Preparation method of polymer fiber with ultrafine fiber grown on surface

Abstract

The present invention belongs to the technical field of fiber materials and relates to a preparation method of polymer fibers with ultrafine fibers grown on the surface. After mixing a matrix-phase polymer and a dispersed-phase polymer to obtain a mixture, melt blending spinning is carried out, and then the fibers obtained by spinning are subjected to ultrasonic oscillation to prepare polymer fibers with ultrafine fibers grown on the surface; the matrix-phase polymer is polypropylene, and the dispersed-phase polymer is PE, PBT, PET or PTT; the proportion of the dispersed-phase polymer in the mixture is 30-50 wt%; the value range of the zero-shear viscosity ratio of the dispersed-phase polymer to the matrix-phase polymer is 0.01-1. The preparation method of the present invention has a simple process, does not require solvent treatment, and the polymer fibers with ultrafine fibers grown on the surface prepared have significantly improved heat preservation, compression resilience and friction properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber materials and relates to a preparation method of polymer fibers with ultrafine fibers grown on the surface. Background Art

[0002] Currently, the research on the preparation and application of bicomponent fibers, including orange segment-shaped fibers and sea-island-shaped fibers, etc., these fibers can form an ultrafine fiber structure on the surface of the matrix fiber through a specific spinning process, thereby improving the performance of the material. However, the bicomponent material formed only through the spinning process has a weak degree of fiber cracking, and its comprehensive performance cannot meet the requirements of some specific applications. It is necessary to open the bicomponent ultrafine fibers to obtain finer fiber morphology and more delicate fiber structure. The methods of opening fibers can be mainly divided into three categories: mechanical fiber opening, chemical solvent fiber opening, and thermal energy fiber opening. However, each of these methods has certain limitations. For example, mechanical fiber opening has high energy consumption; chemical fiber opening pollutes the environment; thermal energy fiber opening damages the performance of the material itself.

[0003] For example, Patent CN 114717749 A combs and hydroentangles Lyocell fibers with another fiber material, and then performs ultrasonic and stirring treatments with sodium hydroxide solution respectively to prepare a hydroentangled nonwoven material containing brush-structured micro / nanofibers. Patent CN 107217512 A uses mechanical methods to pretreat para-aramid to roughen the fiber surface, or adjusts the internal structure of the fiber through processing techniques to reduce the denseness on the fiber surface and produce fibrillation or pore-like structures. Patent CN 105926272 A pretreats a Lyoce11 fiber fabric, then puts it into a concentrated alkali solution, stirs and infiltrates it, obtains the swollen Lyoce11 fiber fabric after swelling treatment, removes the concentrated alkali solution, performs ultrasonic treatment, washes and dries it, and performs sanding treatment. Using the cavitation effect of ultrasonic waves in a liquid medium as an external force to uniformly treat the Lyoce11 fiber product can make the Lyoce1l fibers produce a uniform fibrillation effect faster. However, the use of solvents has a certain degree of impact on both the human body and the environment.

[0004] Therefore, it is of great significance to study a preparation method of polymer fibers with ultrafine fibers grown on the surface to solve the problems existing in the prior art. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art and provide a preparation method of polymer fibers with ultrafine fibers grown on the surface.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a polymer fiber with ultrafine fibers growing on its surface, in which a matrix-phase polymer and a dispersed-phase polymer are mixed to obtain a mixture, followed by melt blending and spinning, and then the spun fiber is subjected to ultrasonic oscillation to obtain a polymer fiber with ultrafine fibers growing on its surface;

[0008] The matrix-phase polymer is polypropylene (PP), and the dispersed-phase polymer is PE, PBT, PET or PTT;

[0009] The proportion of the dispersed-phase polymer in the mixture is 30-50 wt%;

[0010] The ratio of the zero-shear viscosity (viscosity at a shear rate of 0) of the dispersed-phase polymer to the matrix-phase polymer ranges from 0.01 to 1.

[0011] As a preferred technical solution:

[0012] In the method for preparing a polymer fiber with ultrafine fibers growing on its surface as described above, the zero-shear viscosity of the matrix-phase polymer at the spinning temperature is 50-20,000 Pa·s, the zero-shear viscosity of the dispersed-phase polymer at the spinning temperature is 50-1,200 Pa·s, and the spinning temperature is 200-310 °C.

