EP4678799A1

EP4678799A1 - Air-laying web forming equipment and process

Info

Publication number: EP4678799A1
Application number: EP24209250.0A
Authority: EP
Inventors: Fabio Zampollo
Original assignee: Coax Technologies Srl
Current assignee: Coax Technologies Srl
Priority date: 2024-07-12
Filing date: 2024-10-28
Publication date: 2026-01-14

Abstract

The present invention is an equipment and a process for forming fibrous webs by air-laying, as may suitably be part of a converting equipment or process for manufacturing articles such as bed pads, or wipes, or diapers, or feminine hygiene pads or incontinence articles.

Description

Field of the invention

The present invention relates to an equipment and a process for forming fibrous webs by air-laying, as may suitably be part of a converting equipment or process for manufacturing articles such as bed pads, or wipes, or diapers, or feminine hygiene pads or incontinence articles.

Background

Fibrous sheet materials, particularly fibrous sheet materials for absorbing fluids, are manufactured for many uses, for example they are incorporated into absorbent articles such as disposable diapers, incontinent bed pads and catamenial napkins as fluid absorption or fluid transmission and/or diffusion elements, for example, as absorbent cores that are intended to absorb and retain body fluids.
Dry laying and, more specifically, air laying processes are widely used to produce webs from dry fibers, which can in turn be used e.g., as sheet materials for absorbing fluids. Particularly, the air laying process refers to the formation of webs with a random fiber orientation. The fibrous sheet materials produced by air laying processes are soft, flexible and porous, and are particularly suitable for use as liquid absorbent structures in absorbent articles, such as disposable diapers, sanitary napkins, pantiliners, incontinent or bed pads, and wipes.
In US5527171 (Niro ), the deposition of air suspended fibers in homogeneous layers is described by using multiple rows of rotating impellers in a web forming head.
Similarly, US6233787 (Dan-Web / Advanced Nonwoven S/A ) shows an apparatus for uniformly distributing a disintegrated material on a fiber layer forming surface by a stirrer having impellers rotating at a short distance above a collecting surface.
US20030070262 (Oerlikon ) describes two air-lay stations placed one after the other serving for the dry production of a non-woven fiber web, the stations including a fiber feed duct, an air-lay forming head, a perforated screen as collecting surface, and a suction box for supporting the deposition of the fibers on the screen. A separate fiber source is part of each station.
Further, WO200004232 (M&J ) describes the production of a nonwoven web of fibers out of a fibrous material, such as cellulose pulp. The fibrous material is disintegrated by a hammer mill and deposited at the outlet of a forming head on an endless collection wire, thereby forming a web of fibers. Fiber aggregates, referred to as nits, are extracted from the forming head via a transport impeller and a second air duct. Furthermore, the nits are defibrated, i.e., de-agglomerated, and returned to the forming head.
Also WO2004106604A1 (Oerlikon ) aims at avoiding nits by employing a fiber distributor in a forming head at optimizing the rotational speed of the wings of the distributor.
Such production units are typically operated in an "off-line" modus, i.e., the webs produced thereon are prepared at a wide web width for interim storage in roll- or spool-form, or boxed ("festooned") and further transported to a converting place where these are fed into a process for forming articles, such as wipes, bed-pads and the like, including the cutting to size.
Such an approach induces several areas for improvement:

homogeneity of the web is always a concern and gets more relevant when lower basis weights are aimed at.
the fibers should be individualized as much as possible, i.e., the fibers should have little or preferably no connection to other fibers when they are laid down to form the web. Thus, it is desired to obtain maximum disintegration of the fibers as supplied and to maintain the fiber disintegration along the process by avoiding aggregation of fibers or forming of nits - but all this with minimized - or even no - damage to the fibers, such as breaking up fibers.
Preferably, the system should be adapted to allow handling of different types of fibers, such as various types of natural fibers or synthetic fibers.

