EP4311872A1 - Tissus non-tissés fibreux à résistance améliorée à l'état humide, notamment le papier, utilisations de ces tissus à résistance à l'état humide ainsi que leurs procédés de production - Google Patents

Tissus non-tissés fibreux à résistance améliorée à l'état humide, notamment le papier, utilisations de ces tissus à résistance à l'état humide ainsi que leurs procédés de production Download PDF

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Publication number
EP4311872A1
EP4311872A1 EP22187283.1A EP22187283A EP4311872A1 EP 4311872 A1 EP4311872 A1 EP 4311872A1 EP 22187283 A EP22187283 A EP 22187283A EP 4311872 A1 EP4311872 A1 EP 4311872A1
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EP
European Patent Office
Prior art keywords
paper
woven fabric
fibrous non
wet
wet strength
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22187283.1A
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German (de)
English (en)
Inventor
Mathias Stanzel
Nicole Rath
Markus BIESALSKI
Annette ANDRIEU-BRUNSEN
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Technische Universitaet Darmstadt
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Technische Universitaet Darmstadt
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Publication date
Application filed by Technische Universitaet Darmstadt filed Critical Technische Universitaet Darmstadt
Priority to EP22187283.1A priority Critical patent/EP4311872A1/fr
Priority to PCT/EP2023/070614 priority patent/WO2024023105A1/fr
Publication of EP4311872A1 publication Critical patent/EP4311872A1/fr
Pending legal-status Critical Current

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Classifications

    • 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
    • D04H1/04—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres having existing or potential cohesive properties, e.g. natural fibres, prestretched or fibrillated artificial fibres
    • D04H1/26—Wood pulp
    • 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
    • D04H1/587—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 characterised by the bonding agents used
    • 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
    • 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
    • D21H17/03—Non-macromolecular organic compounds
    • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
    • D21H17/13—Silicon-containing compounds
    • 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
    • D21H17/63—Inorganic compounds
    • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
    • D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays
    • 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
    • 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
    • D21H21/22—Agents rendering paper porous, absorbent or bulky
    • D21H21/24—Surfactants
    • 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
    • D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp
    • 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
    • D21H23/32—Addition to the formed paper by contacting paper with an excess of material, e.g. from a reservoir or in a manner necessitating removal of applied excess material from the paper
    • D21H23/42—Paper being at least partly surrounded by the material on both sides
    • 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
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/10—Packing paper

Definitions

  • the present invention relates to environmentally friendly, wet strength improved fibrous non-woven fabrics, preferably paper, impregnated with a mixture comprising a silicon component, further comprising water and/or an alcohol and/or a surfactant and a catalyst (e.g. acidic or basic). Also encompassed are methods for production and uses of such wet strength improved fibrous non-woven fabrics.
  • Paper is essentially a sheet or web of fibrous non-woven fabric (usually cellulose-fibres) to which chemicals are added to improve its properties and quality.
  • fibrous non-woven fabric usually cellulose-fibres
  • the production of pulp and paper requires large amounts of process water and a lot of energy in the form of steam and electricity. Therefore, the main environmental issues related to the pulp and paper industry concern water and air emissions and energy consumption. Waste is also an ever-increasing source of environmental pollution.
  • the pulp for paper production is produced by chemical or mechanical processes either from virgin fibres or by processing waste paper.
  • Untreated paper becomes mechanically unstable when it becomes damp or wet. Due to the splitting of the hydrogen bonds when water enters, the fibre fleece loses its internal cohesion.
  • wet strength agents e.g. polyamidoamine epichlorohydrin (PAAE)
  • PAAE polyamidoamine epichlorohydrin
  • Wet strength agents known in the prior art are water-soluble polymers in the processing state that react with themselves and/or the paper fibres. In the process, water-insoluble cross-links form between the fibres, which stabilise the fibre web.
  • wet strength agents based on melamine and urea-formaldehyde resins and polyamidoamine-epichlorohydrin (PAAE).
  • PAAE polyamidoamine-epichlorohydrin
  • These commercially used wet strength agents are built up from toxic starting substances and are based on petrochemical materials, which at least partially are still present in the final product. Therefore, there are particular health concerns in paper production, and in wastewater and paper disposal, the environmental input of these polymers (or their precursors) cannot be satisfactorily avoided and represents a considerable environmental burden.
  • the chemical linkage also prevents successful recycling, so the increasing use of wet strength agents in the sanitary paper sector has far-reaching consequences for waste paper recycling. For example, the incidence of insoluble particles in the normal dissolving process is steadily in-creasing.
  • wet strength agents must not be confused with sizing chemicals (for example AKD), as the chemo-physical action process is different.
  • sizing chemicals for example AKD
  • a wet-strength, unglued paper is still highly capillary and a superglued paper can only be defibrillated after a long time in contact with water.
  • the present invention solves the aforementioned environmental problems by providing more environmentally friendly wet strength improved fibrous non-woven fabrics, preferably paper, impregnated with wet strength agents based on silicon components, such as silica (SiO 2 ) and aminosilica (SiO 2 -NH 2 )).
  • silicon components such as silica (SiO 2 ) and aminosilica (SiO 2 -NH 2 )).
  • the present invention relates to a wet strength improved fibrous non-woven fabric with an air-dry silica-content of about 0.05 wt.-% or more, 0.1 wt.-% or more, 0.5 wt.-% or more, 1 wt.-% or more, preferably of about 2 wt.-% or more, more preferably of about 5 wt.-% or more, most preferably of about 10 wt-% or more and up to about 30 wt.-% or less, preferably up to about 25 wt-% or less, most preferably up to about 20 wt-% or less; in one aspect between 1 wt.-% to 30 wt.-%, preferably between 2 wt.-% to 25 wt.-%, most preferably between 5 wt.-% to 20 wt.-%.
  • a low silica content of between 0.05 to 5 wt.-% is preferred, since it improves the economics of the process.
  • the silica content is related to the wet-strength and the composition of the impregnation solution.
