PA12 / PA6 parallel composite elastic fiber and preparation method thereof

Abstract

The invention relates to a PA12 / PA6 parallel composite elastic fiber and a preparation method thereof. Nylon 12 is adopted as a high-shrinkage component, PA6 is adopted as a low-shrinkage component, parallel compounding is achieved, industrial production with high spinning speed and no yarn breakage can be achieved, and real production significance is achieved. Meanwhile, the PA12 / PA6 parallel composite elastic fiber is excellent in elastic property, low in modulus, soft and skin-friendly, has excellent dyeing property in an acid dye system, and provides a new solution for elastic high-end fabric.

Description

Technical Field

[0001] This invention belongs to the field of materials and textile applications, specifically relating to a PA12 / PA6 parallel composite elastic fiber and its preparation method. Background Technology

[0002] With the increasing demand for comfort in textiles, elastic fibers are widely used in hosiery, swimwear, sportswear, and high-elasticity fashion. Side-by-side composite fibers, a novel type of elastic fiber, are prepared by arranging two polymers with different structures and properties side-by-side to form a bicomponent composite fiber. Due to the difference in heat shrinkage properties between the two components, side-by-side composite fibers all possess a three-dimensional helical coil structure similar to a spring, giving the fibers excellent elasticity after processing. This structural design solves the problems of traditional spandex fibers, such as difficulty in dyeing, excessive elasticity, complex weaving, and unstable fabric dimensions.

[0003] However, the most representative polyester-based parallel composite elastic fibers currently on the market still have some shortcomings. For example, although T-400 composite elastic fiber has good elastic properties, its widespread application is limited by the high price of PTT raw materials and high production costs. In addition, polyester-based parallel composite elastic fibers often have disadvantages such as a stiff feel and excessively tight elasticity that is difficult to adjust. At the same time, due to the lack of functional groups that can bind with dyes, polyester-based parallel composite elastic fibers can only be dyed with disperse dyes, which requires high temperature and high pressure, resulting in high energy consumption and less vibrant colors after dyeing.

[0004] To overcome these problems, polyamide-based side-by-side composite elastic fibers have emerged. With the domestic production of polyamide raw materials, the production cost of polyamide has gradually decreased, leading to the rapid development of polyamide fibers. Compared with polyester fibers, polyamide fibers possess inherent elasticity and offer better skin-friendliness and comfort. Therefore, using polyamide materials to prepare side-by-side composite fibers not only utilizes the inherent elasticity of the material but also the elasticity provided by the fiber's crimped structure, offering broad application prospects. However, existing polyamide-based side-by-side composite elastic fiber preparation processes are complex, have low production efficiency, and exhibit unstable product performance, requiring further improvement.

[0005] Several invention patents have been issued to address the issues of crimping performance, elastic recovery performance, and processing technology of elastic fibers. For example, CN117107394A discloses a method for preparing polyester / polyesteramide parallel composite elastic fibers. This method involves melt spinning components I and II through a parallel composite spinning assembly to obtain fibers, followed by electron beam irradiation and then hot drawing to obtain polyester / polyesteramide parallel composite elastic fibers. However, this method still requires further optimization in terms of the process parameters for electron beam irradiation and hot drawing, and the design and process are complex, resulting in poor elasticity of the polyester-containing fibers.

[0006] CN117661150A discloses a polyamide side-by-side composite elastic fiber, its preparation method, and its application. This method involves combining a first side-by-side structure and a second side-by-side structure. The first side-by-side structure is a polyamide 56 / 6 copolymer, and the second side-by-side structure includes one or more of polyamide 56, polyamide 6, and polyamide 66. This method improves the crimp and elastic properties of the polyamide side-by-side composite elastic fiber, resulting in a high number of crimps per unit length and a large crimp curvature. However, in the synthesis of the polyamide 56 / 6 copolymer, the ratio of raw materials and reaction conditions still need further optimization. The supply of raw materials is difficult to guarantee in order to improve the high shrinkage rate and mechanical properties of the polyamide 56 / 6 copolymer. Furthermore, the small difference in amide bond density between the two side-by-side structures results in relatively low shrinkage capacity, making it difficult to obtain a composite fiber with high crimp.

