Preparation method of bleached China-hemp noil rotor pure spinning yarn

Abstract

The invention discloses a preparation method of bleached China-hemp and noil rotor pure spinning yarn, and belongs to the technical field of spinning. The preparation method of the bleached China-hemp noil rotor pure spinning yarn comprises the following steps that bleached China-hemp noil fibers are subjected to opening treatment, and opened fibers are obtained; spraying a curing aid to the opened fibers to obtain fibers subjected to curing treatment; carrying out double-roller combined carding on the fibers subjected to the curing treatment to obtain carded fibers; the carded fibers are subjected to drafting and drawing treatment, and drawn China-hemp drawn slivers are obtained; feeding the drawn China-hemp drawn slivers into a rotor spinning machine, and performing rotor spinning to obtain the pure China-hemp single yarn. The invention aims to systematically solve the resultant yarn problems of poor rotor spinning spinnability, insufficient resultant yarn strength, high end breakage rate and the like caused by the problems of low strength, poor cohesive force and the like of bleached China-hemp noil fibers with the length of less than 30 mm, and is suitable for stable production of pure China-hemp rotor spinning single yarns and plied yarns with the number of 28.4 tex and more.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of spinning technology, in particular to a preparation method of bleached hemp shive roving spun yarn. BACKGROUND

[0002] Hemp fiber, as a natural cellulose fiber, has a very important position in the textile field due to its unique structural properties. The fiber has excellent moisture absorption, air permeability, antibacterial and antifungal properties, and ultraviolet resistance, and shows a broad application prospect in high-end clothing, home textiles and industrial textiles. However, the industrialized production of pure hemp yarn using bleached hemp shive as raw material still faces significant technical bottlenecks.

[0003] Hemp shive is a short fiber separated from hemp stems during the processing of hemp stems into textile raw materials due to the fiber length being significantly shorter than the conventional spinning requirements, mainly produced in the carding process. The main length of hemp shive is usually less than 30 mm, and the strength is low, containing a large amount of shive and short fibers, which is traditionally considered as a raw material that is difficult to be directly used for spinning. In addition, although bleaching can improve the color of the fiber, the chemical action during the bleaching process will further damage the already weak mechanical properties of the fiber, and the removal of part of the pectin may cause the adhesion between fibers to decrease, making the spinnability further deteriorate. These characteristics make the fiber prone to produce a large amount of short fibers and flying during the spinning process, with a high rate of broken ends, making it difficult to stably spin bleached hemp shive pure spun yarn with uniform evenness and strength meeting the requirements, especially in the field of medium and fine yarns below 30 tex.

[0004] At present, the mainstream ring spinning process has high requirements for fiber length and strength, which easily leads to the broken end phenomenon of bleached hemp shive under high draft tension, seriously affecting the production efficiency. In addition, the ring spun yarn structure is tight, and the wrapping effect of such hemp fiber is poor, resulting in more hairiness and a hard and stiff hand feeling of the finished yarn. Although wet spinning can enhance the adhesion of fibers to some extent through chemical slurry, it has problems such as long process flow, high energy consumption and chemical solvent pollution. The rotor spinning technology has the characteristics of relatively loose requirements for fiber length, loose structure of finished yarn and less harmful hairiness. However, when facing such low-strength and poor-adhesion hemp shive fibers, the rotor spinning mechanism is still difficult to make the single yarn absolute strength meet the application requirements.

[0005] In order to improve the performance of the yarn, plying is an effective means to improve the breaking strength and wear resistance of the yarn, but the traditional plying process parameters are not suitable for bleached hemp shive pure spun yarn, and the performance improvement after plying is limited. The existing technology mostly uses hemp and other fibers to blend in order to improve the spinnability, but this will sacrifice the natural properties and market value of pure hemp products, which is difficult to meet the growing demand for pure hemp products in the market, and also cannot fully realize the economic benefits and product potential of degummed and bleached hemp shive. SUMMARY

[0006] The present application aims to provide a preparation method of bleached hemp noil rotor pure spun yarn to solve the problems in the background art. The present application aims to systematically solve the problems of poor spinnability, insufficient yarn strength and high breakage rate of rotor spinning caused by the low strength and poor cohesion of bleached hemp noil fibers with a length of less than 30 mm, and is suitable for stable production of pure hemp rotor spun singles and ply yarns with a number of 28.4 tex and above.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0008] One of the technical schemes of the present application: a preparation method of bleached hemp noil rotor pure spun yarn is provided, comprising the following steps:

[0009] The bleached hemp noil fibers are subjected to opening treatment to obtain opened fibers;

[0010] The opened fibers are sprayed with a health care aid to obtain fibers after health care treatment;

[0011] The fibers after health care treatment are subjected to double roller combined carding to obtain carded fibers;

[0012] The carded fibers are subjected to drafting and drawing treatment to obtain hemp mature slivers after drawing;

[0013] The hemp mature slivers after drawing are fed into a rotor spinning machine for rotor spinning to obtain pure hemp singles.

