Fiber and method for producing same

Abstract

This fiber contains a polyketone having a constituent unit represented by general formula (1), and has a knot strength at 25°C of 450 MPa or more. (In general formula (1), R independently represents a linear or branched alkylene group having 2 to 9 carbon atoms.)

Description

Fiber and its manufacturing method

[0001] The present invention relates to fibers and methods for producing the same.

[0002] Fibers spun from polyketones (aliphatic polyketones) obtained by copolymerizing carbon monoxide and olefins have high mechanical strength and heat resistance, and are therefore used for tire cords and the like (see, for example, Patent Document 1).

[0003] Patent Document 2 describes a polyketone fiber spun by a wet spinning method (solution spinning method) using a solution containing zinc chloride, which has high strength (for example, a tensile strength of 7.2 to 14.0 cN / dtex and a knot strength of 2.7 to 3.5 cN / dtex). The density of polyketone is approximately 1.24 g / cm ３ Therefore, this knot strength corresponds to approximately 335 to 434 MPa.) Patent Document 3 also describes that a fishing line made of polyketone fibers spun by a similar method exhibited low elongation and high tensile strength.

[0004] Non-Patent Document 1 describes polyketone fibers obtained by melt spinning polyketone, and states that the take-up speed during melt spinning is 200 to 400 m / min.

[0005] Japanese Patent Laid-Open No. 1-124617 Japanese Patent Laid-Open No. 2001-131825 Japanese Patent Laid-Open No. 2001-148982

[0006] Gupta et al., “Development of High-Strength Fibers from Aliphatic Polyketones by Melt Spinning and Drawing,” Journal of Applied Polymer Science, 2001, Vol. 82, p. 1794-1815

[0007] Patent Documents 2 and 3 describe the production of high-strength polyketone fibers. However, according to the findings of the present inventors, although the polyketone fibers described in these documents have high tensile strength, they are not well balanced with other physical properties, making it difficult to apply them to various applications. For example, fibers used as fishing lines require higher knot strength.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a polyketone fiber having higher knot strength than the polyketone fibers described in Patent Document 2 and Patent Document 3, and a method for producing the same.

[0009] One embodiment of the present invention for solving the above problems relates to the fibers of the following [1] to [8]: [1] A fiber containing a polyketone having a structural unit represented by general formula (1), the fiber having a knot strength of 450 MPa or more at 25°C. (In general formula (1), R independently represents a linear or branched alkylene group having 2 to 9 carbon atoms.) [2] The fiber according to [1], which has a tensile elongation of 10% or more as measured at 25°C and a relative humidity of 50%. [3] The fiber according to [1] or [2], which has a tensile modulus of 10.0 GPa or less as measured at 25°C and a relative humidity of 50%. [4] The fiber according to any one of [1] to [3], which has a crystallinity of 20.0% or more and 50.0% or less as calculated from the heat of fusion measured by differential scanning calorimetry (DSC). [5] The fiber according to any one of [1] to [4], which has a crystalline orientation degree of 0.80 or more and 0.98 or less. [6] The fiber according to any one of [1] to [5], which has a birefringence of 0.040 or more and 0.060 or less. [7] The fiber according to any one of [1] to [6], which has a thread diameter per filament of 40 μm or more. [8] The fiber according to any one of [1] to [7], which is a filament for fishery materials.

[0010] Another embodiment of the present invention for solving the above problem relates to a fiber manufacturing method described below in [9]: [9] A fiber manufacturing method comprising the steps of melt-spinning a polyketone having a structural unit represented by general formula (1) at a take-up speed of 1 m / min or more and 50 m / min or less, and drawing the spun polyketone. (In general formula (1), R independently represents a linear or branched alkylene group having 2 to 9 carbon atoms.)

[0011] According to the present invention, there are provided polyketone fibers having higher knot strength than the polyketone fibers described in Patent Documents 2 and 3, and a method for producing the same.

[0012] One embodiment of the present invention relates to a polyketone fiber, which comprises the polymer polyketone.

[0013] [Polyketone] Polyketone is a polymer having a structural unit represented by general formula (1).

