Method for preparing phosphorous polyphenylene oxide resin with low molecular weight

The invention relates to a method for preparing phosphorous polyphenylene oxide resin with low molecular weight. The method comprises the steps as follows: in step one, phosphorous phenolic compounds and raw material polyphenylene oxide resin are provided, wherein the number average molecular weight of the raw material polyphenylene oxide resin is more than 10000; in step two, the raw material polyphenylene oxide resin is dissolved in solvent so as to prepare a raw material polyphenylene oxide resin solution; in step three, the phosphorous phenolic compounds are added in the raw material polyphenylene oxide resin solution; in step four, initiator is added, and redistribution reaction is performed under the reaction temperature that is more than 60 DEG C under the action of the initiator; and in step five, products that are phosphorous polyphenylene oxide resin with low molecular weight are obtained after the reaction is finished, and the number average molecular weight of the phosphorous polyphenylene oxide resin ranges from 1000 to 6000. In the method, the phosphorous phenolic compounds are dispersed in the polyphenylene oxide resin solution, and the redistribution reaction is performed under the action of the initiator so as to prepare the phosphorous polyphenylene oxide resin with low molecular weight; the prepared phosphorous polyphenylene oxide resin with low molecular weight achieves good manufacturability, and is suitable for matrix resin of composite material of a high-frequency circuit board and the like or addition ingredients of other polymer material.