Processing technology of floss silk and floss silk

Abstract

The application discloses a processing technology and cocoon silk, and processing is performed according to the following steps: S1: swelling dispersion and anti-sticking treatment: placing silk containing sericin in a weak acid buffer prepared from an organic acid, the pH value being 1.0-4.0, and performing swelling treatment by heating, unsaturated fatty acid is added in the weak acid buffer in advance or is added in the initial stage of swelling in step S1, S2: post-treatment: taking out the swelled silk and drying, and performing drying to obtain dispersed single-fiber cocoon silk which does not adhere to each other. Through the two-step cooperation of 'pH-temperature dominant swelling' and 'oleic acid preventing secondary adhesion', the prepared cocoon silk retains 60%-90% of natural sericin and is in a fluffy and dispersed single-fiber state; the cocoon silk replaces the traditional degumming process, reduces pollution, has high spinnability, and the retained sericin has excellent biological activity and biocompatibility, so that the cocoon silk material has higher competitiveness and can become a raw material of biomedical textiles.

Description

Technical Field

[0001] This invention relates to the field of silk processing technology, specifically to a process for processing feathered silk and feathered silk. Feathered silk, as defined in this invention, refers to silk fibers that are in a state of sericin adhesion, minimizing the loss or denaturation of sericin during processing, and preventing sericin from re-adheding in the dried state after processing, ultimately forming dispersed monofibrillary silk fibers containing sericin components. Background Technology

[0002] Silk, as a natural protein fiber, boasts advantages such as skin-friendliness, high breathability, high moisture absorption, and a luxurious, flowing appearance, earning it the title of "Queen of Fibers." However, silk's drawbacks are also well-known: it wrinkles easily, is difficult to manage and wash, has a short lifespan, and offers limited product variety. Consequently, silk's consumer base is not broad, accounting for only 0.5% of the overall textile industry, making it less competitive compared to other fibers and hindering its sustainable development.

[0003] The main reasons for this are as follows: Due to the inherent material properties of natural silk, it lacks combing and spinning characteristics, preventing the silk industry from utilizing advanced textile technologies and equipment to produce high-end and diversified end products. Furthermore, silk fibers produced using traditional processes suffer from the drawbacks of traditional refining techniques, resulting in inferior forming, dyeing, and processing properties in the final silk and its products.

[0004] Currently, silk protein fibers are mainly produced by reeling several silkworm cocoons to form a single strand of silk with a specific diameter. This involves combining the silk from 8-12 cocoons into a single strand, meaning each strand consists of 8-12 individual fibers. This process requires high-quality cocoons. Furthermore, the reeled silk still contains sericin, which becomes sticky after drying and prevents the formation of individual silk fibers. The final product requires the removal of all sericin, leading to environmental pollution.

[0005] Traditional silk spinning involves refining silk reeling byproducts and unreelable cocoons under high-temperature, alkaline conditions. This process largely removes the sericin adhering to the surface of the silk, resulting in highly disordered fibers. These fibers are then combed into individual fibers of varying lengths using a specialized circular carding machine. After manual impurity sorting, fiber removal, and shaping into balls, the fibers are fed into the textile mill. Compared to modern spinning technology, the production efficiency of these two methods is significantly lower. The process is complex, the equipment is outdated, it causes environmental pollution, and the products are limited and inefficient.

[0006] Traditional sericin treatments can fix sericin onto silk fibers. However, traditional sericin-fixing uses a sericining agent to fix the sericin through a cross-linking reaction, but this process fails to break up the sticky sericin, instead making the adhesion even stronger. When sticky silk is subjected to sericin-fixing, it cannot disperse to form individual silk fibers. More seriously, the sericin proteins are completely denatured after sericin-fixing, losing the original biological activity of natural sericin. Furthermore, in practical applications, it is difficult to avoid the biotoxicity problems caused by residual cross-linking agents. This makes traditionally sericin-fixed silk completely unsuitable for use in biomedical fields where safety requirements are extremely high. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a processing method for feathered silk and the feathered silk obtained therefrom. This invention overcomes the technical bottlenecks of traditional processes that degumming damages sericin or cross-linking solidifies sericin, leading to sericin denaturation and toxicity. While achieving single-fiber formation and spinnability of silk, it maximizes the preservation of the natural state of sericin protein, which possesses excellent biocompatibility.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a processing method for molting silkworm silk, characterized by the following steps:

