Field of the invention

The present invention relates to the forming of fibrous composite webs and the resulting fibrous composite webs. The webs comprise at least one, optionally two outer layer(s) of staple fibers, as deposited in a carding process, at least one further layer with hydrophilic short fibers, as may be cellulose fibers, and binder as being mixed with the hydrophilic short fibers. Fibers of the layers are mechanically entangled such as by needlepunching or hydroentangling, also referred to as spunlacing. Such webs are particularly useful as wipes, especially absorbent wipes for personal cleansing or for treatment of surfaces.

Background

For the use as wipes, it is well known to employ substrates with a combination of hydrophilic short fibers, such as cellulosic fibers, providing absorbency at low cost, with strengthening fibers. One approach is to position cellulosic fibers between layers of spunbonded, essentially endless thermoplastic fibers, such as made from polyolefins like polypropylene or polyethylene, or polyester resins. Such an approach is described e.g. in JP9085870A (Oji; 1997).

Other approaches employ longer preformed fibers, also referred to as staple or carding fibers, whereby the different fiber types may be positioned in individual layers. Forming layers of staple fibres in a carding process is well-known, see e.g. US4279060 (Hergeth, 1978), or more recently US2020/0270786 (Dilo).

In order to increase the integrity of such combined layers as required for providing in-use strength of the substrates, it is also well known to entangle fibers, either by punching needles through the structures or by hydroentangling, also interchangeably referred to as spunlacing, process.

Apparatuses for entangling a fibrous web with an array of reciprocating needles are well known, e.g. described in US3849845 (Fehrer), or EP2158348 (Oerlikon). Nonwovens made by employing needling technology are known, e.g. from US9150988 (J&J), or EP2573242 (J&J). With regard to hydroentangling, in EP0593483 the production of spunlace material includes a forming unit having a staple-fiber former and a short fiber former which function to air-lay a layer of staple fiber on a forming wire and to air-lay a layer of short fibers on the staple-fiber layer, so as to form a fibrous web, and an entangling unit for hydroentangling the fibrous web.

Similarly, in W02020/079083 a structure is disclosed that comprises long staple fibers on cellulosic basis, such as viscose/rayon or lyocell fibers, in combination with short absorbent cellulosic pulp fibers. The structure is made by a wet-laying process, and further submitted to a hydroentangling step.

In EP0992338A2 (G-P) another three ply sandwich structured hydroentangled web is disclosed. The top and bottom plies of this web comprise long synthetic fibers having a fiber length of about 30 to 100 mm and the middle ply comprises cellulosic fibers having a fiber length of about 1 to 8 mm. The middle layer cellulosic fiber can optimally be wholly or partially replaced with short synthetic or other natural fibers having a fiber length of about 1 to 8 mm.

Further, in W02007/110497 (Andritz Perfojet) a non-woven is described having a layer of synthetic cellulose fibers (specifically viscose) and a layer of cellulose material (specifically wood fibers).

However, when employing carded staple fibers in an outside layer of the hydroentangled composite web further comprising hydrophilic short fibers, the requirements for in-use strength, and in particular for having a balanced strength both in machine and cross-machine direction, are not satisfied. Further, for such webs it is often desired to increase the relative amount (weight percentage) of the hydrophilic short fibers for liquid handling reasons, which as such results in deteriorating mechanical strength.

Further, the splattering caused by the waterjets during the hydroentanglement step may result in some of the hydrophilic short fibers to be washed away and driven into the support or carrier wire, which causes not only fiber loss in the product, but which also plugs the wire, making the system inoperable. Fiber loss not only results in loss of material but also creates severe problems in the water treatment system by plugging of filters and bio fouling.

Thus the present invention aims at improving these problems of such composite webs, useful as a wipe, and comprising layers of staple fibers and hydrophilic short fibers by intermingling the latter with a binder.

