CA2102399A1

CA2102399A1 - Oriented profiled fibers

Info

Publication number: CA2102399A1
Application number: CA002102399A
Authority: CA
Inventors: Donald H. Hogle; Peter M. Olofson
Original assignee: Individual
Current assignee: 3M Co
Priority date: 1991-10-07
Filing date: 1992-08-14
Publication date: 1993-04-08
Also published as: EP0607174B1; EP0607174A1; DE69220235D1; WO1993007313A1; US5277976A; DE69220235T2; JPH06511292A

Abstract

A method for providing a shaped fiber is provided, which shaped fiber closely replicates the shape of the die orifice. The polymer is spun at a melt temperature close to a minimum flow temperature and under a high drawdown.

Description

2l0?~99 ~" "-P~TENT ATTORNEY DOC~ET NO. 4467~U~AlA

O~IENTED PROFILED FIBERS
B~CRGROUND AND FI~LD OF THE _INYENTION
The present invention relates to orlented, profiled fibers, the cross-section of which closely replicates the shape of the spinneret orifice used to prepare the fiber. The invention also relates to nonwoven webs comprising the oriented, profiled fibers.
~0 U.S. Patent No, 3,508,390 describes a Y-shaped fi~er for fabric applications. The Y-shape is described as providing unique optical and tactile properties. The fiber is described in terms of a modification ratio M, which is indicatlve of the amount 15 of mate~ial in the cen~er core area ~f the ~iber (R').
The modlfication ratios.~or the exemplified orifices are much higher ~han for the fibers indicating that the fiber arms significantly flo~ int:o the central region during the manufacturing process.
PCT Application No. WO 91/0~998 describes a trilobal or quadrilobal die orifice for forming fibers useful in a variety of applications. The application giYeS no indication of the degree of shape retention.
This patent~also reports prefer~ed modifi¢ation ratios ~5 similar to that of U~S. Patent No. 3,508,390, but-no actual modification ratios are reported for the example fibers. However, shape retention would likely be the same as Por U~S. Patent NoO 3,508,390.
Fibers having modified or non circular 30 cross-sections haYe been prepared by conventional fiber manu~acturing techni~ues through ~he use of specially shaped spinneret orifices. However, correlation between the cross-section of f ibers produced from these ~;haped orif ices and the shape of the orif ice is 3s typîcally very low. The extruded polymer tends to invert to a substantially circular cross-section with a gently curved, undulating "amoeba-li3ce" shape rather 5lJE3STl~UTE SHEEl' 210~399 ~ ~ r - 1 ~ '' , f ' .- r~ . . .
than ~he typical crisp, angled shape of the orifice~
Numerous workers have proposed specially designed spinneret orifices which are used to approximate certain fiber cross-sections although generally there 5 is little correspondence between the orifice cxoss-sectional shape and that of the fiber. Orifices are designed primarily to provide fibers with certain overall physical properties or characteristics associated with fi~ers within general classes of 10 shapes. Orifices generally are not designed to provide highly specific shapes. Specialty orifices have been proposed in U.S. Patent Nos. 4,707,409; 4,179,259~
3,860,679; 3,478,389; and 2,9~5,739 and U.K. Patent No.
1,29~,388.
U.S. Pat. No. 4~707!409 (Phillips) discloses a spinneret for the production of fibers having a "four-wing" cross-section. The fiber formed is either fractured în accordance with a p:rior art method or left SlJ ~5T~ HEE~

WO g3~07313 P~/USg2/06136~
,399 2~

unfractured for use as filter material. ~he " f our-wirlg" shape of the f iber is obtairled by use of a higher melt viscos ty polymer and rapid quenching as well as the ~pirmeret orif ice design . The orif ice is 5 de~ined by two in~er~ecting slo~. Each in~ers~ g slot is def ined by three quadrilateral sect on~
connected in series through an angle of le~s than 130 .
The middle s;~uadrilateral sections of each inter~ecting slot have greater widths than the other two lo quadrilateral sections of the same intersecting slot.
Each slot intersects the other slot at its middle quadrilate:ral section to form a generally X-shaped opening. Each of the other two quadrilateral sections of each intersecting slot is ls: nger than t}le middl~
15 quadxilateral section and has an enlarged tip formed at its free extremity.
U. S. Pat. No. 4 ,179, 259 (Belitsin et al, ) discloses a spinneret orif ice designed to produce wool-like ~ibers from synthetlc polymers. The fibers 2 0 are alleged to be absorbent due to c:a~ities ~Eormed as a result of the specialized ori~Eice shapes O The orif ice of orle oiE the di~i~clo~ed spirmerets is a ,~lot with th~e conf iguration of a slightly open polygon ,segm~nt and an L, 'T, Y o,r E ~ hap~d portion adjoining one of the sid~ ,s of the polygQn. The ~ibers produced from this spinner~et orifice have~ cross-sections con-cistirlg of two elemerlts, namely a closed ring shaped @;ection resultir~
- ~rom the closure of the polygon s~Pgment and an Lo T,7 Y, or E shaped ~ection generally approxim~ting th~ L, T, 3 0 Y, or E shape of the orif ice tllat provides an opeII
-apillary char~nel (s,~ which co~unicate,s with the outer ,surface of the fibPr. It i,~s the c~pillary channel(s) that provldes the f ibers wit:h moisture absorptive properties, which as, ertedly can approximate those of 35 natural wool. It is asserted that cri~p is obtained that approximates that of wool. Alle~edly this is due to no,n-uniform coolingc W093/0~313 ~ 1 0 2 3 9 ~ PCT/US92/~66 ~. .. ~

