Polyethylene fiber and preparation method thereof

Abstract

The invention discloses a polyethylene fiber and a preparation method thereof, and the preparation method comprises the following steps: firstly, mixing ultrahigh molecular weight polyethylene, middle-high molecular weight polyethylene and nano oxide according to a certain proportion, then carrying out blending melting, and finally, carrying out two times of high-power hot drafting on a nascent filament by adopting a spinning channel with a high length-diameter ratio and an extended length, so as to obtain the polyethylene fiber. Therefore, the polyethylene fiber is prepared. The spinning process of the preparation method is stable, safe and environment-friendly, the production cost is low, the process is simple, and the preparation method is suitable for industrial application; the polyethylene fiber has high strength and flexibility and can be applied to the field of civil textiles.

Description

Technical Field

[0001] The invention relates to a polyethylene fiber and a preparation method thereof, in particular to a flexible polyethylene fiber and a preparation method thereof, and belongs to the field of textiles. Background Art

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fiber is a high-strength specialty fiber that is widely used in military equipment, marine industry, safety protection, sports equipment and many other fields. At present, the main method for industrial preparation of UHMWPE fiber is gel spinning. Since this method requires the use of solvents such as decahydronaphthalene or mineral oil, it not only has high production costs and high safety risks, but also has large energy consumption and environmental pollution problems. The melt spinning method, which is a commonly used spinning method like the gel spinning method, is suitable for polymers that can be melted or converted into a viscous flow state without significant degradation when heated. This method has the advantages of not requiring solvents and extractants, meeting the requirements of green technology, and a safe and simple preparation process. However, due to the difficulty of directly using the melt spinning method to produce UHMWPE, this method has not yet been applied industrially on a large scale.

[0003] The main reason why the melt spinning method is difficult to apply to the production of UHMWPE is that UHMWPE has an extremely high molecular weight and a large number of macromolecular chains are entangled. Therefore, when the melt spinning method is used to prepare fibers, the melt viscosity is large and the primary filaments are prone to extrusion distortion. The primary filaments cannot achieve subsequent multi-stage hot drawing, which in turn leads to instability in the entire spinning process, limiting the improvement of fiber strength and the spinnability of UHMWPE. Patent CN109385689A discloses a spinning method for blending ultra-high molecular weight polyethylene, in which a certain proportion of ultra-high molecular weight polyethylene and high-density polyethylene are fully mixed and melt-spun and drawn. Due to the addition of high-density polyethylene with a large melt index, the ultra-high molecular weight polyethylene melt fluidity and melt index are improved, and the viscosity of the ultra-high molecular weight polyethylene melt is reduced, and finally a polyethylene fiber with a strength of 14-28 cN / dtex is obtained. However, this method only relies on the addition of HDPE to improve the fluidity of UHMWPE in the molten state, which has a large restriction on the ratio of the two materials. Patent CN108660535A discloses a modified ultra-high molecular weight polyethylene fiber-forming material and a preparation method thereof and a melt spinning fiber-forming method, wherein the special material includes ultra-high molecular weight polyethylene, high-density polyethylene, an antioxidant and a modified nano inorganic filler, wherein the modified nano inorganic filler includes a small particle size filler for realizing the chain extension and node bonding effect of the dispersed phase and a large particle size filler for realizing the embedded wall effect of the dispersed phase, and the nano inorganic filler is silicon dioxide and / or titanium dioxide. However, the modified nano inorganic filler with multi-level particle size increases the complexity of the process, which is not conducive to industrial application. Patent CN109234850A discloses a cross-linked modified ultra-high molecular weight polyethylene fiber and a preparation method thereof, wherein the ultra-high molecular weight polyethylene fiber precursor containing VPOSS is subjected to multi-stage heat drawing treatment, and cross-linking is induced during the last stage of heat drawing treatment to obtain a cross-linked modified ultra-high molecular weight polyethylene fiber with good fiber mechanical properties, creep resistance and heat resistance. However, when the modified substance is directly mixed with ultra-high molecular weight polyethylene, phase separation and incomplete dispersion are likely to occur due to the difference in density and gravity between the modified substance and the ultra-high molecular weight polyethylene, thus affecting the stability of product performance. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a polyethylene fiber having both high strength and flexibility, and to provide a method for preparing the polyethylene fiber with a stable, safe, environmentally friendly and low-cost spinning process.

