Multilayered composite material using nanofibrillated cellulose and thermoplastic matrix polymer
The present invention relates to a multi-layered composite material manufactured by thermocompressing a multi-layered sheet, comprising: a first sheet layer formed from a solution containing nanofibrillated cellulose and a first thermoplastic matrix polymer; and a second sheet layer formed from a solution containing a second thermoplastic matrix polymer. The multi-layered composite material of the present invention has the high strength and high elastic modulus.
1. A method of manufacturing a multi-layered composite material having at least one of a first sheet layer comprising a nanofibrillated cellulose and a first thermoplastic polyamide fiber in a weight ratio of 3:7 to 4:6 and a least one of a second sheet layer comprising a second thermoplastic polyamide fiber without nanofibrillated cellulose are alternately laminated by thermocompressing, wherein the method comprises:
a first step of preparing the first sheet layer, the first step comprising
1) forming a nanofibrillated cellulose suspension by mixing the nanofibrillated cellulose and the first thermoplastic polyamide fiber, wherein the diameter of the nanofibrillated cellulose ranges from 10 nm to 110 nm and the first thermoplastic polyamide fiber has a length ranging from 0.1 mm to 3.0 mm, and
2) drying and compressing the nanofibrillated cellulose suspension to form the first sheet layer having pores;
a second step comprising preparing the second sheet layer wherein the second sheet layer is a hot-melt web or a meltblown nonwoven fabric comprising the second thermoplastic polyamide fiber without nanofibrillated cellulose;
a third step comprising alternately laminating
1) at least one first sheet layer comprising the nanofibrillated cellulose and the first thermoplastic polyamide fiber in a weight ratio of 3:7 to 4:6; and
2) at least one second sheet layer comprising the second thermoplastic polyamide fiber without the nanofibrillated cellulose to form alternately laminated multi-layers; and
a fourth step comprising hot-melting the alternately laminated multi-layers by applying a pressure to the alternately laminated multi-layers at a temperature below the degradation temperature of nanofibrillated cellulose, wherein the second thermoplastic polyamide fiber flows into the pores of the first sheet layer to form a melt-connected polymer matrix between the first thermoplastic polyamide fiber, the second thermoplastic polyamide fiber and the nanofibrillated cellulose of the first sheet layer.
2. The method of claim 1 , wherein the first thermoplastic polyamide fiber and the second thermoplastic polyamide fiber are the same or different polyamides having compatibility with nanofibrillated cellulose.
3. The method of claim 1 , wherein the temperature in the fourth step is in the range of 100° C. to 200° C. when the second layer sheet is a hot-melt web, or in the range of 170° C. to 270° C. when the second layer sheet is a meltblown nonwoven fabric and wherein the applied pressure is in the range of 4 MPa to 110 MPa.