Patent Application
20240295055
The invention relates to a method of making a nonwoven fabric from fibers, wherein continuous filaments of thermoplastic material are made by at least one meltblow spinneret, preferably by at least two meltblow spinnerets, wherein furthermore, pulp short fibers are made by at least one defibrator, wherein in the defibrator at least one short-fiber/air stream is made from the pulp short fibers, wherein the continuous filaments flow from the at least one meltblow spinneret as a filament-air stream and wherein the continuous filaments and the pulp short fibers are deposited in a deposition zone on a foraminous deposition belt to form the nonwoven fabric or to form the nonwoven web. The invention further relates to an apparatus for making a nonwoven fabric from fibers. In the context of the invention, the term fibers means both continuous filaments and short fibers. Due to their quasi-continuous length, continuous filaments differ from short fibers that have significantly shorter lengths of, for example, 0.1 mm to 60 mm. A nonwoven fabric containing at least continuous filaments or meltblown continuous filaments and short fibers or pulp short fibers can be made with the method according to the invention or with the apparatus according to the invention.
Methods and apparatuss of the type mentioned initially are basically known from practice in different embodiments. Nonwoven fabrics that contain pulp short fibers are characterized by a very high liquid absorption capacity. These nonwoven fabrics based on pulp short fibers are used, for example, for liquid-absorbing cloths, such as wiping cloths. The liquid can in particular be water or aqueous liquids. In the maktion of nonwoven fabrics that contain pulp short fibers, it has been shown, however, that there is a conflict of objectives between a high liquid absorption capacity and a sufficient stability or strength of the nonwoven fabric. To stabilize or mechanically stabilize the nonwoven fabrics, it is known to use mixtures of continuous filaments and pulp short fibers for the nonwoven fabrics. The continuous filaments are substantially responsible for the strength or stability of the nonwoven fabric, whilst the pulp short fibers ensure the liquid absorption capacity of the resulting makt. However, there is still a need for improvement in these nonwoven fabrics made from continuous filaments and pulp short fibers with regard to an optimal compromise between the liquid absorption capacity and the mechanical strength. In addition, it has been shown that with the methods known from practice, the uniformity of the distribution of continuous filaments and pulp short fibers in the end makt leaves something to be desired. There is also a need for improvement in this respect, since with a very uniform distribution of continuous filaments and pulp short fibers, a satisfactory compromise between the mechanical strength and the liquid absorption capacity of the nonwoven fabric could be achieved even with a relatively small proportion of continuous filaments.
In contrast, the invention is based on the technical problem of providing a method of the type mentioned initially by means of which a nonwoven fabric made of continuous filaments or meltblown continuous filaments and short fibers or pulp short fibers can be made, which is characterized by an optimal compromise between strength or stability and liquid absorption capacity and in which in particular a high uniformity of the distribution of continuous filaments and pulp short fibers exists. In addition, the invention is based on the technical problem of providing an apparatus for making such a nonwoven fabric.
To solve this technical problem, the invention teaches a method of making a nonwoven fabric from fibers, wherein continuous filaments made of thermoplastic material are made by at least one meltblow spinneret, preferably by at least two meltblow spinnerets, wherein furthermore pulp short fibers are made by at least one defibrator, wherein in the defibrator at least one short-fiber/air stream is made from the pulp short fibers, which is guided through an outlet passage and emerges therefrom and flows with an initial volume flow V1 and a flow direction S1 toward an air-permeable foraminous deposition belt,
In the course of the method according to the invention, molten plastic filaments are made by the meltblow spinneret or the meltblow spinnerets and extruded into a rapid blown air stream. The blown air expediently also emerges from the meltblow spinneret and preferably comprises warm or hot blown air. Filament-air streams of the continuous filaments made and the blown air then flow from the at least one meltblow spinneret or from the meltblow spinnerets parallel to the short fiber-air stream. The configuration of the meltblow spinneret or the meltblow spinnerets, in particular with regard to the exit of the molten plastic filaments and the blown air, is explained in more detail hereinafter.
According to the invention, continuous filaments are made from thermoplastic material. In the course of the method according to the invention, it is preferred that continuous filaments are made from at least one polyolefin. The at least one polyolefin is recommended to be polypropylene and/or polyethylene, preferably polypropylene. In principle, the continuous filaments can also be made from other thermoplastic materials such as polyesters, for example polyethylene terephthalate, or polyamide, as well as from mixtures of the thermoplastic materials mentioned above. It is recommended that the continuous filaments or meltblown continuous filaments have an average filament diameter in the range between 0.2 and 15 μm, preferably between 0.5 and 12 μm, preferably between 0.5 and 10 μm.
In the context of the invention, the term pulp means in particular a fibrous material based on wood pulp or cellulose. Solid pulp is expediently used in the method according to the invention. The term solid pulp means in particular a dry material based on wood pulp or cellulose. In the context of the invention, a web made of solid pulp is particularly preferably used and defibrated into pulp short fibers by the at least one defibrator. The pulp used in the method according to the invention is preferably conditioned. The pulp short fibers made in the at least one defibrator expediently have a length or average length of 0.05 to 5 mm, preferably 0.1 to 4 mm, particularly preferably 0.1 to 3 mm.
