Spinneret Assembly for Sheath-Core Type Composite Fibers

1. Field of the Invention

The present invention relates to a spinneret assembly capable of spinning sheath-core type composite fibers in which the ratio of core component to the sheath component is uniform from a single fiber to another and the core positions are constant.

2. Statement of the Prior Art

A number of spinneret assemblies for obtaining fibers of the sheath-core composite structure from two types of spinning stock solutions have heretofore been known in the prior art. Composite fibers have been spun out of a number of spinning holes open on a spinning plane of such spinneret assemblies. However, little or no attention has been paid to the elimination of ununiformity in the composite structure among fibers, which would result from the location of the spinning holes and the arrangement of the passages through which stock solutions are fed to the spinning holes. One example of such conventional spinneret assemblies is dislcosed in Japanese Patent Publication No. 62-37126, and will now be explained with reference to the drawings. FIG. 12 is a partly omitted, sectional view showing the conventional spinneret assembly, FIG. 13 is a plan view of a first distributor used in the assembly of FIG. 12, and FIG. 14 is a plan view of a second distributor used therein.

In the conventional spinneret assembly shown generally at 1, a stack of a spinneret plate 2, a second distributor 3, a first distributor 4, a filter 5 and a cap 6 are housed in that order from below within a casing 7, as illustrated in FIG. 12, with a gap 8 being provided between the spinneret plate 2 and the second distributor 3 along their full length. In an upper plane of the second-distributor 3, there are an alternate and parallel arrangement of core-component-stock-distributing-grooves 3a and sheath-component-stock-solution-distributing-grooves 3b, as illustrated in FIG. 14. The first-distributor 4 superposed on the second-distributor 3 (i.e., FIG. 13 being superposed on FIG. 14 as such and without changing direction) and shown in FIG. 13 includes core-component-stock-solution-inlet-holes 4a and sheath-component-stock-solution-inlet-holes 4b to which core- and sheath-component-stock-solutions are separately fed through the filter 5 for introduction into the distributing-grooves 3a and 3b in the second-distributor 3. The core- and sheath-component-stock-solutions introduced into the distributing-grooves 3a and 3b are guided to the gap 8 through the associated holes 3c and 3d for regulating the pressures of both component-stock-solutions respectively. In the gap 8, spinning holes 2a are open at positions coaxial with respect to the holes 3c for regulating the pressure of the core-component-stock-solution, so that the core-component-stock-solution is forced substantially straight into the spinning-holes 2a while is surrounded by the sheath-component-stock-solution, and spun out of the spinning plane. In the structure of such a spinneret assembly according to the prior art, the holes 3d for regulating the pressure of the sheath-component-stock-solution in the second-distributor 3 are located at the apexes of a rectangle, and the hole 3c for regulating the pressure of the core-component-stock-solution is located at the center of said rectangle, as shown by a dotted chain line in FIG. 14, whereby the distances of the sheath-component-stock-solution flowing in one spinning hole 2a from the holes 3d are designed to be equalized to make uniform the thickness of the sheath component surrounding the core component. In this respect, this structure is effective. However, even when the holes 3c and 3d and the spinning holes 2a are located as described above, there is a difference in the composite structures between the fiber spun out of the spinning holes 2a located at the ends and the fiber spun out of the holes at the center of the array of the spinning holes. That is, the sheath-component-stock-solution is uniformly fed to the central spinning hole 2a from its surrounding four holes 3d (in this case, one hole 3d serves to feed the stock solution to four spinning holes 2a), whereas a large amount of the sheath-component-stock-solution is fed to the endmost spinning hole 2a from two holes 3d (due to the fact that one hole 3d serves to feed the stock solution to one or two spinning holes 2a alone), so that the ratio of the sheath component to the core component in the composite structures spun out is larger in the endmost holes 2a than in the central hole 2a. In this case, not only is the sheath/core ratio different, but the core positions are also eccentric toward the sheath component being reduced. Even though the illustrated array of spinning holes 2a is changed to a circular one, the aforesaid disadvantage is unavoidable, as long as the construction of the passages for feeding the stock solutions is principally identical.

The present invention has for its object to eliminate the defects of the prior art by the provision of a spinneret assembly capable of spinning sheath/core type composite fibers in which the sheath/core ratio is uniform through fibers and the core positions are constant.

