CN115787133A - A supersoft reinforced flat sea-island fiber and its preparation method - Google Patents

Abstract

The invention relates to the technical field of terylene sea-island fibers, and discloses an ultra-soft reinforced flat sea-island fiber and a preparation method thereof, wherein the sea-island fiber comprises a sea component and an island component; the raw materials of the sea component are water-soluble polyester COPET and a chain extender; the chain extender is styrene-acrylonitrile-glycidyl methacrylate; the raw material of the island component comprises polyester PET; the cross section of the monofilament fiber of the island component is flat. The island component PET of the sea-island fiber is distributed according to a flat shape, and after alkali fiber opening treatment, the sea component is removed, so that the fiber and the fabric thereof are softer, the skin simulation effect is better, and the luster is bright; by adding a proper amount of styrene-acrylonitrile-glycidyl methacrylate as a chain extender into the sea component, the chain extender can react with carbonyl, hydroxyl, carboxyl and other groups of a PET macromolecular chain segment, the length and the average molecular weight of the macromolecular chain segment are improved, and the strength and the wear resistance of the fiber and the fabric thereof are improved.

Description

A supersoft reinforced flat sea-island fiber and its preparation method

technical field

The invention relates to the technical field of polyester sea-island fibers, in particular to a supersoft reinforced flat sea-island fiber and a preparation method thereof.

Background technique

At present, among man-made fibers, sea-island fiber is a superfine chemical fiber that can produce the thinnest monofilament and the best imitation leather effect. Sea-island fibers usually use COPET (water-soluble chip) as the sea component of a single fiber, and ordinary polyester PET as the island component of a single fiber. After the fiber is woven into a fabric, it is opened by alkali to dissolve the sea component COPET, and then the island component PET As the main body of the fabric, this fiber preparation method can obtain fibers with extremely fine monofilament linear density, and the fabric is soft and the performance of imitation leather is good. The island component PET of the existing island-in-the-sea fiber is distributed circularly in a single fiber. After alkali fiber opening, the remaining island components are superfine fibers with conventional round holes. The strength and wear resistance are poor.

The Chinese invention patent with the publication number CN 114892308 A discloses a preparation process of sea-island fibers, which includes the following steps: (1) PET slices, dispersants, antioxidants, modified antistatic agents, PET chain extenders and nano Zinc oxide is mixed, dried, and melt-extruded to obtain a mixed melt one; (2) drying and melt-extruding the COPET slices to obtain a COPET melt; (3) mixing the mixed melt one obtained in step (1) and the step ( 2) The obtained COPET melt enters the spinneret assembly, cools, and is wound and formed. However, the island-in-the-sea fiber is still a superfine fiber with conventional round holes, and its strength and wear resistance are still relatively poor.

Contents of the invention

In order to solve the technical problem of poor strength and wear resistance of sea-island fibers and their fabrics, the present invention provides a supersoft reinforced flat sea-island fiber and its preparation method. The sea-island fiber is obtained by adding styrene- Acrylonitrile-glycidyl methacrylate is used as a chain extender to increase the length and average molecular weight of PET macromolecular segments, and improve the strength and wear resistance of sea-island fibers and their fabrics.

The purpose of the present invention is achieved through the following technical solutions:

In the first aspect, the present invention provides a supersoft reinforced flat island-in-sea fiber, the island-in-sea fiber includes a sea component and an island component; the raw materials of the sea component are water-soluble polyester COPET and a chain extender; the The chain extender is styrene-acrylonitrile-glycidyl methacrylate; the raw material of the island component includes polyester PET; the monofilament fiber cross section of the island component is flat.

In the present invention, on the existing composite spinning equipment, by changing the design of the composite spinneret, the "island" component PET in the fiber is distributed in a flat shape, and after alkali fiber opening treatment, the sea component is removed, and the remaining The island component fiber is flat, the fiber fabric is softer, the imitation leather effect is better, and the luster is bright. And, add appropriate amount of styrene-acrylonitrile-glycidyl methacrylate in the sea component as a ternary random copolymer chain extender, the chain extender contains epoxy structure, can be combined with PET macromolecular chain segment The carbonyl, hydroxyl, and carboxyl groups react to increase the length and average molecular weight of the macromolecular chain segment, and improve the strength and wear resistance of the fiber and its fabric.

Preferably, the chain extender accounts for 1-3% of the mass of the sea component, and accounts for 0.5-1.8% of the total mass of the sea component and the island component.

