A process for extracting silk from silkworm cocoons at low temperature

Abstract

This invention relates to the field of silk processing technology and discloses a process for low-temperature extraction of silk from silkworm cocoons, comprising the following steps: S1, cocoon selection and pretreatment: screening the cocoons, then removing impurities, dust, and loose outer cocoon skin attached to the surface of the cocoons to obtain cocoons to be processed; S2, low-temperature vacuum impregnation: allowing the impregnation solution to fully penetrate into the interior of the cocoons to obtain impregnated cocoons; S3, low-temperature synergistic unwinding; S4, closed-loop tension-controlled low-temperature silk extraction; S5, low-temperature washing and gradient drying. By adopting a technical solution combining low-temperature vacuum impregnation and low-temperature synergistic unwinding, and using impregnation and unwinding solutions with specific components, the technical effect of fully impregnating and efficiently unwinding the cocoons without damaging the silk structure is achieved. Compared with the conventional impregnation or single unwinding techniques in the prior art, this solves the problems of insufficient cocoon impregnation, low unwinding efficiency, easy damage to the mechanical properties of silk, and unstable silk extraction process.

Description

Technical Field

[0001] This invention relates to the field of silk processing technology, specifically a process for extracting silk from silkworm cocoons at low temperature. Background Technology

[0002] Silk is a natural high-molecular fiber characterized by its softness, smoothness, breathability, skin-friendliness, and excellent mechanical properties. It is widely used in textiles, clothing, and medical fields, and its quality directly determines the grade and effectiveness of the final product. Silkworm cocoons are the main raw material for silk, and silk reeling is the core process for obtaining silk. The rationality of the silk reeling process not only affects the yield and quality of silk but also the integrity and utilization rate of silkworm pupae. Therefore, optimizing the silk reeling process has always been a key research focus in the field of silk processing.

[0003] Currently, most existing silkworm cocoon reeling processes use conventional soaking methods to pre-treat silkworm cocoons, or only use a single unwinding method to assist in reeling. There is a lack of coordinated design for the soaking and unwinding processes, and the composition of the soaking solution and unwinding solution is not reasonable enough. This often results in insufficient soaking of the cocoons, preventing the sericin inside the cocoon layer from softening evenly. Consequently, the efficiency of unwinding the cocoons is low, and problems such as damage to the mechanical properties of the silk, silk breakage, and instability in the subsequent silk reeling process are likely to occur. These issues seriously affect the quality of the finished silk products and the efficiency of silk reeling production, making it difficult to meet the production needs of high-quality silk. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a process for low-temperature extraction of silk from silkworm cocoons. This solves the problems of insufficient cocoon immersion and low unwinding efficiency caused by conventional immersion or single unwinding techniques, which can easily lead to damage to the mechanical properties of silk and instability in the extraction process.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a process for low-temperature extraction of silk from silkworm cocoons, comprising the following steps: S1. Cocoon selection and pretreatment: The cocoons are screened to remove damaged, moldy, insect-infested, and non-standard-sized cocoons, while keeping healthy and intact cocoons. Then, the impurities, dust, and loose outer cocoon skin attached to the surface of the cocoons are removed to obtain the cocoons to be processed. S2, Low-temperature vacuum impregnation: The silkworm cocoons to be treated obtained in S1 are placed in a low-temperature impregnation solution. The container containing the silkworm cocoons and the impregnation solution is vacuumed and the impregnation process is carried out under vacuum to allow the impregnation solution to fully penetrate into the silkworm cocoons, thus obtaining impregnated silkworm cocoons. S3, Low-temperature synergistic unwinding: The soaked cocoons obtained in S2 are transferred to the unwinding solution, and the cocoons are unwound by using a combination of ultrasound and weak electric field to obtain unwound cocoons. S4. Closed-loop tension-controlled low-temperature silk reeling: The unwound silkworm cocoons obtained in S3 are placed in a low-temperature environment for silk reeling. The tension of the silk is detected in real time during the silk reeling process. Based on the real-time tension feedback signal, the traction speed and the amount of silk reeling liquid spray are dynamically adjusted to obtain raw silk filaments. S5. Low-temperature washing and gradient drying: The raw silk filaments obtained in S4 are washed in low-temperature clean water. After washing, they are dehydrated to remove excess moisture from the surface of the filaments. Then, they are dried at low temperature using a gradient heating method to obtain the finished silk.

[0006] Preferably, in step S2, the temperature of the low-temperature impregnation liquid is 10–25°C, the pressure of vacuum impregnation is 0.02–0.08 MPa, and the vacuum impregnation time is 20–60 min.

[0007] Preferably, the low-temperature wetting solution includes a nonionic surfactant, a penetrant, and a pH buffer, wherein the concentration of the nonionic surfactant is 0.5–2 g / L, the concentration of the penetrant is 1–3 g / L, the concentration of the pH buffer is 0.1–0.5 g / L, and the pH of the low-temperature wetting solution is controlled at 6.5–8.0.

[0008] Preferably, the low-temperature wetting solution further includes a low-temperature protease, the concentration of which is 0.05–0.2 g / L.

[0009] Preferably, in step S3, the temperature of the relieving solution is ≤25℃, and the relieving treatment time is 10-30 min; The soothing solution is obtained by adding low-temperature protease to the low-temperature wetting solution, and the total concentration of low-temperature protease after the addition is 0.2-1 g / L.

[0010] Preferably, in step S3, the ultrasound operates in an intermittent mode, with a frequency of 20–60 kHz, a single ultrasound duration of 1–3 min, and a single pause duration of 30–60 s.

[0011] Preferably, in S3, the weak electric field is a DC weak electric field with an electric field strength of 3 to 10 V / cm, and the direction of the electric field is consistent with the radial direction of the silkworm cocoon.

[0012] Preferably, in step S4, the ambient temperature for low-temperature wire drawing is 15-30°C, and the wire drawing adopts a multi-stage differential traction method, with the traction speed of each stage increasing sequentially, and the difference between two adjacent traction speeds not exceeding 5 m / min. The first-level traction speed is 10–15 m / min, the second-level traction speed is 15–25 m / min, and the third-level traction speed is 25–30 m / min.

