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WO2025068638A1 - Method for improving strength properties of nonwoven material, nonwoven material and use of strength composition - Google Patents

Method for improving strength properties of nonwoven material, nonwoven material and use of strength composition Download PDF

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Publication number
WO2025068638A1
WO2025068638A1 PCT/FI2024/050506 FI2024050506W WO2025068638A1 WO 2025068638 A1 WO2025068638 A1 WO 2025068638A1 FI 2024050506 W FI2024050506 W FI 2024050506W WO 2025068638 A1 WO2025068638 A1 WO 2025068638A1
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WO
WIPO (PCT)
Prior art keywords
nonwoven material
cellulose
fibres
strength
material web
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PCT/FI2024/050506
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French (fr)
Inventor
Kaisa KARISALMI
Sara MUONA
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Kemira Oyj
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Kemira Oyj
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Publication of WO2025068638A1 publication Critical patent/WO2025068638A1/en
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    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/425—Cellulose series
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/425—Cellulose series
    • D04H1/4258—Regenerated cellulose series
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4266—Natural fibres not provided for in group D04H1/425
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/58—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by applying, incorporating or activating chemical or thermoplastic bonding agents, e.g. adhesives
    • D04H1/64—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by applying, incorporating or activating chemical or thermoplastic bonding agents, e.g. adhesives the bonding agent being applied in wet state, e.g. chemical agents in dispersions or solutions
    • D04H1/641—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by applying, incorporating or activating chemical or thermoplastic bonding agents, e.g. adhesives the bonding agent being applied in wet state, e.g. chemical agents in dispersions or solutions characterised by the chemical composition of the bonding agent
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
    • D04H1/72—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged
    • D04H1/732—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged by fluid current, e.g. air-lay
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
    • D21H17/24—Polysaccharides
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
    • D21H17/24—Polysaccharides
    • D21H17/25—Cellulose
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
    • D21H17/24—Polysaccharides
    • D21H17/25—Cellulose
    • D21H17/26—Ethers thereof
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
    • D21H17/24—Polysaccharides
    • D21H17/28—Starch
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
    • D21H17/24—Polysaccharides
    • D21H17/28—Starch
    • D21H17/29—Starch cationic
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/33—Synthetic macromolecular compounds
    • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H17/37—Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates
    • D21H17/375—Poly(meth)acrylamide
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material
    • D21H19/10—Coatings without pigments
    • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
    • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material
    • D21H19/10—Coatings without pigments
    • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
    • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H19/22—Polyalkenes, e.g. polystyrene
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material
    • D21H19/36—Coatings with pigments
    • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
    • D21H19/54—Starch
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/18—Reinforcing agents
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/18—Reinforcing agents
    • D21H21/20—Wet strength agents
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
    • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
    • D21H23/22—Addition to the formed paper
    • D21H23/50—Spraying or projecting
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
    • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
    • D21H23/22—Addition to the formed paper
    • D21H23/52—Addition to the formed paper by contacting paper with a device carrying the material
    • D21H23/56—Rolls

Definitions

  • the present invention relates to a method for improving strength properties of nonwoven material according to the preamble of the independent claim presented below.
  • the invention also relates to the nonwoven material obtained by the method as well as to a use of a strength composition.
  • Nonwoven materials are nowadays used in a great variety of applications, ranging from hygiene articles to agriculture, automotive industry and more. Nonwoven materials are especially used for industrial and household cleaning purposes, personal hygiene care, beauty care and for medical care. As the environmental consciousness has increased, both among the industry as well as among the consumers, there is a growing interest to reduce the environmental impact of nonwoven production and the nonwovens itself. Due to the large production volumes and broad range of application fields, even small improvements provide significant impact.
  • Nonwoven webs can be manufactured by a wet-laying process where an aqueous fibre dispersion is deposited on a screen, i.e. wire, and the nonwoven web is formed on the screen by draining the water away through the screen.
  • nonwoven webs can be manufactured by an airlaying process where fibres are dispersed in an airstream and deposited on an air-permeable belt, on which a nonwoven web of randomly oriented fibres is formed.
  • the strength properties of both wet-laid and air-laid nonwoven webs can be improved by incorporating synthetic polymer fibres to the fibre dispersion.
  • a bonding agent can be applied on the nonwoven web after its formation.
  • the used bonding agents are synthetic polymers, manufactured from petroleum-based raw materials.
  • the most common polymers used are acrylate polymers and copolymers, styrene-butadiene copolymers and vinyl acetate ethylene copolymers.
  • Nonwoven industry is thus currently using significant amounts of synthetic fibres as well as synthetic bonding agents, i.e. non-renewable raw materials.
  • nonwoven wipes are considered among the most polluting single-use items and identified as one of the most problematic plastic containing products. Consequently, there is an immediate need to reduce use of synthetic fibres and/or synthetic bonding agents in production of nonwoven materials.
  • Another object of the present invention is to provide a nonwoven material with enhanced strength properties.
  • a typical method according to the present invention for improving strength properties of a nonwoven material comprises
  • a strength composition comprising (i) a glyoxylated polyacrylamide and (ii) a natural polymer selected from non-charged and cationically charged polysaccharides, non-charged and cationically charged polysaccharide derivatives, and any of their mixtures.
  • a typical nonwoven material according to the invention is obtained by a method according to the invention, and it has a fibre matrix comprising cellulose-based fibres.
  • a typical use according to the invention of a strength composition comprising (i) glyoxylated polyacrylamide and (ii) a natural polymer selected from noncharged and/or cationically charged polysaccharides, non-charged and cationically charged polysaccharide derivatives, and any mixtures thereof, is for improving strength properties of nonwoven material comprising cellulose- based fibres.
  • a strength composition comprising a mixture of a glyoxylated polyacrylamide and a specific non-charged natural polymer and/or cationically charged natural polymer, improves the wet and/or dry strength properties of the nonwoven material.
  • the strength composition comprising a biobased natural polymer can replace at least a part of fully synthetic binders and/or synthetic fibres which have been conventionally used in nonwoven materials for providing the required strength properties.
  • the present invention thus provides at least similar or even enhanced strength properties for the nonwoven material while enabling the reduction in the amount of used synthetic polymer-based raw materials.
  • the present invention improves the dry tensile strength of the nonwoven material web.
  • the invention thus enables production of nonwoven material web, which shows uniform dry strength properties irrespective of measurement direction. It is assumed that the application of strength composition of the present invention efficiently improves the interbonding of the cellulose-based fibres in the nonwoven material web, either with each other or with the other components of the nonwoven web. Surprisingly, even if the application of the strength composition improves the dry and/or wet strength properties of the nonwoven material web, it usually still maintains its flushability characteristics.
  • the strength composition consists of (i) a glyoxylated polyacrylamide and (ii) a natural polymer selected from non-charged and cationically charged polysaccharides, noncharged and cationically charged polysaccharide derivatives, and any of their mixtures.
  • nonwoven material is understood as an engineered fibrous assembly, primarily planar, which has been given a designed level of structural integrity, i.e. a measurable level of tensile strength, and excluding materials obtained by weaving, knitting or paper making.