Summary

In order to address such problems, the present invention is in a first aspect an equipment for forming a fibrous web exhibiting a machine (x-)direction, a cross (y-) direction and a height (z-)direction comprising

at least one fiber supply for fibrous material;
a continuous collection system
- moving along a machine or x-direction and exhibiting a width or cross-or y-direction, and a height direction perpendicular to both and aligned with gravity,
  comprising a foraminous surface, preferably a foraminous belt running over guide rolls,
- and comprising a vacuum suction system;
at least one forming head comprising
- a forming box comprising
- at least one infeed opening for receiving fibrous material from the at least one fiber supply, and
- an outlet oriented towards a surface of the continuous collection system;
- a fiber distribution homogenization unit comprising at least two fiber distribution homogenization tools, preferably impellers rotating around a vertical axis, the impellers preferably comprising at least two impeller blades;
a connection between the at least one fiber supply unit and the forming box of the forming head comprising
- connection piping;
- venturi effect restriction comprising a narrow venturi section and a widening section;
- a venturi air supply adapted to inject air into said venturi effect restriction and to adjust at least amount, temperature, and humidity of the air.

The equipment may further comprise a refiner unit positioned in the widening section of the venturi effect restriction, comprising at least one pair of rotors with each rotor being adapted to counter-rotate around a cross-directionally extending axis and comprising radially extending fingers, whereby the rotors of the pair of rotors are positioned z-directionally off-set from each other and whereby the fingers of the rotors are adapted to interdigitate.
The refiner unit of the equipment may comprise two pairs of rotating rotors, which are positioned x-directionally off-set from each other, and each two x-directionally off-set rotors are adapted to co-rotate, whereby preferably the fingers of the rotors are adapted to interdigitate.
The fiber supply unit of the equipment may be at least one selected from the group consisting of

a fiber bin comprising an outlet valve;
a bale supply and a fiber picking unit;
a fiber board roll supply and a fiber disintegration unit, preferably a hammer mill, more preferably a hammer mill rotating around a cross-directionally extending axis.

The fiber supply unit(s) of the equipment may comprise

a first fiber supply unit of a first fiber type, preferably comprising a fiber board roll supply and a hammer mill,
a second fiber supply unit of a second fiber type, preferably selected from the group consisting of
fiber bin and an outlet valve;
a bale supply and a fiber picking unit.

Optionally, the first fiber type may exhibit a fiber length distribution that is narrower than the fiber length distribution of the second type of fiber, wherein preferably the second fiber type comprises recycled fibers of the first fiber type.
Preferably, the length of the connection pipe from the fiber supply unit to the forming box on the machine direction is less than about 10 m, or less than about 5 m, or less than about 3 m.
In another aspect, the present invention is a process for forming a fibrous web on a foraminous surface of a web collection system moving along a machine direction. The process comprising the steps of

A - providing an equipment for forming a fibrous web as described herein above;
B 1- providing a supply of first fibers by the first fiber supply unit;
B2 - transferring the first fibers from the at least one fiber supply suspended in an air stream through the connection pipe towards a venturi effect restriction,
- thereby individualizing the short fibers optionally in a disintegration unit, if present;
C - injecting air from the air supply into the venturi effect restriction;
E - transferring the fibers from the venturi effect restriction toward an opening of the forming box of the forming head;
F homogenizing the x-y-directional distribution of the fibers in the forming head by the fiber distribution homogenization unit;
G - collecting the individualized fibers through the outlet of the forming head on a surface of the collection system, thereby forming a fibrous web;
H - transferring the fibrous web to a further processing step preferably a process step for forming absorbent articles,
wherein steps B to H are executed in the given order.

Preferably, the injected air in the step C is adapted to exhibit predetermined temperature, water content, pressure and mass flow, adapted to prevent agglomeration of the fibers.
Optionally, the process may further comprise step
D - after step C and before step E, comprising

providing a supply of second fibers by second fiber supply unit,
and wherein in step E) the fibers, comprising first and second fibers, are transferred from the venturi effect restriction toward an opening of the forming box of the forming head.

Optionally, the process may further comprise during step E of transferring the fibers from the venturi effect restriction toward an opening of the forming box of the forming head,
the following step of
E1 - refining the fibers in the widening section of the venturi effect restriction by guiding the fibers between interdigitating fingers of rotors of the refiner unit,
thereby de-agglomerating fibers which formed nits and clumps.