[0007] In existing technologies, PA66, PA6, and other nylon thermoplastic elastomers are typically used for parallel spinning. For example, CN109355716A provides a production apparatus and method for producing parallel composite elastic fibers of nylon 6 and nylon 66. Nylon 6 and nylon 66 chips are melted into a melt by passing them through a drying tower and an extruder, respectively. The melt is then fed into a spinning box via a metering pump, resulting in parallel composite fibers. The principle of different viscosities and composite ratios is used to improve the fiber's bending curvature and heat resistance. However, choosing PA66 as the low-shrinkage component is problematic because its regular molecular structure leads to numerous hydrogen bonds formed between macromolecules via amide bonds, resulting in high fiber crystallinity and low shrinkage capacity in the amorphous regions. If PA6 is chosen as the other component, the presence of numerous hydrogen bonds also results in low shrinkage. Combining the two does not yield a highly crimped composite fiber. Using nylon elastomers for spinning introduces problems such as complex spinning technology, high raw material costs, and supply limitations.

[0008] CN117051501B discloses a polyamide composite fiber, its preparation method, and its application. The method utilizes a polyamide composite fiber through a combination of components A and B. Component A consists of a polyamide resin and a first metal salt, while component B consists of a copper-coordinated crosslinked copolymer polyamide resin and a second metal salt. The difference in expansion coefficients created by the metal salts introduces internal stress to improve the fiber's dyeability and elasticity durability. However, the introduction of high metal salt content can form coordination bonds with the amino groups at the ends of multiple nylon end groups or the amide groups in the chain, resulting in pseudo-crosslinking. This leads to decreased spinnability and fiber embrittlement, a significant decrease in mechanical properties, and catalytic aging. It also reduces the fiber's light / weather resistance. Furthermore, the metal ions themselves are colored, causing the fiber's base color to darken, yellow, or produce discoloration, making it difficult to dye bright, pure light colors or whites. This poses a serious problem for applications with high color requirements.

[0009] Currently, when selecting two compatible but heat-shrinkable polymers for polyamide-based side-by-side composite elastic fibers, the research and screening of polymer materials with better biomimetic effects have not been sufficient. Summary of the Invention

[0010] To address the above problems, this invention provides a PA12 / PA6 parallel composite elastic fiber and its preparation method. Nylon 12 is used as a high-shrinkage component, and PA6 as a low-shrinkage component; their parallel composite structure enhances elasticity, reduces modulus, improves softness and skin-friendliness, and optimizes the preparation process to improve dyeing performance, resulting in excellent color performance across a variety of colors.

[0011] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0012] A PA12 / PA6 side-by-side composite elastic fiber, made from the following raw materials in parts by weight:

[0013] Parallel Structure A: PA12, 20-80 copies;

[0014] Parallel Structure B: PA6, 80-20 parts;

[0015] The melt index ratio A:B of the two components of the parallel fibers under the test conditions of 235℃ / 2.16kg is 0.3-3, preferably 0.5-2, and more preferably 0.7-1.5.

[0016] Good compatibility between the two components of the parallel composite elastic fiber is a necessary condition for the formation of a three-dimensional crimped structure. PA12 and PA6 are both polyamide polymers with excellent compatibility and no risk of fiber separation. The choice of the viscosity of the two components determines the formation of the parallel fiber structure and affects the final elastic effect. In this invention, the melt index ratio of the two components of the parallel fiber meets the test conditions of 235℃ / 2.16kg, resulting in better spinnability and better elastic performance.

[0017] In one embodiment of the present invention, the mass ratio of the parallel structure A and the parallel structure B of the parallel fibers is (30-70):(70-30), preferably (40-60):(60-40).

[0018] In one embodiment of the present invention, the melt index of PA12 is 3-100 g / 10 min (235 °C, 2.16 kg), preferably 10-60 g / 10 min (235 °C, 2.16 kg).

[0019] In one embodiment of the present invention, the melt index of PA6 is 3-100 g / 10 min (235 °C, 2.16 kg), preferably 10-60 g / 10 min (235 °C, 2.16 kg).

