Directional slow-release aromatic microcapsule prepared by coaxial electrostatic spraying method and provided with semi-embedded anchoring structure and application of directional slow-release aromatic microcapsule

Abstract

The invention relates to the technical field of microcapsules, in particular to a directional slow-release aromatic microcapsule which is prepared by a coaxial electrostatic spraying method and has a semi-embedded anchoring structure and application of the directional slow-release aromatic microcapsule. Comprising the following steps: preparing a core layer solution: mixing aromatic essential oil with a phase change material, wherein the melting point of the phase change material is 28-35 DEG C; a polyurethane urea prepolymer is dissolved in an organic solvent, the polyurethane urea prepolymer is composed of a soft segment and a hard segment, the soft segment is polyether polyol, the hard segment is a reaction product of diisocyanate and a small molecule amine chain extender, and an anchoring enhancer containing catechol groups is further dispersed in the shell solution; a coaxial electrostatic spraying device is adopted, the core layer solution and the shell layer solution are sprayed out through an inner needle head and an outer needle head at the same time, core-shell structure microcapsules are formed under the action of a high-voltage electrostatic field, and the microcapsules are directly deposited on the surface of a base material; according to the method, the integration of microcapsule preparation and anchoring is realized, an additional adhesive is not needed, and the influence of an adhesive film on the hand feeling of a base material is avoided.

Description

A directional sustained-release aromatic microcapsule with a semi-embedded anchoring structure prepared by coaxial electrostatic spraying and its application. Technical Field

[0001] This invention relates to the field of microcapsule technology, specifically to a directional sustained-release aromatic microcapsule with a semi-embedded anchoring structure prepared by coaxial electrostatic spraying and its application. Background Technology

[0002] Microencapsulation technology, which encapsulates active substances in tiny capsules, has been widely applied in food, pharmaceuticals, cosmetics, and textiles. In textiles, applying aromatic microcapsules to fabrics can impart a lasting fragrance, meeting consumer demand for functional textiles. However, applying aromatic microcapsules to textiles, especially high-end silks and other fabrics with high requirements for feel, faces a series of technical challenges: excessively large microcapsule sizes or overly rigid shells can degrade the fabric's feel; weak bonding between microcapsules and fibers leads to insufficient wash resistance; the slow release of aromatic substances during storage results in depletion, while insufficient release during wear prevents targeted sustained release; the way microcapsules adhere to the fabric surface directly affects their performance, and traditional adhesion methods often require an additional adhesive layer between the fabric and the microcapsules, which not only affects the feel but also increases process complexity.

[0003] Regarding the fixation of microcapsules on textiles, existing technologies mainly employ physical adhesion methods assisted by adhesives. For example, prior art document 1 (JP3249829U) discloses a fiber product with temperature-regulating properties, in which microcapsules containing a heat-storing material (n-octadecane) and an outer sheath (polyurea resin) are dispersed and fixed onto the fiber body, including silk, using a fixative. This technology achieves microcapsule fixation by adhering the microcapsules to the fiber surface with a fixative, which then cures to form a film. However, this technology has the following drawbacks: ① An additional fixative is required to adhere the microcapsules to the fiber, and the film formed after curing affects the natural feel and drape of the fabric; ② The microcapsules are only physically attached to the fiber surface by adhesives, rather than embedded within the fiber, resulting in limited interfacial adhesion and difficulty in guaranteeing wash resistance; ③ The introduction of the fixative increases the complexity of the process and may affect the release characteristics of the microcapsules.

[0004] Various technical solutions exist for the preparation of microcapsules, but most employ interfacial polymerization to prepare the microcapsule slurry, which is then applied to fabrics through finishing processes. For example, prior art document 2 (CN121513759A) discloses a method for preparing microcapsules using interfacial polymerization. This method involves dissolving an amino acid-derived polyisocyanate with at least two isocyanate functional groups in a fragrance to form an oil phase, which is then added to an aqueous phase containing a stabilizer, such as lysine triisocyanate (LTI), to form an emulsion. Amino acid reactants, such as lysine and arginine, are then added, and a solidification step is performed to form a core-shell microcapsule slurry. Microcapsules prepared by this method exhibit good stability and can be used in consumer products such as shower gels. However, this method has the following shortcomings: ① The microcapsules prepared by the interfacial polymerization method have a large particle size (D[4,3]-17μm). When applied to the fabric through finishing, the large-particle-size microcapsules will cause the fabric to feel rough and its drape to decrease; ② This method only prepares microcapsule slurry. The combination of microcapsules and fabric requires additional adhesives or finishing processes, and direct anchoring of microcapsules to fibers cannot be achieved; ③ The shell material does not involve the control of soft and hard segments, and cannot achieve intelligent release with controllable glass transition temperature (Tg); ④ It does not involve the interfacial anchoring design between microcapsules and fabric substrate. The microcapsules are only physically attached by adhesives, and it is difficult to balance washability and feel.

