Composite filament yarn and process and spinneret for manufacturing the same

Abstract

 A polyamide/polyurethane composite filament yarn, which filament comprises a polyamide sheath component and a polyurethane eccentric core component exposed with a neck portion of uniform width on the surface of the filament, is manufactured by a process comprising inserting, immediately before extruding from a spinneret orifice, a molten polyurethane flow obliquely from upwards and incorporating said polyurethane flow eccentrically into a molten polyamide flow flowing down in said conduit, while a small part of said polyurethane flow radially projected in a restricted width penetrating through the thinnest portion of said polyamide flow flows down along the inner wall of said conduit. For this process, an employable spinneret comprises a leading duct for polyamide connecting to an orifice via a vertical conduit, another leading duct for polyurethane connecting to an injection pipe obliquely extending therefrom, protruding into said conduit, opening immediately before said orifice and having a slit extending longitudinally at the under side along the entire protruded length.

Description

[0001] The present invention relates to polyamide/­polyurethane composite filament yarns having a crimpability, a process and a spinneret for manufactur­ing the same and hosiery, such as stockings or the like, knitted therewith.

[0002] It is known that composite filaments consisting of polyamide and polyurethane components conjugated eccentrically with each other in a unitary filament have an excellent crimpability (Japanese Patent Application Publication Nos. Sho-55-22,570 and 55-27,175). However, side-by-side type composite filaments, for example, such as shown in Fig. 4, though these are excellent in crimpability, have a drawback such that separation of the components and deterioration of physical properties are caused by bending or abrasion during processing steps or wearing of textile articles composed of such filaments, due to insufficient compatibility of the both components. Another drawback is polyurethane components exposed on the surface of the filament stick to each other due to retarded solidification of polyurethane melt, so that as-spun and wound filament yarns cannot be unwound from a yarn package due to sticking.

[0003] Alternatively, whereas sheath and kidney-like core type composite filaments as shown in Fig. 5 which have been proposed, for example, in Japanese Patent Application Publication No. Sho-55-27,175, have solved the problems presented by the side-by-side type composite filaments, such filaments still have a drawback that a crimp developability by virtue of difference in shrinkage between a high shrinking polyurethane component and a low shrinking polyamide component is poor because the polyurethane core component is completely surrounded with the polyamide sheath component.

[0004] Further, even in combination of a polyamide component with a polycarbonate based polyurethane component, which has been accounted relatively good in compatibility, the adhesiveness between these components are yet insufficient, so that there occurs a phenomenon such that two components split during yarn manufacturing process or wearing of stockings, or the like. For example, in sheath and kidney-like core type composite filaments as shown in Fig. 5, external stresses, such as elongation, bending, abrasion, heat treatment, or the like, concentrate on thin edge portions, C₁∼C₂ and C₁′∼C₂′, where the sheath eventually breaks and the two components separate from each other along the line C₁∼C₁′.

[0005] Therefore, in order to solve those problems of poor adhesiveness of two components, inferior abrasion resistance of articles and sticking of polyurethane components to each other, with which attended are polyamide/polyurethane side-by-side type composite filament yarns, we, the inventors, have proposed in Japanese Patent Application Laid-open No. Sho-63-256,719, as a composite filaments having an excellent crimpability as compared with the above-­mentioned sheath and kidney core type composite filaments, composite filaments as shown in Fig. 6 wherein the most part of a polyurethane component is surrounded with a polyamide component and a small part of the polyurethane component is exposed on the surface of the filament, and a process for spinning such composite filaments with a spinneret as shown in Fig. 2. Namely, the spinneret shown in Fig. 2 comprises a vertical conduit 2 extending from a polyamide leading duct 1, having an orifice 3 of small diameter opening downwards, and an injection pipe 5 extending obliquely downwards from a polyurethane leading duct 4, protruding the tip end portion into said conduit 2. The degree of the protrusion is adjusted to an extent that the inner circumference of the opening tip end of the injection pipe 5 is just tangent internally to the inner circumference of the conduit 2. With such a spinneret, incomplete sheath and core type composite filaments as shown in Fig. 5 are obtained, wherein a polyurethane component B tangent internally to a polyamide component A is barely exposed at the contact point on the surface of the filament.

[0006] In the cross-sectional shape of such a filament, the polyamide component A surrounds the most part of the polyurethane component and decreases gradually its thickness along the periphery, so that stress concentration as aforementioned is relaxed so that excellent adhesion is obtained between the polyamide and polyurethane components, not allowing the both components to split easily and sticking of polyurethane components to each other can be prevented between as-spun filament yarns wound on a take-up roll.

