Preparation method of low-creep surface coating type ultra-high molecular weight polyethylene fiber

Abstract

The invention relates to a preparation method of a low-creep surface coating type ultra-high molecular weight polyethylene fiber, and belongs to the field of high polymer materials. The preparation method comprises the following steps: firstly, preparing a mixed emulsion from an ethylene copolymer and white oil, heating and dissolving the mixed emulsion to prepare a spinning melt, preparing gel-spun yarns by utilizing an extruding and cooling device, extracting and drying the gel-spun yarns, and carrying out multiple thermal stretching to obtain a fiber body; and coating the thermoplastic resin material on the surface of the ultra-high molecular weight polyethylene fiber through dip-coating and drying treatment to obtain the low-creep surface coating type ultra-high molecular weight polyethylene fiber. Compared with the conventional ultra-high molecular weight polyethylene fiber, the low-creep surface coating type ultra-high molecular weight polyethylene fiber disclosed by the invention has better dimensional stability and durability. The preparation method is convenient for industrial production, and the prepared fiber is excellent in comprehensive performance and suitable for application in special fields such as humanoid robot dexterous hand tendon ropes and the like.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a method for preparing low-creep surface-coated ultra-high molecular weight polyethylene fibers. Background Art

[0002] Tendon materials mainly include steel wire rope and polymer fiber materials. Traditional tendon materials such as steel wire and aramid fiber have problems such as heavy weight, poor fatigue resistance, and high friction coefficient. Ultra-high molecular weight polyethylene fiber (UHMWPE fiber) is widely used in bulletproof vests, marine anchor ropes, medical equipment and other fields due to its excellent mechanical properties, wear resistance and chemical corrosion resistance. In the tendon field, UHMWPE fiber has become an ideal material for tendon drive of humanoid robots due to its ultra-high strength (15 times that of steel), low density, wear resistance and good bending properties. However, there is still room for improvement in traditional UHMWPE fiber in terms of molecular weight, creep properties and fiber surface treatment. The following technical bottlenecks still exist in long-term applications:

[0003] 1. Creep phenomenon: Molecular chain slippage under long-term stress leads to deformation accumulation, affecting transmission accuracy;

[0004] 2. Surface treatment requirements: The friction coefficient and wear resistance need to be balanced, and the surface needs to adapt to complex bending conditions.

[0005] When used as a tendon rope, its performance needs to be further improved to meet actual application requirements. Summary of the Invention

[0006] The present invention aims to provide a low-creep surface-coated ultra-high molecular weight polyethylene fiber suitable for tendon ropes. The fiber has a higher molecular weight, excellent creep resistance and an optimized surface coating treatment, thereby significantly improving its overall performance and meeting the application requirements in the field of tendon ropes for dexterous robotic hands.

[0007] A method for preparing a low creep surface-coated ultra-high molecular weight polyethylene fiber comprises the following steps:

[0008] Step 1, preparing a mixed emulsion by mixing ethylene copolymer and white oil;

[0009] Step 2: heating and dissolving the mixed emulsion to obtain a spinning melt, using an extrusion and cooling device to prepare jelly yarns, extracting, drying, and performing multiple heat stretching to obtain a fiber body;

[0010] Step 3: The fiber body is then dipped and dried to coat the thermoplastic resin material on the surface of the ultra-high molecular weight polyethylene fiber to obtain the low creep surface-coated ultra-high molecular weight polyethylene fiber.

[0011] As a further embodiment of the present invention, in step 1, the solid content of the mixed emulsion is 3-8%.

[0012] As a further solution of the present invention, the surface coating material content of the low creep surface coated ultra-high molecular weight polyethylene fiber is ≥1%; and the creep elongation after 100 hours is ≤0.5% at 70° C. and 10% load.

[0013] As a further embodiment of the present invention, the ethylene copolymer is obtained by copolymerizing ethylene and α-olefin, and the α-olefin is one of 1-butene, 1-hexene, and 1-octene.

[0014] As a further embodiment of the present invention, the ethylene copolymer is obtained by copolymerizing ethylene and 1-hexene.

[0015] As a further embodiment of the present invention, the thermoplastic resin material includes acrylic resin or fluorine-containing polymer.

[0016] As a further solution of the present invention, the thermoplastic resin material is further doped with one or more of pigments, flame retardants, ultraviolet absorbers / light stabilizers, graphene, and carbon nanotubes.

[0017] As a further embodiment of the present invention, the thermoplastic resin material is an emulsion composed of polyethylene wax and silicone, a polytetrafluoroethylene aqueous emulsion, or an acrylic resin emulsion.

