JP2025110337A - Manufacturing method of polyphenylene sulfide fiber and polyphenylene sulfide fiber - Google Patents

Abstract

To provide a polyphenylene sulfide fiber enabling efficient fiber production with good operability in spinning and drawing processes through selection of a specific oil agent, and ensuring quality improvement by reducing fluff and monofilament breakage.SOLUTION: Provided is a production method for a polyphenylene sulfide fiber having p-phenylene sulfide units as its main constituent unit, wherein, as an oil agent component, an oil agent containing 5 to 100 mass% of octyl phosphonate based on the total oil agent components is attached so that the oil adhesion amount is 0.3 mass% to 1.5 mass%. Further provided is a polyphenylene sulfide fiber having p-phenylene sulfide units as its main constituent unit, wherein, as an oil agent component, an oil agent containing 5 to 100 mass% of octyl phosphonate based on the total oil agent components is attached so that the oil adhesion amount is 0.3 mass% to 1.5 mass%.SELECTED DRAWING: None

Description

The present invention relates to polyphenylene sulfide fibers and a method for producing polyphenylene sulfide fibers.

In industrial filters, mesh fabrics made of polyphenylene sulfide, polyvinylidene fluoride, liquid crystal polyester, etc. are currently widely used in terms of chemical resistance, dimensional stability, heat durability, etc. In particular, polyphenylene sulfide fabrics are widely used because they have excellent chemical resistance, dimensional stability, and cost performance, and are suitable for fields requiring advanced filter performance and battery separator materials. Accordingly, in recent years, high performance and various functions are required as filter performance. Fibers used in filters are also required to have various functions such as fibers with extremely fine single yarn fineness, fine monofilaments, and fibers with a fairly large fineness, and the required fineness, single yarn fineness, physical properties (strength, shrinkage rate), etc. are widely varied. In addition, the productivity and dimensional stability of fibers are also becoming important.
For example, methods for obtaining polyphenylene sulfide fibers having good dimensional stability are disclosed in Patent Documents 1 and 2.
Patent Document 1 describes a method for producing polyphenylene sulfide fibers in which polyphenylene sulfide fibers are drawn by a direct spin-drawing method under specific drawing conditions, thereby reducing fuzz and yarn breakage.
Furthermore, Patent Document 2 describes that a high-quality polyphenylene sulfide fiber with little fluff or yarn breakage can be produced by specifying the melt flow rate, L/D of the spinneret, cooling method, drawing conditions, etc. and producing the fiber by a direct spinning-drawing method.

Patent No. 4962361 JP 2001-262436 A

However, in the method for producing polyphenylene sulfide fiber in Patent Document 1, specifically, a fiber having a single yarn fineness of 4.4 dtex is described, but when the single yarn fineness is further reduced, the number of fluff increases and a fiber having excellent yarn quality cannot be obtained.
Furthermore, Patent Document 2 specifically describes a single yarn fineness of 4.5 dtex. However, even in this case, when a finer yarn fineness is used, there is a lot of fluff and it is not possible to obtain a yarn of good quality.

Therefore, an object of the present invention is to solve the above problems and to obtain a high-quality polyphenylene sulfide fiber which has good operability in the spinning and drawing steps and little fuzz or single-fiber breakage even when it has a fine fiber size.
Another object of the present invention is to obtain polyphenylene sulfide fibers having good dimensional stability and high quality even if the polyphenylene sulfide fibers are fine.

The present inventors have discovered that by using specific oil components in the oil used in production and specifying the blending ratio, it is possible to obtain a low dry heat shrinkage polyphenylene sulfide fiber (low dry heat shrinkage fiber) that has high quality with reduced fuzz count and good dimensional stability even when it is fine.
That is, firstly, the present invention provides a method for producing a polyphenylene sulfide fiber whose main constituent unit is p-phenylene sulfide, in which an oil containing 5 mass % to 100 mass % of octylphosphonate based on the total oil component is adhered so that the amount of oil adhered is 0.3 mass % to 1.5 mass %.
Secondly, the method for producing polyphenylene sulfide fiber according to 1 above is characterized in that the oil contains, as an oil component, a polyether selected from the group consisting of polyethylene glycol, polypropylene glycol, polybutylene glycol, and copolymer polyethers obtained by copolymerizing two or more of the above glycols.
Thirdly, the above-mentioned first or second method for producing polyphenylene sulfide fibers having a dry heat shrinkage rate at 150° C. of 3.5% or less.
Fourthly, there is provided a polyphenylene sulfide fiber having a main constituent unit being a p-phenylene sulfide unit, to which an oil containing 5 to 100% by mass of octylphosphonate based on the total oil component is adhered such that the amount of oil adhesion is 0.3 to 1.5% by mass.
Fifth, the polyphenylene sulfide fiber has a single yarn fineness of 3.5 dtex or less and a fluff count of 5 or less per 1,000,000 meters.
Sixth, the polyphenylene sulfide fiber according to the above item 4 or 5, which has a dry heat shrinkage rate at 150° C. of 3.5% or less.