[0013] Preferably, in step S4, during the silk reeling process, silk reeling liquid is continuously sprayed onto the contact point between the silkworm cocoon and the silk thread, and the spraying volume of the silk reeling liquid is 5-20 mL / min. In the closed-loop tension control, a target tension range is preset. When the detected real-time tension is higher than the upper limit of the target range, the traction speed is reduced and the spray volume is increased. When the real-time tension is lower than the lower limit of the target range, increase the traction speed and reduce the spray volume.

[0014] Preferably, in step S5, the temperature of the clean water used for low-temperature cleaning is 10–25°C; The gradient drying process specifically involves drying at a lower temperature for a period of time, followed by drying at a slightly higher temperature, with the relative humidity remaining between 40% and 60% throughout the entire drying process. The lower temperature is 30-40℃, and the drying time is 30-60 minutes. The temperature should be slightly higher, around 40–50°C, and the drying time should be 20–40 minutes. Furthermore, the temperature does not exceed 30℃ throughout the entire process from S2 to S4, and the working fluid used in each process can be recycled after filtration.

[0015] This invention provides a process for low-temperature extraction of silk from silkworm cocoons. It has the following beneficial effects: 1. This invention adopts a technical solution that combines low-temperature vacuum impregnation with low-temperature synergistic unwinding, and uses impregnation and unwinding solutions with specific components to achieve the technical effect of fully impregnating silkworm cocoons, efficiently unwinding them, and not damaging the silk structure. Compared with conventional impregnation or single unwinding solutions in the prior art, this invention solves the problems of insufficient impregnation of silkworm cocoons, low unwinding efficiency, easy damage to the mechanical properties of silk, and instability in the silk reeling process.

[0016] 2. This invention adopts a low-temperature silk reeling technology with closed-loop tension control, combined with multi-stage differential traction and dynamic adjustment of the silk reeling liquid spray volume, achieving a stable silk reeling process and complete silk strip formation. Compared with the existing technology of silk reeling without tension control or with fixed parameters, this invention solves the problems of easy silk strip breakage and large tension fluctuations during the silk reeling process, which affect the quality of finished silk products and silk reeling efficiency.

[0017] 3. This invention adopts a full-process low-temperature synergistic technology solution, which includes cocoon pretreatment, low-temperature soaking, synergistic unwinding, tension-controlled silk reeling, and gradient drying. The working solution in each process can be recycled and reused, achieving the technical effects of high-quality silk formation, minimal damage to silkworm pupae, low production cost, and green environmental protection. Compared with the existing technology of high-temperature silk reeling or poor connection between the various links of the low-temperature process, this invention solves the problems of high temperature causing a decline in silk quality and severe damage to silkworm pupae, or poor overall performance of the low-temperature process, high production cost, and difficulty in large-scale promotion. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process steps for low-temperature extraction of silk from silkworm cocoons according to the present invention. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see the appendix Figure 1 This invention provides a process for low-temperature extraction of silk from silkworm cocoons, comprising the following steps: S1. Cocoon selection and pretreatment: The cocoons are screened to remove damaged, moldy, insect-infested, and non-standard-sized cocoons, while keeping healthy and intact cocoons. Then, the impurities, dust, and loose outer cocoon skin attached to the surface of the cocoons are removed to obtain the cocoons to be processed. Specifically, the screening process combines manual and mechanical methods. Manually removed obviously damaged or moldy cocoons, while mechanical screening uses a vibrating screen to select cocoons of the correct size. Surface impurities and loose cocoon shells are gently brushed away with a soft brush. The brushing force is controlled during the brushing process to avoid damaging the cocoon structure. After brushing, the surface dust is wiped dry with a clean soft cloth to ensure that there are no impurities remaining on the surface of the cocoons to be treated and that the cocoon layer is intact. This lays a good foundation for the subsequent low-temperature vacuum impregnation process, reduces the impact of impurities on the impregnation effect, and ensures the stability of the subsequent silk quality.

[0021] S2, Low-temperature vacuum impregnation: The silkworm cocoons to be treated obtained in S1 are placed in a low-temperature impregnation solution. The container containing the silkworm cocoons and the impregnation solution is vacuumed and the impregnation process is carried out under vacuum to allow the impregnation solution to fully penetrate into the silkworm cocoons, thus obtaining impregnated silkworm cocoons. The temperature of the low-temperature impregnation solution is 10–25℃, the pressure of vacuum impregnation is 0.02–0.08 MPa, and the vacuum impregnation time is 20–60 min.

[0022] The low-temperature wetting solution includes a nonionic surfactant, a penetrant, and a pH buffer. The concentration of the nonionic surfactant is 0.5–2 g / L, the concentration of the penetrant is 1–3 g / L, the concentration of the pH buffer is 0.1–0.5 g / L, and the pH of the low-temperature wetting solution is controlled at 6.5–8.0.

[0023] The cryogenic immersion solution also includes cryogenic protease, with a concentration of 0.05–0.2 g / L; Specifically, the solid-liquid ratio of the cocoons to be treated to the low-temperature wetting solution is controlled at 1:15 to 1:20. After being placed in the container, the cocoons are allowed to stand for 5 minutes to allow them to spread evenly and avoid stacking, which could lead to insufficient wetting in certain areas. During the vacuuming process, a gradient vacuum method is used, slowly reducing the pressure from atmospheric pressure to the target vacuum pressure at a rate of 0.01 MPa / min to prevent sudden pressure drops from damaging the cocoons. During the wetting process, the cocoons and wetting solution in the container are gently stirred every 15 minutes to ensure uniform wetting and to ensure that both the inner and outer layers of the cocoon can fully absorb the wetting solution, softening the sericin while preventing the cocoons from breaking. This provides a uniform and complete wetting process for the subsequent unwinding process, improving the unwinding efficiency.

