A method and device for melt spinning of hollow fibers

Abstract

The present invention belongs to the technical field of chemical fiber melt spinning, and relates to a melt spinning method and device for hollow fibers. The method specifically comprises: simultaneously inputting the skin layer melt and the core layer gas into a skin-core composite spinning assembly, and preparing the hollow fibers through a melt spinning process; the temperature of the core layer gas at the moment of being ejected from the skin-core composite spinning assembly is T 1 The pressure of the core gas just ejected from the core-skin composite spinning assembly is P 1 The ambient temperature of melt spinning is T 0 , atmospheric pressure is P 0 , ( P 1 × T 0 ) / T 1 = P 0 +Δ, Δ is 0-0.14MPa, T 1 > T 0 The device includes a core-skin composite spinning assembly, a core gas delivery device, and a skin melt delivery device. The present invention solves the problem that the hollow fiber is easily collapsed inward due to the fiber tension and the strong extrusion between the fibers during the winding process by regulating the temperature and pressure, thereby ensuring the hollowness of the hollow fiber.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical fiber melt spinning, and in particular relates to a melt spinning method and device for hollow fibers. Background Art

[0002] ‌Hollow fiber‌ is a chemical fiber with a tubular cavity, which has a tubular cavity in the axial direction. This structure makes the hollow fiber lightweight, elastic, heat-insulating and sound-absorbing, and has significant advantages in many fields. In the field of textiles and clothing, its hollow structure can effectively block air flow and improve the thermal insulation effect, so it is often used as a filling material for winter clothing, outdoor sports equipment and down jackets. In terms of air filtration, hollow fibers are used to make high-efficiency filters to capture fine particles, which effectively promotes industrial dust removal and air purification processes; in the field of water filtration, hollow fiber membranes rely on microporous structures to remove suspended matter and microorganisms in water, and are widely used in municipal water treatment, household drinking water purification and seawater desalination projects. In the medical field, hollow fibers are used in artificial kidneys with their dialysis function to remove toxins and excess water from the blood, and can also serve as a drug sustained-release system to achieve precise controlled release of drugs. In the construction field, when hollow fibers are used as thermal insulation layers in walls and floors, they can enhance indoor thermal insulation and reduce noise. When used as sound-absorbing materials in soundproof walls and other components, they can optimize the indoor acoustic environment. At the same time, they can also be used as flexible supporting materials to meet the needs of smart wearable devices.

[0003] Patent CN102041562B discloses an antibacterial fiber product and a preparation method thereof, which adopts a melt spinning process, uses two screw machines to feed the skin-core spinneret assembly respectively, and injects a controllable airflow into the core component with the help of a gas flow meter while supplying the core component, so that the core layer is made into a structure with one or more hollow holes, and the core component is mainly distributed on the hole wall of the hollow hole of the core layer, thereby obtaining a hollow fiber. However, during the melt spinning process of the preparation method, the hollow fiber will be affected by process parameters such as temperature, pressure, spinning speed, and physical and chemical properties such as raw material viscosity and crystallinity, resulting in low fiber hollowness, and during the winding process of the hollow fiber, due to the fiber tension and the strong mutual extrusion between fibers, it is easy to cause the hollow channel to be irregular, uneven, or even collapse inward, which seriously affects the application effect of the hollow fiber in various application fields.

[0004] Therefore, it is necessary to provide a method for preparing hollow fibers that can solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to solve the problems in the prior art and to provide a melt spinning method and device for hollow fibers.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A melt spinning method for hollow fibers, wherein a skin layer melt and a core layer gas are simultaneously input into a skin-core composite spinning assembly to prepare the hollow fibers through a melt spinning process;

[0008] The temperature of the core layer gas just ejected from the sheath-core composite spinning component (close to the artificially set temperature of the core layer gas before it is input into the sheath-core composite spinning component) is T1, the pressure of the core layer gas just ejected from the sheath-core composite spinning component is P1, the ambient temperature of melt spinning is T0, the atmospheric pressure is P0 (0.1MPa), (P1×T0) / T1=P0+Δ, Δ is 0-0.14MPa, T1>T0.

