EP4112789A1

EP4112789A1 - Polyphenylene sulfide monofilament, method for manufacturing same, and fiber package

Info

Publication number: EP4112789A1
Application number: EP22773098.3A
Authority: EP
Inventors: Hiroyuki Yamashita
Original assignee: KB Seiren Ltd
Current assignee: KB Seiren Ltd
Priority date: 2021-03-31
Filing date: 2022-03-31
Publication date: 2023-01-04
Also published as: KR20220158749A; US20240018694A1; TW202307298A; CN115413302A; WO2022211116A1; JPWO2022211116A1

Abstract

A polyphenylene sulfide monofilament has a phenylene sulfide unit as a main structural unit and satisfies (1) to (5):(1) a fineness of 6 to 35 dtex;(2) a breaking strength of 3.4 cN/dtex or more;(3) a breaking elongation of 24% to 45%;(4) a 5% modulus of 1.0 to 1.6 cN/dtex; and(5) a 10% modulus of 1.4 to 2.3 cN/dtex.

Description

Technical Field

The present invention relates to a polyphenylene sulfide monofilament and a method of producing the same, and a fiber package of the monofilament. The present application claims priority based on Japanese Patent Application No. 2021-062433 filed on March 31, 2021 , Japanese Patent Application No. 2021-062434 filed on March 31, 2021 , and Japanese Patent Application No. 2021-065544 filed on April 7, 2021 , the entire contents of which are incorporated herein by reference.

Background Art

For industrial filters, mesh woven fabrics made up of polyphenylene sulfide, polyvinylidene fluoride, liquid crystalline polyester, and the like are currently widely used from the standpoints of chemical resistance, dimensional stability, thermal endurance, and the like. In particular, mesh woven fabrics made of polyphenylene sulfide are widely used because of being excellent in chemical resistance, dimensional stability, and cost performance, making them suitable for the fields requiring high filter performance. Furthermore, to address extremely low productivity of fine monofilaments, it has been expected in recent years that costs will be reduced by shortening the process steps by using a direct spinning drawing method.
Patent Literature 1 describes a polyphenylene sulfide monofilament characterized by having a fineness of 25 dtex or less, a strength of 3.0 cN/dtex or more, an elongation of less than 30%, and the like. It also describes that a conventional method is used for producing the monofilament.
Patent Literatures 2 and 3 describe a drum-shaped package made up of a polyphenylene sulfide monofilament obtained by using a direct spinning drawing method in which an undrawn yarn obtained is, without being wound once, continuously drawn and wound up with a winder.

Citation List

Patent Literature

Patent Literature 1: Japanese Patent No. 4844515
Patent Literature 2: International Publication WO 2016/104236
Patent Literature 3: Japanese Patent Application Laid-Open No. 2017-101365

Summary of Invention

Technical Problem

However, in the case where the elongation is less than 30% as in the polyphenylene sulfide monofilaments described in Patent Literatures 1 to 3, yarn breakage would likely occur during spinning, and warp breakage and the like would likely occur during weaving. These lead to a lower yield of mesh woven fabrics and lowered performance thereof. Further, if a monofilament is wound onto a thin pirn with an elongation close to 20%, as in Patent Literature 1,5% modulus and/or 10% modulus will become high, in which case pirn barre may occur during unwinding of the innermost layer of the pirn, leading to impaired quality. Further, in the case of a drum-shaped package as described in Patent Literatures 2 and 3, the yarn may fall off from the bobbin end faces (traverse failure), resulting in unwinding failure of the yarn, or collapsed winding. Moreover, a bobbin suffering traverse failure may cause problems during weaving.
Therefore, an object of the present invention is to obtain a high quality and fine denier polyphenylene sulfide monofilament that hardly suffers yarn breakage, bobbin winding collapse, or barre during unwinding, and is easy to handle during weaving.
Another object of the present invention is to obtain a high quality polyphenylene sulfide monofilament fiber package capable of suppressing yarn breakage as well as formation of scum and streaks during weaving.
Yet another object of the present invention is to obtain the above-described polyphenylene sulfide monofilament by using a direct spinning drawing method with high production efficiency.

Solution to Problem

For a polyphenylene sulfide monofilament, the present inventor sets specific ranges for heat setting temperature and winding tension and specified a bobbin package, to obtain a monofilament having specific fineness, breaking strength, breaking elongation, 5% modulus, and 10% modulus. The inventor has found that with this monofilament, it is possible to obtain a high quality polyphenylene sulfide monofilament that is superior to the conventional monofilaments in terms of spinning operability of the monofilament, prevention of bobbin winding collapse, improvement of barre formation during unwinding, and ease of handling during weaving.
That is, the present invention firstly relates to a polyphenylene sulfide monofilament having a phenylene sulfide unit as a main structural unit and satisfying (1) to (5):

(1) a fineness of 6 to 35 dtex;
(2) a breaking strength of 3.4 cN/dtex or more;
(3) a breaking elongation of 24% to 45%;
(4) a 5% modulus of 1.0 to 1.6 cN/dtex; and
(5) a 10% modulus of 1.4 to 2.3 cN/dtex.

The present invention secondly relates to a pirn-shaped fiber package made up of the above-described polyphenylene sulfide monofilament.
The present invention thirdly relates to the above-described fiber package of the polyphenylene sulfide monofilament, having a winding width of 100 to 250 mm, a taper angle of 30° to 140°, a lead angle of 0.6° to 2°, and a ratio of heat shrinkage stress values of an innermost layer and an outermost layer of the package (or, a heat shrinkage stress ratio between innermost and outermost layers) of 0.85 to 1.15.
The present invention fourthly relates to a method of producing the above-described polyphenylene sulfide monofilament, having the phenylene sulfide unit as the main structural unit, by using a direct spinning drawing method in which a polyphenylene sulfide resin is melt-extruded, cooled and solidified, and an obtained undrawn yarn is, without being wound once, continuously drawn and wound up with a winder, wherein the method satisfies (1) to (4):

(1) the polyphenylene sulfide resin has an MFR of 100 to 250 g/10 min.;
(2) the undrawn yarn is drawn using a non-heated pretension roller and two or more heated godet rollers;
(3) a temperature of the first godet roller is 95°C to 120°C, and a heat setting temperature of the second and subsequent heated godet rollers is 120°C to 250°C; and
(4) a winding tension to the winder is 0.1 to 0.5 cN/dtex.

