Non-cuffing cotton stretch knitted fabric and preparation method thereof

Abstract

This invention discloses a non-curling cotton elastic knitted fabric and its preparation method, belonging to the field of knitted fabric technology. The preparation method includes: knitting cotton staple yarn and polyurethane fiber, pre-setting, dyeing, and finishing to obtain a non-curling cotton elastic knitted fabric; wherein the polyurethane fiber is a polyurethane fiber with temperature-driven shape memory function; during the knitting process, the feeding tension of the polyurethane fiber is controlled to ≤2cN, and the ambient temperature during the knitting process is controlled to be lower than the thermal transition temperature of the polyurethane fiber; during the pre-setting process, the overfeed is controlled to be 30~40%, so that the width change of the fabric after pre-setting is <5%. This invention, by combining the characteristics of temperature-driven shape memory spandex with ambient temperature control, knitting, and pre-setting process control, can eliminate the internal stress of curling at the source, allowing the fabric to remain flat after being cut into pieces.

Description

Technical Field

[0001] This invention relates to a non-curling cotton elastic knitted fabric and its preparation method, belonging to the field of knitted fabric technology. Background Technology

[0002] Lightweight, elastic knitted fabrics are widely used in T-shirts, sun-protective clothing, underwear, and other close-fitting garments due to their softness, high elasticity, and comfort. However, these fabrics often exhibit severe edge curling during production and garment manufacturing. Edge curling is the phenomenon where the selvage of a knitted fabric curls up in its free state, stemming from the internal stress within the bent segments of the loop attempting to straighten them. This problem is particularly pronounced in plain knit fabrics, especially elastic fabrics incorporating highly elastic fibers such as spandex.

[0003] After the fabric enters the garment factory and undergoes spreading and cutting, the curling of individual pieces becomes more severe, significantly impacting the efficiency of sewing processes such as arm seams, quilting, mesh sleeves, sleeve attachment, and mesh hems. This also easily leads to sewing defects, difficulty in controlling garment dimensions, and increased sewing waste. With the development of knitted fabrics towards higher counts, higher needle densities, and lighter weights, and the gradual promotion of automated sewing technology, the constraint of curling on garment production efficiency is becoming increasingly prominent.

[0004] Currently, some technologies have attempted to improve the curling phenomenon during fabric processing. For example, this involves sizing or embedding low-melting-point hot-melt yarns at the fabric edge and then heat-curing them to lock the edge (e.g., CN104060386B), or setting a special jacquard layer structure at the edge to physically resist curling. However, these methods mainly target the temporary fixation of the fabric edge during finishing and cannot solve the problem of curling inside the cut pieces after the fabric is made. Other research involves the application of shape memory polyurethane fibers in the clothing field (e.g., CN101033286A), but it mainly focuses on using its body temperature-triggered shape memory effect to achieve adaptive clothing fit, without addressing the problem of curling in knitted fabric cut pieces by utilizing its "cold state" characteristics below a specific transition temperature.

[0005] Temperature-driven shape memory spandex is a novel smart material whose elasticity can be reversibly controlled with temperature changes: when the ambient temperature is below its specific transition temperature, the elasticity disappears, and it is in a state of no elasticity or weak elasticity, and the shape can be temporarily fixed; when the ambient temperature is above the transition temperature, it regains high elasticity and returns to its initial shape. How to utilize this characteristic to eliminate curling stress at its source and to build a systematic solution that runs through the weaving and finishing processes is currently unknown, and there are no relevant technical reports. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a non-curling cotton elastic knitted fabric and its preparation method. By combining the characteristics of temperature-driven shape memory spandex with environmental temperature control, knitting, and pre-forming process control, the present invention can eliminate curling internal stress at its source, allowing the fabric to remain flat after being cut into pieces.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a non-curling cotton elastic knitted fabric, comprising the following steps: Cotton staple fiber yarn and polyurethane fiber are knitted to obtain cotton elastic single-sided fabric; then the cotton elastic single-sided fabric is pre-shaped, dyed and finished to obtain the non-curling cotton elastic knitted fabric. The polyurethane fiber is a polyurethane fiber with temperature-driven shape memory function; During the knitting process, the feeding tension of the polyurethane fiber is controlled to be ≤2cN, so that the difference between the initial diameter of the polyurethane fiber and the diameter after knitting is <5%, and the difference between the loop length formed by the polyurethane fiber and the loop length formed by the cotton staple fiber is <5%, and the ambient temperature during the knitting process is controlled to be lower than the thermal transition temperature of the polyurethane fiber. During the pre-forming process, the overfeed is controlled to be 30-40% to ensure that the width change of the fabric after pre-forming is less than 5% and the difference in loop length between the cotton staple yarn and the polyurethane fiber is less than 5%.

