BR112021009905A2 - die block with readily exchangeable nozzles for use in making spun-blown fibers - Google Patents

Abstract

SPUN-BLOWN FIBER MANUFACTURING SPUN-BLOWN FIBERS SPUN-BLOWN FIBER BLOCK. The present invention relates to a particular embodiment for a die block for spun-blowing process to form fibers or filaments which can further form a spun-blown weft or non-woven comprising such a spun-blown formed weft, for example, as one layer in a multilayer composite weft. The die block comprises nozzles which are easily removable and preferably chamfered.

Description

SPINNER BLOCK WITH READY-EXCHANGABLE NOZZLES FOR USE IN SPUN-BLOWN FIBER MANUFACTURING FIELD OF THE INVENTION

[001] The present invention relates to equipment adapted to create spun-blown filaments to form superior quality non-woven materials, as well as a process for operating such equipment.

BACKGROUND

[002] Spunmelt is a process in which fibers are spun from molten polymer through a plurality of nozzles in a die block connected to one or more extruders to be formed into a weft, as non-woven wefts or as components thereof. . Spunmelt processes are well known in the art and may include melt-blowing, see, for example, US8017534 (KC, Harvey), spun-bonding, see, for example, US5935512 (KC, Haynes ).

[003] From such technologies, a "hybrid" technology, often referred to as "spun-blowing", was developed and described, for example, in WO2015/171707/US9303334 (Biax, 2014). This technology offers a number of benefits with regard to fiber and weft properties, but also with regard to the equipment and process for manufacturing. However, the equipment is quite inflexible when it comes to replacing individual nozzles, as in the case of uneven wear of the nozzles over time, or if it is necessary to perform filament diameter variation.

[004] Thus, from US6364647, the construction of a similar spun-blowing apparatus in which the nozzles are removable is known. While this provides certain improvements with regard to operation, but also with regard to product flexibility, such a design carries a disadvantage of sharp transition from the polymer feed system to the capillary nozzle, which results in turbulence of the polymer flow. , not only reducing the smoothness of flow through the capillary, but also increasing the propensity for polymer deposits around the mouthpiece opening that may require more frequent cleaning.

[005] Hereinafter, it is an object of the present invention to overcome the problems of spun-blowing technology.

SUMMARY

[006] The present invention is a die block for forming spun-blown filaments comprising molten polymer feed; air supply; a die block comprising an upper plate comprising a polymer feed side, and a lower plate, and a plurality of nozzles; an air distribution plate comprising openings; an external air plate comprising openings; a cover strip fastening means.

[007] The die block, the air distribution plate, the external air plate and the cover strip are assembled in this order and fixed by the fixing means so that the nozzles project through the corresponding openings in the distribution plate. air and further through corresponding openings in the external air plate,

and such that polymer passages are formed for the molten polymer passing from the polymer feed side of the larger plate than through the nozzles; and such that the air passages are formed for passing air from the air supply through the openings in the air distribution plate and the outer air plate.

[008] The openings in the outer plate and in the nozzles are adapted to allow the molten polymer exiting the nozzles and the air flowing through the openings of the outer air plate to be at an angle of less than 30°, preferably less than about 10° and more preferably essentially parallel.

[009] Furthermore, the die body comprises an upper plate positioned towards the molten polymer feed, comprising a polymer feed cavity and upper plate openings having at least at its lower end an upper plate opening diameter; a bottom plate positioned away from the molten polymer feed, comprising bottom plate through holes concentric to the top plate through holes having a top portion positioned towards the top plate with a top portion diameter, optionally with a top portion bevel and an upper portion length and a lower portion positioned opposite the upper portion with a lower portion diameter and a lower portion length, wherein the upper portion diameter is greater than the lower portion diameter.

[010] The nozzles comprise an upper section having an upper section outside diameter and a lower section presenting a lower section outside diameter; a capillary as an internal passage hole through the mouthpiece.

[011] In addition, the upper sections of the nozzles detachably fit into the upper portions of the lower plate, preferably without protruding from them, wherein, in addition, the opening diameter of the upper plate and the opening diameter of the plate bottom or chamfering has a difference of less than 50 µm, preferably less than 20 µm.

[012] The die block may further satisfy one or more of the conditions selected from the group consisting - the inside diameter of the nozzle being less than about 1.25 mm, preferably less than about 0.8 mm; - the outside diameter of the nozzle being less than about 2 mm; - in the mouthpiece having a length of less than about 50 mm; - in the mouthpiece having a length greater than about 10 mm; - in the mouthpiece having an L/d ratio of less than about 50; - in the mouthpiece being executed with a pre-orifice having a diameter greater than about 0.5 mm; - in the nozzle being made with a pre-orifice having a pre-orifice diameter of less than about 4 mm; - in the nozzle presenting transition zones between the sections of different diameters that extend for more than 2 mm, preferably for more than about 4 mm; - on the nozzle showing transition zones between sections of different diameters that extend by less than about more than 2 mm,

preferably by greater than about 4 mm; - in the mouthpiece it is made with a pre-orifice having a length greater than 2 mm, preferably greater than 4 mm, where this length includes the length of a transition zone towards a larger diameter; - in the mouthpiece being made with a pre-orifice having a length greater than 2 mm, preferably less than about 20 mm, preferably less than about 14 mm, more preferably less than about 8 mm, wherein this length includes the length of a transition zone towards a larger diameter; - in the matrix block having a width CD greater than 250, preferably greater than 1500, even more preferably greater than about 2000 mm or even greater than 5000 mm.

