JP6742005B2 - Evaluation method of "softness" in powder cosmetics - Google Patents

Description

TECHNICAL FIELD The present invention relates to a powder cosmetic and a method for objectively evaluating “softness” which is one factor of the feel characteristics of powder raw materials for cosmetics.

Skin care and make-up cosmetics are generally used by directly applying to the skin from the container by the user. Since cosmetics are used every day, not only the functionality but also the feeling of use (feeling) are extremely important factors in the cosmetic effect.

The methods of evaluating the feel characteristics of cosmetics and raw materials are roughly classified into sensory evaluation and physical property evaluation. Sensory evaluation has the merit that it is an evaluation that is close to actual use, but it is a subjective evaluation, so it is greatly affected by the skin condition and psychological condition in addition to individual differences due to the evaluator's sensitivity. .. Therefore, there has been a strong demand for a technique such as an evaluation method and a display method using an objective index that uses a physical device without relying only on a sensory test.

In emulsified cosmetics such as creams and oil-based raw materials, tactile characteristics such as “spread”, “smoothness”, and “moist feeling” are generally evaluated. On the other hand, in powder cosmetics such as powder foundations and powder raw materials for cosmetics, in addition to "spreading", "smoothness" and "moist feeling", "softness" which is a touch characteristic peculiar to the powder is Desired.

Conventionally, an evaluation method based on an objective index by surface friction measurement has been studied as one of the methods for evaluating the feel characteristics of cosmetics and raw materials. For example, tactile characteristics obtained from sensory evaluations such as “spread”, “smoothness”, and “moist feeling”, average friction coefficient (MIU) obtained from surface friction measurement, and/or coefficient of variation (MMD) of average friction coefficient. The correlation with such friction characteristics has been examined (see Patent Document 1, Non-Patent Documents 1 and 2). On the other hand, in powder cosmetics, an example of objectively evaluating the "smoothness" of solid powder cosmetics using a rotary rheometer has been reported (Patent Document 2). However, there is no example in which the "softness" of powder cosmetics and powder raw materials for cosmetics is evaluated.

It is generally known that resins such as silicone elastomers having rubber elasticity, nylon, and polyurethane have high “softness” as a touch property. Since the "softness" of these powders is considered to correlate with the durometer hardness described in JIS K6253, it is expected that the lower the hardness of the raw material, the softer the powder. However, in the actual development site, the elasticity of the raw material alone does not always match the softness of the sensory body.

On the other hand, powder cosmetics such as powder foundations contain inorganic plate-like powders such as mica, talc and sericite. These inorganic plate-like powders are indispensable components for powder cosmetics because they have good spreadability peculiar to the plate-like powders and adherence to the skin. However, many of these inorganic plate-like powders have low "softness" as a touch property due to their hard crystal structure.

It has been reported that an inorganic plate-like powder is given "softness" by surface-treating a resin having rubber elasticity (see Patent Document 3).

In addition, an example in which “softness” is imparted by similarly performing surface treatment has been reported (see Patent Documents 4 and 5). As described above, it is known that "softness" can be imparted also to the inorganic plate-like powder having no rubber elasticity, depending on the type and blending amount of the surface treatment agent.

In the field of cosmetics, powder cosmetics and powder raw materials for cosmetics, which are generally imparted with "softness", have a very high market value because of their favorable feeling of use.

Based on these backgrounds, an objective index of "softness" using a physical device is also required for powder cosmetics and powder raw materials for cosmetics.

JP, 2003-24282, A Japanese Patent No. 4322177 Japanese Patent No. 3963635 Japanese Patent No. 4176054 Japanese Patent No. 4176055

J. Soc. Cosmet. Chem. Japan. Vol. 32, No. 1,59-64 (1998) Performance evaluation of oiliness agent using friction tester 28th IFSCC Conference, 2014 Objective evaluation system of the cleaning oil

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for objectively evaluating the "softness" of a powder cosmetic and a powder raw material for cosmetic using a physical device. And

Under such circumstances, the inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, between the stress relaxation rate obtained from the measurement of the specific powder layer shear force and the "softness" obtained from the sensory evaluation. It was found that there is a high correlation with the above, and the present invention has been completed.

That is, in the present invention, in the powder cosmetics and the powder raw material for cosmetics, the "softness" which is one factor of the feel characteristics is measured by the powder layer shear force measurement by the specific method (initial vertical stress σ, and after stress relaxation). The method of evaluating the stress relaxation rate obtained from (the method of obtaining the stress attenuation rate from the normal stress σ′) of FIG.

