Mild anti-dandruff shampoo composition as well as preparation method and application thereof

Abstract

The invention discloses a mild anti-dandruff shampoo composition as well as a preparation method and application thereof. The shampoo composition comprises selenium disulfide, salicylic acid and a composite suspension system consisting of specific high-yield-value carbomer and pre-dispersed hydrogenated castor oil. By means of the composite suspension system, long-term stable suspension of selenium disulfide is successfully achieved under the pH value of 5.5-6.0, and the limitation that low pH value (4.0-4.5) must be adopted for maintaining suspension in the prior art is broken through. In a word, the shampoo composition disclosed by the invention fundamentally solves the problems of dry washing feeling, large combing resistance and hair damage caused by the dry washing feeling and the large combing resistance while ensuring the anti-dandruff effect, and has excellent stability and excellent use experience.

Description

Technical Field

[0001] This invention relates to the field of daily chemical products technology, specifically to a mild anti-dandruff shampoo composition, its preparation method, and its application. Background Technology

[0002] Selenium disulfide is a recognized highly effective anti-dandruff, anti-seborrheic, and antifungal ingredient, while salicylic acid has excellent keratolytic and pore-cleansing abilities. The combination of the two synergistically enhances the anti-dandruff effect; therefore, shampoos containing selenium disulfide and salicylic acid are very common in the market. Current technologies typically employ two approaches to inhibit selenium disulfide precipitation: one is to forcibly adjust the system's pH to a low range of 4.0-4.5, utilizing the physical barrier effect of anionic micelles at this pH; the other is to use a single high-molecular-weight polymer (such as carbomer) or trihydroxystearin thickener.

[0003] However, existing technologies have the following drawbacks: the healthy isoelectric point of the scalp and hair is about pH 5.5. Long-term use of low-pH products will over-open the hair cuticles, leading to moisture loss, dry hair, and a severe rough feeling during rinsing, which greatly increases combing resistance. This is one of the main reasons for mechanical hair loss during shampooing. Carbomer alone has a significantly reduced viscosity and yield value at pH < 5.5. While trihydroxystearin can provide a rigid network at low pH, it has a high melting point, high dispersion energy consumption, and is prone to causing a sticky residue when used alone. Its long-term suspension stability is also not ideal.

[0004] In summary, existing technologies struggle to simultaneously achieve long-term stable suspension of selenium disulfide and a smooth, comfortable washing experience at a mild pH (5.5-6.0) that aligns with the physiological environment of the scalp.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One of the objectives of this invention is to provide a mild anti-dandruff shampoo composition that achieves long-term stable suspension of selenium disulfide at pH 5.5-6.0. This shampoo composition combines excellent stability with a superior user experience, ensuring anti-dandruff efficacy while fundamentally solving the problems of dryness, high combing resistance, and hair damage caused by low pH.

[0007] The second objective of this invention is to provide a method for preparing a mild anti-dandruff shampoo composition, which is simple in process, has a high success rate, and is easy to industrialize.

[0008] The third objective of this invention is to provide an application of a mild anti-dandruff shampoo composition that is beneficial to fully utilize the biological efficacy of the components while improving the user experience.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In the first aspect, a mild anti-dandruff shampoo composition is mainly composed of an anti-dandruff active system, a complex suspension system, a surfactant system, and a conditioning system; The anti-dandruff active system contains 0.6%-1% by mass of selenium disulfide and 0.1%-0.3% by mass of salicylic acid or salicylate. The composite suspension system is composed of high yield value carbomers and their derivatives, and hydrogenated castor oil and its derivative trihydroxystearin. The surfactant system comprises at least one of anionic surfactants, nonionic surfactants, and amphoteric surfactants. The conditioning system comprises cationic polymers and emulsified silicone oils of different particle sizes; The pH value of the shampoo composition is 5.5-6.0; The selenium disulfide has a particle size D90 of no more than 20 micrometers and is stably suspended in the composite suspension system.

