Method for evaluating the squeaky sensation of hair cleansers

Abstract

To objectively evaluate the creaky feeling of hair felt by hands during rinsing when washing hair with a hair detergent, and to efficiently carry out an evaluation test of the creaky feeling under uniform conditions. [Solution] A test hair cleanser is diluted 150 to 500 times to prepare an aqueous solution, and the dynamic friction coefficient of this aqueous solution is measured using a rotational rheometer. In the aqueous solution, a stationary surface such as a steel plate and a movable surface such as a steel ball are pressed together with a load of 2 to 4 N, and the stationary surface and the movable surface are slid together in this pressed state at a sliding speed of 0.1 to 0.5 cm / sec. The smaller the measured value, the less the squeakiness of the test hair cleanser is evaluated to be. This is the method for evaluating the squeakiness of a hair cleanser.

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating the squeakiness of hair cleansers, which is used to objectively evaluate the squeakiness felt by the hands when rinsing the hair cleanser from the hair with water, as one of the properties of the hair cleanser. [Background technology]

[0002] In general, hair cleansers suitable for washing hair, scalp, etc. are required to have not only cleansing properties for hair and scalp, but also properties that keep the hair surface smooth and reduce squeaking when rinsing with warm water, etc. Hair cleansers that have the property of reducing squeaking do not damage the hair surface during washing and are recognized as shampoos suitable for so-called damaged hair.

[0003] In order to improve or develop such hair cleansers and to efficiently produce them, it is necessary to objectively evaluate, under as uniform conditions as possible, the presence or absence and degree of squeaky feeling felt in the hands when washing hair for hair cleansers of various compositions that have been produced.

[0004] A known conventional method for evaluating the squeakiness of hair involves applying a detergent or hair treatment agent to hair that has been placed radially from the center of a rotating disk, and then washing the hair by lathering it while the rotating disk is rotating.The hair is then rinsed with water, and the rotating hair after rinsing is brought into sliding contact with a protrusion integrated with a torque detector, and the lubricity, which is related to the ease of running fingers through the hair and the squeakiness of the hair, is evaluated by measuring the torque (Patent Document 1).

[0005] There is also a known method of measuring the degree of damage to the hair surface by using a piezoelectric element to measure the creaking sensation felt by a person's hand when dealing with hair damaged by sunlight, dryness, etc. Specifically, a method is known in which the slight catching sensation felt by the fingertips rubbing the hair is measured as stick-slip vibrations using signals output from a piezoelectric element, and the number of times and magnitude of the vibrations are detected are analyzed (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-73584 [Patent Document 2] Patent No. 4671057 Summary of the Invention [Problem to be solved by the invention]

[0007] However, with the prior art described in Patent Document 1, it was not easy to evaluate a large number of prototype hair cleanser samples using uniform hair, and it was not easy to accurately and efficiently conduct a squeaky test. That is, in the evaluation method described in Patent Document 1, test hair of uniform quality is required for each sample number in order to evaluate squeaky properties under the same conditions, but test hair, which is available in limited quantities, is not easy to replace for each evaluation test. Incidentally, if the same hair is used repeatedly in evaluation tests, the hair gradually deteriorates with the number of tests, making the evaluation inaccurate.

[0008] Furthermore, in the evaluation by measuring stick-slip between hairs described in Patent Document 2, uniform hair is required depending on the number of measurements, making it difficult to efficiently carry out a large number of evaluation tests required for the development of hair cleansing agents under uniform conditions.

[0009] Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a method for evaluating hair squeakiness, which is necessary for the development of hair cleansers that have an inhibitory effect on hair squeakiness or for quality control thereof, that does not require uniform hair as a subject for each evaluation test, and that enables evaluation tests of a large number of hair cleansers to be carried out efficiently under uniform conditions. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a method for evaluating the squeaky properties of hair cleansers, in which a test hair cleanser is diluted 150 to 500 times to prepare an aqueous solution, and the dynamic friction coefficient of this aqueous solution is measured using a rotational rheometer (also known as a tribometer).The smaller this measured value, the less squeaky the test hair cleanser is evaluated to be.

[0011] The method for evaluating the squeaky properties of hair cleansers, which is configured by the above-mentioned specific means, measures the squeaky properties of a test hair cleanser against hair by measuring the dynamic friction coefficient of an aqueous solution of the hair cleanser at a specific dilution ratio using a rotational rheometer. Therefore, there is no need to use human hair as a test subject in the evaluation test of the hair cleanser, and the degree of the squeaky property suppression effect can be efficiently evaluated under uniform conditions in correlation with the dynamic friction coefficient.

