A method for preparing a color-changing lip and cheek stick

Abstract

The application provides a preparation method of a color-changing lip and cheek makeup ointment. The method is aimed at the problems of the traditional ointment product, such as difficult control of crystal structure, easy oil separation, blooming, unstable structure and the like in the cooling process, and proposes a crystallization control process based on gradient cooling. The molten mixed ointment material is sequentially cooled to different temperature intervals at a set cooling rate and is left to stay, so that the nucleation stage and the crystal growth stage of the ointment material are coordinately controlled, thereby inducing the formation of small, uniform and stable crystal structure. The ointment material includes A phase, B phase and C phase components, and the final product is obtained through phase separation preparation and subsequent temperature control treatment. The obtained product has the characteristics of single stable crystal form, small crystal particle size, high crystallinity, low oil penetration rate and dense structure, and the product shows good physical stability under heat resistance, cold resistance and centrifugal conditions, and has excellent application performance and makeup holding effect.

Description

Technical Field

[0001] This invention relates to the field of cosmetic technology, specifically to a gradient cooling and crystallization control method applied to anhydrous ointment systems. Background Technology

[0002] Oil-based makeup products (such as lipsticks, cream blushes, and eyeshadow sticks) are typically composed of waxes, oils, and pigments, and belong to a typical anhydrous system. The physical stability, glossiness, smoothness of application, and staying power of these products are highly dependent on the crystallization behavior of the wax components within the oil-based formula.

[0003] In traditional production processes, the cooling methods for greases often involve natural cooling or forced cooling at a single rate, which makes it difficult to precisely control the crystal structure and easily leads to the following problems:

[0004] (1) Sweating: The crystal structure is too loose and cannot effectively lock in the oil components, resulting in oil seepage on the product surface, which affects the user experience and shelf life;

[0005] (2) Blooming: The wax undergoes a polymorphic transformation, resulting in coarsening of the crystals, which causes white frost or granules to appear on the surface of the paste, seriously affecting the appearance quality and the smoothness of application;

[0006] (3) Cracking: Uneven distribution of internal stress during cooling leads to inconsistent shrinkage rates between the paste and the packaging material, resulting in stick detachment, surface depression or cracking.

[0007] (4) Poor gloss and rough application: The uneven crystal structure leads to a decrease in the gloss of the product surface, resulting in a rough or grainy feeling when applying.

[0008] There have been some attempts to improve the cooling process of ointments in the existing technology, such as using staged temperature control combined with emulsification technology to retain active ingredients. However, there is still a lack of systematic research on the precise control of wax crystallization behavior, especially on how to induce the formation of ideal crystal form, inhibit excessive grain growth, and eliminate internal stress through gradient cooling strategies. Summary of the Invention

[0009] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing a color-changing lip and cheek makeup cream, thereby solving the problems mentioned in the background art.

[0010] This invention is achieved through the following technical solution: a method for preparing a color-changing lip and cheek makeup oil, comprising the following steps:

[0011] Includes the following steps:

[0012] (1) A phase preparation: The hydrogenated (styrene / isoprene) copolymer and ethylhexyl palmitate were heated to 115-125°C and homogenized until no visible particles were found in the system. Then, the color-changing powder was added and homogenized until no powder particles were found.

[0013] (2) Preparation of phase B: Synthetic beeswax and synthetic wax are heated to 115-125℃ and melted until there are no lumps. Isopropyl myristate and oily black paste are added and stirred until uniform.

[0014] (3) Mixing phase A and phase B: Mixing phase A and phase B to form a uniform paste;

[0015] (4) Gradient cooling crystallization control step: The molten and mixed paste is cooled to a first temperature at a first cooling rate and held for a first residence time, and then cooled to a second temperature at a second cooling rate and held for a second residence time, wherein: the first cooling rate is 2-3℃ / min, the first temperature is 100℃-105℃, and the first residence time is 3-15 minutes; the second cooling rate is 1-2℃ / min, the second temperature is 80℃-90℃, and the second residence time is 3-15 minutes;

[0016] (5) Post-processing: After the gradient cooling, the C phase component, which is a preservative and a fragrance, is added and stirred. At the same time, vacuum treatment is performed to remove air bubbles, and then it is filled and molded.

