JP2002543298A - Equipment for manufacturing nonwoven webs and methods of using such equipment - Google Patents

Abstract

(57) An apparatus for producing a nonwoven web and a method of using such an apparatus, comprising supplying at least a molten organic polymer to a spinneret (2) for producing a fiber curtain (3). One extruder (1);-a cooling zone (4) for hardening at least the surface of the extruded fibers;-having the form of a narrow chamber with a rectangular cross-section, in which a high-speed airflow is applied to the textile curtain. A suction device (5) for acting to draw said fibers, and means (6) for diverting and slowing down the air flow at the outlet of the drawing slot and evenly distributing the fibers on the receiving belt (7). And means for performing the different manufacturing steps, i.e. the extrusion means, cooling means, fiber drawing assembly and distribution means are separated from one another and the production to be achieved (the nature of the polymer, the production Count of fiber elements, not only by the web weight per unit area of) produced, and also during the rising process of production, wherein the individually capable adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] Technical Field The present invention generally is called by the common name for spunbond, to an improvement of the equipment for producing the nonwoven webs are formed by a continuous synthetic fiber.

[0002] The invention also relates to a method of using such equipment.

The preparation of the prior art spunbond type nonwoven web has a history of decades, and is generally composed of the following: - the hole through a spinneret which is opened, it melted organic polymer Extruding to form bundles or curtains of fibers; thereafter, orienting the extruded fibers by drawing with one or more fluid jet devices, especially compressed air devices; Receiving the fiber bundle in the form of a web on a conveyor belt. It should be noted that the belt is generally placed under the action of a suction source and the speed of the belt is adjusted according to the properties of the web desired to be produced, in particular the weight per unit area.

After production, the web is coalesced, for example by sizing or calendering, preferably by thermal calendering, to bond the fibrous elements together.

[0005] Other coalescing methods are also possible, for example, needling methods (conventional or with a fluid jet) and / or adding an adhesive to the surface or inside the web.

[0006] Numerous proposals have been made for producing such webs, all aimed at making the web or sheet as uniform as possible with high productivity,
And, where possible, they are increasingly aiming to be composed of very fine fiber elements with a count of less than 2 dtex.

[0007] Among the earliest documents for producing such webs, Patent GB-A-93
2 482, according to which the fibers are extruded and, after leaving the spinneret, move through the air a distance sufficient to allow at least the surface of the extruded fibers to solidify. , And then directed to a suction and extension nozzle that produces a high velocity annular air flow.

[0008] To loosen the fiber bundles, the fibers are provided with an electrostatic charge. This static electricity can be obtained from static electricity generators that provide a corona-type effect, located upstream and downstream of the suction nozzle.

Among the various parameters that must be considered to produce a high quality web are the spinneret outlets, depending on the extruded polymer, to even out the accumulation on the receiving belt. It is necessary to adjust the distance between the fiber and the inlet of the drawing system, the speed of the air in the nozzle, and also the speed at which the fibers exit the nozzle.

[0010] In order to solve the problem of uniform accumulation on the conveyor belt, US Pat.
In -3 286 896, the suction device is configured as a long, narrow chamber with a rectangular cross section,
Such an assembly constitutes an extruded fiber suction chamber at the inlet,
It is proposed to provide an additional chamber into which low-pressure air is subsequently blown and a long passage in which high-speed air flows. In order to improve the distribution of the fibers on the receiving surface, an air flow diverting assembly for slowing down the air flow is arranged at the outlet of the drawing chamber, thereby enabling an improved distribution of the fibers.

A system has been proposed in which the fibers pass through the interior of a rectangular suction and drawing chamber, which, if possible, has the width of an extruded fibrous web.
It is described in particular in French patent 2,064,087 (corresponding to patent US Pat. No. 3,802,817), in which the fiber curtain is stretched under the action of a high-speed air flow on both sides.

Further, patent US-A-4 064 605 describes an improvement to such a technique, in which the fibers are actually brought into the drawing chamber by applying a stream of air across the fiber bundle. An additional assembly is provided to cool the fibers before they are introduced.