According to the present invention, this object is achieved by providing annular arrays of spinning holes and forming per one annular array of spinning holes an endless annular passage in which two core-and sheath-component-stock-solutions are combined with each other for flowing thereinto.

FIG. 1 is a view illustrating one embodiment of the present invention using one annular array of spinning holes, which is sectioned by a plane vertical with respect to a spinning plane and extending through three points defined by one spinning hole and the center of said annular array and located midway between the adjacent spinning holes on the side opposite to said center,

FIG. 2 is a sectional view taken along the line II--II of part of FIG. 1,

FIG. 3 is a sectinal view taken along the line III--III of part of the FIG. 1,

FIG. 4 is a sectional view taken along the line IV--IV of FIG. 1,

FIG. 5 is a sectional view taken along the line V--V of FIG. 1,

FIG. 6 is a sectional view taken along the line VI--VI of part of FIG. 1,

FIG. 7 is a sectional view taken along the line VII--VII of part of FIG. 1,

FIG. 8 is an enlarged sectional view taken along the line VIII'VIII of FIG. 3,

FIG. 9 is an enlarged view showing a portion shown at A in FIG. 2, and

FIGS. 10 and 11 are partly sectional views illustrative of another embodiment of the present invention and corresponding to FIGS. 2 and 3, respectively.

Referring now to FIG. 1, one embodiment of the sheath-core type composite spinneret assembly (which may hereinafter be simply called as the spinneret assembly) is generally shown by reference numeral 9, and includes the parts or members to be described successively as below.

(1) An annular array of spinning holes 10 are open on a spinning plane 11 of the spinneret assembly 9 and arranged at equiangular intervals, as illustrated in FIGS. 1 and 2. As illustrated in FIG. 2, the annular array of spinning holes 10 should be provided in at least one row. However, they may be provided in two or three or more rows, as illustrated in FIG. 10. Each spinning hole 10 may be of a round shape or other shapes such as a triangle in section.

(2) As illustrated in FIG. 2, reference numeral 12 indicates a spinning-stock-solutions-combining-passage (hereinafter simply referred to as solutions-combining-passage; hereinafter, simple name is shown in parentheses in same way as this) in the form of an endless annulus, which, as illustrated in FIG. 1, is provided per one row of said spinning holes and arranged on the spinning-stock-solution-feeding-side of said spinning holes and in parallel with the spinning plane 11 and is of a shallow depth, and in which spinning-stock-solution-inlets (inlet) 10a of the respective spinning holes 10 are open. It is preferred that the width w of the solutions-combining-passage 12 be 0.5 to 2.0 times as large as the pitch l of the spinning holes 10 (w and l also indicated in FIG. 9), and the depth thereof be about 0.2 to 1.0 time as large as the sectional diameter of a core-component-stock-solution-outlet-passage 14 (to be described later) of a circle in section (or the longitudinal diameter of the passage 14 of other shapes in section)

(3) As illustrated in FIGS. 1 and 3, a single annular passage 13 for distributing the core-component-stock-solution, being called a core-component-stock-solution-distributing-passage (core-distributing-passage), is arranged on the spinning-stock-solution-feeding-side along the solutions-combining-passage 12. The core-component-stock-solution-outlet-passage (core-outlet-passage) 14 are provided so as to guide the core-component-stock-solution from the core-distributing-passage 13 to the solutions-combining-passage 12 and then to the inlets 10a of the spinning holes 10 which are open in the solutions-combining-passage 12. The core-outlet-passages 14 are located at positions coaxial or eccentrical with respect to the respective spinning holes 10 as illustrated in FIG. 1 as to the former case, and are open in the solutions-combining-passage 12 at said positions. When the core-outlet-passages 14 are provided at positions eccentrical with respect to the spinning holes 10, such positions should preferably be selected in such a manner that no part of the core-outlet-passage 14 depart axially from the inlets 10a of the spinning holes 10. Each core-outlet-passage-14 may be of a circle or other shapes in section. As illustrated in FIGS. 1 and 3, two sheath-component-stock-solution-distributing-passages (sheath-distributing-passage) 15 and 15', both in the annular form, are arranged in parallel with the spinning plane 11 with the core-distributing-passage 13 being sandwiched therebetween. Sheath-component-stock-solution-outlet-passages (sheath-outlet-passage) 16 and 16' are provided to guide the sheath-component-stock-solution from the sheath-distributing-passages 15 and 15' to the solutions-combining-passage 12 and, as illustrated in FIG. 2, are open on both edges of the solutions-combining-passage 12 at positions located substantially in the middle of the adjacent inlets 10a of the spinning holes 10. The sheath-outlet-passages 16 and 16' may preferably be open substantially vertically with respect to the side edges of the solutions-combining-passage 12. More preferably, in order to facilitate the making of this assembly, they extend vertically from the sheath-distributing-passages 15 and 15' to the spinning plane 11, then run in parallel with the spinning plane 11, and finally reach the solutions-combining-passage 12, as illustrated in FIG. 1. The core-distributing-passage 13 and the sheath-distributing-passages 15 and 15' each take on an annular form so as to guide the spinning stock solutions to the solutions-combining-passage 12 in the endless annular form.