[0018] As a further solution of the present invention, during the polyethylene wax / silicone emulsion dipping treatment, the polyethylene wax / silicone emulsion and the fiber body are also subjected to megasonic treatment. After the megasonic treatment, electron beam irradiation is performed; after the electron beam irradiation is completed, drying treatment is performed.

[0019] As a further embodiment of the present invention, the low creep surface coated ultra-high molecular weight polyethylene fiber has a creep elongation of ≤0.3% after 100 hours at 70° C. and 10% load.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The low-creep, surface-coated ultra-high molecular weight polyethylene fiber obtained by this invention exhibits superior dimensional stability and durability compared to conventional ultra-high molecular weight polyethylene fibers. This invention facilitates industrial production, and the resulting fiber exhibits excellent overall performance, making it suitable for specialized applications such as tendon bridles in dexterous humanoid robotic hands.

[0022] 2. When the surface of ultra-high molecular weight polyethylene fiber is coated with an emulsion composed of polyethylene wax and silicone, a polytetrafluoroethylene aqueous emulsion or an acrylic resin emulsion as a thermoplastic resin material to make a coating material, fibers with different comprehensive properties will eventually be made.

[0023] 3. During the process of dipping ultra-high molecular weight polyethylene fibers with polyethylene wax / silicone emulsion, the polyethylene wax / silicone emulsion and the fiber body are subjected to megasonic treatment. After the megasonic treatment, electron beam irradiation is performed and finally the obtained fiber is dried, thereby having lower creep properties. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to specific embodiments. The embodiments described below are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] (1) preparing a mixed emulsion with a solid content of 6% by weight of an ethylene copolymer (the ethylene copolymer is a 1-butene copolymer, wherein the 1-butene accounts for 0.5 mol % and the viscosity-average molecular weight is 9 million) and white oil;

[0027] (2) The mixed emulsion is heated and dissolved (twin-screw extruder, screw diameter 96mm, screw speed 200r / min, screw 1-16 zone temperatures are 118℃, 154℃, 225℃, 257℃, 259℃, 272℃, 273℃, 275℃, 277℃, 278℃, 279℃, 279℃, 281℃, 283℃, 285℃, 287℃) to prepare a spinning melt, and an extrusion and cooling device is used to prepare a gel filament, and the gel filament is extracted, dried and subjected to multiple heat stretching. The spinning melt is metered by a metering pump and extruded through a spinneret, and the spinneret is spun. The plate has 240 holes with a pore size of 1.0 mm, and is cooled and shaped in a water tank (water temperature 25°C) to obtain a gel fiber. After the gel fiber is balanced and static for 24 hours, it is pre-stretched, extracted (the extractant is a hydrocarbon cleaning agent), dried, and hot-stretched (first-level hot stretching at 137°C, second-level hot stretching at 148°C, and third-level hot stretching at 150°C, with a total stretching ratio of 50 times) to obtain a fiber body with a linear density of 1734 dtex, a viscosity-average molecular weight of 4.1785 million, a breaking strength of 36.4 cN / dtex, a modulus of 1453 cN / dtex, and an elongation at break of 2.99%.

[0028] (3) The fiber body was dipped in 8.0% polyethylene wax / silicone emulsion (the mass fraction of polyethylene wax in the polyethylene wax / silicone emulsion was 8%) and then dried at 45°C to obtain fiber 1; wherein, the surface coating material content of fiber 1 (obtained after thermal curing of polyethylene wax / silicone emulsion) was 4.5%, the linear density was 1840 dtex, the breaking strength was 31.2 cN / dtex, the modulus was 1258 cN / dtex, the breaking elongation was 3.11%, and the creep elongation after 100 h at 70°C and 10% load was 0.43%; the yarn abrasion resistance (dry grinding) breaking number was 2108 times (ASTM D6611).

[0029] Comparative Example 1

[0030] In Example 1, the fiber body was not dip-coated and had no coating material on the surface. The viscosity-average molecular weight of the fiber body was 4,178,500. The resulting fiber 01 had a creep elongation of 7.41% after 100 h at 70° C. and 10% load. The yarn abrasion (dry grinding) fracture number was 1,198 times (ASTM D6611).