[0020] PA12 is one of the nylons with the lowest amide bond content, resulting in fewer hydrogen bonds, reduced crystallinity, and increased amorphous region content, thus leading to higher shrinkage. The lower amide group density in the nylon 12 molecular chain (1 amide group per 12 methylene groups) results in greater chain flexibility, lower modulus, and a lower hydrogen bond density compared to nylon 6 (1 amide group per 6 methylene groups). This structural difference leads to superior elastic recovery of nylon 12 fibers during dynamic deformation.

[0021] Due to differences in demand and application, the preferred fiber has a parallel structure A or parallel structure B with a single filament fineness range of 0.45 to 7.00 dtex. Composite fibers within this range have a fineness from 33 dtex to 220 dtex and the number of fibers in a single bundle can range from 12 to 100, which can meet a variety of applications.

[0022] In one embodiment of the present invention, the breaking strength of the PA12 / PA6 parallel composite elastic fiber is ≥4.0 cN / dtex.

[0023] In one embodiment of the present invention, the elongation at break of the PA12 / PA6 parallel composite elastic fiber is ≥50%, more preferably ≥60%.

[0024] In one embodiment of the present invention, the modulus of the PA12 / PA6 parallel composite elastic fiber is ≤35cN / dtex, more preferably ≤30cN / dtex.

[0025] In one embodiment of the present invention, the 150% elongation elastic recovery rate of the PA12 / PA6 parallel composite elastic fiber is ≥90%, more preferably ≥95%.

[0026] In one embodiment of the present invention, the crimp elongation of the PA12 / PA6 parallel composite elastic fiber is ≥350%, more preferably ≥450%.

[0027] In one embodiment of the present invention, the acid dye uptake rate of the PA12 / PA6 parallel composite elastic fiber is ≥90%, more preferably ≥95%.

[0028] Another object of the present invention is to provide a method for preparing PA12 / PA6 side-by-side composite elastic fibers, comprising the following steps: according to the proportions,

[0029] S1. Parallel structure A material and parallel structure B material, dried to a moisture content of less than 50 ppm, are fed into two spinning systems respectively. After melting and filtration, they are quantitatively fed into the parallel composite spinning assembly by a metering pump. The two spinning melts flow separately in the equally long cavities isolated in the parallel composite spinning assembly. When exiting the spinneret, the melt of parallel structure A and the melt of parallel structure B adhere to each other to form nascent filament.

[0030] S2. The nascent filaments are cooled, oiled, hot-rolled, heat-set, and wound into shape.

[0031] In one embodiment of the present invention, in step S2, the hot roller stretching is performed by three pairs of hot rollers or by two pairs of hot rollers.

[0032] In one embodiment of the present invention, the spinning process parameters include: melt spinning temperature of 190-280℃, side blowing temperature of 0-20℃, relative humidity of cooling air of 50-85%, side blowing speed of 0.3-1m / min, stretching ratio of 1.5-5 times, winding speed of 600-6000m / min, and the number of spinnerets on the spinneret used for spinning is 24-500.

[0033] In one embodiment of the present invention, the three pairs of hot rollers can be conventional in the art, such as HGR1, HGR2, and HGR3. Preferably, the three pairs of hot rollers are drawn in such a manner that stretching occurs between HGR1 and HGR2, and cooling and shaping occurs between HGR2 and HGR3.

[0034] In one embodiment of the present invention, the total stretching ratio is preferably 1.5 to 5; the temperature of HGR1 can be 50-160°C; the temperature of HGR2 can be 80-180°C; and the temperature of HGR3 can be 60-180°C.

[0035] HGR stands for Heating Godet Roller.

[0036] In one embodiment of the present invention, step S2, after the winding and forming, may further include a DTY process. As those skilled in the art will know, DTY is short for Drawn-texturing yarn. The DTY process is conventional in the art, generally involving false-twisting the pre-drawn yarn and drawing it into a filament bobbin.

[0037] In one embodiment of the present invention, the texturing temperature in the DTY process can be 100-190°C, preferably 120-180°C.