Styrene-acrylonitrile-glycidyl methacrylate is a functional copolymer with ultra-high epoxy content, which can react with PET macromolecular chains to improve the strength and wear resistance of fibers. However, if it is added too much, it will easily The melt viscosity changes too much, and it is easy to show uneven distribution, which affects the spinnability of the fiber and the uniformity of the quality of the finished product.

Preferably, the molar ratio of the terpolymer of styrene-acrylonitrile-glycidyl methacrylate is 1:1:1.

The terpolymer of styrene-acrylonitrile-glycidyl methacrylate has carbon-carbon double bonds and active epoxy groups that can undergo free radical addition polymerization. The reaction can connect the adjacent polyethylene terephthalate macromolecular segments, which can expand the molecular chain length and improve the macromolecular quality, thereby improving the tensile breaking strength and wear resistance of the polymer. Spend. The ternary copolymerization ratio of styrene-acrylonitrile-glycidyl methacrylate is 1:1:1. After the functional group reacts with polyethylene terephthalate, when the chain extension is carried out, the polyethylene terephthalate will be strengthened. Ethylene phthalate has the strength and toughness, but has little effect on other properties. If the ternary copolymerization ratio deviates from 1:1:1, uneven chain segment strength will easily appear after macromolecular chain extension, and there will be weak points in the chain segment, which will reduce the quality uniformity of the polymer.

Preferably, the flat cross section has an aspect ratio of 1:1-3.

Preferably, the mass percentages of the sea component and the island component are 40-50%: 50-60%, and the sum of the mass percentages of the sea component and the island component is 100%.

The mass ratio of the sea component and the island component needs to be controlled within a reasonable range. As the proportion of the island component increases, its filling degree in the sea will become higher and higher, and the uniformity of distribution will also increase. However, if the island component If there are too many points, it is easy to cause adhesion of island components, rigid fiber morphology and performance.

In the second aspect, the present invention also provides a method for preparing supersoft reinforced flat sea-island fibers, which includes the following steps: before spinning, adding a chain extender in-line to the sea component melt, and then performing sea-island fiber spinning.

The present invention only needs to change the shape of the island component melt channel needle tube of the needle-tube type sea-island composite assembly on the existing two-component composite spinning equipment, from the current circular hole tube shape to a flat tube shape, and through the sea-island composite assembly The chain extender is added online in the component melt, through the high-temperature reaction between the chain extender in the sea component and the island component, the length of the PET macromolecular segment of the island component is extended, and the average molecular weight is increased, which can effectively Improve the strength of the fiber into flattening. Adding a chain extender to the sea component by means of online melt addition and melt mixing can improve the fiber strength while improving the fiber-forming performance of the melt. Compared with the method of adding a chain extender to the island component, its performance Increased stability and higher uniformity of fiber formation. In addition, the flatness of the superfine single fiber that contributes to the formation of the island component is higher, and its cross section becomes a flatter "one" shape, so the fiber and its fabric can be softer and have higher gloss. On the basis of maintaining ideal strength and wear resistance, its performance can well meet the downstream demand, can greatly improve the performance and application space of polyester fiber, effectively expand the application field of polyester, and has good economic and Social benefits, broad market prospects.

Preferably, the spinning process is as follows: the temperature of six zones is set during the screw conveying process of the melt, the temperature of zone two to zone four is not lower than 290°C, the temperature of zone five is lower than 280°C, and the temperature of zone six of the screw does not exceed 275°C.

In order to enable the chain extender to react with PET macromolecules at a high temperature to achieve chain extension, and to stop the chain extension reaction at the rear end of the screw as the temperature decreases to maintain stability, the present invention also improves the existing spinning process. Increase the temperature of the first few zones of the screw, properly reduce the temperature of the last two zones of the screw and the temperature of the subsequent melt spinning, and the temperature of the first zone of the screw can be set according to the feeding situation.

Preferably, the spinning is: the spinning temperature of the melt after being transported by the screw does not exceed 275°C.

Preferably, the spinning speed is 3500-4500 m/min.

Preferably, the fiber strength of the sea-island fibers after alkali fiber opening treatment is greater than 3.0 cN/dtex.