[0005] In addition, existing technologies have attempted to deposit microcapsules directly onto fabric surfaces using electrostatic spraying. For example, some studies have used coaxial electrohydrodynamics to embed menthol in a silk fibroin matrix, with microcapsule sizes of 1-2 μm, which can be directly deposited on the fabric surface and exhibit some wash resistance. However, this research still has the following shortcomings: ① The microcapsule size is still in the micrometer range (1-2 μm), which still has a significant impact on the fabric's feel; ② The shell material is silk fibroin, which does not involve Tg regulation, making it impossible to achieve a smart response of density during storage and flexibility during wear; ③ The microcapsules are only deposited on the fiber surface and do not form an embedded anchoring structure, resulting in limited wash resistance; ④ The chemical bonding design between the microcapsules and fibers is not addressed, leading to insufficient interfacial adhesion.

[0006] In summary, the existing technology lacks a microcapsule and its application method that can simultaneously resolve the following technical contradictions: ① The contradiction between the adhesion of microcapsules to fabrics and the maintenance of hand feel. Improving adhesion often requires increasing the hardness of the shell or adding adhesives, but this degrades the natural hand feel of the fabric; ② The contradiction between the storage stability of aromatic substances and their release during wear. During storage, a dense shell is needed to reduce release loss, while during wear, a flexible shell is needed to accelerate release. The requirements for the shell material properties of the two conflict; ③ The contradiction between the microcapsule particle size and the fabric compatibility. Large-diameter microcapsules have good adhesion but poor hand feel, while small-diameter microcapsules have good hand feel but insufficient adhesion; ④ The contradiction between the interfacial bonding mode of microcapsules and fibers. Adhesive adhesion affects hand feel, physical deposition fastness is insufficient, and there is a lack of anchoring structures that combine good hand feel and high wash resistance.

[0007] Therefore, developing a method for preparing a targeted, sustained-release aromatic microcapsule that can be directly prepared and deposited on the surface of a fabric via coaxial electrostatic spraying to form a semi-embedded anchoring structure, imparting a long-lasting fragrance function to the fabric while fully maintaining its natural feel, and exhibiting zero release during storage and intelligent release during wear, has become a pressing technical problem to be solved in this field. Summary of the Invention

[0008] This invention aims to solve the following technical problems existing in the prior art: how to achieve a firm bond between microcapsules and fabric substrates without using additional adhesives, while maintaining the natural feel of the fabric; how to design shell materials to enable microcapsules to simultaneously possess storage-period density (low release) and wear-period flexibility (high release); how to control the process to enable microcapsules to form a semi-embedded anchoring structure during deposition, achieving dual anchoring through physical interlocking and chemical bonding; how to prepare aromatic microcapsules with fine particle sizes, such as submicron and uniform particle size distribution, making them suitable for high-end fabrics such as silk; and how to overcome the technical prejudice that "functional finishing inevitably degrades the feel," achieving a unity of function and feel.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A directional sustained-release aromatic microcapsule with a semi-embedded anchoring structure, prepared by coaxial electrostatic spraying, is obtained by the following method:

[0011] (1) Preparation of core layer solution: Mix aromatic essential oil with phase change material, wherein the melting point of the phase change material is 28-35℃;

[0012] (2) Preparation of shell solution: Dissolve polyurethane urea prepolymer in an organic solvent. The polyurethane urea prepolymer is composed of soft segments and hard segments. The soft segments are polyether polyols and the hard segments are reaction products of diisocyanate and small molecule amine chain extenders. The shell solution also contains an anchoring reinforcing agent containing catechol groups.

[0013] (3) A coaxial electrostatic spraying device is used to spray the core layer solution and the shell layer solution simultaneously through the inner needle and the outer needle, respectively, to form core-shell structured microcapsules under the action of a high voltage electrostatic field, and directly deposit them on the surface of the substrate.

[0014] (4) Control the receiving distance and spray ambient temperature so that the shell layer is in a semi-cured viscous flow state when the microcapsules reach the substrate. The semi-cured state means that 30%-50% of the solvent in the shell layer has evaporated, and the degree of crosslinking reaction of the polyurethane urea prepolymer is controlled between 30%-60%. At this time, the glass transition temperature (Tg) of the shell layer material is lower than the ambient temperature, and it exhibits a viscous flow state. It can deform under the weight of the microcapsules themselves and partially embed itself into the substrate to form a semi-embedded anchoring structure.

[0015] (5) Hot air post-treatment to completely solidify the shell layer, and the microcapsules and the substrate form a composite interface of physical interlocking and chemical bonding.

[0016] Through the above technical solution, the present invention achieves the following synergistic effects: First, the combination of coaxial electrostatic spraying and semi-curing deposition realizes the integration of microcapsule preparation and anchoring, eliminating the need for additional adhesives and avoiding the influence of adhesive film on the feel of the substrate; Second, semi-curing deposition puts the microcapsules in a viscous flow state, which naturally embeds them into the substrate using residual heat, forming physical intercalation, which together with subsequent chemical bonding constitutes dual anchoring, significantly improving wash resistance.

[0017] Preferably, the core layer solution also contains a lipid-soluble light stabilizer, the mass ratio of the aromatic essential oil to the phase change material is 100:20-40, and the phase change material is at least one of n-octadecane, n-hexadecane, and methyl laurate, with a melting point of 28-32℃.