[0031] Comparative Example 2

[0032] (1) Ethylene homopolymer (viscosity average molecular weight 9.2 million) and white oil were prepared into a mixed emulsion with a solid content of 6%;

[0033] (2) The mixed emulsion is heated and dissolved (twin-screw extruder, screw diameter 96 mm, screw speed 200 r / min, screw zone 1-16 temperatures are 118°C, 154°C, 225°C, 257°C, 259°C, 272°C, 273°C, 275°C, 277°C, 278°C, 279°C, 279°C, 281°C, 283°C, 285°C, 287°C) to prepare a spinning melt, and a gel filament is prepared by an extrusion and cooling device. The gel filament is extracted, dried, and subjected to multiple heat stretching (the spinning melt is metered by a metering pump and extruded through a spinneret, and the spinneret is The plate had 240 holes with a pore size of 1.0 mm. The fibers were cooled and shaped in a water tank (water temperature 25°C) to obtain gel fibers. After the gel fibers were allowed to equilibrate for 24 hours, they were pre-drawn, extracted (using a hydrocarbon detergent as the extractant), dried, and hot-drawn (first-stage hot-drawing at 137°C, second-stage hot-drawing at 148°C, and third-stage hot-drawing at 150°C, with a total draw ratio of 50), to obtain a fiber body with a linear density of 1740 dtex. The fiber body had a viscosity-average molecular weight of 4.2372 million, a breaking strength of 37.2 cN / dtex, a modulus of 1475 cN / dtex, and an elongation at break of 3.03%.

[0034] The fiber body is not treated by dip-coating, and the surface is not coated with material. The final fiber 02 has a creep elongation of 7.76% at 70°C, 10% load, and 100h. The yarn abrasion (dry grinding) breaking frequency is 1233 times (ASTM D6611).

[0035] As can be seen from Example 1 and Comparative Examples 1 and 2, the fiber body treated by dip-coating with the polyethylene wax / silicone emulsion can significantly reduce the creep elongation and improve the abrasion resistance (the yarn abrasion breaking frequency is an important indicator for measuring the abrasion resistance).

[0036] Example 2

[0037] The fiber body of Example 1 is treated by dip-coating with a PTFE aqueous emulsion (the mass fraction of PTFE resin in the PTFE aqueous emulsion is 2%) at a concentration of 2%, and then dried at 45°C to obtain fiber 2. The surface coating material content of fiber 2 is 1.4%, the linear density of the fiber is 1785dtex, the breaking strength is 32.2cN / dtex, the modulus is 1258cN / dtex, the breaking elongation is 3.11%, the creep elongation at 70°C, 10% load, and 100h is 0.42%, and the yarn abrasion (dry grinding) breaking frequency is 1634 times (ASTM D6611).

[0038] As can be seen from Example 1 and Example 2, compared with dip-coating with the polyethylene wax / silicone emulsion, dip-coating with the PTFE aqueous emulsion has no improvement in the creep elongation, but the abrasion resistance will decrease to some extent.

[0039] Example 3

[0040] The fiber body of Example 1 is further treated by dip-coating with a PTFE aqueous emulsion at a concentration of 13%, and then dried at 45°C to obtain fiber 3. The surface coating material content of fiber 3 is 8%, the linear density is 1900dtex, the breaking strength is 30.0cN / dtex, the modulus is 1113cN / dtex, the breaking elongation is 3.11%, the creep elongation at 70°C, 10% load, and 100h is 0.44%, and the yarn abrasion breaking frequency is 3239 times (ASTM D6611).

[0041] As can be seen from Example 2 and Example 3, as the concentration of PTFE resin in the PTFE aqueous emulsion increases, the creep elongation is basically not improved, but the abrasion resistance is significantly improved.

[0042] Example 4

[0043] The fiber body of Example 1 is then dipped in a PTFE aqueous emulsion containing graphene, wherein the concentration (mass fraction) of graphene is 0.1% and the mass fraction of the PTFE resin is 13%; after dipping, it is dried at 45°C to obtain fiber 4, wherein the surface coating material content of fiber 4 is 8%, the linear density is 1910 dtex, the breaking strength is 30.5 cN / dtex, the modulus is 1133 cN / dtex, the breaking elongation is 3.11%, and the creep elongation after 100 h at 70°C and 10% load is 0.44%; the yarn wear-resistant fracture number is 3788 times (ASTM D6611).

[0044] It can be seen from Examples 3 and 4 that by adding graphene to the PTFE aqueous emulsion, there is basically no improvement on the creep elongation, but the wear resistance can be improved to a certain extent.

[0045] Example 5

[0046] The fiber body of Example 1 is then dipped in an acrylic resin emulsion containing nano-carbon black, wherein the mass fraction of the nano-carbon black is 0.8% and the mass fraction of the acrylic resin is 15%. After dipping, the fiber is dried at 45°C to obtain fiber 5, wherein the surface coating material content of fiber 5 is 10%, the linear density is 1936 dtex, the breaking strength is 29.1 cN / dtex, the modulus is 1108 cN / dtex, the breaking elongation is 3.17%, and the creep elongation after 100 h at 70°C and 10% load is 0.45%; the yarn abrasion resistant fracture number is 4108 times (ASTM D6611).