U.S~ Pat. No. 3,8~0,679 (Shemdin) discloses a process for extruding filaments having an asymmetrical T-shaped cross-section. The patentee notes that there is a tende~cy for asymmetrical fibers ~o knee uver s during the melt spinning tendency, which i~ xeduced, for T-shapad fibers, using his orifice deign. Control of the kneeing phenomena is realized by ~electing dimensions of the stem and cross bar~ such that the vi~cous resistance ratio of ~he stem to the cross bar lo falls within a defined numerical range.
U,S. Pat. NoO 30478,389 (Bradley et alO) discloses a spinneret assembly and orifice designs suitable for melt spinning filaments of generally non-circular cross-section. The spinneret i~ madP of a 15 solid plate having an extrusion faoe and a melt face.
Orifire(s) extend between the faces with a cantral open counter bore melt recei~ing portion and a plurality of elongated slots extending fr~m the central portior. In the counter bore, a solid ~pheroid is po~itioned to 20 divert the melt flow t~ward the extremities of the elongated ~lot~O This counteracts the tendency of ¦ extruded melt to assume a circular shape, r~gardless of the ori~ice shape V.S. Pat. ~oO 2,945,~3g ~L~hmic~e~ describes 25 a ~pinner~t for the melt ~xtrusion o fiberc having I non-circular ~hapes which are di~icult to o~tain due j to the tendency o~ e~truded melts to reduce ~urface te~sion ~nd as~ume a circular shape regardless of the extru~i~n orifice- The orifices o~ the spinneret 1 30 consist of slots ~nding with abruptly expanded tips.
i The fib~rs di~closed in this patent are sub~tantially ~ linear, Y ~haped or ~-shaped~
! Brit. ~at. 1,292,3~8 (Champaneria et al.) discloses synthetic hollow filaments (preferably formed 1 5 of P~T) which, in fabrics, provide improved fila~ent ¦ bulkd covering power, soil re~istanre, lu~t~r and dye utilization. The cross-section o~ the filaments along W~93/07313 P~T/US92/~6866 ~8~-3~9 their length is characterized ~y having at least three voids, which together comprise from lO - 35% of the filament ~olum2, extending substantially continuou~ly along ~he length of the filament. Allegedly, the 5 circumference of the filament~ is also substantially free of abrupt changes of curvature, bulges or depressions of ~ufficient magnitud~ to pro~ide a pocket for entr~pping dirt when the filament is in side-by-side contact with other filaments. The lO filament~ are formed ~rom an orifice with four discrete se~ments. Melt polymer extruded from the four segments flows together to form the product filament.
It has also been proposed that improved replication of an orifice shape and departure from a substantially circular fiber cross-section can be achieved by utilizing polymers having higher melt viscosities; see, e.g~, U.S. Patent No. 4,364,99~
(Wei). Wei discloses yarns based on fibers having cross-sections that are longit:udinally splittable when 20 the fibers are passed through a texturizing fluid jet.
The fiber~ were extruded into cross ~ectio~al shapes that had substantially uniform strength such that ~hen they were pa~sed through a texturizing fluid ~et they split randomly in the longitudinal direction with each 25 o~ th~ split ~ections h~ving a re~onabl~ chance of al~o splitting in the transver~e direction to form fr~e ends. Better ret~ntion of a non round *iber ~hape was achleved w th higher molecular weight polym~ræ than with lower molecular weight polymers.
Rapid quenching has al~o ~en di~cus5ed as a method of preserving the cros -~ection of a melt extruded through a n3n-circular oriface. U~S 9 Pat. No.
3,l2l,040 (Shaw ~t al.) de~cribes unoriented polyolefin fibers having a ~ariety of non-circular profiles~ The 35 fibers were extruded directly into water to preserve the cross sectional shape imparted t~ th~m by the spinneret orifice. This process freezes an amorphous WO93/07313 2 1 0 2 3 9 ~ PCT/US92~06866 or unoriented tructure into the fiber and does not acco~modate subse~uent high ratio fiber draw-down and orientation. ~owever, it i~ well known in the fiber industry that fiber properties are signif icantly improved through orîentation. Th~ superior physical properties of the oriented fibers of th~ present invention enabl~ them to retain their shape under conditions where unoriented fibers would be ~ubject to failureO
The surface tension forces of a pol~mer melt have also been used to advantage in the spinning of hollow circular flbers. For example, spinnerets designed for hollow fibers include some with multlple orifices configurated so that extruded melt polymer 15 streams coalesce on exiting the spinneret ~o form a hollow fiber. ~lso, si~gle orifice configuratlons with apertured chamber-like designs are u~ed t~ fo~m annular ~ibers. The extruded polymer on either side of the aperture coalesces on exiting th~ spinneret, to form a 2~ hollow fi~er. Even though these spinneret design~ on a casual incpec~ion thus appear to b~ capabl~ o~
producing fibers which would ignificantly depar~ from a su~s~an~ially circular cros~-&ection, sur~ace t2nsion forces in the molten polymer cause the extrudate to 25 coalesce into hollow fiber~ haYing a cros~ ction that is substantially circular in shape.
It i al~o well kn3wn in the art that unoriented ~iber~ with non-circular cro~s-sections will invert from their original shape toward substantially 30 circular cross-sections when subject d to extensive draw-downs at standard processîng conditions~
The use of specific polymer~ as a means of ncreasing orifice shape retention h.s also been suggested. Polymer~ with high viscosity or ~5 alternatively high molecular weight tpres~ably by decreasing flow YisCosity~ (see Wei abov~ have ~een propo~ed as a means of increasing replication of ~ ` ' b5 ~'~ f' ~ r~

