Fragrant fiber and preparation method thereof

Abstract

The preparation method comprises the following steps: respectively preparing a core layer electrospinning solution and a shell layer electrospinning solution from a phase change copolymer and a SiO2-chitosan composite microcapsule, obtaining a core-shell structure fiber through a coaxial electrospinning technology, and carrying out heat setting at 60 DEG C to enhance the mechanical property and interface bonding force of the fiber. The obtained fiber is stored for 60 days at the temperature of 20-25 DEG C, and the aroma volatilization rate is lower than 10%; in an environment of 30-40 DEG C, the release rate exceeds 85% within 30 min; after being washed for 10 times according to the AATCC standard, the fragrance can still be kept not less than 70%; the breaking strength reaches 1.8-2.0 cN / dtex, the 5% weight loss temperature reaches 230-240 DEG C, and good washing resistance and heat resistance are shown. The equipment used in the method is of a general type in the market, the process parameters are controllable, industrial amplification is easy, and the method is suitable for the fields of clothes, home textiles, functional textiles and the like, and has the excellent performance of long-acting slow release, quick start and repeated washing stability.

Description

Technical Field

[0001] The present invention relates to fiber materials and their preparation technologies, and more specifically to a scented fiber and a preparation method thereof. Background Art

[0002] In recent years, integrating fragrance functions into textiles has become a research hotspot in the fields of clothing, home, and care. Traditional processes mostly involve directly mixing fragrances into the spinning solution or spraying and impregnating fabrics. These methods often release most of the fragrance in a short time but are difficult to maintain the fragrance experience for a long time; after washing several times, the fragrance almost disappears, disappointing consumers.

[0003] To solve this problem, scholars have tried to "wrap" the fragrance with microcapsules, using materials such as polyurea, chitosan, or silane coupling agents as the shell layer, which can indeed delay the diffusion of the fragrance. However, under conditions of high temperature, strong shear, or multiple washes, these shell layers will still break or leak, and the fragrance control effect is not stable.

[0004] At the same time, phase change materials (PCMs) have been favored in temperature-regulating clothing because they can absorb and release heat at different temperatures. The latest research shows that by leveraging the phase change characteristics of phase change copolymers between melting and solidification, the release of active substances in the fiber can be triggered - when the temperature rises, the phase change material softens and the fragrance diffusion accelerates; when the temperature drops, the fragrance is "locked" again. Unfortunately, there are almost no literatures integrating phase change materials and fragrance microcapsules into the same fiber at present. Once the two are simply mixed and used, problems such as poor compatibility and weak interfacial adhesion will be faced, making it difficult to achieve an ideal release curve.

[0005] At the preparation process level, coaxial electrospinning technology can form a clear core-shell structure inside the fiber, allowing microcapsules to be evenly distributed in the fiber core, and the shell layer material forms a protective layer outside, playing a secondary barrier role for the fragrance. However, in actual operation, there are many variables such as the formulations of the core layer solution and the shell layer solution, electrospinning parameters, and environmental temperature and humidity. If not controlled properly, problems such as fiber breakage, microcapsule agglomeration, or unstable electrospinning will occur, further affecting the final fragrance release and mechanical properties.

[0006] Therefore, there is an urgent need for a new method in this field: it can not only "safely" store the fragrance for a long time at normal temperature, but also quickly "wake up" when needed, and can withstand the tests of multiple washes and high-temperature post-treatment. At the same time, this method can be achieved on conventional industrial equipment such as electrospinning and heat setting, and has the characteristics of being scalable and easy to operate. Summary of the Invention

[0007] To solve the above problems, the present invention provides a fragrant fiber and a preparation method thereof. The fiber is prepared by coaxial electrospinning technology, with a core layer embedding fragrance microcapsules, and the shell layer material and the core layer material are tightly combined through a heat setting process, having excellent aroma slow-release performance, thermal stability, and wash resistance.

