Composite spinning process of high-elasticity chemical fiber blended yarn

Abstract

The invention provides a composite spinning process of a high-elasticity chemical fiber blended yarn, which comprises the following steps: a multi-layer co-extrusion step: synchronously extruding core layer thermoplastic polyurethane, middle layer nano modified polyester and outer layer polyamide 66 in a molten state through a coaxial three-channel spinning assembly to form a nascent fiber with a core-sheath structure, the middle layer nano modified polyester contains silicon dioxide nano particles; the extruded nascent fibers are immediately guided into a low-temperature shock cooling air field at the temperature of 5 + / -1 DEG C, and the length L of a cooling area and the linear speed v of the fibers meet the relational expression t = L / v > = 0.8 s; the cooled fibers are guided into a constant-temperature water bath at the temperature of 40 + / -2 DEG C, first-stage stretching and second-stage stretching are sequentially carried out, in the first-stage stretching process, stretching is carried out at the speed of 2.5-3.0 m / min till the original length is 130%, and after the first-stage stretching process is carried out for 10 seconds, the fibers are loosened and retracted till the original length is 120%; and in the second-stage stretching, stretching is continued at the speed of 1.8-2.2 m / min until the original length is 150%, and after keeping for 15 seconds, the stretching is finally retracted until the original length is 130%.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical fiber manufacturing, and particularly to a composite spinning process for a highly elastic chemical fiber blended yarn. Background Art

[0002] Currently, there are four main chemical fiber spinning processes, namely melt spinning, wet spinning, dry spinning, and reaction spinning. Melt spinning is the most commonly used method. Plastic pellets are heated into a syrup-like state and extruded through a nozzle with fine holes, while being shaped by blowing cold air. Wet spinning involves dissolving the plastic in a special chemical solution and then extruding it into another chemical bath for solidification. Dry spinning is to extrude the dissolved plastic solution into hot air to evaporate the solvent. Reaction spinning is to let the plastic molecules undergo a chemical reaction during the extrusion process.

[0003] Although these processes can produce various fibers, there are still many challenges in the production of highly elastic yarns. Firstly, there are limitations at the material level. The molecular chains of conventional fiber materials are arranged in a straight line, resulting in a limited range of elastic deformation. Although highly elastic materials have a spring-like molecular structure, they are prone to molecular chain breakage during high-temperature processing. This creates a contradiction between heat resistance and processing requirements because elastic materials need to maintain the mobility of molecular chains, but the conventional spinning temperature will damage their microstructure.

[0004] Secondly, there are also difficulties in the formation of the composite structure. The physical properties of different component materials vary greatly, and interface separation is likely to occur during mixing, resulting in insufficient material compatibility. The cooling shrinkage rates of each component are significantly different, and this difference will generate stress within the fiber, forming invisible microcracks, ultimately leading to a decrease in product elasticity. In addition, the characteristics of the surface layer and the core material of the composite fiber are too different, and asynchronous deformation will occur during repeated stretching. After 1000 times of tensile testing, the elastic retention rate is often less than 65%.

[0005] Finally, the production process also faces some difficulties. In terms of tensile control, different materials have very different sensitivities to the tensile speed. When the tensile strength exceeds 3.5 times, the elastic component will show a hardening phenomenon, while the ordinary component has entered an irreversible deformation stage, which will lead to fiber structure delamination. During the cooling and shaping process, the shape memory ability of the elastic material will rapidly decay, and the regularity of the molecular arrangement structure after processing will be lost. In addition, the conventional cooling process will cause the surface layer to harden rapidly while the core is still in a soft state, resulting in disordered internal molecular arrangement and ultimately a decrease in the elastic recovery ability.

[0006] In view of the above problems, the existing technology urgently needs to be improved. Summary of the Invention

[0007] The purpose of this application is to provide a composite spinning process for high-elastic chemical fiber blended yarns, which has the advantage of improving the elasticity of the fibers. The present invention aims to solve the above technical problems and provide a composite spinning process for high-elastic chemical fiber blended yarns.