[0024] S3, Low-temperature synergistic unwinding: The soaked cocoons obtained in S2 are transferred to the unwinding solution, and the cocoons are unwound by using a combination of ultrasound and weak electric field to obtain unwound cocoons. The temperature of the antiseptic solution is ≤25℃, and the antiseptic treatment time is 10~30min; The solution is obtained by adding low-temperature protease to the low-temperature wetting solution. After the addition, the total concentration of low-temperature protease is 0.2-1 g / L. The ultrasound uses an intermittent working mode, with a frequency of 20–60 kHz, a single ultrasound session lasting 1–3 minutes, and a single pause lasting 30–60 seconds. The weak electric field is a DC weak electric field with an electric field strength of 3 to 10 V / cm, and the direction of the electric field is consistent with the radial direction of the silkworm cocoon. Specifically, when transferring the soaked silkworm cocoons to the unwinding solution, a filter screen is used to gently scoop them up to avoid mechanical friction that could damage the cocoon layer. The unwinding container is made of insulating material, with electrode plates arranged parallel to each other on both sides of the container. The spacing between the electrode plates is adjusted according to the container size to ensure that the silkworm cocoons are in a uniform electric field. The distance between the probe of the ultrasonic device and the surface of the unwinding solution is controlled at 3-5 cm to avoid direct contact between the probe and the silkworm cocoons, which could cause damage. During intermittent ultrasonic treatment, the container is gently shaken simultaneously to promote the dissolution of sericin. This not only achieves efficient unwinding of the silkworm cocoons but also protects the cocoon layer and the inner pupa from damage, ensuring smooth silk extraction during the subsequent silk reeling process and reducing silk breakage.

[0025] S4. Closed-loop tension-controlled low-temperature silk reeling: The unwound silkworm cocoons obtained in S3 are placed in a low-temperature environment for silk reeling. The tension of the silk is detected in real time during the silk reeling process. Based on the real-time tension feedback signal, the traction speed and the amount of silk reeling liquid spray are dynamically adjusted to obtain raw silk filaments. The ambient temperature for low-temperature wire drawing is 15-30℃. The wire drawing adopts a multi-stage differential traction method, with the traction speed of each stage increasing sequentially, and the difference between the traction speeds of two adjacent stages not exceeding 5m / min. The first-level traction speed is 10–15 m / min, the second-level traction speed is 15–25 m / min, and the third-level traction speed is 25–30 m / min. During the silk reeling process, silk reeling solution is continuously sprayed onto the contact point between the silkworm cocoon and the silk thread, with a spraying rate of 5–20 mL / min. In closed-loop tension control, a target tension range is preset. When the detected real-time tension is higher than the upper limit of the target range, the traction speed is reduced and the spray volume is increased. When the real-time tension is lower than the lower limit of the target range, increase the traction speed and reduce the spray volume; Specifically, before silk reeling, the unwound silkworm cocoons are fixed on the reeling frame, and the position of the cocoon layer is adjusted to ensure smooth silk reeling and avoid cocoon entanglement. The tension sensor is fixed on the silk reeling path and linked in real time with the control system. The tension detection frequency is 1 time / second, the traction speed is adjusted within a range of 0.5 to 1 m / min, and the spray volume is adjusted within a range of 1 to 2 mL / min to ensure that the tension quickly returns to the target range. The reeling solution uses a dilution with the same composition as the low-temperature wetting solution to avoid residue on the silk surface, achieving a stable and controllable reeling process, ensuring complete and uniform silk reeling, improving the overall quality of raw silk, and reducing the silk breakage rate.

[0026] S5. Low-temperature washing and gradient drying: The raw silk filaments obtained in S4 are washed in low-temperature clean water. After washing, they are dehydrated to remove excess water from the surface of the filaments. Then, they are dried at low temperature using a gradient heating method to obtain the finished silk. Among them, the water temperature for low-temperature cleaning is 10-25℃; Gradient drying specifically involves drying at a lower temperature for a period of time, followed by drying at a slightly higher temperature, with the relative humidity throughout the drying process ranging from 40% to 60%. The lower temperature is 30-40℃, and the drying time is 30-60 minutes. The temperature should be slightly higher, around 40–50°C, and the drying time should be 20–40 minutes. Furthermore, the temperature does not exceed 30℃ throughout the entire process from S2 to S4, and the working fluid used in each process can be recycled after filtration. Specifically, low-temperature cleaning uses an immersion method with a liquid-to-solid ratio of 20:1 for water and silk. During immersion, the silk is gently turned over, and the cleaning time is 10-15 minutes. After cleaning, centrifugal dehydration is used with a centrifugal speed of 800-1000 r / min and a dehydration time of 5 minutes to avoid squeezing the silk and causing deformation. Gradient drying uses hot air drying with a hot air speed controlled at 0.5-1 m / s. The temperature rise is slow and gradual, with the time from a lower temperature to a slightly higher temperature being 10 minutes. During the drying process, the silk is turned over regularly to ensure uniform drying and avoid local overheating that could cause the silk to yellow. This method can thoroughly remove residual impurities and moisture from the surface of the silk while protecting the silk fiber structure, allowing the finished silk to maintain good luster and mechanical properties, and improving the quality stability of the finished silk.

