R-parity violation and Peccei-Quinn symmetry in GUTs

We address the question whether it is possible in GUTs to obtain R-parity violation with a large Delta L/Delta B hierarchy of strengths so that the proton is stable while phenomenologically interesting L-violation is present. We consider versions of SU(5) with a built-in Peccei-Quinn symmetry spontaneously broken at an intermediate scale. The PQ symmetry and the field content guarantee a large suppression of the effective B-violating terms by a factor Lambda(PQ)(3)/M(p)M(x)(2) while the effective L-violating terms stay large.