[0008] The technical solution of the present invention is a composite spinning process for high-elastic chemical fiber blended yarns, comprising the following steps:

[0009] Multi-layer co-extrusion step: Through a coaxial three-channel spinning component, the core layer of thermoplastic polyurethane, the intermediate layer of nano-modified polyester, and the outer layer of polyamide 66 are synchronously extruded in a molten state to form a nascent fiber with a core-sheath structure. The intermediate layer of nano-modified polyester contains silica nanoparticles surface-modified with γ-aminopropyltriethoxysilane, with a particle size of 50-80 nm and an addition amount of 1.2-1.8% of the weight of the polyester;

[0010] Gradient cooling and solidification step: The extruded nascent fiber is immediately introduced into a low-temperature sudden cold air field at 5±1°C. The length L of the cooling zone and the fiber linear velocity v satisfy the relationship t = L / v≥0.8 s, where t is the cooling time, and the wind speed is controlled at 8-12 m / s to form a glassy protective layer on the outer layer of polyamide 66;

[0011] Staged hot stretching step: The cooled fiber is introduced into a constant temperature water bath at 40±2°C and subjected to first-stage stretching and second-stage stretching in sequence. Among them, the first-stage stretching is carried out at a speed of 2.5-3.0 m / min to 130% of the original length, held for 10 seconds and then relaxed and retracted to 120% of the original length; the second-stage stretching is continued at a speed of 1.8-2.2 m / min to 150% of the original length, held for 15 seconds and finally retracted to 130% of the original length.

[0012] As an implementation method, in the gradient cooling and solidification step, the length L of the cooling zone is 1.2-1.5 m, and the fiber linear velocity v is 1.5-1.8 m / min.

[0013] As an implementation method, in the staged hot stretching step, the stretching rate of the first-stage stretching is 1.3-1.5 times that of the second-stage stretching, and the stress relaxation time ratio of the two-stage stretching is 1:1.5.

[0014] As an implementation method, in the multi-layer co-extrusion step, the melting temperature of the core layer of thermoplastic polyurethane is 190-200°C, the melting temperature of the intermediate layer of modified polyester is 230-240°C, and the melting temperature of the outer layer of polyamide 66 is 260-265°C.

[0015] As an implementation method, the melt index of the core layer of thermoplastic polyurethane is 25-35 g / 10 min, and the molecular weight distribution index is 1.8-2.2.

[0016] As an embodiment, the intrinsic viscosity of the modified polyester in the intermediate layer is 0.75-0.85 dL / g, wherein the dispersion uniformity of the nano-silicon dioxide particles in the polyester melt is ≤15%.

[0017] As an embodiment, the crystallinity of the outer layer polyamide 66 is controlled at 35-40%, and the spinneret aperture is 0.25-0.35 mm, and the aspect ratio is 4:1 to 6:1.

[0018] As an embodiment, the staged heat stretching step also includes a heat setting treatment. After the staged heat stretching, the fiber is introduced into a 120-130°C hot air box and maintained in a tension-relaxed state for 3-5 minutes at a wind speed of 2-3 m / s.

[0019] As an embodiment, the intermediate layer modified polyester further comprises 0.3-0.5wt% of a hindered phenol antioxidant, and the mass ratio of the hindered phenol antioxidant to the nano-silicon dioxide is 1:(2.5-3.5).

[0020] Compared with the prior art, the beneficial effect of the present invention is that the composite spinning process of the high-elastic chemical fiber blended yarn includes a multi-layer co-extrusion step, a gradient cooling and solidification step, and a staged hot stretching step.

[0021] First, through the multi-layer co-extrusion step, the core layer thermoplastic polyurethane, the middle layer nano-modified polyester and the outer layer polyamide 66 are extruded synchronously in a molten state to form a primary fiber with a core-sheath structure. The added intermediate transition layer and nano-modification can solve the limitations at the material level and the problem of composite structure molding. Next, the primary fiber is immediately introduced into a low-temperature quenching wind field of 5±1°C for gradient cooling and solidification. The cooling zone length L and the fiber linear velocity v satisfy the relationship t=L / v≥0.8 seconds, where t is the cooling time. This takes into account both the protection strength and the feasibility. Finally, the cooled fiber is introduced into a constant temperature water bath at 40±2°C, and the first stage stretching and the second stage stretching are performed in sequence. This staged hot stretching step ensures the elasticity and structural stability of the fiber by controlling the stretching speed and relaxation retraction, and solves the problems of complex stretching control and uncoordinated thermal shrinkage. It should be noted that the synergistic effect of nanoparticle surface modification and two-stage retraction greatly improves the elastic memory effect. The limitation of the mathematical relationship of the cooling parameters ensures the matching of the cooling rate and the molecular relaxation time, meets the deep cooling requirements, and avoids the decrease in elastic recovery rate caused by insufficient crystallinity of the outer layer.

[0022] Therefore, the elasticity of the composite spinning process of the high-elastic chemical fiber blended yarn is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1Process flow diagram of composite spinning for highly elastic chemical fiber blended yarn provided by an embodiment of the present invention; Figure 2 Process flow diagram of composite spinning for highly elastic chemical fiber blended yarn provided by another embodiment of the present invention. Detailed implementation manners

[0027] The following describes clearly and completely the above and other embodiments and advantages of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only partial embodiments of the present invention, rather than all embodiments.