[0005] Technical solution: The method for preparing polyethylene fiber of the present invention comprises the following steps: Step 1: Mix ultra-high molecular weight polyethylene, medium-high molecular weight polyethylene and nano oxide in a weight ratio of 1.9-9: 10-18: 0.1-1; Step 2: The raw materials are blended and melted, the screw temperature is 120-260°C, the melt is ejected to obtain the primary filament, and then the filament is heated and then introduced into the air, and the stretching ratio is 2-10 times; Step 3: subjecting the spun yarn to two high-multiple hot drawing steps, wherein the first step is oil bath drawing at a temperature of 100-150° C. and a drawing multiple of 5-15 times; and the second step is hot air drawing at a drawing multiple of 10-25 times; and polyethylene fiber is obtained.

[0006] This technical solution uses ultra-high molecular weight polyethylene and medium-high molecular weight polyethylene with optimized ratios as the main raw materials to prepare polyethylene fibers. It can not only control the viscosity and fluidity of the melt during the melt spinning process, but also make the product have both high strength and flexibility, solve the problem of poor spinnability of UHMWPE, and broaden its application range. In order to solve the problem of primary fiber distortion and melt fracture caused by UHMWPE during melt spinning, this technical solution also adds nano-oxides to the raw materials, thereby reducing extrusion distortion and improving the spinning continuity of the raw materials. In addition, this technical solution adopts a spinning channel with a high aspect ratio and an extended length to avoid molecular chain entanglement. This technical solution can effectively improve the orderliness of the internal molecular structure of polyethylene fibers, improve the interface performance, form an ordered structure inside the fiber, and the preparation process is safe and environmentally friendly. It also reduces the production difficulty and production cost, and is suitable for promotion and application in the field of civil textiles.

[0007] Preferably, in step 1, the number average molecular weight of the ultra-high molecular weight polyethylene is 1-2 million, and the number average molecular weight of the medium-high molecular weight polyethylene is 500,000-800,000.

[0008] Preferably, in step 1, the nano-oxide is obtained by chemical vapor deposition and has a bulk density of 50-120 g / L.

[0009] This technical solution utilizes gas phase nano-oxide to modify polyethylene. The nano-oxide particles improve the interfacial properties of the spinning matrix blending system, enhance the spinning continuity of the raw materials, and avoid the melt fracture problem in the primary yarn extrusion process.

[0010] Preferably, in step 1, the nano-oxide includes at least one of aluminum oxide, silicon oxide and titanium oxide.

[0011] Preferably, in step 1, the primary particle size of the nano-oxide is 10-50 nm, and the agglomerate particle size is 100-300 nm.

[0012] Preferably, in step 1, the nano-oxide has an amorphous crystalline structure.

[0013] Preferably, in step 2, blending and melting are performed using a single screw blender.

[0014] Preferably, the insulation time is 10-20 minutes.

[0015] The polyethylene fiber of the present invention is prepared by the above preparation method.

[0016] The polyethylene fiber can be used in civilian products such as cool clothing, cool mats, and cushions.

[0017] Preferably, the polyethylene fiber has a breaking strength of 15-19 cN / dtex, an elongation at break of 3.9%-4.5%, and an initial modulus of 620-654 cN / dtex.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The spinning process of the preparation method is stable, safe, and environmentally friendly, and has low production costs and simple processes, and is suitable for industrial applications; 2. The polyethylene fiber has both high strength and flexibility, and can be used in the field of civil textiles. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below through specific implementation methods.

