KR20210112305A - Spinneret block having a nozzle and a single spinneret body for use in the manufacture of spun-blown fibers - Google Patents

Abstract

The present invention may further form a nonwoven or spun-blown web comprising a formed fibrous web, such as, for example, a layer of a multi-layer composite web. It relates to a specific implementation of a die block for a spun-blowing process to form filaments or fibers. The die block includes a unitary spinneret body and a spinneret block having nozzles.

Description

Spinneret block having a nozzle and a single spinneret body for use in the manufacture of spun-blown fibers

The present invention provides equipment adapted to produce filaments of the spun-blown type for forming nonwoven materials of good quality, as well as equipment for making and operating such equipment. it's about how

Spunmelting is a die block (die block) connected to one or more extruders such that the fibers are formed into a web, such as a nonwoven web or components thereof. It is a process in which fibers are spun from a molten polymer through a plurality of nozzles in a die head. Spunmelt processes are well known in the art and include meltblowing (see, eg, US8017534 (K-C)) and spunbonding (see, eg, US5935512 (K-C)).

From this technique, a “hybrid” technique, often referred to as “spun-blowing” has been developed and is described, for example, in US Pat. No. 9303334 (Biax,). This technology provides many advantages regarding fiber and web properties, but also many advantages regarding equipment and processes for manufacturing. However, when implementing these techniques, several hurdles are encountered. As will be described in more detail below, first, it is difficult to precisely align individual nozzles relative to other nozzles, which leads to difficulties in the assembly stage, but air blowing holes ), the annular shrouding air flow can be eccentric and deteriorate the filaments, such as by undesirable bundling of adjacent filaments. and may also weaken the web properties.

Accordingly, it is an object of the present invention to overcome the problems of spun-blowing technology.

In a first aspect, the present invention is a die block for forming meltblown filaments, the die block comprising:

- at least one molten polymer supply;

- air supply;

- spinneret block - the spinneret block,

a spinneret body comprising a polymer supply side, and

a plurality of nozzles forming an array of nozzles

including - ;

- an air distribution plate comprising openings;

- an exterior air plate comprising an opening;

- cover strips; and

- securing means.

the spinnerette block, the air distribution plate, the outside air plate, and the cover strip are mounted in this order and secured by the fixing means,

the nozzle protrudes through a corresponding opening in the air distribution plate and also through a corresponding opening in the outer air plate;

a polymer passage is formed for molten polymer passing through the nozzle from the polymer supply side of the spinnerette body; and

an air passage is formed for air passing through openings in the air distribution plate and the external air plate from the air supply;

The openings in the nozzle and the outer plate are adapted to allow molten polymer to exit the nozzle, the air flowing through the openings in the outer air plate being essentially parallel, the spinnerette body and The nozzle is unitary.

The die block may satisfy at least one of a condition selected from the group comprising:

- the inner diameter of said nozzle is less than about 1.25 mm, preferably less than about 0.8 mm;

- the outer diameter of the nozzle is less than about 2 mm;

- said nozzle exhibits a length of less than about 50 mm;

- said nozzle exhibits a length greater than about 10 mm;

- said nozzle exhibits a length/diameter ratio (L/d ratio) of less than about 50; and

- said die block exhibits a CD width greater than 250, preferably greater than 1500, even more preferably greater than about 2000 mm or greater than 5000 mm.

The present invention also relates to a die block comprising a nozzle and a unitary spinneret body, further comprising pre-holes in the spinneret block, the pre-holes comprising:

extending towards the capillaries from an upper surface located towards the supply of molten polymer in the form of countersinks to the capillary of the nozzle;

preferably having a chamfering angle between 30° and 60°,

Preferably, it represents a diameter of 1.5 to 4 times the inner diameter of the capillary,

preferably greater than about 2 mm, preferably greater than about 4 mm,

preferably less than about 20 mm, preferably less than about 14 mm, more preferably less than about 8 mm, and most preferably less than about 6 mm.

In a preferred embodiment, the transition of the nozzle relative to the base of the spinnerette block exhibits a radius of greater than about 0.1 mm, preferably greater than about 0.3 mm.

wherein the array of nozzles in the die block comprises at least two sub-arrays comprising nozzles different from nozzles of a different sub-array in at least one of dimensions selected from the group comprising: may include:

- the inner diameter of the nozzle;

- the outer diameter of the nozzle; and

- the length of the nozzle.

