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© 2017 Amtek Research International LLC. A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 37 CFR § 1.71(e).
TECHNICAL FIELD
This disclosure relates to melt-blowing thermoplastic materials to make nonwoven fibrous forms and, in particular, to a melt-blown fiber spinneret that includes a body member formed by 3D printing and having, along its width, multiple closely spaced rows of polymer outlet orifices from which streams of polymer fiber melt filaments emerge to form a nonwoven fibrous mat at high throughput.
BACKGROUND INFORMATION
U.S. Pat. No. 3,825,380 describes a conventional so-called Exxon style melt-blown die head in which a nose configuration approximating a triangle in cross section is suitable for use in a melt-blowing process for making fibers from thermoplastic materials. The junction of two exterior surfaces of the triangle forms, at its apex, a truncated edge through which a row of die openings is machined. Air channels are machined in the die head on either side of each die opening. Melt channels terminating in the die openings are supplied with thermoplastic resin from a distribution manifold with individual inputs to each row of die openings. Thermoplastic resin is forced out of the row of die openings in the die head and into an air stream supplied through the air channels to attenuate the thermoplastic resin and thereby form very fine fibers.
Stacking the Exxon style melt-blown die heads to construct multiple rows of die openings necessitates provision of separate thermoplastic resin inlets above and below each row of die openings. This resin inlet arrangement accommodates the cross air stream flow through the air channels on either side of each die opening in the row of die openings. The impact of this configuration is a constraint on a minimum distance between adjacent rows that is set by the diameters of the air cross-holes supplying the air stream to the air channels. A distance of less than about 12.7 mm (0.5 in.) between adjacent rows would be difficult to achieve using conventional machining methods.
SUMMARY OF THE DISCLOSURE
A multi-row melt-blown fiber spinneret enables stacking rows of polymer outlet orifices more closely together than is achievable with conventional melt-blown fiber spinneret designs. The melt-blown fiber spinneret is configured so that gas knife channels and individual intricate small gas knife passage feeds, together with their associated polymer melt flow channels, are formed in the same body member. A preferred gas is an inert gas, air, atmosphere, or other form of gas with a high viscosity after being heated to a desired temperature. The description below refers to process air for use as a preferred gas, which is defined as atmospheric air conditioned by an air compressor or blower system, heated to a preferred temperature of between about 150 ° C. to about 300 ° C. or higher, and delivered to a plenum attached to spinneret 8. The melt-blown fiber spinneret configuration also enables dense side-by-side packing of the polymer outlet orifices in each of the stacked rows of them.
In preferred embodiments, the multiple rows of polymer outlet orifices are supplied with a polymer melt by a single polymer inlet, which delivers the polymer melt to individual polymer melt flow channels within the body member of the melt-blown fiber spinneret. Air knife channels are directed through the body member, in which the polymer melt flow channels are formed by means of islands and air flow passage feeds. All of the components and features are contained within a very small footprint, thereby enabling row center-to-row center separation of 6.35 mm (0.25 in.) or smaller.
The melt-blown fiber spinneret is preferably a unitary or multiple component article, with the body member constructed by operation of a 3D printer for direct metal printing.
Additional aspects and advantages will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B are respective frontal and rear isometric views of an embodiment of a melt-blown fiber spinneret constructed in accordance with the present disclosure.
FIGS. 2, 3, and 4 are respective rear elevation, top plan, and enlarged frontal elevation views of the fiber spinneret of FIGS. 1A and 1B.
FIG. 5 is an enlarged sectional view taken along lines B-B of FIG. 4.
FIG. 6 is an enlarged sectional view taken along lines C-C of FIG. 4.
FIG. 7 is a side view of a body member of the melt-blown fiber spinneret of FIGS. 1A and 1B, showing in broken lines the various fluid flow channels and passage feeds depicted in the three sectional views presented as FIGS. 8, 9, and 10.
FIG. 8 is a sectional view taken along lines A-A of FIG. 7.
FIG. 9 is a sectional view taken along lines D-D of FIG. 7.
FIG. 10 is a sectional view taken along lines E-E of FIG. 7.
FIG. 11 is a fragmentary isometric frontal view of the fiber spinneret of FIGS. 1A and 1B, in which notch portions A and B are removed to illustrate the spatial relationship of the air passage feeds shown in FIGS. 5, 6, and 7.
