A method for producing a ptf e fiber

Abstract

This invention relates to the field of PTFE fiber material technology, specifically to a method for preparing PTFE fiber, comprising the following steps: (1) adding polyethylene oxide to polytetrafluoroethylene emulsion and mixing evenly to obtain a spinning solution; (2) injecting the spinning solution into a coagulation bath through a spinneret for solidification treatment to obtain nascent fibers; (3) sintering the nascent fibers to obtain PTFE fibers. The PTFE fibers prepared using this method have good mechanical properties, with a tensile strength reaching 1.32-1.43 cN / dtex, and the preparation process is simple, saving production costs.

Description

Technical Field

[0001] This invention belongs to the field of PTFE fiber technology, and specifically relates to a method for preparing PTFE fibers. Background Technology

[0002] Polytetrafluoroethylene (PTFE) has excellent corrosion resistance and high temperature resistance. PTFE fibers, including filaments and staple fibers, are used in high-temperature filtration, self-lubrication, chlor-alkali engineering and medical fields, and have obvious application advantages.

[0003] Currently, mass-produced polytetrafluoroethylene (PTFE) fibers are manufactured using the membrane splitting method. The process involves: mixing PTFE resin with lubricating oil → curing → pressing → extruding rods → calendering into sheets → degreasing → longitudinal stretching (or transverse stretching) → heat treatment → membrane splitting → subsequent fiber processing. The disadvantages of this method are that the fibers are relatively coarse and have poor uniformity, and the high micropore content leads to a large thermal shrinkage rate. Fibers prepared by the membrane splitting method face difficulties in controlling fineness, uniformity, mechanical properties, and thermal shrinkage, which has become a technical bottleneck for subsequent nonwoven processing.

[0004] Other methods for preparing polytetrafluoroethylene (PTFE) fibers include carrier spinning, island-of-sea fiber spinning, and electrospinning, all of which can be used to produce ultrafine fibers, but these processes are not yet mature. Carrier spinning utilizes fiber-forming polymers, such as viscose and polyvinyl alcohol, as a carrier for spinning, followed by sintering at high temperatures to carbonize the carrier and remove the fiber-forming polymer. The sintering temperature is typically selected between PTFE's melting point (327℃) and decomposition point (425℃), ensuring that the PTFE particles fully melt and bond together while removing the carrier, thus obtaining PTFE fibers. Traditional carrier PVA decomposition temperatures are high and decomposition times are long, making complete removal difficult through sintering alone. Summary of the Invention

[0005] In view of the problems and shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing PTFE fibers.

[0006] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0007] The first aspect of this invention provides a method for preparing PTFE fibers, comprising the following steps:

[0008] (1) Add polyethylene oxide to polytetrafluoroethylene emulsion and mix evenly to obtain spinning solution;

[0009] (2) The spinning solution is injected into a coagulation bath through a spinneret for solidification treatment to obtain nascent fibers;

[0010] (3) The nascent fiber is sintered to obtain PTFE fiber.

[0011] According to the above preparation method, preferably, the coagulation bath is polyethylene glycol.

[0012] According to the above preparation method, preferably, the molecular weight of the polyethylene glycol is 200-600; more preferably, the molecular weight of the polyethylene glycol is 200, 400, or 600. Most preferably, the molecular weight of the polyethylene glycol is 200.

[0013] According to the above preparation method, preferably, the curing time is 2 to 6 minutes; more preferably, the curing time is 3 to 5 minutes.

[0014] According to the above preparation method, preferably, the curing temperature is 10-100℃.

[0015] According to the above preparation method, preferably, the molecular weight of the polyethylene oxide is 600,000 to 3,000,000. More preferably, the molecular weight of the polyethylene oxide is 2,000,000.

[0016] According to the above preparation method, preferably, the mass ratio of polytetrafluoroethylene to polyethylene oxide in the spinning solution is (1-8):1. More preferably, the mass ratio of polytetrafluoroethylene to polyethylene oxide in the spinning solution is 4:1.

