High-stability fiber and method for producing the same

Abstract

The present invention relates to a highly stable fiber and a method for producing the same. The method includes: (1) continuously adding α-olefin to the polymerization process of ultra-high molecular weight polyethylene to form a branched-modified ultra-high molecular weight polyethylene resin; (2) continuously adding ethylene monomer to the polymerization process of α-olefin to form a poly-α-olefin resin with sparse branched chains; and (3) mixing the branched-modified ultra-high molecular weight polyethylene resin obtained in step (1) and the poly-α-olefin resin with sparse branched chains obtained in step (2), spinning the mixture, and obtaining the fiber by winding. Compared to the prior art, the product of the present invention has good spinnability in the spinning process, the fiber has mechanical strength and elastic modulus comparable to ultra-high molecular weight polyethylene fibers of the same grade, and has excellent morphological stability in the usage environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of processing and manufacturing of polymer materials, relates to ultra-high molecular weight polyethylene fibers, and particularly relates to high-stability fibers and a manufacturing method thereof.

Background Art

[0002] Among the world's three major high-performance fibers, ultra-high molecular weight polyethylene fiber (UHMWPE fiber) is the fiber with the highest specific strength among the currently known industrial fiber materials, and has excellent properties such as high strength, wear resistance, and chemical corrosion resistance. It is widely used in fields such as bulletproof vests, personal protective equipment, and ropes for ocean engineering. However, due to its poor morphological stability performance, it has become the biggest obstacle in its long-term use scenario, which is related to the behavior that its long chains are prone to creep. Currently, the normal temperature creep deformation rate of general ultra-high molecular weight polyethylene fibers is 3.2% - 3.8% (normal temperature). In order to meet the high requirements for creep properties in some special fields such as ropes for ocean engineering, many domestic and foreign enterprises are working on research and development and breakthroughs in improving the creep resistance of UHMWPE fibers. Therefore, many research projects aimed at improving UHMWPE fibers focus on its creep behavior, and most of these projects only focus on optimizing the fiber creep rate by the processing process, and there are limitations in improving the morphological stability.

[0003] UHMWPE fiber is a fiber composed of long chains of linear polyethylene, is similar to high-density polyethylene, is a long-chain non-polar polymer, and has almost no branched chains. Therefore, the intermolecular force is weak, and it interacts only by van der Waals force, and creep behavior due to the slippage of molecular chains under load is likely to occur. Such inherent structural defects are difficult to compensate by optimizing means of the spinning process, and the modification of UHMWPE fibers by conventional technologies mainly includes the following three types.

[0004] 1. Direct modification of UHMWPE fibers, such as by radiation, ultraviolet light, or electron beams, directly affects the fibers and increases the degree of inter-fiber entanglement. However, this method has drawbacks; the fibers are damaged during the modification process, resulting in serious strength loss.

[0005] 2. Modifiers, inorganic materials (graphene, silica, etc.), or branched organic polymers (e.g., various poly-α-olefins) are added during the spinning process. However, the addition of additives affects the spinnability of the fibers, and the improvement effect is not significant, especially with α-olefins, as they account for a small proportion and have a small number of branched chains. Increasing the amount added significantly reduces the mechanical strength of the fibers.

[0006] 3. The molecular weight of UHMWPE itself is modified, and branched chains are added, for example, by copolymerization. However, this method has the drawback that if the amount added is small, the effect is not significant, and if the amount added is large, the spinnability is greatly reduced.

[0007] Patent CN202010061198.X discloses a method for producing creep-resistant ultra-high molecular weight polyethylene fibers. This method involves adding linear α-olefins to the polymerization process of ultra-high molecular weight polyethylene resin to increase the branching degree of the resin, mixing the resulting resin spinning solvent to prepare a homogeneous spinning solution, swelling it, placing it in a twin-screw extruder, extruding it through a spinneret in a spinning box, removing the solvent to obtain primary fibers, and then obtaining the fibers by super-magnification stretching and winding. While this technique improves the creep resistance of the fibers to some extent, the general method of copolymerizing with α-olefins presents two problems. When the branching degree is low, the improvement in creep resistance of the fibers is very limited, and in particular, the performance of the fibers at relatively high temperatures is very poor. Furthermore, temperature is a very important environmental factor in the use of creep-resistant fibers. Although the specific test temperature is not mentioned in this technique, the test is conducted at room temperature, whereas in the present invention it is conducted at relatively high temperatures, making the effect of temperature on creep very important. Furthermore, a high degree of branching can lead to problems such as a significant decrease in the performance of the fiber molding process and the final strength due to the imperfection of the crystal structure. [Overview of the project]

[0008] The object of the present invention is to provide a highly stable fiber and a method for producing the same, which overcomes the drawbacks of the above-mentioned prior art by performing a branching treatment on the fiber molecular chain itself, guaranteeing the mechanical properties of the obtained fiber, and solving the problem of creep resistance of the fiber.

