Classifications

• • 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
  • D21H27/08—Filter paper
• • 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
  • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
  • D21H13/10—Organic non-cellulose fibres
  • D21H13/12—Organic non-cellulose fibres from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H13/14—Polyalkenes, e.g. polystyrene polyethylene
• • 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
  • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
  • D21H13/10—Organic non-cellulose fibres
  • D21H13/20—Organic non-cellulose fibres from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H13/24—Polyesters
• • 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
  • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
  • D21H13/10—Organic non-cellulose fibres
  • D21H13/20—Organic non-cellulose fibres from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H13/26—Polyamides; Polyimides
• • 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
  • D21H15/00—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution
  • D21H15/02—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution characterised by configuration
  • D21H15/10—Composite fibres
• • 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
• • 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
  • D21H17/675—Oxides, hydroxides or carbonates

Definitions

• the invention relates to a filter paper for the production of aqueous extracts, in particular for the production of tea, coffee or other infusion drinks and to bags made from this filter paper, in particular tea bags.
• the filter paper according to the invention is characterized by a low proportion or the complete absence of the commonly used Abacá fibers or sisal fibers, as well as by a property profile that deviates from the prior art. Nevertheless, the filter paper according to the invention offers at least the same performance in use as filter papers known from the prior art.
• aqueous extracts for example crushed tea leaves
• bags for example crushed tea leaves
• the bag is closed and immersed in the usually hot water for a certain time in order to produce the infusion beverage and then removed again from the water.
• Methods in which the bag is not closed and only hung in the hot water instead of being immersed are also known.
• the main advantages of using these bags are simple handling, pre-portioning of the material to be extracted and easy removal of the material to be extracted from the water.
• the filter paper should not disintegrate in the water so that the material to be extracted remains in the bag. It is said to have a high porosity so that the water can easily flow around the material to be extracted by natural or forced convection and the extraction process does not take long. Furthermore, the pores in the filter paper should not be too large so that small particles of the material to be extracted do not fall through the filter paper and remain in the extract. This property is determined by measuring the so-called sand loss. In addition, the filter paper itself should not release any undesirable substances, in particular no undesirable flavors or aromas, into the water. Finally, the filter paper also have mechanical properties that allow the bags to be manufactured industrially at high speed. These include, for example, mechanical strength and ductility, roughness or a heat sealability.
• the proportion of Abacá fibers or sisal fibers in the filter paper from the prior art is generally more than 25% of the paper pulp.
• such filter papers often also contain synthetic fibers, in particular thermoplastic fibers, which provide the filter paper with a heat sealability, so that sealed bags can be produced from the filter paper comparatively simply by sealing the filter paper to itself and no further materials for sealing of the bag are needed.
• the filter papers often also contain agents for increasing the wet strength so that they have sufficient mechanical strength during the production of the aqueous extract.
• the WO2017 / 110365A1 discloses a nonwoven material for a filter comprising a composite polyester fiber in which a low melting point polyester surrounds a high melting point polyester.
• the low melting point polyester has a melting point that is 10 to 140 ° C lower than the melting point of the high melting point polyester.
• the basis weight of the nonwoven material is 150 to 300 g / m 2 , the density 0.25 to 0.40 g / cm 3 and the air permeability per basis weight 0.05 to 0.45 (cm 3 / cm 2 • s) / (g / m 2 ).
• the EP 1 382 373 A1 discloses a heat sealable filter material having at least a first non-heat sealable layer and at least a second heat sealable layer comprising fibers of synthetic material containing an adhesion promoter.
• the first non-heat sealable layer has a basis weight between 8 and 40 g / m 2 and an air permeability of 300 to 4000 l / m 2 • s (DIN ISO 9237).
• the EP 1 215 134 A1 discloses a filter material for the manufacture of filter bags and filter bags for infusion beverages, which comprises so-called superabsorbent fibers, which can absorb large amounts of liquid.
• the superabsorbent fibers consist of (meth) acrylate copolymers.
• the filter material has a basis weight of between 8 and 90 g / m 2 .
• the DE 10 2016 105 235 discloses a filter paper for the manufacture of filters for smoking articles, especially filter cigarettes.