[013] Optionally, the openings in the top plate of the die block satisfy one or more of the conditions selected from the group consisting of - comprising a chamfering at a chamfering angle between 30° and 60° or with a rounded profile, - having a bevel diameter between 1.5 to 4 times the internal diameter of the capillaries, - have a length greater than about 2 mm, preferably greater than about 4 mm, - have a length of less than about 20 mm, preferably less than about 14 mm, more preferably less than about 8 mm, and most preferably a length of about 6 mm; - taper from the polymer supply side towards the opposite side.

[014] The die block nozzles can form an arrangement and further comprise stationary pins, preferably having the same diameters and lengths outside of a nozzle, the stationary pins being positioned on the periphery of the arrangement.

[015] The top plate of a die block may further comprise - at least one row slot o positioned laterally towards the first plate and o oriented parallel to the row of nozzles, - and, optionally, a circumferential slot circumscribing the row of nozzles or the nozzle arrangement, respectively, wherein - at least one row of nozzle holes, preferably two rows of nozzle holes, are positioned in a row groove, thus forming the chamfering section of the nozzles, and - the grooves are adapted to receive a sealant.

[016] The sealant compound can be adapted to prevent, in an assembled state of the die block, the flow of molten polymer - into the nozzle holes which are positioned in the row slot(s), - along from the gap between the first and second die body plates towards contiguous row slots, or nozzle holes, or the outside.

[017] The grooves may have a rounded cross-sectional shape or at least a rounded base, preferably a partial oval cross-sectional shape with a semicircular base and straight sides above.

[018] The grooves may have one or more of the dimensions selected from the group consisting of - a width greater than about 1 mm, preferably greater than about 2 mm, - a width less than about 10 mm, preferably less than about 5 mm, - a depth greater than about 1 mm, preferably greater than about 2 mm, - a depth less than about 10 mm, preferably less than about 5 mm.

[019] The grooves may comprise a sealant which may be selected from the group consisting of acrylic resins, adhesive sealants, butyl rubber, elastic sealants, epoxy thermosets, latex sealants, plastic sealants, polysulfide sealants, polyurethane sealants, sealants rubber, silicone sealants, preferably polysiloxanes, or fluorocarbon polymers, such as PTFE, or urethane sealants, more preferably of the silicon or PTFE type.

[020] The nozzle arrangement of a die block may comprise at least two sub-arrays comprising nozzles that differ from nozzles of a different sub-array in at least one of the dimensions selected from the group consisting of - nozzle inner diameter; - nozzle outside diameter, - nozzle length.

[021] Optionally, the array of die block nozzles comprises at least two sub-arrays, each of the sub-arrays being connected to a separate polymer feed system adapted to feed molten polymer to the sub-array differing in at least one of the characteristics selected from from the group consisting of - polymer type; - polymer flow rate; - polymer pressure; - polymer temperature.

[022] In another aspect, the present invention is a process for forming a non-woven web comprising spun-blown fibers, comprising the steps of - providing the equipment according to any one of the preceding claims, - providing a thermoplastic polymer for form blow-molded fibers, having an MFI of 30 to 2000 for 10 minutes at 2.16 kg at an appropriate material grade temperature, preferably at 210 °C for polypropylene and 190 °C for polyethylene, and - form filaments by applying a pressure less than 7 MPa (70 bar), preferably less than 5 MPa (50 bar), more preferably less than 4.5 MPa (45 bar) in the polymer feed.

BRIEF DESCRIPTION OF THE FIGURES

[023] Fig. 1 shows a spun-blowing equipment according to the state of the art.

[024] Fig. 2 shows a blow fusion equipment according to the state of the art with removable nozzles.

[025] Figs. 3A to F schematically represent particular features of the present invention.

[026] Figs. 4 to 7 represent particular embodiments according to the present invention.

[027] The same numerals in the figures represent the same or equivalent characteristics. Figures are schematic and not to scale.

DETAILED DESCRIPTION

[028] The present invention relates to a particular embodiment for a die block for spun-blowing process to form fibers or filaments that can further form a spun-blown or non-woven weft comprising such a spun-blown weft, for example, as a layer in a multilayer composite weft.

[029] Spunmelting is a process in which fibers are spun from molten polymer through a plurality of nozzles of a die head connected to one or more extruders. The spunmelt process can include blow-melt, continuous filament and the hybrid process as described below in more detail, also referred to as spun-blowing.

[030] Blow melting is a process for producing very fine fibers, typically with a diameter of less than about 10 microns, in which a plurality of molten polymer streams are attenuated using a high-velocity hot gas stream, a as the filaments emerge from the nozzles. The attenuated fibers are then collected in a collector, for example a flat belt or drum collector. A typical melt blow die has about 35 nozzles per inch and a single row of nozzles. The typical blow-melt die uses angled air jets on each side of the nozzle row to attenuate the filaments.

[031] Continuous filament is a process for producing strong fibrous non-woven webs directly from thermoplastic polymers by attenuating the spun filaments using high velocity cold air while cooling the fibers near the spinneret face. The individual fibers are then randomly placed on a collection belt and transported to a binder to give the weft more strength and integrity.

