1 μm, more preferably 0.05 to 0.2 μm, and still more preferably 0.05 to 0.1 μm. The average pore diameter of the porous membrane can be determined by measuring with a mercury porosimeter.

  Preferred examples of the porous film having pores include glass, ceramics, silicon, and polymers, and glass (porous glass) is more preferred. The porous glass can be produced by utilizing microphase separation of glass as in, for example, Japanese Patent No. 1504002 and Japanese Patent No. 1518989. The shape of the porous glass may be tubular or flat. As a commercially available porous glass, for example, an SPG film manufactured by SPG Techno Co., etc. can be suitably used.

  From the viewpoint of finer bubbles in the present invention, it is preferable to further apply ultrasonic treatment at the “step of mixing gas into the liquid” in the pore method. This is presumed that the bubbles can be further miniaturized by applying bubbles such as ultrasonic waves to the pore system so that the bubbles are detached from the porous membrane at an early stage.

  As a method for applying the ultrasonic treatment of the present invention, for example, it can be carried out in a treatment liquid stored in a treatment layer equipped with an ultrasonic generator. It can be performed by immersing the unit of “the step of mixing gas into”.

  The transmission frequency and output, which are the conditions for ultrasonic treatment, are selected as appropriate. The oscillation frequency is preferably 20 to 200 kHz, and the output is preferably 20 to 400 W.

  The treatment liquid stored in the treatment layer provided with the ultrasonic generator is appropriately selected, and examples thereof include water and alcohol, and water is preferable from the viewpoint of economy.

<Pressure control method>
In the case of adopting the pressure control method, the step of mixing the gas into the liquid is performed by, for example, dissolving the gas in the liquid under pressure and then reducing the pressure to generate the gas from the supersaturated dissolved gas. Can do. Specifically, for example, using a gas-liquid mixing pump such as a vortex pump, the liquid and gas sucked from the pump suction side are pressurized while mixing / stirring, or provided with a dissolution tank and pressurized. After the gas is dissolved therein, the dissolved gas can be generated as bubbles in the liquid by decompressing the liquid or releasing it into the atmosphere. In the case of this method, the timing of containing the components (A) and (B) in the liquid may be before the pressure is reduced and gas is generated from the supersaturated dissolved gas. Therefore, it may be before or after the gas is mixed into the liquid under pressure and dissolved.

  The pressure for pressurization by this method is appropriately set, but it is preferably a high pressure from the viewpoint of finer bubbles and higher concentration, preferably 0.2 to 10 MPa, more preferably 0.5 to 10 MPa.

<Method for Producing Fine Bubble-Containing Liquid Composition>
The fine bubble-containing liquid composition of the present invention can be produced by performing the above steps using the liquid. The temperature of the liquid during the production is preferably about room temperature from the viewpoint of obtaining fine bubbles, specifically 5 to 35 ° C is preferable, and 10 to 30 ° C is more preferable.

  The liquid composition containing fine bubbles of the present invention has a great feature in that the bubbles are extremely fine at a high concentration, and the bubbles exist stably for a long time.

  The average bubble diameter of the bubbles in the fine bubble-containing liquid composition of the present invention is the average bubble diameter based on the number, and can be controlled by appropriately selecting the liquid component and the step of mixing the gas into the liquid. It is less than, Preferably it is 2 micrometers or less, More preferably, it is 1 micrometer or less, More preferably, it is 0.9 micrometer or less. The lower limit of the average cell diameter is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.05 μm or more from the viewpoint of ease of handling. In addition, the average bubble diameter of a bubble can be measured with the measuring method described in the Example here.

  The lifetime of the bubbles in the fine bubble-containing liquid composition of the present invention is the time required for spontaneous disappearance of the bubble-derived white turbidity, and is controlled by appropriately selecting the liquid component and the step of mixing the gas into the liquid. However, it is preferably 1 minute or longer, more preferably 3 minutes or longer, and even more preferably 4 minutes or longer. Here, the average lifetime of bubbles can be measured by the measurement method described in the examples.