• the paper has the following properties:
• the filter paper comprises fibers comprising cellulose fibers, at least 80% by weight, preferably at least 90% by weight, particularly preferably at least 95% by weight and very particularly preferably 100% by weight of the filter paper formed by long-fiber cellulose fibers, of the fibers a proportion based on the number of fibers of between 2% and 10%, preferably between 3% and 9% and particularly preferably between 4% and 8% has a length of less than 0.2 mm
• the air permeability of the filter paper is measured according to ISO 2965: 2009 is from 500 cm -1 ⁇ ⁇ kPa -1 and 15000 cm ⁇ min -1 ⁇ kPa -1 cm, and preferably between I 1000 cm -1 ⁇ min -1 ⁇ kPa and 9000 ⁇ min -1 kPa -1 , the number-based average
• the object is to provide a filter paper which can be used for the production of aqueous extracts, in particular infusion beverages such as tea or coffee, and which contains comparatively significantly less or no Abaca fibers or sisal fibers.
• the filter paper should offer the same performance in the production of the aqueous extract as the conventional filter papers.
• the inventors have developed a filter paper whose properties differ from filter papers known from the prior art, but which is in any case no worse than the filter papers known from the prior art with regard to its performance in the production of aqueous extracts.
• this result can be achieved with a roughness, a bending resistance and an air permeability, each of which is lower than that of the filter papers known from the prior art, and of a density which is higher than that from the prior art filter papers known in the art.
• This combination of properties can be achieved by a special mechanical treatment, as described below.
• the filter paper according to the invention comprises long fiber pulp.
• the long fiber pulp can be obtained from conifers such as spruce, pine or fir. It gives the filter paper high strength and air permeability, but does not achieve the same values as Abacá fibers or sisal fibers.
• the proportion of long fiber pulp in the filter paper is preferably at least 70%, particularly preferably at least 80% and very particularly preferably at least 90% in each case based on the mass of the filter paper.
• the entire cellulose in the filter paper according to the invention is formed by long-fiber cellulose.
• part or all of the long-fiber pulp can be replaced by pulp from annual plants such as hemp, flax, kenaf or jute, with the exception of Abacá or Sisal.
• pulps from annual plants are not preferred because they are comparatively expensive, only poorly dewater in paper production and, like Abacá fibers and sisal fibers, are subject to quality fluctuations.
• the proportion of Abacá fibers and sisal fibers taken together is less than 20%, preferably less than 10% and particularly preferably less than 5% of the mass of the filter paper.
• the filter paper according to the invention is essentially free of Abacá fibers and sisal fibers, except for process-related impurities.
• the filter paper according to the invention can contain short fiber pulp.
• the short fiber pulp can be obtained from deciduous trees such as birch, beech or eucalyptus. Short fiber pulp increases the volume of the filter paper and reduces sand loss, but also reduces the strength, which is why the proportion in the filter paper according to the invention should be comparatively low.
• the proportion of short fiber pulp in the invention is preferably Filter paper at most 20%, particularly preferably at most 10% and preferably at least 2%, particularly preferably at least 5% of the paper pulp.
• the filter paper according to the invention can contain thermoplastic fibers. These fibers can comprise a thermoplastic material, which is preferably selected from the group consisting of polyethylene, polypropylene, polyester, such as polyethylene terephthalate, polyamide, polymethacrylate, polyacrylate, polyvinyl acetate, polyvinyl alcohol and polylactide or mixtures thereof. Bicomponent fibers can also be used with preference.
• the thermoplastic fibers provide the filter paper with a heat sealability or improve the filter paper in terms of other properties, such as its pore structure or absorbency.
• the proportion of thermoplastic fibers in the filter paper according to the invention is preferably at least 5%, particularly preferably at least 10% and preferably at most 30%, particularly preferably at most 20%, in each case based on the mass of the filter paper.
• the filter paper according to the invention can also contain fibers from regenerated cellulose, preferably viscose fibers or Tencel® fibers, in order to influence the pore structure and other properties of the filter paper.
• the proportion of fibers made from regenerated cellulose is preferably at most 15% and particularly preferably at most 10% of the mass of the filter paper.
• Fillers are used in many papers to increase the opacity or whiteness of the paper or to replace pulp with cheaper materials.
• Fillers in the filter paper according to the invention can, for example, be selected from the group consisting of calcium carbonate, magnesium carbonate, magnesium hydroxide, aluminum hydroxide, magnesium silicates, aluminum silicates, kaolin and talc or mixtures thereof.
• the proportion of fillers in the filter paper according to the invention is therefore preferably less than 10% of the paper pulp, particularly preferably less than 5% of the paper pulp and very particularly preferably the filter paper according to the invention contains no fillers.