2 3 g r r r r r r ~- 6 ori~ice shape. However, low molecular weight polymers are often desirable at least in terms of processability. For example, low molecular weight polymers exhibit less die swell and have been described 5 as suitable for forming hollow microporous fiber, U.S.
Patent No. 4,405,688 ~Lowery et al). Lowery et al described a specific upward spinning technique at high draw downs and low melt temperatures to obtain uniform high strength hollow microfibers.
Significant problems are associated with the techniques that are described for use in forming non-circular profiled shapes particularly with fibers.
Highly designed orifice shapes are employed to give shapes that are generally ill defined, merely gross ~ 15 approximations of the actual oriface shape and possibly I the actual preferred end shape. The surface tension and flow characteris~ics of the extruded polymer still tend to a circular form. Theref`or2, any s~arp corners or well defined shapes are generally lost before the 1 20 cross-sectional profile of the fiber is locked in by ¦ quenchiny. A further problem arises in that the j orientation of the above described fibers is ! accomplished generally by stretching the ~ibers after they hav~ been quenched. This ls generally limited to .2~ rather low draw rates below the break limit.
I Cons~quently, where a fiber of a certain denier or j decitex is desirPd the die must be at the orde~ of I magnitude of the drawn fiber. This significantly increases costs if small or microfibers are sought due ¦ 30 to the difficulties in milling or otherwise forming ¦ extremely small ori~ices with defined shapes. Finally, I using a rapid quench to preserve shape creates an I extremely unoriented fiber (see Shaw et alO) sacriicing the advantagPs of an oriented fiber for _ 1 35 sh~pe retention.
j A general object of the present invention j seeks to reconcile the often conflicting objectives ~ 9F~35T~

WQ 93/~731~ 2 1 ~ 7 3 9 !~ PCr/US92~Q6~66 . ,. . ~.
_ 7 ~
and resulting problems, of obtaining both oriented and highly structured or prof iled f ibers .

8~Y OF T~LE INVY NTIC3N
ThP present invention discloses extruded, non-circular, profiled, orient2d shapes, p~rticularly f ibers . The method f or makin51 these shapes such as f iber~ inrludes using low temperature extrusion through structured, non-circu~ ar, angulate die orif ice~ coupled l0 with a high speed and high ratio draw downO The inventiorl also discloses nonwoven webs c~mprising the oriented, non-circular, prof iled f ibers .

~RI~F DE~CRXPTION OF ~E DR~WINGB
Figure 1 is a schematic representation c: f one coalf iguration of an oriented t prs:~iled f il~er of -he lPresent invention.
Figure 2 i5 a plan view of an ori~ice of a spinneret used to prepare the f iber of Figure l .
2 0 Figure 3 is arl illustration o a f iber spinning line used to pxepare the f ibers of the present invention .
Figure 4-8 are repxeserltations of cro~;s-secti~ns of f ibers producad as described in Examples 25 5, respec:tively.

The present inventiorl pro~rides for oxiented structured shapes, particularly f ib~rs having a 3 0 non circ:ular prof il~d c:ros~section . ~c~re ~pecifically, the inv~ntion pro~ides a m~thod, and product, wherein the c:ross~section o~ the extrllded article closely r~plic~t:e~ th~ shap.e of the orif ic:e used to prepare the shaped article.
3 5 Fibers f ormed by the present invention are uni~ue in that th~y have been sriented to impart tensile strPngth and elongation properties to the a -- , . , fibers while maintaining the profile imparted to a fiber by the spinneret orifice.
The method of the present invention produces fine denier fibers with high replication of the profile 5 of the much larger original orifice while ~simply and efficiently) producing oriented fibers.
The process initially involves heating a thermoplastic pvlymer (e.g., a polyolefin) to a temperature slightly above the crystalline phase 10 transition temperature of the thermoplastic polymer.
The so-heated polymer is then extruded through a profiled die face that corresponds to the profile of the to be formed, shaped article. The die face orifice can be quite large compared to those previously used to 15 produce profiled shapes or fibers. The shaped article when drawn may also be passed through a conditioning (e.g.,~quench) chamber. This conditioning or quench step has not been found to be critical in producing high resolution p~ofiled fibers, but ra~her is used to 20 control morphology. Any conv~ntional cross-flow ~uench chamber can be used. This is unexpected in that dimensional stability has been attributed to uniform quench in tha pa~t; see/ ~.g.,. Lowery et al~ UOS~
` Patent No. 4,451,9~1. Lowery et al. attributed uniform 25 wall thickness of hollow circular fibers to a uniform quench operation.
The die orifices can be of any suitable shape and area. Generally, however, at the preferred draw ratios employed, fiber die orifices will generally have 30 an overall outside diameter of from 0.13 to 1.3 cm (0~050 to O.S00 in. ~ and a length of at least 0~32 cm (0.125 in.). These dimensions are ~ite large compared to previous orifices for produclng oriented fibers of similar cross-sectional areas where shape retention was 35 a concern. This is of great significance from a manufacturing prospective as it is much more costly and ~a~TI~IITF ~F~

r ~ r ~ f r . .- ~ ~ r r ~ ~ ,, r . ~ ' -- 8 A ~ ~ ~ . . r ~ ~
r 1~ r ~, . r ~ . r . , -dif f icult to produce intricate prof iled orif ices of extremely small cross-.

, ~ :

~: .