[0008] The second aspect of the present invention provides a non-curling cotton elastic knitted fabric, which is obtained by the above-described method for preparing non-curling cotton elastic knitted fabric.

[0009] The present invention has at least the following beneficial effects: This invention utilizes polyurethane fibers with temperature-driven shape memory function, combined with environmental temperature control, knitting, and pre-forming process control, to eliminate curling stress at the source. This allows cotton elastic knitted fabrics to remain flat and curl-free after being cut into pieces, making them suitable for both manual and automated sewing. Attached Figure Description

[0010] Figure 1 This is a schematic diagram illustrating the anti-rolling principle of the knitting process in a specific embodiment of the present invention.

[0011] Figure 2 This is an optical image of a cut piece of non-curling cotton elastic knitted fabric from Example 1.

[0012] Figure 3 An optical image of a garment made from the non-curling cotton elastic knitted fabric of Example 1. Detailed Implementation

[0013] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the present invention will now be described in detail below, but this should not be construed as limiting the scope of the invention.

[0014] It should be noted that, unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0015] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0016] It should be understood that the terms “comprising,” “including,” and / or “containing” as used herein specify the presence of the stated features, integers, steps, components, or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0017] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0018] According to a specific embodiment of the first aspect of the present invention, the present invention provides a method for preparing a non-curling cotton elastic knitted fabric, which includes the following steps: Cotton staple fiber yarn and polyurethane fiber are knitted to obtain cotton elastic single-sided fabric; then the cotton elastic single-sided fabric is pre-shaped, dyed and finished to obtain the non-curling cotton elastic knitted fabric. The polyurethane fiber is a polyurethane fiber with temperature-driven shape memory function; During the knitting process, the feeding tension of the polyurethane fiber is controlled to be ≤2cN, so that the difference between the initial diameter of the polyurethane fiber and the diameter after knitting is <5%, and the difference between the loop length formed by the polyurethane fiber and the loop length formed by the cotton staple fiber is <5%, and the ambient temperature during the knitting process is controlled to be lower than the thermal transition temperature of the polyurethane fiber. During the pre-forming process, the overfeed is controlled to be 30-40% to ensure that the width change of the fabric after pre-forming is less than 5% and the difference in loop length between the cotton staple yarn and the polyurethane fiber is less than 5%.

[0019] In this invention, the non-curling cotton elastic knitted fabric is made from cotton staple yarn and polyurethane fibers with temperature-driven shape memory function through knitting, pre-setting, dyeing, and finishing processes. During the knitting process, the knitting tension of the polyurethane fibers is controlled so that they are bent into loops without being stretched, ensuring that the difference between the initial diameter of the polyurethane fibers and the diameter after knitting is less than 5%, and that the difference between the loop length formed by the polyurethane fibers and the loop length formed by the cotton staple yarn is less than 5%. Furthermore, the ambient temperature during the knitting process is controlled to be lower than the thermal transition temperature of the polyurethane fibers, allowing the polyurethane fibers to be knitted in a "cold" state. At this point, the elastic recovery force of the fibers is "frozen," thus fundamentally avoiding the internal stress caused by the shrinkage of the high-elasticity fibers. This ensures that the resulting cotton elastic single-sided fabric (i.e., the grey fabric) remains non-curling after being removed from the machine. The principle is as follows: Figure 1 As shown. During the pre-setting process, the high temperature temporarily restores the elasticity of the polyurethane fibers. However, since the loop lengths of the two yarns are already highly consistent during knitting, and the pre-setting process is carried out with low tension control and an overfeed of 30-40%, the loops of the cotton staple yarn and the polyurethane fiber are simultaneously heat-set without relative deformation. The width change is <5%, and the difference in length between the loops of the cotton staple yarn and the polyurethane fiber is <5%. After the fabric is cooled, the polyurethane fibers in it return to a "cold" state, permanently locking the flat loop structure.