[0009] S1: Swelling, dispersion and anti-adhesion treatment: The silk containing sericin is placed in a weakly acidic buffer solution prepared with organic acid, with a pH value of 1.0-4.0, for swelling treatment, so that the adhesion points of the sericin in the silk dissolve and the cocoon shell is in a completely swollen and dispersed state. Emulsified and dispersed unsaturated fatty acids are added to the weakly acidic buffer solution in advance, or emulsified and dispersed unsaturated fatty acids are added at the beginning of the swelling in step S1, so that the unsaturated fatty acids penetrate and adhere to the surface of the sericin during the swelling process.

[0010] S2: Post-processing: The swollen silk is removed, dehydrated, and then dried to obtain dispersed single-fiber feathered silk that does not stick together.

[0011] The organic acid includes at least one of tartaric acid, malic acid, citric acid, formic acid, oxalic acid, mandelic acid, and lactic acid, and the unsaturated fatty acid is selected from one of oleic acid, trans oleic acid, myristoleic acid, ricinoleic acid, and palmitoleic acid.

[0012] Preferably, the pH of the weakly acidic buffer solution is 2.0-2.6.

[0013] The weakly acidic buffer solution is formed by mixing an organic acid and a base, wherein the base is sodium hydroxide or potassium hydroxide. The pKa value of the organic acid enables the weakly acidic buffer solution to resist the neutralization effect of silk during the treatment process and to stably maintain its pH value of 2.0-3.

[0014] In the elongation process, which lasts for several hours, pH is the key factor triggering swelling. Because silk sericin has a strong acid-base neutralizing ability, the system pH gradually rises as the reaction proceeds. Therefore, an organic acid with a suitable pKa value must be selected to construct the buffer solution. If an acid with an excessively high pKa (such as acetic acid) is used, even an addition of 10% will not be enough to lower the pH below 2.6; if a strong inorganic acid is used, its buffering capacity is extremely small and it will be quickly neutralized and ineffective by the sericin. Organic acids with pKa values ​​around 2.0-2.6 (such as tartaric acid, malic acid, citric acid, mandelic acid, lactic acid, phenyllactic acid, malonic acid, methylmalonic acid, etc.), or mixtures of the above organic acids, can form a stable buffer environment within this range, meeting the process requirements.

[0015] In the above scheme: the silk containing sericin is natural cocoon shell, raw silk after reeling, or reeling waste; when processing reeling waste, a pure water washing pretreatment step is added before step S1.

[0016] In the above scheme: the bath ratio in S1 is 1:20-50, the mass concentration of unsaturated fatty acids is 0.1%-0.5%, and the unsaturated fatty acids are added before heating.

[0017] In the above scheme, the mass concentration of unsaturated fatty acids is 0.2%.

[0018] In the above scheme: unsaturated fatty acids are emulsified and dispersed as follows: unsaturated fatty acids are added to polyethylene glycol, sodium methyl cocoyl taurate and water, and emulsified by stirring at room temperature. The mass ratio of unsaturated fatty acids: polyethylene glycol: sodium methyl cocoyl taurate: water is 3:1:1:5.

[0019] Other emulsification methods can also be used, as long as they can emulsify and disperse unsaturated fatty acids.

[0020] For example, unsaturated fatty acids: plant emulsifier: sodium dodecylbenzenesulfonate solution (5%): distilled water = 3:1:1:5, emulsify by stirring at room temperature.

[0021] Unsaturated fatty acids: Span80: sodium octadecyl sulfonate solution (5%): surfactant-modified polyether: distilled water = 3:0.5:2:0.5:4, emulsify by stirring at room temperature. Either is acceptable.

[0022] In the above scheme, the swelling treatment is carried out at a temperature of 65-85℃.

[0023] In the above method: the silk containing sericin is first pre-swelled by heat treatment at 40℃-65℃ for 1-3 hours, and then the temperature is raised to 70℃-80℃ to swell until completely dispersed. Preferably, the treatment is carried out at 65℃ for 1 hour, 70℃ for 1 hour, and 80℃ for 2 hours.