[0038] In one embodiment of the present invention, the draw ratio in the DTY process can be 1.0-2.5, preferably 1.2-2.0.

[0039] In one embodiment of the present invention, the winding speed in the DTY process is 300-1000 m / min, preferably 500-700 m / min.

[0040] Compared with the prior art, the present invention provides a PA12 / PA6 side-by-side composite elastic fiber, which has the following beneficial effects:

[0041] (1) This invention uses Nylon 12 as a high-shrinkage component and PA6 as a low-shrinkage component to form a superior parallel composite structure. By rationally selecting the component ratio and melt index ratio of PA12 and PA6, good flow matching and spinnability are achieved, significantly improving production efficiency. It can realize high-speed spinning and non-broken filament industrial production, which has real production significance.

[0042] (2) The PA12 / PA6 parallel composite elastic fiber of the present invention has good elastic properties, with an elastic recovery rate of ≥90% at 150% constant elongation and a crimp elongation of ≥450%.

[0043] (3) The parallel composite structure design of the present invention maintains the excellent elasticity of the fiber, while reducing the modulus and improving the feel. It overcomes the shortcomings of traditional polyester parallel composite elastic fibers, which are too hard to feel and have too tight elasticity that is not easy to adjust, and improves the comfort of the product.

[0044] (4) The PA12 / PA6 parallel composite elastic fiber of the present invention can react with acid dyes to achieve diverse color expression, overcoming the shortcomings of traditional polyester parallel composite elastic fibers that can only be dyed with disperse dyes and have insufficient color brightness. Detailed Implementation

[0045] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0046] Key parameters of the examples and comparative examples are shown in Tables 1, 2, and 3. The PA12 resin used was self-made by Wanhua, PA6-1# was purchased from Hengli Petrochemical TNG-2120, PA6-2# was purchased from Hengyi Petrochemical HY-50S, PA-3# was purchased from Asahi Kasei 14G7, PA66 was purchased from Shenma EPR24, PET was purchased from Hengyi Petrochemical HET-665G, and PTT was purchased from Shenghong Group SH-PTT102.

[0047] Table 1

[0048]

[0049]

[0050] Table 2

[0051] formula Parallel Structure A Intrinsic viscosity Parallel Structure B Intrinsic viscosity Component ratio A:B Comparative Example 3 PET 0.67 dL / g PTT 1.02 dL / g 50：50

[0052] Table 3

[0053] formula Parallel Structure A relative viscosity Parallel Structure B relative viscosity Component ratio A:B Comparative Example 4 PA66 2.5 PA6-3 2.7 50：50

[0054] The method for detecting the performance parameters involved in this invention is as follows:

[0055] (1) Spinning properties

[0056] The spinning condition within 2 hours is evaluated using the following method: no broken yarn is marked as ○, a small number of broken yarns (1 to 3 times) is marked as △, and frequent broken yarns (more than 4 times) are marked as ×. ○ and △ are considered acceptable.

[0057] (2) Fracture strength, elongation at break, and modulus

[0058] Breaking strength, elongation at break, and modulus: The determination of breaking strength and elongation at break can refer to GB / T14344-2008 Test Method for Tensile Properties of Chemical Fibers; apply a pretension of 0.05±0.005cN / dtex, a holding distance of 500mm, a tensile speed of 500mm / min, and the modulus = breaking strength corresponding to 1% elongation at break × 100.

[0059] (3) Curling performance

[0060] Crinkling performance: Test method for shrinkage performance of synthetic fiber textured yarn according to GB / T6506-2017.

[0061] crimp elongation: The percentage ratio of the length of the crimped textured yarn from its natural state to the length of the fiber in its natural state when the crimp structure is completely eliminated under the action of tensile force.

[0062] Curl elongation = (L1-L0) / L0 × 100%

[0063] L0: The length of the textured yarn in its natural state;

[0064] L1: The length of the crimped textured yarn when it is slowly stretched to a straight state under tensile force (tension is 0.2 cN / dtex).