[0018] This invention unexpectedly discovered that co-encapsulating phase change materials with aromatic essential oils and synergistically regulating the soft segments of the shell can produce a "dual temperature amplification effect": the phase change material melts at wearing temperatures such as 32-37°C, not only increasing its own diffusion coefficient but also plasticizing the surrounding polyurethane urea soft segments, further lowering the glass transition temperature (Tg) of the shell, forming a positive feedback loop. This results in a release rate at 37°C that is 3-5 times higher than that stored at 25°C (Examples 1-3), far exceeding the 1.5 times that without phase change materials (Comparative Example 4). This exponential release amplification effect is something that those skilled in the art could not have predicted.

[0019] Preferably, the anchoring enhancer containing catechol groups is dopamine methacrylamide or its derivative, and its mass fraction in the shell is 5-15 parts; the shell solution also contains nano-silica modified with silane coupling agent, with a particle size of 20-50 nm and a mass fraction of 3-8 parts, and the nano-silica forms a dispersed phase in the shell and participates in interfacial chemical bonding.

[0020] This invention further reveals a significant synergistic effect between dopamine anchoring and the semi-embedded structure: physical interlocking provides initial anchoring force, protecting chemical bonds from the direct impact of washing mechanical forces; while the chemical bonds can maintain their connection even when the physical interlocking part loosens, resulting in a plateau-shaped curve of "initial minor detachment - later stable retention" in wash resistance (retention rate ≥70% after 20 washes), far superior to the linear detachment without dopamine (Comparative Example 3, only 43% after 20 washes). Furthermore, experimental observations suggest that dopamine may possess dynamic reversible bonding characteristics in humid environments, endowing the microcapsules with a certain "self-repair" ability—a phenomenon completely unexpected before the application.

[0021] Preferably, in the polyurethane urea prepolymer, the number average molecular weight of the soft segment polyether polyol is 1000-3000, and the hard segment diisocyanate is isophorone diisocyanate or 4,4'-dicyclohexylmethane diisocyanate, with a soft-hard segment mass ratio of 100:80-120; by adjusting the soft-hard segment ratio and the amount of chain extender, the glass transition temperature (Tg) of the final microcapsule shell is controlled between -20°C and 10°C.

[0022] This invention challenges the traditional perception that "the harder the shell, the more wash-resistant it is," unexpectedly discovering that flexible shells (Tg = -15℃ to 5℃) actually exhibit superior wash resistance (71-82% wash resistance in Examples 1-3). Mechanistic analysis shows that flexible shells undergo reversible deformation under washing mechanical forces, absorbing impact energy and resisting brittleness; while rigid shells (Comparative Example 1) are prone to microcracks due to stress concentration, leading to core material leakage. This discovery breaks through the technical bias in the field and provides a completely new approach to microcapsule shell design.

[0023] Preferably, the parameters of the coaxial electrostatic spraying are controlled as follows: inner needle specification is 22-25G, outer needle specification is 16-18G; core flow rate is 0.2-0.5mL / h, shell flow rate is 1.0-2.0mL / h; applied voltage is 10-15kV; receiving distance is 15-20cm; ambient temperature is 23-27℃, and relative humidity is 35-45%.

[0024] Preferably, in step (4), an infrared heating lamp is set above the receiving device to maintain the surface temperature of the substrate at 40-50°C. When the microcapsules reach the surface of the substrate, 30-50% of the shell solvent evaporates and the microcapsules are in a semi-cured viscous flow state. The embedding depth of the semi-embedded anchoring structure is 10-30% of the substrate thickness, and the embedding depth is controlled by adjusting the receiving distance and spraying time.

[0025] Through precise control of the above process parameters, the microcapsules prepared by this invention have an average particle size of 200-500 nm and a particle size distribution CV value ≤10%. The submicron-sized particles allow the microcapsules to be partially embedded in the amorphous region of the fiber without protruding from the fiber surface, producing an unexpected effect of "visual invisibility + tactile invisibility": completely invisible to the naked eye and imperceptible to the touch, yet still providing excellent aroma release function.

[0026] Even more surprisingly, the surface of the microcapsules of this invention exhibits a nanoscale wrinkled structure (undulations of 20-50 nm). Conventionally, a rough surface is expected to increase the coefficient of friction and degrade the feel; however, experiments have shown that these nanofolds actually reduce the actual contact area between fibers, producing a microscopic smoothness similar to the "lotus leaf effect," resulting in a silk bending stiffness of ≤0.15 cN·cm for the deposited microcapsules. 2 / cm, drape coefficient change ≤3%, with no significant difference from untreated silk. The synergy of nano-folds, submicron particle size, and flexible shell forms a "triple guarantee" for maintaining the feel, completely breaking the technical prejudice that "functional finishing inevitably sacrifices feel".

[0027] The present invention further provides the application of the above-mentioned targeted sustained-release aromatic microcapsules in the preparation of intelligent fragrance-controlled textiles, characterized in that the textiles are at least one of silk, cotton, linen, wool, and polyester; under storage conditions at 25°C, the aroma retention rate is ≥90% after 6 months; under wearing conditions at 32-37°C, the aroma release within 24 hours is 3-5 times that under the same storage conditions, achieving body temperature-triggered targeted sustained release.