Finally, the technique is developed to expose the fibers to the air at the spinneret outlet by means of an integrated assembly that allows for cooling, drawing and accumulation of the fibers on the belt. Instead, equipment is manufactured in which the fiber is drawn at the outlet of the spinneret and transported to a receiving belt, which is disclosed in US Pat. No. 4,627,811 and US Pat.
9

Although the configuration of such equipment makes it possible to obtain a nonwoven sheet having a low weight per unit area and good uniformity, this apparatus is complicated and its use is difficult.

Further, in such equipment, the cooling condition at the discharge port of the spinneret is such that the polymer and
It lacks adaptability because it varies according to the fiber count to be produced and the properties of the final web and cannot be easily adjusted.

Furthermore, such equipment is not suitable for producing very fine fibers.

Therefore, a fiber having a fine fiber, that is, a fiber having a count smaller than 2 dtex is produced with high productivity, that is, during the drawing process of the fiber, the fiber is completely and extremely uniformly drawn without being cut. To date, no satisfactory solution has been proposed for designing equipment for the production of spunbonded nonwoven fabrics.

In order to achieve high productivity, that is, to increase the polymer supply at the spinneret outlet, in part, increasing the drawing speed in the drawing slot, together with a high air flow rate, Means that the fibers need to be at a relatively high temperature before drawing to maintain their flexibility.

In addition, drawing a fiber with high productivity also means that the air flow can be reduced at the outlet of the drawing slot, thereby accumulating the fibers uniformly on the receiving conveyor and producing a high quality sheet. To achieve.

[0020] Here Summary of the Invention, can solve all the above problems, a new type of equipment for the production of nonwoven webs from continuous synthetic fibers been found, which form the subject of the present invention.

In general terms, the installation according to the invention is, in a conventional manner, of the type constituted by: feeding a molten organic polymer to a spinneret to produce a textile curtain At least one extruder;-a cooling zone for hardening at least the surface of the extruded fibers;-having the form of a narrow chamber of rectangular cross-section, in which high speed airflow acts on the textile curtain. A suction device for drawing the fibers, and means for deflecting the air flow at the outlet of the drawing slot to reduce the speed and to distribute the fibers uniformly on the receiving belt.

The installation according to the invention is characterized in that the means for performing the different production steps, ie the extrusion means, the cooling means, the fiber drawing assemblies and the distribution means are separated from one another and the production to be achieved (the nature of the polymer, It is characterized in that it can be individually adjusted not only depending on the number of fiber elements to be produced, the weight per unit area of the produced web, but also during the start-up process of production.

Such an arrangement goes against the technological development in the field, which is aimed at producing a fully integrated assembly for cooling, drawing and distribution of the fibers on the conveyor belt. However, by separating the different manufacturing steps from each other, especially in connection with the adaptability in use and the possibility of adjusting the production much more easily according to the yard count and the weight of the web to be manufactured, A number of advantages have been found to be obtained.

According to the invention, preferably and practically: the cooling zone and the fiber drawing zone at the outlet of the spinneret are composed of a plurality of basic modules arranged in parallel according to the width of the product. The opening system itself constitutes an assembly which extends over the entire width of the web to be produced; the cooling at the outlet of the spinneret comprises a plurality of continuous zones for exposing the fiber curtain to a transverse air flow. The speed and temperature of the air flow can be adjusted independently in each zone, the fiber drawing device has a suction slot, the width of which is The opening system, which is arranged at a distance from the outlet of the drawing system, changes the direction of the air flow in the transverse direction, so that the speed of the air flow and the speed of the fibers can be adjusted automatically. Reduced Rutotomoni consists of an assembly which facilitates the uniform integration onto a conveyor by removing the moment of bounces integrated on receiving conveyor, desirably, opening system
Combined with an assembly where the fibers are electrostatically charged before the fibers accumulate on the receiving belt, the assembly may be arranged immediately before the outlet of said opening system or integrated within the latter. The facility has means for controlling all sub-assemblies by computer,
Thereby, the speed of the production line can be automatically increased.