[0014]

[0015] In general formula (1), R independently represents a linear or branched alkylene group having 2 to 9 carbon atoms. R is preferably a linear or branched alkylene group having 2 or 3 carbon atoms.

[0016] The polyketone may have multiple types of structural units in which the alkylene groups constituting R have different numbers of carbon atoms. In this case, the multiple types of structural units may be arranged randomly or in a block form, but are preferably arranged randomly.

[0017] Furthermore, the polyketone preferably has a structural unit in which the alkylene group constituting R has two carbon atoms (a structural unit formed by the reaction of carbon monoxide with ethylene; hereinafter, also referred to simply as a "C2 structural unit"), and may also have a structural unit in which the alkylene group constituting R has three carbon atoms (a structural unit formed by the reaction of carbon monoxide with propylene; hereinafter, also referred to simply as a "C3 structural unit"). In other words, the polyketone may be a binary copolymer having only C2 or C3 structural units, or a terpolymer having C2 structural units and C3 structural units. The polyketone may also be a mixture of a binary copolymer having only C2 or C3 structural units with another polyketone, or a mixture of a terpolymer having C2 structural units and C3 structural units with another polyketone. The mixed polymer is referred to as a polymer blend. From the viewpoint of improving melt processability, the polyketone is preferably a terpolymer having C2 structural units and C3 structural units, or a blend of a terpolymer having C2 structural units and C3 structural units with another polyketone.

[0018] When the polyketone is the above-mentioned terpolymer or a blend of the above-mentioned terpolymer having C2 structural units and C3 structural units with another polyketone, the proportion of the C2 structural units relative to the total amount of the C2 structural units and the C3 structural units is preferably 70 mol% or more and 99 mol% or less, more preferably 80 mol% or more and 95 mol% or less, and even more preferably 85 mol% or more and 92 mol% or less. The higher the proportion of the C3 structural units, the lower the processing temperature of the polyketone can be for spinning, and by suppressing changes during molding such as crosslinking reactions, the tensile properties of the polyketone fiber can be easily improved. The composition ratio of the terpolymer or blend can be calculated using the following procedure. Standardized so that the resonance peak of tetramethylsilane (standard substance) is 0.00 ppm. １When the terpolymer or the blend is measured by H-NMR, the resonance peak measured in the range of 1.07 to 1.20 ppm is considered to be a peak attributable to the C3 structural unit, and the resonance peak measured in the range of 2.40 to 3.15 ppm is considered to be a peak attributable to both the C2 structural unit and the C3 structural unit, and the integral value of each peak is calculated. The composition ratio can be determined by calculating the ratio of the proton numbers from the ratio of the integral values ​​of each peak.

[0019] The polyketone may have structural units other than the structural units represented by general formula (1). For example, the polyketone may contain structural units derived from (meth)acrylic acid esters such as methyl (meth)acrylate and hydroxyethyl (meth)acrylate, (meth)acrylamide, styrene, styrene derivatives such as sodium styrene sulfonate, allyl compounds such as sodium allyl sulfonate, vinylpyrrolidone, and vinyl chloride. However, from the viewpoint of easily balancing properties such as tensile strength, elongation, and tensile modulus, it is preferable that the polyketone contain more structural units represented by general formula (1). Specifically, the proportion of the structural units represented by general formula (1) relative to the amount of all structural units in the polyketone is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 85 mol% or more, and particularly preferably 95 mol% or more.

[0020] In this specification, (meth)acrylate means at least one of acrylate and methacrylate, and (meth)acrylic means at least one of acrylic and methacrylic.

[0021] The polyketone preferably has a weight average molecular weight (Mw) of 30,000 or more and 1,000,000 or less, more preferably 100,000 or more and 500,000 or less, and even more preferably 120,000 or more and 250,000 or less. The polyketone preferably has a number average molecular weight (Mn) of 10,000 or more and 500,000 or less, more preferably 30,000 or more and 300,000 or less, and even more preferably 60,000 or more and 100,000 or less. The molecular weight of the polyketone is measured by gel permeation chromatography (GPC) using hexafluoroisopropanol (HFIP) as a solvent and is a value obtained by conversion using polymethyl methacrylate (PMMA) as a standard substance.

