A flavor microcapsule and its preparation method

Abstract

This invention discloses a fragrance microcapsule and its preparation method, belonging to the field of polymer materials technology. The fragrance microcapsule comprises the following raw materials by mass percentage: 12-13% fragrance, 18.5-22.5% melamine-formaldehyde resin, 1-1.5% nonionic surface emulsifier, 0.3-0.6% acid catalyst, 1.3-3% cationic emulsifier, and 60-65% deionized water; wherein the melamine-formaldehyde resin is composed of highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin. The preparation method involves first dispersing the nonionic surface emulsifier in deionized water, then adding the fragrance and stirring until homogeneous. Next, the melamine-formaldehyde resin, acid catalyst, and cationic emulsifier are added in multiple batches to react, finally obtaining the fragrance microcapsule. The fragrance microcapsule of this invention has good wall toughness, significantly improving thermal stability and fragrance longevity.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a flavor microcapsule and its preparation method. Background Technology

[0002] Fragrances are widely used in food, cosmetics, detergents, textiles, papermaking, and many other fields. Traditional fragrances are characterized by rapid release and short duration of action. Furthermore, some aroma components in fragrances have poor thermal stability, making them highly susceptible to fragrance loss and lack of long-lasting scent due to external factors. To address the issue of fragrance longevity, microencapsulation technology has been applied to the fragrance industry. Microencapsulated fragrances primarily encapsulate the fragrance, controlling its release and improving its stability. However, currently available fragrance microcapsules on the market often have insufficient wall toughness and poor thermal stability. This makes the encapsulation material prone to rupture during storage and use due to changes in external temperature, resulting in reduced fragrance persistence and unsatisfactory scent longevity and storage stability.

[0003] Therefore, a new flavor microcapsule and its preparation method are needed to solve the above problems. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, one of the objectives of the present invention is to provide a fragrance microcapsule with good thermal stability and long-lasting fragrance.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] A flavor microcapsule comprises the following raw materials by mass percentage: 12-13% flavor, 18.5-22.5% melamine-formaldehyde resin, 1-1.5% nonionic surface emulsifier, 0.3-0.6% acid catalyst, 1.3-3% cationic emulsifier, and 60-65% deionized water; wherein the melamine-formaldehyde resin is composed of highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin.

[0007] In a preferred embodiment of the present invention, the mass ratio of the highly methylated melamine-formaldehyde resin, the highly iminomethylated melamine-formaldehyde resin, and the partially methylated melamine-formaldehyde resin is 1:8 to 8.5:1 to 2.

[0008] In a preferred embodiment of the present invention, the nonionic surface emulsifier is selected from at least one of alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, fatty amine polyoxyethylene ether, fluorocarbon surfactant, and alkyl glycoside.

[0009] In a preferred embodiment of the present invention, the acid catalyst is selected from at least one of citric acid, maleic acid, phthalic acid, and alkyl phosphate.

[0010] In a preferred embodiment of the present invention, the cationic emulsifier is dodecyltrimethylammonium chloride and / or dodecyldimethylbenzylammonium chloride.

[0011] A second objective of this invention is to provide a method for preparing the flavor microcapsules as described above, comprising the following steps:

[0012] S1. Add a nonionic surfactant to deionized water, stir and disperse, then add fragrance under stirring conditions, and stir and emulsify at a speed of 600-800 r / min.

[0013] S2. Add a portion of melamine-formaldehyde resin to the mixture obtained in step S1, stir evenly, then add a portion of acid catalyst to adjust the pH to 4.5-6.5; then place the mixture in a water bath at 60-80℃ and stir for 2-3 hours.

[0014] S3. After the reaction is complete, add some cationic emulsifier to the mixture obtained in step S2, stir and disperse, then add some melamine-formaldehyde resin and some acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 55-75℃ for 2-3 hours.

[0015] S4. After the reaction is complete, add the remaining cationic emulsifier to the mixture obtained in step S3, stir and disperse, then add the remaining melamine-formaldehyde resin and the remaining acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 55-65℃ for 2-3 hours; after the reaction is complete, cool, wash with water, and filter to obtain the flavor microcapsules.

