US 3032456 A
Description (OCR text may contain errors)
May 1, 1962 2 Sheets-Sheet 1 Filed April 18, 1955 W. WADE ELASTIC CORD May 1, 1962 2 Sheets-Sheet 2 Filed April 18, 1955 United States Patent 3,032,456 ELASTIC CORD Worth Wade, Rosemont, Pa., assignor to American Viscose Corporation, Philadelphia, Pa., a corporation of Delaware Filed Apr. 18, 1955, Ser. No. 501,931 4 Claims. (Cl. 156-28) This invention relates to a strand-like structure formed of fibers of an elastomeric material and to a method of producing such strand. The term strand is used herein and in the claims to include any elongated bundle of fibers such as a yarn, thread, cord, rope and the like.
Elastic yarns generally are formed by extruding a solution of an elastomeric material through an orifice to form a relatively large mono-filament or by cutting the strands from sheet rubber to form a core having a square cross-section. A yarn of limited stretchability may be formed from such rubber mono-filaments or cores by wrapping with a textile yarn or by twisting the core with a textile yarn. These elastic yarns are used in knitting and weaving but have little or no utility outside the textile field.
The principal purpose of the present invention is to provide a novel elastic strand which will have a wide variety of uses in textiles, cordage and many other industrial fields.
Another object of this invention is to provide a composite strand formed of elastomeric filaments and nonelastomeric fibers.
Another object of this invention is to provide a method of forming a strand from filaments of elastomeric materials.
Other objects and advantages of this invention will become apparent from the description and claims which follow.
In the drawings,
FIGURE 1 is a diagrammatic sectional view of one form of apparatus for the production of strand-like structures in accordance with the present invention;
FIGURE 2 is a diagrammatic sectional view of another form of apparatus for forming strand-like structures in accordance with this invention;
FIGURE 3 is an elevational view of an alternative means for forming elastomeric fibers;
FIGURE 4 is an elevational view of a further means for forming the strand-like structures of this invention;
FIGURE 5 is an elevational view of a strand-like structure of this invention;
FIGURE 6 is a perspective view of another form of strand-like structure made in accordance with this invention;
FIGURE 7 is an elevational view of a further form of strand-like structure made in accordance with this invention; and
FIGURE 8 is a perspective view of a weather-strip embodying a strand-like structure formed in accordance with this invention.
The present invention contemplates the spraying of a liquid containing an elastomeric material to form relatively long discontinuous fibers of the elastomeric material and collecting the fibers in a progressive overlapping relationship in the form of a strand with or without a supporting strand and with or without the inclusion of nonelastomeric fibers.
In the copending application of Howard 0. McMahon and Paul C. Watson, Serial No. 400,240, filed December 24, 1953, there is disclosed and claimed a method of forming reticulated fibrous webs or sheets of elastomeric materials by extruding a liquid dispersion or solution of an elastomeric material into a primary high velocity stream of gas as a relatively large diameter stream of plastic. The high velocity stream of gas attenuates and breaks transversely the stream of plastic to form a plurality of discontinuous fibers or fibrils, partially removes the solvent and partially sets the elastomeric material. A second stream of gas surrounding the primary stream of gas carries the attenuated fibers and fibrils, removes the remainder of the solvent and continues the setting operation. The attenuated fibers or fibrils are collected on a suitable collecting means such as a screen in an adhesive and uncured condition and the fibrils become bonded together at their points of contact to provide a reticulated web or sheet. The elastomeric material is finally cured or vulcanized.
In accordance with the present invention, the elastomeric filaments are collected in the form of a bundle of progressively overlapping filaments which are continuously removed so as to form a strand.