Brief description of the Figures

Fig. 1A and B show side and top views of an equipment according to the present invention.
Fig. 1C and D depict details thereof.
Fig. 1 E and F depict alternative details of an equipment according to the present invention.
Fig. 2 A to D depict a preferred execution of parts of the equipment according to the present invention.
Fig. 3A to B depict further preferred execution of parts of the equipment according to the present invention.
Fig. 4 shows a further option of an equipment according to the present invention.

The figures are schematic only, and not to scale. Same numerals refer to same or equivalent features or elements, single (`) or multiple (", "', ...) apostrophes indicate duplicate features, such a left and right or front and back, etc.

Detailed description

The present invention relates to an air-laying equipment and process for forming a fibrous comprising short fibers, such as natural or man-made fibers.
One type of preferred natural fibers include wood pulp fibers as may be formed by a variety of pulping processes, such as kraft pulp, sulphite pulp, thermomechanical pulp, and the like. Further, the wood fibers may be any of high-average fiber length wood pulp, low-average fiber length wood pulp, or mixtures of the same. One example of suitable high-average length wood pulp fibers include softwood fibers such as, but not limited to, northern softwood, southern softwood, redwood, red cedar, hemlock, pine (e.g., southern pines), spruce (e.g., black spruce), combinations thereof, and the like. One example of suitable low-average length wood pulp fibers includes hardwood fibers, such as, but not limited to, eucalyptus, maple, birch, aspen, and the like.
The fibers may be treated so as to allow optimization of processing and or absorbency properties, The term "treated" as used herein is understood to include any means of introducing the additive to the fiber and/or fibrous matrix, but not limited to, such as coating, spraying, printing, chemical modifications, wet-end additions applications to the fibers as well as blending untreated fibers with treated fibers.
Moreover, if desired, secondary fibers obtained from recycled materials may be used, such as fiber pulp from sources such as, for example, newsprint, reclaimed paperboard, and office waste, or recycled diapers, be it from factory scrap or be it post-consumer recycling.
Man-made fibers may be made from synthetic polymeric, typically thermoplastic material, such as polyolefins, especially polypropylene or polyethylene, or polyesters, or from modified natural materials, such as viscose / rayon, cellulose acetate, or polylactate, polybutyrate, polyvinyl-acetate or - alcohol and the like. Diameters may range from less than about 0.001 mm to more than about 0.2 mm and they come in several different forms such as short fibers (known as staple, or chopped), continuous single fibers (filaments or monofilaments), untwisted bundles of continuous filaments (tow), and twisted bundles of continuous filaments (yarn).
The fibrous material may be delivered as fibrous board or in fibrous sheet form. Fibers may also be delivered in bales, as may be opened prior to be used in the process according to the present invention, or also via bins into which lose fibers are fed and then fed to the further converting. Further, "roughly graded material" may be employed, wherein fibers are present as clusters of several hundred up to several thousand fibers in the roughly graded material.
It is an object of the present invention to dry-lay, or air-lay, such fibrous material to form fibrous webs for being converted into articles comprising such fibrous webs.
Within the present context, a "web" is a manufactured sheet or batt of randomly orientated fibers, bonded by friction, and/or cohesion and/or adhesion, excluding paper and products which are woven, knitted, tufted, stitch-bonded incorporating binding yarns or filaments, or felted by wet-milling, whether or not additionally needled. The basis weight of a web is usually expressed in grams per square meter (g/m² or gsm). A web made on an equipment or by a process according to the present invention may be transferred to further processing equipment or steps for the manufacturing of articles, such as - without limitation - absorbent articles such as wipes, bed-pads, diapers, feminine hygiene or incontinence articles. The present invention is particularly suitable to be employed for the forming of low basis weight webs, such as exhibiting a basis weight of less than about 300 g/m² or less than about 200 g/m² or even less than about 150 g/m².
