The ornamental design for a syntheticresinpaper, as shown and described.
FIG. 1 is a view of the synthetic resin paper; and,
FIG. 2 is a enlarged view of FIG. 1.
The broken lines in the drawings indicate that the pattern of the synthetic resin paper is continuous and may repeat in up, down, right and left directions. The broken lines form no part of the claimed design. The thickness of the synthetic resin paper is de minimus, i.e., it is essentially without visible thickness.