According to a preferred embodiment of the invention, the defibrator is a sawmill. According to the invention, a short-fiber/air stream is made from the pulp short fibers in the defibrator, which is guided through an outlet passage and emerges therefrom with an initial volume flow V1 and flows with a flow direction S1 toward an air-permeable foraminous deposition belt. The outlet passage is expediently part of the defibrator or is connected to the defibrator. In the context of the invention, initial volume flow V1 means the volume flow of the short-fiber/air mixture directly or immediately after exit from the outlet passage.
According to a preferred embodiment of the invention, the air-permeable foraminous deposition belt is a continuously movable and air-permeable foraminous deposition belt, in particular a continuously rotating foraminous deposition belt.
According to the invention, the continuous filaments made flow from the at least one meltblow spinneret as a filament-air stream with an initial volume flow V2 parallel to the short-fiber/air stream. Initial volume flow V2 means in particular the volume flow of the filament-air stream present directly or immediately below the meltblow spinneret after the continuous filaments have been exposed to blown air.
According to the invention, air or process air is aspirated through the foraminous deposition belt in or at least in the deposition zone of the fibers or of the continuous-filament/short-fiber mixture. For this purpose, at least one suction device or a suction blower is expediently arranged below the foraminous deposition belt, in particular below the deposition zone. According to the invention, the volume flow V4 that is aspirated through the foraminous deposition belt, is greater than the sum of the volume flows V1 and V2, so that the following applies: V4>(V1+V2). According to a particularly preferred embodiment of the method according to the invention, the volume flow V4 corresponds to between 1.05 and 30 times, preferably between 5 and 25 times, preferably between 10 and 20 times the sum of the volume flows V1 and V2.
According to a particularly preferred embodiment of the invention, at least two meltblow spinnerets, in particular two meltblow spinnerets, are provided. The continuous filaments particularly preferably flow from the second meltblow spinneret as a second filament-air stream with an initial volume flow V3 parallel to the short-fiber/air stream. Initial volume flow V3 means in particular the volume flow of the filament-air stream located directly or immediately below the meltblow spinneret or second meltblow spinneret after the continuous filaments have been exposed to blown air. It is quite particularly preferred that the volume flow V4 is then greater than the sum of the volume flows V1, V2 and V3, so that in particular the following applies: V4>(V1+V2+V3). According to a particularly preferred embodiment of the method according to the invention, the volume flow V4 corresponds to between 1.05 and 30 times, preferably between 5 and 25 times, preferably between 10 and 20 times the sum of the volume flows V1, V2 and V3.
It has proven successful that the filament-air stream flows in the travel direction F of the foraminous deposition belt upstream of the short-fiber/air stream and that the second filament-air stream preferably flows in the travel direction F of the foraminous deposition belt downstream of the short-fiber/air stream.
It lies within the scope of the invention that the filament-air stream flows with respect to its flow direction S2 at least in regions or sections at an angle α1 to the flow direction S1 of the short-fiber/air stream. The second filament-air stream expediently flows with respect to its flow direction S3 at least in regions or sections at an angle α2 to the flow direction S1 of the short-fiber/air stream. A particularly preferred embodiment of the invention is characterized in that the angle α1 and/or the angle α2 is greater than 10°, particularly preferably greater than 20° and quite particularly preferably greater than 25°. Within the scope of the invention, the two filament-air streams thus flow toward the short-fiber/air stream. That the filament-air stream or the filament-air streams with regard to their flow direction S2 or S3 flow at an angle α1 or α2 to the flow direction S1 of the short-fiber/air stream means in the context of the invention in particular that the flow vector of the filament-air streams runs at an angle α1 or α2 to the flow direction S1 or to the flow vector of the short-fiber/air stream at least in regions or sections. Within the scope of the invention, the terms flow direction and flow vector refer in particular to the mean flow directions or flow vectors of the respective streams.
In the context of the invention, it is particularly preferred that the at least one filament-air stream, in particular the filament-air streams, with respect to their flow direction S2 or S3 flow at least in or just before the contact zone at the angle α1 or α2 to the flow direction S1 of the short-fiber/air stream. Then the angles 1a and 2a in particular mean the angles of inclination in which the filament-air streams meet the short-fiber/air stream in the contact zone. According to a preferred embodiment of the invention, the at least one filament-air stream, in particular the two filament-air streams, flows in terms of their flow direction along the entire flow path—in particular in a straight line or substantially in a straight line—from the respective meltblow spinneret to the contact zone at the angle α1 or α2 to the flow direction S1 of the short-fiber/air stream. It is particularly preferred here that the at least one filament-air stream or the filament-air streams and/or the short-fiber/air stream flow from the meltblow spinnerets or from the outlet passage to the contact zone without guides.
It has already been explained hereinbefore that the angle α1 and/or the angle α2 is greater than 10°, particularly preferably greater than 20°. It has proven useful that the angle α1 and/or the angle α2 is greater than 25°, preferably greater than 30°, preferably greater than 35°, for example greater than 40°. It is recommended that the angle α1 and/or the angle α2 have a value in the range between 10° and 75°, preferably between 20° and 70°, particularly preferably between 25° and 65° and most preferably between 30° and 65°, for example between 35° and 60°. It lies within the scope of the invention that the angles 1a and 2a have the same value, so that the two filament-air streams in the contact zone meet the short-fiber/air stream or the central short-fiber/air stream in particular symmetrically on both sides. However, it is also fundamentally possible that the angles 1a and 2a have different values.