The elastomeric materials satisfactory for the preparation of the products of this invention include both natural rubbers and synthetic rubbers or rubber substitutes. Such elastomeric materials or rubbers, both natural and synthetic, which are soluble in inexpensive, volatile organic solvents are well suited for the production of the strandlike products of this invention. These elastomeric materials include natural rubbers such as crepe rubber, smoked gum rubber, balata, gutta percha and the like, and synthetic rubbers or rubber substitutes such as chloroprene polymers, for example, neoprenes; butadieneacrylonitrile copolymers known as buna-N, for example, Butaprene, Paracril, Ameripol-D, Perbunan, Chemigurn, and Hycar-OR; butadiene-styrene, copolymers, for example, Ameripol-F, Hycar-OS and GR-S; isoprene-isobutylene copolymers, for example, GR-I and butyl; and organic polysulfides, for example, Thiokol. Mixtures of specific elastomeric materials may be utilized to provide desired characteristics. The specific elastomers are enumerated merely as illustrative and are not intended as limitations of the invention.
The spraying or fiber-forming liqud may be formed by dissolving the fiber-forming elastomeric material in a satisfactory organic solvent such as aliphatic and aromatic hydrocarbons, chlorinated hydrocarbons, aralkyl hydrocarbons and the like, those being preferred which will volatilize readily at moderately elevated temperatures. The solvent utilized in forming the spraying liquid will be dependent upon the specific elastomer and upon characteristics desired in the spraying liquid such as volatility of the solvent. For example, solvents which are satisfactory include benzene, naphtha, toluene, xylene, cyclohexanone, ethylene chloride, methylene chloride, carbon tetrachloride, nitroparaffins, ketones and the like. Such inexpensive volatile organic solvents as benzene and naphtha are entirely satisfactory for use in fibrillating liquids containing natural rubber. The spraying liquids may contain from about 5% to about 50% of the fiber forming elastomeric material and preferably contain between about 10% and about 35% rubber or rubber substitute.
The properties and characteristics of the fibers formed from the elastomers may be varied as desired by incorporating additives in the spraying liquid. Substances such as normally employed in preparing finished rubber articles from crude natural rubbers or synthetic rubbers may be added; for example, carbon black, curing or vulcanizing agents such as sulfur, accelerators, antioxidants, plasticizers and the like. Detackifying agents, such as paraffin wax, stearic acid and the like may be incorporated in the spraying liquid so as to decrease the natural adhesive or tacky'nature of the unvulcanized fibers. Coloring agents, such as dyes and pigments may be utilized to pro- I be added to impart desired characteristics and to reduce the cost of the fibers. The amount of the additive may be varied over a wide range as desired. For example, from about 50% to about 150% filler, such as clay, finely divided pigments and the like, based upon the weight of the elastomer, may be incorporated in the spraying liquid. Lesser or greater amounts, however, may be employed depending upon the type of product desired and the characteristics desired.
The additive substances may be mixed with the elastomer as by milling the elastomer and the additive, or the additive substance may be mixed With or dispersed in the solution of the elastomer. By varying the amount of solvent and the amount of additive substance and the de gree of milling, the viscosity of the spraying liquid may be Varied over an extremely wide range. It is possible to utilize spraying liquids in forming the products of this invention which are totally unsuited for use in the usual or conventional spinning methods.
The primary gas stream may be at normal atmospheric or room temperature or any other desired temperature. For example, the temperature may be elevated so as to increase the rate of volatilization of the solvent. The gas may consist of a chemically reactive gas, steam, air or other inert gas such as nitrogen, carbon dioxide and the like. Since the fibers as they are formed by the attenuating effect of the gas stream and the voiatilization of the solvent are tacky or cementitious, particulate material such as solid particles or preformed fibers may be introduced into the primary gas stream so as to provide composite strand-like structures. As the preformed particulate material is brought into contact with the tacky elastomeric fibers, the particulate material adheres to the elastomeric fibers at their points or areas of contact. The fibers with or without the particulate material collected in a progressively overlapping relationship become bonded together at their points of contact in such relationship by the adhesiveness of the tacky elastomeric fibers. The bundle of progressively overlapping fibers with or without the particulate material is continuously removed to form a strandlil e structure.