5~E35TITOT~: SHEE~:T

W093/~7313 2 1 0 2 3 ~ 9 PCT/~S92/~66 sectional areas. Further, this orifice and associatedspinning means can be oxiented in any suitable direction and still obtain significant shape re~ention.
The oriented, profiled shapes of the present 5 invention are prepared by conventional melt s pinning equipment with the thermoplastie pol~mer at temperatures from about 10 - 90C and more preferably from a~out 10 - 50C above the minimum flow temperature (generally the crystalline melt temperature) of the 10 polymer. Spinning the shaped articles of the present ' invention at a temperatur~ as close to the melt temperature of the polymer as possible contributes to producing shaped articles having increased cross-sectional definition or orifice replication.
~5 A variety of extrudabl~ or fiber-formi~g thçrmoplastic polymer~ including9 but not limited to, polyolefins (i.e., polyethylene, polypropylene, etc.), polyesters (i.e., poly~thylene terephthalate~ etc.), polyamides (i.e., nylon 6, nylon 66, etc.~, 20 poly~tyrene, polyvinyl alcohol and poly(meth)acryl~t~s, polyimides, polyaryl sulfides, polyaryl sulfones, polyaramides, polyaryl ethers, etc. are useful in preparing the shaped articles or fiber~ of the present inven~ionO Preferably, the polymers c~n be orient~d to ~5 induce crystallinity for cr~stalline polym~rs and/or improve ~iber properties.
~ relativ~ly hi~h draw down is aonduated as the fiber is @xtruded. This ori~nts the fib~r at or near the spinneret die fa~e rather than in a ~ubsequent 30 operationO The drawdown $ignifieantly r~duces the cross-s~ctional area of the fiber-~ yet surprisingly without losing the prcfile impar~ed by the ~pin~eret orifice. The draw down i~ ganerally at lea~t 10:1, preferably at lea~t S~:1, and more preferably at least 35 about 100:1, with draw downs significantly ~reater than this possible. For these draw down rates, the cross-W~l ~3/07313 PCr/US92/06866 2io~9 - lo - `
sectir:~n of the f iber will be diminished dir~ctly proportional ~o the drawdown ratio.
The ~uenching step i8 not critical to prof ile shape retention and cost ef f ectiYe cross f low cooling S can be employed . The quenchi~g f luid is generally air, but other suitable f luids ::an be employed . ~he -quenching means generally is located close to the spinneret f ace O
Oriented, prof iled f ibers of the present 10 inven~i~n can be formed directly into non-woven webs l~y a numbPr of processes including, bu~ not limited to, spun bond or spun lace processes and cardi~ag or air laying proce~ses.
I t: is anticipated that the invention f ibers 15 could comprise a component of a web for some appïications . For example, wherl the prof iled f ibers are used as absorbents generally at ~ ea~t about lO
weight percent of the oriented, prof ilad f iber~; of the present invention are u~;ed in the f ormed webs .
2 0 Further, the f ibers could be used as f luid tran-~port ~iber~ in nonwo~en webs which may be u ed in combination with absorbent members such as ~ood f luf pads. Other components which could be incorporated into the webs include natural and synthetic tex~ile 2 5 f iberc r binder f ibers, deodoriz ing f ibers, f luid absorbent f ibers, wicking x iber , and part~ culate materlals such ~ as:tivated carbons or ~uper-absoxb~:nt paxticle~; ~
Pref erred f ib~rs f or use as absorberlt or 30 wicking ~i bers should have a partially enclosed longitudinal space with a coextensive lon~itudinal gap along the f iber length ~ This gap places the partially enclosed space in fluid ::ommlmication with th~ area external of the fi}:~er. Preferably, the gap width 35 should b relatively ~laall compared to the cross-~ectional perim~ter of the partially enclosed spac~
( includillg the gap width) . Suit~ble ~ibers f or these wo g3/073l3 2 ~ Z 3 9 ~ PCT/~92tO~66 applications are set forth in the examples. Generally;
the g~p width should be less than 50 percent ~f the enclosed space ~ross-sectional perimeter, preferably less than 30 perrent.
The webs may also be incorporated into multi-layered, nonwoven fabrics comprising at least two layers r` ~ nonwoven webs, wherein at least one nonwoven web coLprises the oriented, profiled fibers of the present invention~
lo As fluid transport fibers, the fibers can be given anisotropic fluid transport properties by orientation of nonwoven webs into which the fibers are incorporated. Other methods of providing anisotropic fluid transport properties includ~ directly laying 15 fibers onto an associated subs~rate ~e~g., a web or absorbent member~ or the use o~ fiber tows~
Basis weights of th~ webs can encoMpa~s a broad range depending on the application~ however they would ganerally range from aboult 25~mtm2 to about 20 5OO~ml~2.
Nonwoven webs produced by the aforementioned proces~es are sub-~tantially non-unified ~nd, as such, generally have limited utility, but their utility can be significantly increased if they are unified or 25 con~olidated. A number of techniques includi~g, but not limited to, thermomechanical ~i.e. ultrasonic~
bonding, pin bonding, water- or ~olv~nt-~a~ed bind~rs~
binder ~iber~, naedle tacking, hydroentanglement or combina~.ion~ of various t~chniques, are suitable ~or 30 cons~iuating the nonwoven webs.
It is also anticipated that the oriented fibers of the pr~sent invention will also find utility in woven and kni~ted fabrics.
The profiled fiber~ pr~pared in accordance 35 with the teaching of he inv~ntlon will have a high retentiQn of the orifice shape. The orîfi~e can ~e WO 93/07313 PCI'/US~2/0~866 ~?,3~9 - 1~
symmetrical or asymmetrical in its conf isuration .
With symmetrical or asymmetrical type oriîices shapes, there is generally a core laember 12, a~; is illustrated in Figure 1, from which radially extending prof ile S elements radia~e outward . These prof il8 elements can be the same or different, with or witllout additional strut:tural elements thereon. However, asymmëtrical shapes su ::h as C-shaped or S-shaped f ibers will not necessarily have a defined core element. ~ef~rring to lo Figure 1, which schematically represents a cross-~;ection 10 of a symmetrical prof iled f iber aocording to the present invention, the f iber comprises a core member 12, structural prof ile elements 14, intersecting components 16, c:hambers 18 and apertures 15 20. Diameter (D~;b) is that of the smallest circumscrib~d circle 2 4 which can be drawn around a cross-sectio~ of the f iber 10, such that all elements of the f iber are included within the circle . Diameter (dm) is that of the largest in~cribed circle 22 that o can be drawn within the inter~ection of a core member or regioll arld structural pro~ile element~ or, if more than one intersection is present~ the largest inscribed -ircle that can be drawn within the largest intersection of f iber structural prof ile elemellts, such 25 that the in~cri~ed circle is totally contained ~ within the intersec:tion structure.
Fis~re 2 sche~atically represent:~ the spinner~t ori~Eice used to prepare the ~ib~r of Figure 1. Diamet~r (Do~f) is that of the smallest circumscribed 3 0 circle 2 6 that can be drawn around the spinrleret orif ice 25, ~uch that all elements o~ th~ orif ice are included within the circle. Diam~ter (dorf) is that of the largest inscribed circle 2 7 that can be drawn within the intersection of a core member orif ica member 3 5 ox regiorl with orif ice ~tructural prof ile elements or, if more than one intersectlon is present, the larg~st - ~ 1 0 2 3 ~ 9 t r . ~ ~