[032] The fiber size is generally less than 250 µm and the average fiber size is in the range of more than about 10 microns and/or less than about 50 microns. The fibers are very strong compared to blow-cast fibers due to the molecular chain alignment that is achieved during attenuation of the crystallizing (solidifying) filaments. A typical continuous filament matrix has several rows of polymer holes, and for a conventional polypropylene-type polymer, the polymer melt flow index (MFI) is generally less than about 500 grams/10 minutes at 2. 16 kg load.

[033] The present invention relates to a hybrid process between a conventional blow-melt process and a conventional continuous filament process, using a multi-row spinneret similar to the spinneret used in continuous filament, except that the nozzles are arranged to allow parallel jets of gas surrounding the spun filaments in order to attenuate and solidify them. Each of the extruded filaments is surrounded by pressurized gas and its temperature can be colder or hotter than the polymer melt. Optionally, the periphery around the array with the filaments can be surrounded by a pressurized gas curtain.

[034] In order to explain the general principles of spun-blowing equipment and the process for forming filaments and other wefts, such as non-woven wefts or components of such wefts, express reference is made to document US9303334 which describes such technology in more details. Thus, Fig. 1 illustrates a die block for such a conventional spun-blowing "hybrid" process. In general, a die block 26 comprises as elements a die body 52, an air distribution plate 70, an outer plate 78 and a cover strip 88. In addition, the nozzles 58 extend from the die body. 52 through openings in distribution plate 70 and outer plate 78, respectively, so that molten material can pass through capillary 60 of nozzle 58 to form filaments 86 at the tip of nozzle 96.

[035] For ease of explanation, the order of the elements referred to below is such that the die body 52, the air distribution plate 70, the outer plate 78 and the cover strip 88 are arranged along the gravity, so that so that the die body 52 is positioned above and attached to the air distribution plate 70, which is positioned above and attached to the outer plate 78, which is positioned above and attached to the cover strip 88, with attachment means not shown.

[036] Fig. 1 shows a cross-sectional view of the die block

26. When positioned on fabrication equipment to form nonwovens, this view corresponds to an xz directional view, with the x direction 12 denoting the fabrication direction, ie the direction of movement of the resulting weft, and the z direction 15 corresponding to height (along gravity). In the embodiment as shown, the three nozzles 58 represent a "column" of the "multi-row" (in the present invention, three-row) matrix block 26. The matrix block comprises a plurality of columns positioned adjacent to the y-direction 18 (i.e., is, perpendicular to the drawing plane and indicated by the circle), so that the columns and rows of nozzles form a nozzle arrangement of a die block. A die body 52 can contain from as few as a dozen nozzles 58 to several thousand of nozzles 58. For a commercial size line, the number of nozzles 58 on the die body 52 can range from about 500 to about 10,000.

[037] The number of rows may vary, as well as the number of columns. Typically, the number of ranks will be greater than 1, often greater than 5, and will be less than about 30, or even less than 15.

Typically, the number of columns will be greater than 50, but it can be greater than about 200, and it can be less than 3,500.

[038] As described in US'334, the nozzles 58 are formed by capillary tubes that are inserted through openings in the die body 52 to form a passage for the molten polymer.

[039] Each of the nozzles 58 has a capillary inner diameter and an outer diameter. The inside diameter can range from about 0.125 mm to about 1.25 mm. The outside diameter of each nozzle 58 should be at least about 0.5 mm. The outside diameter of each nozzle 58 can range from about 0.5 mm to about 2.5 mm.

[040] Typically, the length of a 58 mouthpiece ranges from about 1.27 to about 15.24 centimeters (0.5 to 6 inches).

[041] As the molten polymer only needs to pass through the capillaries of the nozzles, US'334 describes the tubes as being well adjusted and normally welded to the die body, which represents an important difference, when compared to the present invention, as will be described in more detail below in this document.

[042] The molten material 22, as it can be a thermoplastic polymer of the homopolymer type or a mixture of different polymers, is heated to a temperature well above its melting point, in the case of propylene-based polymers normally to at least about of 170°C, often at about 210°C, upstream of die block 26, generally in an extruder (not shown). Optionally, different polymers can be targeted to respectively different nozzle groups.

[043] The yield of polymer through each nozzle 58 is stated in "grams per orifice per minute" ("ghm"). The polymer yield through each nozzle 58 can range from about 0.01 ghm to about 4 ghm.

[044] At its top, i.e. on the side of the upper die body oriented towards the polymer feed, the die block 26 has a cavity 30 and an inlet 28 connected to the cavity 30. The molten material 22 is transported along of the polymer passage from the inlet 28 towards the upper portion of the spinneret body 52, and further through the nozzles downwards. The die body 52 also has one or more gas passages 32 formed therethrough for conveying pressurized gas (air) to an air chamber 54, which is essentially formed between the die body 52 and the air distribution plate 70. The plurality of nozzles 58 extend downwardly from the die body, allowing molten material to flow through capillaries 60 to exit the nozzles and die block down the outer plate at the nozzle tip 96 in the form of filaments. 86.

[045] In addition, a plurality of stationary pins 62 may encircle the nozzle arrangement, secured to the body of the spinneret and extending through openings in the air distribution plate into the openings in the outer air plate.