  • the silica is distributed homogeneously in the wet strength fibrous non-woven fabric in so far that the silica-content on one side of the wet strength fibrous non-woven fabric and the silica-content on another side of the wet strength fibrous non-woven fabric is a ratio of less than 2:1, preferably a ratio of less than 1.5:1, more preferably a ratio of less than 1.25:1, most preferably a ratio of about 1:1.
  • a ratio of less than 2:1 preferably a ratio of less than 1.5:1, more preferably a ratio of less than 1.25:1, most preferably a ratio of about 1:1.
  • Such a distribution can be measured for example by IR-spectroscopy of each surface and calculating the silica content and the ratio between the silica-contents of each surface, respectively.
  • the Cobb 60 -value of the wet strength improved fibrous non-woven fabric after silica-impregnation is about 20% or less reduced as compared to the untreated fibrous non-woven fabric.
  • the reduction of the Cobb 60 -value about 10% or less, more preferably about 5% or less, most preferably about the same as compared to the untreated fibrous non-woven fabric.
  • the "Cobb 60 -value" is defined and measured according to DIN EN ISO 535 (2014-06-00) and describes the amount of water (in gram) which is absorbed by 1 m 2 of material after 60 seconds.
  • untreated fibrous non-woven fabric refers to the same fibrous non-woven fabric but not impregnated with any of the impregnation solutions disclosed in this application and/or otherwise silica treated.
  • the specific surface area determined by BET is about ⁇ 10%, more preferably about ⁇ 5%, most preferably about ⁇ 2% as compared to the untreated fibrous non-woven fabric.
  • B.E.T. or BET Brunauer-Emmett-Teller
  • the inventive wet strength improved fibrous non-woven fabric shows a similar surface and pore distribution and size as untreated fibrous non-woven fabric, thereby having the beneficial effect that water retention and/or permeability remain the same.
  • the swelling capacity of the fibres in the fibrous non-woven fabric is slightly reduced by the silica treatment and this effect adds to the improved wet strength.
  • the swelling in water is one of the important fundamental properties of fibres in the fibrous non-woven fabrics and can be measured by the desiccation rate.
  • this method is exceedingly simple - the fibre samples, fully swollen and containing excess water, are dried very slowly and weighed periodically. It is shown that for a time the moisture is lost at a nearly constant rate. Eventually, however, the drying rate changes and thereafter steadily diminishes. It is believed that this change occurs only after all nonswelling water external to the fibre has evaporated.
  • the swelling capacity of the wet strength improved fibrous non-woven fabric after silica-impregnation is reduced by about 20% or less, more preferably reduced by about 10% or less, even more preferably reduced by about 5% or less, even more preferably reduced by about 2% or less, most preferably reduced by about 1% or less as compared to the untreated fibrous non-woven fabric.
  • the wet strength improved fibrous non-woven fabric of the present invention may be made of any non-woven fabric made from staple fibres (short) and long fibres (continuous long), bonded together by chemical, mechanical, heat or solvent treatment.
  • non-woven fabric is used hereinunder to denote fabrics, such as felt, which are neither woven nor knitted. Some non-woven materials lack sufficient strength unless densified or reinforced by a backing. In one important aspect the fibrous non-woven fabric is paper.
  • the wet strength improved fibrous non-woven fabric of the present invention shows an excellent wet tensile strength according to DIN ISO 3781.
  • the wet tensile strength according to DIN ISO 3781 of the wet strength improved fibrous non-woven fabric according to the invention is about 2 times or more, preferably about 3 times or more, more preferably about 5 times or more, most preferably about 10 times or more higher as compared to the untreated fibrous non-woven fabric.
  • the wet tensile strength is up to about 50 times or less, preferably up to about 35 times or less, more preferably up to about 30 times or less, most preferably up to about 25 times or less higher as compared to the untreated fibrous non-woven fabric.
  • the wet tensile strength is between at least 2 times and up to 30 times, preferably between at least 2.5 times and up to 25 times, more preferably between at least 3 times and up to 20 times, most preferably between at least 4 times and up to 15 times higher as compared to the untreated fibrous non-woven fabric.
  • the absolute wet strength improved fibrous non-woven fabric of the present invention according to DIN ISO 3781 (1994-10) is between 1 and 50 N/15 mm, preferably between 2 and 40 N/15 mm, more preferably between 3 and 35 N/15 mm, most preferably between 4 and 30 N/15 mm.
  • the wet strength improved fibrous non-woven fabric is still wettable and able to absorb water. This is important, since many applications of wet strength improved non-woven fabrics are used to absorb water e.g. kitchen towels (e.g. made of paper), tissue paper and or handkerchiefs or the like, or still need to be permeable for water, such as for example tea-bags or coffee filters.
  • kitchen towels e.g. made of paper
  • the wettability can be quantified by the "contact angle" which is conventionally measured where a liquid-vapor interface meets a solid surface (e.g. water drop on the fibrous non-woven fabric in air). It quantifies the wettability of a solid surface by a liquid via the Young equation.
  • the contact angle of the surface of the wet strength improved fibrous non-woven fabric according to the present invention is less than 100°, more preferably less than 90°, even more preferably less than 75°, most preferably less than 60° on at least both major sides, preferably on all sides of the wet strength improved fibrous non-woven fabric.
  • the present invention relates to a wet strength improving impregnating solution comprising a silicon component for increasing the wet tensile strength of fibrous non-woven fabric resulting in an environmentally friendly and non-toxic final product, in particular paper and board, wherein the impregnation solution further comprises an acidic catalyst, water and/or an alcohol, i.e. a type of organic compound that carries at least one hydroxyl functional group (-OH) bound to a saturated carbon atom (for example ethanol, 1-propanol, 2-propanol, 2-methylpropan-1-ol, 2-methylbutan-2-ol and/or methanol) and follows the general formula C n H 2n+1 OH, and/or a surfactant.
  • an acidic catalyst water and/or an alcohol
  • an alcohol i.e. a type of organic compound that carries at least one hydroxyl functional group (-OH) bound to a saturated carbon atom (for example ethanol, 1-propanol, 2-propanol, 2-methylpropan
  • the wet strength improving impregnating solution comprises tetraethyl orthosilicate (TEOS) as "silicon component" for increasing the wet tensile strength of fibrous non-woven fabric, in particular paper, wherein the impregnation solution further comprises water, ethanol (EtOH) as alcohol and/or SDS (in case of an anionic surfactant) or CTAB (in case of a cationic surfactant) as a surfactant and, preferentially takes place under acidic or basic conditions.