[0013] In the method for preparing a polymer fiber with ultrafine fibers growing on its surface as described above, the interfacial tension between the dispersed-phase polymer and the matrix-phase polymer is not less than 0.5×10 -3 N / m. In a polymer blend system with low interfacial adhesion strength, interfacial debonding is likely to occur, leading to an extreme case of interfacial separation on the fiber surface - fibril separation, while an incompatible polymer blend with high interfacial adhesion strength is conducive to forming a surface with limited interfacial separation, thereby generating deep grooves. Generally speaking, the lower the interfacial tension, the more conducive it is to the contact between the two phases, enabling the molecules of the two phases to approach each other better, thereby increasing the opportunity of intermolecular interaction and being conducive to improving the interfacial adhesion strength.

[0014] In the method for preparing a polymer fiber with ultrafine fibers growing on its surface as described above, during melt blending and spinning, the melt extrusion speed is 2.5×10 -11 ~1.5×10 -8 m 3 / s, the draw ratio is 3.0-5.0, the drawing temperature is 80-160 °C, and the spinning speed is above 16 m / min.

[0015] A preparation method of a polymer fiber with ultrafine fibers grown on its surface as described above, where the aspect ratio of the spinneret holes is 3.0 to 6.0. The aspect ratio of the spinneret holes used during spinning has a significant impact on the surface morphology of the blend fiber. If the aspect ratio is relatively small, the residence time of the melt in the spinneret holes is short, the shear effect is relatively weak, the degree of orientation is low, and the surface of the extruded blend fiber is relatively rough, with more irregular protrusions, depressions, or uneven thicknesses likely to occur, and even surface defects caused by melt fracture may appear. If the aspect ratio is relatively large, the shear and stretching effects on the melt in the spinneret holes are enhanced, the residence time increases, the degree of orientation and uniformity of the melt are improved, which helps to form a smoother and more uniform fiber surface and reduce surface defects. However, if the aspect ratio is too large, the melt pressure drop increases, making extrusion unstable and potentially affecting the fiber surface quality. In actual production, it is also easily affected by the matrix and processing conditions.

[0016] A preparation method of a polymer fiber with ultrafine fibers grown on its surface as described above, where the power of ultrasonic oscillation is 300 to 500 W and the time is 30 to 120 min.

[0017] A preparation method of a polymer fiber with ultrafine fibers grown on its surface as described above, where the diameter of the polymer fiber with ultrafine fibers grown on its surface is 5×10 -5 ~8×10 -5 m, and the diameter of the ultrafine fibers is 2×10 -6 ~8×10 -6 m.

[0018] Principle of the invention:

[0019] Under normal circumstances, when the ratio of the zero-shear viscosity of the dispersed-phase polymer to that of the matrix-phase polymer is between 0.01 and 1, the droplets are most likely to break. In a capillary, the low-viscosity dispersed phase always has a tendency to migrate to areas with a high shear rate. During the spinning process, this phenomenon causes the dispersed phase to migrate more to the fiber surface, resulting in irregular protrusions on the fiber surface; as the content of the dispersed phase increases, the droplet-shaped dispersed phase increases, and the surface of the blend fiber also shows a large number of irregularly distributed protrusions with varying heights. When the content of the dispersed phase further increases to 30%, there are both long and short microfibrils inside the fiber, and the more long microfibrils with strip-shaped protrusions on the fiber surface. After ultrasonic oscillation, a large number of densely distributed ultrafine fibers are finally formed on the surface of the matrix fiber. The reason for the formation of a large number of densely distributed ultrafine fibers on the surface of the matrix fiber after ultrasonic oscillation is that the powerful microjets generated by the cavitation effect produced when ultrasonic waves propagate in a liquid medium impact and shear the fiber surface, breaking some of the relatively weak connections between the fibrils inside the blend fiber and promoting the splitting of fine fibers on the fiber surface, showing the characteristics of ultrafine fibers.