FIG. 12 is a copy of FIG. 5, with the addition of bevels to the air knife channels of the body member of the fiber spinneret shown in FIGS. 1A and 1B.
FIG. 13A is an isometric view and FIG. 13B is a copy of FIG. 12 showing an air knife deflector plate mounted on the body member of the fiber spinneret of FIGS. 1A and 1B.
FIG. 14A is an isometric view and FIG. 14B is a cross-sectional view of an alternative embodiment of the disclosed fiber spinneret, in which a fluid outlet component containing the polymer outlet orifices is a separate component that is attached to the body member of the fiber spinneret.
FIGS. 15A is a diagram showing the air flow patterns produced without an air knife deflector plate mounted to the body member of the fiber spinneret of FIG. 12, and FIG. 15B is a diagram showing the air flow patterns produced with an air knife deflector plate mounted to the body member of the fiber spinneret of FIG. 14B.
FIG. 16 shows, as an alternative embodiment, a body member that implements air knives formed by two converging air knife channels that run on either side of polymer melt flow channels along the length of the body member.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIGS. 1A and 1B are respective frontal and rear isometric views of a melt-blown fiber spinneret 8 (hereafter “fiber spinneret 8”) that includes a body member 10 having on its front side three rows 121, 122, and 123 of polymer outlet orifices positioned between different pairs of four air knives 141, 142, 143, and 144. Body member 10 has an upper air inlet 16 and a lower air inlet 18 into each of which hot air (i.e., 150° C.-300° C. or higher) is delivered from an external process air supply (not shown). Body member 10 has on its rear side a polymer inlet pocket 20 that receives a screen 22 through which thermoplastic fiber-forming material, such as polymer material in melt form, enters. The front side and rear side of body member 10 have a polymer melt outlet surface 24 and a polymer melt inlet surface 26, respectively.
FIGS. 2, 3, and 4 are respective rear elevation, top plan, and frontal elevation views of body member 10. FIG. 2 shows polymer channel support islands 30 that act as a breaker plate (i.e., support) for screen 22. FIG. 3 shows upper air inlet 16 to air knives 141, 142, 143, and 144. Lower air inlet 18 is of the same design configuration as that of upper air inlet 16. FIG. 4 shows the arrangement of rows 121, 122, and 123 of polymer outlet orifices 36 positioned between the different pairs of air knives 141, 142, 143, and 144.
FIGS. 5 and 6 are sectional views taken along, respectively, lines B-B and lines C-C of FIG. 4. FIG. 5 shows a polymer flow channel 121 with a polymer melt entrance end 121e and exit end 121x, a polymer flow channel 122 with a polymer melt entrance end 122e and exit end 122x, and a polymer flow channel 123 with a polymer melt entrance end 123e and exit end 123x. FIGS. 5 and 6 present cross-sectional views taken at different locations along the width of body member 10 to show the positioning of air passage feeds to air knife channels for each one of two sets of air knife channel configurations of air knives 141, 142, 143, and 144. The two sets of air knife channel configurations are grouped in an alternate sequence along rows 121, 122, and 123 of polymer outlet orifices 36.
With reference to FIG. 5, an air knife channel 141, receives from upper air inlet 16 hot process air flow through an air passage feed 141-1 that is connected to a medial opening 141m in air knife channel 141, of air knife 141. Similarly, an air knife channel 144, receives from lower air inlet 18 hot process air flow through an air passage feed 144-1 that is connected to medial opening 144m in air knife channel 144c of air knife 144. An air knife channel 142c receives from upper air inlet 16 hot process air flow through an air passage feed 142-1 that is connected to a distal opening 142d in air knife channel 142c of air knife 142. Similarly, an air knife channel 143c receives from lower air inlet 18 hot process air flow through an air passage feed 143-1 that is connected to a distal opening 143d in air knife channel 143, of air knife 143.
With reference to FIG. 6, an air knife channel 141, receives from upper air inlet 16 hot process air flow through an air passage feed 141-2 that is connected to a distal opening 141d in air knife channel 141, of air knife 141. Similarly, an air knife channel 144, receives from lower air inlet 18 hot process air flow through an air passage feed 144-2 that is connected to distal opening 144d in air knife channel 144, of air knife 144. An air knife channel 142c receives from upper air inlet 16 hot process air flow through an air passage feed 142-2 that is connected to a medial opening 142m in air knife channel 142c of air knife 142. Similarly, an air knife channel 143, receives from lower air inlet 18 hot process air flow through an air passage feed 143-2 that is connected to a medial opening 143m in air knife channel 143, of air knife 143. Although they exhibit a straight line profile in FIGS. 5 and 6, the air passage feeds to the air knife channels may be formed in a curved profile in body member 10.