The array of nozzles may further comprise at least two sub-arrays, each sub-array comprising molten polymer to the other sub-array in at least one of a feature selected from the group comprising: connected to a separate polymer supply system configured to supply:

- polymer type;

- polymer flow rate;

- polymer pressure; and

- Polymer temperature.

In another aspect, the present invention is a method for the manufacture of a die block comprising a spinnerette body and a spinneret block comprising a plurality of nozzles, an air distribution plate, and an external air plate, the method comprising:

providing an integral die block precursor, preferably steel; and

from the one-piece die block precursor

o ■ Nozzle; and

■ air inlet and distribution chamber

A spinnerette block comprising;

o Air distribution plate; and

o Outside air plate

step of machining

including,

The machining is a high-precision CNC processing.

In another aspect, the present invention is a method for the manufacture of a spinnerette block comprising a plurality of nozzles and a spinneret body for use in a die block, the method comprising:

providing a single piece of spinneret block precursor, preferably steel; and

from the one-piece spinnerette block material

Nozzle; and

air flow channels

machining the

including,

The machining is high precision CNC treatment.

In another aspect, the present invention is a process for cleaning a melt blowing apparatus comprising the steps of: providing a spinnerette or die block as described; combusting polymer residues; removing the burnt residue ultrasonically; and blowing pressurized water/steam through the nozzle.

In another aspect, the present invention relates to a process method for forming a nonwoven web comprising meltblown fibers, the method comprising the steps of:

providing equipment as described above;

providing a thermoplastic polymer for forming meltblown (MB) fibers exhibiting a Melt Flow Index (MFI) of 30 to 2000; and

forming filaments by applying, in the polymer supply, a pressure of less than 70 bar, preferably less than 50 bar, more preferably less than 45 bar .

1 shows spun-blowing equipment according to the prior art.
2A-2H illustrate certain features of the present invention.
3, 4A-4D, and 5 show other features of the present invention.

In the drawings, like numbers indicate identical or equivalent features. The drawings are schematic and not to scale.

The present invention relates to filaments or filaments capable of further forming a fibrous web or a nonwoven comprising a formed fibrous web, such as, for example, a layer of a multi-layer composite web. It relates to the specific implementation of a die block for a spun-blowing process to form fibers.

Spunmelt is a process in which fibers are spun from a molten polymer through a plurality of nozzles in a die head connected to one or more extruders. The spunmelt process may include meltblowing, spunbonding and a hybrid process as described in more detail below, also referred to as spun-blowing.

Meltblown is a process for making very fine fibers, typically having a diameter of less than about 10 microns, and a number of molten polymer streams are Emerge, hot, and attenuate using a speed gas stream. The weakened fibers are collected on a flat belt or drum collector. A typical meltblowing die has about 35 nozzles per inch and a single row of nozzles. A typical meltblowing die uses inclined air jets on each side of a row of nozzles to weaken the filament.

Spunbond is produced directly from a thermoplastic polymer by quenching the fibers near the spinneret face and attenuating the spun filaments using cold high speed air. A process for making strong fibrous nonwoven webs. Individual fibers are randomly placed on a collection belt and conveyed to a bonder to provide web added strength and integrity. The fiber size is generally less than 250 μm, and the average fiber size is in the range of about 10 microns to about 50 microns. The fibers are very strong compared to meltblown fibers due to the molecular chain alignment achieved during crystallizing (solidifying) weakening of the filaments. A typical spunbond die has a plurality of rows of polymer holes, and for a typical polymer of the polypropylene type, the polymer melt flow index (MFI) is typically about 500 grams at a 2.16 kg load. )/10 minutes.

The present invention relates to spun-blowing, a hybrid process between a typical meltblown process and a typical spunbond process, using a multi-row spinneret similar to the spinneret used for spunbonding, the nozzle Except for being arranged to allow parallel gas jets to surround the spun filament to weaken and solidify the spun filament. Each of the extruded filaments is shrouded with a pressurized gas, the temperature of which may be colder or hotter than the polymer melt. Optionally, the periphery around all filaments may be surrounded by a curtain of pressurized gas.