[0020] In some embodiments, the heat transition temperature of the polyurethane fiber is above 30°C. By controlling the heat transition temperature above 30°C, it is beneficial to maintain the stability of the fabric in a "cold" state in everyday wearing environments (typically below 30°C), ensuring that the cut pieces do not curl during storage, transportation, and garment making, while restoring elasticity when the garment is worn by the human body (body temperature above 30°C), providing a comfortable wearing experience.

[0021] In some embodiments, the shape fixation rate of the polyurethane fiber is ≥85%, and the shape recovery rate is ≥90%. By controlling the shape fixation rate and shape recovery rate of the polyurethane fiber within the above range, it is beneficial to ensure that it can effectively fix the temporary shape when weaving in a "cold" state, and still maintain good elastic recovery performance after high-temperature setting, thereby achieving reversible "cold-hot" state switching and providing a stable and reliable non-curling effect for the fabric.

[0022] In some embodiments, the linear density of the polyurethane fiber is 10~50D. By controlling the linear density of the polyurethane fiber within the above range, it is beneficial to ensure that the fabric has good elasticity and resilience, while enabling the fiber to form a matching loop structure with the cotton staple fiber yarn during the weaving process. This avoids excessively large loops and internal stress concentration due to excessively high linear density, or insufficient elasticity due to excessively low linear density.

[0023] In some embodiments, the polyurethane fiber is a polyurethane fiber with a semi-crystalline structure. The "semi-crystalline structure" referred to here means that the molecular chains of the polyurethane fiber simultaneously contain crystalline and amorphous regions. The crystalline regions are formed by the regular arrangement of molecular chains and serve as physical cross-linking points. Below the thermal transition temperature, they fix the molecular chains, keeping the fiber in a "cold" state and temporarily "freezing" its elasticity. When the temperature rises above the melting point of the crystalline regions, the crystalline regions melt, the physical cross-linking points disappear, and the fiber regains its high elasticity. By forming the above-mentioned semi-crystalline structure, it is beneficial to endow the polyurethane fiber with a reversible "cold-hot" state switching capability, enabling it to fix a temporary shape below the thermal transition temperature and restore its original shape and elasticity above the thermal transition temperature, thereby achieving a temperature-driven shape memory function.

[0024] In some embodiments, the count of the cotton staple yarn is 20 to 200S.

[0025] In some embodiments, the cotton staple fiber yarn is composed of one or more of the following: 100% cotton, blended yarn of cotton with other textile fibers, and composite yarn of cotton with other textile fibers.

[0026] In some embodiments, the cotton staple fiber yarn is spun using vortex spinning, air-jet spinning, or rotor spinning. By selecting a spinning method that does not involve twisting, it is beneficial to reduce the residual torque of the yarn itself, thereby reducing the tendency of fabric curling caused by internal yarn stress at the source and laying the foundation for obtaining anti-curling fabrics.

[0027] In some embodiments, the cotton elastic single-sided fabric is constructed using a plain knit weave or a variation of the plain knit weave. Using a plain knit weave allows for the uniform application of polyurethane fibers to the reverse side of the fabric, forming a stable elastic coil network. Using a variation of the plain knit weave helps to adjust the balance of the coil structure to a certain extent. Both methods facilitate synchronous heat setting of the coils during subsequent pre-setting processes, enhancing the anti-curling effect.

[0028] In some embodiments, the ambient temperature during the knitting process is controlled to be below 28°C. By controlling the knitting ambient temperature to be below 28°C, it is further beneficial to ensure that the polyurethane fibers are in a "cold" state below the heat transition temperature during the knitting process, so that their elasticity is temporarily "frozen," thereby preventing internal stress from being generated due to elastic recovery force during knitting and eliminating the curling problem at its source.

[0029] In some embodiments, the pre-setting temperature is set to 195~205℃, and the weaving speed is set to 15~25m / min. By controlling the pre-setting temperature within the above range, it is beneficial to allow the polyurethane fibers to temporarily regain their elasticity during the high-temperature setting process. At the same time, by utilizing the consistent loop length already controlled during the weaving stage, it is ensured that the fabric does not deform even in the elastic recovery state. By controlling the weaving speed within the above range, it is beneficial to ensure that the fabric receives sufficient and uniform heat treatment time, ensuring a uniform and consistent setting effect.

