EP4660356A1

EP4660356A1 - Polyamide multifilament, and polyamide monofilament

Info

Publication number: EP4660356A1
Application number: EP24750047.3A
Authority: EP
Inventors: Kazushi Minai; Hisao Shigeno; Takashi Uruma
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2023-01-30
Filing date: 2024-01-23
Publication date: 2025-12-10
Also published as: JPWO2024162095A1; CN120476230A; WO2024162095A1

Abstract

An object of the present invention is to provide a high-strength monofilament having stable product quality with high processing yield by preparing a polyamide multifilament that has excellent fiber separability despite of high strength, which cannot be obtained by conventional techniques. The present invention provides a polyamide multifilament having an interlacing number A (counts/m) of more than 0.3 and less than 3.0 under a low-load tension condition, a ratio A/B of the interlacing number A to an interlacing number B (counts/m) under a high-load tension condition of 1.5 or more, a single yarn fineness of 6 to 40 dtex, and a strength of 7.0 to 11.0 cN/dtex, and also provides a polyamide monofilament obtained by fiber separation of the polyamide multifilament.

Description

TECHNICAL FIELD

The present invention relates to a polyamide multifilament and a polyamide monofilament.

BACKGROUND ART

Conventionally, as a method for efficiently producing a monofilament, a method called "fiber separation" has been proposed in which a multifilament is divided to provide a monofilament.
In polyester fibers, various proposals have been made to provide a monofilament with high processing yield by using this processing method called fiber separation (Patent Documents 1 to 3).
Recently, a technique for fiber separation of multifilaments has been widely used not only in apparel applications but also in general industrial material applications, and the application range of the technique has been expanded. In the field of aromatic polyamide fibers, a proposal has been made to provide an aromatic polyamide multifilament having a small fineness by fiber separation of a multi-strand multifilament with a plurality of yarns combined (Patent Documents 4 and 5).
In high-strength polyamide fibers, it has been described that monofilaments at a certain level of processing yield have been successfully obtained by not interlacing raw yarns in order to eliminate entanglement between single yarns of multifilaments (Patent Document 6).

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

Patent Document 1: Japanese Patent Laid-open Publication No. 2004-277910
Patent Document 2: Japanese Patent Laid-open Publication No. 2007-9341
Patent Document 3: Japanese Patent Laid-open Publication No. 2001-279521
Patent Document 4: Japanese Patent Laid-open Publication No. 2004-011043
Patent Document 5: Japanese Patent Laid-open Publication No. 2015-098664
Patent Document 6: Japanese Patent Laid-open Publication No. 2020-158906

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

However, when "fiber separation" processing of dividing a multifilament to provide a monofilament is applied to a conventional high-strength polyamide multifilament, some problems remain in fiber separation processability and product quality stability of the subsequent monofilament.
In any case described in Patent Documents 1 to 3, the elongation of parent yarn before separation processing for most of the monofilaments is 40% to 60%, and monofilaments obtained by fiber separation of these parent yarns are limited to apparel applications.
For example, Patent Document 3 shows that the fiber separability is favorable by setting the load tension applied to the probe to 0.20 cN/dtex or less in an entanglement method, and discloses that the correlation between the load tension, that is, the interlacing strength and the fiber separation processability, but does not clarify the interlacing number ratio for each load tension. Further, it is not considered that the bundling property of the single filaments constituting the multifilaments is lowered by lowering the interlacing strength, resulting in yarn slippage generated in the fiber package winding, and a decrease in the fiber separation processability associated therewith. In particular, in fibers having high strength and strong stiffness that can be used in industrial applications, the amount of yarn slippage generated in package winding tends to increase, and the low bundling property of single filaments provides a large influence on fiber separation processability. The low yarn bundling property of single filaments easily causes drawing unevenness between single filaments, in addition to the influence on fiber separation processing, and thus physical properties of monofilaments after fiber separation vary.
In addition, aspects in Patent Documents 4 and 5 are different from those in the case of fiber separation of multifilaments to provide monofilaments, and while the interlacing number is defined, the interlacing number for each load tension is not considered.
Further, with the technique described in Patent Document 6, a high fiber separation processing yield comparable to that in conventional polyester apparel applications is not achieved, and there remains a problem in stable fiber separation processability and product quality stability of the physical properties of monofilaments after fiber separation processing.
An object of the present invention is to solve the above problems, and is to provide a high-strength polyamide multifilament excellent in fiber separation processability, and a high-strength polyamide monofilament and a polyamide monofilament obtained by fiber separation of the high-strength polyamide multifilament and having stable product quality.