  • EtOH ethanol
  • CTAB in case of a cationic surfactant
  • HCI hydrochloric acid
  • the present invention also pertains to a wet-strength improving impregnation mixture (option II) comprising the following compounds in weight-%: Compound wt.-% silicon component, such as tetraethyl 3.5 - 16 orthosilicate (TEOS) surfactant, (for example sodium lauryl sulfate or cetrimonium bromide) 0.2 - 1.5 H 2 O 80 - 95 (ad 100%) acid catalyst (e.g. HCI) 0.005- 0.05
  • TEOS orthosilicate
  • the present invention also pertains to a wet-strength improving impregnation mixture (option II) comprising the following compounds in weight-%: Compound wt.-% silicon component, such as tetraethyl orthosilicate (TEOS) 7 - 16 surfactant, (for example sodium lauryl sulfate or cetrimonium bromide) 0.5 - 1.5 H 2 O 80 - 95 (ad 100%) acid catalyst (e.g. HCI) 0.015- 0.04
  • TEOS tetraethyl orthosilicate
  • surfactant for example sodium lauryl sulfate or cetrimonium bromide
  • acid catalyst e.g. HCI
  • the present invention also pertains to a wet-strength improving impregnation mixture (option II) comprising the following compounds in weight-%: Compound wt.-% silicon component, such as tetraethyl orthosilicate (TEOS) about 14.3 surfactant, (for example sodium lauryl sulfate or cetrimonium bromide) about 1.0 H 2 O about 85 (ad 100%) acid catalyst (e.g. HCI) about 0.03
  • TEOS tetraethyl orthosilicate
  • surfactant for example sodium lauryl sulfate or cetrimonium bromide
  • HCI acid catalyst
  • anionic surfactants selected from the group consisting of alkyl carboxylates, alkyl benzene sulfonates, secondary alkyl sulfonates, fatty alcohol sulfates (e.g sodium lauryl sulfate, SDS), alkyl ether sulfates, sulfoacetates and taurides may also be used in some embodiments, in an preferred embodiment cationic surfactants selected from the group consisting of tetraalkylammonium salts of the general formula R 4 N + which differ in their alkylic residue (e.g.
  • the advantageous effect of the cationic surfactant may be used in two different improved embodiments: Either in order to improve the wet-strength of the impregnated fibrous non-woven fabric as compared to mixtures comprising anionic surfactants or to reduce the amount of silicon component, such as TEOS, needed for the impregnation solution, thereby reducing expenses.
  • the present invention also pertains to a wet-strength improving impregnation mixture (option II) comprising the following compounds in weight-%: Compound wt.-% silicon component, such as tetraethyl orthosilicate (TEOS) 1.75 - 8 cationic surfactant (e.g. cetrimonium bromide) 0.2 - 1.5 H 2 O 80 - 95 (ad 100%) acid catalyst (e.g. HCI) 0.005- 0.05
  • TEOS tetraethyl orthosilicate
  • cationic surfactant e.g. cetrimonium bromide
  • HCI acid catalyst
  • the present invention also pertains to a wet-strength improving impregnation mixture (option II) comprising the following compounds in weight-%: Compound wt.-% silicon component, such as tetraethyl orthosilicate (TEOS) 3.5-8 cationic surfactant (e.g. cetrimonium bromide) 0.5 - 1.5 H 2 O 80 - 95 (ad 100%) acid catalyst (e.g. HCI) 0.015- 0.04
  • TEOS tetraethyl orthosilicate
  • cationic surfactant e.g. cetrimonium bromide
  • acid catalyst e.g. HCI
  • the present invention also pertains to a wet-strength improving impregnation mixture (option II) comprising the following compounds in weight-%: Compound wt.-% silicon component, such as tetraethyl orthosilicate (TEOS) about 7 cationic surfactant (e.g. cetrimonium bromide) about 1.0 H 2 O about 85 (ad 100%) acid catalyst (e.g. HCI) about 0.03
  • TEOS tetraethyl orthosilicate
  • HCI acid catalyst
  • the present invention also pertains to a wet-strength improving impregnation mixture (option I) comprising the following compounds in weight-%: Compound wt.-% silicon component, such as tetraethyl orthosilicate (TEOS) 2 - 20 H 2 O 6 - 10 alcohol (e.g. EtOH) 75 - 90 acid catalyst (e.g. HCI) 0.001 - 0.05
  • TEOS tetraethyl orthosilicate
  • EtOH tetraethyl orthosilicate
  • HCI acid catalyst
  • the present invention also pertains to a wet-strength improving impregnation mixture (option I) comprising the following compounds in weight-%: Compound wt.-% silicon component, such as tetraethyl 5-18 orthosilicate (TEOS) H 2 O 6 - 10 alcohol (e.g. EtOH) 75 - 90 acid catalyst (e.g. HCI) 0.01 - 0.04
  • TEOS tetraethyl 5-18 orthosilicate
  • EtOH tetraethyl 5-18 orthosilicate
  • HCI acid catalyst
  • the present invention also pertains to a wet-strength improving impregnation mixture (option I) comprising the following compounds in weight-%: Compound wt.-% silicon component, such as tetraethyl orthosilicate (TEOS) about 9.3 H 2 O about 8 alcohol (e.g. EtOH) about 82.6 acid catalyst (e.g. HCI) about 0.03
  • TEOS tetraethyl orthosilicate
  • EtOH e.g. EtOH
  • HCI acid catalyst
  • the present invention also pertains to a wet-strength improving impregnation mixture (option I) comprising the following compounds in weight-%: Compound wt.-% silicon component, such as tetraethyl orthosilicate (TEOS) about 17.1 H 2 O about 7.4 alcohol (e.g. EtOH) about 75.5 acid catalyst (e.g. HCI) about 0.03
  • TEOS tetraethyl orthosilicate
  • EtOH e.g. EtOH
  • HCI acid catalyst
  • the present invention also pertains to a fibrous non-woven fabric obtained by impregnating the fibrous non-woven fabric with one or more of the mixtures disclosed hereinunder.
