Preprocessing process for low-temperature cocoon unwinding

Abstract

The application relates to the technical field of biological silk production, and specifically discloses a cocoon low-temperature thread-removing pretreatment process, which comprises the following steps: preparing a nanocomposite with a core-shell structure; dispersing the nanocomposite in water to obtain a pretreatment liquid; immersing cocoon in the pretreatment liquid to remove the nanocomposite floating on the surface and form cocoon objects; irradiating the cocoon objects with near-infrared light to make the temperature-sensitive phase change material layer melt and release low-temperature active protease, and obtain pretreated cocoon; and putting the pretreated cocoon into clean water with a temperature of 38-42 DEG C to remove the thread. The nanocomposite with the core-shell structure is loaded into the cocoon through negative pressure penetration and is differentially distributed by using the structural differences of different parts of the cocoon layer. After being heated to the melting point of the temperature-sensitive phase change material layer, the protease is triggered to be released in situ in the cocoon layer, and the effect that the treatment strength and the adhesion strength of the cocoon layer are automatically matched is achieved.

Description

Technical Field

[0001] This application relates to the field of bio-silk production technology, and more specifically, to a pretreatment process for low-temperature silkworm cocoon spinning. Background Technology

[0002] Silk thread pulling is a key process in silk reeling. Its purpose is to find and pull out the silk threads from the surface of the cocoon layer after boiling or removing the silk threads, laying the foundation for subsequent silk reeling processes. The effectiveness of silk thread pulling directly affects the yield, quality, and efficiency of raw silk reeling. Traditional silk thread pulling usually uses a high-temperature silk thread pulling method, placing the cocoon in hot water at near-boiling temperature. The high temperature causes the sericin on the surface of the cocoon layer to swell and dissolve, thereby reducing the adhesion between the cocoon threads and facilitating the pulling out of the silk threads.

[0003] With the development of silk reeling technology, an ultrasonic-assisted low-temperature silk-spinning process has emerged. This process introduces ultrasonic treatment before silk-spinning, utilizing the cavitation effect of ultrasound in liquids to microscopically impact the surface of the cocoon layer, causing the sericin layer to loosen or develop microcracks. However, in practical applications, the cavitation effect of ultrasound is unevenly distributed in the liquid, which can easily lead to differences in the treatment effect of cocoons at different locations within the cocoon cage. Summary of the Invention

[0004] To address the problem that existing low-temperature silkworm cocoon pretreatment methods often result in varying treatment effects for cocoons at different locations within the cocoon cage, this application provides a low-temperature silkworm cocoon pretreatment process.

[0005] This application provides a pretreatment process for low-temperature silkworm cocoon threading, which adopts the following technical solution: A pretreatment process for low-temperature silkworm cocoon threading includes the following steps: S1. Prepare a core-shell structured nanocomposite, the nanocomposite comprising a magnetic core, a photothermal conversion layer coated on the surface of the magnetic core, and a temperature-sensitive phase change material layer coated on the surface of the photothermal conversion layer, wherein the temperature-sensitive phase change material layer is loaded with a low-temperature active protease. S2. Disperse the nanocomposite in water to prepare a suspension with a mass concentration of 0.8-1.5 g / L, add a dispersant, and obtain a pretreated solution; S3. Immerse the silkworm cocoons in the pretreatment solution and maintain them under a vacuum of -0.06 to -0.08 MPa for 6-10 minutes. After releasing the vacuum, remove the silkworm cocoons and remove the nanocomposite material floating on the surface to form silkworm cocoon material. S4. Near-infrared light is used to irradiate the silkworm cocoons. During the irradiation process, the temperature of the main body of the pretreatment solution is controlled at 28-32℃, so that the nanocomposite trapped inside the silkworm cocoons is heated to 44-46℃ under the action of photothermal effect, so that the temperature-sensitive phase change material layer melts and releases low-temperature active protease, hydrolyzes the sericin of the cocoon layer, and obtains pretreated silkworm cocoons. S5. Immerse the pretreated silkworm cocoons in clean water at 38-42℃, supplemented with a frequency of 18-22kHz and a power density of 0.15-0.25W / cm³. 2 The ultrasound was used for tracing.

[0006] By adopting the above technical solution, a core-shell structured nanocomposite is used. It is loaded into the cocoon through negative pressure and differentiated by utilizing the structural differences in different parts of the cocoon layer. Then, near-infrared light irradiation generates heat in the photothermal conversion layer, raising the temperature to the melting point of the temperature-sensitive phase change material layer. This triggers the in-situ release of proteases inside the cocoon layer, hydrolyzing the sericin in different adhesion strength areas. Therefore, the effect of automatic matching between the treatment intensity and the cocoon layer adhesion strength is achieved. This solves the problem that existing low-temperature pretreatment of cocoons easily leads to differences in the treatment effect of cocoons in different locations within the cocoon cage.

[0007] Preferably, in step S1, the magnetic core is Fe3O4 magnetic nanoparticles with a particle size of 100-150 nm and a saturation magnetization of 60-80 emu / g.