[0016] In a preferred embodiment of the present invention, the stirring speed after adding the nonionic surfactant in step S1 is 300-400 r / min and the dispersion time is 2-3 min; the emulsification time after adding the fragrance is 5-15 min.

[0017] In a preferred embodiment of the present invention, the stirring speed after adding melamine-formaldehyde resin in step S2 is 200-300 r / min and the dispersion time is 2-3 min; the stirring speed of the water bath reaction is 300-400 r / min.

[0018] In a preferred embodiment of the present invention, the stirring speed after adding the cationic emulsifier in steps S3 and S4 is 200-300 r / min, the dispersion time is 2-3 min, and the stirring speed of the stirring reaction is 250-350 r / min.

[0019] In a preferred embodiment of the present invention, the mass percentages of melamine-formaldehyde resin added in steps S2, S3, and S4 are 6-7%, 6-8%, and 6.5-7.5%, respectively; the mass percentages of acid catalyst added in steps S2, S3, and S4 are 0.1-0.2%, 0.1-0.18%, and 0.15-0.2%, respectively; and the mass percentages of cationic emulsifier added in steps S3 and S4 are 1-1.2% and 1.2-1.5%, respectively.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The fragrance microcapsules of this invention are made by compounding highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin in a specific ratio to form melamine-formaldehyde resin. This effectively enhances the mechanical flexibility of the fragrance microcapsule wall material, reduces brittleness, prevents it from cracking due to changes in external temperature, and provides good thermal stability, thereby greatly improving the fragrance retention of the fragrance microcapsules. The fragrance microcapsules of this invention utilize nonionic emulsifiers selected based on the charge state of the fragrance substance's surface structure. This enhances the emulsification effect, providing better surface tension, spherical integrity, and density when coated with melamine-formaldehyde resin wall materials. The combination of an acid catalyst with a suitable dissociation constant (dissociation constant > 2.85) and an organic acid with a suitable pH value allows for a highly efficient and gradual reaction, thus improving the coating rate. The use of cationic emulsifiers for secondary coating facilitates the formation of a continuous dispersed phase in the wall material, further enhancing the coating rate. Adjusting the amount of acid catalyst during secondary coating increases the reaction rate and coating rate. To improve high toughness and thermal stability, increasing the amount of acid catalyst with each coating iteration lowers the pH value and reaction temperature, effectively preventing excessively high temperatures from damaging the capsule integrity. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments.

[0023] A flavor microcapsule comprises the following raw materials by mass percentage: 12-13% flavor, 18.5-22.5% melamine-formaldehyde resin, 1-1.5% nonionic surface emulsifier, 0.3-0.6% acid catalyst, 1.3-3% cationic emulsifier, and 60-65% deionized water; wherein the melamine-formaldehyde resin is composed of highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin; the mass ratio of highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin is 1:8-8.5:1-2.

[0024] Specifically, the preferred product model for highly methylated melamine-formaldehyde resin is Allnex CYMEL 350; the preferred product models for highly iminomethylated melamine-formaldehyde resin are Allnex CYMEL 385 and CYMEL328; and the preferred product models for partially methylated melamine-formaldehyde resin are Allnex CYMEL 370 and CYMEL380.

[0025] In the above formulation, the nonionic surface emulsifier is selected from at least one of alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, fatty amine polyoxyethylene ether, fluorocarbon surfactant, and alkyl glycoside. The acid catalyst is selected from at least one of citric acid, maleic acid, phthalic acid, and alkyl phosphate. The cationic emulsifier is dodecyltrimethylammonium chloride and / or dodecyldimethylbenzylammonium chloride.

[0026] The preparation method of the above flavor microcapsules includes the following steps:

[0027] S1. Add a nonionic surfactant to deionized water and disperse it by stirring at 300-400 r / min for 2-3 min. Then add the fragrance while stirring and emulsify by stirring at 600-800 r / min for 5-15 min.

[0028] S2. Add 6-7% by mass of melamine-formaldehyde resin to the mixture obtained in step S1, stir and disperse at 200-300 r / min for 2-3 min, then add 0.1-0.2% by mass of acid catalyst to adjust the pH to 4.5-6.5; then place the mixture in a water bath at 60-80℃ and stir at 300-400 r / min for 2-3 h.

