Cellulose-fiber-dispersing polyolefin resin composite material, pellet and formed body using same, and production method for cellulose-fiber-dispersing polyolefin resin composite material

A cellulose-fiber-dispersing polyolefin resin composite material, comprising:

• a polyolefin resin containing a polypropylene resin;
• and
• a cellulose fiber dispersed in the polyolefin resin,
• wherein a content of the cellulose fiber is 5 mass parts or more and less than 50 mass parts based on a total content of 100 mass parts of the polyolefin resin and the cellulose fiber, and
• wherein a relationship between a water absorption ratio A upon immersing into water at 23° C. for 20 days and a cellulose effective mass ratio determined by performing a thermogravimetric analysis (TGA) satisfies [Formula Ia], and a relationship between a water absorption ratio B upon immersing into water at 80° C. for 20 days and the cellulose effective mass ratio satisfies [Formula Ib]:
• (Water absorption ratio A [%])<(Cellulose effective mass ratio [%])2×0.01, [Formula Ia]
• (Water absorption ratio B [%])<(Cellulose effective mass ratio [%])×0.7. [Formula Ib]
• wherein the water absorption ratio A is determined according to [Formula IIa] based on measured mass values before and after the immersion, into water of 23° C. for 20 days, of a cellulose-fiber-dispersing polyolefin composite material dried in advance until a moisture content was reduced to 0.5 mass % or less,
• wherein the water absorption ratio B is determined according to [Formula IIb] based on measured mass values before and after the immersion, into water of 80° C. for 20 days, of a cellulose-fiber-dispersing polyolefin composite material dried in advance until a moisture content was reduced to 0.5 mass % or less, and
• wherein the cellulose effective mass ratio is determined by performing the thermogravimetric analysis (TGA) under a nitrogen atmosphere on the cellulose-fiber-dispersing polyolefin resin composite material according to [Formula III]:
• (Water absorption ratio A [%])=(mass after immersion [g]−mass before immersion [g])×100/(mass before immersion [g]), [Formula IIa]
• (Water absorption ratio B [%])=(mass after immersion [g]−mass before immersion [g])×100/(mass before immersion [g]), [Formula IIb]
• (Cellulose effective mass ratio [%])=(loss of mass [mg] from 270° C. to 390° C. [mg])×100/(mass [mg] of a composite material sample before being provided for the thermogravimetric analysis), and [Formula III]
• wherein a cellulose fiber dispersibility is less than 20 in terms of a number of mountains.