[0027] The following is a further description with reference to the embodiments: Example 1: A process for low-temperature extraction of silk from silkworm cocoons, comprising the following steps: S1. Cocoon selection and pretreatment: The cocoons are screened to remove damaged, moldy, insect-infested, and non-standard-sized cocoons, while keeping healthy and intact cocoons. Then, the impurities, dust, and loose outer cocoon skin attached to the surface of the cocoons are removed to obtain the cocoons to be processed. S2. Low-temperature vacuum impregnation: The silkworm cocoons obtained in S1 are placed in a low-temperature impregnation solution. The container containing the cocoons and the impregnation solution is evacuated, and the impregnation process is carried out under vacuum to allow the impregnation solution to fully penetrate into the cocoons, resulting in impregnated cocoons. The temperature of the low-temperature impregnation solution is 10℃, the vacuum impregnation pressure is 0.02MPa, and the vacuum impregnation time is 20min. The low-temperature impregnation solution includes a nonionic surfactant, a penetrant, and a pH buffer. The concentration of the nonionic surfactant is 0.5g / L, the concentration of the penetrant is 1g / L, the concentration of the pH buffer is 0.1g / L, and the pH of the low-temperature impregnation solution is controlled at 6.5. The low-temperature impregnation solution also includes a low-temperature protease with a concentration of 0.05g / L. S3. Low-Temperature Synergistic Unwinding: The soaked cocoons obtained in S2 were transferred to the unwinding solution and kept at a low temperature. The cocoons were unwound using a combination of ultrasound and a weak electric field to obtain unwound cocoons. The temperature of the unwinding solution was 25℃, and the unwinding time was 10 min. The unwinding solution was obtained by adding a low-temperature protease to the low-temperature soaking solution, and the total concentration of the low-temperature protease after the addition was 0.2 g / L. The ultrasound was performed in an intermittent working mode with a frequency of 20 kHz, a single ultrasound session lasting 1 min, and a single pause time of 30 s. The weak electric field was a DC weak electric field with an electric field strength of 3 V / cm, and the direction of the electric field was consistent with the radial direction of the cocoon. S4. Closed-loop tension control for low-temperature silk reeling: The unwound silkworm cocoons obtained in S3 are placed in a low-temperature environment for silk reeling. During the reeling process, the tension of the silk strands is monitored in real time. Based on the real-time tension feedback signal, the traction speed and the amount of reeling solution sprayed are dynamically adjusted to obtain raw silk strands. The ambient temperature for low-temperature reeling is 15℃. A multi-stage differential speed traction method is used, with the traction speed increasing sequentially at each stage, and the difference between adjacent traction speeds being 5 m / min. Specifically, the first-stage traction speed is 10 m / min, the second-stage traction speed is 15 m / min, and the third-stage traction speed is 25 m / min. During the reeling process, reeling solution is continuously sprayed onto the contact point between the cocoon and the silk strand at a spray rate of 5 mL / min. In the closed-loop tension control, the preset target tension range is 0.3–0.5 N. When the detected real-time tension is higher than 0.5 N, the traction speed is reduced and the spray rate is increased; when the real-time tension is lower than 0.3 N, the traction speed is increased and the spray rate is decreased. S5. Low-Temperature Cleaning and Gradient Drying: The raw silk filaments obtained in S4 are cleaned in low-temperature water. After cleaning, they are dehydrated to remove excess moisture from the surface of the filaments. Then, they are dried at low temperatures using a gradient heating method to obtain the finished silk. The water temperature for low-temperature cleaning is 10℃. The gradient drying process involves drying at a lower temperature for a period of time, followed by drying at a slightly higher temperature. The relative humidity during the entire drying process is 40%. The lower temperature is 30℃, and the drying time is 30 minutes. The slightly higher temperature is 40℃, and the drying time is 20 minutes. The temperature does not exceed 30℃ throughout the entire process from S2 to S4. The working solutions used in each process can be recycled after filtration.

[0028] Example 2, a process for low-temperature extraction of silk from silkworm cocoons, includes the following steps: S1. Cocoon selection and pretreatment: The cocoons are screened to remove damaged, moldy, insect-infested, and non-standard-sized cocoons, while keeping healthy and intact cocoons. Then, the impurities, dust, and loose outer cocoon skin attached to the surface of the cocoons are removed to obtain the cocoons to be processed. S2. Low-temperature vacuum impregnation: The silkworm cocoons obtained in S1 are placed in a low-temperature impregnation solution. The container containing the cocoons and the impregnation solution is evacuated, and the impregnation process is carried out under vacuum to allow the impregnation solution to fully penetrate into the cocoons, resulting in impregnated cocoons. The temperature of the low-temperature impregnation solution is 18℃, the pressure of vacuum impregnation is 0.05MPa, and the vacuum impregnation time is 40min. The low-temperature impregnation solution includes a nonionic surfactant, a penetrant, and a pH buffer. The concentration of the nonionic surfactant is 1.2g / L, the concentration of the penetrant is 2g / L, the concentration of the pH buffer is 0.3g / L, and the pH of the low-temperature impregnation solution is controlled at 7.2. The low-temperature impregnation solution also includes a low-temperature protease with a concentration of 0.12g / L. S3. Low-Temperature Synergistic Unwinding: The soaked cocoons obtained in S2 were transferred to the unwinding solution and kept at a low temperature. The unwinding treatment was carried out using a combination of ultrasound and a weak electric field to obtain unwound cocoons. The temperature of the unwinding solution was 22℃, and the unwinding treatment time was 20 min. The unwinding solution was obtained by adding a low-temperature protease to the low-temperature soaking solution, and the total concentration of the low-temperature protease after the addition was 0.6 g / L. The ultrasound was performed in an intermittent working mode with a frequency of 40 kHz, a single ultrasound session time of 2 min, and a single pause time of 45 s. The weak electric field was a DC weak electric field with an electric field strength of 6 V / cm, and the direction of the electric field was consistent with the radial direction of the cocoon. S4. Closed-loop tension control for low-temperature silk reeling: The unwound silkworm cocoons obtained in S3 are placed in a low-temperature environment for silk reeling. During the reeling process, the tension of the silk strands is monitored in real time. Based on the real-time tension feedback signal, the traction speed and the amount of reeling solution sprayed are dynamically adjusted to obtain raw silk strands. The ambient temperature for low-temperature reeling is 22℃. A multi-stage differential speed traction method is used, with the traction speed increasing sequentially at each stage, and the difference between adjacent traction speeds being 3 m / min. Specifically, the first-stage traction speed is 12 m / min, the second-stage traction speed is 15 m / min, and the third-stage traction speed is 28 m / min. During the reeling process, reeling solution is continuously sprayed onto the contact point between the cocoon and the silk strand at a spray rate of 12 mL / min. In the closed-loop tension control, the preset target tension range is 0.3–0.5 N. When the detected real-time tension is higher than 0.5 N, the traction speed is reduced and the spray rate is increased; when the real-time tension is lower than 0.3 N, the traction speed is increased and the spray rate is decreased. S5. Low-Temperature Cleaning and Gradient Drying: The raw silk filaments obtained in S4 are cleaned in low-temperature water. After cleaning, they are dehydrated to remove excess moisture from the surface of the filaments. Then, they are dried at low temperatures using a gradient heating method to obtain the finished silk. The water temperature for low-temperature cleaning is 18℃. The gradient drying process involves drying at a lower temperature for a period of time, followed by drying at a slightly higher temperature. The relative humidity is 50% throughout the drying process. The lower temperature is 35℃, and the drying time is 45 minutes. The slightly higher temperature is 45℃, and the drying time is 30 minutes. The temperature does not exceed 30℃ throughout the entire process from S2 to S4. The working solutions used in each process can be recycled after filtration.

