Airlaying process and equipment for adjusting web width by movable housing walls

Abstract

The present invention is an apparatus and a process for forming a fibrous web comprising short fibers and optionally particulate material, whereby the apparatus respectively the process is adapted to provide an easy and quick adjustment of the cross-directional width of the web by varying the distancing of the lateral walls of the housing.

Description

[0001] AIRLAYING PROCESS AND EQUIPMENT

[0002] FOR ADJUSTING WEB WIDTH BY MOVABLE HOUSING WALLS

[0003] Field of the invention

[0004] The present invention relates to an apparatus and a process for forming a fibrous web comprising short fibers and optionally particulate material, whereby the apparatus respectively the process is adapted to provide an easy and quick adjustment of the cross-directional width of the web by varying the distancing of the lateral walls of the housing.

[0005] Background

[0006] The manufacturing of webs comprising short fibers, such as cellulosic fibers, is well known in the art. A particular execution is described in EP 1633912 (Anpap), describing the use of a fiber distributor for air-laying fibers on an endless, air pervious forming wire. The fiber distributor comprises an array of rotatable wings for sweeping supplied fibers in an air stream before being deposited on the upper surface of a forming wire to for a web. The wings are adapted to rotate so as to avoid forming of form nits or enhancing the individualization of the fibers.

[0007] It is also known that the width of the deposited web is dependent on the form and shape of space just above the collector tool, see e.g., US4931357A or EP0307967, showing a housing with fixed lateral walls angled versus the vertical (gravity).

[0008] US2016 / 0355950 (P&G) describes a particular execution of co-forming forming box, wherein short fibers, especially cellulosic or pulp fibers are mixed with particular material, such as superabsorbent polymer (SAP) particles.

[0009] Typically, air-laid structures are produced on large width apparatuses, and the resulting web is then cut / severed to the width required for the resulting articles. Lateral edges may be trimmed off, creating waste, preferably for being recycled into the process.

[0010] However, when air-laid structures are to be applied directly into finished articles, not only the trim ratio should be minimized but there should also be flexibility to adjust the width of the air-laid structure to the required article width without trimming or cutting and with minimum process interruption.

[0011] Summary

[0012] In a first aspect the present invention is an apparatus for forming a web comprising short fibers, preferably cellulosic fibers, and optionally particulate material. The apparatus comprises a supply of individualized short fibers suspended in an air stream; a collector tool comprising a movable foraminous surface for depositing the short fibers and forming a web thereof; a suction system for sucking air through the foraminous surface; a housing comprising o a feed duct for guiding the air stream with the individualized fibers towards the foraminous surface; o a front and a rear feed duct wall and lateral feed duct side walls, each comprising upper and lower ends along gravity; o a homogenization and distribution section; o a downstream opening to allow the short fibers to deposit on the foraminous surface; optionally one or more homogenization and distribution tool(s) in the homogenization and distribution section; optionally a supply system for adding particulate material into the housing.

[0013] The apparatus further comprises at least one lateral dislocating tool for moving at least the lower ends of the lateral sidewalls of the feed duct towards or away from each other.

[0014] In another aspect, the present invention is a process for forming a fibrous web the web comprising short fibers, preferably cellulosic fibers and optionally particulate material. The process comprising the steps of

[0015] - providing an apparatus as described above;

[0016] - feeding the air stream with the short fibers to the housing;

[0017] - sucking the air stream with the short fibers through the downstream opening of the housing and the foraminous surface, thereby depositing the short fibers onto the foraminous surface and moving a thereby formed web by machine-directional movement of the foraminous surface;

[0018] - optionally adding particulate material via the supply system into the housing;

[0019] - optionally homogenize the fiber distribution within the homogenization and distribution section of the housing by the homogenization and distribution tool(s).

[0020] Further, the process comprises the step of adjusting the width of the formed web by adjusting the cross-directional distance of at least the lower ends of the lateral feed duct walls by moving these towards or away from each other by at least one lateral dislocating tool.

[0021] Optionally, the process further comprises the steps of providing a carrier web from a carrier web supply; guiding the carrier web between the foraminous surface of the collector tool; optionally overfolding the lateral side portions of the carrier web around the lateral side margins of the web. Short description of the drawings

[0022] Fig. 1A and B depict an apparatus according to the present invention.

[0023] Fig. 2A and B depict a particular execution of an apparatus according to the present invention.

[0024] Fig. 2C and D depict a product as obtainable by such an execution.

[0025] 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., “Under”, “over” and related terms should be read to be oriented along gravity.

