Process for draw-fracturing yarn the continuous filaments of which each have a cross-section comprising a body section and one or more wing members joined to the body section, the one or more wing members varying up to about twice their minimum thickness along their width, at the junction of the body section and one or more wing members the respective faired surfaces thereof define a radius of concave curvature (Rc) on one side of the cross-section and a generally convex curve located on the other side of the cross-section generally opposite the radius of concave curvature (Rc), the body section comprising about 25 to about 95% of the total mass of the filament and the wing members comprising about 5 to about 75%, the filament being further characterized by a wing-body interaction (WBI) defined by ##STR1## where the ratio of the width of the filament cross-section to the wing member thickness (L.sub.T /Dmin) is .ltoreq.30 the process comprising drawing the yarn to a boiling water shrinkage of .ltoreq.15%, fracturing the wing member portion of the filament utilizing fracturing means, and taking up the yarn.
Many previous efforts have been made to produce spun-like yarns from continuous filament yarns. For example, U.S. Pat. No. 2,783,609 discloses a bulky continuous filament yarn which is described as individual filaments individually convoluted into coils, loops and whorls at random intervals along their lengths, and characterized by the presence of a multitude of ring-like loops irregularly spaced along the yarn surface. U.S. Pat. No. 3,219,739 discloses a process for preparing synthetic fibers having a convoluted structure which imparts high bulk to yarns composed of such fibers. The fibers or filaments will have 20 or more complete convolutions per inch but it is preferred that they have at least 100 complete convolutions per inch. Yarns made from these convoluted filaments do not have free protruding ends like spun or staple yarns and are thus deficient in tactile aesthetics.
Other multifilament yarns which are bulky and have spun-like character include yarns such as that shown in U.S. Pat. No. 3,946,548 wherein the yarn is composed of two portions, i.e., a relatively dense portion and a blooming, relatively sparse portion, alternately occurring along the length of the yarn. The relatively dense portion is in a partially twisted state and individual filaments in this portion are irregularly entangled and cohere to a greater extent than in the relatively sparse portion. The relatively dense portion has protruding filament ends on the yarn surface in a larger number than the relatively sparse portion. The protruding filaments are formed by subjecting the yarn to a high velocity fluid jet to form loops and arches on the yarn surface, false twisting the yarn bundle, and then passing the yarn over a friction member, thereby cutting at least some of the looped and arched filaments on the yarn surface to form filament ends.
Yarns such as the texturized yarns disclosed in U.S. Pat. No. 2,783,609 and bulky multifilament yarns disclosed in U.S. Pat. No. 3,946,548 have their own distinctive characteristics but do not achieve the hand and appearance of the yarns made from the novel filament cross-sections of my invention.
Many attempts have been made to produce bulky yarns having the aesthetic qualities and covering power of spun staple yarns without the necessity of extruding continuous filaments or formation of staple fibers as an intermediate step. For example, U.S. Pat. No. 3,242,035 discloses a product made from a fibrillated film. The product is described as a multifibrous yarn which is made up of a continuous network of fibrils which are of irregular length and have a trapezoidal cross-section wherein the thin dimension is essentially the thickness of the original film strip. The fibrils are interconnected at random points to form a cohesively unitary or one-piece network structure, there being essentially very few separate and distinct fibrils existing in the yarn due to forces of adhesion or entanglement.
In U.S. Pat. No. 3,470,594 there is disclosed another method of making a yarn which has a spun-like appearance. Here, a strip or ribbon of striated film is highly oriented uniaxially in the longitudinal direction and is split into a plurality of individual filaments by a jet of air or other fluid impinging upon the strip in a direction substantially normal to the ribbon. The final product is described as a yarn in which individual continuous filaments formed from the striation are very uniform in cross-section lengthwise of the filaments. At the same time, there is formed from a web a plurality of fibrils having a reduced cross-section relative to the cross-section of the filament. FIGS. 8 and 9 of U.S. Pat. No. 3,470,594 show the actual appearance of yarn made in accordance with the disclosure.
The fibrillated film yarns of the prior art, which are generally characterized by the two disclosures identified above, have not been found to be useful in a commercial sense as a replacement or substitute for spun yarns made of staple fibers. These fibrillated film type yarns do not possess the necessary hand, the necessary strength, yarn uniformity, dye uniformity, or aesthetic structure to be used as an acceptable replacement or substitute for spun yarns for producing knitted and woven apparel fabrics.
Yarns of the type disclosed in U.S. Pat. Nos. 3,857,232 and 3,857,233 are bulky yarns with free protruding ends and are produced by joining two types of filaments together in the yarn bundle. Usually one type filament is a strong filament with the other type filament being a weak filament. One unique feature of the yarns is that the weak filaments are broken in the false twist part of a draw texturing process. The relatively weak filaments which are broken are subsequently entangled with the main yarn bundle via an air jet. Even though these yarns are bulky like staple yarns and have free protruding ends like spun yarns, fabrics produced from these yarns have aesthetics which are only slightly different from fabrics made from false twist textured yarns.
U.S. Pat. No. 4,245,001
Yarns made from the filament cross-sections of this invention, and as disclosed in greater detail in the aforementioned U.S. Pat. No. 4,245,001, have a spun yarn character, the yarn comprising a bundle of continuous filaments, the filaments having a continuous body section with at least one wing member extending from and along the body section, the wing member being intermittently separated from the body section, and a fraction of the separated wing members being broken to provide free protruding ends extending from the body section to provide the spun yarn character of the continuous filament yarn. The yarn is further characterized in that portions of the wing member are separated from the body section to form bridge loops, the wing member portion of the bridge loop being attached at each end thereof to the body section, the wing member portion of the bridge loop being shorter in length than the corresponding body section portion.
The free protruding ends extending from the filaments have a mean separation distance along a filament of about one to about ten millimeters and have a mean length of about one to about ten millimeters. The free protruding ends are randomly distributed along the filaments. The probability density function of the lengths of the free protruding ends on each individual filament is defined by ##EQU1## x>0, otherwise f(x)=0 where f(x) is the probability density function ##EQU2## and R(.xi.) is the log normal probability density function whose mean is .mu..sub.2 +lnw and variance is .sigma..sub.2.sup.2
or
where .mu..sub.2 =mean value of ln(COT.theta.)
with .theta.=angle at which tearing break makes to fiber axis and
w=width of the wing or ##EQU3## ps and for .mu..sub.2 =3.096
.sigma..sub.2 =0.450
0.11 mm.sup.-1 .ltoreq..alpha..ltoreq.2.06 mm.sup.-1
0.ltoreq..beta..ltoreq.1.25 mm.sup.-1
0.0085 mm.ltoreq.w.ltoreq.0.0173 mm
The free protruding ends have a preferential direction of protrusion from the individual filaments and greater than 50% of the free protruding ends initially protrude from the body member in the same direction.