[0020] As the content of the dispersed phase increases, the dispersed phase is extremely prone to coalescence, forming large droplets. With the increase in the content of the dispersed phase, the probability of its collision during the melt processing increases, and the probability of coalescence to form large droplets increases accordingly. According to the capillary theory, large droplets can have a greater deformation ability. An incompatible blend system will form a typical sea-island structure, where the dispersed phase is the island phase and the continuous phase is the sea phase. When the compositions of the two blending components remain unchanged, the determination of the island phase and the sea phase depends on the component viscosities and the ratio of the two components. In most cases, the phase with a higher viscosity will form the island phase, and the phase with a lower viscosity will form the sea phase; the phase with a lower component ratio will form the island phase, and the phase with a higher ratio will form the sea phase. When the viscosity ratio of the dispersed-phase polymer to the matrix-phase polymer > 1, the dispersed phase may be distributed in the matrix and it is difficult to migrate to the surface, and the fiber surface presents a smooth morphology. When the content of the dispersed phase > 50%, the distribution of the dispersed phase and the matrix will change. Specifically, in an incompatible polymer blend, according to the general theory of phase transition and a large number of experimental studies, when the volume fraction of the dispersed phase gradually increases and exceeds 50%, the interaction and spatial distribution state among the dispersed-phase particles will change significantly. The probability of the dispersed-phase particles contacting and connecting with each other increases greatly, and the original continuous phase may be divided into discontinuous parts by the dispersed phase, thus causing the dispersed phase to transform into the continuous phase, forming the so-called "phase inversion" phenomenon, and the viscosity ratio will change accordingly.

[0021] Polymer fibers with ultrafine fibers growing on the surface have significantly improved heat preservation, compression resilience, and friction properties, as follows:

[0022] Improved heat preservation: After a large number of densely distributed ultrafine fibers are formed, the air between the fibers is divided into many tiny air chambers. The air in these air chambers is not easy to flow, and air is a poor conductor of heat, which can effectively hinder the transfer of heat through air convection, thus enhancing the heat preservation performance. At the same time, the ultrafine fibers have a large specific surface area. When exchanging heat with the outside world, more fiber surfaces can absorb and store heat, reducing heat dissipation.

[0023] Improved compression resilience: The addition of ultrafine fibers increases the flexibility and deformability of the fiber aggregate. When subjected to a compressive force, the ultrafine fibers can slide and bend relative to the matrix fibers, dispersing the pressure, making the fiber aggregate more capable of withstanding compression without being overly damaged. Moreover, the ultrafine fibers themselves have a certain elastic recovery ability. After the pressure is removed, they can help the fiber aggregate quickly return to its original shape, improving the compression resilience.

[0024] Improved friction performance: A large number of dense microfibers increase the roughness and contact area of ​​the fiber surface. When in contact with other objects, more fibers interact with the surface of the object, generating more friction. At the same time, the flexibility of the microfibers enables them to better fit the contact surface during the friction process, increasing the effective effect of friction, thereby improving friction performance.

[0025] In some applications, such as when textile fabrics are used to make gloves, improved friction properties can make the gloves better grip objects, less likely to slip, and improve the safety and accuracy of operations. For some fiber products that need to remain in a fixed position, such as fillings, carpets, cushions, etc., good friction properties can make them less likely to slide during use, increasing stability and comfort. In addition, higher friction properties mean that the fiber surface can better resist wear when rubbing against other objects, extending the service life of fiber products and reducing damage and deformation caused by friction.

[0026] Beneficial effects:

[0027] (1) The present invention provides a method for preparing a polymer fiber with ultrafine fibers grown on the surface. An incompatible polymer is formed by adding a dispersed phase into a matrix, and microfibers are formed on the surface of the matrix fiber by a melt blending method. The process is simple and does not require solvent treatment. The microfibers are then deformed into ultrafine fibers by ultrasonic vibration, thereby obtaining a large number of ultrafine fibers on the matrix fiber, forming a structure in which ultrafine fibers are entangled on the matrix, which is used in ultrafine fiber applications such as down.

