Polyamide-6 fiber with curling effect and preparation method thereof

Abstract

The invention discloses a chinlon 6 fiber with a curling effect and a preparation method of the chinlon 6 fiber, and belongs to the technical field of textile fibers. Conventional chinlon 6 is used as a raw material, the structure of a spinneret plate and the direction of an air net are adjusted in the spinning process, temperature and humidity differentiated between the inner side and the outer side are generated in combination with precisely controlled cooling parameters, and internal stress is formed through controllable crystallization rate difference to achieve the self-curling effect of the chinlon 6 fiber. According to the method, the situation that a traditional method depends on chemical auxiliaries or complex equipment modification is avoided, the high elastic recovery rate and the curling stability are achieved only through technological parameter optimization, the cost and complexity are remarkably reduced, the curling degree of the prepared chinlon 6 fiber can be accurately regulated and controlled, and compared with conventional chinlon fibers, the curling performance is excellent; the formed fluffy structure effectively improves the air permeability and comfort, the low boiling water shrinkage can ensure that the fabric does not deform after being washed for multiple times, and the fabric has wide application prospects in the field of textiles such as high-end elastic fabric and functional home textiles.

Description

Technical Field

[0001] The present invention belongs to the technical field of textile fibers, and in particular relates to a nylon 6 fiber with a curling effect and a preparation method thereof. Background Art

[0002] Polyamide (PA), commonly known as nylon, is a heteropolymer containing amide groups (-NHCO-) ​​in its backbone. It can be categorized as either aliphatic or aromatic. It is the earliest developed and most widely used thermoplastic engineering material. Polyamides contain numerous repeating amide groups in their backbone. When used as a plastic, they are called nylon, and when used as a synthetic fiber, they are called polyamides. Various polyamides can be produced depending on the number of carbon atoms in the diamine, dibasic acid, or amino acid. Currently, there are dozens of polyamide varieties, with polyamide 6, polyamide 66, and polyamide 610 being the most widely used.

[0003] Nylon 6 is an aliphatic polyamide with excellent properties, including high mechanical strength, high strength, lightweight, easy dyeing, and easy molding. Due to its excellent strength, abrasion resistance, and elasticity, nylon 6 fiber is widely used in textiles, clothing, engineering plastics, and films. However, the molecular chain segments of nylon 6 contain highly polar amide groups, which easily form hydrogen bonds with water molecules. This leads to disadvantages such as high water absorption, poor dimensional stability, low impact strength in the dry state and at low temperatures, and poor resistance to strong acids and alkalis.

[0004] Traditional nylon 6 fibers are mostly straight filaments with limited bulk and elastic recovery, making them difficult to meet the softness, warmth, and three-dimensional demands of high-end fabrics. To impart curl to the fibers, the industry typically uses mechanical crimping or chemical modification. Mechanical crimping involves post-processing such as false twisting, gear crimping, or hot-box setting on the spun fibers. However, the resulting curl is less stable and easily disappears during subsequent processing or use. Chemical modification, through copolymerization or the addition of additives, alters the polymer's crystallization behavior, causing the fibers to curl spontaneously. This process not only increases raw material costs but can also affect the fiber's mechanical properties and dyeing uniformity.

[0005] A Chinese patent application with publication number CN108914231A, filed on August 13, 2018, discloses a fully drawn nylon 6 yarn with an apparent curly appearance and a production method thereof. The invention involves melting nylon 6 chips and extruding them to produce a nylon 6 melt. The nylon 6 melt is precisely metered by a metering pump, enters a spinning assembly, and is ejected through a spinneret to form a tow. The tow then undergoes monomer extraction, side-blown cooling, bundling and oiling, stretching and shaping, and interlacing, before winding to form the fully drawn nylon 6 yarn with an apparent curvature. However, the fully drawn nylon 6 yarn produced by this invention exhibits only an apparent curvature, rather than a true crimp structure formed by internal stress. This curvature is easily straightened during subsequent processing, and lacks the bulk and dynamic elasticity imparted to fabrics by true crimped fibers.

[0006] Korean Patent Publication No. KR20050036100A, filed on October 15, 2003, discloses self-curling polyamide fibers. The high-latent orientation component is composed of a copolyamide 6 copolymerized with an aromatic compound or a cyclic compound and 1-3-10 mol% of a polyamide 6 or aliphatic compound. The fiber is characterized by a low-potential orientation component composed of 5 mol% of copolyamide 6 in parallel. The latent polyamide fibers of the present invention exhibit excellent elasticity and are inexpensive to manufacture, making them suitable for use as yarns for clothing. While the invention introduces aromatic / cyclic comonomers, which can induce curling in the parallel structure of the "high- and low-latent orientation components," they severely disrupt the regularity of the polyamide 6, potentially leading to decreased breaking strength and fluctuating dye uptake. Furthermore, the comonomers require separate steps to synthesize the "high- and low-latent orientation component" copolymers, making polymerization control difficult, supply stability poor, and expensive.

