CN113355752A - Single-head die for producing melt-blown nonwoven fabrics - Google Patents

Abstract

A tip die (1) for producing meltblown nonwoven fabrics is provided, defining a sagittal plane (1a), a main direction of extension (1b) on the sagittal plane (1a), a first side (10) and a second side (11) mutually delimited by the sagittal plane (1a), and comprising a jet portion (2), at least one extrusion tube (3), a plurality of holes (4), the jet portion (2) extending along the main direction of extension (1b) and being designed, in use, for conveying a polymer fluid towards an external air blade, the at least one extrusion tube (3) being configured to convey the polymer fluid towards the jet portion (2), the plurality of holes (4) being arranged in the jet portion (2), being fluidic by communication with the extrusion tube (3) and communicating with the outside, wherein the holes (4) are arranged along at least one first row (4a) and one second row (4b), the first row (4a) and the second row (4b) are different and are arranged at the first side (10) and the second side (11), respectively.

Description

Single-head die for producing melt-blown nonwoven fabrics

Technical Field

The present invention relates to a tip die for producing melt-blown nonwoven fabrics of the type specified in the preamble of the first claim.

In other words, the invention relates to a die designed to produce a nonwoven fabric from polymer filaments extruded through the die itself, also known by the acronym NW.

Background

As is well known, nonwoven fabrics or NWs are industrial products similar to fabrics, but are obtained by methods other than weaving and knitting. Thus, in non-woven fabrics, the fibers have a random development, without determining any ordered structure, whereas in fabrics, the fibers have two directions, common and orthogonal to each other, commonly referred to as warp and weft.

Currently, depending on the manufacturing technology used, many NW containing products are manufactured, which is mainly related to the way the product itself is used.

In particular, high quality NWs for sanitary and sanitary products are distinguished from low quality NWs for geotextiles (geotex) which is the most important.

From a technical point of view, nonwoven fabrics can be essentially divided into spunlace, spunbond and meltblown.

Hydroentangled fabrics are treated to impart isotropic strength to the material. Due to this property and the possibility of production in various materials such as viscose, polyester, cotton, polyamide and microfibres, and due to the possible finishes (i.e. glossy or perforated) and the various glossy or printed colours, it is recommended to use hydroentangling for hygiene and cleaning industries, automotive and cosmetic industries and industrial or disposable uses.

Spunbond, which is typically made from polypropylene, is a nonwoven fabric that can be used in a variety of ways in agriculture, hygiene and cleaning, construction, furniture, mattresses and other related fields. Through appropriate processing, a range of highly specific products can be manufactured for each industry: fluorescent lamps, soft press lamps, anti-mite, fireproof, antibacterial, anti-static, anti-ultraviolet, etc. In addition, a variety of finishes can be applied to the spunbond, such as printing, lamination, flexographic printing, and self-adhesive printing lamination.

Meltblown NWs are made with specific spinnerets in order to obtain more complex technical features than previous NWs. In fact, meltblown fabrics are characterized by a high filtration capacity of the fibers, both for liquid and gaseous substances.

Traditionally, equipment for producing nonwoven meltblown fabrics has consisted of modules, as shown in fig. 6.

It consists of a box enclosing the equipment for producing the meltblown fibers and all the components necessary for the optimal operation of the process. In addition, known devices generally comprise a first support, a breaker plate, a pointed die, a second support and an air blade.

The breaker plate is designed to direct and filter the polymer (typically polypropylene) to the tip die. The latter is a device comprising a perforated tip portion designed to let the polypropylene exit under pressure, as described above.

The first support is basically an element connecting the box and the breaker plate, whereas the second support is designed to support the air blades and is arranged to enclose the breaker plate and the meltblowing apparatus within the box.

Sometimes, the second support and the plate defining the air vane may be identical, thereby limiting the equipment components. The air blades, on the other hand, consist of a housing that surrounds the tip of the meltblowing apparatus in order to direct a flow of air, which may be non-turbulent, towards the orifice of the tip.

From a procedural point of view, the polymeric material enters the chamber and begins to enter the chamber at a temperature of about 240-.

It is first guided to the first support, then to the breaker plate and finally to the tip die and, in particular, under pressure to the holes arranged on the tips.