[0028] In the field of chemical fiber spinning production processes, although existing melt spinning, wet spinning, dry spinning, and reaction spinning processes can produce various fibers, there are still many problems in the production of highly elastic spun yarns. The main problems include limitations at the material level, difficulties in forming composite structures, and production process challenges. To overcome these limitations, the present invention proposes a composite spinning process for highly elastic chemical fiber blended yarns.

[0029] In one embodiment, the composite spinning process for the highly elastic chemical fiber blended yarn, as Figure 1 shown, includes the following steps: Multi-layer co-extrusion step: Through a coaxial three-channel spinning assembly, the core layer thermoplastic polyurethane, the intermediate layer nano-modified polyester, and the outer layer polyamide 66 are respectively extruded synchronously in a molten state to form a nascent fiber with a core-sheath structure. The intermediate layer nano-modified polyester contains silica nanoparticles surface-modified with γ-aminopropyltriethoxysilane, with a particle size of 50 - 80 nanometers and an addition amount of 1.2 - 1.8% of the weight of the polyester; Gradient cooling and solidification step: The extruded nascent fiber is immediately introduced into a low-temperature sudden cold air field at 5 ± 1 °C. The length L of the cooling zone and the fiber linear velocity v satisfy the relationship t = L / v ≥ 0.8 seconds, where t is the cooling time, and the wind speed is controlled at 8 - 12 meters per second to form a glassy protective layer on the outer layer polyamide 66; Staged hot stretching step: The cooled fiber is introduced into a constant temperature water bath at 40 ± 2 °C and subjected to first-stage stretching and second-stage stretching in sequence. Among them, the first-stage stretching is carried out at a speed of 2.5 - 3.0 meters per minute to stretch to 130% of the original length, and after maintaining for 10 seconds, it is relaxed and retracted to 120% of the original length; The second-stage stretching is continued at a speed of 1.8 - 2.2 meters per minute to stretch to 150% of the original length, and after maintaining for 15 seconds, it is finally retracted to 130% of the original length.

[0030] In this embodiment, the composite spinning process for the highly elastic chemical fiber blended yarn includes a multi-layer co-extrusion step, a gradient cooling and solidification step, and a staged hot stretching step.

[0031] Specifically, the present invention firstly extrude the core layer thermoplastic polyurethane, the middle layer nano-modified polyester and the outer layer polyamide 66 in a molten state synchronously through a multi-layer co-extrusion step to form a primary fiber with a core-sheath structure. The middle layer nano-modified polyester contains silica nanoparticles surface-modified with γ-aminopropyltriethoxysilane, with a particle size of 50-80 nanometers and an addition amount of 1.2-1.8% of the weight of the polyester. Among them, the use of a coaxial double-channel spinning assembly to prepare a skin-core structure fiber belongs to the prior art. On this basis, adding an intermediate transition layer and nano-modification can solve the limitations at the material level and the problem of composite structure molding.

[0032] Next, the nascent fibers are immediately introduced into a low-temperature quenching wind field at 5±1°C for gradient cooling and solidification. The cooling zone length L and the fiber linear velocity v satisfy the relationship t=L / v≥0.8 seconds, where t is the cooling time. By controlling the wind speed to 8-12 meters per second, the outer layer of polyamide 66 forms a glassy protective layer. This step takes into account both protection strength and feasibility through the numerical range (such as 5±1°C) and the proportional relationship (t=L / v).

[0033] Finally, the cooled fiber is introduced into a constant temperature water bath at 40±2℃, and the first and second stage stretching are performed in sequence. The first stage stretching is stretched to 130% of the original length at a speed of 2.5-3.0 meters per minute, and then relaxed and retracted to 120% of the original length after 10 seconds; the second stage stretching is continued to stretch to 150% of the original length at a speed of 1.8-2.2 meters per minute, and finally retracted to 130% of the original length after 15 seconds. This staged thermal stretching step ensures the elasticity and structural stability of the fiber by controlling the stretching speed and relaxation and retraction, and solves the problems of complex stretching control and uncoordinated thermal shrinkage.

[0034] It should be noted that the synergistic effect of nanoparticle surface modification and two-stage retraction, that is, the surface-modified nanoparticles (γ-aminopropyltriethoxysilane) form a molecular bridging network in the middle layer, absorbing stress through interface slip during stretching, and restoring deformation by dynamic bonding of silane groups during retraction. In conjunction with the two-stage retraction operation (120% → 130% final retraction), the molecular chain forms a progressive orientation of "stretching-partial rebound", thereby greatly improving the elastic memory effect.

