A method for producing a sea-island fiber

Abstract

The application belongs to the technical field of microfiber leather and discloses a preparation method of island-in-sea fibers, which comprises the following steps: first, respectively plasticizing and mixing A component (wherein the polymer is a low-viscosity marine resin), B component and C component (wherein the polymer is a mixed resin of a high-viscosity marine resin and an island-phase resin) through different screws, then metering through different metering pumps and respectively entering into respective spinning beam bodies, then conveying the melt in the different spinning beam bodies to a spinneret, and dividing the spinneret holes on the spinneret into a first zone and a second zone, wherein the first zone is designed as a coaxial three-layer structure, three melt streams are discharged from the first zone, merged and continuously flow along the second zone, and then the island-in-sea fibers are formed; wherein the melt index of the low-viscosity marine resin is at least 40 g / 10 min higher than that of the high-viscosity marine resin. Compared with the fixed island fiber, the island-in-sea fiber prepared by the application has a finer fiber diameter, the problem of uneven island-phase fiber diameter of the island-in-sea fiber is solved, and the fiber strength is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of microfiber leather technology and relates to a method for preparing island fiber. Background Technology

[0002] Microfiber synthetic leather (microfiber leather for short) is a type of leather made from microfiber and polyurethane, resembling natural leather in appearance and properties. It is currently the closest synthetic leather to genuine leather in the world, and its superior performance, diverse product range, and ability to replace genuine leather have led to its wide application. Microfiber is the most basic component of microfiber leather. It is typically made by impregnating nonwoven fabrics made from island-island fibers with polyurethane, followed by fiber opening and dissolution to remove the sea-phase fiber structure, thus obtaining the microfiber structure. Island-island fibers are special fibers produced by blending or composite spinning two or more thermodynamically incompatible polymers. The polymers are prepared through processes such as melting, screw extrusion, pre-spinning drafting, bundling, post-spinning drafting, oiling, crimping, and drying and setting.

[0003] Indeterminate island fibers have the highest market share and widest application in the current microfiber leather market due to their relatively simple production process and high production efficiency. The principle is as follows: Under certain conditions, two thermodynamically incompatible polymers with a certain viscosity difference are blended. One polymer with higher viscosity (dispersed phase) is distributed as tiny droplets in the other polymer with lower viscosity (continuous phase). The blended melt is extruded through a spinneret under pressure by a spinning metering pump and subjected to radial stretching to form long, thin microfibers. This is then solidified by cooling, forming a fibrous structure where a high-viscosity polymer (island phase) is dispersed as fine, short fibers within the low-viscosity polymer (sea phase) component. Because the size and distribution of the island phases within the fiber are uneven, it is called an indeterminate island fiber. Its most significant characteristic is that, on the fiber cross-section, the closer to the center, the larger the diameter and the more sparsely distributed the island phases; the closer to the outer layer of the fiber, the smaller the diameter and the more densely distributed the island phases.

[0004] The naturally occurring island-shaped microfiber has the characteristics of small and dense island distribution on the outer layer and large and sparse island distribution on the inner layer, which affects the quality of the final product, PU microfiber synthetic leather.

[0005] The above phenomenon occurs because the blended melt is subjected to shear force when flowing through the spinneret channel, and there is a difference in shear rate within the melt; the closer to the spinneret channel, the greater the shear rate of the melt. During this process, the component with higher viscosity tends to move and aggregate towards the low-shear region (i.e., the central region of the fiber) perpendicular to the extrusion direction, resulting in uneven island phase size in the fiber, ultimately leading to lower fiber strength and poor dyeing effect.

[0006] To address the aforementioned issues, existing technologies also employ island-spinning to achieve uniform island phase size within fibers. This is achieved through composite spinning, where the island and sea components are transported in different spinning boxes and produced via a spinneret with a specialized distribution system. However, due to process limitations, composite spinning produces island-spinning fibers with fewer islands, resulting in a higher fineness of the island-spinning microfibers after opening, typically between 0.05 and 0.08 dtex. In contrast, melt blending produces island-less microfibers with a fineness generally between 0.001 and 0.01 dtex. Melt blending can achieve a finer fiber structure, resulting in a delicate feel and comfortable hand operation, but it suffers from poor fineness uniformity, negatively impacting mechanical properties.