[0007] While existing nylon 6 crimping technology has made varying degrees of progress, due to a lack of precise, coordinated control of cooling dynamics and crystallization behavior, nylon 6 fiber products still suffer from the drawback of "easy crimping but difficult stability." Therefore, a method for preparing nylon 6 fibers that can achieve high-stability, self-crimping without sacrificing fiber strength, requiring no additives or post-processing, and achieved solely through spinning process optimization, has significant application value in addressing the growing market demand for highly elastic fibers and can provide a valuable reference for addressing the pressing technical challenges facing the high-value-added textile industry. Summary of the Invention

[0008] In order to solve the problems existing in the prior art, the present invention provides a nylon 6 fiber with a curling effect and a preparation method thereof. The curling degree of the prepared nylon 6 fiber can be precisely controlled. Compared with conventional nylon fibers, the curling performance is excellent. The fluffy structure formed effectively improves the air permeability and comfort, and the low boiling water shrinkage rate ensures that it will not deform after multiple washings.

[0009] The technical solutions of the present invention are as follows:

[0010] One of the objects of the present invention is to provide a method for preparing nylon 6 fiber with a curling effect, comprising the following steps:

[0011] S1. Melt-extrude spinning-grade nylon 6 chips through a screw extruder. The extrusion temperature is controlled in the following zones: zone 1 250-255°C, zone 2 252-257°C, zone 3 253-258°C, zone 4 255-260°C, and zone 5 255-260°C.

[0012] S2, the melt enters the spinning box and the spinning assembly, and is ejected through the spinneret to form a tow. The spinneret is a flat or flat plate assembly, and the direction of the wire outlet is perpendicular to the side-blowing air mesh;

[0013] S3, after the tow is extracted by the monomer, it is cooled by dual-zone differentiated side blowing:

[0014] Inner cooling zone: temperature 22-23°C, humidity 85-95%;

[0015] External cooling zone: temperature 22-23°C, humidity 65-75%;

[0016] S4. After cooling the filament bundle, the filament bundle is bundled and oiled, and the filament bundle is wound into shape at a production speed of 4500-4800 m / min to obtain the nylon 6 fiber with the curling effect.

[0017] Furthermore, the spinning-grade polyamide 6 chips in S1 are glossy or semi-dull, have a relative viscosity of 2.45-2.50, and a water content of 500 ppm.

[0018] Furthermore, the main engine speed of the screw extruder in S1 is 550-570 r / min.

[0019] Furthermore, the length-to-width ratio of the wire outlet hole of the flat component in S2 is 7:1.

[0020] Furthermore, the length-to-width ratio of the wire hole of the Feng-shaped plate component in S2 is 5:1.

[0021] Furthermore, the wind speed in the inner and outer cooling zones in S3 is 0.5-0.6 m / s.

[0022] Furthermore, the oiling agent used for the bundle oiling in S4 is a nylon oiling agent with a concentration of 12%.

[0023] A second object of the present invention is to provide a nylon 6 fiber with a curling effect.

[0024] Furthermore, the nylon 6 fiber has a curl shrinkage rate of 51.39-53.55%, an elastic recovery rate of ≥93.24%, and a boiling water shrinkage rate of ≤7.47%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This invention, for the first time, achieves true crimping in nylon 6 fibers through precise control of physical internal stress, breaking through the limitations of traditional chemical modification or mechanical deformation. By innovatively utilizing a flat / F-shaped spinneret in a vertical arrangement with a wind screen, the invention creates differentiated cooling environments by regulating the temperature and humidity in both inner and outer zones. This results in rapid cooling and crystallization of the tow near the wind screen, while slowing crystallization on the outer side. This differential molecular chain contraction generates persistent internal stress, resulting in asymmetric crystallization within the nylon 6 fibers. This preparation method replaces hardware modification with process optimization, while avoiding chemical contamination. Dynamic adjustment of process parameters allows precise control of nylon 6 fiber crimp, resolving the existing limitations of poor crimp stability and the compromise between nylon 6 fiber strength.

[0027] 2. The nylon 6 fiber produced by the present invention generates a true curl structure induced by internal stress through asymmetric crystallization, which exhibits high curl stability and balanced mechanical properties while retaining the basic properties of nylon 6. The curl shrinkage rate of the nylon 6 fiber can reach 51.39-53.55%, and the elastic recovery rate can reach 93.24-95.69%, which are significantly higher than those of mechanically curled fibers; the boiling water shrinkage rate is only 6.91-7.47%, proving that the curl structure of the fiber can remain stable under hot and humid environments. At the same time, the breaking strength of the nylon 6 fiber is maintained at 2.56-3.14 cN / dtex, and the elongation at break is maintained at 21.67-27.65%, meeting the dual requirements of durability and ductility for high-elastic fabrics. In addition, the nylon 6 fiber has a homogenization characteristic, and the use of homopolymer slices makes the dyeing consistency better than that of copolymer modified fibers, effectively avoiding color spots on the fabric surface.