  • the cellulose-based fibres, and optional other fibres, are engineered to a level of structural integrity primarily by physical and/or chemical means other than hydrogen bonding between the fibres.
  • the nonwoven material web according to the present invention can be formed from randomly oriented cellulose-based fibres by wet-laying or airlaying.
  • wet-laying an aqueous fibre dispersion comprising cellulose- based fibres and possible other fibres is supplied on a screen and the water is drained through the screen, whereby the fibrous nonwoven web is formed on the screen.
  • air-laying the cellulose-based fibres and possible other fibres are fed by an airstream into a forming head, which provides a homogeneous fibre mix. A controlled part of the fibre mix is removed from the forming head, advanced by air, and deposited on a moving belt, where a randomly oriented nonwoven material web is formed.
  • the manufacturing processes of nonwoven material webs by using wet-laying or air-laying are known for a person skilled art as such.
  • the strength composition is applied to the web, as a post-treatment.
  • the material web is preferably dried before the application of the strength composition.
  • the nonwoven material web is subjected to mechanical bonding, e.g. hydroentanglement or needlepunching, in addition to application of the strength composition.
  • hydroentanglement the web is bonded by using pressurized water jets and in needlepunching the web is bonded by using needles pushed and pulled through the web.
  • the mechanical bonding may be performed before and/or after the application of the strength composition, preferably before the application of the strength composition.
  • the strength composition is applied on a surface of the nonwoven material web.
  • the strength composition is added on the surface of unsized or uncoated nonwoven material web, so that the constituents of the strength composition come into direct contact with the cellulose-based fibres of the nonwoven material web.
  • the strength composition may be applied on the formed nonwoven material web by any suitable application method.
  • the strength composition may be applied to the nonwoven material web by spraying, surface sizing, coating or by bath immersion, preferably by spraying, surface sizing or coating.
  • the application method may be chosen, for example, on basis of desired application amount or available operational equipment.
  • One advantage of the present invention is that existing application equipment intended for application of conventional bonding agents can be used for application of the strength composition according to the present invention.
  • the strength composition can be applied on one large surface of the nonwoven material web or on both large surfaces of the nonwoven material web, preferably on both large surfaces of the nonwoven material web.
  • the strength composition according to the present invention comprises glyoxylated polyacrylamide in combination with a natural polymer, which is selected from non-charged polysaccharides, cationically charged polysaccharides, non-charged polysaccharide derivatives, cationically charged polysaccharide derivatives, and any of their mixtures.
  • the glyoxylated polyacrylamide and the natural polymer are mixed together before their application to the nonwoven material web.
  • the strength composition is a premixture or a pre-formulate which is formed by mixing, prior to application of the strength composition on the nonwoven material web. Typically the strength composition is applied to the nonwoven material web as diluted aqueous solution.
  • the pH of the aqueous solution of the strength composition may be in a range of 2.5 - 10, typically 3 - 9 or 4 - 9.
  • the dry solid content of the aqueous solution of the strength composition when applied on the nonwoven material web, may be in a range of 1 - 50 weight- %, preferably 1 - 20 weight-%, calculated from total weight of the aqueous solution.
  • the dry solids content and the viscosity of the aqueous solution comprising the strength composition can be adjusted depending on the application method used.
  • the strength composition comprises glyoxylated polyacrylamide as one of its components.
  • the strength composition may comprise the glyoxylated polyacrylamide and the natural polymer in a weight ratio from 40:60 to 1 :99, preferably from 45:55 to 3:97, more preferably from 30:70 to 5:95. This means that a major part, even the main part, of the strength composition may comprise the natural polymer, while still providing required strength properties for the nonwoven material.
  • the glyoxylated polyacrylamide can be produced according to the principles of biomass-balance, in which the majority or all of the fossil based raw materials are replaced by biobased and renewable mass-balanced feedstocks.
  • the glyoxylated polyacrylamide may be obtained by reacting a linear polyacrylamide (base polymer) with glyoxal, whereby a polyacrylamide polymer having pendant glyoxylated groups is obtained.
  • a polyacrylamide polymer having pendant glyoxylated groups is obtained.
  • the glyoxylated polyacrylamide is glyoxylated cationic polyacrylamide.
  • the cationic polyacrylamide, which is used as a base polymer may be a copolymer obtained by polymerisation of acrylamide or a primary amine- containing monomer and at least one cationic monomer.
  • the primary amine- containing monomer may be selected from methacrylamide, ethylacrylamide, N-ethyl methacrylamide, N-butyl methacrylamide, or N-ethyl methacrylamide, and any combination thereof.
  • the cationic monomer may be selected from diallyl dimethyl ammonium chloride (DADMAC), [3- (acrylamide)propyl]trimethyl-ammonium chloride (APTAC), and [3- (methacrylamido)propyl]trimethyl-ammonium chloride (MAPTAC) and any combination thereof.
  • the cationic polyacrylamide used as base polymer, and thus the glyoxylated polyacrylamide, respectively, may comprise only one type of cationic monomer, or it may comprise two or more types of cationic monomers.
  • the cationic monomer may be diallyl dimethyl ammonium chloride (DADMAC).
  • the polyacrylamide used as a base polymer for the glyoxylated polyacrylamide may be obtained by a polymerisation of acrylamide or a primary amine-containing monomer and at least 5 mol-%, preferably at least 7 mol-%, more preferably at least 10 mol-%, of at least one cationic monomer, as defined above.
  • cationic polyacrylamide polymer may be obtained by a polymerisation of acrylamide or a primary amine-containing monomer and 5 - 40 mol-%, preferably 7 - 30 mol-%, more preferably 10 - 25 mol-%, sometimes 10 - 20 mol-% of at least one cationic monomer, as defined above. The percentages are calculated based on the total moles of the polymerisable monomers in the polymerisation.
  • Aqueous solution of glyoxylated polyacrylamide may have a pH in a range of 2.7 - 4.0.
  • the strength composition may comprise glyoxylated cationic polyacrylamide, which has a charge density in a range of 0.5 - 2.5 meq/g or 0.5 - 2 meq/g, preferably 0.75 - 1.9 meq/g, more preferably 1 - 1.8 meq/g, at pH 4.3.
  • the charge density can be measured, for example, by using polyelectrolyte titration.
  • the defined charge density values enable effective interaction between the strength composition and the negatively charged groups on the surface of the cellulose-based fibres.
  • the weight average molecular weight of the glyoxylated polyacrylamide, used in the strength composition may be in a range of 100 000 - 1 000 000 g/mol, preferably 200 000 - 700 000 g/mol, more preferably 250 000 - 550 000 g/mol.
  • the weight average molecular weight is determined by using size-exclusion chromatography, calibrated by polyethylene oxide (PEO) calibration standards.
  • the strength composition according to the present invention also comprises, in addition the glyoxylated polyacrylamide, a natural polymer selected from non-charged and/or cationically charged polysaccharides, and/or noncharged and/or cationically charged polysaccharide derivates.