[0024] The logic behind this multi-stage temperature control is as follows: in the initial low-temperature stage, a weak acid is used to gently open the outer layer of sericin adhesion, minimizing sericin degradation; as the reaction progresses, the sericin structure gradually loosens, at which point the temperature is gradually increased to accelerate the swelling and dispersion of the internal sericin. This dynamic control protects the sericin while also considering overall efficiency, making it a key method to overcome the dilemma of "high efficiency and high retention rate being mutually exclusive" in single-factor experiments.

[0025] The silkworm cocooning process is a multi-stage process involving the synergistic effects of a specific pH buffer system, a stepped temperature field, and oleic acid for anti-sticking protection. In a weakly acidic buffer solution that can maintain a stable pH of 2.0-2.6 over a long period, the cocoon shells undergo controlled and limited dissolution of the sericin adhesion points through gradual, multi-stage heating, achieving overall dispersion and complete swelling. During this process (or after swelling), the emulsified and dispersed oleic acid present in the system can encapsulate or isolate the silk fibers, thus completely preventing secondary adhesion during the drying process. Without the synergistic effect of specific pH and temperature, the cocoon shells cannot be effectively dispersed; if there is only swelling without oleic acid, severe adhesion will still occur after drying.

[0026] In the above scheme: In S2, the de-dried silk is first bleached and then dried in a step-by-step manner: pre-drying at 85-95℃ for 30-40 minutes, then baking at 70-75℃ for 1-1.5 hours, and finally letting it stand to dry.

[0027] Silk prepared by the aforementioned process for processing feathered silk. The sericin retention of the feathered silk is 60%-90% of that before processing, the individual fibers are in a discrete and fluffy state, and the sericin does not re-adhere in the dry state; the sericin protein of the feathered silk is in a non-crosslinked and denatured natural state, with excellent bioactivity and biocompatibility, making the silk material more competitive and suitable as a raw material for biomedical textiles.

[0028] This invention, through extensive comparative experiments, confirms that the core driving force of the feathering and swelling process is the system's environmental pH and thermodynamic temperature, and is not clearly related to the specific molecular type of organic acid (e.g., tartaric acid, malic acid, and citric acid have the same effect at the same pH). This invention innovatively breaks down the reaction process into two independent and indispensable steps: "controllable swelling and dispersion by weak acid" and "prevention of secondary adhesion by unsaturated fatty acids," providing a completely new theoretical framework for the silk processing field.

[0029] This invention establishes a specific swelling window of "acidity-low temperature," completely eliminating alkaline and neutral treatment pathways. Through numerous parallel controlled experiments, this invention reveals a counterintuitive phenomenon in sericin swelling: to break up sericin adhesion without damaging it, a synergistic effect of a weakly acidic environment (pH 2.0-2.6) and a low temperature (65℃-80℃) is necessary. Experiments confirm that if alkaline buffer solutions (pH 9-11) such as baking soda or soda ash are used, even at non-extreme temperatures of 75℃-85℃, although swelling occurs, significant degradation and shedding of the sericin occur. Even adding oleic acid cannot salvage the feel, and the sericin remains severely adherent after drying. If a neutral or weakly acidic environment (pH>4) is used, the chemical swelling ability is completely lost, requiring prolonged treatment at temperatures above 85℃ or even 90℃ to barely break up the adhesion. However, once such high temperatures are used, the sericin inevitably suffers irreversible thermal damage. Therefore, "weak acid + medium and low temperature" is not a simple combination of parameters, but a specific optimal range of process parameters that can achieve a perfect balance between "unbinding adhesions" and "preserving natural sericin". This constitutes the core technical barrier of this invention.

[0030] This invention is the first of its kind to create an "anti-neutralization buffer system" to ensure the stability of long-cycle processes.

[0031] Because the feathering and swelling process takes several hours, the sericin, rich in polar amino acids, continuously neutralizes the H+ in the system. + This leads to pH drift. The present invention creatively proposes that an organic acid with a suitable pKa (such as tartaric acid pKa1≈2.98, malic acid pKa1≈3.40, etc.) must be selected to form a buffer solution with the alkali. This not only eliminates acids with excessively high pKa (such as acetic acid, which, even at 10%, cannot reach the target pH), but also eliminates strong inorganic acids with no buffering capacity (which are easily neutralized and rendered ineffective). Simultaneously, it allows for the use of a mixture of multiple organic acids, thereby firmly locking the pH at 2.0-2.6 throughout the entire reaction cycle, ensuring absolute batch-to-batch quality stability.

