CN114395808B

CN114395808B - Method for preparing polytetrafluoroethylene fiber by wet spinning

Info

Publication number: CN114395808B
Application number: CN202210158684.2A
Authority: CN
Inventors: 舒溪; 李小磊; 伍德民
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-02-21
Filing date: 2022-02-21
Publication date: 2023-02-28
Anticipated expiration: 2042-02-21
Also published as: CN114395808A

Abstract

The present disclosure relates to a method for preparing polytetrafluoroethylene fibers by wet spinning, the method comprising: carrying out wet spinning and solidification on the polytetrafluoroethylene spinning solution to obtain nascent fiber, and carrying out post-treatment on the nascent fiber to obtain polytetrafluoroethylene fiber; the spinning solution also contains sodium alginate, wherein M and G are 1 (1-3). The polytetrafluoroethylene fibers are prepared by a wet spinning method, the spinning holes are not blocked after the primary fibers are solidified, the primary fibers are not adhered, the phenomenon of filament breakage is not easy to occur in the forming and washing processes, continuous spinning can be realized, and the micron-sized polytetrafluoroethylene fibers can be obtained finally.

Description

Method for preparing polytetrafluoroethylene fiber by wet spinning

Technical Field

The disclosure relates to the technical field of wet spinning, in particular to a method for preparing polytetrafluoroethylene fibers by using wet spinning, and particularly relates to a method for preparing polytetrafluoroethylene fibers by using wet spinning and micron-sized polytetrafluoroethylene fibers obtained by the method.

Background

The polytetrafluoroethylene has outstanding chemical stability, excellent high and low temperature performance and corrosion resistance, and is widely applied to the industrial fields of chemical industry, petroleum, textile, electronics, machinery and the like. Meanwhile, due to the strong hydrophobicity and the porous performance of the polytetrafluoroethylene, the polytetrafluoroethylene becomes an ideal material for preparing the waterproof breathable textile fiber.

The "insoluble, infusible" nature of polytetrafluoroethylene makes it poorly processable and cannot be formed into fibers or hollow fiber membranes by conventional solution and melt spinning. At present, carrier spinning is one of the main methods for industrially producing polytetrafluoroethylene fibers, and carrier spinning is generally to mix polytetrafluoroethylene emulsion with carriers such as viscose or polyvinyl alcohol aqueous solution to prepare spinning solution, and the finished polytetrafluoroethylene fibers are prepared by spinning, gelling, washing, drying, sintering and stretching the spinning solution.

CN106669465A discloses a polytetrafluoroethylene hollow fiber membrane, which is prepared by utilizing methods such as electrostatic spinning and sintering after preparing a spinning solution. For the polytetrafluoroethylene, the preparation methods of hollow fiber membranes are studied more frequently, and few researches are made on how to prepare polytetrafluoroethylene fibers, and the only researches include the following patents: CN103882541A discloses a polytetrafluoroethylene fiber and a hollow fiber membrane, and a preparation method and application thereof, wherein alginate is used as a carrier, dry-wet spinning is adopted to prepare a finished product of the polytetrafluoroethylene fiber or the hollow fiber membrane, and then a series of post-treatments are carried out to obtain the finished product of the polytetrafluoroethylene fiber. Although this patent application uses so-called dry-wet spinning to produce polytetrafluoroethylene fibers, the final finished fibers have too large a diameter, above 1.0mm, and can only be used in the textile industry, etc.

Therefore, there is a need for a method of preparing polytetrafluoroethylene fibers on a micron scale.

Disclosure of Invention

In order to solve the technical problems, the disclosure provides a method for preparing polytetrafluoroethylene fibers by using wet spinning, the polytetrafluoroethylene fibers are prepared by using the wet spinning method, spun fibers are solidified without blocking spinneret holes, the spun fibers are not adhered, meanwhile, the phenomenon of yarn breakage is not easy to occur in the drafting process, continuous spinning can be realized, and finally, micron-sized polytetrafluoroethylene fibers can be obtained.

In a first aspect, the present disclosure provides a method for preparing polytetrafluoroethylene fibers by wet spinning, the method comprising: carrying out wet spinning and solidification on the polytetrafluoroethylene spinning solution to obtain nascent fiber, and carrying out post-treatment on the nascent fiber to obtain polytetrafluoroethylene fiber;

the spinning solution also contains sodium alginate, wherein M is G and G is 1 (1-3).