[0007] However, whereas the above-mentioned composite filaments proposed by the present inventors, provided with excellent physical properties, have succeeded in obviating all of the aforementioned prior art difficulties, these filaments have been found to have another drawback such that when the spinning is conducted with the above-mentioned spinneret, the cross-­sectional shape of the filament, particularly the width d in Fig. 6 of the exposed polyurethane component, largely varies due to fluctuation of melt viscosity caused by a slight temperature variation.

[0008] Further, both the side-by-side type and sheath and kidney-like core type filaments are attended by a problem of fisheyes caused by a poor stability of polyurethane melt during spinning.

[0009] By the fisheye is meant a local thick portion in drawn filament after spinning, winding and drawing, which causes a poor draw-twisting operability of undrawn filament yarns as well as inferior qualities of articles, such as stockings, composed of the filament yarns.

[0010] Throughout this specification, the number of fisheyes is a value obtained by counting thick portions having a diameter five times the normal diameter of the unitary filament constituting a drawn yarn and converting the count to the number per 1 kg of the filament yarn.

[0011] The first object of the present invention is to constantly provide uniform, incomplete sheath and core type composite filaments consisting of a polyamide and a polyurethane, with excellent physical properties, such as crimpability, abrasion resistance or the like, and exhibiting a good processability with a restrained stickiness of undrawn yarns.

[0012] The second object is to largely reduce fisheyes of drawn yarns by passing a polyamide/polyurethane composite polymer through a constriction in a nozzle to effect fluid orientation.

[0013] A process for manufacturing composite filaments according to the present invention is, in spinning by extruding molten polyamide and polyurethane components simultaneously from a spinneret orifice through a vertical conduit, characterized in that a molten polyurethane component flow is inserted obliquely from upwards and incorporated eccentrically into a molten polyamide component flow flowing down in said conduit, while a small part of said polyurethane component flow radially projected in a restricted width penetrates through the thinnest portion of said polyamide component flow and flows down along the inner wall of said conduit, immediately before being extruded from said spinneret orifice.

[0014] In the above manufacturing process, it is preferred that said polyamide component has a relative viscosity of 2.0∼2.6 determined with 10 mg/mℓ solution in 95.7% sulfuric acid and said polyurethane component has a melt viscosity at 210°C of 20,000∼50,000 poise.

[0015] The above manufacturing process is preferred to further comprises passing the incorporated molten polymer components successively through a constriction and an expanded conduit before extrusion.

[0016] The spinneret of the invention to be used for conducting the above manufacturing process is characterized by a leading duct for the polyamide component connecting to an orifice via a vertical conduit, another leading duct for the polyurethane component connecting to an injection pipe obliquely extending therefrom which injection pipe penetrates and protrudes into said conduit, opening immediately above said orifice and has a slit extending longitudinally at the under side along the entire protruded length.

[0017] The above injection pipe is preferred to have an inside diameter of 30∼80% of that of the conduit.

[0018] Further, said slit is preferred to have, in its projected figure on a horizontal plane, a length of 2∼20% of the inside diameter of said conduit and a width of 0.2∼10% of the circumference of said conduit.

[0019] The spinneret of the invention preferably has a constricted portion between an opening level of the injection pipe and the orifice. This constricted portion is preferred to have a ratio of the length L to the bore diameter D in the range defined by the following equation:
L/D = 1.0 ∼ 3.0

[0020] In the spinneret of the invention, the conduit preferably expands divergently from the constricted portion towards the orifice.

[0021] Further, it is preferred that the constricted portion has a bore diameter in the range of 0.20∼0.45 mm, preferably 0.25∼0.40 mm, and the orifice has an opening diameter in the range 0.5∼0.7 mm.

[0022] The above-described process and spinneret can provide a composite filament yarn of the invention comprising a polyamide sheath component and polyurethane core component arranged eccentrically in said polyamide sheath component in the cross-section of a unitary filament, which is characterized in said polyurethane core component is exposed substantially in a uniform width on the surface of the filament via a polyurethane neck portion penetrating a thin portion of said polyamide sheath component to the surface of the filament.

[0023] In the above composite filament yarn, the polyurethane core component is preferred to be exposed substantially in a uniform width between 2% and 25%, preferably between 3% and 15%, of the circumference of the filament.

[0024] In a preferred embodiment of the composite filaments of the present invention, said exposed width has a standard deviation of not exceeding 2.0%, ideally not exceeding 1.6%, about a mean value.

[0025] Further, the composite filaments of the invention are preferred to have a cross-sectional shape of the polyamide sheath component wherein a thin portion having a thickness of not more than 1/20 of the diameter of the composite filament, extends by a width of not exceeding 1/5, preferably 1/10, of the diameter of the composite filament, and terminates suddenly reducing the thickness. With such a shape, it is easy to maintain a uniform exposed width of the polyurethane core component.