(4) A core-component-stock-solution-feeding-passage (core-feeding-passage) 17 and a sheath-component-stock-solution-feeding-passage (sheath-feeding-passage) 18 are provided to independently feed the core-component-stock-solution and the sheath-component-stock-solution to the core-distributing-passage 13 and the sheath-distributing- passages 15 and 15', respectively. The constructional embodiment will now be explained, by way of example alone, with reference to FIGS. 1 and 4 to 7.

As illustrated in FIG. 1, a core-component-stock-solution-feeding-inlet (core-feeding-inlet) 17aa, a first-core-component-stock-solution-passage (first-core-passage) 17ab and a core-component-stock-solution-pre-filtration-chamber (core-pre-filtration-chamber) 17ac are provided for the core-component-stock-solution and allowed to communicate with one another, while a sheath-component-stock-solution-feeding-inlet (sheath-feeding-inlet) 18aa, a first-sheath-component-stock-solution-passage (first-sheath-passage) 18ab and a sheath-component-stock-solution-pre-filtration-chamber (sheath-pre-filtration-chamber) 18ac are provided for the sheath-component-stock-solution and permitted to communicate with one another. As illustrated in FIG. 5, the core-pre-filtration-chamber 17ac and the sheath-pre-filtration-chamber 18ac are such that one has an circular contour and is located in the middle, while the other concentrically surrounds the one with both the lower ends being located in the same plane parallel with the spinning plane 11. Thus these above-mentioned are defining a first-core-component-stock-solution-feeding-passage-section (first-core-feeding-passage-section) 17a and a first-sheath-component-stock-solution-feeding-passage-section (first-sheath-feeding-passage-section) 18a, respectively. Reference will now be made to the illustrated configuration wherein the core-pre-filtration-chamber 17ac is located in the middle and surrounded by the sheath-pre-filtration-chamber 18ac. However, both chambers may be reversed in their positions. As illustrated, the centrally located core-pre-filtration-chamber 17ac is defined by an cylindrical cavity for its easy making, but it may be in the annular form. As illustrated in FIG. 4, the first-sheath-passage 18ab comprises a number of branched sub-passages so as to feed the sheath-component-stock-solution as uniformly as possible throughout the sheath-pre-filtration-chamber 18ac, and is selectively located in a position which does not intersect the first-core-passage 17ab. It is to be appreciated that for a better understanding, said portion of FIG. 1 is depicted in such a fashion that confusions brought about by making it precisely correspondent to FIGS. 4 and 5 are avoided.

As illustrated in FIG. 1, the core-pre-filtration-chamber 17ac and the sheath-pre-filtration-chamber 18ac are connected through a filter 19 with a core-component-stock-solution post-filtration chamber (core-post-filtration-chamber) 17ba and a sheath-component-stock-solution-post-filtration-chamber (sheath-post-filtration-chamber) 18ba, respectively, both being in the annular form as depicted in FIG. 6, which are in turn connected with a plurality of second-core-component-stock-solution-passages (second-core-passage) 17bb and second-sheath-component-stock-solution-passages (second-sheath-passages) 18bb to guide the core- and sheath-component-stock-solutions to the next feeding passages and arranged in the manner to be described later, thus defining a second-core-component-stock-solution-feeding-passage-section (second-core-feeding-passage-section) 17b and a second-sheath-component-stock-solution-feeding-passage-section (second-sheath-feeding-passage-section) 18b. The second-core-passages 17bb and the second-sheath-passage 18bb are arranged at positions extending radially from the center of the annulus and not overlapping with one another, preferably at alternate and equiangular positions.

