Patent Application
20130029152
1. Field of the Invention
This invention relates to a poly-trimethylene terephthalate solid core fibrillation-resistant synthetic filament, to a spinneret for producing the filament, and to a carpet made therefrom
2. Description of the Art Background
The ability of a tufted carpet made from synthetic polymeric filaments to retain its textured appearance, or “newness”, tends to degrade over time. One cause of this appearance degradation is known as “fibrillation” that is produced by fraying of the carpet's filaments by use.
Various industry standard test methods, e.g., tetrapod walker test (ASTM D5251), hexapod walker test (ASTM D5252), Vetterman drum test (ASTM D5417), chair castor test and Phillips roll chair test are available to measure texture retention. Carpets samples are graded against a subjective scale after they have been subjected to these tests for predetermined number of cycles.
For example, tests performed on carpets made using petroleum-based poly-trimethylene terephthalate fibers having trilobal cross-section with a modification ratio of 2.0 and a 26.5 degree arm angle show significant fibrillation damage after 20,000 cycles in the Phillips roll chair test. Damaged trilobal filaments extracted from worn carpets after such test show severe deformities. One typical mode of deformation is manifested by adjacent lobes of the originally trilobal filament being bent toward each other, resulting in a filament having an elongated, compacted cross section.
In view of the foregoing it is desirable to produce filaments with cross-sections that are inherently more resistant to fibrillation, and are thereby able to provide superior texture retention during accelerated wear tests described above and exceptional durability in use.
In a first aspect the present invention is directed toward a solid core, fibrillation-resistant, synthetic polymeric filament having three substantially equal length convex sides. Each side meets an adjacent side through a substantially rounded tip centered on a respective circle of curvature spaced from the axis of the filament by a distance “a”. Each rounded tip has a radius substantially equal to a length “b”.
Each tip lies on a circumscribed circle having a radius substantially equal to a length (a+b) and the midpoint of each side lies on an inscribed circle having a radius substantially equal to a length “c”. The filament having a modification ratio (MR) defined by the ratio of the radius (a+b) of the circumscribed circle to the radius (c) of the inscribed circle, wherein:
More particularly,
Preferably, the synthetic polymer is substantially poly-trimethylene terephthalate, and more preferably, the poly-trimethylene terephthalate has a 1,3 propane diol that is biologically produced. Alternately, poly-trimethylene terephthalate may come from renewably resourced routes. The synthetic polymer may be pigmented and/or may have a delusterant therein.
The filament has a tenacity greater than 1.5 grams per denier.
In another aspect the present invention is directed to a carpet made from filaments as described above.
In still another aspect the present invention is directed to a spinneret plate having a plurality of orifices formed therein for forming the solid core fibrillation-resistant, synthetic polymeric filament. Each orifice has a center and three sides with each side terminating in a first and a second end point and with a midpoint therebetween.
In a first embodiment of a spinneret in accordance with this aspect of the invention the first end point of one side is connected to the second end point of an adjacent side by a circular end contour having a radius equal to a dimension “C”. The center point of each end contour is disposed a predetermined distance “D” from the center of the orifice.
In accordance with this embodiment:
In an alternate embodiment of a spinneret in accordance with this aspect of the invention the end contour connecting the first end point of one side to the second end point of an adjacent side is defined by at least two linear edges that intersect in an apex.
The first end point of each side is spaced from the second end point of an adjacent side by a baseline that itself intersects with a reference radius emanating from the center point. The intersection point between the baseline and the reference radius lies a distance “G” along the reference radius from the center of the orifice. The baseline has a predetermined length “2F”. The apex is spaced a dimension “E” from an intersection of the baseline and the reference radius.
In accordance with this embodiment:
Regardless of the form taken by the end contour, each side of the orifice may be either substantially concave or substantially linear.
If orifice has substantially concave sides, each side lies on a reference circle having a radius of dimension “B”. The center of the reference circle is located on a reference radius emanating from the center point of the orifice and passing through a midpoint of a side. The center of the reference circle is disposed a predetermined distance “A” along the reference radius from the central axis of the orifice.
The outermost point on each circular end contour lies on a circumscribed circle having a radius “(C+D)” (as defined above) centered on the center of the orifice. The midpoints of each side lying on a inscribed circle having a radius “H”. [In the case of an orifice with concave sides the radius “H” is equal to the value (A−B)].