[0029] S3. After the reaction is complete, add 1-1.2% cationic emulsifier to the mixture obtained in step S2, stir and disperse at 200-300 r / min for 2-3 min, then add 6-8% melamine-formaldehyde resin and 0.1-0.2% acid catalyst, adjust the pH to 4.0-5.5, and react at 55-75℃ with stirring at 250-350 r / min for 2-3 h.

[0030] S4. After the reaction is complete, add the remaining cationic emulsifier to the mixture obtained in step S3, stir and disperse at a speed of 200-300 r / min for 2-3 min, then add the remaining melamine-formaldehyde resin and the remaining acid catalyst, adjust the pH to 4.0-5.5, and react at 55-65℃ with stirring at a speed of 250-350 r / min for 2-3 h. After the reaction is completed, cool, wash with water, and filter to obtain the fragrance microcapsules.

[0031] The reaction equations involved in the above preparation process are as follows:

[0032]

[0033] Example 1

[0034] A flavor microcapsule comprises the following raw materials by mass percentage: 12% flavoring, 18.5% melamine-formaldehyde resin, 1.5% alkylphenol polyoxyethylene ether, 0.5% citric acid, 2.5% dodecyltrimethylammonium chloride, and 65% deionized water. The melamine-formaldehyde resin is composed of highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin in a mass ratio of 1:8:1.

[0035] The preparation method of the above flavor microcapsules includes the following steps:

[0036] S1. Add 1.5% alkylphenol polyoxyethylene ether to deionized water, stir and disperse at 300 r / min for 2.5 min, then add fragrance under stirring, and emulsify at 600 r / min for 10 min.

[0037] S2. Add 6% by mass of melamine-formaldehyde resin to the mixture obtained in step S1, stir and disperse at 300 r / min for 3 min, then add 0.1% by mass of acid catalyst to adjust the pH to 4.5-6.5; then place the mixture in a water bath at 70℃ and stir at 300 r / min for 2 h.

[0038] S3. After the reaction is complete, add 1.2% cationic emulsifier to the mixture obtained in step S2, stir and disperse at 300 r / min for 2-3 min, then add 6.5% melamine-formaldehyde resin and 0.2% acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 250 r / min at 65℃ for 3 h.

[0039] S4. After the reaction is complete, add the remaining cationic emulsifier to the mixture obtained in step S3, stir and disperse at 300 r / min for 3 min, then add the remaining melamine-formaldehyde resin and the remaining acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 350 r / min at 60℃ for 3 h. After the reaction is completed, cool, wash with water, and filter to obtain the fragrance microcapsules.

[0040] Example 2

[0041] A flavor microcapsule comprises the following raw materials by mass percentage: 12% flavor, 22.5% melamine-formaldehyde resin, 1.5% alkylphenol polyoxyethylene ether, 0.5% citric acid, 3.0% dodecyltrimethylammonium chloride, and 60.5% deionized water. The melamine-formaldehyde resin is composed of highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin in a mass ratio of 1:8.5:2.

[0042] The preparation method of the above flavor microcapsules includes the following steps:

[0043] S1. Add 1.5% alkylphenol polyoxyethylene ether to deionized water, stir and disperse at 400 r / min for 3 min, then add fragrance under stirring, and emulsify at 800 r / min for 5 min.

[0044] S2. Add 8% by mass of melamine-formaldehyde resin to the mixture obtained in step S1, stir and disperse at 200 r / min for 2.5 min, then add 0.15% by mass of acid catalyst to adjust the pH to 4.5-6.5; then place the mixture in a water bath at 80℃ and stir at 400 r / min for 2.5 h.

[0045] S3. After the reaction is complete, add 0.2% cationic emulsifier to the mixture obtained in step S2, stir and disperse at 200 r / min for 3 min, then add 8% melamine-formaldehyde resin and 0.15% acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 350 r / min at 75℃ for 2.5 h.

