Cleaning method

Abstract

To provide a cleaning method with an improved cleaning efficiency resulting from an interaction effect between fine bubbles and a surfactant.SOLUTION: A cleaning method uses a cleaning fluid to clean a cleaning target. The cleaning liquid is a mixture of fine bubble water having a proportion of fine bubbles having a particle size in the range of 100 nm±30 nm of 50% or more in fine bubbles having a particle size of 500 nm or less, containing 1×10^5 pieces or more of fine bubbles having a particle size of 500 nm or less per 1 ml, and a surfactant.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a cleaning method, a washing machine, a dishwasher, and a toilet.

Background Art

[0002] In recent years, fine bubbles with a particle size in the range of several tens of nm to several μm, called microbubbles and nanobubbles, have attracted attention, and a technique for cleaning a cleaning target using fine bubble water containing a large number of fine bubbles has been proposed. Here, for example, when cleaning oil stains or the like, it is common to use a surfactant such as a detergent. However, in the conventional configuration, the interaction between the fine bubbles and the surfactant has not been sufficiently verified, and the effect due to the interaction between the fine bubbles and the surfactant has not been sufficiently exerted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, there is provided a cleaning method capable of improving the cleaning efficiency by bringing out the effect of the interaction between the fine bubbles and the surfactant, a washing machine, a dishwasher, and a toilet using this cleaning method.

Means for Solving the Problems

[0005] The cleaning method according to the present embodiment is This is microbubble water containing microbubbles generated by precipitating dissolved air in a liquid, a cleaning method for cleaning a cleaning target with a cleaning liquid obtained by mixing fine bubble water in which the ratio of the number of fine bubbles in the range of 100 nm ± 30 nm to the number of fine bubbles having a particle size of 500 nm or less is 50% or more and the fine bubble water contains 1 × 10^5 or more fine bubbles per 1 ml, and a surfactant.

[0006] Furthermore, the washing machine, dishwasher, and toilet according to this embodiment utilize a cleaning method in which the object to be cleaned is cleaned using a cleaning solution obtained by mixing microbubble water, in which the ratio of microbubbles within the range of particle size 100 nm ± 30 nm to the total number of microbubbles with a particle size of 500 nm or less is 50% or more, and the microbubbles with a particle size of 500 nm or less are 1 × 10^5 or more per 1 ml, with a surfactant. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows a graph of the number distribution of microbubbles of different particle sizes contained in the microbubble water used in the washing method according to one embodiment. [Figure 2] This figure shows the relationship between the particle size and number of microbubbles contained in the microbubble water used in the washing method according to one embodiment. [Figure 3] A table showing the evaluation results of the cleaning performance of a cleaning method according to one embodiment. [Figure 4] This figure shows the evaluation results of the cleaning performance of a cleaning method according to one embodiment, as a graph. [Figure 5] A schematic cross-sectional view showing an example of a microbubble generator used in a cleaning method according to one embodiment. [Figure 6] A cross-sectional view of a microbubble generator used in a cleaning method according to one embodiment, shown along the line X6-X6 in Figure 5. [Figure 7] This diagram schematically shows the configuration of a measurement system for measuring the number distribution of microbubble water particles by particle size used in a washing method according to one embodiment. [Figure 8] This figure shows the results of measurements taken by a measurement system for the microbubble water used in the cleaning method according to one embodiment, as a graph. [Figure 9] A diagram (part 1) conceptually illustrating the interaction between microbubbles and surfactant in a cleaning method according to one embodiment. [Figure 10] A diagram (part 2) conceptually illustrating the interaction between microbubbles and surfactant in a cleaning method according to one embodiment. [Figure 11]Figure (3) conceptually illustrates the interaction between microbubbles and surfactant in a cleaning method according to one embodiment. [Figure 12] Figure (4) conceptually illustrates the interaction between microbubbles and surfactant in a cleaning method according to one embodiment. [Figure 13] Figure (5) conceptually illustrates the interaction between microbubbles and surfactant in a cleaning method according to one embodiment. [Figure 14] A diagram showing the schematic configuration of a washing machine according to one embodiment. [Modes for carrying out the invention]

[0008] One embodiment will be described below with reference to the drawings. As shown in Figures 1 and 2, this embodiment is a cleaning method in which an object to be cleaned is cleaned with a cleaning solution, i.e., a surfactant solution, which is a mixture of microbubble water containing 1 × 10^5 or more microbubbles with a particle size of 500 nm or less per 1 ml, more preferably microbubble water containing 1 × 10^5 or more microbubbles with a particle size of 250 nm or less per 1 ml, and a surfactant. In this embodiment, the surfactant can be a naturally derived surfactant such as soap, or a synthetic surfactant contained in synthetic detergents, etc. The soap or synthetic detergent may be in solid, liquid, or powder form.