  • the strength composition may comprise only one type of polysaccharide or polysaccharide derivate, or it may comprise two or more different non-charged and/or cationically charged polysaccharides, and/or non-charged and/or cationically charged polysaccharide derivates.
  • “derivative” denotes a polysaccharide which has been chemically modified by including its structure additional substituents.
  • the natural polymer may be a polysaccharide derivative selected from non-charged cellulose esters, cationic cellulose esters, non-charged cellulose ethers, cationic cellulose ethers, and any of their mixtures.
  • Cellulose esters and cellulose ethers are preferable polysaccharide derivatives, as they are structurally similar to the cellulose-based fibres of the nonwoven material and thus well compatible with them.
  • Cellulose esters and cellulose ethers are also renewable and possibly even biodegradable materials, and their use for improving the strength properties of nonwoven material can significantly reduce the environmental impact of produced nonwoven material.
  • Polysaccharide derivative may be selected from alkyl celluloses, hydroxyalkyl alkyl celluloses, hydroxyalkyl celluloses, and any of their mixtures.
  • the non-charged or cationic cellulose ether suitable for use in the strength composition of the present invention may be selected from alkyl celluloses, hydroxyalkyl alkyl celluloses, hydroxyalkyl celluloses and any of their mixtures.
  • the cellulose ether may be selected from C1-C4 alkyl celluloses, C1-C4 hydroxyalkyl celluloses, and any mixtures thereof.
  • the natural polymer of the strength composition may comprise or consist of a polysaccharide derivative, which is selected from a group consisting of methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxybutyl cellulose, (hydroxyethyl)methyl cellulose, and (hydroxypropyl)methyl cellulose and any mixtures thereof.
  • the strength composition comprises polysaccharide derivate comprising or consisting of hydroxyethyl cellulose.
  • Cellulose esters suitable for use in the strength composition of the present invention may be selected from short side-chain (C1-C6) cellulose esters, such as cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate pentanoate, cellulose acetate hexanoate, and any mixtures thereof.
  • C1-C6 short side-chain
  • the polysaccharide derivative used in the strength composition may have a number average molecular weight Mn in a range of 50 000 - 400 000 g/mol, preferably 70 000 - 120 000 g/mol, more preferably 80 000 - 100 000 g/mol.
  • the number average molecular weight can be determined by using sizeexclusion chromatography, calibrated by polyethylene oxide (PEO) calibration standards.
  • the strength composition comprises a natural polymer, which is a non-charged or cationically charged polysaccharide selected from starch, modified starch, starch derivatives and any mixtures thereof.
  • Suitable starch derivatives are, for example, alkaline-modified starches; bleached starches; oxidized starches; enzyme-treated starches; acetylated starches; hydroxyalkyl starches, such as hydroxyethyl starch, hydroxypropyl starch; octenyl succinate starches, such as starch sodium octenyl succinate, starch aluminium octenyl succinate; maltodextrin; cyclodextrin; starch phosphates, such as monostarch phosphate, distarch phosphate; cationized starch; dextran; pullulan; glycogen, carboxy methylated starch and any of their mixtures.
  • the natural polymer comprises cationized starch.
  • the cationized starch has a substitution degree in a range of 0.1 - 1 .0, preferably 0.2 - 1.0, more preferably 0.3 - 0.9, even more preferably 0.4 - 0.8.
  • the charge density of the cationized starch can freely be selected depending on the substitution degree and the use pH.
  • the charge density of the cationized starch may be from 0.1 meq/g to 3 meq/g.
  • Cationized starch is widely available in large quantities, and it can be used as a mixture with other noncharged or cationically charged polysaccharides or polysaccharide derivatives.
  • the strength composition comprises a natural polymer selected from hydroxyethyl cellulose, cationic starch or any of their mixtures, more preferably hydroxyethyl cellulose or cationic starch.
  • the obtained aqueous solution may have pH in a range of 5 - 10, for example 6 - 8.5.
  • the strength composition may be added or applied to the nonwoven material web in amount which is 1 - 60 weight-%, preferably 5 - 20 weight-%, calculated from the dry weight of the fibres in the nonwoven material web.
  • the strength composition is applied to a nonwoven material web comprising cellulose-based fibres.
  • the nonwoven material web may comprise 80 - 100 weight-%, preferably 90 - 100 weight-%, more preferably 95 - 100 weight-%, sometimes even 96 - 100 weight-%, of cellulose-based fibres.
  • the non-woven material consists of cellulose- based fibres.
  • the cellulose-based fibres may comprise or be selected from natural cellulose fibres, man-made cellulosic fibres, i.e. man-made fibres of cellulosic origin, and any mixture thereof.
  • Natural cellulose fibres may be selected from wood fibres, such as softwood or hardwood fibres; seed hair fibres, such as cotton, kapok or milkweed fibres; leaf fibres, such as sisal, abaca or pineapple fibres; bast fibres, such as flax, hemp, jute or kenaf fibres; and any combinations thereof.
  • the natural cellulose fibres may also comprise cellulosic fibres of microbiological origin.
  • the natural cellulose fibres may have a fibre length in a range of 0.5 - 3.5 mm, preferably 1 - 3 mm.
  • the man-made cellulosic fibres may comprise regenerated cellulosic fibres, such as viscose fibres, lyocell fibres, modal fibres, acetate fibres, triacetate fibres, cupro fibres or any combinations thereof.
  • the man-made cellulosic fibres may be or comprise InfinnaTM fibres, loncellTM fibres, SpinnovaTM fibres,
  • the man-made cellulosic fibres are preferably staple fibres.
  • the manmade cellulosic fibres may have a fibre length in a range of 3 - 15 mm, preferably 5 - 13 mm, more preferably 5 - 12 mm.
  • the cellulose-based fibres both natural cellulose fibres and man-made cellulosic fibres may comprise virgin fibres or recycled fibres or a mixture of virgin fibres and recycled fibres.
  • the fibre dispersion may also comprise solely virgin fibres and/or solely recycled fibres.
  • the cellulose-based fibres may alternatively or in addition be fibres originating from agricultural waste or residues, or fibres originating from food processing and/or beverage industry waste, such as citrus industry waste.
  • the nonwoven material web may comprise 50 - 100 weight-%, preferably 60 - 99 weight-%, more preferably 60 - 95 weight-%, calculated as dry, of natural cellulose fibres.
  • the nonwoven material web may comprise 0 - 50 weight-%, typically 1 - 40 weight-%, more typically 5 - 40 weight-% of man-made cellulosic fibres.
  • the use of strength composition makes it possible to increase the amount of natural cellulosic fibres in the nonwoven material web, without endangering or reducing its strength properties. Increased amount of natural cellulose fibres makes the nonwoven material more sustainable and easier to deposit after the use.
  • the natural cellulose fibres absorb moisture/water, and may thus provide the nonwoven material with advantageous absorption characteristics.
  • the nonwoven material web may comprise synthetic fibres, such as synthetic polymer fibres, carbon fibres, and/or glass fibres.
  • the synthetic polymer fibres can be thermoplastic polymer fibres, such as polyolefin fibres, e.g. polyethylene fibres, polypropylene fibres; polyamide fibres, such as polyaramid fibres; polyester fibres; polylactide fibres; or any mixture thereof.