SOLUTIONS TO THE PROBLEMS

The present invention has been made as a result of intensive study to solve the above problems, and has the following configurations.

(1) A polyamide multifilament having an interlacing number A (counts/m) of more than 0.3 and less than 3.0 under a low-load tension condition, a ratio A/B of the interlacing number A to an interlacing number B (counts/m) under a high-load tension condition of 1.5 or more, a single yarn fineness of 6 to 40 dtex, and a strength of 7.0 to 11.0 cN/dtex.
(2) The polyamide multifilament according to (1), in which the polyamide multifilament has a single filament number of 8 to 16 and an elongation of 20 to 35%.
(3) The polyamide multifilament according to (1) or (2), in which a coefficient of variation (CV value) for strength of each single filament constituting the multifilament is less than 5.0, and a coefficient of variation for fineness of each single filament constituting the multifilament is less than 5.0.
(4) The polyamide multifilament according to any one of (1) to (3), in which a coefficient of variation (CV value) for an oil component adhesion rate of each single filament constituting the multifilament is less than 10.0.
(5) The polyamide multifilament according to any one of (1) to (3), in which the polyamide multifilament is for fiber separation.
(6) A polyamide monofilament obtained by fiber separation of the polyamide multifilament according to any one of (1) to (3).

EFFECTS OF THE INVENTION

The present invention can provide a high-strength polyamide multifilament having excellent fiber separation processability, and a high-strength monofilament having stable product quality.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1 is a schematic view of a polyamide multifilament production step of the present invention.