The strength of the sea-island fiber is 15-30% higher than that of the conventional sea-island fiber after being opened by alkali; in addition, the bending stiffness of the sea-island fiber is not greater than 1.6cN·cm ² , which is softer than the conventional sea-island fiber; According to the incident angle of 45°, the observation angle of 45°, and the incident illuminance E under the condition of 390lx, the plane contrast gloss of the sea-island fiber and its position is greater than 90, which is more than 50% higher than that of conventional bright fibers and fabrics, indicating that it is more glossy beautiful.

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

(1) By changing the design of the composite spinneret, the "island" component PET in the fiber is distributed in a flat shape. After alkali fiber opening treatment, the sea component is removed, and the remaining island component fibers are flat. The fabric is softer, the effect of imitation leather is better, and the luster is bright;

(2) Add an appropriate amount of styrene-acrylonitrile-glycidyl methacrylate to the sea component as a chain extender, which can react with the carbonyl, hydroxyl, and carboxyl groups of the PET macromolecular chain segment to increase the macromolecular chain. The length and average molecular weight of the segment can improve the strength and wear resistance of the fiber and its fabric.

Description of drawings

Fig. 1 is the production process flow diagram of supersoft reinforced flat island-in-the-sea fiber in the present invention;

Fig. 2 is a schematic diagram of the island component melt conduit of the existing needle tube type sea-island fiber composite assembly;

Fig. 3 is a schematic diagram of the island component melt conduit of the needle-tube sea-island fiber composite component of the present invention.

The reference numerals are: spinning cross-section 1 of sea-island fibers, monofilament cross-section 2 of island component, melt conduit 3 of island component.

Detailed ways

The technical scheme of the present invention is described below with specific embodiment, but protection scope of the present invention is not limited to this:

Example 1

A preparation method of supersoft reinforced flat sea-island fibers is as follows:

As shown in Figure 1, in the existing two-component spinning equipment, its composite spinning assembly is improved, as shown in Figure 2, the melt conduit of the island component is changed from a circular shape to a flat cross section.

Taking the COPET slice as the sea component and the conventional PET slice as the island component, there are 37 islands in total. The mass percentage of the sea component and the island component is 50%:50%, and the aspect ratio of the monofilament cross section of the island component is 1:1. Add styrene-acrylonitrile-glycidyl methacrylate chain extender online at the entrance of the COPET slice of the sea component (the molar ratio of terpolymerization is 1:1:1). 1% of the total mass. As shown in Figure 3, sea-island fiber spinning is carried out afterwards, and it is conveyed by the screw first. The temperature of the first zone of the screw is 278°C, the temperature of the second zone is 290°C, the temperature of the third zone is 295°C, the temperature of the fourth zone is 290°C, and the temperature of the fifth zone is 290°C. The temperature of the six zones is 275°C and the temperature of the sixth zone is 270°C, and then melt spinning is carried out, the temperature of the spinning box is 272°C, and the spinning speed is 4000m/min. Next, the spun filaments are sequentially subjected to side blowing, oiling, pre-network, hot roll stretching, netting and winding forming. The draw ratio is 2.36, the temperature of the first hot roll is 75°C, and the temperature of the second hot roll is 120°C. Made 83dtex/72f (37 islands) supersoft reinforced flat sea-island fiber FDY.

Example 2

A preparation method of supersoft reinforced flat sea-island fibers is as follows:

Taking COPET slices as the sea component and conventional PET slices as the island component, there are 37 islands in total. The mass percentages of the sea component and the island component are 40%: 60%. The length and width of the flat monofilament cross section of the island component The ratio is 1:3. Add styrene-acrylonitrile-glycidyl methacrylate chain extender online at the entrance of the COPET slice of the sea component (the molar ratio of terpolymerization is 1:1:1). 3% of the total mass. Afterwards, sea-island fiber spinning is carried out, and it is conveyed by the screw first. The temperature of the first zone of the screw is 282°C, the temperature of the second zone is 292°C, the temperature of the third zone is 298°C, the temperature of the fourth zone is 295°C, the temperature of the fifth zone is 272°C, and the temperature of the sixth zone is 272°C. The temperature is 268° C., and then melt spinning is carried out, the temperature of the spinning box is 268° C., and the spinning speed is 4000 m/min. Next, the spun filaments are sequentially subjected to side blowing, oiling, pre-network, hot roll stretching, netting and winding forming, the draw ratio is 2.52, the temperature of the first hot roll is 80°C, and the temperature of the second hot roll is 125°C. Made 111dtex/48f (37 islands) super soft reinforced flat sea-island fiber FDY.