[0022] The higher the molecular weight of the polyketone, the fewer the number of terminals, making it easier to increase tensile strength. The lower the molecular weight of the polyketone, the better the fluidity during melt molding, making it easier to increase molding processability. Furthermore, the lower the molecular weight of the polyketone, the less likely melt fracture occurs during melt spinning, making it easier to produce polyketone fibers with a smooth surface. From the perspective of achieving a balance between these factors, the polyketone may contain two types of polyketones with different molecular weights. In other words, the polyketone may have peaks corresponding to multiple molecular weights in the chromatogram obtained by the GPC.

[0023] The melting point (Tm) of the polyketone is preferably 150°C or higher and 250°C or lower, and more preferably 180°C or higher and 230°C or lower. The higher the melting point of the polyketone, the higher the heat resistance of the polyketone fiber. The melting point of the polyketone can be a value obtained by measurement by differential scanning calorimetry (DSC).

[0024] [Polyketone Fiber] The polyketone fiber is a fiber containing polyketone. The various physical properties of the polyketone fiber can be adjusted by the physical properties of the polyketone used as a material, the production conditions, and the like.

[0025] The knot strength of the polyketone fiber measured at 25°C and 50% relative humidity is 450 MPa or more, preferably 450 MPa to 1000 MPa, more preferably 500 MPa to 1000 MPa, and even more preferably 550 MPa to 1000 MPa. The higher the knot strength, the higher the tensile strength (strength in the longitudinal direction) as well as the compressive strength and bending strength, resulting in a better balance of physical properties. Furthermore, the higher the knot strength, the higher the durability when used in applications involving knotting, such as fishing line. The knot strength can be determined by dividing the load at which the knot breaks by the diameter of the polyketone fiber, using a polyketone fiber as a test sample, with a single knot knotted in the center and a length (grip spacing) of 150 mm, with the crosshead speed of the testing machine set to 150 mm / min.

[0026] The polyketone fiber preferably has a strength at break of 600 MPa or more, more preferably 760 MPa to 1000 MPa, and even more preferably 840 MPa to 1000 MPa in a tensile test measured at 25°C and 50% relative humidity. The higher the strength at break, the easier the fiber is to elongate and the more durable it is in various applications. The tensile elongation can be determined by dividing the load at which the fiber breaks by the diameter of the polyketone fiber, using a polyketone fiber having a length (grip spacing) of 150 mm as a test sample and setting the crosshead speed of the testing machine to 150 mm / min.

[0027] The polyketone fiber preferably has a tensile elongation (elongation at break) measured at 25°C and 50% relative humidity of 10% or more, more preferably 15% to 50%, and even more preferably 18% to 30%. The greater the tensile elongation, the easier the fiber is to elongate and the more durable it is in various applications. The tensile elongation can be determined by dividing the elongation at which the fiber breaks by the grip spacing, using a polyketone fiber having a length (grip spacing) of 150 mm as a test sample and setting the crosshead speed of the testing machine to 150 mm / min.

[0028] The polyketone fiber preferably has a tensile modulus of 10.0 GPa or less, more preferably 1.0 GPa to 8.0 GPa, even more preferably 1.5 GPa to 5.0 GPa, and particularly preferably 2.5 GPa to 4.4 GPa, as measured at 25°C and 50% relative humidity. The lower the tensile modulus, the easier the fiber is to stretch. The tensile modulus can be determined by using a polyketone fiber having a length (grip spacing) of 150 mm as a test sample, setting the crosshead speed of the testing machine to 150 mm / min, and measuring the slope of the stress-displacement line at displacements of 0.005 (5%) and 0.025 (2.5%).

[0029] The crystallinity of the polyketone fiber is preferably 20.0% to 50.0%, more preferably 25.0% to 45.0%, even more preferably 30.0% to 40.0%, and particularly preferably 35.0% to 37.0%. The lower the crystallinity, the more flexible the fiber can be. The crystallinity can be determined as the ratio of the heat of fusion measured by differential scanning calorimetry (DSC) using indium (melting point: 156.5°C) as a calibration material to the heat of fusion when the crystallinity is 100%.