[0007] Although fixed-island fibers can achieve a uniform distribution of fiber islands, the actual number of fiber islands produced is relatively small. Therefore, the fineness of the microfiber after opening is relatively large. If the number of islands is to be increased, the resistance of the spinneret tubular body to the flow of marine components will increase, and the flow towards the center will be slow. During long-cycle production, problems such as viscosity fluctuation and increased breakage will occur, and in severe cases, the adhesion between island structures will occur.

[0008] Therefore, it is of great significance to study a method for preparing island-sea fibers in order to solve the above problems. Summary of the Invention

[0009] The purpose of this invention is to solve the problems existing in the prior art and provide a method for preparing island-island fibers. This method reduces the overall shear rate difference and the tendency of internally migrating island structures to move and aggregate by controlling the composition of each layer of melt from the center to the spinneret wall in the spinneret channel, thereby solving the problem of uneven island phase size in amorphous island fibers.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing island-of-sea fibers includes the following steps:

[0012] (1) Raw material preparation;

[0013] The raw materials include component A, component B and component C. The polymer in component A is a low viscosity marine resin, and the polymers in components B and C are a mixture of high viscosity marine resin and island resin. The high viscosity marine resin and island resin in components B and C are the same, and the proportion of island resin in component B is higher than that in component C.

[0014] The melt index of low-viscosity marine resin is at least 40 g / 10 min higher than that of high-viscosity marine resin;

[0015] (2) Screw blending and melt distribution;

[0016] Components A, B, and C are plasticized and mixed by different screws, and then metered by different metering pumps before entering their respective spinning boxes.

[0017] (3) Spinning;

[0018] The melt in different spinning boxes is conveyed to the spinneret. Each spinneret hole on the spinneret is divided into zone one and zone two. Zone one is a coaxial three-layer design, from the outside to the inside corresponding to the A component, B component and C component respectively. After the three melts exit the spinneret hole in zone one, they merge and continue to flow along zone two, and are ejected to form island fibers. The pressure difference between the spinning boxes corresponding to the A component, B component and C component is within 10%.

[0019] As a preferred technical solution:

[0020] In the method for preparing island-island fibers as described above, the length of zone one is L1, and the length of zone two is L2. L1 is 1.0–2.5 mm, and L2 is 10.0–25.0 mm. The purpose of setting zone one is to obtain the flow direction of the target core-sheath structure. Since the components in zone one are more affected by shear force, the length of L1 needs to be extremely short, just enough to achieve the separation of the components. L2 needs to have a certain length to achieve the convergence and extrusion of the melts of components A, B, and C into fibers. If it is too long, it will still lead to poor size uniformity of the island phase.

[0021] In the above-described method for preparing island-island fibers, the marine resin in component A, as well as components B and C, is low-density polyethylene (LDPE); the island resin in components B and C is nylon 6 (PA6).

[0022] The melt index of low-density polyethylene in component A is 40-70 g / 10 min higher than that of low-density polyethylene in components B and C.

[0023] The relative viscosity of nylon 6 (PA6) components B and C is 2.4 to 3.0.

[0024] In the above-described method for preparing island-island fibers, the mass concentration of island phase resin in component B is 65-75%, and the mass concentration of island phase resin in component C is 10-15% lower than that in component B.

[0025] In the above-described method for preparing island fiber, the total mass of raw materials is 100 parts, with component A being 2 to 5 parts, component B being 35 to 60 parts, and component C being 35 to 63 parts.

[0026] In the above-described method for preparing island-sea fiber, the plasticizing temperature of component A is 160–220°C, the plasticizing temperature of component B is 200–280°C, and the plasticizing temperature of component C is 180–260°C.

[0027] In the method for preparing island-of-the-sea fiber described above, the spinning box pressure is 3.5–6.0 MPa, and the temperature of the melts of components A, B, and C entering the spinneret is 265–285°C. If the spinning box pressure is too low, it will be difficult to spin and form fibers normally; if the spinning box pressure is too high, the shear pressure of the melt in the spinneret will be too high, and the probability of island formation will still be relatively high, resulting in poor dimensional uniformity.

[0028] In the above-described method for preparing island-island fibers, the average diameter of the island phase in the island-island fibers is 1.0–1.3 μm, and the diameter CV value is 2.5–5%.

