Process for preparing partially dissolvable and splittable conjugated microfiber

Abstract: There is provided a process for preparing a sub-soluble and splittable, conjugated microfiber with a cross section having matrix orange islands and slightly connected with each other at the tip of the orange island in the matrix center. Conjugated fibers can be made into filaments and staple fibers. Filaments are spinning taken-up and then is carried out texturing by means of a belt nip twister and the resulting texture yarns are sub-dissolved following weaving to split. As to the staple fibers, it is staple fiber processed to obtain staple fibers and followed by processing into non-wovens or spinning to spun yarn and then weaving. Owing to a different splitting method from filament fabrics, staple fibers can be made to fabrics as follows: 1. Suede fabrics; 2. Water resistant and humid permeable, high density fabrics; 3. Peachskin fabrics.

Description: This invention relates to a process for preparing a partially dissolvable and splittable conjugated fiber. Heretofore, the processing of filaments of synthetic fibers, such as for example polyethylene terephtalate (PET), polypropylene (PP), polyamide (PA) and the like, made by a melt spinning method typically includes the steps of: and the processing of staple fibers is: spinning drawing heatsetting crimping drying cutting to staple fiber, wherein it is well known that UDY means "up-drawn yarn", MOY means "medium oriented yarn" and POY "partial oriented yarn" respectively (Man-made Fiber Year Book (CTI) 1986, Fiber Industry, LOY-MOY-POY-HOY-FOY? by H. Treptow, Remscheid-Lennep/FRG). In general, if symthetic leathers want to have genuine leather-like soft surface touch, a titer thereof should be at least below 0.44 dtex (0.4 den). However, fibers of 0.44 dtex (0.4 den) or less can hardly be produced by a conventional spinning method mentioned above. Even if fibers below 0.44 dtex (0.4 den) can be produced, it is difficult to process them by the application of weaving. Now many types of conjugated fibers are available on the market. So Fig. 1A is a cross-sectional view of the conjugated fibers produced by Kanebo, Japan. Fig. 1B is a cross-sectional view of the conjugated fibers produced by Teijin, Japan, and Fig. 1C is a cross-sectional view of the conjugated fibers produced by Toray, Japan. Conjugated fibers of each of Figs. 1A and 1B are of matrix types and are made by conjugated spinning of two different kinds of polymer. But these two types can be put to the production of flat yarns only and they can not be used in false twisting. If they are used in false twisting, it is easy for them to split, this resulting in fluff and in difficulty in weaving. The conjugated fibers of Fig. 1C are of of a sea and lobes type, and they are also made by conjugated spinning of two different type of polymers. The sea component should be completely dissolved to obtain the finer ingredient fibers of lobe. As the sea component must be completely dissolved, the cost is increased. In US-A-4 364 983 a multifilament yarn is disclosed consisting of single filaments of the multicomponent matrix-segment type, wherein the individual components of the yarn show a false-twist crimp and wherein all or part of the individual components, consisting of the matrix and at least three segment fibers split off such matrix, said segment fibers having shrunk by at least 10% in relation to the matrix fiber, are bonded to each other at irregular intervals. In said reference there is no mention about orange-segment shaped lobes in which each orange lobe is connected slightly at the matrix center. From US-A-4 352 705 a process for preparing leatherlike sheet materials is known, which comprises preparing hollow composite fibers each composed of 32-72 alternately arranged segments of polyester or polyamide and polystyrene which are mutually adhered side-by-side and encompass a hollow space, and which extend along the longitudinal axis of the fiber to form a tubular body, the hollow composite fiber having a denier of 1 to 20, and each segment having a denier of 0.01 to 0.5; forming a fabric using thus prepared hollow composite fibers; and applying an elastic polymer to the fabric. With said process it is not possible to obtain polyamide lobes surrounded by sea parts of polyester, in that using the claimed procedure the fiber will break down in the case of high speed belt nip twister. The present invention is directed to the improvement of the above mentioned disadvantages and the improvement is characterized in that the production and the spinning are like those in forming a regular yarn with a dissolving and splitting step performed following the spinning. A more complete understanding of these and other features and advantages of