Making a nonwoven fabric from fibers

Abstract

Method for producing a nonwoven fabric from fibres. Continuous filaments are produced from thermoplastic material by at least one meltblown spinneret. Chopped pulp fibres are also produced by at least one pulping device. In the pulping device, at least one chopped-fibre/air stream is produced from the chopped pulp fibres, is passed through and discharged from an outlet channel and flows with an initial volumetric flow V 1 and a flow direction S 1 in the direction of an air-permeable depositing screen belt. The continuous filaments flow from the at least one meltblown spinneret as a filament/air stream with an initial volumetric flow V 2 in the direction of the chopped-fibre/air stream. The filament/air stream and the chopped-fibre/air stream are brought together above the depositing screen belt in a contact zone and deposited as a mixture of continuous filaments and chopped fibres in a depositing region on the depositing screen belt to form the nonwoven fabric or nonwoven web. In the depositing region of the fibres or of the mixture of continuous filaments and chopped fibres, air or process air is sucked through the depositing screen belt from below with a volumetric flow V 4 . The volumetric flow V 4 is greater than the sum of the volumetric flows V 1 and V 2.

1 . A method of making a nonwoven fabric from fibers, the method comprising the steps of:
 making continuous filaments of thermoplastic material by a meltblow spinneret;   making pulp short fibers by a defibrator in which a short-fiber/air stream is made from the pulp short fibers and is guided through an outlet passage and emerges therefrom and flows with an initial volume flow V 1  and a flow direction S 1  toward an air-permeable foraminous deposition belt;   flowing the continuous filaments from the meltblow spinneret as a filament-air stream with an initial volume flow V 2  toward the short-fiber/air stream,   combining the filament-air stream and the short-fiber/air stream above the foraminous deposition belt in a contact zone and depositing the combined streams as a continuous-filament/short-fiber mixture in a deposition zone on the foraminous deposition belt to form the nonwoven fabric; and   aspirating air or process air with a volume flow V 4  greater than the sum of the volume flows V 1  and V 2  from below through the foraminous deposition belt in the deposition zone of the fibers or of the continuous-filament/short-fiber mixture.   
     
     
         2 . The method according to  claim 1 , wherein
 two meltblow spinnerets are provided and continuous filaments flow from the second meltblow spinneret as a second filament-air stream with an initial volume flow V 3  to toward the short-fiber/air stream,   the volume flow V 4  is greater than the sum of the volume flows V 1 , V 2 , and V 3 , and   the filament-air stream in the travel direction of the foraminous deposition belt flows upstream of the short-fiber/air stream and the second filament-air stream flows in the travel direction of the foraminous deposition belt flows downstream of the short-fiber/air stream.   
     
     
         3 . The method according to  claim 1 , wherein
 the filament-air stream flows with respect to its flow direction S 2  at least in regions or sections at an angle α 1  to the flow direction S 1  of the short-fiber/air stream,   the second filament-air stream flows with respect to its flow direction S 3  at least in regions or sections at an angle α 2  to the flow direction S 1  of the short-fiber/air stream, and   the angle α 1  or the angle α 2  is greater than 10°.   
     
     
         4 . The method according to  claim 1 , wherein the short-fiber/air stream flows from the outlet passage or an outlet passage end perpendicularly or substantially perpendicularly to a surface of the foraminous deposition belt with regard to its flow direction S 1 . 
     
     
         5 . The method according to  claim 1 , further comprising the step of:
 aspirating secondary air in a space between the short-fiber/air stream and the filament-air stream and/or in a space between the short-fiber/air stream and the second filament-air stream.   
     
     
         6 . The method according to  claim 1 , wherein the short-fiber/air stream is accelerated in the outlet passage by a blower of the defibrator. 
     
     
         7 . The method according to  claim 1 , wherein the meltblow spinneret has a plurality of nozzle openings in a row and two air-flow slots running parallel to the row of nozzle openings on both sides, inclined relative to the nozzle openings, and from which blown air emerges. 
     
     
         8 . The method according to  claim 1 , wherein the meltblow spinneret has a plurality of nozzle openings in several rows and each each adjacent an air outflow opening or its own air outflow opening from which blown air emerges. 
     
     
         9 . The method according to  claim 1 , wherein
 the meltblow spinneret has a plurality of outlet openings in several rows in the form of nozzle openings and air outflow openings,   the outlet openings or the nozzle openings and the air outflow openings are spaced apart from one another in a regular and/or irregular pattern, and   each air outflow opening is flanked by at least two of the nozzle openings and/or each nozzle opening is flanked by at least two air outflow openings.   
     
     
         10 . The method according to  claim 1 , wherein the continuous filaments of the filament-air stream between the meltblow spinneret and the foraminous deposition belt on a side of the filament-air stream facing away from the short-fiber/air stream is sprayed with water. 
     
     
         11 . The method according to  claim 1 , wherein the short-fiber/air stream emerges from the outlet passage with a proportion of 0.0138 to 0.0833 kg of pulp short fibers per kg of air. 
     
     
         12 . The method according to  claim 1  wherein the filament-air stream or the filament-air streams emerges from the meltblow spinnerets with a proportion of 0.002 kg to 0.5 kg of the continuous filaments per kg of air. 
     
     
         13 . The method according to  claim 1 , wherein
 the outlet passage is height-adjustable relative to an upper surface of the foraminous deposition belt,   a spacing between the outlet passage end and a foraminous belt surface is between 200 and 1000 mm, and   an amount of secondary air aspirated is controlled by adjusting a height of the outlet passage relative to the foraminous belt surface of the foraminous deposition belt.   
     
     
         14 . The method according to  claim 1 , wherein the short-fiber/air stream relative to a width of the foraminous deposition belt carries or conveys at least 50 (kg/h)/m of the pulp short fibers. 
     
     
         15 . The method according to  claim 1 , further comprising the step of:
 consolidating the nonwoven fabric by a calender such that an embossing pattern is introduced into the nonwoven fabric by the calender.   
     
     
         16 . The method according to  claim 15 , wherein the embossing pattern is configured to be uninterrupted and a basic pattern geometry of the embossing pattern has a pressing area in the range from 20 to 50 mm 2 . 
     
     
         17 . The method according to  claim 16 , wherein the embossing pattern has interruptions and consists of a plurality of elements that are not connected to one another and that each have a compressed area of less than 2 mm 2 . 
     
     
         18 . An apparatus for making a nonwoven fabric from fibers by a method according to  claim 1 , the apparatus comprising:
 the meltblow spinneret for making continuous filaments of thermoplastic material,   the defibrator for making pulp short fibers and having an outlet passage for guiding the pulp short fibers or a short-fiber/air stream,   the air-permeable foraminous deposition belt for deposition of the pulp short fibers and the continuous filaments as a continuous-filament/short-fiber mixture to form a nonwoven fabric, and, and   the suction device for aspirating air or process air through the foraminous deposition belt in the deposition zone of the fibers or the continuous-filament/short-fiber mixture.   
     
     
         19 . The apparatus according to  claim 18 , wherein the apparatus has a first one of the meltblow spinnerets upstream in the travel direction of the foraminous deposition belt of the outlet passage and a second one of the meltblow spinnerets downstream of the outlet passage in the travel direction of the foraminous deposition belt. 
     
     
         20 . A nonwoven fabric made from a continuous-filament/short-fiber mixture according to a method according to  claim 1 .