The present invention fifthly relates to a method of producing the above-described fiber package, made up of the polyphenylene sulfide monofilament having the phenylene sulfide unit as the main structure unit, by using a direct spinning drawing method in which a polyphenylene sulfide resin is melt-extruded, cooled and solidified, and an obtained undrawn yarn is, without being wound once, continuously drawn and wound up on a bobbin with a winder, wherein the method satisfies (1) to (4):

(1) the polyphenylene sulfide resin has an MFR of 100 to 250 g/10 min.;
(2) the undrawn yarn is drawn using a non-heated pretension roller and two or more heated godet rollers;
(3) a temperature of the first godet roller is 95°C to 120°C, and a heat setting temperature of the second (and subsequent) heated godet roller(s) is 120°C to 250°C; and
(4) a winding tension to the winder is 0.1 to 0.5 cN/dtex.

The present invention sixthly relates to a method of producing a fiber package made up of a polyphenylene sulfide monofilament having a phenylene sulfide unit as a main structural unit by using a direct spinning drawing method in which a polyphenylene sulfide resin is melt-extruded, cooled and solidified, and an obtained undrawn yarn is, without being wound once, continuously drawn and wound up on a bobbin in a pirn shape with a winding tension to a winder of 0.1 to 0.5 cN/dtex.
The present invention seventhly relates to the above-described method of producing the fiber package made up of the polyphenylene sulfide monofilament, wherein the obtained undrawn yarn is drawn and wound up on the bobbin after a spin finish is applied to the yarn to achieve an oil pick-up unit of 0.15 to 0.5 mass% for the polyphenylene sulfide monofilament.
The present invention eighthly relates to a method of producing a fiber package made up of a polyphenylene sulfide monofilament having a phenylene sulfide unit as a main structural unit by using a direct spinning drawing method in which a polyphenylene sulfide resin is melt-extruded, cooled and solidified, and an obtained undrawn yarn is, without being wound once, continuously drawn and wound up on a bobbin in a pirn shape by a winder, wherein a spin finish is applied to the undrawn yarn before being wound up on the bobbin to achieve an oil pick-up unit of 0.15 to 0.5 mass% for the polyphenylene sulfide monofilament, and the yarn is wound up on the bobbin in the pirn shape to have a winding width of 100 to 250 mm, a taper angle of 30° to 140°, and a lead angle of 0.6° to 2°.
The present invention ninthly relates to a pirn-shaped polyphenylene sulfide monofilament fiber package having a winding width of 100 to 250 mm, a taper angle of 30° to 140°, a lead angle of 0.6° to 2°, and a heat shrinkage stress ratio between innermost and outermost layers of 0.85 to 1.15.

Advantageous Effects of Invention

The polyphenylene sulfide monofilament of the present invention hardly suffers yarn breakage during spinning, ensures good spinning operability, and can produce a high quality mesh woven fabric excellent in mesh strength durability.
It is also possible to obtain a polyphenylene sulfide monofilament particularly suitable for a pirn-shaped package.
Further, according to the fiber package of the present invention, it is possible to obtain a high quality polyphenylene sulfide monofilament fiber package that is in a good winding state and capable of suppressing yarn breakage as well as formation of scum and streaks during weaving.
Further, the present invention can obtain the above-described polyphenylene sulfide monofilament using the direct spinning drawing method with high production efficiency.

Brief Description of Drawings

FIG. 1 is a schematic front view of a polyphenylene sulfide monofilament fiber package of the present invention.