To describe the general principles of spun-blowing equipment and processes for forming filaments, and other webs such as nonwoven webs or components of such webs, see US9303334, which describes these techniques in more detail. see Accordingly, Figure 1 shows a die block for this “hybrid” spun-blowing process.

In total, the die block 26 includes a spinneret body 52 , an air distribution plate 70 , an outer plate 78 , and a cover strip 88 . Also, nozzle 58 extends from spinneret body 52 through openings in distribution plate 70 and outer plate 78, respectively, so that the molten material passes through capillary 60 of nozzle 58. A filament 86 may be formed at the tip of the nozzle 96 .

Typically, the order of the elements is such that the spinneret body 52, air distribution plate 70, outer plate 78, and cover strip 88 are arranged along gravity, and, for purposes of this description, the spinnerette. The body 52 is positioned over and secured to the air distribution plate 70 , which is positioned over and secured to the outer plate 78 , which is positioned over and secured to the cover strip 88 , fixing means not shown. .

Although the present description has been described with reference to the position of the die block such that the nozzles exhibit a vertical orientation, one skilled in the art would be able to tilt about the CD oriented axis, although this is not necessary, so that the die block is more than 5°, or 15 It can be readily seen that relatively nozzles can be oriented more than 30 degrees, or more than 30 degrees, or more than 45 degrees or more vertically, or typically less than 90 degrees (ie, horizontal).

1 shows a cross-sectional view of a die block 26 . When positioned on the manufacturing equipment for forming the nonwoven, this figure corresponds to an xz-directional view, the x-direction 12 representing the direction of manufacture, ie the direction of movement of the resulting web, z -direction 15 corresponds to height (along gravity). In the implementation as shown, three nozzles 58 represent one "column" of a "multi row" (here, three-row) die block 26 . Since the die block includes a plurality of columns positioned adjacently in the y-direction 18 (ie, indicated by circles perpendicular to the plane of the figure), the columns and rows of nozzles form an array of nozzles in the die block. to form Spinneret body 52 may include a minimum of 10 nozzles 58 to several thousand nozzles 58 . For a commercial size line, the number of nozzles 58 in the spinneret body 52 may range between about 500 and about 10,000. The number of rows may vary, and the number of columns may vary. Typically, the number of rows may be greater than 1, often greater than 5, and will be less than about 30, or even less than 15. Typically, the number of rows will be greater than 50, but may be greater than about 200 and less than 3500.

As described in US'334, the nozzles 58 are formed as capillary tubes that are inserted through openings in the spinneret body 52 to form a passageway for the molten polymer. Each nozzle 58 has an inner capillary diameter and an outer diameter. The inner diameter may range from about 0.125 mm to about 1.25 mm. The outer diameter of each nozzle 58 should be at least about 0.5 mm. The outer diameter of each nozzle 58 may range between about 0.5 mm and about 2.5 mm.

Typically, the length of the nozzle 58 ranges between about 0.5 and about 6 inches.

Since the molten polymer only needs to pass through the capillary of the nozzle, US'334 describes a tube that is fitted tightly to the spinneret body and is typically welded, which is described in more detail below in comparison with the present invention. As can be seen, it represents a significant difference.

The molten material 22, which may be a mixture of different polymers or a thermoplastic polymer of homopolymer type, is fed upstream of the die block 26, typically in an extruder (not shown), For propylene based polymers, it is typically heated to a temperature above its melting point, typically up to at least about 170°C, often up to about 210°C. Optionally, different polymers may each be directed to a different group of nozzles.

The polymer throughput through each nozzle 58 is described as “grams per hole per minute” (“ghm”). The polymer throughput through each nozzle 58 may range between about 0.01 ghm and about 4 ghm.

The die block 26 further includes a cavity 30 and an inlet 28 connected to the cavity 30, towards the polymer feed, and typically an upper part of the spinneret body. is located at (ie against gravity). The molten material 22 is conveyed along the polymer passageway from the inlet 28 towards the top of the spinneret body 52, and is also conveyed downward through the nozzle. Spinneret body 52 also has one or more gas passageways 32 formed therethrough for delivering pressurized gas (air) to air chamber 54 , which includes spinneret body 52 and air distribution plate 70 . It is essentially formed between A plurality of nozzles 58 extend downwardly from the spinneret body so that molten material in the form of filaments 86 exits the nozzle and die block from the nozzle tip 96 downwardly of the outer plate. 60) to flow through.