[0010] Furthermore, the high yield value carbomer is either high yield value Carbopol® 980 or Ultraz 21 / ETD2020; The hydrogenated castor oil is in a pre-gel form formed by pre-dispersing it in a surfactant.

[0011] Furthermore, the mass ratio of high yield value carbomer and hydrogenated castor oil in the composite suspension system is 1:0.5-1:3.

[0012] Furthermore, the mass ratio of selenium disulfide, high yield value carbomer, and hydrogenated castor oil is (0.3-1):(0.1-0.5):(0.2-1).

[0013] Furthermore, the cationic polymer in the conditioning system includes at least one of cationic guar gum, cationic quaternary ammonium salt, and cationic cassia gum; The conditioning system contains emulsified silicone oils with a particle size ≤1μm and large particle size of 20μm, wherein the mass ratio of the small particle size emulsified silicone oil to the large particle size emulsified silicone oil is 1:1 to 3:1.

[0014] Furthermore, the mass ratio of selenium disulfide to salicylic acid in the shampoo composition is 1:0.1-0.5.

[0015] Furthermore, the shampoo composition also contains 0.1%-0.5% by mass of colloidal sulfur. The salicylic acid and colloidal sulfur work together through adsorption dispersion and electrostatic stabilization to help stabilize the selenium disulfide particles in the composite suspension system.

[0016] Secondly, a method for preparing a shampoo composition according to any one of the above claims includes the following steps: Selenium disulfide was added to a composite suspension system consisting of high yield value carbomer and hydrogenated castor oil to obtain the shampoo composition. The preparation method further includes the step of grinding selenium disulfide into a pre-prepared slurry mixture.

[0017] Furthermore, the preparation method includes the following steps: S1: Disperse high yield value carbomer in deionized water, stir evenly, and set aside to obtain an aqueous gel matrix; S2: Hydrogenated castor oil and a portion of surfactant are heated to 80℃-85℃ to melt, and then cooled after high-speed shearing to form a gel-like substance, thus obtaining a pregel. S3: Mix the surfactant, cationic polymer and other water-soluble components evenly, and add the aqueous gel base material obtained in step S1; S4: Salicylic acid, colloidal sulfur, and ultrafine pulverized selenium disulfide (D90≤20μm) slurry are slowly added to the system and continuously homogenized; S5: Add emulsified silicone oil, preservative, fragrance and the pregel obtained in step S2, adjust the pH of the system to 5.5-6.0 with a pH adjuster, homogenize and defoam to obtain the shampoo composition.

[0018] Thirdly, the use of any of the above-mentioned shampoo compositions in personal care products.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: The mild anti-dandruff shampoo composition provided by this invention achieves long-term stable suspension of selenium disulfide at pH 5.5-6.0, breaking through the limitation of traditional technology that requires a low pH (4.0-4.5) to maintain suspension. With the synergistic effect of each component, this shampoo composition has both excellent stability (slight fading after 4 months at 45°C, no particle aggregation, and no obvious deposition) and a superior user experience. While ensuring the anti-dandruff effect, it fundamentally solves the problems of dryness, high combing resistance, and hair damage caused by low pH.

[0020] The preparation method of the mild anti-dandruff shampoo composition provided by the present invention is simple, has a high success rate, and is easy to industrialize.

[0021] The application of the mild anti-dandruff shampoo composition provided by this invention is beneficial to fully exert the biological efficacy of the components, while improving the user experience. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] According to a first aspect of the present invention, a mild anti-dandruff shampoo composition is provided, which mainly comprises an anti-dandruff active system, a complex suspension system, a surfactant system and a conditioning system; The anti-dandruff active system contains 0.6%-1% by mass of selenium disulfide and 0.1%-0.3% by mass of salicylic acid or salicylate. The composite suspension system is composed of high yield value carbomers and their derivatives, and hydrogenated castor oil and its derivative trihydroxystearin; Surfactant systems include at least one of anionic surfactants, nonionic surfactants, and amphoteric surfactants; The conditioning system contains cationic polymers and emulsified silicone oils of different particle sizes; The pH value of the shampoo composition is 5.5-6.0; Selenium disulfide has a particle size D90 of no more than 20 micrometers and is stably suspended in a composite suspension system.