The mean length of the wing member portion of the bridge loops is about 0.2 to about 10.0 millimeters and the mean separation distance of the bridge loops along a filament is about 2 to about 50 millimeters The bridge loops are randomly distributed along the filaments.
The yarns made from filaments of this invention comprise continuous multifilaments of polyester, polyolefin or polyamide polymer, each having at least one body section and having extending therefrom along its length at least one wing member, the body section comprising about 25 to about 95% of the total mass of the filament and the wing member or wing members comprising about 5 to about 75% of the total mass of the filament, the filament being further characterized by a wing-body interaction (WBI) defined by ##STR2## where the ratio of the width of the filament cross-section to the wing member thickness (L.sub.T /Dmin) is .ltoreq.30. The significance of the above symbols will be discussed later herein. The body of each filament remains continuous throughout the fractured yarn and thus provides load-bearing capacity, whereas the wings are broken and provide the free protruding ends.
It should be especially noted that the filament cross-sections disclosed in U.S. Pat. No. 4,245,001 are further characterized by a wing-body interaction defined by ##EQU4## where the ratio of the width of the filament to the wing thickness (L.sub.T /Dmin) is .ltoreq.30. For reasons given below, it should be noted that the numerical value of WBI.gtoreq.10, as disclosed in U.S. Pat. No. 4,245,001, is different from the numerical value of WPI.gtoreq.1 disclosed herein for the filament cross-sections of the present invention.
Although the fractured yarns made from the filament cross-section of the present invention come within the scope of the yarn claims in U.S. Pat. No. 4,245,001, the filament cross-sections of the present invention do not come within the scope of the filament claims in U.S. Pat. No. 4,245,001 because unexpectedly it was found that filament cross-sections having the special geometry disclosed herein will also give sufficient fracturability so as to produce a desirable level of free protruding ends but with wing-body interaction (WBI) values less than ten.
DISCLOSURE OF INVENTION
In accordance with the present invention, I provide a filament having a cross-section which has a body section and one or more wing members joined to the body section. The wing members vary up to about twice their minimum thickness along their width. At the junction of the body section and the one or more wing members the respective faired surfaces thereof define a radius of concave curvature (Rc) on one side of the cross-section and a generally convex curve located on the other side of the cross-section generally opposite the radius of curvature (Rc).
The body section constitutes about 25 to about 95% of the total mass of the filament and the wing member or wing members constitute about 5 to about 75% of the total mass of the filament, with the filament being further characterized by a wing-body interaction (WBI) defined by ##STR3## where the ratio of the width of the filament cross-section to the wing member thickness (L.sub.T /Dmin) is .ltoreq.30.
The cross-section of the filament may have a single wing member, or two or more wing members. The filament cross-section may also have one or more wing members that are curved, or the wing member(s) may be angular.
The filament cross-section may also have two wing members and one of the wing members may be non-identical to the other wing member.
The thickness of the wing member(s) may vary up to about twice the minimum thickness and the greater thickness may be along the free edge of the wing member(s). Stated in another manner, a portion of each wing member may be of a greater thickness than the remainder of the wing member.
The periphery of the body section may define one central convex curve on the one side of the cross-section and one central concave curve located on the other side of the cross-section generally opposite the aforementioned one central convex curve.
The periphery of the body section may also define on the one side of the filament cross-section at least one central convex curve and at least one central concave curve connected together, and on the other side of the cross-section at least one central concave curve and at least one central convex curve connected together.
The periphery of the body section may further define on the one side of the filament cross-section two central convex curves and a central concave curve connected therebetween and on the other side of the cross-section two central concave curves and a central convex curve connected therebetween.
Each of the one or more wing members may have along the periphery of its cross-section on the one side of the filament cross-section a convex curve joined to the aforementioned radius of concave curvature (Rc) and on the other side of the cross-section a concave curve joined to the first-mentioned convex curve that is generally opposite the radius of concave curvature (Rc).
Each of the one or more wing members may also have along the periphery of the filament cross-section on the one side thereof two or more curves alternating in order of convex to concave with the latter-mentioned convex curve being joined to the aforementioned radius of concave curvature (Rc) and on the other side of the cross-section two or more curves alternating in order of concave to convex with the latter-mentioned concave curve being joined to the first-mentioned convex curve that is generally opposite the radius of concave curvature (Rc).
The filament cross-section may have four wing members and a portion of the periphery of the body section defines on one side thereof at least one central concave curve and on the opposite side thereof at least one central concave curve, each central concave curve being located generally offset from the other.
The body section of each filament remains continuous throughout the yarn when the yarn is fractured and thus provides load-bearing capacity, whereas the one or more wing members are broken and provide free protruding ends.
The filaments may be provided with luster-modifying means which may be finely dispersed titanium dioxide (TiO.sub.2) or finely dispersed kaolin clay.
The filament may be comprised of a fiber-forming polyester such as poly(ethylene terephthalate) or poly-(1,4-cyclohexylenedimethylene terephthalate).
The filament disclosed herein may be oriented such that its elongation to break is less than 50% and has been heat stabilized to a boiling water shrinkage of .ltoreq.15%, and thereby rendered fracturable.
In accordance with the present invention, I also provide a fractured yarn comprising filaments having the characteristics as set forth above wherein the yarn is characterized by a denier of about 15 or more, a tenacity of about 1.1 grams per denier or more, an elongation of about 8 percent or more, a modulus of about 25 grams per denier or more, a specific volume in cubic centimeters per gram at one-tenth gram per denier tension of about 1.3 to about 3.0, and with a boiling water shrinkage of .ltoreq.15%.
The fractured yarn may have a laser characterization where the absolute b value is at least 0.25, the absolute value of a/b is at least 100 and the L+7 value ranges up to about 75. The absolute b value may also be about 0.6 to about 0.9, the absolute a/b value may be about 500 to about 1000; and the L+7 value may be about 0 to about 10. The absolute b value may still also be about 1.3 to about 1.7; the absolute a/b value may be about 700 to about 1500; and the L+7 value may be about 0 to about 5. Further, the absolute b value may be about 0.3 to about 0.6; the absolute a/b value may be about 1500 to about 3000; and the L+7 value may be about 25 to about 75.
The fractured yarn disclosed herein may still further be characterized by a normal mode Uster evenness of about 6% or less.
The fractured yarn made from the filaments disclosed herein may be of polyethylene terephthalate.
The filaments after spinning are drawn, heatset, and subjected to an air jet to fracture the wing member or wing members to provide a yarn having spun-like characteristics.
