Method and apparatus for the manufacturing of composite material

Abstract

A method and an apparatus for manufacturing composite material including natural fiber substance, plastic based substance, and agent improving compatibility between the natural fiber substance and the plastic based substance. The substances are mixed together and mechanically pressing and/or dried with heat to remove liquid. A wet mixture with 41-99.8% water is formed at least from the natural fiber substance, the plastic based substance and the compatibility improving agent, whereby to manufacture the composite material having an internal network structure that keeps material together by chemical bonds between the plastic based substance and the natural fiber substance, the wet mixture is fed to a devolatilization process in which substance in liquid form and other gasifying volatile substances or at least a main part thereof are removed by changes in pressure, heat and mechanical mixing, and the structure of the natural fiber substance is modified if needed.

1 . A method for manufacturing of composite material, the composite material comprising a natural fiber substance, a plastic based substance, and an agent improving compatibility improving agent between the natural fiber substance and the plastic based substance, the method comprising:
 mixing the natural fiber substance, the plastic based substance and the compatibility improving agent with each other, and   removing liquid from the formed mixture by at least one of mechanically pressing or by drying with heat, wherein a wet mixture with 41-99.8% water is formed at least from the natural fiber substance, the plastic based substance and the compatibility improving agent, and   feeding the wet mixture into a devolatilization process, in which substance in liquid form and other gasifying volatile substances or at least a main part thereof are being removed by changes in pressure, heat and mechanical mixing in at least two successive phases in a devolatilization arrangement operating on an extruder principle, thereby manufacturing a composite material having an internal network structure that keeps material together by chemical bonds between the plastic based substance and the natural fiber substance.   
     
     
         2 . The method according to  claim 1 , wherein the wet mixture is processed in the devolatilization process in a higher temperature than a softening temperature of the plastic substance therein. 
     
     
         3 . The method according to  claim 1 , wherein the compatibility improving agent to be mixed with water is fed into the wet mixture in a phase of the devolatilization process, wherein the wet mixture does not contain water in liquid form anymore. 
     
     
         4 . The method according to  claim 1 , wherein a precompound formed from the wet mixture in the devolatilization process is fed to a compounding process, in which the precompound being homogenized in the devolatilization process is melt mixed. 
     
     
         5 . The method according to  claim 1 , wherein prior to the feeding of the wet mixture to the devolatilization process, the wet mixture is dried by a mechanical predrier. 
     
     
         6 . The method according to  claim 1 , wherein the wet mixture is fed into an extruder, wherein for carrying out the first phase of the devolatilization process the wet mixture is mixed in an elevated temperature and steam pressure, whereby water/steam, fiber substance and plastic substance form a mixture, in which the plastic substance at least partly starts to melt. 
     
     
         7 . The method according to  claim 6 , wherein a further elevated pressure in the first phase of the devolatilization process is achieved by decreasing the basic volume in the extruder between a screw and a wall thereof into a decreased volume by changing the shape of the screw. 
     
     
         8 . The method according to  claim 6 , wherein the mixture being devolatized is fed for carrying the second phase of the devolatilization process to a releasing space, in order to change the water in the mixture rapidly into steam and for disengaging the water from the fiber and plastic substances, whereafter the formed mixture is transmitted to a compounding zone of the mixing device for further processing thereof. 
     
     
         9 . The method according to  claim 1 , wherein in the devolization process the structure of the natural fiber substance is modified. 
     
     
         10 . An apparatus for manufacturing of composite material, the composite material comprising a natural fiber substance, a plastic based substance, and an agent improving compatibility between the natural fiber substance and the plastic based substance, the apparatus comprising:
 a mixing arrangement for mixing the substances with each other, in order to manufacture the composite material thereafter by mechanically pressing and/or by drying with heat the formed mixture for removing liquid, therefrom, and   a devolatilization arrangement operating on extruder principle, in order to remove substance in liquid form and other gasifying volatile substances or at least a main part thereof by changes in pressure, heat and mechanical mixing taking place in at least two successive phases in the devolatilization arrangement, thereby manufacturing a composite material having an internal network structure that keeps material together by chemical bonds between the plastic based substance and the natural fiber substance, from a wet mixture with 41-99.8% water formed at least from the natural fiber substance, the plastic based substance and the compatibility improving agent.   
     
     
         11 . The apparatus according to  claim 10 , further comprising:
 a compounding arrangement in order to melt mix the homogenized precompound having been achieved in the devolatilization arrangement.   
     
     
         12 . The apparatus according to  claim 10 , further comprising:
 a mechanical predrier.   
     
     
         13 . The apparatus according to  claim 10 , wherein the extruder has a zone that carries out a first phase of the devolatilization process by a changed pitch of a screw in the extruder, a releasing zone that carries out a second phase of the devolatilization process in order to let the devolatized mixture into a free volume, in order to change the water in the mixture rapidly into steam and for disengaging the water from the fiber and plastic substances, and a compounding zone for mixing the processed mixture and to lead the processed mixture for further processing thereof. 
     
     
         14 . The method according to  claim 1 , wherein the natural fiber substance comprises at least one of wood-derived fibers, wood-derived mechanically fiberized fibers, or cellulose fiber made from natural fibers. 
     
     
         15 . The method according to  claim 1 , wherein the plastic based substance comprises at least one of plastic particles having a diameter of less than ˜4000 :m or plastic fibers. 
     
     
         16 . The method according to  claim 1 , wherein the removed liquid comprises water. 
     
     
         17 . The method according to  claim 3 , wherein the compatibility improving agent comprises silane mixed with water. 
     
     
         18 . The method according to  claim 5 , wherein the mechanical predrier at least one of web and suction box arrangements or screw driers. 
     
     
         19 . The method according to  claim 7 , wherein a pitch of the screw is changed. 
     
     
         20 . The method according to  claim 8 , wherein the mixture being devolatized is fed to the releasing space under an atmospheric pressure. 
     
     
         21 . The method according to  claim 9 , wherein in the natural fiber substance comprises cellulose fiber.