Description of Embodiments

The present invention will be described below in detail.
The polyphenylene sulfide resin in the present invention is a polyphenylene sulfide made of a polymer having a phenylene sulfide unit as a main repeating unit (main structural unit). Examples of the phenylene sulfide unit include p-phenylene sulfide unit and m-phenylene sulfide unit. The polyphenylene sulfide may be a homopolymer made up of p-phenylene sulfide units, m-phenylene sulfide units, or the like, or may be a copolymer having them. In terms of heat resistance and processability as well as economical standpoint, the repeating unit of p-phenylene sulfide is preferable. In the polyphenylene sulfide resin, the p-phenylene sulfide repeating unit is contained in an amount of preferably 50 mol% or more, more preferably 70 mol% or more, particularly preferably 90 mol% or more, and further preferably 98 mol% or more.
The polyphenylene sulfide may have a polymer type of crosslinked type, semicrosslinked type, or linear type, among which the linear type is preferable in terms of spinning and drawing ability.
Further, the polyphenylene sulfide may contain various metal oxides, kaolin, silica, and other inorganic substances, as well as coloring agent, delustering agent, flame retardant, antioxidant, ultraviolet absorber, infrared absorber, crystal nucleating agent, fluorescent brightening agent, end group sealing compound, compatibilizer, and other additives, in small amounts within the range that does not impair the effects of the present invention.
The polyphenylene sulfide resin in the present invention preferably has a melt flow rate (MFR) of 100 to 250 g/10 min., and further preferably 130 to 200 g/10 min.. If it is less than 100 g/10 min., the viscosity is too high, impairing the spinning. Further, if it exceeds 250 g/10 min., the viscosity is extremely low, leading to reduced fiber strength, making the yarn unsuitable for commercialization because the strength durability is greatly reduced for use in mesh woven fabrics such as filters.
For the polyphenylene sulfide resin in the present invention, pellets before spinning have a moisture content of preferably 100 ppm or less, and further preferably 10 to 50 ppm. The moisture content exceeding 100 ppm may cause yarn breakage during spinning and/or mixing of bubbles (air bubbles), which may result in degradation of spinning operability.
The pellets of the polyphenylene sulfide resin in the present invention are preferably subjected to vacuum drying as preliminary drying, to remove low molecular weight components as much as possible. In the case of performing the preliminary drying, the drying temperature is preferably 130°C to 190°C, and the drying time is preferably 6 to 12 hours.
The polyphenylene sulfide monofilament of the present invention has a crosssectional shape that is not particularly limited. The outer shape of the polyphenylene sulfide monofilament of the present invention is preferably circular.
The polyphenylene sulfide monofilament of the present invention preferably has a fineness of 6 to 35 dtex. If it exceeds 35 dtex, solidification with cold air becomes difficult, in which case it is difficult to obtain a high quality monofilament, causing problems when the monofilament is used in products such as filters.
The polyphenylene sulfide monofilament of the present invention has a breaking strength of preferably 3.4 cN/dtex or more, and more preferably 3.8 cN/dtex or more, from the standpoint of durability of meshes such as filters. A suitable upper limit is 5 cN/dtex or less.
The polyphenylene sulfide monofilament of the present invention has a breaking elongation of 24% to 45%, preferably 24% to 40%, more preferably 30% to 40%, and further preferably 30% to 35%. With the breaking elongation of less than 24%, yarn breakage occurs frequently during spinning, and reed shaving occurs during weaving, resulting in poor weavability. With the breaking elongation exceeding 45%, the amorphous portion of the filament increases, leading to degraded dimensional stability and reduced durability of the mesh.
The polyphenylene sulfide monofilament of the present invention has a 5% modulus of 1.0 to 1.6 cN/dtex, and preferably 1.2 to 1.6 cN/dtex. Although a higher 5% modulus is more preferable from the standpoint of durability of the mesh, the 5% modulus exceeding 1.6 cN/dtex will cause barre during unwinding of the bobbin inner layer portion, in which case a high quality mesh cannot be obtained. With the 5% modulus of less than 1.0 cN/dtex, dimensional stability and strength durability of the mesh may become poor, or misalignment of mesh weave may easily occur.
The polyphenylene sulfide monofilament of the present invention has a 10% modulus of 1.4 to 2.3 cN/dtex, and preferably 1.7 to 2.1 cN/dtex. Although a higher 10% modulus is more preferable from the standpoint of durability of the mesh, the 10% modulus exceeding 2.3 cN/dtex will cause barre during unwinding of the bobbin inner layer portion, in which case a high quality mesh cannot be obtained. With the 10% modulus of less than 1.4 cN/dtex, dimensional stability and strength durability of the mesh may become poor, or misalignment of mesh weave may easily occur.
The polyphenylene sulfide monofilament as described above is free from barre during unwinding, so it is easy to handle during weaving.
The polyphenylene sulfide monofilament of the present invention has a hot water shrinkage rate of preferably 10% or less, and more preferably 2% to 8%. A lower hot water shrinkage rate is more preferable from the standpoint of dimensional stability of the mesh. If it exceeds 10%, the dimensional stability of the mesh tends to be degraded, which may result in a filter of poor quality.
In the pirn-shaped fiber package of polyphenylene sulfide monofilament in the present invention, a ratio (referred to as heat shrinkage stress ratio between innermost and outermost layers) between a heat shrinkage stress value of the filament in the innermost layer of the fiber package and a heat shrinkage stress value of the filament in the outermost layer of the package is preferably 0.85 to 1.15, and further preferably 0.9 to 1.1. The heat shrinkage stress ratio between the innermost and outermost layers falling outside the range may cause winding collapse or tight winding, or may cause distortion due to the stress difference in a mesh fabric, which may result in a mesh fabric of poor quality.
In the polyphenylene sulfide monofilament of the present invention, from the standpoints of ensuring good post-processing passability and obtaining a mesh woven fabric of good quality, an oil pick-up unit is preferably 0.15 to 0.5 mass%, more preferably 0.15 to 0.45 mass% or 0.2 to 0.5 mass%, and further preferably 0.25 to 0.35 mass%. If it is less than 0.15 mass%, static electricity tends to be generated easily and the ease of handling in weaving or the like tends to be inferior. If it exceeds 0.5 mass%, scum tends to be formed easily during weaving, which may affect the quality of mesh woven fabric or industrial filter, and may cause bobbin collapse in the spinning and winding step.
As a spin finish suitable for the polyphenylene sulfide monofilament in the present invention, a fatty acid ester lubricating agent may be contained in an amount of 30 mass% or more from the standpoints of ensuring smoothness and preventing reed friction, and an antistatic agent and/or emulsifier may also be added as needed. In addition, it is further preferable to add 1 to 3 mass% of modified silicone to the undiluted spin finish to further increase the smoothness. This range is preferred because excessive addition of such modified silicone may cause the yarn to slip in the bobbin during winding, leading to collapsed winding. A suitable method for applying the spin finish is to make an emulsion of 5 to 20 mass% with ion-exchanged water and apply it with an oiling nozzle directly above the pretension roller.
As for the method of producing a polyphenylene sulfide monofilament of the present invention, a monofilament is obtained by spinning and then drawing a yarn. At this time, the direct spinning drawing method, the conventional method, or other method can be used to produce the monofilament. As another method, a parent yarn made up of a multifilament produced using the direct spinning drawing method may be separated to obtain a monofilament. Considering the production steps, cost, and barre during unwinding, production using the direct spinning drawing method is preferable.
The polyphenylene sulfide monofilament of the present invention can be obtained through a spinning step, in which a polyphenylene sulfide resin is melt-extruded, and the following drawing step, in which the yarn is drawn through a non-heated pretension roller and two or more heated godet rollers before being wound up.
A suitable embodiment of the production method will now be described in detail.
In the spinning step, an extruder is used to melt a polyphenylene sulfide resin, and meter and extrude the molten resin from a nozzle. A spin finish is applied to the extruded yarn. The spinning step is followed by the drawing step. In the drawing step, a plurality of godet rollers are used to perform drawing to make crystallization sufficiently and fix the fiber structure, thereby obtaining a drawn yarn. During the drawing step, a relaxation step may be introduced for the purpose of reducing the heat shrinkage rate of the drawn yarn. In this case, a relaxation rate in the relaxation step is preferably 0% to 2% from the standpoint of ease in prevention of the occurrence of barre, and a more preferable range of the relaxation rate is 0% to 1%. If the relaxation rate is less than 0%, the tension between the rollers in the drawing step becomes high, leading to increased orientation of the amorphous portion, and barre and tight bobbin winding may occur frequently. If the relaxation rate exceeds 2%, the orientation of the amorphous portion decreases, in which case it may be difficult to obtain a high quality monofilament that has the 5% modulus and 10% modulus falling within the above-described ranges and the breaking strength and breaking elongation falling within the ranges of the present invention. Further, the yarn may become slack and unable to be wound up.
In the drawing step, for the purpose of eliminating sagging, it is preferable to perform preliminary drawing between a pretension roller and a godet roller 1 at a draw ratio of 1.01 to 1.05, and then perform main drawing with the godet roller 1 and subsequent roller(s). In the main drawing, the drawing is preferably performed by setting the temperature of the godet roller 1 to 95°C to 120°C, and more preferably to 100°C to 115°C. Thereafter, the yarn is introduced to a godet roller 2, where the yarn is drawn while being heat-set. The heat setting temperature at the godet roller 2 is preferably 120°C to 250°C, and more preferably 130°C to 200°C. Thereafter, the yarn may be introduced to yet other godet roller 3 and godet roller 4 for drawing. Further, the relaxation step may be performed as described above for relaxation treatment. In the case of performing further heat setting at the godet roller 3 and subsequent godet roller(s), the temperature is preferably 120°C to 250°C, and more preferably 130°C to 200°C. The godet roller 3 and subsequent godet roller(s) may be non-heated rollers with no heat setting. The yarn that has passed through the rollers is wound up with a winder. The winding tension during winding onto the winder is preferably 0.1 to 0.5 cN/dtex, and further preferably 0.2 to 0.3 cN/dtex.
If the temperature of the godet roller 1 is lower than 95°C, formation of knot-like humps as well as yarn breakage due to the swinging of the yarn on the godet roller will frequently occur. If it exceeds 120°C, the yarn swinging on the godet roller will occur frequently, causing yarn breakage, making it difficult to successfully collect the monofilament. If the temperature of the godet roller 2 and subsequent godet roller(s) for heat setting is lower than 120°C, it will be difficult to obtain the monofilament of the present invention. If it exceeds 250°C, melting down due to the heat would likely occur, making it difficult to wind up the monofilament.
If the winding tension to the winder is less than 0.1 cN/dtex, the tension between the godet roller and the winder is too low, often causing bobbin winding collapse and yarn breakage, making it difficult to successfully collect the monofilament. If it exceeds 0.5 cN/dtex, the bobbin winding will become tight, making it difficult to remove the bobbin from the winder.
The bobbin shape for the polyphenylene sulfide monofilament of the present invention is preferably a pirn shape, with the polyphenylene sulfide monofilament wound up in a tapered shape on a paper tube which is generally used for the direct spinning drawing method. In the direct spinning drawing method, a drum shape is generally adopted. However, in the case of the drum shape, an event ("traverse failure") in which the yarn falls off from the bobbin end faces during winding of the monofilament would likely occur, which leads to collapsed winding in a severe case. When traverse failure occurs, the yarn may be caught on the end faces during unwinding, which may lead to yarn breakage or weaving failure, thereby causing degradation in processing passability or degradation in quality of the products.
The winding conditions for a fiber package made up of the polyphenylene sulfide monofilament of the present invention are as follows. A winding width of an innermost layer portion of the fiber package is 100 to 250 mm, and more preferably 150 to 200 mm. If the winding width is less than 100 mm, the winding volume cannot be increased unless the taper angle is made large, and if the taper angle is increased too much, the event of falling of the yarn from the bobbin end faces (traverse failure) will occur, in which case the yarn may be caught during unwinding, causing yarn breakage or formation of streaks, resulting in poor weaveability. In consideration of the limited end count of the winder and limited winder length, the upper limit of the winding width is preferably 250 mm from the standpoints of fiber package productivity and cost.
A taper angle of the fiber package of the present invention is 30° to 140°, and more preferably 45° to 100°. If the taper angle is less than 30°, although the winding collapse may not occur, before the regular winding volume is reached, the winding width between the ends will decrease with increasing winding thickness, and the approaching ends may ultimately contact each other, in which case the desired winding volume cannot be reached, resulting in poor productivity. If the taper angle exceeds 140°, the yarn may fall off from the tapered portions, which would likely lead to winding collapse. For reference, with the condition of 180° (corresponding to the drum-shaped winding), winding collapse due to traverse failure often occurs.
A lead angle of the fiber package of the present invention is 0.6° to 2°, preferably 0.8° to 2°, and further preferably 0.9° to 1.2°. If the lead angle is less than 0.6°, yarn ribboning will occur on the package surface, leading to bobbin unwinding failure or appearance failure. If the lead angle exceeds 2°, when the yarn is moved to both ends with a traverse motion, the yarn may be repelled by momentum and fall off from the tapered portions, leading to winding collapse. This event would likely frequently occur particularly when the filament fineness is 20 dtex or more.