[0032] This study reveals the "concentration threshold" and "initial osmosis synergy" mechanism of oleic acid.

[0033] The anti-blocking effect of unsaturated fatty acids (such as oleic acid) exhibits a clear concentration marginal effect: 0.1%-0.5% (optimal 0.2%) is sufficient to form perfect steric hindrance during drying, while higher concentrations (0.5%) do not increase the anti-blocking effect but instead increase the oil content. More importantly, comparative experiments have confirmed that "initial addition" of oleic acid is significantly more effective than "addition after swelling." This is because oleic acid requires sufficient penetration time and may synergize with a weakly acidic environment, allowing it to adhere evenly the moment the sericin swells and opens. This finding greatly optimizes the process flow and the final product's fluffiness.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) This invention yields "natural" silk products with significant clinical and industrial application potential. Traditional sericin consolidation processes use cross-linking agents to preserve sericin, resulting in complete denaturation of sericin proteins and making it difficult to avoid the biotoxicity caused by residual cross-linking agents, thus rendering them unsuitable for medical use. However, this invention, through mild physicochemical parameter control, produces feathered silk in a "non-cross-linked, denatured natural state" of sericin proteins, preserving not only the excellent original bioactivity and biocompatibility of sericin but also completely eliminating the toxic risks of chemical cross-linking agents. This allows the material to be directly used as a raw material for high-end biomedical textiles (such as high-end dressings and hemostatic gauze), giving silk fibers extremely high material competitiveness.

[0036] (2) Breaking the traditional process route to achieve cost reduction and efficiency improvement in the industry. This invention enables cocoon shells or waste materials that originally did not have combing properties to be directly converted into dispersed single fibers, which can be directly entered into the short spinning system of modern large-scale textile industry, thus breaking away from the backward traditional silk reeling / spinning route; at the same time, since the integrity of the cocoon shell is no longer required, the pupae can be cut open in the fresh cocoon state to obtain high-value food / health product grade live silkworm pupae, which greatly improves the overall economic utilization rate of silkworm biological resources, and avoids the serious water pollution caused by traditional alkali degumming throughout the process. Attached Figure Description

[0037] Figure 1 Electron micrograph of silk fibers forcibly separated from natural cocoon shells.

[0038] Figure 2 Electron micrograph of silk produced by traditional degumming and refining (with all sericin removed).

[0039] Figure 3 This is an electron microscope image of silkworm silk after the cocoon shell of the present invention has undergone feathering treatment.

[0040] Figure 4 Infrared spectra of three types of silk.

[0041] Figure 5 Infrared characterization of typical degummed silk amide I band (1720-1580 cm⁻¹) -1 The relative intensities of typical peaks, with peak values ​​≈ 1618, 1650, and 1680 cm⁻¹. -1 They are respectively classified as β-folds, random coils or α-helices, and β-turns.

[0042] Figure 6 Infrared characterization of natural cocoon shell amide I band (1720-1580 cm⁻¹) -1 The relative intensity of typical peaks.

[0043] Figure 7Infrared characterization of silkworm serine I band (1720-1580 cm⁻¹) after emergence from natural cocoons. -1 The relative intensity of typical peaks.

[0044] Figure 8 for Figure 5-7 After deconvolution, the relative contents of β-folds, random coils or α-helices and β-turns are calculated based on the peak area.

[0045] Figure 9 The image shows the SDS-PAGE protein electrophoresis diagram of the sericin extracted from the cocoon shell after the silkworm emerges from the cocoon shell, and the degummed silk after extraction in an 8M urea solution at 70 degrees Celsius.

[0046] Figure 10 This is a picture of an unprocessed silkworm cocoon.

[0047] Figure 11 This is a picture of silk fibers after the silkworm cocoons have undergone degumming treatment.

[0048] Figure 12 This is a photograph of the silk fibers from a silkworm cocoon after the eclosion process of this invention. Detailed Implementation

[0049] The present invention will be further described below with reference to embodiments.

[0050] Example 1

[0051] Processing technology of molting silkworms

[0052] 1) Process natural silkworm cocoons (sericite content 25%-30%), remove the silkworm pupae from the cocoon shell, and obtain a cocoon shell weighing 100 grams.