[0009] The object of the present invention can be achieved by the following technical means.

[0010] A method for producing highly stable fibers is: In the polymerization process of ultra-high molecular weight polyethylene, step (1) involves continuously adding α-olefins to form a branched-modified ultra-high molecular weight polyethylene resin, In the polymerization process of α-olefins, step (2) involves continuously adding ethylene monomers to form a poly-α-olefin resin with sparse branched chains, The process includes step (3), which involves mixing the branched-modified ultra-high molecular weight polyethylene resin obtained in step (1) with the branched-chain-sparse poly-α-olefin resin obtained in step (2), spinning the mixture, and then winding the resulting fibers.

[0011] Furthermore, the α-olefin monomer includes one or more of the following: a C3-C8 linear α-olefin, isobutylene with a tertiary or quaternary carbon, 4-methyl-1-pentene, and 6-methyl-1-heptene.

[0012] Furthermore, in the polymerization process of step (1), ethylene and α-olefin are mixed in a molar ratio of 100 to 100,000:1, α-olefin is continuously added, and under the action of a catalyst and solvent oil, the reaction pressure is controlled to 0.1 to 10.0 MPa, the reaction temperature is controlled to 30 to 120°C, and the reaction is carried out for 0.5 to 5 hours to obtain a branched modified ultra-high molecular weight polyethylene resin.

[0013] Furthermore, the solvent oil includes gasoline, n-heptane, hexane and / or isobutane. The catalyst includes metallocene catalysts, single-site catalysts, chromium-based catalysts, and / or Ziegler-Natta catalysts.

[0014] Furthermore, the mass ratio of ethylene, solvent oil, and catalyst is 80-120:80-200:0.01-0.5.

[0015] Furthermore, in the polymerization process of step (2), ethylene and α-olefin are mixed in a molar ratio of 1:100 to 100,000, ethylene is continuously added, and under the action of a catalyst and solvent oil, the reaction pressure is controlled to 0.1 to 10.0 MPa, the reaction temperature is controlled to 30 to 120°C, and the reaction is carried out for 0.5 to 5 hours to obtain a branched modified ultra-high molecular weight polyethylene resin.

[0016] Furthermore, the mass ratio of the α-olefin, solvent oil, and catalyst is 80-120:80-200:1-10.

[0017] More preferably, in step 1), the molar ratio of ethylene to α-olefin is 100 to 100,000:1, preferably 20,000 to 50,000:1, and in step 2), the molar ratio of ethylene to α-olefin is 1:100 to 100,000, preferably 1:10,000 to 50,000.

[0018] Furthermore, in step (3), the mass ratio of the branched-modified ultra-high molecular weight polyethylene resin to the branched-chain sparse poly-α-olefin resin is 15-20:1.

[0019] Furthermore, the spinning described in step (3) is wet spinning, the spinning pre-swelling treatment temperature is 80-100°C, and the treatment time is 1-2 hours. The total extension ratio is between 200 and 250 times.

[0020] The present invention provides a highly stable fiber manufactured by the method described above.

[0021] Compared to the prior art, the present invention has the following advantages and beneficial effects.