EMBODIMENTS OF THE INVENTION

Hereinafter, the present invention will be described in detail.
The raw material used for the polyamide multifilament of the present invention is not particularly limited as long as it is a polyamide such as nylon 6, nylon 66, nylon 12, nylon 46, nylon 410, nylon 56, nylon 510, nylon 610, copolymerized polyamide of nylon 6 and nylon 66, or copolymerized polyamide obtained by copolymerizing nylon 6 with polyalkylene glycol, dicarboxylic acid, amine, or the like. The polyamide multifilament of the present invention may contain, as necessary, a terminal blocking agent such as monocarboxylic acid, a matting agent such as titanium oxide, a polymerization catalyst such as a phosphorus compound, a heat resistance agent, an antioxidant such as a copper compound and a halide of an alkali metal or an alkaline earth metal, and a heat resistance stabilizer as components other than polyamide, but the polyamide component is preferably 95% by weight or more, more preferably 97% by weight or more. The amount of the polyamide component of less than 95% by weight is not preferable, because the mechanical properties of the polyamide are deteriorated.
The polyamide multifilament in the present invention is required to have an interlacing number A of more than 0.3 counts/m and less than 3.0 counts/m under a low-load tension condition. The interlacing number is preferably more than 0.3 counts/m and less than 2.5 counts/m, more preferably more than 0.3 counts/m and less than 2.0 counts/m. The interlacing number A under a low-load tension condition in the present invention is an interlacing number when measured at a trip level of 0.17 cN/dtex, an initial tension of 0.05 cN/dtex, a measurement speed of 10 m/min, and a yarn length of 1000 m using an automatic interlacing degree tester (for example, entanglement tester R-2072 manufactured by Rothschild-Instruments) capable of performing the same procedure as the method described in JIS L 1013 (2010) 8.15, and is, for example, a value obtained by the measurement described in the section of Examples. It has been found that when the interlacing number A under a low-load tension condition as in the present invention is more than 0.3 counts/m and less than 3.0 counts/m, the bundling property between single filaments constituting the multifilament is appropriately imparted, thereby allowing suppression of single yarn slippage during yarn package winding and yarn breakage in the fiber separation step accompanying the single yarn slippage. In the present invention, when the interlacing number under a low-load tension condition is 3.0 counts/m or more, such problems arise as poor fiber separability in the fiber separation step due to excessively high entanglement between single filaments and quality variation of monofilaments after fiber separation due to tension concentration on the highly entangled fibers. The bundling property between single filaments is not imparted in the case where the interlacing number is 0.3 counts/m or less, and thus the yarn slippage during yarn package winding occurs, which causes yarn breakage during fiber separation processing.
In addition, it is important for the polyamide multifilament of the present invention to have the ratio A/B of the interlacing number A (counts/m) under a low-load tension condition to the interlacing number B (counts/m) under a high-load tension condition being 1.5 or more. The ratio A/B is more preferably 2.0 or more, more preferably 2.5 or more. The interlacing number B under a high-load tension condition in the present invention is an interlacing number when measured at a trip level of 0.51 cN/dtex, an initial tension of 0.05 cN/dtex, a measurement speed of 10 m/min, and a yarn length of 1000 m using an automatic interlacing degree tester (for example, entanglement tester R-2072 manufactured by Rothchild-Instruments) capable of performing the same procedure as the method described in JIS L 1013 (2010) 8.15, and is, for example, a value obtained by the measurement described in the section of Examples. The interlacing number ratio A/B is 1.5 or more as in the present invention, meaning that while interlacing is detected under a low-load tension condition, there is a large amount of interlacing that is not detected under a high-load tension condition, and such interlacing has been found to have a form of "mild interlacing", that is, yarn breakage cannot occur due to slipping through the entanglement of single filaments under tension during fiber separation processing, and the characteristics thereof have been clarified. It has been confirmed that within the range of the interlacing number ratio, the single filament bundling property can be imparted to such an extent that the yarn slippage during yarn package winding can be suppressed while the yarn breakage is reduced during the fiber separation processing caused by the entanglement of single filaments, and thus there is a correlation with the success rate of the fiber separation processing. When the ratio of the interlacing number is less than 1.5, excessively high entanglement between single filaments causes poor fiber separability in the fiber separation step and tension concentration on the single filaments having high entanglement, resulting in occurrence of quality variation of monofilaments after fiber separation.
The polyamide multifilament of the present invention has a single filament fineness of 6 to 40 dtex. The single filament fineness is preferably 7 to 37 dtex, and more preferably 8 to 34 dtex. When the single filament fineness is more than 40 dtex, the cooling efficiency during spinning is deteriorated, and thus the raw yarn quality is deteriorated, and high strength quality suitable for industrial use cannot be obtained. When the single filament fineness is less than 6 dtex, entanglement of single filaments easily occurs, and thus it is difficult to control the interlacing number ratio under two types of tension, and it is difficult to exhibit a "mild interlacing" form.
The strength of the polyamide multifilament of the present invention is 7.0 to 11.0 cN/dtex. The strength is preferably 7.5 to 9.5 cN/dtex. When the strength is in such a range, high strength quality can be obtained also for the monofilaments after fiber separation of the multifilament. A strength of less than 7.0 cN/dtex is insufficient for high strength monofilaments for industrial applications. When attempting to obtain a polyamide multifilament having a strength more than 11.0 cN/dtex, mechanical draw is performed at a high ratio, which often causes generation of fuzz and yarn breakage accompanying the generation of fuzz during fiber separation processing.
The elongation of the polyamide multifilament of the present invention is preferably 20.0% to 35.0%. The elongation is more preferably 22.0% to 35.0%. Within this range, a certain degree of stretching is allowed during the fiber separation processing, and thus the fiber separability becomes favorable. In addition, it is possible to increase the toughness and breaking work of the monofilament after the fiber separation and to maintain excellent durability. The strength (cN/dtex) and the elongation (%) are values measured under a constant speed elongation condition shown in JIS L 1013 (1999) 8.5.1 Standard Time Test.
The number of single filaments of the polyamide multifilament of the present invention is preferably 8 to 16. The number is more preferably 12 to 16. When producing monofilaments having the same fineness, the total discharge amount of the polymer increases as the number of single filaments increases, and thus spinning can be performed with favorable uniform dischargeability. In addition, the number of bobbins that can be subjected to fiber separation and wound by a general fiber separator is 16, and thus setting the number of single filaments to a prescribed number allows the multifilament to be formed into a monofilament by one cycle of the fiber separation processing.
Each of the single filaments constituting the polyamide multifilament of the present invention has coefficients of variation (CV value) of less than 5.0 for strength and fineness. Preferably, the coefficients of variation for both are less than 4.0. More preferably, the coefficients of variation for both are less than 3.5. Setting the coefficients of variation within the above preferable range allow a monofilament with stable product quality to be provided. Herein, the coefficients of variation (CV value) for strength and fineness of single filaments are values determined by measuring the strength and fineness of each monofilament obtained by fiber separation of a polyamide multifilament under the conditions of a fiber separation speed of 400 m/min and a fiber separation tension of 0.75 cN/dtex by the method described later, calculating the average value and the standard deviation from the measurement data, and using the following formula: $coefficient of variation (%) = [\begin{array}{l} standard \\ deviation \end{array}] / [average] \times 100 .$