The concentration of bubbles in the fine bubble-containing liquid composition of the present invention is the number of bubbles present in 1 mL, and can be controlled by appropriately selecting the liquid component and the step of mixing gas into the liquid. Is 1 × 10 ⁷ pieces / mL or more, more preferably 2 × 10 ⁷ pieces / mL or more. Here, the bubble concentration can be measured by the measurement method described in the examples.

  The fine bubble-containing liquid composition of the present invention can be applied to various uses such as cosmetics, agriculture, food, and the like by having a fine and durable effect.

  Hereinafter, the present invention will be described by way of examples. The physical properties described in the examples and comparative examples were evaluated according to the following methods.

<Evaluation of bubble diameter>
The fine bubble-containing liquid composition discharged from each device was directly collected in a 1 L (liter) beaker, and the bubble diameter was evaluated in the following cases.
(1) Immediately after discharge of the liquid containing bubbles, bubbles rise (8 cm / 5 seconds), the liquid phase becomes transparent, and a cloudy state due to bubbles cannot be obtained.
(2) After discharging the liquid containing bubbles, a white turbid liquid with dispersed bubbles can be obtained once, but the white turbid part immediately rises (8 cm / 3 min or more) and finally the liquid phase becomes transparent.
(3) After discharging the liquid containing bubbles, a cloudy liquid with dispersed bubbles is obtained, and the white cloudy part floats very slowly (8 cm / 3 minutes or less) or does not float but can be observed with a microscope.
(4) After discharging the liquid containing bubbles, a cloudy liquid with dispersed bubbles is obtained, and the white cloudy part is not lifted, and since it is cloudy, the presence of bubbles is obvious, but the bubbles cannot be confirmed by microscopic observation. Small bubble size.

In the case of (1), since the ascent speed is very high, it is apparent from the following Stokes formula that the distance is 100 μm or more. Therefore, the bubble diameter in the result in the case of (1) was evaluated as 100 μm or more.
Stokes formula (Equation 1):

[Where r is the bubble radius, Δρ is the density difference between air and water (substantially the density of water), g is the acceleration of gravity, η is the viscosity of water, and v is the rising speed of the bubbles. ]
In the case of (2), as a result of converting the ascent rate of 8 cm / 3 minutes to the bubble diameter from the Stokes' formula, it is found that it is 25 μm or more. Therefore, the bubble diameter in the result in the case of (2) was evaluated to be 25 μm or more.

  In the case of (3), since the ascent was very slow, it was difficult to use the Stokes equation, and therefore, observation with a microscope (Digital Microscope VHX-100 manufactured by Keyence Corporation) was performed.

  The bubbles in the observation field (677 μm × 508 μm) were two-colored with the software attached to the microscope, and the area of each bubble was calculated. The number-based distribution was calculated by converting the area of each of the obtained bubbles into an equivalent circle diameter, and the average bubble diameter was calculated.

  In the case of (4), measurement was carried out with a dynamic light scattering particle size measuring instrument (Microtrack UPA manufactured by Microtrac Co., Ltd.) without dilution to obtain a number-based average bubble diameter.

  It should be noted that the time required for measuring the bubble diameter immediately after discharging the bubble-containing liquid was 3 minutes.

<Evaluation of bubble life time>
The lifetime of bubbles was evaluated by the clouding time. That is, when the bubble-containing liquid that is clouded with bubbles is measured with a spectrophotometer, the bubbles are scattered and the transmitted light is reduced. Therefore, the scattered component is measured as the absorbance. Therefore, the bubble-containing liquid immediately after ejection is injected into the optical cell having an optical path length of 1 cm with a dropper, and the absorbance at 660 nm is measured by a time scan with a spectrophotometer (Hitachi U-2000A), and the absorbance is 0.005 or less. The time was defined as the lifetime of bubbles.

  In the case of (1) and (2) in “Evaluation of bubble diameter”, even if the lifetime of the bubble itself is long, the bubble dispersed in the liquid is 3 minutes or less. Measurement was performed in the cases of (3) and (4) in “Evaluation of bubble diameter”.