[0035] It is also important to note that the functionality of the mathematical relationship of the cooling parameters, i.e., the limitation of t = L / v ≥ 0.8s, ensures that: the outer layer is fully vitrified during the quenching stage (DSC test shows crystallinity ≥ 45%), and the inner core maintains a viscoelastic state to retain the activity of the molecular chains (dynamic rheometer measured core layer tanδ = 1.2-1.5). The matching of cooling rate and molecular relaxation time is achieved through the quantitative relationship, which meets the deep cooling requirements and avoids the decrease in elastic recovery rate caused by insufficient crystallinity of the outer layer.

[0036] Therefore, in the process composite spinning provided by this embodiment, the elasticity has been significantly improved, which is also reflected in the elastic recovery rate. It is widely used in the manufacturing of sportswear, medical bandages, and smart textiles, etc.

[0037] In one embodiment, in the composite spinning process of the high-elastic chemical fiber blended yarn, the length L of the cooling zone in the gradient cooling and solidification step is 1.2 - 1.5 m, and the fiber linear velocity v is 1.5 - 1.8 m / min.

[0038] In this embodiment, when L = 1.2 m and v = 1.5 m / min, t = 1.2 / 1.5 × 60 = 48 s > 0.8 s, which can meet the deep cooling requirement. If L < 1.2 m or v > 1.8 m / min, then t < 0.8 s, which will result in insufficient outer layer crystallinity (<40%) and microcracks on the fiber surface.

[0039] In one embodiment, in the composite spinning process of the high-elastic chemical fiber blended yarn, the stretching rate of the first-stage stretching in the staged hot stretching step is 1.3 - 1.5 times that of the second-stage stretching rate, and the stress relaxation time ratio of the two-stage stretching is 1:1.5.

[0040] In one embodiment, in the multi-layer co-extrusion step of the composite spinning process of the high-elastic chemical fiber blended yarn, the melting temperature of the core layer thermoplastic polyurethane is 190 - 200 °C, the melting temperature of the intermediate layer modified polyester is 230 - 240 °C, and the melting temperature of the outer layer polyamide 66 is 260 - 265 °C.

[0041] In one embodiment, in the composite spinning process of the high-elastic chemical fiber blended yarn, the melt index of the core layer thermoplastic polyurethane is 25 - 35 g / 10 min, and the molecular weight distribution index is 1.8 - 2.2.

[0042] In this embodiment, limiting the melt index (MI) and the molecular weight distribution (PDI) can precisely control the melt fluidity: when MI < 25 g / 10 min, the extrusion pressure of the core layer is too high, resulting in a risk of interface delamination; when PDI > 2.2, the difference in molecular chain length is too large, affecting the consistency of elastic recovery.

[0043] In one embodiment, in the composite spinning process of the high-elastic chemical fiber blended yarn, the intrinsic viscosity of the intermediate layer modified polyester is 0.75 - 0.85 dL / g, and the dispersion uniformity of the nano-silica particles in the polyester melt is ≤15%.

[0044] In this embodiment, the intrinsic viscosity of 0.75 - 0.85 dL / g ensures that the melt strength is sufficient to carry the nanoparticles because particle sedimentation occurs when the viscosity < 0.75.

[0045] In one embodiment, for the composite spinning process of the highly elastic chemical fiber blended yarn, the crystallinity of the outer polyamide 66 is controlled at 35 - 40%, the orifice diameter of the spinneret is 0.25 - 0.35 mm, and the length-diameter ratio is 4:1 to 6:1.

[0046] In this embodiment, the crystallinity of 35 - 40% balances the rigidity and toughness of the protective layer: if the crystallinity > 40%, it will cause brittle fracture of the fiber; the limitation of the orifice diameter and length-diameter ratio of the spinneret can ensure the concentricity of the three-layer structure. If the orifice diameter deviation > 0.1 mm, the skin layer thickness will be uneven.

[0047] In one embodiment, for the composite spinning process of the highly elastic chemical fiber blended yarn, as Figure 2 shown, its step of staged hot stretching further includes heat setting treatment. After staged hot stretching, the fiber is introduced into a hot air box at 120 - 130 °C, and is kept in a tension-relaxed state for 3 - 5 minutes, and the treatment wind speed is 2 - 3 m / s.

[0048] In this embodiment, heat setting in the relaxed state eliminates internal stress. When the treatment temperature < 120 °C, the stress residue > 15 MPa, which is measured by residual stress data measurement. And the wind speed of 2 - 3 m / s avoids structural distortion caused by fiber jitter. When the wind speed > 3 m / s, the fiber amplitude > 0.5 mm, which is measured by high-speed photography.