[046] Each of the stationary pins 62 is an elongated solid member with a central longitudinal axis and an outside diameter. Each of the stationary pins 62 is attached to the die body 52 and generally they have an outside diameter similar to the polymer nozzles 58. The outside diameter of each of the stationary pins 62 must remain constant along its length.

[047] The dimension of the outer diameter may vary. The outside diameter of stationary pins 62 can be greater than about 0.25 mm, or greater than about 0.5 mm, or greater than about 0.6 mm, or even greater than about 0.5 mm. 75 mm.

[048] An air distribution plate 70 is attached to the die body 52 having a plurality of openings. Each of the first openings 72 accommodates one of the nozzles 58. If stationary pins 62 are employed, they are accommodated in second openings 74, and each of the third openings 76 is located adjacent the first and second openings, 72 and 74, respectively. When operating the process, pressurized gas, normally air, is flowing along the air passage of the air chamber 54 through the openings 72, which are a thin ring around the nozzles, openings 74, also a small ring around the pins stationary, if present, and third openings 76 as a main passage for air.

[049] An outer air plate 78 is attached to the air distribution plate 70, away from the spinneret body 52. The outer member 78 has a plurality of first openings 80 around the mouthpiece 58. Second enlarged openings 82 surround each other. of stationary pins 62, if present.

[050] In operation, the molten polymer material 22 is extruded through each of the nozzles 58 to form multiple filaments 86 which are intended to be enveloped from ambient air by the pressurized gas, normally, though not necessarily air, emitted through the first openings. flares 80, formed in outer member 78, at a predetermined velocity essentially parallel to the axis of capillaries 60 and therefore the direction of flow of filaments 86 at nozzle tip 96.

[051] The stream of pressurized gas (air) exiting the second flared openings 82 formed in the outer member 78 around the stationary pins, if present, forms an additional envelope air stream, which is also oriented essentially parallel to the axis of the nozzles. and therefore also essentially parallel to the filaments exiting the nozzles, for the purpose of isolating the filaments 86 from the surrounding ambient air, as indicated in Fig. 1 with arrow 94.

[052] In US6364647 (hereinafter referred to as US'647), a system is described (see Fig. 2) in which individual nozzles 58 of the nozzle arrangement are removable from the die body 52. To this end, nozzles 58 are equipped at its upper end (toward the polymer feed 22, which is further covered by the top cover 53) with shoulders 51 so that they can rest firmly in the widest portion of the holes through the die body 52. This provides a series benefits such as the flexibility to change individual nozzles when they are worn out. This also makes it possible to quickly implement and introduce nozzles of different capillary diameters.

[053] During operation, the nozzles are pressed into their openings by the pressure of the molten polymer.

[054] However, this system still has a drawback of abrupt transition from the polymer feed chamber 22 to the plurality of nozzle openings.

[055] As a consequence, deposits of polymeric material can form around the capillary inlet, which can degrade over time and require more frequent cleaning.

[056] Fig. 3A illustrates the principle of the present invention, by showing in a schematic cross-sectional view a die block 126 comprising die block 152, air distribution plate 170, external air plate 178, cover strip 188 and fastening means 199 arranged in the same manner as described in the context of Fig. 1. Further shown is an inlet cavity 130 for the molten polymer 122, an air inlet and distribution chamber 132 (the air supply means not being shown). The die block 152 comprises an upper plate 151 and a lower plate 155, with "upper" indicating positioning toward the polymer feed, and "lower" away from it, as will apply throughout the present description. Nozzles 158 are inserted into bottom plate 155 of die body, forming a polymer passageway leading from inlet cavity 130 through capillaries 160 of nozzles 158 towards nozzle tip 196, where filaments are formed. However, one skilled in the art will readily appreciate that vertical orientation is not essential, but the die block can be tilted about an oriented axis CD such that the nozzles can be oriented with respect to the vertical by more than 5°, or 15°, or 30°, or 45° or even more, but usually less than about 90°.

[057] Fig. 3B schematically shows an enlarged portion of Fig. 3A, focusing on the positioning of the nozzles 158 in the openings through the lower plate 155 and the relative positioning of the openings through the upper plate 151, and Figs. 3C and D schematically show particular embodiments in enlarged cross-sectional view of a single nozzle 158.

[058] A plurality of nozzles 158, in Fig. 3A eight are exemplarily shown, may be arranged in columns and rows forming an arrangement of nozzles as described above for US'334, each having an internal diameter 157, corresponding to the diameter of the nozzle. capillary 160 for the flow of molten fluid. The internal diameter may be greater than about 0.125 mm and/or less than about 1.25 mm. The nozzle 158 is formed in two sections, an upper section 331 and a lower section 335, differing in their outside diameter, while the inside diameter of the capillary 160 remains essentially constant. At its upper end, the capillary 160 may have a bevel 333, preferably with a bevel angle of at least 30° and/or less than 60°, as indicated in Fig. 3C, or with a rounded profile as indicated in Fig. 3D The outside diameter 159 of the lower section 335 of the nozzle 158 may be greater than about 0.5 mm and/or less than about 2.5 mm. The outer diameter 161 of the upper section 331 may be greater than about 0.5 mm and/or less than about 5 mm.

