A method for obtaining acrylic fibers with improved abrasion and mechanical strength properties

Abstract

The invention relates to a method comprising the modifications carried out in the coagulation and washing processes, which are process steps for obtaining acrylic fibers with improved wear values and mechanical strength properties, and to the acrylic fiber products obtained by this method.

Description

[0001] A METHOD FOR OBTAINING ACRYLIC FIBERS WITH IMPROVED ABRASION AND MECHANICAL STRENGTH PROPERTIES

[0002] TECHNICAL FIELD

[0003] The invention relates to a method comprising the modifications carried out in the coagulation and washing processes, which are process steps for obtaining acrylic fibers with improved abrasion values and mechanical strength properties, and to the acrylic fiber products obtained by this method.

[0004] PRIOR ART

[0005] Acrylic fibers are synthetic fibers produced from polyacrylonitrile polymer, characterized by their soft, lightweight, and wool-like properties. Owing to their chemical resistance, color retention capacity, and low moisture absorption, they are used in various technical applications. Acrylic fibers are especially preferred in the textile industry for products such as sweaters, blankets, carpets, socks, and outerwear materials. In addition, they have a versatile range of uses, including furniture upholstery, technical textiles, and UV-resistant fabrics for outdoor use. Their durability and low maintenance requirements make acrylic fibers a popular material.

[0006] Acrylic fibers are expected to exhibit high abrasion resistance values for applications that require durability and long service life. This property enables the products to resist friction, wear, and mechanical stress, thereby extending their lifespan and offering costeffectiveness. Acrylic fibers with high abrasion resistance are particularly preferred in products that are frequently exposed to contact and wear risks, such as carpets, upholstery fabrics, and outdoor textiles. This feature helps maintain the structural integrity of the fiber while also enhancing the aesthetic and functional performance of the product. In addition, due to their abrasion resistance, maintenance requirements are reduced and product longevity is increased, providing convenience for users and contributing to sustainability.

[0007] Various applications are carried out during the production process to ensure that acrylic fibers possess high abrasion resistance values. One of the most critical steps in the production process is the coagulation baths, where optimizing the temperature and solvent concentration values ensures that the fibers attain a homogeneous structure. Optimization of the parameters in the coagulation bath aims to minimize voids that may form in the microstructure of the fibers and to achieve a denser structure. These adjustments promotethe controlled precipitation of polymer chains, enabling the formation of strong bonds between fibrils. As a result, the abrasion resistance of the acrylic fibers is significantly improved, and a more durable structure is obtained.

[0008] In the current acrylic fiber production process in the prior art, improper temperature and solvent concentration adjustments in the coagulation bath lead to irregularities on the fiber surface and structure, resulting in the formation of non-uniform fibers. These defects arise due to the polymer not precipitating homogeneously during coagulation and the solidification process occurring in an uncontrolled manner.

[0009] The formation of non-uniform fibers disrupts the structural integrity of acrylic fibers and causes a significant decrease in their mechanical strength values. Failure to properly control the temperature and concentration parameters during the coagulation process hinders the homogeneous solidification of the polymer and triggers the formation of irregular, weak-point-containing non-uniform fibers.

[0010] In order to eliminate these adverse conditions and to enhance both the abrasion resistance and strength values of acrylic fibers, it has been determined that the parameters used during the coagulation and washing process steps must be optimized in the relevant technical field.

[0011] Optimizing the coagulation and washing process parameters together will ensure the homogeneous solidification of the polymer and prevent the formation of non-uniform fibers. In this way, defects on the surface of the acrylic fibers will be eliminated, fiber homogeneity will be improved, and abrasion resistance and mechanical strength values will be optimized.

[0012] These adjustments significantly improve quality in acrylic fiber production and make it possible to obtain more durable, high-strength performance products by overcoming the limitations of the existing technique. In this way, the production processes will be substantially improved in terms of both efficiency and product durability.

[0013] As a result, all the aforementioned problems have made it necessary to introduce an innovation in the relevant technical field.BRIEF DESCRIPTION OF THE INVENTION

[0014] Although sufficient abrasion resistance can be achieved in the production of acrylic fibers using existing methods in the relevant technical field, the desired level of mechanical strength values cannot be attained. The main reason for this is that the production conditions of the coagulation and washing baths in the current technique do not fully support the proper and homogeneous solidification of the acrylic polymer. As a result, defects such as non-uniform fibers occur, and these defects lead to a significant reduction in the mechanical strength of the acrylic fibers. These drawbacks prevent the simultaneous optimization of abrasion resistance and mechanical strength in acrylic fibers, and such defects in the production process negatively affect product quality and durability. For these reasons, it has become necessary to readjust the parameters used during the coagulation and washing processes. These adjustments represent a critical step toward improving quality and optimizing durability in the production of acrylic fibers.