[0026] The conjugate ratio of the polyamide and polyurethane components is preferably 40/60∼80/20, more preferably 45/55∼70/30, by volume.

[0027] In the above preferred embodiment of the process and spinneret of the invention can provide composite filament yarns having not more than 1,000 fisheyes/kg, preferably not more than 500 fisheyes/kg after drawing.

[0028] The present invention will be explained in more detail hereinafter by way of example with reference to the appended drawings.

Fig. 1 is a schematic vertical cross-sectional view illustrating a spinneret of the invention to be employed in the process of the present invention;

Fig. 2 is a schematic vertical cross-sectional view illustrating a conventional spinneret;

Fig. 3 is a cross-sectional view showing arrangement and shape of the composite filament of the present invention;

Fig. 4 is a cross-sectional view showing a conventional side-by-side type composite filament;

Fig. 5 is cross-sectional view showing a conventional kidney core and complete sheath type composite filament; and

Fig. 6 is a cross-sectional view showing a known core and incomplete sheath type composite filament.

[0029] Referring to Fig. 1, a molten polyamide component is supplied from a polyamide leading duct 1 into a vertical conduit 2 and then extruded from a spinneret orifice 3. A molten polyurethane component is supplied from a polyurethane leading duct 4 and injected through an injection pipe 5 into the conduit 2. This injection pipe 5 extending obliquely from the duct 4, penetrates and protrudes into the conduit 2 and opens immediately before the orifice 3. The inside diameter of the injection pipe 5 is determined in the range between 30% and 80% of the inside diameter of the conduit, depending upon the conjugate ratio of the both components. Additionally, in order to dispose the polyurethane component with an appropriate eccentricity to provide resulting composite filament yarn with a good crimpability, the length of the protrusion and the slanting angle of the injection pipe 5 may be adequately selected so that, in the projected figure on a horizontal plane of the pipe, the inner circumference at the tip end opening of the pipe may reach a distance of about 1/2∼3/4 of the diameter of the conduit 2 and the projected length α of the generating line at the under side of the inner periphery of the pipe may be about 2∼20% of the diameter of the conduit 2.

[0030] One of the most important features of the spinneret according to the present invention is that the injection pipe 5 is provided at its under side with a slit 6 extending along the entire length β of the portion protruded into the conduit. Here, by the under side is meant a portion along the lower generating line in a vertical plane including the longitudinal axis of the pipe. If the position of the slit deviates from the under side, disposition of a neck portion as will be illustrated hereinafter that is formed by the slit also deviates from the thinnest portion of the polyamide sheath, so that the crimpability of the resulting composite filament yarns will be undesirably deteriorated. Further, the slit 6 is preferred to have a width of about 0.2∼10% of the circumference of the conduit 2. If the width is less than 0.2%, the objective cross-sectional conjugate shape cannot be obtained and a core and complete sheath type may be formed. Alternatively, the width should not exceed 10.0%, because when it exceeds 10.0%, the polyurethane component is exposed so excessively on the surface of the filament that drawbacks of side-by-side type composite filament yarns, such as poor abrasion resistance and intense stickiness of wound undrawn yarns, will appear.

[0031] By applying such an injection pipe, the polyurethane component flow is incorporated, with appropriate conjugate ratio and eccentricity, to the polyamide component flow flowing down in the conduit 2, while a part of the polyurethane component flow which is radially projected in a restricted width and penetrates through the thinnest portion of said polyamide flow up to the inner wall of the conduit flows down from the above-described slit 6 along the inner wall of the conduit 2. The projected part of the polyurethane core component is interposed between two split thin portions of the polyamide sheath component. The thus conjugated polymer flow is spun from the orifice 3 to form a composite filament. In this case, since the injection pipe is positioned to open its protruded portion into a level immediately above the orifice, the relative arrangement of the both components is preserved in the spun filament, substantially without being disturbed.

[0032] The spinneret to be employed in the present invention is preferred to have a constricted portion 7 in the conduit for the polyamide/polyurethane conjugated flow to pass through. The constricted portion is most preferred to have a ratio of the length L to the bore diameter D in the range defined by the following equation:
L/D = 1.0 ∼ 3.0
Further, the constricted portion through which the polyamide/polyurethane conjugated flow passes is preferred to have a bore diameter in the range of 0.20∼0.45 mm, preferably 0.25∼0.40 mm, and the conduit after the constricted portion to the orifice is preferred to expand like a trumpet 8 having an opening diameter in the range of 0.5∼0.7 mm. The conjugated molten polyamide/polyurethane components flowing through the constricted portion of 0.20∼0.45 mm diameter are fluid oriented whereby fisheyes of the composite filament yarns can be largely reduced. Thus, no more than 1,000 fisheyes, preferably no more than 500 fisheyes, per 1 kg of yarn, are counted in the composite filament yarn of the present invention produced with the spinneret having the constriction, while no less than about 2,000 fisheyes per 1 kg of yarn are counted in the conventional yarns. If the bore diameter of the constricted portion 7 exceeds 0.45 mm, the fisheye restraining effect becomes insufficient. Alternatively, if it is less than 0.20 mm, a pressure loss at the constricted portion is too large to adapt the spinneret to the practical operation.