The present invention also relates to a method of using such a facility, which method has the following characteristics: In the start-up process, the air temperature in each cooling zone is increased from one zone to the next. And the velocity of the transverse air is adjustable in each zone, and in each of said zones is between 0.5 m / s and 3 m / s, the draw slot is kept at a distance -The production rate is then gradually increased and the parameters of the zone for cooling and heating the fibers are changed to do the following:-increase the speed of the air in the first zone and keep the temperature unchanged To increase the temperature of the second zone, to bring it to the level of the temperature of the first zone, and to increase the speed of air in this zone, Of the air in this area To increase the degree, - at the same time, by narrowing gradually the width of the drawing slot, to reach the rated operating value, gradually increase the stretching pressure.

It should be noted that in the method according to the invention, the air temperature in each cooling zone is generally in the range from 5 ° C. to 60 ° C.

The invention and the advantages provided thereby will be better understood from the following examples, which are given by way of non-limiting example and are illustrated in the accompanying drawings, in which:

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the installation according to the invention consists essentially of at least one extruder, designated by the general reference (1), wherein the extruder comprises, for example, A synthetic polymer such as polyamide, polyethylene, or polyester is supplied to the spinneret (2) to form a fiber curtain (3).

For reference, from a practical point of view, the spinneret has a width of 50
It may consist of 00 perforated plates with holes, for example 0.5 mm in diameter. These holes have a width of 140 m, for example, over 18 rows and at the outlet of the spinneret.
distributed over multiple parallel rows over m.

At the outlet of the spinneret, a cooling assembly (4) is provided which regulates the temperature of the fibers depending on the polymer, which, according to the invention, crosses the fiber curtain (3). It consists of three continuous zones (4a, 4b, 4c) for the application of a typical air flow, the speed and the temperature of the air flow being adjustable.

For reference, the length of this cooling zone is about 1200 mm, and the temperature and speed of each zone decrease from the first zone (4a) to the third zone (4c).

The temperature of the air in this zone is generally between 15 ° C. and 60 ° C., and the velocity of the transverse air itself is between 0.5 m / s and 3 m / s.

Downstream of this cooling zone is arranged the actual drawing assembly (5), which has a slot (6) in the form of an enclosed housing, in which 0.5 ft of air is contained. From 1.5 bar to 1.5 bar.

Generally speaking, such a stretching system may be FR 1 582 147 or GB 932 482
(FIG. 3), which provides for the suction of the textile curtain and its traction by high velocity airflow to enable the drawing to be performed.

As can be seen from FIG. 3, which schematically illustrates such a drawing assembly (5), the drawing assembly (5) is constituted substantially by the actual drawing slot (10) and comprises a collecting device ( Air coming from 11) is introduced into this chamber (10) through a distributor (12) and an acceleration chamber (13).

However, such a suction / stretching assembly is preferably configured such that the width (F) of the slot (10) is changed during operation of the installation, whereby, on the one hand,
It makes it possible to adjust the flow rate of the air flow, thereby adjusting the fineness of the count desired for production and, on the other hand, facilitating the rising movement as explained below.

Generally, for the production of fibers having a count between 1.5 dtx and 3 dtx, the width (F) of the slots is between 3 mm and 10 mm, and the spacing between the slots is It can be increased to 25 mm during the process.

At the outlet of the drawing assembly (5), the fiber bundle (3) is placed on a receiving belt (7)
It is discharged not directly as described in FR 2 064 087 or US 4 064 605 but through an assembly (6) which redirects and decelerates the air jet leaving the slot (5). As a result, the textile curtain is opened, and these fibers are received by the belt (7).
).

Such an assembly may be, for example, in the form of a slot with a divergent wall.

Furthermore, in order to facilitate the spreading of the fiber bundle and the distribution on the receiving surface not to be mottled, these fibers are separated by a “corona” type system, which is connected to a distribution element (6). It may be charged electrostatically in a manner similar to the teaching of GB 932482.

If appropriate, the means for electrostatically charging the fibers may be integrated at the entrance of the divergent wall of the distribution element (6).

[0042] In the type of equipment depicted in the examples accompanying drawings, nonwoven web composed of continuous fibers made from polypropylene, in the present case 38MS
R. The polymer is melted in an extruder with five melting zones and, at the extruder outlet, is filtered by a filter constituted by a stainless steel mesh and led to the actual spinneret (2).