Also, a plurality of stationary pins 62 may surround the array of nozzles, are attached to the spinneret body and extend through the opening in the air distribution plate to the opening in the outer air plate.

Each retaining pin 62 is an elongated, solid member having a longitudinal central axis and an outside diameter. Each retaining pin 62 is secured to the spinneret body 52 and usually has a similar outer diameter to the polymer nozzle 58 . The outer diameter of each locking pin 62 must remain constant throughout its length. The dimensions of the outer diameter may vary. The outer diameter of each securing pin 62 may be at least about 0.25 mm, or at least about 0.5 mm, or at least about 0.6 mm, or even at least about 0.75 mm, and/or less than about 5 mm, or less than about 2 mm.

An air distribution plate (70) is secured to a spinneret body (52) having a plurality of openings. Each one of the first openings 72 receives one of the nozzles 58 . If retaining pins 62 are used, they are received in the second opening 74 and each of the third openings 76 is positioned adjacent to the first and second openings 72 and 74, respectively. When operating the process, pressurized gas, typically air, from the air chamber 54, an opening 72, which is a thin annulus around the nozzle, and also a small annulus around the retaining pin, if present. A small annulus is flowing along the air passage through an opening 74 and a third opening 76 which is the main passageway for air.

An external air plate 78 is secured to an air distribution plate 70 remote from the spinneret body 52 . The outer member 78 has a plurality of first openings 80 surrounding the nozzle 58 . A second enlarged opening 82 surrounds each retaining pin 62 , if present.

In operation, the molten material 22 (polymer) is extruded through each nozzle 58 , so that the axis of the capillary 60 and hence the direction of flow of the filaments 86 at the nozzle tip 96 . A plurality of filaments intended to be shrouded from ambient air with a pressurized gas (air) that is released through a first enlarged opening 80 formed in the outer member 78 at an essentially parallel predetermined velocity. (86) is formed.

If present, the pressurized gas (air) stream exiting the second enlarged opening 82 formed in the outer member 78 around the retaining pin forms another shrouding air stream, which also oriented essentially parallel to the axis, and thus also essentially parallel to the filament exiting the nozzle, isolating the filament 86 from the surrounding ambient air, as indicated by arrow 94 in FIG. 1 . ) is aimed at.

Although the technique of US'334 can be well used to provide a very useful nonwoven material, it is mainly due to inaccuracies induced by inserting the nozzle tube into the spinneret body and respective fixation. Therefore, it was observed that there are certain limitations. Even in the case of adjusting a plurality of nozzle tubes, which can be thousands, with maximum precision, not only at least thermal dilatation during insertion and welding, but also the weld itself, if applied, can build up over the width of the spinnerette block. They tend to cause minute variations and to induce deterioration in the handling of equipment and/or quality of the resulting product:

If the capillary is not precisely centered on the opening 82, the annular air passage around the nozzle will be eccentric, and thus the shrouding effect of the air will impede smooth air flow. This can cause bundling, ie, adjacent filaments blowing towards and sticking together, resulting in a larger fiber size distribution.

Also, despite sophisticated welding and machining tools, there is a high probability of burrs interfering with the smoothness of the flow towards the capillary.

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

Considering a plurality of protruding capillaries and a tightly fitting air distribution plate, the difficulty of proper mounting increases with this variant, but increases the number of nozzles in one mounting step. Thus, there is a practical limit to the y-direction extension of a single spinneret body - of about 500 mm (about 20 inches (in)) - and consequently of a complete die block.

Thus, when using such die blocks in large scale operation, the total y-direction extension can be 2 m, often more than 2.6 m, or even more than 5 meters, multiple die blocks needs to be used, which not only increases the handling complexity but can also affect the quality of the resulting product at least because of the y-directional edge effects of each block.

Also, considering the cleaning process, the relevance aggravated by the increase in deposition around the capillary inlet can be done in one direction, i.e. along the normal process flow direction. Typically, the cleaning process includes a pyrolytic treatment followed by treatment with pressurized steam or water. Also, ultrasonic cleaning, which is a generally preferred process for removing this pyrolytic treatment, will interact very negatively with the connection of the capillary tube to the spinneret body (ie welding or tight fitting). It can't be used properly because it can.