[0029] Example 3, a process for low-temperature extraction of silk from silkworm cocoons, includes the following steps: S1. Cocoon selection and pretreatment: The cocoons are screened to remove damaged, moldy, insect-infested, and non-standard-sized cocoons, while keeping healthy and intact cocoons. Then, the impurities, dust, and loose outer cocoon skin attached to the surface of the cocoons are removed to obtain the cocoons to be processed. S2. Low-temperature vacuum impregnation: The silkworm cocoons obtained in S1 are placed in a low-temperature impregnation solution. The container containing the cocoons and the impregnation solution is evacuated, and the impregnation process is carried out under vacuum to allow the impregnation solution to fully penetrate into the cocoons, resulting in impregnated cocoons. The temperature of the low-temperature impregnation solution is 25℃, the pressure of vacuum impregnation is 0.08MPa, and the vacuum impregnation time is 60min. The low-temperature impregnation solution includes a nonionic surfactant, a penetrant, and a pH buffer. The concentration of the nonionic surfactant is 2g / L, the concentration of the penetrant is 3g / L, the concentration of the pH buffer is 0.5g / L, and the pH of the low-temperature impregnation solution is controlled at 8.0. The low-temperature impregnation solution also includes a low-temperature protease with a concentration of 0.2g / L. S3. Low-Temperature Synergistic Unwinding: The soaked cocoons obtained in S2 were transferred to the unwinding solution and kept at a low temperature. The cocoons were unwound using a combination of ultrasound and a weak electric field to obtain unwound cocoons. The temperature of the unwinding solution was 25℃, and the unwinding treatment time was 30 min. The unwinding solution was obtained by adding a low-temperature protease to the low-temperature soaking solution, and the total concentration of the low-temperature protease after the addition was 1 g / L. The ultrasound was performed in an intermittent working mode with a frequency of 60 kHz, a single ultrasound session time of 3 min, and a single pause time of 60 s. The weak electric field was a DC weak electric field with an electric field strength of 10 V / cm, and the direction of the electric field was consistent with the radial direction of the cocoon. S4. Closed-loop tension control for low-temperature silk reeling: The unwound silkworm cocoons obtained in S3 are placed in a low-temperature environment for silk reeling. The tension of the silk strands is monitored in real time during the reeling process. Based on the real-time tension feedback signal, the traction speed and the amount of reeling solution sprayed are dynamically adjusted to obtain raw silk strands. The ambient temperature for low-temperature reeling is 30℃. A multi-stage differential speed traction method is used, with the traction speed increasing sequentially at each stage, and the difference between adjacent traction speeds being 5 m / min. Specifically, the first-stage traction speed is 15 m / min, the second-stage traction speed is 25 m / min, and the third-stage traction speed is 30 m / min. During the reeling process, reeling solution is continuously sprayed onto the contact point between the cocoon and the silk strand at a spray rate of 20 mL / min. In the closed-loop tension control, the preset target tension range is 0.3–0.5 N. When the detected real-time tension is higher than 0.5 N, the traction speed is reduced and the spray rate is increased; when the real-time tension is lower than 0.3 N, the traction speed is increased and the spray rate is decreased. S5. Low-Temperature Cleaning and Gradient Drying: The raw silk filaments obtained in S4 are cleaned in low-temperature water. After cleaning, they are dehydrated to remove excess moisture from the surface of the filaments. Then, they are dried at low temperatures using a gradient heating method to obtain the finished silk. The water temperature for low-temperature cleaning is 25℃. The gradient drying process involves drying at a lower temperature for a period of time, followed by drying at a slightly higher temperature. The relative humidity throughout the drying process is 60%. The lower temperature is 40℃, and the drying time is 60 minutes. The slightly higher temperature is 50℃, and the drying time is 40 minutes. The temperature does not exceed 30℃ throughout the entire process from S2 to S4. The working solutions used in each process can be recycled after filtration.

[0030] Comparative Example 1 is a process for extracting silk from silkworm cocoons. Unlike Example 2, step S2 does not involve vacuuming. Instead, the silkworm cocoons to be treated are placed in a low-temperature wetting solution for room-temperature wetting without maintaining a vacuum. All other process parameters are the same as in Example 2.

[0031] Comparative Example 2 is a process for extracting silk from silkworm cocoons. Unlike Example 2, step S3 only uses ultrasound for unwinding treatment and does not apply a weak electric field, thus canceling the synergistic effect of ultrasound and weak electric field. All other process parameters are the same as in Example 2.

[0032] Comparative Example 3 is a process for extracting silk from silkworm cocoons. Unlike Example 2, step S4 does not involve closed-loop tension control. The traction speed and the amount of silk extraction liquid sprayed remain constant and are not adjusted based on real-time tension feedback. All other process parameters are the same as in Example 2.

[0033] Comparative Example 4: A process for extracting silk from silkworm cocoons. Unlike Example 2, step S5 uses constant temperature drying instead of gradient drying. The drying temperature is fixed at 45°C and the drying time is 75 minutes. No gradient temperature increase is performed. All other process parameters are the same as in Example 2.

[0034] Comparative Example 5: A process for extracting silk from silkworm cocoons. Unlike Example 2, the low-temperature soaking process in step S2 is omitted. Instead, the silkworm cocoons to be treated obtained in S1 are directly transferred to the unwinding solution in S3 for unwinding treatment. All other process parameters are the same as in Example 2.

[0035] The following section, using experimental examples, further illustrates the performance differences between Comparative Examples 1-5 and Example 2: Experiment Example 1: The breaking strength of raw silk was tested according to GB / T17981-2008. An electronic monofilament tensile strength tester was used. Finished silk samples prepared in the examples and comparative examples were selected, and silk segments with surface damage or abnormal fuzz were removed. First, cut a 500mm long silk segment, set the clamping distance to 300mm, the stretching speed to 100mm / min, and the pre-tension to 0.1cN. Test 10 silk segments in each group of samples, remove the maximum and minimum values ​​and take the average value. Calculate the breaking strength according to the formula: Breaking strength = Load at the time of silk breakage ÷ Silk linear density. During the test, maintain an ambient temperature of 20±2℃ and a relative humidity of 65±3%. The samples were equilibrated in this environment for 24 hours before the test.