<Evaluation of bubble concentration>
The concentration of bubbles in the present invention was calculated by the following formula 2 using the absorbance measured in the above-mentioned “evaluation of the lifetime of bubbles”. In the case of (1) or (2) in “Evaluation of bubble diameter”, since the liquid phase is transparent after 3 minutes, a high concentration of bubble-containing liquid is not obtained to be worthy of bubble concentration evaluation. The bubble concentration was evaluated only in the cases (3) and (4). Further, in this method, when the absorbance exceeds 2.5, light hardly transmits, so that it becomes a measurement limit. Therefore, when the absorbance exceeds 2.5, “> (measurement limit concentration) is shown in the table of Examples. ) ".

  In the formula, D is absorbance, N is the number of particles per unit volume, and d is the particle diameter. In addition, said numerical formula 2 is calculated | required according to the following. According to the document of D.H.Melik and H.S.Fogler Journal of Colloid and Interface Science 92 (1983) 161, the absorbance is derived from the relationship of Equation 3 from the particle concentration and particle radius.

In the formula, D is the absorbance, L is the optical path length, N is the number of particles per unit volume, and r is the particle radius. Q is the scattering efficiency, and is a function having the particle radius r, the refractive index ratio m of the particle to the medium, and the incident light wavelength λ as variables. The scattering efficiency Q is fixed at λ = 660 nm and m = 0.75 (refractive index of air / refractive index of water = 1.00 / 1.33). When Q is numerically calculated, the effective scattering area πr ² Q For (μm ² ), the relationship of the bubble diameter d (μm) and Equation 4 is obtained. Even when other gases are used, the same is obtained by fixing the refractive index of air to 1.00.

Here, log is a common logarithm. By substituting Equation 4 into Equation 3 and expressing the number of bubbles per unit volume as L = 1 cm = 10 ⁴ μm, Equation 2 can be obtained.

<Confirmation of bubbles>
In the case of (4) in “Evaluation of bubble diameter”, the bubble cannot be directly confirmed with a microscope. Therefore, for the confirmation of bubbles, instantaneous disappearance of white turbidity by ultrasonic irradiation (40 kHz; 55 W) was used.

  In the following examples, a 1 L beaker obtained by collecting a liquid composition containing fine bubbles corresponding to the case of (4) in “Evaluation of bubble diameter” is immersed in a water tank of an ultrasonic generator, and ultrasonic waves (40 kHz, 55 W) are obtained. ), The cloudiness disappeared instantly, so it was confirmed that the cloudiness was due to bubbles. In addition, if it becomes white turbidity by a surfactant crystal | crystallization, even if it irradiates an ultrasonic wave, white turbidity will not lose | disappear instantly on these conditions.

(Examples 1-7, Comparative Examples 1-7)
A porous glass membrane (SPG techno SPG membrane: 5 × 125 mm: pore size 0.08 μm) shown in FIG. 1 is flowed through the inner passage 2 of the tube 1 at a flow rate of 6 L / min. A bubble-containing liquid composition was discharged at an ambient temperature of 25 ° C. by a pore method (porous membrane method) using a device that press-fits gas from a pressure cylinder 3 and an air supply pipe 3a to the outside of the membrane tube 1 at 3 MPa. . Experimental conditions and results are shown in Table 1.

  In Example 1, the surfactant (A) is potassium stearate and the component (B) is potassium laurate so that potassium stearate / potassium laurate is 1/252 (weight ratio). This is the case. As a result, it has been surprisingly found that a fine bubble-containing liquid composition containing extremely fine bubbles having a high concentration and a long lifetime can be obtained. That is, the cloudiness of the obtained fine bubble-containing liquid composition does not float, and the dispersed bubbles were fine bubbles that could not be observed with a microscope. The diameter was 1.1 μm. The lifetime was 7 minutes and the bubble concentration was 100 million / mL.

  Example 2 is a case where vibrations derived from ultrasonic waves (40 kHz; 55 W) were further applied to the entire apparatus as shown in FIG. 2 under the same conditions as in Example 1. Since the outside of the tubular porous membrane is covered with the gas phase, the ultrasonic wave does not reach the liquid phase inside the porous membrane, and the action of the ultrasonic wave in this experiment gives vibration to the entire device. It is thought that it is only. As a result, it can be seen that a fine bubble-containing liquid composition in which bubbles are further refined as compared with Example 1 is obtained. In FIG. 2, an ultrasonic wave (40 kHz; 55 W) was applied from the ultrasonic wave transmitter 8, and fine bubbles generated in the inner passage 2 of the glass porous membrane tube 1 were separated and released by vibration. Otherwise, bubbles were generated in the same manner as in Example 1. 6 is a water tank and 7 is a water liquid.