[0033] Furthermore, the divergent trumpet-like conduit formed after the constriction can mitigate, by virtue of a stress relaxing function, a kneeing phenomenon (bending of the extruded polymer immediately after spinning) and prevent filament breakages due to depositing of polymer decomposition products on the rim of the orifice.

[0034] In Fig. 3 showing a cross-section of the thus formed composite filament, a polyurethane core component B is disposed, with adequate conjugate ratio and eccentricity, in a polyamide sheath component A and the polyurethane core component is uniformly exposed on the surface of the filament by a polyurethane neck portion D penetrating the thinnest portion C of said polyamide sheath component A.

[0035] By selecting appropriately the dimension and arrangement of the above-described injection pipe, the exposed width of the neck portion D on the surface of the filament becomes substantially uniform in the range of between 2% and 25%, preferably between 3% and 15%, of the circumference of the filament. If the exposed width is smaller than the above range, the crimpability becomes insufficient, while if the exposed width is too large, it is not preferred because there is apt to appear an ill effect of stickiness as well as deterioration of abrasion resistance due to separation of the two components.

[0036] By virtue of formation of the neck portion D by the aforementioned injection pipe, the shape and exposed width of the neck portion are made uniform and the variation thereof due to influence of temperature condition change or the like becomes extremely small, so that the variation of the exposed width is restrained in a standard deviation about a mean value of not more than 2.0%, in a preferred embodiment not more than 1.6%, within a lot of the same specification, not to mention in the same filament.

[0037] Accordingly, uniform polyamide/polyurethane composite filament undrawn yarns with reduced stickiness can be obtained and knit operability of these yarns is improved, whereby knitted goods of excellent qualities can be obtained with largely decreased knitting defects such as barré or the like.

[0038] The conjugate ratio of the polyamide component to the polyurethane component is preferably within the range of 40/60∼80/20, more preferably 45/55∼70/30, by volume. Satisfactory crimp properties are obtained in the above range.

[0039] Preferable polyamide applicable to the present invention are poly-ε-capramide and copolymers thereof containing not more than 30 mole % of copolymerizable component. Of course, other known polyamides, such as polyhexamethylene adipamide, copolymers thereof, blend polymers thereof, or the like, can be applied.

[0040] Suitable polyurethanes applicable to the present invention are thermoplastic polyurethane elastomers having a hardness of 90∼100, that is determined in accordance with JIS K-6301, the testing method of Shore hardness (A-type). As an example, mention may be made of polyester based polyurethanes, polycaprolactone based polyurethanes, polycarbonate based polyurethanes, or the like. Polyurethanes having a hardness of less than 90 are difficult to balance the melt viscosity with polyamides (difficult to spin with stability), while polyurethanes having a hardness of exceeding 100 are apt to be low in elastic recovery.

[0041] Polyurethane elastomers given a crosslinkage structure in molecules by melt-blending a polyisocyanate compound prior to conjugate spinning, are also preferred for their excellent heat resistance, crimpability and compatibility with polyamides.

[0042] Additionally, from the viewpoint of stickiness, more preferable polyurethanes are polycarbonate based polyurethanes, most preferably polyurethanes comprising soft segments of polycarbonate/polyester blend (blend ratio of two components being 8/2∼4/6).

[0043] It is preferred that the polyamide components to be applied to the process according to the present invention has a relative viscosity within the range of 2.0∼2.6, determined with 10 mg/mℓ solution in 95.7% sulfuric acid, while the polyurethane components have a melt viscosity of 20,000∼50,000 poise, determined with a flow-tester at 210°C. If the viscosity difference decreases beyond the above range, a satisfactory crimpability cannot be assured, while if the viscosity difference is too large, stabilized spinning operation may possibly be impeded due to the aforementioned kneeing phenomenon.

[0044] The spun filament yarn is taken up on a bobbin after solidification by quenching, and then the wound as-spun yarn is drawn at an appropriate draw ratio and further subjected to heat treatment, etc., followed by winding on a pirn, according to the conventional process. Alternatively, after melt-spinning and quenching, the as-spun yarn is, without being taken-up on a roll, subjected to direct drawing or heat treatment. The present invention includes both the above processes.

