REINFORCED MEMBRANES, PROCESS AND APPARATUS FOR MAKING THEM, AND USE THEREOF AS ION-EXCHANGE MEMBRANES IN CHLOR-ALKALI CELLS OR AS CATALYSTS

摘要

Reinforced membranes comprise at least two layers of melt-fabricable fluorinated polymer having side chains containing sulfonyl and/or carboxyl groups in melt fabricable form, and a woven reinforcing fabric comprising warp and weft strands, there being at least one layer of said fluorinated polymer on each side of said reinforcing fabric, the warp and weft strands of said reinforcing fabric defining windows between said strands, each layer of fluorinated polymer over at least 70% of the area in each of at least 90% of said windows being of uniform thickness within plus or minus 10%. Ion-exchange membranes can be derived therefrom by converting the sulfonyl and/or carboxyl groups to ion exchange form. …??Such reinforced membranes can be prepared by (1) continuously bringing at least two films of meltfabricable fluorinated polymer and a web of reinforcing material into face-to-face contact such that proximate surfaces of two of said films contact opposite planar surfaces of said web, and moving the resulting combination of said films and said web vertically, unsupported except at two opposite edges thereof, (2) removing air from between said films at the two opposite edge portions thereof, (3) applying heat to the two outermost opposite planar film surfaces, first in the center portions thereof and progressively moving toward and including the edge portions thereof, and (4) cooling the resulting reinforced membrane. …??Apparatus for making reinforced membranes comprises (a) a frame (1), and mounted on said frame (1),… (b) means (17) for guiding at least two continuous webs of film (11 and 12) and a continuous web of reinforcing material (13) into face-to-face contact such that proximate surfaces of two of said webs of film (11, 12) contact opposite sides of said web of reinforcing material (13),… (c) two sets of flexible endless belts (20 and 21; 42 and not shown) which cooperate to engage opposite sides of the resulting assembly of said webs (11, 12 and 13) at the edge portions thereof and to transport said assembly (11, 12 and 13), each set (say 20) consisting of two belts (20, 21), one belt (20) of each set having a series of perforations (44) along its entire length, each set of belts (20 and 21; 42 and not shown) extending beyond an edge of said assembly (11, 12 and 13), and guide means (23, 24; 26, 27) for said belts (20 and 21, respectively),… (d) vacuum means including two vacuum manifolds (29), one manifold (29) adjacent each said perforated belt (20; 42), for removing air from between said films of said assembly (11, 12, 13) at the edge portions thereof through said perforations (44; 45),… (e) two banks of heaters (46) (31, 32), one bank adjacent each exposed film surface, each bank (say 31) consisting of a plurality of heaters (46) disposed for heating first the center portion of said assembly (11, 12, 13) and then progressively toward and including the edges thereof as said assembly is transported therebetween, to fuse said assembly (11, 12, 13) into a reinforced membrane (33),… (f) means (18, 19) for guiding said assembly (11, 12, 13) between said banks of heaters (31, 32),… (g) a wind-up (34) for collecting said reinforced membrane (33), and… (h) means for driving said wind-up (34). …??The membranes have exceptional uniformity and, in ion-exchange form when used as membranes which separate the compartments of a chloralkali cell, offer the advantages of low operating voltage, low power consumption and high current efficiency, and long useful life without rupture.