|
(11) | EP 0 067 385 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||||||
| (54) | Textured nylon-6 filament |
| (57) A textured nylon-6 continuous filament is characterized by the absence of a spherulitic
ring structure along the periphery of the cross section thereof when the cross section
is viewed under polarized light. |
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates generally to textiles, spinning, twisting, and twining. More particularly, the invention relates to a crimped, continuous nylon-6 filament.
Prior Art Background
[0002] In the majority of textile products, two important functional properties are required--viz., protection and thermal insulation-- both.of which can be statis- fied by adequate bulkiness of the product. In general, a bulky product will have to be made of a bulky fiber or filament, as the basic constructional element of any textile product is the fiber or filament.
[0003] As a consequende, a considerable effort has been made over the years to impart higher bulk to fibers and filaments by texturing or crimping thereof, especially those which are man-made for example, from polyamides such as nylon-6. The present invention is an improved crimped, continuous nylon-6 filament.
Statement of Closest Known Prior Art
[0004] The closest prior art of which the inventors are aware is set forth below.
1. U.S. 3,186,155, Breen, et al., discloses a mono- component synthetic organic filament, such as a nylon-6 filament, which has: (a) alternate S and Z twist sections throughout its length; (b) a random number of turns between twist reversals; (c) a random, continuously varying angle of twist along its length; a random number of twist reversals per inch; at least one S turn and at least one Z turn per inch which have a twist angle averaging-at least 5 degrees.
2. U.S. 4,096,226, Martin, et al., discloses the production of a crimped nylon-6 filament similar to that disclosed in Breen, et al., U.S. 3,186,155, supra. However, the Martin process is an integrated process, in contradistinction to that of Breen, wherein the following steps are effected in immediate succession: (a) melt spinning; (b) drawing the spun filaments at a draw ratio such that the drawn filaments on leaving the drawing stage have an extensibility of between 20 and 35 percent; and (c) texturing the drawn filaments at a velocity of between 800 and 3,000 meters per minute by an air jet process, the temperature of the filaments being between 50 and 180 °C prior to texturing.
3. U.S. 3,975,484, Okada, et al., discloses the production of a crimped nylon-6 filament similar to that disclosed in Breen, et al., U.S. 3,186,155, supra, by a process somewhat similar to that disclosed in Martin, et al., U.S. 4,096,226, supra. Non-circular cross section polyamide filaments are melt spun, allowed to cool, and treated with an oil. Thereupon the filaments are passed around a feed roll having a peripheral speed of more than about 200 meters per minute, passed in contact with a heated body through a contact angle between about 80 ° and 160 ° with the surface temperature of the heated body maintained in the range of about 170°-250°C. The filaments are thereby subjected to one-sided heating and drawing, whereupon they are passed through a steam jet crimper which is supplied with steam at a temperature in the range of about 200-350°C.
4. Theijin Limited, British 1,565,007, discloses a nylon-6 multifilament yarn wherein the individual filaments have an internal microstructure characterized by α-typecrystallinity in combination with y-type crystallinity in a given proportion. In particular, each of the individual filaments of the yarn has a birefringence of at minimum 0,045, a maximum denier of 0.8, an an x-ray diffraction intensity ratio statisfying a specific equation.
[0005] None of the filamentary products described above is dexdribe as having no characteristic spherulitic ring structure along the periphery of the cross section thereof when the cross section is viewed under polarized light. Spherulitic rings normally have a diffused transition to a non-spherulitic core. The depth of the spherulitic ring varies usually from about 10 to about 20 µ.
[0006] Completely unsuggested by the prior art teachings, the crimped nylon-6 continuous filament of the present invention shows a complete absence of a spherulitic ring structure when the cross section thereof is viewed under polarized light. The result of the absence of such a spherulitic ring structure is that the filament is more luxtrous than available prior art filaments under otherwise identical conditions. As a consequende, the fiber producer may increase bulk and cover in a fibrous structure such as a carpet without any loss in luster.
SUMMARY OF THE INVENTION
[0007] In order to furnish a textile fiber which affords increased bulk and cover in a fibrous structure fabricated therefrom without any sacrifice in luster, there is provided a crimped nylon-6 continuous filament characterized by the absence of a spherulitic ring structure along the periphery of the cross section thereof when the cross section is viewed under polarized light.