[0008] To achieve the above object, the present invention provides the following technical solutions, mainly including:

[0009] A fragrant fiber, prepared by coaxial electrospinning technology; consisting of a core layer and a shell layer;

[0010] The core layer is composed of poly(methyl methacrylate - glycolic acid) copolymer (phase change copolymer) with a melting point between 30°C and 40°C;

[0011] At least one fragrance microcapsule is embedded in the core layer, and the mass ratio of the essence to the phase change copolymer is between 1:2 and 1:5;

[0012] The shell layer is composed of a copolymer of polylactic acid and polycaprolactone, and the mass ratio of the two is between 3:1 and 1:1;

[0013] After the fiber is heat set at 60°C and 0.1 MPa for 30 minutes, the core layer and the shell layer are firmly combined;

[0014] The average diameter of the fiber is between 200 nm and 2 μm, and the diameter ratio of the core layer to the shell layer is between 1:1 and 1:3.

[0015] Further, the microcapsule shell material adopts a silica - chitosan composite shell layer formed by in - situ emulsion polymerization of phase change polymer powder and fragrance, and the thickness of the composite shell layer is between 50 nm and 200 nm.

[0016] Further, the solvent system used for coaxial electrospinning is a mixture of dichloromethane, tetrahydrofuran, and dioxane in a volume ratio of 1:1:1, the voltage is 15 kV to 25 kV, the core layer flow rate is between 0.2 mL / h and 0.5 mL / h, the shell layer flow rate is between 0.5 mL / h and 1.0 mL / h, the collection distance is between 12 cm and 18 cm, the experimental environment temperature is about 25°C, and the relative humidity is about 50%.

[0017] Further, the aroma volatilization rate does not exceed 10% after being sealed and stored at normal temperature (20°C to 25°C) for 60 days; the cumulative release rate is not less than 85% within the first 30 minutes at 35°C; and the aroma release performance of not less than 70% is still maintained after 10 times of household washing (water temperature 40°C, rotation speed 1000 rpm).

[0018] Furthermore, 5% to 20% of inorganic nano-reinforcing agents are additionally added to the microcapsules to enhance the mechanical strength and thermal stability of the microcapsules; antibacterial agents such as chitosan derivatives and silver nanoparticles or ultraviolet absorbers such as benzophenone derivatives can be optionally blended in the fibers to endow antibacterial or anti-ultraviolet functions.

[0019] Preparation method

[0020] The present invention also provides a preparation method for the above-mentioned fragrant fibers, comprising the following steps:

[0021] S1: Prepare the core layer solution, dissolve the phase change copolymer, fragrance and nano-reinforcing agent in a mixed solvent of dichloromethane, tetrahydrofuran and dioxane according to the mass ratios of 1:2 to 5:0.05 to 0.2 respectively, and ultrasonically disperse for 10 minutes;

[0022] S2: Prepare the shell layer solution, dissolve polylactic acid, polycaprolactone and optional additives in a mixed solvent of chloroform and dioxane according to the mass ratios of 3:1:0.1 respectively, and magnetically stir until uniform;

[0023] S3: Under the laboratory conditions of 25°C and a relative humidity of 50%, perform coaxial electrospinning at a voltage of 15 kV to 25 kV, with a core-shell flow rate ratio of 0.3:0.6 mL / h, a collection distance of 15 cm to 18 cm, and a rotation rate of the collection device of 500 to 1500 rpm;

[0024] S4: Heat-set the collected fibers at 60°C and 0.1 MPa for 30 minutes, and then slowly cool to room temperature to complete the setting process.

[0025] Preferably, the prepared core layer solution is refrigerated and stored at 0°C to 5°C for no more than 12 hours; the ratio of the inner diameter to the outer diameter of the nozzle is 0.3 mm to 0.8 mm; during the electrospinning process, negative pressure ventilation is performed on the laboratory, and the ventilation rate is 0.5 m / s to 1.0 m / s to improve the solvent evaporation efficiency.