• the person skilled in the art can select further constituents of the filter paper according to the invention, such as wet strength agents or agents for increasing the strength, such as starch, guar or carboxymethyl cellulose, in his experience.
• the person skilled in the art can likewise use process aids, such as, for example, retention aids, in his experience to produce the filter paper according to the invention.
• the filter paper according to the invention has a basis weight of at least 9.0 g / m 2 , preferably at least 10.0 g / m 2 , particularly preferably at least 11.0 g / m 2 and at most 13.5 g / m 2 , preferably at most 13 2 g / m 2 , particularly preferably at most 13.0 g / m 2 .
• the weight per unit area can be measured, for example, in accordance with ISO 536: 2012.
• the density of the filter paper is an important factor that influences the speed at which an aqueous extract can be produced using this filter paper.
• filter papers from the prior art have the lowest possible density of less than 280 kg / m 3 .
• the filter paper according to the invention has a higher density of at least 280 kg / m 3 , preferably at least 290 kg / m 3 and particularly preferably at least 300 kg / m 3 and at most 350 kg / m 3 , preferably at most, due to a special mechanical treatment in paper production 340 kg / m 3 , particularly preferably at most 330 kg / m 3 .
• this higher density has no disadvantages in the preparation of the aqueous extract.
• the filter paper according to the invention preferably has a thickness of at least 38 ⁇ m, particularly preferably at least 40 ⁇ m, very particularly preferably at least 41 ⁇ m and preferably at most 48 ⁇ m, particularly preferably at most 46 ⁇ m, very particularly preferred at most 45 ⁇ m. Due to the special mechanical treatment, the thickness of the filter paper according to the invention lies below that of conventional filter papers. The small thickness can contribute to a faster transport of the water through the filter paper and thus increase the speed with which an aqueous extract can be produced. In addition, a small thickness allows more filter paper to be on a roll of filter paper for a given outer diameter in terms of area.
• the maximum outside diameter of the filter paper roll is limited by the constructional conditions on the processing machines, so that more bags can be produced with the filter paper according to the invention, for example, because the number of bags that can be produced only depends on the area of the filter paper. The number of reel changes is therefore reduced and productivity can be increased.
• density and thickness can be measured on a single layer of filter paper according to ISO 534: 2011.
• the roughness of the filter paper according to the invention is also of technical importance for the further processing of the filter paper, in particular a low roughness reduces the Release of dust during further processing. A slight roughness is also perceived by the consumer as a quality signal.
• the filter paper according to the invention has a roughness of at least 700 ml / min, preferably at least 800 ml / min, particularly preferably at least 850 ml / min and at most 1300 ml / min, preferably at most 1200 ml / min, particularly preferably at most 1100 ml / min.
• the roughness can be measured, for example, according to ISO 8791-2: 2013.
• the air permeability of the filter paper is of great importance for the production of an aqueous extract using the filter paper according to the invention.
• a high permeability to air allows the water to flow comparatively easily through the filter paper during the production of the extract by natural or forced convection, displacing the air, and so the extract can be produced in a short time.
• the filter paper according to the invention has an air permeability of at least 17000 cm / (min ⁇ kPa), preferably at least 18000 cm / (min ⁇ kPa), particularly preferably at least 19000 cm / (min ⁇ kPa) and at most 26000 cm / (min ⁇ kPa), preferably at most 25000 cm / (min ⁇ kPa), particularly preferably at most 24000 cm / (min ⁇ kPa).
• the air permeability of the filter paper according to the invention is thus lower than that of conventional filter papers. However, experiments show that this is not a disadvantage. Air permeability can be measured in accordance with ISO 2965: 2009.
• the filter paper according to the invention can be characterized by a number of mechanical parameters such as bending resistance, elongation at break, tensile strength and energy absorption capacity. To measure these properties, test strips are cut from the filter paper, but the results depend on the direction in which the test strips are removed. A distinction is therefore made in these parameters between the machine direction, i.e. H. the direction in which the filter paper passes through the paper machine when it is manufactured and the transverse direction, i.e. H. the direction in the filter paper plane orthogonal to the machine direction.
• the bending resistance of the filter paper is important for the production of bags from the filter paper and generally for the processing of the filter paper on machines. It should not be too high so that the filter paper does not develop excessive resetting forces during the manufacture of the bags.
