Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Staple length fiber
Reexamination Certificate
2001-06-28
2003-07-01
Morris, Terrel (Department: 1771)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Staple length fiber
C428S359000, C442S414000, C442S415000
Reexamination Certificate
active
06586092
ABSTRACT:
BACKGROUND OF THE INVENTION
Methods for forming fiber batts require the use crimped fibers because uncrimped fibers are very difficult if not impossible to process through textile equipment. In some applications such as speaker cones, high modulus fibers are used in making the cone because these fibers stiffen and improve sound reproduction. Before the present invention, it was necessary to crimp these high modulus fibers before they could be processed to form batts or felts. In the crimping process these stiff fibers are broken and damaged. Fiber is also lost or wasted contributing to an increased in cost for such crimped fibers. Even if no fiber were lost or damaged in crimping, the need for this step, alone, adds both processing time and costs in the production of batts and the products made from these batts.
Speaker cones are generally made from a paper or from a felt. Papers are non-woven webs produced by a wet lay process on paper machines, while non-woven felts are produced from fiber batts that are needled together.
U.S. Pat. No. 4,112,168 teaches a speaker cone produced by impregnating a fiber web with a resin solution, evaporating the solvent to produce a non-woven fabric and then simultaneously laminating to this fabric a gas tight film while molding the fabric into the speaker cone.
In another patent, U.S. Pat. No. 4,359,132, a speaker cone is produced by forming a needled felt from ptextile fibers and polypropylene textile fibers. Textile fibers are crimped fibers that allow easy processing through textile equipment.
British Patent 2 037 1 22 B teaches a speaker cone made of a paper formed on a paper machine from stiff fibers such as p-aramid or carbon fibers.
An object of the present invention is to provide a easily moldable batt using uncrimped high modulus polymer fibers. Such a bat may be molded into high quality speaker cones.
Another object in the present invention is to provide a cardable fiber blend from which the moldable batt may be formed.
Another object of the present invention is to provide a process for producing a fiber batt that does not require crimped high modulus fiber.
Another object of the present invention is to provide a high quality speaker cone and a process for making this speaker cone.
SUMMARY OF INVENTION
The present invention provides an intimate, cardable blend comprising crimped thermoplastic fibers and uncrimped high modulus polymer fibers. It is preferred that the thermoplastic fibers are polyolefin fibers and that the high modulus fibers have a modulus of at least 550 g/denier. It is also preferred that the high modulus fibers are selected from the group consisting of p-aramid, aromatic polyester fibers.
A second embodiment of the present invention is a batt formed from this intimate, cardable blend of fibers.
The present invention also provides a process for forming a fiber batt comprising the steps of:(a) blending together uncrimped high modulus polymer fibers having a modulus of 550 g/denier or more with fibers of a thermoplastic,(b) passing the blend through a device to open the fibers, and(c) forming the fibers into a batt.
In this process it is preferred that the high modulus polymer fibers are selected from the group consisting of p-aramid and aromatic polyester fibers.
In particular it is preferred that the crimped thermoplastic fibers are polyolefin or polyester fibers. For the high modulus polymer fibers, fibers that have a modulus greater than 750 g/denier are particularly preferred. It is also preferred that the batt formed in the present process contains from about 30% to about 70% by weight of high modulus polymer fibers and from about 70% to about 30% by weight crimped thermoplastic fibers.
The present process can be used to produce a molded fiber product when after step (c), the batt is molded in a high temperature, high pressure mold. The batt formed by the present process is particularly suited to be molded to form a speaker cone.
The batt and the molded product made from this batt may be the natural color of the polymer fibers or may be colored to a desired hue and shade by selecting the fibers from the group consisting of natural colored thermoplastic polymer fibers, natural colored high modulus polymer fibers, colored thermoplastic polymer fibers and colored high modulus polymer fibers.
The present invention also provides an improved process for forming a speaker cone comprising the steps of:(a) blending together high modulus polymer fibers having a modulus of 550 g/denier or more with fibers of a thermoplastic polymer, (b) passing the blend through a device to open the fibers, (c) forming the fibers into a batt,(d) heating a mold to about 200° F. and placing the batt in the mold to form a speaker cone,(e) applying a pressure of from 5 to 20 tons to the mold and heating the mold to about 380° F.,(f) allowing the mold to cool to about 200° F. before opening the mold to remove the speaker cone.
In this improved process, it is desirable that the high modulus polymer fibers are selected from the group consisting of p-aramid and aromatic polyester fibers and that the crimped thermoplastic fibers are polyolefin or polyester fibers. High modulus fibers having a modulus of at least 750 g/denier are particularly preferred. It is also desirable that the batt formed contains from about 30% to about 70% by weight of high modulus polymer fibers and from about 70% to about 30% by weight crimped thermoplastic fibers. Also in this process during molding the batt, a polyolefin film can be laminated to at least one face of the batt. The term polyolefin film as used herein also includes fibrous thin layers such as webs or batts and other terms used to describe thin layers of polyethylene. For speaker cones it is particularly desirable that the high modulus fibers are all uncrimped p-aramid fibers and the thermoplastic fiber is polypropylene.
The present invention provides a moldable fiber batt comprising fibers having a modulus of 550 g/denier or more with fibers of a thermoplastic polymer wherein the high modulus polymer fibers are all uncrimped fibers or a mixture of crimped and uncrimped fibers. It is preferable that the high modulus fibers are selected from the group consisting of p-aramid, and fibers and that the crimped thermoplastic fibers are polyolefin or polyester fibers or a mixture of these fibers. Polymer fibers having a modulus greater than 750 g/denier are particularly preferred for use as the high modulus fiber. It is particularly desirable that the high modulus polymer fibers are all uncrimped p-aramid fibers and the thermoplastic polymer fibers are polypropylene.
DETAILED DESCRIPTION
The present invention provides an intimate, cardable fiber blend that may be formed into a batt. This fiber batt is particularly useful in making speaker cones.
As used herein, the term high modulus polymer fiber means a fiber that has a modulus of 550 g/denier or more. High modulus polymer fibers that are particular useful in the present invention include p-aramid and aromatic polyester fibers. Such fibers having a modulus of 750 g/denier or more are particularly preferred. In processing the uncrimped high modulus fibers, the rate of carding may be increased by mixing into the uncrimped high modulus fiber an amount of crimped high modulus fiber.
When speaker cones are the desired product, it is recommended that the amount of crimped high modulus fiber present in a mixture with uncrimped high modulus fiber be less than 50% of the total weight of the mixture of crimped and uncrimped high modulus fiber.
It is believed that the use of uncrimped high modulus fiber is of particular advantage for speaker cones. The presence of uncrimped high modulus fiber produces a cone that, at least when rated subjectively, produces an improved sound reproduction, particularly of the human voice. Thus it is most desirable to use all uncrimped high modulus fiber. The mixing of crimped and uncrimped high modulus fiber as described above allows one to balance sound reproduction quality and rate of carding while realizing benefits from the use of uncrimp
Befumo Jenna-Leigh
E. I. du Pont de Nemours and Company
Morris Terrel
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