[0028] (2) The present invention provides a method for preparing a polymer fiber with ultrafine fibers grown on the surface. The prepared polymer fiber with ultrafine fibers grown on the surface has significantly improved thermal insulation, compression resilience and friction performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The surface temperature variation diagram of different samples before and after ultrasound in Example 1;

[0030] Figure 2 are the zero shear viscosity of the matrix phase polymer, the zero shear viscosity of the dispersed phase polymer, and the zero shear viscosity ratio of the dispersed phase polymer to the matrix phase polymer at different temperatures in Example 1, and the horizontal line in the middle of the figure indicates that the viscosity ratio is 1;

[0031] Figure 3 The surface morphology of the 30% blended fiber treated with ultrasonic vibration at different times in Example 1 are (a) 30min, (b) 60min, (c) 90min, and (d) 120min;

[0032] Figure 4 The system surface structure morphology of the polymer fibers of Comparative Examples 1 to 6;

[0033] Figure 5 System surface structure and morphology diagrams of the polymer fibers of Comparative Examples 7 to 11 and Example 1

[0034] Figure 6 System surface structure and morphology diagram of the polymer fiber of Comparative Example 12 Detailed implementation manners

[0035] The present invention will be further described below in conjunction with the detailed implementation manners. It should be understood that these examples are only used to illustrate the present invention and not 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 also fall within the scope defined by the appended claims of this application.

[0036] The test methods for the performance indicators in the examples and comparative examples of the present invention are as follows:

[0037] (1) Fiber compression and resilience performance:

[0038] Clean the oil agent on the fiber surface with an ethanol solution and air-dry it at room temperature. Cut the fiber into short fibers with a length of 30 - 50 mm, and weigh the same mass of loose fibers and put them into a non-woven fabric bag (sample bag). The size of the sample bag is 6 cm × 6 cm to make the fibers evenly distributed. Use a KES-G5 compression tester to test the samples that have been conditioned for 24 hours. The selected circular probe area is 2 cm 2 , and each sample is tested three times, and the results are averaged.

[0039] The calculation formula is as follows:

[0040] WC ;

[0041] W ;

[0042] ;

[0043] ;

[0044] Among them, WC is the compression work, T0 is the sample thickness, T m is the sample thickness under the maximum pressure p m , T is the thickness of the compressed sample bag, p is the pressure applied to the sample bag per unit area during the compression process, p' is the pressure applied to the sample bag per unit during the compression recovery process, W is the compression recovery work, RC is the compression recovery rate, and LC is the linearity of the compression curve.

[0045] The greater the compression work, the fluffier it is. The compression work recovery rate RC represents the compression elasticity and recovery performance of the sample. The larger this value, the better the compression recovery ability of the fabric.

[0046] The linearity LC of the compression curve represents the buckling degree of the sample compression curve. The larger this value, the easier it is to undergo compression deformation.

[0047] (2) Friction performance:

[0048] Using a fiber friction coefficient tester, under the conditions of a temperature of 25 °C and a relative humidity of 65%, the dynamic friction force of different blended fibers in the fiber-metal roller friction mode was measured, and then the friction coefficient was obtained; the rotational speed of the steel roller was 30 r / min, and the tension applied to the monofilament was 0.2 cN; the experiment was repeated 3 to 5 times and the average value was taken.

[0049] (3) Heat preservation performance:

[0050] The sizing agent on the fiber surface was cleaned with an ethanol solution and air-dried at room temperature. The fibers were cut into short fibers with a length of 30 - 50 mm, and the same mass of loose fibers was weighed and put into a non-woven fabric bag (sample bag). The size of the sample bag was 6 cm × 6 cm to make the fibers evenly distributed. The sample bags with different filling samples were placed on a hot stage, and timing started immediately after placing them. The change in the surface temperature of the sample bag over time within 30 min was recorded by an infrared imager. The hot stage was set at 37 °C; 3 - 5 points were taken and the average value was calculated. The ambient temperature was 20 °C and the ambient relative humidity was 50%.