EXAMPLES

The present invention will be described in detail below by giving examples. It should be noted that the present invention is not limited to the examples described below. Physical properties of filaments in the examples and evaluations are as follows.

A. MFR

The MFR value was measured under the conditions of a temperature of 315.5°C and a load of 5,000 g, in accordance with JIS K 7210 (1999).

B. Fineness

In accordance with JIS L 1013, a sample was wound up at a rate of 120 times/min., using a sizing reel having a frame circumference of 1.125 m, and the mass was metered to obtain the fineness. The measurement was carried out five times, and the average value was calculated.

C. Breaking Strength, Breaking Elongation, 5% Modulus, 10% Modulus

Measurement was carried out in accordance with JIS L 1013, using a tensile tester AGS-1KNG Autograph (registered trademark) manufactured by Shimadzu Corporation, under the conditions of a sample yarn length of 20 cm and a constant tension speed of 20 cm/min.. A breaking strength (cN/dtex) was obtained by dividing a maximum load value in a load-elongation curve by the fineness, and the elongation percentage at that time was taken as the breaking elongation (%). The strength when the elongation percentage is 5% was taken as the 5% modulus (cN/dtex), and the strength when the elongation percentage is 10% was taken as the 10% modulus (cN/dtex).

D. Heat Shrinkage Stress Ratio between Innermost and Outermost Layers

A heat shrinkage stress was measured using a shrinkage stress tester KE-II manufactured by Kanebo Engineering Ltd. A 5 cm-long sample looped and tied at the ends was subjected to an initial load of its fineness x 2/30 (cN) and heated from room temperature at a temperature rise rate of 120°C/min., to measure a heat shrinkage force. With a maximum point of the measured heat shrinkage force being set to a peak of heat shrinkage force (cN), the temperature at that time was set to a heat shrinkage force peak temperature (°C). The maximum value of the heat shrinkage force was divided by twice the fiber fineness to obtain a heat shrinkage stress (cN/dtex). The measurement was carried out five times and the average value was taken as the heat shrinkage stress. A heat shrinkage stress ratio between the innermost and outermost layers (Sr) is obtained by the following expression 1: $Sr = Si / So$
where Sr represents heat shrinkage stress ratio between innermost and outermost layers, Si represents heat shrinkage stress of the innermost layer of the package (measured at a point of 1 mm in winding thickness from the outer diameter of the paper tube), and So represents heat shrinkage stress of the outermost layer of the package (measured at a point after unwinding the surface layer portion of the package for one minute).

E. Spinning Operability

For the spinning operability, "o" was given for good processing passability, "Δ" for slightly poor processing passability, and "x" for being unable to spin.

F. Winding State of Fiber Package

For the winding operability, "o" was given for good winding shape, "Δ"for slightly collapsed winding or insufficient winding volume, and "x" for severely collapsed winding or being unable to wind.