[0036] Experiment Example 2: Following GB / T17981-2008 "Raw Silk", the breaking elongation and breaking strength were tested simultaneously. The elongation at the time of filament breakage was recorded in real time using an electronic monofilament tensile tester. The formula for elongation at break is: Elongation at break = (Elongation at break / Initial clamping length) × 100%, and is rounded to one decimal place. Ten samples were tested in each group. The maximum and minimum values ​​were removed and the average value was taken. The testing environment, sample pretreatment and fracture strength test were completely consistent to ensure data correlation.

[0037] In Experiment 3, the silk breakage rate was tested in accordance with GB / T17981-2008 "Raw Silk" and GB / T28124-2011 "Silk Terminology". The silk drawing equipment used in the process of this invention was adopted, and the silk drawing parameters were kept consistent with those of the corresponding embodiment or comparative example. Continuous filament drawing for 1000m was conducted, and the number of filament breaks during the drawing process was recorded in real time. The breakage rate was calculated using the formula: filament breakage rate = (number of breaks / total filament length × 1000) × 100%, and one decimal place was retained. Each group was tested 3 times, and the average value was taken. The test environment temperature was 22±2℃ and the relative humidity was 55±3% to avoid the influence of environmental airflow on the stability of the filament.

[0038] Experiment Example 4: The whiteness of silk was tested according to GB / T17981-2008 "Raw Silk" and GB / T8424.2-2001 "Textiles - Tests for Color Fastness - Determination of Relative Whiteness". A portable whiteness meter was used to select finished silk samples. Cut a 20mm×20mm sample and lay it flat on the whiteness meter test table, ensuring that the sample is free of wrinkles and impurities. Using a standard white board as a reference, test the reflectance of the sample, which is the whiteness value of the silk. Test 5 different parts of each sample group, remove outliers and take the average value. Keep the test environment free of strong direct light and at a temperature of 20±2℃, and avoid dust contamination of the sample.

[0039] In Experiment 5, referring to GB / T19178-2017 "Silkworm Cocoons" and silk processing industry standards, the survival rate of silkworm pupae was tested. Fifty intact silkworm cocoons after silk reeling were selected, and the cocoon layers were gently peeled open to remove the silkworm pupae, avoiding mechanical damage. Surviving silkworm pupae were distinguished from dead silkworm pupae. The survival rate of silkworm pupae was calculated according to the formula: (Number of surviving silkworm pupae / Total number of silkworm pupae) × 100%, and one decimal place was retained. Three parallel samples were tested in each group, and the average value was taken. During the test, the ambient temperature was maintained at 25±2℃ and the relative humidity at 60±5% to avoid the silkworm pupae dying from temperature and humidity shocks.

[0040] Table 1, Performance Test Data Table

[0041] Based on the differences between Examples 1-3 and Comparative Examples 1-5 and the performance test data table, it can be seen that the synergistic process of cocoon selection and pretreatment, low-temperature vacuum impregnation, low-temperature synergistic unwinding, closed-loop tension control low-temperature spinning, low-temperature washing and gradient drying in this invention has a significant impact on the breaking strength, breaking elongation, spinning breakage rate, whiteness and silkworm pupa survival rate of the finished silk. Moreover, each process step has a good effect of sufficient impregnation, efficient unwinding, stable spinning, excellent forming and reduced damage, thus achieving the dual goals of low-temperature and efficient silk extraction and high performance.

[0042] Comparative Example 1, because it did not perform vacuuming in step S2 and only used room temperature wetting, resulted in the low-temperature wetting solution not being able to fully penetrate into the cocoon. The cocoon was not fully wetting, which led to poor connection with the subsequent unwinding and silk reeling processes. The breaking strength dropped to 3.2 cN / dtex, a decrease of 28.9% compared to Example 2, the breaking elongation dropped to 16.8%, a decrease of 21.9% compared to Example 2, and the silk breakage rate increased to 2.5%, an increase of 733.3% compared to Example 2. The whiteness of the silk and the survival rate of the silkworm pupae also decreased significantly, making it the group with poor overall performance. At the same time, the silk strands were prone to sticking and breaking during the silk reeling process, which could not meet the production requirements of high-quality silk. Comparative Example 2 used a single ultrasonic unwinding process instead of the combined ultrasonic and weak electric field unwinding process, eliminating the effect of the weak electric field. This resulted in a decrease in the unwinding efficiency of the silkworm cocoons, uneven dissolution of sericin, a decrease in breaking strength to 3.5 cN / dtex (22.2% lower than Example 2), a decrease in breaking elongation to 17.5% (18.6% lower than Example 2), and an increase in the silk breakage rate to 1.8% (500.0% higher than Example 2). Although the survival rate of silkworm pupae did not decrease significantly, the mechanical properties of the silk and the stability of silk rewinding were significantly reduced, and sericin was easily left on the surface of the silk, affecting the quality of the silk. Comparative Example 3 lacks a closed-loop tension control process. The traction speed and the amount of spinning solution sprayed are kept constant, and cannot be dynamically adjusted according to the real-time tension of the filament. This results in large tension fluctuations during the spinning process, making the filament prone to breakage or loosening. The breaking strength drops to 3.1 cN / dtex, a decrease of 31.1% compared to Example 2, the breaking elongation drops to 15.9%, a decrease of 26.0% compared to Example 2, the spinning breakage rate rises to 3.7%, an increase of 1133.3% compared to Example 2, and the whiteness of the silk decreases slightly, which seriously affects the spinning efficiency and the quality of the finished silk product. Comparative Example 4 used constant temperature drying instead of gradient drying, eliminating the gradient heating operation, which resulted in uneven drying of the silk, making the surface prone to yellowing and embrittlement. The breaking strength decreased to 3.6 cN / dtex, a decrease of 20.0% compared to Example 2, the breaking elongation decreased to 18.0%, a decrease of 16.3% compared to Example 2, and the silk whiteness decreased to 88.5%, a decrease of 3.9% compared to Example 2. Although the silk breakage rate and silkworm pupa survival rate were not significantly abnormal, the color and mechanical properties of the silk were damaged, and it was prone to breakage and deterioration during long-term storage. Comparative Example 5 omitted the low-temperature soaking process in step S2 and directly unwound the cocoons. As a result, impurities and cocoon skin on the surface of the cocoons were not fully softened and removed, sericin was difficult to dissolve, and the unwound effect was extremely poor. The breaking strength dropped to 2.9 cN / dtex, a decrease of 35.6% compared to Example 2, the breaking elongation dropped to 14.7%, a decrease of 31.6% compared to Example 2, the silk breakage rate increased to 4.2%, an increase of 1300.0% compared to Example 2, the silk whiteness and the survival rate of silkworm pupae were reduced to the lowest level, and silk broke frequently during the silk reeling process, making it impossible to achieve continuous and stable production, which completely failed to meet the basic requirements of silk production.

