Detergency evaluation device and detergency evaluation method

Abstract

To provide a detergency evaluation device capable of easily, quickly, and accurately measuring detergency of any detergent by newly defining a detergency index using osmotic pressure of foam against water, and to provide a detergency evaluation method using the same.SOLUTION: A detergency evaluation deice is provided, comprising two visible light-transmissive transparent substrates sandwiching a sample liquid consisting of a surfactant aqueous solution containing foam, spacers for keeping the two transparent substrates spaced apart by a given distance, clamping means for clamping the two transparent substrates facing each other, and observation means for observing the position of an oil-water interface in the sample liquid.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a detergency evaluation device for quantitatively evaluating the detergency of a sample containing a surfactant or the like, and a detergency evaluation method using the same. [Background technology]

[0002] Detergents containing surfactants exert their cleaning power by absorbing oil with the foam they generate. Until now, it has been extremely difficult to quantify the cleaning power of such foam. In other words, since the ability to absorb oil is exerted by the osmotic pressure of the foam, it is thought that cleaning power can be quantified by measuring the osmotic pressure.

[0003] A conventional method for measuring the osmotic pressure of a foam involves preparing a sufficiently large foam, letting time pass until no more water flows out of the foam, and then determining all of the parameters, such as the type and concentration of surfactant, surface tension, bubble density, bubble size, bubble size distribution, proportion of straight bubble portions, and liquid fraction, and then calculating the osmotic pressure based on these parameters (e.g., Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-020187 A [Patent Document 2] Special Publication No. 06-506609 Summary of the Invention [Problem to be solved by the invention]

[0005] However, quantifying the cleaning power of conventional foam requires many measurement parameters, and the foam state changes over time as the foam collapses and coarsens during the time it takes to produce wastewater, making it difficult to evaluate the cleaning power under conditions that approximate the conditions under which the detergent is actually used.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a detergency evaluation device that can measure the detergency of any detergent easily, quickly, and accurately by newly defining a detergency index using the osmotic pressure of foam against water, and a detergency evaluation method using the same. [Means for solving the problem]

[0007] That is, in order to solve the above problems, the present invention proposes the following means. (1) A cleaning power evaluation device according to a first aspect of the present invention is characterized in that it comprises two transparent substrates transmissive to visible light which sandwich a sample liquid consisting of a surfactant aqueous solution containing foam, a spacer which separates the two transparent substrates at a predetermined distance, a clamping means which clamps the two transparent substrates opposite each other, and an observation means which observes the position of the interface between the foam and water in the sample liquid.

[0008] (2) A second aspect of the present invention relates to the device for evaluating detergency in the first aspect, characterized in that the observation means is an imaging device.

[0009] (3) A method for evaluating cleaning power according to a third aspect of the present invention is a method for evaluating cleaning power using the cleaning power evaluation device of the first or second aspect, characterized in that it comprises, in order, the steps of sandwiching a sample liquid consisting of a surfactant aqueous solution containing foam, which is the object of cleaning power measurement, between two of the transparent substrates; sandwiching the two transparent substrates with the clamping means and standing the transparent substrates upright so that their main surfaces are aligned vertically; and, after a predetermined time has elapsed, determining by the observation means whether the water contained in the sample liquid remains within the foam region or has reached below the foam region.

[0010] (4) A method for evaluating detergency according to a fourth aspect of the present invention is the same as that according to the third aspect, and further comprises determining a limit mass M, which is a mass of water that can be absorbed by the foam of the sample liquid, at a transition line that represents a boundary between whether the water contained in the sample liquid remains within the foam region and is absorbed by the foam, and whether the water reaches below the foam region and is drained from the foam. * A The critical mass of the foam of the reference liquid, which is a surfactant aqueous solution containing the foam to be compared, is M * ref is characterized in that, when β=M * A / M * ref (1) Effect of the Invention

[0011] According to the present invention, by newly defining the detergency index using the osmotic pressure of foam against water, it is possible to provide a detergency evaluation device that can measure the detergency of any detergent easily, quickly, and accurately, and a detergency evaluation method using the same. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing a cleaning power evaluation device according to an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] 1 is a graph showing the correlation between the method for evaluating detergency of the present invention and conventional osmotic pressure measurements. [Figure 4] 1 is a photograph showing an example of oil absorption by foam. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a cleaning power evaluation device according to one embodiment of the present invention and a cleaning power evaluation method using the same will be described with reference to the drawings. Note that each embodiment shown below is specifically described to better understand the gist of the invention, and does not limit the present invention unless otherwise specified. In addition, the drawings used in the following description may show essential parts in an enlarged manner for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as in reality.

[0014] (Detergency evaluation device) FIG. 1 is a schematic diagram showing a cleaning power evaluation device according to one embodiment of the present invention. The cleaning power evaluation device 10 of this embodiment has two transparent substrates 11A, 11B arranged opposite each other, a plurality of spacers 12 arranged between the two transparent substrates 11A, 11B, a clamping means 13 that clamps the two transparent substrates 11A, 11B, and an observation means 14 that observes the sample liquid arranged between the two transparent substrates 11A, 11B.