[0028] The present invention further provides the above-mentioned targeted sustained-release aromatic microcapsules, characterized in that the substrate is at least one of fabric, paper, leather, plastic film, and metal foil; the semi-embedded anchoring structure allows the microcapsules to be partially embedded in the surface layer of the substrate, forming a dual anchoring of physical interlocking and chemical bonding.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] (1) This invention improves the washability from the conventional 8-10 times to more than 20 times through a flexible shell, dopamine anchoring and semi-embedded structure, and the retention rate is ≥70%, thus solving the technical prejudice that "the harder the shell, the more washable".

[0031] (2) This invention achieves a flexural stiffness of ≤0.15 cN·cm in the finished silk by using a triple synergy of submicron particle size, controllable nano-wrinkled surface, and flexible shell. 2 / cm, with a drape coefficient change of ≤3%, showing no significant difference from untreated silk, breaking the industry perception that "function inevitably sacrifices feel".

[0032] This invention achieves precise temperature control by using phase change materials and soft segment regulation to achieve zero release at 25°C (6-month retention rate ≥90%) and accelerated release when worn at 37°C (release ratio 3-5 times), providing a truly intelligent experience of "smells better when worn".

[0033] This invention utilizes an integrated coaxial electrostatic spraying and semi-curing deposition process, eliminating the need for adhesives and post-treatment, and completing the preparation, deposition, and anchoring of microcapsules in one step, simplifying the production process and reducing costs.

[0034] The microcapsules of this invention are not only applicable to silk, but also to cotton, linen, wool, polyester and other fabrics, as well as various substrates such as paper, leather, plastic film, and metal foil, and have good versatility and industrialization prospects. Attached Figure Description

[0035] Figure 1 is a flowchart of the preparation process of the targeted sustained-release aromatic microcapsules of the present invention.

[0036] Figure 2 shows the release performance comparison curves of the microcapsules prepared in Examples 1-3 of the present invention and the comparative documents, showing the retention rate of the microcapsules of the present invention after 6 months of storage at 25°C and the release rate after 24 hours of wearing at 37°C.

[0037] Figure 3 is a comparison of the wash resistance of the microcapsules prepared in Examples 1-3 of the present invention with that in the prior art, showing the retention rate of the microcapsules after 20 washes according to the AATCC61-2A standard. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and the process flow of the present invention shown in FIG1, but the scope of protection of the present invention is not limited thereto. Embodiment 1

[0039] (1) Preparation of core layer solution

[0040] Take 100g of lavender essential oil, the main components of which are linalool and linalyl acetate, add 30g of n-octadecane (melting point 28℃, phase change material) and 3g of vitamin E (lipid-soluble light stabilizer), and stir and mix evenly at 25℃ to obtain a core layer solution.

[0041] (2) Preparation of shell solution

[0042] 100g of polytetrahydrofuran ether diol with a number average molecular weight of 2000 was mixed with 100g of isophorone diisocyanate (IPDI) and reacted at 70°C for 2 hours under nitrogen protection to obtain an NCO-terminated polyurethane prepolymer. 100g of this prepolymer was then added to 10g of dopamine methacrylamide (as an anchoring reinforcing agent), 5g of KH560-modified 30nm nano-silica, and 10g of ethylenediamine (as a chain extender), dissolved in acetone to prepare a shell solution with a solid content of 20wt%.

[0043] (3) Coaxial electrostatic spray deposition

[0044] A coaxial electrostatic spraying device was used, with an inner needle of 22G and an inner diameter of 0.41mm, and an outer needle of 17G and an inner diameter of 1.07mm. The core layer solution was delivered to the inner needle at a flow rate of 0.3mL / h, and the shell layer solution was delivered to the outer needle at a flow rate of 1.5mL / h. A voltage of 12kV was applied, and the receiving distance was 18cm. The ambient temperature was controlled at 25℃, and the relative humidity at 40%. A silk substrate pretreated with 100W plasma for 30s was fixed on the grounded receiving device, and the spraying time was 10 minutes.

[0045] (4) Semi-solid deposition

[0046] An infrared heating lamp was placed above the receiving device to maintain the silk surface temperature at 45°C. By adjusting the spray distance and ambient temperature, the microcapsules reached the substrate surface when approximately 40% of the acetone solvent in the shell had evaporated and the cross-linking degree of the prepolymer was approximately 50% (this degree can be indirectly determined by monitoring the consumption of NCO groups using infrared spectroscopy). At this point, due to the plasticizing effect of the solvent and the low degree of cross-linking, the actual glass transition temperature of the shell material had decreased from -3°C after complete curing to approximately -15°C, still far below the current ambient temperature of 25°C and the substrate surface temperature of 45°C. Therefore, the shell was in a highly viscous flow state. In this state, the microcapsules, relying on their own gravity and residual kinetic energy, partially embedded themselves into the amorphous region of the silk fiber, with an embedding depth of approximately 20% of the fiber diameter.

[0047] (5) Hot air post-treatment

[0048] The deposited silk was placed in an 80°C hot air drying oven for 3 minutes to completely solidify the shell, and the microcapsules formed a composite interface of physical interlocking and chemical bonding with the silk fibers.

[0049] The obtained microcapsules had an average particle size of 320 nm and a particle size distribution CV value of 8.5% (measured by a laser particle size analyzer). The glass transition temperature (Tg) of the shell was -3℃ (measured by differential scanning calorimetry). Example 2

[0050] (1) Preparation of core layer solution

[0051] Take 100g of rose essential oil, add 40g of n-hexadecane (melting point 18℃, phase change material) and 5g of UV-531 (lipid-soluble light stabilizer), and mix well.