[0026] Furthermore, the obtained fragrant fibers are blended with moisture-absorbing and sweat-wicking fibers or antibacterial fibers according to a mass ratio of 10% to 50%, and then woven by a conventional loom; after weaving, the fabric handle can be improved and the functional durability can be enhanced through low-temperature plasma modification or nano-filling finishing processes.

[0027] According to the above technical solutions, compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) Long-lasting and slow-release fragrance: Since the phase change copolymer is in a solid state at normal temperature and the SiO2–chitosan composite shell layer forms multiple barriers, the fragrance molecules are efficiently "sealed". After being stored at 20–25°C for 60 days, the fragrance volatilization rate is lower than 10%, which is significantly better than traditional pre-mixed or simple adsorption-type fragrant fibers.

[0029] (2) Quick start of fragrance: When the ambient temperature reaches the melting point range of the phase change copolymer (30–40 °C), the core layer material changes from solid state to weak gel state, promoting the rapid diffusion of the fragrance. The release rate can exceed 85% within 30 minutes in a 35 °C water bath, meeting the demand for an immediate fragrance experience.

[0030] (3) Excellent wash and wear durability: The composite shell structure penetrates and fuses with the matrix polymer interface during the fiber heat setting process, firmly embedding the microcapsules into the fibers. After washing 10 times according to the AATCC standard (40 °C, 1000 rpm), the fragrance retention can still be ≥70%. The overall performance is stable and reliable, suitable for multiple washes in household and industrial applications.

[0031] (4) High mechanical strength and flexibility: Through Instron 3365 tensile testing, the breaking strength is 1.8–2.0 cN / dtex, fully meeting the requirements of functional textiles for abrasion resistance and tensile strength. Moreover, the fiber web is loose and breathable, with a soft handfeel, taking into account both comfort and durability.

[0032] (5) Excellent thermal stability: The thermogravimetric analysis (TGA) results show that the 5% weight loss temperature of the fiber and the microcapsule shell layer can reach 230–240 °C, higher than the conventional textile finishing temperature, and can withstand post-finishing processes such as high-temperature dyeing and calendering without structural or fragrance loss.

[0033] (6) Controllable process parameters and easy to scale up: Key parameters such as core / shell flow rate, nozzle structure, collection distance, heat setting temperature and pressure have clear optimization ranges, and the operation is simple and clear; the equipment used is of general market models, and it is easy to scale up industrially in existing electrospinning and post-finishing production lines.

[0034] (7) Fragrance diversity and formula adjustability: By replacing the fragrance or adjusting the ratio of the phase change copolymer / microcapsule, fibers of various fragrances such as lemon, citrus, and lavender can be prepared; parameters such as shell thickness and phase change temperature can also be flexibly adjusted according to the application scenarios (such as clothing, home textiles, masks, etc.) to meet personalized needs.

[0035] (8) Environment-friendly and safe: The solvents used can be recycled, and the microcapsule shell layer and fiber matrix materials are all biodegradable or non-toxic polymers, without VOC or residual monomer release, meeting the environmental protection and safety standards of green textiles and functional clothing. Detailed implementation manners

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] Example 1:

[0038] In this embodiment, first, a polymethyl methacrylate-glycolic acid copolymer with a melting point of about 32–38 °C is selected as the phase change material, and it is co-dissolved with citral-type compound essence and SiO2 nano-reinforcing agent in a dichloromethane / tetrahydrofuran / dioxane (1:1:1 volume ratio) mixed solvent. After magnetic stirring for 30 minutes, aggregates are further eliminated by ultrasonic treatment to obtain a homogeneous and transparent core layer precursor solution. Meanwhile, polylactic acid and polycaprolactone are dissolved in chloroform / dioxane (1:1 volume ratio) at a mass ratio of 3:1 and an antibacterial chitosan derivative, and stirred until completely clear to obtain a shell layer solution.