The principle of the spun-blowing process as known from US '334 has thus been described, FIGS. 2a to 2f being a spinneret block 152 , an air distribution plate 170 arranged in the same manner as described in the context of FIG. 1 . , illustrating the principles of the present invention by showing a die block 126 comprising an external air plate 178 and a cover strip 188 . Also shown is one row of a plurality of five nozzles 158 , also arranged in columns and rows forming an array of nozzles as described above. As described herein, the nozzle is oriented vertically along gravity. However, the orientation of the system may be such that the orientation of the nozzle is angled with respect to gravity, and one skilled in the art will readily adapt relative positioning terms such as "above" or "below" accordingly.

Optionally, the array of nozzles may include sub-arrays. Such sub-arrays may preferably include at least one row of nozzles, although not necessarily extending over the entire width of the die block.

In a first implementation of a die block comprising one or more sub-arrays as shown in FIG. 2G , at least one nozzle of the sub-arrays has an inner diameter of a nozzle, an outer diameter of the nozzle, and a length of the nozzle. substantially different from the nozzles of the different sub-array in at least one dimension selected from the group consisting of In this context, the term “substantially different” refers to a difference in each dimension of at least 5%, often greater than 10% thereof.

In another implementation, not exclusive to the other implementation, as shown in FIG. 2H , the nozzles of one sub-array are selected from the group consisting of polymer type, polymer flow rate, polymer pressure, and polymer temperature. In at least one of the selected features it can be connected to a first discrete polymer supply system adapted to supply molten polymer to a different sub-array from the molten polymer fed to a different sub-array. Optionally, the nozzle may be performed using co-axially positioned sub-capillaries to produce bi- or multi-component fibers. This sub-capillary is provided with each different immiscible polymer type.

FIG. 2A shows the elements in an assembled state (with the securing means omitted), whereas in FIG. 2B the spinnerette block 152, air distribution plate 170 and outer air plate 178 are in an exploded view. shown, and FIGS. 2C-2F show these individual elements.

The main feature of the present invention is that the nozzle 158 is not formed separately from the capillary tube and is not inserted into the holes of the spinneret body as shown in US'334. Also, the spinnerette body 153 and nozzle 158 are “unitary” forming a spinnerette block 152 made from a single piece of material. These include laser cutting, flame and plasma cutting, hole-punching, drilling, milling, lathing, picking and placing This can be readily accomplished by modern CNC machining techniques such as placing, sawing, and using these other techniques known in the art for CNC processing.

Referring to Figure 2c, preferably a metal, more preferably a piece of material exhibiting a tough homogeneous composition is selected as a spinneret block pre-cursor 210, which is formed in one piece. is shown as a dotted line circumscribing the spinneret body and nozzle to It can be prepared in a size that generally corresponds to the overall dimensions of a later spinneret block, or its outer dimensions can be shaped in-situ. .

Although not necessarily in the order listed, the various features of the spinneret block are not particularly limited, but are formed in parallel or continuous.

- inlet cavity 130 for molten polymer 122;

- air inlet and distribution chamber 132 (air supply means not shown);

- an array of nozzles 158 each representing an inner diameter 157 and an outer diameter 159 corresponding to the diameter of the capillary for molten fluid flow;

- Another optional securing holes (199).

These elements can be machined with extreme precision, particularly with respect to the size, position and orientation of the nozzle 158 . Also, once programmed, loading a spinneret block precursor into a CNC machining tool to initiate a machining program is a well-known manufacturing process.

Each nozzle 158 has an inner diameter 157 and an outer diameter 159 . The inner diameter may be greater than about 0.125 mm and/or less than about 1.25 mm. The outer diameter of each nozzle 158 is preferably about 0.5 mm, or greater than 1 mm, and/or less than about 2.5 mm. Typically, the length of the nozzle 158 is greater than about 20 mm and/or less than about 150 mm.

Thus, the spin block includes a polymer passageway from the inlet cavity 130 , where the filament is formed, through the capillary of the nozzle 158 and toward the nozzle tip 196 .

Also, due to this high precision, the nozzles 158 are precisely fitted through each nozzle opening 172 of the air distribution plate 170, and the nozzle openings in 172 in the air distribution plate are slightly larger than the outer diameter of the nozzles by 0.1 mm. may be less than, which may be below the annular gap.