[0017] In a preferred embodiment, the ointment body comprises phase A, phase B, and phase C, wherein:

[0018] Phase A: Hydrogenated (styrene / isoprene) copolymer, ethylhexyl palmitate, and color-changing pigment;

[0019] Phase B: Synthetic beeswax, synthetic wax, isopropyl myristate, and oily black paste;

[0020] Phase C: Preservatives and fragrances.

[0021] In a preferred embodiment, the content of each component, by weight percentage, is as follows:

[0022] Hydrogenated (styrene / isoprene) copolymer: 8-10%;

[0023] Ethylhexyl palmitate: 38-42%;

[0024] Color-changing pigment: 0.8–1.0%;

[0025] Synthetic beeswax: 6-8%;

[0026] Synthetic wax: 5-6%;

[0027] Isopropyl myristate: 32-34%;

[0028] Oily black paste: 2.5–3.5%;

[0029] Preservatives: 0.7-0.9%;

[0030] Fragrance: 0.3-0.4%.

[0031] In a preferred embodiment, the oily black paste is a compound system comprising isopropyl myristate, lithium distearate dimethylammonium montmorillonite, lauryl PEG-9 polydimethylsiloxane ethyl polydimethylsiloxane, polyglycerol-3 diisostearate, CI 77499 and triethoxyoctylsilane.

[0032] In step (1), the homogenization speed is 10,000 to 20,000 rpm and the homogenization time is 45 to 60 minutes.

[0033] In a preferred embodiment, the stirring speed in step (2) is 700-1000 rpm and the stirring time is 10-15 minutes.

[0034] In a preferred embodiment, the vacuum pressure in step (5) is -0.8 to -0.95 bar, and the duration is 5 to 10 minutes.

[0035] As a preferred embodiment, the first temperature is 102.5°C and the second temperature is 85°C.

[0036] The color-changing lip and cheek makeup cream prepared by the above method has a fine and uniform crystal structure with an average particle size of 5 to 15 micrometers. Its melting behavior is characterized by a single melting peak, and the oil penetration rate is not higher than 0.5%.

[0037] After adopting the above technical solution, the beneficial effects of the present invention are: (1) Through gradient cooling crystallization control, the obtained ointment product has no layering or crystals being thrown out in the centrifugation test (3000r / min, 20 minutes); after the heat resistance test (50℃, 24 hours) and cold resistance test (-15℃, 24 hours), the product has no obvious difference in appearance from the test, and there is no surface sweating or oil seepage or crystallization and frost phenomenon.

[0038] (2) The product's melting point is controlled within the range of 73±5℃ to ensure that it is in a solid state at room temperature and can be moderately softened when used on the lips to provide a good application experience.

[0039] (3) The product has a black semi-solid ointment appearance and a grape aroma; after application, it turns pink due to changes in pH and body temperature, achieving a color masking effect and providing visual impact; its lip staining properties can achieve the effects of not sticking to cups and not fading.

[0040] (4) The product can pass the 24-hour makeup test and has excellent stability in high and low temperatures and extreme cold and heat. It has excellent rheological balance, static physical strength and dynamic shear thinning sensation.

[0041] (5) The total number of colonies is ≤1000 CFU / ml, and the total number of molds and yeasts is ≤100 CFU / ml, which meets the requirements of the "Cosmetic Safety Technical Specifications" (2015 edition). Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a flowchart of the preparation process.

[0044] Figure 2 This is a DSC thermal analysis curve.

[0045] Figure 3 This is a microscopic image of the material (polarizing microscope).

[0046] Figure 4 This is a comparison chart of oil seepage performance.

