AU2012263373B2

AU2012263373B2 - Polyphenylene sulfide fibers and nonwoven fabric

Info

Publication number: AU2012263373B2
Application number: AU2012263373A
Authority: AU
Inventors: Masashi Ito; Yohei Nakano; Yoshikazu Yakake
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2011-06-02
Filing date: 2012-06-01
Publication date: 2016-11-17
Anticipated expiration: 2032-06-01
Also published as: EP2716800A1; WO2012165608A1; AU2012263373A1; JPWO2012165608A1; US20140187115A1; CN103562446A; CN103562446B; JP5867400B2; KR101948637B1; KR20140032452A; EP2716800A4

Abstract

Provided are: polyphenylene sulfide fibers which are mainly composed of a PPS resin and has excellent heat resistance and thermal bondability at the same time; and a nonwoven fabric which is configured of the fibers. The polyphenylene sulfide fibers are characterized by being mainly composed of a polyphenylene sulfide and having a sum of the crystallinity and the rigid amorphia of 30-90% (inclusive). The crystallinity is preferably 5% or more but less than 25%. A nonwoven fabric is configured using the polyphenylene sulfide fibers. The nonwoven fabric is preferably integrated by thermal bonding or mechanical interlacing.

Description

1

DESCRIPTION

POLYPHENYLENE SULFIDE FIBER AND NONWOVEN FABRIC

TECHNICAL FIELD

The present, invention relates to a fiber comprising a resin comp ris in g pο1ypheny1ene su1fide (here i nafter sometirnes abbreviated to "PPS") as a main component, and a nonwoven fabric comprising the fiber. 10

BACKGROUND ART PPS resins are excellent in heat resistance, flame retardancy and chemical resistance and are therefore suitably used as engIuggiing plots«..ics, films, fibers, nonwoven fabrics, or the like. Especially nonwoven fabrics utilizing these excellent properties are expected to be used in industrial applications such as heat-resistant filters, electrical insulation materials, and battery separators.

However, in cases where a PPS resin is spun into fibers to form a nonwoven fabric, proorems may arise concernincr poor thermal dimensional stability, which may lead to sioni ^ cant thermal shrinkage of the fibers or the nonwoven fabric.

In order to improve the dimensional stability of PPS nonwoven fabrics, there has been proposed, for example, a filament nonwoven fabric produced by spun bonding in which a PPS resin is spun and drawn into filaments, the tilamenfs are temporarily bonded at a temperature not more than the first crystallization temperature of the fabric to be produced, t-he obtained fabric is subjected to heat treatment under strain at H:¥kxg¥Interwoven¥NRPortbl¥DCC¥KXG¥11820919_l.DOC - 25/10/16 2 2012263373 25 Oct 2016 a temperature not less than the first crystallization temperature to promote the crystallization of the filaments, and the fabric is subjected to permanent bonding (see, for example, Patent Literature 1). There has also been proposed a 5 heat-resistant nonwoven fabric produced by spinning and drawing a PPS resin at a high spinning speed of 6, 000 m/min or more to promote the crystallization of the fibers, and thereby to suppress thermal shrinkage (see, for example, Patent Literature 2). These proposals, however, suffer from poor thermal bonding 0 properties.

Thus there has been no proposal for a PPS fiber or PPS nonwoven fabric having both heat resistance and thermal bonding properties .

5 CITATION LIST

PATENT LITERATURE

Patent Literature 1: JP-2008-223209 A

Patent Literature 2: WO 2008/035775 20 Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any 25 other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it) , or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that 2012263373 25 Oct 2016 Η:¥kxg¥Interwoven¥NRPortbl¥DCC¥KXG¥11820919_l. DOC - 25/10/16 3 prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

5 SUMMARY OF INVENTION

In one aspect the present invention seeks to provide a fiber comprising a PPS resin as a main component and having both excellent heat resistance and excellent thermal bonding properties, and a nonwoven fabric comprising the fiber. 0 The reason conventional techniques as described above cannot achieve heat resistance and thermal bonding properties at the same time is probably that promotion of crystallization leads to increase in the thermal dimensional stability on the one hand and, on the other hand, to decrease in the amorphous 5 phase, which can melt and contribute to thermal bonding. The inventors conducted intensive research to simultaneously achieve the above properties that seem incompatible and, as a result, found the following means.

That is, a first aspect of the present invention relates to 20 a polyphenylene sulfide fiber comprising polyphenylene sulfide as a main component and having the sum of the crystallinity and the rigid amorphous fraction of 30% to 90%.

In accordance with one aspect the present invention provides a polyphenylene sulfide fiber comprising polyphenylene 25 sulfide as a main component and having the sum of the 2012263373 25 Oct 2016

HsVkxgVInterwovenVNRPortblVDCCVKXGV11820919_l.DOC - 25/10/16

3A crystallinity and the rigid amorphous fraction of 30% to 70% wherein the crystallinity is not less than 5% and less than 25%. A second aspect of the present invention relates to a nonwoven fabric comprising the polyphenylene sulfide fiber 5 according to the first aspect of the present invention.

The polyphenylene sulfide fiber (hereinafter also referred to as PPS fiber) of the first aspect of the present invention having the sum of the crystallinity and the rigid amorphous fraction of 30% or more, preferably 35% or more, is excellent 0 in thermal dimensional stability. The polyphenylene sulfide fiber having the sum of the crystallinity and the rigid amorphous fraction of 90% or less, more preferably 70% or less, still more preferably 50% or less, is preferred in terms of thermal bonding properties. 5 The crystallinity is not limited to a specific range.

However, the crystallinity is preferably 5% or more, more preferably 10% or more, and still more preferably 15% or more. When a nonwoven web of the fiber having such crystallinity is thermally bonded, the resulting sheet is prevented from 4 breakage due to being wound up around a roll. The crystallinity is preferably less than 25%, more preferably 23% or less, and st ill more pre ferably 20% or less so that a large amount of the amorphous ph a s e (.1 nc 1 uding the rigid amorphous fraction) is pr esent in r h p fiber and contribu tes to excellent thermal bonding properti es for thermal bonding ^ f nonwoven web .

As regards the above-mentioned nonwoven fabric, a production method therefor and the structure thereof are not 10 particularly limited. For example, the nonwoven fabric can be produced by spun bonding in which the PP5 fibers are consolidated bv thermal bonding or mechanical entanglement. ADVANTAGEOUS EFFECTS OF invention 15 The PPS fiber of the present invention has excellent thermal bonding properties while maintaining the properties of a PPS resin, namely, heat resistance, chemical resistance, and flame retardancy. Consequently, the nonwoven fabric of the present invention also has excellent, mechanical strength 'while 20 maintaining the properties of a PPS resin, namely, heat resistance, chemical resistance, and flame retardancy and is therefore usable for various industrial applications.