[0051] Example 1

[0052] A preparation method of a polymer fiber with ultrafine fibers grown on the surface, the specific steps are as follows:

[0053] (1) Preparation of raw materials;

[0054] Matrix phase polymer: polypropylene, the zero-shear viscosity at 200 °C is 18000 Pa·s, the number-average molecular weight is 250000, and the molecular weight distribution index is 3.3;

[0055] Dispersed phase polymer: PE, the zero-shear viscosity at 200 °C is 1100 Pa·s, the number-average molecular weight is 120000, and the molecular weight distribution index is 2.1;

[0056] Figure 2 The zero-shear viscosity ratio of the dispersed phase polymer to the matrix phase polymer at different temperatures is shown. It can be seen that the viscosity of the dispersed phase is lower than that of the matrix under the same test conditions, and the zero-shear viscosity ratio of the system is all <1;

[0057] The interfacial tension between the dispersed phase polymer and the matrix phase polymer is 4.3×10-3 N / m;

[0058] (2) Mix the matrix polymer and the dispersed-phase polymer to obtain a mixture, perform melt blending and pelletizing using a twin-screw extruder, then cool it in a normal-temperature (25 °C) water bath, and immediately cut it with a pelletizer to obtain blended chips; subsequently, place the blended chips in a constant-temperature hot air oven at 100 °C for drying treatment for 24 h;

[0059] Among them, the proportion of the dispersed-phase polymer in the mixture is 30 wt%;

[0060] (3) Perform melt blending and spinning on the product of step (2), then successively perform cooling, drawing, and heat setting. After that, immerse the obtained fibers in an ice-water bath and perform ultrasonic oscillation at a power of 500 W for 30 min, and finally dry them in a constant-temperature hot air oven at 60 °C for 4 h to obtain polymer fibers with ultrafine fibers grown on the surface;

[0061] During melt blending and spinning, the melt extrusion speed is 7.8×10 -9 m 3 / s, the air-cooling temperature is 20 °C, the draw ratio is 3, the drawing temperature is 80 °C, the spinning temperature is 200 °C, the spinning speed is 16 m / min, the aspect ratio of the spinneret hole is 3, and the heat setting temperature is 120 °C;

[0062] The diameter of the finally obtained polymer fibers with ultrafine fibers grown on the surface is 6.5×10 -5 m, the diameter of the ultrafine fibers is 2.4×10 -6 m, the surface friction coefficient of the polymer with ultrafine fibers grown on the surface is 0.075, and the temperature change rate is 0.0039 °C / s.

[0063] The compression properties of the fibers before and after ultrasonic oscillation are shown in Table 1 below. It can be found that the fluffiness of the blended fibers after ultrasonic treatment is significantly improved.

[0064] Table 1

[0065] Specimen <![CDATA[T0 (mm)]]> <![CDATA[T m (mm)]]> <![CDATA[WC((gf·cm) / cm 2 )]]> RC (%) LC Before ultrasonic treatment 4.976 2.183 11.934 34.03 0.253 After ultrasonic treatment 9.226 3.259 35.149 49.08 0.224

[0066] Figure 1 It is a graph of the surface temperature of the specimen bag at different times changing with time. At the moment of placing it on the hot stage, the temperature rises rapidly with the passage of time. After a certain period of time, the temperature change no longer rises significantly and changes slowly until it is basically in a stable state. By comparison, it is found that within 30 min, the temperature change rate of the fibers before ultrasonic treatment is 0.0047 °C / s, and the temperature change rate of the fibers after ultrasonic treatment is 0.0039 °C / s. It can be known that the thermal resistance of the fibers after ultrasonic treatment is higher than that of the fibers before ultrasonic treatment, which indicates that the heat preservation performance is also better than that of the blended fibers before ultrasonic treatment.

[0067] Figure 3Figure showing the surface morphology of 30% blend fibers during ultrasonic oscillation treatment at different times in Example 1. By subjecting the blend fibers to ultrasonic oscillation treatment for different times, it can be seen that microfibers of varying degrees appear on the surface of the blend fibers. When the ultrasonic time is 30 min, the ultrafine fibers are distributed on the fibers in a dispersed manner. As the ultrasonic time increases, the previously dispersed ultrafine fibers rewind and wrap around the matrix fibers. The reason is that the longer the ultrasonic time, the higher the water temperature and the greater the acting force, causing the ultrafine fibers to retract and adhere to the main fibers.

[0068] Comparative Examples 1 - 6

[0069] A method for preparing polymer fibers is basically the same as in Example 1, except that in step (3), the proportions of the dispersed-phase polymer in the mixture are 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt% and 30 wt% respectively, and no ultrasonic oscillation is carried out.