[0047] Figure 5 This is a picture of the finished product of a color-changing lip and cheek makeup cream. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0049] The ointment system is essentially an anhydrous system, consisting of waxes (hard phase) solidified and encapsulating greases (liquid phase). The crystallization process of waxes is divided into two stages: nucleation and growth. The purpose of gradient cooling is to balance the rates of these two stages, promoting the formation of a large number of tiny crystal nuclei and inhibiting their excessive growth, thereby forming a dense and delicate network structure.

[0050] Specifically, the three-stage temperature control mechanism for gradient cooling is as follows:

[0051] (1) Pre-cooling stage: slowly cool down to near the crystallization point of the wax to reduce thermal shock and prevent the surface of the paste from forming a skin while the inside remains liquid;

[0052] (2) Core crystallization stage: Rapidly passing through the crystallization point, using a large temperature difference to induce the generation of a large number of fine crystal nuclei;

[0053] (3) Stabilization stage: Maintain a temperature slightly below the crystallization point to stabilize the crystal arrangement and eliminate thermal stress.

[0054] Furthermore, this invention also achieves homogeneous polymorphic control. Wax raw materials (such as synthetic beeswax, synthetic wax, etc.) have multiple crystal forms, among which:

[0055] Alpha type: the least stable, with a low melting point;

[0056] β′ type: The crystals are small and tightly packed, which is the ideal state pursued by makeup products (combining hardness and luster);

[0057] β type: The most stable but with coarse crystals, which can result in a rough feel.

[0058] This invention uses precise temperature profiles to control the crystal form to the β′ type and suppress its transformation into the coarse β type over time.

[0059] Please see Figure 1 This invention provides a technical solution: a method for preparing a color-changing lip and cheek makeup oil, comprising the following steps:

[0060] (I) Formula Composition

[0061] The ointment comprises the following components by weight percentage:

[0062] Phase A:

[0063] Hydrogenated (styrene / isoprene) copolymer: 8-10%;

[0064] Ethylhexyl palmitate: 38-42%;

[0065] Color-changing pigment: 0.8–1.0%;

[0066] Phase B:

[0067] Synthetic beeswax: 6-8%;

[0068] Synthetic wax: 5-6%;

[0069] Isopropyl myristate: 32-34%;

[0070] Oily black paste: 2.5–3.5%;

[0071] Phase C:

[0072] Preservatives: 0.7-0.9%;

[0073] Fragrance: 0.3-0.4%.

[0074] (II) Preparation process

[0075] The preparation process includes the following steps:

[0076] Step 1: Preparation of Phase A

[0077] Weigh out the prescribed amounts of hydrogenated (styrene / isoprene) copolymer and ethylhexyl palmitate, and add them to the main reaction vessel; heat to 120°C and homogenize at a speed of 10,000 to 20,000 rpm until no visible particles are visible in the ointment; add the prescribed amount of color-changing pigment - Red No. 21, and continue homogenizing until no powder particles are present.

[0078] The total preparation time for phase A is 45–60 minutes.

[0079] Step 2: Preparation of Phase B

[0080] Weigh out the amount of synthetic beeswax and synthetic wax as specified in the formula, heat to 120°C to melt until there are no lumps; add the amount of isopropyl myristate and oily black paste as specified in the formula, and stir at 700-1000 rpm until the mixture is uniform.

[0081] The total preparation time for phase B is 10–15 minutes.

[0082] Step 3: Mix phases A and B

[0083] Mix the A phase obtained in step 1 with the B phase obtained in step 2 until homogeneous.

[0084] Step 4: C-phase preparation—gradient cooling and crystallization control stage

[0085] For crystal preparation, a four-stage gradient cooling path was adopted, as shown in Table 1. When the cooling rate was 2–3 °C / min, the average crystal size (D50) could be controlled between 5–15 mm, and the crystals had a smooth feel. If the rate was >4 °C / min, amorphous fragments were prone to occur, resulting in poor stability.