G. Weaveability and Appearance Evaluation

The polyphenylene sulfide monofilaments obtained were weaved using a Sulzertype weaving machine at a speed of rotation of 300 rpm, to obtain mesh woven fabrics of 420 mesh (yarns/2.54 cm) (6 or more and less than 11 dtex), 225 mesh (yarns/2.54 cm) (11 or more and less than 21 dtex), and 150 mesh (yarns/2.54 cm) (21 to 35 dtex). At this time, weaveability such as scum formation on a reed, states of warp and weft breakage, and the like, and the appearance of the obtained woven fabrics (formation of knots, barre, streaks, and the like) were evaluated.
For the evaluation, "o" was given if both weaveability and appearance were good, "Δ" if either one of them was bad, and "x" if both of them were bad.

H. Mesh Performance Evaluation

The polyphenylene sulfide mesh woven fabrics obtained were heat-set at 160°C for 20 minutes, and the processed woven fabrics (before and after heat setting) were subjected to elongation/recover cycles, to evaluate the appearance thereafter. The elongation/recovery cycle was in accordance with JIS L 1013, and the Shimadzu Corporation AGS-1KNG Autograph (registered trademark) tensile tester was used to perform 10% elongation/recovery cycles for five times under the conditions of the sample length of 20 cm and width of 5 cm, and the constant tension speed of 20 cm/min.. The appearance of each mesh woven fabric at that time was visually observed. Those with no misalignment of mesh weave, no distortion, and no damage were scored as "o", those with distortion or minor damage were scored as "×", and those for which the presence or absence of distortion or damage could not be determined were scored as "Δ".

I. Overall Evaluation

For the four items of spinning operability, winding state, weaveability and appearance evaluation, and mesh performance, those with a score of "o" for all the items were given an overall evaluation of "double-circle", and those with "o" for the spinning operability and "o" or "Δ" for the mesh performance were given an overall evaluation of "o". Of the examples excluding those with the overall evaluation of "double-circle" or "o", those with two or more "Δ"items in the spinning operability, weaveability and appearance evaluation, and mesh performance were given an overall evaluation of "Δ". Those with "x" in either one of the spinning operability and mesh performance were given an overall evaluation of "×".

J. Package Evaluation

For the evaluation, those scored as "o" for both of the winding state and the weaveability and appearance evaluation were given "o", those with "×" for either one of them were given "×", and the rest was given "Δ".

[Example 1]

A p-polyphenylene sulfide resin (moisture content: 20 ppm) with the MFR of 160 g/10 min. was prepared and melted at the spinning temperature of 328°C. A spinneret having two holes (L/D=0.65 mm/0.65 mm) was used to discharge the molten polyphenylene sulfide in a discharge amount to achieve a fineness after drawing of 33 dtex. The discharged polyphenylene sulfide yarn was cooled with a uniflow-type cooling device, and an emersion spin finish was applied to the yarn (OPU=0.3 mass%). The yarn was then taken up with a non-heated pretension roller at a speed of 1,040 m/min., and a tension was applied between the pretension roller and a godet roller 1 (1,058 m/min. in speed, 115°C). The yarn was subjected to main drawing and heat setting at a godet roller 2 (3,520 m/min. in speed, 135°C), subjected to relaxation treatment at a godet roller 3 (3,500 m/min. in speed, non-heated) to reduce the tension, and then wound up onto a winder (3,495 m/min. in speed) with a winding tension of 0.2 cN/dtex, whereby a polyphenylene sulfide monofilament of 33 dtex was wound up on a bobbin in a pirn shape with tapered end faces, with a winding width of 200 mm, a taper angle of 60°, and a lead angle of 1°.

[Example 2]

A polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 1, except that the speed of the pretension roller was set to 920 m/min., the speed of the godet roller 1 was set to 960 m/min., the speed of the winder was changed, and the godet roller 3 was not used.

[Comparative Examples 1,2]

In Comparative Example 1, a polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 2, except that the temperature of the godet roller 2 was changed. Comparative Example 2 was also carried out under these conditions.

[Comparative Examples 3, 4]

In Comparative Example 4, a polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 2, except that the speed and winding tension of the winder were changed. Comparative Example 3 was also carried out under these conditions.

[Comparative Example 5]

A polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 1, except that a p-polyphenylene sulfide resin with the MFR of 300 g/10 min. was used and the speeds of the pretension roller and the godet roller 1 were changed.

[Comparative Example 6]

A polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 2, except that a p-polyphenylene sulfide resin with the MFR of 65 g/10 min. was used and the speeds of the pretension roller and the godet roller 1 were changed.

[Example 3]

A p-polyphenylene sulfide resin with the MFR of 160 g/10 min. was prepared and melted at the spinning temperature of 328°C. A spinneret having two holes (L/D=0.35 mm/0.31 mm) was used to discharge the molten polyphenylene sulfide in a discharge amount to achieve a fineness after drawing of 10 dtex. The discharged polyphenylene sulfide yarn was cooled with a uniflow-type cooling device, and an emersion spin finish was applied to the yarn. The yarn was drawn via the pretension roller and the godet rollers 1,2, and 3 similarly as in Example 1, except that the conditions listed in Table 1 were adopted. The yarn was then wound up onto the winder to obtain a polyphenylene sulfide monofilament of 10 dtex on a bobbin in a tapered shape.

[Example 4]

A p-polyphenylene sulfide resin with the MFR of 160 g/10 min. was prepared and melted at the spinning temperature of 328°C. A spinneret having two holes (L/D=0.4 mm/0.37 mm) was used to discharge the molten polyphenylene sulfide in a discharge amount to achieve a fineness after drawing of 14 dtex. The discharged polyphenylene sulfide yarn was cooled with a uniflow-type cooling device, and an emersion spin finish was applied to the yarn. The yarn was drawn via the pretension roller and the godet rollers 1, 2, and 3 similarly as in Example 1, except that the conditions listed in Table 1 were adopted. The yarn was then wound up onto the winder to obtain a polyphenylene sulfide monofilament of 14 dtex on a bobbin in a tapered shape.

[Example 5]

A polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 1, except that the heat setting temperature of the godet roller 3 was set to 190°C.

[Comparative Examples 7, 8]

Polyphenylene sulfide monofilaments were produced similarly as in Example 1, except that the temperature of the godet roller 1 was changed as indicated in Table 1.

[Comparative Example 9]

A polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 1, except that the pretension roller and the godet roller 1 in Example 1 were reduced in speed to obtain an elongation of 22%, and the temperature of the godet roller 2 was set to 150°C.