INDUSTRIAL APPLICABILITY The present invention objectively evaluates not only the resin having rubber elasticity but also all powder raw materials including inorganic plate-like powder, and the “softness” of powder cosmetics prepared by variously mixing them. Therefore, the stress relaxation rate obtained by measuring the powder layer shear force by a specific method is associated as a physical property index.

Outline of powder layer shear force measuring device

Hereinafter, the powder cosmetic of the present invention and a method of evaluating the feeling of use of the powder raw material for cosmetic will be described based on its preferred embodiments. According to the present invention, it is possible to objectively evaluate "softness" which is one of the feelings of use when the powder cosmetics and the powder raw material for cosmetics are applied to the skin. Here, "softness" with respect to the powder cosmetics and the powder raw material for cosmetics means a feeling such as a feeling of thickness of the powder and a good feeling on the skin.

The evaluation method of the "softness" of the powder cosmetics and the powder raw material for cosmetics of the present invention is carried out by measuring the powder layer shear force using the powder to be evaluated, and the initial normal stress σ and the stress relaxation. The "softness" of the powder cosmetics and the powder raw material for cosmetics is evaluated by the stress relaxation rate (100-(σ'/σ)×100) obtained from the subsequent vertical stress σ'.

In addition, the powder layer shear force measurement test refers to the vertical stress and shear stress when the powder layer is formed by compacting the powder in the vertical direction and then shearing in the horizontal direction at a constant propulsion speed. This is a measurement method for measuring and evaluating the frictional properties and adhesion properties of powder.

In the embodiment of the present invention, the stress relaxation rate obtained from the measurement of powder layer shear force according to the following procedure is evaluated as a physical property index.
(1) Powder is filled inside a cylindrical cell (upper fixed cell, lower movable cell), the upper punch is gently placed, and then vertical stress is gradually applied at a constant speed.
(2) After reaching the specified value σ of the vertical stress, the load of the vertical stress is stopped and the relaxation time of the powder layer is set in the constant volume state.
(3) The value σ′ of the vertical stress at the time when sufficient stress relaxation occurs is read, and the stress relaxation rate is obtained as the attenuation rate of the vertical stress from the specified value.
(4) The obtained stress relaxation rates are compared with each other, and the larger the value, the higher the "softness".

In the operation of applying the cosmetics with the fingertip, delicate force is applied to the fingertip, so that the vertical stress on the fingertip is also low. Therefore, in order to perform the measurement accurately, in the evaluation of the feeling of use of the powder cosmetics and the powder raw material for the cosmetics, the vertical stress to be applied was not the indentation load in which the powder inside the cell was actually pushed, but the pushing force was pushed in. Therefore, it is preferable to control the bottom load, which is the net load applied to the powder, with the load cell. If a load such as the load cell for detecting the bottom load shown in FIG. 1 is used to detect the load, it is possible to eliminate the influence of pressure loss due to friction on the cell wall surface and to specify the actual load applied to the powder layer.

In the evaluation of the feeling of use of the powder cosmetics and the powder raw material for cosmetics, the specified value of the vertical stress applied in step (1) is not particularly limited, but is preferably in the range of 20 to 125 kPa. When the vertical stress is 20 kPa or less, the formation of the powder layer may not be sufficient, and when the vertical stress is 125 kPa or more, it is much higher than the pressure of the fingertip when a person actually sensory-evaluates the powder cosmetics and the powder raw material for cosmetics. Since the measurement is performed under high pressure, the correlation may be low.

In the evaluation of the feeling of use of the powdery cosmetics and the powdery raw material for cosmetics, the relaxation time provided in step (2) is not particularly limited, but is preferably in the range of 50 to 100 seconds. If the relaxation time is 50 seconds or less, stress relaxation may not be sufficient, and accurate measurement may not be possible. When the relaxation time is 100 seconds or less, sufficient stress relaxation can be efficiently obtained.

In the evaluation of the feeling of use of the powder cosmetics and the powder raw material for the cosmetics, the inner diameter of the cylindrical cells (the cylindrical upper fixed cell and the cylindrical lower movable cell) is not particularly limited, but is in the range of 3 to 43 mm. Is preferred. If the inner diameter of the columnar cell is less than 3 mm, it may be difficult to obtain a difference in stress relaxation rate between samples, and if it is greater than 43 mm, the amount of sample used increases and the difference in stress relaxation rate between samples is further increased. Cannot be expected to be effective.