In addition, the coefficient of variation (CV value) for the oil component adhesion rate of each single filament constituting the polyamide multifilament of the present invention is preferably less than 10.0. The coefficient of variation for the oil component adhesion rate is more preferably less than 8.0. Herein, the coefficient of variation (CV value) for the oil component adhesion rate of each single filament is a value determined by measuring the oil component adhesion rate of each monofilament obtained by fiber separation of a polyamide multifilament under the conditions of a fiber separation speed of 400 m/min and a fiber separation tension of 0.75 cN/dtex by the method described later, calculating the average value and the standard deviation from the measurement data, and using the following formula: $coefficient of variation (%) = [\begin{array}{l} standard \\ deviation \end{array}] / [average] \times 100 .$
Setting the coefficient of variation for the oil component adhesion rate within the above preferable range allows the draw tension applied during thermal drawing to become uniform in each monofilament, and drawing unevenness to be suppressed. Further, the friction between the single filaments generated during the fiber separation processing is made uniform, and thus the fiber separability becomes favorable. In addition, an oil agent to be used is not particularly limited as long as it is a known oil agent.
Fig. 1 schematically shows a machine for direct spinning and drawing preferably used in the present invention.
Hereinafter, a method for producing the polyamide multifilament of the present invention will be described with reference to Fig. 1 as an example, but the production method is not limited thereto as long as the polyamide multifilament of the present invention can be obtained.
First, raw material chips of polyamide, which is a raw material of the polyamide multifilament of the present invention, are prepared. As a polymerization method of the polyamide, a known polymerization method can be used.
The sulfuric acid relative viscosity (hereinafter, referred to as viscosity) of the raw material chips of the polyamide multifilament of the present invention is preferably 2.5 to 3.9, and more preferably 3.0 to 3.9. Within such a range, a high-strength polyamide multifilament can be obtained with favorable stringiness. The sulfuric acid relative viscosity refers to a value obtained by dissolving a sample in 98% sulfuric acid and measuring the sulfuric acid relative viscosity at 25°C using an Ostwald viscometer.
Then, the above-described polyamide chips are supplied to an extruder-type spinning machine, fed to a spinneret by a metering pump, and melt-spun. The spinning temperature is set to a value 50°C higher than the melting point of the polymer, and the polymer is preferably discharged from a spinneret 1 having 8 to 16 holes. It is preferable to pass through a heating cylinder 2 surrounding a range of 5 to 300 cm from immediately below the spinneret. The temperature in the heating cylinder is -30 to +30°C in a preferable aspect and is more preferably -15 to +15°C with respect to the melting point of the polymer polyamide. Slowly cooling the spun yarn through a high-temperature atmosphere surrounded by the heating cylinder without immediately cooling the spun yarn allows the molecular orientation of the melt-spun polyamide to be relaxed and the molecular orientation uniformity among the single filaments to be enhanced, and thus can increase the strength of the polyamide multifilament.
The undrawn yarn 5 that has passed through the high temperature atmosphere is then cooled and solidified by blowing air at 10 to 80°C, preferably 10 to 50°C by a cross flow cooling device 3. In addition, when the cooling air is more than 80°C, filament swaying increases during spinning, and thus collision or the like between the single filaments occurs, which causes deterioration of yarn productivity. The cross flow cooling device is preferably a uniflow chimney.
Thereafter, the obtained cooling yarn can be applied with an oil agent by an oil supply device 4 including an oil supply roll, taken up by a take-up roller (1FR) 6, drew, and then wound up, and the oil supply roll is preferably satin finished from the viewpoint of uniform adhesion of the oil agent. Using the oil supply roll subjected to the satin finish increases the contact area between the yarn and the roll, allowing reduction of variations in the oil component adhesion rate between the single filaments. As the oil agent to be applied, a known oil agent can be used, but in order to suppress single yarn winding on the take-up roller (1FR) 6, the adhesion amount is preferably 0.3 to 1.5% by weight, and more preferably 0.5 to 1.0% by weight.
In addition, the spinning speed defined by the rotation speed of the take-up roller (1FR) 6 is preferably 400 to 1200 m/min. When the spinning speed is 400 m/min or more, the final production speed is also sufficient, and the polyamide multifilament can be produced with high production efficiency and at low cost. When the spinning speed is 1200 m/min or less, frequent occurrence of yarn breakage and fuzz can be prevented, which is preferable.
The spun yarn obtained by the methods described above can be subjected to drawing, relaxation heat treatment, winding, and the like using known methods. Specifically exemplifying the case of the two-stage drawing, the spun yarn taken up by the take-up roller (1FR) 6 is wound in the order of a yarn supplying roller (2FR) 7, a first drawing roller (1DR) 8, a second drawing roller (2DR) 10, and a relaxation roller (RR) 11, subjected to a heat treatment and a drawing treatment, and wound around a winder 13.
Pre-stretch drawing is performed between 1FR and 2FR, first stage drawing is performed between 2FR and 1DR, and second stage drawing is performed between 1DR and 2DR. It is preferable that the temperature of 2FR is set to -20°C to +20°C of the glass transition temperature of the polymer, and the temperature of 1DR is set to 100 to 225°C, and pre-stretch drawing and first stage drawing are performed by thermal drawing at around the glass transition temperature. The remaining drawing and heat setting temperatures are typically preferably performed at a high temperature ranging from -20°C to +20°C of the crystallization temperature of the polymer.
Regarding the total draw ratio (hereinafter, also simply referred to as a draw ratio), that is, the ratio between the take-up roller (1FR) 6 and the second drawing roller (2DR) 10, in order to obtain a high-strength polyamide multifilament, it is preferable to employ a high draw ratio, and drawing may be performed at 3.5 to 5.0 times within the fineness range described in the present invention. In addition. The winding speed is typically preferably 1,500 to 4,500 m/min, more preferably 2,000 to 4,500 m/min. In addition, it is preferable that the yarn is wound up into a cheese shape yarn with a winding device under the condition of a winding tension of 0.05 to 0.25 cN/dtex.
In addition, in order to obtain the polyamide multifilament having the interlacing number A and the interlacing number ratio A/B specified in the present invention, it is effective to perform fluid treatment on the yarn using a first interlacing nozzle 9 between the first drawing roller (1DR) 8 and the second drawing roller (2DR) 10 and a second interlacing nozzle 12 between the relaxation roller (RR) 11 and the winder 13 when the yarn is wound into a polyamide multifilament package. In particular, when the multifilament is subjected to fluid treatment under the winding tension specified above, it is preferable to perform the fluid treatment after adjusting the pressure for treatment at the second interlacing nozzle 12 to 0.005 to 0.015 MPa/dtex per unit single filament fineness. The pressure is more preferably 0.005 to 0.010 MPa/dtex.
The method as described above allows production of the polyamide multifilament having high strength and favorable fiber separability described in the present invention.
In addition, the polyamide multifilament obtained by the above method is processed by a known fiber separation method, thereby allowing a high-strength polyamide monofilament with stable product quality to be obtained at high processing yield.