[0022] (1) The present invention synthesizes a branched-modified ultra-high molecular weight polyethylene resin and a poly-α-olefin resin with sparsed branched chains using a two-step independent polymerization method, mixes the obtained resins, spins them, and obtains fibers by winding. In short, two types of polyethylene resins with different micromolecular structures are obtained: "branched-modified polyethylene long chains" and "modified poly-α-olefin long chains with sparsed branched chains." Poly-α-olefins have stronger intermolecular bonding ability than polyethylene chains, and the branched and side chains in the long chains are more controllable than single branching modification, making the polymerization process easier to implement. Researchers found the following in the research process: Fiber creep has two stages: instantaneous deformation when a load is applied (stage 1) and gradual deformation under continuous load (stage 2). A single branched polyethylene molecular chain is difficult to spin due to its molecular chain conformation, limiting the improvement of creep resistance and contributing little to the morphological stability of the fiber at relatively high temperatures. By mixing and compounding the two types of polyolefin long chains used in the present invention, the superior deformation resistance of branched polyethylene fibers in the first creep stage and the superior deformation resistance of poly-α-olefin fibers in the second creep stage can be comprehensively utilized to improve the creep resistance of the fiber.

[0023] (2) Technical effects of the product: The obtained high-stability fiber has 100% morphological stability under conditions of 50°C or below and a breaking load of 80% or below, and three times the morphological stability of conventional polyethylene fiber under conditions of 60°C or below and a breaking load of 50% or below, and the elongation is 15% or less under test conditions of 70°C or below, a breaking load of 300 MPa or below, and 10% or less under test conditions of 400 hours.

[0024] (3) Technical effects of the manufacturing process: The present invention has good spinnability in the spinning process, the fibers have mechanical strength and elastic modulus comparable to ultra-high molecular weight polyethylene fibers of the same grade, and have excellent morphological stability in the usage environment. [Modes for carrying out the invention]

[0025] Hereinafter, embodiments of the present invention will be described in detail. These embodiments are implemented on the premise of the technical means of the present invention and provide detailed embodiments and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0026] The raw materials and equipment used in the present invention are all commercially available products unless otherwise specified.

[0027] The test method for the morphological stability of fibers is to test the linear density of the fibers according to GB / T14343-2008, test the mechanical properties of the fibers according to GB / T19975-2005, and after obtaining the breaking strength of the fibers, conduct the test under the constant load tension conditions of a load of 300 Mpa, a chuck distance of 50 cm, and 400 h to obtain the value of the deformation rate of the fibers.

[0028] (Example 1) The production of highly stable polyolefin fibers includes the following steps.

[0029] (1) Production of branched and modified ultra-high molecular weight polyethylene resin The reaction kettle was heated to 90 °C, evacuated, and then replaced with nitrogen.

[0030] 1 L of n-heptane (solvent), 20 mg of polyethylene catalyst (in this example, SLD-UH01 type catalyst of Shanghai Lide Catalyst Co., Ltd. is used), and C4-C6 α-olefin (in this example, hexene) were added to the kettle.

[0031] Under stirring conditions, ethylene and hexene were continuously added to the reaction kettle at a molar ratio of 50000:1, the pressure was controlled at 6.5 MPa, the reaction temperature was maintained at 70 °C, the stirring speed was set at 800 r / min, and the reaction time was 2 hours.

[0032] After the reaction was completed, it was quickly cooled to room temperature, and the solvent oil was filtered off to obtain ultra-high molecular weight polyethylene resin with a predetermined degree of branching.

[0033] (2) Production of modified poly-α-olefin resin with sparsified branched chains In a separate reaction vessel, the process of step (1) was repeated, but this time using C3-C8 α-olefins (n-butene in this example) and a corresponding amount of ethylene, with a molar ratio of n-butene to ethylene of 100:1.

[0034] Under the same polymerization conditions, a modified poly-α-olefin resin with sparse branched chains was obtained.

[0035] (3) Manufacturing of high-stability fibers The two resins produced in steps (1) and (2) were mixed in a ratio of 15:1, and a spinning solution containing 8 wt% resin was prepared using paraffin oil as a solvent, and gel spinning was performed.

[0036] The spinning pre-swelling treatment temperature was set to 85°C, and the treatment time was set to 1 hour.

[0037] After extraction and drying, the fibers were subjected to four stages of ultra-high-magnification stretching, reaching a total stretching ratio of 200 times, forming highly stable fibers.

[0038] The final obtained fibers were tested under constant load tensile conditions of 70°C, 300 MPa load, 50 cm chuck distance, and 400 hours. The deformation elongation was 1.5%, the breaking strength of the fibers reached 35 cN / dtex, and the breaking modulus was 1250 cN / dtex.

[0039] The above examples illustrate a detailed manufacturing process for high-stability polyolefin fibers, including resin synthesis, mixing, and fiber stretching and testing. This process enables the production of fibers with excellent dimensional stability and high strength, making them suitable for various industrial and commercial applications.