  • the impregnating solution consists of the silicon component.
  • the portion of the silicon component in the impregnating solution is 100% by weight.
  • the impregnating solution may be pure silane.
  • the impregnating solution contains in addition to the silicon component still at least one further component, for example a solvent component such as for example an alcohol or water and/or an acid component.
  • a surfactant for example SDS may be also present in the solution.
  • the portion of the silicon component in the impregnating solution is in a range of 5% by weight to 100% by weight, further preferably 10% by weight to 99% by weight, further preferably 20% by weight to 98% by weight, further preferably 40% by weight to 97% by weight, further preferably 60% by weight to 96% by weight, further preferably 80% by weight to 95% by weight.
  • the silicon component is selected from the group consisting of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate, polydimethoxysiloxane, 1,2-bis(triethoxysilyl)ethane, silicon tetraacetate, (3-Aminopropyl)triethoxysilane, (3-Aminopropyl)trimethoxysilane, N-[3-(Trimethoxysilyl)propyl]ethylenediamine, [3-(2-Aminoethylamino)propyl]trimethoxysilane, N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane, 3-(2-Aminoethylamino)propyldimethoxymethylsilane, Bis[3-(trimethoxysilyl)propyl]amine and mixtures of two or more thereof.
  • TEOS tetraethyl orthosilicate
  • TEOS is a common basic chemical which is not expensive and readily available.
  • the component is pre-condensed (i.e. still liquid).
  • pre-condensed means that only oligomers have already been formed, but that the material is not yet completely polymerized.
  • the impregnating solution contains solvents in a portion which is in a range of 0 to 98% by weight, further preferably of 0.1 to 50% by weight, further preferably of 0.2 to 20% by weight, further preferably of 0.5 to 10% by weight, still further preferably of 1 to 5% by weight.
  • the solvent is selected from the group consisting of water, ethanol and mixtures of two or more thereof. Particularly preferably, the solvent is water.
  • the impregnating solution contains water in a portion which is in a range of 0 to 20% by weight, further preferably of 0.5 to 10% by weight, further preferably of 1 to 5% by weight.
  • the impregnating solution contains an acid, for example HCI (37 wt%) in a portion of 0.001 to 0.2% by weight, further preferably of 0.005 to 0.1% by weight, further preferably of 0.01 to 0.05% by weight.
  • an acid for example HCI (37 wt%) in a portion of 0.001 to 0.2% by weight, further preferably of 0.005 to 0.1% by weight, further preferably of 0.01 to 0.05% by weight.
  • the impregnating solution according to the present invention consists of at least 95% by weight, further preferably at least 98% by weight, further preferably at least 99% by weight, further preferably at least 99.9% by weight, further preferably at least 99.99% by weight of ethanol, water, silicon component and HCl. It is a special advantage of the method according to the present invention that no further components are required in the impregnating solution.
  • the impregnating solution even consists of at least 95% by weight, further preferably at least 98% by weight, further preferably at least 99% by weight, further preferably at least 99.9% by weight, further preferably at least 99.99% by weight of water, silicon component and HCl.
  • the impregnated fibrous non-woven fabric comprises a silicon component (e.g. silica or aminosilica) in a portion of 0.1 to 30% by weight, further preferably of 0.5 to 10% by weight, further preferably of 1 to 5% by weight, further preferably of 1.5 to 7.5% by weight.
  • the impregnated fibrous non-woven fabric consists of the fibre component (in particularly paper) and the impregnating component (SiO 2 ).
  • the impregnated fibrous non-woven fabric comprises the fibre component in a portion of 90 to 99.9% by weight, further preferably of 92.5 to 99.8% by weight, further preferably of 95% by weight to 99.5% by weight.
  • the impregnated fibrous non-woven fabric of the invention consists of the fibre component (e.g. paper) and the impregnating component (e.g. SiO 2 ).
  • the fibrous non-woven fabric may contain further components, preferably however in a portion of at most up to 50% by weight, such as for example 0 to 30% by weight, further preferably up to 25% by weight, further preferably up to 10% by weight, further preferably up to 5% by weight, further preferably up to 2% by weight, further preferably up to 1% by weight, further preferably less than 0.5% by weight.
  • These further components may in particularly be inorganic and/or organic fillers.
  • the portion of the fibre component and the impregnating component in the fibrous non-woven fabric of the present invention is at least 50% by weight, further preferably at least 75% by weight, further preferably at least 90% by weight, further preferably at least 95% by weight, further preferably at least 98% by weight, further preferably at least 99% by weight.
  • the impregnated fibrous non-woven fabric of the invention consists of the fibre component and the impregnating component.
  • the present invention pertains to a process for producing the inventive wet strength improving impregnation solution, comprising the steps of
  • the present invention pertains to method for producing the wet strength improving impregnation solution, comprising the steps of
  • the present invention pertains to method for producing the wet strength improving mixture, comprising the steps of
  • the present invention pertains to method for producing the wet strength improving mixture, comprising the steps of
  • the present invention pertains to any silica coated fibrous non-woven fabric, preferably a paper sheet, obtained by coating the paper with any of the wet strength improving impregnation solutions mentioned hereinunder.
  • a fibrous non-woven fabric preferably a paper sheet, obtained by coating the paper with a wet strength improving impregnation solution comprising 12-20 mL TEOS (1 eq.), 10-45 ⁇ L HCI (37 wt%), 80-88 mL of water (ad 100 mL total liquid), and 0.25-3 g sodium dodecyl sulfate (SDS).
  • a wet strength improving impregnation solution comprising 12-20 mL TEOS (1 eq.), 10-45 ⁇ L HCI (37 wt%), 80-88 mL of water (ad 100 mL total liquid), and 0.25-3 g sodium dodecyl sulfate (SDS).
