Melt blower apparatus and method for forming a fibrous layered web of filter media including a fluid distribution arrangement

ES 2 201 259 T3

DESCRIPTION

Melt blown apparatus and method of forming a layer-like fiber web including a fluid distribution arrangement.

The present invention relates to a spinneret apparatus according to the pre-feature part of claim 1, and to a method for fluid distribution to attenuate pressurized fiber in a meltblown spinneret body according to claim 9.

Nonwoven fiber mats formed by melt blown windrows and melt blown processes for their manufacture have been widely known in the prior art. In this regard, attention is directed to expired patent US-A3,825,380, issued by JW Harding et al. On July 23, 1974, which discloses the formation of one such fibrous mat from molten polymers by means of a apparatus with a simple longitudinally extending swath head, having a front configuration of swaths of triangular cross section, a pair of attenuating air jets directed in opposite directions along the front towards the blown melt fibers that are emitted centrally with the air currents passing in the opposite angular direction, in order to include an angle between the two of the order of thirty (30) to ninety (90) degrees, observing that the jets of attenuated elongated fibers are cooled in the environment before being collected in a screen like a non-woven band and then the attenuating fluid is introduced (figure 1) inside the single head of rows along the side of the same and perpendicular to the flow of molten stream exiting said single row head. In US-A3,942,723 issued by Roy A. Longdon on March 9, 1976, and 4,116,738 issued by David B. Pall on September 26, 1978, yet another single row head structure is described in each of those patents, as set forth in a number of other prior art patents, found only in these patents and a few of the prior art that describe a single row head structure - none of which is specifically indicated here to avoid unnecessary neatness - being able to see that a stream of attenuating fluid is introduced into a source of a simple windrow head from a position substantially opposite to the flow of the melt stream. Furthermore, in US-A-5,080,569, issued by David Gubernick et al. On January 14, 1992, a relatively complicated diversion apparatus is described for obtaining a uniform flow of an attenuating fluid stream in a structure of a simple row head.

EP-A-0,474,422 describes a melt blown die apparatus for producing a nonwoven fibrous web from a polymeric material, according to the preamble of claim 1. The apparatus includes die means for extruding a molten stream of a polymer that includes a cavity with heated means for containing a molten amount of said polymer. The apparatus also includes primary gas means for providing a pressurized gas to an outlet end of the spinneret means and limiting bar means for selectively limiting a flow of the molten quantity of polymer within the heated cavity means.

Although the above techniques teach or suggest various spinnere structures in general, the structures that feed flowable material to the die tip, and melt blown processes, none of them present the unique new spinneret construction and process of Fusion blown to introduce attenuated streams of fluid into multi-head spinner arrangements, as described herein.

The apparatus of the present invention is defined in claim 1, while the fluid distribution method for attenuating the pressurized fiber is defined in claim 9.

According to the new features of the present invention, a direct, inexpensive, easy to manufacture, easy to assemble and maintain apparatus is provided, since it is a unique melt blown process that requires a direct and inexpensive series of phases that provide a Increased production of fibrous filter media with a minimum of both structure and energy consumption. Furthermore, the present invention allows direct and inexpensive modifications to be made to the new apparatus and process to produce various sizes and various characteristics of filter fibers in accordance with changing market demands.

Various other features of the present invention will become apparent to one of ordinary skill in the art after reading the following description.

Preferred embodiments are defined in the supplementary claims.

The present invention is defined in claims 1 and 9, respectively.

It should be understood that various changes may be made by those skilled in the art, in one or more of the phases of the process and in one or more of the various parts of the spinning apparatus described herein, without thereby departing from the scope of the present invention. , as claimed.

Referring to the drawings which schematically show a preferred embodiment of the present invention:

Figure 1 is a schematic cross-sectional view of the general structure incorporating the unitary melt blown die body according to the invention, and a drum collector and winder positioned below, in a spaced relationship, to receive and collect layers of fiber melt blown into a face-to-face nonwoven web, as described in the patent application, further disclosing the structural arrangement of the invention for uniformly introducing attenuating fluid stream into the multi-head melt blown windrow;

Figure 2 is an enlarged view, in cross section, of the new row body structure of Figure 1, with the structural arrangement of the inventive row of the modified Figure 1;

Figure 3 is an isometric view of the single row body described in Figures 1 and 2, modified with the front sections detached and removable, and the fluid passage lip sections of Figures 1 and 2 removed;

Figure 4 is a schematic cross-sectional view, taken along a plane through line 4-4 of Figure 1, describing, longitudinally, the attenua2 fluid feeding structure.