[0065] (4) Elastic recovery

[0066] Elastic recovery: The fiber electronic strength tester LLY06 was used. The ambient temperature was 23℃, the humidity was 65%, the sample clamping distance was 30mm, the tensile speed was 60mm / min, and the fixed elongation value was set to 50%, 100%, and 150% of the clamping distance, respectively.

[0067] Elastic recovery rate = ((L-L1) / (L-L0))×100%;

[0068] In the formula: L0 is the original length of the sample; L is the length of the sample after being stretched to a certain elongation; L1 is the length of the sample after being reset.

[0069] When testing the fiber crimping and elastic properties, the obtained fibers were treated in water at 100℃ for 30 minutes and then dried before testing.

[0070] (5) Staining performance test:

[0071] Rinsing before dyeing: Rinse the fibers in a 2 g / L sodium dodecyl sulfate solution for 1 hour (80°C).

[0072] Staining pH: Add 1% acetic acid

[0073] Dye dosage: 2% (owf)

[0074] Dye type: Acid Black 1 CAS: 1064-48-8

[0075] Temperature: 80℃

[0076] Time: 2 hours

[0077] Bath ratio: 1:12

[0078] The higher the staining rate T (%), the better the staining performance.

[0079] Comparative Example 1

[0080] S1. Weigh parallel structure A: PA12-1# and parallel structure B: PA6-1# in a 50:50 ratio. Dry PA12-1# and PA6-1# to a moisture content of less than 50ppm and feed them into two sets of spinning systems respectively. After melting and filtering, they are quantitatively fed into the parallel composite spinning assembly by a metering pump. The two spinning melts flow separately in the equally long cavities isolated in the parallel composite spinning assembly. When exiting the spinneret, the PA12-1# melt and the PA6-1# melt adhere to each other to form nascent filament.

[0081] S2. The nascent yarn is cooled, oiled, hot-rolled, heat-set, and wound into shape to obtain drawn oriented yarn (FDY).

[0082] The spinning process parameters are as follows: hot roller drawing involves three pairs of hot rollers, melt spinning temperature is 280℃, side blowing temperature is 16℃, cooling air relative humidity is 50%, side blowing speed is 0.6m / min, drawing ratio is 4.0 times, HGR1 temperature is 80℃, HGR2 temperature is 150℃, HGR3 temperature is 90℃, winding speed is 4500m / min, and the number of spinnerets on the spinneret used for spinning is 24.

[0083] Comparative Example 2

[0084] PA12-5# is a parallel structure A, with a melt spinning temperature of 255℃, and other spinning conditions are the same as those in Comparative Example 1.

[0085] Comparative Example 3

[0086] S1. Weigh out parallel structure A: PET with an intrinsic viscosity of 0.67 dL / g and parallel structure B: PTT with an intrinsic viscosity of 1.02 dL / g in a 50:50 ratio. The PET and PTT, dried to a moisture content of less than 50 ppm, are fed into two sets of spinning systems respectively. After melting and filtration, they are quantitatively fed into the parallel composite spinning assembly via a metering pump. The two spinning melts flow separately in the equally long cavities isolated within the parallel composite spinning assembly. When exiting the spinneret, the PET melt and the PTT melt adhere to each other to form nascent filaments.

[0087] S2. The nascent yarn is cooled, oiled, hot-rolled, heat-set, and wound into shape to obtain drawn oriented yarn (FDY).

[0088] The spinning process parameters are as follows: hot roller drawing involves three pairs of hot rollers; melt spinning temperature is 295℃; side blowing temperature is 16℃; cooling air relative humidity is 60%; side blowing speed is 0.6m / min; drawing ratio is 3.1 times; HGR1 temperature is 80℃; HGR2 temperature is 160℃; HGR3 temperature is 100℃; winding speed is 4500m / min; and the number of spinnerets on the spinneret used for spinning is 24.

[0089] Comparative Example 4

[0090] S1. Weigh parallel structure A: PA66 with a relative viscosity of 2.5 and 96wt% sulfuric acid according to a 50:50 ratio, and parallel structure B: PA6 with a relative viscosity of 2.7 and 96wt% sulfuric acid. Dry PA66 and PA6 to a moisture content of less than 50ppm and feed them into two sets of spinning systems respectively. After melting and filtration, they are quantitatively fed into the parallel composite spinning assembly via metering pumps. The two spinning melts flow separately in the equally long, isolated cavities within the parallel composite spinning assembly. When exiting the spinneret, the PA66 melt and the PA6 melt adhere to each other, forming nascent filaments.