In particular for such lower basis weights, it is important that the fiber formation is very homogeneous to provide consistent web performance properties, but also to provide a god quality impression to a consumer. Thus, it is highly preferred, that the basis weight is not fluctuating, and that no nits, clumps or spots are formed.
Fiber aggregates, as nits, clumps, or spots, are in contrast to "individualized" fibers, whereby the latter refers to fibers, which have no contact to neighboring fibers (such as when being suspended in an air stream) or - when such fibers are laid down from such an air stream onto the surface of a collecting device - for which there are essentially no bonding forces. Such bonding forces may be desired at a later stage in the manufacturing process, and may be created by compressing the web or by adding bonding agents, but at the formation stage of the web such bonding is undesired to achieve a homogeneous web structure, at least at a predetermined local region.
Nits are small tangled fiber bundles of typically about or less than about 4 mm² in size, which may decrease the quality of the non-woven web, primarily by deteriorating visual appearance. Often, more than about 100 nits/m² are considered acceptable, though it is more preferred to have less than about 50 nits/m², or less than about 10 nits/m² or even less than about 5 nits/ m². Among other factors, the occurrence of nits may be influenced by adjusting the properties of the transport air, such as water content.
Clumps are fiber aggregates that have a size of more than about 4 mm², but less than about 64 mm². As the clumps exist in a very compact form, these may deteriorate not only the visual appearance but also other quality parameters, such as absorbency. Whilst this might be compensated by increasing the supply of fibers by a quantity of fibers corresponding approximately to the mass of fibers tied up in the clumps, thereby increasing the cost of producing the web, other control mechanisms are preferred, like controlling the air flow, and especially the air temperature, for the transfer air during and after the disintegration step. Often, more than about 50 clumps/m² are acceptable, though it is more preferred to have less than about 20 clumps / m², or less than about 5 clumps / m², or even less than about 3 clumps / m².
Together, nits and clumps may make up for about 2 weight-% in the formed web, but preferably less than about 1.4 w-%, or less than about 1.0 w-%. It should be noted that the proper control of nits and clumps is even more important when the above describe "untreated" pulp is used, as the treatment additives are - among other purposes - often directed towards reducing formation of such aggregates.
Fiber aggregates of more than about 64 mm² are considered "spots" and are not desired to remain in the product to which the web is converted. Henceforth, the region of the web should be rejected, either as a portion of the web or as a defect product after converting the web.
The fiber supply, such as the fiber board, sheet, bale, or from a bin contains some nits already from the start. During the defibration process some of these fibers are opened and formed to good individualized fibers. But at the same time some other fibers are formed into nits - and often more new nits are formed than existing nits are opened.
The present invention is first explained by referring to Fig. 1 A and C, depicting exemplarily an equipment 1000 on which the process for forming a fibrous web 100 can be executed, exhibiting a machine (x-)direction (12), a cross (y-)direction (18) and a height (z-) direction (15).