A suitable technology for such application of binder in a filamentary or fibrous form is known from so called “coform” material technologies, see e.g. EP2265756 (Harvey, K-C) or EP3129535 (Boscolo, Boma), both employing melt-blowing for forming a binder in a fibrous form, or US2015/0322601A1 (Biax) using the so-called spun-blowing for forming a binder in an essentially continuous filamentary form. More recently, particular executions of the spun-blowing technology have been developed, see PCT/EP2018/080293 (unpublished application, Teknoweb Materials), describing a unitary spinblock, or PCT/EP2018/080291 (unpublished application, Teknoweb Materials), describing a spinblock with removable nozzles, or GB 1916086 (unpublished application, Teknoweb Materials), describing a dry-forming process for cellulose and spun-blown fibers. Another approach for intermingling the hydrophilic short fibers with a binder, that may be a high viscosity curable binder is described in GB 1005832 (TKWM, unpublished). Another problem of wipes that gained increased attention relates the reduction of t plastic products on the environment, see e.g. “Commission guidance in accordance with the Directive (EU) 2019/904 of the European Parliament and of the Council of 5 June 2019”, or “Nonwoven industry ’s response to the Eunomia study on the plastics definition [under this Directive ] ” issued by EDANA January 2020. Henceforth, the present invention aims at providing structures for use as wipes and related manufacturing processes that allow reduction of plastic material in such wipes whilst maintaining good processability and usability

Summary

In a first aspect, the present invention is a composite web comprising a first layer of carded staple fibers, a layer of hydrophilic short fibers, and optionally a second layer of carded staple fibers, wherein at least fibers of the layer of hydrophilic short fibers are entangled with the carded staple fibers, and wherein the hydrophilic short fibers are intermingled with a liquefiable binder. The binder is solidified and preferably non-water-soluble at least just prior to the entanglement step. The composite web may further comprise one or more features alone or in combination selected from the list consisting of:

(a) the composite web exhibits a basis weight of more than about 20 g/m ² , preferably more than about 30 g/m ² , or even more than about 40 g/m ² ;

(b) the composite web exhibits a basis weight of less than about 200 g/m ² , preferably less than about 100 g/m ² , more preferably less than about 80 g/m ² ;

(c) the layer of staple fibers exhibits a basis weight of less than about 15 g/m ² ; preferably less than about 10 g/m ² , more preferably less than about 7 g/m ² , and even more preferably less than about 5 g/m ² ;

(d) the composite web comprises more than about 30 w-%, preferably more than about 60 w- %, more preferably more than about 70 w-%, even more preferably more than about 75 w-% and most preferably more than about 80 w-% of hydrophilic short fibers, based on the weight of the composite web;

(e) the composite web comprises less than about 20 w-%, preferably less than about 15 w-%, even more preferably less than about 10 w-% of binder material based on the combined weight of the hydrophilic short fibers and the binder;

(f) the composite web comprises less than about 15 w-%, preferably less than about 10 w-%, even more preferably less than about 5 w-% of binder material based on the weight of the composite web;

(g) the binder is selected from the group consisting of

(gl) meltblown fibers or filaments of thermoplastic polymers; (g2) spunblown fibers or filaments of thermoplastic polymers;

(g3) high concentration curable binder in the form of fibers, filaments, droplets, or coating film, optionally triggered by energy, e.g. heat or radiation, e.g. organic polymers or cellulose derivatives like a combination of carboxy methyl cellulose and citric acid, and preferably biodegradable;

(h) the composite web exhibits a ratio of tensile strength of machine to cross-machine direction of less than about 3.0, preferably less than about 2.0, even more preferably less than about 1.5, but more than about 1.0;

(i) the staple fibers are made of materials of natural origin, preferably made of modified cellulose;

(j) the staple fibers exhibit a length of more than about 6 mm, preferably more than about 10 mm;

(k) the staple fibers exhibit a fineness of more than about 0.5 dTex, preferably more than about 1.0 dTex, more preferably more than about 1.5 dTex;

(l) the staple fibers exhibit a fineness of less than about 10.0 dTex, preferably less than about 5.0 dTex, more preferably less than about 3.0 dTex;

(m) the hydrophilic short fiber are cellulosic based fibers;

(n) the hydrophilic short fibers exhibit a length of less than about 5 mm, preferably less than about 3 mm.