Among the non-adhesive, non-elastomeric materials which may be utilized in the form of preformed fibers are natural fibers such, for example, as wood or pulp fibers, cotton, flax, jute, sisal, kapok, wool, hair and silk and synthetic fibers, for example, cellulosic fibers such as cellulose hydrate, cellulose derivatives such as cellulose esters, mixed cellulose esters, cellulose ethers, mixed cellulose ester-ethers, m xed cellulose ethers, cellulose hydroxy-alkyl ethers, cellulose carboxyalkyl ethers, cellulose ether-xanthates, cellulose xantho-fatty acids, cellulose thiourethanes; fibers made of alginic acid, gelatine, casein; and mineral fibers such as spun glass, asbestos, mineral wool and the like; and fibers made of natural and synthetic resins which are not rendered tacky when the potentially adhesive fibers are rendered tacky; also fibers and filaments made by slitting, cutting or shredding nonfibrous films, such as waste cellophane.
In addition to or as a substitute for such non-elastomeric fibers, particles of various classes may be introduced through the gas stream, such for example as cork dust, wood fiour, leather dust, or flake particles, or fibers of flock length. Products having abrasive properties may be formed by introducing abrasive particles such as emery dust or larger size paritcles. The tackiness of the fibers may be reduced by introducing a detackifier such as powdered talc. Two or more different foreign substances may be introduced into the gas stream and the substances may be of different physical form; for example, one may be in fiber form and the other in powdered form, depending upon the nature and characteristics desired in the final product.
The strand-like structures'may be formed by several procedures. For example, the spraying liquid containing the elastomeric material may be extruded into a vortex gas stream as illustrated diagrammatically in FIGURE 1. The apparatus for forming the strand-like structure consists of a tower 1 which is preferably in the form of a truncated cone provided with an internal spiral fin or flange 2. The fin is positioned Within the tower at an acute angle with respect to a horizontal plane. The width of the fin may be uniform throughout the tower or it may be tapered from a minimum width at the base of the tower to a maximum width at the top of the tower. The Width of the fin at the top of the tower is, of course, limited by the size of the strand withdrawn at the top of the tower and must provide a sufficient opening at the top of the tower to permit the gas to escape.
A spraying unit 3 is positioned adjacent the bottom of the tower. The spinning unit comprisesa spraying liquid conduit 4 provided with a plurality of spaced, upwardly projecting spray tips 5, each of which is provided with a suitable orifice at its upper end, and a gas conduit 6 provided with a plurality of spaced, upwardly projecting nozzles 7 surrounding the spray tips 5. The spray tips 5 are preferably concentric with respect to the nozzles 7. The spraying liquid containing the fiber-forming elastomer is continuously forced up through the spray tips by means of a suitable pump, not shown. A stream of gas such as air is continuously passed through conduit 6 and nozzles 7 by suitable means such as a blower, not shown, at a velocity appreciably higher than the velocity of extrusion of the spraying liquid. The elastomeric composition is forced out of each of the tips 5 as a single continuous plastic stream which is attentuated and broken transversely into discontinuous fibers or fibrils lb of varying length by the high velocity primary gas stream. The velocity of the extrusion and the velocity of the gas may be varied so as to regulate the amount of attenuation and hence the diameter of the fiber or fibrils, and may be increased sufiiciently to regulate the length of the fiber. Simultaneously, solvent is evaporated to partially harden or set the elastomeric fibers.
The relative velocities of extrusion of the spraying liquid and the gas emerging from nozzle 7 may be varied to some extent so as to provide the desired size and length of fiber within certain limits. In general, for a given spraying liquid, the greater the velocity of the gas with respect to the velocity of extrusion, the finer the fiber or fibrils. The relative velocity of the gas flow to the velocity of extrusion may be increased to provide fibrils of shorter length. It is not necessary and in many cases not desirable to heat the primary gas stream.