• the bending resistance of the filter paper according to the invention in the machine direction is at least 50 mN, preferably at least 55 mN, particularly preferably at least 58 mN and at most 75 mN, preferably at most 73 mN, particularly preferably at most 72 mN.
• the bending resistance of the filter paper according to the invention in the machine direction is thus lower than that of filter papers known from the prior art, which often have a bending resistance in the machine direction of more than 80 mN. This results in additional advantages in the mechanical processing of the filter paper.
• This low bending resistance is achieved by the low content of Abacá fibers and sisal fibers in the filter paper according to the invention.
• the bending resistance of the filter paper according to the invention should also be rather low in the transverse direction.
• the bending resistance in the transverse direction should preferably be at least 15 mN, particularly preferably at least 18 mN, very particularly preferably at least 20 mN and at most 28 mN, particularly preferably at most 26 mN, very particularly preferably at most 25 mN.
• the bending resistance of the filter paper according to the invention in the transverse direction is thus also below the bending resistance of conventional filter papers in the transverse direction, which is typically at least about 30 mN.
• the bending resistance of a filter paper both in the machine direction and in the transverse direction can be measured in accordance with ISO 2493-1: 2010, whereby the force to achieve a defined deformation is measured and specified as the bending resistance.
• the elongation at break of the filter paper is relevant for the mechanical processing of the filter paper. In general, a high elongation at break is advantageous because the filter paper can then compensate for small differences in speed in the processing machine, but it should also not be too high, because it is then difficult to cut the filter paper into pieces of a defined size even under low loads.
• the elongation at break of the filter paper according to the invention in the machine direction is preferably at least 1.0%, preferably at least 1.2% and preferably at most 2.0%, particularly preferably at most 1.8%.
• the elongation at break of the filter paper according to the invention in the transverse direction is preferably at least 1.8%, particularly preferably at least 2.4% and preferably at most 3.8%, particularly preferably at most 3.4%.
• the fact that the elongations at break in the machine and transverse directions are relatively similar is a consequence of the special mechanical treatment in which the paper structure is compressed. It thus represents an additional advantage of the filter paper according to the invention.
• the tensile strength of the filter paper should be sufficiently high, especially in the machine direction, so that the filter paper does not tear during its manufacture and processing.
• the tensile strength of the filter paper according to the invention in the machine direction is preferably at least 11.5 N / 15 mm, particularly preferably at least 12.0 N / 15 mm and preferably at most 15.0 N / 15 mm, particularly preferably at most 14.0 N / 15 mm.
• the tensile strength of the filter paper according to the invention is preferably at least 2.5 N / 15 mm, particularly preferably at least 3.0 N / 15 mm and preferably at most 5.0 N / 15 mm, particularly preferably at most 4.5 N / 15 mm.
• the elongation at break and the tensile strength, in both the machine and transverse directions, can be measured in accordance with ISO 1924-2: 2008.
• the filter paper according to the invention has an energy absorption capacity in the machine direction of preferably at least 6.0 J / m 2 , particularly preferably at least 7.0 J / m 2 and preferably at most 11.0 J / m 2 , particularly preferably at most 10.0 J / m 2 .
• the production of the filter paper can mainly follow the methods of conventional paper production.
• the long fiber pulp is suspended in water and ground in a grinding unit.
• the fibrils of the cellulose fibers are exposed and the surface of the fibers is enlarged, which increases the strength of the filter paper made from it, but also reduces its air permeability.
• the pulp fibers are shortened during intensive grinding, which reduces the strength of the filter paper.
• the person skilled in the art is able to determine a favorable degree of grinding as a compromise between strength and air permeability from his experience or through a few experiments.
• the short fiber pulp, synthetic fibers or other fiber material - if present - is also suspended in water and can be ground, although short fiber pulp and synthetic fibers are preferably not ground.
• the suspensions of long-fiber pulp and, if applicable, short-fiber pulp, other fibers, optional fillers, additives and processing aids can be combined and reach the headbox of the paper machine.
• the paper machine is preferably an inclined sieve machine, the sieve being particularly preferably inclined between 15 ° and 25 ° against the horizontal.
• the inclined screen machine has the advantage that suspensions with a very low solids content of about 0.02% can be processed and thus more porous papers can be produced than with Fourdrinier machines.
• the suspension of fibers, water and other components flows from the headbox onto the circulating sieve of the paper machine and can be dewatered through the sieve, partly by means of negative pressure.