ES 2 201 259 T3 tion in cooperation with removable air lip sections; Y

Figure 5 is a slightly reduced cross-sectional view taken through line 55 of Figure 4, also describing details of the manifold assembly for feeding the attenuating fluid stream to the three row heads of the row structure of melt blown of several heads, as represented in the drawings of figure 3.

Referring to figure 1 of the schematic drawings, a spinning group 2 has been schematically represented including a feed hopper for a fluid material 3, a motor-driven extruder 4 (not shown), conduits for feeding the fluid material 6, the unitary spinneret body of the invention 7 and a separate rotating drum collector of non-woven fiber web 8 for collecting the new web of fiber layers 9 to be fed to the winder 10, The entire spinning assembly 2 includes a feed hopper, extruder, feed conduits, die body, collector - either drum or endless type - and winder which are already known in the sector. Figure 1 also presents the structural arrangement of the invention 50 for introducing attenuating fluid streams uniformly within the swath body 7.

With reference to the schematic arrangement of Figures 2 to 5 of the drawings, details can be seen of the particularities of the invention of the new spinning apparatus and of the process for forming the new non-woven web to layers of fibrous filter media 9, as well as the new attenuation fluid arrangement 50. In accordance with the present invention, the longitudinally extending unitary row body 7 may be formed as such a unitary row body member (FIG. 3) from a suitable preselected material which is heat conductive, such as chromium steel. -nickel, it being understood that other types of heat conducting materials, suitable for easy formation, can also be used. The longitudinally extending die body 7 has been unitarily formed therein, either by casting or precision drilling, a series of slotted passages 11, with a preselected spacing, for the flow of fluid material, three of which are grooved passages of material can be seen in the drawings. In order to provide a final layered product, it is to be understood that at least two such slotted passageways are required for the flow of fluid material, extending longitudinally, in each unitary spinneret body, the spacing of the grooved passageways being compatible material 11 with the geometry and size of the drum 8 or of an endless belt collector (not shown). Each slotted fluid material passage 11 has a fluid material receiving inlet 12 to connect with the above-described hopper 3, the extruder 4 and one of the feed conduits 6 arranged outside the unitary die body 7. In addition, each slotted fluid material passage 11 has a slotted fluid material supply outlet 13, which outlet is located in the communicating removable projecting front section, as will be described later in detail. The longitudinally extending unitary row body also carries pairs of spaced apart rows arranged opposite flow passages for attenuation fluid 14, with a pair of opposite spaced rows of attenuation fluid 14 serving the opposite sides of each slotted flow passage. of flowable material 11 in the body 7. Like the slotted passageways for material flow 11, each pair of rows of spaced passageways 14 arranged in opposition may be formed in the unitary row body 7 serving as slotted attenuation fluid passageways, by casting or precision drilling. Each separate passageway for the flow of the attenuation fluid 14 of each pair of separate rows is provided with an attenuation fluid inlet manifold 16 connected to the new and unique fluid distribution arrangement 50, as will be described later in detail. . Also, as described in greater detail below, pairs of opposing attenuation fluid outlets 17 (FIG. 12) are formed by the flanks of a removable projecting front section, having triangular cross section and extending longitudinally, and a pair of detachable lip sections arranged in opposition and mirrored apart, extending longitudinally.

With particular reference to Figure 3 of the drawings, it can be seen that one side of the longitudinally extending unitary row body 7 has three longitudinally extending stepped cross-sectional recesses 18. Each of said longitudinally extending staggered recesses 18 serves to snugly receive, in engaged relationship, the longitudinally extending base portion 21 of a longitudinally extending projecting front section 19 (Figure 2), said front section also being able projection 19 be formed as a simple unitary piece of a suitable heat conducting material, as nickel-chrome steel similar to longitudinally extending unit row body material 7. Each longitudinally extending projecting front section 19 is suitably provided with a series of spaced holes 22 through the longitudinally extending winged portions of the longitudinally extending projecting front section 19 to receive in a mating relationship. the setscrew heads 23 which are housed in the spaced bores 24 in the longitudinally extending unitary row body 7 as can be seen in the Figure 2 of the drawings.