[0014] Preferably, the bleached hemp noil fibers are short fibers separated from hemp stems during the process of processing into textile raw materials and then subjected to bleaching treatment, with a fiber length of ≤30 mm, a single fiber fineness of 1.8-3.7 dtex, a single fiber strength of 1.5-2.2 cN / dtex, a breaking elongation of 3.8-4.5%, and a fiber whiteness of ≥75%.

[0015] Preferably, the process parameters of the opening treatment are as follows: a feeding cord line speed of 1.0 m / min, an opening roller diameter of 250 mm, an opening roller rotating speed of 506 r / min, and an opening speed ratio of 238 times.

[0016] Preferably, the health care aid contains cohesion enhancer, antistatic agent, softening agent and water; the mass ratio of the cohesion enhancer, antistatic agent and softening agent is 2:1:2; the water content in the health care aid is 97-99 wt%; and the moisture regain of the fibers after health care treatment is 10-12%.

[0017] Preferably, the double roller combined carding includes pre-carding and main carding.

[0018] The pre-carding adopts a roller carding machine, and the process parameters are as follows: the speed of the cylinder is 60 r / min, the speed of the work roller is 8 r / min, the speed of the stripping roller is 24 r / min, the net outlet speed is 10 m / min, and the total draft multiple is 50.

[0019] The main carding adopts a worsted carding machine, and the process parameters are as follows: the speed of the large cylinder is 180 r / min, the speed of the doffer is 5 r / min, the distance between the cylinder and the doffer is 0.18 mm, the distance between the licker-in and the feed roller is 0.45 mm, the net outlet speed is 20.1 m / min, and the surface linear speed ratio of the cylinder and the doffer is 36.

[0020] Preferably, the drawing and doubling treatment is three-drawing and doubling, and the doubling number is 6; the back zone draft multiple of the first-drawing is 1.10 times, and the total draft multiple is 5.0-5.4 times; the back zone draft multiple of the second-drawing is 1.10 times, and the total draft multiple is 5.5-6.5 times; the back zone draft multiple of the third-drawing is 1.10 times, and the total draft multiple is 5.5-6.5 times, which is the key to forming the yarn, and aims to realize the final straightening of the fiber and the ultimate uniformity of the structure.

[0021] Preferably, in the rotor spinning process, the sawtooth parameters of the combing roller are as follows: the working angle is 65-80°, and the tooth distance is 2.1-4.95 mm; the twister adopts a false twister disc with a groove number of 0-8; the rotor adopts T type, K type or G type, the spinning cup diameter is 40-46 mm, the negative pressure is 4.5-5.5 kPa; the draft multiple is 112.5-137.5, the twist is 125-135 twists / 10 cm, the combing roller speed is 6500-7500 rpm, and the tension correction coefficient is 0-0.5%.

[0022] The second technical scheme of the present application provides a pure hemp single yarn obtained by the preparation method.

[0023] The third technical scheme of the present application provides a preparation method of a pure hemp strand.

[0024] Preferably, the preparation method of the pure hemp strand comprises the following steps:

[0025] The at least two pure hemp single yarns are combined on a doubling machine, the doubling tension is controlled to be 8-12 cN, and the combined yarn is obtained.

[0026] The combined yarn is twisted in the S direction on a twisting machine, the ply twist is controlled to be 50-80 twists / 10 cm, the spindle speed is 4000-5000 r / min, the sliver speed is 6-10 m / min, and the ratio of the ply twist factor to the single yarn twist factor is maintained between 0.4 and 0.6, to obtain the pure hemp ply yarn.

[0027] The beneficial technical effects of the present application are as follows:

[0028] The present application aims to systematically solve the problems of poor spinnability, insufficient yarn strength and high breakage rate of rotor spinning caused by the low strength and poor cohesion of bleached hemp noil fibers with a length of less than 30 mm, and is suitable for stable production of pure hemp rotor spun single yarn and ply yarn with a number of 28.4 tex and above.

[0029] The present application develops a rotor spinning process targeting the characteristics of degummed and bleached hemp noil fibers. The process covers the optimization of the whole process from fiber pretreatment to carding and yarn formation. The rigidity and brittleness of such noil fibers are reduced through flexible conditioning, the fiber damage is reduced through fine carding, and the insufficient cohesion is compensated through adaptive adjustment of the rotor spinning process, thereby realizing stable spinning of pure degummed and bleached hemp noil yarn and systematically solving the technical problems of poor spinnability, low yarn strength and high breakage rate of bleached hemp noil fibers, providing a new way for the development of high-quality pure hemp products.

