The ornamental design for a syntheticresinpaper, as shown and described.
FIG. 1 is a view of the synthetic resin paper; and,
FIG. 2 is an enlarged view of FIG. 1.
The pattern shown in the claimed design is continuous and may repeat in up, down, right and left directions. The thickness of the synthetic resin paper is de minimus, i.e., it is essentially without visible thickness.