[0029] Invention Mechanism:

[0030] This invention integrates core-sheath composite spinning technology and blend spinning technology to prepare novel blended melt-spun island-island fibers. The resulting island-island fibers have a finer fiber diameter compared to fixed-island fibers, and a more uniform fiber diameter compared to non-fixed-island fibers, with a lower coefficient of variation (CV) for fiber diameter deviation. Compared to non-fixed-island nascent fibers obtained using traditional blend spinning technology, the fiber strength is significantly improved.

[0031] In existing island spinning techniques, the blended melt is subjected to shear forces as it flows through the spinneret channel, and a shear rate difference exists within the melt, increasing closer to the spinneret channel. During this process, the higher viscosity component tends to move and aggregate towards the low-shear region (i.e., the central region of the fiber) perpendicular to the extrusion direction, resulting in uneven island phase size within the fiber and ultimately leading to lower fiber strength.

[0032] This invention controls the composition of each layer of melt entering the spinneret channel from the center to the spinneret wall. Specifically, the outermost layer is a low-viscosity marine resin, and the middle and inner layers are a mixture of high-viscosity marine resin and island resin. The island-to-sea ratio in the middle layer is lower than that in the inner layer.

[0033] On the one hand, the outermost layer of the melt inside the spinneret pipe is a low-viscosity marine resin, which greatly reduces the shear rate of the outermost layer. As is known, when the melt flows through the pipe, the shear rate at the center is zero. This reduces the difference in shear rate from the outer layer to the center of the melt, and correspondingly reduces the tendency of the marine resin in the melt to move and aggregate towards the central region.

[0034] On the other hand, although the above methods reduce the tendency of island-phase resin to move and aggregate towards the center of the spinneret channel, they cannot completely eliminate it. Therefore, in the spinneret channel, the ratio of island-phase resin in the middle layer of the melt is controlled to be lower than that in the inner layer, that is, the content of island-phase resin in the inner layer is lower than that in the middle layer. When the melt flows through the channel, the island-phase resin still tends to move and aggregate towards the center. Ultimately, when exiting the spinneret channel, the goal of uniform island-phase resin size on the fiber cross-section is achieved. In addition, this invention reduces the probability of small droplet collisions in the shear field by pre-forming a loose distribution of central island-phase droplets, thus making the subsequently formed island diameter uniform.

[0035] Beneficial effects:

[0036] (1) This invention integrates core-sheath composite spinning technology and blend spinning technology to prepare a new type of blend melt-spun island fiber. The island fiber obtained has a finer fiber diameter than fixed island fiber and a more uniform fiber diameter than non-fixed island fiber. The fiber diameter deviation coefficient CV value is lower, and the fiber strength is significantly improved compared with the non-fixed island nascent fiber obtained by traditional blend spinning technology.

[0037] (2) By controlling the outermost layer of the melt in the spinneret channel to be a low-viscosity marine resin, the shear rate of the outermost layer can be greatly reduced, which correspondingly reduces the tendency of the island phase resin in the melt to move and aggregate towards the central region. In addition, by controlling the island ratio of the middle layer of the melt to be lower than that of the inner layer, the island phase resin still has the tendency to move and aggregate towards the center. However, due to the low density of the island phase in the center, the probability of island merging is reduced when the outer islands diffuse towards the center, so as to achieve the purpose of smaller diameter and CV value of the island phase in the final island fiber. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the spinneret hole structure on the spinneret plate of the present invention; in the figure, L1 is the length of the first region and L2 is the length of the second region;

[0039] Figure 2 This is a schematic diagram of the radial cross-section of the first and second regions of the spinneret orifice of the present invention; in the figure, a is a schematic diagram of the radial cross-section of the second region of the spinneret orifice of the present invention, and b is a schematic diagram of the radial cross-section of the first region of the spinneret orifice of the present invention.

[0040] Figure 3 This is an electron microscope image of the island fiber obtained in Example 1 of the present invention;

[0041] Figure 4 This is an electron microscope image of the island-sea fiber prepared in Comparative Example 2 of the present invention;

[0042] Among them, 1-component A channel, 2-component B channel, and 3-component C channel. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0044] The test methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0045] Melt Flow Rate: The MFR (melt flow rate) of low-density polyethylene was tested according to GB / T 3682-2000 "Determination of Melt Mass Flow Rate and Melt Volume Flow Rate of Thermoplastic Plastics" under the following conditions: 190℃ * 2.16kg.