[0008] By adopting the above technical solution and using Fe3O4 magnetic nanoparticles as the core, it is possible to ensure that the nanocomposite can smoothly enter the cocoon layer pores during the negative pressure permeation process, and also endow it with the characteristic of being efficiently recyclable under an external magnetic field.

[0009] Preferably, in step S1, the photothermal conversion layer is a polydopamine layer with a thickness of 15-25 nm, the temperature-sensitive phase change material layer is a lauric acid layer with a melting point of 44-46 °C, and the low-temperature active protease is Bacillus subtilis neutral protease.

[0010] By adopting the above technical solution, polydopamine is used as the photothermal conversion layer, which has high photothermal conversion efficiency in the near-infrared region and can generate sufficient temperature rise under low-power laser irradiation. Lauric acid is used as the temperature-sensitive phase change material layer, whose melting point matches the target temperature of photothermal heating, ensuring that the protease is released at the preset temperature. Bacillus subtilis neutral protease is used, which has the best activity in the range of 40-50℃.

[0011] Preferably, in step S1, the preparation of the core-shell structured nanocomposite includes the following steps: 4.5-5.5g of ferrous sulfate heptahydrate was dissolved in 60-80mL of ethylene glycol-water mixed solvent, and 5.0-6.0g of potassium hydroxide was added. After stirring and dissolving, the mixture was reacted at 180-200℃ for 8-12h. After cooling, the mixture was magnetically separated, washed, and dried to obtain Fe3O4 magnetic nanoparticles. The volume ratio of ethylene glycol to water was 65-75:25-35. Take 0.5-1.0g of the Fe3O4 magnetic nanoparticles, ultrasonically disperse them in 200-300mL of Tris buffer, add dopamine hydrochloride to a final concentration of 1.5-2.5mg / mL, stir at room temperature for 5-7h, magnetically separate, wash, and dry to obtain Fe3O4@PDA nanoparticles; Dissolve 0.8-1.2g of lauric acid in 15-25mL of anhydrous ethanol to form the oil phase. Dissolve Bacillus subtilis neutral protease in phosphate buffer to prepare an enzyme solution of 1.5-2.5mg / mL to form the aqueous phase. Mix the oil phase and the aqueous phase at a volume ratio of 3-5:1 and emulsify at 40-45℃ for 15-20min to form an emulsion. Add 0.4-0.6g of the Fe3O4@PDA nanoparticles to the emulsion, ultrasonically disperse for 5-10min, cool to 8-12℃ to solidify lauric acid, centrifuge, wash, and freeze-dry for 12-18h to obtain the Fe3O4@PDA@lauric acid@protease core-shell structured nanocomposite.

[0012] By adopting the above technical solution, Fe3O4 magnetic cores with uniform particle size are synthesized by solvothermal method, polydopamine photothermal layer with controllable thickness is formed by dopamine self-polymerization, and lauric acid phase change layer loaded with protease is coated on the surface of photothermal layer by emulsification-curing method. The two are matched to ensure that the core-shell structure of the nanocomposite is intact, the particle size is uniform and the performance is stable.

[0013] Preferably, in step S2, the dispersant is 0.04-0.06 wt% of a nonionic surfactant.

[0014] By adopting the above technical solution and using nonionic surfactants as dispersants, which have a moderate hydrophilic-lipophilic balance value, the nanocomposite can be effectively dispersed in water without affecting its surface properties and enzyme activity.

[0015] Preferably, in step S3, the removal of the surface-adhered nanocomposite is achieved by spraying the silkworm cocoon with clean water for 20-30 seconds and then draining it at room temperature for 10-15 minutes.

[0016] By adopting the above technical solution, the nanocomposite adhering to the surface is removed by spraying with clean water, which avoids unnecessary treatment of the outside of the cocoon layer by the nanocomposite that has not entered the cocoon layer during the subsequent photothermal activation stage. At the same time, room temperature draining can maintain the stability of the nanocomposite inside the cocoon layer.

[0017] Preferably, in step S4, irradiating the silkworm cocoons with near-infrared light includes the following steps: Near-infrared laser with a wavelength of 808 nm was used to irradiate silkworm cocoons, with a laser power density of 0.5-0.8 W / cm². 2The pulse mode is used, with a pulse duty cycle of 1:3-5 and a total irradiation time of 2-4 minutes. After an interval of 30-60 seconds, irradiation was performed using a near-infrared laser with a wavelength of 1064 nm and a laser power density of 0.1-0.2 W / cm². 2 The continuous irradiation mode is used, with a total irradiation time of 5-8 minutes.

[0018] By adopting the above technical solution and employing a dual-wavelength graded irradiation strategy, the 808nm short-wavelength laser is preferentially applied to the surface and shallow layers of the cocoon, and the pulse mode can avoid excessive heat accumulation and break down the stubborn sericin on the surface. After intermittent heat dissipation, the 1064nm long-wavelength laser is used, which has stronger penetrating power and can be applied to the deep layers of the cocoon, and the continuous mode ensures uniform weakening of the entire layer.