  • a fibrous non-woven fabric preferably a paper sheet, obtained by coating the paper with a wet strength improving impregnation solution comprising 10-20 mL TEOS (1 eq.), 15-40 ⁇ L HCI (37 wt%), 70-85 mL of water, and 0.5-2 g sodium dodecyl sulfate (SDS).
  • a wet strength improving impregnation solution comprising 10-20 mL TEOS (1 eq.), 15-40 ⁇ L HCI (37 wt%), 70-85 mL of water, and 0.5-2 g sodium dodecyl sulfate (SDS).
  • a fibrous non-woven fabric preferably a paper sheet, obtained by coating the paper with a wet strength improving impregnation solution comprising 15.2 mL TEOS (1 eq.), 28 ⁇ L HCI (37 wt%), 84.8 mL of water, and 1g sodium dodecyl sulfate (SDS).
  • a wet strength improving impregnation solution comprising 15.2 mL TEOS (1 eq.), 28 ⁇ L HCI (37 wt%), 84.8 mL of water, and 1g sodium dodecyl sulfate (SDS).
  • a fibrous non-woven fabric preferably a paper sheet, obtained by coating the paper with a wet strength improving impregnation solution comprising 0.5-3 mol-% tetraethyl orthosilicate (TEOS) : 20-60 mol-% EtOH : 5-30 mol-% H 2 O : 0.001-0.2 mol-% HCI (37 wt%).
  • TEOS tetraethyl orthosilicate
  • a fibrous non-woven fabric preferably a paper sheet, obtained by coating the paper with a wet strength improving impregnation solution comprising 1-2 mol-% tetraethyl orthosilicate (TEOS) : 30-50 mol-% EtOH : 10-20 mol-% H 2 O : 0.01-0.05 mol-% HCI (37 wt%).
  • TEOS tetraethyl orthosilicate
  • a fibrous non-woven fabric preferably a paper sheet, obtained by coating the paper with a wet strength improving impregnation solution comprising mixing 1 mol-% tetraethyl orthosilicate (TEOS) : 40 mol-% EtOH : 10 mol-% H 2 O : 0.02 mol-% HCI (37 wt%),
  • TEOS tetraethyl orthosilicate
  • the present invention also relates to a method for the production of a fibrous non-woven fabric with homogeneous silica impregnation, in particularly a fibrous non-woven fabric of the present invention such as described above.
  • the invention also relates to a fibrous non-woven fabric with a homogeneous silica impregnation which can be obtained or has been obtained by the method.
  • the impregnation solution may be added already to the bath comprising the fibres of the fibrous non-woven fabric before the fibrous non-woven fabric itself is produced and dried.
  • the advantage of this process is an evenly distribution of the impregnation solution on all fibres and a simplified process.
  • one disadvantage may be the need of higher volumes of impregnation solution, thus, impregnation solutions with cationic surfactant are preferred.
  • the method comprises then the following steps:
  • the fibrous non-woven fabric is impregnated later during the drying process.
  • the method comprises the following steps:
  • the method for producing the silica coated paper sheet comprises the steps of
  • the method for producing the silica coated paper sheet comprises the steps of
  • the advantage of the described product and process according to the invention compared to the state of the art is an environmentally friendly, non-toxic final product (i.e. only comprising SiO 2 ), which also allows the technical use of the wet-strength improved fibrous non-woven fabric according to the invention in the food industry.
  • the impregnation can be carried out at temperatures below 150 °C (preferably between 4 - 40 °C; or ambient temperature at 20 °C) and atmospheric pressure, which leads to significant energy savings.
  • the impregnation works so fast, the paper can be further treated rather quickly in the production line.
  • a "zick-zack" arrangement of contact elements and/or rolls may be used to dry the paper equally from both sides.
  • a fibrous non-woven fabric is provided.
  • the fibrous non-woven fabric is selected from the group consisting of non-woven paper fabrics, non-woven textile fabrics and non-woven plastic fabrics.
  • the fibrous non-woven fabric is a non-woven paper fabric.
  • the provided non-woven paper fabric has a grammage of 10 - 1000 g/m 2 . In one aspect preferably between 10 - 20 g/m 2 , more preferably 12 - 15 g/m 2 (for example in case of paper for tea-bags).
  • the grammage is preferably between 250 - 1050 g/m 2 , more preferably 300 - 1000 g/m 2 (for example in case of wood pulp boards). In further aspects the grammage is preferably 65 to 120 g/m 2 , further preferably of 70 to 100 g/m 2 , further preferably of 75 to 90 g/m 2 .
  • the fibrous non-woven fabric can be a commercially available fibrous non-woven fabric.
  • the non-woven paper fabric can be a commercially available non-woven paper fabric.
  • the step of providing the fibrous non-woven fabric, in particularly the non-woven paper fabric can also contain the step of the production of the fibrous non-woven fabric, in particularly the non-woven paper fabric.
  • the production of a non-woven paper fabric is preferably conducted with the Rapid-Köthen method, particularly preferably in a sheet forming Rapid-Köthen plant, especially preferably according to DIN 54358 and/or ISO 5269/2 (ISO5269-2:2004(E), "Pulps - Preparation of Laboratory Sheets for Physical Testing - Part 2: Rapid Köthen Method, 2004").
  • additives such as conservation agents, bleaching agents, thickeners, etc. may be used.
  • an impregnating solution which contains a silicon component is provided.
  • the impregnating solution may be a single-component one, thus may consist of one single component. In such a case the impregnating solution may in particularly also be referred to as “impregnating fluid' or "impregnation fluid " .
  • the impregnating solution is preferably stirred for a period of time of 6 to 48 hours, further preferably of 12 to 36 hours, further preferably of 18 to 30 hours, before the impregnating of the fibrous non-woven fabric, in particularly the non-woven paper fabric, is conducted with the impregnating solution according to step c) of the method according to the present invention.
  • the impregnating solution consists of silicon component (in particularly TEOS), preferably, no such stirring is conducted.
  • the step c) of the impregnating of the fibrous non-woven fabric, in particularly the non-woven paper fabric, with the impregnating solution is preferably conducted at a relative air humidity in a range of 10% to 95%, further preferably of 30% to 70%, further preferably 40% to 60%, further preferably 45% to 55% and/or at a temperature in a range of 15 °C to 30 °C, further preferably 20 °C to 25 °C.