[0046] Relative viscosity: The relative viscosity of the island phase resin was determined according to GB / T 12006.1-2009 "Plastics Polyamide Part 1: Determination of viscosity number".

[0047] CV value of diameter: The island fibers prepared in each embodiment were used as samples. Then, under a scanning electron microscope, the diameter values ​​of 10 islands on the cross section of the island fiber were randomly selected, and the deviation coefficient CV value was calculated. The formula for calculating the CV value is: CV value = standard deviation / average value × 100%.

[0048] Breaking strength: First, the breaking strength of the island-island fibers prepared in each example was tested according to GB / T 14337-2008 "Standard Method for Tensile Properties of Chemical Fibers". Then, the fineness of the island-island fibers was tested according to Method B (single fiber vibration tester method) in GB / T 14335-2008 "Test Method for Linear Density of Chemical Fibers". The breaking strength of the fiber was then calculated based on the measured data. The calculation formula is: Breaking strength (cN / dtex) = Breaking strength (cN) / Fineness (dtex).

[0049] Depending on the processing requirements, some functional processing aids, such as antioxidants, colorants, and antistatic agents, can be added to components A, B, and C. In the embodiments of the present invention, 0.5 wt% of antioxidant 1010 (BASF) is added to components A, B, and C respectively to reduce the thermal decomposition of the resin during processing.

[0050] Example 1

[0051] A method for preparing island-of-sea fibers, comprising the following steps:

[0052] (1) Raw material preparation;

[0053] Component A: Low-density polyethylene, melt index of 65 g / 10 min;

[0054] Component B: A mixture of low-density polyethylene (melt index 25 g / 10 min) and nylon 6 (relative viscosity 2.4) resins, wherein the mass concentration of island phase resin is 65%;

[0055] Component C: A mixture of low-density polyethylene (melt index 25 g / 10 min) and nylon 6 (relative viscosity 2.4) resins, wherein the mass concentration of island phase resin is 50%;

[0056] The total mass of raw materials is calculated as 100 parts, with 5 parts of component A, 60 parts of component B, and 35 parts of component C.

[0057] (2) Screw blending and melt distribution;

[0058] Components A, B, and C are plasticized and mixed using different screws, and then metered by different metering pumps before entering their respective spinning boxes A, B, and C. The plasticizing temperature of component A is 160°C, that of component B is 280°C, and that of component C is 180°C.

[0059] (3) Spinning;

[0060] The melt in spinning boxes A, B, and C is respectively conveyed to the spinneret, such as... Figure 1 , Figure 2 As shown, the spinneret holes are divided into Zone 1 and Zone 2. Zone 1 is a coaxial three-layer design, consisting of component A channel 1, component B channel 2, and component C channel 3 from the outside in. Components A, B, and C are introduced into each zone respectively. After exiting Zone 1 of the spinneret holes, the three melts converge and continue to flow along Zone 2, forming island fibers. The length L1 of Zone 1 is 1 mm, and the length L2 of Zone 2 is 10 mm. The pressure of spinning box A is 3.5 MPa, the pressure of spinning box B is 3.6 MPa, and the pressure of spinning box C is 3.8 MPa. The temperature of the melts of components A, B, and C entering the spinneret holes is 265℃.

[0061] The final island fiber (its electron micrograph is shown below) Figure 3 The average diameter of the island phase (as shown) is 1 μm, the diameter CV value is 2.5%, and the breaking strength of the island fiber is 1.8 cN / dtex.

[0062] Comparative Example 1

[0063] A method for preparing island fiber is basically the same as in Example 1, except that the melt index of low-density polyethylene in component A is 25 g / 10 min.

[0064] The final island-island fiber had an average island phase diameter of 1.6 μm, a CV value of 7.5%, and a breaking strength of 1.51 cN / dtex.

[0065] Comparing Comparative Example 1 and Example 1, it can be seen that Comparative Example 1 exhibits a severe island formation trend, resulting in an increase in the island phase diameter and CV value of the prepared island-island fiber, and a decrease in the island-island fiber strength. This is because in Example 1, the three layers of the spinneret zone correspond to the introduction of components A, B, and C from the outside to the inside, respectively. In Comparative Example 1, the melt index of the low-density polyethylene in component A is the same as that in component B, which leads to an increase in the shear rate on the surface of component A. This results in an excessive difference in the shear rate of the melt from the outer layer to the center, increasing the tendency of the island phase resin in the melt to move and aggregate towards the central region. This leads to uneven distribution of island phase size, which in turn increases the island phase diameter and CV value in the island-island fiber, and decreases the island-island fiber strength.