  • the nonwoven material typically comprises synthetic fibres in an amount ⁇ 10 weight-%, preferably ⁇ 5 weight-%, more preferably ⁇ 1 weight-%. According to one embodiment the nonwoven material is free of synthetic fibres selected from synthetic polymer fibres, carbon fibres, and/or glass fibres, especially synthetic polymer fibres.
  • the strength composition according to the present invention may enable production of nonwoven material which provide adequate strength properties without use of synthetic fibres, especially synthetic polymer fibres.
  • the nonwoven material of the present invention obtained by a method according to the invention may have a weight in a range of 10 - 260 g/m 2 , preferably 30 - 150 g/m 2 , more preferably 40 - 70 g/m 2 .
  • the nonwoven material may have, for example, the weight in a range of 30 - 100 g/m 2 , preferably 45 - 90 g/m 2 , more preferably 50 - 70 g/m 2 .
  • the nonwoven material manufactured according to the present invention can be used, for example, as personal and industrial wiping products (personal/ industrial wipes), household items (e.g. tabletops), agricultural items and as geotextiles.
  • the manufactured nonwoven material can preferably be disposed after use by flushing, composting, disintegration, recycling or similar end-of-life methods.
  • the nonwoven material obtained by using the strength composition according to the present invention may have - at least 100%, preferably at least 200%, more preferably at least 300%, sometimes even at least 500%, higher dry tensile strength, and/or
  • nonwoven material according to the present invention usually still maintains its flushability characteristics, despite of the significant improvement in both dry and wet strength properties.
  • glyoxylated polyacrylamide GPAM1 , (Kemira Oyj) and hydroxyethyl cellulose, HEC, (Sigma Aldrich); were prepared for testing.
  • the strength compositions comprised 30 weight-% glyoxylated polyacrylamide and 70 weight-% of cationized starch or HEC.
  • the strength compositions were prepared at 1 weight-% total solids content to provide required viscosity.
  • the used glyoxylated polyacrylamide GPAM1 had a weight average molecular weight ca. 400 000 g/mol and a charge density about 1.6 meq/g. GPAM1 was diluted to 1 weight-% solution with deionized water.
  • Hydroxyethyl cellulose was used as 1 weight-% solution, prepared by measuring cold deionized water into a beaker with a magnetic stirrer and gradually sprinkling the hydroxyethyl cellulose into a vortex under mixing for 1 .5 hours.
  • the cationized starch was used as 1 weight-% solution, prepared by mixing the starch into a room temperature deionized water and heating the mixture to 94 - 98 °C, where the mixture was cooked for 30 minutes. The obtained starch solution was let to cool down to room temperature (about 22 - 25 °C) while mixing.
  • the strength compositions were prepared by mixing appropriate parts of the individual components together.
  • the strength compositions were kept under mixing with a magnetic stirrer for 30 minutes.
  • An air-laid nonwoven material web was manufactured by using pilot airlaying unit (Dan-Web, Denmark) equipment and a fibre dispersion comprising of commercial fluff pulp (Golden isles fluff pulp, GP Cellulose), average fibre length 2 mm, and viscose fibres (1.7 dtex, Kelheim Fibers), fibre length 10 mm.
  • the fibre dispersion comprised 70 weight-% of fluff pulp and 30 weight-% of viscose fibres, calculated as dry.
  • the air-laid nonwoven material web was calendered at 100 °C, speed 1 m/min, gap 0.02 mm, for reduced loftiness and delamination.
  • the strength compositions were applied in desired amount with a spray rig (Campen, Denmark) and dried in a trough-air oven.
  • the nonwoven material web was sprayed with the strength composition on both sides and dried in the through-air oven at 140 °C for 3 min after each spray.
  • the tested strength compositions and applied amounts are given in Table 1.
  • Commercial flushable wet wipe was used as reference.
  • a commercially available acrylic binder and a commercially available biobased binder were used as reference strength compositions.
  • Nonwoven materials prepared above, were conditioned in 23 °C, 50 % relative humidity for 20 minutes before testing.
  • Dry tensile strength EDANA - NWSP 1104R0 (20), five parallel measurements
  • LAC Liquid absorptive capacity
  • Flushability evaluated based by the disintegration in a drainline test.
  • the sheet samples were put in to 1 liter water and shaken for 3 hours at 100 rpm. Direction was changed every 45 minutes. The contents were poured through a 12.5 mm sieve and pass level determined as >50% passes. Two parallel measurements were conducted. The measurements were made for the nonwoven material samples both in machine direction (MD) and machine cross-direction (CD). The measured characteristics of manufactured nonwoven materials are given in Table 2.
  • the strength composition comprising glyoxylated polyacrylamide and polysaccharide/polysaccharide derivative significantly improve strength characteristics of nonwoven material, especially the dry tensile index. At the same time the liquid absorptive capacity and the flushability properties of the nonwoven material were maintained.
  • the present invention thus provides a more sustainable way to produce nonwoven materials, without compromising its performance properties.

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Abstract

The invention relates to a method for improving strength properties of a nonwoven material. The method comprises forming a nonwoven material web comprising cellulose-based fibres and optionally drying the nonwoven material web. A strength composition is applied to the nonwoven material web. The strength composition comprises (i) a glyoxylated polyacrylamide and (ii) a natural polymer selected from non-charged and cationically charged polysaccharides, non-charged and cationically charged polysaccharide derivatives, and any of their mixtures. The invention relates also to the obtained nonwoven material and to the use of the strength composition.

Description

METHOD FOR IMPROVING STRENGTH PROPERTIES OF NONWOVEN
MATERIAL, NONWOVEN MATERIAL AND USE OF STRENGTH
COMPOSITION
The present invention relates to a method for improving strength properties of nonwoven material according to the preamble of the independent claim presented below. The invention also relates to the nonwoven material obtained by the method as well as to a use of a strength composition.
Nonwoven materials are nowadays used in a great variety of applications, ranging from hygiene articles to agriculture, automotive industry and more. Nonwoven materials are especially used for industrial and household cleaning purposes, personal hygiene care, beauty care and for medical care. As the environmental consciousness has increased, both among the industry as well as among the consumers, there is a growing interest to reduce the environmental impact of nonwoven production and the nonwovens itself. Due to the large production volumes and broad range of application fields, even small improvements provide significant impact.