In accordance with the present invention, I further provide a process for melt spinning a filament having a body section and at least one wing member. The process involves (a) melt spinning a filament-forming polymeric material through a spinneret orifice the planar cross-section of which defines intersecting quadrilaterals in connected series with the L/W (length to width ratio) of each quadrilateral varying from 2 to 10 and with one or more of the defined quadrilaterals being greater in width than the width of the remaining quadrilaterals, with the wider quadrilaterals defining body sections and with the remaining quadrilaterials defining wing members (1) to form a filament having a cross-section comprising the aforementioned body section and the aforementioned at least one wing member joined to the body section, the at least one wing member varying up to about twice its minimum thickness along its width, at the junction of the body section and the at least one wing member the respective faired surfaces thereof define a radius of concave curvature (Rc) on one side of the cross-section and a generally convex curve located on the other side of the corss-section generally opposite the radius of curvature (Rc), the body section comprising about 25 to about 95% of the total mass of the filament and the wing member comprising about 5 to about 75%, the filament being further characterized by a wing-body interaction (WBI) defined by ##STR4## where the ratio of the width of the filament cross-section to the wing member thickness (L.sub.T /Dmin) is .ltoreq.30, Dmax is the maximum thickness of the body section as shown in FIG. 2, Dmin is the thickness of the wing member for essentially uniform wing members and the minimum thickness close to the body section when the thickness of the wing member is variable, Rc is the radius of curvature of the intersection of the wing member and body section, Lw is the overall length of an individual wing member and L.sub.T is the overall length of the filament cross-section; (b) quenching the filament at a rate sufficient to maintain at least the aforementioned wing-body interaction (WBI); the spun filament of; and (c) taking up the filament under tension.
The process also involves uniformly drawing to a preselected level of textile utility a yarn comprising filaments having a wing-body interaction (WBI) defined by ##STR5## where the ratio of the width of the filament to the width of the wing member (L.sub.T /Dmin) is .ltoreq.30, Dmax is the thickness or diameter of the body of the cross-section, Dmin is the thickness of the wing member for essentially uniform wing members and the minimum thickness close to the body when the thickness of the wing member is variable, R.sub.c is the radius of curvature of the intersection of the wing member and body section, Lw is the overall length of an individual wing member and L.sub.T is the overall length of the filament cross-section. The yarn is then stabilized to a boiling water shrinkage of .ltoreq.15%; the wing member portion of the filament is fractured utilizing fracturing means; and then the yarn is taken up.
By "selected level of textile utility", it is meant yarns having generally elongations to break from about 8 to about 50%.
The fracturing apparatus may comprise a fluid fracturing jet operating at a brittleness parameter (Bp*) of about 0.03-0.8 for the yarn being fractured. A suitable fracturing jet that may be used is the one disclosed in U.S. Pat. No. 4,095,319 and also in FIG. 20 of the aforementioned U.S. Pat. No. 4,245,001. Details of this jet will also be given herein. The yarn may be a poly(ethylene terephthalate) yarn and the fluid fracturing jet may be operated at a brittleness parameter (Bp*) of about 0.03-0.6, and preferably at a brittleness parameter of about 0.03 to about 0.4.
The specific volume of the fractured yarn may be made to vary along the yarn strand by varying the fracturing jet air pressure.
The filaments of this invention are preferably made from polyester or copolyester polymer. Polymers that are particularly useful are poly(ethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate). These polymers may be modified so as to be basic dyeable, light dyeable, or deep dyeable as is known in the art. These polymers may be produced as disclosed in U.S. Pat. Nos. 3,962,189 and 2,901,466, and by conventional procedures well known in the art of producing fiberforming polyesters. Also the filaments can be made from polymers such as poly(butylene terephthalate), polypropylene, or nylon such as nylon 6 and 66. However, the making of yarns described herein from these polymers is more difficult than the polyesters mentioned above. I believe this is attributable to the increased difficulty in making these polymers behave in a brittle manner during the fracturing process.
In general, it is well known in the art that the preservation of nonround cross-sections is dependent, among other things, on the viscosity-surface tension properties of the melt emerging from a spinneret hole. It is also well known that the higher the inherent viscosity (I.V.) within a given polymer type, the better the shape of the spinneret hole is preserved in the as-spun filament. These ideas obviously apply to the wing-body interaction parameter defined herein.
One major advantage of yarns made from the filaments of this invention is the versatility of such yarns. For example, a yarn with high strength, high frequency of protruding ends, short mean protruding end length with a medium bulk can be made and used to give improved aesthetics in printed goods when compared to goods made from conventional false twist textured yarn. On the other hand, a yarn with medium strength, high frequency of protruding ends with medium to long protruding end length and high bulk can be made and used to give desirable aesthetics in jersey knit fabrics for underwear or for women's outerwear.
The versatility is achieved primarily by manipulating the fracturing jet pressure and the specific cross-section of the filament. In general, increasing the fracturing jet pressure increases the specific volume and decreases the strength of the yarn. By varying the cross-section of the filaments within the parameters set forth herein, the yarn strength at constant fracturing conditions increases with increasing percent body section and the yarn specific volume increases with decreasing percent body section and increasing length/slot width.
Another major advantage of yarns made from filament cross-sections of this invention, when compared to staple yarns, is their uniformity along their length as evidenced by a low % Uster value (described in U.S. Pat. No. 4,245,001). This property translates into excellent knitability and weavability with the added advantage that visually uniform fabrics can be produced which possess distinctively staple-like characteristics, a combination of properties which has been hitherto unachievable.
Another of the major advantages of yarns made from filament cross-sections of this invention when compared to normal textile I.V. yarns in fabrics is excellent resistance to pilling. Random tumble ratings of 4 to 4.5 are very common (ASTM D-1375, "Pilling Resistance and Other Related Surface Characteristics of Textile Fabrics"). This is thought to occur because of the lack of migration of the individual protruding ends in the yarns.
Another major advantage when compared to previous staple-like yarns is the ease with which these yarns can be withdrawn from the package. This is a necessary prerequisite for good processability.
The filaments of this invention may be prepared by spinning the polymer through an orifice which provides a filament cross-section having the necessary wing-body interaction and the ratio of the width of the filament to the wing thickness as set forth earlier herein. The quenching of the fiber (as in melt spinning) must be such as to preserve the required cross-section. The filament is then drawn, heat set to a boiling water shrinkage of .ltoreq.15% and subjected to fracturing forces in a high velocity fracturing jet. Although the shape of the filaments must remain within the limits described, slight variations in the parameters may occur along the length of the filament or from filament to filament in a yarn bundle without adversely affecting the unique properties.