.. .

inscribed circle that can be drawn within the largest intersection of orifice profile element, such that the inscribed circle is totally contained within the intersection structure.
Normalization factors for both symmëtrical and asymmetrical fibers are the ratio of the cross-sectional area, of the orifice or the fiber ~Ao~ and Ar,b), to the square of Drjb or Dorf, respectivelyO Two norm21ization factors result, Xf,b(~lb/D2~,b) and 10 Xorr(AorrlD2osf)~ which can be used to define a structural retention factor (SRF). The SRF is defined by the ratio of Xr,b to Xor~. These normalization fac~ors are influenced by the relative degree of open area included within the orifice or fiber structure. I~ these 15 factors are similar (i.e., the SRF is close to 1~, the ori~ice replication is high. For fibers with low replication, the outer structur~l elemen~s will appear to collapse resulting in relatively high values for XGb and hence larger values for SRF. Fibers with perfect 20 shape retention will have a SRF of l.O, generally the ~ibers of the invention will have a SRF of about 1.4 or les~ and preferably of about 1.2 or less. However, due to the dependence of this test on changes in open ~rea from the or~fice to the fiber, there is a loss in 25 sensitivity of this test (SRF) as a mea~ure of shape re~ention as the oriice shape approaches a circular cross section.
A second structural retention factor ~SRF2) is related to the retention of perimeter. ~ith low 3~ shape retention fibers the action of coalescing of the fiber into a more circular form results in smaller r~tios of perimeter to fiber area. The perim:eters (PO~
and Pr~) are normalized for the die orifice and the fiher by taking the square of the perimeter and ~~
35 dividing thi~ value by the area A~b or Aorr for the fiber S~Jg35TlT13~E 5}~EiET
~. ,.. ~ .. . . ..... . ... ....... ............... ... ... .. . . .. . . ...... . . . . .

., , ~ . . . . . . .
- 13A - ~ ~
, ~ , , , ,; .
or orif ice, respectively . These ratios aré def ined as yO" and Yfib.

5L~ sTlTLlrE~ r 3~07313 ?-~ o?-399 PCI`/US92/06866 For a perf ectly circular die orif ice or f iber, the ratio Yc~ will equal 47~ or about 12 0 6 . I~he SRF2 (Y~"/Yfi,) is a functi~rl of the deviation of Yor~ from Yc~ As a rough guide, generally, the SRF2 for the invention 5 f ibers is below about 4 f or ratios of YOIf to Yc~ greater than 20 and below about 2 for ratio~; of Y"~f to Yc~ of 7 less than al~out 2 0 . This i~; a rough estilaate as SRF2 will approach a value of 1 a the orifice shape approaches that of a circle f or either the invention 10 method or for prior art laethods used for sh pe retention. However, the invention method will still produce a f iber having an SRF2 closer to 1 f or a given die orif ice shape . The orif ice shape used in the invention method i~ non~circular ( e . g ., neither 15 circular nor annular , or the lilce~, such that it has an external open area of at least 10 perc:erlt. Th~
external open area of the die :is def ined as the area outside the die orifice outer perimeter (iOe. ~
excluding open area coml?let~ly cir~umscrib~d by the die 2 o oriI ice~ and inside Do~ Similarly, the external open area of the f ib~rs is grea~er than 10 p~rcent, preferab~y greater than 50 percent. This again exclude~ open area c::omplete:Ly circumscribed by the f iber but not internal f iber open area that is in 2 5 direct ~luid c~m~unication with the ~;pace outsid~ the f iber, suc:h as by a l~ngthwi~e gap in the f iber . With conYentional spinning techrliques using orific:e~ having small gaps, the gap will typic:ally not be replicated in the fiber. :IFor example, in the fiber these gaps will .
30 collaps~ and are typically merely provided in the orifice to form hollow fibers (i.e~ ibers with int~rnal open area, only l?oRsibly in indirect f luid commullicatio2s with the space out~ide the f iber through any f iber eTIds ) .
Figure 3 is a schematic illustration of a suitable f iber spinning apparatus arrangemerlt useful in 6~ .