[0047] From the comparison between Example 5 and other examples, it can be seen that the use of acrylic resin emulsion containing nano carbon black for dipping can significantly improve the wear resistance.

[0048] Example 6

[0049] During the process of dipping the fiber body in Example 1 in a polyethylene wax / silicone emulsion with a concentration of 8.0%, the fiber body immersed in the polyethylene wax / silicone emulsion was also subjected to megasonic treatment at a megasonic frequency of 2.2 MHz; after the megasonic treatment, the fiber body was irradiated with an electron beam with an electron beam energy of 3.6 MeV and a radiation dose of 12 kGy; after the electron beam irradiation, the fiber body was dried at 45°C to obtain fiber 6; wherein, the surface coating material content of fiber 6 was 4.5%, the linear density was 1847 dtex, the breaking strength was 32.5 cN / dtex, the modulus was 1263 cN / dtex, the breaking elongation was 3.12%, and the creep elongation after 100 h at 70°C and 10% load was 0.28%; the yarn abrasion resistance (dry grinding) fracture number was 2123 times (ASTM D6611).

[0050] Comparative Example 3

[0051] During the dipping process of the fiber body of Example 1 with an acrylic resin emulsion containing nano-carbon black (the mass fraction of nano-carbon black is 0.8%, and the mass fraction of acrylic resin is 15%), the acrylic resin emulsion containing nano-carbon black and the fiber body are also subjected to megasonic treatment with a megasonic frequency of 2.2 MHz; after the megasonic treatment, electron beam irradiation is performed with an electron beam energy of 3.6 MeV and a radiation dose of 12 KGy; after the electron beam irradiation, the fiber is dried at 45°C to obtain fiber 03; wherein, the creep elongation of fiber 03 after 100 h at 70°C and 10% load is 0.43%; the number of yarn abrasion-resistant (dry grinding) fractures is 4161 times (ASTM D6611).

[0052] Comparative Example 4

[0053] During the process of dipping the fiber body in Example 1 with an 8.0% concentration of polyethylene wax / silicone emulsion, the polyethylene wax / silicone emulsion and the fiber body were also subjected to megasonic treatment at a megasonic frequency of 2.2 MHz. After the megasonic treatment, the fiber body was dried at 45°C to obtain fiber 04. Among them, the creep elongation of fiber 04 after 100 hours at 70°C and 10% load was 0.44%. The yarn abrasion resistance (dry grinding) fracture number was 2157 times (ASTM D6611).

[0054] Comparative Example 5

[0055] The fiber body in Example 1 was dip-coated with 8.0% polyethylene wax / silicone emulsion, and then the dip-coated fiber body was subjected to electron beam irradiation with an electron beam energy of 3.6 MeV and a radiation dose of 12 KGy. After the electron beam irradiation, it was dried at 45°C to obtain fiber 05. Among them, the surface coating material content of fiber 05 was 4.5%, the linear density was 1847 dtex, the breaking strength was 32.5 cN / dtex, the modulus was 1263 cN / dtex, the breaking elongation was 3.12%, and the creep elongation after 100 h at 70°C and 10% load was 0.45%. The yarn wear-resistant (dry grinding) breaking number was 2169 times (ASTM D6611).

[0056] Comparative Example 6

[0057] The fiber body in Example 1 was first subjected to electron beam irradiation with an electron beam energy of 3.6 MeV and a radiation dose of 12 KGy. After the electron beam irradiation, the fiber body was dip-coated with an 8.0% concentration of polyethylene wax / silicone emulsion, and the polyethylene wax / silicone emulsion and the fiber body were also subjected to megasonic treatment with a megasonic frequency of 2.2 MHz. After the megasonic treatment, the fiber was dried at 45° C. to obtain fiber 06. Among them, the creep elongation of fiber 06 after 100 h at 70° C. and 10% load was 0.49%; the yarn abrasion resistance (dry grinding) fracture number was 2287 times (ASTM D6611).

[0058] Comparative Example 7

[0059] During the process of dipping the fiber body in Example 1 in a polyethylene wax / silicone emulsion with a concentration of 8.0%, the polyethylene wax / silicone emulsion and the fiber body were ultrasonically treated at an ultrasonic frequency of 20 kHz. After the ultrasonic treatment, the fiber body was irradiated with an electron beam energy of 3.6 MeV and a radiation dose of 12 KGy. After the electron beam irradiation, the fiber body was dried at 45°C to obtain fiber 07. Among them, the creep elongation of fiber 07 after 100 h at 70°C and 10% load was 0.44%; the yarn abrasion resistance (dry grinding) fracture number was 1872 times (ASTM D6611).