EXAMPLES

Hereinafter, the present invention will be described in more detail with reference to Examples. The definition and measurement method of each characteristic in the present invention are as follows.

(1) Sulfuric acid relative viscosity (ηr): Using a polymer chip or a raw yarn as a sample, 0.25 g of a sample was dissolved in 25 ml of 98% sulfuric acid, and measurement was performed at 25°C using an Ostwald viscometer to provide the sulfuric acid relative viscosity (ηr) from the following formula. The measured value was calculated from the average value of five samples. ηr = the number of seconds that the sample solution flows down/the number of seconds that only sulfuric acid flows down.
(2) Total fineness: The fineness based on corrected weight was measured under a predetermined load of 0.045 cN/dtex in accordance with JIS L 1013 (1999) 8.3.1 method A and taken as the total fineness.
(3) Number of single filaments: The number of single filaments was calculated by the method of JIS L 1013 (1999) 8.4.
(4) Single filament fineness: The single filament fineness was calculated by dividing the total fineness by the number of single filaments.
(5) Tenacity, strength, and elongation: The measurement was performed under constant speed elongation conditions defined in JIS L 1013 (1999) 8.5.1, Standard Condition Test. A sample was measured using "TENSILON" UCT-100 manufactured by ORIENTEC CORPORATION, at a holding interval of 25 cm and a tensile speed of 30 cm/min. The tenacity was determined from the maximum tenacity in the S-S curve, the elongation was determined from the elongation at the point showing the maximum tenacity in the S-S curve, and the strength was determined by dividing the tenacity by the total fineness. The multifilament sample was taken every 1 m in the longitudinal direction, the measurement was performed at five points, and the average value was obtained from the measurement data.
(6) Interlacing number: Using an entanglement tester R-2072 manufactured by Rothschild-Instruments, the evaluation was performed for a measurement speed of 10 m/min and a yarn length of 1000 m. For the interlacing number A under the low-load tension condition, the trip level was set to 0.17 cN/dtex, for the interlacing number B under the high-load tension condition, the trip level was set to 0.51 cN/dtex, and for the initial tension, both measurement levels were set to 0.05 cN/dtex.
(7) Interlacing number ratio A/B for each load tension: A/B was determined by dividing the interlacing number A (counts/m) measured in (6) above by the interlacing number B (counts/m).
(8) Fiber separation processability: 50 multifilament packages having a multifilament weight of 5.0 kg were subjected to fiber separation using a fiber separator KA-516OF manufactured by AIKI RIOTECH Corporation, and the ratio of packages that were successfully subjected to fiber separation into monofilaments without yarn breakage was represented as a package fullness (%). The fiber separation processing was performed at a fiber separation speed of 400 m/min and a fiber separation tension of 0.75 cN/dtex.
- S: Package fullness is 85% or more
- A: Package fullness of 70% or more and less than 85%
- B: Package fullness of 55% or more and less than 70%
- C: Package fullness of 30% or more and less than 55%.
(9) Coefficient of variation of fineness of each single filament: The fineness of each monofilament obtained from the same package subjected to fiber separation processing under the conditions of (8) above was measured in the same manner as in (2) above, and an average value and a standard deviation were calculated from the measurement data, and the following formula was used: $coefficient of variation (%) = [\begin{array}{l} standard \\ deviation \end{array}] / [average value] \times 100 .$
(10) Coefficient of variation of strength of each single filament: The strength of each monofilament obtained from the same package subjected to fiber separation processing under the conditions of (8) above was measured in the same manner as in (5) above, an average value and a standard deviation were calculated from the measurement data, and the coefficient of variation was calculated from the calculation formula described in (9) above.
(11) Coefficient of variation for oil component adhesion rate of each single filament: The oil component adhesion amount of each monofilament obtained from the same package subjected to fiber separation processing under the conditions of (8) above was measured by a hexane extraction method in accordance with JIS L 1096 (2010) 8.32, the average value and standard deviation of the oil component adhesion rate were calculated from the measurement data, and the coefficient of variation was calculated from the calculation formula described in (9) above.

