Patent ID: 9388287
Filing Date: 2016-07-12
CPC Classification: C08G,C08J,C08L,C09J

Claim Text:
1. A polyimide powder that is an imide of polyamic acid obtained by polymerizing a diamine and at least two acid dianhydrides, wherein a degree of imidization of the polyimide powder is not less than 80%; a specific refractive index increment (dn/dc) of the polyimide powder is 0.100 to 0.1800; and the acid dianhydrides comprise 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, and at least one selected from the group consisting of 4-(2,5-dioxotetrahydrofuran-3)-1,2,3,4-tetrahydronaphtalene-1,2-dicarboxylic anhydride and 4,4′-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride); wherein the imide of the polyamic acid is obtained by lastly injecting the 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride during the polymerization of the diamine and the acid dianhydrides; and wherein the specific refractive index increment (dn/dc) is defined as follows: Specific refractive index increment (dn/dc): the value is that a change rate of refractive index according to the change rate of dilute solution concentration is differentiated and is measured within the range of 0.001 to 0.1 g/ml that is a section of concentration change when detecting a refractive index through injecting the polyimide powder in a state of dilute solution in an organic solvent inside flow cell of differential refractometer.