In a preferred execution, the composite web is essentially free of plastic material and may even be biodegradable. The composite web may be comprised in a wipe for personal cleansing or for hard surface cleaning.

In a second aspect, the present invention is a process for forming a composite web, the process comprising following the steps not necessarily in the following order: providing staple fibers, hydrophilic short fibers; liquefiable binder material; a composite web forming equipment comprising staple fiber supply; a first carding web forming unit; web support; a coforming unit; a mechanical entanglement unit; forming a first layer of carded staple fibers on a web support; forming an intermingled structure by mixing the hydrophilic short fibers with binder; solidifying the binder in the intermingled structure; depositing the intermingled structure of the hydrophilic short fibers with the binder after or prior to the solidification of the binder on the layer of staple fibers on the web support, thereby forming a composite web pre-cursor; submitting the composite web pre-cursor to mechanical entanglement selected from the group consisting of needlepunching or hydroentangling with pressurized waterjets, whereby the staple fibers and the combined hydrophilic short fibers and binder are entangled. Optionally, the process may further comprise one or more features selected from the group consisting of: the step of intermingling hydrophilic short fibers with binder comprises two multi-nozzle units for expelling the binder; executing the step of intermingling in a forming box; forming a second carded staple fiber layer; applying a further mechanical entanglement step on the first carded staple fiber layer; pre-compacting the pre-cursor web prior to the mechanical entanglement step; applying a further curing step after the lay down of the hydrophilic short fibers intermingled with the binder, whereby the curing may be induced by energy, e.g. heat or radiation, e.g. UV-radiation; operating the process as a continuous process at a process speed of more than about 100 m/min, preferably more than about 300 m/min; expelling the liquefied binder in the form of binder jets intermingling with the hydrophilic short fibers, the jets forming o essentially continuous filaments fibers or filament fragments exhibiting a length of more than 8 mm, or more than 20 mm, or more than 40 mm, wherein said filaments or fibers exhibit a diameter of less than about 100pm, or less than about 50 pm, or less than about 10 pm, preferably less than about 5 pm, or even less than about 3 pm; or o binder droplets; or o a partial or complete coating of the hydrophilic short fibers by the binder; forming the layer of staple fibers at a basis weight of less than about 20 g/m ² , preferably less than about 10 g/m ² , more preferably less than about 7 g/m ² , and most preferably less than about 5 g/m ² ; forming the composite web at a basis weight of more than about 30 g/m ² , preferably more than about 40 g/m ² , and less than about 200 g/m ² , preferably less than about 150 g/n preferably less than about 100 g/m ² , or less than about 80 g/m ² ; forming the composite web at a hydrophilic short fiber content of more than about 30 w- %, preferably more than about 40 w-%, more preferably more than about 60 w-%, even more preferably more than about 70 w-% and most preferably more than about 80 w-%, all on the basis of the weight of the composite web; operating the hydro entanglement at a water pressure of more than about 60 bar, preferably more than about 80 bar.

Brief description of the Figures

Fig. 1A and B depict composite webs according to the present invention.

Fig. 2 depicts equipment for executing a process according to the present invention.

Fig. 3 depicts equipment with optional elements for executing a process according to the present invention.

Figures are not to scale. Same numerals refer to same or equivalent features or elements.

Numerals with apostrophes (xx ¹ , xx", . . . ) denote multiple elements, e.g., first - second or left - right.

Detailed description

In a first aspect, the present invention is a composite web comprising at least one layer of hydrophilic short fibers which are intermingled with a binder and combined with at least one layer of staple fibers, each of these layers optionally being made of sub-layers, whereby fibers of a layer of the composite web are mechanically entangled with fibers of the adjacent layer(s), preferably by known processes such as needlepunching or more preferably by hydroentangling, the latter also referred to interchangeably as spunlacing. In a preferred execution, the present invention provides wipes that do not comprise plastic materials according to the above referenced EU Directive.

