Patent Description:
Braided cords having a central core surrounded by a braided jacket (sheath) are conventionally known and used in a wide variety of applications. Often described as "core-sheath" structures, these braided materials are useful in applications such as fishing lines, nets, blind cords, ropes and medical textiles. Such braided cords are disclosed in <CIT>, disclosing the preamble portion of claim <NUM>, <CIT> and <CIT>.

In contrast to core-sheath structures, cords without the braided sheath are more prone to loss of integrity through untwisting and are more prone to damage to the load-bearing fibers through abrasion, cutting, or strand pull out.

In certain applications, such as surgical threads, the characteristics of the braided sheath can profoundly impact the functionality and utility of cords having a core-sheath structure. For example, because conventional sheath structures are typically formed by braiding twisted strands that resist flattening, conventional braided jackets tend to be rigid and thick structures that behave differently from their underlying core structures.

In small core-sheath cords for specialty applications where limited volume is available for passage of the cord, such as medical cords, the thickness of the protective jacket can be a limiting factor. If strands of the protective jacket (sheath) could be selectively flattened, then the volume taken up by the jacket could be minimized - thereby allowing the use of larger core structures (braids or twisted threads) to increase load bearing capacity within the same volume. An ability to selectively flatten the strands of the protective jacket could also allow the diameter of a core-sheath cord to be reduced while still maintaining the load bearing capacity of a conventional core-sheath cord having a larger diameter.

The use of a flattened jacket in a core-sheath structure could also enable the sheath to better conform to the cross-sectional shape of the core, especially in applications where the cross-sectional shape of a core-sheath cord is preferably controlled to enable better manipulation of the cord during use. An ability to control the shape of the jacket in a core-sheath structure could also enable the surface texturing of the core-sheath structure to be tailored to particular applications where surface texture and/or roughness is a factor.

The present inventors have recognized that a need exists to discover methods and materials for producing core-sheath structures having thin braided sheaths that exhibit greater flexibility and controllability compared to conventional sheath structures. For example, a need exists to produce core-sheath cords where the braided sheath is in the form of a flattened jacket that dynamically conforms to the outer surface of the underlying central core while at the same time protecting the cord against damage. A need also exists to produce core-sheath structures where the texture of the braided jacket can be controlled in order to increase or decrease surface roughness compared to conventional jackets, which can be used to impart medical textiles and other cord-like structures with improved properties.

The following disclosure describes the preparation, which is not covered by the claims, and utility of core-sheath structures having selectively-flattened braided sheaths that function to protect the core while at the same time being able to dynamically conform to the outer surface of the core.

Embodiments of the present disclosure, described herein such that one of ordinary skill in this art can make and use them, include the following:.

Additional objects, advantages and other features of the present disclosure will be set forth in part in the description that follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present disclosure without departing from the scope of the claims. The present disclosure encompasses other and different embodiments from those specifically described below, and the details herein are capable of modifications in various respects without departing from the present disclosure. In this regard, the description herein is to be understood as illustrative in nature, and not as restrictive.

Embodiments of this disclosure are explained in the following description in view of figures that show:.

Embodiments of this disclosure include various methods for producing core-sheath structures, the method being not covered by the claims, as well as cords obtained by these methods. Certain, non-limiting applications for the core-sheath structures of the present disclosure are also described herein.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by persons of ordinary skill in the relevant art. In case of conflict, the present specification, including definitions, will control.

Unless stated otherwise, all percentages, parts, ratios, etc., are by weight.

When an amount, concentration, or other value or parameter is given as a range, or a list of upper and lower values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper and lower range limits, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the present disclosure is to be limited to the specific values recited when defining a range.

The use of "a" or "an" to describe the various elements and components herein is merely for convenience and to give a general sense of the disclosure. This description should be read to include one or at least one and the singular also includes the plural unless it is clear that it is otherwise intended.

Unless expressly stated to the contrary, "or" and "and/or" refers to an inclusive and not to an exclusive. For example, a condition A or B, or A and/or B, is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

The terms "about" and "approximately" as used herein refer to being nearly the same as a referenced amount or value, and should be understood to encompass ± <NUM>% of the specified amount or value.

The term "substantially" as used herein, unless otherwise defined, means all or almost all or the vast majority, as would be understood by the person of ordinary skill in the context used. It is intended to take into account some reasonable variance from <NUM>% that would ordinarily occur in industrial-scale or commercial-scale situations.

Throughout the present description, unless otherwise defined and described, technical terms and methods employed to determine associated measurement values are in accordance with the description of ASTM D855 / D885M - 10A (<NUM>), Standard Test Methods for Tire Cords, Tire Cord Fabrics, and Industrial Filament Yarns Made From Man-made Organic-base Fibers, published October <NUM>.

For convenience, many elements of the various embodiments disclosed herein are discussed separately. Although lists of options may be provided and numerical values may be in ranges, the present disclosure should not be considered as being limited to the separately described lists and ranges. Unless stated otherwise, each and every combination possible within the present disclosure should be considered as explicitly disclosed for all purposes.

The materials, methods, and examples herein are illustrative only and, except as specifically stated, are not intended to be limiting. Methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present disclosure.

Embodiments described herein include methods and materials for producing core-sheath structures having shape-controlled jackets (sheaths) that exhibit improved characteristics compared to conventional braided sheaths. Shape-controlled jackets of low thickness can, in some cases, more tightly conform the shape of the sheath to the outer surface of the core in order to control the texturing and surface roughness of the resulting core-sheath structure.

The term "core-sheath structure" as used herein describes cord-like structures having an outer sheath (jacket) of braided strands at least partially surrounding a central core. Different perspectives and embodiments of such core-sheath structures are illustrated in <FIG>, <FIG>, <FIG>, and <FIG>.

<FIG> illustrates the basic components of a core-sheath structure <NUM> including a central core <NUM> that is partially surrounded in this depiction by a biaxial braided jacket (sheath) <NUM> formed of S-strands <NUM> braided in a left-hand direction along a braid axis <NUM> of the core <NUM> and of Z-strands <NUM> braided in a right-hand direction along the braid axis <NUM>.

As shown in <FIG>, the surface of the braided jacket (sheath) <NUM> includes protrusions <NUM> where the S- and Z-strands <NUM> and <NUM> overlap. The distance (S) <NUM> between adjacent protrusions <NUM> situated along the braid axis <NUM> direction of the braided jacket (sheath) <NUM> is indirectly related to the pick count of the braid. In a braided rope or jacket, the "pick count" defines the number of strands rotating in one direction (i.e., the S-strands <NUM> or the Z-strands <NUM> in <FIG>) over one cycle length divided by the cycle length. Pick count is generally expressed in terms of the number of crossovers per inch or per meter. Thus, as the distance (S) <NUM> in <FIG> increases the pick count of the braided jacket (sheath) <NUM> decreases.

Because the central core <NUM> in the depiction of <FIG> is only partially surrounded by the braided jacket (sheath) <NUM>, numerous gaps <NUM> also exist in the braided sheath <NUM> indicating a surface coverage of less than <NUM>%. In other core-sheath structures where the surface coverage of the braided jacket (sheath) <NUM> approaches or exceeds <NUM>%, no gaps <NUM> would exist in the braided sheath <NUM>.

<FIG> also depicts a "plane P" <NUM> that defines a cross section of the core-sheath structure <NUM> at a point along the braid axis <NUM> where the protrusions <NUM> formed by the overlapping S- and Z-strands <NUM> and <NUM> exist. The same "plane P" <NUM> is defined as the plane of the paper in <FIG>, <FIG>, <FIG> and <FIG>.