Yarns made from fractured filaments of the invention have a denier of 15 or more, a tenacity of about 1.1 grams per denier or more, an elongation of about 8 percent or more, a modulus of about 25 grams per denier or more, a specific volume in cubic centimeters per gram at one-tenth gram per denier tension of about 1.3 to 3.0, and a boiling water shrinkage of <15%. The yarn is further characterized by a laser characterization where the absolute b value is at least 0.25, the absolute a/b value is at least 100, and the L+7 value ranges up to about 75. Some particularly useful yarns have an absolute b value of about 0.6 to about 0.9, an absolute a/b value of about 500 to about 1000, and an L+7 value of 0 to about 10. Other particularly useful yarns have an absolute b value of about 1.3 to about 1.7, an absolute a/b value of about 700 to about 1500 and an L+7 value of 0 to about 5. Other yarns of the invention which are particularly useful have an absolute b value of about 0.3 to about 0.6, an absolute a/b value of about 1500 to about 3000, and an L+7 value of about 25 to about 75 and a Uster evenness of about 6% or less. For a discussion of the laser characterization, see U.S. Pat. No. 4,245,001.
For purposes of discussion, the following general definitions will be employed.
By brittle behavior is meant the failure of a material under relatively low strains and/or low stresses. In other words, the "toughness" of the material expressed as the area under the stress-strain curve is relatively low. By the same token, ductile behavior is taken to mean the failure of a material under relatively high strains and/or stresses. In other words, the "toughness" of the material expressed as the area under the stress-strain curve is relatively high.
By fracturable yarn is meant a yarn which at a preselected input temperature, generally room temperature, and when properly processed with respect to frequency and intensity of the energy input will exhibit brittle behavior in some part of the fiber cross-section (wing members in particular) such that a preselected level of free protruding broken sections (wing members) can be realized. It is within the framework of this general definition that the specific cross-section requirements for providing yarns possessing textile utility is defined.
According to the aforementioned U.S. Pat. No. 4,245,001, it is believed that the following basic ideas play important roles in the yarn-making process.
1. A properly specified cross-section such that the body remains continuous and the wing members produce free protruding ends when subjected to preselected processing conditions (WBI.gtoreq.1) in the present invention.
2. A process in which there is a transfer of energy from a preselected source of a specified frequency range and intensity to fibers of the properly specified cross-section at a specified temperature such that the fiber material behaves in a brittle manner (0.03.ltoreq.Bp*.ltoreq.0.80).
Given a properly specified cross-section and a set of process conditions under which the material exhibits brittle behavior, the following sequence of events is believed to occur during the production of desirable yarns of the type disclosed herein.
1. The applied energy and its manner of application generates localized stresses sufficient to initiate cracks near the wing-body intersection. Obviously, low lateral strength helps in this regard.
2. The crack(s) propagates until the wing member(s) and body section are acting as individual pieces with respect to lateral movement, thus having the ability to entangle with neighbor pieces while still being attached to the body at the end of the crack.
3. Because of the intermingling and entangling, the total forces which may act on any given wing member at any instant can be the sum of the forces acting on several fibers. In this manner, the localized stress on a wing member can be sufficient to break the wing member with assistance from the embrittlement which occurs. It is known, for example, that mean stresses generated by a fracturing jet are at least one order of magnitude below the stresses required to break individual pieces (.about.0.2 G/D vs. .about.2 G/D).
4. Finally, it is required that the intensity and effective frequency of the force application and the temperature of the fiber are such that the break in the wing member is of a brittle nature, thereby providing free protruding ends of a desirable length and linear frequency as opposed to loops and/or excessively long free protruding ends which would occur if the material behaved in a more ductile manner.
The following parameters have been found to be especially useful in characterizing the process required to obtain a useful yarn with free protruding ends, as disclosed in U.S. Pat. No. 4,245,001. ##EQU5## where Bp* is defined as the "brittleness parameter" and is dimensionless; .DELTA.E .tau. is a product of strain and stress indicative of relative brittleness, where, in particular
.DELTA.E.sub.na is the extension to break of the potentially fracturable yarn without the proposed fracturing process being operative;
.DELTA.E.sub.a is the extension to break of the potentially fracturable yarn with the proposed fracturing process being operative;
.tau..sub.a is the stress at break of the potentially fracturable yarn with the proposed fracturing process being operative;
.tau..sub.na is the stress at break of the potentially fracturable yarn without the proposed fracturing process being operative.
The input yarn conditions are constant in the a and na modes.
These parameters are also defined in terms of process conditions. As shown in FIG. 28 of U.S. Pat. No. 4,245,001, the basic experiment involves "stringing up" the yarn between two independently driven rolls as shown with the specific speed of the first or feed roll V.sub.1 being preselected. The surface speed of the second or delivery roll V.sub.2 is slowly increased until the yarn breaks with V.sub.2 and the tension g in grams at the break being detected and recorded. This experiment is repeated five times with the proposed fracturing process being operative. In terms of the previously defined variables ##EQU6##
Obviously mechanical damage by dragging over rough surfaces or sharp edges can influence Bp* values. However, for purposes of discussion, the word "process" means the actual part of the fracturing apparatus which is operated to influence fracturing only. In the case of air jets, it is the actual flow of the turbulent fluid with resulting shock waves which is used to fracture the yarn, not the dragging of the yarn over a sharp entrance or exit. Therefore the influence of the turbulently flowing fluid on Bp* is the only relevant parameter, not the mechanical damage. For example, suppose the following measurements were made with V.sub.1 =200 meters/min.
______________________________________
Process
Not Operative
V.sub.2na
218 219 220 221 222
g.sub.na gms.
200 205 195 200 200
Process
Operative V.sub.2a 208 208 209 210 210
g.sub.a gms.
100 95 105 100 100
______________________________________
For this hypothetical example with the yarn at 23.degree. C.
.DELTA.E.sub.a =9 meters/min.
.DELTA.E.sub.na =20 meters/min.
.tau..sub.a =(100 gms.) (209 meters/min.)/(200 meters/min.)
.tau..sub.na =(200 gms.) (220 meters/min.)/(200 meters/min.) thus ##EQU7##
This parameter reflects the complex interactions among the type of energy input (i.e. turbulent fluid jet with associated shock waves), the frequency distribution of the energy input, the intensity of the energy input, the temperature of the yarn at the point of fracture, the residence time within the fracturing process environment, the polymer material from which the yarn is made and its morphology, and possibly even the cross-section shape. Obviously values of Bp* less than one suggest more "brittle" behavior. Values of Bp* of about 0.03 to about 0.80 have been found to be particularly useful. Note that it is possible to have a process (usually a fluid jet) operating on a yarn with a specified fiber cross-section of a specified denier/filament made from a specified polymer which behaves in a perfectly acceptable manner with respect to Bp* and by changing only the specified polymer the resulting Bp* will be an unacceptable value reflected in poorly fractured yarn. Thus acceptable Bp* values for various polymers may require significant changes in the frequency and/or intensity of the energy input and/or the temperature of the yarn and/or the residence time of the yarn within the fracturing process.