[0066] Comparative Example 2

[0067] A method for preparing island fiber is basically the same as in Example 1, except that: component A is not prepared in step (1); the total mass of raw materials is 100 parts, component B is 63.16 parts, and component C is 36.84 parts; component A is not used in steps (2) and (3).

[0068] The final island fiber (its electron micrograph is shown below) Figure 4 The average diameter of the island phase (as shown) is 1.75 μm, the diameter CV value is 9%, and the breaking strength of the island fiber is 1.42 cN / dtex.

[0069] Comparing Comparative Example 2 and Example 1, it can be seen that Comparative Example 2 exhibits a severe island formation trend, resulting in a significant increase in the island phase diameter and CV value of the prepared island-island fiber, and a significant decrease in the strength of the island-island fiber. This is because when component B flows, it contacts the spinneret wall, and the tendency of the marine phase in component B to diffuse towards the surface and the island phase to diffuse towards the interior is significantly increased. In contrast, the outermost layer of Example 1 is pure high melt index low density polyethylene. By controlling the outermost layer of the melt in the spinneret channel to be a low viscosity marine phase resin, the shear rate of the outermost layer can be greatly reduced, avoiding the tendency of the island phase resin in the melt to move and aggregate towards the central region.

[0070] Comparative Example 3

[0071] A method for preparing island fiber is basically the same as in Example 1, except that the mass concentration of island phase resin in components B and C used in steps (1) to (3) is the same, which is 59.5%.

[0072] The final island-island fiber has a CV value of 6.9% for the island phase diameter and a breaking strength of 1.56 cN / dtex.

[0073] Comparing Comparative Example 3 with Example 1, it can be seen that Comparative Example 3 exhibits a severe island-forming tendency, resulting in an increase in the island phase diameter and CV value of the prepared island-island fiber, and a decrease in the island fiber strength. This is because Example 1 controls the island-island ratio in the middle layer of the melt to be lower than that in the inner layer. Although the island phase resin inevitably tends to move and aggregate towards the center, the island phase density in the center is low, and the probability of island-forming decreases when the outer islands diffuse towards the center. Therefore, the island phase diameter CV value in the final prepared island-island fiber is small, and the island fiber strength is high.

[0074] Example 2

[0075] A method for preparing island-of-sea fibers, comprising the following steps:

[0076] (1) Raw material preparation;

[0077] Component A: Low-density polyethylene, melt index of 75 g / 10 min;

[0078] Component B: A mixture of low-density polyethylene (melt index 30 g / 10 min) and nylon 6 (relative viscosity 2.5) resins, wherein the mass concentration of island phase resin is 67.5%;

[0079] Component C: A mixture of low-density polyethylene (melt index 30 g / 10 min) and nylon 6 (relative viscosity 2.5) resins, wherein the mass concentration of island phase resin is 54%;

[0080] The total mass of raw materials is calculated as 100 parts, with 4 parts of component A, 55 parts of component B, and 41 parts of component C.

[0081] (2) Screw blending and melt distribution;

[0082] Components A, B, and C are plasticized and mixed using different screws, and then metered by different metering pumps before entering their respective spinning boxes A, B, and C. The plasticizing temperature of component A is 170°C, that of component B is 260°C, and that of component C is 200°C.

[0083] (3) Spinning;

[0084] The melts in spinning boxes A, B, and C are respectively conveyed to the spinnerets. Each spinneret hole on the spinneret is divided into zone one and zone two. Zone one is a coaxial three-layer design, with components A, B, and C respectively introduced from the outside to the inside. After the three melts exit the spinneret holes in zone one, they merge and continue to flow along zone two, forming island fibers. The length L1 of zone one is 1.8 mm, and the length L2 of zone two is 18 mm. The pressure in spinning boxes A, B, and C is 6 MPa, and the temperature of the melts of components A, B, and C entering the spinneret holes is 270°C.

[0085] The final island-island fiber has an average island phase diameter of 1.15 μm, a diameter CV value of 2.9%, and a breaking strength of 1.84 cN / dtex.