[0052] (2) Preparation of shell solution

[0053] 100g of a polyether polyol (polyethylene glycol) with a number average molecular weight of 1000 was reacted with 80g of 4,4'-dicyclohexylmethane diisocyanate (HMDI) at 70°C for 2 hours under nitrogen protection to obtain an NCO-terminated prepolymer. 100g of this prepolymer was then added to 15g of dopamine methacrylamide, 8g of KH560 modified nano-silica (particle size 20nm), and 15g of diethylenetriamine, dissolved in ethyl acetate to prepare a shell solution with a solid content of 25wt%.

[0054] (3) Coaxial electrostatic spray deposition

[0055] Inner needle 25G, outer needle 18G; core layer flow rate 0.2mL / h, shell layer flow rate 1.0mL / h; voltage 10kV; receiving distance 20cm; ambient temperature 23℃, humidity 35%; silk substrate as above; spraying time 15 minutes.

[0056] (4) Semi-solid deposition

[0057] Infrared heating raises the surface temperature of the silk to 40°C. When the microcapsules arrive, about 30% of the solvent in the shell evaporates, and the embedding depth is about 15%.

[0058] (5) Hot air post-treatment

[0059] Treat with 100℃ hot air for 2 minutes.

[0060] The obtained microcapsules had an average particle size of 280 nm, a CV of 9.2%, and a shell Tg of -12 °C. Example 3

[0061] (1) Preparation of core layer solution

[0062] Take 100g of menthol, add 20g of methyl lauryl ester (melting point 5℃, phase change material) and 1g of UV-531, and mix well.

[0063] (2) Preparation of shell solution

[0064] 100g of polyether polyol (polypropylene glycol) with a number average molecular weight of 3000 was reacted with 120g of IPDI at 70°C for 2 hours under nitrogen protection to obtain an NCO-terminated prepolymer. 100g of this prepolymer was then dissolved in dichloromethane, along with 5g of dopamine methacrylamide (as an anchoring reinforcing agent), 3g of KH560-modified 50nm nano-silica, and 5g of ethylenediamine (as a chain extender), to prepare a shell solution with a solid content of 15wt%.

[0065] (3) Coaxial electrostatic spray deposition

[0066] Inner needle 22G, outer needle 16G; core flow rate 0.5mL / h, shell flow rate 2.0mL / h; voltage 15kV; receiving distance 15cm; ambient temperature 27℃, humidity 45%; spraying time 5 minutes.

[0067] (4) Semi-solid deposition

[0068] Infrared heating raises the surface temperature of the silk to 50°C. When the microcapsules arrive, about 50% of the solvent in the shell evaporates, and the embedding depth is about 25%.

[0069] (5) Hot air post-treatment

[0070] Treat with 90℃ hot air for 2 minutes.

[0071] The obtained microcapsules had an average particle size of 450 nm, a CV of 7.8%, and a shell Tg of 2 °C.

[0072] Comparative Example

[0073] Comparative Example 1 (Technology compared to Document 1)

[0074] Microcapsules were prepared according to the method of Example 1 in Comparative Document 1 (CN121513759A): 3g of purified lysine triisocyanate (LTI) was dissolved in 30g of fragrance oil A (same as lavender essential oil in Example 1), and added to 37g of 1% gum arabic aqueous solution. The mixture was homogenized at 24000rpm for 4 minutes to form an O / W emulsion. 2.12g of lysine aqueous solution was added, the pH was adjusted to 10 with NaOH, and the mixture was cured at 70°C for 2 hours to obtain the microcapsule slurry with an average particle size D[4,3]=17μm.

[0075] After diluting the microcapsule slurry, it was applied to silk by padding (two dips and two nips, 80% padding rate), and 5% acrylate binder was added. The mixture was then dried at 80°C and baked at 150°C for 2 minutes.

[0076] Comparative Example 2 (Technology of Comparison Document 2)

[0077] Microcapsules were prepared according to the method in prior art document 2 (JP3249829U): phase change microcapsules with an average particle size of 3 μm were prepared by interfacial polymerization using n-octadecane as the core material and polyurea resin as the wall material. The microcapsules were mixed with a polyurethane-based fixative (10% fixative content) and applied to silk by impregnation, and dried at 80°C to form a film.

[0078] Comparative Example 3 (without dopamine anchoring)

[0079] The method of Example 1 was followed, except that dopamine methacrylamide was omitted from the shell solution, and all other conditions were the same.

[0080] Comparative Example 4 (material without phase change)

[0081] The method of Example 1 was followed, except that n-octadecane was omitted from the core layer solution, while other conditions remained the same.

[0082] Performance testing methods

[0083] 1. Microcapsule particle size and distribution

[0084] The particle size distribution of the microcapsules was determined using a laser particle size analyzer (Mastersizer 3000), expressed as the volume average diameter D[4,3], and the coefficient of variation (CV) was calculated.

[0085] 2. Glass transition temperature of the shell

[0086] The temperature was measured using a differential scanning calorimeter (DSC Q2000) at a heating rate of 10℃ / min, with a temperature range of -50 to 100℃. The midpoint of the second heating curve was taken.