The preferred range of values of Bp* applies to a single operative process unit such as a single air jet. Obviously cumulative effects are possible and thereby several fracturing process units operating in series, each with a Bp* higher than 0.50 (say 0.50 to 0.80), can be utilized to make the yarn described herein.
Turbulent fluid jets with associated shock waves are particularly useful processes for fracturing the yarns described in this invention. Even though liquids may be used, gases and in particular air, are preferred. The drag forces generated within the jet and the turbulent intermingling of the fibers, characteristics well known in the art, are particularly useful in providing a coherent intermingled structure of the fractured yarns of the type disclosed herein.
For further details on Bp* "brittleness parameter", again see U.S. Pat. No. 4,245,001.
Procedures and instruments discussed herein are defined below.
Specific Volume
The specific volume of the yarn is determined by winding the yarn at a specified tension (normally 0.1 G/D) into a cylindrical slot of known volume (normally 8.044 cm.sup.3). The yarn is wound until the slot is completely filled. The weight of yarn contained in the slot is determined to the nearest 0.1 mg. The specific volume is then defined as ##EQU8##
Boiling Water Shrinkage
The boiling water shrinkage concerns the change in length of a specimen when immersed in boiling water, distilled or demineralized, for a specified time. Either ASTM Test Method D-204 or D-2259 may be used, with the latter method being preferred.
Uster Evenness Test (% U)
ASTM Procedure D 1425--Test for Unevenness of Textile Strands.
Inherent Viscosity
Inherent viscosity of polyester and nylon is determined by measuring the flow time of a solution of known polymer concentration and the flow time of the polymer solvent in a capillary viscometer with an 0.55 mm. capillary and an 0.5 mm. bulb having a flow time of 100.+-.15 seconds and then by calculating the inherent viscosity using the equation ##EQU9## where: ln=natural logarithm
t.sub.s =sample flow time
t.sub.o =solvent blank flow time
C=concentration grams per 100 mm. of solvent
PTCE=60% phenol, 40% tetrachloroethane Inherent viscosity of polypropylene is determined by ASTM Procedure D-1601.
Laser Characterization
The fractured yarn of this invention can be characterized in terms of the hairiness characteristics of the fractured yarn. The apparatus used is disclosed in U.S. patent application Ser. No. 762,704, filed Jan. 26, 1977, (now abandoned) in the name of Don L. Finley and entitled "Hairiometer". The description is incorporated herein by reference.
For purposes of clarification and explanation, the following symbols are used interchangeably.
B=b
M.sub.T =A/B=a/b
Throughout this disclosure the terms
Laser absolute value b=laser .vertline.b.vertline.
Laser absolute value a/b=laser .vertline.a/b.vertline.
will be used also. The words "absolute value" carry the normal mathematical connotation such that
Absolute value of (-3)=.vertline.-3.vertline.=3
or
Absolute value of (3)=.vertline.3.vertline.=3.
The number of filaments protruding from the central region of the yarn of this invention can be thought of as the hairiness of the yarn. The words "hairiness", "hairiness characteristics" and words of similar import mean the nature and extent of the individual filaments that protrude from the central region of the yarn. Thus a yarn with a large number of filaments protruding from the central region would generally be thought of as having high hairiness characteristics and a yarn with a small number of filaments protruding from the central region of the yarn would generally be thought of as having low hairiness characteristics.
A substantially parallel beam of light is positioned so that the beam of light strikes substantially all the filaments protruding from the central region of a running textile yarn. The diffraction patterns created when the beam of light strikes a filament is sensed and counted. The fibers protruding from the central region of the yarn are scanned by the beam of light by incrementally increasing the distance between the running yarn and the axis of the beam of light so that the beam of light strikes a reduced number of filaments after each incremental increase in the distance. The diffraction patterns created when the beam of light strikes a filament are sensed and counted during the scanning. Data on the number of filaments counted at each distance representing the total of the incremental increases and each distance are then collected for typical yarns of this invention. Using the data there is developed a mathematical correlation of the number of filaments counted at each distance representing the total of the incremental increases as a function of a constant value and each distance. Preferably the mathematical correlation is developed by curve fitting an equation to the data points, the hairiness, or free protruding end, characteristics of the yarn are then expressed by mathematical manipulation of the mathematical correlation. A particular yarn to be tested for hairiness is then analyzed in the above-described manner and data representing the number of filaments counted at each distance are collected. The constant value of the mathematical correlation is then determined by correlating with the mathematical correlation, preferably by curve fitting, the collected data representing the number of filaments counted at each distance. The hairiness characteristics of the tested yarn are then determined by evaluating the mathematical expression of the hairiness characteristics of the yarn using the constant value. In addition the hairiness characteristics of the textile yarn are determined by considering the total number of filaments counted when the beam of light is at longer distances from the yarn.
A particular type of light is used to sense the filaments protruding from the central region of the yarn. Preferably the beam of light is a substantially parallel beam of light and also coherent and monochromatic. Although a laser is preferred, other types of substantially parallel coherent, monochromatic beams of light obvious to those skilled in the art can be used. The diameter of the beam of light should be small.
In use, a substantially parallel, coherent, monochromatic beam of light is positioned so that the beam of light strikes substantially all the filaments protruding from the central region of a running textile yarn. Preferably the textile yarn is positioned substantially perpendicular to the axis of the beam of light.
As the running yarn translates along its axis, the beam of light sees filaments protruding from the central region of the yarn as the filaments move through the beam of light. Each time the beam of light sees a filament, a diffraction pattern is created. During a predetermined interval of time a count of the number of filaments that protrude from the central region of the yarn during the interval of time is obtained by sensing and counting the diffraction patterns. By the term "diffraction pattern" we mean any suitable type of diffraction pattern such as a Fraunhofer or Fourier diffraction pattern. Preferably a Fraunhofer diffraction pattern is used.
Next the filaments protruding from the central region of the yarn are scanned by incrementally increasing the distance between the running yarn and the axis of the beam of light so that the beam of light strikes a reduced number of filaments after each incremental increase.
During the scanning function, wherein the distance between the yarn and the beam of light is incrementally increased, the number of filaments is sensed and counted by sensing and counting the number of diffraction patterns created as the filaments in the yarn move through the beam of light.
The number of incremental increases that is used can vary widely depending on the wishes of the operator of the device. In some cases only a few incremental increases can be used while in other cases 15 to 20, or even more, incremental increases can be used. Preferably 15 incremental increases are used. The incremental increases are continued until the longest filaments are no longer seen by the beam of light and consequently there are no filaments used.