[0009] Microbubble water refers to water or a solution containing a large amount of microbubbles with a diameter on the order of nanometers. In other words, the microbubble water used in the cleaning method of this embodiment contains a larger amount of microbubbles with a particle size on the order of nanometers compared to tap water. Microbubbles can be generated, for example, by locally reducing the cross-sectional area of ​​a channel through which a liquid such as water flows, thereby rapidly reducing the pressure of the liquid passing through the channel and causing dissolved air in the liquid to precipitate. Microbubbles can also be generated, for example, by rapidly mixing external air into a liquid such as water passing through a channel.

[0010] The microbubbles used in the cleaning method of this embodiment, as shown in Fig. 1, are set such that the maximum peak P1 of the number distribution for each diameter of the microbubbles with a particle diameter of 500 nm or less, that is, for each particle diameter, falls within the range of a particle diameter of 100 nm ± 70 nm, more preferably within the range of a particle diameter of 100 nm ± 50 nm, and even more preferably within the range of a particle diameter of 100 nm ± 30 nm. In this case, the maximum peak P1 of the number distribution for each particle diameter of the microbubbles appears around a particle diameter of 80 nm.

[0011] Also, the second peak P2 appears around a particle diameter of 140 nm, and the third peak P3 appears around a particle diameter of 110 nm. Also, the fourth peak P4 appears around a particle diameter of about 50 nm, and the fifth peak P5 appears around a particle diameter of 220 nm. In this embodiment, among the number distributions for each diameter of the microbubbles with a particle diameter of 500 nm or less, at least two peaks including the maximum peak P1, in this case, the maximum peak P1 and the third peak P3, fall within the range of a particle diameter of 100 nm ± 30 nm.

[0012] The microbubble water used in the cleaning method of this embodiment is set such that the ratio of the number of microbubbles within the range of a particle diameter of 100 nm ± 30 nm to the number of microbubbles with a particle diameter of 500 nm or less is 50% or more. In the case of this embodiment, as shown in Fig. 2, the microbubble water contains 1.0 × 10^6 or more, in this case, about 1.25 × 10^6 microbubbles with a particle diameter of 500 nm or less per milliliter. Among these, the number of microbubbles within the range of a particle diameter of 100 nm ± 30 nm is about 8.25 × 10^5. Therefore, the ratio of the number of microbubbles within the range of a particle diameter of 100 nm ± 30 nm to the number of microbubbles with a particle diameter of 500 nm or less in the microbubble water is about 66%.

[0013] The inventor of the present application verified the correlation between the number of microbubbles in the cleaning liquid and the improvement rate of the cleaning performance against sebum stains by the following procedure using the above microbubble water. Note that the microbubbles in this verification mean those with a particle diameter of 500 nm or less.

[0014] (Preparation of Contaminating Components of Artificial Sebum Stains) Using chloroform as a solvent, oleic acid and triolein were dissolved to obtain a 50% solution containing 32.5% oleic acid and 17.5% triolein as the contaminating components.

[0015] (Artificial Contamination and Preparation of Samples) 40 ml of the solution of the above contaminating components was impregnated uniformly into a cotton cloth of 150 mm×200 mm, and after natural drying indoors for 24 hours, it was cut into 50 mm square cloth pieces to obtain contaminated cloths. Also, a cotton cloth not impregnated with the solution of the contaminating components was used as the original cloth.

[0016] (Test Method) One of the contaminated cloths was used as a reference piece without washing. Also, six contaminated cloths were washed respectively with six types of cleaning solutions: a cleaning solution containing 1.30×10^6 fine bubbles / ml, a cleaning solution containing 6.5×10^5 fine bubbles / ml, a cleaning solution containing 3.25×10^5 fine bubbles / ml, a cleaning solution containing 2.6×10^5 fine bubbles / ml, a cleaning solution containing 1.60×10^5 fine bubbles / ml, and a cleaning solution without mixed fine bubbles, and then natural drying indoors was carried out for 24 hours. Thereby, evaluation pieces 1 - 5 and a comparison piece were obtained respectively.