[0030] The degree of crystalline orientation of polyketone fibers is preferably 0.80 or more and 0.98 or less, more preferably 0.85 or more and 0.95 or less, and even more preferably 0.90 or more and 0.95 or less. The lower the degree of crystalline orientation, the more flexible the fiber can be. The degree of crystalline orientation can be calculated from the half-width H of the intensity distribution obtained by scanning the (110) plane observed around 2θ = 21° in the circumferential direction in a diffraction image of the fiber obtained by wide-angle X-ray diffraction (WAXD) measurement, using the following formula: degree of crystalline orientation = (180 - H) / 180 × 100 (%)

[0031] The birefringence of polyketone fibers is preferably 0.040 or more and 0.060 or less, more preferably 0.045 or more and 0.055 or less, and even more preferably 0.050 or more and 0.055 or less. The higher the birefringence, the greater the molecular chain orientation and the higher the strength. On the other hand, if it is too high, voids may be generated and the knot strength may decrease. The birefringence can be the value obtained by retardation measurement using a polarizing microscope equipped with a Berek compensator and a sodium lamp as a light source.

[0032] Compared to solution spinning and gel spinning, melt spinning does not require solvent removal, thereby reducing voids and making it easy to produce thick monofilaments with excellent tensile properties in knot strength and elongation. Furthermore, the thicker the fiber diameter, the higher the tensile strength and abrasion resistance of the fiber. From the above perspectives, the polyketone fiber preferably has a fiber diameter per filament of 40 μm or more, more preferably 50 μm to 500 μm, and even more preferably 100 μm to 200 μm. The polyketone fiber may be a monofilament consisting of only a single filament, or a multifilament formed by aggregating multiple filaments. When the polyketone fiber is a multifilament, the fiber diameter of the raw yarn may be 40 μm to 500 μm, and the total fineness may be 200 dtex to 2500 dtex.

[0033] The polyketone fiber of this embodiment can be used for various applications such as tire cords. Furthermore, since the polyketone fiber of this embodiment is resistant to changes in water absorption and has a predetermined tensile strength, elongation, and tensile modulus, it can also be used as a filament for fishery materials such as fishing line and fishing net. In particular, the polyketone fiber of this embodiment has high knot strength, making it suitable for use as fishing line.

[0034] For example, fishing lines include lines (main lines) and leaders, and the polyketone fiber of this embodiment can be used for either of these as a substitute for nylon fibers, which are prone to water absorption. In particular, since the polyketone fiber has a moderately low tensile modulus and is flexible, and is easy to stretch and absorb shock, it can also be suitably used as a leader.

[0035] In addition to the polyketone described above, the polyketone fiber may contain known additives such as other resins, plasticizers, nucleating agents, antioxidants, ultraviolet absorbers, dyes, pigments, heat stabilizers, light stabilizers, fillers, internal mold release agents, matting agents, conductivity imparting agents, charge control agents, antistatic agents, lubricants, and other processing aids.

[0036] From the viewpoint of achieving a good balance among various physical properties, the proportion of the polyketone in the polyketone fiber relative to the total mass of the resin components is preferably 70% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less.

[0037] [Method for producing polyketone fiber] Polyketone fiber can be produced by melt spinning polyketone. The spun polyketone may be drawn as necessary.

[0038] (Melt Spinning) Melt spinning can be performed by a conventional method in which molten polyketone is extruded from a spinneret and the extruded, cooled, and solidified polyketone is taken up at a predetermined take-up speed. Unlike the solution spinning described in Patent Documents 2 and 3, melt spinning is performed without using a solvent, which makes it possible to reduce the occurrence of internal voids and surface roughness that can occur during the solvent removal process after extrusion. Furthermore, melt spinning is also less likely to cause deterioration in physical properties due to components contained in the solution (e.g., metal ions derived from zinc chloride used in Patent Documents 2 and 3) remaining in the polyketone fiber. Therefore, these defects and deterioration in physical properties are reduced, and polyketone fibers with high various physical properties, including knot strength, can be obtained.

[0039] When producing polyketone fibers containing the above-mentioned additives, the resin composition containing these additives may be melted and spun.