BRIEF DESCRIPTION OF THE DRAWING
[0008] For a more complete understanding of the present invention, including the primary object and benefits thereof which are set forth immediately above, reference should be made to the Detailed Descritipn of the Preferred Embodiments, which is set forth below. This detailed description should be read together with the accompanying drawing, wherein:
FIG. 1 depicts two cross sections of crimped nylon-6 continuous filaments of the prior art, which show a characteristic spherulitic ring structure along the periphery of the cross sections; and
FIG. 2 depicts two cross sections of crimped nylon-6 continuous filaments according to the present invention, which show a complete absence of the spherulitic ring structure which is characteristic of the prior art filaments shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0009] Referring now to the drawing, FIG. 1 depicts an available crimped nylon-6 continuous filament (1) of the prior art, which is shown in two cross sections thereof as viewed under a microscope under polarized light. A characteristic spherulitic ring (2) is observed along the periphery of the cross sections. Also seen in the cross sections are small particles (4) of a delustrant such as titanium dioxide. The spherulitic ring (2) is comprised of a multiplicity of individual partial spherulites (3), which, although not visible under ordinary conditions, are visible under polarized light. The filaments depicted here have a modification ratio of between about 2 and 3, i.e., the configuration thereof is commonly referred to as "trilobal".
[0010] To determine the modification ratio as well as the presence or absence of a spherulitic ring structure, the following prodecure is employed. A filament or yarn sample is placed in a suitable embedding agent. A thin section thereof is then cut with a microtome. A photomicrograph of this section is then obtained, and the modification ratio (MR) is calculated, with the use of a template, employing the following equation:
wherein DO = Diameter of circumscribed circle to cross section, and
Dl = Diameter of inscribed circle into cross section.
[0011] The presence or absence of any peripheral ring is determined by visual observation of the section, under polarized lighting (phase-contrast or dark field may also be employed); a photomicrograph can also be obtained under these conditions.
[0012] Depicted in FIG. 2 is one embodiment (5) of the crimped nylon-6 continuous filament according to the present invention, which is shown in two cross sections thereof as viewed under a microscope under polarized light. No spherulitic ring is observed along the periphery of the cross sections, as at (6). Seen in the cross sections are small particles (4) of a celustrant such as titanium dioxide. The filaments depicted here also have a modification ratio as discussed above of between about 2 and 3, i.e., the configuration thereof is commonly referred to as "trilobal".
[0013] To be sure, it is not necessary that delustrants such as titanium dioxide be present in the filaments according to the present invention. Indeed, the same advantages and benefits over the prior art are obtained when a filament according to the present invention is substantially free of any delustrant. Moreover, although a modification ratio of between about 2 and 3 is advantageously employed, filaments according to the present invention may have other cross sectional configurations as well, under which conditions the same advantages and benefits over the prior art are observed. That is to say, filaments of the present invention have a higher luster-- as determined visually-or by any of many standard optical methods known to the skilled artisan--when compared with otherwise equivalent filaments of the prior art which have the same level of crimp, or the same level of delustrant in an amount which is substantially below the saturation level thereof, or the same cross sectional configuration.
[0014] As is understood by those of skill in the art, filaments according to the present invention which are substantially free of any delustrant are considered to be very highly lustrous. If not as much luster is desired, one of the delustrants known to those of skill in the art may be employed. These include not only the usual non-chromatic delustrant and fillers such as titanium dioxide, zinc sulfide, calcium carbonate, glass particles, etc., but also delustering agents which impart color as well. Such include organic and inorganic pigments and dyes that are added to the molten nylon-6 polymer prior to or during extrusion and spinning, or to the nylon-6 polymer in chip form in a dyeing operation prior to extrusion and spinning. When titanium dioxide is employed, it is advantageously present in an amount of not greater than about 0.1 percent by weight.
[0015] The crimped nylon-6 continuous filament of the present invention advantageously has a tank bulk of at least.8 percent and a denier of at least 5. Under these conditions it is expecially suitable for use in the fabrication of a large number of textile structures desirable in today's market. Tank bulk is determined by first measuring the length change in a skein of fiber exposed to boiling water unter two loads of approximately 0.0003 g/dtex (L2) and 0.09 g/dtex (L11', respectively. Thank bulk is then calculated employing the following equation:
[0016] Moreover, especially beneficial results are obtained when the crimped nylon-6 continuous filament according to the present invention has a modification ratio of between about 2 and 3 and a denier of between about 5 and 25. Under these conditions, use of the filament according to the present invention results in carpets having outstanding characteristics.