According to the method for producing polyphenylene sulfide fiber of the present invention, by applying a specific oil agent having specific oil agent components and a specific blending ratio in a specific oil application amount, it is possible to reduce the spinning process and the number of fluff even in the case of fibers with a small single yarn fineness, and to obtain high-quality polyphenylene sulfide fiber.
Furthermore, according to the method for producing polyphenylene sulfide fibers of the present invention, the number of fluffs in fibers having a small single yarn fineness can be reduced, and high-quality low dry heat polyphenylene sulfide fibers can be obtained.

The present invention is described in detail below.

The polyphenylene sulfide resin used in the present invention is a polyphenylene sulfide consisting of a polymer having phenylene sulfide units as the main repeating units. Examples of phenylene sulfide units include p-phenylene sulfide units and m-phenylene sulfide units. The polyphenylene sulfide may be a homopolymer consisting of p-phenylene sulfide units, m-phenylene sulfide units, etc., or a copolymer having these, but from the viewpoints of heat resistance, processability, and economy, the repeating unit of p-phenylene sulfide is preferred.

Polyphenylene sulfide resin polymer types include crosslinked, semi-crosslinked, and linear types, with the linear type being preferred for spinnability and stretchability.

Furthermore, polyphenylene sulfide may contain small amounts of various additives, such as inorganic substances such as various metal oxides, kaolin, and silica, colorants, delustering agents, flame retardants, antioxidants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent brighteners, end group blocking agents, and compatibilizers, within the scope of the invention that does not impair the effects of the invention.

The melt flow rate (MFR) of the polyphenylene sulfide resin used in the present invention is preferably 100 g/10 min to 250 g/10 min. More preferably, it is 130 g/10 min to 200 g/10 min. From the viewpoint of spinning stability, 100 g/10 min or more is preferable. From the viewpoint of maintaining the strength of the fiber and providing strength and durability for suitable use in mesh fabrics such as filters, it is preferable that it is 250 g/10 min or less.

The moisture content of the polyphenylene sulfide resin pellets used in the present invention before spinning is preferably 100 ppm or less, and more preferably 10 ppm to 50 ppm. If it exceeds 100 ppm, it may cause thread breakage during spinning or cause bubbles (air bubbles) to be mixed in, which may reduce spinning operability.

The polyphenylene sulfide resin pellets used in the present invention are preferably pre-dried by vacuum drying to remove as much low molecular weight components as possible, such as moisture and oligomers, and the drying temperature is preferably 130°C to 190°C, and the drying time is preferably 6 hours to 12 hours.

The polyphenylene sulfide fiber of the present invention can be obtained using the polyphenylene sulfide resin described above by the manufacturing method described below.

The polyphenylene sulfide fiber of the present invention may be either a monofilament or a multifilament, but is particularly suitable for use in multifilaments.

The fineness of the polyphenylene sulfide fiber of the present invention is preferably 15 dtex to 1,000 dtex, and more preferably 33 dtex to 500 dtex.

The single yarn fineness of the polyphenylene sulfide fiber of the present invention is preferably 0.8 dtex to 5 dtex, and more preferably 1 dtex to 3.5 dtex.

The number of filaments in the polyphenylene sulfide fiber of the present invention is preferably 12 to 200, and more preferably 18 to 150.