The cross-sectional views of FIGS. 5 and 6 show polymer melt flow channels 501, 502, and 503 that form polymer flow passageways from polymer inlet pocket 20 to the three stacked polymer outlet orifices 36 of rows 121, 122, and 123, respectively. FIGS. 5 and 6 show that the two sets of air knife channels grouped in an alternating sequence are configured so that connections of the pairs of air passage feeds to outermost-positioned air knife channels of air knives 141 and 144 and the pairs of air passage feeds to the middle-positioned air knife channels of air knives 142 and 143 alternate between medial and distal openings to their respective air knife channels along rows 121, 122, and 123 of polymer outlet orifices 36. The configuration of alternating pairs of air knife passage feeds enables closer spacing and thereby more densely side-by-side packing of polymer outlet orifices 36 of the stacked rows 121, 122, and 123. The large number of air passage feeds in a staggered pattern of them across the width of fiber spinneret 8 results in a reduced concentration of air flowing from the individual air passage feeds at the air knife outlet. The spacing between adjacent polymer outlet orifices 36 achievable with this configuration is 0.64 mm (0.025 in.), which facilitates provision of 401 polymer outlet orifices 36 for each of rows 121, 122, and 123 of a 25.4 cm (10 in.) wide fiber spinneret 8.
Close polymer die orifice spacing of up to about 2 orifices/mm (50 holes/in.) is achievable using 3D printing techniques to form a unitary body member 10 made of a nickel-chromium alloy such as Inconel® alloy 718 material or 17-4PH stainless steel. A suitable 3D printer for direct metal printing is a Trumpf TruPrint Series 1000 3D printing system, available from Trumpf Laser-und Systemtechnik, Ditzingen, Germany. Each of polymer outlet orifices 36 formed by 3D printing is finish reamed to size, which is 0.254 mm (0.010 in.) diameter specification. This process reduces greatly the cost as compared to that of drilling holes conventionally.
FIG. 7 is a side view of body member 10 of fiber spinneret 8, showing in broken lines polymer melt flow channels 121, 122, and 123, together with the two sets of air knife channels and their associated air passage feeds of air knives 141, 142, 143, and 144, for use in reference to FIGS. 8, 9, and 10. FIGS. 8, 9, and 10 are sectional views taken along, respectively, lines A-A, D-D, and E-E of FIG. 7. FIG. 8 is a cross-sectional view taken through each of polymer outlet orifices 36 of middle row 122 to show polymer channel islands 60 positioned to balance polymer flow to upper melt flow inlet channels 501 and lower melt flow inlet channels 503. Channel islands 60 do not provide material for passage of air. Channel islands 60 contain no air passage because their presence in middle polymer melt flow channel 122 is for the purpose of balancing the backpressure in the polymer melt flow channels. This balancing of backpressure helps to balance the polymer flow velocity of rows 121, 122, and 123 of polymer outlet orifices 36.
FIG. 9 is a cross-sectional view taken through each of polymer outlet orifices 36 of row 121 and upper melt flow inlet channel 501 to show the air passageway of air knife 142 and islands 62 in upper melt flow inlet channel 501 that provide location for air passage.
FIG. 10 is a cross-sectional view taken through each of polymer outlet orifices 36 of row 123 and lower melt flow inlet channel 503 to show the air passageway of air knife 143 and islands 62 in lower melt flow inlet channel 503 that provide location for air passage.
FIG. 11 is a fragmentary isometric frontal view of body member 10, in which notch portions A and B are removed to illustrate the spatial relationship of the air passage feeds shown in and described with reference to FIGS. 5, 6, and 7. Specifically, notch portions A and B reveal air passage feeds 141-1 and 141-2 of air knife 141 and air passage feeds 142-2 and 142-1 of air knife 142, respectively, on either side of row 121 of polymer outlet orifices 36.
FIG. 12 is a copy of FIG. 5, with the addition of bevels 701, 702, 703, and 704 (collectively, bevels 70) to, respectively, air knife channels 141c, 142c, 143c, and 144c at polymer melt outlet surface 24 of body member 10. Each of bevels 70 has sides 70a and 70b that diverge in the direction toward polymer melt outlet surface 24 to form angled gas channel nozzles.