The fibers may be supplied by various fiber supply units 1110. An exemplary first type of a fiber supply unit 1110 is shown in Fig. 1A to 1D as a roll of a compressed board of fibrous material 120 on an unwind stand 1111 to be fed directly into the fiber disintegration unit 1200 The disintegration unit 1200 aims a "individualizing" the delivered fibers, i.e., breaking up most, preferably all, of the fiber-to-fiber bonds. In a preferred execution, the disintegration unit 1200 is a hammer mill 1210, driven by a drive 1213, as such well known in the art. In the present context, it is preferred that the rotating axis 1218 of the disintegrator is not machine-directionally, and more preferably cross-directionally, oriented. In contrast to many conventional arrangements where the fibers are fed cross-directionally, this provides the benefit that the fibers do not need to change the direction of flow but are already on a machine directional path, easing the suspension in the transporting air. Alternatively, as depicted in Fig. 1E, a second type 1116 of a fiber supply 1110 may deliver fibers in a bale form 1116 from where the fibers are removed by a picking device 1117 for being fed pneumatically to the forming head 1100. An even further third type of fiber supply is depicted in Fig. 1F, showing a bin 1118 of accumulated, relatively loose fibers 130, which are delivered to the piping such as by a rotary valve 1119.
As will be discussed in more detail herein below, more than one fiber supply units may be comprised in the equipment, e.g., to allow use of various fiber supplies, such as different types of fibers or different delivery or packaging formats.
The fibers from the fiber supply units 1110 are delivered to the forming head 1100 via pipe connections 1400 for transferring the individualized fibers in a fiber suspension air stream to a web forming unit 1100. Preferably the length 1405 of the piping 1410 is less than 5 m, or less than 3 m, or less than 2 m, or even less than 1m. The short length carries the advantage of minimizing the forming of nits or clumps, i.e., re-agglomeration of previously individualized fibers. This benefit is enhanced by maintaining the overall direction of movement of the suspended fibers generally along the machine direction of the equipment.
The transport of the fibers and their individualization is essentially induced by including a venturi effect restriction 1420 into the connecting pipe 1410, where air from an air supply 1300 is blown along the flow direction of the fibers towards the web forming head 1100, thereby sucking air from the disintegration unit 1200, thereby maintaining the individualization of the fibers and avoid formation of nits. Via the air supply 1300 the amount, temperature, pressure and humidity (water content) are controlled. The adjustment of these parameter, especially of the temperature and humidity, further reduces the tendency to form nits. The venturi effect is indicated in Fig. 1 by longer small arrows indicating the air flow within the piping 1410 downstream (in the figure right) of the venturi effect restriction 1420 compared to the upstream (in the figure left) side. Fig. 1A and C show the pipe with the venturi effect narrowing 1420 with a first, narrowing section 1422, where the cross-section is reduced towards the narrowest section 1425, from where it is widening again in the widening section 1428, with the sections being executed with straight walls. However, whilst this option is easily to construct, it is often preferred to have smoothly curved section, as schematically indicated in Fig. 1D. The end nozzle 1318 of the air supply is positioned in or close to the narrowest section 1425 of the venturi effect restriction. In the exemplary execution as indicated in Fig. 1B, the end nozzle 1318 is a slot nozzle, as may extend over the full width of the venturi effect restriction 1420. A skilled person will readily realize, that other executions for the end nozzle, such as multiple circular nozzles, may be employed.
This arrangement, with only one fan being required for the air supply 1300, is in contrast to conventional designs, where - in particular for longer distances between fiber supply, disintegration and forming units, a first fan is employed just after the disintegration, and possibly a further fan just prior to the forming unit.
Yet a further optional, and often preferred execution of the present invention includes a further tool for increasing or maintaining the individualization of fibers, i.e., disintegrating poorly separated fibers and avoiding re-agglomeration, i.e., avoiding forming of nits, clumps or spots.
To this end, reference is made to Fig. 2A to D, showing a further disintegrating tool 1350, hereinafter referred to as "refiner unit", which is integrated into the widening venturi section 1428. Such a refiner unit 1350 comprises at least two rotors 1360'. 1360", preferably at least two pairs of rotors 1360', 1360", and 1360‴ and 1360"", respectively. Each rotor 1360 comprises at least two, preferably at least four rows of radial fingers 1365, which are preferably equidistantly arranged along the rotating axes 1362', 1362",... . Rows of fingers may be parallel, but may also be curved vs. CD.