[0015] The present inventors have implemented modifications in the coagulation and washing steps key processes in acrylic fiber production in order to address the aforementioned technical problems. In the coagulation process, an additional coagulation bath has been introduced into the existing method to ensure homogeneous solidification of the polymer and to prevent the formation of non-uniform fibers . In the washing process, a temperature-controlled system is integrated to improve surface homogeneity of the fiber and enhance its mechanical strength. These improvements aim to increase the mechanical strength values while maintaining abrasion resistance.

[0016] An objective of the present invention is to enable the production of acrylic fibers in which the abrasion resistance values of the existing technique are preserved while the mechanical strength values are improved. In current methods, abrasion resistance is achieved; however, the strength values remain insufficient. Therefore, through modifications made in the coagulation and washing processes, the polymer is brought to a more homogeneous structure, thereby increasing the fiber’s load-bearing capacity and durability. As a result, the product becomes both durable and long-lasting.

[0017] Another objective of the invention is to prevent non-uniform fibers defects that occur during acrylic fiber production in the current technique and negatively affect fiber quality. In existing methods, deviations in temperature and concentration in the coagulation bath hinder the proper solidification of the polymer, leading to the formation of such defects. Themethod described in the invention introduces more operationally feasible coagulation conditions, which positively impact production efficiency. The dop defects caused by slight deviations in the difficult-to-implement coagulation conditions of the current technique are prevented through these modifications. Furthermore, with the new adjustments, process parameters are optimized, significantly improving both production quality and process stability.

[0018] DETAILED DESCRIPTION OF THE INVENTION

[0019] In this detailed description, the subject of the invention relates to a method involving modifications carried out in the coagulation and washing processes, which are process steps for the production of acrylic fibers, and is explained with examples provided solely for a better understanding of the subject, without imposing any limiting effect.

[0020] The method of the present invention also includes other process steps known in the art for the production of acrylic fibers, but is particularly distinguished by the modifications made in the coagulation and washing processes. By optimizing these process steps, the present inventors ensure the homogeneous solidification of the polymer, enhance the microstructural integrity of the fiber, and improve both mechanical strength properties and abrasion resistance.

[0021] In the relevant technical field, it is known that modifications in coagulation processes improve the abrasion resistance of acrylic fibers. However, the present inventors argue that the existing technical teachings are insufficient for simultaneously optimizing both the abrasion resistance and mechanical strength of acrylic fibers. In this regard, a newly configured additional coagulation environment has been developed within the production method for obtaining acrylic fibers. Furthermore, it has been determined that in order to improve mechanical strength properties (tenacity value) , optimizations must also be made in the washing processes applied after the coagulation steps.

[0022] The method for acrylic fiber production as disclosed in the invention comprises the following process steps:

[0023] - Preparation of polyacrylonitrile polymers

[0024] In the invention, the process begins with the preparation of polyacrylonitrile polymers to be used as raw material in the subsequent process steps. The main component for thepolymerization process is acrylonitrile. This monomer is supplied in high purity and stabilized prior to the polymerization process. The other monomer, as known in the art, is vinyl acetate.

[0025] In the most preferred embodiment, the polyacrylonitrile polymer comprises acrylonitrile in the range of 90% to 95% by weight and vinyl acetate in the range of 10% to 5% by weight. The scope of protection of the present invention is not limited to the composition of the polymer material. The weight ratios of the monomers given here may vary depending on the desired molecular weight and viscosity value. If preferred, the molecular weight of the polymer may be in the range of 100,000 to 160,000 Daltons. On the other hand, the viscosity value may range from 0.1 to 0.2 cP. Since the molecular weight and viscosity values may vary depending on the intended applications of the resulting acrylic fibers, the scope of protection of the invention is not limited to these values.

[0026] A polyacrylonitrile polymer is obtained from these monomers using methods known in the art.

[0027] - Preparation of the spinning solution for the obtained polyacrylonitrile polymer

[0028] For the preparation of the solution of the obtained polyacrylonitrile polymers, at least one of the solvents dimethylacetamide (to be abbreviated as DMAc) and / or dimethyl sulfoxide (to be abbreviated as DMSO) is used.

[0029] The polyacrylonitrile polymer is added to the solvent in an amount ranging from 15% to 25% by weight. Subsequently, during the preparation of the solution, a mixing process is applied to ensure homogenization.

[0030] To ensure homogeneous dissolution and to accelerate the process, the dissolution temperature is expected to be in the range of 60 to 100°C. This helps the solvent interact more effectively with the polymer and enhances solubility.