[0040] The temperature of the polyketone during extrusion may be equal to or higher than the melting point of the polyketone, and may be, for example, 220° C. or higher and 260° C. or lower. From the viewpoint of sufficiently suppressing thickening due to thermal decomposition and crosslinking and improving knot strength, the temperature is preferably 250° C. or lower, more preferably 240° C. or lower, and even more preferably 235° C. or lower.

[0041] The spinneret for discharging the molten polyketone may be appropriately selected depending on the diameter and cross-sectional shape of each filament of the polyketone fiber to be obtained. For example, the spinneret may have discharge holes in shapes such as circles, squares, triangles, other polygons, and stars. Furthermore, by appropriately reducing the discharge rate per discharge hole, the shear rate when passing through the discharge hole can be reduced, making it difficult for excessive orientation of molecular chains to occur and preventing the formation of a non-uniform structure inside the fiber. This makes it easier to obtain fibers with the desired physical properties.

[0042] The polyketone extruded from the nozzle into the gas phase is then cooled to solidify it into a fibrous form and taken up at a predetermined take-up speed. Cooling may be performed by air cooling or by passing through a cold bath. From the viewpoint of suppressing crystallization of the undrawn yarn, it is preferable to pass through a cold bath, and the temperature of the cold bath is preferably 25°C or less, more preferably 10°C or less, and even more preferably 5°C or less. The solvent used in the cold bath is not limited as long as it does not corrode the polyketone, such as water or silicone oil, but water is more preferable from the viewpoint of production costs.

[0043] The take-up speed is preferably 1 m / min or more and 50 m / min or less, more preferably 1 m / min or more and 30 m / min or less, and even more preferably 1 m / min or more and 20 m / min or less. The draft ratio (the ratio of the take-up speed Vw to the discharge speed V0 (Vw / V0)) is preferably 1.0 or more and 29.0 or less, more preferably 1.0 or more and 15.0 or less, even more preferably 1.0 or more and 10.0 or less, and particularly preferably 1.0 or more and 5.0 or less. By appropriately slowing the take-up speed and increasing the time the yarn spends in the cold bath, it is possible to suppress crystallization of the polyketone, increase the knot strength, and reduce the tensile modulus. Furthermore, by appropriately reducing the draft ratio, it is possible to prevent excessive molecular orientation within the yarn, form a more uniform structure, and facilitate increased knot strength.

[0044] The crystallinity of the resulting undrawn monofilament is preferably 35% or less, more preferably 5% to 30%. By reducing the crystallinity of the undrawn monofilament, the crystallinity of the drawn monofilament produced in the subsequent drawing step can be reduced, and the internal defects due to non-uniformity of the crystals can be reduced, thereby reducing the elastic modulus and increasing the breaking strength and knot strength.

[0045] The degree of crystal orientation of the resulting undrawn monofilament yarn is preferably 0.3 or less, more preferably 0.15 or less. By reducing the degree of crystal orientation of the undrawn yarn, oriented crystallization is suppressed, and the degree of crystallinity of the drawn yarn produced in the subsequent drawing step and internal defects due to non-uniformity of the crystals can be reduced, thereby reducing the elastic modulus of the drawn yarn and increasing the strength at break and knot strength. The lower limit of the degree of crystal orientation of the resulting undrawn monofilament yarn is not particularly limited, but it is preferably 0.0 or more.

[0046] The undrawn monofilament thus obtained may be used as a polyketone fiber as is, or may be drawn. When drawn, the undrawn monofilament produced by melt spinning may be continuously drawn as is, or may be wound up and then drawn in a separate device. In other words, the polyketone fiber may be produced by a one-stage process in which melt spinning and drawing are performed continuously, or by a two-stage process in which melt spinning and drawing are performed separately.

[0047] (Stretching) The stretching may be carried out by a known method suited to the physical properties of the polyketone fiber to be obtained.

[0048] The number of godet rolls used for drawing and the temperature and speed of each roll can be determined as appropriate. For example, the temperature of each roll can be 120°C or higher and 210°C or lower, preferably 150°C or higher and 180°C or lower. When drawing by passing through an oven, the temperature inside the oven can be 120°C or higher and 210°C or lower, preferably 150°C or higher and 180°C or lower. From the viewpoint of suppressing crystallization, the total time the yarn passes through the oven is preferably 1 second or higher and 60 seconds or lower, more preferably 1 second or higher and 20 seconds or lower. The passing time can be calculated by dividing the length of the oven through which the yarn passes by the speed at which the yarn enters the oven.

