WO2021213955A1

WO2021213955A1 - Applying highly viscous curable binder systems to fibrous webs comprising natural fibers

Info

Publication number: WO2021213955A1
Application number: PCT/EP2021/060025
Authority: WO
Inventors: Fabio Zampollo; Henning RÖTTGER
Original assignee: Teknoweb Materials S.R.L.
Priority date: 2020-04-21
Filing date: 2021-04-19
Publication date: 2021-10-28
Also published as: GB202005832D0

Abstract

The present invention relates to forming of bonded fibrous webs and the resulting fibrous webs which are e.g. useful as wipes. Liquid jets of a curable, liquid binder system are applied to the fibers whilst these are suspended in air, and hot air, as expelled concurrently with the binder system jets, induces drying and curing of the binder and its deposition on the fibers' surfaces. Upon lay down of the fibers forming a web, further curing may be induced.

Description

APPLYING HIGHLY VISCOUS CURABLE BINDER SYSTEMS

TO FIBROUS WEBS COMPRISING NATURAL FIBERS

Field of the invention

The present invention relates to forming of bonded fibrous webs and the resulting fibrous webs which are e.g. useful as wipes. Liquid jets of a curable, liquid binder system are applied to the fibers whilst these are suspended in air, and hot air, as expelled concurrently with the binder system jets, induces drying and curing of the binder and its deposition on the fibers surfaces. Upon lay down of the fibers forming a web, further curing may be induced.

Background

The use of curable binder in structures, like webs, that comprise cellulose is well known in the art.

US8273414B2 describes the improvement of wet tensile strength of cellulose-containing web, e.g., paper towels involving applying aqueous binder emulsion to a web, drying and curing a emulsion prepared by polymerizing a monomer mixture in presence of a phosphate ester surfactant.

US20120297560A1 describes a dispersible wet wipe, comprising a wipe substrate having a first outer layer with a tissue web of cellulose fibers and second outer layer with nonwoven web triggerable binder composition, and wetting composition having insolubilizing agent.

In EP1721036A1 (Glatfelter, Hansen), the manufacturing of fibrous webs with low dustiness and good liquid handling and mechanical strength is described. To this end, a mixture of SAM particles and cellulosic fibers can be sprayed on both sides with a high moisture content latex dispersion.

W02014/009506A1 (Glatfelter, Ehmke) describes the application of a self cross-linking latex binder to the cellulosic surface of a web.

A particular category of compositions functioning as binder are described in a co-filed series of publications in the name of ORGANOCLICK AB, namely WO2018/038669A1, W02018/038670A1, and WO2018/038071A1, all relating to bio-based polyelectrolyte complex compositions, hereinafter referred to as the “W02018/0386 families”.

Many of such binder systems are on a solvent or carrier base, wherein the binder compounds are dissolved or dispersed at very small particle size. Often, the solvent or carrier is water, and for ease of handling of the binder solutions and/or for good distribution of the binder system in the structures, the solvent or carrier is present in the binder system in excess, often in great excess.

It also well known to apply binder systems to bonded fibrous structures, by addition to suspensions at the “wet end” of paper making. For formed materials like textiles, woven and nonwoven materials, addition at the “dry end” are known, such as impregnation, various coating techniques like spraying, dipping, roller addition, padding, screen coating, printing, further knife coating, blade coating, wire wound bar coating, round bar coating and crushed foam coating, or indirect coating techniques like direct roll coating, kiss coating, gravure coating and reverse roll coating, or further inkjet and/or slit-die/slot-die coating.

However, all of these methods require that relatively diluted solutions or dispersions of the binder system are applied, requiring for the making of dried webs the need for energy consuming removal of the carrier or solvent. Thus, there is still a need for highly efficient making of dry bonded fibrous webs with a curable binder system.

It is also known to create so called “coform” materials by combining natural fibers, especially cellulose or pulp fibers with synthetic thermoplastic polymer meltblown filaments or fibers, where solidified thermoplastic filaments serve as binder, see e.g. EP2265756 (Harvey, K-C) or EP3129535 (Boscolo, Boma), both employing melt-blowing for the binder fibers, or US2015/0322601A1 (Biax) using the so-called spun-blowing forming for these fibers. More recently, particular executions of the spun-blowing technology have been developed, see PCT/EP2018/080293 (published as W02020/099193A1, Teknoweb Materials), describing a unitary spinblock, or PCT/EP2018/080291 (published as W02020/10, 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.

Surprisingly it has now been found that melt blowing equipment and especially spun- blowing equipment and respective processes for dry-forming fibrous, in particular natural fiber based webs can be modified to provide webs, which are not bonded by the thermoplastic fibers but rather by curable binder systems, whereby a binder system as a solution of the binder compound or as a suspensions of small particles of the binder compound is run through the melt- or spun-blowing equipment and the solution solvent or dispersion carrier, as may be water, is at least partially stripped off by the shielding hot air stream.

Summary

The present invention is a method for forming an essentially dry bonded fibrous web comprising natural fibers, preferably cellulosic fibers, and a curable binder compound. The method comprises the steps of: providing a supply system for a binder system, the binder system comprising a binder compound adapted to attach to the natural fibers, and a solvent or carrier for the binder compound, preferably water, wherein the binder composition is dissolved in the solvent or dispersed in the carrier with a particle size of less than about 50 pm, preferably less than about 10 pm, or more preferably less than about 1 pm; a j et forming system ; a supply system for the natural fibers; a mixing chamber for mixing the natural fibers with the binder system; a fiber collecting system for forming a web pre-cursor from the mix of fibers and binder system; a finishing system for treating the web pre-cursor, comprising heating and compressing units; suspending individualized natural fibers in the mixing chamber in suspension air; pressurizing the binder system and expelling jets of the binder system into the mixing chamber, thereby intermingling the natural fibers and the jets, fractions of jets, optionally formed into droplets of the binder system; collecting the mixture of binder system and natural fibers of a forming system, thereby forming a web pre-cursor; preferably supporting the colleting by vacuum; - treating the web pre-cursor to form the final web exhibiting a pre-determined density, binder system solvent or carrier content, and strength, by applying energy, preferably heating energy.

The jet forming system is adapted to provide jets of the binder system with an essentially annular shroud of air around the jets at a temperature higher than the boiling temperature of the solvent or carrier of the binder system, preferably at least 10°C higher. Further, the process comprises the step of evaporating at least a portion of the solvent or carrier of the binder system, such that the binder system exhibits a higher concentration of the binder composition when contacting and connecting to the fibers, thereby optionally initiating curing of the binder composition.

The method may further comprise one or more steps selected from the group consisting of: adjusting the concentration of binder composition in the binder system to more than about 1 %, preferably more than about 5%, even more preferably more than about 10 %, and even more than about 30 %, and most preferably more than about 50 %, all on weight basis of the binder compounds and carrier or solvent of the binder system(s); adjusting the viscosity measured at 25°C of the binder system prior at the step of supplying it to more than about 1 Pas, preferably more than about 1000 Pas, even more preferably more than about 100.000 Pas; adjusting the temperature of the binder system to be less than about 30°C, less than about 20°C, or less than about 10°C, lower than the boiling point temperature of the solvent / carrier. adjusting the pressure of the solvent system before the jet forming system ... flash evaporation of the solvent / carrier at forming of jets; selecting the binder system being based on natural binder compounds: selecting the binder system such that it exhibits low corrosiveness to steel, especially low pitting corrosiveness, preferably by using stainless steel; arranging the direction of the jets and the shrouding air at an angle of more than about 35°; arranging the direction of the jets and the shrouding air at an angle of less than about 10°; further treating the web pre-cursor to a carrier / solvent content of less than about 15%, preferably less than 10%, or less than about 5%, based on the weight of pre-cursor fibers and binder composition.

Optionally, the supply system for the binder system may comprise an extruder, optionally comprising a degassing step.