[0026] Detailed description

[0027] The present invention relates to the manufacturing of air-laid composite webs comprising short fibers, such as cellulosic fibers, and optionally particulate material, such as superabsorbent polymer (SAP) particles. Without any limitation, such composite webs may be suitably introduced in articles, especially absorbent articles, as may be worn on the lower abdomen, such as diapers, incontinence articles or the like, or as may be placed on a support surface, as may be a bed for bedpads, or meat pads, or the like, or any ground, e.g., for baby change mats.

[0028] The general process and the equipment for manufacturing such composite webs are well known in the art, and express reference is made to the above mentioned EP1633912 (M&J / Anpap) as far as the design of the forming chamber with rotating wings as a homogenization and distribution tool for improved material distribution is concerned.

[0029] As far as the addition of particular material is concerned, reference is made to above referenced US2016 / 0355950 as far as the general principle of combining fibers and particles in a forming box is concerned.

[0030] Without intending to limit the present invention, it is now further explained by referring to Fig. 1 depicting a schematic set-up of a web forming apparatus 1000, exhibiting an x- or machine direction (MD) 2, a z- or height direction 5 and a y- or cross-machine direction (CD) 8. Side view Fig. 1A depicts a short fiber supply 1100 with short fibers suspended, preferably fully individualized, though a small amount of knits may be acceptable, in an air stream, an optional particulate material supply 1150, fed via feed duct 1110 to the homogenization and distribution section 1200 with rotating homogenization and distribution tools 1210 inside the housing 1105. Along gravity, a collector tool 1400, such as the surface 1415 as may be of a foraminous belt 1410 is adapted to receive the short fibres and the particulate material, if present, thereby forming a web 100. The laydown is supported by a suction system 1500 with a suction box 1510 and a vacuum connection 1550. In the schematic cross-sectional view in Fig. IB, it is further shown that the lateral side walls of the feed duct 1120 are tapering towards each other at an inclination angle 1125. In the preferred execution as depicted, both lateral walls exhibit the same inclination angle 1125’, 1125”, though an asymmetric design can be employed. The lateral side walls 1120 are movably connected at their upper end 1123 to a frame (not shown) at hinge 1121, driven by a lateral dislocating tool 1128, such as a side wall drive tool, for adjusting the cross-directional distance of at least the lower ends 1122 of the lateral feed duct walls by moving these towards or away from each other. The narrowing of the lower ends 1122 of the lateral side walls may be by 20% relative to the widest possible crossdirectional distance or by more than 30 %, or by more than 40% or even by more than 50%. For example, a cross-directional distance at the upper end of the forming box feed duct 1123 of 720 mm may taper down to 550 mm at the lower end 1122, corresponding to about 24% narrowing. The sealing towards the ambient may be achieved by maintaining the vertical fixed walls 1127, indicated as dotted lined in the figure, or when removing these, preferably including a sealing tool 1112, such as bellows or the like. Whilst the present explanation refers to essentially plane and straight lateral side walls, the skilled person will readily transfer the teaching also to curved shapes. In the homogenization and distribution section 1200, the apparatus further comprises homogenization and distribution tools 1210 with a homogenization and distribution tool drive 1250. As exemplarily indicated in the figure, the homogenization and distribution tools are arranged in an array, here with each three rows and columns in CD and MD.

[0031] The vacuum box 1510 underneath the collector tool 1400 is exemplarily depicted as a three- chamber system 1515 connected via an adjustable baffle system 1518, to the vacuum source 1550, so as to allow adaptation of the vacuum suction along various cross-directional sections of the collector tool 1400.

[0032] The apparatus 1000 is operated by feeding the short fibers, suspended, preferably fully individualized, though a small amount of knits may be acceptable, in an air stream through the forming box duct feed 1110 towards homogenization and the distribution section 1200, into which particulate material may be added via particulate material feed 1150. In this section, the fibers are homogenized and machine and cross-directionally distributed, and residual poorly disintegrated fibers, such as knits, are further individualized and intermixed with particles, if present.

[0033] The deposition on the collector tool 1400 is limited cross-directionally by the inwardly angled lateral side wall(s) 1120, whereby the angle 1125 is adjusted to a predetermined value according to the desired width 118 of the formed web 100 by lateral dislocating tool 1128 of side walls 1120. The adjustment of the cross-directional deposition width 118 of the web 100 may be further supported by regulating suction in the respective chambers 1515 of the vacuum box up to the maximum web width 119.