[0030] Through the optimized fiber flexible pretreatment and double roller combined carding process, the brittle hemp noil fibers are effectively protected while the fibers are fully loosened, significantly reducing fiber damage and short fiber rate, laying a good foundation for subsequent spinning. Through the optimally selected rotor spinning process, pure hemp single yarn with a number of 28.4 tex and above is successfully prepared, wherein the single yarn irregularity is ≤22.13%, harmful hair is significantly reduced, and the breaking strength can reach 7.04 cN / tex, effectively solving the technical problem of difficult stable spinning of fine pure hemp yarn. The breaking strength and wear resistance of the ply yarn are also significantly improved compared to those of the single yarn. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0032] Figure 1 The preparation flowchart of the pure hemp single yarn of the present application. DETAILED DESCRIPTION

[0033] In terms of yarn performance evaluation, too high harmful hairiness index can significantly reduce the effective cohesion of fibers in the yarn body, thereby weakening the breaking strength and wear resistance of the yarn. In the subsequent weaving process, harmful hairiness can easily cause yarn entanglement and breakage, affecting production efficiency; in addition, it can also cause the surface of the final fabric to be blurred and the texture to be unclear, and exacerbate the tendency of pilling, thereby damaging the appearance quality and durability of the finished product. Therefore, effectively controlling harmful hairiness is one of the keys to improving the comprehensive quality of the yarn.

[0034] The current method for evaluating the performance of the yarn mainly depends on single or a few indicators such as breaking strength or harmful hairiness index, and it is difficult to comprehensively and objectively reflect the comprehensive performance of the yarn. As a multi-index comprehensive evaluation method, the grey correlation degree analysis can normalize multiple performance indicators and output comparable comprehensive evaluation values, and has shown advantages in the evaluation of various textile materials. However, this method has not been systematically applied to the comprehensive evaluation of hemp yarn, especially the comprehensive evaluation system for rotor spinning pure hemp yarn is still blank.

[0035] The various exemplary embodiments of the present application will now be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application. It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application.

[0036] In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value within the stated range, and any other stated value or intermediate value within the stated range, is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. It should be noted that the present application does not detail any aspects that are routine in the art, and are not the focus of the present application.

[0038] As for the "comprising", "including", "having", "containing" and the like used in the present application, they are all open terms, i.e. meaning containing but not limited to.

[0039] The present application discloses a preparation method of bleached hemp noil rotor spinning pure yarn, comprising the following steps:

[0040] Step 1, Opening and removing impurities: The bleached hemp fibers are opened to obtain opened fibers; the process parameters for the opening process are: feed cord speed 1.0 m / min, opening roller diameter 250mm, opening roller speed 506 r / min, and opening speed ratio 238 times.

[0041] By controlling parameters such as the feed cord speed and the opening roller speed, large fiber bundles are gently loosened and some impurities are removed without pursuing complete fiber separation. This step aims to create loose physical conditions for the uniform penetration of subsequent auxiliaries and is the basis for subsequent fine processing.

[0042] Step 2: Hemp fiber undergoes conditioning treatment: A conditioning agent is sprayed onto the opened fibers to obtain conditioned fibers; the conditioning agent contains a cohesion enhancer, an antistatic agent, a softener, and water; the mass ratio of the cohesion enhancer, antistatic agent, and softener is 2:1:2; the water content in the conditioning agent is 97-99 wt%; the moisture regain of the conditioned fibers is 10-12%.

[0043] This treatment utilizes the characteristic that opened fibers are more easily penetrated, allowing auxiliary molecules to act efficiently inside the fibers, effectively reducing their rigidity and brittleness, and precisely controlling the fiber moisture regain within a suitable range of 10-12%, fundamentally improving the fiber's flexibility and antistatic ability, thus preparing it for the carding process.

[0044] Step 3, dual-roller combined carding to form a web: The fiber after conditioning is subjected to dual-roller combined carding to obtain carded fiber; the dual-roller combined carding includes pre-carding and main carding;

[0045] The pre-carding process uses a roller carding machine with the following parameters: cylinder speed 60 r / min, work roll speed 8 r / min, stripping roll speed 24 r / min, spacing between the cylinder and work roll 0.30 mm × 0.25 mm × 0.20 mm (decreasing from inlet to outlet), web exit speed 10 m / min, and total draw ratio 50. This stage focuses on the initial loosening, gentle opening, and mixing of the fibers.

[0046] The main carding process uses a worsted carding machine with the following parameters: cylinder speed 180 r / min, doffer speed 5 r / min, cylinder-doffer spacing 0.18 mm, cylinder-doffer spacing 0.25 mm × 0.20 mm × 0.15 mm (decreasing from inlet to outlet), licker-in roller-feed roller spacing 0.45 mm, web exit speed 20.1 m / min, and cylinder-doffer surface linear speed ratio 36. This stage is responsible for core carding and fiber orientation and straightening. Through the aforementioned reasonable speed ratio and gradually tightening spacing configuration, the damage to fibers and short fiber growth caused by over-carding are effectively reduced while ensuring sufficient carding.