As exemplarily indicated in Fig 2A and C, a first pair of rotors 1360', 1360" is positioned such that the axes 1362' and 1362" are essentially parallel and z-directionally spaced apart from each such that the fingers 1365' and 1365" engage without blocking at the rotation. The direction of the rotation is counter-rotating, such that the fingers create a machine directional central draft of the air with the suspended fibers between them. Preferably, as shown in Figs. 2 a further pair of rotors 1360'" and 1360ʺʺ is positioned machine and flow directionally downstream of the first, with axes 1362'" and 1352ʺʺ parallel to each other and to the ones of the first pair, whereby the fingers of the second pair engage with each other, but also with the fingers of the first pair.
Whilst the radial extension of the fingers 1365 of all rotors 1360 may be the same, it is preferred that the fingers 1365‴ and 1356"" of the second pair are longer than the ones 1365' and 1365" of the first pair, such that the distance of the axes is slight larger than the length of the fingers of the second pair. As indicated in Fig. 2B, the rotation of the second pair of rotors is such that the z-directionally "upper" rotors 1360', 1360'" rotate in the same direction and the "lower" rotors 1360", 1360 ʺʺ rotate also in the same direction, but opposite to the upper ones.
Such an arrangement is particularly useful in the widening section 1428 of the venturi effect restriction 1420, as the larger, downstream rotors create even a further draft for suspending and individualizing the fibers in the air.
Yet a further execution of the present invention comprises two concurrent infeeds of fibers, see Fig. 3 A to C. Whilst in Fig. 1 and 2, the infeed of fibers is depicted as coming from fiber board (Fig. 1 A to D) or from a bale (Fig. 1E) or bin supply (Fig. 1F), Fig. 3 depicts a first fiber supply, here exemplarily shown from fiber board roll unwind 1111 delivering first fibers 130', a second fiber supply, here shown from bales 1116 by a bale picker 1117 delivers second fibers 130" into the venturi effect restriction 1420, preferably just after the end nozzle 1318 of the air supply 1300, thus close or into the narrowest section 1425 of the venturi restriction 1420.
Such a set up may be particularly preferred, if the two types of fibers 130' and 130" are different, especially, if the first fibers are "virgin" fibers 130', i.e., are pure fibers as coming from the fiber manufacturing, whilst the second fibers 130" are recycled fibers, as may come from the separation of off-target factory scrap or even from post-consumer recycled products.
Typically, though not necessarily, the virgin fibers 130' exhibit a fiber length, as may be determined by well-known methods such as using a Kajaani fiber analyzer, that is longer than the one of recycled fibers 130" of the same fiber type, as the recycling process may create some damage to a fraction of the fibers, and the resulting fiber mix 130 typically exhibits a wider fiber length distribution than the virgin pulp.
When considering exemplarily Northern Softwood Kraft fibers as virgin fibers 130', these may exhibit a virgin fiber length average of about 2.5 mm, with a fiber distribution range for 99 w-% of the fibers of between 2.2 mm and 3.0 mm. However, recycling of fibers may shorten fibers 130" to a weight average of less than about 2.2 mm, ranging from less than 2.0 mm, or less than about 1.8 mm to about 2.5 mm for the undamaged fibers. Consequently, the fiber mix 130 may exhibit a fiber length range of from about 2.0 mm or less than about 1.8 mm as the lower limit of the recycled fibers 130" to about 3.0 mm, as the upper limit of the virgin fibers 130', and the average fiber length may be reduced whilst the fiber length distribution may be widened.
An even further enhancement of this approach combines the addition of the dual types of fibers with the refiner approach as discussed in the above. Referring to Fig. 3C, refiners in analogy to the ones as discussed in the context of Figs. 2A to D, are combined with a second fiber infeed, here exemplarily shown as a fiber bale supply 1116. This provides particularly good intermixing of the first (130') and second (130") types of fibers to form a very homogeneous fiber mix 130.