According to a preferred embodiment of the method according to the invention, the short-fiber/air stream flows from the outlet passage or an outlet passage end perpendicularly or substantially perpendicular to the foraminous belt surface of the foraminous deposition belt with regard to its flow direction S1. The flow direction S1 of the short-fiber/air stream is therefore directed in particular perpendicularly or substantially perpendicularly to the foraminous belt surface of the air-permeable foraminous deposition belt. In the context of the invention, this means in particular that the flow vector of the short-fiber/air stream runs perpendicular or substantially perpendicular to the flat extent of the foraminous belt surface.
It lies within the scope of the invention that secondary air is aspirated in the space between the short-fiber/air stream and the filament-air stream and/or in the space between the short-fiber/air stream and the second filament-air stream. The secondary air is aspirated in particular with a volume flow Vsek, wherein Vsek is expediently the total volume flow of the total aspirated secondary air. It is preferred that the following then applies: V4 (V1+V2+Vsek) and/or V4 (V1+V2+V3+Vsek). It is recommended that V4 corresponds to between 1 and 30 times, preferably between 5 and 25 times, preferably between 10 and 20 times the sum of the volume flows V1, V2, Vsek and/or the sum of the volume flows V1, V2, V3, Vsek. In the context of the invention, the expression secondary air means, in particular, additional air aspirated in by the flow movement of the filament-air streams and/or the short-fiber/air stream that does not correspond to the blown air of the meltblow spinnerets and not to the air emerging from the outlet passage with the pulp short fibers. The blown air from the meltblow spinnerets and the air emerging from the outlet passage with the pulp short fibers is referred to in particular as primary air within the scope of the invention. In the context of the invention, the term air also includes air-like gas or fluid mixtures.
The short-fiber/air stream is expediently accelerated in the outlet passage, in particular accelerated by a blower of the defibrator. According to a preferred embodiment, the defibrator therefore has a blower that supplies air to the defibrator. It lies within the scope of the invention that the air flow for making the short-fiber/air stream in the defibrator is made by the defibration process and/or by the blower. According to a preferred embodiment of the invention, the defibrator is a sawmill. Then the air flow to make the short-fiber/air stream is preferably made by the grinding process in the sawmill and/or by the sawmill blower. The short-fiber/air stream accelerated in the outlet passage according to the preferred embodiment emerges from the outlet passage with the initial volume flow V1.
According to a particularly preferred embodiment of the invention, the at least one meltblow spinneret has a plurality of nozzle openings arranged in a row and preferably two air-flow slots which run parallel to the row of nozzle openings on both sides and inclined realtive to the nozzle openings, from which blown air emerges. The at least two, in particular the two, meltblow spinnerets are expediently configured in such a manner. The fact that the meltblow spinneret or the meltblow spinnerets has or have a plurality of nozzle openings arranged in a row means in the context of the invention in particular that the meltblow spinneret has only a single row of nozzle openings. Such meltblow spinnerets are also designated as single-row nozzles. Expediently, the meltblow spinneret or meltblow spinnerets each have at least two, in particular two, air-flow slots which run parallel to the row of nozzle openings on both sides. The parallel course of the air-flow slot on both sides means within the scope of the invention in particular, that the longitudinal extension of the air-flow slot runs parallel to the longitudinal extension of the row of nozzle openings. In addition, it is recommended that the air-flow slots are inclined realtive to the nozzle openings or the row of nozzle openings. This ensures in particular that the blown air emerging from the air-flow slots or the flat blown air stream emerging from the air-flow slots acts on the curtain of extruded continuous filaments from the side or from opposite sides at an angle of attack. The angle of attack of the blown air relative to the flow direction of the continuous filaments made is preferably less than 30°, preferably less than 20°. It is preferred that the continuous filaments from the two air-flow slots of the meltblow spinneret or the meltblow spinnerets are supplied with blown air evenly or symmetrically. In principle, however, it is also possible that the continuous filaments are acted upon unevenly or asymmetrically with regard to the temperature and/or the volume flow of the blown air through the two air-flow slots of the meltblow spinneret.
According to a further preferred embodiment of the invention, the at least one meltblow spinneret has a plurality of nozzle openings arranged in several rows, wherein each nozzle opening is preferably assigned an air outflow opening or its own air outflow opening from which blown air emerges. Such a meltblow spinneret that has nozzle openings arranged in several rows for the outlet of the molten plastic filaments, is also designated as a multi-row nozzle. It lies within the scope of the invention that the at least two, in particular the two, meltblow spinnerets are configured in this way. The fact that each nozzle opening of the meltblow spinneret has an air outflow opening or its own air outflow opening means in the context of the invention in particular that the corresponding air outflow opening is assigned or can be assigned directly to the nozzle opening. It lies within the scope of the invention that the air outflow openings of the meltblow spinneret surround the respective nozzle opening and are in particular arranged coaxially thereto. Blown air then expediently flows coaxially parallel to the plastic melt or to the molten plastic filaments from the air outflow opening assigned to the nozzle opening and expediently surrounds the made filament in the form of a sheath.