[0017] Note that the same amount of detergent was dissolved in each cleaning solution. That is, the cleaning solution for washing the comparison piece is tap water with a commercially available detergent dissolved in a specified amount. Also, the cleaning solutions for washing evaluation pieces 1 - 5 are tap water with the above - specified fine bubbles mixed in and a commercially available detergent dissolved in a specified amount respectively. The dissolved amount of the detergent is, for example, the specified amount described in the handling instructions of the detergent. Also, the washing of the comparison piece and each of evaluation pieces 1 - 5 was carried out with the same operation content using a commercially available washing machine.

[0018] Next, oil violet was dissolved as an oil-soluble dye in an ethanol aqueous solution with a mixing ratio of ethanol:water = 13:7 to obtain a staining solution with a concentration of 0.664 mg / ml. Then, each evaluation piece 1-5 and the comparison piece were immersed in the staining solution for 15 minutes to stain them, and then rinsed with the ethanol aqueous solution followed by water to remove any excess staining solution. After that, the comparison piece and each evaluation piece 1-5 and the comparison piece were air-dried indoors for 24 hours.

[0019] Next, using a colorimeter, the color difference between the original fabric and the reference piece was measured as the pre-wash color difference for each evaluation piece 1-5 and the comparison piece. Furthermore, the color difference between the original fabric and each evaluation piece 1-5 and the comparison piece was measured as the post-wash color difference for each evaluation piece 1-5 and the comparison piece. Then, the degree of cleanliness for each evaluation piece 1-5 and the comparison piece was calculated based on the following equation (1), and the degree of cleanliness of each evaluation piece 1-5 was compared to the degree of cleanliness of the comparison piece. Cleanliness = 1 - (Color difference after cleaning) / (Color difference before cleaning) ... (1)

[0020] The test results are shown in Figure 3. In Figure 3, "Mixing Ratio" refers to the ratio of microbubble water to the total cleaning solution when 100% microbubble water containing 1.30 × 10^6 microbubbles per ml is used as the cleaning solution, and tap water is mixed with this 100% microbubble water to purify the cleaning solution. In Figure 3, "Microbubble Concentration" refers to the number of microbubbles contained per ml of each cleaning solution. In Figure 3, "Logarithmic Value" refers to the microbubble concentration of each cleaning solution expressed as a common logarithm with base 10.

[0021] According to the test results shown in Figure 3, evaluation piece 1, which was washed with a cleaning solution containing 1.30 × 10^6 microbubbles / ml, showed a 19.2% improvement in cleaning performance compared to the control piece washed with a cleaning solution without microbubbles. Evaluation piece 2, which was washed with a cleaning solution containing 6.5 × 10^5 microbubbles / ml, showed a 13.7% improvement in cleaning performance compared to the control piece washed with a cleaning solution without microbubbles. Evaluation piece 3, which was washed with a cleaning solution containing 3.25 × 10^5 microbubbles / ml, showed a 13.0% improvement in cleaning performance compared to the control piece washed with a cleaning solution without microbubbles.

[0022] Furthermore, in evaluation piece 4, which was washed with a cleaning solution containing 2.6 × 10^5 microbubbles / ml, a 12.6% improvement in cleaning performance was observed compared to the comparison piece washed with a cleaning solution that did not contain microbubbles. And in evaluation piece 5, which was washed with a cleaning solution containing 1.60 × 10^5 microbubbles / ml, a 10.7% improvement in cleaning performance was observed compared to the comparison piece washed with a cleaning solution that did not contain microbubbles.

[0023] Figure 4 shows the results for each evaluation piece 1 to 5 in Figure 3, with the horizontal axis representing the logarithm of the number of microbubbles in the cleaning solution and the vertical axis representing the cleaning performance improvement rate. When the horizontal axis in Figure 4, i.e., the concentration of microbubbles in the cleaning solution, is the X-axis, and the vertical axis, i.e., the cleaning performance improvement rate, is the Y-axis, the approximate curve calculated using the least squares method can be expressed by the following equation (2). The correlation coefficient R^2 in this case was 0.908. Y=(5.02×10^(-4))X^(3.25)···(2)

[0024] Figure 4, Equation (2), and its correlation coefficient R^2 show that cleaning performance improves almost linearly, or almost linearly, with increasing amounts of microbubbles in the cleaning solution. In other words, this test revealed a high correlation between the number of microbubbles in the cleaning solution and cleaning performance. According to Equation (2), when the number of microbubbles in the cleaning solution is 1.0 × 10^5 / ml, or X = 5, cleaning performance improves by approximately 9.4% compared to cleaning with a normal cleaning solution that does not contain microbubbles. Furthermore, according to Equation (2), when the number of microbubbles in the cleaning solution is 1.26 × 10^5 / ml, or X = 5.1, cleaning performance improves by approximately 10% compared to cleaning with a normal cleaning solution that does not contain microbubbles. As a result, it was found that including at least 1.0 × 10^5 / ml of microbubbles in the cleaning solution can improve cleaning performance by approximately 10% compared to cleaning with a normal cleaning solution that does not contain microbubbles.