[0019] Preferably, in step S5, the searching time is 3-5 minutes.

[0020] By adopting the above technical solution, the threading time ensures that the thread is fully drawn out, while avoiding excessive dissolution of the weakened sericin or disorder of the cocoon thread due to excessive time.

[0021] Preferably, in step S5, after the search is completed, the wastewater is collected, a magnetic field of 0.2-0.3T is applied, and the nanocomposite in the wastewater is magnetically separated and recovered. After washing and adding fresh protease, it is recycled.

[0022] By adopting the above technical solution, the magnetic core of the nanocomposite is utilized to efficiently recover the detached nanocomposite from the wastewater by applying an external magnetic field after the sieving is completed. After simple regeneration treatment, it can be recycled.

[0023] Preferably, in step S5, during the search, a near-infrared laser with a wavelength of 800-820 nm is used for sustained irradiation, and the laser power density is 0.02-0.05 W / cm². 2 It adopts a continuous irradiation mode.

[0024] By adopting the above technical solution, low-power near-infrared sustained irradiation is used during the threading process to continuously activate the newly exposed sericin interface, prevent temporary secondary adhesion that may occur during the threading process, and ensure the smooth extraction of the thread.

[0025] In summary, this application has the following beneficial effects: 1. Because this application uses a core-shell structured nanocomposite, combined with negative pressure osmosis loading and multi-wavelength near-infrared graded activation, it achieves an adaptive match between the treatment intensity and the cocoon layer adhesion strength. During the negative pressure osmosis process, the denser the cocoon layer, the greater the amount of nanocomposite retained. When irradiated with near-infrared light, these parts generate higher photothermal temperatures due to the enrichment of nanocomposite, preferentially reaching the melting point of the phase change material and releasing proteases to hydrolyze sericin. Meanwhile, the parts with weak adhesion have less retention of nanocomposite, resulting in a smaller temperature rise and lower protease release. This forms a mechanism of on-demand treatment, making the degree of sericin weakening in different parts of the cocoon layer more consistent. This solves the problem that existing low-temperature cocoon pretreatment methods easily lead to differences in the treatment effect of cocoons in different locations within the cocoon cage.

[0026] 2. This application uses multi-wavelength pulsed near-infrared light for graded activation, combined with the precise hydrolysis of low-temperature active protease, to lower the weaving temperature. The 808nm short-wavelength laser preferentially acts on the shallow layer of the cocoon, quickly breaking down the stubborn sericin on the surface. The 1064nm long-wavelength laser penetrates to the deep layer of the cocoon, achieving uniform weakening across the entire layer. The dual-wavelength irradiation, combined with the threshold release characteristics of the temperature-sensitive phase change material, ensures that the protease is released in situ only inside the cocoon layer, avoiding excessive sericin loss. The pretreated cocoons obtained in this way can complete weaving under low-temperature conditions, improving the unwinding rate while reducing heating energy consumption.

[0027] 3. This application constructs a nanocomposite with a Fe3O4 magnetic core and applies a magnetic field after sorting to perform magnetic separation and recovery, thereby realizing the recycling of nanoenzymes. The magnetic core-shell structure endows the nanocomposite with excellent magnetic response performance, allowing it to be adsorbed and recovered under a magnetic field of 0.2-0.3T. After simple cleaning and replenishment with fresh protease, it can be reused. This not only reduces the cost of using nanomaterials but also avoids the environmental risks caused by nanomaterials entering wastewater, making this pretreatment process have good sustainability and economic applicability. Attached Figure Description

[0028] Figure 1 This is a flowchart of a pretreatment process for low-temperature silkworm cocoon sewing provided in this application. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] Technical concept: In the silk production process, the density of the cocoon layer varies in different parts of the cocoon, resulting in uneven distribution of its adhesive strength. The existing ultrasonic-assisted low-temperature unwinding process lacks selectivity in the physical action of ultrasound, making it difficult to adapt to the differences in adhesive strength of the cocoon layer itself. Parts with strong adhesive strength may be under-treated while parts with weak adhesive strength may be over-treated, which is the root cause of the unstable unwinding effect.

[0031] Based on this, this application constructs a core-shell structured nanocomposite with a magnetic core, a photothermal conversion layer, and a temperature-sensitive phase change material layer, and loads a low-temperature active protease into the composite. Under near-infrared light irradiation, the nanocomposite with higher enrichment generates a higher photothermal temperature, preferentially reaching the melting point of the phase change material and releasing the protease to hydrolyze the sericin; while the less enriched parts have a smaller temperature rise and a lower protease release, thus solving the problem of uneven processing caused by the lack of selectivity in existing processes.

[0032] Unless otherwise specified, all experimental methods used below are conventional methods. All materials, reagents, methods, and instruments used, unless otherwise specified, are conventional materials, reagents, methods, and instruments in this field, which can be obtained commercially or prepared according to literature methods by those skilled in the art.