The dry heat shrinkage rate of the polyphenylene sulfide fiber of the present invention at 150°C is preferably 3.5% or less. More preferably, it is 2.5% or less. When the dry heat shrinkage rate is in this range, the fiber has excellent dimensional stability, and is therefore particularly suitable for use in industrial materials that require high precision, high heat resistance, and chemical resistance, such as bag filters, motor binding cords, motor binder tapes, and dryer canvases for papermaking.

The cross-sectional shape of the polyphenylene sulfide fiber of the present invention is not particularly limited, and the outer shape of the fiber may be any shape, such as circular, triangular, rectangular, hollow, etc.

The polyphenylene sulfide fiber of the present invention preferably has an oil and grease adhesion amount of 0.3% to 1.5% by mass in terms of ease of passing through subsequent processes and obtaining woven fabrics, knitted fabrics, and meshes of good quality. More preferably, it is 0.6% to 1.2% by mass. If it is less than 0.3% by mass, fluff, single yarn breakage, and static electricity are likely to occur during stretching, and handling such as weaving tends to be poor. If it exceeds 1.5% by mass, there is a tendency for yarn breakage due to yarn shaking during stretching and for scum generation during weaving, which may affect the quality of mesh fabrics, industrial filters, etc.

The manufacturing method of the present invention makes it possible to obtain fine polyphenylene sulfide fibers with little fuzz, even when using polyphenylene sulfide fibers with low dry heat resistance.

In the following, polyphenylene sulfide fibers with a dry heat shrinkage rate of 3.5% or less at 150°C may be referred to as low dry heat polyphenylene sulfide fibers.

The oil used in the production method of the present invention essentially contains octylphosphonate, which will be described later, and may contain other oil components, such as commonly used polyether-based oils.
The oil agent suitable for use in the production method of the present invention will be described in detail below.

Phosphonates (phosphonates) are suitable oils for use in producing the polyphenylene sulfide fiber of the present invention, which requires low dry heat properties (for example, a shrinkage rate of 3.5% or less when evaluated at 150°C for 20 minutes). Examples of phosphonates (phosphonates) include hexyl pentyl phosphonate, heptyl pentyl phosphonate, octyl pentyl phosphonate, decyl pentyl phosphonate, phenyl pentyl phosphonate, dibutyl pentyl phosphonate, dihexyl phosphonate, heptyl phosphonate, pentyl phosphonate, octyl phosphonate, and phenyl phosphonate. Among these, potassium octyl phosphonate is preferred.

The content of phosphonate in the total oil agent is preferably 5% to 100% by mass, and more preferably 30% to 60% by mass. If it is less than 5% by mass, a good oil film will not be formed on the fiber surface, and the fiber will tend to peel off easily. There is also a risk of yarn breakage during drawing or the yarn winding onto the roll.

The oil agent for the polyphenylene sulfide fiber in the present invention may contain a polyether-based oil agent containing a polyether component such as a single component polyether such as polyethylene glycol, polypropylene glycol, or polybutylene glycol, or a copolymer polyether obtained by copolymerizing two or more of these polyethers. Among these oil agents, copolymer polyethers are preferred, and examples thereof include alkyl PO (polypropylene oxide)/EO (ethylene oxide). The polyether component, which is a smooth component, forms an oil film on the fiber surface, but the use of copolymer polyether makes the oil film stronger, and damage to the fiber in the inner layer of the package caused by tightening during winding is reduced, thereby suppressing variations in physical properties. In addition, the strong oil film makes the oil film less likely to peel off when rubbed against various guides, and it is thought that the friction coefficient of the fiber is reduced, resulting in good passability through higher-level processes.

The average molecular weight of the polyether component is preferably 2,000 to 13,000, and more preferably 3,000 to 10,000. With an average molecular weight of 2,000 or more, a strong oil film can be formed on the fiber surface. If the average molecular weight is 13,000 or less, the viscosity of the oil increases as the average molecular weight of the polyether component (oil) increases, and the coefficient of friction of the fiber surface increases, but this does not tend to affect the passability through higher-level processes.

The polyether-based oil content in the entire oil is preferably 4% to 50% by mass, and more preferably 5% to 30% by mass. If it is less than 4% by mass, a good oil film will not be formed on the fiber surface, making it prone to peeling and reducing the ability to pass through higher-level processes. If it exceeds 50% by mass, smoothness tends to decrease, and the oil viscosity may become too high, causing defects such as contamination of guides and rollers and dyeing spots on the fabric.

