Method for making a composite web

Abstract

A method for making a composite web comprises the steps ofmelt blowing a first flow of thermoplastic material including said first thermoplastic material towards at least one collecting suction surface moving in a feed direction;dispensing a flow of particulate material including a particulate material towards the collecting suction surface in such a way as to intercept the first flow of thermoplastic material in an intercept zone; the first flow of thermoplastic material and the flow of particulate material intercept each other in the intercept zone at an intercept angle of between 1 and 90 sexagesimal degrees, preferably between 15 and 40 sexagesimal degrees.

1 . A method for making a composite web comprising at least a first layer which in turn comprises
 a first mass of meltblown fibres comprising at least a first, melted and blown thermoplastic material;   a particulate material dispersed among the fibres and at least partly adherent thereto,   
       the method comprising the following steps for making said first layer:
 melt blowing a first flow of thermoplastic material comprising said first thermoplastic material towards at least one collecting suction surface moving in a feed direction to obtain said first mass of meltblown fibres; 
 dispensing a flow of particulate material comprising said particulate material towards the collecting suction surface in such a way as to intercept the first flow of thermoplastic material in an intercept zone; 
 
       said method being characterised in that the first flow of thermoplastic material and the flow of particulate material intercept each other in the intercept zone at an intercept angle of between 1 and 90 sexagesimal degrees, preferably between 15 and 40 sexagesimal degrees. 
     
     
         2 . The method according to  claim 1 , wherein the first flow of thermoplastic material and the flow of particulate material intercept each other in the intercept zone at an intercept height with respect to the collecting suction surface which is greater than or equal to zero and less than 300 mm. 
     
     
         3 . The method according to  claim 1 , wherein the flow of particulate material is at a right angle to the collecting suction surface. 
     
     
         4 . The method according to  claim 1 , wherein at the intercept zone an entire cross section of the flow of particulate material, parallel to a feed direction of the collecting suction surface, has entered in the first flow of thermoplastic material. 
     
     
         5 . The method according to  claim 1 , wherein at the intercept zone an entire cross section of the flow of thermoplastic material, parallel to a feed direction of the collecting suction surface, has entered in the first flow of particulate material. 
     
     
         6 . The method according to  claim 1 , wherein the first flow of thermoplastic material is melt blown by at least one nozzle located at a dispensing distance measured along a perpendicular to the collecting suction surface greater than 100 mm and less than 1200 mm, preferably between 250 mm and 400 mm. 
     
     
         7 . The method according to  claim 1 , wherein the first flow of thermoplastic material has a distribution width, measured according to a feed direction of the collecting suction surface, of between 1 mm and 200 mm, preferably between 5 mm and 100 mm. 
     
     
         8 . The method according to  claim 1 , wherein the flow of particulate material has a distribution width, measured along a feed direction of the collecting suction surface, of between 1 mm and 200 mm, preferably equal to 25 mm. 
     
     
         9 . The method according to  claim 1 , wherein the first flow of thermoplastic material comprises a first flow of air and the flow of particulate material comprises a second flow of air, said first and second flow of air having equal speed. 
     
     
         10 . The method according to  claim 1 , comprising a second step of melt blowing on the collecting suction surface at least a second flow of thermoplastic material comprising a second thermoplastic material to form at least a second mass of meltblown fibres on the collecting suction surface, said second mass of meltblown fibres defining a second layer of said composite web on which the first layer of the composite web is positioned, said second step of melt blowing a second flow of thermoplastic material on the collecting suction surface occurring before the step of melt blowing the first flow of thermoplastic material. 
     
     
         11 . The method according to  claim 1 , comprising a third step of melt blowing on the first layer of the composite web at least a third flow of thermoplastic material comprising a third thermoplastic material to form at least a third mass of meltblown fibres on the first layer of the composite web, said third mass of meltblown fibres defining a third layer of said composite web positioned on the first layer of the composite web, said third step of melt blowing a third flow of thermoplastic material occurring after the step of melt blowing the first flow of thermoplastic material. 
     
     
         12 . The method according to  claim 1 , comprising a step of melt blowing a fourth flow of thermoplastic material comprising preferably the first thermoplastic material towards said collecting suction surface in such a way as to intercept the first flow of thermoplastic material and the flow of particulate material, said first flow and fourth flow of thermoplastic material defining an total flow of thermoplastic material to obtain said first mass of meltblown fibres. 
     
     
         13 . The method according to  claim 12 , wherein said step of melt blowing a first flow of thermoplastic material, said step of dispensing a flow of particulate material and said step of melt blowing a fourth flow of thermoplastic material occur towards a first collecting suction surface and a second collecting suction surface relatively positioned in such a way as to define a passage for the total flow of thermoplastic material and the flow of particulate material, said first flow of thermoplastic material, said fourth flow of thermoplastic material and said flow of particulate material intercepting each other at least in part upstream of said passage. 
     
     
         14 . The method according to  claim 13 , wherein said passage has a dimension measured along a direction perpendicular to the first and to the second collecting suction surface of between 1 mm and 20 mm. 
     
     
         15 . The method according to  claim 13 , wherein said first collecting suction surface is in the form of a first collecting suction drum and said second collecting suction surface is in the form of a second collecting suction drum, said first and second collecting suction drums having respective axes of rotation parallel to each other and said passage being defined between a first outer cylindrical collecting surface of the first collecting suction drum and a second outer cylindrical collecting surface of the second collecting suction drum. 
     
     
         16 . The method according to  claim 1 , wherein said step of melt blowing a first flow of thermoplastic material is performed according to a first main trajectory;
 said step of dispensing a flow of particulate material occurs along a second main trajectory;   said first trajectory and said second trajectory intercepting each other in the intercept zone at an intercept angle of between 1 and 90 sexagesimal degrees, preferably between 15 and 40 sexagesimal degrees.   
     
     
         17 . The method according to  claim 1 , wherein said step of melt blowing a first flow of thermoplastic material is performed according to a first main trajectory;
 said step of dispensing a flow of particulate material occurs along a second main trajectory;   said first trajectory and said second trajectory intercepting each other in the intercept zone at an intercept height relative to the sucked collecting surface greater than or equal to zero.   
     
     
         18 . The method according to  claim 1 , wherein said first thermoplastic material is a thermoplastic elastomer. 
     
     
         19 . The method according to  claim 1 , wherein at least said first flow of thermoplastic material comprises a molten hydrophilic additive blown together with said first thermoplastic material. 
     
     
         20 . The method according to  claim 1 , wherein the particulate material comprises one or more compounds selected from the group consisting of: absorbent or superabsorbent material; graphene; odour capturing material, preferably activated carbon, zeolites, carbonates, silicates; chitosan; antibacterial or virucidal materials, preferably titanium dioxide, zinc oxide, copper oxide, colloidal silver, polyethylene glycol. 
     
     
         21 . The method according to  claim 1 , wherein the particulate material comprises an absorbent or superabsorbent polymer material. 
     
     
         22 . A method for making an article, preferably for sanitary, bio-medical or anti-particulate use, comprising a piece of a composite web wherein said piece is made using the method according to  claim 1 . 
     
     
         23 . The method according to  claim 22 , wherein the article is a protective mask for the face, preferably with virucidal and/or bactericidal action. 
     
     
         24 . The method according to  claim 22 , wherein the article is a smoking article and/or a semifinished product for the tobacco industry, preferably a cigarette filter.