In order to insure that a statistically valid filament count is obtained at the initial position and after each incremental increase in distance, the sequence of sensing, counting and incrementally increasing the distance is repeated a number of times and the filament count at each distance averaged. Although the number of times can vary, 8 is a satisfactory number. Thus each of the 16 filament counts would be the average of 8 testing cycles.
Next typical yarns are tested and the average number of filaments counted at each distance is recorded.
The data for the number of filaments counted at each distance representing the total of the incremental increases, N, are mathematically correlated as a function of a constant value and each distance, x. This mathematical correlation can be generally written as N=f(K,x), where N is the number of filaments counted, K is a constant value, and x is each distance. Although a wide variety of means can be used to correlate the N and x data, we prefer that the data are plotted on a coordinate system wherein the values of N are plotted on the positive y axis and the values of x are plotted on the positive x axis. The character of these data can be more fully appreciated by referring to FIG. 21 of U.S. Pat. No. 4,245,001.
In FIG. 21 of U.S. Pat. No. 4,245,001 there are shown various curves representing the relationship between the number of filaments counted N and the distance x.
As will be appreciated from a consideration of the nature of the number of filaments counted as a function of the distance from the central region of the yarn, the largest number of filaments would be counted at the closer distances to the yarn, and the number of filaments counted would decrease as the beam of light moves away from the yarn during scanning. Thus in FIG. 21 of U.S. Pat. No. 4,245,001, when the log of the number of filaments N is plotted versus the distance x, the data are typically represented by a substantially straight line A. Although the particular mathematical correlation that can be used can vary widely depending on the precision that is required, the availability of data processing equipment, the type of yarn being tested, and the like, a mathematical correlation that gives results of entirely suitable accuracy for many textile yarns in N=Ae.sup.-Bx, where N is the number of filaments counted at each distance, A is a constant, e is 2.71828, B is a constant, and x is each distance. This relationship is shown as curve A in FIG. 21 of U.S. Pat. No. 4,245,001. Although this relationship gives entirely satisfactory results for most typical yarns, many other correlations can be used for yarns of a particular character. For example if the filaments protruding from the central region of a yarn are substantially the same length and uniformly distributed, much as in a pipe cleaner, then there would be greater number of filaments counted at the closer distances and the number of filaments counted would diminish rapidly at some distance. This relationship could be expressed by a curve much like curve B in FIG. 21 of U.S. Pat. No. 4,245,001. Also for example, if the N and x data were from a yarn with only a few short filaments protruding from the central region, such as angora yarn, the N versus x data could be represented by curve C wherein a few filaments are counted at closer distances and the number of filaments decreases rapidly as the distance is increased. Although the correlation N=Ae.sup.-Bx gives good results for typical yarns, greater accuracy can be obtained using the correlation N=Ae.sup.-(Bx+Cx.spsp.2.sup.). The correlation N=Ae.sup.-(Bx+Cx.spsp.2.sup.) gives good fits to all curves A, B and C. As will be appreciated, there is an infinite number of correlations that can be used to express the relationship between N and x, both for most typical yarns, and for any particular type of yarn.
Since the general mathematical correlation N=f(K,x) represents the relationship between the N and x data, useful information regarding the hairiness characteristics of the yarn can be mathematically expressed by use of the mathematical correlation. For example the area under the curve of the equation is reflective of the amount of hairiness of the yarn, or the total mass of filaments protruding from the central region of the yarn, M.sub.T, and can be generally represented as ##EQU10## where B and C are greater than 0. Another hairiness characteristic that can be mathematically expressed by manipulation of the mathematical correlation is the slope of the curve of the equation N=f(K,x). The slope of the mathematical correlation, represented as d[N=f(K,x)]/dx, is measured of the general character of the yarn. Thus if the number of filaments N is fairly uniform at shorter distances but rapidly decreases at longer distances, the N versus x curve would be somewhat like curve B in FIG. 21 of U.S. Pat. No. 4,245,001. If the number of filaments N decreased radically at shorter distances, the N versus x curve might be somewhat like curve C in FIG. 21. The slope of these curves would, of course, be different and would represent yarns with radically different hairiness characteristics.
In addition the hairiness characteristics of the yarn can be expressed as the total number of filaments counted when the beam of light is located at the larger distances from the yarn. For example when 16 distances are used in a preferred embodiment, the sum of the filaments counted at distances 7 through 16 can be used as one hairiness characteristic of the yarn, hereinafter called "laser L+7".
Consideration will be given to the various hairiness characteristics using the preferred mathematical correlation, N=Ae.sup.-Bx. The total mass of filaments protruding from the central region of the yarn M.sub.T, is ##EQU11## where B and C are greater than o, which can be resolved to
M.sub.T =A/B
The absolute value of the slope of the logarithm of N, i.e. .vertline.d(ln N)/dx.vertline., where N=Ae.sup.-Bx, is B.
Next, the constant values for the mathematical correlation selected for use are determined by testing a particular yarn for hairiness characteristics by repeating the previously described procedure. First the yarn is positioned so that the beam of light strikes substantially all the filaments protruding from the central region of the yarn without striking the central region of the yarn and the number of filaments in the path of the beam of light is sensed and counted. Then yarn is scanned by incrementally increasing the distance between the running yarn and the axis of the beam of light so that the beam of light strikes a reduced number of filaments after each incremental increase in the distance. The number of filaments in the path of the beam of light is sensed and counted after each incremental increase. The procedure is repeated a number of times and a statistically valid average value of the number of filaments counted at each distance is determined.
The average values of the number of filaments counted at each distance N and the distances x are then used to determine the constant value in the mathematical correlation by correlating, with the mathematical correlation, the number of filaments counted at each distance N and the distance x. Preferably the correlation is accomplished by conventional curve-fitting procedures such as the method of least squares. Thus, since it is known from previous work that the relationship between the number of filaments counted at each distance and each distance can be expressed as some specific expression of the general relationship N=f(K,x), the value of K can be determined by correlating the N and x data obtained with the equation N=f(K,x).
Once the value of K is determined, the hairiness characteristics of the yarn can be determined by using the determined value of K and performing the required mathematics to solve whatever hairiness characteristics equation has been developed. For example if the mathematical correlation to be used is N=Ae.sup.-Bx, then the various values of N and x obtained from testing a particular yarn can be used to determine values of A and B using conventional correlation techniques such as curve fitting using the method of least squares. Once A and B have been determined, the hairiness characteristic, M.sub.T, and the slope of the mathematical correlation can be readily determined.