BRIEF DESCRIPTION OF DRAWINGS 25 Fig. 1 is a graph showing the relation of the boiling water shrinkage to the crystallinity in PPS fibers.

Fig. 2 is a graph showing the relation of the boiling water shrinkage to the sum. of the crystallinity and the rigid amorphous fraction in PPS fibers.

DESCRIPTION OF

EMBODIMENTS

The resin used in the present invention comprises PPS as a main component. Hereinafter, tne resin that is used in the su. ent invention an .d compri ses PPS is aim so referred t o a. s c h θ res in." . PPS is a polymer having, as the repeat ing unit, a phenylene ide unit such as a p- -phenylene sul fide unit and a m- phenylene sulfide unit. Preferred is a substantially lii iar polymer containincf 90 molt or more or a p~pnenyiene sulfide unit because of its heat resistance and spinnability. In cases where PPS is used as a main component to obtain a polymer witn a low melting point, preparation oj_ a polymer by copolymerization of a p-phenylene sulfide unit witn a m-phenylene sulfide unit is preferred in that the flame retardancy and chemical resistance of PPS are not impaired. The copolymerized PPS can be suitably used as a component, for a compo s i t e fiber. nning and. dr a v/ing. The c op o1y me r i zed tent;, as th p fjoQrθθ of being subs tantially ized trichl orobenzene, is pr eferably 0,05

Preferably, PPS is substantially not copolymerized with ti chlorobenzene This is bGtdubS crrc-iilorobenzene has three or more nalocren substituents per ben^e^xe iuQ and thus t±iG copolymerization of PPS with trichlorobenzene results in a branched structure, leading to poor spinnability of the resulting PPS resin ana frequent breakage of the resulting fibers during spi tricnlorobenzene cοi free from copolyme:; mo.1.% or less, and more preferably u.Gi Eioit or isss ·

The PPS content of the PPS resin is preferably 85% by mas or more, more preferably 90% bv •r mass oir more, aiid stirl more pref eraoxy 95% by mass or more in view of hear, resistance, chemical resistance, and the like. To the PP3 resin may be adaea a. nucleator, a matting agent, a pigment., an antifungal agent, an antibacterial agent, a flame retaroanc, a hydxophnic agent, and/or the like to the extent that these do not impair the ex feet, s of the present invention. The PPS resin used in the present invention preferably has a meat flow rate (hereinafter sometimes abbreviated to MFR) measured m accordance with ASTM D1238-70 (measurement temperature: 315.5°C, measurement load: 5 kg) of 100 to 300 g/x0 min. The PPS resin having an MFR of 100 g/10 min or more, more prexerabiv 140 g/10 min or more, has moderate fluidity, which contributes to the suppression of increase in the back pressure of the spinneret during melt spinning and to the pi event.ion o 1 o e a k a vr e χ t n x rx cni + ί ,ι η· .p ι . . -. -, . . x-ed&jjfc o.:. t^e libers during pulling g/10 min or moderately ght, which contributes to increase in strength , . . ^ and heat resistance sufficient for practical use. It is important for the PPS fiber of κ ~ the nresent invention and drawing. The PPS resin ha ving an MFR of 30, 1 ess, more prefer ably 225 g/10 min or less, has high polymer.!, zat ion degree or molecular w< to have the sum of the crystallinity and +- he rigid amorphous fraction of 30% to 90%. ihe crystallinity herein refers to measuring with a differential scanning described later in Examples. ihe rigid, amorphous: fraction herein t those determined by calorimetry (DSC) as ‘-cfers to the remainder left after subtraction of the crystal!ini ‘-ity [%] and. the mobile ·*7 amorphous fraction [%] from the total of the crystal and amorphous fractions (100%) that constitutes the fiber, as shown in the following formula:

Rigid amorphous fraction [%] = 100 [%] - crystallinity [%] - mobile amorphous fraction [%],

The mobile amorphous fraction herein refers to those determined by measuring with a temperature modulated DSC as described later iη Examp1es. 10

The inventors found that not only the crystal fraction but also the rigid amorphous fraction significantly affects the thermal dimensional stability. 2 0

That is, as shown in the relation of the boiling water shrinkage to the crystallinity in Fig. 1, even though the crys taxlini i:y values are substantially the same among the samples having a crystallinity of less than 20%, the boiling water shrinkage greatly varies; however, as shown in the 2. era t. ion of the boiling water shrinkage to the sum. of the crystallinity and the rigid amorphous fraction in Fig. 2, when the rigid amorphous fraction is used as an evaluation factor in adoition to the crystallinity, a strong correlation is observed, which reveals that the rigid amorphous fraction significantly arfects the thermal dimensional stability. Although the mechanism is unclear, the rigid amorphous fraction is an amorphous yet is considered to play a similar role to that of the crystal fraction for the thermal dimensional stability, in Figs. 1 and 2, the data is based on Examples and. Comparative Examples described, later, and. the numbers within the brackets in the graphs correspond to the numbers in Table i a e s c r -i. b e d 1 a t e r . 8

As shown in Fig. 2, the boiling water shrinkage than 20% when the sum of the crystallinity and the rigid amorphous fraction is 3 0 % o r more, and the boiling water shrinkage i s 1 e s s t h a n 10 % when the sum of the crystal Unity and the r i gid amo rphous fraction is 35% or more.

In view of suppression of shrinkage in width, wrinkles, and surface irregularity caused by thermal shrinkage, the boiling water shrinkage is preferably 20% or less, more preferably 15% or less, and still more preferably 10% or less. Consequently, the sum of the crystallinity and the ri gid )n of 30% or more, preferably 35% or more, has . dimensional stability. excellent thermal dime

In view of thermal bonding properties, in addition to the rigid amorphous fraction, preferably the mobile amorphous fraction is also contained in an amount, of 10% or more, more preferably 30% or more, still more 5 preferabl y 50% or more. Although the me chanism is unclear, i t i s c ο n s i dered that, in t h e rma1 bο nd ing , fibers comprising a certain amounl : of the mob i1e amo rpho us fraction more easily u ndergo plastic deformation in accordance with the magnitude of the pressure applied to the fibers for bonding. That is, the sum of the crystallinity and the rigid amorphous fraction in the PP5 fiber is preferably 90% or less, more preferably 70% or less, and still more preferably 50% or less.