The orifice has a modification ratio (“MR”) defined by the ratio of the radius (C+D) of the circumscribed circle to the radius “(A−B)” of the inscribed circle, thus,
“MR”=(C+D)/“(A−B)”,wherein
If orifice has substantially linear sides with circular end contours the outermost point on each end contour again lies on a circumscribed circle having the radius “(C+D)” (as defined above) centered on the center of the orifice while the midpoints of each side lying on a inscribed circle having the radius “H” centered on the center of the orifice.
In the case of an orifice with linear sides and circular end contours the distance “H” (i.e., the radius of the inscribed circle) lies in the range from:
The modification ratio (“MR”) for such an orifice with substantially linear sides is also defined by the ratio of the radius (C+D) of the circumscribed circle to the radius “H” of the inscribed circle, thus,
“MR”=(C+D)/“H”.
The modification ratio (“MR”) lies in the range from about 1.6<“MR”<about 2.5; and more particularly, the modification ratio (“MR”) lies in the range from about 1.7<“MR”<about 2.3.
For orifices having linear sides and linear end contours the distance “H” (i.e., the radius of the inscribed circle) lies in the range from:
The modification ratio (“MR”) for orifices having linear sides and linear end contours is also defined by the ratio of the radius (E+G) of the circumscribed circle to the radius “H” of the inscribed circle, thus,
“MR”=(E+G)/“H”
The modification ratio (“MR”) lies in the range from about 1.6<“MR”<about 2.5, and more particularly, the modification ratio (“MR”) lies in the range from about 1.7<“MR”<about 2.3.
The invention will be more fully understood from the following detailed description taken in connection with the accompanying Figures, which form a part of this application and in which:
Throughout the following detailed description similar reference numerals refer to similar elements in all figures of the drawings.
The filament 10 is preferably fabricated from a poly-trimethylene terephthalate polymeric material. More preferably, the poly-trimethylene terephthalate polymeric material wherein the 1,3 propane diol is biologically produced, although it should also be understood that the 1,3 propane diol derived via a petroleum route may also used in combination with biologically based 1,3 propane diol.
The polymeric material may be pigmented with a solution dyed color additive or a delusterant such as TiO2. Alternatively, the polymeric material may be non-pigmented for later dying. The polymeric material may contain UV stabilizers, anti-oxidants and/or other performance-improving additives (including toughening agents and/or nucleation-inhibiting agents).
The filament may also be fabricated from other polymeric materials, such as polyester, nylon, polypropylene and blends thereof.
As seen from
Each respective side 121, 122, 123 meets with a side adjacent thereto through a substantially rounded tip 141, 142, 143, respectively. The rounded contour of each tip 141, 142, 143 lies on a circle of curvature centered on a respective center point 161, 162, 163. The radius of the circle of curvature of the tips 141, 142, 143 is indicated by the reference character “b”. Each center of curvature 161, 162, 163 is itself spaced by a predetermined distance “a” from the central axis 10A of the filament. Only one center of curvature (161) is shown for clarity of illustration
The outermost point of each tip 141, 142, 143 of the filament 10 lies on a circumscribed circle 24 having a radius substantially equal to a length (a+b). The midpoint 12M1, 12M2, 12M3 of each respective side 121, 122, 123 lies on an inscribed circle 26 centered on the central axis 10A of the filament 10. The radius of the inscribed circle 26 is substantially equal to a length “c”. Accordingly, the filament 10 exhibits a modification ratio (“MR”) defined by the ratio of the radius (a+b) of the circumscribed circle to the radius (c) of the inscribed circle, thus: MR=(a+b)/c.
Mathematical modeling of filaments having trilobal cross-section shows that lobes and the sides are susceptible to failure under compressive, bending and/or torsion loads. The effect of these stresses acting upon the filaments result in fibrillation and the corresponding texture degradation of the filament during wear.
Analyses also indicate that maximum bending stress is imposed on the end contour regions of the filament, while maximum torsion and compression forces are imposed substantially centrally along the sides of the filament. For example, the compressive stress (“σ”) at the contact point between two adjacent filaments has been found to be inversely proportional to the square root of filament diameter “d” when filaments are parallel to each other,
thus,σ=d−1/2.