The stress relaxation rate can be measured using a powder layer shear force measuring device as shown in FIG. This device is characterized in that the vertical stress is detected by the bottom load as described above. In addition to this device, for example, a commercially available powder layer shear force measuring device NS-S500 (manufactured by Nanoseed) can be used for measurement. The room temperature and relative humidity when the powder layer shearing force measurement is performed are preferably room temperature 10 to 35° C. and relative humidity 30 to 65% in consideration of the environment when the cosmetic is used.

Hereinafter, the present invention will be described in more detail with reference to Examples. These do not limit the invention of the present application.

(Example 1)
[Evaluation of the physical properties]
With respect to the powder materials A to C for cosmetics shown in Table 1, the powder layer shearing force was measured as described below to obtain the stress relaxation rate. All of A to C are sericite, but the surface treatment states are different as follows. A is an untreated product that has not been surface-treated, B is a silicone-treated product that is generally treated for the purpose of improving slipperiness (treatment amount 3% by weight), and C is a silicone main chain modified with an amino group. Thus, it is an amino-modified silicone-treated product (treatment amount 5% by weight) imparted with a moist feeling and softness.
Measuring device: Powder layer shear force measuring device (Nano Seeds prototype)
Measurement conditions: room temperature 25°C, relative humidity 50%
Cylindrical upper fixed cell (inner diameter 43mm)
Cylindrical lower movable cell (depth 5 mm)
Powder layer shear band thickness 0.2 mm
Vertical speed 200 μm/sec
Data acquisition speed 100msec
Initial vertical stress of 60 kPa loaded in step (1)
Relaxation time 100 seconds [Sensory evaluation]
Regarding the “softness” of the powdery raw materials A to C shown in Table 1, a usage test was conducted by 8 specialized panels, and each panel member gave an absolute rating on the following 5 scales and gave a rating, and for each sample The average value was calculated as a sensory evaluation value from the total score of all panel members.
1: Very low 2: Low 3: Normal 4: High 5: Very high

(Table 1)

In Table 1 above, a high correlation was observed between the stress relaxation rate obtained from the powder layer shear force measurement and the "softness" obtained by the sensory evaluation.

(Example 2)
[Evaluation of the physical properties]
With respect to the powder cosmetics models D and E shown in Table 2, the powder layer shear force measurement was performed as described below to obtain the stress relaxation rate. Each of D and E is a model face powder prepared by mixing untreated sericite, nylon powder, and isotridecyl isononanoate, but the blending amount of nylon powder, which is generally considered to be soft, is different.
Measuring device: Powder layer shear force measuring device (Nano Seeds prototype)
Measurement conditions: room temperature 25°C, relative humidity 50%
Cylindrical upper fixed cell (inner diameter 43mm)
Cylindrical lower movable cell (depth 5 mm)
Powder layer shear band thickness 0.2 mm
Vertical speed 200 μm/sec
Data acquisition speed 100msec
Initial vertical stress of 60 kPa loaded in step (1)
Relaxation time 100 seconds [Sensory evaluation]
With respect to the “softness” of the powder cosmetics models D and E shown in Table 2, a usage test was conducted by 5 expert panels in the same manner as above, and a sensory evaluation value was calculated.

(Table 2)

Also in Table 2 above, the sensory evaluation result that the powder cosmetics model E containing a large amount of nylon powder had higher “softness” was obtained, and the stress relaxation rate was correspondingly higher. Therefore, a correlation was observed between the stress relaxation rate and "softness".

The evaluation method of the present invention evaluates "softness", which is one factor of the feel characteristics in powder cosmetics and powder raw materials for cosmetics, by associating the stress relaxation rate obtained from powder layer shear force measurement as a physical property index. It can be done. The evaluation method of the present invention can be used for efficient and effective development of powder cosmetics, provision of suitable cosmetics, and advice thereof.

Claims (1)

Powder cosmetic powder, or in powder cosmetic powder material, which is a factor feel characteristics "softness", as a physical property index stress relaxation rate obtained from the powder layer shear force measured in accordance with the following procedure How to evaluate. The specified value of the vertical stress applied in the following procedure (1) is 20<σ<125 kPa.
(1) Powder is filled inside a cylindrical cell (upper fixed cell, lower movable cell), the upper punch is gently placed, and then vertical stress is gradually applied at a constant speed.
(2) After reaching the specified value σ of the vertical stress, the load of the vertical stress is stopped and the relaxation time of the powder layer is set in the constant volume state.
(3) The value σ′ of the vertical stress at the time when sufficient stress relaxation occurs is read, and the stress relaxation rate is obtained as the attenuation rate of the vertical stress from the specified value.
(4) The obtained stress relaxation rates are compared with each other, and the larger the value, the higher the "softness".