[0025] In the above test, microbubble water was generated using the microbubble generator 10 shown in Figures 5 and 6. The microbubble generator 10 is made of synthetic resin, for example, and is formed in a cylindrical shape overall. The microbubble generator 10 has a constricted section 11, a straight section 12, and a protruding section 13. The constricted section 11 and the straight section 12 form a single continuous flow path. In this case, the constricted section 11 side is the input side, and the straight section 12 side is the output side.

[0026] The throttling section 11 is formed in a shape where the inner diameter decreases from the input side to the output side of the microbubble generator 10, that is, in a so-called conical tapered tube shape where the cross-sectional area of ​​the flow path, i.e., the inner diameter, decreases continuously and gradually. The straight section 12 is formed in a cylindrical, so-called straight tube shape where the cross-sectional area of ​​the flow path, i.e., the inner diameter, does not change.

[0027] The protrusions 13 are provided in the middle of the straight section 12 in the longitudinal direction. The purpose of the protrusions 13 is to generate fine bubbles in the liquid passing through the straight section 12 by locally reducing the cross-sectional area through which water can pass. In this embodiment, the straight section 12 is provided with multiple protrusions 13, in this case four. Each protrusion 13 is made up of a rod-shaped member with a pointed tip and protrudes from the inner circumferential surface of the straight section 12 toward the center of the cross-section of the straight section 12. Each protrusion 13 is arranged at equal intervals from each other in the circumferential direction of the cross-section of the straight section 12.

[0028] When water flows into the microbubble generator 10 from the constricted section 11, the flow path cross-sectional area narrows from the constricted section 11 to the straight section 12, increasing the flow velocity due to the so-called Venturi effect in fluid dynamics. Then, the high-speed flow collides with the protrusion 13, causing a rapid decrease in pressure. This allows a large amount of dissolved air in the water to precipitate as microbubbles.

[0029] The performance of the microbubble generator 10 is evaluated by passing water through the microbubble generator 10 once to generate microbubble water, and then measuring the number of microbubbles contained per unit volume, for example, 1 ml, and the number distribution of microbubbles for each particle size. In this embodiment, generating microbubble water by passing water through the microbubble generator 10 only once is referred to as a one-pass process.

[0030] The performance of the microbubble generator 10 is evaluated using a measurement system 20 as shown in Figure 7. The measurement system 20 comprises the microbubble generator 10, a water tank 21, a circulation pump 22, and pipes 23 and 24 connecting the water tank 21 and the circulation pump 22. The microbubble generator 10 is installed in the middle of the pipe 23 connected to the discharge side of the circulation pump 22, that is, in the middle of the pipe 23 leading from the circulation pump 22 to the water tank 21.

[0031] A predetermined amount, for example 10 liters, of ultrapure water W is stored in the tank 21. The circulation pump 22 circulates the ultrapure water W between the tank 21 and the circulation pump 22. At this time, the ultrapure water W is applied to the microbubble generator 10 at a pressure of 0.1 MPa by the action of the circulation pump 22. As a result, microbubbles precipitate in the ultrapure water W that has passed through the microbubble generator 10, becoming microbubble water. The circulation pump 22 is then driven for a predetermined time to circulate the ultrapure water W and pass it through the microbubble generator 10 multiple times, thereby increasing the number of microbubbles contained in the ultrapure water W in the tank 21.

[0032] The inventor of the present invention took samples of ultrapure water W in the water tank 21 at predetermined intervals, for example, about 10 minutes, after starting the operation of the circulation pump 22. The inventor then analyzed each sample using a nanoparticle analyzer (NANOSIGHT LM10, manufactured by Shimadzu Corporation) with the nanoparticle tracking method (also called particle trajectory tracing method) to measure the number of microbubbles per 1 ml.