Example 3

A preparation method of supersoft reinforced flat sea-island fibers is as follows:

Taking COPET slices as the sea component and conventional PET slices as the island component, a total of 37 islands, the mass percentage of the sea component and the island component is 50%: 50%, the length and width of the flat monofilament cross-section of the island component The ratio is 1:2. Add styrene-acrylonitrile-glycidyl methacrylate chain extender online at the entrance of the COPET slice of the sea component (the molar ratio of terpolymerization is 1:1:1). 2% of the total mass. Afterwards, sea-island fiber spinning is carried out, which is conveyed by the screw first. The temperature of the first zone of the screw is 283°C, the temperature of the second zone is 293°C, the temperature of the third zone is 298°C, the temperature of the fourth zone is 295°C, the temperature of the fifth zone is 275°C, and the temperature of the sixth zone is 275°C. The temperature is 272° C., and then melt spinning is carried out, the temperature of the spinning box is 268° C., and the spinning speed is 4000 m/min. Next, the spun filaments are sequentially subjected to side blowing, oiling, pre-network, hot roll stretching, netting and winding forming. The draw ratio is 2.62, the temperature of the first hot roll is 85°C, and the temperature of the second hot roll is 135°C. 111dtex/36f (37 islands) supersoft reinforced flat sea-island fiber FDY was obtained.

Comparative example 1

The difference from Example 3 is that no chain extender is added.

The preparation method of sea-island fiber is:

Taking COPET slices as the sea component and conventional PET slices as the island component, a total of 37 islands, the mass percentage of the sea component and the island component is 50%: 50%, the length and width of the flat monofilament cross-section of the island component The ratio is 1:2. Afterwards, sea-island fiber spinning is carried out, which is conveyed by the screw first. The temperature of the first zone of the screw is 283°C, the temperature of the second zone is 293°C, the temperature of the third zone is 298°C, the temperature of the fourth zone is 295°C, the temperature of the fifth zone is 275°C, and the temperature of the sixth zone is 275°C. The temperature is 272° C., and then melt spinning is carried out, the temperature of the spinning box is 268° C., and the spinning speed is 4000 m/min. Next, the spun filaments are sequentially subjected to side blowing, oiling, pre-network, hot roll stretching, netting and winding forming. The draw ratio is 2.62, the temperature of the first hot roll is 85°C, and the temperature of the second hot roll is 135°C. 111dtex/36f (37 island) sea-island fiber FDY was prepared.

Comparative example 2

The difference from Example 3 is that a chain extender is added online to the island components.

The preparation method of sea-island fiber is:

Taking COPET slices as the sea component and conventional PET slices as the island component, a total of 37 islands, the mass percentage of the sea component and the island component is 50%: 50%, the length and width of the flat monofilament cross-section of the island component The ratio is 1:2. Add styrene-acrylonitrile-glycidyl methacrylate chain extender (terpolymerization molar ratio is 1:1:1) at the entrance of the PET chip of the island component online, and the amount of the chain extender accounted for 2% of the total mass. Afterwards, sea-island fiber spinning is carried out, which is conveyed by the screw first. The temperature of the first zone of the screw is 283°C, the temperature of the second zone is 293°C, the temperature of the third zone is 298°C, the temperature of the fourth zone is 295°C, the temperature of the fifth zone is 275°C, and the temperature of the sixth zone is 275°C. The temperature is 272° C., and then melt spinning is carried out, the temperature of the spinning box is 268° C., and the spinning speed is 4000 m/min. Next, the spun filaments are sequentially subjected to side blowing, oiling, pre-network, hot roll stretching, netting and winding forming. The draw ratio is 2.62, the temperature of the first hot roll is 85°C, and the temperature of the second hot roll is 135°C. 111dtex/36f (37 island) sea-island fiber FDY was prepared.

Comparative example 3

The difference from Example 3 is that the amount of chain extender added online in the sea component is too much.