[0033] Preparation Example 1: Preparation of Fe3O4 Magnetic Nanoparticles Dissolve 5g of ferrous sulfate heptahydrate in 70mL of ethylene glycol-water mixed solvent, with a volume ratio of ethylene glycol to water of 70:30. Add 5.5g of potassium hydroxide and stir magnetically for 30min until completely dissolved. The mixed solution was transferred to a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted at 190 °C for 10 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The black precipitate was separated by a magnet and washed five times each with deionized water and anhydrous ethanol. The precipitate was then dried in a vacuum drying oven at 60°C for 12 hours to obtain Fe3O4 magnetic nanoparticles.

[0034] Preparation Example 2: Preparation of Fe3O4@PDA Core-Shell Structured Nanoparticles Take 0.75 g of Fe3O4 magnetic nanoparticles obtained in Preparation Example 1 and disperse them ultrasonically in 250 mL of Tris buffer. Add dopamine hydrochloride to a final concentration of 2 mg / mL and stir magnetically at room temperature for 6 h. After the reaction was completed, the product was separated by a magnet, washed five times with deionized water to remove unreacted dopamine, and the obtained Fe3O4@PDA nanoparticles were vacuum dried at 50℃ for 10 h.

[0035] Preparation Example 3: Preparation of Fe3O4@PDA@lauric acid@protease core-shell structured nanocomposites Dissolve 1g of lauric acid in 20mL of anhydrous ethanol to prepare the oil phase; The neutral protease of Bacillus subtilis was dissolved in phosphate buffer to prepare an enzyme solution of 2 mg / mL as the aqueous phase; The oil phase and the water phase were mixed at a volume ratio of 4:1 and emulsified in a water bath at 42.5℃ at 900 rpm for 17.5 min to form a water-in-oil emulsion. Add 0.5g of Fe3O4@PDA nanoparticles obtained in Preparation Example 2 to the emulsion and ultrasonically disperse for 7.5min; The system is then slowly cooled to 10°C to allow lauric acid to solidify on the surface of the nanoparticles and form a coating layer. The product was centrifuged at 9000 rpm for 9 min, washed three times with anhydrous ethanol, and freeze-dried for 15 h to obtain a Fe3O4@PDA@lauric acid@protease core-shell structured nanocomposite.

[0036] Preparation Example 4: Preparation of Palmitic Acid Phase Change Material Nanocomposites Dissolve 1g of palmitic acid in 20mL of anhydrous ethanol to form the oil phase; The neutral protease of Bacillus subtilis was dissolved in phosphate buffer to prepare an enzyme solution of 2 mg / mL as the aqueous phase; The oil phase and the water phase were mixed at a volume ratio of 4:1 and emulsified in a water bath at 62.5℃ at 900 rpm for 17.5 min to form an emulsion. Add 0.5g of Fe3O4@PDA nanoparticles obtained in Preparation Example 2 to the emulsion, disperse ultrasonically for 7.5min, and cool to 17.5℃ to solidify palmitic acid; Centrifugation, washing, and freeze-drying for 15 hours yielded a palmitic acid phase change material-coated nanocomposite.

[0037] Preparation Example 5: Preparation of Nanocomposites Without Phase Change Layers 0.5 g of Fe3O4@PDA nanoparticles obtained in Preparation Example 2 were added to 20 mL of Bacillus subtilis neutral protease solution with a concentration of 2 mg / mL, and allowed to stand for 12 h at 4 °C for adsorption. Centrifugation was performed, followed by washing three times with phosphate buffer and freeze-drying for 15 hours to obtain a nanocomposite without a phase change layer.

[0038] Preparation Example 6: Preparation of Non-Magnetic Core Nanocomposites Polydopamine nanospheres with a particle size of 120 nm were prepared according to the method described in the literature. Take 0.5g of polydopamine nanospheres, coat them with a lauric acid phase transition layer and load them with protease in the same manner as in Preparation Example 3, to obtain a nanocomposite with a non-magnetic core.

[0039] To better understand the above technical solutions, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments.

[0040] The following is a further description with reference to the embodiments: Example 1: Please refer to the appendix Figure 1 A pretreatment process for low-temperature silkworm cocoon threading includes the following steps: S1. Prepare a core-shell structured nanocomposite, which includes a magnetic core, a photothermal conversion layer coated on the surface of the magnetic core, and a temperature-sensitive phase change material layer coated on the surface of the photothermal conversion layer, wherein the temperature-sensitive phase change material layer is loaded with a low-temperature active protease. S2. Disperse the nanocomposite in water to prepare a suspension with a mass concentration of 1.15 g / L, add a dispersant to obtain a pretreated solution; S3. Immerse the silkworm cocoons in the pretreatment solution and maintain them under a vacuum of -0.07MPa for 8 minutes. After releasing the vacuum, remove the silkworm cocoons and remove the nanocomposite material floating on the surface to form silkworm cocoon material. S4. Near-infrared light is used to irradiate the silkworm cocoons. During the irradiation process, the temperature of the pretreatment liquid is controlled at 30°C. The nanocomposite trapped inside the silkworm cocoons is heated to 45°C under photothermal action, causing the temperature-sensitive phase change material layer to melt and release low-temperature active protease, which hydrolyzes the sericin of the cocoon layer to obtain pretreated silkworm cocoons. S5. Immerse the pretreated silkworm cocoons in clean water at 38-42℃, supplemented with a frequency of 20kHz and a power density of 0.2W / cm³. 2 The ultrasound was used for tracing.