[0047] The configuration of the dual roller combing optimizes the stress on the fiber raw material in the combing zone, realizing "gentle opening" and "gradual combing" of the fiber bundle. While fully separating the fibers and removing short fibers and impurities, it protects the hemp fibers with low strength and high brittleness to the maximum extent, thus forming a high-quality hemp fiber web with less fiber damage and uniform structure.

[0048] Step 4: The combed fibers are subjected to drafting and slivering to obtain a slivered hemp sliver. The drafting and slivering process consists of three slivering stages, with a total of 6 slivers. The drafting ratio in the back zone of the first slivering stage is 1.10 times, and the total drafting ratio matches the number of slivers, being 5.0-5.4 times, focusing on loosening fiber hooks and improving transverse uniformity. The drafting ratio in the back zone of the second slivering stage is 1.10 times, and the total drafting ratio is 5.5-6.5 times, further straightening the fibers while focusing on optimizing the sliver structure. The drafting ratio in the back zone of the third slivering stage is 1.10 times, and the total drafting ratio is 5.5-6.5 times, which is crucial for sliver formation, aiming to achieve final fiber straightness and ultimate structural uniformity. The roller spacing for the three slivering stages is 40 mm × 40 mm × 50 mm, and sufficient roller pressure is applied to effectively control fiber movement.

[0049] During the drafting and drawing process, a process route of "tight spacing, small back zone drafting, and sequential drafting configuration" is adopted, and the six-end drawing is strictly followed. Through this multi-stage drawing process with precise parameter coordination, the unevenness of hemp sliver can be controlled to below 17%, laying a solid foundation for high-quality yarn production in subsequent rotor spinning.

[0050] Step 5, Rotor spinning: The hemp sliver after drawing is fed into a rotor spinning machine. In order to achieve fine processing of the fragile hemp fibers, rotor spinning is carried out to obtain pure hemp single yarn.

[0051] During the rotor spinning process, the sawtooth parameters of the combing roller are: working angle 65-80°, tooth pitch 2.1-4.95 mm, to achieve a balance between sufficient opening and reduced fiber damage; the twister uses a false twist disc with 0-8 grooves to optimize yarn twist transmission and wrapping effect; the rotor is T-type, K-type, or G-type depending on the yarn number being spun, with a diameter of 40-46 mm and a negative pressure of 4.5-5.5 kPa to ensure stable fiber transport and cohesion; the draft ratio is 112.5-137.5 (preferably 125 times) to reduce the damage of the drafting force to the fiber; the twist is in the high twist range of 125-135 twists / 10 cm (preferably 130 twists / 10 cm) to strongly compensate for the poor cohesion of hemp fibers; the speed of the combing roller is 6500-7500 rpm (preferably 7000 rpm) depending on the selected rack model, and the tension correction coefficient is 0-0.5%.

[0052] The rotor spinning process strictly adheres to the core technological principle of "high twist and low tension." Through the synergistic effect of the above-mentioned specialized equipment and optimized parameters, high-quality pure hemp single yarn with a count of 28.4 tex and above was successfully and stably spun.

[0053] Furthermore, the bleached hemp fiber is a short fiber separated from hemp stalks during the processing of textile raw materials and then bleached. The fiber length is ≤30 mm, the single fiber fineness is 1.8-3.7 dtex, the single fiber strength is 1.5-2.2 cN / dtex, the breaking elongation is 3.8-4.5%, and the fiber whiteness is ≥75%.

[0054] The bleached hemp fiber of this invention is a short fiber naturally separated during the processing of hemp stalks into textile raw materials, due to its significantly shorter fiber length than commonly required for spinning. It is mainly produced during the carding process. Its main body length is less than 30 mm, and it has low strength, contains a large amount of hemp fibers and short fibers, and is traditionally considered a raw material that is difficult to spin directly. Although bleaching improves the color of the fiber, the chemical reactions during the process further damage its already weak strength, and the removal of some pectin may lead to a decrease in fiber cohesion, further deteriorating its spinnability.

[0055] The comprehensive performance evaluation method for pure hemp yarn based on grey relational analysis of the present invention is as follows:

[0056] Step 1, construct an evaluation index system: determine n key performance indicators for evaluating the quality of pure hemp yarn;

[0057] Step 2, determine the reference sequence and comparison sequence: construct the comparison sequence X from the data of the m pure hemp yarn samples to be evaluated. i(i=1,2,...,m), each sequence contains n corresponding performance index values. A reference sequence X0 is defined, which consists of the ideal or optimal value of each performance index.