The preparation method of sea-island fiber is:

Taking COPET slices as the sea component and conventional PET slices as the island component, a total of 37 islands, the mass percentage of the sea component and the island component is 50%: 50%, the length and width of the flat monofilament cross-section of the island component The ratio is 1:2. Add styrene-acrylonitrile-glycidyl methacrylate chain extender online at the entrance of the COPET slice of the sea component (the molar ratio of terpolymerization is 1:1:1). 5% of the total mass. Afterwards, sea-island fiber spinning is carried out, which is conveyed by the screw first. The temperature of the first zone of the screw is 283°C, the temperature of the second zone is 293°C, the temperature of the third zone is 298°C, the temperature of the fourth zone is 295°C, the temperature of the fifth zone is 275°C, and the temperature of the sixth zone is 275°C. The temperature is 272° C., and then melt spinning is carried out, the temperature of the spinning box is 268° C., and the spinning speed is 4000 m/min. Next, the spun filaments are sequentially subjected to side blowing, oiling, pre-network, hot roll stretching, netting and winding forming. The draw ratio is 2.62, the temperature of the first hot roll is 85°C, and the temperature of the second hot roll is 135°C. 111dtex/36f (37 island) sea-island fiber FDY was prepared.

Comparative example 4

The difference from Example 3 is that the aspect ratio of the flat monofilament cross-section of the island component is 1:5.

The preparation method of sea-island fiber is:

Taking COPET slices as the sea component and conventional PET slices as the island component, a total of 37 islands, the mass percentage of the sea component and the island component is 50%: 50%, the length and width of the flat monofilament cross-section of the island component The ratio is 1:5. Add styrene-acrylonitrile-glycidyl methacrylate chain extender online at the entrance of the COPET slice of the sea component (the molar ratio of terpolymerization is 1:1:1). 2% of the total mass. Afterwards, sea-island fiber spinning is carried out, which is conveyed by the screw first. The temperature of the first zone of the screw is 283°C, the temperature of the second zone is 293°C, the temperature of the third zone is 298°C, the temperature of the fourth zone is 295°C, the temperature of the fifth zone is 275°C, and the temperature of the sixth zone is 275°C. The temperature is 272° C., and then melt spinning is carried out, the temperature of the spinning box is 268° C., and the spinning speed is 4000 m/min. Next, the spun filaments are sequentially subjected to side blowing, oiling, pre-network, hot roll stretching, netting and winding forming. The draw ratio is 2.62, the temperature of the first hot roll is 85°C, and the temperature of the second hot roll is 135°C. 111dtex/36f (37 island) sea-island fiber FDY was prepared.

Comparative example 5

The difference from Example 3 is that the cross-section of the monofilament of the island component is not a flat shape, but a conventional circular shape.

The preparation method of sea-island fiber is:

Taking COPET slices as the sea component and conventional PET slices as the island component, a total of 37 islands, the mass percentage of the sea component and the island component is 50%: 50%, and the monofilament cross-section of the island component is a conventional circle . Add styrene-acrylonitrile-glycidyl methacrylate chain extender online at the entrance of the COPET slice of the sea component (the molar ratio of terpolymerization is 1:1:1). 2% of the total mass. Afterwards, sea-island fiber spinning is carried out, which is conveyed by the screw first. The temperature of the first zone of the screw is 283°C, the temperature of the second zone is 293°C, the temperature of the third zone is 298°C, the temperature of the fourth zone is 295°C, the temperature of the fifth zone is 275°C, and the temperature of the sixth zone is 275°C. The temperature is 272° C., and then melt spinning is carried out, the temperature of the spinning box is 268° C., and the spinning speed is 4000 m/min. Next, the spun filaments are sequentially subjected to side blowing, oiling, pre-network, hot roll stretching, netting and winding forming. The draw ratio is 2.62, the temperature of the first hot roll is 85°C, and the temperature of the second hot roll is 135°C. 111dtex/36f (37 island) sea-island fiber FDY was prepared.

Comparative example 6

The difference from Example 3 is that the proportion of the island component in the sea-island fiber is too large.

The preparation method of sea-island fiber is:

Taking COPET slices as the sea component and conventional PET slices as the island component, a total of 45 islands, the mass percentage of the sea component and the island component is 50%: 50%, the length and width of the flat monofilament cross-section of the island component The ratio is 1:2. Add styrene-acrylonitrile-glycidyl methacrylate chain extender online at the entrance of the COPET slice of the sea component (the molar ratio of terpolymerization is 1:1:1). 2% of the total mass. Afterwards, sea-island fiber spinning is carried out, which is conveyed by the screw first. The temperature of the first zone of the screw is 283°C, the temperature of the second zone is 293°C, the temperature of the third zone is 298°C, the temperature of the fourth zone is 295°C, the temperature of the fifth zone is 275°C, and the temperature of the sixth zone is 275°C. The temperature is 272° C., and then melt spinning is carried out, the temperature of the spinning box is 268° C., and the spinning speed is 4000 m/min. Next, the spun filaments are sequentially subjected to side blowing, oiling, pre-network, hot roll stretching, netting and winding forming. The draw ratio is 2.62, the temperature of the first hot roll is 85°C, and the temperature of the second hot roll is 135°C. 111dtex/36f (45 islands) sea-island fiber FDY was prepared.