[0015] The transparent substrates 11A and 11B may be transparent plates that transmit visible light, such as glass plates, acrylic plates, etc. In this embodiment, transparent acrylic plates are used as the transparent substrates 11A and 11B.

[0016] Spacer 12 may be, for example, a thin resin plate or rubber plate, and is disposed, for example, at the four corner positions between transparent substrate 11A and transparent substrate 11B to ensure gap D between transparent substrate 11A and transparent substrate 11B. Such gap D, i.e., the thickness of spacer 12, may be such that capillary action occurs between transparent substrate 11A and transparent substrate 11B.

[0017] The clamping means 13 may be any member capable of clamping the transparent substrates 11A and 11B from the outer surface side in a state in which the substrates are opposed to each other, and may be a clip, a clamp, etc. In this embodiment, a metal clip is used as the clamping means 13.

[0018] The observation means 14 observes and records the state of the sample liquid placed between the two transparent substrates 11A and 11B from the outside of one of the transparent substrates 11A, and can use an imaging device such as a CCD camera or a CMOS camera. The state of the sample liquid may be a still image or a video. In this embodiment, a CMOS camera is used to capture a video of the state of the sample liquid.

[0019] In the cleaning power evaluation device configured as described above, the detergent to be evaluated, i.e., a sample liquid in which a surfactant aqueous solution is foamed to produce foam F, is sandwiched between two transparent substrates 11A and 11B and placed vertically. After a predetermined time has passed, it is observed whether water flows downward from the foam due to its own weight (drainage from the foam), thereby identifying the water absorption power of the foam of the detergent to be evaluated and measuring the cleaning power.

[0020] In other words, in principle, the cleaning power of any detergent can be quantitatively measured simply by measuring the height of the foam at the very limit of drainage and the liquid fraction of the foam. The water absorption power of such foam is almost the same as its oil absorption power, and this makes it possible to investigate the cleaning power of the foam against oily stains and the like from its water absorption power. In other words, by identifying the position of the interface between the foam and water, the cleaning power of the detergent against oily stains and the like can be known.

[0021] (Method of evaluating cleaning power) A method for evaluating detergency according to this embodiment using the device for evaluating detergency configured as above will now be described. When evaluating the detergency of an arbitrary detergent by the method for evaluating detergency of this embodiment, first, a foam F of a sample liquid with a liquid fraction φ is sandwiched between transparent substrates 11A and 11B as shown in Fig. 1. At this time, the foam F to be measured is expanded into a rectangle, and the thickness of the foam is D, the height of the foam is H, and the width of the foam F is W.

[0022] Next, the transparent substrates 11A and 11B sandwiching the foam F are clamped by a metal clip, which is the clamping means 13, and then the transparent substrates 11A and 11B are stood upright so that the main surfaces are aligned vertically. This state is then maintained for a predetermined time, for example, about 5 minutes, and the change in the foam F is captured as a video by the CMOS camera, which is the observation means 14.

[0023] As a result, depending on the liquid fraction φ of the foam F and the foam height H, there are cases where the water flows out from the foam F to the bottom (drained) and cases where the water is retained in the foam F and does not flow out to the bottom (not drained). In this case, when the water is drained, the time required for drainage is about 3 minutes at most, so the retention time should be set to 5 minutes or more to be generous.

[0024] The boundary line (transition line) between the presence or absence of drainage from the foam F is the maximum osmotic pressure Π max The maximum osmotic pressure of foam varies depending on the type of surfactant, the size of the bubbles, and the size distribution of the bubbles, and is a parameter closely linked to the cleaning power of the foam. For example, when foam is placed vertically, two forces act on the foam: the weight of the water it contains and the osmotic pressure. At the transition line, the weight of the water and the maximum osmotic pressure are in balance.

[0025] On the other hand, the maximum osmotic pressure Π of foam under the conditions when the detergent is actually used max When there is less water than the transition line, the maximum osmotic pressure Π max Since the foam can absorb oil until it reaches the height of the transition line and the liquid fraction, respectively, * ,φ * Then, the maximum osmotic pressure Π max The difference between these values ​​indicates the cleaning power of the detergent (see equation (2) below). Π max -Π=ρg(H * φ * -Hφ) ···(2) Here, H=1 cm, φ=0.01 are typical conditions for using detergents, and the cleaning power of the foam can be quantitatively expressed.