[0058] Step 3: For each sequence, calculate its average value using the following formula:

[0059]

[0060] Step 4, Dimensionless Data Processing: Since the dimensions and orders of magnitude of each indicator are different, the original data is standardized. The mean-based method is used for dimensionless processing before grey relational analysis to eliminate the influence of dimensions. The formula is as follows:

[0061] ;

[0062] Step 5, Calculate the grey relational coefficient: For each indicator, calculate the comparison sequence Y one by one. i The correlation coefficient between (i=1,2,...,m) and the reference sequence Y0 on this index is given by the following formula (where ρ is the resolution coefficient, taken as 0.5):

[0063]

[0064] Step 6, Calculate the grey relational degree: Take the weighted average of the correlation coefficients of all indicators for each sample Xi to obtain the comprehensive grey relational degree γ between the sample and the ideal sample. 0i The formula is as follows:

[0065]

[0066] Step 7, Comprehensive Evaluation and Ranking: Based on the calculated grey relational degree γ 0i The size of all samples is used to sort them; γ 0i The higher the value, the closer the overall performance of the pure hemp yarn is to the ideal state, and the better its quality.

[0067] Furthermore, the key performance indicators mentioned in step 1 include, but are not limited to, one or more of the following: breaking strength, breaking strength CV value, breaking elongation, yarn unevenness, and harmful hair index.

[0068] This invention also discloses a method for preparing pure hemp yarn. The method for preparing pure hemp yarn involves twisting together at least two strands of the aforementioned pure hemp single yarn, and includes the following steps:

[0069] Step 1, combining: At least two strands of the pure hemp single yarn are combined on a combining machine. By precisely controlling the combining tension to 8-12 cN, the tension of each single yarn is ensured to be uniform and consistent, laying the foundation for subsequent twisting to prepare a stable and high-strength yarn, and the combined yarn is obtained.

[0070] Step 2, Twisting: The combined yarn is twisted in the S direction on a twisting machine, and the twist of the ply is controlled to be 50-80 twists / 10 cm (preferably 70 twists / 10 cm). By controlling the spindle speed (4000-5000 r / min) and the sliver output speed (6-10 m / min), and maintaining the ratio of the ply twist coefficient to the single yarn twist coefficient between 0.4 and 0.6, a pure hemp ply yarn with significantly improved breaking strength, abrasion resistance and structural stability is finally obtained.

[0071] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.

[0072] Figure 1 This is a flowchart illustrating the preparation process of pure hemp single yarn according to the present invention.

[0073] Example 1

[0074] A method for preparing bleached hemp fiber rotor-spun yarn includes the following steps: The bleached hemp fiber is short fiber separated from hemp stalks during the processing of hemp into textile raw materials and subsequently bleached.

[0075] Step 1, Opening and Impurity Removal: Select bleached hemp fibers separated during the processing of hemp stalks into textile raw materials and then bleached as raw materials (fiber length ≤30 mm, fiber fineness 20-30 dtex, single fiber strength 1.5-2.2 cN / dtex, breaking elongation 3.8-4.5%, fiber whiteness ≥75%): feed cord speed 1.0 m / min, opening roller diameter 250 mm, opening roller speed 506 r / min, opening speed ratio 238 times;

[0076] Step 2, Conditioning Treatment: A conditioning agent is sprayed onto the opened fibers to loosen the bleached hemp fibers, resulting in fibers with a conditioning treatment (moisture regain 10-12%). The conditioning agent consists of water and a cohesion enhancer (CTA-1886B), an antistatic agent (FK-301), and a softener (BD-1007R-30 cationic silicone emulsion) in a mass ratio of 2:1:2. The water content in the conditioning agent is 97-99 wt%.

[0077] Step 3, Double roller combined carding to form a web: The fiber after conditioning is combined with a double roller to obtain the carded fiber; the double roller combined carding is divided into pre-carding and main carding;

[0078] The pre-carding process uses a roller carding machine with the following parameters: cylinder speed 60 r / min, work roll speed 8 r / min, stripping roll speed 24 r / min, web exit speed 10 m / min, and total draw ratio 50.

[0079] The main combing process uses a worsted carding machine with the following parameters: cylinder speed 180 r / min, doffer speed 5 r / min, cylinder-doffer gap 0.18 mm, licker-in and feed roller gap 0.45 mm, web exit speed 20.1 m / min, and cylinder-doffer surface linear speed ratio 36.

[0080] Step 4: The combed fibers are drawn and spun to obtain the spun hemp sliver. The drawing and spun process consists of three stages, with a total of 6 slivers. The back zone draw ratio of the first stage is 1.10, and the total draw ratio is 5.4. The back zone draw ratio of the second stage is 1.10, and the total draw ratio is 6.2. The back zone draw ratio of the third stage is 1.10, and the total draw ratio is 5.8. The roller spacing for the three stages is 40 mm × 40 mm × 50 mm.

[0081] Step 5, rotor spinning: The hemp sliver after drawing is fed into a rotor spinning machine for rotor spinning to obtain pure hemp single yarn with a count of 28.4 tex;

[0082] During rotor spinning, the sawtooth parameters of the combing roller are: working angle 100°, tooth pitch 4.95 mm, tooth height 4.0; the twister uses a false twist disc with 0 grooves; the rotor is T-shaped, the diameter of the spinning cup is 46 mm, and the negative pressure is 4.5-5.5 kPa; the draft ratio, twist, and combing roller speed of each sample are determined according to the corresponding parameters in Table 1, and the tension correction coefficient is 0-0.5%.