As explained above, embodiments of this disclosure include core-sheath structures having shaped-controlled (flattened) jackets of low thickness than can more tightly conform to the outer surface of the core in order to control the texturing and surface roughness of the outside surface of the core-sheath structures. Comparing <FIG> and <FIG> illustrates this feature.

<FIG> illustrates the cross-section of a conventional core-sheath structure <NUM> having a central core <NUM> surrounded by a biaxial braided jacket (sheath) <NUM> formed from twisted S- and Z-strands <NUM> and <NUM> that are braided along the braid axis (not shown), extending outward in a direction perpendicular to the "plane P" <NUM>, of the core <NUM>. As shown in <FIG>, the lateral surface of the braided jacket (sheath) <NUM> includes protrusions <NUM> where the S- and Z-strands <NUM> and <NUM> overlap.

<FIG> also illustrates the maximum and minimum diameters (Dmax & Dmin) <NUM> and <NUM> of the braided sheath <NUM>, as measured within the cross-sectional "plane P" <NUM>. Dmax <NUM> is the maximum diameter as measured between the protrusions <NUM> and <NUM>' situated on opposite sides of the braided sheath <NUM>; whereas Dmin <NUM> is the minimum diameter as measured between non-overlapped S- or Z-strands <NUM> and <NUM>' situated on opposite sides of the braided sheath <NUM>.

Because the braided sheath <NUM> in the conventional core-sheath structure <NUM> of <FIG> is formed using twisted S- and Z-strands that are rigid and resist flattening, large protrusions <NUM> exist on the lateral surface of the braided sheath <NUM> leading to significant texturing and surface roughness of the core-sheath structure <NUM>. In contrast, <FIG> illustrates an embodiment of the present disclosure in which the use of shaped S- and Z-strands leads to a flattened braided sheath having reduced texturing and surface roughness compared to the conventional core-sheath structure <NUM> of <FIG>.

<FIG> illustrates the cross-section of a core-sheath structure <NUM> of the present disclosure having a central core <NUM> surrounded by a flattened braided jacket (sheath) <NUM> formed from non-twisted S- and Z-strands <NUM> and <NUM> that are shaped to have cross-sectional aspect ratios of at least <NUM>:<NUM>. The shaped S- and Z-strands <NUM> and <NUM> are braided along the braid axis (not shown), extending outward in a direction perpendicular to the "plane P" <NUM>, of the core <NUM>. As shown in <FIG>, the lateral surface of the braided jacket (sheath) <NUM> includes significantly smaller protrusions <NUM> (where the shaped Sand Z-strands <NUM> and <NUM> overlap) compared to the protrusions <NUM> in the braided jacket <NUM> of <FIG>.

Importantly, the difference (ΔD) between the Dmax and the Dmin <NUM> and <NUM> of the braided sheath <NUM> in <FIG>-(ΔD = Dmax - Dmin)-is significantly less than the difference ΔD of the braided sheath <NUM> of <FIG> due to the presence of the shaped Sand Z-strands <NUM> and <NUM> in the braided sheath <NUM> of <FIG>.

Because the flattened braided sheath <NUM> in the core-sheath structure <NUM> of <FIG> is formed using non-twisted strands in both the S and Z directions <NUM> and <NUM> that are shaped to have cross-sectional aspect ratios of at least <NUM>:<NUM>, significantly smaller protrusions <NUM> are formed compared to the protrusions <NUM> of <FIG>. Consequently, the use of the shaped S- and Z-strands <NUM> and <NUM> in <FIG> leads to a flattened braided sheath <NUM> having reduced texturing and surface roughness compared to the conventional core-sheath structure <NUM> of <FIG>.

Embodiments described herein include methods for producing core-sheath structures having shape-controlled jackets with areas of low thickness. Some embodiments relate to methods including the steps of (i) shaping at least one filament bundle comprising a plurality of filaments to form at least one shaped strand of filaments, and then (ii) braiding a plurality of strands, including the at least one shaped strand of filaments, over a core to form a core-sheath structure comprising a braided sheath of the strands surrounding the core. Such methods may be performed such that (a) the shaped strand of filaments is an untwisted strand having a twist level of less than <NUM> turn per meter, (b) a cross-sectional aspect ratio of the shaped strand of filaments is at least <NUM>:<NUM> as measured in the braided sheath, (c) a thickness of at least a portion of the braided sheath ranges from about <NUM> to about <NUM>, and/or (d) the braided sheath comprises a synthetic fiber having a tensile strength of greater than <NUM> cN/dtex.

<FIG> illustrate braiding apparatuses that can be used to produce core-sheath structures of the present disclosure.

<FIG> illustrates one embodiment of a braiding apparatus <NUM> that can be used to produce core-sheath structures of the present disclosure. The braiding apparatus <NUM> includes a main enclosure <NUM> that rotates during operation and mounts twelve (<NUM>) carriers <NUM> that independently move along the upper surface of the main enclosure <NUM> in circular carrier paths <NUM> that enable the carriers <NUM> to follow continuous "<FIG>" patterns. Each carrier <NUM> includes a bobbin <NUM> capable of dispensing a filament bundle <NUM> via a guide <NUM> that directs the filament bundle <NUM> towards a central winding shaft <NUM> that be controlled with a winding shaft moving mechanism <NUM> to move in an axial direction. <FIG> illustrates a pull-off orientation for each bobbin <NUM>; however, a roll-off orientation for each bobbin <NUM> also may be used.

Aside from modifications to the braiding apparatus <NUM> that may be performed to enable it to more effectively shape at least one of the filament bundles <NUM> prior to braiding about the central winding shaft <NUM>, the braiding apparatus <NUM> functions in a similar manner compared to conventional braiding apparatuses. That is, a tubular braid sheath may be formed on a core (depicted as the central winding shaft <NUM> in <FIG>) by crossing the strands (including at least one pre-shaped strand) diagonally in such a way that each group of strands pass alternately over and under a group of strands laid in the opposite direction.

In some embodiments modifications enabling a braiding apparatus to more effectively shape at least one of the filament bundles may be performed on a commercially-available braiding apparatus. Braiding equipment is commercially available and units of differing capabilities may be obtained. Suitable braiding equipment may include commercially-available braiders from Steeger USA (Inman, South Carolina USA), Herzog GmbH (Oldenburg, Germany), and other manufacturers, that are designed for the braiding of fine-denier filaments and bundles. However, the equipment available for modification is not limited to any specific manufacturers. Essential to the sheath core design is that the braiding equipment be equipped with the ability to braid around a central core. Upper and lower limits for the number of carriers included in the braiding apparatus are not limited and may be determined according to the desired braid parameters and design. As explained below in greater detail, some embodiments include the use of braiding apparatuses capable of producing triaxial braids that include longitudinal strands.

In some embodiments modifications enabling a braiding apparatus to more effectively shape at least one of the filament bundles <NUM> may be performed on at least one of the carriers <NUM>. <FIG> illustrates one embodiment of a modified braider carrier <NUM> that includes a carrier plate <NUM>, a bobbin <NUM>, at least one strand guide <NUM> (two being depicted in the embodiment of <FIG>), an auto-align swivel <NUM>, and a shaping device <NUM>. The modified braider carrier <NUM> includes an additional function whereby a non-shaped filament bundle <NUM> is guided to the shaping device <NUM> that shapes the filament bundle <NUM> into a shaped strand of filaments <NUM> prior to the shaped strand <NUM> being braided about the central winding shaft (core) <NUM> (see <FIG>).

In some embodiments the least one shaped strand of filaments may be formed by shaping a heated filament bundle, an agitated filament bundle, or a combination thereof. The shaping process may be improved, for example to obtain a shaped strand of filaments having a higher cross-section aspect ratio, by using a heated filament bundle including at least one of a lubricant, a fiber and a surface-coated filament. The presence of a lubricant can improve a heated shaping process by reducing the viscosity of the lubricant. Agitated filaments bundles may be obtained, for example, by applying ultrasound to a filament bundle.