In addition to the above oils, commonly used mineral oils for spinning, fatty acid esters, emulsifiers, extreme pressure agents, antibacterial agents, etc. may also be added as lubricants.

In the present invention, the method of substantially adhering the oil agent to the fiber surface is preferably to use an aqueous emulsion in which the above-mentioned oil is dispersed in water at 1% by mass to 25% by mass relative to the total amount, and more preferably to use an aqueous emulsion at 5% by mass to 20% by mass. Note that if an aqueous emulsion with a high emulsion concentration of more than 25% by mass is used, the physical properties may become unstable when a specified oil is adhered, so in the present invention, it is preferable to adhere the oil agent to the fiber surface using an aqueous emulsion with a low concentration as described above.

The breaking strength of the polyphenylene sulfide fiber of the present invention is preferably 4 cN/dtex or more. More preferably, it is 4.5 cN/dtex or more. If it is 4 cN/dtex or more, the fabric strength will be sufficient even when used in woven fabrics, etc.

The breaking elongation of the polyphenylene sulfide fiber of the present invention is preferably 18% to 28%. More preferably, it is 20% to 25%. If it is less than 18%, there is a risk that fuzz will be generated during fiber production, which will reduce spinning operability, and the quality of the fabric using this fiber will also be reduced. If it exceeds 28%, the dimensional stability of the fabric using this fiber will tend to deteriorate, and the quality of the fabric using this fiber will also be reduced.

The dry heat shrinkage rate of the polyphenylene sulfide fiber of the present invention at 150°C is preferably 3.5% or less. More preferably, it is 2.5% or less. If it exceeds 3.5%, the fabric using this fiber tends to have poor dimensional stability, and there is a risk of the quality of the fabric using this fiber being reduced.

If necessary, the polyphenylene sulfide fiber of the present invention may be entangled using an interlace nozzle (I/L) after passing through the draw roll. In this case, the number of entanglements is preferably 8 pieces/m to 25 pieces/m, and more preferably 10 pieces/m to 20 pieces/m.

The fluff count of the polyphenylene sulfide fiber of the present invention is preferably 5 or less fluffs per 1,000,000 meters when the single yarn fineness is 3.5 dtex or less. Less than 2 fluffs is more preferable, and even more preferable is no fluff (0 fluff count). If the fluff count exceeds 5 fluffs, the fabric using this fiber will have many defects, resulting in a fabric with many unusable fabric portions (so-called C-grade fabric), making it difficult to use in products such as filters that require high precision and performance.

A preferred method for producing the polyphenylene sulfide fiber of the present invention is described in detail below.

The polyphenylene sulfide fiber of the present invention is preferably produced by a conventional method. Specifically, in the first step, a bobbin of undrawn polyphenylene sulfide fiber obtained by melt spinning a polyphenylene sulfide resin in a spinning machine is collected, and then in the second step, an undrawn yarn is drawn from the obtained undrawn yarn bobbin, and drawn and heat-set in a drawing machine to obtain a drawn yarn.

A more specific description of a suitable manufacturing method is given below.

First, polyphenylene sulfide resin pellets are melted and melt spun using an extruder-type spinning machine. The spinning temperature during melt spinning is preferably 300°C to 330°C.

After the resin pellets are melted, the molten resin is filtered through a spinning filter and then extruded from the nozzle holes using a spinning nozzle.

The clearance of the above-mentioned spun filter is preferably 5 μm to 15 μm for fibers of 40 dtex or less, and 15 μm to 30 μm for fibers of more than 40 dtex, from the viewpoint of removing contamination and gel and reducing fuzz.

After the molten resin is spun out of the nozzle holes, the spun thread passes through a heat-retaining tube and a cooling zone installed directly below the spinning thread. In this cooling zone, cold air is blown onto the spun resin, causing it to solidify.

The temperature of the cold air is preferably in the range of 20°C to 30°C.
The speed of the cold air is usually preferably in the range of 20 m/min to 45 m/min, except for the case where the single filament fineness after drawing is as thin as 1.5 dtex or less, in which case the speed is preferably in the range of 20 m/min to 30 m/min.

It is also preferable to start the cooling zone approximately 80 mm to 150 mm below the nozzle.