[0017] According to the above preparation method, preferably, the sintering temperature in step (3) is 350-400℃ and the sintering time is 1-5h; more preferably, the sintering temperature is 360-380℃ and the sintering time is 2-3h.

[0018] According to the above preparation method, preferably, the polytetrafluoroethylene content in the polytetrafluoroethylene emulsion is 60%.

[0019] According to the above preparation method, preferably, the polyethylene oxide is added to the polytetrafluoroethylene emulsion in the form of a polyethylene oxide solution, and the concentration of the polyethylene oxide solution is 4%.

[0020] A second aspect of the present invention provides a PTFE fiber product prepared using the preparation method described in the first aspect above.

[0021] Compared with the prior art, the positive and beneficial effects achieved by the present invention are as follows:

[0022] (1) In this invention, PTFE fibers are prepared by blending PTFE emulsion with PEO solution to form a spinning solution. PEO has the advantages of good water solubility, low decomposition temperature and fast decomposition rate. The spinning solution is injected into the coagulation bath through the spinneret for solidification treatment to obtain nascent fibers. When the nascent fibers are sintered in an air atmosphere, the PEO in the fibers can be completely decomposed and separated from PTFE. At the same time, PTFE is fully melted and bonded during the sintering process, making the PTFE fiber structure more complete. Moreover, the PTFE fibers can obtain better mechanical properties after high-temperature sintering. According to the test, the tensile strength of the prepared PTFE fibers is about 1.32-1.43 cN / dtex. In contrast, the PTFE fibers prepared by wet spinning with PVA as a carrier in the prior art have high PVA viscosity and high decomposition temperature, resulting in high energy consumption in the sintering process. Moreover, PVA is not easy to completely separate from PTFE during the sintering process and is difficult to completely remove. The PVA residue will affect the performance of PTFE fibers, resulting in low tensile strength (≤1.0 cN / dtex) and poor mechanical properties of the prepared PTFE fibers.

[0023] (2) The present invention uses wet spinning technology to prepare PTFE fibers. Polyethylene glycol with a molecular weight of 200 to 600 is used as a coagulation bath. After the PTFE spinning solution is sprayed into the coagulation bath, it can form nascent fibers after solidification treatment. The nascent fibers can be directly sintered to obtain PTFE fibers with a diameter of 10 to 80 μm. The preparation process is simple, saves production costs, and ensures the mechanical properties of PTFE fibers. Attached Figure Description

[0024] Figure 1 The diagram below shows the production equipment for nascent fibers in Example 1; where 1 is the base plate; 2 is the spinning device; 3 is the coagulation bath; and 4 is the collecting device.

[0025] Figure 2 The images shown are scanning electron microscope (SEM) images of the PTFE fibers prepared in Examples 1-1, 2-1 to 2-2; where a is Example 1-1, b is Example 2-1, and c is Example 2-2.

[0026] Figure 3 The diagram shows the diameter statistics of the PTFE fibers prepared in Examples 1-1, 2-1 to 2-2; where a is the fiber diameter distribution diagram, b is the fiber diameter statistics diagram, Mw=200 represents Example 1-1, Mw=400 represents Example 2-1, and Mw=600 represents Example 2-2.

[0027] Figure 4Stress-strain diagrams of PTFE fibers prepared in Examples 1-1, 2-1 to 2-2; wherein Mw = 200 represents Example 1-1, Mw = 400 represents Example 2-1, and Mw = 600 represents Example 2-2. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0030] The experimental materials used in the following embodiments are as follows:

[0031] Polytetrafluoroethylene dispersion (PTFE, 60% solids content, Shanghai Sanai New Materials Co., Ltd.), polyethylene oxide (PEO, Shanghai Aladdin Biochemical Technology Co., Ltd.), polyethylene glycol (PEG, Mw = 200 / 400 / 600Da, Shanghai Maclean Biochemical Technology Co., Ltd.)