[0028] 3. The method for preparing nylon 6 fibers with a curling effect provided by the present invention is characterized by low cost, high efficiency, and strong flexibility. It requires no equipment modification and can be achieved using only universal equipment combined with cooling parameter adjustments. Existing nylon 6 fiber spinning lines can be directly used. This preparation method has precisely controllable process parameters, customizable curling, and flexible switching from low-elastic to high-elastic product lines by adjusting wind speed and humidity. The provided parameter range avoids excessive cooling rates that affect physical properties such as yarn evenness and breaking strength or affect the curling effect, while excessive cooling rates prevent insufficient cooling and shaping. The resulting nylon 6 fiber's curling degree can be precisely controlled, resulting in a fluffy structure that effectively improves breathability and comfort. The low boiling water shrinkage ensures that the fiber retains its shape after repeated washings. It has broad application prospects in textiles such as high-end stretch fabrics and functional home textiles. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of a Feng-shaped plate assembly used in the method for preparing nylon 6 fiber with a curling effect according to the present invention;

[0030] Figure 2This is a schematic structural diagram of a flat assembly used in the method for preparing nylon 6 fiber with a curling effect according to the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with preferred embodiments. The endpoints of the ranges and any values ​​disclosed in the present 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 each range, the endpoint values ​​of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0032] Unless otherwise specified, the experimental methods in the following examples are conventional methods and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0033] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0034] Example 1

[0035] This embodiment provides a method for preparing nylon 6 fiber with a curling effect, comprising the following steps:

[0036] 1) The spinning-grade bright nylon 6 chips were melt-extruded through a screw extruder at a speed of 560 r / min. The extrusion temperature was controlled in the following zones: zone 1 250-255°C, zone 2 252-257°C, zone 3 253-258°C, zone 4 255-260°C, and zone 5 255-260°C;

[0037] 2) The melt enters the spinning manifold and the spinning assembly, and is ejected through the spinneret to form a filament bundle. The spinneret is a shaped plate assembly with an aspect ratio of 5:1, and the direction of the filament outlet is perpendicular to the side-blowing air mesh;

[0038] 3) After the tow is extracted by the monomer, it is cooled by dual-zone differential side blowing with a wind speed of 0.55m / s:

[0039] Inner cooling zone: temperature 22-23°C, humidity 85-95%;

[0040] External cooling zone: temperature 22-23°C, humidity 65-75%;

[0041] 4) After cooling the filament bundle, the filament bundle was oiled with a nylon oil agent having a concentration of 12%, and the filament bundle was wound into shape at a production speed of 4650 m / min to obtain the nylon 6 fiber with the crimping effect.

[0042] Example 2

[0043] This embodiment provides a method for preparing nylon 6 fiber with a curling effect, comprising the following steps:

[0044] 1) The spinning grade semi-dull nylon 6 chips were melt-extruded through a screw extruder at a speed of 550 r / min. The extrusion temperature was controlled in the following zones: zone 1 250-255°C, zone 2 252-257°C, zone 3 253-258°C, zone 4 255-260°C, and zone 5 255-260°C;

[0045] 2) The melt enters the spinning manifold and the spinning assembly, and is ejected through the spinneret to form a filament bundle. The spinneret is a flat component with a filament hole aspect ratio of 7:1, and the filament hole direction is perpendicular to the side blowing screen;

[0046] 3) After the tow is extracted by the monomer, it is cooled by dual-zone differential side blowing with a wind speed of 0.5m / s:

[0047] Inner cooling zone: temperature 22-23°C, humidity 85-95%;

[0048] External cooling zone: temperature 22-23°C, humidity 65-75%;

[0049] 4) After cooling the filament bundle, the filament bundle is oiled with a nylon oil agent having a concentration of 12%, and the filament bundle is wound into shape at a production speed of 4500 m / min to obtain the nylon 6 fiber with the crimping effect.