In another aspect, the present is an equipment for executing such a method for forming an essentially dry bonded fibrous web. Therein, the jet forming system comprises an array of jet forming nozzles, each nozzle comprising a central capillary for the binder system and heating fluid discharge openings, preferably in annular form, around the capillary for hot air. The equipment may further comprise one or more elements selected from the group consisting of: the jet forming system comprising an array of nozzles, preferably of at least 3 rows, or 6 rows or 12 rows, and preferably of at least 10, 100, 1000 nozzles for each row. the jet forming system comprising an array of nozzles, with more than 30 nozzles per cm, or more than 75 nozzles per centimetre or even more than 150, and often less than 200 nozzles per cm. the nozzles of the jet forming system are removable and replaceable the central capillary of the nozzles exhibits a diameter of less than about 600 pm, preferably less than about 350 pm, more preferably less than about 125 pm; the array of nozzles comprises sub-arrays of differing nozzle dimensions.

Brief description of the Figures

Fig. 1A depicts a co-forming process according to prior art (see EP2265756, Harvey, K- C), and Fig. IB a modification thereof suitable for the present invention.

Fig. 2A depicts a co-forming process according to prior art (see EP3129535; Boscolo, Boma), and Fig. 2B a modification thereof suitable for the present invention.

Fig. 3A depicts a co-forming process according to prior art (see US2015/0322601A1; Biax), and Fig. 2B a modification thereof suitable for the present invention.

Fig 4A, B, and C depict details of a spraying block suitable for the present invention.

Fig. 5 depicts a particular web forming process according to the teaching of the present invention.

Figures are not to scale. Same numerals refer to same or equivalent features or elements. Numerals xx' and xx" denote duplicate elements, e.g., first - second or left - right.

Detailed description Process

In one aspect, the present invention aims at applying curable liquid binder systems comprising high concentrations of one or more binder compound(s) in a solvent or carrier, preferably water, in a dry forming process to fibrous webs of natural based fibers, such as without limitation, cellulose or pulp fibers, with the latter being a preferred selection especially due to cost and availability.

Due to the lower solvent or carrier content of a binder system useful for the present invention, the drying and the curing of the binder compound(s) requires less energy. In order to overcome problems that current technologies encounter with increased binder compound levels in the binder system, in particular handling of a viscous binder system and distributing it evenly across the fibers of the web, the present invention is to create a plurality of thin liquid jets of the binder system, each surrounded by an annular stream of hot air, which induces evaporation of the water of the binder solution, increasing the binder compound level in the jets even higher, such that these may break up into streams of short jet fragments, filaments, fibers, or droplets. The jets are introduced into a forming chamber, wherein individualized short fibers, such as natural fibers like cellulose fibers or pulp, are suspended in air. The jets, fragments or drops, which may already be in a pasty or gel-like or even solid state, intermingle with the fibers and are attaching to the surface of the fibers. Also, a certain degree of curing may occur and further support the attachment to the fibers. The fiber / binder mixture is then collected on an air pervious collection screen, where the fibers form a web pre-cursor and the binder compounds attached to the surface of fibers are connecting neighbouring fibers. Upon further heating to induce final drying, curing, and/or optionally gentle compression of the web pre-cursor, e.g., in a nip between two counter rotating rolls, the final web is consolidated to a pre-set degree of loft and strength.

When considering the size of the individual fibers, with cellulose fibers being preferred, the diameter of the jets may be smaller than these.

The amount of binder compound in the final web corresponds to usual levels of more than about 2 weight-%, or more than about 5 weight-%, more than about 10 weight-%, more than about 15 weight-%, though typically less than about 20 weight-%. Concentrations in % in the present invention are concentrations in weight % unless otherwise indicated.

The very fine and even distribution of the binder compounds results in better strength performance as compared to same weight ratios of conventionally applied binder compounds.

It is a particular feature of the present invention that this process can be executed without major changes on equipment as readily available for creating so called co-form materials, referring to forming mixtures of short fibers, typically cellulose fibers, with thermoplastic filaments, of the meltblown or preferably spun-blown type, and described in more detail herein below.

Thus the process comprises the following steps:

- Providing a binder system, comprising at least one binder compound and a solvent or carrier liquid, preferably water. As described in more detail herein below, the binder compounds should be selected from the broad range of available curable solvent or carrier compatible binder compounds, and preferably exhibits a boiling point at ambient pressure well above the one of the solvent or carrier, preferably at least 10°C higher, further allowing high compound concentrations in the solvent or carrier system.

In case of the binder system comprising a particle suspension of the binder compound in the carrier fluid, the particle size is well below the size of the inner diameter of the nozzle capillaries (as described herein below) and should be less than about 50 pm, or less than about 10 pm or less than about 1 pm.

Preferably the solvent or carrier fluid exhibits low corrosiveness, in particular pitting corrosiveness, versus stainless steel, and especially for aqueous binder systems. Preferably, the concentration of the binder compound(s) in the binder system is high at correspondingly low solvent content, and should be more than about 1 %, or more than about 5%, or more than about 10 %, or more than about 30 %, or more than about 50 %, all on weight basis of the binder compounds and carrier or solvent of the binder system(s). The viscosity of the binder solution may be high, exceeding the ones as typically handled in conventional spray applications, and be more than about 1 Pas, or more than about 1.000 Pas, or more than about 100.000 Pas, or even more than about 500.000 Pas, though typically less 1.000.000 Pas. The viscosity can be determined with a Brookfield viscometer DV2T with UL adaptor at 25°C or, when the viscosity is high enough with LV spindle at 10 rpm.

In a particular execution, the binder compounds are of natural origin. Optionally the binder system may comprise several binder compounds.

- Supplying the binder system to a spraying head comprising a multiplicity of nozzles, optionally by degassing the binder system in an extruder.

- Forming jets of binder system through expelling the binder system through the center hole of nozzles, and hot air surrounding the jets, preferably in an annular air flow essentially parallel to the jets, whereby the jets and air streams are discharged into a forming chamber, whereby optionally the liquid binder system jets break up into jet fragments or droplets.

- Evaporating solvent from the binder system by flash drying effect upon pressure reduction and boiling off of the solvent by heating with the hot air.

- Supplying individualized natural fibers to a forming chamber.

- Mixing the jets, jet fragments or droplets with the natural fibers in the forming chamber, whereby preferably all of the residual the binder system, i.e. binder compound and non- evaporated residual solvent or carrier, if present, are adhering to the fibers.

- Depositing the fiber / binder system mixture on a collecting screen, thereby forming a web pre-cursor.

- Removing vapour of the solvent or carrier with the suspension air of the fibers, preferably not through laydown screen.

- Executing one or more treatment(s) of the web pre-cursor, selected from the group consisting of applying heat for finalizing curing and / or adjusting solvent or carrier content for the final bonded web and compressing the web pre-cursor to a pre-determined web density, thereby forming the final web with predetermined properties, especially density, loft, strength, fuzziness.

The connecting between fibers that provides strength of the web may occur already in the forming chamber, during the deposition on the collecting screen, at the heating of the web pre-cursor, or when compressing the web pre-cursor.

Materials

Natural fibers Within the present context, "natural fibers" means an elongate particulate having a limited length exceeding its width or diameter, i.e. a length to width ratio of no more than 200. For purposes of the present disclosure, a "fiber" is an elongate particulate as described above that has a length of less than 3 cm. Fibers are typically considered discontinuous in nature. Non-limiting examples of fibers include hardwood and softwood pulp fibers; hemp bast; bagasse; bamboo; com stalk; cotton; cotton stalk; cotton linters; esparto grass; flax tow; jute bast; kenaf bast; reed; rice straw, sisal; switch grass; wheat straw.