[0030] In some embodiments, the finishing process includes one or more of the following: softening and setting, mercerizing, and liquid ammonia finishing. These finishing processes can be performed in accordance with conventional methods in the art, and the present invention does not impose any particular limitations on them. Furthermore, the dyeing process can also be performed in accordance with conventional methods in the art, and the present invention does not impose any particular limitations on it.

[0031] In some embodiments, the preparation method further includes, after the finishing process, storage, transfer, and garment making. During storage, transfer, and garment making, the ambient temperature is controlled below the thermal transition temperature of the polyurethane fibers. Preferably, the ambient temperature is controlled below 28°C during storage, transfer, and garment making. Garment making includes cutting and sewing, which can be done manually or automatically. During sewing, the ambient temperature and equipment temperature in the sewing workshop are controlled below 28°C, ensuring that the polyurethane fibers in the cut pieces are below their thermal transition temperature, thus keeping the cut pieces processed in a "cold" state. By continuously controlling the ambient temperature below the thermal transition temperature of the polyurethane fibers during storage, transfer, cutting, and sewing, the polyurethane fibers in the cut pieces are kept in a "cold" state, effectively preventing curling, ensuring the smooth progress of the garment making process, and significantly improving sewing efficiency.

[0032] According to a specific embodiment of the second aspect of the present invention, the present invention provides a non-curling cotton elastic knitted fabric, which is obtained by the above-described method for preparing non-curling cotton elastic knitted fabric.

[0033] In some embodiments, the weight of the non-curling cotton elastic knitted fabric is 100~200 g / m². 2 By controlling the fabric weight within the above range, it is beneficial to ensure the fabric's lightweight characteristics while giving it sufficient structural stability, so that it can remain flat and not curl in the cut state.

[0034] In some embodiments, the mass percentage of polyurethane fiber in the non-curling cotton elastic knitted fabric is 5-20%, based on the total mass of 100%. By controlling the mass percentage of polyurethane fiber within the above range, it is beneficial to ensure that the fabric obtains excellent elasticity and resilience while avoiding problems such as excessive internal stress and difficulty in controlling curling caused by excessive elastic fiber content.

[0035] The shape memory polyurethane fiber used in this invention has reversible thermal response characteristics: when the ambient temperature is below its thermal transition temperature, the fiber is in a "cold" state, and its elasticity is temporarily "frozen"; when the ambient temperature is above the thermal transition temperature, the fiber regains its high elasticity and returns to its initial shape. This characteristic provides a flexible processing window for fabric manufacturing while retaining the excellent elasticity of the garment. Unlike existing technologies that use physical bonding or structural constraints for "post-consolidation," this invention utilizes the intelligent properties of the material to achieve reversible control of the curling problem.

[0036] This invention actively eliminates the shrinkage stress of high-elastic fibers through "cold state" weaving. During the knitting process, the ambient temperature is controlled below the thermal transition temperature of the polyurethane fibers, allowing the fibers to be woven in a "cold" state, where their elastic recovery force is "frozen." Simultaneously, low-tension weaving is employed to maintain a high degree of consistency between the loop lengths of the polyurethane fibers and the cotton staple fiber yarn. These two control methods work synergistically to ensure the fabric remains naturally flat after leaving the machine, fundamentally avoiding internal stress caused by the shrinkage of the high-elastic fibers. During the pre-setting process, the high temperature temporarily restores the elasticity of the polyurethane fibers. However, because the loop lengths of the two yarns are already highly consistent during knitting, and the pre-setting process involves low tension control in both warp and weft directions, no additional internal stress is added to the fabric. The loops of the cotton staple fiber yarn and the polyurethane fiber remain relatively stable, preventing the fabric from curling. After cooling, the polyurethane fibers return to a "cold" state, permanently locking the flat loop structure. During the subsequent dyeing process, the fabric re-enters a high-elastic state in the dye bath. Due to the good consistency in loop length with the cotton staple fiber yarn, curling will not occur.