As a preferred technical scheme of the present disclosure, the sodium alginate has M: G =1:2.

In the method, after the spinning solution is sprayed out by a spinning nozzle, sodium alginate reacts with calcium ions (actually, the G unit in the sodium alginate reacts with the calcium ions) in a solidification forming process, under the action of the calcium ions, stable chelates can be formed among the G units, and meanwhile, intermolecular acting force is improved, so that the sodium alginate with M: G being less than or equal to 1 is specifically adopted in the method, the spatial conformation of more G units in the sodium alginate is more favorable for being combined with the calcium ions, spinning holes are not blocked after primary fibers are solidified and formed, the strength of the solidified primary fibers of the calcium alginate/polytetrafluoroethylene is higher, the fibers are not easy to break in a subsequent forming or cleaning process, continuous spinning can be realized, and the fibers with smaller diameters can be obtained.

As a preferable embodiment of the present disclosure, in the spinning solution, the mass of the sodium alginate is 5 to 20% of the mass of the polytetrafluoroethylene, for example, 6%, 8%, 10%, 12%, 15%, 18%, and the like.

In a preferred embodiment of the present disclosure, the coagulation bath used for coagulation is a calcium chloride coagulation bath, and the coagulation bath contains 1 to 3% of ethanol, preferably 1 to 2% of ethanol, based on 100% of the total mass of the coagulation bath.

The addition of a small amount of ethanol in the coagulating bath can regulate and control the ion exchange speed between fibers, improve the strength and elasticity of the fibers and enable the fibers to be better coagulated and formed.

As a preferred embodiment of the present disclosure, the post-treatment includes dispersing, drying, sintering, and stretching.

The post-treatment steps described in the present disclosure include the post-treatment of the polytetrafluoroethylene fibers, such as drying, sintering, stretching, etc., which are conventional in the art, and at the same time, a "dispersing" step is added to disperse the nascent fibers, so that the adhesion phenomenon can be avoided.

As a preferred embodiment of the present disclosure, the dispersing method includes: the nascent fibre is treated, preferably soaked, with an aluminium sulphate solution and/or white oil.

According to the method, the aluminum sulfate solution is used for treating the nascent fiber, and the carboxyl and the hydroxyl in the sodium alginate are subjected to esterification reaction to form lactone, so that the hydrophilic groups on the surface of the nascent fiber can be reduced, and the adhesion of the nascent fiber can be avoided; and the white oil is utilized to treat the nascent fibers, so that the influence of hydrogen bonds can be weakened, therefore, the dispersing method provided by the disclosure can prevent the nascent fibers from being adhered to each other, and the polytetrafluoroethylene fibers with smaller diameters can be obtained through processes such as drying and sintering.

As a preferred embodiment of the present disclosure, the mass concentration of the aluminum sulfate solution is 1 to 5%, for example, 2%, 3%, 4%, etc.

As a preferred technical solution of the present disclosure, the time of the treatment is 5-15min, such as 6min, 8min, 10min, 12min, 14min, etc., preferably 10min.

As a preferred embodiment of the present disclosure, the temperature of the treatment is room temperature.

As a preferred embodiment of the present disclosure, after the primary fiber is treated with an aluminum sulfate solution, the treated primary fiber is washed with ethanol and then dried.

According to the dispersing method provided by the disclosure, the hydrophilicity of sodium alginate can be reduced by using an aluminum sulfate solution, and the sodium alginate is washed by using ethanol, so that on one hand, redundant aluminum sulfate and moisture can be removed, on the other hand, the hydrogen bond effect of ethanol is smaller than that of water in the drying process, the influence of the hydrogen bond can be weakened, and the treated nascent fiber is easier to disperse.

As a preferred embodiment of the present disclosure, the stretching is performed at room temperature.

The method provided by the disclosure can complete stretching at room temperature, can avoid the use of a stretching heating container, and reduces the production cost.

As a specific embodiment of the present disclosure, the method includes the steps of:

(1) Mixing sodium alginate M, G of which is 1 (1-3), a defoaming agent and polytetrafluoroethylene dispersion liquid to prepare spinning solution;

(2) Spinning the spinning solution by a wet method, and forming in a calcium chloride coagulating bath containing 1-2% of ethanol to obtain nascent fiber;

(3) And dispersing the nascent fiber by using an aluminum sulfate solution and/or white oil, and then drying, sintering and stretching to obtain the polytetrafluoroethylene fiber.