[0031] - Introducing the obtained polyacrylonitrile polymer solutions into the coagulation bath and carrying out the processing steps

[0032] In this process step, the transformation of the polymer solution from liquid to solid is achieved, thereby forming the acrylic fibers. This stage is a critical step that directly affects the mechanical strength, abrasion resistance, and homogeneity of the fibers.The innovative aspect of the invention lies in the implementation of the coagulation bath in at least two stages. In this context, the coagulation baths in the process of the invention are referred to as the first coagulation bath and the second coagulation bath, respectively. This two-stage approach enables controlled phase separation of the polymer, thereby improving the microstructural uniformity of the fibers and optimizing both abrasion resistance and mechanical strength.

[0033] What is critical here is the inclusion of the second coagulation bath into the acrylic fiber production process. In the first coagulation bath, the solidification of the polymer solution is initiated, and acrylic fibers with the targeted abrasion resistance are obtained under appropriate parameters. In the second coagulation bath, the remaining solidification process from the first bath is completed, and through the heating of the washing baths, the mechanical properties of the acrylic fibers are enhanced.

[0034] With the method of the present invention, unlike the known methods in the current art, it becomes possible to obtain acrylic fibers with the targeted abrasion resistance and strength values through the optimization of four key parameters. Accordingly, the parameters in question are: the temperatures of the first and second coagulation baths, the concentration of solvents used in these baths, the residence times in the coagulation baths, and the jet stretch speed.

[0035] In the first coagulation bath, at least one of DMAc and / or DMSO is used as the solvent. The weight ratio of this solvent is in the range of 45% to 55% of the total weight of the coagulation bath solution. In the present invention, the amount of solvent in the first coagulation bath has been determined through research to ensure that phase separation from the polyacrylonitrile polymer solution occurs in a controlled manner. If the solvent amount in the first coagulation bath falls below 45% by weight, the coagulation process becomes insufficiently effective, leading to a loss of homogeneity in the fiber structure and deterioration of mechanical properties. On the other hand, if the solvent amount exceeds 55% by weight, phase separation in the solution occurs too rapidly. This results in structural irregularities in the polymer, formation of non-uniform fibers, and production defects. In both cases, the tenacity and abrasion resistance of the fibers are negatively affected, and operational challenges arise in the process.

[0036] The temperature of the first coagulation bath is in the range of 55 to 65°C. This temperature value, together with the solvent content by weight in the first coagulation bath, is of critical importance for ensuring controlled phase separation of the polymer solutionand achieving a homogeneous fiber structure. The specified temperature range balances the diffusion rate between the solvent and the nonsolvent, preventing sudden and rapid precipitation of acrylonitrile polymers, thereby ensuring microstructural uniformity. Additionally, this temperature range enhances the mechanical properties of the fibers, such as strength and abrasion resistance, and provides greater operational tolerance against potential process deviations, thereby increasing production stability. At temperatures lower than the specified range, phase separation in the coagulation bath slows down, the polymer does not fully solidify, and irregular structures are formed. This disrupts fiber homogeneity, weakens mechanical properties, and leads to extended production times. At temperatures higher than the specified range, phase separation occurs too rapidly in the coagulation bath, resulting in sudden precipitation of the polymer, which causes structural irregularities and production defects such as non-uniform fibers.

[0037] In cases where the solvent concentration in the coagulation bath is high, the coagulation rate slows down, leading to a structure prone to the formation of non-uniform fibers. This situation prevents achieving high jet stretch speeds and imposes various limitations on production capacity and quality. To stabilize the structure of the fibers taken from the first coagulation bath, enhance their homogeneity, and ensure proper alignment of the polymer chains, the fibers are introduced into a second coagulation bath. Unlike the first bath, the parameters used in this process step involve higher temperatures and different solvent-nonsolvent ratios. The addition of this second bath allows more flexible adjustment of the concentration, temperature, and stretch speed in the first coagulation bath. Moreover, the second coagulation bath increases the residence time of the acrylic fibers in the coagulation phase. For the second coagulation bath, the solvent concentration, temperature, stretch speed, and coagulation residence time are jointly optimized. This optimization enables the targeted abrasion resistance to be achieved, higher mechanical strength values to be obtained, and the limitations associated with jet stretch speeds to be eliminated. As a result, production capacity has been increased and product quality has been significantly improved.

[0038] The solvent used in the second coagulation bath is generally the same or a similar solvent to that used in the first bath for dissolving the polymer. Accordingly, the second coagulation bath also contains at least one of DMAc and / or DMSO as the solvent.