[0033] Furthermore, the inventors of this application calculated the time required for one circulation of ultrapure water W from the circulation flow rate of ultrapure water W and the initial amount stored in the water tank 21. In this embodiment, the time required for one circulation is approximately 1 minute. The inventors then calculated the number of times the ultrapure water W had passed through the microbubble generator 10 by the time of sampling, based on the time required for one circulation and the sample collection time. In the following description, the number of times calculated in this way, that is, the number of times the ultrapure water W is thought to have passed through the microbubble generator 10 from the time the circulation pump 22 is operated until the time of sampling of each sample, will be referred to as the number of passes.

[0034] Figure 8 plots the number of passes through the microbubble generator on the x-axis and the amount of microbubbles generated on the y-axis for each sample. The results in Figure 8 show that the amount of microbubbles in the ultrapure water W increases linearly as the number of passes through the microbubble generator W increases. In other words, it was found that the more times the ultrapure water W passes through the microbubble generator W, the more concentrated the microbubbles in the ultrapure water W become. That is, according to the results in Figure 8, there is a linear correlation between the number of passes through the microbubble generator W, i.e., the number of times the ultrapure water W is circulated, and the amount of microbubbles in the ultrapure water W.

[0035] According to this, if the number of microbubbles generated when a liquid such as water passes through the microbubble generator 10 once is considered the performance of the microbubble generator 10 in one pass, then this performance in one pass can be determined as follows: At any point after the start of circulation, a sample of ultrapure water W in the water tank 21 is taken, and the number of microbubbles contained in the sample is measured. Then, by dividing the measured number of microbubbles by the number of passes up to the time of sample collection, i.e., the number of circulations, the performance of the microbubble generator 10 in one pass is calculated. The performance calculated in this way, i.e., the number of microbubbles, is first concentrated and then averaged by the number of passes, so the influence of the resolution of the measuring device and microparticles other than microbubbles contained in the water used can be eliminated as much as possible, and an accurate evaluation result can be obtained.

[0036] In this embodiment, as shown in Figure 8, approximately 1.48 × 10^7 microbubbles with a particle size of 500 nm or less are generated per 1 ml after 10.6 circulation cycles. Furthermore, approximately 2.85 × 10^7 microbubbles with a particle size of 500 nm or less are generated per 1 ml after 20.2 circulation cycles. And after 29.8 circulation cycles, approximately 3.95 × 10^7 microbubbles with a particle size of 500 nm or less are generated per 1 ml. From these results, it can be seen that 1.3 to 1.4 × 10^6 microbubbles with a particle size of 500 nm or less are generated per 1 ml after a single pass. Therefore, it was found that the microbubble generator 10 used in the washing method of this embodiment can generate microbubble water containing approximately 1.3 to 1.4 × 10^6 microbubbles with a particle size of 500 nm or less per 1 ml in a single pass at an applied dynamic water pressure of 0.1 MPa.

[0037] Furthermore, in the above cleaning performance test, the microbubble water generated by passing tap water through the microbubble generator 10 only once, i.e., the microbubble water generated in a single pass, was considered 100% microbubble water. This 100% microbubble water contains approximately 1.3 × 10^6 microbubbles per ml with a particle size of 500 nm or less. By using this 100% microbubble water undiluted with tap water, a cleaning solution containing 1.30 × 10^6 microbubbles / ml, used for evaluation piece 1, was obtained. Additionally, by diluting the 100% microbubble water to 50% with tap water, a cleaning solution containing 6.50 × 10^5 microbubbles / ml, used for evaluation piece 2, was obtained.

[0038] Furthermore, by diluting 100% microbubble water to 25% with tap water, a washing solution containing 3.25 × 10^5 bubbles / ml for use in evaluation piece 3 was obtained. Also, by diluting 100% microbubble water to 20% with tap water, a washing solution containing 2.60 × 10^5 bubbles / ml for use in evaluation piece 4 was obtained. And, by diluting 100% microbubble water to 12.5% ​​with tap water, a washing solution containing 1.60 × 10^5 bubbles / ml for use in evaluation piece 5 was obtained.

[0039] Therefore, the washing solutions used for evaluation samples 1 to 5 all exhibit the same peak and proportion of the number distribution of microbubbles by particle size. In other words, as described above, the maximum peak of the number distribution of microbubbles by particle size for particles 500 nm or smaller in all washing solutions used for evaluation samples 1 to 5 falls within the range of 100 nm ± 30 nm. Furthermore, as described above, the proportion of microbubbles within the 100 nm ± 30 nm particle size range to the total number of microbubbles 500 nm or smaller in all washing solutions used for evaluation samples 1 to 5 is 50% or more.

