Method of producing a drying filter

A method of producing shaped drying filters which comprises forming a mixture consisting essentially of particles of silica gel and from 5 to 8 percent by weight based on the weight of the gel of a heat curable powder epoxy resin composition having a particle size of less than 70 microns and having a cure temperature of at least about 180.degree.C. and selected from the group consisting of:

• a. a powdered mixture comprising, as the epoxy resin component, a mixture of i) a solid condensate of epichlorohydrin and bisphenol A, and having an epoxy functionality of at least 1, a molecular weight of from about 900 to 10,000 and a softening point in the range of about 60.degree.-140.degree.C., and ii) a solid condensate of epichlorohydrin and a phenol-formaldehyde resin containing active --OH groups, and having an epoxy functionality of about 3-7, a molecular weight of about 500 to 1500 and a softening point in the range of about 300 to 120.degree.C.;
• and, as a hardener therefor, a solid anhydride or polyanhydride having a melting point about about 50.degree.C., and
• b. a powdered mixture comprising, as the epoxy resin component, a solid condensate of epichlorohydrin or glycerol dichlorohydrin with a dihydric phenol such as resorcinol or bisphenol A, and having an epoxy functionality of at least 1, a molecular weight in the range of about 65.degree.-130.degree.C.;
• and, as a hardener therefor, a solid condensate of trimellitic anhydride and a dihydric alcohol selected from the group consisting of diethylene to pentaethylene glycols, di- and tri-propylene glycol and C.sub.5 -C.sub.8 alkane 2.omega. diols;
• the mixture being formed at a first temperature below the cure temperature of the resin, compressing the mixture to form a shaped body, and heating the compressed mixture to said cure temperature to cure the said resin.