[059] Typically, the overall length 330 of a nozzle 158 may be greater than about 20 mm and/or less than about 150 mm. The length 332 of the upper section 331 can be greater than about 1 mm and/or less than about 50 mm, and the length 334 of the lower section 335 can be greater than about 10 mm and/or less than about 10 mm. about 140 mm.

[060] Each nozzle 158 is fitted into an opening 360 of the lower plate 155 which has an upper portion 361 and a lower portion 365.

[061] The upper portion 361 is adapted to receive the upper section 331 of the nozzle 158 and has a diameter 362 which is not more than 2 mm wider than the outside diameter 161 of the upper section of the nozzle 158. good fit, the diameter 362 is smaller than 50 µm or even smaller than 10 µm larger than the outside diameter 161 of the upper nozzle section and may even be slightly smaller, such as less than 10 µm smaller, such as when the mouthpiece is placed forcefully or at a lower temperature.

[062] The lower portion 365 is adapted to receive the lower section 335 of the nozzle 158 and has a diameter 366 which is not more than 2 mm wider than the outside diameter 159 of the lower section of the nozzle 158. good fit, the diameter 366 is smaller than 50 µm or even smaller than 10 µm larger than the outside diameter 159 of the lower nozzle section and may even be slightly smaller, such as smaller than 10 µm smaller, as when the mouthpiece is placed forcefully or at a lower temperature.

[063] The transition from the upper portion 361 of the opening 360 to the lower portion 365 is preferably sharp, although a small radius or bevel is acceptable. However, this transition must be combined with the transition from the upper section 331 of the nozzle to its lower section 335.

[064] More preferably, the length 332 of the upper section 331 of the nozzle 158 may be the same as the length 364 of the upper portion 361 of the opening 360, so that the differential 369 is zero, although the differential may be less than 10 µm, or less than about 2 µm. A negative differential (ie the nozzle protruding out of the orifice) is not preferred.

[065] The length 368 of the lower portion 365 of the opening 360 may be greater than about 2 mm and/or less than about 100 mm.

[066] The upper plate 151 of the die body 153 comprises openings 370 which are aligned with the axis 339 of the capillary 160 of the nozzle 158 and, therefore, with the openings in the lower plate 155. The opening 370 has at its lower end a diameter 372 which corresponds as closely as possible to the diameter of the capillary 160 or, if present, the chamfer 333.

[067] Preferably, the difference between these diameters is less than about 20 µm, more preferably less than about 10 µm. Furthermore, the displacement of the axis of the aperture 370 with respect to the axis of the capillary is more preferably essentially zero, but preferably less than 5 µm or less than 50 µm. Optionally and often preferably, aperture 370 has a chamfer 375 at its upper end, preferably at an angle of at least 1°, or 10°, or 30°, or 60° and/or less than 90° or any angle between these values. Thus, at the extreme, the chamfer may extend along the entire length of the top plate, so that the cross-sectional view of the opening may correspond to a trapezoid, as indicated by the dotted lines 376 in Fig. 3B and Fig. 3E.

[068] During operation, the openings 370 function as pre-orifices for the capillaries and preferably have a diameter greater than about 1.5 and/or less than about 4 times the diameter of the capillary and a length corresponding to the thickness of the top plate being greater than about 2 mm and/or less than about 20 mm.

[069] Such a pre-orifice provides a smoother flow from the cavity with the molten material to the capillary 160, which in turn will expand the opportunity for a wider process window for the process.

[070] Furthermore, it is also within the scope of the present invention that the die block may, in addition to the nozzles as described above, comprise stationary pins, as described above in the context of US'334 document. Fig. 3F schematically illustrates such a pin which, with its outside dimensions, could correspond to a nozzle 158, except that it has no capillary, but is solid.

[071] In yet another variant of the present invention, which allows expanding the operating range of the equipment, the chamfering can be performed as grooves. For this purpose, the die body is made in a non-unitary way, in two parts, namely a first plate, also referred to as a conical plate, which comprises a polymer supply side, and a second plate positioned opposite the supply side. of polymer. The second plate comprises grooves in the surface towards the first plate which are oriented parallel to the row of nozzles.

[072] Fig. 4 illustrates similarly to Fig. 3A, in Fig. 4A, a die body with a first or "top" plate 151 positioned with its molten polymer receiving cavity 130 towards the feed of polymer, and 4B, in Fig. 4B, a second or "lower" plate 155, positioned opposite the polymer receiving cavity 130 from the first plate or upper plate 151. The second plate further comprises four row slots 140, each for two nozzles, and a circumferential groove

145.

[073] Fig. 4B illustrates a portion of a second plate 155 of a die body with a cross-sectional view along the rows of nozzle rows, here showing eight holes, as holes 156 may represent, adapted to receive nozzles. removable (not shown). In addition, row grooves 140 are shown, which extend parallel to the nozzle rows, preferably having a rounded cross-sectional shape or at least one rounded base embodiment, shown here in exemplary fashion, having a cross-sectional shape of a partial oval with a semicircular base and straight sides above. Preferably, a groove has - a width of greater than about 1 mm, preferably greater than about 2 mm, - a width of less than about 10 mm, preferably less than about 5 mm, - a depth greater than about 5 mm. than about 1 mm, preferably greater than about 2 mm, - a depth of less than about 10 mm, preferably less than about 5 mm. between 1 mm and 12 mm, preferably between 2 and 5 mm. Preferably, the depth is between 1 mm and 10 mm, preferably between 2 and 5 mm. Preferably, the width and spacing of the grooves are selected so that the rows of nozzles are equidistantly spaced.