Nonwoven webs can be manufactured by a wet-laying process where an aqueous fibre dispersion is deposited on a screen, i.e. wire, and the nonwoven web is formed on the screen by draining the water away through the screen. Alternatively, nonwoven webs can be manufactured by an airlaying process where fibres are dispersed in an airstream and deposited on an air-permeable belt, on which a nonwoven web of randomly oriented fibres is formed. The strength properties of both wet-laid and air-laid nonwoven webs can be improved by incorporating synthetic polymer fibres to the fibre dispersion. Alternatively, or in addition, a bonding agent can be applied on the nonwoven web after its formation. The used bonding agents are synthetic polymers, manufactured from petroleum-based raw materials. At the moment, the most common polymers used are acrylate polymers and copolymers, styrene-butadiene copolymers and vinyl acetate ethylene copolymers. Nonwoven industry is thus currently using significant amounts of synthetic fibres as well as synthetic bonding agents, i.e. non-renewable raw materials. As a result, for example nonwoven wipes are considered among the most polluting single-use items and identified as one of the most problematic plastic containing products. Consequently, there is an immediate need to reduce use of synthetic fibres and/or synthetic bonding agents in production of nonwoven materials. Even a small reduction in use of synthetic fibres and/or synthetic bonding agent would provide significant impact, due to the large volumes of nonwoven material produced, used and discarded. However, the properties of the nonwoven materials, i.e. their strength, liquid absorbance capacity and flushability should be maintained on an appropriate level.
It is an object of the present invention to reduce or even eliminate the above- mentioned problems appearing in prior art.
It is an object of the present invention to provide a novel method for improving wet and/or dry strength properties of nonwoven material, especially the dry tensile strength of the nonwoven material.
Another object of the present invention is to provide a nonwoven material with enhanced strength properties.
In order to achieve among others the objects presented above, the invention is characterized by what is presented in the characterizing parts of the enclosed independent claims.
The embodiments and advantages mentioned in this text relate, where applicable, both to the product, the method as well as to the use according to the invention, even though it is not always specifically mentioned. A typical method according to the present invention for improving strength properties of a nonwoven material comprises
- forming a nonwoven material web comprising cellulose-based fibres,
- optionally drying the nonwoven material web, wherein a strength composition is applied to the formed nonwoven material web, the strength composition comprising (i) a glyoxylated polyacrylamide and (ii) a natural polymer selected from non-charged and cationically charged polysaccharides, non-charged and cationically charged polysaccharide derivatives, and any of their mixtures.
A typical nonwoven material according to the invention is obtained by a method according to the invention, and it has a fibre matrix comprising cellulose-based fibres.
A typical use according to the invention of a strength composition comprising (i) glyoxylated polyacrylamide and (ii) a natural polymer selected from noncharged and/or cationically charged polysaccharides, non-charged and cationically charged polysaccharide derivatives, and any mixtures thereof, is for improving strength properties of nonwoven material comprising cellulose- based fibres.
Now it has been surprisingly found that a strength composition, comprising a mixture of a glyoxylated polyacrylamide and a specific non-charged natural polymer and/or cationically charged natural polymer, improves the wet and/or dry strength properties of the nonwoven material. The strength composition comprising a biobased natural polymer can replace at least a part of fully synthetic binders and/or synthetic fibres which have been conventionally used in nonwoven materials for providing the required strength properties. The present invention thus provides at least similar or even enhanced strength properties for the nonwoven material while enabling the reduction in the amount of used synthetic polymer-based raw materials. Especially, the present invention improves the dry tensile strength of the nonwoven material web. An unexpected improvement is seen in dry tensile strength both in machine direction and cross-direction of the nonwoven material web. The invention thus enables production of nonwoven material web, which shows uniform dry strength properties irrespective of measurement direction. It is assumed that the application of strength composition of the present invention efficiently improves the interbonding of the cellulose-based fibres in the nonwoven material web, either with each other or with the other components of the nonwoven web. Surprisingly, even if the application of the strength composition improves the dry and/or wet strength properties of the nonwoven material web, it usually still maintains its flushability characteristics.
According to one embodiment of the invention the strength composition consists of (i) a glyoxylated polyacrylamide and (ii) a natural polymer selected from non-charged and cationically charged polysaccharides, noncharged and cationically charged polysaccharide derivatives, and any of their mixtures.
In the present context, the term “nonwoven material” is understood as an engineered fibrous assembly, primarily planar, which has been given a designed level of structural integrity, i.e. a measurable level of tensile strength, and excluding materials obtained by weaving, knitting or paper making. The cellulose-based fibres, and optional other fibres, are engineered to a level of structural integrity primarily by physical and/or chemical means other than hydrogen bonding between the fibres.
The nonwoven material web according to the present invention can be formed from randomly oriented cellulose-based fibres by wet-laying or airlaying. In the wet-laying, an aqueous fibre dispersion comprising cellulose- based fibres and possible other fibres is supplied on a screen and the water is drained through the screen, whereby the fibrous nonwoven web is formed on the screen. In air-laying the cellulose-based fibres and possible other fibres are fed by an airstream into a forming head, which provides a homogeneous fibre mix. A controlled part of the fibre mix is removed from the forming head, advanced by air, and deposited on a moving belt, where a randomly oriented nonwoven material web is formed. The manufacturing processes of nonwoven material webs by using wet-laying or air-laying are known for a person skilled art as such.
After formation of the non-woven material web the strength composition is applied to the web, as a post-treatment. In case the nonwoven material web is formed by wet-laying, the material web is preferably dried before the application of the strength composition. It is possible that the nonwoven material web is subjected to mechanical bonding, e.g. hydroentanglement or needlepunching, in addition to application of the strength composition. In hydroentanglement the web is bonded by using pressurized water jets and in needlepunching the web is bonded by using needles pushed and pulled through the web. The mechanical bonding may be performed before and/or after the application of the strength composition, preferably before the application of the strength composition.
The strength composition is applied on a surface of the nonwoven material web. Preferably, the strength composition is added on the surface of unsized or uncoated nonwoven material web, so that the constituents of the strength composition come into direct contact with the cellulose-based fibres of the nonwoven material web.
The strength composition may be applied on the formed nonwoven material web by any suitable application method. According to one embodiment of the invention the strength composition may be applied to the nonwoven material web by spraying, surface sizing, coating or by bath immersion, preferably by spraying, surface sizing or coating. The application method may be chosen, for example, on basis of desired application amount or available operational equipment. One advantage of the present invention is that existing application equipment intended for application of conventional bonding agents can be used for application of the strength composition according to the present invention.
The strength composition can be applied on one large surface of the nonwoven material web or on both large surfaces of the nonwoven material web, preferably on both large surfaces of the nonwoven material web.
The strength composition according to the present invention comprises glyoxylated polyacrylamide in combination with a natural polymer, which is selected from non-charged polysaccharides, cationically charged polysaccharides, non-charged polysaccharide derivatives, cationically charged polysaccharide derivatives, and any of their mixtures. The glyoxylated polyacrylamide and the natural polymer are mixed together before their application to the nonwoven material web. According to an embodiment of the present invention, the strength composition is a premixture or a pre-formulate which is formed by mixing, prior to application of the strength composition on the nonwoven material web. Typically the strength composition is applied to the nonwoven material web as diluted aqueous solution. The pH of the aqueous solution of the strength composition may be in a range of 2.5 - 10, typically 3 - 9 or 4 - 9. The dry solid content of the aqueous solution of the strength composition, when applied on the nonwoven material web, may be in a range of 1 - 50 weight- %, preferably 1 - 20 weight-%, calculated from total weight of the aqueous solution. The dry solids content and the viscosity of the aqueous solution comprising the strength composition can be adjusted depending on the application method used.