[0086] Table 1

[0087] stage Step Name Parameter setting range Technical goals Step 1 First cooling phase 120℃ → 102.5℃ (rate: 3℃ / min) Rapidly enter the nucleation frontier Step 2 First stop 102.5℃ (hold for 3–15 minutes) Induced uniform nucleation Step 3 Second cooling phase 102.5℃ → 85℃ (rate: 2~3℃ / min) Controlled crystal growth Step 4 Second stop 85℃ (hold for 3–15 minutes) Stress relief and crystal maturation

[0088] Specifically:

[0089] The mixed material is cooled at a gradient rate of 2-3℃ / min to 102.5℃ (isothermal holding at 102.5℃ to bring the paste to a moderately supercooled state. This temperature is slightly below the crystallization starting point of the high-melting-point component, allowing crystal nuclei to form slowly and uniformly in the oil phase. This method avoids explosive nucleation and loose structure caused by excessively rapid cooling, as well as coarse crystals caused by excessively slow cooling. Ultimately, a dense and tiny crystal nucleus network is formed, laying the foundation for a fine texture.), and held at this temperature for 3-15 minutes, preferably 5 minutes, to ensure that the black paste does not agglomerate or settle.

[0090] The temperature was then gradually reduced to 85°C at a rate of 1–2°C / min (holding at 85°C allows the synthetic wax molecules to transform from the α-type (unstable, loosely arranged) to the β′-type (metastable, fine, and malleable). This temperature is within the main phase transition region, allowing the molecular chains time to rearrange and releasing the thermal stress generated by volume shrinkage. This helps eliminate internal stress, prevents subsequent cracks or shrinkage pores in the paste, and induces the formation of a stable network structure.), and held at this temperature for 3–15 minutes, preferably 5 minutes. The internal material was then tested to ensure no coarsening of crystal particle size or uneven distribution of crystal scattering.

[0091] Add the prescribed amounts of phenoxyethanol and grape flavoring, and stir at 700-1000 rpm for 3 minutes;

[0092] Evacuate to -0.9 bar and maintain for 5-10 minutes to eliminate air bubbles;

[0093] The total preparation time for the C phase is 35–45 minutes.

[0094] Step 5: Filling

[0095] The defoamed material (such as...) Figure 5 The product is then filled into packaging containers to obtain the finished product.

[0096] As one embodiment of the present invention, Embodiment 1

[0097] 1. Prepare color-changing lip and cheek makeup cream according to the following formula and process:

[0098] Parting Raw material name Weight percentage (%) Phase A Hydrogenated (styrene / isoprene) copolymer 9.0 Phase A Ethylhexyl palmitate 40.45 Phase A Color-changing pigment - Red No. 21 0.9 Phase B Synthetic beeswax 7.0 Phase B Synthetic wax 5.5 Phase B Isopropyl myristate 33.0 Phase B Oily black paste 3.0 C phase Phenoxyethanol 0.8 C phase Grape flavoring 0.35 total - 100.0

[0099] 2. Preparation process

[0100] (1) Preparation of phase A: Weigh 9.0 kg of KRATON® G1701 Polymer and 40.45 kg of ethylhexyl palmitate, put them into the reactor, heat to 120°C, and homogenize at 15000 rpm until no visible particles are present (about 50 minutes); add 0.9 kg of RED No. 223W, and continue homogenizing until no powder particles are present.

[0101] (2) Preparation of phase B: Weigh 7.0 kg of synthetic beeswax and 5.5 kg of synthetic wax, heat to 120°C and melt until there are no lumps; add 33.0 kg of IPM and 3.0 kg of BS458_Black Paste, and stir at 850 rpm until the material is uniform (about 12 minutes).

[0102] (3) Mixing phases A and B: Mix phase A and phase B evenly.

[0103] (4) Gradient cooling and crystallization control:

[0104] Cool to 102.5℃ at a rate of 2.5℃ / min and hold for 5 minutes;

[0105] Cool to 85℃ at a rate of 1.5℃ / min and hold for 5 minutes;

[0106] Add 0.8 kg of phenoxyethanol and 0.35 kg of grape flavoring, and stir at 850 rpm for 3 minutes;

[0107] Evacuate to -0.9 bar and hold for 8 minutes to eliminate air bubbles.