To do this, the machine has two spinnerets (1) arranged in series, each of which has 5000 holes with a diameter of 0.5 mm per meter width. .

Further, according to the present invention, each of the cooling zone (4) and the stretching zone (5) is 50 c
It is preferably constituted by a plurality of basic modules having a width of m.

On the other hand, the distribution element (6) itself, which is arranged at the outlet of the stretching zone (5),
It has a continuous slot extending the entire length of the equipment and has the shape of a divergent nozzle, the width of which is 15 mm where the fibers face the area leaving the slot (5).
And 100 mm at a position facing the receiving belt (7).

The distribution element (6) may, if appropriate, be combined with additional means for electrostatically charging the fibers, whereby the dispersion of the fiber bundles and the receiving belt of these fibers ( 7) The above distribution is improved.

This production line is started at a low production rate with the polymer supply set at 0.2 g / min per hole.

During this stand-up process, three continuous sections (4
a, 4b, 4c), the following parameters are maintained between the heating zones, in the course of which the extruded fiber bundles (3) meet the following conditions: In the first place, they are exposed to the transverse air flow leaving each of these zones:-Zone (4a)-Air temperature: 35 ° C-Air velocity: 1 m / sec-Zone (4b)-Air temperature: 20 ° C -Air velocity: 1 m / sec-Area (4c)-Air temperature: 15 ° C-Air velocity: 0.5 m / sec.

In this rising cooling step, the width (F) of the stretching slot (5) is set to 25 mm and the air pressure injected into said slot is set to 0.3 bar.

The stretched bundle passes at the outlet of the stretching slot (5) into a system (6) for opening and distributing said bundle, said system (6) having the shape of a divergent nozzle. The opening has a width of 20 mm at the entrance and a width of about 100 mm at the bottom.

During this rising step, the polymer is collected on the conveyor belt (7) by a “leader”. The leader is spread over the belt to prevent drops of molten polymer from hindering the movement of the belt.

When a uniform supply of polymer is established at the spinneret, the production speed of the production line is gradually increased.

During this speed increase period, the parameters of the zone (4) for cooling / heating the fibers are gradually changed. -Increasing the air velocity in the first section (4a) to 1.5 m / sec without changing the temperature;-increasing the air temperature in the second section (4b) to 30 ° C. The speed is 1
. Increase the temperature of the air in the third zone (4c) to 20 ° C. and increase its speed to 1 m / sec.

Such treatment ensures that at least the surface of the extruded fibers is solidified, so that the fibers do not adhere to each other when they enter the drawing slot (5).

The width of the stretching slot (5) is 25 mm during the rising period.
From 5 to 5 mm, while the stretching air pressure is gradually increased from approximately 0.3 to 1 bar.

During this period, the temperature of the stretched air is controlled and kept constant.

By such a treatment, it is possible to produce with different properties of polymer by equipment in which different areas are fixed relative to each other, and about 1.7 dte.
Production of ultrafine fibers of x or less is also facilitated.

The reason is that by gradually increasing the temperature of the air used in the last two cooling zones (4b) and (4c), it is possible to increase the plasticity of the polymer, thereby facilitating its stretching This makes it possible to make the fibers even thinner.

Finally, the ability to adjust both the drawing air pressure and the drawing slot width during operation allows for optimization of drawing conditions, which naturally results in a high production rate and a fine fiber Production is also realized.

The arrangement of the opening system downstream of the drawing system, independent of the drawing system, also promotes a constant and uniform accumulation of the fibers on the receiving surface (7).

The reason for this is that at the exit of the draw slot, about 5000 m / mi
When producing ultrafine fibers at a high fiber speed of n, the apparatus (6) used in the installation according to the invention reduces the speed of said fibers and the speed of the air flow exiting the drawing slot. This facilitates the distribution of the fibers on the conveyor belt by making it possible and thereby eliminating bouncing phenomena which tend to prevent a constant and uniform accumulation.

All the adjustments of this device are automatically activated and controlled by a process computer operating on the principle of so-called “fuzzy logic” and can take into account a large number of independent parameters.

In the example described above, it is possible to obtain fibers with a count of 1.7 dtex at a polymer feed rate of 0.65 g / min per hole.