Typically, the tip comprises 30 to 50 holes per inch aligned along the primary direction, with a diameter in the range of 0.15 mm to 0.4 mm and a depth of the holes between 10-13 times the diameter.

Once the polymer exits the tip hole, it is impacted by air streams from both sides defined by the air vanes.

The air vane essentially consists of two collecting ducts which extend as far as the discharge space or slot, which extends between 0.7 and 2 mm, wherein the air flows out at an angle of approximately 180 °.

The acceleration of the air inside the blade makes it possible to generate a stream of atomized polymer in contact with the polymer, thereby generating a spray containing very fine particles, which in turn is located at high velocity on the movable carpet.

Thus, the tank comprises, in addition to the polymeric inlet duct, an air inlet duct for feeding the air blades.

The described prior art includes some significant disadvantages.

In particular, as can be seen from the specification, melt blowing technology relies on a particular component configuration and well-defined processes.

In particular, to produce NWs with good properties, the number of holes per inch must be increased, especially to increase the flow rate or throughput of polymer. Drilling holes at diameters below 0.15 mm is very difficult and expensive. Thus, the known techniques have significant physical limitations. Many times, when the blade surrounding the melt blowing tip becomes fouled with polymer, the polymer burns and becomes trapped between the blade and the melt blowing tip, causing melt blowing failure and compromising product quality.

In particular, with the pointed dies of the prior art it is possible to produce high quality non-woven fabrics, but the fabrics do not function well as barriers to water or air. In fact, the shape of the above-mentioned holes does not minimize the presence of voids on the nonwoven fabric, thus reducing its efficiency.

Disclosure of Invention

In this context, the technical task underlying the present invention is to devise a tip die for the production of melt-blown nonwoven fabrics which is able to substantially overcome at least some of the above-mentioned disadvantages.

Within the scope of said technical task, an important object of the present invention is to obtain a pointed die that, unlike the conventional art, allows to produce a nonwoven fabric with greater efficiency, without dimensional constraints in terms of fineness.

Another important object of the invention is to create a pointed mould that allows to greatly reduce the space between one type of fiber and another non-woven fabric, thus increasing the barrier to water or air produced by the fabric itself.

Another object of the invention is to create a tip that can increase the efficiency of NW products without the need to change the structure of the meltblowing apparatus as currently envisaged.

Another task of the present invention is to obtain a tip die compatible with current meltblowing equipment.

The technical task and the specific objects are achieved by a cusp die for the production of melt-blown non-woven fabric according to claim 1.

Preferred technical embodiments are highlighted in the dependent claims.

Drawings

The features and benefits of the present invention will be set forth in the detailed description of some preferred embodiments of the invention which follows, with reference to the accompanying drawings, in which:

FIG. 1 shows a perspective view of a tip die for producing a meltblown nonwoven fabric according to the invention;

FIG. 2 shows a longitudinal view of a tip die for producing a meltblown nonwoven fabric according to the invention;

FIG. 3a is a detailed view of the holes in a tip die for producing meltblown nonwoven fabrics according to the invention;

FIG. 3b shows a perspective view of a tip die for producing a meltblown nonwoven fabric according to the invention; and

FIG. 4 shows a cross-sectional view of a meltblowing apparatus including a tip die for producing a meltblown nonwoven fabric according to the invention;

FIG. 5a shows a detail of the holes in a tip die for producing a melt-blown nonwoven fabric according to the invention in a first example;

FIG. 5b is a detail of the orifices of a tip die for producing meltblown nonwoven fabric according to the invention in a second example;

FIG. 6 shows a cross-sectional view of a prior art meltblowing apparatus;

FIG. 7 shows an arrangement of holes in another example of a tip die for producing meltblown nonwoven fabrics according to the invention; and

fig. 8 shows a detail of the holes in the pointed mould of fig. 7, where the holes are distributed in such a way that they partly overlap the other side.

Detailed Description

In this document, measurements, values, shapes and geometric references (such as perpendicularity and parallelism) when associated with other similar terms such as "almost" or "approximately" or "substantially" should be understood to exclude measurement errors or inaccuracies due to manufacturing and/or fabrication errors, and most importantly, to exclude slight differences in the values, measurements, shapes or geometric references associated therewith. For example, if associated with a value, the terms preferably mean no more than 10% difference from the value itself.