[0009] During the winding process, the hollow fiber is subjected to the strong effects of fiber tension and mutual extrusion between fibers, which easily causes the fiber cortex to collapse inward. To solve this problem, the present invention solves it from two aspects:

[0010] On the one hand, (P1×T0) / T1=P0+Δ is controlled. The reason is that the temperature of the core gas just ejected from the core-skin composite spinning assembly is T1, the pressure of the core gas just ejected from the core-skin composite spinning assembly is P1, the volume of the core gas just ejected from the core-skin composite spinning assembly is V1, the temperature of the core gas just dropped to the ambient temperature of melt spinning along with the skin melt is T2 (approximately equal to the ambient temperature T0 of melt spinning), the pressure of the core gas just dropped to the ambient temperature of melt spinning along with the skin melt is P2, and the volume of the core gas just dropped to the ambient temperature of melt spinning along with the skin melt is V2 (equal to V1), according to the "ideal gas law", P1 / T1=P2 / T2, P2=(P1×T2) / T1, the atmospheric pressure is recorded as P0, if P2 is higher than P0, the pressure difference between the inside and outside of the fiber cortex can offset part of the fiber tension and the mutual compression between the fibers, but P2 should not be too high, otherwise it will cause the fiber cortex to be partially torn, so it is necessary to control P2 to be equal to or slightly higher than P0, so the present invention designs P2=P0+Δ, Δ is 0-0.14MPa, since P2=(P1×T2) / T1, T2≈T0, so (P1×T0) / T1=P0+Δ;

[0011] On the other hand, T1>T0 is controlled because: when T1>T0, it is equivalent to providing a hot air environment inside the cortex melt, especially when the ambient temperature is low, which slows down the cooling rate of the cortex melt, allowing the cortex melt to fully crystallize, and the hollow fiber has a higher degree of crystallinity, thereby making the strength and modulus of the hollow fiber higher, and it is not easy to be squeezed during the winding process to cause deformation of the hollow layer.

[0012] In addition, since T1 > T0, then (P1×T0) / T1 = P0 + Δ = P1×T0 / T1 < P1, from which it can be deduced that P1 - P0 > Δ. Also, since Δ ranges from 0 to 0.14 MPa, thus P1 > P0. The chemical fiber melt is a non-Newtonian fluid. The melt has a certain pressure inside the spinneret hole and mainly flows in a laminar flow. After being ejected from the spinneret hole at high speed, due to changes in external temperature, pressure, boundary resistance, etc., it turns into a turbulent flow, resulting in the melt diffusing in different directions, forming a macroscopic bulking effect. Under the condition that other conditions such as temperature and raw material viscosity remain unchanged, the relationship between the diffusion rate of the melt at the spinneret orifice and the pressure difference can be approximately described by the formula D ∝ ΔP / η(ΔP), where: D is the diffusion rate of the melt at the spinneret orifice, ΔP is the pressure of the melt on the inner wall of the spinneret hole (P) and the pressure of the atmosphere outside the hole on the melt (P1 or P0), the pressure difference between the two (ΔP1 or ΔP0), and η(ΔP) is the viscosity of the fluid at a given pressure difference. Therefore, controlling P1 > P0 makes the pressure difference ΔP1 < ΔP0, and the diffusion rate D of the melt towards the hollow part 内 is less than the diffusion rate D of the melt towards the outside 外 , thereby ensuring the hollowness of the fiber.

[0013] As a preferred technical solution:

[0014] For a melt spinning method of hollow fibers as described above, the core layer gas is compressed air or compressed nitrogen.

[0015] For a melt spinning method of hollow fibers as described above, the skin layer melt is a PET melt, T1 is 295 - 573 K, P1 is 0.105 - 0.24 MPa, T0 is 293 - 313 K, the spinning temperature is 553 - 573 K, the pressure of the skin layer melt at the moment it just sprays out from the skin-core composite spinning component is 1.0 - 5.0 MPa, and the winding speed is 100 - 2000 m / min.

[0016] For a melt spinning method of hollow fibers as described above, in the elevation view of the spinneret hole, the core layer gas channel is circular, the skin layer melt channel is annular, and the two are concentrically arranged. The outer diameter R of the skin layer melt channel is 1.2 - 2.0 mm, the inner diameter R' of the skin layer melt channel is 1.0 - 1.8 mm, the diameter r of the core layer gas channel is 0.4 - 1.0 mm, the pressure of the artificially set core layer gas before it is input into the skin-core composite spinning component is P3, and P1 = P3×r 2 / R' 2 , and the wall thickness of the core layer gas channel = R' - r. In the present invention, the wall surface of the core layer gas channel is set as a hollow structure to prevent or reduce heat exchange in the skin-core composite spinning component of the core layer gas.