[0034] The present invention provides advantages over the current productions, wherein typically the production width of air-laid webs corresponds to the maximum width of the equipment. Whilst thus a relatively high production volume can be achieved via large widths, such machines are not very flexible with regard to adjusting to varying dimensions of the products, as these must be sized in a subsequent cutting step - either resulting in complex size arrangements or in increased lateral trim. The present invention allows to produce flexibly to the production needs, even by a “push button” process adjustment for setting the positioning of the lateral side walls. For a given basis weight of the web, the fiber and air throughput may be reduced concurrently, thereby reducing the required air flow and energy. In an exemplary execution, a machine may produce at nominal maximum width of 920 mm with about 500 kg / hr throughput. If the product requirements require a web width of 530 mm, the present invention allows to reduce the throughput to about 288 kg / hr, avoiding recycling of the 212 kg / hr of trim that would occur otherwise. If a reduced throughput would lead to poorer individualizing of the short fibers, the homogenization and distribution tool would alleviate such a risk.

[0035] Fig. 2A to D refer to a further benefit enabled by the present invention. For certain applications, especially when the web 100 comprises particulates, such as superabsorbent particles, these might not be sufficiently immobilized in the web and thus might be prone to pass through to the foraminous collecting tool 1400. This not only represents loss of material, but may actually damage the collecting belt 1410. Also, it might be desirable to minimize particles losses from the lateral side margins of the web, be it in the further processing of the web, or during use.

[0036] In such instances it might be desirable to support the web by a carrier web 130, such as a tissue or a nonwoven material reducing or even avoiding that particle losses from the web. However, conventional forming system using air knives to trim the lateral side margins of the web, cannot separate through such carriers 130 and thus the options are to either use a carrier web 130 with a width corresponding to the one of the resulting web and separated laterally protruding portions of the web by the air knife. In this instance, the lateral side losses of particles are not addressed. Alternatively, the carrier web 130 exhibits a carrier web width wider than the resulting web width 100 and the outwardly protruding portions are overfolded. Then, however, there is a poor definition of the basis weight of the web in the side margin region. The present invention avoids this dilemma by providing the options of web 100 supported by a carrier web 130 as may be delivered from a carrier web supply 1800 via a carrier web guide system 1830 with a carrier web width 138 providing a well-defined side margin of a predetermined width, which may or may not allow for overfolding 139.

Claims

CLAIMS1. An apparatus ( 1000) for forming a web (100) comprising short fibers, preferably cellulosic fibers, and optionally particulate material, said apparatus comprising a supply of individualized short fibers suspended in an air stream (1100); a collector tool (1400) comprising a movable foraminous surface (1415) for depositing said short fibers and forming a web (100) thereof; a suction system (1500) for sucking air through said foraminous surface (1415); a housing (1105) comprising o a feed duct (1110) for guiding said air stream with said individualized fibers (1100) towards said foraminous surface (1415); o a front and a rear feed duct wall and lateral feed duct side walls (1120), each comprising upper and lower ends along gravity; o a homogenization and distribution section (1200); o a downstream opening (1118) to allow said short fibers to deposit on said foraminous surface (1415); optionally one or more homogenization and distribution tool(s) ( 1210) in said homogenization and distribution section (1200); optionally a supply system (1150) for adding particulate material into said housing; said apparatus being characterized in further comprising at least one lateral dislocating tool (1128) for moving at least said lower ends (1122) of said lateral sidewalls (1120) of said feed duct (1110) towards or away from each other.

2. A process for forming a fibrous web (100), said web (100) comprising short fibers, preferably cellulosic fibers, and optionally particulate material, said process comprising the steps of- providing an apparatus according to claim 1;- feeding said air stream with said short fibers to said housing (1105);- sucking said air stream with said short fibers (1100) through said downstream opening (1118) of said housing and said foraminous surface (1415), thereby depositing said short fibers onto said foraminous surface (1415) and moving a thereby formed web by machinedirectional movement of said foraminous surface (1415);- optionally adding particulate material via said supply system (1150) into said housing (1105);- optionally homogenizing and distributing the fiber within the homogenization and distributionsection (1200) of said housing (1105) by said homogenization and distribution tool(s) (1210); said process being characterized in that it further comprises the step of adjusting the width (118) of said formed web (100) by adjusting the cross-directional distance of at least the lower ends (1122) of the lateral feed duct walls by moving these towards or away from each other by at least one lateral dislocating tool (1128).

3. A process for forming a fibrous web (100) according to claim 2, further comprising the steps of providing a carrier web (130) from a carrier web supply (1800); guiding said carrier web (130) between said foraminous surface of said collector tool (1400); - optionally overfolding the lateral side portions of said carrier web around the lateral side margins of said web (100).

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