FIG. 13A is an isometric view and FIG. 13B is a copy of FIG. 12 showing an air knife deflector component or plate 74 mounted on polymer melt outlet surface 24 of body member 10. Air knife deflector plate 74 is preferably a separate article that is not an integral part of body member 10. Air knife deflector plate 74 can be produced as a separate component part by either 3D printing or other fabrication methods. Air knife deflector plate 74 includes truncated substantially rhombus-shaped air deflection features 761, 762, 763, and 764 (collectively, air deflection features 76).
Each of air deflection features 76 has sides 76a and 76b that converge to an apex. Air deflection features 76 fit within spatially aligned bevels 70, with confronting sides 76a and 70a spaced apart from each other and confronting sides 76b and 70b spaced apart from each other. The complementary shapes of, and spaces between, air deflection features 76 and bevels 70 direct flow of air inwardly toward the polymer fiber melt filament emerging from polymer outlet orifices 36. Specifically, the air space between side 76b of air deflection feature 761 and side 70b of bevel 701, and the air space between side 76a of air deflection feature 762 and side 70a of bevel 702 form angled air knives 141 and 142 directing air flow toward either side of a polymer fiber melt filament emerging from a polymer outlet orifice in row 121. The air space between side 76b of air deflection feature 762 and side 70b of bevel 702, and the air space between side 76a of air deflection feature 763 and side 70a of bevel 703 form angled air knives 142 and 143 directing air flow toward either side of a polymer fiber melt filament emerging from a polymer outlet orifice in row 122. The air space between side 76b of air deflection feature 763 and side 70b of bevel 703, and the air space between side 76a of air deflection feature 764 and side 70a of bevel 704 form angled air knives 143 and 144 directing air flow toward either side of a polymer fiber melt filament emerging from a polymer outlet orifice in row 123.
FIGS. 14A and 14B show an alternative melt-blown fiber spinneret 8′, in which a fluid outlet component 90 containing polymer outlet orifices 36 is mounted to polymer melt outlet surface 24 of body member 10. Output orifices 36 of fluid outlet component 90 are spatially aligned with polymer melt exit ends 121x, 122x, and 123x of corresponding polymer flow channels 501, 502, and 503. Bevels 701, 702, 703, and 704 are positioned in fluid outlet component 90 and receive the respective air deflection features 761, 762, 763, and 764 of air knife deflector plate 74 that is mounted to fluid outlet component 90. The use of fluid outlet component 90 with polymer outlet orifices 36 separate from body member 10 reduces the cost of spinneret 8′ by facilitating reconfiguration of fiber spinneret 8′ without entirely reconstructing it.
FIGS. 15A and 15B are two diagrams showing the air flow patterns produced, respectively, without and with use of air knife deflector plate 74. FIG. 15A shows the directions of air flow developed by air knife channels 141, 142c, 143c, and 144, in the absence of air knife deflector plate 74, as shown in FIG. 12. The air flow is parallel to the polymer fiber streams as they emerge from polymer outlet orifices 36 of rows 121, 122, and 123. FIG. 15B shows the directions of air flow developed by angled air knives 141, 142, 143, and 144, resulting from attachment of air knife deflector plate 74 to fluid outlet component 90, as shown in FIG. 14B. The air flow pinches (i.e., converges inwardly toward) the streams of polymer fiber melt filaments 921, 922, 933 as they emerge from the respective polymer outlet orifices 36 of rows 121, 122, and 123 to facilitate attenuation of the polymer fibers formed.
FIG. 16 shows a body member 10A, which is an alternative embodiment that implements air knives 141, 142, and 143 formed by two converging air knife channels that run on either side of polymer melt flow channels 501, 502, and 503 along the length of body member 10A. Air knife 141 is formed by air knife channels 141and 141c1 that are supplied by air plenums 141up and 141lp, air knife 142 is formed by air knife channels 142,, and 142cl that are supplied by air plenums 142up and 142lp, and air knife 143 is formed by air knife channels 143and 14cl that are supplied by air plenums 143up and 143lp. For each air knife, the two air plenums receive process air from a single port (not shown) located at polymer melt inlet surface 26.
It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. For example, a multi-polymer inlet could be used for making a bi- or tri-component fibrous nonwoven mat. The scope of the invention should, therefore, be determined only with reference to the following claims.
Patent Application
20190040547