[0032] Example 1: Coagulation Bath Screening

[0033] To investigate the effects of different coagulation baths on the properties of the prepared PTFE fibers, Examples 1-1 to 1-8 were conducted in this invention. The specific details of Examples 1-1 to 1-8 are as follows:

[0034] Example 1-1:

[0035] A method for preparing PTFE fibers, comprising the following steps:

[0036] (1) A 4% polyethylene oxide (PEO) solution was added to the PTFE emulsion and stirred at a stirring speed of 60 rpm for 2 hours at room temperature to obtain a spinning solution. The mass ratio of PTFE to PEO in the spinning solution was 4:1, and the molecular weight of PEO was 2,000,000.

[0037] (2) The spinning solution is injected into the coagulation bath from the spinneret and solidified at 25°C for 4 minutes to obtain nascent fibers (the production equipment for nascent fibers is as follows). Figure 1 (as shown); wherein the coagulation bath is polyethylene glycol (PEG), and the molecular weight of the PEG is 200.

[0038] (3) The nascent fibers are sintered to obtain PTFE fibers, wherein the sintering temperature is 380℃ and the sintering time is 1h.

[0039] Examples 1-2:

[0040] The contents of Examples 1-2 are basically the same as those of Examples 1-1, except that the coagulation bath used in step (2) is a saturated sodium sulfate solution.

[0041] Examples 1-3:

[0042] The contents of Examples 1-3 are basically the same as those of Examples 1-1, except that the coagulation bath used in step (2) is dichloromethane.

[0043] Examples 1-4:

[0044] The contents of Examples 1-4 are basically the same as those of Examples 1-1, except that the coagulation bath used is tetrahydrofuran.

[0045] Examples 1-5:

[0046] The contents of Examples 1-5 are basically the same as those of Examples 1-1, except that the coagulation bath used is ethylene glycol.

[0047] Examples 1-6:

[0048] The contents of Examples 1-6 are basically the same as those of Examples 1-1, except that the coagulation bath used is ethanol.

[0049] Examples 1-7:

[0050] The contents of Examples 1-7 are basically the same as those of Examples 1-1, except that the coagulation bath used is isopropanol.

[0051] Examples 1-8:

[0052] The contents of Examples 1-8 are basically the same as those of Examples 1-1, except that the coagulation bath used is N,N dimethylformamide.

[0053] The mechanical properties of the PTFE fibers prepared in Examples 1-1 to 1-8 were analyzed, and the test results are shown in Table 1.

[0054] Table 1. Mechanical property test results of PTFE fibers prepared in Examples 1-1 to 1-8

[0055]

[0056] When using saturated sodium sulfate solution, dichloromethane, tetrahydrofuran, ethylene glycol, ethanol, isopropanol, and N,N-dimethylformamide as the coagulation bath, the spinning solution remains liquid after being injected into the coagulation bath and cannot coagulate to form nascent fibers, leading to experimental failure and the inability to obtain PTFE fibers. Table 1 shows that only when PEG is used as the coagulation bath can PTFE fibers with high tensile strength and high elongation at break be obtained. Therefore, PEG is the preferred coagulation bath.

[0057] Example 2: PEG molecular weight screening in coagulation bath

[0058] To investigate the effect of PEG molecular weight in the coagulation bath on the properties of the prepared PTFE fibers, Examples 2-1 and 2-2 were conducted in this invention. The specific details of Examples 2-1 and 2-2 are as follows:

[0059] Example 2-1:

[0060] The content of Example 2-1 is basically the same as that of Example 1-1, except that the molecular weight of PEG in step (2) is 400.

[0061] Example 2-2:

[0062] The content of Example 2-2 is basically the same as that of Example 1-1, except that the molecular weight of PEG in step (2) is 600.

[0063] The microstructure of the PTFE fibers prepared in Examples 2-1 to 2-2 and Example 1-1 was analyzed by scanning electron microscopy, and the fiber diameters were statistically analyzed. The results are as follows: Figure 2 , Figure 3 As shown.