[0053] 2) Emulsification and dispersion of unsaturated fatty acids: Oleic acid is added to polyethylene glycol, sodium methyl cocoyl taurate and water, and emulsified by stirring at room temperature for 2 hours. The mass ratio of oleic acid: polyethylene glycol: sodium methyl cocoyl taurate: water is 3:1:1:5.

[0054] 3) Place the silk containing sericin in a weakly acidic buffer solution prepared with tartaric acid and either sodium hydroxide or potassium hydroxide, with pH values ​​of 2.0, 2.3, 2.6, 3.0, and 3.5 respectively, at a liquor ratio of 1:50. Heat the solution to induce swelling, dissolving the adhesion points of the sericin in the silk and ensuring the cocoon shell is completely swollen and dispersed.

[0055] Before heating the weakly acidic buffer solution, pre-emulsified and dispersed unsaturated fatty acids are added to allow the unsaturated fatty acids to penetrate and adhere to the sericin surface during the swelling process.

[0056] 4) Remove the swollen silk, dehydrate it, bleach it (the bleaching solution is 30-35% hydrogen peroxide, bath ratio 1:20), and dry it. Pre-dry it at 85-95℃ for 30-40 minutes, then bake it at 70-75℃ for 1-1.5 hours, and finally let it stand to dry, to obtain dispersed monofibrillated silk that does not stick together.

[0057] (1) Effect of temperature on swelling efficiency and sericin retention

[0058] In a tartaric acid buffer solution at pH 2.3 with an oleic acid concentration of 0.2%, swelling temperatures were set at 65℃, 70℃, 75℃, 80℃, and 85℃. With increasing temperature, the complete swelling time significantly decreased (15.5 h at 65℃, 7.5 h at 70℃, 5.5 h at 75℃, 3 h at 80℃, and 2.5 h at 85℃). However, analysis of the sericin content in the treated silk showed a significant positive correlation between temperature and the degree of sericin damage: the sericin content was 22.8% after treatment at 65℃, but plummeted to 6.7% after treatment at 85℃. This indicates that the sericin is severely damaged and dissolved in the solution with increasing temperature.

[0059] (2) The dominant role of pH in the swelling process: Tartaric acid buffer solutions with different pH values ​​(pH 2.0, 2.3, 2.6, 3.0, 3.5) were compared at 75℃. The complete swelling times were 2.5 h, 3 h, 5.5 h, 5.5 h, and 7 h, respectively, with measured gel contents of 17.9%, 18.0%, 20.1%, 21.1%, and 21.8%. The results showed that the swelling efficiency was higher when pH ≤ 2.3; when pH > 2.3, the efficiency decreased and tended to plateau, at which point temperature played a dominant role. When pH > 4, the chemical swelling effect disappeared, and only the high-temperature physical effect remained.

[0060] (3) Effect of organic acid type on swelling effect

[0061] At 75℃ and pH 2.3, tartaric acid, malic acid, and citric acid buffer solutions were compared. The swelling times of the three solutions were highly consistent, and the post-treatment gel contents were 17%, 17%, and 18%, respectively. This indicates that the core driving force of the feathering and swelling stage is the pH and temperature of the environment, and no clear correlation has been found with the specific type and molecular structure of the organic acid. Therefore, malonic acid, methylmalonic acid, formic acid, oxalic acid, mandelic acid, and lactic acid can be selected as long as the pH of the buffer solution meets the requirements.

[0062] (4) The anti-adhesion effect of oleic acid and its optimal concentration

[0063] Under fixed conditions (pH=2.3, 75℃), emulsified oleic acid of different mass fractions (0%, 0.05%, 0.1%, 0.2%, 0.5%) was added to the system. The results showed that oleic acid did not change the swelling time, indicating that it does not participate in chemical swelling; however, the residual rate was weakly positively correlated with the oleic acid concentration, indicating that it has a physical protective effect on sericin. The drying morphology showed that the 0% group was completely adhered; the 0.05% group was slightly softened; the 0.1% group showed further weakening; the 0.2% group reached a loose and ideal state; and there was no significant difference between the 0.5% and 0.2% groups (decreasing marginal effect). Considering that excessive oleic acid would affect the proportion of silk fibroin fibers, 0.2% was determined to be the optimal addition amount. Since oleic acid does not interfere with swelling, it can be added before heating or at the initial stage of heating (during pre-swelling).