  • the impregnating of the fibrous non-woven fabric with the impregnating solution is realized by exposing the fibrous non-woven fabric to the impregnating solution, thus in other words, by bringing the fibrous non-woven fabric into contact with the impregnating solution.
  • the impregnating of the fibrous non-woven fabric with the impregnating solution according to step c) of the method is realized with an impregnating method which is selected from the group consisting of film coating, kiss coating, immersion coating, spray coating, size press, roller coating, blade coating and curtain coating. Immersion coating and spray coating are particularly preferred. Especially preferred is immersion coating.
  • the impregnating solution is uniformly distributed across the surface and the interior of the fibrous non-woven fabric.
  • the impregnating in step c) of the invention is realized by immersing the fibrous non-woven fabric into the impregnating solution.
  • the fibrous non-woven fabric, in particularly the non-woven paper fabric is completely immersed into the impregnating solution.
  • the immersion is conducted such that the fibrous non-woven fabric, in particularly the non-woven paper fabric, is substantially vertically oriented.
  • a vertical orientation means, in other words, that both main surfaces of the fibrous non-woven fabric are arranged such that surface vectors which are orthogonal with respect to the main surfaces are substantially horizontally oriented.
  • the surface vectors of both main surfaces with the vector of the immersion direction each form an angle of at least 70° and at most 110°, further preferably of at least 80° and at most 100°, further preferably of at least 85° and at most 95°.
  • the removal of the fibrous non-woven fabric from the impregnating solution is conducted at a time point 0.1 to 10 seconds, further preferably 1 to 5 seconds after the completion of the immersion of the fibrous non-woven fabric into the impregnating solution.
  • the minimum and maximum time of contact with the impregnation solution depends also on the production process: In case of impregnation by dipping processes up to 30 seconds, up to a minute, up to 5 minutes are still acceptable, whereas in case of size-press systems the contact is much shorter between 0.1 second and 5 seconds. However, the contact should not be significantly below 0.05 second and not much more than 30 minutes.
  • the removal of the fibrous non-woven fabric from the impregnating solution is conducted such that the fibrous non-woven fabric is substantially vertically oriented.
  • a vertical orientation means, in other words, that both main surfaces of the fibrous non-woven fabric are arranged such that surface vectors which are orthogonal with respect to the main surfaces are substantially horizontally oriented.
  • the surface vectors of both main surfaces with the vector of the removal direction each form an angle of at least 70° and at most 110°, further preferably of at least 80° and at most 100°, further preferably of at least 85° and at most 95°.
  • the drying of the fibrous non-woven fabric is conducted at temperatures in a range of 70°C to 190°C.
  • the drying of the fibrous non-woven fabric is conducted at temperatures in a range of 80°C to 180°C, further preferably of 90°C to 170°C, further preferably of 100°C to 160°C, further preferably of 110°C to 150°C, further preferably of 120°C to 140°C, further preferably of 125°C to 135°C.
  • the drying of the fibrous non-woven fabric according to step d) is conducted, until the residual moisture content of the fibrous non-woven fabric is in a range of 3% by weight to 7% by weight.
  • the residual moisture content is determined by means of gravimetric analysis, in particularly according to DIN EN 20287. At higher temperatures, the pulp of the paper may suffer and show discolouration.
  • step d) there is a period of time of at most 60 seconds, preferably at most 45 seconds, further preferably at most 30 seconds, further preferably at most 20 seconds, further preferably at most 10 seconds, further preferably at most 5 seconds, further preferably at most 2 seconds, further preferably at most 1 second.
  • the drying according to step d) of the method according to the present invention is conducted immediately, in other words directly, after the impregnating of the fibrous non-woven fabric with the impregnating solution according to step c) of the method.
  • the impregnating according to step c) is finished, when the fibrous non-woven fabric is no longer exposed to the impregnating solution, or in other words, when the fibrous non-woven fabric is no longer brought into contact with the impregnating solution.
  • the impregnating according to step c) is preferably finished, when the fibrous non-woven fabric again has completely been removed from, for example pulled out of, the impregnating solution.
  • the impregnating according to step c) is preferably finished, when the impregnating solution is no longer sprayed onto the non-woven fabric.
  • the drying according to step d) preferably begins, when the fibrous non-woven fabric enters an environment which is intended for removing humidity and/or condensation products, such as for example an oven.
  • the silicon component of the impregnating solution has still not been converted in a substantial extent into the silicate component of the silica impregnation, when the drying is realized at the increased drying temperatures.
  • This allows the targeted adjustment of the homogeneity of the silica impregnation.
  • the silicon component migrates at the increased drying temperatures depending on the drying conditions, in particularly the environmental pressures, through the non-woven fabric, as long as it has not been converted into a silica impregnation with a polymerization degree which is too high.
  • the migration of the silicon component through the fibrous non-woven fabric at the increased drying temperatures can in particularly be influenced by an adjustment of the environmental pressures during the drying.
  • the migration of the silicon component can in particularly also be influenced by the evaporation of the silicon component and/or the solvent at the increased drying temperatures, because the silicon component together with the solvent migrates through the fibrous non-woven fabric.
  • the method of the present invention is designed such that between the completion of the impregnating according to step c) and the beginning of the drying according to step d) a period of time of at most 60 seconds is provided. Therefore, at the begin of the drying a substantial poly-condensation has still not taken place so that the silicon component which is present in the impregnating solution migrates through the fibrous non-woven fabric, and therefore via the migration the distribution of the silica impregnation can be influenced in a targeted manner.
  • the drying is achieved with the help of a dryer.
  • the dryer is selected from the group consisting of hot air/convective dryers, ovens, drum dryers (contact drying) and IR dryers.
  • it can be dried in an oven, preferably in a drying oven (in some aspects a vacuum oven) or in a muffle furnace.
  • the oven/drying device is preheated, in particularly to the drying temperature so that after the impregnating according to step c) it is possible to start the drying according to step d) very quickly.