Shaping devices <NUM> of many designs and functions can be used in modified braider carriers <NUM> of the present disclosure. For example, <FIG> illustrates one embodiment in which the shaping device <NUM> includes two rollers <NUM> over which the non-shaped filament bundle <NUM> is sequentially passed under tension in order to produce the shaped strand of filaments <NUM>. In other embodiments the shaping device <NUM> functions by tensioning the filament bundle <NUM> over at least one surface (e.g., at least one roller) in order to compress the filament bundle, or functions by tensioning the filament bundle <NUM> over at least one curved surface such that the filaments separate from one another to form a flat fiber band. In other embodiments the shaping may involve squeezing the filament bundle between two surfaces (e.g., two rollers). In still other embodiments, the shaping may involve a gating process in which filaments in the filament bundle pass through separate spaces (e.g., gates, openings) in order to separate the filaments (as single filaments, or as sets of filaments) from one another to form a flat fiber band.

Shaping processes of the present disclosure are not limited to shaping that occurs on the carrier <NUM>, and may involve the use of shaping device(s) positioned between the carrier <NUM> and the central winding shaft (core) <NUM> (see <FIG>). That is, the shaping process may occur on the carrier, between the carrier and the central winding shaft (core), or a combination thereof. Shaping devices positioned between the carrier and the central winding shaft (core) may employ the same designs and functions as the shaping devices on the carrier, or may employ different designs and functions.

Shaping processes of the present disclosure can be used to form shaped strands of filaments having a wide variety of different cross-sectional shapes. For example, the shaping may be performed such that the shaped strand of filaments has a cross section including a curved surface, may be performed such that the shaped strand of filaments has a cross section including a flat surface, or a combination thereof. In some embodiments the shaped strand of filaments may have an oval cross section, while in other embodiments the shaped strand of filaments may have a curved cross section including a convex section and/or a concave section. In other embodiments the shaping may be performed such that the shaped strand of filaments is a flat fiber band having a cross section including a flat surface.

<FIG> illustrates two non-limiting embodiments where the shaping of a filament bundle <NUM> comprising a plurality of filaments <NUM> produces an oval-shaped strand of filaments <NUM> or produces a flat fiber band <NUM> having a cross section including a flat surface. As illustrated in the oval-shaped strand of filaments <NUM>, in some embodiments the width of a shaped strand of filaments having a curved cross section may include at least two monofilaments <NUM> stacked in a transverse direction across the width of the shaped strand. As illustrated in the flat fiber band <NUM>, in some embodiments the width of a shaped strand of filaments may include a single layer of monofilaments <NUM> arranged side-by-side. <FIG> illustrates the aspect ratio calculation for a shaped strand of filaments <NUM> having a curved (oval) cross section.

In some embodiments braided sheaths of the present disclosure may include at least one oval-shaped strand of filaments having an ovality ranging from about <NUM>% to about <NUM>%. Ovality (%) is calculated using the following equation: <MAT> where Max OD is a maximum outside diameter of the strand in micrometers (µm), and Min OD is a minimum outside diameter of the strand in micrometers (µm). In other embodiments the ovality of the oval-shaped strands of filaments may range from about <NUM>% to about <NUM>%, or from about <NUM>% to about <NUM>%.

As explained above, gaps <NUM> (see <FIG>) may exist in the braided sheath <NUM> when the surface coverage is less than <NUM>%. Braiding methods of the present disclosure may include techniques for optimizing the braid pattern of the braided sheath <NUM> to eliminate gaps <NUM> and maximize surface coverage. <FIG> illustrate the before and after effects of performing optimization techniques on braiding methods of the present disclosure.

<FIG> illustrates the surface of a non-optimized braided sheath <NUM> having a surface coverage of less than <NUM>% and including numerous gaps <NUM>. In this particular example, the braided sheath <NUM> is formed from four shaped strands of filaments including two right-hand braided Z-strands <NUM> and <NUM> (designated as strands "A" and "C" in <FIG>) and two left-hand braided S-strands <NUM> and <NUM> (designated as strands "B" and "D" in <FIG>). The actual braid pattern may be varied according to the pattern of interlacing. Common patterns may include plain, twill and panama weaves as well as other braid patterns known to persons of ordinary skill in the relevant art.

Factors that may be altered to adjust and optimize the characteristics of a braided sheath include the pick count of the braiding process, the end count (number of strands) of the braid, and the width of the shaped strands of filaments in the braided sheath. Increasing pick count during the braiding process tends to increase the surface coverage (and reduce gap sizes) of the resulting braided sheath, assuming that the end count of the braid and the width of the shaped strands are held constant. Increasing the end count of the braid also tends to increase the surface coverage (and reduce gap sizes) of the resulting braid, assuming that the pick count of the braid and the width of the shaped strands are held constant. Increasing the width of the shaped strands also tends to increase the surface coverage (and reduce gap sizes) of the resulting braid, assuming that the pick count and end count of the braid are held constant.

As an example of a braid optimization, a core-sheath structure having a four-strand braided sheath is formed over a colored (high-visibility) core material using a method of the present disclosure. The four strands include two right-hand braided Z-strands (designated as strands "A" and "C") and two left-hand braided strands (designated as strands "B" and "D"), see <FIG>. While performing a two-step (shaping and then braiding) method of the present disclosure, the pick count of the braided sheath is incrementally increased while the end count of the braid and the width of the shaped strands are held constant. The width of the shaped strands is held constant by maintaining constant tensioning of the filament bundles passing through the shaping devices <NUM> (see, e.g., <FIG>) during the shaping process. A core-sheath (cord) structure is produced that includes different sections corresponding to the different pick counts produced as the pick count is incrementally increased.

The resulting core-sheath (cord) structure is then visually analyzed using a microscope to measure the sizes of the gaps <NUM> in the different sections corresponding to the different pick counts. For example, the sizes of the gaps <NUM> can be measured using a digital microscope having an optical magnification of about 200x, such as a DINO-LITE™ USB digital microscope. An optimal pick count is determined based on the section where the gaps <NUM> are small enough to produce a surface coverage of about <NUM>%. In other instances, the optimal pick count occurs where the gaps <NUM> are small enough to produce a surface coverage ranging from about <NUM>% to about <NUM>%.

Using the optimal pick count, another core-sheath structure having the four-strand braided sheath is formed over the colored (high-visibility) core material using the method of the present disclosure. While performing the two-step (shaping and then braiding) method, the pick count is held constant at the optimal pick count but the width of the shaped strands is incrementally increased by increasing the tensioning of the filament bundles passing through the shaping devices <NUM> (see, e.g., <FIG>) during the shaping process. A core-sheath (cord) structure is produced that includes different sections corresponding to the different widths of the shaped strands as the tensioning of the filaments passing through the shaping devices <NUM> is incrementally increased.

The resulting core-sheath (cord) structure is then visually analyzed using the microscope to measure the sizes of the gaps <NUM> in the different sections corresponding to the different widths of the shaped strands of filaments. An optimal width is determined based on the section where the gaps <NUM> disappear corresponding to a surface coverage of about <NUM>%. In other instances, the optimal width occurs where the gaps <NUM> are small enough to produce a surface coverage ranging from about <NUM>% to about <NUM>%. Some core-sheath structures may be optimized in a manner such that gaps are deliberately included in the jacket (sheath), or such that strands forming the jacket (sheath) can overlap. Therefore, the surface coverage of optimized core-sheath structures may range from about <NUM>% to about <NUM>% depending upon the intended application.