Fibers particularly useful as components of the fibrous web structure include cellulosic fibers commonly known as 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. Pulps derived from both angiosperm (flowering) trees (also referred to as "hardwood") and gymnosperm (coniferous) trees (also referred to as "softwood") may be utilized. A blend of long, or medium-length, pulp fibers, and short pulp fibers may be suitable for purposes herein. Generally, long and medium-length fibers tend to be larger and more coarse, providing desirable texture and absorption characteristics, while short fibers tend to be finer and softer, enhancing opacity of the structure and adding tactile softness. Including short pulp fibers as a portion of the fiber blend may be beneficial for controllably including consolidated masses of fibers in the blend. It should be noted that the term “natural fibers” 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.

Such cross-linked cellulosic fibers may be crimped, twisted, or curled, or a combination thereof including crimped, twisted, and curled. Exemplary chemically cross-linked cellulosic fibers are disclosed in US5549791, US5137537, US9534329 or US2007/118087. Exemplary cross-linking agents include polycarboxylic acids such as citric acid and/or polyacrylic acids such as acrylic acid and maleic acid copolymers.

For example, the crosslinked cellulosic fibers may have between about 0.5 mole % and about 10.0 mole % of a C2 -C9 polycarboxylic acid cross-linking agent, calculated on a cellulose anhydroglucose molar basis, reacted with the fibers in an intrafiber ester crosslink bond form.

Binder system

Suitable curable binder systems include polymeric materials in the form of aqueous emulsions or solutions and non-aqueous solutions.

Polymer emulsions are often referred to as "latexes", referring very broadly to any aqueous emulsion of a curable or thermoset polymeric material. In order to be compatible with the process and equipment according to the present invention, as described in more detail herein below, the polymeric materials of the binder compounds should be less than about 50 pm, or less than about 10 pm or less than about 1 pm.

The term “solution” means curable binder compounds dissolved in water or other solvents, such as acetone or toluene. Particulate polymeric materials used in emulsion binder systems satisfying the small particle size requirement can range from hard rigid types to those which are soft and rubbery. As a few specific examples, suitable curable binder systems can be made of the following materials: epoxy, phenolic, bismaleimide, polyimide, melamine/formaldehyde, polyester, urethanes, urea, urea/formaldehyde. Without limiting these latter materials, examples include: ethylene vinyl alcohol, polyvinyl acetate, acrylic, polyvinyl acetate acrylate, acrylates, polyvinyl dichloride, ethylene vinyl acetate, ethylene vinyl chloride, polyvinyl chloride, styrene, styrene acrylate, styrene/butadiene, styrene/acrylonitrile, acrylonitrile/butadiene/styrene, ethylene acrylic acid, polyethylene, urethanes, polycarbonate, polyphenylene oxide, polypropylene, polyesters, polyimides. Other suitable binder systems comprise self cross-linking latex binder. The term “latex binder” refers to polymeric materials that are applied to a substrate in an uncured state, typically as an aqueous dispersion of small sized binder compound particles. Upon thermally treating the substrate, both drying off of the water as carrier and thermally induced curing of the latex binder occurs. In view of avoiding undesired components such as formaldehyde as may be released by certain binder formulations, preferred synthetic polymers that can be used in binder latexes include polymers or copolymers of alkylacrylates, vinyl acetates such as ethylene vinyl acetate, and acrylics such as styrene- butadiene acrylic. Latexes useful in the present invention may be prepared by emulsion polymerization of certain olefmic (ethylenically unsaturated) monomers. This emulsion polymerization can be carried out by customary methods using any of a variety anionic, nonionic, cationic, zwitterionic and/or amphoteric emulsifiers to stabilize the resultant latex, including alkyl sulfates, alkylarylalkoxy sulfates, alkylarylsulfonates and alkali metal and/or ammonium salts of alkyl- and alkylaryl-polyglycol ether-sulfates; oxyethylated fatty alcohols or oxyethylated alkylphenols, as well as block copolymers of ethylene oxide and propylene oxide; cationic adducts of primary, secondary or tertiary fatty amines or fatty amine oxyethylates with organic or inorganic acids, and quaternary alkylammonium surfactants; and alkylamidopropylbetaines. The olefmic monomer can be a single type of monomer or can be a mixture of different olefmic monomers, i.e. to form copolymer particles dispersed or emulsified in the aqueous phase. Examples of olefmic monomers that can be used to form latex polymers include C₂-C₄ alkyl and hydroxy alkyl acrylates, such as those selected from the group of propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2- hydroxyethyl acrylate, 2-hydroxypropyl acrylate, ethyl acrylate and mixtures thereof Other examples are C₁-C₄ alkyl or hydroxy alkyl methacrylates selected from the group of propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, ethyl methacrylate, methyl methacrylate, vinyl acetate and mixtures thereof. Also suitable are mixtures of the aforementioned C₂-C₄ alkyl and hydroxy alkyl acrylates and C₁-C₄ alkyl or hydroxy alkyl methacrylates. A preferred execution of such a binder latex are self-crosslinking aqueous polymeric dispersions of a vinylacetate - ethylene copolymer.

Suitable binder system latexes may exhibit a glass-transition temperature of more than about 0°C but less than about 30°C, preferably of between 5°C and 15°C. The polymer dispersion may have a particle size of from 0.01 to about 10 pm, preferably between about 0.1 and 3 pm. A specific execution of such a material is Vinnapas ® 192, commercially available from Wacker Chemie AG, Germany.

For a number of applications, it is desirable that not only the fibers but also the binder system is of natural origin, and optionally be also biodegradable.

Thus, in a first approach, such biodegradable binder systems may be comprising one of polyurethane resin, polyester, aliphatic polyester, polyvinyl alcohol, polycaprolactone, polyhydroxyalkanoate, denatured starch, a natural polymer, a polyisocyanate, polyglycolic acid, polylactic acid, polyhydroxybutyric acid, polyhydroxyvaleric acid, a polyhydroxycarboxylic acids, polybutylene succinate and polybutylene adipate (which can be obtained by poly condensation of polyhydric alcohols and polybasic acids).

In a second approach, such natural based binder systems may comprise tannin, lignin, cellulose, hemicellulose, chitosan or the like, possessing active hydroxyl or amine groups and a polycarboxylic acid or other material capable of forming bonds with the natural based material. The natural based binder systems may comprise further reactants. The reactant may be selected from the group: 1,2, 3, 4- butanetetracarboxylic acid, citric acid, maleic acid, succinic acid, itaconic acid, trans-aconitic acid, cis-aconitic acid, tricarballylic acid, talloid fatty acid and suberin fatty acid and their oligomers, glucosamine, polyethylene glycol, polypropylene glycol, polyglycols, proteins, sugars, polyvinyl alcohol, polyalkylene oxides, polyalkylene alcohols, oligomers or polymers of glycerol, glyoxal, furfuryl alcohol and aldehyde, pentaerythritol , phloroglucinol , eugenol, resorcinols, 1, 2- benzenedicarboxylic acid and anhydride, 1 , 3-benzenedicarboxylic acid, 1,4- benzenedicarboxylic acid, 1 , 2 , 3-benzenetricarboxylic acid, 1, 2, 4-benzenetricarboxylic acid, 1,2, 3, 4- cyclobutanetetracarboxylic acid, tetrahydrofuran- 2 , 3 , 4 , 5-tetracarboxylic acid, 1,2, 4, 5- benzenecarboxybc acid, succinic anhydride, maleic anhydride, poly-maleic acid and their anhydrides and their combinations. In addition to ester and amide bonds also ether and carbon-carbon bonds can be formed but for these alternative cross-linking agents and often a catalyst is required. Alternative reactants can be aldehydes, e.g. acetaldehyde and benzaldehyde, with a nitric acid or furfuryl aldehydes, furfuryl alcohol, monolignols, p-coumaryl alcohol, coniferyl alcohol, sinapyl alcohol, dimethylamine ethanal, suberin fatty acids, e-caprolactam, glycerol, glyoxal, derivatives of lignin and products of pyrolysis and degradation/depolymerization of lignin. The above materials can be used as reactants, cross-linking agents or polymerisation chemicals instead of or in combination with ester bond forming chemicals, such as polycarboxylic acids and anhydrides.