According to a further preferred embodiment of the invention, the at least one meltblow spinneret has a plurality of outlet openings arranged in several rows in the form of nozzle openings and air outflow openings, wherein the outlet openings or the nozzle openings and the air outflow openings are preferably arranged spaced apart from one another in a regular and/or irregular pattern and wherein preferably at least 90% of the air outflow openings, in particular each air outflow opening, are assigned at least two nozzle openings and/or preferably at least 90% of the nozzle openings, in particular each nozzle opening, are assigned at least two air outflow openings. It lies within the scope of the invention that the at least two, in particular the two, meltblow spinnerets are configured in this way. This embodiment of the invention is characterized in that the respective nozzle openings from which the plastic melt or the molten plastic filaments emerge are not directly assigned their own air outflow opening. Rather, each nozzle opening is preferably assigned to at least two air outflow openings. Within the scope of this embodiment, blown air emerges from the air outflow openings. It is preferred that the nozzle openings are configured in such a manner that only the polymer melt emerges from them and that the polymer melt emerges from the nozzle opening in particular without a blown air stream that is directly assigned to the respective nozzle opening or emerges coaxially to the nozzle opening. Expediently, only the blown air emerges from the air outflow openings. In the context of this preferred embodiment, part of the outlet openings of the meltblow spinneret is configured in the form of nozzle openings and part or the other part of the outlet openings is configured in the form of air outflow openings. In the context of this embodiment, it is recommended that the spacings between directly adjacent outlet openings of the meltblow spinneret in at least one nozzle direction are the same or substantially the same across the entire nozzle. It is further preferred that the proportion of nozzle openings in the total number of outlet openings is between 10% and 50%, preferably between 12% and 45%, preferably between 15% and 40%.
If, according to a preferred embodiment of the invention, at least two, in particular two, meltblow spinnerets are provided, it is preferred that the two meltblow spinnerets or all the meltblow spinnerets are configured identically with regard to the nozzle openings and the air outflow openings or the air-flow slots. In principle, however, at least two different meltblow spinnerets can also be combined within the scope of the method according to the invention. It is also preferred that the outlet openings, in particular the nozzle openings and/or the air outflow openings, of the meltblow spinnerets are configured to be round or circular.
The invention has recognized that due to the special flow conditions according to the invention and in particular due to the ratio of the sum of the initial volume flows of the short-fiber/air stream and the filament-air stream or the filament-air streams to the volume flow aspirated through the foraminous deposition belt, a method can be provided by means of which a nonwoven fabric can be made from continuous filaments and pulp short fibers, which is characterized by a very high uniformity of the distribution of continuous filaments and pulp short fibers and in particular by an optimal compromise between stability or strength and liquid absorption ability of the nonwoven fabric. Particularly advantageous results can be achieved if the filament-air stream or the filament-air streams (each) flows or flow at an angle to the flow direction of the short-fiber/air stream and in particular if two filament-air streams flow at an angle on both sides to a central short-fiber/air stream, particularly preferably symmetrically. The continuous-filament/short-fiber mixture deposited on the foraminous deposition belt is expediently a matrix of continuous filaments in which the pulp short fibers are embedded.
According to a preferred embodiment of the method according to the invention, the continuous filaments of the at least one filament-air stream, preferably the filament-air streams, are sprayed with water between the meltblow spinneret and the foraminous deposition belt, in particular on the side of the filament-air stream facing away from the short-fiber/air stream. To spray the continuous filaments with water, preferably one or one water nozzle in each case is preferably provided that is arranged in particular on the side of the respective filament-air stream facing away from the short-fiber/air stream. The at least one water nozzle or the water nozzles is or are expediently located on the outside of the filament-air stream or the filament-air streams. It lies within the scope of the invention that the water nozzle is assigned to the respective meltblow spinneret and is preferably arranged below, in particular directly below, the meltblow spinneret in the filament flow direction. The continuous filaments are thus sprayed with water after, in particular immediately after, emerging from the meltblow spinneret. In this way, a targeted cooling of the continuous filaments made can be achieved.
It is preferred that the short-fiber/air stream emerges from the outlet passage with a proportion of 0.0138 to 0.0833 kg, preferably from 0.0222 to 0.0694 kg, preferably from 0.0277 to 0.05 kg of the pulp short fibers per kg of air. It is recommended that the short-fiber/air stream emerges from the outlet passage with a proportion of pulp short fibers of greater than 0.0138 kg, preferably greater than 0.0222 kg, preferably greater than 0.0277 kg per kg of air. The proportion of pulp short fibers per kg of air can expediently be controlled and/or regulated by means of the speed of the defibrator, in particular can be controlled and/or regulated by the speed of the intake of the defibrator.