Thus, the air flow from the air chamber 132 , defined by the spinnerette block 152 and the air distribution plate 170 , may be in different rows (ie, not visible in the particular cross-section shown in FIG. 2 ). . In addition, the nozzle will also fit very precisely to the nozzle opening 180 of the outer air plate and provide a very precise and concentrically formed annular portion around the nozzle 158 . In operation, this results in a very even annular air shroud surrounding the filaments 186 as they exit the nozzle tip 196 essentially parallel to the filaments, thereby preventing If not, the bundling of the filament is significantly reduced.

Figure 2a also shows (alternatively or jointly) two options for creating an outer diameter curtain described in US'334. In a first option, the air passage openings 183 in the outer air plate are located around the array of nozzles. In a second option, stationary and solid pins 162 , also machined from the same spinneret block precursor, are connected from the spinnerette body through openings 174 in the air distribution plate 174 of the external air plate 178 . Extending into openings 182 , also allowing annular airflow around these fins, similar to the approach as described in US'334.

In addition, the present approach allows much easier fabrication when assembling die blocks by removing practical restrictions on the y-direction size of the die blocks, which are now made in accordance with the teachings of US '334 for a typical 500 mm diameter. can exceed die blocks, now 1000 mm, even 2600 mm (typically the size of a non-woven manufacturing unit in which such die blocks can be included), and even exceed 5000 mm. can

According to the present invention, using a single piece and a single die block over a much larger width, fiber formation and fiber laydown will be more homogeneous compared to having several smaller width die blocks assembled together. (homogeneous) will.

As shown in Figure 3, the present approach is that the change from capillary to spinnerette body can be performed with a radius 310 preferably greater than 0.1 mm, more preferably greater than 0.3 mm. provides another advantage. This will increase the stability and positioning of the nozzles compared to performance according to US'334.

Figures 4a and 4c show an exemplary implementation to reduce, if not avoided, these negative impacts of sharp edges around the opening of the capillary of the nozzle.

In Figure 4a, as a first implementation of a nozzle according to the present invention, a nozzle 158 is typical in the above cited US'647 showing the inner capillary diameter 157 of a capillary 160 for molten fluid flow. Nozzle as described with This inner capillary diameter may range between about 0.125 mm and about 1.25 mm. At its upper end, the capillary 160 is chamfered in a chamfering section 333, which preferably has a chamfering angle of 30° to 60°, which Allows change from capillary to chamfering opening diameter 337 . This chamfer opening diameter may range from greater than about 2 mm or 4 mm to less than about 20 mm or 14 mm, or less than 8 mm. The outer diameter 159 of the lower section 335 of the nozzle 158 should be at least about 0.5 mm, and may range from about 0.5 mm to about 2.5 mm.

Typically, the overall length 330 of the nozzle 158 ranges from about 20 mm to about 150 mm. The length 334 of the lower section 335 may be between about 10 mm and about 140 mm. The length of the chamfered section from the first diameter to the second diameter may be from about 2 mm to about 4 mm or greater.

Optionally, as shown in FIGS. 4B and 4C , the change from the capillary diameter to the chamfer aperture diameter can be determined by a radius, or other gradually changing curve, such as an elliptic or parabolic shape. transitioning curve). As used herein, the term "chamfering" is intended to include the executions mutatis mutandis, which only slightly modify these necessary parts, and the chamfer angle is intended to correspond to the endpoints of a radius or smooth curve. . Another implementation in accordance with the present invention is shown in FIG. 4D , which shows a nozzle 158 having a capillary 160 representing an inner capillary diameter 157 at the nozzle tip. The nozzle also has a chamfered opening diameter 337 towards the polymer feed, which chamfers towards the pre-hole diameter 341 , which is a capillary beyond the pre-hole length 344 . Represents the pre-hole of the lee, and also chamfering towards the inner capillary diameter 157 . In this implementation, the length of the nozzle is defined in addition to the length of the capillary, the length of the pre-hole, if any, and the length(s) of the chamfer section(s).

It may be performed for one or both of the chamfering, as described with respect to FIGS. 4A , or may be performed with a radius as described with respect to FIGS. 4B and 4C .