The crystallinity of the PPS fiber of the present, invention is preferably not less than 5% and less than a5%.

As described in the above Patent Literature 2, it. has been considered that the crystallinity needs to he 20¾ or more to stably impart thermal dimensional stability to a PPS fiber.

However, according to the present invention, even when the crystarlxnity is less than 25%, thermal shrinkage of a Ppg fiber can be reduced by increasing the amount of the rigid amorphous fraction. Conventionally, low crystallinity of a ppg o fiber means the presence of a large amount of the amorohous phase, which results in poor thermal dimensional stabi]i ty· whereat! high crystallinity of a PPS fiber means the presence of a small amount of the amorphous phase, which results in poo^-thermdi bonding properties. According to the present invention i0 the amorphous phase, especially the rigid amorphous fraction is increased to impart thermal dimensional stability, thereby achieving both excellent thermal dimensional stability and excellent thermal bonding properties.

The crystallinity of the PPS fiber of the present invention 15 is 5% or more, more preferably 10% or more, and still more preferably 15% or more. When a nonwoven web of the fiber having such crystallinity is thermally bonded, the resultina sheet is prevented from breakage due to being wound up around a roll. The crystallinity is less than 25%, more preferably 23% 20 or less, and still more preferably 20% or less so that a large amount of the amorphous phase (including the rigid amorohous fraction) is present in the fiber and contributes to excellent thermal bonding properties for thermal bonding of the nonwoven web.

The cross section of the PPS fiber of the present invention may be any shape such as a circular shape, a hollow round shape, an oval shape, a flat shape, a polygonal shape, and a multiloba! shape (such as an X shape and a Y shape).

The PPS fiber of the present invention may be in a 10 5 10 composite form. Examples of the composire form include a coresheath type, an eccentric core-sheath type, an Umishima type, a parallel type, a radial type, and a multilobal type. Among these, preferred is a core-sheath type, which is suitable for achi evi ng exce1.1. ent sp 1 nnabi 1 i ty.

The average single titer fineness of the PPS fiber of the present invention is preferably u.5 to i0 dtex.

When spinning is performed so as to form, fibers havina an average single fiber fineness of 0.5 dtex or more, more preferably 1 dtex or more, still more preferably 2 dtex or more, spinnability of the fibers is assured and frequent breakage of the fibers during spinning can be prevented. an

When spinning is performed so as to form fibers havincr average single fiber fineness of 10 dtex or less, more 15 preferably 5 dtex or less, still more preferably 4 dtex or less, the discharge rate of a molten resin per hole of a spinneret can be suitably reduced, to allow the resulting fibers to sufficiently cool down, thereby preventing reduction in spinnabiiity due to fusion bonding between the fibers. 20 Moreover, when such fibers are formed into a nonwoven fabric, the variation in the mass per unit area of the nonwoven fabric can be reduced, thereby providing excellent quality for the surtaces of the nonwoven fabric. Also in view of the dust collecting performance of the nonwoven fabric used as a filter 25 or the like, the average single fiber fineness is preferably 10 dtex or less, more preferably 5 dtex or less, and still more preferably 4 dtex or less.

The PPS fiber of the present invention can be used as a fiber for forming any type of: fabric such as woven fabrics and 11 nonwoven fabrics but, because of its excellent thermal bonding properties, the PPS fiber of the present invention can be more suitably used as a component fiber of a nonwoven fabric whose structure is fixed by thermal press-bonding.

The PPS nonwoven fabric of the present invention may be a but filament nonwoven fabric or a staple nonwoven fabri filament nonwoven fabric produced by spun bonding is preferred for its excellent, productivity.

The mass per unit area of the nonwoven fabric of the present invention is preferably 10 to 1000 g/m2. The nonwoven fabric having a mass per unit area of 10 g/m2 or more, more erably 100 g/m2 or more, still more pre terably 200 g/m2 or , exhibits a sufficient mechanical strength for practical In ca ses where the non woven fabric is used as a filter or like, the mass per uni t area, is 1000 g/m2 or less, more erably 7 00 g/m2 or less, a. n d s t i 11 mo r e pre feral. )1 y 500 g/m2 ess. T 'he η ο n w o v e n f a b r i -C having such a mass pe r unit area nas moderate air permeability and thus prevents pressure loss froik increas ing. 2 0 The thermal shrinkage rate at 200°C of the PPS nonwoven fabric of the present invention is preferably 5% or less both in the longitudinal and transverse directions. Because of its properties, PPS nonwoven fabrics are often used under high temperature. When the thermal shrinkage rate at 200°C of the 25 PPS nonwoven fabric of the present invention is 5% or less, more preferably 3% or less, reduction in its performance due to oimensj.onai cnange cai be prevented, and such, a PPS nonwoven fabric is suitable for practical use.

The PPc nonwoven faforic of trie present invention preferably has a longitudinal tensile strength retention rate measured by a heat-exposure resistance test in hours of 8 0% or more. The 1οng i tudin a 1 t ensile s trength .more preferably 85% or more, si can be used as a heat-resistant filter or the like that is used under high temperature for a long period of time. The upper limit value of the longitudinal tensile strengtn retention rate is not particularly limited but is preferably 150% or less. t. in the air at 210°C for 150 PPS nonwoven fabric having retention rate of 80% or more i 11 mo r e p r e f e rably 90% or more

Next, a production method for a PPS nonwoven fabric by spun bonding, which is a preferred embodiment for the PPS fiber and PPS nonwoven fabric of the present invention, will be described below.

Spun bonding is a production method that, requires the steps of: melting a resin, spinning the molten resin from a spinneret, solidifying the resulting filamentary streams by cooling, pulling and drawing the filamentary streams by means ; o f an ej ector, collecting the filaments on a moving net to form a nonwoven web, and consol idating the nonwoven web by thermal bonding or mechanical entanglement.

The spinneret and the ejector may be id various shapes such as a circular shape and a rectangular shape. Inter alia, a combination of a rectangular spinneret and a rectangular ejector is preferred because the amount of compressed air to be used is relatively small and the filaments are hardly fusion-bonded or scratch each other.

The spinning temperature for melting and spinning PPS is preferably 290 to 380°C, more preferably 295 to 360°c, and still more preferably 300 to 340°C. The spinning temperature within the above range allows PPS to be brought into a stable molten state and to exh. ibit excelle nt spinning st :abili tv. Examples of the method for cooling the : spun filamentary streams include, for exampl .e, a. method i n wh ich cold air is toreed to blow over the filamentary streams, a method in which the filamentary streams are allowed to cool, down at atmospheric temperature around the filamentary streams, a method in which the distance between the spinneret and the elector is adjusted, and a combination thereof. The cooling conditions can be appropriately adjusted and adopted yn consideration of the discharge rate per hole of the spinneret, the spinning temperature, the atmospheric temperature, and the like.