The resulting sheets can weigh from 10 g / m ² to 150 g / m ² and are very uniform and for a variety of uses, such as hygiene products (baby diapers) and medical or industrial products. Can be used.

Although such equipment makes it possible to obtain ultrafine fibers, it goes without saying that even when the fiber count is large, the production volume of the production line can be significantly increased.

For reference, if 2dtex count fiber is produced in the above example, it would be possible to increase the polymer feed rate to 0.8 g / min per hole.

[Brief description of the drawings]

FIG. 1 is an overall view of equipment configured according to the present invention.

FIG. 2 cools the fiber temperature before the fiber is introduced into the actual drawing slot;
Or, more precisely, a schematic diagram showing details of the assembly for controlling the temperature.

FIG. 3 is a schematic view showing the overall structure of an extension slot.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extruder 2 Spinneret 3 Textile curtain 4 Cooling area 5 Suction device 6 Means for distribution 7 Receiving belt

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CR, CU, CZ, DE, DK, DM, DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR , HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA , ZW (72) Inventor Maggio, Rosario Italy, 21-21 Baresse, Via Sanbito, 79 F term (reference) 4L045 AA05 BA01 DA19 DA41 DA45 4L047 AA14 BA08 BA23

Claims (8)

[Claims] 1. at least one extruder (1) for feeding a molten organic polymer to a spinneret (2) to produce a fiber screen (3); and hardening at least the surface of the extruded fibers. A suction zone (5), which has the form of a narrow chamber with a rectangular cross-section, in which a high-speed air flow acts on the textile curtain to draw said fibers; At the exit, the direction of the air flow is deflected and decelerated, and the fiber
7) means for uniformly distributing on the non-woven web production equipment comprising: (6) means for performing different production steps, ie, extrusion means, cooling means, fiber drawing assembly and dispensing means. Not only depends on the production to be achieved (the nature of the polymer, the count of the fibrous elements produced, the weight per unit area of the web produced), but also during the start-up phase of the production Equipment for the production of nonwoven webs, which can be individually adjusted. 2. A fiber opening system, wherein a cooling zone (3) and a fiber drawing zone (5) at a discharge port of a spinneret are constituted by a plurality of basic modules arranged in parallel according to the width of a product. 2. The installation according to claim 1, characterized in that it consists of an assembly extending over the width of the web to be produced. 3. An assembly (4) having a plurality of continuous sections (4a, 4b, 4c) for cooling at the outlet of the spinneret (2) to expose the textile curtain to a transverse air flow.
3. The installation according to claim 1, wherein the speed and the temperature of the air flow can be adjusted independently in each zone. 4. 4. The fiber drawing device (5) has a suction slot (F), the width of which can be adjusted automatically according to the production on the machine. The equipment according to any one of the above. 5. A fiber opening system (6) spaced from the outlet of the drawing system to redirect air flow laterally to reduce air flow velocity and fiber velocity. 5. An assembly according to claim 1, comprising an assembly which facilitates uniform stacking on the conveyor by removing the bounce at the moment of stacking on the receiving conveyor (7). Equipment. 6. The fiber opening system (6) is combined with an assembly for electrostatically charging the fibers before they are collected on a receiving belt.
Equipment described in. 7. The method according to claim 1, further comprising means for controlling all the sub-assemblies by a computer, whereby the speed of the production line can be automatically increased. Equipment as described in one. 8. The method of using an installation according to claim 1, wherein, during the start-up step, the air temperature inside each of the cooling zones (4a, 4b, 4c) is reduced by one. From one section to the next, the velocity of the traversing air is adjustable in each section, and in each of said sections is between 0.5 m / sec and 3 m / sec, and the draw slot is The production rate is then gradually increased, the parameters of the zone (4) for cooling and heating the fiber are:-increasing the speed of the air in the first zone (4a), Maintaining the same, increasing the temperature of the second zone (4b) and bringing it to the level of the temperature of the first zone,
Increasing the velocity of the air in this area; increasing the temperature of the air in the third area (4c) to increase the velocity of the air in this area; The use method characterized by gradually narrowing the pressure to reach the rated operating value and gradually increasing the stretching air pressure.