[0017] According to the melt spinning method of hollow fibers as described above, the single fiber fineness of the hollow fibers is 4-30.3 dtex, the hollowness is 7.4-35.4%, the coefficient of variation does not exceed 24%, the crystallinity is 17-40%, the tensile strength is 2.1-5.4 cN / dtex, and the tensile modulus is 130-1200 MPa.

[0018] The relationship between crystallinity (Xc) and T1 is as follows:

[0019] ;

[0020] In the formula, It is the crystallinity when the crystallization rate of the cortical melt reaches the maximum; is a constant related to temperature; Tc is the crystallization temperature of the cortical melt; τ is the time factor, which indicates the time required for the crystallization of the cortical melt; n is the temperature index, which ranges from 2 to 3.

[0021] The present invention also provides a hollow fiber melt spinning device for realizing the hollow fiber melt spinning method as described in any one of the above items, comprising a sheath-core composite spinning assembly, a core layer gas conveying device, and a sheath layer melt conveying device;

[0022] The core-skin composite spinning assembly comprises a distribution plate, an upper spinneret plate, and a lower spinneret plate which are arranged in sequence from top to bottom;

[0023] The upper plate and the lower plate of the spinneret are both provided with a plurality of through holes; the through holes in the upper plate of the spinneret are distributed in two concentric circles, the outer circle through holes are marked as through holes a, and the inner circle through holes are marked as through holes b; the through holes in the lower plate of the spinneret are distributed in a circumference, and are marked as through holes c;

[0024] A plurality of independent chambers are formed between the upper spinneret plate and the lower spinneret plate;

[0025] The number of through hole a, through hole b, through hole c and the chamber is the same and corresponds one to one;

[0026] The through hole a is located above the corresponding through hole c, and the hole wall of the through hole a extends downward to the bottom of the corresponding through hole c, and the chamber is connected to the corresponding through hole b and through hole c at the same time;

[0027] The distribution plate is provided with a core layer gas delivery hole and a skin layer melt delivery hole. The core layer gas delivery device, the core layer gas delivery hole and the through hole a are connected in sequence, and the skin layer melt delivery device, the skin layer melt delivery hole and the through hole b are connected in sequence.

[0028] As the preferred technical solution:

[0029] In the above-mentioned hollow fiber melt spinning device, the hole wall of the through hole a extends downward to 0.1-1.0 mm below the corresponding through hole c. The skin layer melt inside the spinneret often has a pressure of several to tens of atmospheres, and the pressure is instantly released at the outlet of the spinneret hole. The present invention can prevent the skin layer melt from backflowing at the outlet of the spinneret hole.

[0030] In the above-mentioned hollow fiber melt spinning device, the through hole c is in the shape of an inverted cone with a larger top and a smaller bottom.

[0031] Beneficial effects:

[0032] The present invention solves the problem that the hollow fiber is easily caused to collapse inward due to the strong effect of fiber tension and mutual extrusion between fibers during the winding process by regulating the temperature of the core layer gas just after it is ejected from the core-sheath composite spinning component, the pressure of the core layer gas just after it is ejected from the core-sheath composite spinning component, and the ambient temperature of the melt spinning, thereby ensuring the hollowness of the hollow fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 , Figure 2 It is a schematic diagram of the cross-sectional structure of the core-skin composite spinning assembly of the present invention;

[0034] Figure 3 Schematic diagram of the distribution plate structure of the present invention, wherein (a) is a schematic diagram of the top view structure, and (b) is a schematic diagram of the cross-sectional structure;

[0035] Figure 4 Schematic diagram of the upper plate structure of the spinneret of the present invention, wherein (a) is a schematic diagram of the top view structure, and (b) is a schematic diagram of the cross-sectional structure;

[0036] Figure 5 Schematic diagram of the spinneret lower plate structure of the present invention, wherein (a) is a schematic diagram of the top view structure, and (b) is a schematic diagram of the cross-sectional structure;

[0037] Figure 6 This is a cross-sectional view of the hollow fiber prepared in Comparative Example 2;

[0038] Figure 7 This is a cross-sectional view of the hollow fiber prepared in Example 5;

[0039] Figure 8 The DSC curve of the hollow fiber prepared in Example 1;

[0040] Fig. 9 This is a cross-sectional view of the hollow fiber prepared in Comparative Example 1;

[0041] Among them, 1-distribution plate, 2-spinneret upper plate, 3-spinneret lower plate, 4-through hole a, 5-through hole b, 6-through hole c, 7-core layer gas delivery hole, 8-skin layer melt delivery hole. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0043] Detection methods of relevant performance indicators in the embodiments and comparative examples:

[0044] Single yarn fineness: refer to the standard GB / T 14343-2008 "Test method for linear density of chemical fiber filaments" to test the fineness of multifilaments. Test 3 groups of each sample and take the average value. Then divide the average value by the number of single yarns per multifilament to get the single yarn fineness.