The island-in-the-sea fibers in the examples and comparative examples were subjected to alkali fiber-opening treatment to dissolve the sea components, and then tested. The specific results are shown in Table 1. Among them, the plane contrast gloss is tested under the condition of 45° incident angle, 45° observation angle, and incident light intensity E of 390 lx.

Table 1

Test items Breaking strength (cN/dtx) Bending stiffness (cN cm²) Flat Contrast Gloss Example 1 3.2 1.2 96 Example 2 3.7 1.4 104 Example 3 4.2 1.6 101 Comparative example 1 2.8 1.8 92 Comparative example 2 3.5 1.3 97 Comparative example 3 3.6 2.0 95 Comparative example 4 4.0 1.1 108 Comparative example 5 4.5 2.6 78 Comparative example 6 4.3 1.8 93

As can be seen from Table 1, Comparative Example 1 shows that compared with conventional island-in-the-sea fibers, the island-in-the-sea microfibers of the present invention are softer, have better imitation leather effects, brighter luster, and better fiber strength and wear resistance. Comparative examples 2-3 show that the addition method and addition ratio of the chain extender will affect its chain extension effect on the PET molecular chain, thereby affecting the fiber performance. Comparative examples 4-5 show that the flat shape of the cross-section of the island component can exert a better synergistic effect with the chain extension effect of the chain extender, resulting in better softness, strength and gloss of the fiber. Comparative Example 6 shows that when the proportion of the island component is too large, the performance of the fiber decreases, and due to the presence of the chain extender, the flat island component is prone to adhesion.

The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by the description of the present invention, or directly or indirectly used in other related technical fields, is the same. included in the scope of patent protection of the present invention.

Claims (10)

1. A kind of supersoft reinforced flat sea-island fiber, is characterized in that, described sea-island fiber comprises sea component and island component; The raw material of described sea component is water-soluble polyester COPET and chain extender; Described chain extender The agent is styrene-acrylonitrile-glycidyl methacrylate; the raw material of the island component includes polyester PET; the monofilament fiber cross section of the island component is flat. 2. supersoft reinforced flat sea-island fiber as claimed in claim 1, is characterized in that, described chain extender accounts for 1～3% of sea component quality, accounts for 0.5～3% of the total mass of sea component and island component. 1.8%. 3. The supersoft reinforced flat sea-island fiber according to claim 1 or 2, characterized in that the molar ratio of the ternary copolymerization of styrene-acrylonitrile-glycidyl methacrylate is 1:1:1. 4. The supersoft reinforced flat sea-island fiber according to claim 1, characterized in that the aspect ratio of the flat cross-section is 1:1~3. 5. supersoft reinforced flat sea-island fiber as claimed in claim 1 or 4, characterized in that, the mass percentages of the sea component and the island component are 40-50%: 50-60%, the sea component and the island The sum of the mass percentages of the components is 100%. 6. A method for preparing supersoft reinforced flat sea-island fibers as claimed in any one of claims 1-5, characterized in that it comprises the steps of: before spinning, adding a chain extender online in the sea component melt, Carry out sea-island fiber spinning again. 7. The preparation method as claimed in claim 6, characterized in that, the spinning is as follows: the temperature of the six zones is set during the screw conveying process of the melt, the temperature of the second zone to the fourth zone is not lower than 290 ° C, and the temperature of the fifth zone is lower than 280°C, the temperature in the sixth zone of the screw does not exceed 275°C. 8. The preparation method according to claim 6 or 7, characterized in that the spinning is: the spinning temperature of the melt after being transported by a screw does not exceed 275°C. 9. preparation method as claimed in claim 8, is characterized in that, the speed of described spinning is 3500～4500m/min. 10. The preparation method according to claim 6, characterized in that the fiber strength of the sea-island fibers after alkali fiber opening treatment is greater than 3.0 cN/dtex.

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