[0020] Example 1: A method for preparing polyethylene fiber This embodiment obtains a polyethylene fiber by the following method, and the specific process is as follows: Ultra-high molecular weight polyethylene with a number average molecular weight of 1.1 million, medium-high molecular weight polyethylene with a number average molecular weight of 550,000, and fumed nano-silica (powder primary particle size 12 nm, agglomerate particle size 110 nm, powder bulk density 55 g / L) were added to a high-speed mixer in a weight ratio of 9.5:90:0.5 for room temperature mixing. Then, the uniformly mixed raw materials were added to a single screw blender for blending and melting. The screw temperature was 120°C. The melt was ejected through a spinneret. Before the nascent yarn entered the air, it was properly insulated and then stretched by a guide roller with a stretching multiple of 2 times. The nascent yarn was subjected to two high-multiple hot stretchings to obtain melt-spun ultra-high molecular weight polyethylene fibers. The temperature of the first oil bath was 100°C, the stretching multiple in the oil bath was 6 times, the hot air length of the second hot air stretching was 10 times, and the total stretching multiple was 15 times. Polyethylene fibers were obtained.

[0021] Example 2: A method for preparing polyethylene fiber This embodiment obtains a polyethylene fiber by the following method, and the specific process is as follows: Ultra-high molecular weight polyethylene with a number average molecular weight of 1.3 million, medium-high molecular weight polyethylene with a number average molecular weight of 650,000, and gas-phase nano-alumina (powder primary particle size 20 nm, agglomerate particle size 150 nm, powder bulk density 72 g / L) were added to a high-speed mixer at a weight ratio of 20:78:2 for room temperature mixing. Then, the uniformly mixed raw materials were added to a single-screw blender for blending and melting. The screw temperature was 200°C. The melt was ejected through a spinneret. Before the nascent yarn entered the air, it was properly insulated and then stretched by a guide roller with a stretching multiple of 5 times. The nascent yarn was subjected to two high-multiple hot stretchings to obtain melt-spun ultra-high molecular weight polyethylene fibers. The temperature of the first oil bath was 120°C, the stretching multiple in the oil bath was 8 times, and the hot air length of the second hot air stretching was 18 times, and the total stretching multiple was 20 times. Polyethylene fibers were obtained.

[0022] Example 3: A method for preparing polyethylene fiber This embodiment obtains a polyethylene fiber by the following method, and the specific process is as follows: Ultra-high molecular weight polyethylene with a number average molecular weight of 1.9 million, medium-high molecular weight polyethylene with a number average molecular weight of 750,000, and gas-phase nano-alumina (powder primary particle size 45 nm, agglomerate particle size 280 nm, powder bulk density 105 g / L) were added to a high-speed mixer in a weight ratio of 45:50:5 for room temperature mixing. Then, the uniformly mixed raw materials were added to a single-screw blender for blending and melting. The screw temperature was 250°C. The melt was ejected through a spinneret. The nascent yarn was properly insulated before entering the air, and then stretched by a guide roller with a stretching multiple of 9 times. The nascent yarn was subjected to two high-multiple hot stretchings to obtain melt-spun ultra-high molecular weight polyethylene fibers. The temperature of the first oil bath was 140°C, the stretching multiple in the oil bath was 14 times, and the hot air length of the second hot air stretching was 22 times, and the total stretching multiple was 40 times. Polyethylene fibers were obtained.

[0023] Comparative Example 1: A method for preparing polyethylene fiber This comparative example obtains a polyethylene fiber by the following method, which is different from the embodiment mainly in that no nano-oxide is added for functional modification. The specific process is as follows: Ultra-high molecular weight polyethylene with a number average molecular weight of 1.9 million and medium-high molecular weight polyethylene with a number average molecular weight of 750,000 are added to a high-speed mixer in a weight ratio of 50:50 for mixing at room temperature. Then, the uniformly mixed raw materials are added to a single screw blender for blending and melting. The screw temperature is 250°C. The melt is ejected through a spinneret. Before the spun yarn enters the air, it is properly insulated and then stretched by a guide roller with a stretching multiple of 9 times. The spun yarn is subjected to two high-multiple hot stretchings to obtain melt-spun ultra-high molecular weight polyethylene fibers. The temperature of the first oil bath is 140°C, the stretching multiple in the oil bath is 14 times, and the hot air length of the second hot air stretching is 22 times, and the total stretching multiple is 40 times. Polyethylene fibers are obtained.