[0024] The suspension mechanism of the suspension system is as follows: After carbomer powder is dispersed in water, an alkaline agent (such as triethanolamine or NaOH) needs to be added for neutralization. The carboxyl groups (-COOH) on the carbomer molecular chain are ionized into negatively charged carboxylate groups (-COO). -The molecular chains extend due to electrostatic repulsion and absorb a large amount of water to swell. The extended long molecular chains intertwine with each other and combine with surrounding water molecules through hydrogen bonds to form a huge, continuous three-dimensional hydrated gel network structure that fills the entire system, greatly increasing the viscosity of the product. The three-dimensional gel network has a high yield value, which means that when the system is at rest, its network structure is strong enough to encapsulate and fix the internal solid particles (such as selenium disulfide), forming a "cage" effect that prevents them from sinking due to gravity. The carbomer molecular chains are negatively charged, which makes the entire gel network negatively charged as well. Through the repulsion of like charges, it can prevent the dispersed particles from re-aggregating and growing larger, further maintaining the stability of the system. Hydrogenated castor oil is a waxy solid obtained by hydrogenating castor oil. Its core suspension component is trihydroxystearin, which has a "crystalline network structure". It needs to be added to the surfactant system at a certain temperature (usually 70-75°C above its melting point) and melted and dispersed by high-speed shearing. During the subsequent cooling process, trihydroxystearin molecules precipitate out of the system, forming extremely small, fibrous or needle-like crystals. These tiny crystals interlock to form a rigid, bird's nest-like crystalline network that runs through the entire liquid system. Solid particles (such as selenium disulfide) are physically "stuck" in the gaps of this microcrystalline network, thus being effectively supported and fixed, unable to move or settle freely. The structural strength of the crystalline network provides most of the yield value required for suspension.

[0025] In the suspension system, carbomer and hydrogenated castor oil complement each other mechanistically. Carbomer provides electrostatic stability and base viscosity, while hydrogenated castor oil provides a strong rigid support network, making the suspension system extremely stable over a wider temperature and pH range with a very high yield value. Therefore, selenium disulfide suspended in a suspension system composed of carbomer and hydrogenated castor oil ensures stable suspension while allowing the shampoo pH to be raised to a milder range. At higher pH values ​​(5.5-6.0), selenium disulfide can remain stably suspended, preventing discoloration and precipitation, fundamentally improving the washing experience and hair care effects.

[0026] The shampoo composition has a pH value between 5.5 and 6.0, which is closer to the isoelectric point of hair and scalp. This helps to significantly reduce friction and astringency during rinsing, further enhancing the comfort of washing and reducing hair loss caused by mechanical pulling. It also has excellent effects in removing dandruff, controlling oil, and relieving itching.

[0027] The shampoo's pH value has been increased from 4.0-4.5 to 5.5-6.0, which is closer to the healthy pH environment of the scalp and hair. This greatly reduces the potential irritation to the scalp caused by low pH and the excessive softening of the hair cuticle, thus improving its gentleness. At the same time, because the pH is close to the isoelectric point of the hair, the electrostatic repulsion between hairs is reduced, and the hair cuticles are better closed. Therefore, the roughness during rinsing is greatly reduced, the hair is easier to comb, and feels smooth, improving the washing experience. In addition, the reduced combing resistance also directly reduces hair breakage and hair loss caused by mechanical pulling when the hair is wet, enhancing the user experience.

[0028] In summary, the shampoo composition of this invention achieves long-term stable suspension of selenium disulfide at pH 5.5-6.0, breaking through the limitations of traditional technologies that require low pH (4.0-4.5) to maintain suspension. With the synergistic effect of each component, it has both excellent stability (slight fading after 4 months at 45℃, no particle aggregation, and no obvious deposition) and a superior user experience. While ensuring dandruff removal efficacy, it fundamentally solves the problems of dryness, high combing resistance, and hair damage caused by low pH.