[0070] As Figure 4 shown, when the component ratio of the added dispersed phase is in the range of 5 - 30 wt%, before ultrasonic oscillation, when the addition amount is less than 30%, only rough structures of varying degrees appear on the fiber surface, and an ultrafine fiber structure appears at 30%.

[0071] Comparative Examples 7 - 11

[0072] A method for preparing polymer fibers is basically the same as in Example 1, except that in step (3), the proportions of the dispersed-phase polymer in the mixture are 5 wt%, 10 wt%, 15 wt%, 20 wt% and 25 wt% respectively.

[0073] As Figure 5 shown, for Comparative Examples 7 - 11 and Example 1, the component ratio of the added dispersed phase is in the range of 5 - 30 wt%. After ultrasonic oscillation, when the addition amount is less than 30 wt%, no obvious change appears on the fiber surface, and a large number of ultrafine fiber structures appear at 30 wt% (i.e., Example 1).

[0074] Comparative Example 12

[0075] A method for preparing polymer fibers is basically the same as in Example 1, except that the zero-shear viscosity of the matrix-phase polymer at the spinning temperature (200 °C) is 300 Pa·s, and the zero-shear viscosity of the dispersed-phase polymer at the spinning temperature (200 °C) is 400 Pa·s, that is, the ratio of the zero-shear viscosity of the dispersed-phase polymer to the matrix-phase polymer is 1.3, and in step (3), the proportion of the dispersed-phase polymer in the mixture is 5 wt%.

[0076] As Figure 6 shown, after ultrasonic oscillation, no ultrafine fiber structure appears on the surface of the finally prepared polymer fibers.

[0077] Comparative Example 13

[0078] A method for preparing a polymer fiber is basically the same as that of Example 1, except that the proportion of the dispersed-phase polymer in the mixture in step (3) is 55 wt%.

[0079] The finally prepared polymer fiber has no ultrafine fiber structure on its surface.

[0080] Example 2

[0081] A method for preparing a polymer fiber with ultrafine fibers grown on its surface comprises the following specific steps:

[0082] (1) Preparation of raw materials;

[0083] Matrix-phase polymer: polypropylene, with a zero-shear viscosity of 1700 Pa·s at 250 °C, a number-average molecular weight of 200000, and a molecular weight distribution index of 3.2;

[0084] Dispersed-phase polymer: PBT, with a zero-shear viscosity of 400 Pa·s at 250 °C, a number-average molecular weight of 30000, and a molecular weight distribution index of 3;

[0085] The interfacial tension between the dispersed-phase polymer and the matrix-phase polymer is 8.3×10 -3 N / m;

[0086] (2) Mix the matrix-phase polymer and the dispersed-phase polymer to obtain a mixture, perform melt blending and pelletizing using a twin-screw extruder, then cool it through a normal-temperature water bath, and immediately cut it with a pelletizer to obtain blended pellets; subsequently, place the blended pellets in a constant-temperature hot-air oven at 120 °C for 48 h for drying treatment;

[0087] Among them, the proportion of the dispersed-phase polymer in the mixture is 40 wt%;

[0088] (3) Perform melt blending and spinning on the product of step (2), then perform cooling, drawing, and heat setting in sequence. After that, immerse the obtained fiber in an ice-water bath and perform ultrasonic oscillation at a power of 450 W for 60 min, and finally dry it in a constant-temperature hot-air oven at 60 °C for 4 h to obtain a polymer fiber with ultrafine fibers grown on its surface;

[0089] During melt blending and spinning, the melt extrusion speed is 7.8×10 -9 m 3 / s, the air-cooling temperature is 20 °C, the draw ratio is 3.5, the drawing temperature is 80 °C, the spinning temperature is 250 °C, the spinning speed is 16 m / min, the aspect ratio of the spinneret hole is 3:1, and the heat setting temperature is 120 °C;

[0090] The diameter of the finally obtained polymer fiber with ultrafine fibers grown on its surface is 6.3×10 -5 m, the diameter of the ultrafine fibers is 3.6×10-6m, the surface friction coefficient of the polymer fiber with ultrafine fibers grown on its surface is 0.068, and the temperature change rate is 0.0039℃ / s.