[0064] Example 2

[0065] Processing technology of molting silkworms

[0066] 1) Process natural silkworm cocoons (sericite content 25%-30%), remove the silkworm pupae from the cocoon shell, and obtain a cocoon shell weighing 100 grams.

[0067] 2) Emulsification and dispersion of unsaturated fatty acids: Add oleic acid to polyethylene glycol, tallow amine and water, and stir and emulsify at room temperature for 2 hours. The mass ratio of oleic acid: polyethylene glycol: sodium methyl cocoyl taurate: water is 3:1:1:5.

[0068] 3) Place the silk containing sericin in a weakly acidic buffer solution prepared with tartaric acid and sodium hydroxide or potassium hydroxide, with a pH of 2.3 and a bath ratio of 1:30. Heat the solution to induce swelling, dissolving the adhesion points of the sericin in the silk and ensuring that the cocoon shell is in a completely swollen and dispersed state. The heating strategy is to pretreat at 65℃ for 1 hour, treat at 70℃ for 1 hour, and treat at 80℃ for 2 hours.

[0069] Before heating the weakly acidic buffer solution, add pre-emulsified and dispersed oleic acid with a mass concentration of 0.2%.

[0070] 4) Remove the swollen silk, dehydrate it, bleach it (bleaching solution is 30-35% hydrogen peroxide, bath ratio 1:20), and dry it. Pre-dry it at 85-95℃ for 30-40 minutes, then bake it at 70-75℃ for 1-1.5 hours. Finally, let it stand and air dry to obtain dispersed monofibrillated silk that does not stick together, with a gum content of about 18-22%.

[0071] Example 3

[0072] Processing technology of molting silkworms

[0073] 1) Process natural silkworm cocoons (sericite content 25%-30%), remove the silkworm pupae from the cocoon shell, and obtain a cocoon shell weighing 100 grams.

[0074] 2) Emulsification and dispersion of unsaturated fatty acids: Trans oleic acid was added to Span80, sodium octadecyl sulfonate solution (5%), surfactant-modified polyether and distilled water, and emulsified at room temperature for 2 hours. The ratio of trans oleic acid: Span80: sodium octadecyl sulfonate solution (5% mass concentration): surfactant-modified polyether: distilled water = 3:0.5:2:0.5:4.

[0075] 3) Place the silk containing sericin in a weakly acidic buffer solution prepared with tartaric acid and sodium hydroxide or potassium hydroxide, with a pH of 2.3 and a bath ratio of 1:25. Heat the solution to induce swelling, dissolving the adhesion points of the sericin in the silk and ensuring that the cocoon shell is in a completely swollen and dispersed state. The heating strategy is to pretreat at 65℃ for 1 hour, treat at 70℃ for 1 hour, and treat at 80℃ for 2 hours.

[0076] Before heating the weakly acidic buffer solution, add pre-emulsified and dispersed oleic acid, with a trans oleic acid mass concentration of 0.2%.

[0077] 4) Remove the swollen silk, dehydrate it, bleach it (using 30-35% hydrogen peroxide at a liquor ratio of 1:20), and then dry it at 85-95℃ for 30-40 minutes, followed by baking at 70-75℃ for 1-1.5 hours. Finally, let it stand and air dry to obtain dispersed, single-fiber feathered silk that does not stick together, with sericin content of 18-22%.

[0078] Example 4

[0079] The rest is the same as in Example 2, except that oleic acid is replaced with myristoleic acid, ricinoleic acid and palmitoleic acid respectively, and each yields dispersed single-fiber feathered silk that does not stick together, with a sericin content of (17-22%).

[0080] Example 5

[0081] The rest is the same as in Example 2, except that the cocoon shells are replaced with cotton board (with a sericin content of about 18%, some of which has been lost in the previous production process). Before treatment, the cotton board is washed with pure water: it is kept warm and washed in pure water at 40°C (liquor ratio 1:30) for 1.5 hours.

[0082] Then, following the process described in Example 2, dispersed, single-fiber feathered silk fibers that do not adhere to each other were obtained, with sericin content ranging from 11% to 14%.

[0083] Comparison of various indicators:

[0084] The silk produced by directly preparing silkworm silk from cocoon shells in this invention has significantly improved various indicators compared to raw silk (untreated cocoon shells) and silkworm silk prepared by traditional degumming and refining processes.

