MXPA00004637A - Process and apparatus for collecting continuous blow spun fibers - Google Patents

Abstract

The present invention provides a process and apparatus (10) for blow spinning continuous fibers. The process utilizes a blow spinning die (20) and a tensioning device (40) to preclude slack in the fiber. The present invention also provides fiber products which utilizes continuous fibers prepared by a blow spinning process.

Description

PROCESS AND APPARATUS FOR COLLECTING BROKEN FIBERS WITH BLOWING, CONTINUOUS I. BACKGROUND AND SUMMARY OF THE INVENTION A. SUMMARY OF THE INVENTION The present invention provides a process and apparatus for generating a one-dimensional, continuous arrangement of carbon fibers based on a small diameter, high strength resin. In general, the present invention provides a blown spinning process which creates a blown spinning product having melt spinning product characteristics at blow spinning speeds. In this way, the current invention improves the uniformity of the product and the production economy. While the present invention is particularly useful in fibers spun with carbonaceous resin blowing, other uses will become apparent from the following description.

B. Background of the Invention Since blown spinning operations are well known in the art, they will be described only in general terms. A typical blown spinning process uses a substance REF: 119499 spinnable, an attenuating medium, usually a gas, and a spinneret containing capillary tubes that form the fibers. During the spinning process, the fibers leave the capillary tubes and come into contact with the attenuating medium which lengthens or stretches each fiber to increase its length while decreasing its diameter. Since the attenuation medium is normally a gas, the speed of rapid cooling of the fibers is also affected. Typically, the fibers prepared by the blown spinning processes are discontinuous, short fibers having lengths of less than 5.08 centimeters (two inches). In contrast, spunbond fibers are generally continuous fibers with essentially infinite lengths. Normally, the fiber length of a spun fiber melt is selected by design, not dictated by the fiber production process. Additionally, spunbond fibers have better denier uniformity than blown fibers. Various types of nozzles can be used to spin the fibers with blowholes. In general, blown spinning nozzles are identified by the method of directing the attenuating gas in contact with the fibers. Two common designs are the annular and slot nozzles. Specifically, in an annular die, the attenuating gas leaves a ring formed around each capillary tube and flows in a direction parallel to the fiber. The attenuation occurs due to the slow advance of the gas on the fiber. In the slot nozzles, the attenuating gas leaves the slots on either side of a tip of the nozzle making contact with the fiber at an angle. The contact angle, as determined by the geometry of the nozzle, is optimized for the spinnable substance to obtain the desired characteristics of the fiber. The present invention has the same application for all types of blown spinning nozzles. Typical blown spinning methods allow spun fibers to fall to a collector surface after attenuation. Depending on the composition of the fibers, this method produces a di or three-dimensional block of randomly ordered, short fibers. Fibers collected in this manner may contain undesirable bends and twists which result in a lower tensile strength of the fiber. The main cause of the curvature and twisting of the fibers is believed to be the turbulence generated by the attenuating gas during the rapid cooling of the fibers. Those skilled in the art have recognized that the process of fiber collection is a critical step in achieving fibers of high tensile strength. Prior art methods for collecting spunblown fibers typically increased the number of bent and twisted fibers by collecting them in a randomized block, three-dimensional. U.S. Patent No. 5,648,041 recent demonstrates the collection of fibers in a two-dimensional block. However, the means to achieve the two-dimensional block requires an additional processing apparatus and rigorous control of the attenuating gas. As demonstrated by melt spinning processes, manufacturers have long recognized that the unidirectional deposit or collection of the fibers, for example in a spindle or coil, would produce the final properties of the fibers. However, prior to the present invention, the means to achieve this goal in a blown spinning process had been discovered. The present invention overcomes the difficulties previously associated with blown spinning of the fibers by providing an apparatus and a process for collecting the blown, continuous blown fibers. Additionally, the process and apparatus of the present invention provides the unidirectional collection of the continuous fibers. As used herein, the term "continuous fibers" means fibers that have an essentially infinite length. The interruption in the length of continuous fibers generally occurs for a particular purpose or due to a manufacturing problem. In addition, the fibers generated by the present invention have improved the uniformity and the tensile strength of the fibers. Finally, the present invention provides a spunbond process which generates a product of the melt spinning type at a speed equivalent to blown spinning.