[0046] S4. After the reaction is complete, add the remaining cationic emulsifier to the mixture obtained in step S3, stir and disperse at 200 r / min for 2.5 min, then add the remaining melamine-formaldehyde resin and the remaining acid catalyst, adjust the pH to 4.0-5.5, and stir at 300 r / min at 55℃ for 2 h. After the reaction is complete, cool, wash with water, and filter to obtain the fragrance microcapsules.

[0047] Example 3

[0048] A flavor microcapsule comprises the following raw materials by mass percentage: 12% flavor, 22.5% melamine-formaldehyde resin, 1.5% alkylphenol polyoxyethylene ether, 0.5% citric acid, 3.0% dodecyltrimethylammonium chloride, and 60.5% deionized water. The melamine-formaldehyde resin is composed of highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin in a mass ratio of 1:8:1.

[0049] The preparation method of the above flavor microcapsules includes the following steps:

[0050] S1. Add 1.5% alkylphenol polyoxyethylene ether to deionized water, stir and disperse at 350 r / min for 2 min, then add fragrance under stirring, and emulsify at 700 r / min for 5 min.

[0051] S2. Add 8% by mass of melamine-formaldehyde resin to the mixture obtained in step S1, stir and disperse at 250 r / min for 2 min, then add 0.15% by mass of acid catalyst to adjust the pH to 4.5-6.5; then place the mixture in a water bath at 65℃ and stir at 350 r / min for 3 h.

[0052] S3. After the reaction is complete, add 0.2% cationic emulsifier to the mixture obtained in step S2, stir and disperse at 250 r / min for 2 min, then add 8% melamine-formaldehyde resin and 0.15% acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 300 r / min at 75℃ for 3 h.

[0053] S4. After the reaction is complete, add the remaining cationic emulsifier to the mixture obtained in step S3, stir and disperse at 250 r / min for 2 min, then add the remaining melamine-formaldehyde resin and the remaining acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 300 r / min at 65℃ for 2 h. After the reaction is completed, cool, wash with water, and filter to obtain the fragrance microcapsules.

[0054] Example 4

[0055] A flavor microcapsule comprises the following raw materials by mass percentage: 12% flavoring, 22.5% melamine-formaldehyde resin, 1.0% alkylphenol polyoxyethylene ether, 0.6% phthalic acid, 1.3% dodecyl dimethyl benzyl ammonium chloride, and 62.6% deionized water. The melamine-formaldehyde resin is composed of highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin in a mass ratio of 1:8:1.

[0056] The preparation method of the above flavor microcapsules includes the following steps:

[0057] S1. Add 1.0% alkylphenol polyoxyethylene ether to deionized water, stir and disperse at 300 r / min for 2.5 min, then add fragrance under stirring, and emulsify at 600 r / min for 10 min.

[0058] S2. Add 7% by mass of melamine-formaldehyde resin to the mixture obtained in step S1, stir and disperse at 300 r / min for 3 min, then add 0.15% by mass of acid catalyst to adjust the pH to 4.5-6.5; then place the mixture in a water bath at 70℃ and stir at 300 r / min for 2 h.

[0059] S3. After the reaction is complete, add 0.2% cationic emulsifier to the mixture obtained in step S2, stir and disperse at 300 r / min for 2-3 min, then add 8% melamine-formaldehyde resin and 0.2% acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 250 r / min at 65℃ for 3 h.

[0060] S4. After the reaction is complete, add the remaining cationic emulsifier to the mixture obtained in step S3, stir and disperse at 300 r / min for 3 min, then add the remaining melamine-formaldehyde resin and the remaining acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 350 r / min at 60℃ for 3 h. After the reaction is completed, cool, wash with water, and filter to obtain the fragrance microcapsules.

[0061] Example 5

[0062] A flavor microcapsule comprises the following raw materials by mass percentage: 12% flavoring, 20.0% melamine-formaldehyde resin, 1.5% alkylphenol polyoxyethylene ether, 0.5% phthalic acid, 3.0% dodecyl dimethyl benzyl ammonium chloride, and 63.0% deionized water. The melamine-formaldehyde resin is composed of highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin in a mass ratio of 1:8:2.