[0045] The polyamide/polyurethane composite filament drawn yarns according to the invention are preferred to have a shrinkage in boiling water of generally 5∼30%, more preferably 7∼25%. If it exceeds 30%, the yarns excessively shrink in the heat treatment process after knitting, so that short sized knitted goods are yielded, while if less than 5%, sufficient crimps do not develop in the heat treatment process after knitting and the articles such as stockings will be lack in stretchability.

[0046] The heat treatment is preferred to be conducted continuously at a relax ratio slightly larger than the shrinkage in boiling water determined with drawn yarns. When the relax ratio during a relax heat treatment is smaller than the shrinkage in boiling water of drawn yarns, the wound yarns develop feeble crimps, while in the case where the heat treatment is conducted at a relax ratio fairly larger than the shrinkage in boiling water, the heat-treated yarns develop ripple-like fine crimps like an elongated spring.

[0047] As a relax heat treatment, there may be a process of heating the yarns traveling through a tube heater with air as a heating medium, a process of hot plate heat treatment wherein the yarns travel on a plate heater, or the like.

[0048] Composite filament yarns according to the present invention are desirably composed of 1∼10 constituent filaments of 3∼30d and have a total fineness of 5∼50d. In particular, as material yarns for stockings which require transparency, it is desired that the total fineness is in the range of 5∼30d and the number of the constituent filaments is in the range of 1∼6. If the unitary filaments constituting the yarn have a fineness of less than 3d, the stockings show an insufficient durability when they are worn. While if more than 30d, the stockings will have stiff hand. Further, the stockings in the present invention include all of the overknee stockings, full length stockings and panty hoses.

[0049] In the case of core and incomplete sheath type composite filaments wherein a polyurethane core component is disposed at the eccentric extremity in cross-section and barely exposed on the surface of the filament, the exposed width is largely varied by a slight change of conditions, as described hereinbefore, resulting in uneven crimp properties, posing a problem of low abrasion resistance and causing local stickiness due to exposed polyurethane components. In contrast, the composite filament yarns of the present invention, since the neck portion has a width evenly stabilized in appropriate size, are prominently excellent in crimp properties, durability and processability. Further, defects of knitted goods, such as barré or the like, decrease largely, whereby knitted goods having excellent qualities can be obtained.

[0050] Furthermore, according to the preferred embodiment of the manufacturing process of the invention, there can be obtained polyamide/polyurethane composite filament drawn yarns having excellent crimp properties and abrasion resistance as well as improved processability and good quality with largely decreased fisheyes. The composite filaments of the present invention can be used alone or in combination with other kinds of fibers, such as polyamide fibers, cotton fibers, polyurethane core covering yarns or the like, according to conventional processes, such as doubling, ply-twisting, intermingling, mix-knitting, mix-weaving or the like. Thus, the composite filament yarns of the invention are suitable for textile products, such as stockings, tights, ladies' lingerie and foundation garments or the like.

[0051] The present invention will be further illustrated in more detail by way of example.

[0052] In the examples and comparative examples, shrinkage percentage, stretch percentage and abrasion resistance which represent crimp property are determined according to the following methods:

[0053] An undrawn yarn is drawn and heat-treated in relax and formed into a skein about 56.25 cm long. Let the length when a load of 0.2 g/d is applied be the initial length ℓ₀. Then a load of 1 g is applied and a crimp developing treatment is conducted in boiling water for 10 minutes. After standing overnight, the length ℓ₁ is determined as the 1 g load is attached.

[0054] The shrinkage percentage is found according to the following equation (1):
Shrinkage percentage (%) = (ℓ₀-ℓ₁)/ℓ₀×100      (1)

[0055] Similarly, a sample in the form of skein is applied with a load of 250 mg and treated in boiling water for 10 minutes followed by standing overnight and then the initial length ℓ₂ is determined. Further applying a load of 0.2 g/d, the length ℓ₃ is determined. The stretch percentage is found according to the following equation (2):
Stretch percentage (%) = (ℓ₃-ℓ₂)/ℓ₂×100      (2)

[0056] The yarn after drawing and heat treatment in relax is circular knitted. After continuously repeating abrasion with a load of 1 kg, separation of two components on the surface of the knitted goods is microscopically observed and evaluated.
Grade 3: no separation observed after 3,000 cycle abrasion.
Grade 4: no separation observed after 5,000 cycle abrasion.

[0057] The quality of the knitted goods is evaluated by observing barré defects of the circular knit which is knitted at a rotation rate of 600 r.p.m. with a usual tubular knitting machine having 4 feeders (400 needles) and then heat-treated in relax in boiling water to develop crimps.