A secondary stream of gas such as air is supplied to the base of the tower 1 by means of a blower 8 and the gas stream entering the tower may be directed through an annular intake 9 beneath the fin 2. The secondary air stream is directed into a vortex or swirling gas flow by the spiral fin 2 thereby creating a reduced pressure or suction along the axis of the tower. The vortex gas fiow carries the fibers 10 toward the axis of the tower and as the fibers come into contact with each, they become bonded together at their points of contact. By continuously withdrawing the collected fiber bundle from the top of the tower, the fibers are deposited in a progressive, overlapping arrangement to form a strand-like structure 11. The fibers remain tacky at the time of deposition and the overlapping fibers ecome bonded together at their points and areas of com tact. The temperature of the secondary stream of gas may be regulated so as to remove all solvent or set the fibers before they emerge from the tower in the form of a strand-like structure. The strand-like structure may then be passed through a suitable heating chamber 12 wherein the elastomeric material is cured or vulcanized and the strandlike structure is accumulated on a take-up spool or drum 13.-
The secondary stream of gas may consist of chemically reactive gas, steam, air or other inert gas and may be supplied at any desired temperature.
In the-formation of composite strand-like structures comprising elastomeric fibers and preformed particulate material, for example, fibers such as rayon, nylon, sisal and the like, or preformed particles, for example, cork dust, emery dust, and the like, the particulate material may be introduced into the secondary gas stream and may be introduced through the blower 8. This preformed particulate material is carried or blown into contact with the spayed elastomeric fibers while these latter fibers are in a tacky or cementitious condition. Wherever the preformed particulate materials contact the tacky elastomeric fibers, they will be bonded together. As the elastomeric and attached particulate material are drawn together by the vortex gas flow, the tacky elastomeric fibers form additional bonding points Where they contact each other or other particulate material. As the fibers are deposited in overlapping arrangement, the overlapping elastomeric fibers become bonded to previously collected fibers and particulate material. The strand-like structure, after emerging from the tower, may be passed through the heating chamber 12 so as to cure or vulcanize the elastomeric material and the cured or vulcanized strand accumulated on the spool or drum 13.
In producing strand-like structures by utilizing the apparatus as shown in FIGURE 2, the elastomeric fibers are collected on a preformed primary filament or strand such as a thin wire, a cellulose fiber yarn, a thermoplastic resin filament and the like. A tower 14 is provided with one or more spraying units 15 each including a gas nozzle 16 and a spray tube 17 provided with a suitable extrusion orifice. A suitable spraying liquid containing the elastomeric material is extruded through the spray tube into a high velocity gas stream emerging from the nozzle 16. A secondary stream of gas may be passed through the tower by means of a suitable blower 18. The preformed filament or thread 19 is continuously drawn through the tower between guide rolls 20 and 21. The fibers formed as described hereinbefore are in a tacky or cementitious condition and bond together at their points of contact and, as they are deposited and collected on the filament 19 they become bonded to the filament and to each other at points and areas of contact. The continuous withdrawal of the filament through the tower results in a deposition and collection of the fibers in a progressive overlapping arrangement. As the fibers are collected on the previously deposited fibers, the overlapping fibers become bonded together at their points and areas of contact to form a coherent strand-like structure 22.
As the strand-like structure emerges from the tower,
it may be passed through a dusting chamber 23 wherein a' detackifier such as talc is applied to the outer surfaces to reduce the tacki'ness. The strand is then passed over guide roll 21 and through a suitable heating chamber 24 wherein the elastomeric material is cured or vulcanized. The cord is accumulated on a suitable spool or take-up drum 25.
The strand-like structure thus formed is shown in FIG- URE 7 and includes a core 26 consisting of the preformed filament or thread and the collected elastomer fiber cover 27. The elastomer fiber cover or sheath 27 comprises the fibers permanently bonded together in a progressive overlapping arrangement. Where the core 26 consists of a filament or strand of low tensile strength, th core filament may be broken to provide an elastic strand by subjecting the strand 22 to longitudinal tension applied be-.
tween spaced pairs of pressure rollers 28 and 29.