[074] Generally, each row slot can belong to at least one row of nozzles, preferably two rows of nozzles belong to a row slot, as shown in the figure. Preferably, although not necessarily, all of the row slots comprise nozzle holes 156, more preferably each row slot comprises two rows of nozzle holes 156. Thus, for the exemplary embodiment in Fig. 4B, eight rows of nozzle holes are provided. positioned in four row slots.

[075] Preferably, the second plate 155 of the die block further comprises a closed circumferential groove 145 parallel to the row grooves as well as perpendicular thereto to circumscribe the nozzle arrangement. Preferably, the x-y directional corners of the circumferential groove 145 are rounded. Preferably, although not necessarily, the circumferential groove has the same cross-sectional shape as the row grooves.

[076] The holes in the second plate are adapted to receive nozzles in the removable nozzle variant and the wider opening of the row slots provides the chamfering effect as described above, allowing a smooth flow of the molten polymer.

[077] In addition, the grooves 140 and 145 are adapted to receive a sealant, allowing to fill selected grooves, but also any gap that may be formed between the first and second plate of the die block. For the row slots, this allows blocking the flow of polymer into the nozzle holes and further into the capillaries of the nozzles connected to this row slot. Furthermore, this allows to avoid the flow from one slot to the adjoining one, otherwise it could occur through a gap between the first and second plate. Thus, by applying the sealant, the nozzle rows can be "turned off", as shown in Fig. 4C, with slots 140' and 145 being filled with a sealant and slots 140' being empty, allowing molten polymer to pass through. . Likewise, the sealant in the circumferential groove prevents leakage of the polymeric material.

[078] For the sealant material, the main requirement is that it withstands operating temperatures, i.e. it does not flow into the capillaries or into the gap at elevated temperatures and therefore must not be fluidized up to temperatures of about 100°C, preferably 180°C, more preferably greater than 230°C or even greater than 500°C or more. Thus, the sealant can be selected from the group consisting of acrylic resins, adhesive sealants, butyl rubber, elastic sealants, epoxy thermosets, latex sealants, plastic sealants, polysulfide sealants, polyurethane sealants, rubber sealants, silicone sealants. , for example, polysiloxanes, fluorocarbon polymers such as PTFE, or urethane sealants, with silicones and PTFE being preferred, and PTFE being most preferred. An exemplary seal may be "3.2 mm PTFE yarn", as commercially available from ATAG Spa, Italy.

[079] Preferably, although not necessarily, a fluid or pasty sealant cures after it has been applied and the die block has been assembled, although pre-cured materials may also be used, such as appropriately sized O-rings.

[080] Preferably, and in particular for fluid or pasty sealants, the amount of sealant is selected so as to slightly overflow the groove, so as to allow compression of small amounts of the sealant in the gaps between the first and second plate. This feature is particularly beneficial for a relatively thin second plate, as it can be less than about 20 mm, more preferably less than about 10 mm, or even less than about 8 mm. During assembly or operation, such relatively thin plates can deform slightly so that, without any sealant, molten polymer sealant can run out of or into an adjoining groove.

[081] In addition, the sealant is adapted to be removed from grooves and holes or capillaries, if penetrated into them, when the die block is dismantled. This removal can be done mechanically only, or by blowing air or liquid through the holes or capillaries, or by any other means that does not damage the structure.

[082] The benefit of slots filled with slots is essentially to allow the expansion of the operating range of the mold block.

[083] It is known that it is preferable from an operational point of view, but also for good product quality, to keep the polymer flow through a capillary within a relatively narrow range. However, for different products or types of products, different basic weft weights are desired. However, when changing from, for example, a lower basis weight, for example 35 g/m2, to a higher one, for example 60 g/m2, the flow rate through the capillaries can be increased, which requires pressures higher operating costs, therefore costs, but can also deteriorate the quality of the resulting fibers, for example, by increasing the stress applied to the polymer molecules. Consequently, a conventional approach is to replace the complete die block with one with a different number of nozzle rows. This implies a great effort both with regard to the work for this exchange, as well as with regard to maintaining a stock of spare parts. As for the latter, nozzles represent a significant part of the costs. Consequently, it is beneficial to keep spare parts to a minimum, as permitted by this aspect of the present invention. To this end, a die block is designed for the upper flow rate, by way of example and for explanatory purposes only, with twelve rows of nozzles, with which a high basis weight product can be satisfactorily produced. When a lower basis weight product is to be made, the outermost row grooves, each connected to two nozzles, can be filled with sealant so that only 8 nozzles are operational and lower basis weights can be made without deterioration of product quality. For even lower basis weight, two or more row slots can be filled, only 4 rows of nozzles will be operational now.

[084] In order to avoid dead space, which can lead to deterioration of the polymer, it is preferable to adapt the holes in the first plate 151 of the die body to the number of unfilled slots, as shown in Fig. 4D, corresponding to the execution shown in Fig. 4C , so that holes through the first plate 151 that would lead to the filled slots 140' in Fig. 4D are omitted. However, replacing several of these boards is significantly easier and less expensive compared to a complete die block.