The staple fibers are pre-formed fibers of discrete length that may be based on synthetic resins but preferably are made of natural materials. The material for synthetic resin based staple fibers is not particularly limited, and the fibers may be made from thermoplastic polymers, such as, for example, polypropylene, polyethylene, polyester, nylon, PLA, etc., or blends or mixtures thereof, or the fibers may comprise different polymers as bi- or multi-component fibers. Examples for staple fibers of natural material origin may be from animal sources, like wool, or plant based materials, like - without intending any limitation - cotton, bamboo, silk fibers. Also modified natural materials may be employed and for particular applications preferred, such as regenerated or “man-made cellulosic fibers” (e.g. rayon / viscose or lyocell fibers).

Within the present context, the length of these fibers is typically more than about 6 mm, or more than about 10 mm or more than about 25 mm, or more than about 30 mm, and typically less than about 100 mm, or less than about 70 mm, or less than about 50 mm. The thickness of such staple fibers is not particularly limited, and is typically more than about 0.5 dTex, or more than about 1 dTex, but typically less than about 20 dTex, or less than about 10 dTex, or less than about 5 dTex. Such staple fibers may exhibit a straight form or may have a curved shape, or may be crimped. Exemplary fibers are viscose fibers, exhibiting a length of about 6 mm and a fiber thickness of 1.8 dTex.

Whilst carded webs often comprise a combination of multiple sub-layers of such oriented fibers, it is preferred for the present invention to keep the thickness and basis weight of a staple fiber layer as low as possible, and hence a layer is preferably not consisting of sub-layers. The basis weight of a layer of staple fibers may be less than about 15 g/m ² , preferably less than about 10 g/m ² , more preferably less than about 7 g/m ² or even less than about 5 g/m ² .

The composite web further comprises a layer comprising hydrophilic short fibers. Within the present context, such fibers typically exhibit a length of less than about 5 mm, or less than about 3 mm, or even less than about 2 mm, or more than about 0.5 mm, or more than about 1 mm. Typically, suitable fibers exhibit a length to diameter ratio of less than about 200.

Fibers particularly useful as hydrophilic short fibers include fibers of natural origin, such as cellulosic fibers, especially wood pulp fibers. Applicable wood pulps include chemical pulps, such as Kraft, sulfite, and sulfate pulps, as well as mechanical pulps including, for example, groundwood, thermomechanical pulp and chemically modified thermomechanical pulp. Chemical pulps, however, may be preferred since they impart a superior tactile sense of softness to webs made therefrom. Also fibers derived from both angiosperm (flowering) trees (also referred to as "hardwood") and gymnosperm (coniferous) trees (also referred to as "softwood") may be utilized. Whilst longer fibers tend to be larger and coarser, providing desirable texture and absorption characteristics, short fibers tend to be finer and softer, enhancing opacity of the structure and adding tactile softness.

It should be noted that the term “fiber of natural material origin” refers to the origin of the fibers, which may be left as such, or be purified, e.g. preferably delignified, or may be further treated, such as without any limitation the fibers may be chemically cross-linked cellulosic fibers.

The hydrophilic short fibers are intermingled with a binder that preferably does not function as a main structural component of the layer or of the composite web. In a first approach, such binder may be in-situ formed thermoplastic liquefiable materials that - when expelled though nozzles - form fine material jets that may solidify upon cooling into fine filaments or fibers, as is well known from so-called “coform” web structures. The above referenced EP2265756

C), describes providing fine discontinuous filaments, whilst EP3129535 (Boscolo, Boma), or US2015/0322601A1 (Biax) describe providing fine essentially continuous filaments. These documents are expressly referred to as far as the coformed web and their process of forming are concerned. Such binder may be formed from a variety of thermoplastic materials, such as without limitation, polypropylene, polyethylene, polyester, nylon, PLA, etc., or blends or mixtures thereof.