The spun yarn is cooled and solidified, and then an oil is applied to it. It is preferable to apply the oil after passing through the cooling zone. The oil can be applied by any known method, such as roll application or guide application.

After applying the oil, the yarn is passed through a godet roll and wound at a specified spinning speed to obtain an undrawn bobbin of polyphenylene sulfide fiber.

The spinning speed is preferably in the range of 800 m/min to 1600 m/min.

Next, the resulting undrawn polyphenylene sulfide yarn is drawn.
In the case of a multifilament that requires low dry heat properties, it is preferable to use, as the drawing device, a device that is composed of a feed roll (1stR) paired with a rubber roller, a roll heater (2ndR) for preheating, multiple roll heaters (3rdR, 4thR) for heat setting, and a draw roll (5thR), and that winds up into a pirn shape by spindle drive.

In this case, the temperature of the 2ndR roll heater is preferably 100°C to 120°C, and more preferably 105°C to 110°C.

The heat setting temperatures for the 3rdR and 4thR may be set appropriately according to the intended use. For example, the heat setting temperature for the 3rdR is preferably in the range of 100°C to 160°C, and the heat setting temperature for the 4thR is preferably in the range of 180°C to 225°C.

The stretching speed is preferably 500 m/min to 1,200 m/min, and more preferably 600 m/min to 1,000 m/min.

The draw ratio is preferably in the range of 1.01 to 1.05 times between the 1st R and the 2nd R, and more preferably 1.01 to 1.03 times. Between the 3rd R and the 4th R, it is preferably 1 to 1.1 times. Between the 4th R and the 5th R, it is preferable to mainly carry out a relaxation treatment, and in this case, it is preferably 0.95 to 0.99 times, and more preferably 0.965 to 0.985 times. Between the 2nd R and the 3rd R, the draw ratio may be adjusted and set according to the target elongation of the fiber (e.g., 23%).
The suitable total draw ratio is in the range of 2 to 4.5 times, although it depends on the spinning and winding speed.

The present invention will be specifically described below with reference to examples. Note that the present invention is not limited to the examples described below. The physical properties and evaluation of the filaments in the examples are as follows.
A. MFR
The MFR value was measured in accordance with JIS K 7210 (1999) under conditions of a temperature of 315.5° C. and a load of 5000 g.
B. Fineness According to JIS L 1013 (2010), a sample was wound at a speed of 120 times/min using a measuring machine with a frame circumference of 1.125 m, and the mass was measured to determine the fineness. This was measured five times, and the average value was taken as the fineness.
C. Breaking strength and breaking elongation According to JIS L 1013 (2010), measurements were performed using a Shimadzu AGS-1KNG Autograph (registered trademark) tensile tester under the conditions of a sample yarn length of 20 cm and a constant tensile speed of 20 cm/min. The breaking strength (cN/dtex) was determined by dividing the maximum load value in the load-elongation curve by the fineness, and the breaking elongation (%) was determined by the elongation at that time.
D. Dry heat shrinkage at 150°C: Measured according to the method of JIS L 1013 (2010) 8.18.2b using a dryer heated to 150°C.
E. Fuzz Evaluation The drawn yarn was placed on a creel, tension was applied to the yarn with a ring tenser, and the yarn was passed through a laser-type detector and measured at a measurement speed of 400 m/min. 100,000 m per yarn was measured and converted to the number per million m. Next, 10 yarns were measured and the average value was calculated to be the number of fuzz per million m.
F. Amount of Adhered Oil 2 g of fiber was sampled using a measuring machine (A), the oil adhering to the fiber was extracted with methanol, the methanol was evaporated, and the amount of the remaining residue (oil) (B) was weighed and calculated as the amount of attached oil (mass %) using the following formula 1.
Amount of oil and fat attached (mass%) = B/A x 100 (Formula 1)
G. Number of entanglements A sample of 1 m was cut out in the longitudinal direction of the fiber, and the fiber was immersed in a bucket of water to count the number of entangled parts. N=3 times was carried out, and the average value was taken as the number of entanglements.
H. Spinning operability If the yarn could not be collected onto a bobbin, could not be wound, or broke just below the nozzle when sucked with an air sucker, it was marked with "X." If the yarn was wound around the godet roller, it was marked with "△." If the yarn could be collected onto an undrawn bobbin without these problems, it was marked with "O."
I. Draw-twist operability If yarn breakage occurred, it was marked "x", if the single yarn was wrapped around the drawing roller, it was marked "Δ", and if a drawn yarn could be obtained without these troubles, it was marked "◯".
J. Overall Evaluation In the above-mentioned H. Spinning operability and I. Draw-twist operability, if there was even one "X", it was rated as "X", if there was at least one "△" except for the "X", it was rated as "△", and if all were "○" and the number of fuzz per 1 million meters was 5 or less, it was rated as "○".