, ;. .
.
.. . . . . .

practicing the method of the present invention. The thermoplastic polymer pellets ar6 ^~u by a conventional hopper mechanism 72 to an extruder 74, shown schematically as a screw extruder but any conventional 5 extruder would suffice. The extruder is generally heated so that the melt exits the extruder at a t~mperature above its crystalline melt temperature or minimum flow viscosity. Preferentially, a metering pump is placed in the polymer feed line 76 before the lo spinneret 78. The fibers 80 are formed in the spinneret and subjected ~o an almost inst~ntaneous draw by Godet rolls 86 via idler rolls 84. The quench chamber is shown as 82 and is located directly beyond the spinneret face. The drawn fibers are then 15 collected on a take-up roll 88 or alternatively they can ba directly fabricated into nonwoven we~s on a rotating drum or conveyer belt. The ~ibers shown here are downwardly spun, however other spin directions are possible.
The following examples are provided to illustrate presently contemplated preferred embodiments and the best mode for practicing ~he invention, but are not intended to be limiting thereof.
~ xamples The extruder used to spin the fibers was a Killon~ lo 9 cm (3/4 inch~, single screw extruder equipped with a screw having an L/D of 30, a compression ratio of 3.3 and a configuration as follows: feed æone length, 7 diameters; transition 30 zone length, 8 diameters; and metering zone length 15 diameters. The extruded polymer melt stream was introduced into a Zenith~ melt pump to minimize pressure variations and subsequently passed through an inline Koch~ Melt Blender (#KMB-100, available from 35 Koch Engineering Co., Wichita, KA) and into the spinneret having the configurations indicated in the examples. The temperature of the polymer melt 21023~9 in the spinneret was recorded ~s the melt temperature.
Pressure in the extruder barrel and downstream of the Zenith~ pump were adjusted to give a polymer throughput of about 1-36 kg/hr (3 lbs/hr~O On emerging from the 5 spinneret orifices, the fibers were passed through ~n air quench chamber, around a free spinning turnaround roller, and onto a Godet roll which was maintained at the speed indicated in the example. Fibers were collected on a bobbin as they cam~ off the Godet roll.
The cruciform spinneret (Fig. 2~ consisted of a 10.62cm X 3.12cm X 1.25cm (4025" x 1.25" x 0.50") stainless steel plate containing three rows of orifices, each row containing 10 orifices shaped like a cruciform. rhe overall width o each orifice (27) was 15 a 6.0mm ~0~241'), with a crossarm length of 408~m (0.192'~ and ~ slot width of 0..30mm (0.012"). The upstream ~aca (melt stream side) of the spinneret had conical shaped holes centered on each orifice which tapered from 10.03mm (0.192") on the spinneret face to 20 an apex at a point 3.0mm (0.12'l~ from the downstream face (air interface side) of the spinneret (55 angle).
The L/D for each orifi~e, as ~neasured from the apex of the conical hole to the downstream fac:e of the spinner~t, ~as 10. 0.
A swastika spinneret was used which consisted of a 10.62cm X 3.12cm X 1.25cm (4.25l' X 1.25" X 0.50") stainless steel plate wi~h a singie row of 12 `orif ices, each orifice shaped like a swastika (four arms each with three segments A, B and C at right ang~es to the 30 proceeding segmen~ . A depression which was 1~ 52mm (0.0&") deep was machined into the upstream face (melt strea~n SidP ) ol~ t:he spinneret lea~ing a 12 . 7mm ( O . 5 " ) thick lip around the perimeter of the spinneret facec The central portic)n of the spinneret was 11.18mm _.
(o. 441-) thick. The orifices were divided into four groups, with each group of three orif ices having the same dimensions . All of the orif ices had identical ~ ~3~?J~ ~r~

2 1 ~ ~ 3 9 9 -- 1 6 A ~ r . . r ~ ' ;

slot widL.hs of 0.15~un (o. 006'l) and identical first length segments of 0.52mm (0.023.") :~

~;LJE~5TIT~J~ !S::;~rr~r 210~39~3 . .- . . . - . .
r r ~ - ~ r ~. ,. , r , .
; r ~ ~ r- ( ~.
~ 17 ~
extPnding from the center of the orifice ~egments A)o The length of segments ~ and C for the orifices of group 1 were 1~08mm ~0.043"~ and 1.68mm (0.067"), respectively, the length of segments B and C for the 5 orifices of group 2 were 1.08mm (0.043") and.1-.52mm (0.60"), respectively, the lengths of segments B and C
for the orifices of group 3 were 1.22mm (0O049ll) and 1.68mm (0.067"~, respectively, and the length of segments B and C for the orifices o~ group 4 were ~0 1.22mm (0.049l') and 1.52mm (0.060"), respectively. The orifice depth for all of the swastika orifices was 1.78mm (0.070"), giving a ~/D of 11.9. The upstream face of the spinneret had conical holes centered on each orifice which were 9.40mm ~0.037'l~ in length and 15 tapered from ~.86mm (0.027") at the spinneret face to 4.32mm (0.017") at the orifice entrance. Shape retention propexties of fibers extruded through the various groups of orifices of the swastika design were substantially identical.
~0 Ex~mple 1 Shaped fibers of the present invention were .
prepared by melt spinning Dow ASPUN~ 6815A, a linear low-density-polyethylene available from Dow Chemical 25 Midland MI, having a melt flow index (MFI) of 12 through the cruciform spinneret ~escribed above at a melt temperature of 138C and the resulting fi~ers cooled in ambient air (i.e., there was no induce~ air flow in the air quench chamber). The fibers were 30 attenuated at a Godet speed of 30.5 m/min. (100 ft/~in.). Fiber characterization data is presented in Tables 1 and 2.