As illustrated in FIG. 1, said second-core-passage 17bb and said second-sheath-passage 18bb are then connected with a core-component-stock-solution-receiving-small-chamber (core-small-chamber) 17ca and a sheath-component-stock-solution-receiving-small-chamber (sheath-small-chamber) 18ca, as shown in FIG. 7, for receiving the core- and sheath-component-stock-solutions, respectively, which are in turn connected with a core-component-stock-solution-inlet-passage (core-inlet-passage) 17cb and sheath-component-stock-solution-inlet-passages (sheath-inlet-passage) 18cb/18cb' to introduce the core- and sheath-component-stock-solutions into aforesaid core-distributing-passage 13 and aforesaid sheath-distributing-passages 15 and 15', respectively, thus defining a third-core-component-stock-solution-feeding-passage-section (third-core-feeding-passage-section) 17c and a third-sheath-component-stock-solution-feeding-passage-section (third-sheath-feeding-passage-section) 18c. Although each sheath-small-chamber 18ca should be of a length sufficient to have two openings of the sheath-inlet-passages 18cb and 18cb' corresponding to the two sheath-distributing-passages 15 and 15' as illustrated in FIG. 7, each core-small-chamber 17ca need not be of the same length as the sheath-small-chamber 18ca, as illustrated.

Said first- to third-core-feeding-passage-sections 17a to 17c and said first- to third-sheath-feeding-passage-sections 18a to 18c provide the successive core-feeding-passage 17 and the successive sheath-feeding-passage 18, respectively.

When the annular array of spinning holes 10 are provided in plural rows, said structure may be repeated in the radial direction of the annulus. In the case of two rows, for instance, the solutions-combining-passage 12, the sheath-outlet-passages 16 and 16', the spinning holes 10 and the like may be disposed as illustrated in FIG. 10. The core-distributing-passage 13, the core-outlet-passage 14, the sheath-distributing-passages 15, 15' and the sheath-outlet-passages 16, 16' may likewise be repeated while made correspondent to the rows of the spinning holes. As illustrated in FIG. 11, it is preferred in this case that, of the two sheath-distributing-passages 15 (outer) and 15' (inner) provided on both sides of each of the inner and outer spinning rows (the adjacent spinning hole rows in the case of three or more rows), the sheath-distributing-passage 15' on inner side of the outer spinning holes row and the sheath-distributing-passage 15 on outer side of the inner spinning holes row be formed into a common single sheath-distributing-passage 15 of a large width, since it is then possible to simplify the arrangement and decrease the required volume, thus making assembling easy. In the third core-feeding-passage-section 17c and the third sheath-feeding-passage-section 18c, the core-small-chambers 17ca and the sheath-small-chambers 18ca are radially extended so as to make connections to the core- and sheath-inlet-passages 17cb and 18cb/18cb' correspondingly required to the increased core- and sheath-distributing-passages 13 and 15 (15').

The spinneret assembly 9 according to the present invention is constructed by including the portions described in the foregoing (1) to (4) as the characteristic ones.

As illustrated in FIG. 1, a stack of a plurality of members and the filter 19 within a casing 20 is fastened by bolts 21 to a spinneret assembly 9, said members being obtained by splitting or dividing the construction comprising the portions as described in (1) to (4) along several proper planes. How to divide the construction is dependent upon at least the possibility with which the members are made and, preferably, the easiness with which the members are made and assembled into a unit. Ordinarily, the uppermost-stage member is called a cap 22, while the lowermost-stage member including the spinning holes 10 is referred to as a spinneret plate 23. One exampale of such division is shown in FIG. 1. In FIG. 1, the cap 22, a first distributor 24 located therebelow (hereinafter named in same manner), a second distributor 25, a third distributor 26, a fourth distributor 27 and the spinneret 23 are successively divided by planes P.sub.1, P.sub.2, P.sub.3, P.sub.4 and P.sub.5. For instance, the first sheath passage 18ab is defined by a groove formed by scraping off on the side of the cap 22 and the plate plane of the first distributor 24 by division with the plane P.sub.1. Other chambers, inlet- and outlet-passages, distributing-passages, solutions-combining-passage, etc. will likewise be appreciated from FIG. 1. In the foregoing example of division, a combination of the cap 22 and the first distributor 24 is provided with the first-core- and sheath-feeding-passage-sections 17a and 18a; the second distributor 25 with the second-core- and sheath-feeding-passage-sections 17b and 18b; the third distributor 26 with the third-core- and sheath-feeding-passage-sections 17c and 18c; the fourth distributor 27 with the core- and sheath-distributing-passages 13, 15 and 15' to the solutions-combining-passage 12; and the spinneret plate 23 with the spinning holes 10. In another aspect of division, as also illustrated in FIG. 1 as an example, division is made by planes P.sub.3 ', P.sub.4 ' and P.sub.5 ' in place of the planes P.sub.3, P.sub.4 and P5.