The binder system may comprise materials selected from the group consisting of tannin, chitosan, starch, cellulose, lignin, hemicellulose, alginic acid, pectins, hyaluronic acid, chitin, glucosamine copolymers, polyglycols, proteins, sugars, e.g. sorbitol, xylitol, sucrose, glucose or fructose, polyvinyl alcohol, hydroxyl or amine containing polymers, polyalkylene oxides, polyalkylene alcohols, fatty acid oligomers and polymers, oligomers or polymers of glycerol, and their derivates and their combinations. Generally, any binder material containing hydroxyl or amine groups capable of reacting with the reactant to form an ester bond are suitable. In particular executions, the binder compound may be selected from lignin, tannin and their combinations. Polyethylene glycol, polyglycols, polyvinyl alcohol, polyalkylene oxides, polyalkylene alcohols and/or oligomers or polymers of glycerol can be used as reactants to modify the binder material. Further, chitosan as a naturally occurring polysaccharide is cationic in nature and composed of mainly (1,4) linked 2-amino-2-deoxy- p-D-glucan. It is soluble in acidic solutions but insoluble in alkaline solutions. Both the amino groups in the chitosan molecule are pH sensitive. Chitosan is a derivative from shells and possesses a primary amine group on its polysaccharide ring which may be grafted onto cellulose by incorporation of a bi-functional cross-linking

The binder compound may be reacted and/or polymerized/cross-linked with the reactant with or without a catalyst. The one or more catalyst(s) may be contained in the natural binder compound. The catalyst may selected from the group consisting of sodium hypophosphite monohydrate, sodium hypophosphite, sodium phosphate, sodium phosphinate monohydrate, titanium dioxide, triethylamine , acid catalysts, e.g. citric acid, and other neutral catalysts and their combinations. The catalyst may be applied in amounts of more than about 2 %, or less than about 5 %, on a weight basis of the binder system.

In a third approach for natural based binder systems, these may comprise

(i) proteins and protein-based compounds such as casein, soya proteins, zein, and gelatin,

(ii) and/or gums and gum-like materials such as gum arabic, gum tragacanth, gum ghatti, Indian gum, mucilage and the like. The organic, optionally hydroxylated, acid according to item (ii) may have 2 to 18 carbon atoms. It can be saturated or unsaturated, the former being preferred. It can be a mono- or poly (e.g. di-) carboxylated acid, the former being preferred. It is preferably selected from citric acid, lactic acid, isoascorbic acid, glycolic acid, malic acid, tartaric acid, glycolic acid, acetic acid, dehydroacetic acid, oleic acid, palmitic acid, stearic acid, behenic acid, palm kernal acid, tallow acid, salicylic acid, ascorbic acid, sorbic acid, benzoic acid, succinic acid, or any combinations thereof. Preferred acids are saturated and hydroxylated and include citric acid, lactic acid, isoascorbic acid or any combinations thereof. Of these, lactic acid together with a corresponding metal salt, such as sodium lactate or potassium lactate, is most preferred.

(iii) and/or polysaccharide-based materials such as starch and processed starch, dextrins, agar, pectin, and the like

(iv) and/or glues derived from animal products such as hides, bones, and fish offal.

In another, fourth approach, the binder system may comprise a carbohydrate component and a salt of an inorganic acid with ammonia wherein the carbohydrate component consists at least partially in cellulose hydrolysate sugars comprising monosaccharides, including dextrose and xylose, disaccharides and polysaccharides. The carbohydrate component may comprise 1 to 95 wt % glucose and 0.5 to 15 wt % xylose, preferably 1 to 10 wt% xylose, the remainder being fructose, mannose, galactose and/or a polysaccharide fraction. The polysaccharide fraction may comprise arabinan, galactan, and/or mannan. The term "cellulose hydrolysate sugars" as used herein means the carbohydrate composition obtainable by hydrolysis of cellulosic material. Cellulosic material contains cellulose and hemicellulose. Cellulose is a linear polysaccharide composed of 6-carbon saccharide units that constitutes the chief part of the cell walls of plants, occurs naturally in such fibrous products as cotton and kapok, and is the raw material of many manufactured goods (e.g. paper). Hemicellulose is a polysaccharide composed of 5 -carbon saccharide units and is present along with cellulose in plant cell walls. While cellulose is strong and resistant to hydrolysis, hemicellulose is much less stable and easier to hydrolysate. It is understood that the hydrolysate sugar composition varies as a function of the feedstock, on the balance between cellulose and hemicellulose and of the hydrolysis process, including acid hydrolysis and enzymatic hydrolysis, and process conditions. Such hydrolysates comprise essentially reducing sugars. Thus the hydrolysate sugar composition comprises monosaccharides, dextrose and xylose, disaccharides, and polysaccharides. The concentration of each of these components in the composition may depend on the feedstock used for hydrolysis purposes, the hydrolysis process and the process conditions. Examples of carbohydrates present are glucose, fructose, sucrose, arabinose, galactose, mannose, xylose, arabinan, galactan, glucan, mannan and xylan.

In a fifth approach, an aqueous curable binder system comprises a carbohydrate compound, a first cross linker selected from carboxyl function bearing compounds which form esters with the carbohydrate compound and a different second cross linker, which is capable of undergoing radical polymerization, and possibly a free radical initiator. The aqueous binder composition may further comprise a reaction product of resulting from the crosslinking between carbohydrate compound and cross linker. The carbohydrate compound may be selected from monosaccharide and/or polysaccharide, and the polysaccharide may comprise at least two, preferably at least 4 saccharide units and up to 106 saccharine units, preferably up to 10000 saccharide units, more preferably up to 5000 or even 3000 saccharide units. The polysaccharide may be selected from native starch and starch derivatives, including but not limited to starch ethers such as carboxymethyl starches, hydroxyalkyl starches, cationic starches, amphoteric starches, starch esters, such as starch acetates, starch phosphates, starch octenyl succinate and starch copolymers, or any other partially hydrolysed starch, acid modified starch, oxide modified starch and partially hydrolysed starch, including but not limited to dextrin, and from polysaccharides derived from cellulose or other natural or synthetic sources, such as chitin.

The binder system compounds may contain a natural cationic polymer, which may have cationic charge densities of more than about 0.4 meq/gm, or more than about 0.9 meq/gm, or more than about 1.2 meq/gm, and often less than about 10 meq/gm. Herein, "cationic charge density" of a polymer refers to the ratio of the number of positive charges on the polymer to the molecular weight of the polymer. The average molecular weight of such natural cationic polymers will generally be between about 10,000 and 10 million, preferably between about 50,000 and about 5 million, more preferably between about 100,000 and about 3 million. Suitable natural cationic polymers may contain cationic nitrogen-containing moieties such as quaternary ammonium or cationic protonated amino moieties. The cationic protonated amines can be primary, secondary, or tertiary amines (preferably secondary or tertiary), depending upon the particular species and the selected pH of the composition. In this approach, any anionic counterions can be used in association with the cationic polymers as long as the polymers remain soluble in water, or the particles in a dispersion do not exceed the processable particles size. Such counterions may include halides (e.g., chloride, fluoride, bromide, iodide), sulfate and methylsulfate. The cationic cellulose polymers may be salts of hydroxyethyl cellulose reacted with trimethyl ammonium substituted epoxide, polymeric quaternary ammonium salts of hydroxyethyl cellulose reacted with lauryl dimethyl ammonium-substituted epoxide or copolymers of etherified cellulose and starch.

A further, sixth, and for certain applications particularly preferred, approach for natural binder system comprises natural polyelectrolyte complex (hereinafter also referred to PEC) compositions. PECs are the association complexes formed between oppositely charged particles. These complexes are formed due to electrostatic interaction between oppositely charged polyions and thereby avoid the use of chemical cross linking agents. Based on their origin, PECs are classified as natural poly electrolytes, synthetic polyelectrolytes and chemically modified biopolymers, with the first ones being of particular interest.

