# US 12,110,636 B2 · Filter paper > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,110,636 B2 - Document ID: US12110636B2 - Status: Granted - Kind: B2 - Application number: 17/043,486 - Filed: 2019-03-04 - Published: 2021-04-29 - Granted: 2024-10-08 - Earliest claimed: 2018-04-04 - Assignees: delfortgroup AG - Applicants: Delfortgroup AG - Inventors: Dieter Möhring; Guido Reiter - Web page: https://patentgrep.com/patent/US12110636B2 ## CPC - D21H 27/08: Filter paper (self-supporting filtering material B01D39/14; making on paper-making machines D21F11/14) - D21H 13/14: Polyalkenes, e.g. polystyrene {polyethylene} - D21H 15/10: Composite fibres - D21H 17/67: Water-insoluble compounds, e.g. fillers, pigments - D21H 17/675: {Oxides, hydroxides or carbonates} - D21H 13/24: Polyesters - D21H 13/26: Polyamides; Polyimides - 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 ## Abstract Described herein is a filter paper for the production of an aqueous extract, comprising softwood pulp, which has the following properties: a basis weight of more than 9.0 g/m2 and less than 13.5 g/m2, a density of more than 280 kg/m3 and less than 350 kg/m3, a roughness of more than 700 ml/min and less than 1300 ml/min, a bending resistance in the machine direction of more than 50 mN and less than 75 mN, and an air permeability of more than 17000 cm/(min·kPa) and less than 26000 cm/(min·kPa), wherein the filter paper is either free from abacá fibers and sisal fibers or, if abacá fibers and/or sisal fibers are present, taken together they make up less than 20% of the paper mass. ## Claims ### Claim 1 A filter paper for the production of an aqueous extract, comprising softwood pulp, which has the following properties: a basis weight of more than 9.0 g/m2 and less than 13.5 g/m2, a density of more than 280 kg/m3 and less than 350 kg/m3, a roughness of more than 700 ml/min and less than 1300 ml/min, a bending resistance in the machine direction of more than 50 mN and less than 75 mN, and an air permeability of more than 17000 cm/(min·kPa) and less than 26000 cm/(min·kPa), wherein the filter paper is either free from abacá fibers and sisal fibers or, if abacá fibers and/or sisal fibers are present, taken together they make up less than 20% of the paper mass, and wherein the content of softwood pulp in the filter paper is at least 70% with respect to the mass of the filter paper. ### Claim 2 (depends on 1) The filter paper according to claim 1, wherein the softwood pulp is sourced from spruce, pine or fir. ### Claim 3 (depends on 1) The filter paper according to claim 1, wherein a content of abacá fibers and sisal fibers taken together is less than 10% of the mass of the filter paper. ### Claim 4 (depends on 1) The filter paper according to claim 1, which further contains hardwood pulp, whereby the hardwood pulp is sourced from birch, beech or eucalyptus, and wherein the content of hardwood pulp is at most 20% of the paper mass. ### Claim 5 (depends on 1) The filter paper according to claim 1, which is free of hardwood pulp. ### Claim 6 (depends on 1) The filter paper according to claim 1, which further contains thermoplastic fibers. ### Claim 7 (depends on 6) The filter paper according to claim 6, wherein the thermoplastic fiber material is selected from the group consisting of polyethylene, polypropylene, polyester polyamide, polymethacrylate, polyacrylate, polyvinyl acetate, polyvinyl alcohol and polylactic acids or mixtures thereof. ### Claim 8 (depends on 6) The filter paper according to claim 6, wherein the content of thermoplastic fibers is at least 5% and at most 30%, respectively with respect to the mass of the filter paper. ### Claim 9 (depends on 1) The filter paper according to claim 1, which contains one or more filler materials which are selected from the group consisting of calcium carbonate, magnesium carbonate, magnesium hydroxide, aluminum hydroxide, magnesium silicates, aluminum silicates, kaolin and talcum or mixtures thereof. ### Claim 10 (depends on 9) The filter paper according to claim 9, wherein the content of filler materials is less than 10% of the paper mass. ### Claim 11 (depends on 1) The filter paper according to claim 1, which is free from filler materials. ### Claim 12 (depends on 1) The filter paper according to claim 1, with a basis weight of at least 10.0 g/m2 and a basis weight of at most 13.2 g/m2. ### Claim 13 (depends on 1) The filter paper according to claim 1, with a density of at least 290 kg/m3 and a density of at most 340 kg/m3. ### Claim 14 (depends on 1) The filter paper according to claim 1, with a thickness of at least 38 μm and a thickness of at most 48 μm. ### Claim 15 (depends on 1) The filter paper according to claim 1, with a roughness in accordance with ISO 8791-2:2013 of at least 800 ml/min and of at most 1200 ml/min. ### Claim 16 (depends on 1) The filter paper according to claim 1, with an air permeability in accordance with ISO 2965:2009 of at least 18000 cm/(min·kPa) and at most 25000 cm/(min·kPa). ### Claim 17 (depends on 1) The filter paper according to claim 1, with a bending resistance in accordance with ISO 2493-1:2010 in the machine direction of at least 55 mN and at