[0040] Generally, microbubbles are classified as follows according to their particle size. For example, bubbles with a particle size of a few micrometers to about 50 micrometers, i.e., on the micro-order, are called microbubbles or fine bubbles. In contrast, bubbles with a particle size of several hundred nanometers to tens of nanometers or less, i.e., on the nano-order, are called nanobubbles or ultrafine bubbles.

[0041] When the particle size of bubbles becomes several hundred nanometers to tens of nanometers or smaller, they become smaller than the wavelength of light and therefore invisible, making the liquid transparent. Furthermore, nano-order microbubbles have characteristics such as a larger total interface area, slower buoyancy, and higher internal pressure compared to micro-order or larger bubbles. For example, micro-order bubbles rise rapidly through the liquid due to their buoyancy and burst and disappear at the liquid surface, resulting in a relatively short residence time in the liquid. On the other hand, nano-order microbubbles have less buoyancy and therefore a longer residence time in the liquid.

[0042] The above test showed that by including microbubbles in a cleaning solution containing a dissolved surfactant, cleaning performance could be improved compared to cleaning with a normal cleaning solution that did not contain microbubbles. This is presumed to be due to the following principle. As shown in Figure 9, normally, when the concentration of surfactant 32 exceeds a certain level, the hydrophobic groups of the surfactant 32 gather together and form micelles, creating aggregates 33 of surfactant 32. The particle size of these aggregates 33 is said to be several tens of nanometers. On the other hand, microbubbles 31 with a particle size of 500 nm or less have a negatively charged surface and are hydrophobic, thus attracting the hydrophobic groups of surfactant 32.

[0043] Therefore, when a detergent containing aggregates 33 of micellar surfactant 32 is mixed with microbubble water containing microbubbles 31 with a particle size of 500 nm or less, the hydrophobic effect of the surface of the microbubbles 31 disrupts the energetically stable state of the aggregates 33, causing the aggregates 33 to break down and the individual molecules of surfactant 32 to disperse, as shown in Figure 10. Then, the dispersed molecules of surfactant 32 are adsorbed onto the surface of the microbubbles 31 through interaction between the hydrophobic groups of the surfactant 32 and the hydrophobic surface of the microbubbles 31. As a result, the surfactant 32 contained in the cleaning solution is adsorbed onto the microbubbles 31 and forms a complex 34.

[0044] As shown in Figure 11, the complex 34 of surfactant 32 and microbubbles 31 is diffused over a wide area in the cleaning solution due to the buoyancy of the microbubbles 31. As a result, the probability of each molecule of surfactant 32 coming into contact with, for example, sebum stain components 36 attached to the fibers 35 is greatly increased. As shown in Figure 12, when the complex 34 of surfactant 32 and microbubbles 31 approaches the stain components 36, the hydrophobic effect of the surface of the stain components 36 disrupts the energetic stability of the surfactant 32 and microbubbles 31, causing deformation and rupture of the microbubbles 31. Then, each molecule of surfactant 32 separates and adsorbs onto the stain components 36, and the impact from the rupture of the microbubbles 31 makes the stain components 36 lift off the fibers 35 and easier to remove.

[0045] In this process, the surfactant 32 enters the gap between the dirt components 36 and the fibers 35, created by the impact of the bursting of the microbubbles 31, thereby promoting the emulsification of the dirt components 36. The surfactant 32 then detaches the dirt components 36 from the fibers 35 by emulsifying them, thereby exhibiting its cleaning ability. In this way, the microbubbles 31 are said to bring out the cleaning ability of the surfactant 32.

[0046] The cleaning method of this embodiment can be applied to a washing machine 40, for example, as shown in Figure 14. The washing machine 40 comprises an outer casing 41, a top cover 42, a water tank 43, a rotating drum 44, a pulsator 45, a motor 46, a water injection device 50, and a microbubble generator 10. The washing machine 40 is a so-called vertical-axis type washing machine in which the rotation axis of the rotating drum 44 is oriented vertically. However, the washing machine is not limited to the vertical-axis type; it may also be a horizontal-axis type so-called drum-type washing machine in which the rotation axis of the rotating drum is tilted horizontally or downward toward the rear.