Natural based polyelectrolyte complex (PEC) compositions are considered environmentally benign, renewable and biodegradable. Particular PEC compositions may comprise chitosan as a cationic polymer, an anionic polymer being represented by polyanions derived from nature, especially polysaccharides, and one or more additives. The anionic biopolymer may be selected from the group consisting of lignin alkali, lignosulfonic acid, and a polysaccharide, preferably chosen from the group consisting of carboxymethyl cellulose (CMC), alginic acid, pectin, carrageenan, gum arabic and nanocrystalline cellulose (NCC), more preferably from the group consisting of carboxymethyl cellulose, alginic acid sodium salt, lignin alkali, NCC and gum arabic, most preferably carboxymethyl cellulose. The concentration of the anion may be in the range of 0.005-30 % by weigth.

Typically, the pH of the PEC composition is below pH 7 and this may be achieved by adding Bronsted acids and/or Lewis acids. Preferably, the pH of the PEC composition is lower than 6.5. Bronsted acids are selected from any organic or inorganic acids, wherein the concentration of the acid is 0.01 - 30 %. Lewis acids are selected from any cationic mono- or multivalent atom, wherein the concentration of the Lewis acid is 0.01-30 %. The PEC composition preferably has a pH value of between 2 and 4. The weight ratio between the cationic polymer and the acid is 1 : 0.01 to 1 :30 in the PEC composition. The acid of the PEC composition may be selected from one or more of acetic acid, acetyl salicylic acid, adipic acid, benzenesulfonic acid, camphorsulfonic acid, citric acid, dihydroxy fumaric acid, formic acid, glycolic acid, glyoxylic acid, hydrochloric acid, lactic acid, malic acid, malonic acid, maleic acid, mandelic acid, oxalic acid, para-toluenesulfonic acid, phtalic acid, pyruvic acid, salicylic acid, sulfuric acid, tartaric acid and succinic acid, more preferably citric acid, oxalic acid and tartaric acid, even more preferably citric acid, and most preferably citric acid monohydrate. The concentration of the PEC in the PEC composition is at least 0.04 wt % PEC, preferably at least 1.5 wt % PEC, more preferably at least 4 wt % PEC, most preferably 4-10 wt % PEC.

The PEC composition may further comprise one or more fatty compounds. The fatty compounds in the PEC composition comprise fat and/or oil and /or fatty acid. The composition's ability to incorporate and transport the fatty compounds gives the opportunity of transferring the hydrophobic properties of named fatty compounds to different materials treated with the PEC composition. The fatty compounds may be present in the PEC composition at a weight ratio of PECTatty compound of 1:0.01 to 1:50, preferably 1:0.05 to 1:20, more preferably 1:0.1 to 1: 10, most preferably 1:0.5 to 1: 1. The one or more fatty compounds according to the present invention are independently of each other selected from the group consisting of natural oil, synthetic oil, liquid wax, liquid resin, fatty acid, fatty alcohol, fatty silanes, fatty siloxanes, fatty amine, fatty amide, fatty epoxide, fatty imine, fatty aldehyde, fatty imide, fatty thiol, fatty sulfate, fatty ester, fatty ketone, other types of lipids; preferably selected from natural oil, wax and/or fatty acid, and mixtures thereof. Further, the PEC composition may comprise one or more additive(s) selected from water soluble plasticizer, defoamer, foaming agent, wetting agent, coalescent agent, catalyst, surfactant, emulsifier, conservative, cross-linker, rheology modifier, filler, nonionic polymer, dye, pigment. The one or more additives are selected depending on the application method and the expected properties of the final material, wherein the concentration of the additive(s) is 0-99 wt%, preferably 0-50 wt%, most preferably 0-30 wt%.

The composition can additionally comprise an acid or basic catalyst which has in particular the role of adjusting the temperature at which crosslinking begins. The catalyst can be chosen from Lewis bases and acids, clays, colloidal or noncolloidal silica, organic amines, quaternary amines, metal oxides, metal sulphates, metal chlorides, urea sulphates, urea chlorides and catalysts based on silicates.

The catalyst can also be a phosphorus-comprising compound, for example an alkali metal hypophosphite salt, an alkali metal phosphite, an alkali metal polyphosphate, an alkali metal hydrogenphosphate, a phosphoric acid or an alkylphosphonic acid. Preferably, the alkali metal is sodium or potassium. The catalyst can also be a compound comprising fluorine and boron, for example tetrafluoroboric acid or a salt of this acid, in particular an alkali metal tetrafluoroborate, such as sodium tetrafluoroborate or potassium tetrafluoroborate, an alkaline earth metal tetrafluoroborate, such as calcium tetrafluoroborate or magnesium tetrafluoroborate, a zinc tetrafluoroborate and an ammonium tetrafluoroborate. Preferably, the catalyst is sodium hypophosphite, sodium phosphite or the mixtures of these compounds.

The amount of catalyst introduced into the composition can represent up to 20 wt%, preferably up to 10%, and advantageously is at least equal to 1%.

Generally, the binder systems suitable for the present invention exhibit high concentrations of binder compound. Preferably, the binder systems are dilutable so as to allow adjustment of flow properties, especially viscosity, e.g., if natural base material exhibit variable properties. Particularly preferred are binder systems comprising water as solvent or carrier.

Equipment

It is a particular feature of the present invention, that the highly viscous solutions or dispersions can be processed in equipment as known for other applications, namely equipment for so called co-forming processes where thermoplastic polymers are extruded as melt-blown or spun-blown filaments through arrays of nozzles, further employing hot drawing or shrouding air, and mixing such fine filaments with natural fibers, such as cellulosic or pulp fibers.

Such equipment is generally well known in the art and can be adapted to be suitable for the present invention.

Fig. 1A depicts an equipment 200 as known from EP2265756A1 (Harvey, K-C) showing two meltblowing units 230, each with polymer supply units 232, two extruders 235, optionally with a polymer pump (not shown) supplying molten polymer to two melt blowing filaments forming heads 236, arranged in an angled position to each other. A fiber supply unit 220 defiberizes pulp board 221 in a defiberization unit 222 and supplies individualized fibers 229 through a fiber nozzle 226, optionally supported by auxiliary air supply 224 through auxiliary air piping 225. The filaments from the meltblowing die nozzle 238 and the individualized fibers from the fiber nozzle tip 228 are mixed in the mixing region 240 and laid down in a lay down system 250 on a collector screen 251 running over collector screen rolls 252, where a web 260 is formed with support of vacuum suction 253. Fig IB depicts a modification of this system suitable for the present invention showing two spraying units 330, each with binder system supply units 332, two binder system pumps 335 supplying the binder system to two spraying heads 336, arranged in an angled position to each other. Alternatively, a pump may be replaced by an extruder, which further may comprise a degassing as may also increase the concentration and viscosity of the binder system. A fiber supply unit 320 defiberizes pulp board 321 in a defiberization unit 322 and supplies individualized fibers 329 through a fiber nozzle 326, optionally supported by auxiliary air supply 324 through auxiliary air piping 325. The jets from the spraying head nozzle 338 and the individualized fibers from the fiber nozzle tip 328 are mixed in the mixing region 340 and laid down in a lay down system 350 on a collector screen 351 running over collector screen rolls 352, where a web pre-cursor 360 is formed with support of vacuum suction 353. The system further comprises a forming chamber 340 with a forming chamber housing 342, such that the fibers and jets are directly fed into this chamber and are mixing therein.

A further melt-blowing coform system 400 is known from EP3129535 (Boscolo, Boma), see Fig. 2A. This system comprises two fiber supply systems 420 with a defiberization unit 422 creating individualized fibers 426 from a fiber board supply 421. These systems are arranged with one centrally positioned meltblowing fiber system 430 with a polymer supply 432, extruder 435 and filament forming head 436 comprising melt blowing air supply 437. The meltblown fibers and the pulp fibers are mixed and - supported by vacuum system 453 and mixing region containment flaps 449 - laid down on a collection screen 451, running over rollers 452. At a compression unit the web is run between two compression rollers 461 and 462.