Alternative fiber-forming means of the type disclosed and claimed in the copending application of Richard P. Foster and Derek E. Till, Serial No. 501,932, filed April 18, 1955, now abandoned, may be utilized in producing the fibrous strands. A fiber-forming unit adapted to replace the spinning unit 3 in the apparatus shown in FIG- URE 1 is illustrated in FIGURE 3. The fiber-forming means includes a circular disc 30 having an upwardlyextending, integral rim or flange 31. A plurality of spaced,
radially extending spray nozzles 32 are mounted on the periphery of the flange. A cover plate 33 is secured to the flange 31 to provide a chamber 34 and an inverted conical shell 35 is secured to the cover plate 33. An impeller comprising a plurality of gas-moving vanes 36 is secured to the circular disc 30. The unit is mounted for rotation in a chamber, as chamber 1, by means of tubular shaft 37 to which the disc 30 is secured as by welding. The fiberforming liquid is supplied to the chamber 34 through the tubular shaft 37 which communicates with a source of the liquid.
A modification of the fiber-forming unit as shown in FIGURE 4 is adapted for use in the apparatus of FIGURE 2. The fiber-forming apparatus consists of a circular disc 38 having an integral rim 39 having a plurality of radially extending spray nozzles 40 mounted in spaced relationship along the periphery of the rim 39. A cover plate 41 is secured to the rim 39 to provide a chamber 42. An impeller comprising a plurality of gas-moving vanes 43 is secured to the circular disc 38. The unit is mounted for rotation by means of a tubular shaft 44 which is secured to the circular disc 38. A guide tube 45 is mounted concentrically within the tubular shaft 44 and extends through an aperture in cover plate 41. The preformed filament or thread 46 is continuously drawn through the guide tube 45. The fiber-forming liquid is continuously supplied to the chamber 42 from a source of the liquid (not shown) through the tubular shaft 44. v
As compared to the fiber-forming units of FIGURES 1 and 2, the units shown in FIGURES 3 and 4 do not require independent means for producing an air blast in forming the fibers since the impellers may be driven from the same power source as the extruding unit. The spinning liquid is supplied under pressure to the chamber of the spinning disc and is extruded through the spray noz-v zles by the centrifugal force created within the disc as it rotates in addition to the supply pressure. As the fiberforming liquid leaves the nozzle, it is subjected to this static extrusion pressure exerted in a radial direction. Simultaneously, the plastic stream is subjected to a tan gential force. The directions 'of these forces which are at right angles to each other are continuously changing with the rotation of the disc. These forces are believed to effect at least a portion of the attenuation of the plastic stream. The outermost end of the plastic or fiber is in the air and the extruded plastic which is just emerging from the extrusion orifice is moving in a circular path with the extrusion orifice. The friction between the end of the fiber and the air is believed to cause a drag which may account for a part of the attenuation of the plastic stream. The air fiow created by the impeller also subjects the fiber to a force which is at an angle to the plane of the extrusion and the tangential forces. As the free end of the fiber is blown upwardly a further drag is probably created with respect to the movement of the nozzle. The combined forces and the frictional drag cause the attenuation and stretching of the fiber and the breaking of the attenuated plastic to form discontinuous fibers. During this period, the major portion of the solvent becomes volatilized to establishthe size of the fibers.
As shown in FIGURE 5, a cord of limited elastic elongation or stretch may be formed from the elastic strand 47 by wrapping or braiding the elastic strand with textile threads, yarns and the like 48. The amount of stretch may be controlled by the number of turns of the textile yarns per unit length. The textile yarns may be wrapped around the elastic strand either before or after the elastomeric material has been cured or vulcanized. If it is desired to provide a bond between the textile yarns and the elastomeric material, the Wrapping is provided prior to curing. Obviously, if no bond is desired, the wrap ping is applied after the elastomeric material has been cured.