<FIG> illustrates the surface of an optimized braided sheath <NUM> having a surface coverage of about <NUM>%, where the right-hand braided Z-strands <NUM> and <NUM> (designated as strands "A" and "C") and the left-hand braided S-strands <NUM> and <NUM> (designated as strands "B" and "D") are tightly packed together without gaps or significant overlap. <FIG> also illustrates the braid axis <NUM> of the core-sheath structure along with the optimized braid angle (θ) <NUM>, direction bias <NUM>, distance (S) <NUM> and strand width (W) <NUM> of the optimized braided sheath <NUM>.

Other braid optimization methods may be used where pick count, end count and strand width are modulated in different orders to obtain different levels of surface coverage with or without gaps. In some embodiments the surface coverage of the braided sheath over the core is at least <NUM>%. In other embodiments the surface coverage may range from about <NUM>% to about <NUM>%. In still other embodiments the surface coverage may exceed <NUM>% - such that adjacent strands at least partially overlap with one another. As explained above, in some embodiments the surface coverage may range from about <NUM>% to about <NUM>%. For example, the surface coverage may range from about <NUM>% to about <NUM>%, or from about <NUM>% to about <NUM>%, or from about <NUM>% to about <NUM>%, or from about <NUM>% to about <NUM>%.

As explained above, in some optimized core-sheath structures the surface coverage may fall significantly below <NUM>% (due to the deliberate presence of gaps) or significantly above <NUM>% (due to strands of the jacket (sheath) being overlapped). Such embodiments can be advantageous, for example, when it is beneficial to obtain a jacket (sheath) of higher surface roughness (due to the presence of gaps and/or protrusions) or when additional protection for the core (due to the presence of overlapping strands) is desired.

The pick count of the braided sheath in a relaxed state (i.e., a natural resting state where no tension is applied to the core-sheath structure) may range from <NUM> to <NUM> filament unit crossovers per meter. In other embodiments the pick count of the braided sheath may range from about <NUM> to <NUM> crossovers per meter, or from about <NUM> to about <NUM> crossovers per meter, or from about <NUM> to <NUM> crossovers per meter, in the relaxed state.

The strand (end) count of the braided sheath depends upon the requirements of the core-sheath structure and the capabilities of the braiding device. Strand (end) counts ranging from <NUM> to more than <NUM> may be employed depending upon the particular application. In some embodiments the strand (end) count of the braided sheath may range from <NUM> to <NUM> ends, and in other applications a strand (end) count limited to about <NUM> ends may be appropriate. For example, the strand (end) count of core-sheath structures of the present disclosure may range from <NUM> to <NUM> ends, or from <NUM> to <NUM> ends, or from <NUM> to <NUM> ends, or from <NUM> to <NUM> ends, or from <NUM> to <NUM> ends. In medical applications, core-sheath structures of the present disclosure often range from <NUM> to <NUM> ends.

The braid angle of the braided sheath in a relaxed state generally ranges from about <NUM>° to about <NUM>°. In other embodiments the braid angle of the S- and Z-strands of the braided sheath in the relaxed state may range from about <NUM>° to about <NUM>°, or from about <NUM>° to about <NUM>°, or from about <NUM>° to about <NUM>°, or from about <NUM>° to about <NUM>°, or from about <NUM>° to <NUM>°.

Braid angle selection can have a profound effect on the properties of core-sheath structures of the present disclosure. For example, reducing the braid angle tends to increase the modulus and/or the strength of the resulting core-sheath structure, due to the load-bearing fibers of the jacket (sheath) being more aligned with the direction of the load (i.e., along the braid axis <NUM>). Braid angle selection can also be used to control load sharing between core and the jacket (sheath). In some embodiments a balance of load sharing between the core and the jacket (sheath) is important for obtaining core-sheath structures having optimal tensile strength and durability properties.

Embodiments of the present disclosure also include core-sheath structures produced by the methods described above. For example, some embodiments relate to core-sheath structures comprising (I) a core and (II) a braided sheath of strands surrounding the core, wherein the braided sheath comprising strands having a braid angle of <NUM>° or more in a relaxed state, and the strands having the braid angle of <NUM>° or more in the relaxed state include at least one shaped strand of filaments. Such core-sheath structures may be produced such that (A) the shaped strand of filaments is an untwisted strand having a twist level of less than <NUM> turn per meter, (B) a cross-sectional aspect ratio of the shaped strand of filaments is at least <NUM>:<NUM> as measured in the braided sheath, (C) a thickness of at least a portion of the braided sheath ranges from about <NUM> to about <NUM>, and/or (D) the braided sheath contains a synthetic fiber having a tensile strength of greater than <NUM> cN/dtex.

Core-sheath structures of the present disclosure include embodiments wherein the braided sheath contains at least one untwisted shaped strand of filaments having a twist level of less than <NUM> turn per meter, or less than <NUM> turn per meter, or less than <NUM> turn per meter.

In some embodiments the cross-sectional aspect ratio of the shaped strand filaments ranges from <NUM>:<NUM> to <NUM>:<NUM>, or ranges from <NUM>:<NUM> to <NUM>:<NUM>, or ranges from <NUM>:<NUM> to <NUM>:<NUM>, or ranges from <NUM>:<NUM> to <NUM>:<NUM>. In other instances the cross-sectional aspect ratio of the shaped strand of filaments may range from about <NUM>:<NUM> to about <NUM>:<NUM> (ovality about <NUM>-<NUM>%), or from about <NUM>:<NUM> to about <NUM>:<NUM> (ovality about <NUM>-<NUM>%), or from about <NUM>:<NUM> to about <NUM>:<NUM> (ovality about <NUM>-<NUM>%), or from about <NUM>:<NUM> to about <NUM>:<NUM> (ovality about <NUM>-<NUM>%).

The thickness of at least a portion of the braided sheath may range from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

As explained above, braided sheaths of the present disclosure may contain a synthetic fiber having a tensile strength of greater than <NUM> cN/dtex. The synthetic fiber may have a tensile strength of at least <NUM> cN/dtex, or at least <NUM> cN/dtex, or at least <NUM> cN/dtex. In some embodiments the synthetic fiber contained in the braided sheath may have a tensile strength ranging from <NUM> cN/dtex to <NUM> cN/dtex, or from <NUM> cN/dtex to <NUM> cN/dtex.

In addition to the synthetic fiber having a tensile strength of greater than <NUM> cN/dtex, braided sheaths in core-sheath structures of the present disclosure may include other synthetic and non-synthetic fibers and filaments having tensile strengths ranging from about <NUM> cN/dtex to about <NUM> cN/dtex. For example, some embodiments include core-sheath structures containing a braided sheath comprising the synthetic fiber having the tensile strength of greater than <NUM> cN/dtex and a synthetic or non-synthetic fiber having a tensile strength of less than <NUM> cN/dtex. In other embodiments the braided sheath does not include a synthetic fiber having a tensile strength of less than <NUM> cN/dtex. Braided sheaths of the present disclosure may also contain both the synthetic fiber having the tensile strength of greater than <NUM> cN/dtex and a non-synthetic fiber having a tensile strength of greater than <NUM> cN/dtex.

Shaped strands of filaments may also have tensile strengths of greater than <NUM> cN/dtex, or may have tensile strengths ranging from about <NUM> cN/dtex to about <NUM> cN/dtex.

As explained above, methods of the present disclosure include a step of shaping at least one filament bundle comprising a plurality of filaments to form at least one shaped strand of filaments. In some embodiments the plurality of filaments contained in the filament bundle may include at least one filament having a non-round cross section. Such filaments having a non-round cross section may be formed by an extrusion process using an extrusion die having a non-round cross-sectional profile. For example, filament bundles of the present disclosure may contain at least one filament having an oval cross section, a triangular cross section, a square cross section, a multilobal cross section, a hollow cross section, or other cross sections known to be produced by extrusion.