[0063] The preparation method of the above flavor microcapsules includes the following steps:

[0064] S1. Add 1.5% alkylphenol polyoxyethylene ether to deionized water, stir and disperse at 300 r / min for 2.5 min, then add fragrance under stirring, and emulsify at 600 r / min for 10 min.

[0065] S2. Add 7% by mass of melamine-formaldehyde resin to the mixture obtained in step S1, stir and disperse at 300 r / min for 3 min, then add 0.2% by mass of acid catalyst to adjust the pH to 4.5-6.5; then place the mixture in a water bath at 70℃ and stir at 300 r / min for 2 h.

[0066] S3. After the reaction is complete, add 1.5% cationic emulsifier to the mixture obtained in step S2, stir and disperse at 300 r / min for 2-3 min, then add 8% melamine-formaldehyde resin and 0.2% acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 250 r / min at 65℃ for 3 h.

[0067] S4. After the reaction is complete, add the remaining cationic emulsifier to the mixture obtained in step S3, stir and disperse at 300 r / min for 3 min, then add the remaining melamine-formaldehyde resin and the remaining acid catalyst, adjust the pH to 4.0-5.5, and stir and react at 350 r / min at 60℃ for 3 h. After the reaction is completed, cool, wash with water, and filter to obtain the fragrance microcapsules.

[0068] Comparative Example 1

[0069] The only difference between this comparative example and Example 1 is that the melamine-formaldehyde resin is composed of highly iminomethyl etherified melamine-formaldehyde resin and partially methyl etherified melamine-formaldehyde resin in a mass ratio of 8:1. All other components are the same as in Example 1. The preparation method of the above flavor microcapsules is the same as in Example 1.

[0070] Comparative Example 2

[0071] The only difference between this comparative example and Example 1 is that the melamine-formaldehyde resin is composed of highly methylated melamine-formaldehyde resin and highly iminomethylated melamine-formaldehyde resin in a mass ratio of 1:8. All other components are the same as in Example 1. The preparation method of the above flavor microcapsules is the same as in Example 1.

[0072] Comparative Example 3

[0073] The only difference between this comparative example and Example 1 is that the flavor microcapsules in this comparative example comprise the following raw materials by mass percentage: flavor 12%, melamine-formaldehyde resin 18.5%, alkylphenol polyoxyethylene ether 0.8%, citric acid 0.5%, dodecyltrimethylammonium chloride 2.5%, and deionized water 65.7%. All other components are the same as in Example 1. The preparation method of the above flavor microcapsules is the same as in Example 1.

[0074] Comparative Example 4

[0075] The only difference between this comparative example and Example 1 is that the flavor microcapsules of this comparative example comprise the following raw materials by mass percentage: flavor 12%, melamine-formaldehyde resin 18.5%, alkylphenol polyoxyethylene ether 1.5%, citric acid 0.2%, dodecyltrimethylammonium chloride 2.5%, and deionized water 65.3%. All other components are the same as in Example 1.

[0076] The preparation method of the above flavor microcapsules includes the following steps:

[0077] S1. Add 1.5% alkylphenol polyoxyethylene ether to deionized water, stir and disperse at 300 r / min for 2.5 min, then add fragrance under stirring, and emulsify at 600 r / min for 10 min.

[0078] S2. Add 6% by mass of melamine-formaldehyde resin to the mixture obtained in step S1, stir and disperse at 300 r / min for 3 min, then add 0.07% by mass of acid catalyst to adjust the pH to 6.8-7.2; then place the mixture in a water bath at 70℃ and stir at 300 r / min for 2 h.

[0079] S3. After the reaction is complete, add 1.2% cationic emulsifier to the mixture obtained in step S2, stir and disperse at 300 r / min for 2-3 min, then add 6.5% melamine-formaldehyde resin and 0.08% acid catalyst, adjust the pH to 6-7, and stir and react at 250 r / min at 65℃ for 3 h.

[0080] S4. After the reaction is complete, add the remaining cationic emulsifier to the mixture obtained in step S3, stir and disperse at 300 r / min for 3 min, then add the remaining melamine-formaldehyde resin and the remaining acid catalyst, adjust the pH to 5-6, and stir and react at 350 r / min at 60℃ for 3 h. After the reaction is completed, cool, wash with water, and filter to obtain the fragrance microcapsules.