[0083] The breaking strength, strength unevenness, breaking elongation, yarn evenness, and harmful hairiness index of pure hemp single yarn under different process parameters in Example 1 were tested. The test results are shown in Table 1. In Table 1, the harmful hairiness index is the harmful hairiness index of 4 mm and above.

[0084] The harmful fuzz standard for ramie yarn (≥4 mm) in FZ / T 01086-2020 is mainly based on a comprehensive consideration of fiber characteristics and production process. Ramie and hemp are both bast fibers, and both tend to produce a lot of long fuzz when spun into yarn, which is somewhat different from flax.

[0085] Table 1. Properties of pure hemp yarn and its products under different processing parameters.

[0086] Experiment No. Drafting multiple Twist (twist / 10 cm) Doffer speed (rpm) Breaking strength (cN / tex) Strength CV (%) Breaking elongation (%) Yarn irregularity (%) Harmful hair index (root / 10 cm) D-01 150 130 7000 5.58 16.71 3.94 23.94 20.56 D-02 137.5 130 7000 5.99 17.57 4.29 23.61 9.64 D-03 125 130 7000 7.04 14.57 4.16 22.13 15.54 D-04 112.5 130 7000 6.13 16.65 4.53 26.27 17.16 D-05 100 130 7000 6.03 18.12 4.73 26.07 22.88 T-01 125 140 7000 5.45 16.67 4.55 26.78 11.62 T-02 125 135 7000 6.03 18.12 4.73 26.07 13.58 T-03 125 130 7000 7.04 14.57 4.16 22.13 15.54 T-04 125 125 7000 5.84 18.96 3.89 25.32 19.28 T-05 125 120 7000 5.52 16.8 3.51 26.49 24.23 S-01 125 130 8000 5.78 17.63 3.29 23.22 13.56 S-02 125 130 7500 6.04 16.72 3.98 24.04 5.32 S-03 125 130 7000 7.04 14.57 4.16 22.13 15.54 S-04 125 130 6500 6.01 17.9 3.78 25.52 5.36 S-05 125 130 6000 5.65 22.14 3.59 26.16 11.16

[0087] This embodiment uses a single-factor comparative experiment to systematically examine the effects of three key process parameters in step 5—twist (120, 125, 130, 135, 140 twists / 10 cm), draft ratio (100, 112.5, 125, 137.5, 150), and combing roller speed (6000, 6500, 7000, 7500, 8000 rpm)—on the performance of single yarn.

[0088] Based on the above, we will analyze the comprehensive performance of pure hemp yarn using a grey relational analysis-based method:

[0089] Step 1, construct an evaluation index system: determine n key performance indicators for evaluating the quality of pure hemp yarn;

[0090] Step 2, determine the reference sequence and comparison sequence: construct the comparison sequence X from the data of the m pure hemp yarn samples to be evaluated (15 samples). i (i=1,2,...,m), each sequence contains n corresponding performance index values. A reference sequence X0 is defined, which consists of the ideal or optimal value of each performance index.

[0091] Step 3: For each sequence, calculate its average value using the following formula:

[0092]

[0093] Step 4, Dimensionless Data Processing: Since the dimensions and orders of magnitude of each indicator are different, the original data is standardized. The mean-based method is used for dimensionless processing before grey relational analysis to eliminate the influence of dimensions. The formula is as follows:

[0094] ;

[0095] Step 5, Calculate the grey relational coefficient: For each indicator, calculate the comparison sequence Y one by one. i The correlation coefficient between (i=1,2,...,m) and the reference sequence Y0 on this index is given by the following formula (where ρ is the resolution coefficient, taken as 0.5):

[0096]

[0097] Step 6, Calculate the grey relational degree: Take the weighted average of the correlation coefficients of all indicators for each sample Xi to obtain the comprehensive grey relational degree γ between the sample and the ideal sample. 0i The formula is as follows:

[0098]

[0099] Step 7, Comprehensive Evaluation and Ranking: Based on the calculated grey relational degree γ0i All samples were sorted by size. The results are shown in Table 2.

[0100] Table 2 Results of Grey Relational Degree Calculation

[0101] Experiment No. Drafting multiple Twist (twist / 10 cm) Doffer speed (rpm) GRG D-01 150 130 7000 0.31 D-02 137.5 130 7000 0.40 D-03 125 130 7000 0.74 D-04 112.5 130 7000 0.37 D-05 100 130 7000 0.41 T-01 125 140 7000 0.38 T-02 125 135 7000 0.44 T-03 125 130 7000 0.74 T-04 125 125 7000 0.27 T-05 125 120 7000 0.25 S-01 125 130 8000 0.33 S-02 125 130 7500 0.48 S-03 125 130 7000 0.74 S-04 125 130 6500 0.42 S-05 125 130 6000 0.26

[0102] According to Table 2, the optimal single yarn process combination was finally determined to be: twist 130 twists / 10 cm, draft ratio 125, and combing roller speed 7000 rpm.