Core-sheath structures of the present disclosure may also include core-sheath structures having a maximum (outer) diameter ranging from about <NUM> to about <NUM>. In other embodiments the outer diameter of the core-sheath structures may range from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

A wide variety of core sizes may also be used in the embodiments of the present disclosure. For example, a maximum diameter of the core may range from about <NUM> to about <NUM>. In other embodiments the maximum diameter of the core may range from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

Core-sheath structures of the present disclosure may employ twisted or non-twisted cores, as well as mono-filament cores. In some embodiments the core comprises at least two core strands twisted together at a twist level of from greater than <NUM> to <NUM> turns per meter. The number of core strands included in the twisted or untwisted core may range from <NUM> to <NUM>, and the twist level of the core or the core strands used to produce a multi-strand core may range from <NUM> to <NUM> turns per meter. Combinations of twisted, non-twisted, and/or braided filaments may also be used to produce cores in the core-sheath structures of the present disclosure.

<FIG> illustrates the cross section of one embodiment of the present disclosure in which the core-sheath structure <NUM> includes a twisted, <NUM>-strand core comprising three strands <NUM> twisted together at a twist level of from greater than <NUM> to <NUM> turns per meter such that the core has a triangular cross section. In this embodiment the triangular <NUM>-strand core is surrounded by a flattened braided jacket (sheath) <NUM> formed from untwisted S- and Z-strands <NUM> and <NUM> that are shaped to have cross-sectional aspect ratios of at least <NUM>:<NUM>. Due to the relatively small size of the protrusions <NUM> where the Sand Z-strands <NUM> and <NUM> overlap, the flattened braided sheath <NUM> tightly conforms to the outer surface of the core such that the cross-sectional shape of outer surface of the sheath <NUM> largely emulates the shape of the outer surface of the triangular core.

As explained above, the production method of the present disclosure can be advantageous because the ability to shape the filament bundle(s) into at least one shaped strand of filaments allows the resulting core-sheath structure to have a thinner braided sheath with less texturing and lower surface roughness compared to conventional core-sheath structures. For example, as illustrated in the comparison between <FIG> and <FIG>, the difference (ΔD) between the maximum diameter of the braided sheath (Dmax) and the minimum diameter of the braided sheath (Dmin) <NUM> and <NUM> of the braided sheath <NUM> in <FIG>-(ΔD = Dmax - Dmin)-is significantly less than the difference ΔD of the braided sheath <NUM> of <FIG>. In some embodiments a ratio of the Dmax to the Dmin ranges from about <NUM>: <NUM> to about <NUM>:<NUM>. In other embodiments the ratio of the Dmax to the Dmin ranges from about <NUM>:<NUM>:<NUM> to about <NUM>:<NUM>, or from about <NUM>:<NUM> to about <NUM>:<NUM>, or from about <NUM>:<NUM> to about <NUM>:<NUM>, or from about <NUM>:<NUM> to about <NUM>:<NUM>.

Another measure of the ability to shape the filament bundles into shaped strands is the flattening factor of the shaped strand of filaments. For core-sheath structures comprising a round core with a circular cross section and a braided sheath consisting of shaped strands and having a surface coverage of <NUM>% or less, flattening factor is defined as: <MAT> where Dmax is a maximum diameter of the braided sheath as measured in a cross-sectional plane of the cord that is perpendicular to a longitudinal axis of the cord in micrometers (µm), Dmin is a minimum diameter of the braided sheath as measured in the cross-sectional plane of the cord that is perpendicular to the longitudinal axis of the cord, in micrometers (µm), and Ds is a minimum diameter of the filament bundle prior to the shaping, as measured in a cross-sectional plane of the filament bundle that is perpendicular to a longitudinal axis of the filament bundle, in micrometers (µm).

Embodiments of the present disclosure include core-sheath structures comprising a round core with a circular cross section and a braided sheath consisting of shaped strands, wherein the flattening factor of the shaped strands ranges from about <NUM> to about <NUM>. In other embodiments the flattening factor may range from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

In some embodiments the core in the core-sheath structures is a surface treated core. For example, the core component surface may be corona or plasma treated prior to application of the braided sheath. Such treatment may create surface imperfections or modifications that enhance contact (surface interaction) between the core and an inner surface of the braided sheath, further enhancing the interaction between the core and the braided sheath.

Another aspect of the present disclosure relates to the proportion of strands used in the braiding step that are shaped strands. In some embodiments all of the strands used in the braiding step are shaped strands, whereas in other embodiments only a fraction of the strands used in the braiding step are shaped strands. For example, in some embodiments all of the S-strands braided in the left-hand direction are shaped strands, whereas all of the Z-strands braided in the right-hand direction are non-shaped strands that are not subjected to the shaping step that occurs before the braiding step, or vice versa. In still other embodiments only a fraction of one or both of the S- and Z-strands may be shaped strands. Embodiments of the present disclosure include core-sheath structures including only one shaped strand in the braided sheath, or including all (<NUM>%) shaped strands in the braided sheath, or including any combination between one shaped strand and <NUM>% of shaped strands in the braided sheath.

Embodiments of the present disclosure of also include core-sheath structures in which the braided sheath is a hybrid jacket including at least one of the shaped strand of filaments having a cross-sectional aspect ratio of at least <NUM>:<NUM> and at least one non-shaped strand of filaments having a cross-sectional aspect ratio of less than <NUM>:<NUM>. For example, in some embodiments the braided sheath is a hybrid jacket including at least one shaped strand of filaments having a cross-sectional aspect ratio of at least <NUM>:<NUM> and at least one twisted (non-shaped) strand of filaments having a twist level of greater than <NUM> to <NUM> turns per meter. As explained above, a twisted filament bundle (i.e., twisted strand) is more rigid and less prone to shaping compared to an untwisted filament bundle.

Hybrid jackets of the present disclosure may also be formed using filament bundles (strands) containing filaments of different diameters (different linear densities). For example, hybrid jackets may be formed by threading high-density strands (formed of high-density filaments, e.g., <NUM>-<NUM> denier-per-filament (dpf) filaments, wherein <NUM>-<NUM> dpf corresponds to <NUM>-<NUM> decitex-per-filament) and low-density
strands (formed of low-density filaments, e.g., <NUM>-<NUM> dpf filaments). Filament bundles formed of high-density (high-dpf) filaments are stiffer and less prone to crushing, but can be more difficult to shape (flatten) using compressive mechanisms-whereas filament bundles formed of low-density (low-dpf) filaments are softer and more flexible, but can be more fragile. Core-sheath structures in some embodiments of the present disclosure contain hybrid jackets formed of shaped strands of high-dpf filaments (<NUM> dpf or greater) threaded in the S-direction and shaped strands of low-dpf filaments (less than <NUM> dpf) threaded in the Z-direction, or vice versa. Embodiments also include the use non-shaped strands of high-dpf filaments and/or low-dpf filaments. The use of high-dpf strands threaded in only one direction can lead to core-sheath structures exhibiting enhanced torsional stiffness in only one rotational direction.