[0040] (Example 2) The production of highly stable polyolefin fibers using an improved process includes the following steps:

[0041] (1) Production of branched modified ultra-high molecular weight polyethylene resin Step (1) of Example 1 was repeated in the reaction vessel, but the molar ratio of ethylene to hexene was adjusted to 40,000:1 and the reaction time was extended to 2 hours.

[0042] (2) Production of modified poly-alpha-olefin resin with sparse branched chains The procedure was carried out according to step (2) of Example 1, but in this example, 4-methyl-1-pentene was used as the α-olefin, and the molar ratio of ethylene to 4-methyl-1-pentene was adjusted to 1:12000.

[0043] (3) Manufacturing of high-stability fibers The two types of resins obtained in steps (1) and (2) were mixed in a ratio of 15:1, and step (3) of Example 1 was carried out, but the resin content in the spinning solution was increased to 10 wt%.

[0044] The spinning pre-swelling treatment temperature was adjusted to 95°C, and the treatment time was set to 1.5 hours.

[0045] The stretching process was adjusted to a three-stage ultra-high magnification stretching, resulting in a total stretching magnification of 220 times.

[0046] After the initial test, the obtained fibers were subjected to constant load tensile conditions of 300 MPa, a chuck distance of 50 cm, and 400 h. The deformation elongation was 0.95%, the breaking strength of the fibers reached 36 cN / dtex, and the breaking modulus was 1300 cN / dtex.

[0047] (Example 3) In step (1), 4-methyl-1-pentene was used as an α-olefin, and ethylene and 4-methyl-1-pentene were polymerized in a molar ratio of 3000:1 for a reaction time of 1.6 hours to obtain a branched modified ultra-high molecular weight polyethylene resin. In step (2), ethylene and n-butene were polymerized in a molar ratio of 1:56000 to obtain a modified poly-α-olefin resin with sparse branched chains.

[0048] Two types of resin were mixed in a ratio of 19:1, resulting in a total resin content of 10 wt% in the spinning solution. The spinning temperature was set to 94°C, and the processing time was 1.2 hours. The draw ratio was set to 240 times.

[0049] The rest is the same as in Example 1.

[0050] The test results showed that the obtained fibers had a deformation elongation of 10.0%, a breaking strength of 36 cN / dtex, and a breaking modulus of 1295 cN / dtex.

[0051] (Example 4) Ethylene and 6-methyl-1-heptene were polymerized in a molar ratio of 81,000:1, with a reaction time of 3.0 hours, to obtain a branched-modified ultra-high molecular weight polyethylene resin. Additionally, ethylene and isobutylene were polymerized in a molar ratio of 1:20,000 to obtain a modified poly-α-olefin resin with sparsely branched chains.

[0052] Two types of resin were mixed in a ratio of 18:1, resulting in a total resin content of 9 wt% in the spinning solution. The spinning temperature was set to 90°C, and the processing time was 1.3 hours. The draw ratio was set to 235 times.

[0053] The rest is the same as in Example 1.

[0054] The obtained fibers had a deformation elongation of 6.7%, a breaking strength of 36.2 cN / dtex, and a breaking modulus of 1280 cN / dtex.

[0055] (Example 5) Ethylene and isobutylene were polymerized in a molar ratio of 100:1 for a reaction time of 1.9 hours to obtain a branched-modified ultra-high molecular weight polyethylene resin. Furthermore, a modified poly-α-olefin resin with sparse branched chains was obtained by polymerizing ethylene and n-hexene in a molar ratio of 1:5000.

[0056] Two types of resin were mixed in a ratio of 20:1, resulting in a total resin content of 8 wt% in the spinning solution. The spinning temperature was set to 97°C, and the processing time was 1.1 hours. The draw ratio was set to 225 times.

[0057] The rest is the same as in Example 1.

[0058] The obtained fibers had a deformation elongation of 2.3%, a breaking strength of 33.8 cN / dtex, and a breaking modulus of 910 cN / dtex.

[0059] (Example 6) Ethylene and n-butene were polymerized in a molar ratio of 46,000:1 for a reaction time of 2.1 hours to obtain a branched-modified ultra-high molecular weight polyethylene resin. Ethylene and 4-methyl-1-pentene were polymerized in a molar ratio of 1:67,000 to obtain a modified poly-α-olefin resin with sparse branched chains.

