By "rubber wood" you mean wood from the rubber tree? As far as I know, Sodium Borate ("Borax") can be used as a treatment on any type of wood, but it is water soluble so it will not remain within the cellular structure of the wood if it is exposed to wet conditions (in which the borax would leach out). This chemical has the ability to inhibit molds, mildew, termites, carpenter ants and fire. It is much less harmful environmentally than the CCA, ACQ, and similar commercial wood treatment chemicals. Too bad it doesn't get enough publicity or use.
I don't know of alternatives, but you could probably look up the trade association for the forest products treatment companies.