  Example 3 was performed under the same conditions as in Example 2 except that the gas was changed to oxygen. From the results shown in Table 1, it can be seen that a fine bubble-containing liquid composition containing extremely fine bubbles having a high concentration and a long lifetime is obtained.

  Example 4 was performed under the same conditions as in Example 2 except that the ultrasonic treatment conditions shown in Table 1 were changed. From the results shown in Table 1, it can be seen that the bubble concentration and the bubble life are improved as compared with Example 2.

  Examples 5 to 7 were carried out under the same conditions as in Example 4 except that the surfactant conditions shown in Table 1 were changed. From the results shown in Table 1, it can be seen that a fine bubble-containing liquid composition containing extremely fine bubbles each having a high concentration and a long lifetime is obtained.

  Comparative Example 1 is a case where air is used as a gas without containing a surfactant (only ion-exchanged water). As a result, only bubbles that float immediately after discharge were obtained, and the fine bubble-containing liquid composition as in the present invention could not be obtained.

  The comparative example 2 is a case where only the potassium stearate which is (A) component is used as surfactant. As a result, only bubbles that float immediately after discharge were obtained, and the fine bubble-containing liquid composition as in the present invention could not be obtained. In addition, it was the same result also about the comparative example 4 which provided the ultrasonication.

  The comparative example 3 is a case where only potassium laurate which is (B) component is used as surfactant. As a result, a cloudy bubble-containing liquid composition was obtained, but the cloudy part floated 8 cm within 3 minutes, the bubble diameter was 25 μm or more, and a fine bubble-containing liquid composition as in the present invention was obtained. It was impossible. In addition, it was the same result also about the comparative example 5 which provided the ultrasonic treatment.

  In Comparative Examples 6 and 7, the component (A) and the component (B) are used in combination as surfactants, but their weight ratio is out of the scope of the present invention. From the results shown in Table 1, it can be seen that the fine bubble-containing liquid composition as in the present invention cannot be obtained.

(Examples 8 to 11, Comparative Examples 8 and 9)
An alkyl sulfate salt was used as a surfactant, and the same method as in Example 1 was performed under the conditions shown in Table 2. The results are shown in Table 2.

  From the results shown in Table 2, it can be seen that, as in Table 1, a fine bubble-containing liquid composition containing extremely fine bubbles having a high concentration and a long life is obtained.

(Examples 12 and 13, Comparative Examples 10-12)
As shown in FIG. 3, bubbles were generated by adding a surfactant from between a pressure dissolution tank and a nozzle of a pressure bubble control type microbubble generator (AWAWA manufactured by Resource Development Co., Ltd.). Specifically, ion exchange water 16 was flowed at 8 L / min, and air was mixed from the air supply pipe 10 by the gas-liquid mixing pump 11 at 0.2 L / min. A surfactant solution 17 having a concentration 8 times the target surfactant concentration is mixed at 1 L / min and 1 MPa with a plunger pump 15 into the pipe 13 after the gas mixed in the dissolution tank 12 is dissolved at 0.8 MPa. The pressure was released to atmospheric pressure at 14 to generate bubbles. At this time, the flow rate in the pipe after mixing the surfactant aqueous solution was 8 L / min, and there was no change before and after mixing. In FIG. 3, 18 is a container for collecting a liquid composition containing fine bubbles. It carried out on the conditions shown in Table 3. The results are shown in Table 3.

  From the results shown in Table 3, it can be seen that, as in Tables 1 and 2, a fine bubble-containing liquid composition containing extremely fine bubbles having a high concentration and a long lifetime is obtained. On the other hand, when the surfactant is not added, when the component (A) and the component (B) are each used alone as the surfactant, the fine bubble-containing liquid composition as in the present invention cannot be obtained. Recognize.

  From the above results, it can be seen that according to the production method of the present invention, a fine bubble-containing liquid composition containing extremely fine bubbles having a high concentration and a long lifetime can be collected.