Whilst it is preferred that the fine filaments are essentially continuous, they may exhibit a length of more than about 1 mm, often more than about 8 mm, or more than about 20 mm or more than about 40 mm, and a filament thickness of less than about 40 pm, or less than about 20 m or less than about 10 pm.

In another approach it is also within the scope of the present invention that the binder may be a non-thermoplastic binder system that is liquefiable such that it can be expelled through the nozzles, but that solidifies thereafter. Typically, the solidification is occurring by curing, i.e. the binder system undergoes an irreversible chemical reaction, that not only renders the binder solid but preferably also insoluble versus water, especially in case of applying hydroentangling, or other liquids as may be contacted during the intended use. The binder system is adapted to form binder jets upon being expelled through the nozzles. These jets may then form filaments or fibers similar to the thermoplastic binder systems, that also intermingle with the hydrophilic short fibers as described in the above. The jets may also form binder droplets that upon intermingling with the fibers form connection points between adjacent fibers and/or that form a partial or complete coating of the fibers. The binder system may comprise a solvent, such as water, that may be partially or completely removable prior to further curing of the binder.

The binder system may be adapted to solidify prior to the laydown of the hydrophilic short fibers intermingled with the binder, or thereafter, optionally a separate treatment step may be applied between the laydown and the entanglement, such as enhancing curing by application of energy, such as by heat or radiation, e.g. with UV rays, or by increasing the adhesive properties of the binder system.

A suitable application of a binder system is described in the above referenced GB2005832 (TKWM, unpublished), whereby curable binder systems are applied at high concentrations and viscosities and expelled through fine nozzles as useable for forming thermoplastic filaments. In a particular execution, such curable binder is based on natural and/or biodegradable materials.

Referring to the figures, a first execution of a composite web 100 according to the present invention is schematically depicted in Fig. 1A, comprising exemplarily one layer 120 of hydrophilic short fibers 125 intermingled with binder 128, which may have a filamentary or particulate form, or a partial or complete coating of the fibers, and a single layer of

(110) positioned z-directionally (8) on top of each other, with the layers extending in the x- direction (5) and y-direction perpendicular to these. Fig. IB depicts a second exemplary execution of a composite web 100, comprising exemplarily one layer 120 of hydrophilic short fibers 125 intermingled with binder 128, which may have a filamentary or particulate form, or a partial or complete coating of the fibers, sandwiched between two layers of carded staple fibers 120’, 120”, which may be, essentially identical, or differ, e.g. in basis weight, fiber property, or fiber arrangement.

The composite web may exhibit basis weights of more than about 20 g/m ² , or more than about 30 g/m ² , or more than about 40 g/m ² . For applications as a cleaning or cleansing wipe, the composite web exhibits typically a basis weight of less than about 200 g/m ² , or less than about 150 g/m ² , or less than about 100 g/m ² or less than about 80 g/m ² , whereby an exemplary execution exhibited a basis weight of about 50 g/m ² . When intended for other applications, such as when used in highly absorbent structures, the basis weights may exceed 200 g/m ² though typically be less than about 500 g/m ² .

Overall, for absorbency and liquid handling performance it is often desirable that the composite web comprising the layers of carded staple fibers and the hydrophilic short fibers intermingled with a binder has a high amount of hydrophilic short fibers without overly compromising on its strength properties. Thus, it is preferred that the amount of hydrophilic short fibers is more than about 30 w-%, or more than about 50 w-%, or more than about 60 w-%, or more than about 70 w-%, or more than about 75 w-% or even more than about 80 w-%, all based on the composite web. The hydrophilic short fibers are intermingled with an amount of binder that may be in the range of less than 20 w-%, or less than 15 w-%, or less than about 10 w-%, or even less than about 5%, when based on the weight of the hydrophilic short fibers, or less than about 15 w-%, or less than about 10 w-% or less than about 5 w-% when based on the total weight of the composite web.