[0091] The compression properties of the fibers before and after ultrasonic oscillation are shown in Table 2 below. It can be found that the bulkiness of the blend fibers after ultrasonic treatment is significantly improved.

[0092] Table 2

[0093] Specimen <![CDATA[T0 (mm)]]> <![CDATA[T m (mm)]]> <![CDATA[WC((gf·cm) / cm 2 )]]> RC (%) LC Before ultrasonic treatment 4.150 1.357 11.108 33.20 0.190 After ultrasonic treatment 8.477 2.510 34.400 48.26 0.208

[0094] Example 3

[0095] A preparation method of a polymer fiber with ultrafine fibers grown on its surface, the specific steps are as follows:

[0096] (1) Preparation of raw materials;

[0097] Matrix-phase polymer: polypropylene, the zero-shear viscosity at 280℃ is 450 Pa·s, the number-average molecular weight is 150,000, and the molecular weight distribution index is 3;

[0098] Dispersed-phase polymer: PET, the zero-shear viscosity at 280℃ is 300 Pa·s, the number-average molecular weight is 20,000, and the molecular weight distribution index is 1.8;

[0099] The interfacial tension between the dispersed-phase polymer and the matrix-phase polymer is 11.5×10 -3 N / m;

[0100] (2) Mix the matrix-phase polymer and the dispersed-phase polymer to obtain a mixture, perform melt blending and pelletizing using a twin-screw extruder, then cool it in a normal-temperature water bath, and immediately cut it with a pelletizer to obtain blend pellets; Subsequently, place the blend pellets in a constant-temperature hot air oven at 150℃ for drying treatment for 48h;

[0101] Among them, the proportion of the dispersed-phase polymer in the mixture is 45wt%;

[0102] (3) Perform melt blending and spinning on the product of step (2), then perform cooling, drawing and heat setting in sequence. After that, immerse the obtained fibers in an ice-water bath and perform ultrasonic oscillation at a power of 400W for 90 min, and finally dry them in a constant-temperature hot air oven at 60℃ for 4h to obtain a polymer fiber with ultrafine fibers grown on its surface;

[0103] During melt blending and spinning, the extrusion speed of the melt is 7.8×10 -9 m 3 / s, the air-cooling temperature is 20 °C, the draw ratio is 4, the drawing temperature is 80 °C, the spinning temperature is 280 °C, the spinning speed is 16 m / min, the aspect ratio of the spinneret hole is 3:1, and the heat setting temperature is 130 °C;

[0104] The diameter of the polymer fiber with ultrafine fibers grown on the surface finally obtained is 5.2×10 -5 m, the diameter of the ultrafine fibers is 5.7×10 -6 m, the surface friction coefficient of the polymer fiber with ultrafine fibers grown on the surface is 0.094, and the temperature change rate is 0.0036 °C / s.

[0105] The compression properties of the fibers before and after ultrasonic oscillation are shown in Table 3 below. It can be found that the fluffiness of the blended fibers is significantly improved after ultrasonic treatment.

[0106] Table 3

[0107] Specimen <![CDATA[T0 (mm)]]> <![CDATA[T m (mm)]]> <![CDATA[WC((gf·cm) / cm 2 )]]> RC (%) LC Before ultrasonic treatment 3.917 1.124 10.875 31.986 0.177 After ultrasonic treatment 8.221 2.254 34.144 45.28 0.214

[0108] Example 4

[0109] A preparation method of a polymer fiber with ultrafine fibers grown on the surface, the specific steps are as follows:

[0110] (1) Preparation of raw materials;

[0111] Matrix-phase polymer: polypropylene, the zero-shear viscosity at 300 °C is 400 Pa·s, the number-average molecular weight is 130,000, and the molecular weight distribution index is 3.1;

[0112] Dispersed-phase polymer: PTT, the zero-shear viscosity at 300 °C is 350 Pa·s, the number-average molecular weight is 25,000, and the molecular weight distribution index is 2.2;

[0113] The interfacial tension between the dispersed-phase polymer and the matrix-phase polymer is 14.8×10 -3 N / m;