most 73 mN. ### Claim 18 (depends on 1) The filter paper according to claim 1, with a bending resistance in accordance with ISO 2493-1:2010 in the cross direction of at least 15 mN and at most 28 mN. ### Claim 19 (depends on 1) The filter paper according to claim 1, which has an elongation at break in the machine direction of at least 1.0% and at most 2.0% and which has an elongation at break in the cross direction of at least 1.8% and at most 3.8%. ### Claim 20 (depends on 1) The filter paper according to claim 1, which has a tensile strength in the machine direction of at least 11.5 N/15 mm and at most 15.0 N/15 mm and which has a tensile strength in the cross direction of at least 2.5 N/15 mm and at most 5.0 N/15 mm. ### Claim 21 (depends on 1) The filter paper according to claim 1, which has a tensile energy absorption in accordance with ISO 1924-2:2008 in the machine direction of at least 6.0 J/m2 and at most 11.0 J/m2. ### Claim 22 (depends on 1) The filter paper according to claim 1, which is packed essentially impermeably to water vapor and has a moisture content of at least 9% and at most 20%. ### Claim 23 A process for manufacturing a filter paper, which is either free from abacá fibers and sisal fibers, or if abacá fibers and/or sisal fibers are present, taken together, these make up less than 20% of the paper mass, wherein the process comprises the following steps: suspending softwood pulp in water and refining at least the softwood pulp in a refiner, delivering a suspension, which contains at least the refined softwood pulp, onto the wire of a paper machine, de-watering the suspension through the wire of the paper machine to form a paper, and pressing the paper with a sufficient pressure to provide the paper with the following properties: a basis weight of more than 9.0 g/m2 and less than 13.5 g/m2, a density of more than 280 kg/m3 and less than 350 kg/m3, a roughness of more than 700 ml/min and less than 1300 ml/min, a bending resistance in the machine direction of more than 50 mN and less than 75 mN, and an air permeability of more than 17000 cm/(min·kPa) and less than 26000 cm/(min·kPa). ### Claim 24 (depends on 23) The process according to claim 23, wherein the filter paper is a filter paper for the production of an aqueous extract, comprising softwood pulp, which has the following properties: a basis weight of more than 9.0 g/m2 and less than 13.5 g/m2, a density of more than 280 kg/m3 and less than 350 kg/m3, a roughness of more than 700 ml/min and less than 1300 ml/min, a bending resistance in the machine direction of more than 50 mN and less than 75 mN, and an air permeability of more than 17000 cm/(min kPa) and less than 26000 cm/(min·kPa), wherein the filter paper is either free from abacá fibers and sisal fibers or, if abacá fibers and/or sisal fibers are present, taken together they make up less than 20% of the paper mass, and wherein the content of softwood pulp in the filter paper is at least 70% with respect to the mass of the filter paper. ### Claim 25 (depends on 23) The process according to claim 23, wherein the paper machine is an inclined-wire machine, wherein the wire is inclined between 15° and 25° relative to the horizontal. ### Claim 26 (depends on 23) The process according to claim 23, wherein, after the wire section, the filter paper runs through a press section, in which it is further de-watered, wherein the press section comprises two rolls which form a nip through which the paper runs and is exposed to a line load of 30 kN/m and at most 100 kN/m. ### Claim 27 (depends on 23) The process according to claim 23, wherein after pressing, the filter paper is dried by hot air, infra-red radiation or contact with heated cylinders. ### Claim 28 (depends on 23) The process according to claim 23, wherein the filter paper in a state with a moisture content of at least 9% and at most 20% is packed essentially impermeable to water vapor. ### Claim 29 (depends on 1) A bag formed from the filter paper according to claim 1, which contains a material to be extracted, wherein the material to be extracted is tea. ### Claim 30 (depends on 1) The filter paper according to claim 1, wherein the content of softwood pulp in the filter paper is at least 90% with respect to the mass of the filter paper. ### Claim 31 (depends on 1) The filter paper according to claim 1, wherein all of the pulp in the filter paper is formed by softwood pulp. ### Claim 32 (depends on 4) The filter paper according to claim 4, wherein the content of hard wood pulp is at least 2% of the paper mass. ### Claim 33 (depends on 6) The filter paper according to claim 6, wherein the thermoplastic fibers are made of polyethylene terephthalate. ### Claim 34 (depends on 12) The filter paper according to claim 12, with a basis weight of at least 11 g/m2 and at most 13.0 g/m2. ### Claim 35 (depends on 1) The filter paper according to claim 1, with a thickness of at least 41 μm and at most 45 μm. ### Claim 36 (depends on 26) The process according to claim 26, wherein the rolls are steel rolls coated with a plastic coating. ### Claim 37 (depends on 27) The process according to claim 27, wherein the drying step comprises humidification.