[0049] The draw ratio is preferably 4.0 to 7.0 times, more preferably 4.5 to 6.5 times, and even more preferably 5.0 to 6.0 times. By appropriately adjusting the draw ratio, the physical properties of the polyketone fiber can be adjusted. A relaxation treatment may be performed after drawing. For example, if the draw ratio is too high, the crystallinity and orientation increase, but voids are more likely to occur, resulting in a decrease in knot strength. If the draw ratio is too low, the birefringence decreases, resulting in a decrease in knot strength.

[0050] The polyketone fibers thus obtained can be suitably used for various applications.

[0051] [Other Embodiments] It goes without saying that the above-described embodiments are exemplary embodiments of the present invention, and the present invention may include embodiments other than the above-described embodiments within the scope of its core technical concept.

[0052] The present invention will be described in detail based on examples, but the present invention is not limited to these examples.

[0053] 1. Preparation of Undrawn Monofilaments 1-1. Materials Four types of polyketone terpolymers were prepared as materials for the polyketone fibers. The weight average molecular weight (Mw), number average molecular weight (Mn), proportion (mol%) of each structural unit relative to the total amount of C2 structural units and C3 structural units, and melting point (Tm) of each polyketone were measured using the methods described below.

[0054] 1-1-1. Mw and Mn The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) using hexafluoroisopropanol (HFIP) as a solvent and converted using polymethyl methacrylate (PMMA) as a standard substance.

[0055] Specifically, 10 mg of each polyketone was dissolved in hexafluoroisopropanol (HFIP) containing 5 mM sodium trifluoroacetate to obtain a 10 mL solution, which was then filtered through a membrane filter to obtain a sample solution. 100 μL of this sample solution was injected into a gel permeation chromatography (GPC) analyzer (HLC-8420GPC, manufactured by Tosoh Corporation), and measurements were carried out under the following conditions. From the chromatogram obtained by the measurement, the weight average molecular weight (Mw) and number average molecular weight (Mn) of each polyketone were calculated using a calibration curve obtained with polymethyl methacrylate (PMMA) of known molecular weight. Apparatus: HLC-8420GPC, manufactured by Tosoh Corporation Column: HFIP 806M x 2 in series, 40°C Eluent: 5 mM CF ３ COONa / HFIP Flow rate: 1.0 mL / min Detector: differential refractometer (RI)

[0056] 1-1-2. Proportion of each structural unit relative to the total amount of C2 structural units and C3 structural units The proportion (mol %) of each structural unit relative to the total amount of C2 structural units and C3 structural units is １ It was calculated from the integral value of the peaks attributed to each structural unit that appeared in the spectrum obtained by H-NMR measurement.

[0057] Specifically, a nuclear magnetic resonance spectrometer (JASCO Corporation, JNM-ECZ600R / S1) was used. １ H-NMR spectra were obtained. For each polyketone, 10 mg of sample was dissolved in 1 ml of hexafluoroisopropanol (HFIP) and diluted with deuterated chloroform (CDCl ３ A measurement solution was prepared by adding 0.5 ml of tetramethylsilane (TMS). Measurements were then performed using tetramethylsilane (TMS) as the standard. Of the peaks in the obtained spectrum, the integral value of the multiplet peak at around 2.77 ppm derived from the C2 and C3 structural units and the integral value of the doublet peak at around 1.13 ppm derived from the C3 structural unit were used to calculate the respective proportions (mol %).

[0058] 1-1-3. Tm The melting points (Tm) shown in Table 1 are values ​​obtained by measurement using differential scanning calorimetry (DSC).

[0059] Specifically, a 2 mg sample of each polyketone was weighed into an aluminum pan and heated at a rate of 20°C / min in a nitrogen atmosphere in the range of 25°C to 250°C using a differential scanning calorimeter (TA Instruments Japan, DSC25) to obtain a DSC curve. The peak top temperature of the endothermic peak based on the melting behavior in this DSC curve was taken as the melting point (Tm) of each polyketone.