The various options for providing fibers 130 suspended and well individualized in the transfer air, are delivering the fibers towards a forming head for forming the airlaid web 100.
Referring exemplarily to Fig. 1A and B, the forming head 1100 may comprise a forming box 1101 with one or more openings 1102, respectively, for receiving the individualized fibers 130 and an outlet 1108 through which the individualized fibers are deposited onto the collection system 1500. The forming head preferably comprises a fiber distribution homogenization unit 1150 for homogenizing the x-y-directional distribution of the fibers. In a particularly preferred execution, the fiber distribution homogenization unit 1150 comprises a multiplicity of homogenization tools 1153, preferably impellers, in Fig. 1 exemplarily but not limiting, shown with two impeller blades, rotating by means of drives 1157 around vertical axes 1155. As indicated in the cross-sectional views of Fig.1A and B, a three-by-three array of such impellers 1153 is schematically shown in the forming head 1100, but - as indicated in the background section - there could be an array of impellers, with two, three, four or even more impellers arranged in the cross-directional rows and three, or four, or five, or six or even more arranged in machine-directional columns. Optionally, the impellers in adjacent rows may be cross-directionally off-set, or the rows and columns may be in an angled position relative to the machine direction. The drive 1157 for the impellers may be a single one connected to the impellers by belts or gear wheels, or multiple drives (not shown). The individualized and x-y-directionally evenly distributed fibers are deposited through the forming box outlet 1108 onto a foraminous surface of a collection system 1500, as may be a rotating drum or, as shown exemplarily, with a the collection belt 1510 moving along the machine direction 12 via collection system guide rolls 1520, further guided by a vacuum suction system 1550 to draw air, but not fibers through the permeable collection belt 1510. The skilled person will readily realize that the collection system may comprised
As depicted in Fig. 4, showing the forming head 1500 and collection system only, optionally, and for certain applications preferably, the collection belt 1510 may comprise alternating regions with high air permeability 1512 and low, or preferably no air permeability 1518. Thus, the machine-directional distribution of the fibers is modified, as the air-entrained fibers are directed within the forming head 1100 with the air stream towards the high permeability regions 1512, there forming fibrous web sections 110 with machine directionally increasing thickness but with fiber free regions 115 between neighboring web sections.
The present invention is particularly suitable for being integrated into a converting process for forming articles, such as bed-pads, or wipes, or absorbent articles, as it obviates the need of processing the "jumbo roll" webs of conventional air-laying equipment and transporting the preformed webs to the article forming converter lines.
Thus, the fibrous web 100 or the fibrous web sections 110 collected on the collection system 1500 may then be transferred to further processing steps 1800, as may be compaction, such as by embossing roller, or addition of further layers, optionally particulate material or another layer of fibers, or enveloping between webs, like nonwovens, or films or composites thereof.
It should be noted that the current invention is very flexible to adjusting the width of the formed webs independently of the type of fiber supply. Thus, the width of the fiber supply may be less than about 90 %, or less than about 70 %, or less than about 50 % or less than about 30 % of the width of the resulting web 100. In an exemplary execution, the fibers were supplied from a fiber board roll 1111 of a width of 500 mm, but can be converted into a web having a width of 830 mm - a suitable size for forming, e.g., bed pads.
In particular when employing a fiber disintegrating unit, a significant reduction in energy is achieved, as the disintegration unit already accelerates the fibers along the machine direction. Further, the short distance transfer from the disintegration unit towards the forming head reduces energy loss and avoids nits forming, in contrast to conventional air-laying equipment, often having a piping length of more than 10 m or even more than 30 m.