In the case where the where the filaments are perpendicular to each other, the compressive stress (“σ”) is inversely proportional to the ⅔rd power of filament diameter, thus, σ=d−2/3.
As will be developed it is believed that the fiber geometry disclosed by this invention reduces these stress levels, resulting in a filament having improved fibrillation resistant properties. Filaments in accordance with the present invention are believed to overcome weaknesses of round as well as trilobal cross-sections under various loading conditions.
In particular, it has been found that forming a filament with more robust end contours and more robust filament tip region will counteract bending stress imposed on the filament. If the radius of the circle of curvature of the tips 141, 142, 143 is kept large stress levels at tips are lowered below the levels occurring at the lobes of a trilobal cross-section.
Likewise, as opposed to filaments having a round cross-section, configuring the filament with flatter, less concave sides result in filaments more able to retain their shape in the face of forces imposed by use. Filaments with large radii 12R1, 12R2, 12R3 relative to the diameter of a round filament having an equivalent cross-sectional area lead to a substantial reduction in the compressive contact stress over round filaments.
Accordingly, filaments in accordance with the present invention exhibit various dimensional parameters and certain relationships therebetween, as follows:
In a more preferred instance:
Preferably, the filament has a tenacity greater than 1.5 grams per denier.
In another aspect the present invention is directed to a spinneret plate 100 for forming a solid core, fibrillation-resistant, synthetic polymeric filament. The plate 100 is a relatively massive member having a plurality of filament-forming orifices 102 provided therethrough. Each orifice has a center 102A. The plate 100 may be fabricated from a material such as stainless steel. Suitable grades of stainless steel include 440C, 316, 17-4 PH, 430, or Carpenter 20. The steel grade selected should be free of internal defects. Typically the orifices are formed through the plate 100 using machining technology such as laser cutting or electrical discharge machining.
An enlarged view of a portion of the surface of a spinneret plate 100 and one of the orifices 102 formed therein is shown
In general, for each embodiment of this aspect of the invention a filament-forming orifice 102 is an aperture having three substantially equal length sides 1121, 1122, 1123. The midpoint 112M1, 112M2, 112M3 of each side lies on an inscribed circle 113 having a radius “H” centered on the center point 102A of the orifice. Each of the sides 1121, 1122, 1123 terminates in a first and a second end point, respectively indicated in the drawings by the Roman numerals I, II.
The first end point I of any one side is connected to the second end point II of an adjacent side by an end contour 114, 114′. The end contour 114, 114′ in each of the embodiments of
In the embodiments illustrated in
The modification ratio (“MR”) of an orifice is defined as the ratio of the radius of a circumscribed circle of the orifice to the radius of the inscribed circle of the orifice.
In a preferred implementation of this embodiment of the invention shown in
Alternatively, in the embodiments illustrated in
The apex 130 of each end contour 114′ lies on a circumscribed circle 121 centered on the center 102A of the orifice. In these Figures the circumscribed circle 121 has a radius “(G+E)”.
In accordance with this embodiment of the invention shown in
The orifices 102 as illustrated in
In the embodiments of
For orifices having concave sides as shown in
More preferably:
For orifices having concave sides (
As the radius of the circle of curvature of the side of the orifice is increased the contour of the side flattens, until at a very large radius the side becomes close to linear.
For orifices having linear sides and circular end contours (
For orifices having linear sides and linear end contours (
Filaments 10 of desired shapes are obtained when polymer is extruded through the spinneret plate 100 and filaments are pulled through a quench chimney 204 by feed rolls 206. Finish is applied to the filaments 10 for downstream processability by a finish roll 208 located prior to the feed rolls 206. The feed rolls 206 are kept at the room temperature or maintained at a temperature above polymer glass transition temperature to effectively draw and orient molecules during the draw process. Draw rolls 210, running at a predetermined speed faster than the feed rolls 206 by the amount of the draw ratio, are heated to a temperature above the glass transition temperature and below the melting point of the polymer to anneal the drawn fiber. At this point the filaments may be collected by a winder 212 through a let down roll 212 or continue for further processing.