[0029] In a preferred embodiment, the high-yield-value carbomer can be high-yield-value Carbopol® 980 or Ultraz 21 / ETD 2020; the hydrogenated castor oil can be in a pre-gel form formed by pre-dispersing it in a surfactant.

[0030] In a preferred embodiment, the mass ratio of high yield value carbomer to hydrogenated castor oil in the composite suspension system can be 1:0.5-1:3, which is more conducive to giving full play to the synergistic suspension effect and making high-density selenium disulfide stably suspended at a higher pH value (5.5-6.0).

[0031] In this invention, the mass ratio of selenium disulfide, high yield value carbomer, and hydrogenated castor oil in the shampoo composition can be (0.3-1):(0.1-0.5):(0.2-1), which is more conducive to further stabilizing the high-density selenium disulfide suspension at a higher pH value (5.5-6.0).

[0032] In a preferred embodiment, the cationic polymer in the conditioning system includes, but is not limited to, at least one of cationic guar gum, cationic quaternary ammonium salt, and cationic cassia gum.

[0033] In this invention, the emulsified silicone oil in the conditioning system can be a small-particle-size emulsified silicone oil with a particle size ≤1μm and a large-particle-size emulsified silicone oil with a particle size 20μm; at the same time, the mass ratio of the small-particle-size emulsified silicone oil to the large-particle-size emulsified silicone oil can be 1:1 to 3:1.

[0034] In a preferred embodiment, the mass ratio of selenium disulfide and salicylic acid in the shampoo composition can be 1:0.1-0.5, which is more conducive to synergistic effects and effectively exerts the functions of dandruff removal and oil control.

[0035] In a preferred embodiment, the shampoo composition may further contain 0.1%-0.5% by mass of colloidal sulfur. Salicylic acid and colloidal sulfur work together to stabilize selenium disulfide particles in the composite suspension system through adsorption dispersion and electrostatic stabilization.

[0036] According to a second aspect of the present invention, a method for preparing the shampoo composition according to any one of the above claims is provided, comprising the following steps: Selenium disulfide was added to a composite suspension system consisting of high yield value carbomer and hydrogenated castor oil to obtain a shampoo composition. The preparation method also includes the step of grinding selenium disulfide into a pre-prepared slurry mixture.

[0037] The preparation method of this invention is simple, has a high success rate, and is easy to industrialize.

[0038] In a preferred embodiment, the preparation method of the present invention includes the following steps: S1: Disperse high yield value carbomer in deionized water, stir evenly, and set aside to obtain an aqueous gel matrix; S2: Hydrogenated castor oil and a portion of surfactant are heated to 80℃-85℃ to melt, and then cooled after high-speed shearing to form a gel-like substance, thus obtaining a pregel. S3: Mix the surfactant, cationic polymer and other water-soluble components evenly, and add the aqueous gel base material obtained in step S1; S4: Salicylic acid, colloidal sulfur, and ultrafine pulverized selenium disulfide (D90≤20μm) slurry are slowly added to the system and continuously homogenized; S5: Add emulsified silicone oil, preservative, fragrance and the pregel obtained in step S2, adjust the pH of the system to 5.5-6.0 with a pH adjuster, homogenize and defoam to obtain the shampoo composition.

[0039] According to a third aspect of the present invention, the use of the shampoo composition described in any of the above claims in a personal care product is provided.

[0040] The application of the shampoo composition of the present invention is beneficial to fully exert the biological efficacy of the components, while improving the user experience.

[0041] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0042] Examples 1-3 Examples 1-3 provide a mild anti-dandruff shampoo composition, the components and their mass fractions and pH values ​​of which are shown in Table 1.

[0043] Comparative Example 1 The only difference between this embodiment and Embodiment 1 is that the shampoo composition does not contain hydrogenated castor oil, but is only suspended using carbomer; Everything else is the same as in Example 1.