II. Brief Description of the Invention The present invention provides an apparatus for spinning the infinitely long, continuous fibers with blowing. The novel apparatus includes a blown spinning nozzle having at least one capillary tube to form a fiber and a means for directing an attenuating gas in contact with the fiber when it exits the capillary tube. The apparatus also provides a means for placing tension on the fiber until it has been rapidly hardened or cooled, i.e., solidified. In addition, the present invention optionally provides for the removal of gases and vapors within the deposition or bundle of fibers prior to the collection of the fibers in a receiving device. In addition, the present invention provides a process for preparing continuous, blown, spun fibers. The inventive process prepares the fibers by heating a spinnable substance and forming the fibers by passing the substance through a spinning nozzle. The fibers are attenuated by an attenuating gas. After the attenuation, the process prevents the formation of a looseness in the fibers by maintaining tension on the fibers by means of a tensioning device. Spunblown, continuous fibers can be collected on the tensioning device or a subsequent device such as a spool or a spool. The present invention further provides a process for preparing blown, straight fibers of a carbonaceous resin. The novel process uses a means to maintain tension on the fiber to prevent slackening prior to the thermosetting or rapid cooling of the fiber. The present invention further includes the step of collecting the fibers as a warp sheet or a bundle of continuous filaments, traversed on a receiving device. If necessary, the present invention provides for the removal of gases and vapors from the fibers prior to collecting the fibers in the receiving device. Preferably, the gases and vapors will be removed by the cross flow ventilation applied to the fibers before the receiving device. Finally, the novel process will also be useful when spinning fibers of substances such as, but not limited to, carbonaceous resins, polyamides including nylons, polyesters such as "Dacron®", polypropylenes, polyurethanes including "Lycra®", polyaramides such as " Kevlar® "and crystalline, liquid materials such as mesophase resin, mesophase solvated resin and Zenite®, where all brands are registered trademarks of El du Pont de Nemours and Company. Additionally, when spinning fibers based on resin, the present invention provides a straight, continuous, spunbond fiber. The fiber is free of twists, bends and other collection defects associated with blown spinning which decrease the mechanical properties of the fiber.

As a result, this invention produces a fiber with a significantly higher tensile strength. In addition, the present invention provides a bundle of continuous, traversed fibers, a warp sheet and a unidirectional filament wick fabric prepared from continuous fibers made by a blown spinning process.

III. Brief Description of the Drawing Figure 1 is a generic representation of the apparatus of the present invention.

IV. Detailed Description A. Apparatus for Spinning and Collecting Fibers With reference to the drawing, the present invention provides a blown spinning apparatus and collection of fibers 10. Apparatus 10 has a blown spinneret, typically shown as 20, a steam removal system and a tensioning device 40 or other suitable means for maintaining tension on the spun fiber. Spunblowing nozzles are well known in the art. In fact, as discussed previously, there are several well known variations of blown spinning nozzles. The present invention is suitable for use with all blown spinning nozzles. For additional information on the function of blown spinning nozzles, please see the following references which are incorporated herein by reference: "Vibration and Stability in the Melt Blowing Process", Ind. Eng. Chem. Res., 1993, 32, 3100-3111 by Rao and Shambaugh; Macroscopic View of the Melt-Blowing Process for Producing Microfibers ", Ind. Eng. Chem. Res. ', 1988, 27, 2363-2372, Shambaugh;" Three-Dimensional Temperature Field of Rectangular Array of Practical Air Jets ", Ind. Eng. Chem. Res., 1994, 33, _7_30-735 Mohammed and Shambaugh, "Superfine Thermoplastic Fibers", by Van A. Wente, Industrial and Engineering Chemistry, Vol. 48, No. 8, August 1956, pp. 1342- 46, and U.S. Patent Nos. 4,847,125; 4,380,570; and No. 5, 286, 182. The optional vapor removal system 30 of the current invention is particularly useful when the spinning substance contains volatile components such as an unreacted monomer or solvated resins solvent component Solvated resins were developed by the assignee of the current invention and are described in U.S. Patent Nos. 5,259,947, 5,437,780, 5,501,788, and 5,538,621 which are incorporated herein by reference. preferred modality, steam removal system 30 is placed between nozzle 20 and tensioning device 40. The preferred steam removal system uses one or more blowers, not shown, in another medium to generate a cross flow or gas or air movement . Cross-flow ventilation effectively removes hydrocarbon vapors or other entrained components from within the fiber bundle and assists in joining the filaments "out of the bundle". The removal of volatile components from within the fiber package or arrangement prior to collection improves the processability of the fiber. Finally, the apparatus of the present invention includes a tensioning device 40. As shown, the device 40 can be as simple as a single spool or spool that exerts tension on the fiber spun with continuous blow. Alternatively, coils, rolls, bolts, additional hot containers and so on may be incorporated before or after device 40 to perform the functions of cold elongation and thermal hardening. The exact configuration or apparatus employed is not critical to the current invention. Preferably, the primary approach is to provide a means for maintaining sufficient tension on the spun fibers, the fibers as they were spun to prevent slackness after the formation of the fiber and during the collection process. The constant tension allows the alignment of the continuous fibers in a linear arrangement which can be collected in some manner known to those skilled in the art such as a warp sheet or a bundle of continuous, traversed filaments.