It is further preferred that the at least one filament-air stream or the filament-air streams emerges or emerge from the meltblow spinnerets with a proportion of 0.002 kg to 0.5 kg, preferably 0.01 kg to 0.25 kg, preferably 0.015 kg up to 0.12 kg, particularly preferably from 0.018 kg to 0.1 kg, of the continuous filaments per kg of air. It is recommended that the at least one filament-air stream, preferably the filament-air streams (each) emerges or emerge from the meltblow spinnerets with a proportion of greater than 0.002 kg, preferably greater than 0.01 kg, preferably greater than 0.015 kg, particularly preferably greater than 0.018 kg of continuous filaments per kg of air. It also lies within the scope of the invention that the filament-air streams, in particular the two filament-air streams, emerge from the meltblow spinnerets with the same proportion of continuous filaments per kg of air. According to an alternative embodiment of the method according to the invention, the filament-air streams, in particular the two filament-air streams, emerge from the meltblow spinnerets with a different proportion of continuous filaments per kg of air. The proportion of continuous filaments with which the filament-air streams emerge from the meltblow spinnerets per kg of air according to a recommended embodiment of the invention, can be adjusted by controlling and/or regulating the mass flow of the thermoplastic material and/or the blown air emerging from the air-flow slots or the air outflow openings of the meltblow spinnerets. According to a particularly preferred embodiment of the invention, the proportion of continuous filaments in the deposited nonwoven fabric is between 10 and 35% by weight, preferably between 15 and 30% by weight, preferably between 20 and 28% by weight.
It has already been explained above that, according to an advantageous embodiment of the invention, the short-fiber/air stream is accelerated in the outlet passage by a blower of the defibrator. In this context, it is preferred that the air aspirated in by the blower of the defibrator is conditioned. Particularly preferably, the conditioned air aspirated in by the blower has a relative humidity of greater than 65% at 28° C.
It is within the scope of the invention that the outlet passage is height-adjustable relative to the foraminous belt surface of the foraminous deposition belt. The spacing a between the outlet passage end and the foraminous belt surface is expediently between 200 and 1000 mm, preferably between 300 and 750 mm, preferably between 400 and 600 mm and particularly preferably between 460 and 530 mm. The outlet passage or the outlet passage end is therefore height-adjustable in these areas relative to the foraminous belt surface of the foraminous deposition belt. Quite particularly preferably, the amount of aspirated secondary air can be controlled and/or regulated by adjusting the height of the outlet passage relative to the foraminous belt surface of the foraminous deposition belt. It is recommended that the height of the outlet passage is set in the course of the method according to the invention in such a way that: V4 (V1+V2+Vsek) and/or V4 (V1+V2+V3+Vsek). The amount of aspirated secondary air means in particular the secondary air or amount of secondary air aspirated in between the short-fiber/air stream and the at least one, preferably the two, filament-air streams. Within the scope of the invention, the term outlet passage end means in particular the end of the outlet passage facing the foraminous deposition belt. The walls of the outlet passage in the region of the outlet passage end are preferably configured in such a manner that the outlet passage end is configured to be constant or divergent or convergent in the internal cross-section. In this way, the subsequent mixing of the continuous filaments and the pulp short fibers in the contact zone can be influenced in particular. The spacing a between the outlet passage end and the foraminous belt surface is measured in particular perpendicular to the foraminous belt surface within the scope of the invention. Due to the controllability and/or regulability of the amount of aspirated secondary air it is possible to influence the flow conditions in a functionally reliable manner, particularly with regard to the secondary air supply. By means of the height adjustment or height adjustability of the outlet passage or the outlet passage end, within the scope of the invention-especially in combination with the angles 1 and/or α2—it is also possible to adjust or regulate the position of the contact zone. The mixing of the continuous filaments and the pulp short fibers can thereby be advantageously influenced, in particular in combination with the configuration of the walls of the outlet passage in the area of the outlet passage end and preferably by a constant internal cross-sectional configuration of the walls of the outlet passage in the area of the outlet passage end.
According to the invention, the filament-air stream, preferably the one or the two filament-air streams, and the short-fiber/air stream are brought together above the foraminous deposition belt in a contact zone. It is recommended that the mixing of the filament-air streams and the short-fiber/air stream takes place in this contact zone. According to a preferred embodiment of the invention, the continuous-filament/short-fiber mixture flows from the contact zone to the foraminous deposition belt as a homogeneous or substantially homogeneous mixture. By combining the short-fiber/air stream and the filament-air streams under the flow conditions according to the invention and the angles preferably provided, an optimal mixing and distribution of the pulp short fibers and the continuous filaments can be accomplished within the scope of the invention, so that following the contact zone a homogeneous or substantially homogeneous continuous-filament/short-fiber mixture flows to the foraminous deposition belt and is deposited to form the nonwoven fabric or nonwoven web. It is advantageous if the continuous-filament/short-fiber mixture flows from the contact zone to the foraminous deposition belt or to the deposition zone perpendicularly or substantially perpendicularly to the foraminous belt surface with respect to its flow direction.
It lies within the scope of the invention that the short-fiber/air stream relative to the width of the foraminous deposition belt carries or conveys at least 50 (kg/h)/m, in particular at least 75 (kg/h)/m, preferably at least 100 (kg/h)/m, particularly preferably at least 200 (kg/h)/m of the pulp short fibers. In the context of the invention, width of the foraminous deposition belt means in particular the largest width of the foraminous deposition belt transversely, in particular perpendicular to the longitudinal extension or to the travel direction of the foraminous deposition belt. It is possible within the scope of the invention that at least two, in particular at least three, preferably at least four defibrators, preferably with the associated blowers and/or outlet passages, are arranged along the width of the foraminous deposition belt. In this way, even when foraminous deposition belts with a width of at least 1 m, in particular of at least 2 m, preferably of at least 3 m, preferably of at least 4 m, a particularly uniform supply of the pulp short fibers or the short-fiber/air stream can be accomplished over the entire width of the foraminous deposition belt.