[0108] (5) Filling: Fill the defoamed material into 4g packaging containers.

[0109] 3. Quality Inspection

[0110] The obtained products were tested using the following methods:

[0111] Testing items Detection methods Test results Appearance / Properties Visual inspection Black / Semi-solid ointment odor Sense of smell Grape flavor color Visual inspection black Melting point WRR capillary method 73.1℃ Centrifugation 3000 r / min, 20 min Normally there is no stratification, and no crystals are ejected. Heat resistant 50℃, 24 hours, return to room temperature There was no significant difference in appearance compared to before the experiment, and no sweating or oil seepage was observed. Cold-resistant -15℃, 24 hours, then return to room temperature There was no significant difference in appearance compared to before the test, and no crystallization or blooming occurred. Hot and cold circulation Cycle at 50 to -15°C for 24 hours. No significant difference in traits compared to before the experiment Total bacterial count Cosmetic Safety Technical Specifications ≤1000 CFU / ml molds and yeasts Cosmetic Safety Technical Specifications ≤100 CFU / ml

[0112] 4. Functional evaluation

[0113] Based on the evaluation of 20 volunteers, the product has the following characteristics:

[0114] It appears black, but turns pink after application, showing a noticeable color change.

[0115] It applies smoothly without any grainy texture;

[0116] After a 24-hour makeup test, the color remained good with no noticeable makeup fading.

[0117] It is non-irritating and comfortable to use.

[0118] Examples 2-5

[0119] Following the same process steps as in Example 1, the gradient cooling parameters were adjusted to prepare a series of products and their performance was investigated. The results are as follows:

[0120] Example First stage cooling rate (°C / min) First stage residence temperature (°C) Second stage cooling rate (°C / min) Second stage residence temperature (°C) Crystalline state Centrifugal stability 2 2.0 102.5 1.0 85 Fine and even qualified 3 3.0 102.5 2.0 85 Fine and even qualified 4 2.5 100.0 1.5 80 Slight graininess qualified 5 2.5 105.0 1.5 90 uniform qualified

[0121] As a comparative example of the present invention:

[0122] Comparative Example 1

[0123] Using the same formula as in Example 1, but employing natural cooling (cooling to 25°C at room temperature), the resulting product exhibited a distinct frost-like substance on its surface, crystals precipitated after centrifugation, and a grainy feel when applied.

[0124] Example 1 and Comparative Example 1 were tested and compared. The testing methods and performance characterization are shown in the table below:

[0125] Testing items Detection methods Example 1 Comparative Example 1 Melting behavior Differential scanning calorimetry, nitrogen protection, 20℃~120℃, heating rate 10℃ / min A single melting peak, symmetrical and concentrated, with a melting point of approximately 60℃~70℃, and stable crystal form. Multi-peaked or shoulder-peaked, with dispersed peak shapes, complex crystal forms, and unstable structures. Crystal morphology Thin-layer samples observed under polarizing microscope at room temperature The crystals are fine needle-like or spherical, evenly distributed, and without obvious agglomeration. The crystals are large, plate-like or blocky, unevenly distributed, and show obvious agglomeration. Crystal grain size (D50) Statistical analysis of microscopic images Approximately 12.4 micrometers, with a concentrated particle size distribution. Approximately 45.8 micrometers in size, with a relatively wide particle size distribution. Structural strength (hardness) Texture analyzer test, cylindrical probe, test depth 5 mm It has high hardness with small fluctuations and a dense and stable structure. Low hardness with large fluctuations, loose structure Oil penetration performance The oil stain diffusion area was measured using the filter paper method, maintaining the environment at 50°C for 24 hours. Oil penetration rate ≤0.4%, oil phase stable The oil seepage rate is approximately 5.2%, indicating significant oil separation. enthalpy of fusion Differential scanning calorimetry calculation Approximately 145 J / g, with high crystallinity. Approximately 118 J / g, with low crystallinity. Appearance stability Visual inspection and storage observation The surface is smooth, without frost or oil separation. The surface is prone to oil separation, resulting in blooming or uneven distribution.