[Comparative Example 10]

A polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 1, except that the pretension roller and the godet roller 1 in Example 1 were increased in speed to obtain an elongation of 50%, and the temperature of the godet roller 2 was set to 150°C.

[Comparative Example 11]

A polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 2, except that the temperature of the godet roller 2 was set to 190°C and the winding tension was changed to 0.6 cN/dtex.

[Comparative Example 12]

A polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 2, except that the temperature of the godet roller 2 was set to 110°C and the bobbin package was changed to a drum shape.

[Example 6]

A fiber package was obtained similarly as in Example 1, except that the taper angle was changed to 120°, the winding speed was adjusted, the winding tension was changed to 0.4 cN/dtex, and the oil pick-up unit was changed to 0.4 mass%.

[Example 7]

A fiber package was obtained similarly as in Example 1, except that the winding speed was adjusted, the winding tension was set to 0.5 cN/dtex, and the lead angle was set to 1.2°.

[Example 8]

A fiber package was obtained similarly as in Example 1, except that the taper angle was changed to 180°, the bobbin shape was changed to a drum shape, and the lead angle was changed to 5°.

[Example 9]

A fiber package was obtained similarly as in Example 1, except that the taper angle was changed to 180°, and the bobbin shape was changed to a drum shape.

[Examples 10, 11]

Fiber packages were obtained similarly as in Example 1, except that the taper angle was changed to 160° and 20°.

[Examples 12, 13]

Fiber packages were obtained similarly as in Example 1, except that the lead angle was changed to 0.5° and 2.5°.

[Examples 14, 15]

Fiber packages were obtained similarly as in Example 1, except that the winding width was changed to 70 mm and 300 mm.

[Comparative Examples 13, 14]

In Comparative Example 13, a polyphenylene sulfide monofilament of 33 dtex was obtained similarly as in Example 2, except that the speed and winding tension of the winder were changed. Comparative Example 14 was carried out similarly to Example 2, except that the speed and winding tension of the winder were changed.

[Comparative Examples 15, 16]

Fiber packages were obtained similarly as in Example 1, except that the oil pick-up unit to the yarn was changed to 0.1 mass% and 0.6 mass%.
Table 1 shows conditions for producing polyphenylene sulfide monofilaments in Examples 1 to 5 and Comparative Examples 1 to 12, physical properties of the yarns, and results of various evaluations (spinning operability, weaveability and appearance evaluation, mesh performance evaluation, and overall evaluation). It should be noted that the strength and elongation in the yarn physical properties in the table are breaking strength and breaking elongation. In the table, PTR represents pretension roller, GR1 represents godet roller 1, GR2 represents godet roller 2, GR3 represents godet roller 3, and W/D represents winder.

[Table 1]

The polyphenylene sulfide monofilaments obtained in Examples 1 to 5 were high strength and high quality monofilaments with few knots. Further, the mesh woven fabrics using the monofilaments obtained in Examples 1 to 5 were free of scum and free of warp and weft breakage, and also were of high quality in terms of appearance without the occurrence of knots, coarse yarn, or abnormal luster due to barre or other factors. They were also sufficient in strength, good in dimensional stability, and had high durability and high quality when used as filters. Among them, the mesh woven fabrics obtained from the monofilaments of Examples 1 and 5 were particularly superior in performance without the occurrence of barre, streaks, and the like.
The mesh woven fabric obtained from the polyphenylene sulfide monofilament obtained in Comparative Example 1, where the heat setting temperature was low, was inferior in dimensional stability, suffered misalignment of mesh weave, was poor in durability of strength, and of poor quality. It is conceivably because the polyphenylene sulfide monofilament obtained in Comparative Example 1 was low in strength and high in hot water shrinkage rate.
The polyphenylene sulfide monofilament obtained in Comparative Example 2, where the heat setting temperature was high, suffered yarn melt down, yarn breakage, and yarn swinging on the godet roller 2, and it was not possible to collect the monofilament on a bobbin.
With the polyphenylene sulfide monofilament obtained in Comparative Example 3, where the winding tension to the winder was set low, the yarn loosened between the godet roller 2 and the winder, often resulting in yarn wrapping around the godet roller 2 or bobbin winding collapse, and it was not possible to successfully collect the monofilament on a bobbin.
With the polyphenylene sulfide monofilament obtained in Comparative Example 4, where the winding tension to the winder was set high, the high winding tension caused tight winding when the winding volume exceeded 1 kg, making it unable to remove the bobbin from the winder, so it was not suitable for bulk production. Further, in the weaveability of the mesh woven fabric obtained with thin winding, the 5% modulus and 10% modulus were high, causing barre to occur in the bobbin inner layer portion and streaks to occur on the mesh woven fabric, resulting in poor quality. With heat setting during weaving, the mesh woven fabric would be stretched, causing misalignment of mesh weave or the like, resulting in poor quality.
The polyphenylene sulfide monofilament obtained in Comparative Example 5, where a polyphenylene sulfide resin with high MFR was used, exhibited extremely low viscosity, resulting in the breakage strength of at most 3.2 cN/dtex even when the breaking elongation was made close to 30%. This caused degradation in durability of the strength of the mesh woven fabric, resulting in poor quality.
The polyphenylene sulfide monofilament obtained in Comparative Example 6, where a polyphenylene sulfide resin with low MFR was used, exhibited extremely high viscosity, and unmelted matters and gels were easily formed. Yarn swinging on the godet roller often occurred, so it was almost impossible to collect the monofilament. The monofilament also had knots, causing frequent warp breakage during weaving. The obtained mesh woven fabric had streaks and knots due to barre, and was considerably poor in quality.
With the polyphenylene sulfide monofilament obtained in Comparative Example 7, where the preliminary heating temperature of the godet roller 1 was set low, that temperature which was lower by about 10°C than the glass transition temperature of the polyphenylene sulfide caused undrawn portions to be created during drawing between the godet rollers 1 and 2, and significantly large yarn swinging occurred on the yarn path after the godet roller 2. With this condition, it was almost impossible to wind up the yarn onto the winder, impairing winding of the monofilament on a bobbin.
With the polyphenylene sulfide monofilament obtained in Comparative Example 8, where the preliminary heating temperature of the godet roller 1 was set high, that temperature which was higher by about 40°C than the glass transition temperature of the polyphenylene sulfide caused the yarn to become slack on the godet roller 1. As a result, significantly large yarn swinging occurred and yarn breakage occurred frequently, so it was not possible to obtain the monofilament.
With the polyphenylene sulfide monofilament obtained in Comparative Example 9, where the elongation of the monofilament was lowered to 22%, yarn breakage would likely occur during spinning due to the low elongation. Further, even though relaxation was applied, the 5% modulus and 10% modulus were high, causing barre during unwinding of the bobbin. The mesh woven fabric using this monofilament suffered streaks due to barre, resulting in poor quality. In terms of performance, the fabric would inherit the factors that occurred during weaving, resulting in inferior performance and poor appearance.
The polyphenylene sulfide monofilament obtained in Comparative Example 10, where the elongation of the monofilament was increased to 50%, exhibited good spinning operability. However, with the considerably low strength, 5% modulus, and 10% modulus, the obtained mesh woven fabric was extremely poor in dimensional stability. The mesh woven fabric also suffered misalignment of mesh weave due to stretching or the like, resulting in extremely poor durability of the strength.
With the polyphenylene sulfide monofilament obtained in Comparative Example 11, where the heat setting temperature was set to 190°C and the winding tension was set to 0.6 cN/dtex, the high winding tension caused tight winding when the winding volume exceeded 1 kg, making it unable to remove the bobbin from the winder, so it was not suitable for mass production. Further, in the evaluation of weaveability of the mesh woven fabric obtained with thin winding, barre occurred in the bobbin inner layer portion during unwinding, and streaks occurred on the fabric, resulting in poor quality. This is conceivably due to the high 10% modulus.
With the polyphenylene sulfide monofilament obtained in Comparative Example 12, where the heat setting temperature was as low as 110°C and the bobbin package was of a drum shape, the heat setting temperature was low, the breaking strength was low, and the hot water shrinkage rate was high. Further, because of the drum shape of the bobbin, there occurred falling of the yarn from the bobbin end faces (traverse failure) during weaving. This lead to yarn breakage or the like due to the bobbin unwinding failure during weaving, degradation in dimensional stability of the mesh woven fabric, and reduction in durability of the strength, thus resulting in poor quality.
As such, the polyphenylene sulfide monofilaments obtained in Examples 1 to 5 were superior in spinning operability, hardly suffering streaks due to barre, reed shaving, formation of scum, knots, and yarn breakage during weaving, and they were of high quality with sufficient strength. The obtained mesh woven fabrics, before and after processing, were almost free of appearance abnormalities such as misalignment of mesh weave, streaks due to barre, and the like, were excellent in dimensional stability and sufficient in strength, so the fabrics were of high quality and usable in high-performance filter applications.
Table 2 shows conditions for producing polyphenylene sulfide monofilaments in Examples 1, 3, 4, and 6 to 16 and Comparative Examples 13 to 15, physical properties of the yarns, and results of various evaluations.