Further, terms such as "first," "second," "higher," "lower," "primary," and "second," when used, do not necessarily identify an order, priority, or relative position, but may simply be used to distinguish one component from another.

Unless otherwise indicated, the measurements and data reported herein are to be considered to be made in the International Standard atmospheric ICAO (ISO 2533: 1975).

With reference to the accompanying drawings, a tip die for producing meltblown nonwoven fabrics according to the invention is generally indicated by reference numeral 1.

The die 1 is basically configured to be placed in a melt-blown nonwoven fabric apparatus.

Thus, the mould 1 preferably has at least partially a pointed or arrowhead shape.

The meltblowing apparatus comprising die 1 includes, in addition to the die, substantially conventional components.

As shown in fig. 4, the apparatus may include a box, a breaker plate, one or more supports, and an air vane.

The box is a generally U-shaped housing device within which the device components are placed.

In particular, the tank preferably comprises at least one main conduit.

The main conduit is preferably designed to enable polymer fluid to pass through the tank.

The main conduit is preferably designed to allow the passage of polymer fluid at about 240-270 c, as occurs with common melt blowing equipment. In practice, the polymer fluid may consist of polypropylene, for example.

The breaker plate preferably comprises at least one or more directional tubes.

The direction tube may be of a convergent type. The directional pipes are preferably fluidic by connection to the main pipe and are in any case designed to guide the polymer fluid or, more precisely, to convey it along a predetermined direction.

Furthermore, between the directional pipe and the main pipe, at least one filter element is usually arranged in such a way that the polymer fluid is filtered before it is discharged from the apparatus.

Thus, the breaker plate is preferably attached to the tank via the first support. Thus, the first support may comprise a connection (if present) arranged between the main pipe and the directional pipe upstream of the filter element.

Thus, the die 1 is preferably designed to be attached downstream of the breaker plate in order to receive the polymer fluid filtered by the breaker plate.

In any case, the mold 1 preferably defines a sagittal plane 1 a.

The sagittal plane 1a is essentially the median plane designed to divide the mould 1 into two adjacent parts placed substantially side by side.

The sagittal plane 1a additionally defines the extension plane along which the mold 1 extends.

Thus, the die 1 is designed to be attached to a breaker plate within the meltblowing apparatus such that the sagittal plane 1a is parallel to the direction defined by the direction tube. In other words, the mould 1 is designed, in use, to be attached to the breaker plate in such a way that the sagittal plane 1a lies on the sagittal plane of the entire apparatus.

Thus, mold 1 defines a first side 10 and a second side 11 relative to the sagittal plane 1 a.

The first 10 and second 11 lateral surfaces are mutually delimited by a sagittal plane 1 a. As shown in fig. 1-5b, they essentially define the left and right sides of the mould 1 when used inside the apparatus.

In addition, the mould 1 defines a main direction of extension 1 b.

The main extension direction 1a is a predetermined direction on the sagittal plane 1 a. The first 10 and second 11 lateral faces extend substantially along a main extension direction 1b lying side by side with respect to the sagittal plane 1 a.

The mould 1 thus comprises a spraying part 2.

The ejection part 2 extends along the main extension direction 1 b. In particular, the ejector part 2 preferably extends in such a way that it defines a part of the first side 10 and at the same time a part of the second side 11.

Thus, the injection portion is preferably substantially divided by the sagittal plane 1a into two mirror halves.

In any case, the injection part 2 is designed to convey the polymer fluid towards the air blades in use. As already suggested, the air blades are elements outside the mould 1. In particular, the air blade is an integral part of the meltblowing apparatus, connected to the first support, generally by a second support, and close to the ejection section 2, in such a way as to enable a controlled flow of air to impinge on the polymer fluid as it emerges from the ejection section 2.

For delivering the polymer fluid to the injection part 2, the die comprises at least one extrusion tube 3.

The extrusion tube 3 is preferably configured to convey the polymer fluid toward the ejection portion 2. In particular, the extruded tube 3 preferably extends along the sagittal plane 1 a. In addition, in use, it is designed to be fluidic by connection with the direction tube of the breaker plate, so that it receives the fluid filtered by the breaker plate.