Next, the filamentary streams that have solidified by cooling are pulled and drawn by compressed air blown from the ejector. The method for pulling and drawing the filamentary streams by means of the ejector and the conditions therefor are not particularly limited, but a method in which the filamentary streams are pulled and drawn by compressed air heated and blown from the ejector, the compressed air being heated to 100°C or more, preferably 140°C or more, more preferably 180°C or more, is preferred in that the crystallization of the pps fiber is suppressed an id at the same time the rigid amorpf iOUS fraction is increased. Since heated compressed air is used, the filamentary Q trearns that are being pulled and drawn are s imu 11. aneo u s 1 y heat t r e a t e d. However, the heat treatra ent duration is extremely short and therefore the rigid amorphous traction, whicn is an intermediate phase between ihe crystal phase and the amorpnous pna.se, can be specifically j ncreased. The upper limit of the temperature of the heated compressed air 14 is not more than the melting point of PPS.

Another method for heat treating the filamentary streams during pulling and drawing include a method in which a heater is disposed before or after the ejector. However, this method is not preferred because the thermal conductivity is inferior to that in the above method in which a hot air of high temperature is directly blown over the fibers, and consequently the heat does not contribute to increase in the rigid amorphous fraction .

The spinning speed is preferably not less than 3, 000 m/'min and less than 6,000 m/min. Spinning at a spinning speed of 3,000 m/min or more, more preferably 3,500 m/min or more, still more preferably 4,000 m/min or more, can produce a PPS fiber having high crystallinity. Consequently, when a resulting nonwoven web is thermally bonded, the resulting sheet is prevented from, breakage due to being wound, up around, a roll. Spinning at a spinning speed less than 6,000 m/min is preferred because excessive increase in the crystallinity can be prevented and excellent spinning stability can be achieved..

Next, the PPS fibers obtained by drawing are collected on a moving net to form a nonwoven web, and the obtained nonwoven web is consolidated by thermal bonding or mechanical entanglement to form a nonwoven fabric.

Preferred method for consolidation into a nonwoven fabric are a thermal bonding method in which thermal press-bonding is performed using various types of rolls such as a roll pair for thermal embossing that is composed of upper and lower rolls each having embossment, on their surfaces, a roll pair for thermal embossing that is composed of a. roll having a flat (smooth) surface and a roll having embossment on its surface, or a roll pair for thermal calendering that is composed of upper and lower flat (smooth) rolls; and a mechanical entanglement method using needle punching or water jet punching. o T n C 3 S Θ S W o 0 thermal p r e s s - b ο n d i n g is performed with a therma1 embos s ina roll pai r, the emboss: uent pattern on the embossina ro.1 'i (ν\ may be circle, oval, square, rectangle, parallelogram, diamond, regular hexagon, or regular octagon, or the like.

The surface temperature of the thermal embossing roll pair is preferably 5 to 30°C lower than the melting point of PPS. By means of the thermal embossing roll pair having a surface temperature not lower than the temperature that is 30°C lower 15 than the melting point of PPS, more preferably a surface temperature not lower than the temperature that is 2 5°C lower than the melting point of PPS, still more preferably a surface temperature not lower than the temperature that is 20°C lower than the melting point of PPS, the nonwoven web i thermally bonded to a sufficient extent and thereby flaking off and fluffing of the resulting nonwoven fabric can be prevented. By means of the thermal embossing roll pair having a surface temperature not higher than the temperature that is 5°C lower than the melting point of PPS, perforation in the press-bonded parts due to fusion of the fibers can be prevented.

The linear pressure applied by the thermal embossing roll pair dur i n g t h e rma1 bond. ing is prefer ably 200 to 1500 N/cm . By mean s of the rolls with a 1 inear pressure of 200 N/cm or more, more p .r e f e r: ab 1 y 3 0 0 N/ cm. or more, the nonvvover : web i s thermally bonded to a sufficient ex :tent and thereby flaking off and 16 flu f f ing O f the r esulting Si". leet can be pre vented. By mean s o f the roil s with a linear pr< ass ure of 1500 N/cm or less, more pre ferabl 100C ) N/cru or 1 ess t U e rais ed portions of r h emb ossmer it are pr evented from biting into the nonwoven fa brie and thereb Y troi lb! ,e remov; ing th e nonwo ven f rabric from the r Ό1 i S or the b.i re akage of : the nonwo1 ven fabric can be prevented.

The bond! .ng area provided bv means of the thermal . embossing roll pair is preferably 8 to 40%. Thermal bond inc j with the roll pair so as to provide a bonding area of 8% or more, more 0 preferably 10% or more, still more preferably 12% or more, can produce a nonwoven fabric having a sufficient strength for practical use. Thermal bonding with the roll pair so as to provi de a bonding area of 40% or less, more preferably 30% or 1. Θ S S f still more preferably 20% or less, can prevent r h 0 5 resul ting nonwoven fabric froi η being formed into a film-1 ike shape that hardly has the advantages of a nonwoven fabric, such as air permeability. When thermal bonding is performed with a pair of upper and lower rolls each having raised and recessed portions, the bonding area herein refers to the ratio of the 0 area where the nonwoven web is in contact with both of the raised por tions of the upper roll and the raised portions of the lower pp] Ί -L ^ -L -L f relative to the total area of the nonwoven fabric. When thermal bonding is performed with a pair of a essed portions and a flat roll, the to the ratio of the area where the with the raise d port.! Olio Or. the r oil portions, rela tive to the total a ire a of the nonwoven fabric.

When the nonwoven fabric is mechanically entangled by 17 needle punching, the shape of the needles and the number of needles per unit area can be appropriately selected and adjusted to perform the entanglement. In particular, the number of needles per unit area is preferably at least 100 per 5 cm2 or more in view of the strength and the retention of the shape of the needles. Preferably, a silicone-based oil agent is sprayed on the nonwoven web before needle punching to prevent cutting of the fibers with the needles and. to enhance the entanglement of the fibers. 10 When the mechanical entanglement is performed by water jet punching, columnar jets of water is preferably used. Usually, for creating columnar jets of water, a method in 'which water is forced out of nozzles 0,05 to 3.0 mm in diameter at a pressure of 1 to 60 MPa is suitably used. For achieving efficient 15 entanglement and consolidation of the nonwoven web, the nonwoven web is preferably treated, at least once, at a pressure of 10 MPa or more, more preferably 15 MPa or more.