[0043] The finished silk prepared in this example exhibits excellent core performance indicators, fully meeting the preset performance requirements: breaking strength ≥3.8cN / dtex, breaking elongation ≥18.0%, silk breakage rate ≤1.2%, silk whiteness ≥86.5%, and silkworm pupa survival rate ≥88.3%. Simultaneously, it achieves low-temperature, high-efficiency silk extraction and comprehensive utilization of silkworm cocoons. The silk strands are intact, without defects such as adhesion, breakage, or yellowing. Its excellent overall performance effectively improves silk quality, reduces silkworm pupa damage during production, and increases the utilization rate of silkworm cocoon resources.

[0044] Among them, Examples 1 and 3, due to the process parameters being at the boundary of the set range, have slightly inferior performance compared to Example 2, but still maintain good overall advantages. Example 1 is suitable for low-cost general-purpose silk production scenarios. By adopting the minimum parameters of each step, the amount of immersion liquid, energy consumption, and production time are controlled, reducing the production cost by 10% compared to Example 2. At the same time, it maintains the basic requirements of silk structure integrity and core performance. It can be widely used in ordinary civilian silk products, industrial silk, and other scenarios with moderate requirements for silk quality. Example 3 is aimed at high-end, high-quality silk demand scenarios. By adopting the maximum parameters of each step, key parameters such as immersion liquid concentration, ultrasonic frequency, and electric field strength are improved, further enhancing the mechanical properties, whiteness, and silk reeling stability of the silk. The survival rate of silkworm pupae is also further improved. The overall performance is better than the preset standard, making it suitable for high-end textiles, medical silk, high-end clothing, and other application scenarios with high requirements for silk quality.

[0045] Example 2 achieves an optimal balance between performance and cost. Its process parameters are highly adaptable, with thorough cocoon selection and pretreatment, sufficient low-temperature vacuum impregnation, efficient low-temperature synergistic unwinding, precise closed-loop tension control, and reasonable low-temperature washing and gradient drying. The finished silk produced has performance that is superior to the preset standard in all aspects. Moreover, the preparation process is stable, the silk reeling efficiency is high, the production cycle is reasonable, and no complex equipment is required, making it easy to achieve large-scale continuous production. Its cost-effectiveness advantage is significant, with a production cost reduction of 8% compared to Example 3, an increase in breaking strength of more than 25% and a reduction in silk breakage rate of more than 70% compared to traditional high-temperature silk reeling processes, and an increase in silk whiteness and silkworm pupa survival rate of more than 10% compared to existing low-temperature silk reeling technologies. It can be widely adapted to various scenarios such as civilian, industrial, and high-end textiles, covering the full range of needs from ordinary silk to high-end high-quality silk.

[0046] The core processes in Examples 1-3 exhibit a deep synergistic effect: cocoon selection and pretreatment, combined with low-temperature vacuum impregnation, remove impurities and loose cocoon shells, laying the foundation for full penetration of the impregnation solution and reducing the risk of silk breakage during subsequent silk reeling; low-temperature vacuum impregnation and low-temperature synergistic unwinding work together to ensure the impregnation solution fully acts on the sericin, and with the synergistic effect of ultrasound and weak electric field, achieve efficient unwinding of cocoons while avoiding damage to silk quality from high temperatures; low-temperature synergistic unwinding and closed-loop tension-controlled low-temperature silk reeling work together to ensure stable silk reeling after unwinding, dynamically adjusting tension and spray volume to ensure uniform and intact silk strands; closed-loop tension-controlled low-temperature silk reeling, combined with low-temperature washing and gradient drying, reduces residue on the silk surface, achieves uniform drying of silk, and improves silk color and mechanical properties; the working solutions used in each process are recycled, further reducing production costs and aligning with the concept of green production.

[0047] Example 2 optimizes the following parameters: low-temperature wetting solution temperature (18℃), vacuum pressure (0.05MPa), wetting time (40min), unwinding solution temperature (22℃), unwinding time (20min), ultrasonic frequency (40kHz), weak electric field strength (6V / cm), multi-level traction speed gradient, and drawing solution spray volume (12mL / min). The gradient drying temperature and time are also adapted to achieve seamless connection between each process step, maximizing the synergistic advantages and fully demonstrating the scientific, rational, and feasible nature of the process parameter range of this invention.

[0048] Comparative Examples 1-5 show that the overall synergistic chain was broken due to the absence or alteration of a single process step: Comparative Example 1 eliminated vacuum impregnation, disrupting the impregnation effect of the silkworm cocoons and the connection with subsequent processes; Comparative Example 2 eliminated the effect of the weak electric field, weakening the disintegration synergistic effect; Comparative Example 3 eliminated closed-loop tension control, losing the guarantee of silk reeling stability; Comparative Example 4 changed the drying method, affecting the quality of silk forming; Comparative Example 5 eliminated the low-temperature impregnation process, disrupting the integrity of the entire process system. All of these examples demonstrate the irreplaceable nature of the key process steps and parameter selections in this invention, further illustrating that the synergistic effect of each process step is the core guarantee for achieving low-temperature and efficient silk reeling, high-quality forming, and comprehensive utilization of silkworm cocoons.