the present invention will become apparent from a careful consideration of the following detailed description of certain embodiments illustrated in the accompanying drawings. In the drawings: Fig. 1A is a cross-sectional view of conjugated microfibers obtained from Kanebo, Japan; Fig. 1B is a cross-sectional view of conjugated microfibers obtained from Teijin, Japan; Fig. 1C is a cross-sectional view of conjugated microfibers obtained from Toray, Japan; Fig. 2 is a schematic diagram of a spinneret according to the invention; Fig. 3A is a cross-sectional view of the fiber according to the invention before splitting; Fig. 3B is a cross-sectional view of the fiber according to the invention after splitting; Fig. 4 is a flow chart explaining an apparatus for finishing the conjugated yarn of the invention by means of a belt nip twister; Fig. 5 is a processing procedure chart for the conjugated micro-staple fiber of the invention. The process according to the present invention is illustrated as follows. Polyester (PET) and polyamide (PA), the starting materials of the invention, in a ratio of PET/PA of 20-80/80-20, are extruded through an extrusion apparatus of a spinneret in Fig. 2. Fibers produced by said apparatus have a cross-section comprising a matrix appearance having orange-segment shaped lobes and connected slightly at the matrix center. These lobes can be in a group of 3 to 12 lobes in accordance with the design of the spinneret. Conjugated fibers of the invention come out from the bores (A) of the spinneret of Fig. 2 at a temperature of 270 to 300°C. During spinning the dynamic viscosity is 2000 to 3500 poises in the case of PET and 800 to 2500 poises in case of PA. An appropriate take-up speed is 500 to 4000 m/min and a draft ratio is 50 to 500. As shown in Fig. 3, the resultant un-drawn conjugated yarn has a matrix with a cross-section comprising orange-segment shaped lobes. The number of the orange lobes is from 3 to 12. The un-drawn yarn obtained by spinning the conjugated filament is subjected to the following procedures. As shown in Fig. 4, the undrawn yarn cake is on a creel 41 through a high speed belt nip twister, and then passes through a yarn cutter 42 to be introduced into a first feed roller 43. It then passes through a primary heater 44 at a temperature of 100 to 180°C, a balloon control plate 46, a short balloon control bar 47, a yarn wire guide 471, a pre-twister guide 472 and thereafter is fed into a nip twister 48 having a twist level of 3000 to 4000 twists per meter and a twister cross angle of 110 to 230 degree. After a passage through a self-force twisting bearing roller 473, the yarn is fed into a second feed roller 49 at a draw ratio (a ratio of the speed of 43 to the speed of 49) between 1.5 and 3.5 and a B/Y ratio (belt speed/yarn speed) between 1.62 and 2.2 and passes through a secondary heater 410 and a third feed roller 411. The second feed roller overfeeds 1.5 to 2.5% and the third feed roller overfeeds 2.0 to 3.5%. Following passage through a yarn feeder 412, an oil roller 413 and finally through a winder 414, the yarn is taken-up as conjugated texture yarn having a titer from 33 to 500 dtex (30 to 450 den). After weaving or knitting the conjugated texture yarn of the invention into a cloth, it should be sub-resolved, i.e. the outermost portion of the PET dissolved to split. A sub-resolving ratio, defined as: (weight of unsplit yarn - weight of split yarn)/(weight of unsplit yarn) usually is in the range of 10 to 40% depending on the type of the finishing fabrics. The desired sub-resolving ratio of raised fabrics is between 10 to 20%, that of high density fabrics between 15 to 40%, and of peach skin fabrics is between 10 to 30%. Following dissolving of the outermost portion of PET for splitting the titer per single filament is in the range of 0.01 to 0.5 wherein it comprises PA and PET. Raised fabrics have a suede leatherlike feel. In case of high density fabrics, such a fabric can be used as water-resistant and humidity permeable fabric suitable for making jackets, coats, casual wears and the like. Following buffing of the fabrics to obtain a peach skin feel, it can be used in forming ladies wears, skirts, slacks and the like. The microfiber of the invention will be un-splittable during the process of conjugate spinning and twisting. The fiber will not split until following weaving or knitting, i.e. until the sea component of the fiber of the cloth is sub-resolved. A cross section of the fiber is shown in Fig. 3A and that afterwards is in Fig. 3B. The process of the invention can also find application in the manufacture of a staple fiber. The same spinneret as in Fig. 2 is employed. It has a hole number of 200 to 300, a through-put temperature of 270 to 300°C, a dynamic viscosity of PET during