[0085] like Figure 1 You can clearly see the sericin sticking and hardening on the surface of the raw silk. This stickiness will cause the silk to feel stiff and hard, and it will not be spinnable.

[0086] Figure 2 This is traditionally degummed and refined silk. The silk surface is smooth and in a state of single-fiber dispersion. The sericin has been almost completely removed, which is reflected in the smooth feel on a macroscopic scale.

[0087] Figure 3 The silk produced in this invention is feathered silk. It is visible that while the sericin is preserved, the surface is smooth and the fibers are dispersed and soft. This is significantly different from the adhesion of raw silk. Macroscopically, it feels fluffy, smooth and soft to the touch.

[0088] Infrared spectrum comparison:

[0089] Comparison of untreated silk, degummed silk, and feathered silk (comparison of solidifying materials for feathered silk). Figure 4 In the infrared spectrum shown, at 3270 cm⁻¹ -1 The nearby absorption peak is attributed to the NH stretching vibration of protein molecules in animal fibers, at 2970 cm⁻¹. -1 2930cm -1 The nearby absorption peaks are attributed to the stretching vibrations of the methyl (CH3) and methylene (CH2) groups. Based on the characteristic infrared peaks of proteins, the peaks are located in the 1700-1600 cm⁻¹ range. -1 The peak of amide I and 1600-1500 cm⁻¹ -1 This is the peak of the amide II band. 1229 cm⁻¹ -1 The nearby characteristic peaks are attributed to the CN stretching vibrations in the peptide bonds of protein molecules. Silk at 1446 cm⁻¹... -1 The nearby characteristic peaks can be attributed to C=C bond stretching vibrations or CH bond in-plane bending vibrations, 1400 cm⁻¹. -1 The nearby absorption peak is attributed to the symmetric bending vibration of CH3. (1062 cm⁻¹) -1 The characteristic peak at 1160 cm⁻¹ is attributed to the C-C stretching vibration in the peptide chain. -1 The characteristic peak at 615 cm⁻¹ belongs to the CO antisymmetric stretching vibration. -1 The characteristic peak at 540 cm⁻¹ belongs to the NH bending vibration. -1 The characteristic peak at that point is attributed to out-of-plane bending vibration at C=O.

[0090] Infrared spectroscopy confirms that the main components of silkworm silk have not changed; it remains protein fiber and retains the unique characteristics of protein fiber.

[0091] Determination of secondary structure of silk fibroin:

[0092] Fourier transform infrared spectroscopy analysis revealed the conformational transformation of the silk fibers from random coil / α-helix to β-sheet induced by the feathering process. Amide I band (1720-1580 cm⁻¹) -1 The relative intensities of the typical peaks changed significantly before and after feathering, indicating an evolution of the secondary structure. To determine the β-sheet content, we deconvolved the amine I band in the Fourier transform infrared spectrum. Figure 5-7 The deconvolution peak diagrams for cocoon shells, degummed silk, and molted silk are shown, with peak values ​​approximately 1618, 1650, and 1680 cm⁻¹, respectively. -1 The peak values ​​were attributed to β-sheet, random coil / α-helix, and β-turn, respectively. Calculations of the peak values ​​in the cocoon shell and the emerging silk indicated an increase in β-sheet within the silk fibers during emergence. Results were obtained through deconvolution calculations of the amide peaks. Figure 8 The β-sheet content of untreated silk was 41.69%, which increased to 56.06% after feathering treatment. The increase in β-sheet content and the evolution of secondary structure indicate that the stability of the material has increased.

[0093]

[0094] The concentration of sericin protein in the material was extracted using 70°C 8M urea, and the molecular weight of the protein was determined by SDS-Page electrophoresis.

[0095] Silkworm silk after natural cocoon shell degumming and natural cocoon shell eclosion treatment was used to extract sericin using 8M urea at 70 degrees Celsius (liquor ratio 1:20). The protein concentration of the supernatant was calculated using a UV spectrophotometer at 280 nm.