For the purpose of improving transportability and controlling the thickness of the nonwoven fabric, the nonwoven 20 web before thermal bonding or mechanical entanglement can be temporarily bonded with calender rolls at 70 to 170°C and at a linear pressure of 50 to 700 N/cm, The calender rolls may be a combination of upper and lower metallic rolls or of a metallic roll with a resin or paper roll. 25 Furtnermore, for the purpose of improving the thermal, stability, tne nonwoven web before thermal bonding or before or alter mechanical entanglement or the nonwoven fabric can be neat treated under strain using a pin tenter, a clip tenter, or the like, or neat treated without strain (under a strain-free 18 condition) using a hot air dryer or the like. The temperature for the heat treatment is preferably in the range of from the crystallization temperature to the melting point of the PPS fiber that forms the nonwoven web or nonwoven fabric,

R

EXAMPLES

Measurement methods (1) Melt flow rate (MFR) (g/10 min)

The MFR of PPS was measured in accordance with ASTM D1238--0 70 under the conditions of a measurement temperature of 315.5°C and a measurement load of 5 kg. (2) Average single fiber fineness (dtex)

Ten pieces of small samples were randomly taken from a nonwoven web collected on a net. The surf aces of the samples were photographed at a ma gni f i c a t i οη o f 500 to 1000 times under a microscope. The widt hs of ten fibers out of each sample, 100 fibers in total, were measured, and. the average values were calculated. The fibers are regarded as fibers having a circular cross section, and therefore the average 'width values 20 of the single fibers were regarded as the average diameter thereof. From the average 'width values, the weights of the single fibers for each 10, 000 m in length 'were calculated based on the solid density of the resin used and rounded off to the first decimal place to determine average single fiber 25 finenesses. (3) Spinning speed (m/niin)

The spinning speed was calculated based on the following formula using the average single fiber fineness (dtex) of a fiber and the discharge rate of the resin per hole of a spinneret having various settings (hereinafter abbreviated to discharge rate per hole) (g/min).

Spinning speed = (10000 x discharge rate per hole)/average single fiber fineness (4) Crystallinity (%)

Three samples were randomly taken from fibers after drawing. The samples rwere subjected to measurement with a differential scanning calorimetry (Q1000, made by TA Instruments, Inc.) under the following conditions. The crystallinity of each sample was then determined by the following formula and the average value thereof was calculated. In the formula, the term "exothermic neat of cold crystallization" refers to the exothermic peak area resulting from, cold crystallization, and the term "endothermic heat of fusion" refers to the endothermic peak area resulting from fusion. The baseline for the calculation of the ±1Θ 3. L { ρ Θ 3. k cl· ,ΊΓ Θ 3.) was a straight I ine c ο η n e c t i n g t h e h e a t flow curve i n the liquid phase after the glass transition of the amorphous phase and the heat flow c urve in the liquid phase after crystal fusion. The baseline intersects the DSC curve and separates the exothermic side from the endothermic side. The heat of fusion of a perfect crystal was 146.2 J/g. - Measurement atmosphere: nitrogen flow (50 ml/min)

- Temperature range: 0 to 350°C - Heating rate: 10°C/min - Amount of sample: 5 mg

Crystallinity = {[(endothermic heat of fusion [J/g]) - 20 [exothermic heat of cold crystallization [ J/g] ) ] /146 2 r -r / - ' L u' g j} x .00 (5) Mobile amorphous fraction (%)

Three samples were randomly taken from, fibers after· a- * ^rawing ® ^P s r a t u r e er the -n each

The samples were subjected to measurement with a t- modulated DSC (Q1000, made by TA instruments, Inc.) Uncj following conditions. The mobile amorphous fraction i ;amo le was determined by the following formula and the average 10 value thereof was calculated. The specific neat of a per feci amorphous solid was 0.2 699 J/g-°C. - Measurement atmosphere: nitrogen flow (50 ml/min) - Temperature range: 60 to 200c,C - Heating rate: 2°C/min 1 5 - Amount of the sample: 5 mg Mobile amorphous fraction [%] = (change in specif transition temperature between before and after glass [ J/g-°C'J } / 0.2 699 [J/a-°Cj x 100 2 0 z o (6) Rigid amorphous fraction (%)

From the crystallinity determined in the above (5) and the mobile amorphous fraction determined in the above (6), the rigia amorphous iraction was calculated by the following formula :

Rigid amorphous fraction [%] = 100 [%] - crystallinity [%] - mobile amorphous fraction f%i ( /) Boiling water shrinkage !% \ ihe fibers alter drawing were randomly taken out, and fi 21 fibers were aligned parallel to each other to give one sample (length: about 10 cm) . A load as described below was applied to the sample and the length (L0) was measured. Then, the sample was immersed in boiling water in a strain-free state for: 2 0 minutes, taken out from the boiling water, and allowed to dry. The same loa d a si above was applied to the sample again and the length (LI) was measured. From the 1 engths L0 and LI, the boiling water shrinkage was calculated and the average value of four samples was determined. The formulas for calculating the below. The load Boiling wate load and the boiling water shrinkage are shown was rounded off to the second decimal place. .9 x discharge rate per hole (g/min) r shrinkage (%) = {(L0 - L1}/L0} x 100 (8) Mass per unit area (g/m2) of nonwoven fabric

In accordance with 6.2 "Mass per unit area (ISO method}" in JIS L 1913: 2010 "Test methods for nonwovens", three test pieces having a size of 20 cm x 25 cm were taken per meter in width, from each sample, the masses (g) of the test pieces in standard conditions were measured, and the average value thereof was expressed in terms of mass per m2 (g/m2) . (9) Tensile strength of nonwoven fabric

In accordance with 6.3.1 "In standard conditions" of 6.3 "Tensile strength and elongation rate (ISO method)" in JIS L 1913: 2010 "Test methods for nonwovens", tensile test was performed at three points in the longitudinal direction of a sample under the conditions of a sample size of 5 cm x 30 cm, a holding interval of 2 0 cm, and a tensile rate of 10 cm /min.