[085] Optionally, the array of nozzles may comprise subarrays. Such a sub-array may include at least one row of nozzles, preferably, although not necessarily, extending the entire width of a die block.

[086] Referring to Fig. 4, a first execution of a die block comprising one or more sub-arrays, the nozzles of at least one of the sub-arrays differ substantially from the nozzles of a different sub-array in at least one of the dimensions selected at from the group consisting of nozzle inside diameter, nozzle outside diameter and nozzle length, in Fig. 4 indicated by the variation of nozzle inside diameter for larger nozzles 158' forming a first arrangement compared to smaller nozzles 158" forming a second arrangement. In the present context, the term "substantially different" refers to a difference in respective size of at least 5%, often greater than 10% thereof.

[087] In an additional embodiment, as depicted in Fig. 5, but not exclusive to the other embodiments, the nozzles of a sub-array may be connected to a separate first polymer feed system via a first molten polymer feed cavity 130' adapted to feed a first type of molten polymer to the first subarray that differs from the molten polymer supplied to a different subarray via a second molten polymer feed cavity 130", whereby the polymers differ by at least one qualitative characteristics, such as polymer type, or quantitative parameters, such as polymer flow rate, polymer pressure, which thus differs by at least 5%, often more than 10%, or polymer temperature, which thus differs at at least 5°C. Optionally, the nozzles can be made with subcapillaries coaxially positioned to create bi- or multi-component fibers, wherein such subcapillaries pillars are fed with different types of polymer, respectively immiscible.

[088] This process window is mainly dictated by - pressure of the molten polymer in the cavity; - temperature of the molten polymer; - capillary diameter; - outside or nozzle diameter, impacting airflow and airflow ratio; - capillary length; - material properties of the molten polymer, as expressed by the Melt Flow Index (MFI), as can be determined by ASTM D1238 and ISO 1133, and for polypropylene as a polymer that can be processed properly with current equipment and processes, it is suitably expressed in units of grams per 10 minutes at 210 °C and 2.16 kg load, while for other material classes the temperature is adjusted to the appropriate temperature, eg 190 °C for polyethylene.

[089] As a comparative example, the equipment and process as described in US'334 document having - a capillary internal diameter of 0.46 mm; - a capillary length of 24 mm; - therefore, an L/d ratio of about 52; and could be operated at a temperature of about 210 °C with a back pressure of 5 to 7 MPa (50 to 70 bar) for a polymer melt with an MFI of less than about 500 [g/10min at 2.16 kg of charge].

[090] In order to achieve comparable fiber dimensions and properties, the equipment of the present invention exhibited exemplary - a capillary diameter of 0.46 mm; - a capillary length of approximately 18 mm: - a pre-orifice diameter of approximately 1.2 mm: - a pre-orifice length (including a 60° chamfer at the inlet and transition to the capillary) of about 6 mm; - henceforth an L/d ratio for the capillary of about 39, which also made it possible to use a polypropylene polymer with an MFI of about 500 [g/10min at 2.16 kg of load] from a back pressure significantly lower than 50 Pub.

[091] A benefit of subjecting the polymer to lower back pressure is that the reduction in mechanical stress results in allowing the production of stronger nonwovens.

[092] In other terms, the present invention provides equipment that can have a lower L/d ratio, which is for a given MFI indicative of resistance to flow and therefore allows operating in a wider process window for MFI. and back pressure.

[093] In addition, the smoother flow from the cavity to the molten polymer 130 to the pre-hole 370, preferably an even smoother flow of polymer into the chamfer, significantly reduces the polymer turbulence around the inlet and therefore also the deposition of polymer residue, allowing longer run times without interruption for cleaning.

Claims (12)