[0044] Comparative Example 2 The only difference between this embodiment and Example 1 is that the shampoo composition does not contain carbomer, but is only suspended with hydrogenated castor oil, and the pH of the system is controlled between 4 and 5. Everything else is the same as in Example 1.

[0045] Comparative Example 3 The only difference between this embodiment and Example 1 is that the shampoo composition does not contain salicylic acid, and the pH of the system is adjusted to around 5.8, relying solely on colloidal sulfur to help stabilize it; Everything else is the same as in Example 1.

[0046] Comparative Example 4 The only difference between this comparative example and Example 1 is that the shampoo composition does not contain colloidal sulfur, and the pH of the system is adjusted to around 5.8, relying solely on salicylic acid for stability. Everything else is the same as in Example 1.

[0047] Comparative Example 5 The only difference between this comparative example and Example 1 is that the pH of the system is adjusted to around 4.6; Everything else is the same as in Example 1.

[0048] Comparative Example 6 The only difference between this comparative example and Example 1 is that the carbomer in the shampoo composition is replaced with acrylate / C10. 30-Alkyl acrylate crosslinking polymer, i.e., replacing Carbomer 980 with Carbomer 2020 or U21, and adjusting the pH of the system to between 5.5 and 6; Everything else is the same as in Example 1.

[0049] Table 1

[0050] Test case The performance of the shampoos of Examples 1-3 and Comparative Examples 1-6 was tested, and the results are shown in Table 2.

[0051] Performance testing methods: The yield stress, thixotropy, and rheological properties of the samples were measured using a Brookfield RST CPS cone / plate rheometer. The combing work of the samples was tested using a Brookfield CT3 texture analyzer with hair strands. The heat resistance test was conducted using a constant temperature oven. The suspension test was conducted using a centrifuge. See Table 2 for details.

[0052] Note: Due to the different shear stress standards selected when using the rheometer for testing, 5Pa and 10Pa are commonly used as the reference, and the measured data will differ. This test uses 5Pa as the reference, and the shear stress is applied and the data is measured from 0-5Pa within 180s. The centrifugation after heat resistance is because the sample is stable when centrifuged at 3000r for 30min after the test. However, during the process of the sample being placed at room temperature for 1-2 years, some transparent water layer will appear on the top, or some selenium disulfide formulations will aggregate.

[0053] Table 2

[0054] As shown in Table 2, the synergistic effect of the composite suspension system is as follows: Examples 1-3 (composite system) have moderate yield stress (0.92Pa-1.50Pa) at pH 5.5-6.0. After centrifugation at 45℃ for 1 month, they all showed no stratification, demonstrating excellent suspension stability. In contrast, Comparative Example 1 (using only carbomer) has a high yield stress (1.91 Pa), but its wet hair combing power is as high as 319.26mJ, and the washing feel is significantly more astringent. This indicates that carbomer alone requires excessively high viscosity to maintain suspension, which impairs the washing feel. In contrast, Comparative Example 2 (using only hydrogenated castor oil, pH 4.56) exhibits extremely low yield stress (0.46 Pa), severe phase separation and particle aggregation occur after aging, and it has the worst combing performance when wet hair (525.42 mJ). This suggests that hydrogenated castor oil alone has a fragile suspension network at low pH and a very poor washing feel. Therefore, the carbomer-hydrogenated castor oil compound system used in this invention is not a simple superposition of the functions of the two, but rather produces a synergistic effect of "1+1>2". It achieves long-term suspension stability far exceeding that of a single component at moderate yield stress, breaking the conventional understanding that "high suspension force must sacrifice washing feel".