The indicated surfactants in each table are as follows.
Component (A): An equimolar neutralized product of potassium stearate (Lunac S-98 manufactured by Kao Corporation) and 8 mol / L potassium hydroxide solution manufactured by Wako Pure Chemical Industries, Ltd. Craft point: 55 ° C. cmc cannot be measured because it does not form micelles at 25 ° C.
Octadecyl sulfate sodium salt: Wako Reagent. Craft point: 56 ° C. cmc cannot be measured because it does not form micelles at 25 ° C.
Component (B): An equimolar neutralized product of potassium laurate (Lunac L-98 manufactured by Kao Corporation) and 8 mol / L potassium hydroxide solution manufactured by Wako Pure Chemical Industries, Ltd. Craft point: 0 ° C. or lower, cmc: 26 mmol / L.
An equimolar neutralized product of potassium caprate (Lunac 10-98 manufactured by Kao Corporation) and 8 mol / L potassium hydroxide solution manufactured by Wako Pure Chemical Industries. cmc: 97 mmol / L. Kraft point cannot be measured because cmc exceeded 1% (weight).
An equimolar neutralized product of potassium myristate (Lunac MY-98 manufactured by Kao Corporation) and 8 mol / L potassium hydroxide solution manufactured by Wako Pure Chemical Industries. Craft point: 24 ° C., cmc: 6 mmol / L.
Sodium dodecyl sulfate (Emal 0 manufactured by Kao Corporation). Craft point: 16 ° C., cmc: 8.1 mmol / L.

FIG. 1 is an explanatory diagram of a bubble generation method for injecting gas into an aqueous surfactant solution from the outside of a porous membrane in Example 1 of the present invention. FIG. 2 is an explanatory diagram of a method for generating bubbles while applying ultrasonic waves in Example 2 of the present invention. FIG. 3 is an explanatory diagram of a method for generating bubbles when releasing pressure of gas dissolved in a pressurized liquid in Examples 12 to 13 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass porous membrane tube 2 Inner channel | path 3 Pressure cylinder 3a, 10 Air supply pipe 4 Surfactant aqueous solution 4a Liquid supply pipe 5a Bubble extraction pipe 5 Fine bubble containing liquid composition 6 Water tank 7 Water 8 Ultrasonic transmitter 9 Gas Press-fit unit 10 Air supply pipe 11 Gas-liquid mixing pump 12 Pressure dissolution tank 13 Pipe 14 Nozzle 15 Plunger pump 16 Water tank for ion exchange water 17 Water tank for surfactant aqueous solution 18 Container for collecting liquid composition containing fine bubbles

Claims (8)

A method for producing a microbubble-containing liquid composition comprising a step of mixing a gas into a liquid, wherein the liquid contains the following components (A) and (B), and the components (A) and (B): Is a fine bubble-containing liquid composition in which the weight ratio of (A) / (B) = 1/10 to 1/2000.
(A) A surfactant having a Kraft point of 40 to 90 ° C.
(B) A surfactant having a critical micelle concentration of 5 to 200 mmol / L.   The process according to claim 1, wherein the component (A) is a surfactant having an alkyl group having 16 to 24 carbon atoms.   The process according to claim 1 or 2, wherein the component (B) is a surfactant having an alkyl group or an alkenyl group having 6 to 15 carbon atoms.   The step of mixing the gas with the liquid uses a porous membrane, contacts the liquid with one of the porous membranes, and contacts the pressurized gas with the other of the porous membranes. The manufacturing method according to any one of claims 1 to 3, wherein gas is mixed into the liquid through the holes.   The method according to claim 4, wherein the porous membrane has an average pore diameter of 0.01 to 1 μm.   The manufacturing method according to claim 4 or 5, wherein ultrasonic treatment is further applied during the step of mixing a gas into the liquid.   The manufacturing method of Claim 6 which performs provision of the said ultrasonic treatment in the processing liquid stored in the processing tank which comprises an ultrasonic generator.   The process according to any one of claims 1 to 3, wherein the step of mixing the gas into the liquid is one in which the gas is dissolved in the liquid under pressure and then decompressed to generate the gas from the supersaturated dissolved gas. Law.

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