[0086] Example 3

[0087] A method for preparing island-of-sea fibers, comprising the following steps:

[0088] (1) Raw material preparation;

[0089] Component A: Low-density polyethylene, melt index of 90 g / 10 min;

[0090] Component B: A mixture of low-density polyethylene (melt index 40 g / 10 min) and nylon 6 (relative viscosity 2.7) resins, wherein the mass concentration of island phase resin is 70%;

[0091] Component C: A mixture of low-density polyethylene (melt index 40 g / 10 min) and nylon 6 (relative viscosity 2.7) resins, wherein the mass concentration of island phase resin is 56.5%;

[0092] The total mass of raw materials is calculated as 100 parts, with component A being 3.5 parts, component B being 50 parts, and component C being 46.5 parts;

[0093] (2) Screw blending and melt distribution;

[0094] Components A, B, and C are plasticized and mixed using different screws, and then metered by different metering pumps before entering their respective spinning boxes A, B, and C. The plasticizing temperature of component A is 180℃, that of component B is 240℃, and that of component C is 220℃.

[0095] (3) Spinning;

[0096] The melts from spinning boxes A, B, and C are respectively conveyed to the spinnerets. Each spinneret on the spinneret is divided into zone one and zone two. Zone one is a coaxial three-layer design, with components A, B, and C respectively introduced from the outside to the inside. After exiting zone one of the spinnerets, the three melts merge and continue to flow along zone two, forming island fibers. The length L1 of zone one is 2.5 mm, and the length L2 of zone two is 25 mm. The pressure in spinning box A is 3.9 MPa, the pressure in spinning box B is 4 MPa, and the pressure in spinning box C is 4.2 MPa. The temperature of the melts of components A, B, and C entering the spinnerets is 275°C.

[0097] The final island-island fiber has an average island phase diameter of 1.21 μm, a diameter CV value of 3.3%, and a breaking strength of 1.96 cN / dtex.

[0098] Example 4

[0099] A method for preparing island-of-sea fibers, comprising the following steps:

[0100] (1) Raw material preparation;

[0101] Component A: Low-density polyethylene, melt index of 90 g / 10 min;

[0102] Component B: A mixture of low-density polyethylene (melt index 45 g / 10 min) and nylon 6 (relative viscosity 2.8) resins, wherein the mass concentration of island phase resin is 72.5%;

[0103] Component C: A mixture of low-density polyethylene (melt index 45 g / 10 min) and nylon 6 (relative viscosity 2.8) resins, wherein the mass concentration of island phase resin is 58.5%, which is 14% lower than that of component B;

[0104] The total mass of raw materials is calculated as 100 parts, with 3 parts of component A, 40 parts of component B, and 57 parts of component C.

[0105] (2) Screw blending and melt distribution;

[0106] Components A, B, and C are plasticized and mixed using different screws, and then metered by different metering pumps before entering their respective spinning boxes A, B, and C. The plasticizing temperature of component A is 200℃, that of component B is 220℃, and that of component C is 240℃.

[0107] (3) Spinning;

[0108] The melts from spinning boxes A, B, and C are respectively conveyed to the spinnerets. Each spinneret on the spinneret is divided into zone one and zone two. Zone one is a coaxial three-layer design, with components A, B, and C respectively introduced from the outside to the inside. After the three melts exit zone one of the spinnerets, they merge and continue to flow along zone two, forming island fibers. The length L1 of zone one is 2 mm, and the length L2 of zone two is 15 mm. The pressure in spinning box A is 4.5 MPa, the pressure in spinning box B is 4.7 MPa, and the pressure in spinning box C is 4.6 MPa. The temperature of the melts of components A, B, and C entering the spinnerets is 280℃.

[0109] The final island-island fiber has an average island phase diameter of 1.26 μm, a diameter CV value of 4.1%, and a breaking strength of 2.02 cN / dtex.

[0110] Example 5

[0111] A method for preparing island-of-sea fibers, comprising the following steps:

[0112] (1) Raw material preparation;

[0113] Component A: Low-density polyethylene, melt index of 100g / 10min;

[0114] Component B: A mixture of low-density polyethylene (melt index 50 g / 10 min) and nylon 6 (relative viscosity 3) resins, wherein the mass concentration of island phase resin is 75%;

[0115] Component C: A mixture of low-density polyethylene (melt index 50 g / 10 min) and nylon 6 (relative viscosity 3) resins, wherein the mass concentration of island phase resin is 65%, which is 10% lower than that of component B.