A rope-like structure may be formed as illustrated in FIGURE 6 by twisting a plurality of elastic strands 49.
The strands may be twisted together either prior to curing the elastomeric material if it is desired to provide a bond between the individual strands 49, or after curing the elastomeric material if no bond is desired between the strands. The strands may be wrapped with textile yarns and the like prior to twisting or the twisted structure may be wrapped with such yarns and the like depending upon the characteristics desired in the finished IO e.
Elomposite cords and ropes may be produced from the cord-like structures consisting of the elastomer fibers and preformed non-elastomer fibers. cords and ropes, of course, will have a limited elasticity but will possess an extremely high impact resistance and a. greater extensibility than similar cords made entirely of non-elastomer fibers.
Rope may also be formed by twisting together one or more of the composite cords, or by combining the cords as described herein with cords formed of conventional fibers and filaments.
Strands formed as described herein also are adapted for the production of such articles as weather stripping as shown in FIGURE 8. The longitudinal marginal edge of web 51 is embedded in the strand 50 which may consist of elastomeric material fibers with or without nonelastomeric fibers. The web may be formed of a woven textile fabric, metal screening, a combination of fabric and metal wire, or any other desired material. The web and strand may be assembled before the elastomeric material is cured. The assembly is provided with a continuous envelope 52 ofrubber or other elastomeric material and the coated assembly finally treated to cure the elastomeric material.
While preferred embodiments of the invention have been shown and described, it is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.
1. In a method of producing a strand, the steps which comprise extruding an elastomeric composition into and within an unconfined, high velocity stream of gas to form a continuous stream of the elastomeric composition, the direction of extrusion being coincident with the direction of gas flow, attenuating the extruded continuous stream of the elastomeric composition, partially setting the elas tomeric composition and breaking the attenuated stream to form elastomeric fibers by maintaining the velocity of the stream of gas at a value greater than the velocity of extrusion of the elastomeric composition and collecting the fibers as an elongated strand wherein the fibers are in progressive overlapping and intermingled relationship and are bonded to each other at their points of contact.
2. In a method of producing a strand, the steps which comprise extruding an elastomeric composition into and within an unconfined, high velocity stream of gas to form These composite a continuous stream of the elastomeric composition, the direction of extrusion being coincident with the direction of gas flow, attenuating theextruded, continuous stream of the elastomeric composition, partially setting the elastomeric composition and breaking the attenuated stream to form fibers by maintaining the velocity of the stream of gas at a value greater than the velocity of extrusion of the elastomeric composition and collecting the fibers in a progressive overlapping and intermingled relationship on a moving supporting strand, the fibers being bonded to each other at their points of contact.
3. In a method of producing a strand, the steps which comprise extruding an elastomeric composition into and within an unconfined, high velocity gas stream to form a continuous stream of the elastomeric composition, the direction of extrusion being coincident with the direction of gas flow, attenuating the extruded, continuous stream of the elastomeric composition, partially setting the elastomeric composition and breaking the attenuated stream to form fibers by maintaining the velocity of the stream of gas at a value greater than the velocity of extrusion of the elastomeric compositon, passing a supporting strand through the mass of fibers, collecting the fibers in a progressive overlapping and intermingled relationship on the supporting strand and bonding the fibers to each other at their points of contact.
4. In a method of producing a strand, the steps which comprise extruding an elastomeric composition into and within an unconfined high velocity gas stream to form a continuous stream of the elastomeric composition, the direction of extrusion being coincident with the direction of gas flow, attenuating the extruded, continuous stream of the elastomeric composition, partially setting the elastomeric composition and breaking the attenuated stream to form fibers by'maintaining the velocity of the stream of gas at a value greater than the velocity of extrusion of the elastomeric composition, passing a supporting strand through the mass of fibers, collecting the fibers in a progressive overlapping and intermingled relationship on the supporting strand, bonding the fibers to each other at their points of contact, and thereafter breaking the supporting strand at a multiplicity of spaced points to form an elastic strand.
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