[0047] The water supply device 50 is located on the top of the outer casing 41 and is installed inside the top cover 42. The water supply device 50 includes a first water supply valve 51, a second water supply valve 52, a third water supply valve 53, a connection port 54, a water supply case 60, and a microbubble generator 10. In other words, in the washing machine 40, the microbubble generator 10 is incorporated into the water supply device 50 as a component of the water supply device 50.

[0048] The connection port 54 is connected to a water source such as a water tap via a hose (not shown). The downstream side of the connection port 54 branches into multiple lines, each connected to the water filling case 60 via water supply valves 51, 52, and 53. In this embodiment, the downstream side of the connection port 54 branches into three lines, each connected to the water filling case 60 via water supply valves 51, 52, and 53.

[0049] The water supply case 60 receives water supplied from the connection port 54 and pours the received water into the water tank 43 and the rotating tank 44 through the water inlet 61. The water supply case 60 has a pull-out detergent case 62 and a fabric softener case 63. Detergent is put into the detergent case 62, and fabric softener is put into the fabric softener case 63.

[0050] In this configuration, when the first water supply valve 51 is opened, tap water supplied from a faucet (not shown) to the connection port 54 passes through the microbubble generator 10 to become microbubble water containing microbubbles, and is supplied to the detergent case 62 in the water supply case 60. The microbubble water supplied to the detergent case 62 after passing through the microbubble generator 10 flows down to the bottom of the water supply case 60, and is then poured into the water tank 43 and the rotating tank 44 from the water inlet 61. At this time, if detergent is contained in the detergent case 62, the detergent is dissolved in the microbubble water supplied to the detergent case 62 and flows down into the water tank 43 and the rotating tank 44 from the water inlet 61.

[0051] Similarly, when the second water supply valve 52 is opened, tap water supplied from a faucet (not shown) to the connection port 54 is supplied to the detergent case 62 in the water supply case 60. The tap water supplied to the detergent case 62 then flows down to the bottom of the water supply case 60 and is subsequently poured into the water tank 43 and the rotating tank 44 from the water inlet 61. At this time, if detergent is contained in the detergent case 62, the detergent is dissolved in the tap water supplied to the detergent case 62 and then flows down into the water tank 43 and the rotating tank 44 from the water inlet 61.

[0052] In this embodiment, the microbubble water supplied by opening the first water supply valve 51, passing through the microbubble generator 10, and the tap water supplied by opening the second water supply valve 52, which bypasses the microbubble generator 10, are mixed in the water supply case 60 or the water tank 43 to form the laundry solution. In this case, the washing machine 40 can adjust the mixing ratio of microbubble water and tap water in the laundry solution by adjusting the opening and closing time and timing of the first water supply valve 51 and the second water supply valve 52. This allows the concentration of microbubbles in the laundry solution to be adjusted as desired.

[0053] Furthermore, when the third water supply valve 53 is opened, tap water supplied from a faucet (not shown) to the connection port 54 is supplied to the fabric softener case 63 inside the water supply case 60. The tap water supplied to the fabric softener case 63 then flows down to the bottom of the water supply case 60 and is then poured into the water tank 43 and the rotating tank 44 from the water inlet 61. At this time, if fabric softener is contained in the fabric softener case 63, the fabric softener is dissolved in the tap water supplied to the fabric softener case 63 and then flows down into the water tank 43 and the rotating tank 44 from the water inlet 61. A microbubble generator 10 may also be provided in the path of the third water supply valve 53.

[0054] Then, with the washing machine 40 storing the washing liquid in the water tank 43 and the rotating tub 44, the motor 46 is driven to rotate the pulsator 45 and agitate the laundry in the rotating tub 44, thereby performing the washing operation. In this case, tap water, not circulating water, is applied to the microbubble generator 10. In other words, in this embodiment, the microbubble water used for the washing liquid is generated by passing tap water through the microbubble generator 10 once, that is, generated in a single pass. The microbubble generator 10 may also be installed in the middle of the circulation path that circulates the washing liquid within the washing machine 40. In this case, the concentration of microbubbles in the washing liquid can be further increased by passing the washing liquid through the microbubble generator 10 multiple times.

[0055] According to the cleaning method and washing machine 40 of the embodiments described above, the object to be cleaned is cleaned with a cleaning solution obtained by mixing fine bubble water containing 1 × 10^5 or more fine bubbles with a particle size of 500 nm or less per 1 ml with a surfactant such as a detergent.

[0056] According to this method, the number and particle size of microbubbles can be optimized for cleaning with surfactants. This allows for the full utilization of the effects of the interaction between microbubbles and surfactants, resulting in improved cleaning efficiency compared to cleaning with a cleaning solution that does not contain microbubbles.