B. Process for Spinning Straight, Continuous Fibers With continuous reference to the drawing, the present invention provides a process for collecting continuous spunblown fibers. As is known in the art, various collection methods can generate a warp sheet, a bundle of continuous, traversed fibers or other products. As previously noted, the process for spinning with blown fibers is well known. However, while the benefits of the collection of spunbond fibers in a unidirectional manner were known, these were not achieved prior to the current invention.

According to the process of the present invention, spunblown fibers are formed by passing a spinnable substance through the capillary tubes of a blown spinneret. When the fibers as they are spun out of the capillary tubes, they are contacted by an attenuating gas. After attenuation, the fibers are optionally passed through a steam removal system 30 in order to remove any unreacted monomers or solvents which may be entrained in the fiber arrangement. Preferably, these materials are removed before collecting the fibers. This is particularly true when preparing solvated resin fibers when the presence of any retained hydrocarbon would degrade the resulting product. The process of vapor removal will be achieved preferentially by the generation of a cross flow suction. Preferably, the cross flow suction will occur after the fiber attenuation and before the collection of the fibers. The cross flow suction can be generated by one or more blowers, compressors or other suitable device, not shown. The steam removal process should not be confused with the common cross-flow rapid cooling step, which typically occurs in the spinning of melted fiber material. The spun fibers of a solvated resin are rapidly cooled and thermoset near the nozzle in the region dominated by rapid expansion and cooling with quenching gas. In this way, solvated resin fibers have already completed the rapid cooling process before vapor removal. After the formation of the fibers, the current invention uses a tensioning device 40 to maintain a constant and uniform force on the fibers. The tension placed on the fibers avoids the curvature and the possible twist of the fibers and allows the collection of fibers spun with blow, infinitely long, continuous. In addition, the application of constant tension_ after the formation of the fibers allows the alignment of the fibers in a linear arrangement which can be collected in a coil as a warp sheet or a bundle of continuous fibers, traversed. The impact of the additional stress on the attenuation of the fiber will vary depending on the spinnable material; however, the additional voltage does not operate as the primary attenuation force. Preferably, the attenuating gas serves this function.

Once the continuous fiber is aligned in a coil or other suitable collection device, the fiber can be cut by further processing. The manner of removal of the coil will determine the characteristics of the final product. If an individual cut is made along the length of the coil, the fiber can be removed as a unidirectional filament wick fabric, aligned with a length equal to the circumference of the coil. If short, straight and uniform length filaments are required, the fiber can be sliced from the coil at specified intervals to achieve the desired length of the filaments. Alternatively, as is known to those skilled in the art, the fibers can be processed in the coil, cut to desired lengths after removal or unwinding and then elongate, fold the warp, spend, or otherwise process desired . In addition, rollers, bolts, hot containers and other well-known devices can be incorporated before or after the continuous fiber is aligned by a tensioning device 40 to perform the functions of cold or hot drawing and thermal curing.

C. Spunbond, Straight, Continuous Blown Carbon Fibers The present invention is particularly useful for spinning continuous fibers of mesophase resin and solvated resins. U.S. Patent No. 5,648,041, discusses the difficulties of producing straight fibers of a solvated resin and in particular a solvated mesophase resin. As noted herein, rapid cooling of the fiber in the turbulence area generated by the attenuating gas tends to generate twists and bends in the fiber. However, by using a tensioning device (40) the present invention provides continuous, blown, spun fibers. In addition, this invention increases the potential for smaller end diameter products while producing fibers with a single, higher filament and composite strength conversion. Finally, the current invention can allow the diameters of the capillary tubes of the spinning nozzle to be larger, thereby reducing the difficulties associated with small capillary tubes such as clogging. Table 1 demonstrates that the fibers of the present invention have improved tensile strength and decreased variation in diameter as they were spun when compared to the fibers prepared by prior art methods. The following test results were obtained from the spun fibers of a single batch of solvated mesophase resin using the same blown spinning nozzle. As shown in Table 1, the fibers of the current invention, which were collected in a coil, had a higher tensile strength and a smaller percentage coefficient of variation in diameter as they were spun than the fibers collected as a block. The percentage of the variation coefficient (% CV, for its acronym in English) in the fiber diameter is the normal deviation divided by the average fiber diameter, expressed as a percentage, of a data set. A smaller CV% indicates an improvement in fiber denier uniformity.