Example 1

[0058] Nylon-6 having a relative viscosity of 2.35 and a polycarbonate based polyurethane having a melt viscosity at 210°C of 32,000 poise and a Shore A hardness of 95 were separately melted and then metered separately at a volume ratio of 50:50. The molten two polymers were conjugate spun, at a take-up speed of 500 m/min., from a spinneret for conjugate spinning as shown in Fig. 1, to form an undrawn yarn of 55d/2f. The spinneret for conjugate spinning used therefor had a conduit of 2 mm I.D. and a polyurethane injection pipe of 1 mm I.D. and 1.26 mm O.D. The conduit and the polyurethane injection pipe made an angle of 35° and the distance between the lowest point of the inner circumference of the tip end opening of the pipe and the nearest inner wall of the conduit (α in Fig. 1) was 0.16 mm. Further, the length of a slit at the under side of the injection pipe (β in Fig. 1) was 0.4 mm and the width of the slit was varied into 6 sizes as follows:
Width of the slit (mm):0.01, 0.02, 0.10, 0.30, 0.50 and 0.70.

[0059] Then, 6 kinds of taken-up undrawn yarns were drawn and heat-treated in relax, and 6 kinds of composite filament yarns of 17d/2f, Y₁, Y₂, Y₃, Y₄, Y₅ and Y₆, were obtained.

[0060] On the other hand, spinning, drawing and relax heat treatment were conducted under the same conditions as the above except that the conjugate spinning spinneret was a conventional side-by-side type, and a side-by-side type composite filament yarn Y₇ was obtained.

[0061] With respect to the state of spinning of the composite filament yarns Y₁∼Y₆, the melt being extruded from the spinneret orifice was substantially perpendicular to the spinneret face and no kneeing phenomenon was observed. In contrast, when the spinneret for side-by-side type conjugate spinning was used, the kneeing phenomenon was observed in the composite filament yarn Y₇ which bent forming an angle of about 140° with the spinneret face.

[0062] Additionally, as a comparative example, spinning, drawing and relax heat treatment were conducted under the same conditions as above except that a conjugate spinning spinneret as shown in Fig. 2 was used, and a core and incomplete sheath type composite filament yarn Y₈ as shown in Fig. 6 was obtained.

[0063] The microscopically observed cross-sectional shapes and yarn properties of these composite filament yarns Y₁∼Y₈ are shown in Table 1.

Table 1

Item	Width of Slit (mm)	Polyurethane Exposed Width (%)		Crimp Property		Abrasion Resistance 1 Kg × 3000 cycle	Sticking of Undrawn Yarn	Barré of Circular Knit
Sample		Mean Value	Standard Deviation	Stretch (%)	Shrinkage (%)
Comparative Y₁	0.01	0	-	140	60.2	○	○	○
Invention Y₂	0.02	3	0.5	180	66.1	○	○	○
Invention Y₃	0.1	10	0.7	198	68.3	○	○	○
Invention Y₅	0.3	15	1.0	230	69.5	○	○	○
Invention Y₅	0.5	25	1.3	233	70.3	Δ	○	○
Comparative Y₆	0.7	30	1.7	250	72.0	×	×	Δ
Comparative Y₇	-	47	3.4	261	73.2	×	×	×
Comparative Y₈	-	11	2.1	220	69.0	○	○	×

[0064] As shown in Table 1, all of the composite filament yarns Y₂∼Y₅ according to the present invention had a cross-sectional shape of unitary filament wherein a polyurethane core was almost lapped in a polyamide sheath, exposing on the surface of the filament with a neck portion having a uniform width of within 25% of the circumference of the filament. Additionally, the filament yarns of the invention showed good results in crimp properties, abrasion resistance and sticking of undrawn yarns.

[0065] In contrast, the conjugate spinning spinneret provided with an injection pipe having a slit 0.01 mm wide, produced a core and complete sheath type composite filament yarn Y₁. Whereas the yarn Y₁ was good in abrasion resistance and sticking of undrawn yarns, it showed poor crimp properties. Alternatively, the composite filament yarn Y₆ produced with the spinneret provided with an injection pipe having a slit 0.7 mm wide, had a polyurethane neck portion having an exposed width of more than 25% of the circumference of the filament. This yarn Y₆ was poor in abrasion resistance and showed sticking of undrawn yarns. Alternatively, the composite filament yarn Y₇ produced with the conventional side-by-side conjugate spinning spinneret, had a polyurethane component exposed width mean value of 47% of the circumference of the filament with a standard deviation about the mean value of 2.0%. This yarn Y₇ had good crimp properties and, however, bad in sticking of undrawn yarn. Circular knitted goods knitted therewith had an inferior quality due to many barré. Alternatively, the comparative example yarn Y₈ had a polyurethane exposed width mean value of 11% of the circumference of the filament with a standard deviation of more than 2.0%. This yarn Y₈ was good in crimp properties, sticking property and abrasion resistance and, however, circular knitted goods knitted therewith had an inferior quality due to many barré.