[0060] Two types of resin were mixed in a ratio of 19:1, resulting in a total resin content of 6 wt% in the spinning solution. The spinning temperature was set to 95°C, and the processing time was 1 hour. The draw ratio was set to 210 times.

[0061] The rest is the same as in Example 1.

[0062] The obtained fibers had a deformation elongation of 2.8%, a breaking strength of 39 cN / dtex, and a breaking modulus of 1330 cN / dtex.

[0063] (Example 7) Ethylene and 6-methyl-1-heptene were polymerized at a molar ratio of 42,000:1 for 0.7 hours to obtain a branched-modified ultra-high molecular weight polyethylene resin. Ethylene and n-hexene were polymerized at a molar ratio of 1:90,000 to obtain a poly-α-olefin resin with sparse branched chains.

[0064] Two types of resin were mixed in a ratio of 15:1, resulting in a total resin content of 7 wt% in the spinning solution. The processing temperature was 87°C, and the processing time was 1.5 hours. The draw ratio was 255 times.

[0065] The rest is the same as in Example 1.

[0066] The obtained fibers had a deformation elongation of 9.5%, a breaking strength of 35 cN / dtex, and a breaking modulus of 1245 cN / dtex.

[0067] (Comparative Example 1) Ethylene and isobutylene were polymerized at a molar ratio of 500,000:1 for 1.8 hours to obtain a branched-modified ultra-high molecular weight polyethylene resin. Ethylene and 4-methyl-1-pentene were polymerized at a molar ratio of 1:5,000,000 to obtain a modified poly-α-olefin resin with sparse branched chains.

[0068] Two types of resin were mixed in a 10:1 ratio, resulting in a total resin content of 8.5 wt% in the spinning solution. The processing temperature was set to 89°C, and the processing time was 1.2 hours.

[0069] The extension ratio was set to 188 times.

[0070] The rest is the same as in Example 1.

[0071] The obtained fibers had a deformation elongation of 15%, a breaking strength of 36 cN / dtex, and a breaking modulus of 1270 cN / dtex.

[0072] Comparative Example 1 simulates the conditions of blended spinning. In both polymerization reactions, the amount of comonomer added was negligible, which corresponds to spinning with a typical ultra-high molecular weight polyethylene resin and poly-4-methyl-1-pentene (PMP). Since polyethylene itself has almost no branched chains, it was found that even with the addition of poly-α-olefin, the deformation resistance of the fiber could not be improved, and it still had a high deformation elongation.

[0073] (Comparative Example 2) Ethylene was polymerized for 0.8 hours without the addition of any other monomers to obtain a general ultra-high molecular weight polyethylene resin.

[0074] The yarn was spun with a resin content of 7.5 wt%, processed at a temperature of 89°C, and processed for 1.2 hours.

[0075] The extension ratio was set to 200 times.

[0076] The fiber fractured after 25 hours and could not complete the 400-hour test process. The tensile strength was 42 cN / dtex and the tensile modulus was 1570 cN / dtex.

[0077] Comparative Example 2 simulated the spinning process of typical ultra-high molecular weight polyethylene, and fibers were obtained without any modifications. Under the test conditions of the present invention, it was found that typical fibers would break before the complete test could be completed.

[0078] (Comparative Example 3) Ethylene and n-hexene were polymerized at a molar ratio of 4000:1 for 1.4 hours to obtain a branched-modified ultra-high molecular weight polyethylene resin.

[0079] This branched, modified ultra-high molecular weight polyethylene resin is used for spinning, with a resin content of 8 wt% in the spinning solution, a processing temperature of 91°C, and a processing time of 1.3 hours.

[0080] The extension ratio was set to 150 times.

[0081] The fiber fractured after 70 hours and could not complete the 400-hour test process. The tensile strength was 28 cN / dtex and the tensile modulus was 760 cN / dtex.

[0082] Comparative Example 3 shows the spinning process of a typical ultra-high molecular weight polyethylene that has been branched and modified with n-hexene. Under the test conditions of the present invention, it was found that the typical fiber broke before the complete test could be completed.

[0083] (Comparative Example 4) Ethylene was polymerized for 1.8 hours without the addition of any other monomers to obtain a general ultra-high molecular weight polyethylene resin.