• the filter paper is formed on the sieve.
• the filter paper then preferably passes through a press section, in which it is dewatered by mechanical pressure, and further preferably a drying section, preferably with rewetting, in which it is dried by elevated temperature, for example by hot air, infrared radiation or contact with heated cylinders.
• a size press or film press can also be integrated into the dryer section.
• the filter paper can be rolled up, then cut and packed in rolls of defined width and length.
• a special feature of the manufacturing process of the filter paper according to the invention that differs from the prior art is that it is compressed with sufficient pressure so that the properties mentioned at the outset are imparted to it.
• This can be achieved, for example, by the filter paper passing through two rollers, preferably two steel rollers, in the press section during its production on the paper machine, which exert mechanical pressure on the filter paper.
• the steel rollers are particularly preferably covered with a plastic cover.
• the line load is preferably at least 30 kN / m and at most 100 kN / m. This mechanical compression of the filter paper reduces the thickness, roughness and air permeability and increases the density, which produces the very specific property profile of the filter paper according to the invention.
• the moisture can be adjusted by moistening the tea bags, but this means additional mechanical effort.
• a further embodiment of the invention is to make the filter paper substantially impermeable to water vapor with respect to the equilibrium state to pack and to provide, for example, in the form of a substantially water vapor impermeable pack.
• the invention therefore also includes filter paper which is packaged essentially impermeable to water vapor, the filter paper having a moisture content of at least 9%, preferably at least 10%, particularly preferably at least 11% and at most 20%, preferably at most 18%, particularly preferably at most 15%.
• the moisture can be measured according to ISO 287: 2009.
• the filter paper in the packaged roll preferably comprises long fiber pulp, the filter paper either being free of Abacá fibers and sisal fibers, or, if Abacá fibers and / or sisal fibers are present, these together less than 20%, particularly preferably less than 10% and very particularly preferably make up less than 5% of the mass of the filter paper.
• the filter paper in the roll which is packaged essentially impervious to water vapor, is particularly preferably a filter paper according to one of the above-mentioned embodiments.
• Such a roll can be made by drying the filter paper to the desired moisture at the end of papermaking, rolling up the filter paper on a roll, and packaging the roll in a substantially water vapor impermeable material.
• the essentially water vapor impermeable material is preferably a plastic film, particularly preferably a film made of polyethylene or polypropylene.
• a suitable packaging paper can likewise preferably be used as the material which is essentially impermeable to water vapor.
• "essentially impermeable to water vapor” means that the moisture of the filter paper in the packaged roll, measured in accordance with ISO 287: 2009, is not less than 8% of the paper pulp after the packaged roll has at least 3 days under the conditions defined in ISO 187: 1990 50% relative humidity and 23 ° C was stored.
• a packaging material is considered "essentially water vapor impermeable" for the purposes of this application if its water vapor transmission rate ( WVTR) measured according to ISO 2528: 2017 at 37 ° C and 90% relative humidity is less than 600 g / (m 2 ⁇ D), preferably less than 400 g / (m 2 ⁇ d) and particularly preferably less than 350 g / (m 2 ⁇ d).
• WVTR water vapor transmission rate
• the packaged roll according to the invention and the filter paper according to the invention can be processed further by means of machines known from the prior art, wherein preferably no further rewetting is required when processing the filter paper.
• sealed bags can be formed from the filter paper, into which the material to be extracted is filled. These bags are preferably tea bags.
• the invention therefore also includes bags filled with extractable material which have been produced from the filter paper according to the invention, the extractable material preferably being tea.
• Three filter papers according to the invention were produced from 100% long fiber pulp on an inclined screen machine.
• the long fiber pulp was ground to a freeness of 20 ° SR, measured in accordance with ISO 5267-1: 1999, and applied as a suspension with 0.016% solids content to the rotating sieve of the inclined sieve machine, which was inclined at 20 ° to the horizontal.
• the filter paper then passed through the press section, being compressed between two plastic-coated steel rollers with a line load of 65 kN / m in order to consolidate the paper structure. Thickness and air permeability were also reduced.
• the filter paper then went through the drying section, in which it was dried to a moisture content of 9.7%.
• the filter paper was rolled up at the end of the paper machine and packed in a polyethylene film, essentially impermeable to water vapor.
• the settings of the paper machine were varied slightly, so that slightly different properties of the filter papers A, B and C resulted.