Example 2

[0066] Nylon-6 having a relative viscosity of 2.35 and a polyurethane comprising soft segments of a blend polymer of polycarbonate and poly-1,6-hexane adipate (blend ratio of 7/3) were conjugate melt-spun with a spinneret same as that used in spinning of the yarn Y₃ in Example 1 except that the diameter of the orifice was 0.50 mm and a constricted portion was provided. Changing the diameter of the constricted portion, seven kinds of composite filament yarns Y₉∼Y₁₄ of the present invention were obtained.

[0067] Comparative example yarn Y₁₅ was a conventional, eccentric kidney-like core and complete sheath type composite filament as shown in Fig. 5, wherein the conjugate ratio of polyamide to polyurethane was 1/1 in area.

[0068] A conventional side-by-side type composite filament yarn Y₁₆ as shown in Fig. 4 was obtained in the same manner as the yarn Y₁₂ of the present invention excepting the conjugate figure.

[0069] Further, as a comparative example, a polyamide/polyurethane composite filament yarn Y₁₇ was obtained in the same manner except that a conjugate spinning spinneret without the constricted portion was used.

[0070] Then, with a drawing machine provided with a plate heater 20 cm long between 2 rolls (the first roll is heated), the as-spun yarns were drawn on the plate heater at a drawing speed of 400 m/min. and a draw ratio of 3.50. Then, the drawn yarns were heat-treated in relax with a relax heat treatment apparatus provided with a plate heater between 2 rolls and composite filament yarns of 20d/2f were obtained. The appearance of the yarn packages of these resulting composite yarns showed slack, wavy crimps developed. The crimp figure did not change maintaining the slack, wavy crimps, when the yarns were unwound from the yarn package.

[0071] The manufacturing conditions and yarn properties of the drawn yarns obtained from the composite filament yarns according to Examples and Comparative Examples are shown in Table 2.

Table 2

Item	Conjugate Figure	Diameter of Contriction (mm)	Crimp Property		Abrasion Resistance (Grade)	Fisheye	Pressure Loss	Sticking of Undrawn Yarn
Sample			Stretch (%)	Shrinkage (%)
Invention Y₉	Fig. 3	0.45	220	67	4	970	105	○
Invention Y₁₀	"	0.40	228	66	"	720	110	○
Invention Y₁₁	"	0.35	225	67	"	330	140	○
Invention Y₁₂	"	0.30	226	68	"	250	160	○
Invention Y₁₃	"	0.25	222	67	"	140	180	○
Invention Y₁₄	"	0.20	220	67	"	90	230	○
Comparative Y₁₅	Fig. 5	0.30	198	60	"	270	170	ⓞ
Comparative Y₁₆	Fig. 4	0.30	250	71	3	240	150	×
Comparative Y₁₇	Fig. 3	0.50	217	66	4	2600	100	○

[0072] As is seen from Table 2, the fisheyes of the composite filament drawn yarns decrease and the pressure loss increases, according as decrease of the diameter of the constricted portion of the conjugate spinning spinneret orifice. From the relation with the pressure loss, the diameter of the constricted portion should be 0.20∼0.45 mm, preferably 0.25∼0.35 mm.

[0073] It is also understood that the composite filament yarns of the present invention is superior to the side-by-side type composite filament yarns, in respect of abrasion resistance and prevention of sticking of undrawn yarns.

Example 3

[0074] The material yarn Y₁₂ for stockings obtained in Example 2 was knit into leg and foot portions with a 4 feeder hosiery knitting machine at a rotation rate of 900 r.p.m. The knitting operation was conducted without difficulties and the resulting stockings had a good quality. In contrast, the material yarns Y₁₇ having many fisheyes could not knit with stability at the rotation rate of 900 r.p.m. due to formation of barré caused by skip stitch, yarn breakage or fluctuation of knitting tension.

Example 4

[0075] Using the material yarn Y₁₂ for stockings obtained in Example 2 and a bulky, texturized yarn of 13d/3f, stockings having leg and foot portions knitted alternately with these yarns with a four feeder hosiery knitting machine (rotation rate of 600 r.p.m.). The resultant stockings were highly stretchable and excellent in transparency and had a beautiful appearance having very few defects.

Claims

1. A composite filament yarn which comprises a polyamide sheath component and a polyurethane core component arranged eccentrically in said polyamide sheath component in the cross-section of a unitary filament, said polyurethane core component being exposed substantially in a uniform width on the surface of the filament via a polyurethane neck portion extending radially from said core component and penetrating the thinnest portion of said polyamide sheath component to the surface of the filament.

