Method of bonding an ultrafiltration membrane assembly

A process for making a composite ultrafiltration membrane assembly comprising the steps of:

• (a) arranging a composite assembly for joining by superposing a coarse-fabric drainage mat on a polymer backing plate member having a relatively low polymer melt temperature, said drainage mat being positioned so as to leave selected edges of said backing plate member uncovered, superposing on said drainage mat a membrane element, said membrane element comprising a thin membrane having a relatively high polymer melt temperature mechanically joined to a porous polymer support member, the dimensions of said membrane element being such that the uncovered edge portions of the backing plate member are in contact with the porous support member of said membrane element, said porous support member of said membrane element having a relatively low polymer melt temperature,
• (b) applying pressure to at least some edges of said composite assembly to bring said porous support member into intimate contact with said backing plate member at said edges and to compact and compress said membrane,
• (c) heating said contacting edges through said membrane to develop in said porous support member and said backing plate member temperatures in excess of the polymer melt temperature of the aforesaid contacting members, but less than the polymer melt temperature of said membrane,
• (d) maintaining said pressure and heat on said edges for a predetermined time whereby the contacting edges of said porous support member and said backing plate member fuse to form a sealed joint and the membrane is compacted.