[0012] Furthermore, in order to maximize the correlation between the measured value of the dynamic friction coefficient measured by the rotational rheometer and the squeaky feeling of hair felt by the hand during rinsing, the aqueous solution is preferably an aqueous solution diluted with water at a dilution ratio of 150 to 500 times or 200 to 400 times the dilution ratio of the hair cleanser to be tested.

[0013] For the same reason, the measurement conditions using the rotational rheometer are preferably such that a stationary surface and a movable surface, each consisting of a steel ball and a flat steel plate, are pressed together in the aqueous solution at a load of 2 to 4 N, more preferably a load of 3 N, and the stationary surface and the movable surface are slid together in this pressed state at a sliding speed of 0.1 to 0.5 cm / sec.

[0014] In addition, in order to further increase the correlation between the tactile sensation of hair that is felt by the hand during rinsing and the dynamic friction coefficient, the numerical range of the dynamic friction coefficient is preferably 0.05 to 0.2, more preferably 0.10 to 0.15, and even more preferably 0.12 to 0.14. [Effects of the Invention]

[0015] This invention provides a method for evaluating the squeaky properties of hair cleansers by measuring the dynamic friction coefficient of an aqueous solution of the test hair cleanser under appropriate conditions using a rotational rheometer. This method has the advantages of eliminating the need to attach test subject hair to the measuring device for each evaluation test and allowing multiple evaluation tests to be carried out efficiently under uniform conditions. [Brief explanation of the drawings]

[0016] [Figure 1] An explanatory diagram showing the sliding state of a steel ball and a steel plate rotating within the cell of a rotational rheometer. [Figure 2] Graph showing the relationship between the dynamic friction coefficient and sliding speed of the hair cleanser diluted 200 times in Example 1 [Figure 3] Graph showing the relationship between the coefficient of dynamic friction and sliding speed of the hair cleanser diluted 500 times in Example 2 [Figure 4] Chart showing the correlation between the dynamic friction coefficient and squeakiness score for hair cleansers [Figure 5] Graph showing the relationship between the coefficient of dynamic friction and sliding speed of the hair cleanser diluted 10 times in Comparative Example 1 [Figure 6] Graph showing the relationship between the coefficient of dynamic friction and sliding speed of the hair cleanser diluted 40 times in Comparative Example 2 [Figure 7] Graph showing the relationship between the dynamic friction coefficient and sliding speed of the hair cleanser diluted 100 times in Comparative Example 3 DETAILED DESCRIPTION OF THE INVENTION

[0017] As a method for evaluating the squeaky properties of a hair cleanser according to an embodiment of the present invention, an aqueous solution is prepared by diluting the test hair cleanser 150 to 500 times, and the dynamic friction coefficient is measured using a rotational rheometer to examine the correlation with the squeaky properties of hair.

[0018] The test hair cleanser can be prepared and used as a test product, but the quality can also be confirmed by comparing the squeaky sensation of the hair cleanser with commercially available shampoos and other products whose components vary depending on the manufacturer.

[0019] The dilution ratio when diluting the test hair cleanser with water or warm water is determined based on the diluted concentration of the hair cleanser during rinsing, and is set to 150 to 500 parts by mass per part by mass of the hair cleanser, preferably to prepare an aqueous solution diluted 200 to 400 times.

[0020] The dilution ratios above were determined assuming the following typical usage conditions for hair cleansers: First, the product is diluted about 5 to 10 times with cold or warm water, and then stirred between the hands and hair to create foam, producing a large amount of coacervate, which reduces the squeaky feeling during rinsing.

[0021] Next, the surface tension and surfactant effect of such foam creates foam that adsorbs dirt from the hair and scalp, and the hair is rinsed with water or warm water to wash it off. At this time, the coacervate and hair cleanser are washed away by successive dilutions with cold or hot water.

[0022] In order to measure the "squeaky feeling" felt when rinsing, it is thought that the appropriate conditions are to prepare a hair cleanser at a specified dilution ratio and measure the dynamic friction coefficient using a rotational rheometer.

[0023] Such dilution ratios are determined by conducting tests using a variety of sliding speeds (0.01 to 100.0 cm / sec) as measurement conditions for the dynamic friction coefficient measured using a rotational rheometer, as described below. The correlation between the results and the "squeakiness score" obtained from the sensory evaluation is calculated as the evaluation index R of the correlation analysis (linear regression model). 2 It is preferable to determine the correlation coefficient so that a strong correlation can be confirmed based on the above.