Optionally, and often preferably, the spinnerette block 152 may include a pre-hole 340 , reference may be made to FIG. 4D , which shows only one nozzle. These pre-holes are positioned upwardly and precisely aligned with the axis of the capillary 160 of the nozzle 158 . The pre-hole may exhibit a diameter of 1.5 to 4 times the diameter of the capillary, and may preferably exhibit a length of about 2 mm to about 20 mm. Preferably, the change from the pre-hole 310 to the capillary 160 is carried out in a gradual fashion, for example with a chamfer angle between 30° and 60° at the inlet, and in the direction of the capillary. .

The pre-holes provide a smoother flow of material molten into the capillary 160 from the cavity, which in turn will broaden the opportunity for a wider process window for the process.

Accordingly, in a second aspect, the present invention relates to operating equipment as described above in a process with a wide process window, which is mainly dictated by:

- the pressure of the molten polymer in the cavity;

- the temperature of the molten polymer;

- the diameter of the capillary;

- the length of the capillary; and

- material properties of the molten polymer, expressed by the Melt Flow Index (MFI). This can be determined by ASTM D1238 and ISO 1133, for polypropylene as a polymer that can be treated appropriately with current equipment and processes, in units of gram per 10 minutes at 210 °C and a load of 2.16 kg. is appropriately expressed as

As a comparative example, the equipment and process described in US'334 may represent:

- capillary inner diameter of 0.46 mm;

- capillary length of 24 mm; and

- Accordingly, an L/d ratio of about 52 (L/d ratio).

It is preferably operated at a temperature of about 210° C. with a back pressure of 50 to 70 bar for a molten polymer having an MFI of less than about 500 [g/10min @ 2.16 kg load]. To achieve comparable fiber dimensions and properties, the equipment of the present invention is exemplarily shown as follows:

- capillary diameter of 0.46 mm;

- capillary length of about 18 mm;

- a pre-hole diameter of about 1.2 mm;

- a free-hole length of about 6 mm (including 60° chamfering at the inlet and at the change to the capillary); and

- L/d ratio for the later capillary of about 39. This would also make it possible to use polypropylene polymers that exhibit an MFI of about 500 [g/10 min @ 2.16 kg load] with a back pressure significantly lower than 50 bar.

One advantage of subjecting the polymer to low back pressure is that the reduction in mechanical stress results in the production of stronger nonwovens.

That is, the present invention can provide equipment capable of exhibiting a lower L/d ratio, which exhibits - for a given MFI - flow resistance, and thus in a wider process window for MFI and back pressure. make it work

Also, the smoother flow of the polymer from the cavity to the pre-hole 340 for the molten polymer 130, preferably in the chamfering, results in a smoother flow of the polymer around the inlet, and thus the turbulence of the polymer around the inlet. It significantly reduces the subsequent polymer residue deposition, allowing longer operating times without interruption for cleaning.

Also, as shown in FIG. 5 , in a very preferred implementation of the present invention, all three element spinneret blocks 126 , air distribution plate 170 and outer air plate 178 are as shown by dashed line 510 . As such, it is manufactured from a single block of material, whereby first stage slabs are separated, from which individual elements are formed by CNC machining as described above.

In another aspect, the present invention enables simpler maintenance of equipment. First, since the spinneret block 152 is now unitary and made of the same material, it can easily withstand ultrasonic treatment without the risk of damaging the connection between the nozzle 158 and the spinnerette body 153 . .

Second, since the nozzle and spinneret body are much sturdier than designs as described, for example, in US '334, the equipment can also be cleaned with water and/or steam at higher pressures, and can also be manufactured It can be cleaned along the direction as well as in the reverse direction (back-flushing).

Accordingly, cleaning of the spinnerette block according to the present invention may comprise the following steps:

- burning respectively pyrolyzing residues;

- ultrasonically loosening the pyrolyzed residue; and

- flushing the ultrasonically loosened pyrolysis residue along the flow direction of the molten polymer and/or optionally in a flow direction opposite to the pressurized water or steam.

