EP1183410B1

EP1183410B1 - Tow and process of making

Info

Publication number: EP1183410B1
Application number: EP00928918A
Authority: EP
Inventors: John Seungun Ahn; Darren Scott Quinn
Original assignee: Advansa BV
Current assignee: Advansa BV
Priority date: 1999-05-10
Filing date: 2000-05-09
Publication date: 2006-07-19
Anticipated expiration: 2020-05-09
Also published as: AU4708200A; JP2002544398A; WO2000068476A1; CN1349571A; EP1183410A1; KR20010112483A; DE60029441T2; DE60029441D1

Description

FIELD OF THE INVENTION

The present invention relates to a tow and battings and articles produced therewith, and processes for making such tow, batting or article.

BACKGROUND OF THE INVENTION

The production of spreadable continuous filament tows with mechanical crimp and processes used to spread the filaments uniformly have been described, for example, in U.S. Patent Nos. 3,730,824 and 3,952,134. In addition, a crimped tow band, which has been run through a spreader is known. Such tow bands are useful for the production of battings that may be used as fiberfill for articles such as pillows, sleeping bags, etc. Such spreadable tows with mechanical crimp are particularly advantageous in their simplified processing requirements for producing useful items and in the relative strength of battings produced from such tows as compared to conventional battings produced from mechanically crimped, carded staple fibers. Mechanically crimped tows and the battings produced from them however suffer in the limited softness, loft and other aesthetic properties, which can be obtained.
In addition, the use of three-dimensionally crimped staple fibers is also well-known in the art. Several methods for imparting a three-dimensional structure exist and include the technologies of asymetrically quenching, bulk continuous filament (BCF) processing, conjugate spinning of two polymers differing only in molecular chain length, and bicomponent spinning of two different polymers or copolymers such as that disclosed in U.S. Patent No. 5,723,215, U.S. Patent No. 3,671,379, and Japanese Patent JP61-32404(B2).
U.S. Patent No. 5,683,811 discloses bicomponent polyester fibers having a spiral crimp. Such polyester fibers may be used in the production of pillows and other filled articles.
Relative to mechanically crimped staple fibers and tows, three-dimensionally crimped staple fibers and articles produced from them are known to offer distinct advantages such as higher loft, softness, improved crimp recovery, shelf appeal, and better compactibility. However, processing of these three-dimensionally crimped staple fibers is often difficult due to the softness and silkiness attributed in part from the crimp structure. Battings made from such fibers likewise have deficiencies in that they are often weak and easily destroyed.
There is thus a need in the art to obtain a method of making and handling three-dimensionally crimped fibers in the production of a tow, which may be spread to produce battings for use in articles, such as sleeping bags, comforters, duvets and pillows.

SUMMARY OF THE INVENTION

In accordance with these needs, there is provided, according to the present invention, a three-dimensionally crimped spreadable continuous filament tow band according to claim 1. Battings and articles comprised of the three-dimensionally crimped spreadable continuous filament tow band are a further aspect of the' invention.
Further objects, features, and advantages of the invention will become apparent from the detailed description that follows:

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic representation showing a bicomponent tow spin and draw process according to the present invention.
Fig. 2 is a schematic representation showing a tow spreading process according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention overcomes the problems associated with the prior art by producing a three-dimensionally crimped tow using a low cohesion tow production process, and a band stacking procedure, which imparts a low cohesion between individual constituent bands thus enabling the combined tow band to be processed through spreading as an integral unit. A tow thus produced can be separated into its component bands through the thickness of the stack. In addition, the tow can still be processed through the spreading apparatus as if it were one single tow line. Each tow band is thus allowed to spread across the width of the spreader uniformly.
The term, "crimp," as used in this description, refers to the waviness or bulk of the fiber. A "three dimensional crimp" thus refers to the bulk or waviness of a fiber in three dimensions, as compared to, for example, a two-dimensional zigzag crimp from mechanical crimping. Three dimensional crimp has been described in the art using various terms including, for example, spiral or helical crimp, omega crimp, three-dimensional random crimp, etc. Three dimensionally crimped fibers are also described to a great extent in the art related to fiber clusters and bulk continuous filament technologies. Methods of obtaining a three-dimensional crimp have also been described. For example, U.S. Patent No. 4,618,531 describes a method of making clusters or randomly-arranged, entangled, spirally-crimped polyester fiberfill. U.S. Patent No. 5,723,215 describes a method of making bicomponent polyester fibers having spiral or helical crimp.
A "tow band," "tow," or "rope band" refers to a large strand of continuous manufactured filaments that are collected in a loose, rope-like form. The tow band of the present invention comprises bicomponent filaments containing at least two polymers. Exemplary polymers for the tow band of the present invention include, but are not limited to, homopolymers, copolymers, and terpolymers of monomers formed into any type of melt spinnable polymers. Such melt spinnable polymers include polyesters, such as polyethylene terephthalate (PET), polybutyene terephthalate (PBT or 4GT), polytrimethylene terephthalate (PTT or 3GT), polypropylene terephthalate, and polyethylene naphthalate (PEN); and polyolefins, such as polypropylene and polyethylene (PE); and combinations thereof, including bicomponent polyester fibers prepared from PET and PTT. Methods of making the homopolymers, copolymers and terpolymers used in the present invention are known in the art and may include the use of catalysts, co-catalysts, and/or chain-branchers to form the copolymers and terpolymers, as known in the art.
The polymers and resultant fibers used in the present invention can comprise conventional additives, which are added during the polymerization process or to the formed polymer, and may contribute towards improving the polymer or fiber properties. Examples of these additives include antistatics, antioxidants, antimicrobials, flameproofing agents, dyestuffs, light stabilizers, polymerization catalysts and auxiliaries, adhesion promoters, delustrants, such as titanium dioxide, matting agents, organic phosphates, and combinations thereof. Other additives that may be applied on fibers, for example, during spinning and/or drawing processes include antistatics, slickening agents, adhesion promoters, antioxidants, antimicrobials, flameproofing agents, lubricants, and combinations thereof. Moreover, such additional additives may be added during various steps of the process as is known in the art.
Of particular value in the production of synthetic fiberfill products is the application of a slickening agent as is known in the art. The slickening agent provides a silky, downlike tactile aesthetic to the fiber or batting and allows the fibers in the final finished article to move past one another during use without matting. Any suitable slickening agent may be used, such as various silicone oils, preferably polyaminosiloxanes. Antistatic and lubricating agents applied to the fiber are also of particular importance due to the assistance they afford during fiber processing. The antistatic agents can be used to prevent generation of static on the tow spreader, and can be applied to the fibers before or after being drawn.
The fibers used in' the present invention may further have any suitable cross-sectional shape. The cross-sectional shapes, for example, may include round, oval, trilobal, shapes with higher numbers of symmetric or asymmetric lobes, dog-boned shape, and hollow fibers having a plurality of holes or voids, preferably about 1 to about 10 holes, as is known in the art. In one embodiment of the invention, the fibers have a trivoid round cross-section.
The fibers in the tow band comprise bicomponent fibers of a first component selected poly(ethylene terephthalate) and copolymers thereof and a second component selected from poly(trimethylene terephthalate) and copolymers thereof, the two components being present in a weight ratio of about 95:5 to about 5:95, preferably about 70:30 to about 30:70. The cross-section of the bicomponent fibers can be side-by-side or eccentric sheath/core When a copolymer of poly(ethylene terephthalate) or poly(trimethylene terephthalate) is used, the comonomer can be selected from linear, cyclic, and branched aliphatic dicarboxylic acids having 4-12 carbon atoms (for example, butanedioic acid, pentanedioic acid, hexanedioic acid, dodecanedioic acid, and 1,4-cyclo-hexanedicarboxylic acid); aromatic dicarboxylic acids other than terephthalic acid and having 8-12 carbon atoms (for example, isophthalic acid and 2,6-naphthalenedicarboxylic acid); linear, cyclic, and branched aliphatic diols having 3-8 carbon atoms (for example, 1,3-propane diol, 1,2-propanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, and 1,4-cyclohexanediol); and aliphatic and araliphatic ether glycols having 4-10 carbon atoms (for example, hydroquinone bis(2-hydroxyethyl)ether, or a poly (ethyleneether) glycol having a molecular weight below about 460, including diethyleneether glycol). Isophthalic acid, pentanedioic acid, hexanedioic acid, 1,3-propane diol, and 1,4-butanediol are preferred because they are readily commercially available and inexpensive. Isophthalic acid is more preferred because copolyesters derived from it discolor less than copolyesters made with some other comonomers. When a copolymer of poly(trimethylene terephthalate) is used, the comonomer is preferably isophthalic acid. 5-sodium-sulfoisophthalate can be used in minor amounts as a dyesite comonomer in either polyester component.