[0091] S2. The nascent yarn is cooled, oiled, hot-rolled, heat-set, and wound into shape to obtain drawn oriented yarn (FDY).

[0092] The spinning process parameters are as follows: hot roller drawing involves three pairs of hot rollers; melt spinning temperature is 295℃; side blowing temperature is 16℃; cooling air relative humidity is 60%; side blowing speed is 0.6m / min; drawing ratio is 3.1 times; HGR1 temperature is 80℃; HGR2 temperature is 160℃; HGR3 temperature is 90℃; winding speed is 4500m / min; and the number of spinnerets on the spinneret used for spinning is 24.

[0093] Example 1

[0094] PA12-2# is a parallel structure A, with a melt spinning temperature of 270℃, and other spinning conditions are the same as those in Comparative Example 1.

[0095] Example 2

[0096] PA12-3# is a parallel structure A, with a melt spinning temperature of 265℃, and other spinning conditions are the same as in Example 1.

[0097] Example 3

[0098] PA12-4# is a parallel structure A, with a melt spinning temperature of 255℃, and other spinning conditions are the same as in Example 1.

[0099] Example 4

[0100] S1. Weigh parallel structure A: PA12-3# and parallel structure B: PA6-2# in a 50:50 ratio. Dry PA12-3# and PA6-2# to a moisture content of less than 50ppm and feed them into two sets of spinning systems respectively. After melting and filtering, they are quantitatively fed into the parallel composite spinning assembly by a metering pump. The two spinning melts flow separately in the equally long cavities isolated in the parallel composite spinning assembly. When exiting the spinneret, the PA12-3# melt and the PA6-2# melt adhere to each other to form nascent filament.

[0101] S2. The nascent filament is cooled, oiled, hot-rolled, heat-set, and wound to form a pre-drawn filament (POY) of the polyamide parallel composite elastic fiber. The POY filament bobbin is then false-twisted and drawn into a stretch textured filament bobbin (DTY).

[0102] The spinning process parameters are as follows: hot roller drawing involves two pairs of hot rollers; melt spinning temperature is 260℃; side blowing temperature is 16℃; cooling air relative humidity is 50%; side blowing speed is 0.6 m / min; draw ratio is 2.6 times; HGR1 temperature is 80℃; HGR2 temperature is 150℃; the POY winding speed is 3200 m / min; and the number of spinnerets on the spinneret used for spinning is 24. In the DTY process, the texturing temperature is 155℃; the draw ratio is 1.5; and the winding speed is 650 m / min.

[0103] Example 5

[0104] PA12-4# is a parallel structure A, with a melt spinning temperature of 255℃, and other spinning conditions are the same as in Example 4.

[0105] Example 6

[0106] PA12-5# is a parallel structure A, with a melt spinning temperature of 242℃, and other spinning conditions are the same as in Example 4.

[0107] Example 7

[0108] The ratio of parallel structure A to parallel structure B is 30:70. The melt spinning temperature is 260°C, and other spinning conditions are the same as in Example 1.

[0109] Example 8

[0110] The ratio of parallel structure A to parallel structure B is 40:60. The melt spinning temperature is 255°C, and other spinning conditions are the same as in Example 1.

[0111] Example 9

[0112] The ratio of parallel structure A to parallel structure B is 70:30. The melt spinning temperature is 255°C, and other spinning conditions are the same as in Example 1.

[0113] The fiber performance test results are shown in Table 4:

[0114] Table 4

[0115]

[0116] The results from the parallel elastic fibers prepared in Examples 1-9 and Comparative Examples 3 and 4 show that the overall crimp elongation and elastic recovery rate of the PA12 / PA6 parallel composite elastic fiber are significantly better than those of Comparative Examples 3 and 4. Furthermore, its modulus is lower than that of Comparative Examples 3 and 4, exhibiting superior flexibility and improved wearing comfort. Compared to Comparative Example 3, it also shows a higher dye uptake rate in the acid dye system, resulting in more vibrant colors. Moreover, it was found that when the ratio of the two components of the parallel fiber is 40-60:60-40, the fiber has a higher crimp elongation and better elastic properties.