[0084] Ethylene and n-hexene were polymerized in a molar ratio of 400:1 for 1.4 hours to obtain a branched-modified ultra-high molecular weight polyethylene resin.

[0085] Two types of resin were mixed in a ratio of 10:1, the total resin content in the spinning solution was 8 wt%, the spinning temperature was 91°C, and the processing time was 1.3 hours.

[0086] The extension ratio was set to 180 times.

[0087] The deformation elongation was 89%, the breaking strength was 32 cN / dtex, and the breaking modulus was 920 cN / dtex.

[0088] Comparative Example 4 simulates the blending process of general ultra-high molecular weight polyethylene and modified poly-α-olefin with a predetermined number of sparsely branched chains. Because the number of branched chains in the poly-α-olefin is reduced by the sparse modification, the molecular bonding ability is decreased, resulting in a decrease in deformation resistance compared to Comparative Example 1. However, it showed a significant improvement compared to the blank sample (Comparative Example 2).

[0089] The basic processes, main features, and advantages of the present invention are shown and described above. Those skilled in the art will understand that the present invention is not limited to the above embodiments, and that the above embodiments and specification are merely for illustrating the principles of the present invention, and that the present invention may also have various variations and improvements without departing from the spirit and scope of the invention, all of which fall within the scope of the claimed invention. The scope of protection of the present invention is defined by the appended claims and equivalents.

Claims

1. In the polymerization process of ultra-high molecular weight polyethylene, step (1) involves continuously adding α-olefins to form a branched-modified ultra-high molecular weight polyethylene resin, In the polymerization process of α-olefins, step (2) involves continuously adding ethylene monomers to form a poly-α-olefin resin with sparse branched chains, The method includes step (3) of mixing the branched-modified ultra-high molecular weight polyethylene resin obtained in step (1) with the branched-chain-sparse poly-α-olefin resin obtained in step (2), spinning the mixture, and winding the fibers. A method for producing highly stable fibers, characterized by the following:

2. The α-olefin monomer comprises one or more of the following: a linear α-olefin of C3 to C8, isobutylene with a tertiary or quaternary carbon, 4-methyl-1-pentene, and 6-methyl-1-heptene. A method for producing highly stable fibers according to claim 1.

3. In the polymerization process of step (1), ethylene and α-olefin are mixed in a molar ratio of 100 to 100,000:1, and under the action of a catalyst and solvent oil, the reaction pressure is controlled to 0.1 to 10.0 MPa, the reaction temperature is controlled to 30 to 120°C, and the reaction is carried out for 0.5 to 5 hours to obtain a branched modified ultra-high molecular weight polyethylene resin. A method for producing highly stable fibers according to claim 1.

4. The solvent oil includes gasoline, n-heptane, hexane and / or isobutane. The catalyst includes metallocene catalysts, single-site catalysts, chromium-based catalysts and / or Ziegler-Natta catalysts. A method for producing highly stable fibers according to claim 3.

5. The mass ratio of ethylene, solvent oil, and catalyst is 80-120:80-200:1-10. A method for producing highly stable fibers according to claim 3.

6. In the polymerization process of step (2), ethylene and α-olefin are mixed in a molar ratio of 1:100 to 100,000, and under the action of a catalyst and solvent oil, the reaction pressure is controlled to 0.1 to 10.0 MPa, the reaction temperature is controlled to 30 to 120°C, and the reaction is carried out for 0.5 to 5 hours to obtain a branched modified ultra-high molecular weight polyethylene resin. A method for producing highly stable fibers according to claim 1.

7. The mass ratio of the α-olefin, solvent oil, and catalyst is 80-120:80-200:0.01-0.

5. A method for producing highly stable fibers according to commodity 6.

8. In step (3), the mass ratio of the branched-modified ultra-high molecular weight polyethylene resin to the branched-chain sparse poly-α-olefin resin is 15 to 20:

1. A method for producing highly stable fibers according to claim 1.

9. The spinning in step (3) is wet spinning, with a pre-spinning swelling temperature of 80-100°C and a processing time of 1-2 hours. The total extension ratio is 200 to 250 times. A method for producing highly stable fibers according to claim 1.

10. A highly stable fiber manufactured by the method described in any one of claims 1 to 9.

Images