<FIG> illustrates the cross-section for a core-sheath structure <NUM> of the present disclosure having a round core <NUM> surrounded by a hybrid braided jacket (sheath) <NUM> formed from shaped S-strands <NUM> having a cross-sectional aspect ratio of at least <NUM>:<NUM> and from non-shaped Z-strands <NUM> having a cross-sectional aspect ratio of less than <NUM>:<NUM>. A comparison of <FIG> and <FIG> illustrates that the presence of the non-shaped Z-strands <NUM> in the embodiment of <FIG> leads to larger protrusions <NUM> where the shaped S-strands <NUM> and the non-shaped Z-strands <NUM> overlap - compared to the embodiment of <FIG> where in the braided sheath <NUM> includes only the shaped S- an Z-strands <NUM> and <NUM>. Thus, embodiments such as the illustration of <FIG> having a hybrid braided sheath can enable the texture and surface area of the outer surface of the resulting core-sheath structures to be controlled.

Core-sheath structures of the present disclosure may also include triaxial braided sheaths comprising, in addition to the S-strands <NUM> braided in the left-hand direction and the Z-strands <NUM> braided in the right-hand direction (see <FIG>), longitudinal strands having a braid angle of less than <NUM>° in a relaxed state. In some embodiments the triaxial braided sheath may include at least one shaped longitudinal strand formed by shaping at least one of the longitudinal strands prior to the braiding of the plurality of strands. For example, a triaxial braided sheath of the present disclosure may include, in addition to the S- and Z-strands, one shaped longitudinal strand, all shaped longitudinal strands, or any combination in between.

<FIG> illustrates a core-sheath structure <NUM> including a central core <NUM> that is partially surrounded by a triaxial braided jacket (sheath) <NUM> formed of S-strands <NUM> braided in the left-hand direction along a braid axis <NUM> of the core <NUM>, Z-strands <NUM> braided in a right-hand direction along the braid axis <NUM>, and longitudinal strands <NUM> braided along the braid axis <NUM> and having a braid angle of less than <NUM>° in a relaxed state.

Core-sheath structures of the present disclosure may also be formed such that the filament bundle further comprises a lubricant, a fiber, a surface-coated filament, or combinations thereof. Lubricants used in the filament bundles of the present disclosure may include at least one of a lubricating filament and a lubricating fiber. Surface-coated filaments may include cross-linked or non-cross-linked silicone polymers as the surface coating.

The mass ratio of a mass of the braided sheath to a mass of the core, per unit length of the core-sheath structure, may range from about <NUM>/<NUM> to about <NUM>/<NUM>. In other embodiments the mass ratio of a mass of the braided sheath to a mass of the core, per unit length of the core-sheath structure, is from about <NUM>/<NUM> to about <NUM>/<NUM>, or from about <NUM>/<NUM> to about <NUM>/<NUM>, or from about <NUM>/<NUM> to about <NUM>/<NUM>, or from about <NUM>/<NUM> to about <NUM>/<NUM>, or from about <NUM>/<NUM> to about <NUM>/<NUM>, or from about <NUM>/<NUM> to about <NUM>/<NUM>, or from about <NUM>/<NUM> to about <NUM>/<NUM>. In some embodiments a linear mass density of the braided sheath is greater than a linear mass density of the core. In other embodiments the linear mass density of the braided sheath is equivalent to the linear mass density of the core, or the linear mass density of the braided sheath is less than the linear mass density of the core.

Core-sheath structures of the present disclosure may have linear mass densities ranging from about <NUM> denier to about <NUM>,<NUM> denier, corresponding to about <NUM> decitex to about <NUM>,<NUM> decitex. In other embodiments the linear mass density of the core-sheath structure may range from about <NUM> denier to about <NUM> denier, corresponding to about <NUM> decitex to about <NUM> decitex, or from about <NUM> denier to about <NUM> denier, corresponding to about <NUM> decitex to about <NUM> decitex, or from about <NUM> denier to about <NUM> denier, corresponding to about <NUM> decitex to about <NUM> decitex, or from about <NUM> denier to about <NUM> denier, corresponding to about <NUM> decitex to about <NUM> decitex, or from about <NUM> denier to about <NUM> denier, corresponding to about <NUM> decitex to about <NUM> decitex, or from about <NUM> denier to about <NUM> denier, corresponding to about <NUM> decitex to about <NUM> decitex.

As explained above, methods of the present disclosure may include a step of shaping at least one filament bundle comprising a plurality of filament to form at least one shaped strand of filaments. In some embodiments the plurality of filaments contains filaments having linear mass densities ranging from about <NUM> to about <NUM> denier, corresponding to about <NUM> to about <NUM> decitex. In other embodiments the linear mass density of the filaments may range from about <NUM> to about <NUM> denier, or from about <NUM> to about <NUM> denier, or from about <NUM> to about <NUM> denier, respectively corresponding to about <NUM> to about <NUM> decitex, or from about <NUM> to about <NUM> decitex, or from about <NUM> to about <NUM> decitex.

Shaped and/or non-shaped strands of the braided sheath may be identical in size, structure and composition, or the strands may differ in any or all of size, structure and composition. Thus, the braided sheath may be constructed of strands of differing denier, braid or twist. Further, the braided sheath may contain strands of differing chemical composition. Thus, braided sheaths of the present disclosure may be designed to control the strength and torque properties of core-sheath structures.

The chemical composition of the strands (or filaments) of the braided sheath may be of any high performance polymer known to provide a combination of high tensile strength, high tenacity and low creep and may be selected from but is not restricted to liquid crystalline polyester filaments, aramid filaments, co-polymer aramid filaments, polyether ether ketone filaments, poly(p-phenylene benzobisoxazole) (PBO) filaments, ultra-high molecular weight polyethylene filaments, high modulus polyethylene filaments, polypropylene filaments, polyethylene terephthalate filaments, polyamide filaments, high-strength polyvinyl alcohol filaments, polyhydroquinone diimidazopyridine (PIPD) filaments, and combinations thereof, just to name a few.

Polyhydroquinone diimidazopyridine (PIPD) filament fibers are based on polymers of the following repeating unit:
<CHM>.

In some embodiments the plurality of filaments contained in the braided sheath includes at least one selected from a liquid crystalline polyester filament, an aramid filament, co-polymer aramid filament, a polyether ether ketone filament, a poly(p-phenylene benzobisoxazole) filament, an ultra-high molecular weight polyethylene filament, a high modulus polyethylene filament, a polypropylene filament, a polyethylene terephthalate filament, a polyamide filament, a polyhydroquinone diimidazopyridine filament, and a high-strength polyvinyl alcohol filament. In other embodiments the plurality of filaments includes at least two of these materials.

In some embodiments shaped and/or non-shaped strands of the braided sheath may contain at least one fiber selected from a liquid crystalline polyester fiber, an aramid fiber, a PBO fiber, an ultra-high molecular weight polyethylene fiber, and a high strength polyvinyl alcohol fiber. In other embodiments the shaped and/or non-shaped strands of the braided sheath may be selected from a liquid crystalline polyester fiber and an aramid fiber, and particularly a liquid crystalline polyester fiber.

Core-sheath structures of the present disclosure may, in some embodiments, include a core comprising at least one selected from the group consisting of a liquid crystalline polyester filament, an aramid filament, co-polymer aramid filament, a polyether ether ketone filament, a poly(phenylene benzobisoxazole) filament, an ultra-high molecular weight polyethylene filament, a polypropylene filament, a high modulus polyethylene filament, a polyethylene terephthalate filament, a polyamide filament, and a high-strength polyvinyl alcohol filament.

Polymerized units may include those illustrated shown in Table <NUM>.

Regarding the polymerized units illustrated in Table <NUM> above, the number of Y substituent groups is equal to the maximum number of substitutable positions in the ring structure, and each Y independently represents a hydrogen atom, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (for example, an alkyl group having <NUM> to <NUM> carbon atoms such as a methyl group, an ethyl group, an isopropyl group, or a t-butyl group), an alkoxy group (for example, a methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, etc.), an aryl group (for example, a phenyl group, a naphthyl group, etc.), an aralkyl group [a benzyl group (a phenylmethyl group), a phenethyl group (a phenylethyl group), etc.], an aryloxy group (for example, a phenoxy group, etc.), an aralkyloxy group (for example, a benzyloxy group, etc.), or mixtures thereof.