Analogous to the set-up as shown in Fig. IB, the corresponding equipment suitable for the present invention, comprising two fiber supply systems 520 with a defiberization unit 522 creating individualized fibers 526 from a fiber board supply 521. These systems are arranged with one centrally positioned binder system spraying unit 530 with a binder system supply 532, binder system pump 535 and jet spraying head 536 comprising spraying air supply 537. The binder system jets and the pulp fibers are mixed and - supported by vacuum system 553 and mixing region containment flaps 549 - laid down on a collection screen 551, running over rollers 552. At a compression unit the web is run between two compression rollers 561 and 562.

A further system which can be adapted to be suitable for the present invention is known from US2015/032601 (Brown / Biax), see Fig. 3A and 3B modified to be suitable for the present invention. This system comprises shrouding of the filaments by hot air, as depicted in Fig. 4A showing an enlarged view of a filament forming head as known from e.g. US9303334, hereinafter referred to as US’334, adapted for the present application.

As shown in Fig. 4A, a spraying head 26 comprises a spraying head body 52, an air distribution plate 70, an exterior plate 78, and a cover strip 88. Further, nozzles 58 extend from the spraying head body 52 through openings of the distribution plate 70 and exterior plate 78, respectively, such that the fluid binder system can pass through the capillary 60 of the nozzle 58 to form jets 86 at the tip of the nozzle 96. The jets may break up into jet fragments 86’, that may further form droplets 86”.

For ease of explanation, the order of the elements referred to in the following is such that the spraying head body 52, the air distribution plate 70, the exterior plate 78, and the cover strip 88 are arranged along gravity, such that the spraying head body 52 is positioned above and secured to the air distribution plate 70, which is positioned above and secured to the exterior plate 78, which is positioned above and secured to the cover strip 88, with securing means not shown.

When such a spraying head 26 is positioned into a manufacturing equipment for forming fibrous webs, this view corresponds to an x-z-directional view, with the x-direction 12 denoting the manufacturing direction, i.e. the direction of movement of the resulting web, and the z-direction 15 corresponding to the height (along gravity). In the execution as depicted, the three nozzles 58 represent one “column” of the “multi row” (here three-row) spraying head 26. The spraying head comprises a plurality of columns which are positioned y-directionally adjacently (i.e. perpendicularly to the plane of drawing and indicated by the circle 18) such that the columns and rows of nozzles form an array of nozzles of a spraying head. A spraying head body 52 can contain from as few as ten nozzles 58 to several thousand nozzles 58. For a commercial size line, the number of nozzles 58 in the spraying head body 52 can range from between about 500 to about 10,000.

The number of rows can vary as well as the number of columns. Typically, the number of rows will be more than 1, often more than 5, and will be less than about 30, or even less than 15. Typically, the number of columns will be more than 50, but can be more than about 200, and may be less than 3500.

The nozzles 58 are formed of capillary tubes that are inserted through openings in the spraying head body 52 to form a passageway for the binder system.

Each of the nozzles 58 has an inside capillary diameter and an outside diameter. The inside diameter can range from between about 0.125 mm to about 1.25 mm. The outside diameter of each nozzle 58 should be at least about 0.5 mm. The outside diameter of each nozzle 58 may range from between about 0.5 mm to about 2.5 mm.

Typically, the length of a nozzle 58 ranges from between about 0.5 to about 6 inches.

As the binder system needs to pass only through the capillaries of the nozzles, the tubes may be tightly fitted and typically welded to the spraying head body. The binder system 22, as described in the above, is pumped into the binder system cavity 30.

The binder system throughput through each nozzle 58 is stated in “gram per hole per minute” (“ghm”) and can range from between about 0.01 ghm to about 4 ghm.

At its top, i.e. on the upper spraying head body side oriented towards the binder system supply, the spraying head 26 has a cavity 30 and an inlet 28 connected to the cavity 30. The binder system 22 is conveyed along the passageway from inlet 28 towards the upper portion of the spraying head body 52, and further via the nozzles downwardly. The spraying head body 52 also has one or more gas passages 32 formed therethrough for conveying pressurized gas (air) to an air chamber 54, which is essentially formed between the spraying head body 52 and the air distribution plate 70. The plurality of nozzles 58 extend downwardly from the spraying head body allowing binder system to flow through the capillaries 60 for exiting the nozzles and the spraying head downward of the exterior plate at nozzle tip 96 in the form of jets 86, that may break up in to jet fragments 86’ or droplets 86”.

Further, a plurality of stationary pins 62 may surround the array of nozzles, affixed to the body and extending through openings of the air distribution plate into the openings of the exterior air plate.

Each of the stationary pins 62 is an elongated, solid member having a longitudinal central axis and an outside diameter. Each of the stationary pins 62 is secured to the spraying head body 52 and usually they have a similar outside diameter compared to the nozzles 58. The outside diameter of each of the stationary pins 62 should remain constant throughout its length. The dimension of the outside diameter can vary. The outside diameter of the stationary pins 62 may be more than about 0.25 mm, or more than about 0.5 mm, or more than about 0.6 mm, or even more than about 0.75 mm.

An air distribution plate 70 is secured to the spraying head body 52 having a plurality of openings. Each one of first openings 72 accommodates one of the nozzles 58. If stationary pins 62 are employed, they are accommodated in second openings 74, and each of the third openings 76 is located adjacent to the first and second openings, 72 and 74 respectively. When operating the process, pressurized gas, typically air, is flowing along air passageways from the air chamber 54 through openings 72, which are a thin annulus around the nozzles, openings 74, also a small annulus around the stationary pins, if present, and third openings 76 as a main passageway for the air.

An exterior air plate 78 is secured to the air distribution plate 70, away from the spraying head body 52. The exterior member 78 has a plurality of first openings 80 surrounding the nozzle 58. Second enlarged openings 82 surround each of the stationary pins 62, if present. In operation, the binder system 22 is forced through each of the nozzles 58 to form multiple jets 86 which are intended to be shrouded from the ambient air by the pressurized gas, typically though not necessarily air, emitted through the first enlarged openings 80, formed in the exterior member 78, at a predetermined velocity essentially parallel to the axis of the capillaries 60 and hence the flow direction of the filaments 86 at the nozzle tip 96. As the pressurized air exhibits a temperature higher than the boiling point of the binder system carrier or solvent, the latter is evaporating or boiling off the binder system. This may be further enhanced by “flash evaporation” due to the pressure drop the binder system is experiencing when leaving the nozzles.

The pressurized gas (air) flow exiting the second enlarged openings 82 formed in the exterior member 78 around the stationary pins, if present, forms a further shrouding air flow, which is also oriented essentially parallel to the axis of the nozzles, and hence also essentially parallel to the jets exiting the nozzles, aiming at isolating the jets 86 from surrounding ambient air, as indicated in Fig. 4A with the arrow 94. The binder system jets, jet fragments or drops can then intermingle with the natural fibers, as explained further herein below.

Preferably, the spraying head may be designed according to the teachings of PCT/EP2019/080293 (published as W02020/099193), to which express reference is made as far as the design of the forming head is concerned. It is relating to a forming head that allows easy manufacturing thereof as well as easy cleaning of the system, see Fig. 4B.

Fig. 4B depicts spraying head 126 comprising spraying head block 152, air distribution plate 170, exterior air plate 178 and cover strip 188 arranged in the same way as described in the context of Fig. 4A. Further shown is one row of a plurality of five nozzles 158, also arranged in columns and rows forming an array of nozzles as described in the above. Optionally, the array of nozzles may comprise sub-arrays. Such a sub-array may include at least one row of nozzles, preferably, though not necessarily extending over the full width of a die block.