[0057] Microbubbles carry a negative charge on their surface. It is believed that the smaller the particle size of the microbubbles, the greater the negative charge on the surface of the microbubbles. Therefore, as the particle size decreases, microbubbles become more adsorbent of surfactants, and as a result, they are more likely to form aggregates with surfactants. However, as the particle size of microbubbles decreases, the surface area of ​​the microbubbles also decreases, so the amount of surfactant that a single microbubble can adsorb decreases.

[0058] In contrast, the microbubble water used in the washing method and washing machine 40 of this embodiment has a maximum peak in the number distribution of microbubbles with a particle diameter of 500 nm or less within the range of 100 nm ± 30 nm. This allows for an appropriate balance between the adsorption capacity of the surfactant due to the electrical properties of the microbubbles and the amount of surfactant adsorbed due to the size of the microbubbles. As a result, the effects of the interaction between microbubbles and surfactants can be more effectively extracted.

[0059] Furthermore, in the cleaning method and the microbubble water used in the washing machine 40 of this embodiment, the ratio of microbubbles with a particle size within the range of 100 nm ± 30 nm to the total number of microbubbles with a particle size of 500 nm or less is 50% or more. This also allows for a more appropriate balance between the adsorption capacity of the surfactant due to the electrical properties of the microbubbles and the amount of surfactant adsorbed due to the size of the microbubbles. As a result, the effects of the interaction between microbubbles and surfactants can be more effectively extracted.

[0060] Furthermore, the microbubble water used in the washing method and washing machine 40 according to this embodiment is generated by passing tap water through the microbubble generator 10 once. This allows for a shorter supply time of microbubble water compared to a method that generates microbubble water by passing tap water through the microbubble generator 10 multiple times. As a result, the washing time can be shortened.

[0061] Furthermore, the cleaning method of the above embodiment is not limited to the washing machine 40, but can also be applied to, for example, dishwashers and toilets. When the washing method of the above embodiment is applied to a dishwasher, the dishwasher washes the dishes to be washed using, for example, the microbubble water generated through the microbubble generator 10 described above. In this case, the microbubble generator 10 can be installed in the middle of the water supply path for supplying tap water from the water supply to the dishwasher, or in the circulation path for circulating the water supplied to the dishwasher. As a result, microbubble water containing microbubbles is supplied into the dishwasher through the microbubble generator 10. Then, when the microbubble water and dish soap are mixed inside the dishwasher, the effects of the interaction between microbubbles and surfactants can be effectively extracted as described above.

[0062] Furthermore, when the cleaning method of the above embodiment is applied to a toilet bowl, the toilet bowl is cleaned using, for example, the microbubble water generated through the microbubble generator 10 described above. In this case, the microbubble generator 10 can be installed in the middle of the water supply path that supplies tap water from the water supply to the toilet bowl. As a result, microbubble water containing microbubbles is supplied to the toilet bowl through the microbubble generator 10. Then, inside the toilet bowl, for example, the detergent that the user puts into the toilet bowl when cleaning the inside of the toilet bowl mixes with the microbubble water supplied to the toilet bowl, thereby effectively bringing out the effects of the interaction between microbubbles and surfactants as described above. In this case, the toilet bowl may also be equipped with a mechanism that automatically supplies detergent together with the microbubble water into the toilet bowl.

[0063] Although one embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0064] In the drawing, 31 represents microbubbles, 32 represents a surfactant, and 40 represents a washing machine.

Claims

[Claim 1] A cleaning method comprising: a microbubble generator having a throttling section on the input side where the inner diameter of the flow path is reduced, a straight section on the output side where the inner diameter of the flow path does not change, and a protruding section that locally reduces the cross-sectional area of ​​the flow path, wherein when ultrapure water is passed through the microbubble generator once at an applied dynamic water pressure of 0.1 MPa, the ratio of microbubbles with a particle diameter of 100 nm ± 30 nm to the total number of microbubbles with a particle diameter of 500 nm or less is 50% or more, and the microbubble water contains 1 × 10^5 or more microbubbles with a particle diameter of 500 nm or less per 1 ml; and a cleaning solution which is a mixture of the microbubble water containing microbubbles generated by passing tap water through the microbubble generator once at an applied dynamic water pressure of 0.1 MPa or more to reduce the pressure of the liquid and precipitate dissolved air in the liquid; and a surfactant.

Images