Claims (10)

A die block for forming meltblown filaments, comprising:
at least one molten polymer supply;
air supply;
spinneret block - The spinneret block comprises a spinneret body comprising a polymer supply side, and a plurality of nozzles forming an array of nozzles. Included - ;
an air distribution plate comprising openings;
an exterior air plate comprising an opening;
cover strips; and
securing means
including,
the spinnerette block, the air distribution plate, the outside air plate, and the cover strip are mounted in this order and secured by the fixing means,
the nozzle protrudes through a corresponding opening in the air distribution plate and also through a corresponding opening in the outer air plate;
a polymer passage is formed for molten polymer passing through the nozzle from the polymer supply side of the spinnerette body; and
an air passage is formed for air passing through openings in the air distribution plate and the external air plate from the air supply;
wherein the openings in the nozzle and the outer plate are adapted to allow molten polymer to exit the nozzle, the air flowing through the openings in the outer air plate being essentially parallel;
The spinnerette body and the nozzle are characterized in that the unitary (unitary),
die block.
According to claim 1,
- the inner diameter of said nozzle is less than about 1.25 mm, preferably less than about 0.8 mm;
- the outer diameter of the nozzle is less than about 2 mm;
- said nozzle exhibits a length of less than about 50 mm;
- said nozzle exhibits a length greater than about 10 mm;
- said nozzle exhibits a length/diameter ratio (L/d ratio) of less than about 50; and
- said die block exhibits a CD width greater than 250, preferably greater than 1500, even more preferably greater than about 2000 mm or greater than 5000 mm
Satisfying at least one of the conditions selected from the group comprising
die block.
3. The method of claim 1 or 2,
Pre-holes in the block
further comprising,
The pre-hole is
extending towards the capillaries from an upper surface located towards the supply of molten polymer in the form of countersinks to the capillary of the nozzle;
preferably having a chamfering angle between 30° and 60°,
Preferably, it represents a diameter of 1.5 to 4 times the inner diameter of the capillary,
preferably greater than about 2 mm, preferably greater than about 4 mm,
preferably less than about 20 mm, preferably less than about 14 mm, more preferably less than about 8 mm, and most preferably less than about 6 mm,
die block.
4. The method according to any one of claims 1 to 3,
wherein the transition of the nozzle relative to the base of the block exhibits a radius greater than about 0.1 mm, preferably greater than about 0.3 mm;
die block.
5. The method according to any one of claims 1 to 4,
The array of nozzles is
- the inner diameter of the nozzle;
- the outer diameter of the nozzle; and
- the length of the nozzle
at least two sub-arrays comprising nozzles different from nozzles of a different sub-array in at least one of dimensions selected from the group comprising:
A die block comprising a.
6. The method according to any one of claims 1 to 5,
The array of nozzles is
at least 2 sub-arrays
further comprising,
Each of the sub-arrays,
- polymer type;
- polymer flow rate;
- polymer pressure; and
- polymer temperature
connected to a separate polymer supply system configured to supply molten polymer to the sub-array different in at least one of the features selected from the group comprising:
die block.
A method for the manufacture of a spinnerette block comprising a plurality of nozzles and a spinnerette body for use in a die block, the method comprising:
- providing an integral spinneret block precursor, preferably steel; and
- from the one-piece spinnerette block material
o Nozzle; and
o air flow channels
machining the
including,
The method of claim 1, wherein the machining is high precision CNC treatment.
A method for the manufacture of a die block comprising a spinnerette body and a plurality of nozzles, an air distribution plate, and an outer air plate, the method comprising:
providing an integral die block precursor, preferably steel; and
from the one-piece die block precursor
o ■ Nozzle; and
■ air inlet and distribution chamber
A spinnerette block comprising;
o Air distribution plate; and
o Outside air plate
step of machining
including,
wherein the machining is high precision CNC processing.
In the process method (Process) for cleaning the melt blowing apparatus (melt blowing apparatus),
providing equipment according to any one of the preceding claims;
combusting polymer residues;
removing the burned residue with ultrasonic waves; and
Blowing pressurized water or steam through the nozzle.
A process method comprising a.
A process method for forming a nonwoven web comprising meltblown fibers comprising:
- providing the equipment according to any one of claims 1 to 6;
- providing a thermoplastic polymer for forming MB fibers, which exhibits a Melt Flow Index (MFI) of 30 to 2000; and
- forming the filaments by applying, in the polymer feed, a pressure of less than 70 bar, preferably less than 50 bar, more preferably less than 45 bar
A process method comprising a.

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