As a preferable embodiment of the present disclosure, the mass concentration of the polytetrafluoroethylene in the spinning solution is 15 to 27%, for example, 16%, 18%, 20%, 22%, 24%, 26%, and the like.

In the present disclosure, the defoaming agent added to the spinning solution is a defoaming agent conventional in the art, and the addition amount is also a conventional addition amount, and is 0.03-0.27% of the mass of the polytetrafluoroethylene.

In a preferred embodiment of the present disclosure, the temperature of the coagulation bath is 20 to 70 ℃, for example, 30 ℃, 40 ℃, 50 ℃, 60 ℃, or the like.

As a preferred technical scheme of the present disclosure, the sintering temperature is 340-400 ℃, such as 350 ℃, 360 ℃, 370 ℃, 380 ℃, 390 ℃ and the like, and the sintering time is 1-10min, such as 2min, 4min, 6min, 8min and the like.

As a preferable embodiment of the present disclosure, the stretching ratio is 2 to 10 times, for example, 2 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, etc., preferably 6 to 7 times.

In a second aspect, the present disclosure provides a polytetrafluoroethylene fiber produced by the method of the first aspect.

The polytetrafluoroethylene fiber with the diameter in the micron order prepared by the method provided by the disclosure is a preferable technical scheme of the disclosure, the diameter of the polytetrafluoroethylene fiber is below 50 μm, preferably 20-40 μm, and the diameter is an average diameter.

Compared with the prior art, the technical scheme provided by the embodiment of the disclosure has the following advantages:

(1) The method provided by the disclosure can obtain the nascent fiber with higher strength, so that the filament breakage in the subsequent forming and washing processes can be ensured to be difficult, and the continuous spinning is realized;

(2) Meanwhile, ethanol is added into the coagulating bath, and aluminum sulfate solution and/or white oil is/are adopted for dispersion in the subsequent process, so that the adhesion among nascent fibers can be avoided, and the polytetrafluoroethylene fibers with smaller diameters can be obtained;

(3) The polytetrafluoroethylene fiber with the diameter of micron order can be successfully prepared by adopting the method provided by the disclosure, and the diameter of the polytetrafluoroethylene fiber can be as small as 20-40 mu m.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure.

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present disclosure, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.

FIG. 1 is a metallographic optical microscope photograph of a polytetrafluoroethylene fiber obtained in example 1;

FIG. 2 is a metallographic optical microscope photograph of a polytetrafluoroethylene fiber obtained in example 2;

FIG. 3 is a metallographic optical microscope photograph of the polytetrafluoroethylene fiber obtained in example 3;

FIG. 4 is a metallographic optical microscope photograph of the polytetrafluoroethylene fiber obtained in comparative example 1;

FIG. 5 is a metallographic optical microscope photograph of the polytetrafluoroethylene fiber obtained in comparative example 2;

FIG. 6 is a metallographic optical microscope photograph of the polytetrafluoroethylene fiber obtained in comparative example 3.

Detailed Description

In order that the above objects, features and advantages of the present disclosure may be more clearly understood, aspects of the present disclosure will be further described below. It should be noted that the embodiments and features of the embodiments of the present disclosure may be combined with each other without conflict.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure, but the present disclosure may be practiced in other ways than those described herein; it is to be understood that the embodiments disclosed in the specification are only a few embodiments of the present disclosure, and not all embodiments.

The diameters of the polytetrafluoroethylene fibers obtained in the following examples were determined using metallographic optical microscope test software by a method comprising: the proportion is determined according to a given scale, then a correct scale is selected according to the magnification of the ocular lens and the objective lens, and the diameter of the fiber is directly determined through measuring the distance between two points by test software.

Example 1

This example provides a method for preparing polytetrafluoroethylene fibers using wet spinning.