[0126] In summary, the table above shows that Example 1 exhibits a single stable crystal form in its melting behavior, with a fine and uniform crystal structure, significantly reduced particle size, and the formation of a dense and continuous spatial network structure. The increased hardness and reduced fluctuations indicate a stable internal support structure for the paste. The significantly reduced oil penetration rate indicates that the oil phase is effectively bound. The increased enthalpy of melting indicates an increased degree of crystallization. Overall, it demonstrates strong thermal stability, a dense structure, and a uniform appearance.

[0127] Comparative Example 1 exhibits polymorphism, with large, unevenly distributed crystals and a loose structure. It has low hardness and poor stability, easily precipitates the oil phase, and shows obvious appearance defects. Its overall performance is significantly inferior to that of Example 1.

[0128] Specifically:

[0129] I. Thermodynamic property testing, such as Figure 2

[0130] The phase transition behavior of the samples was tested using differential scanning calorimetry. The samples were placed in a differential scanning calorimeter and a temperature scan was performed under a nitrogen protective atmosphere. The test temperature range was 20℃ to 120℃, and the heating rate was 10℃ / min.

[0131] In Example 1, the melting peak of the sample showed a single main peak with symmetrical and sharp peak shape. The peak value was concentrated in the range of 60℃ to 70℃, indicating that the internal crystal form of the ointment was relatively simple and mainly stable, with high crystal uniformity.

[0132] In Comparative Example 1, the melting curve showed multiple shoulder peaks or secondary peaks with dispersed peak shapes, indicating that there were different crystal forms or unstable crystal structures in the grease, and that there was obvious phase separation or uneven crystallization.

[0133] II. Crystal morphology detection, such as Figure 3

[0134] The microcrystalline structure of the sample was observed using a polarizing microscope. A thin layer of the sample was spread on a glass slide, and observations were recorded at room temperature.

[0135] In Example 1, the crystals in the field of view exhibit a fine needle-like or spherical structure with uniform distribution. The crystal size is small, with an average particle size D50 of approximately 12.4 micrometers. The particle size distribution is concentrated, and no obvious agglomeration is observed.

[0136] In Comparative Example 1, the crystals exhibit a coarse plate-like or blocky structure with significant size variations. The average particle size D50 is approximately 45.8 micrometers, indicating obvious crystal aggregation and structural inhomogeneity.

[0137] III. Physical Stability Testing

[0138] The hardness of the samples was tested using a texture analyzer with a cylindrical probe and a testing depth of 5 mm. Structural strength was evaluated based on the maximum stress value. Simultaneously, the oil permeability was tested using the filter paper method. The samples were placed in a 50°C environment for 24 hours, and the oil diffusion area was recorded (e.g., ...). Figure 4 And calculate the oil seepage rate.

[0139] In Example 1, the hardness test results were stable with small numerical fluctuations, indicating that the structure was dense and well supported; the oil penetration rate was controlled below 0.4%, and the oil paste had a strong oil-binding ability.

[0140] In Comparative Example 1, the hardness was low and fluctuated greatly, indicating insufficient structural stability; the oil permeation rate was approximately 5.2%, showing obvious oil phase precipitation.

[0141] IV. Overall Performance Comparison

[0142] By comparing and analyzing the key performance indicators of Example 1 and Comparative Example 1, the results show that:

[0143] The average crystal size of Example 1 was significantly reduced from 45.8 micrometers to 12.4 micrometers; the melting enthalpy increased from 118 J / g to 145 J / g, indicating a significant improvement in crystallinity; the oil penetration rate decreased from 5.2% to 0.4%, indicating a significant enhancement in heat resistance; and the appearance was characterized by a smooth surface without any frosting.

[0144] Comparative Example 1 has problems such as large crystals, loose structure and poor stability, and is prone to surface oil separation and appearance defects.