A particularly preferred embodiment of the method according to the invention is characterized in that the nonwoven fabric or the nonwoven web is consolidated by at least one calender, wherein an embossing pattern is preferably introduced into the nonwoven fabric or the nonwoven web by the at least one calender. It is recommended that the consolidation by the at least one calender takes place “inline”. In the context of the invention, this means in particular that the consolidation by the at least one calender takes place following the deposition of the continuous-filament/short-fiber mixture to form the nonwoven fabric or nonwoven web. According to an alternative preferred embodiment of the method according to the invention, the consolidation of the nonwoven fabric or the nonwoven web by the at least one calendar takes place “offline”. In the context of the invention, this means in particular that the nonwoven fabric or the nonwoven web is removed from the foraminous deposition belt after being deposited on the foraminous deposition belt and is wound up and is only unwound again at a later point in time and fed to the at least one calender.
It is recommended that the at least one calender has at least one pair of calender rollers through which the nonwoven fabric or nonwoven web is preferably guided under a contact pressure. Expediently, one of the calender rolls of the calender is a smooth roll with a smooth outer surface and/or one of the calender rolls of the calender has an embossing pattern on its outer surface. According to a preferred embodiment of the invention, the calender or the pair of calender rollers is temperature-controlled. Within the scope of the invention, the temperature of the calender rolls is preferably below the melting point of the thermoplastic material of the continuous filaments. The calender roll temperature is preferably between 50° C. and 150° C. within the scope of the method according to the invention. It is also within the scope of the invention that the linear pressure of the calender roll or rolls is between 10 and 120 daN/cm.
It is particularly preferred that the embossing pattern is configured to be uninterrupted and that the basic pattern geometry of the embossing pattern has a pressing are in the range of 20 to 50 mm2, preferably from 25 to 45 mm2, preferably from 30 to 40 mm2 and particularly preferably from 32.5 to 37.5 mm2. In the context of the invention, basic pattern geometry means in particular the geometry forming the basis of a repeating element of the embossing pattern. In this context, it is understood that the basic pattern geometry or the repeating element is preferably the same size or substantially the same size in each case, so that the resulting embossing pattern is a regular embossing pattern. It is within the scope of the invention that the uninterrupted embossing pattern is a honeycomb-shaped structure whose basic pattern geometry or its repeating element is expediently a hexagon or a regular hexagon. The embossing pattern then preferably consists of a plurality of regular hexagons of the same size, adjacent to one another, wherein the inner surface of the hexagon preferably forms the non-pressed part of the embossing pattern.
According to a further preferred embodiment of the invention, the embossing pattern has interruptions and in particular consists of a plurality of elements that are not connected to one another, preferably of dots and/or lines, wherein the elements expediently each have a pressing area of less than 2 mm2, preferably less than 1.5 mm2, preferably less than 1.1 mm2, particularly preferably less than 0.55 mm2. Within the scope of the invention it is also possible that an uninterrupted embossing pattern is combined with an embossing pattern having interruptions.
It is advantageous that the height of the basic pattern geometry or the elements of the embossing pattern is between 0.3 and 2.0 mm, preferably between 0.4 and 1.8 mm, preferably between 0.5 and 1.6 mm. Height of the pattern basic geometry here means the height difference or the average height difference between the pressing area and the non-pressed areas of the embossing pattern. It also lies within the scope of the invention that the proportion of the pressing area of the embossing pattern to the total surface of the nonwoven fabric or nonwoven web is between 2.5% and 25%, preferably between 5% and 15%, preferably between 5.25% and 12.5%.
With regard to the embodiment of the embossing pattern described hereinbefore, it is also understood that the corresponding roller of the pair of calender rolls that has the embossing pattern, has a complementary embossing pattern on its outer surface. The calender or the calender roll has in particular a pressing surface proportion or a pressing surface of 2.5% to 25%, preferably from 5% to 15% and preferably from 5.25% to 12.5%.
To solve the technical problem, the invention further teaches a device for making a nonwoven fabric from fibers, in particular by a method described hereinbefore, wherein the device has at least one meltblow spinneret, preferably at least two meltblow spinnerets for making continuous filaments of thermoplastic material,
According to a preferred embodiment, the apparatus has at least two, in particular two, meltblow spinnerets. It is preferred that a first meltblow spinneret is arranged upstream of the outlet passage in the travel direction of the foraminous deposition belt and a second meltblow spinneret is arranged downstream of the outlet passage in the travel direction of the foraminous deposition belt.