As will be appreciated by those skilled in the art, the function of determining the constant in the mathematical correlation and performing the mathematics to determine any particular hairiness characteristics can be accomplished either manually or through the use of conventional data processing equipment. For example the N and x values can be recorded on a punched tape and the punched tape can be used as the input to a digital computer which is programmed to mathematically express the hairiness characteristics of the yarn, M.sub.T, by use of the mathematical correlation N=Ae.sup.-Bx. Then the constant values A and B are determined by the computer by curve fitting the number of filaments counted at each distance N and the distance x with the mathematical correlation N=Ae.sup.-Bx, using the method of least squares. Finally the computer evaluates the mathematical expression of the hairiness characteristics of the yarn, M.sub.T, by dividing B into A.
BRIEF DESCRIPTION OF DRAWINGS
The details of my invention will be described in connection with the accompanying drawings in which
FIGS. 1A and 1B are drawings of representative spinneret orifices showing the nature and location of typical measurements to be made;
FIG. 2 is a drawing of a representative filament cross-section having a body section and two wing members and showing where the overall length of a wing member cross-section (L.sub.W) and the overall or total length of a filament cross-section (L.sub.T) are measured, where on the wing member the thickness (Dmin) of the wing member is measured, where on the body section the filament body diameter (Dmax) is measured and the location of the radius of curvature (Rc);
FIG. 3 is a photomicrograph of one embodiment of a spinneret orifice in a spinneret;
FIG. 4 is a photomicrograph of a filament cross-section of a filament spun from the spinneret orifice shown in FIG. 3;
FIG. 5 is a photomicrograph of a second embodiment of a spinneret orifice in a spinneret;
FIG. 6 is a photomicrograph of a filament cross-section of a filament spun from the spinneret orifice shown in FIG. 5;
FIG. 7 is a photomicrograph of a third embodiment of a spinneret orifice in a spinneret;
FIG. 8 is a photomicrograph of a filament cross-section of a filament cross-section spun from the spinneret orifice shown in FIG. 7;
FIG. 9 is a drawing of a spinneret orifice having a single-segment body section and a single-segment wing member having an angle therebetween of about 60.degree.;
FIG. 10 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 9;
FIG. 11 is a drawing of a spinneret orifice having a single-segment body section and a one-segment single wing member having an angle therebetween of about 90.degree.;
FIG. 12 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 11;
FIG. 13 is a drawing of a spinneret orifice having a single-segment body section and a two-segment single wing member;
FIG. 14 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 13;
FIG. 15 is a drawing of a spinneret orifice having a single-segment body section and a one-segment wing member intersecting at about 105.degree. at one end of the body section and another one-segment wing member intersecting at about 90.degree. with the other end of the body section, and with the lengths of the wing members differing from each other;
FIG. 16 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 15;
FIG. 17 is a drawing of a spinneret orifice having a single-segment body section and a one-segment wing member intersecting at about 90.degree. at each end of the body section, and with the lengths of the wing members being the same;
FIG. 18 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 17;
FIG. 19 is a drawing of a spinneret orifice having a single-segment body section and a one-segment wing member intersecting at about 120.degree. at each end of the body section, with each wing member being of the same length as the other;
FIG. 20 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 19;
FIG. 21 is a drawing of a spinneret orifice having a single-segment body section and a two-segment wing member intersecting at about 90.degree. with each other and at each end of the body section, with the segments of the wing member at each end of the body section corresponding in length;
FIG. 22 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 21;
FIG. 23 is a drawing of a spinneret orifice having a single-segment body section and two dual-segment wing members each intersecting with an end of the single-segment body section at about 90.degree. and each segment of the dual-segment wing member intersecting with the other segment at about 75.degree.;
FIG. 24 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 23.
FIG. 25 is a drawing of a spinneret orifice having a single-segment body section and a single-segment wing member intersecting at one end of the single-segment body section at an angle of about 60.degree. and a four-segment wing member intersecting at the other end of the single-segment body section and with each other at an angle of about 60.degree.;
FIG. 26 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 25;
FIG. 27 is a drawing of a spinneret orifice having a dual-segment body section having an angle therebetween of about 60.degree. and having a single-segment wing member intersecting one end of the dual-segment body section at an angle of about 60.degree.;
FIG. 28 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 27;
FIG. 29 is a drawing of a spinneret orifice having a dual-segment body section having an angle therebetween of about 60.degree. and having a single-segment wing member intersecting at each end of the dualsegment body section at an angle of about 60.degree.;
FIG. 30 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 29;
FIG. 31 is a drawing of a spinneret orifice having a dual-segment body section having an angle therebetween of about 90.degree. and having a two-segment wing member intersecting with each other at about 105.degree. and at each end of the dual-segment body section at an angle of about 90.degree.;
FIG. 32 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 31;
FIG. 33 is a drawing of a spinneret orifice having a dual-segment body section having an angle therebetween of about 60.degree. and having a three-segment wing member, as viewed to the left of the body section, intersecting with each other, respectively, at about 90.degree. and 75.degree. and at one end of the dual-body section at an angle of about 60.degree., and a second three-segment wing member, as viewed to the right of the body section, intersecting with each other, respectively, at about 75.degree. and about 60.degree. and at the other end of the dual-segment body section at an angle of about 60.degree., with the lengths of the segments in one wing member differing from those in the other wing member;
FIG. 34 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 33;
FIG. 35 is a drawing of a spinneret orifice having a dual-segment body section having an angle therebetween of about 90.degree. and having a three-segment wing member intersecting with each other and at each end of the dual-segment body section at about 90.degree.;
FIG. 36 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 35;
FIG. 37 is a drawing of a spinneret orifice having a dual-segment body section having an angle therebetween of about 50.degree. and having a three-segment wing member intersecting with each other and at each end of the dual-segment body section at about 50.degree.;
FIG. 38 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 37;
FIG. 39 is a drawing of a spinneret orifice having a dual-segment body section having an angle therebetween of about 60.degree. and having a three-segment wing member, as viewed to the left of the body section, intersecting with each other and at one end of the body section at an angle of about 60.degree., and having a four-segment wing member, as viewed to the right of the body section, intersecting with each other and at the other end of the body section at an angle of about 60.degree., with the lengths of the segments in one wing member differing from those in the other wing member;
FIG. 40 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 39;
FIG. 41 is a drawing of a spinneret orifice having a dual-segment body section having an angle therebetween of about 45.degree. and having a three-segment wing member, as viewed to the left of the body section, intersecting with each other and at one end of the body section at an angle of about 45.degree., and having a four-segment wing member, as viewed to the right of the body section, intersecting with each other at an angle of about 90.degree. and at the other end of the body section at an angle of about 70.degree., with the lengths of the segments in one wing member differing from those in the other wing member;