Liquid crystalline polyester fibers may be obtained by melt spinning of a liquid crystalline polyester resin. The spun fiber may be further heat treated to enhance mechanical properties. The liquid crystalline polyester may be composed of a repeating polymerized unit, for example, derived from an aromatic diol, an aromatic dicarboxylic acid, or an aromatic hydroxycarboxylic acid. The liquid crystalline polyester may optionally further comprise a polymerized unit derived from an aromatic diamine, an aromatic hydroxyamine, and/or an aromatic aminocarboxylic acid.

More specific polymerized units are illustrated in the following structures shown in Tables <NUM>-<NUM> below.

When the polymerized unit in the formulas is a unit which can represent plural structures, two or more units may be used in combination as polymerized units constituting a polymer.

In the polymerized units of Tables <NUM>, <NUM>, and <NUM>, n is an integer of <NUM> or <NUM>, and the respective units n = <NUM>, n = <NUM> may exist alone or in combination; and Y<NUM> and Y<NUM> each independently may be a hydrogen atom, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (for example, an alkyl group having <NUM> to <NUM> carbon atoms such as a methyl group, an ethyl group, an isopropyl group, or a t-butyl group), an alkoxy group (for example, a methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, etc.), an aryl group (for example, a phenyl group, a naphthyl group, etc.), an aralkyl group (a benzyl group (a phenylmethyl group), a phenethyl group (a phenylethyl group), etc.), an aryloxy group (for example, a phenoxy group, etc.), an aralkyloxy group (for example, a benzyloxy group, etc.), or mixtures thereof. Among these groups, Y is preferably a hydrogen atom, a chlorine atom, a bromine atom, or a methyl group.

Z in species (<NUM>) of Table <NUM> may comprise divalent groups represented by the formulae below. <CHM>
<CHM>.

In some embodiments a liquid crystalline polyester may be a combination comprising a naphthalene skeleton as a polymerized unit. Particularly, it may include both a polymerized unit (A) derived from hydroxybenzoic acid and a polymerized unit (B) derived from hydroxynaphthoic acid. For example, the unit (A) may be of formula (A) and the unit (B) may be of formula (B). From the viewpoint of improving melt moldability, a ratio of the units (A) to the units (B) may be in a range of from <NUM>/<NUM> to <NUM>/<NUM>, preferably <NUM>/<NUM> to <NUM>/<NUM>, and more preferably <NUM>/<NUM> to <NUM>/<NUM>. <CHM>
<CHM>.

The total of the polymerized units (A) and the polymerized units (B) may be, for example, about <NUM> mol% or more, or about <NUM> mol% or more, or about <NUM> mol% or more, based on the total polymerized units. In some embodiments the braided sheath may include a liquid crystalline polyester comprising about <NUM> to about <NUM> mol% of the polymerized unit (B) in the polymer.

The melting point as used herein is a main absorption peak temperature which is measured and observed by a differential scanning calorimeter (DSC) (e.g., "TA3000" manufactured by METTLER Co. ) in accordance with the JIS K7121 test method. Specifically, <NUM> to <NUM> of a sample is used in the above-mentioned DSC apparatus and, after the sample is encapsulated in an aluminum pan, nitrogen is allowed to flow as a carrier gas at a flow rate of <NUM> cc/minute and an endothermic peak upon heating at a rate of <NUM>/minute is measured. When a well-defined peak does not appear at the first run in the DSC measurement depending on the type of the polymer, the temperature is raised to a temperature which is <NUM> higher than an expected flow temperature at a temperature rise rate (or heating rate) of <NUM>/minute, followed by complete melting at the same temperature for <NUM> minutes and further cooling to <NUM> at a temperature drop rate (or cooling rate) of -<NUM>/minute. Thereafter, the endothermic peak may be measured at a temperature rise rate of <NUM>/minute.

Commercially available LCPs contained in braided sheaths of the present disclosure may include VECTRAN® HT BLACK manufactured by KURARAY CO. , VECTRAN® HT manufactured by KURARAY CO. , SIVERAS® manufactured by Toray Industries, Inc. , monofilament manufactured by ZEUS and ZXION® manufactured by KB SEIREN, LTD.

Liquid crystalline polyesters may be used alone or in combination in core-sheath structures of the present disclosure.

According to the present invention, "aramid fiber" means a polyamide fiber with high heat resistance and high strength comprising a molecular skeleton composed of an aromatic (benzene) ring. Aramid fibers may be classified into a para-aramid fiber and a meta-aramid fiber according to a chemical structure thereof, with para-aramid fibers being preferably included in some braided sheaths of the present disclosure.

Examples of commercially available aramid and co-polymer aramid fibers include para-aramid fibers, for example, KEVLAR® manufactured by E. du Pont de Nemours and Company, HERACRON® from Kolon Industries Inc. and TWARON® and TECHNORA® manufactured by Teijin Limited; and meta-aramid fibers, for example, NOMEX® manufactured by E. du Pont de Nemours and Company and CONEX® manufactured by Teijin Limited.

When contained in braided sheaths of the present disclosure, aramid fibers may be used alone or in combination. In some embodiments the plurality of filaments contained in shaped and/or non-shaped strands used to prepare the braided sheath may contain a co-polymer aramid filament. For example, in some embodiments the shaped and/or non-shaped strands comprise a copolyparaphenylene / <NUM>,<NUM>'-oxydiphenylene terephthalamide filament. This material is conventionally referred to as TECHNORA® and is available from Teijin.

Polyparaphenylenebenzobisoxazole (poly(p-phenylene-<NUM>,<NUM>-benzobisoxazole) (PBO) fibers are commercially available as ZYLON® AS and ZYLON® HM manufactured by TOYOBO CO.

Core-sheath structures of the present disclosure may also be formed of polyether ether ketone (PEEK) materials such as VICTREX™ PEEK polymers. In some embodiments the use of high-dpf PEEK polymers as components of the jacket (sheath) and/or the core can impart the core-sheath structures with improved tensile properties.

Ultra-high molecular weight polyethylene fibers used in core-sheath structures of the present disclosure may have an intrinsic viscosity in a range of from about <NUM>, or from about <NUM>, or from about <NUM>, to about <NUM>, or to about <NUM>, or to about <NUM> dL/g. When the intrinsic viscosity of the "ultra-high molecular weight polyethylene fiber" is in a range of from about <NUM> to about <NUM> dL/g, fibers having good dimensional stability are obtained.

ASTM standards (for example Test Methods D789, D1243, D1601, and D4603, and Practice D3591) that describe dilute solution viscosity procedures for specific polymers, such as nylon, poly(vinyl chloride), polyethylene, and polyethylene terephthalate) are available. Generally, the polymer is dissolved in dilute solution and a drop time through a capillary tube versus a control sample is measured at a specific temperature.

A weight average molecular weight of the "ultra-high molecular weight polyethylene fiber" may be from about <NUM>,<NUM>, or from about <NUM>,<NUM>, or from about <NUM>,<NUM>, to about <NUM>,<NUM>,<NUM>, or to about <NUM>,<NUM>,<NUM>, or to about <NUM>,<NUM>,<NUM>. When the weight average molecular weight of the "ultra-high molecular weight polyethylene fiber" is in the range of from about <NUM>,<NUM> to about <NUM>,<NUM>,<NUM>, high tensile strength and elastic modulus may be obtained.