[0024] The measurement conditions for the rotational rheometer are preferably such that a stationary surface such as a steel ball and a flat steel plate and a movable surface are pressed together in the aqueous solution with a load of 2 to 4 N, with a load of 3 N as a guide, so as to correspond to the pressure and sliding state applied to hair with the fingertips of a hand during rinsing, and the stationary surface such as a flat steel plate and the movable surface such as a steel ball are slid together in this pressed state at a sliding speed of 0.1 to 0.5 cm / sec.

[0025] In particular, when the dilution ratio is 200 times, if the sliding speed is set to 0.25 cm / sec, the above-mentioned evaluation index R 2 A very strong correlation of 0.7932 (approximately 0.8) was observed.

[0026] The materials, surface conditions such as surface roughness, and configurations of the stationary surface and the movable surface are not particularly limited, and any known material that allows stable measurement of the dynamic friction coefficient can be selected. For example, one or both of the stationary surface and the movable surface can be made of a metal such as stainless steel, or a ceramic such as glass or silicon.

[0027] The arrangement of the stationary surface and the movable surface and the operation in the movable state are not particularly limited, and any device can be used as long as the two surfaces are pressed together under a predetermined load and move relative to each other at an arbitrary speed, causing the contact surfaces to slide in a pressed state, and these can be used as a device called a rheometer.

[0028] For example, a flat plate is placed on the lower side as the stationary surface of the rheometer, and a sphere (for example, a small sphere with a diameter of 1 / 2 inch (12.7 mm), or about 10 to 30 mm) is placed on the upper side. The surface of the sphere is used as the movable surface and pressed against the flat plate with an appropriate pressure, while being rotated at a required rotational speed by an electric motor or the like, thereby enabling the coefficient of dynamic friction in a sliding state at a specified speed and pressure to be measured.

[0029] As shown in Figure 1, the measurement conditions using a commercially available rotational rheometer are as follows: a smooth, flat stainless steel plate 2 is pressed against the bottom of a smooth-surfaced stainless steel ball 1 attached to the tip of a rotating shaft from three sides at a specified pressure (3 N); the pressed surfaces are immersed in aqueous solution D, in which the hair cleanser to be tested has been diluted, contained in cell 3; and the support shaft for steel ball 1 is rotated, causing the steel ball 1 and steel plate 2 to slide against each other at a sliding speed of 0.1 to 0.5 cm / sec, and the dynamic friction coefficient at this time is measured.

[0030] By using such a rotational rheometer to measure the dynamic friction coefficient of a diluted aqueous solution of a hair cleanser at a predetermined, relatively slow speed range, the squeaky feel specific to a particular hair cleanser can be estimated from the value of the dynamic friction coefficient, which is found to have a very strong correlation with the "squeaky feeling" of hair, as will be apparent from the Examples and Comparative Examples described below. [Example]

[0031] [Examples 1 and 2] Five commercially available hair cleansers (shampoos) from different manufacturers (hereinafter abbreviated as SHP.1 to SHP.5) were each diluted 200 times (Example 1) or 500 times (Example 2) with purified water, and the prepared aqueous solutions were placed in a cell along with the test subjects. The dynamic friction coefficients (simply referred to as friction coefficients in Figures 2-7) were measured using a rotational rheometer (Anton Paar: MCR302).

[0032] The measurement conditions were as follows: a tribology system (a cell in the form of a ball on three plates) was set up with a steel ball 1 integrally attached to the tip of a rotating shaft as shown in Figure 1; that is, a smooth-surfaced steel ball 1 (diameter 12.7 mm) was rotated, and smooth, flat steel plates 2 were pressed against its bottom from three sides with a force of 3 N; the dynamic friction coefficient at 37°C was continuously measured at sliding speeds ranging from 0.01 to 100 cm / sec. The results are shown in Figures 2 and 3.

[0033] In addition, a sensory evaluation of "creaky feeling" using SHP.1 to 5 was conducted by 10 subjects using Nakaya's modified Scheffe's paired comparison method as follows. In other words, the original method was "Scheffe's paired comparison method," in which 10 subjects were asked to evaluate a pair of any two samples from SHP.1 to 5 using a paired comparison method, and "Nakaya's modified method" was used, in which one evaluator compared all paired combinations once, regardless of the order of comparison.