It is within the scope of the invention that the at least one meltblow spinneret, preferably the at least two or the two meltblow spinnerets, is/are arranged at an angle of inclination to the outlet passage. The angle of inclination between the meltblow spinnerets and the outlet passage is expediently (in each case) at least 10°, preferably at least 20° and preferably at least 25°. It is further preferred that the angle of inclination between the meltblow spinnerets and the outlet passage (in each case) is at least 30°, particularly preferably at least 35°, for example at least 40°. It is recommended that at least the angle of inclination between a meltblow spinneret and the outlet passage, preferably between both meltblow spinnerets and the outlet passage (in each case) is between 10° and 75°, preferably between 20° and 70°, particularly preferably between 25° and 65° and very particularly preferably between 30° and 65°, for example between 35° and 60°. In this way, filament-air streams can flow from the meltblow spinnerets toward the foraminous deposition belt at the angle α1 or α2 to the flow direction S1 of the short-fiber/air stream and parallel to the short-fiber/air stream. It is recommended that the angle of inclination between the meltblow spinnerets and the outlet passage can be set or adjusted in each case.
It is preferred that the outlet passage is configured to be height-adjustable relative to the foraminous belt surface of the foraminous deposition belt. It has proven successful that the spacing a between the outlet passage end and the foraminous belt surface can be adjusted in a range between 200 and 1000 mm, preferably between 300 and 750 mm, preferably between 400 and 600 mm, particularly preferably between 460 and 530 mm.
According to a preferred embodiment of the apparatus according to the invention, the defibrator has at least one blower for accelerating the pulp short fibers or the short-fiber/air stream in the outlet passage.
The invention further teaches a nonwoven fabric made from a continuous-filament/short-fiber mixture that is made according to the method described hereinabove and/or with an apparatus described hereinabove. The nonwoven fabric preferably has a thickness in the range from 0.1 to 3 mm, preferably from 0.2 to 2 mm and preferably from 0.3 to 1.5 mm. In the context of the invention, thickness of the nonwoven fabric means in particular the greatest thickness of the nonwoven fabric transversely, in particular perpendicular or substantially perpendicular to its flat extension and in particular after a preferably provided consolidation or calendering step.
The invention is based on the finding that the method according to the invention can be used to make a nonwoven fabric from continuous filaments and pulp short fibers that meets all requirements with regard to stability or strength as well as its ability to absorb liquids.
In this respect, as a result of the measures according to the invention it is possible to achieve an optimal compromise between the strength of the nonwoven and the liquid absorption capacity. The flow conditions according to the invention and the preferred arrangement of the meltblow spinneret or the meltblow spinnerets and the outlet passage for the pulp short fibers enable in particular an optimal mixing of the continuous filaments and the pulp short fibers, so that a nonwoven fabric having a very uniform distribution of the continuous filaments and the pulp short fibers results. In this way, a nonwoven fabric that meets all the requirements can be provided with a relatively small proportion of continuous filaments. It should also be emphasized that the measures according to the invention are not very complex and the method according to the invention is therefore characterized by a high economic efficiency. This also applies to the apparatus according to the invention.
The invention is explained in more detail hereinafter using a drawing that only shows an embodiment. In the figures in a schematic representation:
According to the invention, the accelerated short-fiber/air stream 5 emerges from the outlet passage 6 with an initial volume flow V1. In the context of the invention, initial volume flow V1 means in particular the volume flow of the short-fiber/air stream 5 directly or immediately after emerging from the outlet passage 6. The short-fiber/air stream 5 flows toward the foraminous deposition belts 8 in a flow direction S1 that is preferably and in this embodiment vertical or substantially perpendicular to the foraminous belt surface of an air-permeable foraminous deposition belt 8. The air-permeable foraminous deposition belt 8 is expediently designed as an endless continuously circulating foraminous deposition belt 8 in this embodiment.
The continuous filaments made by the meltblow spinnerets 2, 3 flow expediently and in this embodiment as filament-air streams 9, 10 with initial volume flow V2, V3 from the respective meltblow spinnerets 2, 3 parallel to the short-fiber/air stream 5. Initial volume flow V2 or V3 means in particular the volume flow of the filament-air streams 9, 10 present directly or immediately below the meltblow spinnerets 2, 3 after the continuous filaments have been exposed to blown air.
Within the scope of the invention and in this embodiment, a first filament-air stream 9 flows in a travel direction F of the foraminous deposition belt 8 upstream of the short-fiber/air stream 5. The filament-air stream 9 flows with respect to its flow direction S2 at an angle α1 to the flow direction S1 of the short-fiber/air stream 5. The second filament-air stream 10 flows in the travel direction F of the foraminous deposition belt 8 downstream of the short-fiber/air stream 5. This second filament-air stream 10 flows with respect to its flow direction S3 at an angle α2 to the flow direction S1 of the short-fiber/air stream 5. The filament-air streams 9, 10 thus flow preferably and in this embodiment from both sides of the central short-fiber/air stream 5 at the angles α1 and α2 toward the short-fiber/air stream 5. Within the scope of the invention, the angles α1 and α2 are preferably greater than 20°, particularly preferably greater than 25°. In this embodiment according to the figures, the angles α1 and α2 are each approximately 30°. Preferably and within the scope of this embodiment, the angles α1 and α2 have the same value or essentially the same value.