As can also be seen in Figure 2 of the drawings, each longitudinally extending projecting front section 19 is formed so as to provide a longitudinally extending apex portion 26 extending from the base portion 21, this apex portion also being 26 longitudinally grooved at its center as at 11 ', in order to coincide and provide a longitudinally extending or subsequently communicating flowable material supply groove, in the longitudinally extending unitary spinneret body 7 with the flowable material outlet 13 from the slot 11 'adjacent to the apex of the projecting front section in order to cooperate with a longitudinally extending perforated spinning plate mounted at the apex of the longitudinally extending projecting front section 19 (described below).

It should be noted that the longitudinally extending apex portion of the longitudinally extending projecting front section 19 has a triangular cross section, the included angle defining the apex of the upper cross section triangle having been preselected at ninety

ES 2 201 259 T3 and five (95) degrees. It can be seen that the thickness and strength of the projecting front section to prevent breakage near the neighboring tip of the hole of the projecting front section increases as the included angle increases.

The included angle of the triangular cross section is selectively on the order of ninety-five (95) degrees to one hundred twenty (120) degrees, approximately, and is advantageously one hundred and eight (108) degrees, plus or minus two (2) degrees. , approximately. Since the opposite and inwardly inclined side flanks of the longitudinally extending apex portion 26 of the longitudinally extending projecting front section 19, each serve as a wall defining the opposing end portion of the attenuation fluid passages 14 and the parallel and spaced-spaced engaging end faces of the removable lip sections 27 extending longitudinally in mirror image opposition, serve as other definition walls of the terminal parts of the steps 14, the defined attenuating fluid outlets 17 are angularly disposed such on opposite sides of the fluid outlets 13 to lie further in opposition to each other and provide a sinusoidal fibrous flow, like a turbulent impulse, from each flowable material outlets 13, thus increasing the rate of attenuation of the fibrous layer of each outlet 13, in accordance with a feature of the present invention. In accordance with yet another feature of the present invention, the removable lip sections 27, extending longitudinally, as can be seen in Figure 2, are each provided with longitudinally spaced drilled recesses 28 adjacent to the opposite side of the serrated chamfered end edge. one of the opposite lip sections. Said bored recesses 28 serve to receive setscrew heads 29 which, like screws 23, engage in separate bores 31 of the unitary row body 7 to hold the removable lip section pairs 27 in a position defining a pitch. firm. It is to be understood that the spacing and geometric configuration of the lip sections 27 can be varied to determine the speed and angle of the attenuation fluid stream.

As described in the patent application, the longitudinally extending, longitudinally extending, cross-section of each fluid material flow passage 11, groove type, is formed in the unitary row body 7 in a pendant type shape, as is known. in the sector a hanger-type form for the passage of fluid material. As described above the elongated slotted passageways 11 communicate with passages 11 'in the projecting front sections 19 when removably mounted in the stepped recesses 18 of the unitary row body 7. At the apex portion 26 of each projecting front section 19, also in a manner already known in the art, a plate with orifices is formed, as described in the patent application.

Each orifice plate includes at least one row of separate openings that emit fibrous fluid. In accordance with yet another feature of the parent invention, advantageously these spaced openings have an amount of about 12 per cm (thirty [30] per inch), each being of a preselected size and geometric shape to determine size and shape. cross section of the layered fibrous material passing through. It is to be understood that such pairs of lip section 27, protruding front sections 19 can easily be replaced by other types of lip and protruding front sections having different designs, including but not limited to geometrically different hole arrangements and sizes.