[0034] The evaluation criteria were based on which of the pair of samples felt the creakier, which was taken as the strength of the creakiness. This was evaluated on a 7-point scale using integer values ​​from -3 to +3 (the higher the value, the less creakier the evaluation). The results for all combinations were added together to determine the creakiness score for each sample. The results were SHP.1: 0.04, SHP.2: -0.16, SHP.3: 0.04, SHP.4: 0.38, and SHP.5: 0.18.

[0035] For Examples 1 and 2, the correlation coefficient between the "squeaky feeling" score of each hair cleanser and the dynamic friction coefficient at the above-mentioned specified sliding speed was calculated by correlation analysis (Pearson's product-moment correlation coefficient), and the values ​​of this correlation coefficient are shown in Table 1 below.

[0036] [Table 1]

[0037] For Example 1, the relationship between the squeaky feeling score and the dynamic friction coefficient for the five types of hair washes (SHP.1 to SHP.5) at a sliding speed of 0.25 cm / sec and a dilution ratio of 200, which are the cases where the strongest correlation with the "squeaky feeling" score can be confirmed, was plotted. The results are shown in Figure 4.

[0038] As shown in the figure, the results of the regression analysis showed that R 2 The coefficient of determination was obtained as =0.7932, which is approximately 0.8, confirming a high correlation.

[0039] From this, it was found that for the test hair cleansers (SHP.1 to 5) diluted 200 times, when the dynamic friction coefficient was 0.12 to 0.14 when a steel ball was pressed against a flat steel plate with a load of 3N measured by a rheometer, there was a very high correlation with the score for "squeakiness" in the sensory test.

[0040] Therefore, the smaller the measured value of the dynamic friction coefficient under the measurement conditions, the less squeaky the hair cleanser is evaluated to be. In terms of SHP. numbers, the order was 4, 5, (1 or 3), and 2, with the former being evaluated as the less squeaky the hair cleanser is evaluated to be.

[0041] [Comparative Examples 1 to 3] In the same manner as in Example 1, except that aqueous solutions of SHP.1 to SHP.5 were prepared by diluting them 10 times (Comparative Example 1), 40 times (Comparative Example 2), or 100 times (Comparative Example 3) with purified water, the dynamic friction coefficients were measured at sliding speeds of 0.01 to 100 cm / sec using a rotational rheometer (Anton Paar: MCR302). The results are shown in Figure 5 (Comparative Example 1), Figure 6 (Comparative Example 2), and Figure 7 (Comparative Example 3).

[0042] For Comparative Examples 1 to 3, as in Examples 1 and 2, the correlation between the "squeaky feeling" score for each hair cleanser and the dynamic friction coefficient at the sliding speed within the above-mentioned specified range was analyzed, and the calculated Pearson's product-moment correlation coefficient values ​​are also shown in Table 1.

[0043] As is clear from the product-moment correlation coefficient values ​​shown in Table 1, in Comparative Examples 1 to 3, the value was -0.60 even under the conditions where the strongest correlation was observed, and a strong correlation like that observed in Examples 1 and 2 could not be confirmed. Therefore, in Comparative Examples 1 to 3, it was difficult to precisely compare the squeaky properties of each hair cleanser using the dynamic friction coefficient. [Explanation of symbols]

[0044] 1 steel ball 2 steel plate 3 cells D aqueous solution

Claims

1. A method for evaluating the squeakiness of a hair cleanser, comprising: preparing an aqueous solution in which a test hair cleanser is diluted 150 to 500 times; measuring the dynamic friction coefficient of this aqueous solution using a rotational rheometer; measuring the conditions for the rotational rheometer by pressing the stationary surface of a flat plate and the movable surface of a sphere in the aqueous solution with a load of 2 to 4 N; and sliding the stationary surface of the flat plate and the movable surface of the sphere in this pressed state at a sliding speed of 0.1 to 0.5 cm / sec; and evaluating the test hair cleanser such that the smaller the measured dynamic friction coefficient, the less squeakiness it has.

2. 2. The method for evaluating the squeaky properties of a hair cleanser according to claim 1, wherein the aqueous solution is an aqueous solution obtained by diluting the test hair cleanser 200 to 400 times.

3. The method for evaluating the squeaky properties of a hair cleanser according to claim 1 or 2, wherein the measured value of the dynamic friction coefficient is in the range of 0.05 to 0.2.

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