[0041] In step S1, the magnetic core is Fe3O4 magnetic nanoparticles with a particle size of 125 nm and a saturation magnetization of 70 emu / g.

[0042] In step S1, the photothermal conversion layer is a polydopamine layer with a thickness of 20 nm, the thermosensitive phase change material layer is a lauric acid layer with a melting point of 45 °C, and the low-temperature active protease is Bacillus subtilis neutral protease.

[0043] In step S1, the preparation of a core-shell structured nanocomposite includes the following steps: 5g of ferrous sulfate heptahydrate was dissolved in 70mL of ethylene glycol-water mixed solvent, 5.5g of potassium hydroxide was added, and after stirring and dissolving, the mixture was reacted at 190℃ for 10h. After cooling, the mixture was magnetically separated, washed, and dried to obtain Fe3O4 magnetic nanoparticles. The volume ratio of ethylene glycol to water was 70:30. 0.75 g of Fe3O4 magnetic nanoparticles were ultrasonically dispersed in 250 mL of Tris buffer, and dopamine hydrochloride was added to a final concentration of 2 mg / mL. The mixture was stirred at room temperature for 6 h, magnetically separated, washed, and dried to obtain Fe3O4@PDA nanoparticles. 1 g of lauric acid was dissolved in 20 mL of anhydrous ethanol to form the oil phase. Bacillus subtilis neutral protease was dissolved in phosphate buffer to prepare an enzyme solution of 2 mg / mL to form the aqueous phase. The oil phase and the aqueous phase were mixed at a volume ratio of 4:1 and emulsified at 42.5 °C for 17.5 min to form an emulsion. 0.5 g of Fe3O4@PDA nanoparticles were added to the emulsion, ultrasonically dispersed for 7.5 min, cooled to 10 °C to solidify lauric acid, centrifuged, washed, and freeze-dried for 15 h to obtain Fe3O4@PDA@lauric acid@protease core-shell structured nanocomposite.

[0044] In step S2, the dispersant is 0.05 wt% of a nonionic surfactant.

[0045] In step S3, the nanocomposite adhering to the surface is removed by spraying the silkworm cocoon with water for 25 seconds and then draining it at room temperature for 12.5 minutes.

[0046] In step S4, near-infrared light is used to irradiate the silkworm cocoons, including the following steps: Near-infrared laser with a wavelength of 808 nm was used to irradiate silkworm cocoons, with a laser power density of 0.65 W / cm². 2 The pulse mode was used with a pulse duty cycle of 1:4 and a total irradiation time of 3 minutes. After a 45-second interval, irradiation was performed using a near-infrared laser with a wavelength of 1064 nm and a laser power density of 0.15 W / cm². 2 The continuous irradiation mode was used, with a total irradiation time of 6.5 minutes.

[0047] In step S5, the search time is 4 minutes.

[0048] In step S5, after the search is completed, the wastewater is collected, and a magnetic field of 0.25T is applied to magnetically separate and recover the nanocomposite in the wastewater. After washing and adding fresh protease, it is recycled.

[0049] In step S5, during the search, a near-infrared laser with a wavelength of 810 nm is used for sustained irradiation, with a laser power density of 0.035 W / cm². 2 It adopts a continuous irradiation mode.

[0050] Example 2: This example differs from Example 1 above in that: A pretreatment process for low-temperature silkworm cocoon threading includes the following steps: S1. Prepare a core-shell structured nanocomposite, which includes a magnetic core, a photothermal conversion layer coated on the surface of the magnetic core, and a temperature-sensitive phase change material layer coated on the surface of the photothermal conversion layer, wherein the temperature-sensitive phase change material layer is loaded with a low-temperature active protease. S2. Disperse the nanocomposite in water to prepare a suspension with a mass concentration of 1.5 g / L, add a dispersant to obtain a pretreated solution; S3. Immerse the silkworm cocoons in the pretreatment solution and maintain them under a vacuum of -0.08MPa for 10 minutes. After releasing the vacuum, remove the silkworm cocoons and remove the nanocomposite material floating on the surface to form silkworm cocoon material. S4. Near-infrared light is used to irradiate the silkworm cocoons. During the irradiation process, the temperature of the pretreatment liquid is controlled at 32°C. The nanocomposite trapped inside the silkworm cocoons is heated to 46°C under photothermal action, causing the temperature-sensitive phase change material layer to melt and release low-temperature active protease, which hydrolyzes the sericin of the cocoon layer to obtain the pretreated silkworm cocoons. S5. Immerse the pretreated silkworm cocoons in clean water at 42℃, supplemented with a frequency of 22kHz and a power density of 0.25W / cm³. 2 The ultrasound was used for tracing.

