Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Staple length fiber
Reexamination Certificate
1998-09-21
2001-01-30
Edwards, Newton (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Staple length fiber
C428S369000, C264S210500, C264S210800, C264S211140
Reexamination Certificate
active
06180230
ABSTRACT:
The invention relates to permanently crimped fibres obtained by three-dimensional texturing and to a process for manufacturing these fibres.
Fibres made of synthetic material are used in many applications for the manufacture of staple fibre yarns, of textile or covering surfaces, or as filling elements, for example. In the case of the manufacture of textile surfaces of the velvet type, as in the case of covering surfaces such as carpets, wall coverings, etc., the fibres are arranged and held in place on a support surface which may be a woven fabric, a knitted fabric, or a non-woven fabric, a surface made of synthetic or natural material which may or may not be reinforced with fillers.
Fibres are also used for the manufacture of non-woven or felt surfaces which have many applications, such as filtration, soil stabilization, abrasive surfaces, filling or insulating layers, stiffening material, interlining, reinforcing cloth, for example.
In these various applications, the fibres used are generally crimped fibres. Current processes for manufacturing fibres consist in manufacturing, by melt spinning, strands comprising a large number of filaments arranged in parallel. These strands are either collected in cans or are wound onto bobbins or other supports arranged, for example on a creel, in order to form a set of packages. These strands are advantageously assembled into a tow or a bundle which will be fed into a drawing/crimping apparatus.
In general, the drawing is carried out in a roll-type drawing unit, the crimping being obtained by overfeeding the tow onto a surface held in a heated box. The tow builds up on this surface and forms folds. The deformation of the filaments is set by the temperature in the box. Next, the tow is either fed into a chopper, in order to be cut into fibres of the desired length, or it is stored in the form of bales before fed into choppers.
The fibres thus obtained have a low bulk since the crimping is only carried out in one plane the fibre may be described as a zig-zag line.
Furthermore, this crimping process requires slow speeds and cannot therefore be carried out in line with the spinning, i.e. without a step of storing and reworking the tow between the spinning step and the crimping step, especially for high-linear density fibres or filaments.
The object of the invention is, in particular, to remedy these drawbacks by providing a fibre made of synthetic material which has a three-dimensional crimp structure, and therefore a greater bulk, and which can be obtained in an integrated process, without a step of storing and reworking the tow between the spinning step and the tow-chopping step.
The invention provides permanently crimped fibres made of synthetic material which are characterized by the fact that the crimp structures of the fibres lie in at least two intersecting planes.
This three-dimensional crimping makes it possible to obtain fibres which have a bulked appearance, and which, above all, maintain a high crimp content even under tension.
Thus, the fibres of the invention may advantageously have a crimp content of greater than 30% under a tension of 100 mg, of greater than 25% under a tension of 200 mg and even more advantageously a crimp content of greater than 20% under a tension of 400 mg.
By way of comparison, fibres having the same linear density, but with crimp structures lying only in one plane, have a crimp content of less than 30% as soon as a tension of 100 mg is applied.
Crimp content is determined by measuring the length (L
d
) of a flattened fibre from which the crimp structures have been removed and the length (L
f
) of the crimped fibre to which a defined tension is applied. The crimp content (T
f
) is calculated using the formula:
(
L
d
-
L
f
)
×
100
L
d
=
T
f
(
%
)
According to another preferred characteristic of the invention, the crimp structures of the fibres of the invention are loops, or structures in which the fibre is folded back on itself in the form of a pigtail.
This crimping is obtained by a three-dimensional texturing of the filaments. This texturing is carried out, in one embodiment of the invention, by pneumatic packing of the multifilament tow, as will be described below.
According to another characteristic of the invention, the synthetic materials of which the fibres are composed are advantageously a polymer of the polyamide or copolyamide type.
By way of example of polyamides or copolyamides suitable for the invention, mention may be made of polyhexamethylene adipamide, polycaprolactam, copolymers of these two polyamides, or blends thereof. These polyamides may also contain other repeat units such as sulphonate aromatic units as the repeat unit derived from 5-sulphoisophthalic acid or the like, or units derived from other dicarboxylic acids, such as isophthalic or terephthalic acids, or diamines.
The polyamides may also be used with various additives, such as pigments, matting agents, heat or light stabilizers, heat-shielding agents, antimicrobial agents, antifouling agents or the like. This list is in no way exhaustive.
By way of preferred polyamide, mention may be made of polyhexamethylene adipamide and copolymers or blends comprising mostly hexamethylene adipamide units.
The fibres of the invention may have various linear densities. Thus, the fibres may have a linear density equal to a few dtex up to a linear density of several hundred dtex.
In a preferred embodiment of the invention, the fibres advantageously have a linear density of greater than 50 dtex, for example of between 50 and 250 dtex.
The fibres of the invention having, in particular, a high linear density, such as greater than 50 dtex, have feel and roughness properties which are completely unexpected and different from the crimped fibres obtained by mechanical packing.
The length of the fibres according to the invention may vary over wide ranges. However, according to a preferred characteristic of the invention, this length is advantageously between 25 mm and 200 mm.
Other characteristics of the fibres of the invention will appear in the examples given below by way of indication.
The subject of the invention is also a process for manufacturing the fibres described above.
This process consists in spinning a composition of synthetic material in one or more spinnerets at a temperature above the melting point of the said composition so as to obtain a certain number of filaments.
Next, these filaments are cooled using a coolant in order to lower their temperature to a value below or near the T
g
of the polymer. The filaments are then combined at a point, called the convergence point, in order to form a strand. The term “strand” should be understood to mean a combination of mutually parallel filaments.
The strand is optionally subjected to a drawing operation, and then fed into a three-dimensional texturing or pneumatic-packing-texturing step. Advantageously, this crimping is set in the texturing step. The strand thus crimped is advantageously fed into a chopping means in order to chop it into fibres of the desired length. Advantageously, several strands may be combined and fed jointly into the chopper.
These steps are preferably carried out without intermediate storage or reworking of the strand.
Thus, the process of the invention is, in the preferred embodiment of the invention, a continuous and integrated process which comprises, in line, the spinning, drawing, crimping, setting and chopping steps.
Depending on the linear density of the filaments, the spinning rate may vary from 500 m/min to 2500 m/min.
The spinning temperature is between 250° C. and 300° C. The filaments leaving the spinneret are cooled by a fluid which is advantageously either water or air.
Thus, for filaments having a linear density of greater than 50 dtex and preferably greater than 70 dtex, the coolant is advantageously water.
The filaments, after convergence into the form of a strand or bundle, are subjected to a drawing operation, the draw ratio advantageously being between 1 and 5, and preferably between 2 and 4.
This drawing is generally carri
Chaubet Olivier
Cieslak Michel
Prevost Jean-Pierre
Burns Doane Swecker & Mathis L.L.P.
Edwards Newton
Novalis Fibres
LandOfFree
Permanently crimped fibres and method for making same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Permanently crimped fibres and method for making same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Permanently crimped fibres and method for making same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2442500