[Table 2]

For the fiber packages of the polyphenylene sulfide monofilaments obtained in Examples 1, 3, 4, and 6, which were obtained by controlling physical properties such as breaking strength, breaking elongation, 5% modulus, 10% modulus, and the like, bobbin shape, winding manners such as winding tension during winding onto the winder, oil pick-up unit to the yarn, and the like, and winding conditions such as winding width, taper angle, lead angle, and the like, the monofilaments were of high quality with high strength and few knots, and could be produced using the direct spinning drawing method. The fiber packages were good in package winding shape, suffering no shape failure such as tight winding, collapsed winding, and the like, and offered good unwinding property. The hot shrinkage stress ratio between the innermost and outermost layers was also good, and the packages were uniform and of good quality. Further, mesh woven fabrics obtained from the polyphenylene sulfide monofilaments wound in the pirn-shaped package with tapered portions were free of scum and free of warp and weft breakage, and were also of high quality in terms of appearance without the occurrence of streaks, coarse yarn, or abnormal luster due to barre or other factors. Moreover, the fabrics were also sufficient in strength, good in dimensional stability, and were of high quality with high durability as filters.
Among them, those of Examples 1 and 6 were the polyphenylene sulfide mesh woven fabrics of particularly excellent performance, which were good in fiber physical properties, without barre, streaks, and the like.
With the fiber package of the polyphenylene sulfide monofilament obtained in Example 8, where the fiber package was of a drum shape and the lead angle was large, the moving speed of the traverse motion became fast, probably due to the drum shape and the lead angle of 5°, so the yarn would likely be repelled to the outside by momentum, often leading to traverse failure, and the resultant package was poor in yarn unwinding property. Because of such poor unwinding property from the package during weaving, streaks and yarn breakage occurred, resulting in not good quality.
With the fiber package of the polyphenylene sulfide monofilament obtained in Example 9, where the fiber package was of a drum shape, traverse failure would likely occur probably due to the drum shape, although it was reduced compared to Comparative Example 13, and the resultant package was poor in yarn unwinding property. For the weaveability, due to the slightly poor unwinding property from the bobbin, streaks and yarn breakage occurred, and the quality was not good.
With the fiber package of the polyphenylene sulfide monofilament obtained in Example 10, where the fiber package was of a pirn shape close to the drum shape, the traverse failure would likely occur probably due to the approximately drum shape, although it was reduced compared to Example 9, and the resultant package was slightly poor in yarn unwinding property. For the weaveability, due to the slightly poor unwinding property from the bobbin, streaks and yarn breakage occurred, resulting in not good quality.
With the fiber package of the polyphenylene sulfide monofilament obtained in Example 11, where the taper angle was considerably small, although the winding shape was good, a sufficient winding volume could not be reached due to the small taper angle, resulting in high cost and poor production efficiency. The small winding volume lead to joints of yarns (knots) created by bobbin switching during weaving, resulting in degradation of operational efficiency.
With the fiber package of the polyphenylene sulfide monofilament obtained in Example 12, where the lead angle was considerably small, streaks due to ribboning occurred at the center of the surface of the winding bobbin, and they continued to occur during the winding process. This caused appearance failure, and slightly poor unwinding property. Thus, during weaving, streaks and yarn breakage occurred, resulting in not good quality.
With the fiber package of the polyphenylene sulfide monofilament obtained in Example 13, where the lead angle was large, there occurred moderate traverse failure at the tapered portions, and the resultant package was poor in yarn unwinding property. This caused a few streaks and yarn breakage during weaving, resulting in not good quality.
With the fiber package of the polyphenylene sulfide monofilament obtained in Example 14, where the winding width of the package was small, although the winding shape was good, the small winding width lead to an insufficient winding volume, resulting in high cost and poor production efficiency. The small winding volume lead to joints of yarns (knots) created by bobbin switching during weaving, resulting in degradation of operational efficiency. The mesh performance was good.
With the fiber package of the polyphenylene sulfide monofilament obtained in Example 15, where the winding width of the package was large, although the winding shape was good, barre would likely occur during unwinding of the innermost layer. The mesh woven fabric after weaving had streaks, resulting in poor quality.
With the fiber package of the polyphenylene sulfide monofilament obtained in Comparative Example 13, where the winding tension to the winder was high, the high winding tension increased the 10% modulus, and tight winding on the winder occurred when the winding volume reached 1 kg or more, making it unable to obtain a fiber package. Further, the heat shrinkage stress ratio between the innermost and outermost layers greatly collapsed, resulting in monofilament of poor quality.
With the fiber package of the polyphenylene sulfide monofilament obtained in Comparative Example 14, where the winding tension to the winder was low, the low winding tension caused the yarn to loosen between the godet roller 3 and the winder, making it difficult to wind the yarn onto the winder, so it was not possible to obtain a fiber package.
With the fiber package of the polyphenylene sulfide monofilament obtained in Comparative Example 15, where the oil pick-up unit to the yarn was small, the small oil pick-up unit caused yarn breakage due to the swinging of the yarn on the godet roller, making it unable to collect a sufficient amount of yarn.
With the fiber package of the polyphenylene sulfide monofilament obtained in Example 16, where the oil pick-up unit to the yarn was large, the yarn wounded on the bobbin was slippery, which would cause traverse failure with the yarn falling off from the tapered portions, resulting in appearance failure. Further, the yarn was not easily unwound from the bobbin, leading to yarn breakage as well as formation of streaks and scum during weaving, resulting in poor quality.
As such, the fiber packages of the polyphenylene sulfide monofilaments obtained in Examples 1,3,4,6, and 7 were of high quality with sufficient strength, as they were free of tight winding, insufficient winding volume, ribboning, and traverse failure, had little variation in quality between the innermost and outermost layers, suffered no yarn breakage when unwinding during weaving, and were almost free of streaks, reed shaving, scum, and yarn breakage due to barre or unwinding during weaving. The obtained mesh woven fabrics, before and after processing, were almost free of appearance abnormalities such as misalignment of mesh weave, streaks due to barre, and the like, were excellent in dimensional stability with sufficient strength, so the fabrics were particularly of high quality, usable in high-performance filter applications. The polyphenylene sulfide monofilaments obtained in Examples 8 to 16 were all rated "o" for the spinning operability and rated "Δ"or "o" for the mesh performance. However, they could not be said to be sufficient in terms of weaveability and appearance in the package evaluation.