[0051] Example 3: This example differs from Example 1 above in that: A pretreatment process for low-temperature silkworm cocoon threading includes the following steps: S1. Prepare a core-shell structured nanocomposite, which includes a magnetic core, a photothermal conversion layer coated on the surface of the magnetic core, and a temperature-sensitive phase change material layer coated on the surface of the photothermal conversion layer, wherein the temperature-sensitive phase change material layer is loaded with a low-temperature active protease. S2. Disperse the nanocomposite in water to prepare a suspension with a mass concentration of 0.8-1.5 g / L, add a dispersant to obtain a pretreated solution; S3. Immerse the silkworm cocoons in the pretreatment solution and maintain them under a vacuum of -0.06MPa for 6 minutes. After releasing the vacuum, remove the silkworm cocoons and remove the nanocomposite material floating on the surface to form silkworm cocoon material. S4. Near-infrared light is used to irradiate the silkworm cocoons. During the irradiation process, the temperature of the pretreatment liquid is controlled at 28°C. The nanocomposite trapped inside the silkworm cocoons is heated to 44°C under photothermal action, causing the temperature-sensitive phase change material layer to melt and release low-temperature active protease, which hydrolyzes the sericin of the cocoon layer to obtain pretreated silkworm cocoons. S5. Immerse the pretreated silkworm cocoons in clean water at 38℃, supplemented with a frequency of 18kHz and a power density of 0.15W / cm³. 2 The ultrasound was used for tracing.

[0052] Example 4: This example differs from Example 1 above in that: In step S1, palmitic acid is used instead of lauric acid in the temperature-sensitive phase change material layer. The melting point of palmitic acid is 63℃. During the preparation process, the emulsification temperature is adjusted to 62.5℃ and the cooling and curing temperature is adjusted to 17.5℃.

[0053] Example 5: This example differs from Example 1 above in that: In step S1, the low-temperature active protease is replaced by alkaline protease instead of Bacillus subtilis neutral protease. The concentration of the enzyme solution is still 2 mg / mL. The alkaline protease is derived from Bacillus licheniformis and has an enzyme activity of 200,000 U / g.

[0054] Example 6: This example differs from Example 1 above in that: In step S4, the pulse duty cycle is 1:5; After a 45-second interval, irradiation was performed using a near-infrared laser with a wavelength of 1064 nm and a laser power density of 0.15 W / cm². 2 The continuous irradiation mode was used, with a total irradiation time of 7 minutes.

[0055] Example 7: This example differs from Example 1 above in that: In step S2, sodium dodecyl sulfate is used as the dispersant instead of the nonionic surfactant, and the amount added is still 0.05 wt%.

[0056] Comparative Example 1: The silkworm cocoons were directly immersed in hot water at 95-100℃ for threading operation for 5 minutes.

[0057] Comparative Example 2: Silkworm cocoons were immersed in clean water and treated in an ultrasonic cleaner at a frequency of 20kHz and a power density of 0.2W / cm³. 2 The temperature was 30℃ for 15 minutes, and then the sample was transferred to 80℃ clean water for 4 minutes for tracing.

[0058] Comparative Example 3: This comparative example differs from Example 1 above in that: In step S1, when preparing the nanocomposite, there is no thermosensitive phase change material coating step. Instead, the Bacillus subtilis neutral protease is directly mixed with Fe3O4@PDA nanoparticles for adsorption. 0.5g of Fe3O4@PDA nanoparticles are added to 20mL of 2mg / mL protease solution, adsorbed at 4℃ for 12h, and then centrifuged and dried to obtain a nanocomposite without a phase change layer.

[0059] Comparative Example 4: This comparative example differs from Example 1 above in that: In step S1, when preparing the nanocomposite, there is no Fe3O4 core. Instead, 120nm polydopamine nanospheres are used directly as the core, coated with a photothermal conversion layer, and then coated with a lauric acid phase transition layer to load the protease.

[0060] Comparative Example 5: This comparative example differs from Example 1 above in that: In step S4, only 808nm near-infrared laser is used for irradiation, with a laser power density of 0.6W / cm². 2 Continuous irradiation mode, total irradiation time 10 min, no 1064nm irradiation.

[0061] Comparative Example 6: This comparative example differs from Example 1 above in that: In step S3, the vacuum level is maintained for 3 minutes.

[0062] Comparative Example 7: This comparative example differs from Example 1 above in that: In step S4, the silkworm cocoons are irradiated with a near-infrared laser with a wavelength of 808 nm and a laser power density of 1.2 W / cm². 2 ; After an interval of 30-60 seconds, irradiation was performed using a near-infrared laser with a wavelength of 1064 nm and a laser power density of 0.4 W / cm². 2 .