Example 2 Shaped fibers of the present in~ention were prepared according to the procedures of Example 1 except that the melt temperature was 171C.

~ 1 a 2 3 9 !~ ~ r 18 ~ r r r r r . ~ r t r r Example 3 Shaped fibers of the present invention were prepared according to the procedures of Example 1 5 except that the melt temperature was 204C.

xample 4 Shaped fibers of the present invention were prepared according to the procedures of Example 1 10 except that the melt tempexature was 238C~

Example 5 Shaped fibers of the present invention were prepared according to the procedures of Example 1 15 except that the melt temperature w~s 260C.

Exam. Melt No. Temp. Figure Area Diam. Prmtr.
(C) (~) (D) (P) Orifi~e 219,936 336 2690 1 138 427J93~ 402 ~141 .
2 171 539,133 418 215 3 204 ~54,475 398 198~
4 238 759,3~g 3g6 1730 -S 260 856,362 388 1609 30 Table 1 sets forth the cross-sectional area, perimeter and diameter (Df,b and D~3 for the fibers of Examples 1-5 and the orifice from which they were formed ~sing image analysis. Figures 2 and 4-8 show cross-sections for ths orifices and-the fibers subject to this 35 image analysis. As can be seen.in these figures~
resol~tion of the orifice cross-section is qulckly lost _ ~-as the melt temperature is increased at ~he spinning conditions for Example 1.

~ V3~ 3 W~ ~3/07313 2 1~ 2 3 ~ ~ PCT/U~;9~ 66 ,.. ,.~, -- 19 Table 2 sets forth SRF and SRF2 for Examples 1-5 and the cruci:Eo~n orif ice ,.

T~BLE 2 Normali SRF Nc)rmali- SRF2 1 :xam . open zation ~fib zation ~4,f No- Area Factor X Xoff Factor Y Yfib (A/D2) " tP2/A) Cruciform 77.5% 0.1766 363.0 78 . û% ~. 1728 0 . 9~ 1~4 . 0 2 . 2 2 71. 5% 0 . ~240 1 ~ ~7 11~ . 6 3 . 16 3 5~ . 2~6 0 . 3439 1 0 95 72 . 0 5 .
4 51 0 8% 0 . 378~ 2 . 1~ 50 ~ 4 7 . 2 52 . 3% ~ . 3743 2 . 12 45 . 9 7 . 91 The open area f or l:his series of examples is the differerlce b tween the fi}:er cros~3~sectioned area aLnd the area of a circle c:orre~;pondin~ to do~f or dF, ~mE~
Shap2d ~ibers o~ the present invention were pxepared according to the proc:edures of Example 1 except that an 80/20 (wt. /Wt. ) }:~lend Gf Fina 3576X, a 25 p~lypropylene (PP) having an ~F~ of 9, available from Fina Oil and Chemi~al Co., Dallas, TX, and Exxon 3085, a pol~rprop}rlené having an ~FI of ~35, available from Exxon Chemical, Hou~ton~ ~X, was qubstituted~ for the ASPUN~
6815P~, and the melt te~perature was 260C.
3 ~ ~ :
xamples 7 and 8 Shaped f ibers of the present invenl:ion were prepared accoxdlng to the proc:edu~es of Example 6 except that the m~elt temperature was 271C. Fibers from two 35 different orifices were collec*ed and analyzed.:

S~ S14~ET

W~93/07313 2~0~3~ 9 PCr/VS92/06866 Example 9 Shaped fibers of the present invention were prepared according to the procedures of Example l except.
that Tennessee Eastman Tenite~ 10388, a poly(ethylene terephthalate) (PET) having an I.V. of 0.95, available from Tennessee Eastment Chemical~, Kingsport, TN, was substitu~ed ~or the ASPUN~ 6815A, the mPlt temperature was 280C, and the fibers were attenuated at a Godet speed of 15.3 m/min. (50 ft/min~). The PET resin was dried according to the manufacturerls directions prior to using it to prepare the fibers of the invention.

Example lO
Shaped fibers of the present invention were pxepared according to the procedures of Example 9 except that the melt temperature was 300C~

Example ll Shaped fibers of the present invention were prepared accordiny to the procedurPs of Example 9 except that the melt tempera~ur~ was 320C.