Referring again to figure 1 of the drawings, it can be seen that the unitary row body 7 can advantageously be provided with a heating jacket with an electric coil 33, made of an aluminum alloy, which cooperatively surrounds the unitary row body. 7 to conduct heat to fluid passages 11 and 14 thereof. A suitable ceramic insulating jacket 34 cooperatively surrounds the outer face of the heating jacket 33. It is to be understood that the present invention is not to be considered limited to the specific heating and insulation arrangements depicted, but that other heating and insulation arrangements may be used without thereby departing from the scope of the invention described herein.

In accordance with yet another preferred feature of the invention, as can be seen in Figure 1, separate open fluid conduits 38 may be attached to the unitary row body 7 to cooperate along opposite sides of each fluid material supply outlet. 13 at the apex of the projecting front section 19 and the opposing lip sections 27 to treat the layered emitted fibrous material with a cooling and solidifying fluid, as cold or ambient air driven by blower. Such solidification treatment serves to avoid the consequent bonding of the collected fibrous layers with adjacent faces and to reduce the bonding of the individual fibers between each layer, thus increasing the average bulge with consequent increase in dust holding capacity and performance. general.

In carrying out the process of the invention to form a web of non-woven layers of fibrous filter medium in which the adjacent faces of the layers of fibrous filter medium are spaced differently from each other, the fibers of the filter medium being fed sequentially of polymer in heated form - all as described in the original application - advantageously having the polymer medium having a viscosity of the order of at least ten (10) to three hundred (300) poise. The polymer is fed from at least two, and advantageously several, rows of preselected holes, separated as a source from the heated melt blown rows, as fiber to form layers with at least 4 to 20 fibers per centimeter (ten [ 10] to fifty [50] fibers per inch) and, advantageously, at least about 12 per centimeter (thirty [30] fibers per inch) with the fibers in the melt blown spinner sources being heated to a temperature within the appropriate range of 204 to 482 ° C (four hundred [400 ° F ] to nine hundred [900 ° F] degrees Fahrenheit). The melt blown output from each hole of a row of holes of the row source, advantageously ranges from zero point one (0.1) to two point eight (2.8) grams per minute. The attenuated fibers from the hole rows of each row source may advantageously have a diameter

ES 2 201 259 T3 of the order of zero point three (0.3) to twenty (20) microns in diameter, and the polymeric material can be, but is not limited to, polyester with a density of approximately one point four (1, 4) grams per cubic centimeter, a polypropylene having a density of approximately zero point nine (0.9) grams per cubic centimeter or a nylon having a density of approximately one point fourteen (1.14) grams per cubic centimeter.

The fibers emitted from each row of separate holes are attenuated by pairs of air currents that flow directly, in opposition, preferably at a velocity of up to 180 m (six hundred [600] feet) per second, the air currents being advantageously heated at a temperature of approximately 371 ° C (seven hundred [700 ° F] degrees Fahrenheit). Said oppositely directed air streams are oriented to form an angle between the opposing streams greater than about ninety-five (95) degrees, preferably with an approximate value of between ninety-five (95) to one hundred and twenty (120) degrees, and advantageously one hundred and eight (108) degrees, plus or minus two (2) degrees. This angular orientation of the opposing streams of attenuation fluid serves to provide turbulent fiber flow, increasing the rate of attenuated fiber. In accordance with yet another feature of the present invention, a cooling treatment of the attenuated fibers with cold air is applied at the fiber attenuation site to enhance crystallization prior to collecting the fibers on a collector as face-to-face layers, such as a rotating drum or endless belt. This treatment serves to prevent bonding between the faces of adjacent layers and to reduce the bonding of fibers between each layer in order to increase the mean bulk of the filter along with greater dust holding capacity and increased overall performance.

A filter medium is produced with the apparatus and method described herein, said filter medium including a non-woven web of fibrous layers for the filter medium, made of meltblown fibrous material, comprising at least two or more face-to-face layers. freely separable, meltblown, from the fibrous filter media, each layer having a minimum bonded ratio to achieve a maximum bulge fibrous filter media with correspondingly higher dust holding capacity and superior overall performance. Preferably, the fibers of said filter medium can have the order of zero point three (0.3) to twenty (20) microns in diameter and be of a polymeric nature or a polyester with a density of approximately one point four (1.4 ) grams per cubic centimeter or a polypropylene with a density of approximately zero point nine (0.9) grams per cubic centimeter or a nylon with a density of approximately one point fourteen (1.14) grams per cubic centimeter.