[0039] The nonsolvent used in the second coagulation bath is typically water or water-based solutions, which facilitate the separation of the polymer from the solution and its solidification. The solvent contributes to the controlled reorganization of the polymerchains, thereby enhancing homogeneity and slowing down the phase separation process. The nonsolvent, on the other hand, accelerates the separation of the polymer from the solution, completing the formation of the solid phase and helping to stabilize the microstructure. This balance between solvent and nonsolvent ensures controlled phase separation, thereby optimizing fiber homogeneity, mechanical strength, and abrasion resistance. Furthermore, the proper ratio of these components prevents the formation of non-uniform fibers and allows the elimination of irregularities in both the surface and internal structure of the fiber.

[0040] The solvent content in the second coagulation bath ranges from 30% to 50% by weight of the total solution, and these values are determined to ensure controlled phase separation and to enhance the microstructural homogeneity of the fiber. This range supports the orderly solidification of the polymer within the solution, preventing rapid precipitation and the formation of non-uniform fibers. At the same time, the solvent amount has been optimized considering factors such as polymer solubility, fiber mechanical strength properties, and abrasion resistance. Using an appropriate amount of solvent balances the phase separation rate, minimizing irregularities on the fiber surface and internal structure, thereby improving both product quality and process stability. As stated, the solvent content by weight in the second coagulation bath is lower than that in the first coagulation bath, because by this stage, the majority of the polymer’s phase separation process has already occurred, and the goal is to continue with controlled solidification. A lower solvent concentration in this step promotes the homogeneous transition of the polymer from the solution into the solid phase. If a high solvent content, similar to that used in the first coagulation bath, were applied, phase separation could slow down and complete solidification might not occur, leading to structural irregularities. Moreover, a reduced solvent level in the second coagulation bath enhances the effect of the nonsolvent, accelerating the separation of the polymer from the liquid phase. However, since this process proceeds in a controlled manner, sudden precipitation and non-uniform fibers formation are prevented.

[0041] The temperature of the second coagulation bath is in the range of 70 to 100°C. These specified temperature values are critical for completing the phase separation process of the polymer obtained from the first coagulation bath and for further improving the mechanical properties of the fiber. This temperature range solidifies the structural homogeneity of the fiber following the first coagulation bath and contributes to enhancing properties such as strength and abrasion resistance. At the same time, the balance between solvent and nonsolvent is optimized at this stage to prevent defects such as non-uniform fibers and to ensure a more stable production process. The reason why the temperature of the second coagulation bath is higher than that of the first coagulation bath is to complete the phase separation process of the polymer and to optimize the final mechanical properties of the fiber particularly its strength and abrasion resistance. The controlled phase transition that begins in the first coagulation bath proceeds more slowly at lower temperatures, during which the basic structural integrity of the fiber is formed. In the second coagulation bath, the higher temperature accelerates this process, allowing full solidification of the polymer, strengthening of structural homogeneity, and elimination of possible surface defects. Moreover, the elevated temperature enhances the efficiency of the production process and helps prevent errors such as the formation of non-uniform fibers .

[0042] After being processed in the coagulation baths, the polymer solution undergoes a controlled transition from the liquid phase to the solid phase, resulting in a homogeneous fiber structure with high tenacity and abrasion resistance values. The first coagulation bath establishes the fundamental structural integrity of the polymer, while the second coagulation bath reinforces this structure and completes the phase separation process. As a result of the coagulation steps, the microstructure of the fibers is refined, production defects such as non-uniform fibers are minimized, and the mechanical properties of the fibers are optimized.

[0043] - Subjecting the obtained acrylic fibers to washing processes

[0044] The washing process is carried out to remove the residual solvents from the fibers exiting the coagulation baths and to increase their structural purity. One of the innovative aspects of the invention is that these washing processes are performed at a temperature in the range of 70 to 100°C. The main reason for maintaining the washing baths within this temperature range is to bring the fibers closer to their glass transition temperature, thereby enabling a more homogeneous stretchig process. In this way, the regularity of the fiber microstructure is increased, and a product with higher teacity values is obtained. In addition, these temperatures allow more effective removal of the solvent from the fibers, enhancing the purity of the fiber and optimizing its mechanical properties. In previous techniques, since the washing processes were carried out at lower temperatures, such effective solvent removal and mechanical property improvement could not be achieved. With the adjustment implemented in the invention, the performance of the washing processes is improved, making it possible to obtain fibers of high strength propeties and homogeneous structure.- Subjecting the acrylic fibers that have undergone washing processes to stretching processes

[0045] The stretching process is a procedure carried out to improve the mechanical properties of the fibers and to impart the desired physical structure. During this process, the washed acrylic fibers are aligned under a specific drawing force, making them more parallel and homogeneous.