The average value of the strengths ar wh was determined as a longitudinal tensile rounded off to the whole number. tiie samples broke agth (N/5 cm) and (1U) T h e r m a 1 s h r i n k a g e r a t e ( I n a c c o r d a. n c e w i t h 6.10 dry heat conditions" of 6. method)" in JIS L 1913: 2010 measurement was performed, temperature dryer was 200°C for 10 minutes. 0f nonwoven fabric .3 "Dimensional change rate under 10 "Dimensional change rate (JIS "Test methods for nonwovens", the The temperature inside a co^st-nt· and heat treatment was performed (li) Heat-exposure resistance test and. longitudinal tensile strength retention rate

Several necessary quantity of longitudinal samples h-vina a size of 3 0 cm. in length and 5 cm in width were placed in ·, air oven (ΤΑΒΑI SAFETY OVEN SHPS-222, made by ESPEC Corp ) and exposed to hot air at 210°C for 1500 hours at an apr circulation rate of 300 L/min. The tensile strengths of the samples before and after the heat-exposure resistance test were measured by the method described in the above (9), and the longitudinal tensile strength retention rates were calculated by the following formula: .Longitudinal tensile strength retention rate (%) == {longitudinal tensile strength (N/5 cm) after heat-exposure resistance test/longitudinal tensile strength (N/5 cm) before heat-exposure resistance test} x 100.

Example 23 PPS resin A ICO mol% linear polyphenylene sulfide resin that was intentionally not copolymerized with trichlorobenzene (made by Toray Industries, Inc., Product No . E22 80, MFR : 160 g/10 min) was dried in a nitrogen atmosphere at 160°C for 10 hours, and us ed in the fο11owing procedure.

Spinning and forming into nonwoven web

The PPS resin was molten in an extruder, and spun from a rectangular spinneret having a hole diameter of 0.50 mm at a spinning temperature or J20°C and at a discharge rate per hole or i.38 g/mm. The spun filamentary streams were allowed to cool down and solidify between the rectangular spinneret and a rectangular ejector at a distance of 55 cm in an atmosphere at room temperature 12U°C) . Trie filamentary streams that had cooled gowr and soliaifred were passed through, the rectangular ejector and. were pulled ana drawn by compressed air that 'was heated to 230°C with an air heater and blown out from the ejector at an ejector pressure of 0.15 MPa. The filaments were collected on a moving net to f0rm a nonwoven web. ±he obtained filaments had an average single fiber fineness or 2.8 dtex, a crystallinity Qf ig.4%, the sum of the rigid amorphous fraction and the crystallinity of 38.2%, and a boiling water shrinkage of 2.3%. The spinning speed was 4,998 m/min. During tne oue-hour spinning, the occurrence of the breakage of the filaments was zero and thus good spinnability was observed.

Temporary bonding and thermal bo^d'Dig 24

Next, the obtained nonwoven web was temporarily bonded at a linear pressure of 200 N/cm and a temporary bonding temperature of r00°C with a pair of upper and lower metallic calender rolls installed in tne production line. The nonwoven fabric was then thermally bonded at a linear pressure of 1000 N/cm and a thermal bonding temperature of 270°C with a roll pair for embossing which provides a bonding area of 12% and which is composed of an upper metallic embossing roll engraved with a polka dot pattern and a lower metallic roll having a flat surface. Thus, a filament nonwoven fabric of Example 1 was obtained.

The obtained nonwoven fabric had no significant shrinkage in width due to thermal shrinkage by thermal bonding with the embossing roll pair and showed good quality without wrinkles. The obtained, filament nonwoven fabric had a mass per unit area of 24 8 g/m2, a longitudinal tensile strength of 434 N/5 cm, thermal shrinkage rates of 0.0% in the longitudinal direction and 0.1% in the transverse direction, and a longitudinal tensile strength retention rate of 99%.

Example 2 PPS resin, spinning, and forming into nonwoven web

The same PPS resin as in Example 1 was spun and formed into a nonwoven web in the same manner as in Example 1 except that the temperature of the compressed air was 200°C.

The obtained filaments had an average single fiber fineness of 2.8 dtex, a crystallinity of 17.3%, the sum of the rigid amorphous fraction and the crystallinity of 37.3%, and a boiling water shrinkage of 7.0%. The spinning speed was 4,991 m/iiiin. During the one-hour spinning, the occurrence of the breakage of the filaments was zero and thus good spinnability was observed.

Temporary bonding and thermal bonding

Next, the nonwoven web was temporarily bonded and then, thermally bonded in the same manner as in Example 1 to produce a filament nonwoven fabric of Example 2.

The obtained nonwoven fabric had no significant shrinkaae in width due to thermal shrinkage by thermal bonding with the embossing roll pair and showed good quality without wrinkles. The obtained filament nonwoven fabric had a mass per unit area of 253 g/m2, a longitudinal tensile strength of 454 N./5 cm, thermal shrinkage rates of 0.1% in the longitudinal direction and 0.2% rn the transverse direction, and a longitudinal tensile strength retention rate of 99%.

Example 3 PPS resin, spinning, and forming into nonwoven web

The same PPS resin as in Example 1 was spun and formed into a nonwoven web in the same manner as in Example 1 except that the temperature of the compressed air was 140°C.

The obtained filaments had an average single fiber fineness of 2.9 dtex, a crystallinity of 15.1%, the sum of the rigid amorphous traction and the crystallinity of 31.3%, and a boiling water shrinkage of 17.5%. The spinning speed was 4,824 m/min. During the one-hour spinning, the occurrence of the breakage of the filaments was zero and thus good spinnability 26

Temporary bonding and thermal bonding de^t, the nonwoven web was temporarily bonded and then thermally bonded in the same manner as in Example 1 to produce a filament, nonwoven fabric of Example 3.

The obtained nonwoven fabric had no significant shrinkage in w.1.al.h aue lo thermal shrinkage by thermal press-bonding with the embossing roll, pair and showed good, quality without wrmkles. The obtained filament nonwoven fabric had a mass per unit area of 245 g/m2, a longitudinal tensile strength of 472 h/5 era, rhermai shrinkage rates of 0.0% in the longitudinal direction and 0.1% the transverse direction, and a longitudinal tensile strengtn retention rate of 99%.

Example PPS resin, spinning, and forming into nonwoven web

The same PPS resin as in Example 1 was spun and formed into a nonwoven web in the same manner as in Example 1 except that the temperature of the compressed air was 200°C and that the ejector pressure was 0.21 MPa.

The obtained filaments had an average single fiber fineness of 2.4 dtex, a crystallinity of 24.1%, the sum of the rigid amorphous fraction and the crystallinity of 49.2%, and a boiling water shrinkage of 2.2%. The spinning speed was 5,663 m/min. During the one-hour spinning, the occurrence of the breakage of the filaments was zero and thus good spinnability was observed. emporary bonding and thermal bonding 27

Next, the nonwoven web was temporarily bonded and then thermally bonded in the same manner as in Example 1 to produce a filament nonwoven fabric of Example 4.