(1) Dissolving 6G of sodium alginate (G is 1:2) in 194G of deionized water at 70 ℃, cooling to room temperature, adding 0.1G of a non-ionic organic silicon defoamer and 120G of a polytetrafluoroethylene dispersion liquid (the mass fraction of the polytetrafluoroethylene dispersion liquid is 60 percent, namely 120G of the polytetrafluoroethylene dispersion liquid contains 72G of polytetrafluoroethylene), and mixing to prepare a spinning solution with the mass concentration of the polytetrafluoroethylene being 22.5 percent;

(2) Spinning the spinning solution by a wet method at the spinning temperature of 25 ℃ and the pore diameter of a spinneret orifice of 70 mu m, and then forming in a calcium chloride coagulating bath containing 1% by mass of ethanol at the temperature of 25 ℃ to obtain nascent fiber;

(3) And (2) washing the nascent fiber, dispersing by using an aluminum sulfate solution with the concentration of 2%, then washing by using ethanol, finally drying at 100 ℃, sintering at 360 ℃ for 5min, and stretching the sintered fiber in a normal-temperature air medium by the stretching multiple of 6 to obtain the polytetrafluoroethylene fiber.

FIG. 1 is a metallographic optical microscope photograph of the polytetrafluoroethylene fiber obtained in this example, and it can be seen that the diameter of the polytetrafluoroethylene fiber prepared in this example was 23.14. Mu.m.

Example 2

The difference from example 1 is that in this example, the dispersion was carried out with white oil.

FIG. 2 is a metallographic optical microscope photograph of the polytetrafluoroethylene fiber obtained in this example, and it can be seen that the diameter of the polytetrafluoroethylene fiber obtained in this example was 36.88. Mu.m.

Example 3

The difference from example 1 is that in this example, no ethanol was added to the coagulation bath.

In this example, when no ethanol was added to the coagulation bath, the phenomenon of uneven sintering on the fiber surface was increased, and it was found from the comparison between example 1 and example 3 that the addition of ethanol to the coagulation bath can control the ion exchange rate between fibers, so that the exchange rate tended to be mild, and the fiber surface after sintering was more uniform.

FIG. 3 is a metallographic optical microscope photograph of the polytetrafluoroethylene fiber obtained in this example, and it can be seen that the diameter of the polytetrafluoroethylene fiber finally obtained in this example is 35.33. Mu.m.

Example 4

(1) Dissolving 6G of sodium alginate (M: G is 1:2) in 254G of deionized water at 70 ℃, cooling to room temperature, adding 0.1G of nonionic organic silicon defoamer and 90G of polytetrafluoroethylene dispersion, and mixing to prepare spinning solution with the mass concentration of polytetrafluoroethylene being 26.9%;

(2) Spinning the spinning solution by a wet method at the spinning temperature of 25 ℃ and the pore diameter of a spinneret orifice of 70 mu m, and then forming in a calcium chloride coagulating bath at the temperature of 40 ℃ and containing 2 mass percent of ethanol to obtain nascent fiber;

(3) And (3) washing the nascent fiber, dispersing by using an aluminum sulfate solution with the concentration of 4%, then washing by using ethanol, finally drying at 100 ℃, sintering at 400 ℃ for 4min, and stretching the sintered fiber in a normal-temperature air medium by the stretching multiple of 7 times to obtain the polytetrafluoroethylene fiber with the diameter of 26.59 mu m.

Comparative examples 1 to 2

This comparative example provides a method of preparing polytetrafluoroethylene fibers using wet spinning.

The difference from example 1 is that the sodium alginate used in this comparative example is commercially available sodium alginate of chemically pure general type (comparative example 1), M: G =2:1 (comparative example 2).

The performance of the finally obtained fiber is determined by a sintering process and polytetrafluoroethylene, but the mechanical property of the nascent fiber is mainly provided by sodium alginate serving as a carrier, and the chemically pure sodium alginate and the two types of sodium alginate with the M: G =2:1 have small content of G units and limited combination with calcium ions, so that in the comparative example, no matter the sodium alginate provided in the comparative example 1 or the comparative example 2 is adopted, the fiber formed in the processes of solidification and water washing is very easy to break during wet spinning, the blockage of a spinning nozzle is caused, and the continuous spinning cannot be realized.

Meanwhile, the filament breakage phenomenon can cause that continuous filaments cannot be obtained, and further the subsequent drying and stretching process cannot be conveniently carried out, so that the polytetrafluoroethylene fibers finally obtained in comparative examples 1-2 are not subjected to the stretching process, and fig. 4-5 are metallographic optical microscope images of the polytetrafluoroethylene fibers obtained in comparative examples 1-2 respectively, and it can be seen from the images that the diameters of the fibers provided in comparative examples 1-2 are all about 80 μm.