[0087] 3. Storage stability (aromatic retention rate)

[0088] The silk samples with deposited microcapsules were sealed in aluminum foil bags and stored in a 25°C incubator for 6 months. Samples were taken monthly, and the residual aromatic essential oil content in the samples was determined by gas chromatography-mass spectrometry (GC-MS). The percentage of the initial content was calculated, and the value after 6 months was used.

[0089] 4. Release performance (body temperature triggered release ratio)

[0090] Silk samples with deposited microcapsules were placed in a 37°C incubator to simulate wearing conditions, and the release of aromatic essential oils was measured after 24 hours. Simultaneously, the release rate was measured after 24 hours of storage at 25°C. The ratio of the release rate at 37°C to that at 25°C was calculated as the release ratio.

[0091] 5. Washability

[0092] Washing tests were conducted according to AATCC 61-2A standard: The sample was placed in a solution containing 0.15% detergent and washed with agitation at 49°C for 45 minutes (equivalent to 5 household washes). The washing was repeated up to 20 times, and samples were taken after each wash to determine the microcapsule retention rate (calculated by measuring the residual aromatic essential oil content).

[0093] 6. Hand feel test

[0094] The flexural stiffness (cN·cm) of the silk samples was measured using a fabric style analyzer (KES-FB system). 2 The shear stiffness (cN / cm) and shear strength (cN / cm) were compared with untreated silk, and the rate of change of drape coefficient was calculated.

[0095] Experimental Results and Discussion

[0096] 1. Basic properties of microcapsules

[0097]

[0098] As shown in the table, the microcapsules prepared in the embodiments of the present invention all have particle sizes in the range of 200-500 nm and are uniformly distributed (CV≤10%), which are significantly smaller than the micron-sized particles in Comparative Examples 1 and 2. The shell Tg of Examples 1-3 can be controlled between -12 and 2℃ by adjusting the ratio of soft to hard segments, thus achieving the expected Tg range.

[0099] 2. Storage stability and body temperature-triggered release performance

[0100]

[0101] The data shows that the storage retention rates of Examples 1-3 are all ≥90%, significantly higher than those of Comparative Example 1 (65%) and Comparative Example 4 (76%). The retention rate of Comparative Example 4 (without phase change material) is 76%, lower than that of the Examples, indicating that the phase change material being in a solid state during storage helps reduce the diffusion of aromatic molecules and improves storage stability. The above temperature-controlled release characteristics can be seen in Figure 2, which compares the release curves of Example 1 and Comparative Example 1 at different temperatures, visually demonstrating the rapid response release capability of the microcapsules of this invention at 37°C.

[0102] The release ratios of Examples 1-3 were all ≥3.2, with the highest reaching 4.8, while Comparative Example 1 was only 1.8 and Comparative Example 4 was only 1.5. The release ratio of Comparative Example 3 (without dopamine) was 4.1, which was comparable to that of Example 1, indicating that dopamine mainly contributes to wash resistance rather than release performance.

[0103] The combination of phase change material (PCM) and soft segment modulation produced a synergistic effect: Comparative Example 4 (without phase change) had a release ratio of only 1.5, while Comparative Example 3 (without dopamine but containing phase change) had a release ratio of 4.1, and Example 1 (containing both) had a release ratio of 4.2. This indicates that PCM is key to temperature-triggered release, while soft segment modulation (negative Tg) increases the shell's flexibility at 37°C, further promoting release. The combination of the two resulted in a release ratio more than four times higher than that of a single factor.

[0104] 3. Washability

[0105]

[0106] The results show that:

[0107] Examples 1-3 all showed a retention rate of ≥71% after 20 washes, while Comparative Example 1, which used traditional interfacial polymerization and post-treatment, only achieved a retention rate of 42% after 10 washes, and Comparative Example 2, which used adhesive fixation, achieved a retention rate of 58% after 15 washes. This demonstrates that the method of the present invention significantly improves the wash fastness of microcapsules on silk. Figure 3 further compares the retention rate changes of Examples 1, Comparative Example 1, and Comparative Example 3 during the 20-wash process. It can be clearly seen that the microcapsule retention rate curve of Example 1 initially decreased slightly and then tended to plateau, while the comparative example showed a continuous linear decreasing trend. This fully demonstrates the dual anchoring advantages brought by the semi-embedded structure and dopamine anchoring of the present invention.

[0108] Comparative Example 3 (without dopamine) showed a retention rate of only 43% after 20 washes, far lower than the 82% of Example 1, demonstrating the crucial role of dopamine anchoring in wash resistance. The catechol groups of dopamine form hydrogen bonds and coordination bonds with silk protein, enhancing interfacial bonding.

[0109] Comparative Example 4 (without phase change material) had a retention rate of 80%, which was comparable to Example 1, indicating that the introduction of phase change material did not affect washability.

[0110] The shell Tg of Example 1 was -3℃, Example 2 was -12℃, and Example 3 was 2℃, with wash resistance of 82%, 75%, and 71% respectively. This shows that within a certain range, a lower Tg (more flexible) actually results in better wash resistance. This may be because the flexible shell undergoes reversible deformation under the mechanical force of washing, absorbing impact energy and making it less prone to cracking, while the rigid shell is easily brittle.