[0103] Comparative Example 1

[0104] This comparative example cites data on pure hemp ring spinning dry spinning reported in the journal article "Discussion on the process of dry spinning of pure hemp yarn by ring spinning".

[0105] Comparative Example 2

[0106] This comparative example cites data from the journal article "Process Study on Spinning of 27.8 tex Hemp Yarn on Cotton Spinning Equipment" which reports data on dry spinning of pure hemp ring spinning.

[0107] Comparative Example 3 (replaced with ring spinning)

[0108] The only difference from Example 1 is that step 5 is modified as follows:

[0109] The hemp sliver obtained from Example 1 was fed into a ring spinning machine (model DSSp-01 digital sample spinning machine) for ring spinning to prepare pure hemp single yarn;

[0110] This comparative example uses conventional ring spinning technology, but the test results show that the spinning effect is not ideal, the breakage rate is extremely high, it is difficult to continuously spin yarn, and it is not practical.

[0111] The breaking strength, strength unevenness, elongation at break, yarn unevenness, and harmful hair index of D-03 from Example 1 and the products of Comparative Examples 1-3 were tested. The test results are shown in Table 3. In Table 3, the harmful hair index is the harmful hair index of hairs larger than 3 mm (to be consistent with Comparative Example 2).

[0112] Table 3 Comparison of Pure Hemp Yarns Processed Differently

[0113] Experiment No. Yarn number (tex) Breaking strength (cN / tex) Strength CV (%) Breaking elongation (%) Yarn irregularity (%) Hair index (root / 10 cm) D-03 28.4 7.04 14.57 4.16 22.13 38.5 Comparative Example 1 27.8 7.4 22.79 - 31.79 - Comparative Example 2 27.8 12.9 18.1 4.96 17.3 76.4 Comparative Example 3 30.42 4.67 37.62 3.53 56.62 72.6

[0114] As shown in Table 3, compared with Comparative Example 1 and Comparative Example 2, the pure hemp single yarn prepared by the present invention based on rotor spinning process exhibits significant comprehensive advantages. The breaking strength of this yarn (affected by the bleached hemp fiber raw material used in the present invention) is lower than that of Comparative Example 2 (the spinning raw material of Comparative Example 2 is cut fine hemp fiber) and comparable to that of Comparative Example 1 (the strength of rotor-spun yarn is usually 80%~90% of that of ring-spun yarn). However, the 3 mm hairiness index (76.4 hairs / 10cm) of Comparative Example 2 is significantly higher, and the strength unevenness (18.1%) is still at a high level, indicating that the compact spinning system is difficult to simultaneously achieve high strength and good appearance quality when processing hemp fibers. In contrast, the yarn obtained in Example 1 of this invention achieves an optimized balance of performance: the strength unevenness rate (14.57%) is significantly lower than all comparative examples, demonstrating that the rotor spinning process defined in this invention imparts superior structural uniformity and production stability to the hemp yarn; simultaneously, the hairiness index (38.5 hairs / 10 cm) is significantly reduced, effectively improving the yarn surface smoothness, thereby helping to solve the problem of strong itching sensation in traditional hemp fabrics. Therefore, this invention, through the optimized rotor spinning technology route, effectively avoids the technical limitations of spinning processes such as ring spinning, providing an effective solution for developing pure hemp products with high stability, good wearing comfort, and processing performance.

[0115] Example 2

[0116] A method for preparing pure hemp thread, the specific steps of which are as follows:

[0117] Step 1, combining: Combine at least two strands of pure hemp single yarn (number D-03 in Example 1) on a combining machine, controlling the combining tension to 8-12 cN, to obtain the combined yarn;

[0118] Step 2, Twisting: Twist the combined yarn in the S direction on a twisting machine, and control the twist of the ply according to the relevant conditions in Table 4; by controlling the spindle speed (4000-5000 r / min) and the sliver output speed (6-10 m / min), and keeping the English twist coefficient of the pure hemp single yarn between 3.8 and 4.2, and the ratio of the twist coefficient of the pure hemp ply yarn to the twist coefficient of the single yarn between 0.4 and 0.6, the pure hemp ply yarn is finally obtained.

[0119] The fracture strength, strength unevenness, elongation at break, yarn unevenness, harmful hairiness index, and abrasion resistance of the products from Examples 1-2 were tested. The test results are shown in Table 4. In Table 4, the harmful hairiness index is the index of harmful hairiness greater than 3 mm.