The strength composition comprises glyoxylated polyacrylamide as one of its components. According to one embodiment of the present invention, the strength composition may comprise the glyoxylated polyacrylamide and the natural polymer in a weight ratio from 40:60 to 1 :99, preferably from 45:55 to 3:97, more preferably from 30:70 to 5:95. This means that a major part, even the main part, of the strength composition may comprise the natural polymer, while still providing required strength properties for the nonwoven material.
The glyoxylated polyacrylamide can be produced according to the principles of biomass-balance, in which the majority or all of the fossil based raw materials are replaced by biobased and renewable mass-balanced feedstocks.
The glyoxylated polyacrylamide may be obtained by reacting a linear polyacrylamide (base polymer) with glyoxal, whereby a polyacrylamide polymer having pendant glyoxylated groups is obtained. Preferably the glyoxylated polyacrylamide is glyoxylated cationic polyacrylamide. The cationic polyacrylamide, which is used as a base polymer, may be a copolymer obtained by polymerisation of acrylamide or a primary amine- containing monomer and at least one cationic monomer. The primary amine- containing monomer may be selected from methacrylamide, ethylacrylamide, N-ethyl methacrylamide, N-butyl methacrylamide, or N-ethyl methacrylamide, and any combination thereof. The cationic monomer may be selected from diallyl dimethyl ammonium chloride (DADMAC), [3- (acrylamide)propyl]trimethyl-ammonium chloride (APTAC), and [3- (methacrylamido)propyl]trimethyl-ammonium chloride (MAPTAC) and any combination thereof. The cationic polyacrylamide used as base polymer, and thus the glyoxylated polyacrylamide, respectively, may comprise only one type of cationic monomer, or it may comprise two or more types of cationic monomers. Preferably, the cationic monomer may be diallyl dimethyl ammonium chloride (DADMAC).
The polyacrylamide used as a base polymer for the glyoxylated polyacrylamide may be obtained by a polymerisation of acrylamide or a primary amine-containing monomer and at least 5 mol-%, preferably at least 7 mol-%, more preferably at least 10 mol-%, of at least one cationic monomer, as defined above. According to an embodiment of the invention cationic polyacrylamide polymer may be obtained by a polymerisation of acrylamide or a primary amine-containing monomer and 5 - 40 mol-%, preferably 7 - 30 mol-%, more preferably 10 - 25 mol-%, sometimes 10 - 20 mol-% of at least one cationic monomer, as defined above. The percentages are calculated based on the total moles of the polymerisable monomers in the polymerisation.
Aqueous solution of glyoxylated polyacrylamide may have a pH in a range of 2.7 - 4.0.
According to one embodiment of the present invention the strength composition may comprise glyoxylated cationic polyacrylamide, which has a charge density in a range of 0.5 - 2.5 meq/g or 0.5 - 2 meq/g, preferably 0.75 - 1.9 meq/g, more preferably 1 - 1.8 meq/g, at pH 4.3. The charge density can be measured, for example, by using polyelectrolyte titration. The defined charge density values enable effective interaction between the strength composition and the negatively charged groups on the surface of the cellulose-based fibres.
The weight average molecular weight of the glyoxylated polyacrylamide, used in the strength composition, may be in a range of 100 000 - 1 000 000 g/mol, preferably 200 000 - 700 000 g/mol, more preferably 250 000 - 550 000 g/mol. The weight average molecular weight is determined by using size-exclusion chromatography, calibrated by polyethylene oxide (PEO) calibration standards.
The strength composition according to the present invention also comprises, in addition the glyoxylated polyacrylamide, a natural polymer selected from non-charged and/or cationically charged polysaccharides, and/or noncharged and/or cationically charged polysaccharide derivates. The strength composition may comprise only one type of polysaccharide or polysaccharide derivate, or it may comprise two or more different non-charged and/or cationically charged polysaccharides, and/or non-charged and/or cationically charged polysaccharide derivates. In the present context, “derivative” denotes a polysaccharide which has been chemically modified by including its structure additional substituents.
According to one embodiment of the present invention the natural polymer may be a polysaccharide derivative selected from non-charged cellulose esters, cationic cellulose esters, non-charged cellulose ethers, cationic cellulose ethers, and any of their mixtures. Cellulose esters and cellulose ethers are preferable polysaccharide derivatives, as they are structurally similar to the cellulose-based fibres of the nonwoven material and thus well compatible with them. Cellulose esters and cellulose ethers are also renewable and possibly even biodegradable materials, and their use for improving the strength properties of nonwoven material can significantly reduce the environmental impact of produced nonwoven material.
Polysaccharide derivative may be selected from alkyl celluloses, hydroxyalkyl alkyl celluloses, hydroxyalkyl celluloses, and any of their mixtures. For example, the non-charged or cationic cellulose ether suitable for use in the strength composition of the present invention may be selected from alkyl celluloses, hydroxyalkyl alkyl celluloses, hydroxyalkyl celluloses and any of their mixtures. Especially the cellulose ether may be selected from C1-C4 alkyl celluloses, C1-C4 hydroxyalkyl celluloses, and any mixtures thereof. For example, the natural polymer of the strength composition may comprise or consist of a polysaccharide derivative, which is selected from a group consisting of methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxybutyl cellulose, (hydroxyethyl)methyl cellulose, and (hydroxypropyl)methyl cellulose and any mixtures thereof. According to one preferable embodiment of the present invention the strength composition comprises polysaccharide derivate comprising or consisting of hydroxyethyl cellulose.
Cellulose esters suitable for use in the strength composition of the present invention may be selected from short side-chain (C1-C6) cellulose esters, such as cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate pentanoate, cellulose acetate hexanoate, and any mixtures thereof.
The polysaccharide derivative used in the strength composition may have a number average molecular weight Mn in a range of 50 000 - 400 000 g/mol, preferably 70 000 - 120 000 g/mol, more preferably 80 000 - 100 000 g/mol. The number average molecular weight can be determined by using sizeexclusion chromatography, calibrated by polyethylene oxide (PEO) calibration standards.
According to one embodiment, the strength composition comprises a natural polymer, which is a non-charged or cationically charged polysaccharide selected from starch, modified starch, starch derivatives and any mixtures thereof. Suitable starch derivatives are, for example, alkaline-modified starches; bleached starches; oxidized starches; enzyme-treated starches; acetylated starches; hydroxyalkyl starches, such as hydroxyethyl starch, hydroxypropyl starch; octenyl succinate starches, such as starch sodium octenyl succinate, starch aluminium octenyl succinate; maltodextrin; cyclodextrin; starch phosphates, such as monostarch phosphate, distarch phosphate; cationized starch; dextran; pullulan; glycogen, carboxy methylated starch and any of their mixtures.
According to one preferable embodiment the natural polymer comprises cationized starch. In an embodiment according to the present invention, the cationized starch has a substitution degree in a range of 0.1 - 1 .0, preferably 0.2 - 1.0, more preferably 0.3 - 0.9, even more preferably 0.4 - 0.8. The charge density of the cationized starch can freely be selected depending on the substitution degree and the use pH. The charge density of the cationized starch may be from 0.1 meq/g to 3 meq/g. Cationized starch is widely available in large quantities, and it can be used as a mixture with other noncharged or cationically charged polysaccharides or polysaccharide derivatives.