It is further desirable that the composite web exhibits sufficient strength to survive processing, but also various in-use stresses. Thus, the composite web should exhibit a tensile strength in the dry state, when measured according to EDANA NWSP 110.4 (R0) Option A (25 mm wide strip) and along the machine direction (MD) of the composite web of more than about 5 N /25 mm, or more than about 10 N /25 mm, or more than about 20 N /25 mm, or more than about 30 N /25 mm, or more than about 50 N /25 mm but typically less than about 200 N /25mm. The tensile strength along the cross machine direction (CD) is more than about 5 N /25 mm, or more than about 10 N /25 mm, or more than about 20 N /25 mm, or more than about 30 N /25 mm, or more than about 50 N /25 mm but typically less than about 200 N /25mm. However, it is preferred that the ratio of MD to CD dry tensile strength is less than less than about 5.0, or less than about 2.0, less than about 1.5, though typically more than about 1.0. In another aspect, it is preferred that the ratio of specific dry tensile strength with regard to the overall basis weight of the composite web for the machine direction is more than about 0.05, or more than about 0.10, or more than about 0.40, or more than about 0.80, or more than about 1.00 or more than about 1.50, typically less than about 5.00, whilst for the cross-machine direction, it is preferred to be more than about 0.01, or more than about 0.10, or more than about 0.20, or more than about 0.50, or more than about 1.00, though typically less than about 2.00.

An exemplary composite web comprises two layers of carded staple fiber of about 1.8 dTex viscose fibers at a length of about 35 mm, each at a basis weight of about 6 g/m ² , and a layer of northern softwood cellulosic fibers of about 34.2 g/m ² intermingled with about 3.8 g/m ² polypropylene binder filaments, thus exhibiting an overall amount of about 68.4 w-% hydrophilic short fibers, based on the weight of the composite web.

In a further aspect, the present invention is a process for providing a fibrous composite web. Whilst it is also within the scope of the present invention that the carded staple fiber webs can be pre-manufactured and be delivered to the process of forming the composite web, it is preferred that the forming of the carded staple fiber webs is made in situ, i.e. it is part of a single continuous process. Fig. 2 depicts schematically the equipment 1000 on which the process for the manufacturing a composite web can be executed. The arrangement of the equipment units is along the machine or process direction MD 5 and such that execution of certain steps along this process direction results that layers may be placed on each other, forming a z- or height directional (8) structure. The process comprises the following steps:

Providing a first carded staple fiber layer 110 in a carded web supply unit 1100 with a staple fiber supply 1110 and at least one carding unit 1120 forming a carded staple fiber stratum 1115 on a web support 1900, preferably aided by a vacuum suction box 1950’; transferring the layer of carded staple fibers 110 to a hydrophilic short fiber deposition station, preferably a co-forming equipment 1200; intermingling individualized hydrophilic short fibers 1215 from a hydrophilic short fiber supply unit 1210 with a liquefied binder 1223 supplied from a binder supply unit 1220 by means of a multiple nozzle unit 1225 in an intermingling space 1250; depositing the individualized hydrophilic short fibers intermingled with binder (120) onto the layer of carded staple fiber 110, thereby forming the pre-cursor web 210, preferably thereby supporting the laydown by a vacuum suction 1950”; transferring the pre-cursor web 130 to a mechanical entanglement unit 1500, preferably comprising a needlepunching or hydroentangling unit; mechanically treating the composite web pre-cursor with a plurality of needles or high pressure water jets 1510; in case of using high pressure water jets, further comprising the steps of transferring the treated composite web pre-cursor to a drying unit (not shown) and of removing excess water mechanically and thermally to form the composite web 100.