[0049] In one embodiment, for the composite spinning process of the highly elastic chemical fiber blended yarn, the intermediate modified polyester further contains 0.3 - 0.5 wt% of hindered phenol antioxidants, and the mass ratio to nano-silica is 1:(2.5 - 3.5).

[0050] In this embodiment, the hindered phenol antioxidants can act synergistically with the nanoparticles. When the mass ratio is 1:3, the antioxidant efficiency can be increased by about 40%, which is obtained through oxidation induction period testing. And the proportion imbalance (such as 1:2) will cause the surface of the nanoparticles to be overcoated, reducing the interfacial bonding strength.

[0051] The above-described specific embodiments further elaborate on the invention purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. In particular, it is pointed out that for those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A composite spinning process for a high-elastic chemical fiber blended yarn, characterized in that It includes the following steps: Multi-layer co-extrusion step: Through a coaxial three-channel spinning assembly, the core layer of thermoplastic polyurethane, the intermediate layer of nano-modified polyester, and the outer layer of polyamide 66 are synchronously extruded in a molten state to form a nascent fiber with a core-sheath structure. The intermediate layer of nano-modified polyester contains silica nanoparticles surface-modified with γ-aminopropyltriethoxysilane, with a particle size of 50-80 nm and an addition amount of 1.2-1.8% of the weight of the polyester; Gradient cooling and curing step: The extruded nascent fiber is immediately introduced into a low-temperature sudden air-cooling field at 5±1°C. The length L of the cooling zone and the fiber linear velocity v satisfy the relationship t = L / v≥0.8 s, where t is the cooling time, and the wind speed is controlled at 8-12 m / s to form a vitreous protective layer on the outer layer of polyamide 66; Staged hot stretching step: The cooled fiber is introduced into a constant-temperature water bath at 40±2°C and subjected to first-stage stretching and second-stage stretching in sequence. Among them, the first-stage stretching is carried out at a speed of 2.5-3.0 m / min to 130% of the original length, and after maintaining for 10 seconds, it is relaxed and retracted to 120% of the original length; the second-stage stretching is continued at a speed of 1.8-2.2 m / min to 150% of the original length, and after maintaining for 15 seconds, it is finally retracted to 130% of the original length.

2. The composite spinning process of the highly elastic chemical fiber blended yarn according to claim 1, characterized in that, In the gradient cooling and curing step, the length L of the cooling zone is 1.2-1.5 m, and the fiber linear velocity v is 1.5-1.8 m / min.

3. The composite spinning process of the highly elastic chemical fiber blended yarn according to claim 1, characterized in that, In the staged hot stretching step, the stretching rate of the first-stage stretching is 1.3-1.5 times that of the second-stage stretching, and the stress relaxation time ratio of the two-stage stretching is 1:1.

5.

4. The composite spinning process of the highly elastic chemical fiber blended yarn according to claim 1, characterized in that In the multi-layer co-extrusion step, the melting temperature of the core layer of thermoplastic polyurethane is 190-200°C, the melting temperature of the intermediate layer of modified polyester is 230-240°C, and the melting temperature of the outer layer of polyamide 66 is 260-265°C.

5. The composite spinning process of the highly elastic chemical fiber blended yarn according to claim 1, characterized in that, The melt index of the core layer of thermoplastic polyurethane is 25-35 g / 10 min, and the molecular weight distribution index is 1.8-2.

2.

6. The composite spinning process of the highly elastic chemical fiber blended yarn according to claim 1, characterized in that, The intrinsic viscosity of the intermediate layer of modified polyester is 0.75-0.85 dL / g, and the dispersion uniformity of the nano-silica particles in the polyester melt is ≤15%.

7. The composite spinning process of the highly elastic chemical fiber blended yarn according to claim 1, characterized in that, The crystallinity of the outer layer of polyamide 66 is controlled at 35-40%, and the orifice diameter of the spinneret is 0.25-0.35 mm, and the length-diameter ratio is 4:1 to 6:

1.

8. The composite spinning process of the highly elastic chemical fiber blended yarn according to claim 1, characterized in that, It also includes a heat setting treatment step. After the staged hot stretching step, the fiber is introduced into a hot air box at 120-130°C and treated in a tension-relaxed state for 3-5 minutes, and the treatment wind speed is 2-3 m / s.

9. The composite spinning process of the highly elastic chemical fiber blended yarn according to claim 1, characterized in that, The intermediate layer of modified polyester also contains 0.3-0.5 wt% of a hindered phenol antioxidant, and the mass ratio to the nano-silica is 1:(2.5-3.5).

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