As the core- and sheath-component-stock-solutions are fed under pressure through the respective core- and sheath-feeding-inlets 17aa and 18aa, the former passes through the core-feeding-passage 17 into the core-distributing-passage 13, while the latter passes through the sheath-feeding-passage 18 into the sheath-distributing-passages 15 and 15'. When the core-outlet-passage 14 following the core-distributing-passage 13 is located coaxially with respect to the spinning holes 10, as illustrated in FIG. 8, the core-component-stock-solution passes through the solutions-combining-passage 12 and is fed in a straight line into the centers of the spinning holes 10. On the other hand, the sheath-component-stock-solution is guided from the sheath-outlet-passages 16 and 16', and flows, as shown by an arrow in FIG. 9, into the spinning holes 10 in such a manner that the core-component-stock-solution is wrapped therein. In this case, since all the sheath-outlet-passages 16 and 16' are open in the solutions-combining-passage 12 at the positions located substantially in the middle of the inlets 10a of the spinning holes 10, each of those sheath-outlet-passages 16 and 16' serves to equally feed the sheath-component-stock solution into two spinning holes 10. At the same time, since the inlet 10a of one spinning hole 10 is equally spaced away from the openings in the four sheath-outlet-passages 16 and 16', the core-component-stock-solution is wrapped in the sheath-component-stock-solution with a uniform thickness, so that sheath-core type composite fibers having their cores disposed centrally in section are obtained. The sides of a substantial rectangle defined by the openings of the four sheath-outlet-passages 16 and 16' surrounding one spinning hole 10 are w and l in length, as known from FIG. 9. When w is 0.2 to 2.0 times as large as l, there is a sufficient increase in the uniformity of the sheath-component-stock-solution in which the core-component-stock-solution flowing into the spinning hole 10 is wrapped from all directions. When the core-outlet-passages 14 are diposed eccentrially with respect to the spinning holes 10, there are obtained the socalled eccentric core type fibers having their cores disposed eccentrially in section, since the core-component-stock-solution flows eccentrially into the spinning holes 10, so that it is wrapped in the sheath-component-stock-solution with an irregular thickness.

Whether the sheath-core type or the eccentric core type, what is important to obtain a composite structure is that the inflow state of both spinning-component-stock-solutions from the solutions-combining-passage 12 to the spinning holes 10 is equalized throughout all the spinning holes 10 because of the solutions-combining-passage 12 being in the form of an endless annulus, so that the composite structures of the resulting composite fibers are uniform in all respects.

When a mulitiplicity of spinning hole rows are arranged at close intervals to increase the number of the spinning holes 10, it is required to reduce the width of the solutions-combining-passage 12, core-distributing-passage 13 and sheath-distributing-passages 15 and 15'. However, for reason of their annular form and by disposing the core- and sheath-inlet-passages 17cb and 18cb at properly close spacings as viewed in the circumferential direction, it is possible to make the flows of the stock solutions substantially uniform over the entire circumference, so that the fibiers obtained from all the spinning holes 10 are of a uniform composite structure.

According to the sheath-core type composite spinneret assembly of the present invention, the spinning-stock-solutions-combining-passage in the form of an endless annulus is provided per one annular array of the spinning holes so as to combine together the core- and sheath-component-stock-solutions just before the spinning holes, and the sheath-component-stock-solution-outlet-passages are uniformly arranged and made open, whereby the composite structures spun out of all the spinning holes are made so uniform that the sheath-core type composite fibers can be spun, in which the ratio of the core component to the sheath component is uniform all through fibers and the core positions are constant. It is also possible to increase the number of the spinning holes while such composite structures are kept uniform.