In a first execution, the carded staple fiber layer is pre-manufactured and delivered to the process of forming the composite web, such that in the present process set up the carded web supply unit 1100 is an unwinding unit. However, it is preferred that the forming of the carded staple fiber web is made in situ, i.e. it is part of the single continuous process. Thus the carded layer supply unit 1100 comprises a supply of staple fibers 1110. Carding units for forming carded webs are well- known in the art, typically comprising a main cylinder comprising brushes, to which the staple fibers are fed from the staple fiber supply 1110. By interacting with stripper and worker rolls, the fibers are individualized and oriented, typically strongly along the machine direction. The fibrous stratum 1115 is further transferred to a doffer to be taken off the carding unit. At that stage, the layer of staple fibers is essentially unbonded and has very little mechanical integrity. Thus it is positioned onto a web support 1900, preferably a transport belt system with a foraminous web. In order to ease the transfer to the web support, a vacuum suction box 1950’ may be positioned under the web support. When the amount of staple fibers in the composite web should be minimized, it is preferred that no sub-layers but only a single layer of staple layers is formed, and that this is formed at a low basis weight, preferably of less than about 15 g/m ² , preferably less than about 10 g/m ² , more preferably less than about 7 g/m ² or even less than about 5 g/m ² but typically more than about 3g/m ² .

The web support 1900 allows to transfer the layer of staple fibers 110 to the hydrophilic short fiber deposition unit 1200, preferably executed as a coforming equipment. In such a unit, hydrophilic short fibers, as described in the above, are provided from a fiber supply 1210 and individualized before they are intermingled with a stream of liquefied binder in an intermingling zone 1250. The liquefiable binder is supplied from a binder material supply unit 1220’ . The binder is either already liquefied in the supply unit or liquefied, e.g. molten, e.g. in an extruder, between the supply unit 1220 and a multi-nozzle unit 1225, where the binder 1223 is expelled forming binder jets, which are merged with the hydrophilic short fibers, thereby forming an intermingled mixture 120. These jets may be formed into filaments or fibers similar to the thermoplastic binder systems, that also intermingle with the hydrophilic short fibers as described in the above. The jets may be formed into binder droplets that upon intermingling with the fibers are forming connection points between adjacent fibers and/or that are forming a partial or complete coating of the fibers. The binder system may comprise a solvent, such as water, that may be partially o removed prior to further solidification, e.g. by curing of the binder.

The binder system may be solidifying prior to the laydown of the hydrophilic short fibers intermingled with the binder, or thereafter.

In a particular execution, the multi-nozzle unit for expelling the binder and its operation are known, e.g. from melt-blowing equipment for forming thermoplastic discontinuous filaments, see e.g. EP2265756 (Harvey, K-C). However, it is even more preferred to create fine essentially endless filaments by using the equipment and the process as described in US2015/0322601A1 (Biax) when creating fine filaments of thermoplastic material, or in co-pending patent application GB2005832 (TKWM, unpublished), relating to form filaments and optionally droplets or fiber coating from such filaments. Express reference is made to the disclosures of these documents as far as the equipment for forming intermingled webs and respective processes are concerned.

The mixture of hydrophilic short fibers intermingled with the binder 120 is deposited on a web support in a laydown zone, preferably supported by a vacuum suction 1950”. As the layer of carded staple fibers 110 is already positioned on the web support, the mixture of hydrophilic short fibers intermingled with the binder 1223 will be positioned thereon, thereby forming together with the previously laid down layer the pre-cursor 130 of the composite web, comprising the essential components of the composite web.

The pre-cursor 130 is further transferred to a mechanical entanglement unit 1500. A first execution thereof comprises an array of reciprocating needles and is well known, e.g. described in US3849845 (Fehrer), or EP2158348 (Oerlikon). The making of nonwovens made by employing needling technology is known, e.g. from US9150988 (J&J), or EP2573242 (J&J).

An alternative, often preferred mechanical entanglement comprises a hydroentangling unit 1505, as exemplarily depicted in Fig. 2 and well known in the art, see e.g. US6110848A (Bouchette; Georgia-Pacific), EP1775116B1 (G-P), EP1210474A1 (Boscolo, Fleissner), EP2001663A1 (Andritz Perfojet). Hydroentanglement or spunlacing is well known in the industry as a binderless way of connecting fibers together. It operates through a process that entangles individual fibers within a web by the use of high-energy water jets. Fibrous webs are passed under specially designed manifold heads with closely spaced holes which direct waterjets at pressures up to 15 MPa (150 bar), and higher. The energy imparted by these water jets moves and rearranges the fibers in the web in a multitude of directions. As the fibers escape the pressure of the water streams, they move in any direction of freedom available. In the process of moving, they entangle with one another providing significant bonding strength to the fibrous webs.