[0081] Comparative Example 5

[0082] The only difference between this comparative example and Example 1 is that the flavor microcapsules of this comparative example comprise the following raw materials by mass percentage: flavor 12%, melamine-formaldehyde resin 18.5%, alkylphenol polyoxyethylene ether 1.5%, citric acid 0.5%, and deionized water 67.5%. All other components are the same as in Example 1.

[0083] The preparation method of the above flavor microcapsules includes the following steps:

[0084] S1. Add 1.5% alkylphenol polyoxyethylene ether to deionized water, stir and disperse at 300 r / min for 2.5 min, then add fragrance under stirring, and emulsify at 600 r / min for 10 min.

[0085] S2. Add 6% by mass of melamine-formaldehyde resin to the mixture obtained in step S1, stir and disperse at 300 r / min for 3 min, then add 0.1% by mass of acid catalyst to adjust the pH to 4.5-6.5; then place the mixture in a water bath at 70℃ and stir at 300 r / min for 2 h.

[0086] S3. After the reaction is complete, add 6.5% by mass of melamine-formaldehyde resin and 0.2% by mass of acid catalyst to the mixture obtained in step S2, adjust the pH to 4.0-5.5, and stir the mixture at 250 r / min at 65℃ for 3 h.

[0087] S4. After the reaction is complete, add the remaining melamine-formaldehyde resin and the remaining acid catalyst to the mixture obtained in step S3, adjust the pH to 4.0-5.5, and stir at 350 r / min at 60°C for 3 h. After the reaction is completed, cool, wash with water, and filter to obtain the fragrance microcapsules.

[0088] I. Storage stability test

[0089] 200g of a similar commercially available product were respectively... The flavor microcapsules prepared in Examples 1-5 and Comparative Examples 1-5 were placed in 300ml transparent glass bottles and stored in ovens at 45℃ and 55℃ for constant temperature storage. After 168h, the changes in the properties of the samples were observed, and the viscosity and color were measured. The results are shown in Table 1.

[0090] The specific methods for measuring viscosity and color are as follows:

[0091] 1. Appearance / Viscosity:

[0092] Instrument Brand / Model: Brookfield cone-plate viscometer (DV2TRVC-JO, CP-42 rotor)

[0093] Test Procedure / Method: Turn on the constant temperature water bath power supply and set the temperature to 23℃. Ensure the viscometer displays a temperature of 23℃ and connect the sample tray. Ensure the viscometer is placed horizontally, turn on the viscometer power, and press "Next" for automatic calibration to zero. (Torque should be ±0.1 mm; the instrument should be in good condition. If the torque deviates from ±0.1 mm, gently adjust the jewel bearing to zero.) Install the CP-42 rotor, attach the empty sample tray, and begin adjusting the gap (turn on the indicator light, rotate the vernier scale until the yellow light is slightly lit, align with the scale line, rotate one division to the left until the yellow light goes out, align with the scale line again; at this point, the gap between the rotor and the sample cup should be approximately 0.5 mm. Turn off the indicator light, place the sample, and begin measurement to obtain the data.

[0094] 2. Color number:

[0095] Instrument Brand / Model: LANGE L100 620 Colorimeter

[0096] Test Procedure / Method: Turn on the colorimeter; the instrument will begin automatic calibration. After the instrument completes its self-test, click Options → Colorimetric Scale → Colorimetric Value — Hazen. Place a cuvette filled with distilled water in the sample cell and begin calibration. After calibration, remove the cuvette and place the cuvette containing the sample to be tested in the sample cell. Select Measurement. (Note: The cuvette containing distilled water and the cuvette containing the sample to be tested must be placed in the same orientation.) Begin measurement and record the test result reading. Remove the cuvette, close the sample cell lid, and turn off the power.