[0114] (2) Mix the matrix-phase polymer and the dispersed-phase polymer to obtain a mixture, perform melt blending and pelletizing using a twin-screw extruder, then cool it in a normal-temperature water bath, and immediately cut it with a pelletizer to obtain blended pellets; Subsequently, place the blended pellets in a constant-temperature hot air oven at 160 °C for drying treatment for 48 h;

[0115] Among them, the proportion of the dispersed-phase polymer in the mixture is 50 wt%;

[0116] (3) The product of step (2) is subjected to melt blending and spinning, followed by cooling, drawing, and heat setting in sequence. After that, the obtained fibers are immersed in an ice-water bath and subjected to ultrasonic oscillation at a power of 300 W for 120 min, and finally dried in a constant-temperature hot air oven at 60 °C for 4 h to obtain polymer fibers with ultrafine fibers grown on the surface;

[0117] During melt blending and spinning, the extrusion speed of the melt is 7.8×10 -9 m 3 / s, the air-cooling temperature is 20 °C, the draw ratio is 5, the drawing temperature is 80 °C, the spinning temperature is 300 °C, the spinning speed is 16 m / min, the aspect ratio of the spinneret hole is 3:1, and the heat setting temperature is 150 °C;

[0118] The diameter of the finally obtained polymer fibers with ultrafine fibers grown on the surface is 7.9×10 -5 m, the diameter of the ultrafine fibers is 6.5×10 -6 m, the surface friction coefficient of the polymer fibers with ultrafine fibers grown on the surface is 0.088, and the temperature change rate is 0.0038 °C / min.

[0119] The compression properties of the fibers before and after ultrasonic oscillation are shown in Table 4 below. It can be found that the bulkiness of the blended fibers after ultrasonic treatment is significantly improved.

[0120] Table 4

[0121] Specimen <![CDATA[T0 (mm)]]> <![CDATA[T m (mm)]]> <![CDATA[WC((gf·cm) / cm 2 )]]> RC (%) LC Before ultrasonic treatment 4.17 1.425 11.532 33.720 0.192 After ultrasonic treatment 8.823 2.310 32.579 47.72 0.224

Claims

1. A method for preparing a polymer fiber with ultrafine fibers grown on the surface, characterized in that: The matrix phase polymer and the dispersed phase polymer are mixed to obtain a mixture, and then melt-blended and spun, and then the spun fibers are subjected to ultrasonic vibration to obtain polymer fibers with ultrafine fibers grown on the surface; The matrix phase polymer is polypropylene, and the dispersed phase polymer is PE, PBT, PET or PTT; The proportion of dispersed phase polymer in the mixture is 30~50wt%; The zero shear viscosity ratio of the dispersed phase polymer to the matrix phase polymer ranges from 0.01 to 1.

2. The method for preparing a polymer fiber with surface-grown ultrafine fibers according to claim 1, characterized in that: The zero shear viscosity of the matrix phase polymer at the spinning temperature is 50~20000 Pa·s, the zero shear viscosity of the dispersed phase polymer at the spinning temperature is 50~1200 Pa·s, and the spinning temperature is 200~310 ℃.

3. The method for preparing a polymer fiber with surface-grown ultrafine fibers according to claim 2, characterized in that: The interfacial tension between the dispersed phase polymer and the matrix phase polymer is not less than 0.5×10 -3 N / m.

4. The method for preparing a polymer fiber with surface-grown ultrafine fibers according to claim 1, characterized in that: During melt blending spinning, the melt extrusion speed is 2.5×10 -11 ~1.5×10 -8 m 3 / s, the drawing ratio is 3.0~5.0, the drawing temperature is 80~160℃, and the spinning speed is above 16m / min.

5. The method for preparing a polymer fiber with surface-grown ultrafine fibers according to claim 1, characterized in that: The aspect ratio of the spinneret hole is 3.0~6.

0.

6. The method for preparing a polymer fiber with surface-grown ultrafine fibers according to claim 1, characterized in that: The power of ultrasonic oscillation is 300~500W, and the time is 30~120 min.

7. The method for preparing a polymer fiber with surface-grown ultrafine fibers according to claim 1, characterized in that: The diameter of the polymer fiber grown on the surface is 5×10 -5 ~8×10 -5 m, the diameter of the ultrafine fiber is 2×10 -6 ~8×10 -6 m.

Images