The tow band of the present invention may be used to make a batting. A "batting," as used herein, refers to a continuous filament tow band that has been spread to approximately 4 or more times its initial width on a tow spreader and has been cross-lapped to form a plurality of layers. Preferably, the batting has one to five layers of the continuous filament tow band. The batting is then used as fiberfill for articles such as pillows, sleeping bags, cushions, quilts, and insulating garments or articles.
The method of making the three-dimensionally crimped continuous filament spread tow of the present invention comprises first producing fibers with the capability of forming a three-dimensional crimp structure. This can be conducted by any known means, including, but not limited to, asymmetrical quenching, bulk continuous filament (BCF) processing, conjugate spinning of two polymers differing only in molecular chain length, and bicomponent spinning of two different polymers or copolymers. Preferably, the filaments are spun having the capability of forming a three-dimensional crimp, and subsequently drawn to achieve molecular orientation, which forms the crimp or causes the crimps to form.
One example of making a fiber having a three-dimensional crimp structure includes the process of extruding two component polymers through a capillary, spinning the extruded polymers into a filament to form a fiber with two distinct levels of spun orientation and drawing the fiber and releasing the tension such that the three-dimensional crimp forms.
A second method of making a three-dimensionally crimped fiber involves spinning a polymer through a capillary and immediately contacting the polymer stream with a cooling fluid to form a filament such that the filament thus formed will have a spun orientation gradient across its diameter due to the differential rates of cooling throughout the fiber. This "asymmetric quenching," as it is called, may be conducted by known methods. For example, asymmetrical quenching may involve directing a jet of air against one capillary. Alternatively, the filaments may be contacted with a continuously renewed film of water on one side to produce the desired three-dimensional crimp. Following asymmetric quenching, the filament is drawn and tension is released such that three-dimensional crimps form.
Moreover, the methods for preparing three-dimensional crimp may be effected in other manners known in the art. In addition, combinations of two or more of the aforementioned technologies may be employed. For example, using fibers with different cross-sections may attribute to the inclusion of one or more voids or to having a non-round periphery. This may then provide or accentuate the three-dimensional crimp structure of the fibers as well as providing other useful properties.
Other methods for preparing a three-dimensional crimp are known in the art and/or described in literature references, such as Polyester Fibers - Chemistry and Technology, Hermann Ludwig, Wiley-Interscience, 1964. Any of these technologies may be used as the manner of imparting the three-dimensional crimp structure to the fiber.
Once the fibers having the capability of forming a three-dimensional crimp structure is attained, the fibers are grouped to form a plurality of separate ropes. Any number of separate ropes may be made of the fibers having the three-dimensional crimp. There should be at least two ropes, preferably, 2 to 20 ropes, and most preferably, 2 to 10 ropes. These ropes are then subjected to a low cohesion tow production process.
The "low cohesion" tow production process involves drawing under heat the separate ropes simultaneously to form flat ribbons, cooling the ribbons to prevent further drawing, continuously stacking the individual ribbons one atop the others, and compressing the band. The band may be compressed in any suitable apparatus for compression. Preferably, the band is compressed through the nip of a pair of co-rotating rolls. This stacking provides a slight ribbon to ribbon cohesion without forcing the ribbons to be inextricably linked to each other. This stacking may be performed in any desired manner, and preferably, the width of the completed stack is essentially equivalent to the width of each of the previously independent bands. In addition to providing a slight level of cohesion, the compression also removes excess water from the band. A slickening agent may be topically applied subsequent to and/or prior to the compression step.
After the flat ribbons are drawn, stacked, and compressed and/or dewatered, the three-dimensional crimp is formed or accentuated. For example, the three-dimensional crimp may form spontaneously for bicomponent filaments and asymmetrically-crimped filaments once the tension is reduced or removed from the tow band. On the other hand, the three-dimensional crimp may be formed earlier in the tow production process, for example, for BCF fibers, and the reduction or removal of tension results in accentuating the already formed 3-D crimp.