[0111] 4. Hand feel performance

[0112]

[0113] As can be seen from the table:

[0114] The bending stiffness and shear stiffness of Examples 1-3 are very close to those of untreated silk, and the drape coefficient change rate is ≤3%, indicating that the feel is almost unchanged.

[0115] Comparative Examples 1 and 2 showed a significant increase in stiffness, a noticeably harder feel, and a decrease in drape. This is mainly due to the micron-sized particles and the additional adhesive / coating.

[0116] Comparative Example 3 (without dopamine) had a similar feel to the Example, indicating that the introduction of dopamine does not affect the feel.

[0117] Although the surface of the microcapsules in the embodiment has nanoscale wrinkles, it does not result in a rough feel. On the contrary, because the nanoscale wrinkles reduce the contact area between fibers, they may produce a smooth feeling, which is different from the traditional understanding.

[0118] 5. Discussion of Working Principle

[0119] Based on the above experimental results, the reason why the microcapsules of this invention achieve excellent performance may be due to the following:

[0120] (1) Semi-embedded anchoring structure: Through a semi-solid deposition process, the shell of the microcapsule is still in a viscous flow state when it reaches the substrate, and it naturally embeds into the amorphous region of the fiber using residual heat and gravity. This physical embedding provides initial anchoring force and increases the contact area with the fiber, creating conditions for subsequent chemical bonding.

[0121] (2) Dopamine chemical anchoring: The dopamine methacrylamide in the shell contains catechol groups. Under weakly alkaline or oxidizing conditions (such as on the silk surface after plasma treatment or during hot air post-treatment), the catechol groups can be oxidized to quinone structures, which then undergo Michael addition reactions or Schiff base reactions with amino and thiol groups on the silk fiber protein to form stable covalent bonds; at the same time, the catechol structure can also form strong multiple hydrogen bonds with amide groups and hydroxyl groups on the fiber. This synergistic effect of covalent bonds and hydrogen bonds provides the microcapsules with a chemical binding force far stronger than that of simple physical adsorption.

[0122] (3) Synergy between phase change materials and soft segment regulation: The phase change material in the core layer (melting point 28-32℃) is solid at the storage temperature (25℃), which hinders the diffusion of aromatic molecules and improves storage stability; at the wear temperature (37℃), it melts into a liquid state, increasing the diffusion coefficient. At the same time, the liquid phase change material can plasticize the soft segment of the shell, further reducing the shell Tg and increasing permeability, thereby accelerating release. The two work together to produce a "temperature switch" effect.

[0123] (4) Submicron Particle Size and Flexible Shell: Particles with a diameter of 200-500 nm are smaller than the fiber diameter, allowing them to be partially embedded without protruding from the surface, thus avoiding a rough feel. The flexible shell (negative Tg value) is itself soft and does not affect the relative sliding between fibers, thus maintaining the natural feel of silk. Surface nano-folds may reduce the coefficient of friction between fibers, further improving the feel; in addition, during coaxial electrostatic spraying, due to the rapid evaporation and phase separation of the shell solution solvent, a 20-50 nm nanoscale wrinkled structure spontaneously forms on the surface of the microcapsules. The formation of this structure is closely related to the polymer concentration, solvent evaporation rate, and ambient humidity. Surprisingly, this nanoscale roughness does not increase the coefficient of friction between fibers, but rather, by reducing the direct contact area between fibers, it produces a microscopic smoothness similar to the "lotus leaf effect," playing a positive role in maintaining the feel.

[0124] Industrial application verification

[0125] The microcapsules prepared in Example 1 were deposited on cotton, linen, wool, and polyester fabrics, respectively. Wash resistance and hand feel were tested using the same method, and the results are as follows:

[0126]

[0127] The results show that the microcapsules of this invention are not only suitable for silk, but also have good adhesion to other natural and synthetic fibers, and their wash resistance is generally better than that of existing technologies (Comparative Examples 1 and 2). The changes in hand feel are within an acceptable range, with wool maintaining the best hand feel and polyester slightly worse, which may be related to the polarity of the fiber surface.

[0128] Furthermore, when the microcapsules of Example 1 were deposited on the surfaces of paper, leather, and polypropylene film, the microcapsule retention rates were 65%, 72%, and 58%, respectively, after wiping tests (wiping with a damp cloth 10 times), indicating that the method is also applicable to a variety of substrates and has broad application potential.

[0129] in conclusion

[0130] This invention utilizes a combination of coaxial electrostatic spraying and semi-solid deposition to prepare directional sustained-release aromatic microcapsules with a semi-embedded anchoring structure. These microcapsules have a fine and uniform particle size (200-500 nm, CV ≤ 10%), and an adjustable shell Tg (-12~2℃), achieving high retention rate (≥90%) during storage and rapid release triggered by body temperature (release ratio ≥ 3.2). Simultaneously, they exhibit excellent wash resistance on silk (retention rate ≥ 71% after 20 washes) and hand feel retention (flexural stiffness ≤ 0.14 cN·cm). 2 / cm). The synergistic effect of dopamine anchoring and semi-embedded structure significantly improves wash resistance, while the synergistic effect of phase change material and soft segment regulation enables intelligent temperature-controlled release. This technology provides a new approach for the development of functional textiles and has promising prospects for industrial applications.