ExamE~e 1 2 Shaped fibers of the present invention were 2~ prepared according to the procedures of Example l except hat the swastika spinn~ret was substituted for the cruciform ~pinneret, the melt temperatur~ was ~38~, and the air temperature in the quench chamber was:maintained at 35C by an induced air flow.
Table 3 sets forth the cross-sectional dimensions for Examples 6 l2, and Table 4 sets forth the shape re~ention factors SRF and SRF2, as well as percent open area, $UB~TIITE ~;~SE~

W~3/07313 PCl'tl~9~/06~66 3 ~ ~

Exam. Melt No. Temp. Area Diam.Pr~ntr.
(C) (A) (D) (P) 260 28,S23 3~ 1663 7 271 2~, 470 332 . -~60~
8 271 28,30~ 350 ~84 9 280 19, 297 342 145~
1~ 300 31,247 336 1571 11 3~0 76, ~98 33~ 8~0 Swastika 23, 6~5 392 2764 12 138 31, 3~4 ~84 1930 TAE~LE 4 O Normali- S:RF No~mali- SRF2 Exam. Open zation Xf~b ~zation ~4rf No. Area Factor X Xorf FactOr Y Yf,b ~/D ) (P2/A) 6 69 . 79~ ~ . 23~ 1 0 35 97 . 0 3 . 7 7 71.7 00~22 1.26 106 3~4 8 70 . 6 0 . ~31 1 . 31 10~ 3 . 6 9 79 . O 0. 1~ O~ 934 110 ~ 3 . 3 ~4 . 8 O. Z77 1~ 57 7~ . 0 4 .
ll 14.3 0.~73 3.~1 10.3 35.2 Swastika 80. 4 0.154 323 1~ 72.9 0.,213 1.38 l19 2.7 Tables 3 and 4 illuGtratQ the sensi ivity of ~5 PP and PET to melt temperature and the use of a dif f erent die o~if ic:e shape ., PET showed quite a sharp dependence on melt temperature. However, at low melt temperatures, rela1;ive to the polymer melting temperatllre, both PP and PET provided excellent f iber 40 replication oP the oriface shapes.

S~ T~ ~

W~ 93/~7313 ~Cr/US92/~6866 , 3 -- ~ 2 ~

Comparative Examples The~;e examplas (Table 53 repr2sent image analysis performed c:n fibers produced in various prior art patents directed at obtaining shaped (e . g ., non-S circular f ibers or hollow f i3~ers) f ibers . ThP analysiswas perf ormed on the f ibers represented in various f igures f rom these documents .

SUBSTITUTE SHE~

WO 93~07313 2 1 0 2 3 9 ~ PCl/US9~/~6866 ..

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-- o o o o ~ o oo Cl ~ O O ID~ O C~ C7 ~ O O O

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q4 p~ tg S~IB~TIJ~E SHEET

W~9~/073l3 PCT/US92/06B66 ~ 399 24 -In certain of these ~omparative examples (i.e., ~B 1,292,388, U.SO Pat. Nos. 3,772,137 and 4 ,179 , 259 ~, the open area is calculated by excluding area completely circumscribed by the fiber in the cross-section.
For certain patents, it is uncertain if the figures are completely accurate representations of the fibers formed by these patents, howe~er it is reasonable to assume that these are at least valid approximations.
As can be seen, none of the comparati~e example fibers retain the shape of the die orifices to the degree of Examples 1 f 2, 6-9 or 12 as represented by SRF, SRF2 and the percent open area.
The ~arious modifications and alterations of this invention will be appar~nt to those skilled in the art without departing from the scope and spirit of this invention, and this inventiorl should not be restricted to that set forth herein for illustrative purposes.

SUE~STlTl3TE SHE~

Claims

We claim:

1. A method for manufacturing oriented non-circular profiled fibers comprising the steps of:
heating at least a portion of a contained fluid flow path having at least one thermoplastic material inlet and outlets, providing a non-circular profiled orifice at said thermoplastic material outlet which orifice is in communication with a second fluid region, passing a thermoplastic material through said heated portion of said contained fluid flow path such as to heat said material to a temperature about 10-90°C
above its crystalline phase transition temperature or minimum flow viscosity to form a fluid thermoplastic stream, characterized by forming said fluid thermoplastic stream into a profiled stream substantially corresponding to the shape of said orifice while passing said stream from said first into said second fluid region, orienting said profiled stream in said second fluid region by drawing said stream at a draw down rate of at least 10 while cooling said stream with a quenching fluid in said second fluid region, wherein a fiber is formed having a non-circular cross-section defined by:
SRF - Xfib/Xorf < 1.3 where X is defined as the ratio of the fiber or orifice cross-sectional area (A) to the square of the fiber or orifice diameter (D), and SRF2 = Yotr/Yrib < 3.5 for fibers formed from dies where Yorf/4.pi. >
20, or SRF2 = Yorf/fib < 2.0 for fibers formed from dies where Yorf/4.pi. <
20, where Yfib and Yorf are defined as the ratio of the fiber or orifice perimeter squared to the fiber [cross-sectional area] or orifice area (A).

2. The method of claim 1 wherein the thermoplastic is a polyolefin, a polyester or a polyamide and wherein said quenching medium is air.

3. An oriented non-circular fiber and fiber orifice comprising elongate spun fibers characterized by having a non-circular cross-section defined by:
SRF = [Xorf/Xif] Xfib/Yorf < 1.3 where X is defined as the ratio of the fiber or orifice cross-sectional area (A) to the square of the fiber or orifice diameter (D), and SRF2 = Yorf/Yfib < 3.5 for fibers formed from dies where Yorf/4.pi. >
20, or SRF2 = Yorf/Yfib < 2.0 for fibers formed from dies where Yorf/4.pi. <
20, where Yfib and Yorf are [is] defined as the ratio of the fiber or orfice perimeter squared to the fiber [cross-sectional area] or orifice area (A).

4. The non-circular filer of claim 3 wherein SRF2 is less than about 1.1.

5. The non-circular fiber of claim 3 wherein SRF2 is less than about 3.5 for fibers where Yorf/4.pi. is greater than 20 and less than about 2.0 for fibers where Yorf/4.pi. is less than 20.

6. The non-circular fiber of claim 3 wherein the fiber has an external open area of greater than about 10 percent.