[0097] Table 1. Stability of Flavor Microcapsules under Constant Temperature Storage

[0098]

[0099]

[0100] As shown in Table 1, the flavor microcapsules prepared in Examples 1-5 showed little change in viscosity and a small increase in color after being stored at 45°C and 55°C for a period of time, proving that the flavor microcapsules prepared by the present invention have good storage stability. The flavor microcapsules of Comparative Example 1 had a higher viscosity, and an increase in viscous substance at the bottom when stored at 55°C. This is because Comparative Example 1 lacked highly methylated melamine resin with a monomeric structure. Highly methylated melamine resin can reduce the reaction rate and buffer the violent cross-linking reaction during the reaction. The flavor microcapsules of Comparative Example 3 had a lower amount of nonionic surfactant, resulting in fewer spherical microcapsules and a lower coating rate. Due to the increased residual amount of amino resin, the self-cross-linking tendency increased during storage, leading to higher viscosity and poorer flowability. In Comparative Example 4, the flavor microcapsule sample contained unreacted melamine resin residue, resulting in increased viscosity during storage. The microcapsules, amino resin, and aqueous solution formed a discontinuous phase, leading to stratification. Furthermore, the increased amount of residual amino resin increased the tendency for self-crosslinking during storage, resulting in higher viscosity and poorer flowability. In Comparative Example 5, the flavor microcapsules lacked cationic surface emulsifiers, resulting in a significantly reduced encapsulation rate. They were unable to continue forming a dense and effective capsule wall, and the increased amount of unreacted amino resin led to a greater tendency for self-crosslinking during storage, resulting in higher viscosity and poorer flowability.

[0101] II. Fragrance Longevity Test

[0102] A similar commercially available product The fragrance microcapsules prepared in Example 1 at a mass percentage of 1% and the fragrance at a mass percentage of 0.4% (equivalent to the content of the fragrance microcapsules) were added to the cotton fabric finishing agent, respectively. The washing process simulated the wearing conditions of clothing, and after natural air drying, the fabric was placed in a mixing drum for tumbling. After being removed at different times and left to stand for 15 minutes, the degree of fragrance infusion was recorded. The baseline fragrance infusion rate of this fragrance was 18%. The results, based on the recorded fragrance measurement values, are shown in Table 2.

[0103] Table 2 Results of the fragrance retention test of fragrance microcapsules (fragrance rate %)

[0104]

[0105]

[0106] As shown in Table 2, the fragrance microcapsules prepared in Example 1 exhibited a higher fragrance retention rate than commercially available products over time, indicating that the fragrance microcapsules of the present invention can significantly improve the fragrance retention time. In Comparative Example 1, the fragrance microcapsules experienced a significantly increased chance of capsule wall rupture due to the excessively rapid reaction rate, thus reducing the fragrance retention rate. Comparative Example 2, lacking partially methylated melamine resin, showed a lower fragrance retention rate compared to Example 1. This is because the functional groups of the partially methylated melamine resin can react with the imino groups in the high-imino methylated melamine-formaldehyde resin to form methylene bridges, increasing the strength of the capsule wall, reducing the chance of capsule rupture, and thus improving the fragrance retention rate. Comparative Example 3, compared to Example 1, reduced the amount of nonionic surfactant, resulting in fewer spherical microcapsules and a lower coating rate, thus leading to a less desirable fragrance retention rate. Compared to Example 1, the flavor microcapsules in Comparative Example 4 had a lower amount of acid catalyst and a higher pH value, resulting in reduced catalytic effect, incomplete chemical reaction, and a lower encapsulation rate. Additionally, in Comparative Example 4, unreacted melamine-formaldehyde resin residue remained in the solution, causing increased viscosity during storage. This led to the formation of a discontinuous phase between the microcapsules, amino resin, and aqueous solution, resulting in stratification. Compared to Example 1, Comparative Example 5 lacked a cationic surface emulsifier and could not form a dense and effective capsule wall, resulting in a significant decrease in encapsulation rate. This is because the cationic emulsifier forms an active interface on the surface of the spherical microcapsules generated in step S2, allowing the amino resin to continue reacting, which increases the encapsulation probability and capsule wall density during secondary encapsulation.

[0107] In summary, this invention, by using highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin in a specific ratio to form melamine-formaldehyde resin, can effectively enhance the mechanical flexibility of the fragrance microcapsule wall material, reduce brittleness, prevent it from cracking with changes in external temperature, and exhibit good thermal stability. This, in turn, can greatly improve the fragrance loading rate and fragrance retention of the fragrance microcapsules.