[0117] Meanwhile, the spinnability results of Examples 1-9 and Comparative Examples 1 and 2 showed that the spinnability of the two components of the parallel fibers was better and the elasticity was better when the melt index ratio was between 0.7 and 1.5.

[0118] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A PA12 / PA6 side-by-side composite elastic fiber, comprising the following parts by weight of raw materials: Parallel Structure A: PA12, 20-80 copies; Parallel Structure B: PA6, 80-20 parts; in, The melt index ratio A:B of the two components of the parallel fibers under the test conditions of 235℃ / 2.16kg is 0.3-3, preferably 0.5-2, and more preferably 0.7-1.

5.

2. The PA12 / PA6 parallel composite elastic fiber according to claim 1, characterized in that, The mass ratio of the parallel structure A to the parallel structure B is 30-70:70-30, preferably 40-60:60-40.

3. The PA12 / PA6 parallel composite elastic fiber according to claim 1 or 2, characterized in that, The melt flow index of PA12 is 3-100 g / 10 min, 235 °C, 2.16 kg; preferably 10-60 g / 10 min, 235 °C, 2.16 kg.

4. The PA12 / PA6 parallel composite elastic fiber according to any one of claims 1-3, characterized in that, The melt flow index of the PA6 is 3-100 g / 10 min at 235 °C and 2.16 kg; preferably 10-60 g / 10 min at 235 °C and 2.16 kg.

5. The PA12 / PA6 parallel composite elastic fiber according to any one of claims 1-4, characterized in that, The fineness range of the single filaments in the parallel structure A or parallel structure B is 0.45 to 7.00 dtex.

6. The PA12 / PA6 parallel composite elastic fiber according to any one of claims 1-5, characterized in that, The PA12 / PA6 parallel composite elastic fiber has a breaking strength ≥4.0 cN / dtex; breaking elongation ≥50%, more preferably ≥60%; modulus ≤35 cN / dtex, more preferably ≤30 cN / dtex; elastic recovery rate at 150% constant elongation ≥90%, more preferably ≥95%; crimp elongation ≥350%, more preferably ≥450%; and acid dye uptake rate ≥90%, more preferably ≥95%.

7. A method for preparing PA12 / PA6 parallel composite elastic fiber according to any one of claims 1-6, comprising the following steps: according to the ratio, S1. Parallel structure A material and parallel structure B material, dried to a moisture content of less than 50 ppm, are fed into two spinning systems respectively. After melting and filtration, they are quantitatively fed into the parallel composite spinning assembly by a metering pump. The two spinning melts flow separately in the equally long cavities isolated in the parallel composite spinning assembly. When exiting the spinneret, the melt of parallel structure A and the melt of parallel structure B adhere to each other to form nascent filament. S2. The nascent filaments are cooled, oiled, hot-rolled, heat-set, and wound into shape.

8. The method according to claim 7, characterized in that, The spinning process parameters include: melt spinning temperature 190-280℃, side blowing temperature 0-20℃, cooling air relative humidity 50-85%, side blowing speed 0.3-1m / min, stretching ratio 1.5-5 times, winding speed 600-6000m / min, and the number of spinnerets on the spinneret used for spinning is 24-500.

9. The method according to claim 7 or 8, characterized in that, The hot rollers consist of three pairs, including HGR1, HGR2 and HGR3; HGR1 and HGR2 are used for stretching, while HGR2 and HGR3 are used for cooling and shaping.

10. The method according to any one of claims 7-9, characterized in that, In step S2, after the winding and forming, a DTY process is performed; the texturing temperature in the DTY process is 100-190℃, preferably 120-180℃; the draw ratio is 1.0-2.5, preferably 1.2-2.0; and the winding speed is 300-1000m / min, preferably 500-700m / min.

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