(Example 1)

A 5-wt% aqueous solution of copper acetate as an antioxidant was added to and mixed with the nylon 66 chips obtained by the liquid phase polymerization, and 68 ppm of copper with respect to the polymer weight was added and adsorbed. Then, a 50-wt% aqueous solution of potassium iodide and a 20-wt% aqueous solution of potassium bromide were each added and adsorbed so as to be 0.1 parts by weight as potassium with respect to 100 parts by weight of the polymer chip, and solid-phase polymerization was performed using a batch-type solid-phase polymerization apparatus to provide nylon 66 pellets having a sulfuric acid relative viscosity of 3.75. The obtained nylon 66 pellets were supplied to an extruder having a diameter of 110 mm and melted at a melting temperature of 300°C. The discharge amount of the molten polymer was adjusted by a metering pump such that multifilaments having a total fineness of 175 dtex were obtained, and the molten polymer was fed into a spinning pack. Thereafter, filtration was performed through a metal nonwoven fabric filter having a roughness of 40 µm in the spinning pack, and then spinning was performed through a spinneret having 16 circular holes. A heating cylinder having a heating cylinder length of 15 cm was placed 3 cm below the spinneret surface, and heated such that the in-cylinder atmospheric temperature was 250°C. Herein, the in-cylinder atmosphere temperature is an air temperature at a portion 1 cm away from the inner wall at the center of the heating cylinder length. A uniflow-type chimney blowing air from one direction was attached immediately below the heating cylinder, and cold air at 20°C was blown to the yarn at a speed of 35 m/min to cool and solidify the yarn. Thereafter, an oil agent was applied to the yarn with a satin finish oiling roll (oil supply roll).
An undrawn yarn to which the oil agent had been applied was wound and taken up in 1FR rotating at a surface speed of 850 m/min, and then drawn at a total draw ratio of 4.1 times. The take-up yarn was continuously stretched by 5% between the take-up roller and 2FR without being wound up once, and then successively drawn in the first stage at a rotation speed ratio of 2.80 times, then drawn in the second stage at a rotation speed ratio of 1.40 times, and wound up at a speed of 3500 m/min. The roller surfaces of 1FR and 2FR were mirror finished, and 1DR, 2DR, and RR were satin finished. The roller temperatures of 1FR were non-heated, 2FR was 40°C, 1DR was 150°C, 2DR was 225°C, and RR was 150°C. Such melt spinning and drawing provided the nylon 66 multifilament. The entangling treatment was performed by injecting high-pressure air from a direction perpendicular to the traveling yarns in the entangling device. A guide for regulating the traveling yarn was provided in front of and behind the interlacing nozzle, and the pressure of the injected air was set to 0.30 MPa for the first interlacing nozzle and 0.10 MPa for the second interlacing nozzle.