[0064] Depend on Figure 2 and Figure 3 It can be seen that PTFE fibers with a diameter of 10-180μm can be prepared when polyethylene glycol with a molecular weight of 200, 400 or 600 is used as the coagulation bath; however, when PEG200 is used as the coagulation bath, the prepared PTFE fibers are uniform, have the smallest diameter (10μm) and have a smooth surface without obvious impurities.

[0065] The mechanical properties of the PTFE fibers prepared in Examples 2-1 to 2-2 and Example 1-1 were analyzed, and the results are shown in Table 2 and 2-3. Figure 4 As shown.

[0066] Table 2. Mechanical property test results of PTFE fibers prepared in Examples 2-1 to 2-2

[0067]

[0068] From Table 2 and Figure 4 It is known that when PEG200 is used as the coagulation bath, the fiber diameter is the smallest and the mechanical properties are the best. Therefore, PEG200 is the preferred coagulation bath.

[0069] Example 3: PTFE to PEO mass ratio screening

[0070] To investigate the effect of the PTFE to PEO mass ratio on the properties of the prepared PTFE fibers, Examples 3-1 to 3-5 were conducted in this invention. The specific details of Examples 3-1 to 3-5 are as follows:

[0071] Example 3-1:

[0072] The content of Example 3-1 is basically the same as that of Example 1-1, except that in step (1), the mass ratio of PTFE and PEO in the spinning solution is 1:1.

[0073] Example 3-2:

[0074] The content of Example 3-2 is basically the same as that of Example 1-1, except that in step (1), the mass ratio of PTFE and PEO in the spinning solution is 2:1.

[0075] Example 3-3:

[0076] The content of Example 3-3 is basically the same as that of Example 1-1, except that in step (1), the mass ratio of PTFE and PEO in the spinning solution is 3:1.

[0077] Examples 3-4:

[0078] The contents of Examples 3-4 are basically the same as those of Examples 1-1, except that in step (1), the mass ratio of PTFE to PEO in the spinning solution is 5:1.

[0079] Examples 3-5:

[0080] The contents of Examples 3-5 are basically the same as those of Examples 1-1, except that in step (1), the mass ratio of PTFE to PEO in the spinning solution is 6:1.

[0081] The mechanical properties of the PTFE fibers prepared in Examples 3-1 to 3-5 were analyzed, and the test results are shown in Table 3.

[0082] Table 3. Mechanical property test results of PTFE fibers prepared in Examples 3-1 to 3-5

[0083]

[0084] As shown in Table 3, PTFE fibers can be prepared when the mass ratio of PTFE to PEO is (1-6):1. The elongation at break of PTFE fibers can reach more than 220%. As the mass ratio of PTFE to PEO increases, the tensile strength of PTFE fibers shows a trend of first increasing and then decreasing.

[0085] Example 4: PEO molecular weight screening

[0086] To investigate the effect of PEO molecular weight on the properties of the prepared PTFE fibers, Examples 4-1 to 4-3 were conducted in this invention. The specific details of Examples 4-1 to 4-3 are as follows:

[0087] Example 4-1:

[0088] The content of Example 4-1 is basically the same as that of Example 1-1, except that the molecular weight of PEO in step (1) is 600,000.

[0089] Example 4-2:

[0090] The content of Example 2-2 is basically the same as that of Example 1-1, except that the molecular weight of PEO in step (2) is 1,000,000.

[0091] Example 4-3:

[0092] The content of Example 4-3 is basically the same as that of Example 1-1, except that the molecular weight of PEO in step (2) is 5,000,000.

[0093] The mechanical properties of the PTFE fibers prepared in Examples 4-1 to 4-3 were analyzed, and the test results are shown in Table 4.

[0094] Table 4. Mechanical property test results of PTFE fibers prepared in Examples 4-1 to 4-3

[0095]

[0096] As shown in Table 4, the tensile strength and elongation at break of the prepared PTFE fiber reached their highest values ​​when the molecular weight of PEO was 2,000,000. Therefore, the preferred molecular weight of PEO is 2,000,000.