[0045] Hollowness and coefficient of variation: The hollowness of the samples was tested in accordance with the standard FZ / T 50002-2013 "Test method for profile of chemical fibers". 15 valid data were obtained for each sample and the average value was calculated. The average value was used as the hollowness of the sample. The coefficient of variation was calculated using the hollowness of the 15 samples. Coefficient of variation = standard deviation of hollowness / average value of hollowness × 100%;

[0046] Tensile strength and tensile modulus: refer to the standard GB / T 14344-2022 "Test method for tensile properties of chemical fiber filaments" to test the tensile strength and tensile modulus of the fiber. The clamp distance is 200 mm, the tensile speed is 200 mm / min, and 15 valid data are obtained for each sample to calculate the average value;

[0047] Crystallinity calculation method: Taking Example 1 as an example, first obtain the DSC curve of the hollow fiber (such as Figure 8 As shown), then the absolute value of the sum of the integral value of the hollow fiber melting enthalpy and the integral value of the cold crystallization peak is calculated (i.e. |-45.90+19.51|=26.39), and then the absolute value is compared with the melting enthalpy value of PET 100% crystallization (140J / g), thereby obtaining a crystallinity of 18.85%; the remaining embodiments and comparative examples are tested according to this method.

[0048] The skin layer melts used in the following examples and comparative examples are all PET melts with a melting point of 255° C. and an intrinsic viscosity of 0.68 dL / g.

[0049] A hollow fiber melt spinning device used in the following embodiments and comparative examples includes a core-skin composite spinning assembly, a core layer gas delivery device, and a skin layer melt delivery device;

[0050] like Figure 1 , Figure 2 As shown, the core-skin composite spinning assembly includes a distribution plate 1, a spinneret upper plate 2, and a spinneret lower plate 3 which are arranged in sequence from top to bottom;

[0051] like Figure 4 , Figure 5 As shown, the upper plate 2 and the lower plate 3 of the spinneret are both provided with a plurality of through holes; the through holes in the upper plate 2 of the spinneret are distributed in two concentric circles, the outer circle through holes are marked as through holes a4, and the inner circle through holes are marked as through holes b5; the through holes in the lower plate 3 of the spinneret are distributed in a circumferential manner, marked as through holes c6, and the through holes c6 are in an inverted cone shape with a larger top and a smaller bottom;

[0052] A plurality of independent chambers are formed between the upper spinneret plate 2 and the lower spinneret plate 3;

[0053] The number of through hole a 4, through hole b 5, through hole c 6 and the chamber is the same and corresponds one to one;

[0054] like Figure 1 As shown, through hole a4 is located above the corresponding through hole c6, and the hole wall of through hole a4 extends downward to 0.1-1.0 mm below the corresponding through hole c6, and the chamber is connected to the corresponding through hole b5 and through hole c6 at the same time;

[0055] like Figure 3 As shown, the distribution plate 1 is provided with a core layer gas delivery hole 7 and a skin layer melt delivery hole 8, as shown in FIG. Figure 1 As shown, the core layer gas delivery device, the core layer gas delivery hole 7, and the through hole a 4 are connected in sequence, and the skin layer melt delivery device, the skin layer melt delivery hole 8, and the through hole b 5 are connected in sequence;

[0056] The lower section of the through hole a4 is the lower section of the core layer gas channel, and the lower section of the through hole a4 and the lower section of the through hole c6 together form the lower section of the skin layer melt channel;

[0057] In the bottom view of the spinneret, the core layer gas channel is circular, the skin layer melt channel is annular, and the two are arranged concentrically. The outer diameter R of the skin layer melt channel is 1.2-2.0 mm, the inner diameter R' of the skin layer melt channel is 1.0-1.8 mm, and the diameter r of the core layer gas channel is 0.4-1.0 mm.