[0039] To construct the spice microcapsules, the in-situ emulsion polymerization method is adopted: under the stirring conditions of 25 °C and 500 rpm, an aqueous solution containing 2% chitosan and a silicon tetrachloride precursor diluted with acetone are slowly added, and the reaction is terminated after two hours. The obtained reaction solution is centrifuged at 4000 rpm, washed three times with water and twice with ethanol, and then vacuum dried at 60 °C for 12 hours to finally obtain composite microcapsules with a shell layer thickness of about 120 nm and an average particle size of 120 ± 10 nm.

[0040] Next, the above microcapsules, phase change copolymer and nano-SiO2 reinforcing agent (5 wt%) are mixed to prepare a core layer electrospinning solution; the solution obtained by dissolving the PLA / PCL copolymer and chitosan derivative is used as the shell layer electrospinning solution. The two solutions are respectively loaded into the double-channel injection pump of a coaxial electrospinning machine and co-transported at a flow rate of 0.3 mL / h and 0.6 mL / h, and electrospun under a high voltage of 20 kV through a 0.3 / 0.8 mm inner:outer coaxial nozzle. The collection distance is set to 17 cm, the roller rotates at a speed of 1000 rpm, and a negative pressure of 0.8 m / s is maintained under laboratory ventilation conditions to ensure stable fiber formation.

[0041] The obtained fibers are slowly cooled after heat setting treatment at 60 °C and 0.1 MPa for 30 minutes. Their surfaces are smooth, the microcapsules are evenly distributed in the fiber core layer and are tightly combined with the shell layer material. Scanning electron microscope (SEM) observation shows that the fiber diameter is distributed in the range of 500–800 nm, and the microcapsule particles are dispersed without aggregation.

[0042] After preparation, as shown in Table 1, a systematic performance evaluation was conducted on the fragrance fiber. After storing it for 60 days under sealed conditions at 20–25 °C, the residual amount of the fragrance components in the fiber was determined by gas chromatography (GC). The results showed that the aroma volatilization rate was only 8.3%, far lower than that of traditional pre-mixed fibers. When the fiber was placed in a 35 °C constant temperature water bath for 30 minutes, real-time sampling analysis found that the cumulative release rate was as high as 87.0%, which could meet the user's demand for instantaneous fragrance experience. After simulating home laundering according to the AATCC standard (40 °C water bath, 1000 rpm circulation for 10 times), the remaining amount of the fragrance was still measured to be 72.0%, verifying the effectiveness of the microcapsule shell layer and heat setting process in protecting the fragrance.

[0043] Test items Test conditions Test results Aroma volatilization rate Stored sealed at 20–25°C for 60 days 8.3％ Cumulative release rate 35°C, 30 min 87.0％ Aroma retention rate Household washing (40°C, 10 times) 72.0％ Breaking strength Tensile rate 10 mm / min 1.8 cN / dtex Thermogravimetric temperature (5% weight loss) TGA, heating rate 10°C / min 230℃ Microcapsule pressure resistance 150°C, 0.1 MPa No obvious damage

[0044] Table 1

[0045] In the mechanical property test, using an Instron 3365 tensile testing machine at a rate of 10 mm / min, the fiber breaking strength reached 1.8 cN / dtex, fully meeting the mechanical requirements of functional textiles. Thermogravimetric analysis (TGA) showed that its 5% weight loss temperature was as high as 230 °C, indicating that the fiber and the microcapsule shell layer were still structurally stable at high temperatures; in the pressure resistance test under the conditions of 150 °C and 0.1 MPa for 10 minutes, no shell layer damage or cracks were observed by SEM, proving the excellent synergy of the nano-reinforcing agent and the composite shell layer structure.

[0046] Mechanistically, the present invention utilizes the phase change copolymer to transform from a solid state to a weak gel state when the temperature approaches the melting point, driving the rapid diffusion of the fragrance when needed; while the SiO2-chitosan composite shell layer forms a multi-layer barrier at room temperature, effectively inhibiting the escape of the fragrance; the heat setting process promotes the penetration of the core-shell interface and enhances the adhesion between the microcapsules and the matrix; the filling of nano-SiO2 further improves the overall mechanical strength and thermal stability.