According to one preferable embodiment of the present invention the strength composition comprises a natural polymer selected from hydroxyethyl cellulose, cationic starch or any of their mixtures, more preferably hydroxyethyl cellulose or cationic starch.
When the natural polymer is dissolved in water, the obtained aqueous solution may have pH in a range of 5 - 10, for example 6 - 8.5.
The strength composition may be added or applied to the nonwoven material web in amount which is 1 - 60 weight-%, preferably 5 - 20 weight-%, calculated from the dry weight of the fibres in the nonwoven material web.
The strength composition is applied to a nonwoven material web comprising cellulose-based fibres. The nonwoven material web may comprise 80 - 100 weight-%, preferably 90 - 100 weight-%, more preferably 95 - 100 weight-%, sometimes even 96 - 100 weight-%, of cellulose-based fibres. According to one preferable embodiment the non-woven material consists of cellulose- based fibres. The cellulose-based fibres may comprise or be selected from natural cellulose fibres, man-made cellulosic fibres, i.e. man-made fibres of cellulosic origin, and any mixture thereof.
Natural cellulose fibres may be selected from wood fibres, such as softwood or hardwood fibres; seed hair fibres, such as cotton, kapok or milkweed fibres; leaf fibres, such as sisal, abaca or pineapple fibres; bast fibres, such as flax, hemp, jute or kenaf fibres; and any combinations thereof. The natural cellulose fibres may also comprise cellulosic fibres of microbiological origin. The natural cellulose fibres may have a fibre length in a range of 0.5 - 3.5 mm, preferably 1 - 3 mm.
The man-made cellulosic fibres may comprise regenerated cellulosic fibres, such as viscose fibres, lyocell fibres, modal fibres, acetate fibres, triacetate fibres, cupro fibres or any combinations thereof. The man-made cellulosic fibres may be or comprise Infinna™ fibres, loncell™ fibres, Spinnova™ fibres, The man-made cellulosic fibres are preferably staple fibres. The manmade cellulosic fibres may have a fibre length in a range of 3 - 15 mm, preferably 5 - 13 mm, more preferably 5 - 12 mm.
The cellulose-based fibres, both natural cellulose fibres and man-made cellulosic fibres may comprise virgin fibres or recycled fibres or a mixture of virgin fibres and recycled fibres. The fibre dispersion may also comprise solely virgin fibres and/or solely recycled fibres. The cellulose-based fibres may alternatively or in addition be fibres originating from agricultural waste or residues, or fibres originating from food processing and/or beverage industry waste, such as citrus industry waste.
According to one embodiment of the invention, the nonwoven material web may comprise 50 - 100 weight-%, preferably 60 - 99 weight-%, more preferably 60 - 95 weight-%, calculated as dry, of natural cellulose fibres. The nonwoven material web may comprise 0 - 50 weight-%, typically 1 - 40 weight-%, more typically 5 - 40 weight-% of man-made cellulosic fibres. The use of strength composition makes it possible to increase the amount of natural cellulosic fibres in the nonwoven material web, without endangering or reducing its strength properties. Increased amount of natural cellulose fibres makes the nonwoven material more sustainable and easier to deposit after the use. Furthermore, the natural cellulose fibres absorb moisture/water, and may thus provide the nonwoven material with advantageous absorption characteristics.
In addition to cellulose-based fibres the nonwoven material web may comprise synthetic fibres, such as synthetic polymer fibres, carbon fibres, and/or glass fibres. The synthetic polymer fibres can be thermoplastic polymer fibres, such as polyolefin fibres, e.g. polyethylene fibres, polypropylene fibres; polyamide fibres, such as polyaramid fibres; polyester fibres; polylactide fibres; or any mixture thereof. The nonwoven material typically comprises synthetic fibres in an amount <10 weight-%, preferably <5 weight-%, more preferably <1 weight-%. According to one embodiment the nonwoven material is free of synthetic fibres selected from synthetic polymer fibres, carbon fibres, and/or glass fibres, especially synthetic polymer fibres. The strength composition according to the present invention may enable production of nonwoven material which provide adequate strength properties without use of synthetic fibres, especially synthetic polymer fibres.
The nonwoven material of the present invention obtained by a method according to the invention may have a weight in a range of 10 - 260 g/m2, preferably 30 - 150 g/m2, more preferably 40 - 70 g/m2. The nonwoven material may have, for example, the weight in a range of 30 - 100 g/m2, preferably 45 - 90 g/m2, more preferably 50 - 70 g/m2.
The nonwoven material manufactured according to the present invention can be used, for example, as personal and industrial wiping products (personal/ industrial wipes), household items (e.g. tabletops), agricultural items and as geotextiles. The manufactured nonwoven material can preferably be disposed after use by flushing, composting, disintegration, recycling or similar end-of-life methods.
The nonwoven material obtained by using the strength composition according to the present invention may have - at least 100%, preferably at least 200%, more preferably at least 300%, sometimes even at least 500%, higher dry tensile strength, and/or
- at least 50%, preferably at least 75%, more preferably at least 100%, higher wet strength, than an identical nonwoven material manufactured without application of any chemical composition on the nonwoven material web. The nonwoven material according to the present invention usually still maintains its flushability characteristics, despite of the significant improvement in both dry and wet strength properties.
EXPERIMENTAL
Some embodiments of the invention are described in the following nonlimiting examples.
Preparation of Strength Compositions
Strength compositions comprising
1 ) glyoxylated polyacrylamide, GPAM1 , (Kemira Oyj) and cationic starch (Hi- Cat 21370, Roquette); and
2) glyoxylated polyacrylamide, GPAM1 , (Kemira Oyj) and hydroxyethyl cellulose, HEC, (Sigma Aldrich); were prepared for testing. The strength compositions comprised 30 weight-% glyoxylated polyacrylamide and 70 weight-% of cationized starch or HEC. The strength compositions were prepared at 1 weight-% total solids content to provide required viscosity.
The used glyoxylated polyacrylamide GPAM1 had a weight average molecular weight ca. 400 000 g/mol and a charge density about 1.6 meq/g. GPAM1 was diluted to 1 weight-% solution with deionized water.
Hydroxyethyl cellulose (HEC) was used as 1 weight-% solution, prepared by measuring cold deionized water into a beaker with a magnetic stirrer and gradually sprinkling the hydroxyethyl cellulose into a vortex under mixing for 1 .5 hours. The cationized starch was used as 1 weight-% solution, prepared by mixing the starch into a room temperature deionized water and heating the mixture to 94 - 98 °C, where the mixture was cooked for 30 minutes. The obtained starch solution was let to cool down to room temperature (about 22 - 25 °C) while mixing.
The strength compositions were prepared by mixing appropriate parts of the individual components together. The strength compositions were kept under mixing with a magnetic stirrer for 30 minutes.