Other embodiments of the present invention will be apparent to those skilled in the art from a consideration of this specification or the practice of the invention described herein. The above specification is considered to be exemplary only, with the true scope and spirit of the invention indicated by the following claims.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following claims is claimed as property.

Claims (21)

1. An apparatus for spinning continuous fibers, characterized in that it comprises: a blown spinning nozzle having at least one capillary tube for forming a fiber of a mesophase resin; means for directing an attenuating gas on the fiber when it exits the capillary tube, the medium that attenuates the fiber by directing the gas at a suitable contact angle to attenuate the fiber and the angle less than 90 ° to the fiber path; and a means for maintaining tension on the fiber after fiber attenuation.

2. The apparatus according to claim 1, characterized in that it additionally comprises: a means for the expulsion of gases and vapors from the fibers after the attenuation of the fibers.

3. The apparatus according to claim 1, characterized in that the means for maintaining tension on the fibers also provides a means for collecting the fibers.

4. A process for preparing straight, blown, spunbond fibers of a mesophase resin, the process is characterized in that it comprises: passing the mesophase resin through the capillary tubes located inside the blown spinneret to form a resin. mesophase in fibers; attenuate the fibers by contacting the fibers with an attenuating gas at an appropriate contact angle to attenuate the fiber and the angle less than 90 ° to the fiber path; and after attenuation, maintain sufficient tension on the fibers to avoid the formation of a looseness when collecting the fibers in a receiving device.

5. The process according to claim 4, characterized in that the fibers are collected as either a warp sheet or a bundle of continuous filaments, traversed.

6. The process according to claim 5, characterized in that the warp sheet or the bundle of continuous filaments, traversed is further processed in a woven fabric of unidirectional filaments.

7. The process according to claim 5, characterized in that before collecting the fibers in the receiving device, the gases and vapors are removed from the fibers.

8. The process according to claim 4, characterized in that the gases and vapors are removed by the cross-flow ventilation applied to the fibers before the receiving device.

9. A process for preparing spunblown, straight, continuous blown fibers, characterized in that it comprises heating a spinnable substance at a temperature sufficient to allow the substance to flow followed by the formation of continuous fibers as the substance passes into a spinning nozzle and through the fibers. capillary tubes located within the nozzle and attenuation of the fibers when they exit the capillary tube by contacting the fibers with at least one gas stream at an appropriate contact angle to attenuate the fiber and the angle less than 90 ° to the path of the fiber, wherein the improvement comprises: after the fiber attenuation, maintaining the tension on the fibers by means of a tensioning device selected from the group consisting of coils, rolls and reels and combinations thereof.

10. The process according to claim 9, further characterized by including the step of collecting the fibers as a warp sheet or a bundle of continuous, traversed filaments or a spool device positioned to receive the fibers from the tensioning device.

11. The process according to claim 10, characterized in that it includes the step of removing gases and vapors before collecting the fibers. ~

12. The process according to claim 11, characterized in that prior to collecting the fibers, crossflow ventilation is applied to the fibers.

13. A bundle of continuous, traversed fibers, characterized in that it comprises continuous fibers prepared by a blown spinning process.

14. The bundle of continuous fibers traversed according to claim 13, characterized in that the fibers are spun from the group consisting of carbonaceous resins, polyamides, nilons, polyesters, polypropylenes, polyurethanes, polyaramides and crystalline, liquid materials.

15. A warp sheet, characterized in that it comprises continuous fibers prepared by a blown spinning process.

16. The warp sheet according to claim 15, characterized in that the continuous fibers were collected by a means for placing tension on the fiber, the medium that is selected from the group consisting of coils, rolls and spools.

17. A unidirectional filament wick fabric prepared from continuous fibers prepared by a blown spinning process.

18. The unidirectional filament wick fabric according to claim 17, characterized in that the unidirectional filament wick fabric is collected by a means for placing tension on the tissue, the medium that is selected from the group consisting of reels, rolls and spools. .

19. The apparatus according to claim 1, characterized in that the attenuating gas is directed on the fiber substantially and continuously during blown spinning.

20. The apparatus according to claim 1, characterized in that the means for maintaining tension on the fiber is a mechanical device.

21. The apparatus according to claim 1, characterized in that the means for maintaining tension on the fiber is selected from the group consisting of coils, rolls and reels. BREATHING, CONTINUOUS SUMMARY OF THE INVENTION The present invention provides a process and apparatus (10) for spinning continuous fibers with blowing. The process uses a blown spinning nozzle (20) and a tensioning device (40) to prevent looseness in the fiber. The present invention also provides fiber products using continuous fibers prepared by a blown spinning process.