Flame-retardant Filament And Method Of Manufacture Thereof And Protective Sleeves Constructed Therefrom

Abstract

A continuous halogen-free flame-retardant filament and method of forming thereof includes providing MC, a phosphorus compound, and PET, and then, forming a mixture of the MC, phosphorus compound, and PET. And lastly, extruding the mixture to form the halogen-free flame-retardant filament. The filament can be braided, woven or knitted into a variety of fabric constructions, such as, for example, sleeves for protecting wires.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] This invention relates generally to flame-retardant filaments, and more particularly to flame-retardant filaments used as yarn for constructing elongate protective sleeves and to methods of manufacture of the filaments.

[0003] 2. Related Art

[0004] It is known to manufacture fabrics from flame-retardant yarns, wherein the fabrics are used to protect items from exposure to flames. For example, it is known to construct braided, woven or knitted sleeves from fire-retardant yarns to protect elongate items, such as wires, contained within the sleeves. One known compound which has desirable fire-retardant properties is melamine cyanurate (MC).

[0005] The assignee herein is also the assignee of U.S. Pat. No. 6,828,365, wherein MC is compounded with a fire-retardant polyphosphonate filler and a polymer selected from the group consisting of poly(ethylene terephthalate) and poly(ethylene naphthalate) and then extruded to form a fire-retardant monofilament. The addition of the polyphosphonate filler to MC increases the flame-retardancy of the monofilament. Since polyphosphonate is fire-retardant as well, it provides the resulting monofilament with additional fire-retardant properties.

[0006] Current commercially available halogen-free flame-retardant poly(ethylene terephthalate) (FR-PET) is made by adding an organo-phosphorous compound in the polycondensation stage of the PET polymerization process, such as in U.S. Pat. No. 4,086,208, which is incorporated herein by reference in its entirety. Unfortunately, the flame-retardant properties of this phosphorus-containing PET (P-FR-PET) does not meet the most stringent flame test requirements. In particular, the burn time and flame spread distance are too long, and it emits flaming drips.

SUMMARY OF THE INVENTION

[0007] An extruded halogen-free flame-retardant filament consists of melamine cyanurate and phosphorus containing fire-retardant poly(ethylene terephthalate) (MC-P-FR-PET). The filament can be braided, woven or knitted into a variety of fabric constructions, such as, for example, sleeves for protecting wires. The combination of the MC and P-FR-PET provides the fabric constructed therefrom with excellent flame-retardant properties while remaining pliable, and thus, the fabrics can be used in tight quarters around relatively sharp bends.

[0008] Another aspect of the invention includes a method of forming a halogen-free flame-retardant filament. The method consists of: providing MC and P-FR-PET. Then, introducing the MC with the P-FR-PET to form (MC-P-FR-PET). And lastly, extruding the (MC-P-FR-PET) to form the halogen-free flame-retardant filament.

[0009] In one presently preferred construction, the P-FR-PET is made in a polymerization process, and the MC and P-FR-PET are compounded to form a homogenous compound, and then extruded to form a continuous filament. In another presently preferred construction, the MC can be introduced with an organo-phosphorous compound during a PET polymerization process to form a polymerized FR-PET with (MC+phosphorus) composition, and then extruded to form a continuous filament.

[0010] Another aspect of the invention includes a flexible, fire-resistant fabric sleeve for protecting elongate members. The sleeve is constructed at least in part from fire-resistant yarn consisting of (MC-P-FR-PET).

[0011] Accordingly, a halogen-free flame-retardant filament constructed according to the invention has excellent flame-retardant properties, consists of minimal compound ingredients, is economical in manufacture, is useful in constructing sleeves, and has a long life in use.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] These and other features and advantages of the present invention will become more readily apparent and appreciated when considered in connection with the following detailed description of presently preferred embodiments and best mode, appended claims and accompanying drawings, in which:

[0013] FIG. 1 is a flow diagram for a process according to one presently preferred embodiment of the invention for manufacturing a halogen-free fire-retardant filament;

[0014] FIG. 2 is a flow diagram for a process according to another presently preferred embodiment of the invention for manufacturing a halogen-free fire-retardant filament and

[0015] FIG. 3 is a schematic perspective view of a sleeve constructed at least in part from the filament constructed from the method of FIG. 1.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS

[0016] Referring in more detail to the drawings, FIG. 1 diagrams a method 100 for manufacturing a halogen-free flame-retardant filament 102 according to one presently preferred embodiment of the invention. The resulting halogen-free filament 102 consists of melamine cyanurate (MC) 104 and phosphorus containing fire-retardant poly(ethylene terephthalate) (P-FR-PET) 106. The combination of MC 104 and P-FR-PET 106 provide the filament 102 with excellent fire-retardant properties. As such, the filament 102 is useful in the construction, such as by braiding, weaving or knitting, of a fire-retardant fabric, wherein the resulting fabric can be constructed in various forms to provide fire-retardant protection to components. For example, the fabric is useful in constructing a fire-retardant sleeve 108 (FIG. 3) for protecting elongate members, such as wires, from exposure to flames. It should be recognized that the sleeve 108 can be constructed in any suitable fashion, such as an open construction, having a longitudinal access opening, a closed construction, and in a self-wrapping or wrappable construction, as desired. The sleeves are widely useful in a broad array of environments and industries requiring protection for wiring from flame, such as in automotive, aircraft, railway, marine, and aerospace, for example.

[0017] The method of manufacture of the halogen-free filament 102 starts with steps 110 and 112 of providing MC and P-FR-PET. The MC 104 is preferably provided as commercially available MC, which is generally available as a fine powder. A MC powder having a article size of about 2 .mu.m is preferred, with the MC 104 having a percent-by-weight content of about 5-10 percent relative to the MC-P-FR-PET compound.

[0018] The P-FR-PET 106 is also commercially available. Preferably, the phosphorus content is about 3000-8000 ppm in proportion to the P-FR-PET.

[0019] In manufacture, the MC powder 104 and the polymerized P-FR-PET 106 are combined in step 114 to form a substantially homogeneous mixture 116. The mixture 116 of the MC and polymerized P-FR-PET can be compounded together, such as in a twin screw extruder, and then extruded into the continuous filament 102. Accordingly, there are no additional fillers, fibers, or the like added to the mixture 116, and thus, the finished filament 102 contains only MC 104 and polymerized P-FR-PET 106.

[0020] Otherwise, in another aspect of manufacture, rather than compounding the MC with the polymerized P-FR-PET, the MC 104 can be incorporated with an organo-phosphorous compound 118 during a polycondensation stage 120 in a PET polymerization process to form a polymerized FR-(MC+phosphorus) PET composition 116, designated earlier as MC-P-FR-PET. Thereafter, as above, the MC-P-FR-PET composition can be extruded to form the continuous filament 102.

[0021] Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, and any other claims allowed which stem from this application, that the invention may be practiced otherwise than as specifically described and shown.

Claims

1. An extruded halogen-free flame-retardant continuous elongate filament, consisting of: melamine cyanurate; phosphorus compound; and poly(ethylene terephthalate).

2. The filament of claim 1 wherein said phosphorus compound is incorporated in a stage of polycondensation of a poly(ethylene terephthalate) polymerization process to form P-FR-PET.

3. The filament of claim 2 wherein said melamine cyanurate is compounded with said P-FR-PET.

4. The filament of claim 1 wherein said melamine cyanurate and said phosphorous compound are incorporated in a stage of polycondensation of a poly(ethylene terephthalate) polymerization process to form MC-P-FR-PET.

5. A method of forming a halogen-free flame-retardant continuous elongate filament, consisting of the steps of: providing melamine cyanurate; providing a phosphorus compound; providing poly(ethylene terephthalate); forming a compound of said melamine cyanurate, said phosphorous compound and said poly(ethylene terephthalate); and extruding said compound to form said filament.

6. The method of claim 5 wherein the forming a compound step includes incorporating said phosphorus compound in a stage of polycondensation of a poly(ethylene terephthalate) polymerization process to form P-FR-PET.

7. The method of claim 6 wherein the forming a compound step includes compounding said melamine cyanurate with said P-FR-PET.

8. The method of claim 5 wherein the forming a compound step includes incorporating said melamine cyanurate and said phosphorus compound in a stage of polycondensation of a poly(ethylene terephthalate) polymerization process to form MC-P-FR-PET.

9. A flexible, fire-resistant fabric sleeve for protecting elongate members, comprising: at least one yarn, said yarn consisting of: melamine cyanurate; a phosphorus compound; and poly(ethylene terephthalate).

10. The fabric sleeve of claim 9 wherein said at least one yarn is a monofilament.

11. The fabric sleeve of claim 9 wherein said at least one yarn is a multifilament.

12. The fabric sleeve of claim 9 wherein said phosphorus compound is incorporated in a stage of polycondensation of a poly(ethylene terephthalate) polymerization process to form P-FR-PET.

13. The fabric sleeve of claim 12 wherein said melamine cyanurate is compounded with said P-FR-PET.

14. The fabric sleeve of claim 9 wherein said melamine cyanurate and said phosphorous compound are incorporated in a stage of polycondensation of a poly(ethylene terephthalate) polymerization process to form MC-P-FR-PET.