Preferably, the extruded tube 3 extends perpendicularly to the main extension direction 1b of the die 1.

In addition, the die 1 may likewise comprise a plurality of extruded tubes 3 distributed along or parallel to the main extension direction 1b, each extruded tube 3 extending perpendicularly thereto and parallel to the other extruded tubes 3.

Thus, the mould 1 also comprises a plurality of holes 4.

Preferably, the hole 4 is arranged in the injection part 2. In addition, the hole 4 is fluidic by being connected to the extrusion tube 3 and communicates with the outside.

In fact, the holes 4 are configured to discharge the polymer fluid outwards.

In addition, when the mold 1 is used in the apparatus, the holes 4 are arranged at positions close to the air blades. In particular, the holes 4 are preferably arranged close to the mould, or may be arranged astride the tip, or may be astride the tip and half at a position close to the blade.

The holes 4 may all be fluidic by connection with the extruded tube 3, or they may each be fluidic by connection with a single extruded tube 3.

Preferably, but not necessarily, the hole 4 extends perpendicularly to the main direction of extension 1b, parallel to the sagittal plane 1 a.

Advantageously, the holes 4 of the die 1 are not arranged or distributed in a single row as in prior art dies.

In particular, the holes 4 of the mould 1 are arranged along at least one row 4a and a second row 4 b.

The first and second rows 4a, 4b are distinct from each other, i.e. they are not identical. In addition, the rows 4a, 4b are preferably substantially parallel to the main direction of extension 1 b. Even more particularly, at least one of them is not coincident with the main extension direction 1b or does not lie on the sagittal plane 1 a.

Further, the first row 4a is preferably arranged at the first side 10. The second row 4b is preferably arranged at the second side 11.

Even more particularly, as shown in fig. 1-5b, the rows 4a, 4b are preferably arranged to mirror the sagittal plane 1 a.

The fact that the holes 4 are arranged in two rows enables a specific configuration to be created.

Preferably, the holes 4 are arranged alternately in rows 4a, 4b, so that no hole 4 is placed side by side with another hole 4 in a direction perpendicular to the sagittal plane 1 a. In other words, the holes 4 of one row 4a, 4b are placed beside the space separating the two holes 4 of the other row 4b, 4 a.

More specifically, in a preferred embodiment, the holes 4 are staggered along the main extension direction 1 b. In this way, adjacent holes 4 of the same row 4a, 4b are spaced apart by a space smaller than the extension along the row 4a, 4b of holes 4 of another row 4b, 4a placed in parallel with the spacing space.

In other embodiments, adjacent holes 4 of the same row 4a, 4b may define a spacing space substantially equal to the extension of its own row 4a, 4b along the holes 4 of another row 4b, 4a placed side by side with the spacing space.

Alternatively, adjacent holes 4 of the same row 4a, 4b may define a spacing space that is smaller than the extension of the holes 4 of another row 4b, 4a alongside the spacing space along the row along its own row 4a, 4 b. In the latter case, however, it is in any case preferable to limit the spacing space in order to obtain a high-quality nonwoven fabric.

Thus, the arrangement of the holes 4 may be defined according to various configurations.

For example, referring to fig. 2 and 5b, the jetting section 2 may exclusively define the edge 20.

The edge 20 may be a sharp part, i.e. geometrically defining a singular point defining left and right derivatives, corresponding to derivatives on the first 10 and second 11 sides which do not coincide with each other.

Furthermore, the edge 20 is preferably aligned with the main extension direction 1b and lies on the sagittal plane 1 a.

In other words, the edge 20 extends on a sagittal plane 1a parallel to the main direction of extension 1 b.

Thus, the rows 4a, 4b are specularly placed beside the edge 20.

Alternatively, as shown in fig. 1, 3a-3b, 5a, the mold 1 may define two edges 20.

In this case, the two edges 20 extend parallel to the main direction of extension 1b and the sagittal plane 1 a. In addition, the ejection portion 2 defines a flat surface 21.

The planar surface 21 is preferably perpendicular to the sagittal plane 1 a. In addition, the flat surface 21 is substantially delimited by the edge 20 and extends along the main extension direction 1 b.

Then, in this embodiment, at least three different configurations of the holes 4 may be defined.