[0063] Performance testing: The performance of the pretreated silkworm cocoons prepared in Examples 1-7 and Comparative Examples 1-7 was tested according to the following methods: Unwinding rate: The unwinding rate of silkworm cocoons was determined according to the FZ / T 43001-2018 standard "Mulberry Silk Fabrics". 100 cocoons were tested in each group, and the average value was taken. Number of times of roughing per 10,000 meters: When reeling silk on an automatic silk reeling machine, record the number of times roughing occurs during the reeling of 10,000 meters of raw silk, and take the average of 3 tests; Raw silk cleanliness: The cleanliness of raw silk is determined according to GB / T 1798-2008 "Test Methods for Raw Silk". The higher the score, the better the quality of raw silk. Searching temperature: Records the actual water temperature inside the searching pot during the searching process; Nanozyme recovery rate: Weigh the nanocomposite recovered by magnetic separation in step S5, calculate the recovery rate as (recovered mass / initial input mass) × 100%, and take the average of 3 tests. Relative energy consumption: Taking the energy consumption of Comparative Example 1 as 100%, calculate the relative unit energy consumption of each process, mainly including heating energy consumption and ultrasonic / laser equipment energy consumption.

[0064] The test results are shown in Table 1.

[0065] Table 1

[0066] As can be seen from Examples 1 to 7 and Comparative Examples 1 to 7, and in conjunction with Table 1, this application achieves efficient silkworm cocoon reeling at extremely low temperatures by constructing a magnetic core-shell structured nanocomposite and combining it with a synergistic process of negative pressure permeation loading, multi-wavelength near-infrared hierarchical activation, and low-temperature ultrasonic reeling. Photothermal conversion causes the internal temperature of the nanocomposite to rise, triggering the melting of phase change materials and releasing proteases to hydrolyze sericin. At the same time, dual-wavelength irradiation ensures uniform weakening of the shallow and deep layers of the cocoon, thereby improving the unwinding rate and the cleanliness of the raw silk, and reducing the number of reeling cycles and energy consumption.

[0067] As can be seen from Example 1 and Comparative Example 2 and Table 1, the smart responsive nanocomposite used in this application can achieve low-temperature tethering. The composite achieves recyclability through a magnetic core, near-infrared response through a photothermal conversion layer, and programmed release of protease through a temperature-sensitive phase change material layer. In contrast, the ultrasound-assisted low-temperature process without this composite cannot achieve the same tethering effect under the same low-temperature conditions, and the tethering temperature still needs to be maintained at a higher level.

[0068] As can be seen from Example 1 and Comparative Example 3, and Table 1, the temperature-sensitive phase change material layer can control the release of protease. The phase change layer undergoes phase change melting at 44-46℃, allowing the protease to be released in situ inside the cocoon layer, achieving precise hydrolysis of sericin. In contrast, the direct adsorption structure lacking the phase change layer cannot effectively control the timing and location of protease release, resulting in a decrease in the relief effect.

[0069] As can be seen from Example 1 and Comparative Example 4, and Table 1, the magnetic core enables the recycling and reuse of nanozymes. The core endows the nanocomposite with magnetic response properties, enabling it to be efficiently recycled and regenerated by an external magnetic field after decanting. In contrast, the composite without a magnetic core, although having comparable decanting properties, cannot be recycled, resulting in material waste and potential environmental problems.

[0070] As can be seen from Example 1 and Comparative Example 5, and Table 1, dual-wavelength graded irradiation can achieve uniform activation of the cocoon layer at all depths. The 808nm short-wavelength laser preferentially acts on the shallow layer of the cocoon layer to quickly break down surface hard points, while the 1064nm long-wavelength laser penetrates to the deep layer to achieve uniform weakening of the entire layer. However, single-wavelength irradiation cannot take into account the treatment needs of both the shallow and deep layers, resulting in an uneven relief effect.

[0071] As can be seen from Example 1 and Comparative Example 6, and Table 1, negative pressure osmosis can ensure that the nanocomposite is effectively loaded inside the cocoon layer, allowing the pretreatment liquid to fully penetrate the pores of the cocoon layer and achieve the differentiated distribution of the nanocomposite.

[0072] As can be seen from Example 1 and Comparative Example 7, and Table 1, near-infrared laser can effectively release and maintain the activity of proteases, and can raise the temperature inside the cocoon layer to the melting point of the phase change material while avoiding thermal deactivation of the proteases.