the melt spinning process between 2000 and 3500 poises and that for PA being 800 to 2500 poises, as well as a winding speed of 500 to 1500 m/min. The resultant fiber is an un-drawn spin tow of conjugated fiber with a cross section of matrix having orange-segment shaped lobes of one material in a sea of another material as shown in Fig. 3A. After being subjected to the processing procedure of Fig. 5 with a draw ratio of 3.0 to 4.5, a drawing temperature of 70 to 120°C, a heat setting temperature of 40 to 150°C and a drying temperature of 60 to 130°C, the drawn tow of conjugated fiber is formed into a drawn crimped conjugated staple fiber of 0.55 to 5.54 dtex (0.5 to 5 den) having a length of 32 to 102 mm. The resulting conjugated staple fiber can be put to non-woven use or employed for spinning into 130-295 dtex(20-45 counts) spun yarn. The woven fabrics made of the fiber of the invention may be heavy fabrics or light fabrics or there between. These fabrics can be made into jackets, coats, skirts, pants, suits, slacks, vests, gloves and the like. Besides they can be find usages in wiping cloth, glass cleaning cloth, car cleaning cloth, and cleaning cloth for optical instruments and integrated cicuit and also be manufactured to a product of manufacture, such as an ultrafine filter, printing ribbon, synthetic leather, shoes, handbags and suitcases, etc. EXAMPLES Example 1 The production and the yield are normal while conjugated spinning under the following conditions. PET and PA are subjected to conjugated spinning at a temperature of 285°C, extruding through a spinneret having a hole number of 32, a through-put speed of 10 m/min, a through-put mass rate of 0.9 g/min-hole, a winding speed of 1500 m/min, a dynamic viscosity of PET being 2500 poises and that of PA being 1500 poises. The resultant un-drawn conjugated filament has a fineness of 192 dtex (173 den). The parameters of the undrawn filament being twisted by means of the belt nip twister as shown in Fig. 4 are as follows: Texturing machine: MACH CRIMPER 33II (Trade Mark) Speed: 500 m/min Draw ratio: 2.3 Drawing temperature: 140°C B/Y ratio: 1.8 Second overfeed: 2.0% Third overfeed: 2.5% Twist level: 3500 twists per meter Belt cross angle: 115° The drawn-texture yarn obtained from the above-mentioned twisting has a tenacity of 4.1 g/dtex (4.1 g/den), an elongation of 30%, a boiling water shrinkage (BWS) of 11% and a crimp rigidity (CR) of 15%. Example 2 PET and PA are subjected to conjugated spinning at a temperature of 280°C, extruding out through a spinneret having a hole number of 280, a through-put rate of 2.67 m/min, a through-put mass rate of 1 g/min, a take up speed of 1200 m/min, a spin denier of 8.3 dtex (7.5 den), a dynamic viscosity of PET being 1500 poises and that of PA also 1500 poises. An un-drawn spin-tow is produced by conjugated spinning performed under the aforementioned spinning condition. In the process as shown in Fig. 5, the tow is drawn at 80°C with a draw ratio of 3.0, after that the drawn tow is subjected to crimping with a crimper following heat setting, being dried at 110°C and followed by cutting to a conjugated staple fiber of 2.7 dtex (2.5 den) x 51 mm. Said conjugated staple fiber can be used for synthetic leathers through non-woven processing or as fabrics by spinning into spun yarn.

Claims: A process for preparing a conjugated textured yarn of polymer microfilaments comprising a PA central portion surrounded by a PET portion, wherein in a cross-section of the conjugated microfilament PA forms a matrix comprising a plurality of orange-segment shaped lobes all slightly connected at a common center and separated and surrounded by PET, the number of PA orange-segment shaped lobes being in the range 3 to 12 so that upon an outermost surrounding portion of PET being dissolved the remaining PET and PA can be split into 3 to 12 sections of PET and 3 to 12 sections of PA for a corresponding total of 6 to 24 even smaller filaments of PET and PA, the process comprising the steps of: a) separately melting and metering respective flows of said PET and said PA; b) extruding said metered flows of melted PET and PA through a conjugated spinneret with the PET separating the orange-segment shaped PA lobes all slightly connected to a common center and separating said lobes and surrounding the PA, the conjugated fiber being extruded at a temperature of from 270°C to 300°C, a dynamic viscosity during said extrusion being in the range 2000 to 3500 poises for said PET and in the range 800 to 2500 poises for the PA, a take-up speed for the conjugated extruded fiber being in the range 500 to 4000 m/min, and c) passing the undrawn conjugated yarn obtained from the conjugated spinneret through a belt-nip twister with a draw ratio in the range 1.5 to 4.5 at a speed