A bulking jet 220 employing hot air or steam is used to impart a random, three-dimensional curvilinear crimp to the filaments. The resulting bulked filaments are laid on to a rotating drum 224 having a perforated surface. The filaments are cooled under zero tension by pulling air through them using a vacuum pump. Water may additionally be misted onto the filaments on the drum 224 to facilitate cooling. After the filaments have been cooled below the glass transition temperature, filaments are pulled off the drum 224. If desired another finish for mill processing may applied by finish roll 226. The filament bundle is interlaced periodically by an interlacing jet 230 disposed between a pull roll 232 and a let down roll 234, and collected by a winder 236.
The yarn is tufted through a primary backing 304 to form pile tufts 306. The pile tufts 306 may take the level loop form shown in
The carpet 300 is completed by a secondary 308 adhered to the primary backing 304 using an adhesive 310.
Other potential end uses of the filaments of the present invention include luggage, handbags, automotive fabrics.
The test chamber 400 comprises a cylindrical barrel 402 closed at one end by an integral base 404. The opposite end of the barrel 402 receives a lid 406. The lid 406 is secured to the rim of the barrel 402 by bolts 408. Both the base 404 and the lid 406 have an array of axially aligned mounting apertures 410 formed therein.
Access to the interior of the barrel 402 is afforded through a port opening 412 provided in the center of the lid 406. The port opening 412 is closed by a removable hatch 416. The hatch 416 is secured to the lid 406 by a screws 418.
To prepare the chamber for a test, bundles of filaments 10 under test are strung between the base 404 and the lid 406 using the mounting apertures 410. The filaments under test may be conveniently secured to the surfaces of the base 404 and the lid 406, as by tape. Any convenient number of ball bearings 420 (
The dynamics of a filament test using the test chamber 400 are illustrated in
Fiber cross-section images of the filaments tested using the test chamber 400 indicate fibrillation damage to the filaments that is similar to the fibrillation damage done to filaments of a carpet subjected to any of the various industry standard test methods used to measure texture retention. The similarity of fibrillation damage lends confidence to conclusions regarding the fillibration resistance of filaments tested using the chamber 400.
Using a spinning arrangement as shown in
Filaments produced had the following properties:
Two hundred sixty filaments were strung through the rotating ball mill test chamber 400, described earlier, under a tension of approximately 20 gm without imparting any substantial twist to the yarn bundle. One hundred 9 mm stainless steel ball bearings were placed in the chamber. The test was conducted for 16 hours at 100 rpm.
Cross-sectional images of yarn bundles were obtained before and after the 16 hour test using a Hardy plate and an optical microscope and are shown in
Using a spinning arrangement as shown in
Two hundred seventy two filaments were strung through the rotating ball mill test chamber 400, described earlier, under a tension of approximately 20 gm without imparting any substantial twist to the yarn bundle. One hundred 9 mm stainless steel ball bearings were placed in the device. The test was conducted for 16 hours at 100 rpm. Cross-section images of yarn bundles were obtained before and after the 16 hour test using a Hardy plate and an optical microscope and are shown in
Using a spinning arrangement as shown in
The temperature set points for downstream barrels of the 28-mm Warner & Pfleiderer twin extruder, transfer line, pumps, pack and die were in the range of 268-270° C. The spinning throughput was 30 grams per minute. The molten filaments were cooled in the chimney, where the room air was blown past the filaments using a profiled quench with air velocity in the range of 21-30 feet per minute as a function of distance from the spinneret face with higher velocity near the spinneret. Filaments were pulled by a pair of feed rolls at 60° C. at a surface speed of 500 meters per minute through the quench zone. Filaments were coated with a lubricant immediately prior to the feed roll. The coated filaments were drawn by a draw ratio of 3 and annealed by a pair of rolls heated to 160° C. with a surface speed of 1500 meters/minute. The filaments were then wound.
Filaments produced had the following properties:
Two hundred sixty filaments were strung through the rotating ball mill test chamber 400, described earlier, under a tension of approximately 20 gm without imparting any substantial twist to the yarn bundle. One hundred 9 mm stainless steel ball bearings were placed in the device. The test was conducted for 16 hours at 100 rpm. Cross-section images of yarn bundles were obtained before and after the 16 hour test using a Hardy plate and an optical microscope and are shown in
Fibrillation-resistant behavior of cross-section of a filament in accordance with the present invention is easily seen from comparison of the image in