Due to difficulties in determining the weight average molecular weight of "ultra-high molecular weight polyethylene fibers" using GPC methods, it is possible to determine the weight average molecular weight based on a value of the above mentioned intrinsic viscosity according to the equation below mentioned in "<NPL>)".

In some embodiments it may be preferable for the repeating units of a "ultra-high molecular weight polyethylene fiber" to contain substantially ethylene. However, it may be possible to use, in addition to a homopolymer of ethylene, a copolymer of ethylene with a small amount of another monomer, for example, α-olefin, acrylic acid and derivatives thereof, methacrylic acid and derivatives thereof, and vinylsilane and derivatives thereof. The polyethylene fiber may have a partial crosslinked structure. The polyethylene fiber may also be a blend of a high-density polyethylene with an ultra-high molecular weight polyethylene, a blend of a low-density polyethylene with an ultra-high molecular weight polyethylene, or a blend of a high-density polyethylene, a low-density polyethylene with an ultra-high molecular weight polyethylene. The polyethylene fiber may be a combination of two or more ultra-high molecular weight polyethylenes having different weight average molecular weights, or two or more polyethylenes having different molecular weight distributions.

Commercially available "ultra-high molecular weight polyethylene fibers" include DYNEEMA® SK60, DYNEEMA® SK, IZANAS ® SK60 and IZANAS ® SK71 manufactured by TOYOBO CO. ; and SPECTRA FIBER <NUM>® and SPECTRA FIBER <NUM> manufactured by Honeywell, Ltd.

These "ultra-high molecular weight polyethylene fibers" can be used alone or in combination.

The core composition may be of any high performance polymer filament(s) previously described and may be filaments selected from the group consisting of a liquid crystalline polyester filament, an aramid filament, co-polymer aramid filament, a polyether ether ketone filament, a poly(p-phenylene benzobisoxazole) filament, an ultra-high molecular weight polyethylene filament, a high modulus polyethylene filament, a polypropylene filament, a polyethylene terephthalate filament, a polyamide filament, a high-strength polyvinyl alcohol filament and combinations thereof.

The core component filament composition may be selected and structured for specific properties related to the intended end use of the core-sheath structure.

Along with the polymer composition of the core, the weave or braid and/or twist of the braided sheath (jacket) may also be adjusted to control the load sharing contribution of the core and the braided sheath. In this manner the overall tensile strength and dimensional stability of core-sheath structures of the present disclosure can be increased while maintaining or decreasing the overall diameter of the core-sheath structures.

In some embodiments core-sheath structures of the present disclosure may contain an LCP-based core and an LCP-based braided sheath.

In some embodiments the performance and characteristics of core-sheath structures of the present disclosure may be modified and managed by applying finish compositions to the core and/or the braided sheath. For example, at least one of the core and the braided sheath may contain a filament, fiber or strand having a coating of a cross-linked silicone polymer, or a non-cross-linked silicone polymer or a long chain fatty acid. Suitable long chain fatty acids may include stearic acid.

Application of cross-linking silicone polymers, especially to the filaments contained in the strands of the braided sheath and/or the core may provide advantageous performance enhancement to the tensile strength of core-sheath structures of the present invention.

Generally, there are three crosslinking reaction methods available to prepare silicone resins: <NUM>) peroxide cure wherein heat activation of polymerization occurs under the formation of peroxide free radicals; <NUM>) condensation in the presence of a tin salt or titanium alkoxide catalyst under the influence of heat or moisture; and <NUM>) addition reaction chemistry catalyzed by a platinum or rhodium complex which may be temperature- or photo-initiated.

A cross-linked silicone coating may enhance moisture resistance of coated strands and may also enhance the lubricity of the strands such that, when the core-sheath structure is under longitudinal stress, the braid responds more efficiently in comparison to a non-coated structure where frictional interaction may need to be overcome.

Coating compositions of the present disclosure may be applied via surface application techniques which are known to those skilled in the art. These surface application techniques may include simple pumping finish solutions through a finish guide where the fiber comes into contact with the finish and is wicked into the fiber bundle via capillary action. Alternatively, other techniques may include spraying, rolling, or submersion application techniques such as dip coating. Subsequent treatment of the fiber with finish solution applied may include contact with roller or rollers for the purpose of setting the finish and/or influencing the degree of cross linking in a finish formulation. The roller(s) may or may not be heated. The coating composition may then be cured to cause cross-linking of the cross-linkable silicone polymer. When thermal curing is used the temperature may be from about <NUM>, or from about <NUM>, or from about <NUM>, to about <NUM>, or to about <NUM>, or to about <NUM>. The curing temperature may be determined by the thermal stability properties of the filament, fiber or strand and the actual cross-linking system being employed.

The degree of the cross-linking obtained may be controlled to provide differing degrees of flexibility or other surface characteristics to the filament, fiber or strand. The degree of crosslinking may be determined by the method described in <CIT> where the coating is extracted with a solvent which dissolves monomer, but not the crosslinked polymer. The degree of cross-linking may be determined by the difference in weight before and after the extraction.

The degree of cross-linking may be at least about <NUM>%, or at least about <NUM>%, or at least about <NUM>%, based on the total weight of the coating. The maximum degree of cross-linking may be about <NUM>%. The weight of the cross-linked coating may be from about <NUM> wt% to about <NUM> wt%, or to about <NUM> wt%, or to about <NUM> wt%, based on the total weight of the filament, fiber or strand.

Another aspect relates to cords obtained by the methods, such methods not forming part of the claimed invention, disclosed herein for producing core-sheath structures. In some embodiments a maximum diameter of the cord may range from about <NUM> to about <NUM>. In other embodiments the maximum diameter of the cord may range from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

Cords of the present disclosure may be designed to satisfy various properties including break tenacity. In some embodiments a break tenacity of the cord is at least <NUM> cN/dtex. In other embodiments the break tenacity of the cord may range from about <NUM> cN/dtex to about <NUM> cN/dtex, or from about <NUM> cN/dtex to about <NUM> cN/dtex, or from about <NUM> cN/dtex to about <NUM> cN/dtex.

Cords of the present disclosure include tension members that are useful in various applications including medical cords. For example, embodiments of the present disclosure include sutures having core-sheath structures produced by the methods describe herein, as well as catheter navigation cables and assemblies, steering cables and assemblies, device deployment control cables and assemblies, and torque and tension transmission cables and assemblies, just to name a few.

Claim 1:
A cord having a core-sheath structure (<NUM>, <NUM>), comprising:
a core (<NUM>); and
a braided sheath (<NUM>, <NUM>) of strands surrounding the core (<NUM>), the braided sheath (<NUM>, <NUM>) comprising strands (<NUM>, <NUM>, <NUM>, <NUM>) having a braid angle of <NUM>° or more in a relaxed state,
characterized in that:
the strands (<NUM>, <NUM>, <NUM>, <NUM>) having the braid angle of <NUM>° or more in the relaxed state include at least one shaped strand of filaments (<NUM>);
the shaped strand of filaments (<NUM>) is an untwisted strand having a twist level of less than <NUM> turn per meter;
a cross-sectional aspect ratio of the shaped strand of filaments (<NUM>) is at least <NUM>:<NUM>, as measured in the braided sheath (<NUM>, <NUM>);
a thickness of at least a portion of the braided sheath (<NUM>, <NUM>) ranges from about <NUM> to about <NUM>; and
the braided sheath (<NUM>, <NUM>) comprises a synthetic fiber having a tensile strength of greater than <NUM> cN/dtex,
wherein the tensile strength of the synthetic fiber, the thickness of the core and braided sheath (<NUM>, <NUM>), and thereby the cross-sectional aspect ratio of the shaped strand of filaments (<NUM>), are determined in accordance with the methods described in ASTM D855/D885M-10A (<NUM>).