Example 1
A polyphenylene sulfide resin (moisture content: 20 ppm) having an MFR of 160 g/10 min was prepared and melted at a spinning temperature of 328° C. The molten polyphenylene sulfide was discharged using a spinning die (L/D=0.5 mm/0.23 mm) having 72 holes at a discharge rate such that the undrawn fineness was 850 dtex. The discharged polyphenylene sulfide yarn was cooled with cold air at 25° C. in a uniflow type cooling device. Thereafter, an emulsion oil (OPU: 1 mass%) was applied to the yarn using an oiling nozzle. The emulsion oil was prepared by adjusting the spinning oil to 18 mass%, and the spinning oil was prepared by adding 5 mass% of a copolymerized polyether component (alkyl PO/EO) (hereinafter, sometimes referred to as Co-POE), 25 mass% of potassium octylphosphonate (hereinafter, sometimes referred to as Oct-P), and other oil components (Other), which were a fatty acid ester smoothing agent and 70 mass% of a nonionic emulsifier main component. The yarn was then passed through two unheated godet rolls at a speed of 1,550/min, and the bobbin was wound up using a winder to obtain an undrawn bobbin of polyphenylene sulfide fiber. In the next drawing step, a drawing device consisting of a creel, an unheated feed roll (1stR), a heater roll (2ndR) for preheating, two heater rolls (3rdR, 4thR) for heat setting, a draw roll (5thR), and a winding section is used. An undrawn bobbin is placed on the creel, preheated at the 2ndR (100°C), heat set at the 3rdR (110°C) and 4thR (220°C), drawn at DR (draw ratio) between 1st-2ndR x DR between 2nd-3rdR x DR between 3rd-4thR x DR between 4th-5thR = 1.03 x 3.38 x 1.00 x 0.978, and wound at a drawing speed of 800 m/min to obtain a low dry heat polyphenylene sulfide fiber.

Example 2
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 1, except that the oil component ratio was changed to Co-POE:Oct-P:Other=5% by mass:50% by mass:45% by mass.

Example 3
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 1, except that the oil component ratio was changed to Co-POE:Oct-P:Other=0 mass%:50 mass%:50 mass%.

Comparative Example 1
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 1, except that the oil component ratio was changed to Co-POE:Oct-P:Other=5% by mass:0% by mass:95% by mass.

Comparative Example 2
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 1, except that the oil solution was changed to a ratio of the oil solution components Co-POE:Oct-P:Other=20 mass%:3 mass%:77 mass%.

Comparative Example 3
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 1, except that the oil component ratio was changed to Co-POE:Oct-P:Other=0 mass%:0 mass%:100 mass%.

Example 4
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 1, except that the oil component ratio was changed to Co-POE:Oct-P:Other=0 mass%:100 mass%:0 mass%.

Example 5
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 1, except that the oil component ratio was changed to Co-POE:Oct-P:Other=25% by mass:25% by mass:50% by mass.

Example 6
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 1, except that the oil component ratio was changed to Co-POE:Oct-P:Other=45% by mass:25% by mass:30% by mass.

Example 7
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 1, except that the oil component ratio was changed to Co-POE:Oct-P:Other=60% by mass:25% by mass:15% by mass.

[Examples 8 and 9, Comparative Examples 4 and 5]
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 2, except that the amount of oil attached was changed.

Example 10
A low heat polyphenylene sulfide fiber was obtained in the same manner as in Example 2, except that a spinning nozzle with 72 holes (L/D=0.4 mm/0.2 mm) was used and the discharge rate was adjusted so that the undrawn fineness was 410 dtex.