Generally, these waterjets will also draw a small amount of hydrophilic short fiber through the support, which not only represent a loss of material, but also may impede proper function by blocking the support web opening and plugging the filters of the water treatn

However, according to the present invention, the presence of binder intermingled with hydrophilic short fibers reduces this loss of hydrophilic short fibers, enhancing the processing as well as yield. The present process is easy to implement and to operate, and can be run a machine speeds of more than about 100 m/min, often more than about 300 m/min, and typically less than about 1000 m/min.

Fig. 3 depicts the equipment for executing the process as described in the context of Fig. 1, further depicting additional optional elements. It should be noted that each of the additional elements provides an improvement for the process for reaching composite webs with improved properties, but any of these elements may be applied in any combination with any of the other, providing additive or even synergistic improvements.

In the step of intermingling the hydrophilic short fibers with the binder, a second multinozzle unit 1225” in addition to the first 1225 ’ may be employed, providing the same or a different binder from a second binder supply unit 1220”. In preferred execution, the first and the second multi-nozzle unit are positioned in an angled arrangement, with the hydrophilic short fiber being supplied to where the expelled binder of the two units merge. This provides an even better and more homogeneous distribution of the binder across the hydrophilic short fibers.

It is further preferred that the intermingling of the hydrophilic short fibers and the binder is executed in a forming box 1255 allowing a better air flow control. An exemplary execution for such a forming box is described e.g. in US2016/0355950 (P&G), to which express reference is made as far as the arrangement of a forming box is concerned.

Another preferred execution employs a second step for providing staple fibers to be positioned z-directionally (8) onto the hydrophilic short fibers, i.e. downstream in the process direction 5. Thus the equipment comprises in addition to the first carding unit 1100’ a second carded web supply unit 1100”, for which the above description applies mutatis mutandis. This second unit 1100” can be positioned just after the coforming unit 1200 and may be executed identical to or different from the first carded web supply unit 1100’. It creates a second layer 110” of carded staple fibers, as may be of the same fiber material and basis weight, or different. Thus, the layer 120 of hydrophilic short fibers intermingled with the binder can be sandwiched between the carded staple fiber layers 110’ and 110”.

After the first carded staple fiber layer 110’ has been formed, this can be submitted to a pre-consolidation step, e.g. in a second mechanical entanglement unit 1500”, as may be the same design of or different to the first 1500’. Also the operation condition, such as number of needles or waterjets, or the pressure of the latter, may be the same or different.

Optionally, the solidification of the binder may be further enhanced by a further treatment step on a further treatment unit 1600 that may apply energy, such as heat or radiati rays, to the binder, as exemplarily shown to be performed prior to the entanglement step. In case that the entanglement is performed by needlepunching and thusly essentially dry, the final solidification may also be performed after the entanglement step. - Yet a further option relates to an additional pre-compaction unit 1400 positioned between the laydown of the hydrophilic short fibers or second staple fibers and the mechanical entanglement unit 1500’. Such a pre-compaction unit may be a pair or counter-rotating rolls with the pre-cursor being fed into the nip between these, as well known in the art. The composite web pre-cursor may be compressed to a pre-determined interim density, whereby also the surfaces may be smoothened and levelled.

Optionally, when employing hydroentanglement in either of the mechanical entanglement steps, this can be executed in two steps (not shown), with a first entangling process at a low to medium pressure (60-100 bars), and a second at a high pressure (80-250 bars). After the entanglement treatment of the web pre-cursor, the water is removed from the web by squeezing in a nip between to rollers and by thermal drying to finish the composite web.