Commercial bonding agents, used as a reference, were diluted to 3 weight-% solids concentration with deionized water.
Manufacture of Nonwoven Material
An air-laid nonwoven material web was manufactured by using pilot airlaying unit (Dan-Web, Denmark) equipment and a fibre dispersion comprising of commercial fluff pulp (Golden isles fluff pulp, GP Cellulose), average fibre length 2 mm, and viscose fibres (1.7 dtex, Kelheim Fibers), fibre length 10 mm. The fibre dispersion comprised 70 weight-% of fluff pulp and 30 weight-% of viscose fibres, calculated as dry. The air-laid nonwoven material web was calendered at 100 °C, speed 1 m/min, gap 0.02 mm, for reduced loftiness and delamination.
The strength compositions were applied in desired amount with a spray rig (Campen, Denmark) and dried in a trough-air oven. The nonwoven material web was sprayed with the strength composition on both sides and dried in the through-air oven at 140 °C for 3 min after each spray.
The tested strength compositions and applied amounts are given in Table 1. Commercial flushable wet wipe was used as reference. A commercially available acrylic binder and a commercially available biobased binder were used as reference strength compositions.
Table 1 Tested strength compositions and application amounts
Figure imgf000017_0001
Testing of Nonwoven Material
Nonwoven materials, prepared above, were conditioned in 23 °C, 50 % relative humidity for 20 minutes before testing.
The following properties were tested from the samples of nonwoven material by using identified test methods/ Nonwovens Standard Procedures (NWSP): l/l/ef tensile strength: EDANA - NWSP 1104R0 (20), five parallel measurements
Dry tensile strength: EDANA - NWSP 1104R0 (20), five parallel measurements
Liquid absorptive capacity (LAC): EDANA - NWSP 0101 RO (20), five parallel measurements
Flushability: evaluated based by the disintegration in a drainline test. The sheet samples were put in to 1 liter water and shaken for 3 hours at 100 rpm. Direction was changed every 45 minutes. The contents were poured through a 12.5 mm sieve and pass level determined as >50% passes. Two parallel measurements were conducted. The measurements were made for the nonwoven material samples both in machine direction (MD) and machine cross-direction (CD). The measured characteristics of manufactured nonwoven materials are given in Table 2.
Table 2 Characteristics of manufactured nonwoven materials.
Figure imgf000018_0001
From the results of Table 2 it can be clearly seen that the strength composition comprising glyoxylated polyacrylamide and polysaccharide/polysaccharide derivative significantly improve strength characteristics of nonwoven material, especially the dry tensile index. At the same time the liquid absorptive capacity and the flushability properties of the nonwoven material were maintained. The present invention thus provides a more sustainable way to produce nonwoven materials, without compromising its performance properties.
Even if the invention was described with reference to what at present seems to be the most practical and preferred embodiments, it is appreciated that the invention shall not be limited to the embodiments described above, but the invention is intended to cover also different modifications and equivalent technical solutions within the scope of the enclosed claims.

Claims

1. Method for improving strength properties of a nonwoven material, the method comprising
- forming a nonwoven material web comprising cellulose-based fibres,
- optionally drying the nonwoven material web, characterised in that a strength composition is applied to the nonwoven material web, wherein the strength composition comprises (i) a glyoxylated polyacrylamide and (ii) a natural polymer selected from non-charged and cationically charged polysaccharides, non-charged and cationically charged polysaccharide derivatives, and any of their mixtures.
2. Method according to claim 1 , characterised in that the strength composition is applied to the nonwoven material web by spraying, surface sizing, coating or by bath immersion.
3. Method according to claim 1 or 2, characterised in that the nonwoven material web is formed by air-laying or wet-laying.
4. Method according to claim 1 , 2 or 3, characterised in that the strength composition comprises the glyoxylated polyacrylamide and the natural polymer in a weight ratio from 40:60 to 1 :99, preferably from 30:70 to 5:95.
5. Method according to any of the preceding claims 1 - 4, characterised in that the glyoxylated polyacrylamide has a charge density in a range of 0.5 - 2.5 meq/g or 0.5 - 2 meq/g, preferably 0.75 - 1 .9 meq/g, more preferably 1 - 1 .8 meq/g, measured at pH 4.3.
6. Method according to any of preceding claims 1 - 5, characterised in that the glyoxylated polyacrylamide has a weight average molecular weight in a range of 100 000 - 1 000 000 g/mol, preferably 200 000 - 700 000 g/mol, more preferably 250 000 - 550 000 g/mol.
7. Method according to any of the preceding claims 1 - 6, characterised in that the natural polymer is a polysaccharide derivative selected from noncharged and cationic cellulose esters, non-charged and cationic cellulose ethers, and any of their mixtures.
8. Method according to claim 7, characterised in that the polysaccharide derivative is selected from alkyl celluloses, hydroxyalkyl alkyl celluloses, hydroxyalkyl celluloses, and any of their mixtures.
9. Method according to claim 8, characterised in that the polysaccharide derivative is selected from a group consisting of methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxybutyl cellulose, (hydroxyethyl)methyl cellulose, and (hydroxypropyl)methyl cellulose and any mixtures thereof, preferably hydroxyethyl cellulose.
10. Method according to any of preceding claims 1 - 9, characterised in that the polysaccharide derivative has a number average molecular weight Mn in a range of 50 000 - 400 000 g/mol, preferably 70 000 - 120 000 g/mol, more preferably 80 000 - 100 000 g/mol.
11. Method according to any of the preceding claims 1 - 10, characterised in that the natural polymer comprises cationized starch.
12. Method according to any of the preceding claims 1 - 11 , characterised in that the formed nonwoven material web comprises 90 - 100 weight-%, preferably 95 - 100 weight-%, of cellulose-based fibres.
13. Method according to any of the preceding claims 1 - 11 , characterised in that the formed nonwoven material web is subjected to mechanical bonding, e.g. hydroentanglement or needlepunching, performed before and/or after the application of the strength composition.
14. Nonwoven material obtained by a method according to any of claims 1 - 13, having a fibre matrix comprising cellulose-based fibres.
15. Use of a strength composition comprising (i) glyoxylated polyacrylamide and (ii) a natural polymer selected from non-charged and/or cationically charged polysaccharides, non-charged and cationically charged polysaccharide derivatives, and any mixtures thereof, for improving strength properties of nonwoven material comprising cellulose-based fibres.
PCT/FI2024/050506 2023-09-28 2024-09-27 Method for improving strength properties of nonwoven material, nonwoven material and use of strength composition Pending WO2025068638A1 (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021063957A1 (en) * 2019-09-30 2021-04-08 Kelheim Fibres Gmbh Wetlaid web comprising viscose fibre
WO2022117921A1 (en) * 2020-12-02 2022-06-09 Kemira Oyj A treatment system for manufacture of paper, board or the like

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021063957A1 (en) * 2019-09-30 2021-04-08 Kelheim Fibres Gmbh Wetlaid web comprising viscose fibre
WO2022117921A1 (en) * 2020-12-02 2022-06-09 Kemira Oyj A treatment system for manufacture of paper, board or the like

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