[0047] In summary, through the fine design of the microcapsule preparation, electrospinning conditions, heat setting process, and extraction and testing methods, this embodiment has successfully achieved multiple functions of the fragrance fiber, such as "long-term slow release, rapid start, wash-resistant and heat-resistant", and the process parameters are controllable and repeatable. Those skilled in the art can make equivalent substitutions and industrial-scale amplifications of the present invention according to the above description and in combination with the actual equipment conditions.

[0048] Example 2:

[0049] In this example, we selected a citrus fresh-tone compound fragrance (mainly composed of limonene, butyl acetate, and several natural terpenes) as the fragrance core, and prepared microcapsules according to the in-situ emulsion polymerization method of Example 1. The specific operations are as follows:

[0050] Core material preparation: Weigh 12 g of phase change copolymer and 18 g of citrus essence. Add SiO2 nanoparticles (with a particle size of about 25 nm) to a solvent of dichloromethane / tetrahydrofuran / dioxane (1:1:1, volume ratio) at 2% of the total mass, stir for 30 minutes, and ultrasonically disperse for 15 minutes.

[0051] Shell polymerization: Under the conditions of 25 °C and 600 rpm, add 2% chitosan aqueous solution and 5% silicon tetrachloride / acetone solution dropwise to the above mixed solution, and react for 2.5 hours to obtain an emulsion system.

[0052] Drying and collection: After centrifuging at 4000 rpm for 12 minutes, wash three times alternately with pure water and ethanol, and vacuum dry at 60 °C for 14 hours to obtain citrus flavor microcapsules with a shell thickness of about 100 nm and an average particle size of 110 ± 8 nm (measured by SEM).

[0053] Subsequently, dissolve the newly prepared microcapsules (5 g), phase change copolymer (1.2 g), and SiO2 enhancer (0.15 g) in DCM / THF / DOL (100 mL) to obtain a core layer spinning solution; dissolve PLA / PCL (3:1) and chitosan derivative in CHCl3 / DOL (100 mL) to obtain a shell layer spinning solution. Using coaxial electrospinning conditions: inner diameter / outer diameter of the nozzle is 0.3 / 0.8 mm, core / shell flow rate is 0.35 / 0.65 mL / h, voltage is 21 kV, collection distance is 18 cm, roller speed is 1100 rpm, environment temperature is 25 °C, and humidity is 48%, to obtain a fiber web.

[0054] After the fiber is heat-set at 60 °C and 0.12 MPa for 30 minutes and cooled slowly, its surface is smooth, the diameter is distributed between 550 - 700 nm, and the microcapsules are evenly embedded in the core layer. We tested its aroma release and physical properties, and the results are shown in Table 2.

[0055]

[0056] Table 2

[0057] From the above data, it can be seen that the citrus flavor fiber prepared in this example has a lower normal temperature volatilization rate (6.7%) and a higher rapid start release efficiency (91.2%) compared with the previous example, while maintaining excellent wash resistance and mechanical and thermal stability. Especially after increasing the heat-setting pressure and temperature, the mechanical strength of the fiber is slightly improved (2.0 vs. 1.8 cN / dtex), and the thermal weight loss temperature reaches 240 °C, which is more suitable for high-temperature finishing processes.

[0058] In summary, through the optimization of the microcapsule shell thickness and the core / shell ratio, as well as the fine-tuning of the spinning and heat setting parameters, the performance balance of "low volatility, high release, and wash- and heat-resistant" can be achieved in fibers of different fragrance types. Those skilled in the art can scale up the production of this embodiment or make further improvements based on the reference values provided in Table 2 and the aforementioned operation details.