(Example 2)

The procedure was performed in the same manner as in Example 1 except that the pressure of the second interlacing nozzle was 0.07 MPa.

(Example 3)

The procedure was performed in the same manner as in Example 1 except that the pressure of the second interlacing nozzle was 0.13 MPa.

(Example 4)

The procedure was performed in the same manner as in Example 1 except that the total fineness of the polyamide multifilament was set to 110 dtex, the ratio between 1DR and 2DR was changed, and yarns were produced at a total draw ratio of 4.2 times.

(Example 5)

The procedure was performed in the same manner as in Example 1 except that the total fineness of the polyamide multifilament was set to 350 dtex, the ratio between 1DR and 2DR was changed, and yarns were produced at a total draw ratio of 4.5 times.

(Example 6)

The procedure was performed in the same manner as in Example 1 except that a mirror-finished oil supply roll was used.

(Example 7)

The procedure was performed in the same manner as in Example 1 except that the first interlacing nozzle pressure was 0.00 MPa.

(Example 8)

Nylon 6 pellets having a sulfuric acid relative viscosity of 3.30 were melt-spun at 270°C. The discharge amount of the molten polymer was adjusted by a metering pump so as to provide multifilaments having a total fineness of 470 dtex, and spinning was performed through a spinneret having 14 circular holes. The yarn was drawn at a total draw ratio of 4.7 times, and wound up at a winding speed of 2100 m/min. In addition, the temperature of each roller was set to non-heating for 1FR, 40°C for 2FR, 150°C for 1DR, 200°C for 2DR, and 150°C for RR. Nylon 6 multifilaments were obtained by such melt spinning and drawing. The pressure of air injected in the interlacing treatment was set to 0.20 MPa at the first interlacing nozzle and 0.20 MPa at the second interlacing nozzle. The other procedures were performed in the same manner as in Example 1.

(Example 9)

The procedure was performed in the same manner as in Example 8 except that the total fineness of the polyamide multifilament was set to 235 dtex and that multifilaments were produced at a total draw ratio of 4.5 times.

(Example 10)

The procedure was performed in the same manner as in Example 1 except that nylon 410 pellets having a sulfuric acid relative viscosity of 3.60 were used.

(Example 11)

The procedure was performed in the same manner as in Example 8 except that nylon 610 pellets having a sulfuric acid relative viscosity of 3.80 were used.
The physical properties and fiber separation processability of the polyamide multifilaments obtained in Examples 1 to 11, and the coefficients of variation in the physical properties of the monofilaments after fiber separation were evaluated, and the results are shown in Table 1.
As is clear from Table 1, in the polyamide multifilaments of the present invention, the ratio A/B of the low-load tension condition A to the high-load tension condition B is controlled within a prescribed range, thereby achieving favorable fiber separation processability despite of high strength.

(Comparative Example 1)

The procedure was performed in the same manner as in Example 1 except that the pressure of the second interlacing nozzle was 0.00 MPa.

(Comparative Example 2)

The procedure was performed in the same manner as in Example 1 except that the pressure of the second interlacing nozzle was 0.25 MPa.

(Comparative Example 3)

The procedure was performed in the same manner as in Example 1 except that the total fineness of the polyamide multifilament was 78 dtex and the pressure of the second interlacing nozzle was 0.05 MPa.

(Comparative Example 4)

The procedure was performed in the same manner as in Example 1 except that the total fineness of the polyamide multifilament was 700 dtex, the pressure of the second interlacing nozzle was 0.25 MPa, the total draw ratio was 4.5 times, and the winding speed was 2700 m/min.

(Comparative Example 5)

The procedure was performed in the same manner as in Example 1 except that the yarn was produced at a pressure of the second interlacing nozzle of 0.00 MPa and a total draw ratio of 2.7 times.

(Comparative Example 6)

The procedure was performed in the same manner as in Example 8 except that the yarn was produced at a pressure of the second interlacing nozzle of 0.00 MPa and a total draw ratio of 3.3 times.