Claims

A polyphenylene sulfide monofilament having a phenylene sulfide unit as a main structural unit and satisfying (1) to (5):
(1) a fineness of 6 to 35 dtex;

(2) a breaking strength of 3.4 cN/dtex or more;

(3) a breaking elongation of 24% to 45%;

(4) a 5% modulus of 1.0 to 1.6 cN/dtex; and

(5) a 10% modulus of 1.4 to 2.3 cN/dtex.
A pirn-shaped fiber package made up of the polyphenylene sulfide monofilament according to claim 1.
The fiber package of the polyphenylene sulfide monofilament according to claim 2, having a winding width of 100 to 250 mm, a taper angle of 30° to 140°, a lead angle of 0.6° to 2°, and a heat shrinkage stress ratio between innermost and outermost layers of 0.85 to 1.15.
A method of producing the polyphenylene sulfide monofilament having the phenylene sulfide unit as the main structure unit according to claim 1 by using a direct spinning drawing method in which a polyphenylene sulfide resin is melt-extruded, cooled and solidified, and an obtained undrawn yarn is, without being wound once, continuously drawn and wound up with a winder, the method satisfying (1) to (4):
(1) the polyphenylene sulfide resin has an MFR of 100 to 250 g/10 min.;

(2) the undrawn yarn is drawn using a non-heated pretension roller and two or more heated godet rollers;

(3) a temperature of the first godet roller is 95°C to 120°C, and a heat setting temperature of the second and subsequent heated godet rollers is 120°C to 250°C; and

(4) a winding tension to the winder is 0.1 to 0.5 cN/dtex.
A method of producing the fiber package according to claim 2 or 3, the fiber package being made up of the polyphenylene sulfide monofilament having the phenylene sulfide unit as the main structural unit, by using a direct spinning drawing method in which a polyphenylene sulfide resin is melt-extruded, cooled and solidified, and an obtained undrawn yarn is, without being wound once, continuously drawn and wound up on a bobbin with a winder, the method satisfying (1) to (4):
(1) the polyphenylene sulfide resin has an MFR of 100 to 250 g/10 min.;

(2) the undrawn yarn is drawn using a non-heated pretension roller and two or more heated godet rollers;

(3) a temperature of the first godet roller is 95°C to 120°C, and a heat setting temperature of the second and subsequent heated godet rollers is 120°C to 250°C; and

(4) a winding tension to the winder is 0.1 to 0.5 cN/dtex.
A method of producing a fiber package made up of a polyphenylene sulfide monofilament having a phenylene sulfide unit as a main structural unit by using a direct spinning drawing method in which a polyphenylene sulfide resin is melt-extruded, cooled and solidified, and an obtained undrawn yarn is, without being wound once, continuously drawn and wound up on a bobbin in a pirn shape with a winding tension to a winder of 0.1 to 0.5 cN/dtex.
The method of producing the fiber package made up of the polyphenylene sulfide monofilament according to claim 6, wherein the obtained undrawn yarn is drawn and wound up on the bobbin after a spin finish is applied to the yarn to achieve an oil pick-up unit of 0.15 to 0.5 mass% for the polyphenylene sulfide monofilament.
A method of producing a fiber package made up of a polyphenylene sulfide monofilament having a phenylene sulfide unit as a main structural unit by using a direct spinning drawing method in which a polyphenylene sulfide resin is melt-extruded, cooled and solidified, and an obtained undrawn yarn is, without being wound once, continuously drawn and wound up on a bobbin in a pirn shape by a winder, wherein a spin finish is applied to the undrawn yarn before being wound up on the bobbin to achieve an oil pick-up unit of 0.15 to 0.5 mass% for the polyphenylene sulfide monofilament, and the yarn is wound up on the bobbin in the pirn shape to have a winding width of 100 to 250 mm, a taper angle of 30° to 140°, and a lead angle of 0.6° to 2°.
A pirn-shaped polyphenylene sulfide monofilament fiber package having a winding width of 100 to 250 mm, a taper angle of 30° to 140°, a lead angle of 0.6° to 2°, and a heat shrinkage stress ratio between innermost and outermost layers of 0.85 to 1.15.