[0073] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A pretreatment process for low-temperature silkworm cocoon spinning, characterized in that, Includes the following steps: S1. Prepare a core-shell structured nanocomposite, the nanocomposite comprising a magnetic core, a photothermal conversion layer coated on the surface of the magnetic core, and a temperature-sensitive phase change material layer coated on the surface of the photothermal conversion layer, wherein the temperature-sensitive phase change material layer is loaded with a low-temperature active protease. S2. Disperse the nanocomposite in water to prepare a suspension with a mass concentration of 0.8-1.5 g / L, add a dispersant, and obtain a pretreated solution; S3. Immerse the silkworm cocoons in the pretreatment solution and maintain them under a vacuum of -0.06 to -0.08 MPa for 6-10 minutes. After releasing the vacuum, remove the silkworm cocoons and remove the nanocomposite material floating on the surface to form silkworm cocoon material. S4. Near-infrared light is used to irradiate the silkworm cocoons. During the irradiation process, the temperature of the main body of the pretreatment solution is controlled at 28-32℃, so that the nanocomposite trapped inside the silkworm cocoons is heated to 44-46℃ under the action of photothermal effect, so that the temperature-sensitive phase change material layer melts and releases low-temperature active protease, hydrolyzes the sericin of the cocoon layer, and obtains pretreated silkworm cocoons. S5. Immerse the pretreated silkworm cocoons in clean water at 38-42℃, supplemented with a frequency of 18-22kHz and a power density of 0.15-0.25W / cm³. 2 The ultrasound was used for tracing.

2. The pretreatment process for low-temperature silkworm cocoon spinning according to claim 1, characterized in that: In step S1, the magnetic core is Fe3O4 magnetic nanoparticles with a particle size of 100-150 nm and a saturation magnetization of 60-80 emu / g.

3. The pretreatment process for low-temperature silkworm cocoon spinning according to claim 1, characterized in that: In step S1, the photothermal conversion layer is a polydopamine layer with a thickness of 15-25 nm, the thermosensitive phase change material layer is a lauric acid layer with a melting point of 44-46 °C, and the low-temperature active protease is Bacillus subtilis neutral protease.

4. The pretreatment process for low-temperature silkworm cocoon spinning according to claim 1, characterized in that: In step S1, the preparation of the core-shell structured nanocomposite includes the following steps: 4.5-5.5g of ferrous sulfate heptahydrate was dissolved in 60-80mL of ethylene glycol-water mixed solvent, and 5.0-6.0g of potassium hydroxide was added. After stirring and dissolving, the mixture was reacted at 180-200℃ for 8-12h. After cooling, the mixture was magnetically separated, washed, and dried to obtain Fe3O4 magnetic nanoparticles. The volume ratio of ethylene glycol to water was 65-75:25-35. Take 0.5-1.0g of the Fe3O4 magnetic nanoparticles, ultrasonically disperse them in 200-300mL of Tris buffer, add dopamine hydrochloride to a final concentration of 1.5-2.5mg / mL, stir at room temperature for 5-7h, magnetically separate, wash, and dry to obtain Fe3O4@PDA nanoparticles; Dissolve 0.8-1.2g of lauric acid in 15-25mL of anhydrous ethanol to form the oil phase. Dissolve Bacillus subtilis neutral protease in phosphate buffer to prepare an enzyme solution of 1.5-2.5mg / mL to form the aqueous phase. Mix the oil phase and the aqueous phase at a volume ratio of 3-5:1 and emulsify at 40-45℃ for 15-20min to form an emulsion. Add 0.4-0.6g of the Fe3O4@PDA nanoparticles to the emulsion, ultrasonically disperse for 5-10min, cool to 8-12℃ to solidify lauric acid, centrifuge, wash, and freeze-dry for 12-18h to obtain the Fe3O4@PDA@lauric acid@protease core-shell structured nanocomposite.

5. The pretreatment process for low-temperature silkworm cocoon spinning according to claim 1, characterized in that: In step S2, the dispersant is 0.04-0.06 wt% of a nonionic surfactant.

6. The pretreatment process for low-temperature silkworm cocoon spinning according to claim 1, characterized in that: In step S3, the removal of the surface-adhered nanocomposite involves spraying the silkworm cocoon with clean water for 20-30 seconds and then draining it at room temperature for 10-15 minutes.

7. The pretreatment process for low-temperature silkworm cocoon spinning according to claim 1, characterized in that: In step S4, irradiating the silkworm cocoons with near-infrared light includes the following steps: Near-infrared laser with a wavelength of 808 nm was used to irradiate silkworm cocoons, with a laser power density of 0.5-0.8 W / cm². 2 The pulse mode is used, with a pulse duty cycle of 1:3-5 and a total irradiation time of 2-4 minutes. After an interval of 30-60 seconds, irradiation was performed using a near-infrared laser with a wavelength of 1064 nm and a laser power density of 0.1-0.2 W / cm². 2 The continuous irradiation mode is used, with a total irradiation time of 5-8 minutes.

8. The pretreatment process for low-temperature silkworm cocoon spinning according to claim 1, characterized in that: In step S5, the searching time is 3-5 minutes.

9. The pretreatment process for low-temperature silkworm cocoon spinning according to claim 1, characterized in that: In step S5, after the search is completed, the wastewater is collected, and a magnetic field of 0.2-0.3T is applied to magnetically separate and recover the nanocomposite in the wastewater. After washing and adding fresh protease, it is recycled.

10. The pretreatment process for low-temperature silkworm cocoon spinning according to claim 1, characterized in that: In step S5, during the search, a near-infrared laser with a wavelength of 800-820 nm is used for sustained irradiation, with a laser power density of 0.02-0.05 W / cm². 2 It adopts a continuous illumination mode.

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