Expediently and in this embodiment, the filament-air streams 9, 10 and the short-fiber/air stream 5 are brought together above the foraminous deposition belt 8 in a contact zone 11 and are deposited as a continuous-filament/short-fiber mixture 12 in a deposition zone 13 on the foraminous deposition belt 8 to form the nonwoven fabric 1 or web. Preferably and in this embodiment, the filament-air streams 9, 10 flow in the area or just upstream of the contact zone 11 with regard to their flow direction S2 or S3 at the angle α1 or α2 to the flow direction S1 of the short-fiber/air stream 5. In the context of the invention and in this embodiment, the angles α1 and α2 mean in particular the angles of inclination at which the filament-air streams 9, 10 meet the short-fiber/air stream 5 in the contact zone 11. Preferably and in this embodiment, the two filament-air streams 9, 10 flow along the entire flow path from the respective meltblow spinneret 2, 3 to the contact zone 11 with regard to their flow directions S2 or S3 at the angles α1 or α2 to the flow direction S1 of the short-fiber/air stream 5. It is recommended that and in this embodiment the filament-air streams 9, 10 flow in a straight line or substantially in a straight line. Preferably and in this embodiment according to
It is recommended in this embodiment that secondary air is aspirated in spaces between the filament-air streams 9, 10 and the short-fiber/air stream 5. The secondary air is aspirated in particular with a volume flow Vsek, where Vsek is expediently the total volume flow of the total aspirated secondary air. In addition, according to the invention, air or process air with a volume flow V4 is aspirated from below through the foraminous deposition belt 8. For this purpose, within the scope of the invention and in this embodiment, a suction device 16 or blower is provided below the foraminous deposition belt 8, in particular below the deposition zone 13. The volume flow V4 is preferably greater than the sum of the volume flows V1, V2 and V3. More preferably, the volume flow V4 is greater than or equal to the sum of the volume flows V1, V2, V3 and Vsek.
According to a preferred embodiment of the invention, the meltblow spinnerets 2, 3 each have a plurality of nozzle openings 17 arranged in a row and that extrude the molten plastic filaments as part of the method according to the invention. Two air-flow slots 18 preferably run parallel to the row of nozzle openings 17 on both sides. This can be seen in
A further preferred embodiment of the meltblow spinnerets 2, 3 is shown in
Within the scope of the invention and in this embodiment, the filament-air streams 9, 10 are sprayed laterally with water between the meltblow spinneret 2, 3 and the foraminous deposition belt 8 on the sides of the filament-air stream 9, 10 facing away from the short-fiber/air stream 5. For this purpose water nozzles 20 are provided that expediently and in this embodiment on the sides of the respective filament-air stream 9, 10 facing away from the short-fiber/air stream 5. It is recommended that and in this embodiment the water nozzles 20 are therefore located on the outer side of the filament-air streams 9, 10 and are particularly preferably in the filament flow direction below or directly below the meltblow spinnerets 2, 3.
The amount of aspirated secondary air can be controlled with or without feedback in the context of the method according to the invention or with the apparatus according to the invention, preferably by adjusting the height of the outlet passage 6 or the outlet passage end 14 relative to the surface of the foraminous deposition belt 8. It is recommended that the height of the outlet passage 6 be set such that: V4≥(V1+V2+Vsek). The outlet passage 6 is preferably configured to be height-adjustable relative to the surface of the foraminous deposition belt 8. The spacing a between an outlet passage end 14 and the foraminous belt surface is expediently between 200 and 1000 mm, preferably between 300 and 750 mm. In the context of the invention, the spacing a is measured between the outlet passage end 14 and the foraminous belt surface perpendicular to the foraminous belt surface. The walls of the outlet passage 6 in the area of the outlet passage end 14 are preferably and in this embodiment configured in such a way that the outlet passage end 14 is configured to be divergent in the internal cross-section. Due to the height adjustability or height adjustment of the outlet passage 6 and the configuration of the walls of the outlet passage 6 or the outlet passage end 14 the position of the contact zone 11 can be controlled with or without feedback within the scope of the invention, especially in combination with the choice of the angles α1 and α2. As a result, the mixing of the continuous filaments and the pulp short fibers can be advantageously influenced.
It is preferred that the continuous-filament/short-fiber mixture 12 flows from the contact zone 11 to the foraminous deposition belt 8 as a homogeneous or substantially homogeneous mixture. The homogeneous continuous-filament/short-fiber mixture 12 is then expediently deposited in the deposition zone 13 on the foraminous deposition belt 8 to form the nonwoven fabric 1 or the nonwoven web. It is recommended in this embodiment that according to
The nonwoven fabric 1 is consolidated according to a preferred embodiment of the method according to the invention and in this embodiment “inline” by at least one calender 15. In this embodiment, the at least one calender 15 has at least one pair of calender rollers through which the nonwoven fabric 1 is preferably guided under a contact pressure. It is further preferred that an embossing pattern is introduced into the nonwoven fabric 1 or into the nonwoven web by the at least one calender 15. For this purpose, at least one of the calender rolls of the calender 15 can have an embossing pattern on its outer surface.
It is recommended that a height h of the basic pattern geometry or the elements of the embossing pattern is between 0.3 and 2.0 mm. In this embodiment according to
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 118 909.8 | Jul 2021 | DE | national |
| 21186978.9 | Jul 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/070240 | 7/19/2022 | WO |