[0037] Furthermore, this invention extends low-temperature control from the weaving stage to the entire process of storage, transportation, cutting, and sewing, ensuring that the fabric remains "cold" until it is made into garments. Thanks to the consistency of the loop lengths of the two yarns controlled during the weaving stage, even if the polyurethane fibers temporarily regain elasticity during the high-temperature pre-setting process, the fabric does not deform. Cooling after setting permanently locks in the smooth loop structure. In subsequent storage, transportation, and garment-making stages, simple ambient temperature control (e.g., below 28°C) keeps the polyurethane fibers in the cut pieces "cold," effectively preventing curling at the crucial stage before sewing.

[0038] Furthermore, by controlling the ambient temperature in the sewing workshop, this invention allows flat cut pieces to be directly fed into automated sewing equipment, solving the industry pain point that automated equipment cannot handle rolled-up cut pieces and significantly improving sewing efficiency. Examples show that sewing costs can be reduced by 0.53 to 5.4 yuan per piece for styles such as sun-protective clothing, T-shirts, and shirts. The fabric of this invention is suitable for both manual sewing and perfectly adapted to automated garment production lines.

[0039] The technical solutions of the present invention are specifically illustrated below through embodiments, but the present invention is not limited to these embodiments. Of course, various modifications can be made within the scope of the key points of the present invention.

[0040] Example 1

[0041] (1) Raw material performance testing

[0042] The polyurethane fiber (or spandex) with temperature-driven shape memory function used in this embodiment is from Aoshen. Two types of spandex are used: one with a linear density of 20D and an initial diameter of 60μm, and the other with a linear density of 40D and an initial diameter of 120μm. Both have a heat transition temperature of 32℃. Both types of polyurethane fibers are polyurethane fibers with a semi-crystalline structure.

[0043] The deformation fixation rate Rf and shape recovery rate Rr were tested using the following method: The spandex was first equilibrated for 10 minutes under the temperature conditions in Table 1. Two points were taken in the middle of the spandex thread and marked as length L0. Then the spandex was stretched by 100%, both ends were fixed, and it was placed in a refrigerator at 0℃ for 10 minutes. One end of the spandex was loosened, and the distance between the two marked points on the spandex was measured and recorded as L1. The other end of the spandex was loosened, and it was placed under the temperature conditions in Table 1 for 10 minutes. The distance between the two marked points on the spandex was measured and recorded as L2. The above operation was repeated 3 times, and the deformation fixation rate Rf and shape recovery rate Rr were calculated according to formulas (1) and (2) respectively. The average value of the test results was taken as the final result.

[0044] Rf=(L1-L0) / L0 100% Equation (1); Rr=[1-(L2-L0) / L0] 100% Formula (2).

[0045] The test results of the shape fixation rate and shape recovery rate of the spandex used in this embodiment are shown in Table 1.

[0046] Table 1. Shape memory test results of spandex

[0047] (2) Preparation of non-curling cotton elastic knitted fabric

[0048] Non-curling cotton elastic knitted fabrics were obtained by knitting, pre-setting, dyeing, and finishing using 60S cotton yarn + the aforementioned 20D spandex and 30S cotton yarn + the aforementioned 40D spandex, respectively.

[0049] Among them, 60S cotton yarn is pure cotton yarn, and its spinning method is vortex spinning. 30S cotton yarn is pure cotton yarn, and its spinning method is vortex spinning.

[0050] During the knitting process, a low-tension spandex feeder is used to control the feed tension of the spandex at 1.5 cN, ensuring that the difference between the initial diameter of the spandex and the diameter after knitting is less than 5%, and that the difference between the loop length formed by the spandex and the loop length formed by the cotton yarn is less than 5%. The ambient temperature during the knitting process is controlled at 25℃. After knitting, a cotton elastic single-sided fabric (i.e., greige fabric) is obtained. The structure of this cotton elastic single-sided fabric is a plain knit weave with added yarn. In the "cold" state, the spandex is in a non-elastic state, and a low-tension feeder is used to knit it, making the loop length of the spandex and the loop length of the cotton yarn close to ensure that the loop shape of the two yarns in the greige fabric is consistent.

[0051] During the pre-forming process, the overfeed is controlled at 30%, the temperature is set at 195℃, and the fabric speed is set at 20m / min, so that the width change of the fabric after pre-forming is less than 5%, and the difference in loop length between cotton yarn and spandex is less than 5%.