• a fourth filter paper according to the invention was made from 82% long fiber pulp and 18% Abacá fibers.
• the long fiber pulp and the Abacá fibers were ground together to a freeness of 23 ° SR, measured according to ISO 5267-1: 1999, and applied as a suspension with 0.016% solids content to the rotating sieve of the inclined sieve machine inclined at 20 ° to the horizontal.
• the filter paper then passed through the press section, being compressed between two plastic-coated steel rollers with a line load of 60 kN / m in order to consolidate the paper structure. Thickness and air permeability were also reduced.
• the filter paper then went through the drying section, in which it was dried to a moisture content of 10.3%. Finally, the filter paper was rolled up at the end of the paper machine and packed in a polyethylene film, essentially impermeable to water vapor.
• the basis weight, density, thickness, roughness, bending resistance in the machine direction and air permeability were determined from all filter papers according to the invention.
• X, Y, Z three typical, commercially available, non-inventive filter papers, designated X, Y, Z, were microscopically analyzed for their Abacá fiber and sisal fiber content, and also basis weight, density, thickness, roughness, bending resistance in the machine direction and air permeability were determined.
• Table 1 The results are summarized in Table 1 and show the content of Abacá and Sisal fibers (AS), the basis weight (BW), the density (p), the thickness (d), the roughness (R), the bending resistance in the machine direction (BR- MD) and air permeability (AP).
• AS Abacá and Sisal fibers
• BW basis weight
• p density
• d thickness
• R roughness
• AP air permeability
• Table 1 paper AS BW ⁇ d R BR-MD AP % g / m 2 kg / m 3 ⁇ m ml / min mN cm / (minkPa) A 0 13.0 284 42.3 1141 71 20685 B 0 12.7 306 42.1 1050 67 23040 C.
• the filter papers according to the invention are lower in thickness and roughness and higher in density than all filter papers not according to the invention. This difference is caused by the compression of the filter paper, which reduces the roughness and the thickness and increases the density, while the weight per unit area remains the same.
• An inherently undesirable side effect is that this also lowers the air permeability and is lower for all filter papers according to the invention than for the filter papers not according to the invention.
• this slightly lower air permeability has practically no effect when producing an aqueous extract using the filter papers according to the invention.
• filter paper A compared to filter paper Y
• filter paper Y The bending resistance of the filter papers according to the invention, with one exception, filter paper A compared to filter paper Y, is lower than that of the filter papers not according to the invention. This difference is caused on the one hand by the low content of Abacá fibers and sisal fibers, and on the other hand by the reduced thickness due to the mechanical compression.
• Table 2 contains the transverse bending resistance (BR-CD), the tensile strength in the machine direction (F-MD) and in the transverse direction (F-CD), the elongation at break in the machine direction (E-MD) and in the transverse direction (E-CD) and that Energy absorption capacity in the machine direction (TEA-MD).
• BR-CD transverse bending resistance
• F-MD tensile strength in the machine direction
• F-CD the transverse direction
• F-CD tensile strength in the machine direction
• F-CD tensile strength in the transverse direction
• F-CD tensile strength in the transverse direction
• F-CD tensile strength in the transverse direction
• F-CD tensile strength in the transverse direction
• F-CD tensile strength in the transverse direction
• E-MD elongation at break in the machine direction
• E-CD elongation at break in the transverse direction
• E-CD Energy absorption capacity in the machine direction
• the four inventive filter papers A, B, C and D were used to produce tea bags filled with tea without problems on various conventional tea bag machines such as IMA C24, IMA C27 and Teepack Perfecta.
• the tea bags made from the four filter papers according to the invention were compared with three commercially available tea bags of the same geometry and filling, which were produced on the same machines.
• containers with 0.5 liters of tap water with a temperature of 90 ° C were prepared and each tea bag was immersed in one container.
• the tea was visually assessed for the speed of discoloration of the tap water in the container after a few seconds, since this discoloration speed is also the criterion that a consumer observes when making the tea.
• the filter papers according to the invention can be used to produce tea bags with a large or complete absence of Abacá fibers and sisal fibers, the performance of which does not differ from that of conventional tea bags, although this would have been expected due to the technical properties of the filter papers.
• about 10% more tea bags could be produced from a roll with the same outer diameter due to the approximately 10% smaller thickness compared to conventional filter papers, which allows an additional increase in productivity.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Inorganic Chemistry (AREA)
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