[0145] In summary, Example 1 optimizes the temperature control path during the cooling process, enabling the grease to complete uniform nucleation and crystal transformation within a specific temperature range, forming a fine and dense crystal network structure, thereby significantly improving the material's thermal stability, structural strength, and appearance quality.

[0146] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a color-changing lip and cheek makeup oil, characterized in that, Includes the following steps: (1) A phase preparation: The hydrogenated (styrene / isoprene) copolymer and ethylhexyl palmitate were heated to 115-125°C and homogenized until no visible particles were found in the system. Then, the color-changing powder was added and homogenized until no powder particles were found. (2) Preparation of phase B: Synthetic beeswax and synthetic wax are heated to 115-125℃ and melted until there are no lumps. Isopropyl myristate and oily black paste are added and stirred until uniform. (3) Mixing phase A and phase B: Mixing phase A and phase B to form a uniform paste; (4) Gradient cooling crystallization control step: The molten and mixed paste is cooled to a first temperature at a first cooling rate and held for a first residence time, and then cooled to a second temperature at a second cooling rate and held for a second residence time, wherein: the first cooling rate is 2-3℃ / min, the first temperature is 100℃-105℃, and the first residence time is 3-15 minutes; the second cooling rate is 1-2℃ / min, the second temperature is 80℃-90℃, and the second residence time is 3-15 minutes; (5) Post-processing: After the gradient cooling, the C phase component, which is a preservative and a fragrance, is added and stirred. At the same time, vacuum treatment is performed to remove air bubbles, and then it is filled and molded.

2. The method for preparing a color-changing lip and cheek makeup cream as described in claim 1, characterized in that: The ointment material comprises phase A, phase B, and phase C, wherein: Phase A: Hydrogenated (styrene / isoprene) copolymer, ethylhexyl palmitate, and color-changing pigment; Phase B: Synthetic beeswax, synthetic wax, isopropyl myristate, and oily black paste; Phase C: Preservatives and fragrances.

3. The method for preparing a color-changing lip and cheek makeup cream as described in claim 2, characterized in that: The content of each component, by weight percentage, is as follows: Hydrogenated (styrene / isoprene) copolymer: 8-10%; Ethylhexyl palmitate: 38-42%; Color-changing pigment: 0.8–1.0%; Synthetic beeswax: 6-8%; Synthetic wax: 5-6%; Isopropyl myristate: 32-34%; Oily black paste: 2.5–3.5%; Preservatives: 0.7-0.9%; Fragrance: 0.3-0.4%.

4. The method for preparing a color-changing lip and cheek makeup cream as described in claim 3, characterized in that: The oily black paste is a compound system containing isopropyl myristate, lithium distearate dimethylammonium montmorillonite, lauryl PEG-9 polydimethylsiloxane ethyl polydimethylsiloxane, polyglycerol-3 diisostearate, CI 77499 and triethoxyoctylsilane.

5. The method for preparing a color-changing lip and cheek makeup cream as described in claim 1, characterized in that: In step (1), the homogenization speed is 10,000 to 20,000 rpm and the homogenization time is 45 to 60 minutes.

6. The method for preparing a color-changing lip and cheek makeup cream as described in claim 1, characterized in that: In step (2), the stirring speed is 700-1000 rpm and the stirring time is 10-15 minutes.

7. The method for preparing a color-changing lip and cheek makeup cream as described in claim 1, characterized in that: In step (5), the vacuum pressure is -0.8 to -0.95 bar, and the duration is 5 to 10 minutes.

8. The method for preparing a color-changing lip and cheek makeup cream as described in claim 1, characterized in that: The first temperature is 102.5℃, and the second temperature is 85℃.

9. The color-changing lip and cheek makeup cream prepared by the method according to claim 4, characterized in that: Its crystal structure is fine and uniformly distributed, with an average particle size of 5 to 15 micrometers. Its melting behavior is characterized by a single melting peak, and the oil penetration rate is no higher than 0.5%.

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