[0108] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A flavor microcapsule, characterized in that: It includes the following raw materials by mass percentage: fragrance 12-13%, melamine-formaldehyde resin 18.5-22.5%, nonionic surface emulsifier 1-1.5%, acid catalyst 0.3-0.6%, cationic emulsifier 1.3-3%, and deionized water 60-65%; The melamine-formaldehyde resin is composed of highly methylated melamine-formaldehyde resin, highly iminomethylated melamine-formaldehyde resin, and partially methylated melamine-formaldehyde resin. The mass ratio of the highly methylated melamine-formaldehyde resin, the highly imino-methylated melamine-formaldehyde resin, and the partially methylated melamine-formaldehyde resin is 1:8~8.5:1~2. The product model of the highly methylated melamine-formaldehyde resin is CYMEL 350; the product model of the highly iminomethylated melamine-formaldehyde resin is CYMEL 385 or CYMEL328; and the product model of the partially methylated melamine-formaldehyde resin is CYMEL 370 or CYMEL380.

2. The flavor microcapsule according to claim 1, characterized in that: The nonionic surface emulsifier is selected from at least one of alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, fatty amine polyoxyethylene ether, fluorocarbon surfactant, and alkyl glycoside.

3. The flavor microcapsule according to claim 1, characterized in that: The acid catalyst is selected from at least one of citric acid, maleic acid, phthalic acid, and alkyl phosphate.

4. The flavor microcapsule according to claim 1, characterized in that: The cationic emulsifier is dodecyltrimethylammonium chloride and / or dodecyldimethylbenzylammonium chloride.

5. A method for preparing flavor microcapsules as described in any one of claims 1 to 4, characterized in that: Includes the following steps: S1. Add nonionic surface emulsifier to deionized water, stir and disperse, then add fragrance under stirring conditions, and stir emulsify at a speed of 600~800r / min. S2. Add a portion of melamine-formaldehyde resin to the mixture obtained in step S1, stir evenly, then add a portion of acid catalyst to adjust the pH to 4.5~6.5; then place the mixture in a water bath at 60~80℃ and stir for 2~3 hours. S3. After the reaction is complete, add some cationic emulsifier to the mixture obtained in step S2, stir and disperse, then add some melamine-formaldehyde resin and some acid catalyst, adjust the pH to 4.0~5.5, and stir and react at 55~75℃ for 2~3 hours. S4. After the reaction is complete, add the remaining cationic emulsifier to the mixture obtained in step S3, stir and disperse, then add the remaining melamine-formaldehyde resin and the remaining acid catalyst, adjust the pH to 4.0~5.5, and stir and react at 55~65℃ for 2~3 hours; after the reaction is completed, cool, wash with water, and filter to obtain the fragrance microcapsules.

6. The method for preparing flavor microcapsules according to claim 5, characterized in that: In step S1, the stirring speed after adding the nonionic surface emulsifier is 300-400 r / min and the dispersion time is 2-3 min; the emulsification time after adding the fragrance is 5-15 min.

7. The method for preparing flavor microcapsules according to claim 5, characterized in that: In step S2, the stirring speed after adding melamine-formaldehyde resin is 200-300 r / min and the stirring time is 2-3 min; the stirring speed for the water bath reaction is 300-400 r / min.

8. The method for preparing flavor microcapsules according to claim 5, characterized in that: In steps S3 and S4, the stirring speed after adding the cationic emulsifier is 200-300 r / min, the dispersion time is 2-3 min, and the stirring speed for the stirring reaction is 250-350 r / min.

9. The method for preparing flavor microcapsules according to claim 5, characterized in that: The mass percentages of melamine-formaldehyde resin added in steps S2, S3, and S4 are 6-7%, 6-8%, and 6.5-7.5%, respectively; the mass percentages of acid catalyst added in steps S2, S3, and S4 are 0.1-0.2%, 0.1-0.18%, and 0.15-0.2%, respectively; and the mass percentages of cationic emulsifier added in steps S3 and S4 are 1-1.2% and 1.2-1.5%, respectively.

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