The obtained nonwoven fabric had no significant shrinkage in width due to thermal shrinkage by thermal press-bonding with the embossing roll pair and showed good quality without wrinkles. The obtained filament nonwoven fabric had a mass per unit area of 256 g/m2, a longitudinal tensile strength of 421 N/5 cm, thermal shrinkage rates of 0.0% in the longitudinal direction ana 0.1% in the transverse direction, and a longitudinal tensile strength retention rate of 98%. example 5 PPS resin, spinning, and forming into nonwoven web

The same PPS resin as in Example 1 was spun and. formed into a nonwoven web in the same manner as in Example 1 except that the temperature of the compressed air was 200°C and that the ejector pressure was 0.25 MPa.

The obtained filaments had an average single fiber fineness 20 of 2.2 dtex, a crystallinity of 33.0%, the sum of the rigid amorphous fraction and the crystallinity of 67.4%, and a boiling water shrinkage of 2.0%. The spinning speed was 6,198 m/min. In terms of spinnability, during the one-hour spinning, the breakage of the filaments was observed twice.

Temporary bonding and thermal bonding

Next, the nonwoven web was temporarily bonded and then thermally bonded in the same manner as in Example 1 to produce a filament nonwoven. fabric of Example 5. 28

The obtained nonwoven fabric had no significant, shrinkage in width due to thermal shrinkage by thermal press-bonding with the embossing roll pair and showed good quality without wrinkles. The obtained filament nonwoven fabric had a mass per-unit area of 254 g/m2, a longitudinal tensile strength of 245 N/5 cm., thermal shrinkage rates of 0.0% in the longitudinal direction and 0.1% in the transverse direction, and a longitudinal tensile strength retention .rate of 99%. 10 Example 6 PPS resin, spinning, and forming into nonwoven web

The same PPS resin as in Example 1 was spun and formed into xo area

or uOl g/m2, a longitudinal tensile strength of 490 N /5 cm, a nonwoven web in the same manner as in l example 1. 15 Temporary bond. ing and needle punch .ing Next, the nonwovei n web was t(. smporar ily bonded in the same manner as in Example 1. An o i 1 agent- (SM7 0 60: made by Dow Corning T oray Silicone Co., Ltd.) in an amount of 2% by weight relative to t .".he weic jht of the fibers was applied to the 2 0 nonwoven web . The nonwoven web was entangled by needle punching at a density of 300 nee< dies/cm 2 'with a needle having one barb and a barb depth of 0. 0 6 mm to produce a filament nonwoven fabric of Exa mple 6.

The obtained filament nonwoven fabric had a mass per unit thermal shrinkage rates of 1.6% in the longitudinal direction ana 1,8% m the transverse direction, and a. longitudinal tensile strength retention rate of 99%. 29

Example 7 PPS resin, spinning, and forming into nonwoven web

The same PPS resin as in Example 1 was spun and formea into a nonwoven web in the same manner as m Example 1.

Temporary bonding and water jet punching

Next, the nonwoven web was temporarily bonded in the same manner as in Example 1. The front and back surfaces of tne nonwoven web were alternately entangled at a pressure or 15 MPa with a water jet punching (WJP) machine having nozzles with a diameter of 0.10 mm and a pitch of 0.1 mm. The entangled nonwoven web was dried with a hot air dryer whose temperature was set at 100°C to produce a filament nonwoven faoric of Example 7.

The obtained filament nonwoven fabric had a mass per unit area of 285 g/m2, a longitudinal tensile strength of 462 N/5 cm, thermal shrinkage rates of 1.4% in the longitudinal direction and 1.7% in the transverse direction, and a longitudinal tensile strength retention rate of 99%.

Comparative Example 1 PPS resin, spinning, and forming into nonwoven web

The same PPS resin as in Example 1 was spun and formed into a nonwoven web in the same manner as in Example 1 except tnac the compressed air was at normal temperature (30°C) ana that the ejector pressure was 0.15 l· IPa. The obtained filament \s had an average sin gle fiber fineness of 3.1 dtex, a crystal! ini tv of 8.9%, the sum of the rigid amorphous fraction and the c r y s t a i 1.1. n i t y of 10.7%, and a boiling water shrinkage of 61.2%. The spinning speed was 4,435 m/min. During the one-hour spinning, the occurrence of the breakage of the filaments was zero and thus good spinnability was observed.

Temporary bonding and thermal bonding

Next, temporary bonding and subsequent thermal bonding of the nonwoven web were attempted in the same manner as in Example 1. However, significant shrinkage in width was observed in the nonwoven web due to thermal shrinkage during thermal bonding with the embossing roll pair and the nonwoven web shrunk and hardened, and thus embossing was impossible to perform.

Comparative Example 2 PPS resin, spinning, and. forming into nonwoven web

The same PP S resin as i.i n Example 1 was spun and formed into a nonwoven web in the same manner as in Example 1 except that the compressed air w as a t normal temperature (30° C) and that the ejector pressure was 0.20 MPa.

The obtained filaments had an average single fiber fineness of 2.6 dtex, a crystallinity of 18.2%, the sum of the rigid amorphous fraction and the crystallinity of 25.3%, and a boiling water shrinkage of 28.5%. The spinning speed was 5,331 m/min. During the one-hour spinning, the occurrence of the breakage of the filaments was zero and thus good spinnability ivas observed.

Temporary bonding and thermal bonding

Next, temporary bonding and subsequent thermal bonding of the nonwoven web were attempted in the same manner as -in Example 1. However, significant shrinkage fn widtn was observed in the nonwoven web due to thermal shrinkage during thermal bonding with the embossing roll pair and the nonwoven web shrunk and hardened, and thus embossing was impossible to perform.