[0052] During the dyeing process, reactive dyes are used, and biological enzymes are used to remove fabric fuzz. The dyeing temperature is 60℃.

[0053] In the finishing process, a hydrophilic softener is used, with a softener dosage of 20g / L, a setting temperature of 150℃, and a weaving speed of 20m / min.

[0054] Information on the two fabrics in this embodiment is shown in Table 2.

[0055] Table 2 Fabric Information

[0056] (3) Storage, transportation and garment making

[0057] During storage, transportation, and garment manufacturing, the ambient temperature is controlled at 25℃. Specifically, during garment manufacturing, the ambient temperature of the cutting bed is controlled at 25℃, ensuring that the cut pieces remain uncurled after cutting. Figure 2 As shown; and, the ambient temperature during the sewing process is controlled at 25℃ to complete the garment making process, resulting in a garment as shown. Figure 3 As shown.

[0058] Garments made from the non-curling cotton elastic knitted fabric prepared in this embodiment significantly improve sewing efficiency. Compared to the cotton spandex fabric before the curling improvement, it shows a significant advantage in sewing cost savings. The cost advantage is even more pronounced in complex styles, such as sun-protective clothing and shirts. The sewing cost savings statistics are shown in Table 3.

[0059] Table 3. Statistics on Cost Savings in Sewing

[0060] Comparative Example 1

[0061] This comparative example is basically the same as Example 1 (60S cotton yarn + 20D temperature memory spandex), the difference being: during the knitting process, the feeding tension of the spandex is controlled to be 4cN, so that the difference between the initial diameter of the spandex and the diameter after knitting is >5%, and the difference between the loop length formed by the spandex and the loop length formed by the cotton yarn is >5%.

[0062] Comparative Example 2

[0063] This comparative example is basically the same as Example 1 (60S cotton yarn + 20D conventional spandex), the difference being that: the spandex is not the spandex with temperature-driven shape memory function, but conventional 20D spandex (Jiaxing Xiaoxing).

[0064] Comparative Example 3

[0065] This comparative example is basically the same as Example 1 (60S cotton yarn + 20D temperature memory spandex), the difference is that: during the pre-forming process, the overfeed is controlled at 15%, the temperature is set at 195℃, and the fabric speed is set at 20m / min, so that the width change of the fabric after pre-forming is >5%, and the difference in the loop length of cotton yarn and spandex is >5%.

[0066] Comparative Example 4

[0067] This comparative example is basically the same as Example 1 (60S cotton yarn + 20D temperature memory spandex), the difference being that the ambient temperature is controlled at 35°C (higher than the heat transition temperature of spandex) during the knitting process, as well as during storage, transportation and garment making.

[0068] Test Example 1

[0069] The following method was used to test the curling degree of the fabric pieces: The fabric was cut into 30cm × 30cm square pieces and conditioned for 24 hours at a temperature of 21±1℃ and a relative humidity of 65±5%. The pieces were then laid flat on a horizontal surface, and the number of natural curls along the weft edge was measured. Three pieces were tested for each sample, and the average value was taken. The grading criteria for the curling degree are shown in Table 4. The test results are shown in Table 5.

[0070] Table 4. Grading Standards for Curled Edges on Cut Pieces

[0071] Table 5 Results of the curling test

[0072] It can be seen that in Comparative Example 1, conventional tension yarn feeding is used during the knitting process, causing the spandex to bend into loops under relatively high tension. Since the spandex is in a cold state at this time, it is easy to stretch, and conventional tension can cause its diameter change to be >5%. During the pre-setting process, after being heated, the spandex recovers its high elasticity and tends to return to its initial unstretched state, thus exhibiting a strong recovery tendency. This creates a difference in loop size with the cotton yarn, causing the fabric to curl. Furthermore, after the pre-set fabric cools, the spandex enters a cold state, and the fabric is fixed in the curled state. In addition, during the dyeing process, the fabric enters the dyeing vat in a curled state, and the spandex recovers its elasticity again, keeping the fabric in a curled state. Comparative Example 2 uses conventional spandex, which, at room temperature, has a tendency to recover to its initial state (unstretched), i.e., it always generates internal stress in the fabric, causing the fabric to curl. Comparative Example 3 has an overfeed of 15% and a width change of >5%. The overfeed is small, resulting in high warp tension and widening of the fabric, as well as high weft tension, leading to unstable internal stress in the fabric and causing curling. In Comparative Example 4, the ambient temperature was higher than the thermal transition temperature of spandex. Even with low-tension weaving, spandex was in a slightly stretched state. After regaining its elasticity, it still had a tendency to return to its initial state (not stretched), resulting in internal stress in the fabric and causing curling.