Referring to Figures 1, 2, 4 and 5 of the drawings, and particularly Figures 4 and 5, the aforementioned attenuation fluid distribution assembly 50 according to the invention of the present disclosure shows a part thereof positioned outside the row body 7 extending longitudinally in spaced relation opposite the exit face of the row body 7, such that the distribution assembly 50 cooperatively communicates with the attenuation fluid flow passages 14 in the spin body 7 and, in turn, with the aforementioned attenuation fluid outlet pairs 17, through the attenuation fluid manifolds. longitudinally extending attenuators 16 disposed within the row body 7 with manifolds 16 (FIG. 2) connected to attenuation fluid flow passages 14. It should be noted that each of the collectors 16 has a removable filter or elongated fluid strainer 51 arranged therein. The filters or strainers 51 serve to improve the parallel uniform flow and separate the contaminating particles from the attenuation fluid introduced through the passages. separated 15 before said fluids enter the passages 14 connected to the manifolds 16.

As can be seen in Figures 1, 2, 4 and 5 of the drawings, and especially in Figures 4 and 5, a part of the distribution assembly 50 extends longitudinally in a spaced relationship from the row body 7 and in opposing the attenuation fluid outlet pairs 17 and the fluid material outlets 13. As can be seen in Figures 4 and 5, this includes a group of at least two separate parallel first collectors 52, three of said collectors 52 having been shown in Figure 5 to serve the three separate row heads in the row body. unit 7. Each of the external manifolds is connected, through a control valve via a distribution manifold 54, to a common pressurized fluid source. Advantageously, said source and distribution assembly 50 can be sized such that it can supply attenuation fluid to the row body 7 at a speed of up to 180 m (six hundred [600] feet) per second to be heated in the row body 7 to a temperature of approximately 482 ° C (nine hundred [900 ° F] degrees Fahrenheit) before supplying it through the attenuation fluid outlet pairs 17 in the row body 7.

In accordance with the present invention, and as can be seen in Figures 4 and 5 of the drawings, each first distribution manifold 52 is provided with an elongated tapered slot 56 that tapers outward from the inlet of manifold 52 toward the outside. opposite end of the manifold and moving away from, and advantageously, opposite the opposite connecting conduits 59 described below. It is to be understood that the specific general area of ​​the grooves 56 and the angle of inclination can be varied in accordance with the pressure and amount of fluid to be supplied by the attenuation fluid distribution assembly 50. The tapered grooves 56 serve to uniformly supply damping fluid, such as pressurized air, to a group of second manifolds 57, each of which remotely surrounds a manifold 52 to provide an annular fluid mixing chamber 58 between them to receive and mix the fluid that enters uniformly from the tapered groove 57 into the manifold 52. Each surrounding manifold 57 is connected to a group of connecting conduits leading to the face of the row body 7 opposite the face of the row body 7 having the attenuation fluid outlet 17 and the material outlets 13. The conduction conduits 59, which can be flexible, are in turn connected to the passages 15, which are connected to the distribution manifolds 16 in which the removable fluid filters 51 are arranged, the manifolds 16 being connected in turn to the above-described attenuation fluid flow passages 14 and finally to the fluid outlet pairs

ES 2 201 259 T3 attenuation 17. It should also be understood that, even though a part of the distribution assembly 50 has been described being outside the row body 7 and a part inside the row body 7, it would be possible to arrange as much part of the distribution assembly 50 either on the outside or included within the row body 7.

The present application includes the passage of pressurized attenuation fluid, such as air, into a first elongated chamber, externally and opposite the fluid outlets of a melt blown die body; distributing the pressurized fluid uniformly from the first elongated chamber into a second mixing chamber which, advantageously, may be surrounded by the first chamber, and passing the pressurized fluid into the melt blown die body. This method can also include the stages of filtering pollutant particles from the attenuating fluid, either externally or inside the melt blown row, the first chamber being surrounded by a second mixing chamber and with a fluid supply speed of 180 m (six hundred [600] feet) per second and a temperature of up to 482 ° C (nine hundred [900 ° F] degrees Fahrenheit).