Comparative Example 3 PPS resin, spinning, and forming into nonwoven web

The same PPS resin as in Example 1 was spun and formed into a nonwoven web in the same manner as in Example 1 except that the temperature of the compressed air was 2 30cc and that the ejector pressure was 0.10 MPa,

The obtained filaments had an average single fiber fineness of 4.9 dtex, a crystallinity of 9.4%, the sum of the rigid amorphous fraction and the crystallinity of 26.8%, and a boiling 'water shrinkage of 25.0%. The spinning speed was 2,7 94 m/min. During- the one-hour spinning, the occurrence of the breakage of the filaments was zero and thus good spinnability was observed. f i.:

However, the thermal shrinkage rates of men.L nonwoven fabric 'were significantly hign the obtained and were

Temporary bond ling and n .eedle punching Next, the nonwoven web was temporarily bonded in the same manner as in Example 1 and then needle punched in the same manner as in E lx ample 6 to produce a filament nonwoven f abri .c of

Comparative Example 3. in the longitudinal direction and 23.4% in the transverse direction. Moreover, the surfaces of the nonwoven fabric after the heat treatment became wrinkled and irregular. The filament nonwoven fabric had a mass per unit area of 2 95 g/m2 and a o longitudinal tens! le strength o f 4" 72 N/5 cm. The neat-exposure resistance test could not be performed because of the significant thermal shrinkage.

The production and processing conditions and the measurement results of the physical properties and the like in 0 the above Examples and Comparative Examples are shown in Table able 33

Example 1 Example 2 Example 3 Example 4 Example 5 ' Example 6 Example 7 Comparable Example 1 Comparable Example 2 Comparable Example 3 PPS resin MFR g/10 min 160 160 160 160 160 160 160 160 160 160 Spinning temperature °C 320 320 320 320 320 320 320 320 320 320 Hole diameter of spinneret mm 00.5 00.5 sO.5 00.5 00.5 00.5 00,5 00.5 00.5 00.5 Discharge rate per spinneret hole g/min 1.38 1,38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 1.38 Temperature of compressed air °C 230 200 140 200 200 230 230 Normal temperature (30) Norma! temperature (30) 230 Fineness dtex 2.8 2.8 2.9 2.4 2.2 2.8 2.8 3.1 2.6 4.9 Spinning Spinning speed m/min 4998 4991 4824 5663 6198 4998 4998 4435 5331 2794 Crystallinity % 18.4 17.3 15.1 24.1 33.0 18.4 18,4 8.9 18.2 9.4 Mobile amorphous fraction % 61.8 62,7 68,7 50.8 32.6 61.8 61.8 89,3 74.7 73.2 Rigid amorphous fraction % 19.8 20,0 16,2 25.1 34.4 19.8 19.8 1.8 7.1 17.4 Crystallinity + rigid amorphous fraction % 38.2 37.3 31,3 49.2 67.4 38.2 38.2 10,7 25.3 26.8 Boiling water shrinkage % 2.3 7.0 17.5 2.2 2.0 2.3 2.3 61.2 28.5 25.0 Number in Figs. 1 and 2 - (1) (2) (3) (4) (5) (1) (1) (6) (7) (8) Temporary Temperature °C 100 100 100 100 100 100 100 100 100 100 bonding by calendering Linear pressure N/cm 200 200 200 200 200 200 200 200 200 200 Thermal Temperature °C 270 270 270 270 270 - - 270 270 - bonding Linear pressure N/cm 1000 1000 1000 1000 1000 - - 1000 1000 - Needle punching Number of needles needles/cm2 - - - - - 300 - - - 300 Water jet punching Pressure MPa - - - - - - 15 - - - Mass per unit area g/m2 248 253 245 256 254 301 285 - - 295 Tensile strength (longitudinal) N/5 cm 434 454 472 421 245 490 462 - - 472 Nonwoven Thermal Longitudinal % 0 0.1 0 0 0 1.6 1.4 - - 21.2 fabric shrinkage rate Transverse % 0.1 0.2 0.1 0.1 0.1 1.8 1.7 - - 23.4 Longitudinal tensile strength retention rate % 99 99 99 98 99 99 99 - - -

As shown in Table 1, the PPS fibers in Examples 1 to 5 having the sum of the crystallinity and the rigid amorphous fraction of 31.3 to 67.4% could be thermally bonded with the embossing roll pair and moreover thermal shrinkage at 200°c was hardly observed, indicating excellent thermal dimensional stability. Especially, the fibers of Examples I to 4 having the itallinity of to 24.1% wer« exce. .ent m

:maJ bonding properties anc aaltinc fabri hi excel mechanical strength.

For the filament nonwoven fabrics of Examples 6 and 7 obtained by mechanically entangling the nonwoven web having the sum of the crystallinity and the rigid amorphous fraction of 38.2% by needle punching or water jet punching, thermal shrinkage at 200°C was hardly observed, and the fabrics had excellent thermal dimensional stability.

In contrast, the fabrics of Comparative Examples 1 and 2 having the sum of the crystallinity and the rigid amorphous fraction of 10.7% and. 25.3%, respectively, had high boiling water shrinkage rates. Consequently, significant shrinkage in width was observed in the nonwoven webs due to thermal shrinkage during the thermal bonding and the nonwoven webs shrunk and hardened, and thus embossing was impossible to perform. In Comparative Example 3 in 'which the nonwoven web had the sum of the crystallinity and the rigid amorphous fraction of 26.8%, the filament nonwoven fabric obtained by mechanical entangling the nonwoven web by needle punching had significant thermal shrinkage at 200°C and was not suitable for p ract ica i use.

The polyphenylene sulfide fiber and the nonwoven fabric comprising the fiber described in the above embodiments and Examples are illustrated to demonstrate the technical ideas of the present invention. The composition of the resin, the spinning and drawing conditions, the nonwoven web forming conditions, the single fiber fineness, the crystallinity, the r i g i d a morphous fra ction, and the like are not iimi ted to those in the above embod iments a n d E x amp1e s and car: i be mod ifieci in various ways wit hi n the scope of the claim, s of the present invent! O ^ For example, i n the above Examples, the case in w h 1C11 3. nonwoven web is formed by spun bonding has been described. In the present invention, however, the nonwoven web may be formed by other methods. Needless to say, the type of the PPS resin to be used is not limited to those in the above Examples. comprising the polyphenyl ene sulfide invention has excellent mechanical ng the p ropier ties of 3 ρ ρ s res i n, ;, chemical resistanc e, and flame the nonwoven fabric is useful for INDUSTRIAL APPLICABILITY The nonwoven fabric fiber of the present invent lamely, heat resistance various industrial applications including heat-resistant filters, electrical insulation materials, and battery separators .

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A polyphenylene sulfide fiber comprising polyphenylene sulfide as a main component and having the sum of the crystallinity and the rigid amorphous fraction of 30% to 70% wherein the crystallinity is not less than 5% and less than 25%.
2. A nonwoven fabric comprising the polyphenylene sulfide fiber according to claim 1.
3. The nonwoven fabric according to claim 2, which is produced by consolidation by thermal bonding or mechanical entanglement.