[0097] Example 5:

[0098] The content of Example 5 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 30°C for 5 minutes to obtain nascent fibers; in step (3), the sintering temperature is 350°C and the sintering time is 5 hours.

[0099] Example 6:

[0100] The content of Example 6 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 10°C for 6 minutes to obtain nascent fibers; in step (3), the sintering temperature is 400°C and the sintering time is 1 hour.

[0101] Example 7:

[0102] The content of Example 7 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 40°C for 4 minutes to obtain nascent fibers; in step (3), the sintering temperature is 380°C and the sintering time is 2 hours.

[0103] Example 8:

[0104] The content of Example 8 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 60°C for 4 minutes to obtain nascent fibers; in step (3), the sintering temperature is 360°C and the sintering time is 3 hours.

[0105] Example 9:

[0106] The content of Example 9 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 50°C for 4 minutes to obtain nascent fibers; in step (3), the sintering temperature is 380°C and the sintering time is 3 hours.

[0107] Example 10:

[0108] The content of Example 10 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 70°C for 4 minutes to obtain nascent fibers; in step (3), the sintering temperature is 350°C and the sintering time is 4 hours.

[0109] Example 11:

[0110] The content of Example 11 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 80°C for 3 minutes to obtain nascent fibers; in step (3), the sintering temperature is 370°C and the sintering time is 1 hour.

[0111] Example 12:

[0112] The content of Example 12 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 90°C for 3 minutes to obtain nascent fibers; in step (3), the sintering temperature is 380°C and the sintering time is 3 hours.

[0113] Example 13:

[0114] The content of Example 13 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 100°C for 2 minutes to obtain nascent fibers; in step (3), the sintering temperature is 360°C and the sintering time is 1 hour.

[0115] Example 14:

[0116] The content of Example 14 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 20°C for 5 minutes to obtain nascent fibers; in step (3), the sintering temperature is 350°C and the sintering time is 3 hours.

[0117] Example 15:

[0118] The content of Example 15 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 35°C for 4 minutes to obtain nascent fibers; in step (3), the sintering temperature is 380°C and the sintering time is 1 hour.

[0119] Example 16:

[0120] The content of Example 16 is basically the same as that of Example 1-1, except that: in step (2), the spinning solution is injected into the coagulation bath from the spinneret and solidified at 55°C for 4 minutes to obtain nascent fibers; in step (3), the sintering temperature is 380°C and the sintering time is 2 hours.

[0121] The above embodiments are intended to illustrate the essential content of the present invention, but are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of protection of the present invention.

Claims

1. A method for producing a PTFE fiber, characterized by, The method comprises the following steps: (1) adding polyethylene oxide into polytetrafluoroethylene emulsion, mixing uniformly to obtain spinning dope; (2) injecting the spinning dope into coagulation bath through spinneret to perform solidification treatment, and obtaining nascent fiber; (3) performing sintering treatment on the nascent fiber to obtain PTFE fiber. The coagulation bath is polyethylene glycol; the molecular weight of the polyethylene glycol is 200-600; the mass ratio of polytetrafluoroethylene to polyethylene oxide in the spinning dope is (1-6):

1.

2. The production method according to claim 1, characterized by, The solidification treatment time is 2-6 min, and the solidification treatment temperature is 10-100℃.

3. The method of any one of claims 1-2, wherein, The molecular weight of the polyethylene oxide is 600000-3000000.

4. The production method according to claim 3, characterized by, The sintering treatment temperature in step (3) is 350-400℃, and the sintering time is 1-5 h.

5. The preparation method according to claim 4, characterized in that, The content of polytetrafluoroethylene in the polytetrafluoroethylene emulsion is 60%.

6. The preparation method according to claim 4, characterized in that, The polyethylene oxide is added into the polytetrafluoroethylene emulsion in the form of polyethylene oxide solution, and the concentration of the polyethylene oxide solution is 4%.

7. A PTFE fiber product prepared by the preparation method in any of claims 1-6.

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