[0060] The measurement results for the four types of polyketones are shown in Table 1.

[0061]

[0062] 1-2. Melt Spinning The molten POK1 was extruded from a spinneret at 230°C and formed into a fiber, which was then immediately passed through a cold bath of silicone oil (KF-995 manufactured by Shin-Etsu Chemical Co., Ltd.) at −20°C to cool and solidify it, and the fiber was taken up at a take-up speed of 20 m / min and a draft ratio of about 3.0 to obtain an undrawn monofilament 1.

[0063] Undrawn monofilament 2 was obtained in the same manner as in the production of undrawn monofilament 1, except that POK1 was changed to a blend of POK1 and POK2 (POK1 / POK2 = 50 / 50 (mass ratio)).

[0064] Undrawn monofilament 3 was obtained in the same manner as in the production of undrawn monofilament 1, except that POK1 was changed to a blend of POK1 and POK3 (POK1 / POK3 = 90 / 10 (mass ratio)).

[0065] The molten POK4 was extruded from a spinneret at 200°C and formed into a fiber, which was then immediately passed through a water bath at 5°C to cool and solidify it, and taken up at a take-up speed of 15 m / min and a draft ratio of about 5.0 to obtain undrawn monofilament 4.

[0066] 1-3. Measurements The crystallinity, crystalline orientation, and tensile properties of the obtained undrawn monofilaments were measured by the following methods.

[0067] 1-3-1. Crystallinity The crystallinity was measured by differential scanning calorimetry (DSC) using unstretched monofilaments (approximately 2 mg) cut with scissors and placed on an aluminum pan. Indium (melting point: 156.5°C) was used as a calibration material. The heat of fusion when the crystallinity is 100% was set to 227 J / g, and the crystallinity of each unstretched monofilament was calculated from the measured heat of fusion.

[0068] 1-3-2. Crystalline Orientation Degree The crystalline orientation degree was calculated from the half-width H of the intensity distribution obtained by scanning the (110) plane observed around 2θ = 21° in the circumferential direction in a diffraction image of the fiber obtained by wide-angle X-ray diffraction (WAXD) measurement using an undrawn monofilament as a sample, using the following formula: Crystalline orientation degree = (180 - H) / 180 × 100 (%)

[0069] 1-3-3. Tensile Properties Tensile measurements were performed using unstretched monofilaments with a length (grip spacing) of 103 mm as test samples, with the crosshead speed of the testing machine set to 206 mm / min. The strength and elongation at the time of breakage were measured five times and calculated as the average value. The tensile modulus was also calculated as the average value of five measurements from the slope of the stress-displacement line at displacements of 0.005 and 0.025.

[0070] The crystallinity, crystalline orientation, and tensile properties of undrawn monofilaments 1 to 4 are shown in Table 2. For reference, the physical properties of the THMW and TLMW filaments described in Non-Patent Document 1 are also shown in Table 2.

[0071]

[0072] 2. Preparation of Drawn Polyketone Fibers 2-1. Drawing Undrawn Monofilament 1 to Undrawn Monofilament 3 were drawn by dry heat drawing at a draw temperature of 180°C and a draw ratio of 5.0 times, for a passage time of 9 seconds through a drawing oven, to obtain Polyketone Fiber 1 to Polyketone Fiber 3, respectively. Undrawn Monofilament 4 was drawn by dry heat drawing at a draw temperature of 170°C and a draw ratio of 6.0 times, for a passage time of 12 seconds through a drawing oven, to obtain Polyketone Fiber 4. Undrawn Monofilament 1 was drawn by dry heat drawing at a draw temperature of 180°C and a draw ratio of 7.0 times, for a passage time of 9 seconds through a drawing oven, to obtain Polyketone Fiber 5, respectively.

[0073] The crystallinity and crystalline orientation of the obtained polyketone fiber were measured in the same manner as for the undrawn monofilament. The tensile properties, knot strength, and birefringence of the obtained polyketone fiber were measured by the following methods.