[0059] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A scented fiber prepared by coaxial electrospinning technology; consisting of a core layer and a shell layer; characterized in that: The core layer is composed of polymethyl methacrylate-hydroxyacetic acid copolymer with a melting point of 30°C to 40°C; at least one flavor microcapsule is embedded in the core layer, and the mass ratio of the flavor to the phase change copolymer is between 1:2 and 1:5; the shell layer is composed of polylactic acid and polycaprolactone copolymer, and the mass ratio of the two is between 3:1 and 1:1; after heat setting at 60°C and 0.1 MPa for 30 minutes, the core layer and the shell layer are firmly combined; the average fiber diameter is between 200 nanometers and 2 microns, and the ratio of the core layer to the shell layer diameter is between 1:1 and 1:

3.

2. The scented fiber according to claim 1, characterized in that: The microcapsule shell material adopts a silicon dioxide-chitosan composite shell layer formed by in-situ emulsion polymerization of phase change polymer powder and fragrance, and the thickness of the composite shell layer is between 50 nanometers and 200 nanometers.

3. The scented fiber according to claim 1 or 2, characterized in that: The solvent system used for coaxial electrospinning is a mixture of dichloromethane, tetrahydrofuran and dioxane in a volume ratio of 1:1:1, the voltage is 15 kV to 25 kV, the core layer flow rate is between 0.2 ml per hour and 0.5 ml per hour, the shell layer flow rate is between 0.5 ml per hour and 1.0 ml per hour, the collection distance is between 12 cm and 18 cm, the experimental environment temperature is about 25°C, and the relative humidity is about 50%.

4. The scented fiber according to any one of claims 1 to 3, characterized in that: After being sealed and stored at room temperature of 20℃ to 25℃ for 60 days, the aroma volatilization rate does not exceed 10%; the cumulative release rate within the first 30 minutes at 35℃ is not less than 85%; after 10 home washings (water temperature 40℃, rotation speed 1000 revolutions per minute), the aroma release performance is still maintained at not less than 70%.

5. The scented fiber according to any one of claims 1 to 3, characterized in that: An additional 5% to 20% inorganic nano-reinforcement agent is added to the microcapsule to improve the mechanical strength and thermal stability of the microcapsule; chitosan derivatives, silver nanoparticles and other antibacterial agents or benzophenone derivative UV absorbers can be optionally blended into the fiber to impart antibacterial or anti-UV functions.

6. A method for preparing a scented fiber, characterized in that: The following steps are involved: S1: preparing a core layer solution, dissolving the phase change polymer, the fragrance and the nano-enhancer in a mixed solvent of dichloromethane, tetrahydrofuran and dioxane in a mass ratio of 1:2 to 5:0.05 to 0.2, respectively, and performing ultrasonic dispersion for 10 minutes; S2: preparing a shell solution, dissolving polylactic acid, polycaprolactone and optional additives in a mixed solvent of chloroform and dioxane in a mass ratio of 3:1:0.1, respectively, and stirring magnetically until uniform; S3: Coaxial electrospinning was performed at 15 kV to 25 kV, core-to-shell flow ratio of 0.3:0.6 ml / h, collection distance of 15 cm to 18 cm, and collection device rotation rate of 500 to 1500 rpm under laboratory conditions at 25 °C and 50% relative humidity; S4: The collected fibers are heat-set at 60° C. and 0.1 MPa for 30 minutes, and then slowly cooled to room temperature to complete the setting process.

7. The method according to claim 6, characterized in that: The prepared core layer solution is refrigerated and stored at 0°C to 5°C for no more than 12 hours; the ratio of the inner diameter to the outer diameter of the nozzle is 0.3 mm to 0.8 mm; during the electrospinning process, the laboratory is subjected to negative pressure ventilation with a ventilation rate of 0.5 m / s to 1.0 m / s to improve the solvent evaporation efficiency.

8. The method according to claim 6 or 7, characterized in that: The scented fiber is blended with moisture wicking fiber or antibacterial fiber at a mass ratio of 10% to 50%, and then woven on a conventional loom; after weaving, the fabric can be modified by low-temperature plasma or nano-filling finishing process to improve the fabric feel and enhance the durability of its function.

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