Example 11
A low heat-resistant polyphenylene sulfide fiber was obtained in the same manner as in Example 2, except that a spinning nozzle with 72 holes (L/D=0.35 mm/0.18 mm) was used and the discharge rate was adjusted so that the undrawn fineness was 286 dtex.

Comparative Example 6
A low dry heat polyphenylene sulfide fiber was obtained in the same manner as in Example 11, except that the oil component ratio was changed to Co-POE:Oct-P:Other=5% by mass:0% by mass:95% by mass.

The oil conditions, yarn properties, and evaluation results for the low dry heat polyphenylene sulfide fibers of Examples 1 to 11 and Comparative Examples 1 to 6 are shown in Table 1.

The low dry heat polyphenylene sulfide fibers obtained from Examples 1 to 11 were good quality fibers with good spinning and twisting operability, low fiber fuzz, low dry heat shrinkage, excellent dimensional stability, and excellent strength and elongation properties. These fibers were also very good in post-processing passability, and good quality products could be obtained. Among them, the products using the fibers obtained from Examples 2 to 4 and 8 to 11, in which potassium octyl sulfonate was the main oil component, were particularly excellent.
The polyphenylene sulfide fibers obtained from Comparative Examples 1, 3, and 6, which did not contain potassium octylphosphonate in the oil agent component, had a considerable number of single-yarn windings on the draw roll during the drawing process, and single-yarn breaks and fluff were found on the surface and end surface of the wound bobbin. In addition, the average number of fluffs detected per 1 million meters was 8.2 (Comparative Example 1), and 28 (Comparative Example 6), indicating that the fiber had very poor quality and poor draw-twist operability.
The polyphenylene sulfide fiber obtained in Comparative Example 2, in which the oil component contained only 3 mass% potassium octylphosphonate, exhibited a similar phenomenon to that in Comparative Example 1, although to a slightly better extent. The obtained fiber was of very poor quality and also had poor draw-twist operability.
The polyphenylene sulfide fiber obtained in Comparative Example 3, in which neither potassium octylphosphonate nor copolymerized polyether was contained in the oil agent components, had a fiber quality worse than that of Comparative Example 1, with a large amount of fluff, with an average of 35 fluff pieces detected per 1 million meters, indicating very poor fiber quality and poor draw-twist operability.
The polyphenylene sulfide fiber obtained in Comparative Example 4, in which the amount of oil adhering to the fiber was small, had a lot of fluff and was of poor quality, as a result of yarn breakage due to yarn swaying on the godet roll during spinning and yarn swaying at each roll during the drawing process.
The polyphenylene sulfide fiber obtained in Comparative Example 5, in which a large amount of oil was attached to the fiber, suffered from single-fiber breakage due to yarn shaking at the rollers in the drawing step of spinning, and had a lot of fluff and was of poor quality.

In this way, the polyphenylene sulfide fibers (low dry heat yarns) obtained from Examples 1 to 11 were excellent in spinning and twisting operability, had reduced fuzz in the fibers, and were high-quality fibers, due to the selection of specific oil agents and blending amounts. In addition, the fibers also had excellent passability in subsequent processes such as warping, weaving, and processing, resulting in high-quality fabrics and products.

Claims (6)

A method for producing polyphenylene sulfide fibers whose main structural unit is p-phenylene sulfide, in which an oil containing 5% to 100% by mass of octylphosphonate based on the total oil component is applied so that the amount of oil applied is 0.3% to 1.5% by mass. The method for producing polyphenylene sulfide fibers according to claim 1, characterized in that the oil contains a polyether selected from polyethylene glycol, polypropylene glycol, polybutylene glycol, and a copolymer polyether obtained by copolymerizing two or more of the glycols as an oil component. The manufacturing method according to claim 1 or 2, which produces polyphenylene sulfide fiber with a dry heat shrinkage rate of 3.5% or less at 150°C. Polyphenylene sulfide fiber, the main constituent unit of which is p-phenylene sulfide unit, to which an oil containing 5 to 100% by mass of octyl phosphonate based on the total oil component is attached so that the amount of oil attached is 0.3 to 1.5% by mass. Polyphenylene sulfide fiber with a single yarn fineness of 3.5 dtex or less and a fuzz count of 5 or less per 1 million meters. The polyphenylene sulfide fiber according to claim 4 or 5, which has a dry heat shrinkage rate of 3.5% or less at 150°C.