Claims

An equipment (1000) for forming a fibrous web (100) exhibiting a machine (x-)direction (12), a cross (y-) direction (18) and a height (z-)direction (15)
the equipment (1000) comprising
- at least one fiber supply (1110) for fibrous material (130);

- a continuous collection system (1500)
- moving along a machine or x-direction (12) and exhibiting a width or cross-or y-direction (18), and a height direction (15) perpendicular to both and aligned with gravity comprising a foraminous surface, preferably a foraminous belt (1510) running over guide rolls (1520),

- and comprising a vacuum suction system (1550);

- at least one forming head (1100) comprising
a forming box (1101) comprising
- at least one infeed opening (1102) for receiving fibrous material (130) from said at least one fiber supply (1110);

- an outlet (1108) oriented towards a surface of said continuous collection system (1500)

- preferably a fiber distribution homogenization unit (1150) comprising at least two fiber distribution homogenization tools (1153), preferably impellers rotating around a vertical axis (1155), said impellers preferably comprising at least two impeller blades;

- a connection (1400) between said at least one fiber supply unit and said forming box (1101) of said forming head (1100) comprising
- connection piping (1410);

- venturi effect restriction (1420) comprising a narrow venturi section (1425) and a widening section (1428);

- a venturi air supply (1300) adapted to inject air into said venturi effect restriction (1420) and to adjust at least amount, temperature, and humidity of said air.
An equipment according to claim 1, further comprising
- a refiner unit (1350) positioned in said widening section (1428) of said venturi effect restriction (1420) comprising at least one pair of rotors (1360) with each rotor being adapted to counter-rotate around a cross-directionally extending axis (1362) and comprising radially extending fingers (1365),
said rotors (1360) of said pair of rotors are positioned z-directionally off-set from each other and whereby said fingers of said rotors are adapted to interdigitate.
An equipment according to claim 2, wherein said refiner unit (1350) comprises two pairs of rotating rotors (1360), said two pair of rotors are positioned x-directionally off-set from each other, and each two x-directionally off-set rotors are adapted to co-rotate, whereby preferably said fingers of said rotors are adapted to interdigitate.
An equipment (1000) for forming a fibrous web (100) according to any of claims 1 to 3, wherein
said fiber supply unit (1100) is at least one selected from the group consisting of
- a fiber bin (1118) comprising an outlet valve (1119);

- a bale supply (1116) and a fiber picking unit (1117);

- a fiber board roll supply (1111) and a fiber disintegration unit, preferably a hammer mill (1210), more preferably a hammer mill (1210) rotating around a cross-directionally extending axis (1218).
An equipment according to claim 4, comprising
- a first fiber supply unit (1100') of a first fiber type (130'), preferably comprising a fiber board roll supply (1111) and a hammer mill (1210),

- a second fiber supply unit (1100") of a second fiber type (130"), preferably selected from the group consisting of
- fiber bin (1118) and an outlet valve (1119);

- a bale supply (1116) and a fiber picking unit (1117).
An equipment according to claim 5, wherein further
said first fiber type (130') exhibits a fiber length distribution that is narrower than the fiber length distribution of said second type of fiber (130"),

wherein preferably said second fiber type (130") comprises recycled fibers of said first fiber type (130').
An equipment (1000) for forming a fibrous web (100) according to claim 1 or 2, wherein
the length of the connection pipe from the fiber supply unit (1100) to the forming box (1102) on the machine direction is less than about 10 m, or less than about 5 m, or less than about 3 m.
A process for forming a fibrous web (100) on a foraminous surface of a web collection system (1500) moving along a machine direction (12),
the process comprising the steps of
A - providing an equipment (1000) for forming a fibrous web (100) according to any of claims 1 to 7;

B1- providing a supply of first fibers (130') by said first fiber supply unit (1100');

B2- transferring said first fibers (130') from said first fiber supply (1110') suspended in an air stream through said connection pipe (1410) towards a venturi effect restriction (1420),
- thereby individualizing said first fibers (130') optionally in said disintegration unit (1200);

C - injecting air from said air supply (1300) into said venturi effect restriction (1420);

E - transferring said first fibers (130') from said venturi effect restriction (1420) toward an opening (1102) of said forming box (1101) of said forming head (1100);

F homogenizing the x-y-directional distribution of said fibers (130') in said forming head (1100) by said fiber distribution homogenization unit (1150);

G - collecting said individualized fibers (130) through said outlet (1108) of said forming head (1100) on a surface of said collection system (1500), thereby forming a fibrous web (100);

H - transferring said fibrous web to a further processing step (1800) preferably a process step for forming absorbent articles,

wherein steps B to H are executed in the given order.
A process according to claim 8, wherein in said step C the injected air is adapted to exhibit predetermined temperature, water content, pressure and mass flow, adapted to prevent agglomeration of said fibers (130).
A process according to claim 8 or 9, further comprising the step
D - after step C and before step E, comprising
- providing a supply of second fibers (130") by said second fiber supply unit (1100") and wherein in step E) said fibers (130), comprising first (130') and said second fibers (130"), are transferred from said venturi effect restriction (1420) toward an opening (1102) of said forming box (1101) of said forming head (1100).
A process according to any of claims 8 to 10, further comprising during step
E - transferring said fibers (130) from said venturi effect restriction (1420) toward an opening (1102) of said forming box (1101) of said forming head (1100);

the following step of
E1 - refining said fibers in the widening section (1428) of said venturi effect restriction (1420) by guiding said fibers between interdigitating fingers (1365) of rotors (1360) of said refiner unit (1350),

thereby de-agglomerating fibers (130) which formed nits and clumps.