Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Production of continuous or running length
Reexamination Certificate
2000-07-20
2003-05-13
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Production of continuous or running length
C264S103000, C264S210800, C264S211140
Reexamination Certificate
active
06562282
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a melt blowing die apparatus for spinning filaments of molten synthetic fiber material to produce fibrous non-woven thermal insulating mats constructed of thermoplastic fibers and particularly, though not exclusively, to form high loft batts of linear condensation polymers, preferably polyester, for example, polyethylene terephthalate (PET). The mats may be thermally insulating mats in the form of mats, boards or batts with an insulating R value of at least 3.5/inch and preferably at least 4/inch. Specifically, the invention relates to control of the drawn filament by a flow of pressurized air flow parallel to the extruded filaments to provide attenuation of the filaments within an attenuation slot provided in a lower portion of the apparatus.
BACKGROUND OF THE INVENTION
It has been proposed to produce polyester (e.g. PET) non-woven insulating mats, constructed by melt-blowing techniques, having R values of 4.0 or more per inch with mats using substantially continuous fibers of 3-12 microns. However, mass production of high-loft batts suitable for the insulation of building structures have not, in the past, proved economical in spite of extensive research efforts devoted to producing such environmentally friendly products.
PET non-woven fiber mats, specifically for insulating purposes, whether commercial or domestic, have been proposed using melt blowing die equipment in which melted PET is extruded through a plurality of nozzles to form substantially continuous fibers which are then carried by a high velocity gas toward a fiber mat forming location, at which the fibers are laid down with self entanglement, resulting from the highly turbulent accelerating gas flow, to produce the desired batt integrity. It is proposed in the art to produce such insulating batts (and boards) via one or more arrays of nozzles disposed in a straight line arranged over the mat forming location to progressively produce the desired batt configuration as it is conveyed under the array(s). As the fibers are extruded by the nozzles, they are collected on a collection device, in a layer of fibers to form the insulating mats, batts or boards.
U.S. Pat. No. 5,248,247 discloses an aligned nozzle configuration, two slot ducts producing air jets directed to intersect, at an acute angle, the spin line below the nozzle carrying die face (or near it). The role of the air jets is to cause the extruded polymer filaments to be stretched and expose the fibers to turbulent air flow and preferably broken up prior to deposition in a random mass on the moving belt below the die. The main thrust of the patent is directed at the provision of a uniform driving pressure along the entire lateral die length for the air supply system feeding the slot nozzles. It is postulated, in this prior art, that even small variations, along the die length, in this total driving pressure applied to the slot air flow will lead to an unacceptable non-woven product/mat.
Other components of the meltblowing die are elongate plates referred to as air knives (nozzle bars), which form an accelerating air flow channel to, in combination with the die tip nose piece, form converging air flows to attenuate and draw down the extruded fibers to microsized diameters. The air knives are generally elongate plates which have a longitudinal edge tapered to form a knife edge. Two air knives are typically used and are fastened to the face of the die body on opposite sides of the triangular die tip nose piece. The tapered edges of the air knives are aligned with the confronting tapered surfaces of the nose piece and spaced slightly therefrom to form two flow channels which converge at the apex of the nose piece.
The spatial relationship between the air knives and the die tip is defined in the art by parameters known as air-gap and set-back. The air-gap and set-back determine the geometry of the converging air flow passages, and thereby control the airflow properties and the degree of fiber-air interaction.
The prior art melt blowing apparatus as disclosed in U.S. Pat. No. 5,248,247 for production of melt blown filament line is shown generally in
FIG. 1
as comprising an extruder
1
, melt blowing die
4
and a collector drum or conveyor belt
12
. The extruder
1
delivers molten resin through an aligned evenly spaced series of nozzles
6
in the die
4
, where, upon exiting the nozzles
6
, an aligned evenly spaced plurality of filaments (fibers)
2
are extruded to be attenuated and passed down through tapered slits, in a lower portion of the apparatus onto the conveyor belt
12
, by pressurized, converging hot air streams. The tapered slit
11
is formed by adjacent parallel relatively thin nozzle bars
5
through which the combined air/fiber stream passes. The filaments
2
are then collected on the belt
12
to form a mat or fleece of insulation F.
The melt blowing apparatus also includes a source of pressurized air
3
communicating with the die
4
through valved lines
8
and heating elements
7
in order to produce the converging hot air streams
9
. Additionally, baffles and air pressure regulating devices
10
are provided together with the heating elements
7
and valved lines
8
to control the conditioned hot air streams
9
.
As is known to those in the art, the extruder
1
includes an interior cavity where PET chips or similar polymer material are pressurized, heated and melted to produce the molten PET resin. The extruder
1
is provided with the aligned evenly spaced plurality of nozzles
6
communicating with the cavity. The nozzles
6
are supplied with molten PET under pressure to form an aligned evenly spaced plurality of filaments
2
at a desired flow rate.
In conjunction with the molten resin flow, the hot air streams
9
are provided from the pressurized air source
3
via the valved lines
8
into confluence with the filament line
2
substantially adjacent the nozzle
6
. The hot air streams
9
are directed by an outlet oriented so as to introduce each of the air streams into the slit
11
at an acute angle to the direction of the flow of the filaments
2
, thereby attenuating and drawing the filaments
2
downwards towards the conveyor belt
12
as illustrated in FIG.
1
.
The slit
11
does not provide parallel flow controlling walls and is formed by the relative thin nozzle bars in which the slot forming walls converge throughout the vertical height of the slot and thereby fail to provide a controlled flow of the air, passing therethrough, parallel to the filaments and thus do not provide adequate control of filament attenuation and temperature. Here no mention of controlling the temperature of the slot walls is made.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide an improved melt blowing apparatus and method to more effectively control the properties of attenuated filaments formed thereby.
The main objective of the invention is to provide an attenuating air flow in a vertical direction, parallel to the exiting filament direction so that appropriate shearing forces may be applied to the extruded filaments in the attenuating channel. This objective is achieved by means of a small radius Coanda bend or by a suitably designed channel flow, immediately upstream from the entrance to the attenuating channel.
Another object of the invention is to provide adequate fiber entanglement below the die face and the exit plane of the slot discharge, by means of the highly turbulent flow field and the free air entrainment existing in this region.
SUMMARY OF THE INVENTION
Shearing forces applied to an extruding filament of molten synthetic fiber material (polymer) by a suitably configured air/gas flow system provide an important means of influencing and controlling the molecular orientation, crystallinity and crystal orientation in certain high speed fiber spin line applications. The control of both the magnitude and location of the applied shearing forces, through the design characteristics of the air/gas system, is crucial to the achievement of improved and optimi
Arseneau Warren
Johnston Gord W.
Davis & Bujold P.L.L.C.
Rtica, Inc.
Tentoni Leo B.
LandOfFree
Method of melt blowing polymer filaments through alternating... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of melt blowing polymer filaments through alternating..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of melt blowing polymer filaments through alternating... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3022050