(Reference Example 1)

With reference to Examples of Patent Document 6: Japanese Patent Laid-open Publication No. 2020-158906 , the following polyamide multifilament was produced and evaluated. That is, the procedure was performed in the same manner as in Example 1 except that a mirror-finished oil supply roll similar to that used in Example 6 was used, neither the first interlacing nozzle nor the second interlacing nozzle was used, and the interlacing treatment was not performed in any of the period from 1DR to 2DR and the period from RR to winding. The mirror-finished oil supply roll used for applying the oil agent in the present reference example is conventionally widely used.
The physical properties and fiber separation processability of the polyamide multifilaments obtained in Comparative Examples 1 to 6, and the coefficients of variation in the physical properties of the monofilaments after fiber separation were evaluated, and the results are shown in Table 2.
In Comparative Example 1, the polyamide multifilament was produced without performing the interlacing treatment by the second interlacing nozzle, and it can be seen that the interlacing number A under the low-load tension condition is a minute value. In this case, it was suggested that the bundling property between the single filaments was extremely lost, thereby causing frequent yarn slippage during package winding and affecting the fiber separation processability of the polyamide multifilament.
In Comparative Example 2, the pressure of the second interlacing nozzle was 0.25 MPa, and the pressure per single filament fineness was 0.023 MPa/dtex. In this case, the interlacing number A under the low-load tension condition and the interlacing number B under the high-load tension condition have almost the same value, and the normal interlacing mode is adopted. The fiber separation processability of the above polyamide multifilament was significantly deteriorated.
In Comparative Example 3, the total fineness of the polyamide multifilament was 78 dtex, and the single filament fineness was 4.9 dtex. In addition, the pressure of the second interlacing nozzle was 0.05 MPa, and the pressure of the second interlacing nozzle per single filament fineness was controlled to 0.010 MPa/dtex. In this case, the interlacing number A under the low-load tension condition was able to be controlled within the range specified in the present invention, but the interlacing number B under the high-load tension condition also had the same value, and the "mild interlacing" mode was not able to be exhibited. As a result, the fiber separation processability of the above polyamide multifilament was affected.
In Comparative Example 4, the total fineness of the polyamide multifilament was 700 dtex, and the single filament fineness was 43.8 dtex. In this case, the cooling efficiency during spinning was deteriorated and the raw yarn quality was deteriorated, and thus the prescribed strength level was not able to be achieved in the present invention.
Reference Example 1 corresponds to an example in which a polyamide multifilament was produced with reference to the method described in Examples of Patent Document 6. In this case, the second interlacing nozzle was not subjected to the interlacing treatment, and thus the bundling property between the single filaments was extremely deteriorated, thereby leaving a problem of the fiber separation processability and the package fullness of the fiber separation processing. In addition, the mirror-finished oil supply roll material was used and the first interlacing nozzle was not subjected to the interlacing treatment, and thus the coefficient of variation in strength between single filaments and the coefficient of variation in oil component adhesion rate between single filaments were significantly poor, thereby leaving a concern about the product quality stability of the monofilament.

INDUSTRIAL APPLICABILITY

The polyamide multifilament of the present invention has high strength but is excellent in fiber separability, and variation in physical properties between single filaments is suppressed, thus allowing a high-strength monofilament with stable product quality to be provided. As a result, it is possible to expand the application range of the polyamide monofilament and enhance existing products using the monofilament such as sports strings and screen gauzes.

DESCRIPTION OF REFERENCE SIGNS

1:: Spinneret
2:: Heating cylinder
3:: Cross flow cooling device
4:: Oil supply device
5:: Yarn
6:: Take-up roller (1FR)
7:: Yarn supplying roller (2FR)
8:: First drawing roller (1DR)
9:: First interlacing nozzle
10:: Second drawing roller (2DR)
11:: Relaxation roller (RR)
12:: Second interlacing nozzle
13:: Winder

Claims

A polyamide multifilament comprising an interlacing number A (counts/m) of more than 0.3 and less than 3.0 under a low-load tension condition, a ratio A/B of the interlacing number A to an interlacing number B (counts/m) under a high-load tension condition of 1.5 or more, a single filament fineness of 6 to 40 dtex, and a strength of 7.0 to 11.0 cN/dtex.
The polyamide multifilament according to claim 1, wherein the polyamide multifilament has a single filament number of 8 to 16 and an elongation of 20 to 35%.
The polyamide multifilament according to claim 1 or 2, wherein a coefficient of variation (CV value) for fineness of each single filament constituting the multifilament is less than 5.0, and a coefficient of variation (CV value) for strength of each single filament constituting the multifilament is less than 5.0.
The polyamide multifilament according to any one of claims 1 to 3, wherein a coefficient of variation (CV value) for an oil component adhesion rate of each single filament constituting the multifilament is less than 10.0.
The polyamide multifilament according to any one of claims 1 to 3, wherein the polyamide multifilament is for fiber separation.
A polyamide monofilament obtained by fiber separation of the polyamide multifilament according to any one of claims 1 to 3.