[0058] Example 1

[0059] A method for melt spinning a hollow fiber, using the above-mentioned melt spinning device for a hollow fiber, wherein the hole wall of the through hole a extends downward to 1.0 mm below the corresponding through hole c, the outer diameter R of the skin melt channel is 2.0 mm, the inner diameter R' of the skin melt channel is 1.8 mm, and the diameter r of the core gas channel is 1.0 mm, and the specific process is as follows:

[0060] First, set the temperature T1 (295K) of the core gas just ejected from the core-skin composite spinning assembly, the pressure P1 (0.105MPa) of the core gas just ejected from the core-skin composite spinning assembly, the ambient temperature T0 (293K) of melt spinning, and the atmospheric pressure P0 (0.1MPa). At the same time, set the spinning temperature to 568K, the pressure of the skin melt just ejected from the core-skin composite spinning assembly to 2.5MPa, the winding speed to 1000m / min, and the stretching multiple to 1.

[0061] Then, the skin layer melt and the core layer gas (compressed nitrogen) are simultaneously input into the skin-core composite spinning assembly, and hollow fibers are prepared through a melt spinning process.

[0062] The final hollow fiber has a single fiber fineness of 7.2 dtex, a hollowness of 7.4%, a coefficient of variation of 8.5%, a crystallinity of 18.85%, a tensile strength of 2.61 cN / dtex, and a tensile modulus of 200.4 MPa. The DSC curve of the hollow fiber is shown in FIG. Figure 8 shown.

[0063] Comparative Example 1

[0064] A melt spinning method for hollow fibers is basically the same as that of Example 1, except that the pressure P1 of the core layer gas just ejected from the core-skin composite spinning assembly is 0.08 MPa.

[0065] The final hollow fiber is Fig. 9 As shown, the hollowness is 5.8%.

[0066] Compared with Example 1, the hollowness of Comparative Example 1 is worse than that of Example 1. This is because the skin melt undergoes a puffing effect at the spinneret orifice. Since the internal pressure of the fiber is lower than the external atmospheric pressure, the diffusion rate of the melt into the hollow area is higher than the diffusion rate outward, resulting in a decrease in the hollowness of the hollow fiber.

[0067] Example 2

[0068] A method for melt spinning a hollow fiber, using the above-mentioned melt spinning device for a hollow fiber, wherein the hole wall of the through hole a extends downward to 1.0 mm below the corresponding through hole c, the outer diameter R of the skin melt channel is 2.0 mm, the inner diameter R' of the skin melt channel is 1.8 mm, and the diameter r of the core gas channel is 1.0 mm, and the specific process is as follows:

[0069] First, set the temperature T1 (298K) of the core gas just ejected from the core-skin composite spinning assembly, the pressure P1 (0.12MPa) of the core gas just ejected from the core-skin composite spinning assembly, the ambient temperature T0 (293K) of melt spinning, and the atmospheric pressure P0 (0.1MPa). At the same time, set the spinning temperature to 568K, the pressure of the skin melt just ejected from the core-skin composite spinning assembly to 2.5MPa, the winding speed to 100m / min, and the stretching multiple to 1.

[0070] Then, the skin layer melt and the core layer gas (compressed nitrogen) are simultaneously input into the skin-core composite spinning assembly, and hollow fibers are prepared through a melt spinning process.

[0071] The final hollow fiber has a single fiber fineness of 30.3 dtex, a hollowness of 10.1%, a coefficient of variation of 12.3%, a crystallinity of 17.05%, a tensile strength of 2.08 cN / dtex, and a tensile modulus of 131.1 MPa.

[0072] Example 3

[0073] A method for melt spinning a hollow fiber, using the above-mentioned melt spinning device for a hollow fiber, wherein the hole wall of the through hole a extends downward to 1.0 mm below the corresponding through hole c, the outer diameter R of the skin melt channel is 2.0 mm, the inner diameter R' of the skin melt channel is 1.8 mm, and the diameter r of the core gas channel is 1.0 mm, and the specific process is as follows:

[0074] First, set the temperature T1 (313K) of the core gas just ejected from the core-skin composite spinning assembly, the pressure P1 (0.17MPa) of the core gas just ejected from the core-skin composite spinning assembly, the ambient temperature T0 (308K) of melt spinning, and the atmospheric pressure P0 (0.1MPa). At the same time, set the spinning temperature to 563K, the pressure of the skin melt just ejected from the core-skin composite spinning assembly to 4.5MPa, the winding speed to 2000m / min, and the stretching multiple to 1.

[0075] Then, the skin layer melt and the core layer gas (compressed nitrogen) are simultaneously input into the skin-core composite spinning assembly, and hollow fibers are prepared through a melt spinning process.