Following crimp formation, the filaments may be treated to set the crimp. For example, for spontaneously formed three-dimensional crimp tow bands, the filaments are typically heated in a continuous oven to relieve shrinkage tension, heat set the crimp and, if applicable, to complete the curing reaction of the slickening agent. The bands are then cooled to below the glass transition temperature of the polymer such that the crimp is made permanent and packed into a shipping/storage container for transport to the tow spreading process. Other methods of permanently setting the crimp are known in the art and can be used.
In accordance with the present invention, a "low cohesion tow production process" is, thus, one which provides tow band integrity adequate to allow packaging and introduction to a tow spreader as a subsequent processing step, but which allows the tow band to be easily deregistered into individual filaments on the tow spreader. "Deregistering," as used herein, refers to the opening of a tow of continuous crimped filaments such that the crimp structure in each filament is out of synchronization with that of adjacent filaments. Typically, the deregistration will be followed by a spreading step in which the width of the tow band will be increased from 4 to 10 times that of the entering tow band as the band spreads substantially uniformly across the width of the spreader and along the length of the band as it passes through the spreading apparatus.
During the process of making the three-dimensional crimped spreadable continuous tow of the present invention, the filaments or fibers may be treated with any of a number of finishing agents as set forth above. In a preferred embodiment, the filaments are coated with a slickening agent on the draw machine to make filaments soft and slick. Preferably, the slickening agent is a silicone oil. In yet another preferred embodiment, the filaments are treated with an antistatic finish on the draw machine to eliminate static generation on the tow spreader.
The slickening agent is preferably applied after drawing, but prior to heat setting. The heat setting can then cure the slickening agent and bond it to the fiber. Then, after this step, an antistatic agent can be applied.
It is further recognized that additional process steps can readily be added and such steps should be considered within the scope of this invention. The product produced from such process is further within the scope of the present invention.
The following description refers to the figures as examples of how the process of producing the three-dimensionally crimped spreadable continuous filament tow band of the present invention may be conducted.
In Fig. 1, only the minimum essential operational steps for producing a bicomponent spreadable tow involving a bicomponent tow spin and draw process are described.
In Fig. 1, two separate polymers are simultaneously spun through each spinneret capillary in a manner well-known in the art for making bicomponent fibers by first passing the polymers through a device, 1, designed to distribute each polymer to the entrance of each capillary on spinneret, 2.
Polymers are then extruded through the spinneret, quenched with a suitable medium, typically conditioned air, and drawn around one or more godets, 3 & 4. Fibers thus produced from one or more spinnerets are then collected into a suitable collection container, 5, and transported to the separate drawing step.
In the drawing step, multiple spun ropes from separate containers, illustrated by 6, 7, 8, & 9, are combined and separated as necessary to form a plurality of at least two separate ropes, preferably, two to twenty, most preferably, two to ten separate ropes. In the most preferred embodiment, four or more separate ropes are made. These ropes are then drawn separately and simultaneously between a first roll set, 10, and a second roll set, 11, which is operating at a surface speed from 2.5 to 5 times, preferably 3.0 to 3.5 times that of the first set. The draw temperature is controlled by either the use of heated rolls or, as set forth in Fig. 1, by the use of liquid sprays, 12, of which the first series of sprays are operated at a controlled temperature of about 90°C to about 99°C (194°F to 210°F) while the latter sprays are operated between about 15°C to about 70°C (59°F to about 158°F), preferably about 20°C to 40°C (68°F to 104°F). Alternatively, feed rolls 10 could be controlled at the higher temperatures while draw rolls 11 would be controlled at the lower temperature.
Following the draw rolls, the separate bands are pulled by a pair of opposing rolls, 14, through a unit for stacking the bands, which in Fig. 1 is depicted as angled bars, 13. This stacking may be performed in any desired manner, and preferably is done so in order to have the width of the completed stack be essentially equivalent to the width of each of the previously independent bands.
The stacked bands are then deposited under low tension onto a belt, 15, which passes the fiber through an oven, 16. The oven serves to remove shrinkage from the fiber and to cure any siliconized finish, which can be applied to the fiber by any of several known means prior to deposition on the oven belt. Typically, the oven temperature is about 100°C to about 200°C (212°F to about 392°F), preferably about 140°C to about 180°C (284°F to 356°F). Dwell time within the heated zones of the oven typically ranges from 5 to 20 minutes, preferably 7 to 15 minutes. The fiber then passes through a cooling zone operating at ambient temperature for 1 to 5 minutes, preferably 1 to 3 minutes. Following the oven, the fiber is deposited into a suitable storage/shipping container 17 for transport to the tow spreader.
The following description pertains to Fig. 2, which describes one example of the tow spreading process within the scope of the present invention. In Fig. 2, the tow band, 18, comprised of helically crimped fibers, is extracted from the storage/transport container, 19, and pulled through an antifold guide, 20, which serves to remove twists and folds from the band.