[0049] In summary, this invention, through its core technology design of cocoon selection and pretreatment, low-temperature vacuum impregnation, low-temperature synergistic unwinding, closed-loop tension-controlled low-temperature silk reeling, and low-temperature cleaning and gradient drying, combined with the synergistic optimization of various process parameters, effectively solves the technical problems of high temperature, damaged silk quality, and high silk breakage rate in traditional silk reeling processes, as well as the existing low-temperature silk reeling technologies such as insufficient impregnation, low unwinding efficiency, unstable silk reeling, significant damage to silkworm pupae, high production costs, and difficulty in large-scale production. It significantly improves the overall performance and production efficiency of finished silk, realizes low-temperature and efficient silk reeling and high-value applications, simplifies the production process, controls production costs, eliminates the need for complex equipment, and allows for the recycling of the working solution, aligning with the development concepts of green production and efficient utilization, and has broad application prospects.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for low-temperature extraction of silk from silkworm cocoons, characterized in that, Includes the following steps: S1. Cocoon selection and pretreatment: The cocoons are screened to remove damaged, moldy, insect-infested, and non-standard-sized cocoons, while keeping healthy and intact cocoons. Then, the impurities, dust, and loose outer cocoon skin attached to the surface of the cocoons are removed to obtain the cocoons to be processed. S2, Low-temperature vacuum impregnation: The silkworm cocoons to be treated obtained in S1 are placed in a low-temperature impregnation solution. The container containing the silkworm cocoons and the impregnation solution is vacuumed and the impregnation process is carried out under vacuum to allow the impregnation solution to fully penetrate into the silkworm cocoons, thus obtaining impregnated silkworm cocoons. S3, Low-temperature synergistic unwinding: The soaked cocoons obtained in S2 are transferred to the unwinding solution, and the cocoons are unwound by using a combination of ultrasound and weak electric field to obtain unwound cocoons. S4. Closed-loop tension-controlled low-temperature silk reeling: The unwound silkworm cocoons obtained in S3 are placed in a low-temperature environment for silk reeling. The tension of the silk is detected in real time during the silk reeling process. Based on the real-time tension feedback signal, the traction speed and the amount of silk reeling liquid spray are dynamically adjusted to obtain raw silk filaments. S5. Low-temperature washing and gradient drying: The raw silk filaments obtained in S4 are washed in low-temperature clean water. After washing, they are dehydrated to remove excess moisture from the surface of the filaments. Then, they are dried at low temperature using a gradient heating method to obtain the finished silk.

2. The process for low-temperature extraction of silk from silkworm cocoons according to claim 1, characterized in that, In step S2, the temperature of the low-temperature impregnation liquid is 10–25°C, the pressure of vacuum impregnation is 0.02–0.08 MPa, and the vacuum impregnation time is 20–60 min.

3. The process for low-temperature extraction of silk from silkworm cocoons according to claim 2, characterized in that, The low-temperature wetting solution includes a nonionic surfactant, a penetrant, and a pH buffer, wherein the concentration of the nonionic surfactant is 0.5–2 g / L, the concentration of the penetrant is 1–3 g / L, the concentration of the pH buffer is 0.1–0.5 g / L, and the pH of the low-temperature wetting solution is controlled at 6.5–8.

0.

4. The process for low-temperature extraction of silk from silkworm cocoons according to claim 3, characterized in that, The low-temperature wetting solution also includes a low-temperature protease, the concentration of which is 0.05–0.2 g / L.

5. The process for low-temperature extraction of silk from silkworm cocoons according to claim 1, characterized in that, In step S3, the temperature of the relieving solution is ≤25℃, and the relieving treatment time is 10-30 min. The soothing solution is obtained by adding low-temperature protease to the low-temperature wetting solution, and the total concentration of low-temperature protease after the addition is 0.2-1 g / L.

6. The process for low-temperature extraction of silk from silkworm cocoons according to claim 1, characterized in that, In S3, the ultrasound adopts an intermittent working mode, with a frequency of 20-60kHz, a single ultrasound duration of 1-3 minutes, and a single pause time of 30-60 seconds.

7. The process for low-temperature extraction of silk from silkworm cocoons according to claim 1, characterized in that, In S3, the weak electric field is a DC weak electric field with an electric field strength of 3 to 10 V / cm, and the direction of the electric field is consistent with the radial direction of the silkworm cocoon.

8. The process for low-temperature extraction of silk from silkworm cocoons according to claim 1, characterized in that, In S4, the ambient temperature for low-temperature wire drawing is 15-30℃, and the wire drawing adopts a multi-stage differential traction method, with the traction speed of each stage increasing sequentially, and the difference between the traction speeds of adjacent stages not exceeding 5m / min. The first-level traction speed is 10–15 m / min, the second-level traction speed is 15–25 m / min, and the third-level traction speed is 25–30 m / min.

9. The process for low-temperature extraction of silk from silkworm cocoons according to claim 1, characterized in that, In step S4, during the silk reeling process, silk reeling liquid is continuously sprayed onto the contact point between the silkworm cocoon and the silk thread, with a spraying volume of 5-20 mL / min. In the closed-loop tension control, a target tension range is preset. When the detected real-time tension is higher than the upper limit of the target range, the traction speed is reduced and the spray volume is increased. When the real-time tension is lower than the lower limit of the target range, increase the traction speed and reduce the spray volume.

10. The process for low-temperature extraction of silk from silkworm cocoons according to claim 1, characterized in that, In step S5, the temperature of the clean water used for low-temperature cleaning is 10–25°C. The gradient drying process specifically involves drying at a lower temperature for a period of time, followed by drying at a slightly higher temperature, with the relative humidity remaining between 40% and 60% throughout the entire drying process. The lower temperature is 30-40℃, and the drying time is 30-60 minutes. The temperature should be slightly higher, around 40–50°C, and the drying time should be 20–40 minutes. Furthermore, the temperature does not exceed 30℃ throughout the entire process from S2 to S4, and the working fluid used in each process can be recycled after filtration.

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