[0073] Test Example 2

[0074] According to FZ / T 70006-2004 "Test Method for Tensile Elastic Recovery Rate of Knitted Fabrics", three 50mm×200mm samples were cut from the fabrics of the above examples and comparative examples along both the warp and weft directions. The clamping distance was set to 100mm, the stretching speed to 100mm / min, and the return speed to 50mm / min. The test results are shown in Table 6.

[0075] Table 6. Elasticity Test Results

[0076] It can be seen that the fabric in this embodiment of the invention has good elastic elongation and recovery rate.

[0077] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a non-curling cotton elastic knitted fabric, comprising the following steps: Cotton staple fiber yarn and polyurethane fiber are knitted to obtain cotton elastic single-sided fabric; then the cotton elastic single-sided fabric is pre-shaped, dyed and finished to obtain the non-curling cotton elastic knitted fabric. The polyurethane fiber is a polyurethane fiber with temperature-driven shape memory function; During the knitting process, the feeding tension of the polyurethane fiber is controlled to be ≤2cN, so that the difference between the initial diameter of the polyurethane fiber and the diameter after knitting is <5%, and the difference between the loop length formed by the polyurethane fiber and the loop length formed by the cotton staple fiber is <5%, and the ambient temperature during the knitting process is controlled to be lower than the thermal transition temperature of the polyurethane fiber. During the pre-forming process, the overfeed is controlled to be 30-40% to ensure that the width change of the fabric after pre-forming is less than 5% and the difference in loop length between the cotton staple yarn and the polyurethane fiber is less than 5%.

2. The method for preparing non-curling cotton elastic knitted fabric according to claim 1, wherein, The thermal transition temperature of the polyurethane fiber is above 30°C; And / or, the shape fixation rate of the polyurethane fiber is ≥85%, and the shape recovery rate is ≥90%; And / or, the linear density of the polyurethane fiber is 10~50D; And / or, the polyurethane fiber is a polyurethane fiber with a semi-crystalline structure.

3. The method for preparing non-curling cotton elastic knitted fabric according to claim 1, wherein, The count of the cotton staple fiber yarn is 20~200S; And / or, the composition of the cotton staple fiber yarn is one or more of 100% cotton, cotton blended with other textile fibers, and cotton composite with other textile fibers. And / or, the spinning method of the cotton staple fiber yarn is vortex spinning, air-jet spinning or rotor spinning.

4. The method for preparing non-curling cotton elastic knitted fabric according to claim 1, wherein, The cotton elastic single-sided fabric is constructed using a plain knit or a variation of the plain knit structure.

5. The method for preparing non-curling cotton elastic knitted fabric according to claim 1, wherein, The ambient temperature during the knitting process is controlled to be below 28°C.

6. The method for preparing non-curling cotton elastic knitted fabric according to claim 1, wherein, The predetermined temperature is set to 195~205℃, and the weaving speed is set to 15~25m / min.

7. The method for preparing non-curling cotton elastic knitted fabric according to claim 1, wherein, The preparation method further includes, after the finishing process, storage, transportation and garment making, wherein the ambient temperature is controlled to be lower than the thermal transition temperature of the polyurethane fiber during the storage, transportation and garment making processes.

8. The method for preparing non-curling cotton elastic knitted fabric according to claim 7, wherein, During the storage, transportation, and garment manufacturing processes, the ambient temperature is controlled to be below 28°C.

9. A non-curling cotton elastic knitted fabric, which is prepared by the method of any one of claims 1-8 for preparing non-curling cotton elastic knitted fabric.

10. The non-curling cotton elastic knitted fabric according to claim 9, wherein, The weight of the non-curling cotton elastic knitted fabric is 100~200g / m². 2 ; And / or, based on the total mass of the non-curling cotton elastic knitted fabric as 100%, the mass percentage of polyurethane fiber therein is 5-20%.

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