  Asymptotic couplings by reflection are constructed for a class of non-linear
monotone SPDES (stochastic partial differential equations). As applications,
the gradient/H\"older estimates as well as the exponential convergence are
derived for the associated Markov semigroup. The main results are illustrated
by stochastic generalized porous media equations, stochastic $p$-Laplacian
equations, and stochastic generalized fast-diffusion equations. We emphasize
that the gradient estimate is studied at the first time for these equations.