Comparative example 3

The difference from example 1 is that no dispersing step is included in this comparative example, i.e. the following step is carried out directly after step (2):

(3') drying the nascent fiber at 100 ℃, sintering at 360 ℃ for 5min, and stretching the sintered fiber in a normal-temperature air medium by a stretching ratio of 6 times to obtain the polytetrafluoroethylene fiber.

FIG. 6 is a metallographic optical microscope photograph of a polytetrafluoroethylene fiber obtained in this comparative example, and it can be seen from FIG. 6 that although the diameter of the finally obtained fiber was about 31.2 μm, the fiber was sticky and could not be used for subsequent applications; the reason why the adhesion occurs is presumed to be that alginate has a large amount of hydroxyl and carboxyl, the hydrophilicity is strong, the primary fiber is solidified, hydrogen bonds are formed between water molecules and alginate, and intermolecular hydrogen bonds are formed with other water molecules, so that a large hydrogen bond association structure is formed, if the primary fiber is not subjected to dispersion treatment, the fibers gradually get close in the volatilization process of the water molecules on the surface of the primary fiber, the fiber adhesion is caused, and the silk doubling phenomenon occurs after sintering.

As can be seen from the examples and fiber characterization, the methods provided by the present disclosure can yield polytetrafluoroethylene fibers having diameters of 20-40 μm; meanwhile, in the preparation process, the spinning holes are not blocked after the nascent fiber is solidified and formed, the nascent fiber is not adhered after being dispersed, the strength is high, the filament is not easy to break in the stretching process, and the continuous spinning can be realized.

As can be seen from the comparison of example 1 and comparative examples 1-2, the fibers of the present disclosure specifically preferred M: G =1:2, resulted in nascent fibers having higher strength, less tendency to filament breakage during subsequent forming or washing, enabled continuous spinning, and resulted in fibers having smaller diameters. As can be seen from the comparison between example 1 and comparative example 3, the nascent fiber needs to be dried, stretched, etc. after dispersion treatment to ensure that the nascent fiber is not bonded during post-treatment.

It is noted that, in this document, relational terms such as "first" and "second," and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element.

The foregoing are merely exemplary embodiments of the present disclosure, which enable those skilled in the art to understand or practice the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing polytetrafluoroethylene fibers by wet spinning, which is characterized by comprising the following steps: carrying out wet spinning and solidification on the polytetrafluoroethylene spinning solution to obtain nascent fibers, and carrying out post-treatment on the nascent fibers to obtain polytetrafluoroethylene fibers;

the spinning solution also contains sodium alginate, wherein M is G which is 1 (1-3);

the coagulation bath used for coagulation is a calcium chloride coagulation bath, and the coagulation bath contains 1-3% of ethanol based on 100% of the total mass of the coagulation bath;

the post-treatment comprises dispersing, drying, sintering and stretching, and the dispersing method comprises the following steps: the nascent fiber is treated with an aluminum sulfate solution and/or white oil.

2. The method of claim 1, wherein the sodium alginate has M: G =1:2;

and/or in the spinning solution, the mass of the sodium alginate is 5-20% of that of the polytetrafluoroethylene.

3. The method according to claim 1, wherein the coagulation bath contains 1-2% of ethanol based on 100% of the total mass of the coagulation bath.

4. The method according to claim 1, characterized in that the mass concentration of the aluminum sulfate solution is 1-5%.

5. The method according to claim 1, wherein the dispersion time is 5-15 min.

6. The method of claim 1, wherein the temperature of the dispersion is room temperature.

7. The method of claim 1, wherein after treating the virgin fiber with the aluminum sulfate solution, the treated virgin fiber is washed with ethanol and then dried.

8. The method of claim 1, wherein the stretching is performed at room temperature.

9. The process according to claim 1, wherein the mass concentration of the polytetrafluoroethylene in the spinning dope is 15 to 27%;

and/or the temperature of the coagulating bath is 20-70 ℃;

and/or, the sintering temperature is 340-400 ℃, and the sintering time is 1-10 min;

and/or the stretching ratio is 2-10 times.

10. The method of claim 9, wherein the stretching is by a factor of 6 to 7.

11. Polytetrafluoroethylene fibers produced by the process of any of claims 1-10.

12. The polytetrafluoroethylene fiber according to claim 11, wherein the polytetrafluoroethylene fiber has a diameter of less than 50 μm.

13. The polytetrafluoroethylene fiber according to claim 12 wherein the polytetrafluoroethylene fiber has a diameter of 20-40 μm.