of from 300 to 600 m/min, at a drawing temperature of 100-190°C, said nip twister having a twist level of from 3000 to 4000 twists per meter, a belt cross angle of from 110° to 130°C, a ratio of belt speed to yarn speed between 1.62 and 2.2, a second feed roller of said nip twister having an overfeed in the range 1.5 to 2.5%, and a third feed roller of said nip twister having an overfeed of 2.0-3.5%, the conjugated textured yarn thus obtained having a titer of 33 to 500 dtex (30 to 450 den), after partially dissolving the outermost PET layer and splitting the microfilaments the titer per filament in the range of 0.01-0.55 dtex (0.01-0.5 den), the sub- resolving ratio =(weight of unsplit yarn-weight of split yarn)/(weight of unsplit yarn) being of from 0.1 to 0.4. A process for preparing a spun yarn of polymer microfilaments comprising a PA surrounded by a PET, wherein in a cross-section of the conjugated microfilament the PA portion has the form of a matrix comprising a plurality of orange-segment shaped lobes all slightly connected at a common center and separated and surrounded by a PET portion, the number of the orange-segment shaped PA lobes being in the range of 3 to 12, so that upon dissolving an outermost surrounding portion of said PET the remaining PET and PA can be split into 3 to 12 sections of PET and 3 to 12 sections of PA for the corresponding total of 6 to 24 even smaller filaments of PET and PA, the process comprising the steps of: a) separately melting and metering respective flows of said PET and said PA and then extruding the melted PA surrounded by the melted PET through a conjugated spinneret, the conjugated fiber being extruded at a temperature of from 270° to 300°C, a dynamic viscosity during the spinning of 2000-3500 poises for PET and of 800-2500 poises for PA, a take-up speed for the conjugated fiber being extruded from the spinneret being in the range of 500 to 1500 m/min; b) drawing the extruded conjugated fiber at a draw ratio of 3.0-4.5 at a drawing temperature of 70 to 120°C; c) heat setting the drawn conjugated fiber at a temperature of from 40° to 150°C; d) drying the set conjugated fiber at a drying temperature of from 60° to 130°C; e) chopping said dried conjugated fiber into 0.55 to 5.5 dtex (0.5-5.0 den) conjugated staple fibers with a length of 32-102 mm, and f) spinning the conjugated staple fibers into 130-295 dtex (20-45 counts) spun yarn, after partially dissolving the outermost PET layer and splitting the microfilaments, the titer per filament will be in the range of 0.01-0.55 dtex (0.01-0.5 den), the sub- resolving ratio (=weight of unsplit yarn - weight of split yarn)/(weight of unsplit yarn) being in the range of 0.1 to 0.4. A process for preparing an artificial leatherlike material of polymer microfilaments comprising a PA surrounded by a PET, wherein in a cross-section of the conjugated microfilament the PA portion has the form of a matrix comprising a plurality of orange-segment shaped lobes all connected at a common center and separated and surrounded by a PET portion, the number of the orange-segment shaped PA lobes being in the range of 3-12, so that upon dissolving an outermost portion of said PET the remaining PET and the PA can be split into 3-12 sections of PET and 3-12 sections of PA for the corresponding total of 6-24 even smaller filaments of PET and PA, the process comprising the steps of: a) separately melting and metering respective flows of said PET and said PA and then extruding the melted PA surrounded by the melted PET through a conjugated spinneret, the conjugated fiber being extruded at a temperature of from 270° to 300°C, a dynamic viscosity during the spinning being in the range of 2000-3500 poises for PET and 800-2500 poises for PA, a take-up speed for the conjugated fiber being extruded from the spinneret being of from 500 to 1500 m/min; b) drawing the extruded conjugated fiber at a draw ratio of 3.0-4.5 at a drawing temperature of from 70° to 120°C; c) heat setting the drawn conjugated fiber at a temperature of 40-150°C; d) drying the set conjugated fiber at a drying temperature of from 60° to 130°C; e) chopping said dried conjugated fiber into 0.55 to 5.5 dtex (0.5-5.0 den) conjugated staple fibers with a length of 32-102 mm; and f) forming the conjugated staple fibers into an artificial leatherlike material, after partially dissolving the outermost PET layer and splitting the microfilaments, the titer per filament will be of 0.01-0.55 dtex (0.01-0.5 den), the sub-resolving ratio (=weight of unsplit yarn - weight of split yarn)/(weight of unsplit yarn) being in the range of 0.1-0.4.

Inventors: CHEN-LING LIN, CHEN-LING, LIN
Applicants: NANYA PLASTICS CORP, NAN YA PLASTICS CORPORATION
Application year: 1990
Main classification: D01D5
IPC codes: D01D5, D01F8