[0017] In addition to showing no spherulitic ring structure along the periphery of the cross section thereof when the cross section is viewed under polarized light, a crimped nylon-6 continuous filament according to the present invention which has a denier of at least 5 is found to have another significant morphological characteristic, viz: the ratio of Y-form nylon-6 to α-form nylon-6 is at least 1 to 1, and often about 3/1 to 3.5/1, as measured on non-heat treated, undeyed, crimped filamentary material. This compares with Y-form to α-form ratios of about 1/3 to 1/3.5 for available prior art products under the same conditions of treatment. However, after heat setting of the crimped filamentary material of the present invention, the α-form is predominant. Such a phenomenon clearly demonstrates that a higher proportion of the entire filamentary structure of the present invention is rearranged during heat setting, thereby increasing heat setting efficiency over that obtained with prior art products. To determine the crystallinity ratios referred to above, the equitorial x-ray diffraction pattern of the sample is measured and recorded continuously between 2 9 values of 12° and 30°. The alpha crystalline form has a peak at 2 0 = 20.0° to 20.5, and another at 2 9 = 23.2° to 24.0°. The pseudo-gamma form has a single peak at about 2 θ = 21.2°. By visual examination of the curve, one can determine the relative preponderance of a particular crystalline form. Such products accroding to the present invention which have a ratio of y-form nylon-6 to A-form nylon-6 are especially desirable when substantially free of any delustrant, or when a delustrant such as titanium dioxide is present therein in an amount not greater than about 0.1 percent by weight. Moreover, modification ratios of between about 2 and 3 are highly advantageous, as is a tank bulk as specified supra of at least about 8 percent.
[0018] Any of the filaments according to the present invention may be employed in a multifilament yarn--e.g., grouped together with other filaments according to the present invention--which may be interlaced and/or twisted, utilizing standard techniques well-know to those of skill in the art, to produce carpets, upholstery, and other such textile structures having outstanding characteristics.
[0019] The present invention, including its object and benefits, may be better understood by reference to the following illustrative examples:
Example 1
[0020] Nylon-6 chips having a relative viscosity of 2.69 as measured in 96-98% sulfuric acid and containing less than 0.01% titanium dioxide were melted in an extruder and spun at a temperature of 265° through two spinnerettes with 99 irregular shaped holes each at a thruput of 335 grams per minute per spinnerette forming two 99 filament threadlines. The spun filaments were quenched with a crossflow of air at approximately 1.2°C, and were lubricated with an oil spin finish comprising a polyalkoxylated alcohol containing essentially no water. The fiber was stretch pre-tensioned 1 1/1%, pre-heated to 45°C, and stretched 3.25X to a speed of 2119 meters per minute and heated to 165°C. The stretched threadlines were crimped in a hot air texturizer such as that in US Patent 3,908,248, and deposited onto a rotating cooling sieve through which air was moved by means of a vacuum. The sieve moved at a velocity ot 45 meters per minute. The threadlines were unraveled from their plug form on the cooling sieve to a speed of 1732 meters per minute established by a cold pair of godets. The yarns were subsequently interlaced in a conventional air jet and wound up under 200 pond tension on a double cup winder. There was no spherulitic ring structure along the periphery of the cross section of the fiber when viewed under a microscope under polarized light. Some of the fiber produced was processed in a commercial space deying operation and exhibited excellent uniformity and bulk/cover. Other fiber was commercially cabled, continuously heatset, tufted, and dyed into an excellent residential type carpet.
[0021] The fiber exhibited physical properties common to Bulked Continuous Filament (BCF) products including:
Example 2
[0022] A procedure essentially equivalent to that of Example 1 was followed, resulting in a product having the following characteristics:
[0024] In order to produce crimped nylon-6 continuous filaments according to the present invention, it is necessary to orient the fiber before allowing any moisture migration into the fiber. This is advantageously accomplished by employing an essentially non-aqueous spin finish, as utilized in the examples above.
[0025] Although the present invention has been described in detail with respect to certain preferred embodiments thereof, it is understood by those of skill in the art that variations and modifications in this detail may be effected without any departure α-from the spirit and scope of the present invention, as defined in the hereto-appended claims.