[0096]

[0097] The experimental results show that a large amount of silk protein can be dissolved in urea after the silkworms emerge from the molting process. Further analysis of the supernatant using SDS-Page protein electrophoresis gels, with pre-stained proteins ranging from 10kD to 180kD and a separating gel concentration of 15%, yielded the following results. Figure 9 This further confirms that traditionally degummed silk does not release protein, the sericin released from the cocoon shell has a large molecular weight, which is higher than the maximum value of 180k of pre-dyed protein. The molecular weight of sericin in the molted silk has degraded, but there are still a large number of large-molecule sericin proteins, with a protein molecular weight distribution of about 50k-180k and above.

[0098] Processed sample display, whiteness, and fluffiness.

[0099] All indicators are significantly improved compared to untreated silk and traditional degummed refined silk.

[0100] Silk weight – a comparison of treated 100g cocoon shells:

[0101]

[0102] (The above weight baseline data was determined)

[0103] Verify sericin content:

[0104] The sericin content of silk was tested in accordance with industry standard FZ / T 40004-2023, "Test Method for Sericin Content of Silk". This document specifies the test method for sericin content of silk; it is applicable to the determination of sericin content in raw silk, silk floss, and other products. Note: This sericin content test is only valid for silk that has not been solidified and has not used cross-linking agents.

[0105] The actual results are as follows:

[0106]

[0107] This process can also be applied to silk floss, secondary cocoons, and silk reeling byproducts such as slivers, which are not yet refined and degummed but are still bound together by sericin and do not have combing properties. Take slivers as an example.

[0108]

[0109] 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 processing technology for molting silkworm silk, characterized in that, Follow these steps to process: S1: Swelling, dispersion and anti-adhesion treatment: The silk containing sericin is placed in a weakly acidic buffer solution prepared with organic acid, with a pH value of 1.0-4.0, and heated for swelling treatment to dissolve the adhesion points of the sericin in the silk, so that the cocoon shell is in a completely swollen and dispersed state. Emulsified and dispersed unsaturated fatty acids are added to the weakly acidic buffer solution in advance, or emulsified and dispersed unsaturated fatty acids are added at the beginning of the swelling in step S1, so that the unsaturated fatty acids penetrate and adhere to the surface of the sericin during the swelling process. S2: Post-processing: The swollen silk is removed, dehydrated, and then dried to obtain dispersed single-fiber feathered silk that does not stick together.

2. The processing technology for feathered silk according to claim 1, characterized in that: The organic acid includes at least one of tartaric acid, malic acid, citric acid, formic acid, oxalic acid, mandelic acid, and lactic acid, and the unsaturated fatty acid is selected from one of oleic acid, trans oleic acid, myristoleic acid, ricinoleic acid, and palmitoleic acid.

3. The processing technology for the molting silkworm silk according to claim 1, characterized in that: The silk containing sericin is natural cocoon shell, raw silk after reeling, or reeling waste; when processing reeling waste, a pure water washing pretreatment step is added before step S1.

4. The processing method for the feathered silk according to any one of claims 1-3, characterized in that: The bath ratio in S1 is 1:20-50, and the mass concentration of unsaturated fatty acids is 0.1%-0.5%. The unsaturated fatty acids are added before heating.

5. The processing technology for the molting silk according to claim 4, characterized in that: The pH of a weakly acidic buffer solution is 2.0-2.

6.

6. The processing technology for the molting silkworm silk according to claim 5, characterized in that: Unsaturated fatty acids are emulsified and dispersed as follows: Unsaturated fatty acids are added to polyethylene glycol, sodium methyl cocoyl taurate, and water, and emulsified by stirring at room temperature. The mass ratio of unsaturated fatty acids: polyethylene glycol: sodium methyl cocoyl taurate: water is 3:1:1:

5.

7. The processing technology for feathered silk according to claim 6, characterized in that: The swelling treatment is carried out at a temperature of 65-85℃.

8. The processing technology for molting silk according to claim 7, characterized in that: First, the silk containing sericin is pre-swollen by keeping it at 40℃-65℃ for 1-3 hours, and then the temperature is raised to 70℃-80℃ to swell until it is completely dispersed.

9. The processing technology for feathered silk according to claim 7, characterized in that: In S2, the de-dried silk is first bleached and then dried in stages: pre-drying at 85-95℃ for 30-40 minutes, then baking at 70-75℃ for 1-1.5 hours, and finally letting it stand to dry.

10. Silk prepared by the processing method of feathered silk as described in any one of claims 1-9.

Images