[0060] Comparative Example 8

[0061] During the process of dipping the fiber body in Example 1 in an 8.0% polyethylene wax aqueous emulsion (the mass fraction of polyethylene wax in the polyethylene wax aqueous emulsion is 8%), the polyethylene wax aqueous emulsion and the fiber body were also subjected to megasonic treatment at a megasonic frequency of 2.2 MHz; after the megasonic treatment, electron beam irradiation was performed with an electron beam energy of 3.6 MeV and a radiation dose of 12 KGy; after the electron beam irradiation, the fiber was dried at 45°C to obtain fiber 08; wherein, the creep elongation of fiber 08 at 70°C and 10% load for 100 h was 0.91%; the yarn abrasion resistance (dry grinding) fracture number was 2301 times (ASTM D6611).

[0062] From the above, it can be seen that after the ultra-high molecular weight polyethylene fiber is made, during the coating process of the thermoplastic resin material, it is found that when polyethylene wax / silicone emulsion is used as the thermoplastic resin material for coating, megasonic treatment is first performed during the dipping process, and then electron beam irradiation is performed. The combination of the two can further improve the ultra-high molecular weight polyethylene fiber itself or the degree of bonding between it and the coating material, thereby further reducing the creep elongation of the fiber and obtaining a fiber with lower creep; but it has little effect on other properties of the fiber.

[0063] In addition, it should be understood that those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a low creep surface coated ultra-high molecular weight polyethylene fiber, characterized in that: The following steps are involved: Step 1, preparing a mixed emulsion by mixing ethylene copolymer and white oil; Step 2: heating and dissolving the mixed emulsion to obtain a spinning melt, using an extrusion and cooling device to prepare jelly yarns, extracting, drying, and performing multiple heat stretching to obtain a fiber body; Step 3: The fiber body is then dipped and dried to coat the thermoplastic resin material on the surface of the ultra-high molecular weight polyethylene fiber to obtain the low creep surface-coated ultra-high molecular weight polyethylene fiber.

2. The method for preparing the low creep surface coated ultra-high molecular weight polyethylene fiber according to claim 1, wherein: In step 1, the solid content of the mixed emulsion is 3-8%.

3. The method for preparing the low creep surface coated ultra-high molecular weight polyethylene fiber according to claim 1, wherein: The surface coating material content of the low creep surface coated ultra-high molecular weight polyethylene fiber is ≥1%; and the creep elongation after 100 hours is ≤0.5% at 70° C. and 10% load.

4. The method for preparing the low creep surface coated ultra-high molecular weight polyethylene fiber according to claim 1, wherein: The ethylene copolymer is obtained by copolymerizing ethylene and α-olefin, and the α-olefin is one of 1-butene, 1-hexene and 1-octene.

5. The method for preparing the low creep surface coated ultra-high molecular weight polyethylene fiber according to claim 1, wherein: The ethylene copolymer is obtained by copolymerizing ethylene and 1-hexene.

6. The method for preparing the low creep surface coated ultra-high molecular weight polyethylene fiber according to claim 1, wherein: The thermoplastic resin material includes acrylic resin or fluorine-containing polymer.

7. The method for preparing the low creep surface coated ultra-high molecular weight polyethylene fiber according to claim 6, characterized in that: The thermoplastic resin material is further doped with one or more of a pigment, a flame retardant, an ultraviolet absorber / light stabilizer, graphene, and carbon nanotubes.

8. The method for preparing the low creep surface coated ultra-high molecular weight polyethylene fiber according to claim 1, wherein: The thermoplastic resin material is an emulsion composed of polyethylene wax and silicone, a polytetrafluoroethylene aqueous emulsion or an acrylic resin emulsion.

9. The method for preparing the low creep surface coated ultra-high molecular weight polyethylene fiber according to claim 1, wherein: During the polyethylene wax / silicone emulsion dipping process, the polyethylene wax / silicone emulsion and the fiber body are subjected to megasonic treatment. After the megasonic treatment, electron beam irradiation is performed. After the electron beam irradiation is completed, drying is performed.

10. The method for preparing the low creep surface coated ultra-high molecular weight polyethylene fiber according to claim 9, characterized in that: The low creep surface coated ultra-high molecular weight polyethylene fiber has a creep elongation of ≤0.3% after 100 hours at 70° C. and 10% load.