1. A die block for forming spun-blown filaments, comprising molten polymer feed; air supply; a die block comprising an upper plate comprising a polymer feed side, and a lower plate, and a plurality of nozzles; an air distribution plate comprising openings; an external air plate comprising openings; a cover strip attachment means, wherein said die block, said air distribution plate, said outer air plate and said cover strip are assembled in that order and secured by said attachment means in a manner that said nozzles project through corresponding openings in said air distribution plate and further through corresponding openings in said outer air plate, and so that polymer passages are formed for molten polymer passing from said side feeding polymer from the top plate through said nozzles; and such that air passages are formed for air passing from said air supply through openings in said air distribution plate and said external air plate; wherein said openings in said outer plate and said nozzles are adapted to allow molten polymer to exit said nozzles and air flowing through openings in said outer air plate at an angle of less than 30°, preferably less than about 10° and more preferably essentially parallel, characterized in that said die body comprises an upper plate positioned towards the molten polymer feed, comprising a polymer feed cavity and upper plate openings having at least least at its lower end an upper plate opening diameter; a bottom plate positioned away from said molten polymer feed, comprising bottom plate through holes concentric to said top plate through holes having a top portion positioned towards said top plate with a top portion diameter, optionally with a chamfer of upper portion, and an upper portion length and a lower portion positioned opposite said upper portion with a lower portion diameter and a lower portion length, whereby said upper portion diameter is greater than said portion diameter lower, said nozzles comprising an upper section having an upper outside diameter and a lower section having a lower outside diameter; a capillary as an internal through-hole through said nozzle; and wherein said upper sections of said nozzles releasably fit upper portions of said lower plate, preferably without protruding therefrom, wherein, additionally, said upper plate opening diameter and said plate opening diameter lower or said chamfering has a difference of less than 50 µm, preferably less than 20 µm. A die block according to claim 1, satisfying one or more of the conditions selected from the group consisting - the inside diameter of the nozzle being less than about 1.25 mm, preferably less than about 0, 8 mm; - in the external diameter of the nozzle being less than about 2 mm; - in the mouthpiece having a length of less than about 50 mm; - in the mouthpiece having a length greater than about 10 mm; - in the mouthpiece having an L/d ratio of less than about 50; - in the nozzle being made with a pre-orifice having a diameter greater than about 0.5 mm - in the nozzle being made with a pre-orifice having a pre-orifice diameter of less than about 4 mm; - in the nozzle presenting transition zones between the sections of different diameters that extend for more than 2 mm, preferably for more than about 4 mm; - in the mouthpiece having transition zones between the sections of different diameters that extend by less than about more than 2 mm, preferably more than about 4 mm; - in the mouthpiece being made with a pre-orifice having a length greater than 2 mm, preferably greater than 4 mm, where that length includes the length of a transition zone towards a greater diameter; - in the mouthpiece being made with a pre-orifice having a length greater than 2 mm, preferably less than about 20 mm, preferably less than about 14 mm, more preferably less than about 8 mm, wherein this length includes the length of a transition zone towards a larger diameter; - in the matrix block having a width CD greater than 250, preferably greater than 1500, even more preferably greater than about 2000 mm or even greater than 5000 mm. A die block according to claim 1 or 2, wherein said openings in said top plate satisfy one or more of the conditions selected from the group consisting of - comprising a bevel at a bevel angle between 30° and 60°. ° or with a rounded profile, - has a chamfering diameter of between 1.5 to 4 times the internal diameter of said capillaries, - has a length greater than about 2 mm, preferably greater than about 4 mm, - has a length of less than about 20 mm, preferably less than about 14 mm, more preferably less than about 8 mm, and most preferably a length of about 6 mm; - tapering from said polymer supply side towards the opposite side. A die block according to any preceding claim, wherein said nozzles form an array, further comprising stationary pins, preferably having the same outside diameters and lengths as a nozzle, said stationary pins being positioned on the periphery of a nozzle. said arrangement. A die block according to any one of the preceding claims, wherein said top plate further comprises - at least one row slot o positioned on the side towards said first plate and o oriented parallel to said row of nozzles, - and optionally a circumferential groove circumscribing said row of nozzles or said arrangement of nozzles, respectively, wherein - at least one row of nozzle holes is, preferably two rows of nozzle holes are, positioned in a row groove, thus forming said chamfering section of said nozzles, and - said grooves are adapted to receive a sealant. A die block according to claim 5, wherein said sealant compound is adapted to prevent in an assembled state of said die block the flow of molten polymer - into nozzle orifices which are positioned in the ) said row slot(s), - along the gap between said first and said second plate of said die body towards adjacent row slots, or nozzle holes, or the outside. A die block according to claim 5 or 6, wherein said grooves have a rounded cross-sectional shape or a rounded base, preferably a partial oval cross-sectional shape with a semi-circular base and straight sides above. A die block according to any one of claims 5 to 7, wherein said grooves have one or more of the dimensions selected from the group consisting of - a width greater than about 1 mm, preferably greater than about 1 mm. about 2 mm, - a width of less than about 10 mm, preferably less than about 5 mm, - a depth of greater than about 1 mm, preferably greater than about 2 mm, - a depth of less than about 2 mm than about 10 mm, preferably less than about 5 mm. A die block according to any one of claims 5 to 8, wherein at least one of said row grooves comprises a sealant, preferably selected from the group consisting of acrylic resins, adhesive sealants, butyl rubber, elastic sealants, epoxy thermosets, latex sealants, plastic sealants, polysulfide sealants, polyurethane sealants, rubber sealants, silicone sealants, preferably polysiloxanes, or urethane sealants, or fluorocarbon polymers, or more preferably of the silicon or PTFE type. A die block according to any preceding claim, wherein said nozzle arrangement comprises at least two sub-arrays comprising nozzles that differ from nozzles of a sub-array that differs by at least one of the dimensions selected from the group consisting of - inside diameter of the nozzle; - external diameter of the nozzle; - nozzle length. A die block according to any preceding claim, wherein, in addition, said nozzle arrangement comprises at least two sub-arrays, each of said sub-arrays being connected to a separate polymer feed system adapted to feed molten polymer. to said subarray that differs in at least one of the characteristics selected from the group consisting of - polymer type; - polymer flow rate; - polymer pressure; - polymer temperature. A process for forming a non-woven web comprising blow-molded fibers, comprising the steps of - providing the equipment according to any of the preceding claims, - providing a thermoplastic polymer to form blow-molded fibers, having an MFI of 30 to 2000 for 10 minutes at 2.16 kg at an appropriate material grade temperature, preferably at 210 °C for polypropylene and 190 °C for polyethylene, and - form filaments applying a pressure of less than 7 MPa (70 bar), preferably less than 5 MPa (50 bar), more preferably less than 4.5 MPa (45 bar) in the polymer feed.