2. The composite filament yarn according to claim 1, wherein the polyurethane core component is exposed in a width of between 2% and 25% of the circumference of the filament.

3. The composite filament yarn according to claim 1, wherein the polyurethane core component is exposed in a width of between 3% and 15% of the circumference of the filament.

4. The composite filament yarn according to claim 2, wherein the exposed width has a standard deviation about a mean value of not exceeding 2.0%.

5. The composite filament yarn according to claim 2, wherein the exposed width has a standard deviation about a mean value of not exceeding 1.6.

6. The composite filament yarn according to claim 1, wherein the polyamide component and polyurethane component are comprised in a ratio of between 40/60 and 80/20, by volume.

7. The composite filament yarn according to claim 1, wherein the polyamide component and polyurethane component are comprised in a ratio of between 45/55 and 70/30, by volume.

8. The composite filament yarn according to claim 1, wherein the polyamide sheath component has a cross-­sectional shape comprising a thin portion having a thickness of not more than 1/20 of the diameter of the composite filament, extending by a width of not exceeding 1/5 of the diameter of the composite filament and terminating suddenly reducing the thickness.

9. The composite filament drawn yarn comprising a polyamide sheath component and a polyurethane core component arranged eccentrically in said polyamide sheath component and exposed in a small width on the surface of the filament, in the cross-section of a unitary filament, which drawn yarn contains not more than 1,000 fisheyes/kg of yarn.

10. The composite filament drawn yarn according to claim 9, which contains not more than 500 fisheyes/kg of yarn.

11. The composite filament drawn according to claim 9, which exhibits a shrinkage percentage in boiling water of between 5% and 30%.

12. A process for manufacturing a composite filament yarn by extruding molten polyamide and polyurethane components simultaneously from a spinneret orifice through a vertical conduit, which comprises inserting a molten polyurethane component flow obliquely from upwards to thereby incorporate said polyurethane component flow eccentrically into a molten polyamide component flow flowing down in said conduit, while a small part of said polyurethane component flow radially projected in a restricted width penetrates through the thinnest portion of said polyamide component flow and flows down along the inner wall of said conduit, immediately before being extruded from said spinneret orifice.

13. The process according to claim 12, wherein the polyamide component has a relative viscosity of between 2.0 and 2.6 determined with 10 mg/mℓ solution in 95.7% sulfuric acid and the polyurethane component has a melt viscosity at 210°C of between 20,000 and 50,000 poise.

14. The process according to claim 12, which further comprises passing the incorporated molten polymer components successively through a constriction and an expanded conduit before extrusion.

15. A spinneret for manufacturing a composite filament yarn comprising a polyamide sheath component and a polyurethane core component arranged eccentrically in said polyamide sheath component in the cross-section of a unitary filament, said polyurethane core component being exposed substantially in a uniform width on the surface of the filament via a polyurethane neck portion extending radially from said polyurethane core component and penetrating the thinnest portion of said polyamide sheath component, which spinneret comprises a leading duct for polyamide component connecting to an orifice via a vertical conduit, another leading duct for polyurethane component connecting to an injection pipe obliquely extending therefrom which penetrates and protrudes into said conduit, opening immediately above said orifice and has a slit extending longitudinally at the under side along the entire protruded length.

16. The spinneret according to claim 15, wherein the injection pipe has an inside diameter of between 30% and 80% of the inside diameter of the conduit.

17. The spinneret according to claim 15, wherein the slit of the injection pipe, in a projected figure thereof on a horizontal plane, has a length of between 2% and 20% of the inside diameter of the conduit and a width of between 0.2% and 10% of the circumference of the conduit.

18. The spinneret according to claim 15, wherein the conduit has a constricted portion between an opening level of the injection pipe and the orifice.

19. The spinneret according to claim 18, wherein the constricted portion has a ratio of the length (L) to the bore diameter (D) in the range defined by the following equation:
L/D = 1.0 ∼ 3.0

20. The spinneret according to claim 18, wherein the conduit expands divergently from the constricted portion towards the orifice.

21. The spinneret according to claim 20, wherein the constricted portion has a bore diameter in the range of between 0.20 mm and 0.45 mm and the orifice has an opening diameter in the range of between 0.5 mm and 0.7 mm.

22. The spinneret according to claim 21, wherein the constricted portion has a bore diameter in the range of between 0.25 mm and 0.40 mm.

23. Hosiery which comprises a composite filament drawn yarn comprising a polyamide sheath component and a polyurethane core component arranged eccentrically in said polyamide sheath component and exposed in a small width on the surface of the filament, in the cross-­section of a unitary filament, which drawn yarn contains not more than 1,000 fisheyes/kg and exhibits a shrinkage percentage in boiling water of between 5% and 30%.

Drawing