[0076] The final hollow fiber has a single fiber fineness of 7.8 dtex, a hollowness of 21.8%, a coefficient of variation of 21.3%, a crystallinity of 23.34%, a tensile strength of 2.33 cN / dtex, and a tensile modulus of 276.7 MPa.

[0077] Example 4

[0078] A method for melt spinning a hollow fiber, using the above-mentioned melt spinning device for a hollow fiber, wherein the hole wall of the through hole a extends downward to 1.0 mm below the corresponding through hole c, the outer diameter R of the skin melt channel is 2.0 mm, the inner diameter R' of the skin melt channel is 1.8 mm, and the diameter r of the core gas channel is 1.0 mm, and the specific process is as follows:

[0079] First, set the temperature T1 (563K) of the core gas just ejected from the core-skin composite spinning assembly, the pressure P1 (0.21MPa) of the core gas just ejected from the core-skin composite spinning assembly, the ambient temperature T0 (308K) of melt spinning, and the atmospheric pressure P0 (0.1MPa). At the same time, set the spinning temperature to 563K, the pressure of the skin melt just ejected from the core-skin composite spinning assembly to 4.5MPa, the winding speed to 2000m / min, and the stretching multiple to 2 times;

[0080] Then, the skin layer melt and the core layer gas (compressed nitrogen) are simultaneously input into the skin-core composite spinning assembly, and hollow fibers are prepared through a melt spinning process.

[0081] The final hollow fiber has a single fiber fineness of 7.7 dtex, a hollowness of 28.8%, a coefficient of variation of 9.7%, a crystallinity of 36.97%, a tensile strength of 2.98 cN / dtex, and a tensile modulus of 349.4 MPa.

[0082] Example 5

[0083] A method for melt spinning a hollow fiber, using the above-mentioned melt spinning device for a hollow fiber, wherein the hole wall of the through hole a extends downward to 1.0 mm below the corresponding through hole c, the outer diameter R of the skin melt channel is 2.0 mm, the inner diameter R' of the skin melt channel is 1.8 mm, and the diameter r of the core gas channel is 1.0 mm, and the specific process is as follows:

[0084] First, set the temperature T1 (563K) of the core gas just ejected from the core-skin composite spinning assembly, the pressure P1 (0.24MPa) of the core gas just ejected from the core-skin composite spinning assembly, the ambient temperature T0 (308K) of melt spinning, and the atmospheric pressure P0 (0.1MPa). At the same time, set the spinning temperature to 563K, the pressure of the skin melt just ejected from the core-skin composite spinning assembly to 3.5MPa, the winding speed to 1000m / min, and the stretching multiple to 4 times;

[0085] Then, the skin layer melt and the core layer gas (compressed nitrogen) are simultaneously input into the skin-core composite spinning assembly, and hollow fibers are prepared through a melt spinning process.

[0086] The final hollow fiber has a single fiber fineness of 4 dtex, a hollowness of 33.3%, a coefficient of variation of 10%, a crystallinity of 39.12%, a tensile strength of 5.4 cN / dtex, and a tensile modulus of 1187.7 MPa. The cross-sectional view of the hollow fiber is shown in FIG. Figure 7 shown.

[0087] Example 6

[0088] A method for melt spinning a hollow fiber, using the above-mentioned melt spinning device for a hollow fiber, wherein the hole wall of the through hole a extends downward to 1.0 mm below the corresponding through hole c, the outer diameter R of the skin melt channel is 2.0 mm, the inner diameter R' of the skin melt channel is 1.8 mm, and the diameter r of the core gas channel is 1.0 mm, and the specific process is as follows:

[0089] First, set the temperature T1 (558K) of the core gas just ejected from the core-skin composite spinning assembly, the pressure P1 (0.24MPa) of the core gas just ejected from the core-skin composite spinning assembly, the ambient temperature T0 (313K) of melt spinning, and the atmospheric pressure P0 (0.1MPa). At the same time, set the spinning temperature to 558K, the pressure of the skin melt just ejected from the core-skin composite spinning assembly to 3.5MPa, the winding speed to 2000m / min, and the stretching multiple to 2.8 times;

[0090] Then, the skin layer melt and the core layer gas (compressed nitrogen) are simultaneously input into the skin-core composite spinning assembly, and hollow fibers are prepared through a melt spinning process.

[0091] The final hollow fiber has a single fiber fineness of 4.8 dtex, a hollowness of 35.4%, a coefficient of variation of 24%, a crystallinity of 35.07%, a tensile strength of 3.65 cN / dtex, and a tensile modulus of 620.6 MPa.