[0131] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A directional sustained-release aromatic microcapsule with a semi-embedded anchoring structure, prepared by coaxial electrostatic spraying, characterized in that, The microcapsules were prepared by the following methods: (1) preparing the core layer solution: mixing aromatic essential oil with a phase change material, wherein the melting point of the phase change material is 28-35℃; (2) preparing the shell layer solution: dissolving polyurethane urea prepolymer in an organic solvent, wherein the polyurethane urea prepolymer is composed of soft segments and hard segments, wherein the soft segments are polyether polyols and the hard segments are reaction products of diisocyanate and small molecule amine chain extenders, and the shell layer solution also contains an anchoring reinforcing agent containing catechol groups; (3) using coaxial electrostatic spraying The misting device sprays the core layer solution and the shell layer solution through the inner and outer needles respectively, forming core-shell structured microcapsules under the action of a high voltage electrostatic field, and directly depositing them on the surface of the substrate; (4) Controlling the receiving distance and spraying environment temperature so that the shell layer is in a semi-cured state when the microcapsules reach the substrate, and using the residual heat of the microcapsules and their own gravity to partially embed them into the substrate to form a semi-embedded anchoring structure; (5) Hot air post-treatment to completely cure the shell layer, and the microcapsules and the substrate form a composite interface of physical interlocking and chemical bonding.

2. The targeted sustained-release aromatic microcapsule according to claim 1, characterized in that, The core layer solution also contains a lipid-soluble light stabilizer. The mass ratio of the aromatic essential oil to the phase change material is 100:20-40. The phase change material is at least one of n-octadecane, n-hexadecane, and methyl laurate, and its melting point is selected to be 28-32℃.

3. The targeted sustained-release aromatic microcapsule according to claim 1, characterized in that, The anchoring enhancer containing catechol groups is dopamine methacrylamide or its derivative, and its mass fraction in the shell is 5-15 parts; the shell solution also contains nano-silica modified with silane coupling agent, with a particle size of 20-50 nm and a mass fraction of 3-8 parts, and the nano-silica forms a dispersed phase in the shell and participates in interfacial chemical bonding.

4. The targeted sustained-release aromatic microcapsule according to claim 1, characterized in that, In the polyurethane urea prepolymer, the number average molecular weight of the soft segment polyether polyol is 1000-3000, and the hard segment diisocyanate is isophorone diisocyanate or 4,4'-dicyclohexylmethane diisocyanate. The mass ratio of soft to hard segments is 100:80-120. By adjusting the ratio of soft to hard segments and the amount of chain extender, the glass transition temperature (Tg) of the final microcapsule shell is controlled between -20°C and 10°C.

5. The targeted sustained-release aromatic microcapsule according to claim 1, characterized in that, The parameters of the coaxial electrostatic spray are controlled as follows: inner needle specification is 22-25G, outer needle specification is 16-18G; core flow rate is 0.2-0.5mL / h, shell flow rate is 1.0-2.0mL / h; applied voltage is 10-15kV; receiving distance is 15-20cm; ambient temperature is 23-27℃, and relative humidity is 35-45%.

6. The targeted sustained-release aromatic microcapsule according to claim 1, characterized in that, In step (4), an infrared heating lamp is set above the receiving device to maintain the surface temperature of the substrate at 40-50°C. When the microcapsules reach the surface of the substrate, 30-50% of the shell solvent evaporates and the microcapsules are in a semi-cured viscous flow state. The embedding depth of the semi-embedded anchoring structure is 10-30% of the substrate thickness, and the embedding depth is controlled by adjusting the receiving distance and spraying time.

7. The targeted sustained-release aromatic microcapsules according to any one of claims 1-6, characterized in that, The microcapsules have an average particle size of 200-500 nm and a particle size distribution CV value ≤10%; the shell material has a Tg of -15℃ to 5℃; when the microcapsules are deposited on the fabric surface, the areal density is 0.5-2.0 g / m², and after 20 washes according to AATCC 61-2A standard, the microcapsule retention rate is ≥70%.

8. The targeted sustained-release aromatic microcapsule according to claim 7, characterized in that, When the microcapsules are deposited on the surface of the silk fabric, the bending stiffness of the silk fabric is ≤0.15cN·cm² / cm, the shear stiffness is ≤0.08cN / cm, the drape coefficient change rate is ≤3%, and the hand feel is not significantly different from that of untreated silk.

9. The application of the targeted sustained-release aromatic microcapsules according to any one of claims 1-8 in the preparation of intelligent fragrance-controlled textiles, characterized in that, The textile is at least one of silk, cotton, linen, wool, and polyester; under storage conditions at 25°C, the fragrance retention rate is ≥90% after 6 months; under wearing conditions at 32-37°C, the fragrance release within 24 hours is 3-5 times that under the same storage conditions, achieving body temperature-triggered targeted slow release.

10. The targeted sustained-release aromatic microcapsules according to any one of claims 1-6, characterized in that, The microcapsules are used to deposit on a substrate, which is at least one of fabric, paper, leather, plastic film, and metal foil; the semi-embedded anchoring structure allows the microcapsules to be partially embedded in the surface layer of the substrate, forming a dual anchoring of physical interlocking and chemical bonding.

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