FIG. 42 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 41;
FIG. 43 is a drawing of a spinneret orifice having a tapering dual-segment body section having an angle therebetween of about 90.degree. and having a tapering two-segment wing member intersecting with each other at an angle of about 90.degree. and with the body section at an angle of about 75.degree.;
FIG. 44 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 43;
FIG. 45 is a drawing of a spinneret orifice having a three-segment body section intersecting with each other at an angle of about 60.degree. and having a single-segment wing member intersecting at one end of the body section at an angle of about 60.degree.;
FIG. 46 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 45;
FIG. 47 is a drawing of a spinneret orifice having a three-segment body section intersecting with each other at an angle of about 60.degree. and having a single-segment wing member intersecting at each end of the body section at an angle of about 60.degree.;
FIG. 48 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 49;
FIG. 49 is a drawing of a spinneret orifice having a four-segment body section intersecting with each other at an angle of about 60.degree. and having a single-segment wing member intersecting at one end of the body section at an angle of about 60.degree.;
FIG. 50 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 50;
FIG. 51 is a drawing of a spinneret orifice having a three-segment body section intersecting with each other at an angle of about 60.degree. and having two four-segment wing members each intersecting at an end of the body section at an angle of about 60.degree., and each wing member segment intersecting with another wing member segment also at an angle of about 60.degree.;
FIG. 52 illustrates the approximate cross-section a filament cross-section will have when spun from the spinneret orifice shown in FIG. 51;
FIG. 53 is a drawing of a spinneret orifice having a four-segment body section intersecting with each other at an angle of about 30.degree. and having two five-segment wing members each intersecting at an end of the body section at an angle of about 40.degree., and the five segments of each wing member intersecting with each other from the outer end toward the body section, respectively, at angles of about 60.degree., 60.degree., 50.degree. and 45.degree.;
FIG. 54 illustrates the approximate configuration a filament cross-section will have when spun from the spinneret orifice shown in FIG. 53;
FIG. 55 is a drawing of a spinneret orifice having an enlarged two-segment body section intersecting with each other at an angle of about 90.degree. and having two four-segment wing members each intersecting at each end of the body section at an angle of about 90.degree., and each wing member segment intersecting with an adjacent wing member segment at an angle of about 90.degree.;
FIG. 56 illustrates the approximate cross-section a filament cross-section will have when spun from the spinneret orifice shown in FIG. 55;
FIG. 57 is a drawing of a spinneret orifice having a three-segment body section intersecting with each other at an angle of about 60.degree. and four wing members, each, for instance, being in four segments and the segments intersecting with each other at an angle of about 60.degree. with two diagonally opposite wing members intersecting the body section at an angle of about 120.degree. and the other diagonally opposite two wing members intersecting the body section at an angle of about 60.degree.;
FIG. 58 illustrates the approximate cross-section a filament cross-section will have when spun from the spinneret orifice shown in FIG. 57;
FIG. 59 is a photomicrograph of fractured and non-fractured filament cross-sections;
FIG. 60 shows tracings of fibers from a yarn to illustrate bridge loops and free protruding ends; and
FIG. 61 illustrates six classifications of observed events occurring when yarn is fractured.
BEST MODE FOR CARRYING OUT THE INVENTION
In reference to the drawings, I show in FIGS. 4, 6 and 8 photomicrographs of the filament cross-section of typical filaments of my invention. It is critical to this invention that the cross-section of the filaments have geometrical features which are further characterized by a wing-body interaction (WBI) defined by ##STR6## where the ratio of the width of the filament cross-section to the wing member thickness (L.sub.T /Dmin) is .ltoreq.30. The identification of and procedure for measuring these features is described in U.S. Pat. No. 4,245,001 but is repeated here since it is in part relevant to the present invention. It should also be noted that the result of WBI.gtoreq.1 above differs from the result of WBI.gtoreq.10 in the patent because the fiber characteristics disclosed in the patent are somewhat different from those disclosed herein, as heretofore mentioned. Referring in particular to the photomicrograph in FIG. 4, for instance, I illustrate how the fiber cross-sectional shape characterization is accomplished.
1. Make a negative of a filament cross-section at 500X magnification from the undrawn or partially oriented feeder yarns by embedding yarn filaments in wax, slicing the wax into thin sections with a microtome and mounting them on glass slides. Then make a photoenlargement from the negative that will be eight times larger than the original negative. (This procedure is an improvement over the one described in Column 18, lines 37-49 of U.S. Pat. No. 4,245,001.) It is important to note that drafting of undrawn or partially oriented filaments does not change the shape of the filaments. Thus, except for the inherent difficulties in preserving accurate representations of the fiber cross-section at 500X or greater and in cutting fully oriented and heatset fibers, the geometrical characterization can be accomplished using measurements made from the photoenlargements of fully oriented and heatset filaments.
2. Measure Dmin, Dmax, L.sub.W and L.sub.T using any convenient scale. These parameters are shown in FIG. 2, for instance, and are defined as follows:
a. Dmin is the thickness of the wing member for essentially uniform wing members and the minimum thickness close to the body section when the thickness of the wing member is variable.
b. Dmax is the maximum thickness of the body section as shown in FIG. 2.
c. L.sub.T is the overall length of the filament cross-section.
d. L.sub.W is the overall length of an individual wing member.
In all cases the above dimensions are measured from the outside of the "black" to the inside of the "white" in the photomicrograph. It was found more reproducible measurements can be obtained using this procedure. The "black" border is caused primarily by the nonperfect cutting of the sections, the nonperfect alignment of the section perpendicular to the viewing direction, and by interference bands at the edge of the filaments. Thus it is important in producing these photographs to be as careful and especially consistent in the photography and measuring of the cross-sections as is practically possible. Average values are obtained on a minimum of 10 filaments.
3. Measure the radius of curvature (Rc) of the intersection of the wing member and body section as shown in FIG. 2. Use the same length units which were used to measure Dmax, Dmin, etc. One convenient way is to use a circle template and match the curvature of the intersection to a particular circle curvature. Rc is measured at the two possible locations per filament cross-section and the sum total of the Rc's is averaged to get a representative Rc. For example, in FIG. 2 each filament cross-section has 2 Rc's which are averaged to give the final Rc. The averaged Rc's for individual filaments are then averaged to get an Rc which is indicative of the filaments in a complete yarn strand. Rc values are usually determined on a minimum of 20 filaments from at least two different cross-section photographs. It has been found that the ability of these winged cross-sections to provide a usable raw material for fracturing can be characterized by the following combinations of geometrical parameters. ##STR7## where (L.sub.W /Dmin).sup.2 is proportional to the stress at the wing-body intersection if the wing members were considered as cantilevers only and ##EQU12## is proportional to the stress concentration because of retained sharpness of the intersection. For example, see Singer, F. L., Strength of Materials, Harper and Brothers, NY, NY, 1951.
4. To dete