[0092] Comparative Example 2

[0093] A melt spinning method for hollow fibers is basically the same as that of Example 6, except that the temperature T1 of the core layer gas just ejected from the core-skin composite spinning assembly is 313K.

[0094] The final hollow fiber is Figure 6 As shown, the coefficient of variation is 33.5%, the tensile strength is 3.01 cN / dtex, and the tensile modulus is 370.0 MPa.

[0095] Compared with Example 6, the coefficient of variation of Comparative Example 2 increases, and the tensile strength and tensile modulus deteriorate. This is because when T1=T0, a hot air environment cannot be provided inside the skin melt, and the fiber melt is overcooled during the molding process, resulting in mostly amorphous structures and low crystallinity inside the fibers, which makes it impossible to make the strength and modulus of the hollow fiber high. During the winding process, it is easy to be squeezed and cause the hollow layer to deform; and according to the ideal gas formula, the pressure difference between the inside and outside of the hollow fiber is high, which can easily cause ruptures in the local weak parts of the fiber wall, and during the winding process, it is easy to be squeezed and cause the hollow layer to deform.

[0096] Example 7

[0097] A method for melt spinning a hollow fiber, using the above-mentioned melt spinning device for a hollow fiber, wherein the hole wall of the through hole a extends downward to 0.1 mm below the corresponding through hole c, the outer diameter R of the skin melt channel is 1.2 mm, the inner diameter R' of the skin melt channel is 1.0 mm, and the diameter r of the core gas channel is 0.4 mm. The specific process is as follows:

[0098] First, set the temperature T1 (573K) of the core gas just ejected from the core-skin composite spinning assembly, the pressure P1 (0.21MPa) of the core gas just ejected from the core-skin composite spinning assembly, the ambient temperature T0 (308K) of melt spinning, and the atmospheric pressure P0 (0.1MPa). At the same time, set the spinning temperature to 573K, the pressure of the skin melt just ejected from the core-skin composite spinning assembly to 1MPa, the winding speed to 1000m / min, and the stretching multiple to 1.

[0099] Then, the skin layer melt and the core layer gas (compressed air) are simultaneously input into the skin-core composite spinning assembly mentioned above, and hollow fibers are prepared through a melt spinning process.

[0100] The final hollow fiber has a single fiber fineness of 6.5 dtex, a hollowness of 8.9%, a coefficient of variation of 8.5%, a crystallinity of 19.57%, a tensile strength of 2.44 cN / dtex, and a tensile modulus of 203.9 MPa.

[0101] Example 8

[0102] A method for melt spinning a hollow fiber, using the above-mentioned melt spinning device for a hollow fiber, wherein the hole wall of the through hole a extends downward to 0.1 mm below the corresponding through hole c, the outer diameter R of the skin melt channel is 1.2 mm, the inner diameter R' of the skin melt channel is 1.0 mm, and the diameter r of the core gas channel is 0.4 mm. The specific process is as follows:

[0103] First, set the temperature T1 (298K) of the core gas just ejected from the core-skin composite spinning assembly, the pressure P1 (0.11MPa) of the core gas just ejected from the core-skin composite spinning assembly, the ambient temperature T0 (293K) of melt spinning, and the atmospheric pressure P0 (0.1MPa). At the same time, set the spinning temperature to 553K, the pressure of the skin melt just ejected from the core-skin composite spinning assembly to 5MPa, the winding speed to 1000m / min, and the stretching multiple to 2 times;

[0104] Then, the skin layer melt and the core layer gas (compressed air) are simultaneously input into the skin-core composite spinning assembly mentioned above, and hollow fibers are prepared through a melt spinning process.

[0105] The final hollow fiber has a single fiber fineness of 5.4 dtex, a hollowness of 18.4%, a coefficient of variation of 15.2%, a crystallinity of 29.88%, a tensile strength of 3.25 cN / dtex, and a tensile modulus of 271 MPa.