  • the dryer is a hot air dryer. Hot air drying is particularly preferred.
  • the properties of the obtained fibrous non-woven fabrics cannot only be influenced by the above-mentioned method steps, but in particularly also by the prevailing environmental pressure during the drying.
  • the distribution of the content of SiO 2 in the fibrous non-woven fabrics can be controlled in a targeted manner by the pressure conditions during the drying. Fibrous non-woven fabrics with relatively high contents of SiO 2 at both main surfaces can in particularly be obtained with low pressures.
  • the pressure during the drying according to step d) is in a range of 0.1 kPa to 500 kPa, further preferably of 0.2 kPa to 200 kPa. In certain preferred embodiments, the pressure during the drying according to step d) is in a range of 0.1 kPa to 30 kPa, further preferably of 0.2 kPa to 20 kPa, further preferably of 0.5 kPa to 10 kPa, further preferably of 1 kPa to 5 kPa.
  • the pressure during the drying according to step d) is in a range of >30 kPa to 500 kPa, further preferably of 50 kPa to 200 kPa, further preferably of 60 kPa to 150 kPa, further preferably of 70 kPa to 130 kPa, further preferably of 80 kPa to 120 kPa, further preferably of 90 kPa to 110 kPa.
  • Such embodiments are in particularly suitable for the production of such fibrous non-woven fabrics, where the content of SiO 2 at one of both main surfaces is considerably higher than at the other of both main surfaces, while the content of SiO 2 in the center of the fibrous non-woven fabric is lower than at the one of both main surfaces, however higher than at the other of both main surfaces.
  • This is in particularly true, when impregnating solutions with low or medium portions of silicon component are used, in particularly with a portion of silicon component in a range of 0.1% by mol to 3.5% by mol, further preferably of 0.2% by mol to 3% by mol, further preferably of 0.5% by mol to 2.5% by mol, further preferably of 0.9% by mol to 2.2% by mol.
  • the fibrous non-woven fabrics are cooled to a temperature of 15°C to 30°C, further preferably of 20°C to 25°C.
  • the method consists of the mentioned steps. It is a special advantage of the method according to the present invention that the method gets by with very few steps.
  • the present invention also includes papers with increased wet strength produced according to said processes, according to steps a) to d).
  • the present invention also relates to the use of a fibrous non-woven fabric of the present invention, in particularly as packaging material.
  • Preferred uses as packaging material comprise the use as freezing paper, the use for products which come into contact with foodstuffs, such as in particularly (paper) cups and/or (paper) straws, as well as the use as packaging for materials which are protected from liquid, but nevertheless should allow diffusion of moisture.
  • the fibrous non-woven fabrics of the present invention can be used for plastic-free straws and/or pasteboard cups.
  • suitable materials which could be improved in their wet strength are tea bags, kitchen paper, cardboard, map paper, security paper for bank notes, coffee or tea filters, wrapping paper, toilet paper, paper towels, cooking paper, paper labels, display boards, promotional poster, corrugated boards, paper bags, and/or cloths, and the like.
  • the present invention also relates to the use of a fibrous non-woven fabric of the present invention as specialty paper for the use at increased temperatures, in particularly the use of a fibrous non-woven fabric of the present invention as baking paper.
  • the present invention also includes the use of the wet strength agents described for the manufacture of a paper product having increased relative wet strength of greater than 2%, greater than 5%, preferably greater than 10%, most preferably greater than 15% as measured by a tensile elongation test according to ISO 1924-2.
  • papers are measured by tensile elongation strength according to ISO 1924-2 and achieve relative wet strengths above 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% and up to 31%, 32%, 33%, 34%, 35%, 40%, 50%.
  • the method for determining properties under tensile stress is one of the most commonly used methods. It is similar to the method specified in ISO 1924-3. In this part of ISO 1924 (ISO 1924-2) a constant strain rate of 20 mm/min is applied, whereas in ISO 1924-3 the constant strain rate is 100 mm/min.
  • the International Standard was prepared by ISO/TC 6 "Paper, board and pulp” in cooperation with CEN/TC 172 "Fibrous materials, paper and board", whose secretariat is held by DIN.
  • the Standards Committee for Materials Testing (NMP) played a major role in the preparation of the standard.
  • the national mirror committee is the joint committee NA 062-04-26 GA "Physical-technological test methods for paper and board”. For the rest, we refer to the specifications in the corresponding DIN standard.
  • the fibrous non-woven fabric of the present invention is a fibrous non-woven fabric.
  • the fibrous non-woven fabric is selected from the group consisting of non-woven paper fabrics and non-woven textile fabrics.
  • the fibrous non-woven fabric is a non-woven paper fabric.
  • the fibrous non-woven fabrics of the invention have high flexibility.
  • the paper mentioned hereinunder is selected from the group consisting of eucalyptus paper and/or northern bleached softwood kraft (NBSK).
  • NBSK northern bleached softwood kraft
  • cotton linters 80 g/m 2
  • abaca 13 g/m 2
  • Other papers that can be used according to the invention include: Aburatorigami, Affiche paper, Albumin paper, Alfapaper, Amatl, APCO II/II (DIN 16519 T2), Watercolour paper (between 120 g/m 2 up to 850 g/m 2 , for watercolour board from approx.
  • Wet-strength papers produced by the processes or wet-strength agents described are particularly suitable for applications that are naturally exposed to moisture but still require paper stability.
  • Such papers are, for example, packaging papers and cartons, banknote papers, handkerchiefs, paper kitchen crepe and cleaning cloths, cigarette papers, sandwich papers, newsprint papers, filter papers for e.g. tea and coffee, etc.
  • wet-strength impregnation solution and fibrous non-woven fabrics as well as papers in/as products with improved wet tensile strength selected from the group comprising tea bags, kitchen paper, cardboard, map paper, security paper for bank notes, coffee or tea filters, wrapping paper, toilet paper, paper towels, cooking paper, paper labels, display boards, promotional poster, drinking straws, packaging papers, corrugated boards, paper bags, cloths.