In the execution as shown in Fig. 4B, the nozzles 158 are not formed separately as capillary tubes and inserted into holes of the spraying head body 153. Rather, the spraying head body 153 and the nozzles 158 are “unitary” forming the spraying head block 152 as made from a single piece of material. This can conveniently be achieved by modem CNC machining technology, such as employing laser cutting, flame and plasma cutting, hole-punching, drilling, milling, lathing, picking and placing, sawing, and other such technologies as known in the art for CNC treatments.

Thus, in parallel or consecutively, though not necessarily in the listed order, the various features of the spraying head block are formed, especially though not limiting

- an inlet cavity 130 for the binder system 122;

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

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

- optionally further securing holes (199).

Each of the nozzles 158 may have an inside diameter of more than about 0.125 mm and / or less than about 1.25 mm. The outside diameter of each nozzle is preferably more than about 0.5 mm, or more than 1 mm and/or less than about 2.5 mm. Typically, the length of a nozzles is more than about 20 mm and/or less than about 150 mm.

Thus, the spraying head comprises a binder system passageway that goes from the inlet cavity 130 through the capillaries of the nozzles 158 towards the nozzle tip 196, where the binder system jets are formed, that may then break up into jet fragments or droplets.

Fig. 4B further depicts two options (alternatively or jointly) for creating an outer perimeter air curtain. In a first option, air passage openings 183 in the exterior air plate are positioned around the array of nozzles. In a second option, stationary and solid pins 162 also machined from the same spraying head block pre-cursor extend from the spraying head body through openings 174 the air distribution plate into openings 182 of the exterior air plate 178, allowing also an annular air flow around these pins. As described above, the binder system jets, jet fragments or drops can then intermingle with the natural fibers, as explained further herein below.

Alternatively, and for certain set ups even more preferably, the spraying head may be designed according to the teachings of PCT/EP2019/080291 (published as W02020/104190), to which express reference is made as far as the design of the forming head is concerned. The set-up is similar to the one as described in the context of Fig. 4B, however, the spraying head block 126 is not unitary and the nozzles 158 may be individually removed, so as to allow easy cleaning or replacement, optionally easily combining nozzles of different diameter in different regions of the array, see Fig. 4C.

Yet a further system that is particularly useful for certain applications is depicted in Fig. 5. It is the adaptation of a system as known from GB 1916086 (unpublished application), comprising a central supply of natural fibers and two binder system application units, similar to the one depicted in Fig. IB, but employing the spraying technology as explained in the context of Fig. 4 C, with the spraying heads exhibiting arrays of different nozzles sizes and separately controllable air flows.

An apparatus 1000 for forming a commingled web 1900 comprises a forming box 1100. The natural fiber material 1400 is provided by a natural fiber supply system 1410, and a first binder system 1200 and a second binder system 1300 are provided from a first (1210) and a second (1310) binder system supply system to a first (1220) and a second (1320) binder system jet forming system. The materials are supplied to the natural fiber inlet 1114, and first and second binder system inlet 1112, 1113, respectively, of the forming box 1100. Aided by vacuum of the suction box 1700, the commingled material exits the forming box at forming box outlet 1119 as commingled web 1900 laid onto a collector means 1600, such as a moving screen.

The apparatus has a general three-dimensional extension, exhibiting an apparatus height direction 1005, corresponding to the thickness or z-direction of a web as produced thereon. It further exhibits a machine- or x-direction 1002, and a cross- or y-direction (indicated by the “x” representing the fletching of a direction arrow 1008). Thus, Fig. 5 depicts a z-x- directional cross-directional view, wherein the left part, as seen by a viewer, depicts the upstream part 1001, whilst the right part with the commingled web 1900 on the collector means 1600 depicts the downstream part 1009, as the collector means is adapted to move from the upstream to the downstream part, thereby collecting the commingled web at an increasing web height, reaching the final web height or caliper. Cross-directionally, the apparatus is horizontally aligned and has an extension as may be less than 1 m, but often is more than 1 m, for large scale production apparatuses more than 3 m or even more than 5 m, though typically not exceeding 10 m. The web forming apparatus may be a stand-alone, separate, discrete, modular device that can be inserted as such into a larger manufacturing machine, such as an absorbent article or wipe making machine, and/or it may be a fully integrated component of such a larger machine.

A forming box 1100 as suitable for the present invention comprises a housing, an enclosed or partially-enclosed forming chamber 1110 formed by one or more walls through which one or more materials pass through inlets or outlets. A forming box may be made from a wide variety of materials, such as metal, often steel, but also sufficiently stiff polymeric material, such as polycarbonate, or even glass.

The material inlets of the forming box are connected to the respective material supply systems and arranged such that a 1^st binder system inlet 1112 is positioned upstream of the natural fiber inlet 1114, which is positioned upstream of the 2^nd binder system inlet 1113. The natural fiber inlet may be positioned such that the material is streaming through the forming chamber 1110 along gravity generally towards the collector means, though some tilting versus the vertical is acceptable.

The natural fiber inlet 1114 may exhibit a MD directional extension of more than about 0.07 cm, or more than about 0.1 cm, or more than about 0.2 cm, or more than about 0.3 cm and/or less than about 25 cm, or less than about 12.5 cm or less than about 7.5 cm.

The 1^st and the 2^nd binder system inlets 1112 and 1113 are preferably positioned symmetric to the natural fiber inlet as well and tilted to the vertical at between 30° and 90°, preferably at 60° and are adapted to allowing the expelled binder system jets to entangle the downward streaming natural fibers prior to contacting the collector mean’s surface.

The binder system inlets 1112 respectively 1113 may exhibit a MD directional extension of more than about 0.25 cm, more than 1.25 cm or more than about 2.5 cm, and of less than about 40 cm, or less than about 25 cm, or less than about 15 cm.

The commingled materials exit the forming chamber via the forming chamber outlet 1119, positioned towards the collector means, such as a moving belt 1600, further supported by vacuum suction by suction box 1700.

The forming chamber outlet my exhibit a MD extension of more than about 0.25 cm, or more than about 1.25 cm, or more than about 2.5 cm, and/or less than about 75 cm, or less than about 50 cm, or less than about 30 cm.

A particularly preferred execution of a forming box is described in more detail in the above cited US2016335950, to which express reference is made with regard to design, in particular dimensions, of the forming box.

Whilst for ease of explanation the natural fiber inlet as well as the binder system inlets are described in singular, multiple executions of any of these may well be contemplated and executed by using ordinary skills.

Natural fiber material 1400 is delivered to the natural fiber inlet 1114 of the forming box 1100. To this end, the natural fiber material may be delivered in roll or bale form that may then be disintegrated into individualized fibers by conventional means such as hammermill and/or solid additive spreader and/or airlaying equipment such as a forming head, for example a forming head from Dan-Web Machinery A/S, and/or an eductor as described in WO2016/354736 (P&G).

The natural fiber material may be supplied to the inlet 1114 of the forming box by gravity, or by pneumatic transport, or other mechanical feeder or a combination thereof. Further, the apparatus comprises at least two multi-row spraying systems 1220 and 1320, respectively, that may be connected to a common or (as indicated in Fig. 5) to two separate binder system supply systems 1210, 1310, supplying suitable binder systems 1200, 1300 to the spraying units, which are connected to the respective binder jet inlet 1112, 1113 of the forming box 1100.

Within the present context the term “connected” refers to a positioning such that the binder system jets as released by the spraying systems are directly streaming into the forming chamber 1110 of the forming box 1100.

The multi-row spraying systems may be as described in the above in the context of Fig. 4., i.e. a multiplicity of nozzles is arranged in an array of rows and columns and expel binder system jets into the forming chamber 1110.

For the operation, the nozzles are adapted to expel binder system jets through nozzle orifices predominantly along the nozzle centerline, which, as indicated in Fig.5, is inclined versus the natural fiber inlet, here shown as the vertical, such that the spraying head centerlines intercept the trajectories of the natural fiber material stream. Towards the machine directional limits of the array of nozzles, the direction of the jets may deviate outwardly.

Preferably, the binder system supply systems, respectively the spraying heads thereof, comprise sub-arrays of nozzles that are adapted to form pluralities of jets that exhibit different properties.