For example, in the first configuration shown in fig. 3a-3b, 5a, the rows 4a, 4b are preferably arranged and extend over the edge 20. In this way, at least a part of the hole 4 extends over the flat surface 21.

In a second alternative configuration shown in fig. 1, the rows 4a, 4b extend parallel to the edge 20 outside the flat surface 21, so that none of the holes 4 extends through the flat surface 21.

In a third alternative configuration, not shown in the figures, they extend through the flat surface 21 parallel to the edge 20, so that all the holes 4 extend through the flat surface 21.

Of course, the mold 1 can also be manufactured by combining the three configurations. For example, the holes 4 may be arranged in more than two rows 4a, 4b and may be arranged partly on the edge 20 and/or on the flat surface 21 and/or outside the flat surface 21.

In addition, in embodiments in which the ejection portion comprises one edge 20, the apertures 4 may also be arranged in more than two rows 4a, 4 b.

Furthermore, the holes 4 may be distributed in such a way that they are substantially tangential to the edges and may even partially overlap the other of the sides 10, 11, as shown in fig. 7-8.

Of course, the rows 4a, 4b may simply be considered as directions through the centre of the holes 4 of the respective rows 4a, 4 b.

From a geometrical point of view, the holes 4 may have any shape. However, the bore 4 is preferably substantially cylindrical.

Furthermore, the hole 4 preferably defines a minimum diameter of 0.05 mm.

In particular, the arrangement of the holes 4 in more rows 4a, 4b makes it possible to distribute the holes 4 over the entire jet part 2 with a linear density of more than 50 holes/inch evaluated along the main extension direction 1 b.

The linear density of the arrangement of the holes 4 depends, of course, on the size of the holes 4 themselves. In any case, the maximum achievable linear density is about 280 holes/inch, taking into account the smallest size of holes 4 that can be used in the die 1.

Even more conveniently, the maximum linear density is about 250 holes/inch.

For holes 4 of about 0.3 mm in diameter, a conventional die comprises a linear density of 30 to 50 holes/inch, and a distribution of more than 50 holes/inch can be obtained for die 1 due to the distribution of holes 4 along the separate rows 4a, 4 b. Preferably, a uniform distribution of greater than 70 holes/inch.

Basically, the die 1 can always obtain a high linear distribution density for any size of the orifice 4, thereby increasing the flow rate of the polymer fluid ejected by the ejection portion 2.

This density can be achieved due to the arrangement of the holes 4 envisaged in the above described embodiments.

Of course, the density can be increased depending on the size of the holes, including increasing the number of rows.

In addition, it should be noted that the line density is evaluated by considering the projection of the various holes 4 on the sagittal plane 1a along the main extension direction 1 b.

In general, the apparatus comprising the mould 1 may also comprise a container.

The container is preferably designed to collect the polymer particles in a manner that creates a non-woven fabric. It is basically a movable apparatus, such as an apparatus defined by a continuously moving conveyor belt.

When the die 1 is used in a meltblowing apparatus, the container is disposed substantially below the die 1 and is configured to receive the polymer filaments from the orifices 4. The latter facing the container in order to convey the polymer fluid to the container under the action of gravity and with the aid of air coming from the air blades.

The container 6 preferably defines a collection direction substantially parallel to the main extension direction 1 b.

Die 1 operates substantially the same as any prior art die in the production of meltblown nonwoven fabrics previously described in structure.

In any case, the melt-blowing apparatus including the die 1 can produce a high-quality melt-blown nonwoven fabric.

In fact, the die 1 for producing meltblown nonwoven according to the invention has significant advantages.

The mould 1 allows to substantially reduce the space between one fibre and the other non-woven fabric, so as to increase the barrier to water or air produced by the fabric itself.

These features are obtained without changing the operation of the die 1, compared to prior art dies, making any existing meltblowing equipment easy to convert.

Thus, the die 1 makes it possible to improve the efficiency of the meltblowing apparatus on which the die is mounted, and to produce a high-performance nonwoven fabric.

Another advantage is that it is also possible to increase the number of extruded tubes 3 in the die 1, while increasing the flow rate or throughput of polymer.

Various modifications may be made to the invention which fall within the scope of the inventive concept as defined in the claims.