[0046] - Application of finishing (apre) processes to the acrylic fibers subjected to strecthing

[0047] The finishing process is a surface treatment applied to the fibers to improve their physical and chemical properties. This process is carried out to increase the durability of the fibers, enhance their processability, and optimize their end-use performance.

[0048] - Carrying out drying and annealing processes on the acrylic fibers subjected to finishing treatments

[0049] The drying process ensures the complete removal of residual moisture from the fiber after the washing stage. This step is critical for maintaining the mechanical properties and stability of the fibers. The fibers are dried by applying heat, which makes them suitable for subsequent processing steps while also ensuring structural homogeneity.

[0050] The annealing process involves placing the dried fibers, preferably on perforated aluminum carts, into an autoclave where they are treated under controlled temperature and pressure. This process reduces internal stresses within the fibers, enhances microstructural regularity, and optimizes mechanical properties such as strength and elasticity.

[0051] In the method carried out with the process steps and parameters characterized in the invention, the abrasion resistance of the obtained acrylic fibers was compared with that of reference acrylic fibers produced by the prior art; the test results are presented in Table 1.

[0052] Test Unit Sample 1 of the invention Sample 2 of the Ecru (Reference, produced (Ecru) invention (Ecru) by the previous method) Abrasion Resistance cycle 27000 26000 10000

[0053]

[0054] Table 1. Comparison of abrasion resistance between the samples obtained by the method of the invention and the reference samples of the prior artWith reference to Table 1 ; Samples 1 and 2 exhibited high and close values with abrasion resistance of 27,000 and 26,000 cycles, respectively. In contrast, the abrasion resistance of the reference ecru sample produced by the prior art method was measured as 10,000 cycles, and this value clearly demonstrated that the new method significantly improved abrasion resistance. Overall, the samples obtained by the method of the invention showed increased abrasion resistance, and the superior results obtained in the ecru samples clearly revealed the performance, efficiency, and product durability of the method.

[0055] The scope of protection of the invention is defined in the claims provided in the annex and cannot in any way be limited to the examples described in this detailed explanation. Indeed, it is clear that a person skilled in the art may, in light of the above description and without departing from the core concept of the invention, develop similar embodiments.

Claims

CLAIMS1. A method for obtaining acrylic fibers with improved mechanical strength and abrasion resistance values, characterized in that it comprises the following process steps:- introducing the prepared polyacrylonitrile polymer solution into coagulation baths to obtain acrylic fibers in solid form,wherein said coagulation baths consist of two process steps, a first coagulation bath and a second coagulation bath,the temperature of the first coagulation bath being in the range of 55 to 65°C, and the solvent contained in the first coagulation bath being in the range of 45% to 55% by weight,introducing the acrylic fibers obtained from the first coagulation bath into the second coagulation bath and continuing the solidification process,wherein said second coagulation bath has a temperature in the range of 70 to 100°C, and the solvent contained in the second coagulation bath is in the range of 30% to 50% by weight,- subjecting the acrylic fibers obtained in solid form by processing in the coagulation baths to washing processes,wherein said washing processes are carried out at a temperature in the range of 70 to 100°C.

2. A method according to claim 1 , characterized in that the polyacrylonitrile polymers comprise acrylonitrile in an amount of 90% to 95% by weight and vinyl acetate in an amount of 5% to 10% by weight.

3. A method according to any of the preceding claims, characterized in that the polyacrylonitrile polymer solution contains at least one of DMAc and / or DMSO as the solvent.

4. A method according to claim 3, characterized in that the polyacrylonitrile polymer is added into the solvent in an amount of 15% to 25% by weight.

5. A method according to any of the preceding claims, characterized in that the first coagulation bath contains at least one of DMAc and / or DMSO as the solvent.

6. A method according to any of the preceding claims, characterized in that the second coagulation bath contains at least one of DMAc and / or DMSO as the solvent.

7. A method according to any of the preceding claims, characterized in that, after the washing processes, at least one of drafting and finishing processes is applied to the acrylic fibers.

8. A method according to claim 7, characterized in that, after the drafting and finishing processes, at least one of drying or annealing processes is applied to the acrylic fibers.

9. An acrylic fiber obtained by a method according to any of the preceding claims, having a strength value in the range of 37 to 47 cN / T.

10. An acrylic fiber according to claim 9, characterized in that it is used as a raw material in the production of outdoor solutions, awnings, upholstery fabrics, carpets, rugs, outerwear materials, and furniture upholstery.

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