In a first approach to this end, the array of nozzles comprises at least two sub-arrays that are distinct in the geometry of the nozzles, i.e. inner or outer diameter or nozzle length. The spraying blocks may be as described in the above in the context of Fig. 4A, B and more preferably Fig. 4C.

The arrays of nozzles 1225, 1325 comprise sub-arrays 1222, 1322 and 1228, 1328, respectively. Such a sub-array may include at least one row of nozzles, preferably, though not necessarily extending over the full width of a die block. In a particular execution, the nozzles of sub-array 1222, 1322 differ substantially from nozzles of sub-array 1228, 1328 in at least one of the dimensions selected from the group consisting of inner diameter of the nozzle, outer diameter of the nozzle, and length of the nozzle, or their relative spacing. Within the present context, the term “substantially different” refers to a difference in the respective dimension of at least 5%, often more than 10% thereof.

Another approach towards providing binder system jets with different properties includes connecting the nozzles of sub-arrays to separate binder system supply systems.

For any of these variants, the nozzles are preferably executed such that a smooth flow of the molten polymer is enhanced by chamfering the inlet portions of the nozzles. For executions with removable nozzles, the spinneret block may be executed with chamferings being positioned in grooves, that may be filled with a sealing means to selectively exclude certain rows of the die head, as more described in the referenced applications, to which express reference is made as far as the nozzle designs are concerned.

Yet a further approach to inducing differing properties in binder system jets from different nozzles is to solely apply different settings to different heating devices, as described below. Referring to Fig. 5, the apparatus 1000 further comprises a heating system comprising heating devices 1510, 1520, 1530, 1540, positioned adjacent to the binder system jet inlets 1112, 1113 for providing heating fluid(s) at least to the jets of the outer nozzles of the nozzle array exiting from the jet forming systems 1220, 1320. The heating aims at controlling the solvent or carrier content of the binder system jets just after these leave the jet forming nozzle, and thus web properties such as loft, hand, stretchability, and tear strength. Heating also impacts the web properties, e.g. by interfiber fusion and also fiber entanglement.

Preferably, the heating fluid is gaseous, such as air or steam. The impact of heating depends on e.g. the heating fluid properties, especially temperature, and the amount of heating fluid relative to the amount and size of jets to be contacted. The heating fluid is provided at a temperature higher, preferably at least 10°C higher than the temperature of the binder system in the jets when leaving the nozzles.

In a particularly preferred execution of the present invention, heating system is adapted to selectively control the separate heating devices. This is of particular relevance for the execution with nozzle sub-arrays for which filaments may exhibit differing filament properties on the respective upstream and downstream portion of the spraying head. The separate control means for the heating devices now can be impacted and adjusted, such as by being adapted to control temperature respectively energy content of the fluid; amount of the heating fluid stream, as may be expressed as mass flow rate, expressed in mass per time, - or as the momentum, expressed in e.g. [kg*m/ sec], or mass flux, expressed in [kg/(m² * sec)]; velocity of the heating fluid stream when exiting the heating device, typically expressed in meter per seconds; direction of the heating fluid stream relative to the direction of the neighboring jets. Whilst the present equipment has been described by referring to an apparatus comprising a single natural fiber material supply system and two binder system jet forming systems, the skilled person will readily realize that there may be more of these, optionally also including a higher number of heating devices. Further the housing may have additional openings to accommodate other additives, additional heating devices, etc.. Resulting Product

Applying the described binder systems according to the process according to the present invention on an equipment as described, results in a bonded web structure that exhibit a superior balance of properties, in particular loft, softness, strength, linting, ...

Such webs may very suitably be used as wipes as such or in combination with further webs, as may be applied to the surface of the final web or web pre-cursor.

Claims

1311-2400CLAIMS

1. A method for forming an essentially dry bonded fibrous web, the web comprising natural fibers, preferably cellulosic fibers, a curable binder compound said method comprising the steps of providing a supply system for a binder system, said binder system comprising a binder compound adapted to attach to said natural fibers, and a solvent or carrier for said binder compound, preferably water, wherein said binder composition is dissolved in said solvent or dispersed in said carrier with a particle size of less than about 50 pm, preferably less than about 10 pm, or more preferably less than about 1 pm; a jet forming system; a supply system for said natural fibers; a mixing chamber for mixing said natural fibers with said binder system; a fiber collecting system for forming a web pre-cursor from said mix of fibers and binder system; a finishing system for treating said web pre-cursor, comprising heating and compressing units; suspending individualized natural fibers in said mixing chamber in suspension air; pressurizing said binder system, optionally including a degassing step in case of employing an extruder system, and expelling jets of said binder system into said mixing chamber, thereby intermingling said natural fibers and said jets, fractions of jets, optionally formed into droplets of said binder system; collecting said mixture of binder system and natural fibers of a forming system, thereby forming a web pre-cursor; preferably supporting said colleting by vacuum; treating the web pre-cursor to form the final web exhibiting a pre-determined density, binder system solvent or carrier content, and strength, by applying energy, preferably heating energy, wherein said jet forming system is adapted to provide jets of said binder system with an essentially annular shroud of air around said jets at a temperature higher than the boiling temperature of said solvent or carrier of said binder system, preferably at least 10°C higher, and wherein said process further comprises the step of evaporating at least a portion of said solvent or carrier of said binder system, such that the binder system exhibits a higher concentration of said binder composition when contacting and connecting to said fibers thereby optionally initiating curing of said binder composition.

2. A method for forming an essentially dry bonded fibrous web according to claim 1, further comprising one or more steps selected from the group consisting of adjusting the concentration of binder composition in said binder system to more than about 1 %, preferably more than about 5%, even more preferably more than about 10 %, and even more than about 30 %, and most preferably more than about 50 %, all on weight basis of the binder compounds and carrier or solvent of the binder system(s); adjusting the viscosity measured at 25°C of the binder system prior at the step of supplying it to more than about 1 Pas, preferably more than about 1000 Pas, even more preferably more than about 100.000 Pas; - adjusting the temperature of said binder system to be less than about 30°C, less than about 20°C, or less than about 10°C, lower than the boiling point temperature of the solvent / carrier. adjusting the pressure of the solvent system before said jet forming system ... flash evaporation of said solvent / carrier at forming of jets; - selecting the binder system being based on natural binder compounds: selecting said binder system such that it exhibits low corrosiveness to steel, especially low pitting corrosiveness, preferably by using stainless steel; arranging the direction of the jets and the shrouding air at an angle of more than about 35°; - arranging the direction of the jets and the shrouding air at an angle of less than about 10°; further treating the web pre-cursor to a carrier / solvent content of less than about 15%, preferably less than 10%, or less than about 5%, based on the weight of pre-cursor fibers and binder composition.

3. An equipment for executing a method for forming an essentially dry bonded fibrous web according to claims 1 or 2, wherein said jet forming system comprises an array of jet forming nozzles, each nozzle comprising a central capillary for said binder system and heating fluid discharge openings, preferably in annular form, around said capillary for hot air.

4. An equipment for executing a method for forming an essentially dry bonded fibrous web according to claim 3, further comprising one or more elements selected from the group consisting of - the jet forming system comprising an array of nozzles, preferably of at least 3 rows, or 6 rows or 12 rows, and preferably of at least 10, 100, 1000 nozzles for each row; the jet forming system comprising an array of nozzles, with more than 30 nozzles per cm, or more than 75 nozzles per centimetre or even more than 150, and often less than 200 nozzles per cm; - the nozzles of said jet forming system are removable and replaceable; the central capillary of said nozzles exhibits a diameter of less than about 600 pm, preferably less than about 350 pm, more preferably less than about 125 pm; the array of nozzles comprises sub-arrays of differing nozzle dimensions.

5. An equipment for executing a method for forming an essentially dry bonded fibrous web according to claim 3 or 4, further comprising a binder system supply system comprising an extruder, optionally comprising a degassing system.