In particular, at least a portion of the injection portion 2 may include a surface chrome plating designed to reduce the porosity of the contact surface between the polymer fluid and the injection portion 2, thereby increasing the fluidity of the fluid exiting the holes 4 and flowing through a portion of the injection portion 2. Thus, at least a portion of the injection portion 2 between the holes 4, if present, includes a chrome surface plating.

In a meltblowing apparatus including the die 1, the surface chrome plating may also be extended to air blades or air blades to further increase the efficiency of the apparatus.

Thus, at least one of the injection portion 2, in particular the portion of said injection portion 2 between said holes 4 and the air vane, preferably comprises a chrome-plated surface designed to increase the flow rate of the polymer fluid.

Furthermore, it should be noted that the holes 4 arranged in the rows 4a, 4b may have different sizes, i.e. they may each have a different diameter. For example, the two diameters of the holes 4 on the same row 4a, 4b may vary, and alternatively or additionally, the diameters of the holes 4 between different rows 4a, 4b may also vary.

In this context, all details may be replaced by equivalent elements, and the materials, shapes and dimensions may be any.

Claims (13)

1. A tip die (1) for producing a melt-blown nonwoven fabric, defining a sagittal plane (1a), a main direction of extension (1b) on said sagittal plane (1a), a first side (10) and a second side (11) mutually delimited by said sagittal plane (1a), said die (1) comprising

-a jet portion (2) extending along said main extension direction (1b) designed to convey, in use, a polymer fluid towards an external air blade,

-at least one extrusion tube (3) configured to convey the polymer fluid towards the injection portion (2),

-a plurality of holes (4) provided in the ejection portion (2), fluidic and communicating with the outside through a connection with the extrusion tube (3),

the method is characterized in that:

-said holes (4) are arranged along at least a first row (4a) and a second row (4b), said first row (4a) and second row (4b) being different and arranged at said first side (10) and second side (11), respectively.

2. Mould (1) according to claim 1, wherein said rows (4a, 4b) are parallel to said main extension direction (1 b).

3. The mould (1) according to any one of the preceding claims, wherein said rows (4a, 4b) are arranged specularly with respect to said sagittal plane (1 a).

4. The mould (1) according to any one of the preceding claims, wherein said holes (4) are arranged alternately on said rows (4a, 4b) so that none of the holes (4) is placed side by side with another hole (4) in a direction perpendicular to the sagittal plane (1 a).

5. A mould (1) according to any one of the preceding claims, wherein said ejection portion (2) exclusively defines an edge (20) extending on said sagittal plane (1a) parallel to said main direction of extension (1b), said rows (4a, 4b) being specularly placed side by side with respect to said edge (20).

6. A mould (1) according to any one of claims 1 to 4, wherein said ejection portion (2) defines two edges (20) extending parallel to said main extension direction (1b) and a flat surface (21) perpendicular to said sagittal plane (1a), a flat surface (21) being delimited by said edges (20) and extending along said main extension direction (1 b).

7. A mould (1) according to claim 6, wherein said rows (4a, 4b) are arranged and extend on said edge (20) so that at least a portion of said holes (4) extend on said flat surface (21).

8. The mold (1) according to claim 6, wherein said rows (4a, 4b) extend parallel to said edge (20) beyond said flat surface (21) so that none of said holes (4) extends on said flat surface (21).

9. The mold (1) according to claim 6, wherein said rows (4a, 4b) extend parallel to said edges (20) on said flat surface (21) so that all said holes (4) extend on said flat surface (21).

10. The die (1) according to any one of the preceding claims, wherein said holes (4) are cylindrical, define a minimum diameter of 0.05 mm and are distributed on said ejection portion (2) along said main extension direction (1b) with a maximum linear density of 280 holes/inch.

11. An apparatus for melt-blowing a nonwoven fabric, comprising a die (1) according to any one of the preceding claims.

12. The apparatus according to the preceding claim, further comprising air vanes, wherein at least one of a portion of said injection portion 2 between said holes 4 and said air vanes comprises a chrome-surfaced coating designed to increase the flow rate of said polymer fluid.

13. A meltblown nonwoven fabric produced using the meltblown fabric apparatus of claim 11.

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