[0026] The above formula (2) is essential, but the values ​​obtained from this formula (2) are not intuitive, making it difficult to compare and evaluate detergent products. Therefore, using SDS (Sodium Dodecyl Sulfate), a surfactant widely used in research applications, as a reference value for the surfactant, and using the general detergent usage conditions of H = 1 cm, φ = 0.01, the width of foam F = 48 mm, and the foam thickness D = 1.0 mm, the detergency index α can be expressed by the following formula (3). α = (M * A -M0) / (M * ref -M0) · · · (3)

[0027] In this formula (3), M * A indicates the critical mass at the transition line of the foam of detergent A, and M * ref is the critical mass of the foam that serves as the reference (SDS). For example, if the average bubble size of SDS is 0.48 mm and the size dispersion is 10%, then the reference mass is 0.21 g. M0 is the mass at H = 1 cm and φ = 0.01 g. Since M0 changes depending on the foam height H and liquid fraction φ, the cleaning power changes depending on the conditions of actual use.

[0028] In formula (3), M0 is negligibly small, so by removing M0 from α, the maximum detergency index β can be expressed by the following formula (1). β=M * A / M * ref (1) According to equation (1), the cleaning power can be defined by a constant that is not dependent on the conditions of use of the detergent.

[0029] Using the cleaning power evaluation device 10 of this embodiment shown in FIG. 1, the M of foam of the detergent to be measured was * A By measuring the detergency index β and calculating it, it becomes possible to compare the detergency of any two detergents using this detergency index β.

[0030] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims, as well as in the scope and spirit of the invention. EXAMPLES

[0031] Figure 2 shows the drainage conditions for foam when TTAB (Tetradecyltrimethylammonium Bromide) was used as the surfactant and the bubble size was 0.32 mm. In Figure 2, the vertical axis is the liquid fraction φ and the horizontal axis is the foam height H, with an × indicating that drainage occurred from the foam and an ◯ indicating that drainage did not occur.

[0032] According to Figure 2, it was confirmed that the transition line for whether or not the water will be drained can be shown by the solid line Hφ (constant). In other words, the maximum osmotic pressure of the foam is determined by the type of surfactant, the bubble size, and the size distribution, and can be obtained by measuring the transition line.

[0033] Furthermore, Fig. 3 is a graph comparing the maximum osmotic pressure of the present embodiment with a conventionally known osmotic pressure measurement method for various surfactants and bubble sizes. It was confirmed that the conventional osmotic pressure measurement method, which has a large variation in measurement error and statistical error, generally coincides with the measurement of the present embodiment. Here, the osmotic pressure measurement method requires measurement of many parameters such as the surface tension of bubbles, bubble size, bubble size distribution, number of contact bubbles, and bubble contact area.

[0034] Next, we actually verified whether the foam would absorb oil under conditions below the transition line. The results are shown in the photographs of Figure 4. When H=2.7cm and φ=0.021 for the detergent in Figure 4(a), the boundary between the oil and water (shown by the dotted line) is within the foam, and it can be seen that the oil penetrates the foam and absorbs the oil. On the other hand, when H=4.2cm and φ=0.12 for the detergent in Figure 4(b), water is drained from the foam. In other words, Figure 4(a) is below the transition line in Figure 2, and Figure 4(b) is above the transition line in Figure 2.

[0035] From these results, for example, the detergency index β for a household detergent with an average bubble size of 0.10 mm is 0.42 / 0.21=2.0. This index means that it can absorb approximately 2.0 times the mass of oil as the reference SDS. [Explanation of symbols]

[0036] 10...Detergency evaluation device 11A,11B...Transparent substrate 12...Spacer 13...Holding means 14. Observation methods

Claims

1. A cleaning power evaluation device comprising: two transparent substrates that are transparent to visible light and that sandwich a sample liquid consisting of a surfactant aqueous solution containing foam; a spacer that separates the two transparent substrates at a predetermined distance; a clamping means that sandwiches the two transparent substrates opposite each other; and an observation means that observes the position of the interface between the foam and water in the sample liquid.

2. 2. The apparatus for evaluating detergency according to claim 1, wherein the observation means is an image pickup device.

3. 3. A method for evaluating detergency using the device for evaluating detergency according to claim 1 or 2, comprising the steps of: sandwiching a sample liquid, which is an object to be measured for detergency, between two of the transparent substrates and is an aqueous surfactant solution containing foam; a step of clamping the two transparent substrates with the clamping means and standing the transparent substrates upright so that the main surfaces of the transparent substrates are aligned in a vertical direction; a step of determining, after a predetermined time has elapsed, by the observation means, whether the water contained in the sample liquid remains within the foam region or reaches below the foam region; A method for evaluating detergency, comprising the steps of:

4. The limit mass, which is the mass of water that can be absorbed by the foam of the sample liquid, is defined as M at a transition line that represents the boundary between the water contained in the sample liquid remaining within the foam region and being absorbed by the foam, and the water reaching below the foam region and being drained from the foam. ＊ Ａ The limit mass of the water that can be absorbed by the foam of the reference liquid, which is a surfactant aqueous solution containing the foam to be compared, is M ＊ ｒｅｆ 4. The method for evaluating detergency according to claim 3, wherein a detergency index β indicating the cleaning ability of the sample liquid relative to the reference liquid is expressed by the following formula (1): β=M ＊ Ａ / M ＊ ｒｅｆ ・・・(1)

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