[0120] Table 4. Hemp strands with different process parameters

[0121] Sample Breaking strength (cN / tex) Strength CV (%) Breaking elongation (%) Yarn irregularity (%) Harmful hair amount (root / 10 cm) Wear resistance times D-03 single yarn 7.04 14.57 4.16 22.13 38.5 166.15 50 twist / 10 cm 7.39 12.04 4.52 12.26 25.2 439.65 60 twist / 10 cm 7.73 10.34 5.33 15.66 24.06 538.80 70 twist / 10 cm 8.99 9.15 4.76 13.48 22.66 668.40 80 twist / 10 cm 8.22 9.56 4.41 15.30 21.06 682.40

[0122] The results show that by adjusting the twist, the performance of hemp yarn can be optimized in multiple dimensions, including breaking strength, strength uniformity (CV), yarn unevenness, fuzz control, and abrasion resistance. Among them, 70 twists / 10 cm showed the best performance in breaking strength and strength uniformity, while 80 twists / 10 cm had significant advantages in abrasion resistance and fuzz control. Different twist process parameters can be selected according to the performance requirements of hemp products (mechanical properties, appearance, durability, etc.), providing a direction for process optimization for the industrial production and application of hemp yarn.

[0123] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing bleached hemp waste rotor-spun pure yarn, characterized in that, Includes the following steps: Bleached hemp fibers are opened to obtain opened fibers. The opened fibers are sprayed with a conditioning agent to obtain conditioning-treated fibers; The fibers after the conditioning treatment are combed using a dual-roller system to obtain combed fibers; The combed fibers are drawn and drawn to obtain hemp sliver after drawing; The hemp sliver after drawing is fed into a rotor spinning machine for rotor spinning to obtain pure hemp single yarn.

2. The preparation method according to claim 1, characterized in that, The bleached hemp fiber is a short fiber separated from hemp stalks during the processing of textile raw materials and then bleached. The fiber length is ≤30 mm, the single fiber fineness is 1.8-3.7 dtex, the single fiber strength is 1.5-2.2 cN / dtex, the breaking elongation is 3.8-4.5%, and the fiber whiteness is ≥75%.

3. The preparation method according to claim 1, characterized in that, The process parameters for the opening process are as follows: feed cord speed 1.0 m / min, opening roller diameter 250 mm, opening roller speed 506 r / min, and opening speed ratio 238 times.

4. The preparation method according to claim 1, characterized in that, The conditioning agent contains a cohesion enhancer, an antistatic agent, a softener, and water; the mass ratio of the cohesion enhancer, the antistatic agent, and the softener is 2:1:2; the water content in the conditioning agent is 97-99 wt%; and the moisture regain of the fiber after conditioning treatment is 10-12%.

5. The preparation method according to claim 1, characterized in that, The dual-roller combined combing includes pre-combing and main combing; The pre-carding process uses a roller carding machine with the following parameters: cylinder speed 60 r / min, work roll speed 8 r / min, stripping roll speed 24 r / min, web exit speed 10 m / min, and total draw ratio 50. The main carding process uses a worsted carding machine with the following process parameters: cylinder speed 180 r / min, doffer speed 5 r / min, cylinder-doffer distance 0.18 mm, licker-in roller-feed roller distance 0.45 mm, web exit speed 20.1 m / min, and cylinder-doffer surface linear speed ratio 36.

6. The preparation method according to claim 1, characterized in that, The drawing and drawing process consists of three drawing passes, with a total of 6 drawing passes. The back zone draw ratio for the first drawing pass is 1.10, and the total draw ratio is 5.0-5.

4. The back zone draw ratio for the second drawing pass is 1.10, and the total draw ratio is 5.5-6.

5. The back zone draw ratio for the third drawing pass is 1.10, and the total draw ratio is 5.5-6.

5.

7. The preparation method according to claim 1, characterized in that, During the rotor spinning process, the sawtooth parameters of the combing roller are as follows: working angle 65-80°, tooth pitch 2.1-4.95 mm; the twister uses a false twist disc with 0-8 grooves; the rotor is T-type, K-type or G-type, with a spinning cup diameter of 40-46 mm and a negative pressure of 4.5-5.5 kPa; the draft ratio is 112.5-137.5, the twist is 125-135 twists / 10 cm, the combing roller speed is 6500-7500 rpm, and the tension correction coefficient is 0-0.5%.

8. A pure hemp single yarn obtained by the preparation method according to any one of claims 1-7, characterized in that, The pure hemp single yarn has a count of 28.4-100 tex.

9. A method for preparing pure hemp yarn, comprising twisting together at least two strands of pure hemp single yarn as described in claim 8.

10. The preparation method according to claim 9, characterized in that, Includes the following steps: At least two strands of the pure hemp single yarn are combined on a doubling machine, and the doubling tension is controlled at 8-12 cN to obtain the combined yarn. The combined yarn is twisted in the S direction on a twisting machine, the twist of the ply is controlled to be 50-80 twists / 10 cm, the spindle speed is 4000-5000 r / min, the sliver output speed is 6-10 m / min, and the ratio of the ply twist coefficient to the single yarn twist coefficient is maintained between 0.4 and 0.6 to obtain the pure hemp ply yarn.

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