  • the wet-strength improved non-woven material can be particularly used for food contact materials due to their non-toxic nature. This is important for paper cups, especially when holding hot beverage or food (e.g. instant soup cups), microwave pots or other plates and/or cutlery which come in contact with acidic and or hot food or beverage, tea bags, coffee filters, paper straws, and the like. In those instances an aminosilica-content of between 0.7 - 1% is preferred.
  • Lab-engineered paper sheets were prepared using bleached eucalyptus sulfate pulp and Northern bleached softwood kraft (NBSK; pine and spruce) pulp. The pulp was refined in a Voith LR 40 laboratory refiner at 75000 revolutions. Lab-engineered paper sheets with a grammage of 80 ⁇ 1.6 g/m2 were prepared using a Rapid-Köthen sheet former according to DIN 54358 and ISO 5269/2. No additives or fillers were used. Model paper sheets with different fibre ratios of long fibres (LF; NBSK) and short fibres (SF; Eucalyptus) of 100LF:0SF (Eucalyptus), 20LF:80SF, 50LF50SF, and 80LF20SF were prepared.
  • LF long fibres
  • SF short fibres
  • paper was made from mixing the paper fibre pulp suspension with the impregnation solution and drying the paper afterwards.
  • a wet strength was achieved of 1.58 ⁇ 0.1 N/15mm for 20LF80SF with a silica content of 1.28% oven dry and 1.22% air dry.
  • the components of the sol were mixed, stirred for 24 h at room temperature, and used for silica coating of paper sheets using a size press ( Figure 1 ) for bilateral coating with a speed of 5 m/min at a roll pressure of 0.5 - 1.0 bar.
  • a size press Figure 1
  • Freshly coated paper sheets were placed in a preheated oven at 160°C for 5-15 min at atmospheric pressure before cooling down to ambient temperature.
  • a coating emulsion (option II) was prepared as follows.
  • TEOS was mixed with HCI (37 wt%) and stirred for 24 h at room temperature. Then, water and sodium dodecyl sulfate (SDS) were added and the mixture is rigorously stirred for 1 h at room temperature, before applying the obtained emulsion for coating with a size press with a speed of 5 m/min at a roll pressure of 0.5 - 1.0 bar. Freshly coated paper sheets were placed in a preheated oven at 160°C for 5-15 min at atmospheric pressure before cooling down to ambient temperature.
  • SDS sodium dodecyl sulfate
  • the wet-strength of model paper sheets with different fibre ratios of long fibres was 23 ⁇ 4 N/15 mm, i.e. much higher than with other impregnations.
  • option II shows some advantages as compared to option I.
  • EtOH or alcohol in general
  • a security risk or it is more expensive than water.
  • option II is the preferred mixture for impregnation.
  • TGA was performed using a TGA 1 Mettler-Toledo. The samples were heated from 25 °C to 600 °C with a heating rate of 10 K/min under constant air flow of 30 mL/min.
  • Wet tensile strength was determined as an average of 10 samples according to DIN ISO 3781 with a Zwick Z1.0 with a 1 kN load cell using the software testXpert II V3.71 from ZwickRoell GmbH & Co. Kg in a controlled environment with 23 °C and 50 rH%. Thereby, the paper samples were immersed in water for at least 1 h prior to measurements.
  • the silica content of silica coated paper sheets is determined via TGA. Thereby, the silica content can be determined from the plateau of the TGA curves at 550 °C, since silica is stable up to 1700 °C, whereas natural organic fibres are totally combusted. Comparing the values between 550 °C and 600 °C before and after silica coating allows to take the natural ash content of the substrates into account. Furthermore, the weight loss occurring till 150 °C can be assigned to physically adsorbed water and is considered in the calculation to determine the silica content with respect to oven-dry samples.
  • TGA curves of model paper sheets coated with silica via option I and eucalyptus paper sheets coated with silica via option II are depicted in Figure 2 , whereas the calculated silica contents are illustrated in Table 1.
  • Table 1 Calculated silica contents derived from TGA.
  • Eucalyptus paper sheets were investigated with respect to their morphology before and after silica coating using SEM ( Figure 3 ). Silica coated paper sheets coated with option I and option II do not show morphological differences on the micrometer scale compared to uncoated paper sheets. This can be explained due to the low silica amount as deduced from TGA.
  • the wet tensile strength of paper sheets before and after coating with silica was determined according to DIN ISO 3781. Thereby, paper samples of 15 mm width and approximately 120 mm length are immersed in water for 1 h before measurement. The determined values of wet tensile strength are depicted in Figure 4 . Comparing the wet tensile strength before and after silica coating, higher values are obtained due to silica coating for both option I and option II. Thereby, the wet tensile strength of model paper coated with silica via option I show higher values as compared to eucalyptus paper sheets coated with silica via option II. Furthermore, comparing the model paper sheets with different composition of long and short fibres, the wet tensile strength increases more with higher amount of short fibres (eucalyptus).
  • the wet strength was compared for different papers and different mixtures.
  • comparative paper asymmetric impregnated with-type TEOS
  • comparative paper i.e. with a silica content on one side at least 2 times higher than on the other side.
  • silica content is depicted in example 6, table 1.
  • Table 2 Comparison of wet-strength. Paper Untreated Comparative paper (asymmetric impregnated) Option I (cf. example 2) Option II w. anionic surfactant (SDS) (cf. example 2) Option II w. cationic surfactant (cetrimonium bromide) (cf. example 2) wet strength in N/15 mm, determined according to DIN ISO 3781 20LF80SF 0.3 6.2 ⁇ 2 10.2 ⁇ 0.6 7.3 ⁇ 1 24.3 ⁇ 1.3 50LF50SF 0.6 4.1 ⁇ 1 8.3 ⁇ 0.5 12.8 ⁇ 1.5 - 80LF20SF 1.0 3.5 ⁇ 1 7.7 ⁇ 0.4 7.6 ⁇ 0.9 -
EP22187283.1A 2022-07-27 2022-07-27 Tissus non-tissés fibreux à résistance améliorée à l'état humide, notamment le papier, utilisations de ces tissus à résistance à l'état humide ainsi que leurs procédés de production Pending EP4311872A1 (fr)

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