[0116] The total mass of raw materials is calculated as 100 parts, with component A being 2 parts, component B being 35 parts, and component C being 63 parts;

[0117] (2) Screw blending and melt distribution;

[0118] Components A, B, and C are plasticized and mixed using different screws, and then metered by different metering pumps before entering their respective spinning boxes A, B, and C. The plasticizing temperature of component A is 220°C, that of component B is 200°C, and that of component C is 260°C.

[0119] (3) Spinning;

[0120] The melt from spinning boxes A, B, and C is conveyed to the spinneret. Each spinneret hole on the spinneret is divided into zone one and zone two. Zone one is a coaxial three-layer design, with components A, B, and C respectively introduced from the outside to the inside. After exiting zone one of the spinnerets, the three melts merge and continue to flow along zone two, forming island fibers. The length L1 of zone one is 2.3 mm, and the length L2 of zone two is 22.5 mm. The pressure in spinning box A is 5 MPa, the pressure in spinning box B is 5.2 MPa, and the pressure in spinning box C is 5.4 MPa. The temperature of the melts of components A, B, and C entering the spinneret is 285℃.

[0121] The final island-island fiber has an average island phase diameter of 1.3 μm, a diameter CV value of 5%, and a breaking strength of 2.05 cN / dtex.

Claims

1. A method for preparing island-of-sea fibers, characterized in that... Includes the following steps: (1) Raw material preparation; The raw materials include component A, component B and component C. The polymer in component A is a low viscosity marine resin, and the polymers in components B and C are a mixture of high viscosity marine resin and island resin. The high viscosity marine resin and island resin in components B and C are the same, and the proportion of island resin in component B is higher than that in component C. The melt index of low-viscosity marine resin is at least 40 g / 10 min higher than that of high-viscosity marine resin; (2) Screw blending and melt distribution; Components A, B, and C are plasticized and mixed by different screws, and then metered by different metering pumps before entering their respective spinning boxes. (3) Spinning; The melt in different spinning boxes is conveyed to the spinneret. Each spinneret hole on the spinneret is divided into zone one and zone two. Zone one is a coaxial three-layer design, from the outside to the inside corresponding to the A component, B component and C component respectively. After the three melts exit the spinneret hole in zone one, they merge and continue to flow along zone two, and are ejected to form island fibers. The pressure difference between the spinning boxes corresponding to the A component, B component and C component is within 10%.

2. The method for preparing island-of-sea fiber according to claim 1, characterized in that, The length of zone 1 is L1, and the length of zone 2 is L2. L1 is 1.0 to 2.5 mm, and L2 is 10.0 to 25.0 mm.

3. The method for preparing island-of-sea fiber according to claim 1, characterized in that, The marine phase resin in component A, as well as components B and C, is low-density polyethylene; the island phase resin in components B and C is nylon 6. The melt index of low-density polyethylene in component A is 40-70 g / 10 min higher than that of low-density polyethylene in components B and C. The relative viscosity of nylon 6 components B and C is 2.4–3.

0.

4. The method for preparing island-island fiber according to claim 3, characterized in that, The mass concentration of island phase resin in component B is 65-75%, while the mass concentration of island phase resin in component C is 10-15% lower than that in component B.

5. The method for preparing island-of-sea fiber according to claim 1, characterized in that, The total mass of raw materials is calculated in units of 100 parts, with component A consisting of 2 to 5 parts, component B consisting of 35 to 60 parts, and component C consisting of 35 to 63 parts.

6. The method for preparing island-of-sea fiber according to claim 1, characterized in that, The plasticizing temperature of component A is 160–220℃, the plasticizing temperature of component B is 200–280℃, and the plasticizing temperature of component C is 180–260℃.

7. The method for preparing island-of-sea fiber according to claim 1, characterized in that, The spinning box pressure is 3.5–6.0 MPa, and the temperature of the melts of components A, B, and C entering the spinneret is 265–285 °C.

8. The method for preparing island-island fiber according to claim 1, characterized in that, The average diameter of the island phase in the island fiber is 1.0–1.3 μm, and the diameter CV value is 2.5–5%.

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