[0024] Performance Testing The tensile properties of the polyethylene fibers obtained in Examples 1-3 and Comparative Example 1 were tested, and the three indicators of breaking strength, breaking elongation and modulus were specifically tested. The mechanical properties of the fiber were tested using a single fiber strength tester, with a spacing of 20 mm between the upper and lower clamps, a tensile speed of 20 mm / min, and a test temperature of room temperature. Each sample was tested more than 30 times, and the average value of multiple tests was taken as the test data. The breaking strength was the ratio of the breaking strength of a single fiber to the linear density of a single fiber, and the breaking elongation was the ratio of the elongation value of a single fiber stretched from the starting length to the breaking to the starting length. The initial modulus was the ratio of the slope of the tangent line at the maximum point of change in strength with elongation near the origin of the tensile curve to the linear density of a single fiber.

[0025] The test results are shown in Table 1. The three examples used UHMWPE and medium-high molecular weight polyethylene with different molecular weights, raw materials with different ratios, nano-oxides with different specifications, and different spinning conditions to prepare polyethylene fibers, and the breaking strength was 15-19 cN / dtex, the breaking elongation was 3.9%-4.5%, and the initial modulus was 620-654 cN / dtex. These three indicators prove that the polyethylene fibers obtained in the examples have both high strength and flexibility. However, when using raw materials and spinning conditions similar to those in Example 3, since Comparative Example 1 did not use nano-oxides, the breaking strength and modulus of the polyethylene fibers obtained were significantly lower than those in Example 3, that is, the excellent performance of both high strength and flexibility was not achieved.

[0026] Table 1 Polyethylene fiber performance test results Breaking strength (cN / dtex) Elongation at break (%) Initial modulus (cN / dtex) Example 1 15 4.5 620 Example 2 16 4.2 630 Example 3 19 3.9 654 Comparative Example 1 10 4.1 550

Claims

1. A method for preparing polyethylene fiber, characterized in that: The following steps are involved: Step 1: mixing ultra-high molecular weight polyethylene, medium-high molecular weight polyethylene and nano oxide in a weight ratio of 1.9-9: 10-18: 0.1-1; Step 2: The raw materials are blended and melted, the screw temperature is 120-260°C, the melt is ejected to obtain the primary filament, and then the filament is heated and then introduced into the air, and the stretching ratio is 2-10 times; Step 3: subjecting the spun yarn to two high-multiple hot drawing steps, wherein the first step is oil bath drawing at a temperature of 100-150° C. and a drawing multiple of 5-15 times; and the second step is hot air drawing at a drawing multiple of 10-25 times; and polyethylene fiber is obtained.

2. The preparation method according to claim 1, characterized in that: In step 1, the number average molecular weight of the ultra-high molecular weight polyethylene is 1-2 million, and the number average molecular weight of the medium-high molecular weight polyethylene is 500,000-800,000.

3. The preparation method according to claim 1, characterized in that: In step 1, the nano-oxide is obtained by chemical vapor deposition, and the bulk density is 50-120 g / L.

4. The preparation method according to claim 1, characterized in that: In step 1, the nano-oxide includes at least one of aluminum oxide, silicon oxide, and titanium oxide.

5. The preparation method according to claim 1, characterized in that: In step 1, the primary particle size of the nano-oxide is 10-50 nm, and the agglomerate particle size is 100-300 nm.

6. The preparation method according to claim 1, characterized in that: In step 1, the nano-oxide is an amorphous crystalline structure.

7. The preparation method according to claim 1, characterized in that: In step 2, a single screw blender is used for blending and melting.

8. The preparation method according to claim 1, characterized in that: In step 2, the insulation time is 10-20 minutes.

9. A polyethylene fiber produced by the preparation method according to claim 1.

10. The polyethylene fiber according to claim 9, characterized in that The polyethylene fiber has a breaking strength of 15-19 cN / dtex, a breaking elongation of 3.9%-4.5%, and an initial modulus of 620-654 cN / dtex.