[0050] Example 3

[0051] This embodiment provides a method for preparing nylon 6 fiber with a curling effect, comprising the following steps:

[0052] 1) Melt-extrude spinning-grade bright nylon 6 chips through a screw extruder at a speed of 570 r / min. The extrusion temperature is controlled in the following zones: zone 1 250-255°C, zone 2 252-257°C, zone 3 253-258°C, zone 4 255-260°C, and zone 5 255-260°C;

[0053] 2) The melt enters the spinning manifold and the spinning assembly, and is ejected through the spinneret to form a filament bundle. The spinneret is a shaped plate assembly with an aspect ratio of 5:1, and the direction of the filament outlet is perpendicular to the side-blowing air mesh;

[0054] 3) After the tow is extracted by the monomer, it is cooled by dual-zone differential side blowing with a wind speed of 0.6m / s:

[0055] Inner cooling zone: temperature 22-23°C, humidity 85-95%;

[0056] External cooling zone: temperature 22-23°C, humidity 65-75%;

[0057] 4) After cooling the filament bundle, the filament bundle is oiled with a nylon oil agent having a concentration of 12%, and the filament bundle is wound into shape at a production speed of 4800 m / min to obtain the nylon 6 fiber with the crimping effect.

[0058] Performance Testing

[0059] The nylon 6 fibers with curling effect prepared in Examples 1-3 above were tested, and the test results are shown in Table 1:

[0060] Table 1 Physical properties of nylon 6 with curling effect prepared in Examples 1-3

[0061] Example Example 1 Example 2 Example 3 Specification 45D / 8F 70D / 48F 4OD / 34F Breaking strength cN / dtex 2.56 3.14 2.56 Elongation at break % 21.67 24.78 27.65 Boiling water shrinkage% 6.91 7.23 7.47 Oil content% 1.39 1.41 1.43 Curl shrinkage% 51.39 53.55 52.86 Elastic recovery rate% 95.69 93.24 94.18

[0062] The three specifications of self-crimped nylon 6 fibers prepared in Examples 1-3 of the present invention all exhibit excellent performance. First, the curling stability is outstanding, with a curling shrinkage rate of 51.39-53.55% and an elastic recovery rate of 93.24-95.69%, which are significantly higher than those of mechanically curled fibers. Second, the strength and elasticity are synergistically optimized, with a breaking strength of 2.56-3.14 cN / dtex, and high durability. Finally, the wet heat stability is excellent, with a boiling water shrinkage rate of only 6.91-7.47%, and it can withstand subsequent dyeing and finishing processing.

[0063] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing nylon 6 fiber with a curling effect, characterized in that: The following steps are involved: S1. Melt-extrude spinning-grade nylon 6 chips through a screw extruder. The extrusion temperature is controlled in the following zones: zone 1 250-255°C, zone 2 252-257°C, zone 3 253-258°C, zone 4 255-260°C, and zone 5 255-260°C. S2, the melt enters the spinning box and the spinning assembly, and is ejected through the spinneret to form a tow. The spinneret is a flat or flat plate assembly, and the direction of the wire outlet is perpendicular to the side-blowing air mesh; S3, after the tow is extracted by the monomer, it is cooled by dual-zone differentiated side blowing: Inner cooling zone: temperature 22-23°C, humidity 85-95%; External cooling zone: temperature 22-23°C, humidity 65-75%; S4. After cooling the filament bundle, the filament bundle is bundled and oiled, and the filament bundle is wound into shape at a production speed of 4500-4800 m / min to obtain the nylon 6 fiber with the curling effect.

2. The method for preparing nylon 6 fiber with a curling effect according to claim 1, characterized in that: The spinning-grade polyamide 6 chips in S1 are glossy or semi-dull.

3. The method for preparing nylon 6 fiber with a curling effect according to claim 1, characterized in that: The relative viscosity of the spinning-grade polyamide 6 chips in S1 is 2.45-2.50, and the water content is 500 ppm.

4. The method for preparing nylon 6 fiber with a curling effect according to claim 1, characterized in that: The main engine speed of the screw extruder in S1 is 550-570 r / min.

5. The method for preparing nylon 6 fiber with a curling effect according to claim 1, characterized in that: The length-to-width ratio of the wire outlet hole of the flat component in S2 is 7:

1.

6. The method for preparing nylon 6 fiber with a curling effect according to claim 1, characterized in that: The length-to-width ratio of the thread outlet hole of the Feng-shaped plate component in the S2 is 5:

1.

7. The method for preparing nylon 6 fiber with a curling effect according to claim 1, characterized in that: The wind speed in the inner and outer cooling zones in S3 is 0.5-0.6 m / s.

8. The method for preparing nylon 6 fiber with a curling effect according to claim 1, characterized in that: The oiling agent used for the bundle oiling in S4 is a nylon oil agent with a concentration of 12%.

9. Nylon 6 fiber with a curling effect obtained by the preparation method according to any one of claims 1 to 8.

10. The nylon 6 fiber with a curling effect according to claim 9, characterized in that: The nylon 6 fiber has a crimp shrinkage rate of 51.39-53.55%, an elastic recovery rate of ≥93.24%, and a boiling water shrinkage rate of ≤7.47%.

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