Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2002-03-14
2003-12-30
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S373000, C428S374000
Reexamination Certificate
active
06670034
ABSTRACT:
BACKGROUND OF THE INVENTION
Production of filaments and fibers have long been known in the art. Typically, these filaments and fibers are produced utilizing well known extrusion techniques. Generally, this includes the use of a single extruder through which a material, such as a polymeric material, is melted and forced through a die head to form the filament.
Filaments which are produced from such single extrusion processes are generally characterized as monofilaments, although the term “monofilament” has also typically referred to any filaments of indefinite or extreme length. Thus, the term “monofilaments” as used in connection with single extrusion processes may be more particularly characterized as “monoconstitutent” or monocomponent” monofilaments, meaning they are extruded from only one polymer and have a homogeneous cross section throughout the entire length of the fiber. For ease of discussion herein, a “monofilament” will refer to this type of fiber made by this single extrusion process. The term “filament” will refer to what is often termed “monofilament”.
Since a single extruder is employed, the processing conditions and parameters, e.g., temperature (heat) profile, screw speed, shear, die size, die profile, draw ratio, etc., can be controlled and manipulated in a manner which can affect the overall physical or mechanical properties of the monofilament thus produced, since it is well known that these processing conditions can and do affect the morphology, i.e., the general shape, arrangement and function of the crystalline structure within the polymer, which in turn influence the properties of the monofilament. However, it will be appreciated that the morphology of the entire monofilament will be substantially the same throughout the entire filament. While the processing conditions and parameters can be controlled and manipulated to affect the final physical properties of the monofilament, the monofilament itself has a morphology which is essentially identical throughout.
Accordingly, in order to obtain better results, various blends of polymers or copolymers have been employed to improve certain desired physical properties of the monofilaments, depending upon the desired application. Traditional applications for monofilament lines include weed trimmer line, fishing line, and sewing threads. These monofilaments may also be woven into or otherwise processed into various industrial and commercial fabrics for various applications including fabrics for use as papermachine clothing, hosiery, and hook and loop fasteners. It will be appreciated that a blend of polymers may provide a different morphology to the monofilament than would a single polymer since the blend has at least one different ingredient. Thus, the mechanical properties of the monofilament comprising a blend of polymers will differ from the mechanical properties of a monofilament comprising a single ingredient.
Although monofilaments have provided suitable results in most applications, the limitations of monofilaments to one material (i.e., either one ingredient or a blend of ingredients) having one general overall morphology has created interest in multi-structural filaments. By the term “multi-structural,” it is meant that, through the cross section of each filament at any place along the length of the filament, there are two or more discrete regions of extruded components. Multi-structural filaments, as known heretofore, are generally referred to as “multicomponent monofilament” or “composite filaments”. These multi-structural filaments are essentially produced by co-extrusion of two or more polymers in such a manner that each polymer occupies a discrete region that runs the length of the filament. When such a filament consists of two discrete materials or polymeric components, the filament is sometimes referred to as a “bicomponent monofilament.” The actual shape and size of the discrete regions are predetermined by the extrusion control techniques and die packs employed. Typical multi-structural cross sectional configurations include core-sheath, side-by-side, and islands-in-the-stream configurations. Other, more complex configurations may include core-mantle-sheath configurations, islands-in-the-stream configurations having multiple sized islands or core-sheath configurations where the sheath does not completely surround the core, e.g., core-tips configurations.
Heretofore, multi-structural filaments have been produced as bicomponent or multicomponent filaments utilizing two or more extruders working in tandem to force two or more distinct materials (or distinct blends of materials) through different channels in a common die head so as to produce filaments that contain two or more discrete regions of different materials encompassed in the extruded profiles and determined by way of their respective extruders and die head paths. For instance, to produce a core-sheath bicomponent filament, essentially the same extrusion techniques are utilized as were employed in the production of monofilaments, except that two separate extruders are run in tandem and process two different materials. One extruder is used to melt and force a first ingredient into the die pack which will ultimately produce the core of the filament, while the other extruder is used to melt and force a second, different ingredient into the die pack where it follows a different flow path such that it ultimately produces a sheath around the core in producing the filament.
Because two independently controlled extruders are employed which use two different materials, the characteristics of each of these discrete materials and, therefore, the physical properties within each discrete region of the filament made from one of the materials can be adjusted in a manner which is beneficial to the performance characteristics of the bicomponent filament. For example, suppose one ingredient has excellent abrasion resistance and toughness, but lacks dimensional stability. On the other hand, a second ingredient is not as resistant to abrasion but provides greater dimensional stability. Depending upon the application, it may be beneficial to provide a sheath of the abrasion resistance material around the core component having excellent dimensional stability to provide an improved filament. Thus, it will be appreciated that the use of two extruders and two materials allows for increased versatility of the end product's physical performance through control of the materials used, control of the processing conditions and the orientation or configuration under which the materials are extruded, sent through the die pack and drawn.
Although bicomponent filaments are becoming increasingly popular, there are still limitations to filament production using the bicomponent process. First and foremost is the issue of compatibility of the components or ingredients. In the example above relating to an ingredient with excellent abrasion resistance and low dimensional stability and a second ingredient with improved dimensional stability but lower abrasion resistance, the first ingredient could be viewed as nylon while the second might be polyethylene terephthalate (PET). However, it is well known that nylon and PET are not sufficiently compatible with each other to produce a bicomponent filament using just these two materials. If nylon were to be made into a sheath around a PET core, without some additional adhesive, compatibilizing agent, or compatibilizing layer therebetween, the filament would simply fall apart as the two are not sufficiently compatible for filament production. In fact, it is known that external stresses or other forces may be sufficient to cause delamination of these incompatible materials, notwithstanding the additives used to keep them together.
Consequently, many patentees and users of the bicomponent process employ materials that, while similar and compatible, are different in terms of their chemical structure or are blends or copolymers of other processing materials. For example, U.S. Pat. No. 6,207,276 discloses a core-sheath bicomponent fiber
Boyd Chad
Brissette Peter
Tanverdi Atiye E.
Edwards N.
Renner Kenner Greive Bobak Taylor & Weber
Shakespeare Company LLC
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