[0074] 2-2-1. Tensile Properties Polyketone fiber and nylon fiber monofilaments (commercially available nylon fishing line, Ginrin No. 1, manufactured by Toray Industries, Inc.) with a length (grab spacing) of 150 mm were used as test samples. Measurements were performed at 25°C and 50% relative humidity with the crosshead speed of the testing machine set to 150 mm / min. The strength and elongation at break of the monofilament were calculated as the average of five measurements. The values ​​obtained by dividing these by the diameter of the monofilament were used as the strength at break and the elongation at break, respectively. The tensile modulus was also calculated as the average of five measurements from the slope of the stress-displacement line at displacements of 0.005 and 0.025. Similar measurements were also performed on monofilaments of polyketone fiber 1 and nylon fiber stored in pure water at 25°C for 24 hours.

[0075] 2-2-2. Knot Strength Monofilaments of each polyketone fiber and nylon fiber, each 150 mm long (grip spacing) with one single knot in the center, were used as test samples, and measurements were performed at 25°C and 50% relative humidity with a crosshead speed of 150 mm / min using a tensile tester (Tensilon RTF-1210, manufactured by A&D Co., Ltd.). The knot strength of each monofilament was determined by dividing the load at which the knot broke by the diameter of the monofilament. Similar measurements were also performed on monofilaments of polyketone fiber 1 and nylon fiber that had been stored in pure water at 25°C for 24 hours.

[0076] 2-2-3 Birefringence The birefringence of the monofilament was determined by measuring the retardation using a polarizing microscope equipped with a Berek compensator and a sodium lamp as the light source.

[0077] The crystallinity, crystalline orientation, birefringence, and yarn diameter of Polyketone Fiber 1 to Polyketone Fiber 4 are shown in Table 3. The tensile properties and knot strength of Polyketone Fiber 1 to Polyketone Fiber 4 are shown in Table 4. For reference, the physical properties of the filament THMW and TLMH described in Non-Patent Document 1 (calculated from the graph in Non-Patent Document 1) and the physical properties of nylon fiber are shown in Tables 3 and 4.

[0078]

[0079]

[0080] As shown in Tables 3 and 4, the polyketone fiber of the present invention had a higher knot strength than the polyketone fibers (knot strength of approximately 335 to 434 MPa) described in Patent Documents 2 and 3. Furthermore, compared to nylon fibers, the polyketone fiber of the present invention was less susceptible to decreases in strength and tensile modulus due to water absorption.

[0081] This application claims priority from Japanese Patent Application No. 2023-186769, filed October 31, 2023. The entire disclosure and claims of that application as originally filed are incorporated herein by reference.

[0082] The present invention provides polyketone fibers having unprecedented properties, and the polyketone fibers of the present invention are expected to be applied to various fields, including filaments for fishery materials.

Claims

1. A fiber comprising a polyketone having a structural unit represented by general formula (1), the knot strength of which is 450 MPa or more when measured at 25°C and a relative humidity of 50%. (In general formula (1), R independently represents a linear or branched alkylene group having 2 to 9 carbon atoms.) 2. The fiber according to claim 1, which has a tensile elongation of 10% or more measured at 25°C and a relative humidity of 50%.

3. The fiber according to claim 1 or 2, which has a tensile modulus of 10.0 GPa or less measured at 25°C and a relative humidity of 50%.

4. The fiber according to any one of claims 1 to 3, having a crystallinity of 20.0% or more and 50.0% or less, calculated from the heat of fusion measured by differential scanning calorimetry (DSC).

5. The fiber according to any one of claims 1 to 4, having a degree of crystal orientation of 0.80 or more and 0.98 or less.

6. The fiber according to any one of claims 1 to 5, having a birefringence of 0.040 or more and 0.060 or less.

7. The fiber according to any one of claims 1 to 6, wherein the diameter of each filament is 40 μm or more.

8. The fiber according to any one of claims 1 to 7, which is a filament for marine products.

9. A method for producing fibers, comprising the steps of: melt spinning a polyketone having a structural unit represented by general formula (1) at a take-up speed of 1 m / min or more and 50 m / min or less; and drawing the spun polyketone. (In general formula (1), R independently represents a linear or branched alkylene group having 2 to 9 carbon atoms.)

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