The tow of Fig. 2 is then pulled through a series of guides, 21, 22, & 23, before passing into the nip created by a driven pair of opposing cylindrical rolls, 24 & 25. The first of these rolls 24 is metallic and has a helically grooved surface. The second roll is of a composition of rubber-like material and has a smooth surface. From this roll pair, the tow band passes into the nip created by a second pair of opposing rolls, 26 & 27, which are constructed essentially identical to rolls 24 & 25, respectively, and which are driven at a speed higher than that of the first pair. The speed differential coupled with the grooved roll surfaces causes a differential drafting and gripping of the filaments and serves to deregister the tow. These different surfaces and compositions of the rolls may be modified provided that a differential gripping action is achieved as has been described in the art, for example, in U.S. Patent No. 3,423,795.
The deregistered tow then passes through the nip created by a driven pair of opposing smooth rolls, 28 & 29, which serve to isolate the high tension deregistration process from the low tension spreading process which follows.
From the isolation rolls, the tow may pass through a spreading section. For example, the spreading section may contain an air spreading jet, 30, similar to that described by Watson in U.S. Patent No. 3,423,795, and an opposing set of driven metallic rolls, 31 & 32. Air passing through the spreading jet forces the filaments within the tow band to migrate outward from the centerline. From the 1^st spreading section, the tow passes through a 2^nd spreading section comprised air spreading jet, 33 and tension isolation rolls 34 and 35. Spreading section 2 is essentially identical to section 1 with the exception that the air spreading jet and tension isolation rolls are all longer. This increased length allows the tow band to spread wider as it progresses through the machine. Following the 2^nd spreading section, the tow passes through a 3^rd spreading section containing air spreading jet 36 and tension isolation rolls 37 and 38. While essentially similar to the previous spreader section, this section is wider still thus allowing the tow to spread further. The tow passing from the 3^rd spreader section passes into a 4^th spreader section shown by air spreader box 39 and rolls 40 and 41, which while similar to the previous parts are again wider than the previous section.
From this spreader section, the tow may pass down through a nip created by a pair of cross lapper rolls, 42 & 43, which simultaneously pull the spread tow from roll 41 while oscillating perpendicularly above a moving belt, 44, thus forming a layered batting of continuous filaments, 45. The cross-lapped batting may further be drafted by passing through one or more sets of drafting rolls to further reduce and better control the weight per unit area. The batting thus formed may at this point be collected onto rolls, subjected to a resin bonding application rolled into pillows or any of the other processing steps common to fibrous batting manufacturer.
The three-dimensionally crimped spreadable continuous filament tow of the present invention is useful to make battings that exhibit good loft. In particular, the loft created by the three-dimensional crimp from the bicomponent tow of the present invention is superior to the loft of known two-dimensional mechanically crimped tows. The three-dimensionally crimped tow also exhibits other desirable attributes such as better compressibility, softness, increased filling power, strength, and increased warmth.
Furthermore, most three-dimensionally crimped structures typically have difficulty in spreading and separating the fibers from one another since the crimp in each fiber has many random contact points with other fibers. As a result, defects in spreading typical bicomponent tows include open sections caused when a filament from one portion of the band adheres to an adjacent filament as the band is spread, which creates a hole in the web next to the adhered filaments. However, the three-dimensionally crimped spreadable tow of the present invention overcomes these difficulties by stacking the multiple small bands, which reduces fiber cohesion across the band, while the stacking provides cover such that a defect in any one band is masked by the other bands. Moreover, by drawing the tow from a plurality of separate ropes and then stacking the bands, there is enough cohesion transversely across the band to obtain uniform spreading. Accordingly, the three-dimensionally crimped spreadable tows of the present invention are capable of being' uniformly spread to produce battings with high loft, better compressibility, softness, increased filling power, strength, and warmth. Moreover, this arrangement serves to minimize foldovers, splits, and cross-over filaments, which hinder good spreading.

Claims

A tow band comprising a three-dimensionally crimped spreadable continuous filament, wherein the tow band comprises bicomponent fibers comprising a first component selected from the group consisting of poly(ethylene terephthalate) and copolymers thereof and a second component selected from the group consisting of poly(trimethylene terephthalate) and copolymers thereof, the two components being present in a weight ratio of 95:5 to 5:95.
The tow band of claim 1, wherein the tow band comprises helically crimped filaments.
The tow band of claim 1, wherein the two components are present in a weight ratio of between 70:30 to 30:70.
The tow band of claim 1, wherein the first component is a copolymer of poly(ethylene terephthalate), wherein a comonomer used to prepare the copolymer is selected from the group consisting of isophthalic acid, pentanedioic acid, hexanedioic acid, 1,3-propanediol, and 1,4-butanediol.
A batting comprising a three-dimensionally crimped spreadable continuous filament tow band according to claim 1.
A filled article comprised of a three dimensionally crimped, spreadable tow band according to claim 1.