[0106] Example 9

[0107] A method for melt spinning a hollow fiber, using the above-mentioned melt spinning device for a hollow fiber, wherein the hole wall of the through hole a extends downward to 0.1 mm below the corresponding through hole c, the outer diameter R of the skin melt channel is 1.2 mm, the inner diameter R' of the skin melt channel is 1.0 mm, and the diameter r of the core gas channel is 0.4 mm. The specific process is as follows:

[0108] First, set the temperature T1 (313K) of the core gas just ejected from the core-skin composite spinning assembly, the pressure P1 (0.14MPa) of the core gas just ejected from the core-skin composite spinning assembly, the ambient temperature T0 (308K) of melt spinning, and the atmospheric pressure P0 (0.1MPa). At the same time, set the spinning temperature to 563K, the pressure of the skin melt just ejected from the core-skin composite spinning assembly to 4.5MPa, the winding speed to 1000m / min, and the stretching multiple to 3.5 times;

[0109] Then, the skin layer melt and the core layer gas (compressed nitrogen) are simultaneously input into the skin-core composite spinning assembly, and hollow fibers are prepared through a melt spinning process.

[0110] The final hollow fiber has a single fiber fineness of 4.3 dtex, a hollowness of 16.6%, a coefficient of variation of 20.4%, a crystallinity of 37.24%, a tensile strength of 4.36 cN / dtex, and a tensile modulus of 737.1 MPa.

Claims

1. A method for melt spinning a hollow fiber, characterized in that: The skin layer melt and the core layer gas are simultaneously input into the skin-core composite spinning assembly to prepare the hollow fiber through the melt spinning process; The temperature of the core gas just ejected from the core-skin composite spinning assembly is T 1 The pressure of the core gas just ejected from the core-skin composite spinning assembly is P 1 The ambient temperature of melt spinning is T 0 , atmospheric pressure is P 0 , ( P 1 × T 0 ) / T 1 = P 0 +Δ, Δ is 0-0.14MPa, T 1 > T 0 .

2. The melt spinning method of a hollow fiber according to claim 1, characterized in that: The core gas is compressed air or compressed nitrogen.

3. The melt spinning method of a hollow fiber according to claim 1, characterized in that: The skin layer melt is PET melt. T 1 295-573K, P 1 0.105-0.24MPa, T 0 The spinning temperature is 293-313K, the spinning temperature is 553-573K, the pressure of the skin melt just ejected from the skin-core composite spinning component is 1.0-5.0MPa, and the winding speed is 100-2000m / min.

4. The melt spinning method of a hollow fiber according to claim 1, characterized in that: In the bottom view of the spinneret, the core layer gas channel is circular, and the skin layer melt channel is annular. The two are arranged concentrically. The outer diameter of the skin layer melt channel is R The inner diameter of the cortical melt channel is 1.2-2.0 mm. R' The diameter of the core gas channel is 1.0-1.8mm. r 0.4-1.0mm.

5. The melt spinning method of a hollow fiber according to any one of claims 1 to 4, characterized in that: The single fiber fineness of the hollow fiber is 4-30.3 dtex, the hollowness is 7.4-35.4%, the coefficient of variation does not exceed 24%, the crystallinity is 17-40%, the tensile strength is 2.1-5.4 cN / dtex, and the tensile modulus is 130-1200 MPa.

6. A hollow fiber melt spinning device for realizing the hollow fiber melt spinning method according to any one of claims 1 to 5, characterized in that: It includes a skin-core composite spinning assembly, a core layer gas conveying device, and a skin layer melt conveying device; The core-skin composite spinning assembly comprises a distribution plate, an upper spinneret plate, and a lower spinneret plate which are arranged in sequence from top to bottom; The upper plate and the lower plate of the spinneret are both provided with a plurality of through holes; the through holes in the upper plate of the spinneret are distributed in two concentric circles, the outer circle through holes are marked as through holes a, and the inner circle through holes are marked as through holes b; the through holes in the lower plate of the spinneret are distributed in a circumference, and are marked as through holes c; A plurality of independent chambers are formed between the upper plate of the spinneret and the lower plate of the spinneret; The number of through hole a, through hole b, through hole c and the chamber is the same and corresponds one to one; The through hole a is located above the corresponding through hole c, and the hole wall of the through hole a extends downward to the bottom of the corresponding through hole c, and the chamber is connected to the corresponding through hole b and through hole c at the same time; The distribution plate is provided with a core layer gas delivery hole and a skin layer melt delivery hole. The core layer gas delivery device, the core layer gas delivery hole and the through hole a are connected in sequence, and the skin layer melt delivery device, the skin layer melt delivery hole and the through hole b are connected in sequence.

7. A hollow fiber melt spinning device according to claim 6, characterized in that: The hole wall of through hole a extends downward to 0.1-1.0 mm below the corresponding through hole c.

8. The melt spinning device for hollow fibers according to claim 6, characterized in that: The through hole c is in an inverted cone shape with a larger top and a smaller bottom.

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