[0055] As shown in Table 2, the revolutionary improvement in washing feel due to pH increase is evident in Comparative Example 5 (using the same composite suspension system, but with pH adjusted to 4.66). This is the most crucial comparison, as its wet hair combing power (482.36 mJ) and dry hair combing power (40.75 mJ) are several times higher than those of the examples with pH above 5.5 (e.g., Example 2: 183.34 mJ / 25.86 mJ). This significant difference (approximately 60% reduction in combing resistance) directly and quantitatively demonstrates that raising the pH from the traditional low range (~4.5) to the range of this invention (5.5-6.0) plays a decisive role in improving washing feel and reducing combing damage. Furthermore, this invention, through its innovative composite suspension system, successfully ensures stable suspension at this mild pH, thus simultaneously resolving the long-standing contradiction between "stable suspension" and "mild washing feel," achieving unexpected technical results.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A mild anti-dandruff shampoo composition, characterized in that, It mainly consists of an anti-dandruff active system, a composite suspension system, a surfactant system, and a conditioning system; The anti-dandruff active system contains 0.6%-1% by mass of selenium disulfide and 0.1%-0.3% by mass of salicylic acid or salicylate. The composite suspension system is composed of high yield value carbomers and their derivatives, and hydrogenated castor oil and its derivative trihydroxystearin. The surfactant system comprises at least one of anionic surfactants, nonionic surfactants, and amphoteric surfactants. The conditioning system comprises cationic polymers and emulsified silicone oils of different particle sizes; The pH value of the shampoo composition is 5.5-6.0; The selenium disulfide has a particle size D90 of no more than 20 micrometers and is stably suspended in the composite suspension system.

2. The shampoo composition according to claim 1, characterized in that, The high yield value carbomer is either Carbopol® 980 or Ultrez 21 / ETD 2020. The hydrogenated castor oil is in a pre-gel form formed by pre-dispersing it in a surfactant.

3. The shampoo composition according to claim 2, characterized in that, The mass ratio of high yield value carbomer to hydrogenated castor oil in the composite suspension system is 1:0.5-1:

3.

4. The shampoo composition according to any one of claims 1-3, characterized in that, The mass ratio of selenium disulfide, high yield value carbomer, and hydrogenated castor oil is (0.3-1):(0.1-0.5):(0.2-1).

5. The shampoo composition according to claim 4, characterized in that, The cationic polymer in the conditioning system includes at least one of cationic guar gum, cationic quaternary ammonium salt, and cationic cassia gum. The conditioning system contains emulsified silicone oils with a particle size ≤1μm and large particle size of 20μm, wherein the mass ratio of the small particle size emulsified silicone oil to the large particle size emulsified silicone oil is 1:1 to 3:

1.

6. The shampoo composition according to claim 1, characterized in that, The mass ratio of selenium disulfide and salicylic acid in the shampoo composition is 1:0.1-0.

5.

7. The shampoo composition according to claim 1, characterized in that, The shampoo composition also contains 0.1%-0.5% by mass of colloidal sulfur. The salicylic acid and colloidal sulfur work together through adsorption dispersion and electrostatic stabilization to help stabilize the selenium disulfide particles in the composite suspension system.

8. A method for preparing a shampoo composition according to any one of claims 1-7, characterized in that, Includes the following steps: Selenium disulfide was added to a composite suspension system consisting of high yield value carbomer and hydrogenated castor oil to obtain the shampoo composition. The preparation method further includes the step of grinding selenium disulfide into a pre-prepared slurry mixture.

9. The preparation method according to claim 8, characterized in that, The preparation method includes the following steps: S1: Disperse high yield value carbomer in deionized water, stir evenly, and set aside to obtain an aqueous gel matrix; S2: Hydrogenated castor oil and a portion of surfactant are heated to 80℃-85℃ to melt, and then cooled after high-speed shearing to form a gel-like substance, thus obtaining a pregel. S3: Mix the surfactant, cationic polymer and other water-soluble components evenly, and add the aqueous gel base material obtained in step S1; S4: Salicylic acid, colloidal sulfur, and ultrafine pulverized selenium disulfide (D90≤20μm) slurry are slowly added to the system and continuously homogenized; S5: Add emulsified silicone oil, preservative, fragrance and the pregel obtained in step S2, adjust the pH of the system to 5.